2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Implementation of the Transmission Control Protocol(TCP).
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
23 * Pedro Roque : Fast Retransmit/Recovery.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
43 * Andrey Savochkin: Fix RTT measurements in the presence of
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
51 * Andi Kleen: Add tcp_measure_rcv_mss to make
52 * connections with MSS<min(MTU,ann. MSS)
53 * work without delayed acks.
54 * Andi Kleen: Process packets with PSH set in the
56 * J Hadi Salim: ECN support
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
64 #define pr_fmt(fmt) "TCP: " fmt
67 #include <linux/slab.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
70 #include <linux/kernel.h>
71 #include <linux/prefetch.h>
74 #include <net/inet_common.h>
75 #include <linux/ipsec.h>
76 #include <asm/unaligned.h>
77 #include <linux/errqueue.h>
79 int sysctl_tcp_timestamps __read_mostly
= 1;
80 int sysctl_tcp_window_scaling __read_mostly
= 1;
81 int sysctl_tcp_sack __read_mostly
= 1;
82 int sysctl_tcp_fack __read_mostly
= 1;
83 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
84 int sysctl_tcp_max_reordering __read_mostly
= 300;
85 EXPORT_SYMBOL(sysctl_tcp_reordering
);
86 int sysctl_tcp_dsack __read_mostly
= 1;
87 int sysctl_tcp_app_win __read_mostly
= 31;
88 int sysctl_tcp_adv_win_scale __read_mostly
= 1;
89 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
91 /* rfc5961 challenge ack rate limiting */
92 int sysctl_tcp_challenge_ack_limit
= 100;
94 int sysctl_tcp_stdurg __read_mostly
;
95 int sysctl_tcp_rfc1337 __read_mostly
;
96 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
97 int sysctl_tcp_frto __read_mostly
= 2;
99 int sysctl_tcp_thin_dupack __read_mostly
;
101 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
102 int sysctl_tcp_early_retrans __read_mostly
= 3;
103 int sysctl_tcp_invalid_ratelimit __read_mostly
= HZ
/2;
105 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
106 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
107 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
108 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
109 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
110 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
111 #define FLAG_ECE 0x40 /* ECE in this ACK */
112 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
113 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
114 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
115 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
116 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
117 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
119 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
120 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
121 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
122 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
124 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
125 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
127 /* Adapt the MSS value used to make delayed ack decision to the
130 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
132 struct inet_connection_sock
*icsk
= inet_csk(sk
);
133 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
136 icsk
->icsk_ack
.last_seg_size
= 0;
138 /* skb->len may jitter because of SACKs, even if peer
139 * sends good full-sized frames.
141 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
142 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
143 icsk
->icsk_ack
.rcv_mss
= len
;
145 /* Otherwise, we make more careful check taking into account,
146 * that SACKs block is variable.
148 * "len" is invariant segment length, including TCP header.
150 len
+= skb
->data
- skb_transport_header(skb
);
151 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
152 /* If PSH is not set, packet should be
153 * full sized, provided peer TCP is not badly broken.
154 * This observation (if it is correct 8)) allows
155 * to handle super-low mtu links fairly.
157 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
158 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
159 /* Subtract also invariant (if peer is RFC compliant),
160 * tcp header plus fixed timestamp option length.
161 * Resulting "len" is MSS free of SACK jitter.
163 len
-= tcp_sk(sk
)->tcp_header_len
;
164 icsk
->icsk_ack
.last_seg_size
= len
;
166 icsk
->icsk_ack
.rcv_mss
= len
;
170 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
171 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
172 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
176 static void tcp_incr_quickack(struct sock
*sk
)
178 struct inet_connection_sock
*icsk
= inet_csk(sk
);
179 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
183 if (quickacks
> icsk
->icsk_ack
.quick
)
184 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
187 static void tcp_enter_quickack_mode(struct sock
*sk
)
189 struct inet_connection_sock
*icsk
= inet_csk(sk
);
190 tcp_incr_quickack(sk
);
191 icsk
->icsk_ack
.pingpong
= 0;
192 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
195 /* Send ACKs quickly, if "quick" count is not exhausted
196 * and the session is not interactive.
199 static inline bool tcp_in_quickack_mode(const struct sock
*sk
)
201 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
203 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
206 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
208 if (tp
->ecn_flags
& TCP_ECN_OK
)
209 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
212 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
214 if (tcp_hdr(skb
)->cwr
)
215 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
218 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
220 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
223 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
225 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
226 case INET_ECN_NOT_ECT
:
227 /* Funny extension: if ECT is not set on a segment,
228 * and we already seen ECT on a previous segment,
229 * it is probably a retransmit.
231 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
232 tcp_enter_quickack_mode((struct sock
*)tp
);
235 if (tcp_ca_needs_ecn((struct sock
*)tp
))
236 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
238 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
239 /* Better not delay acks, sender can have a very low cwnd */
240 tcp_enter_quickack_mode((struct sock
*)tp
);
241 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
243 tp
->ecn_flags
|= TCP_ECN_SEEN
;
246 if (tcp_ca_needs_ecn((struct sock
*)tp
))
247 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
248 tp
->ecn_flags
|= TCP_ECN_SEEN
;
253 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
255 if (tp
->ecn_flags
& TCP_ECN_OK
)
256 __tcp_ecn_check_ce(tp
, skb
);
259 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
261 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
262 tp
->ecn_flags
&= ~TCP_ECN_OK
;
265 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
267 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
268 tp
->ecn_flags
&= ~TCP_ECN_OK
;
271 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
273 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
278 /* Buffer size and advertised window tuning.
280 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
283 static void tcp_sndbuf_expand(struct sock
*sk
)
285 const struct tcp_sock
*tp
= tcp_sk(sk
);
289 /* Worst case is non GSO/TSO : each frame consumes one skb
290 * and skb->head is kmalloced using power of two area of memory
292 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
294 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
296 per_mss
= roundup_pow_of_two(per_mss
) +
297 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
299 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
300 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
302 /* Fast Recovery (RFC 5681 3.2) :
303 * Cubic needs 1.7 factor, rounded to 2 to include
304 * extra cushion (application might react slowly to POLLOUT)
306 sndmem
= 2 * nr_segs
* per_mss
;
308 if (sk
->sk_sndbuf
< sndmem
)
309 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
312 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
314 * All tcp_full_space() is split to two parts: "network" buffer, allocated
315 * forward and advertised in receiver window (tp->rcv_wnd) and
316 * "application buffer", required to isolate scheduling/application
317 * latencies from network.
318 * window_clamp is maximal advertised window. It can be less than
319 * tcp_full_space(), in this case tcp_full_space() - window_clamp
320 * is reserved for "application" buffer. The less window_clamp is
321 * the smoother our behaviour from viewpoint of network, but the lower
322 * throughput and the higher sensitivity of the connection to losses. 8)
324 * rcv_ssthresh is more strict window_clamp used at "slow start"
325 * phase to predict further behaviour of this connection.
326 * It is used for two goals:
327 * - to enforce header prediction at sender, even when application
328 * requires some significant "application buffer". It is check #1.
329 * - to prevent pruning of receive queue because of misprediction
330 * of receiver window. Check #2.
332 * The scheme does not work when sender sends good segments opening
333 * window and then starts to feed us spaghetti. But it should work
334 * in common situations. Otherwise, we have to rely on queue collapsing.
337 /* Slow part of check#2. */
338 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
340 struct tcp_sock
*tp
= tcp_sk(sk
);
342 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
343 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
345 while (tp
->rcv_ssthresh
<= window
) {
346 if (truesize
<= skb
->len
)
347 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
355 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
357 struct tcp_sock
*tp
= tcp_sk(sk
);
360 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
361 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
362 !tcp_under_memory_pressure(sk
)) {
365 /* Check #2. Increase window, if skb with such overhead
366 * will fit to rcvbuf in future.
368 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
369 incr
= 2 * tp
->advmss
;
371 incr
= __tcp_grow_window(sk
, skb
);
374 incr
= max_t(int, incr
, 2 * skb
->len
);
375 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
377 inet_csk(sk
)->icsk_ack
.quick
|= 1;
382 /* 3. Tuning rcvbuf, when connection enters established state. */
383 static void tcp_fixup_rcvbuf(struct sock
*sk
)
385 u32 mss
= tcp_sk(sk
)->advmss
;
388 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
389 tcp_default_init_rwnd(mss
);
391 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
392 * Allow enough cushion so that sender is not limited by our window
394 if (sysctl_tcp_moderate_rcvbuf
)
397 if (sk
->sk_rcvbuf
< rcvmem
)
398 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
401 /* 4. Try to fixup all. It is made immediately after connection enters
404 void tcp_init_buffer_space(struct sock
*sk
)
406 struct tcp_sock
*tp
= tcp_sk(sk
);
409 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
410 tcp_fixup_rcvbuf(sk
);
411 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
412 tcp_sndbuf_expand(sk
);
414 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
415 tp
->rcvq_space
.time
= tcp_time_stamp
;
416 tp
->rcvq_space
.seq
= tp
->copied_seq
;
418 maxwin
= tcp_full_space(sk
);
420 if (tp
->window_clamp
>= maxwin
) {
421 tp
->window_clamp
= maxwin
;
423 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
424 tp
->window_clamp
= max(maxwin
-
425 (maxwin
>> sysctl_tcp_app_win
),
429 /* Force reservation of one segment. */
430 if (sysctl_tcp_app_win
&&
431 tp
->window_clamp
> 2 * tp
->advmss
&&
432 tp
->window_clamp
+ tp
->advmss
> maxwin
)
433 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
435 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
436 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
439 /* 5. Recalculate window clamp after socket hit its memory bounds. */
440 static void tcp_clamp_window(struct sock
*sk
)
442 struct tcp_sock
*tp
= tcp_sk(sk
);
443 struct inet_connection_sock
*icsk
= inet_csk(sk
);
445 icsk
->icsk_ack
.quick
= 0;
447 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
448 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
449 !tcp_under_memory_pressure(sk
) &&
450 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
451 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
454 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
455 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
458 /* Initialize RCV_MSS value.
459 * RCV_MSS is an our guess about MSS used by the peer.
460 * We haven't any direct information about the MSS.
461 * It's better to underestimate the RCV_MSS rather than overestimate.
462 * Overestimations make us ACKing less frequently than needed.
463 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
465 void tcp_initialize_rcv_mss(struct sock
*sk
)
467 const struct tcp_sock
*tp
= tcp_sk(sk
);
468 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
470 hint
= min(hint
, tp
->rcv_wnd
/ 2);
471 hint
= min(hint
, TCP_MSS_DEFAULT
);
472 hint
= max(hint
, TCP_MIN_MSS
);
474 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
476 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
478 /* Receiver "autotuning" code.
480 * The algorithm for RTT estimation w/o timestamps is based on
481 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
482 * <http://public.lanl.gov/radiant/pubs.html#DRS>
484 * More detail on this code can be found at
485 * <http://staff.psc.edu/jheffner/>,
486 * though this reference is out of date. A new paper
489 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
491 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
497 if (new_sample
!= 0) {
498 /* If we sample in larger samples in the non-timestamp
499 * case, we could grossly overestimate the RTT especially
500 * with chatty applications or bulk transfer apps which
501 * are stalled on filesystem I/O.
503 * Also, since we are only going for a minimum in the
504 * non-timestamp case, we do not smooth things out
505 * else with timestamps disabled convergence takes too
509 m
-= (new_sample
>> 3);
517 /* No previous measure. */
521 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
522 tp
->rcv_rtt_est
.rtt
= new_sample
;
525 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
527 if (tp
->rcv_rtt_est
.time
== 0)
529 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
531 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
534 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
535 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
538 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
539 const struct sk_buff
*skb
)
541 struct tcp_sock
*tp
= tcp_sk(sk
);
542 if (tp
->rx_opt
.rcv_tsecr
&&
543 (TCP_SKB_CB(skb
)->end_seq
-
544 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
545 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
549 * This function should be called every time data is copied to user space.
550 * It calculates the appropriate TCP receive buffer space.
552 void tcp_rcv_space_adjust(struct sock
*sk
)
554 struct tcp_sock
*tp
= tcp_sk(sk
);
558 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
559 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
562 /* Number of bytes copied to user in last RTT */
563 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
564 if (copied
<= tp
->rcvq_space
.space
)
568 * copied = bytes received in previous RTT, our base window
569 * To cope with packet losses, we need a 2x factor
570 * To cope with slow start, and sender growing its cwin by 100 %
571 * every RTT, we need a 4x factor, because the ACK we are sending
572 * now is for the next RTT, not the current one :
573 * <prev RTT . ><current RTT .. ><next RTT .... >
576 if (sysctl_tcp_moderate_rcvbuf
&&
577 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
578 int rcvwin
, rcvmem
, rcvbuf
;
580 /* minimal window to cope with packet losses, assuming
581 * steady state. Add some cushion because of small variations.
583 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
585 /* If rate increased by 25%,
586 * assume slow start, rcvwin = 3 * copied
587 * If rate increased by 50%,
588 * assume sender can use 2x growth, rcvwin = 4 * copied
591 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
593 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
596 rcvwin
+= (rcvwin
>> 1);
599 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
600 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
603 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
, sysctl_tcp_rmem
[2]);
604 if (rcvbuf
> sk
->sk_rcvbuf
) {
605 sk
->sk_rcvbuf
= rcvbuf
;
607 /* Make the window clamp follow along. */
608 tp
->window_clamp
= rcvwin
;
611 tp
->rcvq_space
.space
= copied
;
614 tp
->rcvq_space
.seq
= tp
->copied_seq
;
615 tp
->rcvq_space
.time
= tcp_time_stamp
;
618 /* There is something which you must keep in mind when you analyze the
619 * behavior of the tp->ato delayed ack timeout interval. When a
620 * connection starts up, we want to ack as quickly as possible. The
621 * problem is that "good" TCP's do slow start at the beginning of data
622 * transmission. The means that until we send the first few ACK's the
623 * sender will sit on his end and only queue most of his data, because
624 * he can only send snd_cwnd unacked packets at any given time. For
625 * each ACK we send, he increments snd_cwnd and transmits more of his
628 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
630 struct tcp_sock
*tp
= tcp_sk(sk
);
631 struct inet_connection_sock
*icsk
= inet_csk(sk
);
634 inet_csk_schedule_ack(sk
);
636 tcp_measure_rcv_mss(sk
, skb
);
638 tcp_rcv_rtt_measure(tp
);
640 now
= tcp_time_stamp
;
642 if (!icsk
->icsk_ack
.ato
) {
643 /* The _first_ data packet received, initialize
644 * delayed ACK engine.
646 tcp_incr_quickack(sk
);
647 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
649 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
651 if (m
<= TCP_ATO_MIN
/ 2) {
652 /* The fastest case is the first. */
653 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
654 } else if (m
< icsk
->icsk_ack
.ato
) {
655 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
656 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
657 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
658 } else if (m
> icsk
->icsk_rto
) {
659 /* Too long gap. Apparently sender failed to
660 * restart window, so that we send ACKs quickly.
662 tcp_incr_quickack(sk
);
666 icsk
->icsk_ack
.lrcvtime
= now
;
668 tcp_ecn_check_ce(tp
, skb
);
671 tcp_grow_window(sk
, skb
);
674 /* Called to compute a smoothed rtt estimate. The data fed to this
675 * routine either comes from timestamps, or from segments that were
676 * known _not_ to have been retransmitted [see Karn/Partridge
677 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
678 * piece by Van Jacobson.
679 * NOTE: the next three routines used to be one big routine.
680 * To save cycles in the RFC 1323 implementation it was better to break
681 * it up into three procedures. -- erics
683 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
685 struct tcp_sock
*tp
= tcp_sk(sk
);
686 long m
= mrtt_us
; /* RTT */
687 u32 srtt
= tp
->srtt_us
;
689 /* The following amusing code comes from Jacobson's
690 * article in SIGCOMM '88. Note that rtt and mdev
691 * are scaled versions of rtt and mean deviation.
692 * This is designed to be as fast as possible
693 * m stands for "measurement".
695 * On a 1990 paper the rto value is changed to:
696 * RTO = rtt + 4 * mdev
698 * Funny. This algorithm seems to be very broken.
699 * These formulae increase RTO, when it should be decreased, increase
700 * too slowly, when it should be increased quickly, decrease too quickly
701 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
702 * does not matter how to _calculate_ it. Seems, it was trap
703 * that VJ failed to avoid. 8)
706 m
-= (srtt
>> 3); /* m is now error in rtt est */
707 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
709 m
= -m
; /* m is now abs(error) */
710 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
711 /* This is similar to one of Eifel findings.
712 * Eifel blocks mdev updates when rtt decreases.
713 * This solution is a bit different: we use finer gain
714 * for mdev in this case (alpha*beta).
715 * Like Eifel it also prevents growth of rto,
716 * but also it limits too fast rto decreases,
717 * happening in pure Eifel.
722 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
724 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
725 if (tp
->mdev_us
> tp
->mdev_max_us
) {
726 tp
->mdev_max_us
= tp
->mdev_us
;
727 if (tp
->mdev_max_us
> tp
->rttvar_us
)
728 tp
->rttvar_us
= tp
->mdev_max_us
;
730 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
731 if (tp
->mdev_max_us
< tp
->rttvar_us
)
732 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
733 tp
->rtt_seq
= tp
->snd_nxt
;
734 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
737 /* no previous measure. */
738 srtt
= m
<< 3; /* take the measured time to be rtt */
739 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
740 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
741 tp
->mdev_max_us
= tp
->rttvar_us
;
742 tp
->rtt_seq
= tp
->snd_nxt
;
744 tp
->srtt_us
= max(1U, srtt
);
747 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
748 * Note: TCP stack does not yet implement pacing.
749 * FQ packet scheduler can be used to implement cheap but effective
750 * TCP pacing, to smooth the burst on large writes when packets
751 * in flight is significantly lower than cwnd (or rwin)
753 static void tcp_update_pacing_rate(struct sock
*sk
)
755 const struct tcp_sock
*tp
= tcp_sk(sk
);
758 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
759 rate
= (u64
)tp
->mss_cache
* 2 * (USEC_PER_SEC
<< 3);
761 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
763 if (likely(tp
->srtt_us
))
764 do_div(rate
, tp
->srtt_us
);
766 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
767 * without any lock. We want to make sure compiler wont store
768 * intermediate values in this location.
770 ACCESS_ONCE(sk
->sk_pacing_rate
) = min_t(u64
, rate
,
771 sk
->sk_max_pacing_rate
);
774 /* Calculate rto without backoff. This is the second half of Van Jacobson's
775 * routine referred to above.
777 static void tcp_set_rto(struct sock
*sk
)
779 const struct tcp_sock
*tp
= tcp_sk(sk
);
780 /* Old crap is replaced with new one. 8)
783 * 1. If rtt variance happened to be less 50msec, it is hallucination.
784 * It cannot be less due to utterly erratic ACK generation made
785 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
786 * to do with delayed acks, because at cwnd>2 true delack timeout
787 * is invisible. Actually, Linux-2.4 also generates erratic
788 * ACKs in some circumstances.
790 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
792 /* 2. Fixups made earlier cannot be right.
793 * If we do not estimate RTO correctly without them,
794 * all the algo is pure shit and should be replaced
795 * with correct one. It is exactly, which we pretend to do.
798 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
799 * guarantees that rto is higher.
804 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
806 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
809 cwnd
= TCP_INIT_CWND
;
810 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
814 * Packet counting of FACK is based on in-order assumptions, therefore TCP
815 * disables it when reordering is detected
817 void tcp_disable_fack(struct tcp_sock
*tp
)
819 /* RFC3517 uses different metric in lost marker => reset on change */
821 tp
->lost_skb_hint
= NULL
;
822 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
825 /* Take a notice that peer is sending D-SACKs */
826 static void tcp_dsack_seen(struct tcp_sock
*tp
)
828 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
831 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
834 struct tcp_sock
*tp
= tcp_sk(sk
);
835 if (metric
> tp
->reordering
) {
838 tp
->reordering
= min(sysctl_tcp_max_reordering
, metric
);
840 /* This exciting event is worth to be remembered. 8) */
842 mib_idx
= LINUX_MIB_TCPTSREORDER
;
843 else if (tcp_is_reno(tp
))
844 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
845 else if (tcp_is_fack(tp
))
846 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
848 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
850 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
851 #if FASTRETRANS_DEBUG > 1
852 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
853 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
857 tp
->undo_marker
? tp
->undo_retrans
: 0);
859 tcp_disable_fack(tp
);
863 tcp_disable_early_retrans(tp
);
866 /* This must be called before lost_out is incremented */
867 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
869 if (!tp
->retransmit_skb_hint
||
870 before(TCP_SKB_CB(skb
)->seq
,
871 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
872 tp
->retransmit_skb_hint
= skb
;
875 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
876 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
879 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
881 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
882 tcp_verify_retransmit_hint(tp
, skb
);
884 tp
->lost_out
+= tcp_skb_pcount(skb
);
885 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
889 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
892 tcp_verify_retransmit_hint(tp
, skb
);
894 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
895 tp
->lost_out
+= tcp_skb_pcount(skb
);
896 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
900 /* This procedure tags the retransmission queue when SACKs arrive.
902 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
903 * Packets in queue with these bits set are counted in variables
904 * sacked_out, retrans_out and lost_out, correspondingly.
906 * Valid combinations are:
907 * Tag InFlight Description
908 * 0 1 - orig segment is in flight.
909 * S 0 - nothing flies, orig reached receiver.
910 * L 0 - nothing flies, orig lost by net.
911 * R 2 - both orig and retransmit are in flight.
912 * L|R 1 - orig is lost, retransmit is in flight.
913 * S|R 1 - orig reached receiver, retrans is still in flight.
914 * (L|S|R is logically valid, it could occur when L|R is sacked,
915 * but it is equivalent to plain S and code short-curcuits it to S.
916 * L|S is logically invalid, it would mean -1 packet in flight 8))
918 * These 6 states form finite state machine, controlled by the following events:
919 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
920 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
921 * 3. Loss detection event of two flavors:
922 * A. Scoreboard estimator decided the packet is lost.
923 * A'. Reno "three dupacks" marks head of queue lost.
924 * A''. Its FACK modification, head until snd.fack is lost.
925 * B. SACK arrives sacking SND.NXT at the moment, when the
926 * segment was retransmitted.
927 * 4. D-SACK added new rule: D-SACK changes any tag to S.
929 * It is pleasant to note, that state diagram turns out to be commutative,
930 * so that we are allowed not to be bothered by order of our actions,
931 * when multiple events arrive simultaneously. (see the function below).
933 * Reordering detection.
934 * --------------------
935 * Reordering metric is maximal distance, which a packet can be displaced
936 * in packet stream. With SACKs we can estimate it:
938 * 1. SACK fills old hole and the corresponding segment was not
939 * ever retransmitted -> reordering. Alas, we cannot use it
940 * when segment was retransmitted.
941 * 2. The last flaw is solved with D-SACK. D-SACK arrives
942 * for retransmitted and already SACKed segment -> reordering..
943 * Both of these heuristics are not used in Loss state, when we cannot
944 * account for retransmits accurately.
946 * SACK block validation.
947 * ----------------------
949 * SACK block range validation checks that the received SACK block fits to
950 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
951 * Note that SND.UNA is not included to the range though being valid because
952 * it means that the receiver is rather inconsistent with itself reporting
953 * SACK reneging when it should advance SND.UNA. Such SACK block this is
954 * perfectly valid, however, in light of RFC2018 which explicitly states
955 * that "SACK block MUST reflect the newest segment. Even if the newest
956 * segment is going to be discarded ...", not that it looks very clever
957 * in case of head skb. Due to potentional receiver driven attacks, we
958 * choose to avoid immediate execution of a walk in write queue due to
959 * reneging and defer head skb's loss recovery to standard loss recovery
960 * procedure that will eventually trigger (nothing forbids us doing this).
962 * Implements also blockage to start_seq wrap-around. Problem lies in the
963 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
964 * there's no guarantee that it will be before snd_nxt (n). The problem
965 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
968 * <- outs wnd -> <- wrapzone ->
969 * u e n u_w e_w s n_w
971 * |<------------+------+----- TCP seqno space --------------+---------->|
972 * ...-- <2^31 ->| |<--------...
973 * ...---- >2^31 ------>| |<--------...
975 * Current code wouldn't be vulnerable but it's better still to discard such
976 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
977 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
978 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
979 * equal to the ideal case (infinite seqno space without wrap caused issues).
981 * With D-SACK the lower bound is extended to cover sequence space below
982 * SND.UNA down to undo_marker, which is the last point of interest. Yet
983 * again, D-SACK block must not to go across snd_una (for the same reason as
984 * for the normal SACK blocks, explained above). But there all simplicity
985 * ends, TCP might receive valid D-SACKs below that. As long as they reside
986 * fully below undo_marker they do not affect behavior in anyway and can
987 * therefore be safely ignored. In rare cases (which are more or less
988 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
989 * fragmentation and packet reordering past skb's retransmission. To consider
990 * them correctly, the acceptable range must be extended even more though
991 * the exact amount is rather hard to quantify. However, tp->max_window can
992 * be used as an exaggerated estimate.
994 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
995 u32 start_seq
, u32 end_seq
)
997 /* Too far in future, or reversed (interpretation is ambiguous) */
998 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1001 /* Nasty start_seq wrap-around check (see comments above) */
1002 if (!before(start_seq
, tp
->snd_nxt
))
1005 /* In outstanding window? ...This is valid exit for D-SACKs too.
1006 * start_seq == snd_una is non-sensical (see comments above)
1008 if (after(start_seq
, tp
->snd_una
))
1011 if (!is_dsack
|| !tp
->undo_marker
)
1014 /* ...Then it's D-SACK, and must reside below snd_una completely */
1015 if (after(end_seq
, tp
->snd_una
))
1018 if (!before(start_seq
, tp
->undo_marker
))
1022 if (!after(end_seq
, tp
->undo_marker
))
1025 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1026 * start_seq < undo_marker and end_seq >= undo_marker.
1028 return !before(start_seq
, end_seq
- tp
->max_window
);
1031 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1032 * Event "B". Later note: FACK people cheated me again 8), we have to account
1033 * for reordering! Ugly, but should help.
1035 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1036 * less than what is now known to be received by the other end (derived from
1037 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1038 * retransmitted skbs to avoid some costly processing per ACKs.
1040 static void tcp_mark_lost_retrans(struct sock
*sk
)
1042 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1043 struct tcp_sock
*tp
= tcp_sk(sk
);
1044 struct sk_buff
*skb
;
1046 u32 new_low_seq
= tp
->snd_nxt
;
1047 u32 received_upto
= tcp_highest_sack_seq(tp
);
1049 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1050 !after(received_upto
, tp
->lost_retrans_low
) ||
1051 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1054 tcp_for_write_queue(skb
, sk
) {
1055 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1057 if (skb
== tcp_send_head(sk
))
1059 if (cnt
== tp
->retrans_out
)
1061 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1064 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1067 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1068 * constraint here (see above) but figuring out that at
1069 * least tp->reordering SACK blocks reside between ack_seq
1070 * and received_upto is not easy task to do cheaply with
1071 * the available datastructures.
1073 * Whether FACK should check here for tp->reordering segs
1074 * in-between one could argue for either way (it would be
1075 * rather simple to implement as we could count fack_count
1076 * during the walk and do tp->fackets_out - fack_count).
1078 if (after(received_upto
, ack_seq
)) {
1079 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1080 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1082 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1083 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1085 if (before(ack_seq
, new_low_seq
))
1086 new_low_seq
= ack_seq
;
1087 cnt
+= tcp_skb_pcount(skb
);
1091 if (tp
->retrans_out
)
1092 tp
->lost_retrans_low
= new_low_seq
;
1095 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1096 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1099 struct tcp_sock
*tp
= tcp_sk(sk
);
1100 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1101 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1102 bool dup_sack
= false;
1104 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1107 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1108 } else if (num_sacks
> 1) {
1109 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1110 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1112 if (!after(end_seq_0
, end_seq_1
) &&
1113 !before(start_seq_0
, start_seq_1
)) {
1116 NET_INC_STATS_BH(sock_net(sk
),
1117 LINUX_MIB_TCPDSACKOFORECV
);
1121 /* D-SACK for already forgotten data... Do dumb counting. */
1122 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1123 !after(end_seq_0
, prior_snd_una
) &&
1124 after(end_seq_0
, tp
->undo_marker
))
1130 struct tcp_sacktag_state
{
1133 /* Timestamps for earliest and latest never-retransmitted segment
1134 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1135 * but congestion control should still get an accurate delay signal.
1137 struct skb_mstamp first_sackt
;
1138 struct skb_mstamp last_sackt
;
1142 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1143 * the incoming SACK may not exactly match but we can find smaller MSS
1144 * aligned portion of it that matches. Therefore we might need to fragment
1145 * which may fail and creates some hassle (caller must handle error case
1148 * FIXME: this could be merged to shift decision code
1150 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1151 u32 start_seq
, u32 end_seq
)
1155 unsigned int pkt_len
;
1158 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1159 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1161 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1162 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1163 mss
= tcp_skb_mss(skb
);
1164 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1167 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1171 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1176 /* Round if necessary so that SACKs cover only full MSSes
1177 * and/or the remaining small portion (if present)
1179 if (pkt_len
> mss
) {
1180 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1181 if (!in_sack
&& new_len
< pkt_len
) {
1183 if (new_len
>= skb
->len
)
1188 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
, GFP_ATOMIC
);
1196 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1197 static u8
tcp_sacktag_one(struct sock
*sk
,
1198 struct tcp_sacktag_state
*state
, u8 sacked
,
1199 u32 start_seq
, u32 end_seq
,
1200 int dup_sack
, int pcount
,
1201 const struct skb_mstamp
*xmit_time
)
1203 struct tcp_sock
*tp
= tcp_sk(sk
);
1204 int fack_count
= state
->fack_count
;
1206 /* Account D-SACK for retransmitted packet. */
1207 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1208 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1209 after(end_seq
, tp
->undo_marker
))
1211 if (sacked
& TCPCB_SACKED_ACKED
)
1212 state
->reord
= min(fack_count
, state
->reord
);
1215 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1216 if (!after(end_seq
, tp
->snd_una
))
1219 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1220 if (sacked
& TCPCB_SACKED_RETRANS
) {
1221 /* If the segment is not tagged as lost,
1222 * we do not clear RETRANS, believing
1223 * that retransmission is still in flight.
1225 if (sacked
& TCPCB_LOST
) {
1226 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1227 tp
->lost_out
-= pcount
;
1228 tp
->retrans_out
-= pcount
;
1231 if (!(sacked
& TCPCB_RETRANS
)) {
1232 /* New sack for not retransmitted frame,
1233 * which was in hole. It is reordering.
1235 if (before(start_seq
,
1236 tcp_highest_sack_seq(tp
)))
1237 state
->reord
= min(fack_count
,
1239 if (!after(end_seq
, tp
->high_seq
))
1240 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1241 if (state
->first_sackt
.v64
== 0)
1242 state
->first_sackt
= *xmit_time
;
1243 state
->last_sackt
= *xmit_time
;
1246 if (sacked
& TCPCB_LOST
) {
1247 sacked
&= ~TCPCB_LOST
;
1248 tp
->lost_out
-= pcount
;
1252 sacked
|= TCPCB_SACKED_ACKED
;
1253 state
->flag
|= FLAG_DATA_SACKED
;
1254 tp
->sacked_out
+= pcount
;
1256 fack_count
+= pcount
;
1258 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1259 if (!tcp_is_fack(tp
) && tp
->lost_skb_hint
&&
1260 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1261 tp
->lost_cnt_hint
+= pcount
;
1263 if (fack_count
> tp
->fackets_out
)
1264 tp
->fackets_out
= fack_count
;
1267 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1268 * frames and clear it. undo_retrans is decreased above, L|R frames
1269 * are accounted above as well.
1271 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1272 sacked
&= ~TCPCB_SACKED_RETRANS
;
1273 tp
->retrans_out
-= pcount
;
1279 /* Shift newly-SACKed bytes from this skb to the immediately previous
1280 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1282 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1283 struct tcp_sacktag_state
*state
,
1284 unsigned int pcount
, int shifted
, int mss
,
1287 struct tcp_sock
*tp
= tcp_sk(sk
);
1288 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1289 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1290 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1294 /* Adjust counters and hints for the newly sacked sequence
1295 * range but discard the return value since prev is already
1296 * marked. We must tag the range first because the seq
1297 * advancement below implicitly advances
1298 * tcp_highest_sack_seq() when skb is highest_sack.
1300 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1301 start_seq
, end_seq
, dup_sack
, pcount
,
1304 if (skb
== tp
->lost_skb_hint
)
1305 tp
->lost_cnt_hint
+= pcount
;
1307 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1308 TCP_SKB_CB(skb
)->seq
+= shifted
;
1310 tcp_skb_pcount_add(prev
, pcount
);
1311 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1312 tcp_skb_pcount_add(skb
, -pcount
);
1314 /* When we're adding to gso_segs == 1, gso_size will be zero,
1315 * in theory this shouldn't be necessary but as long as DSACK
1316 * code can come after this skb later on it's better to keep
1317 * setting gso_size to something.
1319 if (!TCP_SKB_CB(prev
)->tcp_gso_size
)
1320 TCP_SKB_CB(prev
)->tcp_gso_size
= mss
;
1322 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1323 if (tcp_skb_pcount(skb
) <= 1)
1324 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1326 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1327 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1330 BUG_ON(!tcp_skb_pcount(skb
));
1331 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1335 /* Whole SKB was eaten :-) */
1337 if (skb
== tp
->retransmit_skb_hint
)
1338 tp
->retransmit_skb_hint
= prev
;
1339 if (skb
== tp
->lost_skb_hint
) {
1340 tp
->lost_skb_hint
= prev
;
1341 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1344 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1345 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1346 TCP_SKB_CB(prev
)->end_seq
++;
1348 if (skb
== tcp_highest_sack(sk
))
1349 tcp_advance_highest_sack(sk
, skb
);
1351 tcp_unlink_write_queue(skb
, sk
);
1352 sk_wmem_free_skb(sk
, skb
);
1354 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1359 /* I wish gso_size would have a bit more sane initialization than
1360 * something-or-zero which complicates things
1362 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1364 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1367 /* Shifting pages past head area doesn't work */
1368 static int skb_can_shift(const struct sk_buff
*skb
)
1370 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1373 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1376 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1377 struct tcp_sacktag_state
*state
,
1378 u32 start_seq
, u32 end_seq
,
1381 struct tcp_sock
*tp
= tcp_sk(sk
);
1382 struct sk_buff
*prev
;
1388 if (!sk_can_gso(sk
))
1391 /* Normally R but no L won't result in plain S */
1393 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1395 if (!skb_can_shift(skb
))
1397 /* This frame is about to be dropped (was ACKed). */
1398 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1401 /* Can only happen with delayed DSACK + discard craziness */
1402 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1404 prev
= tcp_write_queue_prev(sk
, skb
);
1406 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1409 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1410 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1414 pcount
= tcp_skb_pcount(skb
);
1415 mss
= tcp_skb_seglen(skb
);
1417 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1418 * drop this restriction as unnecessary
1420 if (mss
!= tcp_skb_seglen(prev
))
1423 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1425 /* CHECKME: This is non-MSS split case only?, this will
1426 * cause skipped skbs due to advancing loop btw, original
1427 * has that feature too
1429 if (tcp_skb_pcount(skb
) <= 1)
1432 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1434 /* TODO: head merge to next could be attempted here
1435 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1436 * though it might not be worth of the additional hassle
1438 * ...we can probably just fallback to what was done
1439 * previously. We could try merging non-SACKed ones
1440 * as well but it probably isn't going to buy off
1441 * because later SACKs might again split them, and
1442 * it would make skb timestamp tracking considerably
1448 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1450 BUG_ON(len
> skb
->len
);
1452 /* MSS boundaries should be honoured or else pcount will
1453 * severely break even though it makes things bit trickier.
1454 * Optimize common case to avoid most of the divides
1456 mss
= tcp_skb_mss(skb
);
1458 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1459 * drop this restriction as unnecessary
1461 if (mss
!= tcp_skb_seglen(prev
))
1466 } else if (len
< mss
) {
1474 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1475 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1478 if (!skb_shift(prev
, skb
, len
))
1480 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1483 /* Hole filled allows collapsing with the next as well, this is very
1484 * useful when hole on every nth skb pattern happens
1486 if (prev
== tcp_write_queue_tail(sk
))
1488 skb
= tcp_write_queue_next(sk
, prev
);
1490 if (!skb_can_shift(skb
) ||
1491 (skb
== tcp_send_head(sk
)) ||
1492 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1493 (mss
!= tcp_skb_seglen(skb
)))
1497 if (skb_shift(prev
, skb
, len
)) {
1498 pcount
+= tcp_skb_pcount(skb
);
1499 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1503 state
->fack_count
+= pcount
;
1510 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1514 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1515 struct tcp_sack_block
*next_dup
,
1516 struct tcp_sacktag_state
*state
,
1517 u32 start_seq
, u32 end_seq
,
1520 struct tcp_sock
*tp
= tcp_sk(sk
);
1521 struct sk_buff
*tmp
;
1523 tcp_for_write_queue_from(skb
, sk
) {
1525 bool dup_sack
= dup_sack_in
;
1527 if (skb
== tcp_send_head(sk
))
1530 /* queue is in-order => we can short-circuit the walk early */
1531 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1535 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1536 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1537 next_dup
->start_seq
,
1543 /* skb reference here is a bit tricky to get right, since
1544 * shifting can eat and free both this skb and the next,
1545 * so not even _safe variant of the loop is enough.
1548 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1549 start_seq
, end_seq
, dup_sack
);
1558 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1564 if (unlikely(in_sack
< 0))
1568 TCP_SKB_CB(skb
)->sacked
=
1571 TCP_SKB_CB(skb
)->sacked
,
1572 TCP_SKB_CB(skb
)->seq
,
1573 TCP_SKB_CB(skb
)->end_seq
,
1575 tcp_skb_pcount(skb
),
1578 if (!before(TCP_SKB_CB(skb
)->seq
,
1579 tcp_highest_sack_seq(tp
)))
1580 tcp_advance_highest_sack(sk
, skb
);
1583 state
->fack_count
+= tcp_skb_pcount(skb
);
1588 /* Avoid all extra work that is being done by sacktag while walking in
1591 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1592 struct tcp_sacktag_state
*state
,
1595 tcp_for_write_queue_from(skb
, sk
) {
1596 if (skb
== tcp_send_head(sk
))
1599 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1602 state
->fack_count
+= tcp_skb_pcount(skb
);
1607 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1609 struct tcp_sack_block
*next_dup
,
1610 struct tcp_sacktag_state
*state
,
1616 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1617 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1618 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1619 next_dup
->start_seq
, next_dup
->end_seq
,
1626 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1628 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1632 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1633 u32 prior_snd_una
, struct tcp_sacktag_state
*state
)
1635 struct tcp_sock
*tp
= tcp_sk(sk
);
1636 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1637 TCP_SKB_CB(ack_skb
)->sacked
);
1638 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1639 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1640 struct tcp_sack_block
*cache
;
1641 struct sk_buff
*skb
;
1642 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1644 bool found_dup_sack
= false;
1646 int first_sack_index
;
1649 state
->reord
= tp
->packets_out
;
1651 if (!tp
->sacked_out
) {
1652 if (WARN_ON(tp
->fackets_out
))
1653 tp
->fackets_out
= 0;
1654 tcp_highest_sack_reset(sk
);
1657 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1658 num_sacks
, prior_snd_una
);
1660 state
->flag
|= FLAG_DSACKING_ACK
;
1662 /* Eliminate too old ACKs, but take into
1663 * account more or less fresh ones, they can
1664 * contain valid SACK info.
1666 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1669 if (!tp
->packets_out
)
1673 first_sack_index
= 0;
1674 for (i
= 0; i
< num_sacks
; i
++) {
1675 bool dup_sack
= !i
&& found_dup_sack
;
1677 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1678 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1680 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1681 sp
[used_sacks
].start_seq
,
1682 sp
[used_sacks
].end_seq
)) {
1686 if (!tp
->undo_marker
)
1687 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1689 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1691 /* Don't count olds caused by ACK reordering */
1692 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1693 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1695 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1698 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1700 first_sack_index
= -1;
1704 /* Ignore very old stuff early */
1705 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1711 /* order SACK blocks to allow in order walk of the retrans queue */
1712 for (i
= used_sacks
- 1; i
> 0; i
--) {
1713 for (j
= 0; j
< i
; j
++) {
1714 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1715 swap(sp
[j
], sp
[j
+ 1]);
1717 /* Track where the first SACK block goes to */
1718 if (j
== first_sack_index
)
1719 first_sack_index
= j
+ 1;
1724 skb
= tcp_write_queue_head(sk
);
1725 state
->fack_count
= 0;
1728 if (!tp
->sacked_out
) {
1729 /* It's already past, so skip checking against it */
1730 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1732 cache
= tp
->recv_sack_cache
;
1733 /* Skip empty blocks in at head of the cache */
1734 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1739 while (i
< used_sacks
) {
1740 u32 start_seq
= sp
[i
].start_seq
;
1741 u32 end_seq
= sp
[i
].end_seq
;
1742 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1743 struct tcp_sack_block
*next_dup
= NULL
;
1745 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1746 next_dup
= &sp
[i
+ 1];
1748 /* Skip too early cached blocks */
1749 while (tcp_sack_cache_ok(tp
, cache
) &&
1750 !before(start_seq
, cache
->end_seq
))
1753 /* Can skip some work by looking recv_sack_cache? */
1754 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1755 after(end_seq
, cache
->start_seq
)) {
1758 if (before(start_seq
, cache
->start_seq
)) {
1759 skb
= tcp_sacktag_skip(skb
, sk
, state
,
1761 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1768 /* Rest of the block already fully processed? */
1769 if (!after(end_seq
, cache
->end_seq
))
1772 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1776 /* ...tail remains todo... */
1777 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1778 /* ...but better entrypoint exists! */
1779 skb
= tcp_highest_sack(sk
);
1782 state
->fack_count
= tp
->fackets_out
;
1787 skb
= tcp_sacktag_skip(skb
, sk
, state
, cache
->end_seq
);
1788 /* Check overlap against next cached too (past this one already) */
1793 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1794 skb
= tcp_highest_sack(sk
);
1797 state
->fack_count
= tp
->fackets_out
;
1799 skb
= tcp_sacktag_skip(skb
, sk
, state
, start_seq
);
1802 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, state
,
1803 start_seq
, end_seq
, dup_sack
);
1809 /* Clear the head of the cache sack blocks so we can skip it next time */
1810 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1811 tp
->recv_sack_cache
[i
].start_seq
= 0;
1812 tp
->recv_sack_cache
[i
].end_seq
= 0;
1814 for (j
= 0; j
< used_sacks
; j
++)
1815 tp
->recv_sack_cache
[i
++] = sp
[j
];
1817 if ((state
->reord
< tp
->fackets_out
) &&
1818 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1819 tcp_update_reordering(sk
, tp
->fackets_out
- state
->reord
, 0);
1821 tcp_mark_lost_retrans(sk
);
1822 tcp_verify_left_out(tp
);
1825 #if FASTRETRANS_DEBUG > 0
1826 WARN_ON((int)tp
->sacked_out
< 0);
1827 WARN_ON((int)tp
->lost_out
< 0);
1828 WARN_ON((int)tp
->retrans_out
< 0);
1829 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1834 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1835 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1837 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1841 holes
= max(tp
->lost_out
, 1U);
1842 holes
= min(holes
, tp
->packets_out
);
1844 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1845 tp
->sacked_out
= tp
->packets_out
- holes
;
1851 /* If we receive more dupacks than we expected counting segments
1852 * in assumption of absent reordering, interpret this as reordering.
1853 * The only another reason could be bug in receiver TCP.
1855 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1857 struct tcp_sock
*tp
= tcp_sk(sk
);
1858 if (tcp_limit_reno_sacked(tp
))
1859 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1862 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1864 static void tcp_add_reno_sack(struct sock
*sk
)
1866 struct tcp_sock
*tp
= tcp_sk(sk
);
1868 tcp_check_reno_reordering(sk
, 0);
1869 tcp_verify_left_out(tp
);
1872 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1874 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1876 struct tcp_sock
*tp
= tcp_sk(sk
);
1879 /* One ACK acked hole. The rest eat duplicate ACKs. */
1880 if (acked
- 1 >= tp
->sacked_out
)
1883 tp
->sacked_out
-= acked
- 1;
1885 tcp_check_reno_reordering(sk
, acked
);
1886 tcp_verify_left_out(tp
);
1889 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1894 void tcp_clear_retrans(struct tcp_sock
*tp
)
1896 tp
->retrans_out
= 0;
1898 tp
->undo_marker
= 0;
1899 tp
->undo_retrans
= -1;
1900 tp
->fackets_out
= 0;
1904 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1906 tp
->undo_marker
= tp
->snd_una
;
1907 /* Retransmission still in flight may cause DSACKs later. */
1908 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1911 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1912 * and reset tags completely, otherwise preserve SACKs. If receiver
1913 * dropped its ofo queue, we will know this due to reneging detection.
1915 void tcp_enter_loss(struct sock
*sk
)
1917 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1918 struct tcp_sock
*tp
= tcp_sk(sk
);
1919 struct sk_buff
*skb
;
1920 bool new_recovery
= false;
1921 bool is_reneg
; /* is receiver reneging on SACKs? */
1923 /* Reduce ssthresh if it has not yet been made inside this window. */
1924 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1925 !after(tp
->high_seq
, tp
->snd_una
) ||
1926 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1927 new_recovery
= true;
1928 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1929 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1930 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1934 tp
->snd_cwnd_cnt
= 0;
1935 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1937 tp
->retrans_out
= 0;
1940 if (tcp_is_reno(tp
))
1941 tcp_reset_reno_sack(tp
);
1943 skb
= tcp_write_queue_head(sk
);
1944 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1946 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1948 tp
->fackets_out
= 0;
1950 tcp_clear_all_retrans_hints(tp
);
1952 tcp_for_write_queue(skb
, sk
) {
1953 if (skb
== tcp_send_head(sk
))
1956 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1957 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || is_reneg
) {
1958 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1959 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1960 tp
->lost_out
+= tcp_skb_pcount(skb
);
1961 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1964 tcp_verify_left_out(tp
);
1966 /* Timeout in disordered state after receiving substantial DUPACKs
1967 * suggests that the degree of reordering is over-estimated.
1969 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1970 tp
->sacked_out
>= sysctl_tcp_reordering
)
1971 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1972 sysctl_tcp_reordering
);
1973 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1974 tp
->high_seq
= tp
->snd_nxt
;
1975 tcp_ecn_queue_cwr(tp
);
1977 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1978 * loss recovery is underway except recurring timeout(s) on
1979 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1981 tp
->frto
= sysctl_tcp_frto
&&
1982 (new_recovery
|| icsk
->icsk_retransmits
) &&
1983 !inet_csk(sk
)->icsk_mtup
.probe_size
;
1986 /* If ACK arrived pointing to a remembered SACK, it means that our
1987 * remembered SACKs do not reflect real state of receiver i.e.
1988 * receiver _host_ is heavily congested (or buggy).
1990 * To avoid big spurious retransmission bursts due to transient SACK
1991 * scoreboard oddities that look like reneging, we give the receiver a
1992 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
1993 * restore sanity to the SACK scoreboard. If the apparent reneging
1994 * persists until this RTO then we'll clear the SACK scoreboard.
1996 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
1998 if (flag
& FLAG_SACK_RENEGING
) {
1999 struct tcp_sock
*tp
= tcp_sk(sk
);
2000 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2001 msecs_to_jiffies(10));
2003 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2004 delay
, TCP_RTO_MAX
);
2010 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2012 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2015 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2016 * counter when SACK is enabled (without SACK, sacked_out is used for
2019 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2020 * segments up to the highest received SACK block so far and holes in
2023 * With reordering, holes may still be in flight, so RFC3517 recovery
2024 * uses pure sacked_out (total number of SACKed segments) even though
2025 * it violates the RFC that uses duplicate ACKs, often these are equal
2026 * but when e.g. out-of-window ACKs or packet duplication occurs,
2027 * they differ. Since neither occurs due to loss, TCP should really
2030 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2032 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2035 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2037 struct tcp_sock
*tp
= tcp_sk(sk
);
2038 unsigned long delay
;
2040 /* Delay early retransmit and entering fast recovery for
2041 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2042 * available, or RTO is scheduled to fire first.
2044 if (sysctl_tcp_early_retrans
< 2 || sysctl_tcp_early_retrans
> 3 ||
2045 (flag
& FLAG_ECE
) || !tp
->srtt_us
)
2048 delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 5),
2049 msecs_to_jiffies(2));
2051 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2054 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_EARLY_RETRANS
, delay
,
2059 /* Linux NewReno/SACK/FACK/ECN state machine.
2060 * --------------------------------------
2062 * "Open" Normal state, no dubious events, fast path.
2063 * "Disorder" In all the respects it is "Open",
2064 * but requires a bit more attention. It is entered when
2065 * we see some SACKs or dupacks. It is split of "Open"
2066 * mainly to move some processing from fast path to slow one.
2067 * "CWR" CWND was reduced due to some Congestion Notification event.
2068 * It can be ECN, ICMP source quench, local device congestion.
2069 * "Recovery" CWND was reduced, we are fast-retransmitting.
2070 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2072 * tcp_fastretrans_alert() is entered:
2073 * - each incoming ACK, if state is not "Open"
2074 * - when arrived ACK is unusual, namely:
2079 * Counting packets in flight is pretty simple.
2081 * in_flight = packets_out - left_out + retrans_out
2083 * packets_out is SND.NXT-SND.UNA counted in packets.
2085 * retrans_out is number of retransmitted segments.
2087 * left_out is number of segments left network, but not ACKed yet.
2089 * left_out = sacked_out + lost_out
2091 * sacked_out: Packets, which arrived to receiver out of order
2092 * and hence not ACKed. With SACKs this number is simply
2093 * amount of SACKed data. Even without SACKs
2094 * it is easy to give pretty reliable estimate of this number,
2095 * counting duplicate ACKs.
2097 * lost_out: Packets lost by network. TCP has no explicit
2098 * "loss notification" feedback from network (for now).
2099 * It means that this number can be only _guessed_.
2100 * Actually, it is the heuristics to predict lossage that
2101 * distinguishes different algorithms.
2103 * F.e. after RTO, when all the queue is considered as lost,
2104 * lost_out = packets_out and in_flight = retrans_out.
2106 * Essentially, we have now two algorithms counting
2109 * FACK: It is the simplest heuristics. As soon as we decided
2110 * that something is lost, we decide that _all_ not SACKed
2111 * packets until the most forward SACK are lost. I.e.
2112 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2113 * It is absolutely correct estimate, if network does not reorder
2114 * packets. And it loses any connection to reality when reordering
2115 * takes place. We use FACK by default until reordering
2116 * is suspected on the path to this destination.
2118 * NewReno: when Recovery is entered, we assume that one segment
2119 * is lost (classic Reno). While we are in Recovery and
2120 * a partial ACK arrives, we assume that one more packet
2121 * is lost (NewReno). This heuristics are the same in NewReno
2124 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2125 * deflation etc. CWND is real congestion window, never inflated, changes
2126 * only according to classic VJ rules.
2128 * Really tricky (and requiring careful tuning) part of algorithm
2129 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2130 * The first determines the moment _when_ we should reduce CWND and,
2131 * hence, slow down forward transmission. In fact, it determines the moment
2132 * when we decide that hole is caused by loss, rather than by a reorder.
2134 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2135 * holes, caused by lost packets.
2137 * And the most logically complicated part of algorithm is undo
2138 * heuristics. We detect false retransmits due to both too early
2139 * fast retransmit (reordering) and underestimated RTO, analyzing
2140 * timestamps and D-SACKs. When we detect that some segments were
2141 * retransmitted by mistake and CWND reduction was wrong, we undo
2142 * window reduction and abort recovery phase. This logic is hidden
2143 * inside several functions named tcp_try_undo_<something>.
2146 /* This function decides, when we should leave Disordered state
2147 * and enter Recovery phase, reducing congestion window.
2149 * Main question: may we further continue forward transmission
2150 * with the same cwnd?
2152 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2154 struct tcp_sock
*tp
= tcp_sk(sk
);
2157 /* Trick#1: The loss is proven. */
2161 /* Not-A-Trick#2 : Classic rule... */
2162 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2165 /* Trick#4: It is still not OK... But will it be useful to delay
2168 packets_out
= tp
->packets_out
;
2169 if (packets_out
<= tp
->reordering
&&
2170 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2171 !tcp_may_send_now(sk
)) {
2172 /* We have nothing to send. This connection is limited
2173 * either by receiver window or by application.
2178 /* If a thin stream is detected, retransmit after first
2179 * received dupack. Employ only if SACK is supported in order
2180 * to avoid possible corner-case series of spurious retransmissions
2181 * Use only if there are no unsent data.
2183 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2184 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2185 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2188 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2189 * retransmissions due to small network reorderings, we implement
2190 * Mitigation A.3 in the RFC and delay the retransmission for a short
2191 * interval if appropriate.
2193 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2194 (tp
->packets_out
>= (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2195 !tcp_may_send_now(sk
))
2196 return !tcp_pause_early_retransmit(sk
, flag
);
2201 /* Detect loss in event "A" above by marking head of queue up as lost.
2202 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2203 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2204 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2205 * the maximum SACKed segments to pass before reaching this limit.
2207 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2209 struct tcp_sock
*tp
= tcp_sk(sk
);
2210 struct sk_buff
*skb
;
2214 /* Use SACK to deduce losses of new sequences sent during recovery */
2215 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2217 WARN_ON(packets
> tp
->packets_out
);
2218 if (tp
->lost_skb_hint
) {
2219 skb
= tp
->lost_skb_hint
;
2220 cnt
= tp
->lost_cnt_hint
;
2221 /* Head already handled? */
2222 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2225 skb
= tcp_write_queue_head(sk
);
2229 tcp_for_write_queue_from(skb
, sk
) {
2230 if (skb
== tcp_send_head(sk
))
2232 /* TODO: do this better */
2233 /* this is not the most efficient way to do this... */
2234 tp
->lost_skb_hint
= skb
;
2235 tp
->lost_cnt_hint
= cnt
;
2237 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2241 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2242 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2243 cnt
+= tcp_skb_pcount(skb
);
2245 if (cnt
> packets
) {
2246 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2247 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2248 (oldcnt
>= packets
))
2251 mss
= tcp_skb_mss(skb
);
2252 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
,
2259 tcp_skb_mark_lost(tp
, skb
);
2264 tcp_verify_left_out(tp
);
2267 /* Account newly detected lost packet(s) */
2269 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2271 struct tcp_sock
*tp
= tcp_sk(sk
);
2273 if (tcp_is_reno(tp
)) {
2274 tcp_mark_head_lost(sk
, 1, 1);
2275 } else if (tcp_is_fack(tp
)) {
2276 int lost
= tp
->fackets_out
- tp
->reordering
;
2279 tcp_mark_head_lost(sk
, lost
, 0);
2281 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2282 if (sacked_upto
>= 0)
2283 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2284 else if (fast_rexmit
)
2285 tcp_mark_head_lost(sk
, 1, 1);
2289 /* CWND moderation, preventing bursts due to too big ACKs
2290 * in dubious situations.
2292 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2294 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2295 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2296 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2299 /* Nothing was retransmitted or returned timestamp is less
2300 * than timestamp of the first retransmission.
2302 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2304 return !tp
->retrans_stamp
||
2305 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2306 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2309 /* Undo procedures. */
2311 /* We can clear retrans_stamp when there are no retransmissions in the
2312 * window. It would seem that it is trivially available for us in
2313 * tp->retrans_out, however, that kind of assumptions doesn't consider
2314 * what will happen if errors occur when sending retransmission for the
2315 * second time. ...It could the that such segment has only
2316 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2317 * the head skb is enough except for some reneging corner cases that
2318 * are not worth the effort.
2320 * Main reason for all this complexity is the fact that connection dying
2321 * time now depends on the validity of the retrans_stamp, in particular,
2322 * that successive retransmissions of a segment must not advance
2323 * retrans_stamp under any conditions.
2325 static bool tcp_any_retrans_done(const struct sock
*sk
)
2327 const struct tcp_sock
*tp
= tcp_sk(sk
);
2328 struct sk_buff
*skb
;
2330 if (tp
->retrans_out
)
2333 skb
= tcp_write_queue_head(sk
);
2334 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2340 #if FASTRETRANS_DEBUG > 1
2341 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2343 struct tcp_sock
*tp
= tcp_sk(sk
);
2344 struct inet_sock
*inet
= inet_sk(sk
);
2346 if (sk
->sk_family
== AF_INET
) {
2347 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2349 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2350 tp
->snd_cwnd
, tcp_left_out(tp
),
2351 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2354 #if IS_ENABLED(CONFIG_IPV6)
2355 else if (sk
->sk_family
== AF_INET6
) {
2356 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2357 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2359 &np
->daddr
, ntohs(inet
->inet_dport
),
2360 tp
->snd_cwnd
, tcp_left_out(tp
),
2361 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2367 #define DBGUNDO(x...) do { } while (0)
2370 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2372 struct tcp_sock
*tp
= tcp_sk(sk
);
2375 struct sk_buff
*skb
;
2377 tcp_for_write_queue(skb
, sk
) {
2378 if (skb
== tcp_send_head(sk
))
2380 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2383 tcp_clear_all_retrans_hints(tp
);
2386 if (tp
->prior_ssthresh
) {
2387 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2389 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2390 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2392 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2394 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2395 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2396 tcp_ecn_withdraw_cwr(tp
);
2399 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2401 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2402 tp
->undo_marker
= 0;
2405 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2407 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2410 /* People celebrate: "We love our President!" */
2411 static bool tcp_try_undo_recovery(struct sock
*sk
)
2413 struct tcp_sock
*tp
= tcp_sk(sk
);
2415 if (tcp_may_undo(tp
)) {
2418 /* Happy end! We did not retransmit anything
2419 * or our original transmission succeeded.
2421 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2422 tcp_undo_cwnd_reduction(sk
, false);
2423 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2424 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2426 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2428 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2430 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2431 /* Hold old state until something *above* high_seq
2432 * is ACKed. For Reno it is MUST to prevent false
2433 * fast retransmits (RFC2582). SACK TCP is safe. */
2434 tcp_moderate_cwnd(tp
);
2435 if (!tcp_any_retrans_done(sk
))
2436 tp
->retrans_stamp
= 0;
2439 tcp_set_ca_state(sk
, TCP_CA_Open
);
2443 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2444 static bool tcp_try_undo_dsack(struct sock
*sk
)
2446 struct tcp_sock
*tp
= tcp_sk(sk
);
2448 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2449 DBGUNDO(sk
, "D-SACK");
2450 tcp_undo_cwnd_reduction(sk
, false);
2451 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2457 /* Undo during loss recovery after partial ACK or using F-RTO. */
2458 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2460 struct tcp_sock
*tp
= tcp_sk(sk
);
2462 if (frto_undo
|| tcp_may_undo(tp
)) {
2463 tcp_undo_cwnd_reduction(sk
, true);
2465 DBGUNDO(sk
, "partial loss");
2466 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2468 NET_INC_STATS_BH(sock_net(sk
),
2469 LINUX_MIB_TCPSPURIOUSRTOS
);
2470 inet_csk(sk
)->icsk_retransmits
= 0;
2471 if (frto_undo
|| tcp_is_sack(tp
))
2472 tcp_set_ca_state(sk
, TCP_CA_Open
);
2478 /* The cwnd reduction in CWR and Recovery use the PRR algorithm
2479 * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/
2480 * It computes the number of packets to send (sndcnt) based on packets newly
2482 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2483 * cwnd reductions across a full RTT.
2484 * 2) If packets in flight is lower than ssthresh (such as due to excess
2485 * losses and/or application stalls), do not perform any further cwnd
2486 * reductions, but instead slow start up to ssthresh.
2488 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2490 struct tcp_sock
*tp
= tcp_sk(sk
);
2492 tp
->high_seq
= tp
->snd_nxt
;
2493 tp
->tlp_high_seq
= 0;
2494 tp
->snd_cwnd_cnt
= 0;
2495 tp
->prior_cwnd
= tp
->snd_cwnd
;
2496 tp
->prr_delivered
= 0;
2498 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2499 tcp_ecn_queue_cwr(tp
);
2502 static void tcp_cwnd_reduction(struct sock
*sk
, const int prior_unsacked
,
2505 struct tcp_sock
*tp
= tcp_sk(sk
);
2507 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2508 int newly_acked_sacked
= prior_unsacked
-
2509 (tp
->packets_out
- tp
->sacked_out
);
2511 tp
->prr_delivered
+= newly_acked_sacked
;
2512 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
2513 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2515 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2517 sndcnt
= min_t(int, delta
,
2518 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2519 newly_acked_sacked
) + 1);
2522 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
2523 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2526 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2528 struct tcp_sock
*tp
= tcp_sk(sk
);
2530 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2531 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
||
2532 (tp
->undo_marker
&& tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
)) {
2533 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2534 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2536 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2539 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2540 void tcp_enter_cwr(struct sock
*sk
)
2542 struct tcp_sock
*tp
= tcp_sk(sk
);
2544 tp
->prior_ssthresh
= 0;
2545 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2546 tp
->undo_marker
= 0;
2547 tcp_init_cwnd_reduction(sk
);
2548 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2551 EXPORT_SYMBOL(tcp_enter_cwr
);
2553 static void tcp_try_keep_open(struct sock
*sk
)
2555 struct tcp_sock
*tp
= tcp_sk(sk
);
2556 int state
= TCP_CA_Open
;
2558 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2559 state
= TCP_CA_Disorder
;
2561 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2562 tcp_set_ca_state(sk
, state
);
2563 tp
->high_seq
= tp
->snd_nxt
;
2567 static void tcp_try_to_open(struct sock
*sk
, int flag
, const int prior_unsacked
)
2569 struct tcp_sock
*tp
= tcp_sk(sk
);
2571 tcp_verify_left_out(tp
);
2573 if (!tcp_any_retrans_done(sk
))
2574 tp
->retrans_stamp
= 0;
2576 if (flag
& FLAG_ECE
)
2579 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2580 tcp_try_keep_open(sk
);
2582 tcp_cwnd_reduction(sk
, prior_unsacked
, 0);
2586 static void tcp_mtup_probe_failed(struct sock
*sk
)
2588 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2590 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2591 icsk
->icsk_mtup
.probe_size
= 0;
2594 static void tcp_mtup_probe_success(struct sock
*sk
)
2596 struct tcp_sock
*tp
= tcp_sk(sk
);
2597 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2599 /* FIXME: breaks with very large cwnd */
2600 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2601 tp
->snd_cwnd
= tp
->snd_cwnd
*
2602 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2603 icsk
->icsk_mtup
.probe_size
;
2604 tp
->snd_cwnd_cnt
= 0;
2605 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2606 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2608 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2609 icsk
->icsk_mtup
.probe_size
= 0;
2610 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2613 /* Do a simple retransmit without using the backoff mechanisms in
2614 * tcp_timer. This is used for path mtu discovery.
2615 * The socket is already locked here.
2617 void tcp_simple_retransmit(struct sock
*sk
)
2619 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2620 struct tcp_sock
*tp
= tcp_sk(sk
);
2621 struct sk_buff
*skb
;
2622 unsigned int mss
= tcp_current_mss(sk
);
2623 u32 prior_lost
= tp
->lost_out
;
2625 tcp_for_write_queue(skb
, sk
) {
2626 if (skb
== tcp_send_head(sk
))
2628 if (tcp_skb_seglen(skb
) > mss
&&
2629 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2630 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2631 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2632 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2634 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2638 tcp_clear_retrans_hints_partial(tp
);
2640 if (prior_lost
== tp
->lost_out
)
2643 if (tcp_is_reno(tp
))
2644 tcp_limit_reno_sacked(tp
);
2646 tcp_verify_left_out(tp
);
2648 /* Don't muck with the congestion window here.
2649 * Reason is that we do not increase amount of _data_
2650 * in network, but units changed and effective
2651 * cwnd/ssthresh really reduced now.
2653 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2654 tp
->high_seq
= tp
->snd_nxt
;
2655 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2656 tp
->prior_ssthresh
= 0;
2657 tp
->undo_marker
= 0;
2658 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2660 tcp_xmit_retransmit_queue(sk
);
2662 EXPORT_SYMBOL(tcp_simple_retransmit
);
2664 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2666 struct tcp_sock
*tp
= tcp_sk(sk
);
2669 if (tcp_is_reno(tp
))
2670 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2672 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2674 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2676 tp
->prior_ssthresh
= 0;
2679 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2681 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2682 tcp_init_cwnd_reduction(sk
);
2684 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2687 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2688 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2690 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
)
2692 struct tcp_sock
*tp
= tcp_sk(sk
);
2693 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2695 if ((flag
& FLAG_SND_UNA_ADVANCED
) &&
2696 tcp_try_undo_loss(sk
, false))
2699 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2700 /* Step 3.b. A timeout is spurious if not all data are
2701 * lost, i.e., never-retransmitted data are (s)acked.
2703 if ((flag
& FLAG_ORIG_SACK_ACKED
) &&
2704 tcp_try_undo_loss(sk
, true))
2707 if (after(tp
->snd_nxt
, tp
->high_seq
)) {
2708 if (flag
& FLAG_DATA_SACKED
|| is_dupack
)
2709 tp
->frto
= 0; /* Step 3.a. loss was real */
2710 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2711 tp
->high_seq
= tp
->snd_nxt
;
2712 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
2714 if (after(tp
->snd_nxt
, tp
->high_seq
))
2715 return; /* Step 2.b */
2721 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2722 tcp_try_undo_recovery(sk
);
2725 if (tcp_is_reno(tp
)) {
2726 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2727 * delivered. Lower inflight to clock out (re)tranmissions.
2729 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2730 tcp_add_reno_sack(sk
);
2731 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2732 tcp_reset_reno_sack(tp
);
2734 tcp_xmit_retransmit_queue(sk
);
2737 /* Undo during fast recovery after partial ACK. */
2738 static bool tcp_try_undo_partial(struct sock
*sk
, const int acked
,
2739 const int prior_unsacked
)
2741 struct tcp_sock
*tp
= tcp_sk(sk
);
2743 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2744 /* Plain luck! Hole if filled with delayed
2745 * packet, rather than with a retransmit.
2747 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2749 /* We are getting evidence that the reordering degree is higher
2750 * than we realized. If there are no retransmits out then we
2751 * can undo. Otherwise we clock out new packets but do not
2752 * mark more packets lost or retransmit more.
2754 if (tp
->retrans_out
) {
2755 tcp_cwnd_reduction(sk
, prior_unsacked
, 0);
2759 if (!tcp_any_retrans_done(sk
))
2760 tp
->retrans_stamp
= 0;
2762 DBGUNDO(sk
, "partial recovery");
2763 tcp_undo_cwnd_reduction(sk
, true);
2764 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2765 tcp_try_keep_open(sk
);
2771 /* Process an event, which can update packets-in-flight not trivially.
2772 * Main goal of this function is to calculate new estimate for left_out,
2773 * taking into account both packets sitting in receiver's buffer and
2774 * packets lost by network.
2776 * Besides that it does CWND reduction, when packet loss is detected
2777 * and changes state of machine.
2779 * It does _not_ decide what to send, it is made in function
2780 * tcp_xmit_retransmit_queue().
2782 static void tcp_fastretrans_alert(struct sock
*sk
, const int acked
,
2783 const int prior_unsacked
,
2784 bool is_dupack
, int flag
)
2786 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2787 struct tcp_sock
*tp
= tcp_sk(sk
);
2788 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2789 (tcp_fackets_out(tp
) > tp
->reordering
));
2790 int fast_rexmit
= 0;
2792 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2794 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2795 tp
->fackets_out
= 0;
2797 /* Now state machine starts.
2798 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2799 if (flag
& FLAG_ECE
)
2800 tp
->prior_ssthresh
= 0;
2802 /* B. In all the states check for reneging SACKs. */
2803 if (tcp_check_sack_reneging(sk
, flag
))
2806 /* C. Check consistency of the current state. */
2807 tcp_verify_left_out(tp
);
2809 /* D. Check state exit conditions. State can be terminated
2810 * when high_seq is ACKed. */
2811 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2812 WARN_ON(tp
->retrans_out
!= 0);
2813 tp
->retrans_stamp
= 0;
2814 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2815 switch (icsk
->icsk_ca_state
) {
2817 /* CWR is to be held something *above* high_seq
2818 * is ACKed for CWR bit to reach receiver. */
2819 if (tp
->snd_una
!= tp
->high_seq
) {
2820 tcp_end_cwnd_reduction(sk
);
2821 tcp_set_ca_state(sk
, TCP_CA_Open
);
2825 case TCP_CA_Recovery
:
2826 if (tcp_is_reno(tp
))
2827 tcp_reset_reno_sack(tp
);
2828 if (tcp_try_undo_recovery(sk
))
2830 tcp_end_cwnd_reduction(sk
);
2835 /* E. Process state. */
2836 switch (icsk
->icsk_ca_state
) {
2837 case TCP_CA_Recovery
:
2838 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2839 if (tcp_is_reno(tp
) && is_dupack
)
2840 tcp_add_reno_sack(sk
);
2842 if (tcp_try_undo_partial(sk
, acked
, prior_unsacked
))
2844 /* Partial ACK arrived. Force fast retransmit. */
2845 do_lost
= tcp_is_reno(tp
) ||
2846 tcp_fackets_out(tp
) > tp
->reordering
;
2848 if (tcp_try_undo_dsack(sk
)) {
2849 tcp_try_keep_open(sk
);
2854 tcp_process_loss(sk
, flag
, is_dupack
);
2855 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2857 /* Fall through to processing in Open state. */
2859 if (tcp_is_reno(tp
)) {
2860 if (flag
& FLAG_SND_UNA_ADVANCED
)
2861 tcp_reset_reno_sack(tp
);
2863 tcp_add_reno_sack(sk
);
2866 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2867 tcp_try_undo_dsack(sk
);
2869 if (!tcp_time_to_recover(sk
, flag
)) {
2870 tcp_try_to_open(sk
, flag
, prior_unsacked
);
2874 /* MTU probe failure: don't reduce cwnd */
2875 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2876 icsk
->icsk_mtup
.probe_size
&&
2877 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2878 tcp_mtup_probe_failed(sk
);
2879 /* Restores the reduction we did in tcp_mtup_probe() */
2881 tcp_simple_retransmit(sk
);
2885 /* Otherwise enter Recovery state */
2886 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2891 tcp_update_scoreboard(sk
, fast_rexmit
);
2892 tcp_cwnd_reduction(sk
, prior_unsacked
, fast_rexmit
);
2893 tcp_xmit_retransmit_queue(sk
);
2896 static inline bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2897 long seq_rtt_us
, long sack_rtt_us
)
2899 const struct tcp_sock
*tp
= tcp_sk(sk
);
2901 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2902 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2903 * Karn's algorithm forbids taking RTT if some retransmitted data
2904 * is acked (RFC6298).
2906 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2910 seq_rtt_us
= sack_rtt_us
;
2912 /* RTTM Rule: A TSecr value received in a segment is used to
2913 * update the averaged RTT measurement only if the segment
2914 * acknowledges some new data, i.e., only if it advances the
2915 * left edge of the send window.
2916 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2918 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2920 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
2925 tcp_rtt_estimator(sk
, seq_rtt_us
);
2928 /* RFC6298: only reset backoff on valid RTT measurement. */
2929 inet_csk(sk
)->icsk_backoff
= 0;
2933 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2934 static void tcp_synack_rtt_meas(struct sock
*sk
, const u32 synack_stamp
)
2936 struct tcp_sock
*tp
= tcp_sk(sk
);
2937 long seq_rtt_us
= -1L;
2939 if (synack_stamp
&& !tp
->total_retrans
)
2940 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- synack_stamp
);
2942 /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
2943 * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
2946 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, seq_rtt_us
, -1L);
2949 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2951 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2953 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2954 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2957 /* Restart timer after forward progress on connection.
2958 * RFC2988 recommends to restart timer to now+rto.
2960 void tcp_rearm_rto(struct sock
*sk
)
2962 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2963 struct tcp_sock
*tp
= tcp_sk(sk
);
2965 /* If the retrans timer is currently being used by Fast Open
2966 * for SYN-ACK retrans purpose, stay put.
2968 if (tp
->fastopen_rsk
)
2971 if (!tp
->packets_out
) {
2972 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2974 u32 rto
= inet_csk(sk
)->icsk_rto
;
2975 /* Offset the time elapsed after installing regular RTO */
2976 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
2977 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
2978 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
2979 const u32 rto_time_stamp
=
2980 tcp_skb_timestamp(skb
) + rto
;
2981 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
2982 /* delta may not be positive if the socket is locked
2983 * when the retrans timer fires and is rescheduled.
2988 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
2993 /* This function is called when the delayed ER timer fires. TCP enters
2994 * fast recovery and performs fast-retransmit.
2996 void tcp_resume_early_retransmit(struct sock
*sk
)
2998 struct tcp_sock
*tp
= tcp_sk(sk
);
3002 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3003 if (!tp
->do_early_retrans
)
3006 tcp_enter_recovery(sk
, false);
3007 tcp_update_scoreboard(sk
, 1);
3008 tcp_xmit_retransmit_queue(sk
);
3011 /* If we get here, the whole TSO packet has not been acked. */
3012 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3014 struct tcp_sock
*tp
= tcp_sk(sk
);
3017 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3019 packets_acked
= tcp_skb_pcount(skb
);
3020 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3022 packets_acked
-= tcp_skb_pcount(skb
);
3024 if (packets_acked
) {
3025 BUG_ON(tcp_skb_pcount(skb
) == 0);
3026 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3029 return packets_acked
;
3032 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3035 const struct skb_shared_info
*shinfo
;
3037 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3038 if (likely(!(sk
->sk_tsflags
& SOF_TIMESTAMPING_TX_ACK
)))
3041 shinfo
= skb_shinfo(skb
);
3042 if ((shinfo
->tx_flags
& SKBTX_ACK_TSTAMP
) &&
3043 between(shinfo
->tskey
, prior_snd_una
, tcp_sk(sk
)->snd_una
- 1))
3044 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3047 /* Remove acknowledged frames from the retransmission queue. If our packet
3048 * is before the ack sequence we can discard it as it's confirmed to have
3049 * arrived at the other end.
3051 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3053 struct tcp_sacktag_state
*sack
)
3055 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3056 struct skb_mstamp first_ackt
, last_ackt
, now
;
3057 struct tcp_sock
*tp
= tcp_sk(sk
);
3058 u32 prior_sacked
= tp
->sacked_out
;
3059 u32 reord
= tp
->packets_out
;
3060 bool fully_acked
= true;
3061 long sack_rtt_us
= -1L;
3062 long seq_rtt_us
= -1L;
3063 long ca_rtt_us
= -1L;
3064 struct sk_buff
*skb
;
3071 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3072 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3073 u8 sacked
= scb
->sacked
;
3076 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3078 /* Determine how many packets and what bytes were acked, tso and else */
3079 if (after(scb
->end_seq
, tp
->snd_una
)) {
3080 if (tcp_skb_pcount(skb
) == 1 ||
3081 !after(tp
->snd_una
, scb
->seq
))
3084 acked_pcount
= tcp_tso_acked(sk
, skb
);
3088 fully_acked
= false;
3090 /* Speedup tcp_unlink_write_queue() and next loop */
3091 prefetchw(skb
->next
);
3092 acked_pcount
= tcp_skb_pcount(skb
);
3095 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3096 if (sacked
& TCPCB_SACKED_RETRANS
)
3097 tp
->retrans_out
-= acked_pcount
;
3098 flag
|= FLAG_RETRANS_DATA_ACKED
;
3099 } else if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3100 last_ackt
= skb
->skb_mstamp
;
3101 WARN_ON_ONCE(last_ackt
.v64
== 0);
3102 if (!first_ackt
.v64
)
3103 first_ackt
= last_ackt
;
3105 reord
= min(pkts_acked
, reord
);
3106 if (!after(scb
->end_seq
, tp
->high_seq
))
3107 flag
|= FLAG_ORIG_SACK_ACKED
;
3110 if (sacked
& TCPCB_SACKED_ACKED
)
3111 tp
->sacked_out
-= acked_pcount
;
3112 if (sacked
& TCPCB_LOST
)
3113 tp
->lost_out
-= acked_pcount
;
3115 tp
->packets_out
-= acked_pcount
;
3116 pkts_acked
+= acked_pcount
;
3118 /* Initial outgoing SYN's get put onto the write_queue
3119 * just like anything else we transmit. It is not
3120 * true data, and if we misinform our callers that
3121 * this ACK acks real data, we will erroneously exit
3122 * connection startup slow start one packet too
3123 * quickly. This is severely frowned upon behavior.
3125 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3126 flag
|= FLAG_DATA_ACKED
;
3128 flag
|= FLAG_SYN_ACKED
;
3129 tp
->retrans_stamp
= 0;
3135 tcp_unlink_write_queue(skb
, sk
);
3136 sk_wmem_free_skb(sk
, skb
);
3137 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3138 tp
->retransmit_skb_hint
= NULL
;
3139 if (unlikely(skb
== tp
->lost_skb_hint
))
3140 tp
->lost_skb_hint
= NULL
;
3143 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3144 tp
->snd_up
= tp
->snd_una
;
3146 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3147 flag
|= FLAG_SACK_RENEGING
;
3149 skb_mstamp_get(&now
);
3150 if (likely(first_ackt
.v64
)) {
3151 seq_rtt_us
= skb_mstamp_us_delta(&now
, &first_ackt
);
3152 ca_rtt_us
= skb_mstamp_us_delta(&now
, &last_ackt
);
3154 if (sack
->first_sackt
.v64
) {
3155 sack_rtt_us
= skb_mstamp_us_delta(&now
, &sack
->first_sackt
);
3156 ca_rtt_us
= skb_mstamp_us_delta(&now
, &sack
->last_sackt
);
3159 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
);
3161 if (flag
& FLAG_ACKED
) {
3163 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3164 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3165 tcp_mtup_probe_success(sk
);
3168 if (tcp_is_reno(tp
)) {
3169 tcp_remove_reno_sacks(sk
, pkts_acked
);
3173 /* Non-retransmitted hole got filled? That's reordering */
3174 if (reord
< prior_fackets
)
3175 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3177 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3178 prior_sacked
- tp
->sacked_out
;
3179 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3182 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3184 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3185 sack_rtt_us
> skb_mstamp_us_delta(&now
, &skb
->skb_mstamp
)) {
3186 /* Do not re-arm RTO if the sack RTT is measured from data sent
3187 * after when the head was last (re)transmitted. Otherwise the
3188 * timeout may continue to extend in loss recovery.
3193 if (icsk
->icsk_ca_ops
->pkts_acked
)
3194 icsk
->icsk_ca_ops
->pkts_acked(sk
, pkts_acked
, ca_rtt_us
);
3196 #if FASTRETRANS_DEBUG > 0
3197 WARN_ON((int)tp
->sacked_out
< 0);
3198 WARN_ON((int)tp
->lost_out
< 0);
3199 WARN_ON((int)tp
->retrans_out
< 0);
3200 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3201 icsk
= inet_csk(sk
);
3203 pr_debug("Leak l=%u %d\n",
3204 tp
->lost_out
, icsk
->icsk_ca_state
);
3207 if (tp
->sacked_out
) {
3208 pr_debug("Leak s=%u %d\n",
3209 tp
->sacked_out
, icsk
->icsk_ca_state
);
3212 if (tp
->retrans_out
) {
3213 pr_debug("Leak r=%u %d\n",
3214 tp
->retrans_out
, icsk
->icsk_ca_state
);
3215 tp
->retrans_out
= 0;
3222 static void tcp_ack_probe(struct sock
*sk
)
3224 const struct tcp_sock
*tp
= tcp_sk(sk
);
3225 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3227 /* Was it a usable window open? */
3229 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3230 icsk
->icsk_backoff
= 0;
3231 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3232 /* Socket must be waked up by subsequent tcp_data_snd_check().
3233 * This function is not for random using!
3236 unsigned long when
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
3238 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3243 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3245 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3246 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3249 /* Decide wheather to run the increase function of congestion control. */
3250 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3252 if (tcp_in_cwnd_reduction(sk
))
3255 /* If reordering is high then always grow cwnd whenever data is
3256 * delivered regardless of its ordering. Otherwise stay conservative
3257 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3258 * new SACK or ECE mark may first advance cwnd here and later reduce
3259 * cwnd in tcp_fastretrans_alert() based on more states.
3261 if (tcp_sk(sk
)->reordering
> sysctl_tcp_reordering
)
3262 return flag
& FLAG_FORWARD_PROGRESS
;
3264 return flag
& FLAG_DATA_ACKED
;
3267 /* Check that window update is acceptable.
3268 * The function assumes that snd_una<=ack<=snd_next.
3270 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3271 const u32 ack
, const u32 ack_seq
,
3274 return after(ack
, tp
->snd_una
) ||
3275 after(ack_seq
, tp
->snd_wl1
) ||
3276 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3279 /* If we update tp->snd_una, also update tp->bytes_acked */
3280 static void tcp_snd_una_update(struct tcp_sock
*tp
, u32 ack
)
3282 u32 delta
= ack
- tp
->snd_una
;
3284 u64_stats_update_begin(&tp
->syncp
);
3285 tp
->bytes_acked
+= delta
;
3286 u64_stats_update_end(&tp
->syncp
);
3290 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3291 static void tcp_rcv_nxt_update(struct tcp_sock
*tp
, u32 seq
)
3293 u32 delta
= seq
- tp
->rcv_nxt
;
3295 u64_stats_update_begin(&tp
->syncp
);
3296 tp
->bytes_received
+= delta
;
3297 u64_stats_update_end(&tp
->syncp
);
3301 /* Update our send window.
3303 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3304 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3306 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3309 struct tcp_sock
*tp
= tcp_sk(sk
);
3311 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3313 if (likely(!tcp_hdr(skb
)->syn
))
3314 nwin
<<= tp
->rx_opt
.snd_wscale
;
3316 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3317 flag
|= FLAG_WIN_UPDATE
;
3318 tcp_update_wl(tp
, ack_seq
);
3320 if (tp
->snd_wnd
!= nwin
) {
3323 /* Note, it is the only place, where
3324 * fast path is recovered for sending TCP.
3327 tcp_fast_path_check(sk
);
3329 if (nwin
> tp
->max_window
) {
3330 tp
->max_window
= nwin
;
3331 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3336 tcp_snd_una_update(tp
, ack
);
3341 /* Return true if we're currently rate-limiting out-of-window ACKs and
3342 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3343 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3344 * attacks that send repeated SYNs or ACKs for the same connection. To
3345 * do this, we do not send a duplicate SYNACK or ACK if the remote
3346 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3348 bool tcp_oow_rate_limited(struct net
*net
, const struct sk_buff
*skb
,
3349 int mib_idx
, u32
*last_oow_ack_time
)
3351 /* Data packets without SYNs are not likely part of an ACK loop. */
3352 if ((TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
) &&
3354 goto not_rate_limited
;
3356 if (*last_oow_ack_time
) {
3357 s32 elapsed
= (s32
)(tcp_time_stamp
- *last_oow_ack_time
);
3359 if (0 <= elapsed
&& elapsed
< sysctl_tcp_invalid_ratelimit
) {
3360 NET_INC_STATS_BH(net
, mib_idx
);
3361 return true; /* rate-limited: don't send yet! */
3365 *last_oow_ack_time
= tcp_time_stamp
;
3368 return false; /* not rate-limited: go ahead, send dupack now! */
3371 /* RFC 5961 7 [ACK Throttling] */
3372 static void tcp_send_challenge_ack(struct sock
*sk
, const struct sk_buff
*skb
)
3374 /* unprotected vars, we dont care of overwrites */
3375 static u32 challenge_timestamp
;
3376 static unsigned int challenge_count
;
3377 struct tcp_sock
*tp
= tcp_sk(sk
);
3380 /* First check our per-socket dupack rate limit. */
3381 if (tcp_oow_rate_limited(sock_net(sk
), skb
,
3382 LINUX_MIB_TCPACKSKIPPEDCHALLENGE
,
3383 &tp
->last_oow_ack_time
))
3386 /* Then check the check host-wide RFC 5961 rate limit. */
3388 if (now
!= challenge_timestamp
) {
3389 challenge_timestamp
= now
;
3390 challenge_count
= 0;
3392 if (++challenge_count
<= sysctl_tcp_challenge_ack_limit
) {
3393 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3398 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3400 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3401 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3404 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3406 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3407 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3408 * extra check below makes sure this can only happen
3409 * for pure ACK frames. -DaveM
3411 * Not only, also it occurs for expired timestamps.
3414 if (tcp_paws_check(&tp
->rx_opt
, 0))
3415 tcp_store_ts_recent(tp
);
3419 /* This routine deals with acks during a TLP episode.
3420 * We mark the end of a TLP episode on receiving TLP dupack or when
3421 * ack is after tlp_high_seq.
3422 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3424 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3426 struct tcp_sock
*tp
= tcp_sk(sk
);
3428 if (before(ack
, tp
->tlp_high_seq
))
3431 if (flag
& FLAG_DSACKING_ACK
) {
3432 /* This DSACK means original and TLP probe arrived; no loss */
3433 tp
->tlp_high_seq
= 0;
3434 } else if (after(ack
, tp
->tlp_high_seq
)) {
3435 /* ACK advances: there was a loss, so reduce cwnd. Reset
3436 * tlp_high_seq in tcp_init_cwnd_reduction()
3438 tcp_init_cwnd_reduction(sk
);
3439 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3440 tcp_end_cwnd_reduction(sk
);
3441 tcp_try_keep_open(sk
);
3442 NET_INC_STATS_BH(sock_net(sk
),
3443 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3444 } else if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3445 FLAG_NOT_DUP
| FLAG_DATA_SACKED
))) {
3446 /* Pure dupack: original and TLP probe arrived; no loss */
3447 tp
->tlp_high_seq
= 0;
3451 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3453 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3455 if (icsk
->icsk_ca_ops
->in_ack_event
)
3456 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3459 /* This routine deals with incoming acks, but not outgoing ones. */
3460 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3462 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3463 struct tcp_sock
*tp
= tcp_sk(sk
);
3464 struct tcp_sacktag_state sack_state
;
3465 u32 prior_snd_una
= tp
->snd_una
;
3466 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3467 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3468 bool is_dupack
= false;
3470 int prior_packets
= tp
->packets_out
;
3471 const int prior_unsacked
= tp
->packets_out
- tp
->sacked_out
;
3472 int acked
= 0; /* Number of packets newly acked */
3474 sack_state
.first_sackt
.v64
= 0;
3476 /* We very likely will need to access write queue head. */
3477 prefetchw(sk
->sk_write_queue
.next
);
3479 /* If the ack is older than previous acks
3480 * then we can probably ignore it.
3482 if (before(ack
, prior_snd_una
)) {
3483 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3484 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3485 tcp_send_challenge_ack(sk
, skb
);
3491 /* If the ack includes data we haven't sent yet, discard
3492 * this segment (RFC793 Section 3.9).
3494 if (after(ack
, tp
->snd_nxt
))
3497 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3498 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
3501 if (after(ack
, prior_snd_una
)) {
3502 flag
|= FLAG_SND_UNA_ADVANCED
;
3503 icsk
->icsk_retransmits
= 0;
3506 prior_fackets
= tp
->fackets_out
;
3508 /* ts_recent update must be made after we are sure that the packet
3511 if (flag
& FLAG_UPDATE_TS_RECENT
)
3512 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3514 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3515 /* Window is constant, pure forward advance.
3516 * No more checks are required.
3517 * Note, we use the fact that SND.UNA>=SND.WL2.
3519 tcp_update_wl(tp
, ack_seq
);
3520 tcp_snd_una_update(tp
, ack
);
3521 flag
|= FLAG_WIN_UPDATE
;
3523 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3525 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3527 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3529 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3532 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3534 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3536 if (TCP_SKB_CB(skb
)->sacked
)
3537 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3540 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3542 ack_ev_flags
|= CA_ACK_ECE
;
3545 if (flag
& FLAG_WIN_UPDATE
)
3546 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3548 tcp_in_ack_event(sk
, ack_ev_flags
);
3551 /* We passed data and got it acked, remove any soft error
3552 * log. Something worked...
3554 sk
->sk_err_soft
= 0;
3555 icsk
->icsk_probes_out
= 0;
3556 tp
->rcv_tstamp
= tcp_time_stamp
;
3560 /* See if we can take anything off of the retransmit queue. */
3561 acked
= tp
->packets_out
;
3562 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
,
3564 acked
-= tp
->packets_out
;
3566 /* Advance cwnd if state allows */
3567 if (tcp_may_raise_cwnd(sk
, flag
))
3568 tcp_cong_avoid(sk
, ack
, acked
);
3570 if (tcp_ack_is_dubious(sk
, flag
)) {
3571 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3572 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3575 if (tp
->tlp_high_seq
)
3576 tcp_process_tlp_ack(sk
, ack
, flag
);
3578 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
)) {
3579 struct dst_entry
*dst
= __sk_dst_get(sk
);
3584 if (icsk
->icsk_pending
== ICSK_TIME_RETRANS
)
3585 tcp_schedule_loss_probe(sk
);
3586 tcp_update_pacing_rate(sk
);
3590 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3591 if (flag
& FLAG_DSACKING_ACK
)
3592 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3594 /* If this ack opens up a zero window, clear backoff. It was
3595 * being used to time the probes, and is probably far higher than
3596 * it needs to be for normal retransmission.
3598 if (tcp_send_head(sk
))
3601 if (tp
->tlp_high_seq
)
3602 tcp_process_tlp_ack(sk
, ack
, flag
);
3606 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3610 /* If data was SACKed, tag it and see if we should send more data.
3611 * If data was DSACKed, see if we can undo a cwnd reduction.
3613 if (TCP_SKB_CB(skb
)->sacked
) {
3614 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3616 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3620 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3624 static void tcp_parse_fastopen_option(int len
, const unsigned char *cookie
,
3625 bool syn
, struct tcp_fastopen_cookie
*foc
,
3628 /* Valid only in SYN or SYN-ACK with an even length. */
3629 if (!foc
|| !syn
|| len
< 0 || (len
& 1))
3632 if (len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3633 len
<= TCP_FASTOPEN_COOKIE_MAX
)
3634 memcpy(foc
->val
, cookie
, len
);
3641 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3642 * But, this can also be called on packets in the established flow when
3643 * the fast version below fails.
3645 void tcp_parse_options(const struct sk_buff
*skb
,
3646 struct tcp_options_received
*opt_rx
, int estab
,
3647 struct tcp_fastopen_cookie
*foc
)
3649 const unsigned char *ptr
;
3650 const struct tcphdr
*th
= tcp_hdr(skb
);
3651 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3653 ptr
= (const unsigned char *)(th
+ 1);
3654 opt_rx
->saw_tstamp
= 0;
3656 while (length
> 0) {
3657 int opcode
= *ptr
++;
3663 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3668 if (opsize
< 2) /* "silly options" */
3670 if (opsize
> length
)
3671 return; /* don't parse partial options */
3674 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3675 u16 in_mss
= get_unaligned_be16(ptr
);
3677 if (opt_rx
->user_mss
&&
3678 opt_rx
->user_mss
< in_mss
)
3679 in_mss
= opt_rx
->user_mss
;
3680 opt_rx
->mss_clamp
= in_mss
;
3685 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3686 !estab
&& sysctl_tcp_window_scaling
) {
3687 __u8 snd_wscale
= *(__u8
*)ptr
;
3688 opt_rx
->wscale_ok
= 1;
3689 if (snd_wscale
> 14) {
3690 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3695 opt_rx
->snd_wscale
= snd_wscale
;
3698 case TCPOPT_TIMESTAMP
:
3699 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3700 ((estab
&& opt_rx
->tstamp_ok
) ||
3701 (!estab
&& sysctl_tcp_timestamps
))) {
3702 opt_rx
->saw_tstamp
= 1;
3703 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3704 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3707 case TCPOPT_SACK_PERM
:
3708 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3709 !estab
&& sysctl_tcp_sack
) {
3710 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3711 tcp_sack_reset(opt_rx
);
3716 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3717 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3719 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3722 #ifdef CONFIG_TCP_MD5SIG
3725 * The MD5 Hash has already been
3726 * checked (see tcp_v{4,6}_do_rcv()).
3730 case TCPOPT_FASTOPEN
:
3731 tcp_parse_fastopen_option(
3732 opsize
- TCPOLEN_FASTOPEN_BASE
,
3733 ptr
, th
->syn
, foc
, false);
3737 /* Fast Open option shares code 254 using a
3738 * 16 bits magic number.
3740 if (opsize
>= TCPOLEN_EXP_FASTOPEN_BASE
&&
3741 get_unaligned_be16(ptr
) ==
3742 TCPOPT_FASTOPEN_MAGIC
)
3743 tcp_parse_fastopen_option(opsize
-
3744 TCPOLEN_EXP_FASTOPEN_BASE
,
3745 ptr
+ 2, th
->syn
, foc
, true);
3754 EXPORT_SYMBOL(tcp_parse_options
);
3756 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3758 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3760 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3761 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3762 tp
->rx_opt
.saw_tstamp
= 1;
3764 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3767 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3769 tp
->rx_opt
.rcv_tsecr
= 0;
3775 /* Fast parse options. This hopes to only see timestamps.
3776 * If it is wrong it falls back on tcp_parse_options().
3778 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
3779 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3781 /* In the spirit of fast parsing, compare doff directly to constant
3782 * values. Because equality is used, short doff can be ignored here.
3784 if (th
->doff
== (sizeof(*th
) / 4)) {
3785 tp
->rx_opt
.saw_tstamp
= 0;
3787 } else if (tp
->rx_opt
.tstamp_ok
&&
3788 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3789 if (tcp_parse_aligned_timestamp(tp
, th
))
3793 tcp_parse_options(skb
, &tp
->rx_opt
, 1, NULL
);
3794 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3795 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3800 #ifdef CONFIG_TCP_MD5SIG
3802 * Parse MD5 Signature option
3804 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3806 int length
= (th
->doff
<< 2) - sizeof(*th
);
3807 const u8
*ptr
= (const u8
*)(th
+ 1);
3809 /* If the TCP option is too short, we can short cut */
3810 if (length
< TCPOLEN_MD5SIG
)
3813 while (length
> 0) {
3814 int opcode
= *ptr
++;
3825 if (opsize
< 2 || opsize
> length
)
3827 if (opcode
== TCPOPT_MD5SIG
)
3828 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3835 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3838 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3840 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3841 * it can pass through stack. So, the following predicate verifies that
3842 * this segment is not used for anything but congestion avoidance or
3843 * fast retransmit. Moreover, we even are able to eliminate most of such
3844 * second order effects, if we apply some small "replay" window (~RTO)
3845 * to timestamp space.
3847 * All these measures still do not guarantee that we reject wrapped ACKs
3848 * on networks with high bandwidth, when sequence space is recycled fastly,
3849 * but it guarantees that such events will be very rare and do not affect
3850 * connection seriously. This doesn't look nice, but alas, PAWS is really
3853 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3854 * states that events when retransmit arrives after original data are rare.
3855 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3856 * the biggest problem on large power networks even with minor reordering.
3857 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3858 * up to bandwidth of 18Gigabit/sec. 8) ]
3861 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3863 const struct tcp_sock
*tp
= tcp_sk(sk
);
3864 const struct tcphdr
*th
= tcp_hdr(skb
);
3865 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3866 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3868 return (/* 1. Pure ACK with correct sequence number. */
3869 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3871 /* 2. ... and duplicate ACK. */
3872 ack
== tp
->snd_una
&&
3874 /* 3. ... and does not update window. */
3875 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3877 /* 4. ... and sits in replay window. */
3878 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3881 static inline bool tcp_paws_discard(const struct sock
*sk
,
3882 const struct sk_buff
*skb
)
3884 const struct tcp_sock
*tp
= tcp_sk(sk
);
3886 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3887 !tcp_disordered_ack(sk
, skb
);
3890 /* Check segment sequence number for validity.
3892 * Segment controls are considered valid, if the segment
3893 * fits to the window after truncation to the window. Acceptability
3894 * of data (and SYN, FIN, of course) is checked separately.
3895 * See tcp_data_queue(), for example.
3897 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3898 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3899 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3900 * (borrowed from freebsd)
3903 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3905 return !before(end_seq
, tp
->rcv_wup
) &&
3906 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3909 /* When we get a reset we do this. */
3910 void tcp_reset(struct sock
*sk
)
3912 /* We want the right error as BSD sees it (and indeed as we do). */
3913 switch (sk
->sk_state
) {
3915 sk
->sk_err
= ECONNREFUSED
;
3917 case TCP_CLOSE_WAIT
:
3923 sk
->sk_err
= ECONNRESET
;
3925 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3928 if (!sock_flag(sk
, SOCK_DEAD
))
3929 sk
->sk_error_report(sk
);
3935 * Process the FIN bit. This now behaves as it is supposed to work
3936 * and the FIN takes effect when it is validly part of sequence
3937 * space. Not before when we get holes.
3939 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3940 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3943 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3944 * close and we go into CLOSING (and later onto TIME-WAIT)
3946 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3948 static void tcp_fin(struct sock
*sk
)
3950 struct tcp_sock
*tp
= tcp_sk(sk
);
3951 const struct dst_entry
*dst
;
3953 inet_csk_schedule_ack(sk
);
3955 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3956 sock_set_flag(sk
, SOCK_DONE
);
3958 switch (sk
->sk_state
) {
3960 case TCP_ESTABLISHED
:
3961 /* Move to CLOSE_WAIT */
3962 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3963 dst
= __sk_dst_get(sk
);
3964 if (!dst
|| !dst_metric(dst
, RTAX_QUICKACK
))
3965 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3968 case TCP_CLOSE_WAIT
:
3970 /* Received a retransmission of the FIN, do
3975 /* RFC793: Remain in the LAST-ACK state. */
3979 /* This case occurs when a simultaneous close
3980 * happens, we must ack the received FIN and
3981 * enter the CLOSING state.
3984 tcp_set_state(sk
, TCP_CLOSING
);
3987 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3989 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3992 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3993 * cases we should never reach this piece of code.
3995 pr_err("%s: Impossible, sk->sk_state=%d\n",
3996 __func__
, sk
->sk_state
);
4000 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4001 * Probably, we should reset in this case. For now drop them.
4003 __skb_queue_purge(&tp
->out_of_order_queue
);
4004 if (tcp_is_sack(tp
))
4005 tcp_sack_reset(&tp
->rx_opt
);
4008 if (!sock_flag(sk
, SOCK_DEAD
)) {
4009 sk
->sk_state_change(sk
);
4011 /* Do not send POLL_HUP for half duplex close. */
4012 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4013 sk
->sk_state
== TCP_CLOSE
)
4014 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4016 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4020 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4023 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4024 if (before(seq
, sp
->start_seq
))
4025 sp
->start_seq
= seq
;
4026 if (after(end_seq
, sp
->end_seq
))
4027 sp
->end_seq
= end_seq
;
4033 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4035 struct tcp_sock
*tp
= tcp_sk(sk
);
4037 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4040 if (before(seq
, tp
->rcv_nxt
))
4041 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4043 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4045 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4047 tp
->rx_opt
.dsack
= 1;
4048 tp
->duplicate_sack
[0].start_seq
= seq
;
4049 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4053 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4055 struct tcp_sock
*tp
= tcp_sk(sk
);
4057 if (!tp
->rx_opt
.dsack
)
4058 tcp_dsack_set(sk
, seq
, end_seq
);
4060 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4063 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4065 struct tcp_sock
*tp
= tcp_sk(sk
);
4067 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4068 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4069 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4070 tcp_enter_quickack_mode(sk
);
4072 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4073 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4075 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4076 end_seq
= tp
->rcv_nxt
;
4077 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4084 /* These routines update the SACK block as out-of-order packets arrive or
4085 * in-order packets close up the sequence space.
4087 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4090 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4091 struct tcp_sack_block
*swalk
= sp
+ 1;
4093 /* See if the recent change to the first SACK eats into
4094 * or hits the sequence space of other SACK blocks, if so coalesce.
4096 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4097 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4100 /* Zap SWALK, by moving every further SACK up by one slot.
4101 * Decrease num_sacks.
4103 tp
->rx_opt
.num_sacks
--;
4104 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4108 this_sack
++, swalk
++;
4112 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4114 struct tcp_sock
*tp
= tcp_sk(sk
);
4115 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4116 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4122 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4123 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4124 /* Rotate this_sack to the first one. */
4125 for (; this_sack
> 0; this_sack
--, sp
--)
4126 swap(*sp
, *(sp
- 1));
4128 tcp_sack_maybe_coalesce(tp
);
4133 /* Could not find an adjacent existing SACK, build a new one,
4134 * put it at the front, and shift everyone else down. We
4135 * always know there is at least one SACK present already here.
4137 * If the sack array is full, forget about the last one.
4139 if (this_sack
>= TCP_NUM_SACKS
) {
4141 tp
->rx_opt
.num_sacks
--;
4144 for (; this_sack
> 0; this_sack
--, sp
--)
4148 /* Build the new head SACK, and we're done. */
4149 sp
->start_seq
= seq
;
4150 sp
->end_seq
= end_seq
;
4151 tp
->rx_opt
.num_sacks
++;
4154 /* RCV.NXT advances, some SACKs should be eaten. */
4156 static void tcp_sack_remove(struct tcp_sock
*tp
)
4158 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4159 int num_sacks
= tp
->rx_opt
.num_sacks
;
4162 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4163 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4164 tp
->rx_opt
.num_sacks
= 0;
4168 for (this_sack
= 0; this_sack
< num_sacks
;) {
4169 /* Check if the start of the sack is covered by RCV.NXT. */
4170 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4173 /* RCV.NXT must cover all the block! */
4174 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4176 /* Zap this SACK, by moving forward any other SACKS. */
4177 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4178 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4185 tp
->rx_opt
.num_sacks
= num_sacks
;
4189 * tcp_try_coalesce - try to merge skb to prior one
4192 * @from: buffer to add in queue
4193 * @fragstolen: pointer to boolean
4195 * Before queueing skb @from after @to, try to merge them
4196 * to reduce overall memory use and queue lengths, if cost is small.
4197 * Packets in ofo or receive queues can stay a long time.
4198 * Better try to coalesce them right now to avoid future collapses.
4199 * Returns true if caller should free @from instead of queueing it
4201 static bool tcp_try_coalesce(struct sock
*sk
,
4203 struct sk_buff
*from
,
4208 *fragstolen
= false;
4210 /* Its possible this segment overlaps with prior segment in queue */
4211 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4214 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4217 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4218 sk_mem_charge(sk
, delta
);
4219 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4220 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4221 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4222 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4226 /* This one checks to see if we can put data from the
4227 * out_of_order queue into the receive_queue.
4229 static void tcp_ofo_queue(struct sock
*sk
)
4231 struct tcp_sock
*tp
= tcp_sk(sk
);
4232 __u32 dsack_high
= tp
->rcv_nxt
;
4233 struct sk_buff
*skb
, *tail
;
4234 bool fragstolen
, eaten
;
4236 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4237 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4240 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4241 __u32 dsack
= dsack_high
;
4242 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4243 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4244 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4247 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4248 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4249 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4253 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4254 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4255 TCP_SKB_CB(skb
)->end_seq
);
4257 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4258 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4259 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4261 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4262 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4265 kfree_skb_partial(skb
, fragstolen
);
4269 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4270 static int tcp_prune_queue(struct sock
*sk
);
4272 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4275 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4276 !sk_rmem_schedule(sk
, skb
, size
)) {
4278 if (tcp_prune_queue(sk
) < 0)
4281 if (!sk_rmem_schedule(sk
, skb
, size
)) {
4282 if (!tcp_prune_ofo_queue(sk
))
4285 if (!sk_rmem_schedule(sk
, skb
, size
))
4292 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4294 struct tcp_sock
*tp
= tcp_sk(sk
);
4295 struct sk_buff
*skb1
;
4298 tcp_ecn_check_ce(tp
, skb
);
4300 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4301 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4306 /* Disable header prediction. */
4308 inet_csk_schedule_ack(sk
);
4310 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4311 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4312 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4314 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4316 /* Initial out of order segment, build 1 SACK. */
4317 if (tcp_is_sack(tp
)) {
4318 tp
->rx_opt
.num_sacks
= 1;
4319 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4320 tp
->selective_acks
[0].end_seq
=
4321 TCP_SKB_CB(skb
)->end_seq
;
4323 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4327 seq
= TCP_SKB_CB(skb
)->seq
;
4328 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4330 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4333 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4334 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4336 tcp_grow_window(sk
, skb
);
4337 kfree_skb_partial(skb
, fragstolen
);
4341 if (!tp
->rx_opt
.num_sacks
||
4342 tp
->selective_acks
[0].end_seq
!= seq
)
4345 /* Common case: data arrive in order after hole. */
4346 tp
->selective_acks
[0].end_seq
= end_seq
;
4350 /* Find place to insert this segment. */
4352 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4354 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4358 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4361 /* Do skb overlap to previous one? */
4362 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4363 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4364 /* All the bits are present. Drop. */
4365 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4368 tcp_dsack_set(sk
, seq
, end_seq
);
4371 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4372 /* Partial overlap. */
4373 tcp_dsack_set(sk
, seq
,
4374 TCP_SKB_CB(skb1
)->end_seq
);
4376 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4380 skb1
= skb_queue_prev(
4381 &tp
->out_of_order_queue
,
4386 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4388 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4390 /* And clean segments covered by new one as whole. */
4391 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4392 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4394 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4396 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4397 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4401 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4402 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4403 TCP_SKB_CB(skb1
)->end_seq
);
4404 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4409 if (tcp_is_sack(tp
))
4410 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4413 tcp_grow_window(sk
, skb
);
4414 skb_set_owner_r(skb
, sk
);
4418 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4422 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4424 __skb_pull(skb
, hdrlen
);
4426 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4427 tcp_rcv_nxt_update(tcp_sk(sk
), TCP_SKB_CB(skb
)->end_seq
);
4429 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4430 skb_set_owner_r(skb
, sk
);
4435 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4437 struct sk_buff
*skb
;
4443 skb
= alloc_skb(size
, sk
->sk_allocation
);
4447 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4450 if (memcpy_from_msg(skb_put(skb
, size
), msg
, size
))
4453 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4454 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4455 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4457 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4458 WARN_ON_ONCE(fragstolen
); /* should not happen */
4469 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4471 struct tcp_sock
*tp
= tcp_sk(sk
);
4473 bool fragstolen
= false;
4475 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4479 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4481 tcp_ecn_accept_cwr(tp
, skb
);
4483 tp
->rx_opt
.dsack
= 0;
4485 /* Queue data for delivery to the user.
4486 * Packets in sequence go to the receive queue.
4487 * Out of sequence packets to the out_of_order_queue.
4489 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4490 if (tcp_receive_window(tp
) == 0)
4493 /* Ok. In sequence. In window. */
4494 if (tp
->ucopy
.task
== current
&&
4495 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4496 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4497 int chunk
= min_t(unsigned int, skb
->len
,
4500 __set_current_state(TASK_RUNNING
);
4503 if (!skb_copy_datagram_msg(skb
, 0, tp
->ucopy
.msg
, chunk
)) {
4504 tp
->ucopy
.len
-= chunk
;
4505 tp
->copied_seq
+= chunk
;
4506 eaten
= (chunk
== skb
->len
);
4507 tcp_rcv_space_adjust(sk
);
4515 if (skb_queue_len(&sk
->sk_receive_queue
) == 0)
4516 sk_forced_mem_schedule(sk
, skb
->truesize
);
4517 else if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4520 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4522 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4524 tcp_event_data_recv(sk
, skb
);
4525 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4528 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4531 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4532 * gap in queue is filled.
4534 if (skb_queue_empty(&tp
->out_of_order_queue
))
4535 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4538 if (tp
->rx_opt
.num_sacks
)
4539 tcp_sack_remove(tp
);
4541 tcp_fast_path_check(sk
);
4544 kfree_skb_partial(skb
, fragstolen
);
4545 if (!sock_flag(sk
, SOCK_DEAD
))
4546 sk
->sk_data_ready(sk
);
4550 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4551 /* A retransmit, 2nd most common case. Force an immediate ack. */
4552 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4553 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4556 tcp_enter_quickack_mode(sk
);
4557 inet_csk_schedule_ack(sk
);
4563 /* Out of window. F.e. zero window probe. */
4564 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4567 tcp_enter_quickack_mode(sk
);
4569 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4570 /* Partial packet, seq < rcv_next < end_seq */
4571 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4572 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4573 TCP_SKB_CB(skb
)->end_seq
);
4575 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4577 /* If window is closed, drop tail of packet. But after
4578 * remembering D-SACK for its head made in previous line.
4580 if (!tcp_receive_window(tp
))
4585 tcp_data_queue_ofo(sk
, skb
);
4588 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4589 struct sk_buff_head
*list
)
4591 struct sk_buff
*next
= NULL
;
4593 if (!skb_queue_is_last(list
, skb
))
4594 next
= skb_queue_next(list
, skb
);
4596 __skb_unlink(skb
, list
);
4598 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4603 /* Collapse contiguous sequence of skbs head..tail with
4604 * sequence numbers start..end.
4606 * If tail is NULL, this means until the end of the list.
4608 * Segments with FIN/SYN are not collapsed (only because this
4612 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4613 struct sk_buff
*head
, struct sk_buff
*tail
,
4616 struct sk_buff
*skb
, *n
;
4619 /* First, check that queue is collapsible and find
4620 * the point where collapsing can be useful. */
4624 skb_queue_walk_from_safe(list
, skb
, n
) {
4627 /* No new bits? It is possible on ofo queue. */
4628 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4629 skb
= tcp_collapse_one(sk
, skb
, list
);
4635 /* The first skb to collapse is:
4637 * - bloated or contains data before "start" or
4638 * overlaps to the next one.
4640 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4641 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4642 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4643 end_of_skbs
= false;
4647 if (!skb_queue_is_last(list
, skb
)) {
4648 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4650 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4651 end_of_skbs
= false;
4656 /* Decided to skip this, advance start seq. */
4657 start
= TCP_SKB_CB(skb
)->end_seq
;
4660 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4663 while (before(start
, end
)) {
4664 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4665 struct sk_buff
*nskb
;
4667 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4671 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4672 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4673 __skb_queue_before(list
, skb
, nskb
);
4674 skb_set_owner_r(nskb
, sk
);
4676 /* Copy data, releasing collapsed skbs. */
4678 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4679 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4683 size
= min(copy
, size
);
4684 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4686 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4690 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4691 skb
= tcp_collapse_one(sk
, skb
, list
);
4694 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4701 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4702 * and tcp_collapse() them until all the queue is collapsed.
4704 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4706 struct tcp_sock
*tp
= tcp_sk(sk
);
4707 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4708 struct sk_buff
*head
;
4714 start
= TCP_SKB_CB(skb
)->seq
;
4715 end
= TCP_SKB_CB(skb
)->end_seq
;
4719 struct sk_buff
*next
= NULL
;
4721 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4722 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4725 /* Segment is terminated when we see gap or when
4726 * we are at the end of all the queue. */
4728 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4729 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4730 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4731 head
, skb
, start
, end
);
4735 /* Start new segment */
4736 start
= TCP_SKB_CB(skb
)->seq
;
4737 end
= TCP_SKB_CB(skb
)->end_seq
;
4739 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4740 start
= TCP_SKB_CB(skb
)->seq
;
4741 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4742 end
= TCP_SKB_CB(skb
)->end_seq
;
4748 * Purge the out-of-order queue.
4749 * Return true if queue was pruned.
4751 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4753 struct tcp_sock
*tp
= tcp_sk(sk
);
4756 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4757 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4758 __skb_queue_purge(&tp
->out_of_order_queue
);
4760 /* Reset SACK state. A conforming SACK implementation will
4761 * do the same at a timeout based retransmit. When a connection
4762 * is in a sad state like this, we care only about integrity
4763 * of the connection not performance.
4765 if (tp
->rx_opt
.sack_ok
)
4766 tcp_sack_reset(&tp
->rx_opt
);
4773 /* Reduce allocated memory if we can, trying to get
4774 * the socket within its memory limits again.
4776 * Return less than zero if we should start dropping frames
4777 * until the socket owning process reads some of the data
4778 * to stabilize the situation.
4780 static int tcp_prune_queue(struct sock
*sk
)
4782 struct tcp_sock
*tp
= tcp_sk(sk
);
4784 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4786 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4788 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4789 tcp_clamp_window(sk
);
4790 else if (tcp_under_memory_pressure(sk
))
4791 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4793 tcp_collapse_ofo_queue(sk
);
4794 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4795 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4796 skb_peek(&sk
->sk_receive_queue
),
4798 tp
->copied_seq
, tp
->rcv_nxt
);
4801 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4804 /* Collapsing did not help, destructive actions follow.
4805 * This must not ever occur. */
4807 tcp_prune_ofo_queue(sk
);
4809 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4812 /* If we are really being abused, tell the caller to silently
4813 * drop receive data on the floor. It will get retransmitted
4814 * and hopefully then we'll have sufficient space.
4816 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4818 /* Massive buffer overcommit. */
4823 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4825 const struct tcp_sock
*tp
= tcp_sk(sk
);
4827 /* If the user specified a specific send buffer setting, do
4830 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4833 /* If we are under global TCP memory pressure, do not expand. */
4834 if (tcp_under_memory_pressure(sk
))
4837 /* If we are under soft global TCP memory pressure, do not expand. */
4838 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4841 /* If we filled the congestion window, do not expand. */
4842 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
4848 /* When incoming ACK allowed to free some skb from write_queue,
4849 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4850 * on the exit from tcp input handler.
4852 * PROBLEM: sndbuf expansion does not work well with largesend.
4854 static void tcp_new_space(struct sock
*sk
)
4856 struct tcp_sock
*tp
= tcp_sk(sk
);
4858 if (tcp_should_expand_sndbuf(sk
)) {
4859 tcp_sndbuf_expand(sk
);
4860 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4863 sk
->sk_write_space(sk
);
4866 static void tcp_check_space(struct sock
*sk
)
4868 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4869 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4870 /* pairs with tcp_poll() */
4871 smp_mb__after_atomic();
4872 if (sk
->sk_socket
&&
4873 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4878 static inline void tcp_data_snd_check(struct sock
*sk
)
4880 tcp_push_pending_frames(sk
);
4881 tcp_check_space(sk
);
4885 * Check if sending an ack is needed.
4887 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4889 struct tcp_sock
*tp
= tcp_sk(sk
);
4891 /* More than one full frame received... */
4892 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4893 /* ... and right edge of window advances far enough.
4894 * (tcp_recvmsg() will send ACK otherwise). Or...
4896 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4897 /* We ACK each frame or... */
4898 tcp_in_quickack_mode(sk
) ||
4899 /* We have out of order data. */
4900 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4901 /* Then ack it now */
4904 /* Else, send delayed ack. */
4905 tcp_send_delayed_ack(sk
);
4909 static inline void tcp_ack_snd_check(struct sock
*sk
)
4911 if (!inet_csk_ack_scheduled(sk
)) {
4912 /* We sent a data segment already. */
4915 __tcp_ack_snd_check(sk
, 1);
4919 * This routine is only called when we have urgent data
4920 * signaled. Its the 'slow' part of tcp_urg. It could be
4921 * moved inline now as tcp_urg is only called from one
4922 * place. We handle URGent data wrong. We have to - as
4923 * BSD still doesn't use the correction from RFC961.
4924 * For 1003.1g we should support a new option TCP_STDURG to permit
4925 * either form (or just set the sysctl tcp_stdurg).
4928 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
4930 struct tcp_sock
*tp
= tcp_sk(sk
);
4931 u32 ptr
= ntohs(th
->urg_ptr
);
4933 if (ptr
&& !sysctl_tcp_stdurg
)
4935 ptr
+= ntohl(th
->seq
);
4937 /* Ignore urgent data that we've already seen and read. */
4938 if (after(tp
->copied_seq
, ptr
))
4941 /* Do not replay urg ptr.
4943 * NOTE: interesting situation not covered by specs.
4944 * Misbehaving sender may send urg ptr, pointing to segment,
4945 * which we already have in ofo queue. We are not able to fetch
4946 * such data and will stay in TCP_URG_NOTYET until will be eaten
4947 * by recvmsg(). Seems, we are not obliged to handle such wicked
4948 * situations. But it is worth to think about possibility of some
4949 * DoSes using some hypothetical application level deadlock.
4951 if (before(ptr
, tp
->rcv_nxt
))
4954 /* Do we already have a newer (or duplicate) urgent pointer? */
4955 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4958 /* Tell the world about our new urgent pointer. */
4961 /* We may be adding urgent data when the last byte read was
4962 * urgent. To do this requires some care. We cannot just ignore
4963 * tp->copied_seq since we would read the last urgent byte again
4964 * as data, nor can we alter copied_seq until this data arrives
4965 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4967 * NOTE. Double Dutch. Rendering to plain English: author of comment
4968 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4969 * and expect that both A and B disappear from stream. This is _wrong_.
4970 * Though this happens in BSD with high probability, this is occasional.
4971 * Any application relying on this is buggy. Note also, that fix "works"
4972 * only in this artificial test. Insert some normal data between A and B and we will
4973 * decline of BSD again. Verdict: it is better to remove to trap
4976 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4977 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4978 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4980 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4981 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4986 tp
->urg_data
= TCP_URG_NOTYET
;
4989 /* Disable header prediction. */
4993 /* This is the 'fast' part of urgent handling. */
4994 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
4996 struct tcp_sock
*tp
= tcp_sk(sk
);
4998 /* Check if we get a new urgent pointer - normally not. */
5000 tcp_check_urg(sk
, th
);
5002 /* Do we wait for any urgent data? - normally not... */
5003 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5004 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5007 /* Is the urgent pointer pointing into this packet? */
5008 if (ptr
< skb
->len
) {
5010 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5012 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5013 if (!sock_flag(sk
, SOCK_DEAD
))
5014 sk
->sk_data_ready(sk
);
5019 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5021 struct tcp_sock
*tp
= tcp_sk(sk
);
5022 int chunk
= skb
->len
- hlen
;
5026 if (skb_csum_unnecessary(skb
))
5027 err
= skb_copy_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
, chunk
);
5029 err
= skb_copy_and_csum_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
);
5032 tp
->ucopy
.len
-= chunk
;
5033 tp
->copied_seq
+= chunk
;
5034 tcp_rcv_space_adjust(sk
);
5041 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5042 struct sk_buff
*skb
)
5046 if (sock_owned_by_user(sk
)) {
5048 result
= __tcp_checksum_complete(skb
);
5051 result
= __tcp_checksum_complete(skb
);
5056 static inline bool tcp_checksum_complete_user(struct sock
*sk
,
5057 struct sk_buff
*skb
)
5059 return !skb_csum_unnecessary(skb
) &&
5060 __tcp_checksum_complete_user(sk
, skb
);
5063 /* Does PAWS and seqno based validation of an incoming segment, flags will
5064 * play significant role here.
5066 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5067 const struct tcphdr
*th
, int syn_inerr
)
5069 struct tcp_sock
*tp
= tcp_sk(sk
);
5071 /* RFC1323: H1. Apply PAWS check first. */
5072 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
5073 tcp_paws_discard(sk
, skb
)) {
5075 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5076 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5077 LINUX_MIB_TCPACKSKIPPEDPAWS
,
5078 &tp
->last_oow_ack_time
))
5079 tcp_send_dupack(sk
, skb
);
5082 /* Reset is accepted even if it did not pass PAWS. */
5085 /* Step 1: check sequence number */
5086 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5087 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5088 * (RST) segments are validated by checking their SEQ-fields."
5089 * And page 69: "If an incoming segment is not acceptable,
5090 * an acknowledgment should be sent in reply (unless the RST
5091 * bit is set, if so drop the segment and return)".
5096 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5097 LINUX_MIB_TCPACKSKIPPEDSEQ
,
5098 &tp
->last_oow_ack_time
))
5099 tcp_send_dupack(sk
, skb
);
5104 /* Step 2: check RST bit */
5107 * If sequence number exactly matches RCV.NXT, then
5108 * RESET the connection
5110 * Send a challenge ACK
5112 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
)
5115 tcp_send_challenge_ack(sk
, skb
);
5119 /* step 3: check security and precedence [ignored] */
5121 /* step 4: Check for a SYN
5122 * RFC 5961 4.2 : Send a challenge ack
5127 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5128 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5129 tcp_send_challenge_ack(sk
, skb
);
5141 * TCP receive function for the ESTABLISHED state.
5143 * It is split into a fast path and a slow path. The fast path is
5145 * - A zero window was announced from us - zero window probing
5146 * is only handled properly in the slow path.
5147 * - Out of order segments arrived.
5148 * - Urgent data is expected.
5149 * - There is no buffer space left
5150 * - Unexpected TCP flags/window values/header lengths are received
5151 * (detected by checking the TCP header against pred_flags)
5152 * - Data is sent in both directions. Fast path only supports pure senders
5153 * or pure receivers (this means either the sequence number or the ack
5154 * value must stay constant)
5155 * - Unexpected TCP option.
5157 * When these conditions are not satisfied it drops into a standard
5158 * receive procedure patterned after RFC793 to handle all cases.
5159 * The first three cases are guaranteed by proper pred_flags setting,
5160 * the rest is checked inline. Fast processing is turned on in
5161 * tcp_data_queue when everything is OK.
5163 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5164 const struct tcphdr
*th
, unsigned int len
)
5166 struct tcp_sock
*tp
= tcp_sk(sk
);
5168 if (unlikely(!sk
->sk_rx_dst
))
5169 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5171 * Header prediction.
5172 * The code loosely follows the one in the famous
5173 * "30 instruction TCP receive" Van Jacobson mail.
5175 * Van's trick is to deposit buffers into socket queue
5176 * on a device interrupt, to call tcp_recv function
5177 * on the receive process context and checksum and copy
5178 * the buffer to user space. smart...
5180 * Our current scheme is not silly either but we take the
5181 * extra cost of the net_bh soft interrupt processing...
5182 * We do checksum and copy also but from device to kernel.
5185 tp
->rx_opt
.saw_tstamp
= 0;
5187 /* pred_flags is 0xS?10 << 16 + snd_wnd
5188 * if header_prediction is to be made
5189 * 'S' will always be tp->tcp_header_len >> 2
5190 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5191 * turn it off (when there are holes in the receive
5192 * space for instance)
5193 * PSH flag is ignored.
5196 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5197 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5198 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5199 int tcp_header_len
= tp
->tcp_header_len
;
5201 /* Timestamp header prediction: tcp_header_len
5202 * is automatically equal to th->doff*4 due to pred_flags
5206 /* Check timestamp */
5207 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5208 /* No? Slow path! */
5209 if (!tcp_parse_aligned_timestamp(tp
, th
))
5212 /* If PAWS failed, check it more carefully in slow path */
5213 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5216 /* DO NOT update ts_recent here, if checksum fails
5217 * and timestamp was corrupted part, it will result
5218 * in a hung connection since we will drop all
5219 * future packets due to the PAWS test.
5223 if (len
<= tcp_header_len
) {
5224 /* Bulk data transfer: sender */
5225 if (len
== tcp_header_len
) {
5226 /* Predicted packet is in window by definition.
5227 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5228 * Hence, check seq<=rcv_wup reduces to:
5230 if (tcp_header_len
==
5231 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5232 tp
->rcv_nxt
== tp
->rcv_wup
)
5233 tcp_store_ts_recent(tp
);
5235 /* We know that such packets are checksummed
5238 tcp_ack(sk
, skb
, 0);
5240 tcp_data_snd_check(sk
);
5242 } else { /* Header too small */
5243 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5248 bool fragstolen
= false;
5250 if (tp
->ucopy
.task
== current
&&
5251 tp
->copied_seq
== tp
->rcv_nxt
&&
5252 len
- tcp_header_len
<= tp
->ucopy
.len
&&
5253 sock_owned_by_user(sk
)) {
5254 __set_current_state(TASK_RUNNING
);
5256 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
5257 /* Predicted packet is in window by definition.
5258 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5259 * Hence, check seq<=rcv_wup reduces to:
5261 if (tcp_header_len
==
5262 (sizeof(struct tcphdr
) +
5263 TCPOLEN_TSTAMP_ALIGNED
) &&
5264 tp
->rcv_nxt
== tp
->rcv_wup
)
5265 tcp_store_ts_recent(tp
);
5267 tcp_rcv_rtt_measure_ts(sk
, skb
);
5269 __skb_pull(skb
, tcp_header_len
);
5270 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
5271 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5276 if (tcp_checksum_complete_user(sk
, skb
))
5279 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5282 /* Predicted packet is in window by definition.
5283 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5284 * Hence, check seq<=rcv_wup reduces to:
5286 if (tcp_header_len
==
5287 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5288 tp
->rcv_nxt
== tp
->rcv_wup
)
5289 tcp_store_ts_recent(tp
);
5291 tcp_rcv_rtt_measure_ts(sk
, skb
);
5293 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5295 /* Bulk data transfer: receiver */
5296 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5300 tcp_event_data_recv(sk
, skb
);
5302 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5303 /* Well, only one small jumplet in fast path... */
5304 tcp_ack(sk
, skb
, FLAG_DATA
);
5305 tcp_data_snd_check(sk
);
5306 if (!inet_csk_ack_scheduled(sk
))
5310 __tcp_ack_snd_check(sk
, 0);
5313 kfree_skb_partial(skb
, fragstolen
);
5314 sk
->sk_data_ready(sk
);
5320 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5323 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5327 * Standard slow path.
5330 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5334 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5337 tcp_rcv_rtt_measure_ts(sk
, skb
);
5339 /* Process urgent data. */
5340 tcp_urg(sk
, skb
, th
);
5342 /* step 7: process the segment text */
5343 tcp_data_queue(sk
, skb
);
5345 tcp_data_snd_check(sk
);
5346 tcp_ack_snd_check(sk
);
5350 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5351 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5356 EXPORT_SYMBOL(tcp_rcv_established
);
5358 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5360 struct tcp_sock
*tp
= tcp_sk(sk
);
5361 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5363 tcp_set_state(sk
, TCP_ESTABLISHED
);
5366 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5367 security_inet_conn_established(sk
, skb
);
5370 /* Make sure socket is routed, for correct metrics. */
5371 icsk
->icsk_af_ops
->rebuild_header(sk
);
5373 tcp_init_metrics(sk
);
5375 tcp_init_congestion_control(sk
);
5377 /* Prevent spurious tcp_cwnd_restart() on first data
5380 tp
->lsndtime
= tcp_time_stamp
;
5382 tcp_init_buffer_space(sk
);
5384 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5385 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5387 if (!tp
->rx_opt
.snd_wscale
)
5388 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5392 if (!sock_flag(sk
, SOCK_DEAD
)) {
5393 sk
->sk_state_change(sk
);
5394 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5398 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5399 struct tcp_fastopen_cookie
*cookie
)
5401 struct tcp_sock
*tp
= tcp_sk(sk
);
5402 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5403 u16 mss
= tp
->rx_opt
.mss_clamp
, try_exp
= 0;
5404 bool syn_drop
= false;
5406 if (mss
== tp
->rx_opt
.user_mss
) {
5407 struct tcp_options_received opt
;
5409 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5410 tcp_clear_options(&opt
);
5411 opt
.user_mss
= opt
.mss_clamp
= 0;
5412 tcp_parse_options(synack
, &opt
, 0, NULL
);
5413 mss
= opt
.mss_clamp
;
5416 if (!tp
->syn_fastopen
) {
5417 /* Ignore an unsolicited cookie */
5419 } else if (tp
->total_retrans
) {
5420 /* SYN timed out and the SYN-ACK neither has a cookie nor
5421 * acknowledges data. Presumably the remote received only
5422 * the retransmitted (regular) SYNs: either the original
5423 * SYN-data or the corresponding SYN-ACK was dropped.
5425 syn_drop
= (cookie
->len
< 0 && data
);
5426 } else if (cookie
->len
< 0 && !tp
->syn_data
) {
5427 /* We requested a cookie but didn't get it. If we did not use
5428 * the (old) exp opt format then try so next time (try_exp=1).
5429 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5431 try_exp
= tp
->syn_fastopen_exp
? 2 : 1;
5434 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
, try_exp
);
5436 if (data
) { /* Retransmit unacked data in SYN */
5437 tcp_for_write_queue_from(data
, sk
) {
5438 if (data
== tcp_send_head(sk
) ||
5439 __tcp_retransmit_skb(sk
, data
))
5443 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5446 tp
->syn_data_acked
= tp
->syn_data
;
5447 if (tp
->syn_data_acked
)
5448 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
5452 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5453 const struct tcphdr
*th
, unsigned int len
)
5455 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5456 struct tcp_sock
*tp
= tcp_sk(sk
);
5457 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5458 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5460 tcp_parse_options(skb
, &tp
->rx_opt
, 0, &foc
);
5461 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5462 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5466 * "If the state is SYN-SENT then
5467 * first check the ACK bit
5468 * If the ACK bit is set
5469 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5470 * a reset (unless the RST bit is set, if so drop
5471 * the segment and return)"
5473 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5474 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5475 goto reset_and_undo
;
5477 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5478 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5480 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5481 goto reset_and_undo
;
5484 /* Now ACK is acceptable.
5486 * "If the RST bit is set
5487 * If the ACK was acceptable then signal the user "error:
5488 * connection reset", drop the segment, enter CLOSED state,
5489 * delete TCB, and return."
5498 * "fifth, if neither of the SYN or RST bits is set then
5499 * drop the segment and return."
5505 goto discard_and_undo
;
5508 * "If the SYN bit is on ...
5509 * are acceptable then ...
5510 * (our SYN has been ACKed), change the connection
5511 * state to ESTABLISHED..."
5514 tcp_ecn_rcv_synack(tp
, th
);
5516 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5517 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5519 /* Ok.. it's good. Set up sequence numbers and
5520 * move to established.
5522 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5523 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5525 /* RFC1323: The window in SYN & SYN/ACK segments is
5528 tp
->snd_wnd
= ntohs(th
->window
);
5530 if (!tp
->rx_opt
.wscale_ok
) {
5531 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5532 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5535 if (tp
->rx_opt
.saw_tstamp
) {
5536 tp
->rx_opt
.tstamp_ok
= 1;
5537 tp
->tcp_header_len
=
5538 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5539 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5540 tcp_store_ts_recent(tp
);
5542 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5545 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5546 tcp_enable_fack(tp
);
5549 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5550 tcp_initialize_rcv_mss(sk
);
5552 /* Remember, tcp_poll() does not lock socket!
5553 * Change state from SYN-SENT only after copied_seq
5554 * is initialized. */
5555 tp
->copied_seq
= tp
->rcv_nxt
;
5559 tcp_finish_connect(sk
, skb
);
5561 if ((tp
->syn_fastopen
|| tp
->syn_data
) &&
5562 tcp_rcv_fastopen_synack(sk
, skb
, &foc
))
5565 if (sk
->sk_write_pending
||
5566 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5567 icsk
->icsk_ack
.pingpong
) {
5568 /* Save one ACK. Data will be ready after
5569 * several ticks, if write_pending is set.
5571 * It may be deleted, but with this feature tcpdumps
5572 * look so _wonderfully_ clever, that I was not able
5573 * to stand against the temptation 8) --ANK
5575 inet_csk_schedule_ack(sk
);
5576 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5577 tcp_enter_quickack_mode(sk
);
5578 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5579 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5590 /* No ACK in the segment */
5594 * "If the RST bit is set
5596 * Otherwise (no ACK) drop the segment and return."
5599 goto discard_and_undo
;
5603 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5604 tcp_paws_reject(&tp
->rx_opt
, 0))
5605 goto discard_and_undo
;
5608 /* We see SYN without ACK. It is attempt of
5609 * simultaneous connect with crossed SYNs.
5610 * Particularly, it can be connect to self.
5612 tcp_set_state(sk
, TCP_SYN_RECV
);
5614 if (tp
->rx_opt
.saw_tstamp
) {
5615 tp
->rx_opt
.tstamp_ok
= 1;
5616 tcp_store_ts_recent(tp
);
5617 tp
->tcp_header_len
=
5618 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5620 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5623 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5624 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5626 /* RFC1323: The window in SYN & SYN/ACK segments is
5629 tp
->snd_wnd
= ntohs(th
->window
);
5630 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5631 tp
->max_window
= tp
->snd_wnd
;
5633 tcp_ecn_rcv_syn(tp
, th
);
5636 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5637 tcp_initialize_rcv_mss(sk
);
5639 tcp_send_synack(sk
);
5641 /* Note, we could accept data and URG from this segment.
5642 * There are no obstacles to make this (except that we must
5643 * either change tcp_recvmsg() to prevent it from returning data
5644 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5646 * However, if we ignore data in ACKless segments sometimes,
5647 * we have no reasons to accept it sometimes.
5648 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5649 * is not flawless. So, discard packet for sanity.
5650 * Uncomment this return to process the data.
5657 /* "fifth, if neither of the SYN or RST bits is set then
5658 * drop the segment and return."
5662 tcp_clear_options(&tp
->rx_opt
);
5663 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5667 tcp_clear_options(&tp
->rx_opt
);
5668 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5673 * This function implements the receiving procedure of RFC 793 for
5674 * all states except ESTABLISHED and TIME_WAIT.
5675 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5676 * address independent.
5679 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5680 const struct tcphdr
*th
, unsigned int len
)
5682 struct tcp_sock
*tp
= tcp_sk(sk
);
5683 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5684 struct request_sock
*req
;
5689 tp
->rx_opt
.saw_tstamp
= 0;
5691 switch (sk
->sk_state
) {
5705 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5708 /* Now we have several options: In theory there is
5709 * nothing else in the frame. KA9Q has an option to
5710 * send data with the syn, BSD accepts data with the
5711 * syn up to the [to be] advertised window and
5712 * Solaris 2.1 gives you a protocol error. For now
5713 * we just ignore it, that fits the spec precisely
5714 * and avoids incompatibilities. It would be nice in
5715 * future to drop through and process the data.
5717 * Now that TTCP is starting to be used we ought to
5719 * But, this leaves one open to an easy denial of
5720 * service attack, and SYN cookies can't defend
5721 * against this problem. So, we drop the data
5722 * in the interest of security over speed unless
5723 * it's still in use.
5731 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5735 /* Do step6 onward by hand. */
5736 tcp_urg(sk
, skb
, th
);
5738 tcp_data_snd_check(sk
);
5742 req
= tp
->fastopen_rsk
;
5744 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5745 sk
->sk_state
!= TCP_FIN_WAIT1
);
5747 if (!tcp_check_req(sk
, skb
, req
, true))
5751 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5754 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5757 /* step 5: check the ACK field */
5758 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5759 FLAG_UPDATE_TS_RECENT
) > 0;
5761 switch (sk
->sk_state
) {
5766 /* Once we leave TCP_SYN_RECV, we no longer need req
5770 synack_stamp
= tcp_rsk(req
)->snt_synack
;
5771 tp
->total_retrans
= req
->num_retrans
;
5772 reqsk_fastopen_remove(sk
, req
, false);
5774 synack_stamp
= tp
->lsndtime
;
5775 /* Make sure socket is routed, for correct metrics. */
5776 icsk
->icsk_af_ops
->rebuild_header(sk
);
5777 tcp_init_congestion_control(sk
);
5780 tp
->copied_seq
= tp
->rcv_nxt
;
5781 tcp_init_buffer_space(sk
);
5784 tcp_set_state(sk
, TCP_ESTABLISHED
);
5785 sk
->sk_state_change(sk
);
5787 /* Note, that this wakeup is only for marginal crossed SYN case.
5788 * Passively open sockets are not waked up, because
5789 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5792 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5794 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5795 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
5796 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5797 tcp_synack_rtt_meas(sk
, synack_stamp
);
5799 if (tp
->rx_opt
.tstamp_ok
)
5800 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5803 /* Re-arm the timer because data may have been sent out.
5804 * This is similar to the regular data transmission case
5805 * when new data has just been ack'ed.
5807 * (TFO) - we could try to be more aggressive and
5808 * retransmitting any data sooner based on when they
5813 tcp_init_metrics(sk
);
5815 tcp_update_pacing_rate(sk
);
5817 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5818 tp
->lsndtime
= tcp_time_stamp
;
5820 tcp_initialize_rcv_mss(sk
);
5821 tcp_fast_path_on(tp
);
5824 case TCP_FIN_WAIT1
: {
5825 struct dst_entry
*dst
;
5828 /* If we enter the TCP_FIN_WAIT1 state and we are a
5829 * Fast Open socket and this is the first acceptable
5830 * ACK we have received, this would have acknowledged
5831 * our SYNACK so stop the SYNACK timer.
5834 /* Return RST if ack_seq is invalid.
5835 * Note that RFC793 only says to generate a
5836 * DUPACK for it but for TCP Fast Open it seems
5837 * better to treat this case like TCP_SYN_RECV
5842 /* We no longer need the request sock. */
5843 reqsk_fastopen_remove(sk
, req
, false);
5846 if (tp
->snd_una
!= tp
->write_seq
)
5849 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5850 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5852 dst
= __sk_dst_get(sk
);
5856 if (!sock_flag(sk
, SOCK_DEAD
)) {
5857 /* Wake up lingering close() */
5858 sk
->sk_state_change(sk
);
5862 if (tp
->linger2
< 0 ||
5863 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5864 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5866 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5870 tmo
= tcp_fin_time(sk
);
5871 if (tmo
> TCP_TIMEWAIT_LEN
) {
5872 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5873 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5874 /* Bad case. We could lose such FIN otherwise.
5875 * It is not a big problem, but it looks confusing
5876 * and not so rare event. We still can lose it now,
5877 * if it spins in bh_lock_sock(), but it is really
5880 inet_csk_reset_keepalive_timer(sk
, tmo
);
5882 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5889 if (tp
->snd_una
== tp
->write_seq
) {
5890 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5896 if (tp
->snd_una
== tp
->write_seq
) {
5897 tcp_update_metrics(sk
);
5904 /* step 6: check the URG bit */
5905 tcp_urg(sk
, skb
, th
);
5907 /* step 7: process the segment text */
5908 switch (sk
->sk_state
) {
5909 case TCP_CLOSE_WAIT
:
5912 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5916 /* RFC 793 says to queue data in these states,
5917 * RFC 1122 says we MUST send a reset.
5918 * BSD 4.4 also does reset.
5920 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5921 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5922 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5923 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5929 case TCP_ESTABLISHED
:
5930 tcp_data_queue(sk
, skb
);
5935 /* tcp_data could move socket to TIME-WAIT */
5936 if (sk
->sk_state
!= TCP_CLOSE
) {
5937 tcp_data_snd_check(sk
);
5938 tcp_ack_snd_check(sk
);
5947 EXPORT_SYMBOL(tcp_rcv_state_process
);
5949 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
5951 struct inet_request_sock
*ireq
= inet_rsk(req
);
5953 if (family
== AF_INET
)
5954 net_dbg_ratelimited("drop open request from %pI4/%u\n",
5955 &ireq
->ir_rmt_addr
, port
);
5956 #if IS_ENABLED(CONFIG_IPV6)
5957 else if (family
== AF_INET6
)
5958 net_dbg_ratelimited("drop open request from %pI6/%u\n",
5959 &ireq
->ir_v6_rmt_addr
, port
);
5963 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
5965 * If we receive a SYN packet with these bits set, it means a
5966 * network is playing bad games with TOS bits. In order to
5967 * avoid possible false congestion notifications, we disable
5968 * TCP ECN negotiation.
5970 * Exception: tcp_ca wants ECN. This is required for DCTCP
5971 * congestion control: Linux DCTCP asserts ECT on all packets,
5972 * including SYN, which is most optimal solution; however,
5973 * others, such as FreeBSD do not.
5975 static void tcp_ecn_create_request(struct request_sock
*req
,
5976 const struct sk_buff
*skb
,
5977 const struct sock
*listen_sk
,
5978 const struct dst_entry
*dst
)
5980 const struct tcphdr
*th
= tcp_hdr(skb
);
5981 const struct net
*net
= sock_net(listen_sk
);
5982 bool th_ecn
= th
->ece
&& th
->cwr
;
5988 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
5989 ecn_ok
= net
->ipv4
.sysctl_tcp_ecn
|| dst_feature(dst
, RTAX_FEATURE_ECN
);
5991 if ((!ect
&& ecn_ok
) || tcp_ca_needs_ecn(listen_sk
))
5992 inet_rsk(req
)->ecn_ok
= 1;
5995 static void tcp_openreq_init(struct request_sock
*req
,
5996 const struct tcp_options_received
*rx_opt
,
5997 struct sk_buff
*skb
, const struct sock
*sk
)
5999 struct inet_request_sock
*ireq
= inet_rsk(req
);
6001 req
->rcv_wnd
= 0; /* So that tcp_send_synack() knows! */
6003 tcp_rsk(req
)->rcv_isn
= TCP_SKB_CB(skb
)->seq
;
6004 tcp_rsk(req
)->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
6005 tcp_rsk(req
)->snt_synack
= tcp_time_stamp
;
6006 tcp_rsk(req
)->last_oow_ack_time
= 0;
6007 req
->mss
= rx_opt
->mss_clamp
;
6008 req
->ts_recent
= rx_opt
->saw_tstamp
? rx_opt
->rcv_tsval
: 0;
6009 ireq
->tstamp_ok
= rx_opt
->tstamp_ok
;
6010 ireq
->sack_ok
= rx_opt
->sack_ok
;
6011 ireq
->snd_wscale
= rx_opt
->snd_wscale
;
6012 ireq
->wscale_ok
= rx_opt
->wscale_ok
;
6015 ireq
->ir_rmt_port
= tcp_hdr(skb
)->source
;
6016 ireq
->ir_num
= ntohs(tcp_hdr(skb
)->dest
);
6017 ireq
->ir_mark
= inet_request_mark(sk
, skb
);
6020 struct request_sock
*inet_reqsk_alloc(const struct request_sock_ops
*ops
,
6021 struct sock
*sk_listener
)
6023 struct request_sock
*req
= reqsk_alloc(ops
, sk_listener
);
6026 struct inet_request_sock
*ireq
= inet_rsk(req
);
6028 kmemcheck_annotate_bitfield(ireq
, flags
);
6030 atomic64_set(&ireq
->ir_cookie
, 0);
6031 ireq
->ireq_state
= TCP_NEW_SYN_RECV
;
6032 write_pnet(&ireq
->ireq_net
, sock_net(sk_listener
));
6033 ireq
->ireq_family
= sk_listener
->sk_family
;
6038 EXPORT_SYMBOL(inet_reqsk_alloc
);
6041 * Return true if a syncookie should be sent
6043 static bool tcp_syn_flood_action(struct sock
*sk
,
6044 const struct sk_buff
*skb
,
6047 const char *msg
= "Dropping request";
6048 bool want_cookie
= false;
6049 struct listen_sock
*lopt
;
6051 #ifdef CONFIG_SYN_COOKIES
6052 if (sysctl_tcp_syncookies
) {
6053 msg
= "Sending cookies";
6055 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPREQQFULLDOCOOKIES
);
6058 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPREQQFULLDROP
);
6060 lopt
= inet_csk(sk
)->icsk_accept_queue
.listen_opt
;
6061 if (!lopt
->synflood_warned
&& sysctl_tcp_syncookies
!= 2) {
6062 lopt
->synflood_warned
= 1;
6063 pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6064 proto
, ntohs(tcp_hdr(skb
)->dest
), msg
);
6069 static void tcp_reqsk_record_syn(const struct sock
*sk
,
6070 struct request_sock
*req
,
6071 const struct sk_buff
*skb
)
6073 if (tcp_sk(sk
)->save_syn
) {
6074 u32 len
= skb_network_header_len(skb
) + tcp_hdrlen(skb
);
6077 copy
= kmalloc(len
+ sizeof(u32
), GFP_ATOMIC
);
6080 memcpy(©
[1], skb_network_header(skb
), len
);
6081 req
->saved_syn
= copy
;
6086 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
6087 const struct tcp_request_sock_ops
*af_ops
,
6088 struct sock
*sk
, struct sk_buff
*skb
)
6090 struct tcp_options_received tmp_opt
;
6091 struct request_sock
*req
;
6092 struct tcp_sock
*tp
= tcp_sk(sk
);
6093 struct dst_entry
*dst
= NULL
;
6094 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
6095 bool want_cookie
= false, fastopen
;
6097 struct tcp_fastopen_cookie foc
= { .len
= -1 };
6101 /* TW buckets are converted to open requests without
6102 * limitations, they conserve resources and peer is
6103 * evidently real one.
6105 if ((sysctl_tcp_syncookies
== 2 ||
6106 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
6107 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
6113 /* Accept backlog is full. If we have already queued enough
6114 * of warm entries in syn queue, drop request. It is better than
6115 * clogging syn queue with openreqs with exponentially increasing
6118 if (sk_acceptq_is_full(sk
) && inet_csk_reqsk_queue_young(sk
) > 1) {
6119 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
6123 req
= inet_reqsk_alloc(rsk_ops
, sk
);
6127 tcp_rsk(req
)->af_specific
= af_ops
;
6129 tcp_clear_options(&tmp_opt
);
6130 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
6131 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
6132 tcp_parse_options(skb
, &tmp_opt
, 0, want_cookie
? NULL
: &foc
);
6134 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
6135 tcp_clear_options(&tmp_opt
);
6137 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
6138 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
6140 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6141 inet_rsk(req
)->ir_iif
= sk
->sk_bound_dev_if
;
6143 af_ops
->init_req(req
, sk
, skb
);
6145 if (security_inet_conn_request(sk
, skb
, req
))
6148 if (!want_cookie
&& !isn
) {
6149 /* VJ's idea. We save last timestamp seen
6150 * from the destination in peer table, when entering
6151 * state TIME-WAIT, and check against it before
6152 * accepting new connection request.
6154 * If "isn" is not zero, this request hit alive
6155 * timewait bucket, so that all the necessary checks
6156 * are made in the function processing timewait state.
6158 if (tcp_death_row
.sysctl_tw_recycle
) {
6161 dst
= af_ops
->route_req(sk
, &fl
, req
, &strict
);
6163 if (dst
&& strict
&&
6164 !tcp_peer_is_proven(req
, dst
, true,
6165 tmp_opt
.saw_tstamp
)) {
6166 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSPASSIVEREJECTED
);
6167 goto drop_and_release
;
6170 /* Kill the following clause, if you dislike this way. */
6171 else if (!sysctl_tcp_syncookies
&&
6172 (sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
6173 (sysctl_max_syn_backlog
>> 2)) &&
6174 !tcp_peer_is_proven(req
, dst
, false,
6175 tmp_opt
.saw_tstamp
)) {
6176 /* Without syncookies last quarter of
6177 * backlog is filled with destinations,
6178 * proven to be alive.
6179 * It means that we continue to communicate
6180 * to destinations, already remembered
6181 * to the moment of synflood.
6183 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
6185 goto drop_and_release
;
6188 isn
= af_ops
->init_seq(skb
);
6191 dst
= af_ops
->route_req(sk
, &fl
, req
, NULL
);
6196 tcp_ecn_create_request(req
, skb
, sk
, dst
);
6199 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
6200 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
6201 if (!tmp_opt
.tstamp_ok
)
6202 inet_rsk(req
)->ecn_ok
= 0;
6205 tcp_rsk(req
)->snt_isn
= isn
;
6206 tcp_openreq_init_rwin(req
, sk
, dst
);
6207 fastopen
= !want_cookie
&&
6208 tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6209 err
= af_ops
->send_synack(sk
, dst
, &fl
, req
,
6210 skb_get_queue_mapping(skb
), &foc
);
6212 if (err
|| want_cookie
)
6215 tcp_rsk(req
)->tfo_listener
= false;
6216 af_ops
->queue_hash_add(sk
, req
, TCP_TIMEOUT_INIT
);
6218 tcp_reqsk_record_syn(sk
, req
, skb
);
6227 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENDROPS
);
6230 EXPORT_SYMBOL(tcp_conn_request
);