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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: Pedro Roque : Retransmit queue handled by TCP. |
23 | * : Fragmentation on mtu decrease |
24 | * : Segment collapse on retransmit |
25 | * : AF independence |
26 | * |
27 | * Linus Torvalds : send_delayed_ack |
28 | * David S. Miller : Charge memory using the right skb |
29 | * during syn/ack processing. |
30 | * David S. Miller : Output engine completely rewritten. |
31 | * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. |
32 | * Cacophonix Gaul : draft-minshall-nagle-01 |
33 | * J Hadi Salim : ECN support |
34 | * |
35 | */ |
36 | |
37 | #include <net/tcp.h> |
38 | |
39 | #include <linux/compiler.h> |
40 | #include <linux/gfp.h> |
41 | #include <linux/module.h> |
42 | |
43 | /* People can turn this off for buggy TCP's found in printers etc. */ |
44 | int sysctl_tcp_retrans_collapse __read_mostly = 1; |
45 | |
46 | /* People can turn this on to work with those rare, broken TCPs that |
47 | * interpret the window field as a signed quantity. |
48 | */ |
49 | int sysctl_tcp_workaround_signed_windows __read_mostly = 0; |
50 | |
51 | /* This limits the percentage of the congestion window which we |
52 | * will allow a single TSO frame to consume. Building TSO frames |
53 | * which are too large can cause TCP streams to be bursty. |
54 | */ |
55 | int sysctl_tcp_tso_win_divisor __read_mostly = 3; |
56 | |
57 | int sysctl_tcp_mtu_probing __read_mostly = 0; |
58 | int sysctl_tcp_base_mss __read_mostly = 512; |
59 | |
60 | /* By default, RFC2861 behavior. */ |
61 | int sysctl_tcp_slow_start_after_idle __read_mostly = 1; |
62 | |
63 | int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */ |
64 | EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size); |
65 | |
66 | |
67 | /* Account for new data that has been sent to the network. */ |
68 | static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb) |
69 | { |
70 | struct tcp_sock *tp = tcp_sk(sk); |
71 | unsigned int prior_packets = tp->packets_out; |
72 | |
73 | tcp_advance_send_head(sk, skb); |
74 | tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; |
75 | |
76 | /* Don't override Nagle indefinately with F-RTO */ |
77 | if (tp->frto_counter == 2) |
78 | tp->frto_counter = 3; |
79 | |
80 | tp->packets_out += tcp_skb_pcount(skb); |
81 | if (!prior_packets) |
82 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
83 | inet_csk(sk)->icsk_rto, TCP_RTO_MAX); |
84 | } |
85 | |
86 | /* SND.NXT, if window was not shrunk. |
87 | * If window has been shrunk, what should we make? It is not clear at all. |
88 | * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( |
89 | * Anything in between SND.UNA...SND.UNA+SND.WND also can be already |
90 | * invalid. OK, let's make this for now: |
91 | */ |
92 | static inline __u32 tcp_acceptable_seq(struct sock *sk) |
93 | { |
94 | struct tcp_sock *tp = tcp_sk(sk); |
95 | |
96 | if (!before(tcp_wnd_end(tp), tp->snd_nxt)) |
97 | return tp->snd_nxt; |
98 | else |
99 | return tcp_wnd_end(tp); |
100 | } |
101 | |
102 | /* Calculate mss to advertise in SYN segment. |
103 | * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: |
104 | * |
105 | * 1. It is independent of path mtu. |
106 | * 2. Ideally, it is maximal possible segment size i.e. 65535-40. |
107 | * 3. For IPv4 it is reasonable to calculate it from maximal MTU of |
108 | * attached devices, because some buggy hosts are confused by |
109 | * large MSS. |
110 | * 4. We do not make 3, we advertise MSS, calculated from first |
111 | * hop device mtu, but allow to raise it to ip_rt_min_advmss. |
112 | * This may be overridden via information stored in routing table. |
113 | * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, |
114 | * probably even Jumbo". |
115 | */ |
116 | static __u16 tcp_advertise_mss(struct sock *sk) |
117 | { |
118 | struct tcp_sock *tp = tcp_sk(sk); |
119 | struct dst_entry *dst = __sk_dst_get(sk); |
120 | int mss = tp->advmss; |
121 | |
122 | if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) { |
123 | mss = dst_metric(dst, RTAX_ADVMSS); |
124 | tp->advmss = mss; |
125 | } |
126 | |
127 | return (__u16)mss; |
128 | } |
129 | |
130 | /* RFC2861. Reset CWND after idle period longer RTO to "restart window". |
131 | * This is the first part of cwnd validation mechanism. */ |
132 | static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst) |
133 | { |
134 | struct tcp_sock *tp = tcp_sk(sk); |
135 | s32 delta = tcp_time_stamp - tp->lsndtime; |
136 | u32 restart_cwnd = tcp_init_cwnd(tp, dst); |
137 | u32 cwnd = tp->snd_cwnd; |
138 | |
139 | tcp_ca_event(sk, CA_EVENT_CWND_RESTART); |
140 | |
141 | tp->snd_ssthresh = tcp_current_ssthresh(sk); |
142 | restart_cwnd = min(restart_cwnd, cwnd); |
143 | |
144 | while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) |
145 | cwnd >>= 1; |
146 | tp->snd_cwnd = max(cwnd, restart_cwnd); |
147 | tp->snd_cwnd_stamp = tcp_time_stamp; |
148 | tp->snd_cwnd_used = 0; |
149 | } |
150 | |
151 | /* Congestion state accounting after a packet has been sent. */ |
152 | static void tcp_event_data_sent(struct tcp_sock *tp, |
153 | struct sk_buff *skb, struct sock *sk) |
154 | { |
155 | struct inet_connection_sock *icsk = inet_csk(sk); |
156 | const u32 now = tcp_time_stamp; |
157 | |
158 | if (sysctl_tcp_slow_start_after_idle && |
159 | (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)) |
160 | tcp_cwnd_restart(sk, __sk_dst_get(sk)); |
161 | |
162 | tp->lsndtime = now; |
163 | |
164 | /* If it is a reply for ato after last received |
165 | * packet, enter pingpong mode. |
166 | */ |
167 | if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato) |
168 | icsk->icsk_ack.pingpong = 1; |
169 | } |
170 | |
171 | /* Account for an ACK we sent. */ |
172 | static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) |
173 | { |
174 | tcp_dec_quickack_mode(sk, pkts); |
175 | inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); |
176 | } |
177 | |
178 | /* Determine a window scaling and initial window to offer. |
179 | * Based on the assumption that the given amount of space |
180 | * will be offered. Store the results in the tp structure. |
181 | * NOTE: for smooth operation initial space offering should |
182 | * be a multiple of mss if possible. We assume here that mss >= 1. |
183 | * This MUST be enforced by all callers. |
184 | */ |
185 | void tcp_select_initial_window(int __space, __u32 mss, |
186 | __u32 *rcv_wnd, __u32 *window_clamp, |
187 | int wscale_ok, __u8 *rcv_wscale, |
188 | __u32 init_rcv_wnd) |
189 | { |
190 | unsigned int space = (__space < 0 ? 0 : __space); |
191 | |
192 | /* If no clamp set the clamp to the max possible scaled window */ |
193 | if (*window_clamp == 0) |
194 | (*window_clamp) = (65535 << 14); |
195 | space = min(*window_clamp, space); |
196 | |
197 | /* Quantize space offering to a multiple of mss if possible. */ |
198 | if (space > mss) |
199 | space = (space / mss) * mss; |
200 | |
201 | /* NOTE: offering an initial window larger than 32767 |
202 | * will break some buggy TCP stacks. If the admin tells us |
203 | * it is likely we could be speaking with such a buggy stack |
204 | * we will truncate our initial window offering to 32K-1 |
205 | * unless the remote has sent us a window scaling option, |
206 | * which we interpret as a sign the remote TCP is not |
207 | * misinterpreting the window field as a signed quantity. |
208 | */ |
209 | if (sysctl_tcp_workaround_signed_windows) |
210 | (*rcv_wnd) = min(space, MAX_TCP_WINDOW); |
211 | else |
212 | (*rcv_wnd) = space; |
213 | |
214 | (*rcv_wscale) = 0; |
215 | if (wscale_ok) { |
216 | /* Set window scaling on max possible window |
217 | * See RFC1323 for an explanation of the limit to 14 |
218 | */ |
219 | space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); |
220 | space = min_t(u32, space, *window_clamp); |
221 | while (space > 65535 && (*rcv_wscale) < 14) { |
222 | space >>= 1; |
223 | (*rcv_wscale)++; |
224 | } |
225 | } |
226 | |
227 | /* Set initial window to value enough for senders, |
228 | * following RFC2414. Senders, not following this RFC, |
229 | * will be satisfied with 2. |
230 | */ |
231 | if (mss > (1 << *rcv_wscale)) { |
232 | int init_cwnd = 4; |
233 | if (mss > 1460 * 3) |
234 | init_cwnd = 2; |
235 | else if (mss > 1460) |
236 | init_cwnd = 3; |
237 | /* when initializing use the value from init_rcv_wnd |
238 | * rather than the default from above |
239 | */ |
240 | if (init_rcv_wnd && |
241 | (*rcv_wnd > init_rcv_wnd * mss)) |
242 | *rcv_wnd = init_rcv_wnd * mss; |
243 | else if (*rcv_wnd > init_cwnd * mss) |
244 | *rcv_wnd = init_cwnd * mss; |
245 | } |
246 | |
247 | /* Set the clamp no higher than max representable value */ |
248 | (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); |
249 | } |
250 | |
251 | /* Chose a new window to advertise, update state in tcp_sock for the |
252 | * socket, and return result with RFC1323 scaling applied. The return |
253 | * value can be stuffed directly into th->window for an outgoing |
254 | * frame. |
255 | */ |
256 | static u16 tcp_select_window(struct sock *sk) |
257 | { |
258 | struct tcp_sock *tp = tcp_sk(sk); |
259 | u32 cur_win = tcp_receive_window(tp); |
260 | u32 new_win = __tcp_select_window(sk); |
261 | |
262 | /* Never shrink the offered window */ |
263 | if (new_win < cur_win) { |
264 | /* Danger Will Robinson! |
265 | * Don't update rcv_wup/rcv_wnd here or else |
266 | * we will not be able to advertise a zero |
267 | * window in time. --DaveM |
268 | * |
269 | * Relax Will Robinson. |
270 | */ |
271 | new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); |
272 | } |
273 | tp->rcv_wnd = new_win; |
274 | tp->rcv_wup = tp->rcv_nxt; |
275 | |
276 | /* Make sure we do not exceed the maximum possible |
277 | * scaled window. |
278 | */ |
279 | if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows) |
280 | new_win = min(new_win, MAX_TCP_WINDOW); |
281 | else |
282 | new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); |
283 | |
284 | /* RFC1323 scaling applied */ |
285 | new_win >>= tp->rx_opt.rcv_wscale; |
286 | |
287 | /* If we advertise zero window, disable fast path. */ |
288 | if (new_win == 0) |
289 | tp->pred_flags = 0; |
290 | |
291 | return new_win; |
292 | } |
293 | |
294 | /* Packet ECN state for a SYN-ACK */ |
295 | static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb) |
296 | { |
297 | TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_CWR; |
298 | if (!(tp->ecn_flags & TCP_ECN_OK)) |
299 | TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_ECE; |
300 | } |
301 | |
302 | /* Packet ECN state for a SYN. */ |
303 | static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) |
304 | { |
305 | struct tcp_sock *tp = tcp_sk(sk); |
306 | |
307 | tp->ecn_flags = 0; |
308 | if (sysctl_tcp_ecn == 1) { |
309 | TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ECE | TCPCB_FLAG_CWR; |
310 | tp->ecn_flags = TCP_ECN_OK; |
311 | } |
312 | } |
313 | |
314 | static __inline__ void |
315 | TCP_ECN_make_synack(struct request_sock *req, struct tcphdr *th) |
316 | { |
317 | if (inet_rsk(req)->ecn_ok) |
318 | th->ece = 1; |
319 | } |
320 | |
321 | /* Set up ECN state for a packet on a ESTABLISHED socket that is about to |
322 | * be sent. |
323 | */ |
324 | static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb, |
325 | int tcp_header_len) |
326 | { |
327 | struct tcp_sock *tp = tcp_sk(sk); |
328 | |
329 | if (tp->ecn_flags & TCP_ECN_OK) { |
330 | /* Not-retransmitted data segment: set ECT and inject CWR. */ |
331 | if (skb->len != tcp_header_len && |
332 | !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) { |
333 | INET_ECN_xmit(sk); |
334 | if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) { |
335 | tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; |
336 | tcp_hdr(skb)->cwr = 1; |
337 | skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; |
338 | } |
339 | } else { |
340 | /* ACK or retransmitted segment: clear ECT|CE */ |
341 | INET_ECN_dontxmit(sk); |
342 | } |
343 | if (tp->ecn_flags & TCP_ECN_DEMAND_CWR) |
344 | tcp_hdr(skb)->ece = 1; |
345 | } |
346 | } |
347 | |
348 | /* Constructs common control bits of non-data skb. If SYN/FIN is present, |
349 | * auto increment end seqno. |
350 | */ |
351 | static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) |
352 | { |
353 | skb->csum = 0; |
354 | |
355 | TCP_SKB_CB(skb)->flags = flags; |
356 | TCP_SKB_CB(skb)->sacked = 0; |
357 | |
358 | skb_shinfo(skb)->gso_segs = 1; |
359 | skb_shinfo(skb)->gso_size = 0; |
360 | skb_shinfo(skb)->gso_type = 0; |
361 | |
362 | TCP_SKB_CB(skb)->seq = seq; |
363 | if (flags & (TCPCB_FLAG_SYN | TCPCB_FLAG_FIN)) |
364 | seq++; |
365 | TCP_SKB_CB(skb)->end_seq = seq; |
366 | } |
367 | |
368 | static inline int tcp_urg_mode(const struct tcp_sock *tp) |
369 | { |
370 | return tp->snd_una != tp->snd_up; |
371 | } |
372 | |
373 | #define OPTION_SACK_ADVERTISE (1 << 0) |
374 | #define OPTION_TS (1 << 1) |
375 | #define OPTION_MD5 (1 << 2) |
376 | #define OPTION_WSCALE (1 << 3) |
377 | #define OPTION_COOKIE_EXTENSION (1 << 4) |
378 | |
379 | struct tcp_out_options { |
380 | u8 options; /* bit field of OPTION_* */ |
381 | u8 ws; /* window scale, 0 to disable */ |
382 | u8 num_sack_blocks; /* number of SACK blocks to include */ |
383 | u8 hash_size; /* bytes in hash_location */ |
384 | u16 mss; /* 0 to disable */ |
385 | __u32 tsval, tsecr; /* need to include OPTION_TS */ |
386 | __u8 *hash_location; /* temporary pointer, overloaded */ |
387 | }; |
388 | |
389 | /* The sysctl int routines are generic, so check consistency here. |
390 | */ |
391 | static u8 tcp_cookie_size_check(u8 desired) |
392 | { |
393 | if (desired > 0) { |
394 | /* previously specified */ |
395 | return desired; |
396 | } |
397 | if (sysctl_tcp_cookie_size <= 0) { |
398 | /* no default specified */ |
399 | return 0; |
400 | } |
401 | if (sysctl_tcp_cookie_size <= TCP_COOKIE_MIN) { |
402 | /* value too small, specify minimum */ |
403 | return TCP_COOKIE_MIN; |
404 | } |
405 | if (sysctl_tcp_cookie_size >= TCP_COOKIE_MAX) { |
406 | /* value too large, specify maximum */ |
407 | return TCP_COOKIE_MAX; |
408 | } |
409 | if (0x1 & sysctl_tcp_cookie_size) { |
410 | /* 8-bit multiple, illegal, fix it */ |
411 | return (u8)(sysctl_tcp_cookie_size + 0x1); |
412 | } |
413 | return (u8)sysctl_tcp_cookie_size; |
414 | } |
415 | |
416 | /* Write previously computed TCP options to the packet. |
417 | * |
418 | * Beware: Something in the Internet is very sensitive to the ordering of |
419 | * TCP options, we learned this through the hard way, so be careful here. |
420 | * Luckily we can at least blame others for their non-compliance but from |
421 | * inter-operatibility perspective it seems that we're somewhat stuck with |
422 | * the ordering which we have been using if we want to keep working with |
423 | * those broken things (not that it currently hurts anybody as there isn't |
424 | * particular reason why the ordering would need to be changed). |
425 | * |
426 | * At least SACK_PERM as the first option is known to lead to a disaster |
427 | * (but it may well be that other scenarios fail similarly). |
428 | */ |
429 | static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, |
430 | struct tcp_out_options *opts) |
431 | { |
432 | u8 options = opts->options; /* mungable copy */ |
433 | |
434 | /* Having both authentication and cookies for security is redundant, |
435 | * and there's certainly not enough room. Instead, the cookie-less |
436 | * extension variant is proposed. |
437 | * |
438 | * Consider the pessimal case with authentication. The options |
439 | * could look like: |
440 | * COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40 |
441 | */ |
442 | if (unlikely(OPTION_MD5 & options)) { |
443 | if (unlikely(OPTION_COOKIE_EXTENSION & options)) { |
444 | *ptr++ = htonl((TCPOPT_COOKIE << 24) | |
445 | (TCPOLEN_COOKIE_BASE << 16) | |
446 | (TCPOPT_MD5SIG << 8) | |
447 | TCPOLEN_MD5SIG); |
448 | } else { |
449 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
450 | (TCPOPT_NOP << 16) | |
451 | (TCPOPT_MD5SIG << 8) | |
452 | TCPOLEN_MD5SIG); |
453 | } |
454 | options &= ~OPTION_COOKIE_EXTENSION; |
455 | /* overload cookie hash location */ |
456 | opts->hash_location = (__u8 *)ptr; |
457 | ptr += 4; |
458 | } |
459 | |
460 | if (unlikely(opts->mss)) { |
461 | *ptr++ = htonl((TCPOPT_MSS << 24) | |
462 | (TCPOLEN_MSS << 16) | |
463 | opts->mss); |
464 | } |
465 | |
466 | if (likely(OPTION_TS & options)) { |
467 | if (unlikely(OPTION_SACK_ADVERTISE & options)) { |
468 | *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | |
469 | (TCPOLEN_SACK_PERM << 16) | |
470 | (TCPOPT_TIMESTAMP << 8) | |
471 | TCPOLEN_TIMESTAMP); |
472 | options &= ~OPTION_SACK_ADVERTISE; |
473 | } else { |
474 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
475 | (TCPOPT_NOP << 16) | |
476 | (TCPOPT_TIMESTAMP << 8) | |
477 | TCPOLEN_TIMESTAMP); |
478 | } |
479 | *ptr++ = htonl(opts->tsval); |
480 | *ptr++ = htonl(opts->tsecr); |
481 | } |
482 | |
483 | /* Specification requires after timestamp, so do it now. |
484 | * |
485 | * Consider the pessimal case without authentication. The options |
486 | * could look like: |
487 | * MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40 |
488 | */ |
489 | if (unlikely(OPTION_COOKIE_EXTENSION & options)) { |
490 | __u8 *cookie_copy = opts->hash_location; |
491 | u8 cookie_size = opts->hash_size; |
492 | |
493 | /* 8-bit multiple handled in tcp_cookie_size_check() above, |
494 | * and elsewhere. |
495 | */ |
496 | if (0x2 & cookie_size) { |
497 | __u8 *p = (__u8 *)ptr; |
498 | |
499 | /* 16-bit multiple */ |
500 | *p++ = TCPOPT_COOKIE; |
501 | *p++ = TCPOLEN_COOKIE_BASE + cookie_size; |
502 | *p++ = *cookie_copy++; |
503 | *p++ = *cookie_copy++; |
504 | ptr++; |
505 | cookie_size -= 2; |
506 | } else { |
507 | /* 32-bit multiple */ |
508 | *ptr++ = htonl(((TCPOPT_NOP << 24) | |
509 | (TCPOPT_NOP << 16) | |
510 | (TCPOPT_COOKIE << 8) | |
511 | TCPOLEN_COOKIE_BASE) + |
512 | cookie_size); |
513 | } |
514 | |
515 | if (cookie_size > 0) { |
516 | memcpy(ptr, cookie_copy, cookie_size); |
517 | ptr += (cookie_size / 4); |
518 | } |
519 | } |
520 | |
521 | if (unlikely(OPTION_SACK_ADVERTISE & options)) { |
522 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
523 | (TCPOPT_NOP << 16) | |
524 | (TCPOPT_SACK_PERM << 8) | |
525 | TCPOLEN_SACK_PERM); |
526 | } |
527 | |
528 | if (unlikely(OPTION_WSCALE & options)) { |
529 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
530 | (TCPOPT_WINDOW << 16) | |
531 | (TCPOLEN_WINDOW << 8) | |
532 | opts->ws); |
533 | } |
534 | |
535 | if (unlikely(opts->num_sack_blocks)) { |
536 | struct tcp_sack_block *sp = tp->rx_opt.dsack ? |
537 | tp->duplicate_sack : tp->selective_acks; |
538 | int this_sack; |
539 | |
540 | *ptr++ = htonl((TCPOPT_NOP << 24) | |
541 | (TCPOPT_NOP << 16) | |
542 | (TCPOPT_SACK << 8) | |
543 | (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * |
544 | TCPOLEN_SACK_PERBLOCK))); |
545 | |
546 | for (this_sack = 0; this_sack < opts->num_sack_blocks; |
547 | ++this_sack) { |
548 | *ptr++ = htonl(sp[this_sack].start_seq); |
549 | *ptr++ = htonl(sp[this_sack].end_seq); |
550 | } |
551 | |
552 | tp->rx_opt.dsack = 0; |
553 | } |
554 | } |
555 | |
556 | /* Compute TCP options for SYN packets. This is not the final |
557 | * network wire format yet. |
558 | */ |
559 | static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb, |
560 | struct tcp_out_options *opts, |
561 | struct tcp_md5sig_key **md5) { |
562 | struct tcp_sock *tp = tcp_sk(sk); |
563 | struct tcp_cookie_values *cvp = tp->cookie_values; |
564 | unsigned remaining = MAX_TCP_OPTION_SPACE; |
565 | u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ? |
566 | tcp_cookie_size_check(cvp->cookie_desired) : |
567 | 0; |
568 | |
569 | #ifdef CONFIG_TCP_MD5SIG |
570 | *md5 = tp->af_specific->md5_lookup(sk, sk); |
571 | if (*md5) { |
572 | opts->options |= OPTION_MD5; |
573 | remaining -= TCPOLEN_MD5SIG_ALIGNED; |
574 | } |
575 | #else |
576 | *md5 = NULL; |
577 | #endif |
578 | |
579 | /* We always get an MSS option. The option bytes which will be seen in |
580 | * normal data packets should timestamps be used, must be in the MSS |
581 | * advertised. But we subtract them from tp->mss_cache so that |
582 | * calculations in tcp_sendmsg are simpler etc. So account for this |
583 | * fact here if necessary. If we don't do this correctly, as a |
584 | * receiver we won't recognize data packets as being full sized when we |
585 | * should, and thus we won't abide by the delayed ACK rules correctly. |
586 | * SACKs don't matter, we never delay an ACK when we have any of those |
587 | * going out. */ |
588 | opts->mss = tcp_advertise_mss(sk); |
589 | remaining -= TCPOLEN_MSS_ALIGNED; |
590 | |
591 | if (likely(sysctl_tcp_timestamps && *md5 == NULL)) { |
592 | opts->options |= OPTION_TS; |
593 | opts->tsval = TCP_SKB_CB(skb)->when; |
594 | opts->tsecr = tp->rx_opt.ts_recent; |
595 | remaining -= TCPOLEN_TSTAMP_ALIGNED; |
596 | } |
597 | if (likely(sysctl_tcp_window_scaling)) { |
598 | opts->ws = tp->rx_opt.rcv_wscale; |
599 | opts->options |= OPTION_WSCALE; |
600 | remaining -= TCPOLEN_WSCALE_ALIGNED; |
601 | } |
602 | if (likely(sysctl_tcp_sack)) { |
603 | opts->options |= OPTION_SACK_ADVERTISE; |
604 | if (unlikely(!(OPTION_TS & opts->options))) |
605 | remaining -= TCPOLEN_SACKPERM_ALIGNED; |
606 | } |
607 | |
608 | /* Note that timestamps are required by the specification. |
609 | * |
610 | * Odd numbers of bytes are prohibited by the specification, ensuring |
611 | * that the cookie is 16-bit aligned, and the resulting cookie pair is |
612 | * 32-bit aligned. |
613 | */ |
614 | if (*md5 == NULL && |
615 | (OPTION_TS & opts->options) && |
616 | cookie_size > 0) { |
617 | int need = TCPOLEN_COOKIE_BASE + cookie_size; |
618 | |
619 | if (0x2 & need) { |
620 | /* 32-bit multiple */ |
621 | need += 2; /* NOPs */ |
622 | |
623 | if (need > remaining) { |
624 | /* try shrinking cookie to fit */ |
625 | cookie_size -= 2; |
626 | need -= 4; |
627 | } |
628 | } |
629 | while (need > remaining && TCP_COOKIE_MIN <= cookie_size) { |
630 | cookie_size -= 4; |
631 | need -= 4; |
632 | } |
633 | if (TCP_COOKIE_MIN <= cookie_size) { |
634 | opts->options |= OPTION_COOKIE_EXTENSION; |
635 | opts->hash_location = (__u8 *)&cvp->cookie_pair[0]; |
636 | opts->hash_size = cookie_size; |
637 | |
638 | /* Remember for future incarnations. */ |
639 | cvp->cookie_desired = cookie_size; |
640 | |
641 | if (cvp->cookie_desired != cvp->cookie_pair_size) { |
642 | /* Currently use random bytes as a nonce, |
643 | * assuming these are completely unpredictable |
644 | * by hostile users of the same system. |
645 | */ |
646 | get_random_bytes(&cvp->cookie_pair[0], |
647 | cookie_size); |
648 | cvp->cookie_pair_size = cookie_size; |
649 | } |
650 | |
651 | remaining -= need; |
652 | } |
653 | } |
654 | return MAX_TCP_OPTION_SPACE - remaining; |
655 | } |
656 | |
657 | /* Set up TCP options for SYN-ACKs. */ |
658 | static unsigned tcp_synack_options(struct sock *sk, |
659 | struct request_sock *req, |
660 | unsigned mss, struct sk_buff *skb, |
661 | struct tcp_out_options *opts, |
662 | struct tcp_md5sig_key **md5, |
663 | struct tcp_extend_values *xvp) |
664 | { |
665 | struct inet_request_sock *ireq = inet_rsk(req); |
666 | unsigned remaining = MAX_TCP_OPTION_SPACE; |
667 | u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ? |
668 | xvp->cookie_plus : |
669 | 0; |
670 | bool doing_ts = ireq->tstamp_ok; |
671 | |
672 | #ifdef CONFIG_TCP_MD5SIG |
673 | *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req); |
674 | if (*md5) { |
675 | opts->options |= OPTION_MD5; |
676 | remaining -= TCPOLEN_MD5SIG_ALIGNED; |
677 | |
678 | /* We can't fit any SACK blocks in a packet with MD5 + TS |
679 | * options. There was discussion about disabling SACK |
680 | * rather than TS in order to fit in better with old, |
681 | * buggy kernels, but that was deemed to be unnecessary. |
682 | */ |
683 | doing_ts &= !ireq->sack_ok; |
684 | } |
685 | #else |
686 | *md5 = NULL; |
687 | #endif |
688 | |
689 | /* We always send an MSS option. */ |
690 | opts->mss = mss; |
691 | remaining -= TCPOLEN_MSS_ALIGNED; |
692 | |
693 | if (likely(ireq->wscale_ok)) { |
694 | opts->ws = ireq->rcv_wscale; |
695 | opts->options |= OPTION_WSCALE; |
696 | remaining -= TCPOLEN_WSCALE_ALIGNED; |
697 | } |
698 | if (likely(doing_ts)) { |
699 | opts->options |= OPTION_TS; |
700 | opts->tsval = TCP_SKB_CB(skb)->when; |
701 | opts->tsecr = req->ts_recent; |
702 | remaining -= TCPOLEN_TSTAMP_ALIGNED; |
703 | } |
704 | if (likely(ireq->sack_ok)) { |
705 | opts->options |= OPTION_SACK_ADVERTISE; |
706 | if (unlikely(!doing_ts)) |
707 | remaining -= TCPOLEN_SACKPERM_ALIGNED; |
708 | } |
709 | |
710 | /* Similar rationale to tcp_syn_options() applies here, too. |
711 | * If the <SYN> options fit, the same options should fit now! |
712 | */ |
713 | if (*md5 == NULL && |
714 | doing_ts && |
715 | cookie_plus > TCPOLEN_COOKIE_BASE) { |
716 | int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */ |
717 | |
718 | if (0x2 & need) { |
719 | /* 32-bit multiple */ |
720 | need += 2; /* NOPs */ |
721 | } |
722 | if (need <= remaining) { |
723 | opts->options |= OPTION_COOKIE_EXTENSION; |
724 | opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE; |
725 | remaining -= need; |
726 | } else { |
727 | /* There's no error return, so flag it. */ |
728 | xvp->cookie_out_never = 1; /* true */ |
729 | opts->hash_size = 0; |
730 | } |
731 | } |
732 | return MAX_TCP_OPTION_SPACE - remaining; |
733 | } |
734 | |
735 | /* Compute TCP options for ESTABLISHED sockets. This is not the |
736 | * final wire format yet. |
737 | */ |
738 | static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb, |
739 | struct tcp_out_options *opts, |
740 | struct tcp_md5sig_key **md5) { |
741 | struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL; |
742 | struct tcp_sock *tp = tcp_sk(sk); |
743 | unsigned size = 0; |
744 | unsigned int eff_sacks; |
745 | |
746 | #ifdef CONFIG_TCP_MD5SIG |
747 | *md5 = tp->af_specific->md5_lookup(sk, sk); |
748 | if (unlikely(*md5)) { |
749 | opts->options |= OPTION_MD5; |
750 | size += TCPOLEN_MD5SIG_ALIGNED; |
751 | } |
752 | #else |
753 | *md5 = NULL; |
754 | #endif |
755 | |
756 | if (likely(tp->rx_opt.tstamp_ok)) { |
757 | opts->options |= OPTION_TS; |
758 | opts->tsval = tcb ? tcb->when : 0; |
759 | opts->tsecr = tp->rx_opt.ts_recent; |
760 | size += TCPOLEN_TSTAMP_ALIGNED; |
761 | } |
762 | |
763 | eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack; |
764 | if (unlikely(eff_sacks)) { |
765 | const unsigned remaining = MAX_TCP_OPTION_SPACE - size; |
766 | opts->num_sack_blocks = |
767 | min_t(unsigned, eff_sacks, |
768 | (remaining - TCPOLEN_SACK_BASE_ALIGNED) / |
769 | TCPOLEN_SACK_PERBLOCK); |
770 | size += TCPOLEN_SACK_BASE_ALIGNED + |
771 | opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; |
772 | } |
773 | |
774 | return size; |
775 | } |
776 | |
777 | /* This routine actually transmits TCP packets queued in by |
778 | * tcp_do_sendmsg(). This is used by both the initial |
779 | * transmission and possible later retransmissions. |
780 | * All SKB's seen here are completely headerless. It is our |
781 | * job to build the TCP header, and pass the packet down to |
782 | * IP so it can do the same plus pass the packet off to the |
783 | * device. |
784 | * |
785 | * We are working here with either a clone of the original |
786 | * SKB, or a fresh unique copy made by the retransmit engine. |
787 | */ |
788 | static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, |
789 | gfp_t gfp_mask) |
790 | { |
791 | const struct inet_connection_sock *icsk = inet_csk(sk); |
792 | struct inet_sock *inet; |
793 | struct tcp_sock *tp; |
794 | struct tcp_skb_cb *tcb; |
795 | struct tcp_out_options opts; |
796 | unsigned tcp_options_size, tcp_header_size; |
797 | struct tcp_md5sig_key *md5; |
798 | struct tcphdr *th; |
799 | int err; |
800 | |
801 | BUG_ON(!skb || !tcp_skb_pcount(skb)); |
802 | |
803 | /* If congestion control is doing timestamping, we must |
804 | * take such a timestamp before we potentially clone/copy. |
805 | */ |
806 | if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP) |
807 | __net_timestamp(skb); |
808 | |
809 | if (likely(clone_it)) { |
810 | if (unlikely(skb_cloned(skb))) |
811 | skb = pskb_copy(skb, gfp_mask); |
812 | else |
813 | skb = skb_clone(skb, gfp_mask); |
814 | if (unlikely(!skb)) |
815 | return -ENOBUFS; |
816 | } |
817 | |
818 | inet = inet_sk(sk); |
819 | tp = tcp_sk(sk); |
820 | tcb = TCP_SKB_CB(skb); |
821 | memset(&opts, 0, sizeof(opts)); |
822 | |
823 | if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) |
824 | tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); |
825 | else |
826 | tcp_options_size = tcp_established_options(sk, skb, &opts, |
827 | &md5); |
828 | tcp_header_size = tcp_options_size + sizeof(struct tcphdr); |
829 | |
830 | if (tcp_packets_in_flight(tp) == 0) |
831 | tcp_ca_event(sk, CA_EVENT_TX_START); |
832 | |
833 | skb_push(skb, tcp_header_size); |
834 | skb_reset_transport_header(skb); |
835 | skb_set_owner_w(skb, sk); |
836 | |
837 | /* Build TCP header and checksum it. */ |
838 | th = tcp_hdr(skb); |
839 | th->source = inet->inet_sport; |
840 | th->dest = inet->inet_dport; |
841 | th->seq = htonl(tcb->seq); |
842 | th->ack_seq = htonl(tp->rcv_nxt); |
843 | *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | |
844 | tcb->flags); |
845 | |
846 | if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { |
847 | /* RFC1323: The window in SYN & SYN/ACK segments |
848 | * is never scaled. |
849 | */ |
850 | th->window = htons(min(tp->rcv_wnd, 65535U)); |
851 | } else { |
852 | th->window = htons(tcp_select_window(sk)); |
853 | } |
854 | th->check = 0; |
855 | th->urg_ptr = 0; |
856 | |
857 | /* The urg_mode check is necessary during a below snd_una win probe */ |
858 | if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) { |
859 | if (before(tp->snd_up, tcb->seq + 0x10000)) { |
860 | th->urg_ptr = htons(tp->snd_up - tcb->seq); |
861 | th->urg = 1; |
862 | } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) { |
863 | th->urg_ptr = 0xFFFF; |
864 | th->urg = 1; |
865 | } |
866 | } |
867 | |
868 | tcp_options_write((__be32 *)(th + 1), tp, &opts); |
869 | if (likely((tcb->flags & TCPCB_FLAG_SYN) == 0)) |
870 | TCP_ECN_send(sk, skb, tcp_header_size); |
871 | |
872 | #ifdef CONFIG_TCP_MD5SIG |
873 | /* Calculate the MD5 hash, as we have all we need now */ |
874 | if (md5) { |
875 | sk->sk_route_caps &= ~NETIF_F_GSO_MASK; |
876 | tp->af_specific->calc_md5_hash(opts.hash_location, |
877 | md5, sk, NULL, skb); |
878 | } |
879 | #endif |
880 | |
881 | icsk->icsk_af_ops->send_check(sk, skb->len, skb); |
882 | |
883 | if (likely(tcb->flags & TCPCB_FLAG_ACK)) |
884 | tcp_event_ack_sent(sk, tcp_skb_pcount(skb)); |
885 | |
886 | if (skb->len != tcp_header_size) |
887 | tcp_event_data_sent(tp, skb, sk); |
888 | |
889 | if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) |
890 | TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS); |
891 | |
892 | err = icsk->icsk_af_ops->queue_xmit(skb, 0); |
893 | if (likely(err <= 0)) |
894 | return err; |
895 | |
896 | tcp_enter_cwr(sk, 1); |
897 | |
898 | return net_xmit_eval(err); |
899 | } |
900 | |
901 | /* This routine just queues the buffer for sending. |
902 | * |
903 | * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, |
904 | * otherwise socket can stall. |
905 | */ |
906 | static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) |
907 | { |
908 | struct tcp_sock *tp = tcp_sk(sk); |
909 | |
910 | /* Advance write_seq and place onto the write_queue. */ |
911 | tp->write_seq = TCP_SKB_CB(skb)->end_seq; |
912 | skb_header_release(skb); |
913 | tcp_add_write_queue_tail(sk, skb); |
914 | sk->sk_wmem_queued += skb->truesize; |
915 | sk_mem_charge(sk, skb->truesize); |
916 | } |
917 | |
918 | /* Initialize TSO segments for a packet. */ |
919 | static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, |
920 | unsigned int mss_now) |
921 | { |
922 | if (skb->len <= mss_now || !sk_can_gso(sk) || |
923 | skb->ip_summed == CHECKSUM_NONE) { |
924 | /* Avoid the costly divide in the normal |
925 | * non-TSO case. |
926 | */ |
927 | skb_shinfo(skb)->gso_segs = 1; |
928 | skb_shinfo(skb)->gso_size = 0; |
929 | skb_shinfo(skb)->gso_type = 0; |
930 | } else { |
931 | skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now); |
932 | skb_shinfo(skb)->gso_size = mss_now; |
933 | skb_shinfo(skb)->gso_type = sk->sk_gso_type; |
934 | } |
935 | } |
936 | |
937 | /* When a modification to fackets out becomes necessary, we need to check |
938 | * skb is counted to fackets_out or not. |
939 | */ |
940 | static void tcp_adjust_fackets_out(struct sock *sk, struct sk_buff *skb, |
941 | int decr) |
942 | { |
943 | struct tcp_sock *tp = tcp_sk(sk); |
944 | |
945 | if (!tp->sacked_out || tcp_is_reno(tp)) |
946 | return; |
947 | |
948 | if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq)) |
949 | tp->fackets_out -= decr; |
950 | } |
951 | |
952 | /* Pcount in the middle of the write queue got changed, we need to do various |
953 | * tweaks to fix counters |
954 | */ |
955 | static void tcp_adjust_pcount(struct sock *sk, struct sk_buff *skb, int decr) |
956 | { |
957 | struct tcp_sock *tp = tcp_sk(sk); |
958 | |
959 | tp->packets_out -= decr; |
960 | |
961 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) |
962 | tp->sacked_out -= decr; |
963 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) |
964 | tp->retrans_out -= decr; |
965 | if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) |
966 | tp->lost_out -= decr; |
967 | |
968 | /* Reno case is special. Sigh... */ |
969 | if (tcp_is_reno(tp) && decr > 0) |
970 | tp->sacked_out -= min_t(u32, tp->sacked_out, decr); |
971 | |
972 | tcp_adjust_fackets_out(sk, skb, decr); |
973 | |
974 | if (tp->lost_skb_hint && |
975 | before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) && |
976 | (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))) |
977 | tp->lost_cnt_hint -= decr; |
978 | |
979 | tcp_verify_left_out(tp); |
980 | } |
981 | |
982 | /* Function to create two new TCP segments. Shrinks the given segment |
983 | * to the specified size and appends a new segment with the rest of the |
984 | * packet to the list. This won't be called frequently, I hope. |
985 | * Remember, these are still headerless SKBs at this point. |
986 | */ |
987 | int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, |
988 | unsigned int mss_now) |
989 | { |
990 | struct tcp_sock *tp = tcp_sk(sk); |
991 | struct sk_buff *buff; |
992 | int nsize, old_factor; |
993 | int nlen; |
994 | u8 flags; |
995 | |
996 | BUG_ON(len > skb->len); |
997 | |
998 | nsize = skb_headlen(skb) - len; |
999 | if (nsize < 0) |
1000 | nsize = 0; |
1001 | |
1002 | if (skb_cloned(skb) && |
1003 | skb_is_nonlinear(skb) && |
1004 | pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) |
1005 | return -ENOMEM; |
1006 | |
1007 | /* Get a new skb... force flag on. */ |
1008 | buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC); |
1009 | if (buff == NULL) |
1010 | return -ENOMEM; /* We'll just try again later. */ |
1011 | |
1012 | sk->sk_wmem_queued += buff->truesize; |
1013 | sk_mem_charge(sk, buff->truesize); |
1014 | nlen = skb->len - len - nsize; |
1015 | buff->truesize += nlen; |
1016 | skb->truesize -= nlen; |
1017 | |
1018 | /* Correct the sequence numbers. */ |
1019 | TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; |
1020 | TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; |
1021 | TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; |
1022 | |
1023 | /* PSH and FIN should only be set in the second packet. */ |
1024 | flags = TCP_SKB_CB(skb)->flags; |
1025 | TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH); |
1026 | TCP_SKB_CB(buff)->flags = flags; |
1027 | TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; |
1028 | |
1029 | if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) { |
1030 | /* Copy and checksum data tail into the new buffer. */ |
1031 | buff->csum = csum_partial_copy_nocheck(skb->data + len, |
1032 | skb_put(buff, nsize), |
1033 | nsize, 0); |
1034 | |
1035 | skb_trim(skb, len); |
1036 | |
1037 | skb->csum = csum_block_sub(skb->csum, buff->csum, len); |
1038 | } else { |
1039 | skb->ip_summed = CHECKSUM_PARTIAL; |
1040 | skb_split(skb, buff, len); |
1041 | } |
1042 | |
1043 | buff->ip_summed = skb->ip_summed; |
1044 | |
1045 | /* Looks stupid, but our code really uses when of |
1046 | * skbs, which it never sent before. --ANK |
1047 | */ |
1048 | TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; |
1049 | buff->tstamp = skb->tstamp; |
1050 | |
1051 | old_factor = tcp_skb_pcount(skb); |
1052 | |
1053 | /* Fix up tso_factor for both original and new SKB. */ |
1054 | tcp_set_skb_tso_segs(sk, skb, mss_now); |
1055 | tcp_set_skb_tso_segs(sk, buff, mss_now); |
1056 | |
1057 | /* If this packet has been sent out already, we must |
1058 | * adjust the various packet counters. |
1059 | */ |
1060 | if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { |
1061 | int diff = old_factor - tcp_skb_pcount(skb) - |
1062 | tcp_skb_pcount(buff); |
1063 | |
1064 | if (diff) |
1065 | tcp_adjust_pcount(sk, skb, diff); |
1066 | } |
1067 | |
1068 | /* Link BUFF into the send queue. */ |
1069 | skb_header_release(buff); |
1070 | tcp_insert_write_queue_after(skb, buff, sk); |
1071 | |
1072 | return 0; |
1073 | } |
1074 | |
1075 | /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c |
1076 | * eventually). The difference is that pulled data not copied, but |
1077 | * immediately discarded. |
1078 | */ |
1079 | static void __pskb_trim_head(struct sk_buff *skb, int len) |
1080 | { |
1081 | int i, k, eat; |
1082 | |
1083 | eat = len; |
1084 | k = 0; |
1085 | for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { |
1086 | if (skb_shinfo(skb)->frags[i].size <= eat) { |
1087 | put_page(skb_shinfo(skb)->frags[i].page); |
1088 | eat -= skb_shinfo(skb)->frags[i].size; |
1089 | } else { |
1090 | skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i]; |
1091 | if (eat) { |
1092 | skb_shinfo(skb)->frags[k].page_offset += eat; |
1093 | skb_shinfo(skb)->frags[k].size -= eat; |
1094 | eat = 0; |
1095 | } |
1096 | k++; |
1097 | } |
1098 | } |
1099 | skb_shinfo(skb)->nr_frags = k; |
1100 | |
1101 | skb_reset_tail_pointer(skb); |
1102 | skb->data_len -= len; |
1103 | skb->len = skb->data_len; |
1104 | } |
1105 | |
1106 | /* Remove acked data from a packet in the transmit queue. */ |
1107 | int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) |
1108 | { |
1109 | if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) |
1110 | return -ENOMEM; |
1111 | |
1112 | /* If len == headlen, we avoid __skb_pull to preserve alignment. */ |
1113 | if (unlikely(len < skb_headlen(skb))) |
1114 | __skb_pull(skb, len); |
1115 | else |
1116 | __pskb_trim_head(skb, len - skb_headlen(skb)); |
1117 | |
1118 | TCP_SKB_CB(skb)->seq += len; |
1119 | skb->ip_summed = CHECKSUM_PARTIAL; |
1120 | |
1121 | skb->truesize -= len; |
1122 | sk->sk_wmem_queued -= len; |
1123 | sk_mem_uncharge(sk, len); |
1124 | sock_set_flag(sk, SOCK_QUEUE_SHRUNK); |
1125 | |
1126 | /* Any change of skb->len requires recalculation of tso |
1127 | * factor and mss. |
1128 | */ |
1129 | if (tcp_skb_pcount(skb) > 1) |
1130 | tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk)); |
1131 | |
1132 | return 0; |
1133 | } |
1134 | |
1135 | /* Calculate MSS. Not accounting for SACKs here. */ |
1136 | int tcp_mtu_to_mss(struct sock *sk, int pmtu) |
1137 | { |
1138 | struct tcp_sock *tp = tcp_sk(sk); |
1139 | struct inet_connection_sock *icsk = inet_csk(sk); |
1140 | int mss_now; |
1141 | |
1142 | /* Calculate base mss without TCP options: |
1143 | It is MMS_S - sizeof(tcphdr) of rfc1122 |
1144 | */ |
1145 | mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); |
1146 | |
1147 | /* Clamp it (mss_clamp does not include tcp options) */ |
1148 | if (mss_now > tp->rx_opt.mss_clamp) |
1149 | mss_now = tp->rx_opt.mss_clamp; |
1150 | |
1151 | /* Now subtract optional transport overhead */ |
1152 | mss_now -= icsk->icsk_ext_hdr_len; |
1153 | |
1154 | /* Then reserve room for full set of TCP options and 8 bytes of data */ |
1155 | if (mss_now < 48) |
1156 | mss_now = 48; |
1157 | |
1158 | /* Now subtract TCP options size, not including SACKs */ |
1159 | mss_now -= tp->tcp_header_len - sizeof(struct tcphdr); |
1160 | |
1161 | return mss_now; |
1162 | } |
1163 | |
1164 | /* Inverse of above */ |
1165 | int tcp_mss_to_mtu(struct sock *sk, int mss) |
1166 | { |
1167 | struct tcp_sock *tp = tcp_sk(sk); |
1168 | struct inet_connection_sock *icsk = inet_csk(sk); |
1169 | int mtu; |
1170 | |
1171 | mtu = mss + |
1172 | tp->tcp_header_len + |
1173 | icsk->icsk_ext_hdr_len + |
1174 | icsk->icsk_af_ops->net_header_len; |
1175 | |
1176 | return mtu; |
1177 | } |
1178 | |
1179 | /* MTU probing init per socket */ |
1180 | void tcp_mtup_init(struct sock *sk) |
1181 | { |
1182 | struct tcp_sock *tp = tcp_sk(sk); |
1183 | struct inet_connection_sock *icsk = inet_csk(sk); |
1184 | |
1185 | icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1; |
1186 | icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + |
1187 | icsk->icsk_af_ops->net_header_len; |
1188 | icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss); |
1189 | icsk->icsk_mtup.probe_size = 0; |
1190 | } |
1191 | |
1192 | /* This function synchronize snd mss to current pmtu/exthdr set. |
1193 | |
1194 | tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts |
1195 | for TCP options, but includes only bare TCP header. |
1196 | |
1197 | tp->rx_opt.mss_clamp is mss negotiated at connection setup. |
1198 | It is minimum of user_mss and mss received with SYN. |
1199 | It also does not include TCP options. |
1200 | |
1201 | inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. |
1202 | |
1203 | tp->mss_cache is current effective sending mss, including |
1204 | all tcp options except for SACKs. It is evaluated, |
1205 | taking into account current pmtu, but never exceeds |
1206 | tp->rx_opt.mss_clamp. |
1207 | |
1208 | NOTE1. rfc1122 clearly states that advertised MSS |
1209 | DOES NOT include either tcp or ip options. |
1210 | |
1211 | NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache |
1212 | are READ ONLY outside this function. --ANK (980731) |
1213 | */ |
1214 | unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) |
1215 | { |
1216 | struct tcp_sock *tp = tcp_sk(sk); |
1217 | struct inet_connection_sock *icsk = inet_csk(sk); |
1218 | int mss_now; |
1219 | |
1220 | if (icsk->icsk_mtup.search_high > pmtu) |
1221 | icsk->icsk_mtup.search_high = pmtu; |
1222 | |
1223 | mss_now = tcp_mtu_to_mss(sk, pmtu); |
1224 | mss_now = tcp_bound_to_half_wnd(tp, mss_now); |
1225 | |
1226 | /* And store cached results */ |
1227 | icsk->icsk_pmtu_cookie = pmtu; |
1228 | if (icsk->icsk_mtup.enabled) |
1229 | mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); |
1230 | tp->mss_cache = mss_now; |
1231 | |
1232 | return mss_now; |
1233 | } |
1234 | |
1235 | /* Compute the current effective MSS, taking SACKs and IP options, |
1236 | * and even PMTU discovery events into account. |
1237 | */ |
1238 | unsigned int tcp_current_mss(struct sock *sk) |
1239 | { |
1240 | struct tcp_sock *tp = tcp_sk(sk); |
1241 | struct dst_entry *dst = __sk_dst_get(sk); |
1242 | u32 mss_now; |
1243 | unsigned header_len; |
1244 | struct tcp_out_options opts; |
1245 | struct tcp_md5sig_key *md5; |
1246 | |
1247 | mss_now = tp->mss_cache; |
1248 | |
1249 | if (dst) { |
1250 | u32 mtu = dst_mtu(dst); |
1251 | if (mtu != inet_csk(sk)->icsk_pmtu_cookie) |
1252 | mss_now = tcp_sync_mss(sk, mtu); |
1253 | } |
1254 | |
1255 | header_len = tcp_established_options(sk, NULL, &opts, &md5) + |
1256 | sizeof(struct tcphdr); |
1257 | /* The mss_cache is sized based on tp->tcp_header_len, which assumes |
1258 | * some common options. If this is an odd packet (because we have SACK |
1259 | * blocks etc) then our calculated header_len will be different, and |
1260 | * we have to adjust mss_now correspondingly */ |
1261 | if (header_len != tp->tcp_header_len) { |
1262 | int delta = (int) header_len - tp->tcp_header_len; |
1263 | mss_now -= delta; |
1264 | } |
1265 | |
1266 | return mss_now; |
1267 | } |
1268 | |
1269 | /* Congestion window validation. (RFC2861) */ |
1270 | static void tcp_cwnd_validate(struct sock *sk) |
1271 | { |
1272 | struct tcp_sock *tp = tcp_sk(sk); |
1273 | |
1274 | if (tp->packets_out >= tp->snd_cwnd) { |
1275 | /* Network is feed fully. */ |
1276 | tp->snd_cwnd_used = 0; |
1277 | tp->snd_cwnd_stamp = tcp_time_stamp; |
1278 | } else { |
1279 | /* Network starves. */ |
1280 | if (tp->packets_out > tp->snd_cwnd_used) |
1281 | tp->snd_cwnd_used = tp->packets_out; |
1282 | |
1283 | if (sysctl_tcp_slow_start_after_idle && |
1284 | (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto) |
1285 | tcp_cwnd_application_limited(sk); |
1286 | } |
1287 | } |
1288 | |
1289 | /* Returns the portion of skb which can be sent right away without |
1290 | * introducing MSS oddities to segment boundaries. In rare cases where |
1291 | * mss_now != mss_cache, we will request caller to create a small skb |
1292 | * per input skb which could be mostly avoided here (if desired). |
1293 | * |
1294 | * We explicitly want to create a request for splitting write queue tail |
1295 | * to a small skb for Nagle purposes while avoiding unnecessary modulos, |
1296 | * thus all the complexity (cwnd_len is always MSS multiple which we |
1297 | * return whenever allowed by the other factors). Basically we need the |
1298 | * modulo only when the receiver window alone is the limiting factor or |
1299 | * when we would be allowed to send the split-due-to-Nagle skb fully. |
1300 | */ |
1301 | static unsigned int tcp_mss_split_point(struct sock *sk, struct sk_buff *skb, |
1302 | unsigned int mss_now, unsigned int cwnd) |
1303 | { |
1304 | struct tcp_sock *tp = tcp_sk(sk); |
1305 | u32 needed, window, cwnd_len; |
1306 | |
1307 | window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; |
1308 | cwnd_len = mss_now * cwnd; |
1309 | |
1310 | if (likely(cwnd_len <= window && skb != tcp_write_queue_tail(sk))) |
1311 | return cwnd_len; |
1312 | |
1313 | needed = min(skb->len, window); |
1314 | |
1315 | if (cwnd_len <= needed) |
1316 | return cwnd_len; |
1317 | |
1318 | return needed - needed % mss_now; |
1319 | } |
1320 | |
1321 | /* Can at least one segment of SKB be sent right now, according to the |
1322 | * congestion window rules? If so, return how many segments are allowed. |
1323 | */ |
1324 | static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, |
1325 | struct sk_buff *skb) |
1326 | { |
1327 | u32 in_flight, cwnd; |
1328 | |
1329 | /* Don't be strict about the congestion window for the final FIN. */ |
1330 | if ((TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && |
1331 | tcp_skb_pcount(skb) == 1) |
1332 | return 1; |
1333 | |
1334 | in_flight = tcp_packets_in_flight(tp); |
1335 | cwnd = tp->snd_cwnd; |
1336 | if (in_flight < cwnd) |
1337 | return (cwnd - in_flight); |
1338 | |
1339 | return 0; |
1340 | } |
1341 | |
1342 | /* Intialize TSO state of a skb. |
1343 | * This must be invoked the first time we consider transmitting |
1344 | * SKB onto the wire. |
1345 | */ |
1346 | static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, |
1347 | unsigned int mss_now) |
1348 | { |
1349 | int tso_segs = tcp_skb_pcount(skb); |
1350 | |
1351 | if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { |
1352 | tcp_set_skb_tso_segs(sk, skb, mss_now); |
1353 | tso_segs = tcp_skb_pcount(skb); |
1354 | } |
1355 | return tso_segs; |
1356 | } |
1357 | |
1358 | /* Minshall's variant of the Nagle send check. */ |
1359 | static inline int tcp_minshall_check(const struct tcp_sock *tp) |
1360 | { |
1361 | return after(tp->snd_sml, tp->snd_una) && |
1362 | !after(tp->snd_sml, tp->snd_nxt); |
1363 | } |
1364 | |
1365 | /* Return 0, if packet can be sent now without violation Nagle's rules: |
1366 | * 1. It is full sized. |
1367 | * 2. Or it contains FIN. (already checked by caller) |
1368 | * 3. Or TCP_NODELAY was set. |
1369 | * 4. Or TCP_CORK is not set, and all sent packets are ACKed. |
1370 | * With Minshall's modification: all sent small packets are ACKed. |
1371 | */ |
1372 | static inline int tcp_nagle_check(const struct tcp_sock *tp, |
1373 | const struct sk_buff *skb, |
1374 | unsigned mss_now, int nonagle) |
1375 | { |
1376 | return (skb->len < mss_now && |
1377 | ((nonagle & TCP_NAGLE_CORK) || |
1378 | (!nonagle && tp->packets_out && tcp_minshall_check(tp)))); |
1379 | } |
1380 | |
1381 | /* Return non-zero if the Nagle test allows this packet to be |
1382 | * sent now. |
1383 | */ |
1384 | static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb, |
1385 | unsigned int cur_mss, int nonagle) |
1386 | { |
1387 | /* Nagle rule does not apply to frames, which sit in the middle of the |
1388 | * write_queue (they have no chances to get new data). |
1389 | * |
1390 | * This is implemented in the callers, where they modify the 'nonagle' |
1391 | * argument based upon the location of SKB in the send queue. |
1392 | */ |
1393 | if (nonagle & TCP_NAGLE_PUSH) |
1394 | return 1; |
1395 | |
1396 | /* Don't use the nagle rule for urgent data (or for the final FIN). |
1397 | * Nagle can be ignored during F-RTO too (see RFC4138). |
1398 | */ |
1399 | if (tcp_urg_mode(tp) || (tp->frto_counter == 2) || |
1400 | (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)) |
1401 | return 1; |
1402 | |
1403 | if (!tcp_nagle_check(tp, skb, cur_mss, nonagle)) |
1404 | return 1; |
1405 | |
1406 | return 0; |
1407 | } |
1408 | |
1409 | /* Does at least the first segment of SKB fit into the send window? */ |
1410 | static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, |
1411 | unsigned int cur_mss) |
1412 | { |
1413 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; |
1414 | |
1415 | if (skb->len > cur_mss) |
1416 | end_seq = TCP_SKB_CB(skb)->seq + cur_mss; |
1417 | |
1418 | return !after(end_seq, tcp_wnd_end(tp)); |
1419 | } |
1420 | |
1421 | /* This checks if the data bearing packet SKB (usually tcp_send_head(sk)) |
1422 | * should be put on the wire right now. If so, it returns the number of |
1423 | * packets allowed by the congestion window. |
1424 | */ |
1425 | static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb, |
1426 | unsigned int cur_mss, int nonagle) |
1427 | { |
1428 | struct tcp_sock *tp = tcp_sk(sk); |
1429 | unsigned int cwnd_quota; |
1430 | |
1431 | tcp_init_tso_segs(sk, skb, cur_mss); |
1432 | |
1433 | if (!tcp_nagle_test(tp, skb, cur_mss, nonagle)) |
1434 | return 0; |
1435 | |
1436 | cwnd_quota = tcp_cwnd_test(tp, skb); |
1437 | if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss)) |
1438 | cwnd_quota = 0; |
1439 | |
1440 | return cwnd_quota; |
1441 | } |
1442 | |
1443 | /* Test if sending is allowed right now. */ |
1444 | int tcp_may_send_now(struct sock *sk) |
1445 | { |
1446 | struct tcp_sock *tp = tcp_sk(sk); |
1447 | struct sk_buff *skb = tcp_send_head(sk); |
1448 | |
1449 | return (skb && |
1450 | tcp_snd_test(sk, skb, tcp_current_mss(sk), |
1451 | (tcp_skb_is_last(sk, skb) ? |
1452 | tp->nonagle : TCP_NAGLE_PUSH))); |
1453 | } |
1454 | |
1455 | /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet |
1456 | * which is put after SKB on the list. It is very much like |
1457 | * tcp_fragment() except that it may make several kinds of assumptions |
1458 | * in order to speed up the splitting operation. In particular, we |
1459 | * know that all the data is in scatter-gather pages, and that the |
1460 | * packet has never been sent out before (and thus is not cloned). |
1461 | */ |
1462 | static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, |
1463 | unsigned int mss_now) |
1464 | { |
1465 | struct sk_buff *buff; |
1466 | int nlen = skb->len - len; |
1467 | u8 flags; |
1468 | |
1469 | /* All of a TSO frame must be composed of paged data. */ |
1470 | if (skb->len != skb->data_len) |
1471 | return tcp_fragment(sk, skb, len, mss_now); |
1472 | |
1473 | buff = sk_stream_alloc_skb(sk, 0, GFP_ATOMIC); |
1474 | if (unlikely(buff == NULL)) |
1475 | return -ENOMEM; |
1476 | |
1477 | sk->sk_wmem_queued += buff->truesize; |
1478 | sk_mem_charge(sk, buff->truesize); |
1479 | buff->truesize += nlen; |
1480 | skb->truesize -= nlen; |
1481 | |
1482 | /* Correct the sequence numbers. */ |
1483 | TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; |
1484 | TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; |
1485 | TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; |
1486 | |
1487 | /* PSH and FIN should only be set in the second packet. */ |
1488 | flags = TCP_SKB_CB(skb)->flags; |
1489 | TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH); |
1490 | TCP_SKB_CB(buff)->flags = flags; |
1491 | |
1492 | /* This packet was never sent out yet, so no SACK bits. */ |
1493 | TCP_SKB_CB(buff)->sacked = 0; |
1494 | |
1495 | buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL; |
1496 | skb_split(skb, buff, len); |
1497 | |
1498 | /* Fix up tso_factor for both original and new SKB. */ |
1499 | tcp_set_skb_tso_segs(sk, skb, mss_now); |
1500 | tcp_set_skb_tso_segs(sk, buff, mss_now); |
1501 | |
1502 | /* Link BUFF into the send queue. */ |
1503 | skb_header_release(buff); |
1504 | tcp_insert_write_queue_after(skb, buff, sk); |
1505 | |
1506 | return 0; |
1507 | } |
1508 | |
1509 | /* Try to defer sending, if possible, in order to minimize the amount |
1510 | * of TSO splitting we do. View it as a kind of TSO Nagle test. |
1511 | * |
1512 | * This algorithm is from John Heffner. |
1513 | */ |
1514 | static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) |
1515 | { |
1516 | struct tcp_sock *tp = tcp_sk(sk); |
1517 | const struct inet_connection_sock *icsk = inet_csk(sk); |
1518 | u32 send_win, cong_win, limit, in_flight; |
1519 | |
1520 | if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) |
1521 | goto send_now; |
1522 | |
1523 | if (icsk->icsk_ca_state != TCP_CA_Open) |
1524 | goto send_now; |
1525 | |
1526 | /* Defer for less than two clock ticks. */ |
1527 | if (tp->tso_deferred && |
1528 | (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1) |
1529 | goto send_now; |
1530 | |
1531 | in_flight = tcp_packets_in_flight(tp); |
1532 | |
1533 | BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight)); |
1534 | |
1535 | send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; |
1536 | |
1537 | /* From in_flight test above, we know that cwnd > in_flight. */ |
1538 | cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache; |
1539 | |
1540 | limit = min(send_win, cong_win); |
1541 | |
1542 | /* If a full-sized TSO skb can be sent, do it. */ |
1543 | if (limit >= sk->sk_gso_max_size) |
1544 | goto send_now; |
1545 | |
1546 | /* Middle in queue won't get any more data, full sendable already? */ |
1547 | if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len)) |
1548 | goto send_now; |
1549 | |
1550 | if (sysctl_tcp_tso_win_divisor) { |
1551 | u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); |
1552 | |
1553 | /* If at least some fraction of a window is available, |
1554 | * just use it. |
1555 | */ |
1556 | chunk /= sysctl_tcp_tso_win_divisor; |
1557 | if (limit >= chunk) |
1558 | goto send_now; |
1559 | } else { |
1560 | /* Different approach, try not to defer past a single |
1561 | * ACK. Receiver should ACK every other full sized |
1562 | * frame, so if we have space for more than 3 frames |
1563 | * then send now. |
1564 | */ |
1565 | if (limit > tcp_max_burst(tp) * tp->mss_cache) |
1566 | goto send_now; |
1567 | } |
1568 | |
1569 | /* Ok, it looks like it is advisable to defer. */ |
1570 | tp->tso_deferred = 1 | (jiffies << 1); |
1571 | |
1572 | return 1; |
1573 | |
1574 | send_now: |
1575 | tp->tso_deferred = 0; |
1576 | return 0; |
1577 | } |
1578 | |
1579 | /* Create a new MTU probe if we are ready. |
1580 | * MTU probe is regularly attempting to increase the path MTU by |
1581 | * deliberately sending larger packets. This discovers routing |
1582 | * changes resulting in larger path MTUs. |
1583 | * |
1584 | * Returns 0 if we should wait to probe (no cwnd available), |
1585 | * 1 if a probe was sent, |
1586 | * -1 otherwise |
1587 | */ |
1588 | static int tcp_mtu_probe(struct sock *sk) |
1589 | { |
1590 | struct tcp_sock *tp = tcp_sk(sk); |
1591 | struct inet_connection_sock *icsk = inet_csk(sk); |
1592 | struct sk_buff *skb, *nskb, *next; |
1593 | int len; |
1594 | int probe_size; |
1595 | int size_needed; |
1596 | int copy; |
1597 | int mss_now; |
1598 | |
1599 | /* Not currently probing/verifying, |
1600 | * not in recovery, |
1601 | * have enough cwnd, and |
1602 | * not SACKing (the variable headers throw things off) */ |
1603 | if (!icsk->icsk_mtup.enabled || |
1604 | icsk->icsk_mtup.probe_size || |
1605 | inet_csk(sk)->icsk_ca_state != TCP_CA_Open || |
1606 | tp->snd_cwnd < 11 || |
1607 | tp->rx_opt.num_sacks || tp->rx_opt.dsack) |
1608 | return -1; |
1609 | |
1610 | /* Very simple search strategy: just double the MSS. */ |
1611 | mss_now = tcp_current_mss(sk); |
1612 | probe_size = 2 * tp->mss_cache; |
1613 | size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache; |
1614 | if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) { |
1615 | /* TODO: set timer for probe_converge_event */ |
1616 | return -1; |
1617 | } |
1618 | |
1619 | /* Have enough data in the send queue to probe? */ |
1620 | if (tp->write_seq - tp->snd_nxt < size_needed) |
1621 | return -1; |
1622 | |
1623 | if (tp->snd_wnd < size_needed) |
1624 | return -1; |
1625 | if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp))) |
1626 | return 0; |
1627 | |
1628 | /* Do we need to wait to drain cwnd? With none in flight, don't stall */ |
1629 | if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) { |
1630 | if (!tcp_packets_in_flight(tp)) |
1631 | return -1; |
1632 | else |
1633 | return 0; |
1634 | } |
1635 | |
1636 | /* We're allowed to probe. Build it now. */ |
1637 | if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL) |
1638 | return -1; |
1639 | sk->sk_wmem_queued += nskb->truesize; |
1640 | sk_mem_charge(sk, nskb->truesize); |
1641 | |
1642 | skb = tcp_send_head(sk); |
1643 | |
1644 | TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; |
1645 | TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; |
1646 | TCP_SKB_CB(nskb)->flags = TCPCB_FLAG_ACK; |
1647 | TCP_SKB_CB(nskb)->sacked = 0; |
1648 | nskb->csum = 0; |
1649 | nskb->ip_summed = skb->ip_summed; |
1650 | |
1651 | tcp_insert_write_queue_before(nskb, skb, sk); |
1652 | |
1653 | len = 0; |
1654 | tcp_for_write_queue_from_safe(skb, next, sk) { |
1655 | copy = min_t(int, skb->len, probe_size - len); |
1656 | if (nskb->ip_summed) |
1657 | skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); |
1658 | else |
1659 | nskb->csum = skb_copy_and_csum_bits(skb, 0, |
1660 | skb_put(nskb, copy), |
1661 | copy, nskb->csum); |
1662 | |
1663 | if (skb->len <= copy) { |
1664 | /* We've eaten all the data from this skb. |
1665 | * Throw it away. */ |
1666 | TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags; |
1667 | tcp_unlink_write_queue(skb, sk); |
1668 | sk_wmem_free_skb(sk, skb); |
1669 | } else { |
1670 | TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags & |
1671 | ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); |
1672 | if (!skb_shinfo(skb)->nr_frags) { |
1673 | skb_pull(skb, copy); |
1674 | if (skb->ip_summed != CHECKSUM_PARTIAL) |
1675 | skb->csum = csum_partial(skb->data, |
1676 | skb->len, 0); |
1677 | } else { |
1678 | __pskb_trim_head(skb, copy); |
1679 | tcp_set_skb_tso_segs(sk, skb, mss_now); |
1680 | } |
1681 | TCP_SKB_CB(skb)->seq += copy; |
1682 | } |
1683 | |
1684 | len += copy; |
1685 | |
1686 | if (len >= probe_size) |
1687 | break; |
1688 | } |
1689 | tcp_init_tso_segs(sk, nskb, nskb->len); |
1690 | |
1691 | /* We're ready to send. If this fails, the probe will |
1692 | * be resegmented into mss-sized pieces by tcp_write_xmit(). */ |
1693 | TCP_SKB_CB(nskb)->when = tcp_time_stamp; |
1694 | if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { |
1695 | /* Decrement cwnd here because we are sending |
1696 | * effectively two packets. */ |
1697 | tp->snd_cwnd--; |
1698 | tcp_event_new_data_sent(sk, nskb); |
1699 | |
1700 | icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); |
1701 | tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; |
1702 | tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; |
1703 | |
1704 | return 1; |
1705 | } |
1706 | |
1707 | return -1; |
1708 | } |
1709 | |
1710 | /* This routine writes packets to the network. It advances the |
1711 | * send_head. This happens as incoming acks open up the remote |
1712 | * window for us. |
1713 | * |
1714 | * LARGESEND note: !tcp_urg_mode is overkill, only frames between |
1715 | * snd_up-64k-mss .. snd_up cannot be large. However, taking into |
1716 | * account rare use of URG, this is not a big flaw. |
1717 | * |
1718 | * Returns 1, if no segments are in flight and we have queued segments, but |
1719 | * cannot send anything now because of SWS or another problem. |
1720 | */ |
1721 | static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, |
1722 | int push_one, gfp_t gfp) |
1723 | { |
1724 | struct tcp_sock *tp = tcp_sk(sk); |
1725 | struct sk_buff *skb; |
1726 | unsigned int tso_segs, sent_pkts; |
1727 | int cwnd_quota; |
1728 | int result; |
1729 | |
1730 | sent_pkts = 0; |
1731 | |
1732 | if (!push_one) { |
1733 | /* Do MTU probing. */ |
1734 | result = tcp_mtu_probe(sk); |
1735 | if (!result) { |
1736 | return 0; |
1737 | } else if (result > 0) { |
1738 | sent_pkts = 1; |
1739 | } |
1740 | } |
1741 | |
1742 | while ((skb = tcp_send_head(sk))) { |
1743 | unsigned int limit; |
1744 | |
1745 | tso_segs = tcp_init_tso_segs(sk, skb, mss_now); |
1746 | BUG_ON(!tso_segs); |
1747 | |
1748 | cwnd_quota = tcp_cwnd_test(tp, skb); |
1749 | if (!cwnd_quota) |
1750 | break; |
1751 | |
1752 | if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) |
1753 | break; |
1754 | |
1755 | if (tso_segs == 1) { |
1756 | if (unlikely(!tcp_nagle_test(tp, skb, mss_now, |
1757 | (tcp_skb_is_last(sk, skb) ? |
1758 | nonagle : TCP_NAGLE_PUSH)))) |
1759 | break; |
1760 | } else { |
1761 | if (!push_one && tcp_tso_should_defer(sk, skb)) |
1762 | break; |
1763 | } |
1764 | |
1765 | limit = mss_now; |
1766 | if (tso_segs > 1 && !tcp_urg_mode(tp)) |
1767 | limit = tcp_mss_split_point(sk, skb, mss_now, |
1768 | cwnd_quota); |
1769 | |
1770 | if (skb->len > limit && |
1771 | unlikely(tso_fragment(sk, skb, limit, mss_now))) |
1772 | break; |
1773 | |
1774 | TCP_SKB_CB(skb)->when = tcp_time_stamp; |
1775 | |
1776 | if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp))) |
1777 | break; |
1778 | |
1779 | /* Advance the send_head. This one is sent out. |
1780 | * This call will increment packets_out. |
1781 | */ |
1782 | tcp_event_new_data_sent(sk, skb); |
1783 | |
1784 | tcp_minshall_update(tp, mss_now, skb); |
1785 | sent_pkts++; |
1786 | |
1787 | if (push_one) |
1788 | break; |
1789 | } |
1790 | |
1791 | if (likely(sent_pkts)) { |
1792 | tcp_cwnd_validate(sk); |
1793 | return 0; |
1794 | } |
1795 | return !tp->packets_out && tcp_send_head(sk); |
1796 | } |
1797 | |
1798 | /* Push out any pending frames which were held back due to |
1799 | * TCP_CORK or attempt at coalescing tiny packets. |
1800 | * The socket must be locked by the caller. |
1801 | */ |
1802 | void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, |
1803 | int nonagle) |
1804 | { |
1805 | /* If we are closed, the bytes will have to remain here. |
1806 | * In time closedown will finish, we empty the write queue and |
1807 | * all will be happy. |
1808 | */ |
1809 | if (unlikely(sk->sk_state == TCP_CLOSE)) |
1810 | return; |
1811 | |
1812 | if (tcp_write_xmit(sk, cur_mss, nonagle, 0, GFP_ATOMIC)) |
1813 | tcp_check_probe_timer(sk); |
1814 | } |
1815 | |
1816 | /* Send _single_ skb sitting at the send head. This function requires |
1817 | * true push pending frames to setup probe timer etc. |
1818 | */ |
1819 | void tcp_push_one(struct sock *sk, unsigned int mss_now) |
1820 | { |
1821 | struct sk_buff *skb = tcp_send_head(sk); |
1822 | |
1823 | BUG_ON(!skb || skb->len < mss_now); |
1824 | |
1825 | tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation); |
1826 | } |
1827 | |
1828 | /* This function returns the amount that we can raise the |
1829 | * usable window based on the following constraints |
1830 | * |
1831 | * 1. The window can never be shrunk once it is offered (RFC 793) |
1832 | * 2. We limit memory per socket |
1833 | * |
1834 | * RFC 1122: |
1835 | * "the suggested [SWS] avoidance algorithm for the receiver is to keep |
1836 | * RECV.NEXT + RCV.WIN fixed until: |
1837 | * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" |
1838 | * |
1839 | * i.e. don't raise the right edge of the window until you can raise |
1840 | * it at least MSS bytes. |
1841 | * |
1842 | * Unfortunately, the recommended algorithm breaks header prediction, |
1843 | * since header prediction assumes th->window stays fixed. |
1844 | * |
1845 | * Strictly speaking, keeping th->window fixed violates the receiver |
1846 | * side SWS prevention criteria. The problem is that under this rule |
1847 | * a stream of single byte packets will cause the right side of the |
1848 | * window to always advance by a single byte. |
1849 | * |
1850 | * Of course, if the sender implements sender side SWS prevention |
1851 | * then this will not be a problem. |
1852 | * |
1853 | * BSD seems to make the following compromise: |
1854 | * |
1855 | * If the free space is less than the 1/4 of the maximum |
1856 | * space available and the free space is less than 1/2 mss, |
1857 | * then set the window to 0. |
1858 | * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] |
1859 | * Otherwise, just prevent the window from shrinking |
1860 | * and from being larger than the largest representable value. |
1861 | * |
1862 | * This prevents incremental opening of the window in the regime |
1863 | * where TCP is limited by the speed of the reader side taking |
1864 | * data out of the TCP receive queue. It does nothing about |
1865 | * those cases where the window is constrained on the sender side |
1866 | * because the pipeline is full. |
1867 | * |
1868 | * BSD also seems to "accidentally" limit itself to windows that are a |
1869 | * multiple of MSS, at least until the free space gets quite small. |
1870 | * This would appear to be a side effect of the mbuf implementation. |
1871 | * Combining these two algorithms results in the observed behavior |
1872 | * of having a fixed window size at almost all times. |
1873 | * |
1874 | * Below we obtain similar behavior by forcing the offered window to |
1875 | * a multiple of the mss when it is feasible to do so. |
1876 | * |
1877 | * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. |
1878 | * Regular options like TIMESTAMP are taken into account. |
1879 | */ |
1880 | u32 __tcp_select_window(struct sock *sk) |
1881 | { |
1882 | struct inet_connection_sock *icsk = inet_csk(sk); |
1883 | struct tcp_sock *tp = tcp_sk(sk); |
1884 | /* MSS for the peer's data. Previous versions used mss_clamp |
1885 | * here. I don't know if the value based on our guesses |
1886 | * of peer's MSS is better for the performance. It's more correct |
1887 | * but may be worse for the performance because of rcv_mss |
1888 | * fluctuations. --SAW 1998/11/1 |
1889 | */ |
1890 | int mss = icsk->icsk_ack.rcv_mss; |
1891 | int free_space = tcp_space(sk); |
1892 | int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); |
1893 | int window; |
1894 | |
1895 | if (mss > full_space) |
1896 | mss = full_space; |
1897 | |
1898 | if (free_space < (full_space >> 1)) { |
1899 | icsk->icsk_ack.quick = 0; |
1900 | |
1901 | if (tcp_memory_pressure) |
1902 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, |
1903 | 4U * tp->advmss); |
1904 | |
1905 | if (free_space < mss) |
1906 | return 0; |
1907 | } |
1908 | |
1909 | if (free_space > tp->rcv_ssthresh) |
1910 | free_space = tp->rcv_ssthresh; |
1911 | |
1912 | /* Don't do rounding if we are using window scaling, since the |
1913 | * scaled window will not line up with the MSS boundary anyway. |
1914 | */ |
1915 | window = tp->rcv_wnd; |
1916 | if (tp->rx_opt.rcv_wscale) { |
1917 | window = free_space; |
1918 | |
1919 | /* Advertise enough space so that it won't get scaled away. |
1920 | * Import case: prevent zero window announcement if |
1921 | * 1<<rcv_wscale > mss. |
1922 | */ |
1923 | if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) |
1924 | window = (((window >> tp->rx_opt.rcv_wscale) + 1) |
1925 | << tp->rx_opt.rcv_wscale); |
1926 | } else { |
1927 | /* Get the largest window that is a nice multiple of mss. |
1928 | * Window clamp already applied above. |
1929 | * If our current window offering is within 1 mss of the |
1930 | * free space we just keep it. This prevents the divide |
1931 | * and multiply from happening most of the time. |
1932 | * We also don't do any window rounding when the free space |
1933 | * is too small. |
1934 | */ |
1935 | if (window <= free_space - mss || window > free_space) |
1936 | window = (free_space / mss) * mss; |
1937 | else if (mss == full_space && |
1938 | free_space > window + (full_space >> 1)) |
1939 | window = free_space; |
1940 | } |
1941 | |
1942 | return window; |
1943 | } |
1944 | |
1945 | /* Collapses two adjacent SKB's during retransmission. */ |
1946 | static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) |
1947 | { |
1948 | struct tcp_sock *tp = tcp_sk(sk); |
1949 | struct sk_buff *next_skb = tcp_write_queue_next(sk, skb); |
1950 | int skb_size, next_skb_size; |
1951 | |
1952 | skb_size = skb->len; |
1953 | next_skb_size = next_skb->len; |
1954 | |
1955 | BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1); |
1956 | |
1957 | tcp_highest_sack_combine(sk, next_skb, skb); |
1958 | |
1959 | tcp_unlink_write_queue(next_skb, sk); |
1960 | |
1961 | skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size), |
1962 | next_skb_size); |
1963 | |
1964 | if (next_skb->ip_summed == CHECKSUM_PARTIAL) |
1965 | skb->ip_summed = CHECKSUM_PARTIAL; |
1966 | |
1967 | if (skb->ip_summed != CHECKSUM_PARTIAL) |
1968 | skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); |
1969 | |
1970 | /* Update sequence range on original skb. */ |
1971 | TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; |
1972 | |
1973 | /* Merge over control information. This moves PSH/FIN etc. over */ |
1974 | TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(next_skb)->flags; |
1975 | |
1976 | /* All done, get rid of second SKB and account for it so |
1977 | * packet counting does not break. |
1978 | */ |
1979 | TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS; |
1980 | |
1981 | /* changed transmit queue under us so clear hints */ |
1982 | tcp_clear_retrans_hints_partial(tp); |
1983 | if (next_skb == tp->retransmit_skb_hint) |
1984 | tp->retransmit_skb_hint = skb; |
1985 | |
1986 | tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb)); |
1987 | |
1988 | sk_wmem_free_skb(sk, next_skb); |
1989 | } |
1990 | |
1991 | /* Check if coalescing SKBs is legal. */ |
1992 | static int tcp_can_collapse(struct sock *sk, struct sk_buff *skb) |
1993 | { |
1994 | if (tcp_skb_pcount(skb) > 1) |
1995 | return 0; |
1996 | /* TODO: SACK collapsing could be used to remove this condition */ |
1997 | if (skb_shinfo(skb)->nr_frags != 0) |
1998 | return 0; |
1999 | if (skb_cloned(skb)) |
2000 | return 0; |
2001 | if (skb == tcp_send_head(sk)) |
2002 | return 0; |
2003 | /* Some heurestics for collapsing over SACK'd could be invented */ |
2004 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) |
2005 | return 0; |
2006 | |
2007 | return 1; |
2008 | } |
2009 | |
2010 | /* Collapse packets in the retransmit queue to make to create |
2011 | * less packets on the wire. This is only done on retransmission. |
2012 | */ |
2013 | static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, |
2014 | int space) |
2015 | { |
2016 | struct tcp_sock *tp = tcp_sk(sk); |
2017 | struct sk_buff *skb = to, *tmp; |
2018 | int first = 1; |
2019 | |
2020 | if (!sysctl_tcp_retrans_collapse) |
2021 | return; |
2022 | if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) |
2023 | return; |
2024 | |
2025 | tcp_for_write_queue_from_safe(skb, tmp, sk) { |
2026 | if (!tcp_can_collapse(sk, skb)) |
2027 | break; |
2028 | |
2029 | space -= skb->len; |
2030 | |
2031 | if (first) { |
2032 | first = 0; |
2033 | continue; |
2034 | } |
2035 | |
2036 | if (space < 0) |
2037 | break; |
2038 | /* Punt if not enough space exists in the first SKB for |
2039 | * the data in the second |
2040 | */ |
2041 | if (skb->len > skb_tailroom(to)) |
2042 | break; |
2043 | |
2044 | if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp))) |
2045 | break; |
2046 | |
2047 | tcp_collapse_retrans(sk, to); |
2048 | } |
2049 | } |
2050 | |
2051 | /* This retransmits one SKB. Policy decisions and retransmit queue |
2052 | * state updates are done by the caller. Returns non-zero if an |
2053 | * error occurred which prevented the send. |
2054 | */ |
2055 | int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) |
2056 | { |
2057 | struct tcp_sock *tp = tcp_sk(sk); |
2058 | struct inet_connection_sock *icsk = inet_csk(sk); |
2059 | unsigned int cur_mss; |
2060 | int err; |
2061 | |
2062 | /* Inconslusive MTU probe */ |
2063 | if (icsk->icsk_mtup.probe_size) { |
2064 | icsk->icsk_mtup.probe_size = 0; |
2065 | } |
2066 | |
2067 | /* Do not sent more than we queued. 1/4 is reserved for possible |
2068 | * copying overhead: fragmentation, tunneling, mangling etc. |
2069 | */ |
2070 | if (atomic_read(&sk->sk_wmem_alloc) > |
2071 | min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) |
2072 | return -EAGAIN; |
2073 | |
2074 | if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { |
2075 | if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) |
2076 | BUG(); |
2077 | if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) |
2078 | return -ENOMEM; |
2079 | } |
2080 | |
2081 | if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) |
2082 | return -EHOSTUNREACH; /* Routing failure or similar. */ |
2083 | |
2084 | cur_mss = tcp_current_mss(sk); |
2085 | |
2086 | /* If receiver has shrunk his window, and skb is out of |
2087 | * new window, do not retransmit it. The exception is the |
2088 | * case, when window is shrunk to zero. In this case |
2089 | * our retransmit serves as a zero window probe. |
2090 | */ |
2091 | if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) && |
2092 | TCP_SKB_CB(skb)->seq != tp->snd_una) |
2093 | return -EAGAIN; |
2094 | |
2095 | if (skb->len > cur_mss) { |
2096 | if (tcp_fragment(sk, skb, cur_mss, cur_mss)) |
2097 | return -ENOMEM; /* We'll try again later. */ |
2098 | } else { |
2099 | int oldpcount = tcp_skb_pcount(skb); |
2100 | |
2101 | if (unlikely(oldpcount > 1)) { |
2102 | tcp_init_tso_segs(sk, skb, cur_mss); |
2103 | tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb)); |
2104 | } |
2105 | } |
2106 | |
2107 | tcp_retrans_try_collapse(sk, skb, cur_mss); |
2108 | |
2109 | /* Some Solaris stacks overoptimize and ignore the FIN on a |
2110 | * retransmit when old data is attached. So strip it off |
2111 | * since it is cheap to do so and saves bytes on the network. |
2112 | */ |
2113 | if (skb->len > 0 && |
2114 | (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && |
2115 | tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) { |
2116 | if (!pskb_trim(skb, 0)) { |
2117 | /* Reuse, even though it does some unnecessary work */ |
2118 | tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1, |
2119 | TCP_SKB_CB(skb)->flags); |
2120 | skb->ip_summed = CHECKSUM_NONE; |
2121 | } |
2122 | } |
2123 | |
2124 | /* Make a copy, if the first transmission SKB clone we made |
2125 | * is still in somebody's hands, else make a clone. |
2126 | */ |
2127 | TCP_SKB_CB(skb)->when = tcp_time_stamp; |
2128 | |
2129 | err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); |
2130 | |
2131 | if (err == 0) { |
2132 | /* Update global TCP statistics. */ |
2133 | TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS); |
2134 | |
2135 | tp->total_retrans++; |
2136 | |
2137 | #if FASTRETRANS_DEBUG > 0 |
2138 | if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { |
2139 | if (net_ratelimit()) |
2140 | printk(KERN_DEBUG "retrans_out leaked.\n"); |
2141 | } |
2142 | #endif |
2143 | if (!tp->retrans_out) |
2144 | tp->lost_retrans_low = tp->snd_nxt; |
2145 | TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; |
2146 | tp->retrans_out += tcp_skb_pcount(skb); |
2147 | |
2148 | /* Save stamp of the first retransmit. */ |
2149 | if (!tp->retrans_stamp) |
2150 | tp->retrans_stamp = TCP_SKB_CB(skb)->when; |
2151 | |
2152 | tp->undo_retrans++; |
2153 | |
2154 | /* snd_nxt is stored to detect loss of retransmitted segment, |
2155 | * see tcp_input.c tcp_sacktag_write_queue(). |
2156 | */ |
2157 | TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; |
2158 | } |
2159 | return err; |
2160 | } |
2161 | |
2162 | /* Check if we forward retransmits are possible in the current |
2163 | * window/congestion state. |
2164 | */ |
2165 | static int tcp_can_forward_retransmit(struct sock *sk) |
2166 | { |
2167 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2168 | struct tcp_sock *tp = tcp_sk(sk); |
2169 | |
2170 | /* Forward retransmissions are possible only during Recovery. */ |
2171 | if (icsk->icsk_ca_state != TCP_CA_Recovery) |
2172 | return 0; |
2173 | |
2174 | /* No forward retransmissions in Reno are possible. */ |
2175 | if (tcp_is_reno(tp)) |
2176 | return 0; |
2177 | |
2178 | /* Yeah, we have to make difficult choice between forward transmission |
2179 | * and retransmission... Both ways have their merits... |
2180 | * |
2181 | * For now we do not retransmit anything, while we have some new |
2182 | * segments to send. In the other cases, follow rule 3 for |
2183 | * NextSeg() specified in RFC3517. |
2184 | */ |
2185 | |
2186 | if (tcp_may_send_now(sk)) |
2187 | return 0; |
2188 | |
2189 | return 1; |
2190 | } |
2191 | |
2192 | /* This gets called after a retransmit timeout, and the initially |
2193 | * retransmitted data is acknowledged. It tries to continue |
2194 | * resending the rest of the retransmit queue, until either |
2195 | * we've sent it all or the congestion window limit is reached. |
2196 | * If doing SACK, the first ACK which comes back for a timeout |
2197 | * based retransmit packet might feed us FACK information again. |
2198 | * If so, we use it to avoid unnecessarily retransmissions. |
2199 | */ |
2200 | void tcp_xmit_retransmit_queue(struct sock *sk) |
2201 | { |
2202 | const struct inet_connection_sock *icsk = inet_csk(sk); |
2203 | struct tcp_sock *tp = tcp_sk(sk); |
2204 | struct sk_buff *skb; |
2205 | struct sk_buff *hole = NULL; |
2206 | u32 last_lost; |
2207 | int mib_idx; |
2208 | int fwd_rexmitting = 0; |
2209 | |
2210 | if (!tp->lost_out) |
2211 | tp->retransmit_high = tp->snd_una; |
2212 | |
2213 | if (tp->retransmit_skb_hint) { |
2214 | skb = tp->retransmit_skb_hint; |
2215 | last_lost = TCP_SKB_CB(skb)->end_seq; |
2216 | if (after(last_lost, tp->retransmit_high)) |
2217 | last_lost = tp->retransmit_high; |
2218 | } else { |
2219 | skb = tcp_write_queue_head(sk); |
2220 | last_lost = tp->snd_una; |
2221 | } |
2222 | |
2223 | tcp_for_write_queue_from(skb, sk) { |
2224 | __u8 sacked = TCP_SKB_CB(skb)->sacked; |
2225 | |
2226 | if (skb == tcp_send_head(sk)) |
2227 | break; |
2228 | /* we could do better than to assign each time */ |
2229 | if (hole == NULL) |
2230 | tp->retransmit_skb_hint = skb; |
2231 | |
2232 | /* Assume this retransmit will generate |
2233 | * only one packet for congestion window |
2234 | * calculation purposes. This works because |
2235 | * tcp_retransmit_skb() will chop up the |
2236 | * packet to be MSS sized and all the |
2237 | * packet counting works out. |
2238 | */ |
2239 | if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) |
2240 | return; |
2241 | |
2242 | if (fwd_rexmitting) { |
2243 | begin_fwd: |
2244 | if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp))) |
2245 | break; |
2246 | mib_idx = LINUX_MIB_TCPFORWARDRETRANS; |
2247 | |
2248 | } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) { |
2249 | tp->retransmit_high = last_lost; |
2250 | if (!tcp_can_forward_retransmit(sk)) |
2251 | break; |
2252 | /* Backtrack if necessary to non-L'ed skb */ |
2253 | if (hole != NULL) { |
2254 | skb = hole; |
2255 | hole = NULL; |
2256 | } |
2257 | fwd_rexmitting = 1; |
2258 | goto begin_fwd; |
2259 | |
2260 | } else if (!(sacked & TCPCB_LOST)) { |
2261 | if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED))) |
2262 | hole = skb; |
2263 | continue; |
2264 | |
2265 | } else { |
2266 | last_lost = TCP_SKB_CB(skb)->end_seq; |
2267 | if (icsk->icsk_ca_state != TCP_CA_Loss) |
2268 | mib_idx = LINUX_MIB_TCPFASTRETRANS; |
2269 | else |
2270 | mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS; |
2271 | } |
2272 | |
2273 | if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS)) |
2274 | continue; |
2275 | |
2276 | if (tcp_retransmit_skb(sk, skb)) |
2277 | return; |
2278 | NET_INC_STATS_BH(sock_net(sk), mib_idx); |
2279 | |
2280 | if (skb == tcp_write_queue_head(sk)) |
2281 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
2282 | inet_csk(sk)->icsk_rto, |
2283 | TCP_RTO_MAX); |
2284 | } |
2285 | } |
2286 | |
2287 | /* Send a fin. The caller locks the socket for us. This cannot be |
2288 | * allowed to fail queueing a FIN frame under any circumstances. |
2289 | */ |
2290 | void tcp_send_fin(struct sock *sk) |
2291 | { |
2292 | struct tcp_sock *tp = tcp_sk(sk); |
2293 | struct sk_buff *skb = tcp_write_queue_tail(sk); |
2294 | int mss_now; |
2295 | |
2296 | /* Optimization, tack on the FIN if we have a queue of |
2297 | * unsent frames. But be careful about outgoing SACKS |
2298 | * and IP options. |
2299 | */ |
2300 | mss_now = tcp_current_mss(sk); |
2301 | |
2302 | if (tcp_send_head(sk) != NULL) { |
2303 | TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN; |
2304 | TCP_SKB_CB(skb)->end_seq++; |
2305 | tp->write_seq++; |
2306 | } else { |
2307 | /* Socket is locked, keep trying until memory is available. */ |
2308 | for (;;) { |
2309 | skb = alloc_skb_fclone(MAX_TCP_HEADER, |
2310 | sk->sk_allocation); |
2311 | if (skb) |
2312 | break; |
2313 | yield(); |
2314 | } |
2315 | |
2316 | /* Reserve space for headers and prepare control bits. */ |
2317 | skb_reserve(skb, MAX_TCP_HEADER); |
2318 | /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ |
2319 | tcp_init_nondata_skb(skb, tp->write_seq, |
2320 | TCPCB_FLAG_ACK | TCPCB_FLAG_FIN); |
2321 | tcp_queue_skb(sk, skb); |
2322 | } |
2323 | __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF); |
2324 | } |
2325 | |
2326 | /* We get here when a process closes a file descriptor (either due to |
2327 | * an explicit close() or as a byproduct of exit()'ing) and there |
2328 | * was unread data in the receive queue. This behavior is recommended |
2329 | * by RFC 2525, section 2.17. -DaveM |
2330 | */ |
2331 | void tcp_send_active_reset(struct sock *sk, gfp_t priority) |
2332 | { |
2333 | struct sk_buff *skb; |
2334 | |
2335 | /* NOTE: No TCP options attached and we never retransmit this. */ |
2336 | skb = alloc_skb(MAX_TCP_HEADER, priority); |
2337 | if (!skb) { |
2338 | NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); |
2339 | return; |
2340 | } |
2341 | |
2342 | /* Reserve space for headers and prepare control bits. */ |
2343 | skb_reserve(skb, MAX_TCP_HEADER); |
2344 | tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk), |
2345 | TCPCB_FLAG_ACK | TCPCB_FLAG_RST); |
2346 | /* Send it off. */ |
2347 | TCP_SKB_CB(skb)->when = tcp_time_stamp; |
2348 | if (tcp_transmit_skb(sk, skb, 0, priority)) |
2349 | NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); |
2350 | |
2351 | TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS); |
2352 | } |
2353 | |
2354 | /* Send a crossed SYN-ACK during socket establishment. |
2355 | * WARNING: This routine must only be called when we have already sent |
2356 | * a SYN packet that crossed the incoming SYN that caused this routine |
2357 | * to get called. If this assumption fails then the initial rcv_wnd |
2358 | * and rcv_wscale values will not be correct. |
2359 | */ |
2360 | int tcp_send_synack(struct sock *sk) |
2361 | { |
2362 | struct sk_buff *skb; |
2363 | |
2364 | skb = tcp_write_queue_head(sk); |
2365 | if (skb == NULL || !(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN)) { |
2366 | printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n"); |
2367 | return -EFAULT; |
2368 | } |
2369 | if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_ACK)) { |
2370 | if (skb_cloned(skb)) { |
2371 | struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); |
2372 | if (nskb == NULL) |
2373 | return -ENOMEM; |
2374 | tcp_unlink_write_queue(skb, sk); |
2375 | skb_header_release(nskb); |
2376 | __tcp_add_write_queue_head(sk, nskb); |
2377 | sk_wmem_free_skb(sk, skb); |
2378 | sk->sk_wmem_queued += nskb->truesize; |
2379 | sk_mem_charge(sk, nskb->truesize); |
2380 | skb = nskb; |
2381 | } |
2382 | |
2383 | TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK; |
2384 | TCP_ECN_send_synack(tcp_sk(sk), skb); |
2385 | } |
2386 | TCP_SKB_CB(skb)->when = tcp_time_stamp; |
2387 | return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); |
2388 | } |
2389 | |
2390 | /* Prepare a SYN-ACK. */ |
2391 | struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, |
2392 | struct request_sock *req, |
2393 | struct request_values *rvp) |
2394 | { |
2395 | struct tcp_out_options opts; |
2396 | struct tcp_extend_values *xvp = tcp_xv(rvp); |
2397 | struct inet_request_sock *ireq = inet_rsk(req); |
2398 | struct tcp_sock *tp = tcp_sk(sk); |
2399 | const struct tcp_cookie_values *cvp = tp->cookie_values; |
2400 | struct tcphdr *th; |
2401 | struct sk_buff *skb; |
2402 | struct tcp_md5sig_key *md5; |
2403 | int tcp_header_size; |
2404 | int mss; |
2405 | int s_data_desired = 0; |
2406 | |
2407 | if (cvp != NULL && cvp->s_data_constant && cvp->s_data_desired) |
2408 | s_data_desired = cvp->s_data_desired; |
2409 | skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15 + s_data_desired, 1, GFP_ATOMIC); |
2410 | if (skb == NULL) |
2411 | return NULL; |
2412 | |
2413 | /* Reserve space for headers. */ |
2414 | skb_reserve(skb, MAX_TCP_HEADER); |
2415 | |
2416 | skb_dst_set(skb, dst_clone(dst)); |
2417 | |
2418 | mss = dst_metric(dst, RTAX_ADVMSS); |
2419 | if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss) |
2420 | mss = tp->rx_opt.user_mss; |
2421 | |
2422 | if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */ |
2423 | __u8 rcv_wscale; |
2424 | /* Set this up on the first call only */ |
2425 | req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW); |
2426 | /* tcp_full_space because it is guaranteed to be the first packet */ |
2427 | tcp_select_initial_window(tcp_full_space(sk), |
2428 | mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0), |
2429 | &req->rcv_wnd, |
2430 | &req->window_clamp, |
2431 | ireq->wscale_ok, |
2432 | &rcv_wscale, |
2433 | dst_metric(dst, RTAX_INITRWND)); |
2434 | ireq->rcv_wscale = rcv_wscale; |
2435 | } |
2436 | |
2437 | memset(&opts, 0, sizeof(opts)); |
2438 | #ifdef CONFIG_SYN_COOKIES |
2439 | if (unlikely(req->cookie_ts)) |
2440 | TCP_SKB_CB(skb)->when = cookie_init_timestamp(req); |
2441 | else |
2442 | #endif |
2443 | TCP_SKB_CB(skb)->when = tcp_time_stamp; |
2444 | tcp_header_size = tcp_synack_options(sk, req, mss, |
2445 | skb, &opts, &md5, xvp) |
2446 | + sizeof(*th); |
2447 | |
2448 | skb_push(skb, tcp_header_size); |
2449 | skb_reset_transport_header(skb); |
2450 | |
2451 | th = tcp_hdr(skb); |
2452 | memset(th, 0, sizeof(struct tcphdr)); |
2453 | th->syn = 1; |
2454 | th->ack = 1; |
2455 | TCP_ECN_make_synack(req, th); |
2456 | th->source = ireq->loc_port; |
2457 | th->dest = ireq->rmt_port; |
2458 | /* Setting of flags are superfluous here for callers (and ECE is |
2459 | * not even correctly set) |
2460 | */ |
2461 | tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn, |
2462 | TCPCB_FLAG_SYN | TCPCB_FLAG_ACK); |
2463 | |
2464 | if (OPTION_COOKIE_EXTENSION & opts.options) { |
2465 | if (s_data_desired) { |
2466 | u8 *buf = skb_put(skb, s_data_desired); |
2467 | |
2468 | /* copy data directly from the listening socket. */ |
2469 | memcpy(buf, cvp->s_data_payload, s_data_desired); |
2470 | TCP_SKB_CB(skb)->end_seq += s_data_desired; |
2471 | } |
2472 | |
2473 | if (opts.hash_size > 0) { |
2474 | __u32 workspace[SHA_WORKSPACE_WORDS]; |
2475 | u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS]; |
2476 | u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1]; |
2477 | |
2478 | /* Secret recipe depends on the Timestamp, (future) |
2479 | * Sequence and Acknowledgment Numbers, Initiator |
2480 | * Cookie, and others handled by IP variant caller. |
2481 | */ |
2482 | *tail-- ^= opts.tsval; |
2483 | *tail-- ^= tcp_rsk(req)->rcv_isn + 1; |
2484 | *tail-- ^= TCP_SKB_CB(skb)->seq + 1; |
2485 | |
2486 | /* recommended */ |
2487 | *tail-- ^= ((th->dest << 16) | th->source); |
2488 | *tail-- ^= (u32)(unsigned long)cvp; /* per sockopt */ |
2489 | |
2490 | sha_transform((__u32 *)&xvp->cookie_bakery[0], |
2491 | (char *)mess, |
2492 | &workspace[0]); |
2493 | opts.hash_location = |
2494 | (__u8 *)&xvp->cookie_bakery[0]; |
2495 | } |
2496 | } |
2497 | |
2498 | th->seq = htonl(TCP_SKB_CB(skb)->seq); |
2499 | th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1); |
2500 | |
2501 | /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ |
2502 | th->window = htons(min(req->rcv_wnd, 65535U)); |
2503 | tcp_options_write((__be32 *)(th + 1), tp, &opts); |
2504 | th->doff = (tcp_header_size >> 2); |
2505 | TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS); |
2506 | |
2507 | #ifdef CONFIG_TCP_MD5SIG |
2508 | /* Okay, we have all we need - do the md5 hash if needed */ |
2509 | if (md5) { |
2510 | tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, |
2511 | md5, NULL, req, skb); |
2512 | } |
2513 | #endif |
2514 | |
2515 | return skb; |
2516 | } |
2517 | |
2518 | /* Do all connect socket setups that can be done AF independent. */ |
2519 | static void tcp_connect_init(struct sock *sk) |
2520 | { |
2521 | struct dst_entry *dst = __sk_dst_get(sk); |
2522 | struct tcp_sock *tp = tcp_sk(sk); |
2523 | __u8 rcv_wscale; |
2524 | |
2525 | /* We'll fix this up when we get a response from the other end. |
2526 | * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. |
2527 | */ |
2528 | tp->tcp_header_len = sizeof(struct tcphdr) + |
2529 | (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); |
2530 | |
2531 | #ifdef CONFIG_TCP_MD5SIG |
2532 | if (tp->af_specific->md5_lookup(sk, sk) != NULL) |
2533 | tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; |
2534 | #endif |
2535 | |
2536 | /* If user gave his TCP_MAXSEG, record it to clamp */ |
2537 | if (tp->rx_opt.user_mss) |
2538 | tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; |
2539 | tp->max_window = 0; |
2540 | tcp_mtup_init(sk); |
2541 | tcp_sync_mss(sk, dst_mtu(dst)); |
2542 | |
2543 | if (!tp->window_clamp) |
2544 | tp->window_clamp = dst_metric(dst, RTAX_WINDOW); |
2545 | tp->advmss = dst_metric(dst, RTAX_ADVMSS); |
2546 | if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss) |
2547 | tp->advmss = tp->rx_opt.user_mss; |
2548 | |
2549 | tcp_initialize_rcv_mss(sk); |
2550 | |
2551 | tcp_select_initial_window(tcp_full_space(sk), |
2552 | tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), |
2553 | &tp->rcv_wnd, |
2554 | &tp->window_clamp, |
2555 | sysctl_tcp_window_scaling, |
2556 | &rcv_wscale, |
2557 | dst_metric(dst, RTAX_INITRWND)); |
2558 | |
2559 | tp->rx_opt.rcv_wscale = rcv_wscale; |
2560 | tp->rcv_ssthresh = tp->rcv_wnd; |
2561 | |
2562 | sk->sk_err = 0; |
2563 | sock_reset_flag(sk, SOCK_DONE); |
2564 | tp->snd_wnd = 0; |
2565 | tcp_init_wl(tp, 0); |
2566 | tp->snd_una = tp->write_seq; |
2567 | tp->snd_sml = tp->write_seq; |
2568 | tp->snd_up = tp->write_seq; |
2569 | tp->rcv_nxt = 0; |
2570 | tp->rcv_wup = 0; |
2571 | tp->copied_seq = 0; |
2572 | |
2573 | inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; |
2574 | inet_csk(sk)->icsk_retransmits = 0; |
2575 | tcp_clear_retrans(tp); |
2576 | } |
2577 | |
2578 | /* Build a SYN and send it off. */ |
2579 | int tcp_connect(struct sock *sk) |
2580 | { |
2581 | struct tcp_sock *tp = tcp_sk(sk); |
2582 | struct sk_buff *buff; |
2583 | |
2584 | tcp_connect_init(sk); |
2585 | |
2586 | buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation); |
2587 | if (unlikely(buff == NULL)) |
2588 | return -ENOBUFS; |
2589 | |
2590 | /* Reserve space for headers. */ |
2591 | skb_reserve(buff, MAX_TCP_HEADER); |
2592 | |
2593 | tp->snd_nxt = tp->write_seq; |
2594 | tcp_init_nondata_skb(buff, tp->write_seq++, TCPCB_FLAG_SYN); |
2595 | TCP_ECN_send_syn(sk, buff); |
2596 | |
2597 | /* Send it off. */ |
2598 | TCP_SKB_CB(buff)->when = tcp_time_stamp; |
2599 | tp->retrans_stamp = TCP_SKB_CB(buff)->when; |
2600 | skb_header_release(buff); |
2601 | __tcp_add_write_queue_tail(sk, buff); |
2602 | sk->sk_wmem_queued += buff->truesize; |
2603 | sk_mem_charge(sk, buff->truesize); |
2604 | tp->packets_out += tcp_skb_pcount(buff); |
2605 | tcp_transmit_skb(sk, buff, 1, sk->sk_allocation); |
2606 | |
2607 | /* We change tp->snd_nxt after the tcp_transmit_skb() call |
2608 | * in order to make this packet get counted in tcpOutSegs. |
2609 | */ |
2610 | tp->snd_nxt = tp->write_seq; |
2611 | tp->pushed_seq = tp->write_seq; |
2612 | TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS); |
2613 | |
2614 | /* Timer for repeating the SYN until an answer. */ |
2615 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, |
2616 | inet_csk(sk)->icsk_rto, TCP_RTO_MAX); |
2617 | return 0; |
2618 | } |
2619 | |
2620 | /* Send out a delayed ack, the caller does the policy checking |
2621 | * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() |
2622 | * for details. |
2623 | */ |
2624 | void tcp_send_delayed_ack(struct sock *sk) |
2625 | { |
2626 | struct inet_connection_sock *icsk = inet_csk(sk); |
2627 | int ato = icsk->icsk_ack.ato; |
2628 | unsigned long timeout; |
2629 | |
2630 | if (ato > TCP_DELACK_MIN) { |
2631 | const struct tcp_sock *tp = tcp_sk(sk); |
2632 | int max_ato = HZ / 2; |
2633 | |
2634 | if (icsk->icsk_ack.pingpong || |
2635 | (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) |
2636 | max_ato = TCP_DELACK_MAX; |
2637 | |
2638 | /* Slow path, intersegment interval is "high". */ |
2639 | |
2640 | /* If some rtt estimate is known, use it to bound delayed ack. |
2641 | * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements |
2642 | * directly. |
2643 | */ |
2644 | if (tp->srtt) { |
2645 | int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN); |
2646 | |
2647 | if (rtt < max_ato) |
2648 | max_ato = rtt; |
2649 | } |
2650 | |
2651 | ato = min(ato, max_ato); |
2652 | } |
2653 | |
2654 | /* Stay within the limit we were given */ |
2655 | timeout = jiffies + ato; |
2656 | |
2657 | /* Use new timeout only if there wasn't a older one earlier. */ |
2658 | if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { |
2659 | /* If delack timer was blocked or is about to expire, |
2660 | * send ACK now. |
2661 | */ |
2662 | if (icsk->icsk_ack.blocked || |
2663 | time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { |
2664 | tcp_send_ack(sk); |
2665 | return; |
2666 | } |
2667 | |
2668 | if (!time_before(timeout, icsk->icsk_ack.timeout)) |
2669 | timeout = icsk->icsk_ack.timeout; |
2670 | } |
2671 | icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; |
2672 | icsk->icsk_ack.timeout = timeout; |
2673 | sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); |
2674 | } |
2675 | |
2676 | /* This routine sends an ack and also updates the window. */ |
2677 | void tcp_send_ack(struct sock *sk) |
2678 | { |
2679 | struct sk_buff *buff; |
2680 | |
2681 | /* If we have been reset, we may not send again. */ |
2682 | if (sk->sk_state == TCP_CLOSE) |
2683 | return; |
2684 | |
2685 | /* We are not putting this on the write queue, so |
2686 | * tcp_transmit_skb() will set the ownership to this |
2687 | * sock. |
2688 | */ |
2689 | buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); |
2690 | if (buff == NULL) { |
2691 | inet_csk_schedule_ack(sk); |
2692 | inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; |
2693 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, |
2694 | TCP_DELACK_MAX, TCP_RTO_MAX); |
2695 | return; |
2696 | } |
2697 | |
2698 | /* Reserve space for headers and prepare control bits. */ |
2699 | skb_reserve(buff, MAX_TCP_HEADER); |
2700 | tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPCB_FLAG_ACK); |
2701 | |
2702 | /* Send it off, this clears delayed acks for us. */ |
2703 | TCP_SKB_CB(buff)->when = tcp_time_stamp; |
2704 | tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC); |
2705 | } |
2706 | |
2707 | /* This routine sends a packet with an out of date sequence |
2708 | * number. It assumes the other end will try to ack it. |
2709 | * |
2710 | * Question: what should we make while urgent mode? |
2711 | * 4.4BSD forces sending single byte of data. We cannot send |
2712 | * out of window data, because we have SND.NXT==SND.MAX... |
2713 | * |
2714 | * Current solution: to send TWO zero-length segments in urgent mode: |
2715 | * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is |
2716 | * out-of-date with SND.UNA-1 to probe window. |
2717 | */ |
2718 | static int tcp_xmit_probe_skb(struct sock *sk, int urgent) |
2719 | { |
2720 | struct tcp_sock *tp = tcp_sk(sk); |
2721 | struct sk_buff *skb; |
2722 | |
2723 | /* We don't queue it, tcp_transmit_skb() sets ownership. */ |
2724 | skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); |
2725 | if (skb == NULL) |
2726 | return -1; |
2727 | |
2728 | /* Reserve space for headers and set control bits. */ |
2729 | skb_reserve(skb, MAX_TCP_HEADER); |
2730 | /* Use a previous sequence. This should cause the other |
2731 | * end to send an ack. Don't queue or clone SKB, just |
2732 | * send it. |
2733 | */ |
2734 | tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPCB_FLAG_ACK); |
2735 | TCP_SKB_CB(skb)->when = tcp_time_stamp; |
2736 | return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); |
2737 | } |
2738 | |
2739 | /* Initiate keepalive or window probe from timer. */ |
2740 | int tcp_write_wakeup(struct sock *sk) |
2741 | { |
2742 | struct tcp_sock *tp = tcp_sk(sk); |
2743 | struct sk_buff *skb; |
2744 | |
2745 | if (sk->sk_state == TCP_CLOSE) |
2746 | return -1; |
2747 | |
2748 | if ((skb = tcp_send_head(sk)) != NULL && |
2749 | before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) { |
2750 | int err; |
2751 | unsigned int mss = tcp_current_mss(sk); |
2752 | unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; |
2753 | |
2754 | if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) |
2755 | tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; |
2756 | |
2757 | /* We are probing the opening of a window |
2758 | * but the window size is != 0 |
2759 | * must have been a result SWS avoidance ( sender ) |
2760 | */ |
2761 | if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || |
2762 | skb->len > mss) { |
2763 | seg_size = min(seg_size, mss); |
2764 | TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; |
2765 | if (tcp_fragment(sk, skb, seg_size, mss)) |
2766 | return -1; |
2767 | } else if (!tcp_skb_pcount(skb)) |
2768 | tcp_set_skb_tso_segs(sk, skb, mss); |
2769 | |
2770 | TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; |
2771 | TCP_SKB_CB(skb)->when = tcp_time_stamp; |
2772 | err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); |
2773 | if (!err) |
2774 | tcp_event_new_data_sent(sk, skb); |
2775 | return err; |
2776 | } else { |
2777 | if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF)) |
2778 | tcp_xmit_probe_skb(sk, 1); |
2779 | return tcp_xmit_probe_skb(sk, 0); |
2780 | } |
2781 | } |
2782 | |
2783 | /* A window probe timeout has occurred. If window is not closed send |
2784 | * a partial packet else a zero probe. |
2785 | */ |
2786 | void tcp_send_probe0(struct sock *sk) |
2787 | { |
2788 | struct inet_connection_sock *icsk = inet_csk(sk); |
2789 | struct tcp_sock *tp = tcp_sk(sk); |
2790 | int err; |
2791 | |
2792 | err = tcp_write_wakeup(sk); |
2793 | |
2794 | if (tp->packets_out || !tcp_send_head(sk)) { |
2795 | /* Cancel probe timer, if it is not required. */ |
2796 | icsk->icsk_probes_out = 0; |
2797 | icsk->icsk_backoff = 0; |
2798 | return; |
2799 | } |
2800 | |
2801 | if (err <= 0) { |
2802 | if (icsk->icsk_backoff < sysctl_tcp_retries2) |
2803 | icsk->icsk_backoff++; |
2804 | icsk->icsk_probes_out++; |
2805 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, |
2806 | min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), |
2807 | TCP_RTO_MAX); |
2808 | } else { |
2809 | /* If packet was not sent due to local congestion, |
2810 | * do not backoff and do not remember icsk_probes_out. |
2811 | * Let local senders to fight for local resources. |
2812 | * |
2813 | * Use accumulated backoff yet. |
2814 | */ |
2815 | if (!icsk->icsk_probes_out) |
2816 | icsk->icsk_probes_out = 1; |
2817 | inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, |
2818 | min(icsk->icsk_rto << icsk->icsk_backoff, |
2819 | TCP_RESOURCE_PROBE_INTERVAL), |
2820 | TCP_RTO_MAX); |
2821 | } |
2822 | } |
2823 | |
2824 | EXPORT_SYMBOL(tcp_select_initial_window); |
2825 | EXPORT_SYMBOL(tcp_connect); |
2826 | EXPORT_SYMBOL(tcp_make_synack); |
2827 | EXPORT_SYMBOL(tcp_simple_retransmit); |
2828 | EXPORT_SYMBOL(tcp_sync_mss); |
2829 | EXPORT_SYMBOL(tcp_mtup_init); |
2830 |
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