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.
6 * Implementation of the Transmission Control Protocol(TCP).
8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
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>
25 * Pedro Roque : Fast Retransmit/Recovery.
27 * Retransmit queue handled by TCP.
28 * Better retransmit timer handling.
29 * New congestion avoidance.
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 presence of
47 * Andrey Savochkin: Check sequence numbers correctly when
48 * removing SACKs due to in sequence incoming
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
58 * J Hadi Salim: ECN support
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
67 #include <linux/module.h>
68 #include <linux/sysctl.h>
70 #include <net/inet_common.h>
71 #include <linux/ipsec.h>
72 #include <asm/unaligned.h>
73 #include <net/netdma.h>
75 int sysctl_tcp_timestamps __read_mostly
= 1;
76 int sysctl_tcp_window_scaling __read_mostly
= 1;
77 int sysctl_tcp_sack __read_mostly
= 1;
78 int sysctl_tcp_fack __read_mostly
= 1;
79 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
80 int sysctl_tcp_ecn __read_mostly
;
81 int sysctl_tcp_dsack __read_mostly
= 1;
82 int sysctl_tcp_app_win __read_mostly
= 31;
83 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
85 int sysctl_tcp_stdurg __read_mostly
;
86 int sysctl_tcp_rfc1337 __read_mostly
;
87 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
88 int sysctl_tcp_frto __read_mostly
;
89 int sysctl_tcp_nometrics_save __read_mostly
;
91 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
92 int sysctl_tcp_abc __read_mostly
;
94 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
95 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
96 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
97 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
98 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
99 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
100 #define FLAG_ECE 0x40 /* ECE in this ACK */
101 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
102 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
105 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
106 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
107 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
109 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
110 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
111 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
113 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
115 /* Adapt the MSS value used to make delayed ack decision to the
118 static void tcp_measure_rcv_mss(struct sock
*sk
,
119 const struct sk_buff
*skb
)
121 struct inet_connection_sock
*icsk
= inet_csk(sk
);
122 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
125 icsk
->icsk_ack
.last_seg_size
= 0;
127 /* skb->len may jitter because of SACKs, even if peer
128 * sends good full-sized frames.
130 len
= skb_shinfo(skb
)->gso_size
?: skb
->len
;
131 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
132 icsk
->icsk_ack
.rcv_mss
= len
;
134 /* Otherwise, we make more careful check taking into account,
135 * that SACKs block is variable.
137 * "len" is invariant segment length, including TCP header.
139 len
+= skb
->data
- skb
->h
.raw
;
140 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
141 /* If PSH is not set, packet should be
142 * full sized, provided peer TCP is not badly broken.
143 * This observation (if it is correct 8)) allows
144 * to handle super-low mtu links fairly.
146 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
147 !(tcp_flag_word(skb
->h
.th
)&TCP_REMNANT
))) {
148 /* Subtract also invariant (if peer is RFC compliant),
149 * tcp header plus fixed timestamp option length.
150 * Resulting "len" is MSS free of SACK jitter.
152 len
-= tcp_sk(sk
)->tcp_header_len
;
153 icsk
->icsk_ack
.last_seg_size
= len
;
155 icsk
->icsk_ack
.rcv_mss
= len
;
159 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
160 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
161 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
165 static void tcp_incr_quickack(struct sock
*sk
)
167 struct inet_connection_sock
*icsk
= inet_csk(sk
);
168 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
172 if (quickacks
> icsk
->icsk_ack
.quick
)
173 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
176 void tcp_enter_quickack_mode(struct sock
*sk
)
178 struct inet_connection_sock
*icsk
= inet_csk(sk
);
179 tcp_incr_quickack(sk
);
180 icsk
->icsk_ack
.pingpong
= 0;
181 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
184 /* Send ACKs quickly, if "quick" count is not exhausted
185 * and the session is not interactive.
188 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
190 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
191 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
194 /* Buffer size and advertised window tuning.
196 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
199 static void tcp_fixup_sndbuf(struct sock
*sk
)
201 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
202 sizeof(struct sk_buff
);
204 if (sk
->sk_sndbuf
< 3 * sndmem
)
205 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
208 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
210 * All tcp_full_space() is split to two parts: "network" buffer, allocated
211 * forward and advertised in receiver window (tp->rcv_wnd) and
212 * "application buffer", required to isolate scheduling/application
213 * latencies from network.
214 * window_clamp is maximal advertised window. It can be less than
215 * tcp_full_space(), in this case tcp_full_space() - window_clamp
216 * is reserved for "application" buffer. The less window_clamp is
217 * the smoother our behaviour from viewpoint of network, but the lower
218 * throughput and the higher sensitivity of the connection to losses. 8)
220 * rcv_ssthresh is more strict window_clamp used at "slow start"
221 * phase to predict further behaviour of this connection.
222 * It is used for two goals:
223 * - to enforce header prediction at sender, even when application
224 * requires some significant "application buffer". It is check #1.
225 * - to prevent pruning of receive queue because of misprediction
226 * of receiver window. Check #2.
228 * The scheme does not work when sender sends good segments opening
229 * window and then starts to feed us spaghetti. But it should work
230 * in common situations. Otherwise, we have to rely on queue collapsing.
233 /* Slow part of check#2. */
234 static int __tcp_grow_window(const struct sock
*sk
, struct tcp_sock
*tp
,
235 const struct sk_buff
*skb
)
238 int truesize
= tcp_win_from_space(skb
->truesize
)/2;
239 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2])/2;
241 while (tp
->rcv_ssthresh
<= window
) {
242 if (truesize
<= skb
->len
)
243 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
251 static void tcp_grow_window(struct sock
*sk
, struct tcp_sock
*tp
,
255 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
256 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
257 !tcp_memory_pressure
) {
260 /* Check #2. Increase window, if skb with such overhead
261 * will fit to rcvbuf in future.
263 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
266 incr
= __tcp_grow_window(sk
, tp
, skb
);
269 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
, tp
->window_clamp
);
270 inet_csk(sk
)->icsk_ack
.quick
|= 1;
275 /* 3. Tuning rcvbuf, when connection enters established state. */
277 static void tcp_fixup_rcvbuf(struct sock
*sk
)
279 struct tcp_sock
*tp
= tcp_sk(sk
);
280 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
282 /* Try to select rcvbuf so that 4 mss-sized segments
283 * will fit to window and corresponding skbs will fit to our rcvbuf.
284 * (was 3; 4 is minimum to allow fast retransmit to work.)
286 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
288 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
289 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
292 /* 4. Try to fixup all. It is made immediately after connection enters
295 static void tcp_init_buffer_space(struct sock
*sk
)
297 struct tcp_sock
*tp
= tcp_sk(sk
);
300 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
301 tcp_fixup_rcvbuf(sk
);
302 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
303 tcp_fixup_sndbuf(sk
);
305 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
307 maxwin
= tcp_full_space(sk
);
309 if (tp
->window_clamp
>= maxwin
) {
310 tp
->window_clamp
= maxwin
;
312 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
313 tp
->window_clamp
= max(maxwin
-
314 (maxwin
>> sysctl_tcp_app_win
),
318 /* Force reservation of one segment. */
319 if (sysctl_tcp_app_win
&&
320 tp
->window_clamp
> 2 * tp
->advmss
&&
321 tp
->window_clamp
+ tp
->advmss
> maxwin
)
322 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
324 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
325 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
328 /* 5. Recalculate window clamp after socket hit its memory bounds. */
329 static void tcp_clamp_window(struct sock
*sk
, struct tcp_sock
*tp
)
331 struct inet_connection_sock
*icsk
= inet_csk(sk
);
333 icsk
->icsk_ack
.quick
= 0;
335 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
336 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
337 !tcp_memory_pressure
&&
338 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
339 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
342 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
343 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
347 /* Initialize RCV_MSS value.
348 * RCV_MSS is an our guess about MSS used by the peer.
349 * We haven't any direct information about the MSS.
350 * It's better to underestimate the RCV_MSS rather than overestimate.
351 * Overestimations make us ACKing less frequently than needed.
352 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
354 void tcp_initialize_rcv_mss(struct sock
*sk
)
356 struct tcp_sock
*tp
= tcp_sk(sk
);
357 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
359 hint
= min(hint
, tp
->rcv_wnd
/2);
360 hint
= min(hint
, TCP_MIN_RCVMSS
);
361 hint
= max(hint
, TCP_MIN_MSS
);
363 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
366 /* Receiver "autotuning" code.
368 * The algorithm for RTT estimation w/o timestamps is based on
369 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
370 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
372 * More detail on this code can be found at
373 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
374 * though this reference is out of date. A new paper
377 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
379 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
385 if (new_sample
!= 0) {
386 /* If we sample in larger samples in the non-timestamp
387 * case, we could grossly overestimate the RTT especially
388 * with chatty applications or bulk transfer apps which
389 * are stalled on filesystem I/O.
391 * Also, since we are only going for a minimum in the
392 * non-timestamp case, we do not smooth things out
393 * else with timestamps disabled convergence takes too
397 m
-= (new_sample
>> 3);
399 } else if (m
< new_sample
)
402 /* No previous measure. */
406 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
407 tp
->rcv_rtt_est
.rtt
= new_sample
;
410 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
412 if (tp
->rcv_rtt_est
.time
== 0)
414 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
416 tcp_rcv_rtt_update(tp
,
417 jiffies
- tp
->rcv_rtt_est
.time
,
421 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
422 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
425 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
427 struct tcp_sock
*tp
= tcp_sk(sk
);
428 if (tp
->rx_opt
.rcv_tsecr
&&
429 (TCP_SKB_CB(skb
)->end_seq
-
430 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
431 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
435 * This function should be called every time data is copied to user space.
436 * It calculates the appropriate TCP receive buffer space.
438 void tcp_rcv_space_adjust(struct sock
*sk
)
440 struct tcp_sock
*tp
= tcp_sk(sk
);
444 if (tp
->rcvq_space
.time
== 0)
447 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
448 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
449 tp
->rcv_rtt_est
.rtt
== 0)
452 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
454 space
= max(tp
->rcvq_space
.space
, space
);
456 if (tp
->rcvq_space
.space
!= space
) {
459 tp
->rcvq_space
.space
= space
;
461 if (sysctl_tcp_moderate_rcvbuf
&&
462 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
463 int new_clamp
= space
;
465 /* Receive space grows, normalize in order to
466 * take into account packet headers and sk_buff
467 * structure overhead.
472 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
473 16 + sizeof(struct sk_buff
));
474 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
477 space
= min(space
, sysctl_tcp_rmem
[2]);
478 if (space
> sk
->sk_rcvbuf
) {
479 sk
->sk_rcvbuf
= space
;
481 /* Make the window clamp follow along. */
482 tp
->window_clamp
= new_clamp
;
488 tp
->rcvq_space
.seq
= tp
->copied_seq
;
489 tp
->rcvq_space
.time
= tcp_time_stamp
;
492 /* There is something which you must keep in mind when you analyze the
493 * behavior of the tp->ato delayed ack timeout interval. When a
494 * connection starts up, we want to ack as quickly as possible. The
495 * problem is that "good" TCP's do slow start at the beginning of data
496 * transmission. The means that until we send the first few ACK's the
497 * sender will sit on his end and only queue most of his data, because
498 * he can only send snd_cwnd unacked packets at any given time. For
499 * each ACK we send, he increments snd_cwnd and transmits more of his
502 static void tcp_event_data_recv(struct sock
*sk
, struct tcp_sock
*tp
, struct sk_buff
*skb
)
504 struct inet_connection_sock
*icsk
= inet_csk(sk
);
507 inet_csk_schedule_ack(sk
);
509 tcp_measure_rcv_mss(sk
, skb
);
511 tcp_rcv_rtt_measure(tp
);
513 now
= tcp_time_stamp
;
515 if (!icsk
->icsk_ack
.ato
) {
516 /* The _first_ data packet received, initialize
517 * delayed ACK engine.
519 tcp_incr_quickack(sk
);
520 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
522 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
524 if (m
<= TCP_ATO_MIN
/2) {
525 /* The fastest case is the first. */
526 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
527 } else if (m
< icsk
->icsk_ack
.ato
) {
528 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
529 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
530 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
531 } else if (m
> icsk
->icsk_rto
) {
532 /* Too long gap. Apparently sender failed to
533 * restart window, so that we send ACKs quickly.
535 tcp_incr_quickack(sk
);
536 sk_stream_mem_reclaim(sk
);
539 icsk
->icsk_ack
.lrcvtime
= now
;
541 TCP_ECN_check_ce(tp
, skb
);
544 tcp_grow_window(sk
, tp
, skb
);
547 /* Called to compute a smoothed rtt estimate. The data fed to this
548 * routine either comes from timestamps, or from segments that were
549 * known _not_ to have been retransmitted [see Karn/Partridge
550 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
551 * piece by Van Jacobson.
552 * NOTE: the next three routines used to be one big routine.
553 * To save cycles in the RFC 1323 implementation it was better to break
554 * it up into three procedures. -- erics
556 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
558 struct tcp_sock
*tp
= tcp_sk(sk
);
559 long m
= mrtt
; /* RTT */
561 /* The following amusing code comes from Jacobson's
562 * article in SIGCOMM '88. Note that rtt and mdev
563 * are scaled versions of rtt and mean deviation.
564 * This is designed to be as fast as possible
565 * m stands for "measurement".
567 * On a 1990 paper the rto value is changed to:
568 * RTO = rtt + 4 * mdev
570 * Funny. This algorithm seems to be very broken.
571 * These formulae increase RTO, when it should be decreased, increase
572 * too slowly, when it should be increased quickly, decrease too quickly
573 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
574 * does not matter how to _calculate_ it. Seems, it was trap
575 * that VJ failed to avoid. 8)
580 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
581 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
583 m
= -m
; /* m is now abs(error) */
584 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
585 /* This is similar to one of Eifel findings.
586 * Eifel blocks mdev updates when rtt decreases.
587 * This solution is a bit different: we use finer gain
588 * for mdev in this case (alpha*beta).
589 * Like Eifel it also prevents growth of rto,
590 * but also it limits too fast rto decreases,
591 * happening in pure Eifel.
596 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
598 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
599 if (tp
->mdev
> tp
->mdev_max
) {
600 tp
->mdev_max
= tp
->mdev
;
601 if (tp
->mdev_max
> tp
->rttvar
)
602 tp
->rttvar
= tp
->mdev_max
;
604 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
605 if (tp
->mdev_max
< tp
->rttvar
)
606 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
607 tp
->rtt_seq
= tp
->snd_nxt
;
608 tp
->mdev_max
= TCP_RTO_MIN
;
611 /* no previous measure. */
612 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
613 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
614 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
615 tp
->rtt_seq
= tp
->snd_nxt
;
619 /* Calculate rto without backoff. This is the second half of Van Jacobson's
620 * routine referred to above.
622 static inline void tcp_set_rto(struct sock
*sk
)
624 const struct tcp_sock
*tp
= tcp_sk(sk
);
625 /* Old crap is replaced with new one. 8)
628 * 1. If rtt variance happened to be less 50msec, it is hallucination.
629 * It cannot be less due to utterly erratic ACK generation made
630 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
631 * to do with delayed acks, because at cwnd>2 true delack timeout
632 * is invisible. Actually, Linux-2.4 also generates erratic
633 * ACKs in some circumstances.
635 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
637 /* 2. Fixups made earlier cannot be right.
638 * If we do not estimate RTO correctly without them,
639 * all the algo is pure shit and should be replaced
640 * with correct one. It is exactly, which we pretend to do.
644 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
645 * guarantees that rto is higher.
647 static inline void tcp_bound_rto(struct sock
*sk
)
649 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
650 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
653 /* Save metrics learned by this TCP session.
654 This function is called only, when TCP finishes successfully
655 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
657 void tcp_update_metrics(struct sock
*sk
)
659 struct tcp_sock
*tp
= tcp_sk(sk
);
660 struct dst_entry
*dst
= __sk_dst_get(sk
);
662 if (sysctl_tcp_nometrics_save
)
667 if (dst
&& (dst
->flags
&DST_HOST
)) {
668 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
671 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
672 /* This session failed to estimate rtt. Why?
673 * Probably, no packets returned in time.
676 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
677 dst
->metrics
[RTAX_RTT
-1] = 0;
681 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
683 /* If newly calculated rtt larger than stored one,
684 * store new one. Otherwise, use EWMA. Remember,
685 * rtt overestimation is always better than underestimation.
687 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
689 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
691 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
694 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
698 /* Scale deviation to rttvar fixed point */
703 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
704 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
706 dst
->metrics
[RTAX_RTTVAR
-1] -=
707 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
710 if (tp
->snd_ssthresh
>= 0xFFFF) {
711 /* Slow start still did not finish. */
712 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
713 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
714 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
715 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
716 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
717 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
718 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
719 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
720 icsk
->icsk_ca_state
== TCP_CA_Open
) {
721 /* Cong. avoidance phase, cwnd is reliable. */
722 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
723 dst
->metrics
[RTAX_SSTHRESH
-1] =
724 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
725 if (!dst_metric_locked(dst
, RTAX_CWND
))
726 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
728 /* Else slow start did not finish, cwnd is non-sense,
729 ssthresh may be also invalid.
731 if (!dst_metric_locked(dst
, RTAX_CWND
))
732 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
733 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
734 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
735 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
736 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
739 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
740 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
741 tp
->reordering
!= sysctl_tcp_reordering
)
742 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
747 /* Numbers are taken from RFC2414. */
748 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
750 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
753 if (tp
->mss_cache
> 1460)
756 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
758 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
761 /* Set slow start threshold and cwnd not falling to slow start */
762 void tcp_enter_cwr(struct sock
*sk
)
764 struct tcp_sock
*tp
= tcp_sk(sk
);
766 tp
->prior_ssthresh
= 0;
768 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
770 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
771 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
772 tcp_packets_in_flight(tp
) + 1U);
773 tp
->snd_cwnd_cnt
= 0;
774 tp
->high_seq
= tp
->snd_nxt
;
775 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
776 TCP_ECN_queue_cwr(tp
);
778 tcp_set_ca_state(sk
, TCP_CA_CWR
);
782 /* Initialize metrics on socket. */
784 static void tcp_init_metrics(struct sock
*sk
)
786 struct tcp_sock
*tp
= tcp_sk(sk
);
787 struct dst_entry
*dst
= __sk_dst_get(sk
);
794 if (dst_metric_locked(dst
, RTAX_CWND
))
795 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
796 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
797 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
798 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
799 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
801 if (dst_metric(dst
, RTAX_REORDERING
) &&
802 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
803 tp
->rx_opt
.sack_ok
&= ~2;
804 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
807 if (dst_metric(dst
, RTAX_RTT
) == 0)
810 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
813 /* Initial rtt is determined from SYN,SYN-ACK.
814 * The segment is small and rtt may appear much
815 * less than real one. Use per-dst memory
816 * to make it more realistic.
818 * A bit of theory. RTT is time passed after "normal" sized packet
819 * is sent until it is ACKed. In normal circumstances sending small
820 * packets force peer to delay ACKs and calculation is correct too.
821 * The algorithm is adaptive and, provided we follow specs, it
822 * NEVER underestimate RTT. BUT! If peer tries to make some clever
823 * tricks sort of "quick acks" for time long enough to decrease RTT
824 * to low value, and then abruptly stops to do it and starts to delay
825 * ACKs, wait for troubles.
827 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
828 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
829 tp
->rtt_seq
= tp
->snd_nxt
;
831 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
832 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
833 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
837 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
839 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
840 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
844 /* Play conservative. If timestamps are not
845 * supported, TCP will fail to recalculate correct
846 * rtt, if initial rto is too small. FORGET ALL AND RESET!
848 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
850 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
851 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
855 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
858 struct tcp_sock
*tp
= tcp_sk(sk
);
859 if (metric
> tp
->reordering
) {
860 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
862 /* This exciting event is worth to be remembered. 8) */
864 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
866 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
868 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
870 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
871 #if FASTRETRANS_DEBUG > 1
872 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
873 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
877 tp
->undo_marker
? tp
->undo_retrans
: 0);
879 /* Disable FACK yet. */
880 tp
->rx_opt
.sack_ok
&= ~2;
884 /* This procedure tags the retransmission queue when SACKs arrive.
886 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
887 * Packets in queue with these bits set are counted in variables
888 * sacked_out, retrans_out and lost_out, correspondingly.
890 * Valid combinations are:
891 * Tag InFlight Description
892 * 0 1 - orig segment is in flight.
893 * S 0 - nothing flies, orig reached receiver.
894 * L 0 - nothing flies, orig lost by net.
895 * R 2 - both orig and retransmit are in flight.
896 * L|R 1 - orig is lost, retransmit is in flight.
897 * S|R 1 - orig reached receiver, retrans is still in flight.
898 * (L|S|R is logically valid, it could occur when L|R is sacked,
899 * but it is equivalent to plain S and code short-curcuits it to S.
900 * L|S is logically invalid, it would mean -1 packet in flight 8))
902 * These 6 states form finite state machine, controlled by the following events:
903 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
904 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
905 * 3. Loss detection event of one of three flavors:
906 * A. Scoreboard estimator decided the packet is lost.
907 * A'. Reno "three dupacks" marks head of queue lost.
908 * A''. Its FACK modfication, head until snd.fack is lost.
909 * B. SACK arrives sacking data transmitted after never retransmitted
911 * C. SACK arrives sacking SND.NXT at the moment, when the
912 * segment was retransmitted.
913 * 4. D-SACK added new rule: D-SACK changes any tag to S.
915 * It is pleasant to note, that state diagram turns out to be commutative,
916 * so that we are allowed not to be bothered by order of our actions,
917 * when multiple events arrive simultaneously. (see the function below).
919 * Reordering detection.
920 * --------------------
921 * Reordering metric is maximal distance, which a packet can be displaced
922 * in packet stream. With SACKs we can estimate it:
924 * 1. SACK fills old hole and the corresponding segment was not
925 * ever retransmitted -> reordering. Alas, we cannot use it
926 * when segment was retransmitted.
927 * 2. The last flaw is solved with D-SACK. D-SACK arrives
928 * for retransmitted and already SACKed segment -> reordering..
929 * Both of these heuristics are not used in Loss state, when we cannot
930 * account for retransmits accurately.
933 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
935 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
936 struct tcp_sock
*tp
= tcp_sk(sk
);
937 unsigned char *ptr
= ack_skb
->h
.raw
+ TCP_SKB_CB(ack_skb
)->sacked
;
938 struct tcp_sack_block_wire
*sp
= (struct tcp_sack_block_wire
*)(ptr
+2);
939 struct sk_buff
*cached_skb
;
940 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
941 int reord
= tp
->packets_out
;
943 u32 lost_retrans
= 0;
946 int cached_fack_count
;
948 int first_sack_index
;
952 prior_fackets
= tp
->fackets_out
;
954 /* Check for D-SACK. */
955 if (before(ntohl(sp
[0].start_seq
), TCP_SKB_CB(ack_skb
)->ack_seq
)) {
957 tp
->rx_opt
.sack_ok
|= 4;
958 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
959 } else if (num_sacks
> 1 &&
960 !after(ntohl(sp
[0].end_seq
), ntohl(sp
[1].end_seq
)) &&
961 !before(ntohl(sp
[0].start_seq
), ntohl(sp
[1].start_seq
))) {
963 tp
->rx_opt
.sack_ok
|= 4;
964 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
967 /* D-SACK for already forgotten data...
968 * Do dumb counting. */
970 !after(ntohl(sp
[0].end_seq
), prior_snd_una
) &&
971 after(ntohl(sp
[0].end_seq
), tp
->undo_marker
))
974 /* Eliminate too old ACKs, but take into
975 * account more or less fresh ones, they can
976 * contain valid SACK info.
978 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
982 * if the only SACK change is the increase of the end_seq of
983 * the first block then only apply that SACK block
984 * and use retrans queue hinting otherwise slowpath */
986 for (i
= 0; i
< num_sacks
; i
++) {
987 __be32 start_seq
= sp
[i
].start_seq
;
988 __be32 end_seq
= sp
[i
].end_seq
;
991 if (tp
->recv_sack_cache
[i
].start_seq
!= start_seq
)
994 if ((tp
->recv_sack_cache
[i
].start_seq
!= start_seq
) ||
995 (tp
->recv_sack_cache
[i
].end_seq
!= end_seq
))
998 tp
->recv_sack_cache
[i
].start_seq
= start_seq
;
999 tp
->recv_sack_cache
[i
].end_seq
= end_seq
;
1001 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1002 for (; i
< ARRAY_SIZE(tp
->recv_sack_cache
); i
++) {
1003 tp
->recv_sack_cache
[i
].start_seq
= 0;
1004 tp
->recv_sack_cache
[i
].end_seq
= 0;
1007 first_sack_index
= 0;
1012 tp
->fastpath_skb_hint
= NULL
;
1014 /* order SACK blocks to allow in order walk of the retrans queue */
1015 for (i
= num_sacks
-1; i
> 0; i
--) {
1016 for (j
= 0; j
< i
; j
++){
1017 if (after(ntohl(sp
[j
].start_seq
),
1018 ntohl(sp
[j
+1].start_seq
))){
1019 struct tcp_sack_block_wire tmp
;
1025 /* Track where the first SACK block goes to */
1026 if (j
== first_sack_index
)
1027 first_sack_index
= j
+1;
1034 /* clear flag as used for different purpose in following code */
1037 /* Use SACK fastpath hint if valid */
1038 cached_skb
= tp
->fastpath_skb_hint
;
1039 cached_fack_count
= tp
->fastpath_cnt_hint
;
1041 cached_skb
= sk
->sk_write_queue
.next
;
1042 cached_fack_count
= 0;
1045 for (i
=0; i
<num_sacks
; i
++, sp
++) {
1046 struct sk_buff
*skb
;
1047 __u32 start_seq
= ntohl(sp
->start_seq
);
1048 __u32 end_seq
= ntohl(sp
->end_seq
);
1052 fack_count
= cached_fack_count
;
1054 /* Event "B" in the comment above. */
1055 if (after(end_seq
, tp
->high_seq
))
1056 flag
|= FLAG_DATA_LOST
;
1058 sk_stream_for_retrans_queue_from(skb
, sk
) {
1059 int in_sack
, pcount
;
1063 cached_fack_count
= fack_count
;
1064 if (i
== first_sack_index
) {
1065 tp
->fastpath_skb_hint
= skb
;
1066 tp
->fastpath_cnt_hint
= fack_count
;
1069 /* The retransmission queue is always in order, so
1070 * we can short-circuit the walk early.
1072 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1075 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1076 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1078 pcount
= tcp_skb_pcount(skb
);
1080 if (pcount
> 1 && !in_sack
&&
1081 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1082 unsigned int pkt_len
;
1084 in_sack
= !after(start_seq
,
1085 TCP_SKB_CB(skb
)->seq
);
1088 pkt_len
= (start_seq
-
1089 TCP_SKB_CB(skb
)->seq
);
1091 pkt_len
= (end_seq
-
1092 TCP_SKB_CB(skb
)->seq
);
1093 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
))
1095 pcount
= tcp_skb_pcount(skb
);
1098 fack_count
+= pcount
;
1100 sacked
= TCP_SKB_CB(skb
)->sacked
;
1102 /* Account D-SACK for retransmitted packet. */
1103 if ((dup_sack
&& in_sack
) &&
1104 (sacked
& TCPCB_RETRANS
) &&
1105 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1108 /* The frame is ACKed. */
1109 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
1110 if (sacked
&TCPCB_RETRANS
) {
1111 if ((dup_sack
&& in_sack
) &&
1112 (sacked
&TCPCB_SACKED_ACKED
))
1113 reord
= min(fack_count
, reord
);
1115 /* If it was in a hole, we detected reordering. */
1116 if (fack_count
< prior_fackets
&&
1117 !(sacked
&TCPCB_SACKED_ACKED
))
1118 reord
= min(fack_count
, reord
);
1121 /* Nothing to do; acked frame is about to be dropped. */
1125 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1126 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1127 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1128 lost_retrans
= end_seq
;
1133 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1134 if (sacked
& TCPCB_SACKED_RETRANS
) {
1135 /* If the segment is not tagged as lost,
1136 * we do not clear RETRANS, believing
1137 * that retransmission is still in flight.
1139 if (sacked
& TCPCB_LOST
) {
1140 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1141 tp
->lost_out
-= tcp_skb_pcount(skb
);
1142 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1144 /* clear lost hint */
1145 tp
->retransmit_skb_hint
= NULL
;
1148 /* New sack for not retransmitted frame,
1149 * which was in hole. It is reordering.
1151 if (!(sacked
& TCPCB_RETRANS
) &&
1152 fack_count
< prior_fackets
)
1153 reord
= min(fack_count
, reord
);
1155 if (sacked
& TCPCB_LOST
) {
1156 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1157 tp
->lost_out
-= tcp_skb_pcount(skb
);
1159 /* clear lost hint */
1160 tp
->retransmit_skb_hint
= NULL
;
1164 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1165 flag
|= FLAG_DATA_SACKED
;
1166 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1168 if (fack_count
> tp
->fackets_out
)
1169 tp
->fackets_out
= fack_count
;
1171 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1172 reord
= min(fack_count
, reord
);
1175 /* D-SACK. We can detect redundant retransmission
1176 * in S|R and plain R frames and clear it.
1177 * undo_retrans is decreased above, L|R frames
1178 * are accounted above as well.
1181 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1182 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1183 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1184 tp
->retransmit_skb_hint
= NULL
;
1189 /* Check for lost retransmit. This superb idea is
1190 * borrowed from "ratehalving". Event "C".
1191 * Later note: FACK people cheated me again 8),
1192 * we have to account for reordering! Ugly,
1195 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1196 struct sk_buff
*skb
;
1198 sk_stream_for_retrans_queue(skb
, sk
) {
1199 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1201 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1203 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1204 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1206 !before(lost_retrans
,
1207 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1209 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1210 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1212 /* clear lost hint */
1213 tp
->retransmit_skb_hint
= NULL
;
1215 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1216 tp
->lost_out
+= tcp_skb_pcount(skb
);
1217 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1218 flag
|= FLAG_DATA_SACKED
;
1219 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1225 tp
->left_out
= tp
->sacked_out
+ tp
->lost_out
;
1227 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
)
1228 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1230 #if FASTRETRANS_DEBUG > 0
1231 BUG_TRAP((int)tp
->sacked_out
>= 0);
1232 BUG_TRAP((int)tp
->lost_out
>= 0);
1233 BUG_TRAP((int)tp
->retrans_out
>= 0);
1234 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1239 /* F-RTO can only be used if these conditions are satisfied:
1240 * - there must be some unsent new data
1241 * - the advertised window should allow sending it
1243 int tcp_use_frto(const struct sock
*sk
)
1245 const struct tcp_sock
*tp
= tcp_sk(sk
);
1247 return (sysctl_tcp_frto
&& sk
->sk_send_head
&&
1248 !after(TCP_SKB_CB(sk
->sk_send_head
)->end_seq
,
1249 tp
->snd_una
+ tp
->snd_wnd
));
1252 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1253 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1254 * the RTO was spurious.
1256 * Do like tcp_enter_loss() would; when RTO expires the second time it
1258 * "Reduce ssthresh if it has not yet been made inside this window."
1260 void tcp_enter_frto(struct sock
*sk
)
1262 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1263 struct tcp_sock
*tp
= tcp_sk(sk
);
1264 struct sk_buff
*skb
;
1266 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1267 tp
->snd_una
== tp
->high_seq
||
1268 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1269 !icsk
->icsk_retransmits
)) {
1270 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1271 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1272 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1275 /* Have to clear retransmission markers here to keep the bookkeeping
1276 * in shape, even though we are not yet in Loss state.
1277 * If something was really lost, it is eventually caught up
1278 * in tcp_enter_frto_loss.
1280 tp
->retrans_out
= 0;
1281 tp
->undo_marker
= tp
->snd_una
;
1282 tp
->undo_retrans
= 0;
1284 sk_stream_for_retrans_queue(skb
, sk
) {
1285 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1287 tcp_sync_left_out(tp
);
1289 tcp_set_ca_state(sk
, TCP_CA_Open
);
1290 tp
->frto_highmark
= tp
->snd_nxt
;
1291 tp
->frto_counter
= 1;
1294 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1295 * which indicates that we should follow the traditional RTO recovery,
1296 * i.e. mark everything lost and do go-back-N retransmission.
1298 static void tcp_enter_frto_loss(struct sock
*sk
)
1300 struct tcp_sock
*tp
= tcp_sk(sk
);
1301 struct sk_buff
*skb
;
1306 tp
->fackets_out
= 0;
1308 sk_stream_for_retrans_queue(skb
, sk
) {
1309 cnt
+= tcp_skb_pcount(skb
);
1310 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1311 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1313 /* Do not mark those segments lost that were
1314 * forward transmitted after RTO
1316 if (!after(TCP_SKB_CB(skb
)->end_seq
,
1317 tp
->frto_highmark
)) {
1318 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1319 tp
->lost_out
+= tcp_skb_pcount(skb
);
1322 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1323 tp
->fackets_out
= cnt
;
1326 tcp_sync_left_out(tp
);
1328 tp
->snd_cwnd
= tp
->frto_counter
+ tcp_packets_in_flight(tp
)+1;
1329 tp
->snd_cwnd_cnt
= 0;
1330 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1331 tp
->undo_marker
= 0;
1332 tp
->frto_counter
= 0;
1334 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1335 sysctl_tcp_reordering
);
1336 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1337 tp
->high_seq
= tp
->frto_highmark
;
1338 TCP_ECN_queue_cwr(tp
);
1340 clear_all_retrans_hints(tp
);
1343 void tcp_clear_retrans(struct tcp_sock
*tp
)
1346 tp
->retrans_out
= 0;
1348 tp
->fackets_out
= 0;
1352 tp
->undo_marker
= 0;
1353 tp
->undo_retrans
= 0;
1356 /* Enter Loss state. If "how" is not zero, forget all SACK information
1357 * and reset tags completely, otherwise preserve SACKs. If receiver
1358 * dropped its ofo queue, we will know this due to reneging detection.
1360 void tcp_enter_loss(struct sock
*sk
, int how
)
1362 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1363 struct tcp_sock
*tp
= tcp_sk(sk
);
1364 struct sk_buff
*skb
;
1367 /* Reduce ssthresh if it has not yet been made inside this window. */
1368 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1369 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1370 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1371 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1372 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1375 tp
->snd_cwnd_cnt
= 0;
1376 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1378 tp
->bytes_acked
= 0;
1379 tcp_clear_retrans(tp
);
1381 /* Push undo marker, if it was plain RTO and nothing
1382 * was retransmitted. */
1384 tp
->undo_marker
= tp
->snd_una
;
1386 sk_stream_for_retrans_queue(skb
, sk
) {
1387 cnt
+= tcp_skb_pcount(skb
);
1388 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1389 tp
->undo_marker
= 0;
1390 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1391 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1392 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1393 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1394 tp
->lost_out
+= tcp_skb_pcount(skb
);
1396 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1397 tp
->fackets_out
= cnt
;
1400 tcp_sync_left_out(tp
);
1402 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1403 sysctl_tcp_reordering
);
1404 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1405 tp
->high_seq
= tp
->snd_nxt
;
1406 TCP_ECN_queue_cwr(tp
);
1408 clear_all_retrans_hints(tp
);
1411 static int tcp_check_sack_reneging(struct sock
*sk
)
1413 struct sk_buff
*skb
;
1415 /* If ACK arrived pointing to a remembered SACK,
1416 * it means that our remembered SACKs do not reflect
1417 * real state of receiver i.e.
1418 * receiver _host_ is heavily congested (or buggy).
1419 * Do processing similar to RTO timeout.
1421 if ((skb
= skb_peek(&sk
->sk_write_queue
)) != NULL
&&
1422 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1423 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1424 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1426 tcp_enter_loss(sk
, 1);
1427 icsk
->icsk_retransmits
++;
1428 tcp_retransmit_skb(sk
, skb_peek(&sk
->sk_write_queue
));
1429 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1430 icsk
->icsk_rto
, TCP_RTO_MAX
);
1436 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1438 return IsReno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1441 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1443 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1446 static inline int tcp_head_timedout(struct sock
*sk
, struct tcp_sock
*tp
)
1448 return tp
->packets_out
&&
1449 tcp_skb_timedout(sk
, skb_peek(&sk
->sk_write_queue
));
1452 /* Linux NewReno/SACK/FACK/ECN state machine.
1453 * --------------------------------------
1455 * "Open" Normal state, no dubious events, fast path.
1456 * "Disorder" In all the respects it is "Open",
1457 * but requires a bit more attention. It is entered when
1458 * we see some SACKs or dupacks. It is split of "Open"
1459 * mainly to move some processing from fast path to slow one.
1460 * "CWR" CWND was reduced due to some Congestion Notification event.
1461 * It can be ECN, ICMP source quench, local device congestion.
1462 * "Recovery" CWND was reduced, we are fast-retransmitting.
1463 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1465 * tcp_fastretrans_alert() is entered:
1466 * - each incoming ACK, if state is not "Open"
1467 * - when arrived ACK is unusual, namely:
1472 * Counting packets in flight is pretty simple.
1474 * in_flight = packets_out - left_out + retrans_out
1476 * packets_out is SND.NXT-SND.UNA counted in packets.
1478 * retrans_out is number of retransmitted segments.
1480 * left_out is number of segments left network, but not ACKed yet.
1482 * left_out = sacked_out + lost_out
1484 * sacked_out: Packets, which arrived to receiver out of order
1485 * and hence not ACKed. With SACKs this number is simply
1486 * amount of SACKed data. Even without SACKs
1487 * it is easy to give pretty reliable estimate of this number,
1488 * counting duplicate ACKs.
1490 * lost_out: Packets lost by network. TCP has no explicit
1491 * "loss notification" feedback from network (for now).
1492 * It means that this number can be only _guessed_.
1493 * Actually, it is the heuristics to predict lossage that
1494 * distinguishes different algorithms.
1496 * F.e. after RTO, when all the queue is considered as lost,
1497 * lost_out = packets_out and in_flight = retrans_out.
1499 * Essentially, we have now two algorithms counting
1502 * FACK: It is the simplest heuristics. As soon as we decided
1503 * that something is lost, we decide that _all_ not SACKed
1504 * packets until the most forward SACK are lost. I.e.
1505 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1506 * It is absolutely correct estimate, if network does not reorder
1507 * packets. And it loses any connection to reality when reordering
1508 * takes place. We use FACK by default until reordering
1509 * is suspected on the path to this destination.
1511 * NewReno: when Recovery is entered, we assume that one segment
1512 * is lost (classic Reno). While we are in Recovery and
1513 * a partial ACK arrives, we assume that one more packet
1514 * is lost (NewReno). This heuristics are the same in NewReno
1517 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1518 * deflation etc. CWND is real congestion window, never inflated, changes
1519 * only according to classic VJ rules.
1521 * Really tricky (and requiring careful tuning) part of algorithm
1522 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1523 * The first determines the moment _when_ we should reduce CWND and,
1524 * hence, slow down forward transmission. In fact, it determines the moment
1525 * when we decide that hole is caused by loss, rather than by a reorder.
1527 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1528 * holes, caused by lost packets.
1530 * And the most logically complicated part of algorithm is undo
1531 * heuristics. We detect false retransmits due to both too early
1532 * fast retransmit (reordering) and underestimated RTO, analyzing
1533 * timestamps and D-SACKs. When we detect that some segments were
1534 * retransmitted by mistake and CWND reduction was wrong, we undo
1535 * window reduction and abort recovery phase. This logic is hidden
1536 * inside several functions named tcp_try_undo_<something>.
1539 /* This function decides, when we should leave Disordered state
1540 * and enter Recovery phase, reducing congestion window.
1542 * Main question: may we further continue forward transmission
1543 * with the same cwnd?
1545 static int tcp_time_to_recover(struct sock
*sk
, struct tcp_sock
*tp
)
1549 /* Trick#1: The loss is proven. */
1553 /* Not-A-Trick#2 : Classic rule... */
1554 if (tcp_fackets_out(tp
) > tp
->reordering
)
1557 /* Trick#3 : when we use RFC2988 timer restart, fast
1558 * retransmit can be triggered by timeout of queue head.
1560 if (tcp_head_timedout(sk
, tp
))
1563 /* Trick#4: It is still not OK... But will it be useful to delay
1566 packets_out
= tp
->packets_out
;
1567 if (packets_out
<= tp
->reordering
&&
1568 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1569 !tcp_may_send_now(sk
, tp
)) {
1570 /* We have nothing to send. This connection is limited
1571 * either by receiver window or by application.
1579 /* If we receive more dupacks than we expected counting segments
1580 * in assumption of absent reordering, interpret this as reordering.
1581 * The only another reason could be bug in receiver TCP.
1583 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1585 struct tcp_sock
*tp
= tcp_sk(sk
);
1588 holes
= max(tp
->lost_out
, 1U);
1589 holes
= min(holes
, tp
->packets_out
);
1591 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1592 tp
->sacked_out
= tp
->packets_out
- holes
;
1593 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1597 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1599 static void tcp_add_reno_sack(struct sock
*sk
)
1601 struct tcp_sock
*tp
= tcp_sk(sk
);
1603 tcp_check_reno_reordering(sk
, 0);
1604 tcp_sync_left_out(tp
);
1607 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1609 static void tcp_remove_reno_sacks(struct sock
*sk
, struct tcp_sock
*tp
, int acked
)
1612 /* One ACK acked hole. The rest eat duplicate ACKs. */
1613 if (acked
-1 >= tp
->sacked_out
)
1616 tp
->sacked_out
-= acked
-1;
1618 tcp_check_reno_reordering(sk
, acked
);
1619 tcp_sync_left_out(tp
);
1622 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1625 tp
->left_out
= tp
->lost_out
;
1628 /* Mark head of queue up as lost. */
1629 static void tcp_mark_head_lost(struct sock
*sk
, struct tcp_sock
*tp
,
1630 int packets
, u32 high_seq
)
1632 struct sk_buff
*skb
;
1635 BUG_TRAP(packets
<= tp
->packets_out
);
1636 if (tp
->lost_skb_hint
) {
1637 skb
= tp
->lost_skb_hint
;
1638 cnt
= tp
->lost_cnt_hint
;
1640 skb
= sk
->sk_write_queue
.next
;
1644 sk_stream_for_retrans_queue_from(skb
, sk
) {
1645 /* TODO: do this better */
1646 /* this is not the most efficient way to do this... */
1647 tp
->lost_skb_hint
= skb
;
1648 tp
->lost_cnt_hint
= cnt
;
1649 cnt
+= tcp_skb_pcount(skb
);
1650 if (cnt
> packets
|| after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1652 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1653 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1654 tp
->lost_out
+= tcp_skb_pcount(skb
);
1656 /* clear xmit_retransmit_queue hints
1657 * if this is beyond hint */
1658 if(tp
->retransmit_skb_hint
!= NULL
&&
1659 before(TCP_SKB_CB(skb
)->seq
,
1660 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
)) {
1662 tp
->retransmit_skb_hint
= NULL
;
1666 tcp_sync_left_out(tp
);
1669 /* Account newly detected lost packet(s) */
1671 static void tcp_update_scoreboard(struct sock
*sk
, struct tcp_sock
*tp
)
1674 int lost
= tp
->fackets_out
- tp
->reordering
;
1677 tcp_mark_head_lost(sk
, tp
, lost
, tp
->high_seq
);
1679 tcp_mark_head_lost(sk
, tp
, 1, tp
->high_seq
);
1682 /* New heuristics: it is possible only after we switched
1683 * to restart timer each time when something is ACKed.
1684 * Hence, we can detect timed out packets during fast
1685 * retransmit without falling to slow start.
1687 if (!IsReno(tp
) && tcp_head_timedout(sk
, tp
)) {
1688 struct sk_buff
*skb
;
1690 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
1691 : sk
->sk_write_queue
.next
;
1693 sk_stream_for_retrans_queue_from(skb
, sk
) {
1694 if (!tcp_skb_timedout(sk
, skb
))
1697 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1698 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1699 tp
->lost_out
+= tcp_skb_pcount(skb
);
1701 /* clear xmit_retrans hint */
1702 if (tp
->retransmit_skb_hint
&&
1703 before(TCP_SKB_CB(skb
)->seq
,
1704 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1706 tp
->retransmit_skb_hint
= NULL
;
1710 tp
->scoreboard_skb_hint
= skb
;
1712 tcp_sync_left_out(tp
);
1716 /* CWND moderation, preventing bursts due to too big ACKs
1717 * in dubious situations.
1719 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
1721 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
1722 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
1723 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1726 /* Lower bound on congestion window is slow start threshold
1727 * unless congestion avoidance choice decides to overide it.
1729 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
1731 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1733 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
1736 /* Decrease cwnd each second ack. */
1737 static void tcp_cwnd_down(struct sock
*sk
)
1739 struct tcp_sock
*tp
= tcp_sk(sk
);
1740 int decr
= tp
->snd_cwnd_cnt
+ 1;
1742 tp
->snd_cwnd_cnt
= decr
&1;
1745 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
1746 tp
->snd_cwnd
-= decr
;
1748 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
1749 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1752 /* Nothing was retransmitted or returned timestamp is less
1753 * than timestamp of the first retransmission.
1755 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
1757 return !tp
->retrans_stamp
||
1758 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
1759 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
1762 /* Undo procedures. */
1764 #if FASTRETRANS_DEBUG > 1
1765 static void DBGUNDO(struct sock
*sk
, struct tcp_sock
*tp
, const char *msg
)
1767 struct inet_sock
*inet
= inet_sk(sk
);
1768 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1770 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
1771 tp
->snd_cwnd
, tp
->left_out
,
1772 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
1776 #define DBGUNDO(x...) do { } while (0)
1779 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
1781 struct tcp_sock
*tp
= tcp_sk(sk
);
1783 if (tp
->prior_ssthresh
) {
1784 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1786 if (icsk
->icsk_ca_ops
->undo_cwnd
)
1787 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
1789 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
1791 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
1792 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
1793 TCP_ECN_withdraw_cwr(tp
);
1796 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1798 tcp_moderate_cwnd(tp
);
1799 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1801 /* There is something screwy going on with the retrans hints after
1803 clear_all_retrans_hints(tp
);
1806 static inline int tcp_may_undo(struct tcp_sock
*tp
)
1808 return tp
->undo_marker
&&
1809 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
1812 /* People celebrate: "We love our President!" */
1813 static int tcp_try_undo_recovery(struct sock
*sk
, struct tcp_sock
*tp
)
1815 if (tcp_may_undo(tp
)) {
1816 /* Happy end! We did not retransmit anything
1817 * or our original transmission succeeded.
1819 DBGUNDO(sk
, tp
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
1820 tcp_undo_cwr(sk
, 1);
1821 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
1822 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1824 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
1825 tp
->undo_marker
= 0;
1827 if (tp
->snd_una
== tp
->high_seq
&& IsReno(tp
)) {
1828 /* Hold old state until something *above* high_seq
1829 * is ACKed. For Reno it is MUST to prevent false
1830 * fast retransmits (RFC2582). SACK TCP is safe. */
1831 tcp_moderate_cwnd(tp
);
1834 tcp_set_ca_state(sk
, TCP_CA_Open
);
1838 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1839 static void tcp_try_undo_dsack(struct sock
*sk
, struct tcp_sock
*tp
)
1841 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
1842 DBGUNDO(sk
, tp
, "D-SACK");
1843 tcp_undo_cwr(sk
, 1);
1844 tp
->undo_marker
= 0;
1845 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
1849 /* Undo during fast recovery after partial ACK. */
1851 static int tcp_try_undo_partial(struct sock
*sk
, struct tcp_sock
*tp
,
1854 /* Partial ACK arrived. Force Hoe's retransmit. */
1855 int failed
= IsReno(tp
) || tp
->fackets_out
>tp
->reordering
;
1857 if (tcp_may_undo(tp
)) {
1858 /* Plain luck! Hole if filled with delayed
1859 * packet, rather than with a retransmit.
1861 if (tp
->retrans_out
== 0)
1862 tp
->retrans_stamp
= 0;
1864 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
1866 DBGUNDO(sk
, tp
, "Hoe");
1867 tcp_undo_cwr(sk
, 0);
1868 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
1870 /* So... Do not make Hoe's retransmit yet.
1871 * If the first packet was delayed, the rest
1872 * ones are most probably delayed as well.
1879 /* Undo during loss recovery after partial ACK. */
1880 static int tcp_try_undo_loss(struct sock
*sk
, struct tcp_sock
*tp
)
1882 if (tcp_may_undo(tp
)) {
1883 struct sk_buff
*skb
;
1884 sk_stream_for_retrans_queue(skb
, sk
) {
1885 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1888 clear_all_retrans_hints(tp
);
1890 DBGUNDO(sk
, tp
, "partial loss");
1892 tp
->left_out
= tp
->sacked_out
;
1893 tcp_undo_cwr(sk
, 1);
1894 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1895 inet_csk(sk
)->icsk_retransmits
= 0;
1896 tp
->undo_marker
= 0;
1898 tcp_set_ca_state(sk
, TCP_CA_Open
);
1904 static inline void tcp_complete_cwr(struct sock
*sk
)
1906 struct tcp_sock
*tp
= tcp_sk(sk
);
1907 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1908 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1909 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
1912 static void tcp_try_to_open(struct sock
*sk
, struct tcp_sock
*tp
, int flag
)
1914 tp
->left_out
= tp
->sacked_out
;
1916 if (tp
->retrans_out
== 0)
1917 tp
->retrans_stamp
= 0;
1922 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
1923 int state
= TCP_CA_Open
;
1925 if (tp
->left_out
|| tp
->retrans_out
|| tp
->undo_marker
)
1926 state
= TCP_CA_Disorder
;
1928 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
1929 tcp_set_ca_state(sk
, state
);
1930 tp
->high_seq
= tp
->snd_nxt
;
1932 tcp_moderate_cwnd(tp
);
1938 static void tcp_mtup_probe_failed(struct sock
*sk
)
1940 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1942 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
1943 icsk
->icsk_mtup
.probe_size
= 0;
1946 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
1948 struct tcp_sock
*tp
= tcp_sk(sk
);
1949 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1951 /* FIXME: breaks with very large cwnd */
1952 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1953 tp
->snd_cwnd
= tp
->snd_cwnd
*
1954 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
1955 icsk
->icsk_mtup
.probe_size
;
1956 tp
->snd_cwnd_cnt
= 0;
1957 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1958 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
1960 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
1961 icsk
->icsk_mtup
.probe_size
= 0;
1962 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
1966 /* Process an event, which can update packets-in-flight not trivially.
1967 * Main goal of this function is to calculate new estimate for left_out,
1968 * taking into account both packets sitting in receiver's buffer and
1969 * packets lost by network.
1971 * Besides that it does CWND reduction, when packet loss is detected
1972 * and changes state of machine.
1974 * It does _not_ decide what to send, it is made in function
1975 * tcp_xmit_retransmit_queue().
1978 tcp_fastretrans_alert(struct sock
*sk
, u32 prior_snd_una
,
1979 int prior_packets
, int flag
)
1981 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1982 struct tcp_sock
*tp
= tcp_sk(sk
);
1983 int is_dupack
= (tp
->snd_una
== prior_snd_una
&& !(flag
&FLAG_NOT_DUP
));
1985 /* Some technical things:
1986 * 1. Reno does not count dupacks (sacked_out) automatically. */
1987 if (!tp
->packets_out
)
1989 /* 2. SACK counts snd_fack in packets inaccurately. */
1990 if (tp
->sacked_out
== 0)
1991 tp
->fackets_out
= 0;
1993 /* Now state machine starts.
1994 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
1996 tp
->prior_ssthresh
= 0;
1998 /* B. In all the states check for reneging SACKs. */
1999 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
2002 /* C. Process data loss notification, provided it is valid. */
2003 if ((flag
&FLAG_DATA_LOST
) &&
2004 before(tp
->snd_una
, tp
->high_seq
) &&
2005 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2006 tp
->fackets_out
> tp
->reordering
) {
2007 tcp_mark_head_lost(sk
, tp
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
2008 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
2011 /* D. Synchronize left_out to current state. */
2012 tcp_sync_left_out(tp
);
2014 /* E. Check state exit conditions. State can be terminated
2015 * when high_seq is ACKed. */
2016 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2017 if (!sysctl_tcp_frto
)
2018 BUG_TRAP(tp
->retrans_out
== 0);
2019 tp
->retrans_stamp
= 0;
2020 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2021 switch (icsk
->icsk_ca_state
) {
2023 icsk
->icsk_retransmits
= 0;
2024 if (tcp_try_undo_recovery(sk
, tp
))
2029 /* CWR is to be held something *above* high_seq
2030 * is ACKed for CWR bit to reach receiver. */
2031 if (tp
->snd_una
!= tp
->high_seq
) {
2032 tcp_complete_cwr(sk
);
2033 tcp_set_ca_state(sk
, TCP_CA_Open
);
2037 case TCP_CA_Disorder
:
2038 tcp_try_undo_dsack(sk
, tp
);
2039 if (!tp
->undo_marker
||
2040 /* For SACK case do not Open to allow to undo
2041 * catching for all duplicate ACKs. */
2042 IsReno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2043 tp
->undo_marker
= 0;
2044 tcp_set_ca_state(sk
, TCP_CA_Open
);
2048 case TCP_CA_Recovery
:
2050 tcp_reset_reno_sack(tp
);
2051 if (tcp_try_undo_recovery(sk
, tp
))
2053 tcp_complete_cwr(sk
);
2058 /* F. Process state. */
2059 switch (icsk
->icsk_ca_state
) {
2060 case TCP_CA_Recovery
:
2061 if (prior_snd_una
== tp
->snd_una
) {
2062 if (IsReno(tp
) && is_dupack
)
2063 tcp_add_reno_sack(sk
);
2065 int acked
= prior_packets
- tp
->packets_out
;
2067 tcp_remove_reno_sacks(sk
, tp
, acked
);
2068 is_dupack
= tcp_try_undo_partial(sk
, tp
, acked
);
2072 if (flag
&FLAG_DATA_ACKED
)
2073 icsk
->icsk_retransmits
= 0;
2074 if (!tcp_try_undo_loss(sk
, tp
)) {
2075 tcp_moderate_cwnd(tp
);
2076 tcp_xmit_retransmit_queue(sk
);
2079 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2081 /* Loss is undone; fall through to processing in Open state. */
2084 if (tp
->snd_una
!= prior_snd_una
)
2085 tcp_reset_reno_sack(tp
);
2087 tcp_add_reno_sack(sk
);
2090 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2091 tcp_try_undo_dsack(sk
, tp
);
2093 if (!tcp_time_to_recover(sk
, tp
)) {
2094 tcp_try_to_open(sk
, tp
, flag
);
2098 /* MTU probe failure: don't reduce cwnd */
2099 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2100 icsk
->icsk_mtup
.probe_size
&&
2101 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2102 tcp_mtup_probe_failed(sk
);
2103 /* Restores the reduction we did in tcp_mtup_probe() */
2105 tcp_simple_retransmit(sk
);
2109 /* Otherwise enter Recovery state */
2112 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
2114 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
2116 tp
->high_seq
= tp
->snd_nxt
;
2117 tp
->prior_ssthresh
= 0;
2118 tp
->undo_marker
= tp
->snd_una
;
2119 tp
->undo_retrans
= tp
->retrans_out
;
2121 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2122 if (!(flag
&FLAG_ECE
))
2123 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2124 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2125 TCP_ECN_queue_cwr(tp
);
2128 tp
->bytes_acked
= 0;
2129 tp
->snd_cwnd_cnt
= 0;
2130 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2133 if (is_dupack
|| tcp_head_timedout(sk
, tp
))
2134 tcp_update_scoreboard(sk
, tp
);
2136 tcp_xmit_retransmit_queue(sk
);
2139 /* Read draft-ietf-tcplw-high-performance before mucking
2140 * with this code. (Supersedes RFC1323)
2142 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2144 /* RTTM Rule: A TSecr value received in a segment is used to
2145 * update the averaged RTT measurement only if the segment
2146 * acknowledges some new data, i.e., only if it advances the
2147 * left edge of the send window.
2149 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2150 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2152 * Changed: reset backoff as soon as we see the first valid sample.
2153 * If we do not, we get strongly overestimated rto. With timestamps
2154 * samples are accepted even from very old segments: f.e., when rtt=1
2155 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2156 * answer arrives rto becomes 120 seconds! If at least one of segments
2157 * in window is lost... Voila. --ANK (010210)
2159 struct tcp_sock
*tp
= tcp_sk(sk
);
2160 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2161 tcp_rtt_estimator(sk
, seq_rtt
);
2163 inet_csk(sk
)->icsk_backoff
= 0;
2167 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2169 /* We don't have a timestamp. Can only use
2170 * packets that are not retransmitted to determine
2171 * rtt estimates. Also, we must not reset the
2172 * backoff for rto until we get a non-retransmitted
2173 * packet. This allows us to deal with a situation
2174 * where the network delay has increased suddenly.
2175 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2178 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2181 tcp_rtt_estimator(sk
, seq_rtt
);
2183 inet_csk(sk
)->icsk_backoff
= 0;
2187 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2190 const struct tcp_sock
*tp
= tcp_sk(sk
);
2191 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2192 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2193 tcp_ack_saw_tstamp(sk
, flag
);
2194 else if (seq_rtt
>= 0)
2195 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2198 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 rtt
,
2199 u32 in_flight
, int good
)
2201 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2202 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, rtt
, in_flight
, good
);
2203 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2206 /* Restart timer after forward progress on connection.
2207 * RFC2988 recommends to restart timer to now+rto.
2210 static void tcp_ack_packets_out(struct sock
*sk
, struct tcp_sock
*tp
)
2212 if (!tp
->packets_out
) {
2213 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2215 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2219 static int tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
,
2220 __u32 now
, __s32
*seq_rtt
)
2222 struct tcp_sock
*tp
= tcp_sk(sk
);
2223 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2224 __u32 seq
= tp
->snd_una
;
2225 __u32 packets_acked
;
2228 /* If we get here, the whole TSO packet has not been
2231 BUG_ON(!after(scb
->end_seq
, seq
));
2233 packets_acked
= tcp_skb_pcount(skb
);
2234 if (tcp_trim_head(sk
, skb
, seq
- scb
->seq
))
2236 packets_acked
-= tcp_skb_pcount(skb
);
2238 if (packets_acked
) {
2239 __u8 sacked
= scb
->sacked
;
2241 acked
|= FLAG_DATA_ACKED
;
2243 if (sacked
& TCPCB_RETRANS
) {
2244 if (sacked
& TCPCB_SACKED_RETRANS
)
2245 tp
->retrans_out
-= packets_acked
;
2246 acked
|= FLAG_RETRANS_DATA_ACKED
;
2248 } else if (*seq_rtt
< 0)
2249 *seq_rtt
= now
- scb
->when
;
2250 if (sacked
& TCPCB_SACKED_ACKED
)
2251 tp
->sacked_out
-= packets_acked
;
2252 if (sacked
& TCPCB_LOST
)
2253 tp
->lost_out
-= packets_acked
;
2254 if (sacked
& TCPCB_URG
) {
2256 !before(seq
, tp
->snd_up
))
2259 } else if (*seq_rtt
< 0)
2260 *seq_rtt
= now
- scb
->when
;
2262 if (tp
->fackets_out
) {
2263 __u32 dval
= min(tp
->fackets_out
, packets_acked
);
2264 tp
->fackets_out
-= dval
;
2266 tp
->packets_out
-= packets_acked
;
2268 BUG_ON(tcp_skb_pcount(skb
) == 0);
2269 BUG_ON(!before(scb
->seq
, scb
->end_seq
));
2275 static u32
tcp_usrtt(struct timeval
*tv
)
2279 do_gettimeofday(&now
);
2280 return (now
.tv_sec
- tv
->tv_sec
) * 1000000 + (now
.tv_usec
- tv
->tv_usec
);
2283 /* Remove acknowledged frames from the retransmission queue. */
2284 static int tcp_clean_rtx_queue(struct sock
*sk
, __s32
*seq_rtt_p
)
2286 struct tcp_sock
*tp
= tcp_sk(sk
);
2287 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2288 struct sk_buff
*skb
;
2289 __u32 now
= tcp_time_stamp
;
2293 void (*rtt_sample
)(struct sock
*sk
, u32 usrtt
)
2294 = icsk
->icsk_ca_ops
->rtt_sample
;
2295 struct timeval tv
= { .tv_sec
= 0, .tv_usec
= 0 };
2297 while ((skb
= skb_peek(&sk
->sk_write_queue
)) &&
2298 skb
!= sk
->sk_send_head
) {
2299 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2300 __u8 sacked
= scb
->sacked
;
2302 /* If our packet is before the ack sequence we can
2303 * discard it as it's confirmed to have arrived at
2306 if (after(scb
->end_seq
, tp
->snd_una
)) {
2307 if (tcp_skb_pcount(skb
) > 1 &&
2308 after(tp
->snd_una
, scb
->seq
))
2309 acked
|= tcp_tso_acked(sk
, skb
,
2314 /* Initial outgoing SYN's get put onto the write_queue
2315 * just like anything else we transmit. It is not
2316 * true data, and if we misinform our callers that
2317 * this ACK acks real data, we will erroneously exit
2318 * connection startup slow start one packet too
2319 * quickly. This is severely frowned upon behavior.
2321 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2322 acked
|= FLAG_DATA_ACKED
;
2325 acked
|= FLAG_SYN_ACKED
;
2326 tp
->retrans_stamp
= 0;
2329 /* MTU probing checks */
2330 if (icsk
->icsk_mtup
.probe_size
) {
2331 if (!after(tp
->mtu_probe
.probe_seq_end
, TCP_SKB_CB(skb
)->end_seq
)) {
2332 tcp_mtup_probe_success(sk
, skb
);
2337 if (sacked
& TCPCB_RETRANS
) {
2338 if(sacked
& TCPCB_SACKED_RETRANS
)
2339 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2340 acked
|= FLAG_RETRANS_DATA_ACKED
;
2342 } else if (seq_rtt
< 0) {
2343 seq_rtt
= now
- scb
->when
;
2344 skb_get_timestamp(skb
, &tv
);
2346 if (sacked
& TCPCB_SACKED_ACKED
)
2347 tp
->sacked_out
-= tcp_skb_pcount(skb
);
2348 if (sacked
& TCPCB_LOST
)
2349 tp
->lost_out
-= tcp_skb_pcount(skb
);
2350 if (sacked
& TCPCB_URG
) {
2352 !before(scb
->end_seq
, tp
->snd_up
))
2355 } else if (seq_rtt
< 0) {
2356 seq_rtt
= now
- scb
->when
;
2357 skb_get_timestamp(skb
, &tv
);
2359 tcp_dec_pcount_approx(&tp
->fackets_out
, skb
);
2360 tcp_packets_out_dec(tp
, skb
);
2361 __skb_unlink(skb
, &sk
->sk_write_queue
);
2362 sk_stream_free_skb(sk
, skb
);
2363 clear_all_retrans_hints(tp
);
2366 if (acked
&FLAG_ACKED
) {
2367 tcp_ack_update_rtt(sk
, acked
, seq_rtt
);
2368 tcp_ack_packets_out(sk
, tp
);
2369 if (rtt_sample
&& !(acked
& FLAG_RETRANS_DATA_ACKED
))
2370 (*rtt_sample
)(sk
, tcp_usrtt(&tv
));
2372 if (icsk
->icsk_ca_ops
->pkts_acked
)
2373 icsk
->icsk_ca_ops
->pkts_acked(sk
, pkts_acked
);
2376 #if FASTRETRANS_DEBUG > 0
2377 BUG_TRAP((int)tp
->sacked_out
>= 0);
2378 BUG_TRAP((int)tp
->lost_out
>= 0);
2379 BUG_TRAP((int)tp
->retrans_out
>= 0);
2380 if (!tp
->packets_out
&& tp
->rx_opt
.sack_ok
) {
2381 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2383 printk(KERN_DEBUG
"Leak l=%u %d\n",
2384 tp
->lost_out
, icsk
->icsk_ca_state
);
2387 if (tp
->sacked_out
) {
2388 printk(KERN_DEBUG
"Leak s=%u %d\n",
2389 tp
->sacked_out
, icsk
->icsk_ca_state
);
2392 if (tp
->retrans_out
) {
2393 printk(KERN_DEBUG
"Leak r=%u %d\n",
2394 tp
->retrans_out
, icsk
->icsk_ca_state
);
2395 tp
->retrans_out
= 0;
2399 *seq_rtt_p
= seq_rtt
;
2403 static void tcp_ack_probe(struct sock
*sk
)
2405 const struct tcp_sock
*tp
= tcp_sk(sk
);
2406 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2408 /* Was it a usable window open? */
2410 if (!after(TCP_SKB_CB(sk
->sk_send_head
)->end_seq
,
2411 tp
->snd_una
+ tp
->snd_wnd
)) {
2412 icsk
->icsk_backoff
= 0;
2413 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2414 /* Socket must be waked up by subsequent tcp_data_snd_check().
2415 * This function is not for random using!
2418 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2419 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2424 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2426 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2427 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2430 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2432 const struct tcp_sock
*tp
= tcp_sk(sk
);
2433 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2434 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2437 /* Check that window update is acceptable.
2438 * The function assumes that snd_una<=ack<=snd_next.
2440 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2441 const u32 ack_seq
, const u32 nwin
)
2443 return (after(ack
, tp
->snd_una
) ||
2444 after(ack_seq
, tp
->snd_wl1
) ||
2445 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2448 /* Update our send window.
2450 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2451 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2453 static int tcp_ack_update_window(struct sock
*sk
, struct tcp_sock
*tp
,
2454 struct sk_buff
*skb
, u32 ack
, u32 ack_seq
)
2457 u32 nwin
= ntohs(skb
->h
.th
->window
);
2459 if (likely(!skb
->h
.th
->syn
))
2460 nwin
<<= tp
->rx_opt
.snd_wscale
;
2462 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2463 flag
|= FLAG_WIN_UPDATE
;
2464 tcp_update_wl(tp
, ack
, ack_seq
);
2466 if (tp
->snd_wnd
!= nwin
) {
2469 /* Note, it is the only place, where
2470 * fast path is recovered for sending TCP.
2473 tcp_fast_path_check(sk
, tp
);
2475 if (nwin
> tp
->max_window
) {
2476 tp
->max_window
= nwin
;
2477 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
2487 /* A very conservative spurious RTO response algorithm: reduce cwnd and
2488 * continue in congestion avoidance.
2490 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
2492 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2493 tcp_moderate_cwnd(tp
);
2496 /* F-RTO spurious RTO detection algorithm (RFC4138)
2498 * F-RTO affects during two new ACKs following RTO. State (ACK number) is kept
2499 * in frto_counter. When ACK advances window (but not to or beyond highest
2500 * sequence sent before RTO):
2501 * On First ACK, send two new segments out.
2502 * On Second ACK, RTO was likely spurious. Do spurious response (response
2503 * algorithm is not part of the F-RTO detection algorithm
2504 * given in RFC4138 but can be selected separately).
2505 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
2506 * and TCP falls back to conventional RTO recovery.
2508 * Rationale: if the RTO was spurious, new ACKs should arrive from the
2509 * original window even after we transmit two new data segments.
2511 * F-RTO is implemented (mainly) in four functions:
2512 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
2513 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
2514 * called when tcp_use_frto() showed green light
2515 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
2516 * - tcp_enter_frto_loss() is called if there is not enough evidence
2517 * to prove that the RTO is indeed spurious. It transfers the control
2518 * from F-RTO to the conventional RTO recovery
2520 static void tcp_process_frto(struct sock
*sk
, u32 prior_snd_una
, int flag
)
2522 struct tcp_sock
*tp
= tcp_sk(sk
);
2524 tcp_sync_left_out(tp
);
2526 /* Duplicate the behavior from Loss state (fastretrans_alert) */
2527 if (flag
&FLAG_DATA_ACKED
)
2528 inet_csk(sk
)->icsk_retransmits
= 0;
2530 if (tp
->snd_una
== prior_snd_una
||
2531 !before(tp
->snd_una
, tp
->frto_highmark
)) {
2532 tcp_enter_frto_loss(sk
);
2536 if (tp
->frto_counter
== 1) {
2537 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2538 } else /* frto_counter == 2 */ {
2539 tcp_conservative_spur_to_response(tp
);
2542 tp
->frto_counter
= (tp
->frto_counter
+ 1) % 3;
2545 /* This routine deals with incoming acks, but not outgoing ones. */
2546 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2548 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2549 struct tcp_sock
*tp
= tcp_sk(sk
);
2550 u32 prior_snd_una
= tp
->snd_una
;
2551 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2552 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2553 u32 prior_in_flight
;
2557 /* If the ack is newer than sent or older than previous acks
2558 * then we can probably ignore it.
2560 if (after(ack
, tp
->snd_nxt
))
2561 goto uninteresting_ack
;
2563 if (before(ack
, prior_snd_una
))
2566 if (sysctl_tcp_abc
) {
2567 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
2568 tp
->bytes_acked
+= ack
- prior_snd_una
;
2569 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
2570 /* we assume just one segment left network */
2571 tp
->bytes_acked
+= min(ack
- prior_snd_una
, tp
->mss_cache
);
2574 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2575 /* Window is constant, pure forward advance.
2576 * No more checks are required.
2577 * Note, we use the fact that SND.UNA>=SND.WL2.
2579 tcp_update_wl(tp
, ack
, ack_seq
);
2581 flag
|= FLAG_WIN_UPDATE
;
2583 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2585 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
2587 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
2590 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
2592 flag
|= tcp_ack_update_window(sk
, tp
, skb
, ack
, ack_seq
);
2594 if (TCP_SKB_CB(skb
)->sacked
)
2595 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2597 if (TCP_ECN_rcv_ecn_echo(tp
, skb
->h
.th
))
2600 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
2603 /* We passed data and got it acked, remove any soft error
2604 * log. Something worked...
2606 sk
->sk_err_soft
= 0;
2607 tp
->rcv_tstamp
= tcp_time_stamp
;
2608 prior_packets
= tp
->packets_out
;
2612 prior_in_flight
= tcp_packets_in_flight(tp
);
2614 /* See if we can take anything off of the retransmit queue. */
2615 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
2617 if (tp
->frto_counter
)
2618 tcp_process_frto(sk
, prior_snd_una
, flag
);
2620 if (tcp_ack_is_dubious(sk
, flag
)) {
2621 /* Advance CWND, if state allows this. */
2622 if ((flag
& FLAG_DATA_ACKED
) && tcp_may_raise_cwnd(sk
, flag
))
2623 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 0);
2624 tcp_fastretrans_alert(sk
, prior_snd_una
, prior_packets
, flag
);
2626 if ((flag
& FLAG_DATA_ACKED
))
2627 tcp_cong_avoid(sk
, ack
, seq_rtt
, prior_in_flight
, 1);
2630 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
2631 dst_confirm(sk
->sk_dst_cache
);
2636 icsk
->icsk_probes_out
= 0;
2638 /* If this ack opens up a zero window, clear backoff. It was
2639 * being used to time the probes, and is probably far higher than
2640 * it needs to be for normal retransmission.
2642 if (sk
->sk_send_head
)
2647 if (TCP_SKB_CB(skb
)->sacked
)
2648 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2651 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
2656 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2657 * But, this can also be called on packets in the established flow when
2658 * the fast version below fails.
2660 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
2663 struct tcphdr
*th
= skb
->h
.th
;
2664 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
2666 ptr
= (unsigned char *)(th
+ 1);
2667 opt_rx
->saw_tstamp
= 0;
2676 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
2681 if (opsize
< 2) /* "silly options" */
2683 if (opsize
> length
)
2684 return; /* don't parse partial options */
2687 if(opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
2688 u16 in_mss
= ntohs(get_unaligned((__be16
*)ptr
));
2690 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
2691 in_mss
= opt_rx
->user_mss
;
2692 opt_rx
->mss_clamp
= in_mss
;
2697 if(opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
2698 if (sysctl_tcp_window_scaling
) {
2699 __u8 snd_wscale
= *(__u8
*) ptr
;
2700 opt_rx
->wscale_ok
= 1;
2701 if (snd_wscale
> 14) {
2703 printk(KERN_INFO
"tcp_parse_options: Illegal window "
2704 "scaling value %d >14 received.\n",
2708 opt_rx
->snd_wscale
= snd_wscale
;
2711 case TCPOPT_TIMESTAMP
:
2712 if(opsize
==TCPOLEN_TIMESTAMP
) {
2713 if ((estab
&& opt_rx
->tstamp_ok
) ||
2714 (!estab
&& sysctl_tcp_timestamps
)) {
2715 opt_rx
->saw_tstamp
= 1;
2716 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__be32
*)ptr
));
2717 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__be32
*)(ptr
+4)));
2721 case TCPOPT_SACK_PERM
:
2722 if(opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
2723 if (sysctl_tcp_sack
) {
2724 opt_rx
->sack_ok
= 1;
2725 tcp_sack_reset(opt_rx
);
2731 if((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
2732 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
2734 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
2736 #ifdef CONFIG_TCP_MD5SIG
2739 * The MD5 Hash has already been
2740 * checked (see tcp_v{4,6}_do_rcv()).
2751 /* Fast parse options. This hopes to only see timestamps.
2752 * If it is wrong it falls back on tcp_parse_options().
2754 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
2755 struct tcp_sock
*tp
)
2757 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
2758 tp
->rx_opt
.saw_tstamp
= 0;
2760 } else if (tp
->rx_opt
.tstamp_ok
&&
2761 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
2762 __be32
*ptr
= (__be32
*)(th
+ 1);
2763 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
2764 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
2765 tp
->rx_opt
.saw_tstamp
= 1;
2767 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
2769 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
2773 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
2777 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
2779 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
2780 tp
->rx_opt
.ts_recent_stamp
= xtime
.tv_sec
;
2783 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
2785 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
2786 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
2787 * extra check below makes sure this can only happen
2788 * for pure ACK frames. -DaveM
2790 * Not only, also it occurs for expired timestamps.
2793 if((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
2794 xtime
.tv_sec
>= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
2795 tcp_store_ts_recent(tp
);
2799 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
2801 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
2802 * it can pass through stack. So, the following predicate verifies that
2803 * this segment is not used for anything but congestion avoidance or
2804 * fast retransmit. Moreover, we even are able to eliminate most of such
2805 * second order effects, if we apply some small "replay" window (~RTO)
2806 * to timestamp space.
2808 * All these measures still do not guarantee that we reject wrapped ACKs
2809 * on networks with high bandwidth, when sequence space is recycled fastly,
2810 * but it guarantees that such events will be very rare and do not affect
2811 * connection seriously. This doesn't look nice, but alas, PAWS is really
2814 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
2815 * states that events when retransmit arrives after original data are rare.
2816 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
2817 * the biggest problem on large power networks even with minor reordering.
2818 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
2819 * up to bandwidth of 18Gigabit/sec. 8) ]
2822 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
2824 struct tcp_sock
*tp
= tcp_sk(sk
);
2825 struct tcphdr
*th
= skb
->h
.th
;
2826 u32 seq
= TCP_SKB_CB(skb
)->seq
;
2827 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2829 return (/* 1. Pure ACK with correct sequence number. */
2830 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
2832 /* 2. ... and duplicate ACK. */
2833 ack
== tp
->snd_una
&&
2835 /* 3. ... and does not update window. */
2836 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
2838 /* 4. ... and sits in replay window. */
2839 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
2842 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
2844 const struct tcp_sock
*tp
= tcp_sk(sk
);
2845 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
2846 xtime
.tv_sec
< tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
2847 !tcp_disordered_ack(sk
, skb
));
2850 /* Check segment sequence number for validity.
2852 * Segment controls are considered valid, if the segment
2853 * fits to the window after truncation to the window. Acceptability
2854 * of data (and SYN, FIN, of course) is checked separately.
2855 * See tcp_data_queue(), for example.
2857 * Also, controls (RST is main one) are accepted using RCV.WUP instead
2858 * of RCV.NXT. Peer still did not advance his SND.UNA when we
2859 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
2860 * (borrowed from freebsd)
2863 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2865 return !before(end_seq
, tp
->rcv_wup
) &&
2866 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
2869 /* When we get a reset we do this. */
2870 static void tcp_reset(struct sock
*sk
)
2872 /* We want the right error as BSD sees it (and indeed as we do). */
2873 switch (sk
->sk_state
) {
2875 sk
->sk_err
= ECONNREFUSED
;
2877 case TCP_CLOSE_WAIT
:
2883 sk
->sk_err
= ECONNRESET
;
2886 if (!sock_flag(sk
, SOCK_DEAD
))
2887 sk
->sk_error_report(sk
);
2893 * Process the FIN bit. This now behaves as it is supposed to work
2894 * and the FIN takes effect when it is validly part of sequence
2895 * space. Not before when we get holes.
2897 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
2898 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
2901 * If we are in FINWAIT-1, a received FIN indicates simultaneous
2902 * close and we go into CLOSING (and later onto TIME-WAIT)
2904 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
2906 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
2908 struct tcp_sock
*tp
= tcp_sk(sk
);
2910 inet_csk_schedule_ack(sk
);
2912 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
2913 sock_set_flag(sk
, SOCK_DONE
);
2915 switch (sk
->sk_state
) {
2917 case TCP_ESTABLISHED
:
2918 /* Move to CLOSE_WAIT */
2919 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
2920 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
2923 case TCP_CLOSE_WAIT
:
2925 /* Received a retransmission of the FIN, do
2930 /* RFC793: Remain in the LAST-ACK state. */
2934 /* This case occurs when a simultaneous close
2935 * happens, we must ack the received FIN and
2936 * enter the CLOSING state.
2939 tcp_set_state(sk
, TCP_CLOSING
);
2942 /* Received a FIN -- send ACK and enter TIME_WAIT. */
2944 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
2947 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
2948 * cases we should never reach this piece of code.
2950 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
2951 __FUNCTION__
, sk
->sk_state
);
2955 /* It _is_ possible, that we have something out-of-order _after_ FIN.
2956 * Probably, we should reset in this case. For now drop them.
2958 __skb_queue_purge(&tp
->out_of_order_queue
);
2959 if (tp
->rx_opt
.sack_ok
)
2960 tcp_sack_reset(&tp
->rx_opt
);
2961 sk_stream_mem_reclaim(sk
);
2963 if (!sock_flag(sk
, SOCK_DEAD
)) {
2964 sk
->sk_state_change(sk
);
2966 /* Do not send POLL_HUP for half duplex close. */
2967 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
2968 sk
->sk_state
== TCP_CLOSE
)
2969 sk_wake_async(sk
, 1, POLL_HUP
);
2971 sk_wake_async(sk
, 1, POLL_IN
);
2975 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
2977 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
2978 if (before(seq
, sp
->start_seq
))
2979 sp
->start_seq
= seq
;
2980 if (after(end_seq
, sp
->end_seq
))
2981 sp
->end_seq
= end_seq
;
2987 static void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
2989 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
2990 if (before(seq
, tp
->rcv_nxt
))
2991 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
2993 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
2995 tp
->rx_opt
.dsack
= 1;
2996 tp
->duplicate_sack
[0].start_seq
= seq
;
2997 tp
->duplicate_sack
[0].end_seq
= end_seq
;
2998 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
3002 static void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3004 if (!tp
->rx_opt
.dsack
)
3005 tcp_dsack_set(tp
, seq
, end_seq
);
3007 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3010 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3012 struct tcp_sock
*tp
= tcp_sk(sk
);
3014 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3015 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3016 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3017 tcp_enter_quickack_mode(sk
);
3019 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
3020 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3022 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3023 end_seq
= tp
->rcv_nxt
;
3024 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3031 /* These routines update the SACK block as out-of-order packets arrive or
3032 * in-order packets close up the sequence space.
3034 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3037 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3038 struct tcp_sack_block
*swalk
= sp
+1;
3040 /* See if the recent change to the first SACK eats into
3041 * or hits the sequence space of other SACK blocks, if so coalesce.
3043 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
3044 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3047 /* Zap SWALK, by moving every further SACK up by one slot.
3048 * Decrease num_sacks.
3050 tp
->rx_opt
.num_sacks
--;
3051 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3052 for(i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3056 this_sack
++, swalk
++;
3060 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
3064 tmp
= sack1
->start_seq
;
3065 sack1
->start_seq
= sack2
->start_seq
;
3066 sack2
->start_seq
= tmp
;
3068 tmp
= sack1
->end_seq
;
3069 sack1
->end_seq
= sack2
->end_seq
;
3070 sack2
->end_seq
= tmp
;
3073 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3075 struct tcp_sock
*tp
= tcp_sk(sk
);
3076 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3077 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3083 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
3084 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3085 /* Rotate this_sack to the first one. */
3086 for (; this_sack
>0; this_sack
--, sp
--)
3087 tcp_sack_swap(sp
, sp
-1);
3089 tcp_sack_maybe_coalesce(tp
);
3094 /* Could not find an adjacent existing SACK, build a new one,
3095 * put it at the front, and shift everyone else down. We
3096 * always know there is at least one SACK present already here.
3098 * If the sack array is full, forget about the last one.
3100 if (this_sack
>= 4) {
3102 tp
->rx_opt
.num_sacks
--;
3105 for(; this_sack
> 0; this_sack
--, sp
--)
3109 /* Build the new head SACK, and we're done. */
3110 sp
->start_seq
= seq
;
3111 sp
->end_seq
= end_seq
;
3112 tp
->rx_opt
.num_sacks
++;
3113 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3116 /* RCV.NXT advances, some SACKs should be eaten. */
3118 static void tcp_sack_remove(struct tcp_sock
*tp
)
3120 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3121 int num_sacks
= tp
->rx_opt
.num_sacks
;
3124 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3125 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3126 tp
->rx_opt
.num_sacks
= 0;
3127 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3131 for(this_sack
= 0; this_sack
< num_sacks
; ) {
3132 /* Check if the start of the sack is covered by RCV.NXT. */
3133 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3136 /* RCV.NXT must cover all the block! */
3137 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
3139 /* Zap this SACK, by moving forward any other SACKS. */
3140 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3141 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3148 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3149 tp
->rx_opt
.num_sacks
= num_sacks
;
3150 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3154 /* This one checks to see if we can put data from the
3155 * out_of_order queue into the receive_queue.
3157 static void tcp_ofo_queue(struct sock
*sk
)
3159 struct tcp_sock
*tp
= tcp_sk(sk
);
3160 __u32 dsack_high
= tp
->rcv_nxt
;
3161 struct sk_buff
*skb
;
3163 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3164 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3167 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3168 __u32 dsack
= dsack_high
;
3169 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3170 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3171 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
3174 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3175 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3176 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3180 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3181 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3182 TCP_SKB_CB(skb
)->end_seq
);
3184 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3185 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3186 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3188 tcp_fin(skb
, sk
, skb
->h
.th
);
3192 static int tcp_prune_queue(struct sock
*sk
);
3194 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3196 struct tcphdr
*th
= skb
->h
.th
;
3197 struct tcp_sock
*tp
= tcp_sk(sk
);
3200 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3203 __skb_pull(skb
, th
->doff
*4);
3205 TCP_ECN_accept_cwr(tp
, skb
);
3207 if (tp
->rx_opt
.dsack
) {
3208 tp
->rx_opt
.dsack
= 0;
3209 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
3210 4 - tp
->rx_opt
.tstamp_ok
);
3213 /* Queue data for delivery to the user.
3214 * Packets in sequence go to the receive queue.
3215 * Out of sequence packets to the out_of_order_queue.
3217 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3218 if (tcp_receive_window(tp
) == 0)
3221 /* Ok. In sequence. In window. */
3222 if (tp
->ucopy
.task
== current
&&
3223 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3224 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3225 int chunk
= min_t(unsigned int, skb
->len
,
3228 __set_current_state(TASK_RUNNING
);
3231 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3232 tp
->ucopy
.len
-= chunk
;
3233 tp
->copied_seq
+= chunk
;
3234 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3235 tcp_rcv_space_adjust(sk
);
3243 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3244 !sk_stream_rmem_schedule(sk
, skb
))) {
3245 if (tcp_prune_queue(sk
) < 0 ||
3246 !sk_stream_rmem_schedule(sk
, skb
))
3249 sk_stream_set_owner_r(skb
, sk
);
3250 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3252 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3254 tcp_event_data_recv(sk
, tp
, skb
);
3256 tcp_fin(skb
, sk
, th
);
3258 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3261 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3262 * gap in queue is filled.
3264 if (skb_queue_empty(&tp
->out_of_order_queue
))
3265 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3268 if (tp
->rx_opt
.num_sacks
)
3269 tcp_sack_remove(tp
);
3271 tcp_fast_path_check(sk
, tp
);
3275 else if (!sock_flag(sk
, SOCK_DEAD
))
3276 sk
->sk_data_ready(sk
, 0);
3280 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3281 /* A retransmit, 2nd most common case. Force an immediate ack. */
3282 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3283 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3286 tcp_enter_quickack_mode(sk
);
3287 inet_csk_schedule_ack(sk
);
3293 /* Out of window. F.e. zero window probe. */
3294 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3297 tcp_enter_quickack_mode(sk
);
3299 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3300 /* Partial packet, seq < rcv_next < end_seq */
3301 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3302 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3303 TCP_SKB_CB(skb
)->end_seq
);
3305 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3307 /* If window is closed, drop tail of packet. But after
3308 * remembering D-SACK for its head made in previous line.
3310 if (!tcp_receive_window(tp
))
3315 TCP_ECN_check_ce(tp
, skb
);
3317 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3318 !sk_stream_rmem_schedule(sk
, skb
)) {
3319 if (tcp_prune_queue(sk
) < 0 ||
3320 !sk_stream_rmem_schedule(sk
, skb
))
3324 /* Disable header prediction. */
3326 inet_csk_schedule_ack(sk
);
3328 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3329 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3331 sk_stream_set_owner_r(skb
, sk
);
3333 if (!skb_peek(&tp
->out_of_order_queue
)) {
3334 /* Initial out of order segment, build 1 SACK. */
3335 if (tp
->rx_opt
.sack_ok
) {
3336 tp
->rx_opt
.num_sacks
= 1;
3337 tp
->rx_opt
.dsack
= 0;
3338 tp
->rx_opt
.eff_sacks
= 1;
3339 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3340 tp
->selective_acks
[0].end_seq
=
3341 TCP_SKB_CB(skb
)->end_seq
;
3343 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3345 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3346 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3347 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3349 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3350 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3352 if (!tp
->rx_opt
.num_sacks
||
3353 tp
->selective_acks
[0].end_seq
!= seq
)
3356 /* Common case: data arrive in order after hole. */
3357 tp
->selective_acks
[0].end_seq
= end_seq
;
3361 /* Find place to insert this segment. */
3363 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3365 } while ((skb1
= skb1
->prev
) !=
3366 (struct sk_buff
*)&tp
->out_of_order_queue
);
3368 /* Do skb overlap to previous one? */
3369 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3370 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3371 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3372 /* All the bits are present. Drop. */
3374 tcp_dsack_set(tp
, seq
, end_seq
);
3377 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3378 /* Partial overlap. */
3379 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3384 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3386 /* And clean segments covered by new one as whole. */
3387 while ((skb1
= skb
->next
) !=
3388 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3389 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3390 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3391 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3394 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3395 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3400 if (tp
->rx_opt
.sack_ok
)
3401 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3405 /* Collapse contiguous sequence of skbs head..tail with
3406 * sequence numbers start..end.
3407 * Segments with FIN/SYN are not collapsed (only because this
3411 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3412 struct sk_buff
*head
, struct sk_buff
*tail
,
3415 struct sk_buff
*skb
;
3417 /* First, check that queue is collapsible and find
3418 * the point where collapsing can be useful. */
3419 for (skb
= head
; skb
!= tail
; ) {
3420 /* No new bits? It is possible on ofo queue. */
3421 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3422 struct sk_buff
*next
= skb
->next
;
3423 __skb_unlink(skb
, list
);
3425 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3430 /* The first skb to collapse is:
3432 * - bloated or contains data before "start" or
3433 * overlaps to the next one.
3435 if (!skb
->h
.th
->syn
&& !skb
->h
.th
->fin
&&
3436 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3437 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3438 (skb
->next
!= tail
&&
3439 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3442 /* Decided to skip this, advance start seq. */
3443 start
= TCP_SKB_CB(skb
)->end_seq
;
3446 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3449 while (before(start
, end
)) {
3450 struct sk_buff
*nskb
;
3451 int header
= skb_headroom(skb
);
3452 int copy
= SKB_MAX_ORDER(header
, 0);
3454 /* Too big header? This can happen with IPv6. */
3457 if (end
-start
< copy
)
3459 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3462 skb_reserve(nskb
, header
);
3463 memcpy(nskb
->head
, skb
->head
, header
);
3464 nskb
->nh
.raw
= nskb
->head
+ (skb
->nh
.raw
-skb
->head
);
3465 nskb
->h
.raw
= nskb
->head
+ (skb
->h
.raw
-skb
->head
);
3466 nskb
->mac
.raw
= nskb
->head
+ (skb
->mac
.raw
-skb
->head
);
3467 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3468 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3469 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3470 sk_stream_set_owner_r(nskb
, sk
);
3472 /* Copy data, releasing collapsed skbs. */
3474 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3475 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3479 size
= min(copy
, size
);
3480 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3482 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3486 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3487 struct sk_buff
*next
= skb
->next
;
3488 __skb_unlink(skb
, list
);
3490 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3492 if (skb
== tail
|| skb
->h
.th
->syn
|| skb
->h
.th
->fin
)
3499 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3500 * and tcp_collapse() them until all the queue is collapsed.
3502 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3504 struct tcp_sock
*tp
= tcp_sk(sk
);
3505 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3506 struct sk_buff
*head
;
3512 start
= TCP_SKB_CB(skb
)->seq
;
3513 end
= TCP_SKB_CB(skb
)->end_seq
;
3519 /* Segment is terminated when we see gap or when
3520 * we are at the end of all the queue. */
3521 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3522 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3523 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3524 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3525 head
, skb
, start
, end
);
3527 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3529 /* Start new segment */
3530 start
= TCP_SKB_CB(skb
)->seq
;
3531 end
= TCP_SKB_CB(skb
)->end_seq
;
3533 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3534 start
= TCP_SKB_CB(skb
)->seq
;
3535 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3536 end
= TCP_SKB_CB(skb
)->end_seq
;
3541 /* Reduce allocated memory if we can, trying to get
3542 * the socket within its memory limits again.
3544 * Return less than zero if we should start dropping frames
3545 * until the socket owning process reads some of the data
3546 * to stabilize the situation.
3548 static int tcp_prune_queue(struct sock
*sk
)
3550 struct tcp_sock
*tp
= tcp_sk(sk
);
3552 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3554 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3556 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3557 tcp_clamp_window(sk
, tp
);
3558 else if (tcp_memory_pressure
)
3559 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3561 tcp_collapse_ofo_queue(sk
);
3562 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3563 sk
->sk_receive_queue
.next
,
3564 (struct sk_buff
*)&sk
->sk_receive_queue
,
3565 tp
->copied_seq
, tp
->rcv_nxt
);
3566 sk_stream_mem_reclaim(sk
);
3568 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3571 /* Collapsing did not help, destructive actions follow.
3572 * This must not ever occur. */
3574 /* First, purge the out_of_order queue. */
3575 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3576 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3577 __skb_queue_purge(&tp
->out_of_order_queue
);
3579 /* Reset SACK state. A conforming SACK implementation will
3580 * do the same at a timeout based retransmit. When a connection
3581 * is in a sad state like this, we care only about integrity
3582 * of the connection not performance.
3584 if (tp
->rx_opt
.sack_ok
)
3585 tcp_sack_reset(&tp
->rx_opt
);
3586 sk_stream_mem_reclaim(sk
);
3589 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3592 /* If we are really being abused, tell the caller to silently
3593 * drop receive data on the floor. It will get retransmitted
3594 * and hopefully then we'll have sufficient space.
3596 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
3598 /* Massive buffer overcommit. */
3604 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3605 * As additional protections, we do not touch cwnd in retransmission phases,
3606 * and if application hit its sndbuf limit recently.
3608 void tcp_cwnd_application_limited(struct sock
*sk
)
3610 struct tcp_sock
*tp
= tcp_sk(sk
);
3612 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
3613 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
3614 /* Limited by application or receiver window. */
3615 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
3616 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
3617 if (win_used
< tp
->snd_cwnd
) {
3618 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3619 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
3621 tp
->snd_cwnd_used
= 0;
3623 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3626 static int tcp_should_expand_sndbuf(struct sock
*sk
, struct tcp_sock
*tp
)
3628 /* If the user specified a specific send buffer setting, do
3631 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
3634 /* If we are under global TCP memory pressure, do not expand. */
3635 if (tcp_memory_pressure
)
3638 /* If we are under soft global TCP memory pressure, do not expand. */
3639 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
3642 /* If we filled the congestion window, do not expand. */
3643 if (tp
->packets_out
>= tp
->snd_cwnd
)
3649 /* When incoming ACK allowed to free some skb from write_queue,
3650 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3651 * on the exit from tcp input handler.
3653 * PROBLEM: sndbuf expansion does not work well with largesend.
3655 static void tcp_new_space(struct sock
*sk
)
3657 struct tcp_sock
*tp
= tcp_sk(sk
);
3659 if (tcp_should_expand_sndbuf(sk
, tp
)) {
3660 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
3661 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
3662 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
3663 tp
->reordering
+ 1);
3664 sndmem
*= 2*demanded
;
3665 if (sndmem
> sk
->sk_sndbuf
)
3666 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
3667 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3670 sk
->sk_write_space(sk
);
3673 static void tcp_check_space(struct sock
*sk
)
3675 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
3676 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
3677 if (sk
->sk_socket
&&
3678 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
3683 static inline void tcp_data_snd_check(struct sock
*sk
, struct tcp_sock
*tp
)
3685 tcp_push_pending_frames(sk
, tp
);
3686 tcp_check_space(sk
);
3690 * Check if sending an ack is needed.
3692 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
3694 struct tcp_sock
*tp
= tcp_sk(sk
);
3696 /* More than one full frame received... */
3697 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
3698 /* ... and right edge of window advances far enough.
3699 * (tcp_recvmsg() will send ACK otherwise). Or...
3701 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
3702 /* We ACK each frame or... */
3703 tcp_in_quickack_mode(sk
) ||
3704 /* We have out of order data. */
3706 skb_peek(&tp
->out_of_order_queue
))) {
3707 /* Then ack it now */
3710 /* Else, send delayed ack. */
3711 tcp_send_delayed_ack(sk
);
3715 static inline void tcp_ack_snd_check(struct sock
*sk
)
3717 if (!inet_csk_ack_scheduled(sk
)) {
3718 /* We sent a data segment already. */
3721 __tcp_ack_snd_check(sk
, 1);
3725 * This routine is only called when we have urgent data
3726 * signaled. Its the 'slow' part of tcp_urg. It could be
3727 * moved inline now as tcp_urg is only called from one
3728 * place. We handle URGent data wrong. We have to - as
3729 * BSD still doesn't use the correction from RFC961.
3730 * For 1003.1g we should support a new option TCP_STDURG to permit
3731 * either form (or just set the sysctl tcp_stdurg).
3734 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
3736 struct tcp_sock
*tp
= tcp_sk(sk
);
3737 u32 ptr
= ntohs(th
->urg_ptr
);
3739 if (ptr
&& !sysctl_tcp_stdurg
)
3741 ptr
+= ntohl(th
->seq
);
3743 /* Ignore urgent data that we've already seen and read. */
3744 if (after(tp
->copied_seq
, ptr
))
3747 /* Do not replay urg ptr.
3749 * NOTE: interesting situation not covered by specs.
3750 * Misbehaving sender may send urg ptr, pointing to segment,
3751 * which we already have in ofo queue. We are not able to fetch
3752 * such data and will stay in TCP_URG_NOTYET until will be eaten
3753 * by recvmsg(). Seems, we are not obliged to handle such wicked
3754 * situations. But it is worth to think about possibility of some
3755 * DoSes using some hypothetical application level deadlock.
3757 if (before(ptr
, tp
->rcv_nxt
))
3760 /* Do we already have a newer (or duplicate) urgent pointer? */
3761 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
3764 /* Tell the world about our new urgent pointer. */
3767 /* We may be adding urgent data when the last byte read was
3768 * urgent. To do this requires some care. We cannot just ignore
3769 * tp->copied_seq since we would read the last urgent byte again
3770 * as data, nor can we alter copied_seq until this data arrives
3771 * or we break the semantics of SIOCATMARK (and thus sockatmark())
3773 * NOTE. Double Dutch. Rendering to plain English: author of comment
3774 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
3775 * and expect that both A and B disappear from stream. This is _wrong_.
3776 * Though this happens in BSD with high probability, this is occasional.
3777 * Any application relying on this is buggy. Note also, that fix "works"
3778 * only in this artificial test. Insert some normal data between A and B and we will
3779 * decline of BSD again. Verdict: it is better to remove to trap
3782 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
3783 !sock_flag(sk
, SOCK_URGINLINE
) &&
3784 tp
->copied_seq
!= tp
->rcv_nxt
) {
3785 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
3787 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
3788 __skb_unlink(skb
, &sk
->sk_receive_queue
);
3793 tp
->urg_data
= TCP_URG_NOTYET
;
3796 /* Disable header prediction. */
3800 /* This is the 'fast' part of urgent handling. */
3801 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
3803 struct tcp_sock
*tp
= tcp_sk(sk
);
3805 /* Check if we get a new urgent pointer - normally not. */
3807 tcp_check_urg(sk
,th
);
3809 /* Do we wait for any urgent data? - normally not... */
3810 if (tp
->urg_data
== TCP_URG_NOTYET
) {
3811 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
3814 /* Is the urgent pointer pointing into this packet? */
3815 if (ptr
< skb
->len
) {
3817 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
3819 tp
->urg_data
= TCP_URG_VALID
| tmp
;
3820 if (!sock_flag(sk
, SOCK_DEAD
))
3821 sk
->sk_data_ready(sk
, 0);
3826 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
3828 struct tcp_sock
*tp
= tcp_sk(sk
);
3829 int chunk
= skb
->len
- hlen
;
3833 if (skb
->ip_summed
==CHECKSUM_UNNECESSARY
)
3834 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
3836 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
3840 tp
->ucopy
.len
-= chunk
;
3841 tp
->copied_seq
+= chunk
;
3842 tcp_rcv_space_adjust(sk
);
3849 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
3853 if (sock_owned_by_user(sk
)) {
3855 result
= __tcp_checksum_complete(skb
);
3858 result
= __tcp_checksum_complete(skb
);
3863 static inline int tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
3865 return skb
->ip_summed
!= CHECKSUM_UNNECESSARY
&&
3866 __tcp_checksum_complete_user(sk
, skb
);
3869 #ifdef CONFIG_NET_DMA
3870 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
3872 struct tcp_sock
*tp
= tcp_sk(sk
);
3873 int chunk
= skb
->len
- hlen
;
3875 int copied_early
= 0;
3877 if (tp
->ucopy
.wakeup
)
3880 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
3881 tp
->ucopy
.dma_chan
= get_softnet_dma();
3883 if (tp
->ucopy
.dma_chan
&& skb
->ip_summed
== CHECKSUM_UNNECESSARY
) {
3885 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
3886 skb
, hlen
, tp
->ucopy
.iov
, chunk
, tp
->ucopy
.pinned_list
);
3891 tp
->ucopy
.dma_cookie
= dma_cookie
;
3894 tp
->ucopy
.len
-= chunk
;
3895 tp
->copied_seq
+= chunk
;
3896 tcp_rcv_space_adjust(sk
);
3898 if ((tp
->ucopy
.len
== 0) ||
3899 (tcp_flag_word(skb
->h
.th
) & TCP_FLAG_PSH
) ||
3900 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
3901 tp
->ucopy
.wakeup
= 1;
3902 sk
->sk_data_ready(sk
, 0);
3904 } else if (chunk
> 0) {
3905 tp
->ucopy
.wakeup
= 1;
3906 sk
->sk_data_ready(sk
, 0);
3909 return copied_early
;
3911 #endif /* CONFIG_NET_DMA */
3914 * TCP receive function for the ESTABLISHED state.
3916 * It is split into a fast path and a slow path. The fast path is
3918 * - A zero window was announced from us - zero window probing
3919 * is only handled properly in the slow path.
3920 * - Out of order segments arrived.
3921 * - Urgent data is expected.
3922 * - There is no buffer space left
3923 * - Unexpected TCP flags/window values/header lengths are received
3924 * (detected by checking the TCP header against pred_flags)
3925 * - Data is sent in both directions. Fast path only supports pure senders
3926 * or pure receivers (this means either the sequence number or the ack
3927 * value must stay constant)
3928 * - Unexpected TCP option.
3930 * When these conditions are not satisfied it drops into a standard
3931 * receive procedure patterned after RFC793 to handle all cases.
3932 * The first three cases are guaranteed by proper pred_flags setting,
3933 * the rest is checked inline. Fast processing is turned on in
3934 * tcp_data_queue when everything is OK.
3936 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
3937 struct tcphdr
*th
, unsigned len
)
3939 struct tcp_sock
*tp
= tcp_sk(sk
);
3942 * Header prediction.
3943 * The code loosely follows the one in the famous
3944 * "30 instruction TCP receive" Van Jacobson mail.
3946 * Van's trick is to deposit buffers into socket queue
3947 * on a device interrupt, to call tcp_recv function
3948 * on the receive process context and checksum and copy
3949 * the buffer to user space. smart...
3951 * Our current scheme is not silly either but we take the
3952 * extra cost of the net_bh soft interrupt processing...
3953 * We do checksum and copy also but from device to kernel.
3956 tp
->rx_opt
.saw_tstamp
= 0;
3958 /* pred_flags is 0xS?10 << 16 + snd_wnd
3959 * if header_prediction is to be made
3960 * 'S' will always be tp->tcp_header_len >> 2
3961 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
3962 * turn it off (when there are holes in the receive
3963 * space for instance)
3964 * PSH flag is ignored.
3967 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
3968 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3969 int tcp_header_len
= tp
->tcp_header_len
;
3971 /* Timestamp header prediction: tcp_header_len
3972 * is automatically equal to th->doff*4 due to pred_flags
3976 /* Check timestamp */
3977 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
3978 __be32
*ptr
= (__be32
*)(th
+ 1);
3980 /* No? Slow path! */
3981 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3982 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
3985 tp
->rx_opt
.saw_tstamp
= 1;
3987 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3989 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3991 /* If PAWS failed, check it more carefully in slow path */
3992 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
3995 /* DO NOT update ts_recent here, if checksum fails
3996 * and timestamp was corrupted part, it will result
3997 * in a hung connection since we will drop all
3998 * future packets due to the PAWS test.
4002 if (len
<= tcp_header_len
) {
4003 /* Bulk data transfer: sender */
4004 if (len
== tcp_header_len
) {
4005 /* Predicted packet is in window by definition.
4006 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4007 * Hence, check seq<=rcv_wup reduces to:
4009 if (tcp_header_len
==
4010 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4011 tp
->rcv_nxt
== tp
->rcv_wup
)
4012 tcp_store_ts_recent(tp
);
4014 /* We know that such packets are checksummed
4017 tcp_ack(sk
, skb
, 0);
4019 tcp_data_snd_check(sk
, tp
);
4021 } else { /* Header too small */
4022 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4027 int copied_early
= 0;
4029 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4030 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4031 #ifdef CONFIG_NET_DMA
4032 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4037 if (tp
->ucopy
.task
== current
&& sock_owned_by_user(sk
) && !copied_early
) {
4038 __set_current_state(TASK_RUNNING
);
4040 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4044 /* Predicted packet is in window by definition.
4045 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4046 * Hence, check seq<=rcv_wup reduces to:
4048 if (tcp_header_len
==
4049 (sizeof(struct tcphdr
) +
4050 TCPOLEN_TSTAMP_ALIGNED
) &&
4051 tp
->rcv_nxt
== tp
->rcv_wup
)
4052 tcp_store_ts_recent(tp
);
4054 tcp_rcv_rtt_measure_ts(sk
, skb
);
4056 __skb_pull(skb
, tcp_header_len
);
4057 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4058 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
4061 tcp_cleanup_rbuf(sk
, skb
->len
);
4064 if (tcp_checksum_complete_user(sk
, skb
))
4067 /* Predicted packet is in window by definition.
4068 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4069 * Hence, check seq<=rcv_wup reduces to:
4071 if (tcp_header_len
==
4072 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4073 tp
->rcv_nxt
== tp
->rcv_wup
)
4074 tcp_store_ts_recent(tp
);
4076 tcp_rcv_rtt_measure_ts(sk
, skb
);
4078 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4081 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
4083 /* Bulk data transfer: receiver */
4084 __skb_pull(skb
,tcp_header_len
);
4085 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4086 sk_stream_set_owner_r(skb
, sk
);
4087 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4090 tcp_event_data_recv(sk
, tp
, skb
);
4092 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4093 /* Well, only one small jumplet in fast path... */
4094 tcp_ack(sk
, skb
, FLAG_DATA
);
4095 tcp_data_snd_check(sk
, tp
);
4096 if (!inet_csk_ack_scheduled(sk
))
4100 __tcp_ack_snd_check(sk
, 0);
4102 #ifdef CONFIG_NET_DMA
4104 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4110 sk
->sk_data_ready(sk
, 0);
4116 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
4120 * RFC1323: H1. Apply PAWS check first.
4122 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4123 tcp_paws_discard(sk
, skb
)) {
4125 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4126 tcp_send_dupack(sk
, skb
);
4129 /* Resets are accepted even if PAWS failed.
4131 ts_recent update must be made after we are sure
4132 that the packet is in window.
4137 * Standard slow path.
4140 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4141 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4142 * (RST) segments are validated by checking their SEQ-fields."
4143 * And page 69: "If an incoming segment is not acceptable,
4144 * an acknowledgment should be sent in reply (unless the RST bit
4145 * is set, if so drop the segment and return)".
4148 tcp_send_dupack(sk
, skb
);
4157 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4159 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4160 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4161 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4168 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4170 tcp_rcv_rtt_measure_ts(sk
, skb
);
4172 /* Process urgent data. */
4173 tcp_urg(sk
, skb
, th
);
4175 /* step 7: process the segment text */
4176 tcp_data_queue(sk
, skb
);
4178 tcp_data_snd_check(sk
, tp
);
4179 tcp_ack_snd_check(sk
);
4183 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4190 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4191 struct tcphdr
*th
, unsigned len
)
4193 struct tcp_sock
*tp
= tcp_sk(sk
);
4194 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4195 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4197 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4201 * "If the state is SYN-SENT then
4202 * first check the ACK bit
4203 * If the ACK bit is set
4204 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4205 * a reset (unless the RST bit is set, if so drop
4206 * the segment and return)"
4208 * We do not send data with SYN, so that RFC-correct
4211 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4212 goto reset_and_undo
;
4214 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4215 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
4217 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
4218 goto reset_and_undo
;
4221 /* Now ACK is acceptable.
4223 * "If the RST bit is set
4224 * If the ACK was acceptable then signal the user "error:
4225 * connection reset", drop the segment, enter CLOSED state,
4226 * delete TCB, and return."
4235 * "fifth, if neither of the SYN or RST bits is set then
4236 * drop the segment and return."
4242 goto discard_and_undo
;
4245 * "If the SYN bit is on ...
4246 * are acceptable then ...
4247 * (our SYN has been ACKed), change the connection
4248 * state to ESTABLISHED..."
4251 TCP_ECN_rcv_synack(tp
, th
);
4253 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4254 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4256 /* Ok.. it's good. Set up sequence numbers and
4257 * move to established.
4259 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4260 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4262 /* RFC1323: The window in SYN & SYN/ACK segments is
4265 tp
->snd_wnd
= ntohs(th
->window
);
4266 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
4268 if (!tp
->rx_opt
.wscale_ok
) {
4269 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
4270 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
4273 if (tp
->rx_opt
.saw_tstamp
) {
4274 tp
->rx_opt
.tstamp_ok
= 1;
4275 tp
->tcp_header_len
=
4276 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4277 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4278 tcp_store_ts_recent(tp
);
4280 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4283 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_fack
)
4284 tp
->rx_opt
.sack_ok
|= 2;
4287 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4288 tcp_initialize_rcv_mss(sk
);
4290 /* Remember, tcp_poll() does not lock socket!
4291 * Change state from SYN-SENT only after copied_seq
4292 * is initialized. */
4293 tp
->copied_seq
= tp
->rcv_nxt
;
4295 tcp_set_state(sk
, TCP_ESTABLISHED
);
4297 security_inet_conn_established(sk
, skb
);
4299 /* Make sure socket is routed, for correct metrics. */
4300 icsk
->icsk_af_ops
->rebuild_header(sk
);
4302 tcp_init_metrics(sk
);
4304 tcp_init_congestion_control(sk
);
4306 /* Prevent spurious tcp_cwnd_restart() on first data
4309 tp
->lsndtime
= tcp_time_stamp
;
4311 tcp_init_buffer_space(sk
);
4313 if (sock_flag(sk
, SOCK_KEEPOPEN
))
4314 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
4316 if (!tp
->rx_opt
.snd_wscale
)
4317 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4321 if (!sock_flag(sk
, SOCK_DEAD
)) {
4322 sk
->sk_state_change(sk
);
4323 sk_wake_async(sk
, 0, POLL_OUT
);
4326 if (sk
->sk_write_pending
||
4327 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4328 icsk
->icsk_ack
.pingpong
) {
4329 /* Save one ACK. Data will be ready after
4330 * several ticks, if write_pending is set.
4332 * It may be deleted, but with this feature tcpdumps
4333 * look so _wonderfully_ clever, that I was not able
4334 * to stand against the temptation 8) --ANK
4336 inet_csk_schedule_ack(sk
);
4337 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4338 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4339 tcp_incr_quickack(sk
);
4340 tcp_enter_quickack_mode(sk
);
4341 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4342 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4353 /* No ACK in the segment */
4357 * "If the RST bit is set
4359 * Otherwise (no ACK) drop the segment and return."
4362 goto discard_and_undo
;
4366 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4367 goto discard_and_undo
;
4370 /* We see SYN without ACK. It is attempt of
4371 * simultaneous connect with crossed SYNs.
4372 * Particularly, it can be connect to self.
4374 tcp_set_state(sk
, TCP_SYN_RECV
);
4376 if (tp
->rx_opt
.saw_tstamp
) {
4377 tp
->rx_opt
.tstamp_ok
= 1;
4378 tcp_store_ts_recent(tp
);
4379 tp
->tcp_header_len
=
4380 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4382 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4385 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4386 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4388 /* RFC1323: The window in SYN & SYN/ACK segments is
4391 tp
->snd_wnd
= ntohs(th
->window
);
4392 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4393 tp
->max_window
= tp
->snd_wnd
;
4395 TCP_ECN_rcv_syn(tp
, th
);
4398 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4399 tcp_initialize_rcv_mss(sk
);
4402 tcp_send_synack(sk
);
4404 /* Note, we could accept data and URG from this segment.
4405 * There are no obstacles to make this.
4407 * However, if we ignore data in ACKless segments sometimes,
4408 * we have no reasons to accept it sometimes.
4409 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4410 * is not flawless. So, discard packet for sanity.
4411 * Uncomment this return to process the data.
4418 /* "fifth, if neither of the SYN or RST bits is set then
4419 * drop the segment and return."
4423 tcp_clear_options(&tp
->rx_opt
);
4424 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4428 tcp_clear_options(&tp
->rx_opt
);
4429 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4435 * This function implements the receiving procedure of RFC 793 for
4436 * all states except ESTABLISHED and TIME_WAIT.
4437 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4438 * address independent.
4441 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4442 struct tcphdr
*th
, unsigned len
)
4444 struct tcp_sock
*tp
= tcp_sk(sk
);
4445 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4448 tp
->rx_opt
.saw_tstamp
= 0;
4450 switch (sk
->sk_state
) {
4462 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
4465 /* Now we have several options: In theory there is
4466 * nothing else in the frame. KA9Q has an option to
4467 * send data with the syn, BSD accepts data with the
4468 * syn up to the [to be] advertised window and
4469 * Solaris 2.1 gives you a protocol error. For now
4470 * we just ignore it, that fits the spec precisely
4471 * and avoids incompatibilities. It would be nice in
4472 * future to drop through and process the data.
4474 * Now that TTCP is starting to be used we ought to
4476 * But, this leaves one open to an easy denial of
4477 * service attack, and SYN cookies can't defend
4478 * against this problem. So, we drop the data
4479 * in the interest of security over speed unless
4480 * it's still in use.
4488 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4492 /* Do step6 onward by hand. */
4493 tcp_urg(sk
, skb
, th
);
4495 tcp_data_snd_check(sk
, tp
);
4499 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4500 tcp_paws_discard(sk
, skb
)) {
4502 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4503 tcp_send_dupack(sk
, skb
);
4506 /* Reset is accepted even if it did not pass PAWS. */
4509 /* step 1: check sequence number */
4510 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4512 tcp_send_dupack(sk
, skb
);
4516 /* step 2: check RST bit */
4522 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4524 /* step 3: check security and precedence [ignored] */
4528 * Check for a SYN in window.
4530 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4531 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4536 /* step 5: check the ACK field */
4538 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4540 switch(sk
->sk_state
) {
4543 tp
->copied_seq
= tp
->rcv_nxt
;
4545 tcp_set_state(sk
, TCP_ESTABLISHED
);
4546 sk
->sk_state_change(sk
);
4548 /* Note, that this wakeup is only for marginal
4549 * crossed SYN case. Passively open sockets
4550 * are not waked up, because sk->sk_sleep ==
4551 * NULL and sk->sk_socket == NULL.
4553 if (sk
->sk_socket
) {
4554 sk_wake_async(sk
,0,POLL_OUT
);
4557 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4558 tp
->snd_wnd
= ntohs(th
->window
) <<
4559 tp
->rx_opt
.snd_wscale
;
4560 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4561 TCP_SKB_CB(skb
)->seq
);
4563 /* tcp_ack considers this ACK as duplicate
4564 * and does not calculate rtt.
4565 * Fix it at least with timestamps.
4567 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4569 tcp_ack_saw_tstamp(sk
, 0);
4571 if (tp
->rx_opt
.tstamp_ok
)
4572 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4574 /* Make sure socket is routed, for
4577 icsk
->icsk_af_ops
->rebuild_header(sk
);
4579 tcp_init_metrics(sk
);
4581 tcp_init_congestion_control(sk
);
4583 /* Prevent spurious tcp_cwnd_restart() on
4584 * first data packet.
4586 tp
->lsndtime
= tcp_time_stamp
;
4589 tcp_initialize_rcv_mss(sk
);
4590 tcp_init_buffer_space(sk
);
4591 tcp_fast_path_on(tp
);
4598 if (tp
->snd_una
== tp
->write_seq
) {
4599 tcp_set_state(sk
, TCP_FIN_WAIT2
);
4600 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
4601 dst_confirm(sk
->sk_dst_cache
);
4603 if (!sock_flag(sk
, SOCK_DEAD
))
4604 /* Wake up lingering close() */
4605 sk
->sk_state_change(sk
);
4609 if (tp
->linger2
< 0 ||
4610 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4611 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
4613 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4617 tmo
= tcp_fin_time(sk
);
4618 if (tmo
> TCP_TIMEWAIT_LEN
) {
4619 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
4620 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
4621 /* Bad case. We could lose such FIN otherwise.
4622 * It is not a big problem, but it looks confusing
4623 * and not so rare event. We still can lose it now,
4624 * if it spins in bh_lock_sock(), but it is really
4627 inet_csk_reset_keepalive_timer(sk
, tmo
);
4629 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
4637 if (tp
->snd_una
== tp
->write_seq
) {
4638 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4644 if (tp
->snd_una
== tp
->write_seq
) {
4645 tcp_update_metrics(sk
);
4654 /* step 6: check the URG bit */
4655 tcp_urg(sk
, skb
, th
);
4657 /* step 7: process the segment text */
4658 switch (sk
->sk_state
) {
4659 case TCP_CLOSE_WAIT
:
4662 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4666 /* RFC 793 says to queue data in these states,
4667 * RFC 1122 says we MUST send a reset.
4668 * BSD 4.4 also does reset.
4670 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
4671 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4672 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
4673 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4679 case TCP_ESTABLISHED
:
4680 tcp_data_queue(sk
, skb
);
4685 /* tcp_data could move socket to TIME-WAIT */
4686 if (sk
->sk_state
!= TCP_CLOSE
) {
4687 tcp_data_snd_check(sk
, tp
);
4688 tcp_ack_snd_check(sk
);
4698 EXPORT_SYMBOL(sysctl_tcp_ecn
);
4699 EXPORT_SYMBOL(sysctl_tcp_reordering
);
4700 EXPORT_SYMBOL(tcp_parse_options
);
4701 EXPORT_SYMBOL(tcp_rcv_established
);
4702 EXPORT_SYMBOL(tcp_rcv_state_process
);
4703 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);