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>
43 #include <linux/smp_lock.h>
45 /* People can turn this off for buggy TCP's found in printers etc. */
46 int sysctl_tcp_retrans_collapse
= 1;
48 /* This limits the percentage of the congestion window which we
49 * will allow a single TSO frame to consume. Building TSO frames
50 * which are too large can cause TCP streams to be bursty.
52 int sysctl_tcp_tso_win_divisor
= 3;
54 static inline void update_send_head(struct sock
*sk
, struct tcp_sock
*tp
,
57 sk
->sk_send_head
= skb
->next
;
58 if (sk
->sk_send_head
== (struct sk_buff
*)&sk
->sk_write_queue
)
59 sk
->sk_send_head
= NULL
;
60 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
61 tcp_packets_out_inc(sk
, tp
, skb
);
64 /* SND.NXT, if window was not shrunk.
65 * If window has been shrunk, what should we make? It is not clear at all.
66 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
67 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
68 * invalid. OK, let's make this for now:
70 static inline __u32
tcp_acceptable_seq(struct sock
*sk
, struct tcp_sock
*tp
)
72 if (!before(tp
->snd_una
+tp
->snd_wnd
, tp
->snd_nxt
))
75 return tp
->snd_una
+tp
->snd_wnd
;
78 /* Calculate mss to advertise in SYN segment.
79 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
81 * 1. It is independent of path mtu.
82 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
83 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
84 * attached devices, because some buggy hosts are confused by
86 * 4. We do not make 3, we advertise MSS, calculated from first
87 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
88 * This may be overridden via information stored in routing table.
89 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
90 * probably even Jumbo".
92 static __u16
tcp_advertise_mss(struct sock
*sk
)
94 struct tcp_sock
*tp
= tcp_sk(sk
);
95 struct dst_entry
*dst
= __sk_dst_get(sk
);
98 if (dst
&& dst_metric(dst
, RTAX_ADVMSS
) < mss
) {
99 mss
= dst_metric(dst
, RTAX_ADVMSS
);
106 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
107 * This is the first part of cwnd validation mechanism. */
108 static void tcp_cwnd_restart(struct tcp_sock
*tp
, struct dst_entry
*dst
)
110 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
111 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
112 u32 cwnd
= tp
->snd_cwnd
;
114 tcp_ca_event(tp
, CA_EVENT_CWND_RESTART
);
116 tp
->snd_ssthresh
= tcp_current_ssthresh(tp
);
117 restart_cwnd
= min(restart_cwnd
, cwnd
);
119 while ((delta
-= tp
->rto
) > 0 && cwnd
> restart_cwnd
)
121 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
122 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
123 tp
->snd_cwnd_used
= 0;
126 static inline void tcp_event_data_sent(struct tcp_sock
*tp
,
127 struct sk_buff
*skb
, struct sock
*sk
)
129 u32 now
= tcp_time_stamp
;
131 if (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > tp
->rto
)
132 tcp_cwnd_restart(tp
, __sk_dst_get(sk
));
136 /* If it is a reply for ato after last received
137 * packet, enter pingpong mode.
139 if ((u32
)(now
- tp
->ack
.lrcvtime
) < tp
->ack
.ato
)
140 tp
->ack
.pingpong
= 1;
143 static __inline__
void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
145 struct tcp_sock
*tp
= tcp_sk(sk
);
147 tcp_dec_quickack_mode(tp
, pkts
);
148 tcp_clear_xmit_timer(sk
, TCP_TIME_DACK
);
151 /* Determine a window scaling and initial window to offer.
152 * Based on the assumption that the given amount of space
153 * will be offered. Store the results in the tp structure.
154 * NOTE: for smooth operation initial space offering should
155 * be a multiple of mss if possible. We assume here that mss >= 1.
156 * This MUST be enforced by all callers.
158 void tcp_select_initial_window(int __space
, __u32 mss
,
159 __u32
*rcv_wnd
, __u32
*window_clamp
,
160 int wscale_ok
, __u8
*rcv_wscale
)
162 unsigned int space
= (__space
< 0 ? 0 : __space
);
164 /* If no clamp set the clamp to the max possible scaled window */
165 if (*window_clamp
== 0)
166 (*window_clamp
) = (65535 << 14);
167 space
= min(*window_clamp
, space
);
169 /* Quantize space offering to a multiple of mss if possible. */
171 space
= (space
/ mss
) * mss
;
173 /* NOTE: offering an initial window larger than 32767
174 * will break some buggy TCP stacks. We try to be nice.
175 * If we are not window scaling, then this truncates
176 * our initial window offering to 32k. There should also
177 * be a sysctl option to stop being nice.
179 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
182 /* Set window scaling on max possible window
183 * See RFC1323 for an explanation of the limit to 14
185 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
186 while (space
> 65535 && (*rcv_wscale
) < 14) {
192 /* Set initial window to value enough for senders,
193 * following RFC1414. Senders, not following this RFC,
194 * will be satisfied with 2.
196 if (mss
> (1<<*rcv_wscale
)) {
202 if (*rcv_wnd
> init_cwnd
*mss
)
203 *rcv_wnd
= init_cwnd
*mss
;
206 /* Set the clamp no higher than max representable value */
207 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
210 /* Chose a new window to advertise, update state in tcp_sock for the
211 * socket, and return result with RFC1323 scaling applied. The return
212 * value can be stuffed directly into th->window for an outgoing
215 static __inline__ u16
tcp_select_window(struct sock
*sk
)
217 struct tcp_sock
*tp
= tcp_sk(sk
);
218 u32 cur_win
= tcp_receive_window(tp
);
219 u32 new_win
= __tcp_select_window(sk
);
221 /* Never shrink the offered window */
222 if(new_win
< cur_win
) {
223 /* Danger Will Robinson!
224 * Don't update rcv_wup/rcv_wnd here or else
225 * we will not be able to advertise a zero
226 * window in time. --DaveM
228 * Relax Will Robinson.
232 tp
->rcv_wnd
= new_win
;
233 tp
->rcv_wup
= tp
->rcv_nxt
;
235 /* Make sure we do not exceed the maximum possible
238 if (!tp
->rx_opt
.rcv_wscale
)
239 new_win
= min(new_win
, MAX_TCP_WINDOW
);
241 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
243 /* RFC1323 scaling applied */
244 new_win
>>= tp
->rx_opt
.rcv_wscale
;
246 /* If we advertise zero window, disable fast path. */
254 /* This routine actually transmits TCP packets queued in by
255 * tcp_do_sendmsg(). This is used by both the initial
256 * transmission and possible later retransmissions.
257 * All SKB's seen here are completely headerless. It is our
258 * job to build the TCP header, and pass the packet down to
259 * IP so it can do the same plus pass the packet off to the
262 * We are working here with either a clone of the original
263 * SKB, or a fresh unique copy made by the retransmit engine.
265 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
268 struct inet_sock
*inet
= inet_sk(sk
);
269 struct tcp_sock
*tp
= tcp_sk(sk
);
270 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
271 int tcp_header_size
= tp
->tcp_header_len
;
276 BUG_ON(!tcp_skb_pcount(skb
));
278 #define SYSCTL_FLAG_TSTAMPS 0x1
279 #define SYSCTL_FLAG_WSCALE 0x2
280 #define SYSCTL_FLAG_SACK 0x4
282 /* If congestion control is doing timestamping */
283 if (tp
->ca_ops
->rtt_sample
)
284 do_gettimeofday(&skb
->stamp
);
287 if (tcb
->flags
& TCPCB_FLAG_SYN
) {
288 tcp_header_size
= sizeof(struct tcphdr
) + TCPOLEN_MSS
;
289 if(sysctl_tcp_timestamps
) {
290 tcp_header_size
+= TCPOLEN_TSTAMP_ALIGNED
;
291 sysctl_flags
|= SYSCTL_FLAG_TSTAMPS
;
293 if(sysctl_tcp_window_scaling
) {
294 tcp_header_size
+= TCPOLEN_WSCALE_ALIGNED
;
295 sysctl_flags
|= SYSCTL_FLAG_WSCALE
;
297 if(sysctl_tcp_sack
) {
298 sysctl_flags
|= SYSCTL_FLAG_SACK
;
299 if(!(sysctl_flags
& SYSCTL_FLAG_TSTAMPS
))
300 tcp_header_size
+= TCPOLEN_SACKPERM_ALIGNED
;
302 } else if (tp
->rx_opt
.eff_sacks
) {
303 /* A SACK is 2 pad bytes, a 2 byte header, plus
304 * 2 32-bit sequence numbers for each SACK block.
306 tcp_header_size
+= (TCPOLEN_SACK_BASE_ALIGNED
+
307 (tp
->rx_opt
.eff_sacks
* TCPOLEN_SACK_PERBLOCK
));
310 if (tcp_packets_in_flight(tp
) == 0)
311 tcp_ca_event(tp
, CA_EVENT_TX_START
);
313 th
= (struct tcphdr
*) skb_push(skb
, tcp_header_size
);
315 skb_set_owner_w(skb
, sk
);
317 /* Build TCP header and checksum it. */
318 th
->source
= inet
->sport
;
319 th
->dest
= inet
->dport
;
320 th
->seq
= htonl(tcb
->seq
);
321 th
->ack_seq
= htonl(tp
->rcv_nxt
);
322 *(((__u16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) | tcb
->flags
);
323 if (tcb
->flags
& TCPCB_FLAG_SYN
) {
324 /* RFC1323: The window in SYN & SYN/ACK segments
327 th
->window
= htons(tp
->rcv_wnd
);
329 th
->window
= htons(tcp_select_window(sk
));
335 between(tp
->snd_up
, tcb
->seq
+1, tcb
->seq
+0xFFFF)) {
336 th
->urg_ptr
= htons(tp
->snd_up
-tcb
->seq
);
340 if (tcb
->flags
& TCPCB_FLAG_SYN
) {
341 tcp_syn_build_options((__u32
*)(th
+ 1),
342 tcp_advertise_mss(sk
),
343 (sysctl_flags
& SYSCTL_FLAG_TSTAMPS
),
344 (sysctl_flags
& SYSCTL_FLAG_SACK
),
345 (sysctl_flags
& SYSCTL_FLAG_WSCALE
),
346 tp
->rx_opt
.rcv_wscale
,
348 tp
->rx_opt
.ts_recent
);
350 tcp_build_and_update_options((__u32
*)(th
+ 1),
353 TCP_ECN_send(sk
, tp
, skb
, tcp_header_size
);
355 tp
->af_specific
->send_check(sk
, th
, skb
->len
, skb
);
357 if (tcb
->flags
& TCPCB_FLAG_ACK
)
358 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
360 if (skb
->len
!= tcp_header_size
)
361 tcp_event_data_sent(tp
, skb
, sk
);
363 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
365 err
= tp
->af_specific
->queue_xmit(skb
, 0);
371 /* NET_XMIT_CN is special. It does not guarantee,
372 * that this packet is lost. It tells that device
373 * is about to start to drop packets or already
374 * drops some packets of the same priority and
375 * invokes us to send less aggressively.
377 return err
== NET_XMIT_CN
? 0 : err
;
380 #undef SYSCTL_FLAG_TSTAMPS
381 #undef SYSCTL_FLAG_WSCALE
382 #undef SYSCTL_FLAG_SACK
386 /* This routine just queue's the buffer
388 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
389 * otherwise socket can stall.
391 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
393 struct tcp_sock
*tp
= tcp_sk(sk
);
395 /* Advance write_seq and place onto the write_queue. */
396 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
397 skb_header_release(skb
);
398 __skb_queue_tail(&sk
->sk_write_queue
, skb
);
399 sk_charge_skb(sk
, skb
);
401 /* Queue it, remembering where we must start sending. */
402 if (sk
->sk_send_head
== NULL
)
403 sk
->sk_send_head
= skb
;
406 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
408 if (skb
->len
<= mss_now
||
409 !(sk
->sk_route_caps
& NETIF_F_TSO
)) {
410 /* Avoid the costly divide in the normal
413 skb_shinfo(skb
)->tso_segs
= 1;
414 skb_shinfo(skb
)->tso_size
= 0;
418 factor
= skb
->len
+ (mss_now
- 1);
420 skb_shinfo(skb
)->tso_segs
= factor
;
421 skb_shinfo(skb
)->tso_size
= mss_now
;
425 /* Function to create two new TCP segments. Shrinks the given segment
426 * to the specified size and appends a new segment with the rest of the
427 * packet to the list. This won't be called frequently, I hope.
428 * Remember, these are still headerless SKBs at this point.
430 static int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
, unsigned int mss_now
)
432 struct tcp_sock
*tp
= tcp_sk(sk
);
433 struct sk_buff
*buff
;
437 nsize
= skb_headlen(skb
) - len
;
441 if (skb_cloned(skb
) &&
442 skb_is_nonlinear(skb
) &&
443 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
446 /* Get a new skb... force flag on. */
447 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
449 return -ENOMEM
; /* We'll just try again later. */
450 sk_charge_skb(sk
, buff
);
452 /* Correct the sequence numbers. */
453 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
454 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
455 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
457 /* PSH and FIN should only be set in the second packet. */
458 flags
= TCP_SKB_CB(skb
)->flags
;
459 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
460 TCP_SKB_CB(buff
)->flags
= flags
;
461 TCP_SKB_CB(buff
)->sacked
=
462 (TCP_SKB_CB(skb
)->sacked
&
463 (TCPCB_LOST
| TCPCB_EVER_RETRANS
| TCPCB_AT_TAIL
));
464 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_AT_TAIL
;
466 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_HW
) {
467 /* Copy and checksum data tail into the new buffer. */
468 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
, skb_put(buff
, nsize
),
473 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
475 skb
->ip_summed
= CHECKSUM_HW
;
476 skb_split(skb
, buff
, len
);
479 buff
->ip_summed
= skb
->ip_summed
;
481 /* Looks stupid, but our code really uses when of
482 * skbs, which it never sent before. --ANK
484 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
485 buff
->stamp
= skb
->stamp
;
487 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
) {
488 tp
->lost_out
-= tcp_skb_pcount(skb
);
489 tp
->left_out
-= tcp_skb_pcount(skb
);
492 /* Fix up tso_factor for both original and new SKB. */
493 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
494 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
496 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
) {
497 tp
->lost_out
+= tcp_skb_pcount(skb
);
498 tp
->left_out
+= tcp_skb_pcount(skb
);
501 if (TCP_SKB_CB(buff
)->sacked
&TCPCB_LOST
) {
502 tp
->lost_out
+= tcp_skb_pcount(buff
);
503 tp
->left_out
+= tcp_skb_pcount(buff
);
506 /* Link BUFF into the send queue. */
507 skb_header_release(buff
);
508 __skb_append(skb
, buff
);
513 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
514 * eventually). The difference is that pulled data not copied, but
515 * immediately discarded.
517 static unsigned char *__pskb_trim_head(struct sk_buff
*skb
, int len
)
523 for (i
=0; i
<skb_shinfo(skb
)->nr_frags
; i
++) {
524 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
525 put_page(skb_shinfo(skb
)->frags
[i
].page
);
526 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
528 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
530 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
531 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
537 skb_shinfo(skb
)->nr_frags
= k
;
539 skb
->tail
= skb
->data
;
540 skb
->data_len
-= len
;
541 skb
->len
= skb
->data_len
;
545 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
547 if (skb_cloned(skb
) &&
548 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
551 if (len
<= skb_headlen(skb
)) {
552 __skb_pull(skb
, len
);
554 if (__pskb_trim_head(skb
, len
-skb_headlen(skb
)) == NULL
)
558 TCP_SKB_CB(skb
)->seq
+= len
;
559 skb
->ip_summed
= CHECKSUM_HW
;
561 skb
->truesize
-= len
;
562 sk
->sk_wmem_queued
-= len
;
563 sk
->sk_forward_alloc
+= len
;
564 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
566 /* Any change of skb->len requires recalculation of tso
569 if (tcp_skb_pcount(skb
) > 1)
570 tcp_set_skb_tso_segs(sk
, skb
, tcp_current_mss(sk
, 1));
575 /* This function synchronize snd mss to current pmtu/exthdr set.
577 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
578 for TCP options, but includes only bare TCP header.
580 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
581 It is minumum of user_mss and mss received with SYN.
582 It also does not include TCP options.
584 tp->pmtu_cookie is last pmtu, seen by this function.
586 tp->mss_cache is current effective sending mss, including
587 all tcp options except for SACKs. It is evaluated,
588 taking into account current pmtu, but never exceeds
589 tp->rx_opt.mss_clamp.
591 NOTE1. rfc1122 clearly states that advertised MSS
592 DOES NOT include either tcp or ip options.
594 NOTE2. tp->pmtu_cookie and tp->mss_cache are READ ONLY outside
595 this function. --ANK (980731)
598 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
600 struct tcp_sock
*tp
= tcp_sk(sk
);
603 /* Calculate base mss without TCP options:
604 It is MMS_S - sizeof(tcphdr) of rfc1122
606 mss_now
= pmtu
- tp
->af_specific
->net_header_len
- sizeof(struct tcphdr
);
608 /* Clamp it (mss_clamp does not include tcp options) */
609 if (mss_now
> tp
->rx_opt
.mss_clamp
)
610 mss_now
= tp
->rx_opt
.mss_clamp
;
612 /* Now subtract optional transport overhead */
613 mss_now
-= tp
->ext_header_len
;
615 /* Then reserve room for full set of TCP options and 8 bytes of data */
619 /* Now subtract TCP options size, not including SACKs */
620 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
622 /* Bound mss with half of window */
623 if (tp
->max_window
&& mss_now
> (tp
->max_window
>>1))
624 mss_now
= max((tp
->max_window
>>1), 68U - tp
->tcp_header_len
);
626 /* And store cached results */
627 tp
->pmtu_cookie
= pmtu
;
628 tp
->mss_cache
= mss_now
;
633 /* Compute the current effective MSS, taking SACKs and IP options,
634 * and even PMTU discovery events into account.
636 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
637 * cannot be large. However, taking into account rare use of URG, this
640 unsigned int tcp_current_mss(struct sock
*sk
, int large_allowed
)
642 struct tcp_sock
*tp
= tcp_sk(sk
);
643 struct dst_entry
*dst
= __sk_dst_get(sk
);
648 mss_now
= tp
->mss_cache
;
651 (sk
->sk_route_caps
& NETIF_F_TSO
) &&
656 u32 mtu
= dst_mtu(dst
);
657 if (mtu
!= tp
->pmtu_cookie
)
658 mss_now
= tcp_sync_mss(sk
, mtu
);
661 if (tp
->rx_opt
.eff_sacks
)
662 mss_now
-= (TCPOLEN_SACK_BASE_ALIGNED
+
663 (tp
->rx_opt
.eff_sacks
* TCPOLEN_SACK_PERBLOCK
));
665 xmit_size_goal
= mss_now
;
668 xmit_size_goal
= 65535 -
669 tp
->af_specific
->net_header_len
-
670 tp
->ext_header_len
- tp
->tcp_header_len
;
672 if (tp
->max_window
&&
673 (xmit_size_goal
> (tp
->max_window
>> 1)))
674 xmit_size_goal
= max((tp
->max_window
>> 1),
675 68U - tp
->tcp_header_len
);
677 xmit_size_goal
-= (xmit_size_goal
% mss_now
);
679 tp
->xmit_size_goal
= xmit_size_goal
;
684 /* Congestion window validation. (RFC2861) */
686 static inline void tcp_cwnd_validate(struct sock
*sk
, struct tcp_sock
*tp
)
688 __u32 packets_out
= tp
->packets_out
;
690 if (packets_out
>= tp
->snd_cwnd
) {
691 /* Network is feed fully. */
692 tp
->snd_cwnd_used
= 0;
693 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
695 /* Network starves. */
696 if (tp
->packets_out
> tp
->snd_cwnd_used
)
697 tp
->snd_cwnd_used
= tp
->packets_out
;
699 if ((s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= tp
->rto
)
700 tcp_cwnd_application_limited(sk
);
704 static unsigned int tcp_window_allows(struct tcp_sock
*tp
, struct sk_buff
*skb
, unsigned int mss_now
, unsigned int cwnd
)
706 u32 window
, cwnd_len
;
708 window
= (tp
->snd_una
+ tp
->snd_wnd
- TCP_SKB_CB(skb
)->seq
);
709 cwnd_len
= mss_now
* cwnd
;
710 return min(window
, cwnd_len
);
713 /* Can at least one segment of SKB be sent right now, according to the
714 * congestion window rules? If so, return how many segments are allowed.
716 static inline unsigned int tcp_cwnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
)
720 /* Don't be strict about the congestion window for the final FIN. */
721 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
724 in_flight
= tcp_packets_in_flight(tp
);
726 if (in_flight
< cwnd
)
727 return (cwnd
- in_flight
);
732 /* This must be invoked the first time we consider transmitting
735 static inline int tcp_init_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
737 int tso_segs
= tcp_skb_pcount(skb
);
741 skb_shinfo(skb
)->tso_size
!= mss_now
)) {
742 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
743 tso_segs
= tcp_skb_pcount(skb
);
748 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
750 return after(tp
->snd_sml
,tp
->snd_una
) &&
751 !after(tp
->snd_sml
, tp
->snd_nxt
);
754 /* Return 0, if packet can be sent now without violation Nagle's rules:
755 * 1. It is full sized.
756 * 2. Or it contains FIN. (already checked by caller)
757 * 3. Or TCP_NODELAY was set.
758 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
759 * With Minshall's modification: all sent small packets are ACKed.
762 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
763 const struct sk_buff
*skb
,
764 unsigned mss_now
, int nonagle
)
766 return (skb
->len
< mss_now
&&
767 ((nonagle
&TCP_NAGLE_CORK
) ||
770 tcp_minshall_check(tp
))));
773 /* Return non-zero if the Nagle test allows this packet to be
776 static inline int tcp_nagle_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
777 unsigned int cur_mss
, int nonagle
)
779 /* Nagle rule does not apply to frames, which sit in the middle of the
780 * write_queue (they have no chances to get new data).
782 * This is implemented in the callers, where they modify the 'nonagle'
783 * argument based upon the location of SKB in the send queue.
785 if (nonagle
& TCP_NAGLE_PUSH
)
788 /* Don't use the nagle rule for urgent data (or for the final FIN). */
790 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
))
793 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
799 /* Does at least the first segment of SKB fit into the send window? */
800 static inline int tcp_snd_wnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
, unsigned int cur_mss
)
802 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
804 if (skb
->len
> cur_mss
)
805 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
807 return !after(end_seq
, tp
->snd_una
+ tp
->snd_wnd
);
810 /* This checks if the data bearing packet SKB (usually sk->sk_send_head)
811 * should be put on the wire right now. If so, it returns the number of
812 * packets allowed by the congestion window.
814 static unsigned int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
815 unsigned int cur_mss
, int nonagle
)
817 struct tcp_sock
*tp
= tcp_sk(sk
);
818 unsigned int cwnd_quota
;
820 tcp_init_tso_segs(sk
, skb
, cur_mss
);
822 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
825 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
827 !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
833 static inline int tcp_skb_is_last(const struct sock
*sk
,
834 const struct sk_buff
*skb
)
836 return skb
->next
== (struct sk_buff
*)&sk
->sk_write_queue
;
839 int tcp_may_send_now(struct sock
*sk
, struct tcp_sock
*tp
)
841 struct sk_buff
*skb
= sk
->sk_send_head
;
844 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
, 1),
845 (tcp_skb_is_last(sk
, skb
) ?
850 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
851 * which is put after SKB on the list. It is very much like
852 * tcp_fragment() except that it may make several kinds of assumptions
853 * in order to speed up the splitting operation. In particular, we
854 * know that all the data is in scatter-gather pages, and that the
855 * packet has never been sent out before (and thus is not cloned).
857 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
, unsigned int mss_now
)
859 struct sk_buff
*buff
;
860 int nlen
= skb
->len
- len
;
863 /* All of a TSO frame must be composed of paged data. */
864 if (skb
->len
!= skb
->data_len
)
865 return tcp_fragment(sk
, skb
, len
, mss_now
);
867 buff
= sk_stream_alloc_pskb(sk
, 0, 0, GFP_ATOMIC
);
868 if (unlikely(buff
== NULL
))
871 buff
->truesize
= nlen
;
872 skb
->truesize
-= nlen
;
874 /* Correct the sequence numbers. */
875 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
876 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
877 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
879 /* PSH and FIN should only be set in the second packet. */
880 flags
= TCP_SKB_CB(skb
)->flags
;
881 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
882 TCP_SKB_CB(buff
)->flags
= flags
;
884 /* This packet was never sent out yet, so no SACK bits. */
885 TCP_SKB_CB(buff
)->sacked
= 0;
887 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_HW
;
888 skb_split(skb
, buff
, len
);
890 /* Fix up tso_factor for both original and new SKB. */
891 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
892 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
894 /* Link BUFF into the send queue. */
895 skb_header_release(buff
);
896 __skb_append(skb
, buff
);
901 /* Try to defer sending, if possible, in order to minimize the amount
902 * of TSO splitting we do. View it as a kind of TSO Nagle test.
904 * This algorithm is from John Heffner.
906 static int tcp_tso_should_defer(struct sock
*sk
, struct tcp_sock
*tp
, struct sk_buff
*skb
)
908 u32 send_win
, cong_win
, limit
, in_flight
;
910 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
913 if (tp
->ca_state
!= TCP_CA_Open
)
916 in_flight
= tcp_packets_in_flight(tp
);
918 BUG_ON(tcp_skb_pcount(skb
) <= 1 ||
919 (tp
->snd_cwnd
<= in_flight
));
921 send_win
= (tp
->snd_una
+ tp
->snd_wnd
) - TCP_SKB_CB(skb
)->seq
;
923 /* From in_flight test above, we know that cwnd > in_flight. */
924 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
926 limit
= min(send_win
, cong_win
);
928 if (sysctl_tcp_tso_win_divisor
) {
929 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
931 /* If at least some fraction of a window is available,
934 chunk
/= sysctl_tcp_tso_win_divisor
;
938 /* Different approach, try not to defer past a single
939 * ACK. Receiver should ACK every other full sized
940 * frame, so if we have space for more than 3 frames
943 if (limit
> tcp_max_burst(tp
) * tp
->mss_cache
)
947 /* Ok, it looks like it is advisable to defer. */
951 /* This routine writes packets to the network. It advances the
952 * send_head. This happens as incoming acks open up the remote
955 * Returns 1, if no segments are in flight and we have queued segments, but
956 * cannot send anything now because of SWS or another problem.
958 static int tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
)
960 struct tcp_sock
*tp
= tcp_sk(sk
);
962 unsigned int tso_segs
, sent_pkts
;
965 /* If we are closed, the bytes will have to remain here.
966 * In time closedown will finish, we empty the write queue and all
969 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
973 while ((skb
= sk
->sk_send_head
)) {
976 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
979 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
983 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
987 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
988 (tcp_skb_is_last(sk
, skb
) ?
989 nonagle
: TCP_NAGLE_PUSH
))))
992 if (tcp_tso_should_defer(sk
, tp
, skb
))
998 limit
= tcp_window_allows(tp
, skb
,
999 mss_now
, cwnd_quota
);
1001 if (skb
->len
< limit
) {
1002 unsigned int trim
= skb
->len
% mss_now
;
1005 limit
= skb
->len
- trim
;
1009 if (skb
->len
> limit
&&
1010 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1013 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1015 if (unlikely(tcp_transmit_skb(sk
, skb_clone(skb
, GFP_ATOMIC
))))
1018 /* Advance the send_head. This one is sent out.
1019 * This call will increment packets_out.
1021 update_send_head(sk
, tp
, skb
);
1023 tcp_minshall_update(tp
, mss_now
, skb
);
1027 if (likely(sent_pkts
)) {
1028 tcp_cwnd_validate(sk
, tp
);
1031 return !tp
->packets_out
&& sk
->sk_send_head
;
1034 /* Push out any pending frames which were held back due to
1035 * TCP_CORK or attempt at coalescing tiny packets.
1036 * The socket must be locked by the caller.
1038 void __tcp_push_pending_frames(struct sock
*sk
, struct tcp_sock
*tp
,
1039 unsigned int cur_mss
, int nonagle
)
1041 struct sk_buff
*skb
= sk
->sk_send_head
;
1044 if (tcp_write_xmit(sk
, cur_mss
, nonagle
))
1045 tcp_check_probe_timer(sk
, tp
);
1049 /* Send _single_ skb sitting at the send head. This function requires
1050 * true push pending frames to setup probe timer etc.
1052 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
1054 struct tcp_sock
*tp
= tcp_sk(sk
);
1055 struct sk_buff
*skb
= sk
->sk_send_head
;
1056 unsigned int tso_segs
, cwnd_quota
;
1058 BUG_ON(!skb
|| skb
->len
< mss_now
);
1060 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1061 cwnd_quota
= tcp_snd_test(sk
, skb
, mss_now
, TCP_NAGLE_PUSH
);
1063 if (likely(cwnd_quota
)) {
1070 limit
= tcp_window_allows(tp
, skb
,
1071 mss_now
, cwnd_quota
);
1073 if (skb
->len
< limit
) {
1074 unsigned int trim
= skb
->len
% mss_now
;
1077 limit
= skb
->len
- trim
;
1081 if (skb
->len
> limit
&&
1082 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1085 /* Send it out now. */
1086 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1088 if (likely(!tcp_transmit_skb(sk
, skb_clone(skb
, sk
->sk_allocation
)))) {
1089 update_send_head(sk
, tp
, skb
);
1090 tcp_cwnd_validate(sk
, tp
);
1096 /* This function returns the amount that we can raise the
1097 * usable window based on the following constraints
1099 * 1. The window can never be shrunk once it is offered (RFC 793)
1100 * 2. We limit memory per socket
1103 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1104 * RECV.NEXT + RCV.WIN fixed until:
1105 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1107 * i.e. don't raise the right edge of the window until you can raise
1108 * it at least MSS bytes.
1110 * Unfortunately, the recommended algorithm breaks header prediction,
1111 * since header prediction assumes th->window stays fixed.
1113 * Strictly speaking, keeping th->window fixed violates the receiver
1114 * side SWS prevention criteria. The problem is that under this rule
1115 * a stream of single byte packets will cause the right side of the
1116 * window to always advance by a single byte.
1118 * Of course, if the sender implements sender side SWS prevention
1119 * then this will not be a problem.
1121 * BSD seems to make the following compromise:
1123 * If the free space is less than the 1/4 of the maximum
1124 * space available and the free space is less than 1/2 mss,
1125 * then set the window to 0.
1126 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1127 * Otherwise, just prevent the window from shrinking
1128 * and from being larger than the largest representable value.
1130 * This prevents incremental opening of the window in the regime
1131 * where TCP is limited by the speed of the reader side taking
1132 * data out of the TCP receive queue. It does nothing about
1133 * those cases where the window is constrained on the sender side
1134 * because the pipeline is full.
1136 * BSD also seems to "accidentally" limit itself to windows that are a
1137 * multiple of MSS, at least until the free space gets quite small.
1138 * This would appear to be a side effect of the mbuf implementation.
1139 * Combining these two algorithms results in the observed behavior
1140 * of having a fixed window size at almost all times.
1142 * Below we obtain similar behavior by forcing the offered window to
1143 * a multiple of the mss when it is feasible to do so.
1145 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1146 * Regular options like TIMESTAMP are taken into account.
1148 u32
__tcp_select_window(struct sock
*sk
)
1150 struct tcp_sock
*tp
= tcp_sk(sk
);
1151 /* MSS for the peer's data. Previous verions used mss_clamp
1152 * here. I don't know if the value based on our guesses
1153 * of peer's MSS is better for the performance. It's more correct
1154 * but may be worse for the performance because of rcv_mss
1155 * fluctuations. --SAW 1998/11/1
1157 int mss
= tp
->ack
.rcv_mss
;
1158 int free_space
= tcp_space(sk
);
1159 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
1162 if (mss
> full_space
)
1165 if (free_space
< full_space
/2) {
1168 if (tcp_memory_pressure
)
1169 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U*tp
->advmss
);
1171 if (free_space
< mss
)
1175 if (free_space
> tp
->rcv_ssthresh
)
1176 free_space
= tp
->rcv_ssthresh
;
1178 /* Don't do rounding if we are using window scaling, since the
1179 * scaled window will not line up with the MSS boundary anyway.
1181 window
= tp
->rcv_wnd
;
1182 if (tp
->rx_opt
.rcv_wscale
) {
1183 window
= free_space
;
1185 /* Advertise enough space so that it won't get scaled away.
1186 * Import case: prevent zero window announcement if
1187 * 1<<rcv_wscale > mss.
1189 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1190 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1191 << tp
->rx_opt
.rcv_wscale
);
1193 /* Get the largest window that is a nice multiple of mss.
1194 * Window clamp already applied above.
1195 * If our current window offering is within 1 mss of the
1196 * free space we just keep it. This prevents the divide
1197 * and multiply from happening most of the time.
1198 * We also don't do any window rounding when the free space
1201 if (window
<= free_space
- mss
|| window
> free_space
)
1202 window
= (free_space
/mss
)*mss
;
1208 /* Attempt to collapse two adjacent SKB's during retransmission. */
1209 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*skb
, int mss_now
)
1211 struct tcp_sock
*tp
= tcp_sk(sk
);
1212 struct sk_buff
*next_skb
= skb
->next
;
1214 /* The first test we must make is that neither of these two
1215 * SKB's are still referenced by someone else.
1217 if (!skb_cloned(skb
) && !skb_cloned(next_skb
)) {
1218 int skb_size
= skb
->len
, next_skb_size
= next_skb
->len
;
1219 u16 flags
= TCP_SKB_CB(skb
)->flags
;
1221 /* Also punt if next skb has been SACK'd. */
1222 if(TCP_SKB_CB(next_skb
)->sacked
& TCPCB_SACKED_ACKED
)
1225 /* Next skb is out of window. */
1226 if (after(TCP_SKB_CB(next_skb
)->end_seq
, tp
->snd_una
+tp
->snd_wnd
))
1229 /* Punt if not enough space exists in the first SKB for
1230 * the data in the second, or the total combined payload
1231 * would exceed the MSS.
1233 if ((next_skb_size
> skb_tailroom(skb
)) ||
1234 ((skb_size
+ next_skb_size
) > mss_now
))
1237 BUG_ON(tcp_skb_pcount(skb
) != 1 ||
1238 tcp_skb_pcount(next_skb
) != 1);
1240 /* Ok. We will be able to collapse the packet. */
1241 __skb_unlink(next_skb
, next_skb
->list
);
1243 memcpy(skb_put(skb
, next_skb_size
), next_skb
->data
, next_skb_size
);
1245 if (next_skb
->ip_summed
== CHECKSUM_HW
)
1246 skb
->ip_summed
= CHECKSUM_HW
;
1248 if (skb
->ip_summed
!= CHECKSUM_HW
)
1249 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1251 /* Update sequence range on original skb. */
1252 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1254 /* Merge over control information. */
1255 flags
|= TCP_SKB_CB(next_skb
)->flags
; /* This moves PSH/FIN etc. over */
1256 TCP_SKB_CB(skb
)->flags
= flags
;
1258 /* All done, get rid of second SKB and account for it so
1259 * packet counting does not break.
1261 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
&(TCPCB_EVER_RETRANS
|TCPCB_AT_TAIL
);
1262 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_SACKED_RETRANS
)
1263 tp
->retrans_out
-= tcp_skb_pcount(next_skb
);
1264 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_LOST
) {
1265 tp
->lost_out
-= tcp_skb_pcount(next_skb
);
1266 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1268 /* Reno case is special. Sigh... */
1269 if (!tp
->rx_opt
.sack_ok
&& tp
->sacked_out
) {
1270 tcp_dec_pcount_approx(&tp
->sacked_out
, next_skb
);
1271 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1274 /* Not quite right: it can be > snd.fack, but
1275 * it is better to underestimate fackets.
1277 tcp_dec_pcount_approx(&tp
->fackets_out
, next_skb
);
1278 tcp_packets_out_dec(tp
, next_skb
);
1279 sk_stream_free_skb(sk
, next_skb
);
1283 /* Do a simple retransmit without using the backoff mechanisms in
1284 * tcp_timer. This is used for path mtu discovery.
1285 * The socket is already locked here.
1287 void tcp_simple_retransmit(struct sock
*sk
)
1289 struct tcp_sock
*tp
= tcp_sk(sk
);
1290 struct sk_buff
*skb
;
1291 unsigned int mss
= tcp_current_mss(sk
, 0);
1294 sk_stream_for_retrans_queue(skb
, sk
) {
1295 if (skb
->len
> mss
&&
1296 !(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1297 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1298 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1299 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1301 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_LOST
)) {
1302 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1303 tp
->lost_out
+= tcp_skb_pcount(skb
);
1312 tcp_sync_left_out(tp
);
1314 /* Don't muck with the congestion window here.
1315 * Reason is that we do not increase amount of _data_
1316 * in network, but units changed and effective
1317 * cwnd/ssthresh really reduced now.
1319 if (tp
->ca_state
!= TCP_CA_Loss
) {
1320 tp
->high_seq
= tp
->snd_nxt
;
1321 tp
->snd_ssthresh
= tcp_current_ssthresh(tp
);
1322 tp
->prior_ssthresh
= 0;
1323 tp
->undo_marker
= 0;
1324 tcp_set_ca_state(tp
, TCP_CA_Loss
);
1326 tcp_xmit_retransmit_queue(sk
);
1329 /* This retransmits one SKB. Policy decisions and retransmit queue
1330 * state updates are done by the caller. Returns non-zero if an
1331 * error occurred which prevented the send.
1333 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
1335 struct tcp_sock
*tp
= tcp_sk(sk
);
1336 unsigned int cur_mss
= tcp_current_mss(sk
, 0);
1339 /* Do not sent more than we queued. 1/4 is reserved for possible
1340 * copying overhead: frgagmentation, tunneling, mangling etc.
1342 if (atomic_read(&sk
->sk_wmem_alloc
) >
1343 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
1346 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
1347 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1350 if (sk
->sk_route_caps
& NETIF_F_TSO
) {
1351 sk
->sk_route_caps
&= ~NETIF_F_TSO
;
1352 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
1355 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
1359 /* If receiver has shrunk his window, and skb is out of
1360 * new window, do not retransmit it. The exception is the
1361 * case, when window is shrunk to zero. In this case
1362 * our retransmit serves as a zero window probe.
1364 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)
1365 && TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
1368 if (skb
->len
> cur_mss
) {
1369 int old_factor
= tcp_skb_pcount(skb
);
1372 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
1373 return -ENOMEM
; /* We'll try again later. */
1375 /* New SKB created, account for it. */
1376 diff
= old_factor
- tcp_skb_pcount(skb
) -
1377 tcp_skb_pcount(skb
->next
);
1378 tp
->packets_out
-= diff
;
1381 tp
->fackets_out
-= diff
;
1382 if ((int)tp
->fackets_out
< 0)
1383 tp
->fackets_out
= 0;
1387 /* Collapse two adjacent packets if worthwhile and we can. */
1388 if(!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
) &&
1389 (skb
->len
< (cur_mss
>> 1)) &&
1390 (skb
->next
!= sk
->sk_send_head
) &&
1391 (skb
->next
!= (struct sk_buff
*)&sk
->sk_write_queue
) &&
1392 (skb_shinfo(skb
)->nr_frags
== 0 && skb_shinfo(skb
->next
)->nr_frags
== 0) &&
1393 (tcp_skb_pcount(skb
) == 1 && tcp_skb_pcount(skb
->next
) == 1) &&
1394 (sysctl_tcp_retrans_collapse
!= 0))
1395 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
1397 if(tp
->af_specific
->rebuild_header(sk
))
1398 return -EHOSTUNREACH
; /* Routing failure or similar. */
1400 /* Some Solaris stacks overoptimize and ignore the FIN on a
1401 * retransmit when old data is attached. So strip it off
1402 * since it is cheap to do so and saves bytes on the network.
1405 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1406 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
1407 if (!pskb_trim(skb
, 0)) {
1408 TCP_SKB_CB(skb
)->seq
= TCP_SKB_CB(skb
)->end_seq
- 1;
1409 skb_shinfo(skb
)->tso_segs
= 1;
1410 skb_shinfo(skb
)->tso_size
= 0;
1411 skb
->ip_summed
= CHECKSUM_NONE
;
1416 /* Make a copy, if the first transmission SKB clone we made
1417 * is still in somebody's hands, else make a clone.
1419 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1421 err
= tcp_transmit_skb(sk
, (skb_cloned(skb
) ?
1422 pskb_copy(skb
, GFP_ATOMIC
):
1423 skb_clone(skb
, GFP_ATOMIC
)));
1426 /* Update global TCP statistics. */
1427 TCP_INC_STATS(TCP_MIB_RETRANSSEGS
);
1429 tp
->total_retrans
++;
1431 #if FASTRETRANS_DEBUG > 0
1432 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1433 if (net_ratelimit())
1434 printk(KERN_DEBUG
"retrans_out leaked.\n");
1437 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
1438 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1440 /* Save stamp of the first retransmit. */
1441 if (!tp
->retrans_stamp
)
1442 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
1446 /* snd_nxt is stored to detect loss of retransmitted segment,
1447 * see tcp_input.c tcp_sacktag_write_queue().
1449 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
1454 /* This gets called after a retransmit timeout, and the initially
1455 * retransmitted data is acknowledged. It tries to continue
1456 * resending the rest of the retransmit queue, until either
1457 * we've sent it all or the congestion window limit is reached.
1458 * If doing SACK, the first ACK which comes back for a timeout
1459 * based retransmit packet might feed us FACK information again.
1460 * If so, we use it to avoid unnecessarily retransmissions.
1462 void tcp_xmit_retransmit_queue(struct sock
*sk
)
1464 struct tcp_sock
*tp
= tcp_sk(sk
);
1465 struct sk_buff
*skb
;
1466 int packet_cnt
= tp
->lost_out
;
1468 /* First pass: retransmit lost packets. */
1470 sk_stream_for_retrans_queue(skb
, sk
) {
1471 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1473 /* Assume this retransmit will generate
1474 * only one packet for congestion window
1475 * calculation purposes. This works because
1476 * tcp_retransmit_skb() will chop up the
1477 * packet to be MSS sized and all the
1478 * packet counting works out.
1480 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1483 if (sacked
&TCPCB_LOST
) {
1484 if (!(sacked
&(TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))) {
1485 if (tcp_retransmit_skb(sk
, skb
))
1487 if (tp
->ca_state
!= TCP_CA_Loss
)
1488 NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS
);
1490 NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS
);
1493 skb_peek(&sk
->sk_write_queue
))
1494 tcp_reset_xmit_timer(sk
, TCP_TIME_RETRANS
, tp
->rto
);
1497 packet_cnt
-= tcp_skb_pcount(skb
);
1498 if (packet_cnt
<= 0)
1504 /* OK, demanded retransmission is finished. */
1506 /* Forward retransmissions are possible only during Recovery. */
1507 if (tp
->ca_state
!= TCP_CA_Recovery
)
1510 /* No forward retransmissions in Reno are possible. */
1511 if (!tp
->rx_opt
.sack_ok
)
1514 /* Yeah, we have to make difficult choice between forward transmission
1515 * and retransmission... Both ways have their merits...
1517 * For now we do not retransmit anything, while we have some new
1521 if (tcp_may_send_now(sk
, tp
))
1526 sk_stream_for_retrans_queue(skb
, sk
) {
1527 /* Similar to the retransmit loop above we
1528 * can pretend that the retransmitted SKB
1529 * we send out here will be composed of one
1530 * real MSS sized packet because tcp_retransmit_skb()
1531 * will fragment it if necessary.
1533 if (++packet_cnt
> tp
->fackets_out
)
1536 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1539 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
)
1542 /* Ok, retransmit it. */
1543 if (tcp_retransmit_skb(sk
, skb
))
1546 if (skb
== skb_peek(&sk
->sk_write_queue
))
1547 tcp_reset_xmit_timer(sk
, TCP_TIME_RETRANS
, tp
->rto
);
1549 NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS
);
1554 /* Send a fin. The caller locks the socket for us. This cannot be
1555 * allowed to fail queueing a FIN frame under any circumstances.
1557 void tcp_send_fin(struct sock
*sk
)
1559 struct tcp_sock
*tp
= tcp_sk(sk
);
1560 struct sk_buff
*skb
= skb_peek_tail(&sk
->sk_write_queue
);
1563 /* Optimization, tack on the FIN if we have a queue of
1564 * unsent frames. But be careful about outgoing SACKS
1567 mss_now
= tcp_current_mss(sk
, 1);
1569 if (sk
->sk_send_head
!= NULL
) {
1570 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
1571 TCP_SKB_CB(skb
)->end_seq
++;
1574 /* Socket is locked, keep trying until memory is available. */
1576 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_KERNEL
);
1582 /* Reserve space for headers and prepare control bits. */
1583 skb_reserve(skb
, MAX_TCP_HEADER
);
1585 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
1586 TCP_SKB_CB(skb
)->sacked
= 0;
1587 skb_shinfo(skb
)->tso_segs
= 1;
1588 skb_shinfo(skb
)->tso_size
= 0;
1590 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
1591 TCP_SKB_CB(skb
)->seq
= tp
->write_seq
;
1592 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
1593 tcp_queue_skb(sk
, skb
);
1595 __tcp_push_pending_frames(sk
, tp
, mss_now
, TCP_NAGLE_OFF
);
1598 /* We get here when a process closes a file descriptor (either due to
1599 * an explicit close() or as a byproduct of exit()'ing) and there
1600 * was unread data in the receive queue. This behavior is recommended
1601 * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM
1603 void tcp_send_active_reset(struct sock
*sk
, unsigned int __nocast priority
)
1605 struct tcp_sock
*tp
= tcp_sk(sk
);
1606 struct sk_buff
*skb
;
1608 /* NOTE: No TCP options attached and we never retransmit this. */
1609 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
1611 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
1615 /* Reserve space for headers and prepare control bits. */
1616 skb_reserve(skb
, MAX_TCP_HEADER
);
1618 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
1619 TCP_SKB_CB(skb
)->sacked
= 0;
1620 skb_shinfo(skb
)->tso_segs
= 1;
1621 skb_shinfo(skb
)->tso_size
= 0;
1624 TCP_SKB_CB(skb
)->seq
= tcp_acceptable_seq(sk
, tp
);
1625 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
1626 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1627 if (tcp_transmit_skb(sk
, skb
))
1628 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
1631 /* WARNING: This routine must only be called when we have already sent
1632 * a SYN packet that crossed the incoming SYN that caused this routine
1633 * to get called. If this assumption fails then the initial rcv_wnd
1634 * and rcv_wscale values will not be correct.
1636 int tcp_send_synack(struct sock
*sk
)
1638 struct sk_buff
* skb
;
1640 skb
= skb_peek(&sk
->sk_write_queue
);
1641 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_SYN
)) {
1642 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
1645 if (!(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_ACK
)) {
1646 if (skb_cloned(skb
)) {
1647 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
1650 __skb_unlink(skb
, &sk
->sk_write_queue
);
1651 skb_header_release(nskb
);
1652 __skb_queue_head(&sk
->sk_write_queue
, nskb
);
1653 sk_stream_free_skb(sk
, skb
);
1654 sk_charge_skb(sk
, nskb
);
1658 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
1659 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
1661 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1662 return tcp_transmit_skb(sk
, skb_clone(skb
, GFP_ATOMIC
));
1666 * Prepare a SYN-ACK.
1668 struct sk_buff
* tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
1669 struct request_sock
*req
)
1671 struct inet_request_sock
*ireq
= inet_rsk(req
);
1672 struct tcp_sock
*tp
= tcp_sk(sk
);
1674 int tcp_header_size
;
1675 struct sk_buff
*skb
;
1677 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
1681 /* Reserve space for headers. */
1682 skb_reserve(skb
, MAX_TCP_HEADER
);
1684 skb
->dst
= dst_clone(dst
);
1686 tcp_header_size
= (sizeof(struct tcphdr
) + TCPOLEN_MSS
+
1687 (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0) +
1688 (ireq
->wscale_ok
? TCPOLEN_WSCALE_ALIGNED
: 0) +
1689 /* SACK_PERM is in the place of NOP NOP of TS */
1690 ((ireq
->sack_ok
&& !ireq
->tstamp_ok
) ? TCPOLEN_SACKPERM_ALIGNED
: 0));
1691 skb
->h
.th
= th
= (struct tcphdr
*) skb_push(skb
, tcp_header_size
);
1693 memset(th
, 0, sizeof(struct tcphdr
));
1696 if (dst
->dev
->features
&NETIF_F_TSO
)
1698 TCP_ECN_make_synack(req
, th
);
1699 th
->source
= inet_sk(sk
)->sport
;
1700 th
->dest
= ireq
->rmt_port
;
1701 TCP_SKB_CB(skb
)->seq
= tcp_rsk(req
)->snt_isn
;
1702 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
1703 TCP_SKB_CB(skb
)->sacked
= 0;
1704 skb_shinfo(skb
)->tso_segs
= 1;
1705 skb_shinfo(skb
)->tso_size
= 0;
1706 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
1707 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
1708 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
1710 /* Set this up on the first call only */
1711 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
1712 /* tcp_full_space because it is guaranteed to be the first packet */
1713 tcp_select_initial_window(tcp_full_space(sk
),
1714 dst_metric(dst
, RTAX_ADVMSS
) - (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
1719 ireq
->rcv_wscale
= rcv_wscale
;
1722 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
1723 th
->window
= htons(req
->rcv_wnd
);
1725 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1726 tcp_syn_build_options((__u32
*)(th
+ 1), dst_metric(dst
, RTAX_ADVMSS
), ireq
->tstamp_ok
,
1727 ireq
->sack_ok
, ireq
->wscale_ok
, ireq
->rcv_wscale
,
1728 TCP_SKB_CB(skb
)->when
,
1732 th
->doff
= (tcp_header_size
>> 2);
1733 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
1738 * Do all connect socket setups that can be done AF independent.
1740 static inline void tcp_connect_init(struct sock
*sk
)
1742 struct dst_entry
*dst
= __sk_dst_get(sk
);
1743 struct tcp_sock
*tp
= tcp_sk(sk
);
1746 /* We'll fix this up when we get a response from the other end.
1747 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
1749 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
1750 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
1752 /* If user gave his TCP_MAXSEG, record it to clamp */
1753 if (tp
->rx_opt
.user_mss
)
1754 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
1756 tcp_sync_mss(sk
, dst_mtu(dst
));
1758 if (!tp
->window_clamp
)
1759 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
1760 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
1761 tcp_initialize_rcv_mss(sk
);
1763 tcp_select_initial_window(tcp_full_space(sk
),
1764 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
1767 sysctl_tcp_window_scaling
,
1770 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
1771 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
1774 sock_reset_flag(sk
, SOCK_DONE
);
1776 tcp_init_wl(tp
, tp
->write_seq
, 0);
1777 tp
->snd_una
= tp
->write_seq
;
1778 tp
->snd_sml
= tp
->write_seq
;
1783 tp
->rto
= TCP_TIMEOUT_INIT
;
1784 tp
->retransmits
= 0;
1785 tcp_clear_retrans(tp
);
1789 * Build a SYN and send it off.
1791 int tcp_connect(struct sock
*sk
)
1793 struct tcp_sock
*tp
= tcp_sk(sk
);
1794 struct sk_buff
*buff
;
1796 tcp_connect_init(sk
);
1798 buff
= alloc_skb(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
1799 if (unlikely(buff
== NULL
))
1802 /* Reserve space for headers. */
1803 skb_reserve(buff
, MAX_TCP_HEADER
);
1805 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_SYN
;
1806 TCP_ECN_send_syn(sk
, tp
, buff
);
1807 TCP_SKB_CB(buff
)->sacked
= 0;
1808 skb_shinfo(buff
)->tso_segs
= 1;
1809 skb_shinfo(buff
)->tso_size
= 0;
1811 TCP_SKB_CB(buff
)->seq
= tp
->write_seq
++;
1812 TCP_SKB_CB(buff
)->end_seq
= tp
->write_seq
;
1813 tp
->snd_nxt
= tp
->write_seq
;
1814 tp
->pushed_seq
= tp
->write_seq
;
1817 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
1818 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
1819 skb_header_release(buff
);
1820 __skb_queue_tail(&sk
->sk_write_queue
, buff
);
1821 sk_charge_skb(sk
, buff
);
1822 tp
->packets_out
+= tcp_skb_pcount(buff
);
1823 tcp_transmit_skb(sk
, skb_clone(buff
, GFP_KERNEL
));
1824 TCP_INC_STATS(TCP_MIB_ACTIVEOPENS
);
1826 /* Timer for repeating the SYN until an answer. */
1827 tcp_reset_xmit_timer(sk
, TCP_TIME_RETRANS
, tp
->rto
);
1831 /* Send out a delayed ack, the caller does the policy checking
1832 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
1835 void tcp_send_delayed_ack(struct sock
*sk
)
1837 struct tcp_sock
*tp
= tcp_sk(sk
);
1838 int ato
= tp
->ack
.ato
;
1839 unsigned long timeout
;
1841 if (ato
> TCP_DELACK_MIN
) {
1844 if (tp
->ack
.pingpong
|| (tp
->ack
.pending
&TCP_ACK_PUSHED
))
1845 max_ato
= TCP_DELACK_MAX
;
1847 /* Slow path, intersegment interval is "high". */
1849 /* If some rtt estimate is known, use it to bound delayed ack.
1850 * Do not use tp->rto here, use results of rtt measurements
1854 int rtt
= max(tp
->srtt
>>3, TCP_DELACK_MIN
);
1860 ato
= min(ato
, max_ato
);
1863 /* Stay within the limit we were given */
1864 timeout
= jiffies
+ ato
;
1866 /* Use new timeout only if there wasn't a older one earlier. */
1867 if (tp
->ack
.pending
&TCP_ACK_TIMER
) {
1868 /* If delack timer was blocked or is about to expire,
1871 if (tp
->ack
.blocked
|| time_before_eq(tp
->ack
.timeout
, jiffies
+(ato
>>2))) {
1876 if (!time_before(timeout
, tp
->ack
.timeout
))
1877 timeout
= tp
->ack
.timeout
;
1879 tp
->ack
.pending
|= TCP_ACK_SCHED
|TCP_ACK_TIMER
;
1880 tp
->ack
.timeout
= timeout
;
1881 sk_reset_timer(sk
, &tp
->delack_timer
, timeout
);
1884 /* This routine sends an ack and also updates the window. */
1885 void tcp_send_ack(struct sock
*sk
)
1887 /* If we have been reset, we may not send again. */
1888 if (sk
->sk_state
!= TCP_CLOSE
) {
1889 struct tcp_sock
*tp
= tcp_sk(sk
);
1890 struct sk_buff
*buff
;
1892 /* We are not putting this on the write queue, so
1893 * tcp_transmit_skb() will set the ownership to this
1896 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
1898 tcp_schedule_ack(tp
);
1899 tp
->ack
.ato
= TCP_ATO_MIN
;
1900 tcp_reset_xmit_timer(sk
, TCP_TIME_DACK
, TCP_DELACK_MAX
);
1904 /* Reserve space for headers and prepare control bits. */
1905 skb_reserve(buff
, MAX_TCP_HEADER
);
1907 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_ACK
;
1908 TCP_SKB_CB(buff
)->sacked
= 0;
1909 skb_shinfo(buff
)->tso_segs
= 1;
1910 skb_shinfo(buff
)->tso_size
= 0;
1912 /* Send it off, this clears delayed acks for us. */
1913 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(buff
)->end_seq
= tcp_acceptable_seq(sk
, tp
);
1914 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
1915 tcp_transmit_skb(sk
, buff
);
1919 /* This routine sends a packet with an out of date sequence
1920 * number. It assumes the other end will try to ack it.
1922 * Question: what should we make while urgent mode?
1923 * 4.4BSD forces sending single byte of data. We cannot send
1924 * out of window data, because we have SND.NXT==SND.MAX...
1926 * Current solution: to send TWO zero-length segments in urgent mode:
1927 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
1928 * out-of-date with SND.UNA-1 to probe window.
1930 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
1932 struct tcp_sock
*tp
= tcp_sk(sk
);
1933 struct sk_buff
*skb
;
1935 /* We don't queue it, tcp_transmit_skb() sets ownership. */
1936 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
1940 /* Reserve space for headers and set control bits. */
1941 skb_reserve(skb
, MAX_TCP_HEADER
);
1943 TCP_SKB_CB(skb
)->flags
= TCPCB_FLAG_ACK
;
1944 TCP_SKB_CB(skb
)->sacked
= urgent
;
1945 skb_shinfo(skb
)->tso_segs
= 1;
1946 skb_shinfo(skb
)->tso_size
= 0;
1948 /* Use a previous sequence. This should cause the other
1949 * end to send an ack. Don't queue or clone SKB, just
1952 TCP_SKB_CB(skb
)->seq
= urgent
? tp
->snd_una
: tp
->snd_una
- 1;
1953 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
1954 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1955 return tcp_transmit_skb(sk
, skb
);
1958 int tcp_write_wakeup(struct sock
*sk
)
1960 if (sk
->sk_state
!= TCP_CLOSE
) {
1961 struct tcp_sock
*tp
= tcp_sk(sk
);
1962 struct sk_buff
*skb
;
1964 if ((skb
= sk
->sk_send_head
) != NULL
&&
1965 before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)) {
1967 unsigned int mss
= tcp_current_mss(sk
, 0);
1968 unsigned int seg_size
= tp
->snd_una
+tp
->snd_wnd
-TCP_SKB_CB(skb
)->seq
;
1970 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
1971 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
1973 /* We are probing the opening of a window
1974 * but the window size is != 0
1975 * must have been a result SWS avoidance ( sender )
1977 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
1979 seg_size
= min(seg_size
, mss
);
1980 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
1981 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
1983 /* SWS override triggered forced fragmentation.
1984 * Disable TSO, the connection is too sick. */
1985 if (sk
->sk_route_caps
& NETIF_F_TSO
) {
1986 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
1987 sk
->sk_route_caps
&= ~NETIF_F_TSO
;
1989 } else if (!tcp_skb_pcount(skb
))
1990 tcp_set_skb_tso_segs(sk
, skb
, mss
);
1992 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
1993 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1994 err
= tcp_transmit_skb(sk
, skb_clone(skb
, GFP_ATOMIC
));
1996 update_send_head(sk
, tp
, skb
);
2001 between(tp
->snd_up
, tp
->snd_una
+1, tp
->snd_una
+0xFFFF))
2002 tcp_xmit_probe_skb(sk
, TCPCB_URG
);
2003 return tcp_xmit_probe_skb(sk
, 0);
2009 /* A window probe timeout has occurred. If window is not closed send
2010 * a partial packet else a zero probe.
2012 void tcp_send_probe0(struct sock
*sk
)
2014 struct tcp_sock
*tp
= tcp_sk(sk
);
2017 err
= tcp_write_wakeup(sk
);
2019 if (tp
->packets_out
|| !sk
->sk_send_head
) {
2020 /* Cancel probe timer, if it is not required. */
2027 if (tp
->backoff
< sysctl_tcp_retries2
)
2030 tcp_reset_xmit_timer (sk
, TCP_TIME_PROBE0
,
2031 min(tp
->rto
<< tp
->backoff
, TCP_RTO_MAX
));
2033 /* If packet was not sent due to local congestion,
2034 * do not backoff and do not remember probes_out.
2035 * Let local senders to fight for local resources.
2037 * Use accumulated backoff yet.
2039 if (!tp
->probes_out
)
2041 tcp_reset_xmit_timer (sk
, TCP_TIME_PROBE0
,
2042 min(tp
->rto
<< tp
->backoff
, TCP_RESOURCE_PROBE_INTERVAL
));
2046 EXPORT_SYMBOL(tcp_connect
);
2047 EXPORT_SYMBOL(tcp_make_synack
);
2048 EXPORT_SYMBOL(tcp_simple_retransmit
);
2049 EXPORT_SYMBOL(tcp_sync_mss
);