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-rw-r--r--net/ipv4/tcp_input.c4959
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diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
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1/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
9 *
10 * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
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
64 * Angelo Dell'Aera: TCP Westwood+ support
65 */
66
67#include <linux/config.h>
68#include <linux/mm.h>
69#include <linux/module.h>
70#include <linux/sysctl.h>
71#include <net/tcp.h>
72#include <net/inet_common.h>
73#include <linux/ipsec.h>
74#include <asm/unaligned.h>
75
76int sysctl_tcp_timestamps = 1;
77int sysctl_tcp_window_scaling = 1;
78int sysctl_tcp_sack = 1;
79int sysctl_tcp_fack = 1;
80int sysctl_tcp_reordering = TCP_FASTRETRANS_THRESH;
81int sysctl_tcp_ecn;
82int sysctl_tcp_dsack = 1;
83int sysctl_tcp_app_win = 31;
84int sysctl_tcp_adv_win_scale = 2;
85
86int sysctl_tcp_stdurg;
87int sysctl_tcp_rfc1337;
88int sysctl_tcp_max_orphans = NR_FILE;
89int sysctl_tcp_frto;
90int sysctl_tcp_nometrics_save;
91int sysctl_tcp_westwood;
92int sysctl_tcp_vegas_cong_avoid;
93
94int sysctl_tcp_moderate_rcvbuf = 1;
95
96/* Default values of the Vegas variables, in fixed-point representation
97 * with V_PARAM_SHIFT bits to the right of the binary point.
98 */
99#define V_PARAM_SHIFT 1
100int sysctl_tcp_vegas_alpha = 1<<V_PARAM_SHIFT;
101int sysctl_tcp_vegas_beta = 3<<V_PARAM_SHIFT;
102int sysctl_tcp_vegas_gamma = 1<<V_PARAM_SHIFT;
103int sysctl_tcp_bic = 1;
104int sysctl_tcp_bic_fast_convergence = 1;
105int sysctl_tcp_bic_low_window = 14;
106int sysctl_tcp_bic_beta = 819; /* = 819/1024 (BICTCP_BETA_SCALE) */
107
108#define FLAG_DATA 0x01 /* Incoming frame contained data. */
109#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
110#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
111#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
112#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
113#define FLAG_DATA_SACKED 0x20 /* New SACK. */
114#define FLAG_ECE 0x40 /* ECE in this ACK */
115#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
116#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
117
118#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
119#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
120#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
121#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
122
123#define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
124#define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
125#define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
126
127#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
128
129/* Adapt the MSS value used to make delayed ack decision to the
130 * real world.
131 */
132static inline void tcp_measure_rcv_mss(struct tcp_sock *tp,
133 struct sk_buff *skb)
134{
135 unsigned int len, lss;
136
137 lss = tp->ack.last_seg_size;
138 tp->ack.last_seg_size = 0;
139
140 /* skb->len may jitter because of SACKs, even if peer
141 * sends good full-sized frames.
142 */
143 len = skb->len;
144 if (len >= tp->ack.rcv_mss) {
145 tp->ack.rcv_mss = len;
146 } else {
147 /* Otherwise, we make more careful check taking into account,
148 * that SACKs block is variable.
149 *
150 * "len" is invariant segment length, including TCP header.
151 */
152 len += skb->data - skb->h.raw;
153 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) ||
154 /* If PSH is not set, packet should be
155 * full sized, provided peer TCP is not badly broken.
156 * This observation (if it is correct 8)) allows
157 * to handle super-low mtu links fairly.
158 */
159 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) &&
160 !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) {
161 /* Subtract also invariant (if peer is RFC compliant),
162 * tcp header plus fixed timestamp option length.
163 * Resulting "len" is MSS free of SACK jitter.
164 */
165 len -= tp->tcp_header_len;
166 tp->ack.last_seg_size = len;
167 if (len == lss) {
168 tp->ack.rcv_mss = len;
169 return;
170 }
171 }
172 tp->ack.pending |= TCP_ACK_PUSHED;
173 }
174}
175
176static void tcp_incr_quickack(struct tcp_sock *tp)
177{
178 unsigned quickacks = tp->rcv_wnd/(2*tp->ack.rcv_mss);
179
180 if (quickacks==0)
181 quickacks=2;
182 if (quickacks > tp->ack.quick)
183 tp->ack.quick = min(quickacks, TCP_MAX_QUICKACKS);
184}
185
186void tcp_enter_quickack_mode(struct tcp_sock *tp)
187{
188 tcp_incr_quickack(tp);
189 tp->ack.pingpong = 0;
190 tp->ack.ato = TCP_ATO_MIN;
191}
192
193/* Send ACKs quickly, if "quick" count is not exhausted
194 * and the session is not interactive.
195 */
196
197static __inline__ int tcp_in_quickack_mode(struct tcp_sock *tp)
198{
199 return (tp->ack.quick && !tp->ack.pingpong);
200}
201
202/* Buffer size and advertised window tuning.
203 *
204 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
205 */
206
207static void tcp_fixup_sndbuf(struct sock *sk)
208{
209 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 +
210 sizeof(struct sk_buff);
211
212 if (sk->sk_sndbuf < 3 * sndmem)
213 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]);
214}
215
216/* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
217 *
218 * All tcp_full_space() is split to two parts: "network" buffer, allocated
219 * forward and advertised in receiver window (tp->rcv_wnd) and
220 * "application buffer", required to isolate scheduling/application
221 * latencies from network.
222 * window_clamp is maximal advertised window. It can be less than
223 * tcp_full_space(), in this case tcp_full_space() - window_clamp
224 * is reserved for "application" buffer. The less window_clamp is
225 * the smoother our behaviour from viewpoint of network, but the lower
226 * throughput and the higher sensitivity of the connection to losses. 8)
227 *
228 * rcv_ssthresh is more strict window_clamp used at "slow start"
229 * phase to predict further behaviour of this connection.
230 * It is used for two goals:
231 * - to enforce header prediction at sender, even when application
232 * requires some significant "application buffer". It is check #1.
233 * - to prevent pruning of receive queue because of misprediction
234 * of receiver window. Check #2.
235 *
236 * The scheme does not work when sender sends good segments opening
237 * window and then starts to feed us spagetti. But it should work
238 * in common situations. Otherwise, we have to rely on queue collapsing.
239 */
240
241/* Slow part of check#2. */
242static int __tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
243 struct sk_buff *skb)
244{
245 /* Optimize this! */
246 int truesize = tcp_win_from_space(skb->truesize)/2;
247 int window = tcp_full_space(sk)/2;
248
249 while (tp->rcv_ssthresh <= window) {
250 if (truesize <= skb->len)
251 return 2*tp->ack.rcv_mss;
252
253 truesize >>= 1;
254 window >>= 1;
255 }
256 return 0;
257}
258
259static inline void tcp_grow_window(struct sock *sk, struct tcp_sock *tp,
260 struct sk_buff *skb)
261{
262 /* Check #1 */
263 if (tp->rcv_ssthresh < tp->window_clamp &&
264 (int)tp->rcv_ssthresh < tcp_space(sk) &&
265 !tcp_memory_pressure) {
266 int incr;
267
268 /* Check #2. Increase window, if skb with such overhead
269 * will fit to rcvbuf in future.
270 */
271 if (tcp_win_from_space(skb->truesize) <= skb->len)
272 incr = 2*tp->advmss;
273 else
274 incr = __tcp_grow_window(sk, tp, skb);
275
276 if (incr) {
277 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp);
278 tp->ack.quick |= 1;
279 }
280 }
281}
282
283/* 3. Tuning rcvbuf, when connection enters established state. */
284
285static void tcp_fixup_rcvbuf(struct sock *sk)
286{
287 struct tcp_sock *tp = tcp_sk(sk);
288 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff);
289
290 /* Try to select rcvbuf so that 4 mss-sized segments
291 * will fit to window and correspoding skbs will fit to our rcvbuf.
292 * (was 3; 4 is minimum to allow fast retransmit to work.)
293 */
294 while (tcp_win_from_space(rcvmem) < tp->advmss)
295 rcvmem += 128;
296 if (sk->sk_rcvbuf < 4 * rcvmem)
297 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]);
298}
299
300/* 4. Try to fixup all. It is made iimediately after connection enters
301 * established state.
302 */
303static void tcp_init_buffer_space(struct sock *sk)
304{
305 struct tcp_sock *tp = tcp_sk(sk);
306 int maxwin;
307
308 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK))
309 tcp_fixup_rcvbuf(sk);
310 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK))
311 tcp_fixup_sndbuf(sk);
312
313 tp->rcvq_space.space = tp->rcv_wnd;
314
315 maxwin = tcp_full_space(sk);
316
317 if (tp->window_clamp >= maxwin) {
318 tp->window_clamp = maxwin;
319
320 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss)
321 tp->window_clamp = max(maxwin -
322 (maxwin >> sysctl_tcp_app_win),
323 4 * tp->advmss);
324 }
325
326 /* Force reservation of one segment. */
327 if (sysctl_tcp_app_win &&
328 tp->window_clamp > 2 * tp->advmss &&
329 tp->window_clamp + tp->advmss > maxwin)
330 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss);
331
332 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp);
333 tp->snd_cwnd_stamp = tcp_time_stamp;
334}
335
336static void init_bictcp(struct tcp_sock *tp)
337{
338 tp->bictcp.cnt = 0;
339
340 tp->bictcp.last_max_cwnd = 0;
341 tp->bictcp.last_cwnd = 0;
342 tp->bictcp.last_stamp = 0;
343}
344
345/* 5. Recalculate window clamp after socket hit its memory bounds. */
346static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp)
347{
348 struct sk_buff *skb;
349 unsigned int app_win = tp->rcv_nxt - tp->copied_seq;
350 int ofo_win = 0;
351
352 tp->ack.quick = 0;
353
354 skb_queue_walk(&tp->out_of_order_queue, skb) {
355 ofo_win += skb->len;
356 }
357
358 /* If overcommit is due to out of order segments,
359 * do not clamp window. Try to expand rcvbuf instead.
360 */
361 if (ofo_win) {
362 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] &&
363 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) &&
364 !tcp_memory_pressure &&
365 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0])
366 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc),
367 sysctl_tcp_rmem[2]);
368 }
369 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) {
370 app_win += ofo_win;
371 if (atomic_read(&sk->sk_rmem_alloc) >= 2 * sk->sk_rcvbuf)
372 app_win >>= 1;
373 if (app_win > tp->ack.rcv_mss)
374 app_win -= tp->ack.rcv_mss;
375 app_win = max(app_win, 2U*tp->advmss);
376
377 if (!ofo_win)
378 tp->window_clamp = min(tp->window_clamp, app_win);
379 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss);
380 }
381}
382
383/* Receiver "autotuning" code.
384 *
385 * The algorithm for RTT estimation w/o timestamps is based on
386 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
387 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
388 *
389 * More detail on this code can be found at
390 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
391 * though this reference is out of date. A new paper
392 * is pending.
393 */
394static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep)
395{
396 u32 new_sample = tp->rcv_rtt_est.rtt;
397 long m = sample;
398
399 if (m == 0)
400 m = 1;
401
402 if (new_sample != 0) {
403 /* If we sample in larger samples in the non-timestamp
404 * case, we could grossly overestimate the RTT especially
405 * with chatty applications or bulk transfer apps which
406 * are stalled on filesystem I/O.
407 *
408 * Also, since we are only going for a minimum in the
409 * non-timestamp case, we do not smoothe things out
410 * else with timestamps disabled convergance takes too
411 * long.
412 */
413 if (!win_dep) {
414 m -= (new_sample >> 3);
415 new_sample += m;
416 } else if (m < new_sample)
417 new_sample = m << 3;
418 } else {
419 /* No previous mesaure. */
420 new_sample = m << 3;
421 }
422
423 if (tp->rcv_rtt_est.rtt != new_sample)
424 tp->rcv_rtt_est.rtt = new_sample;
425}
426
427static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp)
428{
429 if (tp->rcv_rtt_est.time == 0)
430 goto new_measure;
431 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq))
432 return;
433 tcp_rcv_rtt_update(tp,
434 jiffies - tp->rcv_rtt_est.time,
435 1);
436
437new_measure:
438 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd;
439 tp->rcv_rtt_est.time = tcp_time_stamp;
440}
441
442static inline void tcp_rcv_rtt_measure_ts(struct tcp_sock *tp, struct sk_buff *skb)
443{
444 if (tp->rx_opt.rcv_tsecr &&
445 (TCP_SKB_CB(skb)->end_seq -
446 TCP_SKB_CB(skb)->seq >= tp->ack.rcv_mss))
447 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0);
448}
449
450/*
451 * This function should be called every time data is copied to user space.
452 * It calculates the appropriate TCP receive buffer space.
453 */
454void tcp_rcv_space_adjust(struct sock *sk)
455{
456 struct tcp_sock *tp = tcp_sk(sk);
457 int time;
458 int space;
459
460 if (tp->rcvq_space.time == 0)
461 goto new_measure;
462
463 time = tcp_time_stamp - tp->rcvq_space.time;
464 if (time < (tp->rcv_rtt_est.rtt >> 3) ||
465 tp->rcv_rtt_est.rtt == 0)
466 return;
467
468 space = 2 * (tp->copied_seq - tp->rcvq_space.seq);
469
470 space = max(tp->rcvq_space.space, space);
471
472 if (tp->rcvq_space.space != space) {
473 int rcvmem;
474
475 tp->rcvq_space.space = space;
476
477 if (sysctl_tcp_moderate_rcvbuf) {
478 int new_clamp = space;
479
480 /* Receive space grows, normalize in order to
481 * take into account packet headers and sk_buff
482 * structure overhead.
483 */
484 space /= tp->advmss;
485 if (!space)
486 space = 1;
487 rcvmem = (tp->advmss + MAX_TCP_HEADER +
488 16 + sizeof(struct sk_buff));
489 while (tcp_win_from_space(rcvmem) < tp->advmss)
490 rcvmem += 128;
491 space *= rcvmem;
492 space = min(space, sysctl_tcp_rmem[2]);
493 if (space > sk->sk_rcvbuf) {
494 sk->sk_rcvbuf = space;
495
496 /* Make the window clamp follow along. */
497 tp->window_clamp = new_clamp;
498 }
499 }
500 }
501
502new_measure:
503 tp->rcvq_space.seq = tp->copied_seq;
504 tp->rcvq_space.time = tcp_time_stamp;
505}
506
507/* There is something which you must keep in mind when you analyze the
508 * behavior of the tp->ato delayed ack timeout interval. When a
509 * connection starts up, we want to ack as quickly as possible. The
510 * problem is that "good" TCP's do slow start at the beginning of data
511 * transmission. The means that until we send the first few ACK's the
512 * sender will sit on his end and only queue most of his data, because
513 * he can only send snd_cwnd unacked packets at any given time. For
514 * each ACK we send, he increments snd_cwnd and transmits more of his
515 * queue. -DaveM
516 */
517static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
518{
519 u32 now;
520
521 tcp_schedule_ack(tp);
522
523 tcp_measure_rcv_mss(tp, skb);
524
525 tcp_rcv_rtt_measure(tp);
526
527 now = tcp_time_stamp;
528
529 if (!tp->ack.ato) {
530 /* The _first_ data packet received, initialize
531 * delayed ACK engine.
532 */
533 tcp_incr_quickack(tp);
534 tp->ack.ato = TCP_ATO_MIN;
535 } else {
536 int m = now - tp->ack.lrcvtime;
537
538 if (m <= TCP_ATO_MIN/2) {
539 /* The fastest case is the first. */
540 tp->ack.ato = (tp->ack.ato>>1) + TCP_ATO_MIN/2;
541 } else if (m < tp->ack.ato) {
542 tp->ack.ato = (tp->ack.ato>>1) + m;
543 if (tp->ack.ato > tp->rto)
544 tp->ack.ato = tp->rto;
545 } else if (m > tp->rto) {
546 /* Too long gap. Apparently sender falled to
547 * restart window, so that we send ACKs quickly.
548 */
549 tcp_incr_quickack(tp);
550 sk_stream_mem_reclaim(sk);
551 }
552 }
553 tp->ack.lrcvtime = now;
554
555 TCP_ECN_check_ce(tp, skb);
556
557 if (skb->len >= 128)
558 tcp_grow_window(sk, tp, skb);
559}
560
561/* When starting a new connection, pin down the current choice of
562 * congestion algorithm.
563 */
564void tcp_ca_init(struct tcp_sock *tp)
565{
566 if (sysctl_tcp_westwood)
567 tp->adv_cong = TCP_WESTWOOD;
568 else if (sysctl_tcp_bic)
569 tp->adv_cong = TCP_BIC;
570 else if (sysctl_tcp_vegas_cong_avoid) {
571 tp->adv_cong = TCP_VEGAS;
572 tp->vegas.baseRTT = 0x7fffffff;
573 tcp_vegas_enable(tp);
574 }
575}
576
577/* Do RTT sampling needed for Vegas.
578 * Basically we:
579 * o min-filter RTT samples from within an RTT to get the current
580 * propagation delay + queuing delay (we are min-filtering to try to
581 * avoid the effects of delayed ACKs)
582 * o min-filter RTT samples from a much longer window (forever for now)
583 * to find the propagation delay (baseRTT)
584 */
585static inline void vegas_rtt_calc(struct tcp_sock *tp, __u32 rtt)
586{
587 __u32 vrtt = rtt + 1; /* Never allow zero rtt or baseRTT */
588
589 /* Filter to find propagation delay: */
590 if (vrtt < tp->vegas.baseRTT)
591 tp->vegas.baseRTT = vrtt;
592
593 /* Find the min RTT during the last RTT to find
594 * the current prop. delay + queuing delay:
595 */
596 tp->vegas.minRTT = min(tp->vegas.minRTT, vrtt);
597 tp->vegas.cntRTT++;
598}
599
600/* Called to compute a smoothed rtt estimate. The data fed to this
601 * routine either comes from timestamps, or from segments that were
602 * known _not_ to have been retransmitted [see Karn/Partridge
603 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
604 * piece by Van Jacobson.
605 * NOTE: the next three routines used to be one big routine.
606 * To save cycles in the RFC 1323 implementation it was better to break
607 * it up into three procedures. -- erics
608 */
609static void tcp_rtt_estimator(struct tcp_sock *tp, __u32 mrtt)
610{
611 long m = mrtt; /* RTT */
612
613 if (tcp_vegas_enabled(tp))
614 vegas_rtt_calc(tp, mrtt);
615
616 /* The following amusing code comes from Jacobson's
617 * article in SIGCOMM '88. Note that rtt and mdev
618 * are scaled versions of rtt and mean deviation.
619 * This is designed to be as fast as possible
620 * m stands for "measurement".
621 *
622 * On a 1990 paper the rto value is changed to:
623 * RTO = rtt + 4 * mdev
624 *
625 * Funny. This algorithm seems to be very broken.
626 * These formulae increase RTO, when it should be decreased, increase
627 * too slowly, when it should be incresed fastly, decrease too fastly
628 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
629 * does not matter how to _calculate_ it. Seems, it was trap
630 * that VJ failed to avoid. 8)
631 */
632 if(m == 0)
633 m = 1;
634 if (tp->srtt != 0) {
635 m -= (tp->srtt >> 3); /* m is now error in rtt est */
636 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */
637 if (m < 0) {
638 m = -m; /* m is now abs(error) */
639 m -= (tp->mdev >> 2); /* similar update on mdev */
640 /* This is similar to one of Eifel findings.
641 * Eifel blocks mdev updates when rtt decreases.
642 * This solution is a bit different: we use finer gain
643 * for mdev in this case (alpha*beta).
644 * Like Eifel it also prevents growth of rto,
645 * but also it limits too fast rto decreases,
646 * happening in pure Eifel.
647 */
648 if (m > 0)
649 m >>= 3;
650 } else {
651 m -= (tp->mdev >> 2); /* similar update on mdev */
652 }
653 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
654 if (tp->mdev > tp->mdev_max) {
655 tp->mdev_max = tp->mdev;
656 if (tp->mdev_max > tp->rttvar)
657 tp->rttvar = tp->mdev_max;
658 }
659 if (after(tp->snd_una, tp->rtt_seq)) {
660 if (tp->mdev_max < tp->rttvar)
661 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2;
662 tp->rtt_seq = tp->snd_nxt;
663 tp->mdev_max = TCP_RTO_MIN;
664 }
665 } else {
666 /* no previous measure. */
667 tp->srtt = m<<3; /* take the measured time to be rtt */
668 tp->mdev = m<<1; /* make sure rto = 3*rtt */
669 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
670 tp->rtt_seq = tp->snd_nxt;
671 }
672
673 tcp_westwood_update_rtt(tp, tp->srtt >> 3);
674}
675
676/* Calculate rto without backoff. This is the second half of Van Jacobson's
677 * routine referred to above.
678 */
679static inline void tcp_set_rto(struct tcp_sock *tp)
680{
681 /* Old crap is replaced with new one. 8)
682 *
683 * More seriously:
684 * 1. If rtt variance happened to be less 50msec, it is hallucination.
685 * It cannot be less due to utterly erratic ACK generation made
686 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
687 * to do with delayed acks, because at cwnd>2 true delack timeout
688 * is invisible. Actually, Linux-2.4 also generates erratic
689 * ACKs in some curcumstances.
690 */
691 tp->rto = (tp->srtt >> 3) + tp->rttvar;
692
693 /* 2. Fixups made earlier cannot be right.
694 * If we do not estimate RTO correctly without them,
695 * all the algo is pure shit and should be replaced
696 * with correct one. It is exaclty, which we pretend to do.
697 */
698}
699
700/* NOTE: clamping at TCP_RTO_MIN is not required, current algo
701 * guarantees that rto is higher.
702 */
703static inline void tcp_bound_rto(struct tcp_sock *tp)
704{
705 if (tp->rto > TCP_RTO_MAX)
706 tp->rto = TCP_RTO_MAX;
707}
708
709/* Save metrics learned by this TCP session.
710 This function is called only, when TCP finishes successfully
711 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
712 */
713void tcp_update_metrics(struct sock *sk)
714{
715 struct tcp_sock *tp = tcp_sk(sk);
716 struct dst_entry *dst = __sk_dst_get(sk);
717
718 if (sysctl_tcp_nometrics_save)
719 return;
720
721 dst_confirm(dst);
722
723 if (dst && (dst->flags&DST_HOST)) {
724 int m;
725
726 if (tp->backoff || !tp->srtt) {
727 /* This session failed to estimate rtt. Why?
728 * Probably, no packets returned in time.
729 * Reset our results.
730 */
731 if (!(dst_metric_locked(dst, RTAX_RTT)))
732 dst->metrics[RTAX_RTT-1] = 0;
733 return;
734 }
735
736 m = dst_metric(dst, RTAX_RTT) - tp->srtt;
737
738 /* If newly calculated rtt larger than stored one,
739 * store new one. Otherwise, use EWMA. Remember,
740 * rtt overestimation is always better than underestimation.
741 */
742 if (!(dst_metric_locked(dst, RTAX_RTT))) {
743 if (m <= 0)
744 dst->metrics[RTAX_RTT-1] = tp->srtt;
745 else
746 dst->metrics[RTAX_RTT-1] -= (m>>3);
747 }
748
749 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) {
750 if (m < 0)
751 m = -m;
752
753 /* Scale deviation to rttvar fixed point */
754 m >>= 1;
755 if (m < tp->mdev)
756 m = tp->mdev;
757
758 if (m >= dst_metric(dst, RTAX_RTTVAR))
759 dst->metrics[RTAX_RTTVAR-1] = m;
760 else
761 dst->metrics[RTAX_RTTVAR-1] -=
762 (dst->metrics[RTAX_RTTVAR-1] - m)>>2;
763 }
764
765 if (tp->snd_ssthresh >= 0xFFFF) {
766 /* Slow start still did not finish. */
767 if (dst_metric(dst, RTAX_SSTHRESH) &&
768 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
769 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH))
770 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1;
771 if (!dst_metric_locked(dst, RTAX_CWND) &&
772 tp->snd_cwnd > dst_metric(dst, RTAX_CWND))
773 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd;
774 } else if (tp->snd_cwnd > tp->snd_ssthresh &&
775 tp->ca_state == TCP_CA_Open) {
776 /* Cong. avoidance phase, cwnd is reliable. */
777 if (!dst_metric_locked(dst, RTAX_SSTHRESH))
778 dst->metrics[RTAX_SSTHRESH-1] =
779 max(tp->snd_cwnd >> 1, tp->snd_ssthresh);
780 if (!dst_metric_locked(dst, RTAX_CWND))
781 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1;
782 } else {
783 /* Else slow start did not finish, cwnd is non-sense,
784 ssthresh may be also invalid.
785 */
786 if (!dst_metric_locked(dst, RTAX_CWND))
787 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1;
788 if (dst->metrics[RTAX_SSTHRESH-1] &&
789 !dst_metric_locked(dst, RTAX_SSTHRESH) &&
790 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1])
791 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh;
792 }
793
794 if (!dst_metric_locked(dst, RTAX_REORDERING)) {
795 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering &&
796 tp->reordering != sysctl_tcp_reordering)
797 dst->metrics[RTAX_REORDERING-1] = tp->reordering;
798 }
799 }
800}
801
802/* Numbers are taken from RFC2414. */
803__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst)
804{
805 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0);
806
807 if (!cwnd) {
808 if (tp->mss_cache_std > 1460)
809 cwnd = 2;
810 else
811 cwnd = (tp->mss_cache_std > 1095) ? 3 : 4;
812 }
813 return min_t(__u32, cwnd, tp->snd_cwnd_clamp);
814}
815
816/* Initialize metrics on socket. */
817
818static void tcp_init_metrics(struct sock *sk)
819{
820 struct tcp_sock *tp = tcp_sk(sk);
821 struct dst_entry *dst = __sk_dst_get(sk);
822
823 if (dst == NULL)
824 goto reset;
825
826 dst_confirm(dst);
827
828 if (dst_metric_locked(dst, RTAX_CWND))
829 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND);
830 if (dst_metric(dst, RTAX_SSTHRESH)) {
831 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH);
832 if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
833 tp->snd_ssthresh = tp->snd_cwnd_clamp;
834 }
835 if (dst_metric(dst, RTAX_REORDERING) &&
836 tp->reordering != dst_metric(dst, RTAX_REORDERING)) {
837 tp->rx_opt.sack_ok &= ~2;
838 tp->reordering = dst_metric(dst, RTAX_REORDERING);
839 }
840
841 if (dst_metric(dst, RTAX_RTT) == 0)
842 goto reset;
843
844 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3))
845 goto reset;
846
847 /* Initial rtt is determined from SYN,SYN-ACK.
848 * The segment is small and rtt may appear much
849 * less than real one. Use per-dst memory
850 * to make it more realistic.
851 *
852 * A bit of theory. RTT is time passed after "normal" sized packet
853 * is sent until it is ACKed. In normal curcumstances sending small
854 * packets force peer to delay ACKs and calculation is correct too.
855 * The algorithm is adaptive and, provided we follow specs, it
856 * NEVER underestimate RTT. BUT! If peer tries to make some clever
857 * tricks sort of "quick acks" for time long enough to decrease RTT
858 * to low value, and then abruptly stops to do it and starts to delay
859 * ACKs, wait for troubles.
860 */
861 if (dst_metric(dst, RTAX_RTT) > tp->srtt) {
862 tp->srtt = dst_metric(dst, RTAX_RTT);
863 tp->rtt_seq = tp->snd_nxt;
864 }
865 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) {
866 tp->mdev = dst_metric(dst, RTAX_RTTVAR);
867 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN);
868 }
869 tcp_set_rto(tp);
870 tcp_bound_rto(tp);
871 if (tp->rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp)
872 goto reset;
873 tp->snd_cwnd = tcp_init_cwnd(tp, dst);
874 tp->snd_cwnd_stamp = tcp_time_stamp;
875 return;
876
877reset:
878 /* Play conservative. If timestamps are not
879 * supported, TCP will fail to recalculate correct
880 * rtt, if initial rto is too small. FORGET ALL AND RESET!
881 */
882 if (!tp->rx_opt.saw_tstamp && tp->srtt) {
883 tp->srtt = 0;
884 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT;
885 tp->rto = TCP_TIMEOUT_INIT;
886 }
887}
888
889static void tcp_update_reordering(struct tcp_sock *tp, int metric, int ts)
890{
891 if (metric > tp->reordering) {
892 tp->reordering = min(TCP_MAX_REORDERING, metric);
893
894 /* This exciting event is worth to be remembered. 8) */
895 if (ts)
896 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER);
897 else if (IsReno(tp))
898 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER);
899 else if (IsFack(tp))
900 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER);
901 else
902 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER);
903#if FASTRETRANS_DEBUG > 1
904 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n",
905 tp->rx_opt.sack_ok, tp->ca_state,
906 tp->reordering,
907 tp->fackets_out,
908 tp->sacked_out,
909 tp->undo_marker ? tp->undo_retrans : 0);
910#endif
911 /* Disable FACK yet. */
912 tp->rx_opt.sack_ok &= ~2;
913 }
914}
915
916/* This procedure tags the retransmission queue when SACKs arrive.
917 *
918 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
919 * Packets in queue with these bits set are counted in variables
920 * sacked_out, retrans_out and lost_out, correspondingly.
921 *
922 * Valid combinations are:
923 * Tag InFlight Description
924 * 0 1 - orig segment is in flight.
925 * S 0 - nothing flies, orig reached receiver.
926 * L 0 - nothing flies, orig lost by net.
927 * R 2 - both orig and retransmit are in flight.
928 * L|R 1 - orig is lost, retransmit is in flight.
929 * S|R 1 - orig reached receiver, retrans is still in flight.
930 * (L|S|R is logically valid, it could occur when L|R is sacked,
931 * but it is equivalent to plain S and code short-curcuits it to S.
932 * L|S is logically invalid, it would mean -1 packet in flight 8))
933 *
934 * These 6 states form finite state machine, controlled by the following events:
935 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
936 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
937 * 3. Loss detection event of one of three flavors:
938 * A. Scoreboard estimator decided the packet is lost.
939 * A'. Reno "three dupacks" marks head of queue lost.
940 * A''. Its FACK modfication, head until snd.fack is lost.
941 * B. SACK arrives sacking data transmitted after never retransmitted
942 * hole was sent out.
943 * C. SACK arrives sacking SND.NXT at the moment, when the
944 * segment was retransmitted.
945 * 4. D-SACK added new rule: D-SACK changes any tag to S.
946 *
947 * It is pleasant to note, that state diagram turns out to be commutative,
948 * so that we are allowed not to be bothered by order of our actions,
949 * when multiple events arrive simultaneously. (see the function below).
950 *
951 * Reordering detection.
952 * --------------------
953 * Reordering metric is maximal distance, which a packet can be displaced
954 * in packet stream. With SACKs we can estimate it:
955 *
956 * 1. SACK fills old hole and the corresponding segment was not
957 * ever retransmitted -> reordering. Alas, we cannot use it
958 * when segment was retransmitted.
959 * 2. The last flaw is solved with D-SACK. D-SACK arrives
960 * for retransmitted and already SACKed segment -> reordering..
961 * Both of these heuristics are not used in Loss state, when we cannot
962 * account for retransmits accurately.
963 */
964static int
965tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una)
966{
967 struct tcp_sock *tp = tcp_sk(sk);
968 unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked;
969 struct tcp_sack_block *sp = (struct tcp_sack_block *)(ptr+2);
970 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3;
971 int reord = tp->packets_out;
972 int prior_fackets;
973 u32 lost_retrans = 0;
974 int flag = 0;
975 int i;
976
977 /* So, SACKs for already sent large segments will be lost.
978 * Not good, but alternative is to resegment the queue. */
979 if (sk->sk_route_caps & NETIF_F_TSO) {
980 sk->sk_route_caps &= ~NETIF_F_TSO;
981 sock_set_flag(sk, SOCK_NO_LARGESEND);
982 tp->mss_cache = tp->mss_cache_std;
983 }
984
985 if (!tp->sacked_out)
986 tp->fackets_out = 0;
987 prior_fackets = tp->fackets_out;
988
989 for (i=0; i<num_sacks; i++, sp++) {
990 struct sk_buff *skb;
991 __u32 start_seq = ntohl(sp->start_seq);
992 __u32 end_seq = ntohl(sp->end_seq);
993 int fack_count = 0;
994 int dup_sack = 0;
995
996 /* Check for D-SACK. */
997 if (i == 0) {
998 u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;
999
1000 if (before(start_seq, ack)) {
1001 dup_sack = 1;
1002 tp->rx_opt.sack_ok |= 4;
1003 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);
1004 } else if (num_sacks > 1 &&
1005 !after(end_seq, ntohl(sp[1].end_seq)) &&
1006 !before(start_seq, ntohl(sp[1].start_seq))) {
1007 dup_sack = 1;
1008 tp->rx_opt.sack_ok |= 4;
1009 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
1010 }
1011
1012 /* D-SACK for already forgotten data...
1013 * Do dumb counting. */
1014 if (dup_sack &&
1015 !after(end_seq, prior_snd_una) &&
1016 after(end_seq, tp->undo_marker))
1017 tp->undo_retrans--;
1018
1019 /* Eliminate too old ACKs, but take into
1020 * account more or less fresh ones, they can
1021 * contain valid SACK info.
1022 */
1023 if (before(ack, prior_snd_una - tp->max_window))
1024 return 0;
1025 }
1026
1027 /* Event "B" in the comment above. */
1028 if (after(end_seq, tp->high_seq))
1029 flag |= FLAG_DATA_LOST;
1030
1031 sk_stream_for_retrans_queue(skb, sk) {
1032 u8 sacked = TCP_SKB_CB(skb)->sacked;
1033 int in_sack;
1034
1035 /* The retransmission queue is always in order, so
1036 * we can short-circuit the walk early.
1037 */
1038 if(!before(TCP_SKB_CB(skb)->seq, end_seq))
1039 break;
1040
1041 fack_count += tcp_skb_pcount(skb);
1042
1043 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) &&
1044 !before(end_seq, TCP_SKB_CB(skb)->end_seq);
1045
1046 /* Account D-SACK for retransmitted packet. */
1047 if ((dup_sack && in_sack) &&
1048 (sacked & TCPCB_RETRANS) &&
1049 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker))
1050 tp->undo_retrans--;
1051
1052 /* The frame is ACKed. */
1053 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) {
1054 if (sacked&TCPCB_RETRANS) {
1055 if ((dup_sack && in_sack) &&
1056 (sacked&TCPCB_SACKED_ACKED))
1057 reord = min(fack_count, reord);
1058 } else {
1059 /* If it was in a hole, we detected reordering. */
1060 if (fack_count < prior_fackets &&
1061 !(sacked&TCPCB_SACKED_ACKED))
1062 reord = min(fack_count, reord);
1063 }
1064
1065 /* Nothing to do; acked frame is about to be dropped. */
1066 continue;
1067 }
1068
1069 if ((sacked&TCPCB_SACKED_RETRANS) &&
1070 after(end_seq, TCP_SKB_CB(skb)->ack_seq) &&
1071 (!lost_retrans || after(end_seq, lost_retrans)))
1072 lost_retrans = end_seq;
1073
1074 if (!in_sack)
1075 continue;
1076
1077 if (!(sacked&TCPCB_SACKED_ACKED)) {
1078 if (sacked & TCPCB_SACKED_RETRANS) {
1079 /* If the segment is not tagged as lost,
1080 * we do not clear RETRANS, believing
1081 * that retransmission is still in flight.
1082 */
1083 if (sacked & TCPCB_LOST) {
1084 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS);
1085 tp->lost_out -= tcp_skb_pcount(skb);
1086 tp->retrans_out -= tcp_skb_pcount(skb);
1087 }
1088 } else {
1089 /* New sack for not retransmitted frame,
1090 * which was in hole. It is reordering.
1091 */
1092 if (!(sacked & TCPCB_RETRANS) &&
1093 fack_count < prior_fackets)
1094 reord = min(fack_count, reord);
1095
1096 if (sacked & TCPCB_LOST) {
1097 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1098 tp->lost_out -= tcp_skb_pcount(skb);
1099 }
1100 }
1101
1102 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED;
1103 flag |= FLAG_DATA_SACKED;
1104 tp->sacked_out += tcp_skb_pcount(skb);
1105
1106 if (fack_count > tp->fackets_out)
1107 tp->fackets_out = fack_count;
1108 } else {
1109 if (dup_sack && (sacked&TCPCB_RETRANS))
1110 reord = min(fack_count, reord);
1111 }
1112
1113 /* D-SACK. We can detect redundant retransmission
1114 * in S|R and plain R frames and clear it.
1115 * undo_retrans is decreased above, L|R frames
1116 * are accounted above as well.
1117 */
1118 if (dup_sack &&
1119 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) {
1120 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1121 tp->retrans_out -= tcp_skb_pcount(skb);
1122 }
1123 }
1124 }
1125
1126 /* Check for lost retransmit. This superb idea is
1127 * borrowed from "ratehalving". Event "C".
1128 * Later note: FACK people cheated me again 8),
1129 * we have to account for reordering! Ugly,
1130 * but should help.
1131 */
1132 if (lost_retrans && tp->ca_state == TCP_CA_Recovery) {
1133 struct sk_buff *skb;
1134
1135 sk_stream_for_retrans_queue(skb, sk) {
1136 if (after(TCP_SKB_CB(skb)->seq, lost_retrans))
1137 break;
1138 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1139 continue;
1140 if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) &&
1141 after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) &&
1142 (IsFack(tp) ||
1143 !before(lost_retrans,
1144 TCP_SKB_CB(skb)->ack_seq + tp->reordering *
1145 tp->mss_cache_std))) {
1146 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1147 tp->retrans_out -= tcp_skb_pcount(skb);
1148
1149 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) {
1150 tp->lost_out += tcp_skb_pcount(skb);
1151 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1152 flag |= FLAG_DATA_SACKED;
1153 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT);
1154 }
1155 }
1156 }
1157 }
1158
1159 tp->left_out = tp->sacked_out + tp->lost_out;
1160
1161 if ((reord < tp->fackets_out) && tp->ca_state != TCP_CA_Loss)
1162 tcp_update_reordering(tp, ((tp->fackets_out + 1) - reord), 0);
1163
1164#if FASTRETRANS_DEBUG > 0
1165 BUG_TRAP((int)tp->sacked_out >= 0);
1166 BUG_TRAP((int)tp->lost_out >= 0);
1167 BUG_TRAP((int)tp->retrans_out >= 0);
1168 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0);
1169#endif
1170 return flag;
1171}
1172
1173/* RTO occurred, but do not yet enter loss state. Instead, transmit two new
1174 * segments to see from the next ACKs whether any data was really missing.
1175 * If the RTO was spurious, new ACKs should arrive.
1176 */
1177void tcp_enter_frto(struct sock *sk)
1178{
1179 struct tcp_sock *tp = tcp_sk(sk);
1180 struct sk_buff *skb;
1181
1182 tp->frto_counter = 1;
1183
1184 if (tp->ca_state <= TCP_CA_Disorder ||
1185 tp->snd_una == tp->high_seq ||
1186 (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) {
1187 tp->prior_ssthresh = tcp_current_ssthresh(tp);
1188 if (!tcp_westwood_ssthresh(tp))
1189 tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
1190 }
1191
1192 /* Have to clear retransmission markers here to keep the bookkeeping
1193 * in shape, even though we are not yet in Loss state.
1194 * If something was really lost, it is eventually caught up
1195 * in tcp_enter_frto_loss.
1196 */
1197 tp->retrans_out = 0;
1198 tp->undo_marker = tp->snd_una;
1199 tp->undo_retrans = 0;
1200
1201 sk_stream_for_retrans_queue(skb, sk) {
1202 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS;
1203 }
1204 tcp_sync_left_out(tp);
1205
1206 tcp_set_ca_state(tp, TCP_CA_Open);
1207 tp->frto_highmark = tp->snd_nxt;
1208}
1209
1210/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1211 * which indicates that we should follow the traditional RTO recovery,
1212 * i.e. mark everything lost and do go-back-N retransmission.
1213 */
1214static void tcp_enter_frto_loss(struct sock *sk)
1215{
1216 struct tcp_sock *tp = tcp_sk(sk);
1217 struct sk_buff *skb;
1218 int cnt = 0;
1219
1220 tp->sacked_out = 0;
1221 tp->lost_out = 0;
1222 tp->fackets_out = 0;
1223
1224 sk_stream_for_retrans_queue(skb, sk) {
1225 cnt += tcp_skb_pcount(skb);
1226 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1227 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1228
1229 /* Do not mark those segments lost that were
1230 * forward transmitted after RTO
1231 */
1232 if (!after(TCP_SKB_CB(skb)->end_seq,
1233 tp->frto_highmark)) {
1234 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1235 tp->lost_out += tcp_skb_pcount(skb);
1236 }
1237 } else {
1238 tp->sacked_out += tcp_skb_pcount(skb);
1239 tp->fackets_out = cnt;
1240 }
1241 }
1242 tcp_sync_left_out(tp);
1243
1244 tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1;
1245 tp->snd_cwnd_cnt = 0;
1246 tp->snd_cwnd_stamp = tcp_time_stamp;
1247 tp->undo_marker = 0;
1248 tp->frto_counter = 0;
1249
1250 tp->reordering = min_t(unsigned int, tp->reordering,
1251 sysctl_tcp_reordering);
1252 tcp_set_ca_state(tp, TCP_CA_Loss);
1253 tp->high_seq = tp->frto_highmark;
1254 TCP_ECN_queue_cwr(tp);
1255
1256 init_bictcp(tp);
1257}
1258
1259void tcp_clear_retrans(struct tcp_sock *tp)
1260{
1261 tp->left_out = 0;
1262 tp->retrans_out = 0;
1263
1264 tp->fackets_out = 0;
1265 tp->sacked_out = 0;
1266 tp->lost_out = 0;
1267
1268 tp->undo_marker = 0;
1269 tp->undo_retrans = 0;
1270}
1271
1272/* Enter Loss state. If "how" is not zero, forget all SACK information
1273 * and reset tags completely, otherwise preserve SACKs. If receiver
1274 * dropped its ofo queue, we will know this due to reneging detection.
1275 */
1276void tcp_enter_loss(struct sock *sk, int how)
1277{
1278 struct tcp_sock *tp = tcp_sk(sk);
1279 struct sk_buff *skb;
1280 int cnt = 0;
1281
1282 /* Reduce ssthresh if it has not yet been made inside this window. */
1283 if (tp->ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq ||
1284 (tp->ca_state == TCP_CA_Loss && !tp->retransmits)) {
1285 tp->prior_ssthresh = tcp_current_ssthresh(tp);
1286 tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
1287 }
1288 tp->snd_cwnd = 1;
1289 tp->snd_cwnd_cnt = 0;
1290 tp->snd_cwnd_stamp = tcp_time_stamp;
1291
1292 tcp_clear_retrans(tp);
1293
1294 /* Push undo marker, if it was plain RTO and nothing
1295 * was retransmitted. */
1296 if (!how)
1297 tp->undo_marker = tp->snd_una;
1298
1299 sk_stream_for_retrans_queue(skb, sk) {
1300 cnt += tcp_skb_pcount(skb);
1301 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS)
1302 tp->undo_marker = 0;
1303 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED;
1304 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) {
1305 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;
1306 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1307 tp->lost_out += tcp_skb_pcount(skb);
1308 } else {
1309 tp->sacked_out += tcp_skb_pcount(skb);
1310 tp->fackets_out = cnt;
1311 }
1312 }
1313 tcp_sync_left_out(tp);
1314
1315 tp->reordering = min_t(unsigned int, tp->reordering,
1316 sysctl_tcp_reordering);
1317 tcp_set_ca_state(tp, TCP_CA_Loss);
1318 tp->high_seq = tp->snd_nxt;
1319 TCP_ECN_queue_cwr(tp);
1320}
1321
1322static int tcp_check_sack_reneging(struct sock *sk, struct tcp_sock *tp)
1323{
1324 struct sk_buff *skb;
1325
1326 /* If ACK arrived pointing to a remembered SACK,
1327 * it means that our remembered SACKs do not reflect
1328 * real state of receiver i.e.
1329 * receiver _host_ is heavily congested (or buggy).
1330 * Do processing similar to RTO timeout.
1331 */
1332 if ((skb = skb_peek(&sk->sk_write_queue)) != NULL &&
1333 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {
1334 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING);
1335
1336 tcp_enter_loss(sk, 1);
1337 tp->retransmits++;
1338 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue));
1339 tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
1340 return 1;
1341 }
1342 return 0;
1343}
1344
1345static inline int tcp_fackets_out(struct tcp_sock *tp)
1346{
1347 return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out;
1348}
1349
1350static inline int tcp_skb_timedout(struct tcp_sock *tp, struct sk_buff *skb)
1351{
1352 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > tp->rto);
1353}
1354
1355static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp)
1356{
1357 return tp->packets_out &&
1358 tcp_skb_timedout(tp, skb_peek(&sk->sk_write_queue));
1359}
1360
1361/* Linux NewReno/SACK/FACK/ECN state machine.
1362 * --------------------------------------
1363 *
1364 * "Open" Normal state, no dubious events, fast path.
1365 * "Disorder" In all the respects it is "Open",
1366 * but requires a bit more attention. It is entered when
1367 * we see some SACKs or dupacks. It is split of "Open"
1368 * mainly to move some processing from fast path to slow one.
1369 * "CWR" CWND was reduced due to some Congestion Notification event.
1370 * It can be ECN, ICMP source quench, local device congestion.
1371 * "Recovery" CWND was reduced, we are fast-retransmitting.
1372 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1373 *
1374 * tcp_fastretrans_alert() is entered:
1375 * - each incoming ACK, if state is not "Open"
1376 * - when arrived ACK is unusual, namely:
1377 * * SACK
1378 * * Duplicate ACK.
1379 * * ECN ECE.
1380 *
1381 * Counting packets in flight is pretty simple.
1382 *
1383 * in_flight = packets_out - left_out + retrans_out
1384 *
1385 * packets_out is SND.NXT-SND.UNA counted in packets.
1386 *
1387 * retrans_out is number of retransmitted segments.
1388 *
1389 * left_out is number of segments left network, but not ACKed yet.
1390 *
1391 * left_out = sacked_out + lost_out
1392 *
1393 * sacked_out: Packets, which arrived to receiver out of order
1394 * and hence not ACKed. With SACKs this number is simply
1395 * amount of SACKed data. Even without SACKs
1396 * it is easy to give pretty reliable estimate of this number,
1397 * counting duplicate ACKs.
1398 *
1399 * lost_out: Packets lost by network. TCP has no explicit
1400 * "loss notification" feedback from network (for now).
1401 * It means that this number can be only _guessed_.
1402 * Actually, it is the heuristics to predict lossage that
1403 * distinguishes different algorithms.
1404 *
1405 * F.e. after RTO, when all the queue is considered as lost,
1406 * lost_out = packets_out and in_flight = retrans_out.
1407 *
1408 * Essentially, we have now two algorithms counting
1409 * lost packets.
1410 *
1411 * FACK: It is the simplest heuristics. As soon as we decided
1412 * that something is lost, we decide that _all_ not SACKed
1413 * packets until the most forward SACK are lost. I.e.
1414 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1415 * It is absolutely correct estimate, if network does not reorder
1416 * packets. And it loses any connection to reality when reordering
1417 * takes place. We use FACK by default until reordering
1418 * is suspected on the path to this destination.
1419 *
1420 * NewReno: when Recovery is entered, we assume that one segment
1421 * is lost (classic Reno). While we are in Recovery and
1422 * a partial ACK arrives, we assume that one more packet
1423 * is lost (NewReno). This heuristics are the same in NewReno
1424 * and SACK.
1425 *
1426 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1427 * deflation etc. CWND is real congestion window, never inflated, changes
1428 * only according to classic VJ rules.
1429 *
1430 * Really tricky (and requiring careful tuning) part of algorithm
1431 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1432 * The first determines the moment _when_ we should reduce CWND and,
1433 * hence, slow down forward transmission. In fact, it determines the moment
1434 * when we decide that hole is caused by loss, rather than by a reorder.
1435 *
1436 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1437 * holes, caused by lost packets.
1438 *
1439 * And the most logically complicated part of algorithm is undo
1440 * heuristics. We detect false retransmits due to both too early
1441 * fast retransmit (reordering) and underestimated RTO, analyzing
1442 * timestamps and D-SACKs. When we detect that some segments were
1443 * retransmitted by mistake and CWND reduction was wrong, we undo
1444 * window reduction and abort recovery phase. This logic is hidden
1445 * inside several functions named tcp_try_undo_<something>.
1446 */
1447
1448/* This function decides, when we should leave Disordered state
1449 * and enter Recovery phase, reducing congestion window.
1450 *
1451 * Main question: may we further continue forward transmission
1452 * with the same cwnd?
1453 */
1454static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp)
1455{
1456 __u32 packets_out;
1457
1458 /* Trick#1: The loss is proven. */
1459 if (tp->lost_out)
1460 return 1;
1461
1462 /* Not-A-Trick#2 : Classic rule... */
1463 if (tcp_fackets_out(tp) > tp->reordering)
1464 return 1;
1465
1466 /* Trick#3 : when we use RFC2988 timer restart, fast
1467 * retransmit can be triggered by timeout of queue head.
1468 */
1469 if (tcp_head_timedout(sk, tp))
1470 return 1;
1471
1472 /* Trick#4: It is still not OK... But will it be useful to delay
1473 * recovery more?
1474 */
1475 packets_out = tp->packets_out;
1476 if (packets_out <= tp->reordering &&
1477 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) &&
1478 !tcp_may_send_now(sk, tp)) {
1479 /* We have nothing to send. This connection is limited
1480 * either by receiver window or by application.
1481 */
1482 return 1;
1483 }
1484
1485 return 0;
1486}
1487
1488/* If we receive more dupacks than we expected counting segments
1489 * in assumption of absent reordering, interpret this as reordering.
1490 * The only another reason could be bug in receiver TCP.
1491 */
1492static void tcp_check_reno_reordering(struct tcp_sock *tp, int addend)
1493{
1494 u32 holes;
1495
1496 holes = max(tp->lost_out, 1U);
1497 holes = min(holes, tp->packets_out);
1498
1499 if ((tp->sacked_out + holes) > tp->packets_out) {
1500 tp->sacked_out = tp->packets_out - holes;
1501 tcp_update_reordering(tp, tp->packets_out+addend, 0);
1502 }
1503}
1504
1505/* Emulate SACKs for SACKless connection: account for a new dupack. */
1506
1507static void tcp_add_reno_sack(struct tcp_sock *tp)
1508{
1509 tp->sacked_out++;
1510 tcp_check_reno_reordering(tp, 0);
1511 tcp_sync_left_out(tp);
1512}
1513
1514/* Account for ACK, ACKing some data in Reno Recovery phase. */
1515
1516static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked)
1517{
1518 if (acked > 0) {
1519 /* One ACK acked hole. The rest eat duplicate ACKs. */
1520 if (acked-1 >= tp->sacked_out)
1521 tp->sacked_out = 0;
1522 else
1523 tp->sacked_out -= acked-1;
1524 }
1525 tcp_check_reno_reordering(tp, acked);
1526 tcp_sync_left_out(tp);
1527}
1528
1529static inline void tcp_reset_reno_sack(struct tcp_sock *tp)
1530{
1531 tp->sacked_out = 0;
1532 tp->left_out = tp->lost_out;
1533}
1534
1535/* Mark head of queue up as lost. */
1536static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp,
1537 int packets, u32 high_seq)
1538{
1539 struct sk_buff *skb;
1540 int cnt = packets;
1541
1542 BUG_TRAP(cnt <= tp->packets_out);
1543
1544 sk_stream_for_retrans_queue(skb, sk) {
1545 cnt -= tcp_skb_pcount(skb);
1546 if (cnt < 0 || after(TCP_SKB_CB(skb)->end_seq, high_seq))
1547 break;
1548 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1549 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1550 tp->lost_out += tcp_skb_pcount(skb);
1551 }
1552 }
1553 tcp_sync_left_out(tp);
1554}
1555
1556/* Account newly detected lost packet(s) */
1557
1558static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp)
1559{
1560 if (IsFack(tp)) {
1561 int lost = tp->fackets_out - tp->reordering;
1562 if (lost <= 0)
1563 lost = 1;
1564 tcp_mark_head_lost(sk, tp, lost, tp->high_seq);
1565 } else {
1566 tcp_mark_head_lost(sk, tp, 1, tp->high_seq);
1567 }
1568
1569 /* New heuristics: it is possible only after we switched
1570 * to restart timer each time when something is ACKed.
1571 * Hence, we can detect timed out packets during fast
1572 * retransmit without falling to slow start.
1573 */
1574 if (tcp_head_timedout(sk, tp)) {
1575 struct sk_buff *skb;
1576
1577 sk_stream_for_retrans_queue(skb, sk) {
1578 if (tcp_skb_timedout(tp, skb) &&
1579 !(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) {
1580 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1581 tp->lost_out += tcp_skb_pcount(skb);
1582 }
1583 }
1584 tcp_sync_left_out(tp);
1585 }
1586}
1587
1588/* CWND moderation, preventing bursts due to too big ACKs
1589 * in dubious situations.
1590 */
1591static inline void tcp_moderate_cwnd(struct tcp_sock *tp)
1592{
1593 tp->snd_cwnd = min(tp->snd_cwnd,
1594 tcp_packets_in_flight(tp)+tcp_max_burst(tp));
1595 tp->snd_cwnd_stamp = tcp_time_stamp;
1596}
1597
1598/* Decrease cwnd each second ack. */
1599
1600static void tcp_cwnd_down(struct tcp_sock *tp)
1601{
1602 int decr = tp->snd_cwnd_cnt + 1;
1603 __u32 limit;
1604
1605 /*
1606 * TCP Westwood
1607 * Here limit is evaluated as BWestimation*RTTmin (for obtaining it
1608 * in packets we use mss_cache). If sysctl_tcp_westwood is off
1609 * tcp_westwood_bw_rttmin() returns 0. In such case snd_ssthresh is
1610 * still used as usual. It prevents other strange cases in which
1611 * BWE*RTTmin could assume value 0. It should not happen but...
1612 */
1613
1614 if (!(limit = tcp_westwood_bw_rttmin(tp)))
1615 limit = tp->snd_ssthresh/2;
1616
1617 tp->snd_cwnd_cnt = decr&1;
1618 decr >>= 1;
1619
1620 if (decr && tp->snd_cwnd > limit)
1621 tp->snd_cwnd -= decr;
1622
1623 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1);
1624 tp->snd_cwnd_stamp = tcp_time_stamp;
1625}
1626
1627/* Nothing was retransmitted or returned timestamp is less
1628 * than timestamp of the first retransmission.
1629 */
1630static inline int tcp_packet_delayed(struct tcp_sock *tp)
1631{
1632 return !tp->retrans_stamp ||
1633 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
1634 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0);
1635}
1636
1637/* Undo procedures. */
1638
1639#if FASTRETRANS_DEBUG > 1
1640static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg)
1641{
1642 struct inet_sock *inet = inet_sk(sk);
1643 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1644 msg,
1645 NIPQUAD(inet->daddr), ntohs(inet->dport),
1646 tp->snd_cwnd, tp->left_out,
1647 tp->snd_ssthresh, tp->prior_ssthresh,
1648 tp->packets_out);
1649}
1650#else
1651#define DBGUNDO(x...) do { } while (0)
1652#endif
1653
1654static void tcp_undo_cwr(struct tcp_sock *tp, int undo)
1655{
1656 if (tp->prior_ssthresh) {
1657 if (tcp_is_bic(tp))
1658 tp->snd_cwnd = max(tp->snd_cwnd, tp->bictcp.last_max_cwnd);
1659 else
1660 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1);
1661
1662 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) {
1663 tp->snd_ssthresh = tp->prior_ssthresh;
1664 TCP_ECN_withdraw_cwr(tp);
1665 }
1666 } else {
1667 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh);
1668 }
1669 tcp_moderate_cwnd(tp);
1670 tp->snd_cwnd_stamp = tcp_time_stamp;
1671}
1672
1673static inline int tcp_may_undo(struct tcp_sock *tp)
1674{
1675 return tp->undo_marker &&
1676 (!tp->undo_retrans || tcp_packet_delayed(tp));
1677}
1678
1679/* People celebrate: "We love our President!" */
1680static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp)
1681{
1682 if (tcp_may_undo(tp)) {
1683 /* Happy end! We did not retransmit anything
1684 * or our original transmission succeeded.
1685 */
1686 DBGUNDO(sk, tp, tp->ca_state == TCP_CA_Loss ? "loss" : "retrans");
1687 tcp_undo_cwr(tp, 1);
1688 if (tp->ca_state == TCP_CA_Loss)
1689 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1690 else
1691 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO);
1692 tp->undo_marker = 0;
1693 }
1694 if (tp->snd_una == tp->high_seq && IsReno(tp)) {
1695 /* Hold old state until something *above* high_seq
1696 * is ACKed. For Reno it is MUST to prevent false
1697 * fast retransmits (RFC2582). SACK TCP is safe. */
1698 tcp_moderate_cwnd(tp);
1699 return 1;
1700 }
1701 tcp_set_ca_state(tp, TCP_CA_Open);
1702 return 0;
1703}
1704
1705/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1706static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp)
1707{
1708 if (tp->undo_marker && !tp->undo_retrans) {
1709 DBGUNDO(sk, tp, "D-SACK");
1710 tcp_undo_cwr(tp, 1);
1711 tp->undo_marker = 0;
1712 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO);
1713 }
1714}
1715
1716/* Undo during fast recovery after partial ACK. */
1717
1718static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp,
1719 int acked)
1720{
1721 /* Partial ACK arrived. Force Hoe's retransmit. */
1722 int failed = IsReno(tp) || tp->fackets_out>tp->reordering;
1723
1724 if (tcp_may_undo(tp)) {
1725 /* Plain luck! Hole if filled with delayed
1726 * packet, rather than with a retransmit.
1727 */
1728 if (tp->retrans_out == 0)
1729 tp->retrans_stamp = 0;
1730
1731 tcp_update_reordering(tp, tcp_fackets_out(tp)+acked, 1);
1732
1733 DBGUNDO(sk, tp, "Hoe");
1734 tcp_undo_cwr(tp, 0);
1735 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO);
1736
1737 /* So... Do not make Hoe's retransmit yet.
1738 * If the first packet was delayed, the rest
1739 * ones are most probably delayed as well.
1740 */
1741 failed = 0;
1742 }
1743 return failed;
1744}
1745
1746/* Undo during loss recovery after partial ACK. */
1747static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp)
1748{
1749 if (tcp_may_undo(tp)) {
1750 struct sk_buff *skb;
1751 sk_stream_for_retrans_queue(skb, sk) {
1752 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST;
1753 }
1754 DBGUNDO(sk, tp, "partial loss");
1755 tp->lost_out = 0;
1756 tp->left_out = tp->sacked_out;
1757 tcp_undo_cwr(tp, 1);
1758 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO);
1759 tp->retransmits = 0;
1760 tp->undo_marker = 0;
1761 if (!IsReno(tp))
1762 tcp_set_ca_state(tp, TCP_CA_Open);
1763 return 1;
1764 }
1765 return 0;
1766}
1767
1768static inline void tcp_complete_cwr(struct tcp_sock *tp)
1769{
1770 if (tcp_westwood_cwnd(tp))
1771 tp->snd_ssthresh = tp->snd_cwnd;
1772 else
1773 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
1774 tp->snd_cwnd_stamp = tcp_time_stamp;
1775}
1776
1777static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag)
1778{
1779 tp->left_out = tp->sacked_out;
1780
1781 if (tp->retrans_out == 0)
1782 tp->retrans_stamp = 0;
1783
1784 if (flag&FLAG_ECE)
1785 tcp_enter_cwr(tp);
1786
1787 if (tp->ca_state != TCP_CA_CWR) {
1788 int state = TCP_CA_Open;
1789
1790 if (tp->left_out || tp->retrans_out || tp->undo_marker)
1791 state = TCP_CA_Disorder;
1792
1793 if (tp->ca_state != state) {
1794 tcp_set_ca_state(tp, state);
1795 tp->high_seq = tp->snd_nxt;
1796 }
1797 tcp_moderate_cwnd(tp);
1798 } else {
1799 tcp_cwnd_down(tp);
1800 }
1801}
1802
1803/* Process an event, which can update packets-in-flight not trivially.
1804 * Main goal of this function is to calculate new estimate for left_out,
1805 * taking into account both packets sitting in receiver's buffer and
1806 * packets lost by network.
1807 *
1808 * Besides that it does CWND reduction, when packet loss is detected
1809 * and changes state of machine.
1810 *
1811 * It does _not_ decide what to send, it is made in function
1812 * tcp_xmit_retransmit_queue().
1813 */
1814static void
1815tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una,
1816 int prior_packets, int flag)
1817{
1818 struct tcp_sock *tp = tcp_sk(sk);
1819 int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP));
1820
1821 /* Some technical things:
1822 * 1. Reno does not count dupacks (sacked_out) automatically. */
1823 if (!tp->packets_out)
1824 tp->sacked_out = 0;
1825 /* 2. SACK counts snd_fack in packets inaccurately. */
1826 if (tp->sacked_out == 0)
1827 tp->fackets_out = 0;
1828
1829 /* Now state machine starts.
1830 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1831 if (flag&FLAG_ECE)
1832 tp->prior_ssthresh = 0;
1833
1834 /* B. In all the states check for reneging SACKs. */
1835 if (tp->sacked_out && tcp_check_sack_reneging(sk, tp))
1836 return;
1837
1838 /* C. Process data loss notification, provided it is valid. */
1839 if ((flag&FLAG_DATA_LOST) &&
1840 before(tp->snd_una, tp->high_seq) &&
1841 tp->ca_state != TCP_CA_Open &&
1842 tp->fackets_out > tp->reordering) {
1843 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq);
1844 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS);
1845 }
1846
1847 /* D. Synchronize left_out to current state. */
1848 tcp_sync_left_out(tp);
1849
1850 /* E. Check state exit conditions. State can be terminated
1851 * when high_seq is ACKed. */
1852 if (tp->ca_state == TCP_CA_Open) {
1853 if (!sysctl_tcp_frto)
1854 BUG_TRAP(tp->retrans_out == 0);
1855 tp->retrans_stamp = 0;
1856 } else if (!before(tp->snd_una, tp->high_seq)) {
1857 switch (tp->ca_state) {
1858 case TCP_CA_Loss:
1859 tp->retransmits = 0;
1860 if (tcp_try_undo_recovery(sk, tp))
1861 return;
1862 break;
1863
1864 case TCP_CA_CWR:
1865 /* CWR is to be held something *above* high_seq
1866 * is ACKed for CWR bit to reach receiver. */
1867 if (tp->snd_una != tp->high_seq) {
1868 tcp_complete_cwr(tp);
1869 tcp_set_ca_state(tp, TCP_CA_Open);
1870 }
1871 break;
1872
1873 case TCP_CA_Disorder:
1874 tcp_try_undo_dsack(sk, tp);
1875 if (!tp->undo_marker ||
1876 /* For SACK case do not Open to allow to undo
1877 * catching for all duplicate ACKs. */
1878 IsReno(tp) || tp->snd_una != tp->high_seq) {
1879 tp->undo_marker = 0;
1880 tcp_set_ca_state(tp, TCP_CA_Open);
1881 }
1882 break;
1883
1884 case TCP_CA_Recovery:
1885 if (IsReno(tp))
1886 tcp_reset_reno_sack(tp);
1887 if (tcp_try_undo_recovery(sk, tp))
1888 return;
1889 tcp_complete_cwr(tp);
1890 break;
1891 }
1892 }
1893
1894 /* F. Process state. */
1895 switch (tp->ca_state) {
1896 case TCP_CA_Recovery:
1897 if (prior_snd_una == tp->snd_una) {
1898 if (IsReno(tp) && is_dupack)
1899 tcp_add_reno_sack(tp);
1900 } else {
1901 int acked = prior_packets - tp->packets_out;
1902 if (IsReno(tp))
1903 tcp_remove_reno_sacks(sk, tp, acked);
1904 is_dupack = tcp_try_undo_partial(sk, tp, acked);
1905 }
1906 break;
1907 case TCP_CA_Loss:
1908 if (flag&FLAG_DATA_ACKED)
1909 tp->retransmits = 0;
1910 if (!tcp_try_undo_loss(sk, tp)) {
1911 tcp_moderate_cwnd(tp);
1912 tcp_xmit_retransmit_queue(sk);
1913 return;
1914 }
1915 if (tp->ca_state != TCP_CA_Open)
1916 return;
1917 /* Loss is undone; fall through to processing in Open state. */
1918 default:
1919 if (IsReno(tp)) {
1920 if (tp->snd_una != prior_snd_una)
1921 tcp_reset_reno_sack(tp);
1922 if (is_dupack)
1923 tcp_add_reno_sack(tp);
1924 }
1925
1926 if (tp->ca_state == TCP_CA_Disorder)
1927 tcp_try_undo_dsack(sk, tp);
1928
1929 if (!tcp_time_to_recover(sk, tp)) {
1930 tcp_try_to_open(sk, tp, flag);
1931 return;
1932 }
1933
1934 /* Otherwise enter Recovery state */
1935
1936 if (IsReno(tp))
1937 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY);
1938 else
1939 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY);
1940
1941 tp->high_seq = tp->snd_nxt;
1942 tp->prior_ssthresh = 0;
1943 tp->undo_marker = tp->snd_una;
1944 tp->undo_retrans = tp->retrans_out;
1945
1946 if (tp->ca_state < TCP_CA_CWR) {
1947 if (!(flag&FLAG_ECE))
1948 tp->prior_ssthresh = tcp_current_ssthresh(tp);
1949 tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
1950 TCP_ECN_queue_cwr(tp);
1951 }
1952
1953 tp->snd_cwnd_cnt = 0;
1954 tcp_set_ca_state(tp, TCP_CA_Recovery);
1955 }
1956
1957 if (is_dupack || tcp_head_timedout(sk, tp))
1958 tcp_update_scoreboard(sk, tp);
1959 tcp_cwnd_down(tp);
1960 tcp_xmit_retransmit_queue(sk);
1961}
1962
1963/* Read draft-ietf-tcplw-high-performance before mucking
1964 * with this code. (Superceeds RFC1323)
1965 */
1966static void tcp_ack_saw_tstamp(struct tcp_sock *tp, int flag)
1967{
1968 __u32 seq_rtt;
1969
1970 /* RTTM Rule: A TSecr value received in a segment is used to
1971 * update the averaged RTT measurement only if the segment
1972 * acknowledges some new data, i.e., only if it advances the
1973 * left edge of the send window.
1974 *
1975 * See draft-ietf-tcplw-high-performance-00, section 3.3.
1976 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
1977 *
1978 * Changed: reset backoff as soon as we see the first valid sample.
1979 * If we do not, we get strongly overstimated rto. With timestamps
1980 * samples are accepted even from very old segments: f.e., when rtt=1
1981 * increases to 8, we retransmit 5 times and after 8 seconds delayed
1982 * answer arrives rto becomes 120 seconds! If at least one of segments
1983 * in window is lost... Voila. --ANK (010210)
1984 */
1985 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr;
1986 tcp_rtt_estimator(tp, seq_rtt);
1987 tcp_set_rto(tp);
1988 tp->backoff = 0;
1989 tcp_bound_rto(tp);
1990}
1991
1992static void tcp_ack_no_tstamp(struct tcp_sock *tp, u32 seq_rtt, int flag)
1993{
1994 /* We don't have a timestamp. Can only use
1995 * packets that are not retransmitted to determine
1996 * rtt estimates. Also, we must not reset the
1997 * backoff for rto until we get a non-retransmitted
1998 * packet. This allows us to deal with a situation
1999 * where the network delay has increased suddenly.
2000 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2001 */
2002
2003 if (flag & FLAG_RETRANS_DATA_ACKED)
2004 return;
2005
2006 tcp_rtt_estimator(tp, seq_rtt);
2007 tcp_set_rto(tp);
2008 tp->backoff = 0;
2009 tcp_bound_rto(tp);
2010}
2011
2012static inline void tcp_ack_update_rtt(struct tcp_sock *tp,
2013 int flag, s32 seq_rtt)
2014{
2015 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2016 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr)
2017 tcp_ack_saw_tstamp(tp, flag);
2018 else if (seq_rtt >= 0)
2019 tcp_ack_no_tstamp(tp, seq_rtt, flag);
2020}
2021
2022/*
2023 * Compute congestion window to use.
2024 *
2025 * This is from the implementation of BICTCP in
2026 * Lison-Xu, Kahaled Harfoush, and Injog Rhee.
2027 * "Binary Increase Congestion Control for Fast, Long Distance
2028 * Networks" in InfoComm 2004
2029 * Available from:
2030 * http://www.csc.ncsu.edu/faculty/rhee/export/bitcp.pdf
2031 *
2032 * Unless BIC is enabled and congestion window is large
2033 * this behaves the same as the original Reno.
2034 */
2035static inline __u32 bictcp_cwnd(struct tcp_sock *tp)
2036{
2037 /* orignal Reno behaviour */
2038 if (!tcp_is_bic(tp))
2039 return tp->snd_cwnd;
2040
2041 if (tp->bictcp.last_cwnd == tp->snd_cwnd &&
2042 (s32)(tcp_time_stamp - tp->bictcp.last_stamp) <= (HZ>>5))
2043 return tp->bictcp.cnt;
2044
2045 tp->bictcp.last_cwnd = tp->snd_cwnd;
2046 tp->bictcp.last_stamp = tcp_time_stamp;
2047
2048 /* start off normal */
2049 if (tp->snd_cwnd <= sysctl_tcp_bic_low_window)
2050 tp->bictcp.cnt = tp->snd_cwnd;
2051
2052 /* binary increase */
2053 else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd) {
2054 __u32 dist = (tp->bictcp.last_max_cwnd - tp->snd_cwnd)
2055 / BICTCP_B;
2056
2057 if (dist > BICTCP_MAX_INCREMENT)
2058 /* linear increase */
2059 tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT;
2060 else if (dist <= 1U)
2061 /* binary search increase */
2062 tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR
2063 / BICTCP_B;
2064 else
2065 /* binary search increase */
2066 tp->bictcp.cnt = tp->snd_cwnd / dist;
2067 } else {
2068 /* slow start amd linear increase */
2069 if (tp->snd_cwnd < tp->bictcp.last_max_cwnd + BICTCP_B)
2070 /* slow start */
2071 tp->bictcp.cnt = tp->snd_cwnd * BICTCP_FUNC_OF_MIN_INCR
2072 / BICTCP_B;
2073 else if (tp->snd_cwnd < tp->bictcp.last_max_cwnd
2074 + BICTCP_MAX_INCREMENT*(BICTCP_B-1))
2075 /* slow start */
2076 tp->bictcp.cnt = tp->snd_cwnd * (BICTCP_B-1)
2077 / (tp->snd_cwnd-tp->bictcp.last_max_cwnd);
2078 else
2079 /* linear increase */
2080 tp->bictcp.cnt = tp->snd_cwnd / BICTCP_MAX_INCREMENT;
2081 }
2082 return tp->bictcp.cnt;
2083}
2084
2085/* This is Jacobson's slow start and congestion avoidance.
2086 * SIGCOMM '88, p. 328.
2087 */
2088static inline void reno_cong_avoid(struct tcp_sock *tp)
2089{
2090 if (tp->snd_cwnd <= tp->snd_ssthresh) {
2091 /* In "safe" area, increase. */
2092 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
2093 tp->snd_cwnd++;
2094 } else {
2095 /* In dangerous area, increase slowly.
2096 * In theory this is tp->snd_cwnd += 1 / tp->snd_cwnd
2097 */
2098 if (tp->snd_cwnd_cnt >= bictcp_cwnd(tp)) {
2099 if (tp->snd_cwnd < tp->snd_cwnd_clamp)
2100 tp->snd_cwnd++;
2101 tp->snd_cwnd_cnt=0;
2102 } else
2103 tp->snd_cwnd_cnt++;
2104 }
2105 tp->snd_cwnd_stamp = tcp_time_stamp;
2106}
2107
2108/* This is based on the congestion detection/avoidance scheme described in
2109 * Lawrence S. Brakmo and Larry L. Peterson.
2110 * "TCP Vegas: End to end congestion avoidance on a global internet."
2111 * IEEE Journal on Selected Areas in Communication, 13(8):1465--1480,
2112 * October 1995. Available from:
2113 * ftp://ftp.cs.arizona.edu/xkernel/Papers/jsac.ps
2114 *
2115 * See http://www.cs.arizona.edu/xkernel/ for their implementation.
2116 * The main aspects that distinguish this implementation from the
2117 * Arizona Vegas implementation are:
2118 * o We do not change the loss detection or recovery mechanisms of
2119 * Linux in any way. Linux already recovers from losses quite well,
2120 * using fine-grained timers, NewReno, and FACK.
2121 * o To avoid the performance penalty imposed by increasing cwnd
2122 * only every-other RTT during slow start, we increase during
2123 * every RTT during slow start, just like Reno.
2124 * o Largely to allow continuous cwnd growth during slow start,
2125 * we use the rate at which ACKs come back as the "actual"
2126 * rate, rather than the rate at which data is sent.
2127 * o To speed convergence to the right rate, we set the cwnd
2128 * to achieve the right ("actual") rate when we exit slow start.
2129 * o To filter out the noise caused by delayed ACKs, we use the
2130 * minimum RTT sample observed during the last RTT to calculate
2131 * the actual rate.
2132 * o When the sender re-starts from idle, it waits until it has
2133 * received ACKs for an entire flight of new data before making
2134 * a cwnd adjustment decision. The original Vegas implementation
2135 * assumed senders never went idle.
2136 */
2137static void vegas_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt)
2138{
2139 /* The key players are v_beg_snd_una and v_beg_snd_nxt.
2140 *
2141 * These are so named because they represent the approximate values
2142 * of snd_una and snd_nxt at the beginning of the current RTT. More
2143 * precisely, they represent the amount of data sent during the RTT.
2144 * At the end of the RTT, when we receive an ACK for v_beg_snd_nxt,
2145 * we will calculate that (v_beg_snd_nxt - v_beg_snd_una) outstanding
2146 * bytes of data have been ACKed during the course of the RTT, giving
2147 * an "actual" rate of:
2148 *
2149 * (v_beg_snd_nxt - v_beg_snd_una) / (rtt duration)
2150 *
2151 * Unfortunately, v_beg_snd_una is not exactly equal to snd_una,
2152 * because delayed ACKs can cover more than one segment, so they
2153 * don't line up nicely with the boundaries of RTTs.
2154 *
2155 * Another unfortunate fact of life is that delayed ACKs delay the
2156 * advance of the left edge of our send window, so that the number
2157 * of bytes we send in an RTT is often less than our cwnd will allow.
2158 * So we keep track of our cwnd separately, in v_beg_snd_cwnd.
2159 */
2160
2161 if (after(ack, tp->vegas.beg_snd_nxt)) {
2162 /* Do the Vegas once-per-RTT cwnd adjustment. */
2163 u32 old_wnd, old_snd_cwnd;
2164
2165
2166 /* Here old_wnd is essentially the window of data that was
2167 * sent during the previous RTT, and has all
2168 * been acknowledged in the course of the RTT that ended
2169 * with the ACK we just received. Likewise, old_snd_cwnd
2170 * is the cwnd during the previous RTT.
2171 */
2172 old_wnd = (tp->vegas.beg_snd_nxt - tp->vegas.beg_snd_una) /
2173 tp->mss_cache_std;
2174 old_snd_cwnd = tp->vegas.beg_snd_cwnd;
2175
2176 /* Save the extent of the current window so we can use this
2177 * at the end of the next RTT.
2178 */
2179 tp->vegas.beg_snd_una = tp->vegas.beg_snd_nxt;
2180 tp->vegas.beg_snd_nxt = tp->snd_nxt;
2181 tp->vegas.beg_snd_cwnd = tp->snd_cwnd;
2182
2183 /* Take into account the current RTT sample too, to
2184 * decrease the impact of delayed acks. This double counts
2185 * this sample since we count it for the next window as well,
2186 * but that's not too awful, since we're taking the min,
2187 * rather than averaging.
2188 */
2189 vegas_rtt_calc(tp, seq_rtt);
2190
2191 /* We do the Vegas calculations only if we got enough RTT
2192 * samples that we can be reasonably sure that we got
2193 * at least one RTT sample that wasn't from a delayed ACK.
2194 * If we only had 2 samples total,
2195 * then that means we're getting only 1 ACK per RTT, which
2196 * means they're almost certainly delayed ACKs.
2197 * If we have 3 samples, we should be OK.
2198 */
2199
2200 if (tp->vegas.cntRTT <= 2) {
2201 /* We don't have enough RTT samples to do the Vegas
2202 * calculation, so we'll behave like Reno.
2203 */
2204 if (tp->snd_cwnd > tp->snd_ssthresh)
2205 tp->snd_cwnd++;
2206 } else {
2207 u32 rtt, target_cwnd, diff;
2208
2209 /* We have enough RTT samples, so, using the Vegas
2210 * algorithm, we determine if we should increase or
2211 * decrease cwnd, and by how much.
2212 */
2213
2214 /* Pluck out the RTT we are using for the Vegas
2215 * calculations. This is the min RTT seen during the
2216 * last RTT. Taking the min filters out the effects
2217 * of delayed ACKs, at the cost of noticing congestion
2218 * a bit later.
2219 */
2220 rtt = tp->vegas.minRTT;
2221
2222 /* Calculate the cwnd we should have, if we weren't
2223 * going too fast.
2224 *
2225 * This is:
2226 * (actual rate in segments) * baseRTT
2227 * We keep it as a fixed point number with
2228 * V_PARAM_SHIFT bits to the right of the binary point.
2229 */
2230 target_cwnd = ((old_wnd * tp->vegas.baseRTT)
2231 << V_PARAM_SHIFT) / rtt;
2232
2233 /* Calculate the difference between the window we had,
2234 * and the window we would like to have. This quantity
2235 * is the "Diff" from the Arizona Vegas papers.
2236 *
2237 * Again, this is a fixed point number with
2238 * V_PARAM_SHIFT bits to the right of the binary
2239 * point.
2240 */
2241 diff = (old_wnd << V_PARAM_SHIFT) - target_cwnd;
2242
2243 if (tp->snd_cwnd < tp->snd_ssthresh) {
2244 /* Slow start. */
2245 if (diff > sysctl_tcp_vegas_gamma) {
2246 /* Going too fast. Time to slow down
2247 * and switch to congestion avoidance.
2248 */
2249 tp->snd_ssthresh = 2;
2250
2251 /* Set cwnd to match the actual rate
2252 * exactly:
2253 * cwnd = (actual rate) * baseRTT
2254 * Then we add 1 because the integer
2255 * truncation robs us of full link
2256 * utilization.
2257 */
2258 tp->snd_cwnd = min(tp->snd_cwnd,
2259 (target_cwnd >>
2260 V_PARAM_SHIFT)+1);
2261
2262 }
2263 } else {
2264 /* Congestion avoidance. */
2265 u32 next_snd_cwnd;
2266
2267 /* Figure out where we would like cwnd
2268 * to be.
2269 */
2270 if (diff > sysctl_tcp_vegas_beta) {
2271 /* The old window was too fast, so
2272 * we slow down.
2273 */
2274 next_snd_cwnd = old_snd_cwnd - 1;
2275 } else if (diff < sysctl_tcp_vegas_alpha) {
2276 /* We don't have enough extra packets
2277 * in the network, so speed up.
2278 */
2279 next_snd_cwnd = old_snd_cwnd + 1;
2280 } else {
2281 /* Sending just as fast as we
2282 * should be.
2283 */
2284 next_snd_cwnd = old_snd_cwnd;
2285 }
2286
2287 /* Adjust cwnd upward or downward, toward the
2288 * desired value.
2289 */
2290 if (next_snd_cwnd > tp->snd_cwnd)
2291 tp->snd_cwnd++;
2292 else if (next_snd_cwnd < tp->snd_cwnd)
2293 tp->snd_cwnd--;
2294 }
2295 }
2296
2297 /* Wipe the slate clean for the next RTT. */
2298 tp->vegas.cntRTT = 0;
2299 tp->vegas.minRTT = 0x7fffffff;
2300 }
2301
2302 /* The following code is executed for every ack we receive,
2303 * except for conditions checked in should_advance_cwnd()
2304 * before the call to tcp_cong_avoid(). Mainly this means that
2305 * we only execute this code if the ack actually acked some
2306 * data.
2307 */
2308
2309 /* If we are in slow start, increase our cwnd in response to this ACK.
2310 * (If we are not in slow start then we are in congestion avoidance,
2311 * and adjust our congestion window only once per RTT. See the code
2312 * above.)
2313 */
2314 if (tp->snd_cwnd <= tp->snd_ssthresh)
2315 tp->snd_cwnd++;
2316
2317 /* to keep cwnd from growing without bound */
2318 tp->snd_cwnd = min_t(u32, tp->snd_cwnd, tp->snd_cwnd_clamp);
2319
2320 /* Make sure that we are never so timid as to reduce our cwnd below
2321 * 2 MSS.
2322 *
2323 * Going below 2 MSS would risk huge delayed ACKs from our receiver.
2324 */
2325 tp->snd_cwnd = max(tp->snd_cwnd, 2U);
2326
2327 tp->snd_cwnd_stamp = tcp_time_stamp;
2328}
2329
2330static inline void tcp_cong_avoid(struct tcp_sock *tp, u32 ack, u32 seq_rtt)
2331{
2332 if (tcp_vegas_enabled(tp))
2333 vegas_cong_avoid(tp, ack, seq_rtt);
2334 else
2335 reno_cong_avoid(tp);
2336}
2337
2338/* Restart timer after forward progress on connection.
2339 * RFC2988 recommends to restart timer to now+rto.
2340 */
2341
2342static inline void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp)
2343{
2344 if (!tp->packets_out) {
2345 tcp_clear_xmit_timer(sk, TCP_TIME_RETRANS);
2346 } else {
2347 tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
2348 }
2349}
2350
2351/* There is one downside to this scheme. Although we keep the
2352 * ACK clock ticking, adjusting packet counters and advancing
2353 * congestion window, we do not liberate socket send buffer
2354 * space.
2355 *
2356 * Mucking with skb->truesize and sk->sk_wmem_alloc et al.
2357 * then making a write space wakeup callback is a possible
2358 * future enhancement. WARNING: it is not trivial to make.
2359 */
2360static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb,
2361 __u32 now, __s32 *seq_rtt)
2362{
2363 struct tcp_sock *tp = tcp_sk(sk);
2364 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2365 __u32 seq = tp->snd_una;
2366 __u32 packets_acked;
2367 int acked = 0;
2368
2369 /* If we get here, the whole TSO packet has not been
2370 * acked.
2371 */
2372 BUG_ON(!after(scb->end_seq, seq));
2373
2374 packets_acked = tcp_skb_pcount(skb);
2375 if (tcp_trim_head(sk, skb, seq - scb->seq))
2376 return 0;
2377 packets_acked -= tcp_skb_pcount(skb);
2378
2379 if (packets_acked) {
2380 __u8 sacked = scb->sacked;
2381
2382 acked |= FLAG_DATA_ACKED;
2383 if (sacked) {
2384 if (sacked & TCPCB_RETRANS) {
2385 if (sacked & TCPCB_SACKED_RETRANS)
2386 tp->retrans_out -= packets_acked;
2387 acked |= FLAG_RETRANS_DATA_ACKED;
2388 *seq_rtt = -1;
2389 } else if (*seq_rtt < 0)
2390 *seq_rtt = now - scb->when;
2391 if (sacked & TCPCB_SACKED_ACKED)
2392 tp->sacked_out -= packets_acked;
2393 if (sacked & TCPCB_LOST)
2394 tp->lost_out -= packets_acked;
2395 if (sacked & TCPCB_URG) {
2396 if (tp->urg_mode &&
2397 !before(seq, tp->snd_up))
2398 tp->urg_mode = 0;
2399 }
2400 } else if (*seq_rtt < 0)
2401 *seq_rtt = now - scb->when;
2402
2403 if (tp->fackets_out) {
2404 __u32 dval = min(tp->fackets_out, packets_acked);
2405 tp->fackets_out -= dval;
2406 }
2407 tp->packets_out -= packets_acked;
2408
2409 BUG_ON(tcp_skb_pcount(skb) == 0);
2410 BUG_ON(!before(scb->seq, scb->end_seq));
2411 }
2412
2413 return acked;
2414}
2415
2416
2417/* Remove acknowledged frames from the retransmission queue. */
2418static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p)
2419{
2420 struct tcp_sock *tp = tcp_sk(sk);
2421 struct sk_buff *skb;
2422 __u32 now = tcp_time_stamp;
2423 int acked = 0;
2424 __s32 seq_rtt = -1;
2425
2426 while ((skb = skb_peek(&sk->sk_write_queue)) &&
2427 skb != sk->sk_send_head) {
2428 struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
2429 __u8 sacked = scb->sacked;
2430
2431 /* If our packet is before the ack sequence we can
2432 * discard it as it's confirmed to have arrived at
2433 * the other end.
2434 */
2435 if (after(scb->end_seq, tp->snd_una)) {
2436 if (tcp_skb_pcount(skb) > 1)
2437 acked |= tcp_tso_acked(sk, skb,
2438 now, &seq_rtt);
2439 break;
2440 }
2441
2442 /* Initial outgoing SYN's get put onto the write_queue
2443 * just like anything else we transmit. It is not
2444 * true data, and if we misinform our callers that
2445 * this ACK acks real data, we will erroneously exit
2446 * connection startup slow start one packet too
2447 * quickly. This is severely frowned upon behavior.
2448 */
2449 if (!(scb->flags & TCPCB_FLAG_SYN)) {
2450 acked |= FLAG_DATA_ACKED;
2451 } else {
2452 acked |= FLAG_SYN_ACKED;
2453 tp->retrans_stamp = 0;
2454 }
2455
2456 if (sacked) {
2457 if (sacked & TCPCB_RETRANS) {
2458 if(sacked & TCPCB_SACKED_RETRANS)
2459 tp->retrans_out -= tcp_skb_pcount(skb);
2460 acked |= FLAG_RETRANS_DATA_ACKED;
2461 seq_rtt = -1;
2462 } else if (seq_rtt < 0)
2463 seq_rtt = now - scb->when;
2464 if (sacked & TCPCB_SACKED_ACKED)
2465 tp->sacked_out -= tcp_skb_pcount(skb);
2466 if (sacked & TCPCB_LOST)
2467 tp->lost_out -= tcp_skb_pcount(skb);
2468 if (sacked & TCPCB_URG) {
2469 if (tp->urg_mode &&
2470 !before(scb->end_seq, tp->snd_up))
2471 tp->urg_mode = 0;
2472 }
2473 } else if (seq_rtt < 0)
2474 seq_rtt = now - scb->when;
2475 tcp_dec_pcount_approx(&tp->fackets_out, skb);
2476 tcp_packets_out_dec(tp, skb);
2477 __skb_unlink(skb, skb->list);
2478 sk_stream_free_skb(sk, skb);
2479 }
2480
2481 if (acked&FLAG_ACKED) {
2482 tcp_ack_update_rtt(tp, acked, seq_rtt);
2483 tcp_ack_packets_out(sk, tp);
2484 }
2485
2486#if FASTRETRANS_DEBUG > 0
2487 BUG_TRAP((int)tp->sacked_out >= 0);
2488 BUG_TRAP((int)tp->lost_out >= 0);
2489 BUG_TRAP((int)tp->retrans_out >= 0);
2490 if (!tp->packets_out && tp->rx_opt.sack_ok) {
2491 if (tp->lost_out) {
2492 printk(KERN_DEBUG "Leak l=%u %d\n",
2493 tp->lost_out, tp->ca_state);
2494 tp->lost_out = 0;
2495 }
2496 if (tp->sacked_out) {
2497 printk(KERN_DEBUG "Leak s=%u %d\n",
2498 tp->sacked_out, tp->ca_state);
2499 tp->sacked_out = 0;
2500 }
2501 if (tp->retrans_out) {
2502 printk(KERN_DEBUG "Leak r=%u %d\n",
2503 tp->retrans_out, tp->ca_state);
2504 tp->retrans_out = 0;
2505 }
2506 }
2507#endif
2508 *seq_rtt_p = seq_rtt;
2509 return acked;
2510}
2511
2512static void tcp_ack_probe(struct sock *sk)
2513{
2514 struct tcp_sock *tp = tcp_sk(sk);
2515
2516 /* Was it a usable window open? */
2517
2518 if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq,
2519 tp->snd_una + tp->snd_wnd)) {
2520 tp->backoff = 0;
2521 tcp_clear_xmit_timer(sk, TCP_TIME_PROBE0);
2522 /* Socket must be waked up by subsequent tcp_data_snd_check().
2523 * This function is not for random using!
2524 */
2525 } else {
2526 tcp_reset_xmit_timer(sk, TCP_TIME_PROBE0,
2527 min(tp->rto << tp->backoff, TCP_RTO_MAX));
2528 }
2529}
2530
2531static inline int tcp_ack_is_dubious(struct tcp_sock *tp, int flag)
2532{
2533 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) ||
2534 tp->ca_state != TCP_CA_Open);
2535}
2536
2537static inline int tcp_may_raise_cwnd(struct tcp_sock *tp, int flag)
2538{
2539 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) &&
2540 !((1<<tp->ca_state)&(TCPF_CA_Recovery|TCPF_CA_CWR));
2541}
2542
2543/* Check that window update is acceptable.
2544 * The function assumes that snd_una<=ack<=snd_next.
2545 */
2546static inline int tcp_may_update_window(struct tcp_sock *tp, u32 ack,
2547 u32 ack_seq, u32 nwin)
2548{
2549 return (after(ack, tp->snd_una) ||
2550 after(ack_seq, tp->snd_wl1) ||
2551 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd));
2552}
2553
2554/* Update our send window.
2555 *
2556 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2557 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2558 */
2559static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp,
2560 struct sk_buff *skb, u32 ack, u32 ack_seq)
2561{
2562 int flag = 0;
2563 u32 nwin = ntohs(skb->h.th->window);
2564
2565 if (likely(!skb->h.th->syn))
2566 nwin <<= tp->rx_opt.snd_wscale;
2567
2568 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) {
2569 flag |= FLAG_WIN_UPDATE;
2570 tcp_update_wl(tp, ack, ack_seq);
2571
2572 if (tp->snd_wnd != nwin) {
2573 tp->snd_wnd = nwin;
2574
2575 /* Note, it is the only place, where
2576 * fast path is recovered for sending TCP.
2577 */
2578 tcp_fast_path_check(sk, tp);
2579
2580 if (nwin > tp->max_window) {
2581 tp->max_window = nwin;
2582 tcp_sync_mss(sk, tp->pmtu_cookie);
2583 }
2584 }
2585 }
2586
2587 tp->snd_una = ack;
2588
2589 return flag;
2590}
2591
2592static void tcp_process_frto(struct sock *sk, u32 prior_snd_una)
2593{
2594 struct tcp_sock *tp = tcp_sk(sk);
2595
2596 tcp_sync_left_out(tp);
2597
2598 if (tp->snd_una == prior_snd_una ||
2599 !before(tp->snd_una, tp->frto_highmark)) {
2600 /* RTO was caused by loss, start retransmitting in
2601 * go-back-N slow start
2602 */
2603 tcp_enter_frto_loss(sk);
2604 return;
2605 }
2606
2607 if (tp->frto_counter == 1) {
2608 /* First ACK after RTO advances the window: allow two new
2609 * segments out.
2610 */
2611 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;
2612 } else {
2613 /* Also the second ACK after RTO advances the window.
2614 * The RTO was likely spurious. Reduce cwnd and continue
2615 * in congestion avoidance
2616 */
2617 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh);
2618 tcp_moderate_cwnd(tp);
2619 }
2620
2621 /* F-RTO affects on two new ACKs following RTO.
2622 * At latest on third ACK the TCP behavor is back to normal.
2623 */
2624 tp->frto_counter = (tp->frto_counter + 1) % 3;
2625}
2626
2627/*
2628 * TCP Westwood+
2629 */
2630
2631/*
2632 * @init_westwood
2633 * This function initializes fields used in TCP Westwood+. We can't
2634 * get no information about RTTmin at this time so we simply set it to
2635 * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative
2636 * since in this way we're sure it will be updated in a consistent
2637 * way as soon as possible. It will reasonably happen within the first
2638 * RTT period of the connection lifetime.
2639 */
2640
2641static void init_westwood(struct sock *sk)
2642{
2643 struct tcp_sock *tp = tcp_sk(sk);
2644
2645 tp->westwood.bw_ns_est = 0;
2646 tp->westwood.bw_est = 0;
2647 tp->westwood.accounted = 0;
2648 tp->westwood.cumul_ack = 0;
2649 tp->westwood.rtt_win_sx = tcp_time_stamp;
2650 tp->westwood.rtt = TCP_WESTWOOD_INIT_RTT;
2651 tp->westwood.rtt_min = TCP_WESTWOOD_INIT_RTT;
2652 tp->westwood.snd_una = tp->snd_una;
2653}
2654
2655/*
2656 * @westwood_do_filter
2657 * Low-pass filter. Implemented using constant coeffients.
2658 */
2659
2660static inline __u32 westwood_do_filter(__u32 a, __u32 b)
2661{
2662 return (((7 * a) + b) >> 3);
2663}
2664
2665static void westwood_filter(struct sock *sk, __u32 delta)
2666{
2667 struct tcp_sock *tp = tcp_sk(sk);
2668
2669 tp->westwood.bw_ns_est =
2670 westwood_do_filter(tp->westwood.bw_ns_est,
2671 tp->westwood.bk / delta);
2672 tp->westwood.bw_est =
2673 westwood_do_filter(tp->westwood.bw_est,
2674 tp->westwood.bw_ns_est);
2675}
2676
2677/*
2678 * @westwood_update_rttmin
2679 * It is used to update RTTmin. In this case we MUST NOT use
2680 * WESTWOOD_RTT_MIN minimum bound since we could be on a LAN!
2681 */
2682
2683static inline __u32 westwood_update_rttmin(const struct sock *sk)
2684{
2685 const struct tcp_sock *tp = tcp_sk(sk);
2686 __u32 rttmin = tp->westwood.rtt_min;
2687
2688 if (tp->westwood.rtt != 0 &&
2689 (tp->westwood.rtt < tp->westwood.rtt_min || !rttmin))
2690 rttmin = tp->westwood.rtt;
2691
2692 return rttmin;
2693}
2694
2695/*
2696 * @westwood_acked
2697 * Evaluate increases for dk.
2698 */
2699
2700static inline __u32 westwood_acked(const struct sock *sk)
2701{
2702 const struct tcp_sock *tp = tcp_sk(sk);
2703
2704 return tp->snd_una - tp->westwood.snd_una;
2705}
2706
2707/*
2708 * @westwood_new_window
2709 * It evaluates if we are receiving data inside the same RTT window as
2710 * when we started.
2711 * Return value:
2712 * It returns 0 if we are still evaluating samples in the same RTT
2713 * window, 1 if the sample has to be considered in the next window.
2714 */
2715
2716static int westwood_new_window(const struct sock *sk)
2717{
2718 const struct tcp_sock *tp = tcp_sk(sk);
2719 __u32 left_bound;
2720 __u32 rtt;
2721 int ret = 0;
2722
2723 left_bound = tp->westwood.rtt_win_sx;
2724 rtt = max(tp->westwood.rtt, (u32) TCP_WESTWOOD_RTT_MIN);
2725
2726 /*
2727 * A RTT-window has passed. Be careful since if RTT is less than
2728 * 50ms we don't filter but we continue 'building the sample'.
2729 * This minimum limit was choosen since an estimation on small
2730 * time intervals is better to avoid...
2731 * Obvioulsy on a LAN we reasonably will always have
2732 * right_bound = left_bound + WESTWOOD_RTT_MIN
2733 */
2734
2735 if ((left_bound + rtt) < tcp_time_stamp)
2736 ret = 1;
2737
2738 return ret;
2739}
2740
2741/*
2742 * @westwood_update_window
2743 * It updates RTT evaluation window if it is the right moment to do
2744 * it. If so it calls filter for evaluating bandwidth.
2745 */
2746
2747static void __westwood_update_window(struct sock *sk, __u32 now)
2748{
2749 struct tcp_sock *tp = tcp_sk(sk);
2750 __u32 delta = now - tp->westwood.rtt_win_sx;
2751
2752 if (delta) {
2753 if (tp->westwood.rtt)
2754 westwood_filter(sk, delta);
2755
2756 tp->westwood.bk = 0;
2757 tp->westwood.rtt_win_sx = tcp_time_stamp;
2758 }
2759}
2760
2761
2762static void westwood_update_window(struct sock *sk, __u32 now)
2763{
2764 if (westwood_new_window(sk))
2765 __westwood_update_window(sk, now);
2766}
2767
2768/*
2769 * @__tcp_westwood_fast_bw
2770 * It is called when we are in fast path. In particular it is called when
2771 * header prediction is successfull. In such case infact update is
2772 * straight forward and doesn't need any particular care.
2773 */
2774
2775static void __tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb)
2776{
2777 struct tcp_sock *tp = tcp_sk(sk);
2778
2779 westwood_update_window(sk, tcp_time_stamp);
2780
2781 tp->westwood.bk += westwood_acked(sk);
2782 tp->westwood.snd_una = tp->snd_una;
2783 tp->westwood.rtt_min = westwood_update_rttmin(sk);
2784}
2785
2786static inline void tcp_westwood_fast_bw(struct sock *sk, struct sk_buff *skb)
2787{
2788 if (tcp_is_westwood(tcp_sk(sk)))
2789 __tcp_westwood_fast_bw(sk, skb);
2790}
2791
2792
2793/*
2794 * @westwood_dupack_update
2795 * It updates accounted and cumul_ack when receiving a dupack.
2796 */
2797
2798static void westwood_dupack_update(struct sock *sk)
2799{
2800 struct tcp_sock *tp = tcp_sk(sk);
2801
2802 tp->westwood.accounted += tp->mss_cache_std;
2803 tp->westwood.cumul_ack = tp->mss_cache_std;
2804}
2805
2806static inline int westwood_may_change_cumul(struct tcp_sock *tp)
2807{
2808 return (tp->westwood.cumul_ack > tp->mss_cache_std);
2809}
2810
2811static inline void westwood_partial_update(struct tcp_sock *tp)
2812{
2813 tp->westwood.accounted -= tp->westwood.cumul_ack;
2814 tp->westwood.cumul_ack = tp->mss_cache_std;
2815}
2816
2817static inline void westwood_complete_update(struct tcp_sock *tp)
2818{
2819 tp->westwood.cumul_ack -= tp->westwood.accounted;
2820 tp->westwood.accounted = 0;
2821}
2822
2823/*
2824 * @westwood_acked_count
2825 * This function evaluates cumul_ack for evaluating dk in case of
2826 * delayed or partial acks.
2827 */
2828
2829static inline __u32 westwood_acked_count(struct sock *sk)
2830{
2831 struct tcp_sock *tp = tcp_sk(sk);
2832
2833 tp->westwood.cumul_ack = westwood_acked(sk);
2834
2835 /* If cumul_ack is 0 this is a dupack since it's not moving
2836 * tp->snd_una.
2837 */
2838 if (!(tp->westwood.cumul_ack))
2839 westwood_dupack_update(sk);
2840
2841 if (westwood_may_change_cumul(tp)) {
2842 /* Partial or delayed ack */
2843 if (tp->westwood.accounted >= tp->westwood.cumul_ack)
2844 westwood_partial_update(tp);
2845 else
2846 westwood_complete_update(tp);
2847 }
2848
2849 tp->westwood.snd_una = tp->snd_una;
2850
2851 return tp->westwood.cumul_ack;
2852}
2853
2854
2855/*
2856 * @__tcp_westwood_slow_bw
2857 * It is called when something is going wrong..even if there could
2858 * be no problems! Infact a simple delayed packet may trigger a
2859 * dupack. But we need to be careful in such case.
2860 */
2861
2862static void __tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb)
2863{
2864 struct tcp_sock *tp = tcp_sk(sk);
2865
2866 westwood_update_window(sk, tcp_time_stamp);
2867
2868 tp->westwood.bk += westwood_acked_count(sk);
2869 tp->westwood.rtt_min = westwood_update_rttmin(sk);
2870}
2871
2872static inline void tcp_westwood_slow_bw(struct sock *sk, struct sk_buff *skb)
2873{
2874 if (tcp_is_westwood(tcp_sk(sk)))
2875 __tcp_westwood_slow_bw(sk, skb);
2876}
2877
2878/* This routine deals with incoming acks, but not outgoing ones. */
2879static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag)
2880{
2881 struct tcp_sock *tp = tcp_sk(sk);
2882 u32 prior_snd_una = tp->snd_una;
2883 u32 ack_seq = TCP_SKB_CB(skb)->seq;
2884 u32 ack = TCP_SKB_CB(skb)->ack_seq;
2885 u32 prior_in_flight;
2886 s32 seq_rtt;
2887 int prior_packets;
2888
2889 /* If the ack is newer than sent or older than previous acks
2890 * then we can probably ignore it.
2891 */
2892 if (after(ack, tp->snd_nxt))
2893 goto uninteresting_ack;
2894
2895 if (before(ack, prior_snd_una))
2896 goto old_ack;
2897
2898 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) {
2899 /* Window is constant, pure forward advance.
2900 * No more checks are required.
2901 * Note, we use the fact that SND.UNA>=SND.WL2.
2902 */
2903 tcp_update_wl(tp, ack, ack_seq);
2904 tp->snd_una = ack;
2905 tcp_westwood_fast_bw(sk, skb);
2906 flag |= FLAG_WIN_UPDATE;
2907
2908 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS);
2909 } else {
2910 if (ack_seq != TCP_SKB_CB(skb)->end_seq)
2911 flag |= FLAG_DATA;
2912 else
2913 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS);
2914
2915 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq);
2916
2917 if (TCP_SKB_CB(skb)->sacked)
2918 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2919
2920 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th))
2921 flag |= FLAG_ECE;
2922
2923 tcp_westwood_slow_bw(sk,skb);
2924 }
2925
2926 /* We passed data and got it acked, remove any soft error
2927 * log. Something worked...
2928 */
2929 sk->sk_err_soft = 0;
2930 tp->rcv_tstamp = tcp_time_stamp;
2931 prior_packets = tp->packets_out;
2932 if (!prior_packets)
2933 goto no_queue;
2934
2935 prior_in_flight = tcp_packets_in_flight(tp);
2936
2937 /* See if we can take anything off of the retransmit queue. */
2938 flag |= tcp_clean_rtx_queue(sk, &seq_rtt);
2939
2940 if (tp->frto_counter)
2941 tcp_process_frto(sk, prior_snd_una);
2942
2943 if (tcp_ack_is_dubious(tp, flag)) {
2944 /* Advanve CWND, if state allows this. */
2945 if ((flag & FLAG_DATA_ACKED) &&
2946 (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd) &&
2947 tcp_may_raise_cwnd(tp, flag))
2948 tcp_cong_avoid(tp, ack, seq_rtt);
2949 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);
2950 } else {
2951 if ((flag & FLAG_DATA_ACKED) &&
2952 (tcp_vegas_enabled(tp) || prior_in_flight >= tp->snd_cwnd))
2953 tcp_cong_avoid(tp, ack, seq_rtt);
2954 }
2955
2956 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP))
2957 dst_confirm(sk->sk_dst_cache);
2958
2959 return 1;
2960
2961no_queue:
2962 tp->probes_out = 0;
2963
2964 /* If this ack opens up a zero window, clear backoff. It was
2965 * being used to time the probes, and is probably far higher than
2966 * it needs to be for normal retransmission.
2967 */
2968 if (sk->sk_send_head)
2969 tcp_ack_probe(sk);
2970 return 1;
2971
2972old_ack:
2973 if (TCP_SKB_CB(skb)->sacked)
2974 tcp_sacktag_write_queue(sk, skb, prior_snd_una);
2975
2976uninteresting_ack:
2977 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
2978 return 0;
2979}
2980
2981
2982/* Look for tcp options. Normally only called on SYN and SYNACK packets.
2983 * But, this can also be called on packets in the established flow when
2984 * the fast version below fails.
2985 */
2986void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab)
2987{
2988 unsigned char *ptr;
2989 struct tcphdr *th = skb->h.th;
2990 int length=(th->doff*4)-sizeof(struct tcphdr);
2991
2992 ptr = (unsigned char *)(th + 1);
2993 opt_rx->saw_tstamp = 0;
2994
2995 while(length>0) {
2996 int opcode=*ptr++;
2997 int opsize;
2998
2999 switch (opcode) {
3000 case TCPOPT_EOL:
3001 return;
3002 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
3003 length--;
3004 continue;
3005 default:
3006 opsize=*ptr++;
3007 if (opsize < 2) /* "silly options" */
3008 return;
3009 if (opsize > length)
3010 return; /* don't parse partial options */
3011 switch(opcode) {
3012 case TCPOPT_MSS:
3013 if(opsize==TCPOLEN_MSS && th->syn && !estab) {
3014 u16 in_mss = ntohs(get_unaligned((__u16 *)ptr));
3015 if (in_mss) {
3016 if (opt_rx->user_mss && opt_rx->user_mss < in_mss)
3017 in_mss = opt_rx->user_mss;
3018 opt_rx->mss_clamp = in_mss;
3019 }
3020 }
3021 break;
3022 case TCPOPT_WINDOW:
3023 if(opsize==TCPOLEN_WINDOW && th->syn && !estab)
3024 if (sysctl_tcp_window_scaling) {
3025 __u8 snd_wscale = *(__u8 *) ptr;
3026 opt_rx->wscale_ok = 1;
3027 if (snd_wscale > 14) {
3028 if(net_ratelimit())
3029 printk(KERN_INFO "tcp_parse_options: Illegal window "
3030 "scaling value %d >14 received.\n",
3031 snd_wscale);
3032 snd_wscale = 14;
3033 }
3034 opt_rx->snd_wscale = snd_wscale;
3035 }
3036 break;
3037 case TCPOPT_TIMESTAMP:
3038 if(opsize==TCPOLEN_TIMESTAMP) {
3039 if ((estab && opt_rx->tstamp_ok) ||
3040 (!estab && sysctl_tcp_timestamps)) {
3041 opt_rx->saw_tstamp = 1;
3042 opt_rx->rcv_tsval = ntohl(get_unaligned((__u32 *)ptr));
3043 opt_rx->rcv_tsecr = ntohl(get_unaligned((__u32 *)(ptr+4)));
3044 }
3045 }
3046 break;
3047 case TCPOPT_SACK_PERM:
3048 if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) {
3049 if (sysctl_tcp_sack) {
3050 opt_rx->sack_ok = 1;
3051 tcp_sack_reset(opt_rx);
3052 }
3053 }
3054 break;
3055
3056 case TCPOPT_SACK:
3057 if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) &&
3058 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) &&
3059 opt_rx->sack_ok) {
3060 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th;
3061 }
3062 };
3063 ptr+=opsize-2;
3064 length-=opsize;
3065 };
3066 }
3067}
3068
3069/* Fast parse options. This hopes to only see timestamps.
3070 * If it is wrong it falls back on tcp_parse_options().
3071 */
3072static inline int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th,
3073 struct tcp_sock *tp)
3074{
3075 if (th->doff == sizeof(struct tcphdr)>>2) {
3076 tp->rx_opt.saw_tstamp = 0;
3077 return 0;
3078 } else if (tp->rx_opt.tstamp_ok &&
3079 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) {
3080 __u32 *ptr = (__u32 *)(th + 1);
3081 if (*ptr == ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
3082 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) {
3083 tp->rx_opt.saw_tstamp = 1;
3084 ++ptr;
3085 tp->rx_opt.rcv_tsval = ntohl(*ptr);
3086 ++ptr;
3087 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
3088 return 1;
3089 }
3090 }
3091 tcp_parse_options(skb, &tp->rx_opt, 1);
3092 return 1;
3093}
3094
3095static inline void tcp_store_ts_recent(struct tcp_sock *tp)
3096{
3097 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval;
3098 tp->rx_opt.ts_recent_stamp = xtime.tv_sec;
3099}
3100
3101static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq)
3102{
3103 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) {
3104 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3105 * extra check below makes sure this can only happen
3106 * for pure ACK frames. -DaveM
3107 *
3108 * Not only, also it occurs for expired timestamps.
3109 */
3110
3111 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 ||
3112 xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS)
3113 tcp_store_ts_recent(tp);
3114 }
3115}
3116
3117/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3118 *
3119 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3120 * it can pass through stack. So, the following predicate verifies that
3121 * this segment is not used for anything but congestion avoidance or
3122 * fast retransmit. Moreover, we even are able to eliminate most of such
3123 * second order effects, if we apply some small "replay" window (~RTO)
3124 * to timestamp space.
3125 *
3126 * All these measures still do not guarantee that we reject wrapped ACKs
3127 * on networks with high bandwidth, when sequence space is recycled fastly,
3128 * but it guarantees that such events will be very rare and do not affect
3129 * connection seriously. This doesn't look nice, but alas, PAWS is really
3130 * buggy extension.
3131 *
3132 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3133 * states that events when retransmit arrives after original data are rare.
3134 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3135 * the biggest problem on large power networks even with minor reordering.
3136 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3137 * up to bandwidth of 18Gigabit/sec. 8) ]
3138 */
3139
3140static int tcp_disordered_ack(struct tcp_sock *tp, struct sk_buff *skb)
3141{
3142 struct tcphdr *th = skb->h.th;
3143 u32 seq = TCP_SKB_CB(skb)->seq;
3144 u32 ack = TCP_SKB_CB(skb)->ack_seq;
3145
3146 return (/* 1. Pure ACK with correct sequence number. */
3147 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) &&
3148
3149 /* 2. ... and duplicate ACK. */
3150 ack == tp->snd_una &&
3151
3152 /* 3. ... and does not update window. */
3153 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) &&
3154
3155 /* 4. ... and sits in replay window. */
3156 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (tp->rto*1024)/HZ);
3157}
3158
3159static inline int tcp_paws_discard(struct tcp_sock *tp, struct sk_buff *skb)
3160{
3161 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW &&
3162 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS &&
3163 !tcp_disordered_ack(tp, skb));
3164}
3165
3166/* Check segment sequence number for validity.
3167 *
3168 * Segment controls are considered valid, if the segment
3169 * fits to the window after truncation to the window. Acceptability
3170 * of data (and SYN, FIN, of course) is checked separately.
3171 * See tcp_data_queue(), for example.
3172 *
3173 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3174 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3175 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3176 * (borrowed from freebsd)
3177 */
3178
3179static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq)
3180{
3181 return !before(end_seq, tp->rcv_wup) &&
3182 !after(seq, tp->rcv_nxt + tcp_receive_window(tp));
3183}
3184
3185/* When we get a reset we do this. */
3186static void tcp_reset(struct sock *sk)
3187{
3188 /* We want the right error as BSD sees it (and indeed as we do). */
3189 switch (sk->sk_state) {
3190 case TCP_SYN_SENT:
3191 sk->sk_err = ECONNREFUSED;
3192 break;
3193 case TCP_CLOSE_WAIT:
3194 sk->sk_err = EPIPE;
3195 break;
3196 case TCP_CLOSE:
3197 return;
3198 default:
3199 sk->sk_err = ECONNRESET;
3200 }
3201
3202 if (!sock_flag(sk, SOCK_DEAD))
3203 sk->sk_error_report(sk);
3204
3205 tcp_done(sk);
3206}
3207
3208/*
3209 * Process the FIN bit. This now behaves as it is supposed to work
3210 * and the FIN takes effect when it is validly part of sequence
3211 * space. Not before when we get holes.
3212 *
3213 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3214 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3215 * TIME-WAIT)
3216 *
3217 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3218 * close and we go into CLOSING (and later onto TIME-WAIT)
3219 *
3220 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3221 */
3222static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
3223{
3224 struct tcp_sock *tp = tcp_sk(sk);
3225
3226 tcp_schedule_ack(tp);
3227
3228 sk->sk_shutdown |= RCV_SHUTDOWN;
3229 sock_set_flag(sk, SOCK_DONE);
3230
3231 switch (sk->sk_state) {
3232 case TCP_SYN_RECV:
3233 case TCP_ESTABLISHED:
3234 /* Move to CLOSE_WAIT */
3235 tcp_set_state(sk, TCP_CLOSE_WAIT);
3236 tp->ack.pingpong = 1;
3237 break;
3238
3239 case TCP_CLOSE_WAIT:
3240 case TCP_CLOSING:
3241 /* Received a retransmission of the FIN, do
3242 * nothing.
3243 */
3244 break;
3245 case TCP_LAST_ACK:
3246 /* RFC793: Remain in the LAST-ACK state. */
3247 break;
3248
3249 case TCP_FIN_WAIT1:
3250 /* This case occurs when a simultaneous close
3251 * happens, we must ack the received FIN and
3252 * enter the CLOSING state.
3253 */
3254 tcp_send_ack(sk);
3255 tcp_set_state(sk, TCP_CLOSING);
3256 break;
3257 case TCP_FIN_WAIT2:
3258 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3259 tcp_send_ack(sk);
3260 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
3261 break;
3262 default:
3263 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3264 * cases we should never reach this piece of code.
3265 */
3266 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n",
3267 __FUNCTION__, sk->sk_state);
3268 break;
3269 };
3270
3271 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3272 * Probably, we should reset in this case. For now drop them.
3273 */
3274 __skb_queue_purge(&tp->out_of_order_queue);
3275 if (tp->rx_opt.sack_ok)
3276 tcp_sack_reset(&tp->rx_opt);
3277 sk_stream_mem_reclaim(sk);
3278
3279 if (!sock_flag(sk, SOCK_DEAD)) {
3280 sk->sk_state_change(sk);
3281
3282 /* Do not send POLL_HUP for half duplex close. */
3283 if (sk->sk_shutdown == SHUTDOWN_MASK ||
3284 sk->sk_state == TCP_CLOSE)
3285 sk_wake_async(sk, 1, POLL_HUP);
3286 else
3287 sk_wake_async(sk, 1, POLL_IN);
3288 }
3289}
3290
3291static __inline__ int
3292tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq)
3293{
3294 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) {
3295 if (before(seq, sp->start_seq))
3296 sp->start_seq = seq;
3297 if (after(end_seq, sp->end_seq))
3298 sp->end_seq = end_seq;
3299 return 1;
3300 }
3301 return 0;
3302}
3303
3304static inline void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq)
3305{
3306 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
3307 if (before(seq, tp->rcv_nxt))
3308 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT);
3309 else
3310 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT);
3311
3312 tp->rx_opt.dsack = 1;
3313 tp->duplicate_sack[0].start_seq = seq;
3314 tp->duplicate_sack[0].end_seq = end_seq;
3315 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok);
3316 }
3317}
3318
3319static inline void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq)
3320{
3321 if (!tp->rx_opt.dsack)
3322 tcp_dsack_set(tp, seq, end_seq);
3323 else
3324 tcp_sack_extend(tp->duplicate_sack, seq, end_seq);
3325}
3326
3327static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb)
3328{
3329 struct tcp_sock *tp = tcp_sk(sk);
3330
3331 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
3332 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3333 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3334 tcp_enter_quickack_mode(tp);
3335
3336 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) {
3337 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3338
3339 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))
3340 end_seq = tp->rcv_nxt;
3341 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq);
3342 }
3343 }
3344
3345 tcp_send_ack(sk);
3346}
3347
3348/* These routines update the SACK block as out-of-order packets arrive or
3349 * in-order packets close up the sequence space.
3350 */
3351static void tcp_sack_maybe_coalesce(struct tcp_sock *tp)
3352{
3353 int this_sack;
3354 struct tcp_sack_block *sp = &tp->selective_acks[0];
3355 struct tcp_sack_block *swalk = sp+1;
3356
3357 /* See if the recent change to the first SACK eats into
3358 * or hits the sequence space of other SACK blocks, if so coalesce.
3359 */
3360 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) {
3361 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) {
3362 int i;
3363
3364 /* Zap SWALK, by moving every further SACK up by one slot.
3365 * Decrease num_sacks.
3366 */
3367 tp->rx_opt.num_sacks--;
3368 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3369 for(i=this_sack; i < tp->rx_opt.num_sacks; i++)
3370 sp[i] = sp[i+1];
3371 continue;
3372 }
3373 this_sack++, swalk++;
3374 }
3375}
3376
3377static __inline__ void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2)
3378{
3379 __u32 tmp;
3380
3381 tmp = sack1->start_seq;
3382 sack1->start_seq = sack2->start_seq;
3383 sack2->start_seq = tmp;
3384
3385 tmp = sack1->end_seq;
3386 sack1->end_seq = sack2->end_seq;
3387 sack2->end_seq = tmp;
3388}
3389
3390static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq)
3391{
3392 struct tcp_sock *tp = tcp_sk(sk);
3393 struct tcp_sack_block *sp = &tp->selective_acks[0];
3394 int cur_sacks = tp->rx_opt.num_sacks;
3395 int this_sack;
3396
3397 if (!cur_sacks)
3398 goto new_sack;
3399
3400 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) {
3401 if (tcp_sack_extend(sp, seq, end_seq)) {
3402 /* Rotate this_sack to the first one. */
3403 for (; this_sack>0; this_sack--, sp--)
3404 tcp_sack_swap(sp, sp-1);
3405 if (cur_sacks > 1)
3406 tcp_sack_maybe_coalesce(tp);
3407 return;
3408 }
3409 }
3410
3411 /* Could not find an adjacent existing SACK, build a new one,
3412 * put it at the front, and shift everyone else down. We
3413 * always know there is at least one SACK present already here.
3414 *
3415 * If the sack array is full, forget about the last one.
3416 */
3417 if (this_sack >= 4) {
3418 this_sack--;
3419 tp->rx_opt.num_sacks--;
3420 sp--;
3421 }
3422 for(; this_sack > 0; this_sack--, sp--)
3423 *sp = *(sp-1);
3424
3425new_sack:
3426 /* Build the new head SACK, and we're done. */
3427 sp->start_seq = seq;
3428 sp->end_seq = end_seq;
3429 tp->rx_opt.num_sacks++;
3430 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3431}
3432
3433/* RCV.NXT advances, some SACKs should be eaten. */
3434
3435static void tcp_sack_remove(struct tcp_sock *tp)
3436{
3437 struct tcp_sack_block *sp = &tp->selective_acks[0];
3438 int num_sacks = tp->rx_opt.num_sacks;
3439 int this_sack;
3440
3441 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3442 if (skb_queue_len(&tp->out_of_order_queue) == 0) {
3443 tp->rx_opt.num_sacks = 0;
3444 tp->rx_opt.eff_sacks = tp->rx_opt.dsack;
3445 return;
3446 }
3447
3448 for(this_sack = 0; this_sack < num_sacks; ) {
3449 /* Check if the start of the sack is covered by RCV.NXT. */
3450 if (!before(tp->rcv_nxt, sp->start_seq)) {
3451 int i;
3452
3453 /* RCV.NXT must cover all the block! */
3454 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq));
3455
3456 /* Zap this SACK, by moving forward any other SACKS. */
3457 for (i=this_sack+1; i < num_sacks; i++)
3458 tp->selective_acks[i-1] = tp->selective_acks[i];
3459 num_sacks--;
3460 continue;
3461 }
3462 this_sack++;
3463 sp++;
3464 }
3465 if (num_sacks != tp->rx_opt.num_sacks) {
3466 tp->rx_opt.num_sacks = num_sacks;
3467 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok);
3468 }
3469}
3470
3471/* This one checks to see if we can put data from the
3472 * out_of_order queue into the receive_queue.
3473 */
3474static void tcp_ofo_queue(struct sock *sk)
3475{
3476 struct tcp_sock *tp = tcp_sk(sk);
3477 __u32 dsack_high = tp->rcv_nxt;
3478 struct sk_buff *skb;
3479
3480 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) {
3481 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
3482 break;
3483
3484 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) {
3485 __u32 dsack = dsack_high;
3486 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high))
3487 dsack_high = TCP_SKB_CB(skb)->end_seq;
3488 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack);
3489 }
3490
3491 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3492 SOCK_DEBUG(sk, "ofo packet was already received \n");
3493 __skb_unlink(skb, skb->list);
3494 __kfree_skb(skb);
3495 continue;
3496 }
3497 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
3498 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3499 TCP_SKB_CB(skb)->end_seq);
3500
3501 __skb_unlink(skb, skb->list);
3502 __skb_queue_tail(&sk->sk_receive_queue, skb);
3503 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3504 if(skb->h.th->fin)
3505 tcp_fin(skb, sk, skb->h.th);
3506 }
3507}
3508
3509static int tcp_prune_queue(struct sock *sk);
3510
3511static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
3512{
3513 struct tcphdr *th = skb->h.th;
3514 struct tcp_sock *tp = tcp_sk(sk);
3515 int eaten = -1;
3516
3517 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
3518 goto drop;
3519
3520 th = skb->h.th;
3521 __skb_pull(skb, th->doff*4);
3522
3523 TCP_ECN_accept_cwr(tp, skb);
3524
3525 if (tp->rx_opt.dsack) {
3526 tp->rx_opt.dsack = 0;
3527 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,
3528 4 - tp->rx_opt.tstamp_ok);
3529 }
3530
3531 /* Queue data for delivery to the user.
3532 * Packets in sequence go to the receive queue.
3533 * Out of sequence packets to the out_of_order_queue.
3534 */
3535 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
3536 if (tcp_receive_window(tp) == 0)
3537 goto out_of_window;
3538
3539 /* Ok. In sequence. In window. */
3540 if (tp->ucopy.task == current &&
3541 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len &&
3542 sock_owned_by_user(sk) && !tp->urg_data) {
3543 int chunk = min_t(unsigned int, skb->len,
3544 tp->ucopy.len);
3545
3546 __set_current_state(TASK_RUNNING);
3547
3548 local_bh_enable();
3549 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) {
3550 tp->ucopy.len -= chunk;
3551 tp->copied_seq += chunk;
3552 eaten = (chunk == skb->len && !th->fin);
3553 tcp_rcv_space_adjust(sk);
3554 }
3555 local_bh_disable();
3556 }
3557
3558 if (eaten <= 0) {
3559queue_and_out:
3560 if (eaten < 0 &&
3561 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3562 !sk_stream_rmem_schedule(sk, skb))) {
3563 if (tcp_prune_queue(sk) < 0 ||
3564 !sk_stream_rmem_schedule(sk, skb))
3565 goto drop;
3566 }
3567 sk_stream_set_owner_r(skb, sk);
3568 __skb_queue_tail(&sk->sk_receive_queue, skb);
3569 }
3570 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
3571 if(skb->len)
3572 tcp_event_data_recv(sk, tp, skb);
3573 if(th->fin)
3574 tcp_fin(skb, sk, th);
3575
3576 if (skb_queue_len(&tp->out_of_order_queue)) {
3577 tcp_ofo_queue(sk);
3578
3579 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3580 * gap in queue is filled.
3581 */
3582 if (!skb_queue_len(&tp->out_of_order_queue))
3583 tp->ack.pingpong = 0;
3584 }
3585
3586 if (tp->rx_opt.num_sacks)
3587 tcp_sack_remove(tp);
3588
3589 tcp_fast_path_check(sk, tp);
3590
3591 if (eaten > 0)
3592 __kfree_skb(skb);
3593 else if (!sock_flag(sk, SOCK_DEAD))
3594 sk->sk_data_ready(sk, 0);
3595 return;
3596 }
3597
3598 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
3599 /* A retransmit, 2nd most common case. Force an immediate ack. */
3600 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST);
3601 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3602
3603out_of_window:
3604 tcp_enter_quickack_mode(tp);
3605 tcp_schedule_ack(tp);
3606drop:
3607 __kfree_skb(skb);
3608 return;
3609 }
3610
3611 /* Out of window. F.e. zero window probe. */
3612 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
3613 goto out_of_window;
3614
3615 tcp_enter_quickack_mode(tp);
3616
3617 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
3618 /* Partial packet, seq < rcv_next < end_seq */
3619 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
3620 tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
3621 TCP_SKB_CB(skb)->end_seq);
3622
3623 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
3624
3625 /* If window is closed, drop tail of packet. But after
3626 * remembering D-SACK for its head made in previous line.
3627 */
3628 if (!tcp_receive_window(tp))
3629 goto out_of_window;
3630 goto queue_and_out;
3631 }
3632
3633 TCP_ECN_check_ce(tp, skb);
3634
3635 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf ||
3636 !sk_stream_rmem_schedule(sk, skb)) {
3637 if (tcp_prune_queue(sk) < 0 ||
3638 !sk_stream_rmem_schedule(sk, skb))
3639 goto drop;
3640 }
3641
3642 /* Disable header prediction. */
3643 tp->pred_flags = 0;
3644 tcp_schedule_ack(tp);
3645
3646 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
3647 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
3648
3649 sk_stream_set_owner_r(skb, sk);
3650
3651 if (!skb_peek(&tp->out_of_order_queue)) {
3652 /* Initial out of order segment, build 1 SACK. */
3653 if (tp->rx_opt.sack_ok) {
3654 tp->rx_opt.num_sacks = 1;
3655 tp->rx_opt.dsack = 0;
3656 tp->rx_opt.eff_sacks = 1;
3657 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq;
3658 tp->selective_acks[0].end_seq =
3659 TCP_SKB_CB(skb)->end_seq;
3660 }
3661 __skb_queue_head(&tp->out_of_order_queue,skb);
3662 } else {
3663 struct sk_buff *skb1 = tp->out_of_order_queue.prev;
3664 u32 seq = TCP_SKB_CB(skb)->seq;
3665 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
3666
3667 if (seq == TCP_SKB_CB(skb1)->end_seq) {
3668 __skb_append(skb1, skb);
3669
3670 if (!tp->rx_opt.num_sacks ||
3671 tp->selective_acks[0].end_seq != seq)
3672 goto add_sack;
3673
3674 /* Common case: data arrive in order after hole. */
3675 tp->selective_acks[0].end_seq = end_seq;
3676 return;
3677 }
3678
3679 /* Find place to insert this segment. */
3680 do {
3681 if (!after(TCP_SKB_CB(skb1)->seq, seq))
3682 break;
3683 } while ((skb1 = skb1->prev) !=
3684 (struct sk_buff*)&tp->out_of_order_queue);
3685
3686 /* Do skb overlap to previous one? */
3687 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue &&
3688 before(seq, TCP_SKB_CB(skb1)->end_seq)) {
3689 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3690 /* All the bits are present. Drop. */
3691 __kfree_skb(skb);
3692 tcp_dsack_set(tp, seq, end_seq);
3693 goto add_sack;
3694 }
3695 if (after(seq, TCP_SKB_CB(skb1)->seq)) {
3696 /* Partial overlap. */
3697 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq);
3698 } else {
3699 skb1 = skb1->prev;
3700 }
3701 }
3702 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue);
3703
3704 /* And clean segments covered by new one as whole. */
3705 while ((skb1 = skb->next) !=
3706 (struct sk_buff*)&tp->out_of_order_queue &&
3707 after(end_seq, TCP_SKB_CB(skb1)->seq)) {
3708 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
3709 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq);
3710 break;
3711 }
3712 __skb_unlink(skb1, skb1->list);
3713 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq);
3714 __kfree_skb(skb1);
3715 }
3716
3717add_sack:
3718 if (tp->rx_opt.sack_ok)
3719 tcp_sack_new_ofo_skb(sk, seq, end_seq);
3720 }
3721}
3722
3723/* Collapse contiguous sequence of skbs head..tail with
3724 * sequence numbers start..end.
3725 * Segments with FIN/SYN are not collapsed (only because this
3726 * simplifies code)
3727 */
3728static void
3729tcp_collapse(struct sock *sk, struct sk_buff *head,
3730 struct sk_buff *tail, u32 start, u32 end)
3731{
3732 struct sk_buff *skb;
3733
3734 /* First, check that queue is collapsable and find
3735 * the point where collapsing can be useful. */
3736 for (skb = head; skb != tail; ) {
3737 /* No new bits? It is possible on ofo queue. */
3738 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3739 struct sk_buff *next = skb->next;
3740 __skb_unlink(skb, skb->list);
3741 __kfree_skb(skb);
3742 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3743 skb = next;
3744 continue;
3745 }
3746
3747 /* The first skb to collapse is:
3748 * - not SYN/FIN and
3749 * - bloated or contains data before "start" or
3750 * overlaps to the next one.
3751 */
3752 if (!skb->h.th->syn && !skb->h.th->fin &&
3753 (tcp_win_from_space(skb->truesize) > skb->len ||
3754 before(TCP_SKB_CB(skb)->seq, start) ||
3755 (skb->next != tail &&
3756 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq)))
3757 break;
3758
3759 /* Decided to skip this, advance start seq. */
3760 start = TCP_SKB_CB(skb)->end_seq;
3761 skb = skb->next;
3762 }
3763 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3764 return;
3765
3766 while (before(start, end)) {
3767 struct sk_buff *nskb;
3768 int header = skb_headroom(skb);
3769 int copy = SKB_MAX_ORDER(header, 0);
3770
3771 /* Too big header? This can happen with IPv6. */
3772 if (copy < 0)
3773 return;
3774 if (end-start < copy)
3775 copy = end-start;
3776 nskb = alloc_skb(copy+header, GFP_ATOMIC);
3777 if (!nskb)
3778 return;
3779 skb_reserve(nskb, header);
3780 memcpy(nskb->head, skb->head, header);
3781 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head);
3782 nskb->h.raw = nskb->head + (skb->h.raw-skb->head);
3783 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head);
3784 memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
3785 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start;
3786 __skb_insert(nskb, skb->prev, skb, skb->list);
3787 sk_stream_set_owner_r(nskb, sk);
3788
3789 /* Copy data, releasing collapsed skbs. */
3790 while (copy > 0) {
3791 int offset = start - TCP_SKB_CB(skb)->seq;
3792 int size = TCP_SKB_CB(skb)->end_seq - start;
3793
3794 if (offset < 0) BUG();
3795 if (size > 0) {
3796 size = min(copy, size);
3797 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size))
3798 BUG();
3799 TCP_SKB_CB(nskb)->end_seq += size;
3800 copy -= size;
3801 start += size;
3802 }
3803 if (!before(start, TCP_SKB_CB(skb)->end_seq)) {
3804 struct sk_buff *next = skb->next;
3805 __skb_unlink(skb, skb->list);
3806 __kfree_skb(skb);
3807 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED);
3808 skb = next;
3809 if (skb == tail || skb->h.th->syn || skb->h.th->fin)
3810 return;
3811 }
3812 }
3813 }
3814}
3815
3816/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3817 * and tcp_collapse() them until all the queue is collapsed.
3818 */
3819static void tcp_collapse_ofo_queue(struct sock *sk)
3820{
3821 struct tcp_sock *tp = tcp_sk(sk);
3822 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue);
3823 struct sk_buff *head;
3824 u32 start, end;
3825
3826 if (skb == NULL)
3827 return;
3828
3829 start = TCP_SKB_CB(skb)->seq;
3830 end = TCP_SKB_CB(skb)->end_seq;
3831 head = skb;
3832
3833 for (;;) {
3834 skb = skb->next;
3835
3836 /* Segment is terminated when we see gap or when
3837 * we are at the end of all the queue. */
3838 if (skb == (struct sk_buff *)&tp->out_of_order_queue ||
3839 after(TCP_SKB_CB(skb)->seq, end) ||
3840 before(TCP_SKB_CB(skb)->end_seq, start)) {
3841 tcp_collapse(sk, head, skb, start, end);
3842 head = skb;
3843 if (skb == (struct sk_buff *)&tp->out_of_order_queue)
3844 break;
3845 /* Start new segment */
3846 start = TCP_SKB_CB(skb)->seq;
3847 end = TCP_SKB_CB(skb)->end_seq;
3848 } else {
3849 if (before(TCP_SKB_CB(skb)->seq, start))
3850 start = TCP_SKB_CB(skb)->seq;
3851 if (after(TCP_SKB_CB(skb)->end_seq, end))
3852 end = TCP_SKB_CB(skb)->end_seq;
3853 }
3854 }
3855}
3856
3857/* Reduce allocated memory if we can, trying to get
3858 * the socket within its memory limits again.
3859 *
3860 * Return less than zero if we should start dropping frames
3861 * until the socket owning process reads some of the data
3862 * to stabilize the situation.
3863 */
3864static int tcp_prune_queue(struct sock *sk)
3865{
3866 struct tcp_sock *tp = tcp_sk(sk);
3867
3868 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
3869
3870 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED);
3871
3872 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
3873 tcp_clamp_window(sk, tp);
3874 else if (tcp_memory_pressure)
3875 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss);
3876
3877 tcp_collapse_ofo_queue(sk);
3878 tcp_collapse(sk, sk->sk_receive_queue.next,
3879 (struct sk_buff*)&sk->sk_receive_queue,
3880 tp->copied_seq, tp->rcv_nxt);
3881 sk_stream_mem_reclaim(sk);
3882
3883 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3884 return 0;
3885
3886 /* Collapsing did not help, destructive actions follow.
3887 * This must not ever occur. */
3888
3889 /* First, purge the out_of_order queue. */
3890 if (skb_queue_len(&tp->out_of_order_queue)) {
3891 NET_ADD_STATS_BH(LINUX_MIB_OFOPRUNED,
3892 skb_queue_len(&tp->out_of_order_queue));
3893 __skb_queue_purge(&tp->out_of_order_queue);
3894
3895 /* Reset SACK state. A conforming SACK implementation will
3896 * do the same at a timeout based retransmit. When a connection
3897 * is in a sad state like this, we care only about integrity
3898 * of the connection not performance.
3899 */
3900 if (tp->rx_opt.sack_ok)
3901 tcp_sack_reset(&tp->rx_opt);
3902 sk_stream_mem_reclaim(sk);
3903 }
3904
3905 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf)
3906 return 0;
3907
3908 /* If we are really being abused, tell the caller to silently
3909 * drop receive data on the floor. It will get retransmitted
3910 * and hopefully then we'll have sufficient space.
3911 */
3912 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED);
3913
3914 /* Massive buffer overcommit. */
3915 tp->pred_flags = 0;
3916 return -1;
3917}
3918
3919
3920/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3921 * As additional protections, we do not touch cwnd in retransmission phases,
3922 * and if application hit its sndbuf limit recently.
3923 */
3924void tcp_cwnd_application_limited(struct sock *sk)
3925{
3926 struct tcp_sock *tp = tcp_sk(sk);
3927
3928 if (tp->ca_state == TCP_CA_Open &&
3929 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) {
3930 /* Limited by application or receiver window. */
3931 u32 win_used = max(tp->snd_cwnd_used, 2U);
3932 if (win_used < tp->snd_cwnd) {
3933 tp->snd_ssthresh = tcp_current_ssthresh(tp);
3934 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1;
3935 }
3936 tp->snd_cwnd_used = 0;
3937 }
3938 tp->snd_cwnd_stamp = tcp_time_stamp;
3939}
3940
3941
3942/* When incoming ACK allowed to free some skb from write_queue,
3943 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3944 * on the exit from tcp input handler.
3945 *
3946 * PROBLEM: sndbuf expansion does not work well with largesend.
3947 */
3948static void tcp_new_space(struct sock *sk)
3949{
3950 struct tcp_sock *tp = tcp_sk(sk);
3951
3952 if (tp->packets_out < tp->snd_cwnd &&
3953 !(sk->sk_userlocks & SOCK_SNDBUF_LOCK) &&
3954 !tcp_memory_pressure &&
3955 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) {
3956 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache_std) +
3957 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff),
3958 demanded = max_t(unsigned int, tp->snd_cwnd,
3959 tp->reordering + 1);
3960 sndmem *= 2*demanded;
3961 if (sndmem > sk->sk_sndbuf)
3962 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]);
3963 tp->snd_cwnd_stamp = tcp_time_stamp;
3964 }
3965
3966 sk->sk_write_space(sk);
3967}
3968
3969static inline void tcp_check_space(struct sock *sk)
3970{
3971 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
3972 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
3973 if (sk->sk_socket &&
3974 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
3975 tcp_new_space(sk);
3976 }
3977}
3978
3979static void __tcp_data_snd_check(struct sock *sk, struct sk_buff *skb)
3980{
3981 struct tcp_sock *tp = tcp_sk(sk);
3982
3983 if (after(TCP_SKB_CB(skb)->end_seq, tp->snd_una + tp->snd_wnd) ||
3984 tcp_packets_in_flight(tp) >= tp->snd_cwnd ||
3985 tcp_write_xmit(sk, tp->nonagle))
3986 tcp_check_probe_timer(sk, tp);
3987}
3988
3989static __inline__ void tcp_data_snd_check(struct sock *sk)
3990{
3991 struct sk_buff *skb = sk->sk_send_head;
3992
3993 if (skb != NULL)
3994 __tcp_data_snd_check(sk, skb);
3995 tcp_check_space(sk);
3996}
3997
3998/*
3999 * Check if sending an ack is needed.
4000 */
4001static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible)
4002{
4003 struct tcp_sock *tp = tcp_sk(sk);
4004
4005 /* More than one full frame received... */
4006 if (((tp->rcv_nxt - tp->rcv_wup) > tp->ack.rcv_mss
4007 /* ... and right edge of window advances far enough.
4008 * (tcp_recvmsg() will send ACK otherwise). Or...
4009 */
4010 && __tcp_select_window(sk) >= tp->rcv_wnd) ||
4011 /* We ACK each frame or... */
4012 tcp_in_quickack_mode(tp) ||
4013 /* We have out of order data. */
4014 (ofo_possible &&
4015 skb_peek(&tp->out_of_order_queue))) {
4016 /* Then ack it now */
4017 tcp_send_ack(sk);
4018 } else {
4019 /* Else, send delayed ack. */
4020 tcp_send_delayed_ack(sk);
4021 }
4022}
4023
4024static __inline__ void tcp_ack_snd_check(struct sock *sk)
4025{
4026 struct tcp_sock *tp = tcp_sk(sk);
4027 if (!tcp_ack_scheduled(tp)) {
4028 /* We sent a data segment already. */
4029 return;
4030 }
4031 __tcp_ack_snd_check(sk, 1);
4032}
4033
4034/*
4035 * This routine is only called when we have urgent data
4036 * signalled. Its the 'slow' part of tcp_urg. It could be
4037 * moved inline now as tcp_urg is only called from one
4038 * place. We handle URGent data wrong. We have to - as
4039 * BSD still doesn't use the correction from RFC961.
4040 * For 1003.1g we should support a new option TCP_STDURG to permit
4041 * either form (or just set the sysctl tcp_stdurg).
4042 */
4043
4044static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
4045{
4046 struct tcp_sock *tp = tcp_sk(sk);
4047 u32 ptr = ntohs(th->urg_ptr);
4048
4049 if (ptr && !sysctl_tcp_stdurg)
4050 ptr--;
4051 ptr += ntohl(th->seq);
4052
4053 /* Ignore urgent data that we've already seen and read. */
4054 if (after(tp->copied_seq, ptr))
4055 return;
4056
4057 /* Do not replay urg ptr.
4058 *
4059 * NOTE: interesting situation not covered by specs.
4060 * Misbehaving sender may send urg ptr, pointing to segment,
4061 * which we already have in ofo queue. We are not able to fetch
4062 * such data and will stay in TCP_URG_NOTYET until will be eaten
4063 * by recvmsg(). Seems, we are not obliged to handle such wicked
4064 * situations. But it is worth to think about possibility of some
4065 * DoSes using some hypothetical application level deadlock.
4066 */
4067 if (before(ptr, tp->rcv_nxt))
4068 return;
4069
4070 /* Do we already have a newer (or duplicate) urgent pointer? */
4071 if (tp->urg_data && !after(ptr, tp->urg_seq))
4072 return;
4073
4074 /* Tell the world about our new urgent pointer. */
4075 sk_send_sigurg(sk);
4076
4077 /* We may be adding urgent data when the last byte read was
4078 * urgent. To do this requires some care. We cannot just ignore
4079 * tp->copied_seq since we would read the last urgent byte again
4080 * as data, nor can we alter copied_seq until this data arrives
4081 * or we break the sematics of SIOCATMARK (and thus sockatmark())
4082 *
4083 * NOTE. Double Dutch. Rendering to plain English: author of comment
4084 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4085 * and expect that both A and B disappear from stream. This is _wrong_.
4086 * Though this happens in BSD with high probability, this is occasional.
4087 * Any application relying on this is buggy. Note also, that fix "works"
4088 * only in this artificial test. Insert some normal data between A and B and we will
4089 * decline of BSD again. Verdict: it is better to remove to trap
4090 * buggy users.
4091 */
4092 if (tp->urg_seq == tp->copied_seq && tp->urg_data &&
4093 !sock_flag(sk, SOCK_URGINLINE) &&
4094 tp->copied_seq != tp->rcv_nxt) {
4095 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
4096 tp->copied_seq++;
4097 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) {
4098 __skb_unlink(skb, skb->list);
4099 __kfree_skb(skb);
4100 }
4101 }
4102
4103 tp->urg_data = TCP_URG_NOTYET;
4104 tp->urg_seq = ptr;
4105
4106 /* Disable header prediction. */
4107 tp->pred_flags = 0;
4108}
4109
4110/* This is the 'fast' part of urgent handling. */
4111static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th)
4112{
4113 struct tcp_sock *tp = tcp_sk(sk);
4114
4115 /* Check if we get a new urgent pointer - normally not. */
4116 if (th->urg)
4117 tcp_check_urg(sk,th);
4118
4119 /* Do we wait for any urgent data? - normally not... */
4120 if (tp->urg_data == TCP_URG_NOTYET) {
4121 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) -
4122 th->syn;
4123
4124 /* Is the urgent pointer pointing into this packet? */
4125 if (ptr < skb->len) {
4126 u8 tmp;
4127 if (skb_copy_bits(skb, ptr, &tmp, 1))
4128 BUG();
4129 tp->urg_data = TCP_URG_VALID | tmp;
4130 if (!sock_flag(sk, SOCK_DEAD))
4131 sk->sk_data_ready(sk, 0);
4132 }
4133 }
4134}
4135
4136static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen)
4137{
4138 struct tcp_sock *tp = tcp_sk(sk);
4139 int chunk = skb->len - hlen;
4140 int err;
4141
4142 local_bh_enable();
4143 if (skb->ip_summed==CHECKSUM_UNNECESSARY)
4144 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk);
4145 else
4146 err = skb_copy_and_csum_datagram_iovec(skb, hlen,
4147 tp->ucopy.iov);
4148
4149 if (!err) {
4150 tp->ucopy.len -= chunk;
4151 tp->copied_seq += chunk;
4152 tcp_rcv_space_adjust(sk);
4153 }
4154
4155 local_bh_disable();
4156 return err;
4157}
4158
4159static int __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
4160{
4161 int result;
4162
4163 if (sock_owned_by_user(sk)) {
4164 local_bh_enable();
4165 result = __tcp_checksum_complete(skb);
4166 local_bh_disable();
4167 } else {
4168 result = __tcp_checksum_complete(skb);
4169 }
4170 return result;
4171}
4172
4173static __inline__ int
4174tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb)
4175{
4176 return skb->ip_summed != CHECKSUM_UNNECESSARY &&
4177 __tcp_checksum_complete_user(sk, skb);
4178}
4179
4180/*
4181 * TCP receive function for the ESTABLISHED state.
4182 *
4183 * It is split into a fast path and a slow path. The fast path is
4184 * disabled when:
4185 * - A zero window was announced from us - zero window probing
4186 * is only handled properly in the slow path.
4187 * - Out of order segments arrived.
4188 * - Urgent data is expected.
4189 * - There is no buffer space left
4190 * - Unexpected TCP flags/window values/header lengths are received
4191 * (detected by checking the TCP header against pred_flags)
4192 * - Data is sent in both directions. Fast path only supports pure senders
4193 * or pure receivers (this means either the sequence number or the ack
4194 * value must stay constant)
4195 * - Unexpected TCP option.
4196 *
4197 * When these conditions are not satisfied it drops into a standard
4198 * receive procedure patterned after RFC793 to handle all cases.
4199 * The first three cases are guaranteed by proper pred_flags setting,
4200 * the rest is checked inline. Fast processing is turned on in
4201 * tcp_data_queue when everything is OK.
4202 */
4203int tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
4204 struct tcphdr *th, unsigned len)
4205{
4206 struct tcp_sock *tp = tcp_sk(sk);
4207
4208 /*
4209 * Header prediction.
4210 * The code loosely follows the one in the famous
4211 * "30 instruction TCP receive" Van Jacobson mail.
4212 *
4213 * Van's trick is to deposit buffers into socket queue
4214 * on a device interrupt, to call tcp_recv function
4215 * on the receive process context and checksum and copy
4216 * the buffer to user space. smart...
4217 *
4218 * Our current scheme is not silly either but we take the
4219 * extra cost of the net_bh soft interrupt processing...
4220 * We do checksum and copy also but from device to kernel.
4221 */
4222
4223 tp->rx_opt.saw_tstamp = 0;
4224
4225 /* pred_flags is 0xS?10 << 16 + snd_wnd
4226 * if header_predition is to be made
4227 * 'S' will always be tp->tcp_header_len >> 2
4228 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4229 * turn it off (when there are holes in the receive
4230 * space for instance)
4231 * PSH flag is ignored.
4232 */
4233
4234 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags &&
4235 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
4236 int tcp_header_len = tp->tcp_header_len;
4237
4238 /* Timestamp header prediction: tcp_header_len
4239 * is automatically equal to th->doff*4 due to pred_flags
4240 * match.
4241 */
4242
4243 /* Check timestamp */
4244 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) {
4245 __u32 *ptr = (__u32 *)(th + 1);
4246
4247 /* No? Slow path! */
4248 if (*ptr != ntohl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16)
4249 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP))
4250 goto slow_path;
4251
4252 tp->rx_opt.saw_tstamp = 1;
4253 ++ptr;
4254 tp->rx_opt.rcv_tsval = ntohl(*ptr);
4255 ++ptr;
4256 tp->rx_opt.rcv_tsecr = ntohl(*ptr);
4257
4258 /* If PAWS failed, check it more carefully in slow path */
4259 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0)
4260 goto slow_path;
4261
4262 /* DO NOT update ts_recent here, if checksum fails
4263 * and timestamp was corrupted part, it will result
4264 * in a hung connection since we will drop all
4265 * future packets due to the PAWS test.
4266 */
4267 }
4268
4269 if (len <= tcp_header_len) {
4270 /* Bulk data transfer: sender */
4271 if (len == tcp_header_len) {
4272 /* Predicted packet is in window by definition.
4273 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4274 * Hence, check seq<=rcv_wup reduces to:
4275 */
4276 if (tcp_header_len ==
4277 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4278 tp->rcv_nxt == tp->rcv_wup)
4279 tcp_store_ts_recent(tp);
4280
4281 tcp_rcv_rtt_measure_ts(tp, skb);
4282
4283 /* We know that such packets are checksummed
4284 * on entry.
4285 */
4286 tcp_ack(sk, skb, 0);
4287 __kfree_skb(skb);
4288 tcp_data_snd_check(sk);
4289 return 0;
4290 } else { /* Header too small */
4291 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4292 goto discard;
4293 }
4294 } else {
4295 int eaten = 0;
4296
4297 if (tp->ucopy.task == current &&
4298 tp->copied_seq == tp->rcv_nxt &&
4299 len - tcp_header_len <= tp->ucopy.len &&
4300 sock_owned_by_user(sk)) {
4301 __set_current_state(TASK_RUNNING);
4302
4303 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) {
4304 /* Predicted packet is in window by definition.
4305 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4306 * Hence, check seq<=rcv_wup reduces to:
4307 */
4308 if (tcp_header_len ==
4309 (sizeof(struct tcphdr) +
4310 TCPOLEN_TSTAMP_ALIGNED) &&
4311 tp->rcv_nxt == tp->rcv_wup)
4312 tcp_store_ts_recent(tp);
4313
4314 tcp_rcv_rtt_measure_ts(tp, skb);
4315
4316 __skb_pull(skb, tcp_header_len);
4317 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4318 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER);
4319 eaten = 1;
4320 }
4321 }
4322 if (!eaten) {
4323 if (tcp_checksum_complete_user(sk, skb))
4324 goto csum_error;
4325
4326 /* Predicted packet is in window by definition.
4327 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4328 * Hence, check seq<=rcv_wup reduces to:
4329 */
4330 if (tcp_header_len ==
4331 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) &&
4332 tp->rcv_nxt == tp->rcv_wup)
4333 tcp_store_ts_recent(tp);
4334
4335 tcp_rcv_rtt_measure_ts(tp, skb);
4336
4337 if ((int)skb->truesize > sk->sk_forward_alloc)
4338 goto step5;
4339
4340 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS);
4341
4342 /* Bulk data transfer: receiver */
4343 __skb_pull(skb,tcp_header_len);
4344 __skb_queue_tail(&sk->sk_receive_queue, skb);
4345 sk_stream_set_owner_r(skb, sk);
4346 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq;
4347 }
4348
4349 tcp_event_data_recv(sk, tp, skb);
4350
4351 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) {
4352 /* Well, only one small jumplet in fast path... */
4353 tcp_ack(sk, skb, FLAG_DATA);
4354 tcp_data_snd_check(sk);
4355 if (!tcp_ack_scheduled(tp))
4356 goto no_ack;
4357 }
4358
4359 if (eaten) {
4360 if (tcp_in_quickack_mode(tp)) {
4361 tcp_send_ack(sk);
4362 } else {
4363 tcp_send_delayed_ack(sk);
4364 }
4365 } else {
4366 __tcp_ack_snd_check(sk, 0);
4367 }
4368
4369no_ack:
4370 if (eaten)
4371 __kfree_skb(skb);
4372 else
4373 sk->sk_data_ready(sk, 0);
4374 return 0;
4375 }
4376 }
4377
4378slow_path:
4379 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb))
4380 goto csum_error;
4381
4382 /*
4383 * RFC1323: H1. Apply PAWS check first.
4384 */
4385 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4386 tcp_paws_discard(tp, skb)) {
4387 if (!th->rst) {
4388 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4389 tcp_send_dupack(sk, skb);
4390 goto discard;
4391 }
4392 /* Resets are accepted even if PAWS failed.
4393
4394 ts_recent update must be made after we are sure
4395 that the packet is in window.
4396 */
4397 }
4398
4399 /*
4400 * Standard slow path.
4401 */
4402
4403 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4404 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4405 * (RST) segments are validated by checking their SEQ-fields."
4406 * And page 69: "If an incoming segment is not acceptable,
4407 * an acknowledgment should be sent in reply (unless the RST bit
4408 * is set, if so drop the segment and return)".
4409 */
4410 if (!th->rst)
4411 tcp_send_dupack(sk, skb);
4412 goto discard;
4413 }
4414
4415 if(th->rst) {
4416 tcp_reset(sk);
4417 goto discard;
4418 }
4419
4420 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4421
4422 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4423 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4424 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4425 tcp_reset(sk);
4426 return 1;
4427 }
4428
4429step5:
4430 if(th->ack)
4431 tcp_ack(sk, skb, FLAG_SLOWPATH);
4432
4433 tcp_rcv_rtt_measure_ts(tp, skb);
4434
4435 /* Process urgent data. */
4436 tcp_urg(sk, skb, th);
4437
4438 /* step 7: process the segment text */
4439 tcp_data_queue(sk, skb);
4440
4441 tcp_data_snd_check(sk);
4442 tcp_ack_snd_check(sk);
4443 return 0;
4444
4445csum_error:
4446 TCP_INC_STATS_BH(TCP_MIB_INERRS);
4447
4448discard:
4449 __kfree_skb(skb);
4450 return 0;
4451}
4452
4453static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
4454 struct tcphdr *th, unsigned len)
4455{
4456 struct tcp_sock *tp = tcp_sk(sk);
4457 int saved_clamp = tp->rx_opt.mss_clamp;
4458
4459 tcp_parse_options(skb, &tp->rx_opt, 0);
4460
4461 if (th->ack) {
4462 /* rfc793:
4463 * "If the state is SYN-SENT then
4464 * first check the ACK bit
4465 * If the ACK bit is set
4466 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4467 * a reset (unless the RST bit is set, if so drop
4468 * the segment and return)"
4469 *
4470 * We do not send data with SYN, so that RFC-correct
4471 * test reduces to:
4472 */
4473 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt)
4474 goto reset_and_undo;
4475
4476 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4477 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp,
4478 tcp_time_stamp)) {
4479 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED);
4480 goto reset_and_undo;
4481 }
4482
4483 /* Now ACK is acceptable.
4484 *
4485 * "If the RST bit is set
4486 * If the ACK was acceptable then signal the user "error:
4487 * connection reset", drop the segment, enter CLOSED state,
4488 * delete TCB, and return."
4489 */
4490
4491 if (th->rst) {
4492 tcp_reset(sk);
4493 goto discard;
4494 }
4495
4496 /* rfc793:
4497 * "fifth, if neither of the SYN or RST bits is set then
4498 * drop the segment and return."
4499 *
4500 * See note below!
4501 * --ANK(990513)
4502 */
4503 if (!th->syn)
4504 goto discard_and_undo;
4505
4506 /* rfc793:
4507 * "If the SYN bit is on ...
4508 * are acceptable then ...
4509 * (our SYN has been ACKed), change the connection
4510 * state to ESTABLISHED..."
4511 */
4512
4513 TCP_ECN_rcv_synack(tp, th);
4514 if (tp->ecn_flags&TCP_ECN_OK)
4515 sock_set_flag(sk, SOCK_NO_LARGESEND);
4516
4517 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4518 tcp_ack(sk, skb, FLAG_SLOWPATH);
4519
4520 /* Ok.. it's good. Set up sequence numbers and
4521 * move to established.
4522 */
4523 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4524 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4525
4526 /* RFC1323: The window in SYN & SYN/ACK segments is
4527 * never scaled.
4528 */
4529 tp->snd_wnd = ntohs(th->window);
4530 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq);
4531
4532 if (!tp->rx_opt.wscale_ok) {
4533 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0;
4534 tp->window_clamp = min(tp->window_clamp, 65535U);
4535 }
4536
4537 if (tp->rx_opt.saw_tstamp) {
4538 tp->rx_opt.tstamp_ok = 1;
4539 tp->tcp_header_len =
4540 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4541 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4542 tcp_store_ts_recent(tp);
4543 } else {
4544 tp->tcp_header_len = sizeof(struct tcphdr);
4545 }
4546
4547 if (tp->rx_opt.sack_ok && sysctl_tcp_fack)
4548 tp->rx_opt.sack_ok |= 2;
4549
4550 tcp_sync_mss(sk, tp->pmtu_cookie);
4551 tcp_initialize_rcv_mss(sk);
4552
4553 /* Remember, tcp_poll() does not lock socket!
4554 * Change state from SYN-SENT only after copied_seq
4555 * is initialized. */
4556 tp->copied_seq = tp->rcv_nxt;
4557 mb();
4558 tcp_set_state(sk, TCP_ESTABLISHED);
4559
4560 /* Make sure socket is routed, for correct metrics. */
4561 tp->af_specific->rebuild_header(sk);
4562
4563 tcp_init_metrics(sk);
4564
4565 /* Prevent spurious tcp_cwnd_restart() on first data
4566 * packet.
4567 */
4568 tp->lsndtime = tcp_time_stamp;
4569
4570 tcp_init_buffer_space(sk);
4571
4572 if (sock_flag(sk, SOCK_KEEPOPEN))
4573 tcp_reset_keepalive_timer(sk, keepalive_time_when(tp));
4574
4575 if (!tp->rx_opt.snd_wscale)
4576 __tcp_fast_path_on(tp, tp->snd_wnd);
4577 else
4578 tp->pred_flags = 0;
4579
4580 if (!sock_flag(sk, SOCK_DEAD)) {
4581 sk->sk_state_change(sk);
4582 sk_wake_async(sk, 0, POLL_OUT);
4583 }
4584
4585 if (sk->sk_write_pending || tp->defer_accept || tp->ack.pingpong) {
4586 /* Save one ACK. Data will be ready after
4587 * several ticks, if write_pending is set.
4588 *
4589 * It may be deleted, but with this feature tcpdumps
4590 * look so _wonderfully_ clever, that I was not able
4591 * to stand against the temptation 8) --ANK
4592 */
4593 tcp_schedule_ack(tp);
4594 tp->ack.lrcvtime = tcp_time_stamp;
4595 tp->ack.ato = TCP_ATO_MIN;
4596 tcp_incr_quickack(tp);
4597 tcp_enter_quickack_mode(tp);
4598 tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MAX);
4599
4600discard:
4601 __kfree_skb(skb);
4602 return 0;
4603 } else {
4604 tcp_send_ack(sk);
4605 }
4606 return -1;
4607 }
4608
4609 /* No ACK in the segment */
4610
4611 if (th->rst) {
4612 /* rfc793:
4613 * "If the RST bit is set
4614 *
4615 * Otherwise (no ACK) drop the segment and return."
4616 */
4617
4618 goto discard_and_undo;
4619 }
4620
4621 /* PAWS check. */
4622 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0))
4623 goto discard_and_undo;
4624
4625 if (th->syn) {
4626 /* We see SYN without ACK. It is attempt of
4627 * simultaneous connect with crossed SYNs.
4628 * Particularly, it can be connect to self.
4629 */
4630 tcp_set_state(sk, TCP_SYN_RECV);
4631
4632 if (tp->rx_opt.saw_tstamp) {
4633 tp->rx_opt.tstamp_ok = 1;
4634 tcp_store_ts_recent(tp);
4635 tp->tcp_header_len =
4636 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED;
4637 } else {
4638 tp->tcp_header_len = sizeof(struct tcphdr);
4639 }
4640
4641 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
4642 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;
4643
4644 /* RFC1323: The window in SYN & SYN/ACK segments is
4645 * never scaled.
4646 */
4647 tp->snd_wnd = ntohs(th->window);
4648 tp->snd_wl1 = TCP_SKB_CB(skb)->seq;
4649 tp->max_window = tp->snd_wnd;
4650
4651 TCP_ECN_rcv_syn(tp, th);
4652 if (tp->ecn_flags&TCP_ECN_OK)
4653 sock_set_flag(sk, SOCK_NO_LARGESEND);
4654
4655 tcp_sync_mss(sk, tp->pmtu_cookie);
4656 tcp_initialize_rcv_mss(sk);
4657
4658
4659 tcp_send_synack(sk);
4660#if 0
4661 /* Note, we could accept data and URG from this segment.
4662 * There are no obstacles to make this.
4663 *
4664 * However, if we ignore data in ACKless segments sometimes,
4665 * we have no reasons to accept it sometimes.
4666 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4667 * is not flawless. So, discard packet for sanity.
4668 * Uncomment this return to process the data.
4669 */
4670 return -1;
4671#else
4672 goto discard;
4673#endif
4674 }
4675 /* "fifth, if neither of the SYN or RST bits is set then
4676 * drop the segment and return."
4677 */
4678
4679discard_and_undo:
4680 tcp_clear_options(&tp->rx_opt);
4681 tp->rx_opt.mss_clamp = saved_clamp;
4682 goto discard;
4683
4684reset_and_undo:
4685 tcp_clear_options(&tp->rx_opt);
4686 tp->rx_opt.mss_clamp = saved_clamp;
4687 return 1;
4688}
4689
4690
4691/*
4692 * This function implements the receiving procedure of RFC 793 for
4693 * all states except ESTABLISHED and TIME_WAIT.
4694 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4695 * address independent.
4696 */
4697
4698int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
4699 struct tcphdr *th, unsigned len)
4700{
4701 struct tcp_sock *tp = tcp_sk(sk);
4702 int queued = 0;
4703
4704 tp->rx_opt.saw_tstamp = 0;
4705
4706 switch (sk->sk_state) {
4707 case TCP_CLOSE:
4708 goto discard;
4709
4710 case TCP_LISTEN:
4711 if(th->ack)
4712 return 1;
4713
4714 if(th->rst)
4715 goto discard;
4716
4717 if(th->syn) {
4718 if(tp->af_specific->conn_request(sk, skb) < 0)
4719 return 1;
4720
4721 init_westwood(sk);
4722 init_bictcp(tp);
4723
4724 /* Now we have several options: In theory there is
4725 * nothing else in the frame. KA9Q has an option to
4726 * send data with the syn, BSD accepts data with the
4727 * syn up to the [to be] advertised window and
4728 * Solaris 2.1 gives you a protocol error. For now
4729 * we just ignore it, that fits the spec precisely
4730 * and avoids incompatibilities. It would be nice in
4731 * future to drop through and process the data.
4732 *
4733 * Now that TTCP is starting to be used we ought to
4734 * queue this data.
4735 * But, this leaves one open to an easy denial of
4736 * service attack, and SYN cookies can't defend
4737 * against this problem. So, we drop the data
4738 * in the interest of security over speed.
4739 */
4740 goto discard;
4741 }
4742 goto discard;
4743
4744 case TCP_SYN_SENT:
4745 init_westwood(sk);
4746 init_bictcp(tp);
4747
4748 queued = tcp_rcv_synsent_state_process(sk, skb, th, len);
4749 if (queued >= 0)
4750 return queued;
4751
4752 /* Do step6 onward by hand. */
4753 tcp_urg(sk, skb, th);
4754 __kfree_skb(skb);
4755 tcp_data_snd_check(sk);
4756 return 0;
4757 }
4758
4759 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp &&
4760 tcp_paws_discard(tp, skb)) {
4761 if (!th->rst) {
4762 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED);
4763 tcp_send_dupack(sk, skb);
4764 goto discard;
4765 }
4766 /* Reset is accepted even if it did not pass PAWS. */
4767 }
4768
4769 /* step 1: check sequence number */
4770 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) {
4771 if (!th->rst)
4772 tcp_send_dupack(sk, skb);
4773 goto discard;
4774 }
4775
4776 /* step 2: check RST bit */
4777 if(th->rst) {
4778 tcp_reset(sk);
4779 goto discard;
4780 }
4781
4782 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq);
4783
4784 /* step 3: check security and precedence [ignored] */
4785
4786 /* step 4:
4787 *
4788 * Check for a SYN in window.
4789 */
4790 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
4791 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN);
4792 tcp_reset(sk);
4793 return 1;
4794 }
4795
4796 /* step 5: check the ACK field */
4797 if (th->ack) {
4798 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH);
4799
4800 switch(sk->sk_state) {
4801 case TCP_SYN_RECV:
4802 if (acceptable) {
4803 tp->copied_seq = tp->rcv_nxt;
4804 mb();
4805 tcp_set_state(sk, TCP_ESTABLISHED);
4806 sk->sk_state_change(sk);
4807
4808 /* Note, that this wakeup is only for marginal
4809 * crossed SYN case. Passively open sockets
4810 * are not waked up, because sk->sk_sleep ==
4811 * NULL and sk->sk_socket == NULL.
4812 */
4813 if (sk->sk_socket) {
4814 sk_wake_async(sk,0,POLL_OUT);
4815 }
4816
4817 tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
4818 tp->snd_wnd = ntohs(th->window) <<
4819 tp->rx_opt.snd_wscale;
4820 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq,
4821 TCP_SKB_CB(skb)->seq);
4822
4823 /* tcp_ack considers this ACK as duplicate
4824 * and does not calculate rtt.
4825 * Fix it at least with timestamps.
4826 */
4827 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr &&
4828 !tp->srtt)
4829 tcp_ack_saw_tstamp(tp, 0);
4830
4831 if (tp->rx_opt.tstamp_ok)
4832 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED;
4833
4834 /* Make sure socket is routed, for
4835 * correct metrics.
4836 */
4837 tp->af_specific->rebuild_header(sk);
4838
4839 tcp_init_metrics(sk);
4840
4841 /* Prevent spurious tcp_cwnd_restart() on
4842 * first data packet.
4843 */
4844 tp->lsndtime = tcp_time_stamp;
4845
4846 tcp_initialize_rcv_mss(sk);
4847 tcp_init_buffer_space(sk);
4848 tcp_fast_path_on(tp);
4849 } else {
4850 return 1;
4851 }
4852 break;
4853
4854 case TCP_FIN_WAIT1:
4855 if (tp->snd_una == tp->write_seq) {
4856 tcp_set_state(sk, TCP_FIN_WAIT2);
4857 sk->sk_shutdown |= SEND_SHUTDOWN;
4858 dst_confirm(sk->sk_dst_cache);
4859
4860 if (!sock_flag(sk, SOCK_DEAD))
4861 /* Wake up lingering close() */
4862 sk->sk_state_change(sk);
4863 else {
4864 int tmo;
4865
4866 if (tp->linger2 < 0 ||
4867 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4868 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) {
4869 tcp_done(sk);
4870 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4871 return 1;
4872 }
4873
4874 tmo = tcp_fin_time(tp);
4875 if (tmo > TCP_TIMEWAIT_LEN) {
4876 tcp_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN);
4877 } else if (th->fin || sock_owned_by_user(sk)) {
4878 /* Bad case. We could lose such FIN otherwise.
4879 * It is not a big problem, but it looks confusing
4880 * and not so rare event. We still can lose it now,
4881 * if it spins in bh_lock_sock(), but it is really
4882 * marginal case.
4883 */
4884 tcp_reset_keepalive_timer(sk, tmo);
4885 } else {
4886 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
4887 goto discard;
4888 }
4889 }
4890 }
4891 break;
4892
4893 case TCP_CLOSING:
4894 if (tp->snd_una == tp->write_seq) {
4895 tcp_time_wait(sk, TCP_TIME_WAIT, 0);
4896 goto discard;
4897 }
4898 break;
4899
4900 case TCP_LAST_ACK:
4901 if (tp->snd_una == tp->write_seq) {
4902 tcp_update_metrics(sk);
4903 tcp_done(sk);
4904 goto discard;
4905 }
4906 break;
4907 }
4908 } else
4909 goto discard;
4910
4911 /* step 6: check the URG bit */
4912 tcp_urg(sk, skb, th);
4913
4914 /* step 7: process the segment text */
4915 switch (sk->sk_state) {
4916 case TCP_CLOSE_WAIT:
4917 case TCP_CLOSING:
4918 case TCP_LAST_ACK:
4919 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt))
4920 break;
4921 case TCP_FIN_WAIT1:
4922 case TCP_FIN_WAIT2:
4923 /* RFC 793 says to queue data in these states,
4924 * RFC 1122 says we MUST send a reset.
4925 * BSD 4.4 also does reset.
4926 */
4927 if (sk->sk_shutdown & RCV_SHUTDOWN) {
4928 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq &&
4929 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) {
4930 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA);
4931 tcp_reset(sk);
4932 return 1;
4933 }
4934 }
4935 /* Fall through */
4936 case TCP_ESTABLISHED:
4937 tcp_data_queue(sk, skb);
4938 queued = 1;
4939 break;
4940 }
4941
4942 /* tcp_data could move socket to TIME-WAIT */
4943 if (sk->sk_state != TCP_CLOSE) {
4944 tcp_data_snd_check(sk);
4945 tcp_ack_snd_check(sk);
4946 }
4947
4948 if (!queued) {
4949discard:
4950 __kfree_skb(skb);
4951 }
4952 return 0;
4953}
4954
4955EXPORT_SYMBOL(sysctl_tcp_ecn);
4956EXPORT_SYMBOL(sysctl_tcp_reordering);
4957EXPORT_SYMBOL(tcp_parse_options);
4958EXPORT_SYMBOL(tcp_rcv_established);
4959EXPORT_SYMBOL(tcp_rcv_state_process);
generated by cgit v1.2.2 (git 2.25.0) at 2024-11-05 19:09:25 -0500