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1da177e4 LT |
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 | * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $ | |
9 | * | |
02c30a84 | 10 | * Authors: Ross Biro |
1da177e4 LT |
11 | * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> |
12 | * Mark Evans, <evansmp@uhura.aston.ac.uk> | |
13 | * Corey Minyard <wf-rch!minyard@relay.EU.net> | |
14 | * Florian La Roche, <flla@stud.uni-sb.de> | |
15 | * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> | |
16 | * Linus Torvalds, <torvalds@cs.helsinki.fi> | |
17 | * Alan Cox, <gw4pts@gw4pts.ampr.org> | |
18 | * Matthew Dillon, <dillon@apollo.west.oic.com> | |
19 | * Arnt Gulbrandsen, <agulbra@nvg.unit.no> | |
20 | * Jorge Cwik, <jorge@laser.satlink.net> | |
21 | */ | |
22 | ||
23 | /* | |
24 | * Changes: | |
25 | * Pedro Roque : Fast Retransmit/Recovery. | |
26 | * Two receive queues. | |
27 | * Retransmit queue handled by TCP. | |
28 | * Better retransmit timer handling. | |
29 | * New congestion avoidance. | |
30 | * Header prediction. | |
31 | * Variable renaming. | |
32 | * | |
33 | * Eric : Fast Retransmit. | |
34 | * Randy Scott : MSS option defines. | |
35 | * Eric Schenk : Fixes to slow start algorithm. | |
36 | * Eric Schenk : Yet another double ACK bug. | |
37 | * Eric Schenk : Delayed ACK bug fixes. | |
38 | * Eric Schenk : Floyd style fast retrans war avoidance. | |
39 | * David S. Miller : Don't allow zero congestion window. | |
40 | * Eric Schenk : Fix retransmitter so that it sends | |
41 | * next packet on ack of previous packet. | |
42 | * Andi Kleen : Moved open_request checking here | |
43 | * and process RSTs for open_requests. | |
44 | * Andi Kleen : Better prune_queue, and other fixes. | |
45 | * Andrey Savochkin: Fix RTT measurements in the presnce of | |
46 | * timestamps. | |
47 | * Andrey Savochkin: Check sequence numbers correctly when | |
48 | * removing SACKs due to in sequence incoming | |
49 | * data segments. | |
50 | * Andi Kleen: Make sure we never ack data there is not | |
51 | * enough room for. Also make this condition | |
52 | * a fatal error if it might still happen. | |
53 | * Andi Kleen: Add tcp_measure_rcv_mss to make | |
54 | * connections with MSS<min(MTU,ann. MSS) | |
55 | * work without delayed acks. | |
56 | * Andi Kleen: Process packets with PSH set in the | |
57 | * fast path. | |
58 | * J Hadi Salim: ECN support | |
59 | * Andrei Gurtov, | |
60 | * Pasi Sarolahti, | |
61 | * Panu Kuhlberg: Experimental audit of TCP (re)transmission | |
62 | * engine. Lots of bugs are found. | |
63 | * Pasi Sarolahti: F-RTO for dealing with spurious RTOs | |
1da177e4 LT |
64 | */ |
65 | ||
66 | #include <linux/config.h> | |
67 | #include <linux/mm.h> | |
68 | #include <linux/module.h> | |
69 | #include <linux/sysctl.h> | |
70 | #include <net/tcp.h> | |
71 | #include <net/inet_common.h> | |
72 | #include <linux/ipsec.h> | |
73 | #include <asm/unaligned.h> | |
74 | ||
75 | int sysctl_tcp_timestamps = 1; | |
76 | int sysctl_tcp_window_scaling = 1; | |
77 | int sysctl_tcp_sack = 1; | |
78 | int sysctl_tcp_fack = 1; | |
79 | int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH; | |
80 | int sysctl_tcp_ecn; | |
81 | int sysctl_tcp_dsack = 1; | |
82 | int sysctl_tcp_app_win = 31; | |
83 | int sysctl_tcp_adv_win_scale = 2; | |
84 | ||
85 | int sysctl_tcp_stdurg; | |
86 | int sysctl_tcp_rfc1337; | |
87 | int sysctl_tcp_max_orphans = NR_FILE; | |
88 | int sysctl_tcp_frto; | |
89 | int sysctl_tcp_nometrics_save; | |
1da177e4 LT |
90 | |
91 | int sysctl_tcp_moderate_rcvbuf = 1; | |
92 | ||
1da177e4 LT |
93 | #define FLAG_DATA 0x01 /* Incoming frame contained data. */ |
94 | #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ | |
95 | #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ | |
96 | #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ | |
97 | #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ | |
98 | #define FLAG_DATA_SACKED 0x20 /* New SACK. */ | |
99 | #define FLAG_ECE 0x40 /* ECE in this ACK */ | |
100 | #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ | |
101 | #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ | |
102 | ||
103 | #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) | |
104 | #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) | |
105 | #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) | |
106 | #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) | |
107 | ||
108 | #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0) | |
109 | #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2) | |
110 | #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4) | |
111 | ||
112 | #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) | |
113 | ||
114 | /* Adapt the MSS value used to make delayed ack decision to the | |
115 | * real world. | |
116 | */ | |
117 | static inline void tcp_measure_rcv_mss(struct tcp_sock *tp, | |
118 | struct sk_buff *skb) | |
119 | { | |
120 | unsigned int len, lss; | |
121 | ||
122 | lss = tp->ack.last_seg_size; | |
123 | tp->ack.last_seg_size = 0; | |
124 | ||
125 | /* skb->len may jitter because of SACKs, even if peer | |
126 | * sends good full-sized frames. | |
127 | */ | |
128 | len = skb->len; | |
129 | if (len >= tp->ack.rcv_mss) { | |
130 | tp->ack.rcv_mss = len; | |
131 | } else { | |
132 | /* Otherwise, we make more careful check taking into account, | |
133 | * that SACKs block is variable. | |
134 | * | |
135 | * "len" is invariant segment length, including TCP header. | |
136 | */ | |
137 | len += skb->data - skb->h.raw; | |
138 | if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) || | |
139 | /* If PSH is not set, packet should be | |
140 | * full sized, provided peer TCP is not badly broken. | |
141 | * This observation (if it is correct 8)) allows | |
142 | * to handle super-low mtu links fairly. | |
143 | */ | |
144 | (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && | |
145 | !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) { | |
146 | /* Subtract also invariant (if peer is RFC compliant), | |
147 | * tcp header plus fixed timestamp option length. | |
148 | * Resulting "len" is MSS free of SACK jitter. | |
149 | */ | |
150 | len -= tp->tcp_header_len; | |
151 | tp->ack.last_seg_size = len; | |
152 | if (len == lss) { | |
153 | tp->ack.rcv_mss = len; | |
154 | return; | |
155 | } | |
156 | } | |
157 | tp->ack.pending |= TCP_ACK_PUSHED; | |
158 | } | |
159 | } | |
160 | ||
161 | static void tcp_incr_quickack(struct tcp_sock *tp) | |
162 | { | |
163 | unsigned quickacks = tp->rcv_wnd/(2*tp->ack.rcv_mss); | |
164 | ||
165 | if (quickacks==0) | |
166 | quickacks=2; | |
167 | if (quickacks > tp->ack.quick) | |
168 | tp->ack.quick = min(quickacks, TCP_MAX_QUICKACKS); | |
169 | } | |
170 | ||
171 | void tcp_enter_quickack_mode(struct tcp_sock *tp) | |
172 | { | |
173 | tcp_incr_quickack(tp); | |
174 | tp->ack.pingpong = 0; | |
175 | tp->ack.ato = TCP_ATO_MIN; | |
176 | } | |
177 | ||
178 | /* Send ACKs quickly, if "quick" count is not exhausted | |
179 | * and the session is not interactive. | |
180 | */ | |
181 | ||
182 | static __inline__ int tcp_in_quickack_mode(struct tcp_sock *tp) | |
183 | { | |
184 | return (tp->ack.quick && !tp->ack.pingpong); | |
185 | } | |
186 | ||
187 | /* Buffer size and advertised window tuning. | |
188 | * | |
189 | * 1. Tuning sk->sk_sndbuf, when connection enters established state. | |
190 | */ | |
191 | ||
192 | static void tcp_fixup_sndbuf(struct sock *sk) | |
193 | { | |
194 | int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + | |
195 | sizeof(struct sk_buff); | |
196 | ||
197 | if (sk->sk_sndbuf < 3 * sndmem) | |
198 | sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); | |
199 | } | |
200 | ||
201 | /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) | |
202 | * | |
203 | * All tcp_full_space() is split to two parts: "network" buffer, allocated | |
204 | * forward and advertised in receiver window (tp->rcv_wnd) and | |
205 | * "application buffer", required to isolate scheduling/application | |
206 | * latencies from network. | |
207 | * window_clamp is maximal advertised window. It can be less than | |
208 | * tcp_full_space(), in this case tcp_full_space() - window_clamp | |
209 | * is reserved for "application" buffer. The less window_clamp is | |
210 | * the smoother our behaviour from viewpoint of network, but the lower | |
211 | * throughput and the higher sensitivity of the connection to losses. 8) | |
212 | * | |
213 | * rcv_ssthresh is more strict window_clamp used at "slow start" | |
214 | * phase to predict further behaviour of this connection. | |
215 | * It is used for two goals: | |
216 | * - to enforce header prediction at sender, even when application | |
217 | * requires some significant "application buffer". It is check #1. | |
218 | * - to prevent pruning of receive queue because of misprediction | |
219 | * of receiver window. Check #2. | |
220 | * | |
221 | * The scheme does not work when sender sends good segments opening | |
222 | * window and then starts to feed us spagetti. But it should work | |
223 | * in common situations. Otherwise, we have to rely on queue collapsing. | |
224 | */ | |
225 | ||
226 | /* Slow part of check#2. */ | |
227 | static int __tcp_grow_window(struct sock *sk, struct tcp_sock *tp, | |
228 | struct sk_buff *skb) | |
229 | { | |
230 | /* Optimize this! */ | |
231 | int truesize = tcp_win_from_space(skb->truesize)/2; | |
232 | int window = tcp_full_space(sk)/2; | |
233 | ||
234 | while (tp->rcv_ssthresh <= window) { | |
235 | if (truesize <= skb->len) | |
236 | return 2*tp->ack.rcv_mss; | |
237 | ||
238 | truesize >>= 1; | |
239 | window >>= 1; | |
240 | } | |
241 | return 0; | |
242 | } | |
243 | ||
244 | static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp, | |
245 | struct sk_buff *skb) | |
246 | { | |
247 | /* Check #1 */ | |
248 | if (tp->rcv_ssthresh < tp->window_clamp && | |
249 | (int)tp->rcv_ssthresh < tcp_space(sk) && | |
250 | !tcp_memory_pressure) { | |
251 | int incr; | |
252 | ||
253 | /* Check #2. Increase window, if skb with such overhead | |
254 | * will fit to rcvbuf in future. | |
255 | */ | |
256 | if (tcp_win_from_space(skb->truesize) <= skb->len) | |
257 | incr = 2*tp->advmss; | |
258 | else | |
259 | incr = __tcp_grow_window(sk, tp, skb); | |
260 | ||
261 | if (incr) { | |
262 | tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp); | |
263 | tp->ack.quick |= 1; | |
264 | } | |
265 | } | |
266 | } | |
267 | ||
268 | /* 3. Tuning rcvbuf, when connection enters established state. */ | |
269 | ||
270 | static void tcp_fixup_rcvbuf(struct sock *sk) | |
271 | { | |
272 | struct tcp_sock *tp = tcp_sk(sk); | |
273 | int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); | |
274 | ||
275 | /* Try to select rcvbuf so that 4 mss-sized segments | |
276 | * will fit to window and correspoding skbs will fit to our rcvbuf. | |
277 | * (was 3; 4 is minimum to allow fast retransmit to work.) | |
278 | */ | |
279 | while (tcp_win_from_space(rcvmem) < tp->advmss) | |
280 | rcvmem += 128; | |
281 | if (sk->sk_rcvbuf < 4 * rcvmem) | |
282 | sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); | |
283 | } | |
284 | ||
285 | /* 4. Try to fixup all. It is made iimediately after connection enters | |
286 | * established state. | |
287 | */ | |
288 | static void tcp_init_buffer_space(struct sock *sk) | |
289 | { | |
290 | struct tcp_sock *tp = tcp_sk(sk); | |
291 | int maxwin; | |
292 | ||
293 | if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) | |
294 | tcp_fixup_rcvbuf(sk); | |
295 | if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) | |
296 | tcp_fixup_sndbuf(sk); | |
297 | ||
298 | tp->rcvq_space.space = tp->rcv_wnd; | |
299 | ||
300 | maxwin = tcp_full_space(sk); | |
301 | ||
302 | if (tp->window_clamp >= maxwin) { | |
303 | tp->window_clamp = maxwin; | |
304 | ||
305 | if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) | |
306 | tp->window_clamp = max(maxwin - | |
307 | (maxwin >> sysctl_tcp_app_win), | |
308 | 4 * tp->advmss); | |
309 | } | |
310 | ||
311 | /* Force reservation of one segment. */ | |
312 | if (sysctl_tcp_app_win && | |
313 | tp->window_clamp > 2 * tp->advmss && | |
314 | tp->window_clamp + tp->advmss > maxwin) | |
315 | tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); | |
316 | ||
317 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); | |
318 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
319 | } | |
320 | ||
1da177e4 LT |
321 | /* 5. Recalculate window clamp after socket hit its memory bounds. */ |
322 | static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp) | |
323 | { | |
324 | struct sk_buff *skb; | |
325 | unsigned int app_win = tp->rcv_nxt - tp->copied_seq; | |
326 | int ofo_win = 0; | |
327 | ||
328 | tp->ack.quick = 0; | |
329 | ||
330 | skb_queue_walk(&tp->out_of_order_queue, skb) { | |
331 | ofo_win += skb->len; | |
332 | } | |
333 | ||
334 | /* If overcommit is due to out of order segments, | |
335 | * do not clamp window. Try to expand rcvbuf instead. | |
336 | */ | |
337 | if (ofo_win) { | |
338 | if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && | |
339 | !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && | |
340 | !tcp_memory_pressure && | |
341 | atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) | |
342 | sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), | |
343 | sysctl_tcp_rmem[2]); | |
344 | } | |
345 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) { | |
346 | app_win += ofo_win; | |
347 | if (atomic_read(&sk->sk_rmem_alloc) >= 2 * sk->sk_rcvbuf) | |
348 | app_win >>= 1; | |
349 | if (app_win > tp->ack.rcv_mss) | |
350 | app_win -= tp->ack.rcv_mss; | |
351 | app_win = max(app_win, 2U*tp->advmss); | |
352 | ||
353 | if (!ofo_win) | |
354 | tp->window_clamp = min(tp->window_clamp, app_win); | |
355 | tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss); | |
356 | } | |
357 | } | |
358 | ||
359 | /* Receiver "autotuning" code. | |
360 | * | |
361 | * The algorithm for RTT estimation w/o timestamps is based on | |
362 | * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. | |
363 | * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> | |
364 | * | |
365 | * More detail on this code can be found at | |
366 | * <http://www.psc.edu/~jheffner/senior_thesis.ps>, | |
367 | * though this reference is out of date. A new paper | |
368 | * is pending. | |
369 | */ | |
370 | static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) | |
371 | { | |
372 | u32 new_sample = tp->rcv_rtt_est.rtt; | |
373 | long m = sample; | |
374 | ||
375 | if (m == 0) | |
376 | m = 1; | |
377 | ||
378 | if (new_sample != 0) { | |
379 | /* If we sample in larger samples in the non-timestamp | |
380 | * case, we could grossly overestimate the RTT especially | |
381 | * with chatty applications or bulk transfer apps which | |
382 | * are stalled on filesystem I/O. | |
383 | * | |
384 | * Also, since we are only going for a minimum in the | |
385 | * non-timestamp case, we do not smoothe things out | |
386 | * else with timestamps disabled convergance takes too | |
387 | * long. | |
388 | */ | |
389 | if (!win_dep) { | |
390 | m -= (new_sample >> 3); | |
391 | new_sample += m; | |
392 | } else if (m < new_sample) | |
393 | new_sample = m << 3; | |
394 | } else { | |
395 | /* No previous mesaure. */ | |
396 | new_sample = m << 3; | |
397 | } | |
398 | ||
399 | if (tp->rcv_rtt_est.rtt != new_sample) | |
400 | tp->rcv_rtt_est.rtt = new_sample; | |
401 | } | |
402 | ||
403 | static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) | |
404 | { | |
405 | if (tp->rcv_rtt_est.time == 0) | |
406 | goto new_measure; | |
407 | if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) | |
408 | return; | |
409 | tcp_rcv_rtt_update(tp, | |
410 | jiffies - tp->rcv_rtt_est.time, | |
411 | 1); | |
412 | ||
413 | new_measure: | |
414 | tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; | |
415 | tp->rcv_rtt_est.time = tcp_time_stamp; | |
416 | } | |
417 | ||
418 | static inline void tcp_rcv_rtt_measure_ts(struct tcp_sock *tp, struct sk_buff *skb) | |
419 | { | |
420 | if (tp->rx_opt.rcv_tsecr && | |
421 | (TCP_SKB_CB(skb)->end_seq - | |
422 | TCP_SKB_CB(skb)->seq >= tp->ack.rcv_mss)) | |
423 | tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); | |
424 | } | |
425 | ||
426 | /* | |
427 | * This function should be called every time data is copied to user space. | |
428 | * It calculates the appropriate TCP receive buffer space. | |
429 | */ | |
430 | void tcp_rcv_space_adjust(struct sock *sk) | |
431 | { | |
432 | struct tcp_sock *tp = tcp_sk(sk); | |
433 | int time; | |
434 | int space; | |
435 | ||
436 | if (tp->rcvq_space.time == 0) | |
437 | goto new_measure; | |
438 | ||
439 | time = tcp_time_stamp - tp->rcvq_space.time; | |
440 | if (time < (tp->rcv_rtt_est.rtt >> 3) || | |
441 | tp->rcv_rtt_est.rtt == 0) | |
442 | return; | |
443 | ||
444 | space = 2 * (tp->copied_seq - tp->rcvq_space.seq); | |
445 | ||
446 | space = max(tp->rcvq_space.space, space); | |
447 | ||
448 | if (tp->rcvq_space.space != space) { | |
449 | int rcvmem; | |
450 | ||
451 | tp->rcvq_space.space = space; | |
452 | ||
453 | if (sysctl_tcp_moderate_rcvbuf) { | |
454 | int new_clamp = space; | |
455 | ||
456 | /* Receive space grows, normalize in order to | |
457 | * take into account packet headers and sk_buff | |
458 | * structure overhead. | |
459 | */ | |
460 | space /= tp->advmss; | |
461 | if (!space) | |
462 | space = 1; | |
463 | rcvmem = (tp->advmss + MAX_TCP_HEADER + | |
464 | 16 + sizeof(struct sk_buff)); | |
465 | while (tcp_win_from_space(rcvmem) < tp->advmss) | |
466 | rcvmem += 128; | |
467 | space *= rcvmem; | |
468 | space = min(space, sysctl_tcp_rmem[2]); | |
469 | if (space > sk->sk_rcvbuf) { | |
470 | sk->sk_rcvbuf = space; | |
471 | ||
472 | /* Make the window clamp follow along. */ | |
473 | tp->window_clamp = new_clamp; | |
474 | } | |
475 | } | |
476 | } | |
477 | ||
478 | new_measure: | |
479 | tp->rcvq_space.seq = tp->copied_seq; | |
480 | tp->rcvq_space.time = tcp_time_stamp; | |
481 | } | |
482 | ||
483 | /* There is something which you must keep in mind when you analyze the | |
484 | * behavior of the tp->ato delayed ack timeout interval. When a | |
485 | * connection starts up, we want to ack as quickly as possible. The | |
486 | * problem is that "good" TCP's do slow start at the beginning of data | |
487 | * transmission. The means that until we send the first few ACK's the | |
488 | * sender will sit on his end and only queue most of his data, because | |
489 | * he can only send snd_cwnd unacked packets at any given time. For | |
490 | * each ACK we send, he increments snd_cwnd and transmits more of his | |
491 | * queue. -DaveM | |
492 | */ | |
493 | static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb) | |
494 | { | |
495 | u32 now; | |
496 | ||
497 | tcp_schedule_ack(tp); | |
498 | ||
499 | tcp_measure_rcv_mss(tp, skb); | |
500 | ||
501 | tcp_rcv_rtt_measure(tp); | |
502 | ||
503 | now = tcp_time_stamp; | |
504 | ||
505 | if (!tp->ack.ato) { | |
506 | /* The _first_ data packet received, initialize | |
507 | * delayed ACK engine. | |
508 | */ | |
509 | tcp_incr_quickack(tp); | |
510 | tp->ack.ato = TCP_ATO_MIN; | |
511 | } else { | |
512 | int m = now - tp->ack.lrcvtime; | |
513 | ||
514 | if (m <= TCP_ATO_MIN/2) { | |
515 | /* The fastest case is the first. */ | |
516 | tp->ack.ato = (tp->ack.ato>>1) + TCP_ATO_MIN/2; | |
517 | } else if (m < tp->ack.ato) { | |
518 | tp->ack.ato = (tp->ack.ato>>1) + m; | |
519 | if (tp->ack.ato > tp->rto) | |
520 | tp->ack.ato = tp->rto; | |
521 | } else if (m > tp->rto) { | |
522 | /* Too long gap. Apparently sender falled to | |
523 | * restart window, so that we send ACKs quickly. | |
524 | */ | |
525 | tcp_incr_quickack(tp); | |
526 | sk_stream_mem_reclaim(sk); | |
527 | } | |
528 | } | |
529 | tp->ack.lrcvtime = now; | |
530 | ||
531 | TCP_ECN_check_ce(tp, skb); | |
532 | ||
533 | if (skb->len >= 128) | |
534 | tcp_grow_window(sk, tp, skb); | |
535 | } | |
536 | ||
1da177e4 LT |
537 | /* Called to compute a smoothed rtt estimate. The data fed to this |
538 | * routine either comes from timestamps, or from segments that were | |
539 | * known _not_ to have been retransmitted [see Karn/Partridge | |
540 | * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 | |
541 | * piece by Van Jacobson. | |
542 | * NOTE: the next three routines used to be one big routine. | |
543 | * To save cycles in the RFC 1323 implementation it was better to break | |
544 | * it up into three procedures. -- erics | |
545 | */ | |
317a76f9 | 546 | static void tcp_rtt_estimator(struct tcp_sock *tp, __u32 mrtt, u32 *usrtt) |
1da177e4 LT |
547 | { |
548 | long m = mrtt; /* RTT */ | |
549 | ||
1da177e4 LT |
550 | /* The following amusing code comes from Jacobson's |
551 | * article in SIGCOMM '88. Note that rtt and mdev | |
552 | * are scaled versions of rtt and mean deviation. | |
553 | * This is designed to be as fast as possible | |
554 | * m stands for "measurement". | |
555 | * | |
556 | * On a 1990 paper the rto value is changed to: | |
557 | * RTO = rtt + 4 * mdev | |
558 | * | |
559 | * Funny. This algorithm seems to be very broken. | |
560 | * These formulae increase RTO, when it should be decreased, increase | |
561 | * too slowly, when it should be incresed fastly, decrease too fastly | |
562 | * etc. I guess in BSD RTO takes ONE value, so that it is absolutely | |
563 | * does not matter how to _calculate_ it. Seems, it was trap | |
564 | * that VJ failed to avoid. 8) | |
565 | */ | |
566 | if(m == 0) | |
567 | m = 1; | |
568 | if (tp->srtt != 0) { | |
569 | m -= (tp->srtt >> 3); /* m is now error in rtt est */ | |
570 | tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ | |
571 | if (m < 0) { | |
572 | m = -m; /* m is now abs(error) */ | |
573 | m -= (tp->mdev >> 2); /* similar update on mdev */ | |
574 | /* This is similar to one of Eifel findings. | |
575 | * Eifel blocks mdev updates when rtt decreases. | |
576 | * This solution is a bit different: we use finer gain | |
577 | * for mdev in this case (alpha*beta). | |
578 | * Like Eifel it also prevents growth of rto, | |
579 | * but also it limits too fast rto decreases, | |
580 | * happening in pure Eifel. | |
581 | */ | |
582 | if (m > 0) | |
583 | m >>= 3; | |
584 | } else { | |
585 | m -= (tp->mdev >> 2); /* similar update on mdev */ | |
586 | } | |
587 | tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ | |
588 | if (tp->mdev > tp->mdev_max) { | |
589 | tp->mdev_max = tp->mdev; | |
590 | if (tp->mdev_max > tp->rttvar) | |
591 | tp->rttvar = tp->mdev_max; | |
592 | } | |
593 | if (after(tp->snd_una, tp->rtt_seq)) { | |
594 | if (tp->mdev_max < tp->rttvar) | |
595 | tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; | |
596 | tp->rtt_seq = tp->snd_nxt; | |
597 | tp->mdev_max = TCP_RTO_MIN; | |
598 | } | |
599 | } else { | |
600 | /* no previous measure. */ | |
601 | tp->srtt = m<<3; /* take the measured time to be rtt */ | |
602 | tp->mdev = m<<1; /* make sure rto = 3*rtt */ | |
603 | tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); | |
604 | tp->rtt_seq = tp->snd_nxt; | |
605 | } | |
606 | ||
317a76f9 SH |
607 | if (tp->ca_ops->rtt_sample) |
608 | tp->ca_ops->rtt_sample(tp, *usrtt); | |
1da177e4 LT |
609 | } |
610 | ||
611 | /* Calculate rto without backoff. This is the second half of Van Jacobson's | |
612 | * routine referred to above. | |
613 | */ | |
614 | static inline void tcp_set_rto(struct tcp_sock *tp) | |
615 | { | |
616 | /* Old crap is replaced with new one. 8) | |
617 | * | |
618 | * More seriously: | |
619 | * 1. If rtt variance happened to be less 50msec, it is hallucination. | |
620 | * It cannot be less due to utterly erratic ACK generation made | |
621 | * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ | |
622 | * to do with delayed acks, because at cwnd>2 true delack timeout | |
623 | * is invisible. Actually, Linux-2.4 also generates erratic | |
624 | * ACKs in some curcumstances. | |
625 | */ | |
626 | tp->rto = (tp->srtt >> 3) + tp->rttvar; | |
627 | ||
628 | /* 2. Fixups made earlier cannot be right. | |
629 | * If we do not estimate RTO correctly without them, | |
630 | * all the algo is pure shit and should be replaced | |
631 | * with correct one. It is exaclty, which we pretend to do. | |
632 | */ | |
633 | } | |
634 | ||
635 | /* NOTE: clamping at TCP_RTO_MIN is not required, current algo | |
636 | * guarantees that rto is higher. | |
637 | */ | |
638 | static inline void tcp_bound_rto(struct tcp_sock *tp) | |
639 | { | |
640 | if (tp->rto > TCP_RTO_MAX) | |
641 | tp->rto = TCP_RTO_MAX; | |
642 | } | |
643 | ||
644 | /* Save metrics learned by this TCP session. | |
645 | This function is called only, when TCP finishes successfully | |
646 | i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. | |
647 | */ | |
648 | void tcp_update_metrics(struct sock *sk) | |
649 | { | |
650 | struct tcp_sock *tp = tcp_sk(sk); | |
651 | struct dst_entry *dst = __sk_dst_get(sk); | |
652 | ||
653 | if (sysctl_tcp_nometrics_save) | |
654 | return; | |
655 | ||
656 | dst_confirm(dst); | |
657 | ||
658 | if (dst && (dst->flags&DST_HOST)) { | |
659 | int m; | |
660 | ||
661 | if (tp->backoff || !tp->srtt) { | |
662 | /* This session failed to estimate rtt. Why? | |
663 | * Probably, no packets returned in time. | |
664 | * Reset our results. | |
665 | */ | |
666 | if (!(dst_metric_locked(dst, RTAX_RTT))) | |
667 | dst->metrics[RTAX_RTT-1] = 0; | |
668 | return; | |
669 | } | |
670 | ||
671 | m = dst_metric(dst, RTAX_RTT) - tp->srtt; | |
672 | ||
673 | /* If newly calculated rtt larger than stored one, | |
674 | * store new one. Otherwise, use EWMA. Remember, | |
675 | * rtt overestimation is always better than underestimation. | |
676 | */ | |
677 | if (!(dst_metric_locked(dst, RTAX_RTT))) { | |
678 | if (m <= 0) | |
679 | dst->metrics[RTAX_RTT-1] = tp->srtt; | |
680 | else | |
681 | dst->metrics[RTAX_RTT-1] -= (m>>3); | |
682 | } | |
683 | ||
684 | if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { | |
685 | if (m < 0) | |
686 | m = -m; | |
687 | ||
688 | /* Scale deviation to rttvar fixed point */ | |
689 | m >>= 1; | |
690 | if (m < tp->mdev) | |
691 | m = tp->mdev; | |
692 | ||
693 | if (m >= dst_metric(dst, RTAX_RTTVAR)) | |
694 | dst->metrics[RTAX_RTTVAR-1] = m; | |
695 | else | |
696 | dst->metrics[RTAX_RTTVAR-1] -= | |
697 | (dst->metrics[RTAX_RTTVAR-1] - m)>>2; | |
698 | } | |
699 | ||
700 | if (tp->snd_ssthresh >= 0xFFFF) { | |
701 | /* Slow start still did not finish. */ | |
702 | if (dst_metric(dst, RTAX_SSTHRESH) && | |
703 | !dst_metric_locked(dst, RTAX_SSTHRESH) && | |
704 | (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) | |
705 | dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; | |
706 | if (!dst_metric_locked(dst, RTAX_CWND) && | |
707 | tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) | |
708 | dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; | |
709 | } else if (tp->snd_cwnd > tp->snd_ssthresh && | |
710 | tp->ca_state == TCP_CA_Open) { | |
711 | /* Cong. avoidance phase, cwnd is reliable. */ | |
712 | if (!dst_metric_locked(dst, RTAX_SSTHRESH)) | |
713 | dst->metrics[RTAX_SSTHRESH-1] = | |
714 | max(tp->snd_cwnd >> 1, tp->snd_ssthresh); | |
715 | if (!dst_metric_locked(dst, RTAX_CWND)) | |
716 | dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; | |
717 | } else { | |
718 | /* Else slow start did not finish, cwnd is non-sense, | |
719 | ssthresh may be also invalid. | |
720 | */ | |
721 | if (!dst_metric_locked(dst, RTAX_CWND)) | |
722 | dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; | |
723 | if (dst->metrics[RTAX_SSTHRESH-1] && | |
724 | !dst_metric_locked(dst, RTAX_SSTHRESH) && | |
725 | tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) | |
726 | dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; | |
727 | } | |
728 | ||
729 | if (!dst_metric_locked(dst, RTAX_REORDERING)) { | |
730 | if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && | |
731 | tp->reordering != sysctl_tcp_reordering) | |
732 | dst->metrics[RTAX_REORDERING-1] = tp->reordering; | |
733 | } | |
734 | } | |
735 | } | |
736 | ||
737 | /* Numbers are taken from RFC2414. */ | |
738 | __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) | |
739 | { | |
740 | __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); | |
741 | ||
742 | if (!cwnd) { | |
c1b4a7e6 | 743 | if (tp->mss_cache > 1460) |
1da177e4 LT |
744 | cwnd = 2; |
745 | else | |
c1b4a7e6 | 746 | cwnd = (tp->mss_cache > 1095) ? 3 : 4; |
1da177e4 LT |
747 | } |
748 | return min_t(__u32, cwnd, tp->snd_cwnd_clamp); | |
749 | } | |
750 | ||
751 | /* Initialize metrics on socket. */ | |
752 | ||
753 | static void tcp_init_metrics(struct sock *sk) | |
754 | { | |
755 | struct tcp_sock *tp = tcp_sk(sk); | |
756 | struct dst_entry *dst = __sk_dst_get(sk); | |
757 | ||
758 | if (dst == NULL) | |
759 | goto reset; | |
760 | ||
761 | dst_confirm(dst); | |
762 | ||
763 | if (dst_metric_locked(dst, RTAX_CWND)) | |
764 | tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); | |
765 | if (dst_metric(dst, RTAX_SSTHRESH)) { | |
766 | tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); | |
767 | if (tp->snd_ssthresh > tp->snd_cwnd_clamp) | |
768 | tp->snd_ssthresh = tp->snd_cwnd_clamp; | |
769 | } | |
770 | if (dst_metric(dst, RTAX_REORDERING) && | |
771 | tp->reordering != dst_metric(dst, RTAX_REORDERING)) { | |
772 | tp->rx_opt.sack_ok &= ~2; | |
773 | tp->reordering = dst_metric(dst, RTAX_REORDERING); | |
774 | } | |
775 | ||
776 | if (dst_metric(dst, RTAX_RTT) == 0) | |
777 | goto reset; | |
778 | ||
779 | if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) | |
780 | goto reset; | |
781 | ||
782 | /* Initial rtt is determined from SYN,SYN-ACK. | |
783 | * The segment is small and rtt may appear much | |
784 | * less than real one. Use per-dst memory | |
785 | * to make it more realistic. | |
786 | * | |
787 | * A bit of theory. RTT is time passed after "normal" sized packet | |
788 | * is sent until it is ACKed. In normal curcumstances sending small | |
789 | * packets force peer to delay ACKs and calculation is correct too. | |
790 | * The algorithm is adaptive and, provided we follow specs, it | |
791 | * NEVER underestimate RTT. BUT! If peer tries to make some clever | |
792 | * tricks sort of "quick acks" for time long enough to decrease RTT | |
793 | * to low value, and then abruptly stops to do it and starts to delay | |
794 | * ACKs, wait for troubles. | |
795 | */ | |
796 | if (dst_metric(dst, RTAX_RTT) > tp->srtt) { | |
797 | tp->srtt = dst_metric(dst, RTAX_RTT); | |
798 | tp->rtt_seq = tp->snd_nxt; | |
799 | } | |
800 | if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { | |
801 | tp->mdev = dst_metric(dst, RTAX_RTTVAR); | |
802 | tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); | |
803 | } | |
804 | tcp_set_rto(tp); | |
805 | tcp_bound_rto(tp); | |
806 | if (tp->rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) | |
807 | goto reset; | |
808 | tp->snd_cwnd = tcp_init_cwnd(tp, dst); | |
809 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
810 | return; | |
811 | ||
812 | reset: | |
813 | /* Play conservative. If timestamps are not | |
814 | * supported, TCP will fail to recalculate correct | |
815 | * rtt, if initial rto is too small. FORGET ALL AND RESET! | |
816 | */ | |
817 | if (!tp->rx_opt.saw_tstamp && tp->srtt) { | |
818 | tp->srtt = 0; | |
819 | tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; | |
820 | tp->rto = TCP_TIMEOUT_INIT; | |
821 | } | |
822 | } | |
823 | ||
824 | static void tcp_update_reordering(struct tcp_sock *tp, int metric, int ts) | |
825 | { | |
826 | if (metric > tp->reordering) { | |
827 | tp->reordering = min(TCP_MAX_REORDERING, metric); | |
828 | ||
829 | /* This exciting event is worth to be remembered. 8) */ | |
830 | if (ts) | |
831 | NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); | |
832 | else if (IsReno(tp)) | |
833 | NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); | |
834 | else if (IsFack(tp)) | |
835 | NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); | |
836 | else | |
837 | NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); | |
838 | #if FASTRETRANS_DEBUG > 1 | |
839 | printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", | |
840 | tp->rx_opt.sack_ok, tp->ca_state, | |
841 | tp->reordering, | |
842 | tp->fackets_out, | |
843 | tp->sacked_out, | |
844 | tp->undo_marker ? tp->undo_retrans : 0); | |
845 | #endif | |
846 | /* Disable FACK yet. */ | |
847 | tp->rx_opt.sack_ok &= ~2; | |
848 | } | |
849 | } | |
850 | ||
851 | /* This procedure tags the retransmission queue when SACKs arrive. | |
852 | * | |
853 | * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). | |
854 | * Packets in queue with these bits set are counted in variables | |
855 | * sacked_out, retrans_out and lost_out, correspondingly. | |
856 | * | |
857 | * Valid combinations are: | |
858 | * Tag InFlight Description | |
859 | * 0 1 - orig segment is in flight. | |
860 | * S 0 - nothing flies, orig reached receiver. | |
861 | * L 0 - nothing flies, orig lost by net. | |
862 | * R 2 - both orig and retransmit are in flight. | |
863 | * L|R 1 - orig is lost, retransmit is in flight. | |
864 | * S|R 1 - orig reached receiver, retrans is still in flight. | |
865 | * (L|S|R is logically valid, it could occur when L|R is sacked, | |
866 | * but it is equivalent to plain S and code short-curcuits it to S. | |
867 | * L|S is logically invalid, it would mean -1 packet in flight 8)) | |
868 | * | |
869 | * These 6 states form finite state machine, controlled by the following events: | |
870 | * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) | |
871 | * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) | |
872 | * 3. Loss detection event of one of three flavors: | |
873 | * A. Scoreboard estimator decided the packet is lost. | |
874 | * A'. Reno "three dupacks" marks head of queue lost. | |
875 | * A''. Its FACK modfication, head until snd.fack is lost. | |
876 | * B. SACK arrives sacking data transmitted after never retransmitted | |
877 | * hole was sent out. | |
878 | * C. SACK arrives sacking SND.NXT at the moment, when the | |
879 | * segment was retransmitted. | |
880 | * 4. D-SACK added new rule: D-SACK changes any tag to S. | |
881 | * | |
882 | * It is pleasant to note, that state diagram turns out to be commutative, | |
883 | * so that we are allowed not to be bothered by order of our actions, | |
884 | * when multiple events arrive simultaneously. (see the function below). | |
885 | * | |
886 | * Reordering detection. | |
887 | * -------------------- | |
888 | * Reordering metric is maximal distance, which a packet can be displaced | |
889 | * in packet stream. With SACKs we can estimate it: | |
890 | * | |
891 | * 1. SACK fills old hole and the corresponding segment was not | |
892 | * ever retransmitted -> reordering. Alas, we cannot use it | |
893 | * when segment was retransmitted. | |
894 | * 2. The last flaw is solved with D-SACK. D-SACK arrives | |
895 | * for retransmitted and already SACKed segment -> reordering.. | |
896 | * Both of these heuristics are not used in Loss state, when we cannot | |
897 | * account for retransmits accurately. | |
898 | */ | |
899 | static int | |
900 | tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) | |
901 | { | |
902 | struct tcp_sock *tp = tcp_sk(sk); | |
903 | unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked; | |
904 | struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2); | |
905 | int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; | |
906 | int reord = tp->packets_out; | |
907 | int prior_fackets; | |
908 | u32 lost_retrans = 0; | |
909 | int flag = 0; | |
910 | int i; | |
911 | ||
912 | /* So, SACKs for already sent large segments will be lost. | |
913 | * Not good, but alternative is to resegment the queue. */ | |
914 | if (sk->sk_route_caps & NETIF_F_TSO) { | |
915 | sk->sk_route_caps &= ~NETIF_F_TSO; | |
916 | sock_set_flag(sk, SOCK_NO_LARGESEND); | |
c1b4a7e6 | 917 | tp->mss_cache = tp->mss_cache; |
1da177e4 LT |
918 | } |
919 | ||
920 | if (!tp->sacked_out) | |
921 | tp->fackets_out = 0; | |
922 | prior_fackets = tp->fackets_out; | |
923 | ||
924 | for (i=0; i<num_sacks; i++, sp++) { | |
925 | struct sk_buff *skb; | |
926 | __u32 start_seq = ntohl(sp->start_seq); | |
927 | __u32 end_seq = ntohl(sp->end_seq); | |
928 | int fack_count = 0; | |
929 | int dup_sack = 0; | |
930 | ||
931 | /* Check for D-SACK. */ | |
932 | if (i == 0) { | |
933 | u32 ack = TCP_SKB_CB(ack_skb)->ack_seq; | |
934 | ||
935 | if (before(start_seq, ack)) { | |
936 | dup_sack = 1; | |
937 | tp->rx_opt.sack_ok |= 4; | |
938 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); | |
939 | } else if (num_sacks > 1 && | |
940 | !after(end_seq, ntohl(sp[1].end_seq)) && | |
941 | !before(start_seq, ntohl(sp[1].start_seq))) { | |
942 | dup_sack = 1; | |
943 | tp->rx_opt.sack_ok |= 4; | |
944 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); | |
945 | } | |
946 | ||
947 | /* D-SACK for already forgotten data... | |
948 | * Do dumb counting. */ | |
949 | if (dup_sack && | |
950 | !after(end_seq, prior_snd_una) && | |
951 | after(end_seq, tp->undo_marker)) | |
952 | tp->undo_retrans--; | |
953 | ||
954 | /* Eliminate too old ACKs, but take into | |
955 | * account more or less fresh ones, they can | |
956 | * contain valid SACK info. | |
957 | */ | |
958 | if (before(ack, prior_snd_una - tp->max_window)) | |
959 | return 0; | |
960 | } | |
961 | ||
962 | /* Event "B" in the comment above. */ | |
963 | if (after(end_seq, tp->high_seq)) | |
964 | flag |= FLAG_DATA_LOST; | |
965 | ||
966 | sk_stream_for_retrans_queue(skb, sk) { | |
967 | u8 sacked = TCP_SKB_CB(skb)->sacked; | |
968 | int in_sack; | |
969 | ||
970 | /* The retransmission queue is always in order, so | |
971 | * we can short-circuit the walk early. | |
972 | */ | |
973 | if(!before(TCP_SKB_CB(skb)->seq, end_seq)) | |
974 | break; | |
975 | ||
976 | fack_count += tcp_skb_pcount(skb); | |
977 | ||
978 | in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && | |
979 | !before(end_seq, TCP_SKB_CB(skb)->end_seq); | |
980 | ||
981 | /* Account D-SACK for retransmitted packet. */ | |
982 | if ((dup_sack && in_sack) && | |
983 | (sacked & TCPCB_RETRANS) && | |
984 | after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) | |
985 | tp->undo_retrans--; | |
986 | ||
987 | /* The frame is ACKed. */ | |
988 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) { | |
989 | if (sacked&TCPCB_RETRANS) { | |
990 | if ((dup_sack && in_sack) && | |
991 | (sacked&TCPCB_SACKED_ACKED)) | |
992 | reord = min(fack_count, reord); | |
993 | } else { | |
994 | /* If it was in a hole, we detected reordering. */ | |
995 | if (fack_count < prior_fackets && | |
996 | !(sacked&TCPCB_SACKED_ACKED)) | |
997 | reord = min(fack_count, reord); | |
998 | } | |
999 | ||
1000 | /* Nothing to do; acked frame is about to be dropped. */ | |
1001 | continue; | |
1002 | } | |
1003 | ||
1004 | if ((sacked&TCPCB_SACKED_RETRANS) && | |
1005 | after(end_seq, TCP_SKB_CB(skb)->ack_seq) && | |
1006 | (!lost_retrans || after(end_seq, lost_retrans))) | |
1007 | lost_retrans = end_seq; | |
1008 | ||
1009 | if (!in_sack) | |
1010 | continue; | |
1011 | ||
1012 | if (!(sacked&TCPCB_SACKED_ACKED)) { | |
1013 | if (sacked & TCPCB_SACKED_RETRANS) { | |
1014 | /* If the segment is not tagged as lost, | |
1015 | * we do not clear RETRANS, believing | |
1016 | * that retransmission is still in flight. | |
1017 | */ | |
1018 | if (sacked & TCPCB_LOST) { | |
1019 | TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); | |
1020 | tp->lost_out -= tcp_skb_pcount(skb); | |
1021 | tp->retrans_out -= tcp_skb_pcount(skb); | |
1022 | } | |
1023 | } else { | |
1024 | /* New sack for not retransmitted frame, | |
1025 | * which was in hole. It is reordering. | |
1026 | */ | |
1027 | if (!(sacked & TCPCB_RETRANS) && | |
1028 | fack_count < prior_fackets) | |
1029 | reord = min(fack_count, reord); | |
1030 | ||
1031 | if (sacked & TCPCB_LOST) { | |
1032 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; | |
1033 | tp->lost_out -= tcp_skb_pcount(skb); | |
1034 | } | |
1035 | } | |
1036 | ||
1037 | TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED; | |
1038 | flag |= FLAG_DATA_SACKED; | |
1039 | tp->sacked_out += tcp_skb_pcount(skb); | |
1040 | ||
1041 | if (fack_count > tp->fackets_out) | |
1042 | tp->fackets_out = fack_count; | |
1043 | } else { | |
1044 | if (dup_sack && (sacked&TCPCB_RETRANS)) | |
1045 | reord = min(fack_count, reord); | |
1046 | } | |
1047 | ||
1048 | /* D-SACK. We can detect redundant retransmission | |
1049 | * in S|R and plain R frames and clear it. | |
1050 | * undo_retrans is decreased above, L|R frames | |
1051 | * are accounted above as well. | |
1052 | */ | |
1053 | if (dup_sack && | |
1054 | (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) { | |
1055 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; | |
1056 | tp->retrans_out -= tcp_skb_pcount(skb); | |
1057 | } | |
1058 | } | |
1059 | } | |
1060 | ||
1061 | /* Check for lost retransmit. This superb idea is | |
1062 | * borrowed from "ratehalving". Event "C". | |
1063 | * Later note: FACK people cheated me again 8), | |
1064 | * we have to account for reordering! Ugly, | |
1065 | * but should help. | |
1066 | */ | |
1067 | if (lost_retrans && tp->ca_state == TCP_CA_Recovery) { | |
1068 | struct sk_buff *skb; | |
1069 | ||
1070 | sk_stream_for_retrans_queue(skb, sk) { | |
1071 | if (after(TCP_SKB_CB(skb)->seq, lost_retrans)) | |
1072 | break; | |
1073 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) | |
1074 | continue; | |
1075 | if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) && | |
1076 | after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) && | |
1077 | (IsFack(tp) || | |
1078 | !before(lost_retrans, | |
1079 | TCP_SKB_CB(skb)->ack_seq + tp->reordering * | |
c1b4a7e6 | 1080 | tp->mss_cache))) { |
1da177e4 LT |
1081 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; |
1082 | tp->retrans_out -= tcp_skb_pcount(skb); | |
1083 | ||
1084 | if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) { | |
1085 | tp->lost_out += tcp_skb_pcount(skb); | |
1086 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1087 | flag |= FLAG_DATA_SACKED; | |
1088 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT); | |
1089 | } | |
1090 | } | |
1091 | } | |
1092 | } | |
1093 | ||
1094 | tp->left_out = tp->sacked_out + tp->lost_out; | |
1095 | ||
1096 | if ((reord < tp->fackets_out) && tp->ca_state != TCP_CA_Loss) | |
1097 | tcp_update_reordering(tp, ((tp->fackets_out + 1) - reord), 0); | |
1098 | ||
1099 | #if FASTRETRANS_DEBUG > 0 | |
1100 | BUG_TRAP((int)tp->sacked_out >= 0); | |
1101 | BUG_TRAP((int)tp->lost_out >= 0); | |
1102 | BUG_TRAP((int)tp->retrans_out >= 0); | |
1103 | BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0); | |
1104 | #endif | |
1105 | return flag; | |
1106 | } | |
1107 | ||
1108 | /* RTO occurred, but do not yet enter loss state. Instead, transmit two new | |
1109 | * segments to see from the next ACKs whether any data was really missing. | |
1110 | * If the RTO was spurious, new ACKs should arrive. | |
1111 | */ | |
1112 | void tcp_enter_frto(struct sock *sk) | |
1113 | { | |
1114 | struct tcp_sock *tp = tcp_sk(sk); | |
1115 | struct sk_buff *skb; | |
1116 | ||
1117 | tp->frto_counter = 1; | |
1118 | ||
1119 | if (tp->ca_state <= TCP_CA_Disorder || | |
1120 | tp->snd_una == tp->high_seq || | |
1121 | (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) { | |
1122 | tp->prior_ssthresh = tcp_current_ssthresh(tp); | |
317a76f9 SH |
1123 | tp->snd_ssthresh = tp->ca_ops->ssthresh(tp); |
1124 | tcp_ca_event(tp, CA_EVENT_FRTO); | |
1da177e4 LT |
1125 | } |
1126 | ||
1127 | /* Have to clear retransmission markers here to keep the bookkeeping | |
1128 | * in shape, even though we are not yet in Loss state. | |
1129 | * If something was really lost, it is eventually caught up | |
1130 | * in tcp_enter_frto_loss. | |
1131 | */ | |
1132 | tp->retrans_out = 0; | |
1133 | tp->undo_marker = tp->snd_una; | |
1134 | tp->undo_retrans = 0; | |
1135 | ||
1136 | sk_stream_for_retrans_queue(skb, sk) { | |
1137 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS; | |
1138 | } | |
1139 | tcp_sync_left_out(tp); | |
1140 | ||
1141 | tcp_set_ca_state(tp, TCP_CA_Open); | |
1142 | tp->frto_highmark = tp->snd_nxt; | |
1143 | } | |
1144 | ||
1145 | /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, | |
1146 | * which indicates that we should follow the traditional RTO recovery, | |
1147 | * i.e. mark everything lost and do go-back-N retransmission. | |
1148 | */ | |
1149 | static void tcp_enter_frto_loss(struct sock *sk) | |
1150 | { | |
1151 | struct tcp_sock *tp = tcp_sk(sk); | |
1152 | struct sk_buff *skb; | |
1153 | int cnt = 0; | |
1154 | ||
1155 | tp->sacked_out = 0; | |
1156 | tp->lost_out = 0; | |
1157 | tp->fackets_out = 0; | |
1158 | ||
1159 | sk_stream_for_retrans_queue(skb, sk) { | |
1160 | cnt += tcp_skb_pcount(skb); | |
1161 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; | |
1162 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { | |
1163 | ||
1164 | /* Do not mark those segments lost that were | |
1165 | * forward transmitted after RTO | |
1166 | */ | |
1167 | if (!after(TCP_SKB_CB(skb)->end_seq, | |
1168 | tp->frto_highmark)) { | |
1169 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1170 | tp->lost_out += tcp_skb_pcount(skb); | |
1171 | } | |
1172 | } else { | |
1173 | tp->sacked_out += tcp_skb_pcount(skb); | |
1174 | tp->fackets_out = cnt; | |
1175 | } | |
1176 | } | |
1177 | tcp_sync_left_out(tp); | |
1178 | ||
1179 | tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1; | |
1180 | tp->snd_cwnd_cnt = 0; | |
1181 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1182 | tp->undo_marker = 0; | |
1183 | tp->frto_counter = 0; | |
1184 | ||
1185 | tp->reordering = min_t(unsigned int, tp->reordering, | |
1186 | sysctl_tcp_reordering); | |
1187 | tcp_set_ca_state(tp, TCP_CA_Loss); | |
1188 | tp->high_seq = tp->frto_highmark; | |
1189 | TCP_ECN_queue_cwr(tp); | |
1da177e4 LT |
1190 | } |
1191 | ||
1192 | void tcp_clear_retrans(struct tcp_sock *tp) | |
1193 | { | |
1194 | tp->left_out = 0; | |
1195 | tp->retrans_out = 0; | |
1196 | ||
1197 | tp->fackets_out = 0; | |
1198 | tp->sacked_out = 0; | |
1199 | tp->lost_out = 0; | |
1200 | ||
1201 | tp->undo_marker = 0; | |
1202 | tp->undo_retrans = 0; | |
1203 | } | |
1204 | ||
1205 | /* Enter Loss state. If "how" is not zero, forget all SACK information | |
1206 | * and reset tags completely, otherwise preserve SACKs. If receiver | |
1207 | * dropped its ofo queue, we will know this due to reneging detection. | |
1208 | */ | |
1209 | void tcp_enter_loss(struct sock *sk, int how) | |
1210 | { | |
1211 | struct tcp_sock *tp = tcp_sk(sk); | |
1212 | struct sk_buff *skb; | |
1213 | int cnt = 0; | |
1214 | ||
1215 | /* Reduce ssthresh if it has not yet been made inside this window. */ | |
1216 | if (tp->ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || | |
1217 | (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) { | |
1218 | tp->prior_ssthresh = tcp_current_ssthresh(tp); | |
317a76f9 SH |
1219 | tp->snd_ssthresh = tp->ca_ops->ssthresh(tp); |
1220 | tcp_ca_event(tp, CA_EVENT_LOSS); | |
1da177e4 LT |
1221 | } |
1222 | tp->snd_cwnd = 1; | |
1223 | tp->snd_cwnd_cnt = 0; | |
1224 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1225 | ||
1226 | tcp_clear_retrans(tp); | |
1227 | ||
1228 | /* Push undo marker, if it was plain RTO and nothing | |
1229 | * was retransmitted. */ | |
1230 | if (!how) | |
1231 | tp->undo_marker = tp->snd_una; | |
1232 | ||
1233 | sk_stream_for_retrans_queue(skb, sk) { | |
1234 | cnt += tcp_skb_pcount(skb); | |
1235 | if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) | |
1236 | tp->undo_marker = 0; | |
1237 | TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; | |
1238 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { | |
1239 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; | |
1240 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1241 | tp->lost_out += tcp_skb_pcount(skb); | |
1242 | } else { | |
1243 | tp->sacked_out += tcp_skb_pcount(skb); | |
1244 | tp->fackets_out = cnt; | |
1245 | } | |
1246 | } | |
1247 | tcp_sync_left_out(tp); | |
1248 | ||
1249 | tp->reordering = min_t(unsigned int, tp->reordering, | |
1250 | sysctl_tcp_reordering); | |
1251 | tcp_set_ca_state(tp, TCP_CA_Loss); | |
1252 | tp->high_seq = tp->snd_nxt; | |
1253 | TCP_ECN_queue_cwr(tp); | |
1254 | } | |
1255 | ||
1256 | static int tcp_check_sack_reneging(struct sock *sk, struct tcp_sock *tp) | |
1257 | { | |
1258 | struct sk_buff *skb; | |
1259 | ||
1260 | /* If ACK arrived pointing to a remembered SACK, | |
1261 | * it means that our remembered SACKs do not reflect | |
1262 | * real state of receiver i.e. | |
1263 | * receiver _host_ is heavily congested (or buggy). | |
1264 | * Do processing similar to RTO timeout. | |
1265 | */ | |
1266 | if ((skb = skb_peek(&sk->sk_write_queue)) != NULL && | |
1267 | (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { | |
1268 | NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING); | |
1269 | ||
1270 | tcp_enter_loss(sk, 1); | |
1271 | tp->retransmits++; | |
1272 | tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue)); | |
1273 | tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); | |
1274 | return 1; | |
1275 | } | |
1276 | return 0; | |
1277 | } | |
1278 | ||
1279 | static inline int tcp_fackets_out(struct tcp_sock *tp) | |
1280 | { | |
1281 | return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out; | |
1282 | } | |
1283 | ||
1284 | static inline int tcp_skb_timedout(struct tcp_sock *tp, struct sk_buff *skb) | |
1285 | { | |
1286 | return (tcp_time_stamp - TCP_SKB_CB(skb)->when > tp->rto); | |
1287 | } | |
1288 | ||
1289 | static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp) | |
1290 | { | |
1291 | return tp->packets_out && | |
1292 | tcp_skb_timedout(tp, skb_peek(&sk->sk_write_queue)); | |
1293 | } | |
1294 | ||
1295 | /* Linux NewReno/SACK/FACK/ECN state machine. | |
1296 | * -------------------------------------- | |
1297 | * | |
1298 | * "Open" Normal state, no dubious events, fast path. | |
1299 | * "Disorder" In all the respects it is "Open", | |
1300 | * but requires a bit more attention. It is entered when | |
1301 | * we see some SACKs or dupacks. It is split of "Open" | |
1302 | * mainly to move some processing from fast path to slow one. | |
1303 | * "CWR" CWND was reduced due to some Congestion Notification event. | |
1304 | * It can be ECN, ICMP source quench, local device congestion. | |
1305 | * "Recovery" CWND was reduced, we are fast-retransmitting. | |
1306 | * "Loss" CWND was reduced due to RTO timeout or SACK reneging. | |
1307 | * | |
1308 | * tcp_fastretrans_alert() is entered: | |
1309 | * - each incoming ACK, if state is not "Open" | |
1310 | * - when arrived ACK is unusual, namely: | |
1311 | * * SACK | |
1312 | * * Duplicate ACK. | |
1313 | * * ECN ECE. | |
1314 | * | |
1315 | * Counting packets in flight is pretty simple. | |
1316 | * | |
1317 | * in_flight = packets_out - left_out + retrans_out | |
1318 | * | |
1319 | * packets_out is SND.NXT-SND.UNA counted in packets. | |
1320 | * | |
1321 | * retrans_out is number of retransmitted segments. | |
1322 | * | |
1323 | * left_out is number of segments left network, but not ACKed yet. | |
1324 | * | |
1325 | * left_out = sacked_out + lost_out | |
1326 | * | |
1327 | * sacked_out: Packets, which arrived to receiver out of order | |
1328 | * and hence not ACKed. With SACKs this number is simply | |
1329 | * amount of SACKed data. Even without SACKs | |
1330 | * it is easy to give pretty reliable estimate of this number, | |
1331 | * counting duplicate ACKs. | |
1332 | * | |
1333 | * lost_out: Packets lost by network. TCP has no explicit | |
1334 | * "loss notification" feedback from network (for now). | |
1335 | * It means that this number can be only _guessed_. | |
1336 | * Actually, it is the heuristics to predict lossage that | |
1337 | * distinguishes different algorithms. | |
1338 | * | |
1339 | * F.e. after RTO, when all the queue is considered as lost, | |
1340 | * lost_out = packets_out and in_flight = retrans_out. | |
1341 | * | |
1342 | * Essentially, we have now two algorithms counting | |
1343 | * lost packets. | |
1344 | * | |
1345 | * FACK: It is the simplest heuristics. As soon as we decided | |
1346 | * that something is lost, we decide that _all_ not SACKed | |
1347 | * packets until the most forward SACK are lost. I.e. | |
1348 | * lost_out = fackets_out - sacked_out and left_out = fackets_out. | |
1349 | * It is absolutely correct estimate, if network does not reorder | |
1350 | * packets. And it loses any connection to reality when reordering | |
1351 | * takes place. We use FACK by default until reordering | |
1352 | * is suspected on the path to this destination. | |
1353 | * | |
1354 | * NewReno: when Recovery is entered, we assume that one segment | |
1355 | * is lost (classic Reno). While we are in Recovery and | |
1356 | * a partial ACK arrives, we assume that one more packet | |
1357 | * is lost (NewReno). This heuristics are the same in NewReno | |
1358 | * and SACK. | |
1359 | * | |
1360 | * Imagine, that's all! Forget about all this shamanism about CWND inflation | |
1361 | * deflation etc. CWND is real congestion window, never inflated, changes | |
1362 | * only according to classic VJ rules. | |
1363 | * | |
1364 | * Really tricky (and requiring careful tuning) part of algorithm | |
1365 | * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). | |
1366 | * The first determines the moment _when_ we should reduce CWND and, | |
1367 | * hence, slow down forward transmission. In fact, it determines the moment | |
1368 | * when we decide that hole is caused by loss, rather than by a reorder. | |
1369 | * | |
1370 | * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill | |
1371 | * holes, caused by lost packets. | |
1372 | * | |
1373 | * And the most logically complicated part of algorithm is undo | |
1374 | * heuristics. We detect false retransmits due to both too early | |
1375 | * fast retransmit (reordering) and underestimated RTO, analyzing | |
1376 | * timestamps and D-SACKs. When we detect that some segments were | |
1377 | * retransmitted by mistake and CWND reduction was wrong, we undo | |
1378 | * window reduction and abort recovery phase. This logic is hidden | |
1379 | * inside several functions named tcp_try_undo_<something>. | |
1380 | */ | |
1381 | ||
1382 | /* This function decides, when we should leave Disordered state | |
1383 | * and enter Recovery phase, reducing congestion window. | |
1384 | * | |
1385 | * Main question: may we further continue forward transmission | |
1386 | * with the same cwnd? | |
1387 | */ | |
1388 | static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp) | |
1389 | { | |
1390 | __u32 packets_out; | |
1391 | ||
1392 | /* Trick#1: The loss is proven. */ | |
1393 | if (tp->lost_out) | |
1394 | return 1; | |
1395 | ||
1396 | /* Not-A-Trick#2 : Classic rule... */ | |
1397 | if (tcp_fackets_out(tp) > tp->reordering) | |
1398 | return 1; | |
1399 | ||
1400 | /* Trick#3 : when we use RFC2988 timer restart, fast | |
1401 | * retransmit can be triggered by timeout of queue head. | |
1402 | */ | |
1403 | if (tcp_head_timedout(sk, tp)) | |
1404 | return 1; | |
1405 | ||
1406 | /* Trick#4: It is still not OK... But will it be useful to delay | |
1407 | * recovery more? | |
1408 | */ | |
1409 | packets_out = tp->packets_out; | |
1410 | if (packets_out <= tp->reordering && | |
1411 | tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && | |
1412 | !tcp_may_send_now(sk, tp)) { | |
1413 | /* We have nothing to send. This connection is limited | |
1414 | * either by receiver window or by application. | |
1415 | */ | |
1416 | return 1; | |
1417 | } | |
1418 | ||
1419 | return 0; | |
1420 | } | |
1421 | ||
1422 | /* If we receive more dupacks than we expected counting segments | |
1423 | * in assumption of absent reordering, interpret this as reordering. | |
1424 | * The only another reason could be bug in receiver TCP. | |
1425 | */ | |
1426 | static void tcp_check_reno_reordering(struct tcp_sock *tp, int addend) | |
1427 | { | |
1428 | u32 holes; | |
1429 | ||
1430 | holes = max(tp->lost_out, 1U); | |
1431 | holes = min(holes, tp->packets_out); | |
1432 | ||
1433 | if ((tp->sacked_out + holes) > tp->packets_out) { | |
1434 | tp->sacked_out = tp->packets_out - holes; | |
1435 | tcp_update_reordering(tp, tp->packets_out+addend, 0); | |
1436 | } | |
1437 | } | |
1438 | ||
1439 | /* Emulate SACKs for SACKless connection: account for a new dupack. */ | |
1440 | ||
1441 | static void tcp_add_reno_sack(struct tcp_sock *tp) | |
1442 | { | |
1443 | tp->sacked_out++; | |
1444 | tcp_check_reno_reordering(tp, 0); | |
1445 | tcp_sync_left_out(tp); | |
1446 | } | |
1447 | ||
1448 | /* Account for ACK, ACKing some data in Reno Recovery phase. */ | |
1449 | ||
1450 | static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked) | |
1451 | { | |
1452 | if (acked > 0) { | |
1453 | /* One ACK acked hole. The rest eat duplicate ACKs. */ | |
1454 | if (acked-1 >= tp->sacked_out) | |
1455 | tp->sacked_out = 0; | |
1456 | else | |
1457 | tp->sacked_out -= acked-1; | |
1458 | } | |
1459 | tcp_check_reno_reordering(tp, acked); | |
1460 | tcp_sync_left_out(tp); | |
1461 | } | |
1462 | ||
1463 | static inline void tcp_reset_reno_sack(struct tcp_sock *tp) | |
1464 | { | |
1465 | tp->sacked_out = 0; | |
1466 | tp->left_out = tp->lost_out; | |
1467 | } | |
1468 | ||
1469 | /* Mark head of queue up as lost. */ | |
1470 | static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp, | |
1471 | int packets, u32 high_seq) | |
1472 | { | |
1473 | struct sk_buff *skb; | |
1474 | int cnt = packets; | |
1475 | ||
1476 | BUG_TRAP(cnt <= tp->packets_out); | |
1477 | ||
1478 | sk_stream_for_retrans_queue(skb, sk) { | |
1479 | cnt -= tcp_skb_pcount(skb); | |
1480 | if (cnt < 0 || after(TCP_SKB_CB(skb)->end_seq, high_seq)) | |
1481 | break; | |
1482 | if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { | |
1483 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1484 | tp->lost_out += tcp_skb_pcount(skb); | |
1485 | } | |
1486 | } | |
1487 | tcp_sync_left_out(tp); | |
1488 | } | |
1489 | ||
1490 | /* Account newly detected lost packet(s) */ | |
1491 | ||
1492 | static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp) | |
1493 | { | |
1494 | if (IsFack(tp)) { | |
1495 | int lost = tp->fackets_out - tp->reordering; | |
1496 | if (lost <= 0) | |
1497 | lost = 1; | |
1498 | tcp_mark_head_lost(sk, tp, lost, tp->high_seq); | |
1499 | } else { | |
1500 | tcp_mark_head_lost(sk, tp, 1, tp->high_seq); | |
1501 | } | |
1502 | ||
1503 | /* New heuristics: it is possible only after we switched | |
1504 | * to restart timer each time when something is ACKed. | |
1505 | * Hence, we can detect timed out packets during fast | |
1506 | * retransmit without falling to slow start. | |
1507 | */ | |
1508 | if (tcp_head_timedout(sk, tp)) { | |
1509 | struct sk_buff *skb; | |
1510 | ||
1511 | sk_stream_for_retrans_queue(skb, sk) { | |
1512 | if (tcp_skb_timedout(tp, skb) && | |
1513 | !(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { | |
1514 | TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; | |
1515 | tp->lost_out += tcp_skb_pcount(skb); | |
1516 | } | |
1517 | } | |
1518 | tcp_sync_left_out(tp); | |
1519 | } | |
1520 | } | |
1521 | ||
1522 | /* CWND moderation, preventing bursts due to too big ACKs | |
1523 | * in dubious situations. | |
1524 | */ | |
1525 | static inline void tcp_moderate_cwnd(struct tcp_sock *tp) | |
1526 | { | |
1527 | tp->snd_cwnd = min(tp->snd_cwnd, | |
1528 | tcp_packets_in_flight(tp)+tcp_max_burst(tp)); | |
1529 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1530 | } | |
1531 | ||
1532 | /* Decrease cwnd each second ack. */ | |
1da177e4 LT |
1533 | static void tcp_cwnd_down(struct tcp_sock *tp) |
1534 | { | |
1535 | int decr = tp->snd_cwnd_cnt + 1; | |
1da177e4 LT |
1536 | |
1537 | tp->snd_cwnd_cnt = decr&1; | |
1538 | decr >>= 1; | |
1539 | ||
317a76f9 | 1540 | if (decr && tp->snd_cwnd > tp->ca_ops->min_cwnd(tp)) |
1da177e4 LT |
1541 | tp->snd_cwnd -= decr; |
1542 | ||
1543 | tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1); | |
1544 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1545 | } | |
1546 | ||
1547 | /* Nothing was retransmitted or returned timestamp is less | |
1548 | * than timestamp of the first retransmission. | |
1549 | */ | |
1550 | static inline int tcp_packet_delayed(struct tcp_sock *tp) | |
1551 | { | |
1552 | return !tp->retrans_stamp || | |
1553 | (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && | |
1554 | (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0); | |
1555 | } | |
1556 | ||
1557 | /* Undo procedures. */ | |
1558 | ||
1559 | #if FASTRETRANS_DEBUG > 1 | |
1560 | static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg) | |
1561 | { | |
1562 | struct inet_sock *inet = inet_sk(sk); | |
1563 | printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n", | |
1564 | msg, | |
1565 | NIPQUAD(inet->daddr), ntohs(inet->dport), | |
1566 | tp->snd_cwnd, tp->left_out, | |
1567 | tp->snd_ssthresh, tp->prior_ssthresh, | |
1568 | tp->packets_out); | |
1569 | } | |
1570 | #else | |
1571 | #define DBGUNDO(x...) do { } while (0) | |
1572 | #endif | |
1573 | ||
1574 | static void tcp_undo_cwr(struct tcp_sock *tp, int undo) | |
1575 | { | |
1576 | if (tp->prior_ssthresh) { | |
317a76f9 SH |
1577 | if (tp->ca_ops->undo_cwnd) |
1578 | tp->snd_cwnd = tp->ca_ops->undo_cwnd(tp); | |
1da177e4 LT |
1579 | else |
1580 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1); | |
1581 | ||
1582 | if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { | |
1583 | tp->snd_ssthresh = tp->prior_ssthresh; | |
1584 | TCP_ECN_withdraw_cwr(tp); | |
1585 | } | |
1586 | } else { | |
1587 | tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); | |
1588 | } | |
1589 | tcp_moderate_cwnd(tp); | |
1590 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
1591 | } | |
1592 | ||
1593 | static inline int tcp_may_undo(struct tcp_sock *tp) | |
1594 | { | |
1595 | return tp->undo_marker && | |
1596 | (!tp->undo_retrans || tcp_packet_delayed(tp)); | |
1597 | } | |
1598 | ||
1599 | /* People celebrate: "We love our President!" */ | |
1600 | static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp) | |
1601 | { | |
1602 | if (tcp_may_undo(tp)) { | |
1603 | /* Happy end! We did not retransmit anything | |
1604 | * or our original transmission succeeded. | |
1605 | */ | |
1606 | DBGUNDO(sk, tp, tp->ca_state == TCP_CA_Loss ? "loss" : "retrans"); | |
1607 | tcp_undo_cwr(tp, 1); | |
1608 | if (tp->ca_state == TCP_CA_Loss) | |
1609 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); | |
1610 | else | |
1611 | NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO); | |
1612 | tp->undo_marker = 0; | |
1613 | } | |
1614 | if (tp->snd_una == tp->high_seq && IsReno(tp)) { | |
1615 | /* Hold old state until something *above* high_seq | |
1616 | * is ACKed. For Reno it is MUST to prevent false | |
1617 | * fast retransmits (RFC2582). SACK TCP is safe. */ | |
1618 | tcp_moderate_cwnd(tp); | |
1619 | return 1; | |
1620 | } | |
1621 | tcp_set_ca_state(tp, TCP_CA_Open); | |
1622 | return 0; | |
1623 | } | |
1624 | ||
1625 | /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ | |
1626 | static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp) | |
1627 | { | |
1628 | if (tp->undo_marker && !tp->undo_retrans) { | |
1629 | DBGUNDO(sk, tp, "D-SACK"); | |
1630 | tcp_undo_cwr(tp, 1); | |
1631 | tp->undo_marker = 0; | |
1632 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO); | |
1633 | } | |
1634 | } | |
1635 | ||
1636 | /* Undo during fast recovery after partial ACK. */ | |
1637 | ||
1638 | static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp, | |
1639 | int acked) | |
1640 | { | |
1641 | /* Partial ACK arrived. Force Hoe's retransmit. */ | |
1642 | int failed = IsReno(tp) || tp->fackets_out>tp->reordering; | |
1643 | ||
1644 | if (tcp_may_undo(tp)) { | |
1645 | /* Plain luck! Hole if filled with delayed | |
1646 | * packet, rather than with a retransmit. | |
1647 | */ | |
1648 | if (tp->retrans_out == 0) | |
1649 | tp->retrans_stamp = 0; | |
1650 | ||
1651 | tcp_update_reordering(tp, tcp_fackets_out(tp)+acked, 1); | |
1652 | ||
1653 | DBGUNDO(sk, tp, "Hoe"); | |
1654 | tcp_undo_cwr(tp, 0); | |
1655 | NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO); | |
1656 | ||
1657 | /* So... Do not make Hoe's retransmit yet. | |
1658 | * If the first packet was delayed, the rest | |
1659 | * ones are most probably delayed as well. | |
1660 | */ | |
1661 | failed = 0; | |
1662 | } | |
1663 | return failed; | |
1664 | } | |
1665 | ||
1666 | /* Undo during loss recovery after partial ACK. */ | |
1667 | static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp) | |
1668 | { | |
1669 | if (tcp_may_undo(tp)) { | |
1670 | struct sk_buff *skb; | |
1671 | sk_stream_for_retrans_queue(skb, sk) { | |
1672 | TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; | |
1673 | } | |
1674 | DBGUNDO(sk, tp, "partial loss"); | |
1675 | tp->lost_out = 0; | |
1676 | tp->left_out = tp->sacked_out; | |
1677 | tcp_undo_cwr(tp, 1); | |
1678 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); | |
1679 | tp->retransmits = 0; | |
1680 | tp->undo_marker = 0; | |
1681 | if (!IsReno(tp)) | |
1682 | tcp_set_ca_state(tp, TCP_CA_Open); | |
1683 | return 1; | |
1684 | } | |
1685 | return 0; | |
1686 | } | |
1687 | ||
1688 | static inline void tcp_complete_cwr(struct tcp_sock *tp) | |
1689 | { | |
317a76f9 | 1690 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); |
1da177e4 | 1691 | tp->snd_cwnd_stamp = tcp_time_stamp; |
317a76f9 | 1692 | tcp_ca_event(tp, CA_EVENT_COMPLETE_CWR); |
1da177e4 LT |
1693 | } |
1694 | ||
1695 | static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag) | |
1696 | { | |
1697 | tp->left_out = tp->sacked_out; | |
1698 | ||
1699 | if (tp->retrans_out == 0) | |
1700 | tp->retrans_stamp = 0; | |
1701 | ||
1702 | if (flag&FLAG_ECE) | |
1703 | tcp_enter_cwr(tp); | |
1704 | ||
1705 | if (tp->ca_state != TCP_CA_CWR) { | |
1706 | int state = TCP_CA_Open; | |
1707 | ||
1708 | if (tp->left_out || tp->retrans_out || tp->undo_marker) | |
1709 | state = TCP_CA_Disorder; | |
1710 | ||
1711 | if (tp->ca_state != state) { | |
1712 | tcp_set_ca_state(tp, state); | |
1713 | tp->high_seq = tp->snd_nxt; | |
1714 | } | |
1715 | tcp_moderate_cwnd(tp); | |
1716 | } else { | |
1717 | tcp_cwnd_down(tp); | |
1718 | } | |
1719 | } | |
1720 | ||
1721 | /* Process an event, which can update packets-in-flight not trivially. | |
1722 | * Main goal of this function is to calculate new estimate for left_out, | |
1723 | * taking into account both packets sitting in receiver's buffer and | |
1724 | * packets lost by network. | |
1725 | * | |
1726 | * Besides that it does CWND reduction, when packet loss is detected | |
1727 | * and changes state of machine. | |
1728 | * | |
1729 | * It does _not_ decide what to send, it is made in function | |
1730 | * tcp_xmit_retransmit_queue(). | |
1731 | */ | |
1732 | static void | |
1733 | tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una, | |
1734 | int prior_packets, int flag) | |
1735 | { | |
1736 | struct tcp_sock *tp = tcp_sk(sk); | |
1737 | int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP)); | |
1738 | ||
1739 | /* Some technical things: | |
1740 | * 1. Reno does not count dupacks (sacked_out) automatically. */ | |
1741 | if (!tp->packets_out) | |
1742 | tp->sacked_out = 0; | |
1743 | /* 2. SACK counts snd_fack in packets inaccurately. */ | |
1744 | if (tp->sacked_out == 0) | |
1745 | tp->fackets_out = 0; | |
1746 | ||
1747 | /* Now state machine starts. | |
1748 | * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ | |
1749 | if (flag&FLAG_ECE) | |
1750 | tp->prior_ssthresh = 0; | |
1751 | ||
1752 | /* B. In all the states check for reneging SACKs. */ | |
1753 | if (tp->sacked_out && tcp_check_sack_reneging(sk, tp)) | |
1754 | return; | |
1755 | ||
1756 | /* C. Process data loss notification, provided it is valid. */ | |
1757 | if ((flag&FLAG_DATA_LOST) && | |
1758 | before(tp->snd_una, tp->high_seq) && | |
1759 | tp->ca_state != TCP_CA_Open && | |
1760 | tp->fackets_out > tp->reordering) { | |
1761 | tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq); | |
1762 | NET_INC_STATS_BH(LINUX_MIB_TCPLOSS); | |
1763 | } | |
1764 | ||
1765 | /* D. Synchronize left_out to current state. */ | |
1766 | tcp_sync_left_out(tp); | |
1767 | ||
1768 | /* E. Check state exit conditions. State can be terminated | |
1769 | * when high_seq is ACKed. */ | |
1770 | if (tp->ca_state == TCP_CA_Open) { | |
1771 | if (!sysctl_tcp_frto) | |
1772 | BUG_TRAP(tp->retrans_out == 0); | |
1773 | tp->retrans_stamp = 0; | |
1774 | } else if (!before(tp->snd_una, tp->high_seq)) { | |
1775 | switch (tp->ca_state) { | |
1776 | case TCP_CA_Loss: | |
1777 | tp->retransmits = 0; | |
1778 | if (tcp_try_undo_recovery(sk, tp)) | |
1779 | return; | |
1780 | break; | |
1781 | ||
1782 | case TCP_CA_CWR: | |
1783 | /* CWR is to be held something *above* high_seq | |
1784 | * is ACKed for CWR bit to reach receiver. */ | |
1785 | if (tp->snd_una != tp->high_seq) { | |
1786 | tcp_complete_cwr(tp); | |
1787 | tcp_set_ca_state(tp, TCP_CA_Open); | |
1788 | } | |
1789 | break; | |
1790 | ||
1791 | case TCP_CA_Disorder: | |
1792 | tcp_try_undo_dsack(sk, tp); | |
1793 | if (!tp->undo_marker || | |
1794 | /* For SACK case do not Open to allow to undo | |
1795 | * catching for all duplicate ACKs. */ | |
1796 | IsReno(tp) || tp->snd_una != tp->high_seq) { | |
1797 | tp->undo_marker = 0; | |
1798 | tcp_set_ca_state(tp, TCP_CA_Open); | |
1799 | } | |
1800 | break; | |
1801 | ||
1802 | case TCP_CA_Recovery: | |
1803 | if (IsReno(tp)) | |
1804 | tcp_reset_reno_sack(tp); | |
1805 | if (tcp_try_undo_recovery(sk, tp)) | |
1806 | return; | |
1807 | tcp_complete_cwr(tp); | |
1808 | break; | |
1809 | } | |
1810 | } | |
1811 | ||
1812 | /* F. Process state. */ | |
1813 | switch (tp->ca_state) { | |
1814 | case TCP_CA_Recovery: | |
1815 | if (prior_snd_una == tp->snd_una) { | |
1816 | if (IsReno(tp) && is_dupack) | |
1817 | tcp_add_reno_sack(tp); | |
1818 | } else { | |
1819 | int acked = prior_packets - tp->packets_out; | |
1820 | if (IsReno(tp)) | |
1821 | tcp_remove_reno_sacks(sk, tp, acked); | |
1822 | is_dupack = tcp_try_undo_partial(sk, tp, acked); | |
1823 | } | |
1824 | break; | |
1825 | case TCP_CA_Loss: | |
1826 | if (flag&FLAG_DATA_ACKED) | |
1827 | tp->retransmits = 0; | |
1828 | if (!tcp_try_undo_loss(sk, tp)) { | |
1829 | tcp_moderate_cwnd(tp); | |
1830 | tcp_xmit_retransmit_queue(sk); | |
1831 | return; | |
1832 | } | |
1833 | if (tp->ca_state != TCP_CA_Open) | |
1834 | return; | |
1835 | /* Loss is undone; fall through to processing in Open state. */ | |
1836 | default: | |
1837 | if (IsReno(tp)) { | |
1838 | if (tp->snd_una != prior_snd_una) | |
1839 | tcp_reset_reno_sack(tp); | |
1840 | if (is_dupack) | |
1841 | tcp_add_reno_sack(tp); | |
1842 | } | |
1843 | ||
1844 | if (tp->ca_state == TCP_CA_Disorder) | |
1845 | tcp_try_undo_dsack(sk, tp); | |
1846 | ||
1847 | if (!tcp_time_to_recover(sk, tp)) { | |
1848 | tcp_try_to_open(sk, tp, flag); | |
1849 | return; | |
1850 | } | |
1851 | ||
1852 | /* Otherwise enter Recovery state */ | |
1853 | ||
1854 | if (IsReno(tp)) | |
1855 | NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY); | |
1856 | else | |
1857 | NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY); | |
1858 | ||
1859 | tp->high_seq = tp->snd_nxt; | |
1860 | tp->prior_ssthresh = 0; | |
1861 | tp->undo_marker = tp->snd_una; | |
1862 | tp->undo_retrans = tp->retrans_out; | |
1863 | ||
1864 | if (tp->ca_state < TCP_CA_CWR) { | |
1865 | if (!(flag&FLAG_ECE)) | |
1866 | tp->prior_ssthresh = tcp_current_ssthresh(tp); | |
317a76f9 | 1867 | tp->snd_ssthresh = tp->ca_ops->ssthresh(tp); |
1da177e4 LT |
1868 | TCP_ECN_queue_cwr(tp); |
1869 | } | |
1870 | ||
1871 | tp->snd_cwnd_cnt = 0; | |
1872 | tcp_set_ca_state(tp, TCP_CA_Recovery); | |
1873 | } | |
1874 | ||
1875 | if (is_dupack || tcp_head_timedout(sk, tp)) | |
1876 | tcp_update_scoreboard(sk, tp); | |
1877 | tcp_cwnd_down(tp); | |
1878 | tcp_xmit_retransmit_queue(sk); | |
1879 | } | |
1880 | ||
1881 | /* Read draft-ietf-tcplw-high-performance before mucking | |
1882 | * with this code. (Superceeds RFC1323) | |
1883 | */ | |
317a76f9 | 1884 | static void tcp_ack_saw_tstamp(struct tcp_sock *tp, u32 *usrtt, int flag) |
1da177e4 LT |
1885 | { |
1886 | __u32 seq_rtt; | |
1887 | ||
1888 | /* RTTM Rule: A TSecr value received in a segment is used to | |
1889 | * update the averaged RTT measurement only if the segment | |
1890 | * acknowledges some new data, i.e., only if it advances the | |
1891 | * left edge of the send window. | |
1892 | * | |
1893 | * See draft-ietf-tcplw-high-performance-00, section 3.3. | |
1894 | * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> | |
1895 | * | |
1896 | * Changed: reset backoff as soon as we see the first valid sample. | |
1897 | * If we do not, we get strongly overstimated rto. With timestamps | |
1898 | * samples are accepted even from very old segments: f.e., when rtt=1 | |
1899 | * increases to 8, we retransmit 5 times and after 8 seconds delayed | |
1900 | * answer arrives rto becomes 120 seconds! If at least one of segments | |
1901 | * in window is lost... Voila. --ANK (010210) | |
1902 | */ | |
1903 | seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr; | |
317a76f9 | 1904 | tcp_rtt_estimator(tp, seq_rtt, usrtt); |
1da177e4 LT |
1905 | tcp_set_rto(tp); |
1906 | tp->backoff = 0; | |
1907 | tcp_bound_rto(tp); | |
1908 | } | |
1909 | ||
317a76f9 | 1910 | static void tcp_ack_no_tstamp(struct tcp_sock *tp, u32 seq_rtt, u32 *usrtt, int flag) |
1da177e4 LT |
1911 | { |
1912 | /* We don't have a timestamp. Can only use | |
1913 | * packets that are not retransmitted to determine | |
1914 | * rtt estimates. Also, we must not reset the | |
1915 | * backoff for rto until we get a non-retransmitted | |
1916 | * packet. This allows us to deal with a situation | |
1917 | * where the network delay has increased suddenly. | |
1918 | * I.e. Karn's algorithm. (SIGCOMM '87, p5.) | |
1919 | */ | |
1920 | ||
1921 | if (flag & FLAG_RETRANS_DATA_ACKED) | |
1922 | return; | |
1923 | ||
317a76f9 | 1924 | tcp_rtt_estimator(tp, seq_rtt, usrtt); |
1da177e4 LT |
1925 | tcp_set_rto(tp); |
1926 | tp->backoff = 0; | |
1927 | tcp_bound_rto(tp); | |
1928 | } | |
1929 | ||
1930 | static inline void tcp_ack_update_rtt(struct tcp_sock *tp, | |
317a76f9 | 1931 | int flag, s32 seq_rtt, u32 *usrtt) |
1da177e4 LT |
1932 | { |
1933 | /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ | |
1934 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) | |
317a76f9 | 1935 | tcp_ack_saw_tstamp(tp, usrtt, flag); |
1da177e4 | 1936 | else if (seq_rtt >= 0) |
317a76f9 | 1937 | tcp_ack_no_tstamp(tp, seq_rtt, usrtt, flag); |
1da177e4 LT |
1938 | } |
1939 | ||
317a76f9 SH |
1940 | static inline void tcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32 rtt, |
1941 | u32 in_flight, int good) | |
1da177e4 | 1942 | { |
317a76f9 | 1943 | tp->ca_ops->cong_avoid(tp, ack, rtt, in_flight, good); |
1da177e4 LT |
1944 | tp->snd_cwnd_stamp = tcp_time_stamp; |
1945 | } | |
1946 | ||
1da177e4 LT |
1947 | /* Restart timer after forward progress on connection. |
1948 | * RFC2988 recommends to restart timer to now+rto. | |
1949 | */ | |
1950 | ||
1951 | static inline void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp) | |
1952 | { | |
1953 | if (!tp->packets_out) { | |
1954 | tcp_clear_xmit_timer(sk, TCP_TIME_RETRANS); | |
1955 | } else { | |
1956 | tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto); | |
1957 | } | |
1958 | } | |
1959 | ||
1da177e4 LT |
1960 | static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb, |
1961 | __u32 now, __s32 *seq_rtt) | |
1962 | { | |
1963 | struct tcp_sock *tp = tcp_sk(sk); | |
1964 | struct tcp_skb_cb *scb = TCP_SKB_CB(skb); | |
1965 | __u32 seq = tp->snd_una; | |
1966 | __u32 packets_acked; | |
1967 | int acked = 0; | |
1968 | ||
1969 | /* If we get here, the whole TSO packet has not been | |
1970 | * acked. | |
1971 | */ | |
1972 | BUG_ON(!after(scb->end_seq, seq)); | |
1973 | ||
1974 | packets_acked = tcp_skb_pcount(skb); | |
1975 | if (tcp_trim_head(sk, skb, seq - scb->seq)) | |
1976 | return 0; | |
1977 | packets_acked -= tcp_skb_pcount(skb); | |
1978 | ||
1979 | if (packets_acked) { | |
1980 | __u8 sacked = scb->sacked; | |
1981 | ||
1982 | acked |= FLAG_DATA_ACKED; | |
1983 | if (sacked) { | |
1984 | if (sacked & TCPCB_RETRANS) { | |
1985 | if (sacked & TCPCB_SACKED_RETRANS) | |
1986 | tp->retrans_out -= packets_acked; | |
1987 | acked |= FLAG_RETRANS_DATA_ACKED; | |
1988 | *seq_rtt = -1; | |
1989 | } else if (*seq_rtt < 0) | |
1990 | *seq_rtt = now - scb->when; | |
1991 | if (sacked & TCPCB_SACKED_ACKED) | |
1992 | tp->sacked_out -= packets_acked; | |
1993 | if (sacked & TCPCB_LOST) | |
1994 | tp->lost_out -= packets_acked; | |
1995 | if (sacked & TCPCB_URG) { | |
1996 | if (tp->urg_mode && | |
1997 | !before(seq, tp->snd_up)) | |
1998 | tp->urg_mode = 0; | |
1999 | } | |
2000 | } else if (*seq_rtt < 0) | |
2001 | *seq_rtt = now - scb->when; | |
2002 | ||
2003 | if (tp->fackets_out) { | |
2004 | __u32 dval = min(tp->fackets_out, packets_acked); | |
2005 | tp->fackets_out -= dval; | |
2006 | } | |
2007 | tp->packets_out -= packets_acked; | |
2008 | ||
2009 | BUG_ON(tcp_skb_pcount(skb) == 0); | |
2010 | BUG_ON(!before(scb->seq, scb->end_seq)); | |
2011 | } | |
2012 | ||
2013 | return acked; | |
2014 | } | |
2015 | ||
2016 | ||
2017 | /* Remove acknowledged frames from the retransmission queue. */ | |
317a76f9 | 2018 | static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p, s32 *seq_usrtt) |
1da177e4 LT |
2019 | { |
2020 | struct tcp_sock *tp = tcp_sk(sk); | |
2021 | struct sk_buff *skb; | |
2022 | __u32 now = tcp_time_stamp; | |
2023 | int acked = 0; | |
2024 | __s32 seq_rtt = -1; | |
317a76f9 SH |
2025 | struct timeval usnow; |
2026 | u32 pkts_acked = 0; | |
2027 | ||
2028 | if (seq_usrtt) | |
2029 | do_gettimeofday(&usnow); | |
1da177e4 LT |
2030 | |
2031 | while ((skb = skb_peek(&sk->sk_write_queue)) && | |
2032 | skb != sk->sk_send_head) { | |
2033 | struct tcp_skb_cb *scb = TCP_SKB_CB(skb); | |
2034 | __u8 sacked = scb->sacked; | |
2035 | ||
2036 | /* If our packet is before the ack sequence we can | |
2037 | * discard it as it's confirmed to have arrived at | |
2038 | * the other end. | |
2039 | */ | |
2040 | if (after(scb->end_seq, tp->snd_una)) { | |
cb83199a DM |
2041 | if (tcp_skb_pcount(skb) > 1 && |
2042 | after(tp->snd_una, scb->seq)) | |
1da177e4 LT |
2043 | acked |= tcp_tso_acked(sk, skb, |
2044 | now, &seq_rtt); | |
2045 | break; | |
2046 | } | |
2047 | ||
2048 | /* Initial outgoing SYN's get put onto the write_queue | |
2049 | * just like anything else we transmit. It is not | |
2050 | * true data, and if we misinform our callers that | |
2051 | * this ACK acks real data, we will erroneously exit | |
2052 | * connection startup slow start one packet too | |
2053 | * quickly. This is severely frowned upon behavior. | |
2054 | */ | |
2055 | if (!(scb->flags & TCPCB_FLAG_SYN)) { | |
2056 | acked |= FLAG_DATA_ACKED; | |
317a76f9 | 2057 | ++pkts_acked; |
1da177e4 LT |
2058 | } else { |
2059 | acked |= FLAG_SYN_ACKED; | |
2060 | tp->retrans_stamp = 0; | |
2061 | } | |
2062 | ||
2063 | if (sacked) { | |
2064 | if (sacked & TCPCB_RETRANS) { | |
2065 | if(sacked & TCPCB_SACKED_RETRANS) | |
2066 | tp->retrans_out -= tcp_skb_pcount(skb); | |
2067 | acked |= FLAG_RETRANS_DATA_ACKED; | |
2068 | seq_rtt = -1; | |
2069 | } else if (seq_rtt < 0) | |
2070 | seq_rtt = now - scb->when; | |
317a76f9 SH |
2071 | if (seq_usrtt) |
2072 | *seq_usrtt = (usnow.tv_sec - skb->stamp.tv_sec) * 1000000 | |
2073 | + (usnow.tv_usec - skb->stamp.tv_usec); | |
2074 | ||
1da177e4 LT |
2075 | if (sacked & TCPCB_SACKED_ACKED) |
2076 | tp->sacked_out -= tcp_skb_pcount(skb); | |
2077 | if (sacked & TCPCB_LOST) | |
2078 | tp->lost_out -= tcp_skb_pcount(skb); | |
2079 | if (sacked & TCPCB_URG) { | |
2080 | if (tp->urg_mode && | |
2081 | !before(scb->end_seq, tp->snd_up)) | |
2082 | tp->urg_mode = 0; | |
2083 | } | |
2084 | } else if (seq_rtt < 0) | |
2085 | seq_rtt = now - scb->when; | |
2086 | tcp_dec_pcount_approx(&tp->fackets_out, skb); | |
2087 | tcp_packets_out_dec(tp, skb); | |
2088 | __skb_unlink(skb, skb->list); | |
2089 | sk_stream_free_skb(sk, skb); | |
2090 | } | |
2091 | ||
2092 | if (acked&FLAG_ACKED) { | |
317a76f9 | 2093 | tcp_ack_update_rtt(tp, acked, seq_rtt, seq_usrtt); |
1da177e4 | 2094 | tcp_ack_packets_out(sk, tp); |
317a76f9 SH |
2095 | |
2096 | if (tp->ca_ops->pkts_acked) | |
2097 | tp->ca_ops->pkts_acked(tp, pkts_acked); | |
1da177e4 LT |
2098 | } |
2099 | ||
2100 | #if FASTRETRANS_DEBUG > 0 | |
2101 | BUG_TRAP((int)tp->sacked_out >= 0); | |
2102 | BUG_TRAP((int)tp->lost_out >= 0); | |
2103 | BUG_TRAP((int)tp->retrans_out >= 0); | |
2104 | if (!tp->packets_out && tp->rx_opt.sack_ok) { | |
2105 | if (tp->lost_out) { | |
2106 | printk(KERN_DEBUG "Leak l=%u %d\n", | |
2107 | tp->lost_out, tp->ca_state); | |
2108 | tp->lost_out = 0; | |
2109 | } | |
2110 | if (tp->sacked_out) { | |
2111 | printk(KERN_DEBUG "Leak s=%u %d\n", | |
2112 | tp->sacked_out, tp->ca_state); | |
2113 | tp->sacked_out = 0; | |
2114 | } | |
2115 | if (tp->retrans_out) { | |
2116 | printk(KERN_DEBUG "Leak r=%u %d\n", | |
2117 | tp->retrans_out, tp->ca_state); | |
2118 | tp->retrans_out = 0; | |
2119 | } | |
2120 | } | |
2121 | #endif | |
2122 | *seq_rtt_p = seq_rtt; | |
2123 | return acked; | |
2124 | } | |
2125 | ||
2126 | static void tcp_ack_probe(struct sock *sk) | |
2127 | { | |
2128 | struct tcp_sock *tp = tcp_sk(sk); | |
2129 | ||
2130 | /* Was it a usable window open? */ | |
2131 | ||
2132 | if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq, | |
2133 | tp->snd_una + tp->snd_wnd)) { | |
2134 | tp->backoff = 0; | |
2135 | tcp_clear_xmit_timer(sk, TCP_TIME_PROBE0); | |
2136 | /* Socket must be waked up by subsequent tcp_data_snd_check(). | |
2137 | * This function is not for random using! | |
2138 | */ | |
2139 | } else { | |
2140 | tcp_reset_xmit_timer(sk, TCP_TIME_PROBE0, | |
2141 | min(tp->rto << tp->backoff, TCP_RTO_MAX)); | |
2142 | } | |
2143 | } | |
2144 | ||
2145 | static inline int tcp_ack_is_dubious(struct tcp_sock *tp, int flag) | |
2146 | { | |
2147 | return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || | |
2148 | tp->ca_state != TCP_CA_Open); | |
2149 | } | |
2150 | ||
2151 | static inline int tcp_may_raise_cwnd(struct tcp_sock *tp, int flag) | |
2152 | { | |
2153 | return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && | |
2154 | !((1<<tp->ca_state)&(TCPF_CA_Recovery|TCPF_CA_CWR)); | |
2155 | } | |
2156 | ||
2157 | /* Check that window update is acceptable. | |
2158 | * The function assumes that snd_una<=ack<=snd_next. | |
2159 | */ | |
2160 | static inline int tcp_may_update_window(struct tcp_sock *tp, u32 ack, | |
2161 | u32 ack_seq, u32 nwin) | |
2162 | { | |
2163 | return (after(ack, tp->snd_una) || | |
2164 | after(ack_seq, tp->snd_wl1) || | |
2165 | (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); | |
2166 | } | |
2167 | ||
2168 | /* Update our send window. | |
2169 | * | |
2170 | * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 | |
2171 | * and in FreeBSD. NetBSD's one is even worse.) is wrong. | |
2172 | */ | |
2173 | static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp, | |
2174 | struct sk_buff *skb, u32 ack, u32 ack_seq) | |
2175 | { | |
2176 | int flag = 0; | |
2177 | u32 nwin = ntohs(skb->h.th->window); | |
2178 | ||
2179 | if (likely(!skb->h.th->syn)) | |
2180 | nwin <<= tp->rx_opt.snd_wscale; | |
2181 | ||
2182 | if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { | |
2183 | flag |= FLAG_WIN_UPDATE; | |
2184 | tcp_update_wl(tp, ack, ack_seq); | |
2185 | ||
2186 | if (tp->snd_wnd != nwin) { | |
2187 | tp->snd_wnd = nwin; | |
2188 | ||
2189 | /* Note, it is the only place, where | |
2190 | * fast path is recovered for sending TCP. | |
2191 | */ | |
2192 | tcp_fast_path_check(sk, tp); | |
2193 | ||
2194 | if (nwin > tp->max_window) { | |
2195 | tp->max_window = nwin; | |
2196 | tcp_sync_mss(sk, tp->pmtu_cookie); | |
2197 | } | |
2198 | } | |
2199 | } | |
2200 | ||
2201 | tp->snd_una = ack; | |
2202 | ||
2203 | return flag; | |
2204 | } | |
2205 | ||
2206 | static void tcp_process_frto(struct sock *sk, u32 prior_snd_una) | |
2207 | { | |
2208 | struct tcp_sock *tp = tcp_sk(sk); | |
2209 | ||
2210 | tcp_sync_left_out(tp); | |
2211 | ||
2212 | if (tp->snd_una == prior_snd_una || | |
2213 | !before(tp->snd_una, tp->frto_highmark)) { | |
2214 | /* RTO was caused by loss, start retransmitting in | |
2215 | * go-back-N slow start | |
2216 | */ | |
2217 | tcp_enter_frto_loss(sk); | |
2218 | return; | |
2219 | } | |
2220 | ||
2221 | if (tp->frto_counter == 1) { | |
2222 | /* First ACK after RTO advances the window: allow two new | |
2223 | * segments out. | |
2224 | */ | |
2225 | tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; | |
2226 | } else { | |
2227 | /* Also the second ACK after RTO advances the window. | |
2228 | * The RTO was likely spurious. Reduce cwnd and continue | |
2229 | * in congestion avoidance | |
2230 | */ | |
2231 | tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); | |
2232 | tcp_moderate_cwnd(tp); | |
2233 | } | |
2234 | ||
2235 | /* F-RTO affects on two new ACKs following RTO. | |
2236 | * At latest on third ACK the TCP behavor is back to normal. | |
2237 | */ | |
2238 | tp->frto_counter = (tp->frto_counter + 1) % 3; | |
2239 | } | |
2240 | ||
1da177e4 LT |
2241 | /* This routine deals with incoming acks, but not outgoing ones. */ |
2242 | static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) | |
2243 | { | |
2244 | struct tcp_sock *tp = tcp_sk(sk); | |
2245 | u32 prior_snd_una = tp->snd_una; | |
2246 | u32 ack_seq = TCP_SKB_CB(skb)->seq; | |
2247 | u32 ack = TCP_SKB_CB(skb)->ack_seq; | |
2248 | u32 prior_in_flight; | |
2249 | s32 seq_rtt; | |
317a76f9 | 2250 | s32 seq_usrtt = 0; |
1da177e4 LT |
2251 | int prior_packets; |
2252 | ||
2253 | /* If the ack is newer than sent or older than previous acks | |
2254 | * then we can probably ignore it. | |
2255 | */ | |
2256 | if (after(ack, tp->snd_nxt)) | |
2257 | goto uninteresting_ack; | |
2258 | ||
2259 | if (before(ack, prior_snd_una)) | |
2260 | goto old_ack; | |
2261 | ||
2262 | if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) { | |
2263 | /* Window is constant, pure forward advance. | |
2264 | * No more checks are required. | |
2265 | * Note, we use the fact that SND.UNA>=SND.WL2. | |
2266 | */ | |
2267 | tcp_update_wl(tp, ack, ack_seq); | |
2268 | tp->snd_una = ack; | |
1da177e4 LT |
2269 | flag |= FLAG_WIN_UPDATE; |
2270 | ||
317a76f9 SH |
2271 | tcp_ca_event(tp, CA_EVENT_FAST_ACK); |
2272 | ||
1da177e4 LT |
2273 | NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS); |
2274 | } else { | |
2275 | if (ack_seq != TCP_SKB_CB(skb)->end_seq) | |
2276 | flag |= FLAG_DATA; | |
2277 | else | |
2278 | NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS); | |
2279 | ||
2280 | flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq); | |
2281 | ||
2282 | if (TCP_SKB_CB(skb)->sacked) | |
2283 | flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); | |
2284 | ||
2285 | if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th)) | |
2286 | flag |= FLAG_ECE; | |
2287 | ||
317a76f9 | 2288 | tcp_ca_event(tp, CA_EVENT_SLOW_ACK); |
1da177e4 LT |
2289 | } |
2290 | ||
2291 | /* We passed data and got it acked, remove any soft error | |
2292 | * log. Something worked... | |
2293 | */ | |
2294 | sk->sk_err_soft = 0; | |
2295 | tp->rcv_tstamp = tcp_time_stamp; | |
2296 | prior_packets = tp->packets_out; | |
2297 | if (!prior_packets) | |
2298 | goto no_queue; | |
2299 | ||
2300 | prior_in_flight = tcp_packets_in_flight(tp); | |
2301 | ||
2302 | /* See if we can take anything off of the retransmit queue. */ | |
317a76f9 SH |
2303 | flag |= tcp_clean_rtx_queue(sk, &seq_rtt, |
2304 | tp->ca_ops->rtt_sample ? &seq_usrtt : NULL); | |
1da177e4 LT |
2305 | |
2306 | if (tp->frto_counter) | |
2307 | tcp_process_frto(sk, prior_snd_una); | |
2308 | ||
2309 | if (tcp_ack_is_dubious(tp, flag)) { | |
2310 | /* Advanve CWND, if state allows this. */ | |
317a76f9 SH |
2311 | if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(tp, flag)) |
2312 | tcp_cong_avoid(tp, ack, seq_rtt, prior_in_flight, 0); | |
1da177e4 LT |
2313 | tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag); |
2314 | } else { | |
317a76f9 SH |
2315 | if ((flag & FLAG_DATA_ACKED)) |
2316 | tcp_cong_avoid(tp, ack, seq_rtt, prior_in_flight, 1); | |
1da177e4 LT |
2317 | } |
2318 | ||
2319 | if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP)) | |
2320 | dst_confirm(sk->sk_dst_cache); | |
2321 | ||
2322 | return 1; | |
2323 | ||
2324 | no_queue: | |
2325 | tp->probes_out = 0; | |
2326 | ||
2327 | /* If this ack opens up a zero window, clear backoff. It was | |
2328 | * being used to time the probes, and is probably far higher than | |
2329 | * it needs to be for normal retransmission. | |
2330 | */ | |
2331 | if (sk->sk_send_head) | |
2332 | tcp_ack_probe(sk); | |
2333 | return 1; | |
2334 | ||
2335 | old_ack: | |
2336 | if (TCP_SKB_CB(skb)->sacked) | |
2337 | tcp_sacktag_write_queue(sk, skb, prior_snd_una); | |
2338 | ||
2339 | uninteresting_ack: | |
2340 | SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); | |
2341 | return 0; | |
2342 | } | |
2343 | ||
2344 | ||
2345 | /* Look for tcp options. Normally only called on SYN and SYNACK packets. | |
2346 | * But, this can also be called on packets in the established flow when | |
2347 | * the fast version below fails. | |
2348 | */ | |
2349 | void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab) | |
2350 | { | |
2351 | unsigned char *ptr; | |
2352 | struct tcphdr *th = skb->h.th; | |
2353 | int length=(th->doff*4)-sizeof(struct tcphdr); | |
2354 | ||
2355 | ptr = (unsigned char *)(th + 1); | |
2356 | opt_rx->saw_tstamp = 0; | |
2357 | ||
2358 | while(length>0) { | |
2359 | int opcode=*ptr++; | |
2360 | int opsize; | |
2361 | ||
2362 | switch (opcode) { | |
2363 | case TCPOPT_EOL: | |
2364 | return; | |
2365 | case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ | |
2366 | length--; | |
2367 | continue; | |
2368 | default: | |
2369 | opsize=*ptr++; | |
2370 | if (opsize < 2) /* "silly options" */ | |
2371 | return; | |
2372 | if (opsize > length) | |
2373 | return; /* don't parse partial options */ | |
2374 | switch(opcode) { | |
2375 | case TCPOPT_MSS: | |
2376 | if(opsize==TCPOLEN_MSS && th->syn && !estab) { | |
2377 | u16 in_mss = ntohs(get_unaligned((__u16 *)ptr)); | |
2378 | if (in_mss) { | |
2379 | if (opt_rx->user_mss && opt_rx->user_mss < in_mss) | |
2380 | in_mss = opt_rx->user_mss; | |
2381 | opt_rx->mss_clamp = in_mss; | |
2382 | } | |
2383 | } | |
2384 | break; | |
2385 | case TCPOPT_WINDOW: | |
2386 | if(opsize==TCPOLEN_WINDOW && th->syn && !estab) | |
2387 | if (sysctl_tcp_window_scaling) { | |
2388 | __u8 snd_wscale = *(__u8 *) ptr; | |
2389 | opt_rx->wscale_ok = 1; | |
2390 | if (snd_wscale > 14) { | |
2391 | if(net_ratelimit()) | |
2392 | printk(KERN_INFO "tcp_parse_options: Illegal window " | |
2393 | "scaling value %d >14 received.\n", | |
2394 | snd_wscale); | |
2395 | snd_wscale = 14; | |
2396 | } | |
2397 | opt_rx->snd_wscale = snd_wscale; | |
2398 | } | |
2399 | break; | |
2400 | case TCPOPT_TIMESTAMP: | |
2401 | if(opsize==TCPOLEN_TIMESTAMP) { | |
2402 | if ((estab && opt_rx->tstamp_ok) || | |
2403 | (!estab && sysctl_tcp_timestamps)) { | |
2404 | opt_rx->saw_tstamp = 1; | |
2405 | opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr)); | |
2406 | opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4))); | |
2407 | } | |
2408 | } | |
2409 | break; | |
2410 | case TCPOPT_SACK_PERM: | |
2411 | if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) { | |
2412 | if (sysctl_tcp_sack) { | |
2413 | opt_rx->sack_ok = 1; | |
2414 | tcp_sack_reset(opt_rx); | |
2415 | } | |
2416 | } | |
2417 | break; | |
2418 | ||
2419 | case TCPOPT_SACK: | |
2420 | if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && | |
2421 | !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && | |
2422 | opt_rx->sack_ok) { | |
2423 | TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; | |
2424 | } | |
2425 | }; | |
2426 | ptr+=opsize-2; | |
2427 | length-=opsize; | |
2428 | }; | |
2429 | } | |
2430 | } | |
2431 | ||
2432 | /* Fast parse options. This hopes to only see timestamps. | |
2433 | * If it is wrong it falls back on tcp_parse_options(). | |
2434 | */ | |
2435 | static inline int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, | |
2436 | struct tcp_sock *tp) | |
2437 | { | |
2438 | if (th->doff == sizeof(struct tcphdr)>>2) { | |
2439 | tp->rx_opt.saw_tstamp = 0; | |
2440 | return 0; | |
2441 | } else if (tp->rx_opt.tstamp_ok && | |
2442 | th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { | |
2443 | __u32 *ptr = (__u32 *)(th + 1); | |
2444 | if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | |
2445 | | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { | |
2446 | tp->rx_opt.saw_tstamp = 1; | |
2447 | ++ptr; | |
2448 | tp->rx_opt.rcv_tsval = ntohl(*ptr); | |
2449 | ++ptr; | |
2450 | tp->rx_opt.rcv_tsecr = ntohl(*ptr); | |
2451 | return 1; | |
2452 | } | |
2453 | } | |
2454 | tcp_parse_options(skb, &tp->rx_opt, 1); | |
2455 | return 1; | |
2456 | } | |
2457 | ||
2458 | static inline void tcp_store_ts_recent(struct tcp_sock *tp) | |
2459 | { | |
2460 | tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; | |
2461 | tp->rx_opt.ts_recent_stamp = xtime.tv_sec; | |
2462 | } | |
2463 | ||
2464 | static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) | |
2465 | { | |
2466 | if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { | |
2467 | /* PAWS bug workaround wrt. ACK frames, the PAWS discard | |
2468 | * extra check below makes sure this can only happen | |
2469 | * for pure ACK frames. -DaveM | |
2470 | * | |
2471 | * Not only, also it occurs for expired timestamps. | |
2472 | */ | |
2473 | ||
2474 | if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 || | |
2475 | xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS) | |
2476 | tcp_store_ts_recent(tp); | |
2477 | } | |
2478 | } | |
2479 | ||
2480 | /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM | |
2481 | * | |
2482 | * It is not fatal. If this ACK does _not_ change critical state (seqs, window) | |
2483 | * it can pass through stack. So, the following predicate verifies that | |
2484 | * this segment is not used for anything but congestion avoidance or | |
2485 | * fast retransmit. Moreover, we even are able to eliminate most of such | |
2486 | * second order effects, if we apply some small "replay" window (~RTO) | |
2487 | * to timestamp space. | |
2488 | * | |
2489 | * All these measures still do not guarantee that we reject wrapped ACKs | |
2490 | * on networks with high bandwidth, when sequence space is recycled fastly, | |
2491 | * but it guarantees that such events will be very rare and do not affect | |
2492 | * connection seriously. This doesn't look nice, but alas, PAWS is really | |
2493 | * buggy extension. | |
2494 | * | |
2495 | * [ Later note. Even worse! It is buggy for segments _with_ data. RFC | |
2496 | * states that events when retransmit arrives after original data are rare. | |
2497 | * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is | |
2498 | * the biggest problem on large power networks even with minor reordering. | |
2499 | * OK, let's give it small replay window. If peer clock is even 1hz, it is safe | |
2500 | * up to bandwidth of 18Gigabit/sec. 8) ] | |
2501 | */ | |
2502 | ||
2503 | static int tcp_disordered_ack(struct tcp_sock *tp, struct sk_buff *skb) | |
2504 | { | |
2505 | struct tcphdr *th = skb->h.th; | |
2506 | u32 seq = TCP_SKB_CB(skb)->seq; | |
2507 | u32 ack = TCP_SKB_CB(skb)->ack_seq; | |
2508 | ||
2509 | return (/* 1. Pure ACK with correct sequence number. */ | |
2510 | (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && | |
2511 | ||
2512 | /* 2. ... and duplicate ACK. */ | |
2513 | ack == tp->snd_una && | |
2514 | ||
2515 | /* 3. ... and does not update window. */ | |
2516 | !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && | |
2517 | ||
2518 | /* 4. ... and sits in replay window. */ | |
2519 | (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (tp->rto*1024)/HZ); | |
2520 | } | |
2521 | ||
2522 | static inline int tcp_paws_discard(struct tcp_sock *tp, struct sk_buff *skb) | |
2523 | { | |
2524 | return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW && | |
2525 | xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS && | |
2526 | !tcp_disordered_ack(tp, skb)); | |
2527 | } | |
2528 | ||
2529 | /* Check segment sequence number for validity. | |
2530 | * | |
2531 | * Segment controls are considered valid, if the segment | |
2532 | * fits to the window after truncation to the window. Acceptability | |
2533 | * of data (and SYN, FIN, of course) is checked separately. | |
2534 | * See tcp_data_queue(), for example. | |
2535 | * | |
2536 | * Also, controls (RST is main one) are accepted using RCV.WUP instead | |
2537 | * of RCV.NXT. Peer still did not advance his SND.UNA when we | |
2538 | * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. | |
2539 | * (borrowed from freebsd) | |
2540 | */ | |
2541 | ||
2542 | static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) | |
2543 | { | |
2544 | return !before(end_seq, tp->rcv_wup) && | |
2545 | !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); | |
2546 | } | |
2547 | ||
2548 | /* When we get a reset we do this. */ | |
2549 | static void tcp_reset(struct sock *sk) | |
2550 | { | |
2551 | /* We want the right error as BSD sees it (and indeed as we do). */ | |
2552 | switch (sk->sk_state) { | |
2553 | case TCP_SYN_SENT: | |
2554 | sk->sk_err = ECONNREFUSED; | |
2555 | break; | |
2556 | case TCP_CLOSE_WAIT: | |
2557 | sk->sk_err = EPIPE; | |
2558 | break; | |
2559 | case TCP_CLOSE: | |
2560 | return; | |
2561 | default: | |
2562 | sk->sk_err = ECONNRESET; | |
2563 | } | |
2564 | ||
2565 | if (!sock_flag(sk, SOCK_DEAD)) | |
2566 | sk->sk_error_report(sk); | |
2567 | ||
2568 | tcp_done(sk); | |
2569 | } | |
2570 | ||
2571 | /* | |
2572 | * Process the FIN bit. This now behaves as it is supposed to work | |
2573 | * and the FIN takes effect when it is validly part of sequence | |
2574 | * space. Not before when we get holes. | |
2575 | * | |
2576 | * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT | |
2577 | * (and thence onto LAST-ACK and finally, CLOSE, we never enter | |
2578 | * TIME-WAIT) | |
2579 | * | |
2580 | * If we are in FINWAIT-1, a received FIN indicates simultaneous | |
2581 | * close and we go into CLOSING (and later onto TIME-WAIT) | |
2582 | * | |
2583 | * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. | |
2584 | */ | |
2585 | static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) | |
2586 | { | |
2587 | struct tcp_sock *tp = tcp_sk(sk); | |
2588 | ||
2589 | tcp_schedule_ack(tp); | |
2590 | ||
2591 | sk->sk_shutdown |= RCV_SHUTDOWN; | |
2592 | sock_set_flag(sk, SOCK_DONE); | |
2593 | ||
2594 | switch (sk->sk_state) { | |
2595 | case TCP_SYN_RECV: | |
2596 | case TCP_ESTABLISHED: | |
2597 | /* Move to CLOSE_WAIT */ | |
2598 | tcp_set_state(sk, TCP_CLOSE_WAIT); | |
2599 | tp->ack.pingpong = 1; | |
2600 | break; | |
2601 | ||
2602 | case TCP_CLOSE_WAIT: | |
2603 | case TCP_CLOSING: | |
2604 | /* Received a retransmission of the FIN, do | |
2605 | * nothing. | |
2606 | */ | |
2607 | break; | |
2608 | case TCP_LAST_ACK: | |
2609 | /* RFC793: Remain in the LAST-ACK state. */ | |
2610 | break; | |
2611 | ||
2612 | case TCP_FIN_WAIT1: | |
2613 | /* This case occurs when a simultaneous close | |
2614 | * happens, we must ack the received FIN and | |
2615 | * enter the CLOSING state. | |
2616 | */ | |
2617 | tcp_send_ack(sk); | |
2618 | tcp_set_state(sk, TCP_CLOSING); | |
2619 | break; | |
2620 | case TCP_FIN_WAIT2: | |
2621 | /* Received a FIN -- send ACK and enter TIME_WAIT. */ | |
2622 | tcp_send_ack(sk); | |
2623 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); | |
2624 | break; | |
2625 | default: | |
2626 | /* Only TCP_LISTEN and TCP_CLOSE are left, in these | |
2627 | * cases we should never reach this piece of code. | |
2628 | */ | |
2629 | printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", | |
2630 | __FUNCTION__, sk->sk_state); | |
2631 | break; | |
2632 | }; | |
2633 | ||
2634 | /* It _is_ possible, that we have something out-of-order _after_ FIN. | |
2635 | * Probably, we should reset in this case. For now drop them. | |
2636 | */ | |
2637 | __skb_queue_purge(&tp->out_of_order_queue); | |
2638 | if (tp->rx_opt.sack_ok) | |
2639 | tcp_sack_reset(&tp->rx_opt); | |
2640 | sk_stream_mem_reclaim(sk); | |
2641 | ||
2642 | if (!sock_flag(sk, SOCK_DEAD)) { | |
2643 | sk->sk_state_change(sk); | |
2644 | ||
2645 | /* Do not send POLL_HUP for half duplex close. */ | |
2646 | if (sk->sk_shutdown == SHUTDOWN_MASK || | |
2647 | sk->sk_state == TCP_CLOSE) | |
2648 | sk_wake_async(sk, 1, POLL_HUP); | |
2649 | else | |
2650 | sk_wake_async(sk, 1, POLL_IN); | |
2651 | } | |
2652 | } | |
2653 | ||
2654 | static __inline__ int | |
2655 | tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq) | |
2656 | { | |
2657 | if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { | |
2658 | if (before(seq, sp->start_seq)) | |
2659 | sp->start_seq = seq; | |
2660 | if (after(end_seq, sp->end_seq)) | |
2661 | sp->end_seq = end_seq; | |
2662 | return 1; | |
2663 | } | |
2664 | return 0; | |
2665 | } | |
2666 | ||
2667 | static inline void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq) | |
2668 | { | |
2669 | if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { | |
2670 | if (before(seq, tp->rcv_nxt)) | |
2671 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT); | |
2672 | else | |
2673 | NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT); | |
2674 | ||
2675 | tp->rx_opt.dsack = 1; | |
2676 | tp->duplicate_sack[0].start_seq = seq; | |
2677 | tp->duplicate_sack[0].end_seq = end_seq; | |
2678 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok); | |
2679 | } | |
2680 | } | |
2681 | ||
2682 | static inline void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq) | |
2683 | { | |
2684 | if (!tp->rx_opt.dsack) | |
2685 | tcp_dsack_set(tp, seq, end_seq); | |
2686 | else | |
2687 | tcp_sack_extend(tp->duplicate_sack, seq, end_seq); | |
2688 | } | |
2689 | ||
2690 | static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) | |
2691 | { | |
2692 | struct tcp_sock *tp = tcp_sk(sk); | |
2693 | ||
2694 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && | |
2695 | before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
2696 | NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); | |
2697 | tcp_enter_quickack_mode(tp); | |
2698 | ||
2699 | if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { | |
2700 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; | |
2701 | ||
2702 | if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) | |
2703 | end_seq = tp->rcv_nxt; | |
2704 | tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq); | |
2705 | } | |
2706 | } | |
2707 | ||
2708 | tcp_send_ack(sk); | |
2709 | } | |
2710 | ||
2711 | /* These routines update the SACK block as out-of-order packets arrive or | |
2712 | * in-order packets close up the sequence space. | |
2713 | */ | |
2714 | static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) | |
2715 | { | |
2716 | int this_sack; | |
2717 | struct tcp_sack_block *sp = &tp->selective_acks[0]; | |
2718 | struct tcp_sack_block *swalk = sp+1; | |
2719 | ||
2720 | /* See if the recent change to the first SACK eats into | |
2721 | * or hits the sequence space of other SACK blocks, if so coalesce. | |
2722 | */ | |
2723 | for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) { | |
2724 | if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { | |
2725 | int i; | |
2726 | ||
2727 | /* Zap SWALK, by moving every further SACK up by one slot. | |
2728 | * Decrease num_sacks. | |
2729 | */ | |
2730 | tp->rx_opt.num_sacks--; | |
2731 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); | |
2732 | for(i=this_sack; i < tp->rx_opt.num_sacks; i++) | |
2733 | sp[i] = sp[i+1]; | |
2734 | continue; | |
2735 | } | |
2736 | this_sack++, swalk++; | |
2737 | } | |
2738 | } | |
2739 | ||
2740 | static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2) | |
2741 | { | |
2742 | __u32 tmp; | |
2743 | ||
2744 | tmp = sack1->start_seq; | |
2745 | sack1->start_seq = sack2->start_seq; | |
2746 | sack2->start_seq = tmp; | |
2747 | ||
2748 | tmp = sack1->end_seq; | |
2749 | sack1->end_seq = sack2->end_seq; | |
2750 | sack2->end_seq = tmp; | |
2751 | } | |
2752 | ||
2753 | static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) | |
2754 | { | |
2755 | struct tcp_sock *tp = tcp_sk(sk); | |
2756 | struct tcp_sack_block *sp = &tp->selective_acks[0]; | |
2757 | int cur_sacks = tp->rx_opt.num_sacks; | |
2758 | int this_sack; | |
2759 | ||
2760 | if (!cur_sacks) | |
2761 | goto new_sack; | |
2762 | ||
2763 | for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) { | |
2764 | if (tcp_sack_extend(sp, seq, end_seq)) { | |
2765 | /* Rotate this_sack to the first one. */ | |
2766 | for (; this_sack>0; this_sack--, sp--) | |
2767 | tcp_sack_swap(sp, sp-1); | |
2768 | if (cur_sacks > 1) | |
2769 | tcp_sack_maybe_coalesce(tp); | |
2770 | return; | |
2771 | } | |
2772 | } | |
2773 | ||
2774 | /* Could not find an adjacent existing SACK, build a new one, | |
2775 | * put it at the front, and shift everyone else down. We | |
2776 | * always know there is at least one SACK present already here. | |
2777 | * | |
2778 | * If the sack array is full, forget about the last one. | |
2779 | */ | |
2780 | if (this_sack >= 4) { | |
2781 | this_sack--; | |
2782 | tp->rx_opt.num_sacks--; | |
2783 | sp--; | |
2784 | } | |
2785 | for(; this_sack > 0; this_sack--, sp--) | |
2786 | *sp = *(sp-1); | |
2787 | ||
2788 | new_sack: | |
2789 | /* Build the new head SACK, and we're done. */ | |
2790 | sp->start_seq = seq; | |
2791 | sp->end_seq = end_seq; | |
2792 | tp->rx_opt.num_sacks++; | |
2793 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); | |
2794 | } | |
2795 | ||
2796 | /* RCV.NXT advances, some SACKs should be eaten. */ | |
2797 | ||
2798 | static void tcp_sack_remove(struct tcp_sock *tp) | |
2799 | { | |
2800 | struct tcp_sack_block *sp = &tp->selective_acks[0]; | |
2801 | int num_sacks = tp->rx_opt.num_sacks; | |
2802 | int this_sack; | |
2803 | ||
2804 | /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ | |
b03efcfb | 2805 | if (skb_queue_empty(&tp->out_of_order_queue)) { |
1da177e4 LT |
2806 | tp->rx_opt.num_sacks = 0; |
2807 | tp->rx_opt.eff_sacks = tp->rx_opt.dsack; | |
2808 | return; | |
2809 | } | |
2810 | ||
2811 | for(this_sack = 0; this_sack < num_sacks; ) { | |
2812 | /* Check if the start of the sack is covered by RCV.NXT. */ | |
2813 | if (!before(tp->rcv_nxt, sp->start_seq)) { | |
2814 | int i; | |
2815 | ||
2816 | /* RCV.NXT must cover all the block! */ | |
2817 | BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq)); | |
2818 | ||
2819 | /* Zap this SACK, by moving forward any other SACKS. */ | |
2820 | for (i=this_sack+1; i < num_sacks; i++) | |
2821 | tp->selective_acks[i-1] = tp->selective_acks[i]; | |
2822 | num_sacks--; | |
2823 | continue; | |
2824 | } | |
2825 | this_sack++; | |
2826 | sp++; | |
2827 | } | |
2828 | if (num_sacks != tp->rx_opt.num_sacks) { | |
2829 | tp->rx_opt.num_sacks = num_sacks; | |
2830 | tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); | |
2831 | } | |
2832 | } | |
2833 | ||
2834 | /* This one checks to see if we can put data from the | |
2835 | * out_of_order queue into the receive_queue. | |
2836 | */ | |
2837 | static void tcp_ofo_queue(struct sock *sk) | |
2838 | { | |
2839 | struct tcp_sock *tp = tcp_sk(sk); | |
2840 | __u32 dsack_high = tp->rcv_nxt; | |
2841 | struct sk_buff *skb; | |
2842 | ||
2843 | while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { | |
2844 | if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) | |
2845 | break; | |
2846 | ||
2847 | if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { | |
2848 | __u32 dsack = dsack_high; | |
2849 | if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) | |
2850 | dsack_high = TCP_SKB_CB(skb)->end_seq; | |
2851 | tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack); | |
2852 | } | |
2853 | ||
2854 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { | |
2855 | SOCK_DEBUG(sk, "ofo packet was already received \n"); | |
2856 | __skb_unlink(skb, skb->list); | |
2857 | __kfree_skb(skb); | |
2858 | continue; | |
2859 | } | |
2860 | SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", | |
2861 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, | |
2862 | TCP_SKB_CB(skb)->end_seq); | |
2863 | ||
2864 | __skb_unlink(skb, skb->list); | |
2865 | __skb_queue_tail(&sk->sk_receive_queue, skb); | |
2866 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
2867 | if(skb->h.th->fin) | |
2868 | tcp_fin(skb, sk, skb->h.th); | |
2869 | } | |
2870 | } | |
2871 | ||
2872 | static int tcp_prune_queue(struct sock *sk); | |
2873 | ||
2874 | static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) | |
2875 | { | |
2876 | struct tcphdr *th = skb->h.th; | |
2877 | struct tcp_sock *tp = tcp_sk(sk); | |
2878 | int eaten = -1; | |
2879 | ||
2880 | if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) | |
2881 | goto drop; | |
2882 | ||
1da177e4 LT |
2883 | __skb_pull(skb, th->doff*4); |
2884 | ||
2885 | TCP_ECN_accept_cwr(tp, skb); | |
2886 | ||
2887 | if (tp->rx_opt.dsack) { | |
2888 | tp->rx_opt.dsack = 0; | |
2889 | tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks, | |
2890 | 4 - tp->rx_opt.tstamp_ok); | |
2891 | } | |
2892 | ||
2893 | /* Queue data for delivery to the user. | |
2894 | * Packets in sequence go to the receive queue. | |
2895 | * Out of sequence packets to the out_of_order_queue. | |
2896 | */ | |
2897 | if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { | |
2898 | if (tcp_receive_window(tp) == 0) | |
2899 | goto out_of_window; | |
2900 | ||
2901 | /* Ok. In sequence. In window. */ | |
2902 | if (tp->ucopy.task == current && | |
2903 | tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && | |
2904 | sock_owned_by_user(sk) && !tp->urg_data) { | |
2905 | int chunk = min_t(unsigned int, skb->len, | |
2906 | tp->ucopy.len); | |
2907 | ||
2908 | __set_current_state(TASK_RUNNING); | |
2909 | ||
2910 | local_bh_enable(); | |
2911 | if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { | |
2912 | tp->ucopy.len -= chunk; | |
2913 | tp->copied_seq += chunk; | |
2914 | eaten = (chunk == skb->len && !th->fin); | |
2915 | tcp_rcv_space_adjust(sk); | |
2916 | } | |
2917 | local_bh_disable(); | |
2918 | } | |
2919 | ||
2920 | if (eaten <= 0) { | |
2921 | queue_and_out: | |
2922 | if (eaten < 0 && | |
2923 | (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || | |
2924 | !sk_stream_rmem_schedule(sk, skb))) { | |
2925 | if (tcp_prune_queue(sk) < 0 || | |
2926 | !sk_stream_rmem_schedule(sk, skb)) | |
2927 | goto drop; | |
2928 | } | |
2929 | sk_stream_set_owner_r(skb, sk); | |
2930 | __skb_queue_tail(&sk->sk_receive_queue, skb); | |
2931 | } | |
2932 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
2933 | if(skb->len) | |
2934 | tcp_event_data_recv(sk, tp, skb); | |
2935 | if(th->fin) | |
2936 | tcp_fin(skb, sk, th); | |
2937 | ||
b03efcfb | 2938 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
1da177e4 LT |
2939 | tcp_ofo_queue(sk); |
2940 | ||
2941 | /* RFC2581. 4.2. SHOULD send immediate ACK, when | |
2942 | * gap in queue is filled. | |
2943 | */ | |
b03efcfb | 2944 | if (skb_queue_empty(&tp->out_of_order_queue)) |
1da177e4 LT |
2945 | tp->ack.pingpong = 0; |
2946 | } | |
2947 | ||
2948 | if (tp->rx_opt.num_sacks) | |
2949 | tcp_sack_remove(tp); | |
2950 | ||
2951 | tcp_fast_path_check(sk, tp); | |
2952 | ||
2953 | if (eaten > 0) | |
2954 | __kfree_skb(skb); | |
2955 | else if (!sock_flag(sk, SOCK_DEAD)) | |
2956 | sk->sk_data_ready(sk, 0); | |
2957 | return; | |
2958 | } | |
2959 | ||
2960 | if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { | |
2961 | /* A retransmit, 2nd most common case. Force an immediate ack. */ | |
2962 | NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); | |
2963 | tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); | |
2964 | ||
2965 | out_of_window: | |
2966 | tcp_enter_quickack_mode(tp); | |
2967 | tcp_schedule_ack(tp); | |
2968 | drop: | |
2969 | __kfree_skb(skb); | |
2970 | return; | |
2971 | } | |
2972 | ||
2973 | /* Out of window. F.e. zero window probe. */ | |
2974 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) | |
2975 | goto out_of_window; | |
2976 | ||
2977 | tcp_enter_quickack_mode(tp); | |
2978 | ||
2979 | if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
2980 | /* Partial packet, seq < rcv_next < end_seq */ | |
2981 | SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", | |
2982 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, | |
2983 | TCP_SKB_CB(skb)->end_seq); | |
2984 | ||
2985 | tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); | |
2986 | ||
2987 | /* If window is closed, drop tail of packet. But after | |
2988 | * remembering D-SACK for its head made in previous line. | |
2989 | */ | |
2990 | if (!tcp_receive_window(tp)) | |
2991 | goto out_of_window; | |
2992 | goto queue_and_out; | |
2993 | } | |
2994 | ||
2995 | TCP_ECN_check_ce(tp, skb); | |
2996 | ||
2997 | if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || | |
2998 | !sk_stream_rmem_schedule(sk, skb)) { | |
2999 | if (tcp_prune_queue(sk) < 0 || | |
3000 | !sk_stream_rmem_schedule(sk, skb)) | |
3001 | goto drop; | |
3002 | } | |
3003 | ||
3004 | /* Disable header prediction. */ | |
3005 | tp->pred_flags = 0; | |
3006 | tcp_schedule_ack(tp); | |
3007 | ||
3008 | SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", | |
3009 | tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); | |
3010 | ||
3011 | sk_stream_set_owner_r(skb, sk); | |
3012 | ||
3013 | if (!skb_peek(&tp->out_of_order_queue)) { | |
3014 | /* Initial out of order segment, build 1 SACK. */ | |
3015 | if (tp->rx_opt.sack_ok) { | |
3016 | tp->rx_opt.num_sacks = 1; | |
3017 | tp->rx_opt.dsack = 0; | |
3018 | tp->rx_opt.eff_sacks = 1; | |
3019 | tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; | |
3020 | tp->selective_acks[0].end_seq = | |
3021 | TCP_SKB_CB(skb)->end_seq; | |
3022 | } | |
3023 | __skb_queue_head(&tp->out_of_order_queue,skb); | |
3024 | } else { | |
3025 | struct sk_buff *skb1 = tp->out_of_order_queue.prev; | |
3026 | u32 seq = TCP_SKB_CB(skb)->seq; | |
3027 | u32 end_seq = TCP_SKB_CB(skb)->end_seq; | |
3028 | ||
3029 | if (seq == TCP_SKB_CB(skb1)->end_seq) { | |
3030 | __skb_append(skb1, skb); | |
3031 | ||
3032 | if (!tp->rx_opt.num_sacks || | |
3033 | tp->selective_acks[0].end_seq != seq) | |
3034 | goto add_sack; | |
3035 | ||
3036 | /* Common case: data arrive in order after hole. */ | |
3037 | tp->selective_acks[0].end_seq = end_seq; | |
3038 | return; | |
3039 | } | |
3040 | ||
3041 | /* Find place to insert this segment. */ | |
3042 | do { | |
3043 | if (!after(TCP_SKB_CB(skb1)->seq, seq)) | |
3044 | break; | |
3045 | } while ((skb1 = skb1->prev) != | |
3046 | (struct sk_buff*)&tp->out_of_order_queue); | |
3047 | ||
3048 | /* Do skb overlap to previous one? */ | |
3049 | if (skb1 != (struct sk_buff*)&tp->out_of_order_queue && | |
3050 | before(seq, TCP_SKB_CB(skb1)->end_seq)) { | |
3051 | if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { | |
3052 | /* All the bits are present. Drop. */ | |
3053 | __kfree_skb(skb); | |
3054 | tcp_dsack_set(tp, seq, end_seq); | |
3055 | goto add_sack; | |
3056 | } | |
3057 | if (after(seq, TCP_SKB_CB(skb1)->seq)) { | |
3058 | /* Partial overlap. */ | |
3059 | tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq); | |
3060 | } else { | |
3061 | skb1 = skb1->prev; | |
3062 | } | |
3063 | } | |
3064 | __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue); | |
3065 | ||
3066 | /* And clean segments covered by new one as whole. */ | |
3067 | while ((skb1 = skb->next) != | |
3068 | (struct sk_buff*)&tp->out_of_order_queue && | |
3069 | after(end_seq, TCP_SKB_CB(skb1)->seq)) { | |
3070 | if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { | |
3071 | tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq); | |
3072 | break; | |
3073 | } | |
3074 | __skb_unlink(skb1, skb1->list); | |
3075 | tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); | |
3076 | __kfree_skb(skb1); | |
3077 | } | |
3078 | ||
3079 | add_sack: | |
3080 | if (tp->rx_opt.sack_ok) | |
3081 | tcp_sack_new_ofo_skb(sk, seq, end_seq); | |
3082 | } | |
3083 | } | |
3084 | ||
3085 | /* Collapse contiguous sequence of skbs head..tail with | |
3086 | * sequence numbers start..end. | |
3087 | * Segments with FIN/SYN are not collapsed (only because this | |
3088 | * simplifies code) | |
3089 | */ | |
3090 | static void | |
3091 | tcp_collapse(struct sock *sk, struct sk_buff *head, | |
3092 | struct sk_buff *tail, u32 start, u32 end) | |
3093 | { | |
3094 | struct sk_buff *skb; | |
3095 | ||
3096 | /* First, check that queue is collapsable and find | |
3097 | * the point where collapsing can be useful. */ | |
3098 | for (skb = head; skb != tail; ) { | |
3099 | /* No new bits? It is possible on ofo queue. */ | |
3100 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { | |
3101 | struct sk_buff *next = skb->next; | |
3102 | __skb_unlink(skb, skb->list); | |
3103 | __kfree_skb(skb); | |
3104 | NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); | |
3105 | skb = next; | |
3106 | continue; | |
3107 | } | |
3108 | ||
3109 | /* The first skb to collapse is: | |
3110 | * - not SYN/FIN and | |
3111 | * - bloated or contains data before "start" or | |
3112 | * overlaps to the next one. | |
3113 | */ | |
3114 | if (!skb->h.th->syn && !skb->h.th->fin && | |
3115 | (tcp_win_from_space(skb->truesize) > skb->len || | |
3116 | before(TCP_SKB_CB(skb)->seq, start) || | |
3117 | (skb->next != tail && | |
3118 | TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq))) | |
3119 | break; | |
3120 | ||
3121 | /* Decided to skip this, advance start seq. */ | |
3122 | start = TCP_SKB_CB(skb)->end_seq; | |
3123 | skb = skb->next; | |
3124 | } | |
3125 | if (skb == tail || skb->h.th->syn || skb->h.th->fin) | |
3126 | return; | |
3127 | ||
3128 | while (before(start, end)) { | |
3129 | struct sk_buff *nskb; | |
3130 | int header = skb_headroom(skb); | |
3131 | int copy = SKB_MAX_ORDER(header, 0); | |
3132 | ||
3133 | /* Too big header? This can happen with IPv6. */ | |
3134 | if (copy < 0) | |
3135 | return; | |
3136 | if (end-start < copy) | |
3137 | copy = end-start; | |
3138 | nskb = alloc_skb(copy+header, GFP_ATOMIC); | |
3139 | if (!nskb) | |
3140 | return; | |
3141 | skb_reserve(nskb, header); | |
3142 | memcpy(nskb->head, skb->head, header); | |
3143 | nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head); | |
3144 | nskb->h.raw = nskb->head + (skb->h.raw-skb->head); | |
3145 | nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head); | |
3146 | memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); | |
3147 | TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; | |
3148 | __skb_insert(nskb, skb->prev, skb, skb->list); | |
3149 | sk_stream_set_owner_r(nskb, sk); | |
3150 | ||
3151 | /* Copy data, releasing collapsed skbs. */ | |
3152 | while (copy > 0) { | |
3153 | int offset = start - TCP_SKB_CB(skb)->seq; | |
3154 | int size = TCP_SKB_CB(skb)->end_seq - start; | |
3155 | ||
3156 | if (offset < 0) BUG(); | |
3157 | if (size > 0) { | |
3158 | size = min(copy, size); | |
3159 | if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) | |
3160 | BUG(); | |
3161 | TCP_SKB_CB(nskb)->end_seq += size; | |
3162 | copy -= size; | |
3163 | start += size; | |
3164 | } | |
3165 | if (!before(start, TCP_SKB_CB(skb)->end_seq)) { | |
3166 | struct sk_buff *next = skb->next; | |
3167 | __skb_unlink(skb, skb->list); | |
3168 | __kfree_skb(skb); | |
3169 | NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); | |
3170 | skb = next; | |
3171 | if (skb == tail || skb->h.th->syn || skb->h.th->fin) | |
3172 | return; | |
3173 | } | |
3174 | } | |
3175 | } | |
3176 | } | |
3177 | ||
3178 | /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs | |
3179 | * and tcp_collapse() them until all the queue is collapsed. | |
3180 | */ | |
3181 | static void tcp_collapse_ofo_queue(struct sock *sk) | |
3182 | { | |
3183 | struct tcp_sock *tp = tcp_sk(sk); | |
3184 | struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); | |
3185 | struct sk_buff *head; | |
3186 | u32 start, end; | |
3187 | ||
3188 | if (skb == NULL) | |
3189 | return; | |
3190 | ||
3191 | start = TCP_SKB_CB(skb)->seq; | |
3192 | end = TCP_SKB_CB(skb)->end_seq; | |
3193 | head = skb; | |
3194 | ||
3195 | for (;;) { | |
3196 | skb = skb->next; | |
3197 | ||
3198 | /* Segment is terminated when we see gap or when | |
3199 | * we are at the end of all the queue. */ | |
3200 | if (skb == (struct sk_buff *)&tp->out_of_order_queue || | |
3201 | after(TCP_SKB_CB(skb)->seq, end) || | |
3202 | before(TCP_SKB_CB(skb)->end_seq, start)) { | |
3203 | tcp_collapse(sk, head, skb, start, end); | |
3204 | head = skb; | |
3205 | if (skb == (struct sk_buff *)&tp->out_of_order_queue) | |
3206 | break; | |
3207 | /* Start new segment */ | |
3208 | start = TCP_SKB_CB(skb)->seq; | |
3209 | end = TCP_SKB_CB(skb)->end_seq; | |
3210 | } else { | |
3211 | if (before(TCP_SKB_CB(skb)->seq, start)) | |
3212 | start = TCP_SKB_CB(skb)->seq; | |
3213 | if (after(TCP_SKB_CB(skb)->end_seq, end)) | |
3214 | end = TCP_SKB_CB(skb)->end_seq; | |
3215 | } | |
3216 | } | |
3217 | } | |
3218 | ||
3219 | /* Reduce allocated memory if we can, trying to get | |
3220 | * the socket within its memory limits again. | |
3221 | * | |
3222 | * Return less than zero if we should start dropping frames | |
3223 | * until the socket owning process reads some of the data | |
3224 | * to stabilize the situation. | |
3225 | */ | |
3226 | static int tcp_prune_queue(struct sock *sk) | |
3227 | { | |
3228 | struct tcp_sock *tp = tcp_sk(sk); | |
3229 | ||
3230 | SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); | |
3231 | ||
3232 | NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED); | |
3233 | ||
3234 | if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) | |
3235 | tcp_clamp_window(sk, tp); | |
3236 | else if (tcp_memory_pressure) | |
3237 | tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); | |
3238 | ||
3239 | tcp_collapse_ofo_queue(sk); | |
3240 | tcp_collapse(sk, sk->sk_receive_queue.next, | |
3241 | (struct sk_buff*)&sk->sk_receive_queue, | |
3242 | tp->copied_seq, tp->rcv_nxt); | |
3243 | sk_stream_mem_reclaim(sk); | |
3244 | ||
3245 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) | |
3246 | return 0; | |
3247 | ||
3248 | /* Collapsing did not help, destructive actions follow. | |
3249 | * This must not ever occur. */ | |
3250 | ||
3251 | /* First, purge the out_of_order queue. */ | |
b03efcfb DM |
3252 | if (!skb_queue_empty(&tp->out_of_order_queue)) { |
3253 | NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED); | |
1da177e4 LT |
3254 | __skb_queue_purge(&tp->out_of_order_queue); |
3255 | ||
3256 | /* Reset SACK state. A conforming SACK implementation will | |
3257 | * do the same at a timeout based retransmit. When a connection | |
3258 | * is in a sad state like this, we care only about integrity | |
3259 | * of the connection not performance. | |
3260 | */ | |
3261 | if (tp->rx_opt.sack_ok) | |
3262 | tcp_sack_reset(&tp->rx_opt); | |
3263 | sk_stream_mem_reclaim(sk); | |
3264 | } | |
3265 | ||
3266 | if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) | |
3267 | return 0; | |
3268 | ||
3269 | /* If we are really being abused, tell the caller to silently | |
3270 | * drop receive data on the floor. It will get retransmitted | |
3271 | * and hopefully then we'll have sufficient space. | |
3272 | */ | |
3273 | NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED); | |
3274 | ||
3275 | /* Massive buffer overcommit. */ | |
3276 | tp->pred_flags = 0; | |
3277 | return -1; | |
3278 | } | |
3279 | ||
3280 | ||
3281 | /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. | |
3282 | * As additional protections, we do not touch cwnd in retransmission phases, | |
3283 | * and if application hit its sndbuf limit recently. | |
3284 | */ | |
3285 | void tcp_cwnd_application_limited(struct sock *sk) | |
3286 | { | |
3287 | struct tcp_sock *tp = tcp_sk(sk); | |
3288 | ||
3289 | if (tp->ca_state == TCP_CA_Open && | |
3290 | sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { | |
3291 | /* Limited by application or receiver window. */ | |
3292 | u32 win_used = max(tp->snd_cwnd_used, 2U); | |
3293 | if (win_used < tp->snd_cwnd) { | |
3294 | tp->snd_ssthresh = tcp_current_ssthresh(tp); | |
3295 | tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; | |
3296 | } | |
3297 | tp->snd_cwnd_used = 0; | |
3298 | } | |
3299 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
3300 | } | |
3301 | ||
0d9901df DM |
3302 | static inline int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp) |
3303 | { | |
3304 | /* If the user specified a specific send buffer setting, do | |
3305 | * not modify it. | |
3306 | */ | |
3307 | if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) | |
3308 | return 0; | |
3309 | ||
3310 | /* If we are under global TCP memory pressure, do not expand. */ | |
3311 | if (tcp_memory_pressure) | |
3312 | return 0; | |
3313 | ||
3314 | /* If we are under soft global TCP memory pressure, do not expand. */ | |
3315 | if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) | |
3316 | return 0; | |
3317 | ||
3318 | /* If we filled the congestion window, do not expand. */ | |
3319 | if (tp->packets_out >= tp->snd_cwnd) | |
3320 | return 0; | |
3321 | ||
3322 | return 1; | |
3323 | } | |
1da177e4 LT |
3324 | |
3325 | /* When incoming ACK allowed to free some skb from write_queue, | |
3326 | * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket | |
3327 | * on the exit from tcp input handler. | |
3328 | * | |
3329 | * PROBLEM: sndbuf expansion does not work well with largesend. | |
3330 | */ | |
3331 | static void tcp_new_space(struct sock *sk) | |
3332 | { | |
3333 | struct tcp_sock *tp = tcp_sk(sk); | |
3334 | ||
0d9901df | 3335 | if (tcp_should_expand_sndbuf(sk, tp)) { |
c1b4a7e6 | 3336 | int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + |
1da177e4 LT |
3337 | MAX_TCP_HEADER + 16 + sizeof(struct sk_buff), |
3338 | demanded = max_t(unsigned int, tp->snd_cwnd, | |
3339 | tp->reordering + 1); | |
3340 | sndmem *= 2*demanded; | |
3341 | if (sndmem > sk->sk_sndbuf) | |
3342 | sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); | |
3343 | tp->snd_cwnd_stamp = tcp_time_stamp; | |
3344 | } | |
3345 | ||
3346 | sk->sk_write_space(sk); | |
3347 | } | |
3348 | ||
3349 | static inline void tcp_check_space(struct sock *sk) | |
3350 | { | |
3351 | if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { | |
3352 | sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); | |
3353 | if (sk->sk_socket && | |
3354 | test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) | |
3355 | tcp_new_space(sk); | |
3356 | } | |
3357 | } | |
3358 | ||
55c97f3e | 3359 | static __inline__ void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp) |
1da177e4 | 3360 | { |
55c97f3e | 3361 | tcp_push_pending_frames(sk, tp); |
1da177e4 LT |
3362 | tcp_check_space(sk); |
3363 | } | |
3364 | ||
3365 | /* | |
3366 | * Check if sending an ack is needed. | |
3367 | */ | |
3368 | static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) | |
3369 | { | |
3370 | struct tcp_sock *tp = tcp_sk(sk); | |
3371 | ||
3372 | /* More than one full frame received... */ | |
3373 | if (((tp->rcv_nxt - tp->rcv_wup) > tp->ack.rcv_mss | |
3374 | /* ... and right edge of window advances far enough. | |
3375 | * (tcp_recvmsg() will send ACK otherwise). Or... | |
3376 | */ | |
3377 | && __tcp_select_window(sk) >= tp->rcv_wnd) || | |
3378 | /* We ACK each frame or... */ | |
3379 | tcp_in_quickack_mode(tp) || | |
3380 | /* We have out of order data. */ | |
3381 | (ofo_possible && | |
3382 | skb_peek(&tp->out_of_order_queue))) { | |
3383 | /* Then ack it now */ | |
3384 | tcp_send_ack(sk); | |
3385 | } else { | |
3386 | /* Else, send delayed ack. */ | |
3387 | tcp_send_delayed_ack(sk); | |
3388 | } | |
3389 | } | |
3390 | ||
3391 | static __inline__ void tcp_ack_snd_check(struct sock *sk) | |
3392 | { | |
3393 | struct tcp_sock *tp = tcp_sk(sk); | |
3394 | if (!tcp_ack_scheduled(tp)) { | |
3395 | /* We sent a data segment already. */ | |
3396 | return; | |
3397 | } | |
3398 | __tcp_ack_snd_check(sk, 1); | |
3399 | } | |
3400 | ||
3401 | /* | |
3402 | * This routine is only called when we have urgent data | |
3403 | * signalled. Its the 'slow' part of tcp_urg. It could be | |
3404 | * moved inline now as tcp_urg is only called from one | |
3405 | * place. We handle URGent data wrong. We have to - as | |
3406 | * BSD still doesn't use the correction from RFC961. | |
3407 | * For 1003.1g we should support a new option TCP_STDURG to permit | |
3408 | * either form (or just set the sysctl tcp_stdurg). | |
3409 | */ | |
3410 | ||
3411 | static void tcp_check_urg(struct sock * sk, struct tcphdr * th) | |
3412 | { | |
3413 | struct tcp_sock *tp = tcp_sk(sk); | |
3414 | u32 ptr = ntohs(th->urg_ptr); | |
3415 | ||
3416 | if (ptr && !sysctl_tcp_stdurg) | |
3417 | ptr--; | |
3418 | ptr += ntohl(th->seq); | |
3419 | ||
3420 | /* Ignore urgent data that we've already seen and read. */ | |
3421 | if (after(tp->copied_seq, ptr)) | |
3422 | return; | |
3423 | ||
3424 | /* Do not replay urg ptr. | |
3425 | * | |
3426 | * NOTE: interesting situation not covered by specs. | |
3427 | * Misbehaving sender may send urg ptr, pointing to segment, | |
3428 | * which we already have in ofo queue. We are not able to fetch | |
3429 | * such data and will stay in TCP_URG_NOTYET until will be eaten | |
3430 | * by recvmsg(). Seems, we are not obliged to handle such wicked | |
3431 | * situations. But it is worth to think about possibility of some | |
3432 | * DoSes using some hypothetical application level deadlock. | |
3433 | */ | |
3434 | if (before(ptr, tp->rcv_nxt)) | |
3435 | return; | |
3436 | ||
3437 | /* Do we already have a newer (or duplicate) urgent pointer? */ | |
3438 | if (tp->urg_data && !after(ptr, tp->urg_seq)) | |
3439 | return; | |
3440 | ||
3441 | /* Tell the world about our new urgent pointer. */ | |
3442 | sk_send_sigurg(sk); | |
3443 | ||
3444 | /* We may be adding urgent data when the last byte read was | |
3445 | * urgent. To do this requires some care. We cannot just ignore | |
3446 | * tp->copied_seq since we would read the last urgent byte again | |
3447 | * as data, nor can we alter copied_seq until this data arrives | |
3448 | * or we break the sematics of SIOCATMARK (and thus sockatmark()) | |
3449 | * | |
3450 | * NOTE. Double Dutch. Rendering to plain English: author of comment | |
3451 | * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); | |
3452 | * and expect that both A and B disappear from stream. This is _wrong_. | |
3453 | * Though this happens in BSD with high probability, this is occasional. | |
3454 | * Any application relying on this is buggy. Note also, that fix "works" | |
3455 | * only in this artificial test. Insert some normal data between A and B and we will | |
3456 | * decline of BSD again. Verdict: it is better to remove to trap | |
3457 | * buggy users. | |
3458 | */ | |
3459 | if (tp->urg_seq == tp->copied_seq && tp->urg_data && | |
3460 | !sock_flag(sk, SOCK_URGINLINE) && | |
3461 | tp->copied_seq != tp->rcv_nxt) { | |
3462 | struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); | |
3463 | tp->copied_seq++; | |
3464 | if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { | |
3465 | __skb_unlink(skb, skb->list); | |
3466 | __kfree_skb(skb); | |
3467 | } | |
3468 | } | |
3469 | ||
3470 | tp->urg_data = TCP_URG_NOTYET; | |
3471 | tp->urg_seq = ptr; | |
3472 | ||
3473 | /* Disable header prediction. */ | |
3474 | tp->pred_flags = 0; | |
3475 | } | |
3476 | ||
3477 | /* This is the 'fast' part of urgent handling. */ | |
3478 | static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) | |
3479 | { | |
3480 | struct tcp_sock *tp = tcp_sk(sk); | |
3481 | ||
3482 | /* Check if we get a new urgent pointer - normally not. */ | |
3483 | if (th->urg) | |
3484 | tcp_check_urg(sk,th); | |
3485 | ||
3486 | /* Do we wait for any urgent data? - normally not... */ | |
3487 | if (tp->urg_data == TCP_URG_NOTYET) { | |
3488 | u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - | |
3489 | th->syn; | |
3490 | ||
3491 | /* Is the urgent pointer pointing into this packet? */ | |
3492 | if (ptr < skb->len) { | |
3493 | u8 tmp; | |
3494 | if (skb_copy_bits(skb, ptr, &tmp, 1)) | |
3495 | BUG(); | |
3496 | tp->urg_data = TCP_URG_VALID | tmp; | |
3497 | if (!sock_flag(sk, SOCK_DEAD)) | |
3498 | sk->sk_data_ready(sk, 0); | |
3499 | } | |
3500 | } | |
3501 | } | |
3502 | ||
3503 | static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) | |
3504 | { | |
3505 | struct tcp_sock *tp = tcp_sk(sk); | |
3506 | int chunk = skb->len - hlen; | |
3507 | int err; | |
3508 | ||
3509 | local_bh_enable(); | |
3510 | if (skb->ip_summed==CHECKSUM_UNNECESSARY) | |
3511 | err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); | |
3512 | else | |
3513 | err = skb_copy_and_csum_datagram_iovec(skb, hlen, | |
3514 | tp->ucopy.iov); | |
3515 | ||
3516 | if (!err) { | |
3517 | tp->ucopy.len -= chunk; | |
3518 | tp->copied_seq += chunk; | |
3519 | tcp_rcv_space_adjust(sk); | |
3520 | } | |
3521 | ||
3522 | local_bh_disable(); | |
3523 | return err; | |
3524 | } | |
3525 | ||
3526 | static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) | |
3527 | { | |
3528 | int result; | |
3529 | ||
3530 | if (sock_owned_by_user(sk)) { | |
3531 | local_bh_enable(); | |
3532 | result = __tcp_checksum_complete(skb); | |
3533 | local_bh_disable(); | |
3534 | } else { | |
3535 | result = __tcp_checksum_complete(skb); | |
3536 | } | |
3537 | return result; | |
3538 | } | |
3539 | ||
3540 | static __inline__ int | |
3541 | tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) | |
3542 | { | |
3543 | return skb->ip_summed != CHECKSUM_UNNECESSARY && | |
3544 | __tcp_checksum_complete_user(sk, skb); | |
3545 | } | |
3546 | ||
3547 | /* | |
3548 | * TCP receive function for the ESTABLISHED state. | |
3549 | * | |
3550 | * It is split into a fast path and a slow path. The fast path is | |
3551 | * disabled when: | |
3552 | * - A zero window was announced from us - zero window probing | |
3553 | * is only handled properly in the slow path. | |
3554 | * - Out of order segments arrived. | |
3555 | * - Urgent data is expected. | |
3556 | * - There is no buffer space left | |
3557 | * - Unexpected TCP flags/window values/header lengths are received | |
3558 | * (detected by checking the TCP header against pred_flags) | |
3559 | * - Data is sent in both directions. Fast path only supports pure senders | |
3560 | * or pure receivers (this means either the sequence number or the ack | |
3561 | * value must stay constant) | |
3562 | * - Unexpected TCP option. | |
3563 | * | |
3564 | * When these conditions are not satisfied it drops into a standard | |
3565 | * receive procedure patterned after RFC793 to handle all cases. | |
3566 | * The first three cases are guaranteed by proper pred_flags setting, | |
3567 | * the rest is checked inline. Fast processing is turned on in | |
3568 | * tcp_data_queue when everything is OK. | |
3569 | */ | |
3570 | int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, | |
3571 | struct tcphdr *th, unsigned len) | |
3572 | { | |
3573 | struct tcp_sock *tp = tcp_sk(sk); | |
3574 | ||
3575 | /* | |
3576 | * Header prediction. | |
3577 | * The code loosely follows the one in the famous | |
3578 | * "30 instruction TCP receive" Van Jacobson mail. | |
3579 | * | |
3580 | * Van's trick is to deposit buffers into socket queue | |
3581 | * on a device interrupt, to call tcp_recv function | |
3582 | * on the receive process context and checksum and copy | |
3583 | * the buffer to user space. smart... | |
3584 | * | |
3585 | * Our current scheme is not silly either but we take the | |
3586 | * extra cost of the net_bh soft interrupt processing... | |
3587 | * We do checksum and copy also but from device to kernel. | |
3588 | */ | |
3589 | ||
3590 | tp->rx_opt.saw_tstamp = 0; | |
3591 | ||
3592 | /* pred_flags is 0xS?10 << 16 + snd_wnd | |
3593 | * if header_predition is to be made | |
3594 | * 'S' will always be tp->tcp_header_len >> 2 | |
3595 | * '?' will be 0 for the fast path, otherwise pred_flags is 0 to | |
3596 | * turn it off (when there are holes in the receive | |
3597 | * space for instance) | |
3598 | * PSH flag is ignored. | |
3599 | */ | |
3600 | ||
3601 | if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && | |
3602 | TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { | |
3603 | int tcp_header_len = tp->tcp_header_len; | |
3604 | ||
3605 | /* Timestamp header prediction: tcp_header_len | |
3606 | * is automatically equal to th->doff*4 due to pred_flags | |
3607 | * match. | |
3608 | */ | |
3609 | ||
3610 | /* Check timestamp */ | |
3611 | if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { | |
3612 | __u32 *ptr = (__u32 *)(th + 1); | |
3613 | ||
3614 | /* No? Slow path! */ | |
3615 | if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | |
3616 | | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) | |
3617 | goto slow_path; | |
3618 | ||
3619 | tp->rx_opt.saw_tstamp = 1; | |
3620 | ++ptr; | |
3621 | tp->rx_opt.rcv_tsval = ntohl(*ptr); | |
3622 | ++ptr; | |
3623 | tp->rx_opt.rcv_tsecr = ntohl(*ptr); | |
3624 | ||
3625 | /* If PAWS failed, check it more carefully in slow path */ | |
3626 | if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) | |
3627 | goto slow_path; | |
3628 | ||
3629 | /* DO NOT update ts_recent here, if checksum fails | |
3630 | * and timestamp was corrupted part, it will result | |
3631 | * in a hung connection since we will drop all | |
3632 | * future packets due to the PAWS test. | |
3633 | */ | |
3634 | } | |
3635 | ||
3636 | if (len <= tcp_header_len) { | |
3637 | /* Bulk data transfer: sender */ | |
3638 | if (len == tcp_header_len) { | |
3639 | /* Predicted packet is in window by definition. | |
3640 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. | |
3641 | * Hence, check seq<=rcv_wup reduces to: | |
3642 | */ | |
3643 | if (tcp_header_len == | |
3644 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && | |
3645 | tp->rcv_nxt == tp->rcv_wup) | |
3646 | tcp_store_ts_recent(tp); | |
3647 | ||
3648 | tcp_rcv_rtt_measure_ts(tp, skb); | |
3649 | ||
3650 | /* We know that such packets are checksummed | |
3651 | * on entry. | |
3652 | */ | |
3653 | tcp_ack(sk, skb, 0); | |
3654 | __kfree_skb(skb); | |
55c97f3e | 3655 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
3656 | return 0; |
3657 | } else { /* Header too small */ | |
3658 | TCP_INC_STATS_BH(TCP_MIB_INERRS); | |
3659 | goto discard; | |
3660 | } | |
3661 | } else { | |
3662 | int eaten = 0; | |
3663 | ||
3664 | if (tp->ucopy.task == current && | |
3665 | tp->copied_seq == tp->rcv_nxt && | |
3666 | len - tcp_header_len <= tp->ucopy.len && | |
3667 | sock_owned_by_user(sk)) { | |
3668 | __set_current_state(TASK_RUNNING); | |
3669 | ||
3670 | if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) { | |
3671 | /* Predicted packet is in window by definition. | |
3672 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. | |
3673 | * Hence, check seq<=rcv_wup reduces to: | |
3674 | */ | |
3675 | if (tcp_header_len == | |
3676 | (sizeof(struct tcphdr) + | |
3677 | TCPOLEN_TSTAMP_ALIGNED) && | |
3678 | tp->rcv_nxt == tp->rcv_wup) | |
3679 | tcp_store_ts_recent(tp); | |
3680 | ||
3681 | tcp_rcv_rtt_measure_ts(tp, skb); | |
3682 | ||
3683 | __skb_pull(skb, tcp_header_len); | |
3684 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
3685 | NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER); | |
3686 | eaten = 1; | |
3687 | } | |
3688 | } | |
3689 | if (!eaten) { | |
3690 | if (tcp_checksum_complete_user(sk, skb)) | |
3691 | goto csum_error; | |
3692 | ||
3693 | /* Predicted packet is in window by definition. | |
3694 | * seq == rcv_nxt and rcv_wup <= rcv_nxt. | |
3695 | * Hence, check seq<=rcv_wup reduces to: | |
3696 | */ | |
3697 | if (tcp_header_len == | |
3698 | (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && | |
3699 | tp->rcv_nxt == tp->rcv_wup) | |
3700 | tcp_store_ts_recent(tp); | |
3701 | ||
3702 | tcp_rcv_rtt_measure_ts(tp, skb); | |
3703 | ||
3704 | if ((int)skb->truesize > sk->sk_forward_alloc) | |
3705 | goto step5; | |
3706 | ||
3707 | NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS); | |
3708 | ||
3709 | /* Bulk data transfer: receiver */ | |
3710 | __skb_pull(skb,tcp_header_len); | |
3711 | __skb_queue_tail(&sk->sk_receive_queue, skb); | |
3712 | sk_stream_set_owner_r(skb, sk); | |
3713 | tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; | |
3714 | } | |
3715 | ||
3716 | tcp_event_data_recv(sk, tp, skb); | |
3717 | ||
3718 | if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { | |
3719 | /* Well, only one small jumplet in fast path... */ | |
3720 | tcp_ack(sk, skb, FLAG_DATA); | |
55c97f3e | 3721 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
3722 | if (!tcp_ack_scheduled(tp)) |
3723 | goto no_ack; | |
3724 | } | |
3725 | ||
31432412 | 3726 | __tcp_ack_snd_check(sk, 0); |
1da177e4 LT |
3727 | no_ack: |
3728 | if (eaten) | |
3729 | __kfree_skb(skb); | |
3730 | else | |
3731 | sk->sk_data_ready(sk, 0); | |
3732 | return 0; | |
3733 | } | |
3734 | } | |
3735 | ||
3736 | slow_path: | |
3737 | if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) | |
3738 | goto csum_error; | |
3739 | ||
3740 | /* | |
3741 | * RFC1323: H1. Apply PAWS check first. | |
3742 | */ | |
3743 | if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && | |
3744 | tcp_paws_discard(tp, skb)) { | |
3745 | if (!th->rst) { | |
3746 | NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); | |
3747 | tcp_send_dupack(sk, skb); | |
3748 | goto discard; | |
3749 | } | |
3750 | /* Resets are accepted even if PAWS failed. | |
3751 | ||
3752 | ts_recent update must be made after we are sure | |
3753 | that the packet is in window. | |
3754 | */ | |
3755 | } | |
3756 | ||
3757 | /* | |
3758 | * Standard slow path. | |
3759 | */ | |
3760 | ||
3761 | if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { | |
3762 | /* RFC793, page 37: "In all states except SYN-SENT, all reset | |
3763 | * (RST) segments are validated by checking their SEQ-fields." | |
3764 | * And page 69: "If an incoming segment is not acceptable, | |
3765 | * an acknowledgment should be sent in reply (unless the RST bit | |
3766 | * is set, if so drop the segment and return)". | |
3767 | */ | |
3768 | if (!th->rst) | |
3769 | tcp_send_dupack(sk, skb); | |
3770 | goto discard; | |
3771 | } | |
3772 | ||
3773 | if(th->rst) { | |
3774 | tcp_reset(sk); | |
3775 | goto discard; | |
3776 | } | |
3777 | ||
3778 | tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); | |
3779 | ||
3780 | if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
3781 | TCP_INC_STATS_BH(TCP_MIB_INERRS); | |
3782 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); | |
3783 | tcp_reset(sk); | |
3784 | return 1; | |
3785 | } | |
3786 | ||
3787 | step5: | |
3788 | if(th->ack) | |
3789 | tcp_ack(sk, skb, FLAG_SLOWPATH); | |
3790 | ||
3791 | tcp_rcv_rtt_measure_ts(tp, skb); | |
3792 | ||
3793 | /* Process urgent data. */ | |
3794 | tcp_urg(sk, skb, th); | |
3795 | ||
3796 | /* step 7: process the segment text */ | |
3797 | tcp_data_queue(sk, skb); | |
3798 | ||
55c97f3e | 3799 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
3800 | tcp_ack_snd_check(sk); |
3801 | return 0; | |
3802 | ||
3803 | csum_error: | |
3804 | TCP_INC_STATS_BH(TCP_MIB_INERRS); | |
3805 | ||
3806 | discard: | |
3807 | __kfree_skb(skb); | |
3808 | return 0; | |
3809 | } | |
3810 | ||
3811 | static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, | |
3812 | struct tcphdr *th, unsigned len) | |
3813 | { | |
3814 | struct tcp_sock *tp = tcp_sk(sk); | |
3815 | int saved_clamp = tp->rx_opt.mss_clamp; | |
3816 | ||
3817 | tcp_parse_options(skb, &tp->rx_opt, 0); | |
3818 | ||
3819 | if (th->ack) { | |
3820 | /* rfc793: | |
3821 | * "If the state is SYN-SENT then | |
3822 | * first check the ACK bit | |
3823 | * If the ACK bit is set | |
3824 | * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send | |
3825 | * a reset (unless the RST bit is set, if so drop | |
3826 | * the segment and return)" | |
3827 | * | |
3828 | * We do not send data with SYN, so that RFC-correct | |
3829 | * test reduces to: | |
3830 | */ | |
3831 | if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) | |
3832 | goto reset_and_undo; | |
3833 | ||
3834 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && | |
3835 | !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, | |
3836 | tcp_time_stamp)) { | |
3837 | NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED); | |
3838 | goto reset_and_undo; | |
3839 | } | |
3840 | ||
3841 | /* Now ACK is acceptable. | |
3842 | * | |
3843 | * "If the RST bit is set | |
3844 | * If the ACK was acceptable then signal the user "error: | |
3845 | * connection reset", drop the segment, enter CLOSED state, | |
3846 | * delete TCB, and return." | |
3847 | */ | |
3848 | ||
3849 | if (th->rst) { | |
3850 | tcp_reset(sk); | |
3851 | goto discard; | |
3852 | } | |
3853 | ||
3854 | /* rfc793: | |
3855 | * "fifth, if neither of the SYN or RST bits is set then | |
3856 | * drop the segment and return." | |
3857 | * | |
3858 | * See note below! | |
3859 | * --ANK(990513) | |
3860 | */ | |
3861 | if (!th->syn) | |
3862 | goto discard_and_undo; | |
3863 | ||
3864 | /* rfc793: | |
3865 | * "If the SYN bit is on ... | |
3866 | * are acceptable then ... | |
3867 | * (our SYN has been ACKed), change the connection | |
3868 | * state to ESTABLISHED..." | |
3869 | */ | |
3870 | ||
3871 | TCP_ECN_rcv_synack(tp, th); | |
3872 | if (tp->ecn_flags&TCP_ECN_OK) | |
3873 | sock_set_flag(sk, SOCK_NO_LARGESEND); | |
3874 | ||
3875 | tp->snd_wl1 = TCP_SKB_CB(skb)->seq; | |
3876 | tcp_ack(sk, skb, FLAG_SLOWPATH); | |
3877 | ||
3878 | /* Ok.. it's good. Set up sequence numbers and | |
3879 | * move to established. | |
3880 | */ | |
3881 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; | |
3882 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; | |
3883 | ||
3884 | /* RFC1323: The window in SYN & SYN/ACK segments is | |
3885 | * never scaled. | |
3886 | */ | |
3887 | tp->snd_wnd = ntohs(th->window); | |
3888 | tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq); | |
3889 | ||
3890 | if (!tp->rx_opt.wscale_ok) { | |
3891 | tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; | |
3892 | tp->window_clamp = min(tp->window_clamp, 65535U); | |
3893 | } | |
3894 | ||
3895 | if (tp->rx_opt.saw_tstamp) { | |
3896 | tp->rx_opt.tstamp_ok = 1; | |
3897 | tp->tcp_header_len = | |
3898 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; | |
3899 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; | |
3900 | tcp_store_ts_recent(tp); | |
3901 | } else { | |
3902 | tp->tcp_header_len = sizeof(struct tcphdr); | |
3903 | } | |
3904 | ||
3905 | if (tp->rx_opt.sack_ok && sysctl_tcp_fack) | |
3906 | tp->rx_opt.sack_ok |= 2; | |
3907 | ||
3908 | tcp_sync_mss(sk, tp->pmtu_cookie); | |
3909 | tcp_initialize_rcv_mss(sk); | |
3910 | ||
3911 | /* Remember, tcp_poll() does not lock socket! | |
3912 | * Change state from SYN-SENT only after copied_seq | |
3913 | * is initialized. */ | |
3914 | tp->copied_seq = tp->rcv_nxt; | |
3915 | mb(); | |
3916 | tcp_set_state(sk, TCP_ESTABLISHED); | |
3917 | ||
3918 | /* Make sure socket is routed, for correct metrics. */ | |
3919 | tp->af_specific->rebuild_header(sk); | |
3920 | ||
3921 | tcp_init_metrics(sk); | |
3922 | ||
317a76f9 SH |
3923 | tcp_init_congestion_control(tp); |
3924 | ||
1da177e4 LT |
3925 | /* Prevent spurious tcp_cwnd_restart() on first data |
3926 | * packet. | |
3927 | */ | |
3928 | tp->lsndtime = tcp_time_stamp; | |
3929 | ||
3930 | tcp_init_buffer_space(sk); | |
3931 | ||
3932 | if (sock_flag(sk, SOCK_KEEPOPEN)) | |
3933 | tcp_reset_keepalive_timer(sk, keepalive_time_when(tp)); | |
3934 | ||
3935 | if (!tp->rx_opt.snd_wscale) | |
3936 | __tcp_fast_path_on(tp, tp->snd_wnd); | |
3937 | else | |
3938 | tp->pred_flags = 0; | |
3939 | ||
3940 | if (!sock_flag(sk, SOCK_DEAD)) { | |
3941 | sk->sk_state_change(sk); | |
3942 | sk_wake_async(sk, 0, POLL_OUT); | |
3943 | } | |
3944 | ||
3945 | if (sk->sk_write_pending || tp->defer_accept || tp->ack.pingpong) { | |
3946 | /* Save one ACK. Data will be ready after | |
3947 | * several ticks, if write_pending is set. | |
3948 | * | |
3949 | * It may be deleted, but with this feature tcpdumps | |
3950 | * look so _wonderfully_ clever, that I was not able | |
3951 | * to stand against the temptation 8) --ANK | |
3952 | */ | |
3953 | tcp_schedule_ack(tp); | |
3954 | tp->ack.lrcvtime = tcp_time_stamp; | |
3955 | tp->ack.ato = TCP_ATO_MIN; | |
3956 | tcp_incr_quickack(tp); | |
3957 | tcp_enter_quickack_mode(tp); | |
3958 | tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX); | |
3959 | ||
3960 | discard: | |
3961 | __kfree_skb(skb); | |
3962 | return 0; | |
3963 | } else { | |
3964 | tcp_send_ack(sk); | |
3965 | } | |
3966 | return -1; | |
3967 | } | |
3968 | ||
3969 | /* No ACK in the segment */ | |
3970 | ||
3971 | if (th->rst) { | |
3972 | /* rfc793: | |
3973 | * "If the RST bit is set | |
3974 | * | |
3975 | * Otherwise (no ACK) drop the segment and return." | |
3976 | */ | |
3977 | ||
3978 | goto discard_and_undo; | |
3979 | } | |
3980 | ||
3981 | /* PAWS check. */ | |
3982 | if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0)) | |
3983 | goto discard_and_undo; | |
3984 | ||
3985 | if (th->syn) { | |
3986 | /* We see SYN without ACK. It is attempt of | |
3987 | * simultaneous connect with crossed SYNs. | |
3988 | * Particularly, it can be connect to self. | |
3989 | */ | |
3990 | tcp_set_state(sk, TCP_SYN_RECV); | |
3991 | ||
3992 | if (tp->rx_opt.saw_tstamp) { | |
3993 | tp->rx_opt.tstamp_ok = 1; | |
3994 | tcp_store_ts_recent(tp); | |
3995 | tp->tcp_header_len = | |
3996 | sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; | |
3997 | } else { | |
3998 | tp->tcp_header_len = sizeof(struct tcphdr); | |
3999 | } | |
4000 | ||
4001 | tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; | |
4002 | tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; | |
4003 | ||
4004 | /* RFC1323: The window in SYN & SYN/ACK segments is | |
4005 | * never scaled. | |
4006 | */ | |
4007 | tp->snd_wnd = ntohs(th->window); | |
4008 | tp->snd_wl1 = TCP_SKB_CB(skb)->seq; | |
4009 | tp->max_window = tp->snd_wnd; | |
4010 | ||
4011 | TCP_ECN_rcv_syn(tp, th); | |
4012 | if (tp->ecn_flags&TCP_ECN_OK) | |
4013 | sock_set_flag(sk, SOCK_NO_LARGESEND); | |
4014 | ||
4015 | tcp_sync_mss(sk, tp->pmtu_cookie); | |
4016 | tcp_initialize_rcv_mss(sk); | |
4017 | ||
4018 | ||
4019 | tcp_send_synack(sk); | |
4020 | #if 0 | |
4021 | /* Note, we could accept data and URG from this segment. | |
4022 | * There are no obstacles to make this. | |
4023 | * | |
4024 | * However, if we ignore data in ACKless segments sometimes, | |
4025 | * we have no reasons to accept it sometimes. | |
4026 | * Also, seems the code doing it in step6 of tcp_rcv_state_process | |
4027 | * is not flawless. So, discard packet for sanity. | |
4028 | * Uncomment this return to process the data. | |
4029 | */ | |
4030 | return -1; | |
4031 | #else | |
4032 | goto discard; | |
4033 | #endif | |
4034 | } | |
4035 | /* "fifth, if neither of the SYN or RST bits is set then | |
4036 | * drop the segment and return." | |
4037 | */ | |
4038 | ||
4039 | discard_and_undo: | |
4040 | tcp_clear_options(&tp->rx_opt); | |
4041 | tp->rx_opt.mss_clamp = saved_clamp; | |
4042 | goto discard; | |
4043 | ||
4044 | reset_and_undo: | |
4045 | tcp_clear_options(&tp->rx_opt); | |
4046 | tp->rx_opt.mss_clamp = saved_clamp; | |
4047 | return 1; | |
4048 | } | |
4049 | ||
4050 | ||
4051 | /* | |
4052 | * This function implements the receiving procedure of RFC 793 for | |
4053 | * all states except ESTABLISHED and TIME_WAIT. | |
4054 | * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be | |
4055 | * address independent. | |
4056 | */ | |
4057 | ||
4058 | int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, | |
4059 | struct tcphdr *th, unsigned len) | |
4060 | { | |
4061 | struct tcp_sock *tp = tcp_sk(sk); | |
4062 | int queued = 0; | |
4063 | ||
4064 | tp->rx_opt.saw_tstamp = 0; | |
4065 | ||
4066 | switch (sk->sk_state) { | |
4067 | case TCP_CLOSE: | |
4068 | goto discard; | |
4069 | ||
4070 | case TCP_LISTEN: | |
4071 | if(th->ack) | |
4072 | return 1; | |
4073 | ||
4074 | if(th->rst) | |
4075 | goto discard; | |
4076 | ||
4077 | if(th->syn) { | |
4078 | if(tp->af_specific->conn_request(sk, skb) < 0) | |
4079 | return 1; | |
4080 | ||
1da177e4 LT |
4081 | /* Now we have several options: In theory there is |
4082 | * nothing else in the frame. KA9Q has an option to | |
4083 | * send data with the syn, BSD accepts data with the | |
4084 | * syn up to the [to be] advertised window and | |
4085 | * Solaris 2.1 gives you a protocol error. For now | |
4086 | * we just ignore it, that fits the spec precisely | |
4087 | * and avoids incompatibilities. It would be nice in | |
4088 | * future to drop through and process the data. | |
4089 | * | |
4090 | * Now that TTCP is starting to be used we ought to | |
4091 | * queue this data. | |
4092 | * But, this leaves one open to an easy denial of | |
4093 | * service attack, and SYN cookies can't defend | |
4094 | * against this problem. So, we drop the data | |
4095 | * in the interest of security over speed. | |
4096 | */ | |
4097 | goto discard; | |
4098 | } | |
4099 | goto discard; | |
4100 | ||
4101 | case TCP_SYN_SENT: | |
1da177e4 LT |
4102 | queued = tcp_rcv_synsent_state_process(sk, skb, th, len); |
4103 | if (queued >= 0) | |
4104 | return queued; | |
4105 | ||
4106 | /* Do step6 onward by hand. */ | |
4107 | tcp_urg(sk, skb, th); | |
4108 | __kfree_skb(skb); | |
55c97f3e | 4109 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
4110 | return 0; |
4111 | } | |
4112 | ||
4113 | if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && | |
4114 | tcp_paws_discard(tp, skb)) { | |
4115 | if (!th->rst) { | |
4116 | NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); | |
4117 | tcp_send_dupack(sk, skb); | |
4118 | goto discard; | |
4119 | } | |
4120 | /* Reset is accepted even if it did not pass PAWS. */ | |
4121 | } | |
4122 | ||
4123 | /* step 1: check sequence number */ | |
4124 | if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { | |
4125 | if (!th->rst) | |
4126 | tcp_send_dupack(sk, skb); | |
4127 | goto discard; | |
4128 | } | |
4129 | ||
4130 | /* step 2: check RST bit */ | |
4131 | if(th->rst) { | |
4132 | tcp_reset(sk); | |
4133 | goto discard; | |
4134 | } | |
4135 | ||
4136 | tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); | |
4137 | ||
4138 | /* step 3: check security and precedence [ignored] */ | |
4139 | ||
4140 | /* step 4: | |
4141 | * | |
4142 | * Check for a SYN in window. | |
4143 | */ | |
4144 | if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { | |
4145 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); | |
4146 | tcp_reset(sk); | |
4147 | return 1; | |
4148 | } | |
4149 | ||
4150 | /* step 5: check the ACK field */ | |
4151 | if (th->ack) { | |
4152 | int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); | |
4153 | ||
4154 | switch(sk->sk_state) { | |
4155 | case TCP_SYN_RECV: | |
4156 | if (acceptable) { | |
4157 | tp->copied_seq = tp->rcv_nxt; | |
4158 | mb(); | |
4159 | tcp_set_state(sk, TCP_ESTABLISHED); | |
4160 | sk->sk_state_change(sk); | |
4161 | ||
4162 | /* Note, that this wakeup is only for marginal | |
4163 | * crossed SYN case. Passively open sockets | |
4164 | * are not waked up, because sk->sk_sleep == | |
4165 | * NULL and sk->sk_socket == NULL. | |
4166 | */ | |
4167 | if (sk->sk_socket) { | |
4168 | sk_wake_async(sk,0,POLL_OUT); | |
4169 | } | |
4170 | ||
4171 | tp->snd_una = TCP_SKB_CB(skb)->ack_seq; | |
4172 | tp->snd_wnd = ntohs(th->window) << | |
4173 | tp->rx_opt.snd_wscale; | |
4174 | tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, | |
4175 | TCP_SKB_CB(skb)->seq); | |
4176 | ||
4177 | /* tcp_ack considers this ACK as duplicate | |
4178 | * and does not calculate rtt. | |
4179 | * Fix it at least with timestamps. | |
4180 | */ | |
4181 | if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && | |
4182 | !tp->srtt) | |
317a76f9 | 4183 | tcp_ack_saw_tstamp(tp, 0, 0); |
1da177e4 LT |
4184 | |
4185 | if (tp->rx_opt.tstamp_ok) | |
4186 | tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; | |
4187 | ||
4188 | /* Make sure socket is routed, for | |
4189 | * correct metrics. | |
4190 | */ | |
4191 | tp->af_specific->rebuild_header(sk); | |
4192 | ||
4193 | tcp_init_metrics(sk); | |
4194 | ||
317a76f9 SH |
4195 | tcp_init_congestion_control(tp); |
4196 | ||
1da177e4 LT |
4197 | /* Prevent spurious tcp_cwnd_restart() on |
4198 | * first data packet. | |
4199 | */ | |
4200 | tp->lsndtime = tcp_time_stamp; | |
4201 | ||
4202 | tcp_initialize_rcv_mss(sk); | |
4203 | tcp_init_buffer_space(sk); | |
4204 | tcp_fast_path_on(tp); | |
4205 | } else { | |
4206 | return 1; | |
4207 | } | |
4208 | break; | |
4209 | ||
4210 | case TCP_FIN_WAIT1: | |
4211 | if (tp->snd_una == tp->write_seq) { | |
4212 | tcp_set_state(sk, TCP_FIN_WAIT2); | |
4213 | sk->sk_shutdown |= SEND_SHUTDOWN; | |
4214 | dst_confirm(sk->sk_dst_cache); | |
4215 | ||
4216 | if (!sock_flag(sk, SOCK_DEAD)) | |
4217 | /* Wake up lingering close() */ | |
4218 | sk->sk_state_change(sk); | |
4219 | else { | |
4220 | int tmo; | |
4221 | ||
4222 | if (tp->linger2 < 0 || | |
4223 | (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && | |
4224 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { | |
4225 | tcp_done(sk); | |
4226 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); | |
4227 | return 1; | |
4228 | } | |
4229 | ||
4230 | tmo = tcp_fin_time(tp); | |
4231 | if (tmo > TCP_TIMEWAIT_LEN) { | |
4232 | tcp_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); | |
4233 | } else if (th->fin || sock_owned_by_user(sk)) { | |
4234 | /* Bad case. We could lose such FIN otherwise. | |
4235 | * It is not a big problem, but it looks confusing | |
4236 | * and not so rare event. We still can lose it now, | |
4237 | * if it spins in bh_lock_sock(), but it is really | |
4238 | * marginal case. | |
4239 | */ | |
4240 | tcp_reset_keepalive_timer(sk, tmo); | |
4241 | } else { | |
4242 | tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); | |
4243 | goto discard; | |
4244 | } | |
4245 | } | |
4246 | } | |
4247 | break; | |
4248 | ||
4249 | case TCP_CLOSING: | |
4250 | if (tp->snd_una == tp->write_seq) { | |
4251 | tcp_time_wait(sk, TCP_TIME_WAIT, 0); | |
4252 | goto discard; | |
4253 | } | |
4254 | break; | |
4255 | ||
4256 | case TCP_LAST_ACK: | |
4257 | if (tp->snd_una == tp->write_seq) { | |
4258 | tcp_update_metrics(sk); | |
4259 | tcp_done(sk); | |
4260 | goto discard; | |
4261 | } | |
4262 | break; | |
4263 | } | |
4264 | } else | |
4265 | goto discard; | |
4266 | ||
4267 | /* step 6: check the URG bit */ | |
4268 | tcp_urg(sk, skb, th); | |
4269 | ||
4270 | /* step 7: process the segment text */ | |
4271 | switch (sk->sk_state) { | |
4272 | case TCP_CLOSE_WAIT: | |
4273 | case TCP_CLOSING: | |
4274 | case TCP_LAST_ACK: | |
4275 | if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) | |
4276 | break; | |
4277 | case TCP_FIN_WAIT1: | |
4278 | case TCP_FIN_WAIT2: | |
4279 | /* RFC 793 says to queue data in these states, | |
4280 | * RFC 1122 says we MUST send a reset. | |
4281 | * BSD 4.4 also does reset. | |
4282 | */ | |
4283 | if (sk->sk_shutdown & RCV_SHUTDOWN) { | |
4284 | if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && | |
4285 | after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { | |
4286 | NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); | |
4287 | tcp_reset(sk); | |
4288 | return 1; | |
4289 | } | |
4290 | } | |
4291 | /* Fall through */ | |
4292 | case TCP_ESTABLISHED: | |
4293 | tcp_data_queue(sk, skb); | |
4294 | queued = 1; | |
4295 | break; | |
4296 | } | |
4297 | ||
4298 | /* tcp_data could move socket to TIME-WAIT */ | |
4299 | if (sk->sk_state != TCP_CLOSE) { | |
55c97f3e | 4300 | tcp_data_snd_check(sk, tp); |
1da177e4 LT |
4301 | tcp_ack_snd_check(sk); |
4302 | } | |
4303 | ||
4304 | if (!queued) { | |
4305 | discard: | |
4306 | __kfree_skb(skb); | |
4307 | } | |
4308 | return 0; | |
4309 | } | |
4310 | ||
4311 | EXPORT_SYMBOL(sysctl_tcp_ecn); | |
4312 | EXPORT_SYMBOL(sysctl_tcp_reordering); | |
4313 | EXPORT_SYMBOL(tcp_parse_options); | |
4314 | EXPORT_SYMBOL(tcp_rcv_established); | |
4315 | EXPORT_SYMBOL(tcp_rcv_state_process); |