Root/
1 | /* |
2 | * INET An implementation of the TCP/IP protocol suite for the LINUX |
3 | * operating system. INET is implemented using the BSD Socket |
4 | * interface as the means of communication with the user level. |
5 | * |
6 | * Implementation of the Transmission Control Protocol(TCP). |
7 | * |
8 | * Authors: Ross Biro |
9 | * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> |
10 | * Mark Evans, <evansmp@uhura.aston.ac.uk> |
11 | * Corey Minyard <wf-rch!minyard@relay.EU.net> |
12 | * Florian La Roche, <flla@stud.uni-sb.de> |
13 | * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> |
14 | * Linus Torvalds, <torvalds@cs.helsinki.fi> |
15 | * Alan Cox, <gw4pts@gw4pts.ampr.org> |
16 | * Matthew Dillon, <dillon@apollo.west.oic.com> |
17 | * Arnt Gulbrandsen, <agulbra@nvg.unit.no> |
18 | * Jorge Cwik, <jorge@laser.satlink.net> |
19 | */ |
20 | |
21 | /* |
22 | * Changes: |
23 | * Pedro Roque : Fast Retransmit/Recovery. |
24 | * Two receive queues. |
25 | * Retransmit queue handled by TCP. |
26 | * Better retransmit timer handling. |
27 | * New congestion avoidance. |
28 | * Header prediction. |
29 | * Variable renaming. |
30 | * |
31 | * Eric : Fast Retransmit. |
32 | * Randy Scott : MSS option defines. |
33 | * Eric Schenk : Fixes to slow start algorithm. |
34 | * Eric Schenk : Yet another double ACK bug. |
35 | * Eric Schenk : Delayed ACK bug fixes. |
36 | * Eric Schenk : Floyd style fast retrans war avoidance. |
37 | * David S. Miller : Don't allow zero congestion window. |
38 | * Eric Schenk : Fix retransmitter so that it sends |
39 | * next packet on ack of previous packet. |
40 | * Andi Kleen : Moved open_request checking here |
41 | * and process RSTs for open_requests. |
42 | * Andi Kleen : Better prune_queue, and other fixes. |
43 | * Andrey Savochkin: Fix RTT measurements in the presence of |
44 | * timestamps. |
45 | * Andrey Savochkin: Check sequence numbers correctly when |
46 | * removing SACKs due to in sequence incoming |
47 | * data segments. |
48 | * Andi Kleen: Make sure we never ack data there is not |
49 | * enough room for. Also make this condition |
50 | * a fatal error if it might still happen. |
51 | * Andi Kleen: Add tcp_measure_rcv_mss to make |
52 | * connections with MSS<min(MTU,ann. MSS) |
53 | * work without delayed acks. |
54 | * Andi Kleen: Process packets with PSH set in the |
55 | * fast path. |
56 | * J Hadi Salim: ECN support |
57 | * Andrei Gurtov, |
58 | * Pasi Sarolahti, |
59 | * Panu Kuhlberg: Experimental audit of TCP (re)transmission |
60 | * engine. Lots of bugs are found. |
61 | * Pasi Sarolahti: F-RTO for dealing with spurious RTOs |
62 | */ |
63 | |
64 | #include <linux/mm.h> |
65 | #include <linux/slab.h> |
66 | #include <linux/module.h> |
67 | #include <linux/sysctl.h> |
68 | #include <linux/kernel.h> |
69 | #include <net/dst.h> |
70 | #include <net/tcp.h> |
71 | #include <net/inet_common.h> |
72 | #include <linux/ipsec.h> |
73 | #include <asm/unaligned.h> |
74 | #include <net/netdma.h> |
75 | |
76 | int sysctl_tcp_timestamps __read_mostly = 1; |
77 | int sysctl_tcp_window_scaling __read_mostly = 1; |
78 | int sysctl_tcp_sack __read_mostly = 1; |
79 | int sysctl_tcp_fack __read_mostly = 1; |
80 | int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; |
81 | int sysctl_tcp_ecn __read_mostly = 2; |
82 | int sysctl_tcp_dsack __read_mostly = 1; |
83 | int sysctl_tcp_app_win __read_mostly = 31; |
84 | int sysctl_tcp_adv_win_scale __read_mostly = 2; |
85 | |
86 | int sysctl_tcp_stdurg __read_mostly; |
87 | int sysctl_tcp_rfc1337 __read_mostly; |
88 | int sysctl_tcp_max_orphans __read_mostly = NR_FILE; |
89 | int sysctl_tcp_frto __read_mostly = 2; |
90 | int sysctl_tcp_frto_response __read_mostly; |
91 | int sysctl_tcp_nometrics_save __read_mostly; |
92 | |
93 | int sysctl_tcp_thin_dupack __read_mostly; |
94 | |
95 | int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; |
96 | int sysctl_tcp_abc __read_mostly; |
97 | |
98 | #define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
99 | #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ |
100 | #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ |
101 | #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ |
102 | #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ |
103 | #define FLAG_DATA_SACKED 0x20 /* New SACK. */ |
104 | #define FLAG_ECE 0x40 /* ECE in this ACK */ |
105 | #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ |
106 | #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ |
107 | #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */ |
108 | #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ |
109 | #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ |
110 | #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */ |
111 | #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ |
112 | |
113 | #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) |
114 | #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) |
115 | #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) |
116 | #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) |
117 | #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED) |
118 | |
119 | #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) |
120 | #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) |
121 | |
122 | /* Adapt the MSS value used to make delayed ack decision to the |
123 | * real world. |
124 | */ |
125 | static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) |
126 | { |
127 | struct inet_connection_sock *icsk = inet_csk(sk); |
128 | const unsigned int lss = icsk->icsk_ack.last_seg_size; |
129 | unsigned int len; |
130 | |
131 | icsk->icsk_ack.last_seg_size = 0; |
132 | |
133 | /* skb->len may jitter because of SACKs, even if peer |
134 | * sends good full-sized frames. |
135 | */ |
136 | len = skb_shinfo(skb)->gso_size ? : skb->len; |
137 | if (len >= icsk->icsk_ack.rcv_mss) { |
138 | icsk->icsk_ack.rcv_mss = len; |
139 | } else { |
140 | /* Otherwise, we make more careful check taking into account, |
141 | * that SACKs block is variable. |
142 | * |
143 | * "len" is invariant segment length, including TCP header. |
144 | */ |
145 | len += skb->data - skb_transport_header(skb); |
146 | if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || |
147 | /* If PSH is not set, packet should be |
148 | * full sized, provided peer TCP is not badly broken. |
149 | * This observation (if it is correct 8)) allows |
150 | * to handle super-low mtu links fairly. |
151 | */ |
152 | (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && |
153 | !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { |
154 | /* Subtract also invariant (if peer is RFC compliant), |
155 | * tcp header plus fixed timestamp option length. |
156 | * Resulting "len" is MSS free of SACK jitter. |
157 | */ |
158 | len -= tcp_sk(sk)->tcp_header_len; |
159 | icsk->icsk_ack.last_seg_size = len; |
160 | if (len == lss) { |
161 | icsk->icsk_ack.rcv_mss = len; |
162 | return; |
163 | } |
164 | } |
165 | if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) |
166 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; |
167 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; |
168 | } |
169 | } |
170 | |
171 | static void tcp_incr_quickack(struct sock *sk) |
172 | { |
173 | struct inet_connection_sock *icsk = inet_csk(sk); |
174 | unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); |
175 | |
176 | if (quickacks == 0) |
177 | quickacks = 2; |
178 | if (quickacks > icsk->icsk_ack.quick) |
179 | icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); |
180 | } |
181 | |
182 | void tcp_enter_quickack_mode(struct sock *sk) |
183 | { |
184 | struct inet_connection_sock *icsk = inet_csk(sk); |
185 | tcp_incr_quickack(sk); |
186 | icsk->icsk_ack.pingpong = 0; |
187 | icsk->icsk_ack.ato = TCP_ATO_MIN; |
188 | } |
189 | |
190 | /* Send ACKs quickly, if "quick" count is not exhausted |
191 | * and the session is not interactive. |
192 | */ |
193 | |
194 | static inline int tcp_in_quickack_mode(const struct sock *sk) |
195 | { |
196 | const struct inet_connection_sock *icsk = inet_csk(sk); |
197 | return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; |
198 | } |
199 | |
200 | static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) |
201 | { |
202 | if (tp->ecn_flags & TCP_ECN_OK) |
203 | tp->ecn_flags |= TCP_ECN_QUEUE_CWR; |
204 | } |
205 | |
206 | static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, struct sk_buff *skb) |
207 | { |
208 | if (tcp_hdr(skb)->cwr) |
209 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; |
210 | } |
211 | |
212 | static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) |
213 | { |
214 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; |
215 | } |
216 | |
217 | static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb) |
218 | { |
219 | if (tp->ecn_flags & TCP_ECN_OK) { |
220 | if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags)) |
221 | tp->ecn_flags |= TCP_ECN_DEMAND_CWR; |
222 | /* Funny extension: if ECT is not set on a segment, |
223 | * it is surely retransmit. It is not in ECN RFC, |
224 | * but Linux follows this rule. */ |
225 | else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags))) |
226 | tcp_enter_quickack_mode((struct sock *)tp); |
227 | } |
228 | } |
229 | |
230 | static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th) |
231 | { |
232 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) |
233 | tp->ecn_flags &= ~TCP_ECN_OK; |
234 | } |
235 | |
236 | static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th) |
237 | { |
238 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) |
239 | tp->ecn_flags &= ~TCP_ECN_OK; |
240 | } |
241 | |
242 | static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th) |
243 | { |
244 | if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) |
245 | return 1; |
246 | return 0; |
247 | } |
248 | |
249 | /* Buffer size and advertised window tuning. |
250 | * |
251 | * 1. Tuning sk->sk_sndbuf, when connection enters established state. |
252 | */ |
253 | |
254 | static void tcp_fixup_sndbuf(struct sock *sk) |
255 | { |
256 | int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + |
257 | sizeof(struct sk_buff); |
258 | |
259 | if (sk->sk_sndbuf < 3 * sndmem) |
260 | sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); |
261 | } |
262 | |
263 | /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) |
264 | * |
265 | * All tcp_full_space() is split to two parts: "network" buffer, allocated |
266 | * forward and advertised in receiver window (tp->rcv_wnd) and |
267 | * "application buffer", required to isolate scheduling/application |
268 | * latencies from network. |
269 | * window_clamp is maximal advertised window. It can be less than |
270 | * tcp_full_space(), in this case tcp_full_space() - window_clamp |
271 | * is reserved for "application" buffer. The less window_clamp is |
272 | * the smoother our behaviour from viewpoint of network, but the lower |
273 | * throughput and the higher sensitivity of the connection to losses. 8) |
274 | * |
275 | * rcv_ssthresh is more strict window_clamp used at "slow start" |
276 | * phase to predict further behaviour of this connection. |
277 | * It is used for two goals: |
278 | * - to enforce header prediction at sender, even when application |
279 | * requires some significant "application buffer". It is check #1. |
280 | * - to prevent pruning of receive queue because of misprediction |
281 | * of receiver window. Check #2. |
282 | * |
283 | * The scheme does not work when sender sends good segments opening |
284 | * window and then starts to feed us spaghetti. But it should work |
285 | * in common situations. Otherwise, we have to rely on queue collapsing. |
286 | */ |
287 | |
288 | /* Slow part of check#2. */ |
289 | static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) |
290 | { |
291 | struct tcp_sock *tp = tcp_sk(sk); |
292 | /* Optimize this! */ |
293 | int truesize = tcp_win_from_space(skb->truesize) >> 1; |
294 | int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; |
295 | |
296 | while (tp->rcv_ssthresh <= window) { |
297 | if (truesize <= skb->len) |
298 | return 2 * inet_csk(sk)->icsk_ack.rcv_mss; |
299 | |
300 | truesize >>= 1; |
301 | window >>= 1; |
302 | } |
303 | return 0; |
304 | } |
305 | |
306 | static void tcp_grow_window(struct sock *sk, struct sk_buff *skb) |
307 | { |
308 | struct tcp_sock *tp = tcp_sk(sk); |
309 | |
310 | /* Check #1 */ |
311 | if (tp->rcv_ssthresh < tp->window_clamp && |
312 | (int)tp->rcv_ssthresh < tcp_space(sk) && |
313 | !tcp_memory_pressure) { |
314 | int incr; |
315 | |
316 | /* Check #2. Increase window, if skb with such overhead |
317 | * will fit to rcvbuf in future. |
318 | */ |
319 | if (tcp_win_from_space(skb->truesize) <= skb->len) |
320 | incr = 2 * tp->advmss; |
321 | else |
322 | incr = __tcp_grow_window(sk, skb); |
323 | |
324 | if (incr) { |
325 | tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, |
326 | tp->window_clamp); |
327 | inet_csk(sk)->icsk_ack.quick |= 1; |
328 | } |
329 | } |
330 | } |
331 | |
332 | /* 3. Tuning rcvbuf, when connection enters established state. */ |
333 | |
334 | static void tcp_fixup_rcvbuf(struct sock *sk) |
335 | { |
336 | struct tcp_sock *tp = tcp_sk(sk); |
337 | int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); |
338 | |
339 | /* Try to select rcvbuf so that 4 mss-sized segments |
340 | * will fit to window and corresponding skbs will fit to our rcvbuf. |
341 | * (was 3; 4 is minimum to allow fast retransmit to work.) |
342 | */ |
343 | while (tcp_win_from_space(rcvmem) < tp->advmss) |
344 | rcvmem += 128; |
345 | if (sk->sk_rcvbuf < 4 * rcvmem) |
346 | sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); |
347 | } |
348 | |
349 | /* 4. Try to fixup all. It is made immediately after connection enters |
350 | * established state. |
351 | */ |
352 | static void tcp_init_buffer_space(struct sock *sk) |
353 | { |
354 | struct tcp_sock *tp = tcp_sk(sk); |
355 | int maxwin; |
356 | |
357 | if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) |
358 | tcp_fixup_rcvbuf(sk); |
359 | if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) |
360 | tcp_fixup_sndbuf(sk); |
361 | |
362 | tp->rcvq_space.space = tp->rcv_wnd; |
363 | |
364 | maxwin = tcp_full_space(sk); |
365 | |
366 | if (tp->window_clamp >= maxwin) { |
367 | tp->window_clamp = maxwin; |
368 | |
369 | if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) |
370 | tp->window_clamp = max(maxwin - |
371 | (maxwin >> sysctl_tcp_app_win), |
372 | 4 * tp->advmss); |
373 | } |
374 | |
375 | /* Force reservation of one segment. */ |
376 | if (sysctl_tcp_app_win && |
377 | tp->window_clamp > 2 * tp->advmss && |
378 | tp->window_clamp + tp->advmss > maxwin) |
379 | tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); |
380 | |
381 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); |
382 | tp->snd_cwnd_stamp = tcp_time_stamp; |
383 | } |
384 | |
385 | /* 5. Recalculate window clamp after socket hit its memory bounds. */ |
386 | static void tcp_clamp_window(struct sock *sk) |
387 | { |
388 | struct tcp_sock *tp = tcp_sk(sk); |
389 | struct inet_connection_sock *icsk = inet_csk(sk); |
390 | |
391 | icsk->icsk_ack.quick = 0; |
392 | |
393 | if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && |
394 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && |
395 | !tcp_memory_pressure && |
396 | atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { |
397 | sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), |
398 | sysctl_tcp_rmem[2]); |
399 | } |
400 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) |
401 | tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); |
402 | } |
403 | |
404 | /* Initialize RCV_MSS value. |
405 | * RCV_MSS is an our guess about MSS used by the peer. |
406 | * We haven't any direct information about the MSS. |
407 | * It's better to underestimate the RCV_MSS rather than overestimate. |
408 | * Overestimations make us ACKing less frequently than needed. |
409 | * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). |
410 | */ |
411 | void tcp_initialize_rcv_mss(struct sock *sk) |
412 | { |
413 | struct tcp_sock *tp = tcp_sk(sk); |
414 | unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); |
415 | |
416 | hint = min(hint, tp->rcv_wnd / 2); |
417 | hint = min(hint, TCP_MSS_DEFAULT); |
418 | hint = max(hint, TCP_MIN_MSS); |
419 | |
420 | inet_csk(sk)->icsk_ack.rcv_mss = hint; |
421 | } |
422 | |
423 | /* Receiver "autotuning" code. |
424 | * |
425 | * The algorithm for RTT estimation w/o timestamps is based on |
426 | * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. |
427 | * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> |
428 | * |
429 | * More detail on this code can be found at |
430 | * <http://www.psc.edu/~jheffner/senior_thesis.ps>, |
431 | * though this reference is out of date. A new paper |
432 | * is pending. |
433 | */ |
434 | static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) |
435 | { |
436 | u32 new_sample = tp->rcv_rtt_est.rtt; |
437 | long m = sample; |
438 | |
439 | if (m == 0) |
440 | m = 1; |
441 | |
442 | if (new_sample != 0) { |
443 | /* If we sample in larger samples in the non-timestamp |
444 | * case, we could grossly overestimate the RTT especially |
445 | * with chatty applications or bulk transfer apps which |
446 | * are stalled on filesystem I/O. |
447 | * |
448 | * Also, since we are only going for a minimum in the |
449 | * non-timestamp case, we do not smooth things out |
450 | * else with timestamps disabled convergence takes too |
451 | * long. |
452 | */ |
453 | if (!win_dep) { |
454 | m -= (new_sample >> 3); |
455 | new_sample += m; |
456 | } else if (m < new_sample) |
457 | new_sample = m << 3; |
458 | } else { |
459 | /* No previous measure. */ |
460 | new_sample = m << 3; |
461 | } |
462 | |
463 | if (tp->rcv_rtt_est.rtt != new_sample) |
464 | tp->rcv_rtt_est.rtt = new_sample; |
465 | } |
466 | |
467 | static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) |
468 | { |
469 | if (tp->rcv_rtt_est.time == 0) |
470 | goto new_measure; |
471 | if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) |
472 | return; |
473 | tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1); |
474 | |
475 | new_measure: |
476 | tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; |
477 | tp->rcv_rtt_est.time = tcp_time_stamp; |
478 | } |
479 | |
480 | static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, |
481 | const struct sk_buff *skb) |
482 | { |
483 | struct tcp_sock *tp = tcp_sk(sk); |
484 | if (tp->rx_opt.rcv_tsecr && |
485 | (TCP_SKB_CB(skb)->end_seq - |
486 | TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) |
487 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); |
488 | } |
489 | |
490 | /* |
491 | * This function should be called every time data is copied to user space. |
492 | * It calculates the appropriate TCP receive buffer space. |
493 | */ |
494 | void tcp_rcv_space_adjust(struct sock *sk) |
495 | { |
496 | struct tcp_sock *tp = tcp_sk(sk); |
497 | int time; |
498 | int space; |
499 | |
500 | if (tp->rcvq_space.time == 0) |
501 | goto new_measure; |
502 | |
503 | time = tcp_time_stamp - tp->rcvq_space.time; |
504 | if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) |
505 | return; |
506 | |
507 | space = 2 * (tp->copied_seq - tp->rcvq_space.seq); |
508 | |
509 | space = max(tp->rcvq_space.space, space); |
510 | |
511 | if (tp->rcvq_space.space != space) { |
512 | int rcvmem; |
513 | |
514 | tp->rcvq_space.space = space; |
515 | |
516 | if (sysctl_tcp_moderate_rcvbuf && |
517 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { |
518 | int new_clamp = space; |
519 | |
520 | /* Receive space grows, normalize in order to |
521 | * take into account packet headers and sk_buff |
522 | * structure overhead. |
523 | */ |
524 | space /= tp->advmss; |
525 | if (!space) |
526 | space = 1; |
527 | rcvmem = (tp->advmss + MAX_TCP_HEADER + |
528 | 16 + sizeof(struct sk_buff)); |
529 | while (tcp_win_from_space(rcvmem) < tp->advmss) |
530 | rcvmem += 128; |
531 | space *= rcvmem; |
532 | space = min(space, sysctl_tcp_rmem[2]); |
533 | if (space > sk->sk_rcvbuf) { |
534 | sk->sk_rcvbuf = space; |
535 | |
536 | /* Make the window clamp follow along. */ |
537 | tp->window_clamp = new_clamp; |
538 | } |
539 | } |
540 | } |
541 | |
542 | new_measure: |
543 | tp->rcvq_space.seq = tp->copied_seq; |
544 | tp->rcvq_space.time = tcp_time_stamp; |
545 | } |
546 | |
547 | /* There is something which you must keep in mind when you analyze the |
548 | * behavior of the tp->ato delayed ack timeout interval. When a |
549 | * connection starts up, we want to ack as quickly as possible. The |
550 | * problem is that "good" TCP's do slow start at the beginning of data |
551 | * transmission. The means that until we send the first few ACK's the |
552 | * sender will sit on his end and only queue most of his data, because |
553 | * he can only send snd_cwnd unacked packets at any given time. For |
554 | * each ACK we send, he increments snd_cwnd and transmits more of his |
555 | * queue. -DaveM |
556 | */ |
557 | static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) |
558 | { |
559 | struct tcp_sock *tp = tcp_sk(sk); |
560 | struct inet_connection_sock *icsk = inet_csk(sk); |
561 | u32 now; |
562 | |
563 | inet_csk_schedule_ack(sk); |
564 | |
565 | tcp_measure_rcv_mss(sk, skb); |
566 | |
567 | tcp_rcv_rtt_measure(tp); |
568 | |
569 | now = tcp_time_stamp; |
570 | |
571 | if (!icsk->icsk_ack.ato) { |
572 | /* The _first_ data packet received, initialize |
573 | * delayed ACK engine. |
574 | */ |
575 | tcp_incr_quickack(sk); |
576 | icsk->icsk_ack.ato = TCP_ATO_MIN; |
577 | } else { |
578 | int m = now - icsk->icsk_ack.lrcvtime; |
579 | |
580 | if (m <= TCP_ATO_MIN / 2) { |
581 | /* The fastest case is the first. */ |
582 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; |
583 | } else if (m < icsk->icsk_ack.ato) { |
584 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; |
585 | if (icsk->icsk_ack.ato > icsk->icsk_rto) |
586 | icsk->icsk_ack.ato = icsk->icsk_rto; |
587 | } else if (m > icsk->icsk_rto) { |
588 | /* Too long gap. Apparently sender failed to |
589 | * restart window, so that we send ACKs quickly. |
590 | */ |
591 | tcp_incr_quickack(sk); |
592 | sk_mem_reclaim(sk); |
593 | } |
594 | } |
595 | icsk->icsk_ack.lrcvtime = now; |
596 | |
597 | TCP_ECN_check_ce(tp, skb); |
598 | |
599 | if (skb->len >= 128) |
600 | tcp_grow_window(sk, skb); |
601 | } |
602 | |
603 | /* Called to compute a smoothed rtt estimate. The data fed to this |
604 | * routine either comes from timestamps, or from segments that were |
605 | * known _not_ to have been retransmitted [see Karn/Partridge |
606 | * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 |
607 | * piece by Van Jacobson. |
608 | * NOTE: the next three routines used to be one big routine. |
609 | * To save cycles in the RFC 1323 implementation it was better to break |
610 | * it up into three procedures. -- erics |
611 | */ |
612 | static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) |
613 | { |
614 | struct tcp_sock *tp = tcp_sk(sk); |
615 | long m = mrtt; /* RTT */ |
616 | |
617 | /* The following amusing code comes from Jacobson's |
618 | * article in SIGCOMM '88. Note that rtt and mdev |
619 | * are scaled versions of rtt and mean deviation. |
620 | * This is designed to be as fast as possible |
621 | * m stands for "measurement". |
622 | * |
623 | * On a 1990 paper the rto value is changed to: |
624 | * RTO = rtt + 4 * mdev |
625 | * |
626 | * Funny. This algorithm seems to be very broken. |
627 | * These formulae increase RTO, when it should be decreased, increase |
628 | * too slowly, when it should be increased quickly, decrease too quickly |
629 | * etc. I guess in BSD RTO takes ONE value, so that it is absolutely |
630 | * does not matter how to _calculate_ it. Seems, it was trap |
631 | * that VJ failed to avoid. 8) |
632 | */ |
633 | if (m == 0) |
634 | m = 1; |
635 | if (tp->srtt != 0) { |
636 | m -= (tp->srtt >> 3); /* m is now error in rtt est */ |
637 | tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ |
638 | if (m < 0) { |
639 | m = -m; /* m is now abs(error) */ |
640 | m -= (tp->mdev >> 2); /* similar update on mdev */ |
641 | /* This is similar to one of Eifel findings. |
642 | * Eifel blocks mdev updates when rtt decreases. |
643 | * This solution is a bit different: we use finer gain |
644 | * for mdev in this case (alpha*beta). |
645 | * Like Eifel it also prevents growth of rto, |
646 | * but also it limits too fast rto decreases, |
647 | * happening in pure Eifel. |
648 | */ |
649 | if (m > 0) |
650 | m >>= 3; |
651 | } else { |
652 | m -= (tp->mdev >> 2); /* similar update on mdev */ |
653 | } |
654 | tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ |
655 | if (tp->mdev > tp->mdev_max) { |
656 | tp->mdev_max = tp->mdev; |
657 | if (tp->mdev_max > tp->rttvar) |
658 | tp->rttvar = tp->mdev_max; |
659 | } |
660 | if (after(tp->snd_una, tp->rtt_seq)) { |
661 | if (tp->mdev_max < tp->rttvar) |
662 | tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2; |
663 | tp->rtt_seq = tp->snd_nxt; |
664 | tp->mdev_max = tcp_rto_min(sk); |
665 | } |
666 | } else { |
667 | /* no previous measure. */ |
668 | tp->srtt = m << 3; /* take the measured time to be rtt */ |
669 | tp->mdev = m << 1; /* make sure rto = 3*rtt */ |
670 | tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); |
671 | tp->rtt_seq = tp->snd_nxt; |
672 | } |
673 | } |
674 | |
675 | /* Calculate rto without backoff. This is the second half of Van Jacobson's |
676 | * routine referred to above. |
677 | */ |
678 | static inline void tcp_set_rto(struct sock *sk) |
679 | { |
680 | const struct tcp_sock *tp = tcp_sk(sk); |
681 | /* Old crap is replaced with new one. 8) |
682 | * |
683 | * More seriously: |
684 | * 1. If rtt variance happened to be less 50msec, it is hallucination. |
685 | * It cannot be less due to utterly erratic ACK generation made |
686 | * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ |
687 | * to do with delayed acks, because at cwnd>2 true delack timeout |
688 | * is invisible. Actually, Linux-2.4 also generates erratic |
689 | * ACKs in some circumstances. |
690 | */ |
691 | inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); |
692 | |
693 | /* 2. Fixups made earlier cannot be right. |
694 | * If we do not estimate RTO correctly without them, |
695 | * all the algo is pure shit and should be replaced |
696 | * with correct one. It is exactly, which we pretend to do. |
697 | */ |
698 | |
699 | /* NOTE: clamping at TCP_RTO_MIN is not required, current algo |
700 | * guarantees that rto is higher. |
701 | */ |
702 | tcp_bound_rto(sk); |
703 | } |
704 | |
705 | /* Save metrics learned by this TCP session. |
706 | This function is called only, when TCP finishes successfully |
707 | i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. |
708 | */ |
709 | void tcp_update_metrics(struct sock *sk) |
710 | { |
711 | struct tcp_sock *tp = tcp_sk(sk); |
712 | struct dst_entry *dst = __sk_dst_get(sk); |
713 | |
714 | if (sysctl_tcp_nometrics_save) |
715 | return; |
716 | |
717 | dst_confirm(dst); |
718 | |
719 | if (dst && (dst->flags & DST_HOST)) { |
720 | const struct inet_connection_sock *icsk = inet_csk(sk); |
721 | int m; |
722 | unsigned long rtt; |
723 | |
724 | if (icsk->icsk_backoff || !tp->srtt) { |
725 | /* This session failed to estimate rtt. Why? |
726 | * Probably, no packets returned in time. |
727 | * Reset our results. |
728 | */ |
729 | if (!(dst_metric_locked(dst, RTAX_RTT))) |
730 | dst->metrics[RTAX_RTT - 1] = 0; |
731 | return; |
732 | } |
733 | |
734 | rtt = dst_metric_rtt(dst, RTAX_RTT); |
735 | m = rtt - tp->srtt; |
736 | |
737 | /* If newly calculated rtt larger than stored one, |
738 | * store new one. Otherwise, use EWMA. Remember, |
739 | * rtt overestimation is always better than underestimation. |
740 | */ |
741 | if (!(dst_metric_locked(dst, RTAX_RTT))) { |
742 | if (m <= 0) |
743 | set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt); |
744 | else |
745 | set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3)); |
746 | } |
747 | |
748 | if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { |
749 | unsigned long var; |
750 | if (m < 0) |
751 | m = -m; |
752 | |
753 | /* Scale deviation to rttvar fixed point */ |
754 | m >>= 1; |
755 | if (m < tp->mdev) |
756 | m = tp->mdev; |
757 | |
758 | var = dst_metric_rtt(dst, RTAX_RTTVAR); |
759 | if (m >= var) |
760 | var = m; |
761 | else |
762 | var -= (var - m) >> 2; |
763 | |
764 | set_dst_metric_rtt(dst, RTAX_RTTVAR, var); |
765 | } |
766 | |
767 | if (tcp_in_initial_slowstart(tp)) { |
768 | /* Slow start still did not finish. */ |
769 | if (dst_metric(dst, RTAX_SSTHRESH) && |
770 | !dst_metric_locked(dst, RTAX_SSTHRESH) && |
771 | (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) |
772 | dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; |
773 | if (!dst_metric_locked(dst, RTAX_CWND) && |
774 | tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) |
775 | dst->metrics[RTAX_CWND - 1] = tp->snd_cwnd; |
776 | } else if (tp->snd_cwnd > tp->snd_ssthresh && |
777 | icsk->icsk_ca_state == TCP_CA_Open) { |
778 | /* Cong. avoidance phase, cwnd is reliable. */ |
779 | if (!dst_metric_locked(dst, RTAX_SSTHRESH)) |
780 | dst->metrics[RTAX_SSTHRESH-1] = |
781 | max(tp->snd_cwnd >> 1, tp->snd_ssthresh); |
782 | if (!dst_metric_locked(dst, RTAX_CWND)) |
783 | dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_cwnd) >> 1; |
784 | } else { |
785 | /* Else slow start did not finish, cwnd is non-sense, |
786 | ssthresh may be also invalid. |
787 | */ |
788 | if (!dst_metric_locked(dst, RTAX_CWND)) |
789 | dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_ssthresh) >> 1; |
790 | if (dst_metric(dst, RTAX_SSTHRESH) && |
791 | !dst_metric_locked(dst, RTAX_SSTHRESH) && |
792 | tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH)) |
793 | dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; |
794 | } |
795 | |
796 | if (!dst_metric_locked(dst, RTAX_REORDERING)) { |
797 | if (dst_metric(dst, RTAX_REORDERING) < tp->reordering && |
798 | tp->reordering != sysctl_tcp_reordering) |
799 | dst->metrics[RTAX_REORDERING-1] = tp->reordering; |
800 | } |
801 | } |
802 | } |
803 | |
804 | /* Numbers are taken from RFC3390. |
805 | * |
806 | * John Heffner states: |
807 | * |
808 | * The RFC specifies a window of no more than 4380 bytes |
809 | * unless 2*MSS > 4380. Reading the pseudocode in the RFC |
810 | * is a bit misleading because they use a clamp at 4380 bytes |
811 | * rather than use a multiplier in the relevant range. |
812 | */ |
813 | __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) |
814 | { |
815 | __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); |
816 | |
817 | if (!cwnd) { |
818 | if (tp->mss_cache > 1460) |
819 | cwnd = 2; |
820 | else |
821 | cwnd = (tp->mss_cache > 1095) ? 3 : 4; |
822 | } |
823 | return min_t(__u32, cwnd, tp->snd_cwnd_clamp); |
824 | } |
825 | |
826 | /* Set slow start threshold and cwnd not falling to slow start */ |
827 | void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) |
828 | { |
829 | struct tcp_sock *tp = tcp_sk(sk); |
830 | const struct inet_connection_sock *icsk = inet_csk(sk); |
831 | |
832 | tp->prior_ssthresh = 0; |
833 | tp->bytes_acked = 0; |
834 | if (icsk->icsk_ca_state < TCP_CA_CWR) { |
835 | tp->undo_marker = 0; |
836 | if (set_ssthresh) |
837 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
838 | tp->snd_cwnd = min(tp->snd_cwnd, |
839 | tcp_packets_in_flight(tp) + 1U); |
840 | tp->snd_cwnd_cnt = 0; |
841 | tp->high_seq = tp->snd_nxt; |
842 | tp->snd_cwnd_stamp = tcp_time_stamp; |
843 | TCP_ECN_queue_cwr(tp); |
844 | |
845 | tcp_set_ca_state(sk, TCP_CA_CWR); |
846 | } |
847 | } |
848 | |
849 | /* |
850 | * Packet counting of FACK is based on in-order assumptions, therefore TCP |
851 | * disables it when reordering is detected |
852 | */ |
853 | static void tcp_disable_fack(struct tcp_sock *tp) |
854 | { |
855 | /* RFC3517 uses different metric in lost marker => reset on change */ |
856 | if (tcp_is_fack(tp)) |
857 | tp->lost_skb_hint = NULL; |
858 | tp->rx_opt.sack_ok &= ~2; |
859 | } |
860 | |
861 | /* Take a notice that peer is sending D-SACKs */ |
862 | static void tcp_dsack_seen(struct tcp_sock *tp) |
863 | { |
864 | tp->rx_opt.sack_ok |= 4; |
865 | } |
866 | |
867 | /* Initialize metrics on socket. */ |
868 | |
869 | static void tcp_init_metrics(struct sock *sk) |
870 | { |
871 | struct tcp_sock *tp = tcp_sk(sk); |
872 | struct dst_entry *dst = __sk_dst_get(sk); |
873 | |
874 | if (dst == NULL) |
875 | goto reset; |
876 | |
877 | dst_confirm(dst); |
878 | |
879 | if (dst_metric_locked(dst, RTAX_CWND)) |
880 | tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); |
881 | if (dst_metric(dst, RTAX_SSTHRESH)) { |
882 | tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); |
883 | if (tp->snd_ssthresh > tp->snd_cwnd_clamp) |
884 | tp->snd_ssthresh = tp->snd_cwnd_clamp; |
885 | } |
886 | if (dst_metric(dst, RTAX_REORDERING) && |
887 | tp->reordering != dst_metric(dst, RTAX_REORDERING)) { |
888 | tcp_disable_fack(tp); |
889 | tp->reordering = dst_metric(dst, RTAX_REORDERING); |
890 | } |
891 | |
892 | if (dst_metric(dst, RTAX_RTT) == 0) |
893 | goto reset; |
894 | |
895 | if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) |
896 | goto reset; |
897 | |
898 | /* Initial rtt is determined from SYN,SYN-ACK. |
899 | * The segment is small and rtt may appear much |
900 | * less than real one. Use per-dst memory |
901 | * to make it more realistic. |
902 | * |
903 | * A bit of theory. RTT is time passed after "normal" sized packet |
904 | * is sent until it is ACKed. In normal circumstances sending small |
905 | * packets force peer to delay ACKs and calculation is correct too. |
906 | * The algorithm is adaptive and, provided we follow specs, it |
907 | * NEVER underestimate RTT. BUT! If peer tries to make some clever |
908 | * tricks sort of "quick acks" for time long enough to decrease RTT |
909 | * to low value, and then abruptly stops to do it and starts to delay |
910 | * ACKs, wait for troubles. |
911 | */ |
912 | if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) { |
913 | tp->srtt = dst_metric_rtt(dst, RTAX_RTT); |
914 | tp->rtt_seq = tp->snd_nxt; |
915 | } |
916 | if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) { |
917 | tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR); |
918 | tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); |
919 | } |
920 | tcp_set_rto(sk); |
921 | if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) |
922 | goto reset; |
923 | |
924 | cwnd: |
925 | tp->snd_cwnd = tcp_init_cwnd(tp, dst); |
926 | tp->snd_cwnd_stamp = tcp_time_stamp; |
927 | return; |
928 | |
929 | reset: |
930 | /* Play conservative. If timestamps are not |
931 | * supported, TCP will fail to recalculate correct |
932 | * rtt, if initial rto is too small. FORGET ALL AND RESET! |
933 | */ |
934 | if (!tp->rx_opt.saw_tstamp && tp->srtt) { |
935 | tp->srtt = 0; |
936 | tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; |
937 | inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; |
938 | } |
939 | goto cwnd; |
940 | } |
941 | |
942 | static void tcp_update_reordering(struct sock *sk, const int metric, |
943 | const int ts) |
944 | { |
945 | struct tcp_sock *tp = tcp_sk(sk); |
946 | if (metric > tp->reordering) { |
947 | int mib_idx; |
948 | |
949 | tp->reordering = min(TCP_MAX_REORDERING, metric); |
950 | |
951 | /* This exciting event is worth to be remembered. 8) */ |
952 | if (ts) |
953 | mib_idx = LINUX_MIB_TCPTSREORDER; |
954 | else if (tcp_is_reno(tp)) |
955 | mib_idx = LINUX_MIB_TCPRENOREORDER; |
956 | else if (tcp_is_fack(tp)) |
957 | mib_idx = LINUX_MIB_TCPFACKREORDER; |
958 | else |
959 | mib_idx = LINUX_MIB_TCPSACKREORDER; |
960 | |
961 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
962 | #if FASTRETRANS_DEBUG > 1 |
963 | printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", |
964 | tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, |
965 | tp->reordering, |
966 | tp->fackets_out, |
967 | tp->sacked_out, |
968 | tp->undo_marker ? tp->undo_retrans : 0); |
969 | #endif |
970 | tcp_disable_fack(tp); |
971 | } |
972 | } |
973 | |
974 | /* This must be called before lost_out is incremented */ |
975 | static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) |
976 | { |
977 | if ((tp->retransmit_skb_hint == NULL) || |
978 | before(TCP_SKB_CB(skb)->seq, |
979 | TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) |
980 | tp->retransmit_skb_hint = skb; |
981 | |
982 | if (!tp->lost_out || |
983 | after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) |
984 | tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; |
985 | } |
986 | |
987 | static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) |
988 | { |
989 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
990 | tcp_verify_retransmit_hint(tp, skb); |
991 | |
992 | tp->lost_out += tcp_skb_pcount(skb); |
993 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
994 | } |
995 | } |
996 | |
997 | static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, |
998 | struct sk_buff *skb) |
999 | { |
1000 | tcp_verify_retransmit_hint(tp, skb); |
1001 | |
1002 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
1003 | tp->lost_out += tcp_skb_pcount(skb); |
1004 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
1005 | } |
1006 | } |
1007 | |
1008 | /* This procedure tags the retransmission queue when SACKs arrive. |
1009 | * |
1010 | * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). |
1011 | * Packets in queue with these bits set are counted in variables |
1012 | * sacked_out, retrans_out and lost_out, correspondingly. |
1013 | * |
1014 | * Valid combinations are: |
1015 | * Tag InFlight Description |
1016 | * 0 1 - orig segment is in flight. |
1017 | * S 0 - nothing flies, orig reached receiver. |
1018 | * L 0 - nothing flies, orig lost by net. |
1019 | * R 2 - both orig and retransmit are in flight. |
1020 | * L|R 1 - orig is lost, retransmit is in flight. |
1021 | * S|R 1 - orig reached receiver, retrans is still in flight. |
1022 | * (L|S|R is logically valid, it could occur when L|R is sacked, |
1023 | * but it is equivalent to plain S and code short-curcuits it to S. |
1024 | * L|S is logically invalid, it would mean -1 packet in flight 8)) |
1025 | * |
1026 | * These 6 states form finite state machine, controlled by the following events: |
1027 | * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) |
1028 | * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) |
1029 | * 3. Loss detection event of one of three flavors: |
1030 | * A. Scoreboard estimator decided the packet is lost. |
1031 | * A'. Reno "three dupacks" marks head of queue lost. |
1032 | * A''. Its FACK modfication, head until snd.fack is lost. |
1033 | * B. SACK arrives sacking data transmitted after never retransmitted |
1034 | * hole was sent out. |
1035 | * C. SACK arrives sacking SND.NXT at the moment, when the |
1036 | * segment was retransmitted. |
1037 | * 4. D-SACK added new rule: D-SACK changes any tag to S. |
1038 | * |
1039 | * It is pleasant to note, that state diagram turns out to be commutative, |
1040 | * so that we are allowed not to be bothered by order of our actions, |
1041 | * when multiple events arrive simultaneously. (see the function below). |
1042 | * |
1043 | * Reordering detection. |
1044 | * -------------------- |
1045 | * Reordering metric is maximal distance, which a packet can be displaced |
1046 | * in packet stream. With SACKs we can estimate it: |
1047 | * |
1048 | * 1. SACK fills old hole and the corresponding segment was not |
1049 | * ever retransmitted -> reordering. Alas, we cannot use it |
1050 | * when segment was retransmitted. |
1051 | * 2. The last flaw is solved with D-SACK. D-SACK arrives |
1052 | * for retransmitted and already SACKed segment -> reordering.. |
1053 | * Both of these heuristics are not used in Loss state, when we cannot |
1054 | * account for retransmits accurately. |
1055 | * |
1056 | * SACK block validation. |
1057 | * ---------------------- |
1058 | * |
1059 | * SACK block range validation checks that the received SACK block fits to |
1060 | * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. |
1061 | * Note that SND.UNA is not included to the range though being valid because |
1062 | * it means that the receiver is rather inconsistent with itself reporting |
1063 | * SACK reneging when it should advance SND.UNA. Such SACK block this is |
1064 | * perfectly valid, however, in light of RFC2018 which explicitly states |
1065 | * that "SACK block MUST reflect the newest segment. Even if the newest |
1066 | * segment is going to be discarded ...", not that it looks very clever |
1067 | * in case of head skb. Due to potentional receiver driven attacks, we |
1068 | * choose to avoid immediate execution of a walk in write queue due to |
1069 | * reneging and defer head skb's loss recovery to standard loss recovery |
1070 | * procedure that will eventually trigger (nothing forbids us doing this). |
1071 | * |
1072 | * Implements also blockage to start_seq wrap-around. Problem lies in the |
1073 | * fact that though start_seq (s) is before end_seq (i.e., not reversed), |
1074 | * there's no guarantee that it will be before snd_nxt (n). The problem |
1075 | * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt |
1076 | * wrap (s_w): |
1077 | * |
1078 | * <- outs wnd -> <- wrapzone -> |
1079 | * u e n u_w e_w s n_w |
1080 | * | | | | | | | |
1081 | * |<------------+------+----- TCP seqno space --------------+---------->| |
1082 | * ...-- <2^31 ->| |<--------... |
1083 | * ...---- >2^31 ------>| |<--------... |
1084 | * |
1085 | * Current code wouldn't be vulnerable but it's better still to discard such |
1086 | * crazy SACK blocks. Doing this check for start_seq alone closes somewhat |
1087 | * similar case (end_seq after snd_nxt wrap) as earlier reversed check in |
1088 | * snd_nxt wrap -> snd_una region will then become "well defined", i.e., |
1089 | * equal to the ideal case (infinite seqno space without wrap caused issues). |
1090 | * |
1091 | * With D-SACK the lower bound is extended to cover sequence space below |
1092 | * SND.UNA down to undo_marker, which is the last point of interest. Yet |
1093 | * again, D-SACK block must not to go across snd_una (for the same reason as |
1094 | * for the normal SACK blocks, explained above). But there all simplicity |
1095 | * ends, TCP might receive valid D-SACKs below that. As long as they reside |
1096 | * fully below undo_marker they do not affect behavior in anyway and can |
1097 | * therefore be safely ignored. In rare cases (which are more or less |
1098 | * theoretical ones), the D-SACK will nicely cross that boundary due to skb |
1099 | * fragmentation and packet reordering past skb's retransmission. To consider |
1100 | * them correctly, the acceptable range must be extended even more though |
1101 | * the exact amount is rather hard to quantify. However, tp->max_window can |
1102 | * be used as an exaggerated estimate. |
1103 | */ |
1104 | static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack, |
1105 | u32 start_seq, u32 end_seq) |
1106 | { |
1107 | /* Too far in future, or reversed (interpretation is ambiguous) */ |
1108 | if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) |
1109 | return 0; |
1110 | |
1111 | /* Nasty start_seq wrap-around check (see comments above) */ |
1112 | if (!before(start_seq, tp->snd_nxt)) |
1113 | return 0; |
1114 | |
1115 | /* In outstanding window? ...This is valid exit for D-SACKs too. |
1116 | * start_seq == snd_una is non-sensical (see comments above) |
1117 | */ |
1118 | if (after(start_seq, tp->snd_una)) |
1119 | return 1; |
1120 | |
1121 | if (!is_dsack || !tp->undo_marker) |
1122 | return 0; |
1123 | |
1124 | /* ...Then it's D-SACK, and must reside below snd_una completely */ |
1125 | if (!after(end_seq, tp->snd_una)) |
1126 | return 0; |
1127 | |
1128 | if (!before(start_seq, tp->undo_marker)) |
1129 | return 1; |
1130 | |
1131 | /* Too old */ |
1132 | if (!after(end_seq, tp->undo_marker)) |
1133 | return 0; |
1134 | |
1135 | /* Undo_marker boundary crossing (overestimates a lot). Known already: |
1136 | * start_seq < undo_marker and end_seq >= undo_marker. |
1137 | */ |
1138 | return !before(start_seq, end_seq - tp->max_window); |
1139 | } |
1140 | |
1141 | /* Check for lost retransmit. This superb idea is borrowed from "ratehalving". |
1142 | * Event "C". Later note: FACK people cheated me again 8), we have to account |
1143 | * for reordering! Ugly, but should help. |
1144 | * |
1145 | * Search retransmitted skbs from write_queue that were sent when snd_nxt was |
1146 | * less than what is now known to be received by the other end (derived from |
1147 | * highest SACK block). Also calculate the lowest snd_nxt among the remaining |
1148 | * retransmitted skbs to avoid some costly processing per ACKs. |
1149 | */ |
1150 | static void tcp_mark_lost_retrans(struct sock *sk) |
1151 | { |
1152 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1153 | struct tcp_sock *tp = tcp_sk(sk); |
1154 | struct sk_buff *skb; |
1155 | int cnt = 0; |
1156 | u32 new_low_seq = tp->snd_nxt; |
1157 | u32 received_upto = tcp_highest_sack_seq(tp); |
1158 | |
1159 | if (!tcp_is_fack(tp) || !tp->retrans_out || |
1160 | !after(received_upto, tp->lost_retrans_low) || |
1161 | icsk->icsk_ca_state != TCP_CA_Recovery) |
1162 | return; |
1163 | |
1164 | tcp_for_write_queue(skb, sk) { |
1165 | u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; |
1166 | |
1167 | if (skb == tcp_send_head(sk)) |
1168 | break; |
1169 | if (cnt == tp->retrans_out) |
1170 | break; |
1171 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
1172 | continue; |
1173 | |
1174 | if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) |
1175 | continue; |
1176 | |
1177 | /* TODO: We would like to get rid of tcp_is_fack(tp) only |
1178 | * constraint here (see above) but figuring out that at |
1179 | * least tp->reordering SACK blocks reside between ack_seq |
1180 | * and received_upto is not easy task to do cheaply with |
1181 | * the available datastructures. |
1182 | * |
1183 | * Whether FACK should check here for tp->reordering segs |
1184 | * in-between one could argue for either way (it would be |
1185 | * rather simple to implement as we could count fack_count |
1186 | * during the walk and do tp->fackets_out - fack_count). |
1187 | */ |
1188 | if (after(received_upto, ack_seq)) { |
1189 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
1190 | tp->retrans_out -= tcp_skb_pcount(skb); |
1191 | |
1192 | tcp_skb_mark_lost_uncond_verify(tp, skb); |
1193 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); |
1194 | } else { |
1195 | if (before(ack_seq, new_low_seq)) |
1196 | new_low_seq = ack_seq; |
1197 | cnt += tcp_skb_pcount(skb); |
1198 | } |
1199 | } |
1200 | |
1201 | if (tp->retrans_out) |
1202 | tp->lost_retrans_low = new_low_seq; |
1203 | } |
1204 | |
1205 | static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb, |
1206 | struct tcp_sack_block_wire *sp, int num_sacks, |
1207 | u32 prior_snd_una) |
1208 | { |
1209 | struct tcp_sock *tp = tcp_sk(sk); |
1210 | u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); |
1211 | u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); |
1212 | int dup_sack = 0; |
1213 | |
1214 | if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { |
1215 | dup_sack = 1; |
1216 | tcp_dsack_seen(tp); |
1217 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); |
1218 | } else if (num_sacks > 1) { |
1219 | u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); |
1220 | u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); |
1221 | |
1222 | if (!after(end_seq_0, end_seq_1) && |
1223 | !before(start_seq_0, start_seq_1)) { |
1224 | dup_sack = 1; |
1225 | tcp_dsack_seen(tp); |
1226 | NET_INC_STATS_BH(sock_net(sk), |
1227 | LINUX_MIB_TCPDSACKOFORECV); |
1228 | } |
1229 | } |
1230 | |
1231 | /* D-SACK for already forgotten data... Do dumb counting. */ |
1232 | if (dup_sack && |
1233 | !after(end_seq_0, prior_snd_una) && |
1234 | after(end_seq_0, tp->undo_marker)) |
1235 | tp->undo_retrans--; |
1236 | |
1237 | return dup_sack; |
1238 | } |
1239 | |
1240 | struct tcp_sacktag_state { |
1241 | int reord; |
1242 | int fack_count; |
1243 | int flag; |
1244 | }; |
1245 | |
1246 | /* Check if skb is fully within the SACK block. In presence of GSO skbs, |
1247 | * the incoming SACK may not exactly match but we can find smaller MSS |
1248 | * aligned portion of it that matches. Therefore we might need to fragment |
1249 | * which may fail and creates some hassle (caller must handle error case |
1250 | * returns). |
1251 | * |
1252 | * FIXME: this could be merged to shift decision code |
1253 | */ |
1254 | static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, |
1255 | u32 start_seq, u32 end_seq) |
1256 | { |
1257 | int in_sack, err; |
1258 | unsigned int pkt_len; |
1259 | unsigned int mss; |
1260 | |
1261 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
1262 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); |
1263 | |
1264 | if (tcp_skb_pcount(skb) > 1 && !in_sack && |
1265 | after(TCP_SKB_CB(skb)->end_seq, start_seq)) { |
1266 | mss = tcp_skb_mss(skb); |
1267 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
1268 | |
1269 | if (!in_sack) { |
1270 | pkt_len = start_seq - TCP_SKB_CB(skb)->seq; |
1271 | if (pkt_len < mss) |
1272 | pkt_len = mss; |
1273 | } else { |
1274 | pkt_len = end_seq - TCP_SKB_CB(skb)->seq; |
1275 | if (pkt_len < mss) |
1276 | return -EINVAL; |
1277 | } |
1278 | |
1279 | /* Round if necessary so that SACKs cover only full MSSes |
1280 | * and/or the remaining small portion (if present) |
1281 | */ |
1282 | if (pkt_len > mss) { |
1283 | unsigned int new_len = (pkt_len / mss) * mss; |
1284 | if (!in_sack && new_len < pkt_len) { |
1285 | new_len += mss; |
1286 | if (new_len > skb->len) |
1287 | return 0; |
1288 | } |
1289 | pkt_len = new_len; |
1290 | } |
1291 | err = tcp_fragment(sk, skb, pkt_len, mss); |
1292 | if (err < 0) |
1293 | return err; |
1294 | } |
1295 | |
1296 | return in_sack; |
1297 | } |
1298 | |
1299 | static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, |
1300 | struct tcp_sacktag_state *state, |
1301 | int dup_sack, int pcount) |
1302 | { |
1303 | struct tcp_sock *tp = tcp_sk(sk); |
1304 | u8 sacked = TCP_SKB_CB(skb)->sacked; |
1305 | int fack_count = state->fack_count; |
1306 | |
1307 | /* Account D-SACK for retransmitted packet. */ |
1308 | if (dup_sack && (sacked & TCPCB_RETRANS)) { |
1309 | if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) |
1310 | tp->undo_retrans--; |
1311 | if (sacked & TCPCB_SACKED_ACKED) |
1312 | state->reord = min(fack_count, state->reord); |
1313 | } |
1314 | |
1315 | /* Nothing to do; acked frame is about to be dropped (was ACKed). */ |
1316 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
1317 | return sacked; |
1318 | |
1319 | if (!(sacked & TCPCB_SACKED_ACKED)) { |
1320 | if (sacked & TCPCB_SACKED_RETRANS) { |
1321 | /* If the segment is not tagged as lost, |
1322 | * we do not clear RETRANS, believing |
1323 | * that retransmission is still in flight. |
1324 | */ |
1325 | if (sacked & TCPCB_LOST) { |
1326 | sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); |
1327 | tp->lost_out -= pcount; |
1328 | tp->retrans_out -= pcount; |
1329 | } |
1330 | } else { |
1331 | if (!(sacked & TCPCB_RETRANS)) { |
1332 | /* New sack for not retransmitted frame, |
1333 | * which was in hole. It is reordering. |
1334 | */ |
1335 | if (before(TCP_SKB_CB(skb)->seq, |
1336 | tcp_highest_sack_seq(tp))) |
1337 | state->reord = min(fack_count, |
1338 | state->reord); |
1339 | |
1340 | /* SACK enhanced F-RTO (RFC4138; Appendix B) */ |
1341 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) |
1342 | state->flag |= FLAG_ONLY_ORIG_SACKED; |
1343 | } |
1344 | |
1345 | if (sacked & TCPCB_LOST) { |
1346 | sacked &= ~TCPCB_LOST; |
1347 | tp->lost_out -= pcount; |
1348 | } |
1349 | } |
1350 | |
1351 | sacked |= TCPCB_SACKED_ACKED; |
1352 | state->flag |= FLAG_DATA_SACKED; |
1353 | tp->sacked_out += pcount; |
1354 | |
1355 | fack_count += pcount; |
1356 | |
1357 | /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ |
1358 | if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && |
1359 | before(TCP_SKB_CB(skb)->seq, |
1360 | TCP_SKB_CB(tp->lost_skb_hint)->seq)) |
1361 | tp->lost_cnt_hint += pcount; |
1362 | |
1363 | if (fack_count > tp->fackets_out) |
1364 | tp->fackets_out = fack_count; |
1365 | } |
1366 | |
1367 | /* D-SACK. We can detect redundant retransmission in S|R and plain R |
1368 | * frames and clear it. undo_retrans is decreased above, L|R frames |
1369 | * are accounted above as well. |
1370 | */ |
1371 | if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { |
1372 | sacked &= ~TCPCB_SACKED_RETRANS; |
1373 | tp->retrans_out -= pcount; |
1374 | } |
1375 | |
1376 | return sacked; |
1377 | } |
1378 | |
1379 | static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, |
1380 | struct tcp_sacktag_state *state, |
1381 | unsigned int pcount, int shifted, int mss, |
1382 | int dup_sack) |
1383 | { |
1384 | struct tcp_sock *tp = tcp_sk(sk); |
1385 | struct sk_buff *prev = tcp_write_queue_prev(sk, skb); |
1386 | |
1387 | BUG_ON(!pcount); |
1388 | |
1389 | /* Tweak before seqno plays */ |
1390 | if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint && |
1391 | !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq)) |
1392 | tp->lost_cnt_hint += pcount; |
1393 | |
1394 | TCP_SKB_CB(prev)->end_seq += shifted; |
1395 | TCP_SKB_CB(skb)->seq += shifted; |
1396 | |
1397 | skb_shinfo(prev)->gso_segs += pcount; |
1398 | BUG_ON(skb_shinfo(skb)->gso_segs < pcount); |
1399 | skb_shinfo(skb)->gso_segs -= pcount; |
1400 | |
1401 | /* When we're adding to gso_segs == 1, gso_size will be zero, |
1402 | * in theory this shouldn't be necessary but as long as DSACK |
1403 | * code can come after this skb later on it's better to keep |
1404 | * setting gso_size to something. |
1405 | */ |
1406 | if (!skb_shinfo(prev)->gso_size) { |
1407 | skb_shinfo(prev)->gso_size = mss; |
1408 | skb_shinfo(prev)->gso_type = sk->sk_gso_type; |
1409 | } |
1410 | |
1411 | /* CHECKME: To clear or not to clear? Mimics normal skb currently */ |
1412 | if (skb_shinfo(skb)->gso_segs <= 1) { |
1413 | skb_shinfo(skb)->gso_size = 0; |
1414 | skb_shinfo(skb)->gso_type = 0; |
1415 | } |
1416 | |
1417 | /* We discard results */ |
1418 | tcp_sacktag_one(skb, sk, state, dup_sack, pcount); |
1419 | |
1420 | /* Difference in this won't matter, both ACKed by the same cumul. ACK */ |
1421 | TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); |
1422 | |
1423 | if (skb->len > 0) { |
1424 | BUG_ON(!tcp_skb_pcount(skb)); |
1425 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); |
1426 | return 0; |
1427 | } |
1428 | |
1429 | /* Whole SKB was eaten :-) */ |
1430 | |
1431 | if (skb == tp->retransmit_skb_hint) |
1432 | tp->retransmit_skb_hint = prev; |
1433 | if (skb == tp->scoreboard_skb_hint) |
1434 | tp->scoreboard_skb_hint = prev; |
1435 | if (skb == tp->lost_skb_hint) { |
1436 | tp->lost_skb_hint = prev; |
1437 | tp->lost_cnt_hint -= tcp_skb_pcount(prev); |
1438 | } |
1439 | |
1440 | TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags; |
1441 | if (skb == tcp_highest_sack(sk)) |
1442 | tcp_advance_highest_sack(sk, skb); |
1443 | |
1444 | tcp_unlink_write_queue(skb, sk); |
1445 | sk_wmem_free_skb(sk, skb); |
1446 | |
1447 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); |
1448 | |
1449 | return 1; |
1450 | } |
1451 | |
1452 | /* I wish gso_size would have a bit more sane initialization than |
1453 | * something-or-zero which complicates things |
1454 | */ |
1455 | static int tcp_skb_seglen(struct sk_buff *skb) |
1456 | { |
1457 | return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); |
1458 | } |
1459 | |
1460 | /* Shifting pages past head area doesn't work */ |
1461 | static int skb_can_shift(struct sk_buff *skb) |
1462 | { |
1463 | return !skb_headlen(skb) && skb_is_nonlinear(skb); |
1464 | } |
1465 | |
1466 | /* Try collapsing SACK blocks spanning across multiple skbs to a single |
1467 | * skb. |
1468 | */ |
1469 | static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, |
1470 | struct tcp_sacktag_state *state, |
1471 | u32 start_seq, u32 end_seq, |
1472 | int dup_sack) |
1473 | { |
1474 | struct tcp_sock *tp = tcp_sk(sk); |
1475 | struct sk_buff *prev; |
1476 | int mss; |
1477 | int pcount = 0; |
1478 | int len; |
1479 | int in_sack; |
1480 | |
1481 | if (!sk_can_gso(sk)) |
1482 | goto fallback; |
1483 | |
1484 | /* Normally R but no L won't result in plain S */ |
1485 | if (!dup_sack && |
1486 | (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) |
1487 | goto fallback; |
1488 | if (!skb_can_shift(skb)) |
1489 | goto fallback; |
1490 | /* This frame is about to be dropped (was ACKed). */ |
1491 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
1492 | goto fallback; |
1493 | |
1494 | /* Can only happen with delayed DSACK + discard craziness */ |
1495 | if (unlikely(skb == tcp_write_queue_head(sk))) |
1496 | goto fallback; |
1497 | prev = tcp_write_queue_prev(sk, skb); |
1498 | |
1499 | if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) |
1500 | goto fallback; |
1501 | |
1502 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
1503 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); |
1504 | |
1505 | if (in_sack) { |
1506 | len = skb->len; |
1507 | pcount = tcp_skb_pcount(skb); |
1508 | mss = tcp_skb_seglen(skb); |
1509 | |
1510 | /* TODO: Fix DSACKs to not fragment already SACKed and we can |
1511 | * drop this restriction as unnecessary |
1512 | */ |
1513 | if (mss != tcp_skb_seglen(prev)) |
1514 | goto fallback; |
1515 | } else { |
1516 | if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) |
1517 | goto noop; |
1518 | /* CHECKME: This is non-MSS split case only?, this will |
1519 | * cause skipped skbs due to advancing loop btw, original |
1520 | * has that feature too |
1521 | */ |
1522 | if (tcp_skb_pcount(skb) <= 1) |
1523 | goto noop; |
1524 | |
1525 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
1526 | if (!in_sack) { |
1527 | /* TODO: head merge to next could be attempted here |
1528 | * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), |
1529 | * though it might not be worth of the additional hassle |
1530 | * |
1531 | * ...we can probably just fallback to what was done |
1532 | * previously. We could try merging non-SACKed ones |
1533 | * as well but it probably isn't going to buy off |
1534 | * because later SACKs might again split them, and |
1535 | * it would make skb timestamp tracking considerably |
1536 | * harder problem. |
1537 | */ |
1538 | goto fallback; |
1539 | } |
1540 | |
1541 | len = end_seq - TCP_SKB_CB(skb)->seq; |
1542 | BUG_ON(len < 0); |
1543 | BUG_ON(len > skb->len); |
1544 | |
1545 | /* MSS boundaries should be honoured or else pcount will |
1546 | * severely break even though it makes things bit trickier. |
1547 | * Optimize common case to avoid most of the divides |
1548 | */ |
1549 | mss = tcp_skb_mss(skb); |
1550 | |
1551 | /* TODO: Fix DSACKs to not fragment already SACKed and we can |
1552 | * drop this restriction as unnecessary |
1553 | */ |
1554 | if (mss != tcp_skb_seglen(prev)) |
1555 | goto fallback; |
1556 | |
1557 | if (len == mss) { |
1558 | pcount = 1; |
1559 | } else if (len < mss) { |
1560 | goto noop; |
1561 | } else { |
1562 | pcount = len / mss; |
1563 | len = pcount * mss; |
1564 | } |
1565 | } |
1566 | |
1567 | if (!skb_shift(prev, skb, len)) |
1568 | goto fallback; |
1569 | if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) |
1570 | goto out; |
1571 | |
1572 | /* Hole filled allows collapsing with the next as well, this is very |
1573 | * useful when hole on every nth skb pattern happens |
1574 | */ |
1575 | if (prev == tcp_write_queue_tail(sk)) |
1576 | goto out; |
1577 | skb = tcp_write_queue_next(sk, prev); |
1578 | |
1579 | if (!skb_can_shift(skb) || |
1580 | (skb == tcp_send_head(sk)) || |
1581 | ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || |
1582 | (mss != tcp_skb_seglen(skb))) |
1583 | goto out; |
1584 | |
1585 | len = skb->len; |
1586 | if (skb_shift(prev, skb, len)) { |
1587 | pcount += tcp_skb_pcount(skb); |
1588 | tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); |
1589 | } |
1590 | |
1591 | out: |
1592 | state->fack_count += pcount; |
1593 | return prev; |
1594 | |
1595 | noop: |
1596 | return skb; |
1597 | |
1598 | fallback: |
1599 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); |
1600 | return NULL; |
1601 | } |
1602 | |
1603 | static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, |
1604 | struct tcp_sack_block *next_dup, |
1605 | struct tcp_sacktag_state *state, |
1606 | u32 start_seq, u32 end_seq, |
1607 | int dup_sack_in) |
1608 | { |
1609 | struct tcp_sock *tp = tcp_sk(sk); |
1610 | struct sk_buff *tmp; |
1611 | |
1612 | tcp_for_write_queue_from(skb, sk) { |
1613 | int in_sack = 0; |
1614 | int dup_sack = dup_sack_in; |
1615 | |
1616 | if (skb == tcp_send_head(sk)) |
1617 | break; |
1618 | |
1619 | /* queue is in-order => we can short-circuit the walk early */ |
1620 | if (!before(TCP_SKB_CB(skb)->seq, end_seq)) |
1621 | break; |
1622 | |
1623 | if ((next_dup != NULL) && |
1624 | before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { |
1625 | in_sack = tcp_match_skb_to_sack(sk, skb, |
1626 | next_dup->start_seq, |
1627 | next_dup->end_seq); |
1628 | if (in_sack > 0) |
1629 | dup_sack = 1; |
1630 | } |
1631 | |
1632 | /* skb reference here is a bit tricky to get right, since |
1633 | * shifting can eat and free both this skb and the next, |
1634 | * so not even _safe variant of the loop is enough. |
1635 | */ |
1636 | if (in_sack <= 0) { |
1637 | tmp = tcp_shift_skb_data(sk, skb, state, |
1638 | start_seq, end_seq, dup_sack); |
1639 | if (tmp != NULL) { |
1640 | if (tmp != skb) { |
1641 | skb = tmp; |
1642 | continue; |
1643 | } |
1644 | |
1645 | in_sack = 0; |
1646 | } else { |
1647 | in_sack = tcp_match_skb_to_sack(sk, skb, |
1648 | start_seq, |
1649 | end_seq); |
1650 | } |
1651 | } |
1652 | |
1653 | if (unlikely(in_sack < 0)) |
1654 | break; |
1655 | |
1656 | if (in_sack) { |
1657 | TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk, |
1658 | state, |
1659 | dup_sack, |
1660 | tcp_skb_pcount(skb)); |
1661 | |
1662 | if (!before(TCP_SKB_CB(skb)->seq, |
1663 | tcp_highest_sack_seq(tp))) |
1664 | tcp_advance_highest_sack(sk, skb); |
1665 | } |
1666 | |
1667 | state->fack_count += tcp_skb_pcount(skb); |
1668 | } |
1669 | return skb; |
1670 | } |
1671 | |
1672 | /* Avoid all extra work that is being done by sacktag while walking in |
1673 | * a normal way |
1674 | */ |
1675 | static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, |
1676 | struct tcp_sacktag_state *state, |
1677 | u32 skip_to_seq) |
1678 | { |
1679 | tcp_for_write_queue_from(skb, sk) { |
1680 | if (skb == tcp_send_head(sk)) |
1681 | break; |
1682 | |
1683 | if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) |
1684 | break; |
1685 | |
1686 | state->fack_count += tcp_skb_pcount(skb); |
1687 | } |
1688 | return skb; |
1689 | } |
1690 | |
1691 | static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, |
1692 | struct sock *sk, |
1693 | struct tcp_sack_block *next_dup, |
1694 | struct tcp_sacktag_state *state, |
1695 | u32 skip_to_seq) |
1696 | { |
1697 | if (next_dup == NULL) |
1698 | return skb; |
1699 | |
1700 | if (before(next_dup->start_seq, skip_to_seq)) { |
1701 | skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); |
1702 | skb = tcp_sacktag_walk(skb, sk, NULL, state, |
1703 | next_dup->start_seq, next_dup->end_seq, |
1704 | 1); |
1705 | } |
1706 | |
1707 | return skb; |
1708 | } |
1709 | |
1710 | static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache) |
1711 | { |
1712 | return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
1713 | } |
1714 | |
1715 | static int |
1716 | tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, |
1717 | u32 prior_snd_una) |
1718 | { |
1719 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1720 | struct tcp_sock *tp = tcp_sk(sk); |
1721 | unsigned char *ptr = (skb_transport_header(ack_skb) + |
1722 | TCP_SKB_CB(ack_skb)->sacked); |
1723 | struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); |
1724 | struct tcp_sack_block sp[TCP_NUM_SACKS]; |
1725 | struct tcp_sack_block *cache; |
1726 | struct tcp_sacktag_state state; |
1727 | struct sk_buff *skb; |
1728 | int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); |
1729 | int used_sacks; |
1730 | int found_dup_sack = 0; |
1731 | int i, j; |
1732 | int first_sack_index; |
1733 | |
1734 | state.flag = 0; |
1735 | state.reord = tp->packets_out; |
1736 | |
1737 | if (!tp->sacked_out) { |
1738 | if (WARN_ON(tp->fackets_out)) |
1739 | tp->fackets_out = 0; |
1740 | tcp_highest_sack_reset(sk); |
1741 | } |
1742 | |
1743 | found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, |
1744 | num_sacks, prior_snd_una); |
1745 | if (found_dup_sack) |
1746 | state.flag |= FLAG_DSACKING_ACK; |
1747 | |
1748 | /* Eliminate too old ACKs, but take into |
1749 | * account more or less fresh ones, they can |
1750 | * contain valid SACK info. |
1751 | */ |
1752 | if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) |
1753 | return 0; |
1754 | |
1755 | if (!tp->packets_out) |
1756 | goto out; |
1757 | |
1758 | used_sacks = 0; |
1759 | first_sack_index = 0; |
1760 | for (i = 0; i < num_sacks; i++) { |
1761 | int dup_sack = !i && found_dup_sack; |
1762 | |
1763 | sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); |
1764 | sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); |
1765 | |
1766 | if (!tcp_is_sackblock_valid(tp, dup_sack, |
1767 | sp[used_sacks].start_seq, |
1768 | sp[used_sacks].end_seq)) { |
1769 | int mib_idx; |
1770 | |
1771 | if (dup_sack) { |
1772 | if (!tp->undo_marker) |
1773 | mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; |
1774 | else |
1775 | mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; |
1776 | } else { |
1777 | /* Don't count olds caused by ACK reordering */ |
1778 | if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && |
1779 | !after(sp[used_sacks].end_seq, tp->snd_una)) |
1780 | continue; |
1781 | mib_idx = LINUX_MIB_TCPSACKDISCARD; |
1782 | } |
1783 | |
1784 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
1785 | if (i == 0) |
1786 | first_sack_index = -1; |
1787 | continue; |
1788 | } |
1789 | |
1790 | /* Ignore very old stuff early */ |
1791 | if (!after(sp[used_sacks].end_seq, prior_snd_una)) |
1792 | continue; |
1793 | |
1794 | used_sacks++; |
1795 | } |
1796 | |
1797 | /* order SACK blocks to allow in order walk of the retrans queue */ |
1798 | for (i = used_sacks - 1; i > 0; i--) { |
1799 | for (j = 0; j < i; j++) { |
1800 | if (after(sp[j].start_seq, sp[j + 1].start_seq)) { |
1801 | swap(sp[j], sp[j + 1]); |
1802 | |
1803 | /* Track where the first SACK block goes to */ |
1804 | if (j == first_sack_index) |
1805 | first_sack_index = j + 1; |
1806 | } |
1807 | } |
1808 | } |
1809 | |
1810 | skb = tcp_write_queue_head(sk); |
1811 | state.fack_count = 0; |
1812 | i = 0; |
1813 | |
1814 | if (!tp->sacked_out) { |
1815 | /* It's already past, so skip checking against it */ |
1816 | cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
1817 | } else { |
1818 | cache = tp->recv_sack_cache; |
1819 | /* Skip empty blocks in at head of the cache */ |
1820 | while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && |
1821 | !cache->end_seq) |
1822 | cache++; |
1823 | } |
1824 | |
1825 | while (i < used_sacks) { |
1826 | u32 start_seq = sp[i].start_seq; |
1827 | u32 end_seq = sp[i].end_seq; |
1828 | int dup_sack = (found_dup_sack && (i == first_sack_index)); |
1829 | struct tcp_sack_block *next_dup = NULL; |
1830 | |
1831 | if (found_dup_sack && ((i + 1) == first_sack_index)) |
1832 | next_dup = &sp[i + 1]; |
1833 | |
1834 | /* Event "B" in the comment above. */ |
1835 | if (after(end_seq, tp->high_seq)) |
1836 | state.flag |= FLAG_DATA_LOST; |
1837 | |
1838 | /* Skip too early cached blocks */ |
1839 | while (tcp_sack_cache_ok(tp, cache) && |
1840 | !before(start_seq, cache->end_seq)) |
1841 | cache++; |
1842 | |
1843 | /* Can skip some work by looking recv_sack_cache? */ |
1844 | if (tcp_sack_cache_ok(tp, cache) && !dup_sack && |
1845 | after(end_seq, cache->start_seq)) { |
1846 | |
1847 | /* Head todo? */ |
1848 | if (before(start_seq, cache->start_seq)) { |
1849 | skb = tcp_sacktag_skip(skb, sk, &state, |
1850 | start_seq); |
1851 | skb = tcp_sacktag_walk(skb, sk, next_dup, |
1852 | &state, |
1853 | start_seq, |
1854 | cache->start_seq, |
1855 | dup_sack); |
1856 | } |
1857 | |
1858 | /* Rest of the block already fully processed? */ |
1859 | if (!after(end_seq, cache->end_seq)) |
1860 | goto advance_sp; |
1861 | |
1862 | skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, |
1863 | &state, |
1864 | cache->end_seq); |
1865 | |
1866 | /* ...tail remains todo... */ |
1867 | if (tcp_highest_sack_seq(tp) == cache->end_seq) { |
1868 | /* ...but better entrypoint exists! */ |
1869 | skb = tcp_highest_sack(sk); |
1870 | if (skb == NULL) |
1871 | break; |
1872 | state.fack_count = tp->fackets_out; |
1873 | cache++; |
1874 | goto walk; |
1875 | } |
1876 | |
1877 | skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq); |
1878 | /* Check overlap against next cached too (past this one already) */ |
1879 | cache++; |
1880 | continue; |
1881 | } |
1882 | |
1883 | if (!before(start_seq, tcp_highest_sack_seq(tp))) { |
1884 | skb = tcp_highest_sack(sk); |
1885 | if (skb == NULL) |
1886 | break; |
1887 | state.fack_count = tp->fackets_out; |
1888 | } |
1889 | skb = tcp_sacktag_skip(skb, sk, &state, start_seq); |
1890 | |
1891 | walk: |
1892 | skb = tcp_sacktag_walk(skb, sk, next_dup, &state, |
1893 | start_seq, end_seq, dup_sack); |
1894 | |
1895 | advance_sp: |
1896 | /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct |
1897 | * due to in-order walk |
1898 | */ |
1899 | if (after(end_seq, tp->frto_highmark)) |
1900 | state.flag &= ~FLAG_ONLY_ORIG_SACKED; |
1901 | |
1902 | i++; |
1903 | } |
1904 | |
1905 | /* Clear the head of the cache sack blocks so we can skip it next time */ |
1906 | for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { |
1907 | tp->recv_sack_cache[i].start_seq = 0; |
1908 | tp->recv_sack_cache[i].end_seq = 0; |
1909 | } |
1910 | for (j = 0; j < used_sacks; j++) |
1911 | tp->recv_sack_cache[i++] = sp[j]; |
1912 | |
1913 | tcp_mark_lost_retrans(sk); |
1914 | |
1915 | tcp_verify_left_out(tp); |
1916 | |
1917 | if ((state.reord < tp->fackets_out) && |
1918 | ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) && |
1919 | (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) |
1920 | tcp_update_reordering(sk, tp->fackets_out - state.reord, 0); |
1921 | |
1922 | out: |
1923 | |
1924 | #if FASTRETRANS_DEBUG > 0 |
1925 | WARN_ON((int)tp->sacked_out < 0); |
1926 | WARN_ON((int)tp->lost_out < 0); |
1927 | WARN_ON((int)tp->retrans_out < 0); |
1928 | WARN_ON((int)tcp_packets_in_flight(tp) < 0); |
1929 | #endif |
1930 | return state.flag; |
1931 | } |
1932 | |
1933 | /* Limits sacked_out so that sum with lost_out isn't ever larger than |
1934 | * packets_out. Returns zero if sacked_out adjustement wasn't necessary. |
1935 | */ |
1936 | static int tcp_limit_reno_sacked(struct tcp_sock *tp) |
1937 | { |
1938 | u32 holes; |
1939 | |
1940 | holes = max(tp->lost_out, 1U); |
1941 | holes = min(holes, tp->packets_out); |
1942 | |
1943 | if ((tp->sacked_out + holes) > tp->packets_out) { |
1944 | tp->sacked_out = tp->packets_out - holes; |
1945 | return 1; |
1946 | } |
1947 | return 0; |
1948 | } |
1949 | |
1950 | /* If we receive more dupacks than we expected counting segments |
1951 | * in assumption of absent reordering, interpret this as reordering. |
1952 | * The only another reason could be bug in receiver TCP. |
1953 | */ |
1954 | static void tcp_check_reno_reordering(struct sock *sk, const int addend) |
1955 | { |
1956 | struct tcp_sock *tp = tcp_sk(sk); |
1957 | if (tcp_limit_reno_sacked(tp)) |
1958 | tcp_update_reordering(sk, tp->packets_out + addend, 0); |
1959 | } |
1960 | |
1961 | /* Emulate SACKs for SACKless connection: account for a new dupack. */ |
1962 | |
1963 | static void tcp_add_reno_sack(struct sock *sk) |
1964 | { |
1965 | struct tcp_sock *tp = tcp_sk(sk); |
1966 | tp->sacked_out++; |
1967 | tcp_check_reno_reordering(sk, 0); |
1968 | tcp_verify_left_out(tp); |
1969 | } |
1970 | |
1971 | /* Account for ACK, ACKing some data in Reno Recovery phase. */ |
1972 | |
1973 | static void tcp_remove_reno_sacks(struct sock *sk, int acked) |
1974 | { |
1975 | struct tcp_sock *tp = tcp_sk(sk); |
1976 | |
1977 | if (acked > 0) { |
1978 | /* One ACK acked hole. The rest eat duplicate ACKs. */ |
1979 | if (acked - 1 >= tp->sacked_out) |
1980 | tp->sacked_out = 0; |
1981 | else |
1982 | tp->sacked_out -= acked - 1; |
1983 | } |
1984 | tcp_check_reno_reordering(sk, acked); |
1985 | tcp_verify_left_out(tp); |
1986 | } |
1987 | |
1988 | static inline void tcp_reset_reno_sack(struct tcp_sock *tp) |
1989 | { |
1990 | tp->sacked_out = 0; |
1991 | } |
1992 | |
1993 | static int tcp_is_sackfrto(const struct tcp_sock *tp) |
1994 | { |
1995 | return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp); |
1996 | } |
1997 | |
1998 | /* F-RTO can only be used if TCP has never retransmitted anything other than |
1999 | * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here) |
2000 | */ |
2001 | int tcp_use_frto(struct sock *sk) |
2002 | { |
2003 | const struct tcp_sock *tp = tcp_sk(sk); |
2004 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2005 | struct sk_buff *skb; |
2006 | |
2007 | if (!sysctl_tcp_frto) |
2008 | return 0; |
2009 | |
2010 | /* MTU probe and F-RTO won't really play nicely along currently */ |
2011 | if (icsk->icsk_mtup.probe_size) |
2012 | return 0; |
2013 | |
2014 | if (tcp_is_sackfrto(tp)) |
2015 | return 1; |
2016 | |
2017 | /* Avoid expensive walking of rexmit queue if possible */ |
2018 | if (tp->retrans_out > 1) |
2019 | return 0; |
2020 | |
2021 | skb = tcp_write_queue_head(sk); |
2022 | if (tcp_skb_is_last(sk, skb)) |
2023 | return 1; |
2024 | skb = tcp_write_queue_next(sk, skb); /* Skips head */ |
2025 | tcp_for_write_queue_from(skb, sk) { |
2026 | if (skb == tcp_send_head(sk)) |
2027 | break; |
2028 | if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) |
2029 | return 0; |
2030 | /* Short-circuit when first non-SACKed skb has been checked */ |
2031 | if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) |
2032 | break; |
2033 | } |
2034 | return 1; |
2035 | } |
2036 | |
2037 | /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO |
2038 | * recovery a bit and use heuristics in tcp_process_frto() to detect if |
2039 | * the RTO was spurious. Only clear SACKED_RETRANS of the head here to |
2040 | * keep retrans_out counting accurate (with SACK F-RTO, other than head |
2041 | * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS |
2042 | * bits are handled if the Loss state is really to be entered (in |
2043 | * tcp_enter_frto_loss). |
2044 | * |
2045 | * Do like tcp_enter_loss() would; when RTO expires the second time it |
2046 | * does: |
2047 | * "Reduce ssthresh if it has not yet been made inside this window." |
2048 | */ |
2049 | void tcp_enter_frto(struct sock *sk) |
2050 | { |
2051 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2052 | struct tcp_sock *tp = tcp_sk(sk); |
2053 | struct sk_buff *skb; |
2054 | |
2055 | if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || |
2056 | tp->snd_una == tp->high_seq || |
2057 | ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && |
2058 | !icsk->icsk_retransmits)) { |
2059 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
2060 | /* Our state is too optimistic in ssthresh() call because cwnd |
2061 | * is not reduced until tcp_enter_frto_loss() when previous F-RTO |
2062 | * recovery has not yet completed. Pattern would be this: RTO, |
2063 | * Cumulative ACK, RTO (2xRTO for the same segment does not end |
2064 | * up here twice). |
2065 | * RFC4138 should be more specific on what to do, even though |
2066 | * RTO is quite unlikely to occur after the first Cumulative ACK |
2067 | * due to back-off and complexity of triggering events ... |
2068 | */ |
2069 | if (tp->frto_counter) { |
2070 | u32 stored_cwnd; |
2071 | stored_cwnd = tp->snd_cwnd; |
2072 | tp->snd_cwnd = 2; |
2073 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
2074 | tp->snd_cwnd = stored_cwnd; |
2075 | } else { |
2076 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
2077 | } |
2078 | /* ... in theory, cong.control module could do "any tricks" in |
2079 | * ssthresh(), which means that ca_state, lost bits and lost_out |
2080 | * counter would have to be faked before the call occurs. We |
2081 | * consider that too expensive, unlikely and hacky, so modules |
2082 | * using these in ssthresh() must deal these incompatibility |
2083 | * issues if they receives CA_EVENT_FRTO and frto_counter != 0 |
2084 | */ |
2085 | tcp_ca_event(sk, CA_EVENT_FRTO); |
2086 | } |
2087 | |
2088 | tp->undo_marker = tp->snd_una; |
2089 | tp->undo_retrans = 0; |
2090 | |
2091 | skb = tcp_write_queue_head(sk); |
2092 | if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) |
2093 | tp->undo_marker = 0; |
2094 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { |
2095 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
2096 | tp->retrans_out -= tcp_skb_pcount(skb); |
2097 | } |
2098 | tcp_verify_left_out(tp); |
2099 | |
2100 | /* Too bad if TCP was application limited */ |
2101 | tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); |
2102 | |
2103 | /* Earlier loss recovery underway (see RFC4138; Appendix B). |
2104 | * The last condition is necessary at least in tp->frto_counter case. |
2105 | */ |
2106 | if (tcp_is_sackfrto(tp) && (tp->frto_counter || |
2107 | ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && |
2108 | after(tp->high_seq, tp->snd_una)) { |
2109 | tp->frto_highmark = tp->high_seq; |
2110 | } else { |
2111 | tp->frto_highmark = tp->snd_nxt; |
2112 | } |
2113 | tcp_set_ca_state(sk, TCP_CA_Disorder); |
2114 | tp->high_seq = tp->snd_nxt; |
2115 | tp->frto_counter = 1; |
2116 | } |
2117 | |
2118 | /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, |
2119 | * which indicates that we should follow the traditional RTO recovery, |
2120 | * i.e. mark everything lost and do go-back-N retransmission. |
2121 | */ |
2122 | static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) |
2123 | { |
2124 | struct tcp_sock *tp = tcp_sk(sk); |
2125 | struct sk_buff *skb; |
2126 | |
2127 | tp->lost_out = 0; |
2128 | tp->retrans_out = 0; |
2129 | if (tcp_is_reno(tp)) |
2130 | tcp_reset_reno_sack(tp); |
2131 | |
2132 | tcp_for_write_queue(skb, sk) { |
2133 | if (skb == tcp_send_head(sk)) |
2134 | break; |
2135 | |
2136 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; |
2137 | /* |
2138 | * Count the retransmission made on RTO correctly (only when |
2139 | * waiting for the first ACK and did not get it)... |
2140 | */ |
2141 | if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) { |
2142 | /* For some reason this R-bit might get cleared? */ |
2143 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) |
2144 | tp->retrans_out += tcp_skb_pcount(skb); |
2145 | /* ...enter this if branch just for the first segment */ |
2146 | flag |= FLAG_DATA_ACKED; |
2147 | } else { |
2148 | if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) |
2149 | tp->undo_marker = 0; |
2150 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
2151 | } |
2152 | |
2153 | /* Marking forward transmissions that were made after RTO lost |
2154 | * can cause unnecessary retransmissions in some scenarios, |
2155 | * SACK blocks will mitigate that in some but not in all cases. |
2156 | * We used to not mark them but it was causing break-ups with |
2157 | * receivers that do only in-order receival. |
2158 | * |
2159 | * TODO: we could detect presence of such receiver and select |
2160 | * different behavior per flow. |
2161 | */ |
2162 | if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { |
2163 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
2164 | tp->lost_out += tcp_skb_pcount(skb); |
2165 | tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; |
2166 | } |
2167 | } |
2168 | tcp_verify_left_out(tp); |
2169 | |
2170 | tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; |
2171 | tp->snd_cwnd_cnt = 0; |
2172 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2173 | tp->frto_counter = 0; |
2174 | tp->bytes_acked = 0; |
2175 | |
2176 | tp->reordering = min_t(unsigned int, tp->reordering, |
2177 | sysctl_tcp_reordering); |
2178 | tcp_set_ca_state(sk, TCP_CA_Loss); |
2179 | tp->high_seq = tp->snd_nxt; |
2180 | TCP_ECN_queue_cwr(tp); |
2181 | |
2182 | tcp_clear_all_retrans_hints(tp); |
2183 | } |
2184 | |
2185 | static void tcp_clear_retrans_partial(struct tcp_sock *tp) |
2186 | { |
2187 | tp->retrans_out = 0; |
2188 | tp->lost_out = 0; |
2189 | |
2190 | tp->undo_marker = 0; |
2191 | tp->undo_retrans = 0; |
2192 | } |
2193 | |
2194 | void tcp_clear_retrans(struct tcp_sock *tp) |
2195 | { |
2196 | tcp_clear_retrans_partial(tp); |
2197 | |
2198 | tp->fackets_out = 0; |
2199 | tp->sacked_out = 0; |
2200 | } |
2201 | |
2202 | /* Enter Loss state. If "how" is not zero, forget all SACK information |
2203 | * and reset tags completely, otherwise preserve SACKs. If receiver |
2204 | * dropped its ofo queue, we will know this due to reneging detection. |
2205 | */ |
2206 | void tcp_enter_loss(struct sock *sk, int how) |
2207 | { |
2208 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2209 | struct tcp_sock *tp = tcp_sk(sk); |
2210 | struct sk_buff *skb; |
2211 | |
2212 | /* Reduce ssthresh if it has not yet been made inside this window. */ |
2213 | if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || |
2214 | (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { |
2215 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
2216 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
2217 | tcp_ca_event(sk, CA_EVENT_LOSS); |
2218 | } |
2219 | tp->snd_cwnd = 1; |
2220 | tp->snd_cwnd_cnt = 0; |
2221 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2222 | |
2223 | tp->bytes_acked = 0; |
2224 | tcp_clear_retrans_partial(tp); |
2225 | |
2226 | if (tcp_is_reno(tp)) |
2227 | tcp_reset_reno_sack(tp); |
2228 | |
2229 | if (!how) { |
2230 | /* Push undo marker, if it was plain RTO and nothing |
2231 | * was retransmitted. */ |
2232 | tp->undo_marker = tp->snd_una; |
2233 | } else { |
2234 | tp->sacked_out = 0; |
2235 | tp->fackets_out = 0; |
2236 | } |
2237 | tcp_clear_all_retrans_hints(tp); |
2238 | |
2239 | tcp_for_write_queue(skb, sk) { |
2240 | if (skb == tcp_send_head(sk)) |
2241 | break; |
2242 | |
2243 | if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) |
2244 | tp->undo_marker = 0; |
2245 | TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; |
2246 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { |
2247 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; |
2248 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
2249 | tp->lost_out += tcp_skb_pcount(skb); |
2250 | tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; |
2251 | } |
2252 | } |
2253 | tcp_verify_left_out(tp); |
2254 | |
2255 | tp->reordering = min_t(unsigned int, tp->reordering, |
2256 | sysctl_tcp_reordering); |
2257 | tcp_set_ca_state(sk, TCP_CA_Loss); |
2258 | tp->high_seq = tp->snd_nxt; |
2259 | TCP_ECN_queue_cwr(tp); |
2260 | /* Abort F-RTO algorithm if one is in progress */ |
2261 | tp->frto_counter = 0; |
2262 | } |
2263 | |
2264 | /* If ACK arrived pointing to a remembered SACK, it means that our |
2265 | * remembered SACKs do not reflect real state of receiver i.e. |
2266 | * receiver _host_ is heavily congested (or buggy). |
2267 | * |
2268 | * Do processing similar to RTO timeout. |
2269 | */ |
2270 | static int tcp_check_sack_reneging(struct sock *sk, int flag) |
2271 | { |
2272 | if (flag & FLAG_SACK_RENEGING) { |
2273 | struct inet_connection_sock *icsk = inet_csk(sk); |
2274 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); |
2275 | |
2276 | tcp_enter_loss(sk, 1); |
2277 | icsk->icsk_retransmits++; |
2278 | tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); |
2279 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
2280 | icsk->icsk_rto, TCP_RTO_MAX); |
2281 | return 1; |
2282 | } |
2283 | return 0; |
2284 | } |
2285 | |
2286 | static inline int tcp_fackets_out(struct tcp_sock *tp) |
2287 | { |
2288 | return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out; |
2289 | } |
2290 | |
2291 | /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs |
2292 | * counter when SACK is enabled (without SACK, sacked_out is used for |
2293 | * that purpose). |
2294 | * |
2295 | * Instead, with FACK TCP uses fackets_out that includes both SACKed |
2296 | * segments up to the highest received SACK block so far and holes in |
2297 | * between them. |
2298 | * |
2299 | * With reordering, holes may still be in flight, so RFC3517 recovery |
2300 | * uses pure sacked_out (total number of SACKed segments) even though |
2301 | * it violates the RFC that uses duplicate ACKs, often these are equal |
2302 | * but when e.g. out-of-window ACKs or packet duplication occurs, |
2303 | * they differ. Since neither occurs due to loss, TCP should really |
2304 | * ignore them. |
2305 | */ |
2306 | static inline int tcp_dupack_heuristics(struct tcp_sock *tp) |
2307 | { |
2308 | return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; |
2309 | } |
2310 | |
2311 | static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) |
2312 | { |
2313 | return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); |
2314 | } |
2315 | |
2316 | static inline int tcp_head_timedout(struct sock *sk) |
2317 | { |
2318 | struct tcp_sock *tp = tcp_sk(sk); |
2319 | |
2320 | return tp->packets_out && |
2321 | tcp_skb_timedout(sk, tcp_write_queue_head(sk)); |
2322 | } |
2323 | |
2324 | /* Linux NewReno/SACK/FACK/ECN state machine. |
2325 | * -------------------------------------- |
2326 | * |
2327 | * "Open" Normal state, no dubious events, fast path. |
2328 | * "Disorder" In all the respects it is "Open", |
2329 | * but requires a bit more attention. It is entered when |
2330 | * we see some SACKs or dupacks. It is split of "Open" |
2331 | * mainly to move some processing from fast path to slow one. |
2332 | * "CWR" CWND was reduced due to some Congestion Notification event. |
2333 | * It can be ECN, ICMP source quench, local device congestion. |
2334 | * "Recovery" CWND was reduced, we are fast-retransmitting. |
2335 | * "Loss" CWND was reduced due to RTO timeout or SACK reneging. |
2336 | * |
2337 | * tcp_fastretrans_alert() is entered: |
2338 | * - each incoming ACK, if state is not "Open" |
2339 | * - when arrived ACK is unusual, namely: |
2340 | * * SACK |
2341 | * * Duplicate ACK. |
2342 | * * ECN ECE. |
2343 | * |
2344 | * Counting packets in flight is pretty simple. |
2345 | * |
2346 | * in_flight = packets_out - left_out + retrans_out |
2347 | * |
2348 | * packets_out is SND.NXT-SND.UNA counted in packets. |
2349 | * |
2350 | * retrans_out is number of retransmitted segments. |
2351 | * |
2352 | * left_out is number of segments left network, but not ACKed yet. |
2353 | * |
2354 | * left_out = sacked_out + lost_out |
2355 | * |
2356 | * sacked_out: Packets, which arrived to receiver out of order |
2357 | * and hence not ACKed. With SACKs this number is simply |
2358 | * amount of SACKed data. Even without SACKs |
2359 | * it is easy to give pretty reliable estimate of this number, |
2360 | * counting duplicate ACKs. |
2361 | * |
2362 | * lost_out: Packets lost by network. TCP has no explicit |
2363 | * "loss notification" feedback from network (for now). |
2364 | * It means that this number can be only _guessed_. |
2365 | * Actually, it is the heuristics to predict lossage that |
2366 | * distinguishes different algorithms. |
2367 | * |
2368 | * F.e. after RTO, when all the queue is considered as lost, |
2369 | * lost_out = packets_out and in_flight = retrans_out. |
2370 | * |
2371 | * Essentially, we have now two algorithms counting |
2372 | * lost packets. |
2373 | * |
2374 | * FACK: It is the simplest heuristics. As soon as we decided |
2375 | * that something is lost, we decide that _all_ not SACKed |
2376 | * packets until the most forward SACK are lost. I.e. |
2377 | * lost_out = fackets_out - sacked_out and left_out = fackets_out. |
2378 | * It is absolutely correct estimate, if network does not reorder |
2379 | * packets. And it loses any connection to reality when reordering |
2380 | * takes place. We use FACK by default until reordering |
2381 | * is suspected on the path to this destination. |
2382 | * |
2383 | * NewReno: when Recovery is entered, we assume that one segment |
2384 | * is lost (classic Reno). While we are in Recovery and |
2385 | * a partial ACK arrives, we assume that one more packet |
2386 | * is lost (NewReno). This heuristics are the same in NewReno |
2387 | * and SACK. |
2388 | * |
2389 | * Imagine, that's all! Forget about all this shamanism about CWND inflation |
2390 | * deflation etc. CWND is real congestion window, never inflated, changes |
2391 | * only according to classic VJ rules. |
2392 | * |
2393 | * Really tricky (and requiring careful tuning) part of algorithm |
2394 | * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). |
2395 | * The first determines the moment _when_ we should reduce CWND and, |
2396 | * hence, slow down forward transmission. In fact, it determines the moment |
2397 | * when we decide that hole is caused by loss, rather than by a reorder. |
2398 | * |
2399 | * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill |
2400 | * holes, caused by lost packets. |
2401 | * |
2402 | * And the most logically complicated part of algorithm is undo |
2403 | * heuristics. We detect false retransmits due to both too early |
2404 | * fast retransmit (reordering) and underestimated RTO, analyzing |
2405 | * timestamps and D-SACKs. When we detect that some segments were |
2406 | * retransmitted by mistake and CWND reduction was wrong, we undo |
2407 | * window reduction and abort recovery phase. This logic is hidden |
2408 | * inside several functions named tcp_try_undo_<something>. |
2409 | */ |
2410 | |
2411 | /* This function decides, when we should leave Disordered state |
2412 | * and enter Recovery phase, reducing congestion window. |
2413 | * |
2414 | * Main question: may we further continue forward transmission |
2415 | * with the same cwnd? |
2416 | */ |
2417 | static int tcp_time_to_recover(struct sock *sk) |
2418 | { |
2419 | struct tcp_sock *tp = tcp_sk(sk); |
2420 | __u32 packets_out; |
2421 | |
2422 | /* Do not perform any recovery during F-RTO algorithm */ |
2423 | if (tp->frto_counter) |
2424 | return 0; |
2425 | |
2426 | /* Trick#1: The loss is proven. */ |
2427 | if (tp->lost_out) |
2428 | return 1; |
2429 | |
2430 | /* Not-A-Trick#2 : Classic rule... */ |
2431 | if (tcp_dupack_heuristics(tp) > tp->reordering) |
2432 | return 1; |
2433 | |
2434 | /* Trick#3 : when we use RFC2988 timer restart, fast |
2435 | * retransmit can be triggered by timeout of queue head. |
2436 | */ |
2437 | if (tcp_is_fack(tp) && tcp_head_timedout(sk)) |
2438 | return 1; |
2439 | |
2440 | /* Trick#4: It is still not OK... But will it be useful to delay |
2441 | * recovery more? |
2442 | */ |
2443 | packets_out = tp->packets_out; |
2444 | if (packets_out <= tp->reordering && |
2445 | tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && |
2446 | !tcp_may_send_now(sk)) { |
2447 | /* We have nothing to send. This connection is limited |
2448 | * either by receiver window or by application. |
2449 | */ |
2450 | return 1; |
2451 | } |
2452 | |
2453 | /* If a thin stream is detected, retransmit after first |
2454 | * received dupack. Employ only if SACK is supported in order |
2455 | * to avoid possible corner-case series of spurious retransmissions |
2456 | * Use only if there are no unsent data. |
2457 | */ |
2458 | if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && |
2459 | tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && |
2460 | tcp_is_sack(tp) && !tcp_send_head(sk)) |
2461 | return 1; |
2462 | |
2463 | return 0; |
2464 | } |
2465 | |
2466 | /* New heuristics: it is possible only after we switched to restart timer |
2467 | * each time when something is ACKed. Hence, we can detect timed out packets |
2468 | * during fast retransmit without falling to slow start. |
2469 | * |
2470 | * Usefulness of this as is very questionable, since we should know which of |
2471 | * the segments is the next to timeout which is relatively expensive to find |
2472 | * in general case unless we add some data structure just for that. The |
2473 | * current approach certainly won't find the right one too often and when it |
2474 | * finally does find _something_ it usually marks large part of the window |
2475 | * right away (because a retransmission with a larger timestamp blocks the |
2476 | * loop from advancing). -ij |
2477 | */ |
2478 | static void tcp_timeout_skbs(struct sock *sk) |
2479 | { |
2480 | struct tcp_sock *tp = tcp_sk(sk); |
2481 | struct sk_buff *skb; |
2482 | |
2483 | if (!tcp_is_fack(tp) || !tcp_head_timedout(sk)) |
2484 | return; |
2485 | |
2486 | skb = tp->scoreboard_skb_hint; |
2487 | if (tp->scoreboard_skb_hint == NULL) |
2488 | skb = tcp_write_queue_head(sk); |
2489 | |
2490 | tcp_for_write_queue_from(skb, sk) { |
2491 | if (skb == tcp_send_head(sk)) |
2492 | break; |
2493 | if (!tcp_skb_timedout(sk, skb)) |
2494 | break; |
2495 | |
2496 | tcp_skb_mark_lost(tp, skb); |
2497 | } |
2498 | |
2499 | tp->scoreboard_skb_hint = skb; |
2500 | |
2501 | tcp_verify_left_out(tp); |
2502 | } |
2503 | |
2504 | /* Mark head of queue up as lost. With RFC3517 SACK, the packets is |
2505 | * is against sacked "cnt", otherwise it's against facked "cnt" |
2506 | */ |
2507 | static void tcp_mark_head_lost(struct sock *sk, int packets) |
2508 | { |
2509 | struct tcp_sock *tp = tcp_sk(sk); |
2510 | struct sk_buff *skb; |
2511 | int cnt, oldcnt; |
2512 | int err; |
2513 | unsigned int mss; |
2514 | |
2515 | if (packets == 0) |
2516 | return; |
2517 | |
2518 | WARN_ON(packets > tp->packets_out); |
2519 | if (tp->lost_skb_hint) { |
2520 | skb = tp->lost_skb_hint; |
2521 | cnt = tp->lost_cnt_hint; |
2522 | } else { |
2523 | skb = tcp_write_queue_head(sk); |
2524 | cnt = 0; |
2525 | } |
2526 | |
2527 | tcp_for_write_queue_from(skb, sk) { |
2528 | if (skb == tcp_send_head(sk)) |
2529 | break; |
2530 | /* TODO: do this better */ |
2531 | /* this is not the most efficient way to do this... */ |
2532 | tp->lost_skb_hint = skb; |
2533 | tp->lost_cnt_hint = cnt; |
2534 | |
2535 | if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq)) |
2536 | break; |
2537 | |
2538 | oldcnt = cnt; |
2539 | if (tcp_is_fack(tp) || tcp_is_reno(tp) || |
2540 | (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) |
2541 | cnt += tcp_skb_pcount(skb); |
2542 | |
2543 | if (cnt > packets) { |
2544 | if (tcp_is_sack(tp) || (oldcnt >= packets)) |
2545 | break; |
2546 | |
2547 | mss = skb_shinfo(skb)->gso_size; |
2548 | err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss); |
2549 | if (err < 0) |
2550 | break; |
2551 | cnt = packets; |
2552 | } |
2553 | |
2554 | tcp_skb_mark_lost(tp, skb); |
2555 | } |
2556 | tcp_verify_left_out(tp); |
2557 | } |
2558 | |
2559 | /* Account newly detected lost packet(s) */ |
2560 | |
2561 | static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) |
2562 | { |
2563 | struct tcp_sock *tp = tcp_sk(sk); |
2564 | |
2565 | if (tcp_is_reno(tp)) { |
2566 | tcp_mark_head_lost(sk, 1); |
2567 | } else if (tcp_is_fack(tp)) { |
2568 | int lost = tp->fackets_out - tp->reordering; |
2569 | if (lost <= 0) |
2570 | lost = 1; |
2571 | tcp_mark_head_lost(sk, lost); |
2572 | } else { |
2573 | int sacked_upto = tp->sacked_out - tp->reordering; |
2574 | if (sacked_upto < fast_rexmit) |
2575 | sacked_upto = fast_rexmit; |
2576 | tcp_mark_head_lost(sk, sacked_upto); |
2577 | } |
2578 | |
2579 | tcp_timeout_skbs(sk); |
2580 | } |
2581 | |
2582 | /* CWND moderation, preventing bursts due to too big ACKs |
2583 | * in dubious situations. |
2584 | */ |
2585 | static inline void tcp_moderate_cwnd(struct tcp_sock *tp) |
2586 | { |
2587 | tp->snd_cwnd = min(tp->snd_cwnd, |
2588 | tcp_packets_in_flight(tp) + tcp_max_burst(tp)); |
2589 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2590 | } |
2591 | |
2592 | /* Lower bound on congestion window is slow start threshold |
2593 | * unless congestion avoidance choice decides to overide it. |
2594 | */ |
2595 | static inline u32 tcp_cwnd_min(const struct sock *sk) |
2596 | { |
2597 | const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; |
2598 | |
2599 | return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; |
2600 | } |
2601 | |
2602 | /* Decrease cwnd each second ack. */ |
2603 | static void tcp_cwnd_down(struct sock *sk, int flag) |
2604 | { |
2605 | struct tcp_sock *tp = tcp_sk(sk); |
2606 | int decr = tp->snd_cwnd_cnt + 1; |
2607 | |
2608 | if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) || |
2609 | (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) { |
2610 | tp->snd_cwnd_cnt = decr & 1; |
2611 | decr >>= 1; |
2612 | |
2613 | if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) |
2614 | tp->snd_cwnd -= decr; |
2615 | |
2616 | tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); |
2617 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2618 | } |
2619 | } |
2620 | |
2621 | /* Nothing was retransmitted or returned timestamp is less |
2622 | * than timestamp of the first retransmission. |
2623 | */ |
2624 | static inline int tcp_packet_delayed(struct tcp_sock *tp) |
2625 | { |
2626 | return !tp->retrans_stamp || |
2627 | (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
2628 | before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp)); |
2629 | } |
2630 | |
2631 | /* Undo procedures. */ |
2632 | |
2633 | #if FASTRETRANS_DEBUG > 1 |
2634 | static void DBGUNDO(struct sock *sk, const char *msg) |
2635 | { |
2636 | struct tcp_sock *tp = tcp_sk(sk); |
2637 | struct inet_sock *inet = inet_sk(sk); |
2638 | |
2639 | if (sk->sk_family == AF_INET) { |
2640 | printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", |
2641 | msg, |
2642 | &inet->daddr, ntohs(inet->dport), |
2643 | tp->snd_cwnd, tcp_left_out(tp), |
2644 | tp->snd_ssthresh, tp->prior_ssthresh, |
2645 | tp->packets_out); |
2646 | } |
2647 | #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) |
2648 | else if (sk->sk_family == AF_INET6) { |
2649 | struct ipv6_pinfo *np = inet6_sk(sk); |
2650 | printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", |
2651 | msg, |
2652 | &np->daddr, ntohs(inet->dport), |
2653 | tp->snd_cwnd, tcp_left_out(tp), |
2654 | tp->snd_ssthresh, tp->prior_ssthresh, |
2655 | tp->packets_out); |
2656 | } |
2657 | #endif |
2658 | } |
2659 | #else |
2660 | #define DBGUNDO(x...) do { } while (0) |
2661 | #endif |
2662 | |
2663 | static void tcp_undo_cwr(struct sock *sk, const int undo) |
2664 | { |
2665 | struct tcp_sock *tp = tcp_sk(sk); |
2666 | |
2667 | if (tp->prior_ssthresh) { |
2668 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2669 | |
2670 | if (icsk->icsk_ca_ops->undo_cwnd) |
2671 | tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); |
2672 | else |
2673 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); |
2674 | |
2675 | if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { |
2676 | tp->snd_ssthresh = tp->prior_ssthresh; |
2677 | TCP_ECN_withdraw_cwr(tp); |
2678 | } |
2679 | } else { |
2680 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); |
2681 | } |
2682 | tcp_moderate_cwnd(tp); |
2683 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2684 | } |
2685 | |
2686 | static inline int tcp_may_undo(struct tcp_sock *tp) |
2687 | { |
2688 | return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); |
2689 | } |
2690 | |
2691 | /* People celebrate: "We love our President!" */ |
2692 | static int tcp_try_undo_recovery(struct sock *sk) |
2693 | { |
2694 | struct tcp_sock *tp = tcp_sk(sk); |
2695 | |
2696 | if (tcp_may_undo(tp)) { |
2697 | int mib_idx; |
2698 | |
2699 | /* Happy end! We did not retransmit anything |
2700 | * or our original transmission succeeded. |
2701 | */ |
2702 | DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); |
2703 | tcp_undo_cwr(sk, 1); |
2704 | if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) |
2705 | mib_idx = LINUX_MIB_TCPLOSSUNDO; |
2706 | else |
2707 | mib_idx = LINUX_MIB_TCPFULLUNDO; |
2708 | |
2709 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
2710 | tp->undo_marker = 0; |
2711 | } |
2712 | if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { |
2713 | /* Hold old state until something *above* high_seq |
2714 | * is ACKed. For Reno it is MUST to prevent false |
2715 | * fast retransmits (RFC2582). SACK TCP is safe. */ |
2716 | tcp_moderate_cwnd(tp); |
2717 | return 1; |
2718 | } |
2719 | tcp_set_ca_state(sk, TCP_CA_Open); |
2720 | return 0; |
2721 | } |
2722 | |
2723 | /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ |
2724 | static void tcp_try_undo_dsack(struct sock *sk) |
2725 | { |
2726 | struct tcp_sock *tp = tcp_sk(sk); |
2727 | |
2728 | if (tp->undo_marker && !tp->undo_retrans) { |
2729 | DBGUNDO(sk, "D-SACK"); |
2730 | tcp_undo_cwr(sk, 1); |
2731 | tp->undo_marker = 0; |
2732 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); |
2733 | } |
2734 | } |
2735 | |
2736 | /* We can clear retrans_stamp when there are no retransmissions in the |
2737 | * window. It would seem that it is trivially available for us in |
2738 | * tp->retrans_out, however, that kind of assumptions doesn't consider |
2739 | * what will happen if errors occur when sending retransmission for the |
2740 | * second time. ...It could the that such segment has only |
2741 | * TCPCB_EVER_RETRANS set at the present time. It seems that checking |
2742 | * the head skb is enough except for some reneging corner cases that |
2743 | * are not worth the effort. |
2744 | * |
2745 | * Main reason for all this complexity is the fact that connection dying |
2746 | * time now depends on the validity of the retrans_stamp, in particular, |
2747 | * that successive retransmissions of a segment must not advance |
2748 | * retrans_stamp under any conditions. |
2749 | */ |
2750 | static int tcp_any_retrans_done(struct sock *sk) |
2751 | { |
2752 | struct tcp_sock *tp = tcp_sk(sk); |
2753 | struct sk_buff *skb; |
2754 | |
2755 | if (tp->retrans_out) |
2756 | return 1; |
2757 | |
2758 | skb = tcp_write_queue_head(sk); |
2759 | if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) |
2760 | return 1; |
2761 | |
2762 | return 0; |
2763 | } |
2764 | |
2765 | /* Undo during fast recovery after partial ACK. */ |
2766 | |
2767 | static int tcp_try_undo_partial(struct sock *sk, int acked) |
2768 | { |
2769 | struct tcp_sock *tp = tcp_sk(sk); |
2770 | /* Partial ACK arrived. Force Hoe's retransmit. */ |
2771 | int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering); |
2772 | |
2773 | if (tcp_may_undo(tp)) { |
2774 | /* Plain luck! Hole if filled with delayed |
2775 | * packet, rather than with a retransmit. |
2776 | */ |
2777 | if (!tcp_any_retrans_done(sk)) |
2778 | tp->retrans_stamp = 0; |
2779 | |
2780 | tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); |
2781 | |
2782 | DBGUNDO(sk, "Hoe"); |
2783 | tcp_undo_cwr(sk, 0); |
2784 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); |
2785 | |
2786 | /* So... Do not make Hoe's retransmit yet. |
2787 | * If the first packet was delayed, the rest |
2788 | * ones are most probably delayed as well. |
2789 | */ |
2790 | failed = 0; |
2791 | } |
2792 | return failed; |
2793 | } |
2794 | |
2795 | /* Undo during loss recovery after partial ACK. */ |
2796 | static int tcp_try_undo_loss(struct sock *sk) |
2797 | { |
2798 | struct tcp_sock *tp = tcp_sk(sk); |
2799 | |
2800 | if (tcp_may_undo(tp)) { |
2801 | struct sk_buff *skb; |
2802 | tcp_for_write_queue(skb, sk) { |
2803 | if (skb == tcp_send_head(sk)) |
2804 | break; |
2805 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; |
2806 | } |
2807 | |
2808 | tcp_clear_all_retrans_hints(tp); |
2809 | |
2810 | DBGUNDO(sk, "partial loss"); |
2811 | tp->lost_out = 0; |
2812 | tcp_undo_cwr(sk, 1); |
2813 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); |
2814 | inet_csk(sk)->icsk_retransmits = 0; |
2815 | tp->undo_marker = 0; |
2816 | if (tcp_is_sack(tp)) |
2817 | tcp_set_ca_state(sk, TCP_CA_Open); |
2818 | return 1; |
2819 | } |
2820 | return 0; |
2821 | } |
2822 | |
2823 | static inline void tcp_complete_cwr(struct sock *sk) |
2824 | { |
2825 | struct tcp_sock *tp = tcp_sk(sk); |
2826 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); |
2827 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2828 | tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); |
2829 | } |
2830 | |
2831 | static void tcp_try_keep_open(struct sock *sk) |
2832 | { |
2833 | struct tcp_sock *tp = tcp_sk(sk); |
2834 | int state = TCP_CA_Open; |
2835 | |
2836 | if (tcp_left_out(tp) || tcp_any_retrans_done(sk) || tp->undo_marker) |
2837 | state = TCP_CA_Disorder; |
2838 | |
2839 | if (inet_csk(sk)->icsk_ca_state != state) { |
2840 | tcp_set_ca_state(sk, state); |
2841 | tp->high_seq = tp->snd_nxt; |
2842 | } |
2843 | } |
2844 | |
2845 | static void tcp_try_to_open(struct sock *sk, int flag) |
2846 | { |
2847 | struct tcp_sock *tp = tcp_sk(sk); |
2848 | |
2849 | tcp_verify_left_out(tp); |
2850 | |
2851 | if (!tp->frto_counter && !tcp_any_retrans_done(sk)) |
2852 | tp->retrans_stamp = 0; |
2853 | |
2854 | if (flag & FLAG_ECE) |
2855 | tcp_enter_cwr(sk, 1); |
2856 | |
2857 | if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { |
2858 | tcp_try_keep_open(sk); |
2859 | tcp_moderate_cwnd(tp); |
2860 | } else { |
2861 | tcp_cwnd_down(sk, flag); |
2862 | } |
2863 | } |
2864 | |
2865 | static void tcp_mtup_probe_failed(struct sock *sk) |
2866 | { |
2867 | struct inet_connection_sock *icsk = inet_csk(sk); |
2868 | |
2869 | icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; |
2870 | icsk->icsk_mtup.probe_size = 0; |
2871 | } |
2872 | |
2873 | static void tcp_mtup_probe_success(struct sock *sk) |
2874 | { |
2875 | struct tcp_sock *tp = tcp_sk(sk); |
2876 | struct inet_connection_sock *icsk = inet_csk(sk); |
2877 | |
2878 | /* FIXME: breaks with very large cwnd */ |
2879 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
2880 | tp->snd_cwnd = tp->snd_cwnd * |
2881 | tcp_mss_to_mtu(sk, tp->mss_cache) / |
2882 | icsk->icsk_mtup.probe_size; |
2883 | tp->snd_cwnd_cnt = 0; |
2884 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2885 | tp->rcv_ssthresh = tcp_current_ssthresh(sk); |
2886 | |
2887 | icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; |
2888 | icsk->icsk_mtup.probe_size = 0; |
2889 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
2890 | } |
2891 | |
2892 | /* Do a simple retransmit without using the backoff mechanisms in |
2893 | * tcp_timer. This is used for path mtu discovery. |
2894 | * The socket is already locked here. |
2895 | */ |
2896 | void tcp_simple_retransmit(struct sock *sk) |
2897 | { |
2898 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2899 | struct tcp_sock *tp = tcp_sk(sk); |
2900 | struct sk_buff *skb; |
2901 | unsigned int mss = tcp_current_mss(sk); |
2902 | u32 prior_lost = tp->lost_out; |
2903 | |
2904 | tcp_for_write_queue(skb, sk) { |
2905 | if (skb == tcp_send_head(sk)) |
2906 | break; |
2907 | if (tcp_skb_seglen(skb) > mss && |
2908 | !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { |
2909 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { |
2910 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
2911 | tp->retrans_out -= tcp_skb_pcount(skb); |
2912 | } |
2913 | tcp_skb_mark_lost_uncond_verify(tp, skb); |
2914 | } |
2915 | } |
2916 | |
2917 | tcp_clear_retrans_hints_partial(tp); |
2918 | |
2919 | if (prior_lost == tp->lost_out) |
2920 | return; |
2921 | |
2922 | if (tcp_is_reno(tp)) |
2923 | tcp_limit_reno_sacked(tp); |
2924 | |
2925 | tcp_verify_left_out(tp); |
2926 | |
2927 | /* Don't muck with the congestion window here. |
2928 | * Reason is that we do not increase amount of _data_ |
2929 | * in network, but units changed and effective |
2930 | * cwnd/ssthresh really reduced now. |
2931 | */ |
2932 | if (icsk->icsk_ca_state != TCP_CA_Loss) { |
2933 | tp->high_seq = tp->snd_nxt; |
2934 | tp->snd_ssthresh = tcp_current_ssthresh(sk); |
2935 | tp->prior_ssthresh = 0; |
2936 | tp->undo_marker = 0; |
2937 | tcp_set_ca_state(sk, TCP_CA_Loss); |
2938 | } |
2939 | tcp_xmit_retransmit_queue(sk); |
2940 | } |
2941 | |
2942 | /* Process an event, which can update packets-in-flight not trivially. |
2943 | * Main goal of this function is to calculate new estimate for left_out, |
2944 | * taking into account both packets sitting in receiver's buffer and |
2945 | * packets lost by network. |
2946 | * |
2947 | * Besides that it does CWND reduction, when packet loss is detected |
2948 | * and changes state of machine. |
2949 | * |
2950 | * It does _not_ decide what to send, it is made in function |
2951 | * tcp_xmit_retransmit_queue(). |
2952 | */ |
2953 | static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag) |
2954 | { |
2955 | struct inet_connection_sock *icsk = inet_csk(sk); |
2956 | struct tcp_sock *tp = tcp_sk(sk); |
2957 | int is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); |
2958 | int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && |
2959 | (tcp_fackets_out(tp) > tp->reordering)); |
2960 | int fast_rexmit = 0, mib_idx; |
2961 | |
2962 | if (WARN_ON(!tp->packets_out && tp->sacked_out)) |
2963 | tp->sacked_out = 0; |
2964 | if (WARN_ON(!tp->sacked_out && tp->fackets_out)) |
2965 | tp->fackets_out = 0; |
2966 | |
2967 | /* Now state machine starts. |
2968 | * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ |
2969 | if (flag & FLAG_ECE) |
2970 | tp->prior_ssthresh = 0; |
2971 | |
2972 | /* B. In all the states check for reneging SACKs. */ |
2973 | if (tcp_check_sack_reneging(sk, flag)) |
2974 | return; |
2975 | |
2976 | /* C. Process data loss notification, provided it is valid. */ |
2977 | if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) && |
2978 | before(tp->snd_una, tp->high_seq) && |
2979 | icsk->icsk_ca_state != TCP_CA_Open && |
2980 | tp->fackets_out > tp->reordering) { |
2981 | tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering); |
2982 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS); |
2983 | } |
2984 | |
2985 | /* D. Check consistency of the current state. */ |
2986 | tcp_verify_left_out(tp); |
2987 | |
2988 | /* E. Check state exit conditions. State can be terminated |
2989 | * when high_seq is ACKed. */ |
2990 | if (icsk->icsk_ca_state == TCP_CA_Open) { |
2991 | WARN_ON(tp->retrans_out != 0); |
2992 | tp->retrans_stamp = 0; |
2993 | } else if (!before(tp->snd_una, tp->high_seq)) { |
2994 | switch (icsk->icsk_ca_state) { |
2995 | case TCP_CA_Loss: |
2996 | icsk->icsk_retransmits = 0; |
2997 | if (tcp_try_undo_recovery(sk)) |
2998 | return; |
2999 | break; |
3000 | |
3001 | case TCP_CA_CWR: |
3002 | /* CWR is to be held something *above* high_seq |
3003 | * is ACKed for CWR bit to reach receiver. */ |
3004 | if (tp->snd_una != tp->high_seq) { |
3005 | tcp_complete_cwr(sk); |
3006 | tcp_set_ca_state(sk, TCP_CA_Open); |
3007 | } |
3008 | break; |
3009 | |
3010 | case TCP_CA_Disorder: |
3011 | tcp_try_undo_dsack(sk); |
3012 | if (!tp->undo_marker || |
3013 | /* For SACK case do not Open to allow to undo |
3014 | * catching for all duplicate ACKs. */ |
3015 | tcp_is_reno(tp) || tp->snd_una != tp->high_seq) { |
3016 | tp->undo_marker = 0; |
3017 | tcp_set_ca_state(sk, TCP_CA_Open); |
3018 | } |
3019 | break; |
3020 | |
3021 | case TCP_CA_Recovery: |
3022 | if (tcp_is_reno(tp)) |
3023 | tcp_reset_reno_sack(tp); |
3024 | if (tcp_try_undo_recovery(sk)) |
3025 | return; |
3026 | tcp_complete_cwr(sk); |
3027 | break; |
3028 | } |
3029 | } |
3030 | |
3031 | /* F. Process state. */ |
3032 | switch (icsk->icsk_ca_state) { |
3033 | case TCP_CA_Recovery: |
3034 | if (!(flag & FLAG_SND_UNA_ADVANCED)) { |
3035 | if (tcp_is_reno(tp) && is_dupack) |
3036 | tcp_add_reno_sack(sk); |
3037 | } else |
3038 | do_lost = tcp_try_undo_partial(sk, pkts_acked); |
3039 | break; |
3040 | case TCP_CA_Loss: |
3041 | if (flag & FLAG_DATA_ACKED) |
3042 | icsk->icsk_retransmits = 0; |
3043 | if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED) |
3044 | tcp_reset_reno_sack(tp); |
3045 | if (!tcp_try_undo_loss(sk)) { |
3046 | tcp_moderate_cwnd(tp); |
3047 | tcp_xmit_retransmit_queue(sk); |
3048 | return; |
3049 | } |
3050 | if (icsk->icsk_ca_state != TCP_CA_Open) |
3051 | return; |
3052 | /* Loss is undone; fall through to processing in Open state. */ |
3053 | default: |
3054 | if (tcp_is_reno(tp)) { |
3055 | if (flag & FLAG_SND_UNA_ADVANCED) |
3056 | tcp_reset_reno_sack(tp); |
3057 | if (is_dupack) |
3058 | tcp_add_reno_sack(sk); |
3059 | } |
3060 | |
3061 | if (icsk->icsk_ca_state == TCP_CA_Disorder) |
3062 | tcp_try_undo_dsack(sk); |
3063 | |
3064 | if (!tcp_time_to_recover(sk)) { |
3065 | tcp_try_to_open(sk, flag); |
3066 | return; |
3067 | } |
3068 | |
3069 | /* MTU probe failure: don't reduce cwnd */ |
3070 | if (icsk->icsk_ca_state < TCP_CA_CWR && |
3071 | icsk->icsk_mtup.probe_size && |
3072 | tp->snd_una == tp->mtu_probe.probe_seq_start) { |
3073 | tcp_mtup_probe_failed(sk); |
3074 | /* Restores the reduction we did in tcp_mtup_probe() */ |
3075 | tp->snd_cwnd++; |
3076 | tcp_simple_retransmit(sk); |
3077 | return; |
3078 | } |
3079 | |
3080 | /* Otherwise enter Recovery state */ |
3081 | |
3082 | if (tcp_is_reno(tp)) |
3083 | mib_idx = LINUX_MIB_TCPRENORECOVERY; |
3084 | else |
3085 | mib_idx = LINUX_MIB_TCPSACKRECOVERY; |
3086 | |
3087 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
3088 | |
3089 | tp->high_seq = tp->snd_nxt; |
3090 | tp->prior_ssthresh = 0; |
3091 | tp->undo_marker = tp->snd_una; |
3092 | tp->undo_retrans = tp->retrans_out; |
3093 | |
3094 | if (icsk->icsk_ca_state < TCP_CA_CWR) { |
3095 | if (!(flag & FLAG_ECE)) |
3096 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
3097 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
3098 | TCP_ECN_queue_cwr(tp); |
3099 | } |
3100 | |
3101 | tp->bytes_acked = 0; |
3102 | tp->snd_cwnd_cnt = 0; |
3103 | tcp_set_ca_state(sk, TCP_CA_Recovery); |
3104 | fast_rexmit = 1; |
3105 | } |
3106 | |
3107 | if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) |
3108 | tcp_update_scoreboard(sk, fast_rexmit); |
3109 | tcp_cwnd_down(sk, flag); |
3110 | tcp_xmit_retransmit_queue(sk); |
3111 | } |
3112 | |
3113 | static void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt) |
3114 | { |
3115 | tcp_rtt_estimator(sk, seq_rtt); |
3116 | tcp_set_rto(sk); |
3117 | inet_csk(sk)->icsk_backoff = 0; |
3118 | } |
3119 | |
3120 | /* Read draft-ietf-tcplw-high-performance before mucking |
3121 | * with this code. (Supersedes RFC1323) |
3122 | */ |
3123 | static void tcp_ack_saw_tstamp(struct sock *sk, int flag) |
3124 | { |
3125 | /* RTTM Rule: A TSecr value received in a segment is used to |
3126 | * update the averaged RTT measurement only if the segment |
3127 | * acknowledges some new data, i.e., only if it advances the |
3128 | * left edge of the send window. |
3129 | * |
3130 | * See draft-ietf-tcplw-high-performance-00, section 3.3. |
3131 | * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> |
3132 | * |
3133 | * Changed: reset backoff as soon as we see the first valid sample. |
3134 | * If we do not, we get strongly overestimated rto. With timestamps |
3135 | * samples are accepted even from very old segments: f.e., when rtt=1 |
3136 | * increases to 8, we retransmit 5 times and after 8 seconds delayed |
3137 | * answer arrives rto becomes 120 seconds! If at least one of segments |
3138 | * in window is lost... Voila. --ANK (010210) |
3139 | */ |
3140 | struct tcp_sock *tp = tcp_sk(sk); |
3141 | |
3142 | tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr); |
3143 | } |
3144 | |
3145 | static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) |
3146 | { |
3147 | /* We don't have a timestamp. Can only use |
3148 | * packets that are not retransmitted to determine |
3149 | * rtt estimates. Also, we must not reset the |
3150 | * backoff for rto until we get a non-retransmitted |
3151 | * packet. This allows us to deal with a situation |
3152 | * where the network delay has increased suddenly. |
3153 | * I.e. Karn's algorithm. (SIGCOMM '87, p5.) |
3154 | */ |
3155 | |
3156 | if (flag & FLAG_RETRANS_DATA_ACKED) |
3157 | return; |
3158 | |
3159 | tcp_valid_rtt_meas(sk, seq_rtt); |
3160 | } |
3161 | |
3162 | static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, |
3163 | const s32 seq_rtt) |
3164 | { |
3165 | const struct tcp_sock *tp = tcp_sk(sk); |
3166 | /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ |
3167 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) |
3168 | tcp_ack_saw_tstamp(sk, flag); |
3169 | else if (seq_rtt >= 0) |
3170 | tcp_ack_no_tstamp(sk, seq_rtt, flag); |
3171 | } |
3172 | |
3173 | static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) |
3174 | { |
3175 | const struct inet_connection_sock *icsk = inet_csk(sk); |
3176 | icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight); |
3177 | tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; |
3178 | } |
3179 | |
3180 | /* Restart timer after forward progress on connection. |
3181 | * RFC2988 recommends to restart timer to now+rto. |
3182 | */ |
3183 | static void tcp_rearm_rto(struct sock *sk) |
3184 | { |
3185 | struct tcp_sock *tp = tcp_sk(sk); |
3186 | |
3187 | if (!tp->packets_out) { |
3188 | inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); |
3189 | } else { |
3190 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
3191 | inet_csk(sk)->icsk_rto, TCP_RTO_MAX); |
3192 | } |
3193 | } |
3194 | |
3195 | /* If we get here, the whole TSO packet has not been acked. */ |
3196 | static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) |
3197 | { |
3198 | struct tcp_sock *tp = tcp_sk(sk); |
3199 | u32 packets_acked; |
3200 | |
3201 | BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); |
3202 | |
3203 | packets_acked = tcp_skb_pcount(skb); |
3204 | if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) |
3205 | return 0; |
3206 | packets_acked -= tcp_skb_pcount(skb); |
3207 | |
3208 | if (packets_acked) { |
3209 | BUG_ON(tcp_skb_pcount(skb) == 0); |
3210 | BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); |
3211 | } |
3212 | |
3213 | return packets_acked; |
3214 | } |
3215 | |
3216 | /* Remove acknowledged frames from the retransmission queue. If our packet |
3217 | * is before the ack sequence we can discard it as it's confirmed to have |
3218 | * arrived at the other end. |
3219 | */ |
3220 | static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, |
3221 | u32 prior_snd_una) |
3222 | { |
3223 | struct tcp_sock *tp = tcp_sk(sk); |
3224 | const struct inet_connection_sock *icsk = inet_csk(sk); |
3225 | struct sk_buff *skb; |
3226 | u32 now = tcp_time_stamp; |
3227 | int fully_acked = 1; |
3228 | int flag = 0; |
3229 | u32 pkts_acked = 0; |
3230 | u32 reord = tp->packets_out; |
3231 | u32 prior_sacked = tp->sacked_out; |
3232 | s32 seq_rtt = -1; |
3233 | s32 ca_seq_rtt = -1; |
3234 | ktime_t last_ackt = net_invalid_timestamp(); |
3235 | |
3236 | while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { |
3237 | struct tcp_skb_cb *scb = TCP_SKB_CB(skb); |
3238 | u32 acked_pcount; |
3239 | u8 sacked = scb->sacked; |
3240 | |
3241 | /* Determine how many packets and what bytes were acked, tso and else */ |
3242 | if (after(scb->end_seq, tp->snd_una)) { |
3243 | if (tcp_skb_pcount(skb) == 1 || |
3244 | !after(tp->snd_una, scb->seq)) |
3245 | break; |
3246 | |
3247 | acked_pcount = tcp_tso_acked(sk, skb); |
3248 | if (!acked_pcount) |
3249 | break; |
3250 | |
3251 | fully_acked = 0; |
3252 | } else { |
3253 | acked_pcount = tcp_skb_pcount(skb); |
3254 | } |
3255 | |
3256 | if (sacked & TCPCB_RETRANS) { |
3257 | if (sacked & TCPCB_SACKED_RETRANS) |
3258 | tp->retrans_out -= acked_pcount; |
3259 | flag |= FLAG_RETRANS_DATA_ACKED; |
3260 | ca_seq_rtt = -1; |
3261 | seq_rtt = -1; |
3262 | if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1)) |
3263 | flag |= FLAG_NONHEAD_RETRANS_ACKED; |
3264 | } else { |
3265 | ca_seq_rtt = now - scb->when; |
3266 | last_ackt = skb->tstamp; |
3267 | if (seq_rtt < 0) { |
3268 | seq_rtt = ca_seq_rtt; |
3269 | } |
3270 | if (!(sacked & TCPCB_SACKED_ACKED)) |
3271 | reord = min(pkts_acked, reord); |
3272 | } |
3273 | |
3274 | if (sacked & TCPCB_SACKED_ACKED) |
3275 | tp->sacked_out -= acked_pcount; |
3276 | if (sacked & TCPCB_LOST) |
3277 | tp->lost_out -= acked_pcount; |
3278 | |
3279 | tp->packets_out -= acked_pcount; |
3280 | pkts_acked += acked_pcount; |
3281 | |
3282 | /* Initial outgoing SYN's get put onto the write_queue |
3283 | * just like anything else we transmit. It is not |
3284 | * true data, and if we misinform our callers that |
3285 | * this ACK acks real data, we will erroneously exit |
3286 | * connection startup slow start one packet too |
3287 | * quickly. This is severely frowned upon behavior. |
3288 | */ |
3289 | if (!(scb->flags & TCPCB_FLAG_SYN)) { |
3290 | flag |= FLAG_DATA_ACKED; |
3291 | } else { |
3292 | flag |= FLAG_SYN_ACKED; |
3293 | tp->retrans_stamp = 0; |
3294 | } |
3295 | |
3296 | if (!fully_acked) |
3297 | break; |
3298 | |
3299 | tcp_unlink_write_queue(skb, sk); |
3300 | sk_wmem_free_skb(sk, skb); |
3301 | tp->scoreboard_skb_hint = NULL; |
3302 | if (skb == tp->retransmit_skb_hint) |
3303 | tp->retransmit_skb_hint = NULL; |
3304 | if (skb == tp->lost_skb_hint) |
3305 | tp->lost_skb_hint = NULL; |
3306 | } |
3307 | |
3308 | if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una))) |
3309 | tp->snd_up = tp->snd_una; |
3310 | |
3311 | if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) |
3312 | flag |= FLAG_SACK_RENEGING; |
3313 | |
3314 | if (flag & FLAG_ACKED) { |
3315 | const struct tcp_congestion_ops *ca_ops |
3316 | = inet_csk(sk)->icsk_ca_ops; |
3317 | |
3318 | if (unlikely(icsk->icsk_mtup.probe_size && |
3319 | !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) { |
3320 | tcp_mtup_probe_success(sk); |
3321 | } |
3322 | |
3323 | tcp_ack_update_rtt(sk, flag, seq_rtt); |
3324 | tcp_rearm_rto(sk); |
3325 | |
3326 | if (tcp_is_reno(tp)) { |
3327 | tcp_remove_reno_sacks(sk, pkts_acked); |
3328 | } else { |
3329 | int delta; |
3330 | |
3331 | /* Non-retransmitted hole got filled? That's reordering */ |
3332 | if (reord < prior_fackets) |
3333 | tcp_update_reordering(sk, tp->fackets_out - reord, 0); |
3334 | |
3335 | delta = tcp_is_fack(tp) ? pkts_acked : |
3336 | prior_sacked - tp->sacked_out; |
3337 | tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); |
3338 | } |
3339 | |
3340 | tp->fackets_out -= min(pkts_acked, tp->fackets_out); |
3341 | |
3342 | if (ca_ops->pkts_acked) { |
3343 | s32 rtt_us = -1; |
3344 | |
3345 | /* Is the ACK triggering packet unambiguous? */ |
3346 | if (!(flag & FLAG_RETRANS_DATA_ACKED)) { |
3347 | /* High resolution needed and available? */ |
3348 | if (ca_ops->flags & TCP_CONG_RTT_STAMP && |
3349 | !ktime_equal(last_ackt, |
3350 | net_invalid_timestamp())) |
3351 | rtt_us = ktime_us_delta(ktime_get_real(), |
3352 | last_ackt); |
3353 | else if (ca_seq_rtt > 0) |
3354 | rtt_us = jiffies_to_usecs(ca_seq_rtt); |
3355 | } |
3356 | |
3357 | ca_ops->pkts_acked(sk, pkts_acked, rtt_us); |
3358 | } |
3359 | } |
3360 | |
3361 | #if FASTRETRANS_DEBUG > 0 |
3362 | WARN_ON((int)tp->sacked_out < 0); |
3363 | WARN_ON((int)tp->lost_out < 0); |
3364 | WARN_ON((int)tp->retrans_out < 0); |
3365 | if (!tp->packets_out && tcp_is_sack(tp)) { |
3366 | icsk = inet_csk(sk); |
3367 | if (tp->lost_out) { |
3368 | printk(KERN_DEBUG "Leak l=%u %d\n", |
3369 | tp->lost_out, icsk->icsk_ca_state); |
3370 | tp->lost_out = 0; |
3371 | } |
3372 | if (tp->sacked_out) { |
3373 | printk(KERN_DEBUG "Leak s=%u %d\n", |
3374 | tp->sacked_out, icsk->icsk_ca_state); |
3375 | tp->sacked_out = 0; |
3376 | } |
3377 | if (tp->retrans_out) { |
3378 | printk(KERN_DEBUG "Leak r=%u %d\n", |
3379 | tp->retrans_out, icsk->icsk_ca_state); |
3380 | tp->retrans_out = 0; |
3381 | } |
3382 | } |
3383 | #endif |
3384 | return flag; |
3385 | } |
3386 | |
3387 | static void tcp_ack_probe(struct sock *sk) |
3388 | { |
3389 | const struct tcp_sock *tp = tcp_sk(sk); |
3390 | struct inet_connection_sock *icsk = inet_csk(sk); |
3391 | |
3392 | /* Was it a usable window open? */ |
3393 | |
3394 | if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) { |
3395 | icsk->icsk_backoff = 0; |
3396 | inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); |
3397 | /* Socket must be waked up by subsequent tcp_data_snd_check(). |
3398 | * This function is not for random using! |
3399 | */ |
3400 | } else { |
3401 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, |
3402 | min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), |
3403 | TCP_RTO_MAX); |
3404 | } |
3405 | } |
3406 | |
3407 | static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) |
3408 | { |
3409 | return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || |
3410 | inet_csk(sk)->icsk_ca_state != TCP_CA_Open); |
3411 | } |
3412 | |
3413 | static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) |
3414 | { |
3415 | const struct tcp_sock *tp = tcp_sk(sk); |
3416 | return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && |
3417 | !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); |
3418 | } |
3419 | |
3420 | /* Check that window update is acceptable. |
3421 | * The function assumes that snd_una<=ack<=snd_next. |
3422 | */ |
3423 | static inline int tcp_may_update_window(const struct tcp_sock *tp, |
3424 | const u32 ack, const u32 ack_seq, |
3425 | const u32 nwin) |
3426 | { |
3427 | return (after(ack, tp->snd_una) || |
3428 | after(ack_seq, tp->snd_wl1) || |
3429 | (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); |
3430 | } |
3431 | |
3432 | /* Update our send window. |
3433 | * |
3434 | * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 |
3435 | * and in FreeBSD. NetBSD's one is even worse.) is wrong. |
3436 | */ |
3437 | static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack, |
3438 | u32 ack_seq) |
3439 | { |
3440 | struct tcp_sock *tp = tcp_sk(sk); |
3441 | int flag = 0; |
3442 | u32 nwin = ntohs(tcp_hdr(skb)->window); |
3443 | |
3444 | if (likely(!tcp_hdr(skb)->syn)) |
3445 | nwin <<= tp->rx_opt.snd_wscale; |
3446 | |
3447 | if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { |
3448 | flag |= FLAG_WIN_UPDATE; |
3449 | tcp_update_wl(tp, ack_seq); |
3450 | |
3451 | if (tp->snd_wnd != nwin) { |
3452 | tp->snd_wnd = nwin; |
3453 | |
3454 | /* Note, it is the only place, where |
3455 | * fast path is recovered for sending TCP. |
3456 | */ |
3457 | tp->pred_flags = 0; |
3458 | tcp_fast_path_check(sk); |
3459 | |
3460 | if (nwin > tp->max_window) { |
3461 | tp->max_window = nwin; |
3462 | tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); |
3463 | } |
3464 | } |
3465 | } |
3466 | |
3467 | tp->snd_una = ack; |
3468 | |
3469 | return flag; |
3470 | } |
3471 | |
3472 | /* A very conservative spurious RTO response algorithm: reduce cwnd and |
3473 | * continue in congestion avoidance. |
3474 | */ |
3475 | static void tcp_conservative_spur_to_response(struct tcp_sock *tp) |
3476 | { |
3477 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); |
3478 | tp->snd_cwnd_cnt = 0; |
3479 | tp->bytes_acked = 0; |
3480 | TCP_ECN_queue_cwr(tp); |
3481 | tcp_moderate_cwnd(tp); |
3482 | } |
3483 | |
3484 | /* A conservative spurious RTO response algorithm: reduce cwnd using |
3485 | * rate halving and continue in congestion avoidance. |
3486 | */ |
3487 | static void tcp_ratehalving_spur_to_response(struct sock *sk) |
3488 | { |
3489 | tcp_enter_cwr(sk, 0); |
3490 | } |
3491 | |
3492 | static void tcp_undo_spur_to_response(struct sock *sk, int flag) |
3493 | { |
3494 | if (flag & FLAG_ECE) |
3495 | tcp_ratehalving_spur_to_response(sk); |
3496 | else |
3497 | tcp_undo_cwr(sk, 1); |
3498 | } |
3499 | |
3500 | /* F-RTO spurious RTO detection algorithm (RFC4138) |
3501 | * |
3502 | * F-RTO affects during two new ACKs following RTO (well, almost, see inline |
3503 | * comments). State (ACK number) is kept in frto_counter. When ACK advances |
3504 | * window (but not to or beyond highest sequence sent before RTO): |
3505 | * On First ACK, send two new segments out. |
3506 | * On Second ACK, RTO was likely spurious. Do spurious response (response |
3507 | * algorithm is not part of the F-RTO detection algorithm |
3508 | * given in RFC4138 but can be selected separately). |
3509 | * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss |
3510 | * and TCP falls back to conventional RTO recovery. F-RTO allows overriding |
3511 | * of Nagle, this is done using frto_counter states 2 and 3, when a new data |
3512 | * segment of any size sent during F-RTO, state 2 is upgraded to 3. |
3513 | * |
3514 | * Rationale: if the RTO was spurious, new ACKs should arrive from the |
3515 | * original window even after we transmit two new data segments. |
3516 | * |
3517 | * SACK version: |
3518 | * on first step, wait until first cumulative ACK arrives, then move to |
3519 | * the second step. In second step, the next ACK decides. |
3520 | * |
3521 | * F-RTO is implemented (mainly) in four functions: |
3522 | * - tcp_use_frto() is used to determine if TCP is can use F-RTO |
3523 | * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is |
3524 | * called when tcp_use_frto() showed green light |
3525 | * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm |
3526 | * - tcp_enter_frto_loss() is called if there is not enough evidence |
3527 | * to prove that the RTO is indeed spurious. It transfers the control |
3528 | * from F-RTO to the conventional RTO recovery |
3529 | */ |
3530 | static int tcp_process_frto(struct sock *sk, int flag) |
3531 | { |
3532 | struct tcp_sock *tp = tcp_sk(sk); |
3533 | |
3534 | tcp_verify_left_out(tp); |
3535 | |
3536 | /* Duplicate the behavior from Loss state (fastretrans_alert) */ |
3537 | if (flag & FLAG_DATA_ACKED) |
3538 | inet_csk(sk)->icsk_retransmits = 0; |
3539 | |
3540 | if ((flag & FLAG_NONHEAD_RETRANS_ACKED) || |
3541 | ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED))) |
3542 | tp->undo_marker = 0; |
3543 | |
3544 | if (!before(tp->snd_una, tp->frto_highmark)) { |
3545 | tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); |
3546 | return 1; |
3547 | } |
3548 | |
3549 | if (!tcp_is_sackfrto(tp)) { |
3550 | /* RFC4138 shortcoming in step 2; should also have case c): |
3551 | * ACK isn't duplicate nor advances window, e.g., opposite dir |
3552 | * data, winupdate |
3553 | */ |
3554 | if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP)) |
3555 | return 1; |
3556 | |
3557 | if (!(flag & FLAG_DATA_ACKED)) { |
3558 | tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), |
3559 | flag); |
3560 | return 1; |
3561 | } |
3562 | } else { |
3563 | if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { |
3564 | /* Prevent sending of new data. */ |
3565 | tp->snd_cwnd = min(tp->snd_cwnd, |
3566 | tcp_packets_in_flight(tp)); |
3567 | return 1; |
3568 | } |
3569 | |
3570 | if ((tp->frto_counter >= 2) && |
3571 | (!(flag & FLAG_FORWARD_PROGRESS) || |
3572 | ((flag & FLAG_DATA_SACKED) && |
3573 | !(flag & FLAG_ONLY_ORIG_SACKED)))) { |
3574 | /* RFC4138 shortcoming (see comment above) */ |
3575 | if (!(flag & FLAG_FORWARD_PROGRESS) && |
3576 | (flag & FLAG_NOT_DUP)) |
3577 | return 1; |
3578 | |
3579 | tcp_enter_frto_loss(sk, 3, flag); |
3580 | return 1; |
3581 | } |
3582 | } |
3583 | |
3584 | if (tp->frto_counter == 1) { |
3585 | /* tcp_may_send_now needs to see updated state */ |
3586 | tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; |
3587 | tp->frto_counter = 2; |
3588 | |
3589 | if (!tcp_may_send_now(sk)) |
3590 | tcp_enter_frto_loss(sk, 2, flag); |
3591 | |
3592 | return 1; |
3593 | } else { |
3594 | switch (sysctl_tcp_frto_response) { |
3595 | case 2: |
3596 | tcp_undo_spur_to_response(sk, flag); |
3597 | break; |
3598 | case 1: |
3599 | tcp_conservative_spur_to_response(tp); |
3600 | break; |
3601 | default: |
3602 | tcp_ratehalving_spur_to_response(sk); |
3603 | break; |
3604 | } |
3605 | tp->frto_counter = 0; |
3606 | tp->undo_marker = 0; |
3607 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS); |
3608 | } |
3609 | return 0; |
3610 | } |
3611 | |
3612 | /* This routine deals with incoming acks, but not outgoing ones. */ |
3613 | static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) |
3614 | { |
3615 | struct inet_connection_sock *icsk = inet_csk(sk); |
3616 | struct tcp_sock *tp = tcp_sk(sk); |
3617 | u32 prior_snd_una = tp->snd_una; |
3618 | u32 ack_seq = TCP_SKB_CB(skb)->seq; |
3619 | u32 ack = TCP_SKB_CB(skb)->ack_seq; |
3620 | u32 prior_in_flight; |
3621 | u32 prior_fackets; |
3622 | int prior_packets; |
3623 | int frto_cwnd = 0; |
3624 | |
3625 | /* If the ack is older than previous acks |
3626 | * then we can probably ignore it. |
3627 | */ |
3628 | if (before(ack, prior_snd_una)) |
3629 | goto old_ack; |
3630 | |
3631 | /* If the ack includes data we haven't sent yet, discard |
3632 | * this segment (RFC793 Section 3.9). |
3633 | */ |
3634 | if (after(ack, tp->snd_nxt)) |
3635 | goto invalid_ack; |
3636 | |
3637 | if (after(ack, prior_snd_una)) |
3638 | flag |= FLAG_SND_UNA_ADVANCED; |
3639 | |
3640 | if (sysctl_tcp_abc) { |
3641 | if (icsk->icsk_ca_state < TCP_CA_CWR) |
3642 | tp->bytes_acked += ack - prior_snd_una; |
3643 | else if (icsk->icsk_ca_state == TCP_CA_Loss) |
3644 | /* we assume just one segment left network */ |
3645 | tp->bytes_acked += min(ack - prior_snd_una, |
3646 | tp->mss_cache); |
3647 | } |
3648 | |
3649 | prior_fackets = tp->fackets_out; |
3650 | prior_in_flight = tcp_packets_in_flight(tp); |
3651 | |
3652 | if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) { |
3653 | /* Window is constant, pure forward advance. |
3654 | * No more checks are required. |
3655 | * Note, we use the fact that SND.UNA>=SND.WL2. |
3656 | */ |
3657 | tcp_update_wl(tp, ack_seq); |
3658 | tp->snd_una = ack; |
3659 | flag |= FLAG_WIN_UPDATE; |
3660 | |
3661 | tcp_ca_event(sk, CA_EVENT_FAST_ACK); |
3662 | |
3663 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); |
3664 | } else { |
3665 | if (ack_seq != TCP_SKB_CB(skb)->end_seq) |
3666 | flag |= FLAG_DATA; |
3667 | else |
3668 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS); |
3669 | |
3670 | flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); |
3671 | |
3672 | if (TCP_SKB_CB(skb)->sacked) |
3673 | flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); |
3674 | |
3675 | if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) |
3676 | flag |= FLAG_ECE; |
3677 | |
3678 | tcp_ca_event(sk, CA_EVENT_SLOW_ACK); |
3679 | } |
3680 | |
3681 | /* We passed data and got it acked, remove any soft error |
3682 | * log. Something worked... |
3683 | */ |
3684 | sk->sk_err_soft = 0; |
3685 | icsk->icsk_probes_out = 0; |
3686 | tp->rcv_tstamp = tcp_time_stamp; |
3687 | prior_packets = tp->packets_out; |
3688 | if (!prior_packets) |
3689 | goto no_queue; |
3690 | |
3691 | /* See if we can take anything off of the retransmit queue. */ |
3692 | flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una); |
3693 | |
3694 | if (tp->frto_counter) |
3695 | frto_cwnd = tcp_process_frto(sk, flag); |
3696 | /* Guarantee sacktag reordering detection against wrap-arounds */ |
3697 | if (before(tp->frto_highmark, tp->snd_una)) |
3698 | tp->frto_highmark = 0; |
3699 | |
3700 | if (tcp_ack_is_dubious(sk, flag)) { |
3701 | /* Advance CWND, if state allows this. */ |
3702 | if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && |
3703 | tcp_may_raise_cwnd(sk, flag)) |
3704 | tcp_cong_avoid(sk, ack, prior_in_flight); |
3705 | tcp_fastretrans_alert(sk, prior_packets - tp->packets_out, |
3706 | flag); |
3707 | } else { |
3708 | if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) |
3709 | tcp_cong_avoid(sk, ack, prior_in_flight); |
3710 | } |
3711 | |
3712 | if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) |
3713 | dst_confirm(sk->sk_dst_cache); |
3714 | |
3715 | return 1; |
3716 | |
3717 | no_queue: |
3718 | /* If this ack opens up a zero window, clear backoff. It was |
3719 | * being used to time the probes, and is probably far higher than |
3720 | * it needs to be for normal retransmission. |
3721 | */ |
3722 | if (tcp_send_head(sk)) |
3723 | tcp_ack_probe(sk); |
3724 | return 1; |
3725 | |
3726 | invalid_ack: |
3727 | SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt); |
3728 | return -1; |
3729 | |
3730 | old_ack: |
3731 | if (TCP_SKB_CB(skb)->sacked) { |
3732 | tcp_sacktag_write_queue(sk, skb, prior_snd_una); |
3733 | if (icsk->icsk_ca_state == TCP_CA_Open) |
3734 | tcp_try_keep_open(sk); |
3735 | } |
3736 | |
3737 | SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt); |
3738 | return 0; |
3739 | } |
3740 | |
3741 | /* Look for tcp options. Normally only called on SYN and SYNACK packets. |
3742 | * But, this can also be called on packets in the established flow when |
3743 | * the fast version below fails. |
3744 | */ |
3745 | void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, |
3746 | u8 **hvpp, int estab) |
3747 | { |
3748 | unsigned char *ptr; |
3749 | struct tcphdr *th = tcp_hdr(skb); |
3750 | int length = (th->doff * 4) - sizeof(struct tcphdr); |
3751 | |
3752 | ptr = (unsigned char *)(th + 1); |
3753 | opt_rx->saw_tstamp = 0; |
3754 | |
3755 | while (length > 0) { |
3756 | int opcode = *ptr++; |
3757 | int opsize; |
3758 | |
3759 | switch (opcode) { |
3760 | case TCPOPT_EOL: |
3761 | return; |
3762 | case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ |
3763 | length--; |
3764 | continue; |
3765 | default: |
3766 | opsize = *ptr++; |
3767 | if (opsize < 2) /* "silly options" */ |
3768 | return; |
3769 | if (opsize > length) |
3770 | return; /* don't parse partial options */ |
3771 | switch (opcode) { |
3772 | case TCPOPT_MSS: |
3773 | if (opsize == TCPOLEN_MSS && th->syn && !estab) { |
3774 | u16 in_mss = get_unaligned_be16(ptr); |
3775 | if (in_mss) { |
3776 | if (opt_rx->user_mss && |
3777 | opt_rx->user_mss < in_mss) |
3778 | in_mss = opt_rx->user_mss; |
3779 | opt_rx->mss_clamp = in_mss; |
3780 | } |
3781 | } |
3782 | break; |
3783 | case TCPOPT_WINDOW: |
3784 | if (opsize == TCPOLEN_WINDOW && th->syn && |
3785 | !estab && sysctl_tcp_window_scaling) { |
3786 | __u8 snd_wscale = *(__u8 *)ptr; |
3787 | opt_rx->wscale_ok = 1; |
3788 | if (snd_wscale > 14) { |
3789 | if (net_ratelimit()) |
3790 | printk(KERN_INFO "tcp_parse_options: Illegal window " |
3791 | "scaling value %d >14 received.\n", |
3792 | snd_wscale); |
3793 | snd_wscale = 14; |
3794 | } |
3795 | opt_rx->snd_wscale = snd_wscale; |
3796 | } |
3797 | break; |
3798 | case TCPOPT_TIMESTAMP: |
3799 | if ((opsize == TCPOLEN_TIMESTAMP) && |
3800 | ((estab && opt_rx->tstamp_ok) || |
3801 | (!estab && sysctl_tcp_timestamps))) { |
3802 | opt_rx->saw_tstamp = 1; |
3803 | opt_rx->rcv_tsval = get_unaligned_be32(ptr); |
3804 | opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4); |
3805 | } |
3806 | break; |
3807 | case TCPOPT_SACK_PERM: |
3808 | if (opsize == TCPOLEN_SACK_PERM && th->syn && |
3809 | !estab && sysctl_tcp_sack) { |
3810 | opt_rx->sack_ok = 1; |
3811 | tcp_sack_reset(opt_rx); |
3812 | } |
3813 | break; |
3814 | |
3815 | case TCPOPT_SACK: |
3816 | if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && |
3817 | !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && |
3818 | opt_rx->sack_ok) { |
3819 | TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; |
3820 | } |
3821 | break; |
3822 | #ifdef CONFIG_TCP_MD5SIG |
3823 | case TCPOPT_MD5SIG: |
3824 | /* |
3825 | * The MD5 Hash has already been |
3826 | * checked (see tcp_v{4,6}_do_rcv()). |
3827 | */ |
3828 | break; |
3829 | #endif |
3830 | case TCPOPT_COOKIE: |
3831 | /* This option is variable length. |
3832 | */ |
3833 | switch (opsize) { |
3834 | case TCPOLEN_COOKIE_BASE: |
3835 | /* not yet implemented */ |
3836 | break; |
3837 | case TCPOLEN_COOKIE_PAIR: |
3838 | /* not yet implemented */ |
3839 | break; |
3840 | case TCPOLEN_COOKIE_MIN+0: |
3841 | case TCPOLEN_COOKIE_MIN+2: |
3842 | case TCPOLEN_COOKIE_MIN+4: |
3843 | case TCPOLEN_COOKIE_MIN+6: |
3844 | case TCPOLEN_COOKIE_MAX: |
3845 | /* 16-bit multiple */ |
3846 | opt_rx->cookie_plus = opsize; |
3847 | *hvpp = ptr; |
3848 | default: |
3849 | /* ignore option */ |
3850 | break; |
3851 | }; |
3852 | break; |
3853 | }; |
3854 | |
3855 | ptr += opsize-2; |
3856 | length -= opsize; |
3857 | } |
3858 | } |
3859 | } |
3860 | |
3861 | static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th) |
3862 | { |
3863 | __be32 *ptr = (__be32 *)(th + 1); |
3864 | |
3865 | if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
3866 | | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { |
3867 | tp->rx_opt.saw_tstamp = 1; |
3868 | ++ptr; |
3869 | tp->rx_opt.rcv_tsval = ntohl(*ptr); |
3870 | ++ptr; |
3871 | tp->rx_opt.rcv_tsecr = ntohl(*ptr); |
3872 | return 1; |
3873 | } |
3874 | return 0; |
3875 | } |
3876 | |
3877 | /* Fast parse options. This hopes to only see timestamps. |
3878 | * If it is wrong it falls back on tcp_parse_options(). |
3879 | */ |
3880 | static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, |
3881 | struct tcp_sock *tp, u8 **hvpp) |
3882 | { |
3883 | /* In the spirit of fast parsing, compare doff directly to constant |
3884 | * values. Because equality is used, short doff can be ignored here. |
3885 | */ |
3886 | if (th->doff == (sizeof(*th) / 4)) { |
3887 | tp->rx_opt.saw_tstamp = 0; |
3888 | return 0; |
3889 | } else if (tp->rx_opt.tstamp_ok && |
3890 | th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { |
3891 | if (tcp_parse_aligned_timestamp(tp, th)) |
3892 | return 1; |
3893 | } |
3894 | tcp_parse_options(skb, &tp->rx_opt, hvpp, 1); |
3895 | return 1; |
3896 | } |
3897 | |
3898 | #ifdef CONFIG_TCP_MD5SIG |
3899 | /* |
3900 | * Parse MD5 Signature option |
3901 | */ |
3902 | u8 *tcp_parse_md5sig_option(struct tcphdr *th) |
3903 | { |
3904 | int length = (th->doff << 2) - sizeof (*th); |
3905 | u8 *ptr = (u8*)(th + 1); |
3906 | |
3907 | /* If the TCP option is too short, we can short cut */ |
3908 | if (length < TCPOLEN_MD5SIG) |
3909 | return NULL; |
3910 | |
3911 | while (length > 0) { |
3912 | int opcode = *ptr++; |
3913 | int opsize; |
3914 | |
3915 | switch(opcode) { |
3916 | case TCPOPT_EOL: |
3917 | return NULL; |
3918 | case TCPOPT_NOP: |
3919 | length--; |
3920 | continue; |
3921 | default: |
3922 | opsize = *ptr++; |
3923 | if (opsize < 2 || opsize > length) |
3924 | return NULL; |
3925 | if (opcode == TCPOPT_MD5SIG) |
3926 | return ptr; |
3927 | } |
3928 | ptr += opsize - 2; |
3929 | length -= opsize; |
3930 | } |
3931 | return NULL; |
3932 | } |
3933 | #endif |
3934 | |
3935 | static inline void tcp_store_ts_recent(struct tcp_sock *tp) |
3936 | { |
3937 | tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; |
3938 | tp->rx_opt.ts_recent_stamp = get_seconds(); |
3939 | } |
3940 | |
3941 | static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) |
3942 | { |
3943 | if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { |
3944 | /* PAWS bug workaround wrt. ACK frames, the PAWS discard |
3945 | * extra check below makes sure this can only happen |
3946 | * for pure ACK frames. -DaveM |
3947 | * |
3948 | * Not only, also it occurs for expired timestamps. |
3949 | */ |
3950 | |
3951 | if (tcp_paws_check(&tp->rx_opt, 0)) |
3952 | tcp_store_ts_recent(tp); |
3953 | } |
3954 | } |
3955 | |
3956 | /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM |
3957 | * |
3958 | * It is not fatal. If this ACK does _not_ change critical state (seqs, window) |
3959 | * it can pass through stack. So, the following predicate verifies that |
3960 | * this segment is not used for anything but congestion avoidance or |
3961 | * fast retransmit. Moreover, we even are able to eliminate most of such |
3962 | * second order effects, if we apply some small "replay" window (~RTO) |
3963 | * to timestamp space. |
3964 | * |
3965 | * All these measures still do not guarantee that we reject wrapped ACKs |
3966 | * on networks with high bandwidth, when sequence space is recycled fastly, |
3967 | * but it guarantees that such events will be very rare and do not affect |
3968 | * connection seriously. This doesn't look nice, but alas, PAWS is really |
3969 | * buggy extension. |
3970 | * |
3971 | * [ Later note. Even worse! It is buggy for segments _with_ data. RFC |
3972 | * states that events when retransmit arrives after original data are rare. |
3973 | * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is |
3974 | * the biggest problem on large power networks even with minor reordering. |
3975 | * OK, let's give it small replay window. If peer clock is even 1hz, it is safe |
3976 | * up to bandwidth of 18Gigabit/sec. 8) ] |
3977 | */ |
3978 | |
3979 | static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) |
3980 | { |
3981 | struct tcp_sock *tp = tcp_sk(sk); |
3982 | struct tcphdr *th = tcp_hdr(skb); |
3983 | u32 seq = TCP_SKB_CB(skb)->seq; |
3984 | u32 ack = TCP_SKB_CB(skb)->ack_seq; |
3985 | |
3986 | return (/* 1. Pure ACK with correct sequence number. */ |
3987 | (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && |
3988 | |
3989 | /* 2. ... and duplicate ACK. */ |
3990 | ack == tp->snd_una && |
3991 | |
3992 | /* 3. ... and does not update window. */ |
3993 | !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && |
3994 | |
3995 | /* 4. ... and sits in replay window. */ |
3996 | (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); |
3997 | } |
3998 | |
3999 | static inline int tcp_paws_discard(const struct sock *sk, |
4000 | const struct sk_buff *skb) |
4001 | { |
4002 | const struct tcp_sock *tp = tcp_sk(sk); |
4003 | |
4004 | return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) && |
4005 | !tcp_disordered_ack(sk, skb); |
4006 | } |
4007 | |
4008 | /* Check segment sequence number for validity. |
4009 | * |
4010 | * Segment controls are considered valid, if the segment |
4011 | * fits to the window after truncation to the window. Acceptability |
4012 | * of data (and SYN, FIN, of course) is checked separately. |
4013 | * See tcp_data_queue(), for example. |
4014 | * |
4015 | * Also, controls (RST is main one) are accepted using RCV.WUP instead |
4016 | * of RCV.NXT. Peer still did not advance his SND.UNA when we |
4017 | * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. |
4018 | * (borrowed from freebsd) |
4019 | */ |
4020 | |
4021 | static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) |
4022 | { |
4023 | return !before(end_seq, tp->rcv_wup) && |
4024 | !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); |
4025 | } |
4026 | |
4027 | /* When we get a reset we do this. */ |
4028 | static void tcp_reset(struct sock *sk) |
4029 | { |
4030 | /* We want the right error as BSD sees it (and indeed as we do). */ |
4031 | switch (sk->sk_state) { |
4032 | case TCP_SYN_SENT: |
4033 | sk->sk_err = ECONNREFUSED; |
4034 | break; |
4035 | case TCP_CLOSE_WAIT: |
4036 | sk->sk_err = EPIPE; |
4037 | break; |
4038 | case TCP_CLOSE: |
4039 | return; |
4040 | default: |
4041 | sk->sk_err = ECONNRESET; |
4042 | } |
4043 | |
4044 | if (!sock_flag(sk, SOCK_DEAD)) |
4045 | sk->sk_error_report(sk); |
4046 | |
4047 | tcp_done(sk); |
4048 | } |
4049 | |
4050 | /* |
4051 | * Process the FIN bit. This now behaves as it is supposed to work |
4052 | * and the FIN takes effect when it is validly part of sequence |
4053 | * space. Not before when we get holes. |
4054 | * |
4055 | * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT |
4056 | * (and thence onto LAST-ACK and finally, CLOSE, we never enter |
4057 | * TIME-WAIT) |
4058 | * |
4059 | * If we are in FINWAIT-1, a received FIN indicates simultaneous |
4060 | * close and we go into CLOSING (and later onto TIME-WAIT) |
4061 | * |
4062 | * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. |
4063 | */ |
4064 | static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) |
4065 | { |
4066 | struct tcp_sock *tp = tcp_sk(sk); |
4067 | |
4068 | inet_csk_schedule_ack(sk); |
4069 | |
4070 | sk->sk_shutdown |= RCV_SHUTDOWN; |
4071 | sock_set_flag(sk, SOCK_DONE); |
4072 | |
4073 | switch (sk->sk_state) { |
4074 | case TCP_SYN_RECV: |
4075 | case TCP_ESTABLISHED: |
4076 | /* Move to CLOSE_WAIT */ |
4077 | tcp_set_state(sk, TCP_CLOSE_WAIT); |
4078 | inet_csk(sk)->icsk_ack.pingpong = 1; |
4079 | break; |
4080 | |
4081 | case TCP_CLOSE_WAIT: |
4082 | case TCP_CLOSING: |
4083 | /* Received a retransmission of the FIN, do |
4084 | * nothing. |
4085 | */ |
4086 | break; |
4087 | case TCP_LAST_ACK: |
4088 | /* RFC793: Remain in the LAST-ACK state. */ |
4089 | break; |
4090 | |
4091 | case TCP_FIN_WAIT1: |
4092 | /* This case occurs when a simultaneous close |
4093 | * happens, we must ack the received FIN and |
4094 | * enter the CLOSING state. |
4095 | */ |
4096 | tcp_send_ack(sk); |
4097 | tcp_set_state(sk, TCP_CLOSING); |
4098 | break; |
4099 | case TCP_FIN_WAIT2: |
4100 | /* Received a FIN -- send ACK and enter TIME_WAIT. */ |
4101 | tcp_send_ack(sk); |
4102 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); |
4103 | break; |
4104 | default: |
4105 | /* Only TCP_LISTEN and TCP_CLOSE are left, in these |
4106 | * cases we should never reach this piece of code. |
4107 | */ |
4108 | printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", |
4109 | __func__, sk->sk_state); |
4110 | break; |
4111 | } |
4112 | |
4113 | /* It _is_ possible, that we have something out-of-order _after_ FIN. |
4114 | * Probably, we should reset in this case. For now drop them. |
4115 | */ |
4116 | __skb_queue_purge(&tp->out_of_order_queue); |
4117 | if (tcp_is_sack(tp)) |
4118 | tcp_sack_reset(&tp->rx_opt); |
4119 | sk_mem_reclaim(sk); |
4120 | |
4121 | if (!sock_flag(sk, SOCK_DEAD)) { |
4122 | sk->sk_state_change(sk); |
4123 | |
4124 | /* Do not send POLL_HUP for half duplex close. */ |
4125 | if (sk->sk_shutdown == SHUTDOWN_MASK || |
4126 | sk->sk_state == TCP_CLOSE) |
4127 | sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); |
4128 | else |
4129 | sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); |
4130 | } |
4131 | } |
4132 | |
4133 | static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, |
4134 | u32 end_seq) |
4135 | { |
4136 | if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { |
4137 | if (before(seq, sp->start_seq)) |
4138 | sp->start_seq = seq; |
4139 | if (after(end_seq, sp->end_seq)) |
4140 | sp->end_seq = end_seq; |
4141 | return 1; |
4142 | } |
4143 | return 0; |
4144 | } |
4145 | |
4146 | static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) |
4147 | { |
4148 | struct tcp_sock *tp = tcp_sk(sk); |
4149 | |
4150 | if (tcp_is_sack(tp) && sysctl_tcp_dsack) { |
4151 | int mib_idx; |
4152 | |
4153 | if (before(seq, tp->rcv_nxt)) |
4154 | mib_idx = LINUX_MIB_TCPDSACKOLDSENT; |
4155 | else |
4156 | mib_idx = LINUX_MIB_TCPDSACKOFOSENT; |
4157 | |
4158 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
4159 | |
4160 | tp->rx_opt.dsack = 1; |
4161 | tp->duplicate_sack[0].start_seq = seq; |
4162 | tp->duplicate_sack[0].end_seq = end_seq; |
4163 | } |
4164 | } |
4165 | |
4166 | static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq) |
4167 | { |
4168 | struct tcp_sock *tp = tcp_sk(sk); |
4169 | |
4170 | if (!tp->rx_opt.dsack) |
4171 | tcp_dsack_set(sk, seq, end_seq); |
4172 | else |
4173 | tcp_sack_extend(tp->duplicate_sack, seq, end_seq); |
4174 | } |
4175 | |
4176 | static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) |
4177 | { |
4178 | struct tcp_sock *tp = tcp_sk(sk); |
4179 | |
4180 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
4181 | before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
4182 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); |
4183 | tcp_enter_quickack_mode(sk); |
4184 | |
4185 | if (tcp_is_sack(tp) && sysctl_tcp_dsack) { |
4186 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; |
4187 | |
4188 | if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) |
4189 | end_seq = tp->rcv_nxt; |
4190 | tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq); |
4191 | } |
4192 | } |
4193 | |
4194 | tcp_send_ack(sk); |
4195 | } |
4196 | |
4197 | /* These routines update the SACK block as out-of-order packets arrive or |
4198 | * in-order packets close up the sequence space. |
4199 | */ |
4200 | static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) |
4201 | { |
4202 | int this_sack; |
4203 | struct tcp_sack_block *sp = &tp->selective_acks[0]; |
4204 | struct tcp_sack_block *swalk = sp + 1; |
4205 | |
4206 | /* See if the recent change to the first SACK eats into |
4207 | * or hits the sequence space of other SACK blocks, if so coalesce. |
4208 | */ |
4209 | for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) { |
4210 | if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { |
4211 | int i; |
4212 | |
4213 | /* Zap SWALK, by moving every further SACK up by one slot. |
4214 | * Decrease num_sacks. |
4215 | */ |
4216 | tp->rx_opt.num_sacks--; |
4217 | for (i = this_sack; i < tp->rx_opt.num_sacks; i++) |
4218 | sp[i] = sp[i + 1]; |
4219 | continue; |
4220 | } |
4221 | this_sack++, swalk++; |
4222 | } |
4223 | } |
4224 | |
4225 | static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) |
4226 | { |
4227 | struct tcp_sock *tp = tcp_sk(sk); |
4228 | struct tcp_sack_block *sp = &tp->selective_acks[0]; |
4229 | int cur_sacks = tp->rx_opt.num_sacks; |
4230 | int this_sack; |
4231 | |
4232 | if (!cur_sacks) |
4233 | goto new_sack; |
4234 | |
4235 | for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) { |
4236 | if (tcp_sack_extend(sp, seq, end_seq)) { |
4237 | /* Rotate this_sack to the first one. */ |
4238 | for (; this_sack > 0; this_sack--, sp--) |
4239 | swap(*sp, *(sp - 1)); |
4240 | if (cur_sacks > 1) |
4241 | tcp_sack_maybe_coalesce(tp); |
4242 | return; |
4243 | } |
4244 | } |
4245 | |
4246 | /* Could not find an adjacent existing SACK, build a new one, |
4247 | * put it at the front, and shift everyone else down. We |
4248 | * always know there is at least one SACK present already here. |
4249 | * |
4250 | * If the sack array is full, forget about the last one. |
4251 | */ |
4252 | if (this_sack >= TCP_NUM_SACKS) { |
4253 | this_sack--; |
4254 | tp->rx_opt.num_sacks--; |
4255 | sp--; |
4256 | } |
4257 | for (; this_sack > 0; this_sack--, sp--) |
4258 | *sp = *(sp - 1); |
4259 | |
4260 | new_sack: |
4261 | /* Build the new head SACK, and we're done. */ |
4262 | sp->start_seq = seq; |
4263 | sp->end_seq = end_seq; |
4264 | tp->rx_opt.num_sacks++; |
4265 | } |
4266 | |
4267 | /* RCV.NXT advances, some SACKs should be eaten. */ |
4268 | |
4269 | static void tcp_sack_remove(struct tcp_sock *tp) |
4270 | { |
4271 | struct tcp_sack_block *sp = &tp->selective_acks[0]; |
4272 | int num_sacks = tp->rx_opt.num_sacks; |
4273 | int this_sack; |
4274 | |
4275 | /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ |
4276 | if (skb_queue_empty(&tp->out_of_order_queue)) { |
4277 | tp->rx_opt.num_sacks = 0; |
4278 | return; |
4279 | } |
4280 | |
4281 | for (this_sack = 0; this_sack < num_sacks;) { |
4282 | /* Check if the start of the sack is covered by RCV.NXT. */ |
4283 | if (!before(tp->rcv_nxt, sp->start_seq)) { |
4284 | int i; |
4285 | |
4286 | /* RCV.NXT must cover all the block! */ |
4287 | WARN_ON(before(tp->rcv_nxt, sp->end_seq)); |
4288 | |
4289 | /* Zap this SACK, by moving forward any other SACKS. */ |
4290 | for (i=this_sack+1; i < num_sacks; i++) |
4291 | tp->selective_acks[i-1] = tp->selective_acks[i]; |
4292 | num_sacks--; |
4293 | continue; |
4294 | } |
4295 | this_sack++; |
4296 | sp++; |
4297 | } |
4298 | tp->rx_opt.num_sacks = num_sacks; |
4299 | } |
4300 | |
4301 | /* This one checks to see if we can put data from the |
4302 | * out_of_order queue into the receive_queue. |
4303 | */ |
4304 | static void tcp_ofo_queue(struct sock *sk) |
4305 | { |
4306 | struct tcp_sock *tp = tcp_sk(sk); |
4307 | __u32 dsack_high = tp->rcv_nxt; |
4308 | struct sk_buff *skb; |
4309 | |
4310 | while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { |
4311 | if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) |
4312 | break; |
4313 | |
4314 | if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { |
4315 | __u32 dsack = dsack_high; |
4316 | if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) |
4317 | dsack_high = TCP_SKB_CB(skb)->end_seq; |
4318 | tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack); |
4319 | } |
4320 | |
4321 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { |
4322 | SOCK_DEBUG(sk, "ofo packet was already received \n"); |
4323 | __skb_unlink(skb, &tp->out_of_order_queue); |
4324 | __kfree_skb(skb); |
4325 | continue; |
4326 | } |
4327 | SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", |
4328 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, |
4329 | TCP_SKB_CB(skb)->end_seq); |
4330 | |
4331 | __skb_unlink(skb, &tp->out_of_order_queue); |
4332 | __skb_queue_tail(&sk->sk_receive_queue, skb); |
4333 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
4334 | if (tcp_hdr(skb)->fin) |
4335 | tcp_fin(skb, sk, tcp_hdr(skb)); |
4336 | } |
4337 | } |
4338 | |
4339 | static int tcp_prune_ofo_queue(struct sock *sk); |
4340 | static int tcp_prune_queue(struct sock *sk); |
4341 | |
4342 | static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size) |
4343 | { |
4344 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || |
4345 | !sk_rmem_schedule(sk, size)) { |
4346 | |
4347 | if (tcp_prune_queue(sk) < 0) |
4348 | return -1; |
4349 | |
4350 | if (!sk_rmem_schedule(sk, size)) { |
4351 | if (!tcp_prune_ofo_queue(sk)) |
4352 | return -1; |
4353 | |
4354 | if (!sk_rmem_schedule(sk, size)) |
4355 | return -1; |
4356 | } |
4357 | } |
4358 | return 0; |
4359 | } |
4360 | |
4361 | static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) |
4362 | { |
4363 | struct tcphdr *th = tcp_hdr(skb); |
4364 | struct tcp_sock *tp = tcp_sk(sk); |
4365 | int eaten = -1; |
4366 | |
4367 | if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) |
4368 | goto drop; |
4369 | |
4370 | __skb_pull(skb, th->doff * 4); |
4371 | |
4372 | TCP_ECN_accept_cwr(tp, skb); |
4373 | |
4374 | tp->rx_opt.dsack = 0; |
4375 | |
4376 | /* Queue data for delivery to the user. |
4377 | * Packets in sequence go to the receive queue. |
4378 | * Out of sequence packets to the out_of_order_queue. |
4379 | */ |
4380 | if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { |
4381 | if (tcp_receive_window(tp) == 0) |
4382 | goto out_of_window; |
4383 | |
4384 | /* Ok. In sequence. In window. */ |
4385 | if (tp->ucopy.task == current && |
4386 | tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && |
4387 | sock_owned_by_user(sk) && !tp->urg_data) { |
4388 | int chunk = min_t(unsigned int, skb->len, |
4389 | tp->ucopy.len); |
4390 | |
4391 | __set_current_state(TASK_RUNNING); |
4392 | |
4393 | local_bh_enable(); |
4394 | if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { |
4395 | tp->ucopy.len -= chunk; |
4396 | tp->copied_seq += chunk; |
4397 | eaten = (chunk == skb->len && !th->fin); |
4398 | tcp_rcv_space_adjust(sk); |
4399 | } |
4400 | local_bh_disable(); |
4401 | } |
4402 | |
4403 | if (eaten <= 0) { |
4404 | queue_and_out: |
4405 | if (eaten < 0 && |
4406 | tcp_try_rmem_schedule(sk, skb->truesize)) |
4407 | goto drop; |
4408 | |
4409 | skb_set_owner_r(skb, sk); |
4410 | __skb_queue_tail(&sk->sk_receive_queue, skb); |
4411 | } |
4412 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
4413 | if (skb->len) |
4414 | tcp_event_data_recv(sk, skb); |
4415 | if (th->fin) |
4416 | tcp_fin(skb, sk, th); |
4417 | |
4418 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
4419 | tcp_ofo_queue(sk); |
4420 | |
4421 | /* RFC2581. 4.2. SHOULD send immediate ACK, when |
4422 | * gap in queue is filled. |
4423 | */ |
4424 | if (skb_queue_empty(&tp->out_of_order_queue)) |
4425 | inet_csk(sk)->icsk_ack.pingpong = 0; |
4426 | } |
4427 | |
4428 | if (tp->rx_opt.num_sacks) |
4429 | tcp_sack_remove(tp); |
4430 | |
4431 | tcp_fast_path_check(sk); |
4432 | |
4433 | if (eaten > 0) |
4434 | __kfree_skb(skb); |
4435 | else if (!sock_flag(sk, SOCK_DEAD)) |
4436 | sk->sk_data_ready(sk, 0); |
4437 | return; |
4438 | } |
4439 | |
4440 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { |
4441 | /* A retransmit, 2nd most common case. Force an immediate ack. */ |
4442 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); |
4443 | tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); |
4444 | |
4445 | out_of_window: |
4446 | tcp_enter_quickack_mode(sk); |
4447 | inet_csk_schedule_ack(sk); |
4448 | drop: |
4449 | __kfree_skb(skb); |
4450 | return; |
4451 | } |
4452 | |
4453 | /* Out of window. F.e. zero window probe. */ |
4454 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) |
4455 | goto out_of_window; |
4456 | |
4457 | tcp_enter_quickack_mode(sk); |
4458 | |
4459 | if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
4460 | /* Partial packet, seq < rcv_next < end_seq */ |
4461 | SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", |
4462 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, |
4463 | TCP_SKB_CB(skb)->end_seq); |
4464 | |
4465 | tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); |
4466 | |
4467 | /* If window is closed, drop tail of packet. But after |
4468 | * remembering D-SACK for its head made in previous line. |
4469 | */ |
4470 | if (!tcp_receive_window(tp)) |
4471 | goto out_of_window; |
4472 | goto queue_and_out; |
4473 | } |
4474 | |
4475 | TCP_ECN_check_ce(tp, skb); |
4476 | |
4477 | if (tcp_try_rmem_schedule(sk, skb->truesize)) |
4478 | goto drop; |
4479 | |
4480 | /* Disable header prediction. */ |
4481 | tp->pred_flags = 0; |
4482 | inet_csk_schedule_ack(sk); |
4483 | |
4484 | SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", |
4485 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); |
4486 | |
4487 | skb_set_owner_r(skb, sk); |
4488 | |
4489 | if (!skb_peek(&tp->out_of_order_queue)) { |
4490 | /* Initial out of order segment, build 1 SACK. */ |
4491 | if (tcp_is_sack(tp)) { |
4492 | tp->rx_opt.num_sacks = 1; |
4493 | tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; |
4494 | tp->selective_acks[0].end_seq = |
4495 | TCP_SKB_CB(skb)->end_seq; |
4496 | } |
4497 | __skb_queue_head(&tp->out_of_order_queue, skb); |
4498 | } else { |
4499 | struct sk_buff *skb1 = skb_peek_tail(&tp->out_of_order_queue); |
4500 | u32 seq = TCP_SKB_CB(skb)->seq; |
4501 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; |
4502 | |
4503 | if (seq == TCP_SKB_CB(skb1)->end_seq) { |
4504 | __skb_queue_after(&tp->out_of_order_queue, skb1, skb); |
4505 | |
4506 | if (!tp->rx_opt.num_sacks || |
4507 | tp->selective_acks[0].end_seq != seq) |
4508 | goto add_sack; |
4509 | |
4510 | /* Common case: data arrive in order after hole. */ |
4511 | tp->selective_acks[0].end_seq = end_seq; |
4512 | return; |
4513 | } |
4514 | |
4515 | /* Find place to insert this segment. */ |
4516 | while (1) { |
4517 | if (!after(TCP_SKB_CB(skb1)->seq, seq)) |
4518 | break; |
4519 | if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) { |
4520 | skb1 = NULL; |
4521 | break; |
4522 | } |
4523 | skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1); |
4524 | } |
4525 | |
4526 | /* Do skb overlap to previous one? */ |
4527 | if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) { |
4528 | if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { |
4529 | /* All the bits are present. Drop. */ |
4530 | __kfree_skb(skb); |
4531 | tcp_dsack_set(sk, seq, end_seq); |
4532 | goto add_sack; |
4533 | } |
4534 | if (after(seq, TCP_SKB_CB(skb1)->seq)) { |
4535 | /* Partial overlap. */ |
4536 | tcp_dsack_set(sk, seq, |
4537 | TCP_SKB_CB(skb1)->end_seq); |
4538 | } else { |
4539 | if (skb_queue_is_first(&tp->out_of_order_queue, |
4540 | skb1)) |
4541 | skb1 = NULL; |
4542 | else |
4543 | skb1 = skb_queue_prev( |
4544 | &tp->out_of_order_queue, |
4545 | skb1); |
4546 | } |
4547 | } |
4548 | if (!skb1) |
4549 | __skb_queue_head(&tp->out_of_order_queue, skb); |
4550 | else |
4551 | __skb_queue_after(&tp->out_of_order_queue, skb1, skb); |
4552 | |
4553 | /* And clean segments covered by new one as whole. */ |
4554 | while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) { |
4555 | skb1 = skb_queue_next(&tp->out_of_order_queue, skb); |
4556 | |
4557 | if (!after(end_seq, TCP_SKB_CB(skb1)->seq)) |
4558 | break; |
4559 | if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { |
4560 | tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, |
4561 | end_seq); |
4562 | break; |
4563 | } |
4564 | __skb_unlink(skb1, &tp->out_of_order_queue); |
4565 | tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, |
4566 | TCP_SKB_CB(skb1)->end_seq); |
4567 | __kfree_skb(skb1); |
4568 | } |
4569 | |
4570 | add_sack: |
4571 | if (tcp_is_sack(tp)) |
4572 | tcp_sack_new_ofo_skb(sk, seq, end_seq); |
4573 | } |
4574 | } |
4575 | |
4576 | static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, |
4577 | struct sk_buff_head *list) |
4578 | { |
4579 | struct sk_buff *next = NULL; |
4580 | |
4581 | if (!skb_queue_is_last(list, skb)) |
4582 | next = skb_queue_next(list, skb); |
4583 | |
4584 | __skb_unlink(skb, list); |
4585 | __kfree_skb(skb); |
4586 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED); |
4587 | |
4588 | return next; |
4589 | } |
4590 | |
4591 | /* Collapse contiguous sequence of skbs head..tail with |
4592 | * sequence numbers start..end. |
4593 | * |
4594 | * If tail is NULL, this means until the end of the list. |
4595 | * |
4596 | * Segments with FIN/SYN are not collapsed (only because this |
4597 | * simplifies code) |
4598 | */ |
4599 | static void |
4600 | tcp_collapse(struct sock *sk, struct sk_buff_head *list, |
4601 | struct sk_buff *head, struct sk_buff *tail, |
4602 | u32 start, u32 end) |
4603 | { |
4604 | struct sk_buff *skb, *n; |
4605 | bool end_of_skbs; |
4606 | |
4607 | /* First, check that queue is collapsible and find |
4608 | * the point where collapsing can be useful. */ |
4609 | skb = head; |
4610 | restart: |
4611 | end_of_skbs = true; |
4612 | skb_queue_walk_from_safe(list, skb, n) { |
4613 | if (skb == tail) |
4614 | break; |
4615 | /* No new bits? It is possible on ofo queue. */ |
4616 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { |
4617 | skb = tcp_collapse_one(sk, skb, list); |
4618 | if (!skb) |
4619 | break; |
4620 | goto restart; |
4621 | } |
4622 | |
4623 | /* The first skb to collapse is: |
4624 | * - not SYN/FIN and |
4625 | * - bloated or contains data before "start" or |
4626 | * overlaps to the next one. |
4627 | */ |
4628 | if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && |
4629 | (tcp_win_from_space(skb->truesize) > skb->len || |
4630 | before(TCP_SKB_CB(skb)->seq, start))) { |
4631 | end_of_skbs = false; |
4632 | break; |
4633 | } |
4634 | |
4635 | if (!skb_queue_is_last(list, skb)) { |
4636 | struct sk_buff *next = skb_queue_next(list, skb); |
4637 | if (next != tail && |
4638 | TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) { |
4639 | end_of_skbs = false; |
4640 | break; |
4641 | } |
4642 | } |
4643 | |
4644 | /* Decided to skip this, advance start seq. */ |
4645 | start = TCP_SKB_CB(skb)->end_seq; |
4646 | } |
4647 | if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) |
4648 | return; |
4649 | |
4650 | while (before(start, end)) { |
4651 | struct sk_buff *nskb; |
4652 | unsigned int header = skb_headroom(skb); |
4653 | int copy = SKB_MAX_ORDER(header, 0); |
4654 | |
4655 | /* Too big header? This can happen with IPv6. */ |
4656 | if (copy < 0) |
4657 | return; |
4658 | if (end - start < copy) |
4659 | copy = end - start; |
4660 | nskb = alloc_skb(copy + header, GFP_ATOMIC); |
4661 | if (!nskb) |
4662 | return; |
4663 | |
4664 | skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); |
4665 | skb_set_network_header(nskb, (skb_network_header(skb) - |
4666 | skb->head)); |
4667 | skb_set_transport_header(nskb, (skb_transport_header(skb) - |
4668 | skb->head)); |
4669 | skb_reserve(nskb, header); |
4670 | memcpy(nskb->head, skb->head, header); |
4671 | memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); |
4672 | TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; |
4673 | __skb_queue_before(list, skb, nskb); |
4674 | skb_set_owner_r(nskb, sk); |
4675 | |
4676 | /* Copy data, releasing collapsed skbs. */ |
4677 | while (copy > 0) { |
4678 | int offset = start - TCP_SKB_CB(skb)->seq; |
4679 | int size = TCP_SKB_CB(skb)->end_seq - start; |
4680 | |
4681 | BUG_ON(offset < 0); |
4682 | if (size > 0) { |
4683 | size = min(copy, size); |
4684 | if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) |
4685 | BUG(); |
4686 | TCP_SKB_CB(nskb)->end_seq += size; |
4687 | copy -= size; |
4688 | start += size; |
4689 | } |
4690 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { |
4691 | skb = tcp_collapse_one(sk, skb, list); |
4692 | if (!skb || |
4693 | skb == tail || |
4694 | tcp_hdr(skb)->syn || |
4695 | tcp_hdr(skb)->fin) |
4696 | return; |
4697 | } |
4698 | } |
4699 | } |
4700 | } |
4701 | |
4702 | /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs |
4703 | * and tcp_collapse() them until all the queue is collapsed. |
4704 | */ |
4705 | static void tcp_collapse_ofo_queue(struct sock *sk) |
4706 | { |
4707 | struct tcp_sock *tp = tcp_sk(sk); |
4708 | struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); |
4709 | struct sk_buff *head; |
4710 | u32 start, end; |
4711 | |
4712 | if (skb == NULL) |
4713 | return; |
4714 | |
4715 | start = TCP_SKB_CB(skb)->seq; |
4716 | end = TCP_SKB_CB(skb)->end_seq; |
4717 | head = skb; |
4718 | |
4719 | for (;;) { |
4720 | struct sk_buff *next = NULL; |
4721 | |
4722 | if (!skb_queue_is_last(&tp->out_of_order_queue, skb)) |
4723 | next = skb_queue_next(&tp->out_of_order_queue, skb); |
4724 | skb = next; |
4725 | |
4726 | /* Segment is terminated when we see gap or when |
4727 | * we are at the end of all the queue. */ |
4728 | if (!skb || |
4729 | after(TCP_SKB_CB(skb)->seq, end) || |
4730 | before(TCP_SKB_CB(skb)->end_seq, start)) { |
4731 | tcp_collapse(sk, &tp->out_of_order_queue, |
4732 | head, skb, start, end); |
4733 | head = skb; |
4734 | if (!skb) |
4735 | break; |
4736 | /* Start new segment */ |
4737 | start = TCP_SKB_CB(skb)->seq; |
4738 | end = TCP_SKB_CB(skb)->end_seq; |
4739 | } else { |
4740 | if (before(TCP_SKB_CB(skb)->seq, start)) |
4741 | start = TCP_SKB_CB(skb)->seq; |
4742 | if (after(TCP_SKB_CB(skb)->end_seq, end)) |
4743 | end = TCP_SKB_CB(skb)->end_seq; |
4744 | } |
4745 | } |
4746 | } |
4747 | |
4748 | /* |
4749 | * Purge the out-of-order queue. |
4750 | * Return true if queue was pruned. |
4751 | */ |
4752 | static int tcp_prune_ofo_queue(struct sock *sk) |
4753 | { |
4754 | struct tcp_sock *tp = tcp_sk(sk); |
4755 | int res = 0; |
4756 | |
4757 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
4758 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED); |
4759 | __skb_queue_purge(&tp->out_of_order_queue); |
4760 | |
4761 | /* Reset SACK state. A conforming SACK implementation will |
4762 | * do the same at a timeout based retransmit. When a connection |
4763 | * is in a sad state like this, we care only about integrity |
4764 | * of the connection not performance. |
4765 | */ |
4766 | if (tp->rx_opt.sack_ok) |
4767 | tcp_sack_reset(&tp->rx_opt); |
4768 | sk_mem_reclaim(sk); |
4769 | res = 1; |
4770 | } |
4771 | return res; |
4772 | } |
4773 | |
4774 | /* Reduce allocated memory if we can, trying to get |
4775 | * the socket within its memory limits again. |
4776 | * |
4777 | * Return less than zero if we should start dropping frames |
4778 | * until the socket owning process reads some of the data |
4779 | * to stabilize the situation. |
4780 | */ |
4781 | static int tcp_prune_queue(struct sock *sk) |
4782 | { |
4783 | struct tcp_sock *tp = tcp_sk(sk); |
4784 | |
4785 | SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); |
4786 | |
4787 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED); |
4788 | |
4789 | if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) |
4790 | tcp_clamp_window(sk); |
4791 | else if (tcp_memory_pressure) |
4792 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); |
4793 | |
4794 | tcp_collapse_ofo_queue(sk); |
4795 | if (!skb_queue_empty(&sk->sk_receive_queue)) |
4796 | tcp_collapse(sk, &sk->sk_receive_queue, |
4797 | skb_peek(&sk->sk_receive_queue), |
4798 | NULL, |
4799 | tp->copied_seq, tp->rcv_nxt); |
4800 | sk_mem_reclaim(sk); |
4801 | |
4802 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) |
4803 | return 0; |
4804 | |
4805 | /* Collapsing did not help, destructive actions follow. |
4806 | * This must not ever occur. */ |
4807 | |
4808 | tcp_prune_ofo_queue(sk); |
4809 | |
4810 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) |
4811 | return 0; |
4812 | |
4813 | /* If we are really being abused, tell the caller to silently |
4814 | * drop receive data on the floor. It will get retransmitted |
4815 | * and hopefully then we'll have sufficient space. |
4816 | */ |
4817 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED); |
4818 | |
4819 | /* Massive buffer overcommit. */ |
4820 | tp->pred_flags = 0; |
4821 | return -1; |
4822 | } |
4823 | |
4824 | /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. |
4825 | * As additional protections, we do not touch cwnd in retransmission phases, |
4826 | * and if application hit its sndbuf limit recently. |
4827 | */ |
4828 | void tcp_cwnd_application_limited(struct sock *sk) |
4829 | { |
4830 | struct tcp_sock *tp = tcp_sk(sk); |
4831 | |
4832 | if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && |
4833 | sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { |
4834 | /* Limited by application or receiver window. */ |
4835 | u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); |
4836 | u32 win_used = max(tp->snd_cwnd_used, init_win); |
4837 | if (win_used < tp->snd_cwnd) { |
4838 | tp->snd_ssthresh = tcp_current_ssthresh(sk); |
4839 | tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; |
4840 | } |
4841 | tp->snd_cwnd_used = 0; |
4842 | } |
4843 | tp->snd_cwnd_stamp = tcp_time_stamp; |
4844 | } |
4845 | |
4846 | static int tcp_should_expand_sndbuf(struct sock *sk) |
4847 | { |
4848 | struct tcp_sock *tp = tcp_sk(sk); |
4849 | |
4850 | /* If the user specified a specific send buffer setting, do |
4851 | * not modify it. |
4852 | */ |
4853 | if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) |
4854 | return 0; |
4855 | |
4856 | /* If we are under global TCP memory pressure, do not expand. */ |
4857 | if (tcp_memory_pressure) |
4858 | return 0; |
4859 | |
4860 | /* If we are under soft global TCP memory pressure, do not expand. */ |
4861 | if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) |
4862 | return 0; |
4863 | |
4864 | /* If we filled the congestion window, do not expand. */ |
4865 | if (tp->packets_out >= tp->snd_cwnd) |
4866 | return 0; |
4867 | |
4868 | return 1; |
4869 | } |
4870 | |
4871 | /* When incoming ACK allowed to free some skb from write_queue, |
4872 | * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket |
4873 | * on the exit from tcp input handler. |
4874 | * |
4875 | * PROBLEM: sndbuf expansion does not work well with largesend. |
4876 | */ |
4877 | static void tcp_new_space(struct sock *sk) |
4878 | { |
4879 | struct tcp_sock *tp = tcp_sk(sk); |
4880 | |
4881 | if (tcp_should_expand_sndbuf(sk)) { |
4882 | int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + |
4883 | MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); |
4884 | int demanded = max_t(unsigned int, tp->snd_cwnd, |
4885 | tp->reordering + 1); |
4886 | sndmem *= 2 * demanded; |
4887 | if (sndmem > sk->sk_sndbuf) |
4888 | sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); |
4889 | tp->snd_cwnd_stamp = tcp_time_stamp; |
4890 | } |
4891 | |
4892 | sk->sk_write_space(sk); |
4893 | } |
4894 | |
4895 | static void tcp_check_space(struct sock *sk) |
4896 | { |
4897 | if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { |
4898 | sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); |
4899 | if (sk->sk_socket && |
4900 | test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) |
4901 | tcp_new_space(sk); |
4902 | } |
4903 | } |
4904 | |
4905 | static inline void tcp_data_snd_check(struct sock *sk) |
4906 | { |
4907 | tcp_push_pending_frames(sk); |
4908 | tcp_check_space(sk); |
4909 | } |
4910 | |
4911 | /* |
4912 | * Check if sending an ack is needed. |
4913 | */ |
4914 | static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) |
4915 | { |
4916 | struct tcp_sock *tp = tcp_sk(sk); |
4917 | |
4918 | /* More than one full frame received... */ |
4919 | if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && |
4920 | /* ... and right edge of window advances far enough. |
4921 | * (tcp_recvmsg() will send ACK otherwise). Or... |
4922 | */ |
4923 | __tcp_select_window(sk) >= tp->rcv_wnd) || |
4924 | /* We ACK each frame or... */ |
4925 | tcp_in_quickack_mode(sk) || |
4926 | /* We have out of order data. */ |
4927 | (ofo_possible && skb_peek(&tp->out_of_order_queue))) { |
4928 | /* Then ack it now */ |
4929 | tcp_send_ack(sk); |
4930 | } else { |
4931 | /* Else, send delayed ack. */ |
4932 | tcp_send_delayed_ack(sk); |
4933 | } |
4934 | } |
4935 | |
4936 | static inline void tcp_ack_snd_check(struct sock *sk) |
4937 | { |
4938 | if (!inet_csk_ack_scheduled(sk)) { |
4939 | /* We sent a data segment already. */ |
4940 | return; |
4941 | } |
4942 | __tcp_ack_snd_check(sk, 1); |
4943 | } |
4944 | |
4945 | /* |
4946 | * This routine is only called when we have urgent data |
4947 | * signaled. Its the 'slow' part of tcp_urg. It could be |
4948 | * moved inline now as tcp_urg is only called from one |
4949 | * place. We handle URGent data wrong. We have to - as |
4950 | * BSD still doesn't use the correction from RFC961. |
4951 | * For 1003.1g we should support a new option TCP_STDURG to permit |
4952 | * either form (or just set the sysctl tcp_stdurg). |
4953 | */ |
4954 | |
4955 | static void tcp_check_urg(struct sock *sk, struct tcphdr *th) |
4956 | { |
4957 | struct tcp_sock *tp = tcp_sk(sk); |
4958 | u32 ptr = ntohs(th->urg_ptr); |
4959 | |
4960 | if (ptr && !sysctl_tcp_stdurg) |
4961 | ptr--; |
4962 | ptr += ntohl(th->seq); |
4963 | |
4964 | /* Ignore urgent data that we've already seen and read. */ |
4965 | if (after(tp->copied_seq, ptr)) |
4966 | return; |
4967 | |
4968 | /* Do not replay urg ptr. |
4969 | * |
4970 | * NOTE: interesting situation not covered by specs. |
4971 | * Misbehaving sender may send urg ptr, pointing to segment, |
4972 | * which we already have in ofo queue. We are not able to fetch |
4973 | * such data and will stay in TCP_URG_NOTYET until will be eaten |
4974 | * by recvmsg(). Seems, we are not obliged to handle such wicked |
4975 | * situations. But it is worth to think about possibility of some |
4976 | * DoSes using some hypothetical application level deadlock. |
4977 | */ |
4978 | if (before(ptr, tp->rcv_nxt)) |
4979 | return; |
4980 | |
4981 | /* Do we already have a newer (or duplicate) urgent pointer? */ |
4982 | if (tp->urg_data && !after(ptr, tp->urg_seq)) |
4983 | return; |
4984 | |
4985 | /* Tell the world about our new urgent pointer. */ |
4986 | sk_send_sigurg(sk); |
4987 | |
4988 | /* We may be adding urgent data when the last byte read was |
4989 | * urgent. To do this requires some care. We cannot just ignore |
4990 | * tp->copied_seq since we would read the last urgent byte again |
4991 | * as data, nor can we alter copied_seq until this data arrives |
4992 | * or we break the semantics of SIOCATMARK (and thus sockatmark()) |
4993 | * |
4994 | * NOTE. Double Dutch. Rendering to plain English: author of comment |
4995 | * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); |
4996 | * and expect that both A and B disappear from stream. This is _wrong_. |
4997 | * Though this happens in BSD with high probability, this is occasional. |
4998 | * Any application relying on this is buggy. Note also, that fix "works" |
4999 | * only in this artificial test. Insert some normal data between A and B and we will |
5000 | * decline of BSD again. Verdict: it is better to remove to trap |
5001 | * buggy users. |
5002 | */ |
5003 | if (tp->urg_seq == tp->copied_seq && tp->urg_data && |
5004 | !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) { |
5005 | struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); |
5006 | tp->copied_seq++; |
5007 | if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { |
5008 | __skb_unlink(skb, &sk->sk_receive_queue); |
5009 | __kfree_skb(skb); |
5010 | } |
5011 | } |
5012 | |
5013 | tp->urg_data = TCP_URG_NOTYET; |
5014 | tp->urg_seq = ptr; |
5015 | |
5016 | /* Disable header prediction. */ |
5017 | tp->pred_flags = 0; |
5018 | } |
5019 | |
5020 | /* This is the 'fast' part of urgent handling. */ |
5021 | static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) |
5022 | { |
5023 | struct tcp_sock *tp = tcp_sk(sk); |
5024 | |
5025 | /* Check if we get a new urgent pointer - normally not. */ |
5026 | if (th->urg) |
5027 | tcp_check_urg(sk, th); |
5028 | |
5029 | /* Do we wait for any urgent data? - normally not... */ |
5030 | if (tp->urg_data == TCP_URG_NOTYET) { |
5031 | u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - |
5032 | th->syn; |
5033 | |
5034 | /* Is the urgent pointer pointing into this packet? */ |
5035 | if (ptr < skb->len) { |
5036 | u8 tmp; |
5037 | if (skb_copy_bits(skb, ptr, &tmp, 1)) |
5038 | BUG(); |
5039 | tp->urg_data = TCP_URG_VALID | tmp; |
5040 | if (!sock_flag(sk, SOCK_DEAD)) |
5041 | sk->sk_data_ready(sk, 0); |
5042 | } |
5043 | } |
5044 | } |
5045 | |
5046 | static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) |
5047 | { |
5048 | struct tcp_sock *tp = tcp_sk(sk); |
5049 | int chunk = skb->len - hlen; |
5050 | int err; |
5051 | |
5052 | local_bh_enable(); |
5053 | if (skb_csum_unnecessary(skb)) |
5054 | err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); |
5055 | else |
5056 | err = skb_copy_and_csum_datagram_iovec(skb, hlen, |
5057 | tp->ucopy.iov); |
5058 | |
5059 | if (!err) { |
5060 | tp->ucopy.len -= chunk; |
5061 | tp->copied_seq += chunk; |
5062 | tcp_rcv_space_adjust(sk); |
5063 | } |
5064 | |
5065 | local_bh_disable(); |
5066 | return err; |
5067 | } |
5068 | |
5069 | static __sum16 __tcp_checksum_complete_user(struct sock *sk, |
5070 | struct sk_buff *skb) |
5071 | { |
5072 | __sum16 result; |
5073 | |
5074 | if (sock_owned_by_user(sk)) { |
5075 | local_bh_enable(); |
5076 | result = __tcp_checksum_complete(skb); |
5077 | local_bh_disable(); |
5078 | } else { |
5079 | result = __tcp_checksum_complete(skb); |
5080 | } |
5081 | return result; |
5082 | } |
5083 | |
5084 | static inline int tcp_checksum_complete_user(struct sock *sk, |
5085 | struct sk_buff *skb) |
5086 | { |
5087 | return !skb_csum_unnecessary(skb) && |
5088 | __tcp_checksum_complete_user(sk, skb); |
5089 | } |
5090 | |
5091 | #ifdef CONFIG_NET_DMA |
5092 | static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, |
5093 | int hlen) |
5094 | { |
5095 | struct tcp_sock *tp = tcp_sk(sk); |
5096 | int chunk = skb->len - hlen; |
5097 | int dma_cookie; |
5098 | int copied_early = 0; |
5099 | |
5100 | if (tp->ucopy.wakeup) |
5101 | return 0; |
5102 | |
5103 | if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) |
5104 | tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY); |
5105 | |
5106 | if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { |
5107 | |
5108 | dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, |
5109 | skb, hlen, |
5110 | tp->ucopy.iov, chunk, |
5111 | tp->ucopy.pinned_list); |
5112 | |
5113 | if (dma_cookie < 0) |
5114 | goto out; |
5115 | |
5116 | tp->ucopy.dma_cookie = dma_cookie; |
5117 | copied_early = 1; |
5118 | |
5119 | tp->ucopy.len -= chunk; |
5120 | tp->copied_seq += chunk; |
5121 | tcp_rcv_space_adjust(sk); |
5122 | |
5123 | if ((tp->ucopy.len == 0) || |
5124 | (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || |
5125 | (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { |
5126 | tp->ucopy.wakeup = 1; |
5127 | sk->sk_data_ready(sk, 0); |
5128 | } |
5129 | } else if (chunk > 0) { |
5130 | tp->ucopy.wakeup = 1; |
5131 | sk->sk_data_ready(sk, 0); |
5132 | } |
5133 | out: |
5134 | return copied_early; |
5135 | } |
5136 | #endif /* CONFIG_NET_DMA */ |
5137 | |
5138 | /* Does PAWS and seqno based validation of an incoming segment, flags will |
5139 | * play significant role here. |
5140 | */ |
5141 | static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, |
5142 | struct tcphdr *th, int syn_inerr) |
5143 | { |
5144 | u8 *hash_location; |
5145 | struct tcp_sock *tp = tcp_sk(sk); |
5146 | |
5147 | /* RFC1323: H1. Apply PAWS check first. */ |
5148 | if (tcp_fast_parse_options(skb, th, tp, &hash_location) && |
5149 | tp->rx_opt.saw_tstamp && |
5150 | tcp_paws_discard(sk, skb)) { |
5151 | if (!th->rst) { |
5152 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); |
5153 | tcp_send_dupack(sk, skb); |
5154 | goto discard; |
5155 | } |
5156 | /* Reset is accepted even if it did not pass PAWS. */ |
5157 | } |
5158 | |
5159 | /* Step 1: check sequence number */ |
5160 | if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { |
5161 | /* RFC793, page 37: "In all states except SYN-SENT, all reset |
5162 | * (RST) segments are validated by checking their SEQ-fields." |
5163 | * And page 69: "If an incoming segment is not acceptable, |
5164 | * an acknowledgment should be sent in reply (unless the RST |
5165 | * bit is set, if so drop the segment and return)". |
5166 | */ |
5167 | if (!th->rst) |
5168 | tcp_send_dupack(sk, skb); |
5169 | goto discard; |
5170 | } |
5171 | |
5172 | /* Step 2: check RST bit */ |
5173 | if (th->rst) { |
5174 | tcp_reset(sk); |
5175 | goto discard; |
5176 | } |
5177 | |
5178 | /* ts_recent update must be made after we are sure that the packet |
5179 | * is in window. |
5180 | */ |
5181 | tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); |
5182 | |
5183 | /* step 3: check security and precedence [ignored] */ |
5184 | |
5185 | /* step 4: Check for a SYN in window. */ |
5186 | if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
5187 | if (syn_inerr) |
5188 | TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); |
5189 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN); |
5190 | tcp_reset(sk); |
5191 | return -1; |
5192 | } |
5193 | |
5194 | return 1; |
5195 | |
5196 | discard: |
5197 | __kfree_skb(skb); |
5198 | return 0; |
5199 | } |
5200 | |
5201 | /* |
5202 | * TCP receive function for the ESTABLISHED state. |
5203 | * |
5204 | * It is split into a fast path and a slow path. The fast path is |
5205 | * disabled when: |
5206 | * - A zero window was announced from us - zero window probing |
5207 | * is only handled properly in the slow path. |
5208 | * - Out of order segments arrived. |
5209 | * - Urgent data is expected. |
5210 | * - There is no buffer space left |
5211 | * - Unexpected TCP flags/window values/header lengths are received |
5212 | * (detected by checking the TCP header against pred_flags) |
5213 | * - Data is sent in both directions. Fast path only supports pure senders |
5214 | * or pure receivers (this means either the sequence number or the ack |
5215 | * value must stay constant) |
5216 | * - Unexpected TCP option. |
5217 | * |
5218 | * When these conditions are not satisfied it drops into a standard |
5219 | * receive procedure patterned after RFC793 to handle all cases. |
5220 | * The first three cases are guaranteed by proper pred_flags setting, |
5221 | * the rest is checked inline. Fast processing is turned on in |
5222 | * tcp_data_queue when everything is OK. |
5223 | */ |
5224 | int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, |
5225 | struct tcphdr *th, unsigned len) |
5226 | { |
5227 | struct tcp_sock *tp = tcp_sk(sk); |
5228 | int res; |
5229 | |
5230 | /* |
5231 | * Header prediction. |
5232 | * The code loosely follows the one in the famous |
5233 | * "30 instruction TCP receive" Van Jacobson mail. |
5234 | * |
5235 | * Van's trick is to deposit buffers into socket queue |
5236 | * on a device interrupt, to call tcp_recv function |
5237 | * on the receive process context and checksum and copy |
5238 | * the buffer to user space. smart... |
5239 | * |
5240 | * Our current scheme is not silly either but we take the |
5241 | * extra cost of the net_bh soft interrupt processing... |
5242 | * We do checksum and copy also but from device to kernel. |
5243 | */ |
5244 | |
5245 | tp->rx_opt.saw_tstamp = 0; |
5246 | |
5247 | /* pred_flags is 0xS?10 << 16 + snd_wnd |
5248 | * if header_prediction is to be made |
5249 | * 'S' will always be tp->tcp_header_len >> 2 |
5250 | * '?' will be 0 for the fast path, otherwise pred_flags is 0 to |
5251 | * turn it off (when there are holes in the receive |
5252 | * space for instance) |
5253 | * PSH flag is ignored. |
5254 | */ |
5255 | |
5256 | if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && |
5257 | TCP_SKB_CB(skb)->seq == tp->rcv_nxt && |
5258 | !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { |
5259 | int tcp_header_len = tp->tcp_header_len; |
5260 | |
5261 | /* Timestamp header prediction: tcp_header_len |
5262 | * is automatically equal to th->doff*4 due to pred_flags |
5263 | * match. |
5264 | */ |
5265 | |
5266 | /* Check timestamp */ |
5267 | if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { |
5268 | /* No? Slow path! */ |
5269 | if (!tcp_parse_aligned_timestamp(tp, th)) |
5270 | goto slow_path; |
5271 | |
5272 | /* If PAWS failed, check it more carefully in slow path */ |
5273 | if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) |
5274 | goto slow_path; |
5275 | |
5276 | /* DO NOT update ts_recent here, if checksum fails |
5277 | * and timestamp was corrupted part, it will result |
5278 | * in a hung connection since we will drop all |
5279 | * future packets due to the PAWS test. |
5280 | */ |
5281 | } |
5282 | |
5283 | if (len <= tcp_header_len) { |
5284 | /* Bulk data transfer: sender */ |
5285 | if (len == tcp_header_len) { |
5286 | /* Predicted packet is in window by definition. |
5287 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. |
5288 | * Hence, check seq<=rcv_wup reduces to: |
5289 | */ |
5290 | if (tcp_header_len == |
5291 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && |
5292 | tp->rcv_nxt == tp->rcv_wup) |
5293 | tcp_store_ts_recent(tp); |
5294 | |
5295 | /* We know that such packets are checksummed |
5296 | * on entry. |
5297 | */ |
5298 | tcp_ack(sk, skb, 0); |
5299 | __kfree_skb(skb); |
5300 | tcp_data_snd_check(sk); |
5301 | return 0; |
5302 | } else { /* Header too small */ |
5303 | TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); |
5304 | goto discard; |
5305 | } |
5306 | } else { |
5307 | int eaten = 0; |
5308 | int copied_early = 0; |
5309 | |
5310 | if (tp->copied_seq == tp->rcv_nxt && |
5311 | len - tcp_header_len <= tp->ucopy.len) { |
5312 | #ifdef CONFIG_NET_DMA |
5313 | if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { |
5314 | copied_early = 1; |
5315 | eaten = 1; |
5316 | } |
5317 | #endif |
5318 | if (tp->ucopy.task == current && |
5319 | sock_owned_by_user(sk) && !copied_early) { |
5320 | __set_current_state(TASK_RUNNING); |
5321 | |
5322 | if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) |
5323 | eaten = 1; |
5324 | } |
5325 | if (eaten) { |
5326 | /* Predicted packet is in window by definition. |
5327 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. |
5328 | * Hence, check seq<=rcv_wup reduces to: |
5329 | */ |
5330 | if (tcp_header_len == |
5331 | (sizeof(struct tcphdr) + |
5332 | TCPOLEN_TSTAMP_ALIGNED) && |
5333 | tp->rcv_nxt == tp->rcv_wup) |
5334 | tcp_store_ts_recent(tp); |
5335 | |
5336 | tcp_rcv_rtt_measure_ts(sk, skb); |
5337 | |
5338 | __skb_pull(skb, tcp_header_len); |
5339 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
5340 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER); |
5341 | } |
5342 | if (copied_early) |
5343 | tcp_cleanup_rbuf(sk, skb->len); |
5344 | } |
5345 | if (!eaten) { |
5346 | if (tcp_checksum_complete_user(sk, skb)) |
5347 | goto csum_error; |
5348 | |
5349 | /* Predicted packet is in window by definition. |
5350 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. |
5351 | * Hence, check seq<=rcv_wup reduces to: |
5352 | */ |
5353 | if (tcp_header_len == |
5354 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && |
5355 | tp->rcv_nxt == tp->rcv_wup) |
5356 | tcp_store_ts_recent(tp); |
5357 | |
5358 | tcp_rcv_rtt_measure_ts(sk, skb); |
5359 | |
5360 | if ((int)skb->truesize > sk->sk_forward_alloc) |
5361 | goto step5; |
5362 | |
5363 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS); |
5364 | |
5365 | /* Bulk data transfer: receiver */ |
5366 | __skb_pull(skb, tcp_header_len); |
5367 | __skb_queue_tail(&sk->sk_receive_queue, skb); |
5368 | skb_set_owner_r(skb, sk); |
5369 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
5370 | } |
5371 | |
5372 | tcp_event_data_recv(sk, skb); |
5373 | |
5374 | if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { |
5375 | /* Well, only one small jumplet in fast path... */ |
5376 | tcp_ack(sk, skb, FLAG_DATA); |
5377 | tcp_data_snd_check(sk); |
5378 | if (!inet_csk_ack_scheduled(sk)) |
5379 | goto no_ack; |
5380 | } |
5381 | |
5382 | if (!copied_early || tp->rcv_nxt != tp->rcv_wup) |
5383 | __tcp_ack_snd_check(sk, 0); |
5384 | no_ack: |
5385 | #ifdef CONFIG_NET_DMA |
5386 | if (copied_early) |
5387 | __skb_queue_tail(&sk->sk_async_wait_queue, skb); |
5388 | else |
5389 | #endif |
5390 | if (eaten) |
5391 | __kfree_skb(skb); |
5392 | else |
5393 | sk->sk_data_ready(sk, 0); |
5394 | return 0; |
5395 | } |
5396 | } |
5397 | |
5398 | slow_path: |
5399 | if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb)) |
5400 | goto csum_error; |
5401 | |
5402 | /* |
5403 | * Standard slow path. |
5404 | */ |
5405 | |
5406 | res = tcp_validate_incoming(sk, skb, th, 1); |
5407 | if (res <= 0) |
5408 | return -res; |
5409 | |
5410 | step5: |
5411 | if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) |
5412 | goto discard; |
5413 | |
5414 | tcp_rcv_rtt_measure_ts(sk, skb); |
5415 | |
5416 | /* Process urgent data. */ |
5417 | tcp_urg(sk, skb, th); |
5418 | |
5419 | /* step 7: process the segment text */ |
5420 | tcp_data_queue(sk, skb); |
5421 | |
5422 | tcp_data_snd_check(sk); |
5423 | tcp_ack_snd_check(sk); |
5424 | return 0; |
5425 | |
5426 | csum_error: |
5427 | TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); |
5428 | |
5429 | discard: |
5430 | __kfree_skb(skb); |
5431 | return 0; |
5432 | } |
5433 | |
5434 | static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, |
5435 | struct tcphdr *th, unsigned len) |
5436 | { |
5437 | u8 *hash_location; |
5438 | struct inet_connection_sock *icsk = inet_csk(sk); |
5439 | struct tcp_sock *tp = tcp_sk(sk); |
5440 | struct tcp_cookie_values *cvp = tp->cookie_values; |
5441 | int saved_clamp = tp->rx_opt.mss_clamp; |
5442 | |
5443 | tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0); |
5444 | |
5445 | if (th->ack) { |
5446 | /* rfc793: |
5447 | * "If the state is SYN-SENT then |
5448 | * first check the ACK bit |
5449 | * If the ACK bit is set |
5450 | * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send |
5451 | * a reset (unless the RST bit is set, if so drop |
5452 | * the segment and return)" |
5453 | * |
5454 | * We do not send data with SYN, so that RFC-correct |
5455 | * test reduces to: |
5456 | */ |
5457 | if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) |
5458 | goto reset_and_undo; |
5459 | |
5460 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
5461 | !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, |
5462 | tcp_time_stamp)) { |
5463 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED); |
5464 | goto reset_and_undo; |
5465 | } |
5466 | |
5467 | /* Now ACK is acceptable. |
5468 | * |
5469 | * "If the RST bit is set |
5470 | * If the ACK was acceptable then signal the user "error: |
5471 | * connection reset", drop the segment, enter CLOSED state, |
5472 | * delete TCB, and return." |
5473 | */ |
5474 | |
5475 | if (th->rst) { |
5476 | tcp_reset(sk); |
5477 | goto discard; |
5478 | } |
5479 | |
5480 | /* rfc793: |
5481 | * "fifth, if neither of the SYN or RST bits is set then |
5482 | * drop the segment and return." |
5483 | * |
5484 | * See note below! |
5485 | * --ANK(990513) |
5486 | */ |
5487 | if (!th->syn) |
5488 | goto discard_and_undo; |
5489 | |
5490 | /* rfc793: |
5491 | * "If the SYN bit is on ... |
5492 | * are acceptable then ... |
5493 | * (our SYN has been ACKed), change the connection |
5494 | * state to ESTABLISHED..." |
5495 | */ |
5496 | |
5497 | TCP_ECN_rcv_synack(tp, th); |
5498 | |
5499 | tp->snd_wl1 = TCP_SKB_CB(skb)->seq; |
5500 | tcp_ack(sk, skb, FLAG_SLOWPATH); |
5501 | |
5502 | /* Ok.. it's good. Set up sequence numbers and |
5503 | * move to established. |
5504 | */ |
5505 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; |
5506 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; |
5507 | |
5508 | /* RFC1323: The window in SYN & SYN/ACK segments is |
5509 | * never scaled. |
5510 | */ |
5511 | tp->snd_wnd = ntohs(th->window); |
5512 | tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); |
5513 | |
5514 | if (!tp->rx_opt.wscale_ok) { |
5515 | tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; |
5516 | tp->window_clamp = min(tp->window_clamp, 65535U); |
5517 | } |
5518 | |
5519 | if (tp->rx_opt.saw_tstamp) { |
5520 | tp->rx_opt.tstamp_ok = 1; |
5521 | tp->tcp_header_len = |
5522 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; |
5523 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; |
5524 | tcp_store_ts_recent(tp); |
5525 | } else { |
5526 | tp->tcp_header_len = sizeof(struct tcphdr); |
5527 | } |
5528 | |
5529 | if (tcp_is_sack(tp) && sysctl_tcp_fack) |
5530 | tcp_enable_fack(tp); |
5531 | |
5532 | tcp_mtup_init(sk); |
5533 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
5534 | tcp_initialize_rcv_mss(sk); |
5535 | |
5536 | /* Remember, tcp_poll() does not lock socket! |
5537 | * Change state from SYN-SENT only after copied_seq |
5538 | * is initialized. */ |
5539 | tp->copied_seq = tp->rcv_nxt; |
5540 | |
5541 | if (cvp != NULL && |
5542 | cvp->cookie_pair_size > 0 && |
5543 | tp->rx_opt.cookie_plus > 0) { |
5544 | int cookie_size = tp->rx_opt.cookie_plus |
5545 | - TCPOLEN_COOKIE_BASE; |
5546 | int cookie_pair_size = cookie_size |
5547 | + cvp->cookie_desired; |
5548 | |
5549 | /* A cookie extension option was sent and returned. |
5550 | * Note that each incoming SYNACK replaces the |
5551 | * Responder cookie. The initial exchange is most |
5552 | * fragile, as protection against spoofing relies |
5553 | * entirely upon the sequence and timestamp (above). |
5554 | * This replacement strategy allows the correct pair to |
5555 | * pass through, while any others will be filtered via |
5556 | * Responder verification later. |
5557 | */ |
5558 | if (sizeof(cvp->cookie_pair) >= cookie_pair_size) { |
5559 | memcpy(&cvp->cookie_pair[cvp->cookie_desired], |
5560 | hash_location, cookie_size); |
5561 | cvp->cookie_pair_size = cookie_pair_size; |
5562 | } |
5563 | } |
5564 | |
5565 | smp_mb(); |
5566 | tcp_set_state(sk, TCP_ESTABLISHED); |
5567 | |
5568 | security_inet_conn_established(sk, skb); |
5569 | |
5570 | /* Make sure socket is routed, for correct metrics. */ |
5571 | icsk->icsk_af_ops->rebuild_header(sk); |
5572 | |
5573 | tcp_init_metrics(sk); |
5574 | |
5575 | tcp_init_congestion_control(sk); |
5576 | |
5577 | /* Prevent spurious tcp_cwnd_restart() on first data |
5578 | * packet. |
5579 | */ |
5580 | tp->lsndtime = tcp_time_stamp; |
5581 | |
5582 | tcp_init_buffer_space(sk); |
5583 | |
5584 | if (sock_flag(sk, SOCK_KEEPOPEN)) |
5585 | inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); |
5586 | |
5587 | if (!tp->rx_opt.snd_wscale) |
5588 | __tcp_fast_path_on(tp, tp->snd_wnd); |
5589 | else |
5590 | tp->pred_flags = 0; |
5591 | |
5592 | if (!sock_flag(sk, SOCK_DEAD)) { |
5593 | sk->sk_state_change(sk); |
5594 | sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); |
5595 | } |
5596 | |
5597 | if (sk->sk_write_pending || |
5598 | icsk->icsk_accept_queue.rskq_defer_accept || |
5599 | icsk->icsk_ack.pingpong) { |
5600 | /* Save one ACK. Data will be ready after |
5601 | * several ticks, if write_pending is set. |
5602 | * |
5603 | * It may be deleted, but with this feature tcpdumps |
5604 | * look so _wonderfully_ clever, that I was not able |
5605 | * to stand against the temptation 8) --ANK |
5606 | */ |
5607 | inet_csk_schedule_ack(sk); |
5608 | icsk->icsk_ack.lrcvtime = tcp_time_stamp; |
5609 | icsk->icsk_ack.ato = TCP_ATO_MIN; |
5610 | tcp_incr_quickack(sk); |
5611 | tcp_enter_quickack_mode(sk); |
5612 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, |
5613 | TCP_DELACK_MAX, TCP_RTO_MAX); |
5614 | |
5615 | discard: |
5616 | __kfree_skb(skb); |
5617 | return 0; |
5618 | } else { |
5619 | tcp_send_ack(sk); |
5620 | } |
5621 | return -1; |
5622 | } |
5623 | |
5624 | /* No ACK in the segment */ |
5625 | |
5626 | if (th->rst) { |
5627 | /* rfc793: |
5628 | * "If the RST bit is set |
5629 | * |
5630 | * Otherwise (no ACK) drop the segment and return." |
5631 | */ |
5632 | |
5633 | goto discard_and_undo; |
5634 | } |
5635 | |
5636 | /* PAWS check. */ |
5637 | if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && |
5638 | tcp_paws_reject(&tp->rx_opt, 0)) |
5639 | goto discard_and_undo; |
5640 | |
5641 | if (th->syn) { |
5642 | /* We see SYN without ACK. It is attempt of |
5643 | * simultaneous connect with crossed SYNs. |
5644 | * Particularly, it can be connect to self. |
5645 | */ |
5646 | tcp_set_state(sk, TCP_SYN_RECV); |
5647 | |
5648 | if (tp->rx_opt.saw_tstamp) { |
5649 | tp->rx_opt.tstamp_ok = 1; |
5650 | tcp_store_ts_recent(tp); |
5651 | tp->tcp_header_len = |
5652 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; |
5653 | } else { |
5654 | tp->tcp_header_len = sizeof(struct tcphdr); |
5655 | } |
5656 | |
5657 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; |
5658 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; |
5659 | |
5660 | /* RFC1323: The window in SYN & SYN/ACK segments is |
5661 | * never scaled. |
5662 | */ |
5663 | tp->snd_wnd = ntohs(th->window); |
5664 | tp->snd_wl1 = TCP_SKB_CB(skb)->seq; |
5665 | tp->max_window = tp->snd_wnd; |
5666 | |
5667 | TCP_ECN_rcv_syn(tp, th); |
5668 | |
5669 | tcp_mtup_init(sk); |
5670 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
5671 | tcp_initialize_rcv_mss(sk); |
5672 | |
5673 | tcp_send_synack(sk); |
5674 | #if 0 |
5675 | /* Note, we could accept data and URG from this segment. |
5676 | * There are no obstacles to make this. |
5677 | * |
5678 | * However, if we ignore data in ACKless segments sometimes, |
5679 | * we have no reasons to accept it sometimes. |
5680 | * Also, seems the code doing it in step6 of tcp_rcv_state_process |
5681 | * is not flawless. So, discard packet for sanity. |
5682 | * Uncomment this return to process the data. |
5683 | */ |
5684 | return -1; |
5685 | #else |
5686 | goto discard; |
5687 | #endif |
5688 | } |
5689 | /* "fifth, if neither of the SYN or RST bits is set then |
5690 | * drop the segment and return." |
5691 | */ |
5692 | |
5693 | discard_and_undo: |
5694 | tcp_clear_options(&tp->rx_opt); |
5695 | tp->rx_opt.mss_clamp = saved_clamp; |
5696 | goto discard; |
5697 | |
5698 | reset_and_undo: |
5699 | tcp_clear_options(&tp->rx_opt); |
5700 | tp->rx_opt.mss_clamp = saved_clamp; |
5701 | return 1; |
5702 | } |
5703 | |
5704 | /* |
5705 | * This function implements the receiving procedure of RFC 793 for |
5706 | * all states except ESTABLISHED and TIME_WAIT. |
5707 | * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be |
5708 | * address independent. |
5709 | */ |
5710 | |
5711 | int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, |
5712 | struct tcphdr *th, unsigned len) |
5713 | { |
5714 | struct tcp_sock *tp = tcp_sk(sk); |
5715 | struct inet_connection_sock *icsk = inet_csk(sk); |
5716 | int queued = 0; |
5717 | int res; |
5718 | |
5719 | tp->rx_opt.saw_tstamp = 0; |
5720 | |
5721 | switch (sk->sk_state) { |
5722 | case TCP_CLOSE: |
5723 | goto discard; |
5724 | |
5725 | case TCP_LISTEN: |
5726 | if (th->ack) |
5727 | return 1; |
5728 | |
5729 | if (th->rst) |
5730 | goto discard; |
5731 | |
5732 | if (th->syn) { |
5733 | if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) |
5734 | return 1; |
5735 | |
5736 | /* Now we have several options: In theory there is |
5737 | * nothing else in the frame. KA9Q has an option to |
5738 | * send data with the syn, BSD accepts data with the |
5739 | * syn up to the [to be] advertised window and |
5740 | * Solaris 2.1 gives you a protocol error. For now |
5741 | * we just ignore it, that fits the spec precisely |
5742 | * and avoids incompatibilities. It would be nice in |
5743 | * future to drop through and process the data. |
5744 | * |
5745 | * Now that TTCP is starting to be used we ought to |
5746 | * queue this data. |
5747 | * But, this leaves one open to an easy denial of |
5748 | * service attack, and SYN cookies can't defend |
5749 | * against this problem. So, we drop the data |
5750 | * in the interest of security over speed unless |
5751 | * it's still in use. |
5752 | */ |
5753 | kfree_skb(skb); |
5754 | return 0; |
5755 | } |
5756 | goto discard; |
5757 | |
5758 | case TCP_SYN_SENT: |
5759 | queued = tcp_rcv_synsent_state_process(sk, skb, th, len); |
5760 | if (queued >= 0) |
5761 | return queued; |
5762 | |
5763 | /* Do step6 onward by hand. */ |
5764 | tcp_urg(sk, skb, th); |
5765 | __kfree_skb(skb); |
5766 | tcp_data_snd_check(sk); |
5767 | return 0; |
5768 | } |
5769 | |
5770 | res = tcp_validate_incoming(sk, skb, th, 0); |
5771 | if (res <= 0) |
5772 | return -res; |
5773 | |
5774 | /* step 5: check the ACK field */ |
5775 | if (th->ack) { |
5776 | int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0; |
5777 | |
5778 | switch (sk->sk_state) { |
5779 | case TCP_SYN_RECV: |
5780 | if (acceptable) { |
5781 | tp->copied_seq = tp->rcv_nxt; |
5782 | smp_mb(); |
5783 | tcp_set_state(sk, TCP_ESTABLISHED); |
5784 | sk->sk_state_change(sk); |
5785 | |
5786 | /* Note, that this wakeup is only for marginal |
5787 | * crossed SYN case. Passively open sockets |
5788 | * are not waked up, because sk->sk_sleep == |
5789 | * NULL and sk->sk_socket == NULL. |
5790 | */ |
5791 | if (sk->sk_socket) |
5792 | sk_wake_async(sk, |
5793 | SOCK_WAKE_IO, POLL_OUT); |
5794 | |
5795 | tp->snd_una = TCP_SKB_CB(skb)->ack_seq; |
5796 | tp->snd_wnd = ntohs(th->window) << |
5797 | tp->rx_opt.snd_wscale; |
5798 | tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); |
5799 | |
5800 | /* tcp_ack considers this ACK as duplicate |
5801 | * and does not calculate rtt. |
5802 | * Force it here. |
5803 | */ |
5804 | tcp_ack_update_rtt(sk, 0, 0); |
5805 | |
5806 | if (tp->rx_opt.tstamp_ok) |
5807 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; |
5808 | |
5809 | /* Make sure socket is routed, for |
5810 | * correct metrics. |
5811 | */ |
5812 | icsk->icsk_af_ops->rebuild_header(sk); |
5813 | |
5814 | tcp_init_metrics(sk); |
5815 | |
5816 | tcp_init_congestion_control(sk); |
5817 | |
5818 | /* Prevent spurious tcp_cwnd_restart() on |
5819 | * first data packet. |
5820 | */ |
5821 | tp->lsndtime = tcp_time_stamp; |
5822 | |
5823 | tcp_mtup_init(sk); |
5824 | tcp_initialize_rcv_mss(sk); |
5825 | tcp_init_buffer_space(sk); |
5826 | tcp_fast_path_on(tp); |
5827 | } else { |
5828 | return 1; |
5829 | } |
5830 | break; |
5831 | |
5832 | case TCP_FIN_WAIT1: |
5833 | if (tp->snd_una == tp->write_seq) { |
5834 | tcp_set_state(sk, TCP_FIN_WAIT2); |
5835 | sk->sk_shutdown |= SEND_SHUTDOWN; |
5836 | dst_confirm(sk->sk_dst_cache); |
5837 | |
5838 | if (!sock_flag(sk, SOCK_DEAD)) |
5839 | /* Wake up lingering close() */ |
5840 | sk->sk_state_change(sk); |
5841 | else { |
5842 | int tmo; |
5843 | |
5844 | if (tp->linger2 < 0 || |
5845 | (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
5846 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { |
5847 | tcp_done(sk); |
5848 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); |
5849 | return 1; |
5850 | } |
5851 | |
5852 | tmo = tcp_fin_time(sk); |
5853 | if (tmo > TCP_TIMEWAIT_LEN) { |
5854 | inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); |
5855 | } else if (th->fin || sock_owned_by_user(sk)) { |
5856 | /* Bad case. We could lose such FIN otherwise. |
5857 | * It is not a big problem, but it looks confusing |
5858 | * and not so rare event. We still can lose it now, |
5859 | * if it spins in bh_lock_sock(), but it is really |
5860 | * marginal case. |
5861 | */ |
5862 | inet_csk_reset_keepalive_timer(sk, tmo); |
5863 | } else { |
5864 | tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); |
5865 | goto discard; |
5866 | } |
5867 | } |
5868 | } |
5869 | break; |
5870 | |
5871 | case TCP_CLOSING: |
5872 | if (tp->snd_una == tp->write_seq) { |
5873 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); |
5874 | goto discard; |
5875 | } |
5876 | break; |
5877 | |
5878 | case TCP_LAST_ACK: |
5879 | if (tp->snd_una == tp->write_seq) { |
5880 | tcp_update_metrics(sk); |
5881 | tcp_done(sk); |
5882 | goto discard; |
5883 | } |
5884 | break; |
5885 | } |
5886 | } else |
5887 | goto discard; |
5888 | |
5889 | /* step 6: check the URG bit */ |
5890 | tcp_urg(sk, skb, th); |
5891 | |
5892 | /* step 7: process the segment text */ |
5893 | switch (sk->sk_state) { |
5894 | case TCP_CLOSE_WAIT: |
5895 | case TCP_CLOSING: |
5896 | case TCP_LAST_ACK: |
5897 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) |
5898 | break; |
5899 | case TCP_FIN_WAIT1: |
5900 | case TCP_FIN_WAIT2: |
5901 | /* RFC 793 says to queue data in these states, |
5902 | * RFC 1122 says we MUST send a reset. |
5903 | * BSD 4.4 also does reset. |
5904 | */ |
5905 | if (sk->sk_shutdown & RCV_SHUTDOWN) { |
5906 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
5907 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { |
5908 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); |
5909 | tcp_reset(sk); |
5910 | return 1; |
5911 | } |
5912 | } |
5913 | /* Fall through */ |
5914 | case TCP_ESTABLISHED: |
5915 | tcp_data_queue(sk, skb); |
5916 | queued = 1; |
5917 | break; |
5918 | } |
5919 | |
5920 | /* tcp_data could move socket to TIME-WAIT */ |
5921 | if (sk->sk_state != TCP_CLOSE) { |
5922 | tcp_data_snd_check(sk); |
5923 | tcp_ack_snd_check(sk); |
5924 | } |
5925 | |
5926 | if (!queued) { |
5927 | discard: |
5928 | __kfree_skb(skb); |
5929 | } |
5930 | return 0; |
5931 | } |
5932 | |
5933 | EXPORT_SYMBOL(sysctl_tcp_ecn); |
5934 | EXPORT_SYMBOL(sysctl_tcp_reordering); |
5935 | EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); |
5936 | EXPORT_SYMBOL(tcp_parse_options); |
5937 | #ifdef CONFIG_TCP_MD5SIG |
5938 | EXPORT_SYMBOL(tcp_parse_md5sig_option); |
5939 | #endif |
5940 | EXPORT_SYMBOL(tcp_rcv_established); |
5941 | EXPORT_SYMBOL(tcp_rcv_state_process); |
5942 | EXPORT_SYMBOL(tcp_initialize_rcv_mss); |
5943 |
Branches:
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
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v3.9