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/reciprocal_div.h>
74 #include <net/inet_common.h>
75 #include <linux/ipsec.h>
76 #include <asm/unaligned.h>
77 #include <net/netdma.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 EXPORT_SYMBOL(sysctl_tcp_reordering
);
85 int sysctl_tcp_dsack __read_mostly
= 1;
86 int sysctl_tcp_app_win __read_mostly
= 31;
87 int sysctl_tcp_adv_win_scale __read_mostly
= 1;
88 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
90 /* rfc5961 challenge ack rate limiting */
91 int sysctl_tcp_challenge_ack_limit
= 1000;
93 int sysctl_tcp_stdurg __read_mostly
;
94 int sysctl_tcp_rfc1337 __read_mostly
;
95 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
96 int sysctl_tcp_frto __read_mostly
= 2;
98 int sysctl_tcp_thin_dupack __read_mostly
;
100 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
101 int sysctl_tcp_early_retrans __read_mostly
= 3;
103 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
104 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
105 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
106 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
107 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
108 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
109 #define FLAG_ECE 0x40 /* ECE in this ACK */
110 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
111 #define FLAG_ORIG_SACK_ACKED 0x200 /* Never retransmitted data are (s)acked */
112 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
113 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
114 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
115 #define FLAG_UPDATE_TS_RECENT 0x4000 /* tcp_replace_ts_recent() */
117 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
118 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
119 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
120 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
122 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
123 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
125 /* Adapt the MSS value used to make delayed ack decision to the
128 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
130 struct inet_connection_sock
*icsk
= inet_csk(sk
);
131 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
134 icsk
->icsk_ack
.last_seg_size
= 0;
136 /* skb->len may jitter because of SACKs, even if peer
137 * sends good full-sized frames.
139 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
140 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
141 icsk
->icsk_ack
.rcv_mss
= len
;
143 /* Otherwise, we make more careful check taking into account,
144 * that SACKs block is variable.
146 * "len" is invariant segment length, including TCP header.
148 len
+= skb
->data
- skb_transport_header(skb
);
149 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
150 /* If PSH is not set, packet should be
151 * full sized, provided peer TCP is not badly broken.
152 * This observation (if it is correct 8)) allows
153 * to handle super-low mtu links fairly.
155 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
156 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
157 /* Subtract also invariant (if peer is RFC compliant),
158 * tcp header plus fixed timestamp option length.
159 * Resulting "len" is MSS free of SACK jitter.
161 len
-= tcp_sk(sk
)->tcp_header_len
;
162 icsk
->icsk_ack
.last_seg_size
= len
;
164 icsk
->icsk_ack
.rcv_mss
= len
;
168 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
169 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
170 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
174 static void tcp_incr_quickack(struct sock
*sk
)
176 struct inet_connection_sock
*icsk
= inet_csk(sk
);
177 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
181 if (quickacks
> icsk
->icsk_ack
.quick
)
182 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
185 static void tcp_enter_quickack_mode(struct sock
*sk
)
187 struct inet_connection_sock
*icsk
= inet_csk(sk
);
188 tcp_incr_quickack(sk
);
189 icsk
->icsk_ack
.pingpong
= 0;
190 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
193 /* Send ACKs quickly, if "quick" count is not exhausted
194 * and the session is not interactive.
197 static inline bool tcp_in_quickack_mode(const struct sock
*sk
)
199 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
201 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
204 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
206 if (tp
->ecn_flags
& TCP_ECN_OK
)
207 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
210 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
212 if (tcp_hdr(skb
)->cwr
)
213 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
216 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
218 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
221 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
223 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
226 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
227 case INET_ECN_NOT_ECT
:
228 /* Funny extension: if ECT is not set on a segment,
229 * and we already seen ECT on a previous segment,
230 * it is probably a retransmit.
232 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
233 tcp_enter_quickack_mode((struct sock
*)tp
);
236 if (!(tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)) {
237 /* Better not delay acks, sender can have a very low cwnd */
238 tcp_enter_quickack_mode((struct sock
*)tp
);
239 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
243 tp
->ecn_flags
|= TCP_ECN_SEEN
;
247 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
249 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
250 tp
->ecn_flags
&= ~TCP_ECN_OK
;
253 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
255 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
256 tp
->ecn_flags
&= ~TCP_ECN_OK
;
259 static bool TCP_ECN_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
261 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
266 /* Buffer size and advertised window tuning.
268 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
271 static void tcp_fixup_sndbuf(struct sock
*sk
)
273 int sndmem
= SKB_TRUESIZE(tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
);
275 sndmem
*= TCP_INIT_CWND
;
276 if (sk
->sk_sndbuf
< sndmem
)
277 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
280 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
282 * All tcp_full_space() is split to two parts: "network" buffer, allocated
283 * forward and advertised in receiver window (tp->rcv_wnd) and
284 * "application buffer", required to isolate scheduling/application
285 * latencies from network.
286 * window_clamp is maximal advertised window. It can be less than
287 * tcp_full_space(), in this case tcp_full_space() - window_clamp
288 * is reserved for "application" buffer. The less window_clamp is
289 * the smoother our behaviour from viewpoint of network, but the lower
290 * throughput and the higher sensitivity of the connection to losses. 8)
292 * rcv_ssthresh is more strict window_clamp used at "slow start"
293 * phase to predict further behaviour of this connection.
294 * It is used for two goals:
295 * - to enforce header prediction at sender, even when application
296 * requires some significant "application buffer". It is check #1.
297 * - to prevent pruning of receive queue because of misprediction
298 * of receiver window. Check #2.
300 * The scheme does not work when sender sends good segments opening
301 * window and then starts to feed us spaghetti. But it should work
302 * in common situations. Otherwise, we have to rely on queue collapsing.
305 /* Slow part of check#2. */
306 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
308 struct tcp_sock
*tp
= tcp_sk(sk
);
310 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
311 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
313 while (tp
->rcv_ssthresh
<= window
) {
314 if (truesize
<= skb
->len
)
315 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
323 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
325 struct tcp_sock
*tp
= tcp_sk(sk
);
328 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
329 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
330 !sk_under_memory_pressure(sk
)) {
333 /* Check #2. Increase window, if skb with such overhead
334 * will fit to rcvbuf in future.
336 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
337 incr
= 2 * tp
->advmss
;
339 incr
= __tcp_grow_window(sk
, skb
);
342 incr
= max_t(int, incr
, 2 * skb
->len
);
343 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
345 inet_csk(sk
)->icsk_ack
.quick
|= 1;
350 /* 3. Tuning rcvbuf, when connection enters established state. */
352 static void tcp_fixup_rcvbuf(struct sock
*sk
)
354 u32 mss
= tcp_sk(sk
)->advmss
;
355 u32 icwnd
= TCP_DEFAULT_INIT_RCVWND
;
358 /* Limit to 10 segments if mss <= 1460,
359 * or 14600/mss segments, with a minimum of two segments.
362 icwnd
= max_t(u32
, (1460 * TCP_DEFAULT_INIT_RCVWND
) / mss
, 2);
364 rcvmem
= SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
);
365 while (tcp_win_from_space(rcvmem
) < mss
)
370 if (sk
->sk_rcvbuf
< rcvmem
)
371 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
374 /* 4. Try to fixup all. It is made immediately after connection enters
377 void tcp_init_buffer_space(struct sock
*sk
)
379 struct tcp_sock
*tp
= tcp_sk(sk
);
382 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
383 tcp_fixup_rcvbuf(sk
);
384 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
385 tcp_fixup_sndbuf(sk
);
387 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
389 maxwin
= tcp_full_space(sk
);
391 if (tp
->window_clamp
>= maxwin
) {
392 tp
->window_clamp
= maxwin
;
394 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
395 tp
->window_clamp
= max(maxwin
-
396 (maxwin
>> sysctl_tcp_app_win
),
400 /* Force reservation of one segment. */
401 if (sysctl_tcp_app_win
&&
402 tp
->window_clamp
> 2 * tp
->advmss
&&
403 tp
->window_clamp
+ tp
->advmss
> maxwin
)
404 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
406 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
407 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
410 /* 5. Recalculate window clamp after socket hit its memory bounds. */
411 static void tcp_clamp_window(struct sock
*sk
)
413 struct tcp_sock
*tp
= tcp_sk(sk
);
414 struct inet_connection_sock
*icsk
= inet_csk(sk
);
416 icsk
->icsk_ack
.quick
= 0;
418 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
419 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
420 !sk_under_memory_pressure(sk
) &&
421 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
422 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
425 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
426 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
429 /* Initialize RCV_MSS value.
430 * RCV_MSS is an our guess about MSS used by the peer.
431 * We haven't any direct information about the MSS.
432 * It's better to underestimate the RCV_MSS rather than overestimate.
433 * Overestimations make us ACKing less frequently than needed.
434 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
436 void tcp_initialize_rcv_mss(struct sock
*sk
)
438 const struct tcp_sock
*tp
= tcp_sk(sk
);
439 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
441 hint
= min(hint
, tp
->rcv_wnd
/ 2);
442 hint
= min(hint
, TCP_MSS_DEFAULT
);
443 hint
= max(hint
, TCP_MIN_MSS
);
445 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
447 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
449 /* Receiver "autotuning" code.
451 * The algorithm for RTT estimation w/o timestamps is based on
452 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
453 * <http://public.lanl.gov/radiant/pubs.html#DRS>
455 * More detail on this code can be found at
456 * <http://staff.psc.edu/jheffner/>,
457 * though this reference is out of date. A new paper
460 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
462 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
468 if (new_sample
!= 0) {
469 /* If we sample in larger samples in the non-timestamp
470 * case, we could grossly overestimate the RTT especially
471 * with chatty applications or bulk transfer apps which
472 * are stalled on filesystem I/O.
474 * Also, since we are only going for a minimum in the
475 * non-timestamp case, we do not smooth things out
476 * else with timestamps disabled convergence takes too
480 m
-= (new_sample
>> 3);
488 /* No previous measure. */
492 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
493 tp
->rcv_rtt_est
.rtt
= new_sample
;
496 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
498 if (tp
->rcv_rtt_est
.time
== 0)
500 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
502 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rcv_rtt_est
.time
, 1);
505 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
506 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
509 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
510 const struct sk_buff
*skb
)
512 struct tcp_sock
*tp
= tcp_sk(sk
);
513 if (tp
->rx_opt
.rcv_tsecr
&&
514 (TCP_SKB_CB(skb
)->end_seq
-
515 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
516 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
520 * This function should be called every time data is copied to user space.
521 * It calculates the appropriate TCP receive buffer space.
523 void tcp_rcv_space_adjust(struct sock
*sk
)
525 struct tcp_sock
*tp
= tcp_sk(sk
);
529 if (tp
->rcvq_space
.time
== 0)
532 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
533 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
536 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
538 space
= max(tp
->rcvq_space
.space
, space
);
540 if (tp
->rcvq_space
.space
!= space
) {
543 tp
->rcvq_space
.space
= space
;
545 if (sysctl_tcp_moderate_rcvbuf
&&
546 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
547 int new_clamp
= space
;
549 /* Receive space grows, normalize in order to
550 * take into account packet headers and sk_buff
551 * structure overhead.
556 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
557 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
560 space
= min(space
, sysctl_tcp_rmem
[2]);
561 if (space
> sk
->sk_rcvbuf
) {
562 sk
->sk_rcvbuf
= space
;
564 /* Make the window clamp follow along. */
565 tp
->window_clamp
= new_clamp
;
571 tp
->rcvq_space
.seq
= tp
->copied_seq
;
572 tp
->rcvq_space
.time
= tcp_time_stamp
;
575 /* There is something which you must keep in mind when you analyze the
576 * behavior of the tp->ato delayed ack timeout interval. When a
577 * connection starts up, we want to ack as quickly as possible. The
578 * problem is that "good" TCP's do slow start at the beginning of data
579 * transmission. The means that until we send the first few ACK's the
580 * sender will sit on his end and only queue most of his data, because
581 * he can only send snd_cwnd unacked packets at any given time. For
582 * each ACK we send, he increments snd_cwnd and transmits more of his
585 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
587 struct tcp_sock
*tp
= tcp_sk(sk
);
588 struct inet_connection_sock
*icsk
= inet_csk(sk
);
591 inet_csk_schedule_ack(sk
);
593 tcp_measure_rcv_mss(sk
, skb
);
595 tcp_rcv_rtt_measure(tp
);
597 now
= tcp_time_stamp
;
599 if (!icsk
->icsk_ack
.ato
) {
600 /* The _first_ data packet received, initialize
601 * delayed ACK engine.
603 tcp_incr_quickack(sk
);
604 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
606 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
608 if (m
<= TCP_ATO_MIN
/ 2) {
609 /* The fastest case is the first. */
610 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
611 } else if (m
< icsk
->icsk_ack
.ato
) {
612 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
613 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
614 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
615 } else if (m
> icsk
->icsk_rto
) {
616 /* Too long gap. Apparently sender failed to
617 * restart window, so that we send ACKs quickly.
619 tcp_incr_quickack(sk
);
623 icsk
->icsk_ack
.lrcvtime
= now
;
625 TCP_ECN_check_ce(tp
, skb
);
628 tcp_grow_window(sk
, skb
);
631 /* Called to compute a smoothed rtt estimate. The data fed to this
632 * routine either comes from timestamps, or from segments that were
633 * known _not_ to have been retransmitted [see Karn/Partridge
634 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
635 * piece by Van Jacobson.
636 * NOTE: the next three routines used to be one big routine.
637 * To save cycles in the RFC 1323 implementation it was better to break
638 * it up into three procedures. -- erics
640 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
642 struct tcp_sock
*tp
= tcp_sk(sk
);
643 long m
= mrtt
; /* RTT */
645 /* The following amusing code comes from Jacobson's
646 * article in SIGCOMM '88. Note that rtt and mdev
647 * are scaled versions of rtt and mean deviation.
648 * This is designed to be as fast as possible
649 * m stands for "measurement".
651 * On a 1990 paper the rto value is changed to:
652 * RTO = rtt + 4 * mdev
654 * Funny. This algorithm seems to be very broken.
655 * These formulae increase RTO, when it should be decreased, increase
656 * too slowly, when it should be increased quickly, decrease too quickly
657 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
658 * does not matter how to _calculate_ it. Seems, it was trap
659 * that VJ failed to avoid. 8)
664 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
665 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
667 m
= -m
; /* m is now abs(error) */
668 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
669 /* This is similar to one of Eifel findings.
670 * Eifel blocks mdev updates when rtt decreases.
671 * This solution is a bit different: we use finer gain
672 * for mdev in this case (alpha*beta).
673 * Like Eifel it also prevents growth of rto,
674 * but also it limits too fast rto decreases,
675 * happening in pure Eifel.
680 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
682 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
683 if (tp
->mdev
> tp
->mdev_max
) {
684 tp
->mdev_max
= tp
->mdev
;
685 if (tp
->mdev_max
> tp
->rttvar
)
686 tp
->rttvar
= tp
->mdev_max
;
688 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
689 if (tp
->mdev_max
< tp
->rttvar
)
690 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
691 tp
->rtt_seq
= tp
->snd_nxt
;
692 tp
->mdev_max
= tcp_rto_min(sk
);
695 /* no previous measure. */
696 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
697 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
698 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
699 tp
->rtt_seq
= tp
->snd_nxt
;
703 /* Set the sk_pacing_rate to allow proper sizing of TSO packets.
704 * Note: TCP stack does not yet implement pacing.
705 * FQ packet scheduler can be used to implement cheap but effective
706 * TCP pacing, to smooth the burst on large writes when packets
707 * in flight is significantly lower than cwnd (or rwin)
709 static void tcp_update_pacing_rate(struct sock
*sk
)
711 const struct tcp_sock
*tp
= tcp_sk(sk
);
714 /* set sk_pacing_rate to 200 % of current rate (mss * cwnd / srtt) */
715 rate
= (u64
)tp
->mss_cache
* 2 * (HZ
<< 3);
717 rate
*= max(tp
->snd_cwnd
, tp
->packets_out
);
719 /* Correction for small srtt : minimum srtt being 8 (1 jiffy << 3),
720 * be conservative and assume srtt = 1 (125 us instead of 1.25 ms)
721 * We probably need usec resolution in the future.
722 * Note: This also takes care of possible srtt=0 case,
723 * when tcp_rtt_estimator() was not yet called.
725 if (tp
->srtt
> 8 + 2)
726 do_div(rate
, tp
->srtt
);
728 sk
->sk_pacing_rate
= min_t(u64
, rate
, ~0U);
731 /* Calculate rto without backoff. This is the second half of Van Jacobson's
732 * routine referred to above.
734 void tcp_set_rto(struct sock
*sk
)
736 const struct tcp_sock
*tp
= tcp_sk(sk
);
737 /* Old crap is replaced with new one. 8)
740 * 1. If rtt variance happened to be less 50msec, it is hallucination.
741 * It cannot be less due to utterly erratic ACK generation made
742 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
743 * to do with delayed acks, because at cwnd>2 true delack timeout
744 * is invisible. Actually, Linux-2.4 also generates erratic
745 * ACKs in some circumstances.
747 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
749 /* 2. Fixups made earlier cannot be right.
750 * If we do not estimate RTO correctly without them,
751 * all the algo is pure shit and should be replaced
752 * with correct one. It is exactly, which we pretend to do.
755 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
756 * guarantees that rto is higher.
761 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
763 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
766 cwnd
= TCP_INIT_CWND
;
767 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
771 * Packet counting of FACK is based on in-order assumptions, therefore TCP
772 * disables it when reordering is detected
774 void tcp_disable_fack(struct tcp_sock
*tp
)
776 /* RFC3517 uses different metric in lost marker => reset on change */
778 tp
->lost_skb_hint
= NULL
;
779 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
782 /* Take a notice that peer is sending D-SACKs */
783 static void tcp_dsack_seen(struct tcp_sock
*tp
)
785 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
788 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
791 struct tcp_sock
*tp
= tcp_sk(sk
);
792 if (metric
> tp
->reordering
) {
795 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
797 /* This exciting event is worth to be remembered. 8) */
799 mib_idx
= LINUX_MIB_TCPTSREORDER
;
800 else if (tcp_is_reno(tp
))
801 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
802 else if (tcp_is_fack(tp
))
803 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
805 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
807 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
808 #if FASTRETRANS_DEBUG > 1
809 pr_debug("Disorder%d %d %u f%u s%u rr%d\n",
810 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
814 tp
->undo_marker
? tp
->undo_retrans
: 0);
816 tcp_disable_fack(tp
);
820 tcp_disable_early_retrans(tp
);
823 /* This must be called before lost_out is incremented */
824 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
826 if ((tp
->retransmit_skb_hint
== NULL
) ||
827 before(TCP_SKB_CB(skb
)->seq
,
828 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
829 tp
->retransmit_skb_hint
= skb
;
832 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
833 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
836 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
838 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
839 tcp_verify_retransmit_hint(tp
, skb
);
841 tp
->lost_out
+= tcp_skb_pcount(skb
);
842 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
846 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
849 tcp_verify_retransmit_hint(tp
, skb
);
851 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
852 tp
->lost_out
+= tcp_skb_pcount(skb
);
853 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
857 /* This procedure tags the retransmission queue when SACKs arrive.
859 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
860 * Packets in queue with these bits set are counted in variables
861 * sacked_out, retrans_out and lost_out, correspondingly.
863 * Valid combinations are:
864 * Tag InFlight Description
865 * 0 1 - orig segment is in flight.
866 * S 0 - nothing flies, orig reached receiver.
867 * L 0 - nothing flies, orig lost by net.
868 * R 2 - both orig and retransmit are in flight.
869 * L|R 1 - orig is lost, retransmit is in flight.
870 * S|R 1 - orig reached receiver, retrans is still in flight.
871 * (L|S|R is logically valid, it could occur when L|R is sacked,
872 * but it is equivalent to plain S and code short-curcuits it to S.
873 * L|S is logically invalid, it would mean -1 packet in flight 8))
875 * These 6 states form finite state machine, controlled by the following events:
876 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
877 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
878 * 3. Loss detection event of two flavors:
879 * A. Scoreboard estimator decided the packet is lost.
880 * A'. Reno "three dupacks" marks head of queue lost.
881 * A''. Its FACK modification, head until snd.fack is lost.
882 * B. SACK arrives sacking SND.NXT at the moment, when the
883 * segment was retransmitted.
884 * 4. D-SACK added new rule: D-SACK changes any tag to S.
886 * It is pleasant to note, that state diagram turns out to be commutative,
887 * so that we are allowed not to be bothered by order of our actions,
888 * when multiple events arrive simultaneously. (see the function below).
890 * Reordering detection.
891 * --------------------
892 * Reordering metric is maximal distance, which a packet can be displaced
893 * in packet stream. With SACKs we can estimate it:
895 * 1. SACK fills old hole and the corresponding segment was not
896 * ever retransmitted -> reordering. Alas, we cannot use it
897 * when segment was retransmitted.
898 * 2. The last flaw is solved with D-SACK. D-SACK arrives
899 * for retransmitted and already SACKed segment -> reordering..
900 * Both of these heuristics are not used in Loss state, when we cannot
901 * account for retransmits accurately.
903 * SACK block validation.
904 * ----------------------
906 * SACK block range validation checks that the received SACK block fits to
907 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
908 * Note that SND.UNA is not included to the range though being valid because
909 * it means that the receiver is rather inconsistent with itself reporting
910 * SACK reneging when it should advance SND.UNA. Such SACK block this is
911 * perfectly valid, however, in light of RFC2018 which explicitly states
912 * that "SACK block MUST reflect the newest segment. Even if the newest
913 * segment is going to be discarded ...", not that it looks very clever
914 * in case of head skb. Due to potentional receiver driven attacks, we
915 * choose to avoid immediate execution of a walk in write queue due to
916 * reneging and defer head skb's loss recovery to standard loss recovery
917 * procedure that will eventually trigger (nothing forbids us doing this).
919 * Implements also blockage to start_seq wrap-around. Problem lies in the
920 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
921 * there's no guarantee that it will be before snd_nxt (n). The problem
922 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
925 * <- outs wnd -> <- wrapzone ->
926 * u e n u_w e_w s n_w
928 * |<------------+------+----- TCP seqno space --------------+---------->|
929 * ...-- <2^31 ->| |<--------...
930 * ...---- >2^31 ------>| |<--------...
932 * Current code wouldn't be vulnerable but it's better still to discard such
933 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
934 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
935 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
936 * equal to the ideal case (infinite seqno space without wrap caused issues).
938 * With D-SACK the lower bound is extended to cover sequence space below
939 * SND.UNA down to undo_marker, which is the last point of interest. Yet
940 * again, D-SACK block must not to go across snd_una (for the same reason as
941 * for the normal SACK blocks, explained above). But there all simplicity
942 * ends, TCP might receive valid D-SACKs below that. As long as they reside
943 * fully below undo_marker they do not affect behavior in anyway and can
944 * therefore be safely ignored. In rare cases (which are more or less
945 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
946 * fragmentation and packet reordering past skb's retransmission. To consider
947 * them correctly, the acceptable range must be extended even more though
948 * the exact amount is rather hard to quantify. However, tp->max_window can
949 * be used as an exaggerated estimate.
951 static bool tcp_is_sackblock_valid(struct tcp_sock
*tp
, bool is_dsack
,
952 u32 start_seq
, u32 end_seq
)
954 /* Too far in future, or reversed (interpretation is ambiguous) */
955 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
958 /* Nasty start_seq wrap-around check (see comments above) */
959 if (!before(start_seq
, tp
->snd_nxt
))
962 /* In outstanding window? ...This is valid exit for D-SACKs too.
963 * start_seq == snd_una is non-sensical (see comments above)
965 if (after(start_seq
, tp
->snd_una
))
968 if (!is_dsack
|| !tp
->undo_marker
)
971 /* ...Then it's D-SACK, and must reside below snd_una completely */
972 if (after(end_seq
, tp
->snd_una
))
975 if (!before(start_seq
, tp
->undo_marker
))
979 if (!after(end_seq
, tp
->undo_marker
))
982 /* Undo_marker boundary crossing (overestimates a lot). Known already:
983 * start_seq < undo_marker and end_seq >= undo_marker.
985 return !before(start_seq
, end_seq
- tp
->max_window
);
988 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
989 * Event "B". Later note: FACK people cheated me again 8), we have to account
990 * for reordering! Ugly, but should help.
992 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
993 * less than what is now known to be received by the other end (derived from
994 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
995 * retransmitted skbs to avoid some costly processing per ACKs.
997 static void tcp_mark_lost_retrans(struct sock
*sk
)
999 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1000 struct tcp_sock
*tp
= tcp_sk(sk
);
1001 struct sk_buff
*skb
;
1003 u32 new_low_seq
= tp
->snd_nxt
;
1004 u32 received_upto
= tcp_highest_sack_seq(tp
);
1006 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1007 !after(received_upto
, tp
->lost_retrans_low
) ||
1008 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1011 tcp_for_write_queue(skb
, sk
) {
1012 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1014 if (skb
== tcp_send_head(sk
))
1016 if (cnt
== tp
->retrans_out
)
1018 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1021 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1024 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1025 * constraint here (see above) but figuring out that at
1026 * least tp->reordering SACK blocks reside between ack_seq
1027 * and received_upto is not easy task to do cheaply with
1028 * the available datastructures.
1030 * Whether FACK should check here for tp->reordering segs
1031 * in-between one could argue for either way (it would be
1032 * rather simple to implement as we could count fack_count
1033 * during the walk and do tp->fackets_out - fack_count).
1035 if (after(received_upto
, ack_seq
)) {
1036 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1037 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1039 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1040 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1042 if (before(ack_seq
, new_low_seq
))
1043 new_low_seq
= ack_seq
;
1044 cnt
+= tcp_skb_pcount(skb
);
1048 if (tp
->retrans_out
)
1049 tp
->lost_retrans_low
= new_low_seq
;
1052 static bool tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1053 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1056 struct tcp_sock
*tp
= tcp_sk(sk
);
1057 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1058 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1059 bool dup_sack
= false;
1061 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1064 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1065 } else if (num_sacks
> 1) {
1066 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1067 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1069 if (!after(end_seq_0
, end_seq_1
) &&
1070 !before(start_seq_0
, start_seq_1
)) {
1073 NET_INC_STATS_BH(sock_net(sk
),
1074 LINUX_MIB_TCPDSACKOFORECV
);
1078 /* D-SACK for already forgotten data... Do dumb counting. */
1079 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1080 !after(end_seq_0
, prior_snd_una
) &&
1081 after(end_seq_0
, tp
->undo_marker
))
1087 struct tcp_sacktag_state
{
1093 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1094 * the incoming SACK may not exactly match but we can find smaller MSS
1095 * aligned portion of it that matches. Therefore we might need to fragment
1096 * which may fail and creates some hassle (caller must handle error case
1099 * FIXME: this could be merged to shift decision code
1101 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1102 u32 start_seq
, u32 end_seq
)
1106 unsigned int pkt_len
;
1109 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1110 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1112 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1113 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1114 mss
= tcp_skb_mss(skb
);
1115 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1118 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1122 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1127 /* Round if necessary so that SACKs cover only full MSSes
1128 * and/or the remaining small portion (if present)
1130 if (pkt_len
> mss
) {
1131 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1132 if (!in_sack
&& new_len
< pkt_len
) {
1134 if (new_len
>= skb
->len
)
1139 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
);
1147 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1148 static u8
tcp_sacktag_one(struct sock
*sk
,
1149 struct tcp_sacktag_state
*state
, u8 sacked
,
1150 u32 start_seq
, u32 end_seq
,
1151 bool dup_sack
, int pcount
)
1153 struct tcp_sock
*tp
= tcp_sk(sk
);
1154 int fack_count
= state
->fack_count
;
1156 /* Account D-SACK for retransmitted packet. */
1157 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1158 if (tp
->undo_marker
&& tp
->undo_retrans
> 0 &&
1159 after(end_seq
, tp
->undo_marker
))
1161 if (sacked
& TCPCB_SACKED_ACKED
)
1162 state
->reord
= min(fack_count
, state
->reord
);
1165 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1166 if (!after(end_seq
, tp
->snd_una
))
1169 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1170 if (sacked
& TCPCB_SACKED_RETRANS
) {
1171 /* If the segment is not tagged as lost,
1172 * we do not clear RETRANS, believing
1173 * that retransmission is still in flight.
1175 if (sacked
& TCPCB_LOST
) {
1176 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1177 tp
->lost_out
-= pcount
;
1178 tp
->retrans_out
-= pcount
;
1181 if (!(sacked
& TCPCB_RETRANS
)) {
1182 /* New sack for not retransmitted frame,
1183 * which was in hole. It is reordering.
1185 if (before(start_seq
,
1186 tcp_highest_sack_seq(tp
)))
1187 state
->reord
= min(fack_count
,
1189 if (!after(end_seq
, tp
->high_seq
))
1190 state
->flag
|= FLAG_ORIG_SACK_ACKED
;
1193 if (sacked
& TCPCB_LOST
) {
1194 sacked
&= ~TCPCB_LOST
;
1195 tp
->lost_out
-= pcount
;
1199 sacked
|= TCPCB_SACKED_ACKED
;
1200 state
->flag
|= FLAG_DATA_SACKED
;
1201 tp
->sacked_out
+= pcount
;
1203 fack_count
+= pcount
;
1205 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1206 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1207 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1208 tp
->lost_cnt_hint
+= pcount
;
1210 if (fack_count
> tp
->fackets_out
)
1211 tp
->fackets_out
= fack_count
;
1214 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1215 * frames and clear it. undo_retrans is decreased above, L|R frames
1216 * are accounted above as well.
1218 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1219 sacked
&= ~TCPCB_SACKED_RETRANS
;
1220 tp
->retrans_out
-= pcount
;
1226 /* Shift newly-SACKed bytes from this skb to the immediately previous
1227 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1229 static bool tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1230 struct tcp_sacktag_state
*state
,
1231 unsigned int pcount
, int shifted
, int mss
,
1234 struct tcp_sock
*tp
= tcp_sk(sk
);
1235 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1236 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1237 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1241 /* Adjust counters and hints for the newly sacked sequence
1242 * range but discard the return value since prev is already
1243 * marked. We must tag the range first because the seq
1244 * advancement below implicitly advances
1245 * tcp_highest_sack_seq() when skb is highest_sack.
1247 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1248 start_seq
, end_seq
, dup_sack
, pcount
);
1250 if (skb
== tp
->lost_skb_hint
)
1251 tp
->lost_cnt_hint
+= pcount
;
1253 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1254 TCP_SKB_CB(skb
)->seq
+= shifted
;
1256 skb_shinfo(prev
)->gso_segs
+= pcount
;
1257 BUG_ON(skb_shinfo(skb
)->gso_segs
< pcount
);
1258 skb_shinfo(skb
)->gso_segs
-= pcount
;
1260 /* When we're adding to gso_segs == 1, gso_size will be zero,
1261 * in theory this shouldn't be necessary but as long as DSACK
1262 * code can come after this skb later on it's better to keep
1263 * setting gso_size to something.
1265 if (!skb_shinfo(prev
)->gso_size
) {
1266 skb_shinfo(prev
)->gso_size
= mss
;
1267 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1270 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1271 if (skb_shinfo(skb
)->gso_segs
<= 1) {
1272 skb_shinfo(skb
)->gso_size
= 0;
1273 skb_shinfo(skb
)->gso_type
= 0;
1276 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1277 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1280 BUG_ON(!tcp_skb_pcount(skb
));
1281 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1285 /* Whole SKB was eaten :-) */
1287 if (skb
== tp
->retransmit_skb_hint
)
1288 tp
->retransmit_skb_hint
= prev
;
1289 if (skb
== tp
->scoreboard_skb_hint
)
1290 tp
->scoreboard_skb_hint
= prev
;
1291 if (skb
== tp
->lost_skb_hint
) {
1292 tp
->lost_skb_hint
= prev
;
1293 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1296 TCP_SKB_CB(prev
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1297 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1298 TCP_SKB_CB(prev
)->end_seq
++;
1300 if (skb
== tcp_highest_sack(sk
))
1301 tcp_advance_highest_sack(sk
, skb
);
1303 tcp_unlink_write_queue(skb
, sk
);
1304 sk_wmem_free_skb(sk
, skb
);
1306 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1311 /* I wish gso_size would have a bit more sane initialization than
1312 * something-or-zero which complicates things
1314 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1316 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1319 /* Shifting pages past head area doesn't work */
1320 static int skb_can_shift(const struct sk_buff
*skb
)
1322 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1325 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1328 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1329 struct tcp_sacktag_state
*state
,
1330 u32 start_seq
, u32 end_seq
,
1333 struct tcp_sock
*tp
= tcp_sk(sk
);
1334 struct sk_buff
*prev
;
1340 if (!sk_can_gso(sk
))
1343 /* Normally R but no L won't result in plain S */
1345 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1347 if (!skb_can_shift(skb
))
1349 /* This frame is about to be dropped (was ACKed). */
1350 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1353 /* Can only happen with delayed DSACK + discard craziness */
1354 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1356 prev
= tcp_write_queue_prev(sk
, skb
);
1358 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1361 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1362 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1366 pcount
= tcp_skb_pcount(skb
);
1367 mss
= tcp_skb_seglen(skb
);
1369 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1370 * drop this restriction as unnecessary
1372 if (mss
!= tcp_skb_seglen(prev
))
1375 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1377 /* CHECKME: This is non-MSS split case only?, this will
1378 * cause skipped skbs due to advancing loop btw, original
1379 * has that feature too
1381 if (tcp_skb_pcount(skb
) <= 1)
1384 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1386 /* TODO: head merge to next could be attempted here
1387 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1388 * though it might not be worth of the additional hassle
1390 * ...we can probably just fallback to what was done
1391 * previously. We could try merging non-SACKed ones
1392 * as well but it probably isn't going to buy off
1393 * because later SACKs might again split them, and
1394 * it would make skb timestamp tracking considerably
1400 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1402 BUG_ON(len
> skb
->len
);
1404 /* MSS boundaries should be honoured or else pcount will
1405 * severely break even though it makes things bit trickier.
1406 * Optimize common case to avoid most of the divides
1408 mss
= tcp_skb_mss(skb
);
1410 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1411 * drop this restriction as unnecessary
1413 if (mss
!= tcp_skb_seglen(prev
))
1418 } else if (len
< mss
) {
1426 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1427 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1430 if (!skb_shift(prev
, skb
, len
))
1432 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1435 /* Hole filled allows collapsing with the next as well, this is very
1436 * useful when hole on every nth skb pattern happens
1438 if (prev
== tcp_write_queue_tail(sk
))
1440 skb
= tcp_write_queue_next(sk
, prev
);
1442 if (!skb_can_shift(skb
) ||
1443 (skb
== tcp_send_head(sk
)) ||
1444 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1445 (mss
!= tcp_skb_seglen(skb
)))
1449 if (skb_shift(prev
, skb
, len
)) {
1450 pcount
+= tcp_skb_pcount(skb
);
1451 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1455 state
->fack_count
+= pcount
;
1462 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1466 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1467 struct tcp_sack_block
*next_dup
,
1468 struct tcp_sacktag_state
*state
,
1469 u32 start_seq
, u32 end_seq
,
1472 struct tcp_sock
*tp
= tcp_sk(sk
);
1473 struct sk_buff
*tmp
;
1475 tcp_for_write_queue_from(skb
, sk
) {
1477 bool dup_sack
= dup_sack_in
;
1479 if (skb
== tcp_send_head(sk
))
1482 /* queue is in-order => we can short-circuit the walk early */
1483 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1486 if ((next_dup
!= NULL
) &&
1487 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1488 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1489 next_dup
->start_seq
,
1495 /* skb reference here is a bit tricky to get right, since
1496 * shifting can eat and free both this skb and the next,
1497 * so not even _safe variant of the loop is enough.
1500 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1501 start_seq
, end_seq
, dup_sack
);
1510 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1516 if (unlikely(in_sack
< 0))
1520 TCP_SKB_CB(skb
)->sacked
=
1523 TCP_SKB_CB(skb
)->sacked
,
1524 TCP_SKB_CB(skb
)->seq
,
1525 TCP_SKB_CB(skb
)->end_seq
,
1527 tcp_skb_pcount(skb
));
1529 if (!before(TCP_SKB_CB(skb
)->seq
,
1530 tcp_highest_sack_seq(tp
)))
1531 tcp_advance_highest_sack(sk
, skb
);
1534 state
->fack_count
+= tcp_skb_pcount(skb
);
1539 /* Avoid all extra work that is being done by sacktag while walking in
1542 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1543 struct tcp_sacktag_state
*state
,
1546 tcp_for_write_queue_from(skb
, sk
) {
1547 if (skb
== tcp_send_head(sk
))
1550 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1553 state
->fack_count
+= tcp_skb_pcount(skb
);
1558 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1560 struct tcp_sack_block
*next_dup
,
1561 struct tcp_sacktag_state
*state
,
1564 if (next_dup
== NULL
)
1567 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1568 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1569 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1570 next_dup
->start_seq
, next_dup
->end_seq
,
1577 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1579 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1583 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1586 struct tcp_sock
*tp
= tcp_sk(sk
);
1587 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1588 TCP_SKB_CB(ack_skb
)->sacked
);
1589 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1590 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1591 struct tcp_sack_block
*cache
;
1592 struct tcp_sacktag_state state
;
1593 struct sk_buff
*skb
;
1594 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1596 bool found_dup_sack
= false;
1598 int first_sack_index
;
1601 state
.reord
= tp
->packets_out
;
1603 if (!tp
->sacked_out
) {
1604 if (WARN_ON(tp
->fackets_out
))
1605 tp
->fackets_out
= 0;
1606 tcp_highest_sack_reset(sk
);
1609 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1610 num_sacks
, prior_snd_una
);
1612 state
.flag
|= FLAG_DSACKING_ACK
;
1614 /* Eliminate too old ACKs, but take into
1615 * account more or less fresh ones, they can
1616 * contain valid SACK info.
1618 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1621 if (!tp
->packets_out
)
1625 first_sack_index
= 0;
1626 for (i
= 0; i
< num_sacks
; i
++) {
1627 bool dup_sack
= !i
&& found_dup_sack
;
1629 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1630 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1632 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1633 sp
[used_sacks
].start_seq
,
1634 sp
[used_sacks
].end_seq
)) {
1638 if (!tp
->undo_marker
)
1639 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1641 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1643 /* Don't count olds caused by ACK reordering */
1644 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1645 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1647 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1650 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1652 first_sack_index
= -1;
1656 /* Ignore very old stuff early */
1657 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1663 /* order SACK blocks to allow in order walk of the retrans queue */
1664 for (i
= used_sacks
- 1; i
> 0; i
--) {
1665 for (j
= 0; j
< i
; j
++) {
1666 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1667 swap(sp
[j
], sp
[j
+ 1]);
1669 /* Track where the first SACK block goes to */
1670 if (j
== first_sack_index
)
1671 first_sack_index
= j
+ 1;
1676 skb
= tcp_write_queue_head(sk
);
1677 state
.fack_count
= 0;
1680 if (!tp
->sacked_out
) {
1681 /* It's already past, so skip checking against it */
1682 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1684 cache
= tp
->recv_sack_cache
;
1685 /* Skip empty blocks in at head of the cache */
1686 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1691 while (i
< used_sacks
) {
1692 u32 start_seq
= sp
[i
].start_seq
;
1693 u32 end_seq
= sp
[i
].end_seq
;
1694 bool dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1695 struct tcp_sack_block
*next_dup
= NULL
;
1697 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1698 next_dup
= &sp
[i
+ 1];
1700 /* Skip too early cached blocks */
1701 while (tcp_sack_cache_ok(tp
, cache
) &&
1702 !before(start_seq
, cache
->end_seq
))
1705 /* Can skip some work by looking recv_sack_cache? */
1706 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1707 after(end_seq
, cache
->start_seq
)) {
1710 if (before(start_seq
, cache
->start_seq
)) {
1711 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1713 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1720 /* Rest of the block already fully processed? */
1721 if (!after(end_seq
, cache
->end_seq
))
1724 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1728 /* ...tail remains todo... */
1729 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1730 /* ...but better entrypoint exists! */
1731 skb
= tcp_highest_sack(sk
);
1734 state
.fack_count
= tp
->fackets_out
;
1739 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1740 /* Check overlap against next cached too (past this one already) */
1745 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1746 skb
= tcp_highest_sack(sk
);
1749 state
.fack_count
= tp
->fackets_out
;
1751 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1754 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1755 start_seq
, end_seq
, dup_sack
);
1761 /* Clear the head of the cache sack blocks so we can skip it next time */
1762 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1763 tp
->recv_sack_cache
[i
].start_seq
= 0;
1764 tp
->recv_sack_cache
[i
].end_seq
= 0;
1766 for (j
= 0; j
< used_sacks
; j
++)
1767 tp
->recv_sack_cache
[i
++] = sp
[j
];
1769 tcp_mark_lost_retrans(sk
);
1771 tcp_verify_left_out(tp
);
1773 if ((state
.reord
< tp
->fackets_out
) &&
1774 ((inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
))
1775 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1779 #if FASTRETRANS_DEBUG > 0
1780 WARN_ON((int)tp
->sacked_out
< 0);
1781 WARN_ON((int)tp
->lost_out
< 0);
1782 WARN_ON((int)tp
->retrans_out
< 0);
1783 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1788 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1789 * packets_out. Returns false if sacked_out adjustement wasn't necessary.
1791 static bool tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1795 holes
= max(tp
->lost_out
, 1U);
1796 holes
= min(holes
, tp
->packets_out
);
1798 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1799 tp
->sacked_out
= tp
->packets_out
- holes
;
1805 /* If we receive more dupacks than we expected counting segments
1806 * in assumption of absent reordering, interpret this as reordering.
1807 * The only another reason could be bug in receiver TCP.
1809 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1811 struct tcp_sock
*tp
= tcp_sk(sk
);
1812 if (tcp_limit_reno_sacked(tp
))
1813 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1816 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1818 static void tcp_add_reno_sack(struct sock
*sk
)
1820 struct tcp_sock
*tp
= tcp_sk(sk
);
1822 tcp_check_reno_reordering(sk
, 0);
1823 tcp_verify_left_out(tp
);
1826 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1828 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1830 struct tcp_sock
*tp
= tcp_sk(sk
);
1833 /* One ACK acked hole. The rest eat duplicate ACKs. */
1834 if (acked
- 1 >= tp
->sacked_out
)
1837 tp
->sacked_out
-= acked
- 1;
1839 tcp_check_reno_reordering(sk
, acked
);
1840 tcp_verify_left_out(tp
);
1843 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1848 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
1850 tp
->retrans_out
= 0;
1853 tp
->undo_marker
= 0;
1854 tp
->undo_retrans
= -1;
1857 void tcp_clear_retrans(struct tcp_sock
*tp
)
1859 tcp_clear_retrans_partial(tp
);
1861 tp
->fackets_out
= 0;
1865 /* Enter Loss state. If "how" is not zero, forget all SACK information
1866 * and reset tags completely, otherwise preserve SACKs. If receiver
1867 * dropped its ofo queue, we will know this due to reneging detection.
1869 void tcp_enter_loss(struct sock
*sk
, int how
)
1871 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1872 struct tcp_sock
*tp
= tcp_sk(sk
);
1873 struct sk_buff
*skb
;
1874 bool new_recovery
= false;
1876 /* Reduce ssthresh if it has not yet been made inside this window. */
1877 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
||
1878 !after(tp
->high_seq
, tp
->snd_una
) ||
1879 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1880 new_recovery
= true;
1881 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1882 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1883 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1886 tp
->snd_cwnd_cnt
= 0;
1887 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1889 tcp_clear_retrans_partial(tp
);
1891 if (tcp_is_reno(tp
))
1892 tcp_reset_reno_sack(tp
);
1894 tp
->undo_marker
= tp
->snd_una
;
1897 tp
->fackets_out
= 0;
1899 tcp_clear_all_retrans_hints(tp
);
1901 tcp_for_write_queue(skb
, sk
) {
1902 if (skb
== tcp_send_head(sk
))
1905 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1906 tp
->undo_marker
= 0;
1907 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1908 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1909 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1910 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1911 tp
->lost_out
+= tcp_skb_pcount(skb
);
1912 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1915 tcp_verify_left_out(tp
);
1917 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1918 sysctl_tcp_reordering
);
1919 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1920 tp
->high_seq
= tp
->snd_nxt
;
1921 TCP_ECN_queue_cwr(tp
);
1923 /* F-RTO RFC5682 sec 3.1 step 1: retransmit SND.UNA if no previous
1924 * loss recovery is underway except recurring timeout(s) on
1925 * the same SND.UNA (sec 3.2). Disable F-RTO on path MTU probing
1927 tp
->frto
= sysctl_tcp_frto
&&
1928 (new_recovery
|| icsk
->icsk_retransmits
) &&
1929 !inet_csk(sk
)->icsk_mtup
.probe_size
;
1932 /* If ACK arrived pointing to a remembered SACK, it means that our
1933 * remembered SACKs do not reflect real state of receiver i.e.
1934 * receiver _host_ is heavily congested (or buggy).
1936 * Do processing similar to RTO timeout.
1938 static bool tcp_check_sack_reneging(struct sock
*sk
, int flag
)
1940 if (flag
& FLAG_SACK_RENEGING
) {
1941 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1942 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1944 tcp_enter_loss(sk
, 1);
1945 icsk
->icsk_retransmits
++;
1946 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
1947 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1948 icsk
->icsk_rto
, TCP_RTO_MAX
);
1954 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
1956 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
1959 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
1960 * counter when SACK is enabled (without SACK, sacked_out is used for
1963 * Instead, with FACK TCP uses fackets_out that includes both SACKed
1964 * segments up to the highest received SACK block so far and holes in
1967 * With reordering, holes may still be in flight, so RFC3517 recovery
1968 * uses pure sacked_out (total number of SACKed segments) even though
1969 * it violates the RFC that uses duplicate ACKs, often these are equal
1970 * but when e.g. out-of-window ACKs or packet duplication occurs,
1971 * they differ. Since neither occurs due to loss, TCP should really
1974 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
1976 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
1979 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
1981 struct tcp_sock
*tp
= tcp_sk(sk
);
1982 unsigned long delay
;
1984 /* Delay early retransmit and entering fast recovery for
1985 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
1986 * available, or RTO is scheduled to fire first.
1988 if (sysctl_tcp_early_retrans
< 2 || sysctl_tcp_early_retrans
> 3 ||
1989 (flag
& FLAG_ECE
) || !tp
->srtt
)
1992 delay
= max_t(unsigned long, (tp
->srtt
>> 5), msecs_to_jiffies(2));
1993 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
1996 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_EARLY_RETRANS
, delay
,
2001 static inline int tcp_skb_timedout(const struct sock
*sk
,
2002 const struct sk_buff
*skb
)
2004 return tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
;
2007 static inline int tcp_head_timedout(const struct sock
*sk
)
2009 const struct tcp_sock
*tp
= tcp_sk(sk
);
2011 return tp
->packets_out
&&
2012 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2015 /* Linux NewReno/SACK/FACK/ECN state machine.
2016 * --------------------------------------
2018 * "Open" Normal state, no dubious events, fast path.
2019 * "Disorder" In all the respects it is "Open",
2020 * but requires a bit more attention. It is entered when
2021 * we see some SACKs or dupacks. It is split of "Open"
2022 * mainly to move some processing from fast path to slow one.
2023 * "CWR" CWND was reduced due to some Congestion Notification event.
2024 * It can be ECN, ICMP source quench, local device congestion.
2025 * "Recovery" CWND was reduced, we are fast-retransmitting.
2026 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2028 * tcp_fastretrans_alert() is entered:
2029 * - each incoming ACK, if state is not "Open"
2030 * - when arrived ACK is unusual, namely:
2035 * Counting packets in flight is pretty simple.
2037 * in_flight = packets_out - left_out + retrans_out
2039 * packets_out is SND.NXT-SND.UNA counted in packets.
2041 * retrans_out is number of retransmitted segments.
2043 * left_out is number of segments left network, but not ACKed yet.
2045 * left_out = sacked_out + lost_out
2047 * sacked_out: Packets, which arrived to receiver out of order
2048 * and hence not ACKed. With SACKs this number is simply
2049 * amount of SACKed data. Even without SACKs
2050 * it is easy to give pretty reliable estimate of this number,
2051 * counting duplicate ACKs.
2053 * lost_out: Packets lost by network. TCP has no explicit
2054 * "loss notification" feedback from network (for now).
2055 * It means that this number can be only _guessed_.
2056 * Actually, it is the heuristics to predict lossage that
2057 * distinguishes different algorithms.
2059 * F.e. after RTO, when all the queue is considered as lost,
2060 * lost_out = packets_out and in_flight = retrans_out.
2062 * Essentially, we have now two algorithms counting
2065 * FACK: It is the simplest heuristics. As soon as we decided
2066 * that something is lost, we decide that _all_ not SACKed
2067 * packets until the most forward SACK are lost. I.e.
2068 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2069 * It is absolutely correct estimate, if network does not reorder
2070 * packets. And it loses any connection to reality when reordering
2071 * takes place. We use FACK by default until reordering
2072 * is suspected on the path to this destination.
2074 * NewReno: when Recovery is entered, we assume that one segment
2075 * is lost (classic Reno). While we are in Recovery and
2076 * a partial ACK arrives, we assume that one more packet
2077 * is lost (NewReno). This heuristics are the same in NewReno
2080 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2081 * deflation etc. CWND is real congestion window, never inflated, changes
2082 * only according to classic VJ rules.
2084 * Really tricky (and requiring careful tuning) part of algorithm
2085 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2086 * The first determines the moment _when_ we should reduce CWND and,
2087 * hence, slow down forward transmission. In fact, it determines the moment
2088 * when we decide that hole is caused by loss, rather than by a reorder.
2090 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2091 * holes, caused by lost packets.
2093 * And the most logically complicated part of algorithm is undo
2094 * heuristics. We detect false retransmits due to both too early
2095 * fast retransmit (reordering) and underestimated RTO, analyzing
2096 * timestamps and D-SACKs. When we detect that some segments were
2097 * retransmitted by mistake and CWND reduction was wrong, we undo
2098 * window reduction and abort recovery phase. This logic is hidden
2099 * inside several functions named tcp_try_undo_<something>.
2102 /* This function decides, when we should leave Disordered state
2103 * and enter Recovery phase, reducing congestion window.
2105 * Main question: may we further continue forward transmission
2106 * with the same cwnd?
2108 static bool tcp_time_to_recover(struct sock
*sk
, int flag
)
2110 struct tcp_sock
*tp
= tcp_sk(sk
);
2113 /* Trick#1: The loss is proven. */
2117 /* Not-A-Trick#2 : Classic rule... */
2118 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2121 /* Trick#3 : when we use RFC2988 timer restart, fast
2122 * retransmit can be triggered by timeout of queue head.
2124 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2127 /* Trick#4: It is still not OK... But will it be useful to delay
2130 packets_out
= tp
->packets_out
;
2131 if (packets_out
<= tp
->reordering
&&
2132 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2133 !tcp_may_send_now(sk
)) {
2134 /* We have nothing to send. This connection is limited
2135 * either by receiver window or by application.
2140 /* If a thin stream is detected, retransmit after first
2141 * received dupack. Employ only if SACK is supported in order
2142 * to avoid possible corner-case series of spurious retransmissions
2143 * Use only if there are no unsent data.
2145 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2146 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2147 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2150 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2151 * retransmissions due to small network reorderings, we implement
2152 * Mitigation A.3 in the RFC and delay the retransmission for a short
2153 * interval if appropriate.
2155 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2156 (tp
->packets_out
>= (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2157 !tcp_may_send_now(sk
))
2158 return !tcp_pause_early_retransmit(sk
, flag
);
2163 /* New heuristics: it is possible only after we switched to restart timer
2164 * each time when something is ACKed. Hence, we can detect timed out packets
2165 * during fast retransmit without falling to slow start.
2167 * Usefulness of this as is very questionable, since we should know which of
2168 * the segments is the next to timeout which is relatively expensive to find
2169 * in general case unless we add some data structure just for that. The
2170 * current approach certainly won't find the right one too often and when it
2171 * finally does find _something_ it usually marks large part of the window
2172 * right away (because a retransmission with a larger timestamp blocks the
2173 * loop from advancing). -ij
2175 static void tcp_timeout_skbs(struct sock
*sk
)
2177 struct tcp_sock
*tp
= tcp_sk(sk
);
2178 struct sk_buff
*skb
;
2180 if (!tcp_is_fack(tp
) || !tcp_head_timedout(sk
))
2183 skb
= tp
->scoreboard_skb_hint
;
2184 if (tp
->scoreboard_skb_hint
== NULL
)
2185 skb
= tcp_write_queue_head(sk
);
2187 tcp_for_write_queue_from(skb
, sk
) {
2188 if (skb
== tcp_send_head(sk
))
2190 if (!tcp_skb_timedout(sk
, skb
))
2193 tcp_skb_mark_lost(tp
, skb
);
2196 tp
->scoreboard_skb_hint
= skb
;
2198 tcp_verify_left_out(tp
);
2201 /* Detect loss in event "A" above by marking head of queue up as lost.
2202 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2203 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2204 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2205 * the maximum SACKed segments to pass before reaching this limit.
2207 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2209 struct tcp_sock
*tp
= tcp_sk(sk
);
2210 struct sk_buff
*skb
;
2214 /* Use SACK to deduce losses of new sequences sent during recovery */
2215 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2217 WARN_ON(packets
> tp
->packets_out
);
2218 if (tp
->lost_skb_hint
) {
2219 skb
= tp
->lost_skb_hint
;
2220 cnt
= tp
->lost_cnt_hint
;
2221 /* Head already handled? */
2222 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2225 skb
= tcp_write_queue_head(sk
);
2229 tcp_for_write_queue_from(skb
, sk
) {
2230 if (skb
== tcp_send_head(sk
))
2232 /* TODO: do this better */
2233 /* this is not the most efficient way to do this... */
2234 tp
->lost_skb_hint
= skb
;
2235 tp
->lost_cnt_hint
= cnt
;
2237 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2241 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2242 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2243 cnt
+= tcp_skb_pcount(skb
);
2245 if (cnt
> packets
) {
2246 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2247 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2248 (oldcnt
>= packets
))
2251 mss
= skb_shinfo(skb
)->gso_size
;
2252 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2258 tcp_skb_mark_lost(tp
, skb
);
2263 tcp_verify_left_out(tp
);
2266 /* Account newly detected lost packet(s) */
2268 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2270 struct tcp_sock
*tp
= tcp_sk(sk
);
2272 if (tcp_is_reno(tp
)) {
2273 tcp_mark_head_lost(sk
, 1, 1);
2274 } else if (tcp_is_fack(tp
)) {
2275 int lost
= tp
->fackets_out
- tp
->reordering
;
2278 tcp_mark_head_lost(sk
, lost
, 0);
2280 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2281 if (sacked_upto
>= 0)
2282 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2283 else if (fast_rexmit
)
2284 tcp_mark_head_lost(sk
, 1, 1);
2287 tcp_timeout_skbs(sk
);
2290 /* CWND moderation, preventing bursts due to too big ACKs
2291 * in dubious situations.
2293 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2295 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2296 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2297 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2300 /* Nothing was retransmitted or returned timestamp is less
2301 * than timestamp of the first retransmission.
2303 static inline bool tcp_packet_delayed(const struct tcp_sock
*tp
)
2305 return !tp
->retrans_stamp
||
2306 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2307 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2310 /* Undo procedures. */
2312 #if FASTRETRANS_DEBUG > 1
2313 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2315 struct tcp_sock
*tp
= tcp_sk(sk
);
2316 struct inet_sock
*inet
= inet_sk(sk
);
2318 if (sk
->sk_family
== AF_INET
) {
2319 pr_debug("Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2321 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2322 tp
->snd_cwnd
, tcp_left_out(tp
),
2323 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2326 #if IS_ENABLED(CONFIG_IPV6)
2327 else if (sk
->sk_family
== AF_INET6
) {
2328 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2329 pr_debug("Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2331 &np
->daddr
, ntohs(inet
->inet_dport
),
2332 tp
->snd_cwnd
, tcp_left_out(tp
),
2333 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2339 #define DBGUNDO(x...) do { } while (0)
2342 static void tcp_undo_cwr(struct sock
*sk
, const bool undo_ssthresh
)
2344 struct tcp_sock
*tp
= tcp_sk(sk
);
2346 if (tp
->prior_ssthresh
) {
2347 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2349 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2350 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2352 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2354 if (undo_ssthresh
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2355 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2356 TCP_ECN_withdraw_cwr(tp
);
2359 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2361 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2364 static inline bool tcp_may_undo(const struct tcp_sock
*tp
)
2366 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2369 /* People celebrate: "We love our President!" */
2370 static bool tcp_try_undo_recovery(struct sock
*sk
)
2372 struct tcp_sock
*tp
= tcp_sk(sk
);
2374 if (tcp_may_undo(tp
)) {
2377 /* Happy end! We did not retransmit anything
2378 * or our original transmission succeeded.
2380 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2381 tcp_undo_cwr(sk
, true);
2382 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2383 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2385 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2387 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2388 tp
->undo_marker
= 0;
2390 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2391 /* Hold old state until something *above* high_seq
2392 * is ACKed. For Reno it is MUST to prevent false
2393 * fast retransmits (RFC2582). SACK TCP is safe. */
2394 tcp_moderate_cwnd(tp
);
2397 tcp_set_ca_state(sk
, TCP_CA_Open
);
2401 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2402 static void tcp_try_undo_dsack(struct sock
*sk
)
2404 struct tcp_sock
*tp
= tcp_sk(sk
);
2406 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2407 DBGUNDO(sk
, "D-SACK");
2408 tcp_undo_cwr(sk
, true);
2409 tp
->undo_marker
= 0;
2410 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2414 /* We can clear retrans_stamp when there are no retransmissions in the
2415 * window. It would seem that it is trivially available for us in
2416 * tp->retrans_out, however, that kind of assumptions doesn't consider
2417 * what will happen if errors occur when sending retransmission for the
2418 * second time. ...It could the that such segment has only
2419 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2420 * the head skb is enough except for some reneging corner cases that
2421 * are not worth the effort.
2423 * Main reason for all this complexity is the fact that connection dying
2424 * time now depends on the validity of the retrans_stamp, in particular,
2425 * that successive retransmissions of a segment must not advance
2426 * retrans_stamp under any conditions.
2428 static bool tcp_any_retrans_done(const struct sock
*sk
)
2430 const struct tcp_sock
*tp
= tcp_sk(sk
);
2431 struct sk_buff
*skb
;
2433 if (tp
->retrans_out
)
2436 skb
= tcp_write_queue_head(sk
);
2437 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2443 /* Undo during fast recovery after partial ACK. */
2445 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2447 struct tcp_sock
*tp
= tcp_sk(sk
);
2448 /* Partial ACK arrived. Force Hoe's retransmit. */
2449 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2451 if (tcp_may_undo(tp
)) {
2452 /* Plain luck! Hole if filled with delayed
2453 * packet, rather than with a retransmit.
2455 if (!tcp_any_retrans_done(sk
))
2456 tp
->retrans_stamp
= 0;
2458 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2461 tcp_undo_cwr(sk
, false);
2462 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2464 /* So... Do not make Hoe's retransmit yet.
2465 * If the first packet was delayed, the rest
2466 * ones are most probably delayed as well.
2473 /* Undo during loss recovery after partial ACK or using F-RTO. */
2474 static bool tcp_try_undo_loss(struct sock
*sk
, bool frto_undo
)
2476 struct tcp_sock
*tp
= tcp_sk(sk
);
2478 if (frto_undo
|| tcp_may_undo(tp
)) {
2479 struct sk_buff
*skb
;
2480 tcp_for_write_queue(skb
, sk
) {
2481 if (skb
== tcp_send_head(sk
))
2483 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2486 tcp_clear_all_retrans_hints(tp
);
2488 DBGUNDO(sk
, "partial loss");
2490 tcp_undo_cwr(sk
, true);
2491 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2493 NET_INC_STATS_BH(sock_net(sk
),
2494 LINUX_MIB_TCPSPURIOUSRTOS
);
2495 inet_csk(sk
)->icsk_retransmits
= 0;
2496 tp
->undo_marker
= 0;
2497 if (frto_undo
|| tcp_is_sack(tp
))
2498 tcp_set_ca_state(sk
, TCP_CA_Open
);
2504 /* The cwnd reduction in CWR and Recovery use the PRR algorithm
2505 * https://datatracker.ietf.org/doc/draft-ietf-tcpm-proportional-rate-reduction/
2506 * It computes the number of packets to send (sndcnt) based on packets newly
2508 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2509 * cwnd reductions across a full RTT.
2510 * 2) If packets in flight is lower than ssthresh (such as due to excess
2511 * losses and/or application stalls), do not perform any further cwnd
2512 * reductions, but instead slow start up to ssthresh.
2514 static void tcp_init_cwnd_reduction(struct sock
*sk
, const bool set_ssthresh
)
2516 struct tcp_sock
*tp
= tcp_sk(sk
);
2518 tp
->high_seq
= tp
->snd_nxt
;
2519 tp
->tlp_high_seq
= 0;
2520 tp
->snd_cwnd_cnt
= 0;
2521 tp
->prior_cwnd
= tp
->snd_cwnd
;
2522 tp
->prr_delivered
= 0;
2525 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
2526 TCP_ECN_queue_cwr(tp
);
2529 static void tcp_cwnd_reduction(struct sock
*sk
, int newly_acked_sacked
,
2532 struct tcp_sock
*tp
= tcp_sk(sk
);
2534 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
2536 tp
->prr_delivered
+= newly_acked_sacked
;
2537 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
2538 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
2540 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
2542 sndcnt
= min_t(int, delta
,
2543 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
2544 newly_acked_sacked
) + 1);
2547 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
2548 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
2551 static inline void tcp_end_cwnd_reduction(struct sock
*sk
)
2553 struct tcp_sock
*tp
= tcp_sk(sk
);
2555 /* Reset cwnd to ssthresh in CWR or Recovery (unless it's undone) */
2556 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
||
2557 (tp
->undo_marker
&& tp
->snd_ssthresh
< TCP_INFINITE_SSTHRESH
)) {
2558 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2559 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2561 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2564 /* Enter CWR state. Disable cwnd undo since congestion is proven with ECN */
2565 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
2567 struct tcp_sock
*tp
= tcp_sk(sk
);
2569 tp
->prior_ssthresh
= 0;
2570 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2571 tp
->undo_marker
= 0;
2572 tcp_init_cwnd_reduction(sk
, set_ssthresh
);
2573 tcp_set_ca_state(sk
, TCP_CA_CWR
);
2577 static void tcp_try_keep_open(struct sock
*sk
)
2579 struct tcp_sock
*tp
= tcp_sk(sk
);
2580 int state
= TCP_CA_Open
;
2582 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2583 state
= TCP_CA_Disorder
;
2585 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2586 tcp_set_ca_state(sk
, state
);
2587 tp
->high_seq
= tp
->snd_nxt
;
2591 static void tcp_try_to_open(struct sock
*sk
, int flag
, int newly_acked_sacked
)
2593 struct tcp_sock
*tp
= tcp_sk(sk
);
2595 tcp_verify_left_out(tp
);
2597 if (!tcp_any_retrans_done(sk
))
2598 tp
->retrans_stamp
= 0;
2600 if (flag
& FLAG_ECE
)
2601 tcp_enter_cwr(sk
, 1);
2603 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2604 tcp_try_keep_open(sk
);
2605 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
2606 tcp_moderate_cwnd(tp
);
2608 tcp_cwnd_reduction(sk
, newly_acked_sacked
, 0);
2612 static void tcp_mtup_probe_failed(struct sock
*sk
)
2614 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2616 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2617 icsk
->icsk_mtup
.probe_size
= 0;
2620 static void tcp_mtup_probe_success(struct sock
*sk
)
2622 struct tcp_sock
*tp
= tcp_sk(sk
);
2623 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2625 /* FIXME: breaks with very large cwnd */
2626 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2627 tp
->snd_cwnd
= tp
->snd_cwnd
*
2628 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2629 icsk
->icsk_mtup
.probe_size
;
2630 tp
->snd_cwnd_cnt
= 0;
2631 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2632 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2634 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2635 icsk
->icsk_mtup
.probe_size
= 0;
2636 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2639 /* Do a simple retransmit without using the backoff mechanisms in
2640 * tcp_timer. This is used for path mtu discovery.
2641 * The socket is already locked here.
2643 void tcp_simple_retransmit(struct sock
*sk
)
2645 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2646 struct tcp_sock
*tp
= tcp_sk(sk
);
2647 struct sk_buff
*skb
;
2648 unsigned int mss
= tcp_current_mss(sk
);
2649 u32 prior_lost
= tp
->lost_out
;
2651 tcp_for_write_queue(skb
, sk
) {
2652 if (skb
== tcp_send_head(sk
))
2654 if (tcp_skb_seglen(skb
) > mss
&&
2655 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2656 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2657 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2658 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2660 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2664 tcp_clear_retrans_hints_partial(tp
);
2666 if (prior_lost
== tp
->lost_out
)
2669 if (tcp_is_reno(tp
))
2670 tcp_limit_reno_sacked(tp
);
2672 tcp_verify_left_out(tp
);
2674 /* Don't muck with the congestion window here.
2675 * Reason is that we do not increase amount of _data_
2676 * in network, but units changed and effective
2677 * cwnd/ssthresh really reduced now.
2679 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2680 tp
->high_seq
= tp
->snd_nxt
;
2681 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2682 tp
->prior_ssthresh
= 0;
2683 tp
->undo_marker
= 0;
2684 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2686 tcp_xmit_retransmit_queue(sk
);
2688 EXPORT_SYMBOL(tcp_simple_retransmit
);
2690 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
2692 struct tcp_sock
*tp
= tcp_sk(sk
);
2695 if (tcp_is_reno(tp
))
2696 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2698 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2700 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2702 tp
->prior_ssthresh
= 0;
2703 tp
->undo_marker
= tp
->snd_una
;
2704 tp
->undo_retrans
= tp
->retrans_out
? : -1;
2706 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
2708 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2709 tcp_init_cwnd_reduction(sk
, true);
2711 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2714 /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are
2715 * recovered or spurious. Otherwise retransmits more on partial ACKs.
2717 static void tcp_process_loss(struct sock
*sk
, int flag
, bool is_dupack
)
2719 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2720 struct tcp_sock
*tp
= tcp_sk(sk
);
2721 bool recovered
= !before(tp
->snd_una
, tp
->high_seq
);
2723 if (tp
->frto
) { /* F-RTO RFC5682 sec 3.1 (sack enhanced version). */
2724 /* Step 3.b. A timeout is spurious if not all data are
2725 * lost, i.e., never-retransmitted data are (s)acked.
2727 if (tcp_try_undo_loss(sk
, flag
& FLAG_ORIG_SACK_ACKED
))
2730 if (after(tp
->snd_nxt
, tp
->high_seq
) &&
2731 (flag
& FLAG_DATA_SACKED
|| is_dupack
)) {
2732 tp
->frto
= 0; /* Loss was real: 2nd part of step 3.a */
2733 } else if (flag
& FLAG_SND_UNA_ADVANCED
&& !recovered
) {
2734 tp
->high_seq
= tp
->snd_nxt
;
2735 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
),
2737 if (after(tp
->snd_nxt
, tp
->high_seq
))
2738 return; /* Step 2.b */
2744 /* F-RTO RFC5682 sec 3.1 step 2.a and 1st part of step 3.a */
2745 icsk
->icsk_retransmits
= 0;
2746 tcp_try_undo_recovery(sk
);
2749 if (flag
& FLAG_DATA_ACKED
)
2750 icsk
->icsk_retransmits
= 0;
2751 if (tcp_is_reno(tp
)) {
2752 /* A Reno DUPACK means new data in F-RTO step 2.b above are
2753 * delivered. Lower inflight to clock out (re)tranmissions.
2755 if (after(tp
->snd_nxt
, tp
->high_seq
) && is_dupack
)
2756 tcp_add_reno_sack(sk
);
2757 else if (flag
& FLAG_SND_UNA_ADVANCED
)
2758 tcp_reset_reno_sack(tp
);
2760 if (tcp_try_undo_loss(sk
, false))
2762 tcp_xmit_retransmit_queue(sk
);
2765 /* Process an event, which can update packets-in-flight not trivially.
2766 * Main goal of this function is to calculate new estimate for left_out,
2767 * taking into account both packets sitting in receiver's buffer and
2768 * packets lost by network.
2770 * Besides that it does CWND reduction, when packet loss is detected
2771 * and changes state of machine.
2773 * It does _not_ decide what to send, it is made in function
2774 * tcp_xmit_retransmit_queue().
2776 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
,
2777 int prior_sacked
, int prior_packets
,
2778 bool is_dupack
, int flag
)
2780 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2781 struct tcp_sock
*tp
= tcp_sk(sk
);
2782 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2783 (tcp_fackets_out(tp
) > tp
->reordering
));
2784 int newly_acked_sacked
= 0;
2785 int fast_rexmit
= 0;
2787 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2789 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2790 tp
->fackets_out
= 0;
2792 /* Now state machine starts.
2793 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2794 if (flag
& FLAG_ECE
)
2795 tp
->prior_ssthresh
= 0;
2797 /* B. In all the states check for reneging SACKs. */
2798 if (tcp_check_sack_reneging(sk
, flag
))
2801 /* C. Check consistency of the current state. */
2802 tcp_verify_left_out(tp
);
2804 /* D. Check state exit conditions. State can be terminated
2805 * when high_seq is ACKed. */
2806 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2807 WARN_ON(tp
->retrans_out
!= 0);
2808 tp
->retrans_stamp
= 0;
2809 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2810 switch (icsk
->icsk_ca_state
) {
2812 /* CWR is to be held something *above* high_seq
2813 * is ACKed for CWR bit to reach receiver. */
2814 if (tp
->snd_una
!= tp
->high_seq
) {
2815 tcp_end_cwnd_reduction(sk
);
2816 tcp_set_ca_state(sk
, TCP_CA_Open
);
2820 case TCP_CA_Recovery
:
2821 if (tcp_is_reno(tp
))
2822 tcp_reset_reno_sack(tp
);
2823 if (tcp_try_undo_recovery(sk
))
2825 tcp_end_cwnd_reduction(sk
);
2830 /* E. Process state. */
2831 switch (icsk
->icsk_ca_state
) {
2832 case TCP_CA_Recovery
:
2833 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2834 if (tcp_is_reno(tp
) && is_dupack
)
2835 tcp_add_reno_sack(sk
);
2837 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
2838 newly_acked_sacked
= prior_packets
- tp
->packets_out
+
2839 tp
->sacked_out
- prior_sacked
;
2842 tcp_process_loss(sk
, flag
, is_dupack
);
2843 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2845 /* Fall through to processing in Open state. */
2847 if (tcp_is_reno(tp
)) {
2848 if (flag
& FLAG_SND_UNA_ADVANCED
)
2849 tcp_reset_reno_sack(tp
);
2851 tcp_add_reno_sack(sk
);
2853 newly_acked_sacked
= prior_packets
- tp
->packets_out
+
2854 tp
->sacked_out
- prior_sacked
;
2856 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
2857 tcp_try_undo_dsack(sk
);
2859 if (!tcp_time_to_recover(sk
, flag
)) {
2860 tcp_try_to_open(sk
, flag
, newly_acked_sacked
);
2864 /* MTU probe failure: don't reduce cwnd */
2865 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2866 icsk
->icsk_mtup
.probe_size
&&
2867 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2868 tcp_mtup_probe_failed(sk
);
2869 /* Restores the reduction we did in tcp_mtup_probe() */
2871 tcp_simple_retransmit(sk
);
2875 /* Otherwise enter Recovery state */
2876 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
2880 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
2881 tcp_update_scoreboard(sk
, fast_rexmit
);
2882 tcp_cwnd_reduction(sk
, newly_acked_sacked
, fast_rexmit
);
2883 tcp_xmit_retransmit_queue(sk
);
2886 void tcp_valid_rtt_meas(struct sock
*sk
, u32 seq_rtt
)
2888 tcp_rtt_estimator(sk
, seq_rtt
);
2890 inet_csk(sk
)->icsk_backoff
= 0;
2892 EXPORT_SYMBOL(tcp_valid_rtt_meas
);
2894 /* Read draft-ietf-tcplw-high-performance before mucking
2895 * with this code. (Supersedes RFC1323)
2897 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2899 /* RTTM Rule: A TSecr value received in a segment is used to
2900 * update the averaged RTT measurement only if the segment
2901 * acknowledges some new data, i.e., only if it advances the
2902 * left edge of the send window.
2904 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2905 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2907 * Changed: reset backoff as soon as we see the first valid sample.
2908 * If we do not, we get strongly overestimated rto. With timestamps
2909 * samples are accepted even from very old segments: f.e., when rtt=1
2910 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2911 * answer arrives rto becomes 120 seconds! If at least one of segments
2912 * in window is lost... Voila. --ANK (010210)
2914 struct tcp_sock
*tp
= tcp_sk(sk
);
2916 tcp_valid_rtt_meas(sk
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
2919 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2921 /* We don't have a timestamp. Can only use
2922 * packets that are not retransmitted to determine
2923 * rtt estimates. Also, we must not reset the
2924 * backoff for rto until we get a non-retransmitted
2925 * packet. This allows us to deal with a situation
2926 * where the network delay has increased suddenly.
2927 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2930 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2933 tcp_valid_rtt_meas(sk
, seq_rtt
);
2936 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2939 const struct tcp_sock
*tp
= tcp_sk(sk
);
2940 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2941 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2942 tcp_ack_saw_tstamp(sk
, flag
);
2943 else if (seq_rtt
>= 0)
2944 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2947 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
2949 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2950 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
2951 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2954 /* Restart timer after forward progress on connection.
2955 * RFC2988 recommends to restart timer to now+rto.
2957 void tcp_rearm_rto(struct sock
*sk
)
2959 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2960 struct tcp_sock
*tp
= tcp_sk(sk
);
2962 /* If the retrans timer is currently being used by Fast Open
2963 * for SYN-ACK retrans purpose, stay put.
2965 if (tp
->fastopen_rsk
)
2968 if (!tp
->packets_out
) {
2969 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2971 u32 rto
= inet_csk(sk
)->icsk_rto
;
2972 /* Offset the time elapsed after installing regular RTO */
2973 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
2974 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
2975 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
2976 const u32 rto_time_stamp
= TCP_SKB_CB(skb
)->when
+ rto
;
2977 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
2978 /* delta may not be positive if the socket is locked
2979 * when the retrans timer fires and is rescheduled.
2984 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
2989 /* This function is called when the delayed ER timer fires. TCP enters
2990 * fast recovery and performs fast-retransmit.
2992 void tcp_resume_early_retransmit(struct sock
*sk
)
2994 struct tcp_sock
*tp
= tcp_sk(sk
);
2998 /* Stop if ER is disabled after the delayed ER timer is scheduled */
2999 if (!tp
->do_early_retrans
)
3002 tcp_enter_recovery(sk
, false);
3003 tcp_update_scoreboard(sk
, 1);
3004 tcp_xmit_retransmit_queue(sk
);
3007 /* If we get here, the whole TSO packet has not been acked. */
3008 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3010 struct tcp_sock
*tp
= tcp_sk(sk
);
3013 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3015 packets_acked
= tcp_skb_pcount(skb
);
3016 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3018 packets_acked
-= tcp_skb_pcount(skb
);
3020 if (packets_acked
) {
3021 BUG_ON(tcp_skb_pcount(skb
) == 0);
3022 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3025 return packets_acked
;
3028 /* Remove acknowledged frames from the retransmission queue. If our packet
3029 * is before the ack sequence we can discard it as it's confirmed to have
3030 * arrived at the other end.
3032 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3035 struct tcp_sock
*tp
= tcp_sk(sk
);
3036 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3037 struct sk_buff
*skb
;
3038 u32 now
= tcp_time_stamp
;
3039 int fully_acked
= true;
3042 u32 reord
= tp
->packets_out
;
3043 u32 prior_sacked
= tp
->sacked_out
;
3045 s32 ca_seq_rtt
= -1;
3046 ktime_t last_ackt
= net_invalid_timestamp();
3048 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3049 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3051 u8 sacked
= scb
->sacked
;
3053 /* Determine how many packets and what bytes were acked, tso and else */
3054 if (after(scb
->end_seq
, tp
->snd_una
)) {
3055 if (tcp_skb_pcount(skb
) == 1 ||
3056 !after(tp
->snd_una
, scb
->seq
))
3059 acked_pcount
= tcp_tso_acked(sk
, skb
);
3063 fully_acked
= false;
3065 acked_pcount
= tcp_skb_pcount(skb
);
3068 if (sacked
& TCPCB_RETRANS
) {
3069 if (sacked
& TCPCB_SACKED_RETRANS
)
3070 tp
->retrans_out
-= acked_pcount
;
3071 flag
|= FLAG_RETRANS_DATA_ACKED
;
3075 ca_seq_rtt
= now
- scb
->when
;
3076 last_ackt
= skb
->tstamp
;
3078 seq_rtt
= ca_seq_rtt
;
3080 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
3081 reord
= min(pkts_acked
, reord
);
3082 if (!after(scb
->end_seq
, tp
->high_seq
))
3083 flag
|= FLAG_ORIG_SACK_ACKED
;
3087 if (sacked
& TCPCB_SACKED_ACKED
)
3088 tp
->sacked_out
-= acked_pcount
;
3089 if (sacked
& TCPCB_LOST
)
3090 tp
->lost_out
-= acked_pcount
;
3092 tp
->packets_out
-= acked_pcount
;
3093 pkts_acked
+= acked_pcount
;
3095 /* Initial outgoing SYN's get put onto the write_queue
3096 * just like anything else we transmit. It is not
3097 * true data, and if we misinform our callers that
3098 * this ACK acks real data, we will erroneously exit
3099 * connection startup slow start one packet too
3100 * quickly. This is severely frowned upon behavior.
3102 if (!(scb
->tcp_flags
& TCPHDR_SYN
)) {
3103 flag
|= FLAG_DATA_ACKED
;
3105 flag
|= FLAG_SYN_ACKED
;
3106 tp
->retrans_stamp
= 0;
3112 tcp_unlink_write_queue(skb
, sk
);
3113 sk_wmem_free_skb(sk
, skb
);
3114 tp
->scoreboard_skb_hint
= NULL
;
3115 if (skb
== tp
->retransmit_skb_hint
)
3116 tp
->retransmit_skb_hint
= NULL
;
3117 if (skb
== tp
->lost_skb_hint
)
3118 tp
->lost_skb_hint
= NULL
;
3121 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3122 tp
->snd_up
= tp
->snd_una
;
3124 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3125 flag
|= FLAG_SACK_RENEGING
;
3127 if (flag
& FLAG_ACKED
) {
3128 const struct tcp_congestion_ops
*ca_ops
3129 = inet_csk(sk
)->icsk_ca_ops
;
3131 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3132 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3133 tcp_mtup_probe_success(sk
);
3136 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
3139 if (tcp_is_reno(tp
)) {
3140 tcp_remove_reno_sacks(sk
, pkts_acked
);
3144 /* Non-retransmitted hole got filled? That's reordering */
3145 if (reord
< prior_fackets
)
3146 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3148 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3149 prior_sacked
- tp
->sacked_out
;
3150 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3153 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3155 if (ca_ops
->pkts_acked
) {
3158 /* Is the ACK triggering packet unambiguous? */
3159 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3160 /* High resolution needed and available? */
3161 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
3162 !ktime_equal(last_ackt
,
3163 net_invalid_timestamp()))
3164 rtt_us
= ktime_us_delta(ktime_get_real(),
3166 else if (ca_seq_rtt
>= 0)
3167 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
3170 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
3174 #if FASTRETRANS_DEBUG > 0
3175 WARN_ON((int)tp
->sacked_out
< 0);
3176 WARN_ON((int)tp
->lost_out
< 0);
3177 WARN_ON((int)tp
->retrans_out
< 0);
3178 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3179 icsk
= inet_csk(sk
);
3181 pr_debug("Leak l=%u %d\n",
3182 tp
->lost_out
, icsk
->icsk_ca_state
);
3185 if (tp
->sacked_out
) {
3186 pr_debug("Leak s=%u %d\n",
3187 tp
->sacked_out
, icsk
->icsk_ca_state
);
3190 if (tp
->retrans_out
) {
3191 pr_debug("Leak r=%u %d\n",
3192 tp
->retrans_out
, icsk
->icsk_ca_state
);
3193 tp
->retrans_out
= 0;
3200 static void tcp_ack_probe(struct sock
*sk
)
3202 const struct tcp_sock
*tp
= tcp_sk(sk
);
3203 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3205 /* Was it a usable window open? */
3207 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3208 icsk
->icsk_backoff
= 0;
3209 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3210 /* Socket must be waked up by subsequent tcp_data_snd_check().
3211 * This function is not for random using!
3214 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3215 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3220 static inline bool tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3222 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3223 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3226 static inline bool tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3228 const struct tcp_sock
*tp
= tcp_sk(sk
);
3229 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3230 !tcp_in_cwnd_reduction(sk
);
3233 /* Check that window update is acceptable.
3234 * The function assumes that snd_una<=ack<=snd_next.
3236 static inline bool tcp_may_update_window(const struct tcp_sock
*tp
,
3237 const u32 ack
, const u32 ack_seq
,
3240 return after(ack
, tp
->snd_una
) ||
3241 after(ack_seq
, tp
->snd_wl1
) ||
3242 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3245 /* Update our send window.
3247 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3248 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3250 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3253 struct tcp_sock
*tp
= tcp_sk(sk
);
3255 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3257 if (likely(!tcp_hdr(skb
)->syn
))
3258 nwin
<<= tp
->rx_opt
.snd_wscale
;
3260 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3261 flag
|= FLAG_WIN_UPDATE
;
3262 tcp_update_wl(tp
, ack_seq
);
3264 if (tp
->snd_wnd
!= nwin
) {
3267 /* Note, it is the only place, where
3268 * fast path is recovered for sending TCP.
3271 tcp_fast_path_check(sk
);
3273 if (nwin
> tp
->max_window
) {
3274 tp
->max_window
= nwin
;
3275 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3285 /* RFC 5961 7 [ACK Throttling] */
3286 static void tcp_send_challenge_ack(struct sock
*sk
)
3288 /* unprotected vars, we dont care of overwrites */
3289 static u32 challenge_timestamp
;
3290 static unsigned int challenge_count
;
3291 u32 now
= jiffies
/ HZ
;
3294 if (now
!= challenge_timestamp
) {
3295 u32 half
= (sysctl_tcp_challenge_ack_limit
+ 1) >> 1;
3297 challenge_timestamp
= now
;
3298 ACCESS_ONCE(challenge_count
) = half
+
3299 reciprocal_divide(prandom_u32(),
3300 sysctl_tcp_challenge_ack_limit
);
3302 count
= ACCESS_ONCE(challenge_count
);
3304 ACCESS_ONCE(challenge_count
) = count
- 1;
3305 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPCHALLENGEACK
);
3310 static void tcp_store_ts_recent(struct tcp_sock
*tp
)
3312 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3313 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3316 static void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3318 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3319 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3320 * extra check below makes sure this can only happen
3321 * for pure ACK frames. -DaveM
3323 * Not only, also it occurs for expired timestamps.
3326 if (tcp_paws_check(&tp
->rx_opt
, 0))
3327 tcp_store_ts_recent(tp
);
3331 /* This routine deals with acks during a TLP episode.
3332 * Ref: loss detection algorithm in draft-dukkipati-tcpm-tcp-loss-probe.
3334 static void tcp_process_tlp_ack(struct sock
*sk
, u32 ack
, int flag
)
3336 struct tcp_sock
*tp
= tcp_sk(sk
);
3337 bool is_tlp_dupack
= (ack
== tp
->tlp_high_seq
) &&
3338 !(flag
& (FLAG_SND_UNA_ADVANCED
|
3339 FLAG_NOT_DUP
| FLAG_DATA_SACKED
));
3341 /* Mark the end of TLP episode on receiving TLP dupack or when
3342 * ack is after tlp_high_seq.
3344 if (is_tlp_dupack
) {
3345 tp
->tlp_high_seq
= 0;
3349 if (after(ack
, tp
->tlp_high_seq
)) {
3350 tp
->tlp_high_seq
= 0;
3351 /* Don't reduce cwnd if DSACK arrives for TLP retrans. */
3352 if (!(flag
& FLAG_DSACKING_ACK
)) {
3353 tcp_init_cwnd_reduction(sk
, true);
3354 tcp_set_ca_state(sk
, TCP_CA_CWR
);
3355 tcp_end_cwnd_reduction(sk
);
3356 tcp_try_keep_open(sk
);
3357 NET_INC_STATS_BH(sock_net(sk
),
3358 LINUX_MIB_TCPLOSSPROBERECOVERY
);
3363 /* This routine deals with incoming acks, but not outgoing ones. */
3364 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3366 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3367 struct tcp_sock
*tp
= tcp_sk(sk
);
3368 u32 prior_snd_una
= tp
->snd_una
;
3369 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3370 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3371 bool is_dupack
= false;
3372 u32 prior_in_flight
, prior_cwnd
= tp
->snd_cwnd
, prior_rtt
= tp
->srtt
;
3374 int prior_packets
= tp
->packets_out
;
3375 int prior_sacked
= tp
->sacked_out
;
3377 int previous_packets_out
= 0;
3379 /* If the ack is older than previous acks
3380 * then we can probably ignore it.
3382 if (before(ack
, prior_snd_una
)) {
3383 /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
3384 if (before(ack
, prior_snd_una
- tp
->max_window
)) {
3385 tcp_send_challenge_ack(sk
);
3391 /* If the ack includes data we haven't sent yet, discard
3392 * this segment (RFC793 Section 3.9).
3394 if (after(ack
, tp
->snd_nxt
))
3397 if (icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
3398 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)
3401 if (after(ack
, prior_snd_una
))
3402 flag
|= FLAG_SND_UNA_ADVANCED
;
3404 prior_fackets
= tp
->fackets_out
;
3405 prior_in_flight
= tcp_packets_in_flight(tp
);
3407 /* ts_recent update must be made after we are sure that the packet
3410 if (flag
& FLAG_UPDATE_TS_RECENT
)
3411 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
3413 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3414 /* Window is constant, pure forward advance.
3415 * No more checks are required.
3416 * Note, we use the fact that SND.UNA>=SND.WL2.
3418 tcp_update_wl(tp
, ack_seq
);
3420 flag
|= FLAG_WIN_UPDATE
;
3422 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3424 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3426 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3429 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3431 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3433 if (TCP_SKB_CB(skb
)->sacked
)
3434 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3436 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3439 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3442 /* We passed data and got it acked, remove any soft error
3443 * log. Something worked...
3445 sk
->sk_err_soft
= 0;
3446 icsk
->icsk_probes_out
= 0;
3447 tp
->rcv_tstamp
= tcp_time_stamp
;
3451 /* See if we can take anything off of the retransmit queue. */
3452 previous_packets_out
= tp
->packets_out
;
3453 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
);
3455 pkts_acked
= previous_packets_out
- tp
->packets_out
;
3457 if (tcp_ack_is_dubious(sk
, flag
)) {
3458 /* Advance CWND, if state allows this. */
3459 if ((flag
& FLAG_DATA_ACKED
) && tcp_may_raise_cwnd(sk
, flag
))
3460 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3461 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3462 tcp_fastretrans_alert(sk
, pkts_acked
, prior_sacked
,
3463 prior_packets
, is_dupack
, flag
);
3465 if (flag
& FLAG_DATA_ACKED
)
3466 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3469 if (tp
->tlp_high_seq
)
3470 tcp_process_tlp_ack(sk
, ack
, flag
);
3472 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
)) {
3473 struct dst_entry
*dst
= __sk_dst_get(sk
);
3478 if (icsk
->icsk_pending
== ICSK_TIME_RETRANS
)
3479 tcp_schedule_loss_probe(sk
);
3480 if (tp
->srtt
!= prior_rtt
|| tp
->snd_cwnd
!= prior_cwnd
)
3481 tcp_update_pacing_rate(sk
);
3485 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3486 if (flag
& FLAG_DSACKING_ACK
)
3487 tcp_fastretrans_alert(sk
, pkts_acked
, prior_sacked
,
3488 prior_packets
, is_dupack
, flag
);
3489 /* If this ack opens up a zero window, clear backoff. It was
3490 * being used to time the probes, and is probably far higher than
3491 * it needs to be for normal retransmission.
3493 if (tcp_send_head(sk
))
3496 if (tp
->tlp_high_seq
)
3497 tcp_process_tlp_ack(sk
, ack
, flag
);
3501 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3505 /* If data was SACKed, tag it and see if we should send more data.
3506 * If data was DSACKed, see if we can undo a cwnd reduction.
3508 if (TCP_SKB_CB(skb
)->sacked
) {
3509 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3510 tcp_fastretrans_alert(sk
, pkts_acked
, prior_sacked
,
3511 prior_packets
, is_dupack
, flag
);
3514 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3518 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3519 * But, this can also be called on packets in the established flow when
3520 * the fast version below fails.
3522 void tcp_parse_options(const struct sk_buff
*skb
,
3523 struct tcp_options_received
*opt_rx
, int estab
,
3524 struct tcp_fastopen_cookie
*foc
)
3526 const unsigned char *ptr
;
3527 const struct tcphdr
*th
= tcp_hdr(skb
);
3528 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3530 ptr
= (const unsigned char *)(th
+ 1);
3531 opt_rx
->saw_tstamp
= 0;
3533 while (length
> 0) {
3534 int opcode
= *ptr
++;
3540 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3545 if (opsize
< 2) /* "silly options" */
3547 if (opsize
> length
)
3548 return; /* don't parse partial options */
3551 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3552 u16 in_mss
= get_unaligned_be16(ptr
);
3554 if (opt_rx
->user_mss
&&
3555 opt_rx
->user_mss
< in_mss
)
3556 in_mss
= opt_rx
->user_mss
;
3557 opt_rx
->mss_clamp
= in_mss
;
3562 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3563 !estab
&& sysctl_tcp_window_scaling
) {
3564 __u8 snd_wscale
= *(__u8
*)ptr
;
3565 opt_rx
->wscale_ok
= 1;
3566 if (snd_wscale
> 14) {
3567 net_info_ratelimited("%s: Illegal window scaling value %d >14 received\n",
3572 opt_rx
->snd_wscale
= snd_wscale
;
3575 case TCPOPT_TIMESTAMP
:
3576 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3577 ((estab
&& opt_rx
->tstamp_ok
) ||
3578 (!estab
&& sysctl_tcp_timestamps
))) {
3579 opt_rx
->saw_tstamp
= 1;
3580 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3581 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3584 case TCPOPT_SACK_PERM
:
3585 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3586 !estab
&& sysctl_tcp_sack
) {
3587 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3588 tcp_sack_reset(opt_rx
);
3593 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3594 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3596 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3599 #ifdef CONFIG_TCP_MD5SIG
3602 * The MD5 Hash has already been
3603 * checked (see tcp_v{4,6}_do_rcv()).
3608 /* Fast Open option shares code 254 using a
3609 * 16 bits magic number. It's valid only in
3610 * SYN or SYN-ACK with an even size.
3612 if (opsize
< TCPOLEN_EXP_FASTOPEN_BASE
||
3613 get_unaligned_be16(ptr
) != TCPOPT_FASTOPEN_MAGIC
||
3614 foc
== NULL
|| !th
->syn
|| (opsize
& 1))
3616 foc
->len
= opsize
- TCPOLEN_EXP_FASTOPEN_BASE
;
3617 if (foc
->len
>= TCP_FASTOPEN_COOKIE_MIN
&&
3618 foc
->len
<= TCP_FASTOPEN_COOKIE_MAX
)
3619 memcpy(foc
->val
, ptr
+ 2, foc
->len
);
3620 else if (foc
->len
!= 0)
3630 EXPORT_SYMBOL(tcp_parse_options
);
3632 static bool tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3634 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3636 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3637 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3638 tp
->rx_opt
.saw_tstamp
= 1;
3640 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3643 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
) - tp
->tsoffset
;
3645 tp
->rx_opt
.rcv_tsecr
= 0;
3651 /* Fast parse options. This hopes to only see timestamps.
3652 * If it is wrong it falls back on tcp_parse_options().
3654 static bool tcp_fast_parse_options(const struct sk_buff
*skb
,
3655 const struct tcphdr
*th
, struct tcp_sock
*tp
)
3657 /* In the spirit of fast parsing, compare doff directly to constant
3658 * values. Because equality is used, short doff can be ignored here.
3660 if (th
->doff
== (sizeof(*th
) / 4)) {
3661 tp
->rx_opt
.saw_tstamp
= 0;
3663 } else if (tp
->rx_opt
.tstamp_ok
&&
3664 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3665 if (tcp_parse_aligned_timestamp(tp
, th
))
3669 tcp_parse_options(skb
, &tp
->rx_opt
, 1, NULL
);
3670 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3671 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
3676 #ifdef CONFIG_TCP_MD5SIG
3678 * Parse MD5 Signature option
3680 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3682 int length
= (th
->doff
<< 2) - sizeof(*th
);
3683 const u8
*ptr
= (const u8
*)(th
+ 1);
3685 /* If the TCP option is too short, we can short cut */
3686 if (length
< TCPOLEN_MD5SIG
)
3689 while (length
> 0) {
3690 int opcode
= *ptr
++;
3701 if (opsize
< 2 || opsize
> length
)
3703 if (opcode
== TCPOPT_MD5SIG
)
3704 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
3711 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
3714 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3716 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3717 * it can pass through stack. So, the following predicate verifies that
3718 * this segment is not used for anything but congestion avoidance or
3719 * fast retransmit. Moreover, we even are able to eliminate most of such
3720 * second order effects, if we apply some small "replay" window (~RTO)
3721 * to timestamp space.
3723 * All these measures still do not guarantee that we reject wrapped ACKs
3724 * on networks with high bandwidth, when sequence space is recycled fastly,
3725 * but it guarantees that such events will be very rare and do not affect
3726 * connection seriously. This doesn't look nice, but alas, PAWS is really
3729 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3730 * states that events when retransmit arrives after original data are rare.
3731 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3732 * the biggest problem on large power networks even with minor reordering.
3733 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3734 * up to bandwidth of 18Gigabit/sec. 8) ]
3737 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3739 const struct tcp_sock
*tp
= tcp_sk(sk
);
3740 const struct tcphdr
*th
= tcp_hdr(skb
);
3741 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3742 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3744 return (/* 1. Pure ACK with correct sequence number. */
3745 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3747 /* 2. ... and duplicate ACK. */
3748 ack
== tp
->snd_una
&&
3750 /* 3. ... and does not update window. */
3751 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3753 /* 4. ... and sits in replay window. */
3754 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3757 static inline bool tcp_paws_discard(const struct sock
*sk
,
3758 const struct sk_buff
*skb
)
3760 const struct tcp_sock
*tp
= tcp_sk(sk
);
3762 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
3763 !tcp_disordered_ack(sk
, skb
);
3766 /* Check segment sequence number for validity.
3768 * Segment controls are considered valid, if the segment
3769 * fits to the window after truncation to the window. Acceptability
3770 * of data (and SYN, FIN, of course) is checked separately.
3771 * See tcp_data_queue(), for example.
3773 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3774 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3775 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3776 * (borrowed from freebsd)
3779 static inline bool tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3781 return !before(end_seq
, tp
->rcv_wup
) &&
3782 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3785 /* When we get a reset we do this. */
3786 void tcp_reset(struct sock
*sk
)
3788 /* We want the right error as BSD sees it (and indeed as we do). */
3789 switch (sk
->sk_state
) {
3791 sk
->sk_err
= ECONNREFUSED
;
3793 case TCP_CLOSE_WAIT
:
3799 sk
->sk_err
= ECONNRESET
;
3801 /* This barrier is coupled with smp_rmb() in tcp_poll() */
3804 if (!sock_flag(sk
, SOCK_DEAD
))
3805 sk
->sk_error_report(sk
);
3811 * Process the FIN bit. This now behaves as it is supposed to work
3812 * and the FIN takes effect when it is validly part of sequence
3813 * space. Not before when we get holes.
3815 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3816 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3819 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3820 * close and we go into CLOSING (and later onto TIME-WAIT)
3822 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3824 static void tcp_fin(struct sock
*sk
)
3826 struct tcp_sock
*tp
= tcp_sk(sk
);
3828 inet_csk_schedule_ack(sk
);
3830 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3831 sock_set_flag(sk
, SOCK_DONE
);
3833 switch (sk
->sk_state
) {
3835 case TCP_ESTABLISHED
:
3836 /* Move to CLOSE_WAIT */
3837 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3838 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3841 case TCP_CLOSE_WAIT
:
3843 /* Received a retransmission of the FIN, do
3848 /* RFC793: Remain in the LAST-ACK state. */
3852 /* This case occurs when a simultaneous close
3853 * happens, we must ack the received FIN and
3854 * enter the CLOSING state.
3857 tcp_set_state(sk
, TCP_CLOSING
);
3860 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3862 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3865 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3866 * cases we should never reach this piece of code.
3868 pr_err("%s: Impossible, sk->sk_state=%d\n",
3869 __func__
, sk
->sk_state
);
3873 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3874 * Probably, we should reset in this case. For now drop them.
3876 __skb_queue_purge(&tp
->out_of_order_queue
);
3877 if (tcp_is_sack(tp
))
3878 tcp_sack_reset(&tp
->rx_opt
);
3881 if (!sock_flag(sk
, SOCK_DEAD
)) {
3882 sk
->sk_state_change(sk
);
3884 /* Do not send POLL_HUP for half duplex close. */
3885 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3886 sk
->sk_state
== TCP_CLOSE
)
3887 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
3889 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
3893 static inline bool tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
3896 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3897 if (before(seq
, sp
->start_seq
))
3898 sp
->start_seq
= seq
;
3899 if (after(end_seq
, sp
->end_seq
))
3900 sp
->end_seq
= end_seq
;
3906 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
3908 struct tcp_sock
*tp
= tcp_sk(sk
);
3910 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3913 if (before(seq
, tp
->rcv_nxt
))
3914 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
3916 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
3918 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3920 tp
->rx_opt
.dsack
= 1;
3921 tp
->duplicate_sack
[0].start_seq
= seq
;
3922 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3926 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
3928 struct tcp_sock
*tp
= tcp_sk(sk
);
3930 if (!tp
->rx_opt
.dsack
)
3931 tcp_dsack_set(sk
, seq
, end_seq
);
3933 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3936 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
3938 struct tcp_sock
*tp
= tcp_sk(sk
);
3940 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3941 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3942 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
3943 tcp_enter_quickack_mode(sk
);
3945 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3946 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3948 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3949 end_seq
= tp
->rcv_nxt
;
3950 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3957 /* These routines update the SACK block as out-of-order packets arrive or
3958 * in-order packets close up the sequence space.
3960 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3963 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3964 struct tcp_sack_block
*swalk
= sp
+ 1;
3966 /* See if the recent change to the first SACK eats into
3967 * or hits the sequence space of other SACK blocks, if so coalesce.
3969 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
3970 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3973 /* Zap SWALK, by moving every further SACK up by one slot.
3974 * Decrease num_sacks.
3976 tp
->rx_opt
.num_sacks
--;
3977 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3981 this_sack
++, swalk
++;
3985 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3987 struct tcp_sock
*tp
= tcp_sk(sk
);
3988 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3989 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3995 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
3996 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3997 /* Rotate this_sack to the first one. */
3998 for (; this_sack
> 0; this_sack
--, sp
--)
3999 swap(*sp
, *(sp
- 1));
4001 tcp_sack_maybe_coalesce(tp
);
4006 /* Could not find an adjacent existing SACK, build a new one,
4007 * put it at the front, and shift everyone else down. We
4008 * always know there is at least one SACK present already here.
4010 * If the sack array is full, forget about the last one.
4012 if (this_sack
>= TCP_NUM_SACKS
) {
4014 tp
->rx_opt
.num_sacks
--;
4017 for (; this_sack
> 0; this_sack
--, sp
--)
4021 /* Build the new head SACK, and we're done. */
4022 sp
->start_seq
= seq
;
4023 sp
->end_seq
= end_seq
;
4024 tp
->rx_opt
.num_sacks
++;
4027 /* RCV.NXT advances, some SACKs should be eaten. */
4029 static void tcp_sack_remove(struct tcp_sock
*tp
)
4031 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4032 int num_sacks
= tp
->rx_opt
.num_sacks
;
4035 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4036 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4037 tp
->rx_opt
.num_sacks
= 0;
4041 for (this_sack
= 0; this_sack
< num_sacks
;) {
4042 /* Check if the start of the sack is covered by RCV.NXT. */
4043 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4046 /* RCV.NXT must cover all the block! */
4047 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4049 /* Zap this SACK, by moving forward any other SACKS. */
4050 for (i
=this_sack
+1; i
< num_sacks
; i
++)
4051 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4058 tp
->rx_opt
.num_sacks
= num_sacks
;
4061 /* This one checks to see if we can put data from the
4062 * out_of_order queue into the receive_queue.
4064 static void tcp_ofo_queue(struct sock
*sk
)
4066 struct tcp_sock
*tp
= tcp_sk(sk
);
4067 __u32 dsack_high
= tp
->rcv_nxt
;
4068 struct sk_buff
*skb
;
4070 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4071 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4074 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4075 __u32 dsack
= dsack_high
;
4076 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4077 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4078 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4081 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4082 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4083 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4087 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4088 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4089 TCP_SKB_CB(skb
)->end_seq
);
4091 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4092 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4093 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4094 if (tcp_hdr(skb
)->fin
)
4099 static bool tcp_prune_ofo_queue(struct sock
*sk
);
4100 static int tcp_prune_queue(struct sock
*sk
);
4102 static int tcp_try_rmem_schedule(struct sock
*sk
, struct sk_buff
*skb
,
4105 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4106 !sk_rmem_schedule(sk
, skb
, size
)) {
4108 if (tcp_prune_queue(sk
) < 0)
4111 if (!sk_rmem_schedule(sk
, skb
, size
)) {
4112 if (!tcp_prune_ofo_queue(sk
))
4115 if (!sk_rmem_schedule(sk
, skb
, size
))
4123 * tcp_try_coalesce - try to merge skb to prior one
4126 * @from: buffer to add in queue
4127 * @fragstolen: pointer to boolean
4129 * Before queueing skb @from after @to, try to merge them
4130 * to reduce overall memory use and queue lengths, if cost is small.
4131 * Packets in ofo or receive queues can stay a long time.
4132 * Better try to coalesce them right now to avoid future collapses.
4133 * Returns true if caller should free @from instead of queueing it
4135 static bool tcp_try_coalesce(struct sock
*sk
,
4137 struct sk_buff
*from
,
4142 *fragstolen
= false;
4144 if (tcp_hdr(from
)->fin
)
4147 /* Its possible this segment overlaps with prior segment in queue */
4148 if (TCP_SKB_CB(from
)->seq
!= TCP_SKB_CB(to
)->end_seq
)
4151 if (!skb_try_coalesce(to
, from
, fragstolen
, &delta
))
4154 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4155 sk_mem_charge(sk
, delta
);
4156 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4157 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4158 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4162 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4164 struct tcp_sock
*tp
= tcp_sk(sk
);
4165 struct sk_buff
*skb1
;
4168 TCP_ECN_check_ce(tp
, skb
);
4170 if (unlikely(tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))) {
4171 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFODROP
);
4176 /* Disable header prediction. */
4178 inet_csk_schedule_ack(sk
);
4180 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOQUEUE
);
4181 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4182 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4184 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4186 /* Initial out of order segment, build 1 SACK. */
4187 if (tcp_is_sack(tp
)) {
4188 tp
->rx_opt
.num_sacks
= 1;
4189 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4190 tp
->selective_acks
[0].end_seq
=
4191 TCP_SKB_CB(skb
)->end_seq
;
4193 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4197 seq
= TCP_SKB_CB(skb
)->seq
;
4198 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4200 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4203 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4204 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4206 kfree_skb_partial(skb
, fragstolen
);
4210 if (!tp
->rx_opt
.num_sacks
||
4211 tp
->selective_acks
[0].end_seq
!= seq
)
4214 /* Common case: data arrive in order after hole. */
4215 tp
->selective_acks
[0].end_seq
= end_seq
;
4219 /* Find place to insert this segment. */
4221 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4223 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4227 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4230 /* Do skb overlap to previous one? */
4231 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4232 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4233 /* All the bits are present. Drop. */
4234 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4237 tcp_dsack_set(sk
, seq
, end_seq
);
4240 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4241 /* Partial overlap. */
4242 tcp_dsack_set(sk
, seq
,
4243 TCP_SKB_CB(skb1
)->end_seq
);
4245 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4249 skb1
= skb_queue_prev(
4250 &tp
->out_of_order_queue
,
4255 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4257 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4259 /* And clean segments covered by new one as whole. */
4260 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4261 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4263 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4265 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4266 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4270 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4271 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4272 TCP_SKB_CB(skb1
)->end_seq
);
4273 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPOFOMERGE
);
4278 if (tcp_is_sack(tp
))
4279 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4282 skb_set_owner_r(skb
, sk
);
4285 static int __must_check
tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
,
4289 struct sk_buff
*tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4291 __skb_pull(skb
, hdrlen
);
4293 tcp_try_coalesce(sk
, tail
, skb
, fragstolen
)) ? 1 : 0;
4294 tcp_sk(sk
)->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4296 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4297 skb_set_owner_r(skb
, sk
);
4302 int tcp_send_rcvq(struct sock
*sk
, struct msghdr
*msg
, size_t size
)
4304 struct sk_buff
*skb
= NULL
;
4311 skb
= alloc_skb(size
+ sizeof(*th
), sk
->sk_allocation
);
4315 if (tcp_try_rmem_schedule(sk
, skb
, size
+ sizeof(*th
)))
4318 th
= (struct tcphdr
*)skb_put(skb
, sizeof(*th
));
4319 skb_reset_transport_header(skb
);
4320 memset(th
, 0, sizeof(*th
));
4322 if (memcpy_fromiovec(skb_put(skb
, size
), msg
->msg_iov
, size
))
4325 TCP_SKB_CB(skb
)->seq
= tcp_sk(sk
)->rcv_nxt
;
4326 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ size
;
4327 TCP_SKB_CB(skb
)->ack_seq
= tcp_sk(sk
)->snd_una
- 1;
4329 if (tcp_queue_rcv(sk
, skb
, sizeof(*th
), &fragstolen
)) {
4330 WARN_ON_ONCE(fragstolen
); /* should not happen */
4341 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4343 const struct tcphdr
*th
= tcp_hdr(skb
);
4344 struct tcp_sock
*tp
= tcp_sk(sk
);
4346 bool fragstolen
= false;
4348 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4352 __skb_pull(skb
, th
->doff
* 4);
4354 TCP_ECN_accept_cwr(tp
, skb
);
4356 tp
->rx_opt
.dsack
= 0;
4358 /* Queue data for delivery to the user.
4359 * Packets in sequence go to the receive queue.
4360 * Out of sequence packets to the out_of_order_queue.
4362 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4363 if (tcp_receive_window(tp
) == 0)
4366 /* Ok. In sequence. In window. */
4367 if (tp
->ucopy
.task
== current
&&
4368 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4369 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4370 int chunk
= min_t(unsigned int, skb
->len
,
4373 __set_current_state(TASK_RUNNING
);
4376 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4377 tp
->ucopy
.len
-= chunk
;
4378 tp
->copied_seq
+= chunk
;
4379 eaten
= (chunk
== skb
->len
);
4380 tcp_rcv_space_adjust(sk
);
4388 tcp_try_rmem_schedule(sk
, skb
, skb
->truesize
))
4391 eaten
= tcp_queue_rcv(sk
, skb
, 0, &fragstolen
);
4393 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4395 tcp_event_data_recv(sk
, skb
);
4399 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4402 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4403 * gap in queue is filled.
4405 if (skb_queue_empty(&tp
->out_of_order_queue
))
4406 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4409 if (tp
->rx_opt
.num_sacks
)
4410 tcp_sack_remove(tp
);
4412 tcp_fast_path_check(sk
);
4415 kfree_skb_partial(skb
, fragstolen
);
4416 if (!sock_flag(sk
, SOCK_DEAD
))
4417 sk
->sk_data_ready(sk
, 0);
4421 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4422 /* A retransmit, 2nd most common case. Force an immediate ack. */
4423 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4424 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4427 tcp_enter_quickack_mode(sk
);
4428 inet_csk_schedule_ack(sk
);
4434 /* Out of window. F.e. zero window probe. */
4435 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4438 tcp_enter_quickack_mode(sk
);
4440 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4441 /* Partial packet, seq < rcv_next < end_seq */
4442 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4443 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4444 TCP_SKB_CB(skb
)->end_seq
);
4446 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4448 /* If window is closed, drop tail of packet. But after
4449 * remembering D-SACK for its head made in previous line.
4451 if (!tcp_receive_window(tp
))
4456 tcp_data_queue_ofo(sk
, skb
);
4459 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4460 struct sk_buff_head
*list
)
4462 struct sk_buff
*next
= NULL
;
4464 if (!skb_queue_is_last(list
, skb
))
4465 next
= skb_queue_next(list
, skb
);
4467 __skb_unlink(skb
, list
);
4469 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4474 /* Collapse contiguous sequence of skbs head..tail with
4475 * sequence numbers start..end.
4477 * If tail is NULL, this means until the end of the list.
4479 * Segments with FIN/SYN are not collapsed (only because this
4483 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4484 struct sk_buff
*head
, struct sk_buff
*tail
,
4487 struct sk_buff
*skb
, *n
;
4490 /* First, check that queue is collapsible and find
4491 * the point where collapsing can be useful. */
4495 skb_queue_walk_from_safe(list
, skb
, n
) {
4498 /* No new bits? It is possible on ofo queue. */
4499 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4500 skb
= tcp_collapse_one(sk
, skb
, list
);
4506 /* The first skb to collapse is:
4508 * - bloated or contains data before "start" or
4509 * overlaps to the next one.
4511 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4512 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4513 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4514 end_of_skbs
= false;
4518 if (!skb_queue_is_last(list
, skb
)) {
4519 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4521 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4522 end_of_skbs
= false;
4527 /* Decided to skip this, advance start seq. */
4528 start
= TCP_SKB_CB(skb
)->end_seq
;
4530 if (end_of_skbs
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4533 while (before(start
, end
)) {
4534 struct sk_buff
*nskb
;
4535 unsigned int header
= skb_headroom(skb
);
4536 int copy
= SKB_MAX_ORDER(header
, 0);
4538 /* Too big header? This can happen with IPv6. */
4541 if (end
- start
< copy
)
4543 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4547 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4548 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4550 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4552 skb_reserve(nskb
, header
);
4553 memcpy(nskb
->head
, skb
->head
, header
);
4554 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4555 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4556 __skb_queue_before(list
, skb
, nskb
);
4557 skb_set_owner_r(nskb
, sk
);
4559 /* Copy data, releasing collapsed skbs. */
4561 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4562 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4566 size
= min(copy
, size
);
4567 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4569 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4573 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4574 skb
= tcp_collapse_one(sk
, skb
, list
);
4577 tcp_hdr(skb
)->syn
||
4585 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4586 * and tcp_collapse() them until all the queue is collapsed.
4588 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4590 struct tcp_sock
*tp
= tcp_sk(sk
);
4591 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4592 struct sk_buff
*head
;
4598 start
= TCP_SKB_CB(skb
)->seq
;
4599 end
= TCP_SKB_CB(skb
)->end_seq
;
4603 struct sk_buff
*next
= NULL
;
4605 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4606 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4609 /* Segment is terminated when we see gap or when
4610 * we are at the end of all the queue. */
4612 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4613 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4614 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4615 head
, skb
, start
, end
);
4619 /* Start new segment */
4620 start
= TCP_SKB_CB(skb
)->seq
;
4621 end
= TCP_SKB_CB(skb
)->end_seq
;
4623 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4624 start
= TCP_SKB_CB(skb
)->seq
;
4625 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4626 end
= TCP_SKB_CB(skb
)->end_seq
;
4632 * Purge the out-of-order queue.
4633 * Return true if queue was pruned.
4635 static bool tcp_prune_ofo_queue(struct sock
*sk
)
4637 struct tcp_sock
*tp
= tcp_sk(sk
);
4640 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4641 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4642 __skb_queue_purge(&tp
->out_of_order_queue
);
4644 /* Reset SACK state. A conforming SACK implementation will
4645 * do the same at a timeout based retransmit. When a connection
4646 * is in a sad state like this, we care only about integrity
4647 * of the connection not performance.
4649 if (tp
->rx_opt
.sack_ok
)
4650 tcp_sack_reset(&tp
->rx_opt
);
4657 /* Reduce allocated memory if we can, trying to get
4658 * the socket within its memory limits again.
4660 * Return less than zero if we should start dropping frames
4661 * until the socket owning process reads some of the data
4662 * to stabilize the situation.
4664 static int tcp_prune_queue(struct sock
*sk
)
4666 struct tcp_sock
*tp
= tcp_sk(sk
);
4668 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4670 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4672 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4673 tcp_clamp_window(sk
);
4674 else if (sk_under_memory_pressure(sk
))
4675 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4677 tcp_collapse_ofo_queue(sk
);
4678 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4679 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4680 skb_peek(&sk
->sk_receive_queue
),
4682 tp
->copied_seq
, tp
->rcv_nxt
);
4685 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4688 /* Collapsing did not help, destructive actions follow.
4689 * This must not ever occur. */
4691 tcp_prune_ofo_queue(sk
);
4693 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4696 /* If we are really being abused, tell the caller to silently
4697 * drop receive data on the floor. It will get retransmitted
4698 * and hopefully then we'll have sufficient space.
4700 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4702 /* Massive buffer overcommit. */
4707 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4708 * As additional protections, we do not touch cwnd in retransmission phases,
4709 * and if application hit its sndbuf limit recently.
4711 void tcp_cwnd_application_limited(struct sock
*sk
)
4713 struct tcp_sock
*tp
= tcp_sk(sk
);
4715 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4716 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4717 /* Limited by application or receiver window. */
4718 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4719 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4720 if (win_used
< tp
->snd_cwnd
) {
4721 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4722 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4724 tp
->snd_cwnd_used
= 0;
4726 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4729 static bool tcp_should_expand_sndbuf(const struct sock
*sk
)
4731 const struct tcp_sock
*tp
= tcp_sk(sk
);
4733 /* If the user specified a specific send buffer setting, do
4736 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4739 /* If we are under global TCP memory pressure, do not expand. */
4740 if (sk_under_memory_pressure(sk
))
4743 /* If we are under soft global TCP memory pressure, do not expand. */
4744 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4747 /* If we filled the congestion window, do not expand. */
4748 if (tp
->packets_out
>= tp
->snd_cwnd
)
4754 /* When incoming ACK allowed to free some skb from write_queue,
4755 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4756 * on the exit from tcp input handler.
4758 * PROBLEM: sndbuf expansion does not work well with largesend.
4760 static void tcp_new_space(struct sock
*sk
)
4762 struct tcp_sock
*tp
= tcp_sk(sk
);
4764 if (tcp_should_expand_sndbuf(sk
)) {
4765 int sndmem
= SKB_TRUESIZE(max_t(u32
,
4766 tp
->rx_opt
.mss_clamp
,
4769 int demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4770 tp
->reordering
+ 1);
4771 sndmem
*= 2 * demanded
;
4772 if (sndmem
> sk
->sk_sndbuf
)
4773 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4774 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4777 sk
->sk_write_space(sk
);
4780 static void tcp_check_space(struct sock
*sk
)
4782 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4783 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4784 if (sk
->sk_socket
&&
4785 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4790 static inline void tcp_data_snd_check(struct sock
*sk
)
4792 tcp_push_pending_frames(sk
);
4793 tcp_check_space(sk
);
4797 * Check if sending an ack is needed.
4799 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4801 struct tcp_sock
*tp
= tcp_sk(sk
);
4803 /* More than one full frame received... */
4804 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
4805 /* ... and right edge of window advances far enough.
4806 * (tcp_recvmsg() will send ACK otherwise). Or...
4808 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4809 /* We ACK each frame or... */
4810 tcp_in_quickack_mode(sk
) ||
4811 /* We have out of order data. */
4812 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4813 /* Then ack it now */
4816 /* Else, send delayed ack. */
4817 tcp_send_delayed_ack(sk
);
4821 static inline void tcp_ack_snd_check(struct sock
*sk
)
4823 if (!inet_csk_ack_scheduled(sk
)) {
4824 /* We sent a data segment already. */
4827 __tcp_ack_snd_check(sk
, 1);
4831 * This routine is only called when we have urgent data
4832 * signaled. Its the 'slow' part of tcp_urg. It could be
4833 * moved inline now as tcp_urg is only called from one
4834 * place. We handle URGent data wrong. We have to - as
4835 * BSD still doesn't use the correction from RFC961.
4836 * For 1003.1g we should support a new option TCP_STDURG to permit
4837 * either form (or just set the sysctl tcp_stdurg).
4840 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
4842 struct tcp_sock
*tp
= tcp_sk(sk
);
4843 u32 ptr
= ntohs(th
->urg_ptr
);
4845 if (ptr
&& !sysctl_tcp_stdurg
)
4847 ptr
+= ntohl(th
->seq
);
4849 /* Ignore urgent data that we've already seen and read. */
4850 if (after(tp
->copied_seq
, ptr
))
4853 /* Do not replay urg ptr.
4855 * NOTE: interesting situation not covered by specs.
4856 * Misbehaving sender may send urg ptr, pointing to segment,
4857 * which we already have in ofo queue. We are not able to fetch
4858 * such data and will stay in TCP_URG_NOTYET until will be eaten
4859 * by recvmsg(). Seems, we are not obliged to handle such wicked
4860 * situations. But it is worth to think about possibility of some
4861 * DoSes using some hypothetical application level deadlock.
4863 if (before(ptr
, tp
->rcv_nxt
))
4866 /* Do we already have a newer (or duplicate) urgent pointer? */
4867 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4870 /* Tell the world about our new urgent pointer. */
4873 /* We may be adding urgent data when the last byte read was
4874 * urgent. To do this requires some care. We cannot just ignore
4875 * tp->copied_seq since we would read the last urgent byte again
4876 * as data, nor can we alter copied_seq until this data arrives
4877 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4879 * NOTE. Double Dutch. Rendering to plain English: author of comment
4880 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4881 * and expect that both A and B disappear from stream. This is _wrong_.
4882 * Though this happens in BSD with high probability, this is occasional.
4883 * Any application relying on this is buggy. Note also, that fix "works"
4884 * only in this artificial test. Insert some normal data between A and B and we will
4885 * decline of BSD again. Verdict: it is better to remove to trap
4888 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4889 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4890 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4892 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4893 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4898 tp
->urg_data
= TCP_URG_NOTYET
;
4901 /* Disable header prediction. */
4905 /* This is the 'fast' part of urgent handling. */
4906 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
4908 struct tcp_sock
*tp
= tcp_sk(sk
);
4910 /* Check if we get a new urgent pointer - normally not. */
4912 tcp_check_urg(sk
, th
);
4914 /* Do we wait for any urgent data? - normally not... */
4915 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4916 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4919 /* Is the urgent pointer pointing into this packet? */
4920 if (ptr
< skb
->len
) {
4922 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4924 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4925 if (!sock_flag(sk
, SOCK_DEAD
))
4926 sk
->sk_data_ready(sk
, 0);
4931 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4933 struct tcp_sock
*tp
= tcp_sk(sk
);
4934 int chunk
= skb
->len
- hlen
;
4938 if (skb_csum_unnecessary(skb
))
4939 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4941 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4945 tp
->ucopy
.len
-= chunk
;
4946 tp
->copied_seq
+= chunk
;
4947 tcp_rcv_space_adjust(sk
);
4954 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
4955 struct sk_buff
*skb
)
4959 if (sock_owned_by_user(sk
)) {
4961 result
= __tcp_checksum_complete(skb
);
4964 result
= __tcp_checksum_complete(skb
);
4969 static inline bool tcp_checksum_complete_user(struct sock
*sk
,
4970 struct sk_buff
*skb
)
4972 return !skb_csum_unnecessary(skb
) &&
4973 __tcp_checksum_complete_user(sk
, skb
);
4976 #ifdef CONFIG_NET_DMA
4977 static bool tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
4980 struct tcp_sock
*tp
= tcp_sk(sk
);
4981 int chunk
= skb
->len
- hlen
;
4983 bool copied_early
= false;
4985 if (tp
->ucopy
.wakeup
)
4988 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4989 tp
->ucopy
.dma_chan
= net_dma_find_channel();
4991 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
4993 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4995 tp
->ucopy
.iov
, chunk
,
4996 tp
->ucopy
.pinned_list
);
5001 tp
->ucopy
.dma_cookie
= dma_cookie
;
5002 copied_early
= true;
5004 tp
->ucopy
.len
-= chunk
;
5005 tp
->copied_seq
+= chunk
;
5006 tcp_rcv_space_adjust(sk
);
5008 if ((tp
->ucopy
.len
== 0) ||
5009 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
5010 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
5011 tp
->ucopy
.wakeup
= 1;
5012 sk
->sk_data_ready(sk
, 0);
5014 } else if (chunk
> 0) {
5015 tp
->ucopy
.wakeup
= 1;
5016 sk
->sk_data_ready(sk
, 0);
5019 return copied_early
;
5021 #endif /* CONFIG_NET_DMA */
5023 /* Does PAWS and seqno based validation of an incoming segment, flags will
5024 * play significant role here.
5026 static bool tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5027 const struct tcphdr
*th
, int syn_inerr
)
5029 struct tcp_sock
*tp
= tcp_sk(sk
);
5031 /* RFC1323: H1. Apply PAWS check first. */
5032 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
5033 tcp_paws_discard(sk
, skb
)) {
5035 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5036 tcp_send_dupack(sk
, skb
);
5039 /* Reset is accepted even if it did not pass PAWS. */
5042 /* Step 1: check sequence number */
5043 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5044 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5045 * (RST) segments are validated by checking their SEQ-fields."
5046 * And page 69: "If an incoming segment is not acceptable,
5047 * an acknowledgment should be sent in reply (unless the RST
5048 * bit is set, if so drop the segment and return)".
5053 tcp_send_dupack(sk
, skb
);
5058 /* Step 2: check RST bit */
5061 * If sequence number exactly matches RCV.NXT, then
5062 * RESET the connection
5064 * Send a challenge ACK
5066 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
)
5069 tcp_send_challenge_ack(sk
);
5073 /* step 3: check security and precedence [ignored] */
5075 /* step 4: Check for a SYN
5076 * RFC 5691 4.2 : Send a challenge ack
5081 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5082 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNCHALLENGE
);
5083 tcp_send_challenge_ack(sk
);
5095 * TCP receive function for the ESTABLISHED state.
5097 * It is split into a fast path and a slow path. The fast path is
5099 * - A zero window was announced from us - zero window probing
5100 * is only handled properly in the slow path.
5101 * - Out of order segments arrived.
5102 * - Urgent data is expected.
5103 * - There is no buffer space left
5104 * - Unexpected TCP flags/window values/header lengths are received
5105 * (detected by checking the TCP header against pred_flags)
5106 * - Data is sent in both directions. Fast path only supports pure senders
5107 * or pure receivers (this means either the sequence number or the ack
5108 * value must stay constant)
5109 * - Unexpected TCP option.
5111 * When these conditions are not satisfied it drops into a standard
5112 * receive procedure patterned after RFC793 to handle all cases.
5113 * The first three cases are guaranteed by proper pred_flags setting,
5114 * the rest is checked inline. Fast processing is turned on in
5115 * tcp_data_queue when everything is OK.
5117 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5118 const struct tcphdr
*th
, unsigned int len
)
5120 struct tcp_sock
*tp
= tcp_sk(sk
);
5122 if (unlikely(sk
->sk_rx_dst
== NULL
))
5123 inet_csk(sk
)->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5125 * Header prediction.
5126 * The code loosely follows the one in the famous
5127 * "30 instruction TCP receive" Van Jacobson mail.
5129 * Van's trick is to deposit buffers into socket queue
5130 * on a device interrupt, to call tcp_recv function
5131 * on the receive process context and checksum and copy
5132 * the buffer to user space. smart...
5134 * Our current scheme is not silly either but we take the
5135 * extra cost of the net_bh soft interrupt processing...
5136 * We do checksum and copy also but from device to kernel.
5139 tp
->rx_opt
.saw_tstamp
= 0;
5141 /* pred_flags is 0xS?10 << 16 + snd_wnd
5142 * if header_prediction is to be made
5143 * 'S' will always be tp->tcp_header_len >> 2
5144 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5145 * turn it off (when there are holes in the receive
5146 * space for instance)
5147 * PSH flag is ignored.
5150 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5151 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5152 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5153 int tcp_header_len
= tp
->tcp_header_len
;
5155 /* Timestamp header prediction: tcp_header_len
5156 * is automatically equal to th->doff*4 due to pred_flags
5160 /* Check timestamp */
5161 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5162 /* No? Slow path! */
5163 if (!tcp_parse_aligned_timestamp(tp
, th
))
5166 /* If PAWS failed, check it more carefully in slow path */
5167 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5170 /* DO NOT update ts_recent here, if checksum fails
5171 * and timestamp was corrupted part, it will result
5172 * in a hung connection since we will drop all
5173 * future packets due to the PAWS test.
5177 if (len
<= tcp_header_len
) {
5178 /* Bulk data transfer: sender */
5179 if (len
== tcp_header_len
) {
5180 /* Predicted packet is in window by definition.
5181 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5182 * Hence, check seq<=rcv_wup reduces to:
5184 if (tcp_header_len
==
5185 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5186 tp
->rcv_nxt
== tp
->rcv_wup
)
5187 tcp_store_ts_recent(tp
);
5189 /* We know that such packets are checksummed
5192 tcp_ack(sk
, skb
, 0);
5194 tcp_data_snd_check(sk
);
5196 } else { /* Header too small */
5197 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5202 int copied_early
= 0;
5203 bool fragstolen
= false;
5205 if (tp
->copied_seq
== tp
->rcv_nxt
&&
5206 len
- tcp_header_len
<= tp
->ucopy
.len
) {
5207 #ifdef CONFIG_NET_DMA
5208 if (tp
->ucopy
.task
== current
&&
5209 sock_owned_by_user(sk
) &&
5210 tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
5215 if (tp
->ucopy
.task
== current
&&
5216 sock_owned_by_user(sk
) && !copied_early
) {
5217 __set_current_state(TASK_RUNNING
);
5219 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
5223 /* Predicted packet is in window by definition.
5224 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5225 * Hence, check seq<=rcv_wup reduces to:
5227 if (tcp_header_len
==
5228 (sizeof(struct tcphdr
) +
5229 TCPOLEN_TSTAMP_ALIGNED
) &&
5230 tp
->rcv_nxt
== tp
->rcv_wup
)
5231 tcp_store_ts_recent(tp
);
5233 tcp_rcv_rtt_measure_ts(sk
, skb
);
5235 __skb_pull(skb
, tcp_header_len
);
5236 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5237 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5240 tcp_cleanup_rbuf(sk
, skb
->len
);
5243 if (tcp_checksum_complete_user(sk
, skb
))
5246 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5249 /* Predicted packet is in window by definition.
5250 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5251 * Hence, check seq<=rcv_wup reduces to:
5253 if (tcp_header_len
==
5254 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5255 tp
->rcv_nxt
== tp
->rcv_wup
)
5256 tcp_store_ts_recent(tp
);
5258 tcp_rcv_rtt_measure_ts(sk
, skb
);
5260 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5262 /* Bulk data transfer: receiver */
5263 eaten
= tcp_queue_rcv(sk
, skb
, tcp_header_len
,
5267 tcp_event_data_recv(sk
, skb
);
5269 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5270 /* Well, only one small jumplet in fast path... */
5271 tcp_ack(sk
, skb
, FLAG_DATA
);
5272 tcp_data_snd_check(sk
);
5273 if (!inet_csk_ack_scheduled(sk
))
5277 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
5278 __tcp_ack_snd_check(sk
, 0);
5280 #ifdef CONFIG_NET_DMA
5282 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
5286 kfree_skb_partial(skb
, fragstolen
);
5287 sk
->sk_data_ready(sk
, 0);
5293 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5296 if (!th
->ack
&& !th
->rst
)
5300 * Standard slow path.
5303 if (!tcp_validate_incoming(sk
, skb
, th
, 1))
5307 if (tcp_ack(sk
, skb
, FLAG_SLOWPATH
| FLAG_UPDATE_TS_RECENT
) < 0)
5310 tcp_rcv_rtt_measure_ts(sk
, skb
);
5312 /* Process urgent data. */
5313 tcp_urg(sk
, skb
, th
);
5315 /* step 7: process the segment text */
5316 tcp_data_queue(sk
, skb
);
5318 tcp_data_snd_check(sk
);
5319 tcp_ack_snd_check(sk
);
5323 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_CSUMERRORS
);
5324 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5330 EXPORT_SYMBOL(tcp_rcv_established
);
5332 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5334 struct tcp_sock
*tp
= tcp_sk(sk
);
5335 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5337 tcp_set_state(sk
, TCP_ESTABLISHED
);
5338 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5341 icsk
->icsk_af_ops
->sk_rx_dst_set(sk
, skb
);
5342 security_inet_conn_established(sk
, skb
);
5345 /* Make sure socket is routed, for correct metrics. */
5346 icsk
->icsk_af_ops
->rebuild_header(sk
);
5348 tcp_init_metrics(sk
);
5350 tcp_init_congestion_control(sk
);
5352 /* Prevent spurious tcp_cwnd_restart() on first data
5355 tp
->lsndtime
= tcp_time_stamp
;
5357 tcp_init_buffer_space(sk
);
5359 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5360 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5362 if (!tp
->rx_opt
.snd_wscale
)
5363 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5367 if (!sock_flag(sk
, SOCK_DEAD
)) {
5368 sk
->sk_state_change(sk
);
5369 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5373 static bool tcp_rcv_fastopen_synack(struct sock
*sk
, struct sk_buff
*synack
,
5374 struct tcp_fastopen_cookie
*cookie
)
5376 struct tcp_sock
*tp
= tcp_sk(sk
);
5377 struct sk_buff
*data
= tp
->syn_data
? tcp_write_queue_head(sk
) : NULL
;
5378 u16 mss
= tp
->rx_opt
.mss_clamp
;
5381 if (mss
== tp
->rx_opt
.user_mss
) {
5382 struct tcp_options_received opt
;
5384 /* Get original SYNACK MSS value if user MSS sets mss_clamp */
5385 tcp_clear_options(&opt
);
5386 opt
.user_mss
= opt
.mss_clamp
= 0;
5387 tcp_parse_options(synack
, &opt
, 0, NULL
);
5388 mss
= opt
.mss_clamp
;
5391 if (!tp
->syn_fastopen
) /* Ignore an unsolicited cookie */
5394 /* The SYN-ACK neither has cookie nor acknowledges the data. Presumably
5395 * the remote receives only the retransmitted (regular) SYNs: either
5396 * the original SYN-data or the corresponding SYN-ACK is lost.
5398 syn_drop
= (cookie
->len
<= 0 && data
&& tp
->total_retrans
);
5400 tcp_fastopen_cache_set(sk
, mss
, cookie
, syn_drop
);
5402 if (data
) { /* Retransmit unacked data in SYN */
5403 tcp_for_write_queue_from(data
, sk
) {
5404 if (data
== tcp_send_head(sk
) ||
5405 __tcp_retransmit_skb(sk
, data
))
5411 tp
->syn_data_acked
= tp
->syn_data
;
5415 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5416 const struct tcphdr
*th
, unsigned int len
)
5418 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5419 struct tcp_sock
*tp
= tcp_sk(sk
);
5420 struct tcp_fastopen_cookie foc
= { .len
= -1 };
5421 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5423 tcp_parse_options(skb
, &tp
->rx_opt
, 0, &foc
);
5424 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
5425 tp
->rx_opt
.rcv_tsecr
-= tp
->tsoffset
;
5429 * "If the state is SYN-SENT then
5430 * first check the ACK bit
5431 * If the ACK bit is set
5432 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5433 * a reset (unless the RST bit is set, if so drop
5434 * the segment and return)"
5436 if (!after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_una
) ||
5437 after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
))
5438 goto reset_and_undo
;
5440 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5441 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5443 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5444 goto reset_and_undo
;
5447 /* Now ACK is acceptable.
5449 * "If the RST bit is set
5450 * If the ACK was acceptable then signal the user "error:
5451 * connection reset", drop the segment, enter CLOSED state,
5452 * delete TCB, and return."
5461 * "fifth, if neither of the SYN or RST bits is set then
5462 * drop the segment and return."
5468 goto discard_and_undo
;
5471 * "If the SYN bit is on ...
5472 * are acceptable then ...
5473 * (our SYN has been ACKed), change the connection
5474 * state to ESTABLISHED..."
5477 TCP_ECN_rcv_synack(tp
, th
);
5479 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5480 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5482 /* Ok.. it's good. Set up sequence numbers and
5483 * move to established.
5485 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5486 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5488 /* RFC1323: The window in SYN & SYN/ACK segments is
5491 tp
->snd_wnd
= ntohs(th
->window
);
5493 if (!tp
->rx_opt
.wscale_ok
) {
5494 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5495 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5498 if (tp
->rx_opt
.saw_tstamp
) {
5499 tp
->rx_opt
.tstamp_ok
= 1;
5500 tp
->tcp_header_len
=
5501 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5502 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5503 tcp_store_ts_recent(tp
);
5505 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5508 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5509 tcp_enable_fack(tp
);
5512 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5513 tcp_initialize_rcv_mss(sk
);
5515 /* Remember, tcp_poll() does not lock socket!
5516 * Change state from SYN-SENT only after copied_seq
5517 * is initialized. */
5518 tp
->copied_seq
= tp
->rcv_nxt
;
5522 tcp_finish_connect(sk
, skb
);
5524 if ((tp
->syn_fastopen
|| tp
->syn_data
) &&
5525 tcp_rcv_fastopen_synack(sk
, skb
, &foc
))
5528 if (sk
->sk_write_pending
||
5529 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5530 icsk
->icsk_ack
.pingpong
) {
5531 /* Save one ACK. Data will be ready after
5532 * several ticks, if write_pending is set.
5534 * It may be deleted, but with this feature tcpdumps
5535 * look so _wonderfully_ clever, that I was not able
5536 * to stand against the temptation 8) --ANK
5538 inet_csk_schedule_ack(sk
);
5539 tcp_enter_quickack_mode(sk
);
5540 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5541 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5552 /* No ACK in the segment */
5556 * "If the RST bit is set
5558 * Otherwise (no ACK) drop the segment and return."
5561 goto discard_and_undo
;
5565 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5566 tcp_paws_reject(&tp
->rx_opt
, 0))
5567 goto discard_and_undo
;
5570 /* We see SYN without ACK. It is attempt of
5571 * simultaneous connect with crossed SYNs.
5572 * Particularly, it can be connect to self.
5574 tcp_set_state(sk
, TCP_SYN_RECV
);
5576 if (tp
->rx_opt
.saw_tstamp
) {
5577 tp
->rx_opt
.tstamp_ok
= 1;
5578 tcp_store_ts_recent(tp
);
5579 tp
->tcp_header_len
=
5580 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5582 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5585 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5586 tp
->copied_seq
= tp
->rcv_nxt
;
5587 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5589 /* RFC1323: The window in SYN & SYN/ACK segments is
5592 tp
->snd_wnd
= ntohs(th
->window
);
5593 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5594 tp
->max_window
= tp
->snd_wnd
;
5596 TCP_ECN_rcv_syn(tp
, th
);
5599 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5600 tcp_initialize_rcv_mss(sk
);
5602 tcp_send_synack(sk
);
5604 /* Note, we could accept data and URG from this segment.
5605 * There are no obstacles to make this (except that we must
5606 * either change tcp_recvmsg() to prevent it from returning data
5607 * before 3WHS completes per RFC793, or employ TCP Fast Open).
5609 * However, if we ignore data in ACKless segments sometimes,
5610 * we have no reasons to accept it sometimes.
5611 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5612 * is not flawless. So, discard packet for sanity.
5613 * Uncomment this return to process the data.
5620 /* "fifth, if neither of the SYN or RST bits is set then
5621 * drop the segment and return."
5625 tcp_clear_options(&tp
->rx_opt
);
5626 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5630 tcp_clear_options(&tp
->rx_opt
);
5631 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5636 * This function implements the receiving procedure of RFC 793 for
5637 * all states except ESTABLISHED and TIME_WAIT.
5638 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5639 * address independent.
5642 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5643 const struct tcphdr
*th
, unsigned int len
)
5645 struct tcp_sock
*tp
= tcp_sk(sk
);
5646 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5647 struct request_sock
*req
;
5650 tp
->rx_opt
.saw_tstamp
= 0;
5652 switch (sk
->sk_state
) {
5666 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5669 /* Now we have several options: In theory there is
5670 * nothing else in the frame. KA9Q has an option to
5671 * send data with the syn, BSD accepts data with the
5672 * syn up to the [to be] advertised window and
5673 * Solaris 2.1 gives you a protocol error. For now
5674 * we just ignore it, that fits the spec precisely
5675 * and avoids incompatibilities. It would be nice in
5676 * future to drop through and process the data.
5678 * Now that TTCP is starting to be used we ought to
5680 * But, this leaves one open to an easy denial of
5681 * service attack, and SYN cookies can't defend
5682 * against this problem. So, we drop the data
5683 * in the interest of security over speed unless
5684 * it's still in use.
5692 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5696 /* Do step6 onward by hand. */
5697 tcp_urg(sk
, skb
, th
);
5699 tcp_data_snd_check(sk
);
5703 req
= tp
->fastopen_rsk
;
5705 WARN_ON_ONCE(sk
->sk_state
!= TCP_SYN_RECV
&&
5706 sk
->sk_state
!= TCP_FIN_WAIT1
);
5708 if (tcp_check_req(sk
, skb
, req
, NULL
, true) == NULL
)
5712 if (!th
->ack
&& !th
->rst
)
5715 if (!tcp_validate_incoming(sk
, skb
, th
, 0))
5718 /* step 5: check the ACK field */
5720 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
|
5721 FLAG_UPDATE_TS_RECENT
) > 0;
5723 switch (sk
->sk_state
) {
5726 /* Once we leave TCP_SYN_RECV, we no longer
5727 * need req so release it.
5730 tcp_synack_rtt_meas(sk
, req
);
5731 tp
->total_retrans
= req
->num_retrans
;
5733 reqsk_fastopen_remove(sk
, req
, false);
5735 /* Make sure socket is routed, for
5738 icsk
->icsk_af_ops
->rebuild_header(sk
);
5739 tcp_init_congestion_control(sk
);
5742 tcp_init_buffer_space(sk
);
5743 tp
->copied_seq
= tp
->rcv_nxt
;
5746 tcp_set_state(sk
, TCP_ESTABLISHED
);
5747 sk
->sk_state_change(sk
);
5749 /* Note, that this wakeup is only for marginal
5750 * crossed SYN case. Passively open sockets
5751 * are not waked up, because sk->sk_sleep ==
5752 * NULL and sk->sk_socket == NULL.
5756 SOCK_WAKE_IO
, POLL_OUT
);
5758 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5759 tp
->snd_wnd
= ntohs(th
->window
) <<
5760 tp
->rx_opt
.snd_wscale
;
5761 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5763 if (tp
->rx_opt
.tstamp_ok
)
5764 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5767 /* Re-arm the timer because data may
5768 * have been sent out. This is similar
5769 * to the regular data transmission case
5770 * when new data has just been ack'ed.
5772 * (TFO) - we could try to be more
5773 * aggressive and retranmitting any data
5774 * sooner based on when they were sent
5779 tcp_init_metrics(sk
);
5781 tcp_update_pacing_rate(sk
);
5783 /* Prevent spurious tcp_cwnd_restart() on
5784 * first data packet.
5786 tp
->lsndtime
= tcp_time_stamp
;
5788 tcp_initialize_rcv_mss(sk
);
5789 tcp_fast_path_on(tp
);
5796 /* If we enter the TCP_FIN_WAIT1 state and we are a
5797 * Fast Open socket and this is the first acceptable
5798 * ACK we have received, this would have acknowledged
5799 * our SYNACK so stop the SYNACK timer.
5802 /* Return RST if ack_seq is invalid.
5803 * Note that RFC793 only says to generate a
5804 * DUPACK for it but for TCP Fast Open it seems
5805 * better to treat this case like TCP_SYN_RECV
5810 /* We no longer need the request sock. */
5811 reqsk_fastopen_remove(sk
, req
, false);
5814 if (tp
->snd_una
== tp
->write_seq
) {
5815 struct dst_entry
*dst
;
5817 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5818 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5820 dst
= __sk_dst_get(sk
);
5824 if (!sock_flag(sk
, SOCK_DEAD
))
5825 /* Wake up lingering close() */
5826 sk
->sk_state_change(sk
);
5830 if (tp
->linger2
< 0 ||
5831 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5832 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5834 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5838 tmo
= tcp_fin_time(sk
);
5839 if (tmo
> TCP_TIMEWAIT_LEN
) {
5840 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5841 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5842 /* Bad case. We could lose such FIN otherwise.
5843 * It is not a big problem, but it looks confusing
5844 * and not so rare event. We still can lose it now,
5845 * if it spins in bh_lock_sock(), but it is really
5848 inet_csk_reset_keepalive_timer(sk
, tmo
);
5850 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5858 if (tp
->snd_una
== tp
->write_seq
) {
5859 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5865 if (tp
->snd_una
== tp
->write_seq
) {
5866 tcp_update_metrics(sk
);
5874 /* step 6: check the URG bit */
5875 tcp_urg(sk
, skb
, th
);
5877 /* step 7: process the segment text */
5878 switch (sk
->sk_state
) {
5879 case TCP_CLOSE_WAIT
:
5882 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5886 /* RFC 793 says to queue data in these states,
5887 * RFC 1122 says we MUST send a reset.
5888 * BSD 4.4 also does reset.
5890 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5891 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5892 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5893 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5899 case TCP_ESTABLISHED
:
5900 tcp_data_queue(sk
, skb
);
5905 /* tcp_data could move socket to TIME-WAIT */
5906 if (sk
->sk_state
!= TCP_CLOSE
) {
5907 tcp_data_snd_check(sk
);
5908 tcp_ack_snd_check(sk
);
5917 EXPORT_SYMBOL(tcp_rcv_state_process
);