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 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 sock
*sk
, struct dst_entry
*dst
)
110 struct tcp_sock
*tp
= tcp_sk(sk
);
111 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
112 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
113 u32 cwnd
= tp
->snd_cwnd
;
115 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
117 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
118 restart_cwnd
= min(restart_cwnd
, cwnd
);
120 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
122 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
123 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
124 tp
->snd_cwnd_used
= 0;
127 static void tcp_event_data_sent(struct tcp_sock
*tp
,
128 struct sk_buff
*skb
, struct sock
*sk
)
130 struct inet_connection_sock
*icsk
= inet_csk(sk
);
131 const u32 now
= tcp_time_stamp
;
133 if (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
)
134 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
138 /* If it is a reply for ato after last received
139 * packet, enter pingpong mode.
141 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
142 icsk
->icsk_ack
.pingpong
= 1;
145 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
147 tcp_dec_quickack_mode(sk
, pkts
);
148 inet_csk_clear_xmit_timer(sk
, ICSK_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 RFC2414. 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 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. */
253 static void tcp_build_and_update_options(__u32
*ptr
, struct tcp_sock
*tp
,
256 if (tp
->rx_opt
.tstamp_ok
) {
257 *ptr
++ = __constant_htonl((TCPOPT_NOP
<< 24) |
259 (TCPOPT_TIMESTAMP
<< 8) |
261 *ptr
++ = htonl(tstamp
);
262 *ptr
++ = htonl(tp
->rx_opt
.ts_recent
);
264 if (tp
->rx_opt
.eff_sacks
) {
265 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
? tp
->duplicate_sack
: tp
->selective_acks
;
268 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
271 (TCPOLEN_SACK_BASE
+ (tp
->rx_opt
.eff_sacks
*
272 TCPOLEN_SACK_PERBLOCK
)));
273 for(this_sack
= 0; this_sack
< tp
->rx_opt
.eff_sacks
; this_sack
++) {
274 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
275 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
277 if (tp
->rx_opt
.dsack
) {
278 tp
->rx_opt
.dsack
= 0;
279 tp
->rx_opt
.eff_sacks
--;
284 /* Construct a tcp options header for a SYN or SYN_ACK packet.
285 * If this is every changed make sure to change the definition of
286 * MAX_SYN_SIZE to match the new maximum number of options that you
289 static void tcp_syn_build_options(__u32
*ptr
, int mss
, int ts
, int sack
,
290 int offer_wscale
, int wscale
, __u32 tstamp
,
293 /* We always get an MSS option.
294 * The option bytes which will be seen in normal data
295 * packets should timestamps be used, must be in the MSS
296 * advertised. But we subtract them from tp->mss_cache so
297 * that calculations in tcp_sendmsg are simpler etc.
298 * So account for this fact here if necessary. If we
299 * don't do this correctly, as a receiver we won't
300 * recognize data packets as being full sized when we
301 * should, and thus we won't abide by the delayed ACK
303 * SACKs don't matter, we never delay an ACK when we
304 * have any of those going out.
306 *ptr
++ = htonl((TCPOPT_MSS
<< 24) | (TCPOLEN_MSS
<< 16) | mss
);
309 *ptr
++ = __constant_htonl((TCPOPT_SACK_PERM
<< 24) | (TCPOLEN_SACK_PERM
<< 16) |
310 (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
);
312 *ptr
++ = __constant_htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
313 (TCPOPT_TIMESTAMP
<< 8) | TCPOLEN_TIMESTAMP
);
314 *ptr
++ = htonl(tstamp
); /* TSVAL */
315 *ptr
++ = htonl(ts_recent
); /* TSECR */
317 *ptr
++ = __constant_htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
318 (TCPOPT_SACK_PERM
<< 8) | TCPOLEN_SACK_PERM
);
320 *ptr
++ = htonl((TCPOPT_NOP
<< 24) | (TCPOPT_WINDOW
<< 16) | (TCPOLEN_WINDOW
<< 8) | (wscale
));
323 /* This routine actually transmits TCP packets queued in by
324 * tcp_do_sendmsg(). This is used by both the initial
325 * transmission and possible later retransmissions.
326 * All SKB's seen here are completely headerless. It is our
327 * job to build the TCP header, and pass the packet down to
328 * IP so it can do the same plus pass the packet off to the
331 * We are working here with either a clone of the original
332 * SKB, or a fresh unique copy made by the retransmit engine.
334 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
, gfp_t gfp_mask
)
336 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
337 struct inet_sock
*inet
;
339 struct tcp_skb_cb
*tcb
;
345 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
347 /* If congestion control is doing timestamping, we must
348 * take such a timestamp before we potentially clone/copy.
350 if (icsk
->icsk_ca_ops
->rtt_sample
)
351 __net_timestamp(skb
);
353 if (likely(clone_it
)) {
354 if (unlikely(skb_cloned(skb
)))
355 skb
= pskb_copy(skb
, gfp_mask
);
357 skb
= skb_clone(skb
, gfp_mask
);
364 tcb
= TCP_SKB_CB(skb
);
365 tcp_header_size
= tp
->tcp_header_len
;
367 #define SYSCTL_FLAG_TSTAMPS 0x1
368 #define SYSCTL_FLAG_WSCALE 0x2
369 #define SYSCTL_FLAG_SACK 0x4
372 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
373 tcp_header_size
= sizeof(struct tcphdr
) + TCPOLEN_MSS
;
374 if(sysctl_tcp_timestamps
) {
375 tcp_header_size
+= TCPOLEN_TSTAMP_ALIGNED
;
376 sysctl_flags
|= SYSCTL_FLAG_TSTAMPS
;
378 if (sysctl_tcp_window_scaling
) {
379 tcp_header_size
+= TCPOLEN_WSCALE_ALIGNED
;
380 sysctl_flags
|= SYSCTL_FLAG_WSCALE
;
382 if (sysctl_tcp_sack
) {
383 sysctl_flags
|= SYSCTL_FLAG_SACK
;
384 if (!(sysctl_flags
& SYSCTL_FLAG_TSTAMPS
))
385 tcp_header_size
+= TCPOLEN_SACKPERM_ALIGNED
;
387 } else if (unlikely(tp
->rx_opt
.eff_sacks
)) {
388 /* A SACK is 2 pad bytes, a 2 byte header, plus
389 * 2 32-bit sequence numbers for each SACK block.
391 tcp_header_size
+= (TCPOLEN_SACK_BASE_ALIGNED
+
392 (tp
->rx_opt
.eff_sacks
*
393 TCPOLEN_SACK_PERBLOCK
));
396 if (tcp_packets_in_flight(tp
) == 0)
397 tcp_ca_event(sk
, CA_EVENT_TX_START
);
399 th
= (struct tcphdr
*) skb_push(skb
, tcp_header_size
);
401 skb_set_owner_w(skb
, sk
);
403 /* Build TCP header and checksum it. */
404 th
->source
= inet
->sport
;
405 th
->dest
= inet
->dport
;
406 th
->seq
= htonl(tcb
->seq
);
407 th
->ack_seq
= htonl(tp
->rcv_nxt
);
408 *(((__u16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
411 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
412 /* RFC1323: The window in SYN & SYN/ACK segments
415 th
->window
= htons(tp
->rcv_wnd
);
417 th
->window
= htons(tcp_select_window(sk
));
422 if (unlikely(tp
->urg_mode
&&
423 between(tp
->snd_up
, tcb
->seq
+1, tcb
->seq
+0xFFFF))) {
424 th
->urg_ptr
= htons(tp
->snd_up
-tcb
->seq
);
428 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
429 tcp_syn_build_options((__u32
*)(th
+ 1),
430 tcp_advertise_mss(sk
),
431 (sysctl_flags
& SYSCTL_FLAG_TSTAMPS
),
432 (sysctl_flags
& SYSCTL_FLAG_SACK
),
433 (sysctl_flags
& SYSCTL_FLAG_WSCALE
),
434 tp
->rx_opt
.rcv_wscale
,
436 tp
->rx_opt
.ts_recent
);
438 tcp_build_and_update_options((__u32
*)(th
+ 1),
440 TCP_ECN_send(sk
, tp
, skb
, tcp_header_size
);
443 icsk
->icsk_af_ops
->send_check(sk
, skb
->len
, skb
);
445 if (likely(tcb
->flags
& TCPCB_FLAG_ACK
))
446 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
448 if (skb
->len
!= tcp_header_size
)
449 tcp_event_data_sent(tp
, skb
, sk
);
451 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
453 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, 0);
454 if (unlikely(err
<= 0))
459 /* NET_XMIT_CN is special. It does not guarantee,
460 * that this packet is lost. It tells that device
461 * is about to start to drop packets or already
462 * drops some packets of the same priority and
463 * invokes us to send less aggressively.
465 return err
== NET_XMIT_CN
? 0 : err
;
467 #undef SYSCTL_FLAG_TSTAMPS
468 #undef SYSCTL_FLAG_WSCALE
469 #undef SYSCTL_FLAG_SACK
473 /* This routine just queue's the buffer
475 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
476 * otherwise socket can stall.
478 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
480 struct tcp_sock
*tp
= tcp_sk(sk
);
482 /* Advance write_seq and place onto the write_queue. */
483 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
484 skb_header_release(skb
);
485 __skb_queue_tail(&sk
->sk_write_queue
, skb
);
486 sk_charge_skb(sk
, skb
);
488 /* Queue it, remembering where we must start sending. */
489 if (sk
->sk_send_head
== NULL
)
490 sk
->sk_send_head
= skb
;
493 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
495 if (skb
->len
<= mss_now
||
496 !(sk
->sk_route_caps
& NETIF_F_TSO
)) {
497 /* Avoid the costly divide in the normal
500 skb_shinfo(skb
)->tso_segs
= 1;
501 skb_shinfo(skb
)->tso_size
= 0;
505 factor
= skb
->len
+ (mss_now
- 1);
507 skb_shinfo(skb
)->tso_segs
= factor
;
508 skb_shinfo(skb
)->tso_size
= mss_now
;
512 /* Function to create two new TCP segments. Shrinks the given segment
513 * to the specified size and appends a new segment with the rest of the
514 * packet to the list. This won't be called frequently, I hope.
515 * Remember, these are still headerless SKBs at this point.
517 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
, unsigned int mss_now
)
519 struct tcp_sock
*tp
= tcp_sk(sk
);
520 struct sk_buff
*buff
;
521 int nsize
, old_factor
;
524 BUG_ON(len
> skb
->len
);
526 clear_all_retrans_hints(tp
);
527 nsize
= skb_headlen(skb
) - len
;
531 if (skb_cloned(skb
) &&
532 skb_is_nonlinear(skb
) &&
533 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
536 /* Get a new skb... force flag on. */
537 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
539 return -ENOMEM
; /* We'll just try again later. */
540 sk_charge_skb(sk
, buff
);
542 /* Correct the sequence numbers. */
543 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
544 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
545 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
547 /* PSH and FIN should only be set in the second packet. */
548 flags
= TCP_SKB_CB(skb
)->flags
;
549 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
550 TCP_SKB_CB(buff
)->flags
= flags
;
551 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
552 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_AT_TAIL
;
554 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_HW
) {
555 /* Copy and checksum data tail into the new buffer. */
556 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
, skb_put(buff
, nsize
),
561 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
563 skb
->ip_summed
= CHECKSUM_HW
;
564 skb_split(skb
, buff
, len
);
567 buff
->ip_summed
= skb
->ip_summed
;
569 /* Looks stupid, but our code really uses when of
570 * skbs, which it never sent before. --ANK
572 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
573 buff
->tstamp
= skb
->tstamp
;
575 old_factor
= tcp_skb_pcount(skb
);
577 /* Fix up tso_factor for both original and new SKB. */
578 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
579 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
581 /* If this packet has been sent out already, we must
582 * adjust the various packet counters.
584 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
585 int diff
= old_factor
- tcp_skb_pcount(skb
) -
586 tcp_skb_pcount(buff
);
588 tp
->packets_out
-= diff
;
590 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
591 tp
->sacked_out
-= diff
;
592 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
593 tp
->retrans_out
-= diff
;
595 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
) {
596 tp
->lost_out
-= diff
;
597 tp
->left_out
-= diff
;
601 /* Adjust Reno SACK estimate. */
602 if (!tp
->rx_opt
.sack_ok
) {
603 tp
->sacked_out
-= diff
;
604 if ((int)tp
->sacked_out
< 0)
606 tcp_sync_left_out(tp
);
609 tp
->fackets_out
-= diff
;
610 if ((int)tp
->fackets_out
< 0)
615 /* Link BUFF into the send queue. */
616 skb_header_release(buff
);
617 __skb_append(skb
, buff
, &sk
->sk_write_queue
);
622 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
623 * eventually). The difference is that pulled data not copied, but
624 * immediately discarded.
626 static unsigned char *__pskb_trim_head(struct sk_buff
*skb
, int len
)
632 for (i
=0; i
<skb_shinfo(skb
)->nr_frags
; i
++) {
633 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
634 put_page(skb_shinfo(skb
)->frags
[i
].page
);
635 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
637 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
639 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
640 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
646 skb_shinfo(skb
)->nr_frags
= k
;
648 skb
->tail
= skb
->data
;
649 skb
->data_len
-= len
;
650 skb
->len
= skb
->data_len
;
654 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
656 if (skb_cloned(skb
) &&
657 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
660 if (len
<= skb_headlen(skb
)) {
661 __skb_pull(skb
, len
);
663 if (__pskb_trim_head(skb
, len
-skb_headlen(skb
)) == NULL
)
667 TCP_SKB_CB(skb
)->seq
+= len
;
668 skb
->ip_summed
= CHECKSUM_HW
;
670 skb
->truesize
-= len
;
671 sk
->sk_wmem_queued
-= len
;
672 sk
->sk_forward_alloc
+= len
;
673 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
675 /* Any change of skb->len requires recalculation of tso
678 if (tcp_skb_pcount(skb
) > 1)
679 tcp_set_skb_tso_segs(sk
, skb
, tcp_current_mss(sk
, 1));
684 /* This function synchronize snd mss to current pmtu/exthdr set.
686 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
687 for TCP options, but includes only bare TCP header.
689 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
690 It is minimum of user_mss and mss received with SYN.
691 It also does not include TCP options.
693 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
695 tp->mss_cache is current effective sending mss, including
696 all tcp options except for SACKs. It is evaluated,
697 taking into account current pmtu, but never exceeds
698 tp->rx_opt.mss_clamp.
700 NOTE1. rfc1122 clearly states that advertised MSS
701 DOES NOT include either tcp or ip options.
703 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
704 are READ ONLY outside this function. --ANK (980731)
707 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
709 struct tcp_sock
*tp
= tcp_sk(sk
);
710 struct inet_connection_sock
*icsk
= inet_csk(sk
);
711 /* Calculate base mss without TCP options:
712 It is MMS_S - sizeof(tcphdr) of rfc1122
714 int mss_now
= (pmtu
- icsk
->icsk_af_ops
->net_header_len
-
715 sizeof(struct tcphdr
));
717 /* Clamp it (mss_clamp does not include tcp options) */
718 if (mss_now
> tp
->rx_opt
.mss_clamp
)
719 mss_now
= tp
->rx_opt
.mss_clamp
;
721 /* Now subtract optional transport overhead */
722 mss_now
-= icsk
->icsk_ext_hdr_len
;
724 /* Then reserve room for full set of TCP options and 8 bytes of data */
728 /* Now subtract TCP options size, not including SACKs */
729 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
731 /* Bound mss with half of window */
732 if (tp
->max_window
&& mss_now
> (tp
->max_window
>>1))
733 mss_now
= max((tp
->max_window
>>1), 68U - tp
->tcp_header_len
);
735 /* And store cached results */
736 icsk
->icsk_pmtu_cookie
= pmtu
;
737 tp
->mss_cache
= mss_now
;
742 /* Compute the current effective MSS, taking SACKs and IP options,
743 * and even PMTU discovery events into account.
745 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
746 * cannot be large. However, taking into account rare use of URG, this
749 unsigned int tcp_current_mss(struct sock
*sk
, int large_allowed
)
751 struct tcp_sock
*tp
= tcp_sk(sk
);
752 struct dst_entry
*dst
= __sk_dst_get(sk
);
757 mss_now
= tp
->mss_cache
;
760 (sk
->sk_route_caps
& NETIF_F_TSO
) &&
765 u32 mtu
= dst_mtu(dst
);
766 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
767 mss_now
= tcp_sync_mss(sk
, mtu
);
770 if (tp
->rx_opt
.eff_sacks
)
771 mss_now
-= (TCPOLEN_SACK_BASE_ALIGNED
+
772 (tp
->rx_opt
.eff_sacks
* TCPOLEN_SACK_PERBLOCK
));
774 xmit_size_goal
= mss_now
;
777 xmit_size_goal
= (65535 -
778 inet_csk(sk
)->icsk_af_ops
->net_header_len
-
779 inet_csk(sk
)->icsk_ext_hdr_len
-
782 if (tp
->max_window
&&
783 (xmit_size_goal
> (tp
->max_window
>> 1)))
784 xmit_size_goal
= max((tp
->max_window
>> 1),
785 68U - tp
->tcp_header_len
);
787 xmit_size_goal
-= (xmit_size_goal
% mss_now
);
789 tp
->xmit_size_goal
= xmit_size_goal
;
794 /* Congestion window validation. (RFC2861) */
796 static void tcp_cwnd_validate(struct sock
*sk
, struct tcp_sock
*tp
)
798 __u32 packets_out
= tp
->packets_out
;
800 if (packets_out
>= tp
->snd_cwnd
) {
801 /* Network is feed fully. */
802 tp
->snd_cwnd_used
= 0;
803 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
805 /* Network starves. */
806 if (tp
->packets_out
> tp
->snd_cwnd_used
)
807 tp
->snd_cwnd_used
= tp
->packets_out
;
809 if ((s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
810 tcp_cwnd_application_limited(sk
);
814 static unsigned int tcp_window_allows(struct tcp_sock
*tp
, struct sk_buff
*skb
, unsigned int mss_now
, unsigned int cwnd
)
816 u32 window
, cwnd_len
;
818 window
= (tp
->snd_una
+ tp
->snd_wnd
- TCP_SKB_CB(skb
)->seq
);
819 cwnd_len
= mss_now
* cwnd
;
820 return min(window
, cwnd_len
);
823 /* Can at least one segment of SKB be sent right now, according to the
824 * congestion window rules? If so, return how many segments are allowed.
826 static inline unsigned int tcp_cwnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
)
830 /* Don't be strict about the congestion window for the final FIN. */
831 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
834 in_flight
= tcp_packets_in_flight(tp
);
836 if (in_flight
< cwnd
)
837 return (cwnd
- in_flight
);
842 /* This must be invoked the first time we consider transmitting
845 static int tcp_init_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
847 int tso_segs
= tcp_skb_pcount(skb
);
851 skb_shinfo(skb
)->tso_size
!= mss_now
)) {
852 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
853 tso_segs
= tcp_skb_pcount(skb
);
858 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
860 return after(tp
->snd_sml
,tp
->snd_una
) &&
861 !after(tp
->snd_sml
, tp
->snd_nxt
);
864 /* Return 0, if packet can be sent now without violation Nagle's rules:
865 * 1. It is full sized.
866 * 2. Or it contains FIN. (already checked by caller)
867 * 3. Or TCP_NODELAY was set.
868 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
869 * With Minshall's modification: all sent small packets are ACKed.
872 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
873 const struct sk_buff
*skb
,
874 unsigned mss_now
, int nonagle
)
876 return (skb
->len
< mss_now
&&
877 ((nonagle
&TCP_NAGLE_CORK
) ||
880 tcp_minshall_check(tp
))));
883 /* Return non-zero if the Nagle test allows this packet to be
886 static inline int tcp_nagle_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
887 unsigned int cur_mss
, int nonagle
)
889 /* Nagle rule does not apply to frames, which sit in the middle of the
890 * write_queue (they have no chances to get new data).
892 * This is implemented in the callers, where they modify the 'nonagle'
893 * argument based upon the location of SKB in the send queue.
895 if (nonagle
& TCP_NAGLE_PUSH
)
898 /* Don't use the nagle rule for urgent data (or for the final FIN). */
900 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
))
903 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
909 /* Does at least the first segment of SKB fit into the send window? */
910 static inline int tcp_snd_wnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
, unsigned int cur_mss
)
912 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
914 if (skb
->len
> cur_mss
)
915 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
917 return !after(end_seq
, tp
->snd_una
+ tp
->snd_wnd
);
920 /* This checks if the data bearing packet SKB (usually sk->sk_send_head)
921 * should be put on the wire right now. If so, it returns the number of
922 * packets allowed by the congestion window.
924 static unsigned int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
925 unsigned int cur_mss
, int nonagle
)
927 struct tcp_sock
*tp
= tcp_sk(sk
);
928 unsigned int cwnd_quota
;
930 tcp_init_tso_segs(sk
, skb
, cur_mss
);
932 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
935 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
937 !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
943 static inline int tcp_skb_is_last(const struct sock
*sk
,
944 const struct sk_buff
*skb
)
946 return skb
->next
== (struct sk_buff
*)&sk
->sk_write_queue
;
949 int tcp_may_send_now(struct sock
*sk
, struct tcp_sock
*tp
)
951 struct sk_buff
*skb
= sk
->sk_send_head
;
954 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
, 1),
955 (tcp_skb_is_last(sk
, skb
) ?
960 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
961 * which is put after SKB on the list. It is very much like
962 * tcp_fragment() except that it may make several kinds of assumptions
963 * in order to speed up the splitting operation. In particular, we
964 * know that all the data is in scatter-gather pages, and that the
965 * packet has never been sent out before (and thus is not cloned).
967 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
, unsigned int mss_now
)
969 struct sk_buff
*buff
;
970 int nlen
= skb
->len
- len
;
973 /* All of a TSO frame must be composed of paged data. */
974 if (skb
->len
!= skb
->data_len
)
975 return tcp_fragment(sk
, skb
, len
, mss_now
);
977 buff
= sk_stream_alloc_pskb(sk
, 0, 0, GFP_ATOMIC
);
978 if (unlikely(buff
== NULL
))
981 buff
->truesize
= nlen
;
982 skb
->truesize
-= nlen
;
984 /* Correct the sequence numbers. */
985 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
986 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
987 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
989 /* PSH and FIN should only be set in the second packet. */
990 flags
= TCP_SKB_CB(skb
)->flags
;
991 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
992 TCP_SKB_CB(buff
)->flags
= flags
;
994 /* This packet was never sent out yet, so no SACK bits. */
995 TCP_SKB_CB(buff
)->sacked
= 0;
997 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_HW
;
998 skb_split(skb
, buff
, len
);
1000 /* Fix up tso_factor for both original and new SKB. */
1001 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1002 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1004 /* Link BUFF into the send queue. */
1005 skb_header_release(buff
);
1006 __skb_append(skb
, buff
, &sk
->sk_write_queue
);
1011 /* Try to defer sending, if possible, in order to minimize the amount
1012 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1014 * This algorithm is from John Heffner.
1016 static int tcp_tso_should_defer(struct sock
*sk
, struct tcp_sock
*tp
, struct sk_buff
*skb
)
1018 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1019 u32 send_win
, cong_win
, limit
, in_flight
;
1021 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
1024 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1027 in_flight
= tcp_packets_in_flight(tp
);
1029 BUG_ON(tcp_skb_pcount(skb
) <= 1 ||
1030 (tp
->snd_cwnd
<= in_flight
));
1032 send_win
= (tp
->snd_una
+ tp
->snd_wnd
) - TCP_SKB_CB(skb
)->seq
;
1034 /* From in_flight test above, we know that cwnd > in_flight. */
1035 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1037 limit
= min(send_win
, cong_win
);
1039 if (sysctl_tcp_tso_win_divisor
) {
1040 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1042 /* If at least some fraction of a window is available,
1045 chunk
/= sysctl_tcp_tso_win_divisor
;
1049 /* Different approach, try not to defer past a single
1050 * ACK. Receiver should ACK every other full sized
1051 * frame, so if we have space for more than 3 frames
1054 if (limit
> tcp_max_burst(tp
) * tp
->mss_cache
)
1058 /* Ok, it looks like it is advisable to defer. */
1062 /* This routine writes packets to the network. It advances the
1063 * send_head. This happens as incoming acks open up the remote
1066 * Returns 1, if no segments are in flight and we have queued segments, but
1067 * cannot send anything now because of SWS or another problem.
1069 static int tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
)
1071 struct tcp_sock
*tp
= tcp_sk(sk
);
1072 struct sk_buff
*skb
;
1073 unsigned int tso_segs
, sent_pkts
;
1076 /* If we are closed, the bytes will have to remain here.
1077 * In time closedown will finish, we empty the write queue and all
1080 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
1084 while ((skb
= sk
->sk_send_head
)) {
1087 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1090 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1094 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1097 if (tso_segs
== 1) {
1098 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1099 (tcp_skb_is_last(sk
, skb
) ?
1100 nonagle
: TCP_NAGLE_PUSH
))))
1103 if (tcp_tso_should_defer(sk
, tp
, skb
))
1109 limit
= tcp_window_allows(tp
, skb
,
1110 mss_now
, cwnd_quota
);
1112 if (skb
->len
< limit
) {
1113 unsigned int trim
= skb
->len
% mss_now
;
1116 limit
= skb
->len
- trim
;
1120 if (skb
->len
> limit
&&
1121 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1124 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1126 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
)))
1129 /* Advance the send_head. This one is sent out.
1130 * This call will increment packets_out.
1132 update_send_head(sk
, tp
, skb
);
1134 tcp_minshall_update(tp
, mss_now
, skb
);
1138 if (likely(sent_pkts
)) {
1139 tcp_cwnd_validate(sk
, tp
);
1142 return !tp
->packets_out
&& sk
->sk_send_head
;
1145 /* Push out any pending frames which were held back due to
1146 * TCP_CORK or attempt at coalescing tiny packets.
1147 * The socket must be locked by the caller.
1149 void __tcp_push_pending_frames(struct sock
*sk
, struct tcp_sock
*tp
,
1150 unsigned int cur_mss
, int nonagle
)
1152 struct sk_buff
*skb
= sk
->sk_send_head
;
1155 if (tcp_write_xmit(sk
, cur_mss
, nonagle
))
1156 tcp_check_probe_timer(sk
, tp
);
1160 /* Send _single_ skb sitting at the send head. This function requires
1161 * true push pending frames to setup probe timer etc.
1163 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
1165 struct tcp_sock
*tp
= tcp_sk(sk
);
1166 struct sk_buff
*skb
= sk
->sk_send_head
;
1167 unsigned int tso_segs
, cwnd_quota
;
1169 BUG_ON(!skb
|| skb
->len
< mss_now
);
1171 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1172 cwnd_quota
= tcp_snd_test(sk
, skb
, mss_now
, TCP_NAGLE_PUSH
);
1174 if (likely(cwnd_quota
)) {
1181 limit
= tcp_window_allows(tp
, skb
,
1182 mss_now
, cwnd_quota
);
1184 if (skb
->len
< limit
) {
1185 unsigned int trim
= skb
->len
% mss_now
;
1188 limit
= skb
->len
- trim
;
1192 if (skb
->len
> limit
&&
1193 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1196 /* Send it out now. */
1197 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1199 if (likely(!tcp_transmit_skb(sk
, skb
, 1, sk
->sk_allocation
))) {
1200 update_send_head(sk
, tp
, skb
);
1201 tcp_cwnd_validate(sk
, tp
);
1207 /* This function returns the amount that we can raise the
1208 * usable window based on the following constraints
1210 * 1. The window can never be shrunk once it is offered (RFC 793)
1211 * 2. We limit memory per socket
1214 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1215 * RECV.NEXT + RCV.WIN fixed until:
1216 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1218 * i.e. don't raise the right edge of the window until you can raise
1219 * it at least MSS bytes.
1221 * Unfortunately, the recommended algorithm breaks header prediction,
1222 * since header prediction assumes th->window stays fixed.
1224 * Strictly speaking, keeping th->window fixed violates the receiver
1225 * side SWS prevention criteria. The problem is that under this rule
1226 * a stream of single byte packets will cause the right side of the
1227 * window to always advance by a single byte.
1229 * Of course, if the sender implements sender side SWS prevention
1230 * then this will not be a problem.
1232 * BSD seems to make the following compromise:
1234 * If the free space is less than the 1/4 of the maximum
1235 * space available and the free space is less than 1/2 mss,
1236 * then set the window to 0.
1237 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1238 * Otherwise, just prevent the window from shrinking
1239 * and from being larger than the largest representable value.
1241 * This prevents incremental opening of the window in the regime
1242 * where TCP is limited by the speed of the reader side taking
1243 * data out of the TCP receive queue. It does nothing about
1244 * those cases where the window is constrained on the sender side
1245 * because the pipeline is full.
1247 * BSD also seems to "accidentally" limit itself to windows that are a
1248 * multiple of MSS, at least until the free space gets quite small.
1249 * This would appear to be a side effect of the mbuf implementation.
1250 * Combining these two algorithms results in the observed behavior
1251 * of having a fixed window size at almost all times.
1253 * Below we obtain similar behavior by forcing the offered window to
1254 * a multiple of the mss when it is feasible to do so.
1256 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1257 * Regular options like TIMESTAMP are taken into account.
1259 u32
__tcp_select_window(struct sock
*sk
)
1261 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1262 struct tcp_sock
*tp
= tcp_sk(sk
);
1263 /* MSS for the peer's data. Previous versions used mss_clamp
1264 * here. I don't know if the value based on our guesses
1265 * of peer's MSS is better for the performance. It's more correct
1266 * but may be worse for the performance because of rcv_mss
1267 * fluctuations. --SAW 1998/11/1
1269 int mss
= icsk
->icsk_ack
.rcv_mss
;
1270 int free_space
= tcp_space(sk
);
1271 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
1274 if (mss
> full_space
)
1277 if (free_space
< full_space
/2) {
1278 icsk
->icsk_ack
.quick
= 0;
1280 if (tcp_memory_pressure
)
1281 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U*tp
->advmss
);
1283 if (free_space
< mss
)
1287 if (free_space
> tp
->rcv_ssthresh
)
1288 free_space
= tp
->rcv_ssthresh
;
1290 /* Don't do rounding if we are using window scaling, since the
1291 * scaled window will not line up with the MSS boundary anyway.
1293 window
= tp
->rcv_wnd
;
1294 if (tp
->rx_opt
.rcv_wscale
) {
1295 window
= free_space
;
1297 /* Advertise enough space so that it won't get scaled away.
1298 * Import case: prevent zero window announcement if
1299 * 1<<rcv_wscale > mss.
1301 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1302 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1303 << tp
->rx_opt
.rcv_wscale
);
1305 /* Get the largest window that is a nice multiple of mss.
1306 * Window clamp already applied above.
1307 * If our current window offering is within 1 mss of the
1308 * free space we just keep it. This prevents the divide
1309 * and multiply from happening most of the time.
1310 * We also don't do any window rounding when the free space
1313 if (window
<= free_space
- mss
|| window
> free_space
)
1314 window
= (free_space
/mss
)*mss
;
1320 /* Attempt to collapse two adjacent SKB's during retransmission. */
1321 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*skb
, int mss_now
)
1323 struct tcp_sock
*tp
= tcp_sk(sk
);
1324 struct sk_buff
*next_skb
= skb
->next
;
1326 /* The first test we must make is that neither of these two
1327 * SKB's are still referenced by someone else.
1329 if (!skb_cloned(skb
) && !skb_cloned(next_skb
)) {
1330 int skb_size
= skb
->len
, next_skb_size
= next_skb
->len
;
1331 u16 flags
= TCP_SKB_CB(skb
)->flags
;
1333 /* Also punt if next skb has been SACK'd. */
1334 if(TCP_SKB_CB(next_skb
)->sacked
& TCPCB_SACKED_ACKED
)
1337 /* Next skb is out of window. */
1338 if (after(TCP_SKB_CB(next_skb
)->end_seq
, tp
->snd_una
+tp
->snd_wnd
))
1341 /* Punt if not enough space exists in the first SKB for
1342 * the data in the second, or the total combined payload
1343 * would exceed the MSS.
1345 if ((next_skb_size
> skb_tailroom(skb
)) ||
1346 ((skb_size
+ next_skb_size
) > mss_now
))
1349 BUG_ON(tcp_skb_pcount(skb
) != 1 ||
1350 tcp_skb_pcount(next_skb
) != 1);
1352 /* changing transmit queue under us so clear hints */
1353 clear_all_retrans_hints(tp
);
1355 /* Ok. We will be able to collapse the packet. */
1356 __skb_unlink(next_skb
, &sk
->sk_write_queue
);
1358 memcpy(skb_put(skb
, next_skb_size
), next_skb
->data
, next_skb_size
);
1360 if (next_skb
->ip_summed
== CHECKSUM_HW
)
1361 skb
->ip_summed
= CHECKSUM_HW
;
1363 if (skb
->ip_summed
!= CHECKSUM_HW
)
1364 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1366 /* Update sequence range on original skb. */
1367 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1369 /* Merge over control information. */
1370 flags
|= TCP_SKB_CB(next_skb
)->flags
; /* This moves PSH/FIN etc. over */
1371 TCP_SKB_CB(skb
)->flags
= flags
;
1373 /* All done, get rid of second SKB and account for it so
1374 * packet counting does not break.
1376 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
&(TCPCB_EVER_RETRANS
|TCPCB_AT_TAIL
);
1377 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_SACKED_RETRANS
)
1378 tp
->retrans_out
-= tcp_skb_pcount(next_skb
);
1379 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_LOST
) {
1380 tp
->lost_out
-= tcp_skb_pcount(next_skb
);
1381 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1383 /* Reno case is special. Sigh... */
1384 if (!tp
->rx_opt
.sack_ok
&& tp
->sacked_out
) {
1385 tcp_dec_pcount_approx(&tp
->sacked_out
, next_skb
);
1386 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1389 /* Not quite right: it can be > snd.fack, but
1390 * it is better to underestimate fackets.
1392 tcp_dec_pcount_approx(&tp
->fackets_out
, next_skb
);
1393 tcp_packets_out_dec(tp
, next_skb
);
1394 sk_stream_free_skb(sk
, next_skb
);
1398 /* Do a simple retransmit without using the backoff mechanisms in
1399 * tcp_timer. This is used for path mtu discovery.
1400 * The socket is already locked here.
1402 void tcp_simple_retransmit(struct sock
*sk
)
1404 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1405 struct tcp_sock
*tp
= tcp_sk(sk
);
1406 struct sk_buff
*skb
;
1407 unsigned int mss
= tcp_current_mss(sk
, 0);
1410 sk_stream_for_retrans_queue(skb
, sk
) {
1411 if (skb
->len
> mss
&&
1412 !(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1413 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1414 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1415 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1417 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_LOST
)) {
1418 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1419 tp
->lost_out
+= tcp_skb_pcount(skb
);
1425 clear_all_retrans_hints(tp
);
1430 tcp_sync_left_out(tp
);
1432 /* Don't muck with the congestion window here.
1433 * Reason is that we do not increase amount of _data_
1434 * in network, but units changed and effective
1435 * cwnd/ssthresh really reduced now.
1437 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
1438 tp
->high_seq
= tp
->snd_nxt
;
1439 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1440 tp
->prior_ssthresh
= 0;
1441 tp
->undo_marker
= 0;
1442 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1444 tcp_xmit_retransmit_queue(sk
);
1447 /* This retransmits one SKB. Policy decisions and retransmit queue
1448 * state updates are done by the caller. Returns non-zero if an
1449 * error occurred which prevented the send.
1451 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
1453 struct tcp_sock
*tp
= tcp_sk(sk
);
1454 unsigned int cur_mss
= tcp_current_mss(sk
, 0);
1457 /* Do not sent more than we queued. 1/4 is reserved for possible
1458 * copying overhead: fragmentation, tunneling, mangling etc.
1460 if (atomic_read(&sk
->sk_wmem_alloc
) >
1461 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
1464 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
1465 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1467 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
1471 /* If receiver has shrunk his window, and skb is out of
1472 * new window, do not retransmit it. The exception is the
1473 * case, when window is shrunk to zero. In this case
1474 * our retransmit serves as a zero window probe.
1476 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)
1477 && TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
1480 if (skb
->len
> cur_mss
) {
1481 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
1482 return -ENOMEM
; /* We'll try again later. */
1485 /* Collapse two adjacent packets if worthwhile and we can. */
1486 if(!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
) &&
1487 (skb
->len
< (cur_mss
>> 1)) &&
1488 (skb
->next
!= sk
->sk_send_head
) &&
1489 (skb
->next
!= (struct sk_buff
*)&sk
->sk_write_queue
) &&
1490 (skb_shinfo(skb
)->nr_frags
== 0 && skb_shinfo(skb
->next
)->nr_frags
== 0) &&
1491 (tcp_skb_pcount(skb
) == 1 && tcp_skb_pcount(skb
->next
) == 1) &&
1492 (sysctl_tcp_retrans_collapse
!= 0))
1493 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
1495 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
1496 return -EHOSTUNREACH
; /* Routing failure or similar. */
1498 /* Some Solaris stacks overoptimize and ignore the FIN on a
1499 * retransmit when old data is attached. So strip it off
1500 * since it is cheap to do so and saves bytes on the network.
1503 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1504 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
1505 if (!pskb_trim(skb
, 0)) {
1506 TCP_SKB_CB(skb
)->seq
= TCP_SKB_CB(skb
)->end_seq
- 1;
1507 skb_shinfo(skb
)->tso_segs
= 1;
1508 skb_shinfo(skb
)->tso_size
= 0;
1509 skb
->ip_summed
= CHECKSUM_NONE
;
1514 /* Make a copy, if the first transmission SKB clone we made
1515 * is still in somebody's hands, else make a clone.
1517 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1519 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
1522 /* Update global TCP statistics. */
1523 TCP_INC_STATS(TCP_MIB_RETRANSSEGS
);
1525 tp
->total_retrans
++;
1527 #if FASTRETRANS_DEBUG > 0
1528 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1529 if (net_ratelimit())
1530 printk(KERN_DEBUG
"retrans_out leaked.\n");
1533 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
1534 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1536 /* Save stamp of the first retransmit. */
1537 if (!tp
->retrans_stamp
)
1538 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
1542 /* snd_nxt is stored to detect loss of retransmitted segment,
1543 * see tcp_input.c tcp_sacktag_write_queue().
1545 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
1550 /* This gets called after a retransmit timeout, and the initially
1551 * retransmitted data is acknowledged. It tries to continue
1552 * resending the rest of the retransmit queue, until either
1553 * we've sent it all or the congestion window limit is reached.
1554 * If doing SACK, the first ACK which comes back for a timeout
1555 * based retransmit packet might feed us FACK information again.
1556 * If so, we use it to avoid unnecessarily retransmissions.
1558 void tcp_xmit_retransmit_queue(struct sock
*sk
)
1560 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1561 struct tcp_sock
*tp
= tcp_sk(sk
);
1562 struct sk_buff
*skb
;
1565 if (tp
->retransmit_skb_hint
) {
1566 skb
= tp
->retransmit_skb_hint
;
1567 packet_cnt
= tp
->retransmit_cnt_hint
;
1569 skb
= sk
->sk_write_queue
.next
;
1573 /* First pass: retransmit lost packets. */
1575 sk_stream_for_retrans_queue_from(skb
, sk
) {
1576 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1578 /* we could do better than to assign each time */
1579 tp
->retransmit_skb_hint
= skb
;
1580 tp
->retransmit_cnt_hint
= packet_cnt
;
1582 /* Assume this retransmit will generate
1583 * only one packet for congestion window
1584 * calculation purposes. This works because
1585 * tcp_retransmit_skb() will chop up the
1586 * packet to be MSS sized and all the
1587 * packet counting works out.
1589 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1592 if (sacked
& TCPCB_LOST
) {
1593 if (!(sacked
&(TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))) {
1594 if (tcp_retransmit_skb(sk
, skb
)) {
1595 tp
->retransmit_skb_hint
= NULL
;
1598 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
1599 NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS
);
1601 NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS
);
1604 skb_peek(&sk
->sk_write_queue
))
1605 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1606 inet_csk(sk
)->icsk_rto
,
1610 packet_cnt
+= tcp_skb_pcount(skb
);
1611 if (packet_cnt
>= tp
->lost_out
)
1617 /* OK, demanded retransmission is finished. */
1619 /* Forward retransmissions are possible only during Recovery. */
1620 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1623 /* No forward retransmissions in Reno are possible. */
1624 if (!tp
->rx_opt
.sack_ok
)
1627 /* Yeah, we have to make difficult choice between forward transmission
1628 * and retransmission... Both ways have their merits...
1630 * For now we do not retransmit anything, while we have some new
1634 if (tcp_may_send_now(sk
, tp
))
1637 if (tp
->forward_skb_hint
) {
1638 skb
= tp
->forward_skb_hint
;
1639 packet_cnt
= tp
->forward_cnt_hint
;
1641 skb
= sk
->sk_write_queue
.next
;
1645 sk_stream_for_retrans_queue_from(skb
, sk
) {
1646 tp
->forward_cnt_hint
= packet_cnt
;
1647 tp
->forward_skb_hint
= skb
;
1649 /* Similar to the retransmit loop above we
1650 * can pretend that the retransmitted SKB
1651 * we send out here will be composed of one
1652 * real MSS sized packet because tcp_retransmit_skb()
1653 * will fragment it if necessary.
1655 if (++packet_cnt
> tp
->fackets_out
)
1658 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1661 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
)
1664 /* Ok, retransmit it. */
1665 if (tcp_retransmit_skb(sk
, skb
)) {
1666 tp
->forward_skb_hint
= NULL
;
1670 if (skb
== skb_peek(&sk
->sk_write_queue
))
1671 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1672 inet_csk(sk
)->icsk_rto
,
1675 NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS
);
1680 /* Send a fin. The caller locks the socket for us. This cannot be
1681 * allowed to fail queueing a FIN frame under any circumstances.
1683 void tcp_send_fin(struct sock
*sk
)
1685 struct tcp_sock
*tp
= tcp_sk(sk
);
1686 struct sk_buff
*skb
= skb_peek_tail(&sk
->sk_write_queue
);
1689 /* Optimization, tack on the FIN if we have a queue of
1690 * unsent frames. But be careful about outgoing SACKS
1693 mss_now
= tcp_current_mss(sk
, 1);
1695 if (sk
->sk_send_head
!= NULL
) {
1696 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
1697 TCP_SKB_CB(skb
)->end_seq
++;
1700 /* Socket is locked, keep trying until memory is available. */
1702 skb
= alloc_skb_fclone(MAX_TCP_HEADER
, GFP_KERNEL
);
1708 /* Reserve space for headers and prepare control bits. */
1709 skb_reserve(skb
, MAX_TCP_HEADER
);
1711 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
1712 TCP_SKB_CB(skb
)->sacked
= 0;
1713 skb_shinfo(skb
)->tso_segs
= 1;
1714 skb_shinfo(skb
)->tso_size
= 0;
1716 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
1717 TCP_SKB_CB(skb
)->seq
= tp
->write_seq
;
1718 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
1719 tcp_queue_skb(sk
, skb
);
1721 __tcp_push_pending_frames(sk
, tp
, mss_now
, TCP_NAGLE_OFF
);
1724 /* We get here when a process closes a file descriptor (either due to
1725 * an explicit close() or as a byproduct of exit()'ing) and there
1726 * was unread data in the receive queue. This behavior is recommended
1727 * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM
1729 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
1731 struct tcp_sock
*tp
= tcp_sk(sk
);
1732 struct sk_buff
*skb
;
1734 /* NOTE: No TCP options attached and we never retransmit this. */
1735 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
1737 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
1741 /* Reserve space for headers and prepare control bits. */
1742 skb_reserve(skb
, MAX_TCP_HEADER
);
1744 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
1745 TCP_SKB_CB(skb
)->sacked
= 0;
1746 skb_shinfo(skb
)->tso_segs
= 1;
1747 skb_shinfo(skb
)->tso_size
= 0;
1750 TCP_SKB_CB(skb
)->seq
= tcp_acceptable_seq(sk
, tp
);
1751 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
1752 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1753 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
1754 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
1757 /* WARNING: This routine must only be called when we have already sent
1758 * a SYN packet that crossed the incoming SYN that caused this routine
1759 * to get called. If this assumption fails then the initial rcv_wnd
1760 * and rcv_wscale values will not be correct.
1762 int tcp_send_synack(struct sock
*sk
)
1764 struct sk_buff
* skb
;
1766 skb
= skb_peek(&sk
->sk_write_queue
);
1767 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_SYN
)) {
1768 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
1771 if (!(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_ACK
)) {
1772 if (skb_cloned(skb
)) {
1773 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
1776 __skb_unlink(skb
, &sk
->sk_write_queue
);
1777 skb_header_release(nskb
);
1778 __skb_queue_head(&sk
->sk_write_queue
, nskb
);
1779 sk_stream_free_skb(sk
, skb
);
1780 sk_charge_skb(sk
, nskb
);
1784 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
1785 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
1787 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1788 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
1792 * Prepare a SYN-ACK.
1794 struct sk_buff
* tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
1795 struct request_sock
*req
)
1797 struct inet_request_sock
*ireq
= inet_rsk(req
);
1798 struct tcp_sock
*tp
= tcp_sk(sk
);
1800 int tcp_header_size
;
1801 struct sk_buff
*skb
;
1803 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
1807 /* Reserve space for headers. */
1808 skb_reserve(skb
, MAX_TCP_HEADER
);
1810 skb
->dst
= dst_clone(dst
);
1812 tcp_header_size
= (sizeof(struct tcphdr
) + TCPOLEN_MSS
+
1813 (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0) +
1814 (ireq
->wscale_ok
? TCPOLEN_WSCALE_ALIGNED
: 0) +
1815 /* SACK_PERM is in the place of NOP NOP of TS */
1816 ((ireq
->sack_ok
&& !ireq
->tstamp_ok
) ? TCPOLEN_SACKPERM_ALIGNED
: 0));
1817 skb
->h
.th
= th
= (struct tcphdr
*) skb_push(skb
, tcp_header_size
);
1819 memset(th
, 0, sizeof(struct tcphdr
));
1822 if (dst
->dev
->features
&NETIF_F_TSO
)
1824 TCP_ECN_make_synack(req
, th
);
1825 th
->source
= inet_sk(sk
)->sport
;
1826 th
->dest
= ireq
->rmt_port
;
1827 TCP_SKB_CB(skb
)->seq
= tcp_rsk(req
)->snt_isn
;
1828 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
1829 TCP_SKB_CB(skb
)->sacked
= 0;
1830 skb_shinfo(skb
)->tso_segs
= 1;
1831 skb_shinfo(skb
)->tso_size
= 0;
1832 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
1833 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
1834 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
1836 /* Set this up on the first call only */
1837 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
1838 /* tcp_full_space because it is guaranteed to be the first packet */
1839 tcp_select_initial_window(tcp_full_space(sk
),
1840 dst_metric(dst
, RTAX_ADVMSS
) - (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
1845 ireq
->rcv_wscale
= rcv_wscale
;
1848 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
1849 th
->window
= htons(req
->rcv_wnd
);
1851 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1852 tcp_syn_build_options((__u32
*)(th
+ 1), dst_metric(dst
, RTAX_ADVMSS
), ireq
->tstamp_ok
,
1853 ireq
->sack_ok
, ireq
->wscale_ok
, ireq
->rcv_wscale
,
1854 TCP_SKB_CB(skb
)->when
,
1858 th
->doff
= (tcp_header_size
>> 2);
1859 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
1864 * Do all connect socket setups that can be done AF independent.
1866 static void tcp_connect_init(struct sock
*sk
)
1868 struct dst_entry
*dst
= __sk_dst_get(sk
);
1869 struct tcp_sock
*tp
= tcp_sk(sk
);
1872 /* We'll fix this up when we get a response from the other end.
1873 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
1875 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
1876 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
1878 /* If user gave his TCP_MAXSEG, record it to clamp */
1879 if (tp
->rx_opt
.user_mss
)
1880 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
1882 tcp_sync_mss(sk
, dst_mtu(dst
));
1884 if (!tp
->window_clamp
)
1885 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
1886 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
1887 tcp_initialize_rcv_mss(sk
);
1889 tcp_select_initial_window(tcp_full_space(sk
),
1890 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
1893 sysctl_tcp_window_scaling
,
1896 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
1897 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
1900 sock_reset_flag(sk
, SOCK_DONE
);
1902 tcp_init_wl(tp
, tp
->write_seq
, 0);
1903 tp
->snd_una
= tp
->write_seq
;
1904 tp
->snd_sml
= tp
->write_seq
;
1909 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
1910 inet_csk(sk
)->icsk_retransmits
= 0;
1911 tcp_clear_retrans(tp
);
1915 * Build a SYN and send it off.
1917 int tcp_connect(struct sock
*sk
)
1919 struct tcp_sock
*tp
= tcp_sk(sk
);
1920 struct sk_buff
*buff
;
1922 tcp_connect_init(sk
);
1924 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
1925 if (unlikely(buff
== NULL
))
1928 /* Reserve space for headers. */
1929 skb_reserve(buff
, MAX_TCP_HEADER
);
1931 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_SYN
;
1932 TCP_ECN_send_syn(sk
, tp
, buff
);
1933 TCP_SKB_CB(buff
)->sacked
= 0;
1934 skb_shinfo(buff
)->tso_segs
= 1;
1935 skb_shinfo(buff
)->tso_size
= 0;
1937 TCP_SKB_CB(buff
)->seq
= tp
->write_seq
++;
1938 TCP_SKB_CB(buff
)->end_seq
= tp
->write_seq
;
1939 tp
->snd_nxt
= tp
->write_seq
;
1940 tp
->pushed_seq
= tp
->write_seq
;
1943 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
1944 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
1945 skb_header_release(buff
);
1946 __skb_queue_tail(&sk
->sk_write_queue
, buff
);
1947 sk_charge_skb(sk
, buff
);
1948 tp
->packets_out
+= tcp_skb_pcount(buff
);
1949 tcp_transmit_skb(sk
, buff
, 1, GFP_KERNEL
);
1950 TCP_INC_STATS(TCP_MIB_ACTIVEOPENS
);
1952 /* Timer for repeating the SYN until an answer. */
1953 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1954 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
1958 /* Send out a delayed ack, the caller does the policy checking
1959 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
1962 void tcp_send_delayed_ack(struct sock
*sk
)
1964 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1965 int ato
= icsk
->icsk_ack
.ato
;
1966 unsigned long timeout
;
1968 if (ato
> TCP_DELACK_MIN
) {
1969 const struct tcp_sock
*tp
= tcp_sk(sk
);
1972 if (icsk
->icsk_ack
.pingpong
|| (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
1973 max_ato
= TCP_DELACK_MAX
;
1975 /* Slow path, intersegment interval is "high". */
1977 /* If some rtt estimate is known, use it to bound delayed ack.
1978 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
1982 int rtt
= max(tp
->srtt
>>3, TCP_DELACK_MIN
);
1988 ato
= min(ato
, max_ato
);
1991 /* Stay within the limit we were given */
1992 timeout
= jiffies
+ ato
;
1994 /* Use new timeout only if there wasn't a older one earlier. */
1995 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
1996 /* If delack timer was blocked or is about to expire,
1999 if (icsk
->icsk_ack
.blocked
||
2000 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
2005 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
2006 timeout
= icsk
->icsk_ack
.timeout
;
2008 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
2009 icsk
->icsk_ack
.timeout
= timeout
;
2010 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
2013 /* This routine sends an ack and also updates the window. */
2014 void tcp_send_ack(struct sock
*sk
)
2016 /* If we have been reset, we may not send again. */
2017 if (sk
->sk_state
!= TCP_CLOSE
) {
2018 struct tcp_sock
*tp
= tcp_sk(sk
);
2019 struct sk_buff
*buff
;
2021 /* We are not putting this on the write queue, so
2022 * tcp_transmit_skb() will set the ownership to this
2025 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2027 inet_csk_schedule_ack(sk
);
2028 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
2029 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
2030 TCP_DELACK_MAX
, TCP_RTO_MAX
);
2034 /* Reserve space for headers and prepare control bits. */
2035 skb_reserve(buff
, MAX_TCP_HEADER
);
2037 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_ACK
;
2038 TCP_SKB_CB(buff
)->sacked
= 0;
2039 skb_shinfo(buff
)->tso_segs
= 1;
2040 skb_shinfo(buff
)->tso_size
= 0;
2042 /* Send it off, this clears delayed acks for us. */
2043 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(buff
)->end_seq
= tcp_acceptable_seq(sk
, tp
);
2044 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2045 tcp_transmit_skb(sk
, buff
, 0, GFP_ATOMIC
);
2049 /* This routine sends a packet with an out of date sequence
2050 * number. It assumes the other end will try to ack it.
2052 * Question: what should we make while urgent mode?
2053 * 4.4BSD forces sending single byte of data. We cannot send
2054 * out of window data, because we have SND.NXT==SND.MAX...
2056 * Current solution: to send TWO zero-length segments in urgent mode:
2057 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2058 * out-of-date with SND.UNA-1 to probe window.
2060 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
2062 struct tcp_sock
*tp
= tcp_sk(sk
);
2063 struct sk_buff
*skb
;
2065 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2066 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2070 /* Reserve space for headers and set control bits. */
2071 skb_reserve(skb
, MAX_TCP_HEADER
);
2073 TCP_SKB_CB(skb
)->flags
= TCPCB_FLAG_ACK
;
2074 TCP_SKB_CB(skb
)->sacked
= urgent
;
2075 skb_shinfo(skb
)->tso_segs
= 1;
2076 skb_shinfo(skb
)->tso_size
= 0;
2078 /* Use a previous sequence. This should cause the other
2079 * end to send an ack. Don't queue or clone SKB, just
2082 TCP_SKB_CB(skb
)->seq
= urgent
? tp
->snd_una
: tp
->snd_una
- 1;
2083 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
2084 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2085 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
2088 int tcp_write_wakeup(struct sock
*sk
)
2090 if (sk
->sk_state
!= TCP_CLOSE
) {
2091 struct tcp_sock
*tp
= tcp_sk(sk
);
2092 struct sk_buff
*skb
;
2094 if ((skb
= sk
->sk_send_head
) != NULL
&&
2095 before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)) {
2097 unsigned int mss
= tcp_current_mss(sk
, 0);
2098 unsigned int seg_size
= tp
->snd_una
+tp
->snd_wnd
-TCP_SKB_CB(skb
)->seq
;
2100 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
2101 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
2103 /* We are probing the opening of a window
2104 * but the window size is != 0
2105 * must have been a result SWS avoidance ( sender )
2107 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
2109 seg_size
= min(seg_size
, mss
);
2110 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2111 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
2113 } else if (!tcp_skb_pcount(skb
))
2114 tcp_set_skb_tso_segs(sk
, skb
, mss
);
2116 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2117 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2118 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2120 update_send_head(sk
, tp
, skb
);
2125 between(tp
->snd_up
, tp
->snd_una
+1, tp
->snd_una
+0xFFFF))
2126 tcp_xmit_probe_skb(sk
, TCPCB_URG
);
2127 return tcp_xmit_probe_skb(sk
, 0);
2133 /* A window probe timeout has occurred. If window is not closed send
2134 * a partial packet else a zero probe.
2136 void tcp_send_probe0(struct sock
*sk
)
2138 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2139 struct tcp_sock
*tp
= tcp_sk(sk
);
2142 err
= tcp_write_wakeup(sk
);
2144 if (tp
->packets_out
|| !sk
->sk_send_head
) {
2145 /* Cancel probe timer, if it is not required. */
2146 icsk
->icsk_probes_out
= 0;
2147 icsk
->icsk_backoff
= 0;
2152 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
2153 icsk
->icsk_backoff
++;
2154 icsk
->icsk_probes_out
++;
2155 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2156 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2159 /* If packet was not sent due to local congestion,
2160 * do not backoff and do not remember icsk_probes_out.
2161 * Let local senders to fight for local resources.
2163 * Use accumulated backoff yet.
2165 if (!icsk
->icsk_probes_out
)
2166 icsk
->icsk_probes_out
= 1;
2167 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2168 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
2169 TCP_RESOURCE_PROBE_INTERVAL
),
2174 EXPORT_SYMBOL(tcp_connect
);
2175 EXPORT_SYMBOL(tcp_make_synack
);
2176 EXPORT_SYMBOL(tcp_simple_retransmit
);
2177 EXPORT_SYMBOL(tcp_sync_mss
);
2178 EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor
);