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 __read_mostly
= 1;
48 /* People can turn this on to work with those rare, broken TCPs that
49 * interpret the window field as a signed quantity.
51 int sysctl_tcp_workaround_signed_windows __read_mostly
= 0;
53 /* This limits the percentage of the congestion window which we
54 * will allow a single TSO frame to consume. Building TSO frames
55 * which are too large can cause TCP streams to be bursty.
57 int sysctl_tcp_tso_win_divisor __read_mostly
= 3;
59 int sysctl_tcp_mtu_probing __read_mostly
= 0;
60 int sysctl_tcp_base_mss __read_mostly
= 512;
62 /* By default, RFC2861 behavior. */
63 int sysctl_tcp_slow_start_after_idle __read_mostly
= 1;
65 static void update_send_head(struct sock
*sk
, struct tcp_sock
*tp
,
68 tcp_advance_send_head(sk
, skb
);
69 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
70 tcp_packets_out_inc(sk
, tp
, skb
);
73 /* SND.NXT, if window was not shrunk.
74 * If window has been shrunk, what should we make? It is not clear at all.
75 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
76 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
77 * invalid. OK, let's make this for now:
79 static inline __u32
tcp_acceptable_seq(struct sock
*sk
, struct tcp_sock
*tp
)
81 if (!before(tp
->snd_una
+tp
->snd_wnd
, tp
->snd_nxt
))
84 return tp
->snd_una
+tp
->snd_wnd
;
87 /* Calculate mss to advertise in SYN segment.
88 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
90 * 1. It is independent of path mtu.
91 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
92 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
93 * attached devices, because some buggy hosts are confused by
95 * 4. We do not make 3, we advertise MSS, calculated from first
96 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
97 * This may be overridden via information stored in routing table.
98 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
99 * probably even Jumbo".
101 static __u16
tcp_advertise_mss(struct sock
*sk
)
103 struct tcp_sock
*tp
= tcp_sk(sk
);
104 struct dst_entry
*dst
= __sk_dst_get(sk
);
105 int mss
= tp
->advmss
;
107 if (dst
&& dst_metric(dst
, RTAX_ADVMSS
) < mss
) {
108 mss
= dst_metric(dst
, RTAX_ADVMSS
);
115 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
116 * This is the first part of cwnd validation mechanism. */
117 static void tcp_cwnd_restart(struct sock
*sk
, struct dst_entry
*dst
)
119 struct tcp_sock
*tp
= tcp_sk(sk
);
120 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
121 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
122 u32 cwnd
= tp
->snd_cwnd
;
124 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
126 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
127 restart_cwnd
= min(restart_cwnd
, cwnd
);
129 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
131 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
132 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
133 tp
->snd_cwnd_used
= 0;
136 static void tcp_event_data_sent(struct tcp_sock
*tp
,
137 struct sk_buff
*skb
, struct sock
*sk
)
139 struct inet_connection_sock
*icsk
= inet_csk(sk
);
140 const u32 now
= tcp_time_stamp
;
142 if (sysctl_tcp_slow_start_after_idle
&&
143 (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
))
144 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
148 /* If it is a reply for ato after last received
149 * packet, enter pingpong mode.
151 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
152 icsk
->icsk_ack
.pingpong
= 1;
155 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
157 tcp_dec_quickack_mode(sk
, pkts
);
158 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
161 /* Determine a window scaling and initial window to offer.
162 * Based on the assumption that the given amount of space
163 * will be offered. Store the results in the tp structure.
164 * NOTE: for smooth operation initial space offering should
165 * be a multiple of mss if possible. We assume here that mss >= 1.
166 * This MUST be enforced by all callers.
168 void tcp_select_initial_window(int __space
, __u32 mss
,
169 __u32
*rcv_wnd
, __u32
*window_clamp
,
170 int wscale_ok
, __u8
*rcv_wscale
)
172 unsigned int space
= (__space
< 0 ? 0 : __space
);
174 /* If no clamp set the clamp to the max possible scaled window */
175 if (*window_clamp
== 0)
176 (*window_clamp
) = (65535 << 14);
177 space
= min(*window_clamp
, space
);
179 /* Quantize space offering to a multiple of mss if possible. */
181 space
= (space
/ mss
) * mss
;
183 /* NOTE: offering an initial window larger than 32767
184 * will break some buggy TCP stacks. If the admin tells us
185 * it is likely we could be speaking with such a buggy stack
186 * we will truncate our initial window offering to 32K-1
187 * unless the remote has sent us a window scaling option,
188 * which we interpret as a sign the remote TCP is not
189 * misinterpreting the window field as a signed quantity.
191 if (sysctl_tcp_workaround_signed_windows
)
192 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
198 /* Set window scaling on max possible window
199 * See RFC1323 for an explanation of the limit to 14
201 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
202 space
= min_t(u32
, space
, *window_clamp
);
203 while (space
> 65535 && (*rcv_wscale
) < 14) {
209 /* Set initial window to value enough for senders,
210 * following RFC2414. Senders, not following this RFC,
211 * will be satisfied with 2.
213 if (mss
> (1<<*rcv_wscale
)) {
219 if (*rcv_wnd
> init_cwnd
*mss
)
220 *rcv_wnd
= init_cwnd
*mss
;
223 /* Set the clamp no higher than max representable value */
224 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
227 /* Chose a new window to advertise, update state in tcp_sock for the
228 * socket, and return result with RFC1323 scaling applied. The return
229 * value can be stuffed directly into th->window for an outgoing
232 static u16
tcp_select_window(struct sock
*sk
)
234 struct tcp_sock
*tp
= tcp_sk(sk
);
235 u32 cur_win
= tcp_receive_window(tp
);
236 u32 new_win
= __tcp_select_window(sk
);
238 /* Never shrink the offered window */
239 if (new_win
< cur_win
) {
240 /* Danger Will Robinson!
241 * Don't update rcv_wup/rcv_wnd here or else
242 * we will not be able to advertise a zero
243 * window in time. --DaveM
245 * Relax Will Robinson.
249 tp
->rcv_wnd
= new_win
;
250 tp
->rcv_wup
= tp
->rcv_nxt
;
252 /* Make sure we do not exceed the maximum possible
255 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
256 new_win
= min(new_win
, MAX_TCP_WINDOW
);
258 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
260 /* RFC1323 scaling applied */
261 new_win
>>= tp
->rx_opt
.rcv_wscale
;
263 /* If we advertise zero window, disable fast path. */
270 static void tcp_build_and_update_options(__be32
*ptr
, struct tcp_sock
*tp
,
271 __u32 tstamp
, __u8
**md5_hash
)
273 if (tp
->rx_opt
.tstamp_ok
) {
274 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
276 (TCPOPT_TIMESTAMP
<< 8) |
278 *ptr
++ = htonl(tstamp
);
279 *ptr
++ = htonl(tp
->rx_opt
.ts_recent
);
281 if (tp
->rx_opt
.eff_sacks
) {
282 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
? tp
->duplicate_sack
: tp
->selective_acks
;
285 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
288 (TCPOLEN_SACK_BASE
+ (tp
->rx_opt
.eff_sacks
*
289 TCPOLEN_SACK_PERBLOCK
)));
291 for (this_sack
= 0; this_sack
< tp
->rx_opt
.eff_sacks
; this_sack
++) {
292 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
293 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
296 if (tp
->rx_opt
.dsack
) {
297 tp
->rx_opt
.dsack
= 0;
298 tp
->rx_opt
.eff_sacks
--;
301 #ifdef CONFIG_TCP_MD5SIG
303 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
305 (TCPOPT_MD5SIG
<< 8) |
307 *md5_hash
= (__u8
*)ptr
;
312 /* Construct a tcp options header for a SYN or SYN_ACK packet.
313 * If this is every changed make sure to change the definition of
314 * MAX_SYN_SIZE to match the new maximum number of options that you
317 * Note - that with the RFC2385 TCP option, we make room for the
318 * 16 byte MD5 hash. This will be filled in later, so the pointer for the
319 * location to be filled is passed back up.
321 static void tcp_syn_build_options(__be32
*ptr
, int mss
, int ts
, int sack
,
322 int offer_wscale
, int wscale
, __u32 tstamp
,
323 __u32 ts_recent
, __u8
**md5_hash
)
325 /* We always get an MSS option.
326 * The option bytes which will be seen in normal data
327 * packets should timestamps be used, must be in the MSS
328 * advertised. But we subtract them from tp->mss_cache so
329 * that calculations in tcp_sendmsg are simpler etc.
330 * So account for this fact here if necessary. If we
331 * don't do this correctly, as a receiver we won't
332 * recognize data packets as being full sized when we
333 * should, and thus we won't abide by the delayed ACK
335 * SACKs don't matter, we never delay an ACK when we
336 * have any of those going out.
338 *ptr
++ = htonl((TCPOPT_MSS
<< 24) | (TCPOLEN_MSS
<< 16) | mss
);
341 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
342 (TCPOLEN_SACK_PERM
<< 16) |
343 (TCPOPT_TIMESTAMP
<< 8) |
346 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
348 (TCPOPT_TIMESTAMP
<< 8) |
350 *ptr
++ = htonl(tstamp
); /* TSVAL */
351 *ptr
++ = htonl(ts_recent
); /* TSECR */
353 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
355 (TCPOPT_SACK_PERM
<< 8) |
358 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
359 (TCPOPT_WINDOW
<< 16) |
360 (TCPOLEN_WINDOW
<< 8) |
362 #ifdef CONFIG_TCP_MD5SIG
364 * If MD5 is enabled, then we set the option, and include the size
365 * (always 18). The actual MD5 hash is added just before the
369 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
371 (TCPOPT_MD5SIG
<< 8) |
373 *md5_hash
= (__u8
*) ptr
;
378 /* This routine actually transmits TCP packets queued in by
379 * tcp_do_sendmsg(). This is used by both the initial
380 * transmission and possible later retransmissions.
381 * All SKB's seen here are completely headerless. It is our
382 * job to build the TCP header, and pass the packet down to
383 * IP so it can do the same plus pass the packet off to the
386 * We are working here with either a clone of the original
387 * SKB, or a fresh unique copy made by the retransmit engine.
389 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
, gfp_t gfp_mask
)
391 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
392 struct inet_sock
*inet
;
394 struct tcp_skb_cb
*tcb
;
396 #ifdef CONFIG_TCP_MD5SIG
397 struct tcp_md5sig_key
*md5
;
398 __u8
*md5_hash_location
;
404 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
406 /* If congestion control is doing timestamping, we must
407 * take such a timestamp before we potentially clone/copy.
409 if (icsk
->icsk_ca_ops
->rtt_sample
)
410 __net_timestamp(skb
);
412 if (likely(clone_it
)) {
413 if (unlikely(skb_cloned(skb
)))
414 skb
= pskb_copy(skb
, gfp_mask
);
416 skb
= skb_clone(skb
, gfp_mask
);
423 tcb
= TCP_SKB_CB(skb
);
424 tcp_header_size
= tp
->tcp_header_len
;
426 #define SYSCTL_FLAG_TSTAMPS 0x1
427 #define SYSCTL_FLAG_WSCALE 0x2
428 #define SYSCTL_FLAG_SACK 0x4
431 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
432 tcp_header_size
= sizeof(struct tcphdr
) + TCPOLEN_MSS
;
433 if (sysctl_tcp_timestamps
) {
434 tcp_header_size
+= TCPOLEN_TSTAMP_ALIGNED
;
435 sysctl_flags
|= SYSCTL_FLAG_TSTAMPS
;
437 if (sysctl_tcp_window_scaling
) {
438 tcp_header_size
+= TCPOLEN_WSCALE_ALIGNED
;
439 sysctl_flags
|= SYSCTL_FLAG_WSCALE
;
441 if (sysctl_tcp_sack
) {
442 sysctl_flags
|= SYSCTL_FLAG_SACK
;
443 if (!(sysctl_flags
& SYSCTL_FLAG_TSTAMPS
))
444 tcp_header_size
+= TCPOLEN_SACKPERM_ALIGNED
;
446 } else if (unlikely(tp
->rx_opt
.eff_sacks
)) {
447 /* A SACK is 2 pad bytes, a 2 byte header, plus
448 * 2 32-bit sequence numbers for each SACK block.
450 tcp_header_size
+= (TCPOLEN_SACK_BASE_ALIGNED
+
451 (tp
->rx_opt
.eff_sacks
*
452 TCPOLEN_SACK_PERBLOCK
));
455 if (tcp_packets_in_flight(tp
) == 0)
456 tcp_ca_event(sk
, CA_EVENT_TX_START
);
458 #ifdef CONFIG_TCP_MD5SIG
460 * Are we doing MD5 on this segment? If so - make
463 md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
465 tcp_header_size
+= TCPOLEN_MD5SIG_ALIGNED
;
468 skb_push(skb
, tcp_header_size
);
469 skb_reset_transport_header(skb
);
470 skb_set_owner_w(skb
, sk
);
472 /* Build TCP header and checksum it. */
474 th
->source
= inet
->sport
;
475 th
->dest
= inet
->dport
;
476 th
->seq
= htonl(tcb
->seq
);
477 th
->ack_seq
= htonl(tp
->rcv_nxt
);
478 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
481 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
482 /* RFC1323: The window in SYN & SYN/ACK segments
485 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
487 th
->window
= htons(tcp_select_window(sk
));
492 if (unlikely(tp
->urg_mode
&&
493 between(tp
->snd_up
, tcb
->seq
+1, tcb
->seq
+0xFFFF))) {
494 th
->urg_ptr
= htons(tp
->snd_up
-tcb
->seq
);
498 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
499 tcp_syn_build_options((__be32
*)(th
+ 1),
500 tcp_advertise_mss(sk
),
501 (sysctl_flags
& SYSCTL_FLAG_TSTAMPS
),
502 (sysctl_flags
& SYSCTL_FLAG_SACK
),
503 (sysctl_flags
& SYSCTL_FLAG_WSCALE
),
504 tp
->rx_opt
.rcv_wscale
,
506 tp
->rx_opt
.ts_recent
,
508 #ifdef CONFIG_TCP_MD5SIG
509 md5
? &md5_hash_location
:
513 tcp_build_and_update_options((__be32
*)(th
+ 1),
515 #ifdef CONFIG_TCP_MD5SIG
516 md5
? &md5_hash_location
:
519 TCP_ECN_send(sk
, tp
, skb
, tcp_header_size
);
522 #ifdef CONFIG_TCP_MD5SIG
523 /* Calculate the MD5 hash, as we have all we need now */
525 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
534 icsk
->icsk_af_ops
->send_check(sk
, skb
->len
, skb
);
536 if (likely(tcb
->flags
& TCPCB_FLAG_ACK
))
537 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
539 if (skb
->len
!= tcp_header_size
)
540 tcp_event_data_sent(tp
, skb
, sk
);
542 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
543 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
545 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, 0);
546 if (likely(err
<= 0))
549 tcp_enter_cwr(sk
, 1);
551 return net_xmit_eval(err
);
553 #undef SYSCTL_FLAG_TSTAMPS
554 #undef SYSCTL_FLAG_WSCALE
555 #undef SYSCTL_FLAG_SACK
559 /* This routine just queue's the buffer
561 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
562 * otherwise socket can stall.
564 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
566 struct tcp_sock
*tp
= tcp_sk(sk
);
568 /* Advance write_seq and place onto the write_queue. */
569 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
570 skb_header_release(skb
);
571 tcp_add_write_queue_tail(sk
, skb
);
572 sk_charge_skb(sk
, skb
);
575 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
577 if (skb
->len
<= mss_now
|| !sk_can_gso(sk
)) {
578 /* Avoid the costly divide in the normal
581 skb_shinfo(skb
)->gso_segs
= 1;
582 skb_shinfo(skb
)->gso_size
= 0;
583 skb_shinfo(skb
)->gso_type
= 0;
587 factor
= skb
->len
+ (mss_now
- 1);
589 skb_shinfo(skb
)->gso_segs
= factor
;
590 skb_shinfo(skb
)->gso_size
= mss_now
;
591 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
595 /* Function to create two new TCP segments. Shrinks the given segment
596 * to the specified size and appends a new segment with the rest of the
597 * packet to the list. This won't be called frequently, I hope.
598 * Remember, these are still headerless SKBs at this point.
600 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
, unsigned int mss_now
)
602 struct tcp_sock
*tp
= tcp_sk(sk
);
603 struct sk_buff
*buff
;
604 int nsize
, old_factor
;
608 BUG_ON(len
> skb
->len
);
610 clear_all_retrans_hints(tp
);
611 nsize
= skb_headlen(skb
) - len
;
615 if (skb_cloned(skb
) &&
616 skb_is_nonlinear(skb
) &&
617 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
620 /* Get a new skb... force flag on. */
621 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
623 return -ENOMEM
; /* We'll just try again later. */
625 sk_charge_skb(sk
, buff
);
626 nlen
= skb
->len
- len
- nsize
;
627 buff
->truesize
+= nlen
;
628 skb
->truesize
-= nlen
;
630 /* Correct the sequence numbers. */
631 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
632 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
633 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
635 /* PSH and FIN should only be set in the second packet. */
636 flags
= TCP_SKB_CB(skb
)->flags
;
637 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
638 TCP_SKB_CB(buff
)->flags
= flags
;
639 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
640 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_AT_TAIL
;
642 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
643 /* Copy and checksum data tail into the new buffer. */
644 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
, skb_put(buff
, nsize
),
649 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
651 skb
->ip_summed
= CHECKSUM_PARTIAL
;
652 skb_split(skb
, buff
, len
);
655 buff
->ip_summed
= skb
->ip_summed
;
657 /* Looks stupid, but our code really uses when of
658 * skbs, which it never sent before. --ANK
660 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
661 buff
->tstamp
= skb
->tstamp
;
663 old_factor
= tcp_skb_pcount(skb
);
665 /* Fix up tso_factor for both original and new SKB. */
666 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
667 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
669 /* If this packet has been sent out already, we must
670 * adjust the various packet counters.
672 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
673 int diff
= old_factor
- tcp_skb_pcount(skb
) -
674 tcp_skb_pcount(buff
);
676 tp
->packets_out
-= diff
;
678 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
679 tp
->sacked_out
-= diff
;
680 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
681 tp
->retrans_out
-= diff
;
683 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
) {
684 tp
->lost_out
-= diff
;
685 tp
->left_out
-= diff
;
689 /* Adjust Reno SACK estimate. */
690 if (!tp
->rx_opt
.sack_ok
) {
691 tp
->sacked_out
-= diff
;
692 if ((int)tp
->sacked_out
< 0)
694 tcp_sync_left_out(tp
);
697 tp
->fackets_out
-= diff
;
698 if ((int)tp
->fackets_out
< 0)
703 /* Link BUFF into the send queue. */
704 skb_header_release(buff
);
705 tcp_insert_write_queue_after(skb
, buff
, sk
);
710 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
711 * eventually). The difference is that pulled data not copied, but
712 * immediately discarded.
714 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
720 for (i
=0; i
<skb_shinfo(skb
)->nr_frags
; i
++) {
721 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
722 put_page(skb_shinfo(skb
)->frags
[i
].page
);
723 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
725 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
727 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
728 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
734 skb_shinfo(skb
)->nr_frags
= k
;
736 skb_reset_tail_pointer(skb
);
737 skb
->data_len
-= len
;
738 skb
->len
= skb
->data_len
;
741 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
743 if (skb_cloned(skb
) &&
744 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
747 /* If len == headlen, we avoid __skb_pull to preserve alignment. */
748 if (unlikely(len
< skb_headlen(skb
)))
749 __skb_pull(skb
, len
);
751 __pskb_trim_head(skb
, len
- skb_headlen(skb
));
753 TCP_SKB_CB(skb
)->seq
+= len
;
754 skb
->ip_summed
= CHECKSUM_PARTIAL
;
756 skb
->truesize
-= len
;
757 sk
->sk_wmem_queued
-= len
;
758 sk
->sk_forward_alloc
+= len
;
759 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
761 /* Any change of skb->len requires recalculation of tso
764 if (tcp_skb_pcount(skb
) > 1)
765 tcp_set_skb_tso_segs(sk
, skb
, tcp_current_mss(sk
, 1));
770 /* Not accounting for SACKs here. */
771 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
773 struct tcp_sock
*tp
= tcp_sk(sk
);
774 struct inet_connection_sock
*icsk
= inet_csk(sk
);
777 /* Calculate base mss without TCP options:
778 It is MMS_S - sizeof(tcphdr) of rfc1122
780 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
782 /* Clamp it (mss_clamp does not include tcp options) */
783 if (mss_now
> tp
->rx_opt
.mss_clamp
)
784 mss_now
= tp
->rx_opt
.mss_clamp
;
786 /* Now subtract optional transport overhead */
787 mss_now
-= icsk
->icsk_ext_hdr_len
;
789 /* Then reserve room for full set of TCP options and 8 bytes of data */
793 /* Now subtract TCP options size, not including SACKs */
794 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
799 /* Inverse of above */
800 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
802 struct tcp_sock
*tp
= tcp_sk(sk
);
803 struct inet_connection_sock
*icsk
= inet_csk(sk
);
808 icsk
->icsk_ext_hdr_len
+
809 icsk
->icsk_af_ops
->net_header_len
;
814 void tcp_mtup_init(struct sock
*sk
)
816 struct tcp_sock
*tp
= tcp_sk(sk
);
817 struct inet_connection_sock
*icsk
= inet_csk(sk
);
819 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
820 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
821 icsk
->icsk_af_ops
->net_header_len
;
822 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
823 icsk
->icsk_mtup
.probe_size
= 0;
826 /* This function synchronize snd mss to current pmtu/exthdr set.
828 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
829 for TCP options, but includes only bare TCP header.
831 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
832 It is minimum of user_mss and mss received with SYN.
833 It also does not include TCP options.
835 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
837 tp->mss_cache is current effective sending mss, including
838 all tcp options except for SACKs. It is evaluated,
839 taking into account current pmtu, but never exceeds
840 tp->rx_opt.mss_clamp.
842 NOTE1. rfc1122 clearly states that advertised MSS
843 DOES NOT include either tcp or ip options.
845 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
846 are READ ONLY outside this function. --ANK (980731)
849 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
851 struct tcp_sock
*tp
= tcp_sk(sk
);
852 struct inet_connection_sock
*icsk
= inet_csk(sk
);
855 if (icsk
->icsk_mtup
.search_high
> pmtu
)
856 icsk
->icsk_mtup
.search_high
= pmtu
;
858 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
860 /* Bound mss with half of window */
861 if (tp
->max_window
&& mss_now
> (tp
->max_window
>>1))
862 mss_now
= max((tp
->max_window
>>1), 68U - tp
->tcp_header_len
);
864 /* And store cached results */
865 icsk
->icsk_pmtu_cookie
= pmtu
;
866 if (icsk
->icsk_mtup
.enabled
)
867 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
868 tp
->mss_cache
= mss_now
;
873 /* Compute the current effective MSS, taking SACKs and IP options,
874 * and even PMTU discovery events into account.
876 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
877 * cannot be large. However, taking into account rare use of URG, this
880 unsigned int tcp_current_mss(struct sock
*sk
, int large_allowed
)
882 struct tcp_sock
*tp
= tcp_sk(sk
);
883 struct dst_entry
*dst
= __sk_dst_get(sk
);
888 mss_now
= tp
->mss_cache
;
890 if (large_allowed
&& sk_can_gso(sk
) && !tp
->urg_mode
)
894 u32 mtu
= dst_mtu(dst
);
895 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
896 mss_now
= tcp_sync_mss(sk
, mtu
);
899 if (tp
->rx_opt
.eff_sacks
)
900 mss_now
-= (TCPOLEN_SACK_BASE_ALIGNED
+
901 (tp
->rx_opt
.eff_sacks
* TCPOLEN_SACK_PERBLOCK
));
903 #ifdef CONFIG_TCP_MD5SIG
904 if (tp
->af_specific
->md5_lookup(sk
, sk
))
905 mss_now
-= TCPOLEN_MD5SIG_ALIGNED
;
908 xmit_size_goal
= mss_now
;
911 xmit_size_goal
= (65535 -
912 inet_csk(sk
)->icsk_af_ops
->net_header_len
-
913 inet_csk(sk
)->icsk_ext_hdr_len
-
916 if (tp
->max_window
&&
917 (xmit_size_goal
> (tp
->max_window
>> 1)))
918 xmit_size_goal
= max((tp
->max_window
>> 1),
919 68U - tp
->tcp_header_len
);
921 xmit_size_goal
-= (xmit_size_goal
% mss_now
);
923 tp
->xmit_size_goal
= xmit_size_goal
;
928 /* Congestion window validation. (RFC2861) */
930 static void tcp_cwnd_validate(struct sock
*sk
, struct tcp_sock
*tp
)
932 __u32 packets_out
= tp
->packets_out
;
934 if (packets_out
>= tp
->snd_cwnd
) {
935 /* Network is feed fully. */
936 tp
->snd_cwnd_used
= 0;
937 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
939 /* Network starves. */
940 if (tp
->packets_out
> tp
->snd_cwnd_used
)
941 tp
->snd_cwnd_used
= tp
->packets_out
;
943 if (sysctl_tcp_slow_start_after_idle
&&
944 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
945 tcp_cwnd_application_limited(sk
);
949 static unsigned int tcp_window_allows(struct tcp_sock
*tp
, struct sk_buff
*skb
, unsigned int mss_now
, unsigned int cwnd
)
951 u32 window
, cwnd_len
;
953 window
= (tp
->snd_una
+ tp
->snd_wnd
- TCP_SKB_CB(skb
)->seq
);
954 cwnd_len
= mss_now
* cwnd
;
955 return min(window
, cwnd_len
);
958 /* Can at least one segment of SKB be sent right now, according to the
959 * congestion window rules? If so, return how many segments are allowed.
961 static inline unsigned int tcp_cwnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
)
965 /* Don't be strict about the congestion window for the final FIN. */
966 if ((TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
967 tcp_skb_pcount(skb
) == 1)
970 in_flight
= tcp_packets_in_flight(tp
);
972 if (in_flight
< cwnd
)
973 return (cwnd
- in_flight
);
978 /* This must be invoked the first time we consider transmitting
981 static int tcp_init_tso_segs(struct sock
*sk
, struct sk_buff
*skb
, unsigned int mss_now
)
983 int tso_segs
= tcp_skb_pcount(skb
);
987 tcp_skb_mss(skb
) != mss_now
)) {
988 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
989 tso_segs
= tcp_skb_pcount(skb
);
994 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
996 return after(tp
->snd_sml
,tp
->snd_una
) &&
997 !after(tp
->snd_sml
, tp
->snd_nxt
);
1000 /* Return 0, if packet can be sent now without violation Nagle's rules:
1001 * 1. It is full sized.
1002 * 2. Or it contains FIN. (already checked by caller)
1003 * 3. Or TCP_NODELAY was set.
1004 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1005 * With Minshall's modification: all sent small packets are ACKed.
1008 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
1009 const struct sk_buff
*skb
,
1010 unsigned mss_now
, int nonagle
)
1012 return (skb
->len
< mss_now
&&
1013 ((nonagle
&TCP_NAGLE_CORK
) ||
1016 tcp_minshall_check(tp
))));
1019 /* Return non-zero if the Nagle test allows this packet to be
1022 static inline int tcp_nagle_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1023 unsigned int cur_mss
, int nonagle
)
1025 /* Nagle rule does not apply to frames, which sit in the middle of the
1026 * write_queue (they have no chances to get new data).
1028 * This is implemented in the callers, where they modify the 'nonagle'
1029 * argument based upon the location of SKB in the send queue.
1031 if (nonagle
& TCP_NAGLE_PUSH
)
1034 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1036 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
))
1039 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
1045 /* Does at least the first segment of SKB fit into the send window? */
1046 static inline int tcp_snd_wnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
, unsigned int cur_mss
)
1048 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1050 if (skb
->len
> cur_mss
)
1051 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1053 return !after(end_seq
, tp
->snd_una
+ tp
->snd_wnd
);
1056 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1057 * should be put on the wire right now. If so, it returns the number of
1058 * packets allowed by the congestion window.
1060 static unsigned int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
1061 unsigned int cur_mss
, int nonagle
)
1063 struct tcp_sock
*tp
= tcp_sk(sk
);
1064 unsigned int cwnd_quota
;
1066 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1068 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1071 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1073 !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1079 int tcp_may_send_now(struct sock
*sk
, struct tcp_sock
*tp
)
1081 struct sk_buff
*skb
= tcp_send_head(sk
);
1084 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
, 1),
1085 (tcp_skb_is_last(sk
, skb
) ?
1090 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1091 * which is put after SKB on the list. It is very much like
1092 * tcp_fragment() except that it may make several kinds of assumptions
1093 * in order to speed up the splitting operation. In particular, we
1094 * know that all the data is in scatter-gather pages, and that the
1095 * packet has never been sent out before (and thus is not cloned).
1097 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
, unsigned int mss_now
)
1099 struct sk_buff
*buff
;
1100 int nlen
= skb
->len
- len
;
1103 /* All of a TSO frame must be composed of paged data. */
1104 if (skb
->len
!= skb
->data_len
)
1105 return tcp_fragment(sk
, skb
, len
, mss_now
);
1107 buff
= sk_stream_alloc_pskb(sk
, 0, 0, GFP_ATOMIC
);
1108 if (unlikely(buff
== NULL
))
1111 sk_charge_skb(sk
, buff
);
1112 buff
->truesize
+= nlen
;
1113 skb
->truesize
-= nlen
;
1115 /* Correct the sequence numbers. */
1116 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1117 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1118 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1120 /* PSH and FIN should only be set in the second packet. */
1121 flags
= TCP_SKB_CB(skb
)->flags
;
1122 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
1123 TCP_SKB_CB(buff
)->flags
= flags
;
1125 /* This packet was never sent out yet, so no SACK bits. */
1126 TCP_SKB_CB(buff
)->sacked
= 0;
1128 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1129 skb_split(skb
, buff
, len
);
1131 /* Fix up tso_factor for both original and new SKB. */
1132 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1133 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1135 /* Link BUFF into the send queue. */
1136 skb_header_release(buff
);
1137 tcp_insert_write_queue_after(skb
, buff
, sk
);
1142 /* Try to defer sending, if possible, in order to minimize the amount
1143 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1145 * This algorithm is from John Heffner.
1147 static int tcp_tso_should_defer(struct sock
*sk
, struct tcp_sock
*tp
, struct sk_buff
*skb
)
1149 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1150 u32 send_win
, cong_win
, limit
, in_flight
;
1152 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
1155 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1158 /* Defer for less than two clock ticks. */
1159 if (!tp
->tso_deferred
&& ((jiffies
<<1)>>1) - (tp
->tso_deferred
>>1) > 1)
1162 in_flight
= tcp_packets_in_flight(tp
);
1164 BUG_ON(tcp_skb_pcount(skb
) <= 1 ||
1165 (tp
->snd_cwnd
<= in_flight
));
1167 send_win
= (tp
->snd_una
+ tp
->snd_wnd
) - TCP_SKB_CB(skb
)->seq
;
1169 /* From in_flight test above, we know that cwnd > in_flight. */
1170 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1172 limit
= min(send_win
, cong_win
);
1174 /* If a full-sized TSO skb can be sent, do it. */
1178 if (sysctl_tcp_tso_win_divisor
) {
1179 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1181 /* If at least some fraction of a window is available,
1184 chunk
/= sysctl_tcp_tso_win_divisor
;
1188 /* Different approach, try not to defer past a single
1189 * ACK. Receiver should ACK every other full sized
1190 * frame, so if we have space for more than 3 frames
1193 if (limit
> tcp_max_burst(tp
) * tp
->mss_cache
)
1197 /* Ok, it looks like it is advisable to defer. */
1198 tp
->tso_deferred
= 1 | (jiffies
<<1);
1203 tp
->tso_deferred
= 0;
1207 /* Create a new MTU probe if we are ready.
1208 * Returns 0 if we should wait to probe (no cwnd available),
1209 * 1 if a probe was sent,
1211 static int tcp_mtu_probe(struct sock
*sk
)
1213 struct tcp_sock
*tp
= tcp_sk(sk
);
1214 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1215 struct sk_buff
*skb
, *nskb
, *next
;
1222 /* Not currently probing/verifying,
1224 * have enough cwnd, and
1225 * not SACKing (the variable headers throw things off) */
1226 if (!icsk
->icsk_mtup
.enabled
||
1227 icsk
->icsk_mtup
.probe_size
||
1228 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1229 tp
->snd_cwnd
< 11 ||
1230 tp
->rx_opt
.eff_sacks
)
1233 /* Very simple search strategy: just double the MSS. */
1234 mss_now
= tcp_current_mss(sk
, 0);
1235 probe_size
= 2*tp
->mss_cache
;
1236 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1237 /* TODO: set timer for probe_converge_event */
1241 /* Have enough data in the send queue to probe? */
1243 if ((skb
= tcp_send_head(sk
)) == NULL
)
1245 while ((len
+= skb
->len
) < probe_size
&& !tcp_skb_is_last(sk
, skb
))
1246 skb
= tcp_write_queue_next(sk
, skb
);
1247 if (len
< probe_size
)
1250 /* Receive window check. */
1251 if (after(TCP_SKB_CB(skb
)->seq
+ probe_size
, tp
->snd_una
+ tp
->snd_wnd
)) {
1252 if (tp
->snd_wnd
< probe_size
)
1258 /* Do we need to wait to drain cwnd? */
1259 pif
= tcp_packets_in_flight(tp
);
1260 if (pif
+ 2 > tp
->snd_cwnd
) {
1261 /* With no packets in flight, don't stall. */
1268 /* We're allowed to probe. Build it now. */
1269 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1271 sk_charge_skb(sk
, nskb
);
1273 skb
= tcp_send_head(sk
);
1274 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1275 tcp_advance_send_head(sk
, skb
);
1277 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1278 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1279 TCP_SKB_CB(nskb
)->flags
= TCPCB_FLAG_ACK
;
1280 TCP_SKB_CB(nskb
)->sacked
= 0;
1282 nskb
->ip_summed
= skb
->ip_summed
;
1285 while (len
< probe_size
) {
1286 next
= tcp_write_queue_next(sk
, skb
);
1288 copy
= min_t(int, skb
->len
, probe_size
- len
);
1289 if (nskb
->ip_summed
)
1290 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1292 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1293 skb_put(nskb
, copy
), copy
, nskb
->csum
);
1295 if (skb
->len
<= copy
) {
1296 /* We've eaten all the data from this skb.
1298 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
;
1299 tcp_unlink_write_queue(skb
, sk
);
1300 sk_stream_free_skb(sk
, skb
);
1302 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
&
1303 ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
1304 if (!skb_shinfo(skb
)->nr_frags
) {
1305 skb_pull(skb
, copy
);
1306 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1307 skb
->csum
= csum_partial(skb
->data
, skb
->len
, 0);
1309 __pskb_trim_head(skb
, copy
);
1310 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1312 TCP_SKB_CB(skb
)->seq
+= copy
;
1318 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1320 /* We're ready to send. If this fails, the probe will
1321 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1322 TCP_SKB_CB(nskb
)->when
= tcp_time_stamp
;
1323 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1324 /* Decrement cwnd here because we are sending
1325 * effectively two packets. */
1327 update_send_head(sk
, tp
, nskb
);
1329 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1330 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1331 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1340 /* This routine writes packets to the network. It advances the
1341 * send_head. This happens as incoming acks open up the remote
1344 * Returns 1, if no segments are in flight and we have queued segments, but
1345 * cannot send anything now because of SWS or another problem.
1347 static int tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
)
1349 struct tcp_sock
*tp
= tcp_sk(sk
);
1350 struct sk_buff
*skb
;
1351 unsigned int tso_segs
, sent_pkts
;
1355 /* If we are closed, the bytes will have to remain here.
1356 * In time closedown will finish, we empty the write queue and all
1359 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
1364 /* Do MTU probing. */
1365 if ((result
= tcp_mtu_probe(sk
)) == 0) {
1367 } else if (result
> 0) {
1371 while ((skb
= tcp_send_head(sk
))) {
1374 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1377 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1381 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1384 if (tso_segs
== 1) {
1385 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1386 (tcp_skb_is_last(sk
, skb
) ?
1387 nonagle
: TCP_NAGLE_PUSH
))))
1390 if (tcp_tso_should_defer(sk
, tp
, skb
))
1396 limit
= tcp_window_allows(tp
, skb
,
1397 mss_now
, cwnd_quota
);
1399 if (skb
->len
< limit
) {
1400 unsigned int trim
= skb
->len
% mss_now
;
1403 limit
= skb
->len
- trim
;
1407 if (skb
->len
> limit
&&
1408 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1411 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1413 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
)))
1416 /* Advance the send_head. This one is sent out.
1417 * This call will increment packets_out.
1419 update_send_head(sk
, tp
, skb
);
1421 tcp_minshall_update(tp
, mss_now
, skb
);
1425 if (likely(sent_pkts
)) {
1426 tcp_cwnd_validate(sk
, tp
);
1429 return !tp
->packets_out
&& tcp_send_head(sk
);
1432 /* Push out any pending frames which were held back due to
1433 * TCP_CORK or attempt at coalescing tiny packets.
1434 * The socket must be locked by the caller.
1436 void __tcp_push_pending_frames(struct sock
*sk
, struct tcp_sock
*tp
,
1437 unsigned int cur_mss
, int nonagle
)
1439 struct sk_buff
*skb
= tcp_send_head(sk
);
1442 if (tcp_write_xmit(sk
, cur_mss
, nonagle
))
1443 tcp_check_probe_timer(sk
, tp
);
1447 /* Send _single_ skb sitting at the send head. This function requires
1448 * true push pending frames to setup probe timer etc.
1450 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
1452 struct tcp_sock
*tp
= tcp_sk(sk
);
1453 struct sk_buff
*skb
= tcp_send_head(sk
);
1454 unsigned int tso_segs
, cwnd_quota
;
1456 BUG_ON(!skb
|| skb
->len
< mss_now
);
1458 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1459 cwnd_quota
= tcp_snd_test(sk
, skb
, mss_now
, TCP_NAGLE_PUSH
);
1461 if (likely(cwnd_quota
)) {
1468 limit
= tcp_window_allows(tp
, skb
,
1469 mss_now
, cwnd_quota
);
1471 if (skb
->len
< limit
) {
1472 unsigned int trim
= skb
->len
% mss_now
;
1475 limit
= skb
->len
- trim
;
1479 if (skb
->len
> limit
&&
1480 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1483 /* Send it out now. */
1484 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1486 if (likely(!tcp_transmit_skb(sk
, skb
, 1, sk
->sk_allocation
))) {
1487 update_send_head(sk
, tp
, skb
);
1488 tcp_cwnd_validate(sk
, tp
);
1494 /* This function returns the amount that we can raise the
1495 * usable window based on the following constraints
1497 * 1. The window can never be shrunk once it is offered (RFC 793)
1498 * 2. We limit memory per socket
1501 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1502 * RECV.NEXT + RCV.WIN fixed until:
1503 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1505 * i.e. don't raise the right edge of the window until you can raise
1506 * it at least MSS bytes.
1508 * Unfortunately, the recommended algorithm breaks header prediction,
1509 * since header prediction assumes th->window stays fixed.
1511 * Strictly speaking, keeping th->window fixed violates the receiver
1512 * side SWS prevention criteria. The problem is that under this rule
1513 * a stream of single byte packets will cause the right side of the
1514 * window to always advance by a single byte.
1516 * Of course, if the sender implements sender side SWS prevention
1517 * then this will not be a problem.
1519 * BSD seems to make the following compromise:
1521 * If the free space is less than the 1/4 of the maximum
1522 * space available and the free space is less than 1/2 mss,
1523 * then set the window to 0.
1524 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1525 * Otherwise, just prevent the window from shrinking
1526 * and from being larger than the largest representable value.
1528 * This prevents incremental opening of the window in the regime
1529 * where TCP is limited by the speed of the reader side taking
1530 * data out of the TCP receive queue. It does nothing about
1531 * those cases where the window is constrained on the sender side
1532 * because the pipeline is full.
1534 * BSD also seems to "accidentally" limit itself to windows that are a
1535 * multiple of MSS, at least until the free space gets quite small.
1536 * This would appear to be a side effect of the mbuf implementation.
1537 * Combining these two algorithms results in the observed behavior
1538 * of having a fixed window size at almost all times.
1540 * Below we obtain similar behavior by forcing the offered window to
1541 * a multiple of the mss when it is feasible to do so.
1543 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1544 * Regular options like TIMESTAMP are taken into account.
1546 u32
__tcp_select_window(struct sock
*sk
)
1548 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1549 struct tcp_sock
*tp
= tcp_sk(sk
);
1550 /* MSS for the peer's data. Previous versions used mss_clamp
1551 * here. I don't know if the value based on our guesses
1552 * of peer's MSS is better for the performance. It's more correct
1553 * but may be worse for the performance because of rcv_mss
1554 * fluctuations. --SAW 1998/11/1
1556 int mss
= icsk
->icsk_ack
.rcv_mss
;
1557 int free_space
= tcp_space(sk
);
1558 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
1561 if (mss
> full_space
)
1564 if (free_space
< full_space
/2) {
1565 icsk
->icsk_ack
.quick
= 0;
1567 if (tcp_memory_pressure
)
1568 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
, 4U*tp
->advmss
);
1570 if (free_space
< mss
)
1574 if (free_space
> tp
->rcv_ssthresh
)
1575 free_space
= tp
->rcv_ssthresh
;
1577 /* Don't do rounding if we are using window scaling, since the
1578 * scaled window will not line up with the MSS boundary anyway.
1580 window
= tp
->rcv_wnd
;
1581 if (tp
->rx_opt
.rcv_wscale
) {
1582 window
= free_space
;
1584 /* Advertise enough space so that it won't get scaled away.
1585 * Import case: prevent zero window announcement if
1586 * 1<<rcv_wscale > mss.
1588 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1589 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1590 << tp
->rx_opt
.rcv_wscale
);
1592 /* Get the largest window that is a nice multiple of mss.
1593 * Window clamp already applied above.
1594 * If our current window offering is within 1 mss of the
1595 * free space we just keep it. This prevents the divide
1596 * and multiply from happening most of the time.
1597 * We also don't do any window rounding when the free space
1600 if (window
<= free_space
- mss
|| window
> free_space
)
1601 window
= (free_space
/mss
)*mss
;
1602 else if (mss
== full_space
&&
1603 free_space
> window
+ full_space
/2)
1604 window
= free_space
;
1610 /* Attempt to collapse two adjacent SKB's during retransmission. */
1611 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*skb
, int mss_now
)
1613 struct tcp_sock
*tp
= tcp_sk(sk
);
1614 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
1616 /* The first test we must make is that neither of these two
1617 * SKB's are still referenced by someone else.
1619 if (!skb_cloned(skb
) && !skb_cloned(next_skb
)) {
1620 int skb_size
= skb
->len
, next_skb_size
= next_skb
->len
;
1621 u16 flags
= TCP_SKB_CB(skb
)->flags
;
1623 /* Also punt if next skb has been SACK'd. */
1624 if (TCP_SKB_CB(next_skb
)->sacked
& TCPCB_SACKED_ACKED
)
1627 /* Next skb is out of window. */
1628 if (after(TCP_SKB_CB(next_skb
)->end_seq
, tp
->snd_una
+tp
->snd_wnd
))
1631 /* Punt if not enough space exists in the first SKB for
1632 * the data in the second, or the total combined payload
1633 * would exceed the MSS.
1635 if ((next_skb_size
> skb_tailroom(skb
)) ||
1636 ((skb_size
+ next_skb_size
) > mss_now
))
1639 BUG_ON(tcp_skb_pcount(skb
) != 1 ||
1640 tcp_skb_pcount(next_skb
) != 1);
1642 /* changing transmit queue under us so clear hints */
1643 clear_all_retrans_hints(tp
);
1645 /* Ok. We will be able to collapse the packet. */
1646 tcp_unlink_write_queue(next_skb
, sk
);
1648 skb_copy_from_linear_data(next_skb
,
1649 skb_put(skb
, next_skb_size
),
1652 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
1653 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1655 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1656 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1658 /* Update sequence range on original skb. */
1659 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1661 /* Merge over control information. */
1662 flags
|= TCP_SKB_CB(next_skb
)->flags
; /* This moves PSH/FIN etc. over */
1663 TCP_SKB_CB(skb
)->flags
= flags
;
1665 /* All done, get rid of second SKB and account for it so
1666 * packet counting does not break.
1668 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
&(TCPCB_EVER_RETRANS
|TCPCB_AT_TAIL
);
1669 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_SACKED_RETRANS
)
1670 tp
->retrans_out
-= tcp_skb_pcount(next_skb
);
1671 if (TCP_SKB_CB(next_skb
)->sacked
&TCPCB_LOST
) {
1672 tp
->lost_out
-= tcp_skb_pcount(next_skb
);
1673 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1675 /* Reno case is special. Sigh... */
1676 if (!tp
->rx_opt
.sack_ok
&& tp
->sacked_out
) {
1677 tcp_dec_pcount_approx(&tp
->sacked_out
, next_skb
);
1678 tp
->left_out
-= tcp_skb_pcount(next_skb
);
1681 /* Not quite right: it can be > snd.fack, but
1682 * it is better to underestimate fackets.
1684 tcp_dec_pcount_approx(&tp
->fackets_out
, next_skb
);
1685 tcp_packets_out_dec(tp
, next_skb
);
1686 sk_stream_free_skb(sk
, next_skb
);
1690 /* Do a simple retransmit without using the backoff mechanisms in
1691 * tcp_timer. This is used for path mtu discovery.
1692 * The socket is already locked here.
1694 void tcp_simple_retransmit(struct sock
*sk
)
1696 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1697 struct tcp_sock
*tp
= tcp_sk(sk
);
1698 struct sk_buff
*skb
;
1699 unsigned int mss
= tcp_current_mss(sk
, 0);
1702 tcp_for_write_queue(skb
, sk
) {
1703 if (skb
== tcp_send_head(sk
))
1705 if (skb
->len
> mss
&&
1706 !(TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_ACKED
)) {
1707 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1708 TCP_SKB_CB(skb
)->sacked
&= ~TCPCB_SACKED_RETRANS
;
1709 tp
->retrans_out
-= tcp_skb_pcount(skb
);
1711 if (!(TCP_SKB_CB(skb
)->sacked
&TCPCB_LOST
)) {
1712 TCP_SKB_CB(skb
)->sacked
|= TCPCB_LOST
;
1713 tp
->lost_out
+= tcp_skb_pcount(skb
);
1719 clear_all_retrans_hints(tp
);
1724 tcp_sync_left_out(tp
);
1726 /* Don't muck with the congestion window here.
1727 * Reason is that we do not increase amount of _data_
1728 * in network, but units changed and effective
1729 * cwnd/ssthresh really reduced now.
1731 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
) {
1732 tp
->high_seq
= tp
->snd_nxt
;
1733 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1734 tp
->prior_ssthresh
= 0;
1735 tp
->undo_marker
= 0;
1736 tcp_set_ca_state(sk
, TCP_CA_Loss
);
1738 tcp_xmit_retransmit_queue(sk
);
1741 /* This retransmits one SKB. Policy decisions and retransmit queue
1742 * state updates are done by the caller. Returns non-zero if an
1743 * error occurred which prevented the send.
1745 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
1747 struct tcp_sock
*tp
= tcp_sk(sk
);
1748 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1749 unsigned int cur_mss
= tcp_current_mss(sk
, 0);
1752 /* Inconslusive MTU probe */
1753 if (icsk
->icsk_mtup
.probe_size
) {
1754 icsk
->icsk_mtup
.probe_size
= 0;
1757 /* Do not sent more than we queued. 1/4 is reserved for possible
1758 * copying overhead: fragmentation, tunneling, mangling etc.
1760 if (atomic_read(&sk
->sk_wmem_alloc
) >
1761 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
1764 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
1765 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
1767 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
1771 /* If receiver has shrunk his window, and skb is out of
1772 * new window, do not retransmit it. The exception is the
1773 * case, when window is shrunk to zero. In this case
1774 * our retransmit serves as a zero window probe.
1776 if (!before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)
1777 && TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
1780 if (skb
->len
> cur_mss
) {
1781 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
1782 return -ENOMEM
; /* We'll try again later. */
1785 /* Collapse two adjacent packets if worthwhile and we can. */
1786 if (!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
) &&
1787 (skb
->len
< (cur_mss
>> 1)) &&
1788 (tcp_write_queue_next(sk
, skb
) != tcp_send_head(sk
)) &&
1789 (!tcp_skb_is_last(sk
, skb
)) &&
1790 (skb_shinfo(skb
)->nr_frags
== 0 && skb_shinfo(tcp_write_queue_next(sk
, skb
))->nr_frags
== 0) &&
1791 (tcp_skb_pcount(skb
) == 1 && tcp_skb_pcount(tcp_write_queue_next(sk
, skb
)) == 1) &&
1792 (sysctl_tcp_retrans_collapse
!= 0))
1793 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
1795 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
1796 return -EHOSTUNREACH
; /* Routing failure or similar. */
1798 /* Some Solaris stacks overoptimize and ignore the FIN on a
1799 * retransmit when old data is attached. So strip it off
1800 * since it is cheap to do so and saves bytes on the network.
1803 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1804 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
1805 if (!pskb_trim(skb
, 0)) {
1806 TCP_SKB_CB(skb
)->seq
= TCP_SKB_CB(skb
)->end_seq
- 1;
1807 skb_shinfo(skb
)->gso_segs
= 1;
1808 skb_shinfo(skb
)->gso_size
= 0;
1809 skb_shinfo(skb
)->gso_type
= 0;
1810 skb
->ip_summed
= CHECKSUM_NONE
;
1815 /* Make a copy, if the first transmission SKB clone we made
1816 * is still in somebody's hands, else make a clone.
1818 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1820 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
1823 /* Update global TCP statistics. */
1824 TCP_INC_STATS(TCP_MIB_RETRANSSEGS
);
1826 tp
->total_retrans
++;
1828 #if FASTRETRANS_DEBUG > 0
1829 if (TCP_SKB_CB(skb
)->sacked
&TCPCB_SACKED_RETRANS
) {
1830 if (net_ratelimit())
1831 printk(KERN_DEBUG
"retrans_out leaked.\n");
1834 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
1835 tp
->retrans_out
+= tcp_skb_pcount(skb
);
1837 /* Save stamp of the first retransmit. */
1838 if (!tp
->retrans_stamp
)
1839 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
1843 /* snd_nxt is stored to detect loss of retransmitted segment,
1844 * see tcp_input.c tcp_sacktag_write_queue().
1846 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
1851 /* This gets called after a retransmit timeout, and the initially
1852 * retransmitted data is acknowledged. It tries to continue
1853 * resending the rest of the retransmit queue, until either
1854 * we've sent it all or the congestion window limit is reached.
1855 * If doing SACK, the first ACK which comes back for a timeout
1856 * based retransmit packet might feed us FACK information again.
1857 * If so, we use it to avoid unnecessarily retransmissions.
1859 void tcp_xmit_retransmit_queue(struct sock
*sk
)
1861 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1862 struct tcp_sock
*tp
= tcp_sk(sk
);
1863 struct sk_buff
*skb
;
1866 if (tp
->retransmit_skb_hint
) {
1867 skb
= tp
->retransmit_skb_hint
;
1868 packet_cnt
= tp
->retransmit_cnt_hint
;
1870 skb
= tcp_write_queue_head(sk
);
1874 /* First pass: retransmit lost packets. */
1876 tcp_for_write_queue_from(skb
, sk
) {
1877 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
1879 if (skb
== tcp_send_head(sk
))
1881 /* we could do better than to assign each time */
1882 tp
->retransmit_skb_hint
= skb
;
1883 tp
->retransmit_cnt_hint
= packet_cnt
;
1885 /* Assume this retransmit will generate
1886 * only one packet for congestion window
1887 * calculation purposes. This works because
1888 * tcp_retransmit_skb() will chop up the
1889 * packet to be MSS sized and all the
1890 * packet counting works out.
1892 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1895 if (sacked
& TCPCB_LOST
) {
1896 if (!(sacked
&(TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))) {
1897 if (tcp_retransmit_skb(sk
, skb
)) {
1898 tp
->retransmit_skb_hint
= NULL
;
1901 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
1902 NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS
);
1904 NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS
);
1906 if (skb
== tcp_write_queue_head(sk
))
1907 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1908 inet_csk(sk
)->icsk_rto
,
1912 packet_cnt
+= tcp_skb_pcount(skb
);
1913 if (packet_cnt
>= tp
->lost_out
)
1919 /* OK, demanded retransmission is finished. */
1921 /* Forward retransmissions are possible only during Recovery. */
1922 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
1925 /* No forward retransmissions in Reno are possible. */
1926 if (!tp
->rx_opt
.sack_ok
)
1929 /* Yeah, we have to make difficult choice between forward transmission
1930 * and retransmission... Both ways have their merits...
1932 * For now we do not retransmit anything, while we have some new
1936 if (tcp_may_send_now(sk
, tp
))
1939 if (tp
->forward_skb_hint
) {
1940 skb
= tp
->forward_skb_hint
;
1941 packet_cnt
= tp
->forward_cnt_hint
;
1943 skb
= tcp_write_queue_head(sk
);
1947 tcp_for_write_queue_from(skb
, sk
) {
1948 if (skb
== tcp_send_head(sk
))
1950 tp
->forward_cnt_hint
= packet_cnt
;
1951 tp
->forward_skb_hint
= skb
;
1953 /* Similar to the retransmit loop above we
1954 * can pretend that the retransmitted SKB
1955 * we send out here will be composed of one
1956 * real MSS sized packet because tcp_retransmit_skb()
1957 * will fragment it if necessary.
1959 if (++packet_cnt
> tp
->fackets_out
)
1962 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
1965 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_TAGBITS
)
1968 /* Ok, retransmit it. */
1969 if (tcp_retransmit_skb(sk
, skb
)) {
1970 tp
->forward_skb_hint
= NULL
;
1974 if (skb
== tcp_write_queue_head(sk
))
1975 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
1976 inet_csk(sk
)->icsk_rto
,
1979 NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS
);
1984 /* Send a fin. The caller locks the socket for us. This cannot be
1985 * allowed to fail queueing a FIN frame under any circumstances.
1987 void tcp_send_fin(struct sock
*sk
)
1989 struct tcp_sock
*tp
= tcp_sk(sk
);
1990 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
1993 /* Optimization, tack on the FIN if we have a queue of
1994 * unsent frames. But be careful about outgoing SACKS
1997 mss_now
= tcp_current_mss(sk
, 1);
1999 if (tcp_send_head(sk
) != NULL
) {
2000 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
2001 TCP_SKB_CB(skb
)->end_seq
++;
2004 /* Socket is locked, keep trying until memory is available. */
2006 skb
= alloc_skb_fclone(MAX_TCP_HEADER
, GFP_KERNEL
);
2012 /* Reserve space for headers and prepare control bits. */
2013 skb_reserve(skb
, MAX_TCP_HEADER
);
2015 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
2016 TCP_SKB_CB(skb
)->sacked
= 0;
2017 skb_shinfo(skb
)->gso_segs
= 1;
2018 skb_shinfo(skb
)->gso_size
= 0;
2019 skb_shinfo(skb
)->gso_type
= 0;
2021 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2022 TCP_SKB_CB(skb
)->seq
= tp
->write_seq
;
2023 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
2024 tcp_queue_skb(sk
, skb
);
2026 __tcp_push_pending_frames(sk
, tp
, mss_now
, TCP_NAGLE_OFF
);
2029 /* We get here when a process closes a file descriptor (either due to
2030 * an explicit close() or as a byproduct of exit()'ing) and there
2031 * was unread data in the receive queue. This behavior is recommended
2032 * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM
2034 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2036 struct tcp_sock
*tp
= tcp_sk(sk
);
2037 struct sk_buff
*skb
;
2039 /* NOTE: No TCP options attached and we never retransmit this. */
2040 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2042 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
2046 /* Reserve space for headers and prepare control bits. */
2047 skb_reserve(skb
, MAX_TCP_HEADER
);
2049 TCP_SKB_CB(skb
)->flags
= (TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
2050 TCP_SKB_CB(skb
)->sacked
= 0;
2051 skb_shinfo(skb
)->gso_segs
= 1;
2052 skb_shinfo(skb
)->gso_size
= 0;
2053 skb_shinfo(skb
)->gso_type
= 0;
2056 TCP_SKB_CB(skb
)->seq
= tcp_acceptable_seq(sk
, tp
);
2057 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
2058 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2059 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2060 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED
);
2063 /* WARNING: This routine must only be called when we have already sent
2064 * a SYN packet that crossed the incoming SYN that caused this routine
2065 * to get called. If this assumption fails then the initial rcv_wnd
2066 * and rcv_wscale values will not be correct.
2068 int tcp_send_synack(struct sock
*sk
)
2070 struct sk_buff
* skb
;
2072 skb
= tcp_write_queue_head(sk
);
2073 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_SYN
)) {
2074 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
2077 if (!(TCP_SKB_CB(skb
)->flags
&TCPCB_FLAG_ACK
)) {
2078 if (skb_cloned(skb
)) {
2079 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2082 tcp_unlink_write_queue(skb
, sk
);
2083 skb_header_release(nskb
);
2084 __tcp_add_write_queue_head(sk
, nskb
);
2085 sk_stream_free_skb(sk
, skb
);
2086 sk_charge_skb(sk
, nskb
);
2090 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
2091 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2093 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2094 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2098 * Prepare a SYN-ACK.
2100 struct sk_buff
* tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2101 struct request_sock
*req
)
2103 struct inet_request_sock
*ireq
= inet_rsk(req
);
2104 struct tcp_sock
*tp
= tcp_sk(sk
);
2106 int tcp_header_size
;
2107 struct sk_buff
*skb
;
2108 #ifdef CONFIG_TCP_MD5SIG
2109 struct tcp_md5sig_key
*md5
;
2110 __u8
*md5_hash_location
;
2113 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
2117 /* Reserve space for headers. */
2118 skb_reserve(skb
, MAX_TCP_HEADER
);
2120 skb
->dst
= dst_clone(dst
);
2122 tcp_header_size
= (sizeof(struct tcphdr
) + TCPOLEN_MSS
+
2123 (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0) +
2124 (ireq
->wscale_ok
? TCPOLEN_WSCALE_ALIGNED
: 0) +
2125 /* SACK_PERM is in the place of NOP NOP of TS */
2126 ((ireq
->sack_ok
&& !ireq
->tstamp_ok
) ? TCPOLEN_SACKPERM_ALIGNED
: 0));
2128 #ifdef CONFIG_TCP_MD5SIG
2129 /* Are we doing MD5 on this segment? If so - make room for it */
2130 md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
2132 tcp_header_size
+= TCPOLEN_MD5SIG_ALIGNED
;
2134 skb_push(skb
, tcp_header_size
);
2135 skb_reset_transport_header(skb
);
2138 memset(th
, 0, sizeof(struct tcphdr
));
2141 TCP_ECN_make_synack(req
, th
);
2142 th
->source
= inet_sk(sk
)->sport
;
2143 th
->dest
= ireq
->rmt_port
;
2144 TCP_SKB_CB(skb
)->seq
= tcp_rsk(req
)->snt_isn
;
2145 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ 1;
2146 TCP_SKB_CB(skb
)->sacked
= 0;
2147 skb_shinfo(skb
)->gso_segs
= 1;
2148 skb_shinfo(skb
)->gso_size
= 0;
2149 skb_shinfo(skb
)->gso_type
= 0;
2150 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2151 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
2152 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
2154 /* Set this up on the first call only */
2155 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
2156 /* tcp_full_space because it is guaranteed to be the first packet */
2157 tcp_select_initial_window(tcp_full_space(sk
),
2158 dst_metric(dst
, RTAX_ADVMSS
) - (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
2163 ireq
->rcv_wscale
= rcv_wscale
;
2166 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2167 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2169 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2170 tcp_syn_build_options((__be32
*)(th
+ 1), dst_metric(dst
, RTAX_ADVMSS
), ireq
->tstamp_ok
,
2171 ireq
->sack_ok
, ireq
->wscale_ok
, ireq
->rcv_wscale
,
2172 TCP_SKB_CB(skb
)->when
,
2175 #ifdef CONFIG_TCP_MD5SIG
2176 md5
? &md5_hash_location
:
2182 th
->doff
= (tcp_header_size
>> 2);
2183 TCP_INC_STATS(TCP_MIB_OUTSEGS
);
2185 #ifdef CONFIG_TCP_MD5SIG
2186 /* Okay, we have all we need - do the md5 hash if needed */
2188 tp
->af_specific
->calc_md5_hash(md5_hash_location
,
2191 tcp_hdr(skb
), sk
->sk_protocol
,
2200 * Do all connect socket setups that can be done AF independent.
2202 static void tcp_connect_init(struct sock
*sk
)
2204 struct dst_entry
*dst
= __sk_dst_get(sk
);
2205 struct tcp_sock
*tp
= tcp_sk(sk
);
2208 /* We'll fix this up when we get a response from the other end.
2209 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2211 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2212 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2214 #ifdef CONFIG_TCP_MD5SIG
2215 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2216 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2219 /* If user gave his TCP_MAXSEG, record it to clamp */
2220 if (tp
->rx_opt
.user_mss
)
2221 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2224 tcp_sync_mss(sk
, dst_mtu(dst
));
2226 if (!tp
->window_clamp
)
2227 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2228 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
2229 tcp_initialize_rcv_mss(sk
);
2231 tcp_select_initial_window(tcp_full_space(sk
),
2232 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2235 sysctl_tcp_window_scaling
,
2238 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2239 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2242 sock_reset_flag(sk
, SOCK_DONE
);
2244 tcp_init_wl(tp
, tp
->write_seq
, 0);
2245 tp
->snd_una
= tp
->write_seq
;
2246 tp
->snd_sml
= tp
->write_seq
;
2251 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2252 inet_csk(sk
)->icsk_retransmits
= 0;
2253 tcp_clear_retrans(tp
);
2257 * Build a SYN and send it off.
2259 int tcp_connect(struct sock
*sk
)
2261 struct tcp_sock
*tp
= tcp_sk(sk
);
2262 struct sk_buff
*buff
;
2264 tcp_connect_init(sk
);
2266 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
2267 if (unlikely(buff
== NULL
))
2270 /* Reserve space for headers. */
2271 skb_reserve(buff
, MAX_TCP_HEADER
);
2273 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_SYN
;
2274 TCP_ECN_send_syn(sk
, tp
, buff
);
2275 TCP_SKB_CB(buff
)->sacked
= 0;
2276 skb_shinfo(buff
)->gso_segs
= 1;
2277 skb_shinfo(buff
)->gso_size
= 0;
2278 skb_shinfo(buff
)->gso_type
= 0;
2280 tp
->snd_nxt
= tp
->write_seq
;
2281 TCP_SKB_CB(buff
)->seq
= tp
->write_seq
++;
2282 TCP_SKB_CB(buff
)->end_seq
= tp
->write_seq
;
2285 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2286 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
2287 skb_header_release(buff
);
2288 __tcp_add_write_queue_tail(sk
, buff
);
2289 sk_charge_skb(sk
, buff
);
2290 tp
->packets_out
+= tcp_skb_pcount(buff
);
2291 tcp_transmit_skb(sk
, buff
, 1, GFP_KERNEL
);
2293 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2294 * in order to make this packet get counted in tcpOutSegs.
2296 tp
->snd_nxt
= tp
->write_seq
;
2297 tp
->pushed_seq
= tp
->write_seq
;
2298 TCP_INC_STATS(TCP_MIB_ACTIVEOPENS
);
2300 /* Timer for repeating the SYN until an answer. */
2301 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2302 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2306 /* Send out a delayed ack, the caller does the policy checking
2307 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2310 void tcp_send_delayed_ack(struct sock
*sk
)
2312 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2313 int ato
= icsk
->icsk_ack
.ato
;
2314 unsigned long timeout
;
2316 if (ato
> TCP_DELACK_MIN
) {
2317 const struct tcp_sock
*tp
= tcp_sk(sk
);
2320 if (icsk
->icsk_ack
.pingpong
|| (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
2321 max_ato
= TCP_DELACK_MAX
;
2323 /* Slow path, intersegment interval is "high". */
2325 /* If some rtt estimate is known, use it to bound delayed ack.
2326 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2330 int rtt
= max(tp
->srtt
>>3, TCP_DELACK_MIN
);
2336 ato
= min(ato
, max_ato
);
2339 /* Stay within the limit we were given */
2340 timeout
= jiffies
+ ato
;
2342 /* Use new timeout only if there wasn't a older one earlier. */
2343 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
2344 /* If delack timer was blocked or is about to expire,
2347 if (icsk
->icsk_ack
.blocked
||
2348 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
2353 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
2354 timeout
= icsk
->icsk_ack
.timeout
;
2356 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
2357 icsk
->icsk_ack
.timeout
= timeout
;
2358 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
2361 /* This routine sends an ack and also updates the window. */
2362 void tcp_send_ack(struct sock
*sk
)
2364 /* If we have been reset, we may not send again. */
2365 if (sk
->sk_state
!= TCP_CLOSE
) {
2366 struct tcp_sock
*tp
= tcp_sk(sk
);
2367 struct sk_buff
*buff
;
2369 /* We are not putting this on the write queue, so
2370 * tcp_transmit_skb() will set the ownership to this
2373 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2375 inet_csk_schedule_ack(sk
);
2376 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
2377 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
2378 TCP_DELACK_MAX
, TCP_RTO_MAX
);
2382 /* Reserve space for headers and prepare control bits. */
2383 skb_reserve(buff
, MAX_TCP_HEADER
);
2385 TCP_SKB_CB(buff
)->flags
= TCPCB_FLAG_ACK
;
2386 TCP_SKB_CB(buff
)->sacked
= 0;
2387 skb_shinfo(buff
)->gso_segs
= 1;
2388 skb_shinfo(buff
)->gso_size
= 0;
2389 skb_shinfo(buff
)->gso_type
= 0;
2391 /* Send it off, this clears delayed acks for us. */
2392 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(buff
)->end_seq
= tcp_acceptable_seq(sk
, tp
);
2393 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2394 tcp_transmit_skb(sk
, buff
, 0, GFP_ATOMIC
);
2398 /* This routine sends a packet with an out of date sequence
2399 * number. It assumes the other end will try to ack it.
2401 * Question: what should we make while urgent mode?
2402 * 4.4BSD forces sending single byte of data. We cannot send
2403 * out of window data, because we have SND.NXT==SND.MAX...
2405 * Current solution: to send TWO zero-length segments in urgent mode:
2406 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2407 * out-of-date with SND.UNA-1 to probe window.
2409 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
2411 struct tcp_sock
*tp
= tcp_sk(sk
);
2412 struct sk_buff
*skb
;
2414 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2415 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2419 /* Reserve space for headers and set control bits. */
2420 skb_reserve(skb
, MAX_TCP_HEADER
);
2422 TCP_SKB_CB(skb
)->flags
= TCPCB_FLAG_ACK
;
2423 TCP_SKB_CB(skb
)->sacked
= urgent
;
2424 skb_shinfo(skb
)->gso_segs
= 1;
2425 skb_shinfo(skb
)->gso_size
= 0;
2426 skb_shinfo(skb
)->gso_type
= 0;
2428 /* Use a previous sequence. This should cause the other
2429 * end to send an ack. Don't queue or clone SKB, just
2432 TCP_SKB_CB(skb
)->seq
= urgent
? tp
->snd_una
: tp
->snd_una
- 1;
2433 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(skb
)->seq
;
2434 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2435 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
2438 int tcp_write_wakeup(struct sock
*sk
)
2440 if (sk
->sk_state
!= TCP_CLOSE
) {
2441 struct tcp_sock
*tp
= tcp_sk(sk
);
2442 struct sk_buff
*skb
;
2444 if ((skb
= tcp_send_head(sk
)) != NULL
&&
2445 before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
+tp
->snd_wnd
)) {
2447 unsigned int mss
= tcp_current_mss(sk
, 0);
2448 unsigned int seg_size
= tp
->snd_una
+tp
->snd_wnd
-TCP_SKB_CB(skb
)->seq
;
2450 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
2451 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
2453 /* We are probing the opening of a window
2454 * but the window size is != 0
2455 * must have been a result SWS avoidance ( sender )
2457 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
2459 seg_size
= min(seg_size
, mss
);
2460 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2461 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
2463 } else if (!tcp_skb_pcount(skb
))
2464 tcp_set_skb_tso_segs(sk
, skb
, mss
);
2466 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2467 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2468 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2470 update_send_head(sk
, tp
, skb
);
2475 between(tp
->snd_up
, tp
->snd_una
+1, tp
->snd_una
+0xFFFF))
2476 tcp_xmit_probe_skb(sk
, TCPCB_URG
);
2477 return tcp_xmit_probe_skb(sk
, 0);
2483 /* A window probe timeout has occurred. If window is not closed send
2484 * a partial packet else a zero probe.
2486 void tcp_send_probe0(struct sock
*sk
)
2488 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2489 struct tcp_sock
*tp
= tcp_sk(sk
);
2492 err
= tcp_write_wakeup(sk
);
2494 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
2495 /* Cancel probe timer, if it is not required. */
2496 icsk
->icsk_probes_out
= 0;
2497 icsk
->icsk_backoff
= 0;
2502 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
2503 icsk
->icsk_backoff
++;
2504 icsk
->icsk_probes_out
++;
2505 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2506 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2509 /* If packet was not sent due to local congestion,
2510 * do not backoff and do not remember icsk_probes_out.
2511 * Let local senders to fight for local resources.
2513 * Use accumulated backoff yet.
2515 if (!icsk
->icsk_probes_out
)
2516 icsk
->icsk_probes_out
= 1;
2517 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2518 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
2519 TCP_RESOURCE_PROBE_INTERVAL
),
2524 EXPORT_SYMBOL(tcp_connect
);
2525 EXPORT_SYMBOL(tcp_make_synack
);
2526 EXPORT_SYMBOL(tcp_simple_retransmit
);
2527 EXPORT_SYMBOL(tcp_sync_mss
);
2528 EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor
);
2529 EXPORT_SYMBOL(tcp_mtup_init
);