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 if (tp
->rx_opt
.dsack
)
445 tp
->rx_opt
.dsack
= 0;
449 static unsigned tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
450 struct tcp_out_options
*opts
,
451 struct tcp_md5sig_key
**md5
) {
452 struct tcp_sock
*tp
= tcp_sk(sk
);
455 #ifdef CONFIG_TCP_MD5SIG
456 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
458 opts
->options
|= OPTION_MD5
;
459 size
+= TCPOLEN_MD5SIG_ALIGNED
;
465 /* We always get an MSS option. The option bytes which will be seen in
466 * normal data packets should timestamps be used, must be in the MSS
467 * advertised. But we subtract them from tp->mss_cache so that
468 * calculations in tcp_sendmsg are simpler etc. So account for this
469 * fact here if necessary. If we don't do this correctly, as a
470 * receiver we won't recognize data packets as being full sized when we
471 * should, and thus we won't abide by the delayed ACK rules correctly.
472 * SACKs don't matter, we never delay an ACK when we have any of those
474 opts
->mss
= tcp_advertise_mss(sk
);
475 size
+= TCPOLEN_MSS_ALIGNED
;
477 if (likely(sysctl_tcp_timestamps
&& *md5
== NULL
)) {
478 opts
->options
|= OPTION_TS
;
479 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
480 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
481 size
+= TCPOLEN_TSTAMP_ALIGNED
;
483 if (likely(sysctl_tcp_window_scaling
)) {
484 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
485 if (likely(opts
->ws
))
486 size
+= TCPOLEN_WSCALE_ALIGNED
;
488 if (likely(sysctl_tcp_sack
)) {
489 opts
->options
|= OPTION_SACK_ADVERTISE
;
490 if (unlikely(!(OPTION_TS
& opts
->options
)))
491 size
+= TCPOLEN_SACKPERM_ALIGNED
;
497 static unsigned tcp_synack_options(struct sock
*sk
,
498 struct request_sock
*req
,
499 unsigned mss
, struct sk_buff
*skb
,
500 struct tcp_out_options
*opts
,
501 struct tcp_md5sig_key
**md5
) {
503 struct inet_request_sock
*ireq
= inet_rsk(req
);
506 #ifdef CONFIG_TCP_MD5SIG
507 *md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
509 opts
->options
|= OPTION_MD5
;
510 size
+= TCPOLEN_MD5SIG_ALIGNED
;
516 /* we can't fit any SACK blocks in a packet with MD5 + TS
517 options. There was discussion about disabling SACK rather than TS in
518 order to fit in better with old, buggy kernels, but that was deemed
519 to be unnecessary. */
520 doing_ts
= ireq
->tstamp_ok
&& !(*md5
&& ireq
->sack_ok
);
523 size
+= TCPOLEN_MSS_ALIGNED
;
525 if (likely(ireq
->wscale_ok
)) {
526 opts
->ws
= ireq
->rcv_wscale
;
527 if (likely(opts
->ws
))
528 size
+= TCPOLEN_WSCALE_ALIGNED
;
530 if (likely(doing_ts
)) {
531 opts
->options
|= OPTION_TS
;
532 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
533 opts
->tsecr
= req
->ts_recent
;
534 size
+= TCPOLEN_TSTAMP_ALIGNED
;
536 if (likely(ireq
->sack_ok
)) {
537 opts
->options
|= OPTION_SACK_ADVERTISE
;
538 if (unlikely(!doing_ts
))
539 size
+= TCPOLEN_SACKPERM_ALIGNED
;
545 static unsigned tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
546 struct tcp_out_options
*opts
,
547 struct tcp_md5sig_key
**md5
) {
548 struct tcp_skb_cb
*tcb
= skb
? TCP_SKB_CB(skb
) : NULL
;
549 struct tcp_sock
*tp
= tcp_sk(sk
);
551 unsigned int eff_sacks
;
553 #ifdef CONFIG_TCP_MD5SIG
554 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
555 if (unlikely(*md5
)) {
556 opts
->options
|= OPTION_MD5
;
557 size
+= TCPOLEN_MD5SIG_ALIGNED
;
563 if (likely(tp
->rx_opt
.tstamp_ok
)) {
564 opts
->options
|= OPTION_TS
;
565 opts
->tsval
= tcb
? tcb
->when
: 0;
566 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
567 size
+= TCPOLEN_TSTAMP_ALIGNED
;
570 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
571 if (unlikely(eff_sacks
)) {
572 const unsigned remaining
= MAX_TCP_OPTION_SPACE
- size
;
573 opts
->num_sack_blocks
=
574 min_t(unsigned, eff_sacks
,
575 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
576 TCPOLEN_SACK_PERBLOCK
);
577 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
578 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
584 /* This routine actually transmits TCP packets queued in by
585 * tcp_do_sendmsg(). This is used by both the initial
586 * transmission and possible later retransmissions.
587 * All SKB's seen here are completely headerless. It is our
588 * job to build the TCP header, and pass the packet down to
589 * IP so it can do the same plus pass the packet off to the
592 * We are working here with either a clone of the original
593 * SKB, or a fresh unique copy made by the retransmit engine.
595 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
598 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
599 struct inet_sock
*inet
;
601 struct tcp_skb_cb
*tcb
;
602 struct tcp_out_options opts
;
603 unsigned tcp_options_size
, tcp_header_size
;
604 struct tcp_md5sig_key
*md5
;
605 __u8
*md5_hash_location
;
609 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
611 /* If congestion control is doing timestamping, we must
612 * take such a timestamp before we potentially clone/copy.
614 if (icsk
->icsk_ca_ops
->flags
& TCP_CONG_RTT_STAMP
)
615 __net_timestamp(skb
);
617 if (likely(clone_it
)) {
618 if (unlikely(skb_cloned(skb
)))
619 skb
= pskb_copy(skb
, gfp_mask
);
621 skb
= skb_clone(skb
, gfp_mask
);
628 tcb
= TCP_SKB_CB(skb
);
629 memset(&opts
, 0, sizeof(opts
));
631 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
))
632 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
634 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
636 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
638 if (tcp_packets_in_flight(tp
) == 0)
639 tcp_ca_event(sk
, CA_EVENT_TX_START
);
641 skb_push(skb
, tcp_header_size
);
642 skb_reset_transport_header(skb
);
643 skb_set_owner_w(skb
, sk
);
645 /* Build TCP header and checksum it. */
647 th
->source
= inet
->sport
;
648 th
->dest
= inet
->dport
;
649 th
->seq
= htonl(tcb
->seq
);
650 th
->ack_seq
= htonl(tp
->rcv_nxt
);
651 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
654 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
655 /* RFC1323: The window in SYN & SYN/ACK segments
658 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
660 th
->window
= htons(tcp_select_window(sk
));
665 /* The urg_mode check is necessary during a below snd_una win probe */
666 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
667 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
668 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
670 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
671 th
->urg_ptr
= 0xFFFF;
676 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
, &md5_hash_location
);
677 if (likely((tcb
->flags
& TCPCB_FLAG_SYN
) == 0))
678 TCP_ECN_send(sk
, skb
, tcp_header_size
);
680 #ifdef CONFIG_TCP_MD5SIG
681 /* Calculate the MD5 hash, as we have all we need now */
683 sk
->sk_route_caps
&= ~NETIF_F_GSO_MASK
;
684 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
689 icsk
->icsk_af_ops
->send_check(sk
, skb
->len
, skb
);
691 if (likely(tcb
->flags
& TCPCB_FLAG_ACK
))
692 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
694 if (skb
->len
!= tcp_header_size
)
695 tcp_event_data_sent(tp
, skb
, sk
);
697 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
698 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
700 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, 0);
701 if (likely(err
<= 0))
704 tcp_enter_cwr(sk
, 1);
706 return net_xmit_eval(err
);
709 /* This routine just queue's the buffer
711 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
712 * otherwise socket can stall.
714 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
716 struct tcp_sock
*tp
= tcp_sk(sk
);
718 /* Advance write_seq and place onto the write_queue. */
719 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
720 skb_header_release(skb
);
721 tcp_add_write_queue_tail(sk
, skb
);
722 sk
->sk_wmem_queued
+= skb
->truesize
;
723 sk_mem_charge(sk
, skb
->truesize
);
726 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
,
727 unsigned int mss_now
)
729 if (skb
->len
<= mss_now
|| !sk_can_gso(sk
)) {
730 /* Avoid the costly divide in the normal
733 skb_shinfo(skb
)->gso_segs
= 1;
734 skb_shinfo(skb
)->gso_size
= 0;
735 skb_shinfo(skb
)->gso_type
= 0;
737 skb_shinfo(skb
)->gso_segs
= DIV_ROUND_UP(skb
->len
, mss_now
);
738 skb_shinfo(skb
)->gso_size
= mss_now
;
739 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
743 /* When a modification to fackets out becomes necessary, we need to check
744 * skb is counted to fackets_out or not.
746 static void tcp_adjust_fackets_out(struct sock
*sk
, struct sk_buff
*skb
,
749 struct tcp_sock
*tp
= tcp_sk(sk
);
751 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
754 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
755 tp
->fackets_out
-= decr
;
758 /* Function to create two new TCP segments. Shrinks the given segment
759 * to the specified size and appends a new segment with the rest of the
760 * packet to the list. This won't be called frequently, I hope.
761 * Remember, these are still headerless SKBs at this point.
763 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
764 unsigned int mss_now
)
766 struct tcp_sock
*tp
= tcp_sk(sk
);
767 struct sk_buff
*buff
;
768 int nsize
, old_factor
;
772 BUG_ON(len
> skb
->len
);
774 nsize
= skb_headlen(skb
) - len
;
778 if (skb_cloned(skb
) &&
779 skb_is_nonlinear(skb
) &&
780 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
783 /* Get a new skb... force flag on. */
784 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
786 return -ENOMEM
; /* We'll just try again later. */
788 sk
->sk_wmem_queued
+= buff
->truesize
;
789 sk_mem_charge(sk
, buff
->truesize
);
790 nlen
= skb
->len
- len
- nsize
;
791 buff
->truesize
+= nlen
;
792 skb
->truesize
-= nlen
;
794 /* Correct the sequence numbers. */
795 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
796 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
797 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
799 /* PSH and FIN should only be set in the second packet. */
800 flags
= TCP_SKB_CB(skb
)->flags
;
801 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
| TCPCB_FLAG_PSH
);
802 TCP_SKB_CB(buff
)->flags
= flags
;
803 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
805 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
806 /* Copy and checksum data tail into the new buffer. */
807 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
808 skb_put(buff
, nsize
),
813 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
815 skb
->ip_summed
= CHECKSUM_PARTIAL
;
816 skb_split(skb
, buff
, len
);
819 buff
->ip_summed
= skb
->ip_summed
;
821 /* Looks stupid, but our code really uses when of
822 * skbs, which it never sent before. --ANK
824 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
825 buff
->tstamp
= skb
->tstamp
;
827 old_factor
= tcp_skb_pcount(skb
);
829 /* Fix up tso_factor for both original and new SKB. */
830 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
831 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
833 /* If this packet has been sent out already, we must
834 * adjust the various packet counters.
836 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
837 int diff
= old_factor
- tcp_skb_pcount(skb
) -
838 tcp_skb_pcount(buff
);
840 tp
->packets_out
-= diff
;
842 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
843 tp
->sacked_out
-= diff
;
844 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
845 tp
->retrans_out
-= diff
;
847 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
848 tp
->lost_out
-= diff
;
850 /* Adjust Reno SACK estimate. */
851 if (tcp_is_reno(tp
) && diff
> 0) {
852 tcp_dec_pcount_approx_int(&tp
->sacked_out
, diff
);
853 tcp_verify_left_out(tp
);
855 tcp_adjust_fackets_out(sk
, skb
, diff
);
857 if (tp
->lost_skb_hint
&&
858 before(TCP_SKB_CB(skb
)->seq
,
859 TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
860 (tcp_is_fack(tp
) || TCP_SKB_CB(skb
)->sacked
))
861 tp
->lost_cnt_hint
-= diff
;
864 /* Link BUFF into the send queue. */
865 skb_header_release(buff
);
866 tcp_insert_write_queue_after(skb
, buff
, sk
);
871 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
872 * eventually). The difference is that pulled data not copied, but
873 * immediately discarded.
875 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
881 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
882 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
883 put_page(skb_shinfo(skb
)->frags
[i
].page
);
884 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
886 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
888 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
889 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
895 skb_shinfo(skb
)->nr_frags
= k
;
897 skb_reset_tail_pointer(skb
);
898 skb
->data_len
-= len
;
899 skb
->len
= skb
->data_len
;
902 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
904 if (skb_cloned(skb
) && pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
907 /* If len == headlen, we avoid __skb_pull to preserve alignment. */
908 if (unlikely(len
< skb_headlen(skb
)))
909 __skb_pull(skb
, len
);
911 __pskb_trim_head(skb
, len
- skb_headlen(skb
));
913 TCP_SKB_CB(skb
)->seq
+= len
;
914 skb
->ip_summed
= CHECKSUM_PARTIAL
;
916 skb
->truesize
-= len
;
917 sk
->sk_wmem_queued
-= len
;
918 sk_mem_uncharge(sk
, len
);
919 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
921 /* Any change of skb->len requires recalculation of tso
924 if (tcp_skb_pcount(skb
) > 1)
925 tcp_set_skb_tso_segs(sk
, skb
, tcp_current_mss(sk
, 1));
930 /* Not accounting for SACKs here. */
931 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
933 struct tcp_sock
*tp
= tcp_sk(sk
);
934 struct inet_connection_sock
*icsk
= inet_csk(sk
);
937 /* Calculate base mss without TCP options:
938 It is MMS_S - sizeof(tcphdr) of rfc1122
940 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
942 /* Clamp it (mss_clamp does not include tcp options) */
943 if (mss_now
> tp
->rx_opt
.mss_clamp
)
944 mss_now
= tp
->rx_opt
.mss_clamp
;
946 /* Now subtract optional transport overhead */
947 mss_now
-= icsk
->icsk_ext_hdr_len
;
949 /* Then reserve room for full set of TCP options and 8 bytes of data */
953 /* Now subtract TCP options size, not including SACKs */
954 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
959 /* Inverse of above */
960 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
962 struct tcp_sock
*tp
= tcp_sk(sk
);
963 struct inet_connection_sock
*icsk
= inet_csk(sk
);
968 icsk
->icsk_ext_hdr_len
+
969 icsk
->icsk_af_ops
->net_header_len
;
974 void tcp_mtup_init(struct sock
*sk
)
976 struct tcp_sock
*tp
= tcp_sk(sk
);
977 struct inet_connection_sock
*icsk
= inet_csk(sk
);
979 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
980 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
981 icsk
->icsk_af_ops
->net_header_len
;
982 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
983 icsk
->icsk_mtup
.probe_size
= 0;
986 /* Bound MSS / TSO packet size with the half of the window */
987 static int tcp_bound_to_half_wnd(struct tcp_sock
*tp
, int pktsize
)
989 if (tp
->max_window
&& pktsize
> (tp
->max_window
>> 1))
990 return max(tp
->max_window
>> 1, 68U - tp
->tcp_header_len
);
995 /* This function synchronize snd mss to current pmtu/exthdr set.
997 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
998 for TCP options, but includes only bare TCP header.
1000 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1001 It is minimum of user_mss and mss received with SYN.
1002 It also does not include TCP options.
1004 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1006 tp->mss_cache is current effective sending mss, including
1007 all tcp options except for SACKs. It is evaluated,
1008 taking into account current pmtu, but never exceeds
1009 tp->rx_opt.mss_clamp.
1011 NOTE1. rfc1122 clearly states that advertised MSS
1012 DOES NOT include either tcp or ip options.
1014 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1015 are READ ONLY outside this function. --ANK (980731)
1017 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1019 struct tcp_sock
*tp
= tcp_sk(sk
);
1020 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1023 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1024 icsk
->icsk_mtup
.search_high
= pmtu
;
1026 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1027 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1029 /* And store cached results */
1030 icsk
->icsk_pmtu_cookie
= pmtu
;
1031 if (icsk
->icsk_mtup
.enabled
)
1032 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1033 tp
->mss_cache
= mss_now
;
1038 /* Compute the current effective MSS, taking SACKs and IP options,
1039 * and even PMTU discovery events into account.
1041 unsigned int tcp_current_mss(struct sock
*sk
, int large_allowed
)
1043 struct tcp_sock
*tp
= tcp_sk(sk
);
1044 struct dst_entry
*dst
= __sk_dst_get(sk
);
1048 unsigned header_len
;
1049 struct tcp_out_options opts
;
1050 struct tcp_md5sig_key
*md5
;
1052 mss_now
= tp
->mss_cache
;
1054 if (large_allowed
&& sk_can_gso(sk
))
1058 u32 mtu
= dst_mtu(dst
);
1059 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1060 mss_now
= tcp_sync_mss(sk
, mtu
);
1063 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1064 sizeof(struct tcphdr
);
1065 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1066 * some common options. If this is an odd packet (because we have SACK
1067 * blocks etc) then our calculated header_len will be different, and
1068 * we have to adjust mss_now correspondingly */
1069 if (header_len
!= tp
->tcp_header_len
) {
1070 int delta
= (int) header_len
- tp
->tcp_header_len
;
1074 xmit_size_goal
= mss_now
;
1077 xmit_size_goal
= ((sk
->sk_gso_max_size
- 1) -
1078 inet_csk(sk
)->icsk_af_ops
->net_header_len
-
1079 inet_csk(sk
)->icsk_ext_hdr_len
-
1080 tp
->tcp_header_len
);
1082 xmit_size_goal
= tcp_bound_to_half_wnd(tp
, xmit_size_goal
);
1083 xmit_size_goal
-= (xmit_size_goal
% mss_now
);
1085 tp
->xmit_size_goal
= xmit_size_goal
;
1090 /* Congestion window validation. (RFC2861) */
1091 static void tcp_cwnd_validate(struct sock
*sk
)
1093 struct tcp_sock
*tp
= tcp_sk(sk
);
1095 if (tp
->packets_out
>= tp
->snd_cwnd
) {
1096 /* Network is feed fully. */
1097 tp
->snd_cwnd_used
= 0;
1098 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1100 /* Network starves. */
1101 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1102 tp
->snd_cwnd_used
= tp
->packets_out
;
1104 if (sysctl_tcp_slow_start_after_idle
&&
1105 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1106 tcp_cwnd_application_limited(sk
);
1110 /* Returns the portion of skb which can be sent right away without
1111 * introducing MSS oddities to segment boundaries. In rare cases where
1112 * mss_now != mss_cache, we will request caller to create a small skb
1113 * per input skb which could be mostly avoided here (if desired).
1115 * We explicitly want to create a request for splitting write queue tail
1116 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
1117 * thus all the complexity (cwnd_len is always MSS multiple which we
1118 * return whenever allowed by the other factors). Basically we need the
1119 * modulo only when the receiver window alone is the limiting factor or
1120 * when we would be allowed to send the split-due-to-Nagle skb fully.
1122 static unsigned int tcp_mss_split_point(struct sock
*sk
, struct sk_buff
*skb
,
1123 unsigned int mss_now
, unsigned int cwnd
)
1125 struct tcp_sock
*tp
= tcp_sk(sk
);
1126 u32 needed
, window
, cwnd_len
;
1128 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1129 cwnd_len
= mss_now
* cwnd
;
1131 if (likely(cwnd_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1134 needed
= min(skb
->len
, window
);
1136 if (cwnd_len
<= needed
)
1139 return needed
- needed
% mss_now
;
1142 /* Can at least one segment of SKB be sent right now, according to the
1143 * congestion window rules? If so, return how many segments are allowed.
1145 static inline unsigned int tcp_cwnd_test(struct tcp_sock
*tp
,
1146 struct sk_buff
*skb
)
1148 u32 in_flight
, cwnd
;
1150 /* Don't be strict about the congestion window for the final FIN. */
1151 if ((TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1152 tcp_skb_pcount(skb
) == 1)
1155 in_flight
= tcp_packets_in_flight(tp
);
1156 cwnd
= tp
->snd_cwnd
;
1157 if (in_flight
< cwnd
)
1158 return (cwnd
- in_flight
);
1163 /* This must be invoked the first time we consider transmitting
1164 * SKB onto the wire.
1166 static int tcp_init_tso_segs(struct sock
*sk
, struct sk_buff
*skb
,
1167 unsigned int mss_now
)
1169 int tso_segs
= tcp_skb_pcount(skb
);
1171 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1172 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1173 tso_segs
= tcp_skb_pcount(skb
);
1178 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
1180 return after(tp
->snd_sml
, tp
->snd_una
) &&
1181 !after(tp
->snd_sml
, tp
->snd_nxt
);
1184 /* Return 0, if packet can be sent now without violation Nagle's rules:
1185 * 1. It is full sized.
1186 * 2. Or it contains FIN. (already checked by caller)
1187 * 3. Or TCP_NODELAY was set.
1188 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1189 * With Minshall's modification: all sent small packets are ACKed.
1191 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
1192 const struct sk_buff
*skb
,
1193 unsigned mss_now
, int nonagle
)
1195 return (skb
->len
< mss_now
&&
1196 ((nonagle
& TCP_NAGLE_CORK
) ||
1197 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
))));
1200 /* Return non-zero if the Nagle test allows this packet to be
1203 static inline int tcp_nagle_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1204 unsigned int cur_mss
, int nonagle
)
1206 /* Nagle rule does not apply to frames, which sit in the middle of the
1207 * write_queue (they have no chances to get new data).
1209 * This is implemented in the callers, where they modify the 'nonagle'
1210 * argument based upon the location of SKB in the send queue.
1212 if (nonagle
& TCP_NAGLE_PUSH
)
1215 /* Don't use the nagle rule for urgent data (or for the final FIN).
1216 * Nagle can be ignored during F-RTO too (see RFC4138).
1218 if (tcp_urg_mode(tp
) || (tp
->frto_counter
== 2) ||
1219 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
))
1222 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
1228 /* Does at least the first segment of SKB fit into the send window? */
1229 static inline int tcp_snd_wnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1230 unsigned int cur_mss
)
1232 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1234 if (skb
->len
> cur_mss
)
1235 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1237 return !after(end_seq
, tcp_wnd_end(tp
));
1240 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1241 * should be put on the wire right now. If so, it returns the number of
1242 * packets allowed by the congestion window.
1244 static unsigned int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
1245 unsigned int cur_mss
, int nonagle
)
1247 struct tcp_sock
*tp
= tcp_sk(sk
);
1248 unsigned int cwnd_quota
;
1250 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1252 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1255 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1256 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1262 int tcp_may_send_now(struct sock
*sk
)
1264 struct tcp_sock
*tp
= tcp_sk(sk
);
1265 struct sk_buff
*skb
= tcp_send_head(sk
);
1268 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
, 1),
1269 (tcp_skb_is_last(sk
, skb
) ?
1270 tp
->nonagle
: TCP_NAGLE_PUSH
)));
1273 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1274 * which is put after SKB on the list. It is very much like
1275 * tcp_fragment() except that it may make several kinds of assumptions
1276 * in order to speed up the splitting operation. In particular, we
1277 * know that all the data is in scatter-gather pages, and that the
1278 * packet has never been sent out before (and thus is not cloned).
1280 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1281 unsigned int mss_now
)
1283 struct sk_buff
*buff
;
1284 int nlen
= skb
->len
- len
;
1287 /* All of a TSO frame must be composed of paged data. */
1288 if (skb
->len
!= skb
->data_len
)
1289 return tcp_fragment(sk
, skb
, len
, mss_now
);
1291 buff
= sk_stream_alloc_skb(sk
, 0, GFP_ATOMIC
);
1292 if (unlikely(buff
== NULL
))
1295 sk
->sk_wmem_queued
+= buff
->truesize
;
1296 sk_mem_charge(sk
, buff
->truesize
);
1297 buff
->truesize
+= nlen
;
1298 skb
->truesize
-= nlen
;
1300 /* Correct the sequence numbers. */
1301 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1302 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1303 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1305 /* PSH and FIN should only be set in the second packet. */
1306 flags
= TCP_SKB_CB(skb
)->flags
;
1307 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
| TCPCB_FLAG_PSH
);
1308 TCP_SKB_CB(buff
)->flags
= flags
;
1310 /* This packet was never sent out yet, so no SACK bits. */
1311 TCP_SKB_CB(buff
)->sacked
= 0;
1313 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1314 skb_split(skb
, buff
, len
);
1316 /* Fix up tso_factor for both original and new SKB. */
1317 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1318 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1320 /* Link BUFF into the send queue. */
1321 skb_header_release(buff
);
1322 tcp_insert_write_queue_after(skb
, buff
, sk
);
1327 /* Try to defer sending, if possible, in order to minimize the amount
1328 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1330 * This algorithm is from John Heffner.
1332 static int tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
)
1334 struct tcp_sock
*tp
= tcp_sk(sk
);
1335 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1336 u32 send_win
, cong_win
, limit
, in_flight
;
1338 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
1341 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1344 /* Defer for less than two clock ticks. */
1345 if (tp
->tso_deferred
&&
1346 (((u32
)jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1349 in_flight
= tcp_packets_in_flight(tp
);
1351 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1353 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1355 /* From in_flight test above, we know that cwnd > in_flight. */
1356 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1358 limit
= min(send_win
, cong_win
);
1360 /* If a full-sized TSO skb can be sent, do it. */
1361 if (limit
>= sk
->sk_gso_max_size
)
1364 /* Middle in queue won't get any more data, full sendable already? */
1365 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1368 if (sysctl_tcp_tso_win_divisor
) {
1369 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1371 /* If at least some fraction of a window is available,
1374 chunk
/= sysctl_tcp_tso_win_divisor
;
1378 /* Different approach, try not to defer past a single
1379 * ACK. Receiver should ACK every other full sized
1380 * frame, so if we have space for more than 3 frames
1383 if (limit
> tcp_max_burst(tp
) * tp
->mss_cache
)
1387 /* Ok, it looks like it is advisable to defer. */
1388 tp
->tso_deferred
= 1 | (jiffies
<< 1);
1393 tp
->tso_deferred
= 0;
1397 /* Create a new MTU probe if we are ready.
1398 * Returns 0 if we should wait to probe (no cwnd available),
1399 * 1 if a probe was sent,
1402 static int tcp_mtu_probe(struct sock
*sk
)
1404 struct tcp_sock
*tp
= tcp_sk(sk
);
1405 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1406 struct sk_buff
*skb
, *nskb
, *next
;
1413 /* Not currently probing/verifying,
1415 * have enough cwnd, and
1416 * not SACKing (the variable headers throw things off) */
1417 if (!icsk
->icsk_mtup
.enabled
||
1418 icsk
->icsk_mtup
.probe_size
||
1419 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1420 tp
->snd_cwnd
< 11 ||
1421 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
)
1424 /* Very simple search strategy: just double the MSS. */
1425 mss_now
= tcp_current_mss(sk
, 0);
1426 probe_size
= 2 * tp
->mss_cache
;
1427 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1428 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1429 /* TODO: set timer for probe_converge_event */
1433 /* Have enough data in the send queue to probe? */
1434 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1437 if (tp
->snd_wnd
< size_needed
)
1439 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1442 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1443 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1444 if (!tcp_packets_in_flight(tp
))
1450 /* We're allowed to probe. Build it now. */
1451 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1453 sk
->sk_wmem_queued
+= nskb
->truesize
;
1454 sk_mem_charge(sk
, nskb
->truesize
);
1456 skb
= tcp_send_head(sk
);
1458 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1459 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1460 TCP_SKB_CB(nskb
)->flags
= TCPCB_FLAG_ACK
;
1461 TCP_SKB_CB(nskb
)->sacked
= 0;
1463 nskb
->ip_summed
= skb
->ip_summed
;
1465 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1468 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1469 copy
= min_t(int, skb
->len
, probe_size
- len
);
1470 if (nskb
->ip_summed
)
1471 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1473 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1474 skb_put(nskb
, copy
),
1477 if (skb
->len
<= copy
) {
1478 /* We've eaten all the data from this skb.
1480 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
;
1481 tcp_unlink_write_queue(skb
, sk
);
1482 sk_wmem_free_skb(sk
, skb
);
1484 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
&
1485 ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
1486 if (!skb_shinfo(skb
)->nr_frags
) {
1487 skb_pull(skb
, copy
);
1488 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1489 skb
->csum
= csum_partial(skb
->data
,
1492 __pskb_trim_head(skb
, copy
);
1493 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1495 TCP_SKB_CB(skb
)->seq
+= copy
;
1500 if (len
>= probe_size
)
1503 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1505 /* We're ready to send. If this fails, the probe will
1506 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1507 TCP_SKB_CB(nskb
)->when
= tcp_time_stamp
;
1508 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1509 /* Decrement cwnd here because we are sending
1510 * effectively two packets. */
1512 tcp_event_new_data_sent(sk
, nskb
);
1514 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1515 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1516 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1524 /* This routine writes packets to the network. It advances the
1525 * send_head. This happens as incoming acks open up the remote
1528 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1529 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1530 * account rare use of URG, this is not a big flaw.
1532 * Returns 1, if no segments are in flight and we have queued segments, but
1533 * cannot send anything now because of SWS or another problem.
1535 static int tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
1536 int push_one
, gfp_t gfp
)
1538 struct tcp_sock
*tp
= tcp_sk(sk
);
1539 struct sk_buff
*skb
;
1540 unsigned int tso_segs
, sent_pkts
;
1547 /* Do MTU probing. */
1548 result
= tcp_mtu_probe(sk
);
1551 } else if (result
> 0) {
1556 while ((skb
= tcp_send_head(sk
))) {
1559 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1562 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1566 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1569 if (tso_segs
== 1) {
1570 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1571 (tcp_skb_is_last(sk
, skb
) ?
1572 nonagle
: TCP_NAGLE_PUSH
))))
1575 if (!push_one
&& tcp_tso_should_defer(sk
, skb
))
1580 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
1581 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
1584 if (skb
->len
> limit
&&
1585 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1588 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1590 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
1593 /* Advance the send_head. This one is sent out.
1594 * This call will increment packets_out.
1596 tcp_event_new_data_sent(sk
, skb
);
1598 tcp_minshall_update(tp
, mss_now
, skb
);
1605 if (likely(sent_pkts
)) {
1606 tcp_cwnd_validate(sk
);
1609 return !tp
->packets_out
&& tcp_send_head(sk
);
1612 /* Push out any pending frames which were held back due to
1613 * TCP_CORK or attempt at coalescing tiny packets.
1614 * The socket must be locked by the caller.
1616 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
1619 struct sk_buff
*skb
= tcp_send_head(sk
);
1624 /* If we are closed, the bytes will have to remain here.
1625 * In time closedown will finish, we empty the write queue and
1626 * all will be happy.
1628 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
1631 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0, GFP_ATOMIC
))
1632 tcp_check_probe_timer(sk
);
1635 /* Send _single_ skb sitting at the send head. This function requires
1636 * true push pending frames to setup probe timer etc.
1638 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
1640 struct sk_buff
*skb
= tcp_send_head(sk
);
1642 BUG_ON(!skb
|| skb
->len
< mss_now
);
1644 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
1647 /* This function returns the amount that we can raise the
1648 * usable window based on the following constraints
1650 * 1. The window can never be shrunk once it is offered (RFC 793)
1651 * 2. We limit memory per socket
1654 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1655 * RECV.NEXT + RCV.WIN fixed until:
1656 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1658 * i.e. don't raise the right edge of the window until you can raise
1659 * it at least MSS bytes.
1661 * Unfortunately, the recommended algorithm breaks header prediction,
1662 * since header prediction assumes th->window stays fixed.
1664 * Strictly speaking, keeping th->window fixed violates the receiver
1665 * side SWS prevention criteria. The problem is that under this rule
1666 * a stream of single byte packets will cause the right side of the
1667 * window to always advance by a single byte.
1669 * Of course, if the sender implements sender side SWS prevention
1670 * then this will not be a problem.
1672 * BSD seems to make the following compromise:
1674 * If the free space is less than the 1/4 of the maximum
1675 * space available and the free space is less than 1/2 mss,
1676 * then set the window to 0.
1677 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1678 * Otherwise, just prevent the window from shrinking
1679 * and from being larger than the largest representable value.
1681 * This prevents incremental opening of the window in the regime
1682 * where TCP is limited by the speed of the reader side taking
1683 * data out of the TCP receive queue. It does nothing about
1684 * those cases where the window is constrained on the sender side
1685 * because the pipeline is full.
1687 * BSD also seems to "accidentally" limit itself to windows that are a
1688 * multiple of MSS, at least until the free space gets quite small.
1689 * This would appear to be a side effect of the mbuf implementation.
1690 * Combining these two algorithms results in the observed behavior
1691 * of having a fixed window size at almost all times.
1693 * Below we obtain similar behavior by forcing the offered window to
1694 * a multiple of the mss when it is feasible to do so.
1696 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1697 * Regular options like TIMESTAMP are taken into account.
1699 u32
__tcp_select_window(struct sock
*sk
)
1701 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1702 struct tcp_sock
*tp
= tcp_sk(sk
);
1703 /* MSS for the peer's data. Previous versions used mss_clamp
1704 * here. I don't know if the value based on our guesses
1705 * of peer's MSS is better for the performance. It's more correct
1706 * but may be worse for the performance because of rcv_mss
1707 * fluctuations. --SAW 1998/11/1
1709 int mss
= icsk
->icsk_ack
.rcv_mss
;
1710 int free_space
= tcp_space(sk
);
1711 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
1714 if (mss
> full_space
)
1717 if (free_space
< (full_space
>> 1)) {
1718 icsk
->icsk_ack
.quick
= 0;
1720 if (tcp_memory_pressure
)
1721 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
1724 if (free_space
< mss
)
1728 if (free_space
> tp
->rcv_ssthresh
)
1729 free_space
= tp
->rcv_ssthresh
;
1731 /* Don't do rounding if we are using window scaling, since the
1732 * scaled window will not line up with the MSS boundary anyway.
1734 window
= tp
->rcv_wnd
;
1735 if (tp
->rx_opt
.rcv_wscale
) {
1736 window
= free_space
;
1738 /* Advertise enough space so that it won't get scaled away.
1739 * Import case: prevent zero window announcement if
1740 * 1<<rcv_wscale > mss.
1742 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1743 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1744 << tp
->rx_opt
.rcv_wscale
);
1746 /* Get the largest window that is a nice multiple of mss.
1747 * Window clamp already applied above.
1748 * If our current window offering is within 1 mss of the
1749 * free space we just keep it. This prevents the divide
1750 * and multiply from happening most of the time.
1751 * We also don't do any window rounding when the free space
1754 if (window
<= free_space
- mss
|| window
> free_space
)
1755 window
= (free_space
/ mss
) * mss
;
1756 else if (mss
== full_space
&&
1757 free_space
> window
+ (full_space
>> 1))
1758 window
= free_space
;
1764 /* Collapses two adjacent SKB's during retransmission. */
1765 static void tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
1767 struct tcp_sock
*tp
= tcp_sk(sk
);
1768 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
1769 int skb_size
, next_skb_size
;
1771 skb_size
= skb
->len
;
1772 next_skb_size
= next_skb
->len
;
1774 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
1776 tcp_highest_sack_combine(sk
, next_skb
, skb
);
1778 tcp_unlink_write_queue(next_skb
, sk
);
1780 skb_copy_from_linear_data(next_skb
, skb_put(skb
, next_skb_size
),
1783 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
1784 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1786 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1787 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1789 /* Update sequence range on original skb. */
1790 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1792 /* Merge over control information. This moves PSH/FIN etc. over */
1793 TCP_SKB_CB(skb
)->flags
|= TCP_SKB_CB(next_skb
)->flags
;
1795 /* All done, get rid of second SKB and account for it so
1796 * packet counting does not break.
1798 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
1799 if (TCP_SKB_CB(next_skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1800 tp
->retrans_out
-= tcp_skb_pcount(next_skb
);
1801 if (TCP_SKB_CB(next_skb
)->sacked
& TCPCB_LOST
)
1802 tp
->lost_out
-= tcp_skb_pcount(next_skb
);
1803 /* Reno case is special. Sigh... */
1804 if (tcp_is_reno(tp
) && tp
->sacked_out
)
1805 tcp_dec_pcount_approx(&tp
->sacked_out
, next_skb
);
1807 tcp_adjust_fackets_out(sk
, next_skb
, tcp_skb_pcount(next_skb
));
1808 tp
->packets_out
-= tcp_skb_pcount(next_skb
);
1810 /* changed transmit queue under us so clear hints */
1811 tcp_clear_retrans_hints_partial(tp
);
1812 if (next_skb
== tp
->retransmit_skb_hint
)
1813 tp
->retransmit_skb_hint
= skb
;
1815 sk_wmem_free_skb(sk
, next_skb
);
1818 static int tcp_can_collapse(struct sock
*sk
, struct sk_buff
*skb
)
1820 if (tcp_skb_pcount(skb
) > 1)
1822 /* TODO: SACK collapsing could be used to remove this condition */
1823 if (skb_shinfo(skb
)->nr_frags
!= 0)
1825 if (skb_cloned(skb
))
1827 if (skb
== tcp_send_head(sk
))
1829 /* Some heurestics for collapsing over SACK'd could be invented */
1830 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1836 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
1839 struct tcp_sock
*tp
= tcp_sk(sk
);
1840 struct sk_buff
*skb
= to
, *tmp
;
1843 if (!sysctl_tcp_retrans_collapse
)
1845 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
)
1848 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
1849 if (!tcp_can_collapse(sk
, skb
))
1861 /* Punt if not enough space exists in the first SKB for
1862 * the data in the second
1864 if (skb
->len
> skb_tailroom(to
))
1867 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
1870 tcp_collapse_retrans(sk
, to
);
1874 /* This retransmits one SKB. Policy decisions and retransmit queue
1875 * state updates are done by the caller. Returns non-zero if an
1876 * error occurred which prevented the send.
1878 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
1880 struct tcp_sock
*tp
= tcp_sk(sk
);
1881 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1882 unsigned int cur_mss
;
1885 /* Inconslusive MTU probe */
1886 if (icsk
->icsk_mtup
.probe_size
) {
1887 icsk
->icsk_mtup
.probe_size
= 0;
1890 /* Do not sent more than we queued. 1/4 is reserved for possible
1891 * copying overhead: fragmentation, tunneling, mangling etc.
1893 if (atomic_read(&sk
->sk_wmem_alloc
) >
1894 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
1897 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
1898 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1900 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
1904 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
1905 return -EHOSTUNREACH
; /* Routing failure or similar. */
1907 cur_mss
= tcp_current_mss(sk
, 0);
1909 /* If receiver has shrunk his window, and skb is out of
1910 * new window, do not retransmit it. The exception is the
1911 * case, when window is shrunk to zero. In this case
1912 * our retransmit serves as a zero window probe.
1914 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))
1915 && TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
1918 if (skb
->len
> cur_mss
) {
1919 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
1920 return -ENOMEM
; /* We'll try again later. */
1922 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1925 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
1927 /* Some Solaris stacks overoptimize and ignore the FIN on a
1928 * retransmit when old data is attached. So strip it off
1929 * since it is cheap to do so and saves bytes on the network.
1932 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1933 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
1934 if (!pskb_trim(skb
, 0)) {
1935 /* Reuse, even though it does some unnecessary work */
1936 tcp_init_nondata_skb(skb
, TCP_SKB_CB(skb
)->end_seq
- 1,
1937 TCP_SKB_CB(skb
)->flags
);
1938 skb
->ip_summed
= CHECKSUM_NONE
;
1942 /* Make a copy, if the first transmission SKB clone we made
1943 * is still in somebody's hands, else make a clone.
1945 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1947 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
1950 /* Update global TCP statistics. */
1951 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
1953 tp
->total_retrans
++;
1955 #if FASTRETRANS_DEBUG > 0
1956 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
1957 if (net_ratelimit())
1958 printk(KERN_DEBUG
"retrans_out leaked.\n");
1961 if (!tp
->retrans_out
)
1962 tp
->lost_retrans_low
= tp
->snd_nxt
;
1963 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
1964 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1966 /* Save stamp of the first retransmit. */
1967 if (!tp
->retrans_stamp
)
1968 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
1972 /* snd_nxt is stored to detect loss of retransmitted segment,
1973 * see tcp_input.c tcp_sacktag_write_queue().
1975 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
1980 static int tcp_can_forward_retransmit(struct sock
*sk
)
1982 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1983 struct tcp_sock
*tp
= tcp_sk(sk
);
1985 /* Forward retransmissions are possible only during Recovery. */
1986 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1989 /* No forward retransmissions in Reno are possible. */
1990 if (tcp_is_reno(tp
))
1993 /* Yeah, we have to make difficult choice between forward transmission
1994 * and retransmission... Both ways have their merits...
1996 * For now we do not retransmit anything, while we have some new
1997 * segments to send. In the other cases, follow rule 3 for
1998 * NextSeg() specified in RFC3517.
2001 if (tcp_may_send_now(sk
))
2007 /* This gets called after a retransmit timeout, and the initially
2008 * retransmitted data is acknowledged. It tries to continue
2009 * resending the rest of the retransmit queue, until either
2010 * we've sent it all or the congestion window limit is reached.
2011 * If doing SACK, the first ACK which comes back for a timeout
2012 * based retransmit packet might feed us FACK information again.
2013 * If so, we use it to avoid unnecessarily retransmissions.
2015 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2017 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2018 struct tcp_sock
*tp
= tcp_sk(sk
);
2019 struct sk_buff
*skb
;
2020 struct sk_buff
*hole
= NULL
;
2023 int fwd_rexmitting
= 0;
2026 tp
->retransmit_high
= tp
->snd_una
;
2028 if (tp
->retransmit_skb_hint
) {
2029 skb
= tp
->retransmit_skb_hint
;
2030 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2031 if (after(last_lost
, tp
->retransmit_high
))
2032 last_lost
= tp
->retransmit_high
;
2034 skb
= tcp_write_queue_head(sk
);
2035 last_lost
= tp
->snd_una
;
2038 tcp_for_write_queue_from(skb
, sk
) {
2039 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
2041 if (skb
== tcp_send_head(sk
))
2043 /* we could do better than to assign each time */
2045 tp
->retransmit_skb_hint
= skb
;
2047 /* Assume this retransmit will generate
2048 * only one packet for congestion window
2049 * calculation purposes. This works because
2050 * tcp_retransmit_skb() will chop up the
2051 * packet to be MSS sized and all the
2052 * packet counting works out.
2054 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2057 if (fwd_rexmitting
) {
2059 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2061 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2063 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2064 tp
->retransmit_high
= last_lost
;
2065 if (!tcp_can_forward_retransmit(sk
))
2067 /* Backtrack if necessary to non-L'ed skb */
2075 } else if (!(sacked
& TCPCB_LOST
)) {
2076 if (hole
== NULL
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2081 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2082 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2083 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2085 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2088 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2091 if (tcp_retransmit_skb(sk
, skb
))
2093 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2095 if (skb
== tcp_write_queue_head(sk
))
2096 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2097 inet_csk(sk
)->icsk_rto
,
2102 /* Send a fin. The caller locks the socket for us. This cannot be
2103 * allowed to fail queueing a FIN frame under any circumstances.
2105 void tcp_send_fin(struct sock
*sk
)
2107 struct tcp_sock
*tp
= tcp_sk(sk
);
2108 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2111 /* Optimization, tack on the FIN if we have a queue of
2112 * unsent frames. But be careful about outgoing SACKS
2115 mss_now
= tcp_current_mss(sk
, 1);
2117 if (tcp_send_head(sk
) != NULL
) {
2118 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
2119 TCP_SKB_CB(skb
)->end_seq
++;
2122 /* Socket is locked, keep trying until memory is available. */
2124 skb
= alloc_skb_fclone(MAX_TCP_HEADER
, GFP_KERNEL
);
2130 /* Reserve space for headers and prepare control bits. */
2131 skb_reserve(skb
, MAX_TCP_HEADER
);
2132 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2133 tcp_init_nondata_skb(skb
, tp
->write_seq
,
2134 TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
2135 tcp_queue_skb(sk
, skb
);
2137 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2140 /* We get here when a process closes a file descriptor (either due to
2141 * an explicit close() or as a byproduct of exit()'ing) and there
2142 * was unread data in the receive queue. This behavior is recommended
2143 * by RFC 2525, section 2.17. -DaveM
2145 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2147 struct sk_buff
*skb
;
2149 /* NOTE: No TCP options attached and we never retransmit this. */
2150 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2152 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2156 /* Reserve space for headers and prepare control bits. */
2157 skb_reserve(skb
, MAX_TCP_HEADER
);
2158 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
2159 TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
2161 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2162 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2163 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2165 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
2168 /* WARNING: This routine must only be called when we have already sent
2169 * a SYN packet that crossed the incoming SYN that caused this routine
2170 * to get called. If this assumption fails then the initial rcv_wnd
2171 * and rcv_wscale values will not be correct.
2173 int tcp_send_synack(struct sock
*sk
)
2175 struct sk_buff
*skb
;
2177 skb
= tcp_write_queue_head(sk
);
2178 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
)) {
2179 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
2182 if (!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_ACK
)) {
2183 if (skb_cloned(skb
)) {
2184 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2187 tcp_unlink_write_queue(skb
, sk
);
2188 skb_header_release(nskb
);
2189 __tcp_add_write_queue_head(sk
, nskb
);
2190 sk_wmem_free_skb(sk
, skb
);
2191 sk
->sk_wmem_queued
+= nskb
->truesize
;
2192 sk_mem_charge(sk
, nskb
->truesize
);
2196 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
2197 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2199 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2200 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2204 * Prepare a SYN-ACK.
2206 struct sk_buff
*tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2207 struct request_sock
*req
)
2209 struct inet_request_sock
*ireq
= inet_rsk(req
);
2210 struct tcp_sock
*tp
= tcp_sk(sk
);
2212 int tcp_header_size
;
2213 struct tcp_out_options opts
;
2214 struct sk_buff
*skb
;
2215 struct tcp_md5sig_key
*md5
;
2216 __u8
*md5_hash_location
;
2219 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
2223 /* Reserve space for headers. */
2224 skb_reserve(skb
, MAX_TCP_HEADER
);
2226 skb
->dst
= dst_clone(dst
);
2228 mss
= dst_metric(dst
, RTAX_ADVMSS
);
2229 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< mss
)
2230 mss
= tp
->rx_opt
.user_mss
;
2232 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
2234 /* Set this up on the first call only */
2235 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
2236 /* tcp_full_space because it is guaranteed to be the first packet */
2237 tcp_select_initial_window(tcp_full_space(sk
),
2238 mss
- (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
2243 ireq
->rcv_wscale
= rcv_wscale
;
2246 memset(&opts
, 0, sizeof(opts
));
2247 #ifdef CONFIG_SYN_COOKIES
2248 if (unlikely(req
->cookie_ts
))
2249 TCP_SKB_CB(skb
)->when
= cookie_init_timestamp(req
);
2252 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2253 tcp_header_size
= tcp_synack_options(sk
, req
, mss
,
2255 sizeof(struct tcphdr
);
2257 skb_push(skb
, tcp_header_size
);
2258 skb_reset_transport_header(skb
);
2261 memset(th
, 0, sizeof(struct tcphdr
));
2264 TCP_ECN_make_synack(req
, th
);
2265 th
->source
= ireq
->loc_port
;
2266 th
->dest
= ireq
->rmt_port
;
2267 /* Setting of flags are superfluous here for callers (and ECE is
2268 * not even correctly set)
2270 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
2271 TCPCB_FLAG_SYN
| TCPCB_FLAG_ACK
);
2272 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2273 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
2275 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2276 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2277 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
, &md5_hash_location
);
2278 th
->doff
= (tcp_header_size
>> 2);
2279 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
2281 #ifdef CONFIG_TCP_MD5SIG
2282 /* Okay, we have all we need - do the md5 hash if needed */
2284 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
2285 md5
, NULL
, req
, skb
);
2293 * Do all connect socket setups that can be done AF independent.
2295 static void tcp_connect_init(struct sock
*sk
)
2297 struct dst_entry
*dst
= __sk_dst_get(sk
);
2298 struct tcp_sock
*tp
= tcp_sk(sk
);
2301 /* We'll fix this up when we get a response from the other end.
2302 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2304 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2305 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2307 #ifdef CONFIG_TCP_MD5SIG
2308 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2309 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2312 /* If user gave his TCP_MAXSEG, record it to clamp */
2313 if (tp
->rx_opt
.user_mss
)
2314 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2317 tcp_sync_mss(sk
, dst_mtu(dst
));
2319 if (!tp
->window_clamp
)
2320 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2321 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
2322 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
2323 tp
->advmss
= tp
->rx_opt
.user_mss
;
2325 tcp_initialize_rcv_mss(sk
);
2327 tcp_select_initial_window(tcp_full_space(sk
),
2328 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2331 sysctl_tcp_window_scaling
,
2334 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2335 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2338 sock_reset_flag(sk
, SOCK_DONE
);
2341 tp
->snd_una
= tp
->write_seq
;
2342 tp
->snd_sml
= tp
->write_seq
;
2343 tp
->snd_up
= tp
->write_seq
;
2348 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2349 inet_csk(sk
)->icsk_retransmits
= 0;
2350 tcp_clear_retrans(tp
);
2354 * Build a SYN and send it off.
2356 int tcp_connect(struct sock
*sk
)
2358 struct tcp_sock
*tp
= tcp_sk(sk
);
2359 struct sk_buff
*buff
;
2361 tcp_connect_init(sk
);
2363 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
2364 if (unlikely(buff
== NULL
))
2367 /* Reserve space for headers. */
2368 skb_reserve(buff
, MAX_TCP_HEADER
);
2370 tp
->snd_nxt
= tp
->write_seq
;
2371 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPCB_FLAG_SYN
);
2372 TCP_ECN_send_syn(sk
, buff
);
2375 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2376 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
2377 skb_header_release(buff
);
2378 __tcp_add_write_queue_tail(sk
, buff
);
2379 sk
->sk_wmem_queued
+= buff
->truesize
;
2380 sk_mem_charge(sk
, buff
->truesize
);
2381 tp
->packets_out
+= tcp_skb_pcount(buff
);
2382 tcp_transmit_skb(sk
, buff
, 1, GFP_KERNEL
);
2384 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2385 * in order to make this packet get counted in tcpOutSegs.
2387 tp
->snd_nxt
= tp
->write_seq
;
2388 tp
->pushed_seq
= tp
->write_seq
;
2389 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
2391 /* Timer for repeating the SYN until an answer. */
2392 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2393 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2397 /* Send out a delayed ack, the caller does the policy checking
2398 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2401 void tcp_send_delayed_ack(struct sock
*sk
)
2403 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2404 int ato
= icsk
->icsk_ack
.ato
;
2405 unsigned long timeout
;
2407 if (ato
> TCP_DELACK_MIN
) {
2408 const struct tcp_sock
*tp
= tcp_sk(sk
);
2409 int max_ato
= HZ
/ 2;
2411 if (icsk
->icsk_ack
.pingpong
||
2412 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
2413 max_ato
= TCP_DELACK_MAX
;
2415 /* Slow path, intersegment interval is "high". */
2417 /* If some rtt estimate is known, use it to bound delayed ack.
2418 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2422 int rtt
= max(tp
->srtt
>> 3, TCP_DELACK_MIN
);
2428 ato
= min(ato
, max_ato
);
2431 /* Stay within the limit we were given */
2432 timeout
= jiffies
+ ato
;
2434 /* Use new timeout only if there wasn't a older one earlier. */
2435 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
2436 /* If delack timer was blocked or is about to expire,
2439 if (icsk
->icsk_ack
.blocked
||
2440 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
2445 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
2446 timeout
= icsk
->icsk_ack
.timeout
;
2448 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
2449 icsk
->icsk_ack
.timeout
= timeout
;
2450 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
2453 /* This routine sends an ack and also updates the window. */
2454 void tcp_send_ack(struct sock
*sk
)
2456 struct sk_buff
*buff
;
2458 /* If we have been reset, we may not send again. */
2459 if (sk
->sk_state
== TCP_CLOSE
)
2462 /* We are not putting this on the write queue, so
2463 * tcp_transmit_skb() will set the ownership to this
2466 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2468 inet_csk_schedule_ack(sk
);
2469 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
2470 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
2471 TCP_DELACK_MAX
, TCP_RTO_MAX
);
2475 /* Reserve space for headers and prepare control bits. */
2476 skb_reserve(buff
, MAX_TCP_HEADER
);
2477 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPCB_FLAG_ACK
);
2479 /* Send it off, this clears delayed acks for us. */
2480 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2481 tcp_transmit_skb(sk
, buff
, 0, GFP_ATOMIC
);
2484 /* This routine sends a packet with an out of date sequence
2485 * number. It assumes the other end will try to ack it.
2487 * Question: what should we make while urgent mode?
2488 * 4.4BSD forces sending single byte of data. We cannot send
2489 * out of window data, because we have SND.NXT==SND.MAX...
2491 * Current solution: to send TWO zero-length segments in urgent mode:
2492 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2493 * out-of-date with SND.UNA-1 to probe window.
2495 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
2497 struct tcp_sock
*tp
= tcp_sk(sk
);
2498 struct sk_buff
*skb
;
2500 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2501 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2505 /* Reserve space for headers and set control bits. */
2506 skb_reserve(skb
, MAX_TCP_HEADER
);
2507 /* Use a previous sequence. This should cause the other
2508 * end to send an ack. Don't queue or clone SKB, just
2511 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPCB_FLAG_ACK
);
2512 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2513 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
2516 int tcp_write_wakeup(struct sock
*sk
)
2518 struct tcp_sock
*tp
= tcp_sk(sk
);
2519 struct sk_buff
*skb
;
2521 if (sk
->sk_state
== TCP_CLOSE
)
2524 if ((skb
= tcp_send_head(sk
)) != NULL
&&
2525 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
2527 unsigned int mss
= tcp_current_mss(sk
, 0);
2528 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
2530 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
2531 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
2533 /* We are probing the opening of a window
2534 * but the window size is != 0
2535 * must have been a result SWS avoidance ( sender )
2537 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
2539 seg_size
= min(seg_size
, mss
);
2540 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2541 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
2543 } else if (!tcp_skb_pcount(skb
))
2544 tcp_set_skb_tso_segs(sk
, skb
, mss
);
2546 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2547 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2548 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2550 tcp_event_new_data_sent(sk
, skb
);
2553 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
2554 tcp_xmit_probe_skb(sk
, 1);
2555 return tcp_xmit_probe_skb(sk
, 0);
2559 /* A window probe timeout has occurred. If window is not closed send
2560 * a partial packet else a zero probe.
2562 void tcp_send_probe0(struct sock
*sk
)
2564 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2565 struct tcp_sock
*tp
= tcp_sk(sk
);
2568 err
= tcp_write_wakeup(sk
);
2570 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
2571 /* Cancel probe timer, if it is not required. */
2572 icsk
->icsk_probes_out
= 0;
2573 icsk
->icsk_backoff
= 0;
2578 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
2579 icsk
->icsk_backoff
++;
2580 icsk
->icsk_probes_out
++;
2581 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2582 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2585 /* If packet was not sent due to local congestion,
2586 * do not backoff and do not remember icsk_probes_out.
2587 * Let local senders to fight for local resources.
2589 * Use accumulated backoff yet.
2591 if (!icsk
->icsk_probes_out
)
2592 icsk
->icsk_probes_out
= 1;
2593 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2594 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
2595 TCP_RESOURCE_PROBE_INTERVAL
),
2600 EXPORT_SYMBOL(tcp_select_initial_window
);
2601 EXPORT_SYMBOL(tcp_connect
);
2602 EXPORT_SYMBOL(tcp_make_synack
);
2603 EXPORT_SYMBOL(tcp_simple_retransmit
);
2604 EXPORT_SYMBOL(tcp_sync_mss
);
2605 EXPORT_SYMBOL(tcp_mtup_init
);