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>
22 * Changes: Pedro Roque : Retransmit queue handled by TCP.
23 * : Fragmentation on mtu decrease
24 * : Segment collapse on retransmit
27 * Linus Torvalds : send_delayed_ack
28 * David S. Miller : Charge memory using the right skb
29 * during syn/ack processing.
30 * David S. Miller : Output engine completely rewritten.
31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
32 * Cacophonix Gaul : draft-minshall-nagle-01
33 * J Hadi Salim : ECN support
39 #include <linux/compiler.h>
40 #include <linux/module.h>
42 /* People can turn this off for buggy TCP's found in printers etc. */
43 int sysctl_tcp_retrans_collapse __read_mostly
= 1;
45 /* People can turn this on to work with those rare, broken TCPs that
46 * interpret the window field as a signed quantity.
48 int sysctl_tcp_workaround_signed_windows __read_mostly
= 0;
50 /* This limits the percentage of the congestion window which we
51 * will allow a single TSO frame to consume. Building TSO frames
52 * which are too large can cause TCP streams to be bursty.
54 int sysctl_tcp_tso_win_divisor __read_mostly
= 3;
56 int sysctl_tcp_mtu_probing __read_mostly
= 0;
57 int sysctl_tcp_base_mss __read_mostly
= 512;
59 /* By default, RFC2861 behavior. */
60 int sysctl_tcp_slow_start_after_idle __read_mostly
= 1;
62 static void tcp_event_new_data_sent(struct sock
*sk
, struct sk_buff
*skb
)
64 struct tcp_sock
*tp
= tcp_sk(sk
);
65 unsigned int prior_packets
= tp
->packets_out
;
67 tcp_advance_send_head(sk
, skb
);
68 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
70 /* Don't override Nagle indefinately with F-RTO */
71 if (tp
->frto_counter
== 2)
74 tp
->packets_out
+= tcp_skb_pcount(skb
);
76 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
77 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
80 /* SND.NXT, if window was not shrunk.
81 * If window has been shrunk, what should we make? It is not clear at all.
82 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
83 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
84 * invalid. OK, let's make this for now:
86 static inline __u32
tcp_acceptable_seq(struct sock
*sk
)
88 struct tcp_sock
*tp
= tcp_sk(sk
);
90 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
))
93 return tcp_wnd_end(tp
);
96 /* Calculate mss to advertise in SYN segment.
97 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
99 * 1. It is independent of path mtu.
100 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
101 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
102 * attached devices, because some buggy hosts are confused by
104 * 4. We do not make 3, we advertise MSS, calculated from first
105 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
106 * This may be overridden via information stored in routing table.
107 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
108 * probably even Jumbo".
110 static __u16
tcp_advertise_mss(struct sock
*sk
)
112 struct tcp_sock
*tp
= tcp_sk(sk
);
113 struct dst_entry
*dst
= __sk_dst_get(sk
);
114 int mss
= tp
->advmss
;
116 if (dst
&& dst_metric(dst
, RTAX_ADVMSS
) < mss
) {
117 mss
= dst_metric(dst
, RTAX_ADVMSS
);
124 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
125 * This is the first part of cwnd validation mechanism. */
126 static void tcp_cwnd_restart(struct sock
*sk
, struct dst_entry
*dst
)
128 struct tcp_sock
*tp
= tcp_sk(sk
);
129 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
130 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
131 u32 cwnd
= tp
->snd_cwnd
;
133 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
135 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
136 restart_cwnd
= min(restart_cwnd
, cwnd
);
138 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
140 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
141 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
142 tp
->snd_cwnd_used
= 0;
145 static void tcp_event_data_sent(struct tcp_sock
*tp
,
146 struct sk_buff
*skb
, struct sock
*sk
)
148 struct inet_connection_sock
*icsk
= inet_csk(sk
);
149 const u32 now
= tcp_time_stamp
;
151 if (sysctl_tcp_slow_start_after_idle
&&
152 (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
))
153 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
157 /* If it is a reply for ato after last received
158 * packet, enter pingpong mode.
160 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
161 icsk
->icsk_ack
.pingpong
= 1;
164 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
166 tcp_dec_quickack_mode(sk
, pkts
);
167 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
170 /* Determine a window scaling and initial window to offer.
171 * Based on the assumption that the given amount of space
172 * will be offered. Store the results in the tp structure.
173 * NOTE: for smooth operation initial space offering should
174 * be a multiple of mss if possible. We assume here that mss >= 1.
175 * This MUST be enforced by all callers.
177 void tcp_select_initial_window(int __space
, __u32 mss
,
178 __u32
*rcv_wnd
, __u32
*window_clamp
,
179 int wscale_ok
, __u8
*rcv_wscale
)
181 unsigned int space
= (__space
< 0 ? 0 : __space
);
183 /* If no clamp set the clamp to the max possible scaled window */
184 if (*window_clamp
== 0)
185 (*window_clamp
) = (65535 << 14);
186 space
= min(*window_clamp
, space
);
188 /* Quantize space offering to a multiple of mss if possible. */
190 space
= (space
/ mss
) * mss
;
192 /* NOTE: offering an initial window larger than 32767
193 * will break some buggy TCP stacks. If the admin tells us
194 * it is likely we could be speaking with such a buggy stack
195 * we will truncate our initial window offering to 32K-1
196 * unless the remote has sent us a window scaling option,
197 * which we interpret as a sign the remote TCP is not
198 * misinterpreting the window field as a signed quantity.
200 if (sysctl_tcp_workaround_signed_windows
)
201 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
207 /* Set window scaling on max possible window
208 * See RFC1323 for an explanation of the limit to 14
210 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
211 space
= min_t(u32
, space
, *window_clamp
);
212 while (space
> 65535 && (*rcv_wscale
) < 14) {
218 /* Set initial window to value enough for senders,
219 * following RFC2414. Senders, not following this RFC,
220 * will be satisfied with 2.
222 if (mss
> (1 << *rcv_wscale
)) {
228 if (*rcv_wnd
> init_cwnd
* mss
)
229 *rcv_wnd
= init_cwnd
* mss
;
232 /* Set the clamp no higher than max representable value */
233 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
236 /* Chose a new window to advertise, update state in tcp_sock for the
237 * socket, and return result with RFC1323 scaling applied. The return
238 * value can be stuffed directly into th->window for an outgoing
241 static u16
tcp_select_window(struct sock
*sk
)
243 struct tcp_sock
*tp
= tcp_sk(sk
);
244 u32 cur_win
= tcp_receive_window(tp
);
245 u32 new_win
= __tcp_select_window(sk
);
247 /* Never shrink the offered window */
248 if (new_win
< cur_win
) {
249 /* Danger Will Robinson!
250 * Don't update rcv_wup/rcv_wnd here or else
251 * we will not be able to advertise a zero
252 * window in time. --DaveM
254 * Relax Will Robinson.
256 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
258 tp
->rcv_wnd
= new_win
;
259 tp
->rcv_wup
= tp
->rcv_nxt
;
261 /* Make sure we do not exceed the maximum possible
264 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
265 new_win
= min(new_win
, MAX_TCP_WINDOW
);
267 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
269 /* RFC1323 scaling applied */
270 new_win
>>= tp
->rx_opt
.rcv_wscale
;
272 /* If we advertise zero window, disable fast path. */
279 static inline void TCP_ECN_send_synack(struct tcp_sock
*tp
, struct sk_buff
*skb
)
281 TCP_SKB_CB(skb
)->flags
&= ~TCPCB_FLAG_CWR
;
282 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
283 TCP_SKB_CB(skb
)->flags
&= ~TCPCB_FLAG_ECE
;
286 static inline void TCP_ECN_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
288 struct tcp_sock
*tp
= tcp_sk(sk
);
291 if (sysctl_tcp_ecn
) {
292 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ECE
| TCPCB_FLAG_CWR
;
293 tp
->ecn_flags
= TCP_ECN_OK
;
297 static __inline__
void
298 TCP_ECN_make_synack(struct request_sock
*req
, struct tcphdr
*th
)
300 if (inet_rsk(req
)->ecn_ok
)
304 static inline void TCP_ECN_send(struct sock
*sk
, struct sk_buff
*skb
,
307 struct tcp_sock
*tp
= tcp_sk(sk
);
309 if (tp
->ecn_flags
& TCP_ECN_OK
) {
310 /* Not-retransmitted data segment: set ECT and inject CWR. */
311 if (skb
->len
!= tcp_header_len
&&
312 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
314 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
315 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
316 tcp_hdr(skb
)->cwr
= 1;
317 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
320 /* ACK or retransmitted segment: clear ECT|CE */
321 INET_ECN_dontxmit(sk
);
323 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
324 tcp_hdr(skb
)->ece
= 1;
328 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
329 * auto increment end seqno.
331 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
335 TCP_SKB_CB(skb
)->flags
= flags
;
336 TCP_SKB_CB(skb
)->sacked
= 0;
338 skb_shinfo(skb
)->gso_segs
= 1;
339 skb_shinfo(skb
)->gso_size
= 0;
340 skb_shinfo(skb
)->gso_type
= 0;
342 TCP_SKB_CB(skb
)->seq
= seq
;
343 if (flags
& (TCPCB_FLAG_SYN
| TCPCB_FLAG_FIN
))
345 TCP_SKB_CB(skb
)->end_seq
= seq
;
348 static inline int tcp_urg_mode(const struct tcp_sock
*tp
)
350 return tp
->snd_una
!= tp
->snd_up
;
353 #define OPTION_SACK_ADVERTISE (1 << 0)
354 #define OPTION_TS (1 << 1)
355 #define OPTION_MD5 (1 << 2)
357 struct tcp_out_options
{
358 u8 options
; /* bit field of OPTION_* */
359 u8 ws
; /* window scale, 0 to disable */
360 u8 num_sack_blocks
; /* number of SACK blocks to include */
361 u16 mss
; /* 0 to disable */
362 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
365 /* Beware: Something in the Internet is very sensitive to the ordering of
366 * TCP options, we learned this through the hard way, so be careful here.
367 * Luckily we can at least blame others for their non-compliance but from
368 * inter-operatibility perspective it seems that we're somewhat stuck with
369 * the ordering which we have been using if we want to keep working with
370 * those broken things (not that it currently hurts anybody as there isn't
371 * particular reason why the ordering would need to be changed).
373 * At least SACK_PERM as the first option is known to lead to a disaster
374 * (but it may well be that other scenarios fail similarly).
376 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
377 const struct tcp_out_options
*opts
,
379 if (unlikely(OPTION_MD5
& opts
->options
)) {
380 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
382 (TCPOPT_MD5SIG
<< 8) |
384 *md5_hash
= (__u8
*)ptr
;
390 if (unlikely(opts
->mss
)) {
391 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
392 (TCPOLEN_MSS
<< 16) |
396 if (likely(OPTION_TS
& opts
->options
)) {
397 if (unlikely(OPTION_SACK_ADVERTISE
& opts
->options
)) {
398 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
399 (TCPOLEN_SACK_PERM
<< 16) |
400 (TCPOPT_TIMESTAMP
<< 8) |
403 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
405 (TCPOPT_TIMESTAMP
<< 8) |
408 *ptr
++ = htonl(opts
->tsval
);
409 *ptr
++ = htonl(opts
->tsecr
);
412 if (unlikely(OPTION_SACK_ADVERTISE
& opts
->options
&&
413 !(OPTION_TS
& opts
->options
))) {
414 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
416 (TCPOPT_SACK_PERM
<< 8) |
420 if (unlikely(opts
->ws
)) {
421 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
422 (TCPOPT_WINDOW
<< 16) |
423 (TCPOLEN_WINDOW
<< 8) |
427 if (unlikely(opts
->num_sack_blocks
)) {
428 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
429 tp
->duplicate_sack
: tp
->selective_acks
;
432 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
435 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
436 TCPOLEN_SACK_PERBLOCK
)));
438 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
440 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
441 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
444 tp
->rx_opt
.dsack
= 0;
448 static unsigned tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
449 struct tcp_out_options
*opts
,
450 struct tcp_md5sig_key
**md5
) {
451 struct tcp_sock
*tp
= tcp_sk(sk
);
454 #ifdef CONFIG_TCP_MD5SIG
455 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
457 opts
->options
|= OPTION_MD5
;
458 size
+= TCPOLEN_MD5SIG_ALIGNED
;
464 /* We always get an MSS option. The option bytes which will be seen in
465 * normal data packets should timestamps be used, must be in the MSS
466 * advertised. But we subtract them from tp->mss_cache so that
467 * calculations in tcp_sendmsg are simpler etc. So account for this
468 * fact here if necessary. If we don't do this correctly, as a
469 * receiver we won't recognize data packets as being full sized when we
470 * should, and thus we won't abide by the delayed ACK rules correctly.
471 * SACKs don't matter, we never delay an ACK when we have any of those
473 opts
->mss
= tcp_advertise_mss(sk
);
474 size
+= TCPOLEN_MSS_ALIGNED
;
476 if (likely(sysctl_tcp_timestamps
&& *md5
== NULL
)) {
477 opts
->options
|= OPTION_TS
;
478 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
479 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
480 size
+= TCPOLEN_TSTAMP_ALIGNED
;
482 if (likely(sysctl_tcp_window_scaling
)) {
483 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
484 if (likely(opts
->ws
))
485 size
+= TCPOLEN_WSCALE_ALIGNED
;
487 if (likely(sysctl_tcp_sack
)) {
488 opts
->options
|= OPTION_SACK_ADVERTISE
;
489 if (unlikely(!(OPTION_TS
& opts
->options
)))
490 size
+= TCPOLEN_SACKPERM_ALIGNED
;
496 static unsigned tcp_synack_options(struct sock
*sk
,
497 struct request_sock
*req
,
498 unsigned mss
, struct sk_buff
*skb
,
499 struct tcp_out_options
*opts
,
500 struct tcp_md5sig_key
**md5
) {
502 struct inet_request_sock
*ireq
= inet_rsk(req
);
505 #ifdef CONFIG_TCP_MD5SIG
506 *md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
508 opts
->options
|= OPTION_MD5
;
509 size
+= TCPOLEN_MD5SIG_ALIGNED
;
515 /* we can't fit any SACK blocks in a packet with MD5 + TS
516 options. There was discussion about disabling SACK rather than TS in
517 order to fit in better with old, buggy kernels, but that was deemed
518 to be unnecessary. */
519 doing_ts
= ireq
->tstamp_ok
&& !(*md5
&& ireq
->sack_ok
);
522 size
+= TCPOLEN_MSS_ALIGNED
;
524 if (likely(ireq
->wscale_ok
)) {
525 opts
->ws
= ireq
->rcv_wscale
;
526 if (likely(opts
->ws
))
527 size
+= TCPOLEN_WSCALE_ALIGNED
;
529 if (likely(doing_ts
)) {
530 opts
->options
|= OPTION_TS
;
531 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
532 opts
->tsecr
= req
->ts_recent
;
533 size
+= TCPOLEN_TSTAMP_ALIGNED
;
535 if (likely(ireq
->sack_ok
)) {
536 opts
->options
|= OPTION_SACK_ADVERTISE
;
537 if (unlikely(!doing_ts
))
538 size
+= TCPOLEN_SACKPERM_ALIGNED
;
544 static unsigned tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
545 struct tcp_out_options
*opts
,
546 struct tcp_md5sig_key
**md5
) {
547 struct tcp_skb_cb
*tcb
= skb
? TCP_SKB_CB(skb
) : NULL
;
548 struct tcp_sock
*tp
= tcp_sk(sk
);
550 unsigned int eff_sacks
;
552 #ifdef CONFIG_TCP_MD5SIG
553 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
554 if (unlikely(*md5
)) {
555 opts
->options
|= OPTION_MD5
;
556 size
+= TCPOLEN_MD5SIG_ALIGNED
;
562 if (likely(tp
->rx_opt
.tstamp_ok
)) {
563 opts
->options
|= OPTION_TS
;
564 opts
->tsval
= tcb
? tcb
->when
: 0;
565 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
566 size
+= TCPOLEN_TSTAMP_ALIGNED
;
569 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
570 if (unlikely(eff_sacks
)) {
571 const unsigned remaining
= MAX_TCP_OPTION_SPACE
- size
;
572 opts
->num_sack_blocks
=
573 min_t(unsigned, eff_sacks
,
574 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
575 TCPOLEN_SACK_PERBLOCK
);
576 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
577 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
583 /* This routine actually transmits TCP packets queued in by
584 * tcp_do_sendmsg(). This is used by both the initial
585 * transmission and possible later retransmissions.
586 * All SKB's seen here are completely headerless. It is our
587 * job to build the TCP header, and pass the packet down to
588 * IP so it can do the same plus pass the packet off to the
591 * We are working here with either a clone of the original
592 * SKB, or a fresh unique copy made by the retransmit engine.
594 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
597 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
598 struct inet_sock
*inet
;
600 struct tcp_skb_cb
*tcb
;
601 struct tcp_out_options opts
;
602 unsigned tcp_options_size
, tcp_header_size
;
603 struct tcp_md5sig_key
*md5
;
604 __u8
*md5_hash_location
;
608 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
610 /* If congestion control is doing timestamping, we must
611 * take such a timestamp before we potentially clone/copy.
613 if (icsk
->icsk_ca_ops
->flags
& TCP_CONG_RTT_STAMP
)
614 __net_timestamp(skb
);
616 if (likely(clone_it
)) {
617 if (unlikely(skb_cloned(skb
)))
618 skb
= pskb_copy(skb
, gfp_mask
);
620 skb
= skb_clone(skb
, gfp_mask
);
627 tcb
= TCP_SKB_CB(skb
);
628 memset(&opts
, 0, sizeof(opts
));
630 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
))
631 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
633 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
635 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
637 if (tcp_packets_in_flight(tp
) == 0)
638 tcp_ca_event(sk
, CA_EVENT_TX_START
);
640 skb_push(skb
, tcp_header_size
);
641 skb_reset_transport_header(skb
);
642 skb_set_owner_w(skb
, sk
);
644 /* Build TCP header and checksum it. */
646 th
->source
= inet
->sport
;
647 th
->dest
= inet
->dport
;
648 th
->seq
= htonl(tcb
->seq
);
649 th
->ack_seq
= htonl(tp
->rcv_nxt
);
650 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
653 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
654 /* RFC1323: The window in SYN & SYN/ACK segments
657 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
659 th
->window
= htons(tcp_select_window(sk
));
664 /* The urg_mode check is necessary during a below snd_una win probe */
665 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
666 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
667 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
669 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
670 th
->urg_ptr
= 0xFFFF;
675 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
, &md5_hash_location
);
676 if (likely((tcb
->flags
& TCPCB_FLAG_SYN
) == 0))
677 TCP_ECN_send(sk
, skb
, tcp_header_size
);
679 #ifdef CONFIG_TCP_MD5SIG
680 /* Calculate the MD5 hash, as we have all we need now */
682 sk
->sk_route_caps
&= ~NETIF_F_GSO_MASK
;
683 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
688 icsk
->icsk_af_ops
->send_check(sk
, skb
->len
, skb
);
690 if (likely(tcb
->flags
& TCPCB_FLAG_ACK
))
691 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
693 if (skb
->len
!= tcp_header_size
)
694 tcp_event_data_sent(tp
, skb
, sk
);
696 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
697 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
699 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, 0);
700 if (likely(err
<= 0))
703 tcp_enter_cwr(sk
, 1);
705 return net_xmit_eval(err
);
708 /* This routine just queue's the buffer
710 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
711 * otherwise socket can stall.
713 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
715 struct tcp_sock
*tp
= tcp_sk(sk
);
717 /* Advance write_seq and place onto the write_queue. */
718 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
719 skb_header_release(skb
);
720 tcp_add_write_queue_tail(sk
, skb
);
721 sk
->sk_wmem_queued
+= skb
->truesize
;
722 sk_mem_charge(sk
, skb
->truesize
);
725 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
,
726 unsigned int mss_now
)
728 if (skb
->len
<= mss_now
|| !sk_can_gso(sk
)) {
729 /* Avoid the costly divide in the normal
732 skb_shinfo(skb
)->gso_segs
= 1;
733 skb_shinfo(skb
)->gso_size
= 0;
734 skb_shinfo(skb
)->gso_type
= 0;
736 skb_shinfo(skb
)->gso_segs
= DIV_ROUND_UP(skb
->len
, mss_now
);
737 skb_shinfo(skb
)->gso_size
= mss_now
;
738 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
742 /* When a modification to fackets out becomes necessary, we need to check
743 * skb is counted to fackets_out or not.
745 static void tcp_adjust_fackets_out(struct sock
*sk
, struct sk_buff
*skb
,
748 struct tcp_sock
*tp
= tcp_sk(sk
);
750 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
753 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
754 tp
->fackets_out
-= decr
;
757 /* Function to create two new TCP segments. Shrinks the given segment
758 * to the specified size and appends a new segment with the rest of the
759 * packet to the list. This won't be called frequently, I hope.
760 * Remember, these are still headerless SKBs at this point.
762 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
763 unsigned int mss_now
)
765 struct tcp_sock
*tp
= tcp_sk(sk
);
766 struct sk_buff
*buff
;
767 int nsize
, old_factor
;
771 BUG_ON(len
> skb
->len
);
773 nsize
= skb_headlen(skb
) - len
;
777 if (skb_cloned(skb
) &&
778 skb_is_nonlinear(skb
) &&
779 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
782 /* Get a new skb... force flag on. */
783 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
785 return -ENOMEM
; /* We'll just try again later. */
787 sk
->sk_wmem_queued
+= buff
->truesize
;
788 sk_mem_charge(sk
, buff
->truesize
);
789 nlen
= skb
->len
- len
- nsize
;
790 buff
->truesize
+= nlen
;
791 skb
->truesize
-= nlen
;
793 /* Correct the sequence numbers. */
794 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
795 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
796 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
798 /* PSH and FIN should only be set in the second packet. */
799 flags
= TCP_SKB_CB(skb
)->flags
;
800 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
| TCPCB_FLAG_PSH
);
801 TCP_SKB_CB(buff
)->flags
= flags
;
802 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
804 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
805 /* Copy and checksum data tail into the new buffer. */
806 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
807 skb_put(buff
, nsize
),
812 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
814 skb
->ip_summed
= CHECKSUM_PARTIAL
;
815 skb_split(skb
, buff
, len
);
818 buff
->ip_summed
= skb
->ip_summed
;
820 /* Looks stupid, but our code really uses when of
821 * skbs, which it never sent before. --ANK
823 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
824 buff
->tstamp
= skb
->tstamp
;
826 old_factor
= tcp_skb_pcount(skb
);
828 /* Fix up tso_factor for both original and new SKB. */
829 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
830 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
832 /* If this packet has been sent out already, we must
833 * adjust the various packet counters.
835 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
836 int diff
= old_factor
- tcp_skb_pcount(skb
) -
837 tcp_skb_pcount(buff
);
839 tp
->packets_out
-= diff
;
841 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
842 tp
->sacked_out
-= diff
;
843 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
844 tp
->retrans_out
-= diff
;
846 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
847 tp
->lost_out
-= diff
;
849 /* Adjust Reno SACK estimate. */
850 if (tcp_is_reno(tp
) && diff
> 0) {
851 tcp_dec_pcount_approx_int(&tp
->sacked_out
, diff
);
852 tcp_verify_left_out(tp
);
854 tcp_adjust_fackets_out(sk
, skb
, diff
);
856 if (tp
->lost_skb_hint
&&
857 before(TCP_SKB_CB(skb
)->seq
,
858 TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
859 (tcp_is_fack(tp
) || TCP_SKB_CB(skb
)->sacked
))
860 tp
->lost_cnt_hint
-= diff
;
863 /* Link BUFF into the send queue. */
864 skb_header_release(buff
);
865 tcp_insert_write_queue_after(skb
, buff
, sk
);
870 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
871 * eventually). The difference is that pulled data not copied, but
872 * immediately discarded.
874 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
880 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
881 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
882 put_page(skb_shinfo(skb
)->frags
[i
].page
);
883 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
885 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
887 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
888 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
894 skb_shinfo(skb
)->nr_frags
= k
;
896 skb_reset_tail_pointer(skb
);
897 skb
->data_len
-= len
;
898 skb
->len
= skb
->data_len
;
901 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
903 if (skb_cloned(skb
) && pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
906 /* If len == headlen, we avoid __skb_pull to preserve alignment. */
907 if (unlikely(len
< skb_headlen(skb
)))
908 __skb_pull(skb
, len
);
910 __pskb_trim_head(skb
, len
- skb_headlen(skb
));
912 TCP_SKB_CB(skb
)->seq
+= len
;
913 skb
->ip_summed
= CHECKSUM_PARTIAL
;
915 skb
->truesize
-= len
;
916 sk
->sk_wmem_queued
-= len
;
917 sk_mem_uncharge(sk
, len
);
918 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
920 /* Any change of skb->len requires recalculation of tso
923 if (tcp_skb_pcount(skb
) > 1)
924 tcp_set_skb_tso_segs(sk
, skb
, tcp_current_mss(sk
));
929 /* Not accounting for SACKs here. */
930 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
932 struct tcp_sock
*tp
= tcp_sk(sk
);
933 struct inet_connection_sock
*icsk
= inet_csk(sk
);
936 /* Calculate base mss without TCP options:
937 It is MMS_S - sizeof(tcphdr) of rfc1122
939 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
941 /* Clamp it (mss_clamp does not include tcp options) */
942 if (mss_now
> tp
->rx_opt
.mss_clamp
)
943 mss_now
= tp
->rx_opt
.mss_clamp
;
945 /* Now subtract optional transport overhead */
946 mss_now
-= icsk
->icsk_ext_hdr_len
;
948 /* Then reserve room for full set of TCP options and 8 bytes of data */
952 /* Now subtract TCP options size, not including SACKs */
953 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
958 /* Inverse of above */
959 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
961 struct tcp_sock
*tp
= tcp_sk(sk
);
962 struct inet_connection_sock
*icsk
= inet_csk(sk
);
967 icsk
->icsk_ext_hdr_len
+
968 icsk
->icsk_af_ops
->net_header_len
;
973 void tcp_mtup_init(struct sock
*sk
)
975 struct tcp_sock
*tp
= tcp_sk(sk
);
976 struct inet_connection_sock
*icsk
= inet_csk(sk
);
978 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
979 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
980 icsk
->icsk_af_ops
->net_header_len
;
981 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
982 icsk
->icsk_mtup
.probe_size
= 0;
985 /* This function synchronize snd mss to current pmtu/exthdr set.
987 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
988 for TCP options, but includes only bare TCP header.
990 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
991 It is minimum of user_mss and mss received with SYN.
992 It also does not include TCP options.
994 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
996 tp->mss_cache is current effective sending mss, including
997 all tcp options except for SACKs. It is evaluated,
998 taking into account current pmtu, but never exceeds
999 tp->rx_opt.mss_clamp.
1001 NOTE1. rfc1122 clearly states that advertised MSS
1002 DOES NOT include either tcp or ip options.
1004 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1005 are READ ONLY outside this function. --ANK (980731)
1007 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1009 struct tcp_sock
*tp
= tcp_sk(sk
);
1010 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1013 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1014 icsk
->icsk_mtup
.search_high
= pmtu
;
1016 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1017 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1019 /* And store cached results */
1020 icsk
->icsk_pmtu_cookie
= pmtu
;
1021 if (icsk
->icsk_mtup
.enabled
)
1022 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1023 tp
->mss_cache
= mss_now
;
1028 /* Compute the current effective MSS, taking SACKs and IP options,
1029 * and even PMTU discovery events into account.
1031 unsigned int tcp_current_mss(struct sock
*sk
)
1033 struct tcp_sock
*tp
= tcp_sk(sk
);
1034 struct dst_entry
*dst
= __sk_dst_get(sk
);
1036 unsigned header_len
;
1037 struct tcp_out_options opts
;
1038 struct tcp_md5sig_key
*md5
;
1040 mss_now
= tp
->mss_cache
;
1043 u32 mtu
= dst_mtu(dst
);
1044 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1045 mss_now
= tcp_sync_mss(sk
, mtu
);
1048 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1049 sizeof(struct tcphdr
);
1050 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1051 * some common options. If this is an odd packet (because we have SACK
1052 * blocks etc) then our calculated header_len will be different, and
1053 * we have to adjust mss_now correspondingly */
1054 if (header_len
!= tp
->tcp_header_len
) {
1055 int delta
= (int) header_len
- tp
->tcp_header_len
;
1062 /* Congestion window validation. (RFC2861) */
1063 static void tcp_cwnd_validate(struct sock
*sk
)
1065 struct tcp_sock
*tp
= tcp_sk(sk
);
1067 if (tp
->packets_out
>= tp
->snd_cwnd
) {
1068 /* Network is feed fully. */
1069 tp
->snd_cwnd_used
= 0;
1070 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1072 /* Network starves. */
1073 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1074 tp
->snd_cwnd_used
= tp
->packets_out
;
1076 if (sysctl_tcp_slow_start_after_idle
&&
1077 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1078 tcp_cwnd_application_limited(sk
);
1082 /* Returns the portion of skb which can be sent right away without
1083 * introducing MSS oddities to segment boundaries. In rare cases where
1084 * mss_now != mss_cache, we will request caller to create a small skb
1085 * per input skb which could be mostly avoided here (if desired).
1087 * We explicitly want to create a request for splitting write queue tail
1088 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
1089 * thus all the complexity (cwnd_len is always MSS multiple which we
1090 * return whenever allowed by the other factors). Basically we need the
1091 * modulo only when the receiver window alone is the limiting factor or
1092 * when we would be allowed to send the split-due-to-Nagle skb fully.
1094 static unsigned int tcp_mss_split_point(struct sock
*sk
, struct sk_buff
*skb
,
1095 unsigned int mss_now
, unsigned int cwnd
)
1097 struct tcp_sock
*tp
= tcp_sk(sk
);
1098 u32 needed
, window
, cwnd_len
;
1100 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1101 cwnd_len
= mss_now
* cwnd
;
1103 if (likely(cwnd_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1106 needed
= min(skb
->len
, window
);
1108 if (cwnd_len
<= needed
)
1111 return needed
- needed
% mss_now
;
1114 /* Can at least one segment of SKB be sent right now, according to the
1115 * congestion window rules? If so, return how many segments are allowed.
1117 static inline unsigned int tcp_cwnd_test(struct tcp_sock
*tp
,
1118 struct sk_buff
*skb
)
1120 u32 in_flight
, cwnd
;
1122 /* Don't be strict about the congestion window for the final FIN. */
1123 if ((TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1124 tcp_skb_pcount(skb
) == 1)
1127 in_flight
= tcp_packets_in_flight(tp
);
1128 cwnd
= tp
->snd_cwnd
;
1129 if (in_flight
< cwnd
)
1130 return (cwnd
- in_flight
);
1135 /* This must be invoked the first time we consider transmitting
1136 * SKB onto the wire.
1138 static int tcp_init_tso_segs(struct sock
*sk
, struct sk_buff
*skb
,
1139 unsigned int mss_now
)
1141 int tso_segs
= tcp_skb_pcount(skb
);
1143 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1144 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1145 tso_segs
= tcp_skb_pcount(skb
);
1150 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
1152 return after(tp
->snd_sml
, tp
->snd_una
) &&
1153 !after(tp
->snd_sml
, tp
->snd_nxt
);
1156 /* Return 0, if packet can be sent now without violation Nagle's rules:
1157 * 1. It is full sized.
1158 * 2. Or it contains FIN. (already checked by caller)
1159 * 3. Or TCP_NODELAY was set.
1160 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1161 * With Minshall's modification: all sent small packets are ACKed.
1163 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
1164 const struct sk_buff
*skb
,
1165 unsigned mss_now
, int nonagle
)
1167 return (skb
->len
< mss_now
&&
1168 ((nonagle
& TCP_NAGLE_CORK
) ||
1169 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
))));
1172 /* Return non-zero if the Nagle test allows this packet to be
1175 static inline int tcp_nagle_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1176 unsigned int cur_mss
, int nonagle
)
1178 /* Nagle rule does not apply to frames, which sit in the middle of the
1179 * write_queue (they have no chances to get new data).
1181 * This is implemented in the callers, where they modify the 'nonagle'
1182 * argument based upon the location of SKB in the send queue.
1184 if (nonagle
& TCP_NAGLE_PUSH
)
1187 /* Don't use the nagle rule for urgent data (or for the final FIN).
1188 * Nagle can be ignored during F-RTO too (see RFC4138).
1190 if (tcp_urg_mode(tp
) || (tp
->frto_counter
== 2) ||
1191 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
))
1194 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
1200 /* Does at least the first segment of SKB fit into the send window? */
1201 static inline int tcp_snd_wnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1202 unsigned int cur_mss
)
1204 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1206 if (skb
->len
> cur_mss
)
1207 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1209 return !after(end_seq
, tcp_wnd_end(tp
));
1212 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1213 * should be put on the wire right now. If so, it returns the number of
1214 * packets allowed by the congestion window.
1216 static unsigned int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
1217 unsigned int cur_mss
, int nonagle
)
1219 struct tcp_sock
*tp
= tcp_sk(sk
);
1220 unsigned int cwnd_quota
;
1222 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1224 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1227 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1228 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1234 int tcp_may_send_now(struct sock
*sk
)
1236 struct tcp_sock
*tp
= tcp_sk(sk
);
1237 struct sk_buff
*skb
= tcp_send_head(sk
);
1240 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1241 (tcp_skb_is_last(sk
, skb
) ?
1242 tp
->nonagle
: TCP_NAGLE_PUSH
)));
1245 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1246 * which is put after SKB on the list. It is very much like
1247 * tcp_fragment() except that it may make several kinds of assumptions
1248 * in order to speed up the splitting operation. In particular, we
1249 * know that all the data is in scatter-gather pages, and that the
1250 * packet has never been sent out before (and thus is not cloned).
1252 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1253 unsigned int mss_now
)
1255 struct sk_buff
*buff
;
1256 int nlen
= skb
->len
- len
;
1259 /* All of a TSO frame must be composed of paged data. */
1260 if (skb
->len
!= skb
->data_len
)
1261 return tcp_fragment(sk
, skb
, len
, mss_now
);
1263 buff
= sk_stream_alloc_skb(sk
, 0, GFP_ATOMIC
);
1264 if (unlikely(buff
== NULL
))
1267 sk
->sk_wmem_queued
+= buff
->truesize
;
1268 sk_mem_charge(sk
, buff
->truesize
);
1269 buff
->truesize
+= nlen
;
1270 skb
->truesize
-= nlen
;
1272 /* Correct the sequence numbers. */
1273 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1274 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1275 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1277 /* PSH and FIN should only be set in the second packet. */
1278 flags
= TCP_SKB_CB(skb
)->flags
;
1279 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
| TCPCB_FLAG_PSH
);
1280 TCP_SKB_CB(buff
)->flags
= flags
;
1282 /* This packet was never sent out yet, so no SACK bits. */
1283 TCP_SKB_CB(buff
)->sacked
= 0;
1285 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1286 skb_split(skb
, buff
, len
);
1288 /* Fix up tso_factor for both original and new SKB. */
1289 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1290 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1292 /* Link BUFF into the send queue. */
1293 skb_header_release(buff
);
1294 tcp_insert_write_queue_after(skb
, buff
, sk
);
1299 /* Try to defer sending, if possible, in order to minimize the amount
1300 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1302 * This algorithm is from John Heffner.
1304 static int tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
)
1306 struct tcp_sock
*tp
= tcp_sk(sk
);
1307 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1308 u32 send_win
, cong_win
, limit
, in_flight
;
1310 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
1313 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1316 /* Defer for less than two clock ticks. */
1317 if (tp
->tso_deferred
&&
1318 (((u32
)jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1321 in_flight
= tcp_packets_in_flight(tp
);
1323 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1325 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1327 /* From in_flight test above, we know that cwnd > in_flight. */
1328 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1330 limit
= min(send_win
, cong_win
);
1332 /* If a full-sized TSO skb can be sent, do it. */
1333 if (limit
>= sk
->sk_gso_max_size
)
1336 /* Middle in queue won't get any more data, full sendable already? */
1337 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1340 if (sysctl_tcp_tso_win_divisor
) {
1341 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1343 /* If at least some fraction of a window is available,
1346 chunk
/= sysctl_tcp_tso_win_divisor
;
1350 /* Different approach, try not to defer past a single
1351 * ACK. Receiver should ACK every other full sized
1352 * frame, so if we have space for more than 3 frames
1355 if (limit
> tcp_max_burst(tp
) * tp
->mss_cache
)
1359 /* Ok, it looks like it is advisable to defer. */
1360 tp
->tso_deferred
= 1 | (jiffies
<< 1);
1365 tp
->tso_deferred
= 0;
1369 /* Create a new MTU probe if we are ready.
1370 * Returns 0 if we should wait to probe (no cwnd available),
1371 * 1 if a probe was sent,
1374 static int tcp_mtu_probe(struct sock
*sk
)
1376 struct tcp_sock
*tp
= tcp_sk(sk
);
1377 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1378 struct sk_buff
*skb
, *nskb
, *next
;
1385 /* Not currently probing/verifying,
1387 * have enough cwnd, and
1388 * not SACKing (the variable headers throw things off) */
1389 if (!icsk
->icsk_mtup
.enabled
||
1390 icsk
->icsk_mtup
.probe_size
||
1391 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1392 tp
->snd_cwnd
< 11 ||
1393 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
)
1396 /* Very simple search strategy: just double the MSS. */
1397 mss_now
= tcp_current_mss(sk
);
1398 probe_size
= 2 * tp
->mss_cache
;
1399 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1400 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1401 /* TODO: set timer for probe_converge_event */
1405 /* Have enough data in the send queue to probe? */
1406 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1409 if (tp
->snd_wnd
< size_needed
)
1411 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1414 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1415 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1416 if (!tcp_packets_in_flight(tp
))
1422 /* We're allowed to probe. Build it now. */
1423 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1425 sk
->sk_wmem_queued
+= nskb
->truesize
;
1426 sk_mem_charge(sk
, nskb
->truesize
);
1428 skb
= tcp_send_head(sk
);
1430 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1431 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1432 TCP_SKB_CB(nskb
)->flags
= TCPCB_FLAG_ACK
;
1433 TCP_SKB_CB(nskb
)->sacked
= 0;
1435 nskb
->ip_summed
= skb
->ip_summed
;
1437 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1440 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1441 copy
= min_t(int, skb
->len
, probe_size
- len
);
1442 if (nskb
->ip_summed
)
1443 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1445 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1446 skb_put(nskb
, copy
),
1449 if (skb
->len
<= copy
) {
1450 /* We've eaten all the data from this skb.
1452 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
;
1453 tcp_unlink_write_queue(skb
, sk
);
1454 sk_wmem_free_skb(sk
, skb
);
1456 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
&
1457 ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
1458 if (!skb_shinfo(skb
)->nr_frags
) {
1459 skb_pull(skb
, copy
);
1460 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1461 skb
->csum
= csum_partial(skb
->data
,
1464 __pskb_trim_head(skb
, copy
);
1465 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1467 TCP_SKB_CB(skb
)->seq
+= copy
;
1472 if (len
>= probe_size
)
1475 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1477 /* We're ready to send. If this fails, the probe will
1478 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1479 TCP_SKB_CB(nskb
)->when
= tcp_time_stamp
;
1480 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1481 /* Decrement cwnd here because we are sending
1482 * effectively two packets. */
1484 tcp_event_new_data_sent(sk
, nskb
);
1486 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1487 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1488 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1496 /* This routine writes packets to the network. It advances the
1497 * send_head. This happens as incoming acks open up the remote
1500 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1501 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1502 * account rare use of URG, this is not a big flaw.
1504 * Returns 1, if no segments are in flight and we have queued segments, but
1505 * cannot send anything now because of SWS or another problem.
1507 static int tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
1508 int push_one
, gfp_t gfp
)
1510 struct tcp_sock
*tp
= tcp_sk(sk
);
1511 struct sk_buff
*skb
;
1512 unsigned int tso_segs
, sent_pkts
;
1519 /* Do MTU probing. */
1520 result
= tcp_mtu_probe(sk
);
1523 } else if (result
> 0) {
1528 while ((skb
= tcp_send_head(sk
))) {
1531 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1534 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1538 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1541 if (tso_segs
== 1) {
1542 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1543 (tcp_skb_is_last(sk
, skb
) ?
1544 nonagle
: TCP_NAGLE_PUSH
))))
1547 if (!push_one
&& tcp_tso_should_defer(sk
, skb
))
1552 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
1553 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
1556 if (skb
->len
> limit
&&
1557 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1560 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1562 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
1565 /* Advance the send_head. This one is sent out.
1566 * This call will increment packets_out.
1568 tcp_event_new_data_sent(sk
, skb
);
1570 tcp_minshall_update(tp
, mss_now
, skb
);
1577 if (likely(sent_pkts
)) {
1578 tcp_cwnd_validate(sk
);
1581 return !tp
->packets_out
&& tcp_send_head(sk
);
1584 /* Push out any pending frames which were held back due to
1585 * TCP_CORK or attempt at coalescing tiny packets.
1586 * The socket must be locked by the caller.
1588 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
1591 struct sk_buff
*skb
= tcp_send_head(sk
);
1596 /* If we are closed, the bytes will have to remain here.
1597 * In time closedown will finish, we empty the write queue and
1598 * all will be happy.
1600 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
1603 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0, GFP_ATOMIC
))
1604 tcp_check_probe_timer(sk
);
1607 /* Send _single_ skb sitting at the send head. This function requires
1608 * true push pending frames to setup probe timer etc.
1610 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
1612 struct sk_buff
*skb
= tcp_send_head(sk
);
1614 BUG_ON(!skb
|| skb
->len
< mss_now
);
1616 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
1619 /* This function returns the amount that we can raise the
1620 * usable window based on the following constraints
1622 * 1. The window can never be shrunk once it is offered (RFC 793)
1623 * 2. We limit memory per socket
1626 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1627 * RECV.NEXT + RCV.WIN fixed until:
1628 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1630 * i.e. don't raise the right edge of the window until you can raise
1631 * it at least MSS bytes.
1633 * Unfortunately, the recommended algorithm breaks header prediction,
1634 * since header prediction assumes th->window stays fixed.
1636 * Strictly speaking, keeping th->window fixed violates the receiver
1637 * side SWS prevention criteria. The problem is that under this rule
1638 * a stream of single byte packets will cause the right side of the
1639 * window to always advance by a single byte.
1641 * Of course, if the sender implements sender side SWS prevention
1642 * then this will not be a problem.
1644 * BSD seems to make the following compromise:
1646 * If the free space is less than the 1/4 of the maximum
1647 * space available and the free space is less than 1/2 mss,
1648 * then set the window to 0.
1649 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1650 * Otherwise, just prevent the window from shrinking
1651 * and from being larger than the largest representable value.
1653 * This prevents incremental opening of the window in the regime
1654 * where TCP is limited by the speed of the reader side taking
1655 * data out of the TCP receive queue. It does nothing about
1656 * those cases where the window is constrained on the sender side
1657 * because the pipeline is full.
1659 * BSD also seems to "accidentally" limit itself to windows that are a
1660 * multiple of MSS, at least until the free space gets quite small.
1661 * This would appear to be a side effect of the mbuf implementation.
1662 * Combining these two algorithms results in the observed behavior
1663 * of having a fixed window size at almost all times.
1665 * Below we obtain similar behavior by forcing the offered window to
1666 * a multiple of the mss when it is feasible to do so.
1668 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1669 * Regular options like TIMESTAMP are taken into account.
1671 u32
__tcp_select_window(struct sock
*sk
)
1673 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1674 struct tcp_sock
*tp
= tcp_sk(sk
);
1675 /* MSS for the peer's data. Previous versions used mss_clamp
1676 * here. I don't know if the value based on our guesses
1677 * of peer's MSS is better for the performance. It's more correct
1678 * but may be worse for the performance because of rcv_mss
1679 * fluctuations. --SAW 1998/11/1
1681 int mss
= icsk
->icsk_ack
.rcv_mss
;
1682 int free_space
= tcp_space(sk
);
1683 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
1686 if (mss
> full_space
)
1689 if (free_space
< (full_space
>> 1)) {
1690 icsk
->icsk_ack
.quick
= 0;
1692 if (tcp_memory_pressure
)
1693 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
1696 if (free_space
< mss
)
1700 if (free_space
> tp
->rcv_ssthresh
)
1701 free_space
= tp
->rcv_ssthresh
;
1703 /* Don't do rounding if we are using window scaling, since the
1704 * scaled window will not line up with the MSS boundary anyway.
1706 window
= tp
->rcv_wnd
;
1707 if (tp
->rx_opt
.rcv_wscale
) {
1708 window
= free_space
;
1710 /* Advertise enough space so that it won't get scaled away.
1711 * Import case: prevent zero window announcement if
1712 * 1<<rcv_wscale > mss.
1714 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1715 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1716 << tp
->rx_opt
.rcv_wscale
);
1718 /* Get the largest window that is a nice multiple of mss.
1719 * Window clamp already applied above.
1720 * If our current window offering is within 1 mss of the
1721 * free space we just keep it. This prevents the divide
1722 * and multiply from happening most of the time.
1723 * We also don't do any window rounding when the free space
1726 if (window
<= free_space
- mss
|| window
> free_space
)
1727 window
= (free_space
/ mss
) * mss
;
1728 else if (mss
== full_space
&&
1729 free_space
> window
+ (full_space
>> 1))
1730 window
= free_space
;
1736 /* Collapses two adjacent SKB's during retransmission. */
1737 static void tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
1739 struct tcp_sock
*tp
= tcp_sk(sk
);
1740 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
1741 int skb_size
, next_skb_size
;
1743 skb_size
= skb
->len
;
1744 next_skb_size
= next_skb
->len
;
1746 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
1748 tcp_highest_sack_combine(sk
, next_skb
, skb
);
1750 tcp_unlink_write_queue(next_skb
, sk
);
1752 skb_copy_from_linear_data(next_skb
, skb_put(skb
, next_skb_size
),
1755 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
1756 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1758 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1759 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1761 /* Update sequence range on original skb. */
1762 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1764 /* Merge over control information. This moves PSH/FIN etc. over */
1765 TCP_SKB_CB(skb
)->flags
|= TCP_SKB_CB(next_skb
)->flags
;
1767 /* All done, get rid of second SKB and account for it so
1768 * packet counting does not break.
1770 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
1771 if (TCP_SKB_CB(next_skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1772 tp
->retrans_out
-= tcp_skb_pcount(next_skb
);
1773 if (TCP_SKB_CB(next_skb
)->sacked
& TCPCB_LOST
)
1774 tp
->lost_out
-= tcp_skb_pcount(next_skb
);
1775 /* Reno case is special. Sigh... */
1776 if (tcp_is_reno(tp
) && tp
->sacked_out
)
1777 tcp_dec_pcount_approx(&tp
->sacked_out
, next_skb
);
1779 tcp_adjust_fackets_out(sk
, next_skb
, tcp_skb_pcount(next_skb
));
1780 tp
->packets_out
-= tcp_skb_pcount(next_skb
);
1782 /* changed transmit queue under us so clear hints */
1783 tcp_clear_retrans_hints_partial(tp
);
1784 if (next_skb
== tp
->retransmit_skb_hint
)
1785 tp
->retransmit_skb_hint
= skb
;
1787 sk_wmem_free_skb(sk
, next_skb
);
1790 static int tcp_can_collapse(struct sock
*sk
, struct sk_buff
*skb
)
1792 if (tcp_skb_pcount(skb
) > 1)
1794 /* TODO: SACK collapsing could be used to remove this condition */
1795 if (skb_shinfo(skb
)->nr_frags
!= 0)
1797 if (skb_cloned(skb
))
1799 if (skb
== tcp_send_head(sk
))
1801 /* Some heurestics for collapsing over SACK'd could be invented */
1802 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1808 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
1811 struct tcp_sock
*tp
= tcp_sk(sk
);
1812 struct sk_buff
*skb
= to
, *tmp
;
1815 if (!sysctl_tcp_retrans_collapse
)
1817 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
)
1820 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
1821 if (!tcp_can_collapse(sk
, skb
))
1833 /* Punt if not enough space exists in the first SKB for
1834 * the data in the second
1836 if (skb
->len
> skb_tailroom(to
))
1839 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
1842 tcp_collapse_retrans(sk
, to
);
1846 /* This retransmits one SKB. Policy decisions and retransmit queue
1847 * state updates are done by the caller. Returns non-zero if an
1848 * error occurred which prevented the send.
1850 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
1852 struct tcp_sock
*tp
= tcp_sk(sk
);
1853 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1854 unsigned int cur_mss
;
1857 /* Inconslusive MTU probe */
1858 if (icsk
->icsk_mtup
.probe_size
) {
1859 icsk
->icsk_mtup
.probe_size
= 0;
1862 /* Do not sent more than we queued. 1/4 is reserved for possible
1863 * copying overhead: fragmentation, tunneling, mangling etc.
1865 if (atomic_read(&sk
->sk_wmem_alloc
) >
1866 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
1869 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
1870 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1872 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
1876 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
1877 return -EHOSTUNREACH
; /* Routing failure or similar. */
1879 cur_mss
= tcp_current_mss(sk
);
1881 /* If receiver has shrunk his window, and skb is out of
1882 * new window, do not retransmit it. The exception is the
1883 * case, when window is shrunk to zero. In this case
1884 * our retransmit serves as a zero window probe.
1886 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))
1887 && TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
1890 if (skb
->len
> cur_mss
) {
1891 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
1892 return -ENOMEM
; /* We'll try again later. */
1894 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1897 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
1899 /* Some Solaris stacks overoptimize and ignore the FIN on a
1900 * retransmit when old data is attached. So strip it off
1901 * since it is cheap to do so and saves bytes on the network.
1904 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1905 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
1906 if (!pskb_trim(skb
, 0)) {
1907 /* Reuse, even though it does some unnecessary work */
1908 tcp_init_nondata_skb(skb
, TCP_SKB_CB(skb
)->end_seq
- 1,
1909 TCP_SKB_CB(skb
)->flags
);
1910 skb
->ip_summed
= CHECKSUM_NONE
;
1914 /* Make a copy, if the first transmission SKB clone we made
1915 * is still in somebody's hands, else make a clone.
1917 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1919 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
1922 /* Update global TCP statistics. */
1923 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
1925 tp
->total_retrans
++;
1927 #if FASTRETRANS_DEBUG > 0
1928 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1929 if (net_ratelimit())
1930 printk(KERN_DEBUG
"retrans_out leaked.\n");
1933 if (!tp
->retrans_out
)
1934 tp
->lost_retrans_low
= tp
->snd_nxt
;
1935 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
1936 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1938 /* Save stamp of the first retransmit. */
1939 if (!tp
->retrans_stamp
)
1940 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
1944 /* snd_nxt is stored to detect loss of retransmitted segment,
1945 * see tcp_input.c tcp_sacktag_write_queue().
1947 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
1952 static int tcp_can_forward_retransmit(struct sock
*sk
)
1954 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1955 struct tcp_sock
*tp
= tcp_sk(sk
);
1957 /* Forward retransmissions are possible only during Recovery. */
1958 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1961 /* No forward retransmissions in Reno are possible. */
1962 if (tcp_is_reno(tp
))
1965 /* Yeah, we have to make difficult choice between forward transmission
1966 * and retransmission... Both ways have their merits...
1968 * For now we do not retransmit anything, while we have some new
1969 * segments to send. In the other cases, follow rule 3 for
1970 * NextSeg() specified in RFC3517.
1973 if (tcp_may_send_now(sk
))
1979 /* This gets called after a retransmit timeout, and the initially
1980 * retransmitted data is acknowledged. It tries to continue
1981 * resending the rest of the retransmit queue, until either
1982 * we've sent it all or the congestion window limit is reached.
1983 * If doing SACK, the first ACK which comes back for a timeout
1984 * based retransmit packet might feed us FACK information again.
1985 * If so, we use it to avoid unnecessarily retransmissions.
1987 void tcp_xmit_retransmit_queue(struct sock
*sk
)
1989 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1990 struct tcp_sock
*tp
= tcp_sk(sk
);
1991 struct sk_buff
*skb
;
1992 struct sk_buff
*hole
= NULL
;
1995 int fwd_rexmitting
= 0;
1998 tp
->retransmit_high
= tp
->snd_una
;
2000 if (tp
->retransmit_skb_hint
) {
2001 skb
= tp
->retransmit_skb_hint
;
2002 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2003 if (after(last_lost
, tp
->retransmit_high
))
2004 last_lost
= tp
->retransmit_high
;
2006 skb
= tcp_write_queue_head(sk
);
2007 last_lost
= tp
->snd_una
;
2010 tcp_for_write_queue_from(skb
, sk
) {
2011 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
2013 if (skb
== tcp_send_head(sk
))
2015 /* we could do better than to assign each time */
2017 tp
->retransmit_skb_hint
= skb
;
2019 /* Assume this retransmit will generate
2020 * only one packet for congestion window
2021 * calculation purposes. This works because
2022 * tcp_retransmit_skb() will chop up the
2023 * packet to be MSS sized and all the
2024 * packet counting works out.
2026 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2029 if (fwd_rexmitting
) {
2031 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2033 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2035 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2036 tp
->retransmit_high
= last_lost
;
2037 if (!tcp_can_forward_retransmit(sk
))
2039 /* Backtrack if necessary to non-L'ed skb */
2047 } else if (!(sacked
& TCPCB_LOST
)) {
2048 if (hole
== NULL
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2053 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2054 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2055 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2057 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2060 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2063 if (tcp_retransmit_skb(sk
, skb
))
2065 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2067 if (skb
== tcp_write_queue_head(sk
))
2068 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2069 inet_csk(sk
)->icsk_rto
,
2074 /* Send a fin. The caller locks the socket for us. This cannot be
2075 * allowed to fail queueing a FIN frame under any circumstances.
2077 void tcp_send_fin(struct sock
*sk
)
2079 struct tcp_sock
*tp
= tcp_sk(sk
);
2080 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2083 /* Optimization, tack on the FIN if we have a queue of
2084 * unsent frames. But be careful about outgoing SACKS
2087 mss_now
= tcp_current_mss(sk
);
2089 if (tcp_send_head(sk
) != NULL
) {
2090 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
2091 TCP_SKB_CB(skb
)->end_seq
++;
2094 /* Socket is locked, keep trying until memory is available. */
2096 skb
= alloc_skb_fclone(MAX_TCP_HEADER
, GFP_KERNEL
);
2102 /* Reserve space for headers and prepare control bits. */
2103 skb_reserve(skb
, MAX_TCP_HEADER
);
2104 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2105 tcp_init_nondata_skb(skb
, tp
->write_seq
,
2106 TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
2107 tcp_queue_skb(sk
, skb
);
2109 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2112 /* We get here when a process closes a file descriptor (either due to
2113 * an explicit close() or as a byproduct of exit()'ing) and there
2114 * was unread data in the receive queue. This behavior is recommended
2115 * by RFC 2525, section 2.17. -DaveM
2117 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2119 struct sk_buff
*skb
;
2121 /* NOTE: No TCP options attached and we never retransmit this. */
2122 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2124 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2128 /* Reserve space for headers and prepare control bits. */
2129 skb_reserve(skb
, MAX_TCP_HEADER
);
2130 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
2131 TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
2133 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2134 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2135 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2137 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
2140 /* WARNING: This routine must only be called when we have already sent
2141 * a SYN packet that crossed the incoming SYN that caused this routine
2142 * to get called. If this assumption fails then the initial rcv_wnd
2143 * and rcv_wscale values will not be correct.
2145 int tcp_send_synack(struct sock
*sk
)
2147 struct sk_buff
*skb
;
2149 skb
= tcp_write_queue_head(sk
);
2150 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
)) {
2151 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
2154 if (!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_ACK
)) {
2155 if (skb_cloned(skb
)) {
2156 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2159 tcp_unlink_write_queue(skb
, sk
);
2160 skb_header_release(nskb
);
2161 __tcp_add_write_queue_head(sk
, nskb
);
2162 sk_wmem_free_skb(sk
, skb
);
2163 sk
->sk_wmem_queued
+= nskb
->truesize
;
2164 sk_mem_charge(sk
, nskb
->truesize
);
2168 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
2169 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2171 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2172 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2176 * Prepare a SYN-ACK.
2178 struct sk_buff
*tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2179 struct request_sock
*req
)
2181 struct inet_request_sock
*ireq
= inet_rsk(req
);
2182 struct tcp_sock
*tp
= tcp_sk(sk
);
2184 int tcp_header_size
;
2185 struct tcp_out_options opts
;
2186 struct sk_buff
*skb
;
2187 struct tcp_md5sig_key
*md5
;
2188 __u8
*md5_hash_location
;
2191 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
2195 /* Reserve space for headers. */
2196 skb_reserve(skb
, MAX_TCP_HEADER
);
2198 skb
->dst
= dst_clone(dst
);
2200 mss
= dst_metric(dst
, RTAX_ADVMSS
);
2201 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< mss
)
2202 mss
= tp
->rx_opt
.user_mss
;
2204 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
2206 /* Set this up on the first call only */
2207 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
2208 /* tcp_full_space because it is guaranteed to be the first packet */
2209 tcp_select_initial_window(tcp_full_space(sk
),
2210 mss
- (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
2215 ireq
->rcv_wscale
= rcv_wscale
;
2218 memset(&opts
, 0, sizeof(opts
));
2219 #ifdef CONFIG_SYN_COOKIES
2220 if (unlikely(req
->cookie_ts
))
2221 TCP_SKB_CB(skb
)->when
= cookie_init_timestamp(req
);
2224 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2225 tcp_header_size
= tcp_synack_options(sk
, req
, mss
,
2227 sizeof(struct tcphdr
);
2229 skb_push(skb
, tcp_header_size
);
2230 skb_reset_transport_header(skb
);
2233 memset(th
, 0, sizeof(struct tcphdr
));
2236 TCP_ECN_make_synack(req
, th
);
2237 th
->source
= ireq
->loc_port
;
2238 th
->dest
= ireq
->rmt_port
;
2239 /* Setting of flags are superfluous here for callers (and ECE is
2240 * not even correctly set)
2242 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
2243 TCPCB_FLAG_SYN
| TCPCB_FLAG_ACK
);
2244 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2245 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
2247 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2248 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2249 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
, &md5_hash_location
);
2250 th
->doff
= (tcp_header_size
>> 2);
2251 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
2253 #ifdef CONFIG_TCP_MD5SIG
2254 /* Okay, we have all we need - do the md5 hash if needed */
2256 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
2257 md5
, NULL
, req
, skb
);
2265 * Do all connect socket setups that can be done AF independent.
2267 static void tcp_connect_init(struct sock
*sk
)
2269 struct dst_entry
*dst
= __sk_dst_get(sk
);
2270 struct tcp_sock
*tp
= tcp_sk(sk
);
2273 /* We'll fix this up when we get a response from the other end.
2274 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2276 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2277 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2279 #ifdef CONFIG_TCP_MD5SIG
2280 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2281 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2284 /* If user gave his TCP_MAXSEG, record it to clamp */
2285 if (tp
->rx_opt
.user_mss
)
2286 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2289 tcp_sync_mss(sk
, dst_mtu(dst
));
2291 if (!tp
->window_clamp
)
2292 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2293 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
2294 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
2295 tp
->advmss
= tp
->rx_opt
.user_mss
;
2297 tcp_initialize_rcv_mss(sk
);
2299 tcp_select_initial_window(tcp_full_space(sk
),
2300 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2303 sysctl_tcp_window_scaling
,
2306 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2307 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2310 sock_reset_flag(sk
, SOCK_DONE
);
2313 tp
->snd_una
= tp
->write_seq
;
2314 tp
->snd_sml
= tp
->write_seq
;
2315 tp
->snd_up
= tp
->write_seq
;
2320 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2321 inet_csk(sk
)->icsk_retransmits
= 0;
2322 tcp_clear_retrans(tp
);
2326 * Build a SYN and send it off.
2328 int tcp_connect(struct sock
*sk
)
2330 struct tcp_sock
*tp
= tcp_sk(sk
);
2331 struct sk_buff
*buff
;
2333 tcp_connect_init(sk
);
2335 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
2336 if (unlikely(buff
== NULL
))
2339 /* Reserve space for headers. */
2340 skb_reserve(buff
, MAX_TCP_HEADER
);
2342 tp
->snd_nxt
= tp
->write_seq
;
2343 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPCB_FLAG_SYN
);
2344 TCP_ECN_send_syn(sk
, buff
);
2347 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2348 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
2349 skb_header_release(buff
);
2350 __tcp_add_write_queue_tail(sk
, buff
);
2351 sk
->sk_wmem_queued
+= buff
->truesize
;
2352 sk_mem_charge(sk
, buff
->truesize
);
2353 tp
->packets_out
+= tcp_skb_pcount(buff
);
2354 tcp_transmit_skb(sk
, buff
, 1, GFP_KERNEL
);
2356 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2357 * in order to make this packet get counted in tcpOutSegs.
2359 tp
->snd_nxt
= tp
->write_seq
;
2360 tp
->pushed_seq
= tp
->write_seq
;
2361 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
2363 /* Timer for repeating the SYN until an answer. */
2364 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2365 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2369 /* Send out a delayed ack, the caller does the policy checking
2370 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2373 void tcp_send_delayed_ack(struct sock
*sk
)
2375 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2376 int ato
= icsk
->icsk_ack
.ato
;
2377 unsigned long timeout
;
2379 if (ato
> TCP_DELACK_MIN
) {
2380 const struct tcp_sock
*tp
= tcp_sk(sk
);
2381 int max_ato
= HZ
/ 2;
2383 if (icsk
->icsk_ack
.pingpong
||
2384 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
2385 max_ato
= TCP_DELACK_MAX
;
2387 /* Slow path, intersegment interval is "high". */
2389 /* If some rtt estimate is known, use it to bound delayed ack.
2390 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2394 int rtt
= max(tp
->srtt
>> 3, TCP_DELACK_MIN
);
2400 ato
= min(ato
, max_ato
);
2403 /* Stay within the limit we were given */
2404 timeout
= jiffies
+ ato
;
2406 /* Use new timeout only if there wasn't a older one earlier. */
2407 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
2408 /* If delack timer was blocked or is about to expire,
2411 if (icsk
->icsk_ack
.blocked
||
2412 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
2417 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
2418 timeout
= icsk
->icsk_ack
.timeout
;
2420 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
2421 icsk
->icsk_ack
.timeout
= timeout
;
2422 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
2425 /* This routine sends an ack and also updates the window. */
2426 void tcp_send_ack(struct sock
*sk
)
2428 struct sk_buff
*buff
;
2430 /* If we have been reset, we may not send again. */
2431 if (sk
->sk_state
== TCP_CLOSE
)
2434 /* We are not putting this on the write queue, so
2435 * tcp_transmit_skb() will set the ownership to this
2438 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2440 inet_csk_schedule_ack(sk
);
2441 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
2442 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
2443 TCP_DELACK_MAX
, TCP_RTO_MAX
);
2447 /* Reserve space for headers and prepare control bits. */
2448 skb_reserve(buff
, MAX_TCP_HEADER
);
2449 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPCB_FLAG_ACK
);
2451 /* Send it off, this clears delayed acks for us. */
2452 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2453 tcp_transmit_skb(sk
, buff
, 0, GFP_ATOMIC
);
2456 /* This routine sends a packet with an out of date sequence
2457 * number. It assumes the other end will try to ack it.
2459 * Question: what should we make while urgent mode?
2460 * 4.4BSD forces sending single byte of data. We cannot send
2461 * out of window data, because we have SND.NXT==SND.MAX...
2463 * Current solution: to send TWO zero-length segments in urgent mode:
2464 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2465 * out-of-date with SND.UNA-1 to probe window.
2467 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
2469 struct tcp_sock
*tp
= tcp_sk(sk
);
2470 struct sk_buff
*skb
;
2472 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2473 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2477 /* Reserve space for headers and set control bits. */
2478 skb_reserve(skb
, MAX_TCP_HEADER
);
2479 /* Use a previous sequence. This should cause the other
2480 * end to send an ack. Don't queue or clone SKB, just
2483 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPCB_FLAG_ACK
);
2484 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2485 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
2488 int tcp_write_wakeup(struct sock
*sk
)
2490 struct tcp_sock
*tp
= tcp_sk(sk
);
2491 struct sk_buff
*skb
;
2493 if (sk
->sk_state
== TCP_CLOSE
)
2496 if ((skb
= tcp_send_head(sk
)) != NULL
&&
2497 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
2499 unsigned int mss
= tcp_current_mss(sk
);
2500 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
2502 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
2503 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
2505 /* We are probing the opening of a window
2506 * but the window size is != 0
2507 * must have been a result SWS avoidance ( sender )
2509 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
2511 seg_size
= min(seg_size
, mss
);
2512 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2513 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
2515 } else if (!tcp_skb_pcount(skb
))
2516 tcp_set_skb_tso_segs(sk
, skb
, mss
);
2518 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2519 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2520 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2522 tcp_event_new_data_sent(sk
, skb
);
2525 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
2526 tcp_xmit_probe_skb(sk
, 1);
2527 return tcp_xmit_probe_skb(sk
, 0);
2531 /* A window probe timeout has occurred. If window is not closed send
2532 * a partial packet else a zero probe.
2534 void tcp_send_probe0(struct sock
*sk
)
2536 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2537 struct tcp_sock
*tp
= tcp_sk(sk
);
2540 err
= tcp_write_wakeup(sk
);
2542 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
2543 /* Cancel probe timer, if it is not required. */
2544 icsk
->icsk_probes_out
= 0;
2545 icsk
->icsk_backoff
= 0;
2550 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
2551 icsk
->icsk_backoff
++;
2552 icsk
->icsk_probes_out
++;
2553 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2554 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2557 /* If packet was not sent due to local congestion,
2558 * do not backoff and do not remember icsk_probes_out.
2559 * Let local senders to fight for local resources.
2561 * Use accumulated backoff yet.
2563 if (!icsk
->icsk_probes_out
)
2564 icsk
->icsk_probes_out
= 1;
2565 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2566 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
2567 TCP_RESOURCE_PROBE_INTERVAL
),
2572 EXPORT_SYMBOL(tcp_select_initial_window
);
2573 EXPORT_SYMBOL(tcp_connect
);
2574 EXPORT_SYMBOL(tcp_make_synack
);
2575 EXPORT_SYMBOL(tcp_simple_retransmit
);
2576 EXPORT_SYMBOL(tcp_sync_mss
);
2577 EXPORT_SYMBOL(tcp_mtup_init
);