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_LOST_RETRANS 0x80 /* This ACK marks some retransmission lost */
113 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
114 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
115 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
116 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
117 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
118 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
120 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
121 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
122 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
123 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
125 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
126 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
128 /* Adapt the MSS value used to make delayed ack decision to the
131 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
133 struct inet_connection_sock
*icsk
= inet_csk(sk
);
134 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
137 icsk
->icsk_ack
.last_seg_size
= 0;
139 /* skb->len may jitter because of SACKs, even if peer
140 * sends good full-sized frames.
142 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
143 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
144 icsk
->icsk_ack
.rcv_mss
= len
;
146 /* Otherwise, we make more careful check taking into account,
147 * that SACKs block is variable.
149 * "len" is invariant segment length, including TCP header.
151 len
+= skb
->data
- skb_transport_header(skb
);
152 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
153 /* If PSH is not set, packet should be
154 * full sized, provided peer TCP is not badly broken.
155 * This observation (if it is correct 8)) allows
156 * to handle super-low mtu links fairly.
158 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
159 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
160 /* Subtract also invariant (if peer is RFC compliant),
161 * tcp header plus fixed timestamp option length.
162 * Resulting "len" is MSS free of SACK jitter.
164 len
-= tcp_sk(sk
)->tcp_header_len
;
165 icsk
->icsk_ack
.last_seg_size
= len
;
167 icsk
->icsk_ack
.rcv_mss
= len
;
171 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
172 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
173 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
177 static void tcp_incr_quickack(struct sock
*sk
)
179 struct inet_connection_sock
*icsk
= inet_csk(sk
);
180 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
184 if (quickacks
> icsk
->icsk_ack
.quick
)
185 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
188 static void tcp_enter_quickack_mode(struct sock
*sk
)
190 struct inet_connection_sock
*icsk
= inet_csk(sk
);
191 tcp_incr_quickack(sk
);
192 icsk
->icsk_ack
.pingpong
= 0;
193 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
196 /* Send ACKs quickly, if "quick" count is not exhausted
197 * and the session is not interactive.
200 static bool tcp_in_quickack_mode(struct sock
*sk
)
202 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
203 const struct dst_entry
*dst
= __sk_dst_get(sk
);
205 return (dst
&& dst_metric(dst
, RTAX_QUICKACK
)) ||
206 (icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
);
209 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
211 if (tp
->ecn_flags
& TCP_ECN_OK
)
212 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
215 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
217 if (tcp_hdr(skb
)->cwr
)
218 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
221 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
223 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
226 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
228 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
229 case INET_ECN_NOT_ECT
:
230 /* Funny extension: if ECT is not set on a segment,
231 * and we already seen ECT on a previous segment,
232 * it is probably a retransmit.
234 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
235 tcp_enter_quickack_mode((struct sock
*)tp
);
238 if (tcp_ca_needs_ecn((struct sock
*)tp
))
239 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
241 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
242 /* Better not delay acks, sender can have a very low cwnd */
243 tcp_enter_quickack_mode((struct sock
*)tp
);
244 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
246 tp
->ecn_flags
|= TCP_ECN_SEEN
;
249 if (tcp_ca_needs_ecn((struct sock
*)tp
))
250 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
251 tp
->ecn_flags
|= TCP_ECN_SEEN
;
256 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
258 if (tp
->ecn_flags
& TCP_ECN_OK
)
259 __tcp_ecn_check_ce(tp
, skb
);
262 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
264 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
265 tp
->ecn_flags
&= ~TCP_ECN_OK
;
268 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
270 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
271 tp
->ecn_flags
&= ~TCP_ECN_OK
;
274 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
276 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
281 /* Buffer size and advertised window tuning.
283 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
286 static void tcp_sndbuf_expand(struct sock
*sk
)
288 const struct tcp_sock
*tp
= tcp_sk(sk
);
292 /* Worst case is non GSO/TSO : each frame consumes one skb
293 * and skb->head is kmalloced using power of two area of memory
295 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
297 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
299 per_mss
= roundup_pow_of_two(per_mss
) +
300 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
302 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
303 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
305 /* Fast Recovery (RFC 5681 3.2) :
306 * Cubic needs 1.7 factor, rounded to 2 to include
307 * extra cushion (application might react slowly to POLLOUT)
309 sndmem
= 2 * nr_segs
* per_mss
;
311 if (sk
->sk_sndbuf
< sndmem
)
312 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
315 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
317 * All tcp_full_space() is split to two parts: "network" buffer, allocated
318 * forward and advertised in receiver window (tp->rcv_wnd) and
319 * "application buffer", required to isolate scheduling/application
320 * latencies from network.
321 * window_clamp is maximal advertised window. It can be less than
322 * tcp_full_space(), in this case tcp_full_space() - window_clamp
323 * is reserved for "application" buffer. The less window_clamp is
324 * the smoother our behaviour from viewpoint of network, but the lower
325 * throughput and the higher sensitivity of the connection to losses. 8)
327 * rcv_ssthresh is more strict window_clamp used at "slow start"
328 * phase to predict further behaviour of this connection.
329 * It is used for two goals:
330 * - to enforce header prediction at sender, even when application
331 * requires some significant "application buffer". It is check #1.
332 * - to prevent pruning of receive queue because of misprediction
333 * of receiver window. Check #2.
335 * The scheme does not work when sender sends good segments opening
336 * window and then starts to feed us spaghetti. But it should work
337 * in common situations. Otherwise, we have to rely on queue collapsing.
340 /* Slow part of check#2. */
341 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
343 struct tcp_sock
*tp
= tcp_sk(sk
);
345 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
346 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
348 while (tp
->rcv_ssthresh
<= window
) {
349 if (truesize
<= skb
->len
)
350 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
358 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
360 struct tcp_sock
*tp
= tcp_sk(sk
);
363 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
364 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
365 !tcp_under_memory_pressure(sk
)) {
368 /* Check #2. Increase window, if skb with such overhead
369 * will fit to rcvbuf in future.
371 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
372 incr
= 2 * tp
->advmss
;
374 incr
= __tcp_grow_window(sk
, skb
);
377 incr
= max_t(int, incr
, 2 * skb
->len
);
378 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
380 inet_csk(sk
)->icsk_ack
.quick
|= 1;
385 /* 3. Tuning rcvbuf, when connection enters established state. */
386 static void tcp_fixup_rcvbuf(struct sock
*sk
)
388 u32 mss
= tcp_sk(sk
)->advmss
;
391 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
392 tcp_default_init_rwnd(mss
);
394 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
395 * Allow enough cushion so that sender is not limited by our window
397 if (sysctl_tcp_moderate_rcvbuf
)
400 if (sk
->sk_rcvbuf
< rcvmem
)
401 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
404 /* 4. Try to fixup all. It is made immediately after connection enters
407 void tcp_init_buffer_space(struct sock
*sk
)
409 struct tcp_sock
*tp
= tcp_sk(sk
);
412 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
413 tcp_fixup_rcvbuf(sk
);
414 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
415 tcp_sndbuf_expand(sk
);
417 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
418 tp
->rcvq_space
.time
= tcp_time_stamp
;
419 tp
->rcvq_space
.seq
= tp
->copied_seq
;
421 maxwin
= tcp_full_space(sk
);
423 if (tp
->window_clamp
>= maxwin
) {
424 tp
->window_clamp
= maxwin
;
426 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
427 tp
->window_clamp
= max(maxwin
-
428 (maxwin
>> sysctl_tcp_app_win
),
432 /* Force reservation of one segment. */
433 if (sysctl_tcp_app_win
&&
434 tp
->window_clamp
> 2 * tp
->advmss
&&
435 tp
->window_clamp
+ tp
->advmss
> maxwin
)
436 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
438 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
439 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
442 /* 5. Recalculate window clamp after socket hit its memory bounds. */
443 static void tcp_clamp_window(struct sock
*sk
)
445 struct tcp_sock
*tp
= tcp_sk(sk
);
446 struct inet_connection_sock
*icsk
= inet_csk(sk
);
448 icsk
->icsk_ack
.quick
= 0;
450 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
451 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
452 !tcp_under_memory_pressure(sk
) &&
453 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
454 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
457 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
458 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
461 /* Initialize RCV_MSS value.
462 * RCV_MSS is an our guess about MSS used by the peer.
463 * We haven't any direct information about the MSS.
464 * It's better to underestimate the RCV_MSS rather than overestimate.
465 * Overestimations make us ACKing less frequently than needed.
466 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
468 void tcp_initialize_rcv_mss(struct sock
*sk
)
470 const struct tcp_sock
*tp
= tcp_sk(sk
);
471 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
473 hint
= min(hint
, tp
->rcv_wnd
/ 2);
474 hint
= min(hint
, TCP_MSS_DEFAULT
);
475 hint
= max(hint
, TCP_MIN_MSS
);
477 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
479 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
481 /* Receiver "autotuning" code.
483 * The algorithm for RTT estimation w/o timestamps is based on
484 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
485 * <http://public.lanl.gov/radiant/pubs.html#DRS>
487 * More detail on this code can be found at
488 * <http://staff.psc.edu/jheffner/>,
489 * though this reference is out of date. A new paper
492 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
494 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
500 if (new_sample
!= 0) {
501 /* If we sample in larger samples in the non-timestamp
502 * case, we could grossly overestimate the RTT especially
503 * with chatty applications or bulk transfer apps which
504 * are stalled on filesystem I/O.
506 * Also, since we are only going for a minimum in the
507 * non-timestamp case, we do not smooth things out
508 * else with timestamps disabled convergence takes too
512 m
-= (new_sample
>> 3);
520 /* No previous measure. */
524 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
525 tp
->rcv_rtt_est
.rtt
= new_sample
;
528 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
530 if (tp
->rcv_rtt_est
.time
== 0)
532 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
534 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
537 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
538 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
541 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
542 const struct sk_buff
*skb
)
544 struct tcp_sock
*tp
= tcp_sk(sk
);
545 if (tp
->rx_opt
.rcv_tsecr
&&
546 (TCP_SKB_CB(skb
)->end_seq
-
547 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
548 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
552 * This function should be called every time data is copied to user space.
553 * It calculates the appropriate TCP receive buffer space.
555 void tcp_rcv_space_adjust(struct sock
*sk
)
557 struct tcp_sock
*tp
= tcp_sk(sk
);
561 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
562 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
565 /* Number of bytes copied to user in last RTT */
566 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
567 if (copied
<= tp
->rcvq_space
.space
)
571 * copied = bytes received in previous RTT, our base window
572 * To cope with packet losses, we need a 2x factor
573 * To cope with slow start, and sender growing its cwin by 100 %
574 * every RTT, we need a 4x factor, because the ACK we are sending
575 * now is for the next RTT, not the current one :
576 * <prev RTT . ><current RTT .. ><next RTT .... >
579 if (sysctl_tcp_moderate_rcvbuf
&&
580 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
581 int rcvwin
, rcvmem
, rcvbuf
;
583 /* minimal window to cope with packet losses, assuming
584 * steady state. Add some cushion because of small variations.
586 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
588 /* If rate increased by 25%,
589 * assume slow start, rcvwin = 3 * copied
590 * If rate increased by 50%,
591 * assume sender can use 2x growth, rcvwin = 4 * copied
594 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
596 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
599 rcvwin
+= (rcvwin
>> 1);
602 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
603 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
606 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
, sysctl_tcp_rmem
[2]);
607 if (rcvbuf
> sk
->sk_rcvbuf
) {
608 sk
->sk_rcvbuf
= rcvbuf
;
610 /* Make the window clamp follow along. */
611 tp
->window_clamp
= rcvwin
;
614 tp
->rcvq_space
.space
= copied
;
617 tp
->rcvq_space
.seq
= tp
->copied_seq
;
618 tp
->rcvq_space
.time
= tcp_time_stamp
;
621 /* There is something which you must keep in mind when you analyze the
622 * behavior of the tp->ato delayed ack timeout interval. When a
623 * connection starts up, we want to ack as quickly as possible. The
624 * problem is that "good" TCP's do slow start at the beginning of data
625 * transmission. The means that until we send the first few ACK's the
626 * sender will sit on his end and only queue most of his data, because
627 * he can only send snd_cwnd unacked packets at any given time. For
628 * each ACK we send, he increments snd_cwnd and transmits more of his
631 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
633 struct tcp_sock
*tp
= tcp_sk(sk
);
634 struct inet_connection_sock
*icsk
= inet_csk(sk
);
637 inet_csk_schedule_ack(sk
);
639 tcp_measure_rcv_mss(sk
, skb
);
641 tcp_rcv_rtt_measure(tp
);
643 now
= tcp_time_stamp
;
645 if (!icsk
->icsk_ack
.ato
) {
646 /* The _first_ data packet received, initialize
647 * delayed ACK engine.
649 tcp_incr_quickack(sk
);
650 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
652 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
654 if (m
<= TCP_ATO_MIN
/ 2) {
655 /* The fastest case is the first. */
656 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
657 } else if (m
< icsk
->icsk_ack
.ato
) {
658 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
659 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
660 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
661 } else if (m
> icsk
->icsk_rto
) {
662 /* Too long gap. Apparently sender failed to
663 * restart window, so that we send ACKs quickly.
665 tcp_incr_quickack(sk
);
669 icsk
->icsk_ack
.lrcvtime
= now
;
671 tcp_ecn_check_ce(tp
, skb
);
674 tcp_grow_window(sk
, skb
);
677 /* Called to compute a smoothed rtt estimate. The data fed to this
678 * routine either comes from timestamps, or from segments that were
679 * known _not_ to have been retransmitted [see Karn/Partridge
680 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
681 * piece by Van Jacobson.
682 * NOTE: the next three routines used to be one big routine.
683 * To save cycles in the RFC 1323 implementation it was better to break
684 * it up into three procedures. -- erics
686 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
688 struct tcp_sock
*tp
= tcp_sk(sk
);
689 long m
= mrtt_us
; /* RTT */
690 u32 srtt
= tp
->srtt_us
;
692 /* The following amusing code comes from Jacobson's
693 * article in SIGCOMM '88. Note that rtt and mdev
694 * are scaled versions of rtt and mean deviation.
695 * This is designed to be as fast as possible
696 * m stands for "measurement".
698 * On a 1990 paper the rto value is changed to:
699 * RTO = rtt + 4 * mdev
701 * Funny. This algorithm seems to be very broken.
702 * These formulae increase RTO, when it should be decreased, increase
703 * too slowly, when it should be increased quickly, decrease too quickly
704 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
705 * does not matter how to _calculate_ it. Seems, it was trap
706 * that VJ failed to avoid. 8)
709 m
-= (srtt
>> 3); /* m is now error in rtt est */
710 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
712 m
= -m
; /* m is now abs(error) */
713 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
714 /* This is similar to one of Eifel findings.
715 * Eifel blocks mdev updates when rtt decreases.
716 * This solution is a bit different: we use finer gain
717 * for mdev in this case (alpha*beta).
718 * Like Eifel it also prevents growth of rto,
719 * but also it limits too fast rto decreases,
720 * happening in pure Eifel.
725 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
727 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
728 if (tp
->mdev_us
> tp
->mdev_max_us
) {
729 tp
->mdev_max_us
= tp
->mdev_us
;
730 if (tp
->mdev_max_us
> tp
->rttvar_us
)
731 tp
->rttvar_us
= tp
->mdev_max_us
;
733 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
734 if (tp
->mdev_max_us
< tp
->rttvar_us
)
735 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
736 tp
->rtt_seq
= tp
->snd_nxt
;
737 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
740 /* no previous measure. */
741 srtt
= m
<< 3; /* take the measured time to be rtt */
742 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
743 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
744 tp
->mdev_max_us
= tp
->rttvar_us
;
745 tp
->rtt_seq
= tp
->snd_nxt
;
747 tp
->srtt_us
= max(1U, srtt
);
750 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
751 * Note: TCP stack does not yet implement pacing.
752 * FQ packet scheduler can be used to implement cheap but effective
753 * TCP pacing, to smooth the burst on large writes when packets
754 * in flight is significantly lower than cwnd (or rwin)
756 int sysctl_tcp_pacing_ss_ratio __read_mostly
= 200;
757 int sysctl_tcp_pacing_ca_ratio __read_mostly
= 120;
759 static void tcp_update_pacing_rate(struct sock
*sk
)
761 const struct tcp_sock
*tp
= tcp_sk(sk
);
764 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
765 rate
= (u64
)tp
->mss_cache
* ((USEC_PER_SEC
/ 100) << 3);
767 /* current rate is (cwnd * mss) / srtt
768 * In Slow Start [1], set sk_pacing_rate to 200 % the current rate.
769 * In Congestion Avoidance phase, set it to 120 % the current rate.
771 * [1] : Normal Slow Start condition is (tp->snd_cwnd < tp->snd_ssthresh)
772 * If snd_cwnd >= (tp->snd_ssthresh / 2), we are approaching
773 * end of slow start and should slow down.
775 if (tp
->snd_cwnd
< tp
->snd_ssthresh
/ 2)
776 rate
*= sysctl_tcp_pacing_ss_ratio
;
778 rate
*= sysctl_tcp_pacing_ca_ratio
;
780 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
782 if (likely(tp
->srtt_us
))
783 do_div(rate
, tp
->srtt_us
);
785 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
786 * without any lock. We want to make sure compiler wont store
787 * intermediate values in this location.
789 ACCESS_ONCE(sk
->sk_pacing_rate
) = min_t(u64
, rate
,
790 sk
->sk_max_pacing_rate
);
793 /* Calculate rto without backoff. This is the second half of Van Jacobson's
794 * routine referred to above.
796 static void tcp_set_rto(struct sock
*sk
)
798 const struct tcp_sock
*tp
= tcp_sk(sk
);
799 /* Old crap is replaced with new one. 8)
802 * 1. If rtt variance happened to be less 50msec, it is hallucination.
803 * It cannot be less due to utterly erratic ACK generation made
804 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
805 * to do with delayed acks, because at cwnd>2 true delack timeout
806 * is invisible. Actually, Linux-2.4 also generates erratic
807 * ACKs in some circumstances.
809 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
811 /* 2. Fixups made earlier cannot be right.
812 * If we do not estimate RTO correctly without them,
813 * all the algo is pure shit and should be replaced
814 * with correct one. It is exactly, which we pretend to do.
817 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
818 * guarantees that rto is higher.
823 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
825 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
828 cwnd
= TCP_INIT_CWND
;
829 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
833 * Packet counting of FACK is based on in-order assumptions, therefore TCP
834 * disables it when reordering is detected
836 void tcp_disable_fack(struct tcp_sock
*tp
)
838 /* RFC3517 uses different metric in lost marker => reset on change */
840 tp
->lost_skb_hint
= NULL
;
841 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
844 /* Take a notice that peer is sending D-SACKs */
845 static void tcp_dsack_seen(struct tcp_sock
*tp
)
847 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
850 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
853 struct tcp_sock
*tp
= tcp_sk(sk
);
854 if (metric
> tp
->reordering
) {
857 tp
->reordering
= min(sysctl_tcp_max_reordering
, metric
);
859 /* This exciting event is worth to be remembered. 8) */
861 mib_idx
= LINUX_MIB_TCPTSREORDER
;
862 else if (tcp_is_reno(tp
))
863 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
864 else if (tcp_is_fack(tp
))
865 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
867 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
869 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
870 #if FASTRETRANS_DEBUG > 1
871 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
872 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
876 tp
->undo_marker
? tp
->undo_retrans
: 0);
878 tcp_disable_fack(tp
);
882 tcp_disable_early_retrans(tp
);
885 /* This must be called before lost_out is incremented */
886 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
888 if (!tp
->retransmit_skb_hint
||
889 before(TCP_SKB_CB(skb
)->seq
,
890 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
891 tp
->retransmit_skb_hint
= skb
;
894 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
895 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
898 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
900 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
901 tcp_verify_retransmit_hint(tp
, skb
);
903 tp
->lost_out
+= tcp_skb_pcount(skb
);
904 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
908 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
911 tcp_verify_retransmit_hint(tp
, skb
);
913 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
914 tp
->lost_out
+= tcp_skb_pcount(skb
);
915 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
919 /* This procedure tags the retransmission queue when SACKs arrive.
921 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
922 * Packets in queue with these bits set are counted in variables
923 * sacked_out, retrans_out and lost_out, correspondingly.
925 * Valid combinations are:
926 * Tag InFlight Description
927 * 0 1 - orig segment is in flight.
928 * S 0 - nothing flies, orig reached receiver.
929 * L 0 - nothing flies, orig lost by net.
930 * R 2 - both orig and retransmit are in flight.
931 * L|R 1 - orig is lost, retransmit is in flight.
932 * S|R 1 - orig reached receiver, retrans is still in flight.
933 * (L|S|R is logically valid, it could occur when L|R is sacked,
934 * but it is equivalent to plain S and code short-curcuits it to S.
935 * L|S is logically invalid, it would mean -1 packet in flight 8))
937 * These 6 states form finite state machine, controlled by the following events:
938 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
939 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
940 * 3. Loss detection event of two flavors:
941 * A. Scoreboard estimator decided the packet is lost.
942 * A'. Reno "three dupacks" marks head of queue lost.
943 * A''. Its FACK modification, head until snd.fack is lost.
944 * B. SACK arrives sacking SND.NXT at the moment, when the
945 * segment was retransmitted.
946 * 4. D-SACK added new rule: D-SACK changes any tag to S.
948 * It is pleasant to note, that state diagram turns out to be commutative,
949 * so that we are allowed not to be bothered by order of our actions,
950 * when multiple events arrive simultaneously. (see the function below).
952 * Reordering detection.
953 * --------------------
954 * Reordering metric is maximal distance, which a packet can be displaced
955 * in packet stream. With SACKs we can estimate it:
957 * 1. SACK fills old hole and the corresponding segment was not
958 * ever retransmitted -> reordering. Alas, we cannot use it
959 * when segment was retransmitted.
960 * 2. The last flaw is solved with D-SACK. D-SACK arrives
961 * for retransmitted and already SACKed segment -> reordering..
962 * Both of these heuristics are not used in Loss state, when we cannot
963 * account for retransmits accurately.
965 * SACK block validation.
966 * ----------------------
968 * SACK block range validation checks that the received SACK block fits to
969 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
970 * Note that SND.UNA is not included to the range though being valid because
971 * it means that the receiver is rather inconsistent with itself reporting
972 * SACK reneging when it should advance SND.UNA. Such SACK block this is
973 * perfectly valid, however, in light of RFC2018 which explicitly states
974 * that "SACK block MUST reflect the newest segment. Even if the newest
975 * segment is going to be discarded ...", not that it looks very clever
976 * in case of head skb. Due to potentional receiver driven attacks, we
977 * choose to avoid immediate execution of a walk in write queue due to
978 * reneging and defer head skb's loss recovery to standard loss recovery
979 * procedure that will eventually trigger (nothing forbids us doing this).
981 * Implements also blockage to start_seq wrap-around. Problem lies in the
982 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
983 * there's no guarantee that it will be before snd_nxt (n). The problem
984 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
987 * <- outs wnd -> <- wrapzone ->
988 * u e n u_w e_w s n_w
990 * |<------------+------+----- TCP seqno space --------------+---------->|
991 * ...-- <2^31 ->| |<--------...
992 * ...---- >2^31 ------>| |<--------...
994 * Current code wouldn't be vulnerable but it's better still to discard such
995 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
996 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
997 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
998 * equal to the ideal case (infinite seqno space without wrap caused issues).
1000 * With D-SACK the lower bound is extended to cover sequence space below
1001 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1002 * again, D-SACK block must not to go across snd_una (for the same reason as
1003 * for the normal SACK blocks, explained above). But there all simplicity
1004 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1005 * fully below undo_marker they do not affect behavior in anyway and can
1006 * therefore be safely ignored. In rare cases (which are more or less
1007 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1008 * fragmentation and packet reordering past skb's retransmission. To consider
1009 * them correctly, the acceptable range must be extended even more though
1010 * the exact amount is rather hard to quantify. However, tp->max_window can
1011 * be used as an exaggerated estimate.
1013 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
1014 u32 start_seq
, u32 end_seq
)
1016 /* Too far in future, or reversed (interpretation is ambiguous) */
1017 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1020 /* Nasty start_seq wrap-around check (see comments above) */
1021 if (!before(start_seq
, tp
->snd_nxt
))
1024 /* In outstanding window? ...This is valid exit for D-SACKs too.
1025 * start_seq == snd_una is non-sensical (see comments above)
1027 if (after(start_seq
, tp
->snd_una
))
1030 if (!is_dsack
|| !tp
->undo_marker
)
1033 /* ...Then it's D-SACK, and must reside below snd_una completely */
1034 if (after(end_seq
, tp
->snd_una
))
1037 if (!before(start_seq
, tp
->undo_marker
))
1041 if (!after(end_seq
, tp
->undo_marker
))
1044 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1045 * start_seq < undo_marker and end_seq >= undo_marker.
1047 return !before(start_seq
, end_seq
- tp
->max_window
);
1050 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1051 * Event "B". Later note: FACK people cheated me again 8), we have to account
1052 * for reordering! Ugly, but should help.
1054 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1055 * less than what is now known to be received by the other end (derived from
1056 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1057 * retransmitted skbs to avoid some costly processing per ACKs.
1059 static void tcp_mark_lost_retrans(struct sock
*sk
, int *flag
)
1061 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1062 struct tcp_sock
*tp
= tcp_sk(sk
);
1063 struct sk_buff
*skb
;
1065 u32 new_low_seq
= tp
->snd_nxt
;
1066 u32 received_upto
= tcp_highest_sack_seq(tp
);
1068 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1069 !after(received_upto
, tp
->lost_retrans_low
) ||
1070 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1073 tcp_for_write_queue(skb
, sk
) {
1074 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1076 if (skb
== tcp_send_head(sk
))
1078 if (cnt
== tp
->retrans_out
)
1080 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1083 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1086 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1087 * constraint here (see above) but figuring out that at
1088 * least tp->reordering SACK blocks reside between ack_seq
1089 * and received_upto is not easy task to do cheaply with
1090 * the available datastructures.
1092 * Whether FACK should check here for tp->reordering segs
1093 * in-between one could argue for either way (it would be
1094 * rather simple to implement as we could count fack_count
1095 * during the walk and do tp->fackets_out - fack_count).
1097 if (after(received_upto
, ack_seq
)) {
1098 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1099 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1100 *flag
|= FLAG_LOST_RETRANS
;
1101 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1102 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1104 if (before(ack_seq
, new_low_seq
))
1105 new_low_seq
= ack_seq
;
1106 cnt
+= tcp_skb_pcount(skb
);
1110 if (tp
->retrans_out
)
1111 tp
->lost_retrans_low
= new_low_seq
;
1114 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1115 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1118 struct tcp_sock
*tp
= tcp_sk(sk
);
1119 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1120 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1121 bool dup_sack
= false;
1123 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1126 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1127 } else if (num_sacks
> 1) {
1128 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1129 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1131 if (!after(end_seq_0
, end_seq_1
) &&
1132 !before(start_seq_0
, start_seq_1
)) {
1135 NET_INC_STATS_BH(sock_net(sk
),
1136 LINUX_MIB_TCPDSACKOFORECV
);
1140 /* D-SACK for already forgotten data... Do dumb counting. */
1141 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1142 !after(end_seq_0
, prior_snd_una
) &&
1143 after(end_seq_0
, tp
->undo_marker
))
1149 struct tcp_sacktag_state
{
1152 /* Timestamps for earliest and latest never-retransmitted segment
1153 * that was SACKed. RTO needs the earliest RTT to stay conservative,
1154 * but congestion control should still get an accurate delay signal.
1156 struct skb_mstamp first_sackt
;
1157 struct skb_mstamp last_sackt
;
1161 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1162 * the incoming SACK may not exactly match but we can find smaller MSS
1163 * aligned portion of it that matches. Therefore we might need to fragment
1164 * which may fail and creates some hassle (caller must handle error case
1167 * FIXME: this could be merged to shift decision code
1169 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1170 u32 start_seq
, u32 end_seq
)
1174 unsigned int pkt_len
;
1177 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1178 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1180 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1181 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1182 mss
= tcp_skb_mss(skb
);
1183 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1186 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1190 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1195 /* Round if necessary so that SACKs cover only full MSSes
1196 * and/or the remaining small portion (if present)
1198 if (pkt_len
> mss
) {
1199 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1200 if (!in_sack
&& new_len
< pkt_len
) {
1202 if (new_len
>= skb
->len
)
1207 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
, GFP_ATOMIC
);
1215 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1216 static u8
tcp_sacktag_one(struct sock
*sk
,
1217 struct tcp_sacktag_state
*state
, u8 sacked
,
1218 u32 start_seq
, u32 end_seq
,
1219 int dup_sack
, int pcount
,
1220 const struct skb_mstamp
*xmit_time
)
1222 struct tcp_sock
*tp
= tcp_sk(sk
);
1223 int fack_count
= state
->fack_count
;
1225 /* Account D-SACK for retransmitted packet. */
1226 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1227 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1228 after(end_seq
, tp
->undo_marker
))
1230 if (sacked
& TCPCB_SACKED_ACKED
)
1231 state
->reord
= min(fack_count
, state
->reord
);
1234 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1235 if (!after(end_seq
, tp
->snd_una
))
1238 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1239 if (sacked
& TCPCB_SACKED_RETRANS
) {
1240 /* If the segment is not tagged as lost,
1241 * we do not clear RETRANS, believing
1242 * that retransmission is still in flight.
1244 if (sacked
& TCPCB_LOST
) {
1245 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1246 tp
->lost_out
-= pcount
;
1247 tp
->retrans_out
-= pcount
;
1250 if (!(sacked
& TCPCB_RETRANS
)) {
1251 /* New sack for not retransmitted frame,
1252 * which was in hole. It is reordering.
1254 if (before(start_seq
,
1255 tcp_highest_sack_seq(tp
)))
1256 state
->reord
= min(fack_count
,
1258 if (!after(end_seq
, tp
->high_seq
))
1259 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1260 if (state
->first_sackt
.v64
== 0)
1261 state
->first_sackt
= *xmit_time
;
1262 state
->last_sackt
= *xmit_time
;
1265 if (sacked
& TCPCB_LOST
) {
1266 sacked
&= ~TCPCB_LOST
;
1267 tp
->lost_out
-= pcount
;
1271 sacked
|= TCPCB_SACKED_ACKED
;
1272 state
->flag
|= FLAG_DATA_SACKED
;
1273 tp
->sacked_out
+= pcount
;
1275 fack_count
+= pcount
;
1277 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1278 if (!tcp_is_fack(tp
) && tp
->lost_skb_hint
&&
1279 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1280 tp
->lost_cnt_hint
+= pcount
;
1282 if (fack_count
> tp
->fackets_out
)
1283 tp
->fackets_out
= fack_count
;
1286 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1287 * frames and clear it. undo_retrans is decreased above, L|R frames
1288 * are accounted above as well.
1290 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1291 sacked
&= ~TCPCB_SACKED_RETRANS
;
1292 tp
->retrans_out
-= pcount
;
1298 /* Shift newly-SACKed bytes from this skb to the immediately previous
1299 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1301 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1302 struct tcp_sacktag_state
*state
,
1303 unsigned int pcount
, int shifted
, int mss
,
1306 struct tcp_sock
*tp
= tcp_sk(sk
);
1307 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1308 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1309 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1313 /* Adjust counters and hints for the newly sacked sequence
1314 * range but discard the return value since prev is already
1315 * marked. We must tag the range first because the seq
1316 * advancement below implicitly advances
1317 * tcp_highest_sack_seq() when skb is highest_sack.
1319 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1320 start_seq
, end_seq
, dup_sack
, pcount
,
1323 if (skb
== tp
->lost_skb_hint
)
1324 tp
->lost_cnt_hint
+= pcount
;
1326 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1327 TCP_SKB_CB(skb
)->seq
+= shifted
;
1329 tcp_skb_pcount_add(prev
, pcount
);
1330 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1331 tcp_skb_pcount_add(skb
, -pcount
);
1333 /* When we're adding to gso_segs == 1, gso_size will be zero,
1334 * in theory this shouldn't be necessary but as long as DSACK
1335 * code can come after this skb later on it's better to keep
1336 * setting gso_size to something.
1338 if (!TCP_SKB_CB(prev
)->tcp_gso_size
)
1339 TCP_SKB_CB(prev
)->tcp_gso_size
= mss
;
1341 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1342 if (tcp_skb_pcount(skb
) <= 1)
1343 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1345 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1346 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1349 BUG_ON(!tcp_skb_pcount(skb
));
1350 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1354 /* Whole SKB was eaten :-) */
1356 if (skb
== tp
->retransmit_skb_hint
)
1357 tp
->retransmit_skb_hint
= prev
;
1358 if (skb
== tp
->lost_skb_hint
) {
1359 tp
->lost_skb_hint
= prev
;
1360 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1363 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1364 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1365 TCP_SKB_CB(prev
)->end_seq
++;
1367 if (skb
== tcp_highest_sack(sk
))
1368 tcp_advance_highest_sack(sk
, skb
);
1370 tcp_unlink_write_queue(skb
, sk
);
1371 sk_wmem_free_skb(sk
, skb
);
1373 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1378 /* I wish gso_size would have a bit more sane initialization than
1379 * something-or-zero which complicates things
1381 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1383 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1386 /* Shifting pages past head area doesn't work */
1387 static int skb_can_shift(const struct sk_buff
*skb
)
1389 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1392 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1395 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1396 struct tcp_sacktag_state
*state
,
1397 u32 start_seq
, u32 end_seq
,
1400 struct tcp_sock
*tp
= tcp_sk(sk
);
1401 struct sk_buff
*prev
;
1407 if (!sk_can_gso(sk
))
1410 /* Normally R but no L won't result in plain S */
1412 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1414 if (!skb_can_shift(skb
))
1416 /* This frame is about to be dropped (was ACKed). */
1417 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1420 /* Can only happen with delayed DSACK + discard craziness */
1421 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1423 prev
= tcp_write_queue_prev(sk
, skb
);
1425 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1428 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1429 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1433 pcount
= tcp_skb_pcount(skb
);
1434 mss
= tcp_skb_seglen(skb
);
1436 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1437 * drop this restriction as unnecessary
1439 if (mss
!= tcp_skb_seglen(prev
))
1442 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1444 /* CHECKME: This is non-MSS split case only?, this will
1445 * cause skipped skbs due to advancing loop btw, original
1446 * has that feature too
1448 if (tcp_skb_pcount(skb
) <= 1)
1451 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1453 /* TODO: head merge to next could be attempted here
1454 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1455 * though it might not be worth of the additional hassle
1457 * ...we can probably just fallback to what was done
1458 * previously. We could try merging non-SACKed ones
1459 * as well but it probably isn't going to buy off
1460 * because later SACKs might again split them, and
1461 * it would make skb timestamp tracking considerably
1467 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1469 BUG_ON(len
> skb
->len
);
1471 /* MSS boundaries should be honoured or else pcount will
1472 * severely break even though it makes things bit trickier.
1473 * Optimize common case to avoid most of the divides
1475 mss
= tcp_skb_mss(skb
);
1477 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1478 * drop this restriction as unnecessary
1480 if (mss
!= tcp_skb_seglen(prev
))
1485 } else if (len
< mss
) {
1493 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1494 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1497 if (!skb_shift(prev
, skb
, len
))
1499 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1502 /* Hole filled allows collapsing with the next as well, this is very
1503 * useful when hole on every nth skb pattern happens
1505 if (prev
== tcp_write_queue_tail(sk
))
1507 skb
= tcp_write_queue_next(sk
, prev
);
1509 if (!skb_can_shift(skb
) ||
1510 (skb
== tcp_send_head(sk
)) ||
1511 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1512 (mss
!= tcp_skb_seglen(skb
)))
1516 if (skb_shift(prev
, skb
, len
)) {
1517 pcount
+= tcp_skb_pcount(skb
);
1518 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1522 state
->fack_count
+= pcount
;
1529 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1533 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1534 struct tcp_sack_block
*next_dup
,
1535 struct tcp_sacktag_state
*state
,
1536 u32 start_seq
, u32 end_seq
,
1539 struct tcp_sock
*tp
= tcp_sk(sk
);
1540 struct sk_buff
*tmp
;
1542 tcp_for_write_queue_from(skb
, sk
) {
1544 bool dup_sack
= dup_sack_in
;
1546 if (skb
== tcp_send_head(sk
))
1549 /* queue is in-order => we can short-circuit the walk early */
1550 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1554 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1555 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1556 next_dup
->start_seq
,
1562 /* skb reference here is a bit tricky to get right, since
1563 * shifting can eat and free both this skb and the next,
1564 * so not even _safe variant of the loop is enough.
1567 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1568 start_seq
, end_seq
, dup_sack
);
1577 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1583 if (unlikely(in_sack
< 0))
1587 TCP_SKB_CB(skb
)->sacked
=
1590 TCP_SKB_CB(skb
)->sacked
,
1591 TCP_SKB_CB(skb
)->seq
,
1592 TCP_SKB_CB(skb
)->end_seq
,
1594 tcp_skb_pcount(skb
),
1597 if (!before(TCP_SKB_CB(skb
)->seq
,
1598 tcp_highest_sack_seq(tp
)))
1599 tcp_advance_highest_sack(sk
, skb
);
1602 state
->fack_count
+= tcp_skb_pcount(skb
);
1607 /* Avoid all extra work that is being done by sacktag while walking in
1610 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1611 struct tcp_sacktag_state
*state
,
1614 tcp_for_write_queue_from(skb
, sk
) {
1615 if (skb
== tcp_send_head(sk
))
1618 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1621 state
->fack_count
+= tcp_skb_pcount(skb
);
1626 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1628 struct tcp_sack_block
*next_dup
,
1629 struct tcp_sacktag_state
*state
,
1635 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1636 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1637 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1638 next_dup
->start_seq
, next_dup
->end_seq
,
1645 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1647 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1651 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1652 u32 prior_snd_una
, struct tcp_sacktag_state
*state
)
1654 struct tcp_sock
*tp
= tcp_sk(sk
);
1655 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1656 TCP_SKB_CB(ack_skb
)->sacked
);
1657 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1658 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1659 struct tcp_sack_block
*cache
;
1660 struct sk_buff
*skb
;
1661 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1663 bool found_dup_sack
= false;
1665 int first_sack_index
;
1668 state
->reord
= tp
->packets_out
;
1670 if (!tp
->sacked_out
) {
1671 if (WARN_ON(tp
->fackets_out
))
1672 tp
->fackets_out
= 0;
1673 tcp_highest_sack_reset(sk
);
1676 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1677 num_sacks
, prior_snd_una
);
1679 state
->flag
|= FLAG_DSACKING_ACK
;
1681 /* Eliminate too old ACKs, but take into
1682 * account more or less fresh ones, they can
1683 * contain valid SACK info.
1685 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1688 if (!tp
->packets_out
)
1692 first_sack_index
= 0;
1693 for (i
= 0; i
< num_sacks
; i
++) {
1694 bool dup_sack
= !i
&& found_dup_sack
;
1696 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1697 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1699 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1700 sp
[used_sacks
].start_seq
,
1701 sp
[used_sacks
].end_seq
)) {
1705 if (!tp
->undo_marker
)
1706 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1708 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1710 /* Don't count olds caused by ACK reordering */
1711 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1712 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1714 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1717 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1719 first_sack_index
= -1;
1723 /* Ignore very old stuff early */
1724 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1730 /* order SACK blocks to allow in order walk of the retrans queue */
1731 for (i
= used_sacks
- 1; i
> 0; i
--) {
1732 for (j
= 0; j
< i
; j
++) {
1733 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1734 swap(sp
[j
], sp
[j
+ 1]);
1736 /* Track where the first SACK block goes to */
1737 if (j
== first_sack_index
)
1738 first_sack_index
= j
+ 1;
1743 skb
= tcp_write_queue_head(sk
);
1744 state
->fack_count
= 0;
1747 if (!tp
->sacked_out
) {
1748 /* It's already past, so skip checking against it */
1749 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1751 cache
= tp
->recv_sack_cache
;
1752 /* Skip empty blocks in at head of the cache */
1753 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1758 while (i
< used_sacks
) {
1759 u32 start_seq
= sp
[i
].start_seq
;
1760 u32 end_seq
= sp
[i
].end_seq
;
1761 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1762 struct tcp_sack_block
*next_dup
= NULL
;
1764 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1765 next_dup
= &sp
[i
+ 1];
1767 /* Skip too early cached blocks */
1768 while (tcp_sack_cache_ok(tp
, cache
) &&
1769 !before(start_seq
, cache
->end_seq
))
1772 /* Can skip some work by looking recv_sack_cache? */
1773 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1774 after(end_seq
, cache
->start_seq
)) {
1777 if (before(start_seq
, cache
->start_seq
)) {
1778 skb
= tcp_sacktag_skip(skb
, sk
, state
,
1780 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1787 /* Rest of the block already fully processed? */
1788 if (!after(end_seq
, cache
->end_seq
))
1791 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1795 /* ...tail remains todo... */
1796 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1797 /* ...but better entrypoint exists! */
1798 skb
= tcp_highest_sack(sk
);
1801 state
->fack_count
= tp
->fackets_out
;
1806 skb
= tcp_sacktag_skip(skb
, sk
, state
, cache
->end_seq
);
1807 /* Check overlap against next cached too (past this one already) */
1812 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1813 skb
= tcp_highest_sack(sk
);
1816 state
->fack_count
= tp
->fackets_out
;
1818 skb
= tcp_sacktag_skip(skb
, sk
, state
, start_seq
);
1821 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, state
,
1822 start_seq
, end_seq
, dup_sack
);
1828 /* Clear the head of the cache sack blocks so we can skip it next time */
1829 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1830 tp
->recv_sack_cache
[i
].start_seq
= 0;
1831 tp
->recv_sack_cache
[i
].end_seq
= 0;
1833 for (j
= 0; j
< used_sacks
; j
++)
1834 tp
->recv_sack_cache
[i
++] = sp
[j
];
1836 if ((state
->reord
< tp
->fackets_out
) &&
1837 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1838 tcp_update_reordering(sk
, tp
->fackets_out
- state
->reord
, 0);
1840 tcp_mark_lost_retrans(sk
, &state
->flag
);
1841 tcp_verify_left_out(tp
);
1844 #if FASTRETRANS_DEBUG > 0
1845 WARN_ON((int)tp
->sacked_out
< 0);
1846 WARN_ON((int)tp
->lost_out
< 0);
1847 WARN_ON((int)tp
->retrans_out
< 0);
1848 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1853 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1854 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1856 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1860 holes
= max(tp
->lost_out
, 1U);
1861 holes
= min(holes
, tp
->packets_out
);
1863 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1864 tp
->sacked_out
= tp
->packets_out
- holes
;
1870 /* If we receive more dupacks than we expected counting segments
1871 * in assumption of absent reordering, interpret this as reordering.
1872 * The only another reason could be bug in receiver TCP.
1874 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1876 struct tcp_sock
*tp
= tcp_sk(sk
);
1877 if (tcp_limit_reno_sacked(tp
))
1878 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1881 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1883 static void tcp_add_reno_sack(struct sock
*sk
)
1885 struct tcp_sock
*tp
= tcp_sk(sk
);
1887 tcp_check_reno_reordering(sk
, 0);
1888 tcp_verify_left_out(tp
);
1891 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1893 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1895 struct tcp_sock
*tp
= tcp_sk(sk
);
1898 /* One ACK acked hole. The rest eat duplicate ACKs. */
1899 if (acked
- 1 >= tp
->sacked_out
)
1902 tp
->sacked_out
-= acked
- 1;
1904 tcp_check_reno_reordering(sk
, acked
);
1905 tcp_verify_left_out(tp
);
1908 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1913 void tcp_clear_retrans(struct tcp_sock
*tp
)
1915 tp
->retrans_out
= 0;
1917 tp
->undo_marker
= 0;
1918 tp
->undo_retrans
= -1;
1919 tp
->fackets_out
= 0;
1923 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1925 tp
->undo_marker
= tp
->snd_una
;
1926 /* Retransmission still in flight may cause DSACKs later. */
1927 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1930 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1931 * and reset tags completely, otherwise preserve SACKs. If receiver
1932 * dropped its ofo queue, we will know this due to reneging detection.
1934 void tcp_enter_loss(struct sock
*sk
)
1936 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1937 struct tcp_sock
*tp
= tcp_sk(sk
);
1938 struct sk_buff
*skb
;
1939 bool new_recovery
= icsk
->icsk_ca_state
< TCP_CA_Recovery
;
1940 bool is_reneg
; /* is receiver reneging on SACKs? */
1942 /* Reduce ssthresh if it has not yet been made inside this window. */
1943 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1944 !after(tp
->high_seq
, tp
->snd_una
) ||
1945 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1946 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1947 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1948 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1952 tp
->snd_cwnd_cnt
= 0;
1953 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1955 tp
->retrans_out
= 0;
1958 if (tcp_is_reno(tp
))
1959 tcp_reset_reno_sack(tp
);
1961 skb
= tcp_write_queue_head(sk
);
1962 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1964 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1966 tp
->fackets_out
= 0;
1968 tcp_clear_all_retrans_hints(tp
);
1970 tcp_for_write_queue(skb
, sk
) {
1971 if (skb
== tcp_send_head(sk
))
1974 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1975 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || is_reneg
) {
1976 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1977 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1978 tp
->lost_out
+= tcp_skb_pcount(skb
);
1979 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1982 tcp_verify_left_out(tp
);
1984 /* Timeout in disordered state after receiving substantial DUPACKs
1985 * suggests that the degree of reordering is over-estimated.
1987 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1988 tp
->sacked_out
>= sysctl_tcp_reordering
)
1989 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1990 sysctl_tcp_reordering
);
1991 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1992 tp
->high_seq
= tp
->snd_nxt
;
1993 tcp_ecn_queue_cwr(tp
);
1995 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1996 * loss recovery is underway except recurring timeout(s) on
1997 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1999 tp
->frto
= sysctl_tcp_frto
&&
2000 (new_recovery
|| icsk
->icsk_retransmits
) &&
2001 !inet_csk(sk
)->icsk_mtup
.probe_size
;
2004 /* If ACK arrived pointing to a remembered SACK, it means that our
2005 * remembered SACKs do not reflect real state of receiver i.e.
2006 * receiver _host_ is heavily congested (or buggy).
2008 * To avoid big spurious retransmission bursts due to transient SACK
2009 * scoreboard oddities that look like reneging, we give the receiver a
2010 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2011 * restore sanity to the SACK scoreboard. If the apparent reneging
2012 * persists until this RTO then we'll clear the SACK scoreboard.
2014 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2016 if (flag
& FLAG_SACK_RENEGING
) {
2017 struct tcp_sock
*tp
= tcp_sk(sk
);
2018 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2019 msecs_to_jiffies(10));
2021 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2022 delay
, TCP_RTO_MAX
);
2028 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2030 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2033 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2034 * counter when SACK is enabled (without SACK, sacked_out is used for
2037 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2038 * segments up to the highest received SACK block so far and holes in
2041 * With reordering, holes may still be in flight, so RFC3517 recovery
2042 * uses pure sacked_out (total number of SACKed segments) even though
2043 * it violates the RFC that uses duplicate ACKs, often these are equal
2044 * but when e.g. out-of-window ACKs or packet duplication occurs,
2045 * they differ. Since neither occurs due to loss, TCP should really
2048 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2050 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2053 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2055 struct tcp_sock
*tp
= tcp_sk(sk
);
2056 unsigned long delay
;
2058 /* Delay early retransmit and entering fast recovery for
2059 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2060 * available, or RTO is scheduled to fire first.
2062 if (sysctl_tcp_early_retrans
< 2 || sysctl_tcp_early_retrans
> 3 ||
2063 (flag
& FLAG_ECE
) || !tp
->srtt_us
)
2066 delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 5),
2067 msecs_to_jiffies(2));
2069 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2072 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_EARLY_RETRANS
, delay
,
2077 /* Linux NewReno/SACK/FACK/ECN state machine.
2078 * --------------------------------------
2080 * "Open" Normal state, no dubious events, fast path.
2081 * "Disorder" In all the respects it is "Open",
2082 * but requires a bit more attention. It is entered when
2083 * we see some SACKs or dupacks. It is split of "Open"
2084 * mainly to move some processing from fast path to slow one.
2085 * "CWR" CWND was reduced due to some Congestion Notification event.
2086 * It can be ECN, ICMP source quench, local device congestion.
2087 * "Recovery" CWND was reduced, we are fast-retransmitting.
2088 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2090 * tcp_fastretrans_alert() is entered:
2091 * - each incoming ACK, if state is not "Open"
2092 * - when arrived ACK is unusual, namely:
2097 * Counting packets in flight is pretty simple.
2099 * in_flight = packets_out - left_out + retrans_out
2101 * packets_out is SND.NXT-SND.UNA counted in packets.
2103 * retrans_out is number of retransmitted segments.
2105 * left_out is number of segments left network, but not ACKed yet.
2107 * left_out = sacked_out + lost_out
2109 * sacked_out: Packets, which arrived to receiver out of order
2110 * and hence not ACKed. With SACKs this number is simply
2111 * amount of SACKed data. Even without SACKs
2112 * it is easy to give pretty reliable estimate of this number,
2113 * counting duplicate ACKs.
2115 * lost_out: Packets lost by network. TCP has no explicit
2116 * "loss notification" feedback from network (for now).
2117 * It means that this number can be only _guessed_.
2118 * Actually, it is the heuristics to predict lossage that
2119 * distinguishes different algorithms.
2121 * F.e. after RTO, when all the queue is considered as lost,
2122 * lost_out = packets_out and in_flight = retrans_out.
2124 * Essentially, we have now two algorithms counting
2127 * FACK: It is the simplest heuristics. As soon as we decided
2128 * that something is lost, we decide that _all_ not SACKed
2129 * packets until the most forward SACK are lost. I.e.
2130 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2131 * It is absolutely correct estimate, if network does not reorder
2132 * packets. And it loses any connection to reality when reordering
2133 * takes place. We use FACK by default until reordering
2134 * is suspected on the path to this destination.
2136 * NewReno: when Recovery is entered, we assume that one segment
2137 * is lost (classic Reno). While we are in Recovery and
2138 * a partial ACK arrives, we assume that one more packet
2139 * is lost (NewReno). This heuristics are the same in NewReno
2142 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2143 * deflation etc. CWND is real congestion window, never inflated, changes
2144 * only according to classic VJ rules.
2146 * Really tricky (and requiring careful tuning) part of algorithm
2147 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2148 * The first determines the moment _when_ we should reduce CWND and,
2149 * hence, slow down forward transmission. In fact, it determines the moment
2150 * when we decide that hole is caused by loss, rather than by a reorder.
2152 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2153 * holes, caused by lost packets.
2155 * And the most logically complicated part of algorithm is undo
2156 * heuristics. We detect false retransmits due to both too early
2157 * fast retransmit (reordering) and underestimated RTO, analyzing
2158 * timestamps and D-SACKs. When we detect that some segments were
2159 * retransmitted by mistake and CWND reduction was wrong, we undo
2160 * window reduction and abort recovery phase. This logic is hidden
2161 * inside several functions named tcp_try_undo_<something>.
2164 /* This function decides, when we should leave Disordered state
2165 * and enter Recovery phase, reducing congestion window.
2167 * Main question: may we further continue forward transmission
2168 * with the same cwnd?
2170 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2172 struct tcp_sock
*tp
= tcp_sk(sk
);
2175 /* Trick#1: The loss is proven. */
2179 /* Not-A-Trick#2 : Classic rule... */
2180 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2183 /* Trick#4: It is still not OK... But will it be useful to delay
2186 packets_out
= tp
->packets_out
;
2187 if (packets_out
<= tp
->reordering
&&
2188 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2189 !tcp_may_send_now(sk
)) {
2190 /* We have nothing to send. This connection is limited
2191 * either by receiver window or by application.
2196 /* If a thin stream is detected, retransmit after first
2197 * received dupack. Employ only if SACK is supported in order
2198 * to avoid possible corner-case series of spurious retransmissions
2199 * Use only if there are no unsent data.
2201 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2202 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2203 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2206 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2207 * retransmissions due to small network reorderings, we implement
2208 * Mitigation A.3 in the RFC and delay the retransmission for a short
2209 * interval if appropriate.
2211 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2212 (tp
->packets_out
>= (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2213 !tcp_may_send_now(sk
))
2214 return !tcp_pause_early_retransmit(sk
, flag
);
2219 /* Detect loss in event "A" above by marking head of queue up as lost.
2220 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2221 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2222 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2223 * the maximum SACKed segments to pass before reaching this limit.
2225 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2227 struct tcp_sock
*tp
= tcp_sk(sk
);
2228 struct sk_buff
*skb
;
2232 /* Use SACK to deduce losses of new sequences sent during recovery */
2233 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2235 WARN_ON(packets
> tp
->packets_out
);
2236 if (tp
->lost_skb_hint
) {
2237 skb
= tp
->lost_skb_hint
;
2238 cnt
= tp
->lost_cnt_hint
;
2239 /* Head already handled? */
2240 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2243 skb
= tcp_write_queue_head(sk
);
2247 tcp_for_write_queue_from(skb
, sk
) {
2248 if (skb
== tcp_send_head(sk
))
2250 /* TODO: do this better */
2251 /* this is not the most efficient way to do this... */
2252 tp
->lost_skb_hint
= skb
;
2253 tp
->lost_cnt_hint
= cnt
;
2255 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2259 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2260 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2261 cnt
+= tcp_skb_pcount(skb
);
2263 if (cnt
> packets
) {
2264 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2265 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2266 (oldcnt
>= packets
))
2269 mss
= tcp_skb_mss(skb
);
2270 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
,
2277 tcp_skb_mark_lost(tp
, skb
);
2282 tcp_verify_left_out(tp
);
2285 /* Account newly detected lost packet(s) */
2287 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2289 struct tcp_sock
*tp
= tcp_sk(sk
);
2291 if (tcp_is_reno(tp
)) {
2292 tcp_mark_head_lost(sk
, 1, 1);
2293 } else if (tcp_is_fack(tp
)) {
2294 int lost
= tp
->fackets_out
- tp
->reordering
;
2297 tcp_mark_head_lost(sk
, lost
, 0);
2299 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2300 if (sacked_upto
>= 0)
2301 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2302 else if (fast_rexmit
)
2303 tcp_mark_head_lost(sk
, 1, 1);
2307 /* CWND moderation, preventing bursts due to too big ACKs
2308 * in dubious situations.
2310 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2312 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2313 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2314 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2317 /* Nothing was retransmitted or returned timestamp is less
2318 * than timestamp of the first retransmission.
2320 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2322 return !tp
->retrans_stamp
||
2323 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2324 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2327 /* Undo procedures. */
2329 /* We can clear retrans_stamp when there are no retransmissions in the
2330 * window. It would seem that it is trivially available for us in
2331 * tp->retrans_out, however, that kind of assumptions doesn't consider
2332 * what will happen if errors occur when sending retransmission for the
2333 * second time. ...It could the that such segment has only
2334 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2335 * the head skb is enough except for some reneging corner cases that
2336 * are not worth the effort.
2338 * Main reason for all this complexity is the fact that connection dying
2339 * time now depends on the validity of the retrans_stamp, in particular,
2340 * that successive retransmissions of a segment must not advance
2341 * retrans_stamp under any conditions.
2343 static bool tcp_any_retrans_done(const struct sock
*sk
)
2345 const struct tcp_sock
*tp
= tcp_sk(sk
);
2346 struct sk_buff
*skb
;
2348 if (tp
->retrans_out
)
2351 skb
= tcp_write_queue_head(sk
);
2352 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2358 #if FASTRETRANS_DEBUG > 1
2359 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2361 struct tcp_sock
*tp
= tcp_sk(sk
);
2362 struct inet_sock
*inet
= inet_sk(sk
);
2364 if (sk
->sk_family
== AF_INET
) {
2365 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2367 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2368 tp
->snd_cwnd
, tcp_left_out(tp
),
2369 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2372 #if IS_ENABLED(CONFIG_IPV6)
2373 else if (sk
->sk_family
== AF_INET6
) {
2374 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2375 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2377 &np
->daddr
, ntohs(inet
->inet_dport
),
2378 tp
->snd_cwnd
, tcp_left_out(tp
),
2379 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2385 #define DBGUNDO(x...) do { } while (0)
2388 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2390 struct tcp_sock
*tp
= tcp_sk(sk
);
2393 struct sk_buff
*skb
;
2395 tcp_for_write_queue(skb
, sk
) {
2396 if (skb
== tcp_send_head(sk
))
2398 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2401 tcp_clear_all_retrans_hints(tp
);
2404 if (tp
->prior_ssthresh
) {
2405 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2407 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2408 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2410 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2412 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2413 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2414 tcp_ecn_withdraw_cwr(tp
);
2417 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2419 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2420 tp
->undo_marker
= 0;
2423 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2425 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2428 /* People celebrate: "We love our President!" */
2429 static bool tcp_try_undo_recovery(struct sock
*sk
)
2431 struct tcp_sock
*tp
= tcp_sk(sk
);
2433 if (tcp_may_undo(tp
)) {
2436 /* Happy end! We did not retransmit anything
2437 * or our original transmission succeeded.
2439 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2440 tcp_undo_cwnd_reduction(sk
, false);
2441 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2442 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2444 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2446 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2448 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2449 /* Hold old state until something *above* high_seq
2450 * is ACKed. For Reno it is MUST to prevent false
2451 * fast retransmits (RFC2582). SACK TCP is safe. */
2452 tcp_moderate_cwnd(tp
);
2453 if (!tcp_any_retrans_done(sk
))
2454 tp
->retrans_stamp
= 0;
2457 tcp_set_ca_state(sk
, TCP_CA_Open
);
2461 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2462 static bool tcp_try_undo_dsack(struct sock
*sk
)
2464 struct tcp_sock
*tp
= tcp_sk(sk
);
2466 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2467 DBGUNDO(sk
, "D-SACK");
2468 tcp_undo_cwnd_reduction(sk
, false);
2469 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2475 /* Undo during loss recovery after partial ACK or using F-RTO. */
2476 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2478 struct tcp_sock
*tp
= tcp_sk(sk
);
2480 if (frto_undo
|| tcp_may_undo(tp
)) {
2481 tcp_undo_cwnd_reduction(sk
, true);
2483 DBGUNDO(sk
, "partial loss");
2484 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2486 NET_INC_STATS_BH(sock_net(sk
),
2487 LINUX_MIB_TCPSPURIOUSRTOS
);
2488 inet_csk(sk
)->icsk_retransmits
= 0;
2489 if (frto_undo
|| tcp_is_sack(tp
))
2490 tcp_set_ca_state(sk
, TCP_CA_Open
);
2496 /* The cwnd reduction in CWR and Recovery uses the PRR algorithm in RFC 6937.
2497 * It computes the number of packets to send (sndcnt) based on packets newly
2499 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2500 * cwnd reductions across a full RTT.
2501 * 2) Otherwise PRR uses packet conservation to send as much as delivered.
2502 * But when the retransmits are acked without further losses, PRR
2503 * slow starts cwnd up to ssthresh to speed up the recovery.
2505 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2507 struct tcp_sock
*tp
= tcp_sk(sk
);
2509 tp
->high_seq
= tp
->snd_nxt
;
2510 tp
->tlp_high_seq
= 0;
2511 tp
->snd_cwnd_cnt
= 0;
2512 tp
->prior_cwnd
= tp
->snd_cwnd
;
2513 tp
->prr_delivered
= 0;
2515 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2516 tcp_ecn_queue_cwr(tp
);
2519 static void tcp_cwnd_reduction(struct sock
*sk
, const int prior_unsacked
,
2520 int fast_rexmit
, int flag
)
2522 struct tcp_sock
*tp
= tcp_sk(sk
);
2524 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2525 int newly_acked_sacked
= prior_unsacked
-
2526 (tp
->packets_out
- tp
->sacked_out
);
2528 tp
->prr_delivered
+= newly_acked_sacked
;
2530 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2532 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2533 } else if ((flag
& FLAG_RETRANS_DATA_ACKED
) &&
2534 !(flag
& FLAG_LOST_RETRANS
)) {
2535 sndcnt
= min_t(int, delta
,
2536 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2537 newly_acked_sacked
) + 1);
2539 sndcnt
= min(delta
, newly_acked_sacked
);
2541 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
2542 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2545 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2547 struct tcp_sock
*tp
= tcp_sk(sk
);
2549 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2550 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
||
2551 (tp
->undo_marker
&& tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
)) {
2552 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2553 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2555 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2558 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2559 void tcp_enter_cwr(struct sock
*sk
)
2561 struct tcp_sock
*tp
= tcp_sk(sk
);
2563 tp
->prior_ssthresh
= 0;
2564 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2565 tp
->undo_marker
= 0;
2566 tcp_init_cwnd_reduction(sk
);
2567 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2570 EXPORT_SYMBOL(tcp_enter_cwr
);
2572 static void tcp_try_keep_open(struct sock
*sk
)
2574 struct tcp_sock
*tp
= tcp_sk(sk
);
2575 int state
= TCP_CA_Open
;
2577 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2578 state
= TCP_CA_Disorder
;
2580 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2581 tcp_set_ca_state(sk
, state
);
2582 tp
->high_seq
= tp
->snd_nxt
;
2586 static void tcp_try_to_open(struct sock
*sk
, int flag
, const int prior_unsacked
)
2588 struct tcp_sock
*tp
= tcp_sk(sk
);
2590 tcp_verify_left_out(tp
);
2592 if (!tcp_any_retrans_done(sk
))
2593 tp
->retrans_stamp
= 0;
2595 if (flag
& FLAG_ECE
)
2598 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2599 tcp_try_keep_open(sk
);
2601 tcp_cwnd_reduction(sk
, prior_unsacked
, 0, flag
);
2605 static void tcp_mtup_probe_failed(struct sock
*sk
)
2607 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2609 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2610 icsk
->icsk_mtup
.probe_size
= 0;
2611 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPMTUPFAIL
);
2614 static void tcp_mtup_probe_success(struct sock
*sk
)
2616 struct tcp_sock
*tp
= tcp_sk(sk
);
2617 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2619 /* FIXME: breaks with very large cwnd */
2620 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2621 tp
->snd_cwnd
= tp
->snd_cwnd
*
2622 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2623 icsk
->icsk_mtup
.probe_size
;
2624 tp
->snd_cwnd_cnt
= 0;
2625 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2626 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2628 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2629 icsk
->icsk_mtup
.probe_size
= 0;
2630 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2631 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPMTUPSUCCESS
);
2634 /* Do a simple retransmit without using the backoff mechanisms in
2635 * tcp_timer. This is used for path mtu discovery.
2636 * The socket is already locked here.
2638 void tcp_simple_retransmit(struct sock
*sk
)
2640 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2641 struct tcp_sock
*tp
= tcp_sk(sk
);
2642 struct sk_buff
*skb
;
2643 unsigned int mss
= tcp_current_mss(sk
);
2644 u32 prior_lost
= tp
->lost_out
;
2646 tcp_for_write_queue(skb
, sk
) {
2647 if (skb
== tcp_send_head(sk
))
2649 if (tcp_skb_seglen(skb
) > mss
&&
2650 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2651 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2652 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2653 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2655 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2659 tcp_clear_retrans_hints_partial(tp
);
2661 if (prior_lost
== tp
->lost_out
)
2664 if (tcp_is_reno(tp
))
2665 tcp_limit_reno_sacked(tp
);
2667 tcp_verify_left_out(tp
);
2669 /* Don't muck with the congestion window here.
2670 * Reason is that we do not increase amount of _data_
2671 * in network, but units changed and effective
2672 * cwnd/ssthresh really reduced now.
2674 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2675 tp
->high_seq
= tp
->snd_nxt
;
2676 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2677 tp
->prior_ssthresh
= 0;
2678 tp
->undo_marker
= 0;
2679 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2681 tcp_xmit_retransmit_queue(sk
);
2683 EXPORT_SYMBOL(tcp_simple_retransmit
);
2685 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2687 struct tcp_sock
*tp
= tcp_sk(sk
);
2690 if (tcp_is_reno(tp
))
2691 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2693 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2695 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2697 tp
->prior_ssthresh
= 0;
2700 if (!tcp_in_cwnd_reduction(sk
)) {
2702 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2703 tcp_init_cwnd_reduction(sk
);
2705 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2708 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2709 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2711 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
)
2713 struct tcp_sock
*tp
= tcp_sk(sk
);
2714 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2716 if ((flag
& FLAG_SND_UNA_ADVANCED
) &&
2717 tcp_try_undo_loss(sk
, false))
2720 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2721 /* Step 3.b. A timeout is spurious if not all data are
2722 * lost, i.e., never-retransmitted data are (s)acked.
2724 if ((flag
& FLAG_ORIG_SACK_ACKED
) &&
2725 tcp_try_undo_loss(sk
, true))
2728 if (after(tp
->snd_nxt
, tp
->high_seq
)) {
2729 if (flag
& FLAG_DATA_SACKED
|| is_dupack
)
2730 tp
->frto
= 0; /* Step 3.a. loss was real */
2731 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2732 tp
->high_seq
= tp
->snd_nxt
;
2733 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
2735 if (after(tp
->snd_nxt
, tp
->high_seq
))
2736 return; /* Step 2.b */
2742 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2743 tcp_try_undo_recovery(sk
);
2746 if (tcp_is_reno(tp
)) {
2747 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2748 * delivered. Lower inflight to clock out (re)tranmissions.
2750 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2751 tcp_add_reno_sack(sk
);
2752 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2753 tcp_reset_reno_sack(tp
);
2755 tcp_xmit_retransmit_queue(sk
);
2758 /* Undo during fast recovery after partial ACK. */
2759 static bool tcp_try_undo_partial(struct sock
*sk
, const int acked
,
2760 const int prior_unsacked
, int flag
)
2762 struct tcp_sock
*tp
= tcp_sk(sk
);
2764 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2765 /* Plain luck! Hole if filled with delayed
2766 * packet, rather than with a retransmit.
2768 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2770 /* We are getting evidence that the reordering degree is higher
2771 * than we realized. If there are no retransmits out then we
2772 * can undo. Otherwise we clock out new packets but do not
2773 * mark more packets lost or retransmit more.
2775 if (tp
->retrans_out
) {
2776 tcp_cwnd_reduction(sk
, prior_unsacked
, 0, flag
);
2780 if (!tcp_any_retrans_done(sk
))
2781 tp
->retrans_stamp
= 0;
2783 DBGUNDO(sk
, "partial recovery");
2784 tcp_undo_cwnd_reduction(sk
, true);
2785 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2786 tcp_try_keep_open(sk
);
2792 /* Process an event, which can update packets-in-flight not trivially.
2793 * Main goal of this function is to calculate new estimate for left_out,
2794 * taking into account both packets sitting in receiver's buffer and
2795 * packets lost by network.
2797 * Besides that it does CWND reduction, when packet loss is detected
2798 * and changes state of machine.
2800 * It does _not_ decide what to send, it is made in function
2801 * tcp_xmit_retransmit_queue().
2803 static void tcp_fastretrans_alert(struct sock
*sk
, const int acked
,
2804 const int prior_unsacked
,
2805 bool is_dupack
, int flag
)
2807 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2808 struct tcp_sock
*tp
= tcp_sk(sk
);
2809 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2810 (tcp_fackets_out(tp
) > tp
->reordering
));
2811 int fast_rexmit
= 0;
2813 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2815 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2816 tp
->fackets_out
= 0;
2818 /* Now state machine starts.
2819 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2820 if (flag
& FLAG_ECE
)
2821 tp
->prior_ssthresh
= 0;
2823 /* B. In all the states check for reneging SACKs. */
2824 if (tcp_check_sack_reneging(sk
, flag
))
2827 /* C. Check consistency of the current state. */
2828 tcp_verify_left_out(tp
);
2830 /* D. Check state exit conditions. State can be terminated
2831 * when high_seq is ACKed. */
2832 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2833 WARN_ON(tp
->retrans_out
!= 0);
2834 tp
->retrans_stamp
= 0;
2835 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2836 switch (icsk
->icsk_ca_state
) {
2838 /* CWR is to be held something *above* high_seq
2839 * is ACKed for CWR bit to reach receiver. */
2840 if (tp
->snd_una
!= tp
->high_seq
) {
2841 tcp_end_cwnd_reduction(sk
);
2842 tcp_set_ca_state(sk
, TCP_CA_Open
);
2846 case TCP_CA_Recovery
:
2847 if (tcp_is_reno(tp
))
2848 tcp_reset_reno_sack(tp
);
2849 if (tcp_try_undo_recovery(sk
))
2851 tcp_end_cwnd_reduction(sk
);
2856 /* E. Process state. */
2857 switch (icsk
->icsk_ca_state
) {
2858 case TCP_CA_Recovery
:
2859 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2860 if (tcp_is_reno(tp
) && is_dupack
)
2861 tcp_add_reno_sack(sk
);
2863 if (tcp_try_undo_partial(sk
, acked
, prior_unsacked
, flag
))
2865 /* Partial ACK arrived. Force fast retransmit. */
2866 do_lost
= tcp_is_reno(tp
) ||
2867 tcp_fackets_out(tp
) > tp
->reordering
;
2869 if (tcp_try_undo_dsack(sk
)) {
2870 tcp_try_keep_open(sk
);
2875 tcp_process_loss(sk
, flag
, is_dupack
);
2876 if (icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2877 !(flag
& FLAG_LOST_RETRANS
))
2879 /* Change state if cwnd is undone or retransmits are lost */
2881 if (tcp_is_reno(tp
)) {
2882 if (flag
& FLAG_SND_UNA_ADVANCED
)
2883 tcp_reset_reno_sack(tp
);
2885 tcp_add_reno_sack(sk
);
2888 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2889 tcp_try_undo_dsack(sk
);
2891 if (!tcp_time_to_recover(sk
, flag
)) {
2892 tcp_try_to_open(sk
, flag
, prior_unsacked
);
2896 /* MTU probe failure: don't reduce cwnd */
2897 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2898 icsk
->icsk_mtup
.probe_size
&&
2899 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2900 tcp_mtup_probe_failed(sk
);
2901 /* Restores the reduction we did in tcp_mtup_probe() */
2903 tcp_simple_retransmit(sk
);
2907 /* Otherwise enter Recovery state */
2908 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2913 tcp_update_scoreboard(sk
, fast_rexmit
);
2914 tcp_cwnd_reduction(sk
, prior_unsacked
, fast_rexmit
, flag
);
2915 tcp_xmit_retransmit_queue(sk
);
2918 static inline bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2919 long seq_rtt_us
, long sack_rtt_us
)
2921 const struct tcp_sock
*tp
= tcp_sk(sk
);
2923 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2924 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2925 * Karn's algorithm forbids taking RTT if some retransmitted data
2926 * is acked (RFC6298).
2928 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2932 seq_rtt_us
= sack_rtt_us
;
2934 /* RTTM Rule: A TSecr value received in a segment is used to
2935 * update the averaged RTT measurement only if the segment
2936 * acknowledges some new data, i.e., only if it advances the
2937 * left edge of the send window.
2938 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2940 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2942 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
2947 tcp_rtt_estimator(sk
, seq_rtt_us
);
2950 /* RFC6298: only reset backoff on valid RTT measurement. */
2951 inet_csk(sk
)->icsk_backoff
= 0;
2955 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2956 static void tcp_synack_rtt_meas(struct sock
*sk
, const u32 synack_stamp
)
2958 struct tcp_sock
*tp
= tcp_sk(sk
);
2959 long seq_rtt_us
= -1L;
2961 if (synack_stamp
&& !tp
->total_retrans
)
2962 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- synack_stamp
);
2964 /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
2965 * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
2968 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, seq_rtt_us
, -1L);
2971 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2973 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2975 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2976 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2979 /* Restart timer after forward progress on connection.
2980 * RFC2988 recommends to restart timer to now+rto.
2982 void tcp_rearm_rto(struct sock
*sk
)
2984 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2985 struct tcp_sock
*tp
= tcp_sk(sk
);
2987 /* If the retrans timer is currently being used by Fast Open
2988 * for SYN-ACK retrans purpose, stay put.
2990 if (tp
->fastopen_rsk
)
2993 if (!tp
->packets_out
) {
2994 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2996 u32 rto
= inet_csk(sk
)->icsk_rto
;
2997 /* Offset the time elapsed after installing regular RTO */
2998 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
2999 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
3000 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
3001 const u32 rto_time_stamp
=
3002 tcp_skb_timestamp(skb
) + rto
;
3003 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
3004 /* delta may not be positive if the socket is locked
3005 * when the retrans timer fires and is rescheduled.
3010 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
3015 /* This function is called when the delayed ER timer fires. TCP enters
3016 * fast recovery and performs fast-retransmit.
3018 void tcp_resume_early_retransmit(struct sock
*sk
)
3020 struct tcp_sock
*tp
= tcp_sk(sk
);
3024 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3025 if (!tp
->do_early_retrans
)
3028 tcp_enter_recovery(sk
, false);
3029 tcp_update_scoreboard(sk
, 1);
3030 tcp_xmit_retransmit_queue(sk
);
3033 /* If we get here, the whole TSO packet has not been acked. */
3034 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3036 struct tcp_sock
*tp
= tcp_sk(sk
);
3039 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3041 packets_acked
= tcp_skb_pcount(skb
);
3042 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3044 packets_acked
-= tcp_skb_pcount(skb
);
3046 if (packets_acked
) {
3047 BUG_ON(tcp_skb_pcount(skb
) == 0);
3048 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3051 return packets_acked
;
3054 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3057 const struct skb_shared_info
*shinfo
;
3059 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3060 if (likely(!(sk
->sk_tsflags
& SOF_TIMESTAMPING_TX_ACK
)))
3063 shinfo
= skb_shinfo(skb
);
3064 if ((shinfo
->tx_flags
& SKBTX_ACK_TSTAMP
) &&
3065 between(shinfo
->tskey
, prior_snd_una
, tcp_sk(sk
)->snd_una
- 1))
3066 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3069 /* Remove acknowledged frames from the retransmission queue. If our packet
3070 * is before the ack sequence we can discard it as it's confirmed to have
3071 * arrived at the other end.
3073 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3075 struct tcp_sacktag_state
*sack
)
3077 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3078 struct skb_mstamp first_ackt
, last_ackt
, now
;
3079 struct tcp_sock
*tp
= tcp_sk(sk
);
3080 u32 prior_sacked
= tp
->sacked_out
;
3081 u32 reord
= tp
->packets_out
;
3082 bool fully_acked
= true;
3083 long sack_rtt_us
= -1L;
3084 long seq_rtt_us
= -1L;
3085 long ca_rtt_us
= -1L;
3086 struct sk_buff
*skb
;
3093 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3094 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3095 u8 sacked
= scb
->sacked
;
3098 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3100 /* Determine how many packets and what bytes were acked, tso and else */
3101 if (after(scb
->end_seq
, tp
->snd_una
)) {
3102 if (tcp_skb_pcount(skb
) == 1 ||
3103 !after(tp
->snd_una
, scb
->seq
))
3106 acked_pcount
= tcp_tso_acked(sk
, skb
);
3110 fully_acked
= false;
3112 /* Speedup tcp_unlink_write_queue() and next loop */
3113 prefetchw(skb
->next
);
3114 acked_pcount
= tcp_skb_pcount(skb
);
3117 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3118 if (sacked
& TCPCB_SACKED_RETRANS
)
3119 tp
->retrans_out
-= acked_pcount
;
3120 flag
|= FLAG_RETRANS_DATA_ACKED
;
3121 } else if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3122 last_ackt
= skb
->skb_mstamp
;
3123 WARN_ON_ONCE(last_ackt
.v64
== 0);
3124 if (!first_ackt
.v64
)
3125 first_ackt
= last_ackt
;
3127 reord
= min(pkts_acked
, reord
);
3128 if (!after(scb
->end_seq
, tp
->high_seq
))
3129 flag
|= FLAG_ORIG_SACK_ACKED
;
3132 if (sacked
& TCPCB_SACKED_ACKED
)
3133 tp
->sacked_out
-= acked_pcount
;
3134 if (sacked
& TCPCB_LOST
)
3135 tp
->lost_out
-= acked_pcount
;
3137 tp
->packets_out
-= acked_pcount
;
3138 pkts_acked
+= acked_pcount
;
3140 /* Initial outgoing SYN's get put onto the write_queue
3141 * just like anything else we transmit. It is not
3142 * true data, and if we misinform our callers that
3143 * this ACK acks real data, we will erroneously exit
3144 * connection startup slow start one packet too
3145 * quickly. This is severely frowned upon behavior.
3147 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3148 flag
|= FLAG_DATA_ACKED
;
3150 flag
|= FLAG_SYN_ACKED
;
3151 tp
->retrans_stamp
= 0;
3157 tcp_unlink_write_queue(skb
, sk
);
3158 sk_wmem_free_skb(sk
, skb
);
3159 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3160 tp
->retransmit_skb_hint
= NULL
;
3161 if (unlikely(skb
== tp
->lost_skb_hint
))
3162 tp
->lost_skb_hint
= NULL
;
3165 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3166 tp
->snd_up
= tp
->snd_una
;
3168 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3169 flag
|= FLAG_SACK_RENEGING
;
3171 skb_mstamp_get(&now
);
3172 if (likely(first_ackt
.v64
)) {
3173 seq_rtt_us
= skb_mstamp_us_delta(&now
, &first_ackt
);
3174 ca_rtt_us
= skb_mstamp_us_delta(&now
, &last_ackt
);
3176 if (sack
->first_sackt
.v64
) {
3177 sack_rtt_us
= skb_mstamp_us_delta(&now
, &sack
->first_sackt
);
3178 ca_rtt_us
= skb_mstamp_us_delta(&now
, &sack
->last_sackt
);
3181 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
);
3183 if (flag
& FLAG_ACKED
) {
3185 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3186 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3187 tcp_mtup_probe_success(sk
);
3190 if (tcp_is_reno(tp
)) {
3191 tcp_remove_reno_sacks(sk
, pkts_acked
);
3195 /* Non-retransmitted hole got filled? That's reordering */
3196 if (reord
< prior_fackets
)
3197 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3199 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3200 prior_sacked
- tp
->sacked_out
;
3201 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3204 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3206 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3207 sack_rtt_us
> skb_mstamp_us_delta(&now
, &skb
->skb_mstamp
)) {
3208 /* Do not re-arm RTO if the sack RTT is measured from data sent
3209 * after when the head was last (re)transmitted. Otherwise the
3210 * timeout may continue to extend in loss recovery.
3215 if (icsk
->icsk_ca_ops
->pkts_acked
)
3216 icsk
->icsk_ca_ops
->pkts_acked(sk
, pkts_acked
, ca_rtt_us
);
3218 #if FASTRETRANS_DEBUG > 0
3219 WARN_ON((int)tp
->sacked_out
< 0);
3220 WARN_ON((int)tp
->lost_out
< 0);
3221 WARN_ON((int)tp
->retrans_out
< 0);
3222 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3223 icsk
= inet_csk(sk
);
3225 pr_debug("Leak l=%u %d\n",
3226 tp
->lost_out
, icsk
->icsk_ca_state
);
3229 if (tp
->sacked_out
) {
3230 pr_debug("Leak s=%u %d\n",
3231 tp
->sacked_out
, icsk
->icsk_ca_state
);
3234 if (tp
->retrans_out
) {
3235 pr_debug("Leak r=%u %d\n",
3236 tp
->retrans_out
, icsk
->icsk_ca_state
);
3237 tp
->retrans_out
= 0;
3244 static void tcp_ack_probe(struct sock
*sk
)
3246 const struct tcp_sock
*tp
= tcp_sk(sk
);
3247 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3249 /* Was it a usable window open? */
3251 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3252 icsk
->icsk_backoff
= 0;
3253 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3254 /* Socket must be waked up by subsequent tcp_data_snd_check().
3255 * This function is not for random using!
3258 unsigned long when
= tcp_probe0_when(sk
, TCP_RTO_MAX
);
3260 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3265 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3267 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3268 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3271 /* Decide wheather to run the increase function of congestion control. */
3272 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3274 if (tcp_in_cwnd_reduction(sk
))
3277 /* If reordering is high then always grow cwnd whenever data is
3278 * delivered regardless of its ordering. Otherwise stay conservative
3279 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3280 * new SACK or ECE mark may first advance cwnd here and later reduce
3281 * cwnd in tcp_fastretrans_alert() based on more states.
3283 if (tcp_sk(sk
)->reordering
> sysctl_tcp_reordering
)
3284 return flag
& FLAG_FORWARD_PROGRESS
;
3286 return flag
& FLAG_DATA_ACKED
;
3289 /* Check that window update is acceptable.
3290 * The function assumes that snd_una<=ack<=snd_next.
3292 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3293 const u32 ack
, const u32 ack_seq
,
3296 return after(ack
, tp
->snd_una
) ||
3297 after(ack_seq
, tp
->snd_wl1
) ||
3298 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3301 /* If we update tp->snd_una, also update tp->bytes_acked */
3302 static void tcp_snd_una_update(struct tcp_sock
*tp
, u32 ack
)
3304 u32 delta
= ack
- tp
->snd_una
;
3306 u64_stats_update_begin(&tp
->syncp
);
3307 tp
->bytes_acked
+= delta
;
3308 u64_stats_update_end(&tp
->syncp
);
3312 /* If we update tp->rcv_nxt, also update tp->bytes_received */
3313 static void tcp_rcv_nxt_update(struct tcp_sock
*tp
, u32 seq
)
3315 u32 delta
= seq
- tp
->rcv_nxt
;
3317 u64_stats_update_begin(&tp
->syncp
);
3318 tp
->bytes_received
+= delta
;
3319 u64_stats_update_end(&tp
->syncp
);
3323 /* Update our send window.
3325 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3326 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3328 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3331 struct tcp_sock
*tp
= tcp_sk(sk
);
3333 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3335 if (likely(!tcp_hdr(skb
)->syn
))
3336 nwin
<<= tp
->rx_opt
.snd_wscale
;
3338 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3339 flag
|= FLAG_WIN_UPDATE
;
3340 tcp_update_wl(tp
, ack_seq
);
3342 if (tp
->snd_wnd
!= nwin
) {
3345 /* Note, it is the only place, where
3346 * fast path is recovered for sending TCP.
3349 tcp_fast_path_check(sk
);
3351 if (tcp_send_head(sk
))
3352 tcp_slow_start_after_idle_check(sk
);
3354 if (nwin
> tp
->max_window
) {
3355 tp
->max_window
= nwin
;
3356 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3361 tcp_snd_una_update(tp
, ack
);
3366 /* Return true if we're currently rate-limiting out-of-window ACKs and
3367 * thus shouldn't send a dupack right now. We rate-limit dupacks in
3368 * response to out-of-window SYNs or ACKs to mitigate ACK loops or DoS
3369 * attacks that send repeated SYNs or ACKs for the same connection. To
3370 * do this, we do not send a duplicate SYNACK or ACK if the remote
3371 * endpoint is sending out-of-window SYNs or pure ACKs at a high rate.
3373 bool tcp_oow_rate_limited(struct net
*net
, const struct sk_buff
*skb
,
3374 int mib_idx
, u32
*last_oow_ack_time
)
3376 /* Data packets without SYNs are not likely part of an ACK loop. */
3377 if ((TCP_SKB_CB(skb
)->seq
!= TCP_SKB_CB(skb
)->end_seq
) &&
3379 goto not_rate_limited
;
3381 if (*last_oow_ack_time
) {
3382 s32 elapsed
= (s32
)(tcp_time_stamp
- *last_oow_ack_time
);
3384 if (0 <= elapsed
&& elapsed
< sysctl_tcp_invalid_ratelimit
) {
3385 NET_INC_STATS_BH(net
, mib_idx
);
3386 return true; /* rate-limited: don't send yet! */
3390 *last_oow_ack_time
= tcp_time_stamp
;
3393 return false; /* not rate-limited: go ahead, send dupack now! */
3396 /* RFC 5961 7 [ACK Throttling] */
3397 static void tcp_send_challenge_ack(struct sock
*sk
, const struct sk_buff
*skb
)
3399 /* unprotected vars, we dont care of overwrites */
3400 static u32 challenge_timestamp
;
3401 static unsigned int challenge_count
;
3402 struct tcp_sock
*tp
= tcp_sk(sk
);
3405 /* First check our per-socket dupack rate limit. */
3406 if (tcp_oow_rate_limited(sock_net(sk
), skb
,
3407 LINUX_MIB_TCPACKSKIPPEDCHALLENGE
,
3408 &tp
->last_oow_ack_time
))
3411 /* Then check the check host-wide RFC 5961 rate limit. */
3413 if (now
!= challenge_timestamp
) {
3414 challenge_timestamp
= now
;
3415 challenge_count
= 0;
3417 if (++challenge_count
<= sysctl_tcp_challenge_ack_limit
) {
3418 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3423 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3425 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3426 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3429 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3431 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3432 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3433 * extra check below makes sure this can only happen
3434 * for pure ACK frames. -DaveM
3436 * Not only, also it occurs for expired timestamps.
3439 if (tcp_paws_check(&tp
->rx_opt
, 0))
3440 tcp_store_ts_recent(tp
);
3444 /* This routine deals with acks during a TLP episode.
3445 * We mark the end of a TLP episode on receiving TLP dupack or when
3446 * ack is after tlp_high_seq.
3447 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3449 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3451 struct tcp_sock
*tp
= tcp_sk(sk
);
3453 if (before(ack
, tp
->tlp_high_seq
))
3456 if (flag
& FLAG_DSACKING_ACK
) {
3457 /* This DSACK means original and TLP probe arrived; no loss */
3458 tp
->tlp_high_seq
= 0;
3459 } else if (after(ack
, tp
->tlp_high_seq
)) {
3460 /* ACK advances: there was a loss, so reduce cwnd. Reset
3461 * tlp_high_seq in tcp_init_cwnd_reduction()
3463 tcp_init_cwnd_reduction(sk
);
3464 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3465 tcp_end_cwnd_reduction(sk
);
3466 tcp_try_keep_open(sk
);
3467 NET_INC_STATS_BH(sock_net(sk
),
3468 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3469 } else if (!(flag
& (FLAG_SND_UNA_ADVANCED
|
3470 FLAG_NOT_DUP
| FLAG_DATA_SACKED
))) {
3471 /* Pure dupack: original and TLP probe arrived; no loss */
3472 tp
->tlp_high_seq
= 0;
3476 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3478 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3480 if (icsk
->icsk_ca_ops
->in_ack_event
)
3481 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3484 /* This routine deals with incoming acks, but not outgoing ones. */
3485 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3487 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3488 struct tcp_sock
*tp
= tcp_sk(sk
);
3489 struct tcp_sacktag_state sack_state
;
3490 u32 prior_snd_una
= tp
->snd_una
;
3491 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3492 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3493 bool is_dupack
= false;
3495 int prior_packets
= tp
->packets_out
;
3496 const int prior_unsacked
= tp
->packets_out
- tp
->sacked_out
;
3497 int acked
= 0; /* Number of packets newly acked */
3499 sack_state
.first_sackt
.v64
= 0;
3501 /* We very likely will need to access write queue head. */
3502 prefetchw(sk
->sk_write_queue
.next
);
3504 /* If the ack is older than previous acks
3505 * then we can probably ignore it.
3507 if (before(ack
, prior_snd_una
)) {
3508 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3509 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3510 tcp_send_challenge_ack(sk
, skb
);
3516 /* If the ack includes data we haven't sent yet, discard
3517 * this segment (RFC793 Section 3.9).
3519 if (after(ack
, tp
->snd_nxt
))
3522 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3523 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
3526 if (after(ack
, prior_snd_una
)) {
3527 flag
|= FLAG_SND_UNA_ADVANCED
;
3528 icsk
->icsk_retransmits
= 0;
3531 prior_fackets
= tp
->fackets_out
;
3533 /* ts_recent update must be made after we are sure that the packet
3536 if (flag
& FLAG_UPDATE_TS_RECENT
)
3537 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3539 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3540 /* Window is constant, pure forward advance.
3541 * No more checks are required.
3542 * Note, we use the fact that SND.UNA>=SND.WL2.
3544 tcp_update_wl(tp
, ack_seq
);
3545 tcp_snd_una_update(tp
, ack
);
3546 flag
|= FLAG_WIN_UPDATE
;
3548 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3550 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3552 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3554 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3557 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3559 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3561 if (TCP_SKB_CB(skb
)->sacked
)
3562 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3565 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3567 ack_ev_flags
|= CA_ACK_ECE
;
3570 if (flag
& FLAG_WIN_UPDATE
)
3571 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3573 tcp_in_ack_event(sk
, ack_ev_flags
);
3576 /* We passed data and got it acked, remove any soft error
3577 * log. Something worked...
3579 sk
->sk_err_soft
= 0;
3580 icsk
->icsk_probes_out
= 0;
3581 tp
->rcv_tstamp
= tcp_time_stamp
;
3585 /* See if we can take anything off of the retransmit queue. */
3586 acked
= tp
->packets_out
;
3587 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
,
3589 acked
-= tp
->packets_out
;
3591 if (tcp_ack_is_dubious(sk
, flag
)) {
3592 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3593 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3596 if (tp
->tlp_high_seq
)
3597 tcp_process_tlp_ack(sk
, ack
, flag
);
3599 /* Advance cwnd if state allows */
3600 if (tcp_may_raise_cwnd(sk
, flag
))
3601 tcp_cong_avoid(sk
, ack
, acked
);
3603 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
)) {
3604 struct dst_entry
*dst
= __sk_dst_get(sk
);
3609 if (icsk
->icsk_pending
== ICSK_TIME_RETRANS
)
3610 tcp_schedule_loss_probe(sk
);
3611 tcp_update_pacing_rate(sk
);
3615 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3616 if (flag
& FLAG_DSACKING_ACK
)
3617 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3619 /* If this ack opens up a zero window, clear backoff. It was
3620 * being used to time the probes, and is probably far higher than
3621 * it needs to be for normal retransmission.
3623 if (tcp_send_head(sk
))
3626 if (tp
->tlp_high_seq
)
3627 tcp_process_tlp_ack(sk
, ack
, flag
);
3631 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3635 /* If data was SACKed, tag it and see if we should send more data.
3636 * If data was DSACKed, see if we can undo a cwnd reduction.
3638 if (TCP_SKB_CB(skb
)->sacked
) {
3639 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3641 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3645 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3649 static void tcp_parse_fastopen_option(int len
, const unsigned char *cookie
,
3650 bool syn
, struct tcp_fastopen_cookie
*foc
,
3653 /* Valid only in SYN or SYN-ACK with an even length. */
3654 if (!foc
|| !syn
|| len
< 0 || (len
& 1))
3657 if (len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3658 len
<= TCP_FASTOPEN_COOKIE_MAX
)
3659 memcpy(foc
->val
, cookie
, len
);
3666 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3667 * But, this can also be called on packets in the established flow when
3668 * the fast version below fails.
3670 void tcp_parse_options(const struct sk_buff
*skb
,
3671 struct tcp_options_received
*opt_rx
, int estab
,
3672 struct tcp_fastopen_cookie
*foc
)
3674 const unsigned char *ptr
;
3675 const struct tcphdr
*th
= tcp_hdr(skb
);
3676 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3678 ptr
= (const unsigned char *)(th
+ 1);
3679 opt_rx
->saw_tstamp
= 0;
3681 while (length
> 0) {
3682 int opcode
= *ptr
++;
3688 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3693 if (opsize
< 2) /* "silly options" */
3695 if (opsize
> length
)
3696 return; /* don't parse partial options */
3699 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3700 u16 in_mss
= get_unaligned_be16(ptr
);
3702 if (opt_rx
->user_mss
&&
3703 opt_rx
->user_mss
< in_mss
)
3704 in_mss
= opt_rx
->user_mss
;
3705 opt_rx
->mss_clamp
= in_mss
;
3710 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3711 !estab
&& sysctl_tcp_window_scaling
) {
3712 __u8 snd_wscale
= *(__u8
*)ptr
;
3713 opt_rx
->wscale_ok
= 1;
3714 if (snd_wscale
> 14) {
3715 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3720 opt_rx
->snd_wscale
= snd_wscale
;
3723 case TCPOPT_TIMESTAMP
:
3724 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3725 ((estab
&& opt_rx
->tstamp_ok
) ||
3726 (!estab
&& sysctl_tcp_timestamps
))) {
3727 opt_rx
->saw_tstamp
= 1;
3728 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3729 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3732 case TCPOPT_SACK_PERM
:
3733 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3734 !estab
&& sysctl_tcp_sack
) {
3735 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3736 tcp_sack_reset(opt_rx
);
3741 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3742 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3744 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3747 #ifdef CONFIG_TCP_MD5SIG
3750 * The MD5 Hash has already been
3751 * checked (see tcp_v{4,6}_do_rcv()).
3755 case TCPOPT_FASTOPEN
:
3756 tcp_parse_fastopen_option(
3757 opsize
- TCPOLEN_FASTOPEN_BASE
,
3758 ptr
, th
->syn
, foc
, false);
3762 /* Fast Open option shares code 254 using a
3763 * 16 bits magic number.
3765 if (opsize
>= TCPOLEN_EXP_FASTOPEN_BASE
&&
3766 get_unaligned_be16(ptr
) ==
3767 TCPOPT_FASTOPEN_MAGIC
)
3768 tcp_parse_fastopen_option(opsize
-
3769 TCPOLEN_EXP_FASTOPEN_BASE
,
3770 ptr
+ 2, th
->syn
, foc
, true);
3779 EXPORT_SYMBOL(tcp_parse_options
);
3781 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3783 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3785 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3786 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3787 tp
->rx_opt
.saw_tstamp
= 1;
3789 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3792 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3794 tp
->rx_opt
.rcv_tsecr
= 0;
3800 /* Fast parse options. This hopes to only see timestamps.
3801 * If it is wrong it falls back on tcp_parse_options().
3803 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
3804 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3806 /* In the spirit of fast parsing, compare doff directly to constant
3807 * values. Because equality is used, short doff can be ignored here.
3809 if (th
->doff
== (sizeof(*th
) / 4)) {
3810 tp
->rx_opt
.saw_tstamp
= 0;
3812 } else if (tp
->rx_opt
.tstamp_ok
&&
3813 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3814 if (tcp_parse_aligned_timestamp(tp
, th
))
3818 tcp_parse_options(skb
, &tp
->rx_opt
, 1, NULL
);
3819 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3820 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3825 #ifdef CONFIG_TCP_MD5SIG
3827 * Parse MD5 Signature option
3829 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3831 int length
= (th
->doff
<< 2) - sizeof(*th
);
3832 const u8
*ptr
= (const u8
*)(th
+ 1);
3834 /* If the TCP option is too short, we can short cut */
3835 if (length
< TCPOLEN_MD5SIG
)
3838 while (length
> 0) {
3839 int opcode
= *ptr
++;
3850 if (opsize
< 2 || opsize
> length
)
3852 if (opcode
== TCPOPT_MD5SIG
)
3853 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3860 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3863 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3865 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3866 * it can pass through stack. So, the following predicate verifies that
3867 * this segment is not used for anything but congestion avoidance or
3868 * fast retransmit. Moreover, we even are able to eliminate most of such
3869 * second order effects, if we apply some small "replay" window (~RTO)
3870 * to timestamp space.
3872 * All these measures still do not guarantee that we reject wrapped ACKs
3873 * on networks with high bandwidth, when sequence space is recycled fastly,
3874 * but it guarantees that such events will be very rare and do not affect
3875 * connection seriously. This doesn't look nice, but alas, PAWS is really
3878 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3879 * states that events when retransmit arrives after original data are rare.
3880 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3881 * the biggest problem on large power networks even with minor reordering.
3882 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3883 * up to bandwidth of 18Gigabit/sec. 8) ]
3886 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3888 const struct tcp_sock
*tp
= tcp_sk(sk
);
3889 const struct tcphdr
*th
= tcp_hdr(skb
);
3890 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3891 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3893 return (/* 1. Pure ACK with correct sequence number. */
3894 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3896 /* 2. ... and duplicate ACK. */
3897 ack
== tp
->snd_una
&&
3899 /* 3. ... and does not update window. */
3900 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3902 /* 4. ... and sits in replay window. */
3903 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3906 static inline bool tcp_paws_discard(const struct sock
*sk
,
3907 const struct sk_buff
*skb
)
3909 const struct tcp_sock
*tp
= tcp_sk(sk
);
3911 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3912 !tcp_disordered_ack(sk
, skb
);
3915 /* Check segment sequence number for validity.
3917 * Segment controls are considered valid, if the segment
3918 * fits to the window after truncation to the window. Acceptability
3919 * of data (and SYN, FIN, of course) is checked separately.
3920 * See tcp_data_queue(), for example.
3922 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3923 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3924 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3925 * (borrowed from freebsd)
3928 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3930 return !before(end_seq
, tp
->rcv_wup
) &&
3931 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3934 /* When we get a reset we do this. */
3935 void tcp_reset(struct sock
*sk
)
3937 /* We want the right error as BSD sees it (and indeed as we do). */
3938 switch (sk
->sk_state
) {
3940 sk
->sk_err
= ECONNREFUSED
;
3942 case TCP_CLOSE_WAIT
:
3948 sk
->sk_err
= ECONNRESET
;
3950 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3953 if (!sock_flag(sk
, SOCK_DEAD
))
3954 sk
->sk_error_report(sk
);
3960 * Process the FIN bit. This now behaves as it is supposed to work
3961 * and the FIN takes effect when it is validly part of sequence
3962 * space. Not before when we get holes.
3964 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3965 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3968 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3969 * close and we go into CLOSING (and later onto TIME-WAIT)
3971 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3973 static void tcp_fin(struct sock
*sk
)
3975 struct tcp_sock
*tp
= tcp_sk(sk
);
3977 inet_csk_schedule_ack(sk
);
3979 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3980 sock_set_flag(sk
, SOCK_DONE
);
3982 switch (sk
->sk_state
) {
3984 case TCP_ESTABLISHED
:
3985 /* Move to CLOSE_WAIT */
3986 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3987 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3990 case TCP_CLOSE_WAIT
:
3992 /* Received a retransmission of the FIN, do
3997 /* RFC793: Remain in the LAST-ACK state. */
4001 /* This case occurs when a simultaneous close
4002 * happens, we must ack the received FIN and
4003 * enter the CLOSING state.
4006 tcp_set_state(sk
, TCP_CLOSING
);
4009 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4011 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4014 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4015 * cases we should never reach this piece of code.
4017 pr_err("%s: Impossible, sk->sk_state=%d\n",
4018 __func__
, sk
->sk_state
);
4022 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4023 * Probably, we should reset in this case. For now drop them.
4025 __skb_queue_purge(&tp
->out_of_order_queue
);
4026 if (tcp_is_sack(tp
))
4027 tcp_sack_reset(&tp
->rx_opt
);
4030 if (!sock_flag(sk
, SOCK_DEAD
)) {
4031 sk
->sk_state_change(sk
);
4033 /* Do not send POLL_HUP for half duplex close. */
4034 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4035 sk
->sk_state
== TCP_CLOSE
)
4036 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4038 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4042 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4045 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4046 if (before(seq
, sp
->start_seq
))
4047 sp
->start_seq
= seq
;
4048 if (after(end_seq
, sp
->end_seq
))
4049 sp
->end_seq
= end_seq
;
4055 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4057 struct tcp_sock
*tp
= tcp_sk(sk
);
4059 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4062 if (before(seq
, tp
->rcv_nxt
))
4063 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4065 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4067 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4069 tp
->rx_opt
.dsack
= 1;
4070 tp
->duplicate_sack
[0].start_seq
= seq
;
4071 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4075 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4077 struct tcp_sock
*tp
= tcp_sk(sk
);
4079 if (!tp
->rx_opt
.dsack
)
4080 tcp_dsack_set(sk
, seq
, end_seq
);
4082 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4085 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4087 struct tcp_sock
*tp
= tcp_sk(sk
);
4089 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4090 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4091 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4092 tcp_enter_quickack_mode(sk
);
4094 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4095 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4097 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4098 end_seq
= tp
->rcv_nxt
;
4099 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4106 /* These routines update the SACK block as out-of-order packets arrive or
4107 * in-order packets close up the sequence space.
4109 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4112 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4113 struct tcp_sack_block
*swalk
= sp
+ 1;
4115 /* See if the recent change to the first SACK eats into
4116 * or hits the sequence space of other SACK blocks, if so coalesce.
4118 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4119 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4122 /* Zap SWALK, by moving every further SACK up by one slot.
4123 * Decrease num_sacks.
4125 tp
->rx_opt
.num_sacks
--;
4126 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4130 this_sack
++, swalk
++;
4134 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4136 struct tcp_sock
*tp
= tcp_sk(sk
);
4137 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4138 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4144 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4145 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4146 /* Rotate this_sack to the first one. */
4147 for (; this_sack
> 0; this_sack
--, sp
--)
4148 swap(*sp
, *(sp
- 1));
4150 tcp_sack_maybe_coalesce(tp
);
4155 /* Could not find an adjacent existing SACK, build a new one,
4156 * put it at the front, and shift everyone else down. We
4157 * always know there is at least one SACK present already here.
4159 * If the sack array is full, forget about the last one.
4161 if (this_sack
>= TCP_NUM_SACKS
) {
4163 tp
->rx_opt
.num_sacks
--;
4166 for (; this_sack
> 0; this_sack
--, sp
--)
4170 /* Build the new head SACK, and we're done. */
4171 sp
->start_seq
= seq
;
4172 sp
->end_seq
= end_seq
;
4173 tp
->rx_opt
.num_sacks
++;
4176 /* RCV.NXT advances, some SACKs should be eaten. */
4178 static void tcp_sack_remove(struct tcp_sock
*tp
)
4180 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4181 int num_sacks
= tp
->rx_opt
.num_sacks
;
4184 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4185 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4186 tp
->rx_opt
.num_sacks
= 0;
4190 for (this_sack
= 0; this_sack
< num_sacks
;) {
4191 /* Check if the start of the sack is covered by RCV.NXT. */
4192 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4195 /* RCV.NXT must cover all the block! */
4196 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4198 /* Zap this SACK, by moving forward any other SACKS. */
4199 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4200 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4207 tp
->rx_opt
.num_sacks
= num_sacks
;
4211 * tcp_try_coalesce - try to merge skb to prior one
4214 * @from: buffer to add in queue
4215 * @fragstolen: pointer to boolean
4217 * Before queueing skb @from after @to, try to merge them
4218 * to reduce overall memory use and queue lengths, if cost is small.
4219 * Packets in ofo or receive queues can stay a long time.
4220 * Better try to coalesce them right now to avoid future collapses.
4221 * Returns true if caller should free @from instead of queueing it
4223 static bool tcp_try_coalesce(struct sock
*sk
,
4225 struct sk_buff
*from
,
4230 *fragstolen
= false;
4232 /* Its possible this segment overlaps with prior segment in queue */
4233 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4236 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4239 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4240 sk_mem_charge(sk
, delta
);
4241 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4242 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4243 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4244 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4248 /* This one checks to see if we can put data from the
4249 * out_of_order queue into the receive_queue.
4251 static void tcp_ofo_queue(struct sock
*sk
)
4253 struct tcp_sock
*tp
= tcp_sk(sk
);
4254 __u32 dsack_high
= tp
->rcv_nxt
;
4255 struct sk_buff
*skb
, *tail
;
4256 bool fragstolen
, eaten
;
4258 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4259 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4262 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4263 __u32 dsack
= dsack_high
;
4264 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4265 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4266 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4269 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4270 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4271 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4275 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4276 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4277 TCP_SKB_CB(skb
)->end_seq
);
4279 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4280 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4281 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4283 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4284 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4287 kfree_skb_partial(skb
, fragstolen
);
4291 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4292 static int tcp_prune_queue(struct sock
*sk
);
4294 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4297 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4298 !sk_rmem_schedule(sk
, skb
, size
)) {
4300 if (tcp_prune_queue(sk
) < 0)
4303 if (!sk_rmem_schedule(sk
, skb
, size
)) {
4304 if (!tcp_prune_ofo_queue(sk
))
4307 if (!sk_rmem_schedule(sk
, skb
, size
))
4314 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4316 struct tcp_sock
*tp
= tcp_sk(sk
);
4317 struct sk_buff
*skb1
;
4320 tcp_ecn_check_ce(tp
, skb
);
4322 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4323 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4328 /* Disable header prediction. */
4330 inet_csk_schedule_ack(sk
);
4332 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4333 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4334 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4336 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4338 /* Initial out of order segment, build 1 SACK. */
4339 if (tcp_is_sack(tp
)) {
4340 tp
->rx_opt
.num_sacks
= 1;
4341 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4342 tp
->selective_acks
[0].end_seq
=
4343 TCP_SKB_CB(skb
)->end_seq
;
4345 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4349 seq
= TCP_SKB_CB(skb
)->seq
;
4350 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4352 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4355 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4356 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4358 tcp_grow_window(sk
, skb
);
4359 kfree_skb_partial(skb
, fragstolen
);
4363 if (!tp
->rx_opt
.num_sacks
||
4364 tp
->selective_acks
[0].end_seq
!= seq
)
4367 /* Common case: data arrive in order after hole. */
4368 tp
->selective_acks
[0].end_seq
= end_seq
;
4372 /* Find place to insert this segment. */
4374 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4376 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4380 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4383 /* Do skb overlap to previous one? */
4384 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4385 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4386 /* All the bits are present. Drop. */
4387 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4390 tcp_dsack_set(sk
, seq
, end_seq
);
4393 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4394 /* Partial overlap. */
4395 tcp_dsack_set(sk
, seq
,
4396 TCP_SKB_CB(skb1
)->end_seq
);
4398 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4402 skb1
= skb_queue_prev(
4403 &tp
->out_of_order_queue
,
4408 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4410 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4412 /* And clean segments covered by new one as whole. */
4413 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4414 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4416 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4418 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4419 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4423 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4424 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4425 TCP_SKB_CB(skb1
)->end_seq
);
4426 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4431 if (tcp_is_sack(tp
))
4432 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4435 tcp_grow_window(sk
, skb
);
4436 skb_set_owner_r(skb
, sk
);
4440 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4444 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4446 __skb_pull(skb
, hdrlen
);
4448 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4449 tcp_rcv_nxt_update(tcp_sk(sk
), TCP_SKB_CB(skb
)->end_seq
);
4451 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4452 skb_set_owner_r(skb
, sk
);
4457 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4459 struct sk_buff
*skb
;
4465 skb
= alloc_skb(size
, sk
->sk_allocation
);
4469 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4472 if (memcpy_from_msg(skb_put(skb
, size
), msg
, size
))
4475 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4476 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4477 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4479 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4480 WARN_ON_ONCE(fragstolen
); /* should not happen */
4491 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4493 struct tcp_sock
*tp
= tcp_sk(sk
);
4495 bool fragstolen
= false;
4497 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4501 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4503 tcp_ecn_accept_cwr(tp
, skb
);
4505 tp
->rx_opt
.dsack
= 0;
4507 /* Queue data for delivery to the user.
4508 * Packets in sequence go to the receive queue.
4509 * Out of sequence packets to the out_of_order_queue.
4511 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4512 if (tcp_receive_window(tp
) == 0)
4515 /* Ok. In sequence. In window. */
4516 if (tp
->ucopy
.task
== current
&&
4517 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4518 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4519 int chunk
= min_t(unsigned int, skb
->len
,
4522 __set_current_state(TASK_RUNNING
);
4525 if (!skb_copy_datagram_msg(skb
, 0, tp
->ucopy
.msg
, chunk
)) {
4526 tp
->ucopy
.len
-= chunk
;
4527 tp
->copied_seq
+= chunk
;
4528 eaten
= (chunk
== skb
->len
);
4529 tcp_rcv_space_adjust(sk
);
4537 if (skb_queue_len(&sk
->sk_receive_queue
) == 0)
4538 sk_forced_mem_schedule(sk
, skb
->truesize
);
4539 else if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4542 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4544 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
4546 tcp_event_data_recv(sk
, skb
);
4547 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4550 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4553 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4554 * gap in queue is filled.
4556 if (skb_queue_empty(&tp
->out_of_order_queue
))
4557 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4560 if (tp
->rx_opt
.num_sacks
)
4561 tcp_sack_remove(tp
);
4563 tcp_fast_path_check(sk
);
4566 kfree_skb_partial(skb
, fragstolen
);
4567 if (!sock_flag(sk
, SOCK_DEAD
))
4568 sk
->sk_data_ready(sk
);
4572 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4573 /* A retransmit, 2nd most common case. Force an immediate ack. */
4574 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4575 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4578 tcp_enter_quickack_mode(sk
);
4579 inet_csk_schedule_ack(sk
);
4585 /* Out of window. F.e. zero window probe. */
4586 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4589 tcp_enter_quickack_mode(sk
);
4591 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4592 /* Partial packet, seq < rcv_next < end_seq */
4593 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4594 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4595 TCP_SKB_CB(skb
)->end_seq
);
4597 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4599 /* If window is closed, drop tail of packet. But after
4600 * remembering D-SACK for its head made in previous line.
4602 if (!tcp_receive_window(tp
))
4607 tcp_data_queue_ofo(sk
, skb
);
4610 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4611 struct sk_buff_head
*list
)
4613 struct sk_buff
*next
= NULL
;
4615 if (!skb_queue_is_last(list
, skb
))
4616 next
= skb_queue_next(list
, skb
);
4618 __skb_unlink(skb
, list
);
4620 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4625 /* Collapse contiguous sequence of skbs head..tail with
4626 * sequence numbers start..end.
4628 * If tail is NULL, this means until the end of the list.
4630 * Segments with FIN/SYN are not collapsed (only because this
4634 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4635 struct sk_buff
*head
, struct sk_buff
*tail
,
4638 struct sk_buff
*skb
, *n
;
4641 /* First, check that queue is collapsible and find
4642 * the point where collapsing can be useful. */
4646 skb_queue_walk_from_safe(list
, skb
, n
) {
4649 /* No new bits? It is possible on ofo queue. */
4650 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4651 skb
= tcp_collapse_one(sk
, skb
, list
);
4657 /* The first skb to collapse is:
4659 * - bloated or contains data before "start" or
4660 * overlaps to the next one.
4662 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4663 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4664 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4665 end_of_skbs
= false;
4669 if (!skb_queue_is_last(list
, skb
)) {
4670 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4672 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4673 end_of_skbs
= false;
4678 /* Decided to skip this, advance start seq. */
4679 start
= TCP_SKB_CB(skb
)->end_seq
;
4682 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4685 while (before(start
, end
)) {
4686 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4687 struct sk_buff
*nskb
;
4689 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4693 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4694 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4695 __skb_queue_before(list
, skb
, nskb
);
4696 skb_set_owner_r(nskb
, sk
);
4698 /* Copy data, releasing collapsed skbs. */
4700 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4701 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4705 size
= min(copy
, size
);
4706 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4708 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4712 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4713 skb
= tcp_collapse_one(sk
, skb
, list
);
4716 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4723 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4724 * and tcp_collapse() them until all the queue is collapsed.
4726 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4728 struct tcp_sock
*tp
= tcp_sk(sk
);
4729 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4730 struct sk_buff
*head
;
4736 start
= TCP_SKB_CB(skb
)->seq
;
4737 end
= TCP_SKB_CB(skb
)->end_seq
;
4741 struct sk_buff
*next
= NULL
;
4743 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4744 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4747 /* Segment is terminated when we see gap or when
4748 * we are at the end of all the queue. */
4750 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4751 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4752 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4753 head
, skb
, start
, end
);
4757 /* Start new segment */
4758 start
= TCP_SKB_CB(skb
)->seq
;
4759 end
= TCP_SKB_CB(skb
)->end_seq
;
4761 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4762 start
= TCP_SKB_CB(skb
)->seq
;
4763 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4764 end
= TCP_SKB_CB(skb
)->end_seq
;
4770 * Purge the out-of-order queue.
4771 * Return true if queue was pruned.
4773 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4775 struct tcp_sock
*tp
= tcp_sk(sk
);
4778 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4779 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4780 __skb_queue_purge(&tp
->out_of_order_queue
);
4782 /* Reset SACK state. A conforming SACK implementation will
4783 * do the same at a timeout based retransmit. When a connection
4784 * is in a sad state like this, we care only about integrity
4785 * of the connection not performance.
4787 if (tp
->rx_opt
.sack_ok
)
4788 tcp_sack_reset(&tp
->rx_opt
);
4795 /* Reduce allocated memory if we can, trying to get
4796 * the socket within its memory limits again.
4798 * Return less than zero if we should start dropping frames
4799 * until the socket owning process reads some of the data
4800 * to stabilize the situation.
4802 static int tcp_prune_queue(struct sock
*sk
)
4804 struct tcp_sock
*tp
= tcp_sk(sk
);
4806 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4808 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4810 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4811 tcp_clamp_window(sk
);
4812 else if (tcp_under_memory_pressure(sk
))
4813 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4815 tcp_collapse_ofo_queue(sk
);
4816 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4817 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4818 skb_peek(&sk
->sk_receive_queue
),
4820 tp
->copied_seq
, tp
->rcv_nxt
);
4823 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4826 /* Collapsing did not help, destructive actions follow.
4827 * This must not ever occur. */
4829 tcp_prune_ofo_queue(sk
);
4831 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4834 /* If we are really being abused, tell the caller to silently
4835 * drop receive data on the floor. It will get retransmitted
4836 * and hopefully then we'll have sufficient space.
4838 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4840 /* Massive buffer overcommit. */
4845 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4847 const struct tcp_sock
*tp
= tcp_sk(sk
);
4849 /* If the user specified a specific send buffer setting, do
4852 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4855 /* If we are under global TCP memory pressure, do not expand. */
4856 if (tcp_under_memory_pressure(sk
))
4859 /* If we are under soft global TCP memory pressure, do not expand. */
4860 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4863 /* If we filled the congestion window, do not expand. */
4864 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
4870 /* When incoming ACK allowed to free some skb from write_queue,
4871 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4872 * on the exit from tcp input handler.
4874 * PROBLEM: sndbuf expansion does not work well with largesend.
4876 static void tcp_new_space(struct sock
*sk
)
4878 struct tcp_sock
*tp
= tcp_sk(sk
);
4880 if (tcp_should_expand_sndbuf(sk
)) {
4881 tcp_sndbuf_expand(sk
);
4882 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4885 sk
->sk_write_space(sk
);
4888 static void tcp_check_space(struct sock
*sk
)
4890 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4891 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4892 /* pairs with tcp_poll() */
4893 smp_mb__after_atomic();
4894 if (sk
->sk_socket
&&
4895 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4900 static inline void tcp_data_snd_check(struct sock
*sk
)
4902 tcp_push_pending_frames(sk
);
4903 tcp_check_space(sk
);
4907 * Check if sending an ack is needed.
4909 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4911 struct tcp_sock
*tp
= tcp_sk(sk
);
4913 /* More than one full frame received... */
4914 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4915 /* ... and right edge of window advances far enough.
4916 * (tcp_recvmsg() will send ACK otherwise). Or...
4918 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4919 /* We ACK each frame or... */
4920 tcp_in_quickack_mode(sk
) ||
4921 /* We have out of order data. */
4922 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4923 /* Then ack it now */
4926 /* Else, send delayed ack. */
4927 tcp_send_delayed_ack(sk
);
4931 static inline void tcp_ack_snd_check(struct sock
*sk
)
4933 if (!inet_csk_ack_scheduled(sk
)) {
4934 /* We sent a data segment already. */
4937 __tcp_ack_snd_check(sk
, 1);
4941 * This routine is only called when we have urgent data
4942 * signaled. Its the 'slow' part of tcp_urg. It could be
4943 * moved inline now as tcp_urg is only called from one
4944 * place. We handle URGent data wrong. We have to - as
4945 * BSD still doesn't use the correction from RFC961.
4946 * For 1003.1g we should support a new option TCP_STDURG to permit
4947 * either form (or just set the sysctl tcp_stdurg).
4950 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
4952 struct tcp_sock
*tp
= tcp_sk(sk
);
4953 u32 ptr
= ntohs(th
->urg_ptr
);
4955 if (ptr
&& !sysctl_tcp_stdurg
)
4957 ptr
+= ntohl(th
->seq
);
4959 /* Ignore urgent data that we've already seen and read. */
4960 if (after(tp
->copied_seq
, ptr
))
4963 /* Do not replay urg ptr.
4965 * NOTE: interesting situation not covered by specs.
4966 * Misbehaving sender may send urg ptr, pointing to segment,
4967 * which we already have in ofo queue. We are not able to fetch
4968 * such data and will stay in TCP_URG_NOTYET until will be eaten
4969 * by recvmsg(). Seems, we are not obliged to handle such wicked
4970 * situations. But it is worth to think about possibility of some
4971 * DoSes using some hypothetical application level deadlock.
4973 if (before(ptr
, tp
->rcv_nxt
))
4976 /* Do we already have a newer (or duplicate) urgent pointer? */
4977 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4980 /* Tell the world about our new urgent pointer. */
4983 /* We may be adding urgent data when the last byte read was
4984 * urgent. To do this requires some care. We cannot just ignore
4985 * tp->copied_seq since we would read the last urgent byte again
4986 * as data, nor can we alter copied_seq until this data arrives
4987 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4989 * NOTE. Double Dutch. Rendering to plain English: author of comment
4990 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4991 * and expect that both A and B disappear from stream. This is _wrong_.
4992 * Though this happens in BSD with high probability, this is occasional.
4993 * Any application relying on this is buggy. Note also, that fix "works"
4994 * only in this artificial test. Insert some normal data between A and B and we will
4995 * decline of BSD again. Verdict: it is better to remove to trap
4998 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4999 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5000 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5002 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5003 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5008 tp
->urg_data
= TCP_URG_NOTYET
;
5011 /* Disable header prediction. */
5015 /* This is the 'fast' part of urgent handling. */
5016 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5018 struct tcp_sock
*tp
= tcp_sk(sk
);
5020 /* Check if we get a new urgent pointer - normally not. */
5022 tcp_check_urg(sk
, th
);
5024 /* Do we wait for any urgent data? - normally not... */
5025 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5026 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5029 /* Is the urgent pointer pointing into this packet? */
5030 if (ptr
< skb
->len
) {
5032 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5034 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5035 if (!sock_flag(sk
, SOCK_DEAD
))
5036 sk
->sk_data_ready(sk
);
5041 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5043 struct tcp_sock
*tp
= tcp_sk(sk
);
5044 int chunk
= skb
->len
- hlen
;
5048 if (skb_csum_unnecessary(skb
))
5049 err
= skb_copy_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
, chunk
);
5051 err
= skb_copy_and_csum_datagram_msg(skb
, hlen
, tp
->ucopy
.msg
);
5054 tp
->ucopy
.len
-= chunk
;
5055 tp
->copied_seq
+= chunk
;
5056 tcp_rcv_space_adjust(sk
);
5063 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5064 struct sk_buff
*skb
)
5068 if (sock_owned_by_user(sk
)) {
5070 result
= __tcp_checksum_complete(skb
);
5073 result
= __tcp_checksum_complete(skb
);
5078 static inline bool tcp_checksum_complete_user(struct sock
*sk
,
5079 struct sk_buff
*skb
)
5081 return !skb_csum_unnecessary(skb
) &&
5082 __tcp_checksum_complete_user(sk
, skb
);
5085 /* Does PAWS and seqno based validation of an incoming segment, flags will
5086 * play significant role here.
5088 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5089 const struct tcphdr
*th
, int syn_inerr
)
5091 struct tcp_sock
*tp
= tcp_sk(sk
);
5093 /* RFC1323: H1. Apply PAWS check first. */
5094 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
5095 tcp_paws_discard(sk
, skb
)) {
5097 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5098 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5099 LINUX_MIB_TCPACKSKIPPEDPAWS
,
5100 &tp
->last_oow_ack_time
))
5101 tcp_send_dupack(sk
, skb
);
5104 /* Reset is accepted even if it did not pass PAWS. */
5107 /* Step 1: check sequence number */
5108 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5109 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5110 * (RST) segments are validated by checking their SEQ-fields."
5111 * And page 69: "If an incoming segment is not acceptable,
5112 * an acknowledgment should be sent in reply (unless the RST
5113 * bit is set, if so drop the segment and return)".
5118 if (!tcp_oow_rate_limited(sock_net(sk
), skb
,
5119 LINUX_MIB_TCPACKSKIPPEDSEQ
,
5120 &tp
->last_oow_ack_time
))
5121 tcp_send_dupack(sk
, skb
);
5126 /* Step 2: check RST bit */
5129 * If sequence number exactly matches RCV.NXT, then
5130 * RESET the connection
5132 * Send a challenge ACK
5134 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
)
5137 tcp_send_challenge_ack(sk
, skb
);
5141 /* step 3: check security and precedence [ignored] */
5143 /* step 4: Check for a SYN
5144 * RFC 5961 4.2 : Send a challenge ack
5149 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5150 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5151 tcp_send_challenge_ack(sk
, skb
);
5163 * TCP receive function for the ESTABLISHED state.
5165 * It is split into a fast path and a slow path. The fast path is
5167 * - A zero window was announced from us - zero window probing
5168 * is only handled properly in the slow path.
5169 * - Out of order segments arrived.
5170 * - Urgent data is expected.
5171 * - There is no buffer space left
5172 * - Unexpected TCP flags/window values/header lengths are received
5173 * (detected by checking the TCP header against pred_flags)
5174 * - Data is sent in both directions. Fast path only supports pure senders
5175 * or pure receivers (this means either the sequence number or the ack
5176 * value must stay constant)
5177 * - Unexpected TCP option.
5179 * When these conditions are not satisfied it drops into a standard
5180 * receive procedure patterned after RFC793 to handle all cases.
5181 * The first three cases are guaranteed by proper pred_flags setting,
5182 * the rest is checked inline. Fast processing is turned on in
5183 * tcp_data_queue when everything is OK.
5185 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5186 const struct tcphdr
*th
, unsigned int len
)
5188 struct tcp_sock
*tp
= tcp_sk(sk
);
5190 if (unlikely(!sk
->sk_rx_dst
))
5191 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5193 * Header prediction.
5194 * The code loosely follows the one in the famous
5195 * "30 instruction TCP receive" Van Jacobson mail.
5197 * Van's trick is to deposit buffers into socket queue
5198 * on a device interrupt, to call tcp_recv function
5199 * on the receive process context and checksum and copy
5200 * the buffer to user space. smart...
5202 * Our current scheme is not silly either but we take the
5203 * extra cost of the net_bh soft interrupt processing...
5204 * We do checksum and copy also but from device to kernel.
5207 tp
->rx_opt
.saw_tstamp
= 0;
5209 /* pred_flags is 0xS?10 << 16 + snd_wnd
5210 * if header_prediction is to be made
5211 * 'S' will always be tp->tcp_header_len >> 2
5212 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5213 * turn it off (when there are holes in the receive
5214 * space for instance)
5215 * PSH flag is ignored.
5218 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5219 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5220 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5221 int tcp_header_len
= tp
->tcp_header_len
;
5223 /* Timestamp header prediction: tcp_header_len
5224 * is automatically equal to th->doff*4 due to pred_flags
5228 /* Check timestamp */
5229 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5230 /* No? Slow path! */
5231 if (!tcp_parse_aligned_timestamp(tp
, th
))
5234 /* If PAWS failed, check it more carefully in slow path */
5235 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5238 /* DO NOT update ts_recent here, if checksum fails
5239 * and timestamp was corrupted part, it will result
5240 * in a hung connection since we will drop all
5241 * future packets due to the PAWS test.
5245 if (len
<= tcp_header_len
) {
5246 /* Bulk data transfer: sender */
5247 if (len
== tcp_header_len
) {
5248 /* Predicted packet is in window by definition.
5249 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5250 * Hence, check seq<=rcv_wup reduces to:
5252 if (tcp_header_len
==
5253 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5254 tp
->rcv_nxt
== tp
->rcv_wup
)
5255 tcp_store_ts_recent(tp
);
5257 /* We know that such packets are checksummed
5260 tcp_ack(sk
, skb
, 0);
5262 tcp_data_snd_check(sk
);
5264 } else { /* Header too small */
5265 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5270 bool fragstolen
= false;
5272 if (tp
->ucopy
.task
== current
&&
5273 tp
->copied_seq
== tp
->rcv_nxt
&&
5274 len
- tcp_header_len
<= tp
->ucopy
.len
&&
5275 sock_owned_by_user(sk
)) {
5276 __set_current_state(TASK_RUNNING
);
5278 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
5279 /* Predicted packet is in window by definition.
5280 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5281 * Hence, check seq<=rcv_wup reduces to:
5283 if (tcp_header_len
==
5284 (sizeof(struct tcphdr
) +
5285 TCPOLEN_TSTAMP_ALIGNED
) &&
5286 tp
->rcv_nxt
== tp
->rcv_wup
)
5287 tcp_store_ts_recent(tp
);
5289 tcp_rcv_rtt_measure_ts(sk
, skb
);
5291 __skb_pull(skb
, tcp_header_len
);
5292 tcp_rcv_nxt_update(tp
, TCP_SKB_CB(skb
)->end_seq
);
5293 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5298 if (tcp_checksum_complete_user(sk
, skb
))
5301 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5304 /* Predicted packet is in window by definition.
5305 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5306 * Hence, check seq<=rcv_wup reduces to:
5308 if (tcp_header_len
==
5309 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5310 tp
->rcv_nxt
== tp
->rcv_wup
)
5311 tcp_store_ts_recent(tp
);
5313 tcp_rcv_rtt_measure_ts(sk
, skb
);
5315 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5317 /* Bulk data transfer: receiver */
5318 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5322 tcp_event_data_recv(sk
, skb
);
5324 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5325 /* Well, only one small jumplet in fast path... */
5326 tcp_ack(sk
, skb
, FLAG_DATA
);
5327 tcp_data_snd_check(sk
);
5328 if (!inet_csk_ack_scheduled(sk
))
5332 __tcp_ack_snd_check(sk
, 0);
5335 kfree_skb_partial(skb
, fragstolen
);
5336 sk
->sk_data_ready(sk
);
5342 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5345 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5349 * Standard slow path.
5352 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5356 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5359 tcp_rcv_rtt_measure_ts(sk
, skb
);
5361 /* Process urgent data. */
5362 tcp_urg(sk
, skb
, th
);
5364 /* step 7: process the segment text */
5365 tcp_data_queue(sk
, skb
);
5367 tcp_data_snd_check(sk
);
5368 tcp_ack_snd_check(sk
);
5372 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5373 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5378 EXPORT_SYMBOL(tcp_rcv_established
);
5380 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5382 struct tcp_sock
*tp
= tcp_sk(sk
);
5383 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5385 tcp_set_state(sk
, TCP_ESTABLISHED
);
5388 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5389 security_inet_conn_established(sk
, skb
);
5392 /* Make sure socket is routed, for correct metrics. */
5393 icsk
->icsk_af_ops
->rebuild_header(sk
);
5395 tcp_init_metrics(sk
);
5397 tcp_init_congestion_control(sk
);
5399 /* Prevent spurious tcp_cwnd_restart() on first data
5402 tp
->lsndtime
= tcp_time_stamp
;
5404 tcp_init_buffer_space(sk
);
5406 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5407 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5409 if (!tp
->rx_opt
.snd_wscale
)
5410 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5414 if (!sock_flag(sk
, SOCK_DEAD
)) {
5415 sk
->sk_state_change(sk
);
5416 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5420 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5421 struct tcp_fastopen_cookie
*cookie
)
5423 struct tcp_sock
*tp
= tcp_sk(sk
);
5424 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5425 u16 mss
= tp
->rx_opt
.mss_clamp
, try_exp
= 0;
5426 bool syn_drop
= false;
5428 if (mss
== tp
->rx_opt
.user_mss
) {
5429 struct tcp_options_received opt
;
5431 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5432 tcp_clear_options(&opt
);
5433 opt
.user_mss
= opt
.mss_clamp
= 0;
5434 tcp_parse_options(synack
, &opt
, 0, NULL
);
5435 mss
= opt
.mss_clamp
;
5438 if (!tp
->syn_fastopen
) {
5439 /* Ignore an unsolicited cookie */
5441 } else if (tp
->total_retrans
) {
5442 /* SYN timed out and the SYN-ACK neither has a cookie nor
5443 * acknowledges data. Presumably the remote received only
5444 * the retransmitted (regular) SYNs: either the original
5445 * SYN-data or the corresponding SYN-ACK was dropped.
5447 syn_drop
= (cookie
->len
< 0 && data
);
5448 } else if (cookie
->len
< 0 && !tp
->syn_data
) {
5449 /* We requested a cookie but didn't get it. If we did not use
5450 * the (old) exp opt format then try so next time (try_exp=1).
5451 * Otherwise we go back to use the RFC7413 opt (try_exp=2).
5453 try_exp
= tp
->syn_fastopen_exp
? 2 : 1;
5456 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
, try_exp
);
5458 if (data
) { /* Retransmit unacked data in SYN */
5459 tcp_for_write_queue_from(data
, sk
) {
5460 if (data
== tcp_send_head(sk
) ||
5461 __tcp_retransmit_skb(sk
, data
))
5465 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5468 tp
->syn_data_acked
= tp
->syn_data
;
5469 if (tp
->syn_data_acked
)
5470 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
5474 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5475 const struct tcphdr
*th
, unsigned int len
)
5477 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5478 struct tcp_sock
*tp
= tcp_sk(sk
);
5479 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5480 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5482 tcp_parse_options(skb
, &tp
->rx_opt
, 0, &foc
);
5483 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5484 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5488 * "If the state is SYN-SENT then
5489 * first check the ACK bit
5490 * If the ACK bit is set
5491 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5492 * a reset (unless the RST bit is set, if so drop
5493 * the segment and return)"
5495 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5496 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5497 goto reset_and_undo
;
5499 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5500 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5502 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5503 goto reset_and_undo
;
5506 /* Now ACK is acceptable.
5508 * "If the RST bit is set
5509 * If the ACK was acceptable then signal the user "error:
5510 * connection reset", drop the segment, enter CLOSED state,
5511 * delete TCB, and return."
5520 * "fifth, if neither of the SYN or RST bits is set then
5521 * drop the segment and return."
5527 goto discard_and_undo
;
5530 * "If the SYN bit is on ...
5531 * are acceptable then ...
5532 * (our SYN has been ACKed), change the connection
5533 * state to ESTABLISHED..."
5536 tcp_ecn_rcv_synack(tp
, th
);
5538 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5539 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5541 /* Ok.. it's good. Set up sequence numbers and
5542 * move to established.
5544 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5545 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5547 /* RFC1323: The window in SYN & SYN/ACK segments is
5550 tp
->snd_wnd
= ntohs(th
->window
);
5552 if (!tp
->rx_opt
.wscale_ok
) {
5553 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5554 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5557 if (tp
->rx_opt
.saw_tstamp
) {
5558 tp
->rx_opt
.tstamp_ok
= 1;
5559 tp
->tcp_header_len
=
5560 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5561 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5562 tcp_store_ts_recent(tp
);
5564 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5567 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5568 tcp_enable_fack(tp
);
5571 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5572 tcp_initialize_rcv_mss(sk
);
5574 /* Remember, tcp_poll() does not lock socket!
5575 * Change state from SYN-SENT only after copied_seq
5576 * is initialized. */
5577 tp
->copied_seq
= tp
->rcv_nxt
;
5581 tcp_finish_connect(sk
, skb
);
5583 if ((tp
->syn_fastopen
|| tp
->syn_data
) &&
5584 tcp_rcv_fastopen_synack(sk
, skb
, &foc
))
5587 if (sk
->sk_write_pending
||
5588 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5589 icsk
->icsk_ack
.pingpong
) {
5590 /* Save one ACK. Data will be ready after
5591 * several ticks, if write_pending is set.
5593 * It may be deleted, but with this feature tcpdumps
5594 * look so _wonderfully_ clever, that I was not able
5595 * to stand against the temptation 8) --ANK
5597 inet_csk_schedule_ack(sk
);
5598 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5599 tcp_enter_quickack_mode(sk
);
5600 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5601 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5612 /* No ACK in the segment */
5616 * "If the RST bit is set
5618 * Otherwise (no ACK) drop the segment and return."
5621 goto discard_and_undo
;
5625 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5626 tcp_paws_reject(&tp
->rx_opt
, 0))
5627 goto discard_and_undo
;
5630 /* We see SYN without ACK. It is attempt of
5631 * simultaneous connect with crossed SYNs.
5632 * Particularly, it can be connect to self.
5634 tcp_set_state(sk
, TCP_SYN_RECV
);
5636 if (tp
->rx_opt
.saw_tstamp
) {
5637 tp
->rx_opt
.tstamp_ok
= 1;
5638 tcp_store_ts_recent(tp
);
5639 tp
->tcp_header_len
=
5640 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5642 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5645 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5646 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5648 /* RFC1323: The window in SYN & SYN/ACK segments is
5651 tp
->snd_wnd
= ntohs(th
->window
);
5652 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5653 tp
->max_window
= tp
->snd_wnd
;
5655 tcp_ecn_rcv_syn(tp
, th
);
5658 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5659 tcp_initialize_rcv_mss(sk
);
5661 tcp_send_synack(sk
);
5663 /* Note, we could accept data and URG from this segment.
5664 * There are no obstacles to make this (except that we must
5665 * either change tcp_recvmsg() to prevent it from returning data
5666 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5668 * However, if we ignore data in ACKless segments sometimes,
5669 * we have no reasons to accept it sometimes.
5670 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5671 * is not flawless. So, discard packet for sanity.
5672 * Uncomment this return to process the data.
5679 /* "fifth, if neither of the SYN or RST bits is set then
5680 * drop the segment and return."
5684 tcp_clear_options(&tp
->rx_opt
);
5685 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5689 tcp_clear_options(&tp
->rx_opt
);
5690 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5695 * This function implements the receiving procedure of RFC 793 for
5696 * all states except ESTABLISHED and TIME_WAIT.
5697 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5698 * address independent.
5701 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5702 const struct tcphdr
*th
, unsigned int len
)
5704 struct tcp_sock
*tp
= tcp_sk(sk
);
5705 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5706 struct request_sock
*req
;
5711 tp
->rx_opt
.saw_tstamp
= 0;
5713 switch (sk
->sk_state
) {
5727 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5730 /* Now we have several options: In theory there is
5731 * nothing else in the frame. KA9Q has an option to
5732 * send data with the syn, BSD accepts data with the
5733 * syn up to the [to be] advertised window and
5734 * Solaris 2.1 gives you a protocol error. For now
5735 * we just ignore it, that fits the spec precisely
5736 * and avoids incompatibilities. It would be nice in
5737 * future to drop through and process the data.
5739 * Now that TTCP is starting to be used we ought to
5741 * But, this leaves one open to an easy denial of
5742 * service attack, and SYN cookies can't defend
5743 * against this problem. So, we drop the data
5744 * in the interest of security over speed unless
5745 * it's still in use.
5753 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5757 /* Do step6 onward by hand. */
5758 tcp_urg(sk
, skb
, th
);
5760 tcp_data_snd_check(sk
);
5764 req
= tp
->fastopen_rsk
;
5766 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5767 sk
->sk_state
!= TCP_FIN_WAIT1
);
5769 if (!tcp_check_req(sk
, skb
, req
, true))
5773 if (!th
->ack
&& !th
->rst
&& !th
->syn
)
5776 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5779 /* step 5: check the ACK field */
5780 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5781 FLAG_UPDATE_TS_RECENT
) > 0;
5783 switch (sk
->sk_state
) {
5788 /* Once we leave TCP_SYN_RECV, we no longer need req
5792 synack_stamp
= tcp_rsk(req
)->snt_synack
;
5793 tp
->total_retrans
= req
->num_retrans
;
5794 reqsk_fastopen_remove(sk
, req
, false);
5796 synack_stamp
= tp
->lsndtime
;
5797 /* Make sure socket is routed, for correct metrics. */
5798 icsk
->icsk_af_ops
->rebuild_header(sk
);
5799 tcp_init_congestion_control(sk
);
5802 tp
->copied_seq
= tp
->rcv_nxt
;
5803 tcp_init_buffer_space(sk
);
5806 tcp_set_state(sk
, TCP_ESTABLISHED
);
5807 sk
->sk_state_change(sk
);
5809 /* Note, that this wakeup is only for marginal crossed SYN case.
5810 * Passively open sockets are not waked up, because
5811 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5814 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5816 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5817 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
5818 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5819 tcp_synack_rtt_meas(sk
, synack_stamp
);
5821 if (tp
->rx_opt
.tstamp_ok
)
5822 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5825 /* Re-arm the timer because data may have been sent out.
5826 * This is similar to the regular data transmission case
5827 * when new data has just been ack'ed.
5829 * (TFO) - we could try to be more aggressive and
5830 * retransmitting any data sooner based on when they
5835 tcp_init_metrics(sk
);
5837 tcp_update_pacing_rate(sk
);
5839 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5840 tp
->lsndtime
= tcp_time_stamp
;
5842 tcp_initialize_rcv_mss(sk
);
5843 tcp_fast_path_on(tp
);
5846 case TCP_FIN_WAIT1
: {
5847 struct dst_entry
*dst
;
5850 /* If we enter the TCP_FIN_WAIT1 state and we are a
5851 * Fast Open socket and this is the first acceptable
5852 * ACK we have received, this would have acknowledged
5853 * our SYNACK so stop the SYNACK timer.
5856 /* Return RST if ack_seq is invalid.
5857 * Note that RFC793 only says to generate a
5858 * DUPACK for it but for TCP Fast Open it seems
5859 * better to treat this case like TCP_SYN_RECV
5864 /* We no longer need the request sock. */
5865 reqsk_fastopen_remove(sk
, req
, false);
5868 if (tp
->snd_una
!= tp
->write_seq
)
5871 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5872 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5874 dst
= __sk_dst_get(sk
);
5878 if (!sock_flag(sk
, SOCK_DEAD
)) {
5879 /* Wake up lingering close() */
5880 sk
->sk_state_change(sk
);
5884 if (tp
->linger2
< 0 ||
5885 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5886 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5888 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5892 tmo
= tcp_fin_time(sk
);
5893 if (tmo
> TCP_TIMEWAIT_LEN
) {
5894 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5895 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5896 /* Bad case. We could lose such FIN otherwise.
5897 * It is not a big problem, but it looks confusing
5898 * and not so rare event. We still can lose it now,
5899 * if it spins in bh_lock_sock(), but it is really
5902 inet_csk_reset_keepalive_timer(sk
, tmo
);
5904 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5911 if (tp
->snd_una
== tp
->write_seq
) {
5912 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5918 if (tp
->snd_una
== tp
->write_seq
) {
5919 tcp_update_metrics(sk
);
5926 /* step 6: check the URG bit */
5927 tcp_urg(sk
, skb
, th
);
5929 /* step 7: process the segment text */
5930 switch (sk
->sk_state
) {
5931 case TCP_CLOSE_WAIT
:
5934 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5938 /* RFC 793 says to queue data in these states,
5939 * RFC 1122 says we MUST send a reset.
5940 * BSD 4.4 also does reset.
5942 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5943 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5944 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5945 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5951 case TCP_ESTABLISHED
:
5952 tcp_data_queue(sk
, skb
);
5957 /* tcp_data could move socket to TIME-WAIT */
5958 if (sk
->sk_state
!= TCP_CLOSE
) {
5959 tcp_data_snd_check(sk
);
5960 tcp_ack_snd_check(sk
);
5969 EXPORT_SYMBOL(tcp_rcv_state_process
);
5971 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
5973 struct inet_request_sock
*ireq
= inet_rsk(req
);
5975 if (family
== AF_INET
)
5976 net_dbg_ratelimited("drop open request from %pI4/%u\n",
5977 &ireq
->ir_rmt_addr
, port
);
5978 #if IS_ENABLED(CONFIG_IPV6)
5979 else if (family
== AF_INET6
)
5980 net_dbg_ratelimited("drop open request from %pI6/%u\n",
5981 &ireq
->ir_v6_rmt_addr
, port
);
5985 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
5987 * If we receive a SYN packet with these bits set, it means a
5988 * network is playing bad games with TOS bits. In order to
5989 * avoid possible false congestion notifications, we disable
5990 * TCP ECN negotiation.
5992 * Exception: tcp_ca wants ECN. This is required for DCTCP
5993 * congestion control: Linux DCTCP asserts ECT on all packets,
5994 * including SYN, which is most optimal solution; however,
5995 * others, such as FreeBSD do not.
5997 static void tcp_ecn_create_request(struct request_sock
*req
,
5998 const struct sk_buff
*skb
,
5999 const struct sock
*listen_sk
,
6000 const struct dst_entry
*dst
)
6002 const struct tcphdr
*th
= tcp_hdr(skb
);
6003 const struct net
*net
= sock_net(listen_sk
);
6004 bool th_ecn
= th
->ece
&& th
->cwr
;
6011 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
6012 ecn_ok_dst
= dst_feature(dst
, DST_FEATURE_ECN_MASK
);
6013 ecn_ok
= net
->ipv4
.sysctl_tcp_ecn
|| ecn_ok_dst
;
6015 if ((!ect
&& ecn_ok
) || tcp_ca_needs_ecn(listen_sk
) ||
6016 (ecn_ok_dst
& DST_FEATURE_ECN_CA
))
6017 inet_rsk(req
)->ecn_ok
= 1;
6020 static void tcp_openreq_init(struct request_sock
*req
,
6021 const struct tcp_options_received
*rx_opt
,
6022 struct sk_buff
*skb
, const struct sock
*sk
)
6024 struct inet_request_sock
*ireq
= inet_rsk(req
);
6026 req
->rcv_wnd
= 0; /* So that tcp_send_synack() knows! */
6028 tcp_rsk(req
)->rcv_isn
= TCP_SKB_CB(skb
)->seq
;
6029 tcp_rsk(req
)->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
6030 tcp_rsk(req
)->snt_synack
= tcp_time_stamp
;
6031 tcp_rsk(req
)->last_oow_ack_time
= 0;
6032 req
->mss
= rx_opt
->mss_clamp
;
6033 req
->ts_recent
= rx_opt
->saw_tstamp
? rx_opt
->rcv_tsval
: 0;
6034 ireq
->tstamp_ok
= rx_opt
->tstamp_ok
;
6035 ireq
->sack_ok
= rx_opt
->sack_ok
;
6036 ireq
->snd_wscale
= rx_opt
->snd_wscale
;
6037 ireq
->wscale_ok
= rx_opt
->wscale_ok
;
6040 ireq
->ir_rmt_port
= tcp_hdr(skb
)->source
;
6041 ireq
->ir_num
= ntohs(tcp_hdr(skb
)->dest
);
6042 ireq
->ir_mark
= inet_request_mark(sk
, skb
);
6045 struct request_sock
*inet_reqsk_alloc(const struct request_sock_ops
*ops
,
6046 struct sock
*sk_listener
)
6048 struct request_sock
*req
= reqsk_alloc(ops
, sk_listener
);
6051 struct inet_request_sock
*ireq
= inet_rsk(req
);
6053 kmemcheck_annotate_bitfield(ireq
, flags
);
6055 atomic64_set(&ireq
->ir_cookie
, 0);
6056 ireq
->ireq_state
= TCP_NEW_SYN_RECV
;
6057 write_pnet(&ireq
->ireq_net
, sock_net(sk_listener
));
6058 ireq
->ireq_family
= sk_listener
->sk_family
;
6063 EXPORT_SYMBOL(inet_reqsk_alloc
);
6066 * Return true if a syncookie should be sent
6068 static bool tcp_syn_flood_action(struct sock
*sk
,
6069 const struct sk_buff
*skb
,
6072 const char *msg
= "Dropping request";
6073 bool want_cookie
= false;
6074 struct listen_sock
*lopt
;
6076 #ifdef CONFIG_SYN_COOKIES
6077 if (sysctl_tcp_syncookies
) {
6078 msg
= "Sending cookies";
6080 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPREQQFULLDOCOOKIES
);
6083 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPREQQFULLDROP
);
6085 lopt
= inet_csk(sk
)->icsk_accept_queue
.listen_opt
;
6086 if (!lopt
->synflood_warned
&& sysctl_tcp_syncookies
!= 2) {
6087 lopt
->synflood_warned
= 1;
6088 pr_info("%s: Possible SYN flooding on port %d. %s. Check SNMP counters.\n",
6089 proto
, ntohs(tcp_hdr(skb
)->dest
), msg
);
6094 static void tcp_reqsk_record_syn(const struct sock
*sk
,
6095 struct request_sock
*req
,
6096 const struct sk_buff
*skb
)
6098 if (tcp_sk(sk
)->save_syn
) {
6099 u32 len
= skb_network_header_len(skb
) + tcp_hdrlen(skb
);
6102 copy
= kmalloc(len
+ sizeof(u32
), GFP_ATOMIC
);
6105 memcpy(©
[1], skb_network_header(skb
), len
);
6106 req
->saved_syn
= copy
;
6111 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
6112 const struct tcp_request_sock_ops
*af_ops
,
6113 struct sock
*sk
, struct sk_buff
*skb
)
6115 struct tcp_options_received tmp_opt
;
6116 struct request_sock
*req
;
6117 struct tcp_sock
*tp
= tcp_sk(sk
);
6118 struct dst_entry
*dst
= NULL
;
6119 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
6120 bool want_cookie
= false, fastopen
;
6122 struct tcp_fastopen_cookie foc
= { .len
= -1 };
6126 /* TW buckets are converted to open requests without
6127 * limitations, they conserve resources and peer is
6128 * evidently real one.
6130 if ((sysctl_tcp_syncookies
== 2 ||
6131 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
6132 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
6138 /* Accept backlog is full. If we have already queued enough
6139 * of warm entries in syn queue, drop request. It is better than
6140 * clogging syn queue with openreqs with exponentially increasing
6143 if (sk_acceptq_is_full(sk
) && inet_csk_reqsk_queue_young(sk
) > 1) {
6144 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
6148 req
= inet_reqsk_alloc(rsk_ops
, sk
);
6152 tcp_rsk(req
)->af_specific
= af_ops
;
6154 tcp_clear_options(&tmp_opt
);
6155 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
6156 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
6157 tcp_parse_options(skb
, &tmp_opt
, 0, want_cookie
? NULL
: &foc
);
6159 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
6160 tcp_clear_options(&tmp_opt
);
6162 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
6163 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
6165 /* Note: tcp_v6_init_req() might override ir_iif for link locals */
6166 inet_rsk(req
)->ir_iif
= sk
->sk_bound_dev_if
;
6168 af_ops
->init_req(req
, sk
, skb
);
6170 if (security_inet_conn_request(sk
, skb
, req
))
6173 if (!want_cookie
&& !isn
) {
6174 /* VJ's idea. We save last timestamp seen
6175 * from the destination in peer table, when entering
6176 * state TIME-WAIT, and check against it before
6177 * accepting new connection request.
6179 * If "isn" is not zero, this request hit alive
6180 * timewait bucket, so that all the necessary checks
6181 * are made in the function processing timewait state.
6183 if (tcp_death_row
.sysctl_tw_recycle
) {
6186 dst
= af_ops
->route_req(sk
, &fl
, req
, &strict
);
6188 if (dst
&& strict
&&
6189 !tcp_peer_is_proven(req
, dst
, true,
6190 tmp_opt
.saw_tstamp
)) {
6191 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSPASSIVEREJECTED
);
6192 goto drop_and_release
;
6195 /* Kill the following clause, if you dislike this way. */
6196 else if (!sysctl_tcp_syncookies
&&
6197 (sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
6198 (sysctl_max_syn_backlog
>> 2)) &&
6199 !tcp_peer_is_proven(req
, dst
, false,
6200 tmp_opt
.saw_tstamp
)) {
6201 /* Without syncookies last quarter of
6202 * backlog is filled with destinations,
6203 * proven to be alive.
6204 * It means that we continue to communicate
6205 * to destinations, already remembered
6206 * to the moment of synflood.
6208 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
6210 goto drop_and_release
;
6213 isn
= af_ops
->init_seq(skb
);
6216 dst
= af_ops
->route_req(sk
, &fl
, req
, NULL
);
6221 tcp_ecn_create_request(req
, skb
, sk
, dst
);
6224 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
6225 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
6226 if (!tmp_opt
.tstamp_ok
)
6227 inet_rsk(req
)->ecn_ok
= 0;
6230 tcp_rsk(req
)->snt_isn
= isn
;
6231 tcp_openreq_init_rwin(req
, sk
, dst
);
6232 fastopen
= !want_cookie
&&
6233 tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6234 err
= af_ops
->send_synack(sk
, dst
, &fl
, req
,
6235 skb_get_queue_mapping(skb
), &foc
);
6237 if (err
|| want_cookie
)
6240 tcp_rsk(req
)->tfo_listener
= false;
6241 af_ops
->queue_hash_add(sk
, req
, TCP_TIMEOUT_INIT
);
6243 tcp_reqsk_record_syn(sk
, req
, skb
);
6252 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENDROPS
);
6255 EXPORT_SYMBOL(tcp_conn_request
);