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;
104 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
105 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
106 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
107 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
108 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
109 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
110 #define FLAG_ECE 0x40 /* ECE in this ACK */
111 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
112 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
113 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
114 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
115 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
116 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
118 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
119 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
120 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
121 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
123 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
124 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
126 /* Adapt the MSS value used to make delayed ack decision to the
129 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
131 struct inet_connection_sock
*icsk
= inet_csk(sk
);
132 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
135 icsk
->icsk_ack
.last_seg_size
= 0;
137 /* skb->len may jitter because of SACKs, even if peer
138 * sends good full-sized frames.
140 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
141 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
142 icsk
->icsk_ack
.rcv_mss
= len
;
144 /* Otherwise, we make more careful check taking into account,
145 * that SACKs block is variable.
147 * "len" is invariant segment length, including TCP header.
149 len
+= skb
->data
- skb_transport_header(skb
);
150 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
151 /* If PSH is not set, packet should be
152 * full sized, provided peer TCP is not badly broken.
153 * This observation (if it is correct 8)) allows
154 * to handle super-low mtu links fairly.
156 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
157 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
158 /* Subtract also invariant (if peer is RFC compliant),
159 * tcp header plus fixed timestamp option length.
160 * Resulting "len" is MSS free of SACK jitter.
162 len
-= tcp_sk(sk
)->tcp_header_len
;
163 icsk
->icsk_ack
.last_seg_size
= len
;
165 icsk
->icsk_ack
.rcv_mss
= len
;
169 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
170 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
171 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
175 static void tcp_incr_quickack(struct sock
*sk
)
177 struct inet_connection_sock
*icsk
= inet_csk(sk
);
178 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
182 if (quickacks
> icsk
->icsk_ack
.quick
)
183 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
186 static void tcp_enter_quickack_mode(struct sock
*sk
)
188 struct inet_connection_sock
*icsk
= inet_csk(sk
);
189 tcp_incr_quickack(sk
);
190 icsk
->icsk_ack
.pingpong
= 0;
191 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
194 /* Send ACKs quickly, if "quick" count is not exhausted
195 * and the session is not interactive.
198 static inline bool tcp_in_quickack_mode(const struct sock
*sk
)
200 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
202 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
205 static void tcp_ecn_queue_cwr(struct tcp_sock
*tp
)
207 if (tp
->ecn_flags
& TCP_ECN_OK
)
208 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
211 static void tcp_ecn_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
213 if (tcp_hdr(skb
)->cwr
)
214 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
217 static void tcp_ecn_withdraw_cwr(struct tcp_sock
*tp
)
219 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
222 static void __tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
224 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
225 case INET_ECN_NOT_ECT
:
226 /* Funny extension: if ECT is not set on a segment,
227 * and we already seen ECT on a previous segment,
228 * it is probably a retransmit.
230 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
231 tcp_enter_quickack_mode((struct sock
*)tp
);
234 if (tcp_ca_needs_ecn((struct sock
*)tp
))
235 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_IS_CE
);
237 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
238 /* Better not delay acks, sender can have a very low cwnd */
239 tcp_enter_quickack_mode((struct sock
*)tp
);
240 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
242 tp
->ecn_flags
|= TCP_ECN_SEEN
;
245 if (tcp_ca_needs_ecn((struct sock
*)tp
))
246 tcp_ca_event((struct sock
*)tp
, CA_EVENT_ECN_NO_CE
);
247 tp
->ecn_flags
|= TCP_ECN_SEEN
;
252 static void tcp_ecn_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
254 if (tp
->ecn_flags
& TCP_ECN_OK
)
255 __tcp_ecn_check_ce(tp
, skb
);
258 static void tcp_ecn_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
260 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
261 tp
->ecn_flags
&= ~TCP_ECN_OK
;
264 static void tcp_ecn_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
266 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
267 tp
->ecn_flags
&= ~TCP_ECN_OK
;
270 static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
272 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
277 /* Buffer size and advertised window tuning.
279 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
282 static void tcp_sndbuf_expand(struct sock
*sk
)
284 const struct tcp_sock
*tp
= tcp_sk(sk
);
288 /* Worst case is non GSO/TSO : each frame consumes one skb
289 * and skb->head is kmalloced using power of two area of memory
291 per_mss
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
293 SKB_DATA_ALIGN(sizeof(struct skb_shared_info
));
295 per_mss
= roundup_pow_of_two(per_mss
) +
296 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
298 nr_segs
= max_t(u32
, TCP_INIT_CWND
, tp
->snd_cwnd
);
299 nr_segs
= max_t(u32
, nr_segs
, tp
->reordering
+ 1);
301 /* Fast Recovery (RFC 5681 3.2) :
302 * Cubic needs 1.7 factor, rounded to 2 to include
303 * extra cushion (application might react slowly to POLLOUT)
305 sndmem
= 2 * nr_segs
* per_mss
;
307 if (sk
->sk_sndbuf
< sndmem
)
308 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
311 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
313 * All tcp_full_space() is split to two parts: "network" buffer, allocated
314 * forward and advertised in receiver window (tp->rcv_wnd) and
315 * "application buffer", required to isolate scheduling/application
316 * latencies from network.
317 * window_clamp is maximal advertised window. It can be less than
318 * tcp_full_space(), in this case tcp_full_space() - window_clamp
319 * is reserved for "application" buffer. The less window_clamp is
320 * the smoother our behaviour from viewpoint of network, but the lower
321 * throughput and the higher sensitivity of the connection to losses. 8)
323 * rcv_ssthresh is more strict window_clamp used at "slow start"
324 * phase to predict further behaviour of this connection.
325 * It is used for two goals:
326 * - to enforce header prediction at sender, even when application
327 * requires some significant "application buffer". It is check #1.
328 * - to prevent pruning of receive queue because of misprediction
329 * of receiver window. Check #2.
331 * The scheme does not work when sender sends good segments opening
332 * window and then starts to feed us spaghetti. But it should work
333 * in common situations. Otherwise, we have to rely on queue collapsing.
336 /* Slow part of check#2. */
337 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
339 struct tcp_sock
*tp
= tcp_sk(sk
);
341 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
342 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
344 while (tp
->rcv_ssthresh
<= window
) {
345 if (truesize
<= skb
->len
)
346 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
354 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
356 struct tcp_sock
*tp
= tcp_sk(sk
);
359 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
360 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
361 !sk_under_memory_pressure(sk
)) {
364 /* Check #2. Increase window, if skb with such overhead
365 * will fit to rcvbuf in future.
367 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
368 incr
= 2 * tp
->advmss
;
370 incr
= __tcp_grow_window(sk
, skb
);
373 incr
= max_t(int, incr
, 2 * skb
->len
);
374 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
376 inet_csk(sk
)->icsk_ack
.quick
|= 1;
381 /* 3. Tuning rcvbuf, when connection enters established state. */
382 static void tcp_fixup_rcvbuf(struct sock
*sk
)
384 u32 mss
= tcp_sk(sk
)->advmss
;
387 rcvmem
= 2 * SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
) *
388 tcp_default_init_rwnd(mss
);
390 /* Dynamic Right Sizing (DRS) has 2 to 3 RTT latency
391 * Allow enough cushion so that sender is not limited by our window
393 if (sysctl_tcp_moderate_rcvbuf
)
396 if (sk
->sk_rcvbuf
< rcvmem
)
397 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
400 /* 4. Try to fixup all. It is made immediately after connection enters
403 void tcp_init_buffer_space(struct sock
*sk
)
405 struct tcp_sock
*tp
= tcp_sk(sk
);
408 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
409 tcp_fixup_rcvbuf(sk
);
410 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
411 tcp_sndbuf_expand(sk
);
413 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
414 tp
->rcvq_space
.time
= tcp_time_stamp
;
415 tp
->rcvq_space
.seq
= tp
->copied_seq
;
417 maxwin
= tcp_full_space(sk
);
419 if (tp
->window_clamp
>= maxwin
) {
420 tp
->window_clamp
= maxwin
;
422 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
423 tp
->window_clamp
= max(maxwin
-
424 (maxwin
>> sysctl_tcp_app_win
),
428 /* Force reservation of one segment. */
429 if (sysctl_tcp_app_win
&&
430 tp
->window_clamp
> 2 * tp
->advmss
&&
431 tp
->window_clamp
+ tp
->advmss
> maxwin
)
432 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
434 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
435 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
438 /* 5. Recalculate window clamp after socket hit its memory bounds. */
439 static void tcp_clamp_window(struct sock
*sk
)
441 struct tcp_sock
*tp
= tcp_sk(sk
);
442 struct inet_connection_sock
*icsk
= inet_csk(sk
);
444 icsk
->icsk_ack
.quick
= 0;
446 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
447 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
448 !sk_under_memory_pressure(sk
) &&
449 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
450 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
453 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
454 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
457 /* Initialize RCV_MSS value.
458 * RCV_MSS is an our guess about MSS used by the peer.
459 * We haven't any direct information about the MSS.
460 * It's better to underestimate the RCV_MSS rather than overestimate.
461 * Overestimations make us ACKing less frequently than needed.
462 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
464 void tcp_initialize_rcv_mss(struct sock
*sk
)
466 const struct tcp_sock
*tp
= tcp_sk(sk
);
467 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
469 hint
= min(hint
, tp
->rcv_wnd
/ 2);
470 hint
= min(hint
, TCP_MSS_DEFAULT
);
471 hint
= max(hint
, TCP_MIN_MSS
);
473 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
475 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
477 /* Receiver "autotuning" code.
479 * The algorithm for RTT estimation w/o timestamps is based on
480 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
481 * <http://public.lanl.gov/radiant/pubs.html#DRS>
483 * More detail on this code can be found at
484 * <http://staff.psc.edu/jheffner/>,
485 * though this reference is out of date. A new paper
488 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
490 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
496 if (new_sample
!= 0) {
497 /* If we sample in larger samples in the non-timestamp
498 * case, we could grossly overestimate the RTT especially
499 * with chatty applications or bulk transfer apps which
500 * are stalled on filesystem I/O.
502 * Also, since we are only going for a minimum in the
503 * non-timestamp case, we do not smooth things out
504 * else with timestamps disabled convergence takes too
508 m
-= (new_sample
>> 3);
516 /* No previous measure. */
520 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
521 tp
->rcv_rtt_est
.rtt
= new_sample
;
524 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
526 if (tp
->rcv_rtt_est
.time
== 0)
528 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
530 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
533 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
534 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
537 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
538 const struct sk_buff
*skb
)
540 struct tcp_sock
*tp
= tcp_sk(sk
);
541 if (tp
->rx_opt
.rcv_tsecr
&&
542 (TCP_SKB_CB(skb
)->end_seq
-
543 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
544 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
548 * This function should be called every time data is copied to user space.
549 * It calculates the appropriate TCP receive buffer space.
551 void tcp_rcv_space_adjust(struct sock
*sk
)
553 struct tcp_sock
*tp
= tcp_sk(sk
);
557 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
558 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
561 /* Number of bytes copied to user in last RTT */
562 copied
= tp
->copied_seq
- tp
->rcvq_space
.seq
;
563 if (copied
<= tp
->rcvq_space
.space
)
567 * copied = bytes received in previous RTT, our base window
568 * To cope with packet losses, we need a 2x factor
569 * To cope with slow start, and sender growing its cwin by 100 %
570 * every RTT, we need a 4x factor, because the ACK we are sending
571 * now is for the next RTT, not the current one :
572 * <prev RTT . ><current RTT .. ><next RTT .... >
575 if (sysctl_tcp_moderate_rcvbuf
&&
576 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
577 int rcvwin
, rcvmem
, rcvbuf
;
579 /* minimal window to cope with packet losses, assuming
580 * steady state. Add some cushion because of small variations.
582 rcvwin
= (copied
<< 1) + 16 * tp
->advmss
;
584 /* If rate increased by 25%,
585 * assume slow start, rcvwin = 3 * copied
586 * If rate increased by 50%,
587 * assume sender can use 2x growth, rcvwin = 4 * copied
590 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 2)) {
592 tp
->rcvq_space
.space
+ (tp
->rcvq_space
.space
>> 1))
595 rcvwin
+= (rcvwin
>> 1);
598 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
599 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
602 rcvbuf
= min(rcvwin
/ tp
->advmss
* rcvmem
, sysctl_tcp_rmem
[2]);
603 if (rcvbuf
> sk
->sk_rcvbuf
) {
604 sk
->sk_rcvbuf
= rcvbuf
;
606 /* Make the window clamp follow along. */
607 tp
->window_clamp
= rcvwin
;
610 tp
->rcvq_space
.space
= copied
;
613 tp
->rcvq_space
.seq
= tp
->copied_seq
;
614 tp
->rcvq_space
.time
= tcp_time_stamp
;
617 /* There is something which you must keep in mind when you analyze the
618 * behavior of the tp->ato delayed ack timeout interval. When a
619 * connection starts up, we want to ack as quickly as possible. The
620 * problem is that "good" TCP's do slow start at the beginning of data
621 * transmission. The means that until we send the first few ACK's the
622 * sender will sit on his end and only queue most of his data, because
623 * he can only send snd_cwnd unacked packets at any given time. For
624 * each ACK we send, he increments snd_cwnd and transmits more of his
627 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
629 struct tcp_sock
*tp
= tcp_sk(sk
);
630 struct inet_connection_sock
*icsk
= inet_csk(sk
);
633 inet_csk_schedule_ack(sk
);
635 tcp_measure_rcv_mss(sk
, skb
);
637 tcp_rcv_rtt_measure(tp
);
639 now
= tcp_time_stamp
;
641 if (!icsk
->icsk_ack
.ato
) {
642 /* The _first_ data packet received, initialize
643 * delayed ACK engine.
645 tcp_incr_quickack(sk
);
646 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
648 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
650 if (m
<= TCP_ATO_MIN
/ 2) {
651 /* The fastest case is the first. */
652 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
653 } else if (m
< icsk
->icsk_ack
.ato
) {
654 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
655 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
656 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
657 } else if (m
> icsk
->icsk_rto
) {
658 /* Too long gap. Apparently sender failed to
659 * restart window, so that we send ACKs quickly.
661 tcp_incr_quickack(sk
);
665 icsk
->icsk_ack
.lrcvtime
= now
;
667 tcp_ecn_check_ce(tp
, skb
);
670 tcp_grow_window(sk
, skb
);
673 /* Called to compute a smoothed rtt estimate. The data fed to this
674 * routine either comes from timestamps, or from segments that were
675 * known _not_ to have been retransmitted [see Karn/Partridge
676 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
677 * piece by Van Jacobson.
678 * NOTE: the next three routines used to be one big routine.
679 * To save cycles in the RFC 1323 implementation it was better to break
680 * it up into three procedures. -- erics
682 static void tcp_rtt_estimator(struct sock
*sk
, long mrtt_us
)
684 struct tcp_sock
*tp
= tcp_sk(sk
);
685 long m
= mrtt_us
; /* RTT */
686 u32 srtt
= tp
->srtt_us
;
688 /* The following amusing code comes from Jacobson's
689 * article in SIGCOMM '88. Note that rtt and mdev
690 * are scaled versions of rtt and mean deviation.
691 * This is designed to be as fast as possible
692 * m stands for "measurement".
694 * On a 1990 paper the rto value is changed to:
695 * RTO = rtt + 4 * mdev
697 * Funny. This algorithm seems to be very broken.
698 * These formulae increase RTO, when it should be decreased, increase
699 * too slowly, when it should be increased quickly, decrease too quickly
700 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
701 * does not matter how to _calculate_ it. Seems, it was trap
702 * that VJ failed to avoid. 8)
705 m
-= (srtt
>> 3); /* m is now error in rtt est */
706 srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
708 m
= -m
; /* m is now abs(error) */
709 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
710 /* This is similar to one of Eifel findings.
711 * Eifel blocks mdev updates when rtt decreases.
712 * This solution is a bit different: we use finer gain
713 * for mdev in this case (alpha*beta).
714 * Like Eifel it also prevents growth of rto,
715 * but also it limits too fast rto decreases,
716 * happening in pure Eifel.
721 m
-= (tp
->mdev_us
>> 2); /* similar update on mdev */
723 tp
->mdev_us
+= m
; /* mdev = 3/4 mdev + 1/4 new */
724 if (tp
->mdev_us
> tp
->mdev_max_us
) {
725 tp
->mdev_max_us
= tp
->mdev_us
;
726 if (tp
->mdev_max_us
> tp
->rttvar_us
)
727 tp
->rttvar_us
= tp
->mdev_max_us
;
729 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
730 if (tp
->mdev_max_us
< tp
->rttvar_us
)
731 tp
->rttvar_us
-= (tp
->rttvar_us
- tp
->mdev_max_us
) >> 2;
732 tp
->rtt_seq
= tp
->snd_nxt
;
733 tp
->mdev_max_us
= tcp_rto_min_us(sk
);
736 /* no previous measure. */
737 srtt
= m
<< 3; /* take the measured time to be rtt */
738 tp
->mdev_us
= m
<< 1; /* make sure rto = 3*rtt */
739 tp
->rttvar_us
= max(tp
->mdev_us
, tcp_rto_min_us(sk
));
740 tp
->mdev_max_us
= tp
->rttvar_us
;
741 tp
->rtt_seq
= tp
->snd_nxt
;
743 tp
->srtt_us
= max(1U, srtt
);
746 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
747 * Note: TCP stack does not yet implement pacing.
748 * FQ packet scheduler can be used to implement cheap but effective
749 * TCP pacing, to smooth the burst on large writes when packets
750 * in flight is significantly lower than cwnd (or rwin)
752 static void tcp_update_pacing_rate(struct sock
*sk
)
754 const struct tcp_sock
*tp
= tcp_sk(sk
);
757 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
758 rate
= (u64
)tp
->mss_cache
* 2 * (USEC_PER_SEC
<< 3);
760 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
762 if (likely(tp
->srtt_us
))
763 do_div(rate
, tp
->srtt_us
);
765 /* ACCESS_ONCE() is needed because sch_fq fetches sk_pacing_rate
766 * without any lock. We want to make sure compiler wont store
767 * intermediate values in this location.
769 ACCESS_ONCE(sk
->sk_pacing_rate
) = min_t(u64
, rate
,
770 sk
->sk_max_pacing_rate
);
773 /* Calculate rto without backoff. This is the second half of Van Jacobson's
774 * routine referred to above.
776 static void tcp_set_rto(struct sock
*sk
)
778 const struct tcp_sock
*tp
= tcp_sk(sk
);
779 /* Old crap is replaced with new one. 8)
782 * 1. If rtt variance happened to be less 50msec, it is hallucination.
783 * It cannot be less due to utterly erratic ACK generation made
784 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
785 * to do with delayed acks, because at cwnd>2 true delack timeout
786 * is invisible. Actually, Linux-2.4 also generates erratic
787 * ACKs in some circumstances.
789 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
791 /* 2. Fixups made earlier cannot be right.
792 * If we do not estimate RTO correctly without them,
793 * all the algo is pure shit and should be replaced
794 * with correct one. It is exactly, which we pretend to do.
797 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
798 * guarantees that rto is higher.
803 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
805 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
808 cwnd
= TCP_INIT_CWND
;
809 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
813 * Packet counting of FACK is based on in-order assumptions, therefore TCP
814 * disables it when reordering is detected
816 void tcp_disable_fack(struct tcp_sock
*tp
)
818 /* RFC3517 uses different metric in lost marker => reset on change */
820 tp
->lost_skb_hint
= NULL
;
821 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
824 /* Take a notice that peer is sending D-SACKs */
825 static void tcp_dsack_seen(struct tcp_sock
*tp
)
827 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
830 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
833 struct tcp_sock
*tp
= tcp_sk(sk
);
834 if (metric
> tp
->reordering
) {
837 tp
->reordering
= min(sysctl_tcp_max_reordering
, metric
);
839 /* This exciting event is worth to be remembered. 8) */
841 mib_idx
= LINUX_MIB_TCPTSREORDER
;
842 else if (tcp_is_reno(tp
))
843 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
844 else if (tcp_is_fack(tp
))
845 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
847 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
849 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
850 #if FASTRETRANS_DEBUG > 1
851 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
852 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
856 tp
->undo_marker
? tp
->undo_retrans
: 0);
858 tcp_disable_fack(tp
);
862 tcp_disable_early_retrans(tp
);
865 /* This must be called before lost_out is incremented */
866 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
868 if ((tp
->retransmit_skb_hint
== NULL
) ||
869 before(TCP_SKB_CB(skb
)->seq
,
870 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
871 tp
->retransmit_skb_hint
= skb
;
874 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
875 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
878 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
880 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
881 tcp_verify_retransmit_hint(tp
, skb
);
883 tp
->lost_out
+= tcp_skb_pcount(skb
);
884 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
888 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
891 tcp_verify_retransmit_hint(tp
, skb
);
893 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
894 tp
->lost_out
+= tcp_skb_pcount(skb
);
895 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
899 /* This procedure tags the retransmission queue when SACKs arrive.
901 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
902 * Packets in queue with these bits set are counted in variables
903 * sacked_out, retrans_out and lost_out, correspondingly.
905 * Valid combinations are:
906 * Tag InFlight Description
907 * 0 1 - orig segment is in flight.
908 * S 0 - nothing flies, orig reached receiver.
909 * L 0 - nothing flies, orig lost by net.
910 * R 2 - both orig and retransmit are in flight.
911 * L|R 1 - orig is lost, retransmit is in flight.
912 * S|R 1 - orig reached receiver, retrans is still in flight.
913 * (L|S|R is logically valid, it could occur when L|R is sacked,
914 * but it is equivalent to plain S and code short-curcuits it to S.
915 * L|S is logically invalid, it would mean -1 packet in flight 8))
917 * These 6 states form finite state machine, controlled by the following events:
918 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
919 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
920 * 3. Loss detection event of two flavors:
921 * A. Scoreboard estimator decided the packet is lost.
922 * A'. Reno "three dupacks" marks head of queue lost.
923 * A''. Its FACK modification, head until snd.fack is lost.
924 * B. SACK arrives sacking SND.NXT at the moment, when the
925 * segment was retransmitted.
926 * 4. D-SACK added new rule: D-SACK changes any tag to S.
928 * It is pleasant to note, that state diagram turns out to be commutative,
929 * so that we are allowed not to be bothered by order of our actions,
930 * when multiple events arrive simultaneously. (see the function below).
932 * Reordering detection.
933 * --------------------
934 * Reordering metric is maximal distance, which a packet can be displaced
935 * in packet stream. With SACKs we can estimate it:
937 * 1. SACK fills old hole and the corresponding segment was not
938 * ever retransmitted -> reordering. Alas, we cannot use it
939 * when segment was retransmitted.
940 * 2. The last flaw is solved with D-SACK. D-SACK arrives
941 * for retransmitted and already SACKed segment -> reordering..
942 * Both of these heuristics are not used in Loss state, when we cannot
943 * account for retransmits accurately.
945 * SACK block validation.
946 * ----------------------
948 * SACK block range validation checks that the received SACK block fits to
949 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
950 * Note that SND.UNA is not included to the range though being valid because
951 * it means that the receiver is rather inconsistent with itself reporting
952 * SACK reneging when it should advance SND.UNA. Such SACK block this is
953 * perfectly valid, however, in light of RFC2018 which explicitly states
954 * that "SACK block MUST reflect the newest segment. Even if the newest
955 * segment is going to be discarded ...", not that it looks very clever
956 * in case of head skb. Due to potentional receiver driven attacks, we
957 * choose to avoid immediate execution of a walk in write queue due to
958 * reneging and defer head skb's loss recovery to standard loss recovery
959 * procedure that will eventually trigger (nothing forbids us doing this).
961 * Implements also blockage to start_seq wrap-around. Problem lies in the
962 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
963 * there's no guarantee that it will be before snd_nxt (n). The problem
964 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
967 * <- outs wnd -> <- wrapzone ->
968 * u e n u_w e_w s n_w
970 * |<------------+------+----- TCP seqno space --------------+---------->|
971 * ...-- <2^31 ->| |<--------...
972 * ...---- >2^31 ------>| |<--------...
974 * Current code wouldn't be vulnerable but it's better still to discard such
975 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
976 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
977 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
978 * equal to the ideal case (infinite seqno space without wrap caused issues).
980 * With D-SACK the lower bound is extended to cover sequence space below
981 * SND.UNA down to undo_marker, which is the last point of interest. Yet
982 * again, D-SACK block must not to go across snd_una (for the same reason as
983 * for the normal SACK blocks, explained above). But there all simplicity
984 * ends, TCP might receive valid D-SACKs below that. As long as they reside
985 * fully below undo_marker they do not affect behavior in anyway and can
986 * therefore be safely ignored. In rare cases (which are more or less
987 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
988 * fragmentation and packet reordering past skb's retransmission. To consider
989 * them correctly, the acceptable range must be extended even more though
990 * the exact amount is rather hard to quantify. However, tp->max_window can
991 * be used as an exaggerated estimate.
993 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
994 u32 start_seq
, u32 end_seq
)
996 /* Too far in future, or reversed (interpretation is ambiguous) */
997 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1000 /* Nasty start_seq wrap-around check (see comments above) */
1001 if (!before(start_seq
, tp
->snd_nxt
))
1004 /* In outstanding window? ...This is valid exit for D-SACKs too.
1005 * start_seq == snd_una is non-sensical (see comments above)
1007 if (after(start_seq
, tp
->snd_una
))
1010 if (!is_dsack
|| !tp
->undo_marker
)
1013 /* ...Then it's D-SACK, and must reside below snd_una completely */
1014 if (after(end_seq
, tp
->snd_una
))
1017 if (!before(start_seq
, tp
->undo_marker
))
1021 if (!after(end_seq
, tp
->undo_marker
))
1024 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1025 * start_seq < undo_marker and end_seq >= undo_marker.
1027 return !before(start_seq
, end_seq
- tp
->max_window
);
1030 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1031 * Event "B". Later note: FACK people cheated me again 8), we have to account
1032 * for reordering! Ugly, but should help.
1034 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1035 * less than what is now known to be received by the other end (derived from
1036 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1037 * retransmitted skbs to avoid some costly processing per ACKs.
1039 static void tcp_mark_lost_retrans(struct sock
*sk
)
1041 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1042 struct tcp_sock
*tp
= tcp_sk(sk
);
1043 struct sk_buff
*skb
;
1045 u32 new_low_seq
= tp
->snd_nxt
;
1046 u32 received_upto
= tcp_highest_sack_seq(tp
);
1048 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1049 !after(received_upto
, tp
->lost_retrans_low
) ||
1050 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1053 tcp_for_write_queue(skb
, sk
) {
1054 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1056 if (skb
== tcp_send_head(sk
))
1058 if (cnt
== tp
->retrans_out
)
1060 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1063 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1066 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1067 * constraint here (see above) but figuring out that at
1068 * least tp->reordering SACK blocks reside between ack_seq
1069 * and received_upto is not easy task to do cheaply with
1070 * the available datastructures.
1072 * Whether FACK should check here for tp->reordering segs
1073 * in-between one could argue for either way (it would be
1074 * rather simple to implement as we could count fack_count
1075 * during the walk and do tp->fackets_out - fack_count).
1077 if (after(received_upto
, ack_seq
)) {
1078 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1079 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1081 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1082 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1084 if (before(ack_seq
, new_low_seq
))
1085 new_low_seq
= ack_seq
;
1086 cnt
+= tcp_skb_pcount(skb
);
1090 if (tp
->retrans_out
)
1091 tp
->lost_retrans_low
= new_low_seq
;
1094 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1095 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1098 struct tcp_sock
*tp
= tcp_sk(sk
);
1099 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1100 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1101 bool dup_sack
= false;
1103 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1106 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1107 } else if (num_sacks
> 1) {
1108 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1109 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1111 if (!after(end_seq_0
, end_seq_1
) &&
1112 !before(start_seq_0
, start_seq_1
)) {
1115 NET_INC_STATS_BH(sock_net(sk
),
1116 LINUX_MIB_TCPDSACKOFORECV
);
1120 /* D-SACK for already forgotten data... Do dumb counting. */
1121 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1122 !after(end_seq_0
, prior_snd_una
) &&
1123 after(end_seq_0
, tp
->undo_marker
))
1129 struct tcp_sacktag_state
{
1132 long rtt_us
; /* RTT measured by SACKing never-retransmitted data */
1136 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1137 * the incoming SACK may not exactly match but we can find smaller MSS
1138 * aligned portion of it that matches. Therefore we might need to fragment
1139 * which may fail and creates some hassle (caller must handle error case
1142 * FIXME: this could be merged to shift decision code
1144 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1145 u32 start_seq
, u32 end_seq
)
1149 unsigned int pkt_len
;
1152 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1153 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1155 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1156 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1157 mss
= tcp_skb_mss(skb
);
1158 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1161 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1165 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1170 /* Round if necessary so that SACKs cover only full MSSes
1171 * and/or the remaining small portion (if present)
1173 if (pkt_len
> mss
) {
1174 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1175 if (!in_sack
&& new_len
< pkt_len
) {
1177 if (new_len
>= skb
->len
)
1182 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
, GFP_ATOMIC
);
1190 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1191 static u8
tcp_sacktag_one(struct sock
*sk
,
1192 struct tcp_sacktag_state
*state
, u8 sacked
,
1193 u32 start_seq
, u32 end_seq
,
1194 int dup_sack
, int pcount
,
1195 const struct skb_mstamp
*xmit_time
)
1197 struct tcp_sock
*tp
= tcp_sk(sk
);
1198 int fack_count
= state
->fack_count
;
1200 /* Account D-SACK for retransmitted packet. */
1201 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1202 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1203 after(end_seq
, tp
->undo_marker
))
1205 if (sacked
& TCPCB_SACKED_ACKED
)
1206 state
->reord
= min(fack_count
, state
->reord
);
1209 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1210 if (!after(end_seq
, tp
->snd_una
))
1213 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1214 if (sacked
& TCPCB_SACKED_RETRANS
) {
1215 /* If the segment is not tagged as lost,
1216 * we do not clear RETRANS, believing
1217 * that retransmission is still in flight.
1219 if (sacked
& TCPCB_LOST
) {
1220 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1221 tp
->lost_out
-= pcount
;
1222 tp
->retrans_out
-= pcount
;
1225 if (!(sacked
& TCPCB_RETRANS
)) {
1226 /* New sack for not retransmitted frame,
1227 * which was in hole. It is reordering.
1229 if (before(start_seq
,
1230 tcp_highest_sack_seq(tp
)))
1231 state
->reord
= min(fack_count
,
1233 if (!after(end_seq
, tp
->high_seq
))
1234 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1235 /* Pick the earliest sequence sacked for RTT */
1236 if (state
->rtt_us
< 0) {
1237 struct skb_mstamp now
;
1239 skb_mstamp_get(&now
);
1240 state
->rtt_us
= skb_mstamp_us_delta(&now
,
1245 if (sacked
& TCPCB_LOST
) {
1246 sacked
&= ~TCPCB_LOST
;
1247 tp
->lost_out
-= pcount
;
1251 sacked
|= TCPCB_SACKED_ACKED
;
1252 state
->flag
|= FLAG_DATA_SACKED
;
1253 tp
->sacked_out
+= pcount
;
1255 fack_count
+= pcount
;
1257 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1258 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1259 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1260 tp
->lost_cnt_hint
+= pcount
;
1262 if (fack_count
> tp
->fackets_out
)
1263 tp
->fackets_out
= fack_count
;
1266 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1267 * frames and clear it. undo_retrans is decreased above, L|R frames
1268 * are accounted above as well.
1270 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1271 sacked
&= ~TCPCB_SACKED_RETRANS
;
1272 tp
->retrans_out
-= pcount
;
1278 /* Shift newly-SACKed bytes from this skb to the immediately previous
1279 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1281 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1282 struct tcp_sacktag_state
*state
,
1283 unsigned int pcount
, int shifted
, int mss
,
1286 struct tcp_sock
*tp
= tcp_sk(sk
);
1287 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1288 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1289 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1293 /* Adjust counters and hints for the newly sacked sequence
1294 * range but discard the return value since prev is already
1295 * marked. We must tag the range first because the seq
1296 * advancement below implicitly advances
1297 * tcp_highest_sack_seq() when skb is highest_sack.
1299 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1300 start_seq
, end_seq
, dup_sack
, pcount
,
1303 if (skb
== tp
->lost_skb_hint
)
1304 tp
->lost_cnt_hint
+= pcount
;
1306 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1307 TCP_SKB_CB(skb
)->seq
+= shifted
;
1309 tcp_skb_pcount_add(prev
, pcount
);
1310 BUG_ON(tcp_skb_pcount(skb
) < pcount
);
1311 tcp_skb_pcount_add(skb
, -pcount
);
1313 /* When we're adding to gso_segs == 1, gso_size will be zero,
1314 * in theory this shouldn't be necessary but as long as DSACK
1315 * code can come after this skb later on it's better to keep
1316 * setting gso_size to something.
1318 if (!skb_shinfo(prev
)->gso_size
) {
1319 skb_shinfo(prev
)->gso_size
= mss
;
1320 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1323 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1324 if (tcp_skb_pcount(skb
) <= 1) {
1325 skb_shinfo(skb
)->gso_size
= 0;
1326 skb_shinfo(skb
)->gso_type
= 0;
1329 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1330 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1333 BUG_ON(!tcp_skb_pcount(skb
));
1334 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1338 /* Whole SKB was eaten :-) */
1340 if (skb
== tp
->retransmit_skb_hint
)
1341 tp
->retransmit_skb_hint
= prev
;
1342 if (skb
== tp
->lost_skb_hint
) {
1343 tp
->lost_skb_hint
= prev
;
1344 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1347 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1348 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1349 TCP_SKB_CB(prev
)->end_seq
++;
1351 if (skb
== tcp_highest_sack(sk
))
1352 tcp_advance_highest_sack(sk
, skb
);
1354 tcp_unlink_write_queue(skb
, sk
);
1355 sk_wmem_free_skb(sk
, skb
);
1357 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1362 /* I wish gso_size would have a bit more sane initialization than
1363 * something-or-zero which complicates things
1365 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1367 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1370 /* Shifting pages past head area doesn't work */
1371 static int skb_can_shift(const struct sk_buff
*skb
)
1373 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1376 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1379 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1380 struct tcp_sacktag_state
*state
,
1381 u32 start_seq
, u32 end_seq
,
1384 struct tcp_sock
*tp
= tcp_sk(sk
);
1385 struct sk_buff
*prev
;
1391 if (!sk_can_gso(sk
))
1394 /* Normally R but no L won't result in plain S */
1396 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1398 if (!skb_can_shift(skb
))
1400 /* This frame is about to be dropped (was ACKed). */
1401 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1404 /* Can only happen with delayed DSACK + discard craziness */
1405 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1407 prev
= tcp_write_queue_prev(sk
, skb
);
1409 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1412 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1413 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1417 pcount
= tcp_skb_pcount(skb
);
1418 mss
= tcp_skb_seglen(skb
);
1420 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1421 * drop this restriction as unnecessary
1423 if (mss
!= tcp_skb_seglen(prev
))
1426 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1428 /* CHECKME: This is non-MSS split case only?, this will
1429 * cause skipped skbs due to advancing loop btw, original
1430 * has that feature too
1432 if (tcp_skb_pcount(skb
) <= 1)
1435 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1437 /* TODO: head merge to next could be attempted here
1438 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1439 * though it might not be worth of the additional hassle
1441 * ...we can probably just fallback to what was done
1442 * previously. We could try merging non-SACKed ones
1443 * as well but it probably isn't going to buy off
1444 * because later SACKs might again split them, and
1445 * it would make skb timestamp tracking considerably
1451 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1453 BUG_ON(len
> skb
->len
);
1455 /* MSS boundaries should be honoured or else pcount will
1456 * severely break even though it makes things bit trickier.
1457 * Optimize common case to avoid most of the divides
1459 mss
= tcp_skb_mss(skb
);
1461 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1462 * drop this restriction as unnecessary
1464 if (mss
!= tcp_skb_seglen(prev
))
1469 } else if (len
< mss
) {
1477 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1478 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1481 if (!skb_shift(prev
, skb
, len
))
1483 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1486 /* Hole filled allows collapsing with the next as well, this is very
1487 * useful when hole on every nth skb pattern happens
1489 if (prev
== tcp_write_queue_tail(sk
))
1491 skb
= tcp_write_queue_next(sk
, prev
);
1493 if (!skb_can_shift(skb
) ||
1494 (skb
== tcp_send_head(sk
)) ||
1495 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1496 (mss
!= tcp_skb_seglen(skb
)))
1500 if (skb_shift(prev
, skb
, len
)) {
1501 pcount
+= tcp_skb_pcount(skb
);
1502 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1506 state
->fack_count
+= pcount
;
1513 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1517 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1518 struct tcp_sack_block
*next_dup
,
1519 struct tcp_sacktag_state
*state
,
1520 u32 start_seq
, u32 end_seq
,
1523 struct tcp_sock
*tp
= tcp_sk(sk
);
1524 struct sk_buff
*tmp
;
1526 tcp_for_write_queue_from(skb
, sk
) {
1528 bool dup_sack
= dup_sack_in
;
1530 if (skb
== tcp_send_head(sk
))
1533 /* queue is in-order => we can short-circuit the walk early */
1534 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1537 if ((next_dup
!= NULL
) &&
1538 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1539 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1540 next_dup
->start_seq
,
1546 /* skb reference here is a bit tricky to get right, since
1547 * shifting can eat and free both this skb and the next,
1548 * so not even _safe variant of the loop is enough.
1551 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1552 start_seq
, end_seq
, dup_sack
);
1561 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1567 if (unlikely(in_sack
< 0))
1571 TCP_SKB_CB(skb
)->sacked
=
1574 TCP_SKB_CB(skb
)->sacked
,
1575 TCP_SKB_CB(skb
)->seq
,
1576 TCP_SKB_CB(skb
)->end_seq
,
1578 tcp_skb_pcount(skb
),
1581 if (!before(TCP_SKB_CB(skb
)->seq
,
1582 tcp_highest_sack_seq(tp
)))
1583 tcp_advance_highest_sack(sk
, skb
);
1586 state
->fack_count
+= tcp_skb_pcount(skb
);
1591 /* Avoid all extra work that is being done by sacktag while walking in
1594 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1595 struct tcp_sacktag_state
*state
,
1598 tcp_for_write_queue_from(skb
, sk
) {
1599 if (skb
== tcp_send_head(sk
))
1602 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1605 state
->fack_count
+= tcp_skb_pcount(skb
);
1610 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1612 struct tcp_sack_block
*next_dup
,
1613 struct tcp_sacktag_state
*state
,
1616 if (next_dup
== NULL
)
1619 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1620 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1621 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1622 next_dup
->start_seq
, next_dup
->end_seq
,
1629 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1631 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1635 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1636 u32 prior_snd_una
, long *sack_rtt_us
)
1638 struct tcp_sock
*tp
= tcp_sk(sk
);
1639 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1640 TCP_SKB_CB(ack_skb
)->sacked
);
1641 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1642 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1643 struct tcp_sack_block
*cache
;
1644 struct tcp_sacktag_state state
;
1645 struct sk_buff
*skb
;
1646 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1648 bool found_dup_sack
= false;
1650 int first_sack_index
;
1653 state
.reord
= tp
->packets_out
;
1656 if (!tp
->sacked_out
) {
1657 if (WARN_ON(tp
->fackets_out
))
1658 tp
->fackets_out
= 0;
1659 tcp_highest_sack_reset(sk
);
1662 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1663 num_sacks
, prior_snd_una
);
1665 state
.flag
|= FLAG_DSACKING_ACK
;
1667 /* Eliminate too old ACKs, but take into
1668 * account more or less fresh ones, they can
1669 * contain valid SACK info.
1671 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1674 if (!tp
->packets_out
)
1678 first_sack_index
= 0;
1679 for (i
= 0; i
< num_sacks
; i
++) {
1680 bool dup_sack
= !i
&& found_dup_sack
;
1682 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1683 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1685 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1686 sp
[used_sacks
].start_seq
,
1687 sp
[used_sacks
].end_seq
)) {
1691 if (!tp
->undo_marker
)
1692 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1694 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1696 /* Don't count olds caused by ACK reordering */
1697 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1698 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1700 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1703 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1705 first_sack_index
= -1;
1709 /* Ignore very old stuff early */
1710 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1716 /* order SACK blocks to allow in order walk of the retrans queue */
1717 for (i
= used_sacks
- 1; i
> 0; i
--) {
1718 for (j
= 0; j
< i
; j
++) {
1719 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1720 swap(sp
[j
], sp
[j
+ 1]);
1722 /* Track where the first SACK block goes to */
1723 if (j
== first_sack_index
)
1724 first_sack_index
= j
+ 1;
1729 skb
= tcp_write_queue_head(sk
);
1730 state
.fack_count
= 0;
1733 if (!tp
->sacked_out
) {
1734 /* It's already past, so skip checking against it */
1735 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1737 cache
= tp
->recv_sack_cache
;
1738 /* Skip empty blocks in at head of the cache */
1739 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1744 while (i
< used_sacks
) {
1745 u32 start_seq
= sp
[i
].start_seq
;
1746 u32 end_seq
= sp
[i
].end_seq
;
1747 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1748 struct tcp_sack_block
*next_dup
= NULL
;
1750 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1751 next_dup
= &sp
[i
+ 1];
1753 /* Skip too early cached blocks */
1754 while (tcp_sack_cache_ok(tp
, cache
) &&
1755 !before(start_seq
, cache
->end_seq
))
1758 /* Can skip some work by looking recv_sack_cache? */
1759 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1760 after(end_seq
, cache
->start_seq
)) {
1763 if (before(start_seq
, cache
->start_seq
)) {
1764 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1766 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1773 /* Rest of the block already fully processed? */
1774 if (!after(end_seq
, cache
->end_seq
))
1777 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1781 /* ...tail remains todo... */
1782 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1783 /* ...but better entrypoint exists! */
1784 skb
= tcp_highest_sack(sk
);
1787 state
.fack_count
= tp
->fackets_out
;
1792 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1793 /* Check overlap against next cached too (past this one already) */
1798 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1799 skb
= tcp_highest_sack(sk
);
1802 state
.fack_count
= tp
->fackets_out
;
1804 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1807 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1808 start_seq
, end_seq
, dup_sack
);
1814 /* Clear the head of the cache sack blocks so we can skip it next time */
1815 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1816 tp
->recv_sack_cache
[i
].start_seq
= 0;
1817 tp
->recv_sack_cache
[i
].end_seq
= 0;
1819 for (j
= 0; j
< used_sacks
; j
++)
1820 tp
->recv_sack_cache
[i
++] = sp
[j
];
1822 tcp_mark_lost_retrans(sk
);
1824 tcp_verify_left_out(tp
);
1826 if ((state
.reord
< tp
->fackets_out
) &&
1827 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1828 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1832 #if FASTRETRANS_DEBUG > 0
1833 WARN_ON((int)tp
->sacked_out
< 0);
1834 WARN_ON((int)tp
->lost_out
< 0);
1835 WARN_ON((int)tp
->retrans_out
< 0);
1836 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1838 *sack_rtt_us
= state
.rtt_us
;
1842 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1843 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1845 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1849 holes
= max(tp
->lost_out
, 1U);
1850 holes
= min(holes
, tp
->packets_out
);
1852 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1853 tp
->sacked_out
= tp
->packets_out
- holes
;
1859 /* If we receive more dupacks than we expected counting segments
1860 * in assumption of absent reordering, interpret this as reordering.
1861 * The only another reason could be bug in receiver TCP.
1863 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1865 struct tcp_sock
*tp
= tcp_sk(sk
);
1866 if (tcp_limit_reno_sacked(tp
))
1867 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1870 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1872 static void tcp_add_reno_sack(struct sock
*sk
)
1874 struct tcp_sock
*tp
= tcp_sk(sk
);
1876 tcp_check_reno_reordering(sk
, 0);
1877 tcp_verify_left_out(tp
);
1880 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1882 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1884 struct tcp_sock
*tp
= tcp_sk(sk
);
1887 /* One ACK acked hole. The rest eat duplicate ACKs. */
1888 if (acked
- 1 >= tp
->sacked_out
)
1891 tp
->sacked_out
-= acked
- 1;
1893 tcp_check_reno_reordering(sk
, acked
);
1894 tcp_verify_left_out(tp
);
1897 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1902 void tcp_clear_retrans(struct tcp_sock
*tp
)
1904 tp
->retrans_out
= 0;
1906 tp
->undo_marker
= 0;
1907 tp
->undo_retrans
= -1;
1908 tp
->fackets_out
= 0;
1912 static inline void tcp_init_undo(struct tcp_sock
*tp
)
1914 tp
->undo_marker
= tp
->snd_una
;
1915 /* Retransmission still in flight may cause DSACKs later. */
1916 tp
->undo_retrans
= tp
->retrans_out
? : -1;
1919 /* Enter Loss state. If we detect SACK reneging, forget all SACK information
1920 * and reset tags completely, otherwise preserve SACKs. If receiver
1921 * dropped its ofo queue, we will know this due to reneging detection.
1923 void tcp_enter_loss(struct sock
*sk
)
1925 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1926 struct tcp_sock
*tp
= tcp_sk(sk
);
1927 struct sk_buff
*skb
;
1928 bool new_recovery
= false;
1929 bool is_reneg
; /* is receiver reneging on SACKs? */
1931 /* Reduce ssthresh if it has not yet been made inside this window. */
1932 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1933 !after(tp
->high_seq
, tp
->snd_una
) ||
1934 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1935 new_recovery
= true;
1936 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1937 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1938 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1942 tp
->snd_cwnd_cnt
= 0;
1943 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1945 tp
->retrans_out
= 0;
1948 if (tcp_is_reno(tp
))
1949 tcp_reset_reno_sack(tp
);
1951 skb
= tcp_write_queue_head(sk
);
1952 is_reneg
= skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
);
1954 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1956 tp
->fackets_out
= 0;
1958 tcp_clear_all_retrans_hints(tp
);
1960 tcp_for_write_queue(skb
, sk
) {
1961 if (skb
== tcp_send_head(sk
))
1964 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1965 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || is_reneg
) {
1966 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1967 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1968 tp
->lost_out
+= tcp_skb_pcount(skb
);
1969 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1972 tcp_verify_left_out(tp
);
1974 /* Timeout in disordered state after receiving substantial DUPACKs
1975 * suggests that the degree of reordering is over-estimated.
1977 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
&&
1978 tp
->sacked_out
>= sysctl_tcp_reordering
)
1979 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1980 sysctl_tcp_reordering
);
1981 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1982 tp
->high_seq
= tp
->snd_nxt
;
1983 tcp_ecn_queue_cwr(tp
);
1985 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1986 * loss recovery is underway except recurring timeout(s) on
1987 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1989 tp
->frto
= sysctl_tcp_frto
&&
1990 (new_recovery
|| icsk
->icsk_retransmits
) &&
1991 !inet_csk(sk
)->icsk_mtup
.probe_size
;
1994 /* If ACK arrived pointing to a remembered SACK, it means that our
1995 * remembered SACKs do not reflect real state of receiver i.e.
1996 * receiver _host_ is heavily congested (or buggy).
1998 * To avoid big spurious retransmission bursts due to transient SACK
1999 * scoreboard oddities that look like reneging, we give the receiver a
2000 * little time (max(RTT/2, 10ms)) to send us some more ACKs that will
2001 * restore sanity to the SACK scoreboard. If the apparent reneging
2002 * persists until this RTO then we'll clear the SACK scoreboard.
2004 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2006 if (flag
& FLAG_SACK_RENEGING
) {
2007 struct tcp_sock
*tp
= tcp_sk(sk
);
2008 unsigned long delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 4),
2009 msecs_to_jiffies(10));
2011 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2012 delay
, TCP_RTO_MAX
);
2018 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2020 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2023 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2024 * counter when SACK is enabled (without SACK, sacked_out is used for
2027 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2028 * segments up to the highest received SACK block so far and holes in
2031 * With reordering, holes may still be in flight, so RFC3517 recovery
2032 * uses pure sacked_out (total number of SACKed segments) even though
2033 * it violates the RFC that uses duplicate ACKs, often these are equal
2034 * but when e.g. out-of-window ACKs or packet duplication occurs,
2035 * they differ. Since neither occurs due to loss, TCP should really
2038 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2040 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2043 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2045 struct tcp_sock
*tp
= tcp_sk(sk
);
2046 unsigned long delay
;
2048 /* Delay early retransmit and entering fast recovery for
2049 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2050 * available, or RTO is scheduled to fire first.
2052 if (sysctl_tcp_early_retrans
< 2 || sysctl_tcp_early_retrans
> 3 ||
2053 (flag
& FLAG_ECE
) || !tp
->srtt_us
)
2056 delay
= max(usecs_to_jiffies(tp
->srtt_us
>> 5),
2057 msecs_to_jiffies(2));
2059 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2062 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_EARLY_RETRANS
, delay
,
2067 /* Linux NewReno/SACK/FACK/ECN state machine.
2068 * --------------------------------------
2070 * "Open" Normal state, no dubious events, fast path.
2071 * "Disorder" In all the respects it is "Open",
2072 * but requires a bit more attention. It is entered when
2073 * we see some SACKs or dupacks. It is split of "Open"
2074 * mainly to move some processing from fast path to slow one.
2075 * "CWR" CWND was reduced due to some Congestion Notification event.
2076 * It can be ECN, ICMP source quench, local device congestion.
2077 * "Recovery" CWND was reduced, we are fast-retransmitting.
2078 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2080 * tcp_fastretrans_alert() is entered:
2081 * - each incoming ACK, if state is not "Open"
2082 * - when arrived ACK is unusual, namely:
2087 * Counting packets in flight is pretty simple.
2089 * in_flight = packets_out - left_out + retrans_out
2091 * packets_out is SND.NXT-SND.UNA counted in packets.
2093 * retrans_out is number of retransmitted segments.
2095 * left_out is number of segments left network, but not ACKed yet.
2097 * left_out = sacked_out + lost_out
2099 * sacked_out: Packets, which arrived to receiver out of order
2100 * and hence not ACKed. With SACKs this number is simply
2101 * amount of SACKed data. Even without SACKs
2102 * it is easy to give pretty reliable estimate of this number,
2103 * counting duplicate ACKs.
2105 * lost_out: Packets lost by network. TCP has no explicit
2106 * "loss notification" feedback from network (for now).
2107 * It means that this number can be only _guessed_.
2108 * Actually, it is the heuristics to predict lossage that
2109 * distinguishes different algorithms.
2111 * F.e. after RTO, when all the queue is considered as lost,
2112 * lost_out = packets_out and in_flight = retrans_out.
2114 * Essentially, we have now two algorithms counting
2117 * FACK: It is the simplest heuristics. As soon as we decided
2118 * that something is lost, we decide that _all_ not SACKed
2119 * packets until the most forward SACK are lost. I.e.
2120 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2121 * It is absolutely correct estimate, if network does not reorder
2122 * packets. And it loses any connection to reality when reordering
2123 * takes place. We use FACK by default until reordering
2124 * is suspected on the path to this destination.
2126 * NewReno: when Recovery is entered, we assume that one segment
2127 * is lost (classic Reno). While we are in Recovery and
2128 * a partial ACK arrives, we assume that one more packet
2129 * is lost (NewReno). This heuristics are the same in NewReno
2132 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2133 * deflation etc. CWND is real congestion window, never inflated, changes
2134 * only according to classic VJ rules.
2136 * Really tricky (and requiring careful tuning) part of algorithm
2137 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2138 * The first determines the moment _when_ we should reduce CWND and,
2139 * hence, slow down forward transmission. In fact, it determines the moment
2140 * when we decide that hole is caused by loss, rather than by a reorder.
2142 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2143 * holes, caused by lost packets.
2145 * And the most logically complicated part of algorithm is undo
2146 * heuristics. We detect false retransmits due to both too early
2147 * fast retransmit (reordering) and underestimated RTO, analyzing
2148 * timestamps and D-SACKs. When we detect that some segments were
2149 * retransmitted by mistake and CWND reduction was wrong, we undo
2150 * window reduction and abort recovery phase. This logic is hidden
2151 * inside several functions named tcp_try_undo_<something>.
2154 /* This function decides, when we should leave Disordered state
2155 * and enter Recovery phase, reducing congestion window.
2157 * Main question: may we further continue forward transmission
2158 * with the same cwnd?
2160 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2162 struct tcp_sock
*tp
= tcp_sk(sk
);
2165 /* Trick#1: The loss is proven. */
2169 /* Not-A-Trick#2 : Classic rule... */
2170 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2173 /* Trick#4: It is still not OK... But will it be useful to delay
2176 packets_out
= tp
->packets_out
;
2177 if (packets_out
<= tp
->reordering
&&
2178 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2179 !tcp_may_send_now(sk
)) {
2180 /* We have nothing to send. This connection is limited
2181 * either by receiver window or by application.
2186 /* If a thin stream is detected, retransmit after first
2187 * received dupack. Employ only if SACK is supported in order
2188 * to avoid possible corner-case series of spurious retransmissions
2189 * Use only if there are no unsent data.
2191 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2192 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2193 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2196 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2197 * retransmissions due to small network reorderings, we implement
2198 * Mitigation A.3 in the RFC and delay the retransmission for a short
2199 * interval if appropriate.
2201 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2202 (tp
->packets_out
>= (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2203 !tcp_may_send_now(sk
))
2204 return !tcp_pause_early_retransmit(sk
, flag
);
2209 /* Detect loss in event "A" above by marking head of queue up as lost.
2210 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2211 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2212 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2213 * the maximum SACKed segments to pass before reaching this limit.
2215 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2217 struct tcp_sock
*tp
= tcp_sk(sk
);
2218 struct sk_buff
*skb
;
2222 /* Use SACK to deduce losses of new sequences sent during recovery */
2223 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2225 WARN_ON(packets
> tp
->packets_out
);
2226 if (tp
->lost_skb_hint
) {
2227 skb
= tp
->lost_skb_hint
;
2228 cnt
= tp
->lost_cnt_hint
;
2229 /* Head already handled? */
2230 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2233 skb
= tcp_write_queue_head(sk
);
2237 tcp_for_write_queue_from(skb
, sk
) {
2238 if (skb
== tcp_send_head(sk
))
2240 /* TODO: do this better */
2241 /* this is not the most efficient way to do this... */
2242 tp
->lost_skb_hint
= skb
;
2243 tp
->lost_cnt_hint
= cnt
;
2245 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2249 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2250 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2251 cnt
+= tcp_skb_pcount(skb
);
2253 if (cnt
> packets
) {
2254 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2255 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2256 (oldcnt
>= packets
))
2259 mss
= skb_shinfo(skb
)->gso_size
;
2260 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
,
2267 tcp_skb_mark_lost(tp
, skb
);
2272 tcp_verify_left_out(tp
);
2275 /* Account newly detected lost packet(s) */
2277 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2279 struct tcp_sock
*tp
= tcp_sk(sk
);
2281 if (tcp_is_reno(tp
)) {
2282 tcp_mark_head_lost(sk
, 1, 1);
2283 } else if (tcp_is_fack(tp
)) {
2284 int lost
= tp
->fackets_out
- tp
->reordering
;
2287 tcp_mark_head_lost(sk
, lost
, 0);
2289 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2290 if (sacked_upto
>= 0)
2291 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2292 else if (fast_rexmit
)
2293 tcp_mark_head_lost(sk
, 1, 1);
2297 /* CWND moderation, preventing bursts due to too big ACKs
2298 * in dubious situations.
2300 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2302 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2303 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2304 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2307 /* Nothing was retransmitted or returned timestamp is less
2308 * than timestamp of the first retransmission.
2310 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2312 return !tp
->retrans_stamp
||
2313 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2314 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2317 /* Undo procedures. */
2319 #if FASTRETRANS_DEBUG > 1
2320 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2322 struct tcp_sock
*tp
= tcp_sk(sk
);
2323 struct inet_sock
*inet
= inet_sk(sk
);
2325 if (sk
->sk_family
== AF_INET
) {
2326 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2328 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2329 tp
->snd_cwnd
, tcp_left_out(tp
),
2330 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2333 #if IS_ENABLED(CONFIG_IPV6)
2334 else if (sk
->sk_family
== AF_INET6
) {
2335 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2336 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2338 &np
->daddr
, ntohs(inet
->inet_dport
),
2339 tp
->snd_cwnd
, tcp_left_out(tp
),
2340 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2346 #define DBGUNDO(x...) do { } while (0)
2349 static void tcp_undo_cwnd_reduction(struct sock
*sk
, bool unmark_loss
)
2351 struct tcp_sock
*tp
= tcp_sk(sk
);
2354 struct sk_buff
*skb
;
2356 tcp_for_write_queue(skb
, sk
) {
2357 if (skb
== tcp_send_head(sk
))
2359 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2362 tcp_clear_all_retrans_hints(tp
);
2365 if (tp
->prior_ssthresh
) {
2366 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2368 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2369 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2371 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2373 if (tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2374 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2375 tcp_ecn_withdraw_cwr(tp
);
2378 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2380 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2381 tp
->undo_marker
= 0;
2384 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2386 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2389 /* People celebrate: "We love our President!" */
2390 static bool tcp_try_undo_recovery(struct sock
*sk
)
2392 struct tcp_sock
*tp
= tcp_sk(sk
);
2394 if (tcp_may_undo(tp
)) {
2397 /* Happy end! We did not retransmit anything
2398 * or our original transmission succeeded.
2400 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2401 tcp_undo_cwnd_reduction(sk
, false);
2402 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2403 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2405 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2407 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2409 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2410 /* Hold old state until something *above* high_seq
2411 * is ACKed. For Reno it is MUST to prevent false
2412 * fast retransmits (RFC2582). SACK TCP is safe. */
2413 tcp_moderate_cwnd(tp
);
2416 tcp_set_ca_state(sk
, TCP_CA_Open
);
2420 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2421 static bool tcp_try_undo_dsack(struct sock
*sk
)
2423 struct tcp_sock
*tp
= tcp_sk(sk
);
2425 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2426 DBGUNDO(sk
, "D-SACK");
2427 tcp_undo_cwnd_reduction(sk
, false);
2428 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2434 /* We can clear retrans_stamp when there are no retransmissions in the
2435 * window. It would seem that it is trivially available for us in
2436 * tp->retrans_out, however, that kind of assumptions doesn't consider
2437 * what will happen if errors occur when sending retransmission for the
2438 * second time. ...It could the that such segment has only
2439 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2440 * the head skb is enough except for some reneging corner cases that
2441 * are not worth the effort.
2443 * Main reason for all this complexity is the fact that connection dying
2444 * time now depends on the validity of the retrans_stamp, in particular,
2445 * that successive retransmissions of a segment must not advance
2446 * retrans_stamp under any conditions.
2448 static bool tcp_any_retrans_done(const struct sock
*sk
)
2450 const struct tcp_sock
*tp
= tcp_sk(sk
);
2451 struct sk_buff
*skb
;
2453 if (tp
->retrans_out
)
2456 skb
= tcp_write_queue_head(sk
);
2457 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2463 /* Undo during loss recovery after partial ACK or using F-RTO. */
2464 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2466 struct tcp_sock
*tp
= tcp_sk(sk
);
2468 if (frto_undo
|| tcp_may_undo(tp
)) {
2469 tcp_undo_cwnd_reduction(sk
, true);
2471 DBGUNDO(sk
, "partial loss");
2472 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2474 NET_INC_STATS_BH(sock_net(sk
),
2475 LINUX_MIB_TCPSPURIOUSRTOS
);
2476 inet_csk(sk
)->icsk_retransmits
= 0;
2477 if (frto_undo
|| tcp_is_sack(tp
))
2478 tcp_set_ca_state(sk
, TCP_CA_Open
);
2484 /* The cwnd reduction in CWR and Recovery use the PRR algorithm
2485 * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/
2486 * It computes the number of packets to send (sndcnt) based on packets newly
2488 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2489 * cwnd reductions across a full RTT.
2490 * 2) If packets in flight is lower than ssthresh (such as due to excess
2491 * losses and/or application stalls), do not perform any further cwnd
2492 * reductions, but instead slow start up to ssthresh.
2494 static void tcp_init_cwnd_reduction(struct sock
*sk
)
2496 struct tcp_sock
*tp
= tcp_sk(sk
);
2498 tp
->high_seq
= tp
->snd_nxt
;
2499 tp
->tlp_high_seq
= 0;
2500 tp
->snd_cwnd_cnt
= 0;
2501 tp
->prior_cwnd
= tp
->snd_cwnd
;
2502 tp
->prr_delivered
= 0;
2504 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2505 tcp_ecn_queue_cwr(tp
);
2508 static void tcp_cwnd_reduction(struct sock
*sk
, const int prior_unsacked
,
2511 struct tcp_sock
*tp
= tcp_sk(sk
);
2513 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2514 int newly_acked_sacked
= prior_unsacked
-
2515 (tp
->packets_out
- tp
->sacked_out
);
2517 tp
->prr_delivered
+= newly_acked_sacked
;
2518 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
2519 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2521 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2523 sndcnt
= min_t(int, delta
,
2524 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2525 newly_acked_sacked
) + 1);
2528 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
2529 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2532 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2534 struct tcp_sock
*tp
= tcp_sk(sk
);
2536 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2537 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
||
2538 (tp
->undo_marker
&& tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
)) {
2539 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2540 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2542 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2545 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2546 void tcp_enter_cwr(struct sock
*sk
)
2548 struct tcp_sock
*tp
= tcp_sk(sk
);
2550 tp
->prior_ssthresh
= 0;
2551 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2552 tp
->undo_marker
= 0;
2553 tcp_init_cwnd_reduction(sk
);
2554 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2558 static void tcp_try_keep_open(struct sock
*sk
)
2560 struct tcp_sock
*tp
= tcp_sk(sk
);
2561 int state
= TCP_CA_Open
;
2563 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2564 state
= TCP_CA_Disorder
;
2566 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2567 tcp_set_ca_state(sk
, state
);
2568 tp
->high_seq
= tp
->snd_nxt
;
2572 static void tcp_try_to_open(struct sock
*sk
, int flag
, const int prior_unsacked
)
2574 struct tcp_sock
*tp
= tcp_sk(sk
);
2576 tcp_verify_left_out(tp
);
2578 if (!tcp_any_retrans_done(sk
))
2579 tp
->retrans_stamp
= 0;
2581 if (flag
& FLAG_ECE
)
2584 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2585 tcp_try_keep_open(sk
);
2587 tcp_cwnd_reduction(sk
, prior_unsacked
, 0);
2591 static void tcp_mtup_probe_failed(struct sock
*sk
)
2593 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2595 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2596 icsk
->icsk_mtup
.probe_size
= 0;
2599 static void tcp_mtup_probe_success(struct sock
*sk
)
2601 struct tcp_sock
*tp
= tcp_sk(sk
);
2602 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2604 /* FIXME: breaks with very large cwnd */
2605 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2606 tp
->snd_cwnd
= tp
->snd_cwnd
*
2607 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2608 icsk
->icsk_mtup
.probe_size
;
2609 tp
->snd_cwnd_cnt
= 0;
2610 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2611 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2613 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2614 icsk
->icsk_mtup
.probe_size
= 0;
2615 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2618 /* Do a simple retransmit without using the backoff mechanisms in
2619 * tcp_timer. This is used for path mtu discovery.
2620 * The socket is already locked here.
2622 void tcp_simple_retransmit(struct sock
*sk
)
2624 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2625 struct tcp_sock
*tp
= tcp_sk(sk
);
2626 struct sk_buff
*skb
;
2627 unsigned int mss
= tcp_current_mss(sk
);
2628 u32 prior_lost
= tp
->lost_out
;
2630 tcp_for_write_queue(skb
, sk
) {
2631 if (skb
== tcp_send_head(sk
))
2633 if (tcp_skb_seglen(skb
) > mss
&&
2634 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2635 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2636 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2637 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2639 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2643 tcp_clear_retrans_hints_partial(tp
);
2645 if (prior_lost
== tp
->lost_out
)
2648 if (tcp_is_reno(tp
))
2649 tcp_limit_reno_sacked(tp
);
2651 tcp_verify_left_out(tp
);
2653 /* Don't muck with the congestion window here.
2654 * Reason is that we do not increase amount of _data_
2655 * in network, but units changed and effective
2656 * cwnd/ssthresh really reduced now.
2658 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2659 tp
->high_seq
= tp
->snd_nxt
;
2660 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2661 tp
->prior_ssthresh
= 0;
2662 tp
->undo_marker
= 0;
2663 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2665 tcp_xmit_retransmit_queue(sk
);
2667 EXPORT_SYMBOL(tcp_simple_retransmit
);
2669 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2671 struct tcp_sock
*tp
= tcp_sk(sk
);
2674 if (tcp_is_reno(tp
))
2675 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2677 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2679 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2681 tp
->prior_ssthresh
= 0;
2684 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2686 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2687 tcp_init_cwnd_reduction(sk
);
2689 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2692 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2693 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2695 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
)
2697 struct tcp_sock
*tp
= tcp_sk(sk
);
2698 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2700 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2701 /* Step 3.b. A timeout is spurious if not all data are
2702 * lost, i.e., never-retransmitted data are (s)acked.
2704 if (tcp_try_undo_loss(sk
, flag
& FLAG_ORIG_SACK_ACKED
))
2707 if (after(tp
->snd_nxt
, tp
->high_seq
) &&
2708 (flag
& FLAG_DATA_SACKED
|| is_dupack
)) {
2709 tp
->frto
= 0; /* Loss was real: 2nd part of step 3.a */
2710 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2711 tp
->high_seq
= tp
->snd_nxt
;
2712 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
2714 if (after(tp
->snd_nxt
, tp
->high_seq
))
2715 return; /* Step 2.b */
2721 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2722 tcp_try_undo_recovery(sk
);
2725 if (tcp_is_reno(tp
)) {
2726 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2727 * delivered. Lower inflight to clock out (re)tranmissions.
2729 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2730 tcp_add_reno_sack(sk
);
2731 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2732 tcp_reset_reno_sack(tp
);
2734 if (tcp_try_undo_loss(sk
, false))
2736 tcp_xmit_retransmit_queue(sk
);
2739 /* Undo during fast recovery after partial ACK. */
2740 static bool tcp_try_undo_partial(struct sock
*sk
, const int acked
,
2741 const int prior_unsacked
)
2743 struct tcp_sock
*tp
= tcp_sk(sk
);
2745 if (tp
->undo_marker
&& tcp_packet_delayed(tp
)) {
2746 /* Plain luck! Hole if filled with delayed
2747 * packet, rather than with a retransmit.
2749 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2751 /* We are getting evidence that the reordering degree is higher
2752 * than we realized. If there are no retransmits out then we
2753 * can undo. Otherwise we clock out new packets but do not
2754 * mark more packets lost or retransmit more.
2756 if (tp
->retrans_out
) {
2757 tcp_cwnd_reduction(sk
, prior_unsacked
, 0);
2761 if (!tcp_any_retrans_done(sk
))
2762 tp
->retrans_stamp
= 0;
2764 DBGUNDO(sk
, "partial recovery");
2765 tcp_undo_cwnd_reduction(sk
, true);
2766 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2767 tcp_try_keep_open(sk
);
2773 /* Process an event, which can update packets-in-flight not trivially.
2774 * Main goal of this function is to calculate new estimate for left_out,
2775 * taking into account both packets sitting in receiver's buffer and
2776 * packets lost by network.
2778 * Besides that it does CWND reduction, when packet loss is detected
2779 * and changes state of machine.
2781 * It does _not_ decide what to send, it is made in function
2782 * tcp_xmit_retransmit_queue().
2784 static void tcp_fastretrans_alert(struct sock
*sk
, const int acked
,
2785 const int prior_unsacked
,
2786 bool is_dupack
, int flag
)
2788 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2789 struct tcp_sock
*tp
= tcp_sk(sk
);
2790 bool do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2791 (tcp_fackets_out(tp
) > tp
->reordering
));
2792 int fast_rexmit
= 0;
2794 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2796 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2797 tp
->fackets_out
= 0;
2799 /* Now state machine starts.
2800 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2801 if (flag
& FLAG_ECE
)
2802 tp
->prior_ssthresh
= 0;
2804 /* B. In all the states check for reneging SACKs. */
2805 if (tcp_check_sack_reneging(sk
, flag
))
2808 /* C. Check consistency of the current state. */
2809 tcp_verify_left_out(tp
);
2811 /* D. Check state exit conditions. State can be terminated
2812 * when high_seq is ACKed. */
2813 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2814 WARN_ON(tp
->retrans_out
!= 0);
2815 tp
->retrans_stamp
= 0;
2816 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2817 switch (icsk
->icsk_ca_state
) {
2819 /* CWR is to be held something *above* high_seq
2820 * is ACKed for CWR bit to reach receiver. */
2821 if (tp
->snd_una
!= tp
->high_seq
) {
2822 tcp_end_cwnd_reduction(sk
);
2823 tcp_set_ca_state(sk
, TCP_CA_Open
);
2827 case TCP_CA_Recovery
:
2828 if (tcp_is_reno(tp
))
2829 tcp_reset_reno_sack(tp
);
2830 if (tcp_try_undo_recovery(sk
))
2832 tcp_end_cwnd_reduction(sk
);
2837 /* E. Process state. */
2838 switch (icsk
->icsk_ca_state
) {
2839 case TCP_CA_Recovery
:
2840 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2841 if (tcp_is_reno(tp
) && is_dupack
)
2842 tcp_add_reno_sack(sk
);
2844 if (tcp_try_undo_partial(sk
, acked
, prior_unsacked
))
2846 /* Partial ACK arrived. Force fast retransmit. */
2847 do_lost
= tcp_is_reno(tp
) ||
2848 tcp_fackets_out(tp
) > tp
->reordering
;
2850 if (tcp_try_undo_dsack(sk
)) {
2851 tcp_try_keep_open(sk
);
2856 tcp_process_loss(sk
, flag
, is_dupack
);
2857 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2859 /* Fall through to processing in Open state. */
2861 if (tcp_is_reno(tp
)) {
2862 if (flag
& FLAG_SND_UNA_ADVANCED
)
2863 tcp_reset_reno_sack(tp
);
2865 tcp_add_reno_sack(sk
);
2868 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2869 tcp_try_undo_dsack(sk
);
2871 if (!tcp_time_to_recover(sk
, flag
)) {
2872 tcp_try_to_open(sk
, flag
, prior_unsacked
);
2876 /* MTU probe failure: don't reduce cwnd */
2877 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2878 icsk
->icsk_mtup
.probe_size
&&
2879 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2880 tcp_mtup_probe_failed(sk
);
2881 /* Restores the reduction we did in tcp_mtup_probe() */
2883 tcp_simple_retransmit(sk
);
2887 /* Otherwise enter Recovery state */
2888 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2893 tcp_update_scoreboard(sk
, fast_rexmit
);
2894 tcp_cwnd_reduction(sk
, prior_unsacked
, fast_rexmit
);
2895 tcp_xmit_retransmit_queue(sk
);
2898 static inline bool tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2899 long seq_rtt_us
, long sack_rtt_us
)
2901 const struct tcp_sock
*tp
= tcp_sk(sk
);
2903 /* Prefer RTT measured from ACK's timing to TS-ECR. This is because
2904 * broken middle-boxes or peers may corrupt TS-ECR fields. But
2905 * Karn's algorithm forbids taking RTT if some retransmitted data
2906 * is acked (RFC6298).
2908 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2912 seq_rtt_us
= sack_rtt_us
;
2914 /* RTTM Rule: A TSecr value received in a segment is used to
2915 * update the averaged RTT measurement only if the segment
2916 * acknowledges some new data, i.e., only if it advances the
2917 * left edge of the send window.
2918 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2920 if (seq_rtt_us
< 0 && tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2922 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
2927 tcp_rtt_estimator(sk
, seq_rtt_us
);
2930 /* RFC6298: only reset backoff on valid RTT measurement. */
2931 inet_csk(sk
)->icsk_backoff
= 0;
2935 /* Compute time elapsed between (last) SYNACK and the ACK completing 3WHS. */
2936 static void tcp_synack_rtt_meas(struct sock
*sk
, const u32 synack_stamp
)
2938 struct tcp_sock
*tp
= tcp_sk(sk
);
2939 long seq_rtt_us
= -1L;
2941 if (synack_stamp
&& !tp
->total_retrans
)
2942 seq_rtt_us
= jiffies_to_usecs(tcp_time_stamp
- synack_stamp
);
2944 /* If the ACK acks both the SYNACK and the (Fast Open'd) data packets
2945 * sent in SYN_RECV, SYNACK RTT is the smooth RTT computed in tcp_ack()
2948 tcp_ack_update_rtt(sk
, FLAG_SYN_ACKED
, seq_rtt_us
, -1L);
2951 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 acked
)
2953 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2955 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, acked
);
2956 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2959 /* Restart timer after forward progress on connection.
2960 * RFC2988 recommends to restart timer to now+rto.
2962 void tcp_rearm_rto(struct sock
*sk
)
2964 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2965 struct tcp_sock
*tp
= tcp_sk(sk
);
2967 /* If the retrans timer is currently being used by Fast Open
2968 * for SYN-ACK retrans purpose, stay put.
2970 if (tp
->fastopen_rsk
)
2973 if (!tp
->packets_out
) {
2974 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2976 u32 rto
= inet_csk(sk
)->icsk_rto
;
2977 /* Offset the time elapsed after installing regular RTO */
2978 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
2979 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
2980 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
2981 const u32 rto_time_stamp
=
2982 tcp_skb_timestamp(skb
) + rto
;
2983 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
2984 /* delta may not be positive if the socket is locked
2985 * when the retrans timer fires and is rescheduled.
2990 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
2995 /* This function is called when the delayed ER timer fires. TCP enters
2996 * fast recovery and performs fast-retransmit.
2998 void tcp_resume_early_retransmit(struct sock
*sk
)
3000 struct tcp_sock
*tp
= tcp_sk(sk
);
3004 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3005 if (!tp
->do_early_retrans
)
3008 tcp_enter_recovery(sk
, false);
3009 tcp_update_scoreboard(sk
, 1);
3010 tcp_xmit_retransmit_queue(sk
);
3013 /* If we get here, the whole TSO packet has not been acked. */
3014 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3016 struct tcp_sock
*tp
= tcp_sk(sk
);
3019 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3021 packets_acked
= tcp_skb_pcount(skb
);
3022 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3024 packets_acked
-= tcp_skb_pcount(skb
);
3026 if (packets_acked
) {
3027 BUG_ON(tcp_skb_pcount(skb
) == 0);
3028 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3031 return packets_acked
;
3034 static void tcp_ack_tstamp(struct sock
*sk
, struct sk_buff
*skb
,
3037 const struct skb_shared_info
*shinfo
;
3039 /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */
3040 if (likely(!(sk
->sk_tsflags
& SOF_TIMESTAMPING_TX_ACK
)))
3043 shinfo
= skb_shinfo(skb
);
3044 if ((shinfo
->tx_flags
& SKBTX_ACK_TSTAMP
) &&
3045 between(shinfo
->tskey
, prior_snd_una
, tcp_sk(sk
)->snd_una
- 1))
3046 __skb_tstamp_tx(skb
, NULL
, sk
, SCM_TSTAMP_ACK
);
3049 /* Remove acknowledged frames from the retransmission queue. If our packet
3050 * is before the ack sequence we can discard it as it's confirmed to have
3051 * arrived at the other end.
3053 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3054 u32 prior_snd_una
, long sack_rtt_us
)
3056 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3057 struct skb_mstamp first_ackt
, last_ackt
, now
;
3058 struct tcp_sock
*tp
= tcp_sk(sk
);
3059 u32 prior_sacked
= tp
->sacked_out
;
3060 u32 reord
= tp
->packets_out
;
3061 bool fully_acked
= true;
3062 long ca_seq_rtt_us
= -1L;
3063 long seq_rtt_us
= -1L;
3064 struct sk_buff
*skb
;
3071 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3072 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3073 u8 sacked
= scb
->sacked
;
3076 tcp_ack_tstamp(sk
, skb
, prior_snd_una
);
3078 /* Determine how many packets and what bytes were acked, tso and else */
3079 if (after(scb
->end_seq
, tp
->snd_una
)) {
3080 if (tcp_skb_pcount(skb
) == 1 ||
3081 !after(tp
->snd_una
, scb
->seq
))
3084 acked_pcount
= tcp_tso_acked(sk
, skb
);
3088 fully_acked
= false;
3090 /* Speedup tcp_unlink_write_queue() and next loop */
3091 prefetchw(skb
->next
);
3092 acked_pcount
= tcp_skb_pcount(skb
);
3095 if (unlikely(sacked
& TCPCB_RETRANS
)) {
3096 if (sacked
& TCPCB_SACKED_RETRANS
)
3097 tp
->retrans_out
-= acked_pcount
;
3098 flag
|= FLAG_RETRANS_DATA_ACKED
;
3100 last_ackt
= skb
->skb_mstamp
;
3101 WARN_ON_ONCE(last_ackt
.v64
== 0);
3102 if (!first_ackt
.v64
)
3103 first_ackt
= last_ackt
;
3105 if (!(sacked
& TCPCB_SACKED_ACKED
))
3106 reord
= min(pkts_acked
, reord
);
3107 if (!after(scb
->end_seq
, tp
->high_seq
))
3108 flag
|= FLAG_ORIG_SACK_ACKED
;
3111 if (sacked
& TCPCB_SACKED_ACKED
)
3112 tp
->sacked_out
-= acked_pcount
;
3113 if (sacked
& TCPCB_LOST
)
3114 tp
->lost_out
-= acked_pcount
;
3116 tp
->packets_out
-= acked_pcount
;
3117 pkts_acked
+= acked_pcount
;
3119 /* Initial outgoing SYN's get put onto the write_queue
3120 * just like anything else we transmit. It is not
3121 * true data, and if we misinform our callers that
3122 * this ACK acks real data, we will erroneously exit
3123 * connection startup slow start one packet too
3124 * quickly. This is severely frowned upon behavior.
3126 if (likely(!(scb
->tcp_flags
& TCPHDR_SYN
))) {
3127 flag
|= FLAG_DATA_ACKED
;
3129 flag
|= FLAG_SYN_ACKED
;
3130 tp
->retrans_stamp
= 0;
3136 tcp_unlink_write_queue(skb
, sk
);
3137 sk_wmem_free_skb(sk
, skb
);
3138 if (unlikely(skb
== tp
->retransmit_skb_hint
))
3139 tp
->retransmit_skb_hint
= NULL
;
3140 if (unlikely(skb
== tp
->lost_skb_hint
))
3141 tp
->lost_skb_hint
= NULL
;
3144 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3145 tp
->snd_up
= tp
->snd_una
;
3147 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3148 flag
|= FLAG_SACK_RENEGING
;
3150 skb_mstamp_get(&now
);
3151 if (likely(first_ackt
.v64
)) {
3152 seq_rtt_us
= skb_mstamp_us_delta(&now
, &first_ackt
);
3153 ca_seq_rtt_us
= skb_mstamp_us_delta(&now
, &last_ackt
);
3156 rtt_update
= tcp_ack_update_rtt(sk
, flag
, seq_rtt_us
, sack_rtt_us
);
3158 if (flag
& FLAG_ACKED
) {
3159 const struct tcp_congestion_ops
*ca_ops
3160 = inet_csk(sk
)->icsk_ca_ops
;
3163 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3164 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3165 tcp_mtup_probe_success(sk
);
3168 if (tcp_is_reno(tp
)) {
3169 tcp_remove_reno_sacks(sk
, pkts_acked
);
3173 /* Non-retransmitted hole got filled? That's reordering */
3174 if (reord
< prior_fackets
)
3175 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3177 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3178 prior_sacked
- tp
->sacked_out
;
3179 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3182 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3184 if (ca_ops
->pkts_acked
)
3185 ca_ops
->pkts_acked(sk
, pkts_acked
, ca_seq_rtt_us
);
3187 } else if (skb
&& rtt_update
&& sack_rtt_us
>= 0 &&
3188 sack_rtt_us
> skb_mstamp_us_delta(&now
, &skb
->skb_mstamp
)) {
3189 /* Do not re-arm RTO if the sack RTT is measured from data sent
3190 * after when the head was last (re)transmitted. Otherwise the
3191 * timeout may continue to extend in loss recovery.
3196 #if FASTRETRANS_DEBUG > 0
3197 WARN_ON((int)tp
->sacked_out
< 0);
3198 WARN_ON((int)tp
->lost_out
< 0);
3199 WARN_ON((int)tp
->retrans_out
< 0);
3200 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3201 icsk
= inet_csk(sk
);
3203 pr_debug("Leak l=%u %d\n",
3204 tp
->lost_out
, icsk
->icsk_ca_state
);
3207 if (tp
->sacked_out
) {
3208 pr_debug("Leak s=%u %d\n",
3209 tp
->sacked_out
, icsk
->icsk_ca_state
);
3212 if (tp
->retrans_out
) {
3213 pr_debug("Leak r=%u %d\n",
3214 tp
->retrans_out
, icsk
->icsk_ca_state
);
3215 tp
->retrans_out
= 0;
3222 static void tcp_ack_probe(struct sock
*sk
)
3224 const struct tcp_sock
*tp
= tcp_sk(sk
);
3225 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3227 /* Was it a usable window open? */
3229 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3230 icsk
->icsk_backoff
= 0;
3231 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3232 /* Socket must be waked up by subsequent tcp_data_snd_check().
3233 * This function is not for random using!
3236 unsigned long when
= inet_csk_rto_backoff(icsk
, TCP_RTO_MAX
);
3238 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3243 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3245 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3246 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3249 /* Decide wheather to run the increase function of congestion control. */
3250 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3252 if (tcp_in_cwnd_reduction(sk
))
3255 /* If reordering is high then always grow cwnd whenever data is
3256 * delivered regardless of its ordering. Otherwise stay conservative
3257 * and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
3258 * new SACK or ECE mark may first advance cwnd here and later reduce
3259 * cwnd in tcp_fastretrans_alert() based on more states.
3261 if (tcp_sk(sk
)->reordering
> sysctl_tcp_reordering
)
3262 return flag
& FLAG_FORWARD_PROGRESS
;
3264 return flag
& FLAG_DATA_ACKED
;
3267 /* Check that window update is acceptable.
3268 * The function assumes that snd_una<=ack<=snd_next.
3270 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3271 const u32 ack
, const u32 ack_seq
,
3274 return after(ack
, tp
->snd_una
) ||
3275 after(ack_seq
, tp
->snd_wl1
) ||
3276 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3279 /* Update our send window.
3281 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3282 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3284 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3287 struct tcp_sock
*tp
= tcp_sk(sk
);
3289 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3291 if (likely(!tcp_hdr(skb
)->syn
))
3292 nwin
<<= tp
->rx_opt
.snd_wscale
;
3294 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3295 flag
|= FLAG_WIN_UPDATE
;
3296 tcp_update_wl(tp
, ack_seq
);
3298 if (tp
->snd_wnd
!= nwin
) {
3301 /* Note, it is the only place, where
3302 * fast path is recovered for sending TCP.
3305 tcp_fast_path_check(sk
);
3307 if (nwin
> tp
->max_window
) {
3308 tp
->max_window
= nwin
;
3309 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3319 /* RFC 5961 7 [ACK Throttling] */
3320 static void tcp_send_challenge_ack(struct sock
*sk
)
3322 /* unprotected vars, we dont care of overwrites */
3323 static u32 challenge_timestamp
;
3324 static unsigned int challenge_count
;
3325 u32 now
= jiffies
/ HZ
;
3327 if (now
!= challenge_timestamp
) {
3328 challenge_timestamp
= now
;
3329 challenge_count
= 0;
3331 if (++challenge_count
<= sysctl_tcp_challenge_ack_limit
) {
3332 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3337 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3339 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3340 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3343 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3345 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3346 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3347 * extra check below makes sure this can only happen
3348 * for pure ACK frames. -DaveM
3350 * Not only, also it occurs for expired timestamps.
3353 if (tcp_paws_check(&tp
->rx_opt
, 0))
3354 tcp_store_ts_recent(tp
);
3358 /* This routine deals with acks during a TLP episode.
3359 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3361 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3363 struct tcp_sock
*tp
= tcp_sk(sk
);
3364 bool is_tlp_dupack
= (ack
== tp
->tlp_high_seq
) &&
3365 !(flag
& (FLAG_SND_UNA_ADVANCED
|
3366 FLAG_NOT_DUP
| FLAG_DATA_SACKED
));
3368 /* Mark the end of TLP episode on receiving TLP dupack or when
3369 * ack is after tlp_high_seq.
3371 if (is_tlp_dupack
) {
3372 tp
->tlp_high_seq
= 0;
3376 if (after(ack
, tp
->tlp_high_seq
)) {
3377 tp
->tlp_high_seq
= 0;
3378 /* Don't reduce cwnd if DSACK arrives for TLP retrans. */
3379 if (!(flag
& FLAG_DSACKING_ACK
)) {
3380 tcp_init_cwnd_reduction(sk
);
3381 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3382 tcp_end_cwnd_reduction(sk
);
3383 tcp_try_keep_open(sk
);
3384 NET_INC_STATS_BH(sock_net(sk
),
3385 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3390 static inline void tcp_in_ack_event(struct sock
*sk
, u32 flags
)
3392 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3394 if (icsk
->icsk_ca_ops
->in_ack_event
)
3395 icsk
->icsk_ca_ops
->in_ack_event(sk
, flags
);
3398 /* This routine deals with incoming acks, but not outgoing ones. */
3399 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3401 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3402 struct tcp_sock
*tp
= tcp_sk(sk
);
3403 u32 prior_snd_una
= tp
->snd_una
;
3404 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3405 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3406 bool is_dupack
= false;
3408 int prior_packets
= tp
->packets_out
;
3409 const int prior_unsacked
= tp
->packets_out
- tp
->sacked_out
;
3410 int acked
= 0; /* Number of packets newly acked */
3411 long sack_rtt_us
= -1L;
3413 /* We very likely will need to access write queue head. */
3414 prefetchw(sk
->sk_write_queue
.next
);
3416 /* If the ack is older than previous acks
3417 * then we can probably ignore it.
3419 if (before(ack
, prior_snd_una
)) {
3420 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3421 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3422 tcp_send_challenge_ack(sk
);
3428 /* If the ack includes data we haven't sent yet, discard
3429 * this segment (RFC793 Section 3.9).
3431 if (after(ack
, tp
->snd_nxt
))
3434 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3435 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
3438 if (after(ack
, prior_snd_una
)) {
3439 flag
|= FLAG_SND_UNA_ADVANCED
;
3440 icsk
->icsk_retransmits
= 0;
3443 prior_fackets
= tp
->fackets_out
;
3445 /* ts_recent update must be made after we are sure that the packet
3448 if (flag
& FLAG_UPDATE_TS_RECENT
)
3449 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3451 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3452 /* Window is constant, pure forward advance.
3453 * No more checks are required.
3454 * Note, we use the fact that SND.UNA>=SND.WL2.
3456 tcp_update_wl(tp
, ack_seq
);
3458 flag
|= FLAG_WIN_UPDATE
;
3460 tcp_in_ack_event(sk
, CA_ACK_WIN_UPDATE
);
3462 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3464 u32 ack_ev_flags
= CA_ACK_SLOWPATH
;
3466 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3469 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3471 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3473 if (TCP_SKB_CB(skb
)->sacked
)
3474 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3477 if (tcp_ecn_rcv_ecn_echo(tp
, tcp_hdr(skb
))) {
3479 ack_ev_flags
|= CA_ACK_ECE
;
3482 if (flag
& FLAG_WIN_UPDATE
)
3483 ack_ev_flags
|= CA_ACK_WIN_UPDATE
;
3485 tcp_in_ack_event(sk
, ack_ev_flags
);
3488 /* We passed data and got it acked, remove any soft error
3489 * log. Something worked...
3491 sk
->sk_err_soft
= 0;
3492 icsk
->icsk_probes_out
= 0;
3493 tp
->rcv_tstamp
= tcp_time_stamp
;
3497 /* See if we can take anything off of the retransmit queue. */
3498 acked
= tp
->packets_out
;
3499 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
,
3501 acked
-= tp
->packets_out
;
3503 /* Advance cwnd if state allows */
3504 if (tcp_may_raise_cwnd(sk
, flag
))
3505 tcp_cong_avoid(sk
, ack
, acked
);
3507 if (tcp_ack_is_dubious(sk
, flag
)) {
3508 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3509 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3512 if (tp
->tlp_high_seq
)
3513 tcp_process_tlp_ack(sk
, ack
, flag
);
3515 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
)) {
3516 struct dst_entry
*dst
= __sk_dst_get(sk
);
3521 if (icsk
->icsk_pending
== ICSK_TIME_RETRANS
)
3522 tcp_schedule_loss_probe(sk
);
3523 tcp_update_pacing_rate(sk
);
3527 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3528 if (flag
& FLAG_DSACKING_ACK
)
3529 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3531 /* If this ack opens up a zero window, clear backoff. It was
3532 * being used to time the probes, and is probably far higher than
3533 * it needs to be for normal retransmission.
3535 if (tcp_send_head(sk
))
3538 if (tp
->tlp_high_seq
)
3539 tcp_process_tlp_ack(sk
, ack
, flag
);
3543 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3547 /* If data was SACKed, tag it and see if we should send more data.
3548 * If data was DSACKed, see if we can undo a cwnd reduction.
3550 if (TCP_SKB_CB(skb
)->sacked
) {
3551 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
,
3553 tcp_fastretrans_alert(sk
, acked
, prior_unsacked
,
3557 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3561 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3562 * But, this can also be called on packets in the established flow when
3563 * the fast version below fails.
3565 void tcp_parse_options(const struct sk_buff
*skb
,
3566 struct tcp_options_received
*opt_rx
, int estab
,
3567 struct tcp_fastopen_cookie
*foc
)
3569 const unsigned char *ptr
;
3570 const struct tcphdr
*th
= tcp_hdr(skb
);
3571 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3573 ptr
= (const unsigned char *)(th
+ 1);
3574 opt_rx
->saw_tstamp
= 0;
3576 while (length
> 0) {
3577 int opcode
= *ptr
++;
3583 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3588 if (opsize
< 2) /* "silly options" */
3590 if (opsize
> length
)
3591 return; /* don't parse partial options */
3594 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3595 u16 in_mss
= get_unaligned_be16(ptr
);
3597 if (opt_rx
->user_mss
&&
3598 opt_rx
->user_mss
< in_mss
)
3599 in_mss
= opt_rx
->user_mss
;
3600 opt_rx
->mss_clamp
= in_mss
;
3605 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3606 !estab
&& sysctl_tcp_window_scaling
) {
3607 __u8 snd_wscale
= *(__u8
*)ptr
;
3608 opt_rx
->wscale_ok
= 1;
3609 if (snd_wscale
> 14) {
3610 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3615 opt_rx
->snd_wscale
= snd_wscale
;
3618 case TCPOPT_TIMESTAMP
:
3619 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3620 ((estab
&& opt_rx
->tstamp_ok
) ||
3621 (!estab
&& sysctl_tcp_timestamps
))) {
3622 opt_rx
->saw_tstamp
= 1;
3623 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3624 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3627 case TCPOPT_SACK_PERM
:
3628 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3629 !estab
&& sysctl_tcp_sack
) {
3630 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3631 tcp_sack_reset(opt_rx
);
3636 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3637 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3639 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3642 #ifdef CONFIG_TCP_MD5SIG
3645 * The MD5 Hash has already been
3646 * checked (see tcp_v{4,6}_do_rcv()).
3651 /* Fast Open option shares code 254 using a
3652 * 16 bits magic number. It's valid only in
3653 * SYN or SYN-ACK with an even size.
3655 if (opsize
< TCPOLEN_EXP_FASTOPEN_BASE
||
3656 get_unaligned_be16(ptr
) != TCPOPT_FASTOPEN_MAGIC
||
3657 foc
== NULL
|| !th
->syn
|| (opsize
& 1))
3659 foc
->len
= opsize
- TCPOLEN_EXP_FASTOPEN_BASE
;
3660 if (foc
->len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3661 foc
->len
<= TCP_FASTOPEN_COOKIE_MAX
)
3662 memcpy(foc
->val
, ptr
+ 2, foc
->len
);
3663 else if (foc
->len
!= 0)
3673 EXPORT_SYMBOL(tcp_parse_options
);
3675 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3677 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3679 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3680 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3681 tp
->rx_opt
.saw_tstamp
= 1;
3683 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3686 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3688 tp
->rx_opt
.rcv_tsecr
= 0;
3694 /* Fast parse options. This hopes to only see timestamps.
3695 * If it is wrong it falls back on tcp_parse_options().
3697 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
3698 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3700 /* In the spirit of fast parsing, compare doff directly to constant
3701 * values. Because equality is used, short doff can be ignored here.
3703 if (th
->doff
== (sizeof(*th
) / 4)) {
3704 tp
->rx_opt
.saw_tstamp
= 0;
3706 } else if (tp
->rx_opt
.tstamp_ok
&&
3707 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3708 if (tcp_parse_aligned_timestamp(tp
, th
))
3712 tcp_parse_options(skb
, &tp
->rx_opt
, 1, NULL
);
3713 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3714 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3719 #ifdef CONFIG_TCP_MD5SIG
3721 * Parse MD5 Signature option
3723 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3725 int length
= (th
->doff
<< 2) - sizeof(*th
);
3726 const u8
*ptr
= (const u8
*)(th
+ 1);
3728 /* If the TCP option is too short, we can short cut */
3729 if (length
< TCPOLEN_MD5SIG
)
3732 while (length
> 0) {
3733 int opcode
= *ptr
++;
3744 if (opsize
< 2 || opsize
> length
)
3746 if (opcode
== TCPOPT_MD5SIG
)
3747 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3754 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3757 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3759 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3760 * it can pass through stack. So, the following predicate verifies that
3761 * this segment is not used for anything but congestion avoidance or
3762 * fast retransmit. Moreover, we even are able to eliminate most of such
3763 * second order effects, if we apply some small "replay" window (~RTO)
3764 * to timestamp space.
3766 * All these measures still do not guarantee that we reject wrapped ACKs
3767 * on networks with high bandwidth, when sequence space is recycled fastly,
3768 * but it guarantees that such events will be very rare and do not affect
3769 * connection seriously. This doesn't look nice, but alas, PAWS is really
3772 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3773 * states that events when retransmit arrives after original data are rare.
3774 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3775 * the biggest problem on large power networks even with minor reordering.
3776 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3777 * up to bandwidth of 18Gigabit/sec. 8) ]
3780 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3782 const struct tcp_sock
*tp
= tcp_sk(sk
);
3783 const struct tcphdr
*th
= tcp_hdr(skb
);
3784 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3785 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3787 return (/* 1. Pure ACK with correct sequence number. */
3788 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3790 /* 2. ... and duplicate ACK. */
3791 ack
== tp
->snd_una
&&
3793 /* 3. ... and does not update window. */
3794 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3796 /* 4. ... and sits in replay window. */
3797 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3800 static inline bool tcp_paws_discard(const struct sock
*sk
,
3801 const struct sk_buff
*skb
)
3803 const struct tcp_sock
*tp
= tcp_sk(sk
);
3805 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3806 !tcp_disordered_ack(sk
, skb
);
3809 /* Check segment sequence number for validity.
3811 * Segment controls are considered valid, if the segment
3812 * fits to the window after truncation to the window. Acceptability
3813 * of data (and SYN, FIN, of course) is checked separately.
3814 * See tcp_data_queue(), for example.
3816 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3817 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3818 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3819 * (borrowed from freebsd)
3822 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3824 return !before(end_seq
, tp
->rcv_wup
) &&
3825 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3828 /* When we get a reset we do this. */
3829 void tcp_reset(struct sock
*sk
)
3831 /* We want the right error as BSD sees it (and indeed as we do). */
3832 switch (sk
->sk_state
) {
3834 sk
->sk_err
= ECONNREFUSED
;
3836 case TCP_CLOSE_WAIT
:
3842 sk
->sk_err
= ECONNRESET
;
3844 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3847 if (!sock_flag(sk
, SOCK_DEAD
))
3848 sk
->sk_error_report(sk
);
3854 * Process the FIN bit. This now behaves as it is supposed to work
3855 * and the FIN takes effect when it is validly part of sequence
3856 * space. Not before when we get holes.
3858 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3859 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3862 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3863 * close and we go into CLOSING (and later onto TIME-WAIT)
3865 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3867 static void tcp_fin(struct sock
*sk
)
3869 struct tcp_sock
*tp
= tcp_sk(sk
);
3870 const struct dst_entry
*dst
;
3872 inet_csk_schedule_ack(sk
);
3874 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3875 sock_set_flag(sk
, SOCK_DONE
);
3877 switch (sk
->sk_state
) {
3879 case TCP_ESTABLISHED
:
3880 /* Move to CLOSE_WAIT */
3881 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3882 dst
= __sk_dst_get(sk
);
3883 if (!dst
|| !dst_metric(dst
, RTAX_QUICKACK
))
3884 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3887 case TCP_CLOSE_WAIT
:
3889 /* Received a retransmission of the FIN, do
3894 /* RFC793: Remain in the LAST-ACK state. */
3898 /* This case occurs when a simultaneous close
3899 * happens, we must ack the received FIN and
3900 * enter the CLOSING state.
3903 tcp_set_state(sk
, TCP_CLOSING
);
3906 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3908 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3911 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3912 * cases we should never reach this piece of code.
3914 pr_err("%s: Impossible, sk->sk_state=%d\n",
3915 __func__
, sk
->sk_state
);
3919 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3920 * Probably, we should reset in this case. For now drop them.
3922 __skb_queue_purge(&tp
->out_of_order_queue
);
3923 if (tcp_is_sack(tp
))
3924 tcp_sack_reset(&tp
->rx_opt
);
3927 if (!sock_flag(sk
, SOCK_DEAD
)) {
3928 sk
->sk_state_change(sk
);
3930 /* Do not send POLL_HUP for half duplex close. */
3931 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3932 sk
->sk_state
== TCP_CLOSE
)
3933 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
3935 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
3939 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
3942 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3943 if (before(seq
, sp
->start_seq
))
3944 sp
->start_seq
= seq
;
3945 if (after(end_seq
, sp
->end_seq
))
3946 sp
->end_seq
= end_seq
;
3952 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
3954 struct tcp_sock
*tp
= tcp_sk(sk
);
3956 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3959 if (before(seq
, tp
->rcv_nxt
))
3960 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
3962 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
3964 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3966 tp
->rx_opt
.dsack
= 1;
3967 tp
->duplicate_sack
[0].start_seq
= seq
;
3968 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3972 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
3974 struct tcp_sock
*tp
= tcp_sk(sk
);
3976 if (!tp
->rx_opt
.dsack
)
3977 tcp_dsack_set(sk
, seq
, end_seq
);
3979 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3982 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
3984 struct tcp_sock
*tp
= tcp_sk(sk
);
3986 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3987 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3988 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
3989 tcp_enter_quickack_mode(sk
);
3991 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3992 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3994 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3995 end_seq
= tp
->rcv_nxt
;
3996 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4003 /* These routines update the SACK block as out-of-order packets arrive or
4004 * in-order packets close up the sequence space.
4006 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4009 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4010 struct tcp_sack_block
*swalk
= sp
+ 1;
4012 /* See if the recent change to the first SACK eats into
4013 * or hits the sequence space of other SACK blocks, if so coalesce.
4015 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4016 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4019 /* Zap SWALK, by moving every further SACK up by one slot.
4020 * Decrease num_sacks.
4022 tp
->rx_opt
.num_sacks
--;
4023 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4027 this_sack
++, swalk
++;
4031 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4033 struct tcp_sock
*tp
= tcp_sk(sk
);
4034 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4035 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4041 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4042 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4043 /* Rotate this_sack to the first one. */
4044 for (; this_sack
> 0; this_sack
--, sp
--)
4045 swap(*sp
, *(sp
- 1));
4047 tcp_sack_maybe_coalesce(tp
);
4052 /* Could not find an adjacent existing SACK, build a new one,
4053 * put it at the front, and shift everyone else down. We
4054 * always know there is at least one SACK present already here.
4056 * If the sack array is full, forget about the last one.
4058 if (this_sack
>= TCP_NUM_SACKS
) {
4060 tp
->rx_opt
.num_sacks
--;
4063 for (; this_sack
> 0; this_sack
--, sp
--)
4067 /* Build the new head SACK, and we're done. */
4068 sp
->start_seq
= seq
;
4069 sp
->end_seq
= end_seq
;
4070 tp
->rx_opt
.num_sacks
++;
4073 /* RCV.NXT advances, some SACKs should be eaten. */
4075 static void tcp_sack_remove(struct tcp_sock
*tp
)
4077 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4078 int num_sacks
= tp
->rx_opt
.num_sacks
;
4081 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4082 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4083 tp
->rx_opt
.num_sacks
= 0;
4087 for (this_sack
= 0; this_sack
< num_sacks
;) {
4088 /* Check if the start of the sack is covered by RCV.NXT. */
4089 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4092 /* RCV.NXT must cover all the block! */
4093 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4095 /* Zap this SACK, by moving forward any other SACKS. */
4096 for (i
= this_sack
+1; i
< num_sacks
; i
++)
4097 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4104 tp
->rx_opt
.num_sacks
= num_sacks
;
4108 * tcp_try_coalesce - try to merge skb to prior one
4111 * @from: buffer to add in queue
4112 * @fragstolen: pointer to boolean
4114 * Before queueing skb @from after @to, try to merge them
4115 * to reduce overall memory use and queue lengths, if cost is small.
4116 * Packets in ofo or receive queues can stay a long time.
4117 * Better try to coalesce them right now to avoid future collapses.
4118 * Returns true if caller should free @from instead of queueing it
4120 static bool tcp_try_coalesce(struct sock
*sk
,
4122 struct sk_buff
*from
,
4127 *fragstolen
= false;
4129 /* Its possible this segment overlaps with prior segment in queue */
4130 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4133 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4136 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4137 sk_mem_charge(sk
, delta
);
4138 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4139 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4140 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4141 TCP_SKB_CB(to
)->tcp_flags
|= TCP_SKB_CB(from
)->tcp_flags
;
4145 /* This one checks to see if we can put data from the
4146 * out_of_order queue into the receive_queue.
4148 static void tcp_ofo_queue(struct sock
*sk
)
4150 struct tcp_sock
*tp
= tcp_sk(sk
);
4151 __u32 dsack_high
= tp
->rcv_nxt
;
4152 struct sk_buff
*skb
, *tail
;
4153 bool fragstolen
, eaten
;
4155 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4156 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4159 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4160 __u32 dsack
= dsack_high
;
4161 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4162 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4163 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4166 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4167 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4168 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4172 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4173 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4174 TCP_SKB_CB(skb
)->end_seq
);
4176 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4177 eaten
= tail
&& tcp_try_coalesce(sk
, tail
, skb
, &fragstolen
);
4178 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4180 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4181 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4184 kfree_skb_partial(skb
, fragstolen
);
4188 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4189 static int tcp_prune_queue(struct sock
*sk
);
4191 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4194 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4195 !sk_rmem_schedule(sk
, skb
, size
)) {
4197 if (tcp_prune_queue(sk
) < 0)
4200 if (!sk_rmem_schedule(sk
, skb
, size
)) {
4201 if (!tcp_prune_ofo_queue(sk
))
4204 if (!sk_rmem_schedule(sk
, skb
, size
))
4211 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4213 struct tcp_sock
*tp
= tcp_sk(sk
);
4214 struct sk_buff
*skb1
;
4217 tcp_ecn_check_ce(tp
, skb
);
4219 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4220 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4225 /* Disable header prediction. */
4227 inet_csk_schedule_ack(sk
);
4229 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4230 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4231 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4233 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4235 /* Initial out of order segment, build 1 SACK. */
4236 if (tcp_is_sack(tp
)) {
4237 tp
->rx_opt
.num_sacks
= 1;
4238 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4239 tp
->selective_acks
[0].end_seq
=
4240 TCP_SKB_CB(skb
)->end_seq
;
4242 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4246 seq
= TCP_SKB_CB(skb
)->seq
;
4247 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4249 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4252 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4253 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4255 tcp_grow_window(sk
, skb
);
4256 kfree_skb_partial(skb
, fragstolen
);
4260 if (!tp
->rx_opt
.num_sacks
||
4261 tp
->selective_acks
[0].end_seq
!= seq
)
4264 /* Common case: data arrive in order after hole. */
4265 tp
->selective_acks
[0].end_seq
= end_seq
;
4269 /* Find place to insert this segment. */
4271 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4273 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4277 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4280 /* Do skb overlap to previous one? */
4281 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4282 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4283 /* All the bits are present. Drop. */
4284 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4287 tcp_dsack_set(sk
, seq
, end_seq
);
4290 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4291 /* Partial overlap. */
4292 tcp_dsack_set(sk
, seq
,
4293 TCP_SKB_CB(skb1
)->end_seq
);
4295 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4299 skb1
= skb_queue_prev(
4300 &tp
->out_of_order_queue
,
4305 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4307 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4309 /* And clean segments covered by new one as whole. */
4310 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4311 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4313 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4315 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4316 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4320 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4321 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4322 TCP_SKB_CB(skb1
)->end_seq
);
4323 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4328 if (tcp_is_sack(tp
))
4329 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4332 tcp_grow_window(sk
, skb
);
4333 skb_set_owner_r(skb
, sk
);
4337 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4341 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4343 __skb_pull(skb
, hdrlen
);
4345 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4346 tcp_sk(sk
)->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4348 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4349 skb_set_owner_r(skb
, sk
);
4354 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4356 struct sk_buff
*skb
;
4362 skb
= alloc_skb(size
, sk
->sk_allocation
);
4366 if (tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4369 if (memcpy_fromiovec(skb_put(skb
, size
), msg
->msg_iov
, size
))
4372 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4373 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4374 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4376 if (tcp_queue_rcv(sk
, skb
, 0, &fragstolen
)) {
4377 WARN_ON_ONCE(fragstolen
); /* should not happen */
4388 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4390 struct tcp_sock
*tp
= tcp_sk(sk
);
4392 bool fragstolen
= false;
4394 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4398 __skb_pull(skb
, tcp_hdr(skb
)->doff
* 4);
4400 tcp_ecn_accept_cwr(tp
, skb
);
4402 tp
->rx_opt
.dsack
= 0;
4404 /* Queue data for delivery to the user.
4405 * Packets in sequence go to the receive queue.
4406 * Out of sequence packets to the out_of_order_queue.
4408 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4409 if (tcp_receive_window(tp
) == 0)
4412 /* Ok. In sequence. In window. */
4413 if (tp
->ucopy
.task
== current
&&
4414 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4415 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4416 int chunk
= min_t(unsigned int, skb
->len
,
4419 __set_current_state(TASK_RUNNING
);
4422 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4423 tp
->ucopy
.len
-= chunk
;
4424 tp
->copied_seq
+= chunk
;
4425 eaten
= (chunk
== skb
->len
);
4426 tcp_rcv_space_adjust(sk
);
4434 tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4437 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4439 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4441 tcp_event_data_recv(sk
, skb
);
4442 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
4445 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4448 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4449 * gap in queue is filled.
4451 if (skb_queue_empty(&tp
->out_of_order_queue
))
4452 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4455 if (tp
->rx_opt
.num_sacks
)
4456 tcp_sack_remove(tp
);
4458 tcp_fast_path_check(sk
);
4461 kfree_skb_partial(skb
, fragstolen
);
4462 if (!sock_flag(sk
, SOCK_DEAD
))
4463 sk
->sk_data_ready(sk
);
4467 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4468 /* A retransmit, 2nd most common case. Force an immediate ack. */
4469 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4470 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4473 tcp_enter_quickack_mode(sk
);
4474 inet_csk_schedule_ack(sk
);
4480 /* Out of window. F.e. zero window probe. */
4481 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4484 tcp_enter_quickack_mode(sk
);
4486 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4487 /* Partial packet, seq < rcv_next < end_seq */
4488 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4489 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4490 TCP_SKB_CB(skb
)->end_seq
);
4492 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4494 /* If window is closed, drop tail of packet. But after
4495 * remembering D-SACK for its head made in previous line.
4497 if (!tcp_receive_window(tp
))
4502 tcp_data_queue_ofo(sk
, skb
);
4505 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4506 struct sk_buff_head
*list
)
4508 struct sk_buff
*next
= NULL
;
4510 if (!skb_queue_is_last(list
, skb
))
4511 next
= skb_queue_next(list
, skb
);
4513 __skb_unlink(skb
, list
);
4515 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4520 /* Collapse contiguous sequence of skbs head..tail with
4521 * sequence numbers start..end.
4523 * If tail is NULL, this means until the end of the list.
4525 * Segments with FIN/SYN are not collapsed (only because this
4529 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4530 struct sk_buff
*head
, struct sk_buff
*tail
,
4533 struct sk_buff
*skb
, *n
;
4536 /* First, check that queue is collapsible and find
4537 * the point where collapsing can be useful. */
4541 skb_queue_walk_from_safe(list
, skb
, n
) {
4544 /* No new bits? It is possible on ofo queue. */
4545 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4546 skb
= tcp_collapse_one(sk
, skb
, list
);
4552 /* The first skb to collapse is:
4554 * - bloated or contains data before "start" or
4555 * overlaps to the next one.
4557 if (!(TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)) &&
4558 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4559 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4560 end_of_skbs
= false;
4564 if (!skb_queue_is_last(list
, skb
)) {
4565 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4567 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4568 end_of_skbs
= false;
4573 /* Decided to skip this, advance start seq. */
4574 start
= TCP_SKB_CB(skb
)->end_seq
;
4577 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4580 while (before(start
, end
)) {
4581 int copy
= min_t(int, SKB_MAX_ORDER(0, 0), end
- start
);
4582 struct sk_buff
*nskb
;
4584 nskb
= alloc_skb(copy
, GFP_ATOMIC
);
4588 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4589 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4590 __skb_queue_before(list
, skb
, nskb
);
4591 skb_set_owner_r(nskb
, sk
);
4593 /* Copy data, releasing collapsed skbs. */
4595 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4596 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4600 size
= min(copy
, size
);
4601 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4603 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4607 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4608 skb
= tcp_collapse_one(sk
, skb
, list
);
4611 (TCP_SKB_CB(skb
)->tcp_flags
& (TCPHDR_SYN
| TCPHDR_FIN
)))
4618 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4619 * and tcp_collapse() them until all the queue is collapsed.
4621 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4623 struct tcp_sock
*tp
= tcp_sk(sk
);
4624 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4625 struct sk_buff
*head
;
4631 start
= TCP_SKB_CB(skb
)->seq
;
4632 end
= TCP_SKB_CB(skb
)->end_seq
;
4636 struct sk_buff
*next
= NULL
;
4638 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4639 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4642 /* Segment is terminated when we see gap or when
4643 * we are at the end of all the queue. */
4645 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4646 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4647 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4648 head
, skb
, start
, end
);
4652 /* Start new segment */
4653 start
= TCP_SKB_CB(skb
)->seq
;
4654 end
= TCP_SKB_CB(skb
)->end_seq
;
4656 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4657 start
= TCP_SKB_CB(skb
)->seq
;
4658 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4659 end
= TCP_SKB_CB(skb
)->end_seq
;
4665 * Purge the out-of-order queue.
4666 * Return true if queue was pruned.
4668 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4670 struct tcp_sock
*tp
= tcp_sk(sk
);
4673 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4674 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4675 __skb_queue_purge(&tp
->out_of_order_queue
);
4677 /* Reset SACK state. A conforming SACK implementation will
4678 * do the same at a timeout based retransmit. When a connection
4679 * is in a sad state like this, we care only about integrity
4680 * of the connection not performance.
4682 if (tp
->rx_opt
.sack_ok
)
4683 tcp_sack_reset(&tp
->rx_opt
);
4690 /* Reduce allocated memory if we can, trying to get
4691 * the socket within its memory limits again.
4693 * Return less than zero if we should start dropping frames
4694 * until the socket owning process reads some of the data
4695 * to stabilize the situation.
4697 static int tcp_prune_queue(struct sock
*sk
)
4699 struct tcp_sock
*tp
= tcp_sk(sk
);
4701 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4703 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4705 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4706 tcp_clamp_window(sk
);
4707 else if (sk_under_memory_pressure(sk
))
4708 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4710 tcp_collapse_ofo_queue(sk
);
4711 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4712 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4713 skb_peek(&sk
->sk_receive_queue
),
4715 tp
->copied_seq
, tp
->rcv_nxt
);
4718 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4721 /* Collapsing did not help, destructive actions follow.
4722 * This must not ever occur. */
4724 tcp_prune_ofo_queue(sk
);
4726 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4729 /* If we are really being abused, tell the caller to silently
4730 * drop receive data on the floor. It will get retransmitted
4731 * and hopefully then we'll have sufficient space.
4733 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4735 /* Massive buffer overcommit. */
4740 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4742 const struct tcp_sock
*tp
= tcp_sk(sk
);
4744 /* If the user specified a specific send buffer setting, do
4747 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4750 /* If we are under global TCP memory pressure, do not expand. */
4751 if (sk_under_memory_pressure(sk
))
4754 /* If we are under soft global TCP memory pressure, do not expand. */
4755 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4758 /* If we filled the congestion window, do not expand. */
4759 if (tp
->packets_out
>= tp
->snd_cwnd
)
4765 /* When incoming ACK allowed to free some skb from write_queue,
4766 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4767 * on the exit from tcp input handler.
4769 * PROBLEM: sndbuf expansion does not work well with largesend.
4771 static void tcp_new_space(struct sock
*sk
)
4773 struct tcp_sock
*tp
= tcp_sk(sk
);
4775 if (tcp_should_expand_sndbuf(sk
)) {
4776 tcp_sndbuf_expand(sk
);
4777 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4780 sk
->sk_write_space(sk
);
4783 static void tcp_check_space(struct sock
*sk
)
4785 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4786 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4787 if (sk
->sk_socket
&&
4788 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4793 static inline void tcp_data_snd_check(struct sock
*sk
)
4795 tcp_push_pending_frames(sk
);
4796 tcp_check_space(sk
);
4800 * Check if sending an ack is needed.
4802 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4804 struct tcp_sock
*tp
= tcp_sk(sk
);
4806 /* More than one full frame received... */
4807 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4808 /* ... and right edge of window advances far enough.
4809 * (tcp_recvmsg() will send ACK otherwise). Or...
4811 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4812 /* We ACK each frame or... */
4813 tcp_in_quickack_mode(sk
) ||
4814 /* We have out of order data. */
4815 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4816 /* Then ack it now */
4819 /* Else, send delayed ack. */
4820 tcp_send_delayed_ack(sk
);
4824 static inline void tcp_ack_snd_check(struct sock
*sk
)
4826 if (!inet_csk_ack_scheduled(sk
)) {
4827 /* We sent a data segment already. */
4830 __tcp_ack_snd_check(sk
, 1);
4834 * This routine is only called when we have urgent data
4835 * signaled. Its the 'slow' part of tcp_urg. It could be
4836 * moved inline now as tcp_urg is only called from one
4837 * place. We handle URGent data wrong. We have to - as
4838 * BSD still doesn't use the correction from RFC961.
4839 * For 1003.1g we should support a new option TCP_STDURG to permit
4840 * either form (or just set the sysctl tcp_stdurg).
4843 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
4845 struct tcp_sock
*tp
= tcp_sk(sk
);
4846 u32 ptr
= ntohs(th
->urg_ptr
);
4848 if (ptr
&& !sysctl_tcp_stdurg
)
4850 ptr
+= ntohl(th
->seq
);
4852 /* Ignore urgent data that we've already seen and read. */
4853 if (after(tp
->copied_seq
, ptr
))
4856 /* Do not replay urg ptr.
4858 * NOTE: interesting situation not covered by specs.
4859 * Misbehaving sender may send urg ptr, pointing to segment,
4860 * which we already have in ofo queue. We are not able to fetch
4861 * such data and will stay in TCP_URG_NOTYET until will be eaten
4862 * by recvmsg(). Seems, we are not obliged to handle such wicked
4863 * situations. But it is worth to think about possibility of some
4864 * DoSes using some hypothetical application level deadlock.
4866 if (before(ptr
, tp
->rcv_nxt
))
4869 /* Do we already have a newer (or duplicate) urgent pointer? */
4870 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4873 /* Tell the world about our new urgent pointer. */
4876 /* We may be adding urgent data when the last byte read was
4877 * urgent. To do this requires some care. We cannot just ignore
4878 * tp->copied_seq since we would read the last urgent byte again
4879 * as data, nor can we alter copied_seq until this data arrives
4880 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4882 * NOTE. Double Dutch. Rendering to plain English: author of comment
4883 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4884 * and expect that both A and B disappear from stream. This is _wrong_.
4885 * Though this happens in BSD with high probability, this is occasional.
4886 * Any application relying on this is buggy. Note also, that fix "works"
4887 * only in this artificial test. Insert some normal data between A and B and we will
4888 * decline of BSD again. Verdict: it is better to remove to trap
4891 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4892 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4893 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4895 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4896 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4901 tp
->urg_data
= TCP_URG_NOTYET
;
4904 /* Disable header prediction. */
4908 /* This is the 'fast' part of urgent handling. */
4909 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
4911 struct tcp_sock
*tp
= tcp_sk(sk
);
4913 /* Check if we get a new urgent pointer - normally not. */
4915 tcp_check_urg(sk
, th
);
4917 /* Do we wait for any urgent data? - normally not... */
4918 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4919 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4922 /* Is the urgent pointer pointing into this packet? */
4923 if (ptr
< skb
->len
) {
4925 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4927 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4928 if (!sock_flag(sk
, SOCK_DEAD
))
4929 sk
->sk_data_ready(sk
);
4934 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4936 struct tcp_sock
*tp
= tcp_sk(sk
);
4937 int chunk
= skb
->len
- hlen
;
4941 if (skb_csum_unnecessary(skb
))
4942 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4944 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4948 tp
->ucopy
.len
-= chunk
;
4949 tp
->copied_seq
+= chunk
;
4950 tcp_rcv_space_adjust(sk
);
4957 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
4958 struct sk_buff
*skb
)
4962 if (sock_owned_by_user(sk
)) {
4964 result
= __tcp_checksum_complete(skb
);
4967 result
= __tcp_checksum_complete(skb
);
4972 static inline bool tcp_checksum_complete_user(struct sock
*sk
,
4973 struct sk_buff
*skb
)
4975 return !skb_csum_unnecessary(skb
) &&
4976 __tcp_checksum_complete_user(sk
, skb
);
4979 /* Does PAWS and seqno based validation of an incoming segment, flags will
4980 * play significant role here.
4982 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
4983 const struct tcphdr
*th
, int syn_inerr
)
4985 struct tcp_sock
*tp
= tcp_sk(sk
);
4987 /* RFC1323: H1. Apply PAWS check first. */
4988 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4989 tcp_paws_discard(sk
, skb
)) {
4991 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
4992 tcp_send_dupack(sk
, skb
);
4995 /* Reset is accepted even if it did not pass PAWS. */
4998 /* Step 1: check sequence number */
4999 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5000 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5001 * (RST) segments are validated by checking their SEQ-fields."
5002 * And page 69: "If an incoming segment is not acceptable,
5003 * an acknowledgment should be sent in reply (unless the RST
5004 * bit is set, if so drop the segment and return)".
5009 tcp_send_dupack(sk
, skb
);
5014 /* Step 2: check RST bit */
5017 * If sequence number exactly matches RCV.NXT, then
5018 * RESET the connection
5020 * Send a challenge ACK
5022 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
)
5025 tcp_send_challenge_ack(sk
);
5029 /* step 3: check security and precedence [ignored] */
5031 /* step 4: Check for a SYN
5032 * RFC 5961 4.2 : Send a challenge ack
5037 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5038 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5039 tcp_send_challenge_ack(sk
);
5051 * TCP receive function for the ESTABLISHED state.
5053 * It is split into a fast path and a slow path. The fast path is
5055 * - A zero window was announced from us - zero window probing
5056 * is only handled properly in the slow path.
5057 * - Out of order segments arrived.
5058 * - Urgent data is expected.
5059 * - There is no buffer space left
5060 * - Unexpected TCP flags/window values/header lengths are received
5061 * (detected by checking the TCP header against pred_flags)
5062 * - Data is sent in both directions. Fast path only supports pure senders
5063 * or pure receivers (this means either the sequence number or the ack
5064 * value must stay constant)
5065 * - Unexpected TCP option.
5067 * When these conditions are not satisfied it drops into a standard
5068 * receive procedure patterned after RFC793 to handle all cases.
5069 * The first three cases are guaranteed by proper pred_flags setting,
5070 * the rest is checked inline. Fast processing is turned on in
5071 * tcp_data_queue when everything is OK.
5073 void tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5074 const struct tcphdr
*th
, unsigned int len
)
5076 struct tcp_sock
*tp
= tcp_sk(sk
);
5078 if (unlikely(sk
->sk_rx_dst
== NULL
))
5079 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5081 * Header prediction.
5082 * The code loosely follows the one in the famous
5083 * "30 instruction TCP receive" Van Jacobson mail.
5085 * Van's trick is to deposit buffers into socket queue
5086 * on a device interrupt, to call tcp_recv function
5087 * on the receive process context and checksum and copy
5088 * the buffer to user space. smart...
5090 * Our current scheme is not silly either but we take the
5091 * extra cost of the net_bh soft interrupt processing...
5092 * We do checksum and copy also but from device to kernel.
5095 tp
->rx_opt
.saw_tstamp
= 0;
5097 /* pred_flags is 0xS?10 << 16 + snd_wnd
5098 * if header_prediction is to be made
5099 * 'S' will always be tp->tcp_header_len >> 2
5100 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5101 * turn it off (when there are holes in the receive
5102 * space for instance)
5103 * PSH flag is ignored.
5106 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5107 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5108 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5109 int tcp_header_len
= tp
->tcp_header_len
;
5111 /* Timestamp header prediction: tcp_header_len
5112 * is automatically equal to th->doff*4 due to pred_flags
5116 /* Check timestamp */
5117 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5118 /* No? Slow path! */
5119 if (!tcp_parse_aligned_timestamp(tp
, th
))
5122 /* If PAWS failed, check it more carefully in slow path */
5123 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5126 /* DO NOT update ts_recent here, if checksum fails
5127 * and timestamp was corrupted part, it will result
5128 * in a hung connection since we will drop all
5129 * future packets due to the PAWS test.
5133 if (len
<= tcp_header_len
) {
5134 /* Bulk data transfer: sender */
5135 if (len
== tcp_header_len
) {
5136 /* Predicted packet is in window by definition.
5137 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5138 * Hence, check seq<=rcv_wup reduces to:
5140 if (tcp_header_len
==
5141 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5142 tp
->rcv_nxt
== tp
->rcv_wup
)
5143 tcp_store_ts_recent(tp
);
5145 /* We know that such packets are checksummed
5148 tcp_ack(sk
, skb
, 0);
5150 tcp_data_snd_check(sk
);
5152 } else { /* Header too small */
5153 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5158 bool fragstolen
= false;
5160 if (tp
->ucopy
.task
== current
&&
5161 tp
->copied_seq
== tp
->rcv_nxt
&&
5162 len
- tcp_header_len
<= tp
->ucopy
.len
&&
5163 sock_owned_by_user(sk
)) {
5164 __set_current_state(TASK_RUNNING
);
5166 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
)) {
5167 /* Predicted packet is in window by definition.
5168 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5169 * Hence, check seq<=rcv_wup reduces to:
5171 if (tcp_header_len
==
5172 (sizeof(struct tcphdr
) +
5173 TCPOLEN_TSTAMP_ALIGNED
) &&
5174 tp
->rcv_nxt
== tp
->rcv_wup
)
5175 tcp_store_ts_recent(tp
);
5177 tcp_rcv_rtt_measure_ts(sk
, skb
);
5179 __skb_pull(skb
, tcp_header_len
);
5180 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5181 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5186 if (tcp_checksum_complete_user(sk
, skb
))
5189 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5192 /* Predicted packet is in window by definition.
5193 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5194 * Hence, check seq<=rcv_wup reduces to:
5196 if (tcp_header_len
==
5197 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5198 tp
->rcv_nxt
== tp
->rcv_wup
)
5199 tcp_store_ts_recent(tp
);
5201 tcp_rcv_rtt_measure_ts(sk
, skb
);
5203 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5205 /* Bulk data transfer: receiver */
5206 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5210 tcp_event_data_recv(sk
, skb
);
5212 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5213 /* Well, only one small jumplet in fast path... */
5214 tcp_ack(sk
, skb
, FLAG_DATA
);
5215 tcp_data_snd_check(sk
);
5216 if (!inet_csk_ack_scheduled(sk
))
5220 __tcp_ack_snd_check(sk
, 0);
5223 kfree_skb_partial(skb
, fragstolen
);
5224 sk
->sk_data_ready(sk
);
5230 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5233 if (!th
->ack
&& !th
->rst
)
5237 * Standard slow path.
5240 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5244 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5247 tcp_rcv_rtt_measure_ts(sk
, skb
);
5249 /* Process urgent data. */
5250 tcp_urg(sk
, skb
, th
);
5252 /* step 7: process the segment text */
5253 tcp_data_queue(sk
, skb
);
5255 tcp_data_snd_check(sk
);
5256 tcp_ack_snd_check(sk
);
5260 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5261 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5266 EXPORT_SYMBOL(tcp_rcv_established
);
5268 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5270 struct tcp_sock
*tp
= tcp_sk(sk
);
5271 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5273 tcp_set_state(sk
, TCP_ESTABLISHED
);
5276 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5277 security_inet_conn_established(sk
, skb
);
5280 /* Make sure socket is routed, for correct metrics. */
5281 icsk
->icsk_af_ops
->rebuild_header(sk
);
5283 tcp_init_metrics(sk
);
5285 tcp_init_congestion_control(sk
);
5287 /* Prevent spurious tcp_cwnd_restart() on first data
5290 tp
->lsndtime
= tcp_time_stamp
;
5292 tcp_init_buffer_space(sk
);
5294 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5295 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5297 if (!tp
->rx_opt
.snd_wscale
)
5298 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5302 if (!sock_flag(sk
, SOCK_DEAD
)) {
5303 sk
->sk_state_change(sk
);
5304 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5308 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5309 struct tcp_fastopen_cookie
*cookie
)
5311 struct tcp_sock
*tp
= tcp_sk(sk
);
5312 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5313 u16 mss
= tp
->rx_opt
.mss_clamp
;
5316 if (mss
== tp
->rx_opt
.user_mss
) {
5317 struct tcp_options_received opt
;
5319 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5320 tcp_clear_options(&opt
);
5321 opt
.user_mss
= opt
.mss_clamp
= 0;
5322 tcp_parse_options(synack
, &opt
, 0, NULL
);
5323 mss
= opt
.mss_clamp
;
5326 if (!tp
->syn_fastopen
) /* Ignore an unsolicited cookie */
5329 /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably
5330 * the remote receives only the retransmitted (regular) SYNs: either
5331 * the original SYN-data or the corresponding SYN-ACK is lost.
5333 syn_drop
= (cookie
->len
<= 0 && data
&& tp
->total_retrans
);
5335 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
);
5337 if (data
) { /* Retransmit unacked data in SYN */
5338 tcp_for_write_queue_from(data
, sk
) {
5339 if (data
== tcp_send_head(sk
) ||
5340 __tcp_retransmit_skb(sk
, data
))
5344 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVEFAIL
);
5347 tp
->syn_data_acked
= tp
->syn_data
;
5348 if (tp
->syn_data_acked
)
5349 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
5353 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5354 const struct tcphdr
*th
, unsigned int len
)
5356 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5357 struct tcp_sock
*tp
= tcp_sk(sk
);
5358 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5359 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5361 tcp_parse_options(skb
, &tp
->rx_opt
, 0, &foc
);
5362 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5363 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5367 * "If the state is SYN-SENT then
5368 * first check the ACK bit
5369 * If the ACK bit is set
5370 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5371 * a reset (unless the RST bit is set, if so drop
5372 * the segment and return)"
5374 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5375 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5376 goto reset_and_undo
;
5378 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5379 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5381 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5382 goto reset_and_undo
;
5385 /* Now ACK is acceptable.
5387 * "If the RST bit is set
5388 * If the ACK was acceptable then signal the user "error:
5389 * connection reset", drop the segment, enter CLOSED state,
5390 * delete TCB, and return."
5399 * "fifth, if neither of the SYN or RST bits is set then
5400 * drop the segment and return."
5406 goto discard_and_undo
;
5409 * "If the SYN bit is on ...
5410 * are acceptable then ...
5411 * (our SYN has been ACKed), change the connection
5412 * state to ESTABLISHED..."
5415 tcp_ecn_rcv_synack(tp
, th
);
5417 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5418 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5420 /* Ok.. it's good. Set up sequence numbers and
5421 * move to established.
5423 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5424 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5426 /* RFC1323: The window in SYN & SYN/ACK segments is
5429 tp
->snd_wnd
= ntohs(th
->window
);
5431 if (!tp
->rx_opt
.wscale_ok
) {
5432 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5433 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5436 if (tp
->rx_opt
.saw_tstamp
) {
5437 tp
->rx_opt
.tstamp_ok
= 1;
5438 tp
->tcp_header_len
=
5439 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5440 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5441 tcp_store_ts_recent(tp
);
5443 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5446 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5447 tcp_enable_fack(tp
);
5450 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5451 tcp_initialize_rcv_mss(sk
);
5453 /* Remember, tcp_poll() does not lock socket!
5454 * Change state from SYN-SENT only after copied_seq
5455 * is initialized. */
5456 tp
->copied_seq
= tp
->rcv_nxt
;
5460 tcp_finish_connect(sk
, skb
);
5462 if ((tp
->syn_fastopen
|| tp
->syn_data
) &&
5463 tcp_rcv_fastopen_synack(sk
, skb
, &foc
))
5466 if (sk
->sk_write_pending
||
5467 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5468 icsk
->icsk_ack
.pingpong
) {
5469 /* Save one ACK. Data will be ready after
5470 * several ticks, if write_pending is set.
5472 * It may be deleted, but with this feature tcpdumps
5473 * look so _wonderfully_ clever, that I was not able
5474 * to stand against the temptation 8) --ANK
5476 inet_csk_schedule_ack(sk
);
5477 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5478 tcp_enter_quickack_mode(sk
);
5479 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5480 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5491 /* No ACK in the segment */
5495 * "If the RST bit is set
5497 * Otherwise (no ACK) drop the segment and return."
5500 goto discard_and_undo
;
5504 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5505 tcp_paws_reject(&tp
->rx_opt
, 0))
5506 goto discard_and_undo
;
5509 /* We see SYN without ACK. It is attempt of
5510 * simultaneous connect with crossed SYNs.
5511 * Particularly, it can be connect to self.
5513 tcp_set_state(sk
, TCP_SYN_RECV
);
5515 if (tp
->rx_opt
.saw_tstamp
) {
5516 tp
->rx_opt
.tstamp_ok
= 1;
5517 tcp_store_ts_recent(tp
);
5518 tp
->tcp_header_len
=
5519 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5521 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5524 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5525 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5527 /* RFC1323: The window in SYN & SYN/ACK segments is
5530 tp
->snd_wnd
= ntohs(th
->window
);
5531 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5532 tp
->max_window
= tp
->snd_wnd
;
5534 tcp_ecn_rcv_syn(tp
, th
);
5537 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5538 tcp_initialize_rcv_mss(sk
);
5540 tcp_send_synack(sk
);
5542 /* Note, we could accept data and URG from this segment.
5543 * There are no obstacles to make this (except that we must
5544 * either change tcp_recvmsg() to prevent it from returning data
5545 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5547 * However, if we ignore data in ACKless segments sometimes,
5548 * we have no reasons to accept it sometimes.
5549 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5550 * is not flawless. So, discard packet for sanity.
5551 * Uncomment this return to process the data.
5558 /* "fifth, if neither of the SYN or RST bits is set then
5559 * drop the segment and return."
5563 tcp_clear_options(&tp
->rx_opt
);
5564 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5568 tcp_clear_options(&tp
->rx_opt
);
5569 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5574 * This function implements the receiving procedure of RFC 793 for
5575 * all states except ESTABLISHED and TIME_WAIT.
5576 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5577 * address independent.
5580 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5581 const struct tcphdr
*th
, unsigned int len
)
5583 struct tcp_sock
*tp
= tcp_sk(sk
);
5584 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5585 struct request_sock
*req
;
5590 tp
->rx_opt
.saw_tstamp
= 0;
5592 switch (sk
->sk_state
) {
5606 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5609 /* Now we have several options: In theory there is
5610 * nothing else in the frame. KA9Q has an option to
5611 * send data with the syn, BSD accepts data with the
5612 * syn up to the [to be] advertised window and
5613 * Solaris 2.1 gives you a protocol error. For now
5614 * we just ignore it, that fits the spec precisely
5615 * and avoids incompatibilities. It would be nice in
5616 * future to drop through and process the data.
5618 * Now that TTCP is starting to be used we ought to
5620 * But, this leaves one open to an easy denial of
5621 * service attack, and SYN cookies can't defend
5622 * against this problem. So, we drop the data
5623 * in the interest of security over speed unless
5624 * it's still in use.
5632 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5636 /* Do step6 onward by hand. */
5637 tcp_urg(sk
, skb
, th
);
5639 tcp_data_snd_check(sk
);
5643 req
= tp
->fastopen_rsk
;
5645 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5646 sk
->sk_state
!= TCP_FIN_WAIT1
);
5648 if (tcp_check_req(sk
, skb
, req
, NULL
, true) == NULL
)
5652 if (!th
->ack
&& !th
->rst
)
5655 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5658 /* step 5: check the ACK field */
5659 acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5660 FLAG_UPDATE_TS_RECENT
) > 0;
5662 switch (sk
->sk_state
) {
5667 /* Once we leave TCP_SYN_RECV, we no longer need req
5671 synack_stamp
= tcp_rsk(req
)->snt_synack
;
5672 tp
->total_retrans
= req
->num_retrans
;
5673 reqsk_fastopen_remove(sk
, req
, false);
5675 synack_stamp
= tp
->lsndtime
;
5676 /* Make sure socket is routed, for correct metrics. */
5677 icsk
->icsk_af_ops
->rebuild_header(sk
);
5678 tcp_init_congestion_control(sk
);
5681 tp
->copied_seq
= tp
->rcv_nxt
;
5682 tcp_init_buffer_space(sk
);
5685 tcp_set_state(sk
, TCP_ESTABLISHED
);
5686 sk
->sk_state_change(sk
);
5688 /* Note, that this wakeup is only for marginal crossed SYN case.
5689 * Passively open sockets are not waked up, because
5690 * sk->sk_sleep == NULL and sk->sk_socket == NULL.
5693 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5695 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5696 tp
->snd_wnd
= ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
;
5697 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5698 tcp_synack_rtt_meas(sk
, synack_stamp
);
5700 if (tp
->rx_opt
.tstamp_ok
)
5701 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5704 /* Re-arm the timer because data may have been sent out.
5705 * This is similar to the regular data transmission case
5706 * when new data has just been ack'ed.
5708 * (TFO) - we could try to be more aggressive and
5709 * retransmitting any data sooner based on when they
5714 tcp_init_metrics(sk
);
5716 tcp_update_pacing_rate(sk
);
5718 /* Prevent spurious tcp_cwnd_restart() on first data packet */
5719 tp
->lsndtime
= tcp_time_stamp
;
5721 tcp_initialize_rcv_mss(sk
);
5722 tcp_fast_path_on(tp
);
5725 case TCP_FIN_WAIT1
: {
5726 struct dst_entry
*dst
;
5729 /* If we enter the TCP_FIN_WAIT1 state and we are a
5730 * Fast Open socket and this is the first acceptable
5731 * ACK we have received, this would have acknowledged
5732 * our SYNACK so stop the SYNACK timer.
5735 /* Return RST if ack_seq is invalid.
5736 * Note that RFC793 only says to generate a
5737 * DUPACK for it but for TCP Fast Open it seems
5738 * better to treat this case like TCP_SYN_RECV
5743 /* We no longer need the request sock. */
5744 reqsk_fastopen_remove(sk
, req
, false);
5747 if (tp
->snd_una
!= tp
->write_seq
)
5750 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5751 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5753 dst
= __sk_dst_get(sk
);
5757 if (!sock_flag(sk
, SOCK_DEAD
)) {
5758 /* Wake up lingering close() */
5759 sk
->sk_state_change(sk
);
5763 if (tp
->linger2
< 0 ||
5764 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5765 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5767 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5771 tmo
= tcp_fin_time(sk
);
5772 if (tmo
> TCP_TIMEWAIT_LEN
) {
5773 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5774 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5775 /* Bad case. We could lose such FIN otherwise.
5776 * It is not a big problem, but it looks confusing
5777 * and not so rare event. We still can lose it now,
5778 * if it spins in bh_lock_sock(), but it is really
5781 inet_csk_reset_keepalive_timer(sk
, tmo
);
5783 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5790 if (tp
->snd_una
== tp
->write_seq
) {
5791 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5797 if (tp
->snd_una
== tp
->write_seq
) {
5798 tcp_update_metrics(sk
);
5805 /* step 6: check the URG bit */
5806 tcp_urg(sk
, skb
, th
);
5808 /* step 7: process the segment text */
5809 switch (sk
->sk_state
) {
5810 case TCP_CLOSE_WAIT
:
5813 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5817 /* RFC 793 says to queue data in these states,
5818 * RFC 1122 says we MUST send a reset.
5819 * BSD 4.4 also does reset.
5821 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5822 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5823 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5824 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5830 case TCP_ESTABLISHED
:
5831 tcp_data_queue(sk
, skb
);
5836 /* tcp_data could move socket to TIME-WAIT */
5837 if (sk
->sk_state
!= TCP_CLOSE
) {
5838 tcp_data_snd_check(sk
);
5839 tcp_ack_snd_check(sk
);
5848 EXPORT_SYMBOL(tcp_rcv_state_process
);
5850 static inline void pr_drop_req(struct request_sock
*req
, __u16 port
, int family
)
5852 struct inet_request_sock
*ireq
= inet_rsk(req
);
5854 if (family
== AF_INET
)
5855 LIMIT_NETDEBUG(KERN_DEBUG
pr_fmt("drop open request from %pI4/%u\n"),
5856 &ireq
->ir_rmt_addr
, port
);
5857 #if IS_ENABLED(CONFIG_IPV6)
5858 else if (family
== AF_INET6
)
5859 LIMIT_NETDEBUG(KERN_DEBUG
pr_fmt("drop open request from %pI6/%u\n"),
5860 &ireq
->ir_v6_rmt_addr
, port
);
5864 /* RFC3168 : 6.1.1 SYN packets must not have ECT/ECN bits set
5866 * If we receive a SYN packet with these bits set, it means a
5867 * network is playing bad games with TOS bits. In order to
5868 * avoid possible false congestion notifications, we disable
5869 * TCP ECN negotiation.
5871 * Exception: tcp_ca wants ECN. This is required for DCTCP
5872 * congestion control; it requires setting ECT on all packets,
5873 * including SYN. We inverse the test in this case: If our
5874 * local socket wants ECN, but peer only set ece/cwr (but not
5875 * ECT in IP header) its probably a non-DCTCP aware sender.
5877 static void tcp_ecn_create_request(struct request_sock
*req
,
5878 const struct sk_buff
*skb
,
5879 const struct sock
*listen_sk
)
5881 const struct tcphdr
*th
= tcp_hdr(skb
);
5882 const struct net
*net
= sock_net(listen_sk
);
5883 bool th_ecn
= th
->ece
&& th
->cwr
;
5889 ect
= !INET_ECN_is_not_ect(TCP_SKB_CB(skb
)->ip_dsfield
);
5890 need_ecn
= tcp_ca_needs_ecn(listen_sk
);
5892 if (!ect
&& !need_ecn
&& net
->ipv4
.sysctl_tcp_ecn
)
5893 inet_rsk(req
)->ecn_ok
= 1;
5894 else if (ect
&& need_ecn
)
5895 inet_rsk(req
)->ecn_ok
= 1;
5898 int tcp_conn_request(struct request_sock_ops
*rsk_ops
,
5899 const struct tcp_request_sock_ops
*af_ops
,
5900 struct sock
*sk
, struct sk_buff
*skb
)
5902 struct tcp_options_received tmp_opt
;
5903 struct request_sock
*req
;
5904 struct tcp_sock
*tp
= tcp_sk(sk
);
5905 struct dst_entry
*dst
= NULL
;
5906 __u32 isn
= TCP_SKB_CB(skb
)->tcp_tw_isn
;
5907 bool want_cookie
= false, fastopen
;
5909 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5913 /* TW buckets are converted to open requests without
5914 * limitations, they conserve resources and peer is
5915 * evidently real one.
5917 if ((sysctl_tcp_syncookies
== 2 ||
5918 inet_csk_reqsk_queue_is_full(sk
)) && !isn
) {
5919 want_cookie
= tcp_syn_flood_action(sk
, skb
, rsk_ops
->slab_name
);
5925 /* Accept backlog is full. If we have already queued enough
5926 * of warm entries in syn queue, drop request. It is better than
5927 * clogging syn queue with openreqs with exponentially increasing
5930 if (sk_acceptq_is_full(sk
) && inet_csk_reqsk_queue_young(sk
) > 1) {
5931 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENOVERFLOWS
);
5935 req
= inet_reqsk_alloc(rsk_ops
);
5939 tcp_rsk(req
)->af_specific
= af_ops
;
5941 tcp_clear_options(&tmp_opt
);
5942 tmp_opt
.mss_clamp
= af_ops
->mss_clamp
;
5943 tmp_opt
.user_mss
= tp
->rx_opt
.user_mss
;
5944 tcp_parse_options(skb
, &tmp_opt
, 0, want_cookie
? NULL
: &foc
);
5946 if (want_cookie
&& !tmp_opt
.saw_tstamp
)
5947 tcp_clear_options(&tmp_opt
);
5949 tmp_opt
.tstamp_ok
= tmp_opt
.saw_tstamp
;
5950 tcp_openreq_init(req
, &tmp_opt
, skb
, sk
);
5952 af_ops
->init_req(req
, sk
, skb
);
5954 if (security_inet_conn_request(sk
, skb
, req
))
5957 if (!want_cookie
|| tmp_opt
.tstamp_ok
)
5958 tcp_ecn_create_request(req
, skb
, sk
);
5961 isn
= cookie_init_sequence(af_ops
, sk
, skb
, &req
->mss
);
5962 req
->cookie_ts
= tmp_opt
.tstamp_ok
;
5964 /* VJ's idea. We save last timestamp seen
5965 * from the destination in peer table, when entering
5966 * state TIME-WAIT, and check against it before
5967 * accepting new connection request.
5969 * If "isn" is not zero, this request hit alive
5970 * timewait bucket, so that all the necessary checks
5971 * are made in the function processing timewait state.
5973 if (tcp_death_row
.sysctl_tw_recycle
) {
5976 dst
= af_ops
->route_req(sk
, &fl
, req
, &strict
);
5978 if (dst
&& strict
&&
5979 !tcp_peer_is_proven(req
, dst
, true,
5980 tmp_opt
.saw_tstamp
)) {
5981 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSPASSIVEREJECTED
);
5982 goto drop_and_release
;
5985 /* Kill the following clause, if you dislike this way. */
5986 else if (!sysctl_tcp_syncookies
&&
5987 (sysctl_max_syn_backlog
- inet_csk_reqsk_queue_len(sk
) <
5988 (sysctl_max_syn_backlog
>> 2)) &&
5989 !tcp_peer_is_proven(req
, dst
, false,
5990 tmp_opt
.saw_tstamp
)) {
5991 /* Without syncookies last quarter of
5992 * backlog is filled with destinations,
5993 * proven to be alive.
5994 * It means that we continue to communicate
5995 * to destinations, already remembered
5996 * to the moment of synflood.
5998 pr_drop_req(req
, ntohs(tcp_hdr(skb
)->source
),
6000 goto drop_and_release
;
6003 isn
= af_ops
->init_seq(skb
);
6006 dst
= af_ops
->route_req(sk
, &fl
, req
, NULL
);
6011 tcp_rsk(req
)->snt_isn
= isn
;
6012 tcp_openreq_init_rwin(req
, sk
, dst
);
6013 fastopen
= !want_cookie
&&
6014 tcp_try_fastopen(sk
, skb
, req
, &foc
, dst
);
6015 err
= af_ops
->send_synack(sk
, dst
, &fl
, req
,
6016 skb_get_queue_mapping(skb
), &foc
);
6018 if (err
|| want_cookie
)
6021 tcp_rsk(req
)->listener
= NULL
;
6022 af_ops
->queue_hash_add(sk
, req
, TCP_TIMEOUT_INIT
);
6032 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_LISTENDROPS
);
6035 EXPORT_SYMBOL(tcp_conn_request
);