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_frto_response __read_mostly
;
90 int sysctl_tcp_nometrics_save __read_mostly
;
92 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
93 int sysctl_tcp_abc __read_mostly
;
95 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
96 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
97 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
98 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
99 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
100 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
101 #define FLAG_ECE 0x40 /* ECE in this ACK */
102 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
103 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
105 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
106 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained DSACK info */
108 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
109 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
110 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
111 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
112 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
114 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0)
115 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2)
116 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4)
118 #define IsSackFrto() (sysctl_tcp_frto == 0x2)
120 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
122 /* Adapt the MSS value used to make delayed ack decision to the
125 static void tcp_measure_rcv_mss(struct sock
*sk
,
126 const struct sk_buff
*skb
)
128 struct inet_connection_sock
*icsk
= inet_csk(sk
);
129 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
132 icsk
->icsk_ack
.last_seg_size
= 0;
134 /* skb->len may jitter because of SACKs, even if peer
135 * sends good full-sized frames.
137 len
= skb_shinfo(skb
)->gso_size
?: skb
->len
;
138 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
139 icsk
->icsk_ack
.rcv_mss
= len
;
141 /* Otherwise, we make more careful check taking into account,
142 * that SACKs block is variable.
144 * "len" is invariant segment length, including TCP header.
146 len
+= skb
->data
- skb_transport_header(skb
);
147 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
148 /* If PSH is not set, packet should be
149 * full sized, provided peer TCP is not badly broken.
150 * This observation (if it is correct 8)) allows
151 * to handle super-low mtu links fairly.
153 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
154 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
155 /* Subtract also invariant (if peer is RFC compliant),
156 * tcp header plus fixed timestamp option length.
157 * Resulting "len" is MSS free of SACK jitter.
159 len
-= tcp_sk(sk
)->tcp_header_len
;
160 icsk
->icsk_ack
.last_seg_size
= len
;
162 icsk
->icsk_ack
.rcv_mss
= len
;
166 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
167 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
168 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
172 static void tcp_incr_quickack(struct sock
*sk
)
174 struct inet_connection_sock
*icsk
= inet_csk(sk
);
175 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
179 if (quickacks
> icsk
->icsk_ack
.quick
)
180 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
183 void tcp_enter_quickack_mode(struct sock
*sk
)
185 struct inet_connection_sock
*icsk
= inet_csk(sk
);
186 tcp_incr_quickack(sk
);
187 icsk
->icsk_ack
.pingpong
= 0;
188 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
191 /* Send ACKs quickly, if "quick" count is not exhausted
192 * and the session is not interactive.
195 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
197 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
198 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
201 /* Buffer size and advertised window tuning.
203 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
206 static void tcp_fixup_sndbuf(struct sock
*sk
)
208 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
209 sizeof(struct sk_buff
);
211 if (sk
->sk_sndbuf
< 3 * sndmem
)
212 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
215 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
217 * All tcp_full_space() is split to two parts: "network" buffer, allocated
218 * forward and advertised in receiver window (tp->rcv_wnd) and
219 * "application buffer", required to isolate scheduling/application
220 * latencies from network.
221 * window_clamp is maximal advertised window. It can be less than
222 * tcp_full_space(), in this case tcp_full_space() - window_clamp
223 * is reserved for "application" buffer. The less window_clamp is
224 * the smoother our behaviour from viewpoint of network, but the lower
225 * throughput and the higher sensitivity of the connection to losses. 8)
227 * rcv_ssthresh is more strict window_clamp used at "slow start"
228 * phase to predict further behaviour of this connection.
229 * It is used for two goals:
230 * - to enforce header prediction at sender, even when application
231 * requires some significant "application buffer". It is check #1.
232 * - to prevent pruning of receive queue because of misprediction
233 * of receiver window. Check #2.
235 * The scheme does not work when sender sends good segments opening
236 * window and then starts to feed us spaghetti. But it should work
237 * in common situations. Otherwise, we have to rely on queue collapsing.
240 /* Slow part of check#2. */
241 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
243 struct tcp_sock
*tp
= tcp_sk(sk
);
245 int truesize
= tcp_win_from_space(skb
->truesize
)/2;
246 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2])/2;
248 while (tp
->rcv_ssthresh
<= window
) {
249 if (truesize
<= skb
->len
)
250 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
258 static void tcp_grow_window(struct sock
*sk
,
261 struct tcp_sock
*tp
= tcp_sk(sk
);
264 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
265 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
266 !tcp_memory_pressure
) {
269 /* Check #2. Increase window, if skb with such overhead
270 * will fit to rcvbuf in future.
272 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
275 incr
= __tcp_grow_window(sk
, skb
);
278 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
, tp
->window_clamp
);
279 inet_csk(sk
)->icsk_ack
.quick
|= 1;
284 /* 3. Tuning rcvbuf, when connection enters established state. */
286 static void tcp_fixup_rcvbuf(struct sock
*sk
)
288 struct tcp_sock
*tp
= tcp_sk(sk
);
289 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
291 /* Try to select rcvbuf so that 4 mss-sized segments
292 * will fit to window and corresponding skbs will fit to our rcvbuf.
293 * (was 3; 4 is minimum to allow fast retransmit to work.)
295 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
297 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
298 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
301 /* 4. Try to fixup all. It is made immediately after connection enters
304 static void tcp_init_buffer_space(struct sock
*sk
)
306 struct tcp_sock
*tp
= tcp_sk(sk
);
309 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
310 tcp_fixup_rcvbuf(sk
);
311 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
312 tcp_fixup_sndbuf(sk
);
314 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
316 maxwin
= tcp_full_space(sk
);
318 if (tp
->window_clamp
>= maxwin
) {
319 tp
->window_clamp
= maxwin
;
321 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
322 tp
->window_clamp
= max(maxwin
-
323 (maxwin
>> sysctl_tcp_app_win
),
327 /* Force reservation of one segment. */
328 if (sysctl_tcp_app_win
&&
329 tp
->window_clamp
> 2 * tp
->advmss
&&
330 tp
->window_clamp
+ tp
->advmss
> maxwin
)
331 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
333 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
334 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
337 /* 5. Recalculate window clamp after socket hit its memory bounds. */
338 static void tcp_clamp_window(struct sock
*sk
)
340 struct tcp_sock
*tp
= tcp_sk(sk
);
341 struct inet_connection_sock
*icsk
= inet_csk(sk
);
343 icsk
->icsk_ack
.quick
= 0;
345 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
346 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
347 !tcp_memory_pressure
&&
348 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
349 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
352 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
353 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
357 /* Initialize RCV_MSS value.
358 * RCV_MSS is an our guess about MSS used by the peer.
359 * We haven't any direct information about the MSS.
360 * It's better to underestimate the RCV_MSS rather than overestimate.
361 * Overestimations make us ACKing less frequently than needed.
362 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
364 void tcp_initialize_rcv_mss(struct sock
*sk
)
366 struct tcp_sock
*tp
= tcp_sk(sk
);
367 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
369 hint
= min(hint
, tp
->rcv_wnd
/2);
370 hint
= min(hint
, TCP_MIN_RCVMSS
);
371 hint
= max(hint
, TCP_MIN_MSS
);
373 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
376 /* Receiver "autotuning" code.
378 * The algorithm for RTT estimation w/o timestamps is based on
379 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
380 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
382 * More detail on this code can be found at
383 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
384 * though this reference is out of date. A new paper
387 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
389 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
395 if (new_sample
!= 0) {
396 /* If we sample in larger samples in the non-timestamp
397 * case, we could grossly overestimate the RTT especially
398 * with chatty applications or bulk transfer apps which
399 * are stalled on filesystem I/O.
401 * Also, since we are only going for a minimum in the
402 * non-timestamp case, we do not smooth things out
403 * else with timestamps disabled convergence takes too
407 m
-= (new_sample
>> 3);
409 } else if (m
< new_sample
)
412 /* No previous measure. */
416 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
417 tp
->rcv_rtt_est
.rtt
= new_sample
;
420 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
422 if (tp
->rcv_rtt_est
.time
== 0)
424 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
426 tcp_rcv_rtt_update(tp
,
427 jiffies
- tp
->rcv_rtt_est
.time
,
431 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
432 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
435 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
437 struct tcp_sock
*tp
= tcp_sk(sk
);
438 if (tp
->rx_opt
.rcv_tsecr
&&
439 (TCP_SKB_CB(skb
)->end_seq
-
440 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
441 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
445 * This function should be called every time data is copied to user space.
446 * It calculates the appropriate TCP receive buffer space.
448 void tcp_rcv_space_adjust(struct sock
*sk
)
450 struct tcp_sock
*tp
= tcp_sk(sk
);
454 if (tp
->rcvq_space
.time
== 0)
457 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
458 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
459 tp
->rcv_rtt_est
.rtt
== 0)
462 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
464 space
= max(tp
->rcvq_space
.space
, space
);
466 if (tp
->rcvq_space
.space
!= space
) {
469 tp
->rcvq_space
.space
= space
;
471 if (sysctl_tcp_moderate_rcvbuf
&&
472 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
473 int new_clamp
= space
;
475 /* Receive space grows, normalize in order to
476 * take into account packet headers and sk_buff
477 * structure overhead.
482 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
483 16 + sizeof(struct sk_buff
));
484 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
487 space
= min(space
, sysctl_tcp_rmem
[2]);
488 if (space
> sk
->sk_rcvbuf
) {
489 sk
->sk_rcvbuf
= space
;
491 /* Make the window clamp follow along. */
492 tp
->window_clamp
= new_clamp
;
498 tp
->rcvq_space
.seq
= tp
->copied_seq
;
499 tp
->rcvq_space
.time
= tcp_time_stamp
;
502 /* There is something which you must keep in mind when you analyze the
503 * behavior of the tp->ato delayed ack timeout interval. When a
504 * connection starts up, we want to ack as quickly as possible. The
505 * problem is that "good" TCP's do slow start at the beginning of data
506 * transmission. The means that until we send the first few ACK's the
507 * sender will sit on his end and only queue most of his data, because
508 * he can only send snd_cwnd unacked packets at any given time. For
509 * each ACK we send, he increments snd_cwnd and transmits more of his
512 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
514 struct tcp_sock
*tp
= tcp_sk(sk
);
515 struct inet_connection_sock
*icsk
= inet_csk(sk
);
518 inet_csk_schedule_ack(sk
);
520 tcp_measure_rcv_mss(sk
, skb
);
522 tcp_rcv_rtt_measure(tp
);
524 now
= tcp_time_stamp
;
526 if (!icsk
->icsk_ack
.ato
) {
527 /* The _first_ data packet received, initialize
528 * delayed ACK engine.
530 tcp_incr_quickack(sk
);
531 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
533 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
535 if (m
<= TCP_ATO_MIN
/2) {
536 /* The fastest case is the first. */
537 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
538 } else if (m
< icsk
->icsk_ack
.ato
) {
539 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
540 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
541 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
542 } else if (m
> icsk
->icsk_rto
) {
543 /* Too long gap. Apparently sender failed to
544 * restart window, so that we send ACKs quickly.
546 tcp_incr_quickack(sk
);
547 sk_stream_mem_reclaim(sk
);
550 icsk
->icsk_ack
.lrcvtime
= now
;
552 TCP_ECN_check_ce(tp
, skb
);
555 tcp_grow_window(sk
, skb
);
558 /* Called to compute a smoothed rtt estimate. The data fed to this
559 * routine either comes from timestamps, or from segments that were
560 * known _not_ to have been retransmitted [see Karn/Partridge
561 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
562 * piece by Van Jacobson.
563 * NOTE: the next three routines used to be one big routine.
564 * To save cycles in the RFC 1323 implementation it was better to break
565 * it up into three procedures. -- erics
567 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
569 struct tcp_sock
*tp
= tcp_sk(sk
);
570 long m
= mrtt
; /* RTT */
572 /* The following amusing code comes from Jacobson's
573 * article in SIGCOMM '88. Note that rtt and mdev
574 * are scaled versions of rtt and mean deviation.
575 * This is designed to be as fast as possible
576 * m stands for "measurement".
578 * On a 1990 paper the rto value is changed to:
579 * RTO = rtt + 4 * mdev
581 * Funny. This algorithm seems to be very broken.
582 * These formulae increase RTO, when it should be decreased, increase
583 * too slowly, when it should be increased quickly, decrease too quickly
584 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
585 * does not matter how to _calculate_ it. Seems, it was trap
586 * that VJ failed to avoid. 8)
591 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
592 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
594 m
= -m
; /* m is now abs(error) */
595 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
596 /* This is similar to one of Eifel findings.
597 * Eifel blocks mdev updates when rtt decreases.
598 * This solution is a bit different: we use finer gain
599 * for mdev in this case (alpha*beta).
600 * Like Eifel it also prevents growth of rto,
601 * but also it limits too fast rto decreases,
602 * happening in pure Eifel.
607 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
609 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
610 if (tp
->mdev
> tp
->mdev_max
) {
611 tp
->mdev_max
= tp
->mdev
;
612 if (tp
->mdev_max
> tp
->rttvar
)
613 tp
->rttvar
= tp
->mdev_max
;
615 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
616 if (tp
->mdev_max
< tp
->rttvar
)
617 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
618 tp
->rtt_seq
= tp
->snd_nxt
;
619 tp
->mdev_max
= TCP_RTO_MIN
;
622 /* no previous measure. */
623 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
624 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
625 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
626 tp
->rtt_seq
= tp
->snd_nxt
;
630 /* Calculate rto without backoff. This is the second half of Van Jacobson's
631 * routine referred to above.
633 static inline void tcp_set_rto(struct sock
*sk
)
635 const struct tcp_sock
*tp
= tcp_sk(sk
);
636 /* Old crap is replaced with new one. 8)
639 * 1. If rtt variance happened to be less 50msec, it is hallucination.
640 * It cannot be less due to utterly erratic ACK generation made
641 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
642 * to do with delayed acks, because at cwnd>2 true delack timeout
643 * is invisible. Actually, Linux-2.4 also generates erratic
644 * ACKs in some circumstances.
646 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
648 /* 2. Fixups made earlier cannot be right.
649 * If we do not estimate RTO correctly without them,
650 * all the algo is pure shit and should be replaced
651 * with correct one. It is exactly, which we pretend to do.
655 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
656 * guarantees that rto is higher.
658 static inline void tcp_bound_rto(struct sock
*sk
)
660 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
661 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
664 /* Save metrics learned by this TCP session.
665 This function is called only, when TCP finishes successfully
666 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
668 void tcp_update_metrics(struct sock
*sk
)
670 struct tcp_sock
*tp
= tcp_sk(sk
);
671 struct dst_entry
*dst
= __sk_dst_get(sk
);
673 if (sysctl_tcp_nometrics_save
)
678 if (dst
&& (dst
->flags
&DST_HOST
)) {
679 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
682 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
683 /* This session failed to estimate rtt. Why?
684 * Probably, no packets returned in time.
687 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
688 dst
->metrics
[RTAX_RTT
-1] = 0;
692 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
694 /* If newly calculated rtt larger than stored one,
695 * store new one. Otherwise, use EWMA. Remember,
696 * rtt overestimation is always better than underestimation.
698 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
700 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
702 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
705 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
709 /* Scale deviation to rttvar fixed point */
714 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
715 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
717 dst
->metrics
[RTAX_RTTVAR
-1] -=
718 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
721 if (tp
->snd_ssthresh
>= 0xFFFF) {
722 /* Slow start still did not finish. */
723 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
724 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
725 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
726 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
727 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
728 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
729 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
730 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
731 icsk
->icsk_ca_state
== TCP_CA_Open
) {
732 /* Cong. avoidance phase, cwnd is reliable. */
733 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
734 dst
->metrics
[RTAX_SSTHRESH
-1] =
735 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
736 if (!dst_metric_locked(dst
, RTAX_CWND
))
737 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
739 /* Else slow start did not finish, cwnd is non-sense,
740 ssthresh may be also invalid.
742 if (!dst_metric_locked(dst
, RTAX_CWND
))
743 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
744 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
745 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
746 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
747 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
750 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
751 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
752 tp
->reordering
!= sysctl_tcp_reordering
)
753 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
758 /* Numbers are taken from RFC3390.
760 * John Heffner states:
762 * The RFC specifies a window of no more than 4380 bytes
763 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
764 * is a bit misleading because they use a clamp at 4380 bytes
765 * rather than use a multiplier in the relevant range.
767 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
769 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
772 if (tp
->mss_cache
> 1460)
775 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
777 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
780 /* Set slow start threshold and cwnd not falling to slow start */
781 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
783 struct tcp_sock
*tp
= tcp_sk(sk
);
784 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
786 tp
->prior_ssthresh
= 0;
788 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
791 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
792 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
793 tcp_packets_in_flight(tp
) + 1U);
794 tp
->snd_cwnd_cnt
= 0;
795 tp
->high_seq
= tp
->snd_nxt
;
796 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
797 TCP_ECN_queue_cwr(tp
);
799 tcp_set_ca_state(sk
, TCP_CA_CWR
);
803 /* Initialize metrics on socket. */
805 static void tcp_init_metrics(struct sock
*sk
)
807 struct tcp_sock
*tp
= tcp_sk(sk
);
808 struct dst_entry
*dst
= __sk_dst_get(sk
);
815 if (dst_metric_locked(dst
, RTAX_CWND
))
816 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
817 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
818 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
819 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
820 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
822 if (dst_metric(dst
, RTAX_REORDERING
) &&
823 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
824 tp
->rx_opt
.sack_ok
&= ~2;
825 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
828 if (dst_metric(dst
, RTAX_RTT
) == 0)
831 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
834 /* Initial rtt is determined from SYN,SYN-ACK.
835 * The segment is small and rtt may appear much
836 * less than real one. Use per-dst memory
837 * to make it more realistic.
839 * A bit of theory. RTT is time passed after "normal" sized packet
840 * is sent until it is ACKed. In normal circumstances sending small
841 * packets force peer to delay ACKs and calculation is correct too.
842 * The algorithm is adaptive and, provided we follow specs, it
843 * NEVER underestimate RTT. BUT! If peer tries to make some clever
844 * tricks sort of "quick acks" for time long enough to decrease RTT
845 * to low value, and then abruptly stops to do it and starts to delay
846 * ACKs, wait for troubles.
848 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
849 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
850 tp
->rtt_seq
= tp
->snd_nxt
;
852 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
853 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
854 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
858 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
860 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
861 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
865 /* Play conservative. If timestamps are not
866 * supported, TCP will fail to recalculate correct
867 * rtt, if initial rto is too small. FORGET ALL AND RESET!
869 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
871 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
872 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
876 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
879 struct tcp_sock
*tp
= tcp_sk(sk
);
880 if (metric
> tp
->reordering
) {
881 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
883 /* This exciting event is worth to be remembered. 8) */
885 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
887 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
889 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
891 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
892 #if FASTRETRANS_DEBUG > 1
893 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
894 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
898 tp
->undo_marker
? tp
->undo_retrans
: 0);
900 /* Disable FACK yet. */
901 tp
->rx_opt
.sack_ok
&= ~2;
905 /* This procedure tags the retransmission queue when SACKs arrive.
907 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
908 * Packets in queue with these bits set are counted in variables
909 * sacked_out, retrans_out and lost_out, correspondingly.
911 * Valid combinations are:
912 * Tag InFlight Description
913 * 0 1 - orig segment is in flight.
914 * S 0 - nothing flies, orig reached receiver.
915 * L 0 - nothing flies, orig lost by net.
916 * R 2 - both orig and retransmit are in flight.
917 * L|R 1 - orig is lost, retransmit is in flight.
918 * S|R 1 - orig reached receiver, retrans is still in flight.
919 * (L|S|R is logically valid, it could occur when L|R is sacked,
920 * but it is equivalent to plain S and code short-curcuits it to S.
921 * L|S is logically invalid, it would mean -1 packet in flight 8))
923 * These 6 states form finite state machine, controlled by the following events:
924 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
925 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
926 * 3. Loss detection event of one of three flavors:
927 * A. Scoreboard estimator decided the packet is lost.
928 * A'. Reno "three dupacks" marks head of queue lost.
929 * A''. Its FACK modfication, head until snd.fack is lost.
930 * B. SACK arrives sacking data transmitted after never retransmitted
932 * C. SACK arrives sacking SND.NXT at the moment, when the
933 * segment was retransmitted.
934 * 4. D-SACK added new rule: D-SACK changes any tag to S.
936 * It is pleasant to note, that state diagram turns out to be commutative,
937 * so that we are allowed not to be bothered by order of our actions,
938 * when multiple events arrive simultaneously. (see the function below).
940 * Reordering detection.
941 * --------------------
942 * Reordering metric is maximal distance, which a packet can be displaced
943 * in packet stream. With SACKs we can estimate it:
945 * 1. SACK fills old hole and the corresponding segment was not
946 * ever retransmitted -> reordering. Alas, we cannot use it
947 * when segment was retransmitted.
948 * 2. The last flaw is solved with D-SACK. D-SACK arrives
949 * for retransmitted and already SACKed segment -> reordering..
950 * Both of these heuristics are not used in Loss state, when we cannot
951 * account for retransmits accurately.
954 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
956 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
957 struct tcp_sock
*tp
= tcp_sk(sk
);
958 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
959 TCP_SKB_CB(ack_skb
)->sacked
);
960 struct tcp_sack_block_wire
*sp
= (struct tcp_sack_block_wire
*)(ptr
+2);
961 struct sk_buff
*cached_skb
;
962 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
963 int reord
= tp
->packets_out
;
965 u32 lost_retrans
= 0;
967 int found_dup_sack
= 0;
968 int cached_fack_count
;
970 int first_sack_index
;
974 prior_fackets
= tp
->fackets_out
;
976 /* Check for D-SACK. */
977 if (before(ntohl(sp
[0].start_seq
), TCP_SKB_CB(ack_skb
)->ack_seq
)) {
978 flag
|= FLAG_DSACKING_ACK
;
980 tp
->rx_opt
.sack_ok
|= 4;
981 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
982 } else if (num_sacks
> 1 &&
983 !after(ntohl(sp
[0].end_seq
), ntohl(sp
[1].end_seq
)) &&
984 !before(ntohl(sp
[0].start_seq
), ntohl(sp
[1].start_seq
))) {
985 flag
|= FLAG_DSACKING_ACK
;
987 tp
->rx_opt
.sack_ok
|= 4;
988 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
991 /* D-SACK for already forgotten data...
992 * Do dumb counting. */
993 if (found_dup_sack
&&
994 !after(ntohl(sp
[0].end_seq
), prior_snd_una
) &&
995 after(ntohl(sp
[0].end_seq
), tp
->undo_marker
))
998 /* Eliminate too old ACKs, but take into
999 * account more or less fresh ones, they can
1000 * contain valid SACK info.
1002 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1006 * if the only SACK change is the increase of the end_seq of
1007 * the first block then only apply that SACK block
1008 * and use retrans queue hinting otherwise slowpath */
1010 for (i
= 0; i
< num_sacks
; i
++) {
1011 __be32 start_seq
= sp
[i
].start_seq
;
1012 __be32 end_seq
= sp
[i
].end_seq
;
1015 if (tp
->recv_sack_cache
[i
].start_seq
!= start_seq
)
1018 if ((tp
->recv_sack_cache
[i
].start_seq
!= start_seq
) ||
1019 (tp
->recv_sack_cache
[i
].end_seq
!= end_seq
))
1022 tp
->recv_sack_cache
[i
].start_seq
= start_seq
;
1023 tp
->recv_sack_cache
[i
].end_seq
= end_seq
;
1025 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1026 for (; i
< ARRAY_SIZE(tp
->recv_sack_cache
); i
++) {
1027 tp
->recv_sack_cache
[i
].start_seq
= 0;
1028 tp
->recv_sack_cache
[i
].end_seq
= 0;
1031 first_sack_index
= 0;
1036 tp
->fastpath_skb_hint
= NULL
;
1038 /* order SACK blocks to allow in order walk of the retrans queue */
1039 for (i
= num_sacks
-1; i
> 0; i
--) {
1040 for (j
= 0; j
< i
; j
++){
1041 if (after(ntohl(sp
[j
].start_seq
),
1042 ntohl(sp
[j
+1].start_seq
))){
1043 struct tcp_sack_block_wire tmp
;
1049 /* Track where the first SACK block goes to */
1050 if (j
== first_sack_index
)
1051 first_sack_index
= j
+1;
1058 /* clear flag as used for different purpose in following code */
1061 /* Use SACK fastpath hint if valid */
1062 cached_skb
= tp
->fastpath_skb_hint
;
1063 cached_fack_count
= tp
->fastpath_cnt_hint
;
1065 cached_skb
= tcp_write_queue_head(sk
);
1066 cached_fack_count
= 0;
1069 for (i
=0; i
<num_sacks
; i
++, sp
++) {
1070 struct sk_buff
*skb
;
1071 __u32 start_seq
= ntohl(sp
->start_seq
);
1072 __u32 end_seq
= ntohl(sp
->end_seq
);
1074 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1077 fack_count
= cached_fack_count
;
1079 /* Event "B" in the comment above. */
1080 if (after(end_seq
, tp
->high_seq
))
1081 flag
|= FLAG_DATA_LOST
;
1083 tcp_for_write_queue_from(skb
, sk
) {
1084 int in_sack
, pcount
;
1087 if (skb
== tcp_send_head(sk
))
1091 cached_fack_count
= fack_count
;
1092 if (i
== first_sack_index
) {
1093 tp
->fastpath_skb_hint
= skb
;
1094 tp
->fastpath_cnt_hint
= fack_count
;
1097 /* The retransmission queue is always in order, so
1098 * we can short-circuit the walk early.
1100 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1103 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1104 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1106 pcount
= tcp_skb_pcount(skb
);
1108 if (pcount
> 1 && !in_sack
&&
1109 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1110 unsigned int pkt_len
;
1112 in_sack
= !after(start_seq
,
1113 TCP_SKB_CB(skb
)->seq
);
1116 pkt_len
= (start_seq
-
1117 TCP_SKB_CB(skb
)->seq
);
1119 pkt_len
= (end_seq
-
1120 TCP_SKB_CB(skb
)->seq
);
1121 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
))
1123 pcount
= tcp_skb_pcount(skb
);
1126 fack_count
+= pcount
;
1128 sacked
= TCP_SKB_CB(skb
)->sacked
;
1130 /* Account D-SACK for retransmitted packet. */
1131 if ((dup_sack
&& in_sack
) &&
1132 (sacked
& TCPCB_RETRANS
) &&
1133 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1136 /* The frame is ACKed. */
1137 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
1138 if (sacked
&TCPCB_RETRANS
) {
1139 if ((dup_sack
&& in_sack
) &&
1140 (sacked
&TCPCB_SACKED_ACKED
))
1141 reord
= min(fack_count
, reord
);
1143 /* If it was in a hole, we detected reordering. */
1144 if (fack_count
< prior_fackets
&&
1145 !(sacked
&TCPCB_SACKED_ACKED
))
1146 reord
= min(fack_count
, reord
);
1149 /* Nothing to do; acked frame is about to be dropped. */
1153 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1154 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1155 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1156 lost_retrans
= end_seq
;
1161 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1162 if (sacked
& TCPCB_SACKED_RETRANS
) {
1163 /* If the segment is not tagged as lost,
1164 * we do not clear RETRANS, believing
1165 * that retransmission is still in flight.
1167 if (sacked
& TCPCB_LOST
) {
1168 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1169 tp
->lost_out
-= tcp_skb_pcount(skb
);
1170 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1172 /* clear lost hint */
1173 tp
->retransmit_skb_hint
= NULL
;
1176 /* New sack for not retransmitted frame,
1177 * which was in hole. It is reordering.
1179 if (!(sacked
& TCPCB_RETRANS
) &&
1180 fack_count
< prior_fackets
)
1181 reord
= min(fack_count
, reord
);
1183 if (sacked
& TCPCB_LOST
) {
1184 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1185 tp
->lost_out
-= tcp_skb_pcount(skb
);
1187 /* clear lost hint */
1188 tp
->retransmit_skb_hint
= NULL
;
1190 /* SACK enhanced F-RTO detection.
1191 * Set flag if and only if non-rexmitted
1192 * segments below frto_highmark are
1193 * SACKed (RFC4138; Appendix B).
1194 * Clearing correct due to in-order walk
1196 if (after(end_seq
, tp
->frto_highmark
)) {
1197 flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1199 if (!(sacked
& TCPCB_RETRANS
))
1200 flag
|= FLAG_ONLY_ORIG_SACKED
;
1204 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1205 flag
|= FLAG_DATA_SACKED
;
1206 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1208 if (fack_count
> tp
->fackets_out
)
1209 tp
->fackets_out
= fack_count
;
1211 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1212 reord
= min(fack_count
, reord
);
1215 /* D-SACK. We can detect redundant retransmission
1216 * in S|R and plain R frames and clear it.
1217 * undo_retrans is decreased above, L|R frames
1218 * are accounted above as well.
1221 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1222 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1223 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1224 tp
->retransmit_skb_hint
= NULL
;
1229 /* Check for lost retransmit. This superb idea is
1230 * borrowed from "ratehalving". Event "C".
1231 * Later note: FACK people cheated me again 8),
1232 * we have to account for reordering! Ugly,
1235 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1236 struct sk_buff
*skb
;
1238 tcp_for_write_queue(skb
, sk
) {
1239 if (skb
== tcp_send_head(sk
))
1241 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1243 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1245 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1246 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1248 !before(lost_retrans
,
1249 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1251 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1252 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1254 /* clear lost hint */
1255 tp
->retransmit_skb_hint
= NULL
;
1257 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1258 tp
->lost_out
+= tcp_skb_pcount(skb
);
1259 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1260 flag
|= FLAG_DATA_SACKED
;
1261 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1267 tp
->left_out
= tp
->sacked_out
+ tp
->lost_out
;
1269 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
&&
1270 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1271 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1273 #if FASTRETRANS_DEBUG > 0
1274 BUG_TRAP((int)tp
->sacked_out
>= 0);
1275 BUG_TRAP((int)tp
->lost_out
>= 0);
1276 BUG_TRAP((int)tp
->retrans_out
>= 0);
1277 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1282 /* F-RTO can only be used if TCP has never retransmitted anything other than
1283 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1285 int tcp_use_frto(struct sock
*sk
)
1287 const struct tcp_sock
*tp
= tcp_sk(sk
);
1288 struct sk_buff
*skb
;
1290 if (!sysctl_tcp_frto
)
1296 /* Avoid expensive walking of rexmit queue if possible */
1297 if (tp
->retrans_out
> 1)
1300 skb
= tcp_write_queue_head(sk
);
1301 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
1302 tcp_for_write_queue_from(skb
, sk
) {
1303 if (skb
== tcp_send_head(sk
))
1305 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1307 /* Short-circuit when first non-SACKed skb has been checked */
1308 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
))
1314 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1315 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1316 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1317 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1318 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1319 * bits are handled if the Loss state is really to be entered (in
1320 * tcp_enter_frto_loss).
1322 * Do like tcp_enter_loss() would; when RTO expires the second time it
1324 * "Reduce ssthresh if it has not yet been made inside this window."
1326 void tcp_enter_frto(struct sock
*sk
)
1328 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1329 struct tcp_sock
*tp
= tcp_sk(sk
);
1330 struct sk_buff
*skb
;
1332 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1333 tp
->snd_una
== tp
->high_seq
||
1334 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1335 !icsk
->icsk_retransmits
)) {
1336 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1337 /* Our state is too optimistic in ssthresh() call because cwnd
1338 * is not reduced until tcp_enter_frto_loss() when previous FRTO
1339 * recovery has not yet completed. Pattern would be this: RTO,
1340 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1342 * RFC4138 should be more specific on what to do, even though
1343 * RTO is quite unlikely to occur after the first Cumulative ACK
1344 * due to back-off and complexity of triggering events ...
1346 if (tp
->frto_counter
) {
1348 stored_cwnd
= tp
->snd_cwnd
;
1350 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1351 tp
->snd_cwnd
= stored_cwnd
;
1353 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1355 /* ... in theory, cong.control module could do "any tricks" in
1356 * ssthresh(), which means that ca_state, lost bits and lost_out
1357 * counter would have to be faked before the call occurs. We
1358 * consider that too expensive, unlikely and hacky, so modules
1359 * using these in ssthresh() must deal these incompatibility
1360 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1362 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1365 tp
->undo_marker
= tp
->snd_una
;
1366 tp
->undo_retrans
= 0;
1368 skb
= tcp_write_queue_head(sk
);
1369 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1370 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1371 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1373 tcp_sync_left_out(tp
);
1375 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1376 * The last condition is necessary at least in tp->frto_counter case.
1378 if (IsSackFrto() && (tp
->frto_counter
||
1379 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
1380 after(tp
->high_seq
, tp
->snd_una
)) {
1381 tp
->frto_highmark
= tp
->high_seq
;
1383 tp
->frto_highmark
= tp
->snd_nxt
;
1385 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
1386 tp
->high_seq
= tp
->snd_nxt
;
1387 tp
->frto_counter
= 1;
1390 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1391 * which indicates that we should follow the traditional RTO recovery,
1392 * i.e. mark everything lost and do go-back-N retransmission.
1394 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
1396 struct tcp_sock
*tp
= tcp_sk(sk
);
1397 struct sk_buff
*skb
;
1402 tp
->fackets_out
= 0;
1403 tp
->retrans_out
= 0;
1405 tcp_for_write_queue(skb
, sk
) {
1406 if (skb
== tcp_send_head(sk
))
1408 cnt
+= tcp_skb_pcount(skb
);
1410 * Count the retransmission made on RTO correctly (only when
1411 * waiting for the first ACK and did not get it)...
1413 if ((tp
->frto_counter
== 1) && !(flag
&FLAG_DATA_ACKED
)) {
1414 /* For some reason this R-bit might get cleared? */
1415 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1416 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1417 /* ...enter this if branch just for the first segment */
1418 flag
|= FLAG_DATA_ACKED
;
1420 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1422 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1424 /* Do not mark those segments lost that were
1425 * forward transmitted after RTO
1427 if (!after(TCP_SKB_CB(skb
)->end_seq
,
1428 tp
->frto_highmark
)) {
1429 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1430 tp
->lost_out
+= tcp_skb_pcount(skb
);
1433 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1434 tp
->fackets_out
= cnt
;
1437 tcp_sync_left_out(tp
);
1439 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
1440 tp
->snd_cwnd_cnt
= 0;
1441 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1442 tp
->undo_marker
= 0;
1443 tp
->frto_counter
= 0;
1445 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1446 sysctl_tcp_reordering
);
1447 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1448 tp
->high_seq
= tp
->frto_highmark
;
1449 TCP_ECN_queue_cwr(tp
);
1451 clear_all_retrans_hints(tp
);
1454 void tcp_clear_retrans(struct tcp_sock
*tp
)
1457 tp
->retrans_out
= 0;
1459 tp
->fackets_out
= 0;
1463 tp
->undo_marker
= 0;
1464 tp
->undo_retrans
= 0;
1467 /* Enter Loss state. If "how" is not zero, forget all SACK information
1468 * and reset tags completely, otherwise preserve SACKs. If receiver
1469 * dropped its ofo queue, we will know this due to reneging detection.
1471 void tcp_enter_loss(struct sock
*sk
, int how
)
1473 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1474 struct tcp_sock
*tp
= tcp_sk(sk
);
1475 struct sk_buff
*skb
;
1478 /* Reduce ssthresh if it has not yet been made inside this window. */
1479 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1480 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1481 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1482 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1483 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1486 tp
->snd_cwnd_cnt
= 0;
1487 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1489 tp
->bytes_acked
= 0;
1490 tcp_clear_retrans(tp
);
1492 /* Push undo marker, if it was plain RTO and nothing
1493 * was retransmitted. */
1495 tp
->undo_marker
= tp
->snd_una
;
1497 tcp_for_write_queue(skb
, sk
) {
1498 if (skb
== tcp_send_head(sk
))
1500 cnt
+= tcp_skb_pcount(skb
);
1501 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1502 tp
->undo_marker
= 0;
1503 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1504 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1505 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1506 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1507 tp
->lost_out
+= tcp_skb_pcount(skb
);
1509 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1510 tp
->fackets_out
= cnt
;
1513 tcp_sync_left_out(tp
);
1515 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1516 sysctl_tcp_reordering
);
1517 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1518 tp
->high_seq
= tp
->snd_nxt
;
1519 TCP_ECN_queue_cwr(tp
);
1520 /* Abort FRTO algorithm if one is in progress */
1521 tp
->frto_counter
= 0;
1523 clear_all_retrans_hints(tp
);
1526 static int tcp_check_sack_reneging(struct sock
*sk
)
1528 struct sk_buff
*skb
;
1530 /* If ACK arrived pointing to a remembered SACK,
1531 * it means that our remembered SACKs do not reflect
1532 * real state of receiver i.e.
1533 * receiver _host_ is heavily congested (or buggy).
1534 * Do processing similar to RTO timeout.
1536 if ((skb
= tcp_write_queue_head(sk
)) != NULL
&&
1537 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1538 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1539 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1541 tcp_enter_loss(sk
, 1);
1542 icsk
->icsk_retransmits
++;
1543 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
1544 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1545 icsk
->icsk_rto
, TCP_RTO_MAX
);
1551 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1553 return IsReno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1556 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1558 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1561 static inline int tcp_head_timedout(struct sock
*sk
)
1563 struct tcp_sock
*tp
= tcp_sk(sk
);
1565 return tp
->packets_out
&&
1566 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
1569 /* Linux NewReno/SACK/FACK/ECN state machine.
1570 * --------------------------------------
1572 * "Open" Normal state, no dubious events, fast path.
1573 * "Disorder" In all the respects it is "Open",
1574 * but requires a bit more attention. It is entered when
1575 * we see some SACKs or dupacks. It is split of "Open"
1576 * mainly to move some processing from fast path to slow one.
1577 * "CWR" CWND was reduced due to some Congestion Notification event.
1578 * It can be ECN, ICMP source quench, local device congestion.
1579 * "Recovery" CWND was reduced, we are fast-retransmitting.
1580 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1582 * tcp_fastretrans_alert() is entered:
1583 * - each incoming ACK, if state is not "Open"
1584 * - when arrived ACK is unusual, namely:
1589 * Counting packets in flight is pretty simple.
1591 * in_flight = packets_out - left_out + retrans_out
1593 * packets_out is SND.NXT-SND.UNA counted in packets.
1595 * retrans_out is number of retransmitted segments.
1597 * left_out is number of segments left network, but not ACKed yet.
1599 * left_out = sacked_out + lost_out
1601 * sacked_out: Packets, which arrived to receiver out of order
1602 * and hence not ACKed. With SACKs this number is simply
1603 * amount of SACKed data. Even without SACKs
1604 * it is easy to give pretty reliable estimate of this number,
1605 * counting duplicate ACKs.
1607 * lost_out: Packets lost by network. TCP has no explicit
1608 * "loss notification" feedback from network (for now).
1609 * It means that this number can be only _guessed_.
1610 * Actually, it is the heuristics to predict lossage that
1611 * distinguishes different algorithms.
1613 * F.e. after RTO, when all the queue is considered as lost,
1614 * lost_out = packets_out and in_flight = retrans_out.
1616 * Essentially, we have now two algorithms counting
1619 * FACK: It is the simplest heuristics. As soon as we decided
1620 * that something is lost, we decide that _all_ not SACKed
1621 * packets until the most forward SACK are lost. I.e.
1622 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1623 * It is absolutely correct estimate, if network does not reorder
1624 * packets. And it loses any connection to reality when reordering
1625 * takes place. We use FACK by default until reordering
1626 * is suspected on the path to this destination.
1628 * NewReno: when Recovery is entered, we assume that one segment
1629 * is lost (classic Reno). While we are in Recovery and
1630 * a partial ACK arrives, we assume that one more packet
1631 * is lost (NewReno). This heuristics are the same in NewReno
1634 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1635 * deflation etc. CWND is real congestion window, never inflated, changes
1636 * only according to classic VJ rules.
1638 * Really tricky (and requiring careful tuning) part of algorithm
1639 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1640 * The first determines the moment _when_ we should reduce CWND and,
1641 * hence, slow down forward transmission. In fact, it determines the moment
1642 * when we decide that hole is caused by loss, rather than by a reorder.
1644 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1645 * holes, caused by lost packets.
1647 * And the most logically complicated part of algorithm is undo
1648 * heuristics. We detect false retransmits due to both too early
1649 * fast retransmit (reordering) and underestimated RTO, analyzing
1650 * timestamps and D-SACKs. When we detect that some segments were
1651 * retransmitted by mistake and CWND reduction was wrong, we undo
1652 * window reduction and abort recovery phase. This logic is hidden
1653 * inside several functions named tcp_try_undo_<something>.
1656 /* This function decides, when we should leave Disordered state
1657 * and enter Recovery phase, reducing congestion window.
1659 * Main question: may we further continue forward transmission
1660 * with the same cwnd?
1662 static int tcp_time_to_recover(struct sock
*sk
)
1664 struct tcp_sock
*tp
= tcp_sk(sk
);
1667 /* Do not perform any recovery during FRTO algorithm */
1668 if (tp
->frto_counter
)
1671 /* Trick#1: The loss is proven. */
1675 /* Not-A-Trick#2 : Classic rule... */
1676 if (tcp_fackets_out(tp
) > tp
->reordering
)
1679 /* Trick#3 : when we use RFC2988 timer restart, fast
1680 * retransmit can be triggered by timeout of queue head.
1682 if (tcp_head_timedout(sk
))
1685 /* Trick#4: It is still not OK... But will it be useful to delay
1688 packets_out
= tp
->packets_out
;
1689 if (packets_out
<= tp
->reordering
&&
1690 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1691 !tcp_may_send_now(sk
)) {
1692 /* We have nothing to send. This connection is limited
1693 * either by receiver window or by application.
1701 /* If we receive more dupacks than we expected counting segments
1702 * in assumption of absent reordering, interpret this as reordering.
1703 * The only another reason could be bug in receiver TCP.
1705 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1707 struct tcp_sock
*tp
= tcp_sk(sk
);
1710 holes
= max(tp
->lost_out
, 1U);
1711 holes
= min(holes
, tp
->packets_out
);
1713 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1714 tp
->sacked_out
= tp
->packets_out
- holes
;
1715 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1719 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1721 static void tcp_add_reno_sack(struct sock
*sk
)
1723 struct tcp_sock
*tp
= tcp_sk(sk
);
1725 tcp_check_reno_reordering(sk
, 0);
1726 tcp_sync_left_out(tp
);
1729 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1731 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1733 struct tcp_sock
*tp
= tcp_sk(sk
);
1736 /* One ACK acked hole. The rest eat duplicate ACKs. */
1737 if (acked
-1 >= tp
->sacked_out
)
1740 tp
->sacked_out
-= acked
-1;
1742 tcp_check_reno_reordering(sk
, acked
);
1743 tcp_sync_left_out(tp
);
1746 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1749 tp
->left_out
= tp
->lost_out
;
1752 /* Mark head of queue up as lost. */
1753 static void tcp_mark_head_lost(struct sock
*sk
,
1754 int packets
, u32 high_seq
)
1756 struct tcp_sock
*tp
= tcp_sk(sk
);
1757 struct sk_buff
*skb
;
1760 BUG_TRAP(packets
<= tp
->packets_out
);
1761 if (tp
->lost_skb_hint
) {
1762 skb
= tp
->lost_skb_hint
;
1763 cnt
= tp
->lost_cnt_hint
;
1765 skb
= tcp_write_queue_head(sk
);
1769 tcp_for_write_queue_from(skb
, sk
) {
1770 if (skb
== tcp_send_head(sk
))
1772 /* TODO: do this better */
1773 /* this is not the most efficient way to do this... */
1774 tp
->lost_skb_hint
= skb
;
1775 tp
->lost_cnt_hint
= cnt
;
1776 cnt
+= tcp_skb_pcount(skb
);
1777 if (cnt
> packets
|| after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1779 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1780 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1781 tp
->lost_out
+= tcp_skb_pcount(skb
);
1783 /* clear xmit_retransmit_queue hints
1784 * if this is beyond hint */
1785 if (tp
->retransmit_skb_hint
!= NULL
&&
1786 before(TCP_SKB_CB(skb
)->seq
,
1787 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1788 tp
->retransmit_skb_hint
= NULL
;
1792 tcp_sync_left_out(tp
);
1795 /* Account newly detected lost packet(s) */
1797 static void tcp_update_scoreboard(struct sock
*sk
)
1799 struct tcp_sock
*tp
= tcp_sk(sk
);
1802 int lost
= tp
->fackets_out
- tp
->reordering
;
1805 tcp_mark_head_lost(sk
, lost
, tp
->high_seq
);
1807 tcp_mark_head_lost(sk
, 1, tp
->high_seq
);
1810 /* New heuristics: it is possible only after we switched
1811 * to restart timer each time when something is ACKed.
1812 * Hence, we can detect timed out packets during fast
1813 * retransmit without falling to slow start.
1815 if (!IsReno(tp
) && tcp_head_timedout(sk
)) {
1816 struct sk_buff
*skb
;
1818 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
1819 : tcp_write_queue_head(sk
);
1821 tcp_for_write_queue_from(skb
, sk
) {
1822 if (skb
== tcp_send_head(sk
))
1824 if (!tcp_skb_timedout(sk
, skb
))
1827 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1828 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1829 tp
->lost_out
+= tcp_skb_pcount(skb
);
1831 /* clear xmit_retrans hint */
1832 if (tp
->retransmit_skb_hint
&&
1833 before(TCP_SKB_CB(skb
)->seq
,
1834 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1836 tp
->retransmit_skb_hint
= NULL
;
1840 tp
->scoreboard_skb_hint
= skb
;
1842 tcp_sync_left_out(tp
);
1846 /* CWND moderation, preventing bursts due to too big ACKs
1847 * in dubious situations.
1849 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
1851 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
1852 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
1853 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1856 /* Lower bound on congestion window is slow start threshold
1857 * unless congestion avoidance choice decides to overide it.
1859 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
1861 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1863 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
1866 /* Decrease cwnd each second ack. */
1867 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
1869 struct tcp_sock
*tp
= tcp_sk(sk
);
1870 int decr
= tp
->snd_cwnd_cnt
+ 1;
1872 if ((flag
&(FLAG_ANY_PROGRESS
|FLAG_DSACKING_ACK
)) ||
1873 (IsReno(tp
) && !(flag
&FLAG_NOT_DUP
))) {
1874 tp
->snd_cwnd_cnt
= decr
&1;
1877 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
1878 tp
->snd_cwnd
-= decr
;
1880 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
1881 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1885 /* Nothing was retransmitted or returned timestamp is less
1886 * than timestamp of the first retransmission.
1888 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
1890 return !tp
->retrans_stamp
||
1891 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
1892 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
1895 /* Undo procedures. */
1897 #if FASTRETRANS_DEBUG > 1
1898 static void DBGUNDO(struct sock
*sk
, const char *msg
)
1900 struct tcp_sock
*tp
= tcp_sk(sk
);
1901 struct inet_sock
*inet
= inet_sk(sk
);
1903 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
1905 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
1906 tp
->snd_cwnd
, tp
->left_out
,
1907 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
1911 #define DBGUNDO(x...) do { } while (0)
1914 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
1916 struct tcp_sock
*tp
= tcp_sk(sk
);
1918 if (tp
->prior_ssthresh
) {
1919 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1921 if (icsk
->icsk_ca_ops
->undo_cwnd
)
1922 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
1924 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
1926 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
1927 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
1928 TCP_ECN_withdraw_cwr(tp
);
1931 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
1933 tcp_moderate_cwnd(tp
);
1934 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1936 /* There is something screwy going on with the retrans hints after
1938 clear_all_retrans_hints(tp
);
1941 static inline int tcp_may_undo(struct tcp_sock
*tp
)
1943 return tp
->undo_marker
&&
1944 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
1947 /* People celebrate: "We love our President!" */
1948 static int tcp_try_undo_recovery(struct sock
*sk
)
1950 struct tcp_sock
*tp
= tcp_sk(sk
);
1952 if (tcp_may_undo(tp
)) {
1953 /* Happy end! We did not retransmit anything
1954 * or our original transmission succeeded.
1956 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
1957 tcp_undo_cwr(sk
, 1);
1958 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
1959 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
1961 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
1962 tp
->undo_marker
= 0;
1964 if (tp
->snd_una
== tp
->high_seq
&& IsReno(tp
)) {
1965 /* Hold old state until something *above* high_seq
1966 * is ACKed. For Reno it is MUST to prevent false
1967 * fast retransmits (RFC2582). SACK TCP is safe. */
1968 tcp_moderate_cwnd(tp
);
1971 tcp_set_ca_state(sk
, TCP_CA_Open
);
1975 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
1976 static void tcp_try_undo_dsack(struct sock
*sk
)
1978 struct tcp_sock
*tp
= tcp_sk(sk
);
1980 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
1981 DBGUNDO(sk
, "D-SACK");
1982 tcp_undo_cwr(sk
, 1);
1983 tp
->undo_marker
= 0;
1984 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
1988 /* Undo during fast recovery after partial ACK. */
1990 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
1992 struct tcp_sock
*tp
= tcp_sk(sk
);
1993 /* Partial ACK arrived. Force Hoe's retransmit. */
1994 int failed
= IsReno(tp
) || tp
->fackets_out
>tp
->reordering
;
1996 if (tcp_may_undo(tp
)) {
1997 /* Plain luck! Hole if filled with delayed
1998 * packet, rather than with a retransmit.
2000 if (tp
->retrans_out
== 0)
2001 tp
->retrans_stamp
= 0;
2003 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2006 tcp_undo_cwr(sk
, 0);
2007 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
2009 /* So... Do not make Hoe's retransmit yet.
2010 * If the first packet was delayed, the rest
2011 * ones are most probably delayed as well.
2018 /* Undo during loss recovery after partial ACK. */
2019 static int tcp_try_undo_loss(struct sock
*sk
)
2021 struct tcp_sock
*tp
= tcp_sk(sk
);
2023 if (tcp_may_undo(tp
)) {
2024 struct sk_buff
*skb
;
2025 tcp_for_write_queue(skb
, sk
) {
2026 if (skb
== tcp_send_head(sk
))
2028 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2031 clear_all_retrans_hints(tp
);
2033 DBGUNDO(sk
, "partial loss");
2035 tp
->left_out
= tp
->sacked_out
;
2036 tcp_undo_cwr(sk
, 1);
2037 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2038 inet_csk(sk
)->icsk_retransmits
= 0;
2039 tp
->undo_marker
= 0;
2041 tcp_set_ca_state(sk
, TCP_CA_Open
);
2047 static inline void tcp_complete_cwr(struct sock
*sk
)
2049 struct tcp_sock
*tp
= tcp_sk(sk
);
2050 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2051 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2052 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2055 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2057 struct tcp_sock
*tp
= tcp_sk(sk
);
2059 tcp_sync_left_out(tp
);
2061 if (tp
->retrans_out
== 0)
2062 tp
->retrans_stamp
= 0;
2065 tcp_enter_cwr(sk
, 1);
2067 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2068 int state
= TCP_CA_Open
;
2070 if (tp
->left_out
|| tp
->retrans_out
|| tp
->undo_marker
)
2071 state
= TCP_CA_Disorder
;
2073 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2074 tcp_set_ca_state(sk
, state
);
2075 tp
->high_seq
= tp
->snd_nxt
;
2077 tcp_moderate_cwnd(tp
);
2079 tcp_cwnd_down(sk
, flag
);
2083 static void tcp_mtup_probe_failed(struct sock
*sk
)
2085 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2087 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2088 icsk
->icsk_mtup
.probe_size
= 0;
2091 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
2093 struct tcp_sock
*tp
= tcp_sk(sk
);
2094 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2096 /* FIXME: breaks with very large cwnd */
2097 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2098 tp
->snd_cwnd
= tp
->snd_cwnd
*
2099 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2100 icsk
->icsk_mtup
.probe_size
;
2101 tp
->snd_cwnd_cnt
= 0;
2102 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2103 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2105 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2106 icsk
->icsk_mtup
.probe_size
= 0;
2107 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2111 /* Process an event, which can update packets-in-flight not trivially.
2112 * Main goal of this function is to calculate new estimate for left_out,
2113 * taking into account both packets sitting in receiver's buffer and
2114 * packets lost by network.
2116 * Besides that it does CWND reduction, when packet loss is detected
2117 * and changes state of machine.
2119 * It does _not_ decide what to send, it is made in function
2120 * tcp_xmit_retransmit_queue().
2123 tcp_fastretrans_alert(struct sock
*sk
, int prior_packets
, int flag
)
2125 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2126 struct tcp_sock
*tp
= tcp_sk(sk
);
2127 int is_dupack
= !(flag
&(FLAG_SND_UNA_ADVANCED
|FLAG_NOT_DUP
));
2128 int do_lost
= is_dupack
|| ((flag
&FLAG_DATA_SACKED
) &&
2129 (tp
->fackets_out
> tp
->reordering
));
2131 /* Some technical things:
2132 * 1. Reno does not count dupacks (sacked_out) automatically. */
2133 if (!tp
->packets_out
)
2135 /* 2. SACK counts snd_fack in packets inaccurately. */
2136 if (tp
->sacked_out
== 0)
2137 tp
->fackets_out
= 0;
2139 /* Now state machine starts.
2140 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2142 tp
->prior_ssthresh
= 0;
2144 /* B. In all the states check for reneging SACKs. */
2145 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
2148 /* C. Process data loss notification, provided it is valid. */
2149 if ((flag
&FLAG_DATA_LOST
) &&
2150 before(tp
->snd_una
, tp
->high_seq
) &&
2151 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2152 tp
->fackets_out
> tp
->reordering
) {
2153 tcp_mark_head_lost(sk
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
2154 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
2157 /* D. Synchronize left_out to current state. */
2158 tcp_sync_left_out(tp
);
2160 /* E. Check state exit conditions. State can be terminated
2161 * when high_seq is ACKed. */
2162 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2163 BUG_TRAP(tp
->retrans_out
== 0);
2164 tp
->retrans_stamp
= 0;
2165 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2166 switch (icsk
->icsk_ca_state
) {
2168 icsk
->icsk_retransmits
= 0;
2169 if (tcp_try_undo_recovery(sk
))
2174 /* CWR is to be held something *above* high_seq
2175 * is ACKed for CWR bit to reach receiver. */
2176 if (tp
->snd_una
!= tp
->high_seq
) {
2177 tcp_complete_cwr(sk
);
2178 tcp_set_ca_state(sk
, TCP_CA_Open
);
2182 case TCP_CA_Disorder
:
2183 tcp_try_undo_dsack(sk
);
2184 if (!tp
->undo_marker
||
2185 /* For SACK case do not Open to allow to undo
2186 * catching for all duplicate ACKs. */
2187 IsReno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2188 tp
->undo_marker
= 0;
2189 tcp_set_ca_state(sk
, TCP_CA_Open
);
2193 case TCP_CA_Recovery
:
2195 tcp_reset_reno_sack(tp
);
2196 if (tcp_try_undo_recovery(sk
))
2198 tcp_complete_cwr(sk
);
2203 /* F. Process state. */
2204 switch (icsk
->icsk_ca_state
) {
2205 case TCP_CA_Recovery
:
2206 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2207 if (IsReno(tp
) && is_dupack
)
2208 tcp_add_reno_sack(sk
);
2210 int acked
= prior_packets
- tp
->packets_out
;
2212 tcp_remove_reno_sacks(sk
, acked
);
2213 do_lost
= tcp_try_undo_partial(sk
, acked
);
2217 if (flag
&FLAG_DATA_ACKED
)
2218 icsk
->icsk_retransmits
= 0;
2219 if (!tcp_try_undo_loss(sk
)) {
2220 tcp_moderate_cwnd(tp
);
2221 tcp_xmit_retransmit_queue(sk
);
2224 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2226 /* Loss is undone; fall through to processing in Open state. */
2229 if (flag
& FLAG_SND_UNA_ADVANCED
)
2230 tcp_reset_reno_sack(tp
);
2232 tcp_add_reno_sack(sk
);
2235 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2236 tcp_try_undo_dsack(sk
);
2238 if (!tcp_time_to_recover(sk
)) {
2239 tcp_try_to_open(sk
, flag
);
2243 /* MTU probe failure: don't reduce cwnd */
2244 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2245 icsk
->icsk_mtup
.probe_size
&&
2246 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2247 tcp_mtup_probe_failed(sk
);
2248 /* Restores the reduction we did in tcp_mtup_probe() */
2250 tcp_simple_retransmit(sk
);
2254 /* Otherwise enter Recovery state */
2257 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
2259 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
2261 tp
->high_seq
= tp
->snd_nxt
;
2262 tp
->prior_ssthresh
= 0;
2263 tp
->undo_marker
= tp
->snd_una
;
2264 tp
->undo_retrans
= tp
->retrans_out
;
2266 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2267 if (!(flag
&FLAG_ECE
))
2268 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2269 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2270 TCP_ECN_queue_cwr(tp
);
2273 tp
->bytes_acked
= 0;
2274 tp
->snd_cwnd_cnt
= 0;
2275 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2278 if (do_lost
|| tcp_head_timedout(sk
))
2279 tcp_update_scoreboard(sk
);
2280 tcp_cwnd_down(sk
, flag
);
2281 tcp_xmit_retransmit_queue(sk
);
2284 /* Read draft-ietf-tcplw-high-performance before mucking
2285 * with this code. (Supersedes RFC1323)
2287 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2289 /* RTTM Rule: A TSecr value received in a segment is used to
2290 * update the averaged RTT measurement only if the segment
2291 * acknowledges some new data, i.e., only if it advances the
2292 * left edge of the send window.
2294 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2295 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2297 * Changed: reset backoff as soon as we see the first valid sample.
2298 * If we do not, we get strongly overestimated rto. With timestamps
2299 * samples are accepted even from very old segments: f.e., when rtt=1
2300 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2301 * answer arrives rto becomes 120 seconds! If at least one of segments
2302 * in window is lost... Voila. --ANK (010210)
2304 struct tcp_sock
*tp
= tcp_sk(sk
);
2305 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2306 tcp_rtt_estimator(sk
, seq_rtt
);
2308 inet_csk(sk
)->icsk_backoff
= 0;
2312 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2314 /* We don't have a timestamp. Can only use
2315 * packets that are not retransmitted to determine
2316 * rtt estimates. Also, we must not reset the
2317 * backoff for rto until we get a non-retransmitted
2318 * packet. This allows us to deal with a situation
2319 * where the network delay has increased suddenly.
2320 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2323 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2326 tcp_rtt_estimator(sk
, seq_rtt
);
2328 inet_csk(sk
)->icsk_backoff
= 0;
2332 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2335 const struct tcp_sock
*tp
= tcp_sk(sk
);
2336 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2337 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2338 tcp_ack_saw_tstamp(sk
, flag
);
2339 else if (seq_rtt
>= 0)
2340 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2343 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
,
2344 u32 in_flight
, int good
)
2346 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2347 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
, good
);
2348 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2351 /* Restart timer after forward progress on connection.
2352 * RFC2988 recommends to restart timer to now+rto.
2355 static void tcp_ack_packets_out(struct sock
*sk
)
2357 struct tcp_sock
*tp
= tcp_sk(sk
);
2359 if (!tp
->packets_out
) {
2360 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2362 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2366 static int tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
,
2367 __u32 now
, __s32
*seq_rtt
)
2369 struct tcp_sock
*tp
= tcp_sk(sk
);
2370 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2371 __u32 seq
= tp
->snd_una
;
2372 __u32 packets_acked
;
2375 /* If we get here, the whole TSO packet has not been
2378 BUG_ON(!after(scb
->end_seq
, seq
));
2380 packets_acked
= tcp_skb_pcount(skb
);
2381 if (tcp_trim_head(sk
, skb
, seq
- scb
->seq
))
2383 packets_acked
-= tcp_skb_pcount(skb
);
2385 if (packets_acked
) {
2386 __u8 sacked
= scb
->sacked
;
2388 acked
|= FLAG_DATA_ACKED
;
2390 if (sacked
& TCPCB_RETRANS
) {
2391 if (sacked
& TCPCB_SACKED_RETRANS
)
2392 tp
->retrans_out
-= packets_acked
;
2393 acked
|= FLAG_RETRANS_DATA_ACKED
;
2395 } else if (*seq_rtt
< 0)
2396 *seq_rtt
= now
- scb
->when
;
2397 if (sacked
& TCPCB_SACKED_ACKED
)
2398 tp
->sacked_out
-= packets_acked
;
2399 if (sacked
& TCPCB_LOST
)
2400 tp
->lost_out
-= packets_acked
;
2401 if (sacked
& TCPCB_URG
) {
2403 !before(seq
, tp
->snd_up
))
2406 } else if (*seq_rtt
< 0)
2407 *seq_rtt
= now
- scb
->when
;
2409 if (tp
->fackets_out
) {
2410 __u32 dval
= min(tp
->fackets_out
, packets_acked
);
2411 tp
->fackets_out
-= dval
;
2413 tp
->packets_out
-= packets_acked
;
2415 BUG_ON(tcp_skb_pcount(skb
) == 0);
2416 BUG_ON(!before(scb
->seq
, scb
->end_seq
));
2422 /* Remove acknowledged frames from the retransmission queue. */
2423 static int tcp_clean_rtx_queue(struct sock
*sk
, __s32
*seq_rtt_p
)
2425 struct tcp_sock
*tp
= tcp_sk(sk
);
2426 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2427 struct sk_buff
*skb
;
2428 __u32 now
= tcp_time_stamp
;
2430 int prior_packets
= tp
->packets_out
;
2432 ktime_t last_ackt
= net_invalid_timestamp();
2434 while ((skb
= tcp_write_queue_head(sk
)) &&
2435 skb
!= tcp_send_head(sk
)) {
2436 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2437 __u8 sacked
= scb
->sacked
;
2439 /* If our packet is before the ack sequence we can
2440 * discard it as it's confirmed to have arrived at
2443 if (after(scb
->end_seq
, tp
->snd_una
)) {
2444 if (tcp_skb_pcount(skb
) > 1 &&
2445 after(tp
->snd_una
, scb
->seq
))
2446 acked
|= tcp_tso_acked(sk
, skb
,
2451 /* Initial outgoing SYN's get put onto the write_queue
2452 * just like anything else we transmit. It is not
2453 * true data, and if we misinform our callers that
2454 * this ACK acks real data, we will erroneously exit
2455 * connection startup slow start one packet too
2456 * quickly. This is severely frowned upon behavior.
2458 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2459 acked
|= FLAG_DATA_ACKED
;
2461 acked
|= FLAG_SYN_ACKED
;
2462 tp
->retrans_stamp
= 0;
2465 /* MTU probing checks */
2466 if (icsk
->icsk_mtup
.probe_size
) {
2467 if (!after(tp
->mtu_probe
.probe_seq_end
, TCP_SKB_CB(skb
)->end_seq
)) {
2468 tcp_mtup_probe_success(sk
, skb
);
2473 if (sacked
& TCPCB_RETRANS
) {
2474 if (sacked
& TCPCB_SACKED_RETRANS
)
2475 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2476 acked
|= FLAG_RETRANS_DATA_ACKED
;
2478 } else if (seq_rtt
< 0) {
2479 seq_rtt
= now
- scb
->when
;
2480 last_ackt
= skb
->tstamp
;
2482 if (sacked
& TCPCB_SACKED_ACKED
)
2483 tp
->sacked_out
-= tcp_skb_pcount(skb
);
2484 if (sacked
& TCPCB_LOST
)
2485 tp
->lost_out
-= tcp_skb_pcount(skb
);
2486 if (sacked
& TCPCB_URG
) {
2488 !before(scb
->end_seq
, tp
->snd_up
))
2491 } else if (seq_rtt
< 0) {
2492 seq_rtt
= now
- scb
->when
;
2493 last_ackt
= skb
->tstamp
;
2495 tcp_dec_pcount_approx(&tp
->fackets_out
, skb
);
2496 tcp_packets_out_dec(tp
, skb
);
2497 tcp_unlink_write_queue(skb
, sk
);
2498 sk_stream_free_skb(sk
, skb
);
2499 clear_all_retrans_hints(tp
);
2502 if (acked
&FLAG_ACKED
) {
2503 u32 pkts_acked
= prior_packets
- tp
->packets_out
;
2504 const struct tcp_congestion_ops
*ca_ops
2505 = inet_csk(sk
)->icsk_ca_ops
;
2507 tcp_ack_update_rtt(sk
, acked
, seq_rtt
);
2508 tcp_ack_packets_out(sk
);
2510 if (ca_ops
->pkts_acked
) {
2513 /* Is the ACK triggering packet unambiguous? */
2514 if (!(acked
& FLAG_RETRANS_DATA_ACKED
)) {
2515 /* High resolution needed and available? */
2516 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
2517 !ktime_equal(last_ackt
,
2518 net_invalid_timestamp()))
2519 rtt_us
= ktime_us_delta(ktime_get_real(),
2521 else if (seq_rtt
> 0)
2522 rtt_us
= jiffies_to_usecs(seq_rtt
);
2525 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
2529 #if FASTRETRANS_DEBUG > 0
2530 BUG_TRAP((int)tp
->sacked_out
>= 0);
2531 BUG_TRAP((int)tp
->lost_out
>= 0);
2532 BUG_TRAP((int)tp
->retrans_out
>= 0);
2533 if (!tp
->packets_out
&& tp
->rx_opt
.sack_ok
) {
2534 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2536 printk(KERN_DEBUG
"Leak l=%u %d\n",
2537 tp
->lost_out
, icsk
->icsk_ca_state
);
2540 if (tp
->sacked_out
) {
2541 printk(KERN_DEBUG
"Leak s=%u %d\n",
2542 tp
->sacked_out
, icsk
->icsk_ca_state
);
2545 if (tp
->retrans_out
) {
2546 printk(KERN_DEBUG
"Leak r=%u %d\n",
2547 tp
->retrans_out
, icsk
->icsk_ca_state
);
2548 tp
->retrans_out
= 0;
2552 *seq_rtt_p
= seq_rtt
;
2556 static void tcp_ack_probe(struct sock
*sk
)
2558 const struct tcp_sock
*tp
= tcp_sk(sk
);
2559 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2561 /* Was it a usable window open? */
2563 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2564 tp
->snd_una
+ tp
->snd_wnd
)) {
2565 icsk
->icsk_backoff
= 0;
2566 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2567 /* Socket must be waked up by subsequent tcp_data_snd_check().
2568 * This function is not for random using!
2571 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2572 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2577 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2579 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2580 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2583 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2585 const struct tcp_sock
*tp
= tcp_sk(sk
);
2586 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2587 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2590 /* Check that window update is acceptable.
2591 * The function assumes that snd_una<=ack<=snd_next.
2593 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2594 const u32 ack_seq
, const u32 nwin
)
2596 return (after(ack
, tp
->snd_una
) ||
2597 after(ack_seq
, tp
->snd_wl1
) ||
2598 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2601 /* Update our send window.
2603 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2604 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2606 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
2609 struct tcp_sock
*tp
= tcp_sk(sk
);
2611 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
2613 if (likely(!tcp_hdr(skb
)->syn
))
2614 nwin
<<= tp
->rx_opt
.snd_wscale
;
2616 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2617 flag
|= FLAG_WIN_UPDATE
;
2618 tcp_update_wl(tp
, ack
, ack_seq
);
2620 if (tp
->snd_wnd
!= nwin
) {
2623 /* Note, it is the only place, where
2624 * fast path is recovered for sending TCP.
2627 tcp_fast_path_check(sk
);
2629 if (nwin
> tp
->max_window
) {
2630 tp
->max_window
= nwin
;
2631 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
2641 /* A very conservative spurious RTO response algorithm: reduce cwnd and
2642 * continue in congestion avoidance.
2644 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
2646 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2647 tp
->snd_cwnd_cnt
= 0;
2648 TCP_ECN_queue_cwr(tp
);
2649 tcp_moderate_cwnd(tp
);
2652 /* A conservative spurious RTO response algorithm: reduce cwnd using
2653 * rate halving and continue in congestion avoidance.
2655 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
2657 tcp_enter_cwr(sk
, 0);
2660 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
2663 tcp_ratehalving_spur_to_response(sk
);
2665 tcp_undo_cwr(sk
, 1);
2668 /* F-RTO spurious RTO detection algorithm (RFC4138)
2670 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
2671 * comments). State (ACK number) is kept in frto_counter. When ACK advances
2672 * window (but not to or beyond highest sequence sent before RTO):
2673 * On First ACK, send two new segments out.
2674 * On Second ACK, RTO was likely spurious. Do spurious response (response
2675 * algorithm is not part of the F-RTO detection algorithm
2676 * given in RFC4138 but can be selected separately).
2677 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
2678 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
2679 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
2680 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
2682 * Rationale: if the RTO was spurious, new ACKs should arrive from the
2683 * original window even after we transmit two new data segments.
2686 * on first step, wait until first cumulative ACK arrives, then move to
2687 * the second step. In second step, the next ACK decides.
2689 * F-RTO is implemented (mainly) in four functions:
2690 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
2691 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
2692 * called when tcp_use_frto() showed green light
2693 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
2694 * - tcp_enter_frto_loss() is called if there is not enough evidence
2695 * to prove that the RTO is indeed spurious. It transfers the control
2696 * from F-RTO to the conventional RTO recovery
2698 static int tcp_process_frto(struct sock
*sk
, int flag
)
2700 struct tcp_sock
*tp
= tcp_sk(sk
);
2702 tcp_sync_left_out(tp
);
2704 /* Duplicate the behavior from Loss state (fastretrans_alert) */
2705 if (flag
&FLAG_DATA_ACKED
)
2706 inet_csk(sk
)->icsk_retransmits
= 0;
2708 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
2709 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
2713 if (!IsSackFrto() || IsReno(tp
)) {
2714 /* RFC4138 shortcoming in step 2; should also have case c):
2715 * ACK isn't duplicate nor advances window, e.g., opposite dir
2718 if (!(flag
&FLAG_ANY_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2721 if (!(flag
&FLAG_DATA_ACKED
)) {
2722 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
2727 if (!(flag
&FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
2728 /* Prevent sending of new data. */
2729 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2730 tcp_packets_in_flight(tp
));
2734 if ((tp
->frto_counter
>= 2) &&
2735 (!(flag
&FLAG_FORWARD_PROGRESS
) ||
2736 ((flag
&FLAG_DATA_SACKED
) && !(flag
&FLAG_ONLY_ORIG_SACKED
)))) {
2737 /* RFC4138 shortcoming (see comment above) */
2738 if (!(flag
&FLAG_FORWARD_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2741 tcp_enter_frto_loss(sk
, 3, flag
);
2746 if (tp
->frto_counter
== 1) {
2747 /* Sending of the next skb must be allowed or no FRTO */
2748 if (!tcp_send_head(sk
) ||
2749 after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2750 tp
->snd_una
+ tp
->snd_wnd
)) {
2751 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3),
2756 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2757 tp
->frto_counter
= 2;
2760 switch (sysctl_tcp_frto_response
) {
2762 tcp_undo_spur_to_response(sk
, flag
);
2765 tcp_conservative_spur_to_response(tp
);
2768 tcp_ratehalving_spur_to_response(sk
);
2771 tp
->frto_counter
= 0;
2776 /* This routine deals with incoming acks, but not outgoing ones. */
2777 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2779 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2780 struct tcp_sock
*tp
= tcp_sk(sk
);
2781 u32 prior_snd_una
= tp
->snd_una
;
2782 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2783 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2784 u32 prior_in_flight
;
2789 /* If the ack is newer than sent or older than previous acks
2790 * then we can probably ignore it.
2792 if (after(ack
, tp
->snd_nxt
))
2793 goto uninteresting_ack
;
2795 if (before(ack
, prior_snd_una
))
2798 if (after(ack
, prior_snd_una
))
2799 flag
|= FLAG_SND_UNA_ADVANCED
;
2801 if (sysctl_tcp_abc
) {
2802 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
2803 tp
->bytes_acked
+= ack
- prior_snd_una
;
2804 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
2805 /* we assume just one segment left network */
2806 tp
->bytes_acked
+= min(ack
- prior_snd_una
, tp
->mss_cache
);
2809 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2810 /* Window is constant, pure forward advance.
2811 * No more checks are required.
2812 * Note, we use the fact that SND.UNA>=SND.WL2.
2814 tcp_update_wl(tp
, ack
, ack_seq
);
2816 flag
|= FLAG_WIN_UPDATE
;
2818 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2820 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
2822 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
2825 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
2827 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
2829 if (TCP_SKB_CB(skb
)->sacked
)
2830 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2832 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
2835 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
2838 /* We passed data and got it acked, remove any soft error
2839 * log. Something worked...
2841 sk
->sk_err_soft
= 0;
2842 tp
->rcv_tstamp
= tcp_time_stamp
;
2843 prior_packets
= tp
->packets_out
;
2847 prior_in_flight
= tcp_packets_in_flight(tp
);
2849 /* See if we can take anything off of the retransmit queue. */
2850 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
2852 if (tp
->frto_counter
)
2853 frto_cwnd
= tcp_process_frto(sk
, flag
);
2855 if (tcp_ack_is_dubious(sk
, flag
)) {
2856 /* Advance CWND, if state allows this. */
2857 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
2858 tcp_may_raise_cwnd(sk
, flag
))
2859 tcp_cong_avoid(sk
, ack
, prior_in_flight
, 0);
2860 tcp_fastretrans_alert(sk
, prior_packets
, flag
);
2862 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
2863 tcp_cong_avoid(sk
, ack
, prior_in_flight
, 1);
2866 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
2867 dst_confirm(sk
->sk_dst_cache
);
2872 icsk
->icsk_probes_out
= 0;
2874 /* If this ack opens up a zero window, clear backoff. It was
2875 * being used to time the probes, and is probably far higher than
2876 * it needs to be for normal retransmission.
2878 if (tcp_send_head(sk
))
2883 if (TCP_SKB_CB(skb
)->sacked
)
2884 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
2887 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
2892 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
2893 * But, this can also be called on packets in the established flow when
2894 * the fast version below fails.
2896 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
2899 struct tcphdr
*th
= tcp_hdr(skb
);
2900 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
2902 ptr
= (unsigned char *)(th
+ 1);
2903 opt_rx
->saw_tstamp
= 0;
2905 while (length
> 0) {
2912 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
2917 if (opsize
< 2) /* "silly options" */
2919 if (opsize
> length
)
2920 return; /* don't parse partial options */
2923 if (opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
2924 u16 in_mss
= ntohs(get_unaligned((__be16
*)ptr
));
2926 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
2927 in_mss
= opt_rx
->user_mss
;
2928 opt_rx
->mss_clamp
= in_mss
;
2933 if (opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
2934 if (sysctl_tcp_window_scaling
) {
2935 __u8 snd_wscale
= *(__u8
*) ptr
;
2936 opt_rx
->wscale_ok
= 1;
2937 if (snd_wscale
> 14) {
2938 if (net_ratelimit())
2939 printk(KERN_INFO
"tcp_parse_options: Illegal window "
2940 "scaling value %d >14 received.\n",
2944 opt_rx
->snd_wscale
= snd_wscale
;
2947 case TCPOPT_TIMESTAMP
:
2948 if (opsize
==TCPOLEN_TIMESTAMP
) {
2949 if ((estab
&& opt_rx
->tstamp_ok
) ||
2950 (!estab
&& sysctl_tcp_timestamps
)) {
2951 opt_rx
->saw_tstamp
= 1;
2952 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__be32
*)ptr
));
2953 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__be32
*)(ptr
+4)));
2957 case TCPOPT_SACK_PERM
:
2958 if (opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
2959 if (sysctl_tcp_sack
) {
2960 opt_rx
->sack_ok
= 1;
2961 tcp_sack_reset(opt_rx
);
2967 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
2968 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
2970 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
2973 #ifdef CONFIG_TCP_MD5SIG
2976 * The MD5 Hash has already been
2977 * checked (see tcp_v{4,6}_do_rcv()).
2989 /* Fast parse options. This hopes to only see timestamps.
2990 * If it is wrong it falls back on tcp_parse_options().
2992 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
2993 struct tcp_sock
*tp
)
2995 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
2996 tp
->rx_opt
.saw_tstamp
= 0;
2998 } else if (tp
->rx_opt
.tstamp_ok
&&
2999 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
3000 __be32
*ptr
= (__be32
*)(th
+ 1);
3001 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3002 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3003 tp
->rx_opt
.saw_tstamp
= 1;
3005 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3007 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3011 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
3015 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
3017 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3018 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3021 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3023 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3024 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3025 * extra check below makes sure this can only happen
3026 * for pure ACK frames. -DaveM
3028 * Not only, also it occurs for expired timestamps.
3031 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
3032 get_seconds() >= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
3033 tcp_store_ts_recent(tp
);
3037 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3039 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3040 * it can pass through stack. So, the following predicate verifies that
3041 * this segment is not used for anything but congestion avoidance or
3042 * fast retransmit. Moreover, we even are able to eliminate most of such
3043 * second order effects, if we apply some small "replay" window (~RTO)
3044 * to timestamp space.
3046 * All these measures still do not guarantee that we reject wrapped ACKs
3047 * on networks with high bandwidth, when sequence space is recycled fastly,
3048 * but it guarantees that such events will be very rare and do not affect
3049 * connection seriously. This doesn't look nice, but alas, PAWS is really
3052 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3053 * states that events when retransmit arrives after original data are rare.
3054 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3055 * the biggest problem on large power networks even with minor reordering.
3056 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3057 * up to bandwidth of 18Gigabit/sec. 8) ]
3060 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3062 struct tcp_sock
*tp
= tcp_sk(sk
);
3063 struct tcphdr
*th
= tcp_hdr(skb
);
3064 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3065 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3067 return (/* 1. Pure ACK with correct sequence number. */
3068 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3070 /* 2. ... and duplicate ACK. */
3071 ack
== tp
->snd_una
&&
3073 /* 3. ... and does not update window. */
3074 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3076 /* 4. ... and sits in replay window. */
3077 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3080 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
3082 const struct tcp_sock
*tp
= tcp_sk(sk
);
3083 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
3084 get_seconds() < tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
3085 !tcp_disordered_ack(sk
, skb
));
3088 /* Check segment sequence number for validity.
3090 * Segment controls are considered valid, if the segment
3091 * fits to the window after truncation to the window. Acceptability
3092 * of data (and SYN, FIN, of course) is checked separately.
3093 * See tcp_data_queue(), for example.
3095 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3096 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3097 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3098 * (borrowed from freebsd)
3101 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3103 return !before(end_seq
, tp
->rcv_wup
) &&
3104 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3107 /* When we get a reset we do this. */
3108 static void tcp_reset(struct sock
*sk
)
3110 /* We want the right error as BSD sees it (and indeed as we do). */
3111 switch (sk
->sk_state
) {
3113 sk
->sk_err
= ECONNREFUSED
;
3115 case TCP_CLOSE_WAIT
:
3121 sk
->sk_err
= ECONNRESET
;
3124 if (!sock_flag(sk
, SOCK_DEAD
))
3125 sk
->sk_error_report(sk
);
3131 * Process the FIN bit. This now behaves as it is supposed to work
3132 * and the FIN takes effect when it is validly part of sequence
3133 * space. Not before when we get holes.
3135 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3136 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3139 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3140 * close and we go into CLOSING (and later onto TIME-WAIT)
3142 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3144 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
3146 struct tcp_sock
*tp
= tcp_sk(sk
);
3148 inet_csk_schedule_ack(sk
);
3150 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3151 sock_set_flag(sk
, SOCK_DONE
);
3153 switch (sk
->sk_state
) {
3155 case TCP_ESTABLISHED
:
3156 /* Move to CLOSE_WAIT */
3157 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3158 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3161 case TCP_CLOSE_WAIT
:
3163 /* Received a retransmission of the FIN, do
3168 /* RFC793: Remain in the LAST-ACK state. */
3172 /* This case occurs when a simultaneous close
3173 * happens, we must ack the received FIN and
3174 * enter the CLOSING state.
3177 tcp_set_state(sk
, TCP_CLOSING
);
3180 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3182 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3185 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3186 * cases we should never reach this piece of code.
3188 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
3189 __FUNCTION__
, sk
->sk_state
);
3193 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3194 * Probably, we should reset in this case. For now drop them.
3196 __skb_queue_purge(&tp
->out_of_order_queue
);
3197 if (tp
->rx_opt
.sack_ok
)
3198 tcp_sack_reset(&tp
->rx_opt
);
3199 sk_stream_mem_reclaim(sk
);
3201 if (!sock_flag(sk
, SOCK_DEAD
)) {
3202 sk
->sk_state_change(sk
);
3204 /* Do not send POLL_HUP for half duplex close. */
3205 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3206 sk
->sk_state
== TCP_CLOSE
)
3207 sk_wake_async(sk
, 1, POLL_HUP
);
3209 sk_wake_async(sk
, 1, POLL_IN
);
3213 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
3215 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3216 if (before(seq
, sp
->start_seq
))
3217 sp
->start_seq
= seq
;
3218 if (after(end_seq
, sp
->end_seq
))
3219 sp
->end_seq
= end_seq
;
3225 static void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3227 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
3228 if (before(seq
, tp
->rcv_nxt
))
3229 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
3231 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
3233 tp
->rx_opt
.dsack
= 1;
3234 tp
->duplicate_sack
[0].start_seq
= seq
;
3235 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3236 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
3240 static void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3242 if (!tp
->rx_opt
.dsack
)
3243 tcp_dsack_set(tp
, seq
, end_seq
);
3245 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3248 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3250 struct tcp_sock
*tp
= tcp_sk(sk
);
3252 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3253 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3254 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3255 tcp_enter_quickack_mode(sk
);
3257 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_dsack
) {
3258 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3260 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3261 end_seq
= tp
->rcv_nxt
;
3262 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3269 /* These routines update the SACK block as out-of-order packets arrive or
3270 * in-order packets close up the sequence space.
3272 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3275 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3276 struct tcp_sack_block
*swalk
= sp
+1;
3278 /* See if the recent change to the first SACK eats into
3279 * or hits the sequence space of other SACK blocks, if so coalesce.
3281 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
3282 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3285 /* Zap SWALK, by moving every further SACK up by one slot.
3286 * Decrease num_sacks.
3288 tp
->rx_opt
.num_sacks
--;
3289 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3290 for (i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3294 this_sack
++, swalk
++;
3298 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
3302 tmp
= sack1
->start_seq
;
3303 sack1
->start_seq
= sack2
->start_seq
;
3304 sack2
->start_seq
= tmp
;
3306 tmp
= sack1
->end_seq
;
3307 sack1
->end_seq
= sack2
->end_seq
;
3308 sack2
->end_seq
= tmp
;
3311 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3313 struct tcp_sock
*tp
= tcp_sk(sk
);
3314 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3315 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3321 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
3322 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3323 /* Rotate this_sack to the first one. */
3324 for (; this_sack
>0; this_sack
--, sp
--)
3325 tcp_sack_swap(sp
, sp
-1);
3327 tcp_sack_maybe_coalesce(tp
);
3332 /* Could not find an adjacent existing SACK, build a new one,
3333 * put it at the front, and shift everyone else down. We
3334 * always know there is at least one SACK present already here.
3336 * If the sack array is full, forget about the last one.
3338 if (this_sack
>= 4) {
3340 tp
->rx_opt
.num_sacks
--;
3343 for (; this_sack
> 0; this_sack
--, sp
--)
3347 /* Build the new head SACK, and we're done. */
3348 sp
->start_seq
= seq
;
3349 sp
->end_seq
= end_seq
;
3350 tp
->rx_opt
.num_sacks
++;
3351 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3354 /* RCV.NXT advances, some SACKs should be eaten. */
3356 static void tcp_sack_remove(struct tcp_sock
*tp
)
3358 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3359 int num_sacks
= tp
->rx_opt
.num_sacks
;
3362 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3363 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3364 tp
->rx_opt
.num_sacks
= 0;
3365 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3369 for (this_sack
= 0; this_sack
< num_sacks
; ) {
3370 /* Check if the start of the sack is covered by RCV.NXT. */
3371 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3374 /* RCV.NXT must cover all the block! */
3375 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
3377 /* Zap this SACK, by moving forward any other SACKS. */
3378 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3379 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3386 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3387 tp
->rx_opt
.num_sacks
= num_sacks
;
3388 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3392 /* This one checks to see if we can put data from the
3393 * out_of_order queue into the receive_queue.
3395 static void tcp_ofo_queue(struct sock
*sk
)
3397 struct tcp_sock
*tp
= tcp_sk(sk
);
3398 __u32 dsack_high
= tp
->rcv_nxt
;
3399 struct sk_buff
*skb
;
3401 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3402 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3405 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3406 __u32 dsack
= dsack_high
;
3407 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3408 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3409 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
3412 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3413 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3414 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3418 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3419 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3420 TCP_SKB_CB(skb
)->end_seq
);
3422 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3423 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3424 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3425 if (tcp_hdr(skb
)->fin
)
3426 tcp_fin(skb
, sk
, tcp_hdr(skb
));
3430 static int tcp_prune_queue(struct sock
*sk
);
3432 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3434 struct tcphdr
*th
= tcp_hdr(skb
);
3435 struct tcp_sock
*tp
= tcp_sk(sk
);
3438 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3441 __skb_pull(skb
, th
->doff
*4);
3443 TCP_ECN_accept_cwr(tp
, skb
);
3445 if (tp
->rx_opt
.dsack
) {
3446 tp
->rx_opt
.dsack
= 0;
3447 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
3448 4 - tp
->rx_opt
.tstamp_ok
);
3451 /* Queue data for delivery to the user.
3452 * Packets in sequence go to the receive queue.
3453 * Out of sequence packets to the out_of_order_queue.
3455 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3456 if (tcp_receive_window(tp
) == 0)
3459 /* Ok. In sequence. In window. */
3460 if (tp
->ucopy
.task
== current
&&
3461 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3462 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3463 int chunk
= min_t(unsigned int, skb
->len
,
3466 __set_current_state(TASK_RUNNING
);
3469 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3470 tp
->ucopy
.len
-= chunk
;
3471 tp
->copied_seq
+= chunk
;
3472 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3473 tcp_rcv_space_adjust(sk
);
3481 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3482 !sk_stream_rmem_schedule(sk
, skb
))) {
3483 if (tcp_prune_queue(sk
) < 0 ||
3484 !sk_stream_rmem_schedule(sk
, skb
))
3487 sk_stream_set_owner_r(skb
, sk
);
3488 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3490 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3492 tcp_event_data_recv(sk
, skb
);
3494 tcp_fin(skb
, sk
, th
);
3496 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3499 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3500 * gap in queue is filled.
3502 if (skb_queue_empty(&tp
->out_of_order_queue
))
3503 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3506 if (tp
->rx_opt
.num_sacks
)
3507 tcp_sack_remove(tp
);
3509 tcp_fast_path_check(sk
);
3513 else if (!sock_flag(sk
, SOCK_DEAD
))
3514 sk
->sk_data_ready(sk
, 0);
3518 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3519 /* A retransmit, 2nd most common case. Force an immediate ack. */
3520 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3521 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3524 tcp_enter_quickack_mode(sk
);
3525 inet_csk_schedule_ack(sk
);
3531 /* Out of window. F.e. zero window probe. */
3532 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3535 tcp_enter_quickack_mode(sk
);
3537 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3538 /* Partial packet, seq < rcv_next < end_seq */
3539 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3540 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3541 TCP_SKB_CB(skb
)->end_seq
);
3543 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3545 /* If window is closed, drop tail of packet. But after
3546 * remembering D-SACK for its head made in previous line.
3548 if (!tcp_receive_window(tp
))
3553 TCP_ECN_check_ce(tp
, skb
);
3555 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3556 !sk_stream_rmem_schedule(sk
, skb
)) {
3557 if (tcp_prune_queue(sk
) < 0 ||
3558 !sk_stream_rmem_schedule(sk
, skb
))
3562 /* Disable header prediction. */
3564 inet_csk_schedule_ack(sk
);
3566 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3567 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3569 sk_stream_set_owner_r(skb
, sk
);
3571 if (!skb_peek(&tp
->out_of_order_queue
)) {
3572 /* Initial out of order segment, build 1 SACK. */
3573 if (tp
->rx_opt
.sack_ok
) {
3574 tp
->rx_opt
.num_sacks
= 1;
3575 tp
->rx_opt
.dsack
= 0;
3576 tp
->rx_opt
.eff_sacks
= 1;
3577 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3578 tp
->selective_acks
[0].end_seq
=
3579 TCP_SKB_CB(skb
)->end_seq
;
3581 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3583 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3584 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3585 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3587 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3588 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3590 if (!tp
->rx_opt
.num_sacks
||
3591 tp
->selective_acks
[0].end_seq
!= seq
)
3594 /* Common case: data arrive in order after hole. */
3595 tp
->selective_acks
[0].end_seq
= end_seq
;
3599 /* Find place to insert this segment. */
3601 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3603 } while ((skb1
= skb1
->prev
) !=
3604 (struct sk_buff
*)&tp
->out_of_order_queue
);
3606 /* Do skb overlap to previous one? */
3607 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3608 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3609 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3610 /* All the bits are present. Drop. */
3612 tcp_dsack_set(tp
, seq
, end_seq
);
3615 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3616 /* Partial overlap. */
3617 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3622 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3624 /* And clean segments covered by new one as whole. */
3625 while ((skb1
= skb
->next
) !=
3626 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3627 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3628 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3629 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3632 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3633 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3638 if (tp
->rx_opt
.sack_ok
)
3639 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3643 /* Collapse contiguous sequence of skbs head..tail with
3644 * sequence numbers start..end.
3645 * Segments with FIN/SYN are not collapsed (only because this
3649 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3650 struct sk_buff
*head
, struct sk_buff
*tail
,
3653 struct sk_buff
*skb
;
3655 /* First, check that queue is collapsible and find
3656 * the point where collapsing can be useful. */
3657 for (skb
= head
; skb
!= tail
; ) {
3658 /* No new bits? It is possible on ofo queue. */
3659 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3660 struct sk_buff
*next
= skb
->next
;
3661 __skb_unlink(skb
, list
);
3663 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3668 /* The first skb to collapse is:
3670 * - bloated or contains data before "start" or
3671 * overlaps to the next one.
3673 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
3674 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3675 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3676 (skb
->next
!= tail
&&
3677 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3680 /* Decided to skip this, advance start seq. */
3681 start
= TCP_SKB_CB(skb
)->end_seq
;
3684 if (skb
== tail
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
3687 while (before(start
, end
)) {
3688 struct sk_buff
*nskb
;
3689 int header
= skb_headroom(skb
);
3690 int copy
= SKB_MAX_ORDER(header
, 0);
3692 /* Too big header? This can happen with IPv6. */
3695 if (end
-start
< copy
)
3697 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3701 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
3702 skb_set_network_header(nskb
, (skb_network_header(skb
) -
3704 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
3706 skb_reserve(nskb
, header
);
3707 memcpy(nskb
->head
, skb
->head
, header
);
3708 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3709 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3710 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3711 sk_stream_set_owner_r(nskb
, sk
);
3713 /* Copy data, releasing collapsed skbs. */
3715 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3716 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3720 size
= min(copy
, size
);
3721 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3723 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3727 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3728 struct sk_buff
*next
= skb
->next
;
3729 __skb_unlink(skb
, list
);
3731 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3734 tcp_hdr(skb
)->syn
||
3742 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3743 * and tcp_collapse() them until all the queue is collapsed.
3745 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3747 struct tcp_sock
*tp
= tcp_sk(sk
);
3748 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3749 struct sk_buff
*head
;
3755 start
= TCP_SKB_CB(skb
)->seq
;
3756 end
= TCP_SKB_CB(skb
)->end_seq
;
3762 /* Segment is terminated when we see gap or when
3763 * we are at the end of all the queue. */
3764 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3765 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3766 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3767 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3768 head
, skb
, start
, end
);
3770 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3772 /* Start new segment */
3773 start
= TCP_SKB_CB(skb
)->seq
;
3774 end
= TCP_SKB_CB(skb
)->end_seq
;
3776 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3777 start
= TCP_SKB_CB(skb
)->seq
;
3778 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3779 end
= TCP_SKB_CB(skb
)->end_seq
;
3784 /* Reduce allocated memory if we can, trying to get
3785 * the socket within its memory limits again.
3787 * Return less than zero if we should start dropping frames
3788 * until the socket owning process reads some of the data
3789 * to stabilize the situation.
3791 static int tcp_prune_queue(struct sock
*sk
)
3793 struct tcp_sock
*tp
= tcp_sk(sk
);
3795 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3797 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3799 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3800 tcp_clamp_window(sk
);
3801 else if (tcp_memory_pressure
)
3802 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3804 tcp_collapse_ofo_queue(sk
);
3805 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3806 sk
->sk_receive_queue
.next
,
3807 (struct sk_buff
*)&sk
->sk_receive_queue
,
3808 tp
->copied_seq
, tp
->rcv_nxt
);
3809 sk_stream_mem_reclaim(sk
);
3811 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3814 /* Collapsing did not help, destructive actions follow.
3815 * This must not ever occur. */
3817 /* First, purge the out_of_order queue. */
3818 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3819 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3820 __skb_queue_purge(&tp
->out_of_order_queue
);
3822 /* Reset SACK state. A conforming SACK implementation will
3823 * do the same at a timeout based retransmit. When a connection
3824 * is in a sad state like this, we care only about integrity
3825 * of the connection not performance.
3827 if (tp
->rx_opt
.sack_ok
)
3828 tcp_sack_reset(&tp
->rx_opt
);
3829 sk_stream_mem_reclaim(sk
);
3832 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3835 /* If we are really being abused, tell the caller to silently
3836 * drop receive data on the floor. It will get retransmitted
3837 * and hopefully then we'll have sufficient space.
3839 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
3841 /* Massive buffer overcommit. */
3847 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
3848 * As additional protections, we do not touch cwnd in retransmission phases,
3849 * and if application hit its sndbuf limit recently.
3851 void tcp_cwnd_application_limited(struct sock
*sk
)
3853 struct tcp_sock
*tp
= tcp_sk(sk
);
3855 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
3856 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
3857 /* Limited by application or receiver window. */
3858 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
3859 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
3860 if (win_used
< tp
->snd_cwnd
) {
3861 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3862 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
3864 tp
->snd_cwnd_used
= 0;
3866 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3869 static int tcp_should_expand_sndbuf(struct sock
*sk
)
3871 struct tcp_sock
*tp
= tcp_sk(sk
);
3873 /* If the user specified a specific send buffer setting, do
3876 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
3879 /* If we are under global TCP memory pressure, do not expand. */
3880 if (tcp_memory_pressure
)
3883 /* If we are under soft global TCP memory pressure, do not expand. */
3884 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
3887 /* If we filled the congestion window, do not expand. */
3888 if (tp
->packets_out
>= tp
->snd_cwnd
)
3894 /* When incoming ACK allowed to free some skb from write_queue,
3895 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
3896 * on the exit from tcp input handler.
3898 * PROBLEM: sndbuf expansion does not work well with largesend.
3900 static void tcp_new_space(struct sock
*sk
)
3902 struct tcp_sock
*tp
= tcp_sk(sk
);
3904 if (tcp_should_expand_sndbuf(sk
)) {
3905 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
3906 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
3907 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
3908 tp
->reordering
+ 1);
3909 sndmem
*= 2*demanded
;
3910 if (sndmem
> sk
->sk_sndbuf
)
3911 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
3912 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
3915 sk
->sk_write_space(sk
);
3918 static void tcp_check_space(struct sock
*sk
)
3920 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
3921 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
3922 if (sk
->sk_socket
&&
3923 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
3928 static inline void tcp_data_snd_check(struct sock
*sk
)
3930 tcp_push_pending_frames(sk
);
3931 tcp_check_space(sk
);
3935 * Check if sending an ack is needed.
3937 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
3939 struct tcp_sock
*tp
= tcp_sk(sk
);
3941 /* More than one full frame received... */
3942 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
3943 /* ... and right edge of window advances far enough.
3944 * (tcp_recvmsg() will send ACK otherwise). Or...
3946 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
3947 /* We ACK each frame or... */
3948 tcp_in_quickack_mode(sk
) ||
3949 /* We have out of order data. */
3951 skb_peek(&tp
->out_of_order_queue
))) {
3952 /* Then ack it now */
3955 /* Else, send delayed ack. */
3956 tcp_send_delayed_ack(sk
);
3960 static inline void tcp_ack_snd_check(struct sock
*sk
)
3962 if (!inet_csk_ack_scheduled(sk
)) {
3963 /* We sent a data segment already. */
3966 __tcp_ack_snd_check(sk
, 1);
3970 * This routine is only called when we have urgent data
3971 * signaled. Its the 'slow' part of tcp_urg. It could be
3972 * moved inline now as tcp_urg is only called from one
3973 * place. We handle URGent data wrong. We have to - as
3974 * BSD still doesn't use the correction from RFC961.
3975 * For 1003.1g we should support a new option TCP_STDURG to permit
3976 * either form (or just set the sysctl tcp_stdurg).
3979 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
3981 struct tcp_sock
*tp
= tcp_sk(sk
);
3982 u32 ptr
= ntohs(th
->urg_ptr
);
3984 if (ptr
&& !sysctl_tcp_stdurg
)
3986 ptr
+= ntohl(th
->seq
);
3988 /* Ignore urgent data that we've already seen and read. */
3989 if (after(tp
->copied_seq
, ptr
))
3992 /* Do not replay urg ptr.
3994 * NOTE: interesting situation not covered by specs.
3995 * Misbehaving sender may send urg ptr, pointing to segment,
3996 * which we already have in ofo queue. We are not able to fetch
3997 * such data and will stay in TCP_URG_NOTYET until will be eaten
3998 * by recvmsg(). Seems, we are not obliged to handle such wicked
3999 * situations. But it is worth to think about possibility of some
4000 * DoSes using some hypothetical application level deadlock.
4002 if (before(ptr
, tp
->rcv_nxt
))
4005 /* Do we already have a newer (or duplicate) urgent pointer? */
4006 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4009 /* Tell the world about our new urgent pointer. */
4012 /* We may be adding urgent data when the last byte read was
4013 * urgent. To do this requires some care. We cannot just ignore
4014 * tp->copied_seq since we would read the last urgent byte again
4015 * as data, nor can we alter copied_seq until this data arrives
4016 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4018 * NOTE. Double Dutch. Rendering to plain English: author of comment
4019 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4020 * and expect that both A and B disappear from stream. This is _wrong_.
4021 * Though this happens in BSD with high probability, this is occasional.
4022 * Any application relying on this is buggy. Note also, that fix "works"
4023 * only in this artificial test. Insert some normal data between A and B and we will
4024 * decline of BSD again. Verdict: it is better to remove to trap
4027 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4028 !sock_flag(sk
, SOCK_URGINLINE
) &&
4029 tp
->copied_seq
!= tp
->rcv_nxt
) {
4030 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4032 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4033 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4038 tp
->urg_data
= TCP_URG_NOTYET
;
4041 /* Disable header prediction. */
4045 /* This is the 'fast' part of urgent handling. */
4046 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
4048 struct tcp_sock
*tp
= tcp_sk(sk
);
4050 /* Check if we get a new urgent pointer - normally not. */
4052 tcp_check_urg(sk
,th
);
4054 /* Do we wait for any urgent data? - normally not... */
4055 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4056 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4059 /* Is the urgent pointer pointing into this packet? */
4060 if (ptr
< skb
->len
) {
4062 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4064 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4065 if (!sock_flag(sk
, SOCK_DEAD
))
4066 sk
->sk_data_ready(sk
, 0);
4071 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4073 struct tcp_sock
*tp
= tcp_sk(sk
);
4074 int chunk
= skb
->len
- hlen
;
4078 if (skb_csum_unnecessary(skb
))
4079 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4081 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4085 tp
->ucopy
.len
-= chunk
;
4086 tp
->copied_seq
+= chunk
;
4087 tcp_rcv_space_adjust(sk
);
4094 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4098 if (sock_owned_by_user(sk
)) {
4100 result
= __tcp_checksum_complete(skb
);
4103 result
= __tcp_checksum_complete(skb
);
4108 static inline int tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4110 return !skb_csum_unnecessary(skb
) &&
4111 __tcp_checksum_complete_user(sk
, skb
);
4114 #ifdef CONFIG_NET_DMA
4115 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4117 struct tcp_sock
*tp
= tcp_sk(sk
);
4118 int chunk
= skb
->len
- hlen
;
4120 int copied_early
= 0;
4122 if (tp
->ucopy
.wakeup
)
4125 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4126 tp
->ucopy
.dma_chan
= get_softnet_dma();
4128 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
4130 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4131 skb
, hlen
, tp
->ucopy
.iov
, chunk
, tp
->ucopy
.pinned_list
);
4136 tp
->ucopy
.dma_cookie
= dma_cookie
;
4139 tp
->ucopy
.len
-= chunk
;
4140 tp
->copied_seq
+= chunk
;
4141 tcp_rcv_space_adjust(sk
);
4143 if ((tp
->ucopy
.len
== 0) ||
4144 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
4145 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
4146 tp
->ucopy
.wakeup
= 1;
4147 sk
->sk_data_ready(sk
, 0);
4149 } else if (chunk
> 0) {
4150 tp
->ucopy
.wakeup
= 1;
4151 sk
->sk_data_ready(sk
, 0);
4154 return copied_early
;
4156 #endif /* CONFIG_NET_DMA */
4159 * TCP receive function for the ESTABLISHED state.
4161 * It is split into a fast path and a slow path. The fast path is
4163 * - A zero window was announced from us - zero window probing
4164 * is only handled properly in the slow path.
4165 * - Out of order segments arrived.
4166 * - Urgent data is expected.
4167 * - There is no buffer space left
4168 * - Unexpected TCP flags/window values/header lengths are received
4169 * (detected by checking the TCP header against pred_flags)
4170 * - Data is sent in both directions. Fast path only supports pure senders
4171 * or pure receivers (this means either the sequence number or the ack
4172 * value must stay constant)
4173 * - Unexpected TCP option.
4175 * When these conditions are not satisfied it drops into a standard
4176 * receive procedure patterned after RFC793 to handle all cases.
4177 * The first three cases are guaranteed by proper pred_flags setting,
4178 * the rest is checked inline. Fast processing is turned on in
4179 * tcp_data_queue when everything is OK.
4181 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
4182 struct tcphdr
*th
, unsigned len
)
4184 struct tcp_sock
*tp
= tcp_sk(sk
);
4187 * Header prediction.
4188 * The code loosely follows the one in the famous
4189 * "30 instruction TCP receive" Van Jacobson mail.
4191 * Van's trick is to deposit buffers into socket queue
4192 * on a device interrupt, to call tcp_recv function
4193 * on the receive process context and checksum and copy
4194 * the buffer to user space. smart...
4196 * Our current scheme is not silly either but we take the
4197 * extra cost of the net_bh soft interrupt processing...
4198 * We do checksum and copy also but from device to kernel.
4201 tp
->rx_opt
.saw_tstamp
= 0;
4203 /* pred_flags is 0xS?10 << 16 + snd_wnd
4204 * if header_prediction is to be made
4205 * 'S' will always be tp->tcp_header_len >> 2
4206 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4207 * turn it off (when there are holes in the receive
4208 * space for instance)
4209 * PSH flag is ignored.
4212 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
4213 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4214 int tcp_header_len
= tp
->tcp_header_len
;
4216 /* Timestamp header prediction: tcp_header_len
4217 * is automatically equal to th->doff*4 due to pred_flags
4221 /* Check timestamp */
4222 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
4223 __be32
*ptr
= (__be32
*)(th
+ 1);
4225 /* No? Slow path! */
4226 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4227 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
4230 tp
->rx_opt
.saw_tstamp
= 1;
4232 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4234 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4236 /* If PAWS failed, check it more carefully in slow path */
4237 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
4240 /* DO NOT update ts_recent here, if checksum fails
4241 * and timestamp was corrupted part, it will result
4242 * in a hung connection since we will drop all
4243 * future packets due to the PAWS test.
4247 if (len
<= tcp_header_len
) {
4248 /* Bulk data transfer: sender */
4249 if (len
== tcp_header_len
) {
4250 /* Predicted packet is in window by definition.
4251 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4252 * Hence, check seq<=rcv_wup reduces to:
4254 if (tcp_header_len
==
4255 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4256 tp
->rcv_nxt
== tp
->rcv_wup
)
4257 tcp_store_ts_recent(tp
);
4259 /* We know that such packets are checksummed
4262 tcp_ack(sk
, skb
, 0);
4264 tcp_data_snd_check(sk
);
4266 } else { /* Header too small */
4267 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4272 int copied_early
= 0;
4274 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4275 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4276 #ifdef CONFIG_NET_DMA
4277 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4282 if (tp
->ucopy
.task
== current
&& sock_owned_by_user(sk
) && !copied_early
) {
4283 __set_current_state(TASK_RUNNING
);
4285 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4289 /* Predicted packet is in window by definition.
4290 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4291 * Hence, check seq<=rcv_wup reduces to:
4293 if (tcp_header_len
==
4294 (sizeof(struct tcphdr
) +
4295 TCPOLEN_TSTAMP_ALIGNED
) &&
4296 tp
->rcv_nxt
== tp
->rcv_wup
)
4297 tcp_store_ts_recent(tp
);
4299 tcp_rcv_rtt_measure_ts(sk
, skb
);
4301 __skb_pull(skb
, tcp_header_len
);
4302 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4303 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
4306 tcp_cleanup_rbuf(sk
, skb
->len
);
4309 if (tcp_checksum_complete_user(sk
, skb
))
4312 /* Predicted packet is in window by definition.
4313 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4314 * Hence, check seq<=rcv_wup reduces to:
4316 if (tcp_header_len
==
4317 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4318 tp
->rcv_nxt
== tp
->rcv_wup
)
4319 tcp_store_ts_recent(tp
);
4321 tcp_rcv_rtt_measure_ts(sk
, skb
);
4323 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4326 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
4328 /* Bulk data transfer: receiver */
4329 __skb_pull(skb
,tcp_header_len
);
4330 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4331 sk_stream_set_owner_r(skb
, sk
);
4332 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4335 tcp_event_data_recv(sk
, skb
);
4337 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4338 /* Well, only one small jumplet in fast path... */
4339 tcp_ack(sk
, skb
, FLAG_DATA
);
4340 tcp_data_snd_check(sk
);
4341 if (!inet_csk_ack_scheduled(sk
))
4345 __tcp_ack_snd_check(sk
, 0);
4347 #ifdef CONFIG_NET_DMA
4349 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4355 sk
->sk_data_ready(sk
, 0);
4361 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
4365 * RFC1323: H1. Apply PAWS check first.
4367 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4368 tcp_paws_discard(sk
, skb
)) {
4370 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4371 tcp_send_dupack(sk
, skb
);
4374 /* Resets are accepted even if PAWS failed.
4376 ts_recent update must be made after we are sure
4377 that the packet is in window.
4382 * Standard slow path.
4385 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4386 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4387 * (RST) segments are validated by checking their SEQ-fields."
4388 * And page 69: "If an incoming segment is not acceptable,
4389 * an acknowledgment should be sent in reply (unless the RST bit
4390 * is set, if so drop the segment and return)".
4393 tcp_send_dupack(sk
, skb
);
4402 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4404 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4405 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4406 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4413 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4415 tcp_rcv_rtt_measure_ts(sk
, skb
);
4417 /* Process urgent data. */
4418 tcp_urg(sk
, skb
, th
);
4420 /* step 7: process the segment text */
4421 tcp_data_queue(sk
, skb
);
4423 tcp_data_snd_check(sk
);
4424 tcp_ack_snd_check(sk
);
4428 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4435 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4436 struct tcphdr
*th
, unsigned len
)
4438 struct tcp_sock
*tp
= tcp_sk(sk
);
4439 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4440 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4442 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4446 * "If the state is SYN-SENT then
4447 * first check the ACK bit
4448 * If the ACK bit is set
4449 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4450 * a reset (unless the RST bit is set, if so drop
4451 * the segment and return)"
4453 * We do not send data with SYN, so that RFC-correct
4456 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4457 goto reset_and_undo
;
4459 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4460 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
4462 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
4463 goto reset_and_undo
;
4466 /* Now ACK is acceptable.
4468 * "If the RST bit is set
4469 * If the ACK was acceptable then signal the user "error:
4470 * connection reset", drop the segment, enter CLOSED state,
4471 * delete TCB, and return."
4480 * "fifth, if neither of the SYN or RST bits is set then
4481 * drop the segment and return."
4487 goto discard_and_undo
;
4490 * "If the SYN bit is on ...
4491 * are acceptable then ...
4492 * (our SYN has been ACKed), change the connection
4493 * state to ESTABLISHED..."
4496 TCP_ECN_rcv_synack(tp
, th
);
4498 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4499 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4501 /* Ok.. it's good. Set up sequence numbers and
4502 * move to established.
4504 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4505 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4507 /* RFC1323: The window in SYN & SYN/ACK segments is
4510 tp
->snd_wnd
= ntohs(th
->window
);
4511 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
4513 if (!tp
->rx_opt
.wscale_ok
) {
4514 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
4515 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
4518 if (tp
->rx_opt
.saw_tstamp
) {
4519 tp
->rx_opt
.tstamp_ok
= 1;
4520 tp
->tcp_header_len
=
4521 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4522 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4523 tcp_store_ts_recent(tp
);
4525 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4528 if (tp
->rx_opt
.sack_ok
&& sysctl_tcp_fack
)
4529 tp
->rx_opt
.sack_ok
|= 2;
4532 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4533 tcp_initialize_rcv_mss(sk
);
4535 /* Remember, tcp_poll() does not lock socket!
4536 * Change state from SYN-SENT only after copied_seq
4537 * is initialized. */
4538 tp
->copied_seq
= tp
->rcv_nxt
;
4540 tcp_set_state(sk
, TCP_ESTABLISHED
);
4542 security_inet_conn_established(sk
, skb
);
4544 /* Make sure socket is routed, for correct metrics. */
4545 icsk
->icsk_af_ops
->rebuild_header(sk
);
4547 tcp_init_metrics(sk
);
4549 tcp_init_congestion_control(sk
);
4551 /* Prevent spurious tcp_cwnd_restart() on first data
4554 tp
->lsndtime
= tcp_time_stamp
;
4556 tcp_init_buffer_space(sk
);
4558 if (sock_flag(sk
, SOCK_KEEPOPEN
))
4559 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
4561 if (!tp
->rx_opt
.snd_wscale
)
4562 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4566 if (!sock_flag(sk
, SOCK_DEAD
)) {
4567 sk
->sk_state_change(sk
);
4568 sk_wake_async(sk
, 0, POLL_OUT
);
4571 if (sk
->sk_write_pending
||
4572 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4573 icsk
->icsk_ack
.pingpong
) {
4574 /* Save one ACK. Data will be ready after
4575 * several ticks, if write_pending is set.
4577 * It may be deleted, but with this feature tcpdumps
4578 * look so _wonderfully_ clever, that I was not able
4579 * to stand against the temptation 8) --ANK
4581 inet_csk_schedule_ack(sk
);
4582 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4583 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4584 tcp_incr_quickack(sk
);
4585 tcp_enter_quickack_mode(sk
);
4586 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4587 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4598 /* No ACK in the segment */
4602 * "If the RST bit is set
4604 * Otherwise (no ACK) drop the segment and return."
4607 goto discard_and_undo
;
4611 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4612 goto discard_and_undo
;
4615 /* We see SYN without ACK. It is attempt of
4616 * simultaneous connect with crossed SYNs.
4617 * Particularly, it can be connect to self.
4619 tcp_set_state(sk
, TCP_SYN_RECV
);
4621 if (tp
->rx_opt
.saw_tstamp
) {
4622 tp
->rx_opt
.tstamp_ok
= 1;
4623 tcp_store_ts_recent(tp
);
4624 tp
->tcp_header_len
=
4625 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4627 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4630 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4631 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4633 /* RFC1323: The window in SYN & SYN/ACK segments is
4636 tp
->snd_wnd
= ntohs(th
->window
);
4637 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4638 tp
->max_window
= tp
->snd_wnd
;
4640 TCP_ECN_rcv_syn(tp
, th
);
4643 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4644 tcp_initialize_rcv_mss(sk
);
4647 tcp_send_synack(sk
);
4649 /* Note, we could accept data and URG from this segment.
4650 * There are no obstacles to make this.
4652 * However, if we ignore data in ACKless segments sometimes,
4653 * we have no reasons to accept it sometimes.
4654 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4655 * is not flawless. So, discard packet for sanity.
4656 * Uncomment this return to process the data.
4663 /* "fifth, if neither of the SYN or RST bits is set then
4664 * drop the segment and return."
4668 tcp_clear_options(&tp
->rx_opt
);
4669 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4673 tcp_clear_options(&tp
->rx_opt
);
4674 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4680 * This function implements the receiving procedure of RFC 793 for
4681 * all states except ESTABLISHED and TIME_WAIT.
4682 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4683 * address independent.
4686 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4687 struct tcphdr
*th
, unsigned len
)
4689 struct tcp_sock
*tp
= tcp_sk(sk
);
4690 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4693 tp
->rx_opt
.saw_tstamp
= 0;
4695 switch (sk
->sk_state
) {
4707 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
4710 /* Now we have several options: In theory there is
4711 * nothing else in the frame. KA9Q has an option to
4712 * send data with the syn, BSD accepts data with the
4713 * syn up to the [to be] advertised window and
4714 * Solaris 2.1 gives you a protocol error. For now
4715 * we just ignore it, that fits the spec precisely
4716 * and avoids incompatibilities. It would be nice in
4717 * future to drop through and process the data.
4719 * Now that TTCP is starting to be used we ought to
4721 * But, this leaves one open to an easy denial of
4722 * service attack, and SYN cookies can't defend
4723 * against this problem. So, we drop the data
4724 * in the interest of security over speed unless
4725 * it's still in use.
4733 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4737 /* Do step6 onward by hand. */
4738 tcp_urg(sk
, skb
, th
);
4740 tcp_data_snd_check(sk
);
4744 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4745 tcp_paws_discard(sk
, skb
)) {
4747 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4748 tcp_send_dupack(sk
, skb
);
4751 /* Reset is accepted even if it did not pass PAWS. */
4754 /* step 1: check sequence number */
4755 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4757 tcp_send_dupack(sk
, skb
);
4761 /* step 2: check RST bit */
4767 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4769 /* step 3: check security and precedence [ignored] */
4773 * Check for a SYN in window.
4775 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4776 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4781 /* step 5: check the ACK field */
4783 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4785 switch (sk
->sk_state
) {
4788 tp
->copied_seq
= tp
->rcv_nxt
;
4790 tcp_set_state(sk
, TCP_ESTABLISHED
);
4791 sk
->sk_state_change(sk
);
4793 /* Note, that this wakeup is only for marginal
4794 * crossed SYN case. Passively open sockets
4795 * are not waked up, because sk->sk_sleep ==
4796 * NULL and sk->sk_socket == NULL.
4798 if (sk
->sk_socket
) {
4799 sk_wake_async(sk
,0,POLL_OUT
);
4802 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4803 tp
->snd_wnd
= ntohs(th
->window
) <<
4804 tp
->rx_opt
.snd_wscale
;
4805 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4806 TCP_SKB_CB(skb
)->seq
);
4808 /* tcp_ack considers this ACK as duplicate
4809 * and does not calculate rtt.
4810 * Fix it at least with timestamps.
4812 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4814 tcp_ack_saw_tstamp(sk
, 0);
4816 if (tp
->rx_opt
.tstamp_ok
)
4817 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4819 /* Make sure socket is routed, for
4822 icsk
->icsk_af_ops
->rebuild_header(sk
);
4824 tcp_init_metrics(sk
);
4826 tcp_init_congestion_control(sk
);
4828 /* Prevent spurious tcp_cwnd_restart() on
4829 * first data packet.
4831 tp
->lsndtime
= tcp_time_stamp
;
4834 tcp_initialize_rcv_mss(sk
);
4835 tcp_init_buffer_space(sk
);
4836 tcp_fast_path_on(tp
);
4843 if (tp
->snd_una
== tp
->write_seq
) {
4844 tcp_set_state(sk
, TCP_FIN_WAIT2
);
4845 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
4846 dst_confirm(sk
->sk_dst_cache
);
4848 if (!sock_flag(sk
, SOCK_DEAD
))
4849 /* Wake up lingering close() */
4850 sk
->sk_state_change(sk
);
4854 if (tp
->linger2
< 0 ||
4855 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4856 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
4858 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4862 tmo
= tcp_fin_time(sk
);
4863 if (tmo
> TCP_TIMEWAIT_LEN
) {
4864 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
4865 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
4866 /* Bad case. We could lose such FIN otherwise.
4867 * It is not a big problem, but it looks confusing
4868 * and not so rare event. We still can lose it now,
4869 * if it spins in bh_lock_sock(), but it is really
4872 inet_csk_reset_keepalive_timer(sk
, tmo
);
4874 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
4882 if (tp
->snd_una
== tp
->write_seq
) {
4883 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4889 if (tp
->snd_una
== tp
->write_seq
) {
4890 tcp_update_metrics(sk
);
4899 /* step 6: check the URG bit */
4900 tcp_urg(sk
, skb
, th
);
4902 /* step 7: process the segment text */
4903 switch (sk
->sk_state
) {
4904 case TCP_CLOSE_WAIT
:
4907 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4911 /* RFC 793 says to queue data in these states,
4912 * RFC 1122 says we MUST send a reset.
4913 * BSD 4.4 also does reset.
4915 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
4916 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4917 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
4918 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
4924 case TCP_ESTABLISHED
:
4925 tcp_data_queue(sk
, skb
);
4930 /* tcp_data could move socket to TIME-WAIT */
4931 if (sk
->sk_state
!= TCP_CLOSE
) {
4932 tcp_data_snd_check(sk
);
4933 tcp_ack_snd_check(sk
);
4943 EXPORT_SYMBOL(sysctl_tcp_ecn
);
4944 EXPORT_SYMBOL(sysctl_tcp_reordering
);
4945 EXPORT_SYMBOL(tcp_parse_options
);
4946 EXPORT_SYMBOL(tcp_rcv_established
);
4947 EXPORT_SYMBOL(tcp_rcv_state_process
);
4948 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);