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>
73 #include <net/inet_common.h>
74 #include <linux/ipsec.h>
75 #include <asm/unaligned.h>
76 #include <net/netdma.h>
78 int sysctl_tcp_timestamps __read_mostly
= 1;
79 int sysctl_tcp_window_scaling __read_mostly
= 1;
80 int sysctl_tcp_sack __read_mostly
= 1;
81 int sysctl_tcp_fack __read_mostly
= 1;
82 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
83 EXPORT_SYMBOL(sysctl_tcp_reordering
);
84 int sysctl_tcp_ecn __read_mostly
= 2;
85 EXPORT_SYMBOL(sysctl_tcp_ecn
);
86 int sysctl_tcp_dsack __read_mostly
= 1;
87 int sysctl_tcp_app_win __read_mostly
= 31;
88 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
89 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
91 int sysctl_tcp_stdurg __read_mostly
;
92 int sysctl_tcp_rfc1337 __read_mostly
;
93 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
94 int sysctl_tcp_frto __read_mostly
= 2;
95 int sysctl_tcp_frto_response __read_mostly
;
96 int sysctl_tcp_nometrics_save __read_mostly
;
98 int sysctl_tcp_thin_dupack __read_mostly
;
100 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
101 int sysctl_tcp_abc __read_mostly
;
102 int sysctl_tcp_early_retrans __read_mostly
= 2;
104 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
105 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
106 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
107 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
108 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
109 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
110 #define FLAG_ECE 0x40 /* ECE in this ACK */
111 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
112 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
113 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
114 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
115 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
116 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
118 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
119 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
120 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
121 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
122 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
124 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
125 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
127 /* Adapt the MSS value used to make delayed ack decision to the
130 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
132 struct inet_connection_sock
*icsk
= inet_csk(sk
);
133 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
136 icsk
->icsk_ack
.last_seg_size
= 0;
138 /* skb->len may jitter because of SACKs, even if peer
139 * sends good full-sized frames.
141 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
142 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
143 icsk
->icsk_ack
.rcv_mss
= len
;
145 /* Otherwise, we make more careful check taking into account,
146 * that SACKs block is variable.
148 * "len" is invariant segment length, including TCP header.
150 len
+= skb
->data
- skb_transport_header(skb
);
151 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
152 /* If PSH is not set, packet should be
153 * full sized, provided peer TCP is not badly broken.
154 * This observation (if it is correct 8)) allows
155 * to handle super-low mtu links fairly.
157 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
158 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
159 /* Subtract also invariant (if peer is RFC compliant),
160 * tcp header plus fixed timestamp option length.
161 * Resulting "len" is MSS free of SACK jitter.
163 len
-= tcp_sk(sk
)->tcp_header_len
;
164 icsk
->icsk_ack
.last_seg_size
= len
;
166 icsk
->icsk_ack
.rcv_mss
= len
;
170 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
171 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
172 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
176 static void tcp_incr_quickack(struct sock
*sk
)
178 struct inet_connection_sock
*icsk
= inet_csk(sk
);
179 unsigned int quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
183 if (quickacks
> icsk
->icsk_ack
.quick
)
184 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
187 static void tcp_enter_quickack_mode(struct sock
*sk
)
189 struct inet_connection_sock
*icsk
= inet_csk(sk
);
190 tcp_incr_quickack(sk
);
191 icsk
->icsk_ack
.pingpong
= 0;
192 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
195 /* Send ACKs quickly, if "quick" count is not exhausted
196 * and the session is not interactive.
199 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
201 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
202 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
205 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
207 if (tp
->ecn_flags
& TCP_ECN_OK
)
208 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
211 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
213 if (tcp_hdr(skb
)->cwr
)
214 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
217 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
219 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
222 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
224 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
227 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
228 case INET_ECN_NOT_ECT
:
229 /* Funny extension: if ECT is not set on a segment,
230 * and we already seen ECT on a previous segment,
231 * it is probably a retransmit.
233 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
234 tcp_enter_quickack_mode((struct sock
*)tp
);
237 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
240 tp
->ecn_flags
|= TCP_ECN_SEEN
;
244 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
246 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
247 tp
->ecn_flags
&= ~TCP_ECN_OK
;
250 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
252 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
253 tp
->ecn_flags
&= ~TCP_ECN_OK
;
256 static inline int TCP_ECN_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
258 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
263 /* Buffer size and advertised window tuning.
265 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
268 static void tcp_fixup_sndbuf(struct sock
*sk
)
270 int sndmem
= SKB_TRUESIZE(tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
);
272 sndmem
*= TCP_INIT_CWND
;
273 if (sk
->sk_sndbuf
< sndmem
)
274 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
277 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
279 * All tcp_full_space() is split to two parts: "network" buffer, allocated
280 * forward and advertised in receiver window (tp->rcv_wnd) and
281 * "application buffer", required to isolate scheduling/application
282 * latencies from network.
283 * window_clamp is maximal advertised window. It can be less than
284 * tcp_full_space(), in this case tcp_full_space() - window_clamp
285 * is reserved for "application" buffer. The less window_clamp is
286 * the smoother our behaviour from viewpoint of network, but the lower
287 * throughput and the higher sensitivity of the connection to losses. 8)
289 * rcv_ssthresh is more strict window_clamp used at "slow start"
290 * phase to predict further behaviour of this connection.
291 * It is used for two goals:
292 * - to enforce header prediction at sender, even when application
293 * requires some significant "application buffer". It is check #1.
294 * - to prevent pruning of receive queue because of misprediction
295 * of receiver window. Check #2.
297 * The scheme does not work when sender sends good segments opening
298 * window and then starts to feed us spaghetti. But it should work
299 * in common situations. Otherwise, we have to rely on queue collapsing.
302 /* Slow part of check#2. */
303 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
305 struct tcp_sock
*tp
= tcp_sk(sk
);
307 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
308 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
310 while (tp
->rcv_ssthresh
<= window
) {
311 if (truesize
<= skb
->len
)
312 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
320 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
322 struct tcp_sock
*tp
= tcp_sk(sk
);
325 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
326 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
327 !sk_under_memory_pressure(sk
)) {
330 /* Check #2. Increase window, if skb with such overhead
331 * will fit to rcvbuf in future.
333 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
334 incr
= 2 * tp
->advmss
;
336 incr
= __tcp_grow_window(sk
, skb
);
339 incr
= max_t(int, incr
, 2 * skb
->len
);
340 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
342 inet_csk(sk
)->icsk_ack
.quick
|= 1;
347 /* 3. Tuning rcvbuf, when connection enters established state. */
349 static void tcp_fixup_rcvbuf(struct sock
*sk
)
351 u32 mss
= tcp_sk(sk
)->advmss
;
352 u32 icwnd
= TCP_DEFAULT_INIT_RCVWND
;
355 /* Limit to 10 segments if mss <= 1460,
356 * or 14600/mss segments, with a minimum of two segments.
359 icwnd
= max_t(u32
, (1460 * TCP_DEFAULT_INIT_RCVWND
) / mss
, 2);
361 rcvmem
= SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
);
362 while (tcp_win_from_space(rcvmem
) < mss
)
367 if (sk
->sk_rcvbuf
< rcvmem
)
368 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
371 /* 4. Try to fixup all. It is made immediately after connection enters
374 static void tcp_init_buffer_space(struct sock
*sk
)
376 struct tcp_sock
*tp
= tcp_sk(sk
);
379 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
380 tcp_fixup_rcvbuf(sk
);
381 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
382 tcp_fixup_sndbuf(sk
);
384 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
386 maxwin
= tcp_full_space(sk
);
388 if (tp
->window_clamp
>= maxwin
) {
389 tp
->window_clamp
= maxwin
;
391 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
392 tp
->window_clamp
= max(maxwin
-
393 (maxwin
>> sysctl_tcp_app_win
),
397 /* Force reservation of one segment. */
398 if (sysctl_tcp_app_win
&&
399 tp
->window_clamp
> 2 * tp
->advmss
&&
400 tp
->window_clamp
+ tp
->advmss
> maxwin
)
401 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
403 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
404 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
407 /* 5. Recalculate window clamp after socket hit its memory bounds. */
408 static void tcp_clamp_window(struct sock
*sk
)
410 struct tcp_sock
*tp
= tcp_sk(sk
);
411 struct inet_connection_sock
*icsk
= inet_csk(sk
);
413 icsk
->icsk_ack
.quick
= 0;
415 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
416 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
417 !sk_under_memory_pressure(sk
) &&
418 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
419 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
422 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
423 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
426 /* Initialize RCV_MSS value.
427 * RCV_MSS is an our guess about MSS used by the peer.
428 * We haven't any direct information about the MSS.
429 * It's better to underestimate the RCV_MSS rather than overestimate.
430 * Overestimations make us ACKing less frequently than needed.
431 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
433 void tcp_initialize_rcv_mss(struct sock
*sk
)
435 const struct tcp_sock
*tp
= tcp_sk(sk
);
436 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
438 hint
= min(hint
, tp
->rcv_wnd
/ 2);
439 hint
= min(hint
, TCP_MSS_DEFAULT
);
440 hint
= max(hint
, TCP_MIN_MSS
);
442 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
444 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
446 /* Receiver "autotuning" code.
448 * The algorithm for RTT estimation w/o timestamps is based on
449 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
450 * <http://public.lanl.gov/radiant/pubs.html#DRS>
452 * More detail on this code can be found at
453 * <http://staff.psc.edu/jheffner/>,
454 * though this reference is out of date. A new paper
457 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
459 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
465 if (new_sample
!= 0) {
466 /* If we sample in larger samples in the non-timestamp
467 * case, we could grossly overestimate the RTT especially
468 * with chatty applications or bulk transfer apps which
469 * are stalled on filesystem I/O.
471 * Also, since we are only going for a minimum in the
472 * non-timestamp case, we do not smooth things out
473 * else with timestamps disabled convergence takes too
477 m
-= (new_sample
>> 3);
485 /* No previous measure. */
489 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
490 tp
->rcv_rtt_est
.rtt
= new_sample
;
493 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
495 if (tp
->rcv_rtt_est
.time
== 0)
497 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
499 tcp_rcv_rtt_update(tp
, jiffies
- tp
->rcv_rtt_est
.time
, 1);
502 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
503 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
506 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
507 const struct sk_buff
*skb
)
509 struct tcp_sock
*tp
= tcp_sk(sk
);
510 if (tp
->rx_opt
.rcv_tsecr
&&
511 (TCP_SKB_CB(skb
)->end_seq
-
512 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
513 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
517 * This function should be called every time data is copied to user space.
518 * It calculates the appropriate TCP receive buffer space.
520 void tcp_rcv_space_adjust(struct sock
*sk
)
522 struct tcp_sock
*tp
= tcp_sk(sk
);
526 if (tp
->rcvq_space
.time
== 0)
529 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
530 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
533 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
535 space
= max(tp
->rcvq_space
.space
, space
);
537 if (tp
->rcvq_space
.space
!= space
) {
540 tp
->rcvq_space
.space
= space
;
542 if (sysctl_tcp_moderate_rcvbuf
&&
543 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
544 int new_clamp
= space
;
546 /* Receive space grows, normalize in order to
547 * take into account packet headers and sk_buff
548 * structure overhead.
553 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
554 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
557 space
= min(space
, sysctl_tcp_rmem
[2]);
558 if (space
> sk
->sk_rcvbuf
) {
559 sk
->sk_rcvbuf
= space
;
561 /* Make the window clamp follow along. */
562 tp
->window_clamp
= new_clamp
;
568 tp
->rcvq_space
.seq
= tp
->copied_seq
;
569 tp
->rcvq_space
.time
= tcp_time_stamp
;
572 /* There is something which you must keep in mind when you analyze the
573 * behavior of the tp->ato delayed ack timeout interval. When a
574 * connection starts up, we want to ack as quickly as possible. The
575 * problem is that "good" TCP's do slow start at the beginning of data
576 * transmission. The means that until we send the first few ACK's the
577 * sender will sit on his end and only queue most of his data, because
578 * he can only send snd_cwnd unacked packets at any given time. For
579 * each ACK we send, he increments snd_cwnd and transmits more of his
582 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
584 struct tcp_sock
*tp
= tcp_sk(sk
);
585 struct inet_connection_sock
*icsk
= inet_csk(sk
);
588 inet_csk_schedule_ack(sk
);
590 tcp_measure_rcv_mss(sk
, skb
);
592 tcp_rcv_rtt_measure(tp
);
594 now
= tcp_time_stamp
;
596 if (!icsk
->icsk_ack
.ato
) {
597 /* The _first_ data packet received, initialize
598 * delayed ACK engine.
600 tcp_incr_quickack(sk
);
601 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
603 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
605 if (m
<= TCP_ATO_MIN
/ 2) {
606 /* The fastest case is the first. */
607 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
608 } else if (m
< icsk
->icsk_ack
.ato
) {
609 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
610 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
611 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
612 } else if (m
> icsk
->icsk_rto
) {
613 /* Too long gap. Apparently sender failed to
614 * restart window, so that we send ACKs quickly.
616 tcp_incr_quickack(sk
);
620 icsk
->icsk_ack
.lrcvtime
= now
;
622 TCP_ECN_check_ce(tp
, skb
);
625 tcp_grow_window(sk
, skb
);
628 /* Called to compute a smoothed rtt estimate. The data fed to this
629 * routine either comes from timestamps, or from segments that were
630 * known _not_ to have been retransmitted [see Karn/Partridge
631 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
632 * piece by Van Jacobson.
633 * NOTE: the next three routines used to be one big routine.
634 * To save cycles in the RFC 1323 implementation it was better to break
635 * it up into three procedures. -- erics
637 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
639 struct tcp_sock
*tp
= tcp_sk(sk
);
640 long m
= mrtt
; /* RTT */
642 /* The following amusing code comes from Jacobson's
643 * article in SIGCOMM '88. Note that rtt and mdev
644 * are scaled versions of rtt and mean deviation.
645 * This is designed to be as fast as possible
646 * m stands for "measurement".
648 * On a 1990 paper the rto value is changed to:
649 * RTO = rtt + 4 * mdev
651 * Funny. This algorithm seems to be very broken.
652 * These formulae increase RTO, when it should be decreased, increase
653 * too slowly, when it should be increased quickly, decrease too quickly
654 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
655 * does not matter how to _calculate_ it. Seems, it was trap
656 * that VJ failed to avoid. 8)
661 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
662 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
664 m
= -m
; /* m is now abs(error) */
665 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
666 /* This is similar to one of Eifel findings.
667 * Eifel blocks mdev updates when rtt decreases.
668 * This solution is a bit different: we use finer gain
669 * for mdev in this case (alpha*beta).
670 * Like Eifel it also prevents growth of rto,
671 * but also it limits too fast rto decreases,
672 * happening in pure Eifel.
677 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
679 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
680 if (tp
->mdev
> tp
->mdev_max
) {
681 tp
->mdev_max
= tp
->mdev
;
682 if (tp
->mdev_max
> tp
->rttvar
)
683 tp
->rttvar
= tp
->mdev_max
;
685 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
686 if (tp
->mdev_max
< tp
->rttvar
)
687 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
688 tp
->rtt_seq
= tp
->snd_nxt
;
689 tp
->mdev_max
= tcp_rto_min(sk
);
692 /* no previous measure. */
693 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
694 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
695 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
696 tp
->rtt_seq
= tp
->snd_nxt
;
700 /* Calculate rto without backoff. This is the second half of Van Jacobson's
701 * routine referred to above.
703 static inline void tcp_set_rto(struct sock
*sk
)
705 const struct tcp_sock
*tp
= tcp_sk(sk
);
706 /* Old crap is replaced with new one. 8)
709 * 1. If rtt variance happened to be less 50msec, it is hallucination.
710 * It cannot be less due to utterly erratic ACK generation made
711 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
712 * to do with delayed acks, because at cwnd>2 true delack timeout
713 * is invisible. Actually, Linux-2.4 also generates erratic
714 * ACKs in some circumstances.
716 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
718 /* 2. Fixups made earlier cannot be right.
719 * If we do not estimate RTO correctly without them,
720 * all the algo is pure shit and should be replaced
721 * with correct one. It is exactly, which we pretend to do.
724 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
725 * guarantees that rto is higher.
730 /* Save metrics learned by this TCP session.
731 This function is called only, when TCP finishes successfully
732 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
734 void tcp_update_metrics(struct sock
*sk
)
736 struct tcp_sock
*tp
= tcp_sk(sk
);
737 struct dst_entry
*dst
= __sk_dst_get(sk
);
739 if (sysctl_tcp_nometrics_save
)
744 if (dst
&& (dst
->flags
& DST_HOST
)) {
745 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
749 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
750 /* This session failed to estimate rtt. Why?
751 * Probably, no packets returned in time.
754 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
755 dst_metric_set(dst
, RTAX_RTT
, 0);
759 rtt
= dst_metric_rtt(dst
, RTAX_RTT
);
762 /* If newly calculated rtt larger than stored one,
763 * store new one. Otherwise, use EWMA. Remember,
764 * rtt overestimation is always better than underestimation.
766 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
768 set_dst_metric_rtt(dst
, RTAX_RTT
, tp
->srtt
);
770 set_dst_metric_rtt(dst
, RTAX_RTT
, rtt
- (m
>> 3));
773 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
778 /* Scale deviation to rttvar fixed point */
783 var
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
787 var
-= (var
- m
) >> 2;
789 set_dst_metric_rtt(dst
, RTAX_RTTVAR
, var
);
792 if (tcp_in_initial_slowstart(tp
)) {
793 /* Slow start still did not finish. */
794 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
795 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
796 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
797 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_cwnd
>> 1);
798 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
799 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
800 dst_metric_set(dst
, RTAX_CWND
, tp
->snd_cwnd
);
801 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
802 icsk
->icsk_ca_state
== TCP_CA_Open
) {
803 /* Cong. avoidance phase, cwnd is reliable. */
804 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
805 dst_metric_set(dst
, RTAX_SSTHRESH
,
806 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
));
807 if (!dst_metric_locked(dst
, RTAX_CWND
))
808 dst_metric_set(dst
, RTAX_CWND
,
809 (dst_metric(dst
, RTAX_CWND
) +
812 /* Else slow start did not finish, cwnd is non-sense,
813 ssthresh may be also invalid.
815 if (!dst_metric_locked(dst
, RTAX_CWND
))
816 dst_metric_set(dst
, RTAX_CWND
,
817 (dst_metric(dst
, RTAX_CWND
) +
818 tp
->snd_ssthresh
) >> 1);
819 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
820 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
821 tp
->snd_ssthresh
> dst_metric(dst
, RTAX_SSTHRESH
))
822 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_ssthresh
);
825 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
826 if (dst_metric(dst
, RTAX_REORDERING
) < tp
->reordering
&&
827 tp
->reordering
!= sysctl_tcp_reordering
)
828 dst_metric_set(dst
, RTAX_REORDERING
, tp
->reordering
);
833 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
835 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
838 cwnd
= TCP_INIT_CWND
;
839 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
842 /* Set slow start threshold and cwnd not falling to slow start */
843 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
845 struct tcp_sock
*tp
= tcp_sk(sk
);
846 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
848 tp
->prior_ssthresh
= 0;
850 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
853 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
854 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
855 tcp_packets_in_flight(tp
) + 1U);
856 tp
->snd_cwnd_cnt
= 0;
857 tp
->high_seq
= tp
->snd_nxt
;
858 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
859 TCP_ECN_queue_cwr(tp
);
861 tcp_set_ca_state(sk
, TCP_CA_CWR
);
866 * Packet counting of FACK is based on in-order assumptions, therefore TCP
867 * disables it when reordering is detected
869 static void tcp_disable_fack(struct tcp_sock
*tp
)
871 /* RFC3517 uses different metric in lost marker => reset on change */
873 tp
->lost_skb_hint
= NULL
;
874 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
877 /* Take a notice that peer is sending D-SACKs */
878 static void tcp_dsack_seen(struct tcp_sock
*tp
)
880 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
883 /* Initialize metrics on socket. */
885 static void tcp_init_metrics(struct sock
*sk
)
887 struct tcp_sock
*tp
= tcp_sk(sk
);
888 struct dst_entry
*dst
= __sk_dst_get(sk
);
895 if (dst_metric_locked(dst
, RTAX_CWND
))
896 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
897 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
898 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
899 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
900 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
902 /* ssthresh may have been reduced unnecessarily during.
903 * 3WHS. Restore it back to its initial default.
905 tp
->snd_ssthresh
= TCP_INFINITE_SSTHRESH
;
907 if (dst_metric(dst
, RTAX_REORDERING
) &&
908 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
909 tcp_disable_fack(tp
);
910 tcp_disable_early_retrans(tp
);
911 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
914 if (dst_metric(dst
, RTAX_RTT
) == 0 || tp
->srtt
== 0)
917 /* Initial rtt is determined from SYN,SYN-ACK.
918 * The segment is small and rtt may appear much
919 * less than real one. Use per-dst memory
920 * to make it more realistic.
922 * A bit of theory. RTT is time passed after "normal" sized packet
923 * is sent until it is ACKed. In normal circumstances sending small
924 * packets force peer to delay ACKs and calculation is correct too.
925 * The algorithm is adaptive and, provided we follow specs, it
926 * NEVER underestimate RTT. BUT! If peer tries to make some clever
927 * tricks sort of "quick acks" for time long enough to decrease RTT
928 * to low value, and then abruptly stops to do it and starts to delay
929 * ACKs, wait for troubles.
931 if (dst_metric_rtt(dst
, RTAX_RTT
) > tp
->srtt
) {
932 tp
->srtt
= dst_metric_rtt(dst
, RTAX_RTT
);
933 tp
->rtt_seq
= tp
->snd_nxt
;
935 if (dst_metric_rtt(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
936 tp
->mdev
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
937 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
942 /* RFC6298: 5.7 We've failed to get a valid RTT sample from
943 * 3WHS. This is most likely due to retransmission,
944 * including spurious one. Reset the RTO back to 3secs
945 * from the more aggressive 1sec to avoid more spurious
948 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_FALLBACK
;
949 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_FALLBACK
;
951 /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
952 * retransmitted. In light of RFC6298 more aggressive 1sec
953 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
954 * retransmission has occurred.
956 if (tp
->total_retrans
> 1)
959 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
960 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
963 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
966 struct tcp_sock
*tp
= tcp_sk(sk
);
967 if (metric
> tp
->reordering
) {
970 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
972 /* This exciting event is worth to be remembered. 8) */
974 mib_idx
= LINUX_MIB_TCPTSREORDER
;
975 else if (tcp_is_reno(tp
))
976 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
977 else if (tcp_is_fack(tp
))
978 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
980 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
982 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
983 #if FASTRETRANS_DEBUG > 1
984 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
985 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
989 tp
->undo_marker
? tp
->undo_retrans
: 0);
991 tcp_disable_fack(tp
);
995 tcp_disable_early_retrans(tp
);
998 /* This must be called before lost_out is incremented */
999 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
1001 if ((tp
->retransmit_skb_hint
== NULL
) ||
1002 before(TCP_SKB_CB(skb
)->seq
,
1003 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
1004 tp
->retransmit_skb_hint
= skb
;
1006 if (!tp
->lost_out
||
1007 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
1008 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1011 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
1013 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1014 tcp_verify_retransmit_hint(tp
, skb
);
1016 tp
->lost_out
+= tcp_skb_pcount(skb
);
1017 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1021 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
1022 struct sk_buff
*skb
)
1024 tcp_verify_retransmit_hint(tp
, skb
);
1026 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1027 tp
->lost_out
+= tcp_skb_pcount(skb
);
1028 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1032 /* This procedure tags the retransmission queue when SACKs arrive.
1034 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1035 * Packets in queue with these bits set are counted in variables
1036 * sacked_out, retrans_out and lost_out, correspondingly.
1038 * Valid combinations are:
1039 * Tag InFlight Description
1040 * 0 1 - orig segment is in flight.
1041 * S 0 - nothing flies, orig reached receiver.
1042 * L 0 - nothing flies, orig lost by net.
1043 * R 2 - both orig and retransmit are in flight.
1044 * L|R 1 - orig is lost, retransmit is in flight.
1045 * S|R 1 - orig reached receiver, retrans is still in flight.
1046 * (L|S|R is logically valid, it could occur when L|R is sacked,
1047 * but it is equivalent to plain S and code short-curcuits it to S.
1048 * L|S is logically invalid, it would mean -1 packet in flight 8))
1050 * These 6 states form finite state machine, controlled by the following events:
1051 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1052 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1053 * 3. Loss detection event of two flavors:
1054 * A. Scoreboard estimator decided the packet is lost.
1055 * A'. Reno "three dupacks" marks head of queue lost.
1056 * A''. Its FACK modification, head until snd.fack is lost.
1057 * B. SACK arrives sacking SND.NXT at the moment, when the
1058 * segment was retransmitted.
1059 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1061 * It is pleasant to note, that state diagram turns out to be commutative,
1062 * so that we are allowed not to be bothered by order of our actions,
1063 * when multiple events arrive simultaneously. (see the function below).
1065 * Reordering detection.
1066 * --------------------
1067 * Reordering metric is maximal distance, which a packet can be displaced
1068 * in packet stream. With SACKs we can estimate it:
1070 * 1. SACK fills old hole and the corresponding segment was not
1071 * ever retransmitted -> reordering. Alas, we cannot use it
1072 * when segment was retransmitted.
1073 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1074 * for retransmitted and already SACKed segment -> reordering..
1075 * Both of these heuristics are not used in Loss state, when we cannot
1076 * account for retransmits accurately.
1078 * SACK block validation.
1079 * ----------------------
1081 * SACK block range validation checks that the received SACK block fits to
1082 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1083 * Note that SND.UNA is not included to the range though being valid because
1084 * it means that the receiver is rather inconsistent with itself reporting
1085 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1086 * perfectly valid, however, in light of RFC2018 which explicitly states
1087 * that "SACK block MUST reflect the newest segment. Even if the newest
1088 * segment is going to be discarded ...", not that it looks very clever
1089 * in case of head skb. Due to potentional receiver driven attacks, we
1090 * choose to avoid immediate execution of a walk in write queue due to
1091 * reneging and defer head skb's loss recovery to standard loss recovery
1092 * procedure that will eventually trigger (nothing forbids us doing this).
1094 * Implements also blockage to start_seq wrap-around. Problem lies in the
1095 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1096 * there's no guarantee that it will be before snd_nxt (n). The problem
1097 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1100 * <- outs wnd -> <- wrapzone ->
1101 * u e n u_w e_w s n_w
1103 * |<------------+------+----- TCP seqno space --------------+---------->|
1104 * ...-- <2^31 ->| |<--------...
1105 * ...---- >2^31 ------>| |<--------...
1107 * Current code wouldn't be vulnerable but it's better still to discard such
1108 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1109 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1110 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1111 * equal to the ideal case (infinite seqno space without wrap caused issues).
1113 * With D-SACK the lower bound is extended to cover sequence space below
1114 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1115 * again, D-SACK block must not to go across snd_una (for the same reason as
1116 * for the normal SACK blocks, explained above). But there all simplicity
1117 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1118 * fully below undo_marker they do not affect behavior in anyway and can
1119 * therefore be safely ignored. In rare cases (which are more or less
1120 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1121 * fragmentation and packet reordering past skb's retransmission. To consider
1122 * them correctly, the acceptable range must be extended even more though
1123 * the exact amount is rather hard to quantify. However, tp->max_window can
1124 * be used as an exaggerated estimate.
1126 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1127 u32 start_seq
, u32 end_seq
)
1129 /* Too far in future, or reversed (interpretation is ambiguous) */
1130 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1133 /* Nasty start_seq wrap-around check (see comments above) */
1134 if (!before(start_seq
, tp
->snd_nxt
))
1137 /* In outstanding window? ...This is valid exit for D-SACKs too.
1138 * start_seq == snd_una is non-sensical (see comments above)
1140 if (after(start_seq
, tp
->snd_una
))
1143 if (!is_dsack
|| !tp
->undo_marker
)
1146 /* ...Then it's D-SACK, and must reside below snd_una completely */
1147 if (after(end_seq
, tp
->snd_una
))
1150 if (!before(start_seq
, tp
->undo_marker
))
1154 if (!after(end_seq
, tp
->undo_marker
))
1157 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1158 * start_seq < undo_marker and end_seq >= undo_marker.
1160 return !before(start_seq
, end_seq
- tp
->max_window
);
1163 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1164 * Event "B". Later note: FACK people cheated me again 8), we have to account
1165 * for reordering! Ugly, but should help.
1167 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1168 * less than what is now known to be received by the other end (derived from
1169 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1170 * retransmitted skbs to avoid some costly processing per ACKs.
1172 static void tcp_mark_lost_retrans(struct sock
*sk
)
1174 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1175 struct tcp_sock
*tp
= tcp_sk(sk
);
1176 struct sk_buff
*skb
;
1178 u32 new_low_seq
= tp
->snd_nxt
;
1179 u32 received_upto
= tcp_highest_sack_seq(tp
);
1181 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1182 !after(received_upto
, tp
->lost_retrans_low
) ||
1183 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1186 tcp_for_write_queue(skb
, sk
) {
1187 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1189 if (skb
== tcp_send_head(sk
))
1191 if (cnt
== tp
->retrans_out
)
1193 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1196 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1199 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1200 * constraint here (see above) but figuring out that at
1201 * least tp->reordering SACK blocks reside between ack_seq
1202 * and received_upto is not easy task to do cheaply with
1203 * the available datastructures.
1205 * Whether FACK should check here for tp->reordering segs
1206 * in-between one could argue for either way (it would be
1207 * rather simple to implement as we could count fack_count
1208 * during the walk and do tp->fackets_out - fack_count).
1210 if (after(received_upto
, ack_seq
)) {
1211 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1212 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1214 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1215 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1217 if (before(ack_seq
, new_low_seq
))
1218 new_low_seq
= ack_seq
;
1219 cnt
+= tcp_skb_pcount(skb
);
1223 if (tp
->retrans_out
)
1224 tp
->lost_retrans_low
= new_low_seq
;
1227 static int tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1228 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1231 struct tcp_sock
*tp
= tcp_sk(sk
);
1232 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1233 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1236 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1239 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1240 } else if (num_sacks
> 1) {
1241 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1242 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1244 if (!after(end_seq_0
, end_seq_1
) &&
1245 !before(start_seq_0
, start_seq_1
)) {
1248 NET_INC_STATS_BH(sock_net(sk
),
1249 LINUX_MIB_TCPDSACKOFORECV
);
1253 /* D-SACK for already forgotten data... Do dumb counting. */
1254 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
&&
1255 !after(end_seq_0
, prior_snd_una
) &&
1256 after(end_seq_0
, tp
->undo_marker
))
1262 struct tcp_sacktag_state
{
1268 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1269 * the incoming SACK may not exactly match but we can find smaller MSS
1270 * aligned portion of it that matches. Therefore we might need to fragment
1271 * which may fail and creates some hassle (caller must handle error case
1274 * FIXME: this could be merged to shift decision code
1276 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1277 u32 start_seq
, u32 end_seq
)
1280 unsigned int pkt_len
;
1283 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1284 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1286 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1287 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1288 mss
= tcp_skb_mss(skb
);
1289 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1292 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1296 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1301 /* Round if necessary so that SACKs cover only full MSSes
1302 * and/or the remaining small portion (if present)
1304 if (pkt_len
> mss
) {
1305 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1306 if (!in_sack
&& new_len
< pkt_len
) {
1308 if (new_len
> skb
->len
)
1313 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
);
1321 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1322 static u8
tcp_sacktag_one(struct sock
*sk
,
1323 struct tcp_sacktag_state
*state
, u8 sacked
,
1324 u32 start_seq
, u32 end_seq
,
1325 int dup_sack
, int pcount
)
1327 struct tcp_sock
*tp
= tcp_sk(sk
);
1328 int fack_count
= state
->fack_count
;
1330 /* Account D-SACK for retransmitted packet. */
1331 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1332 if (tp
->undo_marker
&& tp
->undo_retrans
&&
1333 after(end_seq
, tp
->undo_marker
))
1335 if (sacked
& TCPCB_SACKED_ACKED
)
1336 state
->reord
= min(fack_count
, state
->reord
);
1339 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1340 if (!after(end_seq
, tp
->snd_una
))
1343 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1344 if (sacked
& TCPCB_SACKED_RETRANS
) {
1345 /* If the segment is not tagged as lost,
1346 * we do not clear RETRANS, believing
1347 * that retransmission is still in flight.
1349 if (sacked
& TCPCB_LOST
) {
1350 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1351 tp
->lost_out
-= pcount
;
1352 tp
->retrans_out
-= pcount
;
1355 if (!(sacked
& TCPCB_RETRANS
)) {
1356 /* New sack for not retransmitted frame,
1357 * which was in hole. It is reordering.
1359 if (before(start_seq
,
1360 tcp_highest_sack_seq(tp
)))
1361 state
->reord
= min(fack_count
,
1364 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1365 if (!after(end_seq
, tp
->frto_highmark
))
1366 state
->flag
|= FLAG_ONLY_ORIG_SACKED
;
1369 if (sacked
& TCPCB_LOST
) {
1370 sacked
&= ~TCPCB_LOST
;
1371 tp
->lost_out
-= pcount
;
1375 sacked
|= TCPCB_SACKED_ACKED
;
1376 state
->flag
|= FLAG_DATA_SACKED
;
1377 tp
->sacked_out
+= pcount
;
1379 fack_count
+= pcount
;
1381 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1382 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1383 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1384 tp
->lost_cnt_hint
+= pcount
;
1386 if (fack_count
> tp
->fackets_out
)
1387 tp
->fackets_out
= fack_count
;
1390 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1391 * frames and clear it. undo_retrans is decreased above, L|R frames
1392 * are accounted above as well.
1394 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1395 sacked
&= ~TCPCB_SACKED_RETRANS
;
1396 tp
->retrans_out
-= pcount
;
1402 /* Shift newly-SACKed bytes from this skb to the immediately previous
1403 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1405 static int tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1406 struct tcp_sacktag_state
*state
,
1407 unsigned int pcount
, int shifted
, int mss
,
1410 struct tcp_sock
*tp
= tcp_sk(sk
);
1411 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1412 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1413 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1417 /* Adjust counters and hints for the newly sacked sequence
1418 * range but discard the return value since prev is already
1419 * marked. We must tag the range first because the seq
1420 * advancement below implicitly advances
1421 * tcp_highest_sack_seq() when skb is highest_sack.
1423 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1424 start_seq
, end_seq
, dup_sack
, pcount
);
1426 if (skb
== tp
->lost_skb_hint
)
1427 tp
->lost_cnt_hint
+= pcount
;
1429 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1430 TCP_SKB_CB(skb
)->seq
+= shifted
;
1432 skb_shinfo(prev
)->gso_segs
+= pcount
;
1433 BUG_ON(skb_shinfo(skb
)->gso_segs
< pcount
);
1434 skb_shinfo(skb
)->gso_segs
-= pcount
;
1436 /* When we're adding to gso_segs == 1, gso_size will be zero,
1437 * in theory this shouldn't be necessary but as long as DSACK
1438 * code can come after this skb later on it's better to keep
1439 * setting gso_size to something.
1441 if (!skb_shinfo(prev
)->gso_size
) {
1442 skb_shinfo(prev
)->gso_size
= mss
;
1443 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1446 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1447 if (skb_shinfo(skb
)->gso_segs
<= 1) {
1448 skb_shinfo(skb
)->gso_size
= 0;
1449 skb_shinfo(skb
)->gso_type
= 0;
1452 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1453 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1456 BUG_ON(!tcp_skb_pcount(skb
));
1457 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1461 /* Whole SKB was eaten :-) */
1463 if (skb
== tp
->retransmit_skb_hint
)
1464 tp
->retransmit_skb_hint
= prev
;
1465 if (skb
== tp
->scoreboard_skb_hint
)
1466 tp
->scoreboard_skb_hint
= prev
;
1467 if (skb
== tp
->lost_skb_hint
) {
1468 tp
->lost_skb_hint
= prev
;
1469 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1472 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(prev
)->tcp_flags
;
1473 if (skb
== tcp_highest_sack(sk
))
1474 tcp_advance_highest_sack(sk
, skb
);
1476 tcp_unlink_write_queue(skb
, sk
);
1477 sk_wmem_free_skb(sk
, skb
);
1479 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1484 /* I wish gso_size would have a bit more sane initialization than
1485 * something-or-zero which complicates things
1487 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1489 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1492 /* Shifting pages past head area doesn't work */
1493 static int skb_can_shift(const struct sk_buff
*skb
)
1495 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1498 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1501 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1502 struct tcp_sacktag_state
*state
,
1503 u32 start_seq
, u32 end_seq
,
1506 struct tcp_sock
*tp
= tcp_sk(sk
);
1507 struct sk_buff
*prev
;
1513 if (!sk_can_gso(sk
))
1516 /* Normally R but no L won't result in plain S */
1518 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1520 if (!skb_can_shift(skb
))
1522 /* This frame is about to be dropped (was ACKed). */
1523 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1526 /* Can only happen with delayed DSACK + discard craziness */
1527 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1529 prev
= tcp_write_queue_prev(sk
, skb
);
1531 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1534 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1535 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1539 pcount
= tcp_skb_pcount(skb
);
1540 mss
= tcp_skb_seglen(skb
);
1542 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1543 * drop this restriction as unnecessary
1545 if (mss
!= tcp_skb_seglen(prev
))
1548 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1550 /* CHECKME: This is non-MSS split case only?, this will
1551 * cause skipped skbs due to advancing loop btw, original
1552 * has that feature too
1554 if (tcp_skb_pcount(skb
) <= 1)
1557 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1559 /* TODO: head merge to next could be attempted here
1560 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1561 * though it might not be worth of the additional hassle
1563 * ...we can probably just fallback to what was done
1564 * previously. We could try merging non-SACKed ones
1565 * as well but it probably isn't going to buy off
1566 * because later SACKs might again split them, and
1567 * it would make skb timestamp tracking considerably
1573 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1575 BUG_ON(len
> skb
->len
);
1577 /* MSS boundaries should be honoured or else pcount will
1578 * severely break even though it makes things bit trickier.
1579 * Optimize common case to avoid most of the divides
1581 mss
= tcp_skb_mss(skb
);
1583 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1584 * drop this restriction as unnecessary
1586 if (mss
!= tcp_skb_seglen(prev
))
1591 } else if (len
< mss
) {
1599 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1600 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1603 if (!skb_shift(prev
, skb
, len
))
1605 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1608 /* Hole filled allows collapsing with the next as well, this is very
1609 * useful when hole on every nth skb pattern happens
1611 if (prev
== tcp_write_queue_tail(sk
))
1613 skb
= tcp_write_queue_next(sk
, prev
);
1615 if (!skb_can_shift(skb
) ||
1616 (skb
== tcp_send_head(sk
)) ||
1617 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1618 (mss
!= tcp_skb_seglen(skb
)))
1622 if (skb_shift(prev
, skb
, len
)) {
1623 pcount
+= tcp_skb_pcount(skb
);
1624 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1628 state
->fack_count
+= pcount
;
1635 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1639 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1640 struct tcp_sack_block
*next_dup
,
1641 struct tcp_sacktag_state
*state
,
1642 u32 start_seq
, u32 end_seq
,
1645 struct tcp_sock
*tp
= tcp_sk(sk
);
1646 struct sk_buff
*tmp
;
1648 tcp_for_write_queue_from(skb
, sk
) {
1650 int dup_sack
= dup_sack_in
;
1652 if (skb
== tcp_send_head(sk
))
1655 /* queue is in-order => we can short-circuit the walk early */
1656 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1659 if ((next_dup
!= NULL
) &&
1660 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1661 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1662 next_dup
->start_seq
,
1668 /* skb reference here is a bit tricky to get right, since
1669 * shifting can eat and free both this skb and the next,
1670 * so not even _safe variant of the loop is enough.
1673 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1674 start_seq
, end_seq
, dup_sack
);
1683 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1689 if (unlikely(in_sack
< 0))
1693 TCP_SKB_CB(skb
)->sacked
=
1696 TCP_SKB_CB(skb
)->sacked
,
1697 TCP_SKB_CB(skb
)->seq
,
1698 TCP_SKB_CB(skb
)->end_seq
,
1700 tcp_skb_pcount(skb
));
1702 if (!before(TCP_SKB_CB(skb
)->seq
,
1703 tcp_highest_sack_seq(tp
)))
1704 tcp_advance_highest_sack(sk
, skb
);
1707 state
->fack_count
+= tcp_skb_pcount(skb
);
1712 /* Avoid all extra work that is being done by sacktag while walking in
1715 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1716 struct tcp_sacktag_state
*state
,
1719 tcp_for_write_queue_from(skb
, sk
) {
1720 if (skb
== tcp_send_head(sk
))
1723 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1726 state
->fack_count
+= tcp_skb_pcount(skb
);
1731 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1733 struct tcp_sack_block
*next_dup
,
1734 struct tcp_sacktag_state
*state
,
1737 if (next_dup
== NULL
)
1740 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1741 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1742 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1743 next_dup
->start_seq
, next_dup
->end_seq
,
1750 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1752 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1756 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1759 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1760 struct tcp_sock
*tp
= tcp_sk(sk
);
1761 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1762 TCP_SKB_CB(ack_skb
)->sacked
);
1763 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1764 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1765 struct tcp_sack_block
*cache
;
1766 struct tcp_sacktag_state state
;
1767 struct sk_buff
*skb
;
1768 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1770 int found_dup_sack
= 0;
1772 int first_sack_index
;
1775 state
.reord
= tp
->packets_out
;
1777 if (!tp
->sacked_out
) {
1778 if (WARN_ON(tp
->fackets_out
))
1779 tp
->fackets_out
= 0;
1780 tcp_highest_sack_reset(sk
);
1783 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1784 num_sacks
, prior_snd_una
);
1786 state
.flag
|= FLAG_DSACKING_ACK
;
1788 /* Eliminate too old ACKs, but take into
1789 * account more or less fresh ones, they can
1790 * contain valid SACK info.
1792 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1795 if (!tp
->packets_out
)
1799 first_sack_index
= 0;
1800 for (i
= 0; i
< num_sacks
; i
++) {
1801 int dup_sack
= !i
&& found_dup_sack
;
1803 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1804 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1806 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1807 sp
[used_sacks
].start_seq
,
1808 sp
[used_sacks
].end_seq
)) {
1812 if (!tp
->undo_marker
)
1813 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1815 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1817 /* Don't count olds caused by ACK reordering */
1818 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1819 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1821 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1824 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1826 first_sack_index
= -1;
1830 /* Ignore very old stuff early */
1831 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1837 /* order SACK blocks to allow in order walk of the retrans queue */
1838 for (i
= used_sacks
- 1; i
> 0; i
--) {
1839 for (j
= 0; j
< i
; j
++) {
1840 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1841 swap(sp
[j
], sp
[j
+ 1]);
1843 /* Track where the first SACK block goes to */
1844 if (j
== first_sack_index
)
1845 first_sack_index
= j
+ 1;
1850 skb
= tcp_write_queue_head(sk
);
1851 state
.fack_count
= 0;
1854 if (!tp
->sacked_out
) {
1855 /* It's already past, so skip checking against it */
1856 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1858 cache
= tp
->recv_sack_cache
;
1859 /* Skip empty blocks in at head of the cache */
1860 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1865 while (i
< used_sacks
) {
1866 u32 start_seq
= sp
[i
].start_seq
;
1867 u32 end_seq
= sp
[i
].end_seq
;
1868 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1869 struct tcp_sack_block
*next_dup
= NULL
;
1871 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1872 next_dup
= &sp
[i
+ 1];
1874 /* Skip too early cached blocks */
1875 while (tcp_sack_cache_ok(tp
, cache
) &&
1876 !before(start_seq
, cache
->end_seq
))
1879 /* Can skip some work by looking recv_sack_cache? */
1880 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1881 after(end_seq
, cache
->start_seq
)) {
1884 if (before(start_seq
, cache
->start_seq
)) {
1885 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1887 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1894 /* Rest of the block already fully processed? */
1895 if (!after(end_seq
, cache
->end_seq
))
1898 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1902 /* ...tail remains todo... */
1903 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1904 /* ...but better entrypoint exists! */
1905 skb
= tcp_highest_sack(sk
);
1908 state
.fack_count
= tp
->fackets_out
;
1913 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1914 /* Check overlap against next cached too (past this one already) */
1919 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1920 skb
= tcp_highest_sack(sk
);
1923 state
.fack_count
= tp
->fackets_out
;
1925 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1928 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1929 start_seq
, end_seq
, dup_sack
);
1932 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1933 * due to in-order walk
1935 if (after(end_seq
, tp
->frto_highmark
))
1936 state
.flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1941 /* Clear the head of the cache sack blocks so we can skip it next time */
1942 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1943 tp
->recv_sack_cache
[i
].start_seq
= 0;
1944 tp
->recv_sack_cache
[i
].end_seq
= 0;
1946 for (j
= 0; j
< used_sacks
; j
++)
1947 tp
->recv_sack_cache
[i
++] = sp
[j
];
1949 tcp_mark_lost_retrans(sk
);
1951 tcp_verify_left_out(tp
);
1953 if ((state
.reord
< tp
->fackets_out
) &&
1954 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1955 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1956 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1960 #if FASTRETRANS_DEBUG > 0
1961 WARN_ON((int)tp
->sacked_out
< 0);
1962 WARN_ON((int)tp
->lost_out
< 0);
1963 WARN_ON((int)tp
->retrans_out
< 0);
1964 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1969 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1970 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1972 static int tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1976 holes
= max(tp
->lost_out
, 1U);
1977 holes
= min(holes
, tp
->packets_out
);
1979 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1980 tp
->sacked_out
= tp
->packets_out
- holes
;
1986 /* If we receive more dupacks than we expected counting segments
1987 * in assumption of absent reordering, interpret this as reordering.
1988 * The only another reason could be bug in receiver TCP.
1990 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1992 struct tcp_sock
*tp
= tcp_sk(sk
);
1993 if (tcp_limit_reno_sacked(tp
))
1994 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1997 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1999 static void tcp_add_reno_sack(struct sock
*sk
)
2001 struct tcp_sock
*tp
= tcp_sk(sk
);
2003 tcp_check_reno_reordering(sk
, 0);
2004 tcp_verify_left_out(tp
);
2007 /* Account for ACK, ACKing some data in Reno Recovery phase. */
2009 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
2011 struct tcp_sock
*tp
= tcp_sk(sk
);
2014 /* One ACK acked hole. The rest eat duplicate ACKs. */
2015 if (acked
- 1 >= tp
->sacked_out
)
2018 tp
->sacked_out
-= acked
- 1;
2020 tcp_check_reno_reordering(sk
, acked
);
2021 tcp_verify_left_out(tp
);
2024 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
2029 static int tcp_is_sackfrto(const struct tcp_sock
*tp
)
2031 return (sysctl_tcp_frto
== 0x2) && !tcp_is_reno(tp
);
2034 /* F-RTO can only be used if TCP has never retransmitted anything other than
2035 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
2037 int tcp_use_frto(struct sock
*sk
)
2039 const struct tcp_sock
*tp
= tcp_sk(sk
);
2040 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2041 struct sk_buff
*skb
;
2043 if (!sysctl_tcp_frto
)
2046 /* MTU probe and F-RTO won't really play nicely along currently */
2047 if (icsk
->icsk_mtup
.probe_size
)
2050 if (tcp_is_sackfrto(tp
))
2053 /* Avoid expensive walking of rexmit queue if possible */
2054 if (tp
->retrans_out
> 1)
2057 skb
= tcp_write_queue_head(sk
);
2058 if (tcp_skb_is_last(sk
, skb
))
2060 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
2061 tcp_for_write_queue_from(skb
, sk
) {
2062 if (skb
== tcp_send_head(sk
))
2064 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2066 /* Short-circuit when first non-SACKed skb has been checked */
2067 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2073 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2074 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2075 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2076 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2077 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2078 * bits are handled if the Loss state is really to be entered (in
2079 * tcp_enter_frto_loss).
2081 * Do like tcp_enter_loss() would; when RTO expires the second time it
2083 * "Reduce ssthresh if it has not yet been made inside this window."
2085 void tcp_enter_frto(struct sock
*sk
)
2087 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2088 struct tcp_sock
*tp
= tcp_sk(sk
);
2089 struct sk_buff
*skb
;
2091 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
2092 tp
->snd_una
== tp
->high_seq
||
2093 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
2094 !icsk
->icsk_retransmits
)) {
2095 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2096 /* Our state is too optimistic in ssthresh() call because cwnd
2097 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2098 * recovery has not yet completed. Pattern would be this: RTO,
2099 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2101 * RFC4138 should be more specific on what to do, even though
2102 * RTO is quite unlikely to occur after the first Cumulative ACK
2103 * due to back-off and complexity of triggering events ...
2105 if (tp
->frto_counter
) {
2107 stored_cwnd
= tp
->snd_cwnd
;
2109 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2110 tp
->snd_cwnd
= stored_cwnd
;
2112 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2114 /* ... in theory, cong.control module could do "any tricks" in
2115 * ssthresh(), which means that ca_state, lost bits and lost_out
2116 * counter would have to be faked before the call occurs. We
2117 * consider that too expensive, unlikely and hacky, so modules
2118 * using these in ssthresh() must deal these incompatibility
2119 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2121 tcp_ca_event(sk
, CA_EVENT_FRTO
);
2124 tp
->undo_marker
= tp
->snd_una
;
2125 tp
->undo_retrans
= 0;
2127 skb
= tcp_write_queue_head(sk
);
2128 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2129 tp
->undo_marker
= 0;
2130 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2131 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2132 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2134 tcp_verify_left_out(tp
);
2136 /* Too bad if TCP was application limited */
2137 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2139 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2140 * The last condition is necessary at least in tp->frto_counter case.
2142 if (tcp_is_sackfrto(tp
) && (tp
->frto_counter
||
2143 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
2144 after(tp
->high_seq
, tp
->snd_una
)) {
2145 tp
->frto_highmark
= tp
->high_seq
;
2147 tp
->frto_highmark
= tp
->snd_nxt
;
2149 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
2150 tp
->high_seq
= tp
->snd_nxt
;
2151 tp
->frto_counter
= 1;
2154 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2155 * which indicates that we should follow the traditional RTO recovery,
2156 * i.e. mark everything lost and do go-back-N retransmission.
2158 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
2160 struct tcp_sock
*tp
= tcp_sk(sk
);
2161 struct sk_buff
*skb
;
2164 tp
->retrans_out
= 0;
2165 if (tcp_is_reno(tp
))
2166 tcp_reset_reno_sack(tp
);
2168 tcp_for_write_queue(skb
, sk
) {
2169 if (skb
== tcp_send_head(sk
))
2172 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2174 * Count the retransmission made on RTO correctly (only when
2175 * waiting for the first ACK and did not get it)...
2177 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
2178 /* For some reason this R-bit might get cleared? */
2179 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
2180 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2181 /* ...enter this if branch just for the first segment */
2182 flag
|= FLAG_DATA_ACKED
;
2184 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2185 tp
->undo_marker
= 0;
2186 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2189 /* Marking forward transmissions that were made after RTO lost
2190 * can cause unnecessary retransmissions in some scenarios,
2191 * SACK blocks will mitigate that in some but not in all cases.
2192 * We used to not mark them but it was causing break-ups with
2193 * receivers that do only in-order receival.
2195 * TODO: we could detect presence of such receiver and select
2196 * different behavior per flow.
2198 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2199 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2200 tp
->lost_out
+= tcp_skb_pcount(skb
);
2201 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2204 tcp_verify_left_out(tp
);
2206 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
2207 tp
->snd_cwnd_cnt
= 0;
2208 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2209 tp
->frto_counter
= 0;
2210 tp
->bytes_acked
= 0;
2212 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2213 sysctl_tcp_reordering
);
2214 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2215 tp
->high_seq
= tp
->snd_nxt
;
2216 TCP_ECN_queue_cwr(tp
);
2218 tcp_clear_all_retrans_hints(tp
);
2221 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
2223 tp
->retrans_out
= 0;
2226 tp
->undo_marker
= 0;
2227 tp
->undo_retrans
= 0;
2230 void tcp_clear_retrans(struct tcp_sock
*tp
)
2232 tcp_clear_retrans_partial(tp
);
2234 tp
->fackets_out
= 0;
2238 /* Enter Loss state. If "how" is not zero, forget all SACK information
2239 * and reset tags completely, otherwise preserve SACKs. If receiver
2240 * dropped its ofo queue, we will know this due to reneging detection.
2242 void tcp_enter_loss(struct sock
*sk
, int how
)
2244 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2245 struct tcp_sock
*tp
= tcp_sk(sk
);
2246 struct sk_buff
*skb
;
2248 /* Reduce ssthresh if it has not yet been made inside this window. */
2249 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
2250 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
2251 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2252 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2253 tcp_ca_event(sk
, CA_EVENT_LOSS
);
2256 tp
->snd_cwnd_cnt
= 0;
2257 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2259 tp
->bytes_acked
= 0;
2260 tcp_clear_retrans_partial(tp
);
2262 if (tcp_is_reno(tp
))
2263 tcp_reset_reno_sack(tp
);
2266 /* Push undo marker, if it was plain RTO and nothing
2267 * was retransmitted. */
2268 tp
->undo_marker
= tp
->snd_una
;
2271 tp
->fackets_out
= 0;
2273 tcp_clear_all_retrans_hints(tp
);
2275 tcp_for_write_queue(skb
, sk
) {
2276 if (skb
== tcp_send_head(sk
))
2279 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2280 tp
->undo_marker
= 0;
2281 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
2282 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
2283 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
2284 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2285 tp
->lost_out
+= tcp_skb_pcount(skb
);
2286 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2289 tcp_verify_left_out(tp
);
2291 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2292 sysctl_tcp_reordering
);
2293 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2294 tp
->high_seq
= tp
->snd_nxt
;
2295 TCP_ECN_queue_cwr(tp
);
2296 /* Abort F-RTO algorithm if one is in progress */
2297 tp
->frto_counter
= 0;
2300 /* If ACK arrived pointing to a remembered SACK, it means that our
2301 * remembered SACKs do not reflect real state of receiver i.e.
2302 * receiver _host_ is heavily congested (or buggy).
2304 * Do processing similar to RTO timeout.
2306 static int tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2308 if (flag
& FLAG_SACK_RENEGING
) {
2309 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2310 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
2312 tcp_enter_loss(sk
, 1);
2313 icsk
->icsk_retransmits
++;
2314 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
2315 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2316 icsk
->icsk_rto
, TCP_RTO_MAX
);
2322 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2324 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2327 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2328 * counter when SACK is enabled (without SACK, sacked_out is used for
2331 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2332 * segments up to the highest received SACK block so far and holes in
2335 * With reordering, holes may still be in flight, so RFC3517 recovery
2336 * uses pure sacked_out (total number of SACKed segments) even though
2337 * it violates the RFC that uses duplicate ACKs, often these are equal
2338 * but when e.g. out-of-window ACKs or packet duplication occurs,
2339 * they differ. Since neither occurs due to loss, TCP should really
2342 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2344 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2347 static bool tcp_pause_early_retransmit(struct sock
*sk
, int flag
)
2349 struct tcp_sock
*tp
= tcp_sk(sk
);
2350 unsigned long delay
;
2352 /* Delay early retransmit and entering fast recovery for
2353 * max(RTT/4, 2msec) unless ack has ECE mark, no RTT samples
2354 * available, or RTO is scheduled to fire first.
2356 if (sysctl_tcp_early_retrans
< 2 || (flag
& FLAG_ECE
) || !tp
->srtt
)
2359 delay
= max_t(unsigned long, (tp
->srtt
>> 5), msecs_to_jiffies(2));
2360 if (!time_after(inet_csk(sk
)->icsk_timeout
, (jiffies
+ delay
)))
2363 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, delay
, TCP_RTO_MAX
);
2364 tp
->early_retrans_delayed
= 1;
2368 static inline int tcp_skb_timedout(const struct sock
*sk
,
2369 const struct sk_buff
*skb
)
2371 return tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
;
2374 static inline int tcp_head_timedout(const struct sock
*sk
)
2376 const struct tcp_sock
*tp
= tcp_sk(sk
);
2378 return tp
->packets_out
&&
2379 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2382 /* Linux NewReno/SACK/FACK/ECN state machine.
2383 * --------------------------------------
2385 * "Open" Normal state, no dubious events, fast path.
2386 * "Disorder" In all the respects it is "Open",
2387 * but requires a bit more attention. It is entered when
2388 * we see some SACKs or dupacks. It is split of "Open"
2389 * mainly to move some processing from fast path to slow one.
2390 * "CWR" CWND was reduced due to some Congestion Notification event.
2391 * It can be ECN, ICMP source quench, local device congestion.
2392 * "Recovery" CWND was reduced, we are fast-retransmitting.
2393 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2395 * tcp_fastretrans_alert() is entered:
2396 * - each incoming ACK, if state is not "Open"
2397 * - when arrived ACK is unusual, namely:
2402 * Counting packets in flight is pretty simple.
2404 * in_flight = packets_out - left_out + retrans_out
2406 * packets_out is SND.NXT-SND.UNA counted in packets.
2408 * retrans_out is number of retransmitted segments.
2410 * left_out is number of segments left network, but not ACKed yet.
2412 * left_out = sacked_out + lost_out
2414 * sacked_out: Packets, which arrived to receiver out of order
2415 * and hence not ACKed. With SACKs this number is simply
2416 * amount of SACKed data. Even without SACKs
2417 * it is easy to give pretty reliable estimate of this number,
2418 * counting duplicate ACKs.
2420 * lost_out: Packets lost by network. TCP has no explicit
2421 * "loss notification" feedback from network (for now).
2422 * It means that this number can be only _guessed_.
2423 * Actually, it is the heuristics to predict lossage that
2424 * distinguishes different algorithms.
2426 * F.e. after RTO, when all the queue is considered as lost,
2427 * lost_out = packets_out and in_flight = retrans_out.
2429 * Essentially, we have now two algorithms counting
2432 * FACK: It is the simplest heuristics. As soon as we decided
2433 * that something is lost, we decide that _all_ not SACKed
2434 * packets until the most forward SACK are lost. I.e.
2435 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2436 * It is absolutely correct estimate, if network does not reorder
2437 * packets. And it loses any connection to reality when reordering
2438 * takes place. We use FACK by default until reordering
2439 * is suspected on the path to this destination.
2441 * NewReno: when Recovery is entered, we assume that one segment
2442 * is lost (classic Reno). While we are in Recovery and
2443 * a partial ACK arrives, we assume that one more packet
2444 * is lost (NewReno). This heuristics are the same in NewReno
2447 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2448 * deflation etc. CWND is real congestion window, never inflated, changes
2449 * only according to classic VJ rules.
2451 * Really tricky (and requiring careful tuning) part of algorithm
2452 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2453 * The first determines the moment _when_ we should reduce CWND and,
2454 * hence, slow down forward transmission. In fact, it determines the moment
2455 * when we decide that hole is caused by loss, rather than by a reorder.
2457 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2458 * holes, caused by lost packets.
2460 * And the most logically complicated part of algorithm is undo
2461 * heuristics. We detect false retransmits due to both too early
2462 * fast retransmit (reordering) and underestimated RTO, analyzing
2463 * timestamps and D-SACKs. When we detect that some segments were
2464 * retransmitted by mistake and CWND reduction was wrong, we undo
2465 * window reduction and abort recovery phase. This logic is hidden
2466 * inside several functions named tcp_try_undo_<something>.
2469 /* This function decides, when we should leave Disordered state
2470 * and enter Recovery phase, reducing congestion window.
2472 * Main question: may we further continue forward transmission
2473 * with the same cwnd?
2475 static int tcp_time_to_recover(struct sock
*sk
, int flag
)
2477 struct tcp_sock
*tp
= tcp_sk(sk
);
2480 /* Do not perform any recovery during F-RTO algorithm */
2481 if (tp
->frto_counter
)
2484 /* Trick#1: The loss is proven. */
2488 /* Not-A-Trick#2 : Classic rule... */
2489 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2492 /* Trick#3 : when we use RFC2988 timer restart, fast
2493 * retransmit can be triggered by timeout of queue head.
2495 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2498 /* Trick#4: It is still not OK... But will it be useful to delay
2501 packets_out
= tp
->packets_out
;
2502 if (packets_out
<= tp
->reordering
&&
2503 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2504 !tcp_may_send_now(sk
)) {
2505 /* We have nothing to send. This connection is limited
2506 * either by receiver window or by application.
2511 /* If a thin stream is detected, retransmit after first
2512 * received dupack. Employ only if SACK is supported in order
2513 * to avoid possible corner-case series of spurious retransmissions
2514 * Use only if there are no unsent data.
2516 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2517 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2518 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2521 /* Trick#6: TCP early retransmit, per RFC5827. To avoid spurious
2522 * retransmissions due to small network reorderings, we implement
2523 * Mitigation A.3 in the RFC and delay the retransmission for a short
2524 * interval if appropriate.
2526 if (tp
->do_early_retrans
&& !tp
->retrans_out
&& tp
->sacked_out
&&
2527 (tp
->packets_out
== (tp
->sacked_out
+ 1) && tp
->packets_out
< 4) &&
2528 !tcp_may_send_now(sk
))
2529 return !tcp_pause_early_retransmit(sk
, flag
);
2534 /* New heuristics: it is possible only after we switched to restart timer
2535 * each time when something is ACKed. Hence, we can detect timed out packets
2536 * during fast retransmit without falling to slow start.
2538 * Usefulness of this as is very questionable, since we should know which of
2539 * the segments is the next to timeout which is relatively expensive to find
2540 * in general case unless we add some data structure just for that. The
2541 * current approach certainly won't find the right one too often and when it
2542 * finally does find _something_ it usually marks large part of the window
2543 * right away (because a retransmission with a larger timestamp blocks the
2544 * loop from advancing). -ij
2546 static void tcp_timeout_skbs(struct sock
*sk
)
2548 struct tcp_sock
*tp
= tcp_sk(sk
);
2549 struct sk_buff
*skb
;
2551 if (!tcp_is_fack(tp
) || !tcp_head_timedout(sk
))
2554 skb
= tp
->scoreboard_skb_hint
;
2555 if (tp
->scoreboard_skb_hint
== NULL
)
2556 skb
= tcp_write_queue_head(sk
);
2558 tcp_for_write_queue_from(skb
, sk
) {
2559 if (skb
== tcp_send_head(sk
))
2561 if (!tcp_skb_timedout(sk
, skb
))
2564 tcp_skb_mark_lost(tp
, skb
);
2567 tp
->scoreboard_skb_hint
= skb
;
2569 tcp_verify_left_out(tp
);
2572 /* Detect loss in event "A" above by marking head of queue up as lost.
2573 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2574 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2575 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2576 * the maximum SACKed segments to pass before reaching this limit.
2578 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2580 struct tcp_sock
*tp
= tcp_sk(sk
);
2581 struct sk_buff
*skb
;
2585 /* Use SACK to deduce losses of new sequences sent during recovery */
2586 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2588 WARN_ON(packets
> tp
->packets_out
);
2589 if (tp
->lost_skb_hint
) {
2590 skb
= tp
->lost_skb_hint
;
2591 cnt
= tp
->lost_cnt_hint
;
2592 /* Head already handled? */
2593 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2596 skb
= tcp_write_queue_head(sk
);
2600 tcp_for_write_queue_from(skb
, sk
) {
2601 if (skb
== tcp_send_head(sk
))
2603 /* TODO: do this better */
2604 /* this is not the most efficient way to do this... */
2605 tp
->lost_skb_hint
= skb
;
2606 tp
->lost_cnt_hint
= cnt
;
2608 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2612 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2613 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2614 cnt
+= tcp_skb_pcount(skb
);
2616 if (cnt
> packets
) {
2617 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2618 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2619 (oldcnt
>= packets
))
2622 mss
= skb_shinfo(skb
)->gso_size
;
2623 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2629 tcp_skb_mark_lost(tp
, skb
);
2634 tcp_verify_left_out(tp
);
2637 /* Account newly detected lost packet(s) */
2639 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2641 struct tcp_sock
*tp
= tcp_sk(sk
);
2643 if (tcp_is_reno(tp
)) {
2644 tcp_mark_head_lost(sk
, 1, 1);
2645 } else if (tcp_is_fack(tp
)) {
2646 int lost
= tp
->fackets_out
- tp
->reordering
;
2649 tcp_mark_head_lost(sk
, lost
, 0);
2651 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2652 if (sacked_upto
>= 0)
2653 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2654 else if (fast_rexmit
)
2655 tcp_mark_head_lost(sk
, 1, 1);
2658 tcp_timeout_skbs(sk
);
2661 /* CWND moderation, preventing bursts due to too big ACKs
2662 * in dubious situations.
2664 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2666 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2667 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2668 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2671 /* Lower bound on congestion window is slow start threshold
2672 * unless congestion avoidance choice decides to overide it.
2674 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2676 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2678 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2681 /* Decrease cwnd each second ack. */
2682 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2684 struct tcp_sock
*tp
= tcp_sk(sk
);
2685 int decr
= tp
->snd_cwnd_cnt
+ 1;
2687 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2688 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2689 tp
->snd_cwnd_cnt
= decr
& 1;
2692 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2693 tp
->snd_cwnd
-= decr
;
2695 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2696 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2700 /* Nothing was retransmitted or returned timestamp is less
2701 * than timestamp of the first retransmission.
2703 static inline int tcp_packet_delayed(const struct tcp_sock
*tp
)
2705 return !tp
->retrans_stamp
||
2706 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2707 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2710 /* Undo procedures. */
2712 #if FASTRETRANS_DEBUG > 1
2713 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2715 struct tcp_sock
*tp
= tcp_sk(sk
);
2716 struct inet_sock
*inet
= inet_sk(sk
);
2718 if (sk
->sk_family
== AF_INET
) {
2719 printk(KERN_DEBUG
"Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2721 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2722 tp
->snd_cwnd
, tcp_left_out(tp
),
2723 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2726 #if IS_ENABLED(CONFIG_IPV6)
2727 else if (sk
->sk_family
== AF_INET6
) {
2728 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2729 printk(KERN_DEBUG
"Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2731 &np
->daddr
, ntohs(inet
->inet_dport
),
2732 tp
->snd_cwnd
, tcp_left_out(tp
),
2733 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2739 #define DBGUNDO(x...) do { } while (0)
2742 static void tcp_undo_cwr(struct sock
*sk
, const bool undo_ssthresh
)
2744 struct tcp_sock
*tp
= tcp_sk(sk
);
2746 if (tp
->prior_ssthresh
) {
2747 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2749 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2750 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2752 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2754 if (undo_ssthresh
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2755 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2756 TCP_ECN_withdraw_cwr(tp
);
2759 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2761 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2764 static inline int tcp_may_undo(const struct tcp_sock
*tp
)
2766 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2769 /* People celebrate: "We love our President!" */
2770 static int tcp_try_undo_recovery(struct sock
*sk
)
2772 struct tcp_sock
*tp
= tcp_sk(sk
);
2774 if (tcp_may_undo(tp
)) {
2777 /* Happy end! We did not retransmit anything
2778 * or our original transmission succeeded.
2780 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2781 tcp_undo_cwr(sk
, true);
2782 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2783 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2785 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2787 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2788 tp
->undo_marker
= 0;
2790 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2791 /* Hold old state until something *above* high_seq
2792 * is ACKed. For Reno it is MUST to prevent false
2793 * fast retransmits (RFC2582). SACK TCP is safe. */
2794 tcp_moderate_cwnd(tp
);
2797 tcp_set_ca_state(sk
, TCP_CA_Open
);
2801 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2802 static void tcp_try_undo_dsack(struct sock
*sk
)
2804 struct tcp_sock
*tp
= tcp_sk(sk
);
2806 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2807 DBGUNDO(sk
, "D-SACK");
2808 tcp_undo_cwr(sk
, true);
2809 tp
->undo_marker
= 0;
2810 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2814 /* We can clear retrans_stamp when there are no retransmissions in the
2815 * window. It would seem that it is trivially available for us in
2816 * tp->retrans_out, however, that kind of assumptions doesn't consider
2817 * what will happen if errors occur when sending retransmission for the
2818 * second time. ...It could the that such segment has only
2819 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2820 * the head skb is enough except for some reneging corner cases that
2821 * are not worth the effort.
2823 * Main reason for all this complexity is the fact that connection dying
2824 * time now depends on the validity of the retrans_stamp, in particular,
2825 * that successive retransmissions of a segment must not advance
2826 * retrans_stamp under any conditions.
2828 static int tcp_any_retrans_done(const struct sock
*sk
)
2830 const struct tcp_sock
*tp
= tcp_sk(sk
);
2831 struct sk_buff
*skb
;
2833 if (tp
->retrans_out
)
2836 skb
= tcp_write_queue_head(sk
);
2837 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2843 /* Undo during fast recovery after partial ACK. */
2845 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2847 struct tcp_sock
*tp
= tcp_sk(sk
);
2848 /* Partial ACK arrived. Force Hoe's retransmit. */
2849 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2851 if (tcp_may_undo(tp
)) {
2852 /* Plain luck! Hole if filled with delayed
2853 * packet, rather than with a retransmit.
2855 if (!tcp_any_retrans_done(sk
))
2856 tp
->retrans_stamp
= 0;
2858 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2861 tcp_undo_cwr(sk
, false);
2862 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2864 /* So... Do not make Hoe's retransmit yet.
2865 * If the first packet was delayed, the rest
2866 * ones are most probably delayed as well.
2873 /* Undo during loss recovery after partial ACK. */
2874 static int tcp_try_undo_loss(struct sock
*sk
)
2876 struct tcp_sock
*tp
= tcp_sk(sk
);
2878 if (tcp_may_undo(tp
)) {
2879 struct sk_buff
*skb
;
2880 tcp_for_write_queue(skb
, sk
) {
2881 if (skb
== tcp_send_head(sk
))
2883 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2886 tcp_clear_all_retrans_hints(tp
);
2888 DBGUNDO(sk
, "partial loss");
2890 tcp_undo_cwr(sk
, true);
2891 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2892 inet_csk(sk
)->icsk_retransmits
= 0;
2893 tp
->undo_marker
= 0;
2894 if (tcp_is_sack(tp
))
2895 tcp_set_ca_state(sk
, TCP_CA_Open
);
2901 static inline void tcp_complete_cwr(struct sock
*sk
)
2903 struct tcp_sock
*tp
= tcp_sk(sk
);
2905 /* Do not moderate cwnd if it's already undone in cwr or recovery. */
2906 if (tp
->undo_marker
) {
2907 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
)
2908 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2910 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2911 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2913 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2916 static void tcp_try_keep_open(struct sock
*sk
)
2918 struct tcp_sock
*tp
= tcp_sk(sk
);
2919 int state
= TCP_CA_Open
;
2921 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2922 state
= TCP_CA_Disorder
;
2924 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2925 tcp_set_ca_state(sk
, state
);
2926 tp
->high_seq
= tp
->snd_nxt
;
2930 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2932 struct tcp_sock
*tp
= tcp_sk(sk
);
2934 tcp_verify_left_out(tp
);
2936 if (!tp
->frto_counter
&& !tcp_any_retrans_done(sk
))
2937 tp
->retrans_stamp
= 0;
2939 if (flag
& FLAG_ECE
)
2940 tcp_enter_cwr(sk
, 1);
2942 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2943 tcp_try_keep_open(sk
);
2944 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
2945 tcp_moderate_cwnd(tp
);
2947 tcp_cwnd_down(sk
, flag
);
2951 static void tcp_mtup_probe_failed(struct sock
*sk
)
2953 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2955 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2956 icsk
->icsk_mtup
.probe_size
= 0;
2959 static void tcp_mtup_probe_success(struct sock
*sk
)
2961 struct tcp_sock
*tp
= tcp_sk(sk
);
2962 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2964 /* FIXME: breaks with very large cwnd */
2965 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2966 tp
->snd_cwnd
= tp
->snd_cwnd
*
2967 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2968 icsk
->icsk_mtup
.probe_size
;
2969 tp
->snd_cwnd_cnt
= 0;
2970 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2971 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2973 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2974 icsk
->icsk_mtup
.probe_size
= 0;
2975 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2978 /* Do a simple retransmit without using the backoff mechanisms in
2979 * tcp_timer. This is used for path mtu discovery.
2980 * The socket is already locked here.
2982 void tcp_simple_retransmit(struct sock
*sk
)
2984 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2985 struct tcp_sock
*tp
= tcp_sk(sk
);
2986 struct sk_buff
*skb
;
2987 unsigned int mss
= tcp_current_mss(sk
);
2988 u32 prior_lost
= tp
->lost_out
;
2990 tcp_for_write_queue(skb
, sk
) {
2991 if (skb
== tcp_send_head(sk
))
2993 if (tcp_skb_seglen(skb
) > mss
&&
2994 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2995 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2996 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2997 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2999 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
3003 tcp_clear_retrans_hints_partial(tp
);
3005 if (prior_lost
== tp
->lost_out
)
3008 if (tcp_is_reno(tp
))
3009 tcp_limit_reno_sacked(tp
);
3011 tcp_verify_left_out(tp
);
3013 /* Don't muck with the congestion window here.
3014 * Reason is that we do not increase amount of _data_
3015 * in network, but units changed and effective
3016 * cwnd/ssthresh really reduced now.
3018 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
3019 tp
->high_seq
= tp
->snd_nxt
;
3020 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
3021 tp
->prior_ssthresh
= 0;
3022 tp
->undo_marker
= 0;
3023 tcp_set_ca_state(sk
, TCP_CA_Loss
);
3025 tcp_xmit_retransmit_queue(sk
);
3027 EXPORT_SYMBOL(tcp_simple_retransmit
);
3029 /* This function implements the PRR algorithm, specifcally the PRR-SSRB
3030 * (proportional rate reduction with slow start reduction bound) as described in
3031 * http://www.ietf.org/id/draft-mathis-tcpm-proportional-rate-reduction-01.txt.
3032 * It computes the number of packets to send (sndcnt) based on packets newly
3034 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
3035 * cwnd reductions across a full RTT.
3036 * 2) If packets in flight is lower than ssthresh (such as due to excess
3037 * losses and/or application stalls), do not perform any further cwnd
3038 * reductions, but instead slow start up to ssthresh.
3040 static void tcp_update_cwnd_in_recovery(struct sock
*sk
, int newly_acked_sacked
,
3041 int fast_rexmit
, int flag
)
3043 struct tcp_sock
*tp
= tcp_sk(sk
);
3045 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
3047 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
3048 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
3050 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
3052 sndcnt
= min_t(int, delta
,
3053 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
3054 newly_acked_sacked
) + 1);
3057 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
3058 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
3061 static void tcp_enter_recovery(struct sock
*sk
, bool ece_ack
)
3063 struct tcp_sock
*tp
= tcp_sk(sk
);
3066 if (tcp_is_reno(tp
))
3067 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
3069 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
3071 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3073 tp
->high_seq
= tp
->snd_nxt
;
3074 tp
->prior_ssthresh
= 0;
3075 tp
->undo_marker
= tp
->snd_una
;
3076 tp
->undo_retrans
= tp
->retrans_out
;
3078 if (inet_csk(sk
)->icsk_ca_state
< TCP_CA_CWR
) {
3080 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
3081 tp
->snd_ssthresh
= inet_csk(sk
)->icsk_ca_ops
->ssthresh(sk
);
3082 TCP_ECN_queue_cwr(tp
);
3085 tp
->bytes_acked
= 0;
3086 tp
->snd_cwnd_cnt
= 0;
3087 tp
->prior_cwnd
= tp
->snd_cwnd
;
3088 tp
->prr_delivered
= 0;
3090 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
3093 /* Process an event, which can update packets-in-flight not trivially.
3094 * Main goal of this function is to calculate new estimate for left_out,
3095 * taking into account both packets sitting in receiver's buffer and
3096 * packets lost by network.
3098 * Besides that it does CWND reduction, when packet loss is detected
3099 * and changes state of machine.
3101 * It does _not_ decide what to send, it is made in function
3102 * tcp_xmit_retransmit_queue().
3104 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
,
3105 int newly_acked_sacked
, bool is_dupack
,
3108 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3109 struct tcp_sock
*tp
= tcp_sk(sk
);
3110 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
3111 (tcp_fackets_out(tp
) > tp
->reordering
));
3112 int fast_rexmit
= 0;
3114 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
3116 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
3117 tp
->fackets_out
= 0;
3119 /* Now state machine starts.
3120 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
3121 if (flag
& FLAG_ECE
)
3122 tp
->prior_ssthresh
= 0;
3124 /* B. In all the states check for reneging SACKs. */
3125 if (tcp_check_sack_reneging(sk
, flag
))
3128 /* C. Check consistency of the current state. */
3129 tcp_verify_left_out(tp
);
3131 /* D. Check state exit conditions. State can be terminated
3132 * when high_seq is ACKed. */
3133 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
3134 WARN_ON(tp
->retrans_out
!= 0);
3135 tp
->retrans_stamp
= 0;
3136 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
3137 switch (icsk
->icsk_ca_state
) {
3139 icsk
->icsk_retransmits
= 0;
3140 if (tcp_try_undo_recovery(sk
))
3145 /* CWR is to be held something *above* high_seq
3146 * is ACKed for CWR bit to reach receiver. */
3147 if (tp
->snd_una
!= tp
->high_seq
) {
3148 tcp_complete_cwr(sk
);
3149 tcp_set_ca_state(sk
, TCP_CA_Open
);
3153 case TCP_CA_Recovery
:
3154 if (tcp_is_reno(tp
))
3155 tcp_reset_reno_sack(tp
);
3156 if (tcp_try_undo_recovery(sk
))
3158 tcp_complete_cwr(sk
);
3163 /* E. Process state. */
3164 switch (icsk
->icsk_ca_state
) {
3165 case TCP_CA_Recovery
:
3166 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
3167 if (tcp_is_reno(tp
) && is_dupack
)
3168 tcp_add_reno_sack(sk
);
3170 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
3173 if (flag
& FLAG_DATA_ACKED
)
3174 icsk
->icsk_retransmits
= 0;
3175 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
3176 tcp_reset_reno_sack(tp
);
3177 if (!tcp_try_undo_loss(sk
)) {
3178 tcp_moderate_cwnd(tp
);
3179 tcp_xmit_retransmit_queue(sk
);
3182 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
3184 /* Loss is undone; fall through to processing in Open state. */
3186 if (tcp_is_reno(tp
)) {
3187 if (flag
& FLAG_SND_UNA_ADVANCED
)
3188 tcp_reset_reno_sack(tp
);
3190 tcp_add_reno_sack(sk
);
3193 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
3194 tcp_try_undo_dsack(sk
);
3196 if (!tcp_time_to_recover(sk
, flag
)) {
3197 tcp_try_to_open(sk
, flag
);
3201 /* MTU probe failure: don't reduce cwnd */
3202 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
3203 icsk
->icsk_mtup
.probe_size
&&
3204 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
3205 tcp_mtup_probe_failed(sk
);
3206 /* Restores the reduction we did in tcp_mtup_probe() */
3208 tcp_simple_retransmit(sk
);
3212 /* Otherwise enter Recovery state */
3213 tcp_enter_recovery(sk
, (flag
& FLAG_ECE
));
3217 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
3218 tcp_update_scoreboard(sk
, fast_rexmit
);
3219 tp
->prr_delivered
+= newly_acked_sacked
;
3220 tcp_update_cwnd_in_recovery(sk
, newly_acked_sacked
, fast_rexmit
, flag
);
3221 tcp_xmit_retransmit_queue(sk
);
3224 void tcp_valid_rtt_meas(struct sock
*sk
, u32 seq_rtt
)
3226 tcp_rtt_estimator(sk
, seq_rtt
);
3228 inet_csk(sk
)->icsk_backoff
= 0;
3230 EXPORT_SYMBOL(tcp_valid_rtt_meas
);
3232 /* Read draft-ietf-tcplw-high-performance before mucking
3233 * with this code. (Supersedes RFC1323)
3235 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
3237 /* RTTM Rule: A TSecr value received in a segment is used to
3238 * update the averaged RTT measurement only if the segment
3239 * acknowledges some new data, i.e., only if it advances the
3240 * left edge of the send window.
3242 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3243 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3245 * Changed: reset backoff as soon as we see the first valid sample.
3246 * If we do not, we get strongly overestimated rto. With timestamps
3247 * samples are accepted even from very old segments: f.e., when rtt=1
3248 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3249 * answer arrives rto becomes 120 seconds! If at least one of segments
3250 * in window is lost... Voila. --ANK (010210)
3252 struct tcp_sock
*tp
= tcp_sk(sk
);
3254 tcp_valid_rtt_meas(sk
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
3257 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
3259 /* We don't have a timestamp. Can only use
3260 * packets that are not retransmitted to determine
3261 * rtt estimates. Also, we must not reset the
3262 * backoff for rto until we get a non-retransmitted
3263 * packet. This allows us to deal with a situation
3264 * where the network delay has increased suddenly.
3265 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3268 if (flag
& FLAG_RETRANS_DATA_ACKED
)
3271 tcp_valid_rtt_meas(sk
, seq_rtt
);
3274 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
3277 const struct tcp_sock
*tp
= tcp_sk(sk
);
3278 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3279 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3280 tcp_ack_saw_tstamp(sk
, flag
);
3281 else if (seq_rtt
>= 0)
3282 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
3285 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
3287 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3288 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
3289 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
3292 /* Restart timer after forward progress on connection.
3293 * RFC2988 recommends to restart timer to now+rto.
3295 void tcp_rearm_rto(struct sock
*sk
)
3297 struct tcp_sock
*tp
= tcp_sk(sk
);
3299 if (!tp
->packets_out
) {
3300 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3302 u32 rto
= inet_csk(sk
)->icsk_rto
;
3303 /* Offset the time elapsed after installing regular RTO */
3304 if (tp
->early_retrans_delayed
) {
3305 struct sk_buff
*skb
= tcp_write_queue_head(sk
);
3306 const u32 rto_time_stamp
= TCP_SKB_CB(skb
)->when
+ rto
;
3307 s32 delta
= (s32
)(rto_time_stamp
- tcp_time_stamp
);
3308 /* delta may not be positive if the socket is locked
3309 * when the delayed ER timer fires and is rescheduled.
3314 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
, rto
,
3317 tp
->early_retrans_delayed
= 0;
3320 /* This function is called when the delayed ER timer fires. TCP enters
3321 * fast recovery and performs fast-retransmit.
3323 void tcp_resume_early_retransmit(struct sock
*sk
)
3325 struct tcp_sock
*tp
= tcp_sk(sk
);
3329 /* Stop if ER is disabled after the delayed ER timer is scheduled */
3330 if (!tp
->do_early_retrans
)
3333 tcp_enter_recovery(sk
, false);
3334 tcp_update_scoreboard(sk
, 1);
3335 tcp_xmit_retransmit_queue(sk
);
3338 /* If we get here, the whole TSO packet has not been acked. */
3339 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3341 struct tcp_sock
*tp
= tcp_sk(sk
);
3344 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3346 packets_acked
= tcp_skb_pcount(skb
);
3347 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3349 packets_acked
-= tcp_skb_pcount(skb
);
3351 if (packets_acked
) {
3352 BUG_ON(tcp_skb_pcount(skb
) == 0);
3353 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3356 return packets_acked
;
3359 /* Remove acknowledged frames from the retransmission queue. If our packet
3360 * is before the ack sequence we can discard it as it's confirmed to have
3361 * arrived at the other end.
3363 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3366 struct tcp_sock
*tp
= tcp_sk(sk
);
3367 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3368 struct sk_buff
*skb
;
3369 u32 now
= tcp_time_stamp
;
3370 int fully_acked
= 1;
3373 u32 reord
= tp
->packets_out
;
3374 u32 prior_sacked
= tp
->sacked_out
;
3376 s32 ca_seq_rtt
= -1;
3377 ktime_t last_ackt
= net_invalid_timestamp();
3379 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3380 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3382 u8 sacked
= scb
->sacked
;
3384 /* Determine how many packets and what bytes were acked, tso and else */
3385 if (after(scb
->end_seq
, tp
->snd_una
)) {
3386 if (tcp_skb_pcount(skb
) == 1 ||
3387 !after(tp
->snd_una
, scb
->seq
))
3390 acked_pcount
= tcp_tso_acked(sk
, skb
);
3396 acked_pcount
= tcp_skb_pcount(skb
);
3399 if (sacked
& TCPCB_RETRANS
) {
3400 if (sacked
& TCPCB_SACKED_RETRANS
)
3401 tp
->retrans_out
-= acked_pcount
;
3402 flag
|= FLAG_RETRANS_DATA_ACKED
;
3405 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
3406 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
3408 ca_seq_rtt
= now
- scb
->when
;
3409 last_ackt
= skb
->tstamp
;
3411 seq_rtt
= ca_seq_rtt
;
3413 if (!(sacked
& TCPCB_SACKED_ACKED
))
3414 reord
= min(pkts_acked
, reord
);
3417 if (sacked
& TCPCB_SACKED_ACKED
)
3418 tp
->sacked_out
-= acked_pcount
;
3419 if (sacked
& TCPCB_LOST
)
3420 tp
->lost_out
-= acked_pcount
;
3422 tp
->packets_out
-= acked_pcount
;
3423 pkts_acked
+= acked_pcount
;
3425 /* Initial outgoing SYN's get put onto the write_queue
3426 * just like anything else we transmit. It is not
3427 * true data, and if we misinform our callers that
3428 * this ACK acks real data, we will erroneously exit
3429 * connection startup slow start one packet too
3430 * quickly. This is severely frowned upon behavior.
3432 if (!(scb
->tcp_flags
& TCPHDR_SYN
)) {
3433 flag
|= FLAG_DATA_ACKED
;
3435 flag
|= FLAG_SYN_ACKED
;
3436 tp
->retrans_stamp
= 0;
3442 tcp_unlink_write_queue(skb
, sk
);
3443 sk_wmem_free_skb(sk
, skb
);
3444 tp
->scoreboard_skb_hint
= NULL
;
3445 if (skb
== tp
->retransmit_skb_hint
)
3446 tp
->retransmit_skb_hint
= NULL
;
3447 if (skb
== tp
->lost_skb_hint
)
3448 tp
->lost_skb_hint
= NULL
;
3451 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3452 tp
->snd_up
= tp
->snd_una
;
3454 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3455 flag
|= FLAG_SACK_RENEGING
;
3457 if (flag
& FLAG_ACKED
) {
3458 const struct tcp_congestion_ops
*ca_ops
3459 = inet_csk(sk
)->icsk_ca_ops
;
3461 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3462 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3463 tcp_mtup_probe_success(sk
);
3466 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
3469 if (tcp_is_reno(tp
)) {
3470 tcp_remove_reno_sacks(sk
, pkts_acked
);
3474 /* Non-retransmitted hole got filled? That's reordering */
3475 if (reord
< prior_fackets
)
3476 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3478 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3479 prior_sacked
- tp
->sacked_out
;
3480 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3483 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3485 if (ca_ops
->pkts_acked
) {
3488 /* Is the ACK triggering packet unambiguous? */
3489 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3490 /* High resolution needed and available? */
3491 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
3492 !ktime_equal(last_ackt
,
3493 net_invalid_timestamp()))
3494 rtt_us
= ktime_us_delta(ktime_get_real(),
3496 else if (ca_seq_rtt
>= 0)
3497 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
3500 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
3504 #if FASTRETRANS_DEBUG > 0
3505 WARN_ON((int)tp
->sacked_out
< 0);
3506 WARN_ON((int)tp
->lost_out
< 0);
3507 WARN_ON((int)tp
->retrans_out
< 0);
3508 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3509 icsk
= inet_csk(sk
);
3511 printk(KERN_DEBUG
"Leak l=%u %d\n",
3512 tp
->lost_out
, icsk
->icsk_ca_state
);
3515 if (tp
->sacked_out
) {
3516 printk(KERN_DEBUG
"Leak s=%u %d\n",
3517 tp
->sacked_out
, icsk
->icsk_ca_state
);
3520 if (tp
->retrans_out
) {
3521 printk(KERN_DEBUG
"Leak r=%u %d\n",
3522 tp
->retrans_out
, icsk
->icsk_ca_state
);
3523 tp
->retrans_out
= 0;
3530 static void tcp_ack_probe(struct sock
*sk
)
3532 const struct tcp_sock
*tp
= tcp_sk(sk
);
3533 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3535 /* Was it a usable window open? */
3537 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3538 icsk
->icsk_backoff
= 0;
3539 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3540 /* Socket must be waked up by subsequent tcp_data_snd_check().
3541 * This function is not for random using!
3544 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3545 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3550 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3552 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3553 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3556 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3558 const struct tcp_sock
*tp
= tcp_sk(sk
);
3559 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3560 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
3563 /* Check that window update is acceptable.
3564 * The function assumes that snd_una<=ack<=snd_next.
3566 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
3567 const u32 ack
, const u32 ack_seq
,
3570 return after(ack
, tp
->snd_una
) ||
3571 after(ack_seq
, tp
->snd_wl1
) ||
3572 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3575 /* Update our send window.
3577 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3578 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3580 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3583 struct tcp_sock
*tp
= tcp_sk(sk
);
3585 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3587 if (likely(!tcp_hdr(skb
)->syn
))
3588 nwin
<<= tp
->rx_opt
.snd_wscale
;
3590 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3591 flag
|= FLAG_WIN_UPDATE
;
3592 tcp_update_wl(tp
, ack_seq
);
3594 if (tp
->snd_wnd
!= nwin
) {
3597 /* Note, it is the only place, where
3598 * fast path is recovered for sending TCP.
3601 tcp_fast_path_check(sk
);
3603 if (nwin
> tp
->max_window
) {
3604 tp
->max_window
= nwin
;
3605 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3615 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3616 * continue in congestion avoidance.
3618 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3620 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3621 tp
->snd_cwnd_cnt
= 0;
3622 tp
->bytes_acked
= 0;
3623 TCP_ECN_queue_cwr(tp
);
3624 tcp_moderate_cwnd(tp
);
3627 /* A conservative spurious RTO response algorithm: reduce cwnd using
3628 * rate halving and continue in congestion avoidance.
3630 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3632 tcp_enter_cwr(sk
, 0);
3635 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3637 if (flag
& FLAG_ECE
)
3638 tcp_ratehalving_spur_to_response(sk
);
3640 tcp_undo_cwr(sk
, true);
3643 /* F-RTO spurious RTO detection algorithm (RFC4138)
3645 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3646 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3647 * window (but not to or beyond highest sequence sent before RTO):
3648 * On First ACK, send two new segments out.
3649 * On Second ACK, RTO was likely spurious. Do spurious response (response
3650 * algorithm is not part of the F-RTO detection algorithm
3651 * given in RFC4138 but can be selected separately).
3652 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3653 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3654 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3655 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3657 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3658 * original window even after we transmit two new data segments.
3661 * on first step, wait until first cumulative ACK arrives, then move to
3662 * the second step. In second step, the next ACK decides.
3664 * F-RTO is implemented (mainly) in four functions:
3665 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3666 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3667 * called when tcp_use_frto() showed green light
3668 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3669 * - tcp_enter_frto_loss() is called if there is not enough evidence
3670 * to prove that the RTO is indeed spurious. It transfers the control
3671 * from F-RTO to the conventional RTO recovery
3673 static int tcp_process_frto(struct sock
*sk
, int flag
)
3675 struct tcp_sock
*tp
= tcp_sk(sk
);
3677 tcp_verify_left_out(tp
);
3679 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3680 if (flag
& FLAG_DATA_ACKED
)
3681 inet_csk(sk
)->icsk_retransmits
= 0;
3683 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3684 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3685 tp
->undo_marker
= 0;
3687 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3688 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3692 if (!tcp_is_sackfrto(tp
)) {
3693 /* RFC4138 shortcoming in step 2; should also have case c):
3694 * ACK isn't duplicate nor advances window, e.g., opposite dir
3697 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3700 if (!(flag
& FLAG_DATA_ACKED
)) {
3701 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3706 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3707 /* Prevent sending of new data. */
3708 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3709 tcp_packets_in_flight(tp
));
3713 if ((tp
->frto_counter
>= 2) &&
3714 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3715 ((flag
& FLAG_DATA_SACKED
) &&
3716 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3717 /* RFC4138 shortcoming (see comment above) */
3718 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3719 (flag
& FLAG_NOT_DUP
))
3722 tcp_enter_frto_loss(sk
, 3, flag
);
3727 if (tp
->frto_counter
== 1) {
3728 /* tcp_may_send_now needs to see updated state */
3729 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3730 tp
->frto_counter
= 2;
3732 if (!tcp_may_send_now(sk
))
3733 tcp_enter_frto_loss(sk
, 2, flag
);
3737 switch (sysctl_tcp_frto_response
) {
3739 tcp_undo_spur_to_response(sk
, flag
);
3742 tcp_conservative_spur_to_response(tp
);
3745 tcp_ratehalving_spur_to_response(sk
);
3748 tp
->frto_counter
= 0;
3749 tp
->undo_marker
= 0;
3750 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSPURIOUSRTOS
);
3755 /* This routine deals with incoming acks, but not outgoing ones. */
3756 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3758 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3759 struct tcp_sock
*tp
= tcp_sk(sk
);
3760 u32 prior_snd_una
= tp
->snd_una
;
3761 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3762 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3763 bool is_dupack
= false;
3764 u32 prior_in_flight
;
3767 int prior_sacked
= tp
->sacked_out
;
3769 int newly_acked_sacked
= 0;
3772 /* If the ack is older than previous acks
3773 * then we can probably ignore it.
3775 if (before(ack
, prior_snd_una
))
3778 /* If the ack includes data we haven't sent yet, discard
3779 * this segment (RFC793 Section 3.9).
3781 if (after(ack
, tp
->snd_nxt
))
3784 if (tp
->early_retrans_delayed
)
3787 if (after(ack
, prior_snd_una
))
3788 flag
|= FLAG_SND_UNA_ADVANCED
;
3790 if (sysctl_tcp_abc
) {
3791 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3792 tp
->bytes_acked
+= ack
- prior_snd_una
;
3793 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3794 /* we assume just one segment left network */
3795 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3799 prior_fackets
= tp
->fackets_out
;
3800 prior_in_flight
= tcp_packets_in_flight(tp
);
3802 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3803 /* Window is constant, pure forward advance.
3804 * No more checks are required.
3805 * Note, we use the fact that SND.UNA>=SND.WL2.
3807 tcp_update_wl(tp
, ack_seq
);
3809 flag
|= FLAG_WIN_UPDATE
;
3811 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3813 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3815 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3818 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3820 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3822 if (TCP_SKB_CB(skb
)->sacked
)
3823 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3825 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3828 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3831 /* We passed data and got it acked, remove any soft error
3832 * log. Something worked...
3834 sk
->sk_err_soft
= 0;
3835 icsk
->icsk_probes_out
= 0;
3836 tp
->rcv_tstamp
= tcp_time_stamp
;
3837 prior_packets
= tp
->packets_out
;
3841 /* See if we can take anything off of the retransmit queue. */
3842 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
);
3844 pkts_acked
= prior_packets
- tp
->packets_out
;
3845 newly_acked_sacked
= (prior_packets
- prior_sacked
) -
3846 (tp
->packets_out
- tp
->sacked_out
);
3848 if (tp
->frto_counter
)
3849 frto_cwnd
= tcp_process_frto(sk
, flag
);
3850 /* Guarantee sacktag reordering detection against wrap-arounds */
3851 if (before(tp
->frto_highmark
, tp
->snd_una
))
3852 tp
->frto_highmark
= 0;
3854 if (tcp_ack_is_dubious(sk
, flag
)) {
3855 /* Advance CWND, if state allows this. */
3856 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3857 tcp_may_raise_cwnd(sk
, flag
))
3858 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3859 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3860 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3863 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3864 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3867 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3868 dst_confirm(__sk_dst_get(sk
));
3873 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3874 if (flag
& FLAG_DSACKING_ACK
)
3875 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3877 /* If this ack opens up a zero window, clear backoff. It was
3878 * being used to time the probes, and is probably far higher than
3879 * it needs to be for normal retransmission.
3881 if (tcp_send_head(sk
))
3886 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3890 /* If data was SACKed, tag it and see if we should send more data.
3891 * If data was DSACKed, see if we can undo a cwnd reduction.
3893 if (TCP_SKB_CB(skb
)->sacked
) {
3894 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3895 newly_acked_sacked
= tp
->sacked_out
- prior_sacked
;
3896 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3900 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3904 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3905 * But, this can also be called on packets in the established flow when
3906 * the fast version below fails.
3908 void tcp_parse_options(const struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3909 const u8
**hvpp
, int estab
)
3911 const unsigned char *ptr
;
3912 const struct tcphdr
*th
= tcp_hdr(skb
);
3913 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3915 ptr
= (const unsigned char *)(th
+ 1);
3916 opt_rx
->saw_tstamp
= 0;
3918 while (length
> 0) {
3919 int opcode
= *ptr
++;
3925 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3930 if (opsize
< 2) /* "silly options" */
3932 if (opsize
> length
)
3933 return; /* don't parse partial options */
3936 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3937 u16 in_mss
= get_unaligned_be16(ptr
);
3939 if (opt_rx
->user_mss
&&
3940 opt_rx
->user_mss
< in_mss
)
3941 in_mss
= opt_rx
->user_mss
;
3942 opt_rx
->mss_clamp
= in_mss
;
3947 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3948 !estab
&& sysctl_tcp_window_scaling
) {
3949 __u8 snd_wscale
= *(__u8
*)ptr
;
3950 opt_rx
->wscale_ok
= 1;
3951 if (snd_wscale
> 14) {
3952 if (net_ratelimit())
3953 pr_info("%s: Illegal window scaling value %d >14 received\n",
3958 opt_rx
->snd_wscale
= snd_wscale
;
3961 case TCPOPT_TIMESTAMP
:
3962 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3963 ((estab
&& opt_rx
->tstamp_ok
) ||
3964 (!estab
&& sysctl_tcp_timestamps
))) {
3965 opt_rx
->saw_tstamp
= 1;
3966 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3967 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3970 case TCPOPT_SACK_PERM
:
3971 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3972 !estab
&& sysctl_tcp_sack
) {
3973 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3974 tcp_sack_reset(opt_rx
);
3979 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3980 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3982 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3985 #ifdef CONFIG_TCP_MD5SIG
3988 * The MD5 Hash has already been
3989 * checked (see tcp_v{4,6}_do_rcv()).
3994 /* This option is variable length.
3997 case TCPOLEN_COOKIE_BASE
:
3998 /* not yet implemented */
4000 case TCPOLEN_COOKIE_PAIR
:
4001 /* not yet implemented */
4003 case TCPOLEN_COOKIE_MIN
+0:
4004 case TCPOLEN_COOKIE_MIN
+2:
4005 case TCPOLEN_COOKIE_MIN
+4:
4006 case TCPOLEN_COOKIE_MIN
+6:
4007 case TCPOLEN_COOKIE_MAX
:
4008 /* 16-bit multiple */
4009 opt_rx
->cookie_plus
= opsize
;
4024 EXPORT_SYMBOL(tcp_parse_options
);
4026 static int tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
4028 const __be32
*ptr
= (const __be32
*)(th
+ 1);
4030 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4031 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
4032 tp
->rx_opt
.saw_tstamp
= 1;
4034 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4036 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4042 /* Fast parse options. This hopes to only see timestamps.
4043 * If it is wrong it falls back on tcp_parse_options().
4045 static int tcp_fast_parse_options(const struct sk_buff
*skb
,
4046 const struct tcphdr
*th
,
4047 struct tcp_sock
*tp
, const u8
**hvpp
)
4049 /* In the spirit of fast parsing, compare doff directly to constant
4050 * values. Because equality is used, short doff can be ignored here.
4052 if (th
->doff
== (sizeof(*th
) / 4)) {
4053 tp
->rx_opt
.saw_tstamp
= 0;
4055 } else if (tp
->rx_opt
.tstamp_ok
&&
4056 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
4057 if (tcp_parse_aligned_timestamp(tp
, th
))
4060 tcp_parse_options(skb
, &tp
->rx_opt
, hvpp
, 1);
4064 #ifdef CONFIG_TCP_MD5SIG
4066 * Parse MD5 Signature option
4068 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
4070 int length
= (th
->doff
<< 2) - sizeof(*th
);
4071 const u8
*ptr
= (const u8
*)(th
+ 1);
4073 /* If the TCP option is too short, we can short cut */
4074 if (length
< TCPOLEN_MD5SIG
)
4077 while (length
> 0) {
4078 int opcode
= *ptr
++;
4089 if (opsize
< 2 || opsize
> length
)
4091 if (opcode
== TCPOPT_MD5SIG
)
4092 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
4099 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
4102 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
4104 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
4105 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
4108 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
4110 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
4111 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
4112 * extra check below makes sure this can only happen
4113 * for pure ACK frames. -DaveM
4115 * Not only, also it occurs for expired timestamps.
4118 if (tcp_paws_check(&tp
->rx_opt
, 0))
4119 tcp_store_ts_recent(tp
);
4123 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
4125 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
4126 * it can pass through stack. So, the following predicate verifies that
4127 * this segment is not used for anything but congestion avoidance or
4128 * fast retransmit. Moreover, we even are able to eliminate most of such
4129 * second order effects, if we apply some small "replay" window (~RTO)
4130 * to timestamp space.
4132 * All these measures still do not guarantee that we reject wrapped ACKs
4133 * on networks with high bandwidth, when sequence space is recycled fastly,
4134 * but it guarantees that such events will be very rare and do not affect
4135 * connection seriously. This doesn't look nice, but alas, PAWS is really
4138 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
4139 * states that events when retransmit arrives after original data are rare.
4140 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
4141 * the biggest problem on large power networks even with minor reordering.
4142 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
4143 * up to bandwidth of 18Gigabit/sec. 8) ]
4146 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
4148 const struct tcp_sock
*tp
= tcp_sk(sk
);
4149 const struct tcphdr
*th
= tcp_hdr(skb
);
4150 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4151 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
4153 return (/* 1. Pure ACK with correct sequence number. */
4154 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
4156 /* 2. ... and duplicate ACK. */
4157 ack
== tp
->snd_una
&&
4159 /* 3. ... and does not update window. */
4160 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
4162 /* 4. ... and sits in replay window. */
4163 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
4166 static inline int tcp_paws_discard(const struct sock
*sk
,
4167 const struct sk_buff
*skb
)
4169 const struct tcp_sock
*tp
= tcp_sk(sk
);
4171 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
4172 !tcp_disordered_ack(sk
, skb
);
4175 /* Check segment sequence number for validity.
4177 * Segment controls are considered valid, if the segment
4178 * fits to the window after truncation to the window. Acceptability
4179 * of data (and SYN, FIN, of course) is checked separately.
4180 * See tcp_data_queue(), for example.
4182 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4183 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4184 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4185 * (borrowed from freebsd)
4188 static inline int tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
4190 return !before(end_seq
, tp
->rcv_wup
) &&
4191 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
4194 /* When we get a reset we do this. */
4195 static void tcp_reset(struct sock
*sk
)
4197 /* We want the right error as BSD sees it (and indeed as we do). */
4198 switch (sk
->sk_state
) {
4200 sk
->sk_err
= ECONNREFUSED
;
4202 case TCP_CLOSE_WAIT
:
4208 sk
->sk_err
= ECONNRESET
;
4210 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4213 if (!sock_flag(sk
, SOCK_DEAD
))
4214 sk
->sk_error_report(sk
);
4220 * Process the FIN bit. This now behaves as it is supposed to work
4221 * and the FIN takes effect when it is validly part of sequence
4222 * space. Not before when we get holes.
4224 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4225 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4228 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4229 * close and we go into CLOSING (and later onto TIME-WAIT)
4231 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4233 static void tcp_fin(struct sock
*sk
)
4235 struct tcp_sock
*tp
= tcp_sk(sk
);
4237 inet_csk_schedule_ack(sk
);
4239 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4240 sock_set_flag(sk
, SOCK_DONE
);
4242 switch (sk
->sk_state
) {
4244 case TCP_ESTABLISHED
:
4245 /* Move to CLOSE_WAIT */
4246 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4247 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4250 case TCP_CLOSE_WAIT
:
4252 /* Received a retransmission of the FIN, do
4257 /* RFC793: Remain in the LAST-ACK state. */
4261 /* This case occurs when a simultaneous close
4262 * happens, we must ack the received FIN and
4263 * enter the CLOSING state.
4266 tcp_set_state(sk
, TCP_CLOSING
);
4269 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4271 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4274 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4275 * cases we should never reach this piece of code.
4277 pr_err("%s: Impossible, sk->sk_state=%d\n",
4278 __func__
, sk
->sk_state
);
4282 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4283 * Probably, we should reset in this case. For now drop them.
4285 __skb_queue_purge(&tp
->out_of_order_queue
);
4286 if (tcp_is_sack(tp
))
4287 tcp_sack_reset(&tp
->rx_opt
);
4290 if (!sock_flag(sk
, SOCK_DEAD
)) {
4291 sk
->sk_state_change(sk
);
4293 /* Do not send POLL_HUP for half duplex close. */
4294 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4295 sk
->sk_state
== TCP_CLOSE
)
4296 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4298 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4302 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4305 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4306 if (before(seq
, sp
->start_seq
))
4307 sp
->start_seq
= seq
;
4308 if (after(end_seq
, sp
->end_seq
))
4309 sp
->end_seq
= end_seq
;
4315 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4317 struct tcp_sock
*tp
= tcp_sk(sk
);
4319 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4322 if (before(seq
, tp
->rcv_nxt
))
4323 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4325 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4327 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4329 tp
->rx_opt
.dsack
= 1;
4330 tp
->duplicate_sack
[0].start_seq
= seq
;
4331 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4335 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4337 struct tcp_sock
*tp
= tcp_sk(sk
);
4339 if (!tp
->rx_opt
.dsack
)
4340 tcp_dsack_set(sk
, seq
, end_seq
);
4342 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4345 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4347 struct tcp_sock
*tp
= tcp_sk(sk
);
4349 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4350 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4351 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4352 tcp_enter_quickack_mode(sk
);
4354 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4355 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4357 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4358 end_seq
= tp
->rcv_nxt
;
4359 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4366 /* These routines update the SACK block as out-of-order packets arrive or
4367 * in-order packets close up the sequence space.
4369 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4372 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4373 struct tcp_sack_block
*swalk
= sp
+ 1;
4375 /* See if the recent change to the first SACK eats into
4376 * or hits the sequence space of other SACK blocks, if so coalesce.
4378 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4379 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4382 /* Zap SWALK, by moving every further SACK up by one slot.
4383 * Decrease num_sacks.
4385 tp
->rx_opt
.num_sacks
--;
4386 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4390 this_sack
++, swalk
++;
4394 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4396 struct tcp_sock
*tp
= tcp_sk(sk
);
4397 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4398 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4404 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4405 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4406 /* Rotate this_sack to the first one. */
4407 for (; this_sack
> 0; this_sack
--, sp
--)
4408 swap(*sp
, *(sp
- 1));
4410 tcp_sack_maybe_coalesce(tp
);
4415 /* Could not find an adjacent existing SACK, build a new one,
4416 * put it at the front, and shift everyone else down. We
4417 * always know there is at least one SACK present already here.
4419 * If the sack array is full, forget about the last one.
4421 if (this_sack
>= TCP_NUM_SACKS
) {
4423 tp
->rx_opt
.num_sacks
--;
4426 for (; this_sack
> 0; this_sack
--, sp
--)
4430 /* Build the new head SACK, and we're done. */
4431 sp
->start_seq
= seq
;
4432 sp
->end_seq
= end_seq
;
4433 tp
->rx_opt
.num_sacks
++;
4436 /* RCV.NXT advances, some SACKs should be eaten. */
4438 static void tcp_sack_remove(struct tcp_sock
*tp
)
4440 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4441 int num_sacks
= tp
->rx_opt
.num_sacks
;
4444 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4445 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4446 tp
->rx_opt
.num_sacks
= 0;
4450 for (this_sack
= 0; this_sack
< num_sacks
;) {
4451 /* Check if the start of the sack is covered by RCV.NXT. */
4452 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4455 /* RCV.NXT must cover all the block! */
4456 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4458 /* Zap this SACK, by moving forward any other SACKS. */
4459 for (i
=this_sack
+1; i
< num_sacks
; i
++)
4460 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4467 tp
->rx_opt
.num_sacks
= num_sacks
;
4470 /* This one checks to see if we can put data from the
4471 * out_of_order queue into the receive_queue.
4473 static void tcp_ofo_queue(struct sock
*sk
)
4475 struct tcp_sock
*tp
= tcp_sk(sk
);
4476 __u32 dsack_high
= tp
->rcv_nxt
;
4477 struct sk_buff
*skb
;
4479 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4480 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4483 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4484 __u32 dsack
= dsack_high
;
4485 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4486 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4487 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4490 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4491 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4492 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4496 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4497 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4498 TCP_SKB_CB(skb
)->end_seq
);
4500 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4501 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4502 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4503 if (tcp_hdr(skb
)->fin
)
4508 static int tcp_prune_ofo_queue(struct sock
*sk
);
4509 static int tcp_prune_queue(struct sock
*sk
);
4511 static inline int tcp_try_rmem_schedule(struct sock
*sk
, unsigned int size
)
4513 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4514 !sk_rmem_schedule(sk
, size
)) {
4516 if (tcp_prune_queue(sk
) < 0)
4519 if (!sk_rmem_schedule(sk
, size
)) {
4520 if (!tcp_prune_ofo_queue(sk
))
4523 if (!sk_rmem_schedule(sk
, size
))
4531 * tcp_try_coalesce - try to merge skb to prior one
4534 * @from: buffer to add in queue
4535 * @fragstolen: pointer to boolean
4537 * Before queueing skb @from after @to, try to merge them
4538 * to reduce overall memory use and queue lengths, if cost is small.
4539 * Packets in ofo or receive queues can stay a long time.
4540 * Better try to coalesce them right now to avoid future collapses.
4541 * Returns true if caller should free @from instead of queueing it
4543 static bool tcp_try_coalesce(struct sock
*sk
,
4545 struct sk_buff
*from
,
4548 int i
, delta
, len
= from
->len
;
4550 *fragstolen
= false;
4551 if (tcp_hdr(from
)->fin
|| skb_cloned(to
))
4553 if (len
<= skb_tailroom(to
)) {
4554 BUG_ON(skb_copy_bits(from
, 0, skb_put(to
, len
), len
));
4556 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOALESCE
);
4557 TCP_SKB_CB(to
)->end_seq
= TCP_SKB_CB(from
)->end_seq
;
4558 TCP_SKB_CB(to
)->ack_seq
= TCP_SKB_CB(from
)->ack_seq
;
4562 if (skb_has_frag_list(to
) || skb_has_frag_list(from
))
4565 if (skb_headlen(from
) == 0 &&
4566 (skb_shinfo(to
)->nr_frags
+
4567 skb_shinfo(from
)->nr_frags
<= MAX_SKB_FRAGS
)) {
4568 WARN_ON_ONCE(from
->head_frag
);
4569 delta
= from
->truesize
- ksize(from
->head
) -
4570 SKB_DATA_ALIGN(sizeof(struct sk_buff
));
4572 WARN_ON_ONCE(delta
< len
);
4574 memcpy(skb_shinfo(to
)->frags
+ skb_shinfo(to
)->nr_frags
,
4575 skb_shinfo(from
)->frags
,
4576 skb_shinfo(from
)->nr_frags
* sizeof(skb_frag_t
));
4577 skb_shinfo(to
)->nr_frags
+= skb_shinfo(from
)->nr_frags
;
4579 if (skb_cloned(from
))
4580 for (i
= 0; i
< skb_shinfo(from
)->nr_frags
; i
++)
4581 skb_frag_ref(from
, i
);
4583 skb_shinfo(from
)->nr_frags
= 0;
4585 to
->truesize
+= delta
;
4586 atomic_add(delta
, &sk
->sk_rmem_alloc
);
4587 sk_mem_charge(sk
, delta
);
4589 to
->data_len
+= len
;
4592 if (from
->head_frag
) {
4594 unsigned int offset
;
4596 if (skb_shinfo(to
)->nr_frags
+ skb_shinfo(from
)->nr_frags
>= MAX_SKB_FRAGS
)
4598 page
= virt_to_head_page(from
->head
);
4599 offset
= from
->data
- (unsigned char *)page_address(page
);
4600 skb_fill_page_desc(to
, skb_shinfo(to
)->nr_frags
,
4601 page
, offset
, skb_headlen(from
));
4603 if (skb_cloned(from
))
4608 delta
= len
; /* we dont know real truesize... */
4614 static void kfree_skb_partial(struct sk_buff
*skb
, bool head_stolen
)
4617 kmem_cache_free(skbuff_head_cache
, skb
);
4622 static void tcp_data_queue_ofo(struct sock
*sk
, struct sk_buff
*skb
)
4624 struct tcp_sock
*tp
= tcp_sk(sk
);
4625 struct sk_buff
*skb1
;
4628 TCP_ECN_check_ce(tp
, skb
);
4630 if (tcp_try_rmem_schedule(sk
, skb
->truesize
)) {
4631 /* TODO: should increment a counter */
4636 /* Disable header prediction. */
4638 inet_csk_schedule_ack(sk
);
4640 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4641 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4643 skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4645 /* Initial out of order segment, build 1 SACK. */
4646 if (tcp_is_sack(tp
)) {
4647 tp
->rx_opt
.num_sacks
= 1;
4648 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4649 tp
->selective_acks
[0].end_seq
=
4650 TCP_SKB_CB(skb
)->end_seq
;
4652 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4656 seq
= TCP_SKB_CB(skb
)->seq
;
4657 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4659 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4662 if (!tcp_try_coalesce(sk
, skb1
, skb
, &fragstolen
)) {
4663 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4665 kfree_skb_partial(skb
, fragstolen
);
4669 if (!tp
->rx_opt
.num_sacks
||
4670 tp
->selective_acks
[0].end_seq
!= seq
)
4673 /* Common case: data arrive in order after hole. */
4674 tp
->selective_acks
[0].end_seq
= end_seq
;
4678 /* Find place to insert this segment. */
4680 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4682 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4686 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4689 /* Do skb overlap to previous one? */
4690 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4691 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4692 /* All the bits are present. Drop. */
4695 tcp_dsack_set(sk
, seq
, end_seq
);
4698 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4699 /* Partial overlap. */
4700 tcp_dsack_set(sk
, seq
,
4701 TCP_SKB_CB(skb1
)->end_seq
);
4703 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4707 skb1
= skb_queue_prev(
4708 &tp
->out_of_order_queue
,
4713 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4715 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4717 /* And clean segments covered by new one as whole. */
4718 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4719 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4721 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4723 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4724 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4728 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4729 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4730 TCP_SKB_CB(skb1
)->end_seq
);
4735 if (tcp_is_sack(tp
))
4736 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4739 skb_set_owner_r(skb
, sk
);
4743 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4745 const struct tcphdr
*th
= tcp_hdr(skb
);
4746 struct tcp_sock
*tp
= tcp_sk(sk
);
4748 bool fragstolen
= false;
4750 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4754 __skb_pull(skb
, th
->doff
* 4);
4756 TCP_ECN_accept_cwr(tp
, skb
);
4758 tp
->rx_opt
.dsack
= 0;
4760 /* Queue data for delivery to the user.
4761 * Packets in sequence go to the receive queue.
4762 * Out of sequence packets to the out_of_order_queue.
4764 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4765 if (tcp_receive_window(tp
) == 0)
4768 /* Ok. In sequence. In window. */
4769 if (tp
->ucopy
.task
== current
&&
4770 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4771 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4772 int chunk
= min_t(unsigned int, skb
->len
,
4775 __set_current_state(TASK_RUNNING
);
4778 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4779 tp
->ucopy
.len
-= chunk
;
4780 tp
->copied_seq
+= chunk
;
4781 eaten
= (chunk
== skb
->len
);
4782 tcp_rcv_space_adjust(sk
);
4788 struct sk_buff
*tail
;
4791 tcp_try_rmem_schedule(sk
, skb
->truesize
))
4794 tail
= skb_peek_tail(&sk
->sk_receive_queue
);
4796 tcp_try_coalesce(sk
, tail
, skb
,
4797 &fragstolen
)) ? 1 : 0;
4799 skb_set_owner_r(skb
, sk
);
4800 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4803 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4805 tcp_event_data_recv(sk
, skb
);
4809 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4812 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4813 * gap in queue is filled.
4815 if (skb_queue_empty(&tp
->out_of_order_queue
))
4816 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4819 if (tp
->rx_opt
.num_sacks
)
4820 tcp_sack_remove(tp
);
4822 tcp_fast_path_check(sk
);
4825 kfree_skb_partial(skb
, fragstolen
);
4826 else if (!sock_flag(sk
, SOCK_DEAD
))
4827 sk
->sk_data_ready(sk
, 0);
4831 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4832 /* A retransmit, 2nd most common case. Force an immediate ack. */
4833 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4834 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4837 tcp_enter_quickack_mode(sk
);
4838 inet_csk_schedule_ack(sk
);
4844 /* Out of window. F.e. zero window probe. */
4845 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4848 tcp_enter_quickack_mode(sk
);
4850 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4851 /* Partial packet, seq < rcv_next < end_seq */
4852 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4853 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4854 TCP_SKB_CB(skb
)->end_seq
);
4856 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4858 /* If window is closed, drop tail of packet. But after
4859 * remembering D-SACK for its head made in previous line.
4861 if (!tcp_receive_window(tp
))
4866 tcp_data_queue_ofo(sk
, skb
);
4869 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4870 struct sk_buff_head
*list
)
4872 struct sk_buff
*next
= NULL
;
4874 if (!skb_queue_is_last(list
, skb
))
4875 next
= skb_queue_next(list
, skb
);
4877 __skb_unlink(skb
, list
);
4879 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4884 /* Collapse contiguous sequence of skbs head..tail with
4885 * sequence numbers start..end.
4887 * If tail is NULL, this means until the end of the list.
4889 * Segments with FIN/SYN are not collapsed (only because this
4893 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4894 struct sk_buff
*head
, struct sk_buff
*tail
,
4897 struct sk_buff
*skb
, *n
;
4900 /* First, check that queue is collapsible and find
4901 * the point where collapsing can be useful. */
4905 skb_queue_walk_from_safe(list
, skb
, n
) {
4908 /* No new bits? It is possible on ofo queue. */
4909 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4910 skb
= tcp_collapse_one(sk
, skb
, list
);
4916 /* The first skb to collapse is:
4918 * - bloated or contains data before "start" or
4919 * overlaps to the next one.
4921 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4922 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4923 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4924 end_of_skbs
= false;
4928 if (!skb_queue_is_last(list
, skb
)) {
4929 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4931 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4932 end_of_skbs
= false;
4937 /* Decided to skip this, advance start seq. */
4938 start
= TCP_SKB_CB(skb
)->end_seq
;
4940 if (end_of_skbs
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4943 while (before(start
, end
)) {
4944 struct sk_buff
*nskb
;
4945 unsigned int header
= skb_headroom(skb
);
4946 int copy
= SKB_MAX_ORDER(header
, 0);
4948 /* Too big header? This can happen with IPv6. */
4951 if (end
- start
< copy
)
4953 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4957 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4958 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4960 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4962 skb_reserve(nskb
, header
);
4963 memcpy(nskb
->head
, skb
->head
, header
);
4964 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4965 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4966 __skb_queue_before(list
, skb
, nskb
);
4967 skb_set_owner_r(nskb
, sk
);
4969 /* Copy data, releasing collapsed skbs. */
4971 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4972 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4976 size
= min(copy
, size
);
4977 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4979 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4983 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4984 skb
= tcp_collapse_one(sk
, skb
, list
);
4987 tcp_hdr(skb
)->syn
||
4995 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4996 * and tcp_collapse() them until all the queue is collapsed.
4998 static void tcp_collapse_ofo_queue(struct sock
*sk
)
5000 struct tcp_sock
*tp
= tcp_sk(sk
);
5001 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
5002 struct sk_buff
*head
;
5008 start
= TCP_SKB_CB(skb
)->seq
;
5009 end
= TCP_SKB_CB(skb
)->end_seq
;
5013 struct sk_buff
*next
= NULL
;
5015 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
5016 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
5019 /* Segment is terminated when we see gap or when
5020 * we are at the end of all the queue. */
5022 after(TCP_SKB_CB(skb
)->seq
, end
) ||
5023 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
5024 tcp_collapse(sk
, &tp
->out_of_order_queue
,
5025 head
, skb
, start
, end
);
5029 /* Start new segment */
5030 start
= TCP_SKB_CB(skb
)->seq
;
5031 end
= TCP_SKB_CB(skb
)->end_seq
;
5033 if (before(TCP_SKB_CB(skb
)->seq
, start
))
5034 start
= TCP_SKB_CB(skb
)->seq
;
5035 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
5036 end
= TCP_SKB_CB(skb
)->end_seq
;
5042 * Purge the out-of-order queue.
5043 * Return true if queue was pruned.
5045 static int tcp_prune_ofo_queue(struct sock
*sk
)
5047 struct tcp_sock
*tp
= tcp_sk(sk
);
5050 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
5051 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
5052 __skb_queue_purge(&tp
->out_of_order_queue
);
5054 /* Reset SACK state. A conforming SACK implementation will
5055 * do the same at a timeout based retransmit. When a connection
5056 * is in a sad state like this, we care only about integrity
5057 * of the connection not performance.
5059 if (tp
->rx_opt
.sack_ok
)
5060 tcp_sack_reset(&tp
->rx_opt
);
5067 /* Reduce allocated memory if we can, trying to get
5068 * the socket within its memory limits again.
5070 * Return less than zero if we should start dropping frames
5071 * until the socket owning process reads some of the data
5072 * to stabilize the situation.
5074 static int tcp_prune_queue(struct sock
*sk
)
5076 struct tcp_sock
*tp
= tcp_sk(sk
);
5078 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
5080 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
5082 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
5083 tcp_clamp_window(sk
);
5084 else if (sk_under_memory_pressure(sk
))
5085 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
5087 tcp_collapse_ofo_queue(sk
);
5088 if (!skb_queue_empty(&sk
->sk_receive_queue
))
5089 tcp_collapse(sk
, &sk
->sk_receive_queue
,
5090 skb_peek(&sk
->sk_receive_queue
),
5092 tp
->copied_seq
, tp
->rcv_nxt
);
5095 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5098 /* Collapsing did not help, destructive actions follow.
5099 * This must not ever occur. */
5101 tcp_prune_ofo_queue(sk
);
5103 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
5106 /* If we are really being abused, tell the caller to silently
5107 * drop receive data on the floor. It will get retransmitted
5108 * and hopefully then we'll have sufficient space.
5110 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
5112 /* Massive buffer overcommit. */
5117 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
5118 * As additional protections, we do not touch cwnd in retransmission phases,
5119 * and if application hit its sndbuf limit recently.
5121 void tcp_cwnd_application_limited(struct sock
*sk
)
5123 struct tcp_sock
*tp
= tcp_sk(sk
);
5125 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
5126 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
5127 /* Limited by application or receiver window. */
5128 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
5129 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
5130 if (win_used
< tp
->snd_cwnd
) {
5131 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
5132 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
5134 tp
->snd_cwnd_used
= 0;
5136 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
5139 static int tcp_should_expand_sndbuf(const struct sock
*sk
)
5141 const struct tcp_sock
*tp
= tcp_sk(sk
);
5143 /* If the user specified a specific send buffer setting, do
5146 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
5149 /* If we are under global TCP memory pressure, do not expand. */
5150 if (sk_under_memory_pressure(sk
))
5153 /* If we are under soft global TCP memory pressure, do not expand. */
5154 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
5157 /* If we filled the congestion window, do not expand. */
5158 if (tp
->packets_out
>= tp
->snd_cwnd
)
5164 /* When incoming ACK allowed to free some skb from write_queue,
5165 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
5166 * on the exit from tcp input handler.
5168 * PROBLEM: sndbuf expansion does not work well with largesend.
5170 static void tcp_new_space(struct sock
*sk
)
5172 struct tcp_sock
*tp
= tcp_sk(sk
);
5174 if (tcp_should_expand_sndbuf(sk
)) {
5175 int sndmem
= SKB_TRUESIZE(max_t(u32
,
5176 tp
->rx_opt
.mss_clamp
,
5179 int demanded
= max_t(unsigned int, tp
->snd_cwnd
,
5180 tp
->reordering
+ 1);
5181 sndmem
*= 2 * demanded
;
5182 if (sndmem
> sk
->sk_sndbuf
)
5183 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
5184 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
5187 sk
->sk_write_space(sk
);
5190 static void tcp_check_space(struct sock
*sk
)
5192 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
5193 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
5194 if (sk
->sk_socket
&&
5195 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
5200 static inline void tcp_data_snd_check(struct sock
*sk
)
5202 tcp_push_pending_frames(sk
);
5203 tcp_check_space(sk
);
5207 * Check if sending an ack is needed.
5209 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
5211 struct tcp_sock
*tp
= tcp_sk(sk
);
5213 /* More than one full frame received... */
5214 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
5215 /* ... and right edge of window advances far enough.
5216 * (tcp_recvmsg() will send ACK otherwise). Or...
5218 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
5219 /* We ACK each frame or... */
5220 tcp_in_quickack_mode(sk
) ||
5221 /* We have out of order data. */
5222 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
5223 /* Then ack it now */
5226 /* Else, send delayed ack. */
5227 tcp_send_delayed_ack(sk
);
5231 static inline void tcp_ack_snd_check(struct sock
*sk
)
5233 if (!inet_csk_ack_scheduled(sk
)) {
5234 /* We sent a data segment already. */
5237 __tcp_ack_snd_check(sk
, 1);
5241 * This routine is only called when we have urgent data
5242 * signaled. Its the 'slow' part of tcp_urg. It could be
5243 * moved inline now as tcp_urg is only called from one
5244 * place. We handle URGent data wrong. We have to - as
5245 * BSD still doesn't use the correction from RFC961.
5246 * For 1003.1g we should support a new option TCP_STDURG to permit
5247 * either form (or just set the sysctl tcp_stdurg).
5250 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
5252 struct tcp_sock
*tp
= tcp_sk(sk
);
5253 u32 ptr
= ntohs(th
->urg_ptr
);
5255 if (ptr
&& !sysctl_tcp_stdurg
)
5257 ptr
+= ntohl(th
->seq
);
5259 /* Ignore urgent data that we've already seen and read. */
5260 if (after(tp
->copied_seq
, ptr
))
5263 /* Do not replay urg ptr.
5265 * NOTE: interesting situation not covered by specs.
5266 * Misbehaving sender may send urg ptr, pointing to segment,
5267 * which we already have in ofo queue. We are not able to fetch
5268 * such data and will stay in TCP_URG_NOTYET until will be eaten
5269 * by recvmsg(). Seems, we are not obliged to handle such wicked
5270 * situations. But it is worth to think about possibility of some
5271 * DoSes using some hypothetical application level deadlock.
5273 if (before(ptr
, tp
->rcv_nxt
))
5276 /* Do we already have a newer (or duplicate) urgent pointer? */
5277 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5280 /* Tell the world about our new urgent pointer. */
5283 /* We may be adding urgent data when the last byte read was
5284 * urgent. To do this requires some care. We cannot just ignore
5285 * tp->copied_seq since we would read the last urgent byte again
5286 * as data, nor can we alter copied_seq until this data arrives
5287 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5289 * NOTE. Double Dutch. Rendering to plain English: author of comment
5290 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5291 * and expect that both A and B disappear from stream. This is _wrong_.
5292 * Though this happens in BSD with high probability, this is occasional.
5293 * Any application relying on this is buggy. Note also, that fix "works"
5294 * only in this artificial test. Insert some normal data between A and B and we will
5295 * decline of BSD again. Verdict: it is better to remove to trap
5298 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5299 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5300 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5302 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5303 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5308 tp
->urg_data
= TCP_URG_NOTYET
;
5311 /* Disable header prediction. */
5315 /* This is the 'fast' part of urgent handling. */
5316 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5318 struct tcp_sock
*tp
= tcp_sk(sk
);
5320 /* Check if we get a new urgent pointer - normally not. */
5322 tcp_check_urg(sk
, th
);
5324 /* Do we wait for any urgent data? - normally not... */
5325 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5326 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5329 /* Is the urgent pointer pointing into this packet? */
5330 if (ptr
< skb
->len
) {
5332 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5334 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5335 if (!sock_flag(sk
, SOCK_DEAD
))
5336 sk
->sk_data_ready(sk
, 0);
5341 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5343 struct tcp_sock
*tp
= tcp_sk(sk
);
5344 int chunk
= skb
->len
- hlen
;
5348 if (skb_csum_unnecessary(skb
))
5349 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
5351 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
5355 tp
->ucopy
.len
-= chunk
;
5356 tp
->copied_seq
+= chunk
;
5357 tcp_rcv_space_adjust(sk
);
5364 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5365 struct sk_buff
*skb
)
5369 if (sock_owned_by_user(sk
)) {
5371 result
= __tcp_checksum_complete(skb
);
5374 result
= __tcp_checksum_complete(skb
);
5379 static inline int tcp_checksum_complete_user(struct sock
*sk
,
5380 struct sk_buff
*skb
)
5382 return !skb_csum_unnecessary(skb
) &&
5383 __tcp_checksum_complete_user(sk
, skb
);
5386 #ifdef CONFIG_NET_DMA
5387 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
5390 struct tcp_sock
*tp
= tcp_sk(sk
);
5391 int chunk
= skb
->len
- hlen
;
5393 int copied_early
= 0;
5395 if (tp
->ucopy
.wakeup
)
5398 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
5399 tp
->ucopy
.dma_chan
= net_dma_find_channel();
5401 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
5403 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
5405 tp
->ucopy
.iov
, chunk
,
5406 tp
->ucopy
.pinned_list
);
5411 tp
->ucopy
.dma_cookie
= dma_cookie
;
5414 tp
->ucopy
.len
-= chunk
;
5415 tp
->copied_seq
+= chunk
;
5416 tcp_rcv_space_adjust(sk
);
5418 if ((tp
->ucopy
.len
== 0) ||
5419 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
5420 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
5421 tp
->ucopy
.wakeup
= 1;
5422 sk
->sk_data_ready(sk
, 0);
5424 } else if (chunk
> 0) {
5425 tp
->ucopy
.wakeup
= 1;
5426 sk
->sk_data_ready(sk
, 0);
5429 return copied_early
;
5431 #endif /* CONFIG_NET_DMA */
5433 /* Does PAWS and seqno based validation of an incoming segment, flags will
5434 * play significant role here.
5436 static int tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5437 const struct tcphdr
*th
, int syn_inerr
)
5439 const u8
*hash_location
;
5440 struct tcp_sock
*tp
= tcp_sk(sk
);
5442 /* RFC1323: H1. Apply PAWS check first. */
5443 if (tcp_fast_parse_options(skb
, th
, tp
, &hash_location
) &&
5444 tp
->rx_opt
.saw_tstamp
&&
5445 tcp_paws_discard(sk
, skb
)) {
5447 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5448 tcp_send_dupack(sk
, skb
);
5451 /* Reset is accepted even if it did not pass PAWS. */
5454 /* Step 1: check sequence number */
5455 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5456 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5457 * (RST) segments are validated by checking their SEQ-fields."
5458 * And page 69: "If an incoming segment is not acceptable,
5459 * an acknowledgment should be sent in reply (unless the RST
5460 * bit is set, if so drop the segment and return)".
5463 tcp_send_dupack(sk
, skb
);
5467 /* Step 2: check RST bit */
5473 /* ts_recent update must be made after we are sure that the packet
5476 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5478 /* step 3: check security and precedence [ignored] */
5480 /* step 4: Check for a SYN in window. */
5481 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5483 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5484 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
5496 void tcp_queue_rcv(struct sock
*sk
, struct sk_buff
*skb
, int hdrlen
)
5498 __skb_pull(skb
, hdrlen
);
5499 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
5500 skb_set_owner_r(skb
, sk
);
5501 tcp_sk(sk
)->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5505 * TCP receive function for the ESTABLISHED state.
5507 * It is split into a fast path and a slow path. The fast path is
5509 * - A zero window was announced from us - zero window probing
5510 * is only handled properly in the slow path.
5511 * - Out of order segments arrived.
5512 * - Urgent data is expected.
5513 * - There is no buffer space left
5514 * - Unexpected TCP flags/window values/header lengths are received
5515 * (detected by checking the TCP header against pred_flags)
5516 * - Data is sent in both directions. Fast path only supports pure senders
5517 * or pure receivers (this means either the sequence number or the ack
5518 * value must stay constant)
5519 * - Unexpected TCP option.
5521 * When these conditions are not satisfied it drops into a standard
5522 * receive procedure patterned after RFC793 to handle all cases.
5523 * The first three cases are guaranteed by proper pred_flags setting,
5524 * the rest is checked inline. Fast processing is turned on in
5525 * tcp_data_queue when everything is OK.
5527 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5528 const struct tcphdr
*th
, unsigned int len
)
5530 struct tcp_sock
*tp
= tcp_sk(sk
);
5534 * Header prediction.
5535 * The code loosely follows the one in the famous
5536 * "30 instruction TCP receive" Van Jacobson mail.
5538 * Van's trick is to deposit buffers into socket queue
5539 * on a device interrupt, to call tcp_recv function
5540 * on the receive process context and checksum and copy
5541 * the buffer to user space. smart...
5543 * Our current scheme is not silly either but we take the
5544 * extra cost of the net_bh soft interrupt processing...
5545 * We do checksum and copy also but from device to kernel.
5548 tp
->rx_opt
.saw_tstamp
= 0;
5550 /* pred_flags is 0xS?10 << 16 + snd_wnd
5551 * if header_prediction is to be made
5552 * 'S' will always be tp->tcp_header_len >> 2
5553 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5554 * turn it off (when there are holes in the receive
5555 * space for instance)
5556 * PSH flag is ignored.
5559 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5560 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5561 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5562 int tcp_header_len
= tp
->tcp_header_len
;
5564 /* Timestamp header prediction: tcp_header_len
5565 * is automatically equal to th->doff*4 due to pred_flags
5569 /* Check timestamp */
5570 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5571 /* No? Slow path! */
5572 if (!tcp_parse_aligned_timestamp(tp
, th
))
5575 /* If PAWS failed, check it more carefully in slow path */
5576 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5579 /* DO NOT update ts_recent here, if checksum fails
5580 * and timestamp was corrupted part, it will result
5581 * in a hung connection since we will drop all
5582 * future packets due to the PAWS test.
5586 if (len
<= tcp_header_len
) {
5587 /* Bulk data transfer: sender */
5588 if (len
== tcp_header_len
) {
5589 /* Predicted packet is in window by definition.
5590 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5591 * Hence, check seq<=rcv_wup reduces to:
5593 if (tcp_header_len
==
5594 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5595 tp
->rcv_nxt
== tp
->rcv_wup
)
5596 tcp_store_ts_recent(tp
);
5598 /* We know that such packets are checksummed
5601 tcp_ack(sk
, skb
, 0);
5603 tcp_data_snd_check(sk
);
5605 } else { /* Header too small */
5606 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5611 int copied_early
= 0;
5613 if (tp
->copied_seq
== tp
->rcv_nxt
&&
5614 len
- tcp_header_len
<= tp
->ucopy
.len
) {
5615 #ifdef CONFIG_NET_DMA
5616 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
5621 if (tp
->ucopy
.task
== current
&&
5622 sock_owned_by_user(sk
) && !copied_early
) {
5623 __set_current_state(TASK_RUNNING
);
5625 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
5629 /* Predicted packet is in window by definition.
5630 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5631 * Hence, check seq<=rcv_wup reduces to:
5633 if (tcp_header_len
==
5634 (sizeof(struct tcphdr
) +
5635 TCPOLEN_TSTAMP_ALIGNED
) &&
5636 tp
->rcv_nxt
== tp
->rcv_wup
)
5637 tcp_store_ts_recent(tp
);
5639 tcp_rcv_rtt_measure_ts(sk
, skb
);
5641 __skb_pull(skb
, tcp_header_len
);
5642 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5643 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5646 tcp_cleanup_rbuf(sk
, skb
->len
);
5649 if (tcp_checksum_complete_user(sk
, skb
))
5652 /* Predicted packet is in window by definition.
5653 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5654 * Hence, check seq<=rcv_wup reduces to:
5656 if (tcp_header_len
==
5657 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5658 tp
->rcv_nxt
== tp
->rcv_wup
)
5659 tcp_store_ts_recent(tp
);
5661 tcp_rcv_rtt_measure_ts(sk
, skb
);
5663 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5666 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5668 /* Bulk data transfer: receiver */
5669 tcp_queue_rcv(sk
, skb
, tcp_header_len
);
5672 tcp_event_data_recv(sk
, skb
);
5674 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5675 /* Well, only one small jumplet in fast path... */
5676 tcp_ack(sk
, skb
, FLAG_DATA
);
5677 tcp_data_snd_check(sk
);
5678 if (!inet_csk_ack_scheduled(sk
))
5682 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
5683 __tcp_ack_snd_check(sk
, 0);
5685 #ifdef CONFIG_NET_DMA
5687 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
5693 sk
->sk_data_ready(sk
, 0);
5699 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5703 * Standard slow path.
5706 res
= tcp_validate_incoming(sk
, skb
, th
, 1);
5711 if (th
->ack
&& tcp_ack(sk
, skb
, FLAG_SLOWPATH
) < 0)
5714 tcp_rcv_rtt_measure_ts(sk
, skb
);
5716 /* Process urgent data. */
5717 tcp_urg(sk
, skb
, th
);
5719 /* step 7: process the segment text */
5720 tcp_data_queue(sk
, skb
);
5722 tcp_data_snd_check(sk
);
5723 tcp_ack_snd_check(sk
);
5727 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5733 EXPORT_SYMBOL(tcp_rcv_established
);
5735 void tcp_finish_connect(struct sock
*sk
, struct sk_buff
*skb
)
5737 struct tcp_sock
*tp
= tcp_sk(sk
);
5738 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5740 tcp_set_state(sk
, TCP_ESTABLISHED
);
5743 security_inet_conn_established(sk
, skb
);
5745 /* Make sure socket is routed, for correct metrics. */
5746 icsk
->icsk_af_ops
->rebuild_header(sk
);
5748 tcp_init_metrics(sk
);
5750 tcp_init_congestion_control(sk
);
5752 /* Prevent spurious tcp_cwnd_restart() on first data
5755 tp
->lsndtime
= tcp_time_stamp
;
5757 tcp_init_buffer_space(sk
);
5759 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5760 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5762 if (!tp
->rx_opt
.snd_wscale
)
5763 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5767 if (!sock_flag(sk
, SOCK_DEAD
)) {
5768 sk
->sk_state_change(sk
);
5769 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5773 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5774 const struct tcphdr
*th
, unsigned int len
)
5776 const u8
*hash_location
;
5777 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5778 struct tcp_sock
*tp
= tcp_sk(sk
);
5779 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
5780 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5782 tcp_parse_options(skb
, &tp
->rx_opt
, &hash_location
, 0);
5786 * "If the state is SYN-SENT then
5787 * first check the ACK bit
5788 * If the ACK bit is set
5789 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5790 * a reset (unless the RST bit is set, if so drop
5791 * the segment and return)"
5793 * We do not send data with SYN, so that RFC-correct
5796 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
5797 goto reset_and_undo
;
5799 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5800 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5802 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5803 goto reset_and_undo
;
5806 /* Now ACK is acceptable.
5808 * "If the RST bit is set
5809 * If the ACK was acceptable then signal the user "error:
5810 * connection reset", drop the segment, enter CLOSED state,
5811 * delete TCB, and return."
5820 * "fifth, if neither of the SYN or RST bits is set then
5821 * drop the segment and return."
5827 goto discard_and_undo
;
5830 * "If the SYN bit is on ...
5831 * are acceptable then ...
5832 * (our SYN has been ACKed), change the connection
5833 * state to ESTABLISHED..."
5836 TCP_ECN_rcv_synack(tp
, th
);
5838 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5839 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5841 /* Ok.. it's good. Set up sequence numbers and
5842 * move to established.
5844 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5845 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5847 /* RFC1323: The window in SYN & SYN/ACK segments is
5850 tp
->snd_wnd
= ntohs(th
->window
);
5851 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5853 if (!tp
->rx_opt
.wscale_ok
) {
5854 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5855 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5858 if (tp
->rx_opt
.saw_tstamp
) {
5859 tp
->rx_opt
.tstamp_ok
= 1;
5860 tp
->tcp_header_len
=
5861 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5862 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5863 tcp_store_ts_recent(tp
);
5865 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5868 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5869 tcp_enable_fack(tp
);
5872 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5873 tcp_initialize_rcv_mss(sk
);
5875 /* Remember, tcp_poll() does not lock socket!
5876 * Change state from SYN-SENT only after copied_seq
5877 * is initialized. */
5878 tp
->copied_seq
= tp
->rcv_nxt
;
5881 cvp
->cookie_pair_size
> 0 &&
5882 tp
->rx_opt
.cookie_plus
> 0) {
5883 int cookie_size
= tp
->rx_opt
.cookie_plus
5884 - TCPOLEN_COOKIE_BASE
;
5885 int cookie_pair_size
= cookie_size
5886 + cvp
->cookie_desired
;
5888 /* A cookie extension option was sent and returned.
5889 * Note that each incoming SYNACK replaces the
5890 * Responder cookie. The initial exchange is most
5891 * fragile, as protection against spoofing relies
5892 * entirely upon the sequence and timestamp (above).
5893 * This replacement strategy allows the correct pair to
5894 * pass through, while any others will be filtered via
5895 * Responder verification later.
5897 if (sizeof(cvp
->cookie_pair
) >= cookie_pair_size
) {
5898 memcpy(&cvp
->cookie_pair
[cvp
->cookie_desired
],
5899 hash_location
, cookie_size
);
5900 cvp
->cookie_pair_size
= cookie_pair_size
;
5906 tcp_finish_connect(sk
, skb
);
5908 if (sk
->sk_write_pending
||
5909 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5910 icsk
->icsk_ack
.pingpong
) {
5911 /* Save one ACK. Data will be ready after
5912 * several ticks, if write_pending is set.
5914 * It may be deleted, but with this feature tcpdumps
5915 * look so _wonderfully_ clever, that I was not able
5916 * to stand against the temptation 8) --ANK
5918 inet_csk_schedule_ack(sk
);
5919 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5920 tcp_enter_quickack_mode(sk
);
5921 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5922 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5933 /* No ACK in the segment */
5937 * "If the RST bit is set
5939 * Otherwise (no ACK) drop the segment and return."
5942 goto discard_and_undo
;
5946 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5947 tcp_paws_reject(&tp
->rx_opt
, 0))
5948 goto discard_and_undo
;
5951 /* We see SYN without ACK. It is attempt of
5952 * simultaneous connect with crossed SYNs.
5953 * Particularly, it can be connect to self.
5955 tcp_set_state(sk
, TCP_SYN_RECV
);
5957 if (tp
->rx_opt
.saw_tstamp
) {
5958 tp
->rx_opt
.tstamp_ok
= 1;
5959 tcp_store_ts_recent(tp
);
5960 tp
->tcp_header_len
=
5961 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5963 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5966 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5967 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5969 /* RFC1323: The window in SYN & SYN/ACK segments is
5972 tp
->snd_wnd
= ntohs(th
->window
);
5973 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5974 tp
->max_window
= tp
->snd_wnd
;
5976 TCP_ECN_rcv_syn(tp
, th
);
5979 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5980 tcp_initialize_rcv_mss(sk
);
5982 tcp_send_synack(sk
);
5984 /* Note, we could accept data and URG from this segment.
5985 * There are no obstacles to make this.
5987 * However, if we ignore data in ACKless segments sometimes,
5988 * we have no reasons to accept it sometimes.
5989 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5990 * is not flawless. So, discard packet for sanity.
5991 * Uncomment this return to process the data.
5998 /* "fifth, if neither of the SYN or RST bits is set then
5999 * drop the segment and return."
6003 tcp_clear_options(&tp
->rx_opt
);
6004 tp
->rx_opt
.mss_clamp
= saved_clamp
;
6008 tcp_clear_options(&tp
->rx_opt
);
6009 tp
->rx_opt
.mss_clamp
= saved_clamp
;
6014 * This function implements the receiving procedure of RFC 793 for
6015 * all states except ESTABLISHED and TIME_WAIT.
6016 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
6017 * address independent.
6020 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
6021 const struct tcphdr
*th
, unsigned int len
)
6023 struct tcp_sock
*tp
= tcp_sk(sk
);
6024 struct inet_connection_sock
*icsk
= inet_csk(sk
);
6028 tp
->rx_opt
.saw_tstamp
= 0;
6030 switch (sk
->sk_state
) {
6044 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
6047 /* Now we have several options: In theory there is
6048 * nothing else in the frame. KA9Q has an option to
6049 * send data with the syn, BSD accepts data with the
6050 * syn up to the [to be] advertised window and
6051 * Solaris 2.1 gives you a protocol error. For now
6052 * we just ignore it, that fits the spec precisely
6053 * and avoids incompatibilities. It would be nice in
6054 * future to drop through and process the data.
6056 * Now that TTCP is starting to be used we ought to
6058 * But, this leaves one open to an easy denial of
6059 * service attack, and SYN cookies can't defend
6060 * against this problem. So, we drop the data
6061 * in the interest of security over speed unless
6062 * it's still in use.
6070 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
6074 /* Do step6 onward by hand. */
6075 tcp_urg(sk
, skb
, th
);
6077 tcp_data_snd_check(sk
);
6081 res
= tcp_validate_incoming(sk
, skb
, th
, 0);
6085 /* step 5: check the ACK field */
6087 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
) > 0;
6089 switch (sk
->sk_state
) {
6092 tp
->copied_seq
= tp
->rcv_nxt
;
6094 tcp_set_state(sk
, TCP_ESTABLISHED
);
6095 sk
->sk_state_change(sk
);
6097 /* Note, that this wakeup is only for marginal
6098 * crossed SYN case. Passively open sockets
6099 * are not waked up, because sk->sk_sleep ==
6100 * NULL and sk->sk_socket == NULL.
6104 SOCK_WAKE_IO
, POLL_OUT
);
6106 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
6107 tp
->snd_wnd
= ntohs(th
->window
) <<
6108 tp
->rx_opt
.snd_wscale
;
6109 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
6111 if (tp
->rx_opt
.tstamp_ok
)
6112 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
6114 /* Make sure socket is routed, for
6117 icsk
->icsk_af_ops
->rebuild_header(sk
);
6119 tcp_init_metrics(sk
);
6121 tcp_init_congestion_control(sk
);
6123 /* Prevent spurious tcp_cwnd_restart() on
6124 * first data packet.
6126 tp
->lsndtime
= tcp_time_stamp
;
6129 tcp_initialize_rcv_mss(sk
);
6130 tcp_init_buffer_space(sk
);
6131 tcp_fast_path_on(tp
);
6138 if (tp
->snd_una
== tp
->write_seq
) {
6139 tcp_set_state(sk
, TCP_FIN_WAIT2
);
6140 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
6141 dst_confirm(__sk_dst_get(sk
));
6143 if (!sock_flag(sk
, SOCK_DEAD
))
6144 /* Wake up lingering close() */
6145 sk
->sk_state_change(sk
);
6149 if (tp
->linger2
< 0 ||
6150 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6151 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
6153 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6157 tmo
= tcp_fin_time(sk
);
6158 if (tmo
> TCP_TIMEWAIT_LEN
) {
6159 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
6160 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
6161 /* Bad case. We could lose such FIN otherwise.
6162 * It is not a big problem, but it looks confusing
6163 * and not so rare event. We still can lose it now,
6164 * if it spins in bh_lock_sock(), but it is really
6167 inet_csk_reset_keepalive_timer(sk
, tmo
);
6169 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
6177 if (tp
->snd_una
== tp
->write_seq
) {
6178 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
6184 if (tp
->snd_una
== tp
->write_seq
) {
6185 tcp_update_metrics(sk
);
6194 /* step 6: check the URG bit */
6195 tcp_urg(sk
, skb
, th
);
6197 /* step 7: process the segment text */
6198 switch (sk
->sk_state
) {
6199 case TCP_CLOSE_WAIT
:
6202 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
6206 /* RFC 793 says to queue data in these states,
6207 * RFC 1122 says we MUST send a reset.
6208 * BSD 4.4 also does reset.
6210 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
6211 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
6212 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
6213 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6219 case TCP_ESTABLISHED
:
6220 tcp_data_queue(sk
, skb
);
6225 /* tcp_data could move socket to TIME-WAIT */
6226 if (sk
->sk_state
!= TCP_CLOSE
) {
6227 tcp_data_snd_check(sk
);
6228 tcp_ack_snd_check(sk
);
6237 EXPORT_SYMBOL(tcp_rcv_state_process
);