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/slab.h>
66 #include <linux/module.h>
67 #include <linux/sysctl.h>
68 #include <linux/kernel.h>
71 #include <net/inet_common.h>
72 #include <linux/ipsec.h>
73 #include <asm/unaligned.h>
74 #include <net/netdma.h>
76 int sysctl_tcp_timestamps __read_mostly
= 1;
77 int sysctl_tcp_window_scaling __read_mostly
= 1;
78 int sysctl_tcp_sack __read_mostly
= 1;
79 int sysctl_tcp_fack __read_mostly
= 1;
80 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
81 EXPORT_SYMBOL(sysctl_tcp_reordering
);
82 int sysctl_tcp_ecn __read_mostly
= 2;
83 EXPORT_SYMBOL(sysctl_tcp_ecn
);
84 int sysctl_tcp_dsack __read_mostly
= 1;
85 int sysctl_tcp_app_win __read_mostly
= 31;
86 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
87 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
89 int sysctl_tcp_stdurg __read_mostly
;
90 int sysctl_tcp_rfc1337 __read_mostly
;
91 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
92 int sysctl_tcp_frto __read_mostly
= 2;
93 int sysctl_tcp_frto_response __read_mostly
;
94 int sysctl_tcp_nometrics_save __read_mostly
;
96 int sysctl_tcp_thin_dupack __read_mostly
;
98 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
99 int sysctl_tcp_abc __read_mostly
;
101 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
102 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
103 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
104 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
105 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
106 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
107 #define FLAG_ECE 0x40 /* ECE in this ACK */
108 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
109 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
110 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
111 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
112 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
113 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
114 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
116 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
117 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
118 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
119 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
120 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
122 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
123 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
125 /* Adapt the MSS value used to make delayed ack decision to the
128 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
130 struct inet_connection_sock
*icsk
= inet_csk(sk
);
131 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
134 icsk
->icsk_ack
.last_seg_size
= 0;
136 /* skb->len may jitter because of SACKs, even if peer
137 * sends good full-sized frames.
139 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
140 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
141 icsk
->icsk_ack
.rcv_mss
= len
;
143 /* Otherwise, we make more careful check taking into account,
144 * that SACKs block is variable.
146 * "len" is invariant segment length, including TCP header.
148 len
+= skb
->data
- skb_transport_header(skb
);
149 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
150 /* If PSH is not set, packet should be
151 * full sized, provided peer TCP is not badly broken.
152 * This observation (if it is correct 8)) allows
153 * to handle super-low mtu links fairly.
155 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
156 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
157 /* Subtract also invariant (if peer is RFC compliant),
158 * tcp header plus fixed timestamp option length.
159 * Resulting "len" is MSS free of SACK jitter.
161 len
-= tcp_sk(sk
)->tcp_header_len
;
162 icsk
->icsk_ack
.last_seg_size
= len
;
164 icsk
->icsk_ack
.rcv_mss
= len
;
168 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
169 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
170 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
174 static void tcp_incr_quickack(struct sock
*sk
)
176 struct inet_connection_sock
*icsk
= inet_csk(sk
);
177 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
181 if (quickacks
> icsk
->icsk_ack
.quick
)
182 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
185 static void tcp_enter_quickack_mode(struct sock
*sk
)
187 struct inet_connection_sock
*icsk
= inet_csk(sk
);
188 tcp_incr_quickack(sk
);
189 icsk
->icsk_ack
.pingpong
= 0;
190 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
193 /* Send ACKs quickly, if "quick" count is not exhausted
194 * and the session is not interactive.
197 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
199 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
200 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
203 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
205 if (tp
->ecn_flags
& TCP_ECN_OK
)
206 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
209 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, struct sk_buff
*skb
)
211 if (tcp_hdr(skb
)->cwr
)
212 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
215 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
217 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
220 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, struct sk_buff
*skb
)
222 if (tp
->ecn_flags
& TCP_ECN_OK
) {
223 if (INET_ECN_is_ce(TCP_SKB_CB(skb
)->flags
))
224 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
225 /* Funny extension: if ECT is not set on a segment,
226 * it is surely retransmit. It is not in ECN RFC,
227 * but Linux follows this rule. */
228 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb
)->flags
)))
229 tcp_enter_quickack_mode((struct sock
*)tp
);
233 static inline void TCP_ECN_rcv_synack(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 void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, struct tcphdr
*th
)
241 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
242 tp
->ecn_flags
&= ~TCP_ECN_OK
;
245 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock
*tp
, struct tcphdr
*th
)
247 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
252 /* Buffer size and advertised window tuning.
254 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
257 static void tcp_fixup_sndbuf(struct sock
*sk
)
259 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
260 sizeof(struct sk_buff
);
262 if (sk
->sk_sndbuf
< 3 * sndmem
)
263 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
266 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
268 * All tcp_full_space() is split to two parts: "network" buffer, allocated
269 * forward and advertised in receiver window (tp->rcv_wnd) and
270 * "application buffer", required to isolate scheduling/application
271 * latencies from network.
272 * window_clamp is maximal advertised window. It can be less than
273 * tcp_full_space(), in this case tcp_full_space() - window_clamp
274 * is reserved for "application" buffer. The less window_clamp is
275 * the smoother our behaviour from viewpoint of network, but the lower
276 * throughput and the higher sensitivity of the connection to losses. 8)
278 * rcv_ssthresh is more strict window_clamp used at "slow start"
279 * phase to predict further behaviour of this connection.
280 * It is used for two goals:
281 * - to enforce header prediction at sender, even when application
282 * requires some significant "application buffer". It is check #1.
283 * - to prevent pruning of receive queue because of misprediction
284 * of receiver window. Check #2.
286 * The scheme does not work when sender sends good segments opening
287 * window and then starts to feed us spaghetti. But it should work
288 * in common situations. Otherwise, we have to rely on queue collapsing.
291 /* Slow part of check#2. */
292 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
294 struct tcp_sock
*tp
= tcp_sk(sk
);
296 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
297 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
299 while (tp
->rcv_ssthresh
<= window
) {
300 if (truesize
<= skb
->len
)
301 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
309 static void tcp_grow_window(struct sock
*sk
, struct sk_buff
*skb
)
311 struct tcp_sock
*tp
= tcp_sk(sk
);
314 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
315 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
316 !tcp_memory_pressure
) {
319 /* Check #2. Increase window, if skb with such overhead
320 * will fit to rcvbuf in future.
322 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
323 incr
= 2 * tp
->advmss
;
325 incr
= __tcp_grow_window(sk
, skb
);
328 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
330 inet_csk(sk
)->icsk_ack
.quick
|= 1;
335 /* 3. Tuning rcvbuf, when connection enters established state. */
337 static void tcp_fixup_rcvbuf(struct sock
*sk
)
339 struct tcp_sock
*tp
= tcp_sk(sk
);
340 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
342 /* Try to select rcvbuf so that 4 mss-sized segments
343 * will fit to window and corresponding skbs will fit to our rcvbuf.
344 * (was 3; 4 is minimum to allow fast retransmit to work.)
346 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
348 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
349 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
352 /* 4. Try to fixup all. It is made immediately after connection enters
355 static void tcp_init_buffer_space(struct sock
*sk
)
357 struct tcp_sock
*tp
= tcp_sk(sk
);
360 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
361 tcp_fixup_rcvbuf(sk
);
362 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
363 tcp_fixup_sndbuf(sk
);
365 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
367 maxwin
= tcp_full_space(sk
);
369 if (tp
->window_clamp
>= maxwin
) {
370 tp
->window_clamp
= maxwin
;
372 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
373 tp
->window_clamp
= max(maxwin
-
374 (maxwin
>> sysctl_tcp_app_win
),
378 /* Force reservation of one segment. */
379 if (sysctl_tcp_app_win
&&
380 tp
->window_clamp
> 2 * tp
->advmss
&&
381 tp
->window_clamp
+ tp
->advmss
> maxwin
)
382 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
384 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
385 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
388 /* 5. Recalculate window clamp after socket hit its memory bounds. */
389 static void tcp_clamp_window(struct sock
*sk
)
391 struct tcp_sock
*tp
= tcp_sk(sk
);
392 struct inet_connection_sock
*icsk
= inet_csk(sk
);
394 icsk
->icsk_ack
.quick
= 0;
396 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
397 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
398 !tcp_memory_pressure
&&
399 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
400 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
403 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
404 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
407 /* Initialize RCV_MSS value.
408 * RCV_MSS is an our guess about MSS used by the peer.
409 * We haven't any direct information about the MSS.
410 * It's better to underestimate the RCV_MSS rather than overestimate.
411 * Overestimations make us ACKing less frequently than needed.
412 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
414 void tcp_initialize_rcv_mss(struct sock
*sk
)
416 struct tcp_sock
*tp
= tcp_sk(sk
);
417 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
419 hint
= min(hint
, tp
->rcv_wnd
/ 2);
420 hint
= min(hint
, TCP_MSS_DEFAULT
);
421 hint
= max(hint
, TCP_MIN_MSS
);
423 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
425 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
427 /* Receiver "autotuning" code.
429 * The algorithm for RTT estimation w/o timestamps is based on
430 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
431 * <http://public.lanl.gov/radiant/pubs.html#DRS>
433 * More detail on this code can be found at
434 * <http://staff.psc.edu/jheffner/>,
435 * though this reference is out of date. A new paper
438 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
440 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
446 if (new_sample
!= 0) {
447 /* If we sample in larger samples in the non-timestamp
448 * case, we could grossly overestimate the RTT especially
449 * with chatty applications or bulk transfer apps which
450 * are stalled on filesystem I/O.
452 * Also, since we are only going for a minimum in the
453 * non-timestamp case, we do not smooth things out
454 * else with timestamps disabled convergence takes too
458 m
-= (new_sample
>> 3);
460 } else if (m
< new_sample
)
463 /* No previous measure. */
467 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
468 tp
->rcv_rtt_est
.rtt
= new_sample
;
471 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
473 if (tp
->rcv_rtt_est
.time
== 0)
475 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
477 tcp_rcv_rtt_update(tp
, jiffies
- tp
->rcv_rtt_est
.time
, 1);
480 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
481 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
484 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
485 const struct sk_buff
*skb
)
487 struct tcp_sock
*tp
= tcp_sk(sk
);
488 if (tp
->rx_opt
.rcv_tsecr
&&
489 (TCP_SKB_CB(skb
)->end_seq
-
490 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
491 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
495 * This function should be called every time data is copied to user space.
496 * It calculates the appropriate TCP receive buffer space.
498 void tcp_rcv_space_adjust(struct sock
*sk
)
500 struct tcp_sock
*tp
= tcp_sk(sk
);
504 if (tp
->rcvq_space
.time
== 0)
507 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
508 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
511 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
513 space
= max(tp
->rcvq_space
.space
, space
);
515 if (tp
->rcvq_space
.space
!= space
) {
518 tp
->rcvq_space
.space
= space
;
520 if (sysctl_tcp_moderate_rcvbuf
&&
521 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
522 int new_clamp
= space
;
524 /* Receive space grows, normalize in order to
525 * take into account packet headers and sk_buff
526 * structure overhead.
531 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
532 16 + sizeof(struct sk_buff
));
533 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
536 space
= min(space
, sysctl_tcp_rmem
[2]);
537 if (space
> sk
->sk_rcvbuf
) {
538 sk
->sk_rcvbuf
= space
;
540 /* Make the window clamp follow along. */
541 tp
->window_clamp
= new_clamp
;
547 tp
->rcvq_space
.seq
= tp
->copied_seq
;
548 tp
->rcvq_space
.time
= tcp_time_stamp
;
551 /* There is something which you must keep in mind when you analyze the
552 * behavior of the tp->ato delayed ack timeout interval. When a
553 * connection starts up, we want to ack as quickly as possible. The
554 * problem is that "good" TCP's do slow start at the beginning of data
555 * transmission. The means that until we send the first few ACK's the
556 * sender will sit on his end and only queue most of his data, because
557 * he can only send snd_cwnd unacked packets at any given time. For
558 * each ACK we send, he increments snd_cwnd and transmits more of his
561 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
563 struct tcp_sock
*tp
= tcp_sk(sk
);
564 struct inet_connection_sock
*icsk
= inet_csk(sk
);
567 inet_csk_schedule_ack(sk
);
569 tcp_measure_rcv_mss(sk
, skb
);
571 tcp_rcv_rtt_measure(tp
);
573 now
= tcp_time_stamp
;
575 if (!icsk
->icsk_ack
.ato
) {
576 /* The _first_ data packet received, initialize
577 * delayed ACK engine.
579 tcp_incr_quickack(sk
);
580 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
582 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
584 if (m
<= TCP_ATO_MIN
/ 2) {
585 /* The fastest case is the first. */
586 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
587 } else if (m
< icsk
->icsk_ack
.ato
) {
588 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
589 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
590 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
591 } else if (m
> icsk
->icsk_rto
) {
592 /* Too long gap. Apparently sender failed to
593 * restart window, so that we send ACKs quickly.
595 tcp_incr_quickack(sk
);
599 icsk
->icsk_ack
.lrcvtime
= now
;
601 TCP_ECN_check_ce(tp
, skb
);
604 tcp_grow_window(sk
, skb
);
607 /* Called to compute a smoothed rtt estimate. The data fed to this
608 * routine either comes from timestamps, or from segments that were
609 * known _not_ to have been retransmitted [see Karn/Partridge
610 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
611 * piece by Van Jacobson.
612 * NOTE: the next three routines used to be one big routine.
613 * To save cycles in the RFC 1323 implementation it was better to break
614 * it up into three procedures. -- erics
616 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
618 struct tcp_sock
*tp
= tcp_sk(sk
);
619 long m
= mrtt
; /* RTT */
621 /* The following amusing code comes from Jacobson's
622 * article in SIGCOMM '88. Note that rtt and mdev
623 * are scaled versions of rtt and mean deviation.
624 * This is designed to be as fast as possible
625 * m stands for "measurement".
627 * On a 1990 paper the rto value is changed to:
628 * RTO = rtt + 4 * mdev
630 * Funny. This algorithm seems to be very broken.
631 * These formulae increase RTO, when it should be decreased, increase
632 * too slowly, when it should be increased quickly, decrease too quickly
633 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
634 * does not matter how to _calculate_ it. Seems, it was trap
635 * that VJ failed to avoid. 8)
640 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
641 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
643 m
= -m
; /* m is now abs(error) */
644 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
645 /* This is similar to one of Eifel findings.
646 * Eifel blocks mdev updates when rtt decreases.
647 * This solution is a bit different: we use finer gain
648 * for mdev in this case (alpha*beta).
649 * Like Eifel it also prevents growth of rto,
650 * but also it limits too fast rto decreases,
651 * happening in pure Eifel.
656 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
658 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
659 if (tp
->mdev
> tp
->mdev_max
) {
660 tp
->mdev_max
= tp
->mdev
;
661 if (tp
->mdev_max
> tp
->rttvar
)
662 tp
->rttvar
= tp
->mdev_max
;
664 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
665 if (tp
->mdev_max
< tp
->rttvar
)
666 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
667 tp
->rtt_seq
= tp
->snd_nxt
;
668 tp
->mdev_max
= tcp_rto_min(sk
);
671 /* no previous measure. */
672 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
673 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
674 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
675 tp
->rtt_seq
= tp
->snd_nxt
;
679 /* Calculate rto without backoff. This is the second half of Van Jacobson's
680 * routine referred to above.
682 static inline void tcp_set_rto(struct sock
*sk
)
684 const struct tcp_sock
*tp
= tcp_sk(sk
);
685 /* Old crap is replaced with new one. 8)
688 * 1. If rtt variance happened to be less 50msec, it is hallucination.
689 * It cannot be less due to utterly erratic ACK generation made
690 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
691 * to do with delayed acks, because at cwnd>2 true delack timeout
692 * is invisible. Actually, Linux-2.4 also generates erratic
693 * ACKs in some circumstances.
695 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
697 /* 2. Fixups made earlier cannot be right.
698 * If we do not estimate RTO correctly without them,
699 * all the algo is pure shit and should be replaced
700 * with correct one. It is exactly, which we pretend to do.
703 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
704 * guarantees that rto is higher.
709 /* Save metrics learned by this TCP session.
710 This function is called only, when TCP finishes successfully
711 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
713 void tcp_update_metrics(struct sock
*sk
)
715 struct tcp_sock
*tp
= tcp_sk(sk
);
716 struct dst_entry
*dst
= __sk_dst_get(sk
);
718 if (sysctl_tcp_nometrics_save
)
723 if (dst
&& (dst
->flags
& DST_HOST
)) {
724 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
728 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
729 /* This session failed to estimate rtt. Why?
730 * Probably, no packets returned in time.
733 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
734 dst
->metrics
[RTAX_RTT
- 1] = 0;
738 rtt
= dst_metric_rtt(dst
, RTAX_RTT
);
741 /* If newly calculated rtt larger than stored one,
742 * store new one. Otherwise, use EWMA. Remember,
743 * rtt overestimation is always better than underestimation.
745 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
747 set_dst_metric_rtt(dst
, RTAX_RTT
, tp
->srtt
);
749 set_dst_metric_rtt(dst
, RTAX_RTT
, rtt
- (m
>> 3));
752 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
757 /* Scale deviation to rttvar fixed point */
762 var
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
766 var
-= (var
- m
) >> 2;
768 set_dst_metric_rtt(dst
, RTAX_RTTVAR
, var
);
771 if (tcp_in_initial_slowstart(tp
)) {
772 /* Slow start still did not finish. */
773 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
774 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
775 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
776 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
777 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
778 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
779 dst
->metrics
[RTAX_CWND
- 1] = tp
->snd_cwnd
;
780 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
781 icsk
->icsk_ca_state
== TCP_CA_Open
) {
782 /* Cong. avoidance phase, cwnd is reliable. */
783 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
784 dst
->metrics
[RTAX_SSTHRESH
-1] =
785 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
786 if (!dst_metric_locked(dst
, RTAX_CWND
))
787 dst
->metrics
[RTAX_CWND
-1] = (dst_metric(dst
, RTAX_CWND
) + tp
->snd_cwnd
) >> 1;
789 /* Else slow start did not finish, cwnd is non-sense,
790 ssthresh may be also invalid.
792 if (!dst_metric_locked(dst
, RTAX_CWND
))
793 dst
->metrics
[RTAX_CWND
-1] = (dst_metric(dst
, RTAX_CWND
) + tp
->snd_ssthresh
) >> 1;
794 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
795 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
796 tp
->snd_ssthresh
> dst_metric(dst
, RTAX_SSTHRESH
))
797 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
800 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
801 if (dst_metric(dst
, RTAX_REORDERING
) < tp
->reordering
&&
802 tp
->reordering
!= sysctl_tcp_reordering
)
803 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
808 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
810 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
813 cwnd
= rfc3390_bytes_to_packets(tp
->mss_cache
);
814 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
817 /* Set slow start threshold and cwnd not falling to slow start */
818 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
820 struct tcp_sock
*tp
= tcp_sk(sk
);
821 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
823 tp
->prior_ssthresh
= 0;
825 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
828 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
829 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
830 tcp_packets_in_flight(tp
) + 1U);
831 tp
->snd_cwnd_cnt
= 0;
832 tp
->high_seq
= tp
->snd_nxt
;
833 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
834 TCP_ECN_queue_cwr(tp
);
836 tcp_set_ca_state(sk
, TCP_CA_CWR
);
841 * Packet counting of FACK is based on in-order assumptions, therefore TCP
842 * disables it when reordering is detected
844 static void tcp_disable_fack(struct tcp_sock
*tp
)
846 /* RFC3517 uses different metric in lost marker => reset on change */
848 tp
->lost_skb_hint
= NULL
;
849 tp
->rx_opt
.sack_ok
&= ~2;
852 /* Take a notice that peer is sending D-SACKs */
853 static void tcp_dsack_seen(struct tcp_sock
*tp
)
855 tp
->rx_opt
.sack_ok
|= 4;
858 /* Initialize metrics on socket. */
860 static void tcp_init_metrics(struct sock
*sk
)
862 struct tcp_sock
*tp
= tcp_sk(sk
);
863 struct dst_entry
*dst
= __sk_dst_get(sk
);
870 if (dst_metric_locked(dst
, RTAX_CWND
))
871 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
872 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
873 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
874 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
875 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
877 if (dst_metric(dst
, RTAX_REORDERING
) &&
878 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
879 tcp_disable_fack(tp
);
880 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
883 if (dst_metric(dst
, RTAX_RTT
) == 0)
886 if (!tp
->srtt
&& dst_metric_rtt(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
889 /* Initial rtt is determined from SYN,SYN-ACK.
890 * The segment is small and rtt may appear much
891 * less than real one. Use per-dst memory
892 * to make it more realistic.
894 * A bit of theory. RTT is time passed after "normal" sized packet
895 * is sent until it is ACKed. In normal circumstances sending small
896 * packets force peer to delay ACKs and calculation is correct too.
897 * The algorithm is adaptive and, provided we follow specs, it
898 * NEVER underestimate RTT. BUT! If peer tries to make some clever
899 * tricks sort of "quick acks" for time long enough to decrease RTT
900 * to low value, and then abruptly stops to do it and starts to delay
901 * ACKs, wait for troubles.
903 if (dst_metric_rtt(dst
, RTAX_RTT
) > tp
->srtt
) {
904 tp
->srtt
= dst_metric_rtt(dst
, RTAX_RTT
);
905 tp
->rtt_seq
= tp
->snd_nxt
;
907 if (dst_metric_rtt(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
908 tp
->mdev
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
909 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
912 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
916 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
917 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
921 /* Play conservative. If timestamps are not
922 * supported, TCP will fail to recalculate correct
923 * rtt, if initial rto is too small. FORGET ALL AND RESET!
925 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
927 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
928 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
933 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
936 struct tcp_sock
*tp
= tcp_sk(sk
);
937 if (metric
> tp
->reordering
) {
940 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
942 /* This exciting event is worth to be remembered. 8) */
944 mib_idx
= LINUX_MIB_TCPTSREORDER
;
945 else if (tcp_is_reno(tp
))
946 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
947 else if (tcp_is_fack(tp
))
948 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
950 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
952 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
953 #if FASTRETRANS_DEBUG > 1
954 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
955 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
959 tp
->undo_marker
? tp
->undo_retrans
: 0);
961 tcp_disable_fack(tp
);
965 /* This must be called before lost_out is incremented */
966 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
968 if ((tp
->retransmit_skb_hint
== NULL
) ||
969 before(TCP_SKB_CB(skb
)->seq
,
970 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
971 tp
->retransmit_skb_hint
= skb
;
974 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
975 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
978 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
980 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
981 tcp_verify_retransmit_hint(tp
, skb
);
983 tp
->lost_out
+= tcp_skb_pcount(skb
);
984 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
988 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
991 tcp_verify_retransmit_hint(tp
, skb
);
993 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
994 tp
->lost_out
+= tcp_skb_pcount(skb
);
995 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
999 /* This procedure tags the retransmission queue when SACKs arrive.
1001 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1002 * Packets in queue with these bits set are counted in variables
1003 * sacked_out, retrans_out and lost_out, correspondingly.
1005 * Valid combinations are:
1006 * Tag InFlight Description
1007 * 0 1 - orig segment is in flight.
1008 * S 0 - nothing flies, orig reached receiver.
1009 * L 0 - nothing flies, orig lost by net.
1010 * R 2 - both orig and retransmit are in flight.
1011 * L|R 1 - orig is lost, retransmit is in flight.
1012 * S|R 1 - orig reached receiver, retrans is still in flight.
1013 * (L|S|R is logically valid, it could occur when L|R is sacked,
1014 * but it is equivalent to plain S and code short-curcuits it to S.
1015 * L|S is logically invalid, it would mean -1 packet in flight 8))
1017 * These 6 states form finite state machine, controlled by the following events:
1018 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1019 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1020 * 3. Loss detection event of one of three flavors:
1021 * A. Scoreboard estimator decided the packet is lost.
1022 * A'. Reno "three dupacks" marks head of queue lost.
1023 * A''. Its FACK modfication, head until snd.fack is lost.
1024 * B. SACK arrives sacking data transmitted after never retransmitted
1025 * hole was sent out.
1026 * C. SACK arrives sacking SND.NXT at the moment, when the
1027 * segment was retransmitted.
1028 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1030 * It is pleasant to note, that state diagram turns out to be commutative,
1031 * so that we are allowed not to be bothered by order of our actions,
1032 * when multiple events arrive simultaneously. (see the function below).
1034 * Reordering detection.
1035 * --------------------
1036 * Reordering metric is maximal distance, which a packet can be displaced
1037 * in packet stream. With SACKs we can estimate it:
1039 * 1. SACK fills old hole and the corresponding segment was not
1040 * ever retransmitted -> reordering. Alas, we cannot use it
1041 * when segment was retransmitted.
1042 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1043 * for retransmitted and already SACKed segment -> reordering..
1044 * Both of these heuristics are not used in Loss state, when we cannot
1045 * account for retransmits accurately.
1047 * SACK block validation.
1048 * ----------------------
1050 * SACK block range validation checks that the received SACK block fits to
1051 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1052 * Note that SND.UNA is not included to the range though being valid because
1053 * it means that the receiver is rather inconsistent with itself reporting
1054 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1055 * perfectly valid, however, in light of RFC2018 which explicitly states
1056 * that "SACK block MUST reflect the newest segment. Even if the newest
1057 * segment is going to be discarded ...", not that it looks very clever
1058 * in case of head skb. Due to potentional receiver driven attacks, we
1059 * choose to avoid immediate execution of a walk in write queue due to
1060 * reneging and defer head skb's loss recovery to standard loss recovery
1061 * procedure that will eventually trigger (nothing forbids us doing this).
1063 * Implements also blockage to start_seq wrap-around. Problem lies in the
1064 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1065 * there's no guarantee that it will be before snd_nxt (n). The problem
1066 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1069 * <- outs wnd -> <- wrapzone ->
1070 * u e n u_w e_w s n_w
1072 * |<------------+------+----- TCP seqno space --------------+---------->|
1073 * ...-- <2^31 ->| |<--------...
1074 * ...---- >2^31 ------>| |<--------...
1076 * Current code wouldn't be vulnerable but it's better still to discard such
1077 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1078 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1079 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1080 * equal to the ideal case (infinite seqno space without wrap caused issues).
1082 * With D-SACK the lower bound is extended to cover sequence space below
1083 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1084 * again, D-SACK block must not to go across snd_una (for the same reason as
1085 * for the normal SACK blocks, explained above). But there all simplicity
1086 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1087 * fully below undo_marker they do not affect behavior in anyway and can
1088 * therefore be safely ignored. In rare cases (which are more or less
1089 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1090 * fragmentation and packet reordering past skb's retransmission. To consider
1091 * them correctly, the acceptable range must be extended even more though
1092 * the exact amount is rather hard to quantify. However, tp->max_window can
1093 * be used as an exaggerated estimate.
1095 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1096 u32 start_seq
, u32 end_seq
)
1098 /* Too far in future, or reversed (interpretation is ambiguous) */
1099 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1102 /* Nasty start_seq wrap-around check (see comments above) */
1103 if (!before(start_seq
, tp
->snd_nxt
))
1106 /* In outstanding window? ...This is valid exit for D-SACKs too.
1107 * start_seq == snd_una is non-sensical (see comments above)
1109 if (after(start_seq
, tp
->snd_una
))
1112 if (!is_dsack
|| !tp
->undo_marker
)
1115 /* ...Then it's D-SACK, and must reside below snd_una completely */
1116 if (!after(end_seq
, tp
->snd_una
))
1119 if (!before(start_seq
, tp
->undo_marker
))
1123 if (!after(end_seq
, tp
->undo_marker
))
1126 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1127 * start_seq < undo_marker and end_seq >= undo_marker.
1129 return !before(start_seq
, end_seq
- tp
->max_window
);
1132 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1133 * Event "C". Later note: FACK people cheated me again 8), we have to account
1134 * for reordering! Ugly, but should help.
1136 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1137 * less than what is now known to be received by the other end (derived from
1138 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1139 * retransmitted skbs to avoid some costly processing per ACKs.
1141 static void tcp_mark_lost_retrans(struct sock
*sk
)
1143 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1144 struct tcp_sock
*tp
= tcp_sk(sk
);
1145 struct sk_buff
*skb
;
1147 u32 new_low_seq
= tp
->snd_nxt
;
1148 u32 received_upto
= tcp_highest_sack_seq(tp
);
1150 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1151 !after(received_upto
, tp
->lost_retrans_low
) ||
1152 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1155 tcp_for_write_queue(skb
, sk
) {
1156 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1158 if (skb
== tcp_send_head(sk
))
1160 if (cnt
== tp
->retrans_out
)
1162 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1165 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1168 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1169 * constraint here (see above) but figuring out that at
1170 * least tp->reordering SACK blocks reside between ack_seq
1171 * and received_upto is not easy task to do cheaply with
1172 * the available datastructures.
1174 * Whether FACK should check here for tp->reordering segs
1175 * in-between one could argue for either way (it would be
1176 * rather simple to implement as we could count fack_count
1177 * during the walk and do tp->fackets_out - fack_count).
1179 if (after(received_upto
, ack_seq
)) {
1180 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1181 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1183 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1184 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1186 if (before(ack_seq
, new_low_seq
))
1187 new_low_seq
= ack_seq
;
1188 cnt
+= tcp_skb_pcount(skb
);
1192 if (tp
->retrans_out
)
1193 tp
->lost_retrans_low
= new_low_seq
;
1196 static int tcp_check_dsack(struct sock
*sk
, struct sk_buff
*ack_skb
,
1197 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1200 struct tcp_sock
*tp
= tcp_sk(sk
);
1201 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1202 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1205 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1208 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1209 } else if (num_sacks
> 1) {
1210 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1211 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1213 if (!after(end_seq_0
, end_seq_1
) &&
1214 !before(start_seq_0
, start_seq_1
)) {
1217 NET_INC_STATS_BH(sock_net(sk
),
1218 LINUX_MIB_TCPDSACKOFORECV
);
1222 /* D-SACK for already forgotten data... Do dumb counting. */
1224 !after(end_seq_0
, prior_snd_una
) &&
1225 after(end_seq_0
, tp
->undo_marker
))
1231 struct tcp_sacktag_state
{
1237 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1238 * the incoming SACK may not exactly match but we can find smaller MSS
1239 * aligned portion of it that matches. Therefore we might need to fragment
1240 * which may fail and creates some hassle (caller must handle error case
1243 * FIXME: this could be merged to shift decision code
1245 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1246 u32 start_seq
, u32 end_seq
)
1249 unsigned int pkt_len
;
1252 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1253 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1255 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1256 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1257 mss
= tcp_skb_mss(skb
);
1258 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1261 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1265 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1270 /* Round if necessary so that SACKs cover only full MSSes
1271 * and/or the remaining small portion (if present)
1273 if (pkt_len
> mss
) {
1274 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1275 if (!in_sack
&& new_len
< pkt_len
) {
1277 if (new_len
> skb
->len
)
1282 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
);
1290 static u8
tcp_sacktag_one(struct sk_buff
*skb
, struct sock
*sk
,
1291 struct tcp_sacktag_state
*state
,
1292 int dup_sack
, int pcount
)
1294 struct tcp_sock
*tp
= tcp_sk(sk
);
1295 u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1296 int fack_count
= state
->fack_count
;
1298 /* Account D-SACK for retransmitted packet. */
1299 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1300 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1302 if (sacked
& TCPCB_SACKED_ACKED
)
1303 state
->reord
= min(fack_count
, state
->reord
);
1306 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1307 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1310 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1311 if (sacked
& TCPCB_SACKED_RETRANS
) {
1312 /* If the segment is not tagged as lost,
1313 * we do not clear RETRANS, believing
1314 * that retransmission is still in flight.
1316 if (sacked
& TCPCB_LOST
) {
1317 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1318 tp
->lost_out
-= pcount
;
1319 tp
->retrans_out
-= pcount
;
1322 if (!(sacked
& TCPCB_RETRANS
)) {
1323 /* New sack for not retransmitted frame,
1324 * which was in hole. It is reordering.
1326 if (before(TCP_SKB_CB(skb
)->seq
,
1327 tcp_highest_sack_seq(tp
)))
1328 state
->reord
= min(fack_count
,
1331 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1332 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
))
1333 state
->flag
|= FLAG_ONLY_ORIG_SACKED
;
1336 if (sacked
& TCPCB_LOST
) {
1337 sacked
&= ~TCPCB_LOST
;
1338 tp
->lost_out
-= pcount
;
1342 sacked
|= TCPCB_SACKED_ACKED
;
1343 state
->flag
|= FLAG_DATA_SACKED
;
1344 tp
->sacked_out
+= pcount
;
1346 fack_count
+= pcount
;
1348 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1349 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1350 before(TCP_SKB_CB(skb
)->seq
,
1351 TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1352 tp
->lost_cnt_hint
+= pcount
;
1354 if (fack_count
> tp
->fackets_out
)
1355 tp
->fackets_out
= fack_count
;
1358 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1359 * frames and clear it. undo_retrans is decreased above, L|R frames
1360 * are accounted above as well.
1362 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1363 sacked
&= ~TCPCB_SACKED_RETRANS
;
1364 tp
->retrans_out
-= pcount
;
1370 static int tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1371 struct tcp_sacktag_state
*state
,
1372 unsigned int pcount
, int shifted
, int mss
,
1375 struct tcp_sock
*tp
= tcp_sk(sk
);
1376 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1380 /* Tweak before seqno plays */
1381 if (!tcp_is_fack(tp
) && tcp_is_sack(tp
) && tp
->lost_skb_hint
&&
1382 !before(TCP_SKB_CB(tp
->lost_skb_hint
)->seq
, TCP_SKB_CB(skb
)->seq
))
1383 tp
->lost_cnt_hint
+= pcount
;
1385 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1386 TCP_SKB_CB(skb
)->seq
+= shifted
;
1388 skb_shinfo(prev
)->gso_segs
+= pcount
;
1389 BUG_ON(skb_shinfo(skb
)->gso_segs
< pcount
);
1390 skb_shinfo(skb
)->gso_segs
-= pcount
;
1392 /* When we're adding to gso_segs == 1, gso_size will be zero,
1393 * in theory this shouldn't be necessary but as long as DSACK
1394 * code can come after this skb later on it's better to keep
1395 * setting gso_size to something.
1397 if (!skb_shinfo(prev
)->gso_size
) {
1398 skb_shinfo(prev
)->gso_size
= mss
;
1399 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1402 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1403 if (skb_shinfo(skb
)->gso_segs
<= 1) {
1404 skb_shinfo(skb
)->gso_size
= 0;
1405 skb_shinfo(skb
)->gso_type
= 0;
1408 /* We discard results */
1409 tcp_sacktag_one(skb
, sk
, state
, dup_sack
, pcount
);
1411 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1412 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1415 BUG_ON(!tcp_skb_pcount(skb
));
1416 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1420 /* Whole SKB was eaten :-) */
1422 if (skb
== tp
->retransmit_skb_hint
)
1423 tp
->retransmit_skb_hint
= prev
;
1424 if (skb
== tp
->scoreboard_skb_hint
)
1425 tp
->scoreboard_skb_hint
= prev
;
1426 if (skb
== tp
->lost_skb_hint
) {
1427 tp
->lost_skb_hint
= prev
;
1428 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1431 TCP_SKB_CB(skb
)->flags
|= TCP_SKB_CB(prev
)->flags
;
1432 if (skb
== tcp_highest_sack(sk
))
1433 tcp_advance_highest_sack(sk
, skb
);
1435 tcp_unlink_write_queue(skb
, sk
);
1436 sk_wmem_free_skb(sk
, skb
);
1438 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1443 /* I wish gso_size would have a bit more sane initialization than
1444 * something-or-zero which complicates things
1446 static int tcp_skb_seglen(struct sk_buff
*skb
)
1448 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1451 /* Shifting pages past head area doesn't work */
1452 static int skb_can_shift(struct sk_buff
*skb
)
1454 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1457 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1460 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1461 struct tcp_sacktag_state
*state
,
1462 u32 start_seq
, u32 end_seq
,
1465 struct tcp_sock
*tp
= tcp_sk(sk
);
1466 struct sk_buff
*prev
;
1472 if (!sk_can_gso(sk
))
1475 /* Normally R but no L won't result in plain S */
1477 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1479 if (!skb_can_shift(skb
))
1481 /* This frame is about to be dropped (was ACKed). */
1482 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1485 /* Can only happen with delayed DSACK + discard craziness */
1486 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1488 prev
= tcp_write_queue_prev(sk
, skb
);
1490 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1493 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1494 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1498 pcount
= tcp_skb_pcount(skb
);
1499 mss
= tcp_skb_seglen(skb
);
1501 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1502 * drop this restriction as unnecessary
1504 if (mss
!= tcp_skb_seglen(prev
))
1507 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1509 /* CHECKME: This is non-MSS split case only?, this will
1510 * cause skipped skbs due to advancing loop btw, original
1511 * has that feature too
1513 if (tcp_skb_pcount(skb
) <= 1)
1516 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1518 /* TODO: head merge to next could be attempted here
1519 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1520 * though it might not be worth of the additional hassle
1522 * ...we can probably just fallback to what was done
1523 * previously. We could try merging non-SACKed ones
1524 * as well but it probably isn't going to buy off
1525 * because later SACKs might again split them, and
1526 * it would make skb timestamp tracking considerably
1532 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1534 BUG_ON(len
> skb
->len
);
1536 /* MSS boundaries should be honoured or else pcount will
1537 * severely break even though it makes things bit trickier.
1538 * Optimize common case to avoid most of the divides
1540 mss
= tcp_skb_mss(skb
);
1542 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1543 * drop this restriction as unnecessary
1545 if (mss
!= tcp_skb_seglen(prev
))
1550 } else if (len
< mss
) {
1558 if (!skb_shift(prev
, skb
, len
))
1560 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1563 /* Hole filled allows collapsing with the next as well, this is very
1564 * useful when hole on every nth skb pattern happens
1566 if (prev
== tcp_write_queue_tail(sk
))
1568 skb
= tcp_write_queue_next(sk
, prev
);
1570 if (!skb_can_shift(skb
) ||
1571 (skb
== tcp_send_head(sk
)) ||
1572 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1573 (mss
!= tcp_skb_seglen(skb
)))
1577 if (skb_shift(prev
, skb
, len
)) {
1578 pcount
+= tcp_skb_pcount(skb
);
1579 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1583 state
->fack_count
+= pcount
;
1590 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1594 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1595 struct tcp_sack_block
*next_dup
,
1596 struct tcp_sacktag_state
*state
,
1597 u32 start_seq
, u32 end_seq
,
1600 struct tcp_sock
*tp
= tcp_sk(sk
);
1601 struct sk_buff
*tmp
;
1603 tcp_for_write_queue_from(skb
, sk
) {
1605 int dup_sack
= dup_sack_in
;
1607 if (skb
== tcp_send_head(sk
))
1610 /* queue is in-order => we can short-circuit the walk early */
1611 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1614 if ((next_dup
!= NULL
) &&
1615 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1616 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1617 next_dup
->start_seq
,
1623 /* skb reference here is a bit tricky to get right, since
1624 * shifting can eat and free both this skb and the next,
1625 * so not even _safe variant of the loop is enough.
1628 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1629 start_seq
, end_seq
, dup_sack
);
1638 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1644 if (unlikely(in_sack
< 0))
1648 TCP_SKB_CB(skb
)->sacked
= tcp_sacktag_one(skb
, sk
,
1651 tcp_skb_pcount(skb
));
1653 if (!before(TCP_SKB_CB(skb
)->seq
,
1654 tcp_highest_sack_seq(tp
)))
1655 tcp_advance_highest_sack(sk
, skb
);
1658 state
->fack_count
+= tcp_skb_pcount(skb
);
1663 /* Avoid all extra work that is being done by sacktag while walking in
1666 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1667 struct tcp_sacktag_state
*state
,
1670 tcp_for_write_queue_from(skb
, sk
) {
1671 if (skb
== tcp_send_head(sk
))
1674 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1677 state
->fack_count
+= tcp_skb_pcount(skb
);
1682 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1684 struct tcp_sack_block
*next_dup
,
1685 struct tcp_sacktag_state
*state
,
1688 if (next_dup
== NULL
)
1691 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1692 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1693 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1694 next_dup
->start_seq
, next_dup
->end_seq
,
1701 static int tcp_sack_cache_ok(struct tcp_sock
*tp
, struct tcp_sack_block
*cache
)
1703 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1707 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
,
1710 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1711 struct tcp_sock
*tp
= tcp_sk(sk
);
1712 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1713 TCP_SKB_CB(ack_skb
)->sacked
);
1714 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1715 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1716 struct tcp_sack_block
*cache
;
1717 struct tcp_sacktag_state state
;
1718 struct sk_buff
*skb
;
1719 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1721 int found_dup_sack
= 0;
1723 int first_sack_index
;
1726 state
.reord
= tp
->packets_out
;
1728 if (!tp
->sacked_out
) {
1729 if (WARN_ON(tp
->fackets_out
))
1730 tp
->fackets_out
= 0;
1731 tcp_highest_sack_reset(sk
);
1734 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1735 num_sacks
, prior_snd_una
);
1737 state
.flag
|= FLAG_DSACKING_ACK
;
1739 /* Eliminate too old ACKs, but take into
1740 * account more or less fresh ones, they can
1741 * contain valid SACK info.
1743 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1746 if (!tp
->packets_out
)
1750 first_sack_index
= 0;
1751 for (i
= 0; i
< num_sacks
; i
++) {
1752 int dup_sack
= !i
&& found_dup_sack
;
1754 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1755 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1757 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1758 sp
[used_sacks
].start_seq
,
1759 sp
[used_sacks
].end_seq
)) {
1763 if (!tp
->undo_marker
)
1764 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1766 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1768 /* Don't count olds caused by ACK reordering */
1769 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1770 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1772 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1775 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1777 first_sack_index
= -1;
1781 /* Ignore very old stuff early */
1782 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1788 /* order SACK blocks to allow in order walk of the retrans queue */
1789 for (i
= used_sacks
- 1; i
> 0; i
--) {
1790 for (j
= 0; j
< i
; j
++) {
1791 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1792 swap(sp
[j
], sp
[j
+ 1]);
1794 /* Track where the first SACK block goes to */
1795 if (j
== first_sack_index
)
1796 first_sack_index
= j
+ 1;
1801 skb
= tcp_write_queue_head(sk
);
1802 state
.fack_count
= 0;
1805 if (!tp
->sacked_out
) {
1806 /* It's already past, so skip checking against it */
1807 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1809 cache
= tp
->recv_sack_cache
;
1810 /* Skip empty blocks in at head of the cache */
1811 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1816 while (i
< used_sacks
) {
1817 u32 start_seq
= sp
[i
].start_seq
;
1818 u32 end_seq
= sp
[i
].end_seq
;
1819 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1820 struct tcp_sack_block
*next_dup
= NULL
;
1822 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1823 next_dup
= &sp
[i
+ 1];
1825 /* Event "B" in the comment above. */
1826 if (after(end_seq
, tp
->high_seq
))
1827 state
.flag
|= FLAG_DATA_LOST
;
1829 /* Skip too early cached blocks */
1830 while (tcp_sack_cache_ok(tp
, cache
) &&
1831 !before(start_seq
, cache
->end_seq
))
1834 /* Can skip some work by looking recv_sack_cache? */
1835 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1836 after(end_seq
, cache
->start_seq
)) {
1839 if (before(start_seq
, cache
->start_seq
)) {
1840 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1842 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1849 /* Rest of the block already fully processed? */
1850 if (!after(end_seq
, cache
->end_seq
))
1853 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1857 /* ...tail remains todo... */
1858 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1859 /* ...but better entrypoint exists! */
1860 skb
= tcp_highest_sack(sk
);
1863 state
.fack_count
= tp
->fackets_out
;
1868 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1869 /* Check overlap against next cached too (past this one already) */
1874 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1875 skb
= tcp_highest_sack(sk
);
1878 state
.fack_count
= tp
->fackets_out
;
1880 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1883 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1884 start_seq
, end_seq
, dup_sack
);
1887 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1888 * due to in-order walk
1890 if (after(end_seq
, tp
->frto_highmark
))
1891 state
.flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1896 /* Clear the head of the cache sack blocks so we can skip it next time */
1897 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1898 tp
->recv_sack_cache
[i
].start_seq
= 0;
1899 tp
->recv_sack_cache
[i
].end_seq
= 0;
1901 for (j
= 0; j
< used_sacks
; j
++)
1902 tp
->recv_sack_cache
[i
++] = sp
[j
];
1904 tcp_mark_lost_retrans(sk
);
1906 tcp_verify_left_out(tp
);
1908 if ((state
.reord
< tp
->fackets_out
) &&
1909 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1910 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1911 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1915 #if FASTRETRANS_DEBUG > 0
1916 WARN_ON((int)tp
->sacked_out
< 0);
1917 WARN_ON((int)tp
->lost_out
< 0);
1918 WARN_ON((int)tp
->retrans_out
< 0);
1919 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1924 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1925 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1927 static int tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1931 holes
= max(tp
->lost_out
, 1U);
1932 holes
= min(holes
, tp
->packets_out
);
1934 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1935 tp
->sacked_out
= tp
->packets_out
- holes
;
1941 /* If we receive more dupacks than we expected counting segments
1942 * in assumption of absent reordering, interpret this as reordering.
1943 * The only another reason could be bug in receiver TCP.
1945 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1947 struct tcp_sock
*tp
= tcp_sk(sk
);
1948 if (tcp_limit_reno_sacked(tp
))
1949 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1952 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1954 static void tcp_add_reno_sack(struct sock
*sk
)
1956 struct tcp_sock
*tp
= tcp_sk(sk
);
1958 tcp_check_reno_reordering(sk
, 0);
1959 tcp_verify_left_out(tp
);
1962 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1964 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1966 struct tcp_sock
*tp
= tcp_sk(sk
);
1969 /* One ACK acked hole. The rest eat duplicate ACKs. */
1970 if (acked
- 1 >= tp
->sacked_out
)
1973 tp
->sacked_out
-= acked
- 1;
1975 tcp_check_reno_reordering(sk
, acked
);
1976 tcp_verify_left_out(tp
);
1979 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1984 static int tcp_is_sackfrto(const struct tcp_sock
*tp
)
1986 return (sysctl_tcp_frto
== 0x2) && !tcp_is_reno(tp
);
1989 /* F-RTO can only be used if TCP has never retransmitted anything other than
1990 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1992 int tcp_use_frto(struct sock
*sk
)
1994 const struct tcp_sock
*tp
= tcp_sk(sk
);
1995 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1996 struct sk_buff
*skb
;
1998 if (!sysctl_tcp_frto
)
2001 /* MTU probe and F-RTO won't really play nicely along currently */
2002 if (icsk
->icsk_mtup
.probe_size
)
2005 if (tcp_is_sackfrto(tp
))
2008 /* Avoid expensive walking of rexmit queue if possible */
2009 if (tp
->retrans_out
> 1)
2012 skb
= tcp_write_queue_head(sk
);
2013 if (tcp_skb_is_last(sk
, skb
))
2015 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
2016 tcp_for_write_queue_from(skb
, sk
) {
2017 if (skb
== tcp_send_head(sk
))
2019 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2021 /* Short-circuit when first non-SACKed skb has been checked */
2022 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2028 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2029 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2030 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2031 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2032 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2033 * bits are handled if the Loss state is really to be entered (in
2034 * tcp_enter_frto_loss).
2036 * Do like tcp_enter_loss() would; when RTO expires the second time it
2038 * "Reduce ssthresh if it has not yet been made inside this window."
2040 void tcp_enter_frto(struct sock
*sk
)
2042 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2043 struct tcp_sock
*tp
= tcp_sk(sk
);
2044 struct sk_buff
*skb
;
2046 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
2047 tp
->snd_una
== tp
->high_seq
||
2048 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
2049 !icsk
->icsk_retransmits
)) {
2050 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2051 /* Our state is too optimistic in ssthresh() call because cwnd
2052 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2053 * recovery has not yet completed. Pattern would be this: RTO,
2054 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2056 * RFC4138 should be more specific on what to do, even though
2057 * RTO is quite unlikely to occur after the first Cumulative ACK
2058 * due to back-off and complexity of triggering events ...
2060 if (tp
->frto_counter
) {
2062 stored_cwnd
= tp
->snd_cwnd
;
2064 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2065 tp
->snd_cwnd
= stored_cwnd
;
2067 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2069 /* ... in theory, cong.control module could do "any tricks" in
2070 * ssthresh(), which means that ca_state, lost bits and lost_out
2071 * counter would have to be faked before the call occurs. We
2072 * consider that too expensive, unlikely and hacky, so modules
2073 * using these in ssthresh() must deal these incompatibility
2074 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2076 tcp_ca_event(sk
, CA_EVENT_FRTO
);
2079 tp
->undo_marker
= tp
->snd_una
;
2080 tp
->undo_retrans
= 0;
2082 skb
= tcp_write_queue_head(sk
);
2083 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2084 tp
->undo_marker
= 0;
2085 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2086 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2087 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2089 tcp_verify_left_out(tp
);
2091 /* Too bad if TCP was application limited */
2092 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2094 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2095 * The last condition is necessary at least in tp->frto_counter case.
2097 if (tcp_is_sackfrto(tp
) && (tp
->frto_counter
||
2098 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
2099 after(tp
->high_seq
, tp
->snd_una
)) {
2100 tp
->frto_highmark
= tp
->high_seq
;
2102 tp
->frto_highmark
= tp
->snd_nxt
;
2104 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
2105 tp
->high_seq
= tp
->snd_nxt
;
2106 tp
->frto_counter
= 1;
2109 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2110 * which indicates that we should follow the traditional RTO recovery,
2111 * i.e. mark everything lost and do go-back-N retransmission.
2113 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
2115 struct tcp_sock
*tp
= tcp_sk(sk
);
2116 struct sk_buff
*skb
;
2119 tp
->retrans_out
= 0;
2120 if (tcp_is_reno(tp
))
2121 tcp_reset_reno_sack(tp
);
2123 tcp_for_write_queue(skb
, sk
) {
2124 if (skb
== tcp_send_head(sk
))
2127 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2129 * Count the retransmission made on RTO correctly (only when
2130 * waiting for the first ACK and did not get it)...
2132 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
2133 /* For some reason this R-bit might get cleared? */
2134 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
2135 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2136 /* ...enter this if branch just for the first segment */
2137 flag
|= FLAG_DATA_ACKED
;
2139 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2140 tp
->undo_marker
= 0;
2141 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2144 /* Marking forward transmissions that were made after RTO lost
2145 * can cause unnecessary retransmissions in some scenarios,
2146 * SACK blocks will mitigate that in some but not in all cases.
2147 * We used to not mark them but it was causing break-ups with
2148 * receivers that do only in-order receival.
2150 * TODO: we could detect presence of such receiver and select
2151 * different behavior per flow.
2153 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2154 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2155 tp
->lost_out
+= tcp_skb_pcount(skb
);
2156 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2159 tcp_verify_left_out(tp
);
2161 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
2162 tp
->snd_cwnd_cnt
= 0;
2163 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2164 tp
->frto_counter
= 0;
2165 tp
->bytes_acked
= 0;
2167 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2168 sysctl_tcp_reordering
);
2169 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2170 tp
->high_seq
= tp
->snd_nxt
;
2171 TCP_ECN_queue_cwr(tp
);
2173 tcp_clear_all_retrans_hints(tp
);
2176 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
2178 tp
->retrans_out
= 0;
2181 tp
->undo_marker
= 0;
2182 tp
->undo_retrans
= 0;
2185 void tcp_clear_retrans(struct tcp_sock
*tp
)
2187 tcp_clear_retrans_partial(tp
);
2189 tp
->fackets_out
= 0;
2193 /* Enter Loss state. If "how" is not zero, forget all SACK information
2194 * and reset tags completely, otherwise preserve SACKs. If receiver
2195 * dropped its ofo queue, we will know this due to reneging detection.
2197 void tcp_enter_loss(struct sock
*sk
, int how
)
2199 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2200 struct tcp_sock
*tp
= tcp_sk(sk
);
2201 struct sk_buff
*skb
;
2203 /* Reduce ssthresh if it has not yet been made inside this window. */
2204 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
2205 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
2206 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2207 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2208 tcp_ca_event(sk
, CA_EVENT_LOSS
);
2211 tp
->snd_cwnd_cnt
= 0;
2212 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2214 tp
->bytes_acked
= 0;
2215 tcp_clear_retrans_partial(tp
);
2217 if (tcp_is_reno(tp
))
2218 tcp_reset_reno_sack(tp
);
2221 /* Push undo marker, if it was plain RTO and nothing
2222 * was retransmitted. */
2223 tp
->undo_marker
= tp
->snd_una
;
2226 tp
->fackets_out
= 0;
2228 tcp_clear_all_retrans_hints(tp
);
2230 tcp_for_write_queue(skb
, sk
) {
2231 if (skb
== tcp_send_head(sk
))
2234 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2235 tp
->undo_marker
= 0;
2236 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
2237 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
2238 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
2239 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2240 tp
->lost_out
+= tcp_skb_pcount(skb
);
2241 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2244 tcp_verify_left_out(tp
);
2246 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2247 sysctl_tcp_reordering
);
2248 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2249 tp
->high_seq
= tp
->snd_nxt
;
2250 TCP_ECN_queue_cwr(tp
);
2251 /* Abort F-RTO algorithm if one is in progress */
2252 tp
->frto_counter
= 0;
2255 /* If ACK arrived pointing to a remembered SACK, it means that our
2256 * remembered SACKs do not reflect real state of receiver i.e.
2257 * receiver _host_ is heavily congested (or buggy).
2259 * Do processing similar to RTO timeout.
2261 static int tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2263 if (flag
& FLAG_SACK_RENEGING
) {
2264 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2265 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
2267 tcp_enter_loss(sk
, 1);
2268 icsk
->icsk_retransmits
++;
2269 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
2270 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2271 icsk
->icsk_rto
, TCP_RTO_MAX
);
2277 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
2279 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2282 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2283 * counter when SACK is enabled (without SACK, sacked_out is used for
2286 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2287 * segments up to the highest received SACK block so far and holes in
2290 * With reordering, holes may still be in flight, so RFC3517 recovery
2291 * uses pure sacked_out (total number of SACKed segments) even though
2292 * it violates the RFC that uses duplicate ACKs, often these are equal
2293 * but when e.g. out-of-window ACKs or packet duplication occurs,
2294 * they differ. Since neither occurs due to loss, TCP should really
2297 static inline int tcp_dupack_heuristics(struct tcp_sock
*tp
)
2299 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2302 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
2304 return tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
;
2307 static inline int tcp_head_timedout(struct sock
*sk
)
2309 struct tcp_sock
*tp
= tcp_sk(sk
);
2311 return tp
->packets_out
&&
2312 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2315 /* Linux NewReno/SACK/FACK/ECN state machine.
2316 * --------------------------------------
2318 * "Open" Normal state, no dubious events, fast path.
2319 * "Disorder" In all the respects it is "Open",
2320 * but requires a bit more attention. It is entered when
2321 * we see some SACKs or dupacks. It is split of "Open"
2322 * mainly to move some processing from fast path to slow one.
2323 * "CWR" CWND was reduced due to some Congestion Notification event.
2324 * It can be ECN, ICMP source quench, local device congestion.
2325 * "Recovery" CWND was reduced, we are fast-retransmitting.
2326 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2328 * tcp_fastretrans_alert() is entered:
2329 * - each incoming ACK, if state is not "Open"
2330 * - when arrived ACK is unusual, namely:
2335 * Counting packets in flight is pretty simple.
2337 * in_flight = packets_out - left_out + retrans_out
2339 * packets_out is SND.NXT-SND.UNA counted in packets.
2341 * retrans_out is number of retransmitted segments.
2343 * left_out is number of segments left network, but not ACKed yet.
2345 * left_out = sacked_out + lost_out
2347 * sacked_out: Packets, which arrived to receiver out of order
2348 * and hence not ACKed. With SACKs this number is simply
2349 * amount of SACKed data. Even without SACKs
2350 * it is easy to give pretty reliable estimate of this number,
2351 * counting duplicate ACKs.
2353 * lost_out: Packets lost by network. TCP has no explicit
2354 * "loss notification" feedback from network (for now).
2355 * It means that this number can be only _guessed_.
2356 * Actually, it is the heuristics to predict lossage that
2357 * distinguishes different algorithms.
2359 * F.e. after RTO, when all the queue is considered as lost,
2360 * lost_out = packets_out and in_flight = retrans_out.
2362 * Essentially, we have now two algorithms counting
2365 * FACK: It is the simplest heuristics. As soon as we decided
2366 * that something is lost, we decide that _all_ not SACKed
2367 * packets until the most forward SACK are lost. I.e.
2368 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2369 * It is absolutely correct estimate, if network does not reorder
2370 * packets. And it loses any connection to reality when reordering
2371 * takes place. We use FACK by default until reordering
2372 * is suspected on the path to this destination.
2374 * NewReno: when Recovery is entered, we assume that one segment
2375 * is lost (classic Reno). While we are in Recovery and
2376 * a partial ACK arrives, we assume that one more packet
2377 * is lost (NewReno). This heuristics are the same in NewReno
2380 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2381 * deflation etc. CWND is real congestion window, never inflated, changes
2382 * only according to classic VJ rules.
2384 * Really tricky (and requiring careful tuning) part of algorithm
2385 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2386 * The first determines the moment _when_ we should reduce CWND and,
2387 * hence, slow down forward transmission. In fact, it determines the moment
2388 * when we decide that hole is caused by loss, rather than by a reorder.
2390 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2391 * holes, caused by lost packets.
2393 * And the most logically complicated part of algorithm is undo
2394 * heuristics. We detect false retransmits due to both too early
2395 * fast retransmit (reordering) and underestimated RTO, analyzing
2396 * timestamps and D-SACKs. When we detect that some segments were
2397 * retransmitted by mistake and CWND reduction was wrong, we undo
2398 * window reduction and abort recovery phase. This logic is hidden
2399 * inside several functions named tcp_try_undo_<something>.
2402 /* This function decides, when we should leave Disordered state
2403 * and enter Recovery phase, reducing congestion window.
2405 * Main question: may we further continue forward transmission
2406 * with the same cwnd?
2408 static int tcp_time_to_recover(struct sock
*sk
)
2410 struct tcp_sock
*tp
= tcp_sk(sk
);
2413 /* Do not perform any recovery during F-RTO algorithm */
2414 if (tp
->frto_counter
)
2417 /* Trick#1: The loss is proven. */
2421 /* Not-A-Trick#2 : Classic rule... */
2422 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2425 /* Trick#3 : when we use RFC2988 timer restart, fast
2426 * retransmit can be triggered by timeout of queue head.
2428 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2431 /* Trick#4: It is still not OK... But will it be useful to delay
2434 packets_out
= tp
->packets_out
;
2435 if (packets_out
<= tp
->reordering
&&
2436 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2437 !tcp_may_send_now(sk
)) {
2438 /* We have nothing to send. This connection is limited
2439 * either by receiver window or by application.
2444 /* If a thin stream is detected, retransmit after first
2445 * received dupack. Employ only if SACK is supported in order
2446 * to avoid possible corner-case series of spurious retransmissions
2447 * Use only if there are no unsent data.
2449 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2450 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2451 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2457 /* New heuristics: it is possible only after we switched to restart timer
2458 * each time when something is ACKed. Hence, we can detect timed out packets
2459 * during fast retransmit without falling to slow start.
2461 * Usefulness of this as is very questionable, since we should know which of
2462 * the segments is the next to timeout which is relatively expensive to find
2463 * in general case unless we add some data structure just for that. The
2464 * current approach certainly won't find the right one too often and when it
2465 * finally does find _something_ it usually marks large part of the window
2466 * right away (because a retransmission with a larger timestamp blocks the
2467 * loop from advancing). -ij
2469 static void tcp_timeout_skbs(struct sock
*sk
)
2471 struct tcp_sock
*tp
= tcp_sk(sk
);
2472 struct sk_buff
*skb
;
2474 if (!tcp_is_fack(tp
) || !tcp_head_timedout(sk
))
2477 skb
= tp
->scoreboard_skb_hint
;
2478 if (tp
->scoreboard_skb_hint
== NULL
)
2479 skb
= tcp_write_queue_head(sk
);
2481 tcp_for_write_queue_from(skb
, sk
) {
2482 if (skb
== tcp_send_head(sk
))
2484 if (!tcp_skb_timedout(sk
, skb
))
2487 tcp_skb_mark_lost(tp
, skb
);
2490 tp
->scoreboard_skb_hint
= skb
;
2492 tcp_verify_left_out(tp
);
2495 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2496 * is against sacked "cnt", otherwise it's against facked "cnt"
2498 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2500 struct tcp_sock
*tp
= tcp_sk(sk
);
2501 struct sk_buff
*skb
;
2506 WARN_ON(packets
> tp
->packets_out
);
2507 if (tp
->lost_skb_hint
) {
2508 skb
= tp
->lost_skb_hint
;
2509 cnt
= tp
->lost_cnt_hint
;
2510 /* Head already handled? */
2511 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2514 skb
= tcp_write_queue_head(sk
);
2518 tcp_for_write_queue_from(skb
, sk
) {
2519 if (skb
== tcp_send_head(sk
))
2521 /* TODO: do this better */
2522 /* this is not the most efficient way to do this... */
2523 tp
->lost_skb_hint
= skb
;
2524 tp
->lost_cnt_hint
= cnt
;
2526 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->high_seq
))
2530 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2531 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2532 cnt
+= tcp_skb_pcount(skb
);
2534 if (cnt
> packets
) {
2535 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2536 (oldcnt
>= packets
))
2539 mss
= skb_shinfo(skb
)->gso_size
;
2540 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2546 tcp_skb_mark_lost(tp
, skb
);
2551 tcp_verify_left_out(tp
);
2554 /* Account newly detected lost packet(s) */
2556 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2558 struct tcp_sock
*tp
= tcp_sk(sk
);
2560 if (tcp_is_reno(tp
)) {
2561 tcp_mark_head_lost(sk
, 1, 1);
2562 } else if (tcp_is_fack(tp
)) {
2563 int lost
= tp
->fackets_out
- tp
->reordering
;
2566 tcp_mark_head_lost(sk
, lost
, 0);
2568 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2569 if (sacked_upto
>= 0)
2570 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2571 else if (fast_rexmit
)
2572 tcp_mark_head_lost(sk
, 1, 1);
2575 tcp_timeout_skbs(sk
);
2578 /* CWND moderation, preventing bursts due to too big ACKs
2579 * in dubious situations.
2581 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2583 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2584 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2585 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2588 /* Lower bound on congestion window is slow start threshold
2589 * unless congestion avoidance choice decides to overide it.
2591 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2593 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2595 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2598 /* Decrease cwnd each second ack. */
2599 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2601 struct tcp_sock
*tp
= tcp_sk(sk
);
2602 int decr
= tp
->snd_cwnd_cnt
+ 1;
2604 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2605 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2606 tp
->snd_cwnd_cnt
= decr
& 1;
2609 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2610 tp
->snd_cwnd
-= decr
;
2612 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2613 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2617 /* Nothing was retransmitted or returned timestamp is less
2618 * than timestamp of the first retransmission.
2620 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
2622 return !tp
->retrans_stamp
||
2623 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2624 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2627 /* Undo procedures. */
2629 #if FASTRETRANS_DEBUG > 1
2630 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2632 struct tcp_sock
*tp
= tcp_sk(sk
);
2633 struct inet_sock
*inet
= inet_sk(sk
);
2635 if (sk
->sk_family
== AF_INET
) {
2636 printk(KERN_DEBUG
"Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2638 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2639 tp
->snd_cwnd
, tcp_left_out(tp
),
2640 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2643 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
2644 else if (sk
->sk_family
== AF_INET6
) {
2645 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2646 printk(KERN_DEBUG
"Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2648 &np
->daddr
, ntohs(inet
->inet_dport
),
2649 tp
->snd_cwnd
, tcp_left_out(tp
),
2650 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2656 #define DBGUNDO(x...) do { } while (0)
2659 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
2661 struct tcp_sock
*tp
= tcp_sk(sk
);
2663 if (tp
->prior_ssthresh
) {
2664 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2666 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2667 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2669 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2671 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2672 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2673 TCP_ECN_withdraw_cwr(tp
);
2676 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2678 tcp_moderate_cwnd(tp
);
2679 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2682 static inline int tcp_may_undo(struct tcp_sock
*tp
)
2684 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2687 /* People celebrate: "We love our President!" */
2688 static int tcp_try_undo_recovery(struct sock
*sk
)
2690 struct tcp_sock
*tp
= tcp_sk(sk
);
2692 if (tcp_may_undo(tp
)) {
2695 /* Happy end! We did not retransmit anything
2696 * or our original transmission succeeded.
2698 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2699 tcp_undo_cwr(sk
, 1);
2700 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2701 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2703 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2705 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2706 tp
->undo_marker
= 0;
2708 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2709 /* Hold old state until something *above* high_seq
2710 * is ACKed. For Reno it is MUST to prevent false
2711 * fast retransmits (RFC2582). SACK TCP is safe. */
2712 tcp_moderate_cwnd(tp
);
2715 tcp_set_ca_state(sk
, TCP_CA_Open
);
2719 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2720 static void tcp_try_undo_dsack(struct sock
*sk
)
2722 struct tcp_sock
*tp
= tcp_sk(sk
);
2724 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2725 DBGUNDO(sk
, "D-SACK");
2726 tcp_undo_cwr(sk
, 1);
2727 tp
->undo_marker
= 0;
2728 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2732 /* We can clear retrans_stamp when there are no retransmissions in the
2733 * window. It would seem that it is trivially available for us in
2734 * tp->retrans_out, however, that kind of assumptions doesn't consider
2735 * what will happen if errors occur when sending retransmission for the
2736 * second time. ...It could the that such segment has only
2737 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2738 * the head skb is enough except for some reneging corner cases that
2739 * are not worth the effort.
2741 * Main reason for all this complexity is the fact that connection dying
2742 * time now depends on the validity of the retrans_stamp, in particular,
2743 * that successive retransmissions of a segment must not advance
2744 * retrans_stamp under any conditions.
2746 static int tcp_any_retrans_done(struct sock
*sk
)
2748 struct tcp_sock
*tp
= tcp_sk(sk
);
2749 struct sk_buff
*skb
;
2751 if (tp
->retrans_out
)
2754 skb
= tcp_write_queue_head(sk
);
2755 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2761 /* Undo during fast recovery after partial ACK. */
2763 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2765 struct tcp_sock
*tp
= tcp_sk(sk
);
2766 /* Partial ACK arrived. Force Hoe's retransmit. */
2767 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2769 if (tcp_may_undo(tp
)) {
2770 /* Plain luck! Hole if filled with delayed
2771 * packet, rather than with a retransmit.
2773 if (!tcp_any_retrans_done(sk
))
2774 tp
->retrans_stamp
= 0;
2776 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2779 tcp_undo_cwr(sk
, 0);
2780 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2782 /* So... Do not make Hoe's retransmit yet.
2783 * If the first packet was delayed, the rest
2784 * ones are most probably delayed as well.
2791 /* Undo during loss recovery after partial ACK. */
2792 static int tcp_try_undo_loss(struct sock
*sk
)
2794 struct tcp_sock
*tp
= tcp_sk(sk
);
2796 if (tcp_may_undo(tp
)) {
2797 struct sk_buff
*skb
;
2798 tcp_for_write_queue(skb
, sk
) {
2799 if (skb
== tcp_send_head(sk
))
2801 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2804 tcp_clear_all_retrans_hints(tp
);
2806 DBGUNDO(sk
, "partial loss");
2808 tcp_undo_cwr(sk
, 1);
2809 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2810 inet_csk(sk
)->icsk_retransmits
= 0;
2811 tp
->undo_marker
= 0;
2812 if (tcp_is_sack(tp
))
2813 tcp_set_ca_state(sk
, TCP_CA_Open
);
2819 static inline void tcp_complete_cwr(struct sock
*sk
)
2821 struct tcp_sock
*tp
= tcp_sk(sk
);
2822 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2823 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2824 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2827 static void tcp_try_keep_open(struct sock
*sk
)
2829 struct tcp_sock
*tp
= tcp_sk(sk
);
2830 int state
= TCP_CA_Open
;
2832 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
) || tp
->undo_marker
)
2833 state
= TCP_CA_Disorder
;
2835 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2836 tcp_set_ca_state(sk
, state
);
2837 tp
->high_seq
= tp
->snd_nxt
;
2841 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2843 struct tcp_sock
*tp
= tcp_sk(sk
);
2845 tcp_verify_left_out(tp
);
2847 if (!tp
->frto_counter
&& !tcp_any_retrans_done(sk
))
2848 tp
->retrans_stamp
= 0;
2850 if (flag
& FLAG_ECE
)
2851 tcp_enter_cwr(sk
, 1);
2853 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2854 tcp_try_keep_open(sk
);
2855 tcp_moderate_cwnd(tp
);
2857 tcp_cwnd_down(sk
, flag
);
2861 static void tcp_mtup_probe_failed(struct sock
*sk
)
2863 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2865 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2866 icsk
->icsk_mtup
.probe_size
= 0;
2869 static void tcp_mtup_probe_success(struct sock
*sk
)
2871 struct tcp_sock
*tp
= tcp_sk(sk
);
2872 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2874 /* FIXME: breaks with very large cwnd */
2875 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2876 tp
->snd_cwnd
= tp
->snd_cwnd
*
2877 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2878 icsk
->icsk_mtup
.probe_size
;
2879 tp
->snd_cwnd_cnt
= 0;
2880 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2881 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2883 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2884 icsk
->icsk_mtup
.probe_size
= 0;
2885 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2888 /* Do a simple retransmit without using the backoff mechanisms in
2889 * tcp_timer. This is used for path mtu discovery.
2890 * The socket is already locked here.
2892 void tcp_simple_retransmit(struct sock
*sk
)
2894 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2895 struct tcp_sock
*tp
= tcp_sk(sk
);
2896 struct sk_buff
*skb
;
2897 unsigned int mss
= tcp_current_mss(sk
);
2898 u32 prior_lost
= tp
->lost_out
;
2900 tcp_for_write_queue(skb
, sk
) {
2901 if (skb
== tcp_send_head(sk
))
2903 if (tcp_skb_seglen(skb
) > mss
&&
2904 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2905 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2906 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2907 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2909 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2913 tcp_clear_retrans_hints_partial(tp
);
2915 if (prior_lost
== tp
->lost_out
)
2918 if (tcp_is_reno(tp
))
2919 tcp_limit_reno_sacked(tp
);
2921 tcp_verify_left_out(tp
);
2923 /* Don't muck with the congestion window here.
2924 * Reason is that we do not increase amount of _data_
2925 * in network, but units changed and effective
2926 * cwnd/ssthresh really reduced now.
2928 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2929 tp
->high_seq
= tp
->snd_nxt
;
2930 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2931 tp
->prior_ssthresh
= 0;
2932 tp
->undo_marker
= 0;
2933 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2935 tcp_xmit_retransmit_queue(sk
);
2937 EXPORT_SYMBOL(tcp_simple_retransmit
);
2939 /* Process an event, which can update packets-in-flight not trivially.
2940 * Main goal of this function is to calculate new estimate for left_out,
2941 * taking into account both packets sitting in receiver's buffer and
2942 * packets lost by network.
2944 * Besides that it does CWND reduction, when packet loss is detected
2945 * and changes state of machine.
2947 * It does _not_ decide what to send, it is made in function
2948 * tcp_xmit_retransmit_queue().
2950 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
, int flag
)
2952 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2953 struct tcp_sock
*tp
= tcp_sk(sk
);
2954 int is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
2955 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2956 (tcp_fackets_out(tp
) > tp
->reordering
));
2957 int fast_rexmit
= 0, mib_idx
;
2959 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2961 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2962 tp
->fackets_out
= 0;
2964 /* Now state machine starts.
2965 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2966 if (flag
& FLAG_ECE
)
2967 tp
->prior_ssthresh
= 0;
2969 /* B. In all the states check for reneging SACKs. */
2970 if (tcp_check_sack_reneging(sk
, flag
))
2973 /* C. Process data loss notification, provided it is valid. */
2974 if (tcp_is_fack(tp
) && (flag
& FLAG_DATA_LOST
) &&
2975 before(tp
->snd_una
, tp
->high_seq
) &&
2976 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2977 tp
->fackets_out
> tp
->reordering
) {
2978 tcp_mark_head_lost(sk
, tp
->fackets_out
- tp
->reordering
, 0);
2979 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSS
);
2982 /* D. Check consistency of the current state. */
2983 tcp_verify_left_out(tp
);
2985 /* E. Check state exit conditions. State can be terminated
2986 * when high_seq is ACKed. */
2987 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2988 WARN_ON(tp
->retrans_out
!= 0);
2989 tp
->retrans_stamp
= 0;
2990 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2991 switch (icsk
->icsk_ca_state
) {
2993 icsk
->icsk_retransmits
= 0;
2994 if (tcp_try_undo_recovery(sk
))
2999 /* CWR is to be held something *above* high_seq
3000 * is ACKed for CWR bit to reach receiver. */
3001 if (tp
->snd_una
!= tp
->high_seq
) {
3002 tcp_complete_cwr(sk
);
3003 tcp_set_ca_state(sk
, TCP_CA_Open
);
3007 case TCP_CA_Disorder
:
3008 tcp_try_undo_dsack(sk
);
3009 if (!tp
->undo_marker
||
3010 /* For SACK case do not Open to allow to undo
3011 * catching for all duplicate ACKs. */
3012 tcp_is_reno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
3013 tp
->undo_marker
= 0;
3014 tcp_set_ca_state(sk
, TCP_CA_Open
);
3018 case TCP_CA_Recovery
:
3019 if (tcp_is_reno(tp
))
3020 tcp_reset_reno_sack(tp
);
3021 if (tcp_try_undo_recovery(sk
))
3023 tcp_complete_cwr(sk
);
3028 /* F. Process state. */
3029 switch (icsk
->icsk_ca_state
) {
3030 case TCP_CA_Recovery
:
3031 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
3032 if (tcp_is_reno(tp
) && is_dupack
)
3033 tcp_add_reno_sack(sk
);
3035 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
3038 if (flag
& FLAG_DATA_ACKED
)
3039 icsk
->icsk_retransmits
= 0;
3040 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
3041 tcp_reset_reno_sack(tp
);
3042 if (!tcp_try_undo_loss(sk
)) {
3043 tcp_moderate_cwnd(tp
);
3044 tcp_xmit_retransmit_queue(sk
);
3047 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
3049 /* Loss is undone; fall through to processing in Open state. */
3051 if (tcp_is_reno(tp
)) {
3052 if (flag
& FLAG_SND_UNA_ADVANCED
)
3053 tcp_reset_reno_sack(tp
);
3055 tcp_add_reno_sack(sk
);
3058 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
3059 tcp_try_undo_dsack(sk
);
3061 if (!tcp_time_to_recover(sk
)) {
3062 tcp_try_to_open(sk
, flag
);
3066 /* MTU probe failure: don't reduce cwnd */
3067 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
3068 icsk
->icsk_mtup
.probe_size
&&
3069 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
3070 tcp_mtup_probe_failed(sk
);
3071 /* Restores the reduction we did in tcp_mtup_probe() */
3073 tcp_simple_retransmit(sk
);
3077 /* Otherwise enter Recovery state */
3079 if (tcp_is_reno(tp
))
3080 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
3082 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
3084 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3086 tp
->high_seq
= tp
->snd_nxt
;
3087 tp
->prior_ssthresh
= 0;
3088 tp
->undo_marker
= tp
->snd_una
;
3089 tp
->undo_retrans
= tp
->retrans_out
;
3091 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
3092 if (!(flag
& FLAG_ECE
))
3093 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
3094 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
3095 TCP_ECN_queue_cwr(tp
);
3098 tp
->bytes_acked
= 0;
3099 tp
->snd_cwnd_cnt
= 0;
3100 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
3104 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
3105 tcp_update_scoreboard(sk
, fast_rexmit
);
3106 tcp_cwnd_down(sk
, flag
);
3107 tcp_xmit_retransmit_queue(sk
);
3110 static void tcp_valid_rtt_meas(struct sock
*sk
, u32 seq_rtt
)
3112 tcp_rtt_estimator(sk
, seq_rtt
);
3114 inet_csk(sk
)->icsk_backoff
= 0;
3117 /* Read draft-ietf-tcplw-high-performance before mucking
3118 * with this code. (Supersedes RFC1323)
3120 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
3122 /* RTTM Rule: A TSecr value received in a segment is used to
3123 * update the averaged RTT measurement only if the segment
3124 * acknowledges some new data, i.e., only if it advances the
3125 * left edge of the send window.
3127 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3128 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3130 * Changed: reset backoff as soon as we see the first valid sample.
3131 * If we do not, we get strongly overestimated rto. With timestamps
3132 * samples are accepted even from very old segments: f.e., when rtt=1
3133 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3134 * answer arrives rto becomes 120 seconds! If at least one of segments
3135 * in window is lost... Voila. --ANK (010210)
3137 struct tcp_sock
*tp
= tcp_sk(sk
);
3139 tcp_valid_rtt_meas(sk
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
3142 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
3144 /* We don't have a timestamp. Can only use
3145 * packets that are not retransmitted to determine
3146 * rtt estimates. Also, we must not reset the
3147 * backoff for rto until we get a non-retransmitted
3148 * packet. This allows us to deal with a situation
3149 * where the network delay has increased suddenly.
3150 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3153 if (flag
& FLAG_RETRANS_DATA_ACKED
)
3156 tcp_valid_rtt_meas(sk
, seq_rtt
);
3159 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
3162 const struct tcp_sock
*tp
= tcp_sk(sk
);
3163 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3164 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3165 tcp_ack_saw_tstamp(sk
, flag
);
3166 else if (seq_rtt
>= 0)
3167 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
3170 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
3172 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3173 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
3174 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
3177 /* Restart timer after forward progress on connection.
3178 * RFC2988 recommends to restart timer to now+rto.
3180 static void tcp_rearm_rto(struct sock
*sk
)
3182 struct tcp_sock
*tp
= tcp_sk(sk
);
3184 if (!tp
->packets_out
) {
3185 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3187 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3188 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3192 /* If we get here, the whole TSO packet has not been acked. */
3193 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3195 struct tcp_sock
*tp
= tcp_sk(sk
);
3198 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3200 packets_acked
= tcp_skb_pcount(skb
);
3201 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3203 packets_acked
-= tcp_skb_pcount(skb
);
3205 if (packets_acked
) {
3206 BUG_ON(tcp_skb_pcount(skb
) == 0);
3207 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3210 return packets_acked
;
3213 /* Remove acknowledged frames from the retransmission queue. If our packet
3214 * is before the ack sequence we can discard it as it's confirmed to have
3215 * arrived at the other end.
3217 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3220 struct tcp_sock
*tp
= tcp_sk(sk
);
3221 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3222 struct sk_buff
*skb
;
3223 u32 now
= tcp_time_stamp
;
3224 int fully_acked
= 1;
3227 u32 reord
= tp
->packets_out
;
3228 u32 prior_sacked
= tp
->sacked_out
;
3230 s32 ca_seq_rtt
= -1;
3231 ktime_t last_ackt
= net_invalid_timestamp();
3233 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3234 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3236 u8 sacked
= scb
->sacked
;
3238 /* Determine how many packets and what bytes were acked, tso and else */
3239 if (after(scb
->end_seq
, tp
->snd_una
)) {
3240 if (tcp_skb_pcount(skb
) == 1 ||
3241 !after(tp
->snd_una
, scb
->seq
))
3244 acked_pcount
= tcp_tso_acked(sk
, skb
);
3250 acked_pcount
= tcp_skb_pcount(skb
);
3253 if (sacked
& TCPCB_RETRANS
) {
3254 if (sacked
& TCPCB_SACKED_RETRANS
)
3255 tp
->retrans_out
-= acked_pcount
;
3256 flag
|= FLAG_RETRANS_DATA_ACKED
;
3259 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
3260 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
3262 ca_seq_rtt
= now
- scb
->when
;
3263 last_ackt
= skb
->tstamp
;
3265 seq_rtt
= ca_seq_rtt
;
3267 if (!(sacked
& TCPCB_SACKED_ACKED
))
3268 reord
= min(pkts_acked
, reord
);
3271 if (sacked
& TCPCB_SACKED_ACKED
)
3272 tp
->sacked_out
-= acked_pcount
;
3273 if (sacked
& TCPCB_LOST
)
3274 tp
->lost_out
-= acked_pcount
;
3276 tp
->packets_out
-= acked_pcount
;
3277 pkts_acked
+= acked_pcount
;
3279 /* Initial outgoing SYN's get put onto the write_queue
3280 * just like anything else we transmit. It is not
3281 * true data, and if we misinform our callers that
3282 * this ACK acks real data, we will erroneously exit
3283 * connection startup slow start one packet too
3284 * quickly. This is severely frowned upon behavior.
3286 if (!(scb
->flags
& TCPHDR_SYN
)) {
3287 flag
|= FLAG_DATA_ACKED
;
3289 flag
|= FLAG_SYN_ACKED
;
3290 tp
->retrans_stamp
= 0;
3296 tcp_unlink_write_queue(skb
, sk
);
3297 sk_wmem_free_skb(sk
, skb
);
3298 tp
->scoreboard_skb_hint
= NULL
;
3299 if (skb
== tp
->retransmit_skb_hint
)
3300 tp
->retransmit_skb_hint
= NULL
;
3301 if (skb
== tp
->lost_skb_hint
)
3302 tp
->lost_skb_hint
= NULL
;
3305 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3306 tp
->snd_up
= tp
->snd_una
;
3308 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3309 flag
|= FLAG_SACK_RENEGING
;
3311 if (flag
& FLAG_ACKED
) {
3312 const struct tcp_congestion_ops
*ca_ops
3313 = inet_csk(sk
)->icsk_ca_ops
;
3315 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3316 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3317 tcp_mtup_probe_success(sk
);
3320 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
3323 if (tcp_is_reno(tp
)) {
3324 tcp_remove_reno_sacks(sk
, pkts_acked
);
3328 /* Non-retransmitted hole got filled? That's reordering */
3329 if (reord
< prior_fackets
)
3330 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3332 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3333 prior_sacked
- tp
->sacked_out
;
3334 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3337 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3339 if (ca_ops
->pkts_acked
) {
3342 /* Is the ACK triggering packet unambiguous? */
3343 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3344 /* High resolution needed and available? */
3345 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
3346 !ktime_equal(last_ackt
,
3347 net_invalid_timestamp()))
3348 rtt_us
= ktime_us_delta(ktime_get_real(),
3350 else if (ca_seq_rtt
> 0)
3351 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
3354 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
3358 #if FASTRETRANS_DEBUG > 0
3359 WARN_ON((int)tp
->sacked_out
< 0);
3360 WARN_ON((int)tp
->lost_out
< 0);
3361 WARN_ON((int)tp
->retrans_out
< 0);
3362 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3363 icsk
= inet_csk(sk
);
3365 printk(KERN_DEBUG
"Leak l=%u %d\n",
3366 tp
->lost_out
, icsk
->icsk_ca_state
);
3369 if (tp
->sacked_out
) {
3370 printk(KERN_DEBUG
"Leak s=%u %d\n",
3371 tp
->sacked_out
, icsk
->icsk_ca_state
);
3374 if (tp
->retrans_out
) {
3375 printk(KERN_DEBUG
"Leak r=%u %d\n",
3376 tp
->retrans_out
, icsk
->icsk_ca_state
);
3377 tp
->retrans_out
= 0;
3384 static void tcp_ack_probe(struct sock
*sk
)
3386 const struct tcp_sock
*tp
= tcp_sk(sk
);
3387 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3389 /* Was it a usable window open? */
3391 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3392 icsk
->icsk_backoff
= 0;
3393 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3394 /* Socket must be waked up by subsequent tcp_data_snd_check().
3395 * This function is not for random using!
3398 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3399 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3404 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3406 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3407 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3410 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3412 const struct tcp_sock
*tp
= tcp_sk(sk
);
3413 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3414 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
3417 /* Check that window update is acceptable.
3418 * The function assumes that snd_una<=ack<=snd_next.
3420 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
3421 const u32 ack
, const u32 ack_seq
,
3424 return after(ack
, tp
->snd_una
) ||
3425 after(ack_seq
, tp
->snd_wl1
) ||
3426 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3429 /* Update our send window.
3431 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3432 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3434 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
3437 struct tcp_sock
*tp
= tcp_sk(sk
);
3439 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3441 if (likely(!tcp_hdr(skb
)->syn
))
3442 nwin
<<= tp
->rx_opt
.snd_wscale
;
3444 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3445 flag
|= FLAG_WIN_UPDATE
;
3446 tcp_update_wl(tp
, ack_seq
);
3448 if (tp
->snd_wnd
!= nwin
) {
3451 /* Note, it is the only place, where
3452 * fast path is recovered for sending TCP.
3455 tcp_fast_path_check(sk
);
3457 if (nwin
> tp
->max_window
) {
3458 tp
->max_window
= nwin
;
3459 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3469 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3470 * continue in congestion avoidance.
3472 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3474 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3475 tp
->snd_cwnd_cnt
= 0;
3476 tp
->bytes_acked
= 0;
3477 TCP_ECN_queue_cwr(tp
);
3478 tcp_moderate_cwnd(tp
);
3481 /* A conservative spurious RTO response algorithm: reduce cwnd using
3482 * rate halving and continue in congestion avoidance.
3484 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3486 tcp_enter_cwr(sk
, 0);
3489 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3491 if (flag
& FLAG_ECE
)
3492 tcp_ratehalving_spur_to_response(sk
);
3494 tcp_undo_cwr(sk
, 1);
3497 /* F-RTO spurious RTO detection algorithm (RFC4138)
3499 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3500 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3501 * window (but not to or beyond highest sequence sent before RTO):
3502 * On First ACK, send two new segments out.
3503 * On Second ACK, RTO was likely spurious. Do spurious response (response
3504 * algorithm is not part of the F-RTO detection algorithm
3505 * given in RFC4138 but can be selected separately).
3506 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3507 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3508 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3509 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3511 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3512 * original window even after we transmit two new data segments.
3515 * on first step, wait until first cumulative ACK arrives, then move to
3516 * the second step. In second step, the next ACK decides.
3518 * F-RTO is implemented (mainly) in four functions:
3519 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3520 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3521 * called when tcp_use_frto() showed green light
3522 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3523 * - tcp_enter_frto_loss() is called if there is not enough evidence
3524 * to prove that the RTO is indeed spurious. It transfers the control
3525 * from F-RTO to the conventional RTO recovery
3527 static int tcp_process_frto(struct sock
*sk
, int flag
)
3529 struct tcp_sock
*tp
= tcp_sk(sk
);
3531 tcp_verify_left_out(tp
);
3533 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3534 if (flag
& FLAG_DATA_ACKED
)
3535 inet_csk(sk
)->icsk_retransmits
= 0;
3537 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3538 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3539 tp
->undo_marker
= 0;
3541 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3542 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3546 if (!tcp_is_sackfrto(tp
)) {
3547 /* RFC4138 shortcoming in step 2; should also have case c):
3548 * ACK isn't duplicate nor advances window, e.g., opposite dir
3551 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3554 if (!(flag
& FLAG_DATA_ACKED
)) {
3555 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3560 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3561 /* Prevent sending of new data. */
3562 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3563 tcp_packets_in_flight(tp
));
3567 if ((tp
->frto_counter
>= 2) &&
3568 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3569 ((flag
& FLAG_DATA_SACKED
) &&
3570 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3571 /* RFC4138 shortcoming (see comment above) */
3572 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3573 (flag
& FLAG_NOT_DUP
))
3576 tcp_enter_frto_loss(sk
, 3, flag
);
3581 if (tp
->frto_counter
== 1) {
3582 /* tcp_may_send_now needs to see updated state */
3583 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3584 tp
->frto_counter
= 2;
3586 if (!tcp_may_send_now(sk
))
3587 tcp_enter_frto_loss(sk
, 2, flag
);
3591 switch (sysctl_tcp_frto_response
) {
3593 tcp_undo_spur_to_response(sk
, flag
);
3596 tcp_conservative_spur_to_response(tp
);
3599 tcp_ratehalving_spur_to_response(sk
);
3602 tp
->frto_counter
= 0;
3603 tp
->undo_marker
= 0;
3604 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSPURIOUSRTOS
);
3609 /* This routine deals with incoming acks, but not outgoing ones. */
3610 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
3612 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3613 struct tcp_sock
*tp
= tcp_sk(sk
);
3614 u32 prior_snd_una
= tp
->snd_una
;
3615 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3616 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3617 u32 prior_in_flight
;
3622 /* If the ack is older than previous acks
3623 * then we can probably ignore it.
3625 if (before(ack
, prior_snd_una
))
3628 /* If the ack includes data we haven't sent yet, discard
3629 * this segment (RFC793 Section 3.9).
3631 if (after(ack
, tp
->snd_nxt
))
3634 if (after(ack
, prior_snd_una
))
3635 flag
|= FLAG_SND_UNA_ADVANCED
;
3637 if (sysctl_tcp_abc
) {
3638 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3639 tp
->bytes_acked
+= ack
- prior_snd_una
;
3640 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3641 /* we assume just one segment left network */
3642 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3646 prior_fackets
= tp
->fackets_out
;
3647 prior_in_flight
= tcp_packets_in_flight(tp
);
3649 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3650 /* Window is constant, pure forward advance.
3651 * No more checks are required.
3652 * Note, we use the fact that SND.UNA>=SND.WL2.
3654 tcp_update_wl(tp
, ack_seq
);
3656 flag
|= FLAG_WIN_UPDATE
;
3658 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3660 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3662 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3665 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3667 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3669 if (TCP_SKB_CB(skb
)->sacked
)
3670 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3672 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3675 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3678 /* We passed data and got it acked, remove any soft error
3679 * log. Something worked...
3681 sk
->sk_err_soft
= 0;
3682 icsk
->icsk_probes_out
= 0;
3683 tp
->rcv_tstamp
= tcp_time_stamp
;
3684 prior_packets
= tp
->packets_out
;
3688 /* See if we can take anything off of the retransmit queue. */
3689 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
);
3691 if (tp
->frto_counter
)
3692 frto_cwnd
= tcp_process_frto(sk
, flag
);
3693 /* Guarantee sacktag reordering detection against wrap-arounds */
3694 if (before(tp
->frto_highmark
, tp
->snd_una
))
3695 tp
->frto_highmark
= 0;
3697 if (tcp_ack_is_dubious(sk
, flag
)) {
3698 /* Advance CWND, if state allows this. */
3699 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3700 tcp_may_raise_cwnd(sk
, flag
))
3701 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3702 tcp_fastretrans_alert(sk
, prior_packets
- tp
->packets_out
,
3705 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3706 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3709 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3710 dst_confirm(__sk_dst_get(sk
));
3715 /* If this ack opens up a zero window, clear backoff. It was
3716 * being used to time the probes, and is probably far higher than
3717 * it needs to be for normal retransmission.
3719 if (tcp_send_head(sk
))
3724 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3728 if (TCP_SKB_CB(skb
)->sacked
) {
3729 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3730 if (icsk
->icsk_ca_state
== TCP_CA_Open
)
3731 tcp_try_keep_open(sk
);
3734 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3738 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3739 * But, this can also be called on packets in the established flow when
3740 * the fast version below fails.
3742 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3743 u8
**hvpp
, int estab
)
3746 struct tcphdr
*th
= tcp_hdr(skb
);
3747 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3749 ptr
= (unsigned char *)(th
+ 1);
3750 opt_rx
->saw_tstamp
= 0;
3752 while (length
> 0) {
3753 int opcode
= *ptr
++;
3759 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3764 if (opsize
< 2) /* "silly options" */
3766 if (opsize
> length
)
3767 return; /* don't parse partial options */
3770 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3771 u16 in_mss
= get_unaligned_be16(ptr
);
3773 if (opt_rx
->user_mss
&&
3774 opt_rx
->user_mss
< in_mss
)
3775 in_mss
= opt_rx
->user_mss
;
3776 opt_rx
->mss_clamp
= in_mss
;
3781 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3782 !estab
&& sysctl_tcp_window_scaling
) {
3783 __u8 snd_wscale
= *(__u8
*)ptr
;
3784 opt_rx
->wscale_ok
= 1;
3785 if (snd_wscale
> 14) {
3786 if (net_ratelimit())
3787 printk(KERN_INFO
"tcp_parse_options: Illegal window "
3788 "scaling value %d >14 received.\n",
3792 opt_rx
->snd_wscale
= snd_wscale
;
3795 case TCPOPT_TIMESTAMP
:
3796 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3797 ((estab
&& opt_rx
->tstamp_ok
) ||
3798 (!estab
&& sysctl_tcp_timestamps
))) {
3799 opt_rx
->saw_tstamp
= 1;
3800 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3801 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3804 case TCPOPT_SACK_PERM
:
3805 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3806 !estab
&& sysctl_tcp_sack
) {
3807 opt_rx
->sack_ok
= 1;
3808 tcp_sack_reset(opt_rx
);
3813 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3814 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3816 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3819 #ifdef CONFIG_TCP_MD5SIG
3822 * The MD5 Hash has already been
3823 * checked (see tcp_v{4,6}_do_rcv()).
3828 /* This option is variable length.
3831 case TCPOLEN_COOKIE_BASE
:
3832 /* not yet implemented */
3834 case TCPOLEN_COOKIE_PAIR
:
3835 /* not yet implemented */
3837 case TCPOLEN_COOKIE_MIN
+0:
3838 case TCPOLEN_COOKIE_MIN
+2:
3839 case TCPOLEN_COOKIE_MIN
+4:
3840 case TCPOLEN_COOKIE_MIN
+6:
3841 case TCPOLEN_COOKIE_MAX
:
3842 /* 16-bit multiple */
3843 opt_rx
->cookie_plus
= opsize
;
3858 EXPORT_SYMBOL(tcp_parse_options
);
3860 static int tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, struct tcphdr
*th
)
3862 __be32
*ptr
= (__be32
*)(th
+ 1);
3864 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3865 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3866 tp
->rx_opt
.saw_tstamp
= 1;
3868 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3870 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3876 /* Fast parse options. This hopes to only see timestamps.
3877 * If it is wrong it falls back on tcp_parse_options().
3879 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
3880 struct tcp_sock
*tp
, u8
**hvpp
)
3882 /* In the spirit of fast parsing, compare doff directly to constant
3883 * values. Because equality is used, short doff can be ignored here.
3885 if (th
->doff
== (sizeof(*th
) / 4)) {
3886 tp
->rx_opt
.saw_tstamp
= 0;
3888 } else if (tp
->rx_opt
.tstamp_ok
&&
3889 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3890 if (tcp_parse_aligned_timestamp(tp
, th
))
3893 tcp_parse_options(skb
, &tp
->rx_opt
, hvpp
, 1);
3897 #ifdef CONFIG_TCP_MD5SIG
3899 * Parse MD5 Signature option
3901 u8
*tcp_parse_md5sig_option(struct tcphdr
*th
)
3903 int length
= (th
->doff
<< 2) - sizeof (*th
);
3904 u8
*ptr
= (u8
*)(th
+ 1);
3906 /* If the TCP option is too short, we can short cut */
3907 if (length
< TCPOLEN_MD5SIG
)
3910 while (length
> 0) {
3911 int opcode
= *ptr
++;
3922 if (opsize
< 2 || opsize
> length
)
3924 if (opcode
== TCPOPT_MD5SIG
)
3925 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3932 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3935 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
3937 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3938 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3941 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3943 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3944 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3945 * extra check below makes sure this can only happen
3946 * for pure ACK frames. -DaveM
3948 * Not only, also it occurs for expired timestamps.
3951 if (tcp_paws_check(&tp
->rx_opt
, 0))
3952 tcp_store_ts_recent(tp
);
3956 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3958 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3959 * it can pass through stack. So, the following predicate verifies that
3960 * this segment is not used for anything but congestion avoidance or
3961 * fast retransmit. Moreover, we even are able to eliminate most of such
3962 * second order effects, if we apply some small "replay" window (~RTO)
3963 * to timestamp space.
3965 * All these measures still do not guarantee that we reject wrapped ACKs
3966 * on networks with high bandwidth, when sequence space is recycled fastly,
3967 * but it guarantees that such events will be very rare and do not affect
3968 * connection seriously. This doesn't look nice, but alas, PAWS is really
3971 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3972 * states that events when retransmit arrives after original data are rare.
3973 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3974 * the biggest problem on large power networks even with minor reordering.
3975 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3976 * up to bandwidth of 18Gigabit/sec. 8) ]
3979 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3981 struct tcp_sock
*tp
= tcp_sk(sk
);
3982 struct tcphdr
*th
= tcp_hdr(skb
);
3983 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3984 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3986 return (/* 1. Pure ACK with correct sequence number. */
3987 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3989 /* 2. ... and duplicate ACK. */
3990 ack
== tp
->snd_una
&&
3992 /* 3. ... and does not update window. */
3993 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3995 /* 4. ... and sits in replay window. */
3996 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3999 static inline int tcp_paws_discard(const struct sock
*sk
,
4000 const struct sk_buff
*skb
)
4002 const struct tcp_sock
*tp
= tcp_sk(sk
);
4004 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
4005 !tcp_disordered_ack(sk
, skb
);
4008 /* Check segment sequence number for validity.
4010 * Segment controls are considered valid, if the segment
4011 * fits to the window after truncation to the window. Acceptability
4012 * of data (and SYN, FIN, of course) is checked separately.
4013 * See tcp_data_queue(), for example.
4015 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4016 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4017 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4018 * (borrowed from freebsd)
4021 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
4023 return !before(end_seq
, tp
->rcv_wup
) &&
4024 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
4027 /* When we get a reset we do this. */
4028 static void tcp_reset(struct sock
*sk
)
4030 /* We want the right error as BSD sees it (and indeed as we do). */
4031 switch (sk
->sk_state
) {
4033 sk
->sk_err
= ECONNREFUSED
;
4035 case TCP_CLOSE_WAIT
:
4041 sk
->sk_err
= ECONNRESET
;
4043 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4046 if (!sock_flag(sk
, SOCK_DEAD
))
4047 sk
->sk_error_report(sk
);
4053 * Process the FIN bit. This now behaves as it is supposed to work
4054 * and the FIN takes effect when it is validly part of sequence
4055 * space. Not before when we get holes.
4057 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4058 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4061 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4062 * close and we go into CLOSING (and later onto TIME-WAIT)
4064 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4066 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
4068 struct tcp_sock
*tp
= tcp_sk(sk
);
4070 inet_csk_schedule_ack(sk
);
4072 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4073 sock_set_flag(sk
, SOCK_DONE
);
4075 switch (sk
->sk_state
) {
4077 case TCP_ESTABLISHED
:
4078 /* Move to CLOSE_WAIT */
4079 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4080 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4083 case TCP_CLOSE_WAIT
:
4085 /* Received a retransmission of the FIN, do
4090 /* RFC793: Remain in the LAST-ACK state. */
4094 /* This case occurs when a simultaneous close
4095 * happens, we must ack the received FIN and
4096 * enter the CLOSING state.
4099 tcp_set_state(sk
, TCP_CLOSING
);
4102 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4104 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4107 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4108 * cases we should never reach this piece of code.
4110 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
4111 __func__
, sk
->sk_state
);
4115 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4116 * Probably, we should reset in this case. For now drop them.
4118 __skb_queue_purge(&tp
->out_of_order_queue
);
4119 if (tcp_is_sack(tp
))
4120 tcp_sack_reset(&tp
->rx_opt
);
4123 if (!sock_flag(sk
, SOCK_DEAD
)) {
4124 sk
->sk_state_change(sk
);
4126 /* Do not send POLL_HUP for half duplex close. */
4127 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4128 sk
->sk_state
== TCP_CLOSE
)
4129 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4131 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4135 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4138 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4139 if (before(seq
, sp
->start_seq
))
4140 sp
->start_seq
= seq
;
4141 if (after(end_seq
, sp
->end_seq
))
4142 sp
->end_seq
= end_seq
;
4148 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4150 struct tcp_sock
*tp
= tcp_sk(sk
);
4152 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4155 if (before(seq
, tp
->rcv_nxt
))
4156 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4158 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4160 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4162 tp
->rx_opt
.dsack
= 1;
4163 tp
->duplicate_sack
[0].start_seq
= seq
;
4164 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4168 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4170 struct tcp_sock
*tp
= tcp_sk(sk
);
4172 if (!tp
->rx_opt
.dsack
)
4173 tcp_dsack_set(sk
, seq
, end_seq
);
4175 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4178 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
4180 struct tcp_sock
*tp
= tcp_sk(sk
);
4182 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4183 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4184 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4185 tcp_enter_quickack_mode(sk
);
4187 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4188 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4190 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4191 end_seq
= tp
->rcv_nxt
;
4192 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4199 /* These routines update the SACK block as out-of-order packets arrive or
4200 * in-order packets close up the sequence space.
4202 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4205 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4206 struct tcp_sack_block
*swalk
= sp
+ 1;
4208 /* See if the recent change to the first SACK eats into
4209 * or hits the sequence space of other SACK blocks, if so coalesce.
4211 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4212 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4215 /* Zap SWALK, by moving every further SACK up by one slot.
4216 * Decrease num_sacks.
4218 tp
->rx_opt
.num_sacks
--;
4219 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4223 this_sack
++, swalk
++;
4227 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4229 struct tcp_sock
*tp
= tcp_sk(sk
);
4230 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4231 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4237 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4238 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4239 /* Rotate this_sack to the first one. */
4240 for (; this_sack
> 0; this_sack
--, sp
--)
4241 swap(*sp
, *(sp
- 1));
4243 tcp_sack_maybe_coalesce(tp
);
4248 /* Could not find an adjacent existing SACK, build a new one,
4249 * put it at the front, and shift everyone else down. We
4250 * always know there is at least one SACK present already here.
4252 * If the sack array is full, forget about the last one.
4254 if (this_sack
>= TCP_NUM_SACKS
) {
4256 tp
->rx_opt
.num_sacks
--;
4259 for (; this_sack
> 0; this_sack
--, sp
--)
4263 /* Build the new head SACK, and we're done. */
4264 sp
->start_seq
= seq
;
4265 sp
->end_seq
= end_seq
;
4266 tp
->rx_opt
.num_sacks
++;
4269 /* RCV.NXT advances, some SACKs should be eaten. */
4271 static void tcp_sack_remove(struct tcp_sock
*tp
)
4273 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4274 int num_sacks
= tp
->rx_opt
.num_sacks
;
4277 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4278 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4279 tp
->rx_opt
.num_sacks
= 0;
4283 for (this_sack
= 0; this_sack
< num_sacks
;) {
4284 /* Check if the start of the sack is covered by RCV.NXT. */
4285 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4288 /* RCV.NXT must cover all the block! */
4289 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4291 /* Zap this SACK, by moving forward any other SACKS. */
4292 for (i
=this_sack
+1; i
< num_sacks
; i
++)
4293 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4300 tp
->rx_opt
.num_sacks
= num_sacks
;
4303 /* This one checks to see if we can put data from the
4304 * out_of_order queue into the receive_queue.
4306 static void tcp_ofo_queue(struct sock
*sk
)
4308 struct tcp_sock
*tp
= tcp_sk(sk
);
4309 __u32 dsack_high
= tp
->rcv_nxt
;
4310 struct sk_buff
*skb
;
4312 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4313 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4316 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4317 __u32 dsack
= dsack_high
;
4318 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4319 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4320 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4323 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4324 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4325 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4329 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4330 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4331 TCP_SKB_CB(skb
)->end_seq
);
4333 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4334 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4335 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4336 if (tcp_hdr(skb
)->fin
)
4337 tcp_fin(skb
, sk
, tcp_hdr(skb
));
4341 static int tcp_prune_ofo_queue(struct sock
*sk
);
4342 static int tcp_prune_queue(struct sock
*sk
);
4344 static inline int tcp_try_rmem_schedule(struct sock
*sk
, unsigned int size
)
4346 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4347 !sk_rmem_schedule(sk
, size
)) {
4349 if (tcp_prune_queue(sk
) < 0)
4352 if (!sk_rmem_schedule(sk
, size
)) {
4353 if (!tcp_prune_ofo_queue(sk
))
4356 if (!sk_rmem_schedule(sk
, size
))
4363 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4365 struct tcphdr
*th
= tcp_hdr(skb
);
4366 struct tcp_sock
*tp
= tcp_sk(sk
);
4369 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4373 __skb_pull(skb
, th
->doff
* 4);
4375 TCP_ECN_accept_cwr(tp
, skb
);
4377 tp
->rx_opt
.dsack
= 0;
4379 /* Queue data for delivery to the user.
4380 * Packets in sequence go to the receive queue.
4381 * Out of sequence packets to the out_of_order_queue.
4383 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4384 if (tcp_receive_window(tp
) == 0)
4387 /* Ok. In sequence. In window. */
4388 if (tp
->ucopy
.task
== current
&&
4389 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4390 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4391 int chunk
= min_t(unsigned int, skb
->len
,
4394 __set_current_state(TASK_RUNNING
);
4397 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4398 tp
->ucopy
.len
-= chunk
;
4399 tp
->copied_seq
+= chunk
;
4400 eaten
= (chunk
== skb
->len
&& !th
->fin
);
4401 tcp_rcv_space_adjust(sk
);
4409 tcp_try_rmem_schedule(sk
, skb
->truesize
))
4412 skb_set_owner_r(skb
, sk
);
4413 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4415 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4417 tcp_event_data_recv(sk
, skb
);
4419 tcp_fin(skb
, sk
, th
);
4421 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4424 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4425 * gap in queue is filled.
4427 if (skb_queue_empty(&tp
->out_of_order_queue
))
4428 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4431 if (tp
->rx_opt
.num_sacks
)
4432 tcp_sack_remove(tp
);
4434 tcp_fast_path_check(sk
);
4438 else if (!sock_flag(sk
, SOCK_DEAD
))
4439 sk
->sk_data_ready(sk
, 0);
4443 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4444 /* A retransmit, 2nd most common case. Force an immediate ack. */
4445 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4446 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4449 tcp_enter_quickack_mode(sk
);
4450 inet_csk_schedule_ack(sk
);
4456 /* Out of window. F.e. zero window probe. */
4457 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4460 tcp_enter_quickack_mode(sk
);
4462 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4463 /* Partial packet, seq < rcv_next < end_seq */
4464 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4465 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4466 TCP_SKB_CB(skb
)->end_seq
);
4468 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4470 /* If window is closed, drop tail of packet. But after
4471 * remembering D-SACK for its head made in previous line.
4473 if (!tcp_receive_window(tp
))
4478 TCP_ECN_check_ce(tp
, skb
);
4480 if (tcp_try_rmem_schedule(sk
, skb
->truesize
))
4483 /* Disable header prediction. */
4485 inet_csk_schedule_ack(sk
);
4487 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4488 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4490 skb_set_owner_r(skb
, sk
);
4492 if (!skb_peek(&tp
->out_of_order_queue
)) {
4493 /* Initial out of order segment, build 1 SACK. */
4494 if (tcp_is_sack(tp
)) {
4495 tp
->rx_opt
.num_sacks
= 1;
4496 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4497 tp
->selective_acks
[0].end_seq
=
4498 TCP_SKB_CB(skb
)->end_seq
;
4500 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4502 struct sk_buff
*skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4503 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4504 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4506 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4507 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4509 if (!tp
->rx_opt
.num_sacks
||
4510 tp
->selective_acks
[0].end_seq
!= seq
)
4513 /* Common case: data arrive in order after hole. */
4514 tp
->selective_acks
[0].end_seq
= end_seq
;
4518 /* Find place to insert this segment. */
4520 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4522 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4526 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4529 /* Do skb overlap to previous one? */
4530 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4531 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4532 /* All the bits are present. Drop. */
4534 tcp_dsack_set(sk
, seq
, end_seq
);
4537 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4538 /* Partial overlap. */
4539 tcp_dsack_set(sk
, seq
,
4540 TCP_SKB_CB(skb1
)->end_seq
);
4542 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4546 skb1
= skb_queue_prev(
4547 &tp
->out_of_order_queue
,
4552 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4554 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4556 /* And clean segments covered by new one as whole. */
4557 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4558 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4560 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4562 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4563 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4567 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4568 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4569 TCP_SKB_CB(skb1
)->end_seq
);
4574 if (tcp_is_sack(tp
))
4575 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4579 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4580 struct sk_buff_head
*list
)
4582 struct sk_buff
*next
= NULL
;
4584 if (!skb_queue_is_last(list
, skb
))
4585 next
= skb_queue_next(list
, skb
);
4587 __skb_unlink(skb
, list
);
4589 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4594 /* Collapse contiguous sequence of skbs head..tail with
4595 * sequence numbers start..end.
4597 * If tail is NULL, this means until the end of the list.
4599 * Segments with FIN/SYN are not collapsed (only because this
4603 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4604 struct sk_buff
*head
, struct sk_buff
*tail
,
4607 struct sk_buff
*skb
, *n
;
4610 /* First, check that queue is collapsible and find
4611 * the point where collapsing can be useful. */
4615 skb_queue_walk_from_safe(list
, skb
, n
) {
4618 /* No new bits? It is possible on ofo queue. */
4619 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4620 skb
= tcp_collapse_one(sk
, skb
, list
);
4626 /* The first skb to collapse is:
4628 * - bloated or contains data before "start" or
4629 * overlaps to the next one.
4631 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4632 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4633 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4634 end_of_skbs
= false;
4638 if (!skb_queue_is_last(list
, skb
)) {
4639 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4641 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4642 end_of_skbs
= false;
4647 /* Decided to skip this, advance start seq. */
4648 start
= TCP_SKB_CB(skb
)->end_seq
;
4650 if (end_of_skbs
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4653 while (before(start
, end
)) {
4654 struct sk_buff
*nskb
;
4655 unsigned int header
= skb_headroom(skb
);
4656 int copy
= SKB_MAX_ORDER(header
, 0);
4658 /* Too big header? This can happen with IPv6. */
4661 if (end
- start
< copy
)
4663 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4667 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4668 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4670 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4672 skb_reserve(nskb
, header
);
4673 memcpy(nskb
->head
, skb
->head
, header
);
4674 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4675 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4676 __skb_queue_before(list
, skb
, nskb
);
4677 skb_set_owner_r(nskb
, sk
);
4679 /* Copy data, releasing collapsed skbs. */
4681 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4682 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4686 size
= min(copy
, size
);
4687 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4689 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4693 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4694 skb
= tcp_collapse_one(sk
, skb
, list
);
4697 tcp_hdr(skb
)->syn
||
4705 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4706 * and tcp_collapse() them until all the queue is collapsed.
4708 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4710 struct tcp_sock
*tp
= tcp_sk(sk
);
4711 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4712 struct sk_buff
*head
;
4718 start
= TCP_SKB_CB(skb
)->seq
;
4719 end
= TCP_SKB_CB(skb
)->end_seq
;
4723 struct sk_buff
*next
= NULL
;
4725 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4726 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4729 /* Segment is terminated when we see gap or when
4730 * we are at the end of all the queue. */
4732 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4733 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4734 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4735 head
, skb
, start
, end
);
4739 /* Start new segment */
4740 start
= TCP_SKB_CB(skb
)->seq
;
4741 end
= TCP_SKB_CB(skb
)->end_seq
;
4743 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4744 start
= TCP_SKB_CB(skb
)->seq
;
4745 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4746 end
= TCP_SKB_CB(skb
)->end_seq
;
4752 * Purge the out-of-order queue.
4753 * Return true if queue was pruned.
4755 static int tcp_prune_ofo_queue(struct sock
*sk
)
4757 struct tcp_sock
*tp
= tcp_sk(sk
);
4760 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4761 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4762 __skb_queue_purge(&tp
->out_of_order_queue
);
4764 /* Reset SACK state. A conforming SACK implementation will
4765 * do the same at a timeout based retransmit. When a connection
4766 * is in a sad state like this, we care only about integrity
4767 * of the connection not performance.
4769 if (tp
->rx_opt
.sack_ok
)
4770 tcp_sack_reset(&tp
->rx_opt
);
4777 /* Reduce allocated memory if we can, trying to get
4778 * the socket within its memory limits again.
4780 * Return less than zero if we should start dropping frames
4781 * until the socket owning process reads some of the data
4782 * to stabilize the situation.
4784 static int tcp_prune_queue(struct sock
*sk
)
4786 struct tcp_sock
*tp
= tcp_sk(sk
);
4788 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4790 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4792 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4793 tcp_clamp_window(sk
);
4794 else if (tcp_memory_pressure
)
4795 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4797 tcp_collapse_ofo_queue(sk
);
4798 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4799 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4800 skb_peek(&sk
->sk_receive_queue
),
4802 tp
->copied_seq
, tp
->rcv_nxt
);
4805 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4808 /* Collapsing did not help, destructive actions follow.
4809 * This must not ever occur. */
4811 tcp_prune_ofo_queue(sk
);
4813 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4816 /* If we are really being abused, tell the caller to silently
4817 * drop receive data on the floor. It will get retransmitted
4818 * and hopefully then we'll have sufficient space.
4820 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4822 /* Massive buffer overcommit. */
4827 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4828 * As additional protections, we do not touch cwnd in retransmission phases,
4829 * and if application hit its sndbuf limit recently.
4831 void tcp_cwnd_application_limited(struct sock
*sk
)
4833 struct tcp_sock
*tp
= tcp_sk(sk
);
4835 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4836 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4837 /* Limited by application or receiver window. */
4838 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4839 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4840 if (win_used
< tp
->snd_cwnd
) {
4841 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4842 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4844 tp
->snd_cwnd_used
= 0;
4846 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4849 static int tcp_should_expand_sndbuf(struct sock
*sk
)
4851 struct tcp_sock
*tp
= tcp_sk(sk
);
4853 /* If the user specified a specific send buffer setting, do
4856 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4859 /* If we are under global TCP memory pressure, do not expand. */
4860 if (tcp_memory_pressure
)
4863 /* If we are under soft global TCP memory pressure, do not expand. */
4864 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
4867 /* If we filled the congestion window, do not expand. */
4868 if (tp
->packets_out
>= tp
->snd_cwnd
)
4874 /* When incoming ACK allowed to free some skb from write_queue,
4875 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4876 * on the exit from tcp input handler.
4878 * PROBLEM: sndbuf expansion does not work well with largesend.
4880 static void tcp_new_space(struct sock
*sk
)
4882 struct tcp_sock
*tp
= tcp_sk(sk
);
4884 if (tcp_should_expand_sndbuf(sk
)) {
4885 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
4886 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
4887 int demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4888 tp
->reordering
+ 1);
4889 sndmem
*= 2 * demanded
;
4890 if (sndmem
> sk
->sk_sndbuf
)
4891 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4892 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4895 sk
->sk_write_space(sk
);
4898 static void tcp_check_space(struct sock
*sk
)
4900 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4901 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4902 if (sk
->sk_socket
&&
4903 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4908 static inline void tcp_data_snd_check(struct sock
*sk
)
4910 tcp_push_pending_frames(sk
);
4911 tcp_check_space(sk
);
4915 * Check if sending an ack is needed.
4917 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4919 struct tcp_sock
*tp
= tcp_sk(sk
);
4921 /* More than one full frame received... */
4922 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4923 /* ... and right edge of window advances far enough.
4924 * (tcp_recvmsg() will send ACK otherwise). Or...
4926 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4927 /* We ACK each frame or... */
4928 tcp_in_quickack_mode(sk
) ||
4929 /* We have out of order data. */
4930 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4931 /* Then ack it now */
4934 /* Else, send delayed ack. */
4935 tcp_send_delayed_ack(sk
);
4939 static inline void tcp_ack_snd_check(struct sock
*sk
)
4941 if (!inet_csk_ack_scheduled(sk
)) {
4942 /* We sent a data segment already. */
4945 __tcp_ack_snd_check(sk
, 1);
4949 * This routine is only called when we have urgent data
4950 * signaled. Its the 'slow' part of tcp_urg. It could be
4951 * moved inline now as tcp_urg is only called from one
4952 * place. We handle URGent data wrong. We have to - as
4953 * BSD still doesn't use the correction from RFC961.
4954 * For 1003.1g we should support a new option TCP_STDURG to permit
4955 * either form (or just set the sysctl tcp_stdurg).
4958 static void tcp_check_urg(struct sock
*sk
, struct tcphdr
*th
)
4960 struct tcp_sock
*tp
= tcp_sk(sk
);
4961 u32 ptr
= ntohs(th
->urg_ptr
);
4963 if (ptr
&& !sysctl_tcp_stdurg
)
4965 ptr
+= ntohl(th
->seq
);
4967 /* Ignore urgent data that we've already seen and read. */
4968 if (after(tp
->copied_seq
, ptr
))
4971 /* Do not replay urg ptr.
4973 * NOTE: interesting situation not covered by specs.
4974 * Misbehaving sender may send urg ptr, pointing to segment,
4975 * which we already have in ofo queue. We are not able to fetch
4976 * such data and will stay in TCP_URG_NOTYET until will be eaten
4977 * by recvmsg(). Seems, we are not obliged to handle such wicked
4978 * situations. But it is worth to think about possibility of some
4979 * DoSes using some hypothetical application level deadlock.
4981 if (before(ptr
, tp
->rcv_nxt
))
4984 /* Do we already have a newer (or duplicate) urgent pointer? */
4985 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4988 /* Tell the world about our new urgent pointer. */
4991 /* We may be adding urgent data when the last byte read was
4992 * urgent. To do this requires some care. We cannot just ignore
4993 * tp->copied_seq since we would read the last urgent byte again
4994 * as data, nor can we alter copied_seq until this data arrives
4995 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4997 * NOTE. Double Dutch. Rendering to plain English: author of comment
4998 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4999 * and expect that both A and B disappear from stream. This is _wrong_.
5000 * Though this happens in BSD with high probability, this is occasional.
5001 * Any application relying on this is buggy. Note also, that fix "works"
5002 * only in this artificial test. Insert some normal data between A and B and we will
5003 * decline of BSD again. Verdict: it is better to remove to trap
5006 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5007 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5008 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5010 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5011 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5016 tp
->urg_data
= TCP_URG_NOTYET
;
5019 /* Disable header prediction. */
5023 /* This is the 'fast' part of urgent handling. */
5024 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
5026 struct tcp_sock
*tp
= tcp_sk(sk
);
5028 /* Check if we get a new urgent pointer - normally not. */
5030 tcp_check_urg(sk
, th
);
5032 /* Do we wait for any urgent data? - normally not... */
5033 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5034 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5037 /* Is the urgent pointer pointing into this packet? */
5038 if (ptr
< skb
->len
) {
5040 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5042 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5043 if (!sock_flag(sk
, SOCK_DEAD
))
5044 sk
->sk_data_ready(sk
, 0);
5049 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5051 struct tcp_sock
*tp
= tcp_sk(sk
);
5052 int chunk
= skb
->len
- hlen
;
5056 if (skb_csum_unnecessary(skb
))
5057 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
5059 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
5063 tp
->ucopy
.len
-= chunk
;
5064 tp
->copied_seq
+= chunk
;
5065 tcp_rcv_space_adjust(sk
);
5072 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5073 struct sk_buff
*skb
)
5077 if (sock_owned_by_user(sk
)) {
5079 result
= __tcp_checksum_complete(skb
);
5082 result
= __tcp_checksum_complete(skb
);
5087 static inline int tcp_checksum_complete_user(struct sock
*sk
,
5088 struct sk_buff
*skb
)
5090 return !skb_csum_unnecessary(skb
) &&
5091 __tcp_checksum_complete_user(sk
, skb
);
5094 #ifdef CONFIG_NET_DMA
5095 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
5098 struct tcp_sock
*tp
= tcp_sk(sk
);
5099 int chunk
= skb
->len
- hlen
;
5101 int copied_early
= 0;
5103 if (tp
->ucopy
.wakeup
)
5106 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
5107 tp
->ucopy
.dma_chan
= dma_find_channel(DMA_MEMCPY
);
5109 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
5111 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
5113 tp
->ucopy
.iov
, chunk
,
5114 tp
->ucopy
.pinned_list
);
5119 tp
->ucopy
.dma_cookie
= dma_cookie
;
5122 tp
->ucopy
.len
-= chunk
;
5123 tp
->copied_seq
+= chunk
;
5124 tcp_rcv_space_adjust(sk
);
5126 if ((tp
->ucopy
.len
== 0) ||
5127 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
5128 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
5129 tp
->ucopy
.wakeup
= 1;
5130 sk
->sk_data_ready(sk
, 0);
5132 } else if (chunk
> 0) {
5133 tp
->ucopy
.wakeup
= 1;
5134 sk
->sk_data_ready(sk
, 0);
5137 return copied_early
;
5139 #endif /* CONFIG_NET_DMA */
5141 /* Does PAWS and seqno based validation of an incoming segment, flags will
5142 * play significant role here.
5144 static int tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5145 struct tcphdr
*th
, int syn_inerr
)
5148 struct tcp_sock
*tp
= tcp_sk(sk
);
5150 /* RFC1323: H1. Apply PAWS check first. */
5151 if (tcp_fast_parse_options(skb
, th
, tp
, &hash_location
) &&
5152 tp
->rx_opt
.saw_tstamp
&&
5153 tcp_paws_discard(sk
, skb
)) {
5155 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5156 tcp_send_dupack(sk
, skb
);
5159 /* Reset is accepted even if it did not pass PAWS. */
5162 /* Step 1: check sequence number */
5163 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5164 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5165 * (RST) segments are validated by checking their SEQ-fields."
5166 * And page 69: "If an incoming segment is not acceptable,
5167 * an acknowledgment should be sent in reply (unless the RST
5168 * bit is set, if so drop the segment and return)".
5171 tcp_send_dupack(sk
, skb
);
5175 /* Step 2: check RST bit */
5181 /* ts_recent update must be made after we are sure that the packet
5184 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5186 /* step 3: check security and precedence [ignored] */
5188 /* step 4: Check for a SYN in window. */
5189 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5191 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5192 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
5205 * TCP receive function for the ESTABLISHED state.
5207 * It is split into a fast path and a slow path. The fast path is
5209 * - A zero window was announced from us - zero window probing
5210 * is only handled properly in the slow path.
5211 * - Out of order segments arrived.
5212 * - Urgent data is expected.
5213 * - There is no buffer space left
5214 * - Unexpected TCP flags/window values/header lengths are received
5215 * (detected by checking the TCP header against pred_flags)
5216 * - Data is sent in both directions. Fast path only supports pure senders
5217 * or pure receivers (this means either the sequence number or the ack
5218 * value must stay constant)
5219 * - Unexpected TCP option.
5221 * When these conditions are not satisfied it drops into a standard
5222 * receive procedure patterned after RFC793 to handle all cases.
5223 * The first three cases are guaranteed by proper pred_flags setting,
5224 * the rest is checked inline. Fast processing is turned on in
5225 * tcp_data_queue when everything is OK.
5227 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5228 struct tcphdr
*th
, unsigned len
)
5230 struct tcp_sock
*tp
= tcp_sk(sk
);
5234 * Header prediction.
5235 * The code loosely follows the one in the famous
5236 * "30 instruction TCP receive" Van Jacobson mail.
5238 * Van's trick is to deposit buffers into socket queue
5239 * on a device interrupt, to call tcp_recv function
5240 * on the receive process context and checksum and copy
5241 * the buffer to user space. smart...
5243 * Our current scheme is not silly either but we take the
5244 * extra cost of the net_bh soft interrupt processing...
5245 * We do checksum and copy also but from device to kernel.
5248 tp
->rx_opt
.saw_tstamp
= 0;
5250 /* pred_flags is 0xS?10 << 16 + snd_wnd
5251 * if header_prediction is to be made
5252 * 'S' will always be tp->tcp_header_len >> 2
5253 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5254 * turn it off (when there are holes in the receive
5255 * space for instance)
5256 * PSH flag is ignored.
5259 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5260 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5261 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5262 int tcp_header_len
= tp
->tcp_header_len
;
5264 /* Timestamp header prediction: tcp_header_len
5265 * is automatically equal to th->doff*4 due to pred_flags
5269 /* Check timestamp */
5270 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5271 /* No? Slow path! */
5272 if (!tcp_parse_aligned_timestamp(tp
, th
))
5275 /* If PAWS failed, check it more carefully in slow path */
5276 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5279 /* DO NOT update ts_recent here, if checksum fails
5280 * and timestamp was corrupted part, it will result
5281 * in a hung connection since we will drop all
5282 * future packets due to the PAWS test.
5286 if (len
<= tcp_header_len
) {
5287 /* Bulk data transfer: sender */
5288 if (len
== tcp_header_len
) {
5289 /* Predicted packet is in window by definition.
5290 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5291 * Hence, check seq<=rcv_wup reduces to:
5293 if (tcp_header_len
==
5294 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5295 tp
->rcv_nxt
== tp
->rcv_wup
)
5296 tcp_store_ts_recent(tp
);
5298 /* We know that such packets are checksummed
5301 tcp_ack(sk
, skb
, 0);
5303 tcp_data_snd_check(sk
);
5305 } else { /* Header too small */
5306 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5311 int copied_early
= 0;
5313 if (tp
->copied_seq
== tp
->rcv_nxt
&&
5314 len
- tcp_header_len
<= tp
->ucopy
.len
) {
5315 #ifdef CONFIG_NET_DMA
5316 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
5321 if (tp
->ucopy
.task
== current
&&
5322 sock_owned_by_user(sk
) && !copied_early
) {
5323 __set_current_state(TASK_RUNNING
);
5325 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
5329 /* Predicted packet is in window by definition.
5330 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5331 * Hence, check seq<=rcv_wup reduces to:
5333 if (tcp_header_len
==
5334 (sizeof(struct tcphdr
) +
5335 TCPOLEN_TSTAMP_ALIGNED
) &&
5336 tp
->rcv_nxt
== tp
->rcv_wup
)
5337 tcp_store_ts_recent(tp
);
5339 tcp_rcv_rtt_measure_ts(sk
, skb
);
5341 __skb_pull(skb
, tcp_header_len
);
5342 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5343 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5346 tcp_cleanup_rbuf(sk
, skb
->len
);
5349 if (tcp_checksum_complete_user(sk
, skb
))
5352 /* Predicted packet is in window by definition.
5353 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5354 * Hence, check seq<=rcv_wup reduces to:
5356 if (tcp_header_len
==
5357 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5358 tp
->rcv_nxt
== tp
->rcv_wup
)
5359 tcp_store_ts_recent(tp
);
5361 tcp_rcv_rtt_measure_ts(sk
, skb
);
5363 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5366 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5368 /* Bulk data transfer: receiver */
5369 __skb_pull(skb
, tcp_header_len
);
5370 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
5371 skb_set_owner_r(skb
, sk
);
5372 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5375 tcp_event_data_recv(sk
, skb
);
5377 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5378 /* Well, only one small jumplet in fast path... */
5379 tcp_ack(sk
, skb
, FLAG_DATA
);
5380 tcp_data_snd_check(sk
);
5381 if (!inet_csk_ack_scheduled(sk
))
5385 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
5386 __tcp_ack_snd_check(sk
, 0);
5388 #ifdef CONFIG_NET_DMA
5390 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
5396 sk
->sk_data_ready(sk
, 0);
5402 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5406 * Standard slow path.
5409 res
= tcp_validate_incoming(sk
, skb
, th
, 1);
5414 if (th
->ack
&& tcp_ack(sk
, skb
, FLAG_SLOWPATH
) < 0)
5417 tcp_rcv_rtt_measure_ts(sk
, skb
);
5419 /* Process urgent data. */
5420 tcp_urg(sk
, skb
, th
);
5422 /* step 7: process the segment text */
5423 tcp_data_queue(sk
, skb
);
5425 tcp_data_snd_check(sk
);
5426 tcp_ack_snd_check(sk
);
5430 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5436 EXPORT_SYMBOL(tcp_rcv_established
);
5438 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5439 struct tcphdr
*th
, unsigned len
)
5442 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5443 struct tcp_sock
*tp
= tcp_sk(sk
);
5444 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
5445 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5447 tcp_parse_options(skb
, &tp
->rx_opt
, &hash_location
, 0);
5451 * "If the state is SYN-SENT then
5452 * first check the ACK bit
5453 * If the ACK bit is set
5454 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5455 * a reset (unless the RST bit is set, if so drop
5456 * the segment and return)"
5458 * We do not send data with SYN, so that RFC-correct
5461 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
5462 goto reset_and_undo
;
5464 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5465 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5467 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5468 goto reset_and_undo
;
5471 /* Now ACK is acceptable.
5473 * "If the RST bit is set
5474 * If the ACK was acceptable then signal the user "error:
5475 * connection reset", drop the segment, enter CLOSED state,
5476 * delete TCB, and return."
5485 * "fifth, if neither of the SYN or RST bits is set then
5486 * drop the segment and return."
5492 goto discard_and_undo
;
5495 * "If the SYN bit is on ...
5496 * are acceptable then ...
5497 * (our SYN has been ACKed), change the connection
5498 * state to ESTABLISHED..."
5501 TCP_ECN_rcv_synack(tp
, th
);
5503 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5504 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5506 /* Ok.. it's good. Set up sequence numbers and
5507 * move to established.
5509 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5510 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5512 /* RFC1323: The window in SYN & SYN/ACK segments is
5515 tp
->snd_wnd
= ntohs(th
->window
);
5516 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5518 if (!tp
->rx_opt
.wscale_ok
) {
5519 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5520 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5523 if (tp
->rx_opt
.saw_tstamp
) {
5524 tp
->rx_opt
.tstamp_ok
= 1;
5525 tp
->tcp_header_len
=
5526 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5527 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5528 tcp_store_ts_recent(tp
);
5530 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5533 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5534 tcp_enable_fack(tp
);
5537 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5538 tcp_initialize_rcv_mss(sk
);
5540 /* Remember, tcp_poll() does not lock socket!
5541 * Change state from SYN-SENT only after copied_seq
5542 * is initialized. */
5543 tp
->copied_seq
= tp
->rcv_nxt
;
5546 cvp
->cookie_pair_size
> 0 &&
5547 tp
->rx_opt
.cookie_plus
> 0) {
5548 int cookie_size
= tp
->rx_opt
.cookie_plus
5549 - TCPOLEN_COOKIE_BASE
;
5550 int cookie_pair_size
= cookie_size
5551 + cvp
->cookie_desired
;
5553 /* A cookie extension option was sent and returned.
5554 * Note that each incoming SYNACK replaces the
5555 * Responder cookie. The initial exchange is most
5556 * fragile, as protection against spoofing relies
5557 * entirely upon the sequence and timestamp (above).
5558 * This replacement strategy allows the correct pair to
5559 * pass through, while any others will be filtered via
5560 * Responder verification later.
5562 if (sizeof(cvp
->cookie_pair
) >= cookie_pair_size
) {
5563 memcpy(&cvp
->cookie_pair
[cvp
->cookie_desired
],
5564 hash_location
, cookie_size
);
5565 cvp
->cookie_pair_size
= cookie_pair_size
;
5570 tcp_set_state(sk
, TCP_ESTABLISHED
);
5572 security_inet_conn_established(sk
, skb
);
5574 /* Make sure socket is routed, for correct metrics. */
5575 icsk
->icsk_af_ops
->rebuild_header(sk
);
5577 tcp_init_metrics(sk
);
5579 tcp_init_congestion_control(sk
);
5581 /* Prevent spurious tcp_cwnd_restart() on first data
5584 tp
->lsndtime
= tcp_time_stamp
;
5586 tcp_init_buffer_space(sk
);
5588 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5589 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5591 if (!tp
->rx_opt
.snd_wscale
)
5592 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5596 if (!sock_flag(sk
, SOCK_DEAD
)) {
5597 sk
->sk_state_change(sk
);
5598 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5601 if (sk
->sk_write_pending
||
5602 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5603 icsk
->icsk_ack
.pingpong
) {
5604 /* Save one ACK. Data will be ready after
5605 * several ticks, if write_pending is set.
5607 * It may be deleted, but with this feature tcpdumps
5608 * look so _wonderfully_ clever, that I was not able
5609 * to stand against the temptation 8) --ANK
5611 inet_csk_schedule_ack(sk
);
5612 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5613 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
5614 tcp_incr_quickack(sk
);
5615 tcp_enter_quickack_mode(sk
);
5616 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5617 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5628 /* No ACK in the segment */
5632 * "If the RST bit is set
5634 * Otherwise (no ACK) drop the segment and return."
5637 goto discard_and_undo
;
5641 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5642 tcp_paws_reject(&tp
->rx_opt
, 0))
5643 goto discard_and_undo
;
5646 /* We see SYN without ACK. It is attempt of
5647 * simultaneous connect with crossed SYNs.
5648 * Particularly, it can be connect to self.
5650 tcp_set_state(sk
, TCP_SYN_RECV
);
5652 if (tp
->rx_opt
.saw_tstamp
) {
5653 tp
->rx_opt
.tstamp_ok
= 1;
5654 tcp_store_ts_recent(tp
);
5655 tp
->tcp_header_len
=
5656 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5658 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5661 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5662 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5664 /* RFC1323: The window in SYN & SYN/ACK segments is
5667 tp
->snd_wnd
= ntohs(th
->window
);
5668 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5669 tp
->max_window
= tp
->snd_wnd
;
5671 TCP_ECN_rcv_syn(tp
, th
);
5674 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5675 tcp_initialize_rcv_mss(sk
);
5677 tcp_send_synack(sk
);
5679 /* Note, we could accept data and URG from this segment.
5680 * There are no obstacles to make this.
5682 * However, if we ignore data in ACKless segments sometimes,
5683 * we have no reasons to accept it sometimes.
5684 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5685 * is not flawless. So, discard packet for sanity.
5686 * Uncomment this return to process the data.
5693 /* "fifth, if neither of the SYN or RST bits is set then
5694 * drop the segment and return."
5698 tcp_clear_options(&tp
->rx_opt
);
5699 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5703 tcp_clear_options(&tp
->rx_opt
);
5704 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5709 * This function implements the receiving procedure of RFC 793 for
5710 * all states except ESTABLISHED and TIME_WAIT.
5711 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5712 * address independent.
5715 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5716 struct tcphdr
*th
, unsigned len
)
5718 struct tcp_sock
*tp
= tcp_sk(sk
);
5719 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5723 tp
->rx_opt
.saw_tstamp
= 0;
5725 switch (sk
->sk_state
) {
5737 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5740 /* Now we have several options: In theory there is
5741 * nothing else in the frame. KA9Q has an option to
5742 * send data with the syn, BSD accepts data with the
5743 * syn up to the [to be] advertised window and
5744 * Solaris 2.1 gives you a protocol error. For now
5745 * we just ignore it, that fits the spec precisely
5746 * and avoids incompatibilities. It would be nice in
5747 * future to drop through and process the data.
5749 * Now that TTCP is starting to be used we ought to
5751 * But, this leaves one open to an easy denial of
5752 * service attack, and SYN cookies can't defend
5753 * against this problem. So, we drop the data
5754 * in the interest of security over speed unless
5755 * it's still in use.
5763 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5767 /* Do step6 onward by hand. */
5768 tcp_urg(sk
, skb
, th
);
5770 tcp_data_snd_check(sk
);
5774 res
= tcp_validate_incoming(sk
, skb
, th
, 0);
5778 /* step 5: check the ACK field */
5780 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
) > 0;
5782 switch (sk
->sk_state
) {
5785 tp
->copied_seq
= tp
->rcv_nxt
;
5787 tcp_set_state(sk
, TCP_ESTABLISHED
);
5788 sk
->sk_state_change(sk
);
5790 /* Note, that this wakeup is only for marginal
5791 * crossed SYN case. Passively open sockets
5792 * are not waked up, because sk->sk_sleep ==
5793 * NULL and sk->sk_socket == NULL.
5797 SOCK_WAKE_IO
, POLL_OUT
);
5799 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5800 tp
->snd_wnd
= ntohs(th
->window
) <<
5801 tp
->rx_opt
.snd_wscale
;
5802 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5804 /* tcp_ack considers this ACK as duplicate
5805 * and does not calculate rtt.
5808 tcp_ack_update_rtt(sk
, 0, 0);
5810 if (tp
->rx_opt
.tstamp_ok
)
5811 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5813 /* Make sure socket is routed, for
5816 icsk
->icsk_af_ops
->rebuild_header(sk
);
5818 tcp_init_metrics(sk
);
5820 tcp_init_congestion_control(sk
);
5822 /* Prevent spurious tcp_cwnd_restart() on
5823 * first data packet.
5825 tp
->lsndtime
= tcp_time_stamp
;
5828 tcp_initialize_rcv_mss(sk
);
5829 tcp_init_buffer_space(sk
);
5830 tcp_fast_path_on(tp
);
5837 if (tp
->snd_una
== tp
->write_seq
) {
5838 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5839 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5840 dst_confirm(__sk_dst_get(sk
));
5842 if (!sock_flag(sk
, SOCK_DEAD
))
5843 /* Wake up lingering close() */
5844 sk
->sk_state_change(sk
);
5848 if (tp
->linger2
< 0 ||
5849 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5850 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5852 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5856 tmo
= tcp_fin_time(sk
);
5857 if (tmo
> TCP_TIMEWAIT_LEN
) {
5858 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5859 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5860 /* Bad case. We could lose such FIN otherwise.
5861 * It is not a big problem, but it looks confusing
5862 * and not so rare event. We still can lose it now,
5863 * if it spins in bh_lock_sock(), but it is really
5866 inet_csk_reset_keepalive_timer(sk
, tmo
);
5868 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5876 if (tp
->snd_una
== tp
->write_seq
) {
5877 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5883 if (tp
->snd_una
== tp
->write_seq
) {
5884 tcp_update_metrics(sk
);
5893 /* step 6: check the URG bit */
5894 tcp_urg(sk
, skb
, th
);
5896 /* step 7: process the segment text */
5897 switch (sk
->sk_state
) {
5898 case TCP_CLOSE_WAIT
:
5901 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5905 /* RFC 793 says to queue data in these states,
5906 * RFC 1122 says we MUST send a reset.
5907 * BSD 4.4 also does reset.
5909 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5910 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5911 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5912 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5918 case TCP_ESTABLISHED
:
5919 tcp_data_queue(sk
, skb
);
5924 /* tcp_data could move socket to TIME-WAIT */
5925 if (sk
->sk_state
!= TCP_CLOSE
) {
5926 tcp_data_snd_check(sk
);
5927 tcp_ack_snd_check(sk
);
5936 EXPORT_SYMBOL(tcp_rcv_state_process
);