2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Implementation of the Transmission Control Protocol(TCP).
8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
25 * Pedro Roque : Fast Retransmit/Recovery.
27 * Retransmit queue handled by TCP.
28 * Better retransmit timer handling.
29 * New congestion avoidance.
33 * Eric : Fast Retransmit.
34 * Randy Scott : MSS option defines.
35 * Eric Schenk : Fixes to slow start algorithm.
36 * Eric Schenk : Yet another double ACK bug.
37 * Eric Schenk : Delayed ACK bug fixes.
38 * Eric Schenk : Floyd style fast retrans war avoidance.
39 * David S. Miller : Don't allow zero congestion window.
40 * Eric Schenk : Fix retransmitter so that it sends
41 * next packet on ack of previous packet.
42 * Andi Kleen : Moved open_request checking here
43 * and process RSTs for open_requests.
44 * Andi Kleen : Better prune_queue, and other fixes.
45 * Andrey Savochkin: Fix RTT measurements in the presence of
47 * Andrey Savochkin: Check sequence numbers correctly when
48 * removing SACKs due to in sequence incoming
50 * Andi Kleen: Make sure we never ack data there is not
51 * enough room for. Also make this condition
52 * a fatal error if it might still happen.
53 * Andi Kleen: Add tcp_measure_rcv_mss to make
54 * connections with MSS<min(MTU,ann. MSS)
55 * work without delayed acks.
56 * Andi Kleen: Process packets with PSH set in the
58 * J Hadi Salim: ECN support
61 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
62 * engine. Lots of bugs are found.
63 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
67 #include <linux/module.h>
68 #include <linux/sysctl.h>
70 #include <net/inet_common.h>
71 #include <linux/ipsec.h>
72 #include <asm/unaligned.h>
73 #include <net/netdma.h>
75 int sysctl_tcp_timestamps __read_mostly
= 1;
76 int sysctl_tcp_window_scaling __read_mostly
= 1;
77 int sysctl_tcp_sack __read_mostly
= 1;
78 int sysctl_tcp_fack __read_mostly
= 1;
79 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
80 int sysctl_tcp_ecn __read_mostly
;
81 int sysctl_tcp_dsack __read_mostly
= 1;
82 int sysctl_tcp_app_win __read_mostly
= 31;
83 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
85 int sysctl_tcp_stdurg __read_mostly
;
86 int sysctl_tcp_rfc1337 __read_mostly
;
87 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
88 int sysctl_tcp_frto __read_mostly
= 2;
89 int sysctl_tcp_frto_response __read_mostly
;
90 int sysctl_tcp_nometrics_save __read_mostly
;
92 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
93 int sysctl_tcp_abc __read_mostly
;
95 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
96 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
97 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
98 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
99 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
100 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
101 #define FLAG_ECE 0x40 /* ECE in this ACK */
102 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
103 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
104 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
105 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
106 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
107 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
108 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
110 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
111 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
112 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
113 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
114 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
116 #define IsSackFrto() (sysctl_tcp_frto == 0x2)
118 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
119 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
121 /* Adapt the MSS value used to make delayed ack decision to the
124 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
126 struct inet_connection_sock
*icsk
= inet_csk(sk
);
127 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
130 icsk
->icsk_ack
.last_seg_size
= 0;
132 /* skb->len may jitter because of SACKs, even if peer
133 * sends good full-sized frames.
135 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
136 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
137 icsk
->icsk_ack
.rcv_mss
= len
;
139 /* Otherwise, we make more careful check taking into account,
140 * that SACKs block is variable.
142 * "len" is invariant segment length, including TCP header.
144 len
+= skb
->data
- skb_transport_header(skb
);
145 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
146 /* If PSH is not set, packet should be
147 * full sized, provided peer TCP is not badly broken.
148 * This observation (if it is correct 8)) allows
149 * to handle super-low mtu links fairly.
151 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
152 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
153 /* Subtract also invariant (if peer is RFC compliant),
154 * tcp header plus fixed timestamp option length.
155 * Resulting "len" is MSS free of SACK jitter.
157 len
-= tcp_sk(sk
)->tcp_header_len
;
158 icsk
->icsk_ack
.last_seg_size
= len
;
160 icsk
->icsk_ack
.rcv_mss
= len
;
164 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
165 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
166 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
170 static void tcp_incr_quickack(struct sock
*sk
)
172 struct inet_connection_sock
*icsk
= inet_csk(sk
);
173 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
177 if (quickacks
> icsk
->icsk_ack
.quick
)
178 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
181 void tcp_enter_quickack_mode(struct sock
*sk
)
183 struct inet_connection_sock
*icsk
= inet_csk(sk
);
184 tcp_incr_quickack(sk
);
185 icsk
->icsk_ack
.pingpong
= 0;
186 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
189 /* Send ACKs quickly, if "quick" count is not exhausted
190 * and the session is not interactive.
193 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
195 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
196 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
199 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
201 if (tp
->ecn_flags
& TCP_ECN_OK
)
202 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
205 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, struct sk_buff
*skb
)
207 if (tcp_hdr(skb
)->cwr
)
208 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
211 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
213 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
216 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, struct sk_buff
*skb
)
218 if (tp
->ecn_flags
& TCP_ECN_OK
) {
219 if (INET_ECN_is_ce(TCP_SKB_CB(skb
)->flags
))
220 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
221 /* Funny extension: if ECT is not set on a segment,
222 * it is surely retransmit. It is not in ECN RFC,
223 * but Linux follows this rule. */
224 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb
)->flags
)))
225 tcp_enter_quickack_mode((struct sock
*)tp
);
229 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, struct tcphdr
*th
)
231 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
232 tp
->ecn_flags
&= ~TCP_ECN_OK
;
235 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, struct tcphdr
*th
)
237 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
238 tp
->ecn_flags
&= ~TCP_ECN_OK
;
241 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock
*tp
, struct tcphdr
*th
)
243 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
248 /* Buffer size and advertised window tuning.
250 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
253 static void tcp_fixup_sndbuf(struct sock
*sk
)
255 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
256 sizeof(struct sk_buff
);
258 if (sk
->sk_sndbuf
< 3 * sndmem
)
259 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
262 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
264 * All tcp_full_space() is split to two parts: "network" buffer, allocated
265 * forward and advertised in receiver window (tp->rcv_wnd) and
266 * "application buffer", required to isolate scheduling/application
267 * latencies from network.
268 * window_clamp is maximal advertised window. It can be less than
269 * tcp_full_space(), in this case tcp_full_space() - window_clamp
270 * is reserved for "application" buffer. The less window_clamp is
271 * the smoother our behaviour from viewpoint of network, but the lower
272 * throughput and the higher sensitivity of the connection to losses. 8)
274 * rcv_ssthresh is more strict window_clamp used at "slow start"
275 * phase to predict further behaviour of this connection.
276 * It is used for two goals:
277 * - to enforce header prediction at sender, even when application
278 * requires some significant "application buffer". It is check #1.
279 * - to prevent pruning of receive queue because of misprediction
280 * of receiver window. Check #2.
282 * The scheme does not work when sender sends good segments opening
283 * window and then starts to feed us spaghetti. But it should work
284 * in common situations. Otherwise, we have to rely on queue collapsing.
287 /* Slow part of check#2. */
288 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
290 struct tcp_sock
*tp
= tcp_sk(sk
);
292 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
293 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
295 while (tp
->rcv_ssthresh
<= window
) {
296 if (truesize
<= skb
->len
)
297 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
305 static void tcp_grow_window(struct sock
*sk
, struct sk_buff
*skb
)
307 struct tcp_sock
*tp
= tcp_sk(sk
);
310 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
311 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
312 !tcp_memory_pressure
) {
315 /* Check #2. Increase window, if skb with such overhead
316 * will fit to rcvbuf in future.
318 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
319 incr
= 2 * tp
->advmss
;
321 incr
= __tcp_grow_window(sk
, skb
);
324 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
326 inet_csk(sk
)->icsk_ack
.quick
|= 1;
331 /* 3. Tuning rcvbuf, when connection enters established state. */
333 static void tcp_fixup_rcvbuf(struct sock
*sk
)
335 struct tcp_sock
*tp
= tcp_sk(sk
);
336 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
338 /* Try to select rcvbuf so that 4 mss-sized segments
339 * will fit to window and corresponding skbs will fit to our rcvbuf.
340 * (was 3; 4 is minimum to allow fast retransmit to work.)
342 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
344 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
345 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
348 /* 4. Try to fixup all. It is made immediately after connection enters
351 static void tcp_init_buffer_space(struct sock
*sk
)
353 struct tcp_sock
*tp
= tcp_sk(sk
);
356 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
357 tcp_fixup_rcvbuf(sk
);
358 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
359 tcp_fixup_sndbuf(sk
);
361 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
363 maxwin
= tcp_full_space(sk
);
365 if (tp
->window_clamp
>= maxwin
) {
366 tp
->window_clamp
= maxwin
;
368 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
369 tp
->window_clamp
= max(maxwin
-
370 (maxwin
>> sysctl_tcp_app_win
),
374 /* Force reservation of one segment. */
375 if (sysctl_tcp_app_win
&&
376 tp
->window_clamp
> 2 * tp
->advmss
&&
377 tp
->window_clamp
+ tp
->advmss
> maxwin
)
378 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
380 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
381 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
384 /* 5. Recalculate window clamp after socket hit its memory bounds. */
385 static void tcp_clamp_window(struct sock
*sk
)
387 struct tcp_sock
*tp
= tcp_sk(sk
);
388 struct inet_connection_sock
*icsk
= inet_csk(sk
);
390 icsk
->icsk_ack
.quick
= 0;
392 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
393 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
394 !tcp_memory_pressure
&&
395 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
396 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
399 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
400 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
403 /* Initialize RCV_MSS value.
404 * RCV_MSS is an our guess about MSS used by the peer.
405 * We haven't any direct information about the MSS.
406 * It's better to underestimate the RCV_MSS rather than overestimate.
407 * Overestimations make us ACKing less frequently than needed.
408 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
410 void tcp_initialize_rcv_mss(struct sock
*sk
)
412 struct tcp_sock
*tp
= tcp_sk(sk
);
413 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
415 hint
= min(hint
, tp
->rcv_wnd
/ 2);
416 hint
= min(hint
, TCP_MIN_RCVMSS
);
417 hint
= max(hint
, TCP_MIN_MSS
);
419 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
422 /* Receiver "autotuning" code.
424 * The algorithm for RTT estimation w/o timestamps is based on
425 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
426 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
428 * More detail on this code can be found at
429 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
430 * though this reference is out of date. A new paper
433 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
435 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
441 if (new_sample
!= 0) {
442 /* If we sample in larger samples in the non-timestamp
443 * case, we could grossly overestimate the RTT especially
444 * with chatty applications or bulk transfer apps which
445 * are stalled on filesystem I/O.
447 * Also, since we are only going for a minimum in the
448 * non-timestamp case, we do not smooth things out
449 * else with timestamps disabled convergence takes too
453 m
-= (new_sample
>> 3);
455 } else if (m
< new_sample
)
458 /* No previous measure. */
462 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
463 tp
->rcv_rtt_est
.rtt
= new_sample
;
466 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
468 if (tp
->rcv_rtt_est
.time
== 0)
470 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
472 tcp_rcv_rtt_update(tp
, jiffies
- tp
->rcv_rtt_est
.time
, 1);
475 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
476 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
479 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
480 const struct sk_buff
*skb
)
482 struct tcp_sock
*tp
= tcp_sk(sk
);
483 if (tp
->rx_opt
.rcv_tsecr
&&
484 (TCP_SKB_CB(skb
)->end_seq
-
485 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
486 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
490 * This function should be called every time data is copied to user space.
491 * It calculates the appropriate TCP receive buffer space.
493 void tcp_rcv_space_adjust(struct sock
*sk
)
495 struct tcp_sock
*tp
= tcp_sk(sk
);
499 if (tp
->rcvq_space
.time
== 0)
502 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
503 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
506 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
508 space
= max(tp
->rcvq_space
.space
, space
);
510 if (tp
->rcvq_space
.space
!= space
) {
513 tp
->rcvq_space
.space
= space
;
515 if (sysctl_tcp_moderate_rcvbuf
&&
516 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
517 int new_clamp
= space
;
519 /* Receive space grows, normalize in order to
520 * take into account packet headers and sk_buff
521 * structure overhead.
526 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
527 16 + sizeof(struct sk_buff
));
528 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
531 space
= min(space
, sysctl_tcp_rmem
[2]);
532 if (space
> sk
->sk_rcvbuf
) {
533 sk
->sk_rcvbuf
= space
;
535 /* Make the window clamp follow along. */
536 tp
->window_clamp
= new_clamp
;
542 tp
->rcvq_space
.seq
= tp
->copied_seq
;
543 tp
->rcvq_space
.time
= tcp_time_stamp
;
546 /* There is something which you must keep in mind when you analyze the
547 * behavior of the tp->ato delayed ack timeout interval. When a
548 * connection starts up, we want to ack as quickly as possible. The
549 * problem is that "good" TCP's do slow start at the beginning of data
550 * transmission. The means that until we send the first few ACK's the
551 * sender will sit on his end and only queue most of his data, because
552 * he can only send snd_cwnd unacked packets at any given time. For
553 * each ACK we send, he increments snd_cwnd and transmits more of his
556 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
558 struct tcp_sock
*tp
= tcp_sk(sk
);
559 struct inet_connection_sock
*icsk
= inet_csk(sk
);
562 inet_csk_schedule_ack(sk
);
564 tcp_measure_rcv_mss(sk
, skb
);
566 tcp_rcv_rtt_measure(tp
);
568 now
= tcp_time_stamp
;
570 if (!icsk
->icsk_ack
.ato
) {
571 /* The _first_ data packet received, initialize
572 * delayed ACK engine.
574 tcp_incr_quickack(sk
);
575 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
577 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
579 if (m
<= TCP_ATO_MIN
/ 2) {
580 /* The fastest case is the first. */
581 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
582 } else if (m
< icsk
->icsk_ack
.ato
) {
583 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
584 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
585 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
586 } else if (m
> icsk
->icsk_rto
) {
587 /* Too long gap. Apparently sender failed to
588 * restart window, so that we send ACKs quickly.
590 tcp_incr_quickack(sk
);
594 icsk
->icsk_ack
.lrcvtime
= now
;
596 TCP_ECN_check_ce(tp
, skb
);
599 tcp_grow_window(sk
, skb
);
602 static u32
tcp_rto_min(struct sock
*sk
)
604 struct dst_entry
*dst
= __sk_dst_get(sk
);
605 u32 rto_min
= TCP_RTO_MIN
;
607 if (dst
&& dst_metric_locked(dst
, RTAX_RTO_MIN
))
608 rto_min
= dst
->metrics
[RTAX_RTO_MIN
- 1];
612 /* Called to compute a smoothed rtt estimate. The data fed to this
613 * routine either comes from timestamps, or from segments that were
614 * known _not_ to have been retransmitted [see Karn/Partridge
615 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
616 * piece by Van Jacobson.
617 * NOTE: the next three routines used to be one big routine.
618 * To save cycles in the RFC 1323 implementation it was better to break
619 * it up into three procedures. -- erics
621 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
623 struct tcp_sock
*tp
= tcp_sk(sk
);
624 long m
= mrtt
; /* RTT */
626 /* The following amusing code comes from Jacobson's
627 * article in SIGCOMM '88. Note that rtt and mdev
628 * are scaled versions of rtt and mean deviation.
629 * This is designed to be as fast as possible
630 * m stands for "measurement".
632 * On a 1990 paper the rto value is changed to:
633 * RTO = rtt + 4 * mdev
635 * Funny. This algorithm seems to be very broken.
636 * These formulae increase RTO, when it should be decreased, increase
637 * too slowly, when it should be increased quickly, decrease too quickly
638 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
639 * does not matter how to _calculate_ it. Seems, it was trap
640 * that VJ failed to avoid. 8)
645 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
646 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
648 m
= -m
; /* m is now abs(error) */
649 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
650 /* This is similar to one of Eifel findings.
651 * Eifel blocks mdev updates when rtt decreases.
652 * This solution is a bit different: we use finer gain
653 * for mdev in this case (alpha*beta).
654 * Like Eifel it also prevents growth of rto,
655 * but also it limits too fast rto decreases,
656 * happening in pure Eifel.
661 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
663 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
664 if (tp
->mdev
> tp
->mdev_max
) {
665 tp
->mdev_max
= tp
->mdev
;
666 if (tp
->mdev_max
> tp
->rttvar
)
667 tp
->rttvar
= tp
->mdev_max
;
669 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
670 if (tp
->mdev_max
< tp
->rttvar
)
671 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
672 tp
->rtt_seq
= tp
->snd_nxt
;
673 tp
->mdev_max
= tcp_rto_min(sk
);
676 /* no previous measure. */
677 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
678 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
679 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
680 tp
->rtt_seq
= tp
->snd_nxt
;
684 /* Calculate rto without backoff. This is the second half of Van Jacobson's
685 * routine referred to above.
687 static inline void tcp_set_rto(struct sock
*sk
)
689 const struct tcp_sock
*tp
= tcp_sk(sk
);
690 /* Old crap is replaced with new one. 8)
693 * 1. If rtt variance happened to be less 50msec, it is hallucination.
694 * It cannot be less due to utterly erratic ACK generation made
695 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
696 * to do with delayed acks, because at cwnd>2 true delack timeout
697 * is invisible. Actually, Linux-2.4 also generates erratic
698 * ACKs in some circumstances.
700 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
702 /* 2. Fixups made earlier cannot be right.
703 * If we do not estimate RTO correctly without them,
704 * all the algo is pure shit and should be replaced
705 * with correct one. It is exactly, which we pretend to do.
709 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
710 * guarantees that rto is higher.
712 static inline void tcp_bound_rto(struct sock
*sk
)
714 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
715 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
718 /* Save metrics learned by this TCP session.
719 This function is called only, when TCP finishes successfully
720 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
722 void tcp_update_metrics(struct sock
*sk
)
724 struct tcp_sock
*tp
= tcp_sk(sk
);
725 struct dst_entry
*dst
= __sk_dst_get(sk
);
727 if (sysctl_tcp_nometrics_save
)
732 if (dst
&& (dst
->flags
& DST_HOST
)) {
733 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
736 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
737 /* This session failed to estimate rtt. Why?
738 * Probably, no packets returned in time.
741 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
742 dst
->metrics
[RTAX_RTT
- 1] = 0;
746 m
= dst_metric(dst
, RTAX_RTT
) - tp
->srtt
;
748 /* If newly calculated rtt larger than stored one,
749 * store new one. Otherwise, use EWMA. Remember,
750 * rtt overestimation is always better than underestimation.
752 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
754 dst
->metrics
[RTAX_RTT
- 1] = tp
->srtt
;
756 dst
->metrics
[RTAX_RTT
- 1] -= (m
>> 3);
759 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
763 /* Scale deviation to rttvar fixed point */
768 if (m
>= dst_metric(dst
, RTAX_RTTVAR
))
769 dst
->metrics
[RTAX_RTTVAR
- 1] = m
;
771 dst
->metrics
[RTAX_RTTVAR
-1] -=
772 (dst
->metrics
[RTAX_RTTVAR
-1] - m
)>>2;
775 if (tp
->snd_ssthresh
>= 0xFFFF) {
776 /* Slow start still did not finish. */
777 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
778 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
779 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
780 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
781 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
782 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
783 dst
->metrics
[RTAX_CWND
- 1] = tp
->snd_cwnd
;
784 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
785 icsk
->icsk_ca_state
== TCP_CA_Open
) {
786 /* Cong. avoidance phase, cwnd is reliable. */
787 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
788 dst
->metrics
[RTAX_SSTHRESH
-1] =
789 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
790 if (!dst_metric_locked(dst
, RTAX_CWND
))
791 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_cwnd
) >> 1;
793 /* Else slow start did not finish, cwnd is non-sense,
794 ssthresh may be also invalid.
796 if (!dst_metric_locked(dst
, RTAX_CWND
))
797 dst
->metrics
[RTAX_CWND
-1] = (dst
->metrics
[RTAX_CWND
-1] + tp
->snd_ssthresh
) >> 1;
798 if (dst
->metrics
[RTAX_SSTHRESH
-1] &&
799 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
800 tp
->snd_ssthresh
> dst
->metrics
[RTAX_SSTHRESH
-1])
801 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
804 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
805 if (dst
->metrics
[RTAX_REORDERING
-1] < tp
->reordering
&&
806 tp
->reordering
!= sysctl_tcp_reordering
)
807 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
812 /* Numbers are taken from RFC3390.
814 * John Heffner states:
816 * The RFC specifies a window of no more than 4380 bytes
817 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
818 * is a bit misleading because they use a clamp at 4380 bytes
819 * rather than use a multiplier in the relevant range.
821 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
823 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
826 if (tp
->mss_cache
> 1460)
829 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
831 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
834 /* Set slow start threshold and cwnd not falling to slow start */
835 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
837 struct tcp_sock
*tp
= tcp_sk(sk
);
838 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
840 tp
->prior_ssthresh
= 0;
842 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
845 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
846 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
847 tcp_packets_in_flight(tp
) + 1U);
848 tp
->snd_cwnd_cnt
= 0;
849 tp
->high_seq
= tp
->snd_nxt
;
850 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
851 TCP_ECN_queue_cwr(tp
);
853 tcp_set_ca_state(sk
, TCP_CA_CWR
);
858 * Packet counting of FACK is based on in-order assumptions, therefore TCP
859 * disables it when reordering is detected
861 static void tcp_disable_fack(struct tcp_sock
*tp
)
863 /* RFC3517 uses different metric in lost marker => reset on change */
865 tp
->lost_skb_hint
= NULL
;
866 tp
->rx_opt
.sack_ok
&= ~2;
869 /* Take a notice that peer is sending D-SACKs */
870 static void tcp_dsack_seen(struct tcp_sock
*tp
)
872 tp
->rx_opt
.sack_ok
|= 4;
875 /* Initialize metrics on socket. */
877 static void tcp_init_metrics(struct sock
*sk
)
879 struct tcp_sock
*tp
= tcp_sk(sk
);
880 struct dst_entry
*dst
= __sk_dst_get(sk
);
887 if (dst_metric_locked(dst
, RTAX_CWND
))
888 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
889 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
890 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
891 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
892 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
894 if (dst_metric(dst
, RTAX_REORDERING
) &&
895 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
896 tcp_disable_fack(tp
);
897 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
900 if (dst_metric(dst
, RTAX_RTT
) == 0)
903 if (!tp
->srtt
&& dst_metric(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
906 /* Initial rtt is determined from SYN,SYN-ACK.
907 * The segment is small and rtt may appear much
908 * less than real one. Use per-dst memory
909 * to make it more realistic.
911 * A bit of theory. RTT is time passed after "normal" sized packet
912 * is sent until it is ACKed. In normal circumstances sending small
913 * packets force peer to delay ACKs and calculation is correct too.
914 * The algorithm is adaptive and, provided we follow specs, it
915 * NEVER underestimate RTT. BUT! If peer tries to make some clever
916 * tricks sort of "quick acks" for time long enough to decrease RTT
917 * to low value, and then abruptly stops to do it and starts to delay
918 * ACKs, wait for troubles.
920 if (dst_metric(dst
, RTAX_RTT
) > tp
->srtt
) {
921 tp
->srtt
= dst_metric(dst
, RTAX_RTT
);
922 tp
->rtt_seq
= tp
->snd_nxt
;
924 if (dst_metric(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
925 tp
->mdev
= dst_metric(dst
, RTAX_RTTVAR
);
926 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
930 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
932 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
933 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
937 /* Play conservative. If timestamps are not
938 * supported, TCP will fail to recalculate correct
939 * rtt, if initial rto is too small. FORGET ALL AND RESET!
941 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
943 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
944 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
948 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
951 struct tcp_sock
*tp
= tcp_sk(sk
);
952 if (metric
> tp
->reordering
) {
953 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
955 /* This exciting event is worth to be remembered. 8) */
957 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER
);
958 else if (tcp_is_reno(tp
))
959 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER
);
960 else if (tcp_is_fack(tp
))
961 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER
);
963 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER
);
964 #if FASTRETRANS_DEBUG > 1
965 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
966 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
970 tp
->undo_marker
? tp
->undo_retrans
: 0);
972 tcp_disable_fack(tp
);
976 /* This procedure tags the retransmission queue when SACKs arrive.
978 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
979 * Packets in queue with these bits set are counted in variables
980 * sacked_out, retrans_out and lost_out, correspondingly.
982 * Valid combinations are:
983 * Tag InFlight Description
984 * 0 1 - orig segment is in flight.
985 * S 0 - nothing flies, orig reached receiver.
986 * L 0 - nothing flies, orig lost by net.
987 * R 2 - both orig and retransmit are in flight.
988 * L|R 1 - orig is lost, retransmit is in flight.
989 * S|R 1 - orig reached receiver, retrans is still in flight.
990 * (L|S|R is logically valid, it could occur when L|R is sacked,
991 * but it is equivalent to plain S and code short-curcuits it to S.
992 * L|S is logically invalid, it would mean -1 packet in flight 8))
994 * These 6 states form finite state machine, controlled by the following events:
995 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
996 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
997 * 3. Loss detection event of one of three flavors:
998 * A. Scoreboard estimator decided the packet is lost.
999 * A'. Reno "three dupacks" marks head of queue lost.
1000 * A''. Its FACK modfication, head until snd.fack is lost.
1001 * B. SACK arrives sacking data transmitted after never retransmitted
1002 * hole was sent out.
1003 * C. SACK arrives sacking SND.NXT at the moment, when the
1004 * segment was retransmitted.
1005 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1007 * It is pleasant to note, that state diagram turns out to be commutative,
1008 * so that we are allowed not to be bothered by order of our actions,
1009 * when multiple events arrive simultaneously. (see the function below).
1011 * Reordering detection.
1012 * --------------------
1013 * Reordering metric is maximal distance, which a packet can be displaced
1014 * in packet stream. With SACKs we can estimate it:
1016 * 1. SACK fills old hole and the corresponding segment was not
1017 * ever retransmitted -> reordering. Alas, we cannot use it
1018 * when segment was retransmitted.
1019 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1020 * for retransmitted and already SACKed segment -> reordering..
1021 * Both of these heuristics are not used in Loss state, when we cannot
1022 * account for retransmits accurately.
1024 * SACK block validation.
1025 * ----------------------
1027 * SACK block range validation checks that the received SACK block fits to
1028 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1029 * Note that SND.UNA is not included to the range though being valid because
1030 * it means that the receiver is rather inconsistent with itself reporting
1031 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1032 * perfectly valid, however, in light of RFC2018 which explicitly states
1033 * that "SACK block MUST reflect the newest segment. Even if the newest
1034 * segment is going to be discarded ...", not that it looks very clever
1035 * in case of head skb. Due to potentional receiver driven attacks, we
1036 * choose to avoid immediate execution of a walk in write queue due to
1037 * reneging and defer head skb's loss recovery to standard loss recovery
1038 * procedure that will eventually trigger (nothing forbids us doing this).
1040 * Implements also blockage to start_seq wrap-around. Problem lies in the
1041 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1042 * there's no guarantee that it will be before snd_nxt (n). The problem
1043 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1046 * <- outs wnd -> <- wrapzone ->
1047 * u e n u_w e_w s n_w
1049 * |<------------+------+----- TCP seqno space --------------+---------->|
1050 * ...-- <2^31 ->| |<--------...
1051 * ...---- >2^31 ------>| |<--------...
1053 * Current code wouldn't be vulnerable but it's better still to discard such
1054 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1055 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1056 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1057 * equal to the ideal case (infinite seqno space without wrap caused issues).
1059 * With D-SACK the lower bound is extended to cover sequence space below
1060 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1061 * again, D-SACK block must not to go across snd_una (for the same reason as
1062 * for the normal SACK blocks, explained above). But there all simplicity
1063 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1064 * fully below undo_marker they do not affect behavior in anyway and can
1065 * therefore be safely ignored. In rare cases (which are more or less
1066 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1067 * fragmentation and packet reordering past skb's retransmission. To consider
1068 * them correctly, the acceptable range must be extended even more though
1069 * the exact amount is rather hard to quantify. However, tp->max_window can
1070 * be used as an exaggerated estimate.
1072 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1073 u32 start_seq
, u32 end_seq
)
1075 /* Too far in future, or reversed (interpretation is ambiguous) */
1076 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1079 /* Nasty start_seq wrap-around check (see comments above) */
1080 if (!before(start_seq
, tp
->snd_nxt
))
1083 /* In outstanding window? ...This is valid exit for D-SACKs too.
1084 * start_seq == snd_una is non-sensical (see comments above)
1086 if (after(start_seq
, tp
->snd_una
))
1089 if (!is_dsack
|| !tp
->undo_marker
)
1092 /* ...Then it's D-SACK, and must reside below snd_una completely */
1093 if (!after(end_seq
, tp
->snd_una
))
1096 if (!before(start_seq
, tp
->undo_marker
))
1100 if (!after(end_seq
, tp
->undo_marker
))
1103 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1104 * start_seq < undo_marker and end_seq >= undo_marker.
1106 return !before(start_seq
, end_seq
- tp
->max_window
);
1109 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1110 * Event "C". Later note: FACK people cheated me again 8), we have to account
1111 * for reordering! Ugly, but should help.
1113 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1114 * less than what is now known to be received by the other end (derived from
1115 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1116 * retransmitted skbs to avoid some costly processing per ACKs.
1118 static void tcp_mark_lost_retrans(struct sock
*sk
)
1120 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1121 struct tcp_sock
*tp
= tcp_sk(sk
);
1122 struct sk_buff
*skb
;
1124 u32 new_low_seq
= tp
->snd_nxt
;
1125 u32 received_upto
= tcp_highest_sack_seq(tp
);
1127 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1128 !after(received_upto
, tp
->lost_retrans_low
) ||
1129 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1132 tcp_for_write_queue(skb
, sk
) {
1133 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1135 if (skb
== tcp_send_head(sk
))
1137 if (cnt
== tp
->retrans_out
)
1139 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1142 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1145 if (after(received_upto
, ack_seq
) &&
1147 !before(received_upto
,
1148 ack_seq
+ tp
->reordering
* tp
->mss_cache
))) {
1149 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1150 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1152 /* clear lost hint */
1153 tp
->retransmit_skb_hint
= NULL
;
1155 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1156 tp
->lost_out
+= tcp_skb_pcount(skb
);
1157 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1159 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT
);
1161 if (before(ack_seq
, new_low_seq
))
1162 new_low_seq
= ack_seq
;
1163 cnt
+= tcp_skb_pcount(skb
);
1167 if (tp
->retrans_out
)
1168 tp
->lost_retrans_low
= new_low_seq
;
1171 static int tcp_check_dsack(struct tcp_sock
*tp
, struct sk_buff
*ack_skb
,
1172 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1175 u32 start_seq_0
= ntohl(get_unaligned(&sp
[0].start_seq
));
1176 u32 end_seq_0
= ntohl(get_unaligned(&sp
[0].end_seq
));
1179 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1182 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV
);
1183 } else if (num_sacks
> 1) {
1184 u32 end_seq_1
= ntohl(get_unaligned(&sp
[1].end_seq
));
1185 u32 start_seq_1
= ntohl(get_unaligned(&sp
[1].start_seq
));
1187 if (!after(end_seq_0
, end_seq_1
) &&
1188 !before(start_seq_0
, start_seq_1
)) {
1191 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV
);
1195 /* D-SACK for already forgotten data... Do dumb counting. */
1197 !after(end_seq_0
, prior_snd_una
) &&
1198 after(end_seq_0
, tp
->undo_marker
))
1204 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1205 * the incoming SACK may not exactly match but we can find smaller MSS
1206 * aligned portion of it that matches. Therefore we might need to fragment
1207 * which may fail and creates some hassle (caller must handle error case
1210 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1211 u32 start_seq
, u32 end_seq
)
1214 unsigned int pkt_len
;
1216 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1217 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1219 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1220 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1222 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1225 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1227 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1228 err
= tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
);
1236 static int tcp_sacktag_one(struct sk_buff
*skb
, struct sock
*sk
,
1237 int *reord
, int dup_sack
, int fack_count
)
1239 struct tcp_sock
*tp
= tcp_sk(sk
);
1240 u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1243 /* Account D-SACK for retransmitted packet. */
1244 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1245 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1247 if (sacked
& TCPCB_SACKED_ACKED
)
1248 *reord
= min(fack_count
, *reord
);
1251 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1252 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1255 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1256 if (sacked
& TCPCB_SACKED_RETRANS
) {
1257 /* If the segment is not tagged as lost,
1258 * we do not clear RETRANS, believing
1259 * that retransmission is still in flight.
1261 if (sacked
& TCPCB_LOST
) {
1262 TCP_SKB_CB(skb
)->sacked
&=
1263 ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1264 tp
->lost_out
-= tcp_skb_pcount(skb
);
1265 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1267 /* clear lost hint */
1268 tp
->retransmit_skb_hint
= NULL
;
1271 if (!(sacked
& TCPCB_RETRANS
)) {
1272 /* New sack for not retransmitted frame,
1273 * which was in hole. It is reordering.
1275 if (before(TCP_SKB_CB(skb
)->seq
,
1276 tcp_highest_sack_seq(tp
)))
1277 *reord
= min(fack_count
, *reord
);
1279 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1280 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
))
1281 flag
|= FLAG_ONLY_ORIG_SACKED
;
1284 if (sacked
& TCPCB_LOST
) {
1285 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1286 tp
->lost_out
-= tcp_skb_pcount(skb
);
1288 /* clear lost hint */
1289 tp
->retransmit_skb_hint
= NULL
;
1293 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1294 flag
|= FLAG_DATA_SACKED
;
1295 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1297 fack_count
+= tcp_skb_pcount(skb
);
1299 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1300 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1301 before(TCP_SKB_CB(skb
)->seq
,
1302 TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1303 tp
->lost_cnt_hint
+= tcp_skb_pcount(skb
);
1305 if (fack_count
> tp
->fackets_out
)
1306 tp
->fackets_out
= fack_count
;
1308 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
1309 tcp_advance_highest_sack(sk
, skb
);
1312 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1313 * frames and clear it. undo_retrans is decreased above, L|R frames
1314 * are accounted above as well.
1316 if (dup_sack
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)) {
1317 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1318 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1319 tp
->retransmit_skb_hint
= NULL
;
1325 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1326 struct tcp_sack_block
*next_dup
,
1327 u32 start_seq
, u32 end_seq
,
1328 int dup_sack_in
, int *fack_count
,
1329 int *reord
, int *flag
)
1331 tcp_for_write_queue_from(skb
, sk
) {
1333 int dup_sack
= dup_sack_in
;
1335 if (skb
== tcp_send_head(sk
))
1338 /* queue is in-order => we can short-circuit the walk early */
1339 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1342 if ((next_dup
!= NULL
) &&
1343 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1344 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1345 next_dup
->start_seq
,
1352 in_sack
= tcp_match_skb_to_sack(sk
, skb
, start_seq
,
1354 if (unlikely(in_sack
< 0))
1358 *flag
|= tcp_sacktag_one(skb
, sk
, reord
, dup_sack
,
1361 *fack_count
+= tcp_skb_pcount(skb
);
1366 /* Avoid all extra work that is being done by sacktag while walking in
1369 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1370 u32 skip_to_seq
, int *fack_count
)
1372 tcp_for_write_queue_from(skb
, sk
) {
1373 if (skb
== tcp_send_head(sk
))
1376 if (!before(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1379 *fack_count
+= tcp_skb_pcount(skb
);
1384 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1386 struct tcp_sack_block
*next_dup
,
1388 int *fack_count
, int *reord
,
1391 if (next_dup
== NULL
)
1394 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1395 skb
= tcp_sacktag_skip(skb
, sk
, next_dup
->start_seq
, fack_count
);
1396 tcp_sacktag_walk(skb
, sk
, NULL
,
1397 next_dup
->start_seq
, next_dup
->end_seq
,
1398 1, fack_count
, reord
, flag
);
1404 static int tcp_sack_cache_ok(struct tcp_sock
*tp
, struct tcp_sack_block
*cache
)
1406 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1410 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
,
1413 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1414 struct tcp_sock
*tp
= tcp_sk(sk
);
1415 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1416 TCP_SKB_CB(ack_skb
)->sacked
);
1417 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1418 struct tcp_sack_block sp
[4];
1419 struct tcp_sack_block
*cache
;
1420 struct sk_buff
*skb
;
1421 int num_sacks
= (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3;
1423 int reord
= tp
->packets_out
;
1425 int found_dup_sack
= 0;
1428 int first_sack_index
;
1430 if (!tp
->sacked_out
) {
1431 if (WARN_ON(tp
->fackets_out
))
1432 tp
->fackets_out
= 0;
1433 tcp_highest_sack_reset(sk
);
1436 found_dup_sack
= tcp_check_dsack(tp
, ack_skb
, sp_wire
,
1437 num_sacks
, prior_snd_una
);
1439 flag
|= FLAG_DSACKING_ACK
;
1441 /* Eliminate too old ACKs, but take into
1442 * account more or less fresh ones, they can
1443 * contain valid SACK info.
1445 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1448 if (!tp
->packets_out
)
1452 first_sack_index
= 0;
1453 for (i
= 0; i
< num_sacks
; i
++) {
1454 int dup_sack
= !i
&& found_dup_sack
;
1456 sp
[used_sacks
].start_seq
= ntohl(get_unaligned(&sp_wire
[i
].start_seq
));
1457 sp
[used_sacks
].end_seq
= ntohl(get_unaligned(&sp_wire
[i
].end_seq
));
1459 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1460 sp
[used_sacks
].start_seq
,
1461 sp
[used_sacks
].end_seq
)) {
1463 if (!tp
->undo_marker
)
1464 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO
);
1466 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD
);
1468 /* Don't count olds caused by ACK reordering */
1469 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1470 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1472 NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD
);
1475 first_sack_index
= -1;
1479 /* Ignore very old stuff early */
1480 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1486 /* order SACK blocks to allow in order walk of the retrans queue */
1487 for (i
= used_sacks
- 1; i
> 0; i
--) {
1488 for (j
= 0; j
< i
; j
++) {
1489 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1490 struct tcp_sack_block tmp
;
1496 /* Track where the first SACK block goes to */
1497 if (j
== first_sack_index
)
1498 first_sack_index
= j
+ 1;
1503 skb
= tcp_write_queue_head(sk
);
1507 if (!tp
->sacked_out
) {
1508 /* It's already past, so skip checking against it */
1509 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1511 cache
= tp
->recv_sack_cache
;
1512 /* Skip empty blocks in at head of the cache */
1513 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1518 while (i
< used_sacks
) {
1519 u32 start_seq
= sp
[i
].start_seq
;
1520 u32 end_seq
= sp
[i
].end_seq
;
1521 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1522 struct tcp_sack_block
*next_dup
= NULL
;
1524 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1525 next_dup
= &sp
[i
+ 1];
1527 /* Event "B" in the comment above. */
1528 if (after(end_seq
, tp
->high_seq
))
1529 flag
|= FLAG_DATA_LOST
;
1531 /* Skip too early cached blocks */
1532 while (tcp_sack_cache_ok(tp
, cache
) &&
1533 !before(start_seq
, cache
->end_seq
))
1536 /* Can skip some work by looking recv_sack_cache? */
1537 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1538 after(end_seq
, cache
->start_seq
)) {
1541 if (before(start_seq
, cache
->start_seq
)) {
1542 skb
= tcp_sacktag_skip(skb
, sk
, start_seq
,
1544 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1547 dup_sack
, &fack_count
,
1551 /* Rest of the block already fully processed? */
1552 if (!after(end_seq
, cache
->end_seq
))
1555 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1557 &fack_count
, &reord
,
1560 /* ...tail remains todo... */
1561 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1562 /* ...but better entrypoint exists! */
1563 skb
= tcp_highest_sack(sk
);
1566 fack_count
= tp
->fackets_out
;
1571 skb
= tcp_sacktag_skip(skb
, sk
, cache
->end_seq
,
1573 /* Check overlap against next cached too (past this one already) */
1578 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1579 skb
= tcp_highest_sack(sk
);
1582 fack_count
= tp
->fackets_out
;
1584 skb
= tcp_sacktag_skip(skb
, sk
, start_seq
, &fack_count
);
1587 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, start_seq
, end_seq
,
1588 dup_sack
, &fack_count
, &reord
, &flag
);
1591 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1592 * due to in-order walk
1594 if (after(end_seq
, tp
->frto_highmark
))
1595 flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1600 /* Clear the head of the cache sack blocks so we can skip it next time */
1601 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1602 tp
->recv_sack_cache
[i
].start_seq
= 0;
1603 tp
->recv_sack_cache
[i
].end_seq
= 0;
1605 for (j
= 0; j
< used_sacks
; j
++)
1606 tp
->recv_sack_cache
[i
++] = sp
[j
];
1608 tcp_mark_lost_retrans(sk
);
1610 tcp_verify_left_out(tp
);
1612 if ((reord
< tp
->fackets_out
) &&
1613 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1614 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1615 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
1619 #if FASTRETRANS_DEBUG > 0
1620 BUG_TRAP((int)tp
->sacked_out
>= 0);
1621 BUG_TRAP((int)tp
->lost_out
>= 0);
1622 BUG_TRAP((int)tp
->retrans_out
>= 0);
1623 BUG_TRAP((int)tcp_packets_in_flight(tp
) >= 0);
1628 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1629 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1631 int tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1635 holes
= max(tp
->lost_out
, 1U);
1636 holes
= min(holes
, tp
->packets_out
);
1638 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1639 tp
->sacked_out
= tp
->packets_out
- holes
;
1645 /* If we receive more dupacks than we expected counting segments
1646 * in assumption of absent reordering, interpret this as reordering.
1647 * The only another reason could be bug in receiver TCP.
1649 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1651 struct tcp_sock
*tp
= tcp_sk(sk
);
1652 if (tcp_limit_reno_sacked(tp
))
1653 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1656 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1658 static void tcp_add_reno_sack(struct sock
*sk
)
1660 struct tcp_sock
*tp
= tcp_sk(sk
);
1662 tcp_check_reno_reordering(sk
, 0);
1663 tcp_verify_left_out(tp
);
1666 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1668 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1670 struct tcp_sock
*tp
= tcp_sk(sk
);
1673 /* One ACK acked hole. The rest eat duplicate ACKs. */
1674 if (acked
- 1 >= tp
->sacked_out
)
1677 tp
->sacked_out
-= acked
- 1;
1679 tcp_check_reno_reordering(sk
, acked
);
1680 tcp_verify_left_out(tp
);
1683 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1688 /* F-RTO can only be used if TCP has never retransmitted anything other than
1689 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1691 int tcp_use_frto(struct sock
*sk
)
1693 const struct tcp_sock
*tp
= tcp_sk(sk
);
1694 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1695 struct sk_buff
*skb
;
1697 if (!sysctl_tcp_frto
)
1700 /* MTU probe and F-RTO won't really play nicely along currently */
1701 if (icsk
->icsk_mtup
.probe_size
)
1707 /* Avoid expensive walking of rexmit queue if possible */
1708 if (tp
->retrans_out
> 1)
1711 skb
= tcp_write_queue_head(sk
);
1712 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
1713 tcp_for_write_queue_from(skb
, sk
) {
1714 if (skb
== tcp_send_head(sk
))
1716 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1718 /* Short-circuit when first non-SACKed skb has been checked */
1719 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
1725 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1726 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1727 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1728 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1729 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1730 * bits are handled if the Loss state is really to be entered (in
1731 * tcp_enter_frto_loss).
1733 * Do like tcp_enter_loss() would; when RTO expires the second time it
1735 * "Reduce ssthresh if it has not yet been made inside this window."
1737 void tcp_enter_frto(struct sock
*sk
)
1739 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1740 struct tcp_sock
*tp
= tcp_sk(sk
);
1741 struct sk_buff
*skb
;
1743 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1744 tp
->snd_una
== tp
->high_seq
||
1745 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1746 !icsk
->icsk_retransmits
)) {
1747 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1748 /* Our state is too optimistic in ssthresh() call because cwnd
1749 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
1750 * recovery has not yet completed. Pattern would be this: RTO,
1751 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1753 * RFC4138 should be more specific on what to do, even though
1754 * RTO is quite unlikely to occur after the first Cumulative ACK
1755 * due to back-off and complexity of triggering events ...
1757 if (tp
->frto_counter
) {
1759 stored_cwnd
= tp
->snd_cwnd
;
1761 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1762 tp
->snd_cwnd
= stored_cwnd
;
1764 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1766 /* ... in theory, cong.control module could do "any tricks" in
1767 * ssthresh(), which means that ca_state, lost bits and lost_out
1768 * counter would have to be faked before the call occurs. We
1769 * consider that too expensive, unlikely and hacky, so modules
1770 * using these in ssthresh() must deal these incompatibility
1771 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1773 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1776 tp
->undo_marker
= tp
->snd_una
;
1777 tp
->undo_retrans
= 0;
1779 skb
= tcp_write_queue_head(sk
);
1780 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1781 tp
->undo_marker
= 0;
1782 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1783 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1784 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1786 tcp_verify_left_out(tp
);
1788 /* Too bad if TCP was application limited */
1789 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
1791 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1792 * The last condition is necessary at least in tp->frto_counter case.
1794 if (IsSackFrto() && (tp
->frto_counter
||
1795 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
1796 after(tp
->high_seq
, tp
->snd_una
)) {
1797 tp
->frto_highmark
= tp
->high_seq
;
1799 tp
->frto_highmark
= tp
->snd_nxt
;
1801 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
1802 tp
->high_seq
= tp
->snd_nxt
;
1803 tp
->frto_counter
= 1;
1806 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1807 * which indicates that we should follow the traditional RTO recovery,
1808 * i.e. mark everything lost and do go-back-N retransmission.
1810 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
1812 struct tcp_sock
*tp
= tcp_sk(sk
);
1813 struct sk_buff
*skb
;
1816 tp
->retrans_out
= 0;
1817 if (tcp_is_reno(tp
))
1818 tcp_reset_reno_sack(tp
);
1820 tcp_for_write_queue(skb
, sk
) {
1821 if (skb
== tcp_send_head(sk
))
1824 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1826 * Count the retransmission made on RTO correctly (only when
1827 * waiting for the first ACK and did not get it)...
1829 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
1830 /* For some reason this R-bit might get cleared? */
1831 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1832 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1833 /* ...enter this if branch just for the first segment */
1834 flag
|= FLAG_DATA_ACKED
;
1836 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1837 tp
->undo_marker
= 0;
1838 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1841 /* Don't lost mark skbs that were fwd transmitted after RTO */
1842 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) &&
1843 !after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
)) {
1844 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1845 tp
->lost_out
+= tcp_skb_pcount(skb
);
1848 tcp_verify_left_out(tp
);
1850 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
1851 tp
->snd_cwnd_cnt
= 0;
1852 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1853 tp
->frto_counter
= 0;
1854 tp
->bytes_acked
= 0;
1856 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1857 sysctl_tcp_reordering
);
1858 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1859 tp
->high_seq
= tp
->frto_highmark
;
1860 TCP_ECN_queue_cwr(tp
);
1862 tcp_clear_retrans_hints_partial(tp
);
1865 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
1867 tp
->retrans_out
= 0;
1870 tp
->undo_marker
= 0;
1871 tp
->undo_retrans
= 0;
1874 void tcp_clear_retrans(struct tcp_sock
*tp
)
1876 tcp_clear_retrans_partial(tp
);
1878 tp
->fackets_out
= 0;
1882 /* Enter Loss state. If "how" is not zero, forget all SACK information
1883 * and reset tags completely, otherwise preserve SACKs. If receiver
1884 * dropped its ofo queue, we will know this due to reneging detection.
1886 void tcp_enter_loss(struct sock
*sk
, int how
)
1888 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1889 struct tcp_sock
*tp
= tcp_sk(sk
);
1890 struct sk_buff
*skb
;
1892 /* Reduce ssthresh if it has not yet been made inside this window. */
1893 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1894 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1895 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1896 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1897 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1900 tp
->snd_cwnd_cnt
= 0;
1901 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1903 tp
->bytes_acked
= 0;
1904 tcp_clear_retrans_partial(tp
);
1906 if (tcp_is_reno(tp
))
1907 tcp_reset_reno_sack(tp
);
1910 /* Push undo marker, if it was plain RTO and nothing
1911 * was retransmitted. */
1912 tp
->undo_marker
= tp
->snd_una
;
1913 tcp_clear_retrans_hints_partial(tp
);
1916 tp
->fackets_out
= 0;
1917 tcp_clear_all_retrans_hints(tp
);
1920 tcp_for_write_queue(skb
, sk
) {
1921 if (skb
== tcp_send_head(sk
))
1924 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1925 tp
->undo_marker
= 0;
1926 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1927 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1928 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1929 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1930 tp
->lost_out
+= tcp_skb_pcount(skb
);
1933 tcp_verify_left_out(tp
);
1935 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1936 sysctl_tcp_reordering
);
1937 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1938 tp
->high_seq
= tp
->snd_nxt
;
1939 TCP_ECN_queue_cwr(tp
);
1940 /* Abort F-RTO algorithm if one is in progress */
1941 tp
->frto_counter
= 0;
1944 /* If ACK arrived pointing to a remembered SACK, it means that our
1945 * remembered SACKs do not reflect real state of receiver i.e.
1946 * receiver _host_ is heavily congested (or buggy).
1948 * Do processing similar to RTO timeout.
1950 static int tcp_check_sack_reneging(struct sock
*sk
, int flag
)
1952 if (flag
& FLAG_SACK_RENEGING
) {
1953 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1954 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING
);
1956 tcp_enter_loss(sk
, 1);
1957 icsk
->icsk_retransmits
++;
1958 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
1959 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1960 icsk
->icsk_rto
, TCP_RTO_MAX
);
1966 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1968 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
1971 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
1972 * counter when SACK is enabled (without SACK, sacked_out is used for
1975 * Instead, with FACK TCP uses fackets_out that includes both SACKed
1976 * segments up to the highest received SACK block so far and holes in
1979 * With reordering, holes may still be in flight, so RFC3517 recovery
1980 * uses pure sacked_out (total number of SACKed segments) even though
1981 * it violates the RFC that uses duplicate ACKs, often these are equal
1982 * but when e.g. out-of-window ACKs or packet duplication occurs,
1983 * they differ. Since neither occurs due to loss, TCP should really
1986 static inline int tcp_dupack_heurestics(struct tcp_sock
*tp
)
1988 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
1991 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
1993 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
1996 static inline int tcp_head_timedout(struct sock
*sk
)
1998 struct tcp_sock
*tp
= tcp_sk(sk
);
2000 return tp
->packets_out
&&
2001 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2004 /* Linux NewReno/SACK/FACK/ECN state machine.
2005 * --------------------------------------
2007 * "Open" Normal state, no dubious events, fast path.
2008 * "Disorder" In all the respects it is "Open",
2009 * but requires a bit more attention. It is entered when
2010 * we see some SACKs or dupacks. It is split of "Open"
2011 * mainly to move some processing from fast path to slow one.
2012 * "CWR" CWND was reduced due to some Congestion Notification event.
2013 * It can be ECN, ICMP source quench, local device congestion.
2014 * "Recovery" CWND was reduced, we are fast-retransmitting.
2015 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2017 * tcp_fastretrans_alert() is entered:
2018 * - each incoming ACK, if state is not "Open"
2019 * - when arrived ACK is unusual, namely:
2024 * Counting packets in flight is pretty simple.
2026 * in_flight = packets_out - left_out + retrans_out
2028 * packets_out is SND.NXT-SND.UNA counted in packets.
2030 * retrans_out is number of retransmitted segments.
2032 * left_out is number of segments left network, but not ACKed yet.
2034 * left_out = sacked_out + lost_out
2036 * sacked_out: Packets, which arrived to receiver out of order
2037 * and hence not ACKed. With SACKs this number is simply
2038 * amount of SACKed data. Even without SACKs
2039 * it is easy to give pretty reliable estimate of this number,
2040 * counting duplicate ACKs.
2042 * lost_out: Packets lost by network. TCP has no explicit
2043 * "loss notification" feedback from network (for now).
2044 * It means that this number can be only _guessed_.
2045 * Actually, it is the heuristics to predict lossage that
2046 * distinguishes different algorithms.
2048 * F.e. after RTO, when all the queue is considered as lost,
2049 * lost_out = packets_out and in_flight = retrans_out.
2051 * Essentially, we have now two algorithms counting
2054 * FACK: It is the simplest heuristics. As soon as we decided
2055 * that something is lost, we decide that _all_ not SACKed
2056 * packets until the most forward SACK are lost. I.e.
2057 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2058 * It is absolutely correct estimate, if network does not reorder
2059 * packets. And it loses any connection to reality when reordering
2060 * takes place. We use FACK by default until reordering
2061 * is suspected on the path to this destination.
2063 * NewReno: when Recovery is entered, we assume that one segment
2064 * is lost (classic Reno). While we are in Recovery and
2065 * a partial ACK arrives, we assume that one more packet
2066 * is lost (NewReno). This heuristics are the same in NewReno
2069 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2070 * deflation etc. CWND is real congestion window, never inflated, changes
2071 * only according to classic VJ rules.
2073 * Really tricky (and requiring careful tuning) part of algorithm
2074 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2075 * The first determines the moment _when_ we should reduce CWND and,
2076 * hence, slow down forward transmission. In fact, it determines the moment
2077 * when we decide that hole is caused by loss, rather than by a reorder.
2079 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2080 * holes, caused by lost packets.
2082 * And the most logically complicated part of algorithm is undo
2083 * heuristics. We detect false retransmits due to both too early
2084 * fast retransmit (reordering) and underestimated RTO, analyzing
2085 * timestamps and D-SACKs. When we detect that some segments were
2086 * retransmitted by mistake and CWND reduction was wrong, we undo
2087 * window reduction and abort recovery phase. This logic is hidden
2088 * inside several functions named tcp_try_undo_<something>.
2091 /* This function decides, when we should leave Disordered state
2092 * and enter Recovery phase, reducing congestion window.
2094 * Main question: may we further continue forward transmission
2095 * with the same cwnd?
2097 static int tcp_time_to_recover(struct sock
*sk
)
2099 struct tcp_sock
*tp
= tcp_sk(sk
);
2102 /* Do not perform any recovery during F-RTO algorithm */
2103 if (tp
->frto_counter
)
2106 /* Trick#1: The loss is proven. */
2110 /* Not-A-Trick#2 : Classic rule... */
2111 if (tcp_dupack_heurestics(tp
) > tp
->reordering
)
2114 /* Trick#3 : when we use RFC2988 timer restart, fast
2115 * retransmit can be triggered by timeout of queue head.
2117 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2120 /* Trick#4: It is still not OK... But will it be useful to delay
2123 packets_out
= tp
->packets_out
;
2124 if (packets_out
<= tp
->reordering
&&
2125 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2126 !tcp_may_send_now(sk
)) {
2127 /* We have nothing to send. This connection is limited
2128 * either by receiver window or by application.
2136 /* RFC: This is from the original, I doubt that this is necessary at all:
2137 * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
2138 * retransmitted past LOST markings in the first place? I'm not fully sure
2139 * about undo and end of connection cases, which can cause R without L?
2141 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
2143 if ((tp
->retransmit_skb_hint
!= NULL
) &&
2144 before(TCP_SKB_CB(skb
)->seq
,
2145 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
2146 tp
->retransmit_skb_hint
= NULL
;
2149 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2150 * is against sacked "cnt", otherwise it's against facked "cnt"
2152 static void tcp_mark_head_lost(struct sock
*sk
, int packets
)
2154 struct tcp_sock
*tp
= tcp_sk(sk
);
2155 struct sk_buff
*skb
;
2160 BUG_TRAP(packets
<= tp
->packets_out
);
2161 if (tp
->lost_skb_hint
) {
2162 skb
= tp
->lost_skb_hint
;
2163 cnt
= tp
->lost_cnt_hint
;
2165 skb
= tcp_write_queue_head(sk
);
2169 tcp_for_write_queue_from(skb
, sk
) {
2170 if (skb
== tcp_send_head(sk
))
2172 /* TODO: do this better */
2173 /* this is not the most efficient way to do this... */
2174 tp
->lost_skb_hint
= skb
;
2175 tp
->lost_cnt_hint
= cnt
;
2177 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->high_seq
))
2181 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2182 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2183 cnt
+= tcp_skb_pcount(skb
);
2185 if (cnt
> packets
) {
2186 if (tcp_is_sack(tp
) || (oldcnt
>= packets
))
2189 mss
= skb_shinfo(skb
)->gso_size
;
2190 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2196 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_SACKED_ACKED
|TCPCB_LOST
))) {
2197 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2198 tp
->lost_out
+= tcp_skb_pcount(skb
);
2199 tcp_verify_retransmit_hint(tp
, skb
);
2202 tcp_verify_left_out(tp
);
2205 /* Account newly detected lost packet(s) */
2207 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2209 struct tcp_sock
*tp
= tcp_sk(sk
);
2211 if (tcp_is_reno(tp
)) {
2212 tcp_mark_head_lost(sk
, 1);
2213 } else if (tcp_is_fack(tp
)) {
2214 int lost
= tp
->fackets_out
- tp
->reordering
;
2217 tcp_mark_head_lost(sk
, lost
);
2219 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2220 if (sacked_upto
< fast_rexmit
)
2221 sacked_upto
= fast_rexmit
;
2222 tcp_mark_head_lost(sk
, sacked_upto
);
2225 /* New heuristics: it is possible only after we switched
2226 * to restart timer each time when something is ACKed.
2227 * Hence, we can detect timed out packets during fast
2228 * retransmit without falling to slow start.
2230 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
)) {
2231 struct sk_buff
*skb
;
2233 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
2234 : tcp_write_queue_head(sk
);
2236 tcp_for_write_queue_from(skb
, sk
) {
2237 if (skb
== tcp_send_head(sk
))
2239 if (!tcp_skb_timedout(sk
, skb
))
2242 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_SACKED_ACKED
|TCPCB_LOST
))) {
2243 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2244 tp
->lost_out
+= tcp_skb_pcount(skb
);
2245 tcp_verify_retransmit_hint(tp
, skb
);
2249 tp
->scoreboard_skb_hint
= skb
;
2251 tcp_verify_left_out(tp
);
2255 /* CWND moderation, preventing bursts due to too big ACKs
2256 * in dubious situations.
2258 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2260 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2261 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2262 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2265 /* Lower bound on congestion window is slow start threshold
2266 * unless congestion avoidance choice decides to overide it.
2268 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2270 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2272 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2275 /* Decrease cwnd each second ack. */
2276 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2278 struct tcp_sock
*tp
= tcp_sk(sk
);
2279 int decr
= tp
->snd_cwnd_cnt
+ 1;
2281 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2282 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2283 tp
->snd_cwnd_cnt
= decr
& 1;
2286 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2287 tp
->snd_cwnd
-= decr
;
2289 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2290 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2294 /* Nothing was retransmitted or returned timestamp is less
2295 * than timestamp of the first retransmission.
2297 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
2299 return !tp
->retrans_stamp
||
2300 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2301 (__s32
)(tp
->rx_opt
.rcv_tsecr
- tp
->retrans_stamp
) < 0);
2304 /* Undo procedures. */
2306 #if FASTRETRANS_DEBUG > 1
2307 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2309 struct tcp_sock
*tp
= tcp_sk(sk
);
2310 struct inet_sock
*inet
= inet_sk(sk
);
2312 printk(KERN_DEBUG
"Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n",
2314 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
2315 tp
->snd_cwnd
, tcp_left_out(tp
),
2316 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2320 #define DBGUNDO(x...) do { } while (0)
2323 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
2325 struct tcp_sock
*tp
= tcp_sk(sk
);
2327 if (tp
->prior_ssthresh
) {
2328 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2330 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2331 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2333 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2335 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2336 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2337 TCP_ECN_withdraw_cwr(tp
);
2340 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2342 tcp_moderate_cwnd(tp
);
2343 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2345 /* There is something screwy going on with the retrans hints after
2347 tcp_clear_all_retrans_hints(tp
);
2350 static inline int tcp_may_undo(struct tcp_sock
*tp
)
2352 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2355 /* People celebrate: "We love our President!" */
2356 static int tcp_try_undo_recovery(struct sock
*sk
)
2358 struct tcp_sock
*tp
= tcp_sk(sk
);
2360 if (tcp_may_undo(tp
)) {
2361 /* Happy end! We did not retransmit anything
2362 * or our original transmission succeeded.
2364 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2365 tcp_undo_cwr(sk
, 1);
2366 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2367 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2369 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO
);
2370 tp
->undo_marker
= 0;
2372 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2373 /* Hold old state until something *above* high_seq
2374 * is ACKed. For Reno it is MUST to prevent false
2375 * fast retransmits (RFC2582). SACK TCP is safe. */
2376 tcp_moderate_cwnd(tp
);
2379 tcp_set_ca_state(sk
, TCP_CA_Open
);
2383 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2384 static void tcp_try_undo_dsack(struct sock
*sk
)
2386 struct tcp_sock
*tp
= tcp_sk(sk
);
2388 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2389 DBGUNDO(sk
, "D-SACK");
2390 tcp_undo_cwr(sk
, 1);
2391 tp
->undo_marker
= 0;
2392 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO
);
2396 /* Undo during fast recovery after partial ACK. */
2398 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2400 struct tcp_sock
*tp
= tcp_sk(sk
);
2401 /* Partial ACK arrived. Force Hoe's retransmit. */
2402 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2404 if (tcp_may_undo(tp
)) {
2405 /* Plain luck! Hole if filled with delayed
2406 * packet, rather than with a retransmit.
2408 if (tp
->retrans_out
== 0)
2409 tp
->retrans_stamp
= 0;
2411 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2414 tcp_undo_cwr(sk
, 0);
2415 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO
);
2417 /* So... Do not make Hoe's retransmit yet.
2418 * If the first packet was delayed, the rest
2419 * ones are most probably delayed as well.
2426 /* Undo during loss recovery after partial ACK. */
2427 static int tcp_try_undo_loss(struct sock
*sk
)
2429 struct tcp_sock
*tp
= tcp_sk(sk
);
2431 if (tcp_may_undo(tp
)) {
2432 struct sk_buff
*skb
;
2433 tcp_for_write_queue(skb
, sk
) {
2434 if (skb
== tcp_send_head(sk
))
2436 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2439 tcp_clear_all_retrans_hints(tp
);
2441 DBGUNDO(sk
, "partial loss");
2443 tcp_undo_cwr(sk
, 1);
2444 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO
);
2445 inet_csk(sk
)->icsk_retransmits
= 0;
2446 tp
->undo_marker
= 0;
2447 if (tcp_is_sack(tp
))
2448 tcp_set_ca_state(sk
, TCP_CA_Open
);
2454 static inline void tcp_complete_cwr(struct sock
*sk
)
2456 struct tcp_sock
*tp
= tcp_sk(sk
);
2457 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2458 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2459 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2462 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2464 struct tcp_sock
*tp
= tcp_sk(sk
);
2466 tcp_verify_left_out(tp
);
2468 if (tp
->retrans_out
== 0)
2469 tp
->retrans_stamp
= 0;
2471 if (flag
& FLAG_ECE
)
2472 tcp_enter_cwr(sk
, 1);
2474 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2475 int state
= TCP_CA_Open
;
2477 if (tcp_left_out(tp
) || tp
->retrans_out
|| tp
->undo_marker
)
2478 state
= TCP_CA_Disorder
;
2480 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2481 tcp_set_ca_state(sk
, state
);
2482 tp
->high_seq
= tp
->snd_nxt
;
2484 tcp_moderate_cwnd(tp
);
2486 tcp_cwnd_down(sk
, flag
);
2490 static void tcp_mtup_probe_failed(struct sock
*sk
)
2492 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2494 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2495 icsk
->icsk_mtup
.probe_size
= 0;
2498 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
2500 struct tcp_sock
*tp
= tcp_sk(sk
);
2501 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2503 /* FIXME: breaks with very large cwnd */
2504 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2505 tp
->snd_cwnd
= tp
->snd_cwnd
*
2506 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2507 icsk
->icsk_mtup
.probe_size
;
2508 tp
->snd_cwnd_cnt
= 0;
2509 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2510 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2512 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2513 icsk
->icsk_mtup
.probe_size
= 0;
2514 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2517 /* Process an event, which can update packets-in-flight not trivially.
2518 * Main goal of this function is to calculate new estimate for left_out,
2519 * taking into account both packets sitting in receiver's buffer and
2520 * packets lost by network.
2522 * Besides that it does CWND reduction, when packet loss is detected
2523 * and changes state of machine.
2525 * It does _not_ decide what to send, it is made in function
2526 * tcp_xmit_retransmit_queue().
2528 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
, int flag
)
2530 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2531 struct tcp_sock
*tp
= tcp_sk(sk
);
2532 int is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
2533 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2534 (tcp_fackets_out(tp
) > tp
->reordering
));
2535 int fast_rexmit
= 0;
2537 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2539 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2540 tp
->fackets_out
= 0;
2542 /* Now state machine starts.
2543 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2544 if (flag
& FLAG_ECE
)
2545 tp
->prior_ssthresh
= 0;
2547 /* B. In all the states check for reneging SACKs. */
2548 if (tcp_check_sack_reneging(sk
, flag
))
2551 /* C. Process data loss notification, provided it is valid. */
2552 if (tcp_is_fack(tp
) && (flag
& FLAG_DATA_LOST
) &&
2553 before(tp
->snd_una
, tp
->high_seq
) &&
2554 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2555 tp
->fackets_out
> tp
->reordering
) {
2556 tcp_mark_head_lost(sk
, tp
->fackets_out
- tp
->reordering
);
2557 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS
);
2560 /* D. Check consistency of the current state. */
2561 tcp_verify_left_out(tp
);
2563 /* E. Check state exit conditions. State can be terminated
2564 * when high_seq is ACKed. */
2565 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2566 BUG_TRAP(tp
->retrans_out
== 0);
2567 tp
->retrans_stamp
= 0;
2568 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2569 switch (icsk
->icsk_ca_state
) {
2571 icsk
->icsk_retransmits
= 0;
2572 if (tcp_try_undo_recovery(sk
))
2577 /* CWR is to be held something *above* high_seq
2578 * is ACKed for CWR bit to reach receiver. */
2579 if (tp
->snd_una
!= tp
->high_seq
) {
2580 tcp_complete_cwr(sk
);
2581 tcp_set_ca_state(sk
, TCP_CA_Open
);
2585 case TCP_CA_Disorder
:
2586 tcp_try_undo_dsack(sk
);
2587 if (!tp
->undo_marker
||
2588 /* For SACK case do not Open to allow to undo
2589 * catching for all duplicate ACKs. */
2590 tcp_is_reno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2591 tp
->undo_marker
= 0;
2592 tcp_set_ca_state(sk
, TCP_CA_Open
);
2596 case TCP_CA_Recovery
:
2597 if (tcp_is_reno(tp
))
2598 tcp_reset_reno_sack(tp
);
2599 if (tcp_try_undo_recovery(sk
))
2601 tcp_complete_cwr(sk
);
2606 /* F. Process state. */
2607 switch (icsk
->icsk_ca_state
) {
2608 case TCP_CA_Recovery
:
2609 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2610 if (tcp_is_reno(tp
) && is_dupack
)
2611 tcp_add_reno_sack(sk
);
2613 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
2616 if (flag
& FLAG_DATA_ACKED
)
2617 icsk
->icsk_retransmits
= 0;
2618 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
2619 tcp_reset_reno_sack(tp
);
2620 if (!tcp_try_undo_loss(sk
)) {
2621 tcp_moderate_cwnd(tp
);
2622 tcp_xmit_retransmit_queue(sk
);
2625 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2627 /* Loss is undone; fall through to processing in Open state. */
2629 if (tcp_is_reno(tp
)) {
2630 if (flag
& FLAG_SND_UNA_ADVANCED
)
2631 tcp_reset_reno_sack(tp
);
2633 tcp_add_reno_sack(sk
);
2636 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2637 tcp_try_undo_dsack(sk
);
2639 if (!tcp_time_to_recover(sk
)) {
2640 tcp_try_to_open(sk
, flag
);
2644 /* MTU probe failure: don't reduce cwnd */
2645 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2646 icsk
->icsk_mtup
.probe_size
&&
2647 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2648 tcp_mtup_probe_failed(sk
);
2649 /* Restores the reduction we did in tcp_mtup_probe() */
2651 tcp_simple_retransmit(sk
);
2655 /* Otherwise enter Recovery state */
2657 if (tcp_is_reno(tp
))
2658 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY
);
2660 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY
);
2662 tp
->high_seq
= tp
->snd_nxt
;
2663 tp
->prior_ssthresh
= 0;
2664 tp
->undo_marker
= tp
->snd_una
;
2665 tp
->undo_retrans
= tp
->retrans_out
;
2667 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2668 if (!(flag
& FLAG_ECE
))
2669 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2670 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2671 TCP_ECN_queue_cwr(tp
);
2674 tp
->bytes_acked
= 0;
2675 tp
->snd_cwnd_cnt
= 0;
2676 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2680 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
2681 tcp_update_scoreboard(sk
, fast_rexmit
);
2682 tcp_cwnd_down(sk
, flag
);
2683 tcp_xmit_retransmit_queue(sk
);
2686 /* Read draft-ietf-tcplw-high-performance before mucking
2687 * with this code. (Supersedes RFC1323)
2689 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2691 /* RTTM Rule: A TSecr value received in a segment is used to
2692 * update the averaged RTT measurement only if the segment
2693 * acknowledges some new data, i.e., only if it advances the
2694 * left edge of the send window.
2696 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2697 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2699 * Changed: reset backoff as soon as we see the first valid sample.
2700 * If we do not, we get strongly overestimated rto. With timestamps
2701 * samples are accepted even from very old segments: f.e., when rtt=1
2702 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2703 * answer arrives rto becomes 120 seconds! If at least one of segments
2704 * in window is lost... Voila. --ANK (010210)
2706 struct tcp_sock
*tp
= tcp_sk(sk
);
2707 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2708 tcp_rtt_estimator(sk
, seq_rtt
);
2710 inet_csk(sk
)->icsk_backoff
= 0;
2714 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2716 /* We don't have a timestamp. Can only use
2717 * packets that are not retransmitted to determine
2718 * rtt estimates. Also, we must not reset the
2719 * backoff for rto until we get a non-retransmitted
2720 * packet. This allows us to deal with a situation
2721 * where the network delay has increased suddenly.
2722 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2725 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2728 tcp_rtt_estimator(sk
, seq_rtt
);
2730 inet_csk(sk
)->icsk_backoff
= 0;
2734 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2737 const struct tcp_sock
*tp
= tcp_sk(sk
);
2738 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2739 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2740 tcp_ack_saw_tstamp(sk
, flag
);
2741 else if (seq_rtt
>= 0)
2742 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2745 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
2747 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2748 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
2749 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2752 /* Restart timer after forward progress on connection.
2753 * RFC2988 recommends to restart timer to now+rto.
2755 static void tcp_rearm_rto(struct sock
*sk
)
2757 struct tcp_sock
*tp
= tcp_sk(sk
);
2759 if (!tp
->packets_out
) {
2760 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2762 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2763 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2767 /* If we get here, the whole TSO packet has not been acked. */
2768 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
2770 struct tcp_sock
*tp
= tcp_sk(sk
);
2773 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
2775 packets_acked
= tcp_skb_pcount(skb
);
2776 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2778 packets_acked
-= tcp_skb_pcount(skb
);
2780 if (packets_acked
) {
2781 BUG_ON(tcp_skb_pcount(skb
) == 0);
2782 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
2785 return packets_acked
;
2788 /* Remove acknowledged frames from the retransmission queue. If our packet
2789 * is before the ack sequence we can discard it as it's confirmed to have
2790 * arrived at the other end.
2792 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
)
2794 struct tcp_sock
*tp
= tcp_sk(sk
);
2795 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2796 struct sk_buff
*skb
;
2797 u32 now
= tcp_time_stamp
;
2798 int fully_acked
= 1;
2801 u32 reord
= tp
->packets_out
;
2803 s32 ca_seq_rtt
= -1;
2804 ktime_t last_ackt
= net_invalid_timestamp();
2806 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
2807 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2810 u8 sacked
= scb
->sacked
;
2812 /* Determine how many packets and what bytes were acked, tso and else */
2813 if (after(scb
->end_seq
, tp
->snd_una
)) {
2814 if (tcp_skb_pcount(skb
) == 1 ||
2815 !after(tp
->snd_una
, scb
->seq
))
2818 acked_pcount
= tcp_tso_acked(sk
, skb
);
2823 end_seq
= tp
->snd_una
;
2825 acked_pcount
= tcp_skb_pcount(skb
);
2826 end_seq
= scb
->end_seq
;
2829 /* MTU probing checks */
2830 if (fully_acked
&& icsk
->icsk_mtup
.probe_size
&&
2831 !after(tp
->mtu_probe
.probe_seq_end
, scb
->end_seq
)) {
2832 tcp_mtup_probe_success(sk
, skb
);
2835 if (sacked
& TCPCB_RETRANS
) {
2836 if (sacked
& TCPCB_SACKED_RETRANS
)
2837 tp
->retrans_out
-= acked_pcount
;
2838 flag
|= FLAG_RETRANS_DATA_ACKED
;
2841 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
2842 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
2844 ca_seq_rtt
= now
- scb
->when
;
2845 last_ackt
= skb
->tstamp
;
2847 seq_rtt
= ca_seq_rtt
;
2849 if (!(sacked
& TCPCB_SACKED_ACKED
))
2850 reord
= min(pkts_acked
, reord
);
2853 if (sacked
& TCPCB_SACKED_ACKED
)
2854 tp
->sacked_out
-= acked_pcount
;
2855 if (sacked
& TCPCB_LOST
)
2856 tp
->lost_out
-= acked_pcount
;
2858 if (unlikely(tp
->urg_mode
&& !before(end_seq
, tp
->snd_up
)))
2861 tp
->packets_out
-= acked_pcount
;
2862 pkts_acked
+= acked_pcount
;
2864 /* Initial outgoing SYN's get put onto the write_queue
2865 * just like anything else we transmit. It is not
2866 * true data, and if we misinform our callers that
2867 * this ACK acks real data, we will erroneously exit
2868 * connection startup slow start one packet too
2869 * quickly. This is severely frowned upon behavior.
2871 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2872 flag
|= FLAG_DATA_ACKED
;
2874 flag
|= FLAG_SYN_ACKED
;
2875 tp
->retrans_stamp
= 0;
2881 tcp_unlink_write_queue(skb
, sk
);
2882 sk_wmem_free_skb(sk
, skb
);
2883 tcp_clear_all_retrans_hints(tp
);
2886 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2887 flag
|= FLAG_SACK_RENEGING
;
2889 if (flag
& FLAG_ACKED
) {
2890 const struct tcp_congestion_ops
*ca_ops
2891 = inet_csk(sk
)->icsk_ca_ops
;
2893 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
2896 if (tcp_is_reno(tp
)) {
2897 tcp_remove_reno_sacks(sk
, pkts_acked
);
2899 /* Non-retransmitted hole got filled? That's reordering */
2900 if (reord
< prior_fackets
)
2901 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
2904 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
2906 if (ca_ops
->pkts_acked
) {
2909 /* Is the ACK triggering packet unambiguous? */
2910 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
2911 /* High resolution needed and available? */
2912 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
2913 !ktime_equal(last_ackt
,
2914 net_invalid_timestamp()))
2915 rtt_us
= ktime_us_delta(ktime_get_real(),
2917 else if (ca_seq_rtt
> 0)
2918 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
2921 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
2925 #if FASTRETRANS_DEBUG > 0
2926 BUG_TRAP((int)tp
->sacked_out
>= 0);
2927 BUG_TRAP((int)tp
->lost_out
>= 0);
2928 BUG_TRAP((int)tp
->retrans_out
>= 0);
2929 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
2930 icsk
= inet_csk(sk
);
2932 printk(KERN_DEBUG
"Leak l=%u %d\n",
2933 tp
->lost_out
, icsk
->icsk_ca_state
);
2936 if (tp
->sacked_out
) {
2937 printk(KERN_DEBUG
"Leak s=%u %d\n",
2938 tp
->sacked_out
, icsk
->icsk_ca_state
);
2941 if (tp
->retrans_out
) {
2942 printk(KERN_DEBUG
"Leak r=%u %d\n",
2943 tp
->retrans_out
, icsk
->icsk_ca_state
);
2944 tp
->retrans_out
= 0;
2951 static void tcp_ack_probe(struct sock
*sk
)
2953 const struct tcp_sock
*tp
= tcp_sk(sk
);
2954 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2956 /* Was it a usable window open? */
2958 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
2959 icsk
->icsk_backoff
= 0;
2960 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
2961 /* Socket must be waked up by subsequent tcp_data_snd_check().
2962 * This function is not for random using!
2965 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2966 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2971 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
2973 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
2974 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
2977 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
2979 const struct tcp_sock
*tp
= tcp_sk(sk
);
2980 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
2981 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
2984 /* Check that window update is acceptable.
2985 * The function assumes that snd_una<=ack<=snd_next.
2987 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
2988 const u32 ack
, const u32 ack_seq
,
2991 return (after(ack
, tp
->snd_una
) ||
2992 after(ack_seq
, tp
->snd_wl1
) ||
2993 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
2996 /* Update our send window.
2998 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
2999 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3001 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
3004 struct tcp_sock
*tp
= tcp_sk(sk
);
3006 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3008 if (likely(!tcp_hdr(skb
)->syn
))
3009 nwin
<<= tp
->rx_opt
.snd_wscale
;
3011 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3012 flag
|= FLAG_WIN_UPDATE
;
3013 tcp_update_wl(tp
, ack
, ack_seq
);
3015 if (tp
->snd_wnd
!= nwin
) {
3018 /* Note, it is the only place, where
3019 * fast path is recovered for sending TCP.
3022 tcp_fast_path_check(sk
);
3024 if (nwin
> tp
->max_window
) {
3025 tp
->max_window
= nwin
;
3026 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3036 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3037 * continue in congestion avoidance.
3039 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3041 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3042 tp
->snd_cwnd_cnt
= 0;
3043 tp
->bytes_acked
= 0;
3044 TCP_ECN_queue_cwr(tp
);
3045 tcp_moderate_cwnd(tp
);
3048 /* A conservative spurious RTO response algorithm: reduce cwnd using
3049 * rate halving and continue in congestion avoidance.
3051 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3053 tcp_enter_cwr(sk
, 0);
3056 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3058 if (flag
& FLAG_ECE
)
3059 tcp_ratehalving_spur_to_response(sk
);
3061 tcp_undo_cwr(sk
, 1);
3064 /* F-RTO spurious RTO detection algorithm (RFC4138)
3066 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3067 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3068 * window (but not to or beyond highest sequence sent before RTO):
3069 * On First ACK, send two new segments out.
3070 * On Second ACK, RTO was likely spurious. Do spurious response (response
3071 * algorithm is not part of the F-RTO detection algorithm
3072 * given in RFC4138 but can be selected separately).
3073 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3074 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3075 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3076 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3078 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3079 * original window even after we transmit two new data segments.
3082 * on first step, wait until first cumulative ACK arrives, then move to
3083 * the second step. In second step, the next ACK decides.
3085 * F-RTO is implemented (mainly) in four functions:
3086 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3087 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3088 * called when tcp_use_frto() showed green light
3089 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3090 * - tcp_enter_frto_loss() is called if there is not enough evidence
3091 * to prove that the RTO is indeed spurious. It transfers the control
3092 * from F-RTO to the conventional RTO recovery
3094 static int tcp_process_frto(struct sock
*sk
, int flag
)
3096 struct tcp_sock
*tp
= tcp_sk(sk
);
3098 tcp_verify_left_out(tp
);
3100 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3101 if (flag
& FLAG_DATA_ACKED
)
3102 inet_csk(sk
)->icsk_retransmits
= 0;
3104 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3105 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3106 tp
->undo_marker
= 0;
3108 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3109 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3113 if (!IsSackFrto() || tcp_is_reno(tp
)) {
3114 /* RFC4138 shortcoming in step 2; should also have case c):
3115 * ACK isn't duplicate nor advances window, e.g., opposite dir
3118 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3121 if (!(flag
& FLAG_DATA_ACKED
)) {
3122 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3127 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3128 /* Prevent sending of new data. */
3129 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3130 tcp_packets_in_flight(tp
));
3134 if ((tp
->frto_counter
>= 2) &&
3135 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3136 ((flag
& FLAG_DATA_SACKED
) &&
3137 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3138 /* RFC4138 shortcoming (see comment above) */
3139 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3140 (flag
& FLAG_NOT_DUP
))
3143 tcp_enter_frto_loss(sk
, 3, flag
);
3148 if (tp
->frto_counter
== 1) {
3149 /* tcp_may_send_now needs to see updated state */
3150 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3151 tp
->frto_counter
= 2;
3153 if (!tcp_may_send_now(sk
))
3154 tcp_enter_frto_loss(sk
, 2, flag
);
3158 switch (sysctl_tcp_frto_response
) {
3160 tcp_undo_spur_to_response(sk
, flag
);
3163 tcp_conservative_spur_to_response(tp
);
3166 tcp_ratehalving_spur_to_response(sk
);
3169 tp
->frto_counter
= 0;
3170 tp
->undo_marker
= 0;
3171 NET_INC_STATS_BH(LINUX_MIB_TCPSPURIOUSRTOS
);
3176 /* This routine deals with incoming acks, but not outgoing ones. */
3177 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
3179 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3180 struct tcp_sock
*tp
= tcp_sk(sk
);
3181 u32 prior_snd_una
= tp
->snd_una
;
3182 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3183 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3184 u32 prior_in_flight
;
3189 /* If the ack is newer than sent or older than previous acks
3190 * then we can probably ignore it.
3192 if (after(ack
, tp
->snd_nxt
))
3193 goto uninteresting_ack
;
3195 if (before(ack
, prior_snd_una
))
3198 if (after(ack
, prior_snd_una
))
3199 flag
|= FLAG_SND_UNA_ADVANCED
;
3201 if (sysctl_tcp_abc
) {
3202 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3203 tp
->bytes_acked
+= ack
- prior_snd_una
;
3204 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3205 /* we assume just one segment left network */
3206 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3210 prior_fackets
= tp
->fackets_out
;
3211 prior_in_flight
= tcp_packets_in_flight(tp
);
3213 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3214 /* Window is constant, pure forward advance.
3215 * No more checks are required.
3216 * Note, we use the fact that SND.UNA>=SND.WL2.
3218 tcp_update_wl(tp
, ack
, ack_seq
);
3220 flag
|= FLAG_WIN_UPDATE
;
3222 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3224 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS
);
3226 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3229 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS
);
3231 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3233 if (TCP_SKB_CB(skb
)->sacked
)
3234 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3236 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3239 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3242 /* We passed data and got it acked, remove any soft error
3243 * log. Something worked...
3245 sk
->sk_err_soft
= 0;
3246 tp
->rcv_tstamp
= tcp_time_stamp
;
3247 prior_packets
= tp
->packets_out
;
3251 /* See if we can take anything off of the retransmit queue. */
3252 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
);
3254 if (tp
->frto_counter
)
3255 frto_cwnd
= tcp_process_frto(sk
, flag
);
3256 /* Guarantee sacktag reordering detection against wrap-arounds */
3257 if (before(tp
->frto_highmark
, tp
->snd_una
))
3258 tp
->frto_highmark
= 0;
3260 if (tcp_ack_is_dubious(sk
, flag
)) {
3261 /* Advance CWND, if state allows this. */
3262 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3263 tcp_may_raise_cwnd(sk
, flag
))
3264 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3265 tcp_fastretrans_alert(sk
, prior_packets
- tp
->packets_out
,
3268 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3269 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3272 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3273 dst_confirm(sk
->sk_dst_cache
);
3278 icsk
->icsk_probes_out
= 0;
3280 /* If this ack opens up a zero window, clear backoff. It was
3281 * being used to time the probes, and is probably far higher than
3282 * it needs to be for normal retransmission.
3284 if (tcp_send_head(sk
))
3289 if (TCP_SKB_CB(skb
)->sacked
)
3290 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3293 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3297 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3298 * But, this can also be called on packets in the established flow when
3299 * the fast version below fails.
3301 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3305 struct tcphdr
*th
= tcp_hdr(skb
);
3306 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3308 ptr
= (unsigned char *)(th
+ 1);
3309 opt_rx
->saw_tstamp
= 0;
3311 while (length
> 0) {
3312 int opcode
= *ptr
++;
3318 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3323 if (opsize
< 2) /* "silly options" */
3325 if (opsize
> length
)
3326 return; /* don't parse partial options */
3329 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3330 u16 in_mss
= ntohs(get_unaligned((__be16
*)ptr
));
3332 if (opt_rx
->user_mss
&&
3333 opt_rx
->user_mss
< in_mss
)
3334 in_mss
= opt_rx
->user_mss
;
3335 opt_rx
->mss_clamp
= in_mss
;
3340 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3341 !estab
&& sysctl_tcp_window_scaling
) {
3342 __u8 snd_wscale
= *(__u8
*)ptr
;
3343 opt_rx
->wscale_ok
= 1;
3344 if (snd_wscale
> 14) {
3345 if (net_ratelimit())
3346 printk(KERN_INFO
"tcp_parse_options: Illegal window "
3347 "scaling value %d >14 received.\n",
3351 opt_rx
->snd_wscale
= snd_wscale
;
3354 case TCPOPT_TIMESTAMP
:
3355 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3356 ((estab
&& opt_rx
->tstamp_ok
) ||
3357 (!estab
&& sysctl_tcp_timestamps
))) {
3358 opt_rx
->saw_tstamp
= 1;
3359 opt_rx
->rcv_tsval
= ntohl(get_unaligned((__be32
*)ptr
));
3360 opt_rx
->rcv_tsecr
= ntohl(get_unaligned((__be32
*)(ptr
+4)));
3363 case TCPOPT_SACK_PERM
:
3364 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3365 !estab
&& sysctl_tcp_sack
) {
3366 opt_rx
->sack_ok
= 1;
3367 tcp_sack_reset(opt_rx
);
3372 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3373 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3375 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3378 #ifdef CONFIG_TCP_MD5SIG
3381 * The MD5 Hash has already been
3382 * checked (see tcp_v{4,6}_do_rcv()).
3394 /* Fast parse options. This hopes to only see timestamps.
3395 * If it is wrong it falls back on tcp_parse_options().
3397 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
3398 struct tcp_sock
*tp
)
3400 if (th
->doff
== sizeof(struct tcphdr
) >> 2) {
3401 tp
->rx_opt
.saw_tstamp
= 0;
3403 } else if (tp
->rx_opt
.tstamp_ok
&&
3404 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
3405 __be32
*ptr
= (__be32
*)(th
+ 1);
3406 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3407 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3408 tp
->rx_opt
.saw_tstamp
= 1;
3410 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3412 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3416 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
3420 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
3422 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3423 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3426 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3428 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3429 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3430 * extra check below makes sure this can only happen
3431 * for pure ACK frames. -DaveM
3433 * Not only, also it occurs for expired timestamps.
3436 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
3437 get_seconds() >= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
3438 tcp_store_ts_recent(tp
);
3442 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3444 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3445 * it can pass through stack. So, the following predicate verifies that
3446 * this segment is not used for anything but congestion avoidance or
3447 * fast retransmit. Moreover, we even are able to eliminate most of such
3448 * second order effects, if we apply some small "replay" window (~RTO)
3449 * to timestamp space.
3451 * All these measures still do not guarantee that we reject wrapped ACKs
3452 * on networks with high bandwidth, when sequence space is recycled fastly,
3453 * but it guarantees that such events will be very rare and do not affect
3454 * connection seriously. This doesn't look nice, but alas, PAWS is really
3457 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3458 * states that events when retransmit arrives after original data are rare.
3459 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3460 * the biggest problem on large power networks even with minor reordering.
3461 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3462 * up to bandwidth of 18Gigabit/sec. 8) ]
3465 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3467 struct tcp_sock
*tp
= tcp_sk(sk
);
3468 struct tcphdr
*th
= tcp_hdr(skb
);
3469 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3470 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3472 return (/* 1. Pure ACK with correct sequence number. */
3473 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3475 /* 2. ... and duplicate ACK. */
3476 ack
== tp
->snd_una
&&
3478 /* 3. ... and does not update window. */
3479 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3481 /* 4. ... and sits in replay window. */
3482 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3485 static inline int tcp_paws_discard(const struct sock
*sk
,
3486 const struct sk_buff
*skb
)
3488 const struct tcp_sock
*tp
= tcp_sk(sk
);
3489 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
3490 get_seconds() < tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
3491 !tcp_disordered_ack(sk
, skb
));
3494 /* Check segment sequence number for validity.
3496 * Segment controls are considered valid, if the segment
3497 * fits to the window after truncation to the window. Acceptability
3498 * of data (and SYN, FIN, of course) is checked separately.
3499 * See tcp_data_queue(), for example.
3501 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3502 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3503 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3504 * (borrowed from freebsd)
3507 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3509 return !before(end_seq
, tp
->rcv_wup
) &&
3510 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3513 /* When we get a reset we do this. */
3514 static void tcp_reset(struct sock
*sk
)
3516 /* We want the right error as BSD sees it (and indeed as we do). */
3517 switch (sk
->sk_state
) {
3519 sk
->sk_err
= ECONNREFUSED
;
3521 case TCP_CLOSE_WAIT
:
3527 sk
->sk_err
= ECONNRESET
;
3530 if (!sock_flag(sk
, SOCK_DEAD
))
3531 sk
->sk_error_report(sk
);
3537 * Process the FIN bit. This now behaves as it is supposed to work
3538 * and the FIN takes effect when it is validly part of sequence
3539 * space. Not before when we get holes.
3541 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3542 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3545 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3546 * close and we go into CLOSING (and later onto TIME-WAIT)
3548 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3550 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
3552 struct tcp_sock
*tp
= tcp_sk(sk
);
3554 inet_csk_schedule_ack(sk
);
3556 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3557 sock_set_flag(sk
, SOCK_DONE
);
3559 switch (sk
->sk_state
) {
3561 case TCP_ESTABLISHED
:
3562 /* Move to CLOSE_WAIT */
3563 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3564 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3567 case TCP_CLOSE_WAIT
:
3569 /* Received a retransmission of the FIN, do
3574 /* RFC793: Remain in the LAST-ACK state. */
3578 /* This case occurs when a simultaneous close
3579 * happens, we must ack the received FIN and
3580 * enter the CLOSING state.
3583 tcp_set_state(sk
, TCP_CLOSING
);
3586 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3588 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3591 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3592 * cases we should never reach this piece of code.
3594 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
3595 __FUNCTION__
, sk
->sk_state
);
3599 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3600 * Probably, we should reset in this case. For now drop them.
3602 __skb_queue_purge(&tp
->out_of_order_queue
);
3603 if (tcp_is_sack(tp
))
3604 tcp_sack_reset(&tp
->rx_opt
);
3607 if (!sock_flag(sk
, SOCK_DEAD
)) {
3608 sk
->sk_state_change(sk
);
3610 /* Do not send POLL_HUP for half duplex close. */
3611 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3612 sk
->sk_state
== TCP_CLOSE
)
3613 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
3615 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
3619 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
3622 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3623 if (before(seq
, sp
->start_seq
))
3624 sp
->start_seq
= seq
;
3625 if (after(end_seq
, sp
->end_seq
))
3626 sp
->end_seq
= end_seq
;
3632 static void tcp_dsack_set(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3634 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3635 if (before(seq
, tp
->rcv_nxt
))
3636 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT
);
3638 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT
);
3640 tp
->rx_opt
.dsack
= 1;
3641 tp
->duplicate_sack
[0].start_seq
= seq
;
3642 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3643 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ 1,
3644 4 - tp
->rx_opt
.tstamp_ok
);
3648 static void tcp_dsack_extend(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3650 if (!tp
->rx_opt
.dsack
)
3651 tcp_dsack_set(tp
, seq
, end_seq
);
3653 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3656 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3658 struct tcp_sock
*tp
= tcp_sk(sk
);
3660 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3661 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3662 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3663 tcp_enter_quickack_mode(sk
);
3665 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3666 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3668 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3669 end_seq
= tp
->rcv_nxt
;
3670 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3677 /* These routines update the SACK block as out-of-order packets arrive or
3678 * in-order packets close up the sequence space.
3680 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3683 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3684 struct tcp_sack_block
*swalk
= sp
+ 1;
3686 /* See if the recent change to the first SACK eats into
3687 * or hits the sequence space of other SACK blocks, if so coalesce.
3689 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
3690 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3693 /* Zap SWALK, by moving every further SACK up by one slot.
3694 * Decrease num_sacks.
3696 tp
->rx_opt
.num_sacks
--;
3697 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+
3699 4 - tp
->rx_opt
.tstamp_ok
);
3700 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3704 this_sack
++, swalk
++;
3708 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
,
3709 struct tcp_sack_block
*sack2
)
3713 tmp
= sack1
->start_seq
;
3714 sack1
->start_seq
= sack2
->start_seq
;
3715 sack2
->start_seq
= tmp
;
3717 tmp
= sack1
->end_seq
;
3718 sack1
->end_seq
= sack2
->end_seq
;
3719 sack2
->end_seq
= tmp
;
3722 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3724 struct tcp_sock
*tp
= tcp_sk(sk
);
3725 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3726 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3732 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
3733 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3734 /* Rotate this_sack to the first one. */
3735 for (; this_sack
> 0; this_sack
--, sp
--)
3736 tcp_sack_swap(sp
, sp
- 1);
3738 tcp_sack_maybe_coalesce(tp
);
3743 /* Could not find an adjacent existing SACK, build a new one,
3744 * put it at the front, and shift everyone else down. We
3745 * always know there is at least one SACK present already here.
3747 * If the sack array is full, forget about the last one.
3749 if (this_sack
>= 4) {
3751 tp
->rx_opt
.num_sacks
--;
3754 for (; this_sack
> 0; this_sack
--, sp
--)
3758 /* Build the new head SACK, and we're done. */
3759 sp
->start_seq
= seq
;
3760 sp
->end_seq
= end_seq
;
3761 tp
->rx_opt
.num_sacks
++;
3762 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
,
3763 4 - tp
->rx_opt
.tstamp_ok
);
3766 /* RCV.NXT advances, some SACKs should be eaten. */
3768 static void tcp_sack_remove(struct tcp_sock
*tp
)
3770 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3771 int num_sacks
= tp
->rx_opt
.num_sacks
;
3774 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3775 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3776 tp
->rx_opt
.num_sacks
= 0;
3777 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3781 for (this_sack
= 0; this_sack
< num_sacks
;) {
3782 /* Check if the start of the sack is covered by RCV.NXT. */
3783 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3786 /* RCV.NXT must cover all the block! */
3787 BUG_TRAP(!before(tp
->rcv_nxt
, sp
->end_seq
));
3789 /* Zap this SACK, by moving forward any other SACKS. */
3790 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3791 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3798 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3799 tp
->rx_opt
.num_sacks
= num_sacks
;
3800 tp
->rx_opt
.eff_sacks
= min(tp
->rx_opt
.num_sacks
+
3802 4 - tp
->rx_opt
.tstamp_ok
);
3806 /* This one checks to see if we can put data from the
3807 * out_of_order queue into the receive_queue.
3809 static void tcp_ofo_queue(struct sock
*sk
)
3811 struct tcp_sock
*tp
= tcp_sk(sk
);
3812 __u32 dsack_high
= tp
->rcv_nxt
;
3813 struct sk_buff
*skb
;
3815 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3816 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3819 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3820 __u32 dsack
= dsack_high
;
3821 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3822 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3823 tcp_dsack_extend(tp
, TCP_SKB_CB(skb
)->seq
, dsack
);
3826 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3827 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3828 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3832 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3833 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3834 TCP_SKB_CB(skb
)->end_seq
);
3836 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3837 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3838 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3839 if (tcp_hdr(skb
)->fin
)
3840 tcp_fin(skb
, sk
, tcp_hdr(skb
));
3844 static int tcp_prune_queue(struct sock
*sk
);
3846 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3848 struct tcphdr
*th
= tcp_hdr(skb
);
3849 struct tcp_sock
*tp
= tcp_sk(sk
);
3852 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3855 __skb_pull(skb
, th
->doff
* 4);
3857 TCP_ECN_accept_cwr(tp
, skb
);
3859 if (tp
->rx_opt
.dsack
) {
3860 tp
->rx_opt
.dsack
= 0;
3861 tp
->rx_opt
.eff_sacks
= min_t(unsigned int, tp
->rx_opt
.num_sacks
,
3862 4 - tp
->rx_opt
.tstamp_ok
);
3865 /* Queue data for delivery to the user.
3866 * Packets in sequence go to the receive queue.
3867 * Out of sequence packets to the out_of_order_queue.
3869 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3870 if (tcp_receive_window(tp
) == 0)
3873 /* Ok. In sequence. In window. */
3874 if (tp
->ucopy
.task
== current
&&
3875 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3876 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3877 int chunk
= min_t(unsigned int, skb
->len
,
3880 __set_current_state(TASK_RUNNING
);
3883 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3884 tp
->ucopy
.len
-= chunk
;
3885 tp
->copied_seq
+= chunk
;
3886 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3887 tcp_rcv_space_adjust(sk
);
3895 (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3896 !sk_rmem_schedule(sk
, skb
->truesize
))) {
3897 if (tcp_prune_queue(sk
) < 0 ||
3898 !sk_rmem_schedule(sk
, skb
->truesize
))
3901 skb_set_owner_r(skb
, sk
);
3902 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3904 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3906 tcp_event_data_recv(sk
, skb
);
3908 tcp_fin(skb
, sk
, th
);
3910 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
3913 /* RFC2581. 4.2. SHOULD send immediate ACK, when
3914 * gap in queue is filled.
3916 if (skb_queue_empty(&tp
->out_of_order_queue
))
3917 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
3920 if (tp
->rx_opt
.num_sacks
)
3921 tcp_sack_remove(tp
);
3923 tcp_fast_path_check(sk
);
3927 else if (!sock_flag(sk
, SOCK_DEAD
))
3928 sk
->sk_data_ready(sk
, 0);
3932 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3933 /* A retransmit, 2nd most common case. Force an immediate ack. */
3934 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST
);
3935 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3938 tcp_enter_quickack_mode(sk
);
3939 inet_csk_schedule_ack(sk
);
3945 /* Out of window. F.e. zero window probe. */
3946 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
3949 tcp_enter_quickack_mode(sk
);
3951 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3952 /* Partial packet, seq < rcv_next < end_seq */
3953 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
3954 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3955 TCP_SKB_CB(skb
)->end_seq
);
3957 tcp_dsack_set(tp
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
3959 /* If window is closed, drop tail of packet. But after
3960 * remembering D-SACK for its head made in previous line.
3962 if (!tcp_receive_window(tp
))
3967 TCP_ECN_check_ce(tp
, skb
);
3969 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3970 !sk_rmem_schedule(sk
, skb
->truesize
)) {
3971 if (tcp_prune_queue(sk
) < 0 ||
3972 !sk_rmem_schedule(sk
, skb
->truesize
))
3976 /* Disable header prediction. */
3978 inet_csk_schedule_ack(sk
);
3980 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
3981 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
3983 skb_set_owner_r(skb
, sk
);
3985 if (!skb_peek(&tp
->out_of_order_queue
)) {
3986 /* Initial out of order segment, build 1 SACK. */
3987 if (tcp_is_sack(tp
)) {
3988 tp
->rx_opt
.num_sacks
= 1;
3989 tp
->rx_opt
.dsack
= 0;
3990 tp
->rx_opt
.eff_sacks
= 1;
3991 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
3992 tp
->selective_acks
[0].end_seq
=
3993 TCP_SKB_CB(skb
)->end_seq
;
3995 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
3997 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
3998 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3999 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4001 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4002 __skb_append(skb1
, skb
, &tp
->out_of_order_queue
);
4004 if (!tp
->rx_opt
.num_sacks
||
4005 tp
->selective_acks
[0].end_seq
!= seq
)
4008 /* Common case: data arrive in order after hole. */
4009 tp
->selective_acks
[0].end_seq
= end_seq
;
4013 /* Find place to insert this segment. */
4015 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4017 } while ((skb1
= skb1
->prev
) !=
4018 (struct sk_buff
*)&tp
->out_of_order_queue
);
4020 /* Do skb overlap to previous one? */
4021 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
4022 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4023 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4024 /* All the bits are present. Drop. */
4026 tcp_dsack_set(tp
, seq
, end_seq
);
4029 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4030 /* Partial overlap. */
4031 tcp_dsack_set(tp
, seq
,
4032 TCP_SKB_CB(skb1
)->end_seq
);
4037 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
4039 /* And clean segments covered by new one as whole. */
4040 while ((skb1
= skb
->next
) !=
4041 (struct sk_buff
*)&tp
->out_of_order_queue
&&
4042 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
4043 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4044 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
,
4048 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4049 tcp_dsack_extend(tp
, TCP_SKB_CB(skb1
)->seq
,
4050 TCP_SKB_CB(skb1
)->end_seq
);
4055 if (tcp_is_sack(tp
))
4056 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4060 /* Collapse contiguous sequence of skbs head..tail with
4061 * sequence numbers start..end.
4062 * Segments with FIN/SYN are not collapsed (only because this
4066 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4067 struct sk_buff
*head
, struct sk_buff
*tail
,
4070 struct sk_buff
*skb
;
4072 /* First, check that queue is collapsible and find
4073 * the point where collapsing can be useful. */
4074 for (skb
= head
; skb
!= tail
;) {
4075 /* No new bits? It is possible on ofo queue. */
4076 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4077 struct sk_buff
*next
= skb
->next
;
4078 __skb_unlink(skb
, list
);
4080 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
4085 /* The first skb to collapse is:
4087 * - bloated or contains data before "start" or
4088 * overlaps to the next one.
4090 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4091 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4092 before(TCP_SKB_CB(skb
)->seq
, start
) ||
4093 (skb
->next
!= tail
&&
4094 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
4097 /* Decided to skip this, advance start seq. */
4098 start
= TCP_SKB_CB(skb
)->end_seq
;
4101 if (skb
== tail
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4104 while (before(start
, end
)) {
4105 struct sk_buff
*nskb
;
4106 unsigned int header
= skb_headroom(skb
);
4107 int copy
= SKB_MAX_ORDER(header
, 0);
4109 /* Too big header? This can happen with IPv6. */
4112 if (end
- start
< copy
)
4114 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4118 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4119 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4121 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4123 skb_reserve(nskb
, header
);
4124 memcpy(nskb
->head
, skb
->head
, header
);
4125 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4126 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4127 __skb_insert(nskb
, skb
->prev
, skb
, list
);
4128 skb_set_owner_r(nskb
, sk
);
4130 /* Copy data, releasing collapsed skbs. */
4132 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4133 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4137 size
= min(copy
, size
);
4138 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4140 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4144 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4145 struct sk_buff
*next
= skb
->next
;
4146 __skb_unlink(skb
, list
);
4148 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED
);
4151 tcp_hdr(skb
)->syn
||
4159 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4160 * and tcp_collapse() them until all the queue is collapsed.
4162 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4164 struct tcp_sock
*tp
= tcp_sk(sk
);
4165 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4166 struct sk_buff
*head
;
4172 start
= TCP_SKB_CB(skb
)->seq
;
4173 end
= TCP_SKB_CB(skb
)->end_seq
;
4179 /* Segment is terminated when we see gap or when
4180 * we are at the end of all the queue. */
4181 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
4182 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4183 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4184 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4185 head
, skb
, start
, end
);
4187 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
4189 /* Start new segment */
4190 start
= TCP_SKB_CB(skb
)->seq
;
4191 end
= TCP_SKB_CB(skb
)->end_seq
;
4193 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4194 start
= TCP_SKB_CB(skb
)->seq
;
4195 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4196 end
= TCP_SKB_CB(skb
)->end_seq
;
4201 /* Reduce allocated memory if we can, trying to get
4202 * the socket within its memory limits again.
4204 * Return less than zero if we should start dropping frames
4205 * until the socket owning process reads some of the data
4206 * to stabilize the situation.
4208 static int tcp_prune_queue(struct sock
*sk
)
4210 struct tcp_sock
*tp
= tcp_sk(sk
);
4212 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4214 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED
);
4216 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4217 tcp_clamp_window(sk
);
4218 else if (tcp_memory_pressure
)
4219 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4221 tcp_collapse_ofo_queue(sk
);
4222 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4223 sk
->sk_receive_queue
.next
,
4224 (struct sk_buff
*)&sk
->sk_receive_queue
,
4225 tp
->copied_seq
, tp
->rcv_nxt
);
4228 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4231 /* Collapsing did not help, destructive actions follow.
4232 * This must not ever occur. */
4234 /* First, purge the out_of_order queue. */
4235 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4236 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED
);
4237 __skb_queue_purge(&tp
->out_of_order_queue
);
4239 /* Reset SACK state. A conforming SACK implementation will
4240 * do the same at a timeout based retransmit. When a connection
4241 * is in a sad state like this, we care only about integrity
4242 * of the connection not performance.
4244 if (tcp_is_sack(tp
))
4245 tcp_sack_reset(&tp
->rx_opt
);
4249 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4252 /* If we are really being abused, tell the caller to silently
4253 * drop receive data on the floor. It will get retransmitted
4254 * and hopefully then we'll have sufficient space.
4256 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED
);
4258 /* Massive buffer overcommit. */
4263 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4264 * As additional protections, we do not touch cwnd in retransmission phases,
4265 * and if application hit its sndbuf limit recently.
4267 void tcp_cwnd_application_limited(struct sock
*sk
)
4269 struct tcp_sock
*tp
= tcp_sk(sk
);
4271 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4272 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4273 /* Limited by application or receiver window. */
4274 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4275 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4276 if (win_used
< tp
->snd_cwnd
) {
4277 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4278 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4280 tp
->snd_cwnd_used
= 0;
4282 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4285 static int tcp_should_expand_sndbuf(struct sock
*sk
)
4287 struct tcp_sock
*tp
= tcp_sk(sk
);
4289 /* If the user specified a specific send buffer setting, do
4292 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4295 /* If we are under global TCP memory pressure, do not expand. */
4296 if (tcp_memory_pressure
)
4299 /* If we are under soft global TCP memory pressure, do not expand. */
4300 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
4303 /* If we filled the congestion window, do not expand. */
4304 if (tp
->packets_out
>= tp
->snd_cwnd
)
4310 /* When incoming ACK allowed to free some skb from write_queue,
4311 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4312 * on the exit from tcp input handler.
4314 * PROBLEM: sndbuf expansion does not work well with largesend.
4316 static void tcp_new_space(struct sock
*sk
)
4318 struct tcp_sock
*tp
= tcp_sk(sk
);
4320 if (tcp_should_expand_sndbuf(sk
)) {
4321 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
4322 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
4323 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4324 tp
->reordering
+ 1);
4325 sndmem
*= 2 * demanded
;
4326 if (sndmem
> sk
->sk_sndbuf
)
4327 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4328 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4331 sk
->sk_write_space(sk
);
4334 static void tcp_check_space(struct sock
*sk
)
4336 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4337 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4338 if (sk
->sk_socket
&&
4339 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4344 static inline void tcp_data_snd_check(struct sock
*sk
)
4346 tcp_push_pending_frames(sk
);
4347 tcp_check_space(sk
);
4351 * Check if sending an ack is needed.
4353 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4355 struct tcp_sock
*tp
= tcp_sk(sk
);
4357 /* More than one full frame received... */
4358 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
4359 /* ... and right edge of window advances far enough.
4360 * (tcp_recvmsg() will send ACK otherwise). Or...
4362 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4363 /* We ACK each frame or... */
4364 tcp_in_quickack_mode(sk
) ||
4365 /* We have out of order data. */
4366 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4367 /* Then ack it now */
4370 /* Else, send delayed ack. */
4371 tcp_send_delayed_ack(sk
);
4375 static inline void tcp_ack_snd_check(struct sock
*sk
)
4377 if (!inet_csk_ack_scheduled(sk
)) {
4378 /* We sent a data segment already. */
4381 __tcp_ack_snd_check(sk
, 1);
4385 * This routine is only called when we have urgent data
4386 * signaled. Its the 'slow' part of tcp_urg. It could be
4387 * moved inline now as tcp_urg is only called from one
4388 * place. We handle URGent data wrong. We have to - as
4389 * BSD still doesn't use the correction from RFC961.
4390 * For 1003.1g we should support a new option TCP_STDURG to permit
4391 * either form (or just set the sysctl tcp_stdurg).
4394 static void tcp_check_urg(struct sock
*sk
, struct tcphdr
*th
)
4396 struct tcp_sock
*tp
= tcp_sk(sk
);
4397 u32 ptr
= ntohs(th
->urg_ptr
);
4399 if (ptr
&& !sysctl_tcp_stdurg
)
4401 ptr
+= ntohl(th
->seq
);
4403 /* Ignore urgent data that we've already seen and read. */
4404 if (after(tp
->copied_seq
, ptr
))
4407 /* Do not replay urg ptr.
4409 * NOTE: interesting situation not covered by specs.
4410 * Misbehaving sender may send urg ptr, pointing to segment,
4411 * which we already have in ofo queue. We are not able to fetch
4412 * such data and will stay in TCP_URG_NOTYET until will be eaten
4413 * by recvmsg(). Seems, we are not obliged to handle such wicked
4414 * situations. But it is worth to think about possibility of some
4415 * DoSes using some hypothetical application level deadlock.
4417 if (before(ptr
, tp
->rcv_nxt
))
4420 /* Do we already have a newer (or duplicate) urgent pointer? */
4421 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4424 /* Tell the world about our new urgent pointer. */
4427 /* We may be adding urgent data when the last byte read was
4428 * urgent. To do this requires some care. We cannot just ignore
4429 * tp->copied_seq since we would read the last urgent byte again
4430 * as data, nor can we alter copied_seq until this data arrives
4431 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4433 * NOTE. Double Dutch. Rendering to plain English: author of comment
4434 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4435 * and expect that both A and B disappear from stream. This is _wrong_.
4436 * Though this happens in BSD with high probability, this is occasional.
4437 * Any application relying on this is buggy. Note also, that fix "works"
4438 * only in this artificial test. Insert some normal data between A and B and we will
4439 * decline of BSD again. Verdict: it is better to remove to trap
4442 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4443 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4444 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4446 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4447 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4452 tp
->urg_data
= TCP_URG_NOTYET
;
4455 /* Disable header prediction. */
4459 /* This is the 'fast' part of urgent handling. */
4460 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
4462 struct tcp_sock
*tp
= tcp_sk(sk
);
4464 /* Check if we get a new urgent pointer - normally not. */
4466 tcp_check_urg(sk
, th
);
4468 /* Do we wait for any urgent data? - normally not... */
4469 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4470 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4473 /* Is the urgent pointer pointing into this packet? */
4474 if (ptr
< skb
->len
) {
4476 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4478 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4479 if (!sock_flag(sk
, SOCK_DEAD
))
4480 sk
->sk_data_ready(sk
, 0);
4485 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4487 struct tcp_sock
*tp
= tcp_sk(sk
);
4488 int chunk
= skb
->len
- hlen
;
4492 if (skb_csum_unnecessary(skb
))
4493 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4495 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4499 tp
->ucopy
.len
-= chunk
;
4500 tp
->copied_seq
+= chunk
;
4501 tcp_rcv_space_adjust(sk
);
4508 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
4509 struct sk_buff
*skb
)
4513 if (sock_owned_by_user(sk
)) {
4515 result
= __tcp_checksum_complete(skb
);
4518 result
= __tcp_checksum_complete(skb
);
4523 static inline int tcp_checksum_complete_user(struct sock
*sk
,
4524 struct sk_buff
*skb
)
4526 return !skb_csum_unnecessary(skb
) &&
4527 __tcp_checksum_complete_user(sk
, skb
);
4530 #ifdef CONFIG_NET_DMA
4531 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
4534 struct tcp_sock
*tp
= tcp_sk(sk
);
4535 int chunk
= skb
->len
- hlen
;
4537 int copied_early
= 0;
4539 if (tp
->ucopy
.wakeup
)
4542 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4543 tp
->ucopy
.dma_chan
= get_softnet_dma();
4545 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
4547 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4549 tp
->ucopy
.iov
, chunk
,
4550 tp
->ucopy
.pinned_list
);
4555 tp
->ucopy
.dma_cookie
= dma_cookie
;
4558 tp
->ucopy
.len
-= chunk
;
4559 tp
->copied_seq
+= chunk
;
4560 tcp_rcv_space_adjust(sk
);
4562 if ((tp
->ucopy
.len
== 0) ||
4563 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
4564 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
4565 tp
->ucopy
.wakeup
= 1;
4566 sk
->sk_data_ready(sk
, 0);
4568 } else if (chunk
> 0) {
4569 tp
->ucopy
.wakeup
= 1;
4570 sk
->sk_data_ready(sk
, 0);
4573 return copied_early
;
4575 #endif /* CONFIG_NET_DMA */
4578 * TCP receive function for the ESTABLISHED state.
4580 * It is split into a fast path and a slow path. The fast path is
4582 * - A zero window was announced from us - zero window probing
4583 * is only handled properly in the slow path.
4584 * - Out of order segments arrived.
4585 * - Urgent data is expected.
4586 * - There is no buffer space left
4587 * - Unexpected TCP flags/window values/header lengths are received
4588 * (detected by checking the TCP header against pred_flags)
4589 * - Data is sent in both directions. Fast path only supports pure senders
4590 * or pure receivers (this means either the sequence number or the ack
4591 * value must stay constant)
4592 * - Unexpected TCP option.
4594 * When these conditions are not satisfied it drops into a standard
4595 * receive procedure patterned after RFC793 to handle all cases.
4596 * The first three cases are guaranteed by proper pred_flags setting,
4597 * the rest is checked inline. Fast processing is turned on in
4598 * tcp_data_queue when everything is OK.
4600 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
4601 struct tcphdr
*th
, unsigned len
)
4603 struct tcp_sock
*tp
= tcp_sk(sk
);
4606 * Header prediction.
4607 * The code loosely follows the one in the famous
4608 * "30 instruction TCP receive" Van Jacobson mail.
4610 * Van's trick is to deposit buffers into socket queue
4611 * on a device interrupt, to call tcp_recv function
4612 * on the receive process context and checksum and copy
4613 * the buffer to user space. smart...
4615 * Our current scheme is not silly either but we take the
4616 * extra cost of the net_bh soft interrupt processing...
4617 * We do checksum and copy also but from device to kernel.
4620 tp
->rx_opt
.saw_tstamp
= 0;
4622 /* pred_flags is 0xS?10 << 16 + snd_wnd
4623 * if header_prediction is to be made
4624 * 'S' will always be tp->tcp_header_len >> 2
4625 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4626 * turn it off (when there are holes in the receive
4627 * space for instance)
4628 * PSH flag is ignored.
4631 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
4632 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4633 int tcp_header_len
= tp
->tcp_header_len
;
4635 /* Timestamp header prediction: tcp_header_len
4636 * is automatically equal to th->doff*4 due to pred_flags
4640 /* Check timestamp */
4641 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
4642 __be32
*ptr
= (__be32
*)(th
+ 1);
4644 /* No? Slow path! */
4645 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4646 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
4649 tp
->rx_opt
.saw_tstamp
= 1;
4651 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4653 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4655 /* If PAWS failed, check it more carefully in slow path */
4656 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
4659 /* DO NOT update ts_recent here, if checksum fails
4660 * and timestamp was corrupted part, it will result
4661 * in a hung connection since we will drop all
4662 * future packets due to the PAWS test.
4666 if (len
<= tcp_header_len
) {
4667 /* Bulk data transfer: sender */
4668 if (len
== tcp_header_len
) {
4669 /* Predicted packet is in window by definition.
4670 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4671 * Hence, check seq<=rcv_wup reduces to:
4673 if (tcp_header_len
==
4674 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4675 tp
->rcv_nxt
== tp
->rcv_wup
)
4676 tcp_store_ts_recent(tp
);
4678 /* We know that such packets are checksummed
4681 tcp_ack(sk
, skb
, 0);
4683 tcp_data_snd_check(sk
);
4685 } else { /* Header too small */
4686 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4691 int copied_early
= 0;
4693 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4694 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4695 #ifdef CONFIG_NET_DMA
4696 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4701 if (tp
->ucopy
.task
== current
&&
4702 sock_owned_by_user(sk
) && !copied_early
) {
4703 __set_current_state(TASK_RUNNING
);
4705 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4709 /* Predicted packet is in window by definition.
4710 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4711 * Hence, check seq<=rcv_wup reduces to:
4713 if (tcp_header_len
==
4714 (sizeof(struct tcphdr
) +
4715 TCPOLEN_TSTAMP_ALIGNED
) &&
4716 tp
->rcv_nxt
== tp
->rcv_wup
)
4717 tcp_store_ts_recent(tp
);
4719 tcp_rcv_rtt_measure_ts(sk
, skb
);
4721 __skb_pull(skb
, tcp_header_len
);
4722 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4723 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER
);
4726 tcp_cleanup_rbuf(sk
, skb
->len
);
4729 if (tcp_checksum_complete_user(sk
, skb
))
4732 /* Predicted packet is in window by definition.
4733 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4734 * Hence, check seq<=rcv_wup reduces to:
4736 if (tcp_header_len
==
4737 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4738 tp
->rcv_nxt
== tp
->rcv_wup
)
4739 tcp_store_ts_recent(tp
);
4741 tcp_rcv_rtt_measure_ts(sk
, skb
);
4743 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4746 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS
);
4748 /* Bulk data transfer: receiver */
4749 __skb_pull(skb
, tcp_header_len
);
4750 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4751 skb_set_owner_r(skb
, sk
);
4752 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4755 tcp_event_data_recv(sk
, skb
);
4757 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4758 /* Well, only one small jumplet in fast path... */
4759 tcp_ack(sk
, skb
, FLAG_DATA
);
4760 tcp_data_snd_check(sk
);
4761 if (!inet_csk_ack_scheduled(sk
))
4765 __tcp_ack_snd_check(sk
, 0);
4767 #ifdef CONFIG_NET_DMA
4769 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4775 sk
->sk_data_ready(sk
, 0);
4781 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
4785 * RFC1323: H1. Apply PAWS check first.
4787 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4788 tcp_paws_discard(sk
, skb
)) {
4790 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
4791 tcp_send_dupack(sk
, skb
);
4794 /* Resets are accepted even if PAWS failed.
4796 ts_recent update must be made after we are sure
4797 that the packet is in window.
4802 * Standard slow path.
4805 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4806 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4807 * (RST) segments are validated by checking their SEQ-fields."
4808 * And page 69: "If an incoming segment is not acceptable,
4809 * an acknowledgment should be sent in reply (unless the RST bit
4810 * is set, if so drop the segment and return)".
4813 tcp_send_dupack(sk
, skb
);
4822 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4824 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4825 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4826 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
4833 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4835 tcp_rcv_rtt_measure_ts(sk
, skb
);
4837 /* Process urgent data. */
4838 tcp_urg(sk
, skb
, th
);
4840 /* step 7: process the segment text */
4841 tcp_data_queue(sk
, skb
);
4843 tcp_data_snd_check(sk
);
4844 tcp_ack_snd_check(sk
);
4848 TCP_INC_STATS_BH(TCP_MIB_INERRS
);
4855 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4856 struct tcphdr
*th
, unsigned len
)
4858 struct tcp_sock
*tp
= tcp_sk(sk
);
4859 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4860 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4862 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4866 * "If the state is SYN-SENT then
4867 * first check the ACK bit
4868 * If the ACK bit is set
4869 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4870 * a reset (unless the RST bit is set, if so drop
4871 * the segment and return)"
4873 * We do not send data with SYN, so that RFC-correct
4876 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4877 goto reset_and_undo
;
4879 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4880 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
4882 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED
);
4883 goto reset_and_undo
;
4886 /* Now ACK is acceptable.
4888 * "If the RST bit is set
4889 * If the ACK was acceptable then signal the user "error:
4890 * connection reset", drop the segment, enter CLOSED state,
4891 * delete TCB, and return."
4900 * "fifth, if neither of the SYN or RST bits is set then
4901 * drop the segment and return."
4907 goto discard_and_undo
;
4910 * "If the SYN bit is on ...
4911 * are acceptable then ...
4912 * (our SYN has been ACKed), change the connection
4913 * state to ESTABLISHED..."
4916 TCP_ECN_rcv_synack(tp
, th
);
4918 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
4919 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4921 /* Ok.. it's good. Set up sequence numbers and
4922 * move to established.
4924 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
4925 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
4927 /* RFC1323: The window in SYN & SYN/ACK segments is
4930 tp
->snd_wnd
= ntohs(th
->window
);
4931 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
4933 if (!tp
->rx_opt
.wscale_ok
) {
4934 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
4935 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
4938 if (tp
->rx_opt
.saw_tstamp
) {
4939 tp
->rx_opt
.tstamp_ok
= 1;
4940 tp
->tcp_header_len
=
4941 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
4942 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
4943 tcp_store_ts_recent(tp
);
4945 tp
->tcp_header_len
= sizeof(struct tcphdr
);
4948 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
4949 tcp_enable_fack(tp
);
4952 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
4953 tcp_initialize_rcv_mss(sk
);
4955 /* Remember, tcp_poll() does not lock socket!
4956 * Change state from SYN-SENT only after copied_seq
4957 * is initialized. */
4958 tp
->copied_seq
= tp
->rcv_nxt
;
4960 tcp_set_state(sk
, TCP_ESTABLISHED
);
4962 security_inet_conn_established(sk
, skb
);
4964 /* Make sure socket is routed, for correct metrics. */
4965 icsk
->icsk_af_ops
->rebuild_header(sk
);
4967 tcp_init_metrics(sk
);
4969 tcp_init_congestion_control(sk
);
4971 /* Prevent spurious tcp_cwnd_restart() on first data
4974 tp
->lsndtime
= tcp_time_stamp
;
4976 tcp_init_buffer_space(sk
);
4978 if (sock_flag(sk
, SOCK_KEEPOPEN
))
4979 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
4981 if (!tp
->rx_opt
.snd_wscale
)
4982 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
4986 if (!sock_flag(sk
, SOCK_DEAD
)) {
4987 sk
->sk_state_change(sk
);
4988 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
4991 if (sk
->sk_write_pending
||
4992 icsk
->icsk_accept_queue
.rskq_defer_accept
||
4993 icsk
->icsk_ack
.pingpong
) {
4994 /* Save one ACK. Data will be ready after
4995 * several ticks, if write_pending is set.
4997 * It may be deleted, but with this feature tcpdumps
4998 * look so _wonderfully_ clever, that I was not able
4999 * to stand against the temptation 8) --ANK
5001 inet_csk_schedule_ack(sk
);
5002 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5003 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
5004 tcp_incr_quickack(sk
);
5005 tcp_enter_quickack_mode(sk
);
5006 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5007 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5018 /* No ACK in the segment */
5022 * "If the RST bit is set
5024 * Otherwise (no ACK) drop the segment and return."
5027 goto discard_and_undo
;
5031 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5032 tcp_paws_check(&tp
->rx_opt
, 0))
5033 goto discard_and_undo
;
5036 /* We see SYN without ACK. It is attempt of
5037 * simultaneous connect with crossed SYNs.
5038 * Particularly, it can be connect to self.
5040 tcp_set_state(sk
, TCP_SYN_RECV
);
5042 if (tp
->rx_opt
.saw_tstamp
) {
5043 tp
->rx_opt
.tstamp_ok
= 1;
5044 tcp_store_ts_recent(tp
);
5045 tp
->tcp_header_len
=
5046 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5048 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5051 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5052 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5054 /* RFC1323: The window in SYN & SYN/ACK segments is
5057 tp
->snd_wnd
= ntohs(th
->window
);
5058 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5059 tp
->max_window
= tp
->snd_wnd
;
5061 TCP_ECN_rcv_syn(tp
, th
);
5064 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5065 tcp_initialize_rcv_mss(sk
);
5067 tcp_send_synack(sk
);
5069 /* Note, we could accept data and URG from this segment.
5070 * There are no obstacles to make this.
5072 * However, if we ignore data in ACKless segments sometimes,
5073 * we have no reasons to accept it sometimes.
5074 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5075 * is not flawless. So, discard packet for sanity.
5076 * Uncomment this return to process the data.
5083 /* "fifth, if neither of the SYN or RST bits is set then
5084 * drop the segment and return."
5088 tcp_clear_options(&tp
->rx_opt
);
5089 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5093 tcp_clear_options(&tp
->rx_opt
);
5094 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5099 * This function implements the receiving procedure of RFC 793 for
5100 * all states except ESTABLISHED and TIME_WAIT.
5101 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5102 * address independent.
5105 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5106 struct tcphdr
*th
, unsigned len
)
5108 struct tcp_sock
*tp
= tcp_sk(sk
);
5109 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5112 tp
->rx_opt
.saw_tstamp
= 0;
5114 switch (sk
->sk_state
) {
5126 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5129 /* Now we have several options: In theory there is
5130 * nothing else in the frame. KA9Q has an option to
5131 * send data with the syn, BSD accepts data with the
5132 * syn up to the [to be] advertised window and
5133 * Solaris 2.1 gives you a protocol error. For now
5134 * we just ignore it, that fits the spec precisely
5135 * and avoids incompatibilities. It would be nice in
5136 * future to drop through and process the data.
5138 * Now that TTCP is starting to be used we ought to
5140 * But, this leaves one open to an easy denial of
5141 * service attack, and SYN cookies can't defend
5142 * against this problem. So, we drop the data
5143 * in the interest of security over speed unless
5144 * it's still in use.
5152 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5156 /* Do step6 onward by hand. */
5157 tcp_urg(sk
, skb
, th
);
5159 tcp_data_snd_check(sk
);
5163 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
5164 tcp_paws_discard(sk
, skb
)) {
5166 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED
);
5167 tcp_send_dupack(sk
, skb
);
5170 /* Reset is accepted even if it did not pass PAWS. */
5173 /* step 1: check sequence number */
5174 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5176 tcp_send_dupack(sk
, skb
);
5180 /* step 2: check RST bit */
5186 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5188 /* step 3: check security and precedence [ignored] */
5192 * Check for a SYN in window.
5194 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5195 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN
);
5200 /* step 5: check the ACK field */
5202 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5204 switch (sk
->sk_state
) {
5207 tp
->copied_seq
= tp
->rcv_nxt
;
5209 tcp_set_state(sk
, TCP_ESTABLISHED
);
5210 sk
->sk_state_change(sk
);
5212 /* Note, that this wakeup is only for marginal
5213 * crossed SYN case. Passively open sockets
5214 * are not waked up, because sk->sk_sleep ==
5215 * NULL and sk->sk_socket == NULL.
5219 SOCK_WAKE_IO
, POLL_OUT
);
5221 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5222 tp
->snd_wnd
= ntohs(th
->window
) <<
5223 tp
->rx_opt
.snd_wscale
;
5224 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
5225 TCP_SKB_CB(skb
)->seq
);
5227 /* tcp_ack considers this ACK as duplicate
5228 * and does not calculate rtt.
5229 * Fix it at least with timestamps.
5231 if (tp
->rx_opt
.saw_tstamp
&&
5232 tp
->rx_opt
.rcv_tsecr
&& !tp
->srtt
)
5233 tcp_ack_saw_tstamp(sk
, 0);
5235 if (tp
->rx_opt
.tstamp_ok
)
5236 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5238 /* Make sure socket is routed, for
5241 icsk
->icsk_af_ops
->rebuild_header(sk
);
5243 tcp_init_metrics(sk
);
5245 tcp_init_congestion_control(sk
);
5247 /* Prevent spurious tcp_cwnd_restart() on
5248 * first data packet.
5250 tp
->lsndtime
= tcp_time_stamp
;
5253 tcp_initialize_rcv_mss(sk
);
5254 tcp_init_buffer_space(sk
);
5255 tcp_fast_path_on(tp
);
5262 if (tp
->snd_una
== tp
->write_seq
) {
5263 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5264 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5265 dst_confirm(sk
->sk_dst_cache
);
5267 if (!sock_flag(sk
, SOCK_DEAD
))
5268 /* Wake up lingering close() */
5269 sk
->sk_state_change(sk
);
5273 if (tp
->linger2
< 0 ||
5274 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5275 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5277 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
5281 tmo
= tcp_fin_time(sk
);
5282 if (tmo
> TCP_TIMEWAIT_LEN
) {
5283 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5284 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5285 /* Bad case. We could lose such FIN otherwise.
5286 * It is not a big problem, but it looks confusing
5287 * and not so rare event. We still can lose it now,
5288 * if it spins in bh_lock_sock(), but it is really
5291 inet_csk_reset_keepalive_timer(sk
, tmo
);
5293 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5301 if (tp
->snd_una
== tp
->write_seq
) {
5302 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5308 if (tp
->snd_una
== tp
->write_seq
) {
5309 tcp_update_metrics(sk
);
5318 /* step 6: check the URG bit */
5319 tcp_urg(sk
, skb
, th
);
5321 /* step 7: process the segment text */
5322 switch (sk
->sk_state
) {
5323 case TCP_CLOSE_WAIT
:
5326 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5330 /* RFC 793 says to queue data in these states,
5331 * RFC 1122 says we MUST send a reset.
5332 * BSD 4.4 also does reset.
5334 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5335 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5336 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5337 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA
);
5343 case TCP_ESTABLISHED
:
5344 tcp_data_queue(sk
, skb
);
5349 /* tcp_data could move socket to TIME-WAIT */
5350 if (sk
->sk_state
!= TCP_CLOSE
) {
5351 tcp_data_snd_check(sk
);
5352 tcp_ack_snd_check(sk
);
5362 EXPORT_SYMBOL(sysctl_tcp_ecn
);
5363 EXPORT_SYMBOL(sysctl_tcp_reordering
);
5364 EXPORT_SYMBOL(tcp_parse_options
);
5365 EXPORT_SYMBOL(tcp_rcv_established
);
5366 EXPORT_SYMBOL(tcp_rcv_state_process
);
5367 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);