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).
8 * Version: $Id: tcp_output.c,v 1.146 2002/02/01 22:01:04 davem Exp $
11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
24 * Changes: Pedro Roque : Retransmit queue handled by TCP.
25 * : Fragmentation on mtu decrease
26 * : Segment collapse on retransmit
29 * Linus Torvalds : send_delayed_ack
30 * David S. Miller : Charge memory using the right skb
31 * during syn/ack processing.
32 * David S. Miller : Output engine completely rewritten.
33 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
34 * Cacophonix Gaul : draft-minshall-nagle-01
35 * J Hadi Salim : ECN support
41 #include <linux/compiler.h>
42 #include <linux/module.h>
44 /* People can turn this off for buggy TCP's found in printers etc. */
45 int sysctl_tcp_retrans_collapse __read_mostly
= 1;
47 /* People can turn this on to work with those rare, broken TCPs that
48 * interpret the window field as a signed quantity.
50 int sysctl_tcp_workaround_signed_windows __read_mostly
= 0;
52 /* This limits the percentage of the congestion window which we
53 * will allow a single TSO frame to consume. Building TSO frames
54 * which are too large can cause TCP streams to be bursty.
56 int sysctl_tcp_tso_win_divisor __read_mostly
= 3;
58 int sysctl_tcp_mtu_probing __read_mostly
= 0;
59 int sysctl_tcp_base_mss __read_mostly
= 512;
61 /* By default, RFC2861 behavior. */
62 int sysctl_tcp_slow_start_after_idle __read_mostly
= 1;
64 static void tcp_event_new_data_sent(struct sock
*sk
, struct sk_buff
*skb
)
66 struct tcp_sock
*tp
= tcp_sk(sk
);
67 unsigned int prior_packets
= tp
->packets_out
;
69 tcp_advance_send_head(sk
, skb
);
70 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
72 /* Don't override Nagle indefinately with F-RTO */
73 if (tp
->frto_counter
== 2)
76 tp
->packets_out
+= tcp_skb_pcount(skb
);
78 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
79 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
82 /* SND.NXT, if window was not shrunk.
83 * If window has been shrunk, what should we make? It is not clear at all.
84 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
85 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
86 * invalid. OK, let's make this for now:
88 static inline __u32
tcp_acceptable_seq(struct sock
*sk
)
90 struct tcp_sock
*tp
= tcp_sk(sk
);
92 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
))
95 return tcp_wnd_end(tp
);
98 /* Calculate mss to advertise in SYN segment.
99 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
101 * 1. It is independent of path mtu.
102 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
103 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
104 * attached devices, because some buggy hosts are confused by
106 * 4. We do not make 3, we advertise MSS, calculated from first
107 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
108 * This may be overridden via information stored in routing table.
109 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
110 * probably even Jumbo".
112 static __u16
tcp_advertise_mss(struct sock
*sk
)
114 struct tcp_sock
*tp
= tcp_sk(sk
);
115 struct dst_entry
*dst
= __sk_dst_get(sk
);
116 int mss
= tp
->advmss
;
118 if (dst
&& dst_metric(dst
, RTAX_ADVMSS
) < mss
) {
119 mss
= dst_metric(dst
, RTAX_ADVMSS
);
126 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
127 * This is the first part of cwnd validation mechanism. */
128 static void tcp_cwnd_restart(struct sock
*sk
, struct dst_entry
*dst
)
130 struct tcp_sock
*tp
= tcp_sk(sk
);
131 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
132 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
133 u32 cwnd
= tp
->snd_cwnd
;
135 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
137 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
138 restart_cwnd
= min(restart_cwnd
, cwnd
);
140 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
142 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
143 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
144 tp
->snd_cwnd_used
= 0;
147 static void tcp_event_data_sent(struct tcp_sock
*tp
,
148 struct sk_buff
*skb
, struct sock
*sk
)
150 struct inet_connection_sock
*icsk
= inet_csk(sk
);
151 const u32 now
= tcp_time_stamp
;
153 if (sysctl_tcp_slow_start_after_idle
&&
154 (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
))
155 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
159 /* If it is a reply for ato after last received
160 * packet, enter pingpong mode.
162 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
163 icsk
->icsk_ack
.pingpong
= 1;
166 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
168 tcp_dec_quickack_mode(sk
, pkts
);
169 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
172 /* Determine a window scaling and initial window to offer.
173 * Based on the assumption that the given amount of space
174 * will be offered. Store the results in the tp structure.
175 * NOTE: for smooth operation initial space offering should
176 * be a multiple of mss if possible. We assume here that mss >= 1.
177 * This MUST be enforced by all callers.
179 void tcp_select_initial_window(int __space
, __u32 mss
,
180 __u32
*rcv_wnd
, __u32
*window_clamp
,
181 int wscale_ok
, __u8
*rcv_wscale
)
183 unsigned int space
= (__space
< 0 ? 0 : __space
);
185 /* If no clamp set the clamp to the max possible scaled window */
186 if (*window_clamp
== 0)
187 (*window_clamp
) = (65535 << 14);
188 space
= min(*window_clamp
, space
);
190 /* Quantize space offering to a multiple of mss if possible. */
192 space
= (space
/ mss
) * mss
;
194 /* NOTE: offering an initial window larger than 32767
195 * will break some buggy TCP stacks. If the admin tells us
196 * it is likely we could be speaking with such a buggy stack
197 * we will truncate our initial window offering to 32K-1
198 * unless the remote has sent us a window scaling option,
199 * which we interpret as a sign the remote TCP is not
200 * misinterpreting the window field as a signed quantity.
202 if (sysctl_tcp_workaround_signed_windows
)
203 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
209 /* Set window scaling on max possible window
210 * See RFC1323 for an explanation of the limit to 14
212 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
213 space
= min_t(u32
, space
, *window_clamp
);
214 while (space
> 65535 && (*rcv_wscale
) < 14) {
220 /* Set initial window to value enough for senders,
221 * following RFC2414. Senders, not following this RFC,
222 * will be satisfied with 2.
224 if (mss
> (1<<*rcv_wscale
)) {
230 if (*rcv_wnd
> init_cwnd
*mss
)
231 *rcv_wnd
= init_cwnd
*mss
;
234 /* Set the clamp no higher than max representable value */
235 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
238 /* Chose a new window to advertise, update state in tcp_sock for the
239 * socket, and return result with RFC1323 scaling applied. The return
240 * value can be stuffed directly into th->window for an outgoing
243 static u16
tcp_select_window(struct sock
*sk
)
245 struct tcp_sock
*tp
= tcp_sk(sk
);
246 u32 cur_win
= tcp_receive_window(tp
);
247 u32 new_win
= __tcp_select_window(sk
);
249 /* Never shrink the offered window */
250 if (new_win
< cur_win
) {
251 /* Danger Will Robinson!
252 * Don't update rcv_wup/rcv_wnd here or else
253 * we will not be able to advertise a zero
254 * window in time. --DaveM
256 * Relax Will Robinson.
260 tp
->rcv_wnd
= new_win
;
261 tp
->rcv_wup
= tp
->rcv_nxt
;
263 /* Make sure we do not exceed the maximum possible
266 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
267 new_win
= min(new_win
, MAX_TCP_WINDOW
);
269 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
271 /* RFC1323 scaling applied */
272 new_win
>>= tp
->rx_opt
.rcv_wscale
;
274 /* If we advertise zero window, disable fast path. */
281 static inline void TCP_ECN_send_synack(struct tcp_sock
*tp
,
284 TCP_SKB_CB(skb
)->flags
&= ~TCPCB_FLAG_CWR
;
285 if (!(tp
->ecn_flags
&TCP_ECN_OK
))
286 TCP_SKB_CB(skb
)->flags
&= ~TCPCB_FLAG_ECE
;
289 static inline void TCP_ECN_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
291 struct tcp_sock
*tp
= tcp_sk(sk
);
294 if (sysctl_tcp_ecn
) {
295 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ECE
|TCPCB_FLAG_CWR
;
296 tp
->ecn_flags
= TCP_ECN_OK
;
300 static __inline__
void
301 TCP_ECN_make_synack(struct request_sock
*req
, struct tcphdr
*th
)
303 if (inet_rsk(req
)->ecn_ok
)
307 static inline void TCP_ECN_send(struct sock
*sk
, struct sk_buff
*skb
,
310 struct tcp_sock
*tp
= tcp_sk(sk
);
312 if (tp
->ecn_flags
& TCP_ECN_OK
) {
313 /* Not-retransmitted data segment: set ECT and inject CWR. */
314 if (skb
->len
!= tcp_header_len
&&
315 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
317 if (tp
->ecn_flags
&TCP_ECN_QUEUE_CWR
) {
318 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
319 tcp_hdr(skb
)->cwr
= 1;
320 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
323 /* ACK or retransmitted segment: clear ECT|CE */
324 INET_ECN_dontxmit(sk
);
326 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
327 tcp_hdr(skb
)->ece
= 1;
331 static void tcp_build_and_update_options(__be32
*ptr
, struct tcp_sock
*tp
,
332 __u32 tstamp
, __u8
**md5_hash
)
334 if (tp
->rx_opt
.tstamp_ok
) {
335 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
337 (TCPOPT_TIMESTAMP
<< 8) |
339 *ptr
++ = htonl(tstamp
);
340 *ptr
++ = htonl(tp
->rx_opt
.ts_recent
);
342 if (tp
->rx_opt
.eff_sacks
) {
343 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
? tp
->duplicate_sack
: tp
->selective_acks
;
346 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
349 (TCPOLEN_SACK_BASE
+ (tp
->rx_opt
.eff_sacks
*
350 TCPOLEN_SACK_PERBLOCK
)));
352 for (this_sack
= 0; this_sack
< tp
->rx_opt
.eff_sacks
; this_sack
++) {
353 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
354 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
357 if (tp
->rx_opt
.dsack
) {
358 tp
->rx_opt
.dsack
= 0;
359 tp
->rx_opt
.eff_sacks
--;
362 #ifdef CONFIG_TCP_MD5SIG
364 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
366 (TCPOPT_MD5SIG
<< 8) |
368 *md5_hash
= (__u8
*)ptr
;
373 /* Construct a tcp options header for a SYN or SYN_ACK packet.
374 * If this is every changed make sure to change the definition of
375 * MAX_SYN_SIZE to match the new maximum number of options that you
378 * Note - that with the RFC2385 TCP option, we make room for the
379 * 16 byte MD5 hash. This will be filled in later, so the pointer for the
380 * location to be filled is passed back up.
382 static void tcp_syn_build_options(__be32
*ptr
, int mss
, int ts
, int sack
,
383 int offer_wscale
, int wscale
, __u32 tstamp
,
384 __u32 ts_recent
, __u8
**md5_hash
)
386 /* We always get an MSS option.
387 * The option bytes which will be seen in normal data
388 * packets should timestamps be used, must be in the MSS
389 * advertised. But we subtract them from tp->mss_cache so
390 * that calculations in tcp_sendmsg are simpler etc.
391 * So account for this fact here if necessary. If we
392 * don't do this correctly, as a receiver we won't
393 * recognize data packets as being full sized when we
394 * should, and thus we won't abide by the delayed ACK
396 * SACKs don't matter, we never delay an ACK when we
397 * have any of those going out.
399 *ptr
++ = htonl((TCPOPT_MSS
<< 24) | (TCPOLEN_MSS
<< 16) | mss
);
402 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
403 (TCPOLEN_SACK_PERM
<< 16) |
404 (TCPOPT_TIMESTAMP
<< 8) |
407 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
409 (TCPOPT_TIMESTAMP
<< 8) |
411 *ptr
++ = htonl(tstamp
); /* TSVAL */
412 *ptr
++ = htonl(ts_recent
); /* TSECR */
414 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
416 (TCPOPT_SACK_PERM
<< 8) |
419 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
420 (TCPOPT_WINDOW
<< 16) |
421 (TCPOLEN_WINDOW
<< 8) |
423 #ifdef CONFIG_TCP_MD5SIG
425 * If MD5 is enabled, then we set the option, and include the size
426 * (always 18). The actual MD5 hash is added just before the
430 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
432 (TCPOPT_MD5SIG
<< 8) |
434 *md5_hash
= (__u8
*) ptr
;
439 /* This routine actually transmits TCP packets queued in by
440 * tcp_do_sendmsg(). This is used by both the initial
441 * transmission and possible later retransmissions.
442 * All SKB's seen here are completely headerless. It is our
443 * job to build the TCP header, and pass the packet down to
444 * IP so it can do the same plus pass the packet off to the
447 * We are working here with either a clone of the original
448 * SKB, or a fresh unique copy made by the retransmit engine.
450 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
, gfp_t gfp_mask
)
452 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
453 struct inet_sock
*inet
;
455 struct tcp_skb_cb
*tcb
;
457 #ifdef CONFIG_TCP_MD5SIG
458 struct tcp_md5sig_key
*md5
;
459 __u8
*md5_hash_location
;
465 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
467 /* If congestion control is doing timestamping, we must
468 * take such a timestamp before we potentially clone/copy.
470 if (icsk
->icsk_ca_ops
->flags
& TCP_CONG_RTT_STAMP
)
471 __net_timestamp(skb
);
473 if (likely(clone_it
)) {
474 if (unlikely(skb_cloned(skb
)))
475 skb
= pskb_copy(skb
, gfp_mask
);
477 skb
= skb_clone(skb
, gfp_mask
);
484 tcb
= TCP_SKB_CB(skb
);
485 tcp_header_size
= tp
->tcp_header_len
;
487 #define SYSCTL_FLAG_TSTAMPS 0x1
488 #define SYSCTL_FLAG_WSCALE 0x2
489 #define SYSCTL_FLAG_SACK 0x4
492 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
493 tcp_header_size
= sizeof(struct tcphdr
) + TCPOLEN_MSS
;
494 if (sysctl_tcp_timestamps
) {
495 tcp_header_size
+= TCPOLEN_TSTAMP_ALIGNED
;
496 sysctl_flags
|= SYSCTL_FLAG_TSTAMPS
;
498 if (sysctl_tcp_window_scaling
) {
499 tcp_header_size
+= TCPOLEN_WSCALE_ALIGNED
;
500 sysctl_flags
|= SYSCTL_FLAG_WSCALE
;
502 if (sysctl_tcp_sack
) {
503 sysctl_flags
|= SYSCTL_FLAG_SACK
;
504 if (!(sysctl_flags
& SYSCTL_FLAG_TSTAMPS
))
505 tcp_header_size
+= TCPOLEN_SACKPERM_ALIGNED
;
507 } else if (unlikely(tp
->rx_opt
.eff_sacks
)) {
508 /* A SACK is 2 pad bytes, a 2 byte header, plus
509 * 2 32-bit sequence numbers for each SACK block.
511 tcp_header_size
+= (TCPOLEN_SACK_BASE_ALIGNED
+
512 (tp
->rx_opt
.eff_sacks
*
513 TCPOLEN_SACK_PERBLOCK
));
516 if (tcp_packets_in_flight(tp
) == 0)
517 tcp_ca_event(sk
, CA_EVENT_TX_START
);
519 #ifdef CONFIG_TCP_MD5SIG
521 * Are we doing MD5 on this segment? If so - make
524 md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
526 tcp_header_size
+= TCPOLEN_MD5SIG_ALIGNED
;
529 skb_push(skb
, tcp_header_size
);
530 skb_reset_transport_header(skb
);
531 skb_set_owner_w(skb
, sk
);
533 /* Build TCP header and checksum it. */
535 th
->source
= inet
->sport
;
536 th
->dest
= inet
->dport
;
537 th
->seq
= htonl(tcb
->seq
);
538 th
->ack_seq
= htonl(tp
->rcv_nxt
);
539 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
542 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
543 /* RFC1323: The window in SYN & SYN/ACK segments
546 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
548 th
->window
= htons(tcp_select_window(sk
));
553 if (unlikely(tp
->urg_mode
&&
554 between(tp
->snd_up
, tcb
->seq
+1, tcb
->seq
+0xFFFF))) {
555 th
->urg_ptr
= htons(tp
->snd_up
-tcb
->seq
);
559 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
560 tcp_syn_build_options((__be32
*)(th
+ 1),
561 tcp_advertise_mss(sk
),
562 (sysctl_flags
& SYSCTL_FLAG_TSTAMPS
),
563 (sysctl_flags
& SYSCTL_FLAG_SACK
),
564 (sysctl_flags
& SYSCTL_FLAG_WSCALE
),
565 tp
->rx_opt
.rcv_wscale
,
567 tp
->rx_opt
.ts_recent
,
569 #ifdef CONFIG_TCP_MD5SIG
570 md5
? &md5_hash_location
:
574 tcp_build_and_update_options((__be32
*)(th
+ 1),
576 #ifdef CONFIG_TCP_MD5SIG
577 md5
? &md5_hash_location
:
580 TCP_ECN_send(sk
, skb
, tcp_header_size
);
583 #ifdef CONFIG_TCP_MD5SIG
584 /* Calculate the MD5 hash, as we have all we need now */
586 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
595 icsk
->icsk_af_ops
->send_check(sk
, skb
->len
, skb
);
597 if (likely(tcb
->flags
& TCPCB_FLAG_ACK
))
598 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
600 if (skb
->len
!= tcp_header_size
)
601 tcp_event_data_sent(tp
, skb
, sk
);
603 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
604 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
606 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, 0);
607 if (likely(err
<= 0))
610 tcp_enter_cwr(sk
, 1);
612 return net_xmit_eval(err
);
614 #undef SYSCTL_FLAG_TSTAMPS
615 #undef SYSCTL_FLAG_WSCALE
616 #undef SYSCTL_FLAG_SACK
620 /* This routine just queue's the buffer
622 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
623 * otherwise socket can stall.
625 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
627 struct tcp_sock
*tp
= tcp_sk(sk
);
629 /* Advance write_seq and place onto the write_queue. */
630 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
631 skb_header_release(skb
);
632 tcp_add_write_queue_tail(sk
, skb
);
633 sk
->sk_wmem_queued
+= skb
->truesize
;
634 sk_mem_charge(sk
, skb
->truesize
);
637 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
639 if (skb
->len
<= mss_now
|| !sk_can_gso(sk
)) {
640 /* Avoid the costly divide in the normal
643 skb_shinfo(skb
)->gso_segs
= 1;
644 skb_shinfo(skb
)->gso_size
= 0;
645 skb_shinfo(skb
)->gso_type
= 0;
647 skb_shinfo(skb
)->gso_segs
= DIV_ROUND_UP(skb
->len
, mss_now
);
648 skb_shinfo(skb
)->gso_size
= mss_now
;
649 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
653 /* When a modification to fackets out becomes necessary, we need to check
654 * skb is counted to fackets_out or not.
656 static void tcp_adjust_fackets_out(struct sock
*sk
, struct sk_buff
*skb
,
659 struct tcp_sock
*tp
= tcp_sk(sk
);
661 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
664 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
665 tp
->fackets_out
-= decr
;
668 /* Function to create two new TCP segments. Shrinks the given segment
669 * to the specified size and appends a new segment with the rest of the
670 * packet to the list. This won't be called frequently, I hope.
671 * Remember, these are still headerless SKBs at this point.
673 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
, unsigned int mss_now
)
675 struct tcp_sock
*tp
= tcp_sk(sk
);
676 struct sk_buff
*buff
;
677 int nsize
, old_factor
;
681 BUG_ON(len
> skb
->len
);
683 tcp_clear_retrans_hints_partial(tp
);
684 nsize
= skb_headlen(skb
) - len
;
688 if (skb_cloned(skb
) &&
689 skb_is_nonlinear(skb
) &&
690 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
693 /* Get a new skb... force flag on. */
694 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
696 return -ENOMEM
; /* We'll just try again later. */
698 sk
->sk_wmem_queued
+= buff
->truesize
;
699 sk_mem_charge(sk
, buff
->truesize
);
700 nlen
= skb
->len
- len
- nsize
;
701 buff
->truesize
+= nlen
;
702 skb
->truesize
-= nlen
;
704 /* Correct the sequence numbers. */
705 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
706 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
707 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
709 /* PSH and FIN should only be set in the second packet. */
710 flags
= TCP_SKB_CB(skb
)->flags
;
711 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
712 TCP_SKB_CB(buff
)->flags
= flags
;
713 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
715 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
716 /* Copy and checksum data tail into the new buffer. */
717 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
, skb_put(buff
, nsize
),
722 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
724 skb
->ip_summed
= CHECKSUM_PARTIAL
;
725 skb_split(skb
, buff
, len
);
728 buff
->ip_summed
= skb
->ip_summed
;
730 /* Looks stupid, but our code really uses when of
731 * skbs, which it never sent before. --ANK
733 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
734 buff
->tstamp
= skb
->tstamp
;
736 old_factor
= tcp_skb_pcount(skb
);
738 /* Fix up tso_factor for both original and new SKB. */
739 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
740 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
742 /* If this packet has been sent out already, we must
743 * adjust the various packet counters.
745 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
746 int diff
= old_factor
- tcp_skb_pcount(skb
) -
747 tcp_skb_pcount(buff
);
749 tp
->packets_out
-= diff
;
751 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
752 tp
->sacked_out
-= diff
;
753 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
754 tp
->retrans_out
-= diff
;
756 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
757 tp
->lost_out
-= diff
;
759 /* Adjust Reno SACK estimate. */
760 if (tcp_is_reno(tp
) && diff
> 0) {
761 tcp_dec_pcount_approx_int(&tp
->sacked_out
, diff
);
762 tcp_verify_left_out(tp
);
764 tcp_adjust_fackets_out(sk
, skb
, diff
);
767 /* Link BUFF into the send queue. */
768 skb_header_release(buff
);
769 tcp_insert_write_queue_after(skb
, buff
, sk
);
774 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
775 * eventually). The difference is that pulled data not copied, but
776 * immediately discarded.
778 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
784 for (i
=0; i
<skb_shinfo(skb
)->nr_frags
; i
++) {
785 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
786 put_page(skb_shinfo(skb
)->frags
[i
].page
);
787 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
789 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
791 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
792 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
798 skb_shinfo(skb
)->nr_frags
= k
;
800 skb_reset_tail_pointer(skb
);
801 skb
->data_len
-= len
;
802 skb
->len
= skb
->data_len
;
805 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
807 if (skb_cloned(skb
) &&
808 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
811 /* If len == headlen, we avoid __skb_pull to preserve alignment. */
812 if (unlikely(len
< skb_headlen(skb
)))
813 __skb_pull(skb
, len
);
815 __pskb_trim_head(skb
, len
- skb_headlen(skb
));
817 TCP_SKB_CB(skb
)->seq
+= len
;
818 skb
->ip_summed
= CHECKSUM_PARTIAL
;
820 skb
->truesize
-= len
;
821 sk
->sk_wmem_queued
-= len
;
822 sk_mem_uncharge(sk
, len
);
823 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
825 /* Any change of skb->len requires recalculation of tso
828 if (tcp_skb_pcount(skb
) > 1)
829 tcp_set_skb_tso_segs(sk
, skb
, tcp_current_mss(sk
, 1));
834 /* Not accounting for SACKs here. */
835 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
837 struct tcp_sock
*tp
= tcp_sk(sk
);
838 struct inet_connection_sock
*icsk
= inet_csk(sk
);
841 /* Calculate base mss without TCP options:
842 It is MMS_S - sizeof(tcphdr) of rfc1122
844 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
846 /* Clamp it (mss_clamp does not include tcp options) */
847 if (mss_now
> tp
->rx_opt
.mss_clamp
)
848 mss_now
= tp
->rx_opt
.mss_clamp
;
850 /* Now subtract optional transport overhead */
851 mss_now
-= icsk
->icsk_ext_hdr_len
;
853 /* Then reserve room for full set of TCP options and 8 bytes of data */
857 /* Now subtract TCP options size, not including SACKs */
858 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
863 /* Inverse of above */
864 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
866 struct tcp_sock
*tp
= tcp_sk(sk
);
867 struct inet_connection_sock
*icsk
= inet_csk(sk
);
872 icsk
->icsk_ext_hdr_len
+
873 icsk
->icsk_af_ops
->net_header_len
;
878 void tcp_mtup_init(struct sock
*sk
)
880 struct tcp_sock
*tp
= tcp_sk(sk
);
881 struct inet_connection_sock
*icsk
= inet_csk(sk
);
883 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
884 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
885 icsk
->icsk_af_ops
->net_header_len
;
886 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
887 icsk
->icsk_mtup
.probe_size
= 0;
890 /* This function synchronize snd mss to current pmtu/exthdr set.
892 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
893 for TCP options, but includes only bare TCP header.
895 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
896 It is minimum of user_mss and mss received with SYN.
897 It also does not include TCP options.
899 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
901 tp->mss_cache is current effective sending mss, including
902 all tcp options except for SACKs. It is evaluated,
903 taking into account current pmtu, but never exceeds
904 tp->rx_opt.mss_clamp.
906 NOTE1. rfc1122 clearly states that advertised MSS
907 DOES NOT include either tcp or ip options.
909 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
910 are READ ONLY outside this function. --ANK (980731)
913 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
915 struct tcp_sock
*tp
= tcp_sk(sk
);
916 struct inet_connection_sock
*icsk
= inet_csk(sk
);
919 if (icsk
->icsk_mtup
.search_high
> pmtu
)
920 icsk
->icsk_mtup
.search_high
= pmtu
;
922 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
924 /* Bound mss with half of window */
925 if (tp
->max_window
&& mss_now
> (tp
->max_window
>>1))
926 mss_now
= max((tp
->max_window
>>1), 68U - tp
->tcp_header_len
);
928 /* And store cached results */
929 icsk
->icsk_pmtu_cookie
= pmtu
;
930 if (icsk
->icsk_mtup
.enabled
)
931 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
932 tp
->mss_cache
= mss_now
;
937 /* Compute the current effective MSS, taking SACKs and IP options,
938 * and even PMTU discovery events into account.
940 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
941 * cannot be large. However, taking into account rare use of URG, this
944 unsigned int tcp_current_mss(struct sock
*sk
, int large_allowed
)
946 struct tcp_sock
*tp
= tcp_sk(sk
);
947 struct dst_entry
*dst
= __sk_dst_get(sk
);
952 mss_now
= tp
->mss_cache
;
954 if (large_allowed
&& sk_can_gso(sk
) && !tp
->urg_mode
)
958 u32 mtu
= dst_mtu(dst
);
959 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
960 mss_now
= tcp_sync_mss(sk
, mtu
);
963 if (tp
->rx_opt
.eff_sacks
)
964 mss_now
-= (TCPOLEN_SACK_BASE_ALIGNED
+
965 (tp
->rx_opt
.eff_sacks
* TCPOLEN_SACK_PERBLOCK
));
967 #ifdef CONFIG_TCP_MD5SIG
968 if (tp
->af_specific
->md5_lookup(sk
, sk
))
969 mss_now
-= TCPOLEN_MD5SIG_ALIGNED
;
972 xmit_size_goal
= mss_now
;
975 xmit_size_goal
= (65535 -
976 inet_csk(sk
)->icsk_af_ops
->net_header_len
-
977 inet_csk(sk
)->icsk_ext_hdr_len
-
980 if (tp
->max_window
&&
981 (xmit_size_goal
> (tp
->max_window
>> 1)))
982 xmit_size_goal
= max((tp
->max_window
>> 1),
983 68U - tp
->tcp_header_len
);
985 xmit_size_goal
-= (xmit_size_goal
% mss_now
);
987 tp
->xmit_size_goal
= xmit_size_goal
;
992 /* Congestion window validation. (RFC2861) */
994 static void tcp_cwnd_validate(struct sock
*sk
)
996 struct tcp_sock
*tp
= tcp_sk(sk
);
997 __u32 packets_out
= tp
->packets_out
;
999 if (packets_out
>= tp
->snd_cwnd
) {
1000 /* Network is feed fully. */
1001 tp
->snd_cwnd_used
= 0;
1002 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1004 /* Network starves. */
1005 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1006 tp
->snd_cwnd_used
= tp
->packets_out
;
1008 if (sysctl_tcp_slow_start_after_idle
&&
1009 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1010 tcp_cwnd_application_limited(sk
);
1014 /* Returns the portion of skb which can be sent right away without
1015 * introducing MSS oddities to segment boundaries. In rare cases where
1016 * mss_now != mss_cache, we will request caller to create a small skb
1017 * per input skb which could be mostly avoided here (if desired).
1019 static unsigned int tcp_mss_split_point(struct sock
*sk
, struct sk_buff
*skb
,
1020 unsigned int mss_now
,
1023 struct tcp_sock
*tp
= tcp_sk(sk
);
1024 u32 needed
, window
, cwnd_len
;
1026 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1027 cwnd_len
= mss_now
* cwnd
;
1029 if (likely(cwnd_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1032 if (skb
== tcp_write_queue_tail(sk
) && cwnd_len
<= skb
->len
)
1035 needed
= min(skb
->len
, window
);
1036 return needed
- needed
% mss_now
;
1039 /* Can at least one segment of SKB be sent right now, according to the
1040 * congestion window rules? If so, return how many segments are allowed.
1042 static inline unsigned int tcp_cwnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
)
1044 u32 in_flight
, cwnd
;
1046 /* Don't be strict about the congestion window for the final FIN. */
1047 if ((TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1048 tcp_skb_pcount(skb
) == 1)
1051 in_flight
= tcp_packets_in_flight(tp
);
1052 cwnd
= tp
->snd_cwnd
;
1053 if (in_flight
< cwnd
)
1054 return (cwnd
- in_flight
);
1059 /* This must be invoked the first time we consider transmitting
1060 * SKB onto the wire.
1062 static int tcp_init_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
1064 int tso_segs
= tcp_skb_pcount(skb
);
1068 tcp_skb_mss(skb
) != mss_now
)) {
1069 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1070 tso_segs
= tcp_skb_pcount(skb
);
1075 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
1077 return after(tp
->snd_sml
,tp
->snd_una
) &&
1078 !after(tp
->snd_sml
, tp
->snd_nxt
);
1081 /* Return 0, if packet can be sent now without violation Nagle's rules:
1082 * 1. It is full sized.
1083 * 2. Or it contains FIN. (already checked by caller)
1084 * 3. Or TCP_NODELAY was set.
1085 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1086 * With Minshall's modification: all sent small packets are ACKed.
1089 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
1090 const struct sk_buff
*skb
,
1091 unsigned mss_now
, int nonagle
)
1093 return (skb
->len
< mss_now
&&
1094 ((nonagle
&TCP_NAGLE_CORK
) ||
1097 tcp_minshall_check(tp
))));
1100 /* Return non-zero if the Nagle test allows this packet to be
1103 static inline int tcp_nagle_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1104 unsigned int cur_mss
, int nonagle
)
1106 /* Nagle rule does not apply to frames, which sit in the middle of the
1107 * write_queue (they have no chances to get new data).
1109 * This is implemented in the callers, where they modify the 'nonagle'
1110 * argument based upon the location of SKB in the send queue.
1112 if (nonagle
& TCP_NAGLE_PUSH
)
1115 /* Don't use the nagle rule for urgent data (or for the final FIN).
1116 * Nagle can be ignored during F-RTO too (see RFC4138).
1118 if (tp
->urg_mode
|| (tp
->frto_counter
== 2) ||
1119 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
))
1122 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
1128 /* Does at least the first segment of SKB fit into the send window? */
1129 static inline int tcp_snd_wnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
, unsigned int cur_mss
)
1131 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1133 if (skb
->len
> cur_mss
)
1134 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1136 return !after(end_seq
, tcp_wnd_end(tp
));
1139 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1140 * should be put on the wire right now. If so, it returns the number of
1141 * packets allowed by the congestion window.
1143 static unsigned int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
1144 unsigned int cur_mss
, int nonagle
)
1146 struct tcp_sock
*tp
= tcp_sk(sk
);
1147 unsigned int cwnd_quota
;
1149 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1151 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1154 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1156 !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1162 int tcp_may_send_now(struct sock
*sk
)
1164 struct tcp_sock
*tp
= tcp_sk(sk
);
1165 struct sk_buff
*skb
= tcp_send_head(sk
);
1168 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
, 1),
1169 (tcp_skb_is_last(sk
, skb
) ?
1170 tp
->nonagle
: TCP_NAGLE_PUSH
)));
1173 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1174 * which is put after SKB on the list. It is very much like
1175 * tcp_fragment() except that it may make several kinds of assumptions
1176 * in order to speed up the splitting operation. In particular, we
1177 * know that all the data is in scatter-gather pages, and that the
1178 * packet has never been sent out before (and thus is not cloned).
1180 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
, unsigned int mss_now
)
1182 struct sk_buff
*buff
;
1183 int nlen
= skb
->len
- len
;
1186 /* All of a TSO frame must be composed of paged data. */
1187 if (skb
->len
!= skb
->data_len
)
1188 return tcp_fragment(sk
, skb
, len
, mss_now
);
1190 buff
= sk_stream_alloc_skb(sk
, 0, GFP_ATOMIC
);
1191 if (unlikely(buff
== NULL
))
1194 sk
->sk_wmem_queued
+= buff
->truesize
;
1195 sk_mem_charge(sk
, buff
->truesize
);
1196 buff
->truesize
+= nlen
;
1197 skb
->truesize
-= nlen
;
1199 /* Correct the sequence numbers. */
1200 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1201 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1202 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1204 /* PSH and FIN should only be set in the second packet. */
1205 flags
= TCP_SKB_CB(skb
)->flags
;
1206 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
1207 TCP_SKB_CB(buff
)->flags
= flags
;
1209 /* This packet was never sent out yet, so no SACK bits. */
1210 TCP_SKB_CB(buff
)->sacked
= 0;
1212 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1213 skb_split(skb
, buff
, len
);
1215 /* Fix up tso_factor for both original and new SKB. */
1216 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1217 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1219 /* Link BUFF into the send queue. */
1220 skb_header_release(buff
);
1221 tcp_insert_write_queue_after(skb
, buff
, sk
);
1226 /* Try to defer sending, if possible, in order to minimize the amount
1227 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1229 * This algorithm is from John Heffner.
1231 static int tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
)
1233 struct tcp_sock
*tp
= tcp_sk(sk
);
1234 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1235 u32 send_win
, cong_win
, limit
, in_flight
;
1237 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
1240 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1243 /* Defer for less than two clock ticks. */
1244 if (tp
->tso_deferred
&&
1245 ((jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1248 in_flight
= tcp_packets_in_flight(tp
);
1250 BUG_ON(tcp_skb_pcount(skb
) <= 1 ||
1251 (tp
->snd_cwnd
<= in_flight
));
1253 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1255 /* From in_flight test above, we know that cwnd > in_flight. */
1256 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1258 limit
= min(send_win
, cong_win
);
1260 /* If a full-sized TSO skb can be sent, do it. */
1264 if (sysctl_tcp_tso_win_divisor
) {
1265 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1267 /* If at least some fraction of a window is available,
1270 chunk
/= sysctl_tcp_tso_win_divisor
;
1274 /* Different approach, try not to defer past a single
1275 * ACK. Receiver should ACK every other full sized
1276 * frame, so if we have space for more than 3 frames
1279 if (limit
> tcp_max_burst(tp
) * tp
->mss_cache
)
1283 /* Ok, it looks like it is advisable to defer. */
1284 tp
->tso_deferred
= 1 | (jiffies
<<1);
1289 tp
->tso_deferred
= 0;
1293 /* Create a new MTU probe if we are ready.
1294 * Returns 0 if we should wait to probe (no cwnd available),
1295 * 1 if a probe was sent,
1297 static int tcp_mtu_probe(struct sock
*sk
)
1299 struct tcp_sock
*tp
= tcp_sk(sk
);
1300 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1301 struct sk_buff
*skb
, *nskb
, *next
;
1308 /* Not currently probing/verifying,
1310 * have enough cwnd, and
1311 * not SACKing (the variable headers throw things off) */
1312 if (!icsk
->icsk_mtup
.enabled
||
1313 icsk
->icsk_mtup
.probe_size
||
1314 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1315 tp
->snd_cwnd
< 11 ||
1316 tp
->rx_opt
.eff_sacks
)
1319 /* Very simple search strategy: just double the MSS. */
1320 mss_now
= tcp_current_mss(sk
, 0);
1321 probe_size
= 2*tp
->mss_cache
;
1322 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1323 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1324 /* TODO: set timer for probe_converge_event */
1328 /* Have enough data in the send queue to probe? */
1329 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1332 if (tp
->snd_wnd
< size_needed
)
1334 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1337 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1338 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1339 if (!tcp_packets_in_flight(tp
))
1345 /* We're allowed to probe. Build it now. */
1346 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1348 sk
->sk_wmem_queued
+= nskb
->truesize
;
1349 sk_mem_charge(sk
, nskb
->truesize
);
1351 skb
= tcp_send_head(sk
);
1353 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1354 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1355 TCP_SKB_CB(nskb
)->flags
= TCPCB_FLAG_ACK
;
1356 TCP_SKB_CB(nskb
)->sacked
= 0;
1358 nskb
->ip_summed
= skb
->ip_summed
;
1360 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1363 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1364 copy
= min_t(int, skb
->len
, probe_size
- len
);
1365 if (nskb
->ip_summed
)
1366 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1368 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1369 skb_put(nskb
, copy
), copy
, nskb
->csum
);
1371 if (skb
->len
<= copy
) {
1372 /* We've eaten all the data from this skb.
1374 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
;
1375 tcp_unlink_write_queue(skb
, sk
);
1376 sk_wmem_free_skb(sk
, skb
);
1378 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
&
1379 ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
1380 if (!skb_shinfo(skb
)->nr_frags
) {
1381 skb_pull(skb
, copy
);
1382 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1383 skb
->csum
= csum_partial(skb
->data
, skb
->len
, 0);
1385 __pskb_trim_head(skb
, copy
);
1386 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1388 TCP_SKB_CB(skb
)->seq
+= copy
;
1393 if (len
>= probe_size
)
1396 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1398 /* We're ready to send. If this fails, the probe will
1399 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1400 TCP_SKB_CB(nskb
)->when
= tcp_time_stamp
;
1401 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1402 /* Decrement cwnd here because we are sending
1403 * effectively two packets. */
1405 tcp_event_new_data_sent(sk
, nskb
);
1407 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1408 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1409 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1418 /* This routine writes packets to the network. It advances the
1419 * send_head. This happens as incoming acks open up the remote
1422 * Returns 1, if no segments are in flight and we have queued segments, but
1423 * cannot send anything now because of SWS or another problem.
1425 static int tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
)
1427 struct tcp_sock
*tp
= tcp_sk(sk
);
1428 struct sk_buff
*skb
;
1429 unsigned int tso_segs
, sent_pkts
;
1433 /* If we are closed, the bytes will have to remain here.
1434 * In time closedown will finish, we empty the write queue and all
1437 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
1442 /* Do MTU probing. */
1443 if ((result
= tcp_mtu_probe(sk
)) == 0) {
1445 } else if (result
> 0) {
1449 while ((skb
= tcp_send_head(sk
))) {
1452 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1455 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1459 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1462 if (tso_segs
== 1) {
1463 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1464 (tcp_skb_is_last(sk
, skb
) ?
1465 nonagle
: TCP_NAGLE_PUSH
))))
1468 if (tcp_tso_should_defer(sk
, skb
))
1474 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
1477 if (skb
->len
> limit
&&
1478 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1481 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1483 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
)))
1486 /* Advance the send_head. This one is sent out.
1487 * This call will increment packets_out.
1489 tcp_event_new_data_sent(sk
, skb
);
1491 tcp_minshall_update(tp
, mss_now
, skb
);
1495 if (likely(sent_pkts
)) {
1496 tcp_cwnd_validate(sk
);
1499 return !tp
->packets_out
&& tcp_send_head(sk
);
1502 /* Push out any pending frames which were held back due to
1503 * TCP_CORK or attempt at coalescing tiny packets.
1504 * The socket must be locked by the caller.
1506 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
1509 struct sk_buff
*skb
= tcp_send_head(sk
);
1512 if (tcp_write_xmit(sk
, cur_mss
, nonagle
))
1513 tcp_check_probe_timer(sk
);
1517 /* Send _single_ skb sitting at the send head. This function requires
1518 * true push pending frames to setup probe timer etc.
1520 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
1522 struct sk_buff
*skb
= tcp_send_head(sk
);
1523 unsigned int tso_segs
, cwnd_quota
;
1525 BUG_ON(!skb
|| skb
->len
< mss_now
);
1527 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1528 cwnd_quota
= tcp_snd_test(sk
, skb
, mss_now
, TCP_NAGLE_PUSH
);
1530 if (likely(cwnd_quota
)) {
1537 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
1540 if (skb
->len
> limit
&&
1541 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1544 /* Send it out now. */
1545 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1547 if (likely(!tcp_transmit_skb(sk
, skb
, 1, sk
->sk_allocation
))) {
1548 tcp_event_new_data_sent(sk
, skb
);
1549 tcp_cwnd_validate(sk
);
1555 /* This function returns the amount that we can raise the
1556 * usable window based on the following constraints
1558 * 1. The window can never be shrunk once it is offered (RFC 793)
1559 * 2. We limit memory per socket
1562 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1563 * RECV.NEXT + RCV.WIN fixed until:
1564 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1566 * i.e. don't raise the right edge of the window until you can raise
1567 * it at least MSS bytes.
1569 * Unfortunately, the recommended algorithm breaks header prediction,
1570 * since header prediction assumes th->window stays fixed.
1572 * Strictly speaking, keeping th->window fixed violates the receiver
1573 * side SWS prevention criteria. The problem is that under this rule
1574 * a stream of single byte packets will cause the right side of the
1575 * window to always advance by a single byte.
1577 * Of course, if the sender implements sender side SWS prevention
1578 * then this will not be a problem.
1580 * BSD seems to make the following compromise:
1582 * If the free space is less than the 1/4 of the maximum
1583 * space available and the free space is less than 1/2 mss,
1584 * then set the window to 0.
1585 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1586 * Otherwise, just prevent the window from shrinking
1587 * and from being larger than the largest representable value.
1589 * This prevents incremental opening of the window in the regime
1590 * where TCP is limited by the speed of the reader side taking
1591 * data out of the TCP receive queue. It does nothing about
1592 * those cases where the window is constrained on the sender side
1593 * because the pipeline is full.
1595 * BSD also seems to "accidentally" limit itself to windows that are a
1596 * multiple of MSS, at least until the free space gets quite small.
1597 * This would appear to be a side effect of the mbuf implementation.
1598 * Combining these two algorithms results in the observed behavior
1599 * of having a fixed window size at almost all times.
1601 * Below we obtain similar behavior by forcing the offered window to
1602 * a multiple of the mss when it is feasible to do so.
1604 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1605 * Regular options like TIMESTAMP are taken into account.
1607 u32
__tcp_select_window(struct sock
*sk
)
1609 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1610 struct tcp_sock
*tp
= tcp_sk(sk
);
1611 /* MSS for the peer's data. Previous versions used mss_clamp
1612 * here. I don't know if the value based on our guesses
1613 * of peer's MSS is better for the performance. It's more correct
1614 * but may be worse for the performance because of rcv_mss
1615 * fluctuations. --SAW 1998/11/1
1617 int mss
= icsk
->icsk_ack
.rcv_mss
;
1618 int free_space
= tcp_space(sk
);
1619 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
1622 if (mss
> full_space
)
1625 if (free_space
< (full_space
>> 1)) {
1626 icsk
->icsk_ack
.quick
= 0;
1628 if (tcp_memory_pressure
)
1629 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U*tp
->advmss
);
1631 if (free_space
< mss
)
1635 if (free_space
> tp
->rcv_ssthresh
)
1636 free_space
= tp
->rcv_ssthresh
;
1638 /* Don't do rounding if we are using window scaling, since the
1639 * scaled window will not line up with the MSS boundary anyway.
1641 window
= tp
->rcv_wnd
;
1642 if (tp
->rx_opt
.rcv_wscale
) {
1643 window
= free_space
;
1645 /* Advertise enough space so that it won't get scaled away.
1646 * Import case: prevent zero window announcement if
1647 * 1<<rcv_wscale > mss.
1649 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1650 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1651 << tp
->rx_opt
.rcv_wscale
);
1653 /* Get the largest window that is a nice multiple of mss.
1654 * Window clamp already applied above.
1655 * If our current window offering is within 1 mss of the
1656 * free space we just keep it. This prevents the divide
1657 * and multiply from happening most of the time.
1658 * We also don't do any window rounding when the free space
1661 if (window
<= free_space
- mss
|| window
> free_space
)
1662 window
= (free_space
/mss
)*mss
;
1663 else if (mss
== full_space
&&
1664 free_space
> window
+ (full_space
>> 1))
1665 window
= free_space
;
1671 /* Attempt to collapse two adjacent SKB's during retransmission. */
1672 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*skb
, int mss_now
)
1674 struct tcp_sock
*tp
= tcp_sk(sk
);
1675 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
1677 /* The first test we must make is that neither of these two
1678 * SKB's are still referenced by someone else.
1680 if (!skb_cloned(skb
) && !skb_cloned(next_skb
)) {
1681 int skb_size
= skb
->len
, next_skb_size
= next_skb
->len
;
1682 u16 flags
= TCP_SKB_CB(skb
)->flags
;
1684 /* Also punt if next skb has been SACK'd. */
1685 if (TCP_SKB_CB(next_skb
)->sacked
& TCPCB_SACKED_ACKED
)
1688 /* Next skb is out of window. */
1689 if (after(TCP_SKB_CB(next_skb
)->end_seq
, tcp_wnd_end(tp
)))
1692 /* Punt if not enough space exists in the first SKB for
1693 * the data in the second, or the total combined payload
1694 * would exceed the MSS.
1696 if ((next_skb_size
> skb_tailroom(skb
)) ||
1697 ((skb_size
+ next_skb_size
) > mss_now
))
1700 BUG_ON(tcp_skb_pcount(skb
) != 1 ||
1701 tcp_skb_pcount(next_skb
) != 1);
1703 tcp_highest_sack_combine(sk
, next_skb
, skb
);
1705 /* Ok. We will be able to collapse the packet. */
1706 tcp_unlink_write_queue(next_skb
, sk
);
1708 skb_copy_from_linear_data(next_skb
,
1709 skb_put(skb
, next_skb_size
),
1712 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
1713 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1715 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1716 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1718 /* Update sequence range on original skb. */
1719 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1721 /* Merge over control information. */
1722 flags
|= TCP_SKB_CB(next_skb
)->flags
; /* This moves PSH/FIN etc. over */
1723 TCP_SKB_CB(skb
)->flags
= flags
;
1725 /* All done, get rid of second SKB and account for it so
1726 * packet counting does not break.
1728 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
1729 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_SACKED_RETRANS
)
1730 tp
->retrans_out
-= tcp_skb_pcount(next_skb
);
1731 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_LOST
)
1732 tp
->lost_out
-= tcp_skb_pcount(next_skb
);
1733 /* Reno case is special. Sigh... */
1734 if (tcp_is_reno(tp
) && tp
->sacked_out
)
1735 tcp_dec_pcount_approx(&tp
->sacked_out
, next_skb
);
1737 tcp_adjust_fackets_out(sk
, next_skb
, tcp_skb_pcount(next_skb
));
1738 tp
->packets_out
-= tcp_skb_pcount(next_skb
);
1740 /* changed transmit queue under us so clear hints */
1741 tcp_clear_retrans_hints_partial(tp
);
1743 sk_wmem_free_skb(sk
, next_skb
);
1747 /* Do a simple retransmit without using the backoff mechanisms in
1748 * tcp_timer. This is used for path mtu discovery.
1749 * The socket is already locked here.
1751 void tcp_simple_retransmit(struct sock
*sk
)
1753 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1754 struct tcp_sock
*tp
= tcp_sk(sk
);
1755 struct sk_buff
*skb
;
1756 unsigned int mss
= tcp_current_mss(sk
, 0);
1759 tcp_for_write_queue(skb
, sk
) {
1760 if (skb
== tcp_send_head(sk
))
1762 if (skb
->len
> mss
&&
1763 !(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1764 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1765 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1766 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1768 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_LOST
)) {
1769 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1770 tp
->lost_out
+= tcp_skb_pcount(skb
);
1776 tcp_clear_all_retrans_hints(tp
);
1781 tcp_verify_left_out(tp
);
1783 /* Don't muck with the congestion window here.
1784 * Reason is that we do not increase amount of _data_
1785 * in network, but units changed and effective
1786 * cwnd/ssthresh really reduced now.
1788 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
1789 tp
->high_seq
= tp
->snd_nxt
;
1790 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1791 tp
->prior_ssthresh
= 0;
1792 tp
->undo_marker
= 0;
1793 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1795 tcp_xmit_retransmit_queue(sk
);
1798 /* This retransmits one SKB. Policy decisions and retransmit queue
1799 * state updates are done by the caller. Returns non-zero if an
1800 * error occurred which prevented the send.
1802 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
1804 struct tcp_sock
*tp
= tcp_sk(sk
);
1805 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1806 unsigned int cur_mss
= tcp_current_mss(sk
, 0);
1809 /* Inconslusive MTU probe */
1810 if (icsk
->icsk_mtup
.probe_size
) {
1811 icsk
->icsk_mtup
.probe_size
= 0;
1814 /* Do not sent more than we queued. 1/4 is reserved for possible
1815 * copying overhead: fragmentation, tunneling, mangling etc.
1817 if (atomic_read(&sk
->sk_wmem_alloc
) >
1818 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
1821 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
1822 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1824 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
1828 /* If receiver has shrunk his window, and skb is out of
1829 * new window, do not retransmit it. The exception is the
1830 * case, when window is shrunk to zero. In this case
1831 * our retransmit serves as a zero window probe.
1833 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))
1834 && TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
1837 if (skb
->len
> cur_mss
) {
1838 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
1839 return -ENOMEM
; /* We'll try again later. */
1842 /* Collapse two adjacent packets if worthwhile and we can. */
1843 if (!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
) &&
1844 (skb
->len
< (cur_mss
>> 1)) &&
1845 (tcp_write_queue_next(sk
, skb
) != tcp_send_head(sk
)) &&
1846 (!tcp_skb_is_last(sk
, skb
)) &&
1847 (skb_shinfo(skb
)->nr_frags
== 0 && skb_shinfo(tcp_write_queue_next(sk
, skb
))->nr_frags
== 0) &&
1848 (tcp_skb_pcount(skb
) == 1 && tcp_skb_pcount(tcp_write_queue_next(sk
, skb
)) == 1) &&
1849 (sysctl_tcp_retrans_collapse
!= 0))
1850 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
1852 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
1853 return -EHOSTUNREACH
; /* Routing failure or similar. */
1855 /* Some Solaris stacks overoptimize and ignore the FIN on a
1856 * retransmit when old data is attached. So strip it off
1857 * since it is cheap to do so and saves bytes on the network.
1860 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1861 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
1862 if (!pskb_trim(skb
, 0)) {
1863 TCP_SKB_CB(skb
)->seq
= TCP_SKB_CB(skb
)->end_seq
- 1;
1864 skb_shinfo(skb
)->gso_segs
= 1;
1865 skb_shinfo(skb
)->gso_size
= 0;
1866 skb_shinfo(skb
)->gso_type
= 0;
1867 skb
->ip_summed
= CHECKSUM_NONE
;
1872 /* Make a copy, if the first transmission SKB clone we made
1873 * is still in somebody's hands, else make a clone.
1875 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1877 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
1880 /* Update global TCP statistics. */
1881 TCP_INC_STATS(TCP_MIB_RETRANSSEGS
);
1883 tp
->total_retrans
++;
1885 #if FASTRETRANS_DEBUG > 0
1886 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1887 if (net_ratelimit())
1888 printk(KERN_DEBUG
"retrans_out leaked.\n");
1891 if (!tp
->retrans_out
)
1892 tp
->lost_retrans_low
= tp
->snd_nxt
;
1893 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
1894 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1896 /* Save stamp of the first retransmit. */
1897 if (!tp
->retrans_stamp
)
1898 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
1902 /* snd_nxt is stored to detect loss of retransmitted segment,
1903 * see tcp_input.c tcp_sacktag_write_queue().
1905 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
1910 /* This gets called after a retransmit timeout, and the initially
1911 * retransmitted data is acknowledged. It tries to continue
1912 * resending the rest of the retransmit queue, until either
1913 * we've sent it all or the congestion window limit is reached.
1914 * If doing SACK, the first ACK which comes back for a timeout
1915 * based retransmit packet might feed us FACK information again.
1916 * If so, we use it to avoid unnecessarily retransmissions.
1918 void tcp_xmit_retransmit_queue(struct sock
*sk
)
1920 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1921 struct tcp_sock
*tp
= tcp_sk(sk
);
1922 struct sk_buff
*skb
;
1925 if (tp
->retransmit_skb_hint
) {
1926 skb
= tp
->retransmit_skb_hint
;
1927 packet_cnt
= tp
->retransmit_cnt_hint
;
1929 skb
= tcp_write_queue_head(sk
);
1933 /* First pass: retransmit lost packets. */
1935 tcp_for_write_queue_from(skb
, sk
) {
1936 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1938 if (skb
== tcp_send_head(sk
))
1940 /* we could do better than to assign each time */
1941 tp
->retransmit_skb_hint
= skb
;
1942 tp
->retransmit_cnt_hint
= packet_cnt
;
1944 /* Assume this retransmit will generate
1945 * only one packet for congestion window
1946 * calculation purposes. This works because
1947 * tcp_retransmit_skb() will chop up the
1948 * packet to be MSS sized and all the
1949 * packet counting works out.
1951 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1954 if (sacked
& TCPCB_LOST
) {
1955 if (!(sacked
&(TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))) {
1956 if (tcp_retransmit_skb(sk
, skb
)) {
1957 tp
->retransmit_skb_hint
= NULL
;
1960 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
1961 NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS
);
1963 NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS
);
1965 if (skb
== tcp_write_queue_head(sk
))
1966 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1967 inet_csk(sk
)->icsk_rto
,
1971 packet_cnt
+= tcp_skb_pcount(skb
);
1972 if (packet_cnt
>= tp
->lost_out
)
1978 /* OK, demanded retransmission is finished. */
1980 /* Forward retransmissions are possible only during Recovery. */
1981 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1984 /* No forward retransmissions in Reno are possible. */
1985 if (tcp_is_reno(tp
))
1988 /* Yeah, we have to make difficult choice between forward transmission
1989 * and retransmission... Both ways have their merits...
1991 * For now we do not retransmit anything, while we have some new
1992 * segments to send. In the other cases, follow rule 3 for
1993 * NextSeg() specified in RFC3517.
1996 if (tcp_may_send_now(sk
))
1999 /* If nothing is SACKed, highest_sack in the loop won't be valid */
2000 if (!tp
->sacked_out
)
2003 if (tp
->forward_skb_hint
)
2004 skb
= tp
->forward_skb_hint
;
2006 skb
= tcp_write_queue_head(sk
);
2008 tcp_for_write_queue_from(skb
, sk
) {
2009 if (skb
== tcp_send_head(sk
))
2011 tp
->forward_skb_hint
= skb
;
2013 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2016 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2019 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
)
2022 /* Ok, retransmit it. */
2023 if (tcp_retransmit_skb(sk
, skb
)) {
2024 tp
->forward_skb_hint
= NULL
;
2028 if (skb
== tcp_write_queue_head(sk
))
2029 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2030 inet_csk(sk
)->icsk_rto
,
2033 NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS
);
2038 /* Send a fin. The caller locks the socket for us. This cannot be
2039 * allowed to fail queueing a FIN frame under any circumstances.
2041 void tcp_send_fin(struct sock
*sk
)
2043 struct tcp_sock
*tp
= tcp_sk(sk
);
2044 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2047 /* Optimization, tack on the FIN if we have a queue of
2048 * unsent frames. But be careful about outgoing SACKS
2051 mss_now
= tcp_current_mss(sk
, 1);
2053 if (tcp_send_head(sk
) != NULL
) {
2054 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
2055 TCP_SKB_CB(skb
)->end_seq
++;
2058 /* Socket is locked, keep trying until memory is available. */
2060 skb
= alloc_skb_fclone(MAX_TCP_HEADER
, GFP_KERNEL
);
2066 /* Reserve space for headers and prepare control bits. */
2067 skb_reserve(skb
, MAX_TCP_HEADER
);
2069 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
2070 TCP_SKB_CB(skb
)->sacked
= 0;
2071 skb_shinfo(skb
)->gso_segs
= 1;
2072 skb_shinfo(skb
)->gso_size
= 0;
2073 skb_shinfo(skb
)->gso_type
= 0;
2075 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2076 TCP_SKB_CB(skb
)->seq
= tp
->write_seq
;
2077 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
2078 tcp_queue_skb(sk
, skb
);
2080 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2083 /* We get here when a process closes a file descriptor (either due to
2084 * an explicit close() or as a byproduct of exit()'ing) and there
2085 * was unread data in the receive queue. This behavior is recommended
2086 * by RFC 2525, section 2.17. -DaveM
2088 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2090 struct sk_buff
*skb
;
2092 /* NOTE: No TCP options attached and we never retransmit this. */
2093 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2095 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
2099 /* Reserve space for headers and prepare control bits. */
2100 skb_reserve(skb
, MAX_TCP_HEADER
);
2102 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
2103 TCP_SKB_CB(skb
)->sacked
= 0;
2104 skb_shinfo(skb
)->gso_segs
= 1;
2105 skb_shinfo(skb
)->gso_size
= 0;
2106 skb_shinfo(skb
)->gso_type
= 0;
2109 TCP_SKB_CB(skb
)->seq
= tcp_acceptable_seq(sk
);
2110 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
2111 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2112 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2113 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
2116 /* WARNING: This routine must only be called when we have already sent
2117 * a SYN packet that crossed the incoming SYN that caused this routine
2118 * to get called. If this assumption fails then the initial rcv_wnd
2119 * and rcv_wscale values will not be correct.
2121 int tcp_send_synack(struct sock
*sk
)
2123 struct sk_buff
* skb
;
2125 skb
= tcp_write_queue_head(sk
);
2126 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_SYN
)) {
2127 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
2130 if (!(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_ACK
)) {
2131 if (skb_cloned(skb
)) {
2132 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2135 tcp_unlink_write_queue(skb
, sk
);
2136 skb_header_release(nskb
);
2137 __tcp_add_write_queue_head(sk
, nskb
);
2138 sk_wmem_free_skb(sk
, skb
);
2139 sk
->sk_wmem_queued
+= nskb
->truesize
;
2140 sk_mem_charge(sk
, nskb
->truesize
);
2144 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
2145 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2147 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2148 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2152 * Prepare a SYN-ACK.
2154 struct sk_buff
* tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2155 struct request_sock
*req
)
2157 struct inet_request_sock
*ireq
= inet_rsk(req
);
2158 struct tcp_sock
*tp
= tcp_sk(sk
);
2160 int tcp_header_size
;
2161 struct sk_buff
*skb
;
2162 #ifdef CONFIG_TCP_MD5SIG
2163 struct tcp_md5sig_key
*md5
;
2164 __u8
*md5_hash_location
;
2167 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
2171 /* Reserve space for headers. */
2172 skb_reserve(skb
, MAX_TCP_HEADER
);
2174 skb
->dst
= dst_clone(dst
);
2176 tcp_header_size
= (sizeof(struct tcphdr
) + TCPOLEN_MSS
+
2177 (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0) +
2178 (ireq
->wscale_ok
? TCPOLEN_WSCALE_ALIGNED
: 0) +
2179 /* SACK_PERM is in the place of NOP NOP of TS */
2180 ((ireq
->sack_ok
&& !ireq
->tstamp_ok
) ? TCPOLEN_SACKPERM_ALIGNED
: 0));
2182 #ifdef CONFIG_TCP_MD5SIG
2183 /* Are we doing MD5 on this segment? If so - make room for it */
2184 md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
2186 tcp_header_size
+= TCPOLEN_MD5SIG_ALIGNED
;
2188 skb_push(skb
, tcp_header_size
);
2189 skb_reset_transport_header(skb
);
2192 memset(th
, 0, sizeof(struct tcphdr
));
2195 TCP_ECN_make_synack(req
, th
);
2196 th
->source
= inet_sk(sk
)->sport
;
2197 th
->dest
= ireq
->rmt_port
;
2198 TCP_SKB_CB(skb
)->seq
= tcp_rsk(req
)->snt_isn
;
2199 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
2200 TCP_SKB_CB(skb
)->sacked
= 0;
2201 skb_shinfo(skb
)->gso_segs
= 1;
2202 skb_shinfo(skb
)->gso_size
= 0;
2203 skb_shinfo(skb
)->gso_type
= 0;
2204 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2205 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
2206 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
2208 /* Set this up on the first call only */
2209 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
2210 /* tcp_full_space because it is guaranteed to be the first packet */
2211 tcp_select_initial_window(tcp_full_space(sk
),
2212 dst_metric(dst
, RTAX_ADVMSS
) - (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
2217 ireq
->rcv_wscale
= rcv_wscale
;
2220 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2221 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2223 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2224 tcp_syn_build_options((__be32
*)(th
+ 1), dst_metric(dst
, RTAX_ADVMSS
), ireq
->tstamp_ok
,
2225 ireq
->sack_ok
, ireq
->wscale_ok
, ireq
->rcv_wscale
,
2226 TCP_SKB_CB(skb
)->when
,
2229 #ifdef CONFIG_TCP_MD5SIG
2230 md5
? &md5_hash_location
:
2236 th
->doff
= (tcp_header_size
>> 2);
2237 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
2239 #ifdef CONFIG_TCP_MD5SIG
2240 /* Okay, we have all we need - do the md5 hash if needed */
2242 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
2245 tcp_hdr(skb
), sk
->sk_protocol
,
2254 * Do all connect socket setups that can be done AF independent.
2256 static void tcp_connect_init(struct sock
*sk
)
2258 struct dst_entry
*dst
= __sk_dst_get(sk
);
2259 struct tcp_sock
*tp
= tcp_sk(sk
);
2262 /* We'll fix this up when we get a response from the other end.
2263 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2265 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2266 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2268 #ifdef CONFIG_TCP_MD5SIG
2269 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2270 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2273 /* If user gave his TCP_MAXSEG, record it to clamp */
2274 if (tp
->rx_opt
.user_mss
)
2275 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2278 tcp_sync_mss(sk
, dst_mtu(dst
));
2280 if (!tp
->window_clamp
)
2281 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2282 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
2283 tcp_initialize_rcv_mss(sk
);
2285 tcp_select_initial_window(tcp_full_space(sk
),
2286 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2289 sysctl_tcp_window_scaling
,
2292 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2293 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2296 sock_reset_flag(sk
, SOCK_DONE
);
2298 tcp_init_wl(tp
, tp
->write_seq
, 0);
2299 tp
->snd_una
= tp
->write_seq
;
2300 tp
->snd_sml
= tp
->write_seq
;
2305 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2306 inet_csk(sk
)->icsk_retransmits
= 0;
2307 tcp_clear_retrans(tp
);
2311 * Build a SYN and send it off.
2313 int tcp_connect(struct sock
*sk
)
2315 struct tcp_sock
*tp
= tcp_sk(sk
);
2316 struct sk_buff
*buff
;
2318 tcp_connect_init(sk
);
2320 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
2321 if (unlikely(buff
== NULL
))
2324 /* Reserve space for headers. */
2325 skb_reserve(buff
, MAX_TCP_HEADER
);
2327 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_SYN
;
2328 TCP_ECN_send_syn(sk
, buff
);
2329 TCP_SKB_CB(buff
)->sacked
= 0;
2330 skb_shinfo(buff
)->gso_segs
= 1;
2331 skb_shinfo(buff
)->gso_size
= 0;
2332 skb_shinfo(buff
)->gso_type
= 0;
2334 tp
->snd_nxt
= tp
->write_seq
;
2335 TCP_SKB_CB(buff
)->seq
= tp
->write_seq
++;
2336 TCP_SKB_CB(buff
)->end_seq
= tp
->write_seq
;
2339 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2340 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
2341 skb_header_release(buff
);
2342 __tcp_add_write_queue_tail(sk
, buff
);
2343 sk
->sk_wmem_queued
+= buff
->truesize
;
2344 sk_mem_charge(sk
, buff
->truesize
);
2345 tp
->packets_out
+= tcp_skb_pcount(buff
);
2346 tcp_transmit_skb(sk
, buff
, 1, GFP_KERNEL
);
2348 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2349 * in order to make this packet get counted in tcpOutSegs.
2351 tp
->snd_nxt
= tp
->write_seq
;
2352 tp
->pushed_seq
= tp
->write_seq
;
2353 TCP_INC_STATS(TCP_MIB_ACTIVEOPENS
);
2355 /* Timer for repeating the SYN until an answer. */
2356 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2357 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2361 /* Send out a delayed ack, the caller does the policy checking
2362 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2365 void tcp_send_delayed_ack(struct sock
*sk
)
2367 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2368 int ato
= icsk
->icsk_ack
.ato
;
2369 unsigned long timeout
;
2371 if (ato
> TCP_DELACK_MIN
) {
2372 const struct tcp_sock
*tp
= tcp_sk(sk
);
2375 if (icsk
->icsk_ack
.pingpong
|| (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
2376 max_ato
= TCP_DELACK_MAX
;
2378 /* Slow path, intersegment interval is "high". */
2380 /* If some rtt estimate is known, use it to bound delayed ack.
2381 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2385 int rtt
= max(tp
->srtt
>>3, TCP_DELACK_MIN
);
2391 ato
= min(ato
, max_ato
);
2394 /* Stay within the limit we were given */
2395 timeout
= jiffies
+ ato
;
2397 /* Use new timeout only if there wasn't a older one earlier. */
2398 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
2399 /* If delack timer was blocked or is about to expire,
2402 if (icsk
->icsk_ack
.blocked
||
2403 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
2408 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
2409 timeout
= icsk
->icsk_ack
.timeout
;
2411 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
2412 icsk
->icsk_ack
.timeout
= timeout
;
2413 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
2416 /* This routine sends an ack and also updates the window. */
2417 void tcp_send_ack(struct sock
*sk
)
2419 /* If we have been reset, we may not send again. */
2420 if (sk
->sk_state
!= TCP_CLOSE
) {
2421 struct sk_buff
*buff
;
2423 /* We are not putting this on the write queue, so
2424 * tcp_transmit_skb() will set the ownership to this
2427 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2429 inet_csk_schedule_ack(sk
);
2430 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
2431 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
2432 TCP_DELACK_MAX
, TCP_RTO_MAX
);
2436 /* Reserve space for headers and prepare control bits. */
2437 skb_reserve(buff
, MAX_TCP_HEADER
);
2439 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_ACK
;
2440 TCP_SKB_CB(buff
)->sacked
= 0;
2441 skb_shinfo(buff
)->gso_segs
= 1;
2442 skb_shinfo(buff
)->gso_size
= 0;
2443 skb_shinfo(buff
)->gso_type
= 0;
2445 /* Send it off, this clears delayed acks for us. */
2446 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(buff
)->end_seq
= tcp_acceptable_seq(sk
);
2447 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2448 tcp_transmit_skb(sk
, buff
, 0, GFP_ATOMIC
);
2452 /* This routine sends a packet with an out of date sequence
2453 * number. It assumes the other end will try to ack it.
2455 * Question: what should we make while urgent mode?
2456 * 4.4BSD forces sending single byte of data. We cannot send
2457 * out of window data, because we have SND.NXT==SND.MAX...
2459 * Current solution: to send TWO zero-length segments in urgent mode:
2460 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2461 * out-of-date with SND.UNA-1 to probe window.
2463 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
2465 struct tcp_sock
*tp
= tcp_sk(sk
);
2466 struct sk_buff
*skb
;
2468 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2469 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2473 /* Reserve space for headers and set control bits. */
2474 skb_reserve(skb
, MAX_TCP_HEADER
);
2476 TCP_SKB_CB(skb
)->flags
= TCPCB_FLAG_ACK
;
2477 TCP_SKB_CB(skb
)->sacked
= 0;
2478 skb_shinfo(skb
)->gso_segs
= 1;
2479 skb_shinfo(skb
)->gso_size
= 0;
2480 skb_shinfo(skb
)->gso_type
= 0;
2482 /* Use a previous sequence. This should cause the other
2483 * end to send an ack. Don't queue or clone SKB, just
2486 TCP_SKB_CB(skb
)->seq
= urgent
? tp
->snd_una
: tp
->snd_una
- 1;
2487 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
2488 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2489 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
2492 int tcp_write_wakeup(struct sock
*sk
)
2494 if (sk
->sk_state
!= TCP_CLOSE
) {
2495 struct tcp_sock
*tp
= tcp_sk(sk
);
2496 struct sk_buff
*skb
;
2498 if ((skb
= tcp_send_head(sk
)) != NULL
&&
2499 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
2501 unsigned int mss
= tcp_current_mss(sk
, 0);
2502 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
2504 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
2505 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
2507 /* We are probing the opening of a window
2508 * but the window size is != 0
2509 * must have been a result SWS avoidance ( sender )
2511 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
2513 seg_size
= min(seg_size
, mss
);
2514 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2515 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
2517 } else if (!tcp_skb_pcount(skb
))
2518 tcp_set_skb_tso_segs(sk
, skb
, mss
);
2520 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2521 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2522 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2524 tcp_event_new_data_sent(sk
, skb
);
2528 between(tp
->snd_up
, tp
->snd_una
+1, tp
->snd_una
+0xFFFF))
2529 tcp_xmit_probe_skb(sk
, 1);
2530 return tcp_xmit_probe_skb(sk
, 0);
2536 /* A window probe timeout has occurred. If window is not closed send
2537 * a partial packet else a zero probe.
2539 void tcp_send_probe0(struct sock
*sk
)
2541 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2542 struct tcp_sock
*tp
= tcp_sk(sk
);
2545 err
= tcp_write_wakeup(sk
);
2547 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
2548 /* Cancel probe timer, if it is not required. */
2549 icsk
->icsk_probes_out
= 0;
2550 icsk
->icsk_backoff
= 0;
2555 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
2556 icsk
->icsk_backoff
++;
2557 icsk
->icsk_probes_out
++;
2558 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2559 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2562 /* If packet was not sent due to local congestion,
2563 * do not backoff and do not remember icsk_probes_out.
2564 * Let local senders to fight for local resources.
2566 * Use accumulated backoff yet.
2568 if (!icsk
->icsk_probes_out
)
2569 icsk
->icsk_probes_out
= 1;
2570 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2571 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
2572 TCP_RESOURCE_PROBE_INTERVAL
),
2577 EXPORT_SYMBOL(tcp_connect
);
2578 EXPORT_SYMBOL(tcp_make_synack
);
2579 EXPORT_SYMBOL(tcp_simple_retransmit
);
2580 EXPORT_SYMBOL(tcp_sync_mss
);
2581 EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor
);
2582 EXPORT_SYMBOL(tcp_mtup_init
);