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
= 8;
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 inline void tcp_tso_set_push(struct sk_buff
*skb
)
408 /* Force push to be on for any TSO frames to workaround
409 * problems with busted implementations like Mac OS-X that
410 * hold off socket receive wakeups until push is seen.
412 if (tcp_skb_pcount(skb
) > 1)
413 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
416 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
)
418 struct tcp_sock
*tp
= tcp_sk(sk
);
420 if (skb
->len
<= tp
->mss_cache_std
||
421 !(sk
->sk_route_caps
& NETIF_F_TSO
)) {
422 /* Avoid the costly divide in the normal
425 skb_shinfo(skb
)->tso_segs
= 1;
426 skb_shinfo(skb
)->tso_size
= 0;
430 factor
= skb
->len
+ (tp
->mss_cache_std
- 1);
431 factor
/= tp
->mss_cache_std
;
432 skb_shinfo(skb
)->tso_segs
= factor
;
433 skb_shinfo(skb
)->tso_size
= tp
->mss_cache_std
;
437 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
439 return after(tp
->snd_sml
,tp
->snd_una
) &&
440 !after(tp
->snd_sml
, tp
->snd_nxt
);
443 /* Return 0, if packet can be sent now without violation Nagle's rules:
444 * 1. It is full sized.
445 * 2. Or it contains FIN.
446 * 3. Or TCP_NODELAY was set.
447 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
448 * With Minshall's modification: all sent small packets are ACKed.
451 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
452 const struct sk_buff
*skb
,
453 unsigned mss_now
, int nonagle
)
455 return (skb
->len
< mss_now
&&
456 !(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
457 ((nonagle
&TCP_NAGLE_CORK
) ||
460 tcp_minshall_check(tp
))));
463 /* This checks if the data bearing packet SKB (usually sk->sk_send_head)
464 * should be put on the wire right now.
466 static int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
467 unsigned cur_mss
, int nonagle
)
469 struct tcp_sock
*tp
= tcp_sk(sk
);
470 int pkts
= tcp_skb_pcount(skb
);
473 tcp_set_skb_tso_segs(sk
, skb
);
474 pkts
= tcp_skb_pcount(skb
);
477 /* RFC 1122 - section 4.2.3.4
481 * a) The right edge of this frame exceeds the window
482 * b) There are packets in flight and we have a small segment
483 * [SWS avoidance and Nagle algorithm]
484 * (part of SWS is done on packetization)
485 * Minshall version sounds: there are no _small_
486 * segments in flight. (tcp_nagle_check)
487 * c) We have too many packets 'in flight'
489 * Don't use the nagle rule for urgent data (or
490 * for the final FIN -DaveM).
492 * Also, Nagle rule does not apply to frames, which
493 * sit in the middle of queue (they have no chances
494 * to get new data) and if room at tail of skb is
495 * not enough to save something seriously (<32 for now).
498 /* Don't be strict about the congestion window for the
499 * final FIN frame. -DaveM
501 return (((nonagle
&TCP_NAGLE_PUSH
) || tp
->urg_mode
502 || !tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
)) &&
503 (((tcp_packets_in_flight(tp
) + (pkts
-1)) < tp
->snd_cwnd
) ||
504 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)) &&
505 !after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
+ tp
->snd_wnd
));
508 static inline int tcp_skb_is_last(const struct sock
*sk
,
509 const struct sk_buff
*skb
)
511 return skb
->next
== (struct sk_buff
*)&sk
->sk_write_queue
;
514 int tcp_may_send_now(struct sock
*sk
, struct tcp_sock
*tp
)
516 struct sk_buff
*skb
= sk
->sk_send_head
;
519 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
, 1),
520 (tcp_skb_is_last(sk
, skb
) ?
526 /* Send _single_ skb sitting at the send head. This function requires
527 * true push pending frames to setup probe timer etc.
529 void tcp_push_one(struct sock
*sk
, unsigned cur_mss
)
531 struct tcp_sock
*tp
= tcp_sk(sk
);
532 struct sk_buff
*skb
= sk
->sk_send_head
;
534 if (tcp_snd_test(sk
, skb
, cur_mss
, TCP_NAGLE_PUSH
)) {
535 /* Send it out now. */
536 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
537 tcp_tso_set_push(skb
);
538 if (!tcp_transmit_skb(sk
, skb_clone(skb
, sk
->sk_allocation
))) {
539 sk
->sk_send_head
= NULL
;
540 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
541 tcp_packets_out_inc(sk
, tp
, skb
);
547 /* Function to create two new TCP segments. Shrinks the given segment
548 * to the specified size and appends a new segment with the rest of the
549 * packet to the list. This won't be called frequently, I hope.
550 * Remember, these are still headerless SKBs at this point.
552 static int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
554 struct tcp_sock
*tp
= tcp_sk(sk
);
555 struct sk_buff
*buff
;
559 nsize
= skb_headlen(skb
) - len
;
563 if (skb_cloned(skb
) &&
564 skb_is_nonlinear(skb
) &&
565 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
568 /* Get a new skb... force flag on. */
569 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
571 return -ENOMEM
; /* We'll just try again later. */
572 sk_charge_skb(sk
, buff
);
574 /* Correct the sequence numbers. */
575 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
576 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
577 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
579 /* PSH and FIN should only be set in the second packet. */
580 flags
= TCP_SKB_CB(skb
)->flags
;
581 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
582 TCP_SKB_CB(buff
)->flags
= flags
;
583 TCP_SKB_CB(buff
)->sacked
=
584 (TCP_SKB_CB(skb
)->sacked
&
585 (TCPCB_LOST
| TCPCB_EVER_RETRANS
| TCPCB_AT_TAIL
));
586 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_AT_TAIL
;
588 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_HW
) {
589 /* Copy and checksum data tail into the new buffer. */
590 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
, skb_put(buff
, nsize
),
595 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
597 skb
->ip_summed
= CHECKSUM_HW
;
598 skb_split(skb
, buff
, len
);
601 buff
->ip_summed
= skb
->ip_summed
;
603 /* Looks stupid, but our code really uses when of
604 * skbs, which it never sent before. --ANK
606 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
607 buff
->stamp
= skb
->stamp
;
609 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
) {
610 tp
->lost_out
-= tcp_skb_pcount(skb
);
611 tp
->left_out
-= tcp_skb_pcount(skb
);
614 /* Fix up tso_factor for both original and new SKB. */
615 tcp_set_skb_tso_segs(sk
, skb
);
616 tcp_set_skb_tso_segs(sk
, buff
);
618 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
) {
619 tp
->lost_out
+= tcp_skb_pcount(skb
);
620 tp
->left_out
+= tcp_skb_pcount(skb
);
623 if (TCP_SKB_CB(buff
)->sacked
&TCPCB_LOST
) {
624 tp
->lost_out
+= tcp_skb_pcount(buff
);
625 tp
->left_out
+= tcp_skb_pcount(buff
);
628 /* Link BUFF into the send queue. */
629 skb_header_release(buff
);
630 __skb_append(skb
, buff
);
635 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
636 * eventually). The difference is that pulled data not copied, but
637 * immediately discarded.
639 static unsigned char *__pskb_trim_head(struct sk_buff
*skb
, int len
)
645 for (i
=0; i
<skb_shinfo(skb
)->nr_frags
; i
++) {
646 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
647 put_page(skb_shinfo(skb
)->frags
[i
].page
);
648 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
650 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
652 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
653 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
659 skb_shinfo(skb
)->nr_frags
= k
;
661 skb
->tail
= skb
->data
;
662 skb
->data_len
-= len
;
663 skb
->len
= skb
->data_len
;
667 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
669 if (skb_cloned(skb
) &&
670 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
673 if (len
<= skb_headlen(skb
)) {
674 __skb_pull(skb
, len
);
676 if (__pskb_trim_head(skb
, len
-skb_headlen(skb
)) == NULL
)
680 TCP_SKB_CB(skb
)->seq
+= len
;
681 skb
->ip_summed
= CHECKSUM_HW
;
683 skb
->truesize
-= len
;
684 sk
->sk_wmem_queued
-= len
;
685 sk
->sk_forward_alloc
+= len
;
686 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
688 /* Any change of skb->len requires recalculation of tso
691 if (tcp_skb_pcount(skb
) > 1)
692 tcp_set_skb_tso_segs(sk
, skb
);
697 /* This function synchronize snd mss to current pmtu/exthdr set.
699 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
700 for TCP options, but includes only bare TCP header.
702 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
703 It is minumum of user_mss and mss received with SYN.
704 It also does not include TCP options.
706 tp->pmtu_cookie is last pmtu, seen by this function.
708 tp->mss_cache is current effective sending mss, including
709 all tcp options except for SACKs. It is evaluated,
710 taking into account current pmtu, but never exceeds
711 tp->rx_opt.mss_clamp.
713 NOTE1. rfc1122 clearly states that advertised MSS
714 DOES NOT include either tcp or ip options.
716 NOTE2. tp->pmtu_cookie and tp->mss_cache are READ ONLY outside
717 this function. --ANK (980731)
720 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
722 struct tcp_sock
*tp
= tcp_sk(sk
);
725 /* Calculate base mss without TCP options:
726 It is MMS_S - sizeof(tcphdr) of rfc1122
728 mss_now
= pmtu
- tp
->af_specific
->net_header_len
- sizeof(struct tcphdr
);
730 /* Clamp it (mss_clamp does not include tcp options) */
731 if (mss_now
> tp
->rx_opt
.mss_clamp
)
732 mss_now
= tp
->rx_opt
.mss_clamp
;
734 /* Now subtract optional transport overhead */
735 mss_now
-= tp
->ext_header_len
;
737 /* Then reserve room for full set of TCP options and 8 bytes of data */
741 /* Now subtract TCP options size, not including SACKs */
742 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
744 /* Bound mss with half of window */
745 if (tp
->max_window
&& mss_now
> (tp
->max_window
>>1))
746 mss_now
= max((tp
->max_window
>>1), 68U - tp
->tcp_header_len
);
748 /* And store cached results */
749 tp
->pmtu_cookie
= pmtu
;
750 tp
->mss_cache
= tp
->mss_cache_std
= mss_now
;
755 /* Compute the current effective MSS, taking SACKs and IP options,
756 * and even PMTU discovery events into account.
758 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
759 * cannot be large. However, taking into account rare use of URG, this
763 unsigned int tcp_current_mss(struct sock
*sk
, int large
)
765 struct tcp_sock
*tp
= tcp_sk(sk
);
766 struct dst_entry
*dst
= __sk_dst_get(sk
);
767 unsigned int do_large
, mss_now
;
769 mss_now
= tp
->mss_cache_std
;
771 u32 mtu
= dst_mtu(dst
);
772 if (mtu
!= tp
->pmtu_cookie
)
773 mss_now
= tcp_sync_mss(sk
, mtu
);
777 (sk
->sk_route_caps
& NETIF_F_TSO
) &&
781 unsigned int large_mss
, factor
, limit
;
783 large_mss
= 65535 - tp
->af_specific
->net_header_len
-
784 tp
->ext_header_len
- tp
->tcp_header_len
;
786 if (tp
->max_window
&& large_mss
> (tp
->max_window
>>1))
787 large_mss
= max((tp
->max_window
>>1),
788 68U - tp
->tcp_header_len
);
790 factor
= large_mss
/ mss_now
;
792 /* Always keep large mss multiple of real mss, but
793 * do not exceed 1/tso_win_divisor of the congestion window
794 * so we can keep the ACK clock ticking and minimize
797 limit
= tp
->snd_cwnd
;
798 if (sysctl_tcp_tso_win_divisor
)
799 limit
/= sysctl_tcp_tso_win_divisor
;
800 limit
= max(1U, limit
);
804 tp
->mss_cache
= mss_now
* factor
;
806 mss_now
= tp
->mss_cache
;
809 if (tp
->rx_opt
.eff_sacks
)
810 mss_now
-= (TCPOLEN_SACK_BASE_ALIGNED
+
811 (tp
->rx_opt
.eff_sacks
* TCPOLEN_SACK_PERBLOCK
));
815 /* Congestion window validation. (RFC2861) */
817 static inline void tcp_cwnd_validate(struct sock
*sk
, struct tcp_sock
*tp
)
819 __u32 packets_out
= tp
->packets_out
;
821 if (packets_out
>= tp
->snd_cwnd
) {
822 /* Network is feed fully. */
823 tp
->snd_cwnd_used
= 0;
824 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
826 /* Network starves. */
827 if (tp
->packets_out
> tp
->snd_cwnd_used
)
828 tp
->snd_cwnd_used
= tp
->packets_out
;
830 if ((s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= tp
->rto
)
831 tcp_cwnd_application_limited(sk
);
835 /* This routine writes packets to the network. It advances the
836 * send_head. This happens as incoming acks open up the remote
839 * Returns 1, if no segments are in flight and we have queued segments, but
840 * cannot send anything now because of SWS or another problem.
842 static int tcp_write_xmit(struct sock
*sk
, int nonagle
)
844 struct tcp_sock
*tp
= tcp_sk(sk
);
846 unsigned int mss_now
;
849 /* If we are closed, the bytes will have to remain here.
850 * In time closedown will finish, we empty the write queue and all
853 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
857 /* Account for SACKS, we may need to fragment due to this.
858 * It is just like the real MSS changing on us midstream.
859 * We also handle things correctly when the user adds some
860 * IP options mid-stream. Silly to do, but cover it.
862 mss_now
= tcp_current_mss(sk
, 1);
864 while ((skb
= sk
->sk_send_head
) &&
865 tcp_snd_test(sk
, skb
, mss_now
,
866 tcp_skb_is_last(sk
, skb
) ? nonagle
:
868 if (skb
->len
> mss_now
) {
869 if (tcp_fragment(sk
, skb
, mss_now
))
873 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
874 tcp_tso_set_push(skb
);
875 if (tcp_transmit_skb(sk
, skb_clone(skb
, GFP_ATOMIC
)))
878 /* Advance the send_head. This one is sent out.
879 * This call will increment packets_out.
881 update_send_head(sk
, tp
, skb
);
883 tcp_minshall_update(tp
, mss_now
, skb
);
888 tcp_cwnd_validate(sk
, tp
);
892 return !tp
->packets_out
&& sk
->sk_send_head
;
895 /* Push out any pending frames which were held back due to
896 * TCP_CORK or attempt at coalescing tiny packets.
897 * The socket must be locked by the caller.
899 void __tcp_push_pending_frames(struct sock
*sk
, struct tcp_sock
*tp
,
900 unsigned cur_mss
, int nonagle
)
902 struct sk_buff
*skb
= sk
->sk_send_head
;
905 if (!tcp_skb_is_last(sk
, skb
))
906 nonagle
= TCP_NAGLE_PUSH
;
907 if (!tcp_snd_test(sk
, skb
, cur_mss
, nonagle
) ||
908 tcp_write_xmit(sk
, nonagle
))
909 tcp_check_probe_timer(sk
, tp
);
913 void __tcp_data_snd_check(struct sock
*sk
, struct sk_buff
*skb
)
915 struct tcp_sock
*tp
= tcp_sk(sk
);
917 if (after(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
+ tp
->snd_wnd
) ||
918 tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
||
919 tcp_write_xmit(sk
, tp
->nonagle
))
920 tcp_check_probe_timer(sk
, tp
);
923 /* This function returns the amount that we can raise the
924 * usable window based on the following constraints
926 * 1. The window can never be shrunk once it is offered (RFC 793)
927 * 2. We limit memory per socket
930 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
931 * RECV.NEXT + RCV.WIN fixed until:
932 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
934 * i.e. don't raise the right edge of the window until you can raise
935 * it at least MSS bytes.
937 * Unfortunately, the recommended algorithm breaks header prediction,
938 * since header prediction assumes th->window stays fixed.
940 * Strictly speaking, keeping th->window fixed violates the receiver
941 * side SWS prevention criteria. The problem is that under this rule
942 * a stream of single byte packets will cause the right side of the
943 * window to always advance by a single byte.
945 * Of course, if the sender implements sender side SWS prevention
946 * then this will not be a problem.
948 * BSD seems to make the following compromise:
950 * If the free space is less than the 1/4 of the maximum
951 * space available and the free space is less than 1/2 mss,
952 * then set the window to 0.
953 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
954 * Otherwise, just prevent the window from shrinking
955 * and from being larger than the largest representable value.
957 * This prevents incremental opening of the window in the regime
958 * where TCP is limited by the speed of the reader side taking
959 * data out of the TCP receive queue. It does nothing about
960 * those cases where the window is constrained on the sender side
961 * because the pipeline is full.
963 * BSD also seems to "accidentally" limit itself to windows that are a
964 * multiple of MSS, at least until the free space gets quite small.
965 * This would appear to be a side effect of the mbuf implementation.
966 * Combining these two algorithms results in the observed behavior
967 * of having a fixed window size at almost all times.
969 * Below we obtain similar behavior by forcing the offered window to
970 * a multiple of the mss when it is feasible to do so.
972 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
973 * Regular options like TIMESTAMP are taken into account.
975 u32
__tcp_select_window(struct sock
*sk
)
977 struct tcp_sock
*tp
= tcp_sk(sk
);
978 /* MSS for the peer's data. Previous verions used mss_clamp
979 * here. I don't know if the value based on our guesses
980 * of peer's MSS is better for the performance. It's more correct
981 * but may be worse for the performance because of rcv_mss
982 * fluctuations. --SAW 1998/11/1
984 int mss
= tp
->ack
.rcv_mss
;
985 int free_space
= tcp_space(sk
);
986 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
989 if (mss
> full_space
)
992 if (free_space
< full_space
/2) {
995 if (tcp_memory_pressure
)
996 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U*tp
->advmss
);
998 if (free_space
< mss
)
1002 if (free_space
> tp
->rcv_ssthresh
)
1003 free_space
= tp
->rcv_ssthresh
;
1005 /* Don't do rounding if we are using window scaling, since the
1006 * scaled window will not line up with the MSS boundary anyway.
1008 window
= tp
->rcv_wnd
;
1009 if (tp
->rx_opt
.rcv_wscale
) {
1010 window
= free_space
;
1012 /* Advertise enough space so that it won't get scaled away.
1013 * Import case: prevent zero window announcement if
1014 * 1<<rcv_wscale > mss.
1016 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1017 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1018 << tp
->rx_opt
.rcv_wscale
);
1020 /* Get the largest window that is a nice multiple of mss.
1021 * Window clamp already applied above.
1022 * If our current window offering is within 1 mss of the
1023 * free space we just keep it. This prevents the divide
1024 * and multiply from happening most of the time.
1025 * We also don't do any window rounding when the free space
1028 if (window
<= free_space
- mss
|| window
> free_space
)
1029 window
= (free_space
/mss
)*mss
;
1035 /* Attempt to collapse two adjacent SKB's during retransmission. */
1036 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*skb
, int mss_now
)
1038 struct tcp_sock
*tp
= tcp_sk(sk
);
1039 struct sk_buff
*next_skb
= skb
->next
;
1041 /* The first test we must make is that neither of these two
1042 * SKB's are still referenced by someone else.
1044 if (!skb_cloned(skb
) && !skb_cloned(next_skb
)) {
1045 int skb_size
= skb
->len
, next_skb_size
= next_skb
->len
;
1046 u16 flags
= TCP_SKB_CB(skb
)->flags
;
1048 /* Also punt if next skb has been SACK'd. */
1049 if(TCP_SKB_CB(next_skb
)->sacked
& TCPCB_SACKED_ACKED
)
1052 /* Next skb is out of window. */
1053 if (after(TCP_SKB_CB(next_skb
)->end_seq
, tp
->snd_una
+tp
->snd_wnd
))
1056 /* Punt if not enough space exists in the first SKB for
1057 * the data in the second, or the total combined payload
1058 * would exceed the MSS.
1060 if ((next_skb_size
> skb_tailroom(skb
)) ||
1061 ((skb_size
+ next_skb_size
) > mss_now
))
1064 BUG_ON(tcp_skb_pcount(skb
) != 1 ||
1065 tcp_skb_pcount(next_skb
) != 1);
1067 /* Ok. We will be able to collapse the packet. */
1068 __skb_unlink(next_skb
, next_skb
->list
);
1070 memcpy(skb_put(skb
, next_skb_size
), next_skb
->data
, next_skb_size
);
1072 if (next_skb
->ip_summed
== CHECKSUM_HW
)
1073 skb
->ip_summed
= CHECKSUM_HW
;
1075 if (skb
->ip_summed
!= CHECKSUM_HW
)
1076 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1078 /* Update sequence range on original skb. */
1079 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1081 /* Merge over control information. */
1082 flags
|= TCP_SKB_CB(next_skb
)->flags
; /* This moves PSH/FIN etc. over */
1083 TCP_SKB_CB(skb
)->flags
= flags
;
1085 /* All done, get rid of second SKB and account for it so
1086 * packet counting does not break.
1088 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
&(TCPCB_EVER_RETRANS
|TCPCB_AT_TAIL
);
1089 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_SACKED_RETRANS
)
1090 tp
->retrans_out
-= tcp_skb_pcount(next_skb
);
1091 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_LOST
) {
1092 tp
->lost_out
-= tcp_skb_pcount(next_skb
);
1093 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1095 /* Reno case is special. Sigh... */
1096 if (!tp
->rx_opt
.sack_ok
&& tp
->sacked_out
) {
1097 tcp_dec_pcount_approx(&tp
->sacked_out
, next_skb
);
1098 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1101 /* Not quite right: it can be > snd.fack, but
1102 * it is better to underestimate fackets.
1104 tcp_dec_pcount_approx(&tp
->fackets_out
, next_skb
);
1105 tcp_packets_out_dec(tp
, next_skb
);
1106 sk_stream_free_skb(sk
, next_skb
);
1110 /* Do a simple retransmit without using the backoff mechanisms in
1111 * tcp_timer. This is used for path mtu discovery.
1112 * The socket is already locked here.
1114 void tcp_simple_retransmit(struct sock
*sk
)
1116 struct tcp_sock
*tp
= tcp_sk(sk
);
1117 struct sk_buff
*skb
;
1118 unsigned int mss
= tcp_current_mss(sk
, 0);
1121 sk_stream_for_retrans_queue(skb
, sk
) {
1122 if (skb
->len
> mss
&&
1123 !(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1124 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1125 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1126 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1128 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_LOST
)) {
1129 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1130 tp
->lost_out
+= tcp_skb_pcount(skb
);
1139 tcp_sync_left_out(tp
);
1141 /* Don't muck with the congestion window here.
1142 * Reason is that we do not increase amount of _data_
1143 * in network, but units changed and effective
1144 * cwnd/ssthresh really reduced now.
1146 if (tp
->ca_state
!= TCP_CA_Loss
) {
1147 tp
->high_seq
= tp
->snd_nxt
;
1148 tp
->snd_ssthresh
= tcp_current_ssthresh(tp
);
1149 tp
->prior_ssthresh
= 0;
1150 tp
->undo_marker
= 0;
1151 tcp_set_ca_state(tp
, TCP_CA_Loss
);
1153 tcp_xmit_retransmit_queue(sk
);
1156 /* This retransmits one SKB. Policy decisions and retransmit queue
1157 * state updates are done by the caller. Returns non-zero if an
1158 * error occurred which prevented the send.
1160 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
1162 struct tcp_sock
*tp
= tcp_sk(sk
);
1163 unsigned int cur_mss
= tcp_current_mss(sk
, 0);
1166 /* Do not sent more than we queued. 1/4 is reserved for possible
1167 * copying overhead: frgagmentation, tunneling, mangling etc.
1169 if (atomic_read(&sk
->sk_wmem_alloc
) >
1170 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
1173 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
1174 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1177 if (sk
->sk_route_caps
& NETIF_F_TSO
) {
1178 sk
->sk_route_caps
&= ~NETIF_F_TSO
;
1179 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
1180 tp
->mss_cache
= tp
->mss_cache_std
;
1183 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
1187 /* If receiver has shrunk his window, and skb is out of
1188 * new window, do not retransmit it. The exception is the
1189 * case, when window is shrunk to zero. In this case
1190 * our retransmit serves as a zero window probe.
1192 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)
1193 && TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
1196 if (skb
->len
> cur_mss
) {
1197 int old_factor
= tcp_skb_pcount(skb
);
1200 if (tcp_fragment(sk
, skb
, cur_mss
))
1201 return -ENOMEM
; /* We'll try again later. */
1203 /* New SKB created, account for it. */
1204 new_factor
= tcp_skb_pcount(skb
);
1205 tp
->packets_out
-= old_factor
- new_factor
;
1206 tp
->packets_out
+= tcp_skb_pcount(skb
->next
);
1209 /* Collapse two adjacent packets if worthwhile and we can. */
1210 if(!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
) &&
1211 (skb
->len
< (cur_mss
>> 1)) &&
1212 (skb
->next
!= sk
->sk_send_head
) &&
1213 (skb
->next
!= (struct sk_buff
*)&sk
->sk_write_queue
) &&
1214 (skb_shinfo(skb
)->nr_frags
== 0 && skb_shinfo(skb
->next
)->nr_frags
== 0) &&
1215 (tcp_skb_pcount(skb
) == 1 && tcp_skb_pcount(skb
->next
) == 1) &&
1216 (sysctl_tcp_retrans_collapse
!= 0))
1217 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
1219 if(tp
->af_specific
->rebuild_header(sk
))
1220 return -EHOSTUNREACH
; /* Routing failure or similar. */
1222 /* Some Solaris stacks overoptimize and ignore the FIN on a
1223 * retransmit when old data is attached. So strip it off
1224 * since it is cheap to do so and saves bytes on the network.
1227 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1228 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
1229 if (!pskb_trim(skb
, 0)) {
1230 TCP_SKB_CB(skb
)->seq
= TCP_SKB_CB(skb
)->end_seq
- 1;
1231 skb_shinfo(skb
)->tso_segs
= 1;
1232 skb_shinfo(skb
)->tso_size
= 0;
1233 skb
->ip_summed
= CHECKSUM_NONE
;
1238 /* Make a copy, if the first transmission SKB clone we made
1239 * is still in somebody's hands, else make a clone.
1241 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1242 tcp_tso_set_push(skb
);
1244 err
= tcp_transmit_skb(sk
, (skb_cloned(skb
) ?
1245 pskb_copy(skb
, GFP_ATOMIC
):
1246 skb_clone(skb
, GFP_ATOMIC
)));
1249 /* Update global TCP statistics. */
1250 TCP_INC_STATS(TCP_MIB_RETRANSSEGS
);
1252 tp
->total_retrans
++;
1254 #if FASTRETRANS_DEBUG > 0
1255 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1256 if (net_ratelimit())
1257 printk(KERN_DEBUG
"retrans_out leaked.\n");
1260 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
1261 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1263 /* Save stamp of the first retransmit. */
1264 if (!tp
->retrans_stamp
)
1265 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
1269 /* snd_nxt is stored to detect loss of retransmitted segment,
1270 * see tcp_input.c tcp_sacktag_write_queue().
1272 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
1277 /* This gets called after a retransmit timeout, and the initially
1278 * retransmitted data is acknowledged. It tries to continue
1279 * resending the rest of the retransmit queue, until either
1280 * we've sent it all or the congestion window limit is reached.
1281 * If doing SACK, the first ACK which comes back for a timeout
1282 * based retransmit packet might feed us FACK information again.
1283 * If so, we use it to avoid unnecessarily retransmissions.
1285 void tcp_xmit_retransmit_queue(struct sock
*sk
)
1287 struct tcp_sock
*tp
= tcp_sk(sk
);
1288 struct sk_buff
*skb
;
1289 int packet_cnt
= tp
->lost_out
;
1291 /* First pass: retransmit lost packets. */
1293 sk_stream_for_retrans_queue(skb
, sk
) {
1294 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1296 /* Assume this retransmit will generate
1297 * only one packet for congestion window
1298 * calculation purposes. This works because
1299 * tcp_retransmit_skb() will chop up the
1300 * packet to be MSS sized and all the
1301 * packet counting works out.
1303 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1306 if (sacked
&TCPCB_LOST
) {
1307 if (!(sacked
&(TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))) {
1308 if (tcp_retransmit_skb(sk
, skb
))
1310 if (tp
->ca_state
!= TCP_CA_Loss
)
1311 NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS
);
1313 NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS
);
1316 skb_peek(&sk
->sk_write_queue
))
1317 tcp_reset_xmit_timer(sk
, TCP_TIME_RETRANS
, tp
->rto
);
1320 packet_cnt
-= tcp_skb_pcount(skb
);
1321 if (packet_cnt
<= 0)
1327 /* OK, demanded retransmission is finished. */
1329 /* Forward retransmissions are possible only during Recovery. */
1330 if (tp
->ca_state
!= TCP_CA_Recovery
)
1333 /* No forward retransmissions in Reno are possible. */
1334 if (!tp
->rx_opt
.sack_ok
)
1337 /* Yeah, we have to make difficult choice between forward transmission
1338 * and retransmission... Both ways have their merits...
1340 * For now we do not retransmit anything, while we have some new
1344 if (tcp_may_send_now(sk
, tp
))
1349 sk_stream_for_retrans_queue(skb
, sk
) {
1350 /* Similar to the retransmit loop above we
1351 * can pretend that the retransmitted SKB
1352 * we send out here will be composed of one
1353 * real MSS sized packet because tcp_retransmit_skb()
1354 * will fragment it if necessary.
1356 if (++packet_cnt
> tp
->fackets_out
)
1359 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1362 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
)
1365 /* Ok, retransmit it. */
1366 if (tcp_retransmit_skb(sk
, skb
))
1369 if (skb
== skb_peek(&sk
->sk_write_queue
))
1370 tcp_reset_xmit_timer(sk
, TCP_TIME_RETRANS
, tp
->rto
);
1372 NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS
);
1377 /* Send a fin. The caller locks the socket for us. This cannot be
1378 * allowed to fail queueing a FIN frame under any circumstances.
1380 void tcp_send_fin(struct sock
*sk
)
1382 struct tcp_sock
*tp
= tcp_sk(sk
);
1383 struct sk_buff
*skb
= skb_peek_tail(&sk
->sk_write_queue
);
1386 /* Optimization, tack on the FIN if we have a queue of
1387 * unsent frames. But be careful about outgoing SACKS
1390 mss_now
= tcp_current_mss(sk
, 1);
1392 if (sk
->sk_send_head
!= NULL
) {
1393 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
1394 TCP_SKB_CB(skb
)->end_seq
++;
1397 /* Socket is locked, keep trying until memory is available. */
1399 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_KERNEL
);
1405 /* Reserve space for headers and prepare control bits. */
1406 skb_reserve(skb
, MAX_TCP_HEADER
);
1408 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
1409 TCP_SKB_CB(skb
)->sacked
= 0;
1410 skb_shinfo(skb
)->tso_segs
= 1;
1411 skb_shinfo(skb
)->tso_size
= 0;
1413 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
1414 TCP_SKB_CB(skb
)->seq
= tp
->write_seq
;
1415 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
1416 tcp_queue_skb(sk
, skb
);
1418 __tcp_push_pending_frames(sk
, tp
, mss_now
, TCP_NAGLE_OFF
);
1421 /* We get here when a process closes a file descriptor (either due to
1422 * an explicit close() or as a byproduct of exit()'ing) and there
1423 * was unread data in the receive queue. This behavior is recommended
1424 * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM
1426 void tcp_send_active_reset(struct sock
*sk
, int priority
)
1428 struct tcp_sock
*tp
= tcp_sk(sk
);
1429 struct sk_buff
*skb
;
1431 /* NOTE: No TCP options attached and we never retransmit this. */
1432 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
1434 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
1438 /* Reserve space for headers and prepare control bits. */
1439 skb_reserve(skb
, MAX_TCP_HEADER
);
1441 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
1442 TCP_SKB_CB(skb
)->sacked
= 0;
1443 skb_shinfo(skb
)->tso_segs
= 1;
1444 skb_shinfo(skb
)->tso_size
= 0;
1447 TCP_SKB_CB(skb
)->seq
= tcp_acceptable_seq(sk
, tp
);
1448 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
1449 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1450 if (tcp_transmit_skb(sk
, skb
))
1451 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
1454 /* WARNING: This routine must only be called when we have already sent
1455 * a SYN packet that crossed the incoming SYN that caused this routine
1456 * to get called. If this assumption fails then the initial rcv_wnd
1457 * and rcv_wscale values will not be correct.
1459 int tcp_send_synack(struct sock
*sk
)
1461 struct sk_buff
* skb
;
1463 skb
= skb_peek(&sk
->sk_write_queue
);
1464 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_SYN
)) {
1465 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
1468 if (!(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_ACK
)) {
1469 if (skb_cloned(skb
)) {
1470 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
1473 __skb_unlink(skb
, &sk
->sk_write_queue
);
1474 skb_header_release(nskb
);
1475 __skb_queue_head(&sk
->sk_write_queue
, nskb
);
1476 sk_stream_free_skb(sk
, skb
);
1477 sk_charge_skb(sk
, nskb
);
1481 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
1482 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
1484 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1485 return tcp_transmit_skb(sk
, skb_clone(skb
, GFP_ATOMIC
));
1489 * Prepare a SYN-ACK.
1491 struct sk_buff
* tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
1492 struct request_sock
*req
)
1494 struct inet_request_sock
*ireq
= inet_rsk(req
);
1495 struct tcp_sock
*tp
= tcp_sk(sk
);
1497 int tcp_header_size
;
1498 struct sk_buff
*skb
;
1500 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
1504 /* Reserve space for headers. */
1505 skb_reserve(skb
, MAX_TCP_HEADER
);
1507 skb
->dst
= dst_clone(dst
);
1509 tcp_header_size
= (sizeof(struct tcphdr
) + TCPOLEN_MSS
+
1510 (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0) +
1511 (ireq
->wscale_ok
? TCPOLEN_WSCALE_ALIGNED
: 0) +
1512 /* SACK_PERM is in the place of NOP NOP of TS */
1513 ((ireq
->sack_ok
&& !ireq
->tstamp_ok
) ? TCPOLEN_SACKPERM_ALIGNED
: 0));
1514 skb
->h
.th
= th
= (struct tcphdr
*) skb_push(skb
, tcp_header_size
);
1516 memset(th
, 0, sizeof(struct tcphdr
));
1519 if (dst
->dev
->features
&NETIF_F_TSO
)
1521 TCP_ECN_make_synack(req
, th
);
1522 th
->source
= inet_sk(sk
)->sport
;
1523 th
->dest
= ireq
->rmt_port
;
1524 TCP_SKB_CB(skb
)->seq
= tcp_rsk(req
)->snt_isn
;
1525 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
1526 TCP_SKB_CB(skb
)->sacked
= 0;
1527 skb_shinfo(skb
)->tso_segs
= 1;
1528 skb_shinfo(skb
)->tso_size
= 0;
1529 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
1530 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
1531 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
1533 /* Set this up on the first call only */
1534 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
1535 /* tcp_full_space because it is guaranteed to be the first packet */
1536 tcp_select_initial_window(tcp_full_space(sk
),
1537 dst_metric(dst
, RTAX_ADVMSS
) - (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
1542 ireq
->rcv_wscale
= rcv_wscale
;
1545 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
1546 th
->window
= htons(req
->rcv_wnd
);
1548 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1549 tcp_syn_build_options((__u32
*)(th
+ 1), dst_metric(dst
, RTAX_ADVMSS
), ireq
->tstamp_ok
,
1550 ireq
->sack_ok
, ireq
->wscale_ok
, ireq
->rcv_wscale
,
1551 TCP_SKB_CB(skb
)->when
,
1555 th
->doff
= (tcp_header_size
>> 2);
1556 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
1561 * Do all connect socket setups that can be done AF independent.
1563 static inline void tcp_connect_init(struct sock
*sk
)
1565 struct dst_entry
*dst
= __sk_dst_get(sk
);
1566 struct tcp_sock
*tp
= tcp_sk(sk
);
1569 /* We'll fix this up when we get a response from the other end.
1570 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
1572 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
1573 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
1575 /* If user gave his TCP_MAXSEG, record it to clamp */
1576 if (tp
->rx_opt
.user_mss
)
1577 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
1579 tcp_sync_mss(sk
, dst_mtu(dst
));
1581 if (!tp
->window_clamp
)
1582 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
1583 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
1584 tcp_initialize_rcv_mss(sk
);
1586 tcp_select_initial_window(tcp_full_space(sk
),
1587 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
1590 sysctl_tcp_window_scaling
,
1593 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
1594 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
1597 sock_reset_flag(sk
, SOCK_DONE
);
1599 tcp_init_wl(tp
, tp
->write_seq
, 0);
1600 tp
->snd_una
= tp
->write_seq
;
1601 tp
->snd_sml
= tp
->write_seq
;
1606 tp
->rto
= TCP_TIMEOUT_INIT
;
1607 tp
->retransmits
= 0;
1608 tcp_clear_retrans(tp
);
1612 * Build a SYN and send it off.
1614 int tcp_connect(struct sock
*sk
)
1616 struct tcp_sock
*tp
= tcp_sk(sk
);
1617 struct sk_buff
*buff
;
1619 tcp_connect_init(sk
);
1621 buff
= alloc_skb(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
1622 if (unlikely(buff
== NULL
))
1625 /* Reserve space for headers. */
1626 skb_reserve(buff
, MAX_TCP_HEADER
);
1628 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_SYN
;
1629 TCP_ECN_send_syn(sk
, tp
, buff
);
1630 TCP_SKB_CB(buff
)->sacked
= 0;
1631 skb_shinfo(buff
)->tso_segs
= 1;
1632 skb_shinfo(buff
)->tso_size
= 0;
1634 TCP_SKB_CB(buff
)->seq
= tp
->write_seq
++;
1635 TCP_SKB_CB(buff
)->end_seq
= tp
->write_seq
;
1636 tp
->snd_nxt
= tp
->write_seq
;
1637 tp
->pushed_seq
= tp
->write_seq
;
1640 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
1641 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
1642 skb_header_release(buff
);
1643 __skb_queue_tail(&sk
->sk_write_queue
, buff
);
1644 sk_charge_skb(sk
, buff
);
1645 tp
->packets_out
+= tcp_skb_pcount(buff
);
1646 tcp_transmit_skb(sk
, skb_clone(buff
, GFP_KERNEL
));
1647 TCP_INC_STATS(TCP_MIB_ACTIVEOPENS
);
1649 /* Timer for repeating the SYN until an answer. */
1650 tcp_reset_xmit_timer(sk
, TCP_TIME_RETRANS
, tp
->rto
);
1654 /* Send out a delayed ack, the caller does the policy checking
1655 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
1658 void tcp_send_delayed_ack(struct sock
*sk
)
1660 struct tcp_sock
*tp
= tcp_sk(sk
);
1661 int ato
= tp
->ack
.ato
;
1662 unsigned long timeout
;
1664 if (ato
> TCP_DELACK_MIN
) {
1667 if (tp
->ack
.pingpong
|| (tp
->ack
.pending
&TCP_ACK_PUSHED
))
1668 max_ato
= TCP_DELACK_MAX
;
1670 /* Slow path, intersegment interval is "high". */
1672 /* If some rtt estimate is known, use it to bound delayed ack.
1673 * Do not use tp->rto here, use results of rtt measurements
1677 int rtt
= max(tp
->srtt
>>3, TCP_DELACK_MIN
);
1683 ato
= min(ato
, max_ato
);
1686 /* Stay within the limit we were given */
1687 timeout
= jiffies
+ ato
;
1689 /* Use new timeout only if there wasn't a older one earlier. */
1690 if (tp
->ack
.pending
&TCP_ACK_TIMER
) {
1691 /* If delack timer was blocked or is about to expire,
1694 if (tp
->ack
.blocked
|| time_before_eq(tp
->ack
.timeout
, jiffies
+(ato
>>2))) {
1699 if (!time_before(timeout
, tp
->ack
.timeout
))
1700 timeout
= tp
->ack
.timeout
;
1702 tp
->ack
.pending
|= TCP_ACK_SCHED
|TCP_ACK_TIMER
;
1703 tp
->ack
.timeout
= timeout
;
1704 sk_reset_timer(sk
, &tp
->delack_timer
, timeout
);
1707 /* This routine sends an ack and also updates the window. */
1708 void tcp_send_ack(struct sock
*sk
)
1710 /* If we have been reset, we may not send again. */
1711 if (sk
->sk_state
!= TCP_CLOSE
) {
1712 struct tcp_sock
*tp
= tcp_sk(sk
);
1713 struct sk_buff
*buff
;
1715 /* We are not putting this on the write queue, so
1716 * tcp_transmit_skb() will set the ownership to this
1719 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
1721 tcp_schedule_ack(tp
);
1722 tp
->ack
.ato
= TCP_ATO_MIN
;
1723 tcp_reset_xmit_timer(sk
, TCP_TIME_DACK
, TCP_DELACK_MAX
);
1727 /* Reserve space for headers and prepare control bits. */
1728 skb_reserve(buff
, MAX_TCP_HEADER
);
1730 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_ACK
;
1731 TCP_SKB_CB(buff
)->sacked
= 0;
1732 skb_shinfo(buff
)->tso_segs
= 1;
1733 skb_shinfo(buff
)->tso_size
= 0;
1735 /* Send it off, this clears delayed acks for us. */
1736 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(buff
)->end_seq
= tcp_acceptable_seq(sk
, tp
);
1737 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
1738 tcp_transmit_skb(sk
, buff
);
1742 /* This routine sends a packet with an out of date sequence
1743 * number. It assumes the other end will try to ack it.
1745 * Question: what should we make while urgent mode?
1746 * 4.4BSD forces sending single byte of data. We cannot send
1747 * out of window data, because we have SND.NXT==SND.MAX...
1749 * Current solution: to send TWO zero-length segments in urgent mode:
1750 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
1751 * out-of-date with SND.UNA-1 to probe window.
1753 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
1755 struct tcp_sock
*tp
= tcp_sk(sk
);
1756 struct sk_buff
*skb
;
1758 /* We don't queue it, tcp_transmit_skb() sets ownership. */
1759 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
1763 /* Reserve space for headers and set control bits. */
1764 skb_reserve(skb
, MAX_TCP_HEADER
);
1766 TCP_SKB_CB(skb
)->flags
= TCPCB_FLAG_ACK
;
1767 TCP_SKB_CB(skb
)->sacked
= urgent
;
1768 skb_shinfo(skb
)->tso_segs
= 1;
1769 skb_shinfo(skb
)->tso_size
= 0;
1771 /* Use a previous sequence. This should cause the other
1772 * end to send an ack. Don't queue or clone SKB, just
1775 TCP_SKB_CB(skb
)->seq
= urgent
? tp
->snd_una
: tp
->snd_una
- 1;
1776 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
1777 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1778 return tcp_transmit_skb(sk
, skb
);
1781 int tcp_write_wakeup(struct sock
*sk
)
1783 if (sk
->sk_state
!= TCP_CLOSE
) {
1784 struct tcp_sock
*tp
= tcp_sk(sk
);
1785 struct sk_buff
*skb
;
1787 if ((skb
= sk
->sk_send_head
) != NULL
&&
1788 before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)) {
1790 unsigned int mss
= tcp_current_mss(sk
, 0);
1791 unsigned int seg_size
= tp
->snd_una
+tp
->snd_wnd
-TCP_SKB_CB(skb
)->seq
;
1793 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
1794 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
1796 /* We are probing the opening of a window
1797 * but the window size is != 0
1798 * must have been a result SWS avoidance ( sender )
1800 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
1802 seg_size
= min(seg_size
, mss
);
1803 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
1804 if (tcp_fragment(sk
, skb
, seg_size
))
1806 /* SWS override triggered forced fragmentation.
1807 * Disable TSO, the connection is too sick. */
1808 if (sk
->sk_route_caps
& NETIF_F_TSO
) {
1809 sock_set_flag(sk
, SOCK_NO_LARGESEND
);
1810 sk
->sk_route_caps
&= ~NETIF_F_TSO
;
1811 tp
->mss_cache
= tp
->mss_cache_std
;
1813 } else if (!tcp_skb_pcount(skb
))
1814 tcp_set_skb_tso_segs(sk
, skb
);
1816 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
1817 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1818 tcp_tso_set_push(skb
);
1819 err
= tcp_transmit_skb(sk
, skb_clone(skb
, GFP_ATOMIC
));
1821 update_send_head(sk
, tp
, skb
);
1826 between(tp
->snd_up
, tp
->snd_una
+1, tp
->snd_una
+0xFFFF))
1827 tcp_xmit_probe_skb(sk
, TCPCB_URG
);
1828 return tcp_xmit_probe_skb(sk
, 0);
1834 /* A window probe timeout has occurred. If window is not closed send
1835 * a partial packet else a zero probe.
1837 void tcp_send_probe0(struct sock
*sk
)
1839 struct tcp_sock
*tp
= tcp_sk(sk
);
1842 err
= tcp_write_wakeup(sk
);
1844 if (tp
->packets_out
|| !sk
->sk_send_head
) {
1845 /* Cancel probe timer, if it is not required. */
1852 if (tp
->backoff
< sysctl_tcp_retries2
)
1855 tcp_reset_xmit_timer (sk
, TCP_TIME_PROBE0
,
1856 min(tp
->rto
<< tp
->backoff
, TCP_RTO_MAX
));
1858 /* If packet was not sent due to local congestion,
1859 * do not backoff and do not remember probes_out.
1860 * Let local senders to fight for local resources.
1862 * Use accumulated backoff yet.
1864 if (!tp
->probes_out
)
1866 tcp_reset_xmit_timer (sk
, TCP_TIME_PROBE0
,
1867 min(tp
->rto
<< tp
->backoff
, TCP_RESOURCE_PROBE_INTERVAL
));
1871 EXPORT_SYMBOL(tcp_connect
);
1872 EXPORT_SYMBOL(tcp_make_synack
);
1873 EXPORT_SYMBOL(tcp_simple_retransmit
);
1874 EXPORT_SYMBOL(tcp_sync_mss
);