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 | #define pr_fmt(fmt) "TCP: " fmt |
65 | |
66 | #include <linux/mm.h> |
67 | #include <linux/slab.h> |
68 | #include <linux/module.h> |
69 | #include <linux/sysctl.h> |
70 | #include <linux/kernel.h> |
71 | #include <net/dst.h> |
72 | #include <net/tcp.h> |
73 | #include <net/inet_common.h> |
74 | #include <linux/ipsec.h> |
75 | #include <asm/unaligned.h> |
76 | #include <net/netdma.h> |
77 | |
78 | int sysctl_tcp_timestamps __read_mostly = 1; |
79 | int sysctl_tcp_window_scaling __read_mostly = 1; |
80 | int sysctl_tcp_sack __read_mostly = 1; |
81 | int sysctl_tcp_fack __read_mostly = 1; |
82 | int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; |
83 | EXPORT_SYMBOL(sysctl_tcp_reordering); |
84 | int sysctl_tcp_dsack __read_mostly = 1; |
85 | int sysctl_tcp_app_win __read_mostly = 31; |
86 | int sysctl_tcp_adv_win_scale __read_mostly = 1; |
87 | EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); |
88 | |
89 | /* rfc5961 challenge ack rate limiting */ |
90 | int sysctl_tcp_challenge_ack_limit = 100; |
91 | |
92 | int sysctl_tcp_stdurg __read_mostly; |
93 | int sysctl_tcp_rfc1337 __read_mostly; |
94 | int sysctl_tcp_max_orphans __read_mostly = NR_FILE; |
95 | int sysctl_tcp_frto __read_mostly = 2; |
96 | |
97 | int sysctl_tcp_thin_dupack __read_mostly; |
98 | |
99 | int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; |
100 | int sysctl_tcp_early_retrans __read_mostly = 3; |
101 | |
102 | #define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
103 | #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ |
104 | #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ |
105 | #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ |
106 | #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ |
107 | #define FLAG_DATA_SACKED 0x20 /* New SACK. */ |
108 | #define FLAG_ECE 0x40 /* ECE in this ACK */ |
109 | #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ |
110 | #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */ |
111 | #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ |
112 | #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ |
113 | #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ |
114 | #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */ |
115 | |
116 | #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) |
117 | #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) |
118 | #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) |
119 | #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) |
120 | |
121 | #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) |
122 | #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) |
123 | |
124 | /* Adapt the MSS value used to make delayed ack decision to the |
125 | * real world. |
126 | */ |
127 | static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) |
128 | { |
129 | struct inet_connection_sock *icsk = inet_csk(sk); |
130 | const unsigned int lss = icsk->icsk_ack.last_seg_size; |
131 | unsigned int len; |
132 | |
133 | icsk->icsk_ack.last_seg_size = 0; |
134 | |
135 | /* skb->len may jitter because of SACKs, even if peer |
136 | * sends good full-sized frames. |
137 | */ |
138 | len = skb_shinfo(skb)->gso_size ? : skb->len; |
139 | if (len >= icsk->icsk_ack.rcv_mss) { |
140 | icsk->icsk_ack.rcv_mss = len; |
141 | } else { |
142 | /* Otherwise, we make more careful check taking into account, |
143 | * that SACKs block is variable. |
144 | * |
145 | * "len" is invariant segment length, including TCP header. |
146 | */ |
147 | len += skb->data - skb_transport_header(skb); |
148 | if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || |
149 | /* If PSH is not set, packet should be |
150 | * full sized, provided peer TCP is not badly broken. |
151 | * This observation (if it is correct 8)) allows |
152 | * to handle super-low mtu links fairly. |
153 | */ |
154 | (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && |
155 | !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { |
156 | /* Subtract also invariant (if peer is RFC compliant), |
157 | * tcp header plus fixed timestamp option length. |
158 | * Resulting "len" is MSS free of SACK jitter. |
159 | */ |
160 | len -= tcp_sk(sk)->tcp_header_len; |
161 | icsk->icsk_ack.last_seg_size = len; |
162 | if (len == lss) { |
163 | icsk->icsk_ack.rcv_mss = len; |
164 | return; |
165 | } |
166 | } |
167 | if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) |
168 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; |
169 | icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; |
170 | } |
171 | } |
172 | |
173 | static void tcp_incr_quickack(struct sock *sk) |
174 | { |
175 | struct inet_connection_sock *icsk = inet_csk(sk); |
176 | unsigned int quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); |
177 | |
178 | if (quickacks == 0) |
179 | quickacks = 2; |
180 | if (quickacks > icsk->icsk_ack.quick) |
181 | icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); |
182 | } |
183 | |
184 | static void tcp_enter_quickack_mode(struct sock *sk) |
185 | { |
186 | struct inet_connection_sock *icsk = inet_csk(sk); |
187 | tcp_incr_quickack(sk); |
188 | icsk->icsk_ack.pingpong = 0; |
189 | icsk->icsk_ack.ato = TCP_ATO_MIN; |
190 | } |
191 | |
192 | /* Send ACKs quickly, if "quick" count is not exhausted |
193 | * and the session is not interactive. |
194 | */ |
195 | |
196 | static inline bool tcp_in_quickack_mode(const struct sock *sk) |
197 | { |
198 | const struct inet_connection_sock *icsk = inet_csk(sk); |
199 | |
200 | return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; |
201 | } |
202 | |
203 | static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) |
204 | { |
205 | if (tp->ecn_flags & TCP_ECN_OK) |
206 | tp->ecn_flags |= TCP_ECN_QUEUE_CWR; |
207 | } |
208 | |
209 | static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) |
210 | { |
211 | if (tcp_hdr(skb)->cwr) |
212 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; |
213 | } |
214 | |
215 | static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) |
216 | { |
217 | tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; |
218 | } |
219 | |
220 | static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) |
221 | { |
222 | if (!(tp->ecn_flags & TCP_ECN_OK)) |
223 | return; |
224 | |
225 | switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { |
226 | case INET_ECN_NOT_ECT: |
227 | /* Funny extension: if ECT is not set on a segment, |
228 | * and we already seen ECT on a previous segment, |
229 | * it is probably a retransmit. |
230 | */ |
231 | if (tp->ecn_flags & TCP_ECN_SEEN) |
232 | tcp_enter_quickack_mode((struct sock *)tp); |
233 | break; |
234 | case INET_ECN_CE: |
235 | if (!(tp->ecn_flags & TCP_ECN_DEMAND_CWR)) { |
236 | /* Better not delay acks, sender can have a very low cwnd */ |
237 | tcp_enter_quickack_mode((struct sock *)tp); |
238 | tp->ecn_flags |= TCP_ECN_DEMAND_CWR; |
239 | } |
240 | /* fallinto */ |
241 | default: |
242 | tp->ecn_flags |= TCP_ECN_SEEN; |
243 | } |
244 | } |
245 | |
246 | static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) |
247 | { |
248 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) |
249 | tp->ecn_flags &= ~TCP_ECN_OK; |
250 | } |
251 | |
252 | static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) |
253 | { |
254 | if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) |
255 | tp->ecn_flags &= ~TCP_ECN_OK; |
256 | } |
257 | |
258 | static bool TCP_ECN_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) |
259 | { |
260 | if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) |
261 | return true; |
262 | return false; |
263 | } |
264 | |
265 | /* Buffer size and advertised window tuning. |
266 | * |
267 | * 1. Tuning sk->sk_sndbuf, when connection enters established state. |
268 | */ |
269 | |
270 | static void tcp_sndbuf_expand(struct sock *sk) |
271 | { |
272 | const struct tcp_sock *tp = tcp_sk(sk); |
273 | int sndmem, per_mss; |
274 | u32 nr_segs; |
275 | |
276 | /* Worst case is non GSO/TSO : each frame consumes one skb |
277 | * and skb->head is kmalloced using power of two area of memory |
278 | */ |
279 | per_mss = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + |
280 | MAX_TCP_HEADER + |
281 | SKB_DATA_ALIGN(sizeof(struct skb_shared_info)); |
282 | |
283 | per_mss = roundup_pow_of_two(per_mss) + |
284 | SKB_DATA_ALIGN(sizeof(struct sk_buff)); |
285 | |
286 | nr_segs = max_t(u32, TCP_INIT_CWND, tp->snd_cwnd); |
287 | nr_segs = max_t(u32, nr_segs, tp->reordering + 1); |
288 | |
289 | /* Fast Recovery (RFC 5681 3.2) : |
290 | * Cubic needs 1.7 factor, rounded to 2 to include |
291 | * extra cushion (application might react slowly to POLLOUT) |
292 | */ |
293 | sndmem = 2 * nr_segs * per_mss; |
294 | |
295 | if (sk->sk_sndbuf < sndmem) |
296 | sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); |
297 | } |
298 | |
299 | /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) |
300 | * |
301 | * All tcp_full_space() is split to two parts: "network" buffer, allocated |
302 | * forward and advertised in receiver window (tp->rcv_wnd) and |
303 | * "application buffer", required to isolate scheduling/application |
304 | * latencies from network. |
305 | * window_clamp is maximal advertised window. It can be less than |
306 | * tcp_full_space(), in this case tcp_full_space() - window_clamp |
307 | * is reserved for "application" buffer. The less window_clamp is |
308 | * the smoother our behaviour from viewpoint of network, but the lower |
309 | * throughput and the higher sensitivity of the connection to losses. 8) |
310 | * |
311 | * rcv_ssthresh is more strict window_clamp used at "slow start" |
312 | * phase to predict further behaviour of this connection. |
313 | * It is used for two goals: |
314 | * - to enforce header prediction at sender, even when application |
315 | * requires some significant "application buffer". It is check #1. |
316 | * - to prevent pruning of receive queue because of misprediction |
317 | * of receiver window. Check #2. |
318 | * |
319 | * The scheme does not work when sender sends good segments opening |
320 | * window and then starts to feed us spaghetti. But it should work |
321 | * in common situations. Otherwise, we have to rely on queue collapsing. |
322 | */ |
323 | |
324 | /* Slow part of check#2. */ |
325 | static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) |
326 | { |
327 | struct tcp_sock *tp = tcp_sk(sk); |
328 | /* Optimize this! */ |
329 | int truesize = tcp_win_from_space(skb->truesize) >> 1; |
330 | int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; |
331 | |
332 | while (tp->rcv_ssthresh <= window) { |
333 | if (truesize <= skb->len) |
334 | return 2 * inet_csk(sk)->icsk_ack.rcv_mss; |
335 | |
336 | truesize >>= 1; |
337 | window >>= 1; |
338 | } |
339 | return 0; |
340 | } |
341 | |
342 | static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb) |
343 | { |
344 | struct tcp_sock *tp = tcp_sk(sk); |
345 | |
346 | /* Check #1 */ |
347 | if (tp->rcv_ssthresh < tp->window_clamp && |
348 | (int)tp->rcv_ssthresh < tcp_space(sk) && |
349 | !sk_under_memory_pressure(sk)) { |
350 | int incr; |
351 | |
352 | /* Check #2. Increase window, if skb with such overhead |
353 | * will fit to rcvbuf in future. |
354 | */ |
355 | if (tcp_win_from_space(skb->truesize) <= skb->len) |
356 | incr = 2 * tp->advmss; |
357 | else |
358 | incr = __tcp_grow_window(sk, skb); |
359 | |
360 | if (incr) { |
361 | incr = max_t(int, incr, 2 * skb->len); |
362 | tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, |
363 | tp->window_clamp); |
364 | inet_csk(sk)->icsk_ack.quick |= 1; |
365 | } |
366 | } |
367 | } |
368 | |
369 | /* 3. Tuning rcvbuf, when connection enters established state. */ |
370 | static void tcp_fixup_rcvbuf(struct sock *sk) |
371 | { |
372 | u32 mss = tcp_sk(sk)->advmss; |
373 | int rcvmem; |
374 | |
375 | rcvmem = 2 * SKB_TRUESIZE(mss + MAX_TCP_HEADER) * |
376 | tcp_default_init_rwnd(mss); |
377 | |
378 | /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency |
379 | * Allow enough cushion so that sender is not limited by our window |
380 | */ |
381 | if (sysctl_tcp_moderate_rcvbuf) |
382 | rcvmem <<= 2; |
383 | |
384 | if (sk->sk_rcvbuf < rcvmem) |
385 | sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]); |
386 | } |
387 | |
388 | /* 4. Try to fixup all. It is made immediately after connection enters |
389 | * established state. |
390 | */ |
391 | void tcp_init_buffer_space(struct sock *sk) |
392 | { |
393 | struct tcp_sock *tp = tcp_sk(sk); |
394 | int maxwin; |
395 | |
396 | if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) |
397 | tcp_fixup_rcvbuf(sk); |
398 | if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) |
399 | tcp_sndbuf_expand(sk); |
400 | |
401 | tp->rcvq_space.space = tp->rcv_wnd; |
402 | tp->rcvq_space.time = tcp_time_stamp; |
403 | tp->rcvq_space.seq = tp->copied_seq; |
404 | |
405 | maxwin = tcp_full_space(sk); |
406 | |
407 | if (tp->window_clamp >= maxwin) { |
408 | tp->window_clamp = maxwin; |
409 | |
410 | if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) |
411 | tp->window_clamp = max(maxwin - |
412 | (maxwin >> sysctl_tcp_app_win), |
413 | 4 * tp->advmss); |
414 | } |
415 | |
416 | /* Force reservation of one segment. */ |
417 | if (sysctl_tcp_app_win && |
418 | tp->window_clamp > 2 * tp->advmss && |
419 | tp->window_clamp + tp->advmss > maxwin) |
420 | tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); |
421 | |
422 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); |
423 | tp->snd_cwnd_stamp = tcp_time_stamp; |
424 | } |
425 | |
426 | /* 5. Recalculate window clamp after socket hit its memory bounds. */ |
427 | static void tcp_clamp_window(struct sock *sk) |
428 | { |
429 | struct tcp_sock *tp = tcp_sk(sk); |
430 | struct inet_connection_sock *icsk = inet_csk(sk); |
431 | |
432 | icsk->icsk_ack.quick = 0; |
433 | |
434 | if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && |
435 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && |
436 | !sk_under_memory_pressure(sk) && |
437 | sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) { |
438 | sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), |
439 | sysctl_tcp_rmem[2]); |
440 | } |
441 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) |
442 | tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); |
443 | } |
444 | |
445 | /* Initialize RCV_MSS value. |
446 | * RCV_MSS is an our guess about MSS used by the peer. |
447 | * We haven't any direct information about the MSS. |
448 | * It's better to underestimate the RCV_MSS rather than overestimate. |
449 | * Overestimations make us ACKing less frequently than needed. |
450 | * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). |
451 | */ |
452 | void tcp_initialize_rcv_mss(struct sock *sk) |
453 | { |
454 | const struct tcp_sock *tp = tcp_sk(sk); |
455 | unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); |
456 | |
457 | hint = min(hint, tp->rcv_wnd / 2); |
458 | hint = min(hint, TCP_MSS_DEFAULT); |
459 | hint = max(hint, TCP_MIN_MSS); |
460 | |
461 | inet_csk(sk)->icsk_ack.rcv_mss = hint; |
462 | } |
463 | EXPORT_SYMBOL(tcp_initialize_rcv_mss); |
464 | |
465 | /* Receiver "autotuning" code. |
466 | * |
467 | * The algorithm for RTT estimation w/o timestamps is based on |
468 | * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. |
469 | * <http://public.lanl.gov/radiant/pubs.html#DRS> |
470 | * |
471 | * More detail on this code can be found at |
472 | * <http://staff.psc.edu/jheffner/>, |
473 | * though this reference is out of date. A new paper |
474 | * is pending. |
475 | */ |
476 | static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) |
477 | { |
478 | u32 new_sample = tp->rcv_rtt_est.rtt; |
479 | long m = sample; |
480 | |
481 | if (m == 0) |
482 | m = 1; |
483 | |
484 | if (new_sample != 0) { |
485 | /* If we sample in larger samples in the non-timestamp |
486 | * case, we could grossly overestimate the RTT especially |
487 | * with chatty applications or bulk transfer apps which |
488 | * are stalled on filesystem I/O. |
489 | * |
490 | * Also, since we are only going for a minimum in the |
491 | * non-timestamp case, we do not smooth things out |
492 | * else with timestamps disabled convergence takes too |
493 | * long. |
494 | */ |
495 | if (!win_dep) { |
496 | m -= (new_sample >> 3); |
497 | new_sample += m; |
498 | } else { |
499 | m <<= 3; |
500 | if (m < new_sample) |
501 | new_sample = m; |
502 | } |
503 | } else { |
504 | /* No previous measure. */ |
505 | new_sample = m << 3; |
506 | } |
507 | |
508 | if (tp->rcv_rtt_est.rtt != new_sample) |
509 | tp->rcv_rtt_est.rtt = new_sample; |
510 | } |
511 | |
512 | static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) |
513 | { |
514 | if (tp->rcv_rtt_est.time == 0) |
515 | goto new_measure; |
516 | if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) |
517 | return; |
518 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rcv_rtt_est.time, 1); |
519 | |
520 | new_measure: |
521 | tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; |
522 | tp->rcv_rtt_est.time = tcp_time_stamp; |
523 | } |
524 | |
525 | static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, |
526 | const struct sk_buff *skb) |
527 | { |
528 | struct tcp_sock *tp = tcp_sk(sk); |
529 | if (tp->rx_opt.rcv_tsecr && |
530 | (TCP_SKB_CB(skb)->end_seq - |
531 | TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) |
532 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); |
533 | } |
534 | |
535 | /* |
536 | * This function should be called every time data is copied to user space. |
537 | * It calculates the appropriate TCP receive buffer space. |
538 | */ |
539 | void tcp_rcv_space_adjust(struct sock *sk) |
540 | { |
541 | struct tcp_sock *tp = tcp_sk(sk); |
542 | int time; |
543 | int copied; |
544 | |
545 | time = tcp_time_stamp - tp->rcvq_space.time; |
546 | if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) |
547 | return; |
548 | |
549 | /* Number of bytes copied to user in last RTT */ |
550 | copied = tp->copied_seq - tp->rcvq_space.seq; |
551 | if (copied <= tp->rcvq_space.space) |
552 | goto new_measure; |
553 | |
554 | /* A bit of theory : |
555 | * copied = bytes received in previous RTT, our base window |
556 | * To cope with packet losses, we need a 2x factor |
557 | * To cope with slow start, and sender growing its cwin by 100 % |
558 | * every RTT, we need a 4x factor, because the ACK we are sending |
559 | * now is for the next RTT, not the current one : |
560 | * <prev RTT . ><current RTT .. ><next RTT .... > |
561 | */ |
562 | |
563 | if (sysctl_tcp_moderate_rcvbuf && |
564 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { |
565 | int rcvwin, rcvmem, rcvbuf; |
566 | |
567 | /* minimal window to cope with packet losses, assuming |
568 | * steady state. Add some cushion because of small variations. |
569 | */ |
570 | rcvwin = (copied << 1) + 16 * tp->advmss; |
571 | |
572 | /* If rate increased by 25%, |
573 | * assume slow start, rcvwin = 3 * copied |
574 | * If rate increased by 50%, |
575 | * assume sender can use 2x growth, rcvwin = 4 * copied |
576 | */ |
577 | if (copied >= |
578 | tp->rcvq_space.space + (tp->rcvq_space.space >> 2)) { |
579 | if (copied >= |
580 | tp->rcvq_space.space + (tp->rcvq_space.space >> 1)) |
581 | rcvwin <<= 1; |
582 | else |
583 | rcvwin += (rcvwin >> 1); |
584 | } |
585 | |
586 | rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); |
587 | while (tcp_win_from_space(rcvmem) < tp->advmss) |
588 | rcvmem += 128; |
589 | |
590 | rcvbuf = min(rcvwin / tp->advmss * rcvmem, sysctl_tcp_rmem[2]); |
591 | if (rcvbuf > sk->sk_rcvbuf) { |
592 | sk->sk_rcvbuf = rcvbuf; |
593 | |
594 | /* Make the window clamp follow along. */ |
595 | tp->window_clamp = rcvwin; |
596 | } |
597 | } |
598 | tp->rcvq_space.space = copied; |
599 | |
600 | new_measure: |
601 | tp->rcvq_space.seq = tp->copied_seq; |
602 | tp->rcvq_space.time = tcp_time_stamp; |
603 | } |
604 | |
605 | /* There is something which you must keep in mind when you analyze the |
606 | * behavior of the tp->ato delayed ack timeout interval. When a |
607 | * connection starts up, we want to ack as quickly as possible. The |
608 | * problem is that "good" TCP's do slow start at the beginning of data |
609 | * transmission. The means that until we send the first few ACK's the |
610 | * sender will sit on his end and only queue most of his data, because |
611 | * he can only send snd_cwnd unacked packets at any given time. For |
612 | * each ACK we send, he increments snd_cwnd and transmits more of his |
613 | * queue. -DaveM |
614 | */ |
615 | static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) |
616 | { |
617 | struct tcp_sock *tp = tcp_sk(sk); |
618 | struct inet_connection_sock *icsk = inet_csk(sk); |
619 | u32 now; |
620 | |
621 | inet_csk_schedule_ack(sk); |
622 | |
623 | tcp_measure_rcv_mss(sk, skb); |
624 | |
625 | tcp_rcv_rtt_measure(tp); |
626 | |
627 | now = tcp_time_stamp; |
628 | |
629 | if (!icsk->icsk_ack.ato) { |
630 | /* The _first_ data packet received, initialize |
631 | * delayed ACK engine. |
632 | */ |
633 | tcp_incr_quickack(sk); |
634 | icsk->icsk_ack.ato = TCP_ATO_MIN; |
635 | } else { |
636 | int m = now - icsk->icsk_ack.lrcvtime; |
637 | |
638 | if (m <= TCP_ATO_MIN / 2) { |
639 | /* The fastest case is the first. */ |
640 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; |
641 | } else if (m < icsk->icsk_ack.ato) { |
642 | icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; |
643 | if (icsk->icsk_ack.ato > icsk->icsk_rto) |
644 | icsk->icsk_ack.ato = icsk->icsk_rto; |
645 | } else if (m > icsk->icsk_rto) { |
646 | /* Too long gap. Apparently sender failed to |
647 | * restart window, so that we send ACKs quickly. |
648 | */ |
649 | tcp_incr_quickack(sk); |
650 | sk_mem_reclaim(sk); |
651 | } |
652 | } |
653 | icsk->icsk_ack.lrcvtime = now; |
654 | |
655 | TCP_ECN_check_ce(tp, skb); |
656 | |
657 | if (skb->len >= 128) |
658 | tcp_grow_window(sk, skb); |
659 | } |
660 | |
661 | /* Called to compute a smoothed rtt estimate. The data fed to this |
662 | * routine either comes from timestamps, or from segments that were |
663 | * known _not_ to have been retransmitted [see Karn/Partridge |
664 | * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 |
665 | * piece by Van Jacobson. |
666 | * NOTE: the next three routines used to be one big routine. |
667 | * To save cycles in the RFC 1323 implementation it was better to break |
668 | * it up into three procedures. -- erics |
669 | */ |
670 | static void tcp_rtt_estimator(struct sock *sk, long mrtt_us) |
671 | { |
672 | struct tcp_sock *tp = tcp_sk(sk); |
673 | long m = mrtt_us; /* RTT */ |
674 | u32 srtt = tp->srtt_us; |
675 | |
676 | /* The following amusing code comes from Jacobson's |
677 | * article in SIGCOMM '88. Note that rtt and mdev |
678 | * are scaled versions of rtt and mean deviation. |
679 | * This is designed to be as fast as possible |
680 | * m stands for "measurement". |
681 | * |
682 | * On a 1990 paper the rto value is changed to: |
683 | * RTO = rtt + 4 * mdev |
684 | * |
685 | * Funny. This algorithm seems to be very broken. |
686 | * These formulae increase RTO, when it should be decreased, increase |
687 | * too slowly, when it should be increased quickly, decrease too quickly |
688 | * etc. I guess in BSD RTO takes ONE value, so that it is absolutely |
689 | * does not matter how to _calculate_ it. Seems, it was trap |
690 | * that VJ failed to avoid. 8) |
691 | */ |
692 | if (srtt != 0) { |
693 | m -= (srtt >> 3); /* m is now error in rtt est */ |
694 | srtt += m; /* rtt = 7/8 rtt + 1/8 new */ |
695 | if (m < 0) { |
696 | m = -m; /* m is now abs(error) */ |
697 | m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
698 | /* This is similar to one of Eifel findings. |
699 | * Eifel blocks mdev updates when rtt decreases. |
700 | * This solution is a bit different: we use finer gain |
701 | * for mdev in this case (alpha*beta). |
702 | * Like Eifel it also prevents growth of rto, |
703 | * but also it limits too fast rto decreases, |
704 | * happening in pure Eifel. |
705 | */ |
706 | if (m > 0) |
707 | m >>= 3; |
708 | } else { |
709 | m -= (tp->mdev_us >> 2); /* similar update on mdev */ |
710 | } |
711 | tp->mdev_us += m; /* mdev = 3/4 mdev + 1/4 new */ |
712 | if (tp->mdev_us > tp->mdev_max_us) { |
713 | tp->mdev_max_us = tp->mdev_us; |
714 | if (tp->mdev_max_us > tp->rttvar_us) |
715 | tp->rttvar_us = tp->mdev_max_us; |
716 | } |
717 | if (after(tp->snd_una, tp->rtt_seq)) { |
718 | if (tp->mdev_max_us < tp->rttvar_us) |
719 | tp->rttvar_us -= (tp->rttvar_us - tp->mdev_max_us) >> 2; |
720 | tp->rtt_seq = tp->snd_nxt; |
721 | tp->mdev_max_us = tcp_rto_min_us(sk); |
722 | } |
723 | } else { |
724 | /* no previous measure. */ |
725 | srtt = m << 3; /* take the measured time to be rtt */ |
726 | tp->mdev_us = m << 1; /* make sure rto = 3*rtt */ |
727 | tp->rttvar_us = max(tp->mdev_us, tcp_rto_min_us(sk)); |
728 | tp->mdev_max_us = tp->rttvar_us; |
729 | tp->rtt_seq = tp->snd_nxt; |
730 | } |
731 | tp->srtt_us = max(1U, srtt); |
732 | } |
733 | |
734 | /* Set the sk_pacing_rate to allow proper sizing of TSO packets. |
735 | * Note: TCP stack does not yet implement pacing. |
736 | * FQ packet scheduler can be used to implement cheap but effective |
737 | * TCP pacing, to smooth the burst on large writes when packets |
738 | * in flight is significantly lower than cwnd (or rwin) |
739 | */ |
740 | static void tcp_update_pacing_rate(struct sock *sk) |
741 | { |
742 | const struct tcp_sock *tp = tcp_sk(sk); |
743 | u64 rate; |
744 | |
745 | /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */ |
746 | rate = (u64)tp->mss_cache * 2 * (USEC_PER_SEC << 3); |
747 | |
748 | rate *= max(tp->snd_cwnd, tp->packets_out); |
749 | |
750 | if (likely(tp->srtt_us)) |
751 | do_div(rate, tp->srtt_us); |
752 | |
753 | /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate |
754 | * without any lock. We want to make sure compiler wont store |
755 | * intermediate values in this location. |
756 | */ |
757 | ACCESS_ONCE(sk->sk_pacing_rate) = min_t(u64, rate, |
758 | sk->sk_max_pacing_rate); |
759 | } |
760 | |
761 | /* Calculate rto without backoff. This is the second half of Van Jacobson's |
762 | * routine referred to above. |
763 | */ |
764 | static void tcp_set_rto(struct sock *sk) |
765 | { |
766 | const struct tcp_sock *tp = tcp_sk(sk); |
767 | /* Old crap is replaced with new one. 8) |
768 | * |
769 | * More seriously: |
770 | * 1. If rtt variance happened to be less 50msec, it is hallucination. |
771 | * It cannot be less due to utterly erratic ACK generation made |
772 | * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ |
773 | * to do with delayed acks, because at cwnd>2 true delack timeout |
774 | * is invisible. Actually, Linux-2.4 also generates erratic |
775 | * ACKs in some circumstances. |
776 | */ |
777 | inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); |
778 | |
779 | /* 2. Fixups made earlier cannot be right. |
780 | * If we do not estimate RTO correctly without them, |
781 | * all the algo is pure shit and should be replaced |
782 | * with correct one. It is exactly, which we pretend to do. |
783 | */ |
784 | |
785 | /* NOTE: clamping at TCP_RTO_MIN is not required, current algo |
786 | * guarantees that rto is higher. |
787 | */ |
788 | tcp_bound_rto(sk); |
789 | } |
790 | |
791 | __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst) |
792 | { |
793 | __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); |
794 | |
795 | if (!cwnd) |
796 | cwnd = TCP_INIT_CWND; |
797 | return min_t(__u32, cwnd, tp->snd_cwnd_clamp); |
798 | } |
799 | |
800 | /* |
801 | * Packet counting of FACK is based on in-order assumptions, therefore TCP |
802 | * disables it when reordering is detected |
803 | */ |
804 | void tcp_disable_fack(struct tcp_sock *tp) |
805 | { |
806 | /* RFC3517 uses different metric in lost marker => reset on change */ |
807 | if (tcp_is_fack(tp)) |
808 | tp->lost_skb_hint = NULL; |
809 | tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED; |
810 | } |
811 | |
812 | /* Take a notice that peer is sending D-SACKs */ |
813 | static void tcp_dsack_seen(struct tcp_sock *tp) |
814 | { |
815 | tp->rx_opt.sack_ok |= TCP_DSACK_SEEN; |
816 | } |
817 | |
818 | static void tcp_update_reordering(struct sock *sk, const int metric, |
819 | const int ts) |
820 | { |
821 | struct tcp_sock *tp = tcp_sk(sk); |
822 | if (metric > tp->reordering) { |
823 | int mib_idx; |
824 | |
825 | tp->reordering = min(TCP_MAX_REORDERING, metric); |
826 | |
827 | /* This exciting event is worth to be remembered. 8) */ |
828 | if (ts) |
829 | mib_idx = LINUX_MIB_TCPTSREORDER; |
830 | else if (tcp_is_reno(tp)) |
831 | mib_idx = LINUX_MIB_TCPRENOREORDER; |
832 | else if (tcp_is_fack(tp)) |
833 | mib_idx = LINUX_MIB_TCPFACKREORDER; |
834 | else |
835 | mib_idx = LINUX_MIB_TCPSACKREORDER; |
836 | |
837 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
838 | #if FASTRETRANS_DEBUG > 1 |
839 | pr_debug("Disorder%d %d %u f%u s%u rr%d\n", |
840 | tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, |
841 | tp->reordering, |
842 | tp->fackets_out, |
843 | tp->sacked_out, |
844 | tp->undo_marker ? tp->undo_retrans : 0); |
845 | #endif |
846 | tcp_disable_fack(tp); |
847 | } |
848 | |
849 | if (metric > 0) |
850 | tcp_disable_early_retrans(tp); |
851 | } |
852 | |
853 | /* This must be called before lost_out is incremented */ |
854 | static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) |
855 | { |
856 | if ((tp->retransmit_skb_hint == NULL) || |
857 | before(TCP_SKB_CB(skb)->seq, |
858 | TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) |
859 | tp->retransmit_skb_hint = skb; |
860 | |
861 | if (!tp->lost_out || |
862 | after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) |
863 | tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; |
864 | } |
865 | |
866 | static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) |
867 | { |
868 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
869 | tcp_verify_retransmit_hint(tp, skb); |
870 | |
871 | tp->lost_out += tcp_skb_pcount(skb); |
872 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
873 | } |
874 | } |
875 | |
876 | static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, |
877 | struct sk_buff *skb) |
878 | { |
879 | tcp_verify_retransmit_hint(tp, skb); |
880 | |
881 | if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { |
882 | tp->lost_out += tcp_skb_pcount(skb); |
883 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
884 | } |
885 | } |
886 | |
887 | /* This procedure tags the retransmission queue when SACKs arrive. |
888 | * |
889 | * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). |
890 | * Packets in queue with these bits set are counted in variables |
891 | * sacked_out, retrans_out and lost_out, correspondingly. |
892 | * |
893 | * Valid combinations are: |
894 | * Tag InFlight Description |
895 | * 0 1 - orig segment is in flight. |
896 | * S 0 - nothing flies, orig reached receiver. |
897 | * L 0 - nothing flies, orig lost by net. |
898 | * R 2 - both orig and retransmit are in flight. |
899 | * L|R 1 - orig is lost, retransmit is in flight. |
900 | * S|R 1 - orig reached receiver, retrans is still in flight. |
901 | * (L|S|R is logically valid, it could occur when L|R is sacked, |
902 | * but it is equivalent to plain S and code short-curcuits it to S. |
903 | * L|S is logically invalid, it would mean -1 packet in flight 8)) |
904 | * |
905 | * These 6 states form finite state machine, controlled by the following events: |
906 | * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) |
907 | * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) |
908 | * 3. Loss detection event of two flavors: |
909 | * A. Scoreboard estimator decided the packet is lost. |
910 | * A'. Reno "three dupacks" marks head of queue lost. |
911 | * A''. Its FACK modification, head until snd.fack is lost. |
912 | * B. SACK arrives sacking SND.NXT at the moment, when the |
913 | * segment was retransmitted. |
914 | * 4. D-SACK added new rule: D-SACK changes any tag to S. |
915 | * |
916 | * It is pleasant to note, that state diagram turns out to be commutative, |
917 | * so that we are allowed not to be bothered by order of our actions, |
918 | * when multiple events arrive simultaneously. (see the function below). |
919 | * |
920 | * Reordering detection. |
921 | * -------------------- |
922 | * Reordering metric is maximal distance, which a packet can be displaced |
923 | * in packet stream. With SACKs we can estimate it: |
924 | * |
925 | * 1. SACK fills old hole and the corresponding segment was not |
926 | * ever retransmitted -> reordering. Alas, we cannot use it |
927 | * when segment was retransmitted. |
928 | * 2. The last flaw is solved with D-SACK. D-SACK arrives |
929 | * for retransmitted and already SACKed segment -> reordering.. |
930 | * Both of these heuristics are not used in Loss state, when we cannot |
931 | * account for retransmits accurately. |
932 | * |
933 | * SACK block validation. |
934 | * ---------------------- |
935 | * |
936 | * SACK block range validation checks that the received SACK block fits to |
937 | * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. |
938 | * Note that SND.UNA is not included to the range though being valid because |
939 | * it means that the receiver is rather inconsistent with itself reporting |
940 | * SACK reneging when it should advance SND.UNA. Such SACK block this is |
941 | * perfectly valid, however, in light of RFC2018 which explicitly states |
942 | * that "SACK block MUST reflect the newest segment. Even if the newest |
943 | * segment is going to be discarded ...", not that it looks very clever |
944 | * in case of head skb. Due to potentional receiver driven attacks, we |
945 | * choose to avoid immediate execution of a walk in write queue due to |
946 | * reneging and defer head skb's loss recovery to standard loss recovery |
947 | * procedure that will eventually trigger (nothing forbids us doing this). |
948 | * |
949 | * Implements also blockage to start_seq wrap-around. Problem lies in the |
950 | * fact that though start_seq (s) is before end_seq (i.e., not reversed), |
951 | * there's no guarantee that it will be before snd_nxt (n). The problem |
952 | * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt |
953 | * wrap (s_w): |
954 | * |
955 | * <- outs wnd -> <- wrapzone -> |
956 | * u e n u_w e_w s n_w |
957 | * | | | | | | | |
958 | * |<------------+------+----- TCP seqno space --------------+---------->| |
959 | * ...-- <2^31 ->| |<--------... |
960 | * ...---- >2^31 ------>| |<--------... |
961 | * |
962 | * Current code wouldn't be vulnerable but it's better still to discard such |
963 | * crazy SACK blocks. Doing this check for start_seq alone closes somewhat |
964 | * similar case (end_seq after snd_nxt wrap) as earlier reversed check in |
965 | * snd_nxt wrap -> snd_una region will then become "well defined", i.e., |
966 | * equal to the ideal case (infinite seqno space without wrap caused issues). |
967 | * |
968 | * With D-SACK the lower bound is extended to cover sequence space below |
969 | * SND.UNA down to undo_marker, which is the last point of interest. Yet |
970 | * again, D-SACK block must not to go across snd_una (for the same reason as |
971 | * for the normal SACK blocks, explained above). But there all simplicity |
972 | * ends, TCP might receive valid D-SACKs below that. As long as they reside |
973 | * fully below undo_marker they do not affect behavior in anyway and can |
974 | * therefore be safely ignored. In rare cases (which are more or less |
975 | * theoretical ones), the D-SACK will nicely cross that boundary due to skb |
976 | * fragmentation and packet reordering past skb's retransmission. To consider |
977 | * them correctly, the acceptable range must be extended even more though |
978 | * the exact amount is rather hard to quantify. However, tp->max_window can |
979 | * be used as an exaggerated estimate. |
980 | */ |
981 | static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack, |
982 | u32 start_seq, u32 end_seq) |
983 | { |
984 | /* Too far in future, or reversed (interpretation is ambiguous) */ |
985 | if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) |
986 | return false; |
987 | |
988 | /* Nasty start_seq wrap-around check (see comments above) */ |
989 | if (!before(start_seq, tp->snd_nxt)) |
990 | return false; |
991 | |
992 | /* In outstanding window? ...This is valid exit for D-SACKs too. |
993 | * start_seq == snd_una is non-sensical (see comments above) |
994 | */ |
995 | if (after(start_seq, tp->snd_una)) |
996 | return true; |
997 | |
998 | if (!is_dsack || !tp->undo_marker) |
999 | return false; |
1000 | |
1001 | /* ...Then it's D-SACK, and must reside below snd_una completely */ |
1002 | if (after(end_seq, tp->snd_una)) |
1003 | return false; |
1004 | |
1005 | if (!before(start_seq, tp->undo_marker)) |
1006 | return true; |
1007 | |
1008 | /* Too old */ |
1009 | if (!after(end_seq, tp->undo_marker)) |
1010 | return false; |
1011 | |
1012 | /* Undo_marker boundary crossing (overestimates a lot). Known already: |
1013 | * start_seq < undo_marker and end_seq >= undo_marker. |
1014 | */ |
1015 | return !before(start_seq, end_seq - tp->max_window); |
1016 | } |
1017 | |
1018 | /* Check for lost retransmit. This superb idea is borrowed from "ratehalving". |
1019 | * Event "B". Later note: FACK people cheated me again 8), we have to account |
1020 | * for reordering! Ugly, but should help. |
1021 | * |
1022 | * Search retransmitted skbs from write_queue that were sent when snd_nxt was |
1023 | * less than what is now known to be received by the other end (derived from |
1024 | * highest SACK block). Also calculate the lowest snd_nxt among the remaining |
1025 | * retransmitted skbs to avoid some costly processing per ACKs. |
1026 | */ |
1027 | static void tcp_mark_lost_retrans(struct sock *sk) |
1028 | { |
1029 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1030 | struct tcp_sock *tp = tcp_sk(sk); |
1031 | struct sk_buff *skb; |
1032 | int cnt = 0; |
1033 | u32 new_low_seq = tp->snd_nxt; |
1034 | u32 received_upto = tcp_highest_sack_seq(tp); |
1035 | |
1036 | if (!tcp_is_fack(tp) || !tp->retrans_out || |
1037 | !after(received_upto, tp->lost_retrans_low) || |
1038 | icsk->icsk_ca_state != TCP_CA_Recovery) |
1039 | return; |
1040 | |
1041 | tcp_for_write_queue(skb, sk) { |
1042 | u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; |
1043 | |
1044 | if (skb == tcp_send_head(sk)) |
1045 | break; |
1046 | if (cnt == tp->retrans_out) |
1047 | break; |
1048 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
1049 | continue; |
1050 | |
1051 | if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) |
1052 | continue; |
1053 | |
1054 | /* TODO: We would like to get rid of tcp_is_fack(tp) only |
1055 | * constraint here (see above) but figuring out that at |
1056 | * least tp->reordering SACK blocks reside between ack_seq |
1057 | * and received_upto is not easy task to do cheaply with |
1058 | * the available datastructures. |
1059 | * |
1060 | * Whether FACK should check here for tp->reordering segs |
1061 | * in-between one could argue for either way (it would be |
1062 | * rather simple to implement as we could count fack_count |
1063 | * during the walk and do tp->fackets_out - fack_count). |
1064 | */ |
1065 | if (after(received_upto, ack_seq)) { |
1066 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
1067 | tp->retrans_out -= tcp_skb_pcount(skb); |
1068 | |
1069 | tcp_skb_mark_lost_uncond_verify(tp, skb); |
1070 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); |
1071 | } else { |
1072 | if (before(ack_seq, new_low_seq)) |
1073 | new_low_seq = ack_seq; |
1074 | cnt += tcp_skb_pcount(skb); |
1075 | } |
1076 | } |
1077 | |
1078 | if (tp->retrans_out) |
1079 | tp->lost_retrans_low = new_low_seq; |
1080 | } |
1081 | |
1082 | static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb, |
1083 | struct tcp_sack_block_wire *sp, int num_sacks, |
1084 | u32 prior_snd_una) |
1085 | { |
1086 | struct tcp_sock *tp = tcp_sk(sk); |
1087 | u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); |
1088 | u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); |
1089 | bool dup_sack = false; |
1090 | |
1091 | if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { |
1092 | dup_sack = true; |
1093 | tcp_dsack_seen(tp); |
1094 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); |
1095 | } else if (num_sacks > 1) { |
1096 | u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); |
1097 | u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); |
1098 | |
1099 | if (!after(end_seq_0, end_seq_1) && |
1100 | !before(start_seq_0, start_seq_1)) { |
1101 | dup_sack = true; |
1102 | tcp_dsack_seen(tp); |
1103 | NET_INC_STATS_BH(sock_net(sk), |
1104 | LINUX_MIB_TCPDSACKOFORECV); |
1105 | } |
1106 | } |
1107 | |
1108 | /* D-SACK for already forgotten data... Do dumb counting. */ |
1109 | if (dup_sack && tp->undo_marker && tp->undo_retrans && |
1110 | !after(end_seq_0, prior_snd_una) && |
1111 | after(end_seq_0, tp->undo_marker)) |
1112 | tp->undo_retrans--; |
1113 | |
1114 | return dup_sack; |
1115 | } |
1116 | |
1117 | struct tcp_sacktag_state { |
1118 | int reord; |
1119 | int fack_count; |
1120 | long rtt_us; /* RTT measured by SACKing never-retransmitted data */ |
1121 | int flag; |
1122 | }; |
1123 | |
1124 | /* Check if skb is fully within the SACK block. In presence of GSO skbs, |
1125 | * the incoming SACK may not exactly match but we can find smaller MSS |
1126 | * aligned portion of it that matches. Therefore we might need to fragment |
1127 | * which may fail and creates some hassle (caller must handle error case |
1128 | * returns). |
1129 | * |
1130 | * FIXME: this could be merged to shift decision code |
1131 | */ |
1132 | static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, |
1133 | u32 start_seq, u32 end_seq) |
1134 | { |
1135 | int err; |
1136 | bool in_sack; |
1137 | unsigned int pkt_len; |
1138 | unsigned int mss; |
1139 | |
1140 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
1141 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); |
1142 | |
1143 | if (tcp_skb_pcount(skb) > 1 && !in_sack && |
1144 | after(TCP_SKB_CB(skb)->end_seq, start_seq)) { |
1145 | mss = tcp_skb_mss(skb); |
1146 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
1147 | |
1148 | if (!in_sack) { |
1149 | pkt_len = start_seq - TCP_SKB_CB(skb)->seq; |
1150 | if (pkt_len < mss) |
1151 | pkt_len = mss; |
1152 | } else { |
1153 | pkt_len = end_seq - TCP_SKB_CB(skb)->seq; |
1154 | if (pkt_len < mss) |
1155 | return -EINVAL; |
1156 | } |
1157 | |
1158 | /* Round if necessary so that SACKs cover only full MSSes |
1159 | * and/or the remaining small portion (if present) |
1160 | */ |
1161 | if (pkt_len > mss) { |
1162 | unsigned int new_len = (pkt_len / mss) * mss; |
1163 | if (!in_sack && new_len < pkt_len) { |
1164 | new_len += mss; |
1165 | if (new_len > skb->len) |
1166 | return 0; |
1167 | } |
1168 | pkt_len = new_len; |
1169 | } |
1170 | err = tcp_fragment(sk, skb, pkt_len, mss); |
1171 | if (err < 0) |
1172 | return err; |
1173 | } |
1174 | |
1175 | return in_sack; |
1176 | } |
1177 | |
1178 | /* Mark the given newly-SACKed range as such, adjusting counters and hints. */ |
1179 | static u8 tcp_sacktag_one(struct sock *sk, |
1180 | struct tcp_sacktag_state *state, u8 sacked, |
1181 | u32 start_seq, u32 end_seq, |
1182 | int dup_sack, int pcount, |
1183 | const struct skb_mstamp *xmit_time) |
1184 | { |
1185 | struct tcp_sock *tp = tcp_sk(sk); |
1186 | int fack_count = state->fack_count; |
1187 | |
1188 | /* Account D-SACK for retransmitted packet. */ |
1189 | if (dup_sack && (sacked & TCPCB_RETRANS)) { |
1190 | if (tp->undo_marker && tp->undo_retrans && |
1191 | after(end_seq, tp->undo_marker)) |
1192 | tp->undo_retrans--; |
1193 | if (sacked & TCPCB_SACKED_ACKED) |
1194 | state->reord = min(fack_count, state->reord); |
1195 | } |
1196 | |
1197 | /* Nothing to do; acked frame is about to be dropped (was ACKed). */ |
1198 | if (!after(end_seq, tp->snd_una)) |
1199 | return sacked; |
1200 | |
1201 | if (!(sacked & TCPCB_SACKED_ACKED)) { |
1202 | if (sacked & TCPCB_SACKED_RETRANS) { |
1203 | /* If the segment is not tagged as lost, |
1204 | * we do not clear RETRANS, believing |
1205 | * that retransmission is still in flight. |
1206 | */ |
1207 | if (sacked & TCPCB_LOST) { |
1208 | sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); |
1209 | tp->lost_out -= pcount; |
1210 | tp->retrans_out -= pcount; |
1211 | } |
1212 | } else { |
1213 | if (!(sacked & TCPCB_RETRANS)) { |
1214 | /* New sack for not retransmitted frame, |
1215 | * which was in hole. It is reordering. |
1216 | */ |
1217 | if (before(start_seq, |
1218 | tcp_highest_sack_seq(tp))) |
1219 | state->reord = min(fack_count, |
1220 | state->reord); |
1221 | if (!after(end_seq, tp->high_seq)) |
1222 | state->flag |= FLAG_ORIG_SACK_ACKED; |
1223 | /* Pick the earliest sequence sacked for RTT */ |
1224 | if (state->rtt_us < 0) { |
1225 | struct skb_mstamp now; |
1226 | |
1227 | skb_mstamp_get(&now); |
1228 | state->rtt_us = skb_mstamp_us_delta(&now, |
1229 | xmit_time); |
1230 | } |
1231 | } |
1232 | |
1233 | if (sacked & TCPCB_LOST) { |
1234 | sacked &= ~TCPCB_LOST; |
1235 | tp->lost_out -= pcount; |
1236 | } |
1237 | } |
1238 | |
1239 | sacked |= TCPCB_SACKED_ACKED; |
1240 | state->flag |= FLAG_DATA_SACKED; |
1241 | tp->sacked_out += pcount; |
1242 | |
1243 | fack_count += pcount; |
1244 | |
1245 | /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ |
1246 | if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && |
1247 | before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq)) |
1248 | tp->lost_cnt_hint += pcount; |
1249 | |
1250 | if (fack_count > tp->fackets_out) |
1251 | tp->fackets_out = fack_count; |
1252 | } |
1253 | |
1254 | /* D-SACK. We can detect redundant retransmission in S|R and plain R |
1255 | * frames and clear it. undo_retrans is decreased above, L|R frames |
1256 | * are accounted above as well. |
1257 | */ |
1258 | if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { |
1259 | sacked &= ~TCPCB_SACKED_RETRANS; |
1260 | tp->retrans_out -= pcount; |
1261 | } |
1262 | |
1263 | return sacked; |
1264 | } |
1265 | |
1266 | /* Shift newly-SACKed bytes from this skb to the immediately previous |
1267 | * already-SACKed sk_buff. Mark the newly-SACKed bytes as such. |
1268 | */ |
1269 | static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, |
1270 | struct tcp_sacktag_state *state, |
1271 | unsigned int pcount, int shifted, int mss, |
1272 | bool dup_sack) |
1273 | { |
1274 | struct tcp_sock *tp = tcp_sk(sk); |
1275 | struct sk_buff *prev = tcp_write_queue_prev(sk, skb); |
1276 | u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */ |
1277 | u32 end_seq = start_seq + shifted; /* end of newly-SACKed */ |
1278 | |
1279 | BUG_ON(!pcount); |
1280 | |
1281 | /* Adjust counters and hints for the newly sacked sequence |
1282 | * range but discard the return value since prev is already |
1283 | * marked. We must tag the range first because the seq |
1284 | * advancement below implicitly advances |
1285 | * tcp_highest_sack_seq() when skb is highest_sack. |
1286 | */ |
1287 | tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked, |
1288 | start_seq, end_seq, dup_sack, pcount, |
1289 | &skb->skb_mstamp); |
1290 | |
1291 | if (skb == tp->lost_skb_hint) |
1292 | tp->lost_cnt_hint += pcount; |
1293 | |
1294 | TCP_SKB_CB(prev)->end_seq += shifted; |
1295 | TCP_SKB_CB(skb)->seq += shifted; |
1296 | |
1297 | skb_shinfo(prev)->gso_segs += pcount; |
1298 | BUG_ON(skb_shinfo(skb)->gso_segs < pcount); |
1299 | skb_shinfo(skb)->gso_segs -= pcount; |
1300 | |
1301 | /* When we're adding to gso_segs == 1, gso_size will be zero, |
1302 | * in theory this shouldn't be necessary but as long as DSACK |
1303 | * code can come after this skb later on it's better to keep |
1304 | * setting gso_size to something. |
1305 | */ |
1306 | if (!skb_shinfo(prev)->gso_size) { |
1307 | skb_shinfo(prev)->gso_size = mss; |
1308 | skb_shinfo(prev)->gso_type = sk->sk_gso_type; |
1309 | } |
1310 | |
1311 | /* CHECKME: To clear or not to clear? Mimics normal skb currently */ |
1312 | if (skb_shinfo(skb)->gso_segs <= 1) { |
1313 | skb_shinfo(skb)->gso_size = 0; |
1314 | skb_shinfo(skb)->gso_type = 0; |
1315 | } |
1316 | |
1317 | /* Difference in this won't matter, both ACKed by the same cumul. ACK */ |
1318 | TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); |
1319 | |
1320 | if (skb->len > 0) { |
1321 | BUG_ON(!tcp_skb_pcount(skb)); |
1322 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); |
1323 | return false; |
1324 | } |
1325 | |
1326 | /* Whole SKB was eaten :-) */ |
1327 | |
1328 | if (skb == tp->retransmit_skb_hint) |
1329 | tp->retransmit_skb_hint = prev; |
1330 | if (skb == tp->lost_skb_hint) { |
1331 | tp->lost_skb_hint = prev; |
1332 | tp->lost_cnt_hint -= tcp_skb_pcount(prev); |
1333 | } |
1334 | |
1335 | TCP_SKB_CB(prev)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; |
1336 | if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) |
1337 | TCP_SKB_CB(prev)->end_seq++; |
1338 | |
1339 | if (skb == tcp_highest_sack(sk)) |
1340 | tcp_advance_highest_sack(sk, skb); |
1341 | |
1342 | tcp_unlink_write_queue(skb, sk); |
1343 | sk_wmem_free_skb(sk, skb); |
1344 | |
1345 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); |
1346 | |
1347 | return true; |
1348 | } |
1349 | |
1350 | /* I wish gso_size would have a bit more sane initialization than |
1351 | * something-or-zero which complicates things |
1352 | */ |
1353 | static int tcp_skb_seglen(const struct sk_buff *skb) |
1354 | { |
1355 | return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); |
1356 | } |
1357 | |
1358 | /* Shifting pages past head area doesn't work */ |
1359 | static int skb_can_shift(const struct sk_buff *skb) |
1360 | { |
1361 | return !skb_headlen(skb) && skb_is_nonlinear(skb); |
1362 | } |
1363 | |
1364 | /* Try collapsing SACK blocks spanning across multiple skbs to a single |
1365 | * skb. |
1366 | */ |
1367 | static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, |
1368 | struct tcp_sacktag_state *state, |
1369 | u32 start_seq, u32 end_seq, |
1370 | bool dup_sack) |
1371 | { |
1372 | struct tcp_sock *tp = tcp_sk(sk); |
1373 | struct sk_buff *prev; |
1374 | int mss; |
1375 | int pcount = 0; |
1376 | int len; |
1377 | int in_sack; |
1378 | |
1379 | if (!sk_can_gso(sk)) |
1380 | goto fallback; |
1381 | |
1382 | /* Normally R but no L won't result in plain S */ |
1383 | if (!dup_sack && |
1384 | (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) |
1385 | goto fallback; |
1386 | if (!skb_can_shift(skb)) |
1387 | goto fallback; |
1388 | /* This frame is about to be dropped (was ACKed). */ |
1389 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
1390 | goto fallback; |
1391 | |
1392 | /* Can only happen with delayed DSACK + discard craziness */ |
1393 | if (unlikely(skb == tcp_write_queue_head(sk))) |
1394 | goto fallback; |
1395 | prev = tcp_write_queue_prev(sk, skb); |
1396 | |
1397 | if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) |
1398 | goto fallback; |
1399 | |
1400 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && |
1401 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); |
1402 | |
1403 | if (in_sack) { |
1404 | len = skb->len; |
1405 | pcount = tcp_skb_pcount(skb); |
1406 | mss = tcp_skb_seglen(skb); |
1407 | |
1408 | /* TODO: Fix DSACKs to not fragment already SACKed and we can |
1409 | * drop this restriction as unnecessary |
1410 | */ |
1411 | if (mss != tcp_skb_seglen(prev)) |
1412 | goto fallback; |
1413 | } else { |
1414 | if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) |
1415 | goto noop; |
1416 | /* CHECKME: This is non-MSS split case only?, this will |
1417 | * cause skipped skbs due to advancing loop btw, original |
1418 | * has that feature too |
1419 | */ |
1420 | if (tcp_skb_pcount(skb) <= 1) |
1421 | goto noop; |
1422 | |
1423 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); |
1424 | if (!in_sack) { |
1425 | /* TODO: head merge to next could be attempted here |
1426 | * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), |
1427 | * though it might not be worth of the additional hassle |
1428 | * |
1429 | * ...we can probably just fallback to what was done |
1430 | * previously. We could try merging non-SACKed ones |
1431 | * as well but it probably isn't going to buy off |
1432 | * because later SACKs might again split them, and |
1433 | * it would make skb timestamp tracking considerably |
1434 | * harder problem. |
1435 | */ |
1436 | goto fallback; |
1437 | } |
1438 | |
1439 | len = end_seq - TCP_SKB_CB(skb)->seq; |
1440 | BUG_ON(len < 0); |
1441 | BUG_ON(len > skb->len); |
1442 | |
1443 | /* MSS boundaries should be honoured or else pcount will |
1444 | * severely break even though it makes things bit trickier. |
1445 | * Optimize common case to avoid most of the divides |
1446 | */ |
1447 | mss = tcp_skb_mss(skb); |
1448 | |
1449 | /* TODO: Fix DSACKs to not fragment already SACKed and we can |
1450 | * drop this restriction as unnecessary |
1451 | */ |
1452 | if (mss != tcp_skb_seglen(prev)) |
1453 | goto fallback; |
1454 | |
1455 | if (len == mss) { |
1456 | pcount = 1; |
1457 | } else if (len < mss) { |
1458 | goto noop; |
1459 | } else { |
1460 | pcount = len / mss; |
1461 | len = pcount * mss; |
1462 | } |
1463 | } |
1464 | |
1465 | /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */ |
1466 | if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una)) |
1467 | goto fallback; |
1468 | |
1469 | if (!skb_shift(prev, skb, len)) |
1470 | goto fallback; |
1471 | if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) |
1472 | goto out; |
1473 | |
1474 | /* Hole filled allows collapsing with the next as well, this is very |
1475 | * useful when hole on every nth skb pattern happens |
1476 | */ |
1477 | if (prev == tcp_write_queue_tail(sk)) |
1478 | goto out; |
1479 | skb = tcp_write_queue_next(sk, prev); |
1480 | |
1481 | if (!skb_can_shift(skb) || |
1482 | (skb == tcp_send_head(sk)) || |
1483 | ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || |
1484 | (mss != tcp_skb_seglen(skb))) |
1485 | goto out; |
1486 | |
1487 | len = skb->len; |
1488 | if (skb_shift(prev, skb, len)) { |
1489 | pcount += tcp_skb_pcount(skb); |
1490 | tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); |
1491 | } |
1492 | |
1493 | out: |
1494 | state->fack_count += pcount; |
1495 | return prev; |
1496 | |
1497 | noop: |
1498 | return skb; |
1499 | |
1500 | fallback: |
1501 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); |
1502 | return NULL; |
1503 | } |
1504 | |
1505 | static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, |
1506 | struct tcp_sack_block *next_dup, |
1507 | struct tcp_sacktag_state *state, |
1508 | u32 start_seq, u32 end_seq, |
1509 | bool dup_sack_in) |
1510 | { |
1511 | struct tcp_sock *tp = tcp_sk(sk); |
1512 | struct sk_buff *tmp; |
1513 | |
1514 | tcp_for_write_queue_from(skb, sk) { |
1515 | int in_sack = 0; |
1516 | bool dup_sack = dup_sack_in; |
1517 | |
1518 | if (skb == tcp_send_head(sk)) |
1519 | break; |
1520 | |
1521 | /* queue is in-order => we can short-circuit the walk early */ |
1522 | if (!before(TCP_SKB_CB(skb)->seq, end_seq)) |
1523 | break; |
1524 | |
1525 | if ((next_dup != NULL) && |
1526 | before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { |
1527 | in_sack = tcp_match_skb_to_sack(sk, skb, |
1528 | next_dup->start_seq, |
1529 | next_dup->end_seq); |
1530 | if (in_sack > 0) |
1531 | dup_sack = true; |
1532 | } |
1533 | |
1534 | /* skb reference here is a bit tricky to get right, since |
1535 | * shifting can eat and free both this skb and the next, |
1536 | * so not even _safe variant of the loop is enough. |
1537 | */ |
1538 | if (in_sack <= 0) { |
1539 | tmp = tcp_shift_skb_data(sk, skb, state, |
1540 | start_seq, end_seq, dup_sack); |
1541 | if (tmp != NULL) { |
1542 | if (tmp != skb) { |
1543 | skb = tmp; |
1544 | continue; |
1545 | } |
1546 | |
1547 | in_sack = 0; |
1548 | } else { |
1549 | in_sack = tcp_match_skb_to_sack(sk, skb, |
1550 | start_seq, |
1551 | end_seq); |
1552 | } |
1553 | } |
1554 | |
1555 | if (unlikely(in_sack < 0)) |
1556 | break; |
1557 | |
1558 | if (in_sack) { |
1559 | TCP_SKB_CB(skb)->sacked = |
1560 | tcp_sacktag_one(sk, |
1561 | state, |
1562 | TCP_SKB_CB(skb)->sacked, |
1563 | TCP_SKB_CB(skb)->seq, |
1564 | TCP_SKB_CB(skb)->end_seq, |
1565 | dup_sack, |
1566 | tcp_skb_pcount(skb), |
1567 | &skb->skb_mstamp); |
1568 | |
1569 | if (!before(TCP_SKB_CB(skb)->seq, |
1570 | tcp_highest_sack_seq(tp))) |
1571 | tcp_advance_highest_sack(sk, skb); |
1572 | } |
1573 | |
1574 | state->fack_count += tcp_skb_pcount(skb); |
1575 | } |
1576 | return skb; |
1577 | } |
1578 | |
1579 | /* Avoid all extra work that is being done by sacktag while walking in |
1580 | * a normal way |
1581 | */ |
1582 | static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, |
1583 | struct tcp_sacktag_state *state, |
1584 | u32 skip_to_seq) |
1585 | { |
1586 | tcp_for_write_queue_from(skb, sk) { |
1587 | if (skb == tcp_send_head(sk)) |
1588 | break; |
1589 | |
1590 | if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) |
1591 | break; |
1592 | |
1593 | state->fack_count += tcp_skb_pcount(skb); |
1594 | } |
1595 | return skb; |
1596 | } |
1597 | |
1598 | static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, |
1599 | struct sock *sk, |
1600 | struct tcp_sack_block *next_dup, |
1601 | struct tcp_sacktag_state *state, |
1602 | u32 skip_to_seq) |
1603 | { |
1604 | if (next_dup == NULL) |
1605 | return skb; |
1606 | |
1607 | if (before(next_dup->start_seq, skip_to_seq)) { |
1608 | skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); |
1609 | skb = tcp_sacktag_walk(skb, sk, NULL, state, |
1610 | next_dup->start_seq, next_dup->end_seq, |
1611 | 1); |
1612 | } |
1613 | |
1614 | return skb; |
1615 | } |
1616 | |
1617 | static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache) |
1618 | { |
1619 | return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
1620 | } |
1621 | |
1622 | static int |
1623 | tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb, |
1624 | u32 prior_snd_una, long *sack_rtt_us) |
1625 | { |
1626 | struct tcp_sock *tp = tcp_sk(sk); |
1627 | const unsigned char *ptr = (skb_transport_header(ack_skb) + |
1628 | TCP_SKB_CB(ack_skb)->sacked); |
1629 | struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); |
1630 | struct tcp_sack_block sp[TCP_NUM_SACKS]; |
1631 | struct tcp_sack_block *cache; |
1632 | struct tcp_sacktag_state state; |
1633 | struct sk_buff *skb; |
1634 | int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); |
1635 | int used_sacks; |
1636 | bool found_dup_sack = false; |
1637 | int i, j; |
1638 | int first_sack_index; |
1639 | |
1640 | state.flag = 0; |
1641 | state.reord = tp->packets_out; |
1642 | state.rtt_us = -1L; |
1643 | |
1644 | if (!tp->sacked_out) { |
1645 | if (WARN_ON(tp->fackets_out)) |
1646 | tp->fackets_out = 0; |
1647 | tcp_highest_sack_reset(sk); |
1648 | } |
1649 | |
1650 | found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, |
1651 | num_sacks, prior_snd_una); |
1652 | if (found_dup_sack) |
1653 | state.flag |= FLAG_DSACKING_ACK; |
1654 | |
1655 | /* Eliminate too old ACKs, but take into |
1656 | * account more or less fresh ones, they can |
1657 | * contain valid SACK info. |
1658 | */ |
1659 | if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) |
1660 | return 0; |
1661 | |
1662 | if (!tp->packets_out) |
1663 | goto out; |
1664 | |
1665 | used_sacks = 0; |
1666 | first_sack_index = 0; |
1667 | for (i = 0; i < num_sacks; i++) { |
1668 | bool dup_sack = !i && found_dup_sack; |
1669 | |
1670 | sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); |
1671 | sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); |
1672 | |
1673 | if (!tcp_is_sackblock_valid(tp, dup_sack, |
1674 | sp[used_sacks].start_seq, |
1675 | sp[used_sacks].end_seq)) { |
1676 | int mib_idx; |
1677 | |
1678 | if (dup_sack) { |
1679 | if (!tp->undo_marker) |
1680 | mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; |
1681 | else |
1682 | mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; |
1683 | } else { |
1684 | /* Don't count olds caused by ACK reordering */ |
1685 | if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && |
1686 | !after(sp[used_sacks].end_seq, tp->snd_una)) |
1687 | continue; |
1688 | mib_idx = LINUX_MIB_TCPSACKDISCARD; |
1689 | } |
1690 | |
1691 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
1692 | if (i == 0) |
1693 | first_sack_index = -1; |
1694 | continue; |
1695 | } |
1696 | |
1697 | /* Ignore very old stuff early */ |
1698 | if (!after(sp[used_sacks].end_seq, prior_snd_una)) |
1699 | continue; |
1700 | |
1701 | used_sacks++; |
1702 | } |
1703 | |
1704 | /* order SACK blocks to allow in order walk of the retrans queue */ |
1705 | for (i = used_sacks - 1; i > 0; i--) { |
1706 | for (j = 0; j < i; j++) { |
1707 | if (after(sp[j].start_seq, sp[j + 1].start_seq)) { |
1708 | swap(sp[j], sp[j + 1]); |
1709 | |
1710 | /* Track where the first SACK block goes to */ |
1711 | if (j == first_sack_index) |
1712 | first_sack_index = j + 1; |
1713 | } |
1714 | } |
1715 | } |
1716 | |
1717 | skb = tcp_write_queue_head(sk); |
1718 | state.fack_count = 0; |
1719 | i = 0; |
1720 | |
1721 | if (!tp->sacked_out) { |
1722 | /* It's already past, so skip checking against it */ |
1723 | cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); |
1724 | } else { |
1725 | cache = tp->recv_sack_cache; |
1726 | /* Skip empty blocks in at head of the cache */ |
1727 | while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && |
1728 | !cache->end_seq) |
1729 | cache++; |
1730 | } |
1731 | |
1732 | while (i < used_sacks) { |
1733 | u32 start_seq = sp[i].start_seq; |
1734 | u32 end_seq = sp[i].end_seq; |
1735 | bool dup_sack = (found_dup_sack && (i == first_sack_index)); |
1736 | struct tcp_sack_block *next_dup = NULL; |
1737 | |
1738 | if (found_dup_sack && ((i + 1) == first_sack_index)) |
1739 | next_dup = &sp[i + 1]; |
1740 | |
1741 | /* Skip too early cached blocks */ |
1742 | while (tcp_sack_cache_ok(tp, cache) && |
1743 | !before(start_seq, cache->end_seq)) |
1744 | cache++; |
1745 | |
1746 | /* Can skip some work by looking recv_sack_cache? */ |
1747 | if (tcp_sack_cache_ok(tp, cache) && !dup_sack && |
1748 | after(end_seq, cache->start_seq)) { |
1749 | |
1750 | /* Head todo? */ |
1751 | if (before(start_seq, cache->start_seq)) { |
1752 | skb = tcp_sacktag_skip(skb, sk, &state, |
1753 | start_seq); |
1754 | skb = tcp_sacktag_walk(skb, sk, next_dup, |
1755 | &state, |
1756 | start_seq, |
1757 | cache->start_seq, |
1758 | dup_sack); |
1759 | } |
1760 | |
1761 | /* Rest of the block already fully processed? */ |
1762 | if (!after(end_seq, cache->end_seq)) |
1763 | goto advance_sp; |
1764 | |
1765 | skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, |
1766 | &state, |
1767 | cache->end_seq); |
1768 | |
1769 | /* ...tail remains todo... */ |
1770 | if (tcp_highest_sack_seq(tp) == cache->end_seq) { |
1771 | /* ...but better entrypoint exists! */ |
1772 | skb = tcp_highest_sack(sk); |
1773 | if (skb == NULL) |
1774 | break; |
1775 | state.fack_count = tp->fackets_out; |
1776 | cache++; |
1777 | goto walk; |
1778 | } |
1779 | |
1780 | skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq); |
1781 | /* Check overlap against next cached too (past this one already) */ |
1782 | cache++; |
1783 | continue; |
1784 | } |
1785 | |
1786 | if (!before(start_seq, tcp_highest_sack_seq(tp))) { |
1787 | skb = tcp_highest_sack(sk); |
1788 | if (skb == NULL) |
1789 | break; |
1790 | state.fack_count = tp->fackets_out; |
1791 | } |
1792 | skb = tcp_sacktag_skip(skb, sk, &state, start_seq); |
1793 | |
1794 | walk: |
1795 | skb = tcp_sacktag_walk(skb, sk, next_dup, &state, |
1796 | start_seq, end_seq, dup_sack); |
1797 | |
1798 | advance_sp: |
1799 | i++; |
1800 | } |
1801 | |
1802 | /* Clear the head of the cache sack blocks so we can skip it next time */ |
1803 | for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { |
1804 | tp->recv_sack_cache[i].start_seq = 0; |
1805 | tp->recv_sack_cache[i].end_seq = 0; |
1806 | } |
1807 | for (j = 0; j < used_sacks; j++) |
1808 | tp->recv_sack_cache[i++] = sp[j]; |
1809 | |
1810 | tcp_mark_lost_retrans(sk); |
1811 | |
1812 | tcp_verify_left_out(tp); |
1813 | |
1814 | if ((state.reord < tp->fackets_out) && |
1815 | ((inet_csk(sk)->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker)) |
1816 | tcp_update_reordering(sk, tp->fackets_out - state.reord, 0); |
1817 | |
1818 | out: |
1819 | |
1820 | #if FASTRETRANS_DEBUG > 0 |
1821 | WARN_ON((int)tp->sacked_out < 0); |
1822 | WARN_ON((int)tp->lost_out < 0); |
1823 | WARN_ON((int)tp->retrans_out < 0); |
1824 | WARN_ON((int)tcp_packets_in_flight(tp) < 0); |
1825 | #endif |
1826 | *sack_rtt_us = state.rtt_us; |
1827 | return state.flag; |
1828 | } |
1829 | |
1830 | /* Limits sacked_out so that sum with lost_out isn't ever larger than |
1831 | * packets_out. Returns false if sacked_out adjustement wasn't necessary. |
1832 | */ |
1833 | static bool tcp_limit_reno_sacked(struct tcp_sock *tp) |
1834 | { |
1835 | u32 holes; |
1836 | |
1837 | holes = max(tp->lost_out, 1U); |
1838 | holes = min(holes, tp->packets_out); |
1839 | |
1840 | if ((tp->sacked_out + holes) > tp->packets_out) { |
1841 | tp->sacked_out = tp->packets_out - holes; |
1842 | return true; |
1843 | } |
1844 | return false; |
1845 | } |
1846 | |
1847 | /* If we receive more dupacks than we expected counting segments |
1848 | * in assumption of absent reordering, interpret this as reordering. |
1849 | * The only another reason could be bug in receiver TCP. |
1850 | */ |
1851 | static void tcp_check_reno_reordering(struct sock *sk, const int addend) |
1852 | { |
1853 | struct tcp_sock *tp = tcp_sk(sk); |
1854 | if (tcp_limit_reno_sacked(tp)) |
1855 | tcp_update_reordering(sk, tp->packets_out + addend, 0); |
1856 | } |
1857 | |
1858 | /* Emulate SACKs for SACKless connection: account for a new dupack. */ |
1859 | |
1860 | static void tcp_add_reno_sack(struct sock *sk) |
1861 | { |
1862 | struct tcp_sock *tp = tcp_sk(sk); |
1863 | tp->sacked_out++; |
1864 | tcp_check_reno_reordering(sk, 0); |
1865 | tcp_verify_left_out(tp); |
1866 | } |
1867 | |
1868 | /* Account for ACK, ACKing some data in Reno Recovery phase. */ |
1869 | |
1870 | static void tcp_remove_reno_sacks(struct sock *sk, int acked) |
1871 | { |
1872 | struct tcp_sock *tp = tcp_sk(sk); |
1873 | |
1874 | if (acked > 0) { |
1875 | /* One ACK acked hole. The rest eat duplicate ACKs. */ |
1876 | if (acked - 1 >= tp->sacked_out) |
1877 | tp->sacked_out = 0; |
1878 | else |
1879 | tp->sacked_out -= acked - 1; |
1880 | } |
1881 | tcp_check_reno_reordering(sk, acked); |
1882 | tcp_verify_left_out(tp); |
1883 | } |
1884 | |
1885 | static inline void tcp_reset_reno_sack(struct tcp_sock *tp) |
1886 | { |
1887 | tp->sacked_out = 0; |
1888 | } |
1889 | |
1890 | static void tcp_clear_retrans_partial(struct tcp_sock *tp) |
1891 | { |
1892 | tp->retrans_out = 0; |
1893 | tp->lost_out = 0; |
1894 | |
1895 | tp->undo_marker = 0; |
1896 | tp->undo_retrans = 0; |
1897 | } |
1898 | |
1899 | void tcp_clear_retrans(struct tcp_sock *tp) |
1900 | { |
1901 | tcp_clear_retrans_partial(tp); |
1902 | |
1903 | tp->fackets_out = 0; |
1904 | tp->sacked_out = 0; |
1905 | } |
1906 | |
1907 | /* Enter Loss state. If "how" is not zero, forget all SACK information |
1908 | * and reset tags completely, otherwise preserve SACKs. If receiver |
1909 | * dropped its ofo queue, we will know this due to reneging detection. |
1910 | */ |
1911 | void tcp_enter_loss(struct sock *sk, int how) |
1912 | { |
1913 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1914 | struct tcp_sock *tp = tcp_sk(sk); |
1915 | struct sk_buff *skb; |
1916 | bool new_recovery = false; |
1917 | |
1918 | /* Reduce ssthresh if it has not yet been made inside this window. */ |
1919 | if (icsk->icsk_ca_state <= TCP_CA_Disorder || |
1920 | !after(tp->high_seq, tp->snd_una) || |
1921 | (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { |
1922 | new_recovery = true; |
1923 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
1924 | tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); |
1925 | tcp_ca_event(sk, CA_EVENT_LOSS); |
1926 | } |
1927 | tp->snd_cwnd = 1; |
1928 | tp->snd_cwnd_cnt = 0; |
1929 | tp->snd_cwnd_stamp = tcp_time_stamp; |
1930 | |
1931 | tcp_clear_retrans_partial(tp); |
1932 | |
1933 | if (tcp_is_reno(tp)) |
1934 | tcp_reset_reno_sack(tp); |
1935 | |
1936 | tp->undo_marker = tp->snd_una; |
1937 | if (how) { |
1938 | tp->sacked_out = 0; |
1939 | tp->fackets_out = 0; |
1940 | } |
1941 | tcp_clear_all_retrans_hints(tp); |
1942 | |
1943 | tcp_for_write_queue(skb, sk) { |
1944 | if (skb == tcp_send_head(sk)) |
1945 | break; |
1946 | |
1947 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) |
1948 | tp->undo_marker = 0; |
1949 | |
1950 | TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; |
1951 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { |
1952 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; |
1953 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; |
1954 | tp->lost_out += tcp_skb_pcount(skb); |
1955 | tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; |
1956 | } |
1957 | } |
1958 | tcp_verify_left_out(tp); |
1959 | |
1960 | /* Timeout in disordered state after receiving substantial DUPACKs |
1961 | * suggests that the degree of reordering is over-estimated. |
1962 | */ |
1963 | if (icsk->icsk_ca_state <= TCP_CA_Disorder && |
1964 | tp->sacked_out >= sysctl_tcp_reordering) |
1965 | tp->reordering = min_t(unsigned int, tp->reordering, |
1966 | sysctl_tcp_reordering); |
1967 | tcp_set_ca_state(sk, TCP_CA_Loss); |
1968 | tp->high_seq = tp->snd_nxt; |
1969 | TCP_ECN_queue_cwr(tp); |
1970 | |
1971 | /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous |
1972 | * loss recovery is underway except recurring timeout(s) on |
1973 | * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing |
1974 | */ |
1975 | tp->frto = sysctl_tcp_frto && |
1976 | (new_recovery || icsk->icsk_retransmits) && |
1977 | !inet_csk(sk)->icsk_mtup.probe_size; |
1978 | } |
1979 | |
1980 | /* If ACK arrived pointing to a remembered SACK, it means that our |
1981 | * remembered SACKs do not reflect real state of receiver i.e. |
1982 | * receiver _host_ is heavily congested (or buggy). |
1983 | * |
1984 | * Do processing similar to RTO timeout. |
1985 | */ |
1986 | static bool tcp_check_sack_reneging(struct sock *sk, int flag) |
1987 | { |
1988 | if (flag & FLAG_SACK_RENEGING) { |
1989 | struct inet_connection_sock *icsk = inet_csk(sk); |
1990 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); |
1991 | |
1992 | tcp_enter_loss(sk, 1); |
1993 | icsk->icsk_retransmits++; |
1994 | tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); |
1995 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
1996 | icsk->icsk_rto, TCP_RTO_MAX); |
1997 | return true; |
1998 | } |
1999 | return false; |
2000 | } |
2001 | |
2002 | static inline int tcp_fackets_out(const struct tcp_sock *tp) |
2003 | { |
2004 | return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out; |
2005 | } |
2006 | |
2007 | /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs |
2008 | * counter when SACK is enabled (without SACK, sacked_out is used for |
2009 | * that purpose). |
2010 | * |
2011 | * Instead, with FACK TCP uses fackets_out that includes both SACKed |
2012 | * segments up to the highest received SACK block so far and holes in |
2013 | * between them. |
2014 | * |
2015 | * With reordering, holes may still be in flight, so RFC3517 recovery |
2016 | * uses pure sacked_out (total number of SACKed segments) even though |
2017 | * it violates the RFC that uses duplicate ACKs, often these are equal |
2018 | * but when e.g. out-of-window ACKs or packet duplication occurs, |
2019 | * they differ. Since neither occurs due to loss, TCP should really |
2020 | * ignore them. |
2021 | */ |
2022 | static inline int tcp_dupack_heuristics(const struct tcp_sock *tp) |
2023 | { |
2024 | return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; |
2025 | } |
2026 | |
2027 | static bool tcp_pause_early_retransmit(struct sock *sk, int flag) |
2028 | { |
2029 | struct tcp_sock *tp = tcp_sk(sk); |
2030 | unsigned long delay; |
2031 | |
2032 | /* Delay early retransmit and entering fast recovery for |
2033 | * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples |
2034 | * available, or RTO is scheduled to fire first. |
2035 | */ |
2036 | if (sysctl_tcp_early_retrans < 2 || sysctl_tcp_early_retrans > 3 || |
2037 | (flag & FLAG_ECE) || !tp->srtt_us) |
2038 | return false; |
2039 | |
2040 | delay = max(usecs_to_jiffies(tp->srtt_us >> 5), |
2041 | msecs_to_jiffies(2)); |
2042 | |
2043 | if (!time_after(inet_csk(sk)->icsk_timeout, (jiffies + delay))) |
2044 | return false; |
2045 | |
2046 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_EARLY_RETRANS, delay, |
2047 | TCP_RTO_MAX); |
2048 | return true; |
2049 | } |
2050 | |
2051 | /* Linux NewReno/SACK/FACK/ECN state machine. |
2052 | * -------------------------------------- |
2053 | * |
2054 | * "Open" Normal state, no dubious events, fast path. |
2055 | * "Disorder" In all the respects it is "Open", |
2056 | * but requires a bit more attention. It is entered when |
2057 | * we see some SACKs or dupacks. It is split of "Open" |
2058 | * mainly to move some processing from fast path to slow one. |
2059 | * "CWR" CWND was reduced due to some Congestion Notification event. |
2060 | * It can be ECN, ICMP source quench, local device congestion. |
2061 | * "Recovery" CWND was reduced, we are fast-retransmitting. |
2062 | * "Loss" CWND was reduced due to RTO timeout or SACK reneging. |
2063 | * |
2064 | * tcp_fastretrans_alert() is entered: |
2065 | * - each incoming ACK, if state is not "Open" |
2066 | * - when arrived ACK is unusual, namely: |
2067 | * * SACK |
2068 | * * Duplicate ACK. |
2069 | * * ECN ECE. |
2070 | * |
2071 | * Counting packets in flight is pretty simple. |
2072 | * |
2073 | * in_flight = packets_out - left_out + retrans_out |
2074 | * |
2075 | * packets_out is SND.NXT-SND.UNA counted in packets. |
2076 | * |
2077 | * retrans_out is number of retransmitted segments. |
2078 | * |
2079 | * left_out is number of segments left network, but not ACKed yet. |
2080 | * |
2081 | * left_out = sacked_out + lost_out |
2082 | * |
2083 | * sacked_out: Packets, which arrived to receiver out of order |
2084 | * and hence not ACKed. With SACKs this number is simply |
2085 | * amount of SACKed data. Even without SACKs |
2086 | * it is easy to give pretty reliable estimate of this number, |
2087 | * counting duplicate ACKs. |
2088 | * |
2089 | * lost_out: Packets lost by network. TCP has no explicit |
2090 | * "loss notification" feedback from network (for now). |
2091 | * It means that this number can be only _guessed_. |
2092 | * Actually, it is the heuristics to predict lossage that |
2093 | * distinguishes different algorithms. |
2094 | * |
2095 | * F.e. after RTO, when all the queue is considered as lost, |
2096 | * lost_out = packets_out and in_flight = retrans_out. |
2097 | * |
2098 | * Essentially, we have now two algorithms counting |
2099 | * lost packets. |
2100 | * |
2101 | * FACK: It is the simplest heuristics. As soon as we decided |
2102 | * that something is lost, we decide that _all_ not SACKed |
2103 | * packets until the most forward SACK are lost. I.e. |
2104 | * lost_out = fackets_out - sacked_out and left_out = fackets_out. |
2105 | * It is absolutely correct estimate, if network does not reorder |
2106 | * packets. And it loses any connection to reality when reordering |
2107 | * takes place. We use FACK by default until reordering |
2108 | * is suspected on the path to this destination. |
2109 | * |
2110 | * NewReno: when Recovery is entered, we assume that one segment |
2111 | * is lost (classic Reno). While we are in Recovery and |
2112 | * a partial ACK arrives, we assume that one more packet |
2113 | * is lost (NewReno). This heuristics are the same in NewReno |
2114 | * and SACK. |
2115 | * |
2116 | * Imagine, that's all! Forget about all this shamanism about CWND inflation |
2117 | * deflation etc. CWND is real congestion window, never inflated, changes |
2118 | * only according to classic VJ rules. |
2119 | * |
2120 | * Really tricky (and requiring careful tuning) part of algorithm |
2121 | * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). |
2122 | * The first determines the moment _when_ we should reduce CWND and, |
2123 | * hence, slow down forward transmission. In fact, it determines the moment |
2124 | * when we decide that hole is caused by loss, rather than by a reorder. |
2125 | * |
2126 | * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill |
2127 | * holes, caused by lost packets. |
2128 | * |
2129 | * And the most logically complicated part of algorithm is undo |
2130 | * heuristics. We detect false retransmits due to both too early |
2131 | * fast retransmit (reordering) and underestimated RTO, analyzing |
2132 | * timestamps and D-SACKs. When we detect that some segments were |
2133 | * retransmitted by mistake and CWND reduction was wrong, we undo |
2134 | * window reduction and abort recovery phase. This logic is hidden |
2135 | * inside several functions named tcp_try_undo_<something>. |
2136 | */ |
2137 | |
2138 | /* This function decides, when we should leave Disordered state |
2139 | * and enter Recovery phase, reducing congestion window. |
2140 | * |
2141 | * Main question: may we further continue forward transmission |
2142 | * with the same cwnd? |
2143 | */ |
2144 | static bool tcp_time_to_recover(struct sock *sk, int flag) |
2145 | { |
2146 | struct tcp_sock *tp = tcp_sk(sk); |
2147 | __u32 packets_out; |
2148 | |
2149 | /* Trick#1: The loss is proven. */ |
2150 | if (tp->lost_out) |
2151 | return true; |
2152 | |
2153 | /* Not-A-Trick#2 : Classic rule... */ |
2154 | if (tcp_dupack_heuristics(tp) > tp->reordering) |
2155 | return true; |
2156 | |
2157 | /* Trick#4: It is still not OK... But will it be useful to delay |
2158 | * recovery more? |
2159 | */ |
2160 | packets_out = tp->packets_out; |
2161 | if (packets_out <= tp->reordering && |
2162 | tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && |
2163 | !tcp_may_send_now(sk)) { |
2164 | /* We have nothing to send. This connection is limited |
2165 | * either by receiver window or by application. |
2166 | */ |
2167 | return true; |
2168 | } |
2169 | |
2170 | /* If a thin stream is detected, retransmit after first |
2171 | * received dupack. Employ only if SACK is supported in order |
2172 | * to avoid possible corner-case series of spurious retransmissions |
2173 | * Use only if there are no unsent data. |
2174 | */ |
2175 | if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && |
2176 | tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && |
2177 | tcp_is_sack(tp) && !tcp_send_head(sk)) |
2178 | return true; |
2179 | |
2180 | /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious |
2181 | * retransmissions due to small network reorderings, we implement |
2182 | * Mitigation A.3 in the RFC and delay the retransmission for a short |
2183 | * interval if appropriate. |
2184 | */ |
2185 | if (tp->do_early_retrans && !tp->retrans_out && tp->sacked_out && |
2186 | (tp->packets_out >= (tp->sacked_out + 1) && tp->packets_out < 4) && |
2187 | !tcp_may_send_now(sk)) |
2188 | return !tcp_pause_early_retransmit(sk, flag); |
2189 | |
2190 | return false; |
2191 | } |
2192 | |
2193 | /* Detect loss in event "A" above by marking head of queue up as lost. |
2194 | * For FACK or non-SACK(Reno) senders, the first "packets" number of segments |
2195 | * are considered lost. For RFC3517 SACK, a segment is considered lost if it |
2196 | * has at least tp->reordering SACKed seqments above it; "packets" refers to |
2197 | * the maximum SACKed segments to pass before reaching this limit. |
2198 | */ |
2199 | static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head) |
2200 | { |
2201 | struct tcp_sock *tp = tcp_sk(sk); |
2202 | struct sk_buff *skb; |
2203 | int cnt, oldcnt; |
2204 | int err; |
2205 | unsigned int mss; |
2206 | /* Use SACK to deduce losses of new sequences sent during recovery */ |
2207 | const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq; |
2208 | |
2209 | WARN_ON(packets > tp->packets_out); |
2210 | if (tp->lost_skb_hint) { |
2211 | skb = tp->lost_skb_hint; |
2212 | cnt = tp->lost_cnt_hint; |
2213 | /* Head already handled? */ |
2214 | if (mark_head && skb != tcp_write_queue_head(sk)) |
2215 | return; |
2216 | } else { |
2217 | skb = tcp_write_queue_head(sk); |
2218 | cnt = 0; |
2219 | } |
2220 | |
2221 | tcp_for_write_queue_from(skb, sk) { |
2222 | if (skb == tcp_send_head(sk)) |
2223 | break; |
2224 | /* TODO: do this better */ |
2225 | /* this is not the most efficient way to do this... */ |
2226 | tp->lost_skb_hint = skb; |
2227 | tp->lost_cnt_hint = cnt; |
2228 | |
2229 | if (after(TCP_SKB_CB(skb)->end_seq, loss_high)) |
2230 | break; |
2231 | |
2232 | oldcnt = cnt; |
2233 | if (tcp_is_fack(tp) || tcp_is_reno(tp) || |
2234 | (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) |
2235 | cnt += tcp_skb_pcount(skb); |
2236 | |
2237 | if (cnt > packets) { |
2238 | if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) || |
2239 | (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) || |
2240 | (oldcnt >= packets)) |
2241 | break; |
2242 | |
2243 | mss = skb_shinfo(skb)->gso_size; |
2244 | err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss); |
2245 | if (err < 0) |
2246 | break; |
2247 | cnt = packets; |
2248 | } |
2249 | |
2250 | tcp_skb_mark_lost(tp, skb); |
2251 | |
2252 | if (mark_head) |
2253 | break; |
2254 | } |
2255 | tcp_verify_left_out(tp); |
2256 | } |
2257 | |
2258 | /* Account newly detected lost packet(s) */ |
2259 | |
2260 | static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) |
2261 | { |
2262 | struct tcp_sock *tp = tcp_sk(sk); |
2263 | |
2264 | if (tcp_is_reno(tp)) { |
2265 | tcp_mark_head_lost(sk, 1, 1); |
2266 | } else if (tcp_is_fack(tp)) { |
2267 | int lost = tp->fackets_out - tp->reordering; |
2268 | if (lost <= 0) |
2269 | lost = 1; |
2270 | tcp_mark_head_lost(sk, lost, 0); |
2271 | } else { |
2272 | int sacked_upto = tp->sacked_out - tp->reordering; |
2273 | if (sacked_upto >= 0) |
2274 | tcp_mark_head_lost(sk, sacked_upto, 0); |
2275 | else if (fast_rexmit) |
2276 | tcp_mark_head_lost(sk, 1, 1); |
2277 | } |
2278 | } |
2279 | |
2280 | /* CWND moderation, preventing bursts due to too big ACKs |
2281 | * in dubious situations. |
2282 | */ |
2283 | static inline void tcp_moderate_cwnd(struct tcp_sock *tp) |
2284 | { |
2285 | tp->snd_cwnd = min(tp->snd_cwnd, |
2286 | tcp_packets_in_flight(tp) + tcp_max_burst(tp)); |
2287 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2288 | } |
2289 | |
2290 | /* Nothing was retransmitted or returned timestamp is less |
2291 | * than timestamp of the first retransmission. |
2292 | */ |
2293 | static inline bool tcp_packet_delayed(const struct tcp_sock *tp) |
2294 | { |
2295 | return !tp->retrans_stamp || |
2296 | (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
2297 | before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp)); |
2298 | } |
2299 | |
2300 | /* Undo procedures. */ |
2301 | |
2302 | #if FASTRETRANS_DEBUG > 1 |
2303 | static void DBGUNDO(struct sock *sk, const char *msg) |
2304 | { |
2305 | struct tcp_sock *tp = tcp_sk(sk); |
2306 | struct inet_sock *inet = inet_sk(sk); |
2307 | |
2308 | if (sk->sk_family == AF_INET) { |
2309 | pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", |
2310 | msg, |
2311 | &inet->inet_daddr, ntohs(inet->inet_dport), |
2312 | tp->snd_cwnd, tcp_left_out(tp), |
2313 | tp->snd_ssthresh, tp->prior_ssthresh, |
2314 | tp->packets_out); |
2315 | } |
2316 | #if IS_ENABLED(CONFIG_IPV6) |
2317 | else if (sk->sk_family == AF_INET6) { |
2318 | struct ipv6_pinfo *np = inet6_sk(sk); |
2319 | pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", |
2320 | msg, |
2321 | &np->daddr, ntohs(inet->inet_dport), |
2322 | tp->snd_cwnd, tcp_left_out(tp), |
2323 | tp->snd_ssthresh, tp->prior_ssthresh, |
2324 | tp->packets_out); |
2325 | } |
2326 | #endif |
2327 | } |
2328 | #else |
2329 | #define DBGUNDO(x...) do { } while (0) |
2330 | #endif |
2331 | |
2332 | static void tcp_undo_cwnd_reduction(struct sock *sk, bool unmark_loss) |
2333 | { |
2334 | struct tcp_sock *tp = tcp_sk(sk); |
2335 | |
2336 | if (unmark_loss) { |
2337 | struct sk_buff *skb; |
2338 | |
2339 | tcp_for_write_queue(skb, sk) { |
2340 | if (skb == tcp_send_head(sk)) |
2341 | break; |
2342 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; |
2343 | } |
2344 | tp->lost_out = 0; |
2345 | tcp_clear_all_retrans_hints(tp); |
2346 | } |
2347 | |
2348 | if (tp->prior_ssthresh) { |
2349 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2350 | |
2351 | if (icsk->icsk_ca_ops->undo_cwnd) |
2352 | tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); |
2353 | else |
2354 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); |
2355 | |
2356 | if (tp->prior_ssthresh > tp->snd_ssthresh) { |
2357 | tp->snd_ssthresh = tp->prior_ssthresh; |
2358 | TCP_ECN_withdraw_cwr(tp); |
2359 | } |
2360 | } else { |
2361 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); |
2362 | } |
2363 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2364 | tp->undo_marker = 0; |
2365 | } |
2366 | |
2367 | static inline bool tcp_may_undo(const struct tcp_sock *tp) |
2368 | { |
2369 | return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); |
2370 | } |
2371 | |
2372 | /* People celebrate: "We love our President!" */ |
2373 | static bool tcp_try_undo_recovery(struct sock *sk) |
2374 | { |
2375 | struct tcp_sock *tp = tcp_sk(sk); |
2376 | |
2377 | if (tcp_may_undo(tp)) { |
2378 | int mib_idx; |
2379 | |
2380 | /* Happy end! We did not retransmit anything |
2381 | * or our original transmission succeeded. |
2382 | */ |
2383 | DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); |
2384 | tcp_undo_cwnd_reduction(sk, false); |
2385 | if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) |
2386 | mib_idx = LINUX_MIB_TCPLOSSUNDO; |
2387 | else |
2388 | mib_idx = LINUX_MIB_TCPFULLUNDO; |
2389 | |
2390 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
2391 | } |
2392 | if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { |
2393 | /* Hold old state until something *above* high_seq |
2394 | * is ACKed. For Reno it is MUST to prevent false |
2395 | * fast retransmits (RFC2582). SACK TCP is safe. */ |
2396 | tcp_moderate_cwnd(tp); |
2397 | return true; |
2398 | } |
2399 | tcp_set_ca_state(sk, TCP_CA_Open); |
2400 | return false; |
2401 | } |
2402 | |
2403 | /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ |
2404 | static bool tcp_try_undo_dsack(struct sock *sk) |
2405 | { |
2406 | struct tcp_sock *tp = tcp_sk(sk); |
2407 | |
2408 | if (tp->undo_marker && !tp->undo_retrans) { |
2409 | DBGUNDO(sk, "D-SACK"); |
2410 | tcp_undo_cwnd_reduction(sk, false); |
2411 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); |
2412 | return true; |
2413 | } |
2414 | return false; |
2415 | } |
2416 | |
2417 | /* We can clear retrans_stamp when there are no retransmissions in the |
2418 | * window. It would seem that it is trivially available for us in |
2419 | * tp->retrans_out, however, that kind of assumptions doesn't consider |
2420 | * what will happen if errors occur when sending retransmission for the |
2421 | * second time. ...It could the that such segment has only |
2422 | * TCPCB_EVER_RETRANS set at the present time. It seems that checking |
2423 | * the head skb is enough except for some reneging corner cases that |
2424 | * are not worth the effort. |
2425 | * |
2426 | * Main reason for all this complexity is the fact that connection dying |
2427 | * time now depends on the validity of the retrans_stamp, in particular, |
2428 | * that successive retransmissions of a segment must not advance |
2429 | * retrans_stamp under any conditions. |
2430 | */ |
2431 | static bool tcp_any_retrans_done(const struct sock *sk) |
2432 | { |
2433 | const struct tcp_sock *tp = tcp_sk(sk); |
2434 | struct sk_buff *skb; |
2435 | |
2436 | if (tp->retrans_out) |
2437 | return true; |
2438 | |
2439 | skb = tcp_write_queue_head(sk); |
2440 | if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) |
2441 | return true; |
2442 | |
2443 | return false; |
2444 | } |
2445 | |
2446 | /* Undo during loss recovery after partial ACK or using F-RTO. */ |
2447 | static bool tcp_try_undo_loss(struct sock *sk, bool frto_undo) |
2448 | { |
2449 | struct tcp_sock *tp = tcp_sk(sk); |
2450 | |
2451 | if (frto_undo || tcp_may_undo(tp)) { |
2452 | tcp_undo_cwnd_reduction(sk, true); |
2453 | |
2454 | DBGUNDO(sk, "partial loss"); |
2455 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); |
2456 | if (frto_undo) |
2457 | NET_INC_STATS_BH(sock_net(sk), |
2458 | LINUX_MIB_TCPSPURIOUSRTOS); |
2459 | inet_csk(sk)->icsk_retransmits = 0; |
2460 | if (frto_undo || tcp_is_sack(tp)) |
2461 | tcp_set_ca_state(sk, TCP_CA_Open); |
2462 | return true; |
2463 | } |
2464 | return false; |
2465 | } |
2466 | |
2467 | /* The cwnd reduction in CWR and Recovery use the PRR algorithm |
2468 | * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/ |
2469 | * It computes the number of packets to send (sndcnt) based on packets newly |
2470 | * delivered: |
2471 | * 1) If the packets in flight is larger than ssthresh, PRR spreads the |
2472 | * cwnd reductions across a full RTT. |
2473 | * 2) If packets in flight is lower than ssthresh (such as due to excess |
2474 | * losses and/or application stalls), do not perform any further cwnd |
2475 | * reductions, but instead slow start up to ssthresh. |
2476 | */ |
2477 | static void tcp_init_cwnd_reduction(struct sock *sk, const bool set_ssthresh) |
2478 | { |
2479 | struct tcp_sock *tp = tcp_sk(sk); |
2480 | |
2481 | tp->high_seq = tp->snd_nxt; |
2482 | tp->tlp_high_seq = 0; |
2483 | tp->snd_cwnd_cnt = 0; |
2484 | tp->prior_cwnd = tp->snd_cwnd; |
2485 | tp->prr_delivered = 0; |
2486 | tp->prr_out = 0; |
2487 | if (set_ssthresh) |
2488 | tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk); |
2489 | TCP_ECN_queue_cwr(tp); |
2490 | } |
2491 | |
2492 | static void tcp_cwnd_reduction(struct sock *sk, const int prior_unsacked, |
2493 | int fast_rexmit) |
2494 | { |
2495 | struct tcp_sock *tp = tcp_sk(sk); |
2496 | int sndcnt = 0; |
2497 | int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp); |
2498 | int newly_acked_sacked = prior_unsacked - |
2499 | (tp->packets_out - tp->sacked_out); |
2500 | |
2501 | tp->prr_delivered += newly_acked_sacked; |
2502 | if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) { |
2503 | u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered + |
2504 | tp->prior_cwnd - 1; |
2505 | sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out; |
2506 | } else { |
2507 | sndcnt = min_t(int, delta, |
2508 | max_t(int, tp->prr_delivered - tp->prr_out, |
2509 | newly_acked_sacked) + 1); |
2510 | } |
2511 | |
2512 | sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0)); |
2513 | tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt; |
2514 | } |
2515 | |
2516 | static inline void tcp_end_cwnd_reduction(struct sock *sk) |
2517 | { |
2518 | struct tcp_sock *tp = tcp_sk(sk); |
2519 | |
2520 | /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */ |
2521 | if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR || |
2522 | (tp->undo_marker && tp->snd_ssthresh < TCP_INFINITE_SSTHRESH)) { |
2523 | tp->snd_cwnd = tp->snd_ssthresh; |
2524 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2525 | } |
2526 | tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); |
2527 | } |
2528 | |
2529 | /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */ |
2530 | void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) |
2531 | { |
2532 | struct tcp_sock *tp = tcp_sk(sk); |
2533 | |
2534 | tp->prior_ssthresh = 0; |
2535 | if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) { |
2536 | tp->undo_marker = 0; |
2537 | tcp_init_cwnd_reduction(sk, set_ssthresh); |
2538 | tcp_set_ca_state(sk, TCP_CA_CWR); |
2539 | } |
2540 | } |
2541 | |
2542 | static void tcp_try_keep_open(struct sock *sk) |
2543 | { |
2544 | struct tcp_sock *tp = tcp_sk(sk); |
2545 | int state = TCP_CA_Open; |
2546 | |
2547 | if (tcp_left_out(tp) || tcp_any_retrans_done(sk)) |
2548 | state = TCP_CA_Disorder; |
2549 | |
2550 | if (inet_csk(sk)->icsk_ca_state != state) { |
2551 | tcp_set_ca_state(sk, state); |
2552 | tp->high_seq = tp->snd_nxt; |
2553 | } |
2554 | } |
2555 | |
2556 | static void tcp_try_to_open(struct sock *sk, int flag, const int prior_unsacked) |
2557 | { |
2558 | struct tcp_sock *tp = tcp_sk(sk); |
2559 | |
2560 | tcp_verify_left_out(tp); |
2561 | |
2562 | if (!tcp_any_retrans_done(sk)) |
2563 | tp->retrans_stamp = 0; |
2564 | |
2565 | if (flag & FLAG_ECE) |
2566 | tcp_enter_cwr(sk, 1); |
2567 | |
2568 | if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { |
2569 | tcp_try_keep_open(sk); |
2570 | } else { |
2571 | tcp_cwnd_reduction(sk, prior_unsacked, 0); |
2572 | } |
2573 | } |
2574 | |
2575 | static void tcp_mtup_probe_failed(struct sock *sk) |
2576 | { |
2577 | struct inet_connection_sock *icsk = inet_csk(sk); |
2578 | |
2579 | icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; |
2580 | icsk->icsk_mtup.probe_size = 0; |
2581 | } |
2582 | |
2583 | static void tcp_mtup_probe_success(struct sock *sk) |
2584 | { |
2585 | struct tcp_sock *tp = tcp_sk(sk); |
2586 | struct inet_connection_sock *icsk = inet_csk(sk); |
2587 | |
2588 | /* FIXME: breaks with very large cwnd */ |
2589 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
2590 | tp->snd_cwnd = tp->snd_cwnd * |
2591 | tcp_mss_to_mtu(sk, tp->mss_cache) / |
2592 | icsk->icsk_mtup.probe_size; |
2593 | tp->snd_cwnd_cnt = 0; |
2594 | tp->snd_cwnd_stamp = tcp_time_stamp; |
2595 | tp->snd_ssthresh = tcp_current_ssthresh(sk); |
2596 | |
2597 | icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; |
2598 | icsk->icsk_mtup.probe_size = 0; |
2599 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
2600 | } |
2601 | |
2602 | /* Do a simple retransmit without using the backoff mechanisms in |
2603 | * tcp_timer. This is used for path mtu discovery. |
2604 | * The socket is already locked here. |
2605 | */ |
2606 | void tcp_simple_retransmit(struct sock *sk) |
2607 | { |
2608 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2609 | struct tcp_sock *tp = tcp_sk(sk); |
2610 | struct sk_buff *skb; |
2611 | unsigned int mss = tcp_current_mss(sk); |
2612 | u32 prior_lost = tp->lost_out; |
2613 | |
2614 | tcp_for_write_queue(skb, sk) { |
2615 | if (skb == tcp_send_head(sk)) |
2616 | break; |
2617 | if (tcp_skb_seglen(skb) > mss && |
2618 | !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { |
2619 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { |
2620 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
2621 | tp->retrans_out -= tcp_skb_pcount(skb); |
2622 | } |
2623 | tcp_skb_mark_lost_uncond_verify(tp, skb); |
2624 | } |
2625 | } |
2626 | |
2627 | tcp_clear_retrans_hints_partial(tp); |
2628 | |
2629 | if (prior_lost == tp->lost_out) |
2630 | return; |
2631 | |
2632 | if (tcp_is_reno(tp)) |
2633 | tcp_limit_reno_sacked(tp); |
2634 | |
2635 | tcp_verify_left_out(tp); |
2636 | |
2637 | /* Don't muck with the congestion window here. |
2638 | * Reason is that we do not increase amount of _data_ |
2639 | * in network, but units changed and effective |
2640 | * cwnd/ssthresh really reduced now. |
2641 | */ |
2642 | if (icsk->icsk_ca_state != TCP_CA_Loss) { |
2643 | tp->high_seq = tp->snd_nxt; |
2644 | tp->snd_ssthresh = tcp_current_ssthresh(sk); |
2645 | tp->prior_ssthresh = 0; |
2646 | tp->undo_marker = 0; |
2647 | tcp_set_ca_state(sk, TCP_CA_Loss); |
2648 | } |
2649 | tcp_xmit_retransmit_queue(sk); |
2650 | } |
2651 | EXPORT_SYMBOL(tcp_simple_retransmit); |
2652 | |
2653 | static void tcp_enter_recovery(struct sock *sk, bool ece_ack) |
2654 | { |
2655 | struct tcp_sock *tp = tcp_sk(sk); |
2656 | int mib_idx; |
2657 | |
2658 | if (tcp_is_reno(tp)) |
2659 | mib_idx = LINUX_MIB_TCPRENORECOVERY; |
2660 | else |
2661 | mib_idx = LINUX_MIB_TCPSACKRECOVERY; |
2662 | |
2663 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
2664 | |
2665 | tp->prior_ssthresh = 0; |
2666 | tp->undo_marker = tp->snd_una; |
2667 | tp->undo_retrans = tp->retrans_out; |
2668 | |
2669 | if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) { |
2670 | if (!ece_ack) |
2671 | tp->prior_ssthresh = tcp_current_ssthresh(sk); |
2672 | tcp_init_cwnd_reduction(sk, true); |
2673 | } |
2674 | tcp_set_ca_state(sk, TCP_CA_Recovery); |
2675 | } |
2676 | |
2677 | /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are |
2678 | * recovered or spurious. Otherwise retransmits more on partial ACKs. |
2679 | */ |
2680 | static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack) |
2681 | { |
2682 | struct inet_connection_sock *icsk = inet_csk(sk); |
2683 | struct tcp_sock *tp = tcp_sk(sk); |
2684 | bool recovered = !before(tp->snd_una, tp->high_seq); |
2685 | |
2686 | if (tp->frto) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */ |
2687 | /* Step 3.b. A timeout is spurious if not all data are |
2688 | * lost, i.e., never-retransmitted data are (s)acked. |
2689 | */ |
2690 | if (tcp_try_undo_loss(sk, flag & FLAG_ORIG_SACK_ACKED)) |
2691 | return; |
2692 | |
2693 | if (after(tp->snd_nxt, tp->high_seq) && |
2694 | (flag & FLAG_DATA_SACKED || is_dupack)) { |
2695 | tp->frto = 0; /* Loss was real: 2nd part of step 3.a */ |
2696 | } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) { |
2697 | tp->high_seq = tp->snd_nxt; |
2698 | __tcp_push_pending_frames(sk, tcp_current_mss(sk), |
2699 | TCP_NAGLE_OFF); |
2700 | if (after(tp->snd_nxt, tp->high_seq)) |
2701 | return; /* Step 2.b */ |
2702 | tp->frto = 0; |
2703 | } |
2704 | } |
2705 | |
2706 | if (recovered) { |
2707 | /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */ |
2708 | icsk->icsk_retransmits = 0; |
2709 | tcp_try_undo_recovery(sk); |
2710 | return; |
2711 | } |
2712 | if (flag & FLAG_DATA_ACKED) |
2713 | icsk->icsk_retransmits = 0; |
2714 | if (tcp_is_reno(tp)) { |
2715 | /* A Reno DUPACK means new data in F-RTO step 2.b above are |
2716 | * delivered. Lower inflight to clock out (re)tranmissions. |
2717 | */ |
2718 | if (after(tp->snd_nxt, tp->high_seq) && is_dupack) |
2719 | tcp_add_reno_sack(sk); |
2720 | else if (flag & FLAG_SND_UNA_ADVANCED) |
2721 | tcp_reset_reno_sack(tp); |
2722 | } |
2723 | if (tcp_try_undo_loss(sk, false)) |
2724 | return; |
2725 | tcp_xmit_retransmit_queue(sk); |
2726 | } |
2727 | |
2728 | /* Undo during fast recovery after partial ACK. */ |
2729 | static bool tcp_try_undo_partial(struct sock *sk, const int acked, |
2730 | const int prior_unsacked) |
2731 | { |
2732 | struct tcp_sock *tp = tcp_sk(sk); |
2733 | |
2734 | if (tp->undo_marker && tcp_packet_delayed(tp)) { |
2735 | /* Plain luck! Hole if filled with delayed |
2736 | * packet, rather than with a retransmit. |
2737 | */ |
2738 | tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); |
2739 | |
2740 | /* We are getting evidence that the reordering degree is higher |
2741 | * than we realized. If there are no retransmits out then we |
2742 | * can undo. Otherwise we clock out new packets but do not |
2743 | * mark more packets lost or retransmit more. |
2744 | */ |
2745 | if (tp->retrans_out) { |
2746 | tcp_cwnd_reduction(sk, prior_unsacked, 0); |
2747 | return true; |
2748 | } |
2749 | |
2750 | if (!tcp_any_retrans_done(sk)) |
2751 | tp->retrans_stamp = 0; |
2752 | |
2753 | DBGUNDO(sk, "partial recovery"); |
2754 | tcp_undo_cwnd_reduction(sk, true); |
2755 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); |
2756 | tcp_try_keep_open(sk); |
2757 | return true; |
2758 | } |
2759 | return false; |
2760 | } |
2761 | |
2762 | /* Process an event, which can update packets-in-flight not trivially. |
2763 | * Main goal of this function is to calculate new estimate for left_out, |
2764 | * taking into account both packets sitting in receiver's buffer and |
2765 | * packets lost by network. |
2766 | * |
2767 | * Besides that it does CWND reduction, when packet loss is detected |
2768 | * and changes state of machine. |
2769 | * |
2770 | * It does _not_ decide what to send, it is made in function |
2771 | * tcp_xmit_retransmit_queue(). |
2772 | */ |
2773 | static void tcp_fastretrans_alert(struct sock *sk, const int acked, |
2774 | const int prior_unsacked, |
2775 | bool is_dupack, int flag) |
2776 | { |
2777 | struct inet_connection_sock *icsk = inet_csk(sk); |
2778 | struct tcp_sock *tp = tcp_sk(sk); |
2779 | bool do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && |
2780 | (tcp_fackets_out(tp) > tp->reordering)); |
2781 | int fast_rexmit = 0; |
2782 | |
2783 | if (WARN_ON(!tp->packets_out && tp->sacked_out)) |
2784 | tp->sacked_out = 0; |
2785 | if (WARN_ON(!tp->sacked_out && tp->fackets_out)) |
2786 | tp->fackets_out = 0; |
2787 | |
2788 | /* Now state machine starts. |
2789 | * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ |
2790 | if (flag & FLAG_ECE) |
2791 | tp->prior_ssthresh = 0; |
2792 | |
2793 | /* B. In all the states check for reneging SACKs. */ |
2794 | if (tcp_check_sack_reneging(sk, flag)) |
2795 | return; |
2796 | |
2797 | /* C. Check consistency of the current state. */ |
2798 | tcp_verify_left_out(tp); |
2799 | |
2800 | /* D. Check state exit conditions. State can be terminated |
2801 | * when high_seq is ACKed. */ |
2802 | if (icsk->icsk_ca_state == TCP_CA_Open) { |
2803 | WARN_ON(tp->retrans_out != 0); |
2804 | tp->retrans_stamp = 0; |
2805 | } else if (!before(tp->snd_una, tp->high_seq)) { |
2806 | switch (icsk->icsk_ca_state) { |
2807 | case TCP_CA_CWR: |
2808 | /* CWR is to be held something *above* high_seq |
2809 | * is ACKed for CWR bit to reach receiver. */ |
2810 | if (tp->snd_una != tp->high_seq) { |
2811 | tcp_end_cwnd_reduction(sk); |
2812 | tcp_set_ca_state(sk, TCP_CA_Open); |
2813 | } |
2814 | break; |
2815 | |
2816 | case TCP_CA_Recovery: |
2817 | if (tcp_is_reno(tp)) |
2818 | tcp_reset_reno_sack(tp); |
2819 | if (tcp_try_undo_recovery(sk)) |
2820 | return; |
2821 | tcp_end_cwnd_reduction(sk); |
2822 | break; |
2823 | } |
2824 | } |
2825 | |
2826 | /* E. Process state. */ |
2827 | switch (icsk->icsk_ca_state) { |
2828 | case TCP_CA_Recovery: |
2829 | if (!(flag & FLAG_SND_UNA_ADVANCED)) { |
2830 | if (tcp_is_reno(tp) && is_dupack) |
2831 | tcp_add_reno_sack(sk); |
2832 | } else { |
2833 | if (tcp_try_undo_partial(sk, acked, prior_unsacked)) |
2834 | return; |
2835 | /* Partial ACK arrived. Force fast retransmit. */ |
2836 | do_lost = tcp_is_reno(tp) || |
2837 | tcp_fackets_out(tp) > tp->reordering; |
2838 | } |
2839 | if (tcp_try_undo_dsack(sk)) { |
2840 | tcp_try_keep_open(sk); |
2841 | return; |
2842 | } |
2843 | break; |
2844 | case TCP_CA_Loss: |
2845 | tcp_process_loss(sk, flag, is_dupack); |
2846 | if (icsk->icsk_ca_state != TCP_CA_Open) |
2847 | return; |
2848 | /* Fall through to processing in Open state. */ |
2849 | default: |
2850 | if (tcp_is_reno(tp)) { |
2851 | if (flag & FLAG_SND_UNA_ADVANCED) |
2852 | tcp_reset_reno_sack(tp); |
2853 | if (is_dupack) |
2854 | tcp_add_reno_sack(sk); |
2855 | } |
2856 | |
2857 | if (icsk->icsk_ca_state <= TCP_CA_Disorder) |
2858 | tcp_try_undo_dsack(sk); |
2859 | |
2860 | if (!tcp_time_to_recover(sk, flag)) { |
2861 | tcp_try_to_open(sk, flag, prior_unsacked); |
2862 | return; |
2863 | } |
2864 | |
2865 | /* MTU probe failure: don't reduce cwnd */ |
2866 | if (icsk->icsk_ca_state < TCP_CA_CWR && |
2867 | icsk->icsk_mtup.probe_size && |
2868 | tp->snd_una == tp->mtu_probe.probe_seq_start) { |
2869 | tcp_mtup_probe_failed(sk); |
2870 | /* Restores the reduction we did in tcp_mtup_probe() */ |
2871 | tp->snd_cwnd++; |
2872 | tcp_simple_retransmit(sk); |
2873 | return; |
2874 | } |
2875 | |
2876 | /* Otherwise enter Recovery state */ |
2877 | tcp_enter_recovery(sk, (flag & FLAG_ECE)); |
2878 | fast_rexmit = 1; |
2879 | } |
2880 | |
2881 | if (do_lost) |
2882 | tcp_update_scoreboard(sk, fast_rexmit); |
2883 | tcp_cwnd_reduction(sk, prior_unsacked, fast_rexmit); |
2884 | tcp_xmit_retransmit_queue(sk); |
2885 | } |
2886 | |
2887 | static inline bool tcp_ack_update_rtt(struct sock *sk, const int flag, |
2888 | long seq_rtt_us, long sack_rtt_us) |
2889 | { |
2890 | const struct tcp_sock *tp = tcp_sk(sk); |
2891 | |
2892 | /* Prefer RTT measured from ACK's timing to TS-ECR. This is because |
2893 | * broken middle-boxes or peers may corrupt TS-ECR fields. But |
2894 | * Karn's algorithm forbids taking RTT if some retransmitted data |
2895 | * is acked (RFC6298). |
2896 | */ |
2897 | if (flag & FLAG_RETRANS_DATA_ACKED) |
2898 | seq_rtt_us = -1L; |
2899 | |
2900 | if (seq_rtt_us < 0) |
2901 | seq_rtt_us = sack_rtt_us; |
2902 | |
2903 | /* RTTM Rule: A TSecr value received in a segment is used to |
2904 | * update the averaged RTT measurement only if the segment |
2905 | * acknowledges some new data, i.e., only if it advances the |
2906 | * left edge of the send window. |
2907 | * See draft-ietf-tcplw-high-performance-00, section 3.3. |
2908 | */ |
2909 | if (seq_rtt_us < 0 && tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
2910 | flag & FLAG_ACKED) |
2911 | seq_rtt_us = jiffies_to_usecs(tcp_time_stamp - tp->rx_opt.rcv_tsecr); |
2912 | |
2913 | if (seq_rtt_us < 0) |
2914 | return false; |
2915 | |
2916 | tcp_rtt_estimator(sk, seq_rtt_us); |
2917 | tcp_set_rto(sk); |
2918 | |
2919 | /* RFC6298: only reset backoff on valid RTT measurement. */ |
2920 | inet_csk(sk)->icsk_backoff = 0; |
2921 | return true; |
2922 | } |
2923 | |
2924 | /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */ |
2925 | static void tcp_synack_rtt_meas(struct sock *sk, const u32 synack_stamp) |
2926 | { |
2927 | struct tcp_sock *tp = tcp_sk(sk); |
2928 | long seq_rtt_us = -1L; |
2929 | |
2930 | if (synack_stamp && !tp->total_retrans) |
2931 | seq_rtt_us = jiffies_to_usecs(tcp_time_stamp - synack_stamp); |
2932 | |
2933 | /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets |
2934 | * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack() |
2935 | */ |
2936 | if (!tp->srtt_us) |
2937 | tcp_ack_update_rtt(sk, FLAG_SYN_ACKED, seq_rtt_us, -1L); |
2938 | } |
2939 | |
2940 | static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 acked, u32 in_flight) |
2941 | { |
2942 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2943 | icsk->icsk_ca_ops->cong_avoid(sk, ack, acked, in_flight); |
2944 | tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; |
2945 | } |
2946 | |
2947 | /* Restart timer after forward progress on connection. |
2948 | * RFC2988 recommends to restart timer to now+rto. |
2949 | */ |
2950 | void tcp_rearm_rto(struct sock *sk) |
2951 | { |
2952 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2953 | struct tcp_sock *tp = tcp_sk(sk); |
2954 | |
2955 | /* If the retrans timer is currently being used by Fast Open |
2956 | * for SYN-ACK retrans purpose, stay put. |
2957 | */ |
2958 | if (tp->fastopen_rsk) |
2959 | return; |
2960 | |
2961 | if (!tp->packets_out) { |
2962 | inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); |
2963 | } else { |
2964 | u32 rto = inet_csk(sk)->icsk_rto; |
2965 | /* Offset the time elapsed after installing regular RTO */ |
2966 | if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS || |
2967 | icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) { |
2968 | struct sk_buff *skb = tcp_write_queue_head(sk); |
2969 | const u32 rto_time_stamp = TCP_SKB_CB(skb)->when + rto; |
2970 | s32 delta = (s32)(rto_time_stamp - tcp_time_stamp); |
2971 | /* delta may not be positive if the socket is locked |
2972 | * when the retrans timer fires and is rescheduled. |
2973 | */ |
2974 | if (delta > 0) |
2975 | rto = delta; |
2976 | } |
2977 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, rto, |
2978 | TCP_RTO_MAX); |
2979 | } |
2980 | } |
2981 | |
2982 | /* This function is called when the delayed ER timer fires. TCP enters |
2983 | * fast recovery and performs fast-retransmit. |
2984 | */ |
2985 | void tcp_resume_early_retransmit(struct sock *sk) |
2986 | { |
2987 | struct tcp_sock *tp = tcp_sk(sk); |
2988 | |
2989 | tcp_rearm_rto(sk); |
2990 | |
2991 | /* Stop if ER is disabled after the delayed ER timer is scheduled */ |
2992 | if (!tp->do_early_retrans) |
2993 | return; |
2994 | |
2995 | tcp_enter_recovery(sk, false); |
2996 | tcp_update_scoreboard(sk, 1); |
2997 | tcp_xmit_retransmit_queue(sk); |
2998 | } |
2999 | |
3000 | /* If we get here, the whole TSO packet has not been acked. */ |
3001 | static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) |
3002 | { |
3003 | struct tcp_sock *tp = tcp_sk(sk); |
3004 | u32 packets_acked; |
3005 | |
3006 | BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); |
3007 | |
3008 | packets_acked = tcp_skb_pcount(skb); |
3009 | if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) |
3010 | return 0; |
3011 | packets_acked -= tcp_skb_pcount(skb); |
3012 | |
3013 | if (packets_acked) { |
3014 | BUG_ON(tcp_skb_pcount(skb) == 0); |
3015 | BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); |
3016 | } |
3017 | |
3018 | return packets_acked; |
3019 | } |
3020 | |
3021 | /* Remove acknowledged frames from the retransmission queue. If our packet |
3022 | * is before the ack sequence we can discard it as it's confirmed to have |
3023 | * arrived at the other end. |
3024 | */ |
3025 | static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, |
3026 | u32 prior_snd_una, long sack_rtt_us) |
3027 | { |
3028 | const struct inet_connection_sock *icsk = inet_csk(sk); |
3029 | struct skb_mstamp first_ackt, last_ackt, now; |
3030 | struct tcp_sock *tp = tcp_sk(sk); |
3031 | u32 prior_sacked = tp->sacked_out; |
3032 | u32 reord = tp->packets_out; |
3033 | bool fully_acked = true; |
3034 | long ca_seq_rtt_us = -1L; |
3035 | long seq_rtt_us = -1L; |
3036 | struct sk_buff *skb; |
3037 | u32 pkts_acked = 0; |
3038 | bool rtt_update; |
3039 | int flag = 0; |
3040 | |
3041 | first_ackt.v64 = 0; |
3042 | |
3043 | while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { |
3044 | struct tcp_skb_cb *scb = TCP_SKB_CB(skb); |
3045 | u8 sacked = scb->sacked; |
3046 | u32 acked_pcount; |
3047 | |
3048 | /* Determine how many packets and what bytes were acked, tso and else */ |
3049 | if (after(scb->end_seq, tp->snd_una)) { |
3050 | if (tcp_skb_pcount(skb) == 1 || |
3051 | !after(tp->snd_una, scb->seq)) |
3052 | break; |
3053 | |
3054 | acked_pcount = tcp_tso_acked(sk, skb); |
3055 | if (!acked_pcount) |
3056 | break; |
3057 | |
3058 | fully_acked = false; |
3059 | } else { |
3060 | acked_pcount = tcp_skb_pcount(skb); |
3061 | } |
3062 | |
3063 | if (sacked & TCPCB_RETRANS) { |
3064 | if (sacked & TCPCB_SACKED_RETRANS) |
3065 | tp->retrans_out -= acked_pcount; |
3066 | flag |= FLAG_RETRANS_DATA_ACKED; |
3067 | } else { |
3068 | last_ackt = skb->skb_mstamp; |
3069 | WARN_ON_ONCE(last_ackt.v64 == 0); |
3070 | if (!first_ackt.v64) |
3071 | first_ackt = last_ackt; |
3072 | |
3073 | if (!(sacked & TCPCB_SACKED_ACKED)) |
3074 | reord = min(pkts_acked, reord); |
3075 | if (!after(scb->end_seq, tp->high_seq)) |
3076 | flag |= FLAG_ORIG_SACK_ACKED; |
3077 | } |
3078 | |
3079 | if (sacked & TCPCB_SACKED_ACKED) |
3080 | tp->sacked_out -= acked_pcount; |
3081 | if (sacked & TCPCB_LOST) |
3082 | tp->lost_out -= acked_pcount; |
3083 | |
3084 | tp->packets_out -= acked_pcount; |
3085 | pkts_acked += acked_pcount; |
3086 | |
3087 | /* Initial outgoing SYN's get put onto the write_queue |
3088 | * just like anything else we transmit. It is not |
3089 | * true data, and if we misinform our callers that |
3090 | * this ACK acks real data, we will erroneously exit |
3091 | * connection startup slow start one packet too |
3092 | * quickly. This is severely frowned upon behavior. |
3093 | */ |
3094 | if (!(scb->tcp_flags & TCPHDR_SYN)) { |
3095 | flag |= FLAG_DATA_ACKED; |
3096 | } else { |
3097 | flag |= FLAG_SYN_ACKED; |
3098 | tp->retrans_stamp = 0; |
3099 | } |
3100 | |
3101 | if (!fully_acked) |
3102 | break; |
3103 | |
3104 | tcp_unlink_write_queue(skb, sk); |
3105 | sk_wmem_free_skb(sk, skb); |
3106 | if (skb == tp->retransmit_skb_hint) |
3107 | tp->retransmit_skb_hint = NULL; |
3108 | if (skb == tp->lost_skb_hint) |
3109 | tp->lost_skb_hint = NULL; |
3110 | } |
3111 | |
3112 | if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una))) |
3113 | tp->snd_up = tp->snd_una; |
3114 | |
3115 | if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) |
3116 | flag |= FLAG_SACK_RENEGING; |
3117 | |
3118 | skb_mstamp_get(&now); |
3119 | if (first_ackt.v64) { |
3120 | seq_rtt_us = skb_mstamp_us_delta(&now, &first_ackt); |
3121 | ca_seq_rtt_us = skb_mstamp_us_delta(&now, &last_ackt); |
3122 | } |
3123 | |
3124 | rtt_update = tcp_ack_update_rtt(sk, flag, seq_rtt_us, sack_rtt_us); |
3125 | |
3126 | if (flag & FLAG_ACKED) { |
3127 | const struct tcp_congestion_ops *ca_ops |
3128 | = inet_csk(sk)->icsk_ca_ops; |
3129 | |
3130 | tcp_rearm_rto(sk); |
3131 | if (unlikely(icsk->icsk_mtup.probe_size && |
3132 | !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) { |
3133 | tcp_mtup_probe_success(sk); |
3134 | } |
3135 | |
3136 | if (tcp_is_reno(tp)) { |
3137 | tcp_remove_reno_sacks(sk, pkts_acked); |
3138 | } else { |
3139 | int delta; |
3140 | |
3141 | /* Non-retransmitted hole got filled? That's reordering */ |
3142 | if (reord < prior_fackets) |
3143 | tcp_update_reordering(sk, tp->fackets_out - reord, 0); |
3144 | |
3145 | delta = tcp_is_fack(tp) ? pkts_acked : |
3146 | prior_sacked - tp->sacked_out; |
3147 | tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); |
3148 | } |
3149 | |
3150 | tp->fackets_out -= min(pkts_acked, tp->fackets_out); |
3151 | |
3152 | if (ca_ops->pkts_acked) |
3153 | ca_ops->pkts_acked(sk, pkts_acked, ca_seq_rtt_us); |
3154 | |
3155 | } else if (skb && rtt_update && sack_rtt_us >= 0 && |
3156 | sack_rtt_us > skb_mstamp_us_delta(&now, &skb->skb_mstamp)) { |
3157 | /* Do not re-arm RTO if the sack RTT is measured from data sent |
3158 | * after when the head was last (re)transmitted. Otherwise the |
3159 | * timeout may continue to extend in loss recovery. |
3160 | */ |
3161 | tcp_rearm_rto(sk); |
3162 | } |
3163 | |
3164 | #if FASTRETRANS_DEBUG > 0 |
3165 | WARN_ON((int)tp->sacked_out < 0); |
3166 | WARN_ON((int)tp->lost_out < 0); |
3167 | WARN_ON((int)tp->retrans_out < 0); |
3168 | if (!tp->packets_out && tcp_is_sack(tp)) { |
3169 | icsk = inet_csk(sk); |
3170 | if (tp->lost_out) { |
3171 | pr_debug("Leak l=%u %d\n", |
3172 | tp->lost_out, icsk->icsk_ca_state); |
3173 | tp->lost_out = 0; |
3174 | } |
3175 | if (tp->sacked_out) { |
3176 | pr_debug("Leak s=%u %d\n", |
3177 | tp->sacked_out, icsk->icsk_ca_state); |
3178 | tp->sacked_out = 0; |
3179 | } |
3180 | if (tp->retrans_out) { |
3181 | pr_debug("Leak r=%u %d\n", |
3182 | tp->retrans_out, icsk->icsk_ca_state); |
3183 | tp->retrans_out = 0; |
3184 | } |
3185 | } |
3186 | #endif |
3187 | return flag; |
3188 | } |
3189 | |
3190 | static void tcp_ack_probe(struct sock *sk) |
3191 | { |
3192 | const struct tcp_sock *tp = tcp_sk(sk); |
3193 | struct inet_connection_sock *icsk = inet_csk(sk); |
3194 | |
3195 | /* Was it a usable window open? */ |
3196 | |
3197 | if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) { |
3198 | icsk->icsk_backoff = 0; |
3199 | inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); |
3200 | /* Socket must be waked up by subsequent tcp_data_snd_check(). |
3201 | * This function is not for random using! |
3202 | */ |
3203 | } else { |
3204 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, |
3205 | min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), |
3206 | TCP_RTO_MAX); |
3207 | } |
3208 | } |
3209 | |
3210 | static inline bool tcp_ack_is_dubious(const struct sock *sk, const int flag) |
3211 | { |
3212 | return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || |
3213 | inet_csk(sk)->icsk_ca_state != TCP_CA_Open; |
3214 | } |
3215 | |
3216 | /* Decide wheather to run the increase function of congestion control. */ |
3217 | static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag) |
3218 | { |
3219 | if (tcp_in_cwnd_reduction(sk)) |
3220 | return false; |
3221 | |
3222 | /* If reordering is high then always grow cwnd whenever data is |
3223 | * delivered regardless of its ordering. Otherwise stay conservative |
3224 | * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/ |
3225 | * new SACK or ECE mark may first advance cwnd here and later reduce |
3226 | * cwnd in tcp_fastretrans_alert() based on more states. |
3227 | */ |
3228 | if (tcp_sk(sk)->reordering > sysctl_tcp_reordering) |
3229 | return flag & FLAG_FORWARD_PROGRESS; |
3230 | |
3231 | return flag & FLAG_DATA_ACKED; |
3232 | } |
3233 | |
3234 | /* Check that window update is acceptable. |
3235 | * The function assumes that snd_una<=ack<=snd_next. |
3236 | */ |
3237 | static inline bool tcp_may_update_window(const struct tcp_sock *tp, |
3238 | const u32 ack, const u32 ack_seq, |
3239 | const u32 nwin) |
3240 | { |
3241 | return after(ack, tp->snd_una) || |
3242 | after(ack_seq, tp->snd_wl1) || |
3243 | (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd); |
3244 | } |
3245 | |
3246 | /* Update our send window. |
3247 | * |
3248 | * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 |
3249 | * and in FreeBSD. NetBSD's one is even worse.) is wrong. |
3250 | */ |
3251 | static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack, |
3252 | u32 ack_seq) |
3253 | { |
3254 | struct tcp_sock *tp = tcp_sk(sk); |
3255 | int flag = 0; |
3256 | u32 nwin = ntohs(tcp_hdr(skb)->window); |
3257 | |
3258 | if (likely(!tcp_hdr(skb)->syn)) |
3259 | nwin <<= tp->rx_opt.snd_wscale; |
3260 | |
3261 | if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { |
3262 | flag |= FLAG_WIN_UPDATE; |
3263 | tcp_update_wl(tp, ack_seq); |
3264 | |
3265 | if (tp->snd_wnd != nwin) { |
3266 | tp->snd_wnd = nwin; |
3267 | |
3268 | /* Note, it is the only place, where |
3269 | * fast path is recovered for sending TCP. |
3270 | */ |
3271 | tp->pred_flags = 0; |
3272 | tcp_fast_path_check(sk); |
3273 | |
3274 | if (nwin > tp->max_window) { |
3275 | tp->max_window = nwin; |
3276 | tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); |
3277 | } |
3278 | } |
3279 | } |
3280 | |
3281 | tp->snd_una = ack; |
3282 | |
3283 | return flag; |
3284 | } |
3285 | |
3286 | /* RFC 5961 7 [ACK Throttling] */ |
3287 | static void tcp_send_challenge_ack(struct sock *sk) |
3288 | { |
3289 | /* unprotected vars, we dont care of overwrites */ |
3290 | static u32 challenge_timestamp; |
3291 | static unsigned int challenge_count; |
3292 | u32 now = jiffies / HZ; |
3293 | |
3294 | if (now != challenge_timestamp) { |
3295 | challenge_timestamp = now; |
3296 | challenge_count = 0; |
3297 | } |
3298 | if (++challenge_count <= sysctl_tcp_challenge_ack_limit) { |
3299 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPCHALLENGEACK); |
3300 | tcp_send_ack(sk); |
3301 | } |
3302 | } |
3303 | |
3304 | static void tcp_store_ts_recent(struct tcp_sock *tp) |
3305 | { |
3306 | tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; |
3307 | tp->rx_opt.ts_recent_stamp = get_seconds(); |
3308 | } |
3309 | |
3310 | static void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) |
3311 | { |
3312 | if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { |
3313 | /* PAWS bug workaround wrt. ACK frames, the PAWS discard |
3314 | * extra check below makes sure this can only happen |
3315 | * for pure ACK frames. -DaveM |
3316 | * |
3317 | * Not only, also it occurs for expired timestamps. |
3318 | */ |
3319 | |
3320 | if (tcp_paws_check(&tp->rx_opt, 0)) |
3321 | tcp_store_ts_recent(tp); |
3322 | } |
3323 | } |
3324 | |
3325 | /* This routine deals with acks during a TLP episode. |
3326 | * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe. |
3327 | */ |
3328 | static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag) |
3329 | { |
3330 | struct tcp_sock *tp = tcp_sk(sk); |
3331 | bool is_tlp_dupack = (ack == tp->tlp_high_seq) && |
3332 | !(flag & (FLAG_SND_UNA_ADVANCED | |
3333 | FLAG_NOT_DUP | FLAG_DATA_SACKED)); |
3334 | |
3335 | /* Mark the end of TLP episode on receiving TLP dupack or when |
3336 | * ack is after tlp_high_seq. |
3337 | */ |
3338 | if (is_tlp_dupack) { |
3339 | tp->tlp_high_seq = 0; |
3340 | return; |
3341 | } |
3342 | |
3343 | if (after(ack, tp->tlp_high_seq)) { |
3344 | tp->tlp_high_seq = 0; |
3345 | /* Don't reduce cwnd if DSACK arrives for TLP retrans. */ |
3346 | if (!(flag & FLAG_DSACKING_ACK)) { |
3347 | tcp_init_cwnd_reduction(sk, true); |
3348 | tcp_set_ca_state(sk, TCP_CA_CWR); |
3349 | tcp_end_cwnd_reduction(sk); |
3350 | tcp_try_keep_open(sk); |
3351 | NET_INC_STATS_BH(sock_net(sk), |
3352 | LINUX_MIB_TCPLOSSPROBERECOVERY); |
3353 | } |
3354 | } |
3355 | } |
3356 | |
3357 | /* This routine deals with incoming acks, but not outgoing ones. */ |
3358 | static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) |
3359 | { |
3360 | struct inet_connection_sock *icsk = inet_csk(sk); |
3361 | struct tcp_sock *tp = tcp_sk(sk); |
3362 | u32 prior_snd_una = tp->snd_una; |
3363 | u32 ack_seq = TCP_SKB_CB(skb)->seq; |
3364 | u32 ack = TCP_SKB_CB(skb)->ack_seq; |
3365 | bool is_dupack = false; |
3366 | u32 prior_in_flight; |
3367 | u32 prior_fackets; |
3368 | int prior_packets = tp->packets_out; |
3369 | const int prior_unsacked = tp->packets_out - tp->sacked_out; |
3370 | int acked = 0; /* Number of packets newly acked */ |
3371 | long sack_rtt_us = -1L; |
3372 | |
3373 | /* If the ack is older than previous acks |
3374 | * then we can probably ignore it. |
3375 | */ |
3376 | if (before(ack, prior_snd_una)) { |
3377 | /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */ |
3378 | if (before(ack, prior_snd_una - tp->max_window)) { |
3379 | tcp_send_challenge_ack(sk); |
3380 | return -1; |
3381 | } |
3382 | goto old_ack; |
3383 | } |
3384 | |
3385 | /* If the ack includes data we haven't sent yet, discard |
3386 | * this segment (RFC793 Section 3.9). |
3387 | */ |
3388 | if (after(ack, tp->snd_nxt)) |
3389 | goto invalid_ack; |
3390 | |
3391 | if (icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS || |
3392 | icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) |
3393 | tcp_rearm_rto(sk); |
3394 | |
3395 | if (after(ack, prior_snd_una)) |
3396 | flag |= FLAG_SND_UNA_ADVANCED; |
3397 | |
3398 | prior_fackets = tp->fackets_out; |
3399 | prior_in_flight = tcp_packets_in_flight(tp); |
3400 | |
3401 | /* ts_recent update must be made after we are sure that the packet |
3402 | * is in window. |
3403 | */ |
3404 | if (flag & FLAG_UPDATE_TS_RECENT) |
3405 | tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); |
3406 | |
3407 | if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) { |
3408 | /* Window is constant, pure forward advance. |
3409 | * No more checks are required. |
3410 | * Note, we use the fact that SND.UNA>=SND.WL2. |
3411 | */ |
3412 | tcp_update_wl(tp, ack_seq); |
3413 | tp->snd_una = ack; |
3414 | flag |= FLAG_WIN_UPDATE; |
3415 | |
3416 | tcp_ca_event(sk, CA_EVENT_FAST_ACK); |
3417 | |
3418 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); |
3419 | } else { |
3420 | if (ack_seq != TCP_SKB_CB(skb)->end_seq) |
3421 | flag |= FLAG_DATA; |
3422 | else |
3423 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS); |
3424 | |
3425 | flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); |
3426 | |
3427 | if (TCP_SKB_CB(skb)->sacked) |
3428 | flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una, |
3429 | &sack_rtt_us); |
3430 | |
3431 | if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) |
3432 | flag |= FLAG_ECE; |
3433 | |
3434 | tcp_ca_event(sk, CA_EVENT_SLOW_ACK); |
3435 | } |
3436 | |
3437 | /* We passed data and got it acked, remove any soft error |
3438 | * log. Something worked... |
3439 | */ |
3440 | sk->sk_err_soft = 0; |
3441 | icsk->icsk_probes_out = 0; |
3442 | tp->rcv_tstamp = tcp_time_stamp; |
3443 | if (!prior_packets) |
3444 | goto no_queue; |
3445 | |
3446 | /* See if we can take anything off of the retransmit queue. */ |
3447 | acked = tp->packets_out; |
3448 | flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una, |
3449 | sack_rtt_us); |
3450 | acked -= tp->packets_out; |
3451 | |
3452 | /* Advance cwnd if state allows */ |
3453 | if (tcp_may_raise_cwnd(sk, flag)) |
3454 | tcp_cong_avoid(sk, ack, acked, prior_in_flight); |
3455 | |
3456 | if (tcp_ack_is_dubious(sk, flag)) { |
3457 | is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); |
3458 | tcp_fastretrans_alert(sk, acked, prior_unsacked, |
3459 | is_dupack, flag); |
3460 | } |
3461 | if (tp->tlp_high_seq) |
3462 | tcp_process_tlp_ack(sk, ack, flag); |
3463 | |
3464 | if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) { |
3465 | struct dst_entry *dst = __sk_dst_get(sk); |
3466 | if (dst) |
3467 | dst_confirm(dst); |
3468 | } |
3469 | |
3470 | if (icsk->icsk_pending == ICSK_TIME_RETRANS) |
3471 | tcp_schedule_loss_probe(sk); |
3472 | tcp_update_pacing_rate(sk); |
3473 | return 1; |
3474 | |
3475 | no_queue: |
3476 | /* If data was DSACKed, see if we can undo a cwnd reduction. */ |
3477 | if (flag & FLAG_DSACKING_ACK) |
3478 | tcp_fastretrans_alert(sk, acked, prior_unsacked, |
3479 | is_dupack, flag); |
3480 | /* If this ack opens up a zero window, clear backoff. It was |
3481 | * being used to time the probes, and is probably far higher than |
3482 | * it needs to be for normal retransmission. |
3483 | */ |
3484 | if (tcp_send_head(sk)) |
3485 | tcp_ack_probe(sk); |
3486 | |
3487 | if (tp->tlp_high_seq) |
3488 | tcp_process_tlp_ack(sk, ack, flag); |
3489 | return 1; |
3490 | |
3491 | invalid_ack: |
3492 | SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt); |
3493 | return -1; |
3494 | |
3495 | old_ack: |
3496 | /* If data was SACKed, tag it and see if we should send more data. |
3497 | * If data was DSACKed, see if we can undo a cwnd reduction. |
3498 | */ |
3499 | if (TCP_SKB_CB(skb)->sacked) { |
3500 | flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una, |
3501 | &sack_rtt_us); |
3502 | tcp_fastretrans_alert(sk, acked, prior_unsacked, |
3503 | is_dupack, flag); |
3504 | } |
3505 | |
3506 | SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt); |
3507 | return 0; |
3508 | } |
3509 | |
3510 | /* Look for tcp options. Normally only called on SYN and SYNACK packets. |
3511 | * But, this can also be called on packets in the established flow when |
3512 | * the fast version below fails. |
3513 | */ |
3514 | void tcp_parse_options(const struct sk_buff *skb, |
3515 | struct tcp_options_received *opt_rx, int estab, |
3516 | struct tcp_fastopen_cookie *foc) |
3517 | { |
3518 | const unsigned char *ptr; |
3519 | const struct tcphdr *th = tcp_hdr(skb); |
3520 | int length = (th->doff * 4) - sizeof(struct tcphdr); |
3521 | |
3522 | ptr = (const unsigned char *)(th + 1); |
3523 | opt_rx->saw_tstamp = 0; |
3524 | |
3525 | while (length > 0) { |
3526 | int opcode = *ptr++; |
3527 | int opsize; |
3528 | |
3529 | switch (opcode) { |
3530 | case TCPOPT_EOL: |
3531 | return; |
3532 | case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ |
3533 | length--; |
3534 | continue; |
3535 | default: |
3536 | opsize = *ptr++; |
3537 | if (opsize < 2) /* "silly options" */ |
3538 | return; |
3539 | if (opsize > length) |
3540 | return; /* don't parse partial options */ |
3541 | switch (opcode) { |
3542 | case TCPOPT_MSS: |
3543 | if (opsize == TCPOLEN_MSS && th->syn && !estab) { |
3544 | u16 in_mss = get_unaligned_be16(ptr); |
3545 | if (in_mss) { |
3546 | if (opt_rx->user_mss && |
3547 | opt_rx->user_mss < in_mss) |
3548 | in_mss = opt_rx->user_mss; |
3549 | opt_rx->mss_clamp = in_mss; |
3550 | } |
3551 | } |
3552 | break; |
3553 | case TCPOPT_WINDOW: |
3554 | if (opsize == TCPOLEN_WINDOW && th->syn && |
3555 | !estab && sysctl_tcp_window_scaling) { |
3556 | __u8 snd_wscale = *(__u8 *)ptr; |
3557 | opt_rx->wscale_ok = 1; |
3558 | if (snd_wscale > 14) { |
3559 | net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n", |
3560 | __func__, |
3561 | snd_wscale); |
3562 | snd_wscale = 14; |
3563 | } |
3564 | opt_rx->snd_wscale = snd_wscale; |
3565 | } |
3566 | break; |
3567 | case TCPOPT_TIMESTAMP: |
3568 | if ((opsize == TCPOLEN_TIMESTAMP) && |
3569 | ((estab && opt_rx->tstamp_ok) || |
3570 | (!estab && sysctl_tcp_timestamps))) { |
3571 | opt_rx->saw_tstamp = 1; |
3572 | opt_rx->rcv_tsval = get_unaligned_be32(ptr); |
3573 | opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4); |
3574 | } |
3575 | break; |
3576 | case TCPOPT_SACK_PERM: |
3577 | if (opsize == TCPOLEN_SACK_PERM && th->syn && |
3578 | !estab && sysctl_tcp_sack) { |
3579 | opt_rx->sack_ok = TCP_SACK_SEEN; |
3580 | tcp_sack_reset(opt_rx); |
3581 | } |
3582 | break; |
3583 | |
3584 | case TCPOPT_SACK: |
3585 | if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && |
3586 | !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && |
3587 | opt_rx->sack_ok) { |
3588 | TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; |
3589 | } |
3590 | break; |
3591 | #ifdef CONFIG_TCP_MD5SIG |
3592 | case TCPOPT_MD5SIG: |
3593 | /* |
3594 | * The MD5 Hash has already been |
3595 | * checked (see tcp_v{4,6}_do_rcv()). |
3596 | */ |
3597 | break; |
3598 | #endif |
3599 | case TCPOPT_EXP: |
3600 | /* Fast Open option shares code 254 using a |
3601 | * 16 bits magic number. It's valid only in |
3602 | * SYN or SYN-ACK with an even size. |
3603 | */ |
3604 | if (opsize < TCPOLEN_EXP_FASTOPEN_BASE || |
3605 | get_unaligned_be16(ptr) != TCPOPT_FASTOPEN_MAGIC || |
3606 | foc == NULL || !th->syn || (opsize & 1)) |
3607 | break; |
3608 | foc->len = opsize - TCPOLEN_EXP_FASTOPEN_BASE; |
3609 | if (foc->len >= TCP_FASTOPEN_COOKIE_MIN && |
3610 | foc->len <= TCP_FASTOPEN_COOKIE_MAX) |
3611 | memcpy(foc->val, ptr + 2, foc->len); |
3612 | else if (foc->len != 0) |
3613 | foc->len = -1; |
3614 | break; |
3615 | |
3616 | } |
3617 | ptr += opsize-2; |
3618 | length -= opsize; |
3619 | } |
3620 | } |
3621 | } |
3622 | EXPORT_SYMBOL(tcp_parse_options); |
3623 | |
3624 | static bool tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th) |
3625 | { |
3626 | const __be32 *ptr = (const __be32 *)(th + 1); |
3627 | |
3628 | if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
3629 | | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { |
3630 | tp->rx_opt.saw_tstamp = 1; |
3631 | ++ptr; |
3632 | tp->rx_opt.rcv_tsval = ntohl(*ptr); |
3633 | ++ptr; |
3634 | if (*ptr) |
3635 | tp->rx_opt.rcv_tsecr = ntohl(*ptr) - tp->tsoffset; |
3636 | else |
3637 | tp->rx_opt.rcv_tsecr = 0; |
3638 | return true; |
3639 | } |
3640 | return false; |
3641 | } |
3642 | |
3643 | /* Fast parse options. This hopes to only see timestamps. |
3644 | * If it is wrong it falls back on tcp_parse_options(). |
3645 | */ |
3646 | static bool tcp_fast_parse_options(const struct sk_buff *skb, |
3647 | const struct tcphdr *th, struct tcp_sock *tp) |
3648 | { |
3649 | /* In the spirit of fast parsing, compare doff directly to constant |
3650 | * values. Because equality is used, short doff can be ignored here. |
3651 | */ |
3652 | if (th->doff == (sizeof(*th) / 4)) { |
3653 | tp->rx_opt.saw_tstamp = 0; |
3654 | return false; |
3655 | } else if (tp->rx_opt.tstamp_ok && |
3656 | th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { |
3657 | if (tcp_parse_aligned_timestamp(tp, th)) |
3658 | return true; |
3659 | } |
3660 | |
3661 | tcp_parse_options(skb, &tp->rx_opt, 1, NULL); |
3662 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) |
3663 | tp->rx_opt.rcv_tsecr -= tp->tsoffset; |
3664 | |
3665 | return true; |
3666 | } |
3667 | |
3668 | #ifdef CONFIG_TCP_MD5SIG |
3669 | /* |
3670 | * Parse MD5 Signature option |
3671 | */ |
3672 | const u8 *tcp_parse_md5sig_option(const struct tcphdr *th) |
3673 | { |
3674 | int length = (th->doff << 2) - sizeof(*th); |
3675 | const u8 *ptr = (const u8 *)(th + 1); |
3676 | |
3677 | /* If the TCP option is too short, we can short cut */ |
3678 | if (length < TCPOLEN_MD5SIG) |
3679 | return NULL; |
3680 | |
3681 | while (length > 0) { |
3682 | int opcode = *ptr++; |
3683 | int opsize; |
3684 | |
3685 | switch (opcode) { |
3686 | case TCPOPT_EOL: |
3687 | return NULL; |
3688 | case TCPOPT_NOP: |
3689 | length--; |
3690 | continue; |
3691 | default: |
3692 | opsize = *ptr++; |
3693 | if (opsize < 2 || opsize > length) |
3694 | return NULL; |
3695 | if (opcode == TCPOPT_MD5SIG) |
3696 | return opsize == TCPOLEN_MD5SIG ? ptr : NULL; |
3697 | } |
3698 | ptr += opsize - 2; |
3699 | length -= opsize; |
3700 | } |
3701 | return NULL; |
3702 | } |
3703 | EXPORT_SYMBOL(tcp_parse_md5sig_option); |
3704 | #endif |
3705 | |
3706 | /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM |
3707 | * |
3708 | * It is not fatal. If this ACK does _not_ change critical state (seqs, window) |
3709 | * it can pass through stack. So, the following predicate verifies that |
3710 | * this segment is not used for anything but congestion avoidance or |
3711 | * fast retransmit. Moreover, we even are able to eliminate most of such |
3712 | * second order effects, if we apply some small "replay" window (~RTO) |
3713 | * to timestamp space. |
3714 | * |
3715 | * All these measures still do not guarantee that we reject wrapped ACKs |
3716 | * on networks with high bandwidth, when sequence space is recycled fastly, |
3717 | * but it guarantees that such events will be very rare and do not affect |
3718 | * connection seriously. This doesn't look nice, but alas, PAWS is really |
3719 | * buggy extension. |
3720 | * |
3721 | * [ Later note. Even worse! It is buggy for segments _with_ data. RFC |
3722 | * states that events when retransmit arrives after original data are rare. |
3723 | * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is |
3724 | * the biggest problem on large power networks even with minor reordering. |
3725 | * OK, let's give it small replay window. If peer clock is even 1hz, it is safe |
3726 | * up to bandwidth of 18Gigabit/sec. 8) ] |
3727 | */ |
3728 | |
3729 | static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) |
3730 | { |
3731 | const struct tcp_sock *tp = tcp_sk(sk); |
3732 | const struct tcphdr *th = tcp_hdr(skb); |
3733 | u32 seq = TCP_SKB_CB(skb)->seq; |
3734 | u32 ack = TCP_SKB_CB(skb)->ack_seq; |
3735 | |
3736 | return (/* 1. Pure ACK with correct sequence number. */ |
3737 | (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && |
3738 | |
3739 | /* 2. ... and duplicate ACK. */ |
3740 | ack == tp->snd_una && |
3741 | |
3742 | /* 3. ... and does not update window. */ |
3743 | !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && |
3744 | |
3745 | /* 4. ... and sits in replay window. */ |
3746 | (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); |
3747 | } |
3748 | |
3749 | static inline bool tcp_paws_discard(const struct sock *sk, |
3750 | const struct sk_buff *skb) |
3751 | { |
3752 | const struct tcp_sock *tp = tcp_sk(sk); |
3753 | |
3754 | return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) && |
3755 | !tcp_disordered_ack(sk, skb); |
3756 | } |
3757 | |
3758 | /* Check segment sequence number for validity. |
3759 | * |
3760 | * Segment controls are considered valid, if the segment |
3761 | * fits to the window after truncation to the window. Acceptability |
3762 | * of data (and SYN, FIN, of course) is checked separately. |
3763 | * See tcp_data_queue(), for example. |
3764 | * |
3765 | * Also, controls (RST is main one) are accepted using RCV.WUP instead |
3766 | * of RCV.NXT. Peer still did not advance his SND.UNA when we |
3767 | * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. |
3768 | * (borrowed from freebsd) |
3769 | */ |
3770 | |
3771 | static inline bool tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq) |
3772 | { |
3773 | return !before(end_seq, tp->rcv_wup) && |
3774 | !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); |
3775 | } |
3776 | |
3777 | /* When we get a reset we do this. */ |
3778 | void tcp_reset(struct sock *sk) |
3779 | { |
3780 | /* We want the right error as BSD sees it (and indeed as we do). */ |
3781 | switch (sk->sk_state) { |
3782 | case TCP_SYN_SENT: |
3783 | sk->sk_err = ECONNREFUSED; |
3784 | break; |
3785 | case TCP_CLOSE_WAIT: |
3786 | sk->sk_err = EPIPE; |
3787 | break; |
3788 | case TCP_CLOSE: |
3789 | return; |
3790 | default: |
3791 | sk->sk_err = ECONNRESET; |
3792 | } |
3793 | /* This barrier is coupled with smp_rmb() in tcp_poll() */ |
3794 | smp_wmb(); |
3795 | |
3796 | if (!sock_flag(sk, SOCK_DEAD)) |
3797 | sk->sk_error_report(sk); |
3798 | |
3799 | tcp_done(sk); |
3800 | } |
3801 | |
3802 | /* |
3803 | * Process the FIN bit. This now behaves as it is supposed to work |
3804 | * and the FIN takes effect when it is validly part of sequence |
3805 | * space. Not before when we get holes. |
3806 | * |
3807 | * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT |
3808 | * (and thence onto LAST-ACK and finally, CLOSE, we never enter |
3809 | * TIME-WAIT) |
3810 | * |
3811 | * If we are in FINWAIT-1, a received FIN indicates simultaneous |
3812 | * close and we go into CLOSING (and later onto TIME-WAIT) |
3813 | * |
3814 | * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. |
3815 | */ |
3816 | static void tcp_fin(struct sock *sk) |
3817 | { |
3818 | struct tcp_sock *tp = tcp_sk(sk); |
3819 | const struct dst_entry *dst; |
3820 | |
3821 | inet_csk_schedule_ack(sk); |
3822 | |
3823 | sk->sk_shutdown |= RCV_SHUTDOWN; |
3824 | sock_set_flag(sk, SOCK_DONE); |
3825 | |
3826 | switch (sk->sk_state) { |
3827 | case TCP_SYN_RECV: |
3828 | case TCP_ESTABLISHED: |
3829 | /* Move to CLOSE_WAIT */ |
3830 | tcp_set_state(sk, TCP_CLOSE_WAIT); |
3831 | dst = __sk_dst_get(sk); |
3832 | if (!dst || !dst_metric(dst, RTAX_QUICKACK)) |
3833 | inet_csk(sk)->icsk_ack.pingpong = 1; |
3834 | break; |
3835 | |
3836 | case TCP_CLOSE_WAIT: |
3837 | case TCP_CLOSING: |
3838 | /* Received a retransmission of the FIN, do |
3839 | * nothing. |
3840 | */ |
3841 | break; |
3842 | case TCP_LAST_ACK: |
3843 | /* RFC793: Remain in the LAST-ACK state. */ |
3844 | break; |
3845 | |
3846 | case TCP_FIN_WAIT1: |
3847 | /* This case occurs when a simultaneous close |
3848 | * happens, we must ack the received FIN and |
3849 | * enter the CLOSING state. |
3850 | */ |
3851 | tcp_send_ack(sk); |
3852 | tcp_set_state(sk, TCP_CLOSING); |
3853 | break; |
3854 | case TCP_FIN_WAIT2: |
3855 | /* Received a FIN -- send ACK and enter TIME_WAIT. */ |
3856 | tcp_send_ack(sk); |
3857 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); |
3858 | break; |
3859 | default: |
3860 | /* Only TCP_LISTEN and TCP_CLOSE are left, in these |
3861 | * cases we should never reach this piece of code. |
3862 | */ |
3863 | pr_err("%s: Impossible, sk->sk_state=%d\n", |
3864 | __func__, sk->sk_state); |
3865 | break; |
3866 | } |
3867 | |
3868 | /* It _is_ possible, that we have something out-of-order _after_ FIN. |
3869 | * Probably, we should reset in this case. For now drop them. |
3870 | */ |
3871 | __skb_queue_purge(&tp->out_of_order_queue); |
3872 | if (tcp_is_sack(tp)) |
3873 | tcp_sack_reset(&tp->rx_opt); |
3874 | sk_mem_reclaim(sk); |
3875 | |
3876 | if (!sock_flag(sk, SOCK_DEAD)) { |
3877 | sk->sk_state_change(sk); |
3878 | |
3879 | /* Do not send POLL_HUP for half duplex close. */ |
3880 | if (sk->sk_shutdown == SHUTDOWN_MASK || |
3881 | sk->sk_state == TCP_CLOSE) |
3882 | sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); |
3883 | else |
3884 | sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); |
3885 | } |
3886 | } |
3887 | |
3888 | static inline bool tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, |
3889 | u32 end_seq) |
3890 | { |
3891 | if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { |
3892 | if (before(seq, sp->start_seq)) |
3893 | sp->start_seq = seq; |
3894 | if (after(end_seq, sp->end_seq)) |
3895 | sp->end_seq = end_seq; |
3896 | return true; |
3897 | } |
3898 | return false; |
3899 | } |
3900 | |
3901 | static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) |
3902 | { |
3903 | struct tcp_sock *tp = tcp_sk(sk); |
3904 | |
3905 | if (tcp_is_sack(tp) && sysctl_tcp_dsack) { |
3906 | int mib_idx; |
3907 | |
3908 | if (before(seq, tp->rcv_nxt)) |
3909 | mib_idx = LINUX_MIB_TCPDSACKOLDSENT; |
3910 | else |
3911 | mib_idx = LINUX_MIB_TCPDSACKOFOSENT; |
3912 | |
3913 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
3914 | |
3915 | tp->rx_opt.dsack = 1; |
3916 | tp->duplicate_sack[0].start_seq = seq; |
3917 | tp->duplicate_sack[0].end_seq = end_seq; |
3918 | } |
3919 | } |
3920 | |
3921 | static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq) |
3922 | { |
3923 | struct tcp_sock *tp = tcp_sk(sk); |
3924 | |
3925 | if (!tp->rx_opt.dsack) |
3926 | tcp_dsack_set(sk, seq, end_seq); |
3927 | else |
3928 | tcp_sack_extend(tp->duplicate_sack, seq, end_seq); |
3929 | } |
3930 | |
3931 | static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb) |
3932 | { |
3933 | struct tcp_sock *tp = tcp_sk(sk); |
3934 | |
3935 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
3936 | before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
3937 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); |
3938 | tcp_enter_quickack_mode(sk); |
3939 | |
3940 | if (tcp_is_sack(tp) && sysctl_tcp_dsack) { |
3941 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; |
3942 | |
3943 | if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) |
3944 | end_seq = tp->rcv_nxt; |
3945 | tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq); |
3946 | } |
3947 | } |
3948 | |
3949 | tcp_send_ack(sk); |
3950 | } |
3951 | |
3952 | /* These routines update the SACK block as out-of-order packets arrive or |
3953 | * in-order packets close up the sequence space. |
3954 | */ |
3955 | static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) |
3956 | { |
3957 | int this_sack; |
3958 | struct tcp_sack_block *sp = &tp->selective_acks[0]; |
3959 | struct tcp_sack_block *swalk = sp + 1; |
3960 | |
3961 | /* See if the recent change to the first SACK eats into |
3962 | * or hits the sequence space of other SACK blocks, if so coalesce. |
3963 | */ |
3964 | for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) { |
3965 | if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { |
3966 | int i; |
3967 | |
3968 | /* Zap SWALK, by moving every further SACK up by one slot. |
3969 | * Decrease num_sacks. |
3970 | */ |
3971 | tp->rx_opt.num_sacks--; |
3972 | for (i = this_sack; i < tp->rx_opt.num_sacks; i++) |
3973 | sp[i] = sp[i + 1]; |
3974 | continue; |
3975 | } |
3976 | this_sack++, swalk++; |
3977 | } |
3978 | } |
3979 | |
3980 | static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) |
3981 | { |
3982 | struct tcp_sock *tp = tcp_sk(sk); |
3983 | struct tcp_sack_block *sp = &tp->selective_acks[0]; |
3984 | int cur_sacks = tp->rx_opt.num_sacks; |
3985 | int this_sack; |
3986 | |
3987 | if (!cur_sacks) |
3988 | goto new_sack; |
3989 | |
3990 | for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) { |
3991 | if (tcp_sack_extend(sp, seq, end_seq)) { |
3992 | /* Rotate this_sack to the first one. */ |
3993 | for (; this_sack > 0; this_sack--, sp--) |
3994 | swap(*sp, *(sp - 1)); |
3995 | if (cur_sacks > 1) |
3996 | tcp_sack_maybe_coalesce(tp); |
3997 | return; |
3998 | } |
3999 | } |
4000 | |
4001 | /* Could not find an adjacent existing SACK, build a new one, |
4002 | * put it at the front, and shift everyone else down. We |
4003 | * always know there is at least one SACK present already here. |
4004 | * |
4005 | * If the sack array is full, forget about the last one. |
4006 | */ |
4007 | if (this_sack >= TCP_NUM_SACKS) { |
4008 | this_sack--; |
4009 | tp->rx_opt.num_sacks--; |
4010 | sp--; |
4011 | } |
4012 | for (; this_sack > 0; this_sack--, sp--) |
4013 | *sp = *(sp - 1); |
4014 | |
4015 | new_sack: |
4016 | /* Build the new head SACK, and we're done. */ |
4017 | sp->start_seq = seq; |
4018 | sp->end_seq = end_seq; |
4019 | tp->rx_opt.num_sacks++; |
4020 | } |
4021 | |
4022 | /* RCV.NXT advances, some SACKs should be eaten. */ |
4023 | |
4024 | static void tcp_sack_remove(struct tcp_sock *tp) |
4025 | { |
4026 | struct tcp_sack_block *sp = &tp->selective_acks[0]; |
4027 | int num_sacks = tp->rx_opt.num_sacks; |
4028 | int this_sack; |
4029 | |
4030 | /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ |
4031 | if (skb_queue_empty(&tp->out_of_order_queue)) { |
4032 | tp->rx_opt.num_sacks = 0; |
4033 | return; |
4034 | } |
4035 | |
4036 | for (this_sack = 0; this_sack < num_sacks;) { |
4037 | /* Check if the start of the sack is covered by RCV.NXT. */ |
4038 | if (!before(tp->rcv_nxt, sp->start_seq)) { |
4039 | int i; |
4040 | |
4041 | /* RCV.NXT must cover all the block! */ |
4042 | WARN_ON(before(tp->rcv_nxt, sp->end_seq)); |
4043 | |
4044 | /* Zap this SACK, by moving forward any other SACKS. */ |
4045 | for (i = this_sack+1; i < num_sacks; i++) |
4046 | tp->selective_acks[i-1] = tp->selective_acks[i]; |
4047 | num_sacks--; |
4048 | continue; |
4049 | } |
4050 | this_sack++; |
4051 | sp++; |
4052 | } |
4053 | tp->rx_opt.num_sacks = num_sacks; |
4054 | } |
4055 | |
4056 | /* This one checks to see if we can put data from the |
4057 | * out_of_order queue into the receive_queue. |
4058 | */ |
4059 | static void tcp_ofo_queue(struct sock *sk) |
4060 | { |
4061 | struct tcp_sock *tp = tcp_sk(sk); |
4062 | __u32 dsack_high = tp->rcv_nxt; |
4063 | struct sk_buff *skb; |
4064 | |
4065 | while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { |
4066 | if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) |
4067 | break; |
4068 | |
4069 | if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { |
4070 | __u32 dsack = dsack_high; |
4071 | if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) |
4072 | dsack_high = TCP_SKB_CB(skb)->end_seq; |
4073 | tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack); |
4074 | } |
4075 | |
4076 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { |
4077 | SOCK_DEBUG(sk, "ofo packet was already received\n"); |
4078 | __skb_unlink(skb, &tp->out_of_order_queue); |
4079 | __kfree_skb(skb); |
4080 | continue; |
4081 | } |
4082 | SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", |
4083 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, |
4084 | TCP_SKB_CB(skb)->end_seq); |
4085 | |
4086 | __skb_unlink(skb, &tp->out_of_order_queue); |
4087 | __skb_queue_tail(&sk->sk_receive_queue, skb); |
4088 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
4089 | if (tcp_hdr(skb)->fin) |
4090 | tcp_fin(sk); |
4091 | } |
4092 | } |
4093 | |
4094 | static bool tcp_prune_ofo_queue(struct sock *sk); |
4095 | static int tcp_prune_queue(struct sock *sk); |
4096 | |
4097 | static int tcp_try_rmem_schedule(struct sock *sk, struct sk_buff *skb, |
4098 | unsigned int size) |
4099 | { |
4100 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || |
4101 | !sk_rmem_schedule(sk, skb, size)) { |
4102 | |
4103 | if (tcp_prune_queue(sk) < 0) |
4104 | return -1; |
4105 | |
4106 | if (!sk_rmem_schedule(sk, skb, size)) { |
4107 | if (!tcp_prune_ofo_queue(sk)) |
4108 | return -1; |
4109 | |
4110 | if (!sk_rmem_schedule(sk, skb, size)) |
4111 | return -1; |
4112 | } |
4113 | } |
4114 | return 0; |
4115 | } |
4116 | |
4117 | /** |
4118 | * tcp_try_coalesce - try to merge skb to prior one |
4119 | * @sk: socket |
4120 | * @to: prior buffer |
4121 | * @from: buffer to add in queue |
4122 | * @fragstolen: pointer to boolean |
4123 | * |
4124 | * Before queueing skb @from after @to, try to merge them |
4125 | * to reduce overall memory use and queue lengths, if cost is small. |
4126 | * Packets in ofo or receive queues can stay a long time. |
4127 | * Better try to coalesce them right now to avoid future collapses. |
4128 | * Returns true if caller should free @from instead of queueing it |
4129 | */ |
4130 | static bool tcp_try_coalesce(struct sock *sk, |
4131 | struct sk_buff *to, |
4132 | struct sk_buff *from, |
4133 | bool *fragstolen) |
4134 | { |
4135 | int delta; |
4136 | |
4137 | *fragstolen = false; |
4138 | |
4139 | if (tcp_hdr(from)->fin) |
4140 | return false; |
4141 | |
4142 | /* Its possible this segment overlaps with prior segment in queue */ |
4143 | if (TCP_SKB_CB(from)->seq != TCP_SKB_CB(to)->end_seq) |
4144 | return false; |
4145 | |
4146 | if (!skb_try_coalesce(to, from, fragstolen, &delta)) |
4147 | return false; |
4148 | |
4149 | atomic_add(delta, &sk->sk_rmem_alloc); |
4150 | sk_mem_charge(sk, delta); |
4151 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOALESCE); |
4152 | TCP_SKB_CB(to)->end_seq = TCP_SKB_CB(from)->end_seq; |
4153 | TCP_SKB_CB(to)->ack_seq = TCP_SKB_CB(from)->ack_seq; |
4154 | return true; |
4155 | } |
4156 | |
4157 | static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) |
4158 | { |
4159 | struct tcp_sock *tp = tcp_sk(sk); |
4160 | struct sk_buff *skb1; |
4161 | u32 seq, end_seq; |
4162 | |
4163 | TCP_ECN_check_ce(tp, skb); |
4164 | |
4165 | if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) { |
4166 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFODROP); |
4167 | __kfree_skb(skb); |
4168 | return; |
4169 | } |
4170 | |
4171 | /* Disable header prediction. */ |
4172 | tp->pred_flags = 0; |
4173 | inet_csk_schedule_ack(sk); |
4174 | |
4175 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOQUEUE); |
4176 | SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", |
4177 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); |
4178 | |
4179 | skb1 = skb_peek_tail(&tp->out_of_order_queue); |
4180 | if (!skb1) { |
4181 | /* Initial out of order segment, build 1 SACK. */ |
4182 | if (tcp_is_sack(tp)) { |
4183 | tp->rx_opt.num_sacks = 1; |
4184 | tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; |
4185 | tp->selective_acks[0].end_seq = |
4186 | TCP_SKB_CB(skb)->end_seq; |
4187 | } |
4188 | __skb_queue_head(&tp->out_of_order_queue, skb); |
4189 | goto end; |
4190 | } |
4191 | |
4192 | seq = TCP_SKB_CB(skb)->seq; |
4193 | end_seq = TCP_SKB_CB(skb)->end_seq; |
4194 | |
4195 | if (seq == TCP_SKB_CB(skb1)->end_seq) { |
4196 | bool fragstolen; |
4197 | |
4198 | if (!tcp_try_coalesce(sk, skb1, skb, &fragstolen)) { |
4199 | __skb_queue_after(&tp->out_of_order_queue, skb1, skb); |
4200 | } else { |
4201 | tcp_grow_window(sk, skb); |
4202 | kfree_skb_partial(skb, fragstolen); |
4203 | skb = NULL; |
4204 | } |
4205 | |
4206 | if (!tp->rx_opt.num_sacks || |
4207 | tp->selective_acks[0].end_seq != seq) |
4208 | goto add_sack; |
4209 | |
4210 | /* Common case: data arrive in order after hole. */ |
4211 | tp->selective_acks[0].end_seq = end_seq; |
4212 | goto end; |
4213 | } |
4214 | |
4215 | /* Find place to insert this segment. */ |
4216 | while (1) { |
4217 | if (!after(TCP_SKB_CB(skb1)->seq, seq)) |
4218 | break; |
4219 | if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) { |
4220 | skb1 = NULL; |
4221 | break; |
4222 | } |
4223 | skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1); |
4224 | } |
4225 | |
4226 | /* Do skb overlap to previous one? */ |
4227 | if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) { |
4228 | if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { |
4229 | /* All the bits are present. Drop. */ |
4230 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE); |
4231 | __kfree_skb(skb); |
4232 | skb = NULL; |
4233 | tcp_dsack_set(sk, seq, end_seq); |
4234 | goto add_sack; |
4235 | } |
4236 | if (after(seq, TCP_SKB_CB(skb1)->seq)) { |
4237 | /* Partial overlap. */ |
4238 | tcp_dsack_set(sk, seq, |
4239 | TCP_SKB_CB(skb1)->end_seq); |
4240 | } else { |
4241 | if (skb_queue_is_first(&tp->out_of_order_queue, |
4242 | skb1)) |
4243 | skb1 = NULL; |
4244 | else |
4245 | skb1 = skb_queue_prev( |
4246 | &tp->out_of_order_queue, |
4247 | skb1); |
4248 | } |
4249 | } |
4250 | if (!skb1) |
4251 | __skb_queue_head(&tp->out_of_order_queue, skb); |
4252 | else |
4253 | __skb_queue_after(&tp->out_of_order_queue, skb1, skb); |
4254 | |
4255 | /* And clean segments covered by new one as whole. */ |
4256 | while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) { |
4257 | skb1 = skb_queue_next(&tp->out_of_order_queue, skb); |
4258 | |
4259 | if (!after(end_seq, TCP_SKB_CB(skb1)->seq)) |
4260 | break; |
4261 | if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { |
4262 | tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, |
4263 | end_seq); |
4264 | break; |
4265 | } |
4266 | __skb_unlink(skb1, &tp->out_of_order_queue); |
4267 | tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, |
4268 | TCP_SKB_CB(skb1)->end_seq); |
4269 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE); |
4270 | __kfree_skb(skb1); |
4271 | } |
4272 | |
4273 | add_sack: |
4274 | if (tcp_is_sack(tp)) |
4275 | tcp_sack_new_ofo_skb(sk, seq, end_seq); |
4276 | end: |
4277 | if (skb) { |
4278 | tcp_grow_window(sk, skb); |
4279 | skb_set_owner_r(skb, sk); |
4280 | } |
4281 | } |
4282 | |
4283 | static int __must_check tcp_queue_rcv(struct sock *sk, struct sk_buff *skb, int hdrlen, |
4284 | bool *fragstolen) |
4285 | { |
4286 | int eaten; |
4287 | struct sk_buff *tail = skb_peek_tail(&sk->sk_receive_queue); |
4288 | |
4289 | __skb_pull(skb, hdrlen); |
4290 | eaten = (tail && |
4291 | tcp_try_coalesce(sk, tail, skb, fragstolen)) ? 1 : 0; |
4292 | tcp_sk(sk)->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
4293 | if (!eaten) { |
4294 | __skb_queue_tail(&sk->sk_receive_queue, skb); |
4295 | skb_set_owner_r(skb, sk); |
4296 | } |
4297 | return eaten; |
4298 | } |
4299 | |
4300 | int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size) |
4301 | { |
4302 | struct sk_buff *skb = NULL; |
4303 | struct tcphdr *th; |
4304 | bool fragstolen; |
4305 | |
4306 | if (size == 0) |
4307 | return 0; |
4308 | |
4309 | skb = alloc_skb(size + sizeof(*th), sk->sk_allocation); |
4310 | if (!skb) |
4311 | goto err; |
4312 | |
4313 | if (tcp_try_rmem_schedule(sk, skb, size + sizeof(*th))) |
4314 | goto err_free; |
4315 | |
4316 | th = (struct tcphdr *)skb_put(skb, sizeof(*th)); |
4317 | skb_reset_transport_header(skb); |
4318 | memset(th, 0, sizeof(*th)); |
4319 | |
4320 | if (memcpy_fromiovec(skb_put(skb, size), msg->msg_iov, size)) |
4321 | goto err_free; |
4322 | |
4323 | TCP_SKB_CB(skb)->seq = tcp_sk(sk)->rcv_nxt; |
4324 | TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + size; |
4325 | TCP_SKB_CB(skb)->ack_seq = tcp_sk(sk)->snd_una - 1; |
4326 | |
4327 | if (tcp_queue_rcv(sk, skb, sizeof(*th), &fragstolen)) { |
4328 | WARN_ON_ONCE(fragstolen); /* should not happen */ |
4329 | __kfree_skb(skb); |
4330 | } |
4331 | return size; |
4332 | |
4333 | err_free: |
4334 | kfree_skb(skb); |
4335 | err: |
4336 | return -ENOMEM; |
4337 | } |
4338 | |
4339 | static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) |
4340 | { |
4341 | const struct tcphdr *th = tcp_hdr(skb); |
4342 | struct tcp_sock *tp = tcp_sk(sk); |
4343 | int eaten = -1; |
4344 | bool fragstolen = false; |
4345 | |
4346 | if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) |
4347 | goto drop; |
4348 | |
4349 | skb_dst_drop(skb); |
4350 | __skb_pull(skb, th->doff * 4); |
4351 | |
4352 | TCP_ECN_accept_cwr(tp, skb); |
4353 | |
4354 | tp->rx_opt.dsack = 0; |
4355 | |
4356 | /* Queue data for delivery to the user. |
4357 | * Packets in sequence go to the receive queue. |
4358 | * Out of sequence packets to the out_of_order_queue. |
4359 | */ |
4360 | if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { |
4361 | if (tcp_receive_window(tp) == 0) |
4362 | goto out_of_window; |
4363 | |
4364 | /* Ok. In sequence. In window. */ |
4365 | if (tp->ucopy.task == current && |
4366 | tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && |
4367 | sock_owned_by_user(sk) && !tp->urg_data) { |
4368 | int chunk = min_t(unsigned int, skb->len, |
4369 | tp->ucopy.len); |
4370 | |
4371 | __set_current_state(TASK_RUNNING); |
4372 | |
4373 | local_bh_enable(); |
4374 | if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { |
4375 | tp->ucopy.len -= chunk; |
4376 | tp->copied_seq += chunk; |
4377 | eaten = (chunk == skb->len); |
4378 | tcp_rcv_space_adjust(sk); |
4379 | } |
4380 | local_bh_disable(); |
4381 | } |
4382 | |
4383 | if (eaten <= 0) { |
4384 | queue_and_out: |
4385 | if (eaten < 0 && |
4386 | tcp_try_rmem_schedule(sk, skb, skb->truesize)) |
4387 | goto drop; |
4388 | |
4389 | eaten = tcp_queue_rcv(sk, skb, 0, &fragstolen); |
4390 | } |
4391 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
4392 | if (skb->len) |
4393 | tcp_event_data_recv(sk, skb); |
4394 | if (th->fin) |
4395 | tcp_fin(sk); |
4396 | |
4397 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
4398 | tcp_ofo_queue(sk); |
4399 | |
4400 | /* RFC2581. 4.2. SHOULD send immediate ACK, when |
4401 | * gap in queue is filled. |
4402 | */ |
4403 | if (skb_queue_empty(&tp->out_of_order_queue)) |
4404 | inet_csk(sk)->icsk_ack.pingpong = 0; |
4405 | } |
4406 | |
4407 | if (tp->rx_opt.num_sacks) |
4408 | tcp_sack_remove(tp); |
4409 | |
4410 | tcp_fast_path_check(sk); |
4411 | |
4412 | if (eaten > 0) |
4413 | kfree_skb_partial(skb, fragstolen); |
4414 | if (!sock_flag(sk, SOCK_DEAD)) |
4415 | sk->sk_data_ready(sk); |
4416 | return; |
4417 | } |
4418 | |
4419 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { |
4420 | /* A retransmit, 2nd most common case. Force an immediate ack. */ |
4421 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); |
4422 | tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); |
4423 | |
4424 | out_of_window: |
4425 | tcp_enter_quickack_mode(sk); |
4426 | inet_csk_schedule_ack(sk); |
4427 | drop: |
4428 | __kfree_skb(skb); |
4429 | return; |
4430 | } |
4431 | |
4432 | /* Out of window. F.e. zero window probe. */ |
4433 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) |
4434 | goto out_of_window; |
4435 | |
4436 | tcp_enter_quickack_mode(sk); |
4437 | |
4438 | if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { |
4439 | /* Partial packet, seq < rcv_next < end_seq */ |
4440 | SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", |
4441 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, |
4442 | TCP_SKB_CB(skb)->end_seq); |
4443 | |
4444 | tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); |
4445 | |
4446 | /* If window is closed, drop tail of packet. But after |
4447 | * remembering D-SACK for its head made in previous line. |
4448 | */ |
4449 | if (!tcp_receive_window(tp)) |
4450 | goto out_of_window; |
4451 | goto queue_and_out; |
4452 | } |
4453 | |
4454 | tcp_data_queue_ofo(sk, skb); |
4455 | } |
4456 | |
4457 | static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, |
4458 | struct sk_buff_head *list) |
4459 | { |
4460 | struct sk_buff *next = NULL; |
4461 | |
4462 | if (!skb_queue_is_last(list, skb)) |
4463 | next = skb_queue_next(list, skb); |
4464 | |
4465 | __skb_unlink(skb, list); |
4466 | __kfree_skb(skb); |
4467 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED); |
4468 | |
4469 | return next; |
4470 | } |
4471 | |
4472 | /* Collapse contiguous sequence of skbs head..tail with |
4473 | * sequence numbers start..end. |
4474 | * |
4475 | * If tail is NULL, this means until the end of the list. |
4476 | * |
4477 | * Segments with FIN/SYN are not collapsed (only because this |
4478 | * simplifies code) |
4479 | */ |
4480 | static void |
4481 | tcp_collapse(struct sock *sk, struct sk_buff_head *list, |
4482 | struct sk_buff *head, struct sk_buff *tail, |
4483 | u32 start, u32 end) |
4484 | { |
4485 | struct sk_buff *skb, *n; |
4486 | bool end_of_skbs; |
4487 | |
4488 | /* First, check that queue is collapsible and find |
4489 | * the point where collapsing can be useful. */ |
4490 | skb = head; |
4491 | restart: |
4492 | end_of_skbs = true; |
4493 | skb_queue_walk_from_safe(list, skb, n) { |
4494 | if (skb == tail) |
4495 | break; |
4496 | /* No new bits? It is possible on ofo queue. */ |
4497 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { |
4498 | skb = tcp_collapse_one(sk, skb, list); |
4499 | if (!skb) |
4500 | break; |
4501 | goto restart; |
4502 | } |
4503 | |
4504 | /* The first skb to collapse is: |
4505 | * - not SYN/FIN and |
4506 | * - bloated or contains data before "start" or |
4507 | * overlaps to the next one. |
4508 | */ |
4509 | if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && |
4510 | (tcp_win_from_space(skb->truesize) > skb->len || |
4511 | before(TCP_SKB_CB(skb)->seq, start))) { |
4512 | end_of_skbs = false; |
4513 | break; |
4514 | } |
4515 | |
4516 | if (!skb_queue_is_last(list, skb)) { |
4517 | struct sk_buff *next = skb_queue_next(list, skb); |
4518 | if (next != tail && |
4519 | TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) { |
4520 | end_of_skbs = false; |
4521 | break; |
4522 | } |
4523 | } |
4524 | |
4525 | /* Decided to skip this, advance start seq. */ |
4526 | start = TCP_SKB_CB(skb)->end_seq; |
4527 | } |
4528 | if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) |
4529 | return; |
4530 | |
4531 | while (before(start, end)) { |
4532 | struct sk_buff *nskb; |
4533 | unsigned int header = skb_headroom(skb); |
4534 | int copy = SKB_MAX_ORDER(header, 0); |
4535 | |
4536 | /* Too big header? This can happen with IPv6. */ |
4537 | if (copy < 0) |
4538 | return; |
4539 | if (end - start < copy) |
4540 | copy = end - start; |
4541 | nskb = alloc_skb(copy + header, GFP_ATOMIC); |
4542 | if (!nskb) |
4543 | return; |
4544 | |
4545 | skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); |
4546 | skb_set_network_header(nskb, (skb_network_header(skb) - |
4547 | skb->head)); |
4548 | skb_set_transport_header(nskb, (skb_transport_header(skb) - |
4549 | skb->head)); |
4550 | skb_reserve(nskb, header); |
4551 | memcpy(nskb->head, skb->head, header); |
4552 | memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); |
4553 | TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; |
4554 | __skb_queue_before(list, skb, nskb); |
4555 | skb_set_owner_r(nskb, sk); |
4556 | |
4557 | /* Copy data, releasing collapsed skbs. */ |
4558 | while (copy > 0) { |
4559 | int offset = start - TCP_SKB_CB(skb)->seq; |
4560 | int size = TCP_SKB_CB(skb)->end_seq - start; |
4561 | |
4562 | BUG_ON(offset < 0); |
4563 | if (size > 0) { |
4564 | size = min(copy, size); |
4565 | if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) |
4566 | BUG(); |
4567 | TCP_SKB_CB(nskb)->end_seq += size; |
4568 | copy -= size; |
4569 | start += size; |
4570 | } |
4571 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { |
4572 | skb = tcp_collapse_one(sk, skb, list); |
4573 | if (!skb || |
4574 | skb == tail || |
4575 | tcp_hdr(skb)->syn || |
4576 | tcp_hdr(skb)->fin) |
4577 | return; |
4578 | } |
4579 | } |
4580 | } |
4581 | } |
4582 | |
4583 | /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs |
4584 | * and tcp_collapse() them until all the queue is collapsed. |
4585 | */ |
4586 | static void tcp_collapse_ofo_queue(struct sock *sk) |
4587 | { |
4588 | struct tcp_sock *tp = tcp_sk(sk); |
4589 | struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); |
4590 | struct sk_buff *head; |
4591 | u32 start, end; |
4592 | |
4593 | if (skb == NULL) |
4594 | return; |
4595 | |
4596 | start = TCP_SKB_CB(skb)->seq; |
4597 | end = TCP_SKB_CB(skb)->end_seq; |
4598 | head = skb; |
4599 | |
4600 | for (;;) { |
4601 | struct sk_buff *next = NULL; |
4602 | |
4603 | if (!skb_queue_is_last(&tp->out_of_order_queue, skb)) |
4604 | next = skb_queue_next(&tp->out_of_order_queue, skb); |
4605 | skb = next; |
4606 | |
4607 | /* Segment is terminated when we see gap or when |
4608 | * we are at the end of all the queue. */ |
4609 | if (!skb || |
4610 | after(TCP_SKB_CB(skb)->seq, end) || |
4611 | before(TCP_SKB_CB(skb)->end_seq, start)) { |
4612 | tcp_collapse(sk, &tp->out_of_order_queue, |
4613 | head, skb, start, end); |
4614 | head = skb; |
4615 | if (!skb) |
4616 | break; |
4617 | /* Start new segment */ |
4618 | start = TCP_SKB_CB(skb)->seq; |
4619 | end = TCP_SKB_CB(skb)->end_seq; |
4620 | } else { |
4621 | if (before(TCP_SKB_CB(skb)->seq, start)) |
4622 | start = TCP_SKB_CB(skb)->seq; |
4623 | if (after(TCP_SKB_CB(skb)->end_seq, end)) |
4624 | end = TCP_SKB_CB(skb)->end_seq; |
4625 | } |
4626 | } |
4627 | } |
4628 | |
4629 | /* |
4630 | * Purge the out-of-order queue. |
4631 | * Return true if queue was pruned. |
4632 | */ |
4633 | static bool tcp_prune_ofo_queue(struct sock *sk) |
4634 | { |
4635 | struct tcp_sock *tp = tcp_sk(sk); |
4636 | bool res = false; |
4637 | |
4638 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
4639 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED); |
4640 | __skb_queue_purge(&tp->out_of_order_queue); |
4641 | |
4642 | /* Reset SACK state. A conforming SACK implementation will |
4643 | * do the same at a timeout based retransmit. When a connection |
4644 | * is in a sad state like this, we care only about integrity |
4645 | * of the connection not performance. |
4646 | */ |
4647 | if (tp->rx_opt.sack_ok) |
4648 | tcp_sack_reset(&tp->rx_opt); |
4649 | sk_mem_reclaim(sk); |
4650 | res = true; |
4651 | } |
4652 | return res; |
4653 | } |
4654 | |
4655 | /* Reduce allocated memory if we can, trying to get |
4656 | * the socket within its memory limits again. |
4657 | * |
4658 | * Return less than zero if we should start dropping frames |
4659 | * until the socket owning process reads some of the data |
4660 | * to stabilize the situation. |
4661 | */ |
4662 | static int tcp_prune_queue(struct sock *sk) |
4663 | { |
4664 | struct tcp_sock *tp = tcp_sk(sk); |
4665 | |
4666 | SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); |
4667 | |
4668 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED); |
4669 | |
4670 | if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) |
4671 | tcp_clamp_window(sk); |
4672 | else if (sk_under_memory_pressure(sk)) |
4673 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); |
4674 | |
4675 | tcp_collapse_ofo_queue(sk); |
4676 | if (!skb_queue_empty(&sk->sk_receive_queue)) |
4677 | tcp_collapse(sk, &sk->sk_receive_queue, |
4678 | skb_peek(&sk->sk_receive_queue), |
4679 | NULL, |
4680 | tp->copied_seq, tp->rcv_nxt); |
4681 | sk_mem_reclaim(sk); |
4682 | |
4683 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) |
4684 | return 0; |
4685 | |
4686 | /* Collapsing did not help, destructive actions follow. |
4687 | * This must not ever occur. */ |
4688 | |
4689 | tcp_prune_ofo_queue(sk); |
4690 | |
4691 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) |
4692 | return 0; |
4693 | |
4694 | /* If we are really being abused, tell the caller to silently |
4695 | * drop receive data on the floor. It will get retransmitted |
4696 | * and hopefully then we'll have sufficient space. |
4697 | */ |
4698 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED); |
4699 | |
4700 | /* Massive buffer overcommit. */ |
4701 | tp->pred_flags = 0; |
4702 | return -1; |
4703 | } |
4704 | |
4705 | /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. |
4706 | * As additional protections, we do not touch cwnd in retransmission phases, |
4707 | * and if application hit its sndbuf limit recently. |
4708 | */ |
4709 | void tcp_cwnd_application_limited(struct sock *sk) |
4710 | { |
4711 | struct tcp_sock *tp = tcp_sk(sk); |
4712 | |
4713 | if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && |
4714 | sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { |
4715 | /* Limited by application or receiver window. */ |
4716 | u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); |
4717 | u32 win_used = max(tp->snd_cwnd_used, init_win); |
4718 | if (win_used < tp->snd_cwnd) { |
4719 | tp->snd_ssthresh = tcp_current_ssthresh(sk); |
4720 | tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; |
4721 | } |
4722 | tp->snd_cwnd_used = 0; |
4723 | } |
4724 | tp->snd_cwnd_stamp = tcp_time_stamp; |
4725 | } |
4726 | |
4727 | static bool tcp_should_expand_sndbuf(const struct sock *sk) |
4728 | { |
4729 | const struct tcp_sock *tp = tcp_sk(sk); |
4730 | |
4731 | /* If the user specified a specific send buffer setting, do |
4732 | * not modify it. |
4733 | */ |
4734 | if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) |
4735 | return false; |
4736 | |
4737 | /* If we are under global TCP memory pressure, do not expand. */ |
4738 | if (sk_under_memory_pressure(sk)) |
4739 | return false; |
4740 | |
4741 | /* If we are under soft global TCP memory pressure, do not expand. */ |
4742 | if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0)) |
4743 | return false; |
4744 | |
4745 | /* If we filled the congestion window, do not expand. */ |
4746 | if (tp->packets_out >= tp->snd_cwnd) |
4747 | return false; |
4748 | |
4749 | return true; |
4750 | } |
4751 | |
4752 | /* When incoming ACK allowed to free some skb from write_queue, |
4753 | * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket |
4754 | * on the exit from tcp input handler. |
4755 | * |
4756 | * PROBLEM: sndbuf expansion does not work well with largesend. |
4757 | */ |
4758 | static void tcp_new_space(struct sock *sk) |
4759 | { |
4760 | struct tcp_sock *tp = tcp_sk(sk); |
4761 | |
4762 | if (tcp_should_expand_sndbuf(sk)) { |
4763 | tcp_sndbuf_expand(sk); |
4764 | tp->snd_cwnd_stamp = tcp_time_stamp; |
4765 | } |
4766 | |
4767 | sk->sk_write_space(sk); |
4768 | } |
4769 | |
4770 | static void tcp_check_space(struct sock *sk) |
4771 | { |
4772 | if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { |
4773 | sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); |
4774 | if (sk->sk_socket && |
4775 | test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) |
4776 | tcp_new_space(sk); |
4777 | } |
4778 | } |
4779 | |
4780 | static inline void tcp_data_snd_check(struct sock *sk) |
4781 | { |
4782 | tcp_push_pending_frames(sk); |
4783 | tcp_check_space(sk); |
4784 | } |
4785 | |
4786 | /* |
4787 | * Check if sending an ack is needed. |
4788 | */ |
4789 | static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) |
4790 | { |
4791 | struct tcp_sock *tp = tcp_sk(sk); |
4792 | |
4793 | /* More than one full frame received... */ |
4794 | if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && |
4795 | /* ... and right edge of window advances far enough. |
4796 | * (tcp_recvmsg() will send ACK otherwise). Or... |
4797 | */ |
4798 | __tcp_select_window(sk) >= tp->rcv_wnd) || |
4799 | /* We ACK each frame or... */ |
4800 | tcp_in_quickack_mode(sk) || |
4801 | /* We have out of order data. */ |
4802 | (ofo_possible && skb_peek(&tp->out_of_order_queue))) { |
4803 | /* Then ack it now */ |
4804 | tcp_send_ack(sk); |
4805 | } else { |
4806 | /* Else, send delayed ack. */ |
4807 | tcp_send_delayed_ack(sk); |
4808 | } |
4809 | } |
4810 | |
4811 | static inline void tcp_ack_snd_check(struct sock *sk) |
4812 | { |
4813 | if (!inet_csk_ack_scheduled(sk)) { |
4814 | /* We sent a data segment already. */ |
4815 | return; |
4816 | } |
4817 | __tcp_ack_snd_check(sk, 1); |
4818 | } |
4819 | |
4820 | /* |
4821 | * This routine is only called when we have urgent data |
4822 | * signaled. Its the 'slow' part of tcp_urg. It could be |
4823 | * moved inline now as tcp_urg is only called from one |
4824 | * place. We handle URGent data wrong. We have to - as |
4825 | * BSD still doesn't use the correction from RFC961. |
4826 | * For 1003.1g we should support a new option TCP_STDURG to permit |
4827 | * either form (or just set the sysctl tcp_stdurg). |
4828 | */ |
4829 | |
4830 | static void tcp_check_urg(struct sock *sk, const struct tcphdr *th) |
4831 | { |
4832 | struct tcp_sock *tp = tcp_sk(sk); |
4833 | u32 ptr = ntohs(th->urg_ptr); |
4834 | |
4835 | if (ptr && !sysctl_tcp_stdurg) |
4836 | ptr--; |
4837 | ptr += ntohl(th->seq); |
4838 | |
4839 | /* Ignore urgent data that we've already seen and read. */ |
4840 | if (after(tp->copied_seq, ptr)) |
4841 | return; |
4842 | |
4843 | /* Do not replay urg ptr. |
4844 | * |
4845 | * NOTE: interesting situation not covered by specs. |
4846 | * Misbehaving sender may send urg ptr, pointing to segment, |
4847 | * which we already have in ofo queue. We are not able to fetch |
4848 | * such data and will stay in TCP_URG_NOTYET until will be eaten |
4849 | * by recvmsg(). Seems, we are not obliged to handle such wicked |
4850 | * situations. But it is worth to think about possibility of some |
4851 | * DoSes using some hypothetical application level deadlock. |
4852 | */ |
4853 | if (before(ptr, tp->rcv_nxt)) |
4854 | return; |
4855 | |
4856 | /* Do we already have a newer (or duplicate) urgent pointer? */ |
4857 | if (tp->urg_data && !after(ptr, tp->urg_seq)) |
4858 | return; |
4859 | |
4860 | /* Tell the world about our new urgent pointer. */ |
4861 | sk_send_sigurg(sk); |
4862 | |
4863 | /* We may be adding urgent data when the last byte read was |
4864 | * urgent. To do this requires some care. We cannot just ignore |
4865 | * tp->copied_seq since we would read the last urgent byte again |
4866 | * as data, nor can we alter copied_seq until this data arrives |
4867 | * or we break the semantics of SIOCATMARK (and thus sockatmark()) |
4868 | * |
4869 | * NOTE. Double Dutch. Rendering to plain English: author of comment |
4870 | * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); |
4871 | * and expect that both A and B disappear from stream. This is _wrong_. |
4872 | * Though this happens in BSD with high probability, this is occasional. |
4873 | * Any application relying on this is buggy. Note also, that fix "works" |
4874 | * only in this artificial test. Insert some normal data between A and B and we will |
4875 | * decline of BSD again. Verdict: it is better to remove to trap |
4876 | * buggy users. |
4877 | */ |
4878 | if (tp->urg_seq == tp->copied_seq && tp->urg_data && |
4879 | !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) { |
4880 | struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); |
4881 | tp->copied_seq++; |
4882 | if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { |
4883 | __skb_unlink(skb, &sk->sk_receive_queue); |
4884 | __kfree_skb(skb); |
4885 | } |
4886 | } |
4887 | |
4888 | tp->urg_data = TCP_URG_NOTYET; |
4889 | tp->urg_seq = ptr; |
4890 | |
4891 | /* Disable header prediction. */ |
4892 | tp->pred_flags = 0; |
4893 | } |
4894 | |
4895 | /* This is the 'fast' part of urgent handling. */ |
4896 | static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th) |
4897 | { |
4898 | struct tcp_sock *tp = tcp_sk(sk); |
4899 | |
4900 | /* Check if we get a new urgent pointer - normally not. */ |
4901 | if (th->urg) |
4902 | tcp_check_urg(sk, th); |
4903 | |
4904 | /* Do we wait for any urgent data? - normally not... */ |
4905 | if (tp->urg_data == TCP_URG_NOTYET) { |
4906 | u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - |
4907 | th->syn; |
4908 | |
4909 | /* Is the urgent pointer pointing into this packet? */ |
4910 | if (ptr < skb->len) { |
4911 | u8 tmp; |
4912 | if (skb_copy_bits(skb, ptr, &tmp, 1)) |
4913 | BUG(); |
4914 | tp->urg_data = TCP_URG_VALID | tmp; |
4915 | if (!sock_flag(sk, SOCK_DEAD)) |
4916 | sk->sk_data_ready(sk); |
4917 | } |
4918 | } |
4919 | } |
4920 | |
4921 | static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) |
4922 | { |
4923 | struct tcp_sock *tp = tcp_sk(sk); |
4924 | int chunk = skb->len - hlen; |
4925 | int err; |
4926 | |
4927 | local_bh_enable(); |
4928 | if (skb_csum_unnecessary(skb)) |
4929 | err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); |
4930 | else |
4931 | err = skb_copy_and_csum_datagram_iovec(skb, hlen, |
4932 | tp->ucopy.iov); |
4933 | |
4934 | if (!err) { |
4935 | tp->ucopy.len -= chunk; |
4936 | tp->copied_seq += chunk; |
4937 | tcp_rcv_space_adjust(sk); |
4938 | } |
4939 | |
4940 | local_bh_disable(); |
4941 | return err; |
4942 | } |
4943 | |
4944 | static __sum16 __tcp_checksum_complete_user(struct sock *sk, |
4945 | struct sk_buff *skb) |
4946 | { |
4947 | __sum16 result; |
4948 | |
4949 | if (sock_owned_by_user(sk)) { |
4950 | local_bh_enable(); |
4951 | result = __tcp_checksum_complete(skb); |
4952 | local_bh_disable(); |
4953 | } else { |
4954 | result = __tcp_checksum_complete(skb); |
4955 | } |
4956 | return result; |
4957 | } |
4958 | |
4959 | static inline bool tcp_checksum_complete_user(struct sock *sk, |
4960 | struct sk_buff *skb) |
4961 | { |
4962 | return !skb_csum_unnecessary(skb) && |
4963 | __tcp_checksum_complete_user(sk, skb); |
4964 | } |
4965 | |
4966 | #ifdef CONFIG_NET_DMA |
4967 | static bool tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, |
4968 | int hlen) |
4969 | { |
4970 | struct tcp_sock *tp = tcp_sk(sk); |
4971 | int chunk = skb->len - hlen; |
4972 | int dma_cookie; |
4973 | bool copied_early = false; |
4974 | |
4975 | if (tp->ucopy.wakeup) |
4976 | return false; |
4977 | |
4978 | if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) |
4979 | tp->ucopy.dma_chan = net_dma_find_channel(); |
4980 | |
4981 | if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { |
4982 | |
4983 | dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, |
4984 | skb, hlen, |
4985 | tp->ucopy.iov, chunk, |
4986 | tp->ucopy.pinned_list); |
4987 | |
4988 | if (dma_cookie < 0) |
4989 | goto out; |
4990 | |
4991 | tp->ucopy.dma_cookie = dma_cookie; |
4992 | copied_early = true; |
4993 | |
4994 | tp->ucopy.len -= chunk; |
4995 | tp->copied_seq += chunk; |
4996 | tcp_rcv_space_adjust(sk); |
4997 | |
4998 | if ((tp->ucopy.len == 0) || |
4999 | (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || |
5000 | (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { |
5001 | tp->ucopy.wakeup = 1; |
5002 | sk->sk_data_ready(sk); |
5003 | } |
5004 | } else if (chunk > 0) { |
5005 | tp->ucopy.wakeup = 1; |
5006 | sk->sk_data_ready(sk); |
5007 | } |
5008 | out: |
5009 | return copied_early; |
5010 | } |
5011 | #endif /* CONFIG_NET_DMA */ |
5012 | |
5013 | /* Does PAWS and seqno based validation of an incoming segment, flags will |
5014 | * play significant role here. |
5015 | */ |
5016 | static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, |
5017 | const struct tcphdr *th, int syn_inerr) |
5018 | { |
5019 | struct tcp_sock *tp = tcp_sk(sk); |
5020 | |
5021 | /* RFC1323: H1. Apply PAWS check first. */ |
5022 | if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && |
5023 | tcp_paws_discard(sk, skb)) { |
5024 | if (!th->rst) { |
5025 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); |
5026 | tcp_send_dupack(sk, skb); |
5027 | goto discard; |
5028 | } |
5029 | /* Reset is accepted even if it did not pass PAWS. */ |
5030 | } |
5031 | |
5032 | /* Step 1: check sequence number */ |
5033 | if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { |
5034 | /* RFC793, page 37: "In all states except SYN-SENT, all reset |
5035 | * (RST) segments are validated by checking their SEQ-fields." |
5036 | * And page 69: "If an incoming segment is not acceptable, |
5037 | * an acknowledgment should be sent in reply (unless the RST |
5038 | * bit is set, if so drop the segment and return)". |
5039 | */ |
5040 | if (!th->rst) { |
5041 | if (th->syn) |
5042 | goto syn_challenge; |
5043 | tcp_send_dupack(sk, skb); |
5044 | } |
5045 | goto discard; |
5046 | } |
5047 | |
5048 | /* Step 2: check RST bit */ |
5049 | if (th->rst) { |
5050 | /* RFC 5961 3.2 : |
5051 | * If sequence number exactly matches RCV.NXT, then |
5052 | * RESET the connection |
5053 | * else |
5054 | * Send a challenge ACK |
5055 | */ |
5056 | if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) |
5057 | tcp_reset(sk); |
5058 | else |
5059 | tcp_send_challenge_ack(sk); |
5060 | goto discard; |
5061 | } |
5062 | |
5063 | /* step 3: check security and precedence [ignored] */ |
5064 | |
5065 | /* step 4: Check for a SYN |
5066 | * RFC 5691 4.2 : Send a challenge ack |
5067 | */ |
5068 | if (th->syn) { |
5069 | syn_challenge: |
5070 | if (syn_inerr) |
5071 | TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); |
5072 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE); |
5073 | tcp_send_challenge_ack(sk); |
5074 | goto discard; |
5075 | } |
5076 | |
5077 | return true; |
5078 | |
5079 | discard: |
5080 | __kfree_skb(skb); |
5081 | return false; |
5082 | } |
5083 | |
5084 | /* |
5085 | * TCP receive function for the ESTABLISHED state. |
5086 | * |
5087 | * It is split into a fast path and a slow path. The fast path is |
5088 | * disabled when: |
5089 | * - A zero window was announced from us - zero window probing |
5090 | * is only handled properly in the slow path. |
5091 | * - Out of order segments arrived. |
5092 | * - Urgent data is expected. |
5093 | * - There is no buffer space left |
5094 | * - Unexpected TCP flags/window values/header lengths are received |
5095 | * (detected by checking the TCP header against pred_flags) |
5096 | * - Data is sent in both directions. Fast path only supports pure senders |
5097 | * or pure receivers (this means either the sequence number or the ack |
5098 | * value must stay constant) |
5099 | * - Unexpected TCP option. |
5100 | * |
5101 | * When these conditions are not satisfied it drops into a standard |
5102 | * receive procedure patterned after RFC793 to handle all cases. |
5103 | * The first three cases are guaranteed by proper pred_flags setting, |
5104 | * the rest is checked inline. Fast processing is turned on in |
5105 | * tcp_data_queue when everything is OK. |
5106 | */ |
5107 | void tcp_rcv_established(struct sock *sk, struct sk_buff *skb, |
5108 | const struct tcphdr *th, unsigned int len) |
5109 | { |
5110 | struct tcp_sock *tp = tcp_sk(sk); |
5111 | |
5112 | if (unlikely(sk->sk_rx_dst == NULL)) |
5113 | inet_csk(sk)->icsk_af_ops->sk_rx_dst_set(sk, skb); |
5114 | /* |
5115 | * Header prediction. |
5116 | * The code loosely follows the one in the famous |
5117 | * "30 instruction TCP receive" Van Jacobson mail. |
5118 | * |
5119 | * Van's trick is to deposit buffers into socket queue |
5120 | * on a device interrupt, to call tcp_recv function |
5121 | * on the receive process context and checksum and copy |
5122 | * the buffer to user space. smart... |
5123 | * |
5124 | * Our current scheme is not silly either but we take the |
5125 | * extra cost of the net_bh soft interrupt processing... |
5126 | * We do checksum and copy also but from device to kernel. |
5127 | */ |
5128 | |
5129 | tp->rx_opt.saw_tstamp = 0; |
5130 | |
5131 | /* pred_flags is 0xS?10 << 16 + snd_wnd |
5132 | * if header_prediction is to be made |
5133 | * 'S' will always be tp->tcp_header_len >> 2 |
5134 | * '?' will be 0 for the fast path, otherwise pred_flags is 0 to |
5135 | * turn it off (when there are holes in the receive |
5136 | * space for instance) |
5137 | * PSH flag is ignored. |
5138 | */ |
5139 | |
5140 | if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && |
5141 | TCP_SKB_CB(skb)->seq == tp->rcv_nxt && |
5142 | !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { |
5143 | int tcp_header_len = tp->tcp_header_len; |
5144 | |
5145 | /* Timestamp header prediction: tcp_header_len |
5146 | * is automatically equal to th->doff*4 due to pred_flags |
5147 | * match. |
5148 | */ |
5149 | |
5150 | /* Check timestamp */ |
5151 | if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { |
5152 | /* No? Slow path! */ |
5153 | if (!tcp_parse_aligned_timestamp(tp, th)) |
5154 | goto slow_path; |
5155 | |
5156 | /* If PAWS failed, check it more carefully in slow path */ |
5157 | if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) |
5158 | goto slow_path; |
5159 | |
5160 | /* DO NOT update ts_recent here, if checksum fails |
5161 | * and timestamp was corrupted part, it will result |
5162 | * in a hung connection since we will drop all |
5163 | * future packets due to the PAWS test. |
5164 | */ |
5165 | } |
5166 | |
5167 | if (len <= tcp_header_len) { |
5168 | /* Bulk data transfer: sender */ |
5169 | if (len == tcp_header_len) { |
5170 | /* Predicted packet is in window by definition. |
5171 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. |
5172 | * Hence, check seq<=rcv_wup reduces to: |
5173 | */ |
5174 | if (tcp_header_len == |
5175 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && |
5176 | tp->rcv_nxt == tp->rcv_wup) |
5177 | tcp_store_ts_recent(tp); |
5178 | |
5179 | /* We know that such packets are checksummed |
5180 | * on entry. |
5181 | */ |
5182 | tcp_ack(sk, skb, 0); |
5183 | __kfree_skb(skb); |
5184 | tcp_data_snd_check(sk); |
5185 | return; |
5186 | } else { /* Header too small */ |
5187 | TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); |
5188 | goto discard; |
5189 | } |
5190 | } else { |
5191 | int eaten = 0; |
5192 | int copied_early = 0; |
5193 | bool fragstolen = false; |
5194 | |
5195 | if (tp->copied_seq == tp->rcv_nxt && |
5196 | len - tcp_header_len <= tp->ucopy.len) { |
5197 | #ifdef CONFIG_NET_DMA |
5198 | if (tp->ucopy.task == current && |
5199 | sock_owned_by_user(sk) && |
5200 | tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { |
5201 | copied_early = 1; |
5202 | eaten = 1; |
5203 | } |
5204 | #endif |
5205 | if (tp->ucopy.task == current && |
5206 | sock_owned_by_user(sk) && !copied_early) { |
5207 | __set_current_state(TASK_RUNNING); |
5208 | |
5209 | if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) |
5210 | eaten = 1; |
5211 | } |
5212 | if (eaten) { |
5213 | /* Predicted packet is in window by definition. |
5214 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. |
5215 | * Hence, check seq<=rcv_wup reduces to: |
5216 | */ |
5217 | if (tcp_header_len == |
5218 | (sizeof(struct tcphdr) + |
5219 | TCPOLEN_TSTAMP_ALIGNED) && |
5220 | tp->rcv_nxt == tp->rcv_wup) |
5221 | tcp_store_ts_recent(tp); |
5222 | |
5223 | tcp_rcv_rtt_measure_ts(sk, skb); |
5224 | |
5225 | __skb_pull(skb, tcp_header_len); |
5226 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; |
5227 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER); |
5228 | } |
5229 | if (copied_early) |
5230 | tcp_cleanup_rbuf(sk, skb->len); |
5231 | } |
5232 | if (!eaten) { |
5233 | if (tcp_checksum_complete_user(sk, skb)) |
5234 | goto csum_error; |
5235 | |
5236 | if ((int)skb->truesize > sk->sk_forward_alloc) |
5237 | goto step5; |
5238 | |
5239 | /* Predicted packet is in window by definition. |
5240 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. |
5241 | * Hence, check seq<=rcv_wup reduces to: |
5242 | */ |
5243 | if (tcp_header_len == |
5244 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && |
5245 | tp->rcv_nxt == tp->rcv_wup) |
5246 | tcp_store_ts_recent(tp); |
5247 | |
5248 | tcp_rcv_rtt_measure_ts(sk, skb); |
5249 | |
5250 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS); |
5251 | |
5252 | /* Bulk data transfer: receiver */ |
5253 | eaten = tcp_queue_rcv(sk, skb, tcp_header_len, |
5254 | &fragstolen); |
5255 | } |
5256 | |
5257 | tcp_event_data_recv(sk, skb); |
5258 | |
5259 | if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { |
5260 | /* Well, only one small jumplet in fast path... */ |
5261 | tcp_ack(sk, skb, FLAG_DATA); |
5262 | tcp_data_snd_check(sk); |
5263 | if (!inet_csk_ack_scheduled(sk)) |
5264 | goto no_ack; |
5265 | } |
5266 | |
5267 | if (!copied_early || tp->rcv_nxt != tp->rcv_wup) |
5268 | __tcp_ack_snd_check(sk, 0); |
5269 | no_ack: |
5270 | #ifdef CONFIG_NET_DMA |
5271 | if (copied_early) |
5272 | __skb_queue_tail(&sk->sk_async_wait_queue, skb); |
5273 | else |
5274 | #endif |
5275 | if (eaten) |
5276 | kfree_skb_partial(skb, fragstolen); |
5277 | sk->sk_data_ready(sk); |
5278 | return; |
5279 | } |
5280 | } |
5281 | |
5282 | slow_path: |
5283 | if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb)) |
5284 | goto csum_error; |
5285 | |
5286 | if (!th->ack && !th->rst) |
5287 | goto discard; |
5288 | |
5289 | /* |
5290 | * Standard slow path. |
5291 | */ |
5292 | |
5293 | if (!tcp_validate_incoming(sk, skb, th, 1)) |
5294 | return; |
5295 | |
5296 | step5: |
5297 | if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0) |
5298 | goto discard; |
5299 | |
5300 | tcp_rcv_rtt_measure_ts(sk, skb); |
5301 | |
5302 | /* Process urgent data. */ |
5303 | tcp_urg(sk, skb, th); |
5304 | |
5305 | /* step 7: process the segment text */ |
5306 | tcp_data_queue(sk, skb); |
5307 | |
5308 | tcp_data_snd_check(sk); |
5309 | tcp_ack_snd_check(sk); |
5310 | return; |
5311 | |
5312 | csum_error: |
5313 | TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_CSUMERRORS); |
5314 | TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); |
5315 | |
5316 | discard: |
5317 | __kfree_skb(skb); |
5318 | } |
5319 | EXPORT_SYMBOL(tcp_rcv_established); |
5320 | |
5321 | void tcp_finish_connect(struct sock *sk, struct sk_buff *skb) |
5322 | { |
5323 | struct tcp_sock *tp = tcp_sk(sk); |
5324 | struct inet_connection_sock *icsk = inet_csk(sk); |
5325 | |
5326 | tcp_set_state(sk, TCP_ESTABLISHED); |
5327 | |
5328 | if (skb != NULL) { |
5329 | icsk->icsk_af_ops->sk_rx_dst_set(sk, skb); |
5330 | security_inet_conn_established(sk, skb); |
5331 | } |
5332 | |
5333 | /* Make sure socket is routed, for correct metrics. */ |
5334 | icsk->icsk_af_ops->rebuild_header(sk); |
5335 | |
5336 | tcp_init_metrics(sk); |
5337 | |
5338 | tcp_init_congestion_control(sk); |
5339 | |
5340 | /* Prevent spurious tcp_cwnd_restart() on first data |
5341 | * packet. |
5342 | */ |
5343 | tp->lsndtime = tcp_time_stamp; |
5344 | |
5345 | tcp_init_buffer_space(sk); |
5346 | |
5347 | if (sock_flag(sk, SOCK_KEEPOPEN)) |
5348 | inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); |
5349 | |
5350 | if (!tp->rx_opt.snd_wscale) |
5351 | __tcp_fast_path_on(tp, tp->snd_wnd); |
5352 | else |
5353 | tp->pred_flags = 0; |
5354 | |
5355 | if (!sock_flag(sk, SOCK_DEAD)) { |
5356 | sk->sk_state_change(sk); |
5357 | sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); |
5358 | } |
5359 | } |
5360 | |
5361 | static bool tcp_rcv_fastopen_synack(struct sock *sk, struct sk_buff *synack, |
5362 | struct tcp_fastopen_cookie *cookie) |
5363 | { |
5364 | struct tcp_sock *tp = tcp_sk(sk); |
5365 | struct sk_buff *data = tp->syn_data ? tcp_write_queue_head(sk) : NULL; |
5366 | u16 mss = tp->rx_opt.mss_clamp; |
5367 | bool syn_drop; |
5368 | |
5369 | if (mss == tp->rx_opt.user_mss) { |
5370 | struct tcp_options_received opt; |
5371 | |
5372 | /* Get original SYNACK MSS value if user MSS sets mss_clamp */ |
5373 | tcp_clear_options(&opt); |
5374 | opt.user_mss = opt.mss_clamp = 0; |
5375 | tcp_parse_options(synack, &opt, 0, NULL); |
5376 | mss = opt.mss_clamp; |
5377 | } |
5378 | |
5379 | if (!tp->syn_fastopen) /* Ignore an unsolicited cookie */ |
5380 | cookie->len = -1; |
5381 | |
5382 | /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably |
5383 | * the remote receives only the retransmitted (regular) SYNs: either |
5384 | * the original SYN-data or the corresponding SYN-ACK is lost. |
5385 | */ |
5386 | syn_drop = (cookie->len <= 0 && data && tp->total_retrans); |
5387 | |
5388 | tcp_fastopen_cache_set(sk, mss, cookie, syn_drop); |
5389 | |
5390 | if (data) { /* Retransmit unacked data in SYN */ |
5391 | tcp_for_write_queue_from(data, sk) { |
5392 | if (data == tcp_send_head(sk) || |
5393 | __tcp_retransmit_skb(sk, data)) |
5394 | break; |
5395 | } |
5396 | tcp_rearm_rto(sk); |
5397 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVEFAIL); |
5398 | return true; |
5399 | } |
5400 | tp->syn_data_acked = tp->syn_data; |
5401 | if (tp->syn_data_acked) |
5402 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE); |
5403 | return false; |
5404 | } |
5405 | |
5406 | static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, |
5407 | const struct tcphdr *th, unsigned int len) |
5408 | { |
5409 | struct inet_connection_sock *icsk = inet_csk(sk); |
5410 | struct tcp_sock *tp = tcp_sk(sk); |
5411 | struct tcp_fastopen_cookie foc = { .len = -1 }; |
5412 | int saved_clamp = tp->rx_opt.mss_clamp; |
5413 | |
5414 | tcp_parse_options(skb, &tp->rx_opt, 0, &foc); |
5415 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) |
5416 | tp->rx_opt.rcv_tsecr -= tp->tsoffset; |
5417 | |
5418 | if (th->ack) { |
5419 | /* rfc793: |
5420 | * "If the state is SYN-SENT then |
5421 | * first check the ACK bit |
5422 | * If the ACK bit is set |
5423 | * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send |
5424 | * a reset (unless the RST bit is set, if so drop |
5425 | * the segment and return)" |
5426 | */ |
5427 | if (!after(TCP_SKB_CB(skb)->ack_seq, tp->snd_una) || |
5428 | after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) |
5429 | goto reset_and_undo; |
5430 | |
5431 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && |
5432 | !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, |
5433 | tcp_time_stamp)) { |
5434 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED); |
5435 | goto reset_and_undo; |
5436 | } |
5437 | |
5438 | /* Now ACK is acceptable. |
5439 | * |
5440 | * "If the RST bit is set |
5441 | * If the ACK was acceptable then signal the user "error: |
5442 | * connection reset", drop the segment, enter CLOSED state, |
5443 | * delete TCB, and return." |
5444 | */ |
5445 | |
5446 | if (th->rst) { |
5447 | tcp_reset(sk); |
5448 | goto discard; |
5449 | } |
5450 | |
5451 | /* rfc793: |
5452 | * "fifth, if neither of the SYN or RST bits is set then |
5453 | * drop the segment and return." |
5454 | * |
5455 | * See note below! |
5456 | * --ANK(990513) |
5457 | */ |
5458 | if (!th->syn) |
5459 | goto discard_and_undo; |
5460 | |
5461 | /* rfc793: |
5462 | * "If the SYN bit is on ... |
5463 | * are acceptable then ... |
5464 | * (our SYN has been ACKed), change the connection |
5465 | * state to ESTABLISHED..." |
5466 | */ |
5467 | |
5468 | TCP_ECN_rcv_synack(tp, th); |
5469 | |
5470 | tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); |
5471 | tcp_ack(sk, skb, FLAG_SLOWPATH); |
5472 | |
5473 | /* Ok.. it's good. Set up sequence numbers and |
5474 | * move to established. |
5475 | */ |
5476 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; |
5477 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; |
5478 | |
5479 | /* RFC1323: The window in SYN & SYN/ACK segments is |
5480 | * never scaled. |
5481 | */ |
5482 | tp->snd_wnd = ntohs(th->window); |
5483 | |
5484 | if (!tp->rx_opt.wscale_ok) { |
5485 | tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; |
5486 | tp->window_clamp = min(tp->window_clamp, 65535U); |
5487 | } |
5488 | |
5489 | if (tp->rx_opt.saw_tstamp) { |
5490 | tp->rx_opt.tstamp_ok = 1; |
5491 | tp->tcp_header_len = |
5492 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; |
5493 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; |
5494 | tcp_store_ts_recent(tp); |
5495 | } else { |
5496 | tp->tcp_header_len = sizeof(struct tcphdr); |
5497 | } |
5498 | |
5499 | if (tcp_is_sack(tp) && sysctl_tcp_fack) |
5500 | tcp_enable_fack(tp); |
5501 | |
5502 | tcp_mtup_init(sk); |
5503 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
5504 | tcp_initialize_rcv_mss(sk); |
5505 | |
5506 | /* Remember, tcp_poll() does not lock socket! |
5507 | * Change state from SYN-SENT only after copied_seq |
5508 | * is initialized. */ |
5509 | tp->copied_seq = tp->rcv_nxt; |
5510 | |
5511 | smp_mb(); |
5512 | |
5513 | tcp_finish_connect(sk, skb); |
5514 | |
5515 | if ((tp->syn_fastopen || tp->syn_data) && |
5516 | tcp_rcv_fastopen_synack(sk, skb, &foc)) |
5517 | return -1; |
5518 | |
5519 | if (sk->sk_write_pending || |
5520 | icsk->icsk_accept_queue.rskq_defer_accept || |
5521 | icsk->icsk_ack.pingpong) { |
5522 | /* Save one ACK. Data will be ready after |
5523 | * several ticks, if write_pending is set. |
5524 | * |
5525 | * It may be deleted, but with this feature tcpdumps |
5526 | * look so _wonderfully_ clever, that I was not able |
5527 | * to stand against the temptation 8) --ANK |
5528 | */ |
5529 | inet_csk_schedule_ack(sk); |
5530 | icsk->icsk_ack.lrcvtime = tcp_time_stamp; |
5531 | tcp_enter_quickack_mode(sk); |
5532 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, |
5533 | TCP_DELACK_MAX, TCP_RTO_MAX); |
5534 | |
5535 | discard: |
5536 | __kfree_skb(skb); |
5537 | return 0; |
5538 | } else { |
5539 | tcp_send_ack(sk); |
5540 | } |
5541 | return -1; |
5542 | } |
5543 | |
5544 | /* No ACK in the segment */ |
5545 | |
5546 | if (th->rst) { |
5547 | /* rfc793: |
5548 | * "If the RST bit is set |
5549 | * |
5550 | * Otherwise (no ACK) drop the segment and return." |
5551 | */ |
5552 | |
5553 | goto discard_and_undo; |
5554 | } |
5555 | |
5556 | /* PAWS check. */ |
5557 | if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && |
5558 | tcp_paws_reject(&tp->rx_opt, 0)) |
5559 | goto discard_and_undo; |
5560 | |
5561 | if (th->syn) { |
5562 | /* We see SYN without ACK. It is attempt of |
5563 | * simultaneous connect with crossed SYNs. |
5564 | * Particularly, it can be connect to self. |
5565 | */ |
5566 | tcp_set_state(sk, TCP_SYN_RECV); |
5567 | |
5568 | if (tp->rx_opt.saw_tstamp) { |
5569 | tp->rx_opt.tstamp_ok = 1; |
5570 | tcp_store_ts_recent(tp); |
5571 | tp->tcp_header_len = |
5572 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; |
5573 | } else { |
5574 | tp->tcp_header_len = sizeof(struct tcphdr); |
5575 | } |
5576 | |
5577 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; |
5578 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; |
5579 | |
5580 | /* RFC1323: The window in SYN & SYN/ACK segments is |
5581 | * never scaled. |
5582 | */ |
5583 | tp->snd_wnd = ntohs(th->window); |
5584 | tp->snd_wl1 = TCP_SKB_CB(skb)->seq; |
5585 | tp->max_window = tp->snd_wnd; |
5586 | |
5587 | TCP_ECN_rcv_syn(tp, th); |
5588 | |
5589 | tcp_mtup_init(sk); |
5590 | tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); |
5591 | tcp_initialize_rcv_mss(sk); |
5592 | |
5593 | tcp_send_synack(sk); |
5594 | #if 0 |
5595 | /* Note, we could accept data and URG from this segment. |
5596 | * There are no obstacles to make this (except that we must |
5597 | * either change tcp_recvmsg() to prevent it from returning data |
5598 | * before 3WHS completes per RFC793, or employ TCP Fast Open). |
5599 | * |
5600 | * However, if we ignore data in ACKless segments sometimes, |
5601 | * we have no reasons to accept it sometimes. |
5602 | * Also, seems the code doing it in step6 of tcp_rcv_state_process |
5603 | * is not flawless. So, discard packet for sanity. |
5604 | * Uncomment this return to process the data. |
5605 | */ |
5606 | return -1; |
5607 | #else |
5608 | goto discard; |
5609 | #endif |
5610 | } |
5611 | /* "fifth, if neither of the SYN or RST bits is set then |
5612 | * drop the segment and return." |
5613 | */ |
5614 | |
5615 | discard_and_undo: |
5616 | tcp_clear_options(&tp->rx_opt); |
5617 | tp->rx_opt.mss_clamp = saved_clamp; |
5618 | goto discard; |
5619 | |
5620 | reset_and_undo: |
5621 | tcp_clear_options(&tp->rx_opt); |
5622 | tp->rx_opt.mss_clamp = saved_clamp; |
5623 | return 1; |
5624 | } |
5625 | |
5626 | /* |
5627 | * This function implements the receiving procedure of RFC 793 for |
5628 | * all states except ESTABLISHED and TIME_WAIT. |
5629 | * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be |
5630 | * address independent. |
5631 | */ |
5632 | |
5633 | int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, |
5634 | const struct tcphdr *th, unsigned int len) |
5635 | { |
5636 | struct tcp_sock *tp = tcp_sk(sk); |
5637 | struct inet_connection_sock *icsk = inet_csk(sk); |
5638 | struct request_sock *req; |
5639 | int queued = 0; |
5640 | bool acceptable; |
5641 | u32 synack_stamp; |
5642 | |
5643 | tp->rx_opt.saw_tstamp = 0; |
5644 | |
5645 | switch (sk->sk_state) { |
5646 | case TCP_CLOSE: |
5647 | goto discard; |
5648 | |
5649 | case TCP_LISTEN: |
5650 | if (th->ack) |
5651 | return 1; |
5652 | |
5653 | if (th->rst) |
5654 | goto discard; |
5655 | |
5656 | if (th->syn) { |
5657 | if (th->fin) |
5658 | goto discard; |
5659 | if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) |
5660 | return 1; |
5661 | |
5662 | /* Now we have several options: In theory there is |
5663 | * nothing else in the frame. KA9Q has an option to |
5664 | * send data with the syn, BSD accepts data with the |
5665 | * syn up to the [to be] advertised window and |
5666 | * Solaris 2.1 gives you a protocol error. For now |
5667 | * we just ignore it, that fits the spec precisely |
5668 | * and avoids incompatibilities. It would be nice in |
5669 | * future to drop through and process the data. |
5670 | * |
5671 | * Now that TTCP is starting to be used we ought to |
5672 | * queue this data. |
5673 | * But, this leaves one open to an easy denial of |
5674 | * service attack, and SYN cookies can't defend |
5675 | * against this problem. So, we drop the data |
5676 | * in the interest of security over speed unless |
5677 | * it's still in use. |
5678 | */ |
5679 | kfree_skb(skb); |
5680 | return 0; |
5681 | } |
5682 | goto discard; |
5683 | |
5684 | case TCP_SYN_SENT: |
5685 | queued = tcp_rcv_synsent_state_process(sk, skb, th, len); |
5686 | if (queued >= 0) |
5687 | return queued; |
5688 | |
5689 | /* Do step6 onward by hand. */ |
5690 | tcp_urg(sk, skb, th); |
5691 | __kfree_skb(skb); |
5692 | tcp_data_snd_check(sk); |
5693 | return 0; |
5694 | } |
5695 | |
5696 | req = tp->fastopen_rsk; |
5697 | if (req != NULL) { |
5698 | WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && |
5699 | sk->sk_state != TCP_FIN_WAIT1); |
5700 | |
5701 | if (tcp_check_req(sk, skb, req, NULL, true) == NULL) |
5702 | goto discard; |
5703 | } |
5704 | |
5705 | if (!th->ack && !th->rst) |
5706 | goto discard; |
5707 | |
5708 | if (!tcp_validate_incoming(sk, skb, th, 0)) |
5709 | return 0; |
5710 | |
5711 | /* step 5: check the ACK field */ |
5712 | acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH | |
5713 | FLAG_UPDATE_TS_RECENT) > 0; |
5714 | |
5715 | switch (sk->sk_state) { |
5716 | case TCP_SYN_RECV: |
5717 | if (!acceptable) |
5718 | return 1; |
5719 | |
5720 | /* Once we leave TCP_SYN_RECV, we no longer need req |
5721 | * so release it. |
5722 | */ |
5723 | if (req) { |
5724 | synack_stamp = tcp_rsk(req)->snt_synack; |
5725 | tp->total_retrans = req->num_retrans; |
5726 | reqsk_fastopen_remove(sk, req, false); |
5727 | } else { |
5728 | synack_stamp = tp->lsndtime; |
5729 | /* Make sure socket is routed, for correct metrics. */ |
5730 | icsk->icsk_af_ops->rebuild_header(sk); |
5731 | tcp_init_congestion_control(sk); |
5732 | |
5733 | tcp_mtup_init(sk); |
5734 | tp->copied_seq = tp->rcv_nxt; |
5735 | tcp_init_buffer_space(sk); |
5736 | } |
5737 | smp_mb(); |
5738 | tcp_set_state(sk, TCP_ESTABLISHED); |
5739 | sk->sk_state_change(sk); |
5740 | |
5741 | /* Note, that this wakeup is only for marginal crossed SYN case. |
5742 | * Passively open sockets are not waked up, because |
5743 | * sk->sk_sleep == NULL and sk->sk_socket == NULL. |
5744 | */ |
5745 | if (sk->sk_socket) |
5746 | sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); |
5747 | |
5748 | tp->snd_una = TCP_SKB_CB(skb)->ack_seq; |
5749 | tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale; |
5750 | tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); |
5751 | tcp_synack_rtt_meas(sk, synack_stamp); |
5752 | |
5753 | if (tp->rx_opt.tstamp_ok) |
5754 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; |
5755 | |
5756 | if (req) { |
5757 | /* Re-arm the timer because data may have been sent out. |
5758 | * This is similar to the regular data transmission case |
5759 | * when new data has just been ack'ed. |
5760 | * |
5761 | * (TFO) - we could try to be more aggressive and |
5762 | * retransmitting any data sooner based on when they |
5763 | * are sent out. |
5764 | */ |
5765 | tcp_rearm_rto(sk); |
5766 | } else |
5767 | tcp_init_metrics(sk); |
5768 | |
5769 | tcp_update_pacing_rate(sk); |
5770 | |
5771 | /* Prevent spurious tcp_cwnd_restart() on first data packet */ |
5772 | tp->lsndtime = tcp_time_stamp; |
5773 | |
5774 | tcp_initialize_rcv_mss(sk); |
5775 | tcp_fast_path_on(tp); |
5776 | break; |
5777 | |
5778 | case TCP_FIN_WAIT1: { |
5779 | struct dst_entry *dst; |
5780 | int tmo; |
5781 | |
5782 | /* If we enter the TCP_FIN_WAIT1 state and we are a |
5783 | * Fast Open socket and this is the first acceptable |
5784 | * ACK we have received, this would have acknowledged |
5785 | * our SYNACK so stop the SYNACK timer. |
5786 | */ |
5787 | if (req != NULL) { |
5788 | /* Return RST if ack_seq is invalid. |
5789 | * Note that RFC793 only says to generate a |
5790 | * DUPACK for it but for TCP Fast Open it seems |
5791 | * better to treat this case like TCP_SYN_RECV |
5792 | * above. |
5793 | */ |
5794 | if (!acceptable) |
5795 | return 1; |
5796 | /* We no longer need the request sock. */ |
5797 | reqsk_fastopen_remove(sk, req, false); |
5798 | tcp_rearm_rto(sk); |
5799 | } |
5800 | if (tp->snd_una != tp->write_seq) |
5801 | break; |
5802 | |
5803 | tcp_set_state(sk, TCP_FIN_WAIT2); |
5804 | sk->sk_shutdown |= SEND_SHUTDOWN; |
5805 | |
5806 | dst = __sk_dst_get(sk); |
5807 | if (dst) |
5808 | dst_confirm(dst); |
5809 | |
5810 | if (!sock_flag(sk, SOCK_DEAD)) { |
5811 | /* Wake up lingering close() */ |
5812 | sk->sk_state_change(sk); |
5813 | break; |
5814 | } |
5815 | |
5816 | if (tp->linger2 < 0 || |
5817 | (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
5818 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { |
5819 | tcp_done(sk); |
5820 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); |
5821 | return 1; |
5822 | } |
5823 | |
5824 | tmo = tcp_fin_time(sk); |
5825 | if (tmo > TCP_TIMEWAIT_LEN) { |
5826 | inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); |
5827 | } else if (th->fin || sock_owned_by_user(sk)) { |
5828 | /* Bad case. We could lose such FIN otherwise. |
5829 | * It is not a big problem, but it looks confusing |
5830 | * and not so rare event. We still can lose it now, |
5831 | * if it spins in bh_lock_sock(), but it is really |
5832 | * marginal case. |
5833 | */ |
5834 | inet_csk_reset_keepalive_timer(sk, tmo); |
5835 | } else { |
5836 | tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); |
5837 | goto discard; |
5838 | } |
5839 | break; |
5840 | } |
5841 | |
5842 | case TCP_CLOSING: |
5843 | if (tp->snd_una == tp->write_seq) { |
5844 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); |
5845 | goto discard; |
5846 | } |
5847 | break; |
5848 | |
5849 | case TCP_LAST_ACK: |
5850 | if (tp->snd_una == tp->write_seq) { |
5851 | tcp_update_metrics(sk); |
5852 | tcp_done(sk); |
5853 | goto discard; |
5854 | } |
5855 | break; |
5856 | } |
5857 | |
5858 | /* step 6: check the URG bit */ |
5859 | tcp_urg(sk, skb, th); |
5860 | |
5861 | /* step 7: process the segment text */ |
5862 | switch (sk->sk_state) { |
5863 | case TCP_CLOSE_WAIT: |
5864 | case TCP_CLOSING: |
5865 | case TCP_LAST_ACK: |
5866 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) |
5867 | break; |
5868 | case TCP_FIN_WAIT1: |
5869 | case TCP_FIN_WAIT2: |
5870 | /* RFC 793 says to queue data in these states, |
5871 | * RFC 1122 says we MUST send a reset. |
5872 | * BSD 4.4 also does reset. |
5873 | */ |
5874 | if (sk->sk_shutdown & RCV_SHUTDOWN) { |
5875 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && |
5876 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { |
5877 | NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); |
5878 | tcp_reset(sk); |
5879 | return 1; |
5880 | } |
5881 | } |
5882 | /* Fall through */ |
5883 | case TCP_ESTABLISHED: |
5884 | tcp_data_queue(sk, skb); |
5885 | queued = 1; |
5886 | break; |
5887 | } |
5888 | |
5889 | /* tcp_data could move socket to TIME-WAIT */ |
5890 | if (sk->sk_state != TCP_CLOSE) { |
5891 | tcp_data_snd_check(sk); |
5892 | tcp_ack_snd_check(sk); |
5893 | } |
5894 | |
5895 | if (!queued) { |
5896 | discard: |
5897 | __kfree_skb(skb); |
5898 | } |
5899 | return 0; |
5900 | } |
5901 | EXPORT_SYMBOL(tcp_rcv_state_process); |
5902 |
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od-2011-09-18
v2.6.34-rc5
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