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
65 #include <linux/module.h>
66 #include <linux/sysctl.h>
69 #include <net/inet_common.h>
70 #include <linux/ipsec.h>
71 #include <asm/unaligned.h>
72 #include <net/netdma.h>
74 int sysctl_tcp_timestamps __read_mostly
= 1;
75 int sysctl_tcp_window_scaling __read_mostly
= 1;
76 int sysctl_tcp_sack __read_mostly
= 1;
77 int sysctl_tcp_fack __read_mostly
= 1;
78 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
79 int sysctl_tcp_ecn __read_mostly
;
80 int sysctl_tcp_dsack __read_mostly
= 1;
81 int sysctl_tcp_app_win __read_mostly
= 31;
82 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
84 int sysctl_tcp_stdurg __read_mostly
;
85 int sysctl_tcp_rfc1337 __read_mostly
;
86 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
87 int sysctl_tcp_frto __read_mostly
= 2;
88 int sysctl_tcp_frto_response __read_mostly
;
89 int sysctl_tcp_nometrics_save __read_mostly
;
91 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
92 int sysctl_tcp_abc __read_mostly
;
94 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
95 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
96 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
97 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
98 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
99 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
100 #define FLAG_ECE 0x40 /* ECE in this ACK */
101 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */
102 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
103 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
104 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
105 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
106 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
107 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
109 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
110 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
111 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
112 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
113 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
115 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
116 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
118 /* Adapt the MSS value used to make delayed ack decision to the
121 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
123 struct inet_connection_sock
*icsk
= inet_csk(sk
);
124 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
127 icsk
->icsk_ack
.last_seg_size
= 0;
129 /* skb->len may jitter because of SACKs, even if peer
130 * sends good full-sized frames.
132 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
133 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
134 icsk
->icsk_ack
.rcv_mss
= len
;
136 /* Otherwise, we make more careful check taking into account,
137 * that SACKs block is variable.
139 * "len" is invariant segment length, including TCP header.
141 len
+= skb
->data
- skb_transport_header(skb
);
142 if (len
>= TCP_MIN_RCVMSS
+ sizeof(struct tcphdr
) ||
143 /* If PSH is not set, packet should be
144 * full sized, provided peer TCP is not badly broken.
145 * This observation (if it is correct 8)) allows
146 * to handle super-low mtu links fairly.
148 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
149 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
150 /* Subtract also invariant (if peer is RFC compliant),
151 * tcp header plus fixed timestamp option length.
152 * Resulting "len" is MSS free of SACK jitter.
154 len
-= tcp_sk(sk
)->tcp_header_len
;
155 icsk
->icsk_ack
.last_seg_size
= len
;
157 icsk
->icsk_ack
.rcv_mss
= len
;
161 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
162 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
163 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
167 static void tcp_incr_quickack(struct sock
*sk
)
169 struct inet_connection_sock
*icsk
= inet_csk(sk
);
170 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
174 if (quickacks
> icsk
->icsk_ack
.quick
)
175 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
178 void tcp_enter_quickack_mode(struct sock
*sk
)
180 struct inet_connection_sock
*icsk
= inet_csk(sk
);
181 tcp_incr_quickack(sk
);
182 icsk
->icsk_ack
.pingpong
= 0;
183 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
186 /* Send ACKs quickly, if "quick" count is not exhausted
187 * and the session is not interactive.
190 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
192 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
193 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
196 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
198 if (tp
->ecn_flags
& TCP_ECN_OK
)
199 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
202 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, struct sk_buff
*skb
)
204 if (tcp_hdr(skb
)->cwr
)
205 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
208 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
210 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
213 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, struct sk_buff
*skb
)
215 if (tp
->ecn_flags
& TCP_ECN_OK
) {
216 if (INET_ECN_is_ce(TCP_SKB_CB(skb
)->flags
))
217 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
218 /* Funny extension: if ECT is not set on a segment,
219 * it is surely retransmit. It is not in ECN RFC,
220 * but Linux follows this rule. */
221 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb
)->flags
)))
222 tcp_enter_quickack_mode((struct sock
*)tp
);
226 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, struct tcphdr
*th
)
228 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
229 tp
->ecn_flags
&= ~TCP_ECN_OK
;
232 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, struct tcphdr
*th
)
234 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
235 tp
->ecn_flags
&= ~TCP_ECN_OK
;
238 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock
*tp
, struct tcphdr
*th
)
240 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
245 /* Buffer size and advertised window tuning.
247 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
250 static void tcp_fixup_sndbuf(struct sock
*sk
)
252 int sndmem
= tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
+ 16 +
253 sizeof(struct sk_buff
);
255 if (sk
->sk_sndbuf
< 3 * sndmem
)
256 sk
->sk_sndbuf
= min(3 * sndmem
, sysctl_tcp_wmem
[2]);
259 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
261 * All tcp_full_space() is split to two parts: "network" buffer, allocated
262 * forward and advertised in receiver window (tp->rcv_wnd) and
263 * "application buffer", required to isolate scheduling/application
264 * latencies from network.
265 * window_clamp is maximal advertised window. It can be less than
266 * tcp_full_space(), in this case tcp_full_space() - window_clamp
267 * is reserved for "application" buffer. The less window_clamp is
268 * the smoother our behaviour from viewpoint of network, but the lower
269 * throughput and the higher sensitivity of the connection to losses. 8)
271 * rcv_ssthresh is more strict window_clamp used at "slow start"
272 * phase to predict further behaviour of this connection.
273 * It is used for two goals:
274 * - to enforce header prediction at sender, even when application
275 * requires some significant "application buffer". It is check #1.
276 * - to prevent pruning of receive queue because of misprediction
277 * of receiver window. Check #2.
279 * The scheme does not work when sender sends good segments opening
280 * window and then starts to feed us spaghetti. But it should work
281 * in common situations. Otherwise, we have to rely on queue collapsing.
284 /* Slow part of check#2. */
285 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
287 struct tcp_sock
*tp
= tcp_sk(sk
);
289 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
290 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
292 while (tp
->rcv_ssthresh
<= window
) {
293 if (truesize
<= skb
->len
)
294 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
302 static void tcp_grow_window(struct sock
*sk
, struct sk_buff
*skb
)
304 struct tcp_sock
*tp
= tcp_sk(sk
);
307 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
308 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
309 !tcp_memory_pressure
) {
312 /* Check #2. Increase window, if skb with such overhead
313 * will fit to rcvbuf in future.
315 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
316 incr
= 2 * tp
->advmss
;
318 incr
= __tcp_grow_window(sk
, skb
);
321 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
323 inet_csk(sk
)->icsk_ack
.quick
|= 1;
328 /* 3. Tuning rcvbuf, when connection enters established state. */
330 static void tcp_fixup_rcvbuf(struct sock
*sk
)
332 struct tcp_sock
*tp
= tcp_sk(sk
);
333 int rcvmem
= tp
->advmss
+ MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
);
335 /* Try to select rcvbuf so that 4 mss-sized segments
336 * will fit to window and corresponding skbs will fit to our rcvbuf.
337 * (was 3; 4 is minimum to allow fast retransmit to work.)
339 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
341 if (sk
->sk_rcvbuf
< 4 * rcvmem
)
342 sk
->sk_rcvbuf
= min(4 * rcvmem
, sysctl_tcp_rmem
[2]);
345 /* 4. Try to fixup all. It is made immediately after connection enters
348 static void tcp_init_buffer_space(struct sock
*sk
)
350 struct tcp_sock
*tp
= tcp_sk(sk
);
353 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
354 tcp_fixup_rcvbuf(sk
);
355 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
356 tcp_fixup_sndbuf(sk
);
358 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
360 maxwin
= tcp_full_space(sk
);
362 if (tp
->window_clamp
>= maxwin
) {
363 tp
->window_clamp
= maxwin
;
365 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
366 tp
->window_clamp
= max(maxwin
-
367 (maxwin
>> sysctl_tcp_app_win
),
371 /* Force reservation of one segment. */
372 if (sysctl_tcp_app_win
&&
373 tp
->window_clamp
> 2 * tp
->advmss
&&
374 tp
->window_clamp
+ tp
->advmss
> maxwin
)
375 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
377 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
378 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
381 /* 5. Recalculate window clamp after socket hit its memory bounds. */
382 static void tcp_clamp_window(struct sock
*sk
)
384 struct tcp_sock
*tp
= tcp_sk(sk
);
385 struct inet_connection_sock
*icsk
= inet_csk(sk
);
387 icsk
->icsk_ack
.quick
= 0;
389 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
390 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
391 !tcp_memory_pressure
&&
392 atomic_read(&tcp_memory_allocated
) < sysctl_tcp_mem
[0]) {
393 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
396 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
397 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
400 /* Initialize RCV_MSS value.
401 * RCV_MSS is an our guess about MSS used by the peer.
402 * We haven't any direct information about the MSS.
403 * It's better to underestimate the RCV_MSS rather than overestimate.
404 * Overestimations make us ACKing less frequently than needed.
405 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
407 void tcp_initialize_rcv_mss(struct sock
*sk
)
409 struct tcp_sock
*tp
= tcp_sk(sk
);
410 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
412 hint
= min(hint
, tp
->rcv_wnd
/ 2);
413 hint
= min(hint
, TCP_MIN_RCVMSS
);
414 hint
= max(hint
, TCP_MIN_MSS
);
416 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
419 /* Receiver "autotuning" code.
421 * The algorithm for RTT estimation w/o timestamps is based on
422 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
423 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps>
425 * More detail on this code can be found at
426 * <http://www.psc.edu/~jheffner/senior_thesis.ps>,
427 * though this reference is out of date. A new paper
430 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
432 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
438 if (new_sample
!= 0) {
439 /* If we sample in larger samples in the non-timestamp
440 * case, we could grossly overestimate the RTT especially
441 * with chatty applications or bulk transfer apps which
442 * are stalled on filesystem I/O.
444 * Also, since we are only going for a minimum in the
445 * non-timestamp case, we do not smooth things out
446 * else with timestamps disabled convergence takes too
450 m
-= (new_sample
>> 3);
452 } else if (m
< new_sample
)
455 /* No previous measure. */
459 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
460 tp
->rcv_rtt_est
.rtt
= new_sample
;
463 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
465 if (tp
->rcv_rtt_est
.time
== 0)
467 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
469 tcp_rcv_rtt_update(tp
, jiffies
- tp
->rcv_rtt_est
.time
, 1);
472 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
473 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
476 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
477 const struct sk_buff
*skb
)
479 struct tcp_sock
*tp
= tcp_sk(sk
);
480 if (tp
->rx_opt
.rcv_tsecr
&&
481 (TCP_SKB_CB(skb
)->end_seq
-
482 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
483 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
487 * This function should be called every time data is copied to user space.
488 * It calculates the appropriate TCP receive buffer space.
490 void tcp_rcv_space_adjust(struct sock
*sk
)
492 struct tcp_sock
*tp
= tcp_sk(sk
);
496 if (tp
->rcvq_space
.time
== 0)
499 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
500 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
503 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
505 space
= max(tp
->rcvq_space
.space
, space
);
507 if (tp
->rcvq_space
.space
!= space
) {
510 tp
->rcvq_space
.space
= space
;
512 if (sysctl_tcp_moderate_rcvbuf
&&
513 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
514 int new_clamp
= space
;
516 /* Receive space grows, normalize in order to
517 * take into account packet headers and sk_buff
518 * structure overhead.
523 rcvmem
= (tp
->advmss
+ MAX_TCP_HEADER
+
524 16 + sizeof(struct sk_buff
));
525 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
528 space
= min(space
, sysctl_tcp_rmem
[2]);
529 if (space
> sk
->sk_rcvbuf
) {
530 sk
->sk_rcvbuf
= space
;
532 /* Make the window clamp follow along. */
533 tp
->window_clamp
= new_clamp
;
539 tp
->rcvq_space
.seq
= tp
->copied_seq
;
540 tp
->rcvq_space
.time
= tcp_time_stamp
;
543 /* There is something which you must keep in mind when you analyze the
544 * behavior of the tp->ato delayed ack timeout interval. When a
545 * connection starts up, we want to ack as quickly as possible. The
546 * problem is that "good" TCP's do slow start at the beginning of data
547 * transmission. The means that until we send the first few ACK's the
548 * sender will sit on his end and only queue most of his data, because
549 * he can only send snd_cwnd unacked packets at any given time. For
550 * each ACK we send, he increments snd_cwnd and transmits more of his
553 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
555 struct tcp_sock
*tp
= tcp_sk(sk
);
556 struct inet_connection_sock
*icsk
= inet_csk(sk
);
559 inet_csk_schedule_ack(sk
);
561 tcp_measure_rcv_mss(sk
, skb
);
563 tcp_rcv_rtt_measure(tp
);
565 now
= tcp_time_stamp
;
567 if (!icsk
->icsk_ack
.ato
) {
568 /* The _first_ data packet received, initialize
569 * delayed ACK engine.
571 tcp_incr_quickack(sk
);
572 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
574 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
576 if (m
<= TCP_ATO_MIN
/ 2) {
577 /* The fastest case is the first. */
578 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
579 } else if (m
< icsk
->icsk_ack
.ato
) {
580 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
581 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
582 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
583 } else if (m
> icsk
->icsk_rto
) {
584 /* Too long gap. Apparently sender failed to
585 * restart window, so that we send ACKs quickly.
587 tcp_incr_quickack(sk
);
591 icsk
->icsk_ack
.lrcvtime
= now
;
593 TCP_ECN_check_ce(tp
, skb
);
596 tcp_grow_window(sk
, skb
);
599 static u32
tcp_rto_min(struct sock
*sk
)
601 struct dst_entry
*dst
= __sk_dst_get(sk
);
602 u32 rto_min
= TCP_RTO_MIN
;
604 if (dst
&& dst_metric_locked(dst
, RTAX_RTO_MIN
))
605 rto_min
= dst_metric_rtt(dst
, RTAX_RTO_MIN
);
609 /* Called to compute a smoothed rtt estimate. The data fed to this
610 * routine either comes from timestamps, or from segments that were
611 * known _not_ to have been retransmitted [see Karn/Partridge
612 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
613 * piece by Van Jacobson.
614 * NOTE: the next three routines used to be one big routine.
615 * To save cycles in the RFC 1323 implementation it was better to break
616 * it up into three procedures. -- erics
618 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
620 struct tcp_sock
*tp
= tcp_sk(sk
);
621 long m
= mrtt
; /* RTT */
623 /* The following amusing code comes from Jacobson's
624 * article in SIGCOMM '88. Note that rtt and mdev
625 * are scaled versions of rtt and mean deviation.
626 * This is designed to be as fast as possible
627 * m stands for "measurement".
629 * On a 1990 paper the rto value is changed to:
630 * RTO = rtt + 4 * mdev
632 * Funny. This algorithm seems to be very broken.
633 * These formulae increase RTO, when it should be decreased, increase
634 * too slowly, when it should be increased quickly, decrease too quickly
635 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
636 * does not matter how to _calculate_ it. Seems, it was trap
637 * that VJ failed to avoid. 8)
642 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
643 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
645 m
= -m
; /* m is now abs(error) */
646 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
647 /* This is similar to one of Eifel findings.
648 * Eifel blocks mdev updates when rtt decreases.
649 * This solution is a bit different: we use finer gain
650 * for mdev in this case (alpha*beta).
651 * Like Eifel it also prevents growth of rto,
652 * but also it limits too fast rto decreases,
653 * happening in pure Eifel.
658 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
660 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
661 if (tp
->mdev
> tp
->mdev_max
) {
662 tp
->mdev_max
= tp
->mdev
;
663 if (tp
->mdev_max
> tp
->rttvar
)
664 tp
->rttvar
= tp
->mdev_max
;
666 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
667 if (tp
->mdev_max
< tp
->rttvar
)
668 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
669 tp
->rtt_seq
= tp
->snd_nxt
;
670 tp
->mdev_max
= tcp_rto_min(sk
);
673 /* no previous measure. */
674 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
675 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
676 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
677 tp
->rtt_seq
= tp
->snd_nxt
;
681 /* Calculate rto without backoff. This is the second half of Van Jacobson's
682 * routine referred to above.
684 static inline void tcp_set_rto(struct sock
*sk
)
686 const struct tcp_sock
*tp
= tcp_sk(sk
);
687 /* Old crap is replaced with new one. 8)
690 * 1. If rtt variance happened to be less 50msec, it is hallucination.
691 * It cannot be less due to utterly erratic ACK generation made
692 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
693 * to do with delayed acks, because at cwnd>2 true delack timeout
694 * is invisible. Actually, Linux-2.4 also generates erratic
695 * ACKs in some circumstances.
697 inet_csk(sk
)->icsk_rto
= (tp
->srtt
>> 3) + tp
->rttvar
;
699 /* 2. Fixups made earlier cannot be right.
700 * If we do not estimate RTO correctly without them,
701 * all the algo is pure shit and should be replaced
702 * with correct one. It is exactly, which we pretend to do.
706 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
707 * guarantees that rto is higher.
709 static inline void tcp_bound_rto(struct sock
*sk
)
711 if (inet_csk(sk
)->icsk_rto
> TCP_RTO_MAX
)
712 inet_csk(sk
)->icsk_rto
= TCP_RTO_MAX
;
715 /* Save metrics learned by this TCP session.
716 This function is called only, when TCP finishes successfully
717 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
719 void tcp_update_metrics(struct sock
*sk
)
721 struct tcp_sock
*tp
= tcp_sk(sk
);
722 struct dst_entry
*dst
= __sk_dst_get(sk
);
724 if (sysctl_tcp_nometrics_save
)
729 if (dst
&& (dst
->flags
& DST_HOST
)) {
730 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
734 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
735 /* This session failed to estimate rtt. Why?
736 * Probably, no packets returned in time.
739 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
740 dst
->metrics
[RTAX_RTT
- 1] = 0;
744 rtt
= dst_metric_rtt(dst
, RTAX_RTT
);
747 /* If newly calculated rtt larger than stored one,
748 * store new one. Otherwise, use EWMA. Remember,
749 * rtt overestimation is always better than underestimation.
751 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
753 set_dst_metric_rtt(dst
, RTAX_RTT
, tp
->srtt
);
755 set_dst_metric_rtt(dst
, RTAX_RTT
, rtt
- (m
>> 3));
758 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
763 /* Scale deviation to rttvar fixed point */
768 var
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
772 var
-= (var
- m
) >> 2;
774 set_dst_metric_rtt(dst
, RTAX_RTTVAR
, var
);
777 if (tp
->snd_ssthresh
>= 0xFFFF) {
778 /* Slow start still did not finish. */
779 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
780 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
781 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
782 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_cwnd
>> 1;
783 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
784 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
785 dst
->metrics
[RTAX_CWND
- 1] = tp
->snd_cwnd
;
786 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
787 icsk
->icsk_ca_state
== TCP_CA_Open
) {
788 /* Cong. avoidance phase, cwnd is reliable. */
789 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
790 dst
->metrics
[RTAX_SSTHRESH
-1] =
791 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
);
792 if (!dst_metric_locked(dst
, RTAX_CWND
))
793 dst
->metrics
[RTAX_CWND
-1] = (dst_metric(dst
, RTAX_CWND
) + tp
->snd_cwnd
) >> 1;
795 /* Else slow start did not finish, cwnd is non-sense,
796 ssthresh may be also invalid.
798 if (!dst_metric_locked(dst
, RTAX_CWND
))
799 dst
->metrics
[RTAX_CWND
-1] = (dst_metric(dst
, RTAX_CWND
) + tp
->snd_ssthresh
) >> 1;
800 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
801 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
802 tp
->snd_ssthresh
> dst_metric(dst
, RTAX_SSTHRESH
))
803 dst
->metrics
[RTAX_SSTHRESH
-1] = tp
->snd_ssthresh
;
806 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
807 if (dst_metric(dst
, RTAX_REORDERING
) < tp
->reordering
&&
808 tp
->reordering
!= sysctl_tcp_reordering
)
809 dst
->metrics
[RTAX_REORDERING
-1] = tp
->reordering
;
814 /* Numbers are taken from RFC3390.
816 * John Heffner states:
818 * The RFC specifies a window of no more than 4380 bytes
819 * unless 2*MSS > 4380. Reading the pseudocode in the RFC
820 * is a bit misleading because they use a clamp at 4380 bytes
821 * rather than use a multiplier in the relevant range.
823 __u32
tcp_init_cwnd(struct tcp_sock
*tp
, struct dst_entry
*dst
)
825 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
828 if (tp
->mss_cache
> 1460)
831 cwnd
= (tp
->mss_cache
> 1095) ? 3 : 4;
833 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
836 /* Set slow start threshold and cwnd not falling to slow start */
837 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
839 struct tcp_sock
*tp
= tcp_sk(sk
);
840 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
842 tp
->prior_ssthresh
= 0;
844 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
847 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
848 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
849 tcp_packets_in_flight(tp
) + 1U);
850 tp
->snd_cwnd_cnt
= 0;
851 tp
->high_seq
= tp
->snd_nxt
;
852 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
853 TCP_ECN_queue_cwr(tp
);
855 tcp_set_ca_state(sk
, TCP_CA_CWR
);
860 * Packet counting of FACK is based on in-order assumptions, therefore TCP
861 * disables it when reordering is detected
863 static void tcp_disable_fack(struct tcp_sock
*tp
)
865 /* RFC3517 uses different metric in lost marker => reset on change */
867 tp
->lost_skb_hint
= NULL
;
868 tp
->rx_opt
.sack_ok
&= ~2;
871 /* Take a notice that peer is sending D-SACKs */
872 static void tcp_dsack_seen(struct tcp_sock
*tp
)
874 tp
->rx_opt
.sack_ok
|= 4;
877 /* Initialize metrics on socket. */
879 static void tcp_init_metrics(struct sock
*sk
)
881 struct tcp_sock
*tp
= tcp_sk(sk
);
882 struct dst_entry
*dst
= __sk_dst_get(sk
);
889 if (dst_metric_locked(dst
, RTAX_CWND
))
890 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
891 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
892 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
893 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
894 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
896 if (dst_metric(dst
, RTAX_REORDERING
) &&
897 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
898 tcp_disable_fack(tp
);
899 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
902 if (dst_metric(dst
, RTAX_RTT
) == 0)
905 if (!tp
->srtt
&& dst_metric_rtt(dst
, RTAX_RTT
) < (TCP_TIMEOUT_INIT
<< 3))
908 /* Initial rtt is determined from SYN,SYN-ACK.
909 * The segment is small and rtt may appear much
910 * less than real one. Use per-dst memory
911 * to make it more realistic.
913 * A bit of theory. RTT is time passed after "normal" sized packet
914 * is sent until it is ACKed. In normal circumstances sending small
915 * packets force peer to delay ACKs and calculation is correct too.
916 * The algorithm is adaptive and, provided we follow specs, it
917 * NEVER underestimate RTT. BUT! If peer tries to make some clever
918 * tricks sort of "quick acks" for time long enough to decrease RTT
919 * to low value, and then abruptly stops to do it and starts to delay
920 * ACKs, wait for troubles.
922 if (dst_metric_rtt(dst
, RTAX_RTT
) > tp
->srtt
) {
923 tp
->srtt
= dst_metric_rtt(dst
, RTAX_RTT
);
924 tp
->rtt_seq
= tp
->snd_nxt
;
926 if (dst_metric_rtt(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
927 tp
->mdev
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
928 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
932 if (inet_csk(sk
)->icsk_rto
< TCP_TIMEOUT_INIT
&& !tp
->rx_opt
.saw_tstamp
)
934 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
935 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
939 /* Play conservative. If timestamps are not
940 * supported, TCP will fail to recalculate correct
941 * rtt, if initial rto is too small. FORGET ALL AND RESET!
943 if (!tp
->rx_opt
.saw_tstamp
&& tp
->srtt
) {
945 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_INIT
;
946 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
950 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
953 struct tcp_sock
*tp
= tcp_sk(sk
);
954 if (metric
> tp
->reordering
) {
957 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
959 /* This exciting event is worth to be remembered. 8) */
961 mib_idx
= LINUX_MIB_TCPTSREORDER
;
962 else if (tcp_is_reno(tp
))
963 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
964 else if (tcp_is_fack(tp
))
965 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
967 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
969 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
970 #if FASTRETRANS_DEBUG > 1
971 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
972 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
976 tp
->undo_marker
? tp
->undo_retrans
: 0);
978 tcp_disable_fack(tp
);
982 /* This procedure tags the retransmission queue when SACKs arrive.
984 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
985 * Packets in queue with these bits set are counted in variables
986 * sacked_out, retrans_out and lost_out, correspondingly.
988 * Valid combinations are:
989 * Tag InFlight Description
990 * 0 1 - orig segment is in flight.
991 * S 0 - nothing flies, orig reached receiver.
992 * L 0 - nothing flies, orig lost by net.
993 * R 2 - both orig and retransmit are in flight.
994 * L|R 1 - orig is lost, retransmit is in flight.
995 * S|R 1 - orig reached receiver, retrans is still in flight.
996 * (L|S|R is logically valid, it could occur when L|R is sacked,
997 * but it is equivalent to plain S and code short-curcuits it to S.
998 * L|S is logically invalid, it would mean -1 packet in flight 8))
1000 * These 6 states form finite state machine, controlled by the following events:
1001 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1002 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1003 * 3. Loss detection event of one of three flavors:
1004 * A. Scoreboard estimator decided the packet is lost.
1005 * A'. Reno "three dupacks" marks head of queue lost.
1006 * A''. Its FACK modfication, head until snd.fack is lost.
1007 * B. SACK arrives sacking data transmitted after never retransmitted
1008 * hole was sent out.
1009 * C. SACK arrives sacking SND.NXT at the moment, when the
1010 * segment was retransmitted.
1011 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1013 * It is pleasant to note, that state diagram turns out to be commutative,
1014 * so that we are allowed not to be bothered by order of our actions,
1015 * when multiple events arrive simultaneously. (see the function below).
1017 * Reordering detection.
1018 * --------------------
1019 * Reordering metric is maximal distance, which a packet can be displaced
1020 * in packet stream. With SACKs we can estimate it:
1022 * 1. SACK fills old hole and the corresponding segment was not
1023 * ever retransmitted -> reordering. Alas, we cannot use it
1024 * when segment was retransmitted.
1025 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1026 * for retransmitted and already SACKed segment -> reordering..
1027 * Both of these heuristics are not used in Loss state, when we cannot
1028 * account for retransmits accurately.
1030 * SACK block validation.
1031 * ----------------------
1033 * SACK block range validation checks that the received SACK block fits to
1034 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1035 * Note that SND.UNA is not included to the range though being valid because
1036 * it means that the receiver is rather inconsistent with itself reporting
1037 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1038 * perfectly valid, however, in light of RFC2018 which explicitly states
1039 * that "SACK block MUST reflect the newest segment. Even if the newest
1040 * segment is going to be discarded ...", not that it looks very clever
1041 * in case of head skb. Due to potentional receiver driven attacks, we
1042 * choose to avoid immediate execution of a walk in write queue due to
1043 * reneging and defer head skb's loss recovery to standard loss recovery
1044 * procedure that will eventually trigger (nothing forbids us doing this).
1046 * Implements also blockage to start_seq wrap-around. Problem lies in the
1047 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1048 * there's no guarantee that it will be before snd_nxt (n). The problem
1049 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1052 * <- outs wnd -> <- wrapzone ->
1053 * u e n u_w e_w s n_w
1055 * |<------------+------+----- TCP seqno space --------------+---------->|
1056 * ...-- <2^31 ->| |<--------...
1057 * ...---- >2^31 ------>| |<--------...
1059 * Current code wouldn't be vulnerable but it's better still to discard such
1060 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1061 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1062 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1063 * equal to the ideal case (infinite seqno space without wrap caused issues).
1065 * With D-SACK the lower bound is extended to cover sequence space below
1066 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1067 * again, D-SACK block must not to go across snd_una (for the same reason as
1068 * for the normal SACK blocks, explained above). But there all simplicity
1069 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1070 * fully below undo_marker they do not affect behavior in anyway and can
1071 * therefore be safely ignored. In rare cases (which are more or less
1072 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1073 * fragmentation and packet reordering past skb's retransmission. To consider
1074 * them correctly, the acceptable range must be extended even more though
1075 * the exact amount is rather hard to quantify. However, tp->max_window can
1076 * be used as an exaggerated estimate.
1078 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1079 u32 start_seq
, u32 end_seq
)
1081 /* Too far in future, or reversed (interpretation is ambiguous) */
1082 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1085 /* Nasty start_seq wrap-around check (see comments above) */
1086 if (!before(start_seq
, tp
->snd_nxt
))
1089 /* In outstanding window? ...This is valid exit for D-SACKs too.
1090 * start_seq == snd_una is non-sensical (see comments above)
1092 if (after(start_seq
, tp
->snd_una
))
1095 if (!is_dsack
|| !tp
->undo_marker
)
1098 /* ...Then it's D-SACK, and must reside below snd_una completely */
1099 if (!after(end_seq
, tp
->snd_una
))
1102 if (!before(start_seq
, tp
->undo_marker
))
1106 if (!after(end_seq
, tp
->undo_marker
))
1109 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1110 * start_seq < undo_marker and end_seq >= undo_marker.
1112 return !before(start_seq
, end_seq
- tp
->max_window
);
1115 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1116 * Event "C". Later note: FACK people cheated me again 8), we have to account
1117 * for reordering! Ugly, but should help.
1119 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1120 * less than what is now known to be received by the other end (derived from
1121 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1122 * retransmitted skbs to avoid some costly processing per ACKs.
1124 static void tcp_mark_lost_retrans(struct sock
*sk
)
1126 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1127 struct tcp_sock
*tp
= tcp_sk(sk
);
1128 struct sk_buff
*skb
;
1130 u32 new_low_seq
= tp
->snd_nxt
;
1131 u32 received_upto
= tcp_highest_sack_seq(tp
);
1133 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1134 !after(received_upto
, tp
->lost_retrans_low
) ||
1135 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1138 tcp_for_write_queue(skb
, sk
) {
1139 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1141 if (skb
== tcp_send_head(sk
))
1143 if (cnt
== tp
->retrans_out
)
1145 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1148 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1151 if (after(received_upto
, ack_seq
) &&
1153 !before(received_upto
,
1154 ack_seq
+ tp
->reordering
* tp
->mss_cache
))) {
1155 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1156 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1158 /* clear lost hint */
1159 tp
->retransmit_skb_hint
= NULL
;
1161 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1162 tp
->lost_out
+= tcp_skb_pcount(skb
);
1163 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1165 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1167 if (before(ack_seq
, new_low_seq
))
1168 new_low_seq
= ack_seq
;
1169 cnt
+= tcp_skb_pcount(skb
);
1173 if (tp
->retrans_out
)
1174 tp
->lost_retrans_low
= new_low_seq
;
1177 static int tcp_check_dsack(struct sock
*sk
, struct sk_buff
*ack_skb
,
1178 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1181 struct tcp_sock
*tp
= tcp_sk(sk
);
1182 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1183 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1186 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1189 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1190 } else if (num_sacks
> 1) {
1191 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1192 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1194 if (!after(end_seq_0
, end_seq_1
) &&
1195 !before(start_seq_0
, start_seq_1
)) {
1198 NET_INC_STATS_BH(sock_net(sk
),
1199 LINUX_MIB_TCPDSACKOFORECV
);
1203 /* D-SACK for already forgotten data... Do dumb counting. */
1205 !after(end_seq_0
, prior_snd_una
) &&
1206 after(end_seq_0
, tp
->undo_marker
))
1212 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1213 * the incoming SACK may not exactly match but we can find smaller MSS
1214 * aligned portion of it that matches. Therefore we might need to fragment
1215 * which may fail and creates some hassle (caller must handle error case
1218 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1219 u32 start_seq
, u32 end_seq
)
1222 unsigned int pkt_len
;
1224 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1225 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1227 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1228 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1230 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1233 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1235 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1236 err
= tcp_fragment(sk
, skb
, pkt_len
, skb_shinfo(skb
)->gso_size
);
1244 static int tcp_sacktag_one(struct sk_buff
*skb
, struct sock
*sk
,
1245 int *reord
, int dup_sack
, int fack_count
)
1247 struct tcp_sock
*tp
= tcp_sk(sk
);
1248 u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1251 /* Account D-SACK for retransmitted packet. */
1252 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1253 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->undo_marker
))
1255 if (sacked
& TCPCB_SACKED_ACKED
)
1256 *reord
= min(fack_count
, *reord
);
1259 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1260 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1263 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1264 if (sacked
& TCPCB_SACKED_RETRANS
) {
1265 /* If the segment is not tagged as lost,
1266 * we do not clear RETRANS, believing
1267 * that retransmission is still in flight.
1269 if (sacked
& TCPCB_LOST
) {
1270 TCP_SKB_CB(skb
)->sacked
&=
1271 ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1272 tp
->lost_out
-= tcp_skb_pcount(skb
);
1273 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1275 /* clear lost hint */
1276 tp
->retransmit_skb_hint
= NULL
;
1279 if (!(sacked
& TCPCB_RETRANS
)) {
1280 /* New sack for not retransmitted frame,
1281 * which was in hole. It is reordering.
1283 if (before(TCP_SKB_CB(skb
)->seq
,
1284 tcp_highest_sack_seq(tp
)))
1285 *reord
= min(fack_count
, *reord
);
1287 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1288 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->frto_highmark
))
1289 flag
|= FLAG_ONLY_ORIG_SACKED
;
1292 if (sacked
& TCPCB_LOST
) {
1293 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1294 tp
->lost_out
-= tcp_skb_pcount(skb
);
1296 /* clear lost hint */
1297 tp
->retransmit_skb_hint
= NULL
;
1301 TCP_SKB_CB(skb
)->sacked
|= TCPCB_SACKED_ACKED
;
1302 flag
|= FLAG_DATA_SACKED
;
1303 tp
->sacked_out
+= tcp_skb_pcount(skb
);
1305 fack_count
+= tcp_skb_pcount(skb
);
1307 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1308 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1309 before(TCP_SKB_CB(skb
)->seq
,
1310 TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1311 tp
->lost_cnt_hint
+= tcp_skb_pcount(skb
);
1313 if (fack_count
> tp
->fackets_out
)
1314 tp
->fackets_out
= fack_count
;
1316 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
1317 tcp_advance_highest_sack(sk
, skb
);
1320 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1321 * frames and clear it. undo_retrans is decreased above, L|R frames
1322 * are accounted above as well.
1324 if (dup_sack
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)) {
1325 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1326 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1327 tp
->retransmit_skb_hint
= NULL
;
1333 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1334 struct tcp_sack_block
*next_dup
,
1335 u32 start_seq
, u32 end_seq
,
1336 int dup_sack_in
, int *fack_count
,
1337 int *reord
, int *flag
)
1339 tcp_for_write_queue_from(skb
, sk
) {
1341 int dup_sack
= dup_sack_in
;
1343 if (skb
== tcp_send_head(sk
))
1346 /* queue is in-order => we can short-circuit the walk early */
1347 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1350 if ((next_dup
!= NULL
) &&
1351 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1352 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1353 next_dup
->start_seq
,
1360 in_sack
= tcp_match_skb_to_sack(sk
, skb
, start_seq
,
1362 if (unlikely(in_sack
< 0))
1366 *flag
|= tcp_sacktag_one(skb
, sk
, reord
, dup_sack
,
1369 *fack_count
+= tcp_skb_pcount(skb
);
1374 /* Avoid all extra work that is being done by sacktag while walking in
1377 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1378 u32 skip_to_seq
, int *fack_count
)
1380 tcp_for_write_queue_from(skb
, sk
) {
1381 if (skb
== tcp_send_head(sk
))
1384 if (!before(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1387 *fack_count
+= tcp_skb_pcount(skb
);
1392 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1394 struct tcp_sack_block
*next_dup
,
1396 int *fack_count
, int *reord
,
1399 if (next_dup
== NULL
)
1402 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1403 skb
= tcp_sacktag_skip(skb
, sk
, next_dup
->start_seq
, fack_count
);
1404 skb
= tcp_sacktag_walk(skb
, sk
, NULL
,
1405 next_dup
->start_seq
, next_dup
->end_seq
,
1406 1, fack_count
, reord
, flag
);
1412 static int tcp_sack_cache_ok(struct tcp_sock
*tp
, struct tcp_sack_block
*cache
)
1414 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1418 tcp_sacktag_write_queue(struct sock
*sk
, struct sk_buff
*ack_skb
,
1421 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1422 struct tcp_sock
*tp
= tcp_sk(sk
);
1423 unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1424 TCP_SKB_CB(ack_skb
)->sacked
);
1425 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1426 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1427 struct tcp_sack_block
*cache
;
1428 struct sk_buff
*skb
;
1429 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1431 int reord
= tp
->packets_out
;
1433 int found_dup_sack
= 0;
1436 int first_sack_index
;
1438 if (!tp
->sacked_out
) {
1439 if (WARN_ON(tp
->fackets_out
))
1440 tp
->fackets_out
= 0;
1441 tcp_highest_sack_reset(sk
);
1444 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1445 num_sacks
, prior_snd_una
);
1447 flag
|= FLAG_DSACKING_ACK
;
1449 /* Eliminate too old ACKs, but take into
1450 * account more or less fresh ones, they can
1451 * contain valid SACK info.
1453 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1456 if (!tp
->packets_out
)
1460 first_sack_index
= 0;
1461 for (i
= 0; i
< num_sacks
; i
++) {
1462 int dup_sack
= !i
&& found_dup_sack
;
1464 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1465 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1467 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1468 sp
[used_sacks
].start_seq
,
1469 sp
[used_sacks
].end_seq
)) {
1473 if (!tp
->undo_marker
)
1474 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1476 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1478 /* Don't count olds caused by ACK reordering */
1479 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1480 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1482 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1485 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1487 first_sack_index
= -1;
1491 /* Ignore very old stuff early */
1492 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1498 /* order SACK blocks to allow in order walk of the retrans queue */
1499 for (i
= used_sacks
- 1; i
> 0; i
--) {
1500 for (j
= 0; j
< i
; j
++) {
1501 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1502 struct tcp_sack_block tmp
;
1508 /* Track where the first SACK block goes to */
1509 if (j
== first_sack_index
)
1510 first_sack_index
= j
+ 1;
1515 skb
= tcp_write_queue_head(sk
);
1519 if (!tp
->sacked_out
) {
1520 /* It's already past, so skip checking against it */
1521 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1523 cache
= tp
->recv_sack_cache
;
1524 /* Skip empty blocks in at head of the cache */
1525 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1530 while (i
< used_sacks
) {
1531 u32 start_seq
= sp
[i
].start_seq
;
1532 u32 end_seq
= sp
[i
].end_seq
;
1533 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1534 struct tcp_sack_block
*next_dup
= NULL
;
1536 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1537 next_dup
= &sp
[i
+ 1];
1539 /* Event "B" in the comment above. */
1540 if (after(end_seq
, tp
->high_seq
))
1541 flag
|= FLAG_DATA_LOST
;
1543 /* Skip too early cached blocks */
1544 while (tcp_sack_cache_ok(tp
, cache
) &&
1545 !before(start_seq
, cache
->end_seq
))
1548 /* Can skip some work by looking recv_sack_cache? */
1549 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1550 after(end_seq
, cache
->start_seq
)) {
1553 if (before(start_seq
, cache
->start_seq
)) {
1554 skb
= tcp_sacktag_skip(skb
, sk
, start_seq
,
1556 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1559 dup_sack
, &fack_count
,
1563 /* Rest of the block already fully processed? */
1564 if (!after(end_seq
, cache
->end_seq
))
1567 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1569 &fack_count
, &reord
,
1572 /* ...tail remains todo... */
1573 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1574 /* ...but better entrypoint exists! */
1575 skb
= tcp_highest_sack(sk
);
1578 fack_count
= tp
->fackets_out
;
1583 skb
= tcp_sacktag_skip(skb
, sk
, cache
->end_seq
,
1585 /* Check overlap against next cached too (past this one already) */
1590 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1591 skb
= tcp_highest_sack(sk
);
1594 fack_count
= tp
->fackets_out
;
1596 skb
= tcp_sacktag_skip(skb
, sk
, start_seq
, &fack_count
);
1599 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, start_seq
, end_seq
,
1600 dup_sack
, &fack_count
, &reord
, &flag
);
1603 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1604 * due to in-order walk
1606 if (after(end_seq
, tp
->frto_highmark
))
1607 flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1612 /* Clear the head of the cache sack blocks so we can skip it next time */
1613 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1614 tp
->recv_sack_cache
[i
].start_seq
= 0;
1615 tp
->recv_sack_cache
[i
].end_seq
= 0;
1617 for (j
= 0; j
< used_sacks
; j
++)
1618 tp
->recv_sack_cache
[i
++] = sp
[j
];
1620 tcp_mark_lost_retrans(sk
);
1622 tcp_verify_left_out(tp
);
1624 if ((reord
< tp
->fackets_out
) &&
1625 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1626 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1627 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
1631 #if FASTRETRANS_DEBUG > 0
1632 WARN_ON((int)tp
->sacked_out
< 0);
1633 WARN_ON((int)tp
->lost_out
< 0);
1634 WARN_ON((int)tp
->retrans_out
< 0);
1635 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1640 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1641 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1643 int tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1647 holes
= max(tp
->lost_out
, 1U);
1648 holes
= min(holes
, tp
->packets_out
);
1650 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1651 tp
->sacked_out
= tp
->packets_out
- holes
;
1657 /* If we receive more dupacks than we expected counting segments
1658 * in assumption of absent reordering, interpret this as reordering.
1659 * The only another reason could be bug in receiver TCP.
1661 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1663 struct tcp_sock
*tp
= tcp_sk(sk
);
1664 if (tcp_limit_reno_sacked(tp
))
1665 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1668 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1670 static void tcp_add_reno_sack(struct sock
*sk
)
1672 struct tcp_sock
*tp
= tcp_sk(sk
);
1674 tcp_check_reno_reordering(sk
, 0);
1675 tcp_verify_left_out(tp
);
1678 /* Account for ACK, ACKing some data in Reno Recovery phase. */
1680 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
1682 struct tcp_sock
*tp
= tcp_sk(sk
);
1685 /* One ACK acked hole. The rest eat duplicate ACKs. */
1686 if (acked
- 1 >= tp
->sacked_out
)
1689 tp
->sacked_out
-= acked
- 1;
1691 tcp_check_reno_reordering(sk
, acked
);
1692 tcp_verify_left_out(tp
);
1695 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
1700 static int tcp_is_sackfrto(const struct tcp_sock
*tp
)
1702 return (sysctl_tcp_frto
== 0x2) && !tcp_is_reno(tp
);
1705 /* F-RTO can only be used if TCP has never retransmitted anything other than
1706 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
1708 int tcp_use_frto(struct sock
*sk
)
1710 const struct tcp_sock
*tp
= tcp_sk(sk
);
1711 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1712 struct sk_buff
*skb
;
1714 if (!sysctl_tcp_frto
)
1717 /* MTU probe and F-RTO won't really play nicely along currently */
1718 if (icsk
->icsk_mtup
.probe_size
)
1721 if (tcp_is_sackfrto(tp
))
1724 /* Avoid expensive walking of rexmit queue if possible */
1725 if (tp
->retrans_out
> 1)
1728 skb
= tcp_write_queue_head(sk
);
1729 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
1730 tcp_for_write_queue_from(skb
, sk
) {
1731 if (skb
== tcp_send_head(sk
))
1733 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1735 /* Short-circuit when first non-SACKed skb has been checked */
1736 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
1742 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
1743 * recovery a bit and use heuristics in tcp_process_frto() to detect if
1744 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
1745 * keep retrans_out counting accurate (with SACK F-RTO, other than head
1746 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
1747 * bits are handled if the Loss state is really to be entered (in
1748 * tcp_enter_frto_loss).
1750 * Do like tcp_enter_loss() would; when RTO expires the second time it
1752 * "Reduce ssthresh if it has not yet been made inside this window."
1754 void tcp_enter_frto(struct sock
*sk
)
1756 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1757 struct tcp_sock
*tp
= tcp_sk(sk
);
1758 struct sk_buff
*skb
;
1760 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
1761 tp
->snd_una
== tp
->high_seq
||
1762 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
1763 !icsk
->icsk_retransmits
)) {
1764 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1765 /* Our state is too optimistic in ssthresh() call because cwnd
1766 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
1767 * recovery has not yet completed. Pattern would be this: RTO,
1768 * Cumulative ACK, RTO (2xRTO for the same segment does not end
1770 * RFC4138 should be more specific on what to do, even though
1771 * RTO is quite unlikely to occur after the first Cumulative ACK
1772 * due to back-off and complexity of triggering events ...
1774 if (tp
->frto_counter
) {
1776 stored_cwnd
= tp
->snd_cwnd
;
1778 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1779 tp
->snd_cwnd
= stored_cwnd
;
1781 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1783 /* ... in theory, cong.control module could do "any tricks" in
1784 * ssthresh(), which means that ca_state, lost bits and lost_out
1785 * counter would have to be faked before the call occurs. We
1786 * consider that too expensive, unlikely and hacky, so modules
1787 * using these in ssthresh() must deal these incompatibility
1788 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
1790 tcp_ca_event(sk
, CA_EVENT_FRTO
);
1793 tp
->undo_marker
= tp
->snd_una
;
1794 tp
->undo_retrans
= 0;
1796 skb
= tcp_write_queue_head(sk
);
1797 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1798 tp
->undo_marker
= 0;
1799 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1800 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1801 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1803 tcp_verify_left_out(tp
);
1805 /* Too bad if TCP was application limited */
1806 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
1808 /* Earlier loss recovery underway (see RFC4138; Appendix B).
1809 * The last condition is necessary at least in tp->frto_counter case.
1811 if (tcp_is_sackfrto(tp
) && (tp
->frto_counter
||
1812 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
1813 after(tp
->high_seq
, tp
->snd_una
)) {
1814 tp
->frto_highmark
= tp
->high_seq
;
1816 tp
->frto_highmark
= tp
->snd_nxt
;
1818 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
1819 tp
->high_seq
= tp
->snd_nxt
;
1820 tp
->frto_counter
= 1;
1823 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
1824 * which indicates that we should follow the traditional RTO recovery,
1825 * i.e. mark everything lost and do go-back-N retransmission.
1827 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
1829 struct tcp_sock
*tp
= tcp_sk(sk
);
1830 struct sk_buff
*skb
;
1833 tp
->retrans_out
= 0;
1834 if (tcp_is_reno(tp
))
1835 tcp_reset_reno_sack(tp
);
1837 tcp_for_write_queue(skb
, sk
) {
1838 if (skb
== tcp_send_head(sk
))
1841 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
1843 * Count the retransmission made on RTO correctly (only when
1844 * waiting for the first ACK and did not get it)...
1846 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
1847 /* For some reason this R-bit might get cleared? */
1848 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1849 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1850 /* ...enter this if branch just for the first segment */
1851 flag
|= FLAG_DATA_ACKED
;
1853 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1854 tp
->undo_marker
= 0;
1855 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1858 /* Marking forward transmissions that were made after RTO lost
1859 * can cause unnecessary retransmissions in some scenarios,
1860 * SACK blocks will mitigate that in some but not in all cases.
1861 * We used to not mark them but it was causing break-ups with
1862 * receivers that do only in-order receival.
1864 * TODO: we could detect presence of such receiver and select
1865 * different behavior per flow.
1867 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
1868 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1869 tp
->lost_out
+= tcp_skb_pcount(skb
);
1872 tcp_verify_left_out(tp
);
1874 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
1875 tp
->snd_cwnd_cnt
= 0;
1876 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1877 tp
->frto_counter
= 0;
1878 tp
->bytes_acked
= 0;
1880 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1881 sysctl_tcp_reordering
);
1882 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1883 tp
->high_seq
= tp
->snd_nxt
;
1884 TCP_ECN_queue_cwr(tp
);
1886 tcp_clear_retrans_hints_partial(tp
);
1889 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
1891 tp
->retrans_out
= 0;
1894 tp
->undo_marker
= 0;
1895 tp
->undo_retrans
= 0;
1898 void tcp_clear_retrans(struct tcp_sock
*tp
)
1900 tcp_clear_retrans_partial(tp
);
1902 tp
->fackets_out
= 0;
1906 /* Enter Loss state. If "how" is not zero, forget all SACK information
1907 * and reset tags completely, otherwise preserve SACKs. If receiver
1908 * dropped its ofo queue, we will know this due to reneging detection.
1910 void tcp_enter_loss(struct sock
*sk
, int how
)
1912 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1913 struct tcp_sock
*tp
= tcp_sk(sk
);
1914 struct sk_buff
*skb
;
1916 /* Reduce ssthresh if it has not yet been made inside this window. */
1917 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
1918 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
1919 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
1920 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
1921 tcp_ca_event(sk
, CA_EVENT_LOSS
);
1924 tp
->snd_cwnd_cnt
= 0;
1925 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1927 tp
->bytes_acked
= 0;
1928 tcp_clear_retrans_partial(tp
);
1930 if (tcp_is_reno(tp
))
1931 tcp_reset_reno_sack(tp
);
1934 /* Push undo marker, if it was plain RTO and nothing
1935 * was retransmitted. */
1936 tp
->undo_marker
= tp
->snd_una
;
1937 tcp_clear_retrans_hints_partial(tp
);
1940 tp
->fackets_out
= 0;
1941 tcp_clear_all_retrans_hints(tp
);
1944 tcp_for_write_queue(skb
, sk
) {
1945 if (skb
== tcp_send_head(sk
))
1948 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
1949 tp
->undo_marker
= 0;
1950 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
1951 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
1952 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
1953 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1954 tp
->lost_out
+= tcp_skb_pcount(skb
);
1957 tcp_verify_left_out(tp
);
1959 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
1960 sysctl_tcp_reordering
);
1961 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1962 tp
->high_seq
= tp
->snd_nxt
;
1963 TCP_ECN_queue_cwr(tp
);
1964 /* Abort F-RTO algorithm if one is in progress */
1965 tp
->frto_counter
= 0;
1968 /* If ACK arrived pointing to a remembered SACK, it means that our
1969 * remembered SACKs do not reflect real state of receiver i.e.
1970 * receiver _host_ is heavily congested (or buggy).
1972 * Do processing similar to RTO timeout.
1974 static int tcp_check_sack_reneging(struct sock
*sk
, int flag
)
1976 if (flag
& FLAG_SACK_RENEGING
) {
1977 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1978 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
1980 tcp_enter_loss(sk
, 1);
1981 icsk
->icsk_retransmits
++;
1982 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
1983 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1984 icsk
->icsk_rto
, TCP_RTO_MAX
);
1990 static inline int tcp_fackets_out(struct tcp_sock
*tp
)
1992 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
1995 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
1996 * counter when SACK is enabled (without SACK, sacked_out is used for
1999 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2000 * segments up to the highest received SACK block so far and holes in
2003 * With reordering, holes may still be in flight, so RFC3517 recovery
2004 * uses pure sacked_out (total number of SACKed segments) even though
2005 * it violates the RFC that uses duplicate ACKs, often these are equal
2006 * but when e.g. out-of-window ACKs or packet duplication occurs,
2007 * they differ. Since neither occurs due to loss, TCP should really
2010 static inline int tcp_dupack_heurestics(struct tcp_sock
*tp
)
2012 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2015 static inline int tcp_skb_timedout(struct sock
*sk
, struct sk_buff
*skb
)
2017 return (tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
);
2020 static inline int tcp_head_timedout(struct sock
*sk
)
2022 struct tcp_sock
*tp
= tcp_sk(sk
);
2024 return tp
->packets_out
&&
2025 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2028 /* Linux NewReno/SACK/FACK/ECN state machine.
2029 * --------------------------------------
2031 * "Open" Normal state, no dubious events, fast path.
2032 * "Disorder" In all the respects it is "Open",
2033 * but requires a bit more attention. It is entered when
2034 * we see some SACKs or dupacks. It is split of "Open"
2035 * mainly to move some processing from fast path to slow one.
2036 * "CWR" CWND was reduced due to some Congestion Notification event.
2037 * It can be ECN, ICMP source quench, local device congestion.
2038 * "Recovery" CWND was reduced, we are fast-retransmitting.
2039 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2041 * tcp_fastretrans_alert() is entered:
2042 * - each incoming ACK, if state is not "Open"
2043 * - when arrived ACK is unusual, namely:
2048 * Counting packets in flight is pretty simple.
2050 * in_flight = packets_out - left_out + retrans_out
2052 * packets_out is SND.NXT-SND.UNA counted in packets.
2054 * retrans_out is number of retransmitted segments.
2056 * left_out is number of segments left network, but not ACKed yet.
2058 * left_out = sacked_out + lost_out
2060 * sacked_out: Packets, which arrived to receiver out of order
2061 * and hence not ACKed. With SACKs this number is simply
2062 * amount of SACKed data. Even without SACKs
2063 * it is easy to give pretty reliable estimate of this number,
2064 * counting duplicate ACKs.
2066 * lost_out: Packets lost by network. TCP has no explicit
2067 * "loss notification" feedback from network (for now).
2068 * It means that this number can be only _guessed_.
2069 * Actually, it is the heuristics to predict lossage that
2070 * distinguishes different algorithms.
2072 * F.e. after RTO, when all the queue is considered as lost,
2073 * lost_out = packets_out and in_flight = retrans_out.
2075 * Essentially, we have now two algorithms counting
2078 * FACK: It is the simplest heuristics. As soon as we decided
2079 * that something is lost, we decide that _all_ not SACKed
2080 * packets until the most forward SACK are lost. I.e.
2081 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2082 * It is absolutely correct estimate, if network does not reorder
2083 * packets. And it loses any connection to reality when reordering
2084 * takes place. We use FACK by default until reordering
2085 * is suspected on the path to this destination.
2087 * NewReno: when Recovery is entered, we assume that one segment
2088 * is lost (classic Reno). While we are in Recovery and
2089 * a partial ACK arrives, we assume that one more packet
2090 * is lost (NewReno). This heuristics are the same in NewReno
2093 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2094 * deflation etc. CWND is real congestion window, never inflated, changes
2095 * only according to classic VJ rules.
2097 * Really tricky (and requiring careful tuning) part of algorithm
2098 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2099 * The first determines the moment _when_ we should reduce CWND and,
2100 * hence, slow down forward transmission. In fact, it determines the moment
2101 * when we decide that hole is caused by loss, rather than by a reorder.
2103 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2104 * holes, caused by lost packets.
2106 * And the most logically complicated part of algorithm is undo
2107 * heuristics. We detect false retransmits due to both too early
2108 * fast retransmit (reordering) and underestimated RTO, analyzing
2109 * timestamps and D-SACKs. When we detect that some segments were
2110 * retransmitted by mistake and CWND reduction was wrong, we undo
2111 * window reduction and abort recovery phase. This logic is hidden
2112 * inside several functions named tcp_try_undo_<something>.
2115 /* This function decides, when we should leave Disordered state
2116 * and enter Recovery phase, reducing congestion window.
2118 * Main question: may we further continue forward transmission
2119 * with the same cwnd?
2121 static int tcp_time_to_recover(struct sock
*sk
)
2123 struct tcp_sock
*tp
= tcp_sk(sk
);
2126 /* Do not perform any recovery during F-RTO algorithm */
2127 if (tp
->frto_counter
)
2130 /* Trick#1: The loss is proven. */
2134 /* Not-A-Trick#2 : Classic rule... */
2135 if (tcp_dupack_heurestics(tp
) > tp
->reordering
)
2138 /* Trick#3 : when we use RFC2988 timer restart, fast
2139 * retransmit can be triggered by timeout of queue head.
2141 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2144 /* Trick#4: It is still not OK... But will it be useful to delay
2147 packets_out
= tp
->packets_out
;
2148 if (packets_out
<= tp
->reordering
&&
2149 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2150 !tcp_may_send_now(sk
)) {
2151 /* We have nothing to send. This connection is limited
2152 * either by receiver window or by application.
2160 /* RFC: This is from the original, I doubt that this is necessary at all:
2161 * clear xmit_retrans hint if seq of this skb is beyond hint. How could we
2162 * retransmitted past LOST markings in the first place? I'm not fully sure
2163 * about undo and end of connection cases, which can cause R without L?
2165 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
2167 if ((tp
->retransmit_skb_hint
!= NULL
) &&
2168 before(TCP_SKB_CB(skb
)->seq
,
2169 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
2170 tp
->retransmit_skb_hint
= NULL
;
2173 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is
2174 * is against sacked "cnt", otherwise it's against facked "cnt"
2176 static void tcp_mark_head_lost(struct sock
*sk
, int packets
)
2178 struct tcp_sock
*tp
= tcp_sk(sk
);
2179 struct sk_buff
*skb
;
2184 WARN_ON(packets
> tp
->packets_out
);
2185 if (tp
->lost_skb_hint
) {
2186 skb
= tp
->lost_skb_hint
;
2187 cnt
= tp
->lost_cnt_hint
;
2189 skb
= tcp_write_queue_head(sk
);
2193 tcp_for_write_queue_from(skb
, sk
) {
2194 if (skb
== tcp_send_head(sk
))
2196 /* TODO: do this better */
2197 /* this is not the most efficient way to do this... */
2198 tp
->lost_skb_hint
= skb
;
2199 tp
->lost_cnt_hint
= cnt
;
2201 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->high_seq
))
2205 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2206 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2207 cnt
+= tcp_skb_pcount(skb
);
2209 if (cnt
> packets
) {
2210 if (tcp_is_sack(tp
) || (oldcnt
>= packets
))
2213 mss
= skb_shinfo(skb
)->gso_size
;
2214 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2220 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_SACKED_ACKED
|TCPCB_LOST
))) {
2221 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2222 tp
->lost_out
+= tcp_skb_pcount(skb
);
2223 tcp_verify_retransmit_hint(tp
, skb
);
2226 tcp_verify_left_out(tp
);
2229 /* Account newly detected lost packet(s) */
2231 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2233 struct tcp_sock
*tp
= tcp_sk(sk
);
2235 if (tcp_is_reno(tp
)) {
2236 tcp_mark_head_lost(sk
, 1);
2237 } else if (tcp_is_fack(tp
)) {
2238 int lost
= tp
->fackets_out
- tp
->reordering
;
2241 tcp_mark_head_lost(sk
, lost
);
2243 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2244 if (sacked_upto
< fast_rexmit
)
2245 sacked_upto
= fast_rexmit
;
2246 tcp_mark_head_lost(sk
, sacked_upto
);
2249 /* New heuristics: it is possible only after we switched
2250 * to restart timer each time when something is ACKed.
2251 * Hence, we can detect timed out packets during fast
2252 * retransmit without falling to slow start.
2254 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
)) {
2255 struct sk_buff
*skb
;
2257 skb
= tp
->scoreboard_skb_hint
? tp
->scoreboard_skb_hint
2258 : tcp_write_queue_head(sk
);
2260 tcp_for_write_queue_from(skb
, sk
) {
2261 if (skb
== tcp_send_head(sk
))
2263 if (!tcp_skb_timedout(sk
, skb
))
2266 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_SACKED_ACKED
|TCPCB_LOST
))) {
2267 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2268 tp
->lost_out
+= tcp_skb_pcount(skb
);
2269 tcp_verify_retransmit_hint(tp
, skb
);
2273 tp
->scoreboard_skb_hint
= skb
;
2275 tcp_verify_left_out(tp
);
2279 /* CWND moderation, preventing bursts due to too big ACKs
2280 * in dubious situations.
2282 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2284 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2285 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2286 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2289 /* Lower bound on congestion window is slow start threshold
2290 * unless congestion avoidance choice decides to overide it.
2292 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2294 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2296 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2299 /* Decrease cwnd each second ack. */
2300 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2302 struct tcp_sock
*tp
= tcp_sk(sk
);
2303 int decr
= tp
->snd_cwnd_cnt
+ 1;
2305 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2306 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2307 tp
->snd_cwnd_cnt
= decr
& 1;
2310 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2311 tp
->snd_cwnd
-= decr
;
2313 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2314 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2318 /* Nothing was retransmitted or returned timestamp is less
2319 * than timestamp of the first retransmission.
2321 static inline int tcp_packet_delayed(struct tcp_sock
*tp
)
2323 return !tp
->retrans_stamp
||
2324 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2325 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2328 /* Undo procedures. */
2330 #if FASTRETRANS_DEBUG > 1
2331 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2333 struct tcp_sock
*tp
= tcp_sk(sk
);
2334 struct inet_sock
*inet
= inet_sk(sk
);
2336 if (sk
->sk_family
== AF_INET
) {
2337 printk(KERN_DEBUG
"Undo %s " NIPQUAD_FMT
"/%u c%u l%u ss%u/%u p%u\n",
2339 NIPQUAD(inet
->daddr
), ntohs(inet
->dport
),
2340 tp
->snd_cwnd
, tcp_left_out(tp
),
2341 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2344 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
2345 else if (sk
->sk_family
== AF_INET6
) {
2346 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2347 printk(KERN_DEBUG
"Undo %s " NIP6_FMT
"/%u c%u l%u ss%u/%u p%u\n",
2349 NIP6(np
->daddr
), ntohs(inet
->dport
),
2350 tp
->snd_cwnd
, tcp_left_out(tp
),
2351 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2357 #define DBGUNDO(x...) do { } while (0)
2360 static void tcp_undo_cwr(struct sock
*sk
, const int undo
)
2362 struct tcp_sock
*tp
= tcp_sk(sk
);
2364 if (tp
->prior_ssthresh
) {
2365 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2367 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2368 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2370 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2372 if (undo
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2373 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2374 TCP_ECN_withdraw_cwr(tp
);
2377 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2379 tcp_moderate_cwnd(tp
);
2380 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2382 /* There is something screwy going on with the retrans hints after
2384 tcp_clear_all_retrans_hints(tp
);
2387 static inline int tcp_may_undo(struct tcp_sock
*tp
)
2389 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2392 /* People celebrate: "We love our President!" */
2393 static int tcp_try_undo_recovery(struct sock
*sk
)
2395 struct tcp_sock
*tp
= tcp_sk(sk
);
2397 if (tcp_may_undo(tp
)) {
2400 /* Happy end! We did not retransmit anything
2401 * or our original transmission succeeded.
2403 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2404 tcp_undo_cwr(sk
, 1);
2405 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2406 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2408 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2410 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2411 tp
->undo_marker
= 0;
2413 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2414 /* Hold old state until something *above* high_seq
2415 * is ACKed. For Reno it is MUST to prevent false
2416 * fast retransmits (RFC2582). SACK TCP is safe. */
2417 tcp_moderate_cwnd(tp
);
2420 tcp_set_ca_state(sk
, TCP_CA_Open
);
2424 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2425 static void tcp_try_undo_dsack(struct sock
*sk
)
2427 struct tcp_sock
*tp
= tcp_sk(sk
);
2429 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2430 DBGUNDO(sk
, "D-SACK");
2431 tcp_undo_cwr(sk
, 1);
2432 tp
->undo_marker
= 0;
2433 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2437 /* Undo during fast recovery after partial ACK. */
2439 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2441 struct tcp_sock
*tp
= tcp_sk(sk
);
2442 /* Partial ACK arrived. Force Hoe's retransmit. */
2443 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2445 if (tcp_may_undo(tp
)) {
2446 /* Plain luck! Hole if filled with delayed
2447 * packet, rather than with a retransmit.
2449 if (tp
->retrans_out
== 0)
2450 tp
->retrans_stamp
= 0;
2452 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2455 tcp_undo_cwr(sk
, 0);
2456 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2458 /* So... Do not make Hoe's retransmit yet.
2459 * If the first packet was delayed, the rest
2460 * ones are most probably delayed as well.
2467 /* Undo during loss recovery after partial ACK. */
2468 static int tcp_try_undo_loss(struct sock
*sk
)
2470 struct tcp_sock
*tp
= tcp_sk(sk
);
2472 if (tcp_may_undo(tp
)) {
2473 struct sk_buff
*skb
;
2474 tcp_for_write_queue(skb
, sk
) {
2475 if (skb
== tcp_send_head(sk
))
2477 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2480 tcp_clear_all_retrans_hints(tp
);
2482 DBGUNDO(sk
, "partial loss");
2484 tcp_undo_cwr(sk
, 1);
2485 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2486 inet_csk(sk
)->icsk_retransmits
= 0;
2487 tp
->undo_marker
= 0;
2488 if (tcp_is_sack(tp
))
2489 tcp_set_ca_state(sk
, TCP_CA_Open
);
2495 static inline void tcp_complete_cwr(struct sock
*sk
)
2497 struct tcp_sock
*tp
= tcp_sk(sk
);
2498 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2499 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2500 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2503 static void tcp_try_keep_open(struct sock
*sk
)
2505 struct tcp_sock
*tp
= tcp_sk(sk
);
2506 int state
= TCP_CA_Open
;
2508 if (tcp_left_out(tp
) || tp
->retrans_out
|| tp
->undo_marker
)
2509 state
= TCP_CA_Disorder
;
2511 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2512 tcp_set_ca_state(sk
, state
);
2513 tp
->high_seq
= tp
->snd_nxt
;
2517 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2519 struct tcp_sock
*tp
= tcp_sk(sk
);
2521 tcp_verify_left_out(tp
);
2523 if (!tp
->frto_counter
&& tp
->retrans_out
== 0)
2524 tp
->retrans_stamp
= 0;
2526 if (flag
& FLAG_ECE
)
2527 tcp_enter_cwr(sk
, 1);
2529 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2530 tcp_try_keep_open(sk
);
2531 tcp_moderate_cwnd(tp
);
2533 tcp_cwnd_down(sk
, flag
);
2537 static void tcp_mtup_probe_failed(struct sock
*sk
)
2539 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2541 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2542 icsk
->icsk_mtup
.probe_size
= 0;
2545 static void tcp_mtup_probe_success(struct sock
*sk
, struct sk_buff
*skb
)
2547 struct tcp_sock
*tp
= tcp_sk(sk
);
2548 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2550 /* FIXME: breaks with very large cwnd */
2551 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2552 tp
->snd_cwnd
= tp
->snd_cwnd
*
2553 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2554 icsk
->icsk_mtup
.probe_size
;
2555 tp
->snd_cwnd_cnt
= 0;
2556 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2557 tp
->rcv_ssthresh
= tcp_current_ssthresh(sk
);
2559 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2560 icsk
->icsk_mtup
.probe_size
= 0;
2561 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2564 /* Process an event, which can update packets-in-flight not trivially.
2565 * Main goal of this function is to calculate new estimate for left_out,
2566 * taking into account both packets sitting in receiver's buffer and
2567 * packets lost by network.
2569 * Besides that it does CWND reduction, when packet loss is detected
2570 * and changes state of machine.
2572 * It does _not_ decide what to send, it is made in function
2573 * tcp_xmit_retransmit_queue().
2575 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
, int flag
)
2577 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2578 struct tcp_sock
*tp
= tcp_sk(sk
);
2579 int is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
2580 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
2581 (tcp_fackets_out(tp
) > tp
->reordering
));
2582 int fast_rexmit
= 0, mib_idx
;
2584 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
2586 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
2587 tp
->fackets_out
= 0;
2589 /* Now state machine starts.
2590 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
2591 if (flag
& FLAG_ECE
)
2592 tp
->prior_ssthresh
= 0;
2594 /* B. In all the states check for reneging SACKs. */
2595 if (tcp_check_sack_reneging(sk
, flag
))
2598 /* C. Process data loss notification, provided it is valid. */
2599 if (tcp_is_fack(tp
) && (flag
& FLAG_DATA_LOST
) &&
2600 before(tp
->snd_una
, tp
->high_seq
) &&
2601 icsk
->icsk_ca_state
!= TCP_CA_Open
&&
2602 tp
->fackets_out
> tp
->reordering
) {
2603 tcp_mark_head_lost(sk
, tp
->fackets_out
- tp
->reordering
);
2604 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSS
);
2607 /* D. Check consistency of the current state. */
2608 tcp_verify_left_out(tp
);
2610 /* E. Check state exit conditions. State can be terminated
2611 * when high_seq is ACKed. */
2612 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
2613 WARN_ON(tp
->retrans_out
!= 0);
2614 tp
->retrans_stamp
= 0;
2615 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
2616 switch (icsk
->icsk_ca_state
) {
2618 icsk
->icsk_retransmits
= 0;
2619 if (tcp_try_undo_recovery(sk
))
2624 /* CWR is to be held something *above* high_seq
2625 * is ACKed for CWR bit to reach receiver. */
2626 if (tp
->snd_una
!= tp
->high_seq
) {
2627 tcp_complete_cwr(sk
);
2628 tcp_set_ca_state(sk
, TCP_CA_Open
);
2632 case TCP_CA_Disorder
:
2633 tcp_try_undo_dsack(sk
);
2634 if (!tp
->undo_marker
||
2635 /* For SACK case do not Open to allow to undo
2636 * catching for all duplicate ACKs. */
2637 tcp_is_reno(tp
) || tp
->snd_una
!= tp
->high_seq
) {
2638 tp
->undo_marker
= 0;
2639 tcp_set_ca_state(sk
, TCP_CA_Open
);
2643 case TCP_CA_Recovery
:
2644 if (tcp_is_reno(tp
))
2645 tcp_reset_reno_sack(tp
);
2646 if (tcp_try_undo_recovery(sk
))
2648 tcp_complete_cwr(sk
);
2653 /* F. Process state. */
2654 switch (icsk
->icsk_ca_state
) {
2655 case TCP_CA_Recovery
:
2656 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
2657 if (tcp_is_reno(tp
) && is_dupack
)
2658 tcp_add_reno_sack(sk
);
2660 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
2663 if (flag
& FLAG_DATA_ACKED
)
2664 icsk
->icsk_retransmits
= 0;
2665 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
2666 tcp_reset_reno_sack(tp
);
2667 if (!tcp_try_undo_loss(sk
)) {
2668 tcp_moderate_cwnd(tp
);
2669 tcp_xmit_retransmit_queue(sk
);
2672 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
2674 /* Loss is undone; fall through to processing in Open state. */
2676 if (tcp_is_reno(tp
)) {
2677 if (flag
& FLAG_SND_UNA_ADVANCED
)
2678 tcp_reset_reno_sack(tp
);
2680 tcp_add_reno_sack(sk
);
2683 if (icsk
->icsk_ca_state
== TCP_CA_Disorder
)
2684 tcp_try_undo_dsack(sk
);
2686 if (!tcp_time_to_recover(sk
)) {
2687 tcp_try_to_open(sk
, flag
);
2691 /* MTU probe failure: don't reduce cwnd */
2692 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
2693 icsk
->icsk_mtup
.probe_size
&&
2694 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
2695 tcp_mtup_probe_failed(sk
);
2696 /* Restores the reduction we did in tcp_mtup_probe() */
2698 tcp_simple_retransmit(sk
);
2702 /* Otherwise enter Recovery state */
2704 if (tcp_is_reno(tp
))
2705 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
2707 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
2709 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2711 tp
->high_seq
= tp
->snd_nxt
;
2712 tp
->prior_ssthresh
= 0;
2713 tp
->undo_marker
= tp
->snd_una
;
2714 tp
->undo_retrans
= tp
->retrans_out
;
2716 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
2717 if (!(flag
& FLAG_ECE
))
2718 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2719 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2720 TCP_ECN_queue_cwr(tp
);
2723 tp
->bytes_acked
= 0;
2724 tp
->snd_cwnd_cnt
= 0;
2725 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
2729 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
2730 tcp_update_scoreboard(sk
, fast_rexmit
);
2731 tcp_cwnd_down(sk
, flag
);
2732 tcp_xmit_retransmit_queue(sk
);
2735 /* Read draft-ietf-tcplw-high-performance before mucking
2736 * with this code. (Supersedes RFC1323)
2738 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
2740 /* RTTM Rule: A TSecr value received in a segment is used to
2741 * update the averaged RTT measurement only if the segment
2742 * acknowledges some new data, i.e., only if it advances the
2743 * left edge of the send window.
2745 * See draft-ietf-tcplw-high-performance-00, section 3.3.
2746 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
2748 * Changed: reset backoff as soon as we see the first valid sample.
2749 * If we do not, we get strongly overestimated rto. With timestamps
2750 * samples are accepted even from very old segments: f.e., when rtt=1
2751 * increases to 8, we retransmit 5 times and after 8 seconds delayed
2752 * answer arrives rto becomes 120 seconds! If at least one of segments
2753 * in window is lost... Voila. --ANK (010210)
2755 struct tcp_sock
*tp
= tcp_sk(sk
);
2756 const __u32 seq_rtt
= tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
;
2757 tcp_rtt_estimator(sk
, seq_rtt
);
2759 inet_csk(sk
)->icsk_backoff
= 0;
2763 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
2765 /* We don't have a timestamp. Can only use
2766 * packets that are not retransmitted to determine
2767 * rtt estimates. Also, we must not reset the
2768 * backoff for rto until we get a non-retransmitted
2769 * packet. This allows us to deal with a situation
2770 * where the network delay has increased suddenly.
2771 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
2774 if (flag
& FLAG_RETRANS_DATA_ACKED
)
2777 tcp_rtt_estimator(sk
, seq_rtt
);
2779 inet_csk(sk
)->icsk_backoff
= 0;
2783 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
2786 const struct tcp_sock
*tp
= tcp_sk(sk
);
2787 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
2788 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
2789 tcp_ack_saw_tstamp(sk
, flag
);
2790 else if (seq_rtt
>= 0)
2791 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
2794 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
2796 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2797 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
2798 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
2801 /* Restart timer after forward progress on connection.
2802 * RFC2988 recommends to restart timer to now+rto.
2804 static void tcp_rearm_rto(struct sock
*sk
)
2806 struct tcp_sock
*tp
= tcp_sk(sk
);
2808 if (!tp
->packets_out
) {
2809 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
2811 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2812 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2816 /* If we get here, the whole TSO packet has not been acked. */
2817 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
2819 struct tcp_sock
*tp
= tcp_sk(sk
);
2822 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
2824 packets_acked
= tcp_skb_pcount(skb
);
2825 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2827 packets_acked
-= tcp_skb_pcount(skb
);
2829 if (packets_acked
) {
2830 BUG_ON(tcp_skb_pcount(skb
) == 0);
2831 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
2834 return packets_acked
;
2837 /* Remove acknowledged frames from the retransmission queue. If our packet
2838 * is before the ack sequence we can discard it as it's confirmed to have
2839 * arrived at the other end.
2841 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
)
2843 struct tcp_sock
*tp
= tcp_sk(sk
);
2844 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2845 struct sk_buff
*skb
;
2846 u32 now
= tcp_time_stamp
;
2847 int fully_acked
= 1;
2850 u32 reord
= tp
->packets_out
;
2852 s32 ca_seq_rtt
= -1;
2853 ktime_t last_ackt
= net_invalid_timestamp();
2855 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
2856 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
2859 u8 sacked
= scb
->sacked
;
2861 /* Determine how many packets and what bytes were acked, tso and else */
2862 if (after(scb
->end_seq
, tp
->snd_una
)) {
2863 if (tcp_skb_pcount(skb
) == 1 ||
2864 !after(tp
->snd_una
, scb
->seq
))
2867 acked_pcount
= tcp_tso_acked(sk
, skb
);
2872 end_seq
= tp
->snd_una
;
2874 acked_pcount
= tcp_skb_pcount(skb
);
2875 end_seq
= scb
->end_seq
;
2878 /* MTU probing checks */
2879 if (fully_acked
&& icsk
->icsk_mtup
.probe_size
&&
2880 !after(tp
->mtu_probe
.probe_seq_end
, scb
->end_seq
)) {
2881 tcp_mtup_probe_success(sk
, skb
);
2884 if (sacked
& TCPCB_RETRANS
) {
2885 if (sacked
& TCPCB_SACKED_RETRANS
)
2886 tp
->retrans_out
-= acked_pcount
;
2887 flag
|= FLAG_RETRANS_DATA_ACKED
;
2890 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
2891 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
2893 ca_seq_rtt
= now
- scb
->when
;
2894 last_ackt
= skb
->tstamp
;
2896 seq_rtt
= ca_seq_rtt
;
2898 if (!(sacked
& TCPCB_SACKED_ACKED
))
2899 reord
= min(pkts_acked
, reord
);
2902 if (sacked
& TCPCB_SACKED_ACKED
)
2903 tp
->sacked_out
-= acked_pcount
;
2904 if (sacked
& TCPCB_LOST
)
2905 tp
->lost_out
-= acked_pcount
;
2907 if (unlikely(tp
->urg_mode
&& !before(end_seq
, tp
->snd_up
)))
2910 tp
->packets_out
-= acked_pcount
;
2911 pkts_acked
+= acked_pcount
;
2913 /* Initial outgoing SYN's get put onto the write_queue
2914 * just like anything else we transmit. It is not
2915 * true data, and if we misinform our callers that
2916 * this ACK acks real data, we will erroneously exit
2917 * connection startup slow start one packet too
2918 * quickly. This is severely frowned upon behavior.
2920 if (!(scb
->flags
& TCPCB_FLAG_SYN
)) {
2921 flag
|= FLAG_DATA_ACKED
;
2923 flag
|= FLAG_SYN_ACKED
;
2924 tp
->retrans_stamp
= 0;
2930 tcp_unlink_write_queue(skb
, sk
);
2931 sk_wmem_free_skb(sk
, skb
);
2932 tcp_clear_all_retrans_hints(tp
);
2935 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2936 flag
|= FLAG_SACK_RENEGING
;
2938 if (flag
& FLAG_ACKED
) {
2939 const struct tcp_congestion_ops
*ca_ops
2940 = inet_csk(sk
)->icsk_ca_ops
;
2942 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
2945 if (tcp_is_reno(tp
)) {
2946 tcp_remove_reno_sacks(sk
, pkts_acked
);
2948 /* Non-retransmitted hole got filled? That's reordering */
2949 if (reord
< prior_fackets
)
2950 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
2953 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
2955 if (ca_ops
->pkts_acked
) {
2958 /* Is the ACK triggering packet unambiguous? */
2959 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
2960 /* High resolution needed and available? */
2961 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
2962 !ktime_equal(last_ackt
,
2963 net_invalid_timestamp()))
2964 rtt_us
= ktime_us_delta(ktime_get_real(),
2966 else if (ca_seq_rtt
> 0)
2967 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
2970 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
2974 #if FASTRETRANS_DEBUG > 0
2975 WARN_ON((int)tp
->sacked_out
< 0);
2976 WARN_ON((int)tp
->lost_out
< 0);
2977 WARN_ON((int)tp
->retrans_out
< 0);
2978 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
2979 icsk
= inet_csk(sk
);
2981 printk(KERN_DEBUG
"Leak l=%u %d\n",
2982 tp
->lost_out
, icsk
->icsk_ca_state
);
2985 if (tp
->sacked_out
) {
2986 printk(KERN_DEBUG
"Leak s=%u %d\n",
2987 tp
->sacked_out
, icsk
->icsk_ca_state
);
2990 if (tp
->retrans_out
) {
2991 printk(KERN_DEBUG
"Leak r=%u %d\n",
2992 tp
->retrans_out
, icsk
->icsk_ca_state
);
2993 tp
->retrans_out
= 0;
3000 static void tcp_ack_probe(struct sock
*sk
)
3002 const struct tcp_sock
*tp
= tcp_sk(sk
);
3003 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3005 /* Was it a usable window open? */
3007 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3008 icsk
->icsk_backoff
= 0;
3009 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3010 /* Socket must be waked up by subsequent tcp_data_snd_check().
3011 * This function is not for random using!
3014 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3015 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3020 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3022 return (!(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3023 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
);
3026 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3028 const struct tcp_sock
*tp
= tcp_sk(sk
);
3029 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3030 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
3033 /* Check that window update is acceptable.
3034 * The function assumes that snd_una<=ack<=snd_next.
3036 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
3037 const u32 ack
, const u32 ack_seq
,
3040 return (after(ack
, tp
->snd_una
) ||
3041 after(ack_seq
, tp
->snd_wl1
) ||
3042 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
));
3045 /* Update our send window.
3047 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3048 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3050 static int tcp_ack_update_window(struct sock
*sk
, struct sk_buff
*skb
, u32 ack
,
3053 struct tcp_sock
*tp
= tcp_sk(sk
);
3055 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3057 if (likely(!tcp_hdr(skb
)->syn
))
3058 nwin
<<= tp
->rx_opt
.snd_wscale
;
3060 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3061 flag
|= FLAG_WIN_UPDATE
;
3062 tcp_update_wl(tp
, ack
, ack_seq
);
3064 if (tp
->snd_wnd
!= nwin
) {
3067 /* Note, it is the only place, where
3068 * fast path is recovered for sending TCP.
3071 tcp_fast_path_check(sk
);
3073 if (nwin
> tp
->max_window
) {
3074 tp
->max_window
= nwin
;
3075 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3085 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3086 * continue in congestion avoidance.
3088 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3090 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3091 tp
->snd_cwnd_cnt
= 0;
3092 tp
->bytes_acked
= 0;
3093 TCP_ECN_queue_cwr(tp
);
3094 tcp_moderate_cwnd(tp
);
3097 /* A conservative spurious RTO response algorithm: reduce cwnd using
3098 * rate halving and continue in congestion avoidance.
3100 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3102 tcp_enter_cwr(sk
, 0);
3105 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3107 if (flag
& FLAG_ECE
)
3108 tcp_ratehalving_spur_to_response(sk
);
3110 tcp_undo_cwr(sk
, 1);
3113 /* F-RTO spurious RTO detection algorithm (RFC4138)
3115 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3116 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3117 * window (but not to or beyond highest sequence sent before RTO):
3118 * On First ACK, send two new segments out.
3119 * On Second ACK, RTO was likely spurious. Do spurious response (response
3120 * algorithm is not part of the F-RTO detection algorithm
3121 * given in RFC4138 but can be selected separately).
3122 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3123 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3124 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3125 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3127 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3128 * original window even after we transmit two new data segments.
3131 * on first step, wait until first cumulative ACK arrives, then move to
3132 * the second step. In second step, the next ACK decides.
3134 * F-RTO is implemented (mainly) in four functions:
3135 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3136 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3137 * called when tcp_use_frto() showed green light
3138 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3139 * - tcp_enter_frto_loss() is called if there is not enough evidence
3140 * to prove that the RTO is indeed spurious. It transfers the control
3141 * from F-RTO to the conventional RTO recovery
3143 static int tcp_process_frto(struct sock
*sk
, int flag
)
3145 struct tcp_sock
*tp
= tcp_sk(sk
);
3147 tcp_verify_left_out(tp
);
3149 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3150 if (flag
& FLAG_DATA_ACKED
)
3151 inet_csk(sk
)->icsk_retransmits
= 0;
3153 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3154 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3155 tp
->undo_marker
= 0;
3157 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3158 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3162 if (!tcp_is_sackfrto(tp
)) {
3163 /* RFC4138 shortcoming in step 2; should also have case c):
3164 * ACK isn't duplicate nor advances window, e.g., opposite dir
3167 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3170 if (!(flag
& FLAG_DATA_ACKED
)) {
3171 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3176 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3177 /* Prevent sending of new data. */
3178 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3179 tcp_packets_in_flight(tp
));
3183 if ((tp
->frto_counter
>= 2) &&
3184 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3185 ((flag
& FLAG_DATA_SACKED
) &&
3186 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3187 /* RFC4138 shortcoming (see comment above) */
3188 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3189 (flag
& FLAG_NOT_DUP
))
3192 tcp_enter_frto_loss(sk
, 3, flag
);
3197 if (tp
->frto_counter
== 1) {
3198 /* tcp_may_send_now needs to see updated state */
3199 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3200 tp
->frto_counter
= 2;
3202 if (!tcp_may_send_now(sk
))
3203 tcp_enter_frto_loss(sk
, 2, flag
);
3207 switch (sysctl_tcp_frto_response
) {
3209 tcp_undo_spur_to_response(sk
, flag
);
3212 tcp_conservative_spur_to_response(tp
);
3215 tcp_ratehalving_spur_to_response(sk
);
3218 tp
->frto_counter
= 0;
3219 tp
->undo_marker
= 0;
3220 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSPURIOUSRTOS
);
3225 /* This routine deals with incoming acks, but not outgoing ones. */
3226 static int tcp_ack(struct sock
*sk
, struct sk_buff
*skb
, int flag
)
3228 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3229 struct tcp_sock
*tp
= tcp_sk(sk
);
3230 u32 prior_snd_una
= tp
->snd_una
;
3231 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3232 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3233 u32 prior_in_flight
;
3238 /* If the ack is newer than sent or older than previous acks
3239 * then we can probably ignore it.
3241 if (after(ack
, tp
->snd_nxt
))
3242 goto uninteresting_ack
;
3244 if (before(ack
, prior_snd_una
))
3247 if (after(ack
, prior_snd_una
))
3248 flag
|= FLAG_SND_UNA_ADVANCED
;
3250 if (sysctl_tcp_abc
) {
3251 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3252 tp
->bytes_acked
+= ack
- prior_snd_una
;
3253 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3254 /* we assume just one segment left network */
3255 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3259 prior_fackets
= tp
->fackets_out
;
3260 prior_in_flight
= tcp_packets_in_flight(tp
);
3262 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3263 /* Window is constant, pure forward advance.
3264 * No more checks are required.
3265 * Note, we use the fact that SND.UNA>=SND.WL2.
3267 tcp_update_wl(tp
, ack
, ack_seq
);
3269 flag
|= FLAG_WIN_UPDATE
;
3271 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3273 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3275 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3278 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3280 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3282 if (TCP_SKB_CB(skb
)->sacked
)
3283 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3285 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3288 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3291 /* We passed data and got it acked, remove any soft error
3292 * log. Something worked...
3294 sk
->sk_err_soft
= 0;
3295 icsk
->icsk_probes_out
= 0;
3296 tp
->rcv_tstamp
= tcp_time_stamp
;
3297 prior_packets
= tp
->packets_out
;
3301 /* See if we can take anything off of the retransmit queue. */
3302 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
);
3304 if (tp
->frto_counter
)
3305 frto_cwnd
= tcp_process_frto(sk
, flag
);
3306 /* Guarantee sacktag reordering detection against wrap-arounds */
3307 if (before(tp
->frto_highmark
, tp
->snd_una
))
3308 tp
->frto_highmark
= 0;
3310 if (tcp_ack_is_dubious(sk
, flag
)) {
3311 /* Advance CWND, if state allows this. */
3312 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3313 tcp_may_raise_cwnd(sk
, flag
))
3314 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3315 tcp_fastretrans_alert(sk
, prior_packets
- tp
->packets_out
,
3318 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3319 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3322 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3323 dst_confirm(sk
->sk_dst_cache
);
3328 /* If this ack opens up a zero window, clear backoff. It was
3329 * being used to time the probes, and is probably far higher than
3330 * it needs to be for normal retransmission.
3332 if (tcp_send_head(sk
))
3337 if (TCP_SKB_CB(skb
)->sacked
) {
3338 tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3339 if (icsk
->icsk_ca_state
== TCP_CA_Open
)
3340 tcp_try_keep_open(sk
);
3344 SOCK_DEBUG(sk
, "Ack %u out of %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3348 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3349 * But, this can also be called on packets in the established flow when
3350 * the fast version below fails.
3352 void tcp_parse_options(struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3356 struct tcphdr
*th
= tcp_hdr(skb
);
3357 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3359 ptr
= (unsigned char *)(th
+ 1);
3360 opt_rx
->saw_tstamp
= 0;
3362 while (length
> 0) {
3363 int opcode
= *ptr
++;
3369 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3374 if (opsize
< 2) /* "silly options" */
3376 if (opsize
> length
)
3377 return; /* don't parse partial options */
3380 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3381 u16 in_mss
= get_unaligned_be16(ptr
);
3383 if (opt_rx
->user_mss
&&
3384 opt_rx
->user_mss
< in_mss
)
3385 in_mss
= opt_rx
->user_mss
;
3386 opt_rx
->mss_clamp
= in_mss
;
3391 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3392 !estab
&& sysctl_tcp_window_scaling
) {
3393 __u8 snd_wscale
= *(__u8
*)ptr
;
3394 opt_rx
->wscale_ok
= 1;
3395 if (snd_wscale
> 14) {
3396 if (net_ratelimit())
3397 printk(KERN_INFO
"tcp_parse_options: Illegal window "
3398 "scaling value %d >14 received.\n",
3402 opt_rx
->snd_wscale
= snd_wscale
;
3405 case TCPOPT_TIMESTAMP
:
3406 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3407 ((estab
&& opt_rx
->tstamp_ok
) ||
3408 (!estab
&& sysctl_tcp_timestamps
))) {
3409 opt_rx
->saw_tstamp
= 1;
3410 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3411 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3414 case TCPOPT_SACK_PERM
:
3415 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3416 !estab
&& sysctl_tcp_sack
) {
3417 opt_rx
->sack_ok
= 1;
3418 tcp_sack_reset(opt_rx
);
3423 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3424 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3426 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3429 #ifdef CONFIG_TCP_MD5SIG
3432 * The MD5 Hash has already been
3433 * checked (see tcp_v{4,6}_do_rcv()).
3445 /* Fast parse options. This hopes to only see timestamps.
3446 * If it is wrong it falls back on tcp_parse_options().
3448 static int tcp_fast_parse_options(struct sk_buff
*skb
, struct tcphdr
*th
,
3449 struct tcp_sock
*tp
)
3451 if (th
->doff
== sizeof(struct tcphdr
) >> 2) {
3452 tp
->rx_opt
.saw_tstamp
= 0;
3454 } else if (tp
->rx_opt
.tstamp_ok
&&
3455 th
->doff
== (sizeof(struct tcphdr
)>>2)+(TCPOLEN_TSTAMP_ALIGNED
>>2)) {
3456 __be32
*ptr
= (__be32
*)(th
+ 1);
3457 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3458 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3459 tp
->rx_opt
.saw_tstamp
= 1;
3461 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3463 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3467 tcp_parse_options(skb
, &tp
->rx_opt
, 1);
3471 #ifdef CONFIG_TCP_MD5SIG
3473 * Parse MD5 Signature option
3475 u8
*tcp_parse_md5sig_option(struct tcphdr
*th
)
3477 int length
= (th
->doff
<< 2) - sizeof (*th
);
3478 u8
*ptr
= (u8
*)(th
+ 1);
3480 /* If the TCP option is too short, we can short cut */
3481 if (length
< TCPOLEN_MD5SIG
)
3484 while (length
> 0) {
3485 int opcode
= *ptr
++;
3496 if (opsize
< 2 || opsize
> length
)
3498 if (opcode
== TCPOPT_MD5SIG
)
3508 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
3510 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
3511 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
3514 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
3516 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
3517 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
3518 * extra check below makes sure this can only happen
3519 * for pure ACK frames. -DaveM
3521 * Not only, also it occurs for expired timestamps.
3524 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) >= 0 ||
3525 get_seconds() >= tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
)
3526 tcp_store_ts_recent(tp
);
3530 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
3532 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
3533 * it can pass through stack. So, the following predicate verifies that
3534 * this segment is not used for anything but congestion avoidance or
3535 * fast retransmit. Moreover, we even are able to eliminate most of such
3536 * second order effects, if we apply some small "replay" window (~RTO)
3537 * to timestamp space.
3539 * All these measures still do not guarantee that we reject wrapped ACKs
3540 * on networks with high bandwidth, when sequence space is recycled fastly,
3541 * but it guarantees that such events will be very rare and do not affect
3542 * connection seriously. This doesn't look nice, but alas, PAWS is really
3545 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
3546 * states that events when retransmit arrives after original data are rare.
3547 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
3548 * the biggest problem on large power networks even with minor reordering.
3549 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
3550 * up to bandwidth of 18Gigabit/sec. 8) ]
3553 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
3555 struct tcp_sock
*tp
= tcp_sk(sk
);
3556 struct tcphdr
*th
= tcp_hdr(skb
);
3557 u32 seq
= TCP_SKB_CB(skb
)->seq
;
3558 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3560 return (/* 1. Pure ACK with correct sequence number. */
3561 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
3563 /* 2. ... and duplicate ACK. */
3564 ack
== tp
->snd_una
&&
3566 /* 3. ... and does not update window. */
3567 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
3569 /* 4. ... and sits in replay window. */
3570 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
3573 static inline int tcp_paws_discard(const struct sock
*sk
,
3574 const struct sk_buff
*skb
)
3576 const struct tcp_sock
*tp
= tcp_sk(sk
);
3577 return ((s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) > TCP_PAWS_WINDOW
&&
3578 get_seconds() < tp
->rx_opt
.ts_recent_stamp
+ TCP_PAWS_24DAYS
&&
3579 !tcp_disordered_ack(sk
, skb
));
3582 /* Check segment sequence number for validity.
3584 * Segment controls are considered valid, if the segment
3585 * fits to the window after truncation to the window. Acceptability
3586 * of data (and SYN, FIN, of course) is checked separately.
3587 * See tcp_data_queue(), for example.
3589 * Also, controls (RST is main one) are accepted using RCV.WUP instead
3590 * of RCV.NXT. Peer still did not advance his SND.UNA when we
3591 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
3592 * (borrowed from freebsd)
3595 static inline int tcp_sequence(struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
3597 return !before(end_seq
, tp
->rcv_wup
) &&
3598 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
3601 /* When we get a reset we do this. */
3602 static void tcp_reset(struct sock
*sk
)
3604 /* We want the right error as BSD sees it (and indeed as we do). */
3605 switch (sk
->sk_state
) {
3607 sk
->sk_err
= ECONNREFUSED
;
3609 case TCP_CLOSE_WAIT
:
3615 sk
->sk_err
= ECONNRESET
;
3618 if (!sock_flag(sk
, SOCK_DEAD
))
3619 sk
->sk_error_report(sk
);
3625 * Process the FIN bit. This now behaves as it is supposed to work
3626 * and the FIN takes effect when it is validly part of sequence
3627 * space. Not before when we get holes.
3629 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
3630 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
3633 * If we are in FINWAIT-1, a received FIN indicates simultaneous
3634 * close and we go into CLOSING (and later onto TIME-WAIT)
3636 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
3638 static void tcp_fin(struct sk_buff
*skb
, struct sock
*sk
, struct tcphdr
*th
)
3640 struct tcp_sock
*tp
= tcp_sk(sk
);
3642 inet_csk_schedule_ack(sk
);
3644 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
3645 sock_set_flag(sk
, SOCK_DONE
);
3647 switch (sk
->sk_state
) {
3649 case TCP_ESTABLISHED
:
3650 /* Move to CLOSE_WAIT */
3651 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
3652 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
3655 case TCP_CLOSE_WAIT
:
3657 /* Received a retransmission of the FIN, do
3662 /* RFC793: Remain in the LAST-ACK state. */
3666 /* This case occurs when a simultaneous close
3667 * happens, we must ack the received FIN and
3668 * enter the CLOSING state.
3671 tcp_set_state(sk
, TCP_CLOSING
);
3674 /* Received a FIN -- send ACK and enter TIME_WAIT. */
3676 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
3679 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
3680 * cases we should never reach this piece of code.
3682 printk(KERN_ERR
"%s: Impossible, sk->sk_state=%d\n",
3683 __func__
, sk
->sk_state
);
3687 /* It _is_ possible, that we have something out-of-order _after_ FIN.
3688 * Probably, we should reset in this case. For now drop them.
3690 __skb_queue_purge(&tp
->out_of_order_queue
);
3691 if (tcp_is_sack(tp
))
3692 tcp_sack_reset(&tp
->rx_opt
);
3695 if (!sock_flag(sk
, SOCK_DEAD
)) {
3696 sk
->sk_state_change(sk
);
3698 /* Do not send POLL_HUP for half duplex close. */
3699 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
3700 sk
->sk_state
== TCP_CLOSE
)
3701 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
3703 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
3707 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
3710 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
3711 if (before(seq
, sp
->start_seq
))
3712 sp
->start_seq
= seq
;
3713 if (after(end_seq
, sp
->end_seq
))
3714 sp
->end_seq
= end_seq
;
3720 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
3722 struct tcp_sock
*tp
= tcp_sk(sk
);
3724 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3727 if (before(seq
, tp
->rcv_nxt
))
3728 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
3730 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
3732 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3734 tp
->rx_opt
.dsack
= 1;
3735 tp
->duplicate_sack
[0].start_seq
= seq
;
3736 tp
->duplicate_sack
[0].end_seq
= end_seq
;
3737 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.num_sacks
+ 1;
3741 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
3743 struct tcp_sock
*tp
= tcp_sk(sk
);
3745 if (!tp
->rx_opt
.dsack
)
3746 tcp_dsack_set(sk
, seq
, end_seq
);
3748 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
3751 static void tcp_send_dupack(struct sock
*sk
, struct sk_buff
*skb
)
3753 struct tcp_sock
*tp
= tcp_sk(sk
);
3755 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
3756 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
3757 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
3758 tcp_enter_quickack_mode(sk
);
3760 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
3761 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
3763 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
3764 end_seq
= tp
->rcv_nxt
;
3765 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
3772 /* These routines update the SACK block as out-of-order packets arrive or
3773 * in-order packets close up the sequence space.
3775 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
3778 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3779 struct tcp_sack_block
*swalk
= sp
+ 1;
3781 /* See if the recent change to the first SACK eats into
3782 * or hits the sequence space of other SACK blocks, if so coalesce.
3784 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
3785 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
3788 /* Zap SWALK, by moving every further SACK up by one slot.
3789 * Decrease num_sacks.
3791 tp
->rx_opt
.num_sacks
--;
3792 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.num_sacks
+
3794 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
3798 this_sack
++, swalk
++;
3802 static inline void tcp_sack_swap(struct tcp_sack_block
*sack1
,
3803 struct tcp_sack_block
*sack2
)
3807 tmp
= sack1
->start_seq
;
3808 sack1
->start_seq
= sack2
->start_seq
;
3809 sack2
->start_seq
= tmp
;
3811 tmp
= sack1
->end_seq
;
3812 sack1
->end_seq
= sack2
->end_seq
;
3813 sack2
->end_seq
= tmp
;
3816 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
3818 struct tcp_sock
*tp
= tcp_sk(sk
);
3819 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3820 int cur_sacks
= tp
->rx_opt
.num_sacks
;
3826 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
3827 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
3828 /* Rotate this_sack to the first one. */
3829 for (; this_sack
> 0; this_sack
--, sp
--)
3830 tcp_sack_swap(sp
, sp
- 1);
3832 tcp_sack_maybe_coalesce(tp
);
3837 /* Could not find an adjacent existing SACK, build a new one,
3838 * put it at the front, and shift everyone else down. We
3839 * always know there is at least one SACK present already here.
3841 * If the sack array is full, forget about the last one.
3843 if (this_sack
>= TCP_NUM_SACKS
) {
3845 tp
->rx_opt
.num_sacks
--;
3848 for (; this_sack
> 0; this_sack
--, sp
--)
3852 /* Build the new head SACK, and we're done. */
3853 sp
->start_seq
= seq
;
3854 sp
->end_seq
= end_seq
;
3855 tp
->rx_opt
.num_sacks
++;
3856 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
3859 /* RCV.NXT advances, some SACKs should be eaten. */
3861 static void tcp_sack_remove(struct tcp_sock
*tp
)
3863 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
3864 int num_sacks
= tp
->rx_opt
.num_sacks
;
3867 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
3868 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
3869 tp
->rx_opt
.num_sacks
= 0;
3870 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.dsack
;
3874 for (this_sack
= 0; this_sack
< num_sacks
;) {
3875 /* Check if the start of the sack is covered by RCV.NXT. */
3876 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
3879 /* RCV.NXT must cover all the block! */
3880 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
3882 /* Zap this SACK, by moving forward any other SACKS. */
3883 for (i
=this_sack
+1; i
< num_sacks
; i
++)
3884 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
3891 if (num_sacks
!= tp
->rx_opt
.num_sacks
) {
3892 tp
->rx_opt
.num_sacks
= num_sacks
;
3893 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.num_sacks
+
3898 /* This one checks to see if we can put data from the
3899 * out_of_order queue into the receive_queue.
3901 static void tcp_ofo_queue(struct sock
*sk
)
3903 struct tcp_sock
*tp
= tcp_sk(sk
);
3904 __u32 dsack_high
= tp
->rcv_nxt
;
3905 struct sk_buff
*skb
;
3907 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
3908 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
3911 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
3912 __u32 dsack
= dsack_high
;
3913 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
3914 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
3915 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
3918 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
3919 SOCK_DEBUG(sk
, "ofo packet was already received \n");
3920 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3924 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
3925 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
3926 TCP_SKB_CB(skb
)->end_seq
);
3928 __skb_unlink(skb
, &tp
->out_of_order_queue
);
3929 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
3930 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
3931 if (tcp_hdr(skb
)->fin
)
3932 tcp_fin(skb
, sk
, tcp_hdr(skb
));
3936 static int tcp_prune_ofo_queue(struct sock
*sk
);
3937 static int tcp_prune_queue(struct sock
*sk
);
3939 static inline int tcp_try_rmem_schedule(struct sock
*sk
, unsigned int size
)
3941 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
3942 !sk_rmem_schedule(sk
, size
)) {
3944 if (tcp_prune_queue(sk
) < 0)
3947 if (!sk_rmem_schedule(sk
, size
)) {
3948 if (!tcp_prune_ofo_queue(sk
))
3951 if (!sk_rmem_schedule(sk
, size
))
3958 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
3960 struct tcphdr
*th
= tcp_hdr(skb
);
3961 struct tcp_sock
*tp
= tcp_sk(sk
);
3964 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
3967 __skb_pull(skb
, th
->doff
* 4);
3969 TCP_ECN_accept_cwr(tp
, skb
);
3971 if (tp
->rx_opt
.dsack
) {
3972 tp
->rx_opt
.dsack
= 0;
3973 tp
->rx_opt
.eff_sacks
= tp
->rx_opt
.num_sacks
;
3976 /* Queue data for delivery to the user.
3977 * Packets in sequence go to the receive queue.
3978 * Out of sequence packets to the out_of_order_queue.
3980 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
3981 if (tcp_receive_window(tp
) == 0)
3984 /* Ok. In sequence. In window. */
3985 if (tp
->ucopy
.task
== current
&&
3986 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
3987 sock_owned_by_user(sk
) && !tp
->urg_data
) {
3988 int chunk
= min_t(unsigned int, skb
->len
,
3991 __set_current_state(TASK_RUNNING
);
3994 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
3995 tp
->ucopy
.len
-= chunk
;
3996 tp
->copied_seq
+= chunk
;
3997 eaten
= (chunk
== skb
->len
&& !th
->fin
);
3998 tcp_rcv_space_adjust(sk
);
4006 tcp_try_rmem_schedule(sk
, skb
->truesize
))
4009 skb_set_owner_r(skb
, sk
);
4010 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4012 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4014 tcp_event_data_recv(sk
, skb
);
4016 tcp_fin(skb
, sk
, th
);
4018 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4021 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4022 * gap in queue is filled.
4024 if (skb_queue_empty(&tp
->out_of_order_queue
))
4025 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4028 if (tp
->rx_opt
.num_sacks
)
4029 tcp_sack_remove(tp
);
4031 tcp_fast_path_check(sk
);
4035 else if (!sock_flag(sk
, SOCK_DEAD
))
4036 sk
->sk_data_ready(sk
, 0);
4040 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4041 /* A retransmit, 2nd most common case. Force an immediate ack. */
4042 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4043 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4046 tcp_enter_quickack_mode(sk
);
4047 inet_csk_schedule_ack(sk
);
4053 /* Out of window. F.e. zero window probe. */
4054 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4057 tcp_enter_quickack_mode(sk
);
4059 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4060 /* Partial packet, seq < rcv_next < end_seq */
4061 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4062 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4063 TCP_SKB_CB(skb
)->end_seq
);
4065 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4067 /* If window is closed, drop tail of packet. But after
4068 * remembering D-SACK for its head made in previous line.
4070 if (!tcp_receive_window(tp
))
4075 TCP_ECN_check_ce(tp
, skb
);
4077 if (tcp_try_rmem_schedule(sk
, skb
->truesize
))
4080 /* Disable header prediction. */
4082 inet_csk_schedule_ack(sk
);
4084 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4085 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4087 skb_set_owner_r(skb
, sk
);
4089 if (!skb_peek(&tp
->out_of_order_queue
)) {
4090 /* Initial out of order segment, build 1 SACK. */
4091 if (tcp_is_sack(tp
)) {
4092 tp
->rx_opt
.num_sacks
= 1;
4093 tp
->rx_opt
.dsack
= 0;
4094 tp
->rx_opt
.eff_sacks
= 1;
4095 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4096 tp
->selective_acks
[0].end_seq
=
4097 TCP_SKB_CB(skb
)->end_seq
;
4099 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4101 struct sk_buff
*skb1
= tp
->out_of_order_queue
.prev
;
4102 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4103 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4105 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4106 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4108 if (!tp
->rx_opt
.num_sacks
||
4109 tp
->selective_acks
[0].end_seq
!= seq
)
4112 /* Common case: data arrive in order after hole. */
4113 tp
->selective_acks
[0].end_seq
= end_seq
;
4117 /* Find place to insert this segment. */
4119 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4121 } while ((skb1
= skb1
->prev
) !=
4122 (struct sk_buff
*)&tp
->out_of_order_queue
);
4124 /* Do skb overlap to previous one? */
4125 if (skb1
!= (struct sk_buff
*)&tp
->out_of_order_queue
&&
4126 before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4127 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4128 /* All the bits are present. Drop. */
4130 tcp_dsack_set(sk
, seq
, end_seq
);
4133 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4134 /* Partial overlap. */
4135 tcp_dsack_set(sk
, seq
,
4136 TCP_SKB_CB(skb1
)->end_seq
);
4141 __skb_insert(skb
, skb1
, skb1
->next
, &tp
->out_of_order_queue
);
4143 /* And clean segments covered by new one as whole. */
4144 while ((skb1
= skb
->next
) !=
4145 (struct sk_buff
*)&tp
->out_of_order_queue
&&
4146 after(end_seq
, TCP_SKB_CB(skb1
)->seq
)) {
4147 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4148 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4152 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4153 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4154 TCP_SKB_CB(skb1
)->end_seq
);
4159 if (tcp_is_sack(tp
))
4160 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4164 /* Collapse contiguous sequence of skbs head..tail with
4165 * sequence numbers start..end.
4166 * Segments with FIN/SYN are not collapsed (only because this
4170 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4171 struct sk_buff
*head
, struct sk_buff
*tail
,
4174 struct sk_buff
*skb
;
4176 /* First, check that queue is collapsible and find
4177 * the point where collapsing can be useful. */
4178 for (skb
= head
; skb
!= tail
;) {
4179 /* No new bits? It is possible on ofo queue. */
4180 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4181 struct sk_buff
*next
= skb
->next
;
4182 __skb_unlink(skb
, list
);
4184 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4189 /* The first skb to collapse is:
4191 * - bloated or contains data before "start" or
4192 * overlaps to the next one.
4194 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4195 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4196 before(TCP_SKB_CB(skb
)->seq
, start
) ||
4197 (skb
->next
!= tail
&&
4198 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
->next
)->seq
)))
4201 /* Decided to skip this, advance start seq. */
4202 start
= TCP_SKB_CB(skb
)->end_seq
;
4205 if (skb
== tail
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4208 while (before(start
, end
)) {
4209 struct sk_buff
*nskb
;
4210 unsigned int header
= skb_headroom(skb
);
4211 int copy
= SKB_MAX_ORDER(header
, 0);
4213 /* Too big header? This can happen with IPv6. */
4216 if (end
- start
< copy
)
4218 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4222 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4223 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4225 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4227 skb_reserve(nskb
, header
);
4228 memcpy(nskb
->head
, skb
->head
, header
);
4229 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4230 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4231 __skb_insert(nskb
, skb
->prev
, skb
, list
);
4232 skb_set_owner_r(nskb
, sk
);
4234 /* Copy data, releasing collapsed skbs. */
4236 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4237 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4241 size
= min(copy
, size
);
4242 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4244 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4248 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4249 struct sk_buff
*next
= skb
->next
;
4250 __skb_unlink(skb
, list
);
4252 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4255 tcp_hdr(skb
)->syn
||
4263 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4264 * and tcp_collapse() them until all the queue is collapsed.
4266 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4268 struct tcp_sock
*tp
= tcp_sk(sk
);
4269 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4270 struct sk_buff
*head
;
4276 start
= TCP_SKB_CB(skb
)->seq
;
4277 end
= TCP_SKB_CB(skb
)->end_seq
;
4283 /* Segment is terminated when we see gap or when
4284 * we are at the end of all the queue. */
4285 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
||
4286 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4287 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4288 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4289 head
, skb
, start
, end
);
4291 if (skb
== (struct sk_buff
*)&tp
->out_of_order_queue
)
4293 /* Start new segment */
4294 start
= TCP_SKB_CB(skb
)->seq
;
4295 end
= TCP_SKB_CB(skb
)->end_seq
;
4297 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4298 start
= TCP_SKB_CB(skb
)->seq
;
4299 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4300 end
= TCP_SKB_CB(skb
)->end_seq
;
4306 * Purge the out-of-order queue.
4307 * Return true if queue was pruned.
4309 static int tcp_prune_ofo_queue(struct sock
*sk
)
4311 struct tcp_sock
*tp
= tcp_sk(sk
);
4314 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4315 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4316 __skb_queue_purge(&tp
->out_of_order_queue
);
4318 /* Reset SACK state. A conforming SACK implementation will
4319 * do the same at a timeout based retransmit. When a connection
4320 * is in a sad state like this, we care only about integrity
4321 * of the connection not performance.
4323 if (tp
->rx_opt
.sack_ok
)
4324 tcp_sack_reset(&tp
->rx_opt
);
4331 /* Reduce allocated memory if we can, trying to get
4332 * the socket within its memory limits again.
4334 * Return less than zero if we should start dropping frames
4335 * until the socket owning process reads some of the data
4336 * to stabilize the situation.
4338 static int tcp_prune_queue(struct sock
*sk
)
4340 struct tcp_sock
*tp
= tcp_sk(sk
);
4342 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4344 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4346 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4347 tcp_clamp_window(sk
);
4348 else if (tcp_memory_pressure
)
4349 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4351 tcp_collapse_ofo_queue(sk
);
4352 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4353 sk
->sk_receive_queue
.next
,
4354 (struct sk_buff
*)&sk
->sk_receive_queue
,
4355 tp
->copied_seq
, tp
->rcv_nxt
);
4358 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4361 /* Collapsing did not help, destructive actions follow.
4362 * This must not ever occur. */
4364 tcp_prune_ofo_queue(sk
);
4366 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4369 /* If we are really being abused, tell the caller to silently
4370 * drop receive data on the floor. It will get retransmitted
4371 * and hopefully then we'll have sufficient space.
4373 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4375 /* Massive buffer overcommit. */
4380 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4381 * As additional protections, we do not touch cwnd in retransmission phases,
4382 * and if application hit its sndbuf limit recently.
4384 void tcp_cwnd_application_limited(struct sock
*sk
)
4386 struct tcp_sock
*tp
= tcp_sk(sk
);
4388 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4389 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4390 /* Limited by application or receiver window. */
4391 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4392 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4393 if (win_used
< tp
->snd_cwnd
) {
4394 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4395 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4397 tp
->snd_cwnd_used
= 0;
4399 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4402 static int tcp_should_expand_sndbuf(struct sock
*sk
)
4404 struct tcp_sock
*tp
= tcp_sk(sk
);
4406 /* If the user specified a specific send buffer setting, do
4409 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4412 /* If we are under global TCP memory pressure, do not expand. */
4413 if (tcp_memory_pressure
)
4416 /* If we are under soft global TCP memory pressure, do not expand. */
4417 if (atomic_read(&tcp_memory_allocated
) >= sysctl_tcp_mem
[0])
4420 /* If we filled the congestion window, do not expand. */
4421 if (tp
->packets_out
>= tp
->snd_cwnd
)
4427 /* When incoming ACK allowed to free some skb from write_queue,
4428 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4429 * on the exit from tcp input handler.
4431 * PROBLEM: sndbuf expansion does not work well with largesend.
4433 static void tcp_new_space(struct sock
*sk
)
4435 struct tcp_sock
*tp
= tcp_sk(sk
);
4437 if (tcp_should_expand_sndbuf(sk
)) {
4438 int sndmem
= max_t(u32
, tp
->rx_opt
.mss_clamp
, tp
->mss_cache
) +
4439 MAX_TCP_HEADER
+ 16 + sizeof(struct sk_buff
),
4440 demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4441 tp
->reordering
+ 1);
4442 sndmem
*= 2 * demanded
;
4443 if (sndmem
> sk
->sk_sndbuf
)
4444 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4445 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4448 sk
->sk_write_space(sk
);
4451 static void tcp_check_space(struct sock
*sk
)
4453 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4454 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4455 if (sk
->sk_socket
&&
4456 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4461 static inline void tcp_data_snd_check(struct sock
*sk
)
4463 tcp_push_pending_frames(sk
);
4464 tcp_check_space(sk
);
4468 * Check if sending an ack is needed.
4470 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
4472 struct tcp_sock
*tp
= tcp_sk(sk
);
4474 /* More than one full frame received... */
4475 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
4476 /* ... and right edge of window advances far enough.
4477 * (tcp_recvmsg() will send ACK otherwise). Or...
4479 && __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
4480 /* We ACK each frame or... */
4481 tcp_in_quickack_mode(sk
) ||
4482 /* We have out of order data. */
4483 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
4484 /* Then ack it now */
4487 /* Else, send delayed ack. */
4488 tcp_send_delayed_ack(sk
);
4492 static inline void tcp_ack_snd_check(struct sock
*sk
)
4494 if (!inet_csk_ack_scheduled(sk
)) {
4495 /* We sent a data segment already. */
4498 __tcp_ack_snd_check(sk
, 1);
4502 * This routine is only called when we have urgent data
4503 * signaled. Its the 'slow' part of tcp_urg. It could be
4504 * moved inline now as tcp_urg is only called from one
4505 * place. We handle URGent data wrong. We have to - as
4506 * BSD still doesn't use the correction from RFC961.
4507 * For 1003.1g we should support a new option TCP_STDURG to permit
4508 * either form (or just set the sysctl tcp_stdurg).
4511 static void tcp_check_urg(struct sock
*sk
, struct tcphdr
*th
)
4513 struct tcp_sock
*tp
= tcp_sk(sk
);
4514 u32 ptr
= ntohs(th
->urg_ptr
);
4516 if (ptr
&& !sysctl_tcp_stdurg
)
4518 ptr
+= ntohl(th
->seq
);
4520 /* Ignore urgent data that we've already seen and read. */
4521 if (after(tp
->copied_seq
, ptr
))
4524 /* Do not replay urg ptr.
4526 * NOTE: interesting situation not covered by specs.
4527 * Misbehaving sender may send urg ptr, pointing to segment,
4528 * which we already have in ofo queue. We are not able to fetch
4529 * such data and will stay in TCP_URG_NOTYET until will be eaten
4530 * by recvmsg(). Seems, we are not obliged to handle such wicked
4531 * situations. But it is worth to think about possibility of some
4532 * DoSes using some hypothetical application level deadlock.
4534 if (before(ptr
, tp
->rcv_nxt
))
4537 /* Do we already have a newer (or duplicate) urgent pointer? */
4538 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
4541 /* Tell the world about our new urgent pointer. */
4544 /* We may be adding urgent data when the last byte read was
4545 * urgent. To do this requires some care. We cannot just ignore
4546 * tp->copied_seq since we would read the last urgent byte again
4547 * as data, nor can we alter copied_seq until this data arrives
4548 * or we break the semantics of SIOCATMARK (and thus sockatmark())
4550 * NOTE. Double Dutch. Rendering to plain English: author of comment
4551 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
4552 * and expect that both A and B disappear from stream. This is _wrong_.
4553 * Though this happens in BSD with high probability, this is occasional.
4554 * Any application relying on this is buggy. Note also, that fix "works"
4555 * only in this artificial test. Insert some normal data between A and B and we will
4556 * decline of BSD again. Verdict: it is better to remove to trap
4559 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
4560 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
4561 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
4563 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4564 __skb_unlink(skb
, &sk
->sk_receive_queue
);
4569 tp
->urg_data
= TCP_URG_NOTYET
;
4572 /* Disable header prediction. */
4576 /* This is the 'fast' part of urgent handling. */
4577 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, struct tcphdr
*th
)
4579 struct tcp_sock
*tp
= tcp_sk(sk
);
4581 /* Check if we get a new urgent pointer - normally not. */
4583 tcp_check_urg(sk
, th
);
4585 /* Do we wait for any urgent data? - normally not... */
4586 if (tp
->urg_data
== TCP_URG_NOTYET
) {
4587 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
4590 /* Is the urgent pointer pointing into this packet? */
4591 if (ptr
< skb
->len
) {
4593 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
4595 tp
->urg_data
= TCP_URG_VALID
| tmp
;
4596 if (!sock_flag(sk
, SOCK_DEAD
))
4597 sk
->sk_data_ready(sk
, 0);
4602 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
4604 struct tcp_sock
*tp
= tcp_sk(sk
);
4605 int chunk
= skb
->len
- hlen
;
4609 if (skb_csum_unnecessary(skb
))
4610 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
4612 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
4616 tp
->ucopy
.len
-= chunk
;
4617 tp
->copied_seq
+= chunk
;
4618 tcp_rcv_space_adjust(sk
);
4625 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
4626 struct sk_buff
*skb
)
4630 if (sock_owned_by_user(sk
)) {
4632 result
= __tcp_checksum_complete(skb
);
4635 result
= __tcp_checksum_complete(skb
);
4640 static inline int tcp_checksum_complete_user(struct sock
*sk
,
4641 struct sk_buff
*skb
)
4643 return !skb_csum_unnecessary(skb
) &&
4644 __tcp_checksum_complete_user(sk
, skb
);
4647 #ifdef CONFIG_NET_DMA
4648 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
4651 struct tcp_sock
*tp
= tcp_sk(sk
);
4652 int chunk
= skb
->len
- hlen
;
4654 int copied_early
= 0;
4656 if (tp
->ucopy
.wakeup
)
4659 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
4660 tp
->ucopy
.dma_chan
= get_softnet_dma();
4662 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
4664 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
4666 tp
->ucopy
.iov
, chunk
,
4667 tp
->ucopy
.pinned_list
);
4672 tp
->ucopy
.dma_cookie
= dma_cookie
;
4675 tp
->ucopy
.len
-= chunk
;
4676 tp
->copied_seq
+= chunk
;
4677 tcp_rcv_space_adjust(sk
);
4679 if ((tp
->ucopy
.len
== 0) ||
4680 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
4681 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
4682 tp
->ucopy
.wakeup
= 1;
4683 sk
->sk_data_ready(sk
, 0);
4685 } else if (chunk
> 0) {
4686 tp
->ucopy
.wakeup
= 1;
4687 sk
->sk_data_ready(sk
, 0);
4690 return copied_early
;
4692 #endif /* CONFIG_NET_DMA */
4695 * TCP receive function for the ESTABLISHED state.
4697 * It is split into a fast path and a slow path. The fast path is
4699 * - A zero window was announced from us - zero window probing
4700 * is only handled properly in the slow path.
4701 * - Out of order segments arrived.
4702 * - Urgent data is expected.
4703 * - There is no buffer space left
4704 * - Unexpected TCP flags/window values/header lengths are received
4705 * (detected by checking the TCP header against pred_flags)
4706 * - Data is sent in both directions. Fast path only supports pure senders
4707 * or pure receivers (this means either the sequence number or the ack
4708 * value must stay constant)
4709 * - Unexpected TCP option.
4711 * When these conditions are not satisfied it drops into a standard
4712 * receive procedure patterned after RFC793 to handle all cases.
4713 * The first three cases are guaranteed by proper pred_flags setting,
4714 * the rest is checked inline. Fast processing is turned on in
4715 * tcp_data_queue when everything is OK.
4717 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
4718 struct tcphdr
*th
, unsigned len
)
4720 struct tcp_sock
*tp
= tcp_sk(sk
);
4723 * Header prediction.
4724 * The code loosely follows the one in the famous
4725 * "30 instruction TCP receive" Van Jacobson mail.
4727 * Van's trick is to deposit buffers into socket queue
4728 * on a device interrupt, to call tcp_recv function
4729 * on the receive process context and checksum and copy
4730 * the buffer to user space. smart...
4732 * Our current scheme is not silly either but we take the
4733 * extra cost of the net_bh soft interrupt processing...
4734 * We do checksum and copy also but from device to kernel.
4737 tp
->rx_opt
.saw_tstamp
= 0;
4739 /* pred_flags is 0xS?10 << 16 + snd_wnd
4740 * if header_prediction is to be made
4741 * 'S' will always be tp->tcp_header_len >> 2
4742 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
4743 * turn it off (when there are holes in the receive
4744 * space for instance)
4745 * PSH flag is ignored.
4748 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
4749 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4750 int tcp_header_len
= tp
->tcp_header_len
;
4752 /* Timestamp header prediction: tcp_header_len
4753 * is automatically equal to th->doff*4 due to pred_flags
4757 /* Check timestamp */
4758 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
4759 __be32
*ptr
= (__be32
*)(th
+ 1);
4761 /* No? Slow path! */
4762 if (*ptr
!= htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
4763 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
))
4766 tp
->rx_opt
.saw_tstamp
= 1;
4768 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
4770 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
4772 /* If PAWS failed, check it more carefully in slow path */
4773 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
4776 /* DO NOT update ts_recent here, if checksum fails
4777 * and timestamp was corrupted part, it will result
4778 * in a hung connection since we will drop all
4779 * future packets due to the PAWS test.
4783 if (len
<= tcp_header_len
) {
4784 /* Bulk data transfer: sender */
4785 if (len
== tcp_header_len
) {
4786 /* Predicted packet is in window by definition.
4787 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4788 * Hence, check seq<=rcv_wup reduces to:
4790 if (tcp_header_len
==
4791 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4792 tp
->rcv_nxt
== tp
->rcv_wup
)
4793 tcp_store_ts_recent(tp
);
4795 /* We know that such packets are checksummed
4798 tcp_ack(sk
, skb
, 0);
4800 tcp_data_snd_check(sk
);
4802 } else { /* Header too small */
4803 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
4808 int copied_early
= 0;
4810 if (tp
->copied_seq
== tp
->rcv_nxt
&&
4811 len
- tcp_header_len
<= tp
->ucopy
.len
) {
4812 #ifdef CONFIG_NET_DMA
4813 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
4818 if (tp
->ucopy
.task
== current
&&
4819 sock_owned_by_user(sk
) && !copied_early
) {
4820 __set_current_state(TASK_RUNNING
);
4822 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
4826 /* Predicted packet is in window by definition.
4827 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4828 * Hence, check seq<=rcv_wup reduces to:
4830 if (tcp_header_len
==
4831 (sizeof(struct tcphdr
) +
4832 TCPOLEN_TSTAMP_ALIGNED
) &&
4833 tp
->rcv_nxt
== tp
->rcv_wup
)
4834 tcp_store_ts_recent(tp
);
4836 tcp_rcv_rtt_measure_ts(sk
, skb
);
4838 __skb_pull(skb
, tcp_header_len
);
4839 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4840 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
4843 tcp_cleanup_rbuf(sk
, skb
->len
);
4846 if (tcp_checksum_complete_user(sk
, skb
))
4849 /* Predicted packet is in window by definition.
4850 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
4851 * Hence, check seq<=rcv_wup reduces to:
4853 if (tcp_header_len
==
4854 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
4855 tp
->rcv_nxt
== tp
->rcv_wup
)
4856 tcp_store_ts_recent(tp
);
4858 tcp_rcv_rtt_measure_ts(sk
, skb
);
4860 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
4863 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
4865 /* Bulk data transfer: receiver */
4866 __skb_pull(skb
, tcp_header_len
);
4867 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4868 skb_set_owner_r(skb
, sk
);
4869 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4872 tcp_event_data_recv(sk
, skb
);
4874 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
4875 /* Well, only one small jumplet in fast path... */
4876 tcp_ack(sk
, skb
, FLAG_DATA
);
4877 tcp_data_snd_check(sk
);
4878 if (!inet_csk_ack_scheduled(sk
))
4882 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
4883 __tcp_ack_snd_check(sk
, 0);
4885 #ifdef CONFIG_NET_DMA
4887 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
4893 sk
->sk_data_ready(sk
, 0);
4899 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
4903 * RFC1323: H1. Apply PAWS check first.
4905 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
4906 tcp_paws_discard(sk
, skb
)) {
4908 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
4909 tcp_send_dupack(sk
, skb
);
4912 /* Resets are accepted even if PAWS failed.
4914 ts_recent update must be made after we are sure
4915 that the packet is in window.
4920 * Standard slow path.
4923 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
4924 /* RFC793, page 37: "In all states except SYN-SENT, all reset
4925 * (RST) segments are validated by checking their SEQ-fields."
4926 * And page 69: "If an incoming segment is not acceptable,
4927 * an acknowledgment should be sent in reply (unless the RST bit
4928 * is set, if so drop the segment and return)".
4931 tcp_send_dupack(sk
, skb
);
4940 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
4942 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4943 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
4944 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
4951 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
4953 tcp_rcv_rtt_measure_ts(sk
, skb
);
4955 /* Process urgent data. */
4956 tcp_urg(sk
, skb
, th
);
4958 /* step 7: process the segment text */
4959 tcp_data_queue(sk
, skb
);
4961 tcp_data_snd_check(sk
);
4962 tcp_ack_snd_check(sk
);
4966 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
4973 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
4974 struct tcphdr
*th
, unsigned len
)
4976 struct tcp_sock
*tp
= tcp_sk(sk
);
4977 struct inet_connection_sock
*icsk
= inet_csk(sk
);
4978 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
4980 tcp_parse_options(skb
, &tp
->rx_opt
, 0);
4984 * "If the state is SYN-SENT then
4985 * first check the ACK bit
4986 * If the ACK bit is set
4987 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
4988 * a reset (unless the RST bit is set, if so drop
4989 * the segment and return)"
4991 * We do not send data with SYN, so that RFC-correct
4994 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
4995 goto reset_and_undo
;
4997 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
4998 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5000 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5001 goto reset_and_undo
;
5004 /* Now ACK is acceptable.
5006 * "If the RST bit is set
5007 * If the ACK was acceptable then signal the user "error:
5008 * connection reset", drop the segment, enter CLOSED state,
5009 * delete TCB, and return."
5018 * "fifth, if neither of the SYN or RST bits is set then
5019 * drop the segment and return."
5025 goto discard_and_undo
;
5028 * "If the SYN bit is on ...
5029 * are acceptable then ...
5030 * (our SYN has been ACKed), change the connection
5031 * state to ESTABLISHED..."
5034 TCP_ECN_rcv_synack(tp
, th
);
5036 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5037 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5039 /* Ok.. it's good. Set up sequence numbers and
5040 * move to established.
5042 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5043 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5045 /* RFC1323: The window in SYN & SYN/ACK segments is
5048 tp
->snd_wnd
= ntohs(th
->window
);
5049 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
, TCP_SKB_CB(skb
)->seq
);
5051 if (!tp
->rx_opt
.wscale_ok
) {
5052 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5053 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5056 if (tp
->rx_opt
.saw_tstamp
) {
5057 tp
->rx_opt
.tstamp_ok
= 1;
5058 tp
->tcp_header_len
=
5059 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5060 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5061 tcp_store_ts_recent(tp
);
5063 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5066 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5067 tcp_enable_fack(tp
);
5070 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5071 tcp_initialize_rcv_mss(sk
);
5073 /* Remember, tcp_poll() does not lock socket!
5074 * Change state from SYN-SENT only after copied_seq
5075 * is initialized. */
5076 tp
->copied_seq
= tp
->rcv_nxt
;
5078 tcp_set_state(sk
, TCP_ESTABLISHED
);
5080 security_inet_conn_established(sk
, skb
);
5082 /* Make sure socket is routed, for correct metrics. */
5083 icsk
->icsk_af_ops
->rebuild_header(sk
);
5085 tcp_init_metrics(sk
);
5087 tcp_init_congestion_control(sk
);
5089 /* Prevent spurious tcp_cwnd_restart() on first data
5092 tp
->lsndtime
= tcp_time_stamp
;
5094 tcp_init_buffer_space(sk
);
5096 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5097 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5099 if (!tp
->rx_opt
.snd_wscale
)
5100 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5104 if (!sock_flag(sk
, SOCK_DEAD
)) {
5105 sk
->sk_state_change(sk
);
5106 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5109 if (sk
->sk_write_pending
||
5110 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5111 icsk
->icsk_ack
.pingpong
) {
5112 /* Save one ACK. Data will be ready after
5113 * several ticks, if write_pending is set.
5115 * It may be deleted, but with this feature tcpdumps
5116 * look so _wonderfully_ clever, that I was not able
5117 * to stand against the temptation 8) --ANK
5119 inet_csk_schedule_ack(sk
);
5120 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5121 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
5122 tcp_incr_quickack(sk
);
5123 tcp_enter_quickack_mode(sk
);
5124 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5125 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5136 /* No ACK in the segment */
5140 * "If the RST bit is set
5142 * Otherwise (no ACK) drop the segment and return."
5145 goto discard_and_undo
;
5149 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5150 tcp_paws_check(&tp
->rx_opt
, 0))
5151 goto discard_and_undo
;
5154 /* We see SYN without ACK. It is attempt of
5155 * simultaneous connect with crossed SYNs.
5156 * Particularly, it can be connect to self.
5158 tcp_set_state(sk
, TCP_SYN_RECV
);
5160 if (tp
->rx_opt
.saw_tstamp
) {
5161 tp
->rx_opt
.tstamp_ok
= 1;
5162 tcp_store_ts_recent(tp
);
5163 tp
->tcp_header_len
=
5164 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5166 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5169 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5170 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5172 /* RFC1323: The window in SYN & SYN/ACK segments is
5175 tp
->snd_wnd
= ntohs(th
->window
);
5176 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5177 tp
->max_window
= tp
->snd_wnd
;
5179 TCP_ECN_rcv_syn(tp
, th
);
5182 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5183 tcp_initialize_rcv_mss(sk
);
5185 tcp_send_synack(sk
);
5187 /* Note, we could accept data and URG from this segment.
5188 * There are no obstacles to make this.
5190 * However, if we ignore data in ACKless segments sometimes,
5191 * we have no reasons to accept it sometimes.
5192 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5193 * is not flawless. So, discard packet for sanity.
5194 * Uncomment this return to process the data.
5201 /* "fifth, if neither of the SYN or RST bits is set then
5202 * drop the segment and return."
5206 tcp_clear_options(&tp
->rx_opt
);
5207 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5211 tcp_clear_options(&tp
->rx_opt
);
5212 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5217 * This function implements the receiving procedure of RFC 793 for
5218 * all states except ESTABLISHED and TIME_WAIT.
5219 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5220 * address independent.
5223 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5224 struct tcphdr
*th
, unsigned len
)
5226 struct tcp_sock
*tp
= tcp_sk(sk
);
5227 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5230 tp
->rx_opt
.saw_tstamp
= 0;
5232 switch (sk
->sk_state
) {
5244 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5247 /* Now we have several options: In theory there is
5248 * nothing else in the frame. KA9Q has an option to
5249 * send data with the syn, BSD accepts data with the
5250 * syn up to the [to be] advertised window and
5251 * Solaris 2.1 gives you a protocol error. For now
5252 * we just ignore it, that fits the spec precisely
5253 * and avoids incompatibilities. It would be nice in
5254 * future to drop through and process the data.
5256 * Now that TTCP is starting to be used we ought to
5258 * But, this leaves one open to an easy denial of
5259 * service attack, and SYN cookies can't defend
5260 * against this problem. So, we drop the data
5261 * in the interest of security over speed unless
5262 * it's still in use.
5270 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5274 /* Do step6 onward by hand. */
5275 tcp_urg(sk
, skb
, th
);
5277 tcp_data_snd_check(sk
);
5281 if (tcp_fast_parse_options(skb
, th
, tp
) && tp
->rx_opt
.saw_tstamp
&&
5282 tcp_paws_discard(sk
, skb
)) {
5284 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5285 tcp_send_dupack(sk
, skb
);
5288 /* Reset is accepted even if it did not pass PAWS. */
5291 /* step 1: check sequence number */
5292 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5294 tcp_send_dupack(sk
, skb
);
5298 /* step 2: check RST bit */
5304 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5306 /* step 3: check security and precedence [ignored] */
5310 * Check for a SYN in window.
5312 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5313 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
5318 /* step 5: check the ACK field */
5320 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5322 switch (sk
->sk_state
) {
5325 tp
->copied_seq
= tp
->rcv_nxt
;
5327 tcp_set_state(sk
, TCP_ESTABLISHED
);
5328 sk
->sk_state_change(sk
);
5330 /* Note, that this wakeup is only for marginal
5331 * crossed SYN case. Passively open sockets
5332 * are not waked up, because sk->sk_sleep ==
5333 * NULL and sk->sk_socket == NULL.
5337 SOCK_WAKE_IO
, POLL_OUT
);
5339 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5340 tp
->snd_wnd
= ntohs(th
->window
) <<
5341 tp
->rx_opt
.snd_wscale
;
5342 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->ack_seq
,
5343 TCP_SKB_CB(skb
)->seq
);
5345 /* tcp_ack considers this ACK as duplicate
5346 * and does not calculate rtt.
5347 * Fix it at least with timestamps.
5349 if (tp
->rx_opt
.saw_tstamp
&&
5350 tp
->rx_opt
.rcv_tsecr
&& !tp
->srtt
)
5351 tcp_ack_saw_tstamp(sk
, 0);
5353 if (tp
->rx_opt
.tstamp_ok
)
5354 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5356 /* Make sure socket is routed, for
5359 icsk
->icsk_af_ops
->rebuild_header(sk
);
5361 tcp_init_metrics(sk
);
5363 tcp_init_congestion_control(sk
);
5365 /* Prevent spurious tcp_cwnd_restart() on
5366 * first data packet.
5368 tp
->lsndtime
= tcp_time_stamp
;
5371 tcp_initialize_rcv_mss(sk
);
5372 tcp_init_buffer_space(sk
);
5373 tcp_fast_path_on(tp
);
5380 if (tp
->snd_una
== tp
->write_seq
) {
5381 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5382 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5383 dst_confirm(sk
->sk_dst_cache
);
5385 if (!sock_flag(sk
, SOCK_DEAD
))
5386 /* Wake up lingering close() */
5387 sk
->sk_state_change(sk
);
5391 if (tp
->linger2
< 0 ||
5392 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5393 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5395 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5399 tmo
= tcp_fin_time(sk
);
5400 if (tmo
> TCP_TIMEWAIT_LEN
) {
5401 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5402 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5403 /* Bad case. We could lose such FIN otherwise.
5404 * It is not a big problem, but it looks confusing
5405 * and not so rare event. We still can lose it now,
5406 * if it spins in bh_lock_sock(), but it is really
5409 inet_csk_reset_keepalive_timer(sk
, tmo
);
5411 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5419 if (tp
->snd_una
== tp
->write_seq
) {
5420 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5426 if (tp
->snd_una
== tp
->write_seq
) {
5427 tcp_update_metrics(sk
);
5436 /* step 6: check the URG bit */
5437 tcp_urg(sk
, skb
, th
);
5439 /* step 7: process the segment text */
5440 switch (sk
->sk_state
) {
5441 case TCP_CLOSE_WAIT
:
5444 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5448 /* RFC 793 says to queue data in these states,
5449 * RFC 1122 says we MUST send a reset.
5450 * BSD 4.4 also does reset.
5452 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5453 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5454 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5455 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5461 case TCP_ESTABLISHED
:
5462 tcp_data_queue(sk
, skb
);
5467 /* tcp_data could move socket to TIME-WAIT */
5468 if (sk
->sk_state
!= TCP_CLOSE
) {
5469 tcp_data_snd_check(sk
);
5470 tcp_ack_snd_check(sk
);
5480 EXPORT_SYMBOL(sysctl_tcp_ecn
);
5481 EXPORT_SYMBOL(sysctl_tcp_reordering
);
5482 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
5483 EXPORT_SYMBOL(tcp_parse_options
);
5484 #ifdef CONFIG_TCP_MD5SIG
5485 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
5487 EXPORT_SYMBOL(tcp_rcv_established
);
5488 EXPORT_SYMBOL(tcp_rcv_state_process
);
5489 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);