2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
6 * Implementation of the Transmission Control Protocol(TCP).
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
23 * Pedro Roque : Fast Retransmit/Recovery.
25 * Retransmit queue handled by TCP.
26 * Better retransmit timer handling.
27 * New congestion avoidance.
31 * Eric : Fast Retransmit.
32 * Randy Scott : MSS option defines.
33 * Eric Schenk : Fixes to slow start algorithm.
34 * Eric Schenk : Yet another double ACK bug.
35 * Eric Schenk : Delayed ACK bug fixes.
36 * Eric Schenk : Floyd style fast retrans war avoidance.
37 * David S. Miller : Don't allow zero congestion window.
38 * Eric Schenk : Fix retransmitter so that it sends
39 * next packet on ack of previous packet.
40 * Andi Kleen : Moved open_request checking here
41 * and process RSTs for open_requests.
42 * Andi Kleen : Better prune_queue, and other fixes.
43 * Andrey Savochkin: Fix RTT measurements in the presence of
45 * Andrey Savochkin: Check sequence numbers correctly when
46 * removing SACKs due to in sequence incoming
48 * Andi Kleen: Make sure we never ack data there is not
49 * enough room for. Also make this condition
50 * a fatal error if it might still happen.
51 * Andi Kleen: Add tcp_measure_rcv_mss to make
52 * connections with MSS<min(MTU,ann. MSS)
53 * work without delayed acks.
54 * Andi Kleen: Process packets with PSH set in the
56 * J Hadi Salim: ECN support
59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission
60 * engine. Lots of bugs are found.
61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs
64 #define pr_fmt(fmt) "TCP: " fmt
67 #include <linux/slab.h>
68 #include <linux/module.h>
69 #include <linux/sysctl.h>
70 #include <linux/kernel.h>
73 #include <net/inet_common.h>
74 #include <linux/ipsec.h>
75 #include <asm/unaligned.h>
76 #include <net/netdma.h>
78 int sysctl_tcp_timestamps __read_mostly
= 1;
79 int sysctl_tcp_window_scaling __read_mostly
= 1;
80 int sysctl_tcp_sack __read_mostly
= 1;
81 int sysctl_tcp_fack __read_mostly
= 1;
82 int sysctl_tcp_reordering __read_mostly
= TCP_FASTRETRANS_THRESH
;
83 EXPORT_SYMBOL(sysctl_tcp_reordering
);
84 int sysctl_tcp_ecn __read_mostly
= 2;
85 EXPORT_SYMBOL(sysctl_tcp_ecn
);
86 int sysctl_tcp_dsack __read_mostly
= 1;
87 int sysctl_tcp_app_win __read_mostly
= 31;
88 int sysctl_tcp_adv_win_scale __read_mostly
= 2;
89 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale
);
91 int sysctl_tcp_stdurg __read_mostly
;
92 int sysctl_tcp_rfc1337 __read_mostly
;
93 int sysctl_tcp_max_orphans __read_mostly
= NR_FILE
;
94 int sysctl_tcp_frto __read_mostly
= 2;
95 int sysctl_tcp_frto_response __read_mostly
;
96 int sysctl_tcp_nometrics_save __read_mostly
;
98 int sysctl_tcp_thin_dupack __read_mostly
;
100 int sysctl_tcp_moderate_rcvbuf __read_mostly
= 1;
101 int sysctl_tcp_abc __read_mostly
;
103 #define FLAG_DATA 0x01 /* Incoming frame contained data. */
104 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */
105 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */
106 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */
107 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */
108 #define FLAG_DATA_SACKED 0x20 /* New SACK. */
109 #define FLAG_ECE 0x40 /* ECE in this ACK */
110 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/
111 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */
112 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */
113 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */
114 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */
115 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */
117 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED)
118 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED)
119 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE)
120 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED)
121 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED)
123 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH)
124 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH))
126 /* Adapt the MSS value used to make delayed ack decision to the
129 static void tcp_measure_rcv_mss(struct sock
*sk
, const struct sk_buff
*skb
)
131 struct inet_connection_sock
*icsk
= inet_csk(sk
);
132 const unsigned int lss
= icsk
->icsk_ack
.last_seg_size
;
135 icsk
->icsk_ack
.last_seg_size
= 0;
137 /* skb->len may jitter because of SACKs, even if peer
138 * sends good full-sized frames.
140 len
= skb_shinfo(skb
)->gso_size
? : skb
->len
;
141 if (len
>= icsk
->icsk_ack
.rcv_mss
) {
142 icsk
->icsk_ack
.rcv_mss
= len
;
144 /* Otherwise, we make more careful check taking into account,
145 * that SACKs block is variable.
147 * "len" is invariant segment length, including TCP header.
149 len
+= skb
->data
- skb_transport_header(skb
);
150 if (len
>= TCP_MSS_DEFAULT
+ sizeof(struct tcphdr
) ||
151 /* If PSH is not set, packet should be
152 * full sized, provided peer TCP is not badly broken.
153 * This observation (if it is correct 8)) allows
154 * to handle super-low mtu links fairly.
156 (len
>= TCP_MIN_MSS
+ sizeof(struct tcphdr
) &&
157 !(tcp_flag_word(tcp_hdr(skb
)) & TCP_REMNANT
))) {
158 /* Subtract also invariant (if peer is RFC compliant),
159 * tcp header plus fixed timestamp option length.
160 * Resulting "len" is MSS free of SACK jitter.
162 len
-= tcp_sk(sk
)->tcp_header_len
;
163 icsk
->icsk_ack
.last_seg_size
= len
;
165 icsk
->icsk_ack
.rcv_mss
= len
;
169 if (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
)
170 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED2
;
171 icsk
->icsk_ack
.pending
|= ICSK_ACK_PUSHED
;
175 static void tcp_incr_quickack(struct sock
*sk
)
177 struct inet_connection_sock
*icsk
= inet_csk(sk
);
178 unsigned quickacks
= tcp_sk(sk
)->rcv_wnd
/ (2 * icsk
->icsk_ack
.rcv_mss
);
182 if (quickacks
> icsk
->icsk_ack
.quick
)
183 icsk
->icsk_ack
.quick
= min(quickacks
, TCP_MAX_QUICKACKS
);
186 static void tcp_enter_quickack_mode(struct sock
*sk
)
188 struct inet_connection_sock
*icsk
= inet_csk(sk
);
189 tcp_incr_quickack(sk
);
190 icsk
->icsk_ack
.pingpong
= 0;
191 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
194 /* Send ACKs quickly, if "quick" count is not exhausted
195 * and the session is not interactive.
198 static inline int tcp_in_quickack_mode(const struct sock
*sk
)
200 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
201 return icsk
->icsk_ack
.quick
&& !icsk
->icsk_ack
.pingpong
;
204 static inline void TCP_ECN_queue_cwr(struct tcp_sock
*tp
)
206 if (tp
->ecn_flags
& TCP_ECN_OK
)
207 tp
->ecn_flags
|= TCP_ECN_QUEUE_CWR
;
210 static inline void TCP_ECN_accept_cwr(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
212 if (tcp_hdr(skb
)->cwr
)
213 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
216 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock
*tp
)
218 tp
->ecn_flags
&= ~TCP_ECN_DEMAND_CWR
;
221 static inline void TCP_ECN_check_ce(struct tcp_sock
*tp
, const struct sk_buff
*skb
)
223 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
226 switch (TCP_SKB_CB(skb
)->ip_dsfield
& INET_ECN_MASK
) {
227 case INET_ECN_NOT_ECT
:
228 /* Funny extension: if ECT is not set on a segment,
229 * and we already seen ECT on a previous segment,
230 * it is probably a retransmit.
232 if (tp
->ecn_flags
& TCP_ECN_SEEN
)
233 tcp_enter_quickack_mode((struct sock
*)tp
);
236 tp
->ecn_flags
|= TCP_ECN_DEMAND_CWR
;
239 tp
->ecn_flags
|= TCP_ECN_SEEN
;
243 static inline void TCP_ECN_rcv_synack(struct tcp_sock
*tp
, const struct tcphdr
*th
)
245 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| th
->cwr
))
246 tp
->ecn_flags
&= ~TCP_ECN_OK
;
249 static inline void TCP_ECN_rcv_syn(struct tcp_sock
*tp
, const struct tcphdr
*th
)
251 if ((tp
->ecn_flags
& TCP_ECN_OK
) && (!th
->ece
|| !th
->cwr
))
252 tp
->ecn_flags
&= ~TCP_ECN_OK
;
255 static inline int TCP_ECN_rcv_ecn_echo(const struct tcp_sock
*tp
, const struct tcphdr
*th
)
257 if (th
->ece
&& !th
->syn
&& (tp
->ecn_flags
& TCP_ECN_OK
))
262 /* Buffer size and advertised window tuning.
264 * 1. Tuning sk->sk_sndbuf, when connection enters established state.
267 static void tcp_fixup_sndbuf(struct sock
*sk
)
269 int sndmem
= SKB_TRUESIZE(tcp_sk(sk
)->rx_opt
.mss_clamp
+ MAX_TCP_HEADER
);
271 sndmem
*= TCP_INIT_CWND
;
272 if (sk
->sk_sndbuf
< sndmem
)
273 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
276 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh)
278 * All tcp_full_space() is split to two parts: "network" buffer, allocated
279 * forward and advertised in receiver window (tp->rcv_wnd) and
280 * "application buffer", required to isolate scheduling/application
281 * latencies from network.
282 * window_clamp is maximal advertised window. It can be less than
283 * tcp_full_space(), in this case tcp_full_space() - window_clamp
284 * is reserved for "application" buffer. The less window_clamp is
285 * the smoother our behaviour from viewpoint of network, but the lower
286 * throughput and the higher sensitivity of the connection to losses. 8)
288 * rcv_ssthresh is more strict window_clamp used at "slow start"
289 * phase to predict further behaviour of this connection.
290 * It is used for two goals:
291 * - to enforce header prediction at sender, even when application
292 * requires some significant "application buffer". It is check #1.
293 * - to prevent pruning of receive queue because of misprediction
294 * of receiver window. Check #2.
296 * The scheme does not work when sender sends good segments opening
297 * window and then starts to feed us spaghetti. But it should work
298 * in common situations. Otherwise, we have to rely on queue collapsing.
301 /* Slow part of check#2. */
302 static int __tcp_grow_window(const struct sock
*sk
, const struct sk_buff
*skb
)
304 struct tcp_sock
*tp
= tcp_sk(sk
);
306 int truesize
= tcp_win_from_space(skb
->truesize
) >> 1;
307 int window
= tcp_win_from_space(sysctl_tcp_rmem
[2]) >> 1;
309 while (tp
->rcv_ssthresh
<= window
) {
310 if (truesize
<= skb
->len
)
311 return 2 * inet_csk(sk
)->icsk_ack
.rcv_mss
;
319 static void tcp_grow_window(struct sock
*sk
, const struct sk_buff
*skb
)
321 struct tcp_sock
*tp
= tcp_sk(sk
);
324 if (tp
->rcv_ssthresh
< tp
->window_clamp
&&
325 (int)tp
->rcv_ssthresh
< tcp_space(sk
) &&
326 !sk_under_memory_pressure(sk
)) {
329 /* Check #2. Increase window, if skb with such overhead
330 * will fit to rcvbuf in future.
332 if (tcp_win_from_space(skb
->truesize
) <= skb
->len
)
333 incr
= 2 * tp
->advmss
;
335 incr
= __tcp_grow_window(sk
, skb
);
338 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
+ incr
,
340 inet_csk(sk
)->icsk_ack
.quick
|= 1;
345 /* 3. Tuning rcvbuf, when connection enters established state. */
347 static void tcp_fixup_rcvbuf(struct sock
*sk
)
349 u32 mss
= tcp_sk(sk
)->advmss
;
350 u32 icwnd
= TCP_DEFAULT_INIT_RCVWND
;
353 /* Limit to 10 segments if mss <= 1460,
354 * or 14600/mss segments, with a minimum of two segments.
357 icwnd
= max_t(u32
, (1460 * TCP_DEFAULT_INIT_RCVWND
) / mss
, 2);
359 rcvmem
= SKB_TRUESIZE(mss
+ MAX_TCP_HEADER
);
360 while (tcp_win_from_space(rcvmem
) < mss
)
365 if (sk
->sk_rcvbuf
< rcvmem
)
366 sk
->sk_rcvbuf
= min(rcvmem
, sysctl_tcp_rmem
[2]);
369 /* 4. Try to fixup all. It is made immediately after connection enters
372 static void tcp_init_buffer_space(struct sock
*sk
)
374 struct tcp_sock
*tp
= tcp_sk(sk
);
377 if (!(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
))
378 tcp_fixup_rcvbuf(sk
);
379 if (!(sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
))
380 tcp_fixup_sndbuf(sk
);
382 tp
->rcvq_space
.space
= tp
->rcv_wnd
;
384 maxwin
= tcp_full_space(sk
);
386 if (tp
->window_clamp
>= maxwin
) {
387 tp
->window_clamp
= maxwin
;
389 if (sysctl_tcp_app_win
&& maxwin
> 4 * tp
->advmss
)
390 tp
->window_clamp
= max(maxwin
-
391 (maxwin
>> sysctl_tcp_app_win
),
395 /* Force reservation of one segment. */
396 if (sysctl_tcp_app_win
&&
397 tp
->window_clamp
> 2 * tp
->advmss
&&
398 tp
->window_clamp
+ tp
->advmss
> maxwin
)
399 tp
->window_clamp
= max(2 * tp
->advmss
, maxwin
- tp
->advmss
);
401 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, tp
->window_clamp
);
402 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
405 /* 5. Recalculate window clamp after socket hit its memory bounds. */
406 static void tcp_clamp_window(struct sock
*sk
)
408 struct tcp_sock
*tp
= tcp_sk(sk
);
409 struct inet_connection_sock
*icsk
= inet_csk(sk
);
411 icsk
->icsk_ack
.quick
= 0;
413 if (sk
->sk_rcvbuf
< sysctl_tcp_rmem
[2] &&
414 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
) &&
415 !sk_under_memory_pressure(sk
) &&
416 sk_memory_allocated(sk
) < sk_prot_mem_limits(sk
, 0)) {
417 sk
->sk_rcvbuf
= min(atomic_read(&sk
->sk_rmem_alloc
),
420 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
)
421 tp
->rcv_ssthresh
= min(tp
->window_clamp
, 2U * tp
->advmss
);
424 /* Initialize RCV_MSS value.
425 * RCV_MSS is an our guess about MSS used by the peer.
426 * We haven't any direct information about the MSS.
427 * It's better to underestimate the RCV_MSS rather than overestimate.
428 * Overestimations make us ACKing less frequently than needed.
429 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss().
431 void tcp_initialize_rcv_mss(struct sock
*sk
)
433 const struct tcp_sock
*tp
= tcp_sk(sk
);
434 unsigned int hint
= min_t(unsigned int, tp
->advmss
, tp
->mss_cache
);
436 hint
= min(hint
, tp
->rcv_wnd
/ 2);
437 hint
= min(hint
, TCP_MSS_DEFAULT
);
438 hint
= max(hint
, TCP_MIN_MSS
);
440 inet_csk(sk
)->icsk_ack
.rcv_mss
= hint
;
442 EXPORT_SYMBOL(tcp_initialize_rcv_mss
);
444 /* Receiver "autotuning" code.
446 * The algorithm for RTT estimation w/o timestamps is based on
447 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL.
448 * <http://public.lanl.gov/radiant/pubs.html#DRS>
450 * More detail on this code can be found at
451 * <http://staff.psc.edu/jheffner/>,
452 * though this reference is out of date. A new paper
455 static void tcp_rcv_rtt_update(struct tcp_sock
*tp
, u32 sample
, int win_dep
)
457 u32 new_sample
= tp
->rcv_rtt_est
.rtt
;
463 if (new_sample
!= 0) {
464 /* If we sample in larger samples in the non-timestamp
465 * case, we could grossly overestimate the RTT especially
466 * with chatty applications or bulk transfer apps which
467 * are stalled on filesystem I/O.
469 * Also, since we are only going for a minimum in the
470 * non-timestamp case, we do not smooth things out
471 * else with timestamps disabled convergence takes too
475 m
-= (new_sample
>> 3);
477 } else if (m
< new_sample
)
480 /* No previous measure. */
484 if (tp
->rcv_rtt_est
.rtt
!= new_sample
)
485 tp
->rcv_rtt_est
.rtt
= new_sample
;
488 static inline void tcp_rcv_rtt_measure(struct tcp_sock
*tp
)
490 if (tp
->rcv_rtt_est
.time
== 0)
492 if (before(tp
->rcv_nxt
, tp
->rcv_rtt_est
.seq
))
494 tcp_rcv_rtt_update(tp
, jiffies
- tp
->rcv_rtt_est
.time
, 1);
497 tp
->rcv_rtt_est
.seq
= tp
->rcv_nxt
+ tp
->rcv_wnd
;
498 tp
->rcv_rtt_est
.time
= tcp_time_stamp
;
501 static inline void tcp_rcv_rtt_measure_ts(struct sock
*sk
,
502 const struct sk_buff
*skb
)
504 struct tcp_sock
*tp
= tcp_sk(sk
);
505 if (tp
->rx_opt
.rcv_tsecr
&&
506 (TCP_SKB_CB(skb
)->end_seq
-
507 TCP_SKB_CB(skb
)->seq
>= inet_csk(sk
)->icsk_ack
.rcv_mss
))
508 tcp_rcv_rtt_update(tp
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
, 0);
512 * This function should be called every time data is copied to user space.
513 * It calculates the appropriate TCP receive buffer space.
515 void tcp_rcv_space_adjust(struct sock
*sk
)
517 struct tcp_sock
*tp
= tcp_sk(sk
);
521 if (tp
->rcvq_space
.time
== 0)
524 time
= tcp_time_stamp
- tp
->rcvq_space
.time
;
525 if (time
< (tp
->rcv_rtt_est
.rtt
>> 3) || tp
->rcv_rtt_est
.rtt
== 0)
528 space
= 2 * (tp
->copied_seq
- tp
->rcvq_space
.seq
);
530 space
= max(tp
->rcvq_space
.space
, space
);
532 if (tp
->rcvq_space
.space
!= space
) {
535 tp
->rcvq_space
.space
= space
;
537 if (sysctl_tcp_moderate_rcvbuf
&&
538 !(sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
)) {
539 int new_clamp
= space
;
541 /* Receive space grows, normalize in order to
542 * take into account packet headers and sk_buff
543 * structure overhead.
548 rcvmem
= SKB_TRUESIZE(tp
->advmss
+ MAX_TCP_HEADER
);
549 while (tcp_win_from_space(rcvmem
) < tp
->advmss
)
552 space
= min(space
, sysctl_tcp_rmem
[2]);
553 if (space
> sk
->sk_rcvbuf
) {
554 sk
->sk_rcvbuf
= space
;
556 /* Make the window clamp follow along. */
557 tp
->window_clamp
= new_clamp
;
563 tp
->rcvq_space
.seq
= tp
->copied_seq
;
564 tp
->rcvq_space
.time
= tcp_time_stamp
;
567 /* There is something which you must keep in mind when you analyze the
568 * behavior of the tp->ato delayed ack timeout interval. When a
569 * connection starts up, we want to ack as quickly as possible. The
570 * problem is that "good" TCP's do slow start at the beginning of data
571 * transmission. The means that until we send the first few ACK's the
572 * sender will sit on his end and only queue most of his data, because
573 * he can only send snd_cwnd unacked packets at any given time. For
574 * each ACK we send, he increments snd_cwnd and transmits more of his
577 static void tcp_event_data_recv(struct sock
*sk
, struct sk_buff
*skb
)
579 struct tcp_sock
*tp
= tcp_sk(sk
);
580 struct inet_connection_sock
*icsk
= inet_csk(sk
);
583 inet_csk_schedule_ack(sk
);
585 tcp_measure_rcv_mss(sk
, skb
);
587 tcp_rcv_rtt_measure(tp
);
589 now
= tcp_time_stamp
;
591 if (!icsk
->icsk_ack
.ato
) {
592 /* The _first_ data packet received, initialize
593 * delayed ACK engine.
595 tcp_incr_quickack(sk
);
596 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
598 int m
= now
- icsk
->icsk_ack
.lrcvtime
;
600 if (m
<= TCP_ATO_MIN
/ 2) {
601 /* The fastest case is the first. */
602 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + TCP_ATO_MIN
/ 2;
603 } else if (m
< icsk
->icsk_ack
.ato
) {
604 icsk
->icsk_ack
.ato
= (icsk
->icsk_ack
.ato
>> 1) + m
;
605 if (icsk
->icsk_ack
.ato
> icsk
->icsk_rto
)
606 icsk
->icsk_ack
.ato
= icsk
->icsk_rto
;
607 } else if (m
> icsk
->icsk_rto
) {
608 /* Too long gap. Apparently sender failed to
609 * restart window, so that we send ACKs quickly.
611 tcp_incr_quickack(sk
);
615 icsk
->icsk_ack
.lrcvtime
= now
;
617 TCP_ECN_check_ce(tp
, skb
);
620 tcp_grow_window(sk
, skb
);
623 /* Called to compute a smoothed rtt estimate. The data fed to this
624 * routine either comes from timestamps, or from segments that were
625 * known _not_ to have been retransmitted [see Karn/Partridge
626 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88
627 * piece by Van Jacobson.
628 * NOTE: the next three routines used to be one big routine.
629 * To save cycles in the RFC 1323 implementation it was better to break
630 * it up into three procedures. -- erics
632 static void tcp_rtt_estimator(struct sock
*sk
, const __u32 mrtt
)
634 struct tcp_sock
*tp
= tcp_sk(sk
);
635 long m
= mrtt
; /* RTT */
637 /* The following amusing code comes from Jacobson's
638 * article in SIGCOMM '88. Note that rtt and mdev
639 * are scaled versions of rtt and mean deviation.
640 * This is designed to be as fast as possible
641 * m stands for "measurement".
643 * On a 1990 paper the rto value is changed to:
644 * RTO = rtt + 4 * mdev
646 * Funny. This algorithm seems to be very broken.
647 * These formulae increase RTO, when it should be decreased, increase
648 * too slowly, when it should be increased quickly, decrease too quickly
649 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely
650 * does not matter how to _calculate_ it. Seems, it was trap
651 * that VJ failed to avoid. 8)
656 m
-= (tp
->srtt
>> 3); /* m is now error in rtt est */
657 tp
->srtt
+= m
; /* rtt = 7/8 rtt + 1/8 new */
659 m
= -m
; /* m is now abs(error) */
660 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
661 /* This is similar to one of Eifel findings.
662 * Eifel blocks mdev updates when rtt decreases.
663 * This solution is a bit different: we use finer gain
664 * for mdev in this case (alpha*beta).
665 * Like Eifel it also prevents growth of rto,
666 * but also it limits too fast rto decreases,
667 * happening in pure Eifel.
672 m
-= (tp
->mdev
>> 2); /* similar update on mdev */
674 tp
->mdev
+= m
; /* mdev = 3/4 mdev + 1/4 new */
675 if (tp
->mdev
> tp
->mdev_max
) {
676 tp
->mdev_max
= tp
->mdev
;
677 if (tp
->mdev_max
> tp
->rttvar
)
678 tp
->rttvar
= tp
->mdev_max
;
680 if (after(tp
->snd_una
, tp
->rtt_seq
)) {
681 if (tp
->mdev_max
< tp
->rttvar
)
682 tp
->rttvar
-= (tp
->rttvar
- tp
->mdev_max
) >> 2;
683 tp
->rtt_seq
= tp
->snd_nxt
;
684 tp
->mdev_max
= tcp_rto_min(sk
);
687 /* no previous measure. */
688 tp
->srtt
= m
<< 3; /* take the measured time to be rtt */
689 tp
->mdev
= m
<< 1; /* make sure rto = 3*rtt */
690 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
691 tp
->rtt_seq
= tp
->snd_nxt
;
695 /* Calculate rto without backoff. This is the second half of Van Jacobson's
696 * routine referred to above.
698 static inline void tcp_set_rto(struct sock
*sk
)
700 const struct tcp_sock
*tp
= tcp_sk(sk
);
701 /* Old crap is replaced with new one. 8)
704 * 1. If rtt variance happened to be less 50msec, it is hallucination.
705 * It cannot be less due to utterly erratic ACK generation made
706 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_
707 * to do with delayed acks, because at cwnd>2 true delack timeout
708 * is invisible. Actually, Linux-2.4 also generates erratic
709 * ACKs in some circumstances.
711 inet_csk(sk
)->icsk_rto
= __tcp_set_rto(tp
);
713 /* 2. Fixups made earlier cannot be right.
714 * If we do not estimate RTO correctly without them,
715 * all the algo is pure shit and should be replaced
716 * with correct one. It is exactly, which we pretend to do.
719 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo
720 * guarantees that rto is higher.
725 /* Save metrics learned by this TCP session.
726 This function is called only, when TCP finishes successfully
727 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE.
729 void tcp_update_metrics(struct sock
*sk
)
731 struct tcp_sock
*tp
= tcp_sk(sk
);
732 struct dst_entry
*dst
= __sk_dst_get(sk
);
734 if (sysctl_tcp_nometrics_save
)
739 if (dst
&& (dst
->flags
& DST_HOST
)) {
740 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
744 if (icsk
->icsk_backoff
|| !tp
->srtt
) {
745 /* This session failed to estimate rtt. Why?
746 * Probably, no packets returned in time.
749 if (!(dst_metric_locked(dst
, RTAX_RTT
)))
750 dst_metric_set(dst
, RTAX_RTT
, 0);
754 rtt
= dst_metric_rtt(dst
, RTAX_RTT
);
757 /* If newly calculated rtt larger than stored one,
758 * store new one. Otherwise, use EWMA. Remember,
759 * rtt overestimation is always better than underestimation.
761 if (!(dst_metric_locked(dst
, RTAX_RTT
))) {
763 set_dst_metric_rtt(dst
, RTAX_RTT
, tp
->srtt
);
765 set_dst_metric_rtt(dst
, RTAX_RTT
, rtt
- (m
>> 3));
768 if (!(dst_metric_locked(dst
, RTAX_RTTVAR
))) {
773 /* Scale deviation to rttvar fixed point */
778 var
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
782 var
-= (var
- m
) >> 2;
784 set_dst_metric_rtt(dst
, RTAX_RTTVAR
, var
);
787 if (tcp_in_initial_slowstart(tp
)) {
788 /* Slow start still did not finish. */
789 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
790 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
791 (tp
->snd_cwnd
>> 1) > dst_metric(dst
, RTAX_SSTHRESH
))
792 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_cwnd
>> 1);
793 if (!dst_metric_locked(dst
, RTAX_CWND
) &&
794 tp
->snd_cwnd
> dst_metric(dst
, RTAX_CWND
))
795 dst_metric_set(dst
, RTAX_CWND
, tp
->snd_cwnd
);
796 } else if (tp
->snd_cwnd
> tp
->snd_ssthresh
&&
797 icsk
->icsk_ca_state
== TCP_CA_Open
) {
798 /* Cong. avoidance phase, cwnd is reliable. */
799 if (!dst_metric_locked(dst
, RTAX_SSTHRESH
))
800 dst_metric_set(dst
, RTAX_SSTHRESH
,
801 max(tp
->snd_cwnd
>> 1, tp
->snd_ssthresh
));
802 if (!dst_metric_locked(dst
, RTAX_CWND
))
803 dst_metric_set(dst
, RTAX_CWND
,
804 (dst_metric(dst
, RTAX_CWND
) +
807 /* Else slow start did not finish, cwnd is non-sense,
808 ssthresh may be also invalid.
810 if (!dst_metric_locked(dst
, RTAX_CWND
))
811 dst_metric_set(dst
, RTAX_CWND
,
812 (dst_metric(dst
, RTAX_CWND
) +
813 tp
->snd_ssthresh
) >> 1);
814 if (dst_metric(dst
, RTAX_SSTHRESH
) &&
815 !dst_metric_locked(dst
, RTAX_SSTHRESH
) &&
816 tp
->snd_ssthresh
> dst_metric(dst
, RTAX_SSTHRESH
))
817 dst_metric_set(dst
, RTAX_SSTHRESH
, tp
->snd_ssthresh
);
820 if (!dst_metric_locked(dst
, RTAX_REORDERING
)) {
821 if (dst_metric(dst
, RTAX_REORDERING
) < tp
->reordering
&&
822 tp
->reordering
!= sysctl_tcp_reordering
)
823 dst_metric_set(dst
, RTAX_REORDERING
, tp
->reordering
);
828 __u32
tcp_init_cwnd(const struct tcp_sock
*tp
, const struct dst_entry
*dst
)
830 __u32 cwnd
= (dst
? dst_metric(dst
, RTAX_INITCWND
) : 0);
833 cwnd
= TCP_INIT_CWND
;
834 return min_t(__u32
, cwnd
, tp
->snd_cwnd_clamp
);
837 /* Set slow start threshold and cwnd not falling to slow start */
838 void tcp_enter_cwr(struct sock
*sk
, const int set_ssthresh
)
840 struct tcp_sock
*tp
= tcp_sk(sk
);
841 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
843 tp
->prior_ssthresh
= 0;
845 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
848 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
849 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
850 tcp_packets_in_flight(tp
) + 1U);
851 tp
->snd_cwnd_cnt
= 0;
852 tp
->high_seq
= tp
->snd_nxt
;
853 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
854 TCP_ECN_queue_cwr(tp
);
856 tcp_set_ca_state(sk
, TCP_CA_CWR
);
861 * Packet counting of FACK is based on in-order assumptions, therefore TCP
862 * disables it when reordering is detected
864 static void tcp_disable_fack(struct tcp_sock
*tp
)
866 /* RFC3517 uses different metric in lost marker => reset on change */
868 tp
->lost_skb_hint
= NULL
;
869 tp
->rx_opt
.sack_ok
&= ~TCP_FACK_ENABLED
;
872 /* Take a notice that peer is sending D-SACKs */
873 static void tcp_dsack_seen(struct tcp_sock
*tp
)
875 tp
->rx_opt
.sack_ok
|= TCP_DSACK_SEEN
;
878 /* Initialize metrics on socket. */
880 static void tcp_init_metrics(struct sock
*sk
)
882 struct tcp_sock
*tp
= tcp_sk(sk
);
883 struct dst_entry
*dst
= __sk_dst_get(sk
);
890 if (dst_metric_locked(dst
, RTAX_CWND
))
891 tp
->snd_cwnd_clamp
= dst_metric(dst
, RTAX_CWND
);
892 if (dst_metric(dst
, RTAX_SSTHRESH
)) {
893 tp
->snd_ssthresh
= dst_metric(dst
, RTAX_SSTHRESH
);
894 if (tp
->snd_ssthresh
> tp
->snd_cwnd_clamp
)
895 tp
->snd_ssthresh
= tp
->snd_cwnd_clamp
;
897 /* ssthresh may have been reduced unnecessarily during.
898 * 3WHS. Restore it back to its initial default.
900 tp
->snd_ssthresh
= TCP_INFINITE_SSTHRESH
;
902 if (dst_metric(dst
, RTAX_REORDERING
) &&
903 tp
->reordering
!= dst_metric(dst
, RTAX_REORDERING
)) {
904 tcp_disable_fack(tp
);
905 tp
->reordering
= dst_metric(dst
, RTAX_REORDERING
);
908 if (dst_metric(dst
, RTAX_RTT
) == 0 || tp
->srtt
== 0)
911 /* Initial rtt is determined from SYN,SYN-ACK.
912 * The segment is small and rtt may appear much
913 * less than real one. Use per-dst memory
914 * to make it more realistic.
916 * A bit of theory. RTT is time passed after "normal" sized packet
917 * is sent until it is ACKed. In normal circumstances sending small
918 * packets force peer to delay ACKs and calculation is correct too.
919 * The algorithm is adaptive and, provided we follow specs, it
920 * NEVER underestimate RTT. BUT! If peer tries to make some clever
921 * tricks sort of "quick acks" for time long enough to decrease RTT
922 * to low value, and then abruptly stops to do it and starts to delay
923 * ACKs, wait for troubles.
925 if (dst_metric_rtt(dst
, RTAX_RTT
) > tp
->srtt
) {
926 tp
->srtt
= dst_metric_rtt(dst
, RTAX_RTT
);
927 tp
->rtt_seq
= tp
->snd_nxt
;
929 if (dst_metric_rtt(dst
, RTAX_RTTVAR
) > tp
->mdev
) {
930 tp
->mdev
= dst_metric_rtt(dst
, RTAX_RTTVAR
);
931 tp
->mdev_max
= tp
->rttvar
= max(tp
->mdev
, tcp_rto_min(sk
));
936 /* RFC2988bis: We've failed to get a valid RTT sample from
937 * 3WHS. This is most likely due to retransmission,
938 * including spurious one. Reset the RTO back to 3secs
939 * from the more aggressive 1sec to avoid more spurious
942 tp
->mdev
= tp
->mdev_max
= tp
->rttvar
= TCP_TIMEOUT_FALLBACK
;
943 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_FALLBACK
;
945 /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been
946 * retransmitted. In light of RFC2988bis' more aggressive 1sec
947 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK
948 * retransmission has occurred.
950 if (tp
->total_retrans
> 1)
953 tp
->snd_cwnd
= tcp_init_cwnd(tp
, dst
);
954 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
957 static void tcp_update_reordering(struct sock
*sk
, const int metric
,
960 struct tcp_sock
*tp
= tcp_sk(sk
);
961 if (metric
> tp
->reordering
) {
964 tp
->reordering
= min(TCP_MAX_REORDERING
, metric
);
966 /* This exciting event is worth to be remembered. 8) */
968 mib_idx
= LINUX_MIB_TCPTSREORDER
;
969 else if (tcp_is_reno(tp
))
970 mib_idx
= LINUX_MIB_TCPRENOREORDER
;
971 else if (tcp_is_fack(tp
))
972 mib_idx
= LINUX_MIB_TCPFACKREORDER
;
974 mib_idx
= LINUX_MIB_TCPSACKREORDER
;
976 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
977 #if FASTRETRANS_DEBUG > 1
978 printk(KERN_DEBUG
"Disorder%d %d %u f%u s%u rr%d\n",
979 tp
->rx_opt
.sack_ok
, inet_csk(sk
)->icsk_ca_state
,
983 tp
->undo_marker
? tp
->undo_retrans
: 0);
985 tcp_disable_fack(tp
);
989 /* This must be called before lost_out is incremented */
990 static void tcp_verify_retransmit_hint(struct tcp_sock
*tp
, struct sk_buff
*skb
)
992 if ((tp
->retransmit_skb_hint
== NULL
) ||
993 before(TCP_SKB_CB(skb
)->seq
,
994 TCP_SKB_CB(tp
->retransmit_skb_hint
)->seq
))
995 tp
->retransmit_skb_hint
= skb
;
998 after(TCP_SKB_CB(skb
)->end_seq
, tp
->retransmit_high
))
999 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
1002 static void tcp_skb_mark_lost(struct tcp_sock
*tp
, struct sk_buff
*skb
)
1004 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1005 tcp_verify_retransmit_hint(tp
, skb
);
1007 tp
->lost_out
+= tcp_skb_pcount(skb
);
1008 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1012 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock
*tp
,
1013 struct sk_buff
*skb
)
1015 tcp_verify_retransmit_hint(tp
, skb
);
1017 if (!(TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_ACKED
))) {
1018 tp
->lost_out
+= tcp_skb_pcount(skb
);
1019 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1023 /* This procedure tags the retransmission queue when SACKs arrive.
1025 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
1026 * Packets in queue with these bits set are counted in variables
1027 * sacked_out, retrans_out and lost_out, correspondingly.
1029 * Valid combinations are:
1030 * Tag InFlight Description
1031 * 0 1 - orig segment is in flight.
1032 * S 0 - nothing flies, orig reached receiver.
1033 * L 0 - nothing flies, orig lost by net.
1034 * R 2 - both orig and retransmit are in flight.
1035 * L|R 1 - orig is lost, retransmit is in flight.
1036 * S|R 1 - orig reached receiver, retrans is still in flight.
1037 * (L|S|R is logically valid, it could occur when L|R is sacked,
1038 * but it is equivalent to plain S and code short-curcuits it to S.
1039 * L|S is logically invalid, it would mean -1 packet in flight 8))
1041 * These 6 states form finite state machine, controlled by the following events:
1042 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue())
1043 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue())
1044 * 3. Loss detection event of two flavors:
1045 * A. Scoreboard estimator decided the packet is lost.
1046 * A'. Reno "three dupacks" marks head of queue lost.
1047 * A''. Its FACK modification, head until snd.fack is lost.
1048 * B. SACK arrives sacking SND.NXT at the moment, when the
1049 * segment was retransmitted.
1050 * 4. D-SACK added new rule: D-SACK changes any tag to S.
1052 * It is pleasant to note, that state diagram turns out to be commutative,
1053 * so that we are allowed not to be bothered by order of our actions,
1054 * when multiple events arrive simultaneously. (see the function below).
1056 * Reordering detection.
1057 * --------------------
1058 * Reordering metric is maximal distance, which a packet can be displaced
1059 * in packet stream. With SACKs we can estimate it:
1061 * 1. SACK fills old hole and the corresponding segment was not
1062 * ever retransmitted -> reordering. Alas, we cannot use it
1063 * when segment was retransmitted.
1064 * 2. The last flaw is solved with D-SACK. D-SACK arrives
1065 * for retransmitted and already SACKed segment -> reordering..
1066 * Both of these heuristics are not used in Loss state, when we cannot
1067 * account for retransmits accurately.
1069 * SACK block validation.
1070 * ----------------------
1072 * SACK block range validation checks that the received SACK block fits to
1073 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT.
1074 * Note that SND.UNA is not included to the range though being valid because
1075 * it means that the receiver is rather inconsistent with itself reporting
1076 * SACK reneging when it should advance SND.UNA. Such SACK block this is
1077 * perfectly valid, however, in light of RFC2018 which explicitly states
1078 * that "SACK block MUST reflect the newest segment. Even if the newest
1079 * segment is going to be discarded ...", not that it looks very clever
1080 * in case of head skb. Due to potentional receiver driven attacks, we
1081 * choose to avoid immediate execution of a walk in write queue due to
1082 * reneging and defer head skb's loss recovery to standard loss recovery
1083 * procedure that will eventually trigger (nothing forbids us doing this).
1085 * Implements also blockage to start_seq wrap-around. Problem lies in the
1086 * fact that though start_seq (s) is before end_seq (i.e., not reversed),
1087 * there's no guarantee that it will be before snd_nxt (n). The problem
1088 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt
1091 * <- outs wnd -> <- wrapzone ->
1092 * u e n u_w e_w s n_w
1094 * |<------------+------+----- TCP seqno space --------------+---------->|
1095 * ...-- <2^31 ->| |<--------...
1096 * ...---- >2^31 ------>| |<--------...
1098 * Current code wouldn't be vulnerable but it's better still to discard such
1099 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat
1100 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in
1101 * snd_nxt wrap -> snd_una region will then become "well defined", i.e.,
1102 * equal to the ideal case (infinite seqno space without wrap caused issues).
1104 * With D-SACK the lower bound is extended to cover sequence space below
1105 * SND.UNA down to undo_marker, which is the last point of interest. Yet
1106 * again, D-SACK block must not to go across snd_una (for the same reason as
1107 * for the normal SACK blocks, explained above). But there all simplicity
1108 * ends, TCP might receive valid D-SACKs below that. As long as they reside
1109 * fully below undo_marker they do not affect behavior in anyway and can
1110 * therefore be safely ignored. In rare cases (which are more or less
1111 * theoretical ones), the D-SACK will nicely cross that boundary due to skb
1112 * fragmentation and packet reordering past skb's retransmission. To consider
1113 * them correctly, the acceptable range must be extended even more though
1114 * the exact amount is rather hard to quantify. However, tp->max_window can
1115 * be used as an exaggerated estimate.
1117 static int tcp_is_sackblock_valid(struct tcp_sock
*tp
, int is_dsack
,
1118 u32 start_seq
, u32 end_seq
)
1120 /* Too far in future, or reversed (interpretation is ambiguous) */
1121 if (after(end_seq
, tp
->snd_nxt
) || !before(start_seq
, end_seq
))
1124 /* Nasty start_seq wrap-around check (see comments above) */
1125 if (!before(start_seq
, tp
->snd_nxt
))
1128 /* In outstanding window? ...This is valid exit for D-SACKs too.
1129 * start_seq == snd_una is non-sensical (see comments above)
1131 if (after(start_seq
, tp
->snd_una
))
1134 if (!is_dsack
|| !tp
->undo_marker
)
1137 /* ...Then it's D-SACK, and must reside below snd_una completely */
1138 if (after(end_seq
, tp
->snd_una
))
1141 if (!before(start_seq
, tp
->undo_marker
))
1145 if (!after(end_seq
, tp
->undo_marker
))
1148 /* Undo_marker boundary crossing (overestimates a lot). Known already:
1149 * start_seq < undo_marker and end_seq >= undo_marker.
1151 return !before(start_seq
, end_seq
- tp
->max_window
);
1154 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
1155 * Event "B". Later note: FACK people cheated me again 8), we have to account
1156 * for reordering! Ugly, but should help.
1158 * Search retransmitted skbs from write_queue that were sent when snd_nxt was
1159 * less than what is now known to be received by the other end (derived from
1160 * highest SACK block). Also calculate the lowest snd_nxt among the remaining
1161 * retransmitted skbs to avoid some costly processing per ACKs.
1163 static void tcp_mark_lost_retrans(struct sock
*sk
)
1165 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1166 struct tcp_sock
*tp
= tcp_sk(sk
);
1167 struct sk_buff
*skb
;
1169 u32 new_low_seq
= tp
->snd_nxt
;
1170 u32 received_upto
= tcp_highest_sack_seq(tp
);
1172 if (!tcp_is_fack(tp
) || !tp
->retrans_out
||
1173 !after(received_upto
, tp
->lost_retrans_low
) ||
1174 icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1177 tcp_for_write_queue(skb
, sk
) {
1178 u32 ack_seq
= TCP_SKB_CB(skb
)->ack_seq
;
1180 if (skb
== tcp_send_head(sk
))
1182 if (cnt
== tp
->retrans_out
)
1184 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1187 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
))
1190 /* TODO: We would like to get rid of tcp_is_fack(tp) only
1191 * constraint here (see above) but figuring out that at
1192 * least tp->reordering SACK blocks reside between ack_seq
1193 * and received_upto is not easy task to do cheaply with
1194 * the available datastructures.
1196 * Whether FACK should check here for tp->reordering segs
1197 * in-between one could argue for either way (it would be
1198 * rather simple to implement as we could count fack_count
1199 * during the walk and do tp->fackets_out - fack_count).
1201 if (after(received_upto
, ack_seq
)) {
1202 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1203 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1205 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
1206 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSTRETRANSMIT
);
1208 if (before(ack_seq
, new_low_seq
))
1209 new_low_seq
= ack_seq
;
1210 cnt
+= tcp_skb_pcount(skb
);
1214 if (tp
->retrans_out
)
1215 tp
->lost_retrans_low
= new_low_seq
;
1218 static int tcp_check_dsack(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1219 struct tcp_sack_block_wire
*sp
, int num_sacks
,
1222 struct tcp_sock
*tp
= tcp_sk(sk
);
1223 u32 start_seq_0
= get_unaligned_be32(&sp
[0].start_seq
);
1224 u32 end_seq_0
= get_unaligned_be32(&sp
[0].end_seq
);
1227 if (before(start_seq_0
, TCP_SKB_CB(ack_skb
)->ack_seq
)) {
1230 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKRECV
);
1231 } else if (num_sacks
> 1) {
1232 u32 end_seq_1
= get_unaligned_be32(&sp
[1].end_seq
);
1233 u32 start_seq_1
= get_unaligned_be32(&sp
[1].start_seq
);
1235 if (!after(end_seq_0
, end_seq_1
) &&
1236 !before(start_seq_0
, start_seq_1
)) {
1239 NET_INC_STATS_BH(sock_net(sk
),
1240 LINUX_MIB_TCPDSACKOFORECV
);
1244 /* D-SACK for already forgotten data... Do dumb counting. */
1245 if (dup_sack
&& tp
->undo_marker
&& tp
->undo_retrans
&&
1246 !after(end_seq_0
, prior_snd_una
) &&
1247 after(end_seq_0
, tp
->undo_marker
))
1253 struct tcp_sacktag_state
{
1259 /* Check if skb is fully within the SACK block. In presence of GSO skbs,
1260 * the incoming SACK may not exactly match but we can find smaller MSS
1261 * aligned portion of it that matches. Therefore we might need to fragment
1262 * which may fail and creates some hassle (caller must handle error case
1265 * FIXME: this could be merged to shift decision code
1267 static int tcp_match_skb_to_sack(struct sock
*sk
, struct sk_buff
*skb
,
1268 u32 start_seq
, u32 end_seq
)
1271 unsigned int pkt_len
;
1274 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1275 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1277 if (tcp_skb_pcount(skb
) > 1 && !in_sack
&&
1278 after(TCP_SKB_CB(skb
)->end_seq
, start_seq
)) {
1279 mss
= tcp_skb_mss(skb
);
1280 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1283 pkt_len
= start_seq
- TCP_SKB_CB(skb
)->seq
;
1287 pkt_len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1292 /* Round if necessary so that SACKs cover only full MSSes
1293 * and/or the remaining small portion (if present)
1295 if (pkt_len
> mss
) {
1296 unsigned int new_len
= (pkt_len
/ mss
) * mss
;
1297 if (!in_sack
&& new_len
< pkt_len
) {
1299 if (new_len
> skb
->len
)
1304 err
= tcp_fragment(sk
, skb
, pkt_len
, mss
);
1312 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */
1313 static u8
tcp_sacktag_one(struct sock
*sk
,
1314 struct tcp_sacktag_state
*state
, u8 sacked
,
1315 u32 start_seq
, u32 end_seq
,
1316 int dup_sack
, int pcount
)
1318 struct tcp_sock
*tp
= tcp_sk(sk
);
1319 int fack_count
= state
->fack_count
;
1321 /* Account D-SACK for retransmitted packet. */
1322 if (dup_sack
&& (sacked
& TCPCB_RETRANS
)) {
1323 if (tp
->undo_marker
&& tp
->undo_retrans
&&
1324 after(end_seq
, tp
->undo_marker
))
1326 if (sacked
& TCPCB_SACKED_ACKED
)
1327 state
->reord
= min(fack_count
, state
->reord
);
1330 /* Nothing to do; acked frame is about to be dropped (was ACKed). */
1331 if (!after(end_seq
, tp
->snd_una
))
1334 if (!(sacked
& TCPCB_SACKED_ACKED
)) {
1335 if (sacked
& TCPCB_SACKED_RETRANS
) {
1336 /* If the segment is not tagged as lost,
1337 * we do not clear RETRANS, believing
1338 * that retransmission is still in flight.
1340 if (sacked
& TCPCB_LOST
) {
1341 sacked
&= ~(TCPCB_LOST
|TCPCB_SACKED_RETRANS
);
1342 tp
->lost_out
-= pcount
;
1343 tp
->retrans_out
-= pcount
;
1346 if (!(sacked
& TCPCB_RETRANS
)) {
1347 /* New sack for not retransmitted frame,
1348 * which was in hole. It is reordering.
1350 if (before(start_seq
,
1351 tcp_highest_sack_seq(tp
)))
1352 state
->reord
= min(fack_count
,
1355 /* SACK enhanced F-RTO (RFC4138; Appendix B) */
1356 if (!after(end_seq
, tp
->frto_highmark
))
1357 state
->flag
|= FLAG_ONLY_ORIG_SACKED
;
1360 if (sacked
& TCPCB_LOST
) {
1361 sacked
&= ~TCPCB_LOST
;
1362 tp
->lost_out
-= pcount
;
1366 sacked
|= TCPCB_SACKED_ACKED
;
1367 state
->flag
|= FLAG_DATA_SACKED
;
1368 tp
->sacked_out
+= pcount
;
1370 fack_count
+= pcount
;
1372 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */
1373 if (!tcp_is_fack(tp
) && (tp
->lost_skb_hint
!= NULL
) &&
1374 before(start_seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
))
1375 tp
->lost_cnt_hint
+= pcount
;
1377 if (fack_count
> tp
->fackets_out
)
1378 tp
->fackets_out
= fack_count
;
1381 /* D-SACK. We can detect redundant retransmission in S|R and plain R
1382 * frames and clear it. undo_retrans is decreased above, L|R frames
1383 * are accounted above as well.
1385 if (dup_sack
&& (sacked
& TCPCB_SACKED_RETRANS
)) {
1386 sacked
&= ~TCPCB_SACKED_RETRANS
;
1387 tp
->retrans_out
-= pcount
;
1393 /* Shift newly-SACKed bytes from this skb to the immediately previous
1394 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such.
1396 static int tcp_shifted_skb(struct sock
*sk
, struct sk_buff
*skb
,
1397 struct tcp_sacktag_state
*state
,
1398 unsigned int pcount
, int shifted
, int mss
,
1401 struct tcp_sock
*tp
= tcp_sk(sk
);
1402 struct sk_buff
*prev
= tcp_write_queue_prev(sk
, skb
);
1403 u32 start_seq
= TCP_SKB_CB(skb
)->seq
; /* start of newly-SACKed */
1404 u32 end_seq
= start_seq
+ shifted
; /* end of newly-SACKed */
1408 /* Adjust counters and hints for the newly sacked sequence
1409 * range but discard the return value since prev is already
1410 * marked. We must tag the range first because the seq
1411 * advancement below implicitly advances
1412 * tcp_highest_sack_seq() when skb is highest_sack.
1414 tcp_sacktag_one(sk
, state
, TCP_SKB_CB(skb
)->sacked
,
1415 start_seq
, end_seq
, dup_sack
, pcount
);
1417 if (skb
== tp
->lost_skb_hint
)
1418 tp
->lost_cnt_hint
+= pcount
;
1420 TCP_SKB_CB(prev
)->end_seq
+= shifted
;
1421 TCP_SKB_CB(skb
)->seq
+= shifted
;
1423 skb_shinfo(prev
)->gso_segs
+= pcount
;
1424 BUG_ON(skb_shinfo(skb
)->gso_segs
< pcount
);
1425 skb_shinfo(skb
)->gso_segs
-= pcount
;
1427 /* When we're adding to gso_segs == 1, gso_size will be zero,
1428 * in theory this shouldn't be necessary but as long as DSACK
1429 * code can come after this skb later on it's better to keep
1430 * setting gso_size to something.
1432 if (!skb_shinfo(prev
)->gso_size
) {
1433 skb_shinfo(prev
)->gso_size
= mss
;
1434 skb_shinfo(prev
)->gso_type
= sk
->sk_gso_type
;
1437 /* CHECKME: To clear or not to clear? Mimics normal skb currently */
1438 if (skb_shinfo(skb
)->gso_segs
<= 1) {
1439 skb_shinfo(skb
)->gso_size
= 0;
1440 skb_shinfo(skb
)->gso_type
= 0;
1443 /* Difference in this won't matter, both ACKed by the same cumul. ACK */
1444 TCP_SKB_CB(prev
)->sacked
|= (TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
);
1447 BUG_ON(!tcp_skb_pcount(skb
));
1448 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTED
);
1452 /* Whole SKB was eaten :-) */
1454 if (skb
== tp
->retransmit_skb_hint
)
1455 tp
->retransmit_skb_hint
= prev
;
1456 if (skb
== tp
->scoreboard_skb_hint
)
1457 tp
->scoreboard_skb_hint
= prev
;
1458 if (skb
== tp
->lost_skb_hint
) {
1459 tp
->lost_skb_hint
= prev
;
1460 tp
->lost_cnt_hint
-= tcp_skb_pcount(prev
);
1463 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(prev
)->tcp_flags
;
1464 if (skb
== tcp_highest_sack(sk
))
1465 tcp_advance_highest_sack(sk
, skb
);
1467 tcp_unlink_write_queue(skb
, sk
);
1468 sk_wmem_free_skb(sk
, skb
);
1470 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKMERGED
);
1475 /* I wish gso_size would have a bit more sane initialization than
1476 * something-or-zero which complicates things
1478 static int tcp_skb_seglen(const struct sk_buff
*skb
)
1480 return tcp_skb_pcount(skb
) == 1 ? skb
->len
: tcp_skb_mss(skb
);
1483 /* Shifting pages past head area doesn't work */
1484 static int skb_can_shift(const struct sk_buff
*skb
)
1486 return !skb_headlen(skb
) && skb_is_nonlinear(skb
);
1489 /* Try collapsing SACK blocks spanning across multiple skbs to a single
1492 static struct sk_buff
*tcp_shift_skb_data(struct sock
*sk
, struct sk_buff
*skb
,
1493 struct tcp_sacktag_state
*state
,
1494 u32 start_seq
, u32 end_seq
,
1497 struct tcp_sock
*tp
= tcp_sk(sk
);
1498 struct sk_buff
*prev
;
1504 if (!sk_can_gso(sk
))
1507 /* Normally R but no L won't result in plain S */
1509 (TCP_SKB_CB(skb
)->sacked
& (TCPCB_LOST
|TCPCB_SACKED_RETRANS
)) == TCPCB_SACKED_RETRANS
)
1511 if (!skb_can_shift(skb
))
1513 /* This frame is about to be dropped (was ACKed). */
1514 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1517 /* Can only happen with delayed DSACK + discard craziness */
1518 if (unlikely(skb
== tcp_write_queue_head(sk
)))
1520 prev
= tcp_write_queue_prev(sk
, skb
);
1522 if ((TCP_SKB_CB(prev
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
)
1525 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
) &&
1526 !before(end_seq
, TCP_SKB_CB(skb
)->end_seq
);
1530 pcount
= tcp_skb_pcount(skb
);
1531 mss
= tcp_skb_seglen(skb
);
1533 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1534 * drop this restriction as unnecessary
1536 if (mss
!= tcp_skb_seglen(prev
))
1539 if (!after(TCP_SKB_CB(skb
)->end_seq
, start_seq
))
1541 /* CHECKME: This is non-MSS split case only?, this will
1542 * cause skipped skbs due to advancing loop btw, original
1543 * has that feature too
1545 if (tcp_skb_pcount(skb
) <= 1)
1548 in_sack
= !after(start_seq
, TCP_SKB_CB(skb
)->seq
);
1550 /* TODO: head merge to next could be attempted here
1551 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)),
1552 * though it might not be worth of the additional hassle
1554 * ...we can probably just fallback to what was done
1555 * previously. We could try merging non-SACKed ones
1556 * as well but it probably isn't going to buy off
1557 * because later SACKs might again split them, and
1558 * it would make skb timestamp tracking considerably
1564 len
= end_seq
- TCP_SKB_CB(skb
)->seq
;
1566 BUG_ON(len
> skb
->len
);
1568 /* MSS boundaries should be honoured or else pcount will
1569 * severely break even though it makes things bit trickier.
1570 * Optimize common case to avoid most of the divides
1572 mss
= tcp_skb_mss(skb
);
1574 /* TODO: Fix DSACKs to not fragment already SACKed and we can
1575 * drop this restriction as unnecessary
1577 if (mss
!= tcp_skb_seglen(prev
))
1582 } else if (len
< mss
) {
1590 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */
1591 if (!after(TCP_SKB_CB(skb
)->seq
+ len
, tp
->snd_una
))
1594 if (!skb_shift(prev
, skb
, len
))
1596 if (!tcp_shifted_skb(sk
, skb
, state
, pcount
, len
, mss
, dup_sack
))
1599 /* Hole filled allows collapsing with the next as well, this is very
1600 * useful when hole on every nth skb pattern happens
1602 if (prev
== tcp_write_queue_tail(sk
))
1604 skb
= tcp_write_queue_next(sk
, prev
);
1606 if (!skb_can_shift(skb
) ||
1607 (skb
== tcp_send_head(sk
)) ||
1608 ((TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
) != TCPCB_SACKED_ACKED
) ||
1609 (mss
!= tcp_skb_seglen(skb
)))
1613 if (skb_shift(prev
, skb
, len
)) {
1614 pcount
+= tcp_skb_pcount(skb
);
1615 tcp_shifted_skb(sk
, skb
, state
, tcp_skb_pcount(skb
), len
, mss
, 0);
1619 state
->fack_count
+= pcount
;
1626 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_SACKSHIFTFALLBACK
);
1630 static struct sk_buff
*tcp_sacktag_walk(struct sk_buff
*skb
, struct sock
*sk
,
1631 struct tcp_sack_block
*next_dup
,
1632 struct tcp_sacktag_state
*state
,
1633 u32 start_seq
, u32 end_seq
,
1636 struct tcp_sock
*tp
= tcp_sk(sk
);
1637 struct sk_buff
*tmp
;
1639 tcp_for_write_queue_from(skb
, sk
) {
1641 int dup_sack
= dup_sack_in
;
1643 if (skb
== tcp_send_head(sk
))
1646 /* queue is in-order => we can short-circuit the walk early */
1647 if (!before(TCP_SKB_CB(skb
)->seq
, end_seq
))
1650 if ((next_dup
!= NULL
) &&
1651 before(TCP_SKB_CB(skb
)->seq
, next_dup
->end_seq
)) {
1652 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1653 next_dup
->start_seq
,
1659 /* skb reference here is a bit tricky to get right, since
1660 * shifting can eat and free both this skb and the next,
1661 * so not even _safe variant of the loop is enough.
1664 tmp
= tcp_shift_skb_data(sk
, skb
, state
,
1665 start_seq
, end_seq
, dup_sack
);
1674 in_sack
= tcp_match_skb_to_sack(sk
, skb
,
1680 if (unlikely(in_sack
< 0))
1684 TCP_SKB_CB(skb
)->sacked
=
1687 TCP_SKB_CB(skb
)->sacked
,
1688 TCP_SKB_CB(skb
)->seq
,
1689 TCP_SKB_CB(skb
)->end_seq
,
1691 tcp_skb_pcount(skb
));
1693 if (!before(TCP_SKB_CB(skb
)->seq
,
1694 tcp_highest_sack_seq(tp
)))
1695 tcp_advance_highest_sack(sk
, skb
);
1698 state
->fack_count
+= tcp_skb_pcount(skb
);
1703 /* Avoid all extra work that is being done by sacktag while walking in
1706 static struct sk_buff
*tcp_sacktag_skip(struct sk_buff
*skb
, struct sock
*sk
,
1707 struct tcp_sacktag_state
*state
,
1710 tcp_for_write_queue_from(skb
, sk
) {
1711 if (skb
== tcp_send_head(sk
))
1714 if (after(TCP_SKB_CB(skb
)->end_seq
, skip_to_seq
))
1717 state
->fack_count
+= tcp_skb_pcount(skb
);
1722 static struct sk_buff
*tcp_maybe_skipping_dsack(struct sk_buff
*skb
,
1724 struct tcp_sack_block
*next_dup
,
1725 struct tcp_sacktag_state
*state
,
1728 if (next_dup
== NULL
)
1731 if (before(next_dup
->start_seq
, skip_to_seq
)) {
1732 skb
= tcp_sacktag_skip(skb
, sk
, state
, next_dup
->start_seq
);
1733 skb
= tcp_sacktag_walk(skb
, sk
, NULL
, state
,
1734 next_dup
->start_seq
, next_dup
->end_seq
,
1741 static int tcp_sack_cache_ok(const struct tcp_sock
*tp
, const struct tcp_sack_block
*cache
)
1743 return cache
< tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1747 tcp_sacktag_write_queue(struct sock
*sk
, const struct sk_buff
*ack_skb
,
1750 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1751 struct tcp_sock
*tp
= tcp_sk(sk
);
1752 const unsigned char *ptr
= (skb_transport_header(ack_skb
) +
1753 TCP_SKB_CB(ack_skb
)->sacked
);
1754 struct tcp_sack_block_wire
*sp_wire
= (struct tcp_sack_block_wire
*)(ptr
+2);
1755 struct tcp_sack_block sp
[TCP_NUM_SACKS
];
1756 struct tcp_sack_block
*cache
;
1757 struct tcp_sacktag_state state
;
1758 struct sk_buff
*skb
;
1759 int num_sacks
= min(TCP_NUM_SACKS
, (ptr
[1] - TCPOLEN_SACK_BASE
) >> 3);
1761 int found_dup_sack
= 0;
1763 int first_sack_index
;
1766 state
.reord
= tp
->packets_out
;
1768 if (!tp
->sacked_out
) {
1769 if (WARN_ON(tp
->fackets_out
))
1770 tp
->fackets_out
= 0;
1771 tcp_highest_sack_reset(sk
);
1774 found_dup_sack
= tcp_check_dsack(sk
, ack_skb
, sp_wire
,
1775 num_sacks
, prior_snd_una
);
1777 state
.flag
|= FLAG_DSACKING_ACK
;
1779 /* Eliminate too old ACKs, but take into
1780 * account more or less fresh ones, they can
1781 * contain valid SACK info.
1783 if (before(TCP_SKB_CB(ack_skb
)->ack_seq
, prior_snd_una
- tp
->max_window
))
1786 if (!tp
->packets_out
)
1790 first_sack_index
= 0;
1791 for (i
= 0; i
< num_sacks
; i
++) {
1792 int dup_sack
= !i
&& found_dup_sack
;
1794 sp
[used_sacks
].start_seq
= get_unaligned_be32(&sp_wire
[i
].start_seq
);
1795 sp
[used_sacks
].end_seq
= get_unaligned_be32(&sp_wire
[i
].end_seq
);
1797 if (!tcp_is_sackblock_valid(tp
, dup_sack
,
1798 sp
[used_sacks
].start_seq
,
1799 sp
[used_sacks
].end_seq
)) {
1803 if (!tp
->undo_marker
)
1804 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDNOUNDO
;
1806 mib_idx
= LINUX_MIB_TCPDSACKIGNOREDOLD
;
1808 /* Don't count olds caused by ACK reordering */
1809 if ((TCP_SKB_CB(ack_skb
)->ack_seq
!= tp
->snd_una
) &&
1810 !after(sp
[used_sacks
].end_seq
, tp
->snd_una
))
1812 mib_idx
= LINUX_MIB_TCPSACKDISCARD
;
1815 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
1817 first_sack_index
= -1;
1821 /* Ignore very old stuff early */
1822 if (!after(sp
[used_sacks
].end_seq
, prior_snd_una
))
1828 /* order SACK blocks to allow in order walk of the retrans queue */
1829 for (i
= used_sacks
- 1; i
> 0; i
--) {
1830 for (j
= 0; j
< i
; j
++) {
1831 if (after(sp
[j
].start_seq
, sp
[j
+ 1].start_seq
)) {
1832 swap(sp
[j
], sp
[j
+ 1]);
1834 /* Track where the first SACK block goes to */
1835 if (j
== first_sack_index
)
1836 first_sack_index
= j
+ 1;
1841 skb
= tcp_write_queue_head(sk
);
1842 state
.fack_count
= 0;
1845 if (!tp
->sacked_out
) {
1846 /* It's already past, so skip checking against it */
1847 cache
= tp
->recv_sack_cache
+ ARRAY_SIZE(tp
->recv_sack_cache
);
1849 cache
= tp
->recv_sack_cache
;
1850 /* Skip empty blocks in at head of the cache */
1851 while (tcp_sack_cache_ok(tp
, cache
) && !cache
->start_seq
&&
1856 while (i
< used_sacks
) {
1857 u32 start_seq
= sp
[i
].start_seq
;
1858 u32 end_seq
= sp
[i
].end_seq
;
1859 int dup_sack
= (found_dup_sack
&& (i
== first_sack_index
));
1860 struct tcp_sack_block
*next_dup
= NULL
;
1862 if (found_dup_sack
&& ((i
+ 1) == first_sack_index
))
1863 next_dup
= &sp
[i
+ 1];
1865 /* Skip too early cached blocks */
1866 while (tcp_sack_cache_ok(tp
, cache
) &&
1867 !before(start_seq
, cache
->end_seq
))
1870 /* Can skip some work by looking recv_sack_cache? */
1871 if (tcp_sack_cache_ok(tp
, cache
) && !dup_sack
&&
1872 after(end_seq
, cache
->start_seq
)) {
1875 if (before(start_seq
, cache
->start_seq
)) {
1876 skb
= tcp_sacktag_skip(skb
, sk
, &state
,
1878 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
,
1885 /* Rest of the block already fully processed? */
1886 if (!after(end_seq
, cache
->end_seq
))
1889 skb
= tcp_maybe_skipping_dsack(skb
, sk
, next_dup
,
1893 /* ...tail remains todo... */
1894 if (tcp_highest_sack_seq(tp
) == cache
->end_seq
) {
1895 /* ...but better entrypoint exists! */
1896 skb
= tcp_highest_sack(sk
);
1899 state
.fack_count
= tp
->fackets_out
;
1904 skb
= tcp_sacktag_skip(skb
, sk
, &state
, cache
->end_seq
);
1905 /* Check overlap against next cached too (past this one already) */
1910 if (!before(start_seq
, tcp_highest_sack_seq(tp
))) {
1911 skb
= tcp_highest_sack(sk
);
1914 state
.fack_count
= tp
->fackets_out
;
1916 skb
= tcp_sacktag_skip(skb
, sk
, &state
, start_seq
);
1919 skb
= tcp_sacktag_walk(skb
, sk
, next_dup
, &state
,
1920 start_seq
, end_seq
, dup_sack
);
1923 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct
1924 * due to in-order walk
1926 if (after(end_seq
, tp
->frto_highmark
))
1927 state
.flag
&= ~FLAG_ONLY_ORIG_SACKED
;
1932 /* Clear the head of the cache sack blocks so we can skip it next time */
1933 for (i
= 0; i
< ARRAY_SIZE(tp
->recv_sack_cache
) - used_sacks
; i
++) {
1934 tp
->recv_sack_cache
[i
].start_seq
= 0;
1935 tp
->recv_sack_cache
[i
].end_seq
= 0;
1937 for (j
= 0; j
< used_sacks
; j
++)
1938 tp
->recv_sack_cache
[i
++] = sp
[j
];
1940 tcp_mark_lost_retrans(sk
);
1942 tcp_verify_left_out(tp
);
1944 if ((state
.reord
< tp
->fackets_out
) &&
1945 ((icsk
->icsk_ca_state
!= TCP_CA_Loss
) || tp
->undo_marker
) &&
1946 (!tp
->frto_highmark
|| after(tp
->snd_una
, tp
->frto_highmark
)))
1947 tcp_update_reordering(sk
, tp
->fackets_out
- state
.reord
, 0);
1951 #if FASTRETRANS_DEBUG > 0
1952 WARN_ON((int)tp
->sacked_out
< 0);
1953 WARN_ON((int)tp
->lost_out
< 0);
1954 WARN_ON((int)tp
->retrans_out
< 0);
1955 WARN_ON((int)tcp_packets_in_flight(tp
) < 0);
1960 /* Limits sacked_out so that sum with lost_out isn't ever larger than
1961 * packets_out. Returns zero if sacked_out adjustement wasn't necessary.
1963 static int tcp_limit_reno_sacked(struct tcp_sock
*tp
)
1967 holes
= max(tp
->lost_out
, 1U);
1968 holes
= min(holes
, tp
->packets_out
);
1970 if ((tp
->sacked_out
+ holes
) > tp
->packets_out
) {
1971 tp
->sacked_out
= tp
->packets_out
- holes
;
1977 /* If we receive more dupacks than we expected counting segments
1978 * in assumption of absent reordering, interpret this as reordering.
1979 * The only another reason could be bug in receiver TCP.
1981 static void tcp_check_reno_reordering(struct sock
*sk
, const int addend
)
1983 struct tcp_sock
*tp
= tcp_sk(sk
);
1984 if (tcp_limit_reno_sacked(tp
))
1985 tcp_update_reordering(sk
, tp
->packets_out
+ addend
, 0);
1988 /* Emulate SACKs for SACKless connection: account for a new dupack. */
1990 static void tcp_add_reno_sack(struct sock
*sk
)
1992 struct tcp_sock
*tp
= tcp_sk(sk
);
1994 tcp_check_reno_reordering(sk
, 0);
1995 tcp_verify_left_out(tp
);
1998 /* Account for ACK, ACKing some data in Reno Recovery phase. */
2000 static void tcp_remove_reno_sacks(struct sock
*sk
, int acked
)
2002 struct tcp_sock
*tp
= tcp_sk(sk
);
2005 /* One ACK acked hole. The rest eat duplicate ACKs. */
2006 if (acked
- 1 >= tp
->sacked_out
)
2009 tp
->sacked_out
-= acked
- 1;
2011 tcp_check_reno_reordering(sk
, acked
);
2012 tcp_verify_left_out(tp
);
2015 static inline void tcp_reset_reno_sack(struct tcp_sock
*tp
)
2020 static int tcp_is_sackfrto(const struct tcp_sock
*tp
)
2022 return (sysctl_tcp_frto
== 0x2) && !tcp_is_reno(tp
);
2025 /* F-RTO can only be used if TCP has never retransmitted anything other than
2026 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here)
2028 int tcp_use_frto(struct sock
*sk
)
2030 const struct tcp_sock
*tp
= tcp_sk(sk
);
2031 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2032 struct sk_buff
*skb
;
2034 if (!sysctl_tcp_frto
)
2037 /* MTU probe and F-RTO won't really play nicely along currently */
2038 if (icsk
->icsk_mtup
.probe_size
)
2041 if (tcp_is_sackfrto(tp
))
2044 /* Avoid expensive walking of rexmit queue if possible */
2045 if (tp
->retrans_out
> 1)
2048 skb
= tcp_write_queue_head(sk
);
2049 if (tcp_skb_is_last(sk
, skb
))
2051 skb
= tcp_write_queue_next(sk
, skb
); /* Skips head */
2052 tcp_for_write_queue_from(skb
, sk
) {
2053 if (skb
== tcp_send_head(sk
))
2055 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2057 /* Short-circuit when first non-SACKed skb has been checked */
2058 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2064 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO
2065 * recovery a bit and use heuristics in tcp_process_frto() to detect if
2066 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to
2067 * keep retrans_out counting accurate (with SACK F-RTO, other than head
2068 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS
2069 * bits are handled if the Loss state is really to be entered (in
2070 * tcp_enter_frto_loss).
2072 * Do like tcp_enter_loss() would; when RTO expires the second time it
2074 * "Reduce ssthresh if it has not yet been made inside this window."
2076 void tcp_enter_frto(struct sock
*sk
)
2078 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2079 struct tcp_sock
*tp
= tcp_sk(sk
);
2080 struct sk_buff
*skb
;
2082 if ((!tp
->frto_counter
&& icsk
->icsk_ca_state
<= TCP_CA_Disorder
) ||
2083 tp
->snd_una
== tp
->high_seq
||
2084 ((icsk
->icsk_ca_state
== TCP_CA_Loss
|| tp
->frto_counter
) &&
2085 !icsk
->icsk_retransmits
)) {
2086 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2087 /* Our state is too optimistic in ssthresh() call because cwnd
2088 * is not reduced until tcp_enter_frto_loss() when previous F-RTO
2089 * recovery has not yet completed. Pattern would be this: RTO,
2090 * Cumulative ACK, RTO (2xRTO for the same segment does not end
2092 * RFC4138 should be more specific on what to do, even though
2093 * RTO is quite unlikely to occur after the first Cumulative ACK
2094 * due to back-off and complexity of triggering events ...
2096 if (tp
->frto_counter
) {
2098 stored_cwnd
= tp
->snd_cwnd
;
2100 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2101 tp
->snd_cwnd
= stored_cwnd
;
2103 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2105 /* ... in theory, cong.control module could do "any tricks" in
2106 * ssthresh(), which means that ca_state, lost bits and lost_out
2107 * counter would have to be faked before the call occurs. We
2108 * consider that too expensive, unlikely and hacky, so modules
2109 * using these in ssthresh() must deal these incompatibility
2110 * issues if they receives CA_EVENT_FRTO and frto_counter != 0
2112 tcp_ca_event(sk
, CA_EVENT_FRTO
);
2115 tp
->undo_marker
= tp
->snd_una
;
2116 tp
->undo_retrans
= 0;
2118 skb
= tcp_write_queue_head(sk
);
2119 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2120 tp
->undo_marker
= 0;
2121 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2122 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2123 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2125 tcp_verify_left_out(tp
);
2127 /* Too bad if TCP was application limited */
2128 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2130 /* Earlier loss recovery underway (see RFC4138; Appendix B).
2131 * The last condition is necessary at least in tp->frto_counter case.
2133 if (tcp_is_sackfrto(tp
) && (tp
->frto_counter
||
2134 ((1 << icsk
->icsk_ca_state
) & (TCPF_CA_Recovery
|TCPF_CA_Loss
))) &&
2135 after(tp
->high_seq
, tp
->snd_una
)) {
2136 tp
->frto_highmark
= tp
->high_seq
;
2138 tp
->frto_highmark
= tp
->snd_nxt
;
2140 tcp_set_ca_state(sk
, TCP_CA_Disorder
);
2141 tp
->high_seq
= tp
->snd_nxt
;
2142 tp
->frto_counter
= 1;
2145 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO,
2146 * which indicates that we should follow the traditional RTO recovery,
2147 * i.e. mark everything lost and do go-back-N retransmission.
2149 static void tcp_enter_frto_loss(struct sock
*sk
, int allowed_segments
, int flag
)
2151 struct tcp_sock
*tp
= tcp_sk(sk
);
2152 struct sk_buff
*skb
;
2155 tp
->retrans_out
= 0;
2156 if (tcp_is_reno(tp
))
2157 tcp_reset_reno_sack(tp
);
2159 tcp_for_write_queue(skb
, sk
) {
2160 if (skb
== tcp_send_head(sk
))
2163 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2165 * Count the retransmission made on RTO correctly (only when
2166 * waiting for the first ACK and did not get it)...
2168 if ((tp
->frto_counter
== 1) && !(flag
& FLAG_DATA_ACKED
)) {
2169 /* For some reason this R-bit might get cleared? */
2170 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
2171 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2172 /* ...enter this if branch just for the first segment */
2173 flag
|= FLAG_DATA_ACKED
;
2175 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2176 tp
->undo_marker
= 0;
2177 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2180 /* Marking forward transmissions that were made after RTO lost
2181 * can cause unnecessary retransmissions in some scenarios,
2182 * SACK blocks will mitigate that in some but not in all cases.
2183 * We used to not mark them but it was causing break-ups with
2184 * receivers that do only in-order receival.
2186 * TODO: we could detect presence of such receiver and select
2187 * different behavior per flow.
2189 if (!(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2190 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2191 tp
->lost_out
+= tcp_skb_pcount(skb
);
2192 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2195 tcp_verify_left_out(tp
);
2197 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + allowed_segments
;
2198 tp
->snd_cwnd_cnt
= 0;
2199 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2200 tp
->frto_counter
= 0;
2201 tp
->bytes_acked
= 0;
2203 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2204 sysctl_tcp_reordering
);
2205 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2206 tp
->high_seq
= tp
->snd_nxt
;
2207 TCP_ECN_queue_cwr(tp
);
2209 tcp_clear_all_retrans_hints(tp
);
2212 static void tcp_clear_retrans_partial(struct tcp_sock
*tp
)
2214 tp
->retrans_out
= 0;
2217 tp
->undo_marker
= 0;
2218 tp
->undo_retrans
= 0;
2221 void tcp_clear_retrans(struct tcp_sock
*tp
)
2223 tcp_clear_retrans_partial(tp
);
2225 tp
->fackets_out
= 0;
2229 /* Enter Loss state. If "how" is not zero, forget all SACK information
2230 * and reset tags completely, otherwise preserve SACKs. If receiver
2231 * dropped its ofo queue, we will know this due to reneging detection.
2233 void tcp_enter_loss(struct sock
*sk
, int how
)
2235 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2236 struct tcp_sock
*tp
= tcp_sk(sk
);
2237 struct sk_buff
*skb
;
2239 /* Reduce ssthresh if it has not yet been made inside this window. */
2240 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
|| tp
->snd_una
== tp
->high_seq
||
2241 (icsk
->icsk_ca_state
== TCP_CA_Loss
&& !icsk
->icsk_retransmits
)) {
2242 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2243 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
2244 tcp_ca_event(sk
, CA_EVENT_LOSS
);
2247 tp
->snd_cwnd_cnt
= 0;
2248 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2250 tp
->bytes_acked
= 0;
2251 tcp_clear_retrans_partial(tp
);
2253 if (tcp_is_reno(tp
))
2254 tcp_reset_reno_sack(tp
);
2257 /* Push undo marker, if it was plain RTO and nothing
2258 * was retransmitted. */
2259 tp
->undo_marker
= tp
->snd_una
;
2262 tp
->fackets_out
= 0;
2264 tcp_clear_all_retrans_hints(tp
);
2266 tcp_for_write_queue(skb
, sk
) {
2267 if (skb
== tcp_send_head(sk
))
2270 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_RETRANS
)
2271 tp
->undo_marker
= 0;
2272 TCP_SKB_CB(skb
)->sacked
&= (~TCPCB_TAGBITS
)|TCPCB_SACKED_ACKED
;
2273 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
) || how
) {
2274 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_ACKED
;
2275 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
2276 tp
->lost_out
+= tcp_skb_pcount(skb
);
2277 tp
->retransmit_high
= TCP_SKB_CB(skb
)->end_seq
;
2280 tcp_verify_left_out(tp
);
2282 tp
->reordering
= min_t(unsigned int, tp
->reordering
,
2283 sysctl_tcp_reordering
);
2284 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2285 tp
->high_seq
= tp
->snd_nxt
;
2286 TCP_ECN_queue_cwr(tp
);
2287 /* Abort F-RTO algorithm if one is in progress */
2288 tp
->frto_counter
= 0;
2291 /* If ACK arrived pointing to a remembered SACK, it means that our
2292 * remembered SACKs do not reflect real state of receiver i.e.
2293 * receiver _host_ is heavily congested (or buggy).
2295 * Do processing similar to RTO timeout.
2297 static int tcp_check_sack_reneging(struct sock
*sk
, int flag
)
2299 if (flag
& FLAG_SACK_RENEGING
) {
2300 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2301 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSACKRENEGING
);
2303 tcp_enter_loss(sk
, 1);
2304 icsk
->icsk_retransmits
++;
2305 tcp_retransmit_skb(sk
, tcp_write_queue_head(sk
));
2306 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2307 icsk
->icsk_rto
, TCP_RTO_MAX
);
2313 static inline int tcp_fackets_out(const struct tcp_sock
*tp
)
2315 return tcp_is_reno(tp
) ? tp
->sacked_out
+ 1 : tp
->fackets_out
;
2318 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs
2319 * counter when SACK is enabled (without SACK, sacked_out is used for
2322 * Instead, with FACK TCP uses fackets_out that includes both SACKed
2323 * segments up to the highest received SACK block so far and holes in
2326 * With reordering, holes may still be in flight, so RFC3517 recovery
2327 * uses pure sacked_out (total number of SACKed segments) even though
2328 * it violates the RFC that uses duplicate ACKs, often these are equal
2329 * but when e.g. out-of-window ACKs or packet duplication occurs,
2330 * they differ. Since neither occurs due to loss, TCP should really
2333 static inline int tcp_dupack_heuristics(const struct tcp_sock
*tp
)
2335 return tcp_is_fack(tp
) ? tp
->fackets_out
: tp
->sacked_out
+ 1;
2338 static inline int tcp_skb_timedout(const struct sock
*sk
,
2339 const struct sk_buff
*skb
)
2341 return tcp_time_stamp
- TCP_SKB_CB(skb
)->when
> inet_csk(sk
)->icsk_rto
;
2344 static inline int tcp_head_timedout(const struct sock
*sk
)
2346 const struct tcp_sock
*tp
= tcp_sk(sk
);
2348 return tp
->packets_out
&&
2349 tcp_skb_timedout(sk
, tcp_write_queue_head(sk
));
2352 /* Linux NewReno/SACK/FACK/ECN state machine.
2353 * --------------------------------------
2355 * "Open" Normal state, no dubious events, fast path.
2356 * "Disorder" In all the respects it is "Open",
2357 * but requires a bit more attention. It is entered when
2358 * we see some SACKs or dupacks. It is split of "Open"
2359 * mainly to move some processing from fast path to slow one.
2360 * "CWR" CWND was reduced due to some Congestion Notification event.
2361 * It can be ECN, ICMP source quench, local device congestion.
2362 * "Recovery" CWND was reduced, we are fast-retransmitting.
2363 * "Loss" CWND was reduced due to RTO timeout or SACK reneging.
2365 * tcp_fastretrans_alert() is entered:
2366 * - each incoming ACK, if state is not "Open"
2367 * - when arrived ACK is unusual, namely:
2372 * Counting packets in flight is pretty simple.
2374 * in_flight = packets_out - left_out + retrans_out
2376 * packets_out is SND.NXT-SND.UNA counted in packets.
2378 * retrans_out is number of retransmitted segments.
2380 * left_out is number of segments left network, but not ACKed yet.
2382 * left_out = sacked_out + lost_out
2384 * sacked_out: Packets, which arrived to receiver out of order
2385 * and hence not ACKed. With SACKs this number is simply
2386 * amount of SACKed data. Even without SACKs
2387 * it is easy to give pretty reliable estimate of this number,
2388 * counting duplicate ACKs.
2390 * lost_out: Packets lost by network. TCP has no explicit
2391 * "loss notification" feedback from network (for now).
2392 * It means that this number can be only _guessed_.
2393 * Actually, it is the heuristics to predict lossage that
2394 * distinguishes different algorithms.
2396 * F.e. after RTO, when all the queue is considered as lost,
2397 * lost_out = packets_out and in_flight = retrans_out.
2399 * Essentially, we have now two algorithms counting
2402 * FACK: It is the simplest heuristics. As soon as we decided
2403 * that something is lost, we decide that _all_ not SACKed
2404 * packets until the most forward SACK are lost. I.e.
2405 * lost_out = fackets_out - sacked_out and left_out = fackets_out.
2406 * It is absolutely correct estimate, if network does not reorder
2407 * packets. And it loses any connection to reality when reordering
2408 * takes place. We use FACK by default until reordering
2409 * is suspected on the path to this destination.
2411 * NewReno: when Recovery is entered, we assume that one segment
2412 * is lost (classic Reno). While we are in Recovery and
2413 * a partial ACK arrives, we assume that one more packet
2414 * is lost (NewReno). This heuristics are the same in NewReno
2417 * Imagine, that's all! Forget about all this shamanism about CWND inflation
2418 * deflation etc. CWND is real congestion window, never inflated, changes
2419 * only according to classic VJ rules.
2421 * Really tricky (and requiring careful tuning) part of algorithm
2422 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue().
2423 * The first determines the moment _when_ we should reduce CWND and,
2424 * hence, slow down forward transmission. In fact, it determines the moment
2425 * when we decide that hole is caused by loss, rather than by a reorder.
2427 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill
2428 * holes, caused by lost packets.
2430 * And the most logically complicated part of algorithm is undo
2431 * heuristics. We detect false retransmits due to both too early
2432 * fast retransmit (reordering) and underestimated RTO, analyzing
2433 * timestamps and D-SACKs. When we detect that some segments were
2434 * retransmitted by mistake and CWND reduction was wrong, we undo
2435 * window reduction and abort recovery phase. This logic is hidden
2436 * inside several functions named tcp_try_undo_<something>.
2439 /* This function decides, when we should leave Disordered state
2440 * and enter Recovery phase, reducing congestion window.
2442 * Main question: may we further continue forward transmission
2443 * with the same cwnd?
2445 static int tcp_time_to_recover(struct sock
*sk
)
2447 struct tcp_sock
*tp
= tcp_sk(sk
);
2450 /* Do not perform any recovery during F-RTO algorithm */
2451 if (tp
->frto_counter
)
2454 /* Trick#1: The loss is proven. */
2458 /* Not-A-Trick#2 : Classic rule... */
2459 if (tcp_dupack_heuristics(tp
) > tp
->reordering
)
2462 /* Trick#3 : when we use RFC2988 timer restart, fast
2463 * retransmit can be triggered by timeout of queue head.
2465 if (tcp_is_fack(tp
) && tcp_head_timedout(sk
))
2468 /* Trick#4: It is still not OK... But will it be useful to delay
2471 packets_out
= tp
->packets_out
;
2472 if (packets_out
<= tp
->reordering
&&
2473 tp
->sacked_out
>= max_t(__u32
, packets_out
/2, sysctl_tcp_reordering
) &&
2474 !tcp_may_send_now(sk
)) {
2475 /* We have nothing to send. This connection is limited
2476 * either by receiver window or by application.
2481 /* If a thin stream is detected, retransmit after first
2482 * received dupack. Employ only if SACK is supported in order
2483 * to avoid possible corner-case series of spurious retransmissions
2484 * Use only if there are no unsent data.
2486 if ((tp
->thin_dupack
|| sysctl_tcp_thin_dupack
) &&
2487 tcp_stream_is_thin(tp
) && tcp_dupack_heuristics(tp
) > 1 &&
2488 tcp_is_sack(tp
) && !tcp_send_head(sk
))
2494 /* New heuristics: it is possible only after we switched to restart timer
2495 * each time when something is ACKed. Hence, we can detect timed out packets
2496 * during fast retransmit without falling to slow start.
2498 * Usefulness of this as is very questionable, since we should know which of
2499 * the segments is the next to timeout which is relatively expensive to find
2500 * in general case unless we add some data structure just for that. The
2501 * current approach certainly won't find the right one too often and when it
2502 * finally does find _something_ it usually marks large part of the window
2503 * right away (because a retransmission with a larger timestamp blocks the
2504 * loop from advancing). -ij
2506 static void tcp_timeout_skbs(struct sock
*sk
)
2508 struct tcp_sock
*tp
= tcp_sk(sk
);
2509 struct sk_buff
*skb
;
2511 if (!tcp_is_fack(tp
) || !tcp_head_timedout(sk
))
2514 skb
= tp
->scoreboard_skb_hint
;
2515 if (tp
->scoreboard_skb_hint
== NULL
)
2516 skb
= tcp_write_queue_head(sk
);
2518 tcp_for_write_queue_from(skb
, sk
) {
2519 if (skb
== tcp_send_head(sk
))
2521 if (!tcp_skb_timedout(sk
, skb
))
2524 tcp_skb_mark_lost(tp
, skb
);
2527 tp
->scoreboard_skb_hint
= skb
;
2529 tcp_verify_left_out(tp
);
2532 /* Detect loss in event "A" above by marking head of queue up as lost.
2533 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments
2534 * are considered lost. For RFC3517 SACK, a segment is considered lost if it
2535 * has at least tp->reordering SACKed seqments above it; "packets" refers to
2536 * the maximum SACKed segments to pass before reaching this limit.
2538 static void tcp_mark_head_lost(struct sock
*sk
, int packets
, int mark_head
)
2540 struct tcp_sock
*tp
= tcp_sk(sk
);
2541 struct sk_buff
*skb
;
2545 /* Use SACK to deduce losses of new sequences sent during recovery */
2546 const u32 loss_high
= tcp_is_sack(tp
) ? tp
->snd_nxt
: tp
->high_seq
;
2548 WARN_ON(packets
> tp
->packets_out
);
2549 if (tp
->lost_skb_hint
) {
2550 skb
= tp
->lost_skb_hint
;
2551 cnt
= tp
->lost_cnt_hint
;
2552 /* Head already handled? */
2553 if (mark_head
&& skb
!= tcp_write_queue_head(sk
))
2556 skb
= tcp_write_queue_head(sk
);
2560 tcp_for_write_queue_from(skb
, sk
) {
2561 if (skb
== tcp_send_head(sk
))
2563 /* TODO: do this better */
2564 /* this is not the most efficient way to do this... */
2565 tp
->lost_skb_hint
= skb
;
2566 tp
->lost_cnt_hint
= cnt
;
2568 if (after(TCP_SKB_CB(skb
)->end_seq
, loss_high
))
2572 if (tcp_is_fack(tp
) || tcp_is_reno(tp
) ||
2573 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
2574 cnt
+= tcp_skb_pcount(skb
);
2576 if (cnt
> packets
) {
2577 if ((tcp_is_sack(tp
) && !tcp_is_fack(tp
)) ||
2578 (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
) ||
2579 (oldcnt
>= packets
))
2582 mss
= skb_shinfo(skb
)->gso_size
;
2583 err
= tcp_fragment(sk
, skb
, (packets
- oldcnt
) * mss
, mss
);
2589 tcp_skb_mark_lost(tp
, skb
);
2594 tcp_verify_left_out(tp
);
2597 /* Account newly detected lost packet(s) */
2599 static void tcp_update_scoreboard(struct sock
*sk
, int fast_rexmit
)
2601 struct tcp_sock
*tp
= tcp_sk(sk
);
2603 if (tcp_is_reno(tp
)) {
2604 tcp_mark_head_lost(sk
, 1, 1);
2605 } else if (tcp_is_fack(tp
)) {
2606 int lost
= tp
->fackets_out
- tp
->reordering
;
2609 tcp_mark_head_lost(sk
, lost
, 0);
2611 int sacked_upto
= tp
->sacked_out
- tp
->reordering
;
2612 if (sacked_upto
>= 0)
2613 tcp_mark_head_lost(sk
, sacked_upto
, 0);
2614 else if (fast_rexmit
)
2615 tcp_mark_head_lost(sk
, 1, 1);
2618 tcp_timeout_skbs(sk
);
2621 /* CWND moderation, preventing bursts due to too big ACKs
2622 * in dubious situations.
2624 static inline void tcp_moderate_cwnd(struct tcp_sock
*tp
)
2626 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
2627 tcp_packets_in_flight(tp
) + tcp_max_burst(tp
));
2628 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2631 /* Lower bound on congestion window is slow start threshold
2632 * unless congestion avoidance choice decides to overide it.
2634 static inline u32
tcp_cwnd_min(const struct sock
*sk
)
2636 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
2638 return ca_ops
->min_cwnd
? ca_ops
->min_cwnd(sk
) : tcp_sk(sk
)->snd_ssthresh
;
2641 /* Decrease cwnd each second ack. */
2642 static void tcp_cwnd_down(struct sock
*sk
, int flag
)
2644 struct tcp_sock
*tp
= tcp_sk(sk
);
2645 int decr
= tp
->snd_cwnd_cnt
+ 1;
2647 if ((flag
& (FLAG_ANY_PROGRESS
| FLAG_DSACKING_ACK
)) ||
2648 (tcp_is_reno(tp
) && !(flag
& FLAG_NOT_DUP
))) {
2649 tp
->snd_cwnd_cnt
= decr
& 1;
2652 if (decr
&& tp
->snd_cwnd
> tcp_cwnd_min(sk
))
2653 tp
->snd_cwnd
-= decr
;
2655 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tcp_packets_in_flight(tp
) + 1);
2656 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2660 /* Nothing was retransmitted or returned timestamp is less
2661 * than timestamp of the first retransmission.
2663 static inline int tcp_packet_delayed(const struct tcp_sock
*tp
)
2665 return !tp
->retrans_stamp
||
2666 (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
2667 before(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
));
2670 /* Undo procedures. */
2672 #if FASTRETRANS_DEBUG > 1
2673 static void DBGUNDO(struct sock
*sk
, const char *msg
)
2675 struct tcp_sock
*tp
= tcp_sk(sk
);
2676 struct inet_sock
*inet
= inet_sk(sk
);
2678 if (sk
->sk_family
== AF_INET
) {
2679 printk(KERN_DEBUG
"Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n",
2681 &inet
->inet_daddr
, ntohs(inet
->inet_dport
),
2682 tp
->snd_cwnd
, tcp_left_out(tp
),
2683 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2686 #if IS_ENABLED(CONFIG_IPV6)
2687 else if (sk
->sk_family
== AF_INET6
) {
2688 struct ipv6_pinfo
*np
= inet6_sk(sk
);
2689 printk(KERN_DEBUG
"Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n",
2691 &np
->daddr
, ntohs(inet
->inet_dport
),
2692 tp
->snd_cwnd
, tcp_left_out(tp
),
2693 tp
->snd_ssthresh
, tp
->prior_ssthresh
,
2699 #define DBGUNDO(x...) do { } while (0)
2702 static void tcp_undo_cwr(struct sock
*sk
, const bool undo_ssthresh
)
2704 struct tcp_sock
*tp
= tcp_sk(sk
);
2706 if (tp
->prior_ssthresh
) {
2707 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2709 if (icsk
->icsk_ca_ops
->undo_cwnd
)
2710 tp
->snd_cwnd
= icsk
->icsk_ca_ops
->undo_cwnd(sk
);
2712 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
<< 1);
2714 if (undo_ssthresh
&& tp
->prior_ssthresh
> tp
->snd_ssthresh
) {
2715 tp
->snd_ssthresh
= tp
->prior_ssthresh
;
2716 TCP_ECN_withdraw_cwr(tp
);
2719 tp
->snd_cwnd
= max(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2721 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2724 static inline int tcp_may_undo(const struct tcp_sock
*tp
)
2726 return tp
->undo_marker
&& (!tp
->undo_retrans
|| tcp_packet_delayed(tp
));
2729 /* People celebrate: "We love our President!" */
2730 static int tcp_try_undo_recovery(struct sock
*sk
)
2732 struct tcp_sock
*tp
= tcp_sk(sk
);
2734 if (tcp_may_undo(tp
)) {
2737 /* Happy end! We did not retransmit anything
2738 * or our original transmission succeeded.
2740 DBGUNDO(sk
, inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
? "loss" : "retrans");
2741 tcp_undo_cwr(sk
, true);
2742 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Loss
)
2743 mib_idx
= LINUX_MIB_TCPLOSSUNDO
;
2745 mib_idx
= LINUX_MIB_TCPFULLUNDO
;
2747 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2748 tp
->undo_marker
= 0;
2750 if (tp
->snd_una
== tp
->high_seq
&& tcp_is_reno(tp
)) {
2751 /* Hold old state until something *above* high_seq
2752 * is ACKed. For Reno it is MUST to prevent false
2753 * fast retransmits (RFC2582). SACK TCP is safe. */
2754 tcp_moderate_cwnd(tp
);
2757 tcp_set_ca_state(sk
, TCP_CA_Open
);
2761 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */
2762 static void tcp_try_undo_dsack(struct sock
*sk
)
2764 struct tcp_sock
*tp
= tcp_sk(sk
);
2766 if (tp
->undo_marker
&& !tp
->undo_retrans
) {
2767 DBGUNDO(sk
, "D-SACK");
2768 tcp_undo_cwr(sk
, true);
2769 tp
->undo_marker
= 0;
2770 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPDSACKUNDO
);
2774 /* We can clear retrans_stamp when there are no retransmissions in the
2775 * window. It would seem that it is trivially available for us in
2776 * tp->retrans_out, however, that kind of assumptions doesn't consider
2777 * what will happen if errors occur when sending retransmission for the
2778 * second time. ...It could the that such segment has only
2779 * TCPCB_EVER_RETRANS set at the present time. It seems that checking
2780 * the head skb is enough except for some reneging corner cases that
2781 * are not worth the effort.
2783 * Main reason for all this complexity is the fact that connection dying
2784 * time now depends on the validity of the retrans_stamp, in particular,
2785 * that successive retransmissions of a segment must not advance
2786 * retrans_stamp under any conditions.
2788 static int tcp_any_retrans_done(const struct sock
*sk
)
2790 const struct tcp_sock
*tp
= tcp_sk(sk
);
2791 struct sk_buff
*skb
;
2793 if (tp
->retrans_out
)
2796 skb
= tcp_write_queue_head(sk
);
2797 if (unlikely(skb
&& TCP_SKB_CB(skb
)->sacked
& TCPCB_EVER_RETRANS
))
2803 /* Undo during fast recovery after partial ACK. */
2805 static int tcp_try_undo_partial(struct sock
*sk
, int acked
)
2807 struct tcp_sock
*tp
= tcp_sk(sk
);
2808 /* Partial ACK arrived. Force Hoe's retransmit. */
2809 int failed
= tcp_is_reno(tp
) || (tcp_fackets_out(tp
) > tp
->reordering
);
2811 if (tcp_may_undo(tp
)) {
2812 /* Plain luck! Hole if filled with delayed
2813 * packet, rather than with a retransmit.
2815 if (!tcp_any_retrans_done(sk
))
2816 tp
->retrans_stamp
= 0;
2818 tcp_update_reordering(sk
, tcp_fackets_out(tp
) + acked
, 1);
2821 tcp_undo_cwr(sk
, false);
2822 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPARTIALUNDO
);
2824 /* So... Do not make Hoe's retransmit yet.
2825 * If the first packet was delayed, the rest
2826 * ones are most probably delayed as well.
2833 /* Undo during loss recovery after partial ACK. */
2834 static int tcp_try_undo_loss(struct sock
*sk
)
2836 struct tcp_sock
*tp
= tcp_sk(sk
);
2838 if (tcp_may_undo(tp
)) {
2839 struct sk_buff
*skb
;
2840 tcp_for_write_queue(skb
, sk
) {
2841 if (skb
== tcp_send_head(sk
))
2843 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_LOST
;
2846 tcp_clear_all_retrans_hints(tp
);
2848 DBGUNDO(sk
, "partial loss");
2850 tcp_undo_cwr(sk
, true);
2851 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPLOSSUNDO
);
2852 inet_csk(sk
)->icsk_retransmits
= 0;
2853 tp
->undo_marker
= 0;
2854 if (tcp_is_sack(tp
))
2855 tcp_set_ca_state(sk
, TCP_CA_Open
);
2861 static inline void tcp_complete_cwr(struct sock
*sk
)
2863 struct tcp_sock
*tp
= tcp_sk(sk
);
2865 /* Do not moderate cwnd if it's already undone in cwr or recovery. */
2866 if (tp
->undo_marker
) {
2867 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_CWR
)
2868 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
2870 tp
->snd_cwnd
= tp
->snd_ssthresh
;
2871 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2873 tcp_ca_event(sk
, CA_EVENT_COMPLETE_CWR
);
2876 static void tcp_try_keep_open(struct sock
*sk
)
2878 struct tcp_sock
*tp
= tcp_sk(sk
);
2879 int state
= TCP_CA_Open
;
2881 if (tcp_left_out(tp
) || tcp_any_retrans_done(sk
))
2882 state
= TCP_CA_Disorder
;
2884 if (inet_csk(sk
)->icsk_ca_state
!= state
) {
2885 tcp_set_ca_state(sk
, state
);
2886 tp
->high_seq
= tp
->snd_nxt
;
2890 static void tcp_try_to_open(struct sock
*sk
, int flag
)
2892 struct tcp_sock
*tp
= tcp_sk(sk
);
2894 tcp_verify_left_out(tp
);
2896 if (!tp
->frto_counter
&& !tcp_any_retrans_done(sk
))
2897 tp
->retrans_stamp
= 0;
2899 if (flag
& FLAG_ECE
)
2900 tcp_enter_cwr(sk
, 1);
2902 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_CWR
) {
2903 tcp_try_keep_open(sk
);
2904 if (inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
2905 tcp_moderate_cwnd(tp
);
2907 tcp_cwnd_down(sk
, flag
);
2911 static void tcp_mtup_probe_failed(struct sock
*sk
)
2913 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2915 icsk
->icsk_mtup
.search_high
= icsk
->icsk_mtup
.probe_size
- 1;
2916 icsk
->icsk_mtup
.probe_size
= 0;
2919 static void tcp_mtup_probe_success(struct sock
*sk
)
2921 struct tcp_sock
*tp
= tcp_sk(sk
);
2922 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2924 /* FIXME: breaks with very large cwnd */
2925 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
2926 tp
->snd_cwnd
= tp
->snd_cwnd
*
2927 tcp_mss_to_mtu(sk
, tp
->mss_cache
) /
2928 icsk
->icsk_mtup
.probe_size
;
2929 tp
->snd_cwnd_cnt
= 0;
2930 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
2931 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2933 icsk
->icsk_mtup
.search_low
= icsk
->icsk_mtup
.probe_size
;
2934 icsk
->icsk_mtup
.probe_size
= 0;
2935 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
2938 /* Do a simple retransmit without using the backoff mechanisms in
2939 * tcp_timer. This is used for path mtu discovery.
2940 * The socket is already locked here.
2942 void tcp_simple_retransmit(struct sock
*sk
)
2944 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2945 struct tcp_sock
*tp
= tcp_sk(sk
);
2946 struct sk_buff
*skb
;
2947 unsigned int mss
= tcp_current_mss(sk
);
2948 u32 prior_lost
= tp
->lost_out
;
2950 tcp_for_write_queue(skb
, sk
) {
2951 if (skb
== tcp_send_head(sk
))
2953 if (tcp_skb_seglen(skb
) > mss
&&
2954 !(TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)) {
2955 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2956 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
2957 tp
->retrans_out
-= tcp_skb_pcount(skb
);
2959 tcp_skb_mark_lost_uncond_verify(tp
, skb
);
2963 tcp_clear_retrans_hints_partial(tp
);
2965 if (prior_lost
== tp
->lost_out
)
2968 if (tcp_is_reno(tp
))
2969 tcp_limit_reno_sacked(tp
);
2971 tcp_verify_left_out(tp
);
2973 /* Don't muck with the congestion window here.
2974 * Reason is that we do not increase amount of _data_
2975 * in network, but units changed and effective
2976 * cwnd/ssthresh really reduced now.
2978 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
2979 tp
->high_seq
= tp
->snd_nxt
;
2980 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
2981 tp
->prior_ssthresh
= 0;
2982 tp
->undo_marker
= 0;
2983 tcp_set_ca_state(sk
, TCP_CA_Loss
);
2985 tcp_xmit_retransmit_queue(sk
);
2987 EXPORT_SYMBOL(tcp_simple_retransmit
);
2989 /* This function implements the PRR algorithm, specifcally the PRR-SSRB
2990 * (proportional rate reduction with slow start reduction bound) as described in
2991 * http://www.ietf.org/id/draft-mathis-tcpm-proportional-rate-reduction-01.txt.
2992 * It computes the number of packets to send (sndcnt) based on packets newly
2994 * 1) If the packets in flight is larger than ssthresh, PRR spreads the
2995 * cwnd reductions across a full RTT.
2996 * 2) If packets in flight is lower than ssthresh (such as due to excess
2997 * losses and/or application stalls), do not perform any further cwnd
2998 * reductions, but instead slow start up to ssthresh.
3000 static void tcp_update_cwnd_in_recovery(struct sock
*sk
, int newly_acked_sacked
,
3001 int fast_rexmit
, int flag
)
3003 struct tcp_sock
*tp
= tcp_sk(sk
);
3005 int delta
= tp
->snd_ssthresh
- tcp_packets_in_flight(tp
);
3007 if (tcp_packets_in_flight(tp
) > tp
->snd_ssthresh
) {
3008 u64 dividend
= (u64
)tp
->snd_ssthresh
* tp
->prr_delivered
+
3010 sndcnt
= div_u64(dividend
, tp
->prior_cwnd
) - tp
->prr_out
;
3012 sndcnt
= min_t(int, delta
,
3013 max_t(int, tp
->prr_delivered
- tp
->prr_out
,
3014 newly_acked_sacked
) + 1);
3017 sndcnt
= max(sndcnt
, (fast_rexmit
? 1 : 0));
3018 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + sndcnt
;
3021 /* Process an event, which can update packets-in-flight not trivially.
3022 * Main goal of this function is to calculate new estimate for left_out,
3023 * taking into account both packets sitting in receiver's buffer and
3024 * packets lost by network.
3026 * Besides that it does CWND reduction, when packet loss is detected
3027 * and changes state of machine.
3029 * It does _not_ decide what to send, it is made in function
3030 * tcp_xmit_retransmit_queue().
3032 static void tcp_fastretrans_alert(struct sock
*sk
, int pkts_acked
,
3033 int newly_acked_sacked
, bool is_dupack
,
3036 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3037 struct tcp_sock
*tp
= tcp_sk(sk
);
3038 int do_lost
= is_dupack
|| ((flag
& FLAG_DATA_SACKED
) &&
3039 (tcp_fackets_out(tp
) > tp
->reordering
));
3040 int fast_rexmit
= 0, mib_idx
;
3042 if (WARN_ON(!tp
->packets_out
&& tp
->sacked_out
))
3044 if (WARN_ON(!tp
->sacked_out
&& tp
->fackets_out
))
3045 tp
->fackets_out
= 0;
3047 /* Now state machine starts.
3048 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */
3049 if (flag
& FLAG_ECE
)
3050 tp
->prior_ssthresh
= 0;
3052 /* B. In all the states check for reneging SACKs. */
3053 if (tcp_check_sack_reneging(sk
, flag
))
3056 /* C. Check consistency of the current state. */
3057 tcp_verify_left_out(tp
);
3059 /* D. Check state exit conditions. State can be terminated
3060 * when high_seq is ACKed. */
3061 if (icsk
->icsk_ca_state
== TCP_CA_Open
) {
3062 WARN_ON(tp
->retrans_out
!= 0);
3063 tp
->retrans_stamp
= 0;
3064 } else if (!before(tp
->snd_una
, tp
->high_seq
)) {
3065 switch (icsk
->icsk_ca_state
) {
3067 icsk
->icsk_retransmits
= 0;
3068 if (tcp_try_undo_recovery(sk
))
3073 /* CWR is to be held something *above* high_seq
3074 * is ACKed for CWR bit to reach receiver. */
3075 if (tp
->snd_una
!= tp
->high_seq
) {
3076 tcp_complete_cwr(sk
);
3077 tcp_set_ca_state(sk
, TCP_CA_Open
);
3081 case TCP_CA_Recovery
:
3082 if (tcp_is_reno(tp
))
3083 tcp_reset_reno_sack(tp
);
3084 if (tcp_try_undo_recovery(sk
))
3086 tcp_complete_cwr(sk
);
3091 /* E. Process state. */
3092 switch (icsk
->icsk_ca_state
) {
3093 case TCP_CA_Recovery
:
3094 if (!(flag
& FLAG_SND_UNA_ADVANCED
)) {
3095 if (tcp_is_reno(tp
) && is_dupack
)
3096 tcp_add_reno_sack(sk
);
3098 do_lost
= tcp_try_undo_partial(sk
, pkts_acked
);
3101 if (flag
& FLAG_DATA_ACKED
)
3102 icsk
->icsk_retransmits
= 0;
3103 if (tcp_is_reno(tp
) && flag
& FLAG_SND_UNA_ADVANCED
)
3104 tcp_reset_reno_sack(tp
);
3105 if (!tcp_try_undo_loss(sk
)) {
3106 tcp_moderate_cwnd(tp
);
3107 tcp_xmit_retransmit_queue(sk
);
3110 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
3112 /* Loss is undone; fall through to processing in Open state. */
3114 if (tcp_is_reno(tp
)) {
3115 if (flag
& FLAG_SND_UNA_ADVANCED
)
3116 tcp_reset_reno_sack(tp
);
3118 tcp_add_reno_sack(sk
);
3121 if (icsk
->icsk_ca_state
<= TCP_CA_Disorder
)
3122 tcp_try_undo_dsack(sk
);
3124 if (!tcp_time_to_recover(sk
)) {
3125 tcp_try_to_open(sk
, flag
);
3129 /* MTU probe failure: don't reduce cwnd */
3130 if (icsk
->icsk_ca_state
< TCP_CA_CWR
&&
3131 icsk
->icsk_mtup
.probe_size
&&
3132 tp
->snd_una
== tp
->mtu_probe
.probe_seq_start
) {
3133 tcp_mtup_probe_failed(sk
);
3134 /* Restores the reduction we did in tcp_mtup_probe() */
3136 tcp_simple_retransmit(sk
);
3140 /* Otherwise enter Recovery state */
3142 if (tcp_is_reno(tp
))
3143 mib_idx
= LINUX_MIB_TCPRENORECOVERY
;
3145 mib_idx
= LINUX_MIB_TCPSACKRECOVERY
;
3147 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
3149 tp
->high_seq
= tp
->snd_nxt
;
3150 tp
->prior_ssthresh
= 0;
3151 tp
->undo_marker
= tp
->snd_una
;
3152 tp
->undo_retrans
= tp
->retrans_out
;
3154 if (icsk
->icsk_ca_state
< TCP_CA_CWR
) {
3155 if (!(flag
& FLAG_ECE
))
3156 tp
->prior_ssthresh
= tcp_current_ssthresh(sk
);
3157 tp
->snd_ssthresh
= icsk
->icsk_ca_ops
->ssthresh(sk
);
3158 TCP_ECN_queue_cwr(tp
);
3161 tp
->bytes_acked
= 0;
3162 tp
->snd_cwnd_cnt
= 0;
3163 tp
->prior_cwnd
= tp
->snd_cwnd
;
3164 tp
->prr_delivered
= 0;
3166 tcp_set_ca_state(sk
, TCP_CA_Recovery
);
3170 if (do_lost
|| (tcp_is_fack(tp
) && tcp_head_timedout(sk
)))
3171 tcp_update_scoreboard(sk
, fast_rexmit
);
3172 tp
->prr_delivered
+= newly_acked_sacked
;
3173 tcp_update_cwnd_in_recovery(sk
, newly_acked_sacked
, fast_rexmit
, flag
);
3174 tcp_xmit_retransmit_queue(sk
);
3177 void tcp_valid_rtt_meas(struct sock
*sk
, u32 seq_rtt
)
3179 tcp_rtt_estimator(sk
, seq_rtt
);
3181 inet_csk(sk
)->icsk_backoff
= 0;
3183 EXPORT_SYMBOL(tcp_valid_rtt_meas
);
3185 /* Read draft-ietf-tcplw-high-performance before mucking
3186 * with this code. (Supersedes RFC1323)
3188 static void tcp_ack_saw_tstamp(struct sock
*sk
, int flag
)
3190 /* RTTM Rule: A TSecr value received in a segment is used to
3191 * update the averaged RTT measurement only if the segment
3192 * acknowledges some new data, i.e., only if it advances the
3193 * left edge of the send window.
3195 * See draft-ietf-tcplw-high-performance-00, section 3.3.
3196 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru>
3198 * Changed: reset backoff as soon as we see the first valid sample.
3199 * If we do not, we get strongly overestimated rto. With timestamps
3200 * samples are accepted even from very old segments: f.e., when rtt=1
3201 * increases to 8, we retransmit 5 times and after 8 seconds delayed
3202 * answer arrives rto becomes 120 seconds! If at least one of segments
3203 * in window is lost... Voila. --ANK (010210)
3205 struct tcp_sock
*tp
= tcp_sk(sk
);
3207 tcp_valid_rtt_meas(sk
, tcp_time_stamp
- tp
->rx_opt
.rcv_tsecr
);
3210 static void tcp_ack_no_tstamp(struct sock
*sk
, u32 seq_rtt
, int flag
)
3212 /* We don't have a timestamp. Can only use
3213 * packets that are not retransmitted to determine
3214 * rtt estimates. Also, we must not reset the
3215 * backoff for rto until we get a non-retransmitted
3216 * packet. This allows us to deal with a situation
3217 * where the network delay has increased suddenly.
3218 * I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3221 if (flag
& FLAG_RETRANS_DATA_ACKED
)
3224 tcp_valid_rtt_meas(sk
, seq_rtt
);
3227 static inline void tcp_ack_update_rtt(struct sock
*sk
, const int flag
,
3230 const struct tcp_sock
*tp
= tcp_sk(sk
);
3231 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */
3232 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
)
3233 tcp_ack_saw_tstamp(sk
, flag
);
3234 else if (seq_rtt
>= 0)
3235 tcp_ack_no_tstamp(sk
, seq_rtt
, flag
);
3238 static void tcp_cong_avoid(struct sock
*sk
, u32 ack
, u32 in_flight
)
3240 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3241 icsk
->icsk_ca_ops
->cong_avoid(sk
, ack
, in_flight
);
3242 tcp_sk(sk
)->snd_cwnd_stamp
= tcp_time_stamp
;
3245 /* Restart timer after forward progress on connection.
3246 * RFC2988 recommends to restart timer to now+rto.
3248 static void tcp_rearm_rto(struct sock
*sk
)
3250 const struct tcp_sock
*tp
= tcp_sk(sk
);
3252 if (!tp
->packets_out
) {
3253 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_RETRANS
);
3255 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3256 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3260 /* If we get here, the whole TSO packet has not been acked. */
3261 static u32
tcp_tso_acked(struct sock
*sk
, struct sk_buff
*skb
)
3263 struct tcp_sock
*tp
= tcp_sk(sk
);
3266 BUG_ON(!after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
));
3268 packets_acked
= tcp_skb_pcount(skb
);
3269 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
3271 packets_acked
-= tcp_skb_pcount(skb
);
3273 if (packets_acked
) {
3274 BUG_ON(tcp_skb_pcount(skb
) == 0);
3275 BUG_ON(!before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
));
3278 return packets_acked
;
3281 /* Remove acknowledged frames from the retransmission queue. If our packet
3282 * is before the ack sequence we can discard it as it's confirmed to have
3283 * arrived at the other end.
3285 static int tcp_clean_rtx_queue(struct sock
*sk
, int prior_fackets
,
3288 struct tcp_sock
*tp
= tcp_sk(sk
);
3289 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
3290 struct sk_buff
*skb
;
3291 u32 now
= tcp_time_stamp
;
3292 int fully_acked
= 1;
3295 u32 reord
= tp
->packets_out
;
3296 u32 prior_sacked
= tp
->sacked_out
;
3298 s32 ca_seq_rtt
= -1;
3299 ktime_t last_ackt
= net_invalid_timestamp();
3301 while ((skb
= tcp_write_queue_head(sk
)) && skb
!= tcp_send_head(sk
)) {
3302 struct tcp_skb_cb
*scb
= TCP_SKB_CB(skb
);
3304 u8 sacked
= scb
->sacked
;
3306 /* Determine how many packets and what bytes were acked, tso and else */
3307 if (after(scb
->end_seq
, tp
->snd_una
)) {
3308 if (tcp_skb_pcount(skb
) == 1 ||
3309 !after(tp
->snd_una
, scb
->seq
))
3312 acked_pcount
= tcp_tso_acked(sk
, skb
);
3318 acked_pcount
= tcp_skb_pcount(skb
);
3321 if (sacked
& TCPCB_RETRANS
) {
3322 if (sacked
& TCPCB_SACKED_RETRANS
)
3323 tp
->retrans_out
-= acked_pcount
;
3324 flag
|= FLAG_RETRANS_DATA_ACKED
;
3327 if ((flag
& FLAG_DATA_ACKED
) || (acked_pcount
> 1))
3328 flag
|= FLAG_NONHEAD_RETRANS_ACKED
;
3330 ca_seq_rtt
= now
- scb
->when
;
3331 last_ackt
= skb
->tstamp
;
3333 seq_rtt
= ca_seq_rtt
;
3335 if (!(sacked
& TCPCB_SACKED_ACKED
))
3336 reord
= min(pkts_acked
, reord
);
3339 if (sacked
& TCPCB_SACKED_ACKED
)
3340 tp
->sacked_out
-= acked_pcount
;
3341 if (sacked
& TCPCB_LOST
)
3342 tp
->lost_out
-= acked_pcount
;
3344 tp
->packets_out
-= acked_pcount
;
3345 pkts_acked
+= acked_pcount
;
3347 /* Initial outgoing SYN's get put onto the write_queue
3348 * just like anything else we transmit. It is not
3349 * true data, and if we misinform our callers that
3350 * this ACK acks real data, we will erroneously exit
3351 * connection startup slow start one packet too
3352 * quickly. This is severely frowned upon behavior.
3354 if (!(scb
->tcp_flags
& TCPHDR_SYN
)) {
3355 flag
|= FLAG_DATA_ACKED
;
3357 flag
|= FLAG_SYN_ACKED
;
3358 tp
->retrans_stamp
= 0;
3364 tcp_unlink_write_queue(skb
, sk
);
3365 sk_wmem_free_skb(sk
, skb
);
3366 tp
->scoreboard_skb_hint
= NULL
;
3367 if (skb
== tp
->retransmit_skb_hint
)
3368 tp
->retransmit_skb_hint
= NULL
;
3369 if (skb
== tp
->lost_skb_hint
)
3370 tp
->lost_skb_hint
= NULL
;
3373 if (likely(between(tp
->snd_up
, prior_snd_una
, tp
->snd_una
)))
3374 tp
->snd_up
= tp
->snd_una
;
3376 if (skb
&& (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
))
3377 flag
|= FLAG_SACK_RENEGING
;
3379 if (flag
& FLAG_ACKED
) {
3380 const struct tcp_congestion_ops
*ca_ops
3381 = inet_csk(sk
)->icsk_ca_ops
;
3383 if (unlikely(icsk
->icsk_mtup
.probe_size
&&
3384 !after(tp
->mtu_probe
.probe_seq_end
, tp
->snd_una
))) {
3385 tcp_mtup_probe_success(sk
);
3388 tcp_ack_update_rtt(sk
, flag
, seq_rtt
);
3391 if (tcp_is_reno(tp
)) {
3392 tcp_remove_reno_sacks(sk
, pkts_acked
);
3396 /* Non-retransmitted hole got filled? That's reordering */
3397 if (reord
< prior_fackets
)
3398 tcp_update_reordering(sk
, tp
->fackets_out
- reord
, 0);
3400 delta
= tcp_is_fack(tp
) ? pkts_acked
:
3401 prior_sacked
- tp
->sacked_out
;
3402 tp
->lost_cnt_hint
-= min(tp
->lost_cnt_hint
, delta
);
3405 tp
->fackets_out
-= min(pkts_acked
, tp
->fackets_out
);
3407 if (ca_ops
->pkts_acked
) {
3410 /* Is the ACK triggering packet unambiguous? */
3411 if (!(flag
& FLAG_RETRANS_DATA_ACKED
)) {
3412 /* High resolution needed and available? */
3413 if (ca_ops
->flags
& TCP_CONG_RTT_STAMP
&&
3414 !ktime_equal(last_ackt
,
3415 net_invalid_timestamp()))
3416 rtt_us
= ktime_us_delta(ktime_get_real(),
3418 else if (ca_seq_rtt
>= 0)
3419 rtt_us
= jiffies_to_usecs(ca_seq_rtt
);
3422 ca_ops
->pkts_acked(sk
, pkts_acked
, rtt_us
);
3426 #if FASTRETRANS_DEBUG > 0
3427 WARN_ON((int)tp
->sacked_out
< 0);
3428 WARN_ON((int)tp
->lost_out
< 0);
3429 WARN_ON((int)tp
->retrans_out
< 0);
3430 if (!tp
->packets_out
&& tcp_is_sack(tp
)) {
3431 icsk
= inet_csk(sk
);
3433 printk(KERN_DEBUG
"Leak l=%u %d\n",
3434 tp
->lost_out
, icsk
->icsk_ca_state
);
3437 if (tp
->sacked_out
) {
3438 printk(KERN_DEBUG
"Leak s=%u %d\n",
3439 tp
->sacked_out
, icsk
->icsk_ca_state
);
3442 if (tp
->retrans_out
) {
3443 printk(KERN_DEBUG
"Leak r=%u %d\n",
3444 tp
->retrans_out
, icsk
->icsk_ca_state
);
3445 tp
->retrans_out
= 0;
3452 static void tcp_ack_probe(struct sock
*sk
)
3454 const struct tcp_sock
*tp
= tcp_sk(sk
);
3455 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3457 /* Was it a usable window open? */
3459 if (!after(TCP_SKB_CB(tcp_send_head(sk
))->end_seq
, tcp_wnd_end(tp
))) {
3460 icsk
->icsk_backoff
= 0;
3461 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_PROBE0
);
3462 /* Socket must be waked up by subsequent tcp_data_snd_check().
3463 * This function is not for random using!
3466 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3467 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3472 static inline int tcp_ack_is_dubious(const struct sock
*sk
, const int flag
)
3474 return !(flag
& FLAG_NOT_DUP
) || (flag
& FLAG_CA_ALERT
) ||
3475 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
;
3478 static inline int tcp_may_raise_cwnd(const struct sock
*sk
, const int flag
)
3480 const struct tcp_sock
*tp
= tcp_sk(sk
);
3481 return (!(flag
& FLAG_ECE
) || tp
->snd_cwnd
< tp
->snd_ssthresh
) &&
3482 !((1 << inet_csk(sk
)->icsk_ca_state
) & (TCPF_CA_Recovery
| TCPF_CA_CWR
));
3485 /* Check that window update is acceptable.
3486 * The function assumes that snd_una<=ack<=snd_next.
3488 static inline int tcp_may_update_window(const struct tcp_sock
*tp
,
3489 const u32 ack
, const u32 ack_seq
,
3492 return after(ack
, tp
->snd_una
) ||
3493 after(ack_seq
, tp
->snd_wl1
) ||
3494 (ack_seq
== tp
->snd_wl1
&& nwin
> tp
->snd_wnd
);
3497 /* Update our send window.
3499 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2
3500 * and in FreeBSD. NetBSD's one is even worse.) is wrong.
3502 static int tcp_ack_update_window(struct sock
*sk
, const struct sk_buff
*skb
, u32 ack
,
3505 struct tcp_sock
*tp
= tcp_sk(sk
);
3507 u32 nwin
= ntohs(tcp_hdr(skb
)->window
);
3509 if (likely(!tcp_hdr(skb
)->syn
))
3510 nwin
<<= tp
->rx_opt
.snd_wscale
;
3512 if (tcp_may_update_window(tp
, ack
, ack_seq
, nwin
)) {
3513 flag
|= FLAG_WIN_UPDATE
;
3514 tcp_update_wl(tp
, ack_seq
);
3516 if (tp
->snd_wnd
!= nwin
) {
3519 /* Note, it is the only place, where
3520 * fast path is recovered for sending TCP.
3523 tcp_fast_path_check(sk
);
3525 if (nwin
> tp
->max_window
) {
3526 tp
->max_window
= nwin
;
3527 tcp_sync_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
);
3537 /* A very conservative spurious RTO response algorithm: reduce cwnd and
3538 * continue in congestion avoidance.
3540 static void tcp_conservative_spur_to_response(struct tcp_sock
*tp
)
3542 tp
->snd_cwnd
= min(tp
->snd_cwnd
, tp
->snd_ssthresh
);
3543 tp
->snd_cwnd_cnt
= 0;
3544 tp
->bytes_acked
= 0;
3545 TCP_ECN_queue_cwr(tp
);
3546 tcp_moderate_cwnd(tp
);
3549 /* A conservative spurious RTO response algorithm: reduce cwnd using
3550 * rate halving and continue in congestion avoidance.
3552 static void tcp_ratehalving_spur_to_response(struct sock
*sk
)
3554 tcp_enter_cwr(sk
, 0);
3557 static void tcp_undo_spur_to_response(struct sock
*sk
, int flag
)
3559 if (flag
& FLAG_ECE
)
3560 tcp_ratehalving_spur_to_response(sk
);
3562 tcp_undo_cwr(sk
, true);
3565 /* F-RTO spurious RTO detection algorithm (RFC4138)
3567 * F-RTO affects during two new ACKs following RTO (well, almost, see inline
3568 * comments). State (ACK number) is kept in frto_counter. When ACK advances
3569 * window (but not to or beyond highest sequence sent before RTO):
3570 * On First ACK, send two new segments out.
3571 * On Second ACK, RTO was likely spurious. Do spurious response (response
3572 * algorithm is not part of the F-RTO detection algorithm
3573 * given in RFC4138 but can be selected separately).
3574 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss
3575 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding
3576 * of Nagle, this is done using frto_counter states 2 and 3, when a new data
3577 * segment of any size sent during F-RTO, state 2 is upgraded to 3.
3579 * Rationale: if the RTO was spurious, new ACKs should arrive from the
3580 * original window even after we transmit two new data segments.
3583 * on first step, wait until first cumulative ACK arrives, then move to
3584 * the second step. In second step, the next ACK decides.
3586 * F-RTO is implemented (mainly) in four functions:
3587 * - tcp_use_frto() is used to determine if TCP is can use F-RTO
3588 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is
3589 * called when tcp_use_frto() showed green light
3590 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm
3591 * - tcp_enter_frto_loss() is called if there is not enough evidence
3592 * to prove that the RTO is indeed spurious. It transfers the control
3593 * from F-RTO to the conventional RTO recovery
3595 static int tcp_process_frto(struct sock
*sk
, int flag
)
3597 struct tcp_sock
*tp
= tcp_sk(sk
);
3599 tcp_verify_left_out(tp
);
3601 /* Duplicate the behavior from Loss state (fastretrans_alert) */
3602 if (flag
& FLAG_DATA_ACKED
)
3603 inet_csk(sk
)->icsk_retransmits
= 0;
3605 if ((flag
& FLAG_NONHEAD_RETRANS_ACKED
) ||
3606 ((tp
->frto_counter
>= 2) && (flag
& FLAG_RETRANS_DATA_ACKED
)))
3607 tp
->undo_marker
= 0;
3609 if (!before(tp
->snd_una
, tp
->frto_highmark
)) {
3610 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 2 : 3), flag
);
3614 if (!tcp_is_sackfrto(tp
)) {
3615 /* RFC4138 shortcoming in step 2; should also have case c):
3616 * ACK isn't duplicate nor advances window, e.g., opposite dir
3619 if (!(flag
& FLAG_ANY_PROGRESS
) && (flag
& FLAG_NOT_DUP
))
3622 if (!(flag
& FLAG_DATA_ACKED
)) {
3623 tcp_enter_frto_loss(sk
, (tp
->frto_counter
== 1 ? 0 : 3),
3628 if (!(flag
& FLAG_DATA_ACKED
) && (tp
->frto_counter
== 1)) {
3629 /* Prevent sending of new data. */
3630 tp
->snd_cwnd
= min(tp
->snd_cwnd
,
3631 tcp_packets_in_flight(tp
));
3635 if ((tp
->frto_counter
>= 2) &&
3636 (!(flag
& FLAG_FORWARD_PROGRESS
) ||
3637 ((flag
& FLAG_DATA_SACKED
) &&
3638 !(flag
& FLAG_ONLY_ORIG_SACKED
)))) {
3639 /* RFC4138 shortcoming (see comment above) */
3640 if (!(flag
& FLAG_FORWARD_PROGRESS
) &&
3641 (flag
& FLAG_NOT_DUP
))
3644 tcp_enter_frto_loss(sk
, 3, flag
);
3649 if (tp
->frto_counter
== 1) {
3650 /* tcp_may_send_now needs to see updated state */
3651 tp
->snd_cwnd
= tcp_packets_in_flight(tp
) + 2;
3652 tp
->frto_counter
= 2;
3654 if (!tcp_may_send_now(sk
))
3655 tcp_enter_frto_loss(sk
, 2, flag
);
3659 switch (sysctl_tcp_frto_response
) {
3661 tcp_undo_spur_to_response(sk
, flag
);
3664 tcp_conservative_spur_to_response(tp
);
3667 tcp_ratehalving_spur_to_response(sk
);
3670 tp
->frto_counter
= 0;
3671 tp
->undo_marker
= 0;
3672 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSPURIOUSRTOS
);
3677 /* This routine deals with incoming acks, but not outgoing ones. */
3678 static int tcp_ack(struct sock
*sk
, const struct sk_buff
*skb
, int flag
)
3680 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3681 struct tcp_sock
*tp
= tcp_sk(sk
);
3682 u32 prior_snd_una
= tp
->snd_una
;
3683 u32 ack_seq
= TCP_SKB_CB(skb
)->seq
;
3684 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
3685 bool is_dupack
= false;
3686 u32 prior_in_flight
;
3689 int prior_sacked
= tp
->sacked_out
;
3691 int newly_acked_sacked
= 0;
3694 /* If the ack is older than previous acks
3695 * then we can probably ignore it.
3697 if (before(ack
, prior_snd_una
))
3700 /* If the ack includes data we haven't sent yet, discard
3701 * this segment (RFC793 Section 3.9).
3703 if (after(ack
, tp
->snd_nxt
))
3706 if (after(ack
, prior_snd_una
))
3707 flag
|= FLAG_SND_UNA_ADVANCED
;
3709 if (sysctl_tcp_abc
) {
3710 if (icsk
->icsk_ca_state
< TCP_CA_CWR
)
3711 tp
->bytes_acked
+= ack
- prior_snd_una
;
3712 else if (icsk
->icsk_ca_state
== TCP_CA_Loss
)
3713 /* we assume just one segment left network */
3714 tp
->bytes_acked
+= min(ack
- prior_snd_una
,
3718 prior_fackets
= tp
->fackets_out
;
3719 prior_in_flight
= tcp_packets_in_flight(tp
);
3721 if (!(flag
& FLAG_SLOWPATH
) && after(ack
, prior_snd_una
)) {
3722 /* Window is constant, pure forward advance.
3723 * No more checks are required.
3724 * Note, we use the fact that SND.UNA>=SND.WL2.
3726 tcp_update_wl(tp
, ack_seq
);
3728 flag
|= FLAG_WIN_UPDATE
;
3730 tcp_ca_event(sk
, CA_EVENT_FAST_ACK
);
3732 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPACKS
);
3734 if (ack_seq
!= TCP_SKB_CB(skb
)->end_seq
)
3737 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPPUREACKS
);
3739 flag
|= tcp_ack_update_window(sk
, skb
, ack
, ack_seq
);
3741 if (TCP_SKB_CB(skb
)->sacked
)
3742 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3744 if (TCP_ECN_rcv_ecn_echo(tp
, tcp_hdr(skb
)))
3747 tcp_ca_event(sk
, CA_EVENT_SLOW_ACK
);
3750 /* We passed data and got it acked, remove any soft error
3751 * log. Something worked...
3753 sk
->sk_err_soft
= 0;
3754 icsk
->icsk_probes_out
= 0;
3755 tp
->rcv_tstamp
= tcp_time_stamp
;
3756 prior_packets
= tp
->packets_out
;
3760 /* See if we can take anything off of the retransmit queue. */
3761 flag
|= tcp_clean_rtx_queue(sk
, prior_fackets
, prior_snd_una
);
3763 pkts_acked
= prior_packets
- tp
->packets_out
;
3764 newly_acked_sacked
= (prior_packets
- prior_sacked
) -
3765 (tp
->packets_out
- tp
->sacked_out
);
3767 if (tp
->frto_counter
)
3768 frto_cwnd
= tcp_process_frto(sk
, flag
);
3769 /* Guarantee sacktag reordering detection against wrap-arounds */
3770 if (before(tp
->frto_highmark
, tp
->snd_una
))
3771 tp
->frto_highmark
= 0;
3773 if (tcp_ack_is_dubious(sk
, flag
)) {
3774 /* Advance CWND, if state allows this. */
3775 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
&&
3776 tcp_may_raise_cwnd(sk
, flag
))
3777 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3778 is_dupack
= !(flag
& (FLAG_SND_UNA_ADVANCED
| FLAG_NOT_DUP
));
3779 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3782 if ((flag
& FLAG_DATA_ACKED
) && !frto_cwnd
)
3783 tcp_cong_avoid(sk
, ack
, prior_in_flight
);
3786 if ((flag
& FLAG_FORWARD_PROGRESS
) || !(flag
& FLAG_NOT_DUP
))
3787 dst_confirm(__sk_dst_get(sk
));
3792 /* If data was DSACKed, see if we can undo a cwnd reduction. */
3793 if (flag
& FLAG_DSACKING_ACK
)
3794 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3796 /* If this ack opens up a zero window, clear backoff. It was
3797 * being used to time the probes, and is probably far higher than
3798 * it needs to be for normal retransmission.
3800 if (tcp_send_head(sk
))
3805 SOCK_DEBUG(sk
, "Ack %u after %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3809 /* If data was SACKed, tag it and see if we should send more data.
3810 * If data was DSACKed, see if we can undo a cwnd reduction.
3812 if (TCP_SKB_CB(skb
)->sacked
) {
3813 flag
|= tcp_sacktag_write_queue(sk
, skb
, prior_snd_una
);
3814 newly_acked_sacked
= tp
->sacked_out
- prior_sacked
;
3815 tcp_fastretrans_alert(sk
, pkts_acked
, newly_acked_sacked
,
3819 SOCK_DEBUG(sk
, "Ack %u before %u:%u\n", ack
, tp
->snd_una
, tp
->snd_nxt
);
3823 /* Look for tcp options. Normally only called on SYN and SYNACK packets.
3824 * But, this can also be called on packets in the established flow when
3825 * the fast version below fails.
3827 void tcp_parse_options(const struct sk_buff
*skb
, struct tcp_options_received
*opt_rx
,
3828 const u8
**hvpp
, int estab
)
3830 const unsigned char *ptr
;
3831 const struct tcphdr
*th
= tcp_hdr(skb
);
3832 int length
= (th
->doff
* 4) - sizeof(struct tcphdr
);
3834 ptr
= (const unsigned char *)(th
+ 1);
3835 opt_rx
->saw_tstamp
= 0;
3837 while (length
> 0) {
3838 int opcode
= *ptr
++;
3844 case TCPOPT_NOP
: /* Ref: RFC 793 section 3.1 */
3849 if (opsize
< 2) /* "silly options" */
3851 if (opsize
> length
)
3852 return; /* don't parse partial options */
3855 if (opsize
== TCPOLEN_MSS
&& th
->syn
&& !estab
) {
3856 u16 in_mss
= get_unaligned_be16(ptr
);
3858 if (opt_rx
->user_mss
&&
3859 opt_rx
->user_mss
< in_mss
)
3860 in_mss
= opt_rx
->user_mss
;
3861 opt_rx
->mss_clamp
= in_mss
;
3866 if (opsize
== TCPOLEN_WINDOW
&& th
->syn
&&
3867 !estab
&& sysctl_tcp_window_scaling
) {
3868 __u8 snd_wscale
= *(__u8
*)ptr
;
3869 opt_rx
->wscale_ok
= 1;
3870 if (snd_wscale
> 14) {
3871 if (net_ratelimit())
3872 pr_info("%s: Illegal window scaling value %d >14 received\n",
3877 opt_rx
->snd_wscale
= snd_wscale
;
3880 case TCPOPT_TIMESTAMP
:
3881 if ((opsize
== TCPOLEN_TIMESTAMP
) &&
3882 ((estab
&& opt_rx
->tstamp_ok
) ||
3883 (!estab
&& sysctl_tcp_timestamps
))) {
3884 opt_rx
->saw_tstamp
= 1;
3885 opt_rx
->rcv_tsval
= get_unaligned_be32(ptr
);
3886 opt_rx
->rcv_tsecr
= get_unaligned_be32(ptr
+ 4);
3889 case TCPOPT_SACK_PERM
:
3890 if (opsize
== TCPOLEN_SACK_PERM
&& th
->syn
&&
3891 !estab
&& sysctl_tcp_sack
) {
3892 opt_rx
->sack_ok
= TCP_SACK_SEEN
;
3893 tcp_sack_reset(opt_rx
);
3898 if ((opsize
>= (TCPOLEN_SACK_BASE
+ TCPOLEN_SACK_PERBLOCK
)) &&
3899 !((opsize
- TCPOLEN_SACK_BASE
) % TCPOLEN_SACK_PERBLOCK
) &&
3901 TCP_SKB_CB(skb
)->sacked
= (ptr
- 2) - (unsigned char *)th
;
3904 #ifdef CONFIG_TCP_MD5SIG
3907 * The MD5 Hash has already been
3908 * checked (see tcp_v{4,6}_do_rcv()).
3913 /* This option is variable length.
3916 case TCPOLEN_COOKIE_BASE
:
3917 /* not yet implemented */
3919 case TCPOLEN_COOKIE_PAIR
:
3920 /* not yet implemented */
3922 case TCPOLEN_COOKIE_MIN
+0:
3923 case TCPOLEN_COOKIE_MIN
+2:
3924 case TCPOLEN_COOKIE_MIN
+4:
3925 case TCPOLEN_COOKIE_MIN
+6:
3926 case TCPOLEN_COOKIE_MAX
:
3927 /* 16-bit multiple */
3928 opt_rx
->cookie_plus
= opsize
;
3943 EXPORT_SYMBOL(tcp_parse_options
);
3945 static int tcp_parse_aligned_timestamp(struct tcp_sock
*tp
, const struct tcphdr
*th
)
3947 const __be32
*ptr
= (const __be32
*)(th
+ 1);
3949 if (*ptr
== htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16)
3950 | (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
)) {
3951 tp
->rx_opt
.saw_tstamp
= 1;
3953 tp
->rx_opt
.rcv_tsval
= ntohl(*ptr
);
3955 tp
->rx_opt
.rcv_tsecr
= ntohl(*ptr
);
3961 /* Fast parse options. This hopes to only see timestamps.
3962 * If it is wrong it falls back on tcp_parse_options().
3964 static int tcp_fast_parse_options(const struct sk_buff
*skb
,
3965 const struct tcphdr
*th
,
3966 struct tcp_sock
*tp
, const u8
**hvpp
)
3968 /* In the spirit of fast parsing, compare doff directly to constant
3969 * values. Because equality is used, short doff can be ignored here.
3971 if (th
->doff
== (sizeof(*th
) / 4)) {
3972 tp
->rx_opt
.saw_tstamp
= 0;
3974 } else if (tp
->rx_opt
.tstamp_ok
&&
3975 th
->doff
== ((sizeof(*th
) + TCPOLEN_TSTAMP_ALIGNED
) / 4)) {
3976 if (tcp_parse_aligned_timestamp(tp
, th
))
3979 tcp_parse_options(skb
, &tp
->rx_opt
, hvpp
, 1);
3983 #ifdef CONFIG_TCP_MD5SIG
3985 * Parse MD5 Signature option
3987 const u8
*tcp_parse_md5sig_option(const struct tcphdr
*th
)
3989 int length
= (th
->doff
<< 2) - sizeof(*th
);
3990 const u8
*ptr
= (const u8
*)(th
+ 1);
3992 /* If the TCP option is too short, we can short cut */
3993 if (length
< TCPOLEN_MD5SIG
)
3996 while (length
> 0) {
3997 int opcode
= *ptr
++;
4008 if (opsize
< 2 || opsize
> length
)
4010 if (opcode
== TCPOPT_MD5SIG
)
4011 return opsize
== TCPOLEN_MD5SIG
? ptr
: NULL
;
4018 EXPORT_SYMBOL(tcp_parse_md5sig_option
);
4021 static inline void tcp_store_ts_recent(struct tcp_sock
*tp
)
4023 tp
->rx_opt
.ts_recent
= tp
->rx_opt
.rcv_tsval
;
4024 tp
->rx_opt
.ts_recent_stamp
= get_seconds();
4027 static inline void tcp_replace_ts_recent(struct tcp_sock
*tp
, u32 seq
)
4029 if (tp
->rx_opt
.saw_tstamp
&& !after(seq
, tp
->rcv_wup
)) {
4030 /* PAWS bug workaround wrt. ACK frames, the PAWS discard
4031 * extra check below makes sure this can only happen
4032 * for pure ACK frames. -DaveM
4034 * Not only, also it occurs for expired timestamps.
4037 if (tcp_paws_check(&tp
->rx_opt
, 0))
4038 tcp_store_ts_recent(tp
);
4042 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM
4044 * It is not fatal. If this ACK does _not_ change critical state (seqs, window)
4045 * it can pass through stack. So, the following predicate verifies that
4046 * this segment is not used for anything but congestion avoidance or
4047 * fast retransmit. Moreover, we even are able to eliminate most of such
4048 * second order effects, if we apply some small "replay" window (~RTO)
4049 * to timestamp space.
4051 * All these measures still do not guarantee that we reject wrapped ACKs
4052 * on networks with high bandwidth, when sequence space is recycled fastly,
4053 * but it guarantees that such events will be very rare and do not affect
4054 * connection seriously. This doesn't look nice, but alas, PAWS is really
4057 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC
4058 * states that events when retransmit arrives after original data are rare.
4059 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is
4060 * the biggest problem on large power networks even with minor reordering.
4061 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe
4062 * up to bandwidth of 18Gigabit/sec. 8) ]
4065 static int tcp_disordered_ack(const struct sock
*sk
, const struct sk_buff
*skb
)
4067 const struct tcp_sock
*tp
= tcp_sk(sk
);
4068 const struct tcphdr
*th
= tcp_hdr(skb
);
4069 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4070 u32 ack
= TCP_SKB_CB(skb
)->ack_seq
;
4072 return (/* 1. Pure ACK with correct sequence number. */
4073 (th
->ack
&& seq
== TCP_SKB_CB(skb
)->end_seq
&& seq
== tp
->rcv_nxt
) &&
4075 /* 2. ... and duplicate ACK. */
4076 ack
== tp
->snd_una
&&
4078 /* 3. ... and does not update window. */
4079 !tcp_may_update_window(tp
, ack
, seq
, ntohs(th
->window
) << tp
->rx_opt
.snd_wscale
) &&
4081 /* 4. ... and sits in replay window. */
4082 (s32
)(tp
->rx_opt
.ts_recent
- tp
->rx_opt
.rcv_tsval
) <= (inet_csk(sk
)->icsk_rto
* 1024) / HZ
);
4085 static inline int tcp_paws_discard(const struct sock
*sk
,
4086 const struct sk_buff
*skb
)
4088 const struct tcp_sock
*tp
= tcp_sk(sk
);
4090 return !tcp_paws_check(&tp
->rx_opt
, TCP_PAWS_WINDOW
) &&
4091 !tcp_disordered_ack(sk
, skb
);
4094 /* Check segment sequence number for validity.
4096 * Segment controls are considered valid, if the segment
4097 * fits to the window after truncation to the window. Acceptability
4098 * of data (and SYN, FIN, of course) is checked separately.
4099 * See tcp_data_queue(), for example.
4101 * Also, controls (RST is main one) are accepted using RCV.WUP instead
4102 * of RCV.NXT. Peer still did not advance his SND.UNA when we
4103 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP.
4104 * (borrowed from freebsd)
4107 static inline int tcp_sequence(const struct tcp_sock
*tp
, u32 seq
, u32 end_seq
)
4109 return !before(end_seq
, tp
->rcv_wup
) &&
4110 !after(seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
));
4113 /* When we get a reset we do this. */
4114 static void tcp_reset(struct sock
*sk
)
4116 /* We want the right error as BSD sees it (and indeed as we do). */
4117 switch (sk
->sk_state
) {
4119 sk
->sk_err
= ECONNREFUSED
;
4121 case TCP_CLOSE_WAIT
:
4127 sk
->sk_err
= ECONNRESET
;
4129 /* This barrier is coupled with smp_rmb() in tcp_poll() */
4132 if (!sock_flag(sk
, SOCK_DEAD
))
4133 sk
->sk_error_report(sk
);
4139 * Process the FIN bit. This now behaves as it is supposed to work
4140 * and the FIN takes effect when it is validly part of sequence
4141 * space. Not before when we get holes.
4143 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4144 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4147 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4148 * close and we go into CLOSING (and later onto TIME-WAIT)
4150 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4152 static void tcp_fin(struct sock
*sk
)
4154 struct tcp_sock
*tp
= tcp_sk(sk
);
4156 inet_csk_schedule_ack(sk
);
4158 sk
->sk_shutdown
|= RCV_SHUTDOWN
;
4159 sock_set_flag(sk
, SOCK_DONE
);
4161 switch (sk
->sk_state
) {
4163 case TCP_ESTABLISHED
:
4164 /* Move to CLOSE_WAIT */
4165 tcp_set_state(sk
, TCP_CLOSE_WAIT
);
4166 inet_csk(sk
)->icsk_ack
.pingpong
= 1;
4169 case TCP_CLOSE_WAIT
:
4171 /* Received a retransmission of the FIN, do
4176 /* RFC793: Remain in the LAST-ACK state. */
4180 /* This case occurs when a simultaneous close
4181 * happens, we must ack the received FIN and
4182 * enter the CLOSING state.
4185 tcp_set_state(sk
, TCP_CLOSING
);
4188 /* Received a FIN -- send ACK and enter TIME_WAIT. */
4190 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
4193 /* Only TCP_LISTEN and TCP_CLOSE are left, in these
4194 * cases we should never reach this piece of code.
4196 pr_err("%s: Impossible, sk->sk_state=%d\n",
4197 __func__
, sk
->sk_state
);
4201 /* It _is_ possible, that we have something out-of-order _after_ FIN.
4202 * Probably, we should reset in this case. For now drop them.
4204 __skb_queue_purge(&tp
->out_of_order_queue
);
4205 if (tcp_is_sack(tp
))
4206 tcp_sack_reset(&tp
->rx_opt
);
4209 if (!sock_flag(sk
, SOCK_DEAD
)) {
4210 sk
->sk_state_change(sk
);
4212 /* Do not send POLL_HUP for half duplex close. */
4213 if (sk
->sk_shutdown
== SHUTDOWN_MASK
||
4214 sk
->sk_state
== TCP_CLOSE
)
4215 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_HUP
);
4217 sk_wake_async(sk
, SOCK_WAKE_WAITD
, POLL_IN
);
4221 static inline int tcp_sack_extend(struct tcp_sack_block
*sp
, u32 seq
,
4224 if (!after(seq
, sp
->end_seq
) && !after(sp
->start_seq
, end_seq
)) {
4225 if (before(seq
, sp
->start_seq
))
4226 sp
->start_seq
= seq
;
4227 if (after(end_seq
, sp
->end_seq
))
4228 sp
->end_seq
= end_seq
;
4234 static void tcp_dsack_set(struct sock
*sk
, u32 seq
, u32 end_seq
)
4236 struct tcp_sock
*tp
= tcp_sk(sk
);
4238 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4241 if (before(seq
, tp
->rcv_nxt
))
4242 mib_idx
= LINUX_MIB_TCPDSACKOLDSENT
;
4244 mib_idx
= LINUX_MIB_TCPDSACKOFOSENT
;
4246 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
4248 tp
->rx_opt
.dsack
= 1;
4249 tp
->duplicate_sack
[0].start_seq
= seq
;
4250 tp
->duplicate_sack
[0].end_seq
= end_seq
;
4254 static void tcp_dsack_extend(struct sock
*sk
, u32 seq
, u32 end_seq
)
4256 struct tcp_sock
*tp
= tcp_sk(sk
);
4258 if (!tp
->rx_opt
.dsack
)
4259 tcp_dsack_set(sk
, seq
, end_seq
);
4261 tcp_sack_extend(tp
->duplicate_sack
, seq
, end_seq
);
4264 static void tcp_send_dupack(struct sock
*sk
, const struct sk_buff
*skb
)
4266 struct tcp_sock
*tp
= tcp_sk(sk
);
4268 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
4269 before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4270 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4271 tcp_enter_quickack_mode(sk
);
4273 if (tcp_is_sack(tp
) && sysctl_tcp_dsack
) {
4274 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4276 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
))
4277 end_seq
= tp
->rcv_nxt
;
4278 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, end_seq
);
4285 /* These routines update the SACK block as out-of-order packets arrive or
4286 * in-order packets close up the sequence space.
4288 static void tcp_sack_maybe_coalesce(struct tcp_sock
*tp
)
4291 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4292 struct tcp_sack_block
*swalk
= sp
+ 1;
4294 /* See if the recent change to the first SACK eats into
4295 * or hits the sequence space of other SACK blocks, if so coalesce.
4297 for (this_sack
= 1; this_sack
< tp
->rx_opt
.num_sacks
;) {
4298 if (tcp_sack_extend(sp
, swalk
->start_seq
, swalk
->end_seq
)) {
4301 /* Zap SWALK, by moving every further SACK up by one slot.
4302 * Decrease num_sacks.
4304 tp
->rx_opt
.num_sacks
--;
4305 for (i
= this_sack
; i
< tp
->rx_opt
.num_sacks
; i
++)
4309 this_sack
++, swalk
++;
4313 static void tcp_sack_new_ofo_skb(struct sock
*sk
, u32 seq
, u32 end_seq
)
4315 struct tcp_sock
*tp
= tcp_sk(sk
);
4316 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4317 int cur_sacks
= tp
->rx_opt
.num_sacks
;
4323 for (this_sack
= 0; this_sack
< cur_sacks
; this_sack
++, sp
++) {
4324 if (tcp_sack_extend(sp
, seq
, end_seq
)) {
4325 /* Rotate this_sack to the first one. */
4326 for (; this_sack
> 0; this_sack
--, sp
--)
4327 swap(*sp
, *(sp
- 1));
4329 tcp_sack_maybe_coalesce(tp
);
4334 /* Could not find an adjacent existing SACK, build a new one,
4335 * put it at the front, and shift everyone else down. We
4336 * always know there is at least one SACK present already here.
4338 * If the sack array is full, forget about the last one.
4340 if (this_sack
>= TCP_NUM_SACKS
) {
4342 tp
->rx_opt
.num_sacks
--;
4345 for (; this_sack
> 0; this_sack
--, sp
--)
4349 /* Build the new head SACK, and we're done. */
4350 sp
->start_seq
= seq
;
4351 sp
->end_seq
= end_seq
;
4352 tp
->rx_opt
.num_sacks
++;
4355 /* RCV.NXT advances, some SACKs should be eaten. */
4357 static void tcp_sack_remove(struct tcp_sock
*tp
)
4359 struct tcp_sack_block
*sp
= &tp
->selective_acks
[0];
4360 int num_sacks
= tp
->rx_opt
.num_sacks
;
4363 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */
4364 if (skb_queue_empty(&tp
->out_of_order_queue
)) {
4365 tp
->rx_opt
.num_sacks
= 0;
4369 for (this_sack
= 0; this_sack
< num_sacks
;) {
4370 /* Check if the start of the sack is covered by RCV.NXT. */
4371 if (!before(tp
->rcv_nxt
, sp
->start_seq
)) {
4374 /* RCV.NXT must cover all the block! */
4375 WARN_ON(before(tp
->rcv_nxt
, sp
->end_seq
));
4377 /* Zap this SACK, by moving forward any other SACKS. */
4378 for (i
=this_sack
+1; i
< num_sacks
; i
++)
4379 tp
->selective_acks
[i
-1] = tp
->selective_acks
[i
];
4386 tp
->rx_opt
.num_sacks
= num_sacks
;
4389 /* This one checks to see if we can put data from the
4390 * out_of_order queue into the receive_queue.
4392 static void tcp_ofo_queue(struct sock
*sk
)
4394 struct tcp_sock
*tp
= tcp_sk(sk
);
4395 __u32 dsack_high
= tp
->rcv_nxt
;
4396 struct sk_buff
*skb
;
4398 while ((skb
= skb_peek(&tp
->out_of_order_queue
)) != NULL
) {
4399 if (after(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
4402 if (before(TCP_SKB_CB(skb
)->seq
, dsack_high
)) {
4403 __u32 dsack
= dsack_high
;
4404 if (before(TCP_SKB_CB(skb
)->end_seq
, dsack_high
))
4405 dsack_high
= TCP_SKB_CB(skb
)->end_seq
;
4406 tcp_dsack_extend(sk
, TCP_SKB_CB(skb
)->seq
, dsack
);
4409 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4410 SOCK_DEBUG(sk
, "ofo packet was already received\n");
4411 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4415 SOCK_DEBUG(sk
, "ofo requeuing : rcv_next %X seq %X - %X\n",
4416 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4417 TCP_SKB_CB(skb
)->end_seq
);
4419 __skb_unlink(skb
, &tp
->out_of_order_queue
);
4420 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4421 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4422 if (tcp_hdr(skb
)->fin
)
4427 static int tcp_prune_ofo_queue(struct sock
*sk
);
4428 static int tcp_prune_queue(struct sock
*sk
);
4430 static inline int tcp_try_rmem_schedule(struct sock
*sk
, unsigned int size
)
4432 if (atomic_read(&sk
->sk_rmem_alloc
) > sk
->sk_rcvbuf
||
4433 !sk_rmem_schedule(sk
, size
)) {
4435 if (tcp_prune_queue(sk
) < 0)
4438 if (!sk_rmem_schedule(sk
, size
)) {
4439 if (!tcp_prune_ofo_queue(sk
))
4442 if (!sk_rmem_schedule(sk
, size
))
4449 static void tcp_data_queue(struct sock
*sk
, struct sk_buff
*skb
)
4451 const struct tcphdr
*th
= tcp_hdr(skb
);
4452 struct tcp_sock
*tp
= tcp_sk(sk
);
4455 if (TCP_SKB_CB(skb
)->seq
== TCP_SKB_CB(skb
)->end_seq
)
4459 __skb_pull(skb
, th
->doff
* 4);
4461 TCP_ECN_accept_cwr(tp
, skb
);
4463 tp
->rx_opt
.dsack
= 0;
4465 /* Queue data for delivery to the user.
4466 * Packets in sequence go to the receive queue.
4467 * Out of sequence packets to the out_of_order_queue.
4469 if (TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
) {
4470 if (tcp_receive_window(tp
) == 0)
4473 /* Ok. In sequence. In window. */
4474 if (tp
->ucopy
.task
== current
&&
4475 tp
->copied_seq
== tp
->rcv_nxt
&& tp
->ucopy
.len
&&
4476 sock_owned_by_user(sk
) && !tp
->urg_data
) {
4477 int chunk
= min_t(unsigned int, skb
->len
,
4480 __set_current_state(TASK_RUNNING
);
4483 if (!skb_copy_datagram_iovec(skb
, 0, tp
->ucopy
.iov
, chunk
)) {
4484 tp
->ucopy
.len
-= chunk
;
4485 tp
->copied_seq
+= chunk
;
4486 eaten
= (chunk
== skb
->len
);
4487 tcp_rcv_space_adjust(sk
);
4495 tcp_try_rmem_schedule(sk
, skb
->truesize
))
4498 skb_set_owner_r(skb
, sk
);
4499 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
4501 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
4503 tcp_event_data_recv(sk
, skb
);
4507 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4510 /* RFC2581. 4.2. SHOULD send immediate ACK, when
4511 * gap in queue is filled.
4513 if (skb_queue_empty(&tp
->out_of_order_queue
))
4514 inet_csk(sk
)->icsk_ack
.pingpong
= 0;
4517 if (tp
->rx_opt
.num_sacks
)
4518 tcp_sack_remove(tp
);
4520 tcp_fast_path_check(sk
);
4524 else if (!sock_flag(sk
, SOCK_DEAD
))
4525 sk
->sk_data_ready(sk
, 0);
4529 if (!after(TCP_SKB_CB(skb
)->end_seq
, tp
->rcv_nxt
)) {
4530 /* A retransmit, 2nd most common case. Force an immediate ack. */
4531 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_DELAYEDACKLOST
);
4532 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4535 tcp_enter_quickack_mode(sk
);
4536 inet_csk_schedule_ack(sk
);
4542 /* Out of window. F.e. zero window probe. */
4543 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
+ tcp_receive_window(tp
)))
4546 tcp_enter_quickack_mode(sk
);
4548 if (before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
4549 /* Partial packet, seq < rcv_next < end_seq */
4550 SOCK_DEBUG(sk
, "partial packet: rcv_next %X seq %X - %X\n",
4551 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
,
4552 TCP_SKB_CB(skb
)->end_seq
);
4554 tcp_dsack_set(sk
, TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
);
4556 /* If window is closed, drop tail of packet. But after
4557 * remembering D-SACK for its head made in previous line.
4559 if (!tcp_receive_window(tp
))
4564 TCP_ECN_check_ce(tp
, skb
);
4566 if (tcp_try_rmem_schedule(sk
, skb
->truesize
))
4569 /* Disable header prediction. */
4571 inet_csk_schedule_ack(sk
);
4573 SOCK_DEBUG(sk
, "out of order segment: rcv_next %X seq %X - %X\n",
4574 tp
->rcv_nxt
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
);
4576 skb_set_owner_r(skb
, sk
);
4578 if (!skb_peek(&tp
->out_of_order_queue
)) {
4579 /* Initial out of order segment, build 1 SACK. */
4580 if (tcp_is_sack(tp
)) {
4581 tp
->rx_opt
.num_sacks
= 1;
4582 tp
->selective_acks
[0].start_seq
= TCP_SKB_CB(skb
)->seq
;
4583 tp
->selective_acks
[0].end_seq
=
4584 TCP_SKB_CB(skb
)->end_seq
;
4586 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4588 struct sk_buff
*skb1
= skb_peek_tail(&tp
->out_of_order_queue
);
4589 u32 seq
= TCP_SKB_CB(skb
)->seq
;
4590 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
4592 if (seq
== TCP_SKB_CB(skb1
)->end_seq
) {
4593 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4595 if (!tp
->rx_opt
.num_sacks
||
4596 tp
->selective_acks
[0].end_seq
!= seq
)
4599 /* Common case: data arrive in order after hole. */
4600 tp
->selective_acks
[0].end_seq
= end_seq
;
4604 /* Find place to insert this segment. */
4606 if (!after(TCP_SKB_CB(skb1
)->seq
, seq
))
4608 if (skb_queue_is_first(&tp
->out_of_order_queue
, skb1
)) {
4612 skb1
= skb_queue_prev(&tp
->out_of_order_queue
, skb1
);
4615 /* Do skb overlap to previous one? */
4616 if (skb1
&& before(seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4617 if (!after(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4618 /* All the bits are present. Drop. */
4620 tcp_dsack_set(sk
, seq
, end_seq
);
4623 if (after(seq
, TCP_SKB_CB(skb1
)->seq
)) {
4624 /* Partial overlap. */
4625 tcp_dsack_set(sk
, seq
,
4626 TCP_SKB_CB(skb1
)->end_seq
);
4628 if (skb_queue_is_first(&tp
->out_of_order_queue
,
4632 skb1
= skb_queue_prev(
4633 &tp
->out_of_order_queue
,
4638 __skb_queue_head(&tp
->out_of_order_queue
, skb
);
4640 __skb_queue_after(&tp
->out_of_order_queue
, skb1
, skb
);
4642 /* And clean segments covered by new one as whole. */
4643 while (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
)) {
4644 skb1
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4646 if (!after(end_seq
, TCP_SKB_CB(skb1
)->seq
))
4648 if (before(end_seq
, TCP_SKB_CB(skb1
)->end_seq
)) {
4649 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4653 __skb_unlink(skb1
, &tp
->out_of_order_queue
);
4654 tcp_dsack_extend(sk
, TCP_SKB_CB(skb1
)->seq
,
4655 TCP_SKB_CB(skb1
)->end_seq
);
4660 if (tcp_is_sack(tp
))
4661 tcp_sack_new_ofo_skb(sk
, seq
, end_seq
);
4665 static struct sk_buff
*tcp_collapse_one(struct sock
*sk
, struct sk_buff
*skb
,
4666 struct sk_buff_head
*list
)
4668 struct sk_buff
*next
= NULL
;
4670 if (!skb_queue_is_last(list
, skb
))
4671 next
= skb_queue_next(list
, skb
);
4673 __skb_unlink(skb
, list
);
4675 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRCVCOLLAPSED
);
4680 /* Collapse contiguous sequence of skbs head..tail with
4681 * sequence numbers start..end.
4683 * If tail is NULL, this means until the end of the list.
4685 * Segments with FIN/SYN are not collapsed (only because this
4689 tcp_collapse(struct sock
*sk
, struct sk_buff_head
*list
,
4690 struct sk_buff
*head
, struct sk_buff
*tail
,
4693 struct sk_buff
*skb
, *n
;
4696 /* First, check that queue is collapsible and find
4697 * the point where collapsing can be useful. */
4701 skb_queue_walk_from_safe(list
, skb
, n
) {
4704 /* No new bits? It is possible on ofo queue. */
4705 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4706 skb
= tcp_collapse_one(sk
, skb
, list
);
4712 /* The first skb to collapse is:
4714 * - bloated or contains data before "start" or
4715 * overlaps to the next one.
4717 if (!tcp_hdr(skb
)->syn
&& !tcp_hdr(skb
)->fin
&&
4718 (tcp_win_from_space(skb
->truesize
) > skb
->len
||
4719 before(TCP_SKB_CB(skb
)->seq
, start
))) {
4720 end_of_skbs
= false;
4724 if (!skb_queue_is_last(list
, skb
)) {
4725 struct sk_buff
*next
= skb_queue_next(list
, skb
);
4727 TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(next
)->seq
) {
4728 end_of_skbs
= false;
4733 /* Decided to skip this, advance start seq. */
4734 start
= TCP_SKB_CB(skb
)->end_seq
;
4736 if (end_of_skbs
|| tcp_hdr(skb
)->syn
|| tcp_hdr(skb
)->fin
)
4739 while (before(start
, end
)) {
4740 struct sk_buff
*nskb
;
4741 unsigned int header
= skb_headroom(skb
);
4742 int copy
= SKB_MAX_ORDER(header
, 0);
4744 /* Too big header? This can happen with IPv6. */
4747 if (end
- start
< copy
)
4749 nskb
= alloc_skb(copy
+ header
, GFP_ATOMIC
);
4753 skb_set_mac_header(nskb
, skb_mac_header(skb
) - skb
->head
);
4754 skb_set_network_header(nskb
, (skb_network_header(skb
) -
4756 skb_set_transport_header(nskb
, (skb_transport_header(skb
) -
4758 skb_reserve(nskb
, header
);
4759 memcpy(nskb
->head
, skb
->head
, header
);
4760 memcpy(nskb
->cb
, skb
->cb
, sizeof(skb
->cb
));
4761 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(nskb
)->end_seq
= start
;
4762 __skb_queue_before(list
, skb
, nskb
);
4763 skb_set_owner_r(nskb
, sk
);
4765 /* Copy data, releasing collapsed skbs. */
4767 int offset
= start
- TCP_SKB_CB(skb
)->seq
;
4768 int size
= TCP_SKB_CB(skb
)->end_seq
- start
;
4772 size
= min(copy
, size
);
4773 if (skb_copy_bits(skb
, offset
, skb_put(nskb
, size
), size
))
4775 TCP_SKB_CB(nskb
)->end_seq
+= size
;
4779 if (!before(start
, TCP_SKB_CB(skb
)->end_seq
)) {
4780 skb
= tcp_collapse_one(sk
, skb
, list
);
4783 tcp_hdr(skb
)->syn
||
4791 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs
4792 * and tcp_collapse() them until all the queue is collapsed.
4794 static void tcp_collapse_ofo_queue(struct sock
*sk
)
4796 struct tcp_sock
*tp
= tcp_sk(sk
);
4797 struct sk_buff
*skb
= skb_peek(&tp
->out_of_order_queue
);
4798 struct sk_buff
*head
;
4804 start
= TCP_SKB_CB(skb
)->seq
;
4805 end
= TCP_SKB_CB(skb
)->end_seq
;
4809 struct sk_buff
*next
= NULL
;
4811 if (!skb_queue_is_last(&tp
->out_of_order_queue
, skb
))
4812 next
= skb_queue_next(&tp
->out_of_order_queue
, skb
);
4815 /* Segment is terminated when we see gap or when
4816 * we are at the end of all the queue. */
4818 after(TCP_SKB_CB(skb
)->seq
, end
) ||
4819 before(TCP_SKB_CB(skb
)->end_seq
, start
)) {
4820 tcp_collapse(sk
, &tp
->out_of_order_queue
,
4821 head
, skb
, start
, end
);
4825 /* Start new segment */
4826 start
= TCP_SKB_CB(skb
)->seq
;
4827 end
= TCP_SKB_CB(skb
)->end_seq
;
4829 if (before(TCP_SKB_CB(skb
)->seq
, start
))
4830 start
= TCP_SKB_CB(skb
)->seq
;
4831 if (after(TCP_SKB_CB(skb
)->end_seq
, end
))
4832 end
= TCP_SKB_CB(skb
)->end_seq
;
4838 * Purge the out-of-order queue.
4839 * Return true if queue was pruned.
4841 static int tcp_prune_ofo_queue(struct sock
*sk
)
4843 struct tcp_sock
*tp
= tcp_sk(sk
);
4846 if (!skb_queue_empty(&tp
->out_of_order_queue
)) {
4847 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_OFOPRUNED
);
4848 __skb_queue_purge(&tp
->out_of_order_queue
);
4850 /* Reset SACK state. A conforming SACK implementation will
4851 * do the same at a timeout based retransmit. When a connection
4852 * is in a sad state like this, we care only about integrity
4853 * of the connection not performance.
4855 if (tp
->rx_opt
.sack_ok
)
4856 tcp_sack_reset(&tp
->rx_opt
);
4863 /* Reduce allocated memory if we can, trying to get
4864 * the socket within its memory limits again.
4866 * Return less than zero if we should start dropping frames
4867 * until the socket owning process reads some of the data
4868 * to stabilize the situation.
4870 static int tcp_prune_queue(struct sock
*sk
)
4872 struct tcp_sock
*tp
= tcp_sk(sk
);
4874 SOCK_DEBUG(sk
, "prune_queue: c=%x\n", tp
->copied_seq
);
4876 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PRUNECALLED
);
4878 if (atomic_read(&sk
->sk_rmem_alloc
) >= sk
->sk_rcvbuf
)
4879 tcp_clamp_window(sk
);
4880 else if (sk_under_memory_pressure(sk
))
4881 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U * tp
->advmss
);
4883 tcp_collapse_ofo_queue(sk
);
4884 if (!skb_queue_empty(&sk
->sk_receive_queue
))
4885 tcp_collapse(sk
, &sk
->sk_receive_queue
,
4886 skb_peek(&sk
->sk_receive_queue
),
4888 tp
->copied_seq
, tp
->rcv_nxt
);
4891 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4894 /* Collapsing did not help, destructive actions follow.
4895 * This must not ever occur. */
4897 tcp_prune_ofo_queue(sk
);
4899 if (atomic_read(&sk
->sk_rmem_alloc
) <= sk
->sk_rcvbuf
)
4902 /* If we are really being abused, tell the caller to silently
4903 * drop receive data on the floor. It will get retransmitted
4904 * and hopefully then we'll have sufficient space.
4906 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_RCVPRUNED
);
4908 /* Massive buffer overcommit. */
4913 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
4914 * As additional protections, we do not touch cwnd in retransmission phases,
4915 * and if application hit its sndbuf limit recently.
4917 void tcp_cwnd_application_limited(struct sock
*sk
)
4919 struct tcp_sock
*tp
= tcp_sk(sk
);
4921 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
4922 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
4923 /* Limited by application or receiver window. */
4924 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
4925 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
4926 if (win_used
< tp
->snd_cwnd
) {
4927 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
4928 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
4930 tp
->snd_cwnd_used
= 0;
4932 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4935 static int tcp_should_expand_sndbuf(const struct sock
*sk
)
4937 const struct tcp_sock
*tp
= tcp_sk(sk
);
4939 /* If the user specified a specific send buffer setting, do
4942 if (sk
->sk_userlocks
& SOCK_SNDBUF_LOCK
)
4945 /* If we are under global TCP memory pressure, do not expand. */
4946 if (sk_under_memory_pressure(sk
))
4949 /* If we are under soft global TCP memory pressure, do not expand. */
4950 if (sk_memory_allocated(sk
) >= sk_prot_mem_limits(sk
, 0))
4953 /* If we filled the congestion window, do not expand. */
4954 if (tp
->packets_out
>= tp
->snd_cwnd
)
4960 /* When incoming ACK allowed to free some skb from write_queue,
4961 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket
4962 * on the exit from tcp input handler.
4964 * PROBLEM: sndbuf expansion does not work well with largesend.
4966 static void tcp_new_space(struct sock
*sk
)
4968 struct tcp_sock
*tp
= tcp_sk(sk
);
4970 if (tcp_should_expand_sndbuf(sk
)) {
4971 int sndmem
= SKB_TRUESIZE(max_t(u32
,
4972 tp
->rx_opt
.mss_clamp
,
4975 int demanded
= max_t(unsigned int, tp
->snd_cwnd
,
4976 tp
->reordering
+ 1);
4977 sndmem
*= 2 * demanded
;
4978 if (sndmem
> sk
->sk_sndbuf
)
4979 sk
->sk_sndbuf
= min(sndmem
, sysctl_tcp_wmem
[2]);
4980 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
4983 sk
->sk_write_space(sk
);
4986 static void tcp_check_space(struct sock
*sk
)
4988 if (sock_flag(sk
, SOCK_QUEUE_SHRUNK
)) {
4989 sock_reset_flag(sk
, SOCK_QUEUE_SHRUNK
);
4990 if (sk
->sk_socket
&&
4991 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
))
4996 static inline void tcp_data_snd_check(struct sock
*sk
)
4998 tcp_push_pending_frames(sk
);
4999 tcp_check_space(sk
);
5003 * Check if sending an ack is needed.
5005 static void __tcp_ack_snd_check(struct sock
*sk
, int ofo_possible
)
5007 struct tcp_sock
*tp
= tcp_sk(sk
);
5009 /* More than one full frame received... */
5010 if (((tp
->rcv_nxt
- tp
->rcv_wup
) > inet_csk(sk
)->icsk_ack
.rcv_mss
&&
5011 /* ... and right edge of window advances far enough.
5012 * (tcp_recvmsg() will send ACK otherwise). Or...
5014 __tcp_select_window(sk
) >= tp
->rcv_wnd
) ||
5015 /* We ACK each frame or... */
5016 tcp_in_quickack_mode(sk
) ||
5017 /* We have out of order data. */
5018 (ofo_possible
&& skb_peek(&tp
->out_of_order_queue
))) {
5019 /* Then ack it now */
5022 /* Else, send delayed ack. */
5023 tcp_send_delayed_ack(sk
);
5027 static inline void tcp_ack_snd_check(struct sock
*sk
)
5029 if (!inet_csk_ack_scheduled(sk
)) {
5030 /* We sent a data segment already. */
5033 __tcp_ack_snd_check(sk
, 1);
5037 * This routine is only called when we have urgent data
5038 * signaled. Its the 'slow' part of tcp_urg. It could be
5039 * moved inline now as tcp_urg is only called from one
5040 * place. We handle URGent data wrong. We have to - as
5041 * BSD still doesn't use the correction from RFC961.
5042 * For 1003.1g we should support a new option TCP_STDURG to permit
5043 * either form (or just set the sysctl tcp_stdurg).
5046 static void tcp_check_urg(struct sock
*sk
, const struct tcphdr
*th
)
5048 struct tcp_sock
*tp
= tcp_sk(sk
);
5049 u32 ptr
= ntohs(th
->urg_ptr
);
5051 if (ptr
&& !sysctl_tcp_stdurg
)
5053 ptr
+= ntohl(th
->seq
);
5055 /* Ignore urgent data that we've already seen and read. */
5056 if (after(tp
->copied_seq
, ptr
))
5059 /* Do not replay urg ptr.
5061 * NOTE: interesting situation not covered by specs.
5062 * Misbehaving sender may send urg ptr, pointing to segment,
5063 * which we already have in ofo queue. We are not able to fetch
5064 * such data and will stay in TCP_URG_NOTYET until will be eaten
5065 * by recvmsg(). Seems, we are not obliged to handle such wicked
5066 * situations. But it is worth to think about possibility of some
5067 * DoSes using some hypothetical application level deadlock.
5069 if (before(ptr
, tp
->rcv_nxt
))
5072 /* Do we already have a newer (or duplicate) urgent pointer? */
5073 if (tp
->urg_data
&& !after(ptr
, tp
->urg_seq
))
5076 /* Tell the world about our new urgent pointer. */
5079 /* We may be adding urgent data when the last byte read was
5080 * urgent. To do this requires some care. We cannot just ignore
5081 * tp->copied_seq since we would read the last urgent byte again
5082 * as data, nor can we alter copied_seq until this data arrives
5083 * or we break the semantics of SIOCATMARK (and thus sockatmark())
5085 * NOTE. Double Dutch. Rendering to plain English: author of comment
5086 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB);
5087 * and expect that both A and B disappear from stream. This is _wrong_.
5088 * Though this happens in BSD with high probability, this is occasional.
5089 * Any application relying on this is buggy. Note also, that fix "works"
5090 * only in this artificial test. Insert some normal data between A and B and we will
5091 * decline of BSD again. Verdict: it is better to remove to trap
5094 if (tp
->urg_seq
== tp
->copied_seq
&& tp
->urg_data
&&
5095 !sock_flag(sk
, SOCK_URGINLINE
) && tp
->copied_seq
!= tp
->rcv_nxt
) {
5096 struct sk_buff
*skb
= skb_peek(&sk
->sk_receive_queue
);
5098 if (skb
&& !before(tp
->copied_seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5099 __skb_unlink(skb
, &sk
->sk_receive_queue
);
5104 tp
->urg_data
= TCP_URG_NOTYET
;
5107 /* Disable header prediction. */
5111 /* This is the 'fast' part of urgent handling. */
5112 static void tcp_urg(struct sock
*sk
, struct sk_buff
*skb
, const struct tcphdr
*th
)
5114 struct tcp_sock
*tp
= tcp_sk(sk
);
5116 /* Check if we get a new urgent pointer - normally not. */
5118 tcp_check_urg(sk
, th
);
5120 /* Do we wait for any urgent data? - normally not... */
5121 if (tp
->urg_data
== TCP_URG_NOTYET
) {
5122 u32 ptr
= tp
->urg_seq
- ntohl(th
->seq
) + (th
->doff
* 4) -
5125 /* Is the urgent pointer pointing into this packet? */
5126 if (ptr
< skb
->len
) {
5128 if (skb_copy_bits(skb
, ptr
, &tmp
, 1))
5130 tp
->urg_data
= TCP_URG_VALID
| tmp
;
5131 if (!sock_flag(sk
, SOCK_DEAD
))
5132 sk
->sk_data_ready(sk
, 0);
5137 static int tcp_copy_to_iovec(struct sock
*sk
, struct sk_buff
*skb
, int hlen
)
5139 struct tcp_sock
*tp
= tcp_sk(sk
);
5140 int chunk
= skb
->len
- hlen
;
5144 if (skb_csum_unnecessary(skb
))
5145 err
= skb_copy_datagram_iovec(skb
, hlen
, tp
->ucopy
.iov
, chunk
);
5147 err
= skb_copy_and_csum_datagram_iovec(skb
, hlen
,
5151 tp
->ucopy
.len
-= chunk
;
5152 tp
->copied_seq
+= chunk
;
5153 tcp_rcv_space_adjust(sk
);
5160 static __sum16
__tcp_checksum_complete_user(struct sock
*sk
,
5161 struct sk_buff
*skb
)
5165 if (sock_owned_by_user(sk
)) {
5167 result
= __tcp_checksum_complete(skb
);
5170 result
= __tcp_checksum_complete(skb
);
5175 static inline int tcp_checksum_complete_user(struct sock
*sk
,
5176 struct sk_buff
*skb
)
5178 return !skb_csum_unnecessary(skb
) &&
5179 __tcp_checksum_complete_user(sk
, skb
);
5182 #ifdef CONFIG_NET_DMA
5183 static int tcp_dma_try_early_copy(struct sock
*sk
, struct sk_buff
*skb
,
5186 struct tcp_sock
*tp
= tcp_sk(sk
);
5187 int chunk
= skb
->len
- hlen
;
5189 int copied_early
= 0;
5191 if (tp
->ucopy
.wakeup
)
5194 if (!tp
->ucopy
.dma_chan
&& tp
->ucopy
.pinned_list
)
5195 tp
->ucopy
.dma_chan
= dma_find_channel(DMA_MEMCPY
);
5197 if (tp
->ucopy
.dma_chan
&& skb_csum_unnecessary(skb
)) {
5199 dma_cookie
= dma_skb_copy_datagram_iovec(tp
->ucopy
.dma_chan
,
5201 tp
->ucopy
.iov
, chunk
,
5202 tp
->ucopy
.pinned_list
);
5207 tp
->ucopy
.dma_cookie
= dma_cookie
;
5210 tp
->ucopy
.len
-= chunk
;
5211 tp
->copied_seq
+= chunk
;
5212 tcp_rcv_space_adjust(sk
);
5214 if ((tp
->ucopy
.len
== 0) ||
5215 (tcp_flag_word(tcp_hdr(skb
)) & TCP_FLAG_PSH
) ||
5216 (atomic_read(&sk
->sk_rmem_alloc
) > (sk
->sk_rcvbuf
>> 1))) {
5217 tp
->ucopy
.wakeup
= 1;
5218 sk
->sk_data_ready(sk
, 0);
5220 } else if (chunk
> 0) {
5221 tp
->ucopy
.wakeup
= 1;
5222 sk
->sk_data_ready(sk
, 0);
5225 return copied_early
;
5227 #endif /* CONFIG_NET_DMA */
5229 /* Does PAWS and seqno based validation of an incoming segment, flags will
5230 * play significant role here.
5232 static int tcp_validate_incoming(struct sock
*sk
, struct sk_buff
*skb
,
5233 const struct tcphdr
*th
, int syn_inerr
)
5235 const u8
*hash_location
;
5236 struct tcp_sock
*tp
= tcp_sk(sk
);
5238 /* RFC1323: H1. Apply PAWS check first. */
5239 if (tcp_fast_parse_options(skb
, th
, tp
, &hash_location
) &&
5240 tp
->rx_opt
.saw_tstamp
&&
5241 tcp_paws_discard(sk
, skb
)) {
5243 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSESTABREJECTED
);
5244 tcp_send_dupack(sk
, skb
);
5247 /* Reset is accepted even if it did not pass PAWS. */
5250 /* Step 1: check sequence number */
5251 if (!tcp_sequence(tp
, TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(skb
)->end_seq
)) {
5252 /* RFC793, page 37: "In all states except SYN-SENT, all reset
5253 * (RST) segments are validated by checking their SEQ-fields."
5254 * And page 69: "If an incoming segment is not acceptable,
5255 * an acknowledgment should be sent in reply (unless the RST
5256 * bit is set, if so drop the segment and return)".
5259 tcp_send_dupack(sk
, skb
);
5263 /* Step 2: check RST bit */
5269 /* ts_recent update must be made after we are sure that the packet
5272 tcp_replace_ts_recent(tp
, TCP_SKB_CB(skb
)->seq
);
5274 /* step 3: check security and precedence [ignored] */
5276 /* step 4: Check for a SYN in window. */
5277 if (th
->syn
&& !before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
)) {
5279 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5280 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONSYN
);
5293 * TCP receive function for the ESTABLISHED state.
5295 * It is split into a fast path and a slow path. The fast path is
5297 * - A zero window was announced from us - zero window probing
5298 * is only handled properly in the slow path.
5299 * - Out of order segments arrived.
5300 * - Urgent data is expected.
5301 * - There is no buffer space left
5302 * - Unexpected TCP flags/window values/header lengths are received
5303 * (detected by checking the TCP header against pred_flags)
5304 * - Data is sent in both directions. Fast path only supports pure senders
5305 * or pure receivers (this means either the sequence number or the ack
5306 * value must stay constant)
5307 * - Unexpected TCP option.
5309 * When these conditions are not satisfied it drops into a standard
5310 * receive procedure patterned after RFC793 to handle all cases.
5311 * The first three cases are guaranteed by proper pred_flags setting,
5312 * the rest is checked inline. Fast processing is turned on in
5313 * tcp_data_queue when everything is OK.
5315 int tcp_rcv_established(struct sock
*sk
, struct sk_buff
*skb
,
5316 const struct tcphdr
*th
, unsigned int len
)
5318 struct tcp_sock
*tp
= tcp_sk(sk
);
5322 * Header prediction.
5323 * The code loosely follows the one in the famous
5324 * "30 instruction TCP receive" Van Jacobson mail.
5326 * Van's trick is to deposit buffers into socket queue
5327 * on a device interrupt, to call tcp_recv function
5328 * on the receive process context and checksum and copy
5329 * the buffer to user space. smart...
5331 * Our current scheme is not silly either but we take the
5332 * extra cost of the net_bh soft interrupt processing...
5333 * We do checksum and copy also but from device to kernel.
5336 tp
->rx_opt
.saw_tstamp
= 0;
5338 /* pred_flags is 0xS?10 << 16 + snd_wnd
5339 * if header_prediction is to be made
5340 * 'S' will always be tp->tcp_header_len >> 2
5341 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to
5342 * turn it off (when there are holes in the receive
5343 * space for instance)
5344 * PSH flag is ignored.
5347 if ((tcp_flag_word(th
) & TCP_HP_BITS
) == tp
->pred_flags
&&
5348 TCP_SKB_CB(skb
)->seq
== tp
->rcv_nxt
&&
5349 !after(TCP_SKB_CB(skb
)->ack_seq
, tp
->snd_nxt
)) {
5350 int tcp_header_len
= tp
->tcp_header_len
;
5352 /* Timestamp header prediction: tcp_header_len
5353 * is automatically equal to th->doff*4 due to pred_flags
5357 /* Check timestamp */
5358 if (tcp_header_len
== sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) {
5359 /* No? Slow path! */
5360 if (!tcp_parse_aligned_timestamp(tp
, th
))
5363 /* If PAWS failed, check it more carefully in slow path */
5364 if ((s32
)(tp
->rx_opt
.rcv_tsval
- tp
->rx_opt
.ts_recent
) < 0)
5367 /* DO NOT update ts_recent here, if checksum fails
5368 * and timestamp was corrupted part, it will result
5369 * in a hung connection since we will drop all
5370 * future packets due to the PAWS test.
5374 if (len
<= tcp_header_len
) {
5375 /* Bulk data transfer: sender */
5376 if (len
== tcp_header_len
) {
5377 /* Predicted packet is in window by definition.
5378 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5379 * Hence, check seq<=rcv_wup reduces to:
5381 if (tcp_header_len
==
5382 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5383 tp
->rcv_nxt
== tp
->rcv_wup
)
5384 tcp_store_ts_recent(tp
);
5386 /* We know that such packets are checksummed
5389 tcp_ack(sk
, skb
, 0);
5391 tcp_data_snd_check(sk
);
5393 } else { /* Header too small */
5394 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5399 int copied_early
= 0;
5401 if (tp
->copied_seq
== tp
->rcv_nxt
&&
5402 len
- tcp_header_len
<= tp
->ucopy
.len
) {
5403 #ifdef CONFIG_NET_DMA
5404 if (tcp_dma_try_early_copy(sk
, skb
, tcp_header_len
)) {
5409 if (tp
->ucopy
.task
== current
&&
5410 sock_owned_by_user(sk
) && !copied_early
) {
5411 __set_current_state(TASK_RUNNING
);
5413 if (!tcp_copy_to_iovec(sk
, skb
, tcp_header_len
))
5417 /* Predicted packet is in window by definition.
5418 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5419 * Hence, check seq<=rcv_wup reduces to:
5421 if (tcp_header_len
==
5422 (sizeof(struct tcphdr
) +
5423 TCPOLEN_TSTAMP_ALIGNED
) &&
5424 tp
->rcv_nxt
== tp
->rcv_wup
)
5425 tcp_store_ts_recent(tp
);
5427 tcp_rcv_rtt_measure_ts(sk
, skb
);
5429 __skb_pull(skb
, tcp_header_len
);
5430 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5431 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITSTOUSER
);
5434 tcp_cleanup_rbuf(sk
, skb
->len
);
5437 if (tcp_checksum_complete_user(sk
, skb
))
5440 /* Predicted packet is in window by definition.
5441 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
5442 * Hence, check seq<=rcv_wup reduces to:
5444 if (tcp_header_len
==
5445 (sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
) &&
5446 tp
->rcv_nxt
== tp
->rcv_wup
)
5447 tcp_store_ts_recent(tp
);
5449 tcp_rcv_rtt_measure_ts(sk
, skb
);
5451 if ((int)skb
->truesize
> sk
->sk_forward_alloc
)
5454 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPHPHITS
);
5456 /* Bulk data transfer: receiver */
5457 __skb_pull(skb
, tcp_header_len
);
5458 __skb_queue_tail(&sk
->sk_receive_queue
, skb
);
5459 skb_set_owner_r(skb
, sk
);
5460 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->end_seq
;
5463 tcp_event_data_recv(sk
, skb
);
5465 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_una
) {
5466 /* Well, only one small jumplet in fast path... */
5467 tcp_ack(sk
, skb
, FLAG_DATA
);
5468 tcp_data_snd_check(sk
);
5469 if (!inet_csk_ack_scheduled(sk
))
5473 if (!copied_early
|| tp
->rcv_nxt
!= tp
->rcv_wup
)
5474 __tcp_ack_snd_check(sk
, 0);
5476 #ifdef CONFIG_NET_DMA
5478 __skb_queue_tail(&sk
->sk_async_wait_queue
, skb
);
5484 sk
->sk_data_ready(sk
, 0);
5490 if (len
< (th
->doff
<< 2) || tcp_checksum_complete_user(sk
, skb
))
5494 * Standard slow path.
5497 res
= tcp_validate_incoming(sk
, skb
, th
, 1);
5502 if (th
->ack
&& tcp_ack(sk
, skb
, FLAG_SLOWPATH
) < 0)
5505 tcp_rcv_rtt_measure_ts(sk
, skb
);
5507 /* Process urgent data. */
5508 tcp_urg(sk
, skb
, th
);
5510 /* step 7: process the segment text */
5511 tcp_data_queue(sk
, skb
);
5513 tcp_data_snd_check(sk
);
5514 tcp_ack_snd_check(sk
);
5518 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_INERRS
);
5524 EXPORT_SYMBOL(tcp_rcv_established
);
5526 static int tcp_rcv_synsent_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5527 const struct tcphdr
*th
, unsigned int len
)
5529 const u8
*hash_location
;
5530 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5531 struct tcp_sock
*tp
= tcp_sk(sk
);
5532 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
5533 int saved_clamp
= tp
->rx_opt
.mss_clamp
;
5535 tcp_parse_options(skb
, &tp
->rx_opt
, &hash_location
, 0);
5539 * "If the state is SYN-SENT then
5540 * first check the ACK bit
5541 * If the ACK bit is set
5542 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send
5543 * a reset (unless the RST bit is set, if so drop
5544 * the segment and return)"
5546 * We do not send data with SYN, so that RFC-correct
5549 if (TCP_SKB_CB(skb
)->ack_seq
!= tp
->snd_nxt
)
5550 goto reset_and_undo
;
5552 if (tp
->rx_opt
.saw_tstamp
&& tp
->rx_opt
.rcv_tsecr
&&
5553 !between(tp
->rx_opt
.rcv_tsecr
, tp
->retrans_stamp
,
5555 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_PAWSACTIVEREJECTED
);
5556 goto reset_and_undo
;
5559 /* Now ACK is acceptable.
5561 * "If the RST bit is set
5562 * If the ACK was acceptable then signal the user "error:
5563 * connection reset", drop the segment, enter CLOSED state,
5564 * delete TCB, and return."
5573 * "fifth, if neither of the SYN or RST bits is set then
5574 * drop the segment and return."
5580 goto discard_and_undo
;
5583 * "If the SYN bit is on ...
5584 * are acceptable then ...
5585 * (our SYN has been ACKed), change the connection
5586 * state to ESTABLISHED..."
5589 TCP_ECN_rcv_synack(tp
, th
);
5591 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5592 tcp_ack(sk
, skb
, FLAG_SLOWPATH
);
5594 /* Ok.. it's good. Set up sequence numbers and
5595 * move to established.
5597 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5598 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5600 /* RFC1323: The window in SYN & SYN/ACK segments is
5603 tp
->snd_wnd
= ntohs(th
->window
);
5604 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5606 if (!tp
->rx_opt
.wscale_ok
) {
5607 tp
->rx_opt
.snd_wscale
= tp
->rx_opt
.rcv_wscale
= 0;
5608 tp
->window_clamp
= min(tp
->window_clamp
, 65535U);
5611 if (tp
->rx_opt
.saw_tstamp
) {
5612 tp
->rx_opt
.tstamp_ok
= 1;
5613 tp
->tcp_header_len
=
5614 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5615 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5616 tcp_store_ts_recent(tp
);
5618 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5621 if (tcp_is_sack(tp
) && sysctl_tcp_fack
)
5622 tcp_enable_fack(tp
);
5625 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5626 tcp_initialize_rcv_mss(sk
);
5628 /* Remember, tcp_poll() does not lock socket!
5629 * Change state from SYN-SENT only after copied_seq
5630 * is initialized. */
5631 tp
->copied_seq
= tp
->rcv_nxt
;
5634 cvp
->cookie_pair_size
> 0 &&
5635 tp
->rx_opt
.cookie_plus
> 0) {
5636 int cookie_size
= tp
->rx_opt
.cookie_plus
5637 - TCPOLEN_COOKIE_BASE
;
5638 int cookie_pair_size
= cookie_size
5639 + cvp
->cookie_desired
;
5641 /* A cookie extension option was sent and returned.
5642 * Note that each incoming SYNACK replaces the
5643 * Responder cookie. The initial exchange is most
5644 * fragile, as protection against spoofing relies
5645 * entirely upon the sequence and timestamp (above).
5646 * This replacement strategy allows the correct pair to
5647 * pass through, while any others will be filtered via
5648 * Responder verification later.
5650 if (sizeof(cvp
->cookie_pair
) >= cookie_pair_size
) {
5651 memcpy(&cvp
->cookie_pair
[cvp
->cookie_desired
],
5652 hash_location
, cookie_size
);
5653 cvp
->cookie_pair_size
= cookie_pair_size
;
5658 tcp_set_state(sk
, TCP_ESTABLISHED
);
5660 security_inet_conn_established(sk
, skb
);
5662 /* Make sure socket is routed, for correct metrics. */
5663 icsk
->icsk_af_ops
->rebuild_header(sk
);
5665 tcp_init_metrics(sk
);
5667 tcp_init_congestion_control(sk
);
5669 /* Prevent spurious tcp_cwnd_restart() on first data
5672 tp
->lsndtime
= tcp_time_stamp
;
5674 tcp_init_buffer_space(sk
);
5676 if (sock_flag(sk
, SOCK_KEEPOPEN
))
5677 inet_csk_reset_keepalive_timer(sk
, keepalive_time_when(tp
));
5679 if (!tp
->rx_opt
.snd_wscale
)
5680 __tcp_fast_path_on(tp
, tp
->snd_wnd
);
5684 if (!sock_flag(sk
, SOCK_DEAD
)) {
5685 sk
->sk_state_change(sk
);
5686 sk_wake_async(sk
, SOCK_WAKE_IO
, POLL_OUT
);
5689 if (sk
->sk_write_pending
||
5690 icsk
->icsk_accept_queue
.rskq_defer_accept
||
5691 icsk
->icsk_ack
.pingpong
) {
5692 /* Save one ACK. Data will be ready after
5693 * several ticks, if write_pending is set.
5695 * It may be deleted, but with this feature tcpdumps
5696 * look so _wonderfully_ clever, that I was not able
5697 * to stand against the temptation 8) --ANK
5699 inet_csk_schedule_ack(sk
);
5700 icsk
->icsk_ack
.lrcvtime
= tcp_time_stamp
;
5701 icsk
->icsk_ack
.ato
= TCP_ATO_MIN
;
5702 tcp_incr_quickack(sk
);
5703 tcp_enter_quickack_mode(sk
);
5704 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
5705 TCP_DELACK_MAX
, TCP_RTO_MAX
);
5716 /* No ACK in the segment */
5720 * "If the RST bit is set
5722 * Otherwise (no ACK) drop the segment and return."
5725 goto discard_and_undo
;
5729 if (tp
->rx_opt
.ts_recent_stamp
&& tp
->rx_opt
.saw_tstamp
&&
5730 tcp_paws_reject(&tp
->rx_opt
, 0))
5731 goto discard_and_undo
;
5734 /* We see SYN without ACK. It is attempt of
5735 * simultaneous connect with crossed SYNs.
5736 * Particularly, it can be connect to self.
5738 tcp_set_state(sk
, TCP_SYN_RECV
);
5740 if (tp
->rx_opt
.saw_tstamp
) {
5741 tp
->rx_opt
.tstamp_ok
= 1;
5742 tcp_store_ts_recent(tp
);
5743 tp
->tcp_header_len
=
5744 sizeof(struct tcphdr
) + TCPOLEN_TSTAMP_ALIGNED
;
5746 tp
->tcp_header_len
= sizeof(struct tcphdr
);
5749 tp
->rcv_nxt
= TCP_SKB_CB(skb
)->seq
+ 1;
5750 tp
->rcv_wup
= TCP_SKB_CB(skb
)->seq
+ 1;
5752 /* RFC1323: The window in SYN & SYN/ACK segments is
5755 tp
->snd_wnd
= ntohs(th
->window
);
5756 tp
->snd_wl1
= TCP_SKB_CB(skb
)->seq
;
5757 tp
->max_window
= tp
->snd_wnd
;
5759 TCP_ECN_rcv_syn(tp
, th
);
5762 tcp_sync_mss(sk
, icsk
->icsk_pmtu_cookie
);
5763 tcp_initialize_rcv_mss(sk
);
5765 tcp_send_synack(sk
);
5767 /* Note, we could accept data and URG from this segment.
5768 * There are no obstacles to make this.
5770 * However, if we ignore data in ACKless segments sometimes,
5771 * we have no reasons to accept it sometimes.
5772 * Also, seems the code doing it in step6 of tcp_rcv_state_process
5773 * is not flawless. So, discard packet for sanity.
5774 * Uncomment this return to process the data.
5781 /* "fifth, if neither of the SYN or RST bits is set then
5782 * drop the segment and return."
5786 tcp_clear_options(&tp
->rx_opt
);
5787 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5791 tcp_clear_options(&tp
->rx_opt
);
5792 tp
->rx_opt
.mss_clamp
= saved_clamp
;
5797 * This function implements the receiving procedure of RFC 793 for
5798 * all states except ESTABLISHED and TIME_WAIT.
5799 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be
5800 * address independent.
5803 int tcp_rcv_state_process(struct sock
*sk
, struct sk_buff
*skb
,
5804 const struct tcphdr
*th
, unsigned int len
)
5806 struct tcp_sock
*tp
= tcp_sk(sk
);
5807 struct inet_connection_sock
*icsk
= inet_csk(sk
);
5811 tp
->rx_opt
.saw_tstamp
= 0;
5813 switch (sk
->sk_state
) {
5827 if (icsk
->icsk_af_ops
->conn_request(sk
, skb
) < 0)
5830 /* Now we have several options: In theory there is
5831 * nothing else in the frame. KA9Q has an option to
5832 * send data with the syn, BSD accepts data with the
5833 * syn up to the [to be] advertised window and
5834 * Solaris 2.1 gives you a protocol error. For now
5835 * we just ignore it, that fits the spec precisely
5836 * and avoids incompatibilities. It would be nice in
5837 * future to drop through and process the data.
5839 * Now that TTCP is starting to be used we ought to
5841 * But, this leaves one open to an easy denial of
5842 * service attack, and SYN cookies can't defend
5843 * against this problem. So, we drop the data
5844 * in the interest of security over speed unless
5845 * it's still in use.
5853 queued
= tcp_rcv_synsent_state_process(sk
, skb
, th
, len
);
5857 /* Do step6 onward by hand. */
5858 tcp_urg(sk
, skb
, th
);
5860 tcp_data_snd_check(sk
);
5864 res
= tcp_validate_incoming(sk
, skb
, th
, 0);
5868 /* step 5: check the ACK field */
5870 int acceptable
= tcp_ack(sk
, skb
, FLAG_SLOWPATH
) > 0;
5872 switch (sk
->sk_state
) {
5875 tp
->copied_seq
= tp
->rcv_nxt
;
5877 tcp_set_state(sk
, TCP_ESTABLISHED
);
5878 sk
->sk_state_change(sk
);
5880 /* Note, that this wakeup is only for marginal
5881 * crossed SYN case. Passively open sockets
5882 * are not waked up, because sk->sk_sleep ==
5883 * NULL and sk->sk_socket == NULL.
5887 SOCK_WAKE_IO
, POLL_OUT
);
5889 tp
->snd_una
= TCP_SKB_CB(skb
)->ack_seq
;
5890 tp
->snd_wnd
= ntohs(th
->window
) <<
5891 tp
->rx_opt
.snd_wscale
;
5892 tcp_init_wl(tp
, TCP_SKB_CB(skb
)->seq
);
5894 if (tp
->rx_opt
.tstamp_ok
)
5895 tp
->advmss
-= TCPOLEN_TSTAMP_ALIGNED
;
5897 /* Make sure socket is routed, for
5900 icsk
->icsk_af_ops
->rebuild_header(sk
);
5902 tcp_init_metrics(sk
);
5904 tcp_init_congestion_control(sk
);
5906 /* Prevent spurious tcp_cwnd_restart() on
5907 * first data packet.
5909 tp
->lsndtime
= tcp_time_stamp
;
5912 tcp_initialize_rcv_mss(sk
);
5913 tcp_init_buffer_space(sk
);
5914 tcp_fast_path_on(tp
);
5921 if (tp
->snd_una
== tp
->write_seq
) {
5922 tcp_set_state(sk
, TCP_FIN_WAIT2
);
5923 sk
->sk_shutdown
|= SEND_SHUTDOWN
;
5924 dst_confirm(__sk_dst_get(sk
));
5926 if (!sock_flag(sk
, SOCK_DEAD
))
5927 /* Wake up lingering close() */
5928 sk
->sk_state_change(sk
);
5932 if (tp
->linger2
< 0 ||
5933 (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5934 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
))) {
5936 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
5940 tmo
= tcp_fin_time(sk
);
5941 if (tmo
> TCP_TIMEWAIT_LEN
) {
5942 inet_csk_reset_keepalive_timer(sk
, tmo
- TCP_TIMEWAIT_LEN
);
5943 } else if (th
->fin
|| sock_owned_by_user(sk
)) {
5944 /* Bad case. We could lose such FIN otherwise.
5945 * It is not a big problem, but it looks confusing
5946 * and not so rare event. We still can lose it now,
5947 * if it spins in bh_lock_sock(), but it is really
5950 inet_csk_reset_keepalive_timer(sk
, tmo
);
5952 tcp_time_wait(sk
, TCP_FIN_WAIT2
, tmo
);
5960 if (tp
->snd_una
== tp
->write_seq
) {
5961 tcp_time_wait(sk
, TCP_TIME_WAIT
, 0);
5967 if (tp
->snd_una
== tp
->write_seq
) {
5968 tcp_update_metrics(sk
);
5977 /* step 6: check the URG bit */
5978 tcp_urg(sk
, skb
, th
);
5980 /* step 7: process the segment text */
5981 switch (sk
->sk_state
) {
5982 case TCP_CLOSE_WAIT
:
5985 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->rcv_nxt
))
5989 /* RFC 793 says to queue data in these states,
5990 * RFC 1122 says we MUST send a reset.
5991 * BSD 4.4 also does reset.
5993 if (sk
->sk_shutdown
& RCV_SHUTDOWN
) {
5994 if (TCP_SKB_CB(skb
)->end_seq
!= TCP_SKB_CB(skb
)->seq
&&
5995 after(TCP_SKB_CB(skb
)->end_seq
- th
->fin
, tp
->rcv_nxt
)) {
5996 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPABORTONDATA
);
6002 case TCP_ESTABLISHED
:
6003 tcp_data_queue(sk
, skb
);
6008 /* tcp_data could move socket to TIME-WAIT */
6009 if (sk
->sk_state
!= TCP_CLOSE
) {
6010 tcp_data_snd_check(sk
);
6011 tcp_ack_snd_check(sk
);
6020 EXPORT_SYMBOL(tcp_rcv_state_process
);