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
= 2;
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 */
107 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
109 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
110 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
111 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
112 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
113 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
115 #define IsSackFrto() (sysctl_tcp_frto == 0x2)
117 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
118 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
120 /* Adapt the MSS value used to make delayed ack decision to the
123 static void tcp_measure_rcv_mss(struct sock
*sk
,
124 const struct sk_buff
*skb
)
126 struct inet_connection_sock
*icsk
= inet_csk(sk
);
127 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
130 icsk
->icsk_ack
.last_seg_size
= 0;
132 /* skb->len may jitter because of SACKs, even if peer
133 * sends good full-sized frames.
135 len
= skb_shinfo(skb
)->gso_size
?: skb
->len
;
136 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
137 icsk
->icsk_ack
.rcv_mss
= len
;
139 /* Otherwise, we make more careful check taking into account,
140 * that SACKs block is variable.
142 * "len" is invariant segment length, including TCP header.
144 len
+= skb
->data
- skb_transport_header(skb
);
145 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
146 /* If PSH is not set, packet should be
147 * full sized, provided peer TCP is not badly broken.
148 * This observation (if it is correct 8)) allows
149 * to handle super-low mtu links fairly.
151 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
152 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
153 /* Subtract also invariant (if peer is RFC compliant),
154 * tcp header plus fixed timestamp option length.
155 * Resulting "len" is MSS free of SACK jitter.
157 len
-= tcp_sk(sk
)->tcp_header_len
;
158 icsk
->icsk_ack
.last_seg_size
= len
;
160 icsk
->icsk_ack
.rcv_mss
= len
;
164 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
165 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
166 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
170 static void tcp_incr_quickack(struct sock
*sk
)
172 struct inet_connection_sock
*icsk
= inet_csk(sk
);
173 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
177 if (quickacks
> icsk
->icsk_ack
.quick
)
178 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
181 void tcp_enter_quickack_mode(struct sock
*sk
)
183 struct inet_connection_sock
*icsk
= inet_csk(sk
);
184 tcp_incr_quickack(sk
);
185 icsk
->icsk_ack
.pingpong
= 0;
186 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
189 /* Send ACKs quickly, if "quick" count is not exhausted
190 * and the session is not interactive.
193 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
195 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
196 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
199 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
201 if (tp
->ecn_flags
&TCP_ECN_OK
)
202 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
205 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, struct sk_buff
*skb
)
207 if (tcp_hdr(skb
)->cwr
)
208 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
211 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
213 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
216 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, struct sk_buff
*skb
)
218 if (tp
->ecn_flags
&TCP_ECN_OK
) {
219 if (INET_ECN_is_ce(TCP_SKB_CB(skb
)->flags
))
220 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
221 /* Funny extension: if ECT is not set on a segment,
222 * it is surely retransmit. It is not in ECN RFC,
223 * but Linux follows this rule. */
224 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb
)->flags
)))
225 tcp_enter_quickack_mode((struct sock
*)tp
);
229 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, struct tcphdr
*th
)
231 if ((tp
->ecn_flags
&TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
232 tp
->ecn_flags
&= ~TCP_ECN_OK
;
235 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, struct tcphdr
*th
)
237 if ((tp
->ecn_flags
&TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
238 tp
->ecn_flags
&= ~TCP_ECN_OK
;
241 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock
*tp
, struct tcphdr
*th
)
243 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
&TCP_ECN_OK
))
248 /* Buffer size and advertised window tuning.
250 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
253 static void tcp_fixup_sndbuf(struct sock
*sk
)
255 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
256 sizeof(struct sk_buff
);
258 if (sk
->sk_sndbuf
< 3 * sndmem
)
259 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
262 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
264 * All tcp_full_space() is split to two parts: "network" buffer, allocated
265 * forward and advertised in receiver window (tp->rcv_wnd) and
266 * "application buffer", required to isolate scheduling/application
267 * latencies from network.
268 * window_clamp is maximal advertised window. It can be less than
269 * tcp_full_space(), in this case tcp_full_space() - window_clamp
270 * is reserved for "application" buffer. The less window_clamp is
271 * the smoother our behaviour from viewpoint of network, but the lower
272 * throughput and the higher sensitivity of the connection to losses. 8)
274 * rcv_ssthresh is more strict window_clamp used at "slow start"
275 * phase to predict further behaviour of this connection.
276 * It is used for two goals:
277 * - to enforce header prediction at sender, even when application
278 * requires some significant "application buffer". It is check #1.
279 * - to prevent pruning of receive queue because of misprediction
280 * of receiver window. Check #2.
282 * The scheme does not work when sender sends good segments opening
283 * window and then starts to feed us spaghetti. But it should work
284 * in common situations. Otherwise, we have to rely on queue collapsing.
287 /* Slow part of check#2. */
288 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
290 struct tcp_sock
*tp
= tcp_sk(sk
);
292 int truesize
= tcp_win_from_space(skb
->truesize
)/2;
293 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2])/2;
295 while (tp
->rcv_ssthresh
<= window
) {
296 if (truesize
<= skb
->len
)
297 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
305 static void tcp_grow_window(struct sock
*sk
,
308 struct tcp_sock
*tp
= tcp_sk(sk
);
311 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
312 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
313 !tcp_memory_pressure
) {
316 /* Check #2. Increase window, if skb with such overhead
317 * will fit to rcvbuf in future.
319 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
322 incr
= __tcp_grow_window(sk
, skb
);
325 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
, tp
->window_clamp
);
326 inet_csk(sk
)->icsk_ack
.quick
|= 1;
331 /* 3. Tuning rcvbuf, when connection enters established state. */
333 static void tcp_fixup_rcvbuf(struct sock
*sk
)
335 struct tcp_sock
*tp
= tcp_sk(sk
);
336 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
338 /* Try to select rcvbuf so that 4 mss-sized segments
339 * will fit to window and corresponding skbs will fit to our rcvbuf.
340 * (was 3; 4 is minimum to allow fast retransmit to work.)
342 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
344 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
345 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
348 /* 4. Try to fixup all. It is made immediately after connection enters
351 static void tcp_init_buffer_space(struct sock
*sk
)
353 struct tcp_sock
*tp
= tcp_sk(sk
);
356 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
357 tcp_fixup_rcvbuf(sk
);
358 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
359 tcp_fixup_sndbuf(sk
);
361 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
363 maxwin
= tcp_full_space(sk
);
365 if (tp
->window_clamp
>= maxwin
) {
366 tp
->window_clamp
= maxwin
;
368 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
369 tp
->window_clamp
= max(maxwin
-
370 (maxwin
>> sysctl_tcp_app_win
),
374 /* Force reservation of one segment. */
375 if (sysctl_tcp_app_win
&&
376 tp
->window_clamp
> 2 * tp
->advmss
&&
377 tp
->window_clamp
+ tp
->advmss
> maxwin
)
378 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
380 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
381 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
384 /* 5. Recalculate window clamp after socket hit its memory bounds. */
385 static void tcp_clamp_window(struct sock
*sk
)
387 struct tcp_sock
*tp
= tcp_sk(sk
);
388 struct inet_connection_sock
*icsk
= inet_csk(sk
);
390 icsk
->icsk_ack
.quick
= 0;
392 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
393 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
394 !tcp_memory_pressure
&&
395 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
396 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
399 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
400 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U*tp
->advmss
);
404 /* Initialize RCV_MSS value.
405 * RCV_MSS is an our guess about MSS used by the peer.
406 * We haven't any direct information about the MSS.
407 * It's better to underestimate the RCV_MSS rather than overestimate.
408 * Overestimations make us ACKing less frequently than needed.
409 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
411 void tcp_initialize_rcv_mss(struct sock
*sk
)
413 struct tcp_sock
*tp
= tcp_sk(sk
);
414 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
416 hint
= min(hint
, tp
->rcv_wnd
/2);
417 hint
= min(hint
, TCP_MIN_RCVMSS
);
418 hint
= max(hint
, TCP_MIN_MSS
);
420 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
423 /* Receiver "autotuning" code.
425 * The algorithm for RTT estimation w/o timestamps is based on
426 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
427 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
429 * More detail on this code can be found at
430 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
431 * though this reference is out of date. A new paper
434 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
436 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
442 if (new_sample
!= 0) {
443 /* If we sample in larger samples in the non-timestamp
444 * case, we could grossly overestimate the RTT especially
445 * with chatty applications or bulk transfer apps which
446 * are stalled on filesystem I/O.
448 * Also, since we are only going for a minimum in the
449 * non-timestamp case, we do not smooth things out
450 * else with timestamps disabled convergence takes too
454 m
-= (new_sample
>> 3);
456 } else if (m
< new_sample
)
459 /* No previous measure. */
463 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
464 tp
->rcv_rtt_est
.rtt
= new_sample
;
467 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
469 if (tp
->rcv_rtt_est
.time
== 0)
471 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
473 tcp_rcv_rtt_update(tp
,
474 jiffies
- tp
->rcv_rtt_est
.time
,
478 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
479 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
482 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
, const struct sk_buff
*skb
)
484 struct tcp_sock
*tp
= tcp_sk(sk
);
485 if (tp
->rx_opt
.rcv_tsecr
&&
486 (TCP_SKB_CB(skb
)->end_seq
-
487 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
488 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
492 * This function should be called every time data is copied to user space.
493 * It calculates the appropriate TCP receive buffer space.
495 void tcp_rcv_space_adjust(struct sock
*sk
)
497 struct tcp_sock
*tp
= tcp_sk(sk
);
501 if (tp
->rcvq_space
.time
== 0)
504 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
505 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) ||
506 tp
->rcv_rtt_est
.rtt
== 0)
509 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
511 space
= max(tp
->rcvq_space
.space
, space
);
513 if (tp
->rcvq_space
.space
!= space
) {
516 tp
->rcvq_space
.space
= space
;
518 if (sysctl_tcp_moderate_rcvbuf
&&
519 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
520 int new_clamp
= space
;
522 /* Receive space grows, normalize in order to
523 * take into account packet headers and sk_buff
524 * structure overhead.
529 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
530 16 + sizeof(struct sk_buff
));
531 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
534 space
= min(space
, sysctl_tcp_rmem
[2]);
535 if (space
> sk
->sk_rcvbuf
) {
536 sk
->sk_rcvbuf
= space
;
538 /* Make the window clamp follow along. */
539 tp
->window_clamp
= new_clamp
;
545 tp
->rcvq_space
.seq
= tp
->copied_seq
;
546 tp
->rcvq_space
.time
= tcp_time_stamp
;
549 /* There is something which you must keep in mind when you analyze the
550 * behavior of the tp->ato delayed ack timeout interval. When a
551 * connection starts up, we want to ack as quickly as possible. The
552 * problem is that "good" TCP's do slow start at the beginning of data
553 * transmission. The means that until we send the first few ACK's the
554 * sender will sit on his end and only queue most of his data, because
555 * he can only send snd_cwnd unacked packets at any given time. For
556 * each ACK we send, he increments snd_cwnd and transmits more of his
559 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
561 struct tcp_sock
*tp
= tcp_sk(sk
);
562 struct inet_connection_sock
*icsk
= inet_csk(sk
);
565 inet_csk_schedule_ack(sk
);
567 tcp_measure_rcv_mss(sk
, skb
);
569 tcp_rcv_rtt_measure(tp
);
571 now
= tcp_time_stamp
;
573 if (!icsk
->icsk_ack
.ato
) {
574 /* The _first_ data packet received, initialize
575 * delayed ACK engine.
577 tcp_incr_quickack(sk
);
578 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
580 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
582 if (m
<= TCP_ATO_MIN
/2) {
583 /* The fastest case is the first. */
584 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
585 } else if (m
< icsk
->icsk_ack
.ato
) {
586 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
587 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
588 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
589 } else if (m
> icsk
->icsk_rto
) {
590 /* Too long gap. Apparently sender failed to
591 * restart window, so that we send ACKs quickly.
593 tcp_incr_quickack(sk
);
594 sk_stream_mem_reclaim(sk
);
597 icsk
->icsk_ack
.lrcvtime
= now
;
599 TCP_ECN_check_ce(tp
, skb
);
602 tcp_grow_window(sk
, skb
);
605 static u32
tcp_rto_min(struct sock
*sk
)
607 struct dst_entry
*dst
= __sk_dst_get(sk
);
608 u32 rto_min
= TCP_RTO_MIN
;
610 if (dst
&& dst_metric_locked(dst
, RTAX_RTO_MIN
))
611 rto_min
= dst
->metrics
[RTAX_RTO_MIN
-1];
615 /* Called to compute a smoothed rtt estimate. The data fed to this
616 * routine either comes from timestamps, or from segments that were
617 * known _not_ to have been retransmitted [see Karn/Partridge
618 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
619 * piece by Van Jacobson.
620 * NOTE: the next three routines used to be one big routine.
621 * To save cycles in the RFC 1323 implementation it was better to break
622 * it up into three procedures. -- erics
624 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
626 struct tcp_sock
*tp
= tcp_sk(sk
);
627 long m
= mrtt
; /* RTT */
629 /* The following amusing code comes from Jacobson's
630 * article in SIGCOMM '88. Note that rtt and mdev
631 * are scaled versions of rtt and mean deviation.
632 * This is designed to be as fast as possible
633 * m stands for "measurement".
635 * On a 1990 paper the rto value is changed to:
636 * RTO = rtt + 4 * mdev
638 * Funny. This algorithm seems to be very broken.
639 * These formulae increase RTO, when it should be decreased, increase
640 * too slowly, when it should be increased quickly, decrease too quickly
641 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
642 * does not matter how to _calculate_ it. Seems, it was trap
643 * that VJ failed to avoid. 8)
648 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
649 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
651 m
= -m
; /* m is now abs(error) */
652 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
653 /* This is similar to one of Eifel findings.
654 * Eifel blocks mdev updates when rtt decreases.
655 * This solution is a bit different: we use finer gain
656 * for mdev in this case (alpha*beta).
657 * Like Eifel it also prevents growth of rto,
658 * but also it limits too fast rto decreases,
659 * happening in pure Eifel.
664 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
666 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
667 if (tp
->mdev
> tp
->mdev_max
) {
668 tp
->mdev_max
= tp
->mdev
;
669 if (tp
->mdev_max
> tp
->rttvar
)
670 tp
->rttvar
= tp
->mdev_max
;
672 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
673 if (tp
->mdev_max
< tp
->rttvar
)
674 tp
->rttvar
-= (tp
->rttvar
-tp
->mdev_max
)>>2;
675 tp
->rtt_seq
= tp
->snd_nxt
;
676 tp
->mdev_max
= tcp_rto_min(sk
);
679 /* no previous measure. */
680 tp
->srtt
= m
<<3; /* take the measured time to be rtt */
681 tp
->mdev
= m
<<1; /* make sure rto = 3*rtt */
682 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
683 tp
->rtt_seq
= tp
->snd_nxt
;
687 /* Calculate rto without backoff. This is the second half of Van Jacobson's
688 * routine referred to above.
690 static inline void tcp_set_rto(struct sock
*sk
)
692 const struct tcp_sock
*tp
= tcp_sk(sk
);
693 /* Old crap is replaced with new one. 8)
696 * 1. If rtt variance happened to be less 50msec, it is hallucination.
697 * It cannot be less due to utterly erratic ACK generation made
698 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
699 * to do with delayed acks, because at cwnd>2 true delack timeout
700 * is invisible. Actually, Linux-2.4 also generates erratic
701 * ACKs in some circumstances.
703 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
705 /* 2. Fixups made earlier cannot be right.
706 * If we do not estimate RTO correctly without them,
707 * all the algo is pure shit and should be replaced
708 * with correct one. It is exactly, which we pretend to do.
712 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
713 * guarantees that rto is higher.
715 static inline void tcp_bound_rto(struct sock
*sk
)
717 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
718 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
721 /* Save metrics learned by this TCP session.
722 This function is called only, when TCP finishes successfully
723 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
725 void tcp_update_metrics(struct sock
*sk
)
727 struct tcp_sock
*tp
= tcp_sk(sk
);
728 struct dst_entry
*dst
= __sk_dst_get(sk
);
730 if (sysctl_tcp_nometrics_save
)
735 if (dst
&& (dst
->flags
&DST_HOST
)) {
736 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
739 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
740 /* This session failed to estimate rtt. Why?
741 * Probably, no packets returned in time.
744 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
745 dst
->metrics
[RTAX_RTT
-1] = 0;
749 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
751 /* If newly calculated rtt larger than stored one,
752 * store new one. Otherwise, use EWMA. Remember,
753 * rtt overestimation is always better than underestimation.
755 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
757 dst
->metrics
[RTAX_RTT
-1] = tp
->srtt
;
759 dst
->metrics
[RTAX_RTT
-1] -= (m
>>3);
762 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
766 /* Scale deviation to rttvar fixed point */
771 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
772 dst
->metrics
[RTAX_RTTVAR
-1] = m
;
774 dst
->metrics
[RTAX_RTTVAR
-1] -=
775 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
778 if (tp
->snd_ssthresh
>= 0xFFFF) {
779 /* Slow start still did not finish. */
780 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
781 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
782 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
783 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
784 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
785 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
786 dst
->metrics
[RTAX_CWND
-1] = tp
->snd_cwnd
;
787 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
788 icsk
->icsk_ca_state
== TCP_CA_Open
) {
789 /* Cong. avoidance phase, cwnd is reliable. */
790 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
791 dst
->metrics
[RTAX_SSTHRESH
-1] =
792 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
793 if (!dst_metric_locked(dst
, RTAX_CWND
))
794 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
796 /* Else slow start did not finish, cwnd is non-sense,
797 ssthresh may be also invalid.
799 if (!dst_metric_locked(dst
, RTAX_CWND
))
800 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
801 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
802 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
803 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
804 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
807 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
808 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
809 tp
->reordering
!= sysctl_tcp_reordering
)
810 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
815 /* Numbers are taken from RFC3390.
817 * John Heffner states:
819 * The RFC specifies a window of no more than 4380 bytes
820 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
821 * is a bit misleading because they use a clamp at 4380 bytes
822 * rather than use a multiplier in the relevant range.
824 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
826 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
829 if (tp
->mss_cache
> 1460)
832 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
834 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
837 /* Set slow start threshold and cwnd not falling to slow start */
838 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
840 struct tcp_sock
*tp
= tcp_sk(sk
);
841 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
843 tp
->prior_ssthresh
= 0;
845 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
848 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
849 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
850 tcp_packets_in_flight(tp
) + 1U);
851 tp
->snd_cwnd_cnt
= 0;
852 tp
->high_seq
= tp
->snd_nxt
;
853 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
854 TCP_ECN_queue_cwr(tp
);
856 tcp_set_ca_state(sk
, TCP_CA_CWR
);
861 * Packet counting of FACK is based on in-order assumptions, therefore TCP
862 * disables it when reordering is detected
864 static void tcp_disable_fack(struct tcp_sock
*tp
)
866 tp
->rx_opt
.sack_ok
&= ~2;
869 /* Take a notice that peer is sending DSACKs */
870 static void tcp_dsack_seen(struct tcp_sock
*tp
)
872 tp
->rx_opt
.sack_ok
|= 4;
875 /* Initialize metrics on socket. */
877 static void tcp_init_metrics(struct sock
*sk
)
879 struct tcp_sock
*tp
= tcp_sk(sk
);
880 struct dst_entry
*dst
= __sk_dst_get(sk
);
887 if (dst_metric_locked(dst
, RTAX_CWND
))
888 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
889 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
890 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
891 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
892 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
894 if (dst_metric(dst
, RTAX_REORDERING
) &&
895 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
896 tcp_disable_fack(tp
);
897 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
900 if (dst_metric(dst
, RTAX_RTT
) == 0)
903 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
906 /* Initial rtt is determined from SYN,SYN-ACK.
907 * The segment is small and rtt may appear much
908 * less than real one. Use per-dst memory
909 * to make it more realistic.
911 * A bit of theory. RTT is time passed after "normal" sized packet
912 * is sent until it is ACKed. In normal circumstances sending small
913 * packets force peer to delay ACKs and calculation is correct too.
914 * The algorithm is adaptive and, provided we follow specs, it
915 * NEVER underestimate RTT. BUT! If peer tries to make some clever
916 * tricks sort of "quick acks" for time long enough to decrease RTT
917 * to low value, and then abruptly stops to do it and starts to delay
918 * ACKs, wait for troubles.
920 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
921 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
922 tp
->rtt_seq
= tp
->snd_nxt
;
924 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
925 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
926 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, TCP_RTO_MIN
);
930 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
932 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
933 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
937 /* Play conservative. If timestamps are not
938 * supported, TCP will fail to recalculate correct
939 * rtt, if initial rto is too small. FORGET ALL AND RESET!
941 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
943 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
944 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
948 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
951 struct tcp_sock
*tp
= tcp_sk(sk
);
952 if (metric
> tp
->reordering
) {
953 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
955 /* This exciting event is worth to be remembered. 8) */
957 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
958 else if (tcp_is_reno(tp
))
959 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
960 else if (tcp_is_fack(tp
))
961 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
963 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
964 #if FASTRETRANS_DEBUG > 1
965 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
966 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
970 tp
->undo_marker
? tp
->undo_retrans
: 0);
972 tcp_disable_fack(tp
);
976 /* This procedure tags the retransmission queue when SACKs arrive.
978 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
979 * Packets in queue with these bits set are counted in variables
980 * sacked_out, retrans_out and lost_out, correspondingly.
982 * Valid combinations are:
983 * Tag InFlight Description
984 * 0 1 - orig segment is in flight.
985 * S 0 - nothing flies, orig reached receiver.
986 * L 0 - nothing flies, orig lost by net.
987 * R 2 - both orig and retransmit are in flight.
988 * L|R 1 - orig is lost, retransmit is in flight.
989 * S|R 1 - orig reached receiver, retrans is still in flight.
990 * (L|S|R is logically valid, it could occur when L|R is sacked,
991 * but it is equivalent to plain S and code short-curcuits it to S.
992 * L|S is logically invalid, it would mean -1 packet in flight 8))
994 * These 6 states form finite state machine, controlled by the following events:
995 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
996 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
997 * 3. Loss detection event of one of three flavors:
998 * A. Scoreboard estimator decided the packet is lost.
999 * A'. Reno "three dupacks" marks head of queue lost.
1000 * A''. Its FACK modfication, head until snd.fack is lost.
1001 * B. SACK arrives sacking data transmitted after never retransmitted
1002 * hole was sent out.
1003 * C. SACK arrives sacking SND.NXT at the moment, when the
1004 * segment was retransmitted.
1005 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1007 * It is pleasant to note, that state diagram turns out to be commutative,
1008 * so that we are allowed not to be bothered by order of our actions,
1009 * when multiple events arrive simultaneously. (see the function below).
1011 * Reordering detection.
1012 * --------------------
1013 * Reordering metric is maximal distance, which a packet can be displaced
1014 * in packet stream. With SACKs we can estimate it:
1016 * 1. SACK fills old hole and the corresponding segment was not
1017 * ever retransmitted -> reordering. Alas, we cannot use it
1018 * when segment was retransmitted.
1019 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1020 * for retransmitted and already SACKed segment -> reordering..
1021 * Both of these heuristics are not used in Loss state, when we cannot
1022 * account for retransmits accurately.
1024 * SACK block validation.
1025 * ----------------------
1027 * SACK block range validation checks that the received SACK block fits to
1028 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1029 * Note that SND.UNA is not included to the range though being valid because
1030 * it means that the receiver is rather inconsistent with itself reporting
1031 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1032 * perfectly valid, however, in light of RFC2018 which explicitly states
1033 * that "SACK block MUST reflect the newest segment. Even if the newest
1034 * segment is going to be discarded ...", not that it looks very clever
1035 * in case of head skb. Due to potentional receiver driven attacks, we
1036 * choose to avoid immediate execution of a walk in write queue due to
1037 * reneging and defer head skb's loss recovery to standard loss recovery
1038 * procedure that will eventually trigger (nothing forbids us doing this).
1040 * Implements also blockage to start_seq wrap-around. Problem lies in the
1041 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1042 * there's no guarantee that it will be before snd_nxt (n). The problem
1043 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1046 * <- outs wnd -> <- wrapzone ->
1047 * u e n u_w e_w s n_w
1049 * |<------------+------+----- TCP seqno space --------------+---------->|
1050 * ...-- <2^31 ->| |<--------...
1051 * ...---- >2^31 ------>| |<--------...
1053 * Current code wouldn't be vulnerable but it's better still to discard such
1054 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1055 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1056 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1057 * equal to the ideal case (infinite seqno space without wrap caused issues).
1059 * With D-SACK the lower bound is extended to cover sequence space below
1060 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1061 * again, DSACK block must not to go across snd_una (for the same reason as
1062 * for the normal SACK blocks, explained above). But there all simplicity
1063 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1064 * fully below undo_marker they do not affect behavior in anyway and can
1065 * therefore be safely ignored. In rare cases (which are more or less
1066 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1067 * fragmentation and packet reordering past skb's retransmission. To consider
1068 * them correctly, the acceptable range must be extended even more though
1069 * the exact amount is rather hard to quantify. However, tp->max_window can
1070 * be used as an exaggerated estimate.
1072 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1073 u32 start_seq
, u32 end_seq
)
1075 /* Too far in future, or reversed (interpretation is ambiguous) */
1076 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1079 /* Nasty start_seq wrap-around check (see comments above) */
1080 if (!before(start_seq
, tp
->snd_nxt
))
1083 /* In outstanding window? ...This is valid exit for DSACKs too.
1084 * start_seq == snd_una is non-sensical (see comments above)
1086 if (after(start_seq
, tp
->snd_una
))
1089 if (!is_dsack
|| !tp
->undo_marker
)
1092 /* ...Then it's D-SACK, and must reside below snd_una completely */
1093 if (!after(end_seq
, tp
->snd_una
))
1096 if (!before(start_seq
, tp
->undo_marker
))
1100 if (!after(end_seq
, tp
->undo_marker
))
1103 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1104 * start_seq < undo_marker and end_seq >= undo_marker.
1106 return !before(start_seq
, end_seq
- tp
->max_window
);
1110 static int tcp_check_dsack(struct tcp_sock
*tp
, struct sk_buff
*ack_skb
,
1111 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1114 u32 start_seq_0
= ntohl(get_unaligned(&sp
[0].start_seq
));
1115 u32 end_seq_0
= ntohl(get_unaligned(&sp
[0].end_seq
));
1118 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1121 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
1122 } else if (num_sacks
> 1) {
1123 u32 end_seq_1
= ntohl(get_unaligned(&sp
[1].end_seq
));
1124 u32 start_seq_1
= ntohl(get_unaligned(&sp
[1].start_seq
));
1126 if (!after(end_seq_0
, end_seq_1
) &&
1127 !before(start_seq_0
, start_seq_1
)) {
1130 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
1134 /* D-SACK for already forgotten data... Do dumb counting. */
1136 !after(end_seq_0
, prior_snd_una
) &&
1137 after(end_seq_0
, tp
->undo_marker
))
1144 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
, u32 prior_snd_una
)
1146 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1147 struct tcp_sock
*tp
= tcp_sk(sk
);
1148 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1149 TCP_SKB_CB(ack_skb
)->sacked
);
1150 struct tcp_sack_block_wire
*sp
= (struct tcp_sack_block_wire
*)(ptr
+2);
1151 struct sk_buff
*cached_skb
;
1152 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
)>>3;
1153 int reord
= tp
->packets_out
;
1155 u32 lost_retrans
= 0;
1157 int found_dup_sack
= 0;
1158 int cached_fack_count
;
1160 int first_sack_index
;
1162 if (!tp
->sacked_out
) {
1163 tp
->fackets_out
= 0;
1164 tp
->highest_sack
= tp
->snd_una
;
1166 prior_fackets
= tp
->fackets_out
;
1168 found_dup_sack
= tcp_check_dsack(tp
, ack_skb
, sp
,
1169 num_sacks
, prior_snd_una
);
1171 flag
|= FLAG_DSACKING_ACK
;
1173 /* Eliminate too old ACKs, but take into
1174 * account more or less fresh ones, they can
1175 * contain valid SACK info.
1177 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1181 * if the only SACK change is the increase of the end_seq of
1182 * the first block then only apply that SACK block
1183 * and use retrans queue hinting otherwise slowpath */
1185 for (i
= 0; i
< num_sacks
; i
++) {
1186 __be32 start_seq
= sp
[i
].start_seq
;
1187 __be32 end_seq
= sp
[i
].end_seq
;
1190 if (tp
->recv_sack_cache
[i
].start_seq
!= start_seq
)
1193 if ((tp
->recv_sack_cache
[i
].start_seq
!= start_seq
) ||
1194 (tp
->recv_sack_cache
[i
].end_seq
!= end_seq
))
1197 tp
->recv_sack_cache
[i
].start_seq
= start_seq
;
1198 tp
->recv_sack_cache
[i
].end_seq
= end_seq
;
1200 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */
1201 for (; i
< ARRAY_SIZE(tp
->recv_sack_cache
); i
++) {
1202 tp
->recv_sack_cache
[i
].start_seq
= 0;
1203 tp
->recv_sack_cache
[i
].end_seq
= 0;
1206 first_sack_index
= 0;
1211 tp
->fastpath_skb_hint
= NULL
;
1213 /* order SACK blocks to allow in order walk of the retrans queue */
1214 for (i
= num_sacks
-1; i
> 0; i
--) {
1215 for (j
= 0; j
< i
; j
++){
1216 if (after(ntohl(sp
[j
].start_seq
),
1217 ntohl(sp
[j
+1].start_seq
))){
1218 struct tcp_sack_block_wire tmp
;
1224 /* Track where the first SACK block goes to */
1225 if (j
== first_sack_index
)
1226 first_sack_index
= j
+1;
1233 /* clear flag as used for different purpose in following code */
1236 /* Use SACK fastpath hint if valid */
1237 cached_skb
= tp
->fastpath_skb_hint
;
1238 cached_fack_count
= tp
->fastpath_cnt_hint
;
1240 cached_skb
= tcp_write_queue_head(sk
);
1241 cached_fack_count
= 0;
1244 for (i
=0; i
<num_sacks
; i
++, sp
++) {
1245 struct sk_buff
*skb
;
1246 __u32 start_seq
= ntohl(sp
->start_seq
);
1247 __u32 end_seq
= ntohl(sp
->end_seq
);
1249 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1251 if (!tcp_is_sackblock_valid(tp
, dup_sack
, start_seq
, end_seq
)) {
1253 if (!tp
->undo_marker
)
1254 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO
);
1256 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD
);
1258 /* Don't count olds caused by ACK reordering */
1259 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1260 !after(end_seq
, tp
->snd_una
))
1262 NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD
);
1268 fack_count
= cached_fack_count
;
1270 /* Event "B" in the comment above. */
1271 if (after(end_seq
, tp
->high_seq
))
1272 flag
|= FLAG_DATA_LOST
;
1274 tcp_for_write_queue_from(skb
, sk
) {
1275 int in_sack
, pcount
;
1278 if (skb
== tcp_send_head(sk
))
1282 cached_fack_count
= fack_count
;
1283 if (i
== first_sack_index
) {
1284 tp
->fastpath_skb_hint
= skb
;
1285 tp
->fastpath_cnt_hint
= fack_count
;
1288 /* The retransmission queue is always in order, so
1289 * we can short-circuit the walk early.
1291 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1294 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1295 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1297 pcount
= tcp_skb_pcount(skb
);
1299 if (pcount
> 1 && !in_sack
&&
1300 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1301 unsigned int pkt_len
;
1303 in_sack
= !after(start_seq
,
1304 TCP_SKB_CB(skb
)->seq
);
1307 pkt_len
= (start_seq
-
1308 TCP_SKB_CB(skb
)->seq
);
1310 pkt_len
= (end_seq
-
1311 TCP_SKB_CB(skb
)->seq
);
1312 if (tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
))
1314 pcount
= tcp_skb_pcount(skb
);
1317 fack_count
+= pcount
;
1319 sacked
= TCP_SKB_CB(skb
)->sacked
;
1321 /* Account D-SACK for retransmitted packet. */
1322 if ((dup_sack
&& in_sack
) &&
1323 (sacked
& TCPCB_RETRANS
) &&
1324 after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1327 /* The frame is ACKed. */
1328 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
)) {
1329 if (sacked
&TCPCB_RETRANS
) {
1330 if ((dup_sack
&& in_sack
) &&
1331 (sacked
&TCPCB_SACKED_ACKED
))
1332 reord
= min(fack_count
, reord
);
1334 /* If it was in a hole, we detected reordering. */
1335 if (fack_count
< prior_fackets
&&
1336 !(sacked
&TCPCB_SACKED_ACKED
))
1337 reord
= min(fack_count
, reord
);
1340 /* Nothing to do; acked frame is about to be dropped. */
1344 if ((sacked
&TCPCB_SACKED_RETRANS
) &&
1345 after(end_seq
, TCP_SKB_CB(skb
)->ack_seq
) &&
1346 (!lost_retrans
|| after(end_seq
, lost_retrans
)))
1347 lost_retrans
= end_seq
;
1352 if (!(sacked
&TCPCB_SACKED_ACKED
)) {
1353 if (sacked
& TCPCB_SACKED_RETRANS
) {
1354 /* If the segment is not tagged as lost,
1355 * we do not clear RETRANS, believing
1356 * that retransmission is still in flight.
1358 if (sacked
& TCPCB_LOST
) {
1359 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1360 tp
->lost_out
-= tcp_skb_pcount(skb
);
1361 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1363 /* clear lost hint */
1364 tp
->retransmit_skb_hint
= NULL
;
1367 /* New sack for not retransmitted frame,
1368 * which was in hole. It is reordering.
1370 if (!(sacked
& TCPCB_RETRANS
) &&
1371 fack_count
< prior_fackets
)
1372 reord
= min(fack_count
, reord
);
1374 if (sacked
& TCPCB_LOST
) {
1375 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1376 tp
->lost_out
-= tcp_skb_pcount(skb
);
1378 /* clear lost hint */
1379 tp
->retransmit_skb_hint
= NULL
;
1381 /* SACK enhanced F-RTO detection.
1382 * Set flag if and only if non-rexmitted
1383 * segments below frto_highmark are
1384 * SACKed (RFC4138; Appendix B).
1385 * Clearing correct due to in-order walk
1387 if (after(end_seq
, tp
->frto_highmark
)) {
1388 flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1390 if (!(sacked
& TCPCB_RETRANS
))
1391 flag
|= FLAG_ONLY_ORIG_SACKED
;
1395 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1396 flag
|= FLAG_DATA_SACKED
;
1397 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1399 if (fack_count
> tp
->fackets_out
)
1400 tp
->fackets_out
= fack_count
;
1402 if (after(TCP_SKB_CB(skb
)->seq
,
1404 tp
->highest_sack
= TCP_SKB_CB(skb
)->seq
;
1406 if (dup_sack
&& (sacked
&TCPCB_RETRANS
))
1407 reord
= min(fack_count
, reord
);
1410 /* D-SACK. We can detect redundant retransmission
1411 * in S|R and plain R frames and clear it.
1412 * undo_retrans is decreased above, L|R frames
1413 * are accounted above as well.
1416 (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
)) {
1417 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1418 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1419 tp
->retransmit_skb_hint
= NULL
;
1424 /* Check for lost retransmit. This superb idea is
1425 * borrowed from "ratehalving". Event "C".
1426 * Later note: FACK people cheated me again 8),
1427 * we have to account for reordering! Ugly,
1430 if (lost_retrans
&& icsk
->icsk_ca_state
== TCP_CA_Recovery
) {
1431 struct sk_buff
*skb
;
1433 tcp_for_write_queue(skb
, sk
) {
1434 if (skb
== tcp_send_head(sk
))
1436 if (after(TCP_SKB_CB(skb
)->seq
, lost_retrans
))
1438 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1440 if ((TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) &&
1441 after(lost_retrans
, TCP_SKB_CB(skb
)->ack_seq
) &&
1443 !before(lost_retrans
,
1444 TCP_SKB_CB(skb
)->ack_seq
+ tp
->reordering
*
1446 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1447 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1449 /* clear lost hint */
1450 tp
->retransmit_skb_hint
= NULL
;
1452 if (!(TCP_SKB_CB(skb
)->sacked
&(TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1453 tp
->lost_out
+= tcp_skb_pcount(skb
);
1454 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1455 flag
|= FLAG_DATA_SACKED
;
1456 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1462 tcp_verify_left_out(tp
);
1464 if ((reord
< tp
->fackets_out
) && icsk
->icsk_ca_state
!= TCP_CA_Loss
&&
1465 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1466 tcp_update_reordering(sk
, ((tp
->fackets_out
+ 1) - reord
), 0);
1468 #if FASTRETRANS_DEBUG > 0
1469 BUG_TRAP((int)tp
->sacked_out
>= 0);
1470 BUG_TRAP((int)tp
->lost_out
>= 0);
1471 BUG_TRAP((int)tp
->retrans_out
>= 0);
1472 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1477 /* If we receive more dupacks than we expected counting segments
1478 * in assumption of absent reordering, interpret this as reordering.
1479 * The only another reason could be bug in receiver TCP.
1481 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1483 struct tcp_sock
*tp
= tcp_sk(sk
);
1486 holes
= max(tp
->lost_out
, 1U);
1487 holes
= min(holes
, tp
->packets_out
);
1489 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1490 tp
->sacked_out
= tp
->packets_out
- holes
;
1491 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1495 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1497 static void tcp_add_reno_sack(struct sock
*sk
)
1499 struct tcp_sock
*tp
= tcp_sk(sk
);
1501 tcp_check_reno_reordering(sk
, 0);
1502 tcp_verify_left_out(tp
);
1505 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1507 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1509 struct tcp_sock
*tp
= tcp_sk(sk
);
1512 /* One ACK acked hole. The rest eat duplicate ACKs. */
1513 if (acked
-1 >= tp
->sacked_out
)
1516 tp
->sacked_out
-= acked
-1;
1518 tcp_check_reno_reordering(sk
, acked
);
1519 tcp_verify_left_out(tp
);
1522 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1527 /* F-RTO can only be used if TCP has never retransmitted anything other than
1528 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1530 int tcp_use_frto(struct sock
*sk
)
1532 const struct tcp_sock
*tp
= tcp_sk(sk
);
1533 struct sk_buff
*skb
;
1535 if (!sysctl_tcp_frto
)
1541 /* Avoid expensive walking of rexmit queue if possible */
1542 if (tp
->retrans_out
> 1)
1545 skb
= tcp_write_queue_head(sk
);
1546 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
1547 tcp_for_write_queue_from(skb
, sk
) {
1548 if (skb
== tcp_send_head(sk
))
1550 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1552 /* Short-circuit when first non-SACKed skb has been checked */
1553 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
))
1559 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1560 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1561 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1562 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1563 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1564 * bits are handled if the Loss state is really to be entered (in
1565 * tcp_enter_frto_loss).
1567 * Do like tcp_enter_loss() would; when RTO expires the second time it
1569 * "Reduce ssthresh if it has not yet been made inside this window."
1571 void tcp_enter_frto(struct sock
*sk
)
1573 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1574 struct tcp_sock
*tp
= tcp_sk(sk
);
1575 struct sk_buff
*skb
;
1577 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1578 tp
->snd_una
== tp
->high_seq
||
1579 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1580 !icsk
->icsk_retransmits
)) {
1581 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1582 /* Our state is too optimistic in ssthresh() call because cwnd
1583 * is not reduced until tcp_enter_frto_loss() when previous FRTO
1584 * recovery has not yet completed. Pattern would be this: RTO,
1585 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1587 * RFC4138 should be more specific on what to do, even though
1588 * RTO is quite unlikely to occur after the first Cumulative ACK
1589 * due to back-off and complexity of triggering events ...
1591 if (tp
->frto_counter
) {
1593 stored_cwnd
= tp
->snd_cwnd
;
1595 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1596 tp
->snd_cwnd
= stored_cwnd
;
1598 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1600 /* ... in theory, cong.control module could do "any tricks" in
1601 * ssthresh(), which means that ca_state, lost bits and lost_out
1602 * counter would have to be faked before the call occurs. We
1603 * consider that too expensive, unlikely and hacky, so modules
1604 * using these in ssthresh() must deal these incompatibility
1605 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1607 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1610 tp
->undo_marker
= tp
->snd_una
;
1611 tp
->undo_retrans
= 0;
1613 skb
= tcp_write_queue_head(sk
);
1614 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1615 tp
->undo_marker
= 0;
1616 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1617 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1618 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1620 tcp_verify_left_out(tp
);
1622 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1623 * The last condition is necessary at least in tp->frto_counter case.
1625 if (IsSackFrto() && (tp
->frto_counter
||
1626 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
1627 after(tp
->high_seq
, tp
->snd_una
)) {
1628 tp
->frto_highmark
= tp
->high_seq
;
1630 tp
->frto_highmark
= tp
->snd_nxt
;
1632 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
1633 tp
->high_seq
= tp
->snd_nxt
;
1634 tp
->frto_counter
= 1;
1637 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1638 * which indicates that we should follow the traditional RTO recovery,
1639 * i.e. mark everything lost and do go-back-N retransmission.
1641 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
1643 struct tcp_sock
*tp
= tcp_sk(sk
);
1644 struct sk_buff
*skb
;
1647 tp
->retrans_out
= 0;
1648 if (tcp_is_reno(tp
))
1649 tcp_reset_reno_sack(tp
);
1651 tcp_for_write_queue(skb
, sk
) {
1652 if (skb
== tcp_send_head(sk
))
1655 * Count the retransmission made on RTO correctly (only when
1656 * waiting for the first ACK and did not get it)...
1658 if ((tp
->frto_counter
== 1) && !(flag
&FLAG_DATA_ACKED
)) {
1659 /* For some reason this R-bit might get cleared? */
1660 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1661 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1662 /* ...enter this if branch just for the first segment */
1663 flag
|= FLAG_DATA_ACKED
;
1665 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1666 tp
->undo_marker
= 0;
1667 TCP_SKB_CB(skb
)->sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1670 /* Don't lost mark skbs that were fwd transmitted after RTO */
1671 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) &&
1672 !after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
)) {
1673 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1674 tp
->lost_out
+= tcp_skb_pcount(skb
);
1677 tcp_verify_left_out(tp
);
1679 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
1680 tp
->snd_cwnd_cnt
= 0;
1681 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1682 tp
->frto_counter
= 0;
1684 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1685 sysctl_tcp_reordering
);
1686 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1687 tp
->high_seq
= tp
->frto_highmark
;
1688 TCP_ECN_queue_cwr(tp
);
1690 tcp_clear_retrans_hints_partial(tp
);
1693 void tcp_clear_retrans(struct tcp_sock
*tp
)
1695 tp
->retrans_out
= 0;
1697 tp
->fackets_out
= 0;
1701 tp
->undo_marker
= 0;
1702 tp
->undo_retrans
= 0;
1705 /* Enter Loss state. If "how" is not zero, forget all SACK information
1706 * and reset tags completely, otherwise preserve SACKs. If receiver
1707 * dropped its ofo queue, we will know this due to reneging detection.
1709 void tcp_enter_loss(struct sock
*sk
, int how
)
1711 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1712 struct tcp_sock
*tp
= tcp_sk(sk
);
1713 struct sk_buff
*skb
;
1716 /* Reduce ssthresh if it has not yet been made inside this window. */
1717 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1718 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1719 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1720 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1721 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1724 tp
->snd_cwnd_cnt
= 0;
1725 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1727 tp
->bytes_acked
= 0;
1728 tcp_clear_retrans(tp
);
1731 /* Push undo marker, if it was plain RTO and nothing
1732 * was retransmitted. */
1733 tp
->undo_marker
= tp
->snd_una
;
1734 tcp_clear_retrans_hints_partial(tp
);
1736 tcp_clear_all_retrans_hints(tp
);
1739 tcp_for_write_queue(skb
, sk
) {
1740 if (skb
== tcp_send_head(sk
))
1742 cnt
+= tcp_skb_pcount(skb
);
1743 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_RETRANS
)
1744 tp
->undo_marker
= 0;
1745 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1746 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1747 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1748 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1749 tp
->lost_out
+= tcp_skb_pcount(skb
);
1751 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1752 tp
->fackets_out
= cnt
;
1755 tcp_verify_left_out(tp
);
1757 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1758 sysctl_tcp_reordering
);
1759 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1760 tp
->high_seq
= tp
->snd_nxt
;
1761 TCP_ECN_queue_cwr(tp
);
1762 /* Abort FRTO algorithm if one is in progress */
1763 tp
->frto_counter
= 0;
1766 static int tcp_check_sack_reneging(struct sock
*sk
)
1768 struct sk_buff
*skb
;
1770 /* If ACK arrived pointing to a remembered SACK,
1771 * it means that our remembered SACKs do not reflect
1772 * real state of receiver i.e.
1773 * receiver _host_ is heavily congested (or buggy).
1774 * Do processing similar to RTO timeout.
1776 if ((skb
= tcp_write_queue_head(sk
)) != NULL
&&
1777 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1778 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1779 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1781 tcp_enter_loss(sk
, 1);
1782 icsk
->icsk_retransmits
++;
1783 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
1784 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1785 icsk
->icsk_rto
, TCP_RTO_MAX
);
1791 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1793 return tcp_is_reno(tp
) ? tp
->sacked_out
+1 : tp
->fackets_out
;
1796 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1798 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1801 static inline int tcp_head_timedout(struct sock
*sk
)
1803 struct tcp_sock
*tp
= tcp_sk(sk
);
1805 return tp
->packets_out
&&
1806 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
1809 /* Linux NewReno/SACK/FACK/ECN state machine.
1810 * --------------------------------------
1812 * "Open" Normal state, no dubious events, fast path.
1813 * "Disorder" In all the respects it is "Open",
1814 * but requires a bit more attention. It is entered when
1815 * we see some SACKs or dupacks. It is split of "Open"
1816 * mainly to move some processing from fast path to slow one.
1817 * "CWR" CWND was reduced due to some Congestion Notification event.
1818 * It can be ECN, ICMP source quench, local device congestion.
1819 * "Recovery" CWND was reduced, we are fast-retransmitting.
1820 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
1822 * tcp_fastretrans_alert() is entered:
1823 * - each incoming ACK, if state is not "Open"
1824 * - when arrived ACK is unusual, namely:
1829 * Counting packets in flight is pretty simple.
1831 * in_flight = packets_out - left_out + retrans_out
1833 * packets_out is SND.NXT-SND.UNA counted in packets.
1835 * retrans_out is number of retransmitted segments.
1837 * left_out is number of segments left network, but not ACKed yet.
1839 * left_out = sacked_out + lost_out
1841 * sacked_out: Packets, which arrived to receiver out of order
1842 * and hence not ACKed. With SACKs this number is simply
1843 * amount of SACKed data. Even without SACKs
1844 * it is easy to give pretty reliable estimate of this number,
1845 * counting duplicate ACKs.
1847 * lost_out: Packets lost by network. TCP has no explicit
1848 * "loss notification" feedback from network (for now).
1849 * It means that this number can be only _guessed_.
1850 * Actually, it is the heuristics to predict lossage that
1851 * distinguishes different algorithms.
1853 * F.e. after RTO, when all the queue is considered as lost,
1854 * lost_out = packets_out and in_flight = retrans_out.
1856 * Essentially, we have now two algorithms counting
1859 * FACK: It is the simplest heuristics. As soon as we decided
1860 * that something is lost, we decide that _all_ not SACKed
1861 * packets until the most forward SACK are lost. I.e.
1862 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
1863 * It is absolutely correct estimate, if network does not reorder
1864 * packets. And it loses any connection to reality when reordering
1865 * takes place. We use FACK by default until reordering
1866 * is suspected on the path to this destination.
1868 * NewReno: when Recovery is entered, we assume that one segment
1869 * is lost (classic Reno). While we are in Recovery and
1870 * a partial ACK arrives, we assume that one more packet
1871 * is lost (NewReno). This heuristics are the same in NewReno
1874 * Imagine, that's all! Forget about all this shamanism about CWND inflation
1875 * deflation etc. CWND is real congestion window, never inflated, changes
1876 * only according to classic VJ rules.
1878 * Really tricky (and requiring careful tuning) part of algorithm
1879 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
1880 * The first determines the moment _when_ we should reduce CWND and,
1881 * hence, slow down forward transmission. In fact, it determines the moment
1882 * when we decide that hole is caused by loss, rather than by a reorder.
1884 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
1885 * holes, caused by lost packets.
1887 * And the most logically complicated part of algorithm is undo
1888 * heuristics. We detect false retransmits due to both too early
1889 * fast retransmit (reordering) and underestimated RTO, analyzing
1890 * timestamps and D-SACKs. When we detect that some segments were
1891 * retransmitted by mistake and CWND reduction was wrong, we undo
1892 * window reduction and abort recovery phase. This logic is hidden
1893 * inside several functions named tcp_try_undo_<something>.
1896 /* This function decides, when we should leave Disordered state
1897 * and enter Recovery phase, reducing congestion window.
1899 * Main question: may we further continue forward transmission
1900 * with the same cwnd?
1902 static int tcp_time_to_recover(struct sock
*sk
)
1904 struct tcp_sock
*tp
= tcp_sk(sk
);
1907 /* Do not perform any recovery during FRTO algorithm */
1908 if (tp
->frto_counter
)
1911 /* Trick#1: The loss is proven. */
1915 /* Not-A-Trick#2 : Classic rule... */
1916 if (tcp_fackets_out(tp
) > tp
->reordering
)
1919 /* Trick#3 : when we use RFC2988 timer restart, fast
1920 * retransmit can be triggered by timeout of queue head.
1922 if (tcp_head_timedout(sk
))
1925 /* Trick#4: It is still not OK... But will it be useful to delay
1928 packets_out
= tp
->packets_out
;
1929 if (packets_out
<= tp
->reordering
&&
1930 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
1931 !tcp_may_send_now(sk
)) {
1932 /* We have nothing to send. This connection is limited
1933 * either by receiver window or by application.
1941 /* RFC: This is from the original, I doubt that this is necessary at all:
1942 * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
1943 * retransmitted past LOST markings in the first place? I'm not fully sure
1944 * about undo and end of connection cases, which can cause R without L?
1946 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
,
1947 struct sk_buff
*skb
)
1949 if ((tp
->retransmit_skb_hint
!= NULL
) &&
1950 before(TCP_SKB_CB(skb
)->seq
,
1951 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1952 tp
->retransmit_skb_hint
= NULL
;
1955 /* Mark head of queue up as lost. */
1956 static void tcp_mark_head_lost(struct sock
*sk
,
1957 int packets
, u32 high_seq
)
1959 struct tcp_sock
*tp
= tcp_sk(sk
);
1960 struct sk_buff
*skb
;
1963 BUG_TRAP(packets
<= tp
->packets_out
);
1964 if (tp
->lost_skb_hint
) {
1965 skb
= tp
->lost_skb_hint
;
1966 cnt
= tp
->lost_cnt_hint
;
1968 skb
= tcp_write_queue_head(sk
);
1972 tcp_for_write_queue_from(skb
, sk
) {
1973 if (skb
== tcp_send_head(sk
))
1975 /* TODO: do this better */
1976 /* this is not the most efficient way to do this... */
1977 tp
->lost_skb_hint
= skb
;
1978 tp
->lost_cnt_hint
= cnt
;
1979 cnt
+= tcp_skb_pcount(skb
);
1980 if (cnt
> packets
|| after(TCP_SKB_CB(skb
)->end_seq
, high_seq
))
1982 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
1983 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1984 tp
->lost_out
+= tcp_skb_pcount(skb
);
1985 tcp_verify_retransmit_hint(tp
, skb
);
1988 tcp_verify_left_out(tp
);
1991 /* Account newly detected lost packet(s) */
1993 static void tcp_update_scoreboard(struct sock
*sk
)
1995 struct tcp_sock
*tp
= tcp_sk(sk
);
1997 if (tcp_is_fack(tp
)) {
1998 int lost
= tp
->fackets_out
- tp
->reordering
;
2001 tcp_mark_head_lost(sk
, lost
, tp
->high_seq
);
2003 tcp_mark_head_lost(sk
, 1, tp
->high_seq
);
2006 /* New heuristics: it is possible only after we switched
2007 * to restart timer each time when something is ACKed.
2008 * Hence, we can detect timed out packets during fast
2009 * retransmit without falling to slow start.
2011 if (!tcp_is_reno(tp
) && tcp_head_timedout(sk
)) {
2012 struct sk_buff
*skb
;
2014 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
2015 : tcp_write_queue_head(sk
);
2017 tcp_for_write_queue_from(skb
, sk
) {
2018 if (skb
== tcp_send_head(sk
))
2020 if (!tcp_skb_timedout(sk
, skb
))
2023 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_TAGBITS
)) {
2024 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2025 tp
->lost_out
+= tcp_skb_pcount(skb
);
2026 tcp_verify_retransmit_hint(tp
, skb
);
2030 tp
->scoreboard_skb_hint
= skb
;
2032 tcp_verify_left_out(tp
);
2036 /* CWND moderation, preventing bursts due to too big ACKs
2037 * in dubious situations.
2039 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2041 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2042 tcp_packets_in_flight(tp
)+tcp_max_burst(tp
));
2043 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2046 /* Lower bound on congestion window is slow start threshold
2047 * unless congestion avoidance choice decides to overide it.
2049 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2051 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2053 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2056 /* Decrease cwnd each second ack. */
2057 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2059 struct tcp_sock
*tp
= tcp_sk(sk
);
2060 int decr
= tp
->snd_cwnd_cnt
+ 1;
2062 if ((flag
&(FLAG_ANY_PROGRESS
|FLAG_DSACKING_ACK
)) ||
2063 (tcp_is_reno(tp
) && !(flag
&FLAG_NOT_DUP
))) {
2064 tp
->snd_cwnd_cnt
= decr
&1;
2067 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2068 tp
->snd_cwnd
-= decr
;
2070 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
)+1);
2071 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2075 /* Nothing was retransmitted or returned timestamp is less
2076 * than timestamp of the first retransmission.
2078 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
2080 return !tp
->retrans_stamp
||
2081 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2082 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
2085 /* Undo procedures. */
2087 #if FASTRETRANS_DEBUG > 1
2088 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2090 struct tcp_sock
*tp
= tcp_sk(sk
);
2091 struct inet_sock
*inet
= inet_sk(sk
);
2093 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
2095 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
2096 tp
->snd_cwnd
, tcp_left_out(tp
),
2097 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2101 #define DBGUNDO(x...) do { } while (0)
2104 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
2106 struct tcp_sock
*tp
= tcp_sk(sk
);
2108 if (tp
->prior_ssthresh
) {
2109 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2111 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2112 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2114 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<<1);
2116 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2117 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2118 TCP_ECN_withdraw_cwr(tp
);
2121 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2123 tcp_moderate_cwnd(tp
);
2124 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2126 /* There is something screwy going on with the retrans hints after
2128 tcp_clear_all_retrans_hints(tp
);
2131 static inline int tcp_may_undo(struct tcp_sock
*tp
)
2133 return tp
->undo_marker
&&
2134 (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2137 /* People celebrate: "We love our President!" */
2138 static int tcp_try_undo_recovery(struct sock
*sk
)
2140 struct tcp_sock
*tp
= tcp_sk(sk
);
2142 if (tcp_may_undo(tp
)) {
2143 /* Happy end! We did not retransmit anything
2144 * or our original transmission succeeded.
2146 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2147 tcp_undo_cwr(sk
, 1);
2148 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2149 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2151 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
2152 tp
->undo_marker
= 0;
2154 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2155 /* Hold old state until something *above* high_seq
2156 * is ACKed. For Reno it is MUST to prevent false
2157 * fast retransmits (RFC2582). SACK TCP is safe. */
2158 tcp_moderate_cwnd(tp
);
2161 tcp_set_ca_state(sk
, TCP_CA_Open
);
2165 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2166 static void tcp_try_undo_dsack(struct sock
*sk
)
2168 struct tcp_sock
*tp
= tcp_sk(sk
);
2170 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2171 DBGUNDO(sk
, "D-SACK");
2172 tcp_undo_cwr(sk
, 1);
2173 tp
->undo_marker
= 0;
2174 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
2178 /* Undo during fast recovery after partial ACK. */
2180 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2182 struct tcp_sock
*tp
= tcp_sk(sk
);
2183 /* Partial ACK arrived. Force Hoe's retransmit. */
2184 int failed
= tcp_is_reno(tp
) || tp
->fackets_out
>tp
->reordering
;
2186 if (tcp_may_undo(tp
)) {
2187 /* Plain luck! Hole if filled with delayed
2188 * packet, rather than with a retransmit.
2190 if (tp
->retrans_out
== 0)
2191 tp
->retrans_stamp
= 0;
2193 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2196 tcp_undo_cwr(sk
, 0);
2197 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
2199 /* So... Do not make Hoe's retransmit yet.
2200 * If the first packet was delayed, the rest
2201 * ones are most probably delayed as well.
2208 /* Undo during loss recovery after partial ACK. */
2209 static int tcp_try_undo_loss(struct sock
*sk
)
2211 struct tcp_sock
*tp
= tcp_sk(sk
);
2213 if (tcp_may_undo(tp
)) {
2214 struct sk_buff
*skb
;
2215 tcp_for_write_queue(skb
, sk
) {
2216 if (skb
== tcp_send_head(sk
))
2218 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2221 tcp_clear_all_retrans_hints(tp
);
2223 DBGUNDO(sk
, "partial loss");
2225 tcp_undo_cwr(sk
, 1);
2226 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2227 inet_csk(sk
)->icsk_retransmits
= 0;
2228 tp
->undo_marker
= 0;
2229 if (tcp_is_sack(tp
))
2230 tcp_set_ca_state(sk
, TCP_CA_Open
);
2236 static inline void tcp_complete_cwr(struct sock
*sk
)
2238 struct tcp_sock
*tp
= tcp_sk(sk
);
2239 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2240 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2241 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2244 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2246 struct tcp_sock
*tp
= tcp_sk(sk
);
2248 tcp_verify_left_out(tp
);
2250 if (tp
->retrans_out
== 0)
2251 tp
->retrans_stamp
= 0;
2254 tcp_enter_cwr(sk
, 1);
2256 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2257 int state
= TCP_CA_Open
;
2259 if (tcp_left_out(tp
) || tp
->retrans_out
|| tp
->undo_marker
)
2260 state
= TCP_CA_Disorder
;
2262 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2263 tcp_set_ca_state(sk
, state
);
2264 tp
->high_seq
= tp
->snd_nxt
;
2266 tcp_moderate_cwnd(tp
);
2268 tcp_cwnd_down(sk
, flag
);
2272 static void tcp_mtup_probe_failed(struct sock
*sk
)
2274 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2276 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2277 icsk
->icsk_mtup
.probe_size
= 0;
2280 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
2282 struct tcp_sock
*tp
= tcp_sk(sk
);
2283 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2285 /* FIXME: breaks with very large cwnd */
2286 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2287 tp
->snd_cwnd
= tp
->snd_cwnd
*
2288 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2289 icsk
->icsk_mtup
.probe_size
;
2290 tp
->snd_cwnd_cnt
= 0;
2291 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2292 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2294 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2295 icsk
->icsk_mtup
.probe_size
= 0;
2296 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2300 /* Process an event, which can update packets-in-flight not trivially.
2301 * Main goal of this function is to calculate new estimate for left_out,
2302 * taking into account both packets sitting in receiver's buffer and
2303 * packets lost by network.
2305 * Besides that it does CWND reduction, when packet loss is detected
2306 * and changes state of machine.
2308 * It does _not_ decide what to send, it is made in function
2309 * tcp_xmit_retransmit_queue().
2312 tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
, int flag
)
2314 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2315 struct tcp_sock
*tp
= tcp_sk(sk
);
2316 int is_dupack
= !(flag
&(FLAG_SND_UNA_ADVANCED
|FLAG_NOT_DUP
));
2317 int do_lost
= is_dupack
|| ((flag
&FLAG_DATA_SACKED
) &&
2318 (tp
->fackets_out
> tp
->reordering
));
2320 /* Some technical things:
2321 * 1. Reno does not count dupacks (sacked_out) automatically. */
2322 if (!tp
->packets_out
)
2325 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2326 tp
->fackets_out
= 0;
2328 /* Now state machine starts.
2329 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2331 tp
->prior_ssthresh
= 0;
2333 /* B. In all the states check for reneging SACKs. */
2334 if (tp
->sacked_out
&& tcp_check_sack_reneging(sk
))
2337 /* C. Process data loss notification, provided it is valid. */
2338 if ((flag
&FLAG_DATA_LOST
) &&
2339 before(tp
->snd_una
, tp
->high_seq
) &&
2340 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2341 tp
->fackets_out
> tp
->reordering
) {
2342 tcp_mark_head_lost(sk
, tp
->fackets_out
-tp
->reordering
, tp
->high_seq
);
2343 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
2346 /* D. Check consistency of the current state. */
2347 tcp_verify_left_out(tp
);
2349 /* E. Check state exit conditions. State can be terminated
2350 * when high_seq is ACKed. */
2351 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2352 BUG_TRAP(tp
->retrans_out
== 0);
2353 tp
->retrans_stamp
= 0;
2354 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2355 switch (icsk
->icsk_ca_state
) {
2357 icsk
->icsk_retransmits
= 0;
2358 if (tcp_try_undo_recovery(sk
))
2363 /* CWR is to be held something *above* high_seq
2364 * is ACKed for CWR bit to reach receiver. */
2365 if (tp
->snd_una
!= tp
->high_seq
) {
2366 tcp_complete_cwr(sk
);
2367 tcp_set_ca_state(sk
, TCP_CA_Open
);
2371 case TCP_CA_Disorder
:
2372 tcp_try_undo_dsack(sk
);
2373 if (!tp
->undo_marker
||
2374 /* For SACK case do not Open to allow to undo
2375 * catching for all duplicate ACKs. */
2376 tcp_is_reno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2377 tp
->undo_marker
= 0;
2378 tcp_set_ca_state(sk
, TCP_CA_Open
);
2382 case TCP_CA_Recovery
:
2383 if (tcp_is_reno(tp
))
2384 tcp_reset_reno_sack(tp
);
2385 if (tcp_try_undo_recovery(sk
))
2387 tcp_complete_cwr(sk
);
2392 /* F. Process state. */
2393 switch (icsk
->icsk_ca_state
) {
2394 case TCP_CA_Recovery
:
2395 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2396 if (tcp_is_reno(tp
) && is_dupack
)
2397 tcp_add_reno_sack(sk
);
2399 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
2402 if (flag
&FLAG_DATA_ACKED
)
2403 icsk
->icsk_retransmits
= 0;
2404 if (!tcp_try_undo_loss(sk
)) {
2405 tcp_moderate_cwnd(tp
);
2406 tcp_xmit_retransmit_queue(sk
);
2409 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2411 /* Loss is undone; fall through to processing in Open state. */
2413 if (tcp_is_reno(tp
)) {
2414 if (flag
& FLAG_SND_UNA_ADVANCED
)
2415 tcp_reset_reno_sack(tp
);
2417 tcp_add_reno_sack(sk
);
2420 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2421 tcp_try_undo_dsack(sk
);
2423 if (!tcp_time_to_recover(sk
)) {
2424 tcp_try_to_open(sk
, flag
);
2428 /* MTU probe failure: don't reduce cwnd */
2429 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2430 icsk
->icsk_mtup
.probe_size
&&
2431 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2432 tcp_mtup_probe_failed(sk
);
2433 /* Restores the reduction we did in tcp_mtup_probe() */
2435 tcp_simple_retransmit(sk
);
2439 /* Otherwise enter Recovery state */
2441 if (tcp_is_reno(tp
))
2442 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
2444 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
2446 tp
->high_seq
= tp
->snd_nxt
;
2447 tp
->prior_ssthresh
= 0;
2448 tp
->undo_marker
= tp
->snd_una
;
2449 tp
->undo_retrans
= tp
->retrans_out
;
2451 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2452 if (!(flag
&FLAG_ECE
))
2453 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2454 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2455 TCP_ECN_queue_cwr(tp
);
2458 tp
->bytes_acked
= 0;
2459 tp
->snd_cwnd_cnt
= 0;
2460 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2463 if (do_lost
|| tcp_head_timedout(sk
))
2464 tcp_update_scoreboard(sk
);
2465 tcp_cwnd_down(sk
, flag
);
2466 tcp_xmit_retransmit_queue(sk
);
2469 /* Read draft-ietf-tcplw-high-performance before mucking
2470 * with this code. (Supersedes RFC1323)
2472 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2474 /* RTTM Rule: A TSecr value received in a segment is used to
2475 * update the averaged RTT measurement only if the segment
2476 * acknowledges some new data, i.e., only if it advances the
2477 * left edge of the send window.
2479 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2480 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2482 * Changed: reset backoff as soon as we see the first valid sample.
2483 * If we do not, we get strongly overestimated rto. With timestamps
2484 * samples are accepted even from very old segments: f.e., when rtt=1
2485 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2486 * answer arrives rto becomes 120 seconds! If at least one of segments
2487 * in window is lost... Voila. --ANK (010210)
2489 struct tcp_sock
*tp
= tcp_sk(sk
);
2490 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2491 tcp_rtt_estimator(sk
, seq_rtt
);
2493 inet_csk(sk
)->icsk_backoff
= 0;
2497 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2499 /* We don't have a timestamp. Can only use
2500 * packets that are not retransmitted to determine
2501 * rtt estimates. Also, we must not reset the
2502 * backoff for rto until we get a non-retransmitted
2503 * packet. This allows us to deal with a situation
2504 * where the network delay has increased suddenly.
2505 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2508 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2511 tcp_rtt_estimator(sk
, seq_rtt
);
2513 inet_csk(sk
)->icsk_backoff
= 0;
2517 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2520 const struct tcp_sock
*tp
= tcp_sk(sk
);
2521 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2522 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2523 tcp_ack_saw_tstamp(sk
, flag
);
2524 else if (seq_rtt
>= 0)
2525 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2528 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
,
2529 u32 in_flight
, int good
)
2531 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2532 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
, good
);
2533 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2536 /* Restart timer after forward progress on connection.
2537 * RFC2988 recommends to restart timer to now+rto.
2539 static void tcp_rearm_rto(struct sock
*sk
)
2541 struct tcp_sock
*tp
= tcp_sk(sk
);
2543 if (!tp
->packets_out
) {
2544 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2546 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2550 /* If we get here, the whole TSO packet has not been acked. */
2551 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
2553 struct tcp_sock
*tp
= tcp_sk(sk
);
2556 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
2558 packets_acked
= tcp_skb_pcount(skb
);
2559 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2561 packets_acked
-= tcp_skb_pcount(skb
);
2563 if (packets_acked
) {
2564 BUG_ON(tcp_skb_pcount(skb
) == 0);
2565 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
2568 return packets_acked
;
2571 /* Remove acknowledged frames from the retransmission queue. If our packet
2572 * is before the ack sequence we can discard it as it's confirmed to have
2573 * arrived at the other end.
2575 static int tcp_clean_rtx_queue(struct sock
*sk
, s32
*seq_rtt_p
)
2577 struct tcp_sock
*tp
= tcp_sk(sk
);
2578 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2579 struct sk_buff
*skb
;
2580 u32 now
= tcp_time_stamp
;
2581 int fully_acked
= 1;
2583 int prior_packets
= tp
->packets_out
;
2585 ktime_t last_ackt
= net_invalid_timestamp();
2587 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
2588 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2591 u8 sacked
= scb
->sacked
;
2593 if (after(scb
->end_seq
, tp
->snd_una
)) {
2594 if (tcp_skb_pcount(skb
) == 1 ||
2595 !after(tp
->snd_una
, scb
->seq
))
2598 packets_acked
= tcp_tso_acked(sk
, skb
);
2603 end_seq
= tp
->snd_una
;
2605 packets_acked
= tcp_skb_pcount(skb
);
2606 end_seq
= scb
->end_seq
;
2609 /* MTU probing checks */
2610 if (fully_acked
&& icsk
->icsk_mtup
.probe_size
&&
2611 !after(tp
->mtu_probe
.probe_seq_end
, scb
->end_seq
)) {
2612 tcp_mtup_probe_success(sk
, skb
);
2616 if (sacked
& TCPCB_RETRANS
) {
2617 if (sacked
& TCPCB_SACKED_RETRANS
)
2618 tp
->retrans_out
-= packets_acked
;
2619 flag
|= FLAG_RETRANS_DATA_ACKED
;
2621 if ((flag
& FLAG_DATA_ACKED
) ||
2622 (packets_acked
> 1))
2623 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
2624 } else if (seq_rtt
< 0) {
2625 seq_rtt
= now
- scb
->when
;
2627 last_ackt
= skb
->tstamp
;
2630 if (sacked
& TCPCB_SACKED_ACKED
)
2631 tp
->sacked_out
-= packets_acked
;
2632 if (sacked
& TCPCB_LOST
)
2633 tp
->lost_out
-= packets_acked
;
2635 if ((sacked
& TCPCB_URG
) && tp
->urg_mode
&&
2636 !before(end_seq
, tp
->snd_up
))
2638 } else if (seq_rtt
< 0) {
2639 seq_rtt
= now
- scb
->when
;
2641 last_ackt
= skb
->tstamp
;
2643 tp
->packets_out
-= packets_acked
;
2645 /* Initial outgoing SYN's get put onto the write_queue
2646 * just like anything else we transmit. It is not
2647 * true data, and if we misinform our callers that
2648 * this ACK acks real data, we will erroneously exit
2649 * connection startup slow start one packet too
2650 * quickly. This is severely frowned upon behavior.
2652 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2653 flag
|= FLAG_DATA_ACKED
;
2655 flag
|= FLAG_SYN_ACKED
;
2656 tp
->retrans_stamp
= 0;
2662 tcp_unlink_write_queue(skb
, sk
);
2663 sk_stream_free_skb(sk
, skb
);
2664 tcp_clear_all_retrans_hints(tp
);
2667 if (flag
& FLAG_ACKED
) {
2668 u32 pkts_acked
= prior_packets
- tp
->packets_out
;
2669 const struct tcp_congestion_ops
*ca_ops
2670 = inet_csk(sk
)->icsk_ca_ops
;
2672 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
2675 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
2676 /* hint's skb might be NULL but we don't need to care */
2677 tp
->fastpath_cnt_hint
-= min_t(u32
, pkts_acked
,
2678 tp
->fastpath_cnt_hint
);
2679 if (tcp_is_reno(tp
))
2680 tcp_remove_reno_sacks(sk
, pkts_acked
);
2682 if (ca_ops
->pkts_acked
) {
2685 /* Is the ACK triggering packet unambiguous? */
2686 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
2687 /* High resolution needed and available? */
2688 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
2689 !ktime_equal(last_ackt
,
2690 net_invalid_timestamp()))
2691 rtt_us
= ktime_us_delta(ktime_get_real(),
2693 else if (seq_rtt
> 0)
2694 rtt_us
= jiffies_to_usecs(seq_rtt
);
2697 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
2701 #if FASTRETRANS_DEBUG > 0
2702 BUG_TRAP((int)tp
->sacked_out
>= 0);
2703 BUG_TRAP((int)tp
->lost_out
>= 0);
2704 BUG_TRAP((int)tp
->retrans_out
>= 0);
2705 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
2706 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2708 printk(KERN_DEBUG
"Leak l=%u %d\n",
2709 tp
->lost_out
, icsk
->icsk_ca_state
);
2712 if (tp
->sacked_out
) {
2713 printk(KERN_DEBUG
"Leak s=%u %d\n",
2714 tp
->sacked_out
, icsk
->icsk_ca_state
);
2717 if (tp
->retrans_out
) {
2718 printk(KERN_DEBUG
"Leak r=%u %d\n",
2719 tp
->retrans_out
, icsk
->icsk_ca_state
);
2720 tp
->retrans_out
= 0;
2724 *seq_rtt_p
= seq_rtt
;
2728 static void tcp_ack_probe(struct sock
*sk
)
2730 const struct tcp_sock
*tp
= tcp_sk(sk
);
2731 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2733 /* Was it a usable window open? */
2735 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2736 tp
->snd_una
+ tp
->snd_wnd
)) {
2737 icsk
->icsk_backoff
= 0;
2738 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2739 /* Socket must be waked up by subsequent tcp_data_snd_check().
2740 * This function is not for random using!
2743 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2744 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2749 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2751 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2752 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2755 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2757 const struct tcp_sock
*tp
= tcp_sk(sk
);
2758 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2759 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2762 /* Check that window update is acceptable.
2763 * The function assumes that snd_una<=ack<=snd_next.
2765 static inline int tcp_may_update_window(const struct tcp_sock
*tp
, const u32 ack
,
2766 const u32 ack_seq
, const u32 nwin
)
2768 return (after(ack
, tp
->snd_una
) ||
2769 after(ack_seq
, tp
->snd_wl1
) ||
2770 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2773 /* Update our send window.
2775 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2776 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
2778 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
2781 struct tcp_sock
*tp
= tcp_sk(sk
);
2783 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
2785 if (likely(!tcp_hdr(skb
)->syn
))
2786 nwin
<<= tp
->rx_opt
.snd_wscale
;
2788 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
2789 flag
|= FLAG_WIN_UPDATE
;
2790 tcp_update_wl(tp
, ack
, ack_seq
);
2792 if (tp
->snd_wnd
!= nwin
) {
2795 /* Note, it is the only place, where
2796 * fast path is recovered for sending TCP.
2799 tcp_fast_path_check(sk
);
2801 if (nwin
> tp
->max_window
) {
2802 tp
->max_window
= nwin
;
2803 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
2813 /* A very conservative spurious RTO response algorithm: reduce cwnd and
2814 * continue in congestion avoidance.
2816 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
2818 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2819 tp
->snd_cwnd_cnt
= 0;
2820 TCP_ECN_queue_cwr(tp
);
2821 tcp_moderate_cwnd(tp
);
2824 /* A conservative spurious RTO response algorithm: reduce cwnd using
2825 * rate halving and continue in congestion avoidance.
2827 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
2829 tcp_enter_cwr(sk
, 0);
2832 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
2835 tcp_ratehalving_spur_to_response(sk
);
2837 tcp_undo_cwr(sk
, 1);
2840 /* F-RTO spurious RTO detection algorithm (RFC4138)
2842 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
2843 * comments). State (ACK number) is kept in frto_counter. When ACK advances
2844 * window (but not to or beyond highest sequence sent before RTO):
2845 * On First ACK, send two new segments out.
2846 * On Second ACK, RTO was likely spurious. Do spurious response (response
2847 * algorithm is not part of the F-RTO detection algorithm
2848 * given in RFC4138 but can be selected separately).
2849 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
2850 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
2851 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
2852 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
2854 * Rationale: if the RTO was spurious, new ACKs should arrive from the
2855 * original window even after we transmit two new data segments.
2858 * on first step, wait until first cumulative ACK arrives, then move to
2859 * the second step. In second step, the next ACK decides.
2861 * F-RTO is implemented (mainly) in four functions:
2862 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
2863 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
2864 * called when tcp_use_frto() showed green light
2865 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
2866 * - tcp_enter_frto_loss() is called if there is not enough evidence
2867 * to prove that the RTO is indeed spurious. It transfers the control
2868 * from F-RTO to the conventional RTO recovery
2870 static int tcp_process_frto(struct sock
*sk
, int flag
)
2872 struct tcp_sock
*tp
= tcp_sk(sk
);
2874 tcp_verify_left_out(tp
);
2876 /* Duplicate the behavior from Loss state (fastretrans_alert) */
2877 if (flag
&FLAG_DATA_ACKED
)
2878 inet_csk(sk
)->icsk_retransmits
= 0;
2880 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
2881 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
2882 tp
->undo_marker
= 0;
2884 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
2885 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
2889 if (!IsSackFrto() || tcp_is_reno(tp
)) {
2890 /* RFC4138 shortcoming in step 2; should also have case c):
2891 * ACK isn't duplicate nor advances window, e.g., opposite dir
2894 if (!(flag
&FLAG_ANY_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2897 if (!(flag
&FLAG_DATA_ACKED
)) {
2898 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
2903 if (!(flag
&FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
2904 /* Prevent sending of new data. */
2905 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2906 tcp_packets_in_flight(tp
));
2910 if ((tp
->frto_counter
>= 2) &&
2911 (!(flag
&FLAG_FORWARD_PROGRESS
) ||
2912 ((flag
&FLAG_DATA_SACKED
) && !(flag
&FLAG_ONLY_ORIG_SACKED
)))) {
2913 /* RFC4138 shortcoming (see comment above) */
2914 if (!(flag
&FLAG_FORWARD_PROGRESS
) && (flag
&FLAG_NOT_DUP
))
2917 tcp_enter_frto_loss(sk
, 3, flag
);
2922 if (tp
->frto_counter
== 1) {
2923 /* Sending of the next skb must be allowed or no FRTO */
2924 if (!tcp_send_head(sk
) ||
2925 after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
,
2926 tp
->snd_una
+ tp
->snd_wnd
)) {
2927 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3),
2932 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
2933 tp
->frto_counter
= 2;
2936 switch (sysctl_tcp_frto_response
) {
2938 tcp_undo_spur_to_response(sk
, flag
);
2941 tcp_conservative_spur_to_response(tp
);
2944 tcp_ratehalving_spur_to_response(sk
);
2947 tp
->frto_counter
= 0;
2948 tp
->undo_marker
= 0;
2949 NET_INC_STATS_BH(LINUX_MIB_TCPSPURIOUSRTOS
);
2954 /* This routine deals with incoming acks, but not outgoing ones. */
2955 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
2957 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2958 struct tcp_sock
*tp
= tcp_sk(sk
);
2959 u32 prior_snd_una
= tp
->snd_una
;
2960 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
2961 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
2962 u32 prior_in_flight
;
2967 /* If the ack is newer than sent or older than previous acks
2968 * then we can probably ignore it.
2970 if (after(ack
, tp
->snd_nxt
))
2971 goto uninteresting_ack
;
2973 if (before(ack
, prior_snd_una
))
2976 if (after(ack
, prior_snd_una
))
2977 flag
|= FLAG_SND_UNA_ADVANCED
;
2979 if (sysctl_tcp_abc
) {
2980 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
2981 tp
->bytes_acked
+= ack
- prior_snd_una
;
2982 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
2983 /* we assume just one segment left network */
2984 tp
->bytes_acked
+= min(ack
- prior_snd_una
, tp
->mss_cache
);
2987 if (!(flag
&FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
2988 /* Window is constant, pure forward advance.
2989 * No more checks are required.
2990 * Note, we use the fact that SND.UNA>=SND.WL2.
2992 tcp_update_wl(tp
, ack
, ack_seq
);
2994 flag
|= FLAG_WIN_UPDATE
;
2996 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
2998 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
3000 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3003 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
3005 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3007 if (TCP_SKB_CB(skb
)->sacked
)
3008 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3010 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3013 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3016 /* We passed data and got it acked, remove any soft error
3017 * log. Something worked...
3019 sk
->sk_err_soft
= 0;
3020 tp
->rcv_tstamp
= tcp_time_stamp
;
3021 prior_packets
= tp
->packets_out
;
3025 prior_in_flight
= tcp_packets_in_flight(tp
);
3027 /* See if we can take anything off of the retransmit queue. */
3028 flag
|= tcp_clean_rtx_queue(sk
, &seq_rtt
);
3030 if (tp
->frto_counter
)
3031 frto_cwnd
= tcp_process_frto(sk
, flag
);
3033 if (tcp_ack_is_dubious(sk
, flag
)) {
3034 /* Advance CWND, if state allows this. */
3035 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3036 tcp_may_raise_cwnd(sk
, flag
))
3037 tcp_cong_avoid(sk
, ack
, prior_in_flight
, 0);
3038 tcp_fastretrans_alert(sk
, prior_packets
- tp
->packets_out
, flag
);
3040 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3041 tcp_cong_avoid(sk
, ack
, prior_in_flight
, 1);
3044 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
&FLAG_NOT_DUP
))
3045 dst_confirm(sk
->sk_dst_cache
);
3050 icsk
->icsk_probes_out
= 0;
3052 /* If this ack opens up a zero window, clear backoff. It was
3053 * being used to time the probes, and is probably far higher than
3054 * it needs to be for normal retransmission.
3056 if (tcp_send_head(sk
))
3061 if (TCP_SKB_CB(skb
)->sacked
)
3062 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3065 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3070 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3071 * But, this can also be called on packets in the established flow when
3072 * the fast version below fails.
3074 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
, int estab
)
3077 struct tcphdr
*th
= tcp_hdr(skb
);
3078 int length
=(th
->doff
*4)-sizeof(struct tcphdr
);
3080 ptr
= (unsigned char *)(th
+ 1);
3081 opt_rx
->saw_tstamp
= 0;
3083 while (length
> 0) {
3090 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3095 if (opsize
< 2) /* "silly options" */
3097 if (opsize
> length
)
3098 return; /* don't parse partial options */
3101 if (opsize
==TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3102 u16 in_mss
= ntohs(get_unaligned((__be16
*)ptr
));
3104 if (opt_rx
->user_mss
&& opt_rx
->user_mss
< in_mss
)
3105 in_mss
= opt_rx
->user_mss
;
3106 opt_rx
->mss_clamp
= in_mss
;
3111 if (opsize
==TCPOLEN_WINDOW
&& th
->syn
&& !estab
)
3112 if (sysctl_tcp_window_scaling
) {
3113 __u8 snd_wscale
= *(__u8
*) ptr
;
3114 opt_rx
->wscale_ok
= 1;
3115 if (snd_wscale
> 14) {
3116 if (net_ratelimit())
3117 printk(KERN_INFO
"tcp_parse_options: Illegal window "
3118 "scaling value %d >14 received.\n",
3122 opt_rx
->snd_wscale
= snd_wscale
;
3125 case TCPOPT_TIMESTAMP
:
3126 if (opsize
==TCPOLEN_TIMESTAMP
) {
3127 if ((estab
&& opt_rx
->tstamp_ok
) ||
3128 (!estab
&& sysctl_tcp_timestamps
)) {
3129 opt_rx
->saw_tstamp
= 1;
3130 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__be32
*)ptr
));
3131 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__be32
*)(ptr
+4)));
3135 case TCPOPT_SACK_PERM
:
3136 if (opsize
==TCPOLEN_SACK_PERM
&& th
->syn
&& !estab
) {
3137 if (sysctl_tcp_sack
) {
3138 opt_rx
->sack_ok
= 1;
3139 tcp_sack_reset(opt_rx
);
3145 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3146 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3148 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3151 #ifdef CONFIG_TCP_MD5SIG
3154 * The MD5 Hash has already been
3155 * checked (see tcp_v{4,6}_do_rcv()).
3167 /* Fast parse options. This hopes to only see timestamps.
3168 * If it is wrong it falls back on tcp_parse_options().
3170 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
3171 struct tcp_sock
*tp
)
3173 if (th
->doff
== sizeof(struct tcphdr
)>>2) {
3174 tp
->rx_opt
.saw_tstamp
= 0;
3176 } else if (tp
->rx_opt
.tstamp_ok
&&
3177 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
3178 __be32
*ptr
= (__be32
*)(th
+ 1);
3179 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3180 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3181 tp
->rx_opt
.saw_tstamp
= 1;
3183 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3185 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3189 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
3193 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
3195 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3196 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3199 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3201 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3202 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3203 * extra check below makes sure this can only happen
3204 * for pure ACK frames. -DaveM
3206 * Not only, also it occurs for expired timestamps.
3209 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
3210 get_seconds() >= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
3211 tcp_store_ts_recent(tp
);
3215 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3217 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3218 * it can pass through stack. So, the following predicate verifies that
3219 * this segment is not used for anything but congestion avoidance or
3220 * fast retransmit. Moreover, we even are able to eliminate most of such
3221 * second order effects, if we apply some small "replay" window (~RTO)
3222 * to timestamp space.
3224 * All these measures still do not guarantee that we reject wrapped ACKs
3225 * on networks with high bandwidth, when sequence space is recycled fastly,
3226 * but it guarantees that such events will be very rare and do not affect
3227 * connection seriously. This doesn't look nice, but alas, PAWS is really
3230 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3231 * states that events when retransmit arrives after original data are rare.
3232 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3233 * the biggest problem on large power networks even with minor reordering.
3234 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3235 * up to bandwidth of 18Gigabit/sec. 8) ]
3238 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3240 struct tcp_sock
*tp
= tcp_sk(sk
);
3241 struct tcphdr
*th
= tcp_hdr(skb
);
3242 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3243 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3245 return (/* 1. Pure ACK with correct sequence number. */
3246 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3248 /* 2. ... and duplicate ACK. */
3249 ack
== tp
->snd_una
&&
3251 /* 3. ... and does not update window. */
3252 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3254 /* 4. ... and sits in replay window. */
3255 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3258 static inline int tcp_paws_discard(const struct sock
*sk
, const struct sk_buff
*skb
)
3260 const struct tcp_sock
*tp
= tcp_sk(sk
);
3261 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
3262 get_seconds() < tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
3263 !tcp_disordered_ack(sk
, skb
));
3266 /* Check segment sequence number for validity.
3268 * Segment controls are considered valid, if the segment
3269 * fits to the window after truncation to the window. Acceptability
3270 * of data (and SYN, FIN, of course) is checked separately.
3271 * See tcp_data_queue(), for example.
3273 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3274 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3275 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3276 * (borrowed from freebsd)
3279 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3281 return !before(end_seq
, tp
->rcv_wup
) &&
3282 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3285 /* When we get a reset we do this. */
3286 static void tcp_reset(struct sock
*sk
)
3288 /* We want the right error as BSD sees it (and indeed as we do). */
3289 switch (sk
->sk_state
) {
3291 sk
->sk_err
= ECONNREFUSED
;
3293 case TCP_CLOSE_WAIT
:
3299 sk
->sk_err
= ECONNRESET
;
3302 if (!sock_flag(sk
, SOCK_DEAD
))
3303 sk
->sk_error_report(sk
);
3309 * Process the FIN bit. This now behaves as it is supposed to work
3310 * and the FIN takes effect when it is validly part of sequence
3311 * space. Not before when we get holes.
3313 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3314 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3317 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3318 * close and we go into CLOSING (and later onto TIME-WAIT)
3320 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3322 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
3324 struct tcp_sock
*tp
= tcp_sk(sk
);
3326 inet_csk_schedule_ack(sk
);
3328 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3329 sock_set_flag(sk
, SOCK_DONE
);
3331 switch (sk
->sk_state
) {
3333 case TCP_ESTABLISHED
:
3334 /* Move to CLOSE_WAIT */
3335 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3336 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3339 case TCP_CLOSE_WAIT
:
3341 /* Received a retransmission of the FIN, do
3346 /* RFC793: Remain in the LAST-ACK state. */
3350 /* This case occurs when a simultaneous close
3351 * happens, we must ack the received FIN and
3352 * enter the CLOSING state.
3355 tcp_set_state(sk
, TCP_CLOSING
);
3358 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3360 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3363 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3364 * cases we should never reach this piece of code.
3366 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
3367 __FUNCTION__
, sk
->sk_state
);
3371 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3372 * Probably, we should reset in this case. For now drop them.
3374 __skb_queue_purge(&tp
->out_of_order_queue
);
3375 if (tcp_is_sack(tp
))
3376 tcp_sack_reset(&tp
->rx_opt
);
3377 sk_stream_mem_reclaim(sk
);
3379 if (!sock_flag(sk
, SOCK_DEAD
)) {
3380 sk
->sk_state_change(sk
);
3382 /* Do not send POLL_HUP for half duplex close. */
3383 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3384 sk
->sk_state
== TCP_CLOSE
)
3385 sk_wake_async(sk
, 1, POLL_HUP
);
3387 sk_wake_async(sk
, 1, POLL_IN
);
3391 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
, u32 end_seq
)
3393 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3394 if (before(seq
, sp
->start_seq
))
3395 sp
->start_seq
= seq
;
3396 if (after(end_seq
, sp
->end_seq
))
3397 sp
->end_seq
= end_seq
;
3403 static void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3405 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3406 if (before(seq
, tp
->rcv_nxt
))
3407 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
3409 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
3411 tp
->rx_opt
.dsack
= 1;
3412 tp
->duplicate_sack
[0].start_seq
= seq
;
3413 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3414 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1, 4 - tp
->rx_opt
.tstamp_ok
);
3418 static void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3420 if (!tp
->rx_opt
.dsack
)
3421 tcp_dsack_set(tp
, seq
, end_seq
);
3423 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3426 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3428 struct tcp_sock
*tp
= tcp_sk(sk
);
3430 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3431 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3432 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3433 tcp_enter_quickack_mode(sk
);
3435 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3436 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3438 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3439 end_seq
= tp
->rcv_nxt
;
3440 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3447 /* These routines update the SACK block as out-of-order packets arrive or
3448 * in-order packets close up the sequence space.
3450 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3453 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3454 struct tcp_sack_block
*swalk
= sp
+1;
3456 /* See if the recent change to the first SACK eats into
3457 * or hits the sequence space of other SACK blocks, if so coalesce.
3459 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
; ) {
3460 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3463 /* Zap SWALK, by moving every further SACK up by one slot.
3464 * Decrease num_sacks.
3466 tp
->rx_opt
.num_sacks
--;
3467 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3468 for (i
=this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3472 this_sack
++, swalk
++;
3476 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
, struct tcp_sack_block
*sack2
)
3480 tmp
= sack1
->start_seq
;
3481 sack1
->start_seq
= sack2
->start_seq
;
3482 sack2
->start_seq
= tmp
;
3484 tmp
= sack1
->end_seq
;
3485 sack1
->end_seq
= sack2
->end_seq
;
3486 sack2
->end_seq
= tmp
;
3489 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3491 struct tcp_sock
*tp
= tcp_sk(sk
);
3492 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3493 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3499 for (this_sack
=0; this_sack
<cur_sacks
; this_sack
++, sp
++) {
3500 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3501 /* Rotate this_sack to the first one. */
3502 for (; this_sack
>0; this_sack
--, sp
--)
3503 tcp_sack_swap(sp
, sp
-1);
3505 tcp_sack_maybe_coalesce(tp
);
3510 /* Could not find an adjacent existing SACK, build a new one,
3511 * put it at the front, and shift everyone else down. We
3512 * always know there is at least one SACK present already here.
3514 * If the sack array is full, forget about the last one.
3516 if (this_sack
>= 4) {
3518 tp
->rx_opt
.num_sacks
--;
3521 for (; this_sack
> 0; this_sack
--, sp
--)
3525 /* Build the new head SACK, and we're done. */
3526 sp
->start_seq
= seq
;
3527 sp
->end_seq
= end_seq
;
3528 tp
->rx_opt
.num_sacks
++;
3529 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3532 /* RCV.NXT advances, some SACKs should be eaten. */
3534 static void tcp_sack_remove(struct tcp_sock
*tp
)
3536 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3537 int num_sacks
= tp
->rx_opt
.num_sacks
;
3540 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3541 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3542 tp
->rx_opt
.num_sacks
= 0;
3543 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3547 for (this_sack
= 0; this_sack
< num_sacks
; ) {
3548 /* Check if the start of the sack is covered by RCV.NXT. */
3549 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3552 /* RCV.NXT must cover all the block! */
3553 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
3555 /* Zap this SACK, by moving forward any other SACKS. */
3556 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3557 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3564 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3565 tp
->rx_opt
.num_sacks
= num_sacks
;
3566 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
, 4 - tp
->rx_opt
.tstamp_ok
);
3570 /* This one checks to see if we can put data from the
3571 * out_of_order queue into the receive_queue.
3573 static void tcp_ofo_queue(struct sock
*sk
)
3575 struct tcp_sock
*tp
= tcp_sk(sk
);
3576 __u32 dsack_high
= tp
->rcv_nxt
;
3577 struct sk_buff
*skb
;
3579 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3580 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3583 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3584 __u32 dsack
= dsack_high
;
3585 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3586 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3587 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
3590 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3591 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3592 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3596 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3597 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3598 TCP_SKB_CB(skb
)->end_seq
);
3600 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3601 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3602 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3603 if (tcp_hdr(skb
)->fin
)
3604 tcp_fin(skb
, sk
, tcp_hdr(skb
));
3608 static int tcp_prune_queue(struct sock
*sk
);
3610 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3612 struct tcphdr
*th
= tcp_hdr(skb
);
3613 struct tcp_sock
*tp
= tcp_sk(sk
);
3616 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3619 __skb_pull(skb
, th
->doff
*4);
3621 TCP_ECN_accept_cwr(tp
, skb
);
3623 if (tp
->rx_opt
.dsack
) {
3624 tp
->rx_opt
.dsack
= 0;
3625 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
3626 4 - tp
->rx_opt
.tstamp_ok
);
3629 /* Queue data for delivery to the user.
3630 * Packets in sequence go to the receive queue.
3631 * Out of sequence packets to the out_of_order_queue.
3633 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3634 if (tcp_receive_window(tp
) == 0)
3637 /* Ok. In sequence. In window. */
3638 if (tp
->ucopy
.task
== current
&&
3639 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3640 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3641 int chunk
= min_t(unsigned int, skb
->len
,
3644 __set_current_state(TASK_RUNNING
);
3647 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3648 tp
->ucopy
.len
-= chunk
;
3649 tp
->copied_seq
+= chunk
;
3650 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3651 tcp_rcv_space_adjust(sk
);
3659 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3660 !sk_stream_rmem_schedule(sk
, skb
))) {
3661 if (tcp_prune_queue(sk
) < 0 ||
3662 !sk_stream_rmem_schedule(sk
, skb
))
3665 sk_stream_set_owner_r(skb
, sk
);
3666 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3668 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3670 tcp_event_data_recv(sk
, skb
);
3672 tcp_fin(skb
, sk
, th
);
3674 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3677 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3678 * gap in queue is filled.
3680 if (skb_queue_empty(&tp
->out_of_order_queue
))
3681 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3684 if (tp
->rx_opt
.num_sacks
)
3685 tcp_sack_remove(tp
);
3687 tcp_fast_path_check(sk
);
3691 else if (!sock_flag(sk
, SOCK_DEAD
))
3692 sk
->sk_data_ready(sk
, 0);
3696 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3697 /* A retransmit, 2nd most common case. Force an immediate ack. */
3698 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3699 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3702 tcp_enter_quickack_mode(sk
);
3703 inet_csk_schedule_ack(sk
);
3709 /* Out of window. F.e. zero window probe. */
3710 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3713 tcp_enter_quickack_mode(sk
);
3715 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3716 /* Partial packet, seq < rcv_next < end_seq */
3717 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3718 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3719 TCP_SKB_CB(skb
)->end_seq
);
3721 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3723 /* If window is closed, drop tail of packet. But after
3724 * remembering D-SACK for its head made in previous line.
3726 if (!tcp_receive_window(tp
))
3731 TCP_ECN_check_ce(tp
, skb
);
3733 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3734 !sk_stream_rmem_schedule(sk
, skb
)) {
3735 if (tcp_prune_queue(sk
) < 0 ||
3736 !sk_stream_rmem_schedule(sk
, skb
))
3740 /* Disable header prediction. */
3742 inet_csk_schedule_ack(sk
);
3744 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3745 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3747 sk_stream_set_owner_r(skb
, sk
);
3749 if (!skb_peek(&tp
->out_of_order_queue
)) {
3750 /* Initial out of order segment, build 1 SACK. */
3751 if (tcp_is_sack(tp
)) {
3752 tp
->rx_opt
.num_sacks
= 1;
3753 tp
->rx_opt
.dsack
= 0;
3754 tp
->rx_opt
.eff_sacks
= 1;
3755 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3756 tp
->selective_acks
[0].end_seq
=
3757 TCP_SKB_CB(skb
)->end_seq
;
3759 __skb_queue_head(&tp
->out_of_order_queue
,skb
);
3761 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3762 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3763 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3765 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
3766 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
3768 if (!tp
->rx_opt
.num_sacks
||
3769 tp
->selective_acks
[0].end_seq
!= seq
)
3772 /* Common case: data arrive in order after hole. */
3773 tp
->selective_acks
[0].end_seq
= end_seq
;
3777 /* Find place to insert this segment. */
3779 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
3781 } while ((skb1
= skb1
->prev
) !=
3782 (struct sk_buff
*)&tp
->out_of_order_queue
);
3784 /* Do skb overlap to previous one? */
3785 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
3786 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3787 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3788 /* All the bits are present. Drop. */
3790 tcp_dsack_set(tp
, seq
, end_seq
);
3793 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
3794 /* Partial overlap. */
3795 tcp_dsack_set(tp
, seq
, TCP_SKB_CB(skb1
)->end_seq
);
3800 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
3802 /* And clean segments covered by new one as whole. */
3803 while ((skb1
= skb
->next
) !=
3804 (struct sk_buff
*)&tp
->out_of_order_queue
&&
3805 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
3806 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
3807 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, end_seq
);
3810 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
3811 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
, TCP_SKB_CB(skb1
)->end_seq
);
3816 if (tcp_is_sack(tp
))
3817 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
3821 /* Collapse contiguous sequence of skbs head..tail with
3822 * sequence numbers start..end.
3823 * Segments with FIN/SYN are not collapsed (only because this
3827 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
3828 struct sk_buff
*head
, struct sk_buff
*tail
,
3831 struct sk_buff
*skb
;
3833 /* First, check that queue is collapsible and find
3834 * the point where collapsing can be useful. */
3835 for (skb
= head
; skb
!= tail
; ) {
3836 /* No new bits? It is possible on ofo queue. */
3837 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3838 struct sk_buff
*next
= skb
->next
;
3839 __skb_unlink(skb
, list
);
3841 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3846 /* The first skb to collapse is:
3848 * - bloated or contains data before "start" or
3849 * overlaps to the next one.
3851 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
3852 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
3853 before(TCP_SKB_CB(skb
)->seq
, start
) ||
3854 (skb
->next
!= tail
&&
3855 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
3858 /* Decided to skip this, advance start seq. */
3859 start
= TCP_SKB_CB(skb
)->end_seq
;
3862 if (skb
== tail
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
3865 while (before(start
, end
)) {
3866 struct sk_buff
*nskb
;
3867 int header
= skb_headroom(skb
);
3868 int copy
= SKB_MAX_ORDER(header
, 0);
3870 /* Too big header? This can happen with IPv6. */
3873 if (end
-start
< copy
)
3875 nskb
= alloc_skb(copy
+header
, GFP_ATOMIC
);
3879 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
3880 skb_set_network_header(nskb
, (skb_network_header(skb
) -
3882 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
3884 skb_reserve(nskb
, header
);
3885 memcpy(nskb
->head
, skb
->head
, header
);
3886 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
3887 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
3888 __skb_insert(nskb
, skb
->prev
, skb
, list
);
3889 sk_stream_set_owner_r(nskb
, sk
);
3891 /* Copy data, releasing collapsed skbs. */
3893 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
3894 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
3898 size
= min(copy
, size
);
3899 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
3901 TCP_SKB_CB(nskb
)->end_seq
+= size
;
3905 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
3906 struct sk_buff
*next
= skb
->next
;
3907 __skb_unlink(skb
, list
);
3909 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
3912 tcp_hdr(skb
)->syn
||
3920 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
3921 * and tcp_collapse() them until all the queue is collapsed.
3923 static void tcp_collapse_ofo_queue(struct sock
*sk
)
3925 struct tcp_sock
*tp
= tcp_sk(sk
);
3926 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
3927 struct sk_buff
*head
;
3933 start
= TCP_SKB_CB(skb
)->seq
;
3934 end
= TCP_SKB_CB(skb
)->end_seq
;
3940 /* Segment is terminated when we see gap or when
3941 * we are at the end of all the queue. */
3942 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
3943 after(TCP_SKB_CB(skb
)->seq
, end
) ||
3944 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
3945 tcp_collapse(sk
, &tp
->out_of_order_queue
,
3946 head
, skb
, start
, end
);
3948 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
3950 /* Start new segment */
3951 start
= TCP_SKB_CB(skb
)->seq
;
3952 end
= TCP_SKB_CB(skb
)->end_seq
;
3954 if (before(TCP_SKB_CB(skb
)->seq
, start
))
3955 start
= TCP_SKB_CB(skb
)->seq
;
3956 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
3957 end
= TCP_SKB_CB(skb
)->end_seq
;
3962 /* Reduce allocated memory if we can, trying to get
3963 * the socket within its memory limits again.
3965 * Return less than zero if we should start dropping frames
3966 * until the socket owning process reads some of the data
3967 * to stabilize the situation.
3969 static int tcp_prune_queue(struct sock
*sk
)
3971 struct tcp_sock
*tp
= tcp_sk(sk
);
3973 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
3975 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
3977 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
3978 tcp_clamp_window(sk
);
3979 else if (tcp_memory_pressure
)
3980 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
3982 tcp_collapse_ofo_queue(sk
);
3983 tcp_collapse(sk
, &sk
->sk_receive_queue
,
3984 sk
->sk_receive_queue
.next
,
3985 (struct sk_buff
*)&sk
->sk_receive_queue
,
3986 tp
->copied_seq
, tp
->rcv_nxt
);
3987 sk_stream_mem_reclaim(sk
);
3989 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
3992 /* Collapsing did not help, destructive actions follow.
3993 * This must not ever occur. */
3995 /* First, purge the out_of_order queue. */
3996 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3997 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
3998 __skb_queue_purge(&tp
->out_of_order_queue
);
4000 /* Reset SACK state. A conforming SACK implementation will
4001 * do the same at a timeout based retransmit. When a connection
4002 * is in a sad state like this, we care only about integrity
4003 * of the connection not performance.
4005 if (tcp_is_sack(tp
))
4006 tcp_sack_reset(&tp
->rx_opt
);
4007 sk_stream_mem_reclaim(sk
);
4010 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4013 /* If we are really being abused, tell the caller to silently
4014 * drop receive data on the floor. It will get retransmitted
4015 * and hopefully then we'll have sufficient space.
4017 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
4019 /* Massive buffer overcommit. */
4025 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4026 * As additional protections, we do not touch cwnd in retransmission phases,
4027 * and if application hit its sndbuf limit recently.
4029 void tcp_cwnd_application_limited(struct sock
*sk
)
4031 struct tcp_sock
*tp
= tcp_sk(sk
);
4033 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4034 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4035 /* Limited by application or receiver window. */
4036 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4037 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4038 if (win_used
< tp
->snd_cwnd
) {
4039 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4040 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4042 tp
->snd_cwnd_used
= 0;
4044 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4047 static int tcp_should_expand_sndbuf(struct sock
*sk
)
4049 struct tcp_sock
*tp
= tcp_sk(sk
);
4051 /* If the user specified a specific send buffer setting, do
4054 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4057 /* If we are under global TCP memory pressure, do not expand. */
4058 if (tcp_memory_pressure
)
4061 /* If we are under soft global TCP memory pressure, do not expand. */
4062 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
4065 /* If we filled the congestion window, do not expand. */
4066 if (tp
->packets_out
>= tp
->snd_cwnd
)
4072 /* When incoming ACK allowed to free some skb from write_queue,
4073 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4074 * on the exit from tcp input handler.
4076 * PROBLEM: sndbuf expansion does not work well with largesend.
4078 static void tcp_new_space(struct sock
*sk
)
4080 struct tcp_sock
*tp
= tcp_sk(sk
);
4082 if (tcp_should_expand_sndbuf(sk
)) {
4083 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
4084 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
4085 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4086 tp
->reordering
+ 1);
4087 sndmem
*= 2*demanded
;
4088 if (sndmem
> sk
->sk_sndbuf
)
4089 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4090 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4093 sk
->sk_write_space(sk
);
4096 static void tcp_check_space(struct sock
*sk
)
4098 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4099 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4100 if (sk
->sk_socket
&&
4101 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4106 static inline void tcp_data_snd_check(struct sock
*sk
)
4108 tcp_push_pending_frames(sk
);
4109 tcp_check_space(sk
);
4113 * Check if sending an ack is needed.
4115 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4117 struct tcp_sock
*tp
= tcp_sk(sk
);
4119 /* More than one full frame received... */
4120 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
4121 /* ... and right edge of window advances far enough.
4122 * (tcp_recvmsg() will send ACK otherwise). Or...
4124 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4125 /* We ACK each frame or... */
4126 tcp_in_quickack_mode(sk
) ||
4127 /* We have out of order data. */
4129 skb_peek(&tp
->out_of_order_queue
))) {
4130 /* Then ack it now */
4133 /* Else, send delayed ack. */
4134 tcp_send_delayed_ack(sk
);
4138 static inline void tcp_ack_snd_check(struct sock
*sk
)
4140 if (!inet_csk_ack_scheduled(sk
)) {
4141 /* We sent a data segment already. */
4144 __tcp_ack_snd_check(sk
, 1);
4148 * This routine is only called when we have urgent data
4149 * signaled. Its the 'slow' part of tcp_urg. It could be
4150 * moved inline now as tcp_urg is only called from one
4151 * place. We handle URGent data wrong. We have to - as
4152 * BSD still doesn't use the correction from RFC961.
4153 * For 1003.1g we should support a new option TCP_STDURG to permit
4154 * either form (or just set the sysctl tcp_stdurg).
4157 static void tcp_check_urg(struct sock
* sk
, struct tcphdr
* th
)
4159 struct tcp_sock
*tp
= tcp_sk(sk
);
4160 u32 ptr
= ntohs(th
->urg_ptr
);
4162 if (ptr
&& !sysctl_tcp_stdurg
)
4164 ptr
+= ntohl(th
->seq
);
4166 /* Ignore urgent data that we've already seen and read. */
4167 if (after(tp
->copied_seq
, ptr
))
4170 /* Do not replay urg ptr.
4172 * NOTE: interesting situation not covered by specs.
4173 * Misbehaving sender may send urg ptr, pointing to segment,
4174 * which we already have in ofo queue. We are not able to fetch
4175 * such data and will stay in TCP_URG_NOTYET until will be eaten
4176 * by recvmsg(). Seems, we are not obliged to handle such wicked
4177 * situations. But it is worth to think about possibility of some
4178 * DoSes using some hypothetical application level deadlock.
4180 if (before(ptr
, tp
->rcv_nxt
))
4183 /* Do we already have a newer (or duplicate) urgent pointer? */
4184 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4187 /* Tell the world about our new urgent pointer. */
4190 /* We may be adding urgent data when the last byte read was
4191 * urgent. To do this requires some care. We cannot just ignore
4192 * tp->copied_seq since we would read the last urgent byte again
4193 * as data, nor can we alter copied_seq until this data arrives
4194 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4196 * NOTE. Double Dutch. Rendering to plain English: author of comment
4197 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4198 * and expect that both A and B disappear from stream. This is _wrong_.
4199 * Though this happens in BSD with high probability, this is occasional.
4200 * Any application relying on this is buggy. Note also, that fix "works"
4201 * only in this artificial test. Insert some normal data between A and B and we will
4202 * decline of BSD again. Verdict: it is better to remove to trap
4205 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4206 !sock_flag(sk
, SOCK_URGINLINE
) &&
4207 tp
->copied_seq
!= tp
->rcv_nxt
) {
4208 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4210 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4211 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4216 tp
->urg_data
= TCP_URG_NOTYET
;
4219 /* Disable header prediction. */
4223 /* This is the 'fast' part of urgent handling. */
4224 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
4226 struct tcp_sock
*tp
= tcp_sk(sk
);
4228 /* Check if we get a new urgent pointer - normally not. */
4230 tcp_check_urg(sk
,th
);
4232 /* Do we wait for any urgent data? - normally not... */
4233 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4234 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4237 /* Is the urgent pointer pointing into this packet? */
4238 if (ptr
< skb
->len
) {
4240 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4242 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4243 if (!sock_flag(sk
, SOCK_DEAD
))
4244 sk
->sk_data_ready(sk
, 0);
4249 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4251 struct tcp_sock
*tp
= tcp_sk(sk
);
4252 int chunk
= skb
->len
- hlen
;
4256 if (skb_csum_unnecessary(skb
))
4257 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4259 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4263 tp
->ucopy
.len
-= chunk
;
4264 tp
->copied_seq
+= chunk
;
4265 tcp_rcv_space_adjust(sk
);
4272 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4276 if (sock_owned_by_user(sk
)) {
4278 result
= __tcp_checksum_complete(skb
);
4281 result
= __tcp_checksum_complete(skb
);
4286 static inline int tcp_checksum_complete_user(struct sock
*sk
, struct sk_buff
*skb
)
4288 return !skb_csum_unnecessary(skb
) &&
4289 __tcp_checksum_complete_user(sk
, skb
);
4292 #ifdef CONFIG_NET_DMA
4293 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4295 struct tcp_sock
*tp
= tcp_sk(sk
);
4296 int chunk
= skb
->len
- hlen
;
4298 int copied_early
= 0;
4300 if (tp
->ucopy
.wakeup
)
4303 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4304 tp
->ucopy
.dma_chan
= get_softnet_dma();
4306 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
4308 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4309 skb
, hlen
, tp
->ucopy
.iov
, chunk
, tp
->ucopy
.pinned_list
);
4314 tp
->ucopy
.dma_cookie
= dma_cookie
;
4317 tp
->ucopy
.len
-= chunk
;
4318 tp
->copied_seq
+= chunk
;
4319 tcp_rcv_space_adjust(sk
);
4321 if ((tp
->ucopy
.len
== 0) ||
4322 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
4323 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
4324 tp
->ucopy
.wakeup
= 1;
4325 sk
->sk_data_ready(sk
, 0);
4327 } else if (chunk
> 0) {
4328 tp
->ucopy
.wakeup
= 1;
4329 sk
->sk_data_ready(sk
, 0);
4332 return copied_early
;
4334 #endif /* CONFIG_NET_DMA */
4337 * TCP receive function for the ESTABLISHED state.
4339 * It is split into a fast path and a slow path. The fast path is
4341 * - A zero window was announced from us - zero window probing
4342 * is only handled properly in the slow path.
4343 * - Out of order segments arrived.
4344 * - Urgent data is expected.
4345 * - There is no buffer space left
4346 * - Unexpected TCP flags/window values/header lengths are received
4347 * (detected by checking the TCP header against pred_flags)
4348 * - Data is sent in both directions. Fast path only supports pure senders
4349 * or pure receivers (this means either the sequence number or the ack
4350 * value must stay constant)
4351 * - Unexpected TCP option.
4353 * When these conditions are not satisfied it drops into a standard
4354 * receive procedure patterned after RFC793 to handle all cases.
4355 * The first three cases are guaranteed by proper pred_flags setting,
4356 * the rest is checked inline. Fast processing is turned on in
4357 * tcp_data_queue when everything is OK.
4359 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
4360 struct tcphdr
*th
, unsigned len
)
4362 struct tcp_sock
*tp
= tcp_sk(sk
);
4365 * Header prediction.
4366 * The code loosely follows the one in the famous
4367 * "30 instruction TCP receive" Van Jacobson mail.
4369 * Van's trick is to deposit buffers into socket queue
4370 * on a device interrupt, to call tcp_recv function
4371 * on the receive process context and checksum and copy
4372 * the buffer to user space. smart...
4374 * Our current scheme is not silly either but we take the
4375 * extra cost of the net_bh soft interrupt processing...
4376 * We do checksum and copy also but from device to kernel.
4379 tp
->rx_opt
.saw_tstamp
= 0;
4381 /* pred_flags is 0xS?10 << 16 + snd_wnd
4382 * if header_prediction is to be made
4383 * 'S' will always be tp->tcp_header_len >> 2
4384 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4385 * turn it off (when there are holes in the receive
4386 * space for instance)
4387 * PSH flag is ignored.
4390 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
4391 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4392 int tcp_header_len
= tp
->tcp_header_len
;
4394 /* Timestamp header prediction: tcp_header_len
4395 * is automatically equal to th->doff*4 due to pred_flags
4399 /* Check timestamp */
4400 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
4401 __be32
*ptr
= (__be32
*)(th
+ 1);
4403 /* No? Slow path! */
4404 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4405 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
4408 tp
->rx_opt
.saw_tstamp
= 1;
4410 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4412 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4414 /* If PAWS failed, check it more carefully in slow path */
4415 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
4418 /* DO NOT update ts_recent here, if checksum fails
4419 * and timestamp was corrupted part, it will result
4420 * in a hung connection since we will drop all
4421 * future packets due to the PAWS test.
4425 if (len
<= tcp_header_len
) {
4426 /* Bulk data transfer: sender */
4427 if (len
== tcp_header_len
) {
4428 /* Predicted packet is in window by definition.
4429 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4430 * Hence, check seq<=rcv_wup reduces to:
4432 if (tcp_header_len
==
4433 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4434 tp
->rcv_nxt
== tp
->rcv_wup
)
4435 tcp_store_ts_recent(tp
);
4437 /* We know that such packets are checksummed
4440 tcp_ack(sk
, skb
, 0);
4442 tcp_data_snd_check(sk
);
4444 } else { /* Header too small */
4445 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4450 int copied_early
= 0;
4452 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4453 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4454 #ifdef CONFIG_NET_DMA
4455 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4460 if (tp
->ucopy
.task
== current
&& sock_owned_by_user(sk
) && !copied_early
) {
4461 __set_current_state(TASK_RUNNING
);
4463 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4467 /* Predicted packet is in window by definition.
4468 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4469 * Hence, check seq<=rcv_wup reduces to:
4471 if (tcp_header_len
==
4472 (sizeof(struct tcphdr
) +
4473 TCPOLEN_TSTAMP_ALIGNED
) &&
4474 tp
->rcv_nxt
== tp
->rcv_wup
)
4475 tcp_store_ts_recent(tp
);
4477 tcp_rcv_rtt_measure_ts(sk
, skb
);
4479 __skb_pull(skb
, tcp_header_len
);
4480 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4481 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
4484 tcp_cleanup_rbuf(sk
, skb
->len
);
4487 if (tcp_checksum_complete_user(sk
, skb
))
4490 /* Predicted packet is in window by definition.
4491 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4492 * Hence, check seq<=rcv_wup reduces to:
4494 if (tcp_header_len
==
4495 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4496 tp
->rcv_nxt
== tp
->rcv_wup
)
4497 tcp_store_ts_recent(tp
);
4499 tcp_rcv_rtt_measure_ts(sk
, skb
);
4501 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4504 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
4506 /* Bulk data transfer: receiver */
4507 __skb_pull(skb
,tcp_header_len
);
4508 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4509 sk_stream_set_owner_r(skb
, sk
);
4510 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4513 tcp_event_data_recv(sk
, skb
);
4515 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4516 /* Well, only one small jumplet in fast path... */
4517 tcp_ack(sk
, skb
, FLAG_DATA
);
4518 tcp_data_snd_check(sk
);
4519 if (!inet_csk_ack_scheduled(sk
))
4523 __tcp_ack_snd_check(sk
, 0);
4525 #ifdef CONFIG_NET_DMA
4527 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4533 sk
->sk_data_ready(sk
, 0);
4539 if (len
< (th
->doff
<<2) || tcp_checksum_complete_user(sk
, skb
))
4543 * RFC1323: H1. Apply PAWS check first.
4545 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4546 tcp_paws_discard(sk
, skb
)) {
4548 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4549 tcp_send_dupack(sk
, skb
);
4552 /* Resets are accepted even if PAWS failed.
4554 ts_recent update must be made after we are sure
4555 that the packet is in window.
4560 * Standard slow path.
4563 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4564 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4565 * (RST) segments are validated by checking their SEQ-fields."
4566 * And page 69: "If an incoming segment is not acceptable,
4567 * an acknowledgment should be sent in reply (unless the RST bit
4568 * is set, if so drop the segment and return)".
4571 tcp_send_dupack(sk
, skb
);
4580 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4582 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4583 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4584 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4591 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4593 tcp_rcv_rtt_measure_ts(sk
, skb
);
4595 /* Process urgent data. */
4596 tcp_urg(sk
, skb
, th
);
4598 /* step 7: process the segment text */
4599 tcp_data_queue(sk
, skb
);
4601 tcp_data_snd_check(sk
);
4602 tcp_ack_snd_check(sk
);
4606 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4613 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4614 struct tcphdr
*th
, unsigned len
)
4616 struct tcp_sock
*tp
= tcp_sk(sk
);
4617 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4618 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4620 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4624 * "If the state is SYN-SENT then
4625 * first check the ACK bit
4626 * If the ACK bit is set
4627 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4628 * a reset (unless the RST bit is set, if so drop
4629 * the segment and return)"
4631 * We do not send data with SYN, so that RFC-correct
4634 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4635 goto reset_and_undo
;
4637 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4638 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
4640 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
4641 goto reset_and_undo
;
4644 /* Now ACK is acceptable.
4646 * "If the RST bit is set
4647 * If the ACK was acceptable then signal the user "error:
4648 * connection reset", drop the segment, enter CLOSED state,
4649 * delete TCB, and return."
4658 * "fifth, if neither of the SYN or RST bits is set then
4659 * drop the segment and return."
4665 goto discard_and_undo
;
4668 * "If the SYN bit is on ...
4669 * are acceptable then ...
4670 * (our SYN has been ACKed), change the connection
4671 * state to ESTABLISHED..."
4674 TCP_ECN_rcv_synack(tp
, th
);
4676 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4677 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4679 /* Ok.. it's good. Set up sequence numbers and
4680 * move to established.
4682 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4683 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4685 /* RFC1323: The window in SYN & SYN/ACK segments is
4688 tp
->snd_wnd
= ntohs(th
->window
);
4689 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
4691 if (!tp
->rx_opt
.wscale_ok
) {
4692 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
4693 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
4696 if (tp
->rx_opt
.saw_tstamp
) {
4697 tp
->rx_opt
.tstamp_ok
= 1;
4698 tp
->tcp_header_len
=
4699 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4700 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4701 tcp_store_ts_recent(tp
);
4703 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4706 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
4707 tcp_enable_fack(tp
);
4710 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4711 tcp_initialize_rcv_mss(sk
);
4713 /* Remember, tcp_poll() does not lock socket!
4714 * Change state from SYN-SENT only after copied_seq
4715 * is initialized. */
4716 tp
->copied_seq
= tp
->rcv_nxt
;
4718 tcp_set_state(sk
, TCP_ESTABLISHED
);
4720 security_inet_conn_established(sk
, skb
);
4722 /* Make sure socket is routed, for correct metrics. */
4723 icsk
->icsk_af_ops
->rebuild_header(sk
);
4725 tcp_init_metrics(sk
);
4727 tcp_init_congestion_control(sk
);
4729 /* Prevent spurious tcp_cwnd_restart() on first data
4732 tp
->lsndtime
= tcp_time_stamp
;
4734 tcp_init_buffer_space(sk
);
4736 if (sock_flag(sk
, SOCK_KEEPOPEN
))
4737 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
4739 if (!tp
->rx_opt
.snd_wscale
)
4740 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4744 if (!sock_flag(sk
, SOCK_DEAD
)) {
4745 sk
->sk_state_change(sk
);
4746 sk_wake_async(sk
, 0, POLL_OUT
);
4749 if (sk
->sk_write_pending
||
4750 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4751 icsk
->icsk_ack
.pingpong
) {
4752 /* Save one ACK. Data will be ready after
4753 * several ticks, if write_pending is set.
4755 * It may be deleted, but with this feature tcpdumps
4756 * look so _wonderfully_ clever, that I was not able
4757 * to stand against the temptation 8) --ANK
4759 inet_csk_schedule_ack(sk
);
4760 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
4761 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
4762 tcp_incr_quickack(sk
);
4763 tcp_enter_quickack_mode(sk
);
4764 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
4765 TCP_DELACK_MAX
, TCP_RTO_MAX
);
4776 /* No ACK in the segment */
4780 * "If the RST bit is set
4782 * Otherwise (no ACK) drop the segment and return."
4785 goto discard_and_undo
;
4789 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&& tcp_paws_check(&tp
->rx_opt
, 0))
4790 goto discard_and_undo
;
4793 /* We see SYN without ACK. It is attempt of
4794 * simultaneous connect with crossed SYNs.
4795 * Particularly, it can be connect to self.
4797 tcp_set_state(sk
, TCP_SYN_RECV
);
4799 if (tp
->rx_opt
.saw_tstamp
) {
4800 tp
->rx_opt
.tstamp_ok
= 1;
4801 tcp_store_ts_recent(tp
);
4802 tp
->tcp_header_len
=
4803 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4805 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4808 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4809 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4811 /* RFC1323: The window in SYN & SYN/ACK segments is
4814 tp
->snd_wnd
= ntohs(th
->window
);
4815 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4816 tp
->max_window
= tp
->snd_wnd
;
4818 TCP_ECN_rcv_syn(tp
, th
);
4821 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4822 tcp_initialize_rcv_mss(sk
);
4825 tcp_send_synack(sk
);
4827 /* Note, we could accept data and URG from this segment.
4828 * There are no obstacles to make this.
4830 * However, if we ignore data in ACKless segments sometimes,
4831 * we have no reasons to accept it sometimes.
4832 * Also, seems the code doing it in step6 of tcp_rcv_state_process
4833 * is not flawless. So, discard packet for sanity.
4834 * Uncomment this return to process the data.
4841 /* "fifth, if neither of the SYN or RST bits is set then
4842 * drop the segment and return."
4846 tcp_clear_options(&tp
->rx_opt
);
4847 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4851 tcp_clear_options(&tp
->rx_opt
);
4852 tp
->rx_opt
.mss_clamp
= saved_clamp
;
4858 * This function implements the receiving procedure of RFC 793 for
4859 * all states except ESTABLISHED and TIME_WAIT.
4860 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
4861 * address independent.
4864 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4865 struct tcphdr
*th
, unsigned len
)
4867 struct tcp_sock
*tp
= tcp_sk(sk
);
4868 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4871 tp
->rx_opt
.saw_tstamp
= 0;
4873 switch (sk
->sk_state
) {
4885 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
4888 /* Now we have several options: In theory there is
4889 * nothing else in the frame. KA9Q has an option to
4890 * send data with the syn, BSD accepts data with the
4891 * syn up to the [to be] advertised window and
4892 * Solaris 2.1 gives you a protocol error. For now
4893 * we just ignore it, that fits the spec precisely
4894 * and avoids incompatibilities. It would be nice in
4895 * future to drop through and process the data.
4897 * Now that TTCP is starting to be used we ought to
4899 * But, this leaves one open to an easy denial of
4900 * service attack, and SYN cookies can't defend
4901 * against this problem. So, we drop the data
4902 * in the interest of security over speed unless
4903 * it's still in use.
4911 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
4915 /* Do step6 onward by hand. */
4916 tcp_urg(sk
, skb
, th
);
4918 tcp_data_snd_check(sk
);
4922 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4923 tcp_paws_discard(sk
, skb
)) {
4925 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4926 tcp_send_dupack(sk
, skb
);
4929 /* Reset is accepted even if it did not pass PAWS. */
4932 /* step 1: check sequence number */
4933 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4935 tcp_send_dupack(sk
, skb
);
4939 /* step 2: check RST bit */
4945 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4947 /* step 3: check security and precedence [ignored] */
4951 * Check for a SYN in window.
4953 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4954 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4959 /* step 5: check the ACK field */
4961 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4963 switch (sk
->sk_state
) {
4966 tp
->copied_seq
= tp
->rcv_nxt
;
4968 tcp_set_state(sk
, TCP_ESTABLISHED
);
4969 sk
->sk_state_change(sk
);
4971 /* Note, that this wakeup is only for marginal
4972 * crossed SYN case. Passively open sockets
4973 * are not waked up, because sk->sk_sleep ==
4974 * NULL and sk->sk_socket == NULL.
4976 if (sk
->sk_socket
) {
4977 sk_wake_async(sk
,0,POLL_OUT
);
4980 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
4981 tp
->snd_wnd
= ntohs(th
->window
) <<
4982 tp
->rx_opt
.snd_wscale
;
4983 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
4984 TCP_SKB_CB(skb
)->seq
);
4986 /* tcp_ack considers this ACK as duplicate
4987 * and does not calculate rtt.
4988 * Fix it at least with timestamps.
4990 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4992 tcp_ack_saw_tstamp(sk
, 0);
4994 if (tp
->rx_opt
.tstamp_ok
)
4995 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4997 /* Make sure socket is routed, for
5000 icsk
->icsk_af_ops
->rebuild_header(sk
);
5002 tcp_init_metrics(sk
);
5004 tcp_init_congestion_control(sk
);
5006 /* Prevent spurious tcp_cwnd_restart() on
5007 * first data packet.
5009 tp
->lsndtime
= tcp_time_stamp
;
5012 tcp_initialize_rcv_mss(sk
);
5013 tcp_init_buffer_space(sk
);
5014 tcp_fast_path_on(tp
);
5021 if (tp
->snd_una
== tp
->write_seq
) {
5022 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5023 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5024 dst_confirm(sk
->sk_dst_cache
);
5026 if (!sock_flag(sk
, SOCK_DEAD
))
5027 /* Wake up lingering close() */
5028 sk
->sk_state_change(sk
);
5032 if (tp
->linger2
< 0 ||
5033 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5034 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5036 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
5040 tmo
= tcp_fin_time(sk
);
5041 if (tmo
> TCP_TIMEWAIT_LEN
) {
5042 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5043 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5044 /* Bad case. We could lose such FIN otherwise.
5045 * It is not a big problem, but it looks confusing
5046 * and not so rare event. We still can lose it now,
5047 * if it spins in bh_lock_sock(), but it is really
5050 inet_csk_reset_keepalive_timer(sk
, tmo
);
5052 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5060 if (tp
->snd_una
== tp
->write_seq
) {
5061 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5067 if (tp
->snd_una
== tp
->write_seq
) {
5068 tcp_update_metrics(sk
);
5077 /* step 6: check the URG bit */
5078 tcp_urg(sk
, skb
, th
);
5080 /* step 7: process the segment text */
5081 switch (sk
->sk_state
) {
5082 case TCP_CLOSE_WAIT
:
5085 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5089 /* RFC 793 says to queue data in these states,
5090 * RFC 1122 says we MUST send a reset.
5091 * BSD 4.4 also does reset.
5093 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5094 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5095 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5096 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
5102 case TCP_ESTABLISHED
:
5103 tcp_data_queue(sk
, skb
);
5108 /* tcp_data could move socket to TIME-WAIT */
5109 if (sk
->sk_state
!= TCP_CLOSE
) {
5110 tcp_data_snd_check(sk
);
5111 tcp_ack_snd_check(sk
);
5121 EXPORT_SYMBOL(sysctl_tcp_ecn
);
5122 EXPORT_SYMBOL(sysctl_tcp_reordering
);
5123 EXPORT_SYMBOL(tcp_parse_options
);
5124 EXPORT_SYMBOL(tcp_rcv_established
);
5125 EXPORT_SYMBOL(tcp_rcv_state_process
);
5126 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);