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).
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
23 * Pedro Roque : Fast Retransmit/Recovery.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
43 * Andrey Savochkin: Fix RTT measurements in the presence of
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
51 * Andi Kleen: Add tcp_measure_rcv_mss to make
52 * connections with MSS<min(MTU,ann. MSS)
53 * work without delayed acks.
54 * Andi Kleen: Process packets with PSH set in the
56 * J Hadi Salim: ECN support
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
65 #include <linux/module.h>
66 #include <linux/sysctl.h>
67 #include <linux/kernel.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
= 2;
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 D-SACK info */
107 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
108 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
110 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
111 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
112 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
113 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
114 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
116 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
117 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
119 /* Adapt the MSS value used to make delayed ack decision to the
122 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
124 struct inet_connection_sock
*icsk
= inet_csk(sk
);
125 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
128 icsk
->icsk_ack
.last_seg_size
= 0;
130 /* skb->len may jitter because of SACKs, even if peer
131 * sends good full-sized frames.
133 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
134 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
135 icsk
->icsk_ack
.rcv_mss
= len
;
137 /* Otherwise, we make more careful check taking into account,
138 * that SACKs block is variable.
140 * "len" is invariant segment length, including TCP header.
142 len
+= skb
->data
- skb_transport_header(skb
);
143 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
144 /* If PSH is not set, packet should be
145 * full sized, provided peer TCP is not badly broken.
146 * This observation (if it is correct 8)) allows
147 * to handle super-low mtu links fairly.
149 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
150 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
151 /* Subtract also invariant (if peer is RFC compliant),
152 * tcp header plus fixed timestamp option length.
153 * Resulting "len" is MSS free of SACK jitter.
155 len
-= tcp_sk(sk
)->tcp_header_len
;
156 icsk
->icsk_ack
.last_seg_size
= len
;
158 icsk
->icsk_ack
.rcv_mss
= len
;
162 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
163 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
164 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
168 static void tcp_incr_quickack(struct sock
*sk
)
170 struct inet_connection_sock
*icsk
= inet_csk(sk
);
171 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
175 if (quickacks
> icsk
->icsk_ack
.quick
)
176 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
179 void tcp_enter_quickack_mode(struct sock
*sk
)
181 struct inet_connection_sock
*icsk
= inet_csk(sk
);
182 tcp_incr_quickack(sk
);
183 icsk
->icsk_ack
.pingpong
= 0;
184 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
187 /* Send ACKs quickly, if "quick" count is not exhausted
188 * and the session is not interactive.
191 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
193 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
194 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
197 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
199 if (tp
->ecn_flags
& TCP_ECN_OK
)
200 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
203 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, struct sk_buff
*skb
)
205 if (tcp_hdr(skb
)->cwr
)
206 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
209 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
211 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
214 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, struct sk_buff
*skb
)
216 if (tp
->ecn_flags
& TCP_ECN_OK
) {
217 if (INET_ECN_is_ce(TCP_SKB_CB(skb
)->flags
))
218 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
219 /* Funny extension: if ECT is not set on a segment,
220 * it is surely retransmit. It is not in ECN RFC,
221 * but Linux follows this rule. */
222 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb
)->flags
)))
223 tcp_enter_quickack_mode((struct sock
*)tp
);
227 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, struct tcphdr
*th
)
229 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
230 tp
->ecn_flags
&= ~TCP_ECN_OK
;
233 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, struct tcphdr
*th
)
235 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
236 tp
->ecn_flags
&= ~TCP_ECN_OK
;
239 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock
*tp
, struct tcphdr
*th
)
241 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
246 /* Buffer size and advertised window tuning.
248 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
251 static void tcp_fixup_sndbuf(struct sock
*sk
)
253 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
254 sizeof(struct sk_buff
);
256 if (sk
->sk_sndbuf
< 3 * sndmem
)
257 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
260 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
262 * All tcp_full_space() is split to two parts: "network" buffer, allocated
263 * forward and advertised in receiver window (tp->rcv_wnd) and
264 * "application buffer", required to isolate scheduling/application
265 * latencies from network.
266 * window_clamp is maximal advertised window. It can be less than
267 * tcp_full_space(), in this case tcp_full_space() - window_clamp
268 * is reserved for "application" buffer. The less window_clamp is
269 * the smoother our behaviour from viewpoint of network, but the lower
270 * throughput and the higher sensitivity of the connection to losses. 8)
272 * rcv_ssthresh is more strict window_clamp used at "slow start"
273 * phase to predict further behaviour of this connection.
274 * It is used for two goals:
275 * - to enforce header prediction at sender, even when application
276 * requires some significant "application buffer". It is check #1.
277 * - to prevent pruning of receive queue because of misprediction
278 * of receiver window. Check #2.
280 * The scheme does not work when sender sends good segments opening
281 * window and then starts to feed us spaghetti. But it should work
282 * in common situations. Otherwise, we have to rely on queue collapsing.
285 /* Slow part of check#2. */
286 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
288 struct tcp_sock
*tp
= tcp_sk(sk
);
290 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
291 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
293 while (tp
->rcv_ssthresh
<= window
) {
294 if (truesize
<= skb
->len
)
295 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
303 static void tcp_grow_window(struct sock
*sk
, struct sk_buff
*skb
)
305 struct tcp_sock
*tp
= tcp_sk(sk
);
308 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
309 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
310 !tcp_memory_pressure
) {
313 /* Check #2. Increase window, if skb with such overhead
314 * will fit to rcvbuf in future.
316 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
317 incr
= 2 * tp
->advmss
;
319 incr
= __tcp_grow_window(sk
, skb
);
322 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
324 inet_csk(sk
)->icsk_ack
.quick
|= 1;
329 /* 3. Tuning rcvbuf, when connection enters established state. */
331 static void tcp_fixup_rcvbuf(struct sock
*sk
)
333 struct tcp_sock
*tp
= tcp_sk(sk
);
334 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
336 /* Try to select rcvbuf so that 4 mss-sized segments
337 * will fit to window and corresponding skbs will fit to our rcvbuf.
338 * (was 3; 4 is minimum to allow fast retransmit to work.)
340 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
342 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
343 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
346 /* 4. Try to fixup all. It is made immediately after connection enters
349 static void tcp_init_buffer_space(struct sock
*sk
)
351 struct tcp_sock
*tp
= tcp_sk(sk
);
354 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
355 tcp_fixup_rcvbuf(sk
);
356 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
357 tcp_fixup_sndbuf(sk
);
359 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
361 maxwin
= tcp_full_space(sk
);
363 if (tp
->window_clamp
>= maxwin
) {
364 tp
->window_clamp
= maxwin
;
366 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
367 tp
->window_clamp
= max(maxwin
-
368 (maxwin
>> sysctl_tcp_app_win
),
372 /* Force reservation of one segment. */
373 if (sysctl_tcp_app_win
&&
374 tp
->window_clamp
> 2 * tp
->advmss
&&
375 tp
->window_clamp
+ tp
->advmss
> maxwin
)
376 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
378 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
379 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
382 /* 5. Recalculate window clamp after socket hit its memory bounds. */
383 static void tcp_clamp_window(struct sock
*sk
)
385 struct tcp_sock
*tp
= tcp_sk(sk
);
386 struct inet_connection_sock
*icsk
= inet_csk(sk
);
388 icsk
->icsk_ack
.quick
= 0;
390 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
391 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
392 !tcp_memory_pressure
&&
393 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
394 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
397 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
398 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
401 /* Initialize RCV_MSS value.
402 * RCV_MSS is an our guess about MSS used by the peer.
403 * We haven't any direct information about the MSS.
404 * It's better to underestimate the RCV_MSS rather than overestimate.
405 * Overestimations make us ACKing less frequently than needed.
406 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
408 void tcp_initialize_rcv_mss(struct sock
*sk
)
410 struct tcp_sock
*tp
= tcp_sk(sk
);
411 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
413 hint
= min(hint
, tp
->rcv_wnd
/ 2);
414 hint
= min(hint
, TCP_MSS_DEFAULT
);
415 hint
= max(hint
, TCP_MIN_MSS
);
417 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
420 /* Receiver "autotuning" code.
422 * The algorithm for RTT estimation w/o timestamps is based on
423 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
424 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
426 * More detail on this code can be found at
427 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
428 * though this reference is out of date. A new paper
431 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
433 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
439 if (new_sample
!= 0) {
440 /* If we sample in larger samples in the non-timestamp
441 * case, we could grossly overestimate the RTT especially
442 * with chatty applications or bulk transfer apps which
443 * are stalled on filesystem I/O.
445 * Also, since we are only going for a minimum in the
446 * non-timestamp case, we do not smooth things out
447 * else with timestamps disabled convergence takes too
451 m
-= (new_sample
>> 3);
453 } else if (m
< new_sample
)
456 /* No previous measure. */
460 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
461 tp
->rcv_rtt_est
.rtt
= new_sample
;
464 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
466 if (tp
->rcv_rtt_est
.time
== 0)
468 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
470 tcp_rcv_rtt_update(tp
, jiffies
- tp
->rcv_rtt_est
.time
, 1);
473 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
474 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
477 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
478 const struct sk_buff
*skb
)
480 struct tcp_sock
*tp
= tcp_sk(sk
);
481 if (tp
->rx_opt
.rcv_tsecr
&&
482 (TCP_SKB_CB(skb
)->end_seq
-
483 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
484 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
488 * This function should be called every time data is copied to user space.
489 * It calculates the appropriate TCP receive buffer space.
491 void tcp_rcv_space_adjust(struct sock
*sk
)
493 struct tcp_sock
*tp
= tcp_sk(sk
);
497 if (tp
->rcvq_space
.time
== 0)
500 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
501 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
504 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
506 space
= max(tp
->rcvq_space
.space
, space
);
508 if (tp
->rcvq_space
.space
!= space
) {
511 tp
->rcvq_space
.space
= space
;
513 if (sysctl_tcp_moderate_rcvbuf
&&
514 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
515 int new_clamp
= space
;
517 /* Receive space grows, normalize in order to
518 * take into account packet headers and sk_buff
519 * structure overhead.
524 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
525 16 + sizeof(struct sk_buff
));
526 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
529 space
= min(space
, sysctl_tcp_rmem
[2]);
530 if (space
> sk
->sk_rcvbuf
) {
531 sk
->sk_rcvbuf
= space
;
533 /* Make the window clamp follow along. */
534 tp
->window_clamp
= new_clamp
;
540 tp
->rcvq_space
.seq
= tp
->copied_seq
;
541 tp
->rcvq_space
.time
= tcp_time_stamp
;
544 /* There is something which you must keep in mind when you analyze the
545 * behavior of the tp->ato delayed ack timeout interval. When a
546 * connection starts up, we want to ack as quickly as possible. The
547 * problem is that "good" TCP's do slow start at the beginning of data
548 * transmission. The means that until we send the first few ACK's the
549 * sender will sit on his end and only queue most of his data, because
550 * he can only send snd_cwnd unacked packets at any given time. For
551 * each ACK we send, he increments snd_cwnd and transmits more of his
554 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
556 struct tcp_sock
*tp
= tcp_sk(sk
);
557 struct inet_connection_sock
*icsk
= inet_csk(sk
);
560 inet_csk_schedule_ack(sk
);
562 tcp_measure_rcv_mss(sk
, skb
);
564 tcp_rcv_rtt_measure(tp
);
566 now
= tcp_time_stamp
;
568 if (!icsk
->icsk_ack
.ato
) {
569 /* The _first_ data packet received, initialize
570 * delayed ACK engine.
572 tcp_incr_quickack(sk
);
573 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
575 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
577 if (m
<= TCP_ATO_MIN
/ 2) {
578 /* The fastest case is the first. */
579 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
580 } else if (m
< icsk
->icsk_ack
.ato
) {
581 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
582 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
583 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
584 } else if (m
> icsk
->icsk_rto
) {
585 /* Too long gap. Apparently sender failed to
586 * restart window, so that we send ACKs quickly.
588 tcp_incr_quickack(sk
);
592 icsk
->icsk_ack
.lrcvtime
= now
;
594 TCP_ECN_check_ce(tp
, skb
);
597 tcp_grow_window(sk
, skb
);
600 /* Called to compute a smoothed rtt estimate. The data fed to this
601 * routine either comes from timestamps, or from segments that were
602 * known _not_ to have been retransmitted [see Karn/Partridge
603 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
604 * piece by Van Jacobson.
605 * NOTE: the next three routines used to be one big routine.
606 * To save cycles in the RFC 1323 implementation it was better to break
607 * it up into three procedures. -- erics
609 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
611 struct tcp_sock
*tp
= tcp_sk(sk
);
612 long m
= mrtt
; /* RTT */
614 /* The following amusing code comes from Jacobson's
615 * article in SIGCOMM '88. Note that rtt and mdev
616 * are scaled versions of rtt and mean deviation.
617 * This is designed to be as fast as possible
618 * m stands for "measurement".
620 * On a 1990 paper the rto value is changed to:
621 * RTO = rtt + 4 * mdev
623 * Funny. This algorithm seems to be very broken.
624 * These formulae increase RTO, when it should be decreased, increase
625 * too slowly, when it should be increased quickly, decrease too quickly
626 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
627 * does not matter how to _calculate_ it. Seems, it was trap
628 * that VJ failed to avoid. 8)
633 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
634 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
636 m
= -m
; /* m is now abs(error) */
637 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
638 /* This is similar to one of Eifel findings.
639 * Eifel blocks mdev updates when rtt decreases.
640 * This solution is a bit different: we use finer gain
641 * for mdev in this case (alpha*beta).
642 * Like Eifel it also prevents growth of rto,
643 * but also it limits too fast rto decreases,
644 * happening in pure Eifel.
649 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
651 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
652 if (tp
->mdev
> tp
->mdev_max
) {
653 tp
->mdev_max
= tp
->mdev
;
654 if (tp
->mdev_max
> tp
->rttvar
)
655 tp
->rttvar
= tp
->mdev_max
;
657 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
658 if (tp
->mdev_max
< tp
->rttvar
)
659 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
660 tp
->rtt_seq
= tp
->snd_nxt
;
661 tp
->mdev_max
= tcp_rto_min(sk
);
664 /* no previous measure. */
665 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
666 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
667 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
668 tp
->rtt_seq
= tp
->snd_nxt
;
672 /* Calculate rto without backoff. This is the second half of Van Jacobson's
673 * routine referred to above.
675 static inline void tcp_set_rto(struct sock
*sk
)
677 const struct tcp_sock
*tp
= tcp_sk(sk
);
678 /* Old crap is replaced with new one. 8)
681 * 1. If rtt variance happened to be less 50msec, it is hallucination.
682 * It cannot be less due to utterly erratic ACK generation made
683 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
684 * to do with delayed acks, because at cwnd>2 true delack timeout
685 * is invisible. Actually, Linux-2.4 also generates erratic
686 * ACKs in some circumstances.
688 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
690 /* 2. Fixups made earlier cannot be right.
691 * If we do not estimate RTO correctly without them,
692 * all the algo is pure shit and should be replaced
693 * with correct one. It is exactly, which we pretend to do.
696 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
697 * guarantees that rto is higher.
702 /* Save metrics learned by this TCP session.
703 This function is called only, when TCP finishes successfully
704 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
706 void tcp_update_metrics(struct sock
*sk
)
708 struct tcp_sock
*tp
= tcp_sk(sk
);
709 struct dst_entry
*dst
= __sk_dst_get(sk
);
711 if (sysctl_tcp_nometrics_save
)
716 if (dst
&& (dst
->flags
& DST_HOST
)) {
717 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
721 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
722 /* This session failed to estimate rtt. Why?
723 * Probably, no packets returned in time.
726 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
727 dst
->metrics
[RTAX_RTT
- 1] = 0;
731 rtt
= dst_metric_rtt(dst
, RTAX_RTT
);
734 /* If newly calculated rtt larger than stored one,
735 * store new one. Otherwise, use EWMA. Remember,
736 * rtt overestimation is always better than underestimation.
738 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
740 set_dst_metric_rtt(dst
, RTAX_RTT
, tp
->srtt
);
742 set_dst_metric_rtt(dst
, RTAX_RTT
, rtt
- (m
>> 3));
745 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
750 /* Scale deviation to rttvar fixed point */
755 var
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
759 var
-= (var
- m
) >> 2;
761 set_dst_metric_rtt(dst
, RTAX_RTTVAR
, var
);
764 if (tcp_in_initial_slowstart(tp
)) {
765 /* Slow start still did not finish. */
766 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
767 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
768 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
769 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
770 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
771 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
772 dst
->metrics
[RTAX_CWND
- 1] = tp
->snd_cwnd
;
773 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
774 icsk
->icsk_ca_state
== TCP_CA_Open
) {
775 /* Cong. avoidance phase, cwnd is reliable. */
776 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
777 dst
->metrics
[RTAX_SSTHRESH
-1] =
778 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
779 if (!dst_metric_locked(dst
, RTAX_CWND
))
780 dst
->metrics
[RTAX_CWND
-1] = (dst_metric(dst
, RTAX_CWND
) + tp
->snd_cwnd
) >> 1;
782 /* Else slow start did not finish, cwnd is non-sense,
783 ssthresh may be also invalid.
785 if (!dst_metric_locked(dst
, RTAX_CWND
))
786 dst
->metrics
[RTAX_CWND
-1] = (dst_metric(dst
, RTAX_CWND
) + tp
->snd_ssthresh
) >> 1;
787 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
788 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
789 tp
->snd_ssthresh
> dst_metric(dst
, RTAX_SSTHRESH
))
790 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
793 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
794 if (dst_metric(dst
, RTAX_REORDERING
) < tp
->reordering
&&
795 tp
->reordering
!= sysctl_tcp_reordering
)
796 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
801 /* Numbers are taken from RFC3390.
803 * John Heffner states:
805 * The RFC specifies a window of no more than 4380 bytes
806 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
807 * is a bit misleading because they use a clamp at 4380 bytes
808 * rather than use a multiplier in the relevant range.
810 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
812 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
815 if (tp
->mss_cache
> 1460)
818 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
820 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
823 /* Set slow start threshold and cwnd not falling to slow start */
824 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
826 struct tcp_sock
*tp
= tcp_sk(sk
);
827 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
829 tp
->prior_ssthresh
= 0;
831 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
834 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
835 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
836 tcp_packets_in_flight(tp
) + 1U);
837 tp
->snd_cwnd_cnt
= 0;
838 tp
->high_seq
= tp
->snd_nxt
;
839 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
840 TCP_ECN_queue_cwr(tp
);
842 tcp_set_ca_state(sk
, TCP_CA_CWR
);
847 * Packet counting of FACK is based on in-order assumptions, therefore TCP
848 * disables it when reordering is detected
850 static void tcp_disable_fack(struct tcp_sock
*tp
)
852 /* RFC3517 uses different metric in lost marker => reset on change */
854 tp
->lost_skb_hint
= NULL
;
855 tp
->rx_opt
.sack_ok
&= ~2;
858 /* Take a notice that peer is sending D-SACKs */
859 static void tcp_dsack_seen(struct tcp_sock
*tp
)
861 tp
->rx_opt
.sack_ok
|= 4;
864 /* Initialize metrics on socket. */
866 static void tcp_init_metrics(struct sock
*sk
)
868 struct tcp_sock
*tp
= tcp_sk(sk
);
869 struct dst_entry
*dst
= __sk_dst_get(sk
);
876 if (dst_metric_locked(dst
, RTAX_CWND
))
877 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
878 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
879 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
880 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
881 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
883 if (dst_metric(dst
, RTAX_REORDERING
) &&
884 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
885 tcp_disable_fack(tp
);
886 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
889 if (dst_metric(dst
, RTAX_RTT
) == 0)
892 if (!tp
->srtt
&& dst_metric_rtt(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
895 /* Initial rtt is determined from SYN,SYN-ACK.
896 * The segment is small and rtt may appear much
897 * less than real one. Use per-dst memory
898 * to make it more realistic.
900 * A bit of theory. RTT is time passed after "normal" sized packet
901 * is sent until it is ACKed. In normal circumstances sending small
902 * packets force peer to delay ACKs and calculation is correct too.
903 * The algorithm is adaptive and, provided we follow specs, it
904 * NEVER underestimate RTT. BUT! If peer tries to make some clever
905 * tricks sort of "quick acks" for time long enough to decrease RTT
906 * to low value, and then abruptly stops to do it and starts to delay
907 * ACKs, wait for troubles.
909 if (dst_metric_rtt(dst
, RTAX_RTT
) > tp
->srtt
) {
910 tp
->srtt
= dst_metric_rtt(dst
, RTAX_RTT
);
911 tp
->rtt_seq
= tp
->snd_nxt
;
913 if (dst_metric_rtt(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
914 tp
->mdev
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
915 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
918 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
922 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
923 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
927 /* Play conservative. If timestamps are not
928 * supported, TCP will fail to recalculate correct
929 * rtt, if initial rto is too small. FORGET ALL AND RESET!
931 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
933 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
934 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
939 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
942 struct tcp_sock
*tp
= tcp_sk(sk
);
943 if (metric
> tp
->reordering
) {
946 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
948 /* This exciting event is worth to be remembered. 8) */
950 mib_idx
= LINUX_MIB_TCPTSREORDER
;
951 else if (tcp_is_reno(tp
))
952 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
953 else if (tcp_is_fack(tp
))
954 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
956 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
958 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
959 #if FASTRETRANS_DEBUG > 1
960 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
961 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
965 tp
->undo_marker
? tp
->undo_retrans
: 0);
967 tcp_disable_fack(tp
);
971 /* This must be called before lost_out is incremented */
972 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
974 if ((tp
->retransmit_skb_hint
== NULL
) ||
975 before(TCP_SKB_CB(skb
)->seq
,
976 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
977 tp
->retransmit_skb_hint
= skb
;
980 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
981 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
984 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
986 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
987 tcp_verify_retransmit_hint(tp
, skb
);
989 tp
->lost_out
+= tcp_skb_pcount(skb
);
990 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
994 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
997 tcp_verify_retransmit_hint(tp
, skb
);
999 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1000 tp
->lost_out
+= tcp_skb_pcount(skb
);
1001 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1005 /* This procedure tags the retransmission queue when SACKs arrive.
1007 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1008 * Packets in queue with these bits set are counted in variables
1009 * sacked_out, retrans_out and lost_out, correspondingly.
1011 * Valid combinations are:
1012 * Tag InFlight Description
1013 * 0 1 - orig segment is in flight.
1014 * S 0 - nothing flies, orig reached receiver.
1015 * L 0 - nothing flies, orig lost by net.
1016 * R 2 - both orig and retransmit are in flight.
1017 * L|R 1 - orig is lost, retransmit is in flight.
1018 * S|R 1 - orig reached receiver, retrans is still in flight.
1019 * (L|S|R is logically valid, it could occur when L|R is sacked,
1020 * but it is equivalent to plain S and code short-curcuits it to S.
1021 * L|S is logically invalid, it would mean -1 packet in flight 8))
1023 * These 6 states form finite state machine, controlled by the following events:
1024 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1025 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1026 * 3. Loss detection event of one of three flavors:
1027 * A. Scoreboard estimator decided the packet is lost.
1028 * A'. Reno "three dupacks" marks head of queue lost.
1029 * A''. Its FACK modfication, head until snd.fack is lost.
1030 * B. SACK arrives sacking data transmitted after never retransmitted
1031 * hole was sent out.
1032 * C. SACK arrives sacking SND.NXT at the moment, when the
1033 * segment was retransmitted.
1034 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1036 * It is pleasant to note, that state diagram turns out to be commutative,
1037 * so that we are allowed not to be bothered by order of our actions,
1038 * when multiple events arrive simultaneously. (see the function below).
1040 * Reordering detection.
1041 * --------------------
1042 * Reordering metric is maximal distance, which a packet can be displaced
1043 * in packet stream. With SACKs we can estimate it:
1045 * 1. SACK fills old hole and the corresponding segment was not
1046 * ever retransmitted -> reordering. Alas, we cannot use it
1047 * when segment was retransmitted.
1048 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1049 * for retransmitted and already SACKed segment -> reordering..
1050 * Both of these heuristics are not used in Loss state, when we cannot
1051 * account for retransmits accurately.
1053 * SACK block validation.
1054 * ----------------------
1056 * SACK block range validation checks that the received SACK block fits to
1057 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1058 * Note that SND.UNA is not included to the range though being valid because
1059 * it means that the receiver is rather inconsistent with itself reporting
1060 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1061 * perfectly valid, however, in light of RFC2018 which explicitly states
1062 * that "SACK block MUST reflect the newest segment. Even if the newest
1063 * segment is going to be discarded ...", not that it looks very clever
1064 * in case of head skb. Due to potentional receiver driven attacks, we
1065 * choose to avoid immediate execution of a walk in write queue due to
1066 * reneging and defer head skb's loss recovery to standard loss recovery
1067 * procedure that will eventually trigger (nothing forbids us doing this).
1069 * Implements also blockage to start_seq wrap-around. Problem lies in the
1070 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1071 * there's no guarantee that it will be before snd_nxt (n). The problem
1072 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1075 * <- outs wnd -> <- wrapzone ->
1076 * u e n u_w e_w s n_w
1078 * |<------------+------+----- TCP seqno space --------------+---------->|
1079 * ...-- <2^31 ->| |<--------...
1080 * ...---- >2^31 ------>| |<--------...
1082 * Current code wouldn't be vulnerable but it's better still to discard such
1083 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1084 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1085 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1086 * equal to the ideal case (infinite seqno space without wrap caused issues).
1088 * With D-SACK the lower bound is extended to cover sequence space below
1089 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1090 * again, D-SACK block must not to go across snd_una (for the same reason as
1091 * for the normal SACK blocks, explained above). But there all simplicity
1092 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1093 * fully below undo_marker they do not affect behavior in anyway and can
1094 * therefore be safely ignored. In rare cases (which are more or less
1095 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1096 * fragmentation and packet reordering past skb's retransmission. To consider
1097 * them correctly, the acceptable range must be extended even more though
1098 * the exact amount is rather hard to quantify. However, tp->max_window can
1099 * be used as an exaggerated estimate.
1101 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1102 u32 start_seq
, u32 end_seq
)
1104 /* Too far in future, or reversed (interpretation is ambiguous) */
1105 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1108 /* Nasty start_seq wrap-around check (see comments above) */
1109 if (!before(start_seq
, tp
->snd_nxt
))
1112 /* In outstanding window? ...This is valid exit for D-SACKs too.
1113 * start_seq == snd_una is non-sensical (see comments above)
1115 if (after(start_seq
, tp
->snd_una
))
1118 if (!is_dsack
|| !tp
->undo_marker
)
1121 /* ...Then it's D-SACK, and must reside below snd_una completely */
1122 if (!after(end_seq
, tp
->snd_una
))
1125 if (!before(start_seq
, tp
->undo_marker
))
1129 if (!after(end_seq
, tp
->undo_marker
))
1132 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1133 * start_seq < undo_marker and end_seq >= undo_marker.
1135 return !before(start_seq
, end_seq
- tp
->max_window
);
1138 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1139 * Event "C". Later note: FACK people cheated me again 8), we have to account
1140 * for reordering! Ugly, but should help.
1142 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1143 * less than what is now known to be received by the other end (derived from
1144 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1145 * retransmitted skbs to avoid some costly processing per ACKs.
1147 static void tcp_mark_lost_retrans(struct sock
*sk
)
1149 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1150 struct tcp_sock
*tp
= tcp_sk(sk
);
1151 struct sk_buff
*skb
;
1153 u32 new_low_seq
= tp
->snd_nxt
;
1154 u32 received_upto
= tcp_highest_sack_seq(tp
);
1156 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1157 !after(received_upto
, tp
->lost_retrans_low
) ||
1158 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1161 tcp_for_write_queue(skb
, sk
) {
1162 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1164 if (skb
== tcp_send_head(sk
))
1166 if (cnt
== tp
->retrans_out
)
1168 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1171 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1174 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1175 * constraint here (see above) but figuring out that at
1176 * least tp->reordering SACK blocks reside between ack_seq
1177 * and received_upto is not easy task to do cheaply with
1178 * the available datastructures.
1180 * Whether FACK should check here for tp->reordering segs
1181 * in-between one could argue for either way (it would be
1182 * rather simple to implement as we could count fack_count
1183 * during the walk and do tp->fackets_out - fack_count).
1185 if (after(received_upto
, ack_seq
)) {
1186 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1187 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1189 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1190 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1192 if (before(ack_seq
, new_low_seq
))
1193 new_low_seq
= ack_seq
;
1194 cnt
+= tcp_skb_pcount(skb
);
1198 if (tp
->retrans_out
)
1199 tp
->lost_retrans_low
= new_low_seq
;
1202 static int tcp_check_dsack(struct sock
*sk
, struct sk_buff
*ack_skb
,
1203 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1206 struct tcp_sock
*tp
= tcp_sk(sk
);
1207 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1208 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1211 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1214 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1215 } else if (num_sacks
> 1) {
1216 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1217 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1219 if (!after(end_seq_0
, end_seq_1
) &&
1220 !before(start_seq_0
, start_seq_1
)) {
1223 NET_INC_STATS_BH(sock_net(sk
),
1224 LINUX_MIB_TCPDSACKOFORECV
);
1228 /* D-SACK for already forgotten data... Do dumb counting. */
1230 !after(end_seq_0
, prior_snd_una
) &&
1231 after(end_seq_0
, tp
->undo_marker
))
1237 struct tcp_sacktag_state
{
1243 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1244 * the incoming SACK may not exactly match but we can find smaller MSS
1245 * aligned portion of it that matches. Therefore we might need to fragment
1246 * which may fail and creates some hassle (caller must handle error case
1249 * FIXME: this could be merged to shift decision code
1251 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1252 u32 start_seq
, u32 end_seq
)
1255 unsigned int pkt_len
;
1258 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1259 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1261 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1262 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1263 mss
= tcp_skb_mss(skb
);
1264 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1267 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1271 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1276 /* Round if necessary so that SACKs cover only full MSSes
1277 * and/or the remaining small portion (if present)
1279 if (pkt_len
> mss
) {
1280 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1281 if (!in_sack
&& new_len
< pkt_len
) {
1283 if (new_len
> skb
->len
)
1288 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
);
1296 static u8
tcp_sacktag_one(struct sk_buff
*skb
, struct sock
*sk
,
1297 struct tcp_sacktag_state
*state
,
1298 int dup_sack
, int pcount
)
1300 struct tcp_sock
*tp
= tcp_sk(sk
);
1301 u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1302 int fack_count
= state
->fack_count
;
1304 /* Account D-SACK for retransmitted packet. */
1305 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1306 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1308 if (sacked
& TCPCB_SACKED_ACKED
)
1309 state
->reord
= min(fack_count
, state
->reord
);
1312 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1313 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1316 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1317 if (sacked
& TCPCB_SACKED_RETRANS
) {
1318 /* If the segment is not tagged as lost,
1319 * we do not clear RETRANS, believing
1320 * that retransmission is still in flight.
1322 if (sacked
& TCPCB_LOST
) {
1323 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1324 tp
->lost_out
-= pcount
;
1325 tp
->retrans_out
-= pcount
;
1328 if (!(sacked
& TCPCB_RETRANS
)) {
1329 /* New sack for not retransmitted frame,
1330 * which was in hole. It is reordering.
1332 if (before(TCP_SKB_CB(skb
)->seq
,
1333 tcp_highest_sack_seq(tp
)))
1334 state
->reord
= min(fack_count
,
1337 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1338 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
))
1339 state
->flag
|= FLAG_ONLY_ORIG_SACKED
;
1342 if (sacked
& TCPCB_LOST
) {
1343 sacked
&= ~TCPCB_LOST
;
1344 tp
->lost_out
-= pcount
;
1348 sacked
|= TCPCB_SACKED_ACKED
;
1349 state
->flag
|= FLAG_DATA_SACKED
;
1350 tp
->sacked_out
+= pcount
;
1352 fack_count
+= pcount
;
1354 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1355 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1356 before(TCP_SKB_CB(skb
)->seq
,
1357 TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1358 tp
->lost_cnt_hint
+= pcount
;
1360 if (fack_count
> tp
->fackets_out
)
1361 tp
->fackets_out
= fack_count
;
1364 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1365 * frames and clear it. undo_retrans is decreased above, L|R frames
1366 * are accounted above as well.
1368 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1369 sacked
&= ~TCPCB_SACKED_RETRANS
;
1370 tp
->retrans_out
-= pcount
;
1376 static int tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1377 struct tcp_sacktag_state
*state
,
1378 unsigned int pcount
, int shifted
, int mss
,
1381 struct tcp_sock
*tp
= tcp_sk(sk
);
1382 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1386 /* Tweak before seqno plays */
1387 if (!tcp_is_fack(tp
) && tcp_is_sack(tp
) && tp
->lost_skb_hint
&&
1388 !before(TCP_SKB_CB(tp
->lost_skb_hint
)->seq
, TCP_SKB_CB(skb
)->seq
))
1389 tp
->lost_cnt_hint
+= pcount
;
1391 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1392 TCP_SKB_CB(skb
)->seq
+= shifted
;
1394 skb_shinfo(prev
)->gso_segs
+= pcount
;
1395 BUG_ON(skb_shinfo(skb
)->gso_segs
< pcount
);
1396 skb_shinfo(skb
)->gso_segs
-= pcount
;
1398 /* When we're adding to gso_segs == 1, gso_size will be zero,
1399 * in theory this shouldn't be necessary but as long as DSACK
1400 * code can come after this skb later on it's better to keep
1401 * setting gso_size to something.
1403 if (!skb_shinfo(prev
)->gso_size
) {
1404 skb_shinfo(prev
)->gso_size
= mss
;
1405 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1408 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1409 if (skb_shinfo(skb
)->gso_segs
<= 1) {
1410 skb_shinfo(skb
)->gso_size
= 0;
1411 skb_shinfo(skb
)->gso_type
= 0;
1414 /* We discard results */
1415 tcp_sacktag_one(skb
, sk
, state
, dup_sack
, pcount
);
1417 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1418 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1421 BUG_ON(!tcp_skb_pcount(skb
));
1422 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1426 /* Whole SKB was eaten :-) */
1428 if (skb
== tp
->retransmit_skb_hint
)
1429 tp
->retransmit_skb_hint
= prev
;
1430 if (skb
== tp
->scoreboard_skb_hint
)
1431 tp
->scoreboard_skb_hint
= prev
;
1432 if (skb
== tp
->lost_skb_hint
) {
1433 tp
->lost_skb_hint
= prev
;
1434 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1437 TCP_SKB_CB(skb
)->flags
|= TCP_SKB_CB(prev
)->flags
;
1438 if (skb
== tcp_highest_sack(sk
))
1439 tcp_advance_highest_sack(sk
, skb
);
1441 tcp_unlink_write_queue(skb
, sk
);
1442 sk_wmem_free_skb(sk
, skb
);
1444 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1449 /* I wish gso_size would have a bit more sane initialization than
1450 * something-or-zero which complicates things
1452 static int tcp_skb_seglen(struct sk_buff
*skb
)
1454 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1457 /* Shifting pages past head area doesn't work */
1458 static int skb_can_shift(struct sk_buff
*skb
)
1460 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1463 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1466 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1467 struct tcp_sacktag_state
*state
,
1468 u32 start_seq
, u32 end_seq
,
1471 struct tcp_sock
*tp
= tcp_sk(sk
);
1472 struct sk_buff
*prev
;
1478 if (!sk_can_gso(sk
))
1481 /* Normally R but no L won't result in plain S */
1483 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1485 if (!skb_can_shift(skb
))
1487 /* This frame is about to be dropped (was ACKed). */
1488 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1491 /* Can only happen with delayed DSACK + discard craziness */
1492 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1494 prev
= tcp_write_queue_prev(sk
, skb
);
1496 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1499 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1500 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1504 pcount
= tcp_skb_pcount(skb
);
1505 mss
= tcp_skb_seglen(skb
);
1507 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1508 * drop this restriction as unnecessary
1510 if (mss
!= tcp_skb_seglen(prev
))
1513 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1515 /* CHECKME: This is non-MSS split case only?, this will
1516 * cause skipped skbs due to advancing loop btw, original
1517 * has that feature too
1519 if (tcp_skb_pcount(skb
) <= 1)
1522 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1524 /* TODO: head merge to next could be attempted here
1525 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1526 * though it might not be worth of the additional hassle
1528 * ...we can probably just fallback to what was done
1529 * previously. We could try merging non-SACKed ones
1530 * as well but it probably isn't going to buy off
1531 * because later SACKs might again split them, and
1532 * it would make skb timestamp tracking considerably
1538 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1540 BUG_ON(len
> skb
->len
);
1542 /* MSS boundaries should be honoured or else pcount will
1543 * severely break even though it makes things bit trickier.
1544 * Optimize common case to avoid most of the divides
1546 mss
= tcp_skb_mss(skb
);
1548 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1549 * drop this restriction as unnecessary
1551 if (mss
!= tcp_skb_seglen(prev
))
1556 } else if (len
< mss
) {
1564 if (!skb_shift(prev
, skb
, len
))
1566 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1569 /* Hole filled allows collapsing with the next as well, this is very
1570 * useful when hole on every nth skb pattern happens
1572 if (prev
== tcp_write_queue_tail(sk
))
1574 skb
= tcp_write_queue_next(sk
, prev
);
1576 if (!skb_can_shift(skb
) ||
1577 (skb
== tcp_send_head(sk
)) ||
1578 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1579 (mss
!= tcp_skb_seglen(skb
)))
1583 if (skb_shift(prev
, skb
, len
)) {
1584 pcount
+= tcp_skb_pcount(skb
);
1585 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1589 state
->fack_count
+= pcount
;
1596 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1600 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1601 struct tcp_sack_block
*next_dup
,
1602 struct tcp_sacktag_state
*state
,
1603 u32 start_seq
, u32 end_seq
,
1606 struct tcp_sock
*tp
= tcp_sk(sk
);
1607 struct sk_buff
*tmp
;
1609 tcp_for_write_queue_from(skb
, sk
) {
1611 int dup_sack
= dup_sack_in
;
1613 if (skb
== tcp_send_head(sk
))
1616 /* queue is in-order => we can short-circuit the walk early */
1617 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1620 if ((next_dup
!= NULL
) &&
1621 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1622 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1623 next_dup
->start_seq
,
1629 /* skb reference here is a bit tricky to get right, since
1630 * shifting can eat and free both this skb and the next,
1631 * so not even _safe variant of the loop is enough.
1634 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1635 start_seq
, end_seq
, dup_sack
);
1644 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1650 if (unlikely(in_sack
< 0))
1654 TCP_SKB_CB(skb
)->sacked
= tcp_sacktag_one(skb
, sk
,
1657 tcp_skb_pcount(skb
));
1659 if (!before(TCP_SKB_CB(skb
)->seq
,
1660 tcp_highest_sack_seq(tp
)))
1661 tcp_advance_highest_sack(sk
, skb
);
1664 state
->fack_count
+= tcp_skb_pcount(skb
);
1669 /* Avoid all extra work that is being done by sacktag while walking in
1672 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1673 struct tcp_sacktag_state
*state
,
1676 tcp_for_write_queue_from(skb
, sk
) {
1677 if (skb
== tcp_send_head(sk
))
1680 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1683 state
->fack_count
+= tcp_skb_pcount(skb
);
1688 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1690 struct tcp_sack_block
*next_dup
,
1691 struct tcp_sacktag_state
*state
,
1694 if (next_dup
== NULL
)
1697 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1698 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1699 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1700 next_dup
->start_seq
, next_dup
->end_seq
,
1707 static int tcp_sack_cache_ok(struct tcp_sock
*tp
, struct tcp_sack_block
*cache
)
1709 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1713 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
,
1716 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1717 struct tcp_sock
*tp
= tcp_sk(sk
);
1718 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1719 TCP_SKB_CB(ack_skb
)->sacked
);
1720 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1721 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1722 struct tcp_sack_block
*cache
;
1723 struct tcp_sacktag_state state
;
1724 struct sk_buff
*skb
;
1725 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1727 int found_dup_sack
= 0;
1729 int first_sack_index
;
1732 state
.reord
= tp
->packets_out
;
1734 if (!tp
->sacked_out
) {
1735 if (WARN_ON(tp
->fackets_out
))
1736 tp
->fackets_out
= 0;
1737 tcp_highest_sack_reset(sk
);
1740 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1741 num_sacks
, prior_snd_una
);
1743 state
.flag
|= FLAG_DSACKING_ACK
;
1745 /* Eliminate too old ACKs, but take into
1746 * account more or less fresh ones, they can
1747 * contain valid SACK info.
1749 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1752 if (!tp
->packets_out
)
1756 first_sack_index
= 0;
1757 for (i
= 0; i
< num_sacks
; i
++) {
1758 int dup_sack
= !i
&& found_dup_sack
;
1760 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1761 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1763 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1764 sp
[used_sacks
].start_seq
,
1765 sp
[used_sacks
].end_seq
)) {
1769 if (!tp
->undo_marker
)
1770 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1772 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1774 /* Don't count olds caused by ACK reordering */
1775 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1776 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1778 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1781 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1783 first_sack_index
= -1;
1787 /* Ignore very old stuff early */
1788 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1794 /* order SACK blocks to allow in order walk of the retrans queue */
1795 for (i
= used_sacks
- 1; i
> 0; i
--) {
1796 for (j
= 0; j
< i
; j
++) {
1797 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1798 swap(sp
[j
], sp
[j
+ 1]);
1800 /* Track where the first SACK block goes to */
1801 if (j
== first_sack_index
)
1802 first_sack_index
= j
+ 1;
1807 skb
= tcp_write_queue_head(sk
);
1808 state
.fack_count
= 0;
1811 if (!tp
->sacked_out
) {
1812 /* It's already past, so skip checking against it */
1813 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1815 cache
= tp
->recv_sack_cache
;
1816 /* Skip empty blocks in at head of the cache */
1817 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1822 while (i
< used_sacks
) {
1823 u32 start_seq
= sp
[i
].start_seq
;
1824 u32 end_seq
= sp
[i
].end_seq
;
1825 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1826 struct tcp_sack_block
*next_dup
= NULL
;
1828 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1829 next_dup
= &sp
[i
+ 1];
1831 /* Event "B" in the comment above. */
1832 if (after(end_seq
, tp
->high_seq
))
1833 state
.flag
|= FLAG_DATA_LOST
;
1835 /* Skip too early cached blocks */
1836 while (tcp_sack_cache_ok(tp
, cache
) &&
1837 !before(start_seq
, cache
->end_seq
))
1840 /* Can skip some work by looking recv_sack_cache? */
1841 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1842 after(end_seq
, cache
->start_seq
)) {
1845 if (before(start_seq
, cache
->start_seq
)) {
1846 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1848 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1855 /* Rest of the block already fully processed? */
1856 if (!after(end_seq
, cache
->end_seq
))
1859 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1863 /* ...tail remains todo... */
1864 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1865 /* ...but better entrypoint exists! */
1866 skb
= tcp_highest_sack(sk
);
1869 state
.fack_count
= tp
->fackets_out
;
1874 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1875 /* Check overlap against next cached too (past this one already) */
1880 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1881 skb
= tcp_highest_sack(sk
);
1884 state
.fack_count
= tp
->fackets_out
;
1886 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1889 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1890 start_seq
, end_seq
, dup_sack
);
1893 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1894 * due to in-order walk
1896 if (after(end_seq
, tp
->frto_highmark
))
1897 state
.flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1902 /* Clear the head of the cache sack blocks so we can skip it next time */
1903 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1904 tp
->recv_sack_cache
[i
].start_seq
= 0;
1905 tp
->recv_sack_cache
[i
].end_seq
= 0;
1907 for (j
= 0; j
< used_sacks
; j
++)
1908 tp
->recv_sack_cache
[i
++] = sp
[j
];
1910 tcp_mark_lost_retrans(sk
);
1912 tcp_verify_left_out(tp
);
1914 if ((state
.reord
< tp
->fackets_out
) &&
1915 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1916 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1917 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1921 #if FASTRETRANS_DEBUG > 0
1922 WARN_ON((int)tp
->sacked_out
< 0);
1923 WARN_ON((int)tp
->lost_out
< 0);
1924 WARN_ON((int)tp
->retrans_out
< 0);
1925 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1930 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1931 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1933 static int tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1937 holes
= max(tp
->lost_out
, 1U);
1938 holes
= min(holes
, tp
->packets_out
);
1940 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1941 tp
->sacked_out
= tp
->packets_out
- holes
;
1947 /* If we receive more dupacks than we expected counting segments
1948 * in assumption of absent reordering, interpret this as reordering.
1949 * The only another reason could be bug in receiver TCP.
1951 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1953 struct tcp_sock
*tp
= tcp_sk(sk
);
1954 if (tcp_limit_reno_sacked(tp
))
1955 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1958 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1960 static void tcp_add_reno_sack(struct sock
*sk
)
1962 struct tcp_sock
*tp
= tcp_sk(sk
);
1964 tcp_check_reno_reordering(sk
, 0);
1965 tcp_verify_left_out(tp
);
1968 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1970 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1972 struct tcp_sock
*tp
= tcp_sk(sk
);
1975 /* One ACK acked hole. The rest eat duplicate ACKs. */
1976 if (acked
- 1 >= tp
->sacked_out
)
1979 tp
->sacked_out
-= acked
- 1;
1981 tcp_check_reno_reordering(sk
, acked
);
1982 tcp_verify_left_out(tp
);
1985 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1990 static int tcp_is_sackfrto(const struct tcp_sock
*tp
)
1992 return (sysctl_tcp_frto
== 0x2) && !tcp_is_reno(tp
);
1995 /* F-RTO can only be used if TCP has never retransmitted anything other than
1996 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1998 int tcp_use_frto(struct sock
*sk
)
2000 const struct tcp_sock
*tp
= tcp_sk(sk
);
2001 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2002 struct sk_buff
*skb
;
2004 if (!sysctl_tcp_frto
)
2007 /* MTU probe and F-RTO won't really play nicely along currently */
2008 if (icsk
->icsk_mtup
.probe_size
)
2011 if (tcp_is_sackfrto(tp
))
2014 /* Avoid expensive walking of rexmit queue if possible */
2015 if (tp
->retrans_out
> 1)
2018 skb
= tcp_write_queue_head(sk
);
2019 if (tcp_skb_is_last(sk
, skb
))
2021 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
2022 tcp_for_write_queue_from(skb
, sk
) {
2023 if (skb
== tcp_send_head(sk
))
2025 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2027 /* Short-circuit when first non-SACKed skb has been checked */
2028 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2034 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2035 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2036 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2037 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2038 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2039 * bits are handled if the Loss state is really to be entered (in
2040 * tcp_enter_frto_loss).
2042 * Do like tcp_enter_loss() would; when RTO expires the second time it
2044 * "Reduce ssthresh if it has not yet been made inside this window."
2046 void tcp_enter_frto(struct sock
*sk
)
2048 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2049 struct tcp_sock
*tp
= tcp_sk(sk
);
2050 struct sk_buff
*skb
;
2052 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
2053 tp
->snd_una
== tp
->high_seq
||
2054 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
2055 !icsk
->icsk_retransmits
)) {
2056 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2057 /* Our state is too optimistic in ssthresh() call because cwnd
2058 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2059 * recovery has not yet completed. Pattern would be this: RTO,
2060 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2062 * RFC4138 should be more specific on what to do, even though
2063 * RTO is quite unlikely to occur after the first Cumulative ACK
2064 * due to back-off and complexity of triggering events ...
2066 if (tp
->frto_counter
) {
2068 stored_cwnd
= tp
->snd_cwnd
;
2070 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2071 tp
->snd_cwnd
= stored_cwnd
;
2073 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2075 /* ... in theory, cong.control module could do "any tricks" in
2076 * ssthresh(), which means that ca_state, lost bits and lost_out
2077 * counter would have to be faked before the call occurs. We
2078 * consider that too expensive, unlikely and hacky, so modules
2079 * using these in ssthresh() must deal these incompatibility
2080 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2082 tcp_ca_event(sk
, CA_EVENT_FRTO
);
2085 tp
->undo_marker
= tp
->snd_una
;
2086 tp
->undo_retrans
= 0;
2088 skb
= tcp_write_queue_head(sk
);
2089 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2090 tp
->undo_marker
= 0;
2091 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2092 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2093 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2095 tcp_verify_left_out(tp
);
2097 /* Too bad if TCP was application limited */
2098 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2100 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2101 * The last condition is necessary at least in tp->frto_counter case.
2103 if (tcp_is_sackfrto(tp
) && (tp
->frto_counter
||
2104 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
2105 after(tp
->high_seq
, tp
->snd_una
)) {
2106 tp
->frto_highmark
= tp
->high_seq
;
2108 tp
->frto_highmark
= tp
->snd_nxt
;
2110 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
2111 tp
->high_seq
= tp
->snd_nxt
;
2112 tp
->frto_counter
= 1;
2115 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2116 * which indicates that we should follow the traditional RTO recovery,
2117 * i.e. mark everything lost and do go-back-N retransmission.
2119 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
2121 struct tcp_sock
*tp
= tcp_sk(sk
);
2122 struct sk_buff
*skb
;
2125 tp
->retrans_out
= 0;
2126 if (tcp_is_reno(tp
))
2127 tcp_reset_reno_sack(tp
);
2129 tcp_for_write_queue(skb
, sk
) {
2130 if (skb
== tcp_send_head(sk
))
2133 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2135 * Count the retransmission made on RTO correctly (only when
2136 * waiting for the first ACK and did not get it)...
2138 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
2139 /* For some reason this R-bit might get cleared? */
2140 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
2141 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2142 /* ...enter this if branch just for the first segment */
2143 flag
|= FLAG_DATA_ACKED
;
2145 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2146 tp
->undo_marker
= 0;
2147 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2150 /* Marking forward transmissions that were made after RTO lost
2151 * can cause unnecessary retransmissions in some scenarios,
2152 * SACK blocks will mitigate that in some but not in all cases.
2153 * We used to not mark them but it was causing break-ups with
2154 * receivers that do only in-order receival.
2156 * TODO: we could detect presence of such receiver and select
2157 * different behavior per flow.
2159 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2160 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2161 tp
->lost_out
+= tcp_skb_pcount(skb
);
2162 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2165 tcp_verify_left_out(tp
);
2167 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
2168 tp
->snd_cwnd_cnt
= 0;
2169 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2170 tp
->frto_counter
= 0;
2171 tp
->bytes_acked
= 0;
2173 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2174 sysctl_tcp_reordering
);
2175 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2176 tp
->high_seq
= tp
->snd_nxt
;
2177 TCP_ECN_queue_cwr(tp
);
2179 tcp_clear_all_retrans_hints(tp
);
2182 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
2184 tp
->retrans_out
= 0;
2187 tp
->undo_marker
= 0;
2188 tp
->undo_retrans
= 0;
2191 void tcp_clear_retrans(struct tcp_sock
*tp
)
2193 tcp_clear_retrans_partial(tp
);
2195 tp
->fackets_out
= 0;
2199 /* Enter Loss state. If "how" is not zero, forget all SACK information
2200 * and reset tags completely, otherwise preserve SACKs. If receiver
2201 * dropped its ofo queue, we will know this due to reneging detection.
2203 void tcp_enter_loss(struct sock
*sk
, int how
)
2205 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2206 struct tcp_sock
*tp
= tcp_sk(sk
);
2207 struct sk_buff
*skb
;
2209 /* Reduce ssthresh if it has not yet been made inside this window. */
2210 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
2211 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
2212 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2213 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2214 tcp_ca_event(sk
, CA_EVENT_LOSS
);
2217 tp
->snd_cwnd_cnt
= 0;
2218 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2220 tp
->bytes_acked
= 0;
2221 tcp_clear_retrans_partial(tp
);
2223 if (tcp_is_reno(tp
))
2224 tcp_reset_reno_sack(tp
);
2227 /* Push undo marker, if it was plain RTO and nothing
2228 * was retransmitted. */
2229 tp
->undo_marker
= tp
->snd_una
;
2232 tp
->fackets_out
= 0;
2234 tcp_clear_all_retrans_hints(tp
);
2236 tcp_for_write_queue(skb
, sk
) {
2237 if (skb
== tcp_send_head(sk
))
2240 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2241 tp
->undo_marker
= 0;
2242 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
2243 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
2244 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
2245 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2246 tp
->lost_out
+= tcp_skb_pcount(skb
);
2247 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2250 tcp_verify_left_out(tp
);
2252 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2253 sysctl_tcp_reordering
);
2254 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2255 tp
->high_seq
= tp
->snd_nxt
;
2256 TCP_ECN_queue_cwr(tp
);
2257 /* Abort F-RTO algorithm if one is in progress */
2258 tp
->frto_counter
= 0;
2261 /* If ACK arrived pointing to a remembered SACK, it means that our
2262 * remembered SACKs do not reflect real state of receiver i.e.
2263 * receiver _host_ is heavily congested (or buggy).
2265 * Do processing similar to RTO timeout.
2267 static int tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2269 if (flag
& FLAG_SACK_RENEGING
) {
2270 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2271 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
2273 tcp_enter_loss(sk
, 1);
2274 icsk
->icsk_retransmits
++;
2275 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
2276 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2277 icsk
->icsk_rto
, TCP_RTO_MAX
);
2283 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
2285 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2288 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2289 * counter when SACK is enabled (without SACK, sacked_out is used for
2292 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2293 * segments up to the highest received SACK block so far and holes in
2296 * With reordering, holes may still be in flight, so RFC3517 recovery
2297 * uses pure sacked_out (total number of SACKed segments) even though
2298 * it violates the RFC that uses duplicate ACKs, often these are equal
2299 * but when e.g. out-of-window ACKs or packet duplication occurs,
2300 * they differ. Since neither occurs due to loss, TCP should really
2303 static inline int tcp_dupack_heuristics(struct tcp_sock
*tp
)
2305 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2308 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
2310 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
2313 static inline int tcp_head_timedout(struct sock
*sk
)
2315 struct tcp_sock
*tp
= tcp_sk(sk
);
2317 return tp
->packets_out
&&
2318 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2321 /* Linux NewReno/SACK/FACK/ECN state machine.
2322 * --------------------------------------
2324 * "Open" Normal state, no dubious events, fast path.
2325 * "Disorder" In all the respects it is "Open",
2326 * but requires a bit more attention. It is entered when
2327 * we see some SACKs or dupacks. It is split of "Open"
2328 * mainly to move some processing from fast path to slow one.
2329 * "CWR" CWND was reduced due to some Congestion Notification event.
2330 * It can be ECN, ICMP source quench, local device congestion.
2331 * "Recovery" CWND was reduced, we are fast-retransmitting.
2332 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2334 * tcp_fastretrans_alert() is entered:
2335 * - each incoming ACK, if state is not "Open"
2336 * - when arrived ACK is unusual, namely:
2341 * Counting packets in flight is pretty simple.
2343 * in_flight = packets_out - left_out + retrans_out
2345 * packets_out is SND.NXT-SND.UNA counted in packets.
2347 * retrans_out is number of retransmitted segments.
2349 * left_out is number of segments left network, but not ACKed yet.
2351 * left_out = sacked_out + lost_out
2353 * sacked_out: Packets, which arrived to receiver out of order
2354 * and hence not ACKed. With SACKs this number is simply
2355 * amount of SACKed data. Even without SACKs
2356 * it is easy to give pretty reliable estimate of this number,
2357 * counting duplicate ACKs.
2359 * lost_out: Packets lost by network. TCP has no explicit
2360 * "loss notification" feedback from network (for now).
2361 * It means that this number can be only _guessed_.
2362 * Actually, it is the heuristics to predict lossage that
2363 * distinguishes different algorithms.
2365 * F.e. after RTO, when all the queue is considered as lost,
2366 * lost_out = packets_out and in_flight = retrans_out.
2368 * Essentially, we have now two algorithms counting
2371 * FACK: It is the simplest heuristics. As soon as we decided
2372 * that something is lost, we decide that _all_ not SACKed
2373 * packets until the most forward SACK are lost. I.e.
2374 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2375 * It is absolutely correct estimate, if network does not reorder
2376 * packets. And it loses any connection to reality when reordering
2377 * takes place. We use FACK by default until reordering
2378 * is suspected on the path to this destination.
2380 * NewReno: when Recovery is entered, we assume that one segment
2381 * is lost (classic Reno). While we are in Recovery and
2382 * a partial ACK arrives, we assume that one more packet
2383 * is lost (NewReno). This heuristics are the same in NewReno
2386 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2387 * deflation etc. CWND is real congestion window, never inflated, changes
2388 * only according to classic VJ rules.
2390 * Really tricky (and requiring careful tuning) part of algorithm
2391 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2392 * The first determines the moment _when_ we should reduce CWND and,
2393 * hence, slow down forward transmission. In fact, it determines the moment
2394 * when we decide that hole is caused by loss, rather than by a reorder.
2396 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2397 * holes, caused by lost packets.
2399 * And the most logically complicated part of algorithm is undo
2400 * heuristics. We detect false retransmits due to both too early
2401 * fast retransmit (reordering) and underestimated RTO, analyzing
2402 * timestamps and D-SACKs. When we detect that some segments were
2403 * retransmitted by mistake and CWND reduction was wrong, we undo
2404 * window reduction and abort recovery phase. This logic is hidden
2405 * inside several functions named tcp_try_undo_<something>.
2408 /* This function decides, when we should leave Disordered state
2409 * and enter Recovery phase, reducing congestion window.
2411 * Main question: may we further continue forward transmission
2412 * with the same cwnd?
2414 static int tcp_time_to_recover(struct sock
*sk
)
2416 struct tcp_sock
*tp
= tcp_sk(sk
);
2419 /* Do not perform any recovery during F-RTO algorithm */
2420 if (tp
->frto_counter
)
2423 /* Trick#1: The loss is proven. */
2427 /* Not-A-Trick#2 : Classic rule... */
2428 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2431 /* Trick#3 : when we use RFC2988 timer restart, fast
2432 * retransmit can be triggered by timeout of queue head.
2434 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2437 /* Trick#4: It is still not OK... But will it be useful to delay
2440 packets_out
= tp
->packets_out
;
2441 if (packets_out
<= tp
->reordering
&&
2442 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2443 !tcp_may_send_now(sk
)) {
2444 /* We have nothing to send. This connection is limited
2445 * either by receiver window or by application.
2453 /* New heuristics: it is possible only after we switched to restart timer
2454 * each time when something is ACKed. Hence, we can detect timed out packets
2455 * during fast retransmit without falling to slow start.
2457 * Usefulness of this as is very questionable, since we should know which of
2458 * the segments is the next to timeout which is relatively expensive to find
2459 * in general case unless we add some data structure just for that. The
2460 * current approach certainly won't find the right one too often and when it
2461 * finally does find _something_ it usually marks large part of the window
2462 * right away (because a retransmission with a larger timestamp blocks the
2463 * loop from advancing). -ij
2465 static void tcp_timeout_skbs(struct sock
*sk
)
2467 struct tcp_sock
*tp
= tcp_sk(sk
);
2468 struct sk_buff
*skb
;
2470 if (!tcp_is_fack(tp
) || !tcp_head_timedout(sk
))
2473 skb
= tp
->scoreboard_skb_hint
;
2474 if (tp
->scoreboard_skb_hint
== NULL
)
2475 skb
= tcp_write_queue_head(sk
);
2477 tcp_for_write_queue_from(skb
, sk
) {
2478 if (skb
== tcp_send_head(sk
))
2480 if (!tcp_skb_timedout(sk
, skb
))
2483 tcp_skb_mark_lost(tp
, skb
);
2486 tp
->scoreboard_skb_hint
= skb
;
2488 tcp_verify_left_out(tp
);
2491 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2492 * is against sacked "cnt", otherwise it's against facked "cnt"
2494 static void tcp_mark_head_lost(struct sock
*sk
, int packets
)
2496 struct tcp_sock
*tp
= tcp_sk(sk
);
2497 struct sk_buff
*skb
;
2502 WARN_ON(packets
> tp
->packets_out
);
2503 if (tp
->lost_skb_hint
) {
2504 skb
= tp
->lost_skb_hint
;
2505 cnt
= tp
->lost_cnt_hint
;
2507 skb
= tcp_write_queue_head(sk
);
2511 tcp_for_write_queue_from(skb
, sk
) {
2512 if (skb
== tcp_send_head(sk
))
2514 /* TODO: do this better */
2515 /* this is not the most efficient way to do this... */
2516 tp
->lost_skb_hint
= skb
;
2517 tp
->lost_cnt_hint
= cnt
;
2519 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->high_seq
))
2523 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2524 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2525 cnt
+= tcp_skb_pcount(skb
);
2527 if (cnt
> packets
) {
2528 if (tcp_is_sack(tp
) || (oldcnt
>= packets
))
2531 mss
= skb_shinfo(skb
)->gso_size
;
2532 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2538 tcp_skb_mark_lost(tp
, skb
);
2540 tcp_verify_left_out(tp
);
2543 /* Account newly detected lost packet(s) */
2545 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2547 struct tcp_sock
*tp
= tcp_sk(sk
);
2549 if (tcp_is_reno(tp
)) {
2550 tcp_mark_head_lost(sk
, 1);
2551 } else if (tcp_is_fack(tp
)) {
2552 int lost
= tp
->fackets_out
- tp
->reordering
;
2555 tcp_mark_head_lost(sk
, lost
);
2557 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2558 if (sacked_upto
< fast_rexmit
)
2559 sacked_upto
= fast_rexmit
;
2560 tcp_mark_head_lost(sk
, sacked_upto
);
2563 tcp_timeout_skbs(sk
);
2566 /* CWND moderation, preventing bursts due to too big ACKs
2567 * in dubious situations.
2569 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2571 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2572 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2573 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2576 /* Lower bound on congestion window is slow start threshold
2577 * unless congestion avoidance choice decides to overide it.
2579 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2581 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2583 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2586 /* Decrease cwnd each second ack. */
2587 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2589 struct tcp_sock
*tp
= tcp_sk(sk
);
2590 int decr
= tp
->snd_cwnd_cnt
+ 1;
2592 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2593 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2594 tp
->snd_cwnd_cnt
= decr
& 1;
2597 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2598 tp
->snd_cwnd
-= decr
;
2600 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2601 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2605 /* Nothing was retransmitted or returned timestamp is less
2606 * than timestamp of the first retransmission.
2608 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
2610 return !tp
->retrans_stamp
||
2611 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2612 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2615 /* Undo procedures. */
2617 #if FASTRETRANS_DEBUG > 1
2618 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2620 struct tcp_sock
*tp
= tcp_sk(sk
);
2621 struct inet_sock
*inet
= inet_sk(sk
);
2623 if (sk
->sk_family
== AF_INET
) {
2624 printk(KERN_DEBUG
"Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2626 &inet
->daddr
, ntohs(inet
->dport
),
2627 tp
->snd_cwnd
, tcp_left_out(tp
),
2628 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2631 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
2632 else if (sk
->sk_family
== AF_INET6
) {
2633 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2634 printk(KERN_DEBUG
"Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2636 &np
->daddr
, ntohs(inet
->dport
),
2637 tp
->snd_cwnd
, tcp_left_out(tp
),
2638 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2644 #define DBGUNDO(x...) do { } while (0)
2647 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
2649 struct tcp_sock
*tp
= tcp_sk(sk
);
2651 if (tp
->prior_ssthresh
) {
2652 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2654 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2655 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2657 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2659 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2660 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2661 TCP_ECN_withdraw_cwr(tp
);
2664 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2666 tcp_moderate_cwnd(tp
);
2667 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2670 static inline int tcp_may_undo(struct tcp_sock
*tp
)
2672 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2675 /* People celebrate: "We love our President!" */
2676 static int tcp_try_undo_recovery(struct sock
*sk
)
2678 struct tcp_sock
*tp
= tcp_sk(sk
);
2680 if (tcp_may_undo(tp
)) {
2683 /* Happy end! We did not retransmit anything
2684 * or our original transmission succeeded.
2686 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2687 tcp_undo_cwr(sk
, 1);
2688 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2689 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2691 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2693 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2694 tp
->undo_marker
= 0;
2696 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2697 /* Hold old state until something *above* high_seq
2698 * is ACKed. For Reno it is MUST to prevent false
2699 * fast retransmits (RFC2582). SACK TCP is safe. */
2700 tcp_moderate_cwnd(tp
);
2703 tcp_set_ca_state(sk
, TCP_CA_Open
);
2707 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2708 static void tcp_try_undo_dsack(struct sock
*sk
)
2710 struct tcp_sock
*tp
= tcp_sk(sk
);
2712 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2713 DBGUNDO(sk
, "D-SACK");
2714 tcp_undo_cwr(sk
, 1);
2715 tp
->undo_marker
= 0;
2716 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2720 /* We can clear retrans_stamp when there are no retransmissions in the
2721 * window. It would seem that it is trivially available for us in
2722 * tp->retrans_out, however, that kind of assumptions doesn't consider
2723 * what will happen if errors occur when sending retransmission for the
2724 * second time. ...It could the that such segment has only
2725 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2726 * the head skb is enough except for some reneging corner cases that
2727 * are not worth the effort.
2729 * Main reason for all this complexity is the fact that connection dying
2730 * time now depends on the validity of the retrans_stamp, in particular,
2731 * that successive retransmissions of a segment must not advance
2732 * retrans_stamp under any conditions.
2734 static int tcp_any_retrans_done(struct sock
*sk
)
2736 struct tcp_sock
*tp
= tcp_sk(sk
);
2737 struct sk_buff
*skb
;
2739 if (tp
->retrans_out
)
2742 skb
= tcp_write_queue_head(sk
);
2743 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2749 /* Undo during fast recovery after partial ACK. */
2751 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2753 struct tcp_sock
*tp
= tcp_sk(sk
);
2754 /* Partial ACK arrived. Force Hoe's retransmit. */
2755 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2757 if (tcp_may_undo(tp
)) {
2758 /* Plain luck! Hole if filled with delayed
2759 * packet, rather than with a retransmit.
2761 if (!tcp_any_retrans_done(sk
))
2762 tp
->retrans_stamp
= 0;
2764 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2767 tcp_undo_cwr(sk
, 0);
2768 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2770 /* So... Do not make Hoe's retransmit yet.
2771 * If the first packet was delayed, the rest
2772 * ones are most probably delayed as well.
2779 /* Undo during loss recovery after partial ACK. */
2780 static int tcp_try_undo_loss(struct sock
*sk
)
2782 struct tcp_sock
*tp
= tcp_sk(sk
);
2784 if (tcp_may_undo(tp
)) {
2785 struct sk_buff
*skb
;
2786 tcp_for_write_queue(skb
, sk
) {
2787 if (skb
== tcp_send_head(sk
))
2789 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2792 tcp_clear_all_retrans_hints(tp
);
2794 DBGUNDO(sk
, "partial loss");
2796 tcp_undo_cwr(sk
, 1);
2797 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2798 inet_csk(sk
)->icsk_retransmits
= 0;
2799 tp
->undo_marker
= 0;
2800 if (tcp_is_sack(tp
))
2801 tcp_set_ca_state(sk
, TCP_CA_Open
);
2807 static inline void tcp_complete_cwr(struct sock
*sk
)
2809 struct tcp_sock
*tp
= tcp_sk(sk
);
2810 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2811 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2812 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2815 static void tcp_try_keep_open(struct sock
*sk
)
2817 struct tcp_sock
*tp
= tcp_sk(sk
);
2818 int state
= TCP_CA_Open
;
2820 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
) || tp
->undo_marker
)
2821 state
= TCP_CA_Disorder
;
2823 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2824 tcp_set_ca_state(sk
, state
);
2825 tp
->high_seq
= tp
->snd_nxt
;
2829 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2831 struct tcp_sock
*tp
= tcp_sk(sk
);
2833 tcp_verify_left_out(tp
);
2835 if (!tp
->frto_counter
&& !tcp_any_retrans_done(sk
))
2836 tp
->retrans_stamp
= 0;
2838 if (flag
& FLAG_ECE
)
2839 tcp_enter_cwr(sk
, 1);
2841 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2842 tcp_try_keep_open(sk
);
2843 tcp_moderate_cwnd(tp
);
2845 tcp_cwnd_down(sk
, flag
);
2849 static void tcp_mtup_probe_failed(struct sock
*sk
)
2851 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2853 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2854 icsk
->icsk_mtup
.probe_size
= 0;
2857 static void tcp_mtup_probe_success(struct sock
*sk
)
2859 struct tcp_sock
*tp
= tcp_sk(sk
);
2860 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2862 /* FIXME: breaks with very large cwnd */
2863 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2864 tp
->snd_cwnd
= tp
->snd_cwnd
*
2865 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2866 icsk
->icsk_mtup
.probe_size
;
2867 tp
->snd_cwnd_cnt
= 0;
2868 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2869 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2871 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2872 icsk
->icsk_mtup
.probe_size
= 0;
2873 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2876 /* Do a simple retransmit without using the backoff mechanisms in
2877 * tcp_timer. This is used for path mtu discovery.
2878 * The socket is already locked here.
2880 void tcp_simple_retransmit(struct sock
*sk
)
2882 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2883 struct tcp_sock
*tp
= tcp_sk(sk
);
2884 struct sk_buff
*skb
;
2885 unsigned int mss
= tcp_current_mss(sk
);
2886 u32 prior_lost
= tp
->lost_out
;
2888 tcp_for_write_queue(skb
, sk
) {
2889 if (skb
== tcp_send_head(sk
))
2891 if (tcp_skb_seglen(skb
) > mss
&&
2892 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2893 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2894 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2895 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2897 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2901 tcp_clear_retrans_hints_partial(tp
);
2903 if (prior_lost
== tp
->lost_out
)
2906 if (tcp_is_reno(tp
))
2907 tcp_limit_reno_sacked(tp
);
2909 tcp_verify_left_out(tp
);
2911 /* Don't muck with the congestion window here.
2912 * Reason is that we do not increase amount of _data_
2913 * in network, but units changed and effective
2914 * cwnd/ssthresh really reduced now.
2916 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2917 tp
->high_seq
= tp
->snd_nxt
;
2918 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2919 tp
->prior_ssthresh
= 0;
2920 tp
->undo_marker
= 0;
2921 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2923 tcp_xmit_retransmit_queue(sk
);
2926 /* Process an event, which can update packets-in-flight not trivially.
2927 * Main goal of this function is to calculate new estimate for left_out,
2928 * taking into account both packets sitting in receiver's buffer and
2929 * packets lost by network.
2931 * Besides that it does CWND reduction, when packet loss is detected
2932 * and changes state of machine.
2934 * It does _not_ decide what to send, it is made in function
2935 * tcp_xmit_retransmit_queue().
2937 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
, int flag
)
2939 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2940 struct tcp_sock
*tp
= tcp_sk(sk
);
2941 int is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
2942 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2943 (tcp_fackets_out(tp
) > tp
->reordering
));
2944 int fast_rexmit
= 0, mib_idx
;
2946 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2948 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2949 tp
->fackets_out
= 0;
2951 /* Now state machine starts.
2952 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2953 if (flag
& FLAG_ECE
)
2954 tp
->prior_ssthresh
= 0;
2956 /* B. In all the states check for reneging SACKs. */
2957 if (tcp_check_sack_reneging(sk
, flag
))
2960 /* C. Process data loss notification, provided it is valid. */
2961 if (tcp_is_fack(tp
) && (flag
& FLAG_DATA_LOST
) &&
2962 before(tp
->snd_una
, tp
->high_seq
) &&
2963 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2964 tp
->fackets_out
> tp
->reordering
) {
2965 tcp_mark_head_lost(sk
, tp
->fackets_out
- tp
->reordering
);
2966 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSS
);
2969 /* D. Check consistency of the current state. */
2970 tcp_verify_left_out(tp
);
2972 /* E. Check state exit conditions. State can be terminated
2973 * when high_seq is ACKed. */
2974 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2975 WARN_ON(tp
->retrans_out
!= 0);
2976 tp
->retrans_stamp
= 0;
2977 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2978 switch (icsk
->icsk_ca_state
) {
2980 icsk
->icsk_retransmits
= 0;
2981 if (tcp_try_undo_recovery(sk
))
2986 /* CWR is to be held something *above* high_seq
2987 * is ACKed for CWR bit to reach receiver. */
2988 if (tp
->snd_una
!= tp
->high_seq
) {
2989 tcp_complete_cwr(sk
);
2990 tcp_set_ca_state(sk
, TCP_CA_Open
);
2994 case TCP_CA_Disorder
:
2995 tcp_try_undo_dsack(sk
);
2996 if (!tp
->undo_marker
||
2997 /* For SACK case do not Open to allow to undo
2998 * catching for all duplicate ACKs. */
2999 tcp_is_reno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
3000 tp
->undo_marker
= 0;
3001 tcp_set_ca_state(sk
, TCP_CA_Open
);
3005 case TCP_CA_Recovery
:
3006 if (tcp_is_reno(tp
))
3007 tcp_reset_reno_sack(tp
);
3008 if (tcp_try_undo_recovery(sk
))
3010 tcp_complete_cwr(sk
);
3015 /* F. Process state. */
3016 switch (icsk
->icsk_ca_state
) {
3017 case TCP_CA_Recovery
:
3018 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
3019 if (tcp_is_reno(tp
) && is_dupack
)
3020 tcp_add_reno_sack(sk
);
3022 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
3025 if (flag
& FLAG_DATA_ACKED
)
3026 icsk
->icsk_retransmits
= 0;
3027 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
3028 tcp_reset_reno_sack(tp
);
3029 if (!tcp_try_undo_loss(sk
)) {
3030 tcp_moderate_cwnd(tp
);
3031 tcp_xmit_retransmit_queue(sk
);
3034 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
3036 /* Loss is undone; fall through to processing in Open state. */
3038 if (tcp_is_reno(tp
)) {
3039 if (flag
& FLAG_SND_UNA_ADVANCED
)
3040 tcp_reset_reno_sack(tp
);
3042 tcp_add_reno_sack(sk
);
3045 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
3046 tcp_try_undo_dsack(sk
);
3048 if (!tcp_time_to_recover(sk
)) {
3049 tcp_try_to_open(sk
, flag
);
3053 /* MTU probe failure: don't reduce cwnd */
3054 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
3055 icsk
->icsk_mtup
.probe_size
&&
3056 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
3057 tcp_mtup_probe_failed(sk
);
3058 /* Restores the reduction we did in tcp_mtup_probe() */
3060 tcp_simple_retransmit(sk
);
3064 /* Otherwise enter Recovery state */
3066 if (tcp_is_reno(tp
))
3067 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
3069 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
3071 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3073 tp
->high_seq
= tp
->snd_nxt
;
3074 tp
->prior_ssthresh
= 0;
3075 tp
->undo_marker
= tp
->snd_una
;
3076 tp
->undo_retrans
= tp
->retrans_out
;
3078 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
3079 if (!(flag
& FLAG_ECE
))
3080 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
3081 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
3082 TCP_ECN_queue_cwr(tp
);
3085 tp
->bytes_acked
= 0;
3086 tp
->snd_cwnd_cnt
= 0;
3087 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
3091 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
3092 tcp_update_scoreboard(sk
, fast_rexmit
);
3093 tcp_cwnd_down(sk
, flag
);
3094 tcp_xmit_retransmit_queue(sk
);
3097 static void tcp_valid_rtt_meas(struct sock
*sk
, u32 seq_rtt
)
3099 tcp_rtt_estimator(sk
, seq_rtt
);
3101 inet_csk(sk
)->icsk_backoff
= 0;
3104 /* Read draft-ietf-tcplw-high-performance before mucking
3105 * with this code. (Supersedes RFC1323)
3107 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
3109 /* RTTM Rule: A TSecr value received in a segment is used to
3110 * update the averaged RTT measurement only if the segment
3111 * acknowledges some new data, i.e., only if it advances the
3112 * left edge of the send window.
3114 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3115 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3117 * Changed: reset backoff as soon as we see the first valid sample.
3118 * If we do not, we get strongly overestimated rto. With timestamps
3119 * samples are accepted even from very old segments: f.e., when rtt=1
3120 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3121 * answer arrives rto becomes 120 seconds! If at least one of segments
3122 * in window is lost... Voila. --ANK (010210)
3124 struct tcp_sock
*tp
= tcp_sk(sk
);
3126 tcp_valid_rtt_meas(sk
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
3129 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
3131 /* We don't have a timestamp. Can only use
3132 * packets that are not retransmitted to determine
3133 * rtt estimates. Also, we must not reset the
3134 * backoff for rto until we get a non-retransmitted
3135 * packet. This allows us to deal with a situation
3136 * where the network delay has increased suddenly.
3137 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3140 if (flag
& FLAG_RETRANS_DATA_ACKED
)
3143 tcp_valid_rtt_meas(sk
, seq_rtt
);
3146 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
3149 const struct tcp_sock
*tp
= tcp_sk(sk
);
3150 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3151 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3152 tcp_ack_saw_tstamp(sk
, flag
);
3153 else if (seq_rtt
>= 0)
3154 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
3157 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
3159 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3160 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
3161 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
3164 /* Restart timer after forward progress on connection.
3165 * RFC2988 recommends to restart timer to now+rto.
3167 static void tcp_rearm_rto(struct sock
*sk
)
3169 struct tcp_sock
*tp
= tcp_sk(sk
);
3171 if (!tp
->packets_out
) {
3172 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3174 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3175 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3179 /* If we get here, the whole TSO packet has not been acked. */
3180 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3182 struct tcp_sock
*tp
= tcp_sk(sk
);
3185 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3187 packets_acked
= tcp_skb_pcount(skb
);
3188 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3190 packets_acked
-= tcp_skb_pcount(skb
);
3192 if (packets_acked
) {
3193 BUG_ON(tcp_skb_pcount(skb
) == 0);
3194 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3197 return packets_acked
;
3200 /* Remove acknowledged frames from the retransmission queue. If our packet
3201 * is before the ack sequence we can discard it as it's confirmed to have
3202 * arrived at the other end.
3204 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3207 struct tcp_sock
*tp
= tcp_sk(sk
);
3208 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3209 struct sk_buff
*skb
;
3210 u32 now
= tcp_time_stamp
;
3211 int fully_acked
= 1;
3214 u32 reord
= tp
->packets_out
;
3215 u32 prior_sacked
= tp
->sacked_out
;
3217 s32 ca_seq_rtt
= -1;
3218 ktime_t last_ackt
= net_invalid_timestamp();
3220 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3221 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3223 u8 sacked
= scb
->sacked
;
3225 /* Determine how many packets and what bytes were acked, tso and else */
3226 if (after(scb
->end_seq
, tp
->snd_una
)) {
3227 if (tcp_skb_pcount(skb
) == 1 ||
3228 !after(tp
->snd_una
, scb
->seq
))
3231 acked_pcount
= tcp_tso_acked(sk
, skb
);
3237 acked_pcount
= tcp_skb_pcount(skb
);
3240 if (sacked
& TCPCB_RETRANS
) {
3241 if (sacked
& TCPCB_SACKED_RETRANS
)
3242 tp
->retrans_out
-= acked_pcount
;
3243 flag
|= FLAG_RETRANS_DATA_ACKED
;
3246 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
3247 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
3249 ca_seq_rtt
= now
- scb
->when
;
3250 last_ackt
= skb
->tstamp
;
3252 seq_rtt
= ca_seq_rtt
;
3254 if (!(sacked
& TCPCB_SACKED_ACKED
))
3255 reord
= min(pkts_acked
, reord
);
3258 if (sacked
& TCPCB_SACKED_ACKED
)
3259 tp
->sacked_out
-= acked_pcount
;
3260 if (sacked
& TCPCB_LOST
)
3261 tp
->lost_out
-= acked_pcount
;
3263 tp
->packets_out
-= acked_pcount
;
3264 pkts_acked
+= acked_pcount
;
3266 /* Initial outgoing SYN's get put onto the write_queue
3267 * just like anything else we transmit. It is not
3268 * true data, and if we misinform our callers that
3269 * this ACK acks real data, we will erroneously exit
3270 * connection startup slow start one packet too
3271 * quickly. This is severely frowned upon behavior.
3273 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
3274 flag
|= FLAG_DATA_ACKED
;
3276 flag
|= FLAG_SYN_ACKED
;
3277 tp
->retrans_stamp
= 0;
3283 tcp_unlink_write_queue(skb
, sk
);
3284 sk_wmem_free_skb(sk
, skb
);
3285 tp
->scoreboard_skb_hint
= NULL
;
3286 if (skb
== tp
->retransmit_skb_hint
)
3287 tp
->retransmit_skb_hint
= NULL
;
3288 if (skb
== tp
->lost_skb_hint
)
3289 tp
->lost_skb_hint
= NULL
;
3292 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3293 tp
->snd_up
= tp
->snd_una
;
3295 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3296 flag
|= FLAG_SACK_RENEGING
;
3298 if (flag
& FLAG_ACKED
) {
3299 const struct tcp_congestion_ops
*ca_ops
3300 = inet_csk(sk
)->icsk_ca_ops
;
3302 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3303 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3304 tcp_mtup_probe_success(sk
);
3307 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
3310 if (tcp_is_reno(tp
)) {
3311 tcp_remove_reno_sacks(sk
, pkts_acked
);
3315 /* Non-retransmitted hole got filled? That's reordering */
3316 if (reord
< prior_fackets
)
3317 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3319 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3320 prior_sacked
- tp
->sacked_out
;
3321 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3324 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3326 if (ca_ops
->pkts_acked
) {
3329 /* Is the ACK triggering packet unambiguous? */
3330 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3331 /* High resolution needed and available? */
3332 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
3333 !ktime_equal(last_ackt
,
3334 net_invalid_timestamp()))
3335 rtt_us
= ktime_us_delta(ktime_get_real(),
3337 else if (ca_seq_rtt
> 0)
3338 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
3341 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
3345 #if FASTRETRANS_DEBUG > 0
3346 WARN_ON((int)tp
->sacked_out
< 0);
3347 WARN_ON((int)tp
->lost_out
< 0);
3348 WARN_ON((int)tp
->retrans_out
< 0);
3349 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3350 icsk
= inet_csk(sk
);
3352 printk(KERN_DEBUG
"Leak l=%u %d\n",
3353 tp
->lost_out
, icsk
->icsk_ca_state
);
3356 if (tp
->sacked_out
) {
3357 printk(KERN_DEBUG
"Leak s=%u %d\n",
3358 tp
->sacked_out
, icsk
->icsk_ca_state
);
3361 if (tp
->retrans_out
) {
3362 printk(KERN_DEBUG
"Leak r=%u %d\n",
3363 tp
->retrans_out
, icsk
->icsk_ca_state
);
3364 tp
->retrans_out
= 0;
3371 static void tcp_ack_probe(struct sock
*sk
)
3373 const struct tcp_sock
*tp
= tcp_sk(sk
);
3374 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3376 /* Was it a usable window open? */
3378 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3379 icsk
->icsk_backoff
= 0;
3380 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3381 /* Socket must be waked up by subsequent tcp_data_snd_check().
3382 * This function is not for random using!
3385 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3386 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3391 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3393 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3394 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
3397 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3399 const struct tcp_sock
*tp
= tcp_sk(sk
);
3400 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3401 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
3404 /* Check that window update is acceptable.
3405 * The function assumes that snd_una<=ack<=snd_next.
3407 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
3408 const u32 ack
, const u32 ack_seq
,
3411 return (after(ack
, tp
->snd_una
) ||
3412 after(ack_seq
, tp
->snd_wl1
) ||
3413 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
3416 /* Update our send window.
3418 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3419 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3421 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
3424 struct tcp_sock
*tp
= tcp_sk(sk
);
3426 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3428 if (likely(!tcp_hdr(skb
)->syn
))
3429 nwin
<<= tp
->rx_opt
.snd_wscale
;
3431 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3432 flag
|= FLAG_WIN_UPDATE
;
3433 tcp_update_wl(tp
, ack_seq
);
3435 if (tp
->snd_wnd
!= nwin
) {
3438 /* Note, it is the only place, where
3439 * fast path is recovered for sending TCP.
3442 tcp_fast_path_check(sk
);
3444 if (nwin
> tp
->max_window
) {
3445 tp
->max_window
= nwin
;
3446 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3456 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3457 * continue in congestion avoidance.
3459 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3461 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3462 tp
->snd_cwnd_cnt
= 0;
3463 tp
->bytes_acked
= 0;
3464 TCP_ECN_queue_cwr(tp
);
3465 tcp_moderate_cwnd(tp
);
3468 /* A conservative spurious RTO response algorithm: reduce cwnd using
3469 * rate halving and continue in congestion avoidance.
3471 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3473 tcp_enter_cwr(sk
, 0);
3476 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3478 if (flag
& FLAG_ECE
)
3479 tcp_ratehalving_spur_to_response(sk
);
3481 tcp_undo_cwr(sk
, 1);
3484 /* F-RTO spurious RTO detection algorithm (RFC4138)
3486 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3487 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3488 * window (but not to or beyond highest sequence sent before RTO):
3489 * On First ACK, send two new segments out.
3490 * On Second ACK, RTO was likely spurious. Do spurious response (response
3491 * algorithm is not part of the F-RTO detection algorithm
3492 * given in RFC4138 but can be selected separately).
3493 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3494 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3495 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3496 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3498 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3499 * original window even after we transmit two new data segments.
3502 * on first step, wait until first cumulative ACK arrives, then move to
3503 * the second step. In second step, the next ACK decides.
3505 * F-RTO is implemented (mainly) in four functions:
3506 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3507 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3508 * called when tcp_use_frto() showed green light
3509 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3510 * - tcp_enter_frto_loss() is called if there is not enough evidence
3511 * to prove that the RTO is indeed spurious. It transfers the control
3512 * from F-RTO to the conventional RTO recovery
3514 static int tcp_process_frto(struct sock
*sk
, int flag
)
3516 struct tcp_sock
*tp
= tcp_sk(sk
);
3518 tcp_verify_left_out(tp
);
3520 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3521 if (flag
& FLAG_DATA_ACKED
)
3522 inet_csk(sk
)->icsk_retransmits
= 0;
3524 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3525 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3526 tp
->undo_marker
= 0;
3528 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3529 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3533 if (!tcp_is_sackfrto(tp
)) {
3534 /* RFC4138 shortcoming in step 2; should also have case c):
3535 * ACK isn't duplicate nor advances window, e.g., opposite dir
3538 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3541 if (!(flag
& FLAG_DATA_ACKED
)) {
3542 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3547 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3548 /* Prevent sending of new data. */
3549 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3550 tcp_packets_in_flight(tp
));
3554 if ((tp
->frto_counter
>= 2) &&
3555 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3556 ((flag
& FLAG_DATA_SACKED
) &&
3557 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3558 /* RFC4138 shortcoming (see comment above) */
3559 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3560 (flag
& FLAG_NOT_DUP
))
3563 tcp_enter_frto_loss(sk
, 3, flag
);
3568 if (tp
->frto_counter
== 1) {
3569 /* tcp_may_send_now needs to see updated state */
3570 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3571 tp
->frto_counter
= 2;
3573 if (!tcp_may_send_now(sk
))
3574 tcp_enter_frto_loss(sk
, 2, flag
);
3578 switch (sysctl_tcp_frto_response
) {
3580 tcp_undo_spur_to_response(sk
, flag
);
3583 tcp_conservative_spur_to_response(tp
);
3586 tcp_ratehalving_spur_to_response(sk
);
3589 tp
->frto_counter
= 0;
3590 tp
->undo_marker
= 0;
3591 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSPURIOUSRTOS
);
3596 /* This routine deals with incoming acks, but not outgoing ones. */
3597 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
3599 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3600 struct tcp_sock
*tp
= tcp_sk(sk
);
3601 u32 prior_snd_una
= tp
->snd_una
;
3602 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3603 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3604 u32 prior_in_flight
;
3609 /* If the ack is older than previous acks
3610 * then we can probably ignore it.
3612 if (before(ack
, prior_snd_una
))
3615 /* If the ack includes data we haven't sent yet, discard
3616 * this segment (RFC793 Section 3.9).
3618 if (after(ack
, tp
->snd_nxt
))
3621 if (after(ack
, prior_snd_una
))
3622 flag
|= FLAG_SND_UNA_ADVANCED
;
3624 if (sysctl_tcp_abc
) {
3625 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3626 tp
->bytes_acked
+= ack
- prior_snd_una
;
3627 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3628 /* we assume just one segment left network */
3629 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3633 prior_fackets
= tp
->fackets_out
;
3634 prior_in_flight
= tcp_packets_in_flight(tp
);
3636 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3637 /* Window is constant, pure forward advance.
3638 * No more checks are required.
3639 * Note, we use the fact that SND.UNA>=SND.WL2.
3641 tcp_update_wl(tp
, ack_seq
);
3643 flag
|= FLAG_WIN_UPDATE
;
3645 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3647 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3649 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3652 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3654 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3656 if (TCP_SKB_CB(skb
)->sacked
)
3657 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3659 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3662 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3665 /* We passed data and got it acked, remove any soft error
3666 * log. Something worked...
3668 sk
->sk_err_soft
= 0;
3669 icsk
->icsk_probes_out
= 0;
3670 tp
->rcv_tstamp
= tcp_time_stamp
;
3671 prior_packets
= tp
->packets_out
;
3675 /* See if we can take anything off of the retransmit queue. */
3676 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
);
3678 if (tp
->frto_counter
)
3679 frto_cwnd
= tcp_process_frto(sk
, flag
);
3680 /* Guarantee sacktag reordering detection against wrap-arounds */
3681 if (before(tp
->frto_highmark
, tp
->snd_una
))
3682 tp
->frto_highmark
= 0;
3684 if (tcp_ack_is_dubious(sk
, flag
)) {
3685 /* Advance CWND, if state allows this. */
3686 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3687 tcp_may_raise_cwnd(sk
, flag
))
3688 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3689 tcp_fastretrans_alert(sk
, prior_packets
- tp
->packets_out
,
3692 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3693 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3696 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3697 dst_confirm(sk
->sk_dst_cache
);
3702 /* If this ack opens up a zero window, clear backoff. It was
3703 * being used to time the probes, and is probably far higher than
3704 * it needs to be for normal retransmission.
3706 if (tcp_send_head(sk
))
3711 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3715 if (TCP_SKB_CB(skb
)->sacked
) {
3716 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3717 if (icsk
->icsk_ca_state
== TCP_CA_Open
)
3718 tcp_try_keep_open(sk
);
3721 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3725 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3726 * But, this can also be called on packets in the established flow when
3727 * the fast version below fails.
3729 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3730 u8
**hvpp
, int estab
, struct dst_entry
*dst
)
3733 struct tcphdr
*th
= tcp_hdr(skb
);
3734 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3736 ptr
= (unsigned char *)(th
+ 1);
3737 opt_rx
->saw_tstamp
= 0;
3739 while (length
> 0) {
3740 int opcode
= *ptr
++;
3746 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3751 if (opsize
< 2) /* "silly options" */
3753 if (opsize
> length
)
3754 return; /* don't parse partial options */
3757 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3758 u16 in_mss
= get_unaligned_be16(ptr
);
3760 if (opt_rx
->user_mss
&&
3761 opt_rx
->user_mss
< in_mss
)
3762 in_mss
= opt_rx
->user_mss
;
3763 opt_rx
->mss_clamp
= in_mss
;
3768 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3769 !estab
&& sysctl_tcp_window_scaling
&&
3770 !dst_feature(dst
, RTAX_FEATURE_NO_WSCALE
)) {
3771 __u8 snd_wscale
= *(__u8
*)ptr
;
3772 opt_rx
->wscale_ok
= 1;
3773 if (snd_wscale
> 14) {
3774 if (net_ratelimit())
3775 printk(KERN_INFO
"tcp_parse_options: Illegal window "
3776 "scaling value %d >14 received.\n",
3780 opt_rx
->snd_wscale
= snd_wscale
;
3783 case TCPOPT_TIMESTAMP
:
3784 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3785 ((estab
&& opt_rx
->tstamp_ok
) ||
3786 (!estab
&& sysctl_tcp_timestamps
&&
3787 !dst_feature(dst
, RTAX_FEATURE_NO_TSTAMP
)))) {
3788 opt_rx
->saw_tstamp
= 1;
3789 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3790 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3793 case TCPOPT_SACK_PERM
:
3794 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3795 !estab
&& sysctl_tcp_sack
&&
3796 !dst_feature(dst
, RTAX_FEATURE_NO_SACK
)) {
3797 opt_rx
->sack_ok
= 1;
3798 tcp_sack_reset(opt_rx
);
3803 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3804 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3806 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3809 #ifdef CONFIG_TCP_MD5SIG
3812 * The MD5 Hash has already been
3813 * checked (see tcp_v{4,6}_do_rcv()).
3818 /* This option is variable length.
3821 case TCPOLEN_COOKIE_BASE
:
3822 /* not yet implemented */
3824 case TCPOLEN_COOKIE_PAIR
:
3825 /* not yet implemented */
3827 case TCPOLEN_COOKIE_MIN
+0:
3828 case TCPOLEN_COOKIE_MIN
+2:
3829 case TCPOLEN_COOKIE_MIN
+4:
3830 case TCPOLEN_COOKIE_MIN
+6:
3831 case TCPOLEN_COOKIE_MAX
:
3832 /* 16-bit multiple */
3833 opt_rx
->cookie_plus
= opsize
;
3848 static int tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, struct tcphdr
*th
)
3850 __be32
*ptr
= (__be32
*)(th
+ 1);
3852 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3853 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3854 tp
->rx_opt
.saw_tstamp
= 1;
3856 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3858 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3864 /* Fast parse options. This hopes to only see timestamps.
3865 * If it is wrong it falls back on tcp_parse_options().
3867 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
3868 struct tcp_sock
*tp
, u8
**hvpp
)
3870 /* In the spirit of fast parsing, compare doff directly to constant
3871 * values. Because equality is used, short doff can be ignored here.
3873 if (th
->doff
== (sizeof(*th
) / 4)) {
3874 tp
->rx_opt
.saw_tstamp
= 0;
3876 } else if (tp
->rx_opt
.tstamp_ok
&&
3877 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3878 if (tcp_parse_aligned_timestamp(tp
, th
))
3881 tcp_parse_options(skb
, &tp
->rx_opt
, hvpp
, 1, NULL
);
3885 #ifdef CONFIG_TCP_MD5SIG
3887 * Parse MD5 Signature option
3889 u8
*tcp_parse_md5sig_option(struct tcphdr
*th
)
3891 int length
= (th
->doff
<< 2) - sizeof (*th
);
3892 u8
*ptr
= (u8
*)(th
+ 1);
3894 /* If the TCP option is too short, we can short cut */
3895 if (length
< TCPOLEN_MD5SIG
)
3898 while (length
> 0) {
3899 int opcode
= *ptr
++;
3910 if (opsize
< 2 || opsize
> length
)
3912 if (opcode
== TCPOPT_MD5SIG
)
3922 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
3924 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3925 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3928 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3930 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3931 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3932 * extra check below makes sure this can only happen
3933 * for pure ACK frames. -DaveM
3935 * Not only, also it occurs for expired timestamps.
3938 if (tcp_paws_check(&tp
->rx_opt
, 0))
3939 tcp_store_ts_recent(tp
);
3943 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3945 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3946 * it can pass through stack. So, the following predicate verifies that
3947 * this segment is not used for anything but congestion avoidance or
3948 * fast retransmit. Moreover, we even are able to eliminate most of such
3949 * second order effects, if we apply some small "replay" window (~RTO)
3950 * to timestamp space.
3952 * All these measures still do not guarantee that we reject wrapped ACKs
3953 * on networks with high bandwidth, when sequence space is recycled fastly,
3954 * but it guarantees that such events will be very rare and do not affect
3955 * connection seriously. This doesn't look nice, but alas, PAWS is really
3958 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3959 * states that events when retransmit arrives after original data are rare.
3960 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3961 * the biggest problem on large power networks even with minor reordering.
3962 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3963 * up to bandwidth of 18Gigabit/sec. 8) ]
3966 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3968 struct tcp_sock
*tp
= tcp_sk(sk
);
3969 struct tcphdr
*th
= tcp_hdr(skb
);
3970 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3971 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3973 return (/* 1. Pure ACK with correct sequence number. */
3974 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3976 /* 2. ... and duplicate ACK. */
3977 ack
== tp
->snd_una
&&
3979 /* 3. ... and does not update window. */
3980 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3982 /* 4. ... and sits in replay window. */
3983 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3986 static inline int tcp_paws_discard(const struct sock
*sk
,
3987 const struct sk_buff
*skb
)
3989 const struct tcp_sock
*tp
= tcp_sk(sk
);
3991 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3992 !tcp_disordered_ack(sk
, skb
);
3995 /* Check segment sequence number for validity.
3997 * Segment controls are considered valid, if the segment
3998 * fits to the window after truncation to the window. Acceptability
3999 * of data (and SYN, FIN, of course) is checked separately.
4000 * See tcp_data_queue(), for example.
4002 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4003 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4004 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4005 * (borrowed from freebsd)
4008 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
4010 return !before(end_seq
, tp
->rcv_wup
) &&
4011 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
4014 /* When we get a reset we do this. */
4015 static void tcp_reset(struct sock
*sk
)
4017 /* We want the right error as BSD sees it (and indeed as we do). */
4018 switch (sk
->sk_state
) {
4020 sk
->sk_err
= ECONNREFUSED
;
4022 case TCP_CLOSE_WAIT
:
4028 sk
->sk_err
= ECONNRESET
;
4031 if (!sock_flag(sk
, SOCK_DEAD
))
4032 sk
->sk_error_report(sk
);
4038 * Process the FIN bit. This now behaves as it is supposed to work
4039 * and the FIN takes effect when it is validly part of sequence
4040 * space. Not before when we get holes.
4042 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4043 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4046 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4047 * close and we go into CLOSING (and later onto TIME-WAIT)
4049 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4051 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
4053 struct tcp_sock
*tp
= tcp_sk(sk
);
4055 inet_csk_schedule_ack(sk
);
4057 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4058 sock_set_flag(sk
, SOCK_DONE
);
4060 switch (sk
->sk_state
) {
4062 case TCP_ESTABLISHED
:
4063 /* Move to CLOSE_WAIT */
4064 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4065 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4068 case TCP_CLOSE_WAIT
:
4070 /* Received a retransmission of the FIN, do
4075 /* RFC793: Remain in the LAST-ACK state. */
4079 /* This case occurs when a simultaneous close
4080 * happens, we must ack the received FIN and
4081 * enter the CLOSING state.
4084 tcp_set_state(sk
, TCP_CLOSING
);
4087 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4089 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4092 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4093 * cases we should never reach this piece of code.
4095 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
4096 __func__
, sk
->sk_state
);
4100 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4101 * Probably, we should reset in this case. For now drop them.
4103 __skb_queue_purge(&tp
->out_of_order_queue
);
4104 if (tcp_is_sack(tp
))
4105 tcp_sack_reset(&tp
->rx_opt
);
4108 if (!sock_flag(sk
, SOCK_DEAD
)) {
4109 sk
->sk_state_change(sk
);
4111 /* Do not send POLL_HUP for half duplex close. */
4112 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4113 sk
->sk_state
== TCP_CLOSE
)
4114 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4116 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4120 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4123 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4124 if (before(seq
, sp
->start_seq
))
4125 sp
->start_seq
= seq
;
4126 if (after(end_seq
, sp
->end_seq
))
4127 sp
->end_seq
= end_seq
;
4133 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4135 struct tcp_sock
*tp
= tcp_sk(sk
);
4136 struct dst_entry
*dst
= __sk_dst_get(sk
);
4138 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
&&
4139 !dst_feature(dst
, RTAX_FEATURE_NO_DSACK
)) {
4142 if (before(seq
, tp
->rcv_nxt
))
4143 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4145 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4147 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4149 tp
->rx_opt
.dsack
= 1;
4150 tp
->duplicate_sack
[0].start_seq
= seq
;
4151 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4155 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4157 struct tcp_sock
*tp
= tcp_sk(sk
);
4159 if (!tp
->rx_opt
.dsack
)
4160 tcp_dsack_set(sk
, seq
, end_seq
);
4162 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4165 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
4167 struct tcp_sock
*tp
= tcp_sk(sk
);
4168 struct dst_entry
*dst
= __sk_dst_get(sk
);
4170 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4171 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4172 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4173 tcp_enter_quickack_mode(sk
);
4175 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
&&
4176 !dst_feature(dst
, RTAX_FEATURE_NO_DSACK
)) {
4177 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4179 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4180 end_seq
= tp
->rcv_nxt
;
4181 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4188 /* These routines update the SACK block as out-of-order packets arrive or
4189 * in-order packets close up the sequence space.
4191 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4194 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4195 struct tcp_sack_block
*swalk
= sp
+ 1;
4197 /* See if the recent change to the first SACK eats into
4198 * or hits the sequence space of other SACK blocks, if so coalesce.
4200 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4201 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4204 /* Zap SWALK, by moving every further SACK up by one slot.
4205 * Decrease num_sacks.
4207 tp
->rx_opt
.num_sacks
--;
4208 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4212 this_sack
++, swalk
++;
4216 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4218 struct tcp_sock
*tp
= tcp_sk(sk
);
4219 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4220 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4226 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4227 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4228 /* Rotate this_sack to the first one. */
4229 for (; this_sack
> 0; this_sack
--, sp
--)
4230 swap(*sp
, *(sp
- 1));
4232 tcp_sack_maybe_coalesce(tp
);
4237 /* Could not find an adjacent existing SACK, build a new one,
4238 * put it at the front, and shift everyone else down. We
4239 * always know there is at least one SACK present already here.
4241 * If the sack array is full, forget about the last one.
4243 if (this_sack
>= TCP_NUM_SACKS
) {
4245 tp
->rx_opt
.num_sacks
--;
4248 for (; this_sack
> 0; this_sack
--, sp
--)
4252 /* Build the new head SACK, and we're done. */
4253 sp
->start_seq
= seq
;
4254 sp
->end_seq
= end_seq
;
4255 tp
->rx_opt
.num_sacks
++;
4258 /* RCV.NXT advances, some SACKs should be eaten. */
4260 static void tcp_sack_remove(struct tcp_sock
*tp
)
4262 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4263 int num_sacks
= tp
->rx_opt
.num_sacks
;
4266 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4267 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4268 tp
->rx_opt
.num_sacks
= 0;
4272 for (this_sack
= 0; this_sack
< num_sacks
;) {
4273 /* Check if the start of the sack is covered by RCV.NXT. */
4274 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4277 /* RCV.NXT must cover all the block! */
4278 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4280 /* Zap this SACK, by moving forward any other SACKS. */
4281 for (i
=this_sack
+1; i
< num_sacks
; i
++)
4282 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4289 tp
->rx_opt
.num_sacks
= num_sacks
;
4292 /* This one checks to see if we can put data from the
4293 * out_of_order queue into the receive_queue.
4295 static void tcp_ofo_queue(struct sock
*sk
)
4297 struct tcp_sock
*tp
= tcp_sk(sk
);
4298 __u32 dsack_high
= tp
->rcv_nxt
;
4299 struct sk_buff
*skb
;
4301 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4302 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4305 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4306 __u32 dsack
= dsack_high
;
4307 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4308 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4309 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4312 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4313 SOCK_DEBUG(sk
, "ofo packet was already received \n");
4314 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4318 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4319 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4320 TCP_SKB_CB(skb
)->end_seq
);
4322 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4323 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4324 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4325 if (tcp_hdr(skb
)->fin
)
4326 tcp_fin(skb
, sk
, tcp_hdr(skb
));
4330 static int tcp_prune_ofo_queue(struct sock
*sk
);
4331 static int tcp_prune_queue(struct sock
*sk
);
4333 static inline int tcp_try_rmem_schedule(struct sock
*sk
, unsigned int size
)
4335 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4336 !sk_rmem_schedule(sk
, size
)) {
4338 if (tcp_prune_queue(sk
) < 0)
4341 if (!sk_rmem_schedule(sk
, size
)) {
4342 if (!tcp_prune_ofo_queue(sk
))
4345 if (!sk_rmem_schedule(sk
, size
))
4352 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4354 struct tcphdr
*th
= tcp_hdr(skb
);
4355 struct tcp_sock
*tp
= tcp_sk(sk
);
4358 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4361 __skb_pull(skb
, th
->doff
* 4);
4363 TCP_ECN_accept_cwr(tp
, skb
);
4365 tp
->rx_opt
.dsack
= 0;
4367 /* Queue data for delivery to the user.
4368 * Packets in sequence go to the receive queue.
4369 * Out of sequence packets to the out_of_order_queue.
4371 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4372 if (tcp_receive_window(tp
) == 0)
4375 /* Ok. In sequence. In window. */
4376 if (tp
->ucopy
.task
== current
&&
4377 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4378 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4379 int chunk
= min_t(unsigned int, skb
->len
,
4382 __set_current_state(TASK_RUNNING
);
4385 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4386 tp
->ucopy
.len
-= chunk
;
4387 tp
->copied_seq
+= chunk
;
4388 eaten
= (chunk
== skb
->len
&& !th
->fin
);
4389 tcp_rcv_space_adjust(sk
);
4397 tcp_try_rmem_schedule(sk
, skb
->truesize
))
4400 skb_set_owner_r(skb
, sk
);
4401 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4403 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4405 tcp_event_data_recv(sk
, skb
);
4407 tcp_fin(skb
, sk
, th
);
4409 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4412 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4413 * gap in queue is filled.
4415 if (skb_queue_empty(&tp
->out_of_order_queue
))
4416 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4419 if (tp
->rx_opt
.num_sacks
)
4420 tcp_sack_remove(tp
);
4422 tcp_fast_path_check(sk
);
4426 else if (!sock_flag(sk
, SOCK_DEAD
))
4427 sk
->sk_data_ready(sk
, 0);
4431 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4432 /* A retransmit, 2nd most common case. Force an immediate ack. */
4433 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4434 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4437 tcp_enter_quickack_mode(sk
);
4438 inet_csk_schedule_ack(sk
);
4444 /* Out of window. F.e. zero window probe. */
4445 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4448 tcp_enter_quickack_mode(sk
);
4450 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4451 /* Partial packet, seq < rcv_next < end_seq */
4452 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4453 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4454 TCP_SKB_CB(skb
)->end_seq
);
4456 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4458 /* If window is closed, drop tail of packet. But after
4459 * remembering D-SACK for its head made in previous line.
4461 if (!tcp_receive_window(tp
))
4466 TCP_ECN_check_ce(tp
, skb
);
4468 if (tcp_try_rmem_schedule(sk
, skb
->truesize
))
4471 /* Disable header prediction. */
4473 inet_csk_schedule_ack(sk
);
4475 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4476 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4478 skb_set_owner_r(skb
, sk
);
4480 if (!skb_peek(&tp
->out_of_order_queue
)) {
4481 /* Initial out of order segment, build 1 SACK. */
4482 if (tcp_is_sack(tp
)) {
4483 tp
->rx_opt
.num_sacks
= 1;
4484 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4485 tp
->selective_acks
[0].end_seq
=
4486 TCP_SKB_CB(skb
)->end_seq
;
4488 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4490 struct sk_buff
*skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4491 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4492 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4494 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4495 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4497 if (!tp
->rx_opt
.num_sacks
||
4498 tp
->selective_acks
[0].end_seq
!= seq
)
4501 /* Common case: data arrive in order after hole. */
4502 tp
->selective_acks
[0].end_seq
= end_seq
;
4506 /* Find place to insert this segment. */
4508 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4510 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4514 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4517 /* Do skb overlap to previous one? */
4518 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4519 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4520 /* All the bits are present. Drop. */
4522 tcp_dsack_set(sk
, seq
, end_seq
);
4525 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4526 /* Partial overlap. */
4527 tcp_dsack_set(sk
, seq
,
4528 TCP_SKB_CB(skb1
)->end_seq
);
4530 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4534 skb1
= skb_queue_prev(
4535 &tp
->out_of_order_queue
,
4540 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4542 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4544 /* And clean segments covered by new one as whole. */
4545 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4546 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4548 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4550 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4551 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4555 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4556 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4557 TCP_SKB_CB(skb1
)->end_seq
);
4562 if (tcp_is_sack(tp
))
4563 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4567 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4568 struct sk_buff_head
*list
)
4570 struct sk_buff
*next
= NULL
;
4572 if (!skb_queue_is_last(list
, skb
))
4573 next
= skb_queue_next(list
, skb
);
4575 __skb_unlink(skb
, list
);
4577 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4582 /* Collapse contiguous sequence of skbs head..tail with
4583 * sequence numbers start..end.
4585 * If tail is NULL, this means until the end of the list.
4587 * Segments with FIN/SYN are not collapsed (only because this
4591 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4592 struct sk_buff
*head
, struct sk_buff
*tail
,
4595 struct sk_buff
*skb
, *n
;
4598 /* First, check that queue is collapsible and find
4599 * the point where collapsing can be useful. */
4603 skb_queue_walk_from_safe(list
, skb
, n
) {
4606 /* No new bits? It is possible on ofo queue. */
4607 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4608 skb
= tcp_collapse_one(sk
, skb
, list
);
4614 /* The first skb to collapse is:
4616 * - bloated or contains data before "start" or
4617 * overlaps to the next one.
4619 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4620 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4621 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4622 end_of_skbs
= false;
4626 if (!skb_queue_is_last(list
, skb
)) {
4627 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4629 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4630 end_of_skbs
= false;
4635 /* Decided to skip this, advance start seq. */
4636 start
= TCP_SKB_CB(skb
)->end_seq
;
4638 if (end_of_skbs
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4641 while (before(start
, end
)) {
4642 struct sk_buff
*nskb
;
4643 unsigned int header
= skb_headroom(skb
);
4644 int copy
= SKB_MAX_ORDER(header
, 0);
4646 /* Too big header? This can happen with IPv6. */
4649 if (end
- start
< copy
)
4651 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4655 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4656 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4658 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4660 skb_reserve(nskb
, header
);
4661 memcpy(nskb
->head
, skb
->head
, header
);
4662 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4663 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4664 __skb_queue_before(list
, skb
, nskb
);
4665 skb_set_owner_r(nskb
, sk
);
4667 /* Copy data, releasing collapsed skbs. */
4669 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4670 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4674 size
= min(copy
, size
);
4675 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4677 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4681 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4682 skb
= tcp_collapse_one(sk
, skb
, list
);
4685 tcp_hdr(skb
)->syn
||
4693 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4694 * and tcp_collapse() them until all the queue is collapsed.
4696 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4698 struct tcp_sock
*tp
= tcp_sk(sk
);
4699 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4700 struct sk_buff
*head
;
4706 start
= TCP_SKB_CB(skb
)->seq
;
4707 end
= TCP_SKB_CB(skb
)->end_seq
;
4711 struct sk_buff
*next
= NULL
;
4713 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4714 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4717 /* Segment is terminated when we see gap or when
4718 * we are at the end of all the queue. */
4720 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4721 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4722 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4723 head
, skb
, start
, end
);
4727 /* Start new segment */
4728 start
= TCP_SKB_CB(skb
)->seq
;
4729 end
= TCP_SKB_CB(skb
)->end_seq
;
4731 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4732 start
= TCP_SKB_CB(skb
)->seq
;
4733 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4734 end
= TCP_SKB_CB(skb
)->end_seq
;
4740 * Purge the out-of-order queue.
4741 * Return true if queue was pruned.
4743 static int tcp_prune_ofo_queue(struct sock
*sk
)
4745 struct tcp_sock
*tp
= tcp_sk(sk
);
4748 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4749 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4750 __skb_queue_purge(&tp
->out_of_order_queue
);
4752 /* Reset SACK state. A conforming SACK implementation will
4753 * do the same at a timeout based retransmit. When a connection
4754 * is in a sad state like this, we care only about integrity
4755 * of the connection not performance.
4757 if (tp
->rx_opt
.sack_ok
)
4758 tcp_sack_reset(&tp
->rx_opt
);
4765 /* Reduce allocated memory if we can, trying to get
4766 * the socket within its memory limits again.
4768 * Return less than zero if we should start dropping frames
4769 * until the socket owning process reads some of the data
4770 * to stabilize the situation.
4772 static int tcp_prune_queue(struct sock
*sk
)
4774 struct tcp_sock
*tp
= tcp_sk(sk
);
4776 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4778 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4780 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4781 tcp_clamp_window(sk
);
4782 else if (tcp_memory_pressure
)
4783 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4785 tcp_collapse_ofo_queue(sk
);
4786 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4787 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4788 skb_peek(&sk
->sk_receive_queue
),
4790 tp
->copied_seq
, tp
->rcv_nxt
);
4793 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4796 /* Collapsing did not help, destructive actions follow.
4797 * This must not ever occur. */
4799 tcp_prune_ofo_queue(sk
);
4801 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4804 /* If we are really being abused, tell the caller to silently
4805 * drop receive data on the floor. It will get retransmitted
4806 * and hopefully then we'll have sufficient space.
4808 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4810 /* Massive buffer overcommit. */
4815 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4816 * As additional protections, we do not touch cwnd in retransmission phases,
4817 * and if application hit its sndbuf limit recently.
4819 void tcp_cwnd_application_limited(struct sock
*sk
)
4821 struct tcp_sock
*tp
= tcp_sk(sk
);
4823 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4824 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4825 /* Limited by application or receiver window. */
4826 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4827 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4828 if (win_used
< tp
->snd_cwnd
) {
4829 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4830 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4832 tp
->snd_cwnd_used
= 0;
4834 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4837 static int tcp_should_expand_sndbuf(struct sock
*sk
)
4839 struct tcp_sock
*tp
= tcp_sk(sk
);
4841 /* If the user specified a specific send buffer setting, do
4844 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4847 /* If we are under global TCP memory pressure, do not expand. */
4848 if (tcp_memory_pressure
)
4851 /* If we are under soft global TCP memory pressure, do not expand. */
4852 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
4855 /* If we filled the congestion window, do not expand. */
4856 if (tp
->packets_out
>= tp
->snd_cwnd
)
4862 /* When incoming ACK allowed to free some skb from write_queue,
4863 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4864 * on the exit from tcp input handler.
4866 * PROBLEM: sndbuf expansion does not work well with largesend.
4868 static void tcp_new_space(struct sock
*sk
)
4870 struct tcp_sock
*tp
= tcp_sk(sk
);
4872 if (tcp_should_expand_sndbuf(sk
)) {
4873 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
4874 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
4875 int demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4876 tp
->reordering
+ 1);
4877 sndmem
*= 2 * demanded
;
4878 if (sndmem
> sk
->sk_sndbuf
)
4879 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4880 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4883 sk
->sk_write_space(sk
);
4886 static void tcp_check_space(struct sock
*sk
)
4888 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4889 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4890 if (sk
->sk_socket
&&
4891 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4896 static inline void tcp_data_snd_check(struct sock
*sk
)
4898 tcp_push_pending_frames(sk
);
4899 tcp_check_space(sk
);
4903 * Check if sending an ack is needed.
4905 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4907 struct tcp_sock
*tp
= tcp_sk(sk
);
4909 /* More than one full frame received... */
4910 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4911 /* ... and right edge of window advances far enough.
4912 * (tcp_recvmsg() will send ACK otherwise). Or...
4914 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4915 /* We ACK each frame or... */
4916 tcp_in_quickack_mode(sk
) ||
4917 /* We have out of order data. */
4918 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4919 /* Then ack it now */
4922 /* Else, send delayed ack. */
4923 tcp_send_delayed_ack(sk
);
4927 static inline void tcp_ack_snd_check(struct sock
*sk
)
4929 if (!inet_csk_ack_scheduled(sk
)) {
4930 /* We sent a data segment already. */
4933 __tcp_ack_snd_check(sk
, 1);
4937 * This routine is only called when we have urgent data
4938 * signaled. Its the 'slow' part of tcp_urg. It could be
4939 * moved inline now as tcp_urg is only called from one
4940 * place. We handle URGent data wrong. We have to - as
4941 * BSD still doesn't use the correction from RFC961.
4942 * For 1003.1g we should support a new option TCP_STDURG to permit
4943 * either form (or just set the sysctl tcp_stdurg).
4946 static void tcp_check_urg(struct sock
*sk
, struct tcphdr
*th
)
4948 struct tcp_sock
*tp
= tcp_sk(sk
);
4949 u32 ptr
= ntohs(th
->urg_ptr
);
4951 if (ptr
&& !sysctl_tcp_stdurg
)
4953 ptr
+= ntohl(th
->seq
);
4955 /* Ignore urgent data that we've already seen and read. */
4956 if (after(tp
->copied_seq
, ptr
))
4959 /* Do not replay urg ptr.
4961 * NOTE: interesting situation not covered by specs.
4962 * Misbehaving sender may send urg ptr, pointing to segment,
4963 * which we already have in ofo queue. We are not able to fetch
4964 * such data and will stay in TCP_URG_NOTYET until will be eaten
4965 * by recvmsg(). Seems, we are not obliged to handle such wicked
4966 * situations. But it is worth to think about possibility of some
4967 * DoSes using some hypothetical application level deadlock.
4969 if (before(ptr
, tp
->rcv_nxt
))
4972 /* Do we already have a newer (or duplicate) urgent pointer? */
4973 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4976 /* Tell the world about our new urgent pointer. */
4979 /* We may be adding urgent data when the last byte read was
4980 * urgent. To do this requires some care. We cannot just ignore
4981 * tp->copied_seq since we would read the last urgent byte again
4982 * as data, nor can we alter copied_seq until this data arrives
4983 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4985 * NOTE. Double Dutch. Rendering to plain English: author of comment
4986 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4987 * and expect that both A and B disappear from stream. This is _wrong_.
4988 * Though this happens in BSD with high probability, this is occasional.
4989 * Any application relying on this is buggy. Note also, that fix "works"
4990 * only in this artificial test. Insert some normal data between A and B and we will
4991 * decline of BSD again. Verdict: it is better to remove to trap
4994 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4995 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4996 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4998 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4999 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5004 tp
->urg_data
= TCP_URG_NOTYET
;
5007 /* Disable header prediction. */
5011 /* This is the 'fast' part of urgent handling. */
5012 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
5014 struct tcp_sock
*tp
= tcp_sk(sk
);
5016 /* Check if we get a new urgent pointer - normally not. */
5018 tcp_check_urg(sk
, th
);
5020 /* Do we wait for any urgent data? - normally not... */
5021 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5022 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5025 /* Is the urgent pointer pointing into this packet? */
5026 if (ptr
< skb
->len
) {
5028 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5030 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5031 if (!sock_flag(sk
, SOCK_DEAD
))
5032 sk
->sk_data_ready(sk
, 0);
5037 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5039 struct tcp_sock
*tp
= tcp_sk(sk
);
5040 int chunk
= skb
->len
- hlen
;
5044 if (skb_csum_unnecessary(skb
))
5045 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
5047 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
5051 tp
->ucopy
.len
-= chunk
;
5052 tp
->copied_seq
+= chunk
;
5053 tcp_rcv_space_adjust(sk
);
5060 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5061 struct sk_buff
*skb
)
5065 if (sock_owned_by_user(sk
)) {
5067 result
= __tcp_checksum_complete(skb
);
5070 result
= __tcp_checksum_complete(skb
);
5075 static inline int tcp_checksum_complete_user(struct sock
*sk
,
5076 struct sk_buff
*skb
)
5078 return !skb_csum_unnecessary(skb
) &&
5079 __tcp_checksum_complete_user(sk
, skb
);
5082 #ifdef CONFIG_NET_DMA
5083 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
5086 struct tcp_sock
*tp
= tcp_sk(sk
);
5087 int chunk
= skb
->len
- hlen
;
5089 int copied_early
= 0;
5091 if (tp
->ucopy
.wakeup
)
5094 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
5095 tp
->ucopy
.dma_chan
= dma_find_channel(DMA_MEMCPY
);
5097 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
5099 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
5101 tp
->ucopy
.iov
, chunk
,
5102 tp
->ucopy
.pinned_list
);
5107 tp
->ucopy
.dma_cookie
= dma_cookie
;
5110 tp
->ucopy
.len
-= chunk
;
5111 tp
->copied_seq
+= chunk
;
5112 tcp_rcv_space_adjust(sk
);
5114 if ((tp
->ucopy
.len
== 0) ||
5115 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
5116 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
5117 tp
->ucopy
.wakeup
= 1;
5118 sk
->sk_data_ready(sk
, 0);
5120 } else if (chunk
> 0) {
5121 tp
->ucopy
.wakeup
= 1;
5122 sk
->sk_data_ready(sk
, 0);
5125 return copied_early
;
5127 #endif /* CONFIG_NET_DMA */
5129 /* Does PAWS and seqno based validation of an incoming segment, flags will
5130 * play significant role here.
5132 static int tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5133 struct tcphdr
*th
, int syn_inerr
)
5136 struct tcp_sock
*tp
= tcp_sk(sk
);
5138 /* RFC1323: H1. Apply PAWS check first. */
5139 if (tcp_fast_parse_options(skb
, th
, tp
, &hash_location
) &&
5140 tp
->rx_opt
.saw_tstamp
&&
5141 tcp_paws_discard(sk
, skb
)) {
5143 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5144 tcp_send_dupack(sk
, skb
);
5147 /* Reset is accepted even if it did not pass PAWS. */
5150 /* Step 1: check sequence number */
5151 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5152 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5153 * (RST) segments are validated by checking their SEQ-fields."
5154 * And page 69: "If an incoming segment is not acceptable,
5155 * an acknowledgment should be sent in reply (unless the RST
5156 * bit is set, if so drop the segment and return)".
5159 tcp_send_dupack(sk
, skb
);
5163 /* Step 2: check RST bit */
5169 /* ts_recent update must be made after we are sure that the packet
5172 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5174 /* step 3: check security and precedence [ignored] */
5176 /* step 4: Check for a SYN in window. */
5177 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5179 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5180 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
5193 * TCP receive function for the ESTABLISHED state.
5195 * It is split into a fast path and a slow path. The fast path is
5197 * - A zero window was announced from us - zero window probing
5198 * is only handled properly in the slow path.
5199 * - Out of order segments arrived.
5200 * - Urgent data is expected.
5201 * - There is no buffer space left
5202 * - Unexpected TCP flags/window values/header lengths are received
5203 * (detected by checking the TCP header against pred_flags)
5204 * - Data is sent in both directions. Fast path only supports pure senders
5205 * or pure receivers (this means either the sequence number or the ack
5206 * value must stay constant)
5207 * - Unexpected TCP option.
5209 * When these conditions are not satisfied it drops into a standard
5210 * receive procedure patterned after RFC793 to handle all cases.
5211 * The first three cases are guaranteed by proper pred_flags setting,
5212 * the rest is checked inline. Fast processing is turned on in
5213 * tcp_data_queue when everything is OK.
5215 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5216 struct tcphdr
*th
, unsigned len
)
5218 struct tcp_sock
*tp
= tcp_sk(sk
);
5222 * Header prediction.
5223 * The code loosely follows the one in the famous
5224 * "30 instruction TCP receive" Van Jacobson mail.
5226 * Van's trick is to deposit buffers into socket queue
5227 * on a device interrupt, to call tcp_recv function
5228 * on the receive process context and checksum and copy
5229 * the buffer to user space. smart...
5231 * Our current scheme is not silly either but we take the
5232 * extra cost of the net_bh soft interrupt processing...
5233 * We do checksum and copy also but from device to kernel.
5236 tp
->rx_opt
.saw_tstamp
= 0;
5238 /* pred_flags is 0xS?10 << 16 + snd_wnd
5239 * if header_prediction is to be made
5240 * 'S' will always be tp->tcp_header_len >> 2
5241 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5242 * turn it off (when there are holes in the receive
5243 * space for instance)
5244 * PSH flag is ignored.
5247 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5248 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5249 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5250 int tcp_header_len
= tp
->tcp_header_len
;
5252 /* Timestamp header prediction: tcp_header_len
5253 * is automatically equal to th->doff*4 due to pred_flags
5257 /* Check timestamp */
5258 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5259 /* No? Slow path! */
5260 if (!tcp_parse_aligned_timestamp(tp
, th
))
5263 /* If PAWS failed, check it more carefully in slow path */
5264 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5267 /* DO NOT update ts_recent here, if checksum fails
5268 * and timestamp was corrupted part, it will result
5269 * in a hung connection since we will drop all
5270 * future packets due to the PAWS test.
5274 if (len
<= tcp_header_len
) {
5275 /* Bulk data transfer: sender */
5276 if (len
== tcp_header_len
) {
5277 /* Predicted packet is in window by definition.
5278 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5279 * Hence, check seq<=rcv_wup reduces to:
5281 if (tcp_header_len
==
5282 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5283 tp
->rcv_nxt
== tp
->rcv_wup
)
5284 tcp_store_ts_recent(tp
);
5286 /* We know that such packets are checksummed
5289 tcp_ack(sk
, skb
, 0);
5291 tcp_data_snd_check(sk
);
5293 } else { /* Header too small */
5294 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5299 int copied_early
= 0;
5301 if (tp
->copied_seq
== tp
->rcv_nxt
&&
5302 len
- tcp_header_len
<= tp
->ucopy
.len
) {
5303 #ifdef CONFIG_NET_DMA
5304 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
5309 if (tp
->ucopy
.task
== current
&&
5310 sock_owned_by_user(sk
) && !copied_early
) {
5311 __set_current_state(TASK_RUNNING
);
5313 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
5317 /* Predicted packet is in window by definition.
5318 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5319 * Hence, check seq<=rcv_wup reduces to:
5321 if (tcp_header_len
==
5322 (sizeof(struct tcphdr
) +
5323 TCPOLEN_TSTAMP_ALIGNED
) &&
5324 tp
->rcv_nxt
== tp
->rcv_wup
)
5325 tcp_store_ts_recent(tp
);
5327 tcp_rcv_rtt_measure_ts(sk
, skb
);
5329 __skb_pull(skb
, tcp_header_len
);
5330 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5331 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5334 tcp_cleanup_rbuf(sk
, skb
->len
);
5337 if (tcp_checksum_complete_user(sk
, skb
))
5340 /* Predicted packet is in window by definition.
5341 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5342 * Hence, check seq<=rcv_wup reduces to:
5344 if (tcp_header_len
==
5345 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5346 tp
->rcv_nxt
== tp
->rcv_wup
)
5347 tcp_store_ts_recent(tp
);
5349 tcp_rcv_rtt_measure_ts(sk
, skb
);
5351 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5354 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5356 /* Bulk data transfer: receiver */
5357 __skb_pull(skb
, tcp_header_len
);
5358 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
5359 skb_set_owner_r(skb
, sk
);
5360 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5363 tcp_event_data_recv(sk
, skb
);
5365 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5366 /* Well, only one small jumplet in fast path... */
5367 tcp_ack(sk
, skb
, FLAG_DATA
);
5368 tcp_data_snd_check(sk
);
5369 if (!inet_csk_ack_scheduled(sk
))
5373 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
5374 __tcp_ack_snd_check(sk
, 0);
5376 #ifdef CONFIG_NET_DMA
5378 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
5384 sk
->sk_data_ready(sk
, 0);
5390 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5394 * Standard slow path.
5397 res
= tcp_validate_incoming(sk
, skb
, th
, 1);
5402 if (th
->ack
&& tcp_ack(sk
, skb
, FLAG_SLOWPATH
) < 0)
5405 tcp_rcv_rtt_measure_ts(sk
, skb
);
5407 /* Process urgent data. */
5408 tcp_urg(sk
, skb
, th
);
5410 /* step 7: process the segment text */
5411 tcp_data_queue(sk
, skb
);
5413 tcp_data_snd_check(sk
);
5414 tcp_ack_snd_check(sk
);
5418 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5425 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5426 struct tcphdr
*th
, unsigned len
)
5429 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5430 struct tcp_sock
*tp
= tcp_sk(sk
);
5431 struct dst_entry
*dst
= __sk_dst_get(sk
);
5432 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
5433 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5435 tcp_parse_options(skb
, &tp
->rx_opt
, &hash_location
, 0, dst
);
5439 * "If the state is SYN-SENT then
5440 * first check the ACK bit
5441 * If the ACK bit is set
5442 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5443 * a reset (unless the RST bit is set, if so drop
5444 * the segment and return)"
5446 * We do not send data with SYN, so that RFC-correct
5449 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
5450 goto reset_and_undo
;
5452 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5453 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5455 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5456 goto reset_and_undo
;
5459 /* Now ACK is acceptable.
5461 * "If the RST bit is set
5462 * If the ACK was acceptable then signal the user "error:
5463 * connection reset", drop the segment, enter CLOSED state,
5464 * delete TCB, and return."
5473 * "fifth, if neither of the SYN or RST bits is set then
5474 * drop the segment and return."
5480 goto discard_and_undo
;
5483 * "If the SYN bit is on ...
5484 * are acceptable then ...
5485 * (our SYN has been ACKed), change the connection
5486 * state to ESTABLISHED..."
5489 TCP_ECN_rcv_synack(tp
, th
);
5491 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5492 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5494 /* Ok.. it's good. Set up sequence numbers and
5495 * move to established.
5497 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5498 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5500 /* RFC1323: The window in SYN & SYN/ACK segments is
5503 tp
->snd_wnd
= ntohs(th
->window
);
5504 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5506 if (!tp
->rx_opt
.wscale_ok
) {
5507 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5508 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5511 if (tp
->rx_opt
.saw_tstamp
) {
5512 tp
->rx_opt
.tstamp_ok
= 1;
5513 tp
->tcp_header_len
=
5514 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5515 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5516 tcp_store_ts_recent(tp
);
5518 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5521 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5522 tcp_enable_fack(tp
);
5525 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5526 tcp_initialize_rcv_mss(sk
);
5528 /* Remember, tcp_poll() does not lock socket!
5529 * Change state from SYN-SENT only after copied_seq
5530 * is initialized. */
5531 tp
->copied_seq
= tp
->rcv_nxt
;
5534 cvp
->cookie_pair_size
> 0 &&
5535 tp
->rx_opt
.cookie_plus
> 0) {
5536 int cookie_size
= tp
->rx_opt
.cookie_plus
5537 - TCPOLEN_COOKIE_BASE
;
5538 int cookie_pair_size
= cookie_size
5539 + cvp
->cookie_desired
;
5541 /* A cookie extension option was sent and returned.
5542 * Note that each incoming SYNACK replaces the
5543 * Responder cookie. The initial exchange is most
5544 * fragile, as protection against spoofing relies
5545 * entirely upon the sequence and timestamp (above).
5546 * This replacement strategy allows the correct pair to
5547 * pass through, while any others will be filtered via
5548 * Responder verification later.
5550 if (sizeof(cvp
->cookie_pair
) >= cookie_pair_size
) {
5551 memcpy(&cvp
->cookie_pair
[cvp
->cookie_desired
],
5552 hash_location
, cookie_size
);
5553 cvp
->cookie_pair_size
= cookie_pair_size
;
5558 tcp_set_state(sk
, TCP_ESTABLISHED
);
5560 security_inet_conn_established(sk
, skb
);
5562 /* Make sure socket is routed, for correct metrics. */
5563 icsk
->icsk_af_ops
->rebuild_header(sk
);
5565 tcp_init_metrics(sk
);
5567 tcp_init_congestion_control(sk
);
5569 /* Prevent spurious tcp_cwnd_restart() on first data
5572 tp
->lsndtime
= tcp_time_stamp
;
5574 tcp_init_buffer_space(sk
);
5576 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5577 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5579 if (!tp
->rx_opt
.snd_wscale
)
5580 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5584 if (!sock_flag(sk
, SOCK_DEAD
)) {
5585 sk
->sk_state_change(sk
);
5586 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5589 if (sk
->sk_write_pending
||
5590 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5591 icsk
->icsk_ack
.pingpong
) {
5592 /* Save one ACK. Data will be ready after
5593 * several ticks, if write_pending is set.
5595 * It may be deleted, but with this feature tcpdumps
5596 * look so _wonderfully_ clever, that I was not able
5597 * to stand against the temptation 8) --ANK
5599 inet_csk_schedule_ack(sk
);
5600 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5601 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
5602 tcp_incr_quickack(sk
);
5603 tcp_enter_quickack_mode(sk
);
5604 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5605 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5616 /* No ACK in the segment */
5620 * "If the RST bit is set
5622 * Otherwise (no ACK) drop the segment and return."
5625 goto discard_and_undo
;
5629 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5630 tcp_paws_reject(&tp
->rx_opt
, 0))
5631 goto discard_and_undo
;
5634 /* We see SYN without ACK. It is attempt of
5635 * simultaneous connect with crossed SYNs.
5636 * Particularly, it can be connect to self.
5638 tcp_set_state(sk
, TCP_SYN_RECV
);
5640 if (tp
->rx_opt
.saw_tstamp
) {
5641 tp
->rx_opt
.tstamp_ok
= 1;
5642 tcp_store_ts_recent(tp
);
5643 tp
->tcp_header_len
=
5644 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5646 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5649 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5650 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5652 /* RFC1323: The window in SYN & SYN/ACK segments is
5655 tp
->snd_wnd
= ntohs(th
->window
);
5656 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5657 tp
->max_window
= tp
->snd_wnd
;
5659 TCP_ECN_rcv_syn(tp
, th
);
5662 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5663 tcp_initialize_rcv_mss(sk
);
5665 tcp_send_synack(sk
);
5667 /* Note, we could accept data and URG from this segment.
5668 * There are no obstacles to make this.
5670 * However, if we ignore data in ACKless segments sometimes,
5671 * we have no reasons to accept it sometimes.
5672 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5673 * is not flawless. So, discard packet for sanity.
5674 * Uncomment this return to process the data.
5681 /* "fifth, if neither of the SYN or RST bits is set then
5682 * drop the segment and return."
5686 tcp_clear_options(&tp
->rx_opt
);
5687 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5691 tcp_clear_options(&tp
->rx_opt
);
5692 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5697 * This function implements the receiving procedure of RFC 793 for
5698 * all states except ESTABLISHED and TIME_WAIT.
5699 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5700 * address independent.
5703 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5704 struct tcphdr
*th
, unsigned len
)
5706 struct tcp_sock
*tp
= tcp_sk(sk
);
5707 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5711 tp
->rx_opt
.saw_tstamp
= 0;
5713 switch (sk
->sk_state
) {
5725 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5728 /* Now we have several options: In theory there is
5729 * nothing else in the frame. KA9Q has an option to
5730 * send data with the syn, BSD accepts data with the
5731 * syn up to the [to be] advertised window and
5732 * Solaris 2.1 gives you a protocol error. For now
5733 * we just ignore it, that fits the spec precisely
5734 * and avoids incompatibilities. It would be nice in
5735 * future to drop through and process the data.
5737 * Now that TTCP is starting to be used we ought to
5739 * But, this leaves one open to an easy denial of
5740 * service attack, and SYN cookies can't defend
5741 * against this problem. So, we drop the data
5742 * in the interest of security over speed unless
5743 * it's still in use.
5751 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5755 /* Do step6 onward by hand. */
5756 tcp_urg(sk
, skb
, th
);
5758 tcp_data_snd_check(sk
);
5762 res
= tcp_validate_incoming(sk
, skb
, th
, 0);
5766 /* step 5: check the ACK field */
5768 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
) > 0;
5770 switch (sk
->sk_state
) {
5773 tp
->copied_seq
= tp
->rcv_nxt
;
5775 tcp_set_state(sk
, TCP_ESTABLISHED
);
5776 sk
->sk_state_change(sk
);
5778 /* Note, that this wakeup is only for marginal
5779 * crossed SYN case. Passively open sockets
5780 * are not waked up, because sk->sk_sleep ==
5781 * NULL and sk->sk_socket == NULL.
5785 SOCK_WAKE_IO
, POLL_OUT
);
5787 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5788 tp
->snd_wnd
= ntohs(th
->window
) <<
5789 tp
->rx_opt
.snd_wscale
;
5790 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5792 /* tcp_ack considers this ACK as duplicate
5793 * and does not calculate rtt.
5794 * Fix it at least with timestamps.
5796 if (tp
->rx_opt
.saw_tstamp
&&
5797 tp
->rx_opt
.rcv_tsecr
&& !tp
->srtt
)
5798 tcp_ack_saw_tstamp(sk
, 0);
5800 if (tp
->rx_opt
.tstamp_ok
)
5801 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5803 /* Make sure socket is routed, for
5806 icsk
->icsk_af_ops
->rebuild_header(sk
);
5808 tcp_init_metrics(sk
);
5810 tcp_init_congestion_control(sk
);
5812 /* Prevent spurious tcp_cwnd_restart() on
5813 * first data packet.
5815 tp
->lsndtime
= tcp_time_stamp
;
5818 tcp_initialize_rcv_mss(sk
);
5819 tcp_init_buffer_space(sk
);
5820 tcp_fast_path_on(tp
);
5827 if (tp
->snd_una
== tp
->write_seq
) {
5828 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5829 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5830 dst_confirm(sk
->sk_dst_cache
);
5832 if (!sock_flag(sk
, SOCK_DEAD
))
5833 /* Wake up lingering close() */
5834 sk
->sk_state_change(sk
);
5838 if (tp
->linger2
< 0 ||
5839 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5840 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5842 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5846 tmo
= tcp_fin_time(sk
);
5847 if (tmo
> TCP_TIMEWAIT_LEN
) {
5848 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5849 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5850 /* Bad case. We could lose such FIN otherwise.
5851 * It is not a big problem, but it looks confusing
5852 * and not so rare event. We still can lose it now,
5853 * if it spins in bh_lock_sock(), but it is really
5856 inet_csk_reset_keepalive_timer(sk
, tmo
);
5858 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5866 if (tp
->snd_una
== tp
->write_seq
) {
5867 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5873 if (tp
->snd_una
== tp
->write_seq
) {
5874 tcp_update_metrics(sk
);
5883 /* step 6: check the URG bit */
5884 tcp_urg(sk
, skb
, th
);
5886 /* step 7: process the segment text */
5887 switch (sk
->sk_state
) {
5888 case TCP_CLOSE_WAIT
:
5891 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5895 /* RFC 793 says to queue data in these states,
5896 * RFC 1122 says we MUST send a reset.
5897 * BSD 4.4 also does reset.
5899 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5900 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5901 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5902 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5908 case TCP_ESTABLISHED
:
5909 tcp_data_queue(sk
, skb
);
5914 /* tcp_data could move socket to TIME-WAIT */
5915 if (sk
->sk_state
!= TCP_CLOSE
) {
5916 tcp_data_snd_check(sk
);
5917 tcp_ack_snd_check(sk
);
5927 EXPORT_SYMBOL(sysctl_tcp_ecn
);
5928 EXPORT_SYMBOL(sysctl_tcp_reordering
);
5929 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
5930 EXPORT_SYMBOL(tcp_parse_options
);
5931 #ifdef CONFIG_TCP_MD5SIG
5932 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
5934 EXPORT_SYMBOL(tcp_rcv_established
);
5935 EXPORT_SYMBOL(tcp_rcv_state_process
);
5936 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);