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).
9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
10 * Mark Evans, <evansmp@uhura.aston.ac.uk>
11 * Corey Minyard <wf-rch!minyard@relay.EU.net>
12 * Florian La Roche, <flla@stud.uni-sb.de>
13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
14 * Linus Torvalds, <torvalds@cs.helsinki.fi>
15 * Alan Cox, <gw4pts@gw4pts.ampr.org>
16 * Matthew Dillon, <dillon@apollo.west.oic.com>
17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
18 * Jorge Cwik, <jorge@laser.satlink.net>
22 * Changes: Pedro Roque : Retransmit queue handled by TCP.
23 * : Fragmentation on mtu decrease
24 * : Segment collapse on retransmit
27 * Linus Torvalds : send_delayed_ack
28 * David S. Miller : Charge memory using the right skb
29 * during syn/ack processing.
30 * David S. Miller : Output engine completely rewritten.
31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
32 * Cacophonix Gaul : draft-minshall-nagle-01
33 * J Hadi Salim : ECN support
39 #include <linux/compiler.h>
40 #include <linux/gfp.h>
41 #include <linux/module.h>
43 /* People can turn this off for buggy TCP's found in printers etc. */
44 int sysctl_tcp_retrans_collapse __read_mostly
= 1;
46 /* People can turn this on to work with those rare, broken TCPs that
47 * interpret the window field as a signed quantity.
49 int sysctl_tcp_workaround_signed_windows __read_mostly
= 0;
51 /* This limits the percentage of the congestion window which we
52 * will allow a single TSO frame to consume. Building TSO frames
53 * which are too large can cause TCP streams to be bursty.
55 int sysctl_tcp_tso_win_divisor __read_mostly
= 3;
57 int sysctl_tcp_mtu_probing __read_mostly
= 0;
58 int sysctl_tcp_base_mss __read_mostly
= 512;
60 /* By default, RFC2861 behavior. */
61 int sysctl_tcp_slow_start_after_idle __read_mostly
= 1;
63 int sysctl_tcp_cookie_size __read_mostly
= 0; /* TCP_COOKIE_MAX */
64 EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size
);
67 /* Account for new data that has been sent to the network. */
68 static void tcp_event_new_data_sent(struct sock
*sk
, struct sk_buff
*skb
)
70 struct tcp_sock
*tp
= tcp_sk(sk
);
71 unsigned int prior_packets
= tp
->packets_out
;
73 tcp_advance_send_head(sk
, skb
);
74 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
76 /* Don't override Nagle indefinately with F-RTO */
77 if (tp
->frto_counter
== 2)
80 tp
->packets_out
+= tcp_skb_pcount(skb
);
82 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
83 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
86 /* SND.NXT, if window was not shrunk.
87 * If window has been shrunk, what should we make? It is not clear at all.
88 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
89 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
90 * invalid. OK, let's make this for now:
92 static inline __u32
tcp_acceptable_seq(struct sock
*sk
)
94 struct tcp_sock
*tp
= tcp_sk(sk
);
96 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
))
99 return tcp_wnd_end(tp
);
102 /* Calculate mss to advertise in SYN segment.
103 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
105 * 1. It is independent of path mtu.
106 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
107 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
108 * attached devices, because some buggy hosts are confused by
110 * 4. We do not make 3, we advertise MSS, calculated from first
111 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
112 * This may be overridden via information stored in routing table.
113 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
114 * probably even Jumbo".
116 static __u16
tcp_advertise_mss(struct sock
*sk
)
118 struct tcp_sock
*tp
= tcp_sk(sk
);
119 struct dst_entry
*dst
= __sk_dst_get(sk
);
120 int mss
= tp
->advmss
;
122 if (dst
&& dst_metric(dst
, RTAX_ADVMSS
) < mss
) {
123 mss
= dst_metric(dst
, RTAX_ADVMSS
);
130 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
131 * This is the first part of cwnd validation mechanism. */
132 static void tcp_cwnd_restart(struct sock
*sk
, struct dst_entry
*dst
)
134 struct tcp_sock
*tp
= tcp_sk(sk
);
135 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
136 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
137 u32 cwnd
= tp
->snd_cwnd
;
139 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
141 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
142 restart_cwnd
= min(restart_cwnd
, cwnd
);
144 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
146 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
147 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
148 tp
->snd_cwnd_used
= 0;
151 /* Congestion state accounting after a packet has been sent. */
152 static void tcp_event_data_sent(struct tcp_sock
*tp
,
153 struct sk_buff
*skb
, struct sock
*sk
)
155 struct inet_connection_sock
*icsk
= inet_csk(sk
);
156 const u32 now
= tcp_time_stamp
;
158 if (sysctl_tcp_slow_start_after_idle
&&
159 (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
))
160 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
164 /* If it is a reply for ato after last received
165 * packet, enter pingpong mode.
167 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
168 icsk
->icsk_ack
.pingpong
= 1;
171 /* Account for an ACK we sent. */
172 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
174 tcp_dec_quickack_mode(sk
, pkts
);
175 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
178 /* Determine a window scaling and initial window to offer.
179 * Based on the assumption that the given amount of space
180 * will be offered. Store the results in the tp structure.
181 * NOTE: for smooth operation initial space offering should
182 * be a multiple of mss if possible. We assume here that mss >= 1.
183 * This MUST be enforced by all callers.
185 void tcp_select_initial_window(int __space
, __u32 mss
,
186 __u32
*rcv_wnd
, __u32
*window_clamp
,
187 int wscale_ok
, __u8
*rcv_wscale
,
190 unsigned int space
= (__space
< 0 ? 0 : __space
);
192 /* If no clamp set the clamp to the max possible scaled window */
193 if (*window_clamp
== 0)
194 (*window_clamp
) = (65535 << 14);
195 space
= min(*window_clamp
, space
);
197 /* Quantize space offering to a multiple of mss if possible. */
199 space
= (space
/ mss
) * mss
;
201 /* NOTE: offering an initial window larger than 32767
202 * will break some buggy TCP stacks. If the admin tells us
203 * it is likely we could be speaking with such a buggy stack
204 * we will truncate our initial window offering to 32K-1
205 * unless the remote has sent us a window scaling option,
206 * which we interpret as a sign the remote TCP is not
207 * misinterpreting the window field as a signed quantity.
209 if (sysctl_tcp_workaround_signed_windows
)
210 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
216 /* Set window scaling on max possible window
217 * See RFC1323 for an explanation of the limit to 14
219 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
220 space
= min_t(u32
, space
, *window_clamp
);
221 while (space
> 65535 && (*rcv_wscale
) < 14) {
227 /* Set initial window to value enough for senders,
228 * following RFC2414. Senders, not following this RFC,
229 * will be satisfied with 2.
231 if (mss
> (1 << *rcv_wscale
)) {
237 /* when initializing use the value from init_rcv_wnd
238 * rather than the default from above
241 *rcv_wnd
= min(*rcv_wnd
, init_rcv_wnd
* mss
);
243 *rcv_wnd
= min(*rcv_wnd
, init_cwnd
* mss
);
246 /* Set the clamp no higher than max representable value */
247 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
250 /* Chose a new window to advertise, update state in tcp_sock for the
251 * socket, and return result with RFC1323 scaling applied. The return
252 * value can be stuffed directly into th->window for an outgoing
255 static u16
tcp_select_window(struct sock
*sk
)
257 struct tcp_sock
*tp
= tcp_sk(sk
);
258 u32 cur_win
= tcp_receive_window(tp
);
259 u32 new_win
= __tcp_select_window(sk
);
261 /* Never shrink the offered window */
262 if (new_win
< cur_win
) {
263 /* Danger Will Robinson!
264 * Don't update rcv_wup/rcv_wnd here or else
265 * we will not be able to advertise a zero
266 * window in time. --DaveM
268 * Relax Will Robinson.
270 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
272 tp
->rcv_wnd
= new_win
;
273 tp
->rcv_wup
= tp
->rcv_nxt
;
275 /* Make sure we do not exceed the maximum possible
278 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
279 new_win
= min(new_win
, MAX_TCP_WINDOW
);
281 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
283 /* RFC1323 scaling applied */
284 new_win
>>= tp
->rx_opt
.rcv_wscale
;
286 /* If we advertise zero window, disable fast path. */
293 /* Packet ECN state for a SYN-ACK */
294 static inline void TCP_ECN_send_synack(struct tcp_sock
*tp
, struct sk_buff
*skb
)
296 TCP_SKB_CB(skb
)->flags
&= ~TCPCB_FLAG_CWR
;
297 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
298 TCP_SKB_CB(skb
)->flags
&= ~TCPCB_FLAG_ECE
;
301 /* Packet ECN state for a SYN. */
302 static inline void TCP_ECN_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
304 struct tcp_sock
*tp
= tcp_sk(sk
);
307 if (sysctl_tcp_ecn
== 1) {
308 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ECE
| TCPCB_FLAG_CWR
;
309 tp
->ecn_flags
= TCP_ECN_OK
;
313 static __inline__
void
314 TCP_ECN_make_synack(struct request_sock
*req
, struct tcphdr
*th
)
316 if (inet_rsk(req
)->ecn_ok
)
320 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
323 static inline void TCP_ECN_send(struct sock
*sk
, struct sk_buff
*skb
,
326 struct tcp_sock
*tp
= tcp_sk(sk
);
328 if (tp
->ecn_flags
& TCP_ECN_OK
) {
329 /* Not-retransmitted data segment: set ECT and inject CWR. */
330 if (skb
->len
!= tcp_header_len
&&
331 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
333 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
334 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
335 tcp_hdr(skb
)->cwr
= 1;
336 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
339 /* ACK or retransmitted segment: clear ECT|CE */
340 INET_ECN_dontxmit(sk
);
342 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
343 tcp_hdr(skb
)->ece
= 1;
347 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
348 * auto increment end seqno.
350 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
354 TCP_SKB_CB(skb
)->flags
= flags
;
355 TCP_SKB_CB(skb
)->sacked
= 0;
357 skb_shinfo(skb
)->gso_segs
= 1;
358 skb_shinfo(skb
)->gso_size
= 0;
359 skb_shinfo(skb
)->gso_type
= 0;
361 TCP_SKB_CB(skb
)->seq
= seq
;
362 if (flags
& (TCPCB_FLAG_SYN
| TCPCB_FLAG_FIN
))
364 TCP_SKB_CB(skb
)->end_seq
= seq
;
367 static inline int tcp_urg_mode(const struct tcp_sock
*tp
)
369 return tp
->snd_una
!= tp
->snd_up
;
372 #define OPTION_SACK_ADVERTISE (1 << 0)
373 #define OPTION_TS (1 << 1)
374 #define OPTION_MD5 (1 << 2)
375 #define OPTION_WSCALE (1 << 3)
376 #define OPTION_COOKIE_EXTENSION (1 << 4)
378 struct tcp_out_options
{
379 u8 options
; /* bit field of OPTION_* */
380 u8 ws
; /* window scale, 0 to disable */
381 u8 num_sack_blocks
; /* number of SACK blocks to include */
382 u8 hash_size
; /* bytes in hash_location */
383 u16 mss
; /* 0 to disable */
384 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
385 __u8
*hash_location
; /* temporary pointer, overloaded */
388 /* The sysctl int routines are generic, so check consistency here.
390 static u8
tcp_cookie_size_check(u8 desired
)
393 /* previously specified */
396 if (sysctl_tcp_cookie_size
<= 0) {
397 /* no default specified */
400 if (sysctl_tcp_cookie_size
<= TCP_COOKIE_MIN
) {
401 /* value too small, specify minimum */
402 return TCP_COOKIE_MIN
;
404 if (sysctl_tcp_cookie_size
>= TCP_COOKIE_MAX
) {
405 /* value too large, specify maximum */
406 return TCP_COOKIE_MAX
;
408 if (0x1 & sysctl_tcp_cookie_size
) {
409 /* 8-bit multiple, illegal, fix it */
410 return (u8
)(sysctl_tcp_cookie_size
+ 0x1);
412 return (u8
)sysctl_tcp_cookie_size
;
415 /* Write previously computed TCP options to the packet.
417 * Beware: Something in the Internet is very sensitive to the ordering of
418 * TCP options, we learned this through the hard way, so be careful here.
419 * Luckily we can at least blame others for their non-compliance but from
420 * inter-operatibility perspective it seems that we're somewhat stuck with
421 * the ordering which we have been using if we want to keep working with
422 * those broken things (not that it currently hurts anybody as there isn't
423 * particular reason why the ordering would need to be changed).
425 * At least SACK_PERM as the first option is known to lead to a disaster
426 * (but it may well be that other scenarios fail similarly).
428 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
429 struct tcp_out_options
*opts
)
431 u8 options
= opts
->options
; /* mungable copy */
433 /* Having both authentication and cookies for security is redundant,
434 * and there's certainly not enough room. Instead, the cookie-less
435 * extension variant is proposed.
437 * Consider the pessimal case with authentication. The options
439 * COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40
441 if (unlikely(OPTION_MD5
& options
)) {
442 if (unlikely(OPTION_COOKIE_EXTENSION
& options
)) {
443 *ptr
++ = htonl((TCPOPT_COOKIE
<< 24) |
444 (TCPOLEN_COOKIE_BASE
<< 16) |
445 (TCPOPT_MD5SIG
<< 8) |
448 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
450 (TCPOPT_MD5SIG
<< 8) |
453 options
&= ~OPTION_COOKIE_EXTENSION
;
454 /* overload cookie hash location */
455 opts
->hash_location
= (__u8
*)ptr
;
459 if (unlikely(opts
->mss
)) {
460 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
461 (TCPOLEN_MSS
<< 16) |
465 if (likely(OPTION_TS
& options
)) {
466 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
467 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
468 (TCPOLEN_SACK_PERM
<< 16) |
469 (TCPOPT_TIMESTAMP
<< 8) |
471 options
&= ~OPTION_SACK_ADVERTISE
;
473 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
475 (TCPOPT_TIMESTAMP
<< 8) |
478 *ptr
++ = htonl(opts
->tsval
);
479 *ptr
++ = htonl(opts
->tsecr
);
482 /* Specification requires after timestamp, so do it now.
484 * Consider the pessimal case without authentication. The options
486 * MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40
488 if (unlikely(OPTION_COOKIE_EXTENSION
& options
)) {
489 __u8
*cookie_copy
= opts
->hash_location
;
490 u8 cookie_size
= opts
->hash_size
;
492 /* 8-bit multiple handled in tcp_cookie_size_check() above,
495 if (0x2 & cookie_size
) {
496 __u8
*p
= (__u8
*)ptr
;
498 /* 16-bit multiple */
499 *p
++ = TCPOPT_COOKIE
;
500 *p
++ = TCPOLEN_COOKIE_BASE
+ cookie_size
;
501 *p
++ = *cookie_copy
++;
502 *p
++ = *cookie_copy
++;
506 /* 32-bit multiple */
507 *ptr
++ = htonl(((TCPOPT_NOP
<< 24) |
509 (TCPOPT_COOKIE
<< 8) |
510 TCPOLEN_COOKIE_BASE
) +
514 if (cookie_size
> 0) {
515 memcpy(ptr
, cookie_copy
, cookie_size
);
516 ptr
+= (cookie_size
/ 4);
520 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
521 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
523 (TCPOPT_SACK_PERM
<< 8) |
527 if (unlikely(OPTION_WSCALE
& options
)) {
528 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
529 (TCPOPT_WINDOW
<< 16) |
530 (TCPOLEN_WINDOW
<< 8) |
534 if (unlikely(opts
->num_sack_blocks
)) {
535 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
536 tp
->duplicate_sack
: tp
->selective_acks
;
539 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
542 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
543 TCPOLEN_SACK_PERBLOCK
)));
545 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
547 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
548 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
551 tp
->rx_opt
.dsack
= 0;
555 /* Compute TCP options for SYN packets. This is not the final
556 * network wire format yet.
558 static unsigned tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
559 struct tcp_out_options
*opts
,
560 struct tcp_md5sig_key
**md5
) {
561 struct tcp_sock
*tp
= tcp_sk(sk
);
562 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
563 unsigned remaining
= MAX_TCP_OPTION_SPACE
;
564 u8 cookie_size
= (!tp
->rx_opt
.cookie_out_never
&& cvp
!= NULL
) ?
565 tcp_cookie_size_check(cvp
->cookie_desired
) :
568 #ifdef CONFIG_TCP_MD5SIG
569 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
571 opts
->options
|= OPTION_MD5
;
572 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
578 /* We always get an MSS option. The option bytes which will be seen in
579 * normal data packets should timestamps be used, must be in the MSS
580 * advertised. But we subtract them from tp->mss_cache so that
581 * calculations in tcp_sendmsg are simpler etc. So account for this
582 * fact here if necessary. If we don't do this correctly, as a
583 * receiver we won't recognize data packets as being full sized when we
584 * should, and thus we won't abide by the delayed ACK rules correctly.
585 * SACKs don't matter, we never delay an ACK when we have any of those
587 opts
->mss
= tcp_advertise_mss(sk
);
588 remaining
-= TCPOLEN_MSS_ALIGNED
;
590 if (likely(sysctl_tcp_timestamps
&& *md5
== NULL
)) {
591 opts
->options
|= OPTION_TS
;
592 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
593 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
594 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
596 if (likely(sysctl_tcp_window_scaling
)) {
597 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
598 opts
->options
|= OPTION_WSCALE
;
599 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
601 if (likely(sysctl_tcp_sack
)) {
602 opts
->options
|= OPTION_SACK_ADVERTISE
;
603 if (unlikely(!(OPTION_TS
& opts
->options
)))
604 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
607 /* Note that timestamps are required by the specification.
609 * Odd numbers of bytes are prohibited by the specification, ensuring
610 * that the cookie is 16-bit aligned, and the resulting cookie pair is
614 (OPTION_TS
& opts
->options
) &&
616 int need
= TCPOLEN_COOKIE_BASE
+ cookie_size
;
619 /* 32-bit multiple */
620 need
+= 2; /* NOPs */
622 if (need
> remaining
) {
623 /* try shrinking cookie to fit */
628 while (need
> remaining
&& TCP_COOKIE_MIN
<= cookie_size
) {
632 if (TCP_COOKIE_MIN
<= cookie_size
) {
633 opts
->options
|= OPTION_COOKIE_EXTENSION
;
634 opts
->hash_location
= (__u8
*)&cvp
->cookie_pair
[0];
635 opts
->hash_size
= cookie_size
;
637 /* Remember for future incarnations. */
638 cvp
->cookie_desired
= cookie_size
;
640 if (cvp
->cookie_desired
!= cvp
->cookie_pair_size
) {
641 /* Currently use random bytes as a nonce,
642 * assuming these are completely unpredictable
643 * by hostile users of the same system.
645 get_random_bytes(&cvp
->cookie_pair
[0],
647 cvp
->cookie_pair_size
= cookie_size
;
653 return MAX_TCP_OPTION_SPACE
- remaining
;
656 /* Set up TCP options for SYN-ACKs. */
657 static unsigned tcp_synack_options(struct sock
*sk
,
658 struct request_sock
*req
,
659 unsigned mss
, struct sk_buff
*skb
,
660 struct tcp_out_options
*opts
,
661 struct tcp_md5sig_key
**md5
,
662 struct tcp_extend_values
*xvp
)
664 struct inet_request_sock
*ireq
= inet_rsk(req
);
665 unsigned remaining
= MAX_TCP_OPTION_SPACE
;
666 u8 cookie_plus
= (xvp
!= NULL
&& !xvp
->cookie_out_never
) ?
670 #ifdef CONFIG_TCP_MD5SIG
671 *md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
673 opts
->options
|= OPTION_MD5
;
674 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
676 /* We can't fit any SACK blocks in a packet with MD5 + TS
677 * options. There was discussion about disabling SACK
678 * rather than TS in order to fit in better with old,
679 * buggy kernels, but that was deemed to be unnecessary.
681 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
687 /* We always send an MSS option. */
689 remaining
-= TCPOLEN_MSS_ALIGNED
;
691 if (likely(ireq
->wscale_ok
)) {
692 opts
->ws
= ireq
->rcv_wscale
;
693 opts
->options
|= OPTION_WSCALE
;
694 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
696 if (likely(ireq
->tstamp_ok
)) {
697 opts
->options
|= OPTION_TS
;
698 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
699 opts
->tsecr
= req
->ts_recent
;
700 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
702 if (likely(ireq
->sack_ok
)) {
703 opts
->options
|= OPTION_SACK_ADVERTISE
;
704 if (unlikely(!ireq
->tstamp_ok
))
705 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
708 /* Similar rationale to tcp_syn_options() applies here, too.
709 * If the <SYN> options fit, the same options should fit now!
713 cookie_plus
> TCPOLEN_COOKIE_BASE
) {
714 int need
= cookie_plus
; /* has TCPOLEN_COOKIE_BASE */
717 /* 32-bit multiple */
718 need
+= 2; /* NOPs */
720 if (need
<= remaining
) {
721 opts
->options
|= OPTION_COOKIE_EXTENSION
;
722 opts
->hash_size
= cookie_plus
- TCPOLEN_COOKIE_BASE
;
725 /* There's no error return, so flag it. */
726 xvp
->cookie_out_never
= 1; /* true */
730 return MAX_TCP_OPTION_SPACE
- remaining
;
733 /* Compute TCP options for ESTABLISHED sockets. This is not the
734 * final wire format yet.
736 static unsigned tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
737 struct tcp_out_options
*opts
,
738 struct tcp_md5sig_key
**md5
) {
739 struct tcp_skb_cb
*tcb
= skb
? TCP_SKB_CB(skb
) : NULL
;
740 struct tcp_sock
*tp
= tcp_sk(sk
);
742 unsigned int eff_sacks
;
744 #ifdef CONFIG_TCP_MD5SIG
745 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
746 if (unlikely(*md5
)) {
747 opts
->options
|= OPTION_MD5
;
748 size
+= TCPOLEN_MD5SIG_ALIGNED
;
754 if (likely(tp
->rx_opt
.tstamp_ok
)) {
755 opts
->options
|= OPTION_TS
;
756 opts
->tsval
= tcb
? tcb
->when
: 0;
757 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
758 size
+= TCPOLEN_TSTAMP_ALIGNED
;
761 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
762 if (unlikely(eff_sacks
)) {
763 const unsigned remaining
= MAX_TCP_OPTION_SPACE
- size
;
764 opts
->num_sack_blocks
=
765 min_t(unsigned, eff_sacks
,
766 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
767 TCPOLEN_SACK_PERBLOCK
);
768 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
769 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
775 /* This routine actually transmits TCP packets queued in by
776 * tcp_do_sendmsg(). This is used by both the initial
777 * transmission and possible later retransmissions.
778 * All SKB's seen here are completely headerless. It is our
779 * job to build the TCP header, and pass the packet down to
780 * IP so it can do the same plus pass the packet off to the
783 * We are working here with either a clone of the original
784 * SKB, or a fresh unique copy made by the retransmit engine.
786 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
789 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
790 struct inet_sock
*inet
;
792 struct tcp_skb_cb
*tcb
;
793 struct tcp_out_options opts
;
794 unsigned tcp_options_size
, tcp_header_size
;
795 struct tcp_md5sig_key
*md5
;
799 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
801 /* If congestion control is doing timestamping, we must
802 * take such a timestamp before we potentially clone/copy.
804 if (icsk
->icsk_ca_ops
->flags
& TCP_CONG_RTT_STAMP
)
805 __net_timestamp(skb
);
807 if (likely(clone_it
)) {
808 if (unlikely(skb_cloned(skb
)))
809 skb
= pskb_copy(skb
, gfp_mask
);
811 skb
= skb_clone(skb
, gfp_mask
);
818 tcb
= TCP_SKB_CB(skb
);
819 memset(&opts
, 0, sizeof(opts
));
821 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
))
822 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
824 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
826 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
828 if (tcp_packets_in_flight(tp
) == 0)
829 tcp_ca_event(sk
, CA_EVENT_TX_START
);
831 skb_push(skb
, tcp_header_size
);
832 skb_reset_transport_header(skb
);
833 skb_set_owner_w(skb
, sk
);
835 /* Build TCP header and checksum it. */
837 th
->source
= inet
->inet_sport
;
838 th
->dest
= inet
->inet_dport
;
839 th
->seq
= htonl(tcb
->seq
);
840 th
->ack_seq
= htonl(tp
->rcv_nxt
);
841 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
844 if (unlikely(tcb
->flags
& TCPCB_FLAG_SYN
)) {
845 /* RFC1323: The window in SYN & SYN/ACK segments
848 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
850 th
->window
= htons(tcp_select_window(sk
));
855 /* The urg_mode check is necessary during a below snd_una win probe */
856 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
857 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
858 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
860 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
861 th
->urg_ptr
= 0xFFFF;
866 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
867 if (likely((tcb
->flags
& TCPCB_FLAG_SYN
) == 0))
868 TCP_ECN_send(sk
, skb
, tcp_header_size
);
870 #ifdef CONFIG_TCP_MD5SIG
871 /* Calculate the MD5 hash, as we have all we need now */
873 sk
->sk_route_caps
&= ~NETIF_F_GSO_MASK
;
874 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
879 icsk
->icsk_af_ops
->send_check(sk
, skb
->len
, skb
);
881 if (likely(tcb
->flags
& TCPCB_FLAG_ACK
))
882 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
884 if (skb
->len
!= tcp_header_size
)
885 tcp_event_data_sent(tp
, skb
, sk
);
887 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
888 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
890 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, 0);
891 if (likely(err
<= 0))
894 tcp_enter_cwr(sk
, 1);
896 return net_xmit_eval(err
);
899 /* This routine just queues the buffer for sending.
901 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
902 * otherwise socket can stall.
904 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
906 struct tcp_sock
*tp
= tcp_sk(sk
);
908 /* Advance write_seq and place onto the write_queue. */
909 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
910 skb_header_release(skb
);
911 tcp_add_write_queue_tail(sk
, skb
);
912 sk
->sk_wmem_queued
+= skb
->truesize
;
913 sk_mem_charge(sk
, skb
->truesize
);
916 /* Initialize TSO segments for a packet. */
917 static void tcp_set_skb_tso_segs(struct sock
*sk
, struct sk_buff
*skb
,
918 unsigned int mss_now
)
920 if (skb
->len
<= mss_now
|| !sk_can_gso(sk
) ||
921 skb
->ip_summed
== CHECKSUM_NONE
) {
922 /* Avoid the costly divide in the normal
925 skb_shinfo(skb
)->gso_segs
= 1;
926 skb_shinfo(skb
)->gso_size
= 0;
927 skb_shinfo(skb
)->gso_type
= 0;
929 skb_shinfo(skb
)->gso_segs
= DIV_ROUND_UP(skb
->len
, mss_now
);
930 skb_shinfo(skb
)->gso_size
= mss_now
;
931 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
935 /* When a modification to fackets out becomes necessary, we need to check
936 * skb is counted to fackets_out or not.
938 static void tcp_adjust_fackets_out(struct sock
*sk
, struct sk_buff
*skb
,
941 struct tcp_sock
*tp
= tcp_sk(sk
);
943 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
946 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
947 tp
->fackets_out
-= decr
;
950 /* Pcount in the middle of the write queue got changed, we need to do various
951 * tweaks to fix counters
953 static void tcp_adjust_pcount(struct sock
*sk
, struct sk_buff
*skb
, int decr
)
955 struct tcp_sock
*tp
= tcp_sk(sk
);
957 tp
->packets_out
-= decr
;
959 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
960 tp
->sacked_out
-= decr
;
961 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
962 tp
->retrans_out
-= decr
;
963 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
964 tp
->lost_out
-= decr
;
966 /* Reno case is special. Sigh... */
967 if (tcp_is_reno(tp
) && decr
> 0)
968 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
970 tcp_adjust_fackets_out(sk
, skb
, decr
);
972 if (tp
->lost_skb_hint
&&
973 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
974 (tcp_is_fack(tp
) || (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)))
975 tp
->lost_cnt_hint
-= decr
;
977 tcp_verify_left_out(tp
);
980 /* Function to create two new TCP segments. Shrinks the given segment
981 * to the specified size and appends a new segment with the rest of the
982 * packet to the list. This won't be called frequently, I hope.
983 * Remember, these are still headerless SKBs at this point.
985 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
986 unsigned int mss_now
)
988 struct tcp_sock
*tp
= tcp_sk(sk
);
989 struct sk_buff
*buff
;
990 int nsize
, old_factor
;
994 BUG_ON(len
> skb
->len
);
996 nsize
= skb_headlen(skb
) - len
;
1000 if (skb_cloned(skb
) &&
1001 skb_is_nonlinear(skb
) &&
1002 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
1005 /* Get a new skb... force flag on. */
1006 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
1008 return -ENOMEM
; /* We'll just try again later. */
1010 sk
->sk_wmem_queued
+= buff
->truesize
;
1011 sk_mem_charge(sk
, buff
->truesize
);
1012 nlen
= skb
->len
- len
- nsize
;
1013 buff
->truesize
+= nlen
;
1014 skb
->truesize
-= nlen
;
1016 /* Correct the sequence numbers. */
1017 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1018 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1019 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1021 /* PSH and FIN should only be set in the second packet. */
1022 flags
= TCP_SKB_CB(skb
)->flags
;
1023 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
| TCPCB_FLAG_PSH
);
1024 TCP_SKB_CB(buff
)->flags
= flags
;
1025 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1027 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
1028 /* Copy and checksum data tail into the new buffer. */
1029 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
1030 skb_put(buff
, nsize
),
1035 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
1037 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1038 skb_split(skb
, buff
, len
);
1041 buff
->ip_summed
= skb
->ip_summed
;
1043 /* Looks stupid, but our code really uses when of
1044 * skbs, which it never sent before. --ANK
1046 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
1047 buff
->tstamp
= skb
->tstamp
;
1049 old_factor
= tcp_skb_pcount(skb
);
1051 /* Fix up tso_factor for both original and new SKB. */
1052 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1053 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1055 /* If this packet has been sent out already, we must
1056 * adjust the various packet counters.
1058 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1059 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1060 tcp_skb_pcount(buff
);
1063 tcp_adjust_pcount(sk
, skb
, diff
);
1066 /* Link BUFF into the send queue. */
1067 skb_header_release(buff
);
1068 tcp_insert_write_queue_after(skb
, buff
, sk
);
1073 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1074 * eventually). The difference is that pulled data not copied, but
1075 * immediately discarded.
1077 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
1083 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
1084 if (skb_shinfo(skb
)->frags
[i
].size
<= eat
) {
1085 put_page(skb_shinfo(skb
)->frags
[i
].page
);
1086 eat
-= skb_shinfo(skb
)->frags
[i
].size
;
1088 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
1090 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
1091 skb_shinfo(skb
)->frags
[k
].size
-= eat
;
1097 skb_shinfo(skb
)->nr_frags
= k
;
1099 skb_reset_tail_pointer(skb
);
1100 skb
->data_len
-= len
;
1101 skb
->len
= skb
->data_len
;
1104 /* Remove acked data from a packet in the transmit queue. */
1105 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1107 if (skb_cloned(skb
) && pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
1110 /* If len == headlen, we avoid __skb_pull to preserve alignment. */
1111 if (unlikely(len
< skb_headlen(skb
)))
1112 __skb_pull(skb
, len
);
1114 __pskb_trim_head(skb
, len
- skb_headlen(skb
));
1116 TCP_SKB_CB(skb
)->seq
+= len
;
1117 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1119 skb
->truesize
-= len
;
1120 sk
->sk_wmem_queued
-= len
;
1121 sk_mem_uncharge(sk
, len
);
1122 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
1124 /* Any change of skb->len requires recalculation of tso
1127 if (tcp_skb_pcount(skb
) > 1)
1128 tcp_set_skb_tso_segs(sk
, skb
, tcp_current_mss(sk
));
1133 /* Calculate MSS. Not accounting for SACKs here. */
1134 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1136 struct tcp_sock
*tp
= tcp_sk(sk
);
1137 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1140 /* Calculate base mss without TCP options:
1141 It is MMS_S - sizeof(tcphdr) of rfc1122
1143 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1145 /* Clamp it (mss_clamp does not include tcp options) */
1146 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1147 mss_now
= tp
->rx_opt
.mss_clamp
;
1149 /* Now subtract optional transport overhead */
1150 mss_now
-= icsk
->icsk_ext_hdr_len
;
1152 /* Then reserve room for full set of TCP options and 8 bytes of data */
1156 /* Now subtract TCP options size, not including SACKs */
1157 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
1162 /* Inverse of above */
1163 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1165 struct tcp_sock
*tp
= tcp_sk(sk
);
1166 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1170 tp
->tcp_header_len
+
1171 icsk
->icsk_ext_hdr_len
+
1172 icsk
->icsk_af_ops
->net_header_len
;
1177 /* MTU probing init per socket */
1178 void tcp_mtup_init(struct sock
*sk
)
1180 struct tcp_sock
*tp
= tcp_sk(sk
);
1181 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1183 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
1184 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1185 icsk
->icsk_af_ops
->net_header_len
;
1186 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
1187 icsk
->icsk_mtup
.probe_size
= 0;
1190 /* This function synchronize snd mss to current pmtu/exthdr set.
1192 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1193 for TCP options, but includes only bare TCP header.
1195 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1196 It is minimum of user_mss and mss received with SYN.
1197 It also does not include TCP options.
1199 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1201 tp->mss_cache is current effective sending mss, including
1202 all tcp options except for SACKs. It is evaluated,
1203 taking into account current pmtu, but never exceeds
1204 tp->rx_opt.mss_clamp.
1206 NOTE1. rfc1122 clearly states that advertised MSS
1207 DOES NOT include either tcp or ip options.
1209 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1210 are READ ONLY outside this function. --ANK (980731)
1212 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1214 struct tcp_sock
*tp
= tcp_sk(sk
);
1215 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1218 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1219 icsk
->icsk_mtup
.search_high
= pmtu
;
1221 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1222 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1224 /* And store cached results */
1225 icsk
->icsk_pmtu_cookie
= pmtu
;
1226 if (icsk
->icsk_mtup
.enabled
)
1227 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1228 tp
->mss_cache
= mss_now
;
1233 /* Compute the current effective MSS, taking SACKs and IP options,
1234 * and even PMTU discovery events into account.
1236 unsigned int tcp_current_mss(struct sock
*sk
)
1238 struct tcp_sock
*tp
= tcp_sk(sk
);
1239 struct dst_entry
*dst
= __sk_dst_get(sk
);
1241 unsigned header_len
;
1242 struct tcp_out_options opts
;
1243 struct tcp_md5sig_key
*md5
;
1245 mss_now
= tp
->mss_cache
;
1248 u32 mtu
= dst_mtu(dst
);
1249 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1250 mss_now
= tcp_sync_mss(sk
, mtu
);
1253 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1254 sizeof(struct tcphdr
);
1255 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1256 * some common options. If this is an odd packet (because we have SACK
1257 * blocks etc) then our calculated header_len will be different, and
1258 * we have to adjust mss_now correspondingly */
1259 if (header_len
!= tp
->tcp_header_len
) {
1260 int delta
= (int) header_len
- tp
->tcp_header_len
;
1267 /* Congestion window validation. (RFC2861) */
1268 static void tcp_cwnd_validate(struct sock
*sk
)
1270 struct tcp_sock
*tp
= tcp_sk(sk
);
1272 if (tp
->packets_out
>= tp
->snd_cwnd
) {
1273 /* Network is feed fully. */
1274 tp
->snd_cwnd_used
= 0;
1275 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1277 /* Network starves. */
1278 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1279 tp
->snd_cwnd_used
= tp
->packets_out
;
1281 if (sysctl_tcp_slow_start_after_idle
&&
1282 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1283 tcp_cwnd_application_limited(sk
);
1287 /* Returns the portion of skb which can be sent right away without
1288 * introducing MSS oddities to segment boundaries. In rare cases where
1289 * mss_now != mss_cache, we will request caller to create a small skb
1290 * per input skb which could be mostly avoided here (if desired).
1292 * We explicitly want to create a request for splitting write queue tail
1293 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
1294 * thus all the complexity (cwnd_len is always MSS multiple which we
1295 * return whenever allowed by the other factors). Basically we need the
1296 * modulo only when the receiver window alone is the limiting factor or
1297 * when we would be allowed to send the split-due-to-Nagle skb fully.
1299 static unsigned int tcp_mss_split_point(struct sock
*sk
, struct sk_buff
*skb
,
1300 unsigned int mss_now
, unsigned int cwnd
)
1302 struct tcp_sock
*tp
= tcp_sk(sk
);
1303 u32 needed
, window
, cwnd_len
;
1305 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1306 cwnd_len
= mss_now
* cwnd
;
1308 if (likely(cwnd_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1311 needed
= min(skb
->len
, window
);
1313 if (cwnd_len
<= needed
)
1316 return needed
- needed
% mss_now
;
1319 /* Can at least one segment of SKB be sent right now, according to the
1320 * congestion window rules? If so, return how many segments are allowed.
1322 static inline unsigned int tcp_cwnd_test(struct tcp_sock
*tp
,
1323 struct sk_buff
*skb
)
1325 u32 in_flight
, cwnd
;
1327 /* Don't be strict about the congestion window for the final FIN. */
1328 if ((TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
1329 tcp_skb_pcount(skb
) == 1)
1332 in_flight
= tcp_packets_in_flight(tp
);
1333 cwnd
= tp
->snd_cwnd
;
1334 if (in_flight
< cwnd
)
1335 return (cwnd
- in_flight
);
1340 /* Intialize TSO state of a skb.
1341 * This must be invoked the first time we consider transmitting
1342 * SKB onto the wire.
1344 static int tcp_init_tso_segs(struct sock
*sk
, struct sk_buff
*skb
,
1345 unsigned int mss_now
)
1347 int tso_segs
= tcp_skb_pcount(skb
);
1349 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1350 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1351 tso_segs
= tcp_skb_pcount(skb
);
1356 /* Minshall's variant of the Nagle send check. */
1357 static inline int tcp_minshall_check(const struct tcp_sock
*tp
)
1359 return after(tp
->snd_sml
, tp
->snd_una
) &&
1360 !after(tp
->snd_sml
, tp
->snd_nxt
);
1363 /* Return 0, if packet can be sent now without violation Nagle's rules:
1364 * 1. It is full sized.
1365 * 2. Or it contains FIN. (already checked by caller)
1366 * 3. Or TCP_NODELAY was set.
1367 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1368 * With Minshall's modification: all sent small packets are ACKed.
1370 static inline int tcp_nagle_check(const struct tcp_sock
*tp
,
1371 const struct sk_buff
*skb
,
1372 unsigned mss_now
, int nonagle
)
1374 return (skb
->len
< mss_now
&&
1375 ((nonagle
& TCP_NAGLE_CORK
) ||
1376 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
))));
1379 /* Return non-zero if the Nagle test allows this packet to be
1382 static inline int tcp_nagle_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1383 unsigned int cur_mss
, int nonagle
)
1385 /* Nagle rule does not apply to frames, which sit in the middle of the
1386 * write_queue (they have no chances to get new data).
1388 * This is implemented in the callers, where they modify the 'nonagle'
1389 * argument based upon the location of SKB in the send queue.
1391 if (nonagle
& TCP_NAGLE_PUSH
)
1394 /* Don't use the nagle rule for urgent data (or for the final FIN).
1395 * Nagle can be ignored during F-RTO too (see RFC4138).
1397 if (tcp_urg_mode(tp
) || (tp
->frto_counter
== 2) ||
1398 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
))
1401 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
1407 /* Does at least the first segment of SKB fit into the send window? */
1408 static inline int tcp_snd_wnd_test(struct tcp_sock
*tp
, struct sk_buff
*skb
,
1409 unsigned int cur_mss
)
1411 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1413 if (skb
->len
> cur_mss
)
1414 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1416 return !after(end_seq
, tcp_wnd_end(tp
));
1419 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1420 * should be put on the wire right now. If so, it returns the number of
1421 * packets allowed by the congestion window.
1423 static unsigned int tcp_snd_test(struct sock
*sk
, struct sk_buff
*skb
,
1424 unsigned int cur_mss
, int nonagle
)
1426 struct tcp_sock
*tp
= tcp_sk(sk
);
1427 unsigned int cwnd_quota
;
1429 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1431 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1434 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1435 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1441 /* Test if sending is allowed right now. */
1442 int tcp_may_send_now(struct sock
*sk
)
1444 struct tcp_sock
*tp
= tcp_sk(sk
);
1445 struct sk_buff
*skb
= tcp_send_head(sk
);
1448 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1449 (tcp_skb_is_last(sk
, skb
) ?
1450 tp
->nonagle
: TCP_NAGLE_PUSH
)));
1453 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1454 * which is put after SKB on the list. It is very much like
1455 * tcp_fragment() except that it may make several kinds of assumptions
1456 * in order to speed up the splitting operation. In particular, we
1457 * know that all the data is in scatter-gather pages, and that the
1458 * packet has never been sent out before (and thus is not cloned).
1460 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1461 unsigned int mss_now
)
1463 struct sk_buff
*buff
;
1464 int nlen
= skb
->len
- len
;
1467 /* All of a TSO frame must be composed of paged data. */
1468 if (skb
->len
!= skb
->data_len
)
1469 return tcp_fragment(sk
, skb
, len
, mss_now
);
1471 buff
= sk_stream_alloc_skb(sk
, 0, GFP_ATOMIC
);
1472 if (unlikely(buff
== NULL
))
1475 sk
->sk_wmem_queued
+= buff
->truesize
;
1476 sk_mem_charge(sk
, buff
->truesize
);
1477 buff
->truesize
+= nlen
;
1478 skb
->truesize
-= nlen
;
1480 /* Correct the sequence numbers. */
1481 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1482 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1483 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1485 /* PSH and FIN should only be set in the second packet. */
1486 flags
= TCP_SKB_CB(skb
)->flags
;
1487 TCP_SKB_CB(skb
)->flags
= flags
& ~(TCPCB_FLAG_FIN
| TCPCB_FLAG_PSH
);
1488 TCP_SKB_CB(buff
)->flags
= flags
;
1490 /* This packet was never sent out yet, so no SACK bits. */
1491 TCP_SKB_CB(buff
)->sacked
= 0;
1493 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1494 skb_split(skb
, buff
, len
);
1496 /* Fix up tso_factor for both original and new SKB. */
1497 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1498 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1500 /* Link BUFF into the send queue. */
1501 skb_header_release(buff
);
1502 tcp_insert_write_queue_after(skb
, buff
, sk
);
1507 /* Try to defer sending, if possible, in order to minimize the amount
1508 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1510 * This algorithm is from John Heffner.
1512 static int tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
)
1514 struct tcp_sock
*tp
= tcp_sk(sk
);
1515 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1516 u32 send_win
, cong_win
, limit
, in_flight
;
1519 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
)
1522 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1525 /* Defer for less than two clock ticks. */
1526 if (tp
->tso_deferred
&&
1527 (((u32
)jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1530 in_flight
= tcp_packets_in_flight(tp
);
1532 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1534 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1536 /* From in_flight test above, we know that cwnd > in_flight. */
1537 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1539 limit
= min(send_win
, cong_win
);
1541 /* If a full-sized TSO skb can be sent, do it. */
1542 if (limit
>= sk
->sk_gso_max_size
)
1545 /* Middle in queue won't get any more data, full sendable already? */
1546 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1549 win_divisor
= ACCESS_ONCE(sysctl_tcp_tso_win_divisor
);
1551 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1553 /* If at least some fraction of a window is available,
1556 chunk
/= win_divisor
;
1560 /* Different approach, try not to defer past a single
1561 * ACK. Receiver should ACK every other full sized
1562 * frame, so if we have space for more than 3 frames
1565 if (limit
> tcp_max_burst(tp
) * tp
->mss_cache
)
1569 /* Ok, it looks like it is advisable to defer. */
1570 tp
->tso_deferred
= 1 | (jiffies
<< 1);
1575 tp
->tso_deferred
= 0;
1579 /* Create a new MTU probe if we are ready.
1580 * MTU probe is regularly attempting to increase the path MTU by
1581 * deliberately sending larger packets. This discovers routing
1582 * changes resulting in larger path MTUs.
1584 * Returns 0 if we should wait to probe (no cwnd available),
1585 * 1 if a probe was sent,
1588 static int tcp_mtu_probe(struct sock
*sk
)
1590 struct tcp_sock
*tp
= tcp_sk(sk
);
1591 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1592 struct sk_buff
*skb
, *nskb
, *next
;
1599 /* Not currently probing/verifying,
1601 * have enough cwnd, and
1602 * not SACKing (the variable headers throw things off) */
1603 if (!icsk
->icsk_mtup
.enabled
||
1604 icsk
->icsk_mtup
.probe_size
||
1605 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1606 tp
->snd_cwnd
< 11 ||
1607 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
)
1610 /* Very simple search strategy: just double the MSS. */
1611 mss_now
= tcp_current_mss(sk
);
1612 probe_size
= 2 * tp
->mss_cache
;
1613 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1614 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1615 /* TODO: set timer for probe_converge_event */
1619 /* Have enough data in the send queue to probe? */
1620 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1623 if (tp
->snd_wnd
< size_needed
)
1625 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1628 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1629 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1630 if (!tcp_packets_in_flight(tp
))
1636 /* We're allowed to probe. Build it now. */
1637 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1639 sk
->sk_wmem_queued
+= nskb
->truesize
;
1640 sk_mem_charge(sk
, nskb
->truesize
);
1642 skb
= tcp_send_head(sk
);
1644 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1645 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1646 TCP_SKB_CB(nskb
)->flags
= TCPCB_FLAG_ACK
;
1647 TCP_SKB_CB(nskb
)->sacked
= 0;
1649 nskb
->ip_summed
= skb
->ip_summed
;
1651 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1654 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1655 copy
= min_t(int, skb
->len
, probe_size
- len
);
1656 if (nskb
->ip_summed
)
1657 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1659 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1660 skb_put(nskb
, copy
),
1663 if (skb
->len
<= copy
) {
1664 /* We've eaten all the data from this skb.
1666 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
;
1667 tcp_unlink_write_queue(skb
, sk
);
1668 sk_wmem_free_skb(sk
, skb
);
1670 TCP_SKB_CB(nskb
)->flags
|= TCP_SKB_CB(skb
)->flags
&
1671 ~(TCPCB_FLAG_FIN
|TCPCB_FLAG_PSH
);
1672 if (!skb_shinfo(skb
)->nr_frags
) {
1673 skb_pull(skb
, copy
);
1674 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1675 skb
->csum
= csum_partial(skb
->data
,
1678 __pskb_trim_head(skb
, copy
);
1679 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1681 TCP_SKB_CB(skb
)->seq
+= copy
;
1686 if (len
>= probe_size
)
1689 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1691 /* We're ready to send. If this fails, the probe will
1692 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1693 TCP_SKB_CB(nskb
)->when
= tcp_time_stamp
;
1694 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1695 /* Decrement cwnd here because we are sending
1696 * effectively two packets. */
1698 tcp_event_new_data_sent(sk
, nskb
);
1700 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1701 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1702 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1710 /* This routine writes packets to the network. It advances the
1711 * send_head. This happens as incoming acks open up the remote
1714 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1715 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1716 * account rare use of URG, this is not a big flaw.
1718 * Returns 1, if no segments are in flight and we have queued segments, but
1719 * cannot send anything now because of SWS or another problem.
1721 static int tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
1722 int push_one
, gfp_t gfp
)
1724 struct tcp_sock
*tp
= tcp_sk(sk
);
1725 struct sk_buff
*skb
;
1726 unsigned int tso_segs
, sent_pkts
;
1733 /* Do MTU probing. */
1734 result
= tcp_mtu_probe(sk
);
1737 } else if (result
> 0) {
1742 while ((skb
= tcp_send_head(sk
))) {
1745 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1748 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1752 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1755 if (tso_segs
== 1) {
1756 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1757 (tcp_skb_is_last(sk
, skb
) ?
1758 nonagle
: TCP_NAGLE_PUSH
))))
1761 if (!push_one
&& tcp_tso_should_defer(sk
, skb
))
1766 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
1767 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
1770 if (skb
->len
> limit
&&
1771 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
)))
1774 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1776 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
1779 /* Advance the send_head. This one is sent out.
1780 * This call will increment packets_out.
1782 tcp_event_new_data_sent(sk
, skb
);
1784 tcp_minshall_update(tp
, mss_now
, skb
);
1791 if (likely(sent_pkts
)) {
1792 tcp_cwnd_validate(sk
);
1795 return !tp
->packets_out
&& tcp_send_head(sk
);
1798 /* Push out any pending frames which were held back due to
1799 * TCP_CORK or attempt at coalescing tiny packets.
1800 * The socket must be locked by the caller.
1802 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
1805 /* If we are closed, the bytes will have to remain here.
1806 * In time closedown will finish, we empty the write queue and
1807 * all will be happy.
1809 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
1812 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0, GFP_ATOMIC
))
1813 tcp_check_probe_timer(sk
);
1816 /* Send _single_ skb sitting at the send head. This function requires
1817 * true push pending frames to setup probe timer etc.
1819 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
1821 struct sk_buff
*skb
= tcp_send_head(sk
);
1823 BUG_ON(!skb
|| skb
->len
< mss_now
);
1825 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
1828 /* This function returns the amount that we can raise the
1829 * usable window based on the following constraints
1831 * 1. The window can never be shrunk once it is offered (RFC 793)
1832 * 2. We limit memory per socket
1835 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1836 * RECV.NEXT + RCV.WIN fixed until:
1837 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1839 * i.e. don't raise the right edge of the window until you can raise
1840 * it at least MSS bytes.
1842 * Unfortunately, the recommended algorithm breaks header prediction,
1843 * since header prediction assumes th->window stays fixed.
1845 * Strictly speaking, keeping th->window fixed violates the receiver
1846 * side SWS prevention criteria. The problem is that under this rule
1847 * a stream of single byte packets will cause the right side of the
1848 * window to always advance by a single byte.
1850 * Of course, if the sender implements sender side SWS prevention
1851 * then this will not be a problem.
1853 * BSD seems to make the following compromise:
1855 * If the free space is less than the 1/4 of the maximum
1856 * space available and the free space is less than 1/2 mss,
1857 * then set the window to 0.
1858 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1859 * Otherwise, just prevent the window from shrinking
1860 * and from being larger than the largest representable value.
1862 * This prevents incremental opening of the window in the regime
1863 * where TCP is limited by the speed of the reader side taking
1864 * data out of the TCP receive queue. It does nothing about
1865 * those cases where the window is constrained on the sender side
1866 * because the pipeline is full.
1868 * BSD also seems to "accidentally" limit itself to windows that are a
1869 * multiple of MSS, at least until the free space gets quite small.
1870 * This would appear to be a side effect of the mbuf implementation.
1871 * Combining these two algorithms results in the observed behavior
1872 * of having a fixed window size at almost all times.
1874 * Below we obtain similar behavior by forcing the offered window to
1875 * a multiple of the mss when it is feasible to do so.
1877 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1878 * Regular options like TIMESTAMP are taken into account.
1880 u32
__tcp_select_window(struct sock
*sk
)
1882 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1883 struct tcp_sock
*tp
= tcp_sk(sk
);
1884 /* MSS for the peer's data. Previous versions used mss_clamp
1885 * here. I don't know if the value based on our guesses
1886 * of peer's MSS is better for the performance. It's more correct
1887 * but may be worse for the performance because of rcv_mss
1888 * fluctuations. --SAW 1998/11/1
1890 int mss
= icsk
->icsk_ack
.rcv_mss
;
1891 int free_space
= tcp_space(sk
);
1892 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
1895 if (mss
> full_space
)
1898 if (free_space
< (full_space
>> 1)) {
1899 icsk
->icsk_ack
.quick
= 0;
1901 if (tcp_memory_pressure
)
1902 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
1905 if (free_space
< mss
)
1909 if (free_space
> tp
->rcv_ssthresh
)
1910 free_space
= tp
->rcv_ssthresh
;
1912 /* Don't do rounding if we are using window scaling, since the
1913 * scaled window will not line up with the MSS boundary anyway.
1915 window
= tp
->rcv_wnd
;
1916 if (tp
->rx_opt
.rcv_wscale
) {
1917 window
= free_space
;
1919 /* Advertise enough space so that it won't get scaled away.
1920 * Import case: prevent zero window announcement if
1921 * 1<<rcv_wscale > mss.
1923 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
1924 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
1925 << tp
->rx_opt
.rcv_wscale
);
1927 /* Get the largest window that is a nice multiple of mss.
1928 * Window clamp already applied above.
1929 * If our current window offering is within 1 mss of the
1930 * free space we just keep it. This prevents the divide
1931 * and multiply from happening most of the time.
1932 * We also don't do any window rounding when the free space
1935 if (window
<= free_space
- mss
|| window
> free_space
)
1936 window
= (free_space
/ mss
) * mss
;
1937 else if (mss
== full_space
&&
1938 free_space
> window
+ (full_space
>> 1))
1939 window
= free_space
;
1945 /* Collapses two adjacent SKB's during retransmission. */
1946 static void tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
1948 struct tcp_sock
*tp
= tcp_sk(sk
);
1949 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
1950 int skb_size
, next_skb_size
;
1952 skb_size
= skb
->len
;
1953 next_skb_size
= next_skb
->len
;
1955 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
1957 tcp_highest_sack_combine(sk
, next_skb
, skb
);
1959 tcp_unlink_write_queue(next_skb
, sk
);
1961 skb_copy_from_linear_data(next_skb
, skb_put(skb
, next_skb_size
),
1964 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
1965 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1967 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1968 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
1970 /* Update sequence range on original skb. */
1971 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
1973 /* Merge over control information. This moves PSH/FIN etc. over */
1974 TCP_SKB_CB(skb
)->flags
|= TCP_SKB_CB(next_skb
)->flags
;
1976 /* All done, get rid of second SKB and account for it so
1977 * packet counting does not break.
1979 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
1981 /* changed transmit queue under us so clear hints */
1982 tcp_clear_retrans_hints_partial(tp
);
1983 if (next_skb
== tp
->retransmit_skb_hint
)
1984 tp
->retransmit_skb_hint
= skb
;
1986 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
1988 sk_wmem_free_skb(sk
, next_skb
);
1991 /* Check if coalescing SKBs is legal. */
1992 static int tcp_can_collapse(struct sock
*sk
, struct sk_buff
*skb
)
1994 if (tcp_skb_pcount(skb
) > 1)
1996 /* TODO: SACK collapsing could be used to remove this condition */
1997 if (skb_shinfo(skb
)->nr_frags
!= 0)
1999 if (skb_cloned(skb
))
2001 if (skb
== tcp_send_head(sk
))
2003 /* Some heurestics for collapsing over SACK'd could be invented */
2004 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2010 /* Collapse packets in the retransmit queue to make to create
2011 * less packets on the wire. This is only done on retransmission.
2013 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
2016 struct tcp_sock
*tp
= tcp_sk(sk
);
2017 struct sk_buff
*skb
= to
, *tmp
;
2020 if (!sysctl_tcp_retrans_collapse
)
2022 if (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
)
2025 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
2026 if (!tcp_can_collapse(sk
, skb
))
2038 /* Punt if not enough space exists in the first SKB for
2039 * the data in the second
2041 if (skb
->len
> skb_tailroom(to
))
2044 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
2047 tcp_collapse_retrans(sk
, to
);
2051 /* This retransmits one SKB. Policy decisions and retransmit queue
2052 * state updates are done by the caller. Returns non-zero if an
2053 * error occurred which prevented the send.
2055 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2057 struct tcp_sock
*tp
= tcp_sk(sk
);
2058 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2059 unsigned int cur_mss
;
2062 /* Inconslusive MTU probe */
2063 if (icsk
->icsk_mtup
.probe_size
) {
2064 icsk
->icsk_mtup
.probe_size
= 0;
2067 /* Do not sent more than we queued. 1/4 is reserved for possible
2068 * copying overhead: fragmentation, tunneling, mangling etc.
2070 if (atomic_read(&sk
->sk_wmem_alloc
) >
2071 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
2074 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
2075 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
2077 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2081 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
2082 return -EHOSTUNREACH
; /* Routing failure or similar. */
2084 cur_mss
= tcp_current_mss(sk
);
2086 /* If receiver has shrunk his window, and skb is out of
2087 * new window, do not retransmit it. The exception is the
2088 * case, when window is shrunk to zero. In this case
2089 * our retransmit serves as a zero window probe.
2091 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
)) &&
2092 TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
2095 if (skb
->len
> cur_mss
) {
2096 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
2097 return -ENOMEM
; /* We'll try again later. */
2099 int oldpcount
= tcp_skb_pcount(skb
);
2101 if (unlikely(oldpcount
> 1)) {
2102 tcp_init_tso_segs(sk
, skb
, cur_mss
);
2103 tcp_adjust_pcount(sk
, skb
, oldpcount
- tcp_skb_pcount(skb
));
2107 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
2109 /* Some Solaris stacks overoptimize and ignore the FIN on a
2110 * retransmit when old data is attached. So strip it off
2111 * since it is cheap to do so and saves bytes on the network.
2114 (TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_FIN
) &&
2115 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
2116 if (!pskb_trim(skb
, 0)) {
2117 /* Reuse, even though it does some unnecessary work */
2118 tcp_init_nondata_skb(skb
, TCP_SKB_CB(skb
)->end_seq
- 1,
2119 TCP_SKB_CB(skb
)->flags
);
2120 skb
->ip_summed
= CHECKSUM_NONE
;
2124 /* Make a copy, if the first transmission SKB clone we made
2125 * is still in somebody's hands, else make a clone.
2127 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2129 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2132 /* Update global TCP statistics. */
2133 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
2135 tp
->total_retrans
++;
2137 #if FASTRETRANS_DEBUG > 0
2138 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2139 if (net_ratelimit())
2140 printk(KERN_DEBUG
"retrans_out leaked.\n");
2143 if (!tp
->retrans_out
)
2144 tp
->lost_retrans_low
= tp
->snd_nxt
;
2145 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
2146 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2148 /* Save stamp of the first retransmit. */
2149 if (!tp
->retrans_stamp
)
2150 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
2154 /* snd_nxt is stored to detect loss of retransmitted segment,
2155 * see tcp_input.c tcp_sacktag_write_queue().
2157 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
2162 /* Check if we forward retransmits are possible in the current
2163 * window/congestion state.
2165 static int tcp_can_forward_retransmit(struct sock
*sk
)
2167 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2168 struct tcp_sock
*tp
= tcp_sk(sk
);
2170 /* Forward retransmissions are possible only during Recovery. */
2171 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
2174 /* No forward retransmissions in Reno are possible. */
2175 if (tcp_is_reno(tp
))
2178 /* Yeah, we have to make difficult choice between forward transmission
2179 * and retransmission... Both ways have their merits...
2181 * For now we do not retransmit anything, while we have some new
2182 * segments to send. In the other cases, follow rule 3 for
2183 * NextSeg() specified in RFC3517.
2186 if (tcp_may_send_now(sk
))
2192 /* This gets called after a retransmit timeout, and the initially
2193 * retransmitted data is acknowledged. It tries to continue
2194 * resending the rest of the retransmit queue, until either
2195 * we've sent it all or the congestion window limit is reached.
2196 * If doing SACK, the first ACK which comes back for a timeout
2197 * based retransmit packet might feed us FACK information again.
2198 * If so, we use it to avoid unnecessarily retransmissions.
2200 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2202 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2203 struct tcp_sock
*tp
= tcp_sk(sk
);
2204 struct sk_buff
*skb
;
2205 struct sk_buff
*hole
= NULL
;
2208 int fwd_rexmitting
= 0;
2210 if (!tp
->packets_out
)
2214 tp
->retransmit_high
= tp
->snd_una
;
2216 if (tp
->retransmit_skb_hint
) {
2217 skb
= tp
->retransmit_skb_hint
;
2218 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2219 if (after(last_lost
, tp
->retransmit_high
))
2220 last_lost
= tp
->retransmit_high
;
2222 skb
= tcp_write_queue_head(sk
);
2223 last_lost
= tp
->snd_una
;
2226 tcp_for_write_queue_from(skb
, sk
) {
2227 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
2229 if (skb
== tcp_send_head(sk
))
2231 /* we could do better than to assign each time */
2233 tp
->retransmit_skb_hint
= skb
;
2235 /* Assume this retransmit will generate
2236 * only one packet for congestion window
2237 * calculation purposes. This works because
2238 * tcp_retransmit_skb() will chop up the
2239 * packet to be MSS sized and all the
2240 * packet counting works out.
2242 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2245 if (fwd_rexmitting
) {
2247 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2249 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2251 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2252 tp
->retransmit_high
= last_lost
;
2253 if (!tcp_can_forward_retransmit(sk
))
2255 /* Backtrack if necessary to non-L'ed skb */
2263 } else if (!(sacked
& TCPCB_LOST
)) {
2264 if (hole
== NULL
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2269 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2270 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2271 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2273 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2276 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2279 if (tcp_retransmit_skb(sk
, skb
))
2281 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2283 if (skb
== tcp_write_queue_head(sk
))
2284 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2285 inet_csk(sk
)->icsk_rto
,
2290 /* Send a fin. The caller locks the socket for us. This cannot be
2291 * allowed to fail queueing a FIN frame under any circumstances.
2293 void tcp_send_fin(struct sock
*sk
)
2295 struct tcp_sock
*tp
= tcp_sk(sk
);
2296 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2299 /* Optimization, tack on the FIN if we have a queue of
2300 * unsent frames. But be careful about outgoing SACKS
2303 mss_now
= tcp_current_mss(sk
);
2305 if (tcp_send_head(sk
) != NULL
) {
2306 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_FIN
;
2307 TCP_SKB_CB(skb
)->end_seq
++;
2310 /* Socket is locked, keep trying until memory is available. */
2312 skb
= alloc_skb_fclone(MAX_TCP_HEADER
,
2319 /* Reserve space for headers and prepare control bits. */
2320 skb_reserve(skb
, MAX_TCP_HEADER
);
2321 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2322 tcp_init_nondata_skb(skb
, tp
->write_seq
,
2323 TCPCB_FLAG_ACK
| TCPCB_FLAG_FIN
);
2324 tcp_queue_skb(sk
, skb
);
2326 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2329 /* We get here when a process closes a file descriptor (either due to
2330 * an explicit close() or as a byproduct of exit()'ing) and there
2331 * was unread data in the receive queue. This behavior is recommended
2332 * by RFC 2525, section 2.17. -DaveM
2334 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2336 struct sk_buff
*skb
;
2338 /* NOTE: No TCP options attached and we never retransmit this. */
2339 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2341 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2345 /* Reserve space for headers and prepare control bits. */
2346 skb_reserve(skb
, MAX_TCP_HEADER
);
2347 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
2348 TCPCB_FLAG_ACK
| TCPCB_FLAG_RST
);
2350 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2351 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2352 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2354 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
2357 /* Send a crossed SYN-ACK during socket establishment.
2358 * WARNING: This routine must only be called when we have already sent
2359 * a SYN packet that crossed the incoming SYN that caused this routine
2360 * to get called. If this assumption fails then the initial rcv_wnd
2361 * and rcv_wscale values will not be correct.
2363 int tcp_send_synack(struct sock
*sk
)
2365 struct sk_buff
*skb
;
2367 skb
= tcp_write_queue_head(sk
);
2368 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_SYN
)) {
2369 printk(KERN_DEBUG
"tcp_send_synack: wrong queue state\n");
2372 if (!(TCP_SKB_CB(skb
)->flags
& TCPCB_FLAG_ACK
)) {
2373 if (skb_cloned(skb
)) {
2374 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2377 tcp_unlink_write_queue(skb
, sk
);
2378 skb_header_release(nskb
);
2379 __tcp_add_write_queue_head(sk
, nskb
);
2380 sk_wmem_free_skb(sk
, skb
);
2381 sk
->sk_wmem_queued
+= nskb
->truesize
;
2382 sk_mem_charge(sk
, nskb
->truesize
);
2386 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_ACK
;
2387 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2389 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2390 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2393 /* Prepare a SYN-ACK. */
2394 struct sk_buff
*tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2395 struct request_sock
*req
,
2396 struct request_values
*rvp
)
2398 struct tcp_out_options opts
;
2399 struct tcp_extend_values
*xvp
= tcp_xv(rvp
);
2400 struct inet_request_sock
*ireq
= inet_rsk(req
);
2401 struct tcp_sock
*tp
= tcp_sk(sk
);
2402 const struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
2404 struct sk_buff
*skb
;
2405 struct tcp_md5sig_key
*md5
;
2406 int tcp_header_size
;
2408 int s_data_desired
= 0;
2410 if (cvp
!= NULL
&& cvp
->s_data_constant
&& cvp
->s_data_desired
)
2411 s_data_desired
= cvp
->s_data_desired
;
2412 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15 + s_data_desired
, 1, GFP_ATOMIC
);
2416 /* Reserve space for headers. */
2417 skb_reserve(skb
, MAX_TCP_HEADER
);
2419 skb_dst_set(skb
, dst_clone(dst
));
2421 mss
= dst_metric(dst
, RTAX_ADVMSS
);
2422 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< mss
)
2423 mss
= tp
->rx_opt
.user_mss
;
2425 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
2427 /* Set this up on the first call only */
2428 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
2429 /* tcp_full_space because it is guaranteed to be the first packet */
2430 tcp_select_initial_window(tcp_full_space(sk
),
2431 mss
- (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
2436 dst_metric(dst
, RTAX_INITRWND
));
2437 ireq
->rcv_wscale
= rcv_wscale
;
2440 memset(&opts
, 0, sizeof(opts
));
2441 #ifdef CONFIG_SYN_COOKIES
2442 if (unlikely(req
->cookie_ts
))
2443 TCP_SKB_CB(skb
)->when
= cookie_init_timestamp(req
);
2446 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2447 tcp_header_size
= tcp_synack_options(sk
, req
, mss
,
2448 skb
, &opts
, &md5
, xvp
)
2451 skb_push(skb
, tcp_header_size
);
2452 skb_reset_transport_header(skb
);
2455 memset(th
, 0, sizeof(struct tcphdr
));
2458 TCP_ECN_make_synack(req
, th
);
2459 th
->source
= ireq
->loc_port
;
2460 th
->dest
= ireq
->rmt_port
;
2461 /* Setting of flags are superfluous here for callers (and ECE is
2462 * not even correctly set)
2464 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
2465 TCPCB_FLAG_SYN
| TCPCB_FLAG_ACK
);
2467 if (OPTION_COOKIE_EXTENSION
& opts
.options
) {
2468 if (s_data_desired
) {
2469 u8
*buf
= skb_put(skb
, s_data_desired
);
2471 /* copy data directly from the listening socket. */
2472 memcpy(buf
, cvp
->s_data_payload
, s_data_desired
);
2473 TCP_SKB_CB(skb
)->end_seq
+= s_data_desired
;
2476 if (opts
.hash_size
> 0) {
2477 __u32 workspace
[SHA_WORKSPACE_WORDS
];
2478 u32
*mess
= &xvp
->cookie_bakery
[COOKIE_DIGEST_WORDS
];
2479 u32
*tail
= &mess
[COOKIE_MESSAGE_WORDS
-1];
2481 /* Secret recipe depends on the Timestamp, (future)
2482 * Sequence and Acknowledgment Numbers, Initiator
2483 * Cookie, and others handled by IP variant caller.
2485 *tail
-- ^= opts
.tsval
;
2486 *tail
-- ^= tcp_rsk(req
)->rcv_isn
+ 1;
2487 *tail
-- ^= TCP_SKB_CB(skb
)->seq
+ 1;
2490 *tail
-- ^= ((th
->dest
<< 16) | th
->source
);
2491 *tail
-- ^= (u32
)(unsigned long)cvp
; /* per sockopt */
2493 sha_transform((__u32
*)&xvp
->cookie_bakery
[0],
2496 opts
.hash_location
=
2497 (__u8
*)&xvp
->cookie_bakery
[0];
2501 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2502 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
2504 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2505 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2506 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
2507 th
->doff
= (tcp_header_size
>> 2);
2508 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
2510 #ifdef CONFIG_TCP_MD5SIG
2511 /* Okay, we have all we need - do the md5 hash if needed */
2513 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
2514 md5
, NULL
, req
, skb
);
2521 /* Do all connect socket setups that can be done AF independent. */
2522 static void tcp_connect_init(struct sock
*sk
)
2524 struct dst_entry
*dst
= __sk_dst_get(sk
);
2525 struct tcp_sock
*tp
= tcp_sk(sk
);
2528 /* We'll fix this up when we get a response from the other end.
2529 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2531 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2532 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2534 #ifdef CONFIG_TCP_MD5SIG
2535 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2536 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2539 /* If user gave his TCP_MAXSEG, record it to clamp */
2540 if (tp
->rx_opt
.user_mss
)
2541 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2544 tcp_sync_mss(sk
, dst_mtu(dst
));
2546 if (!tp
->window_clamp
)
2547 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2548 tp
->advmss
= dst_metric(dst
, RTAX_ADVMSS
);
2549 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
2550 tp
->advmss
= tp
->rx_opt
.user_mss
;
2552 tcp_initialize_rcv_mss(sk
);
2554 tcp_select_initial_window(tcp_full_space(sk
),
2555 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2558 sysctl_tcp_window_scaling
,
2560 dst_metric(dst
, RTAX_INITRWND
));
2562 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2563 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2566 sock_reset_flag(sk
, SOCK_DONE
);
2569 tp
->snd_una
= tp
->write_seq
;
2570 tp
->snd_sml
= tp
->write_seq
;
2571 tp
->snd_up
= tp
->write_seq
;
2576 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2577 inet_csk(sk
)->icsk_retransmits
= 0;
2578 tcp_clear_retrans(tp
);
2581 /* Build a SYN and send it off. */
2582 int tcp_connect(struct sock
*sk
)
2584 struct tcp_sock
*tp
= tcp_sk(sk
);
2585 struct sk_buff
*buff
;
2587 tcp_connect_init(sk
);
2589 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
2590 if (unlikely(buff
== NULL
))
2593 /* Reserve space for headers. */
2594 skb_reserve(buff
, MAX_TCP_HEADER
);
2596 tp
->snd_nxt
= tp
->write_seq
;
2597 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPCB_FLAG_SYN
);
2598 TCP_ECN_send_syn(sk
, buff
);
2601 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2602 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
;
2603 skb_header_release(buff
);
2604 __tcp_add_write_queue_tail(sk
, buff
);
2605 sk
->sk_wmem_queued
+= buff
->truesize
;
2606 sk_mem_charge(sk
, buff
->truesize
);
2607 tp
->packets_out
+= tcp_skb_pcount(buff
);
2608 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
2610 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2611 * in order to make this packet get counted in tcpOutSegs.
2613 tp
->snd_nxt
= tp
->write_seq
;
2614 tp
->pushed_seq
= tp
->write_seq
;
2615 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
2617 /* Timer for repeating the SYN until an answer. */
2618 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2619 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2623 /* Send out a delayed ack, the caller does the policy checking
2624 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2627 void tcp_send_delayed_ack(struct sock
*sk
)
2629 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2630 int ato
= icsk
->icsk_ack
.ato
;
2631 unsigned long timeout
;
2633 if (ato
> TCP_DELACK_MIN
) {
2634 const struct tcp_sock
*tp
= tcp_sk(sk
);
2635 int max_ato
= HZ
/ 2;
2637 if (icsk
->icsk_ack
.pingpong
||
2638 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
2639 max_ato
= TCP_DELACK_MAX
;
2641 /* Slow path, intersegment interval is "high". */
2643 /* If some rtt estimate is known, use it to bound delayed ack.
2644 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2648 int rtt
= max(tp
->srtt
>> 3, TCP_DELACK_MIN
);
2654 ato
= min(ato
, max_ato
);
2657 /* Stay within the limit we were given */
2658 timeout
= jiffies
+ ato
;
2660 /* Use new timeout only if there wasn't a older one earlier. */
2661 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
2662 /* If delack timer was blocked or is about to expire,
2665 if (icsk
->icsk_ack
.blocked
||
2666 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
2671 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
2672 timeout
= icsk
->icsk_ack
.timeout
;
2674 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
2675 icsk
->icsk_ack
.timeout
= timeout
;
2676 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
2679 /* This routine sends an ack and also updates the window. */
2680 void tcp_send_ack(struct sock
*sk
)
2682 struct sk_buff
*buff
;
2684 /* If we have been reset, we may not send again. */
2685 if (sk
->sk_state
== TCP_CLOSE
)
2688 /* We are not putting this on the write queue, so
2689 * tcp_transmit_skb() will set the ownership to this
2692 buff
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2694 inet_csk_schedule_ack(sk
);
2695 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
2696 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
2697 TCP_DELACK_MAX
, TCP_RTO_MAX
);
2701 /* Reserve space for headers and prepare control bits. */
2702 skb_reserve(buff
, MAX_TCP_HEADER
);
2703 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPCB_FLAG_ACK
);
2705 /* Send it off, this clears delayed acks for us. */
2706 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2707 tcp_transmit_skb(sk
, buff
, 0, GFP_ATOMIC
);
2710 /* This routine sends a packet with an out of date sequence
2711 * number. It assumes the other end will try to ack it.
2713 * Question: what should we make while urgent mode?
2714 * 4.4BSD forces sending single byte of data. We cannot send
2715 * out of window data, because we have SND.NXT==SND.MAX...
2717 * Current solution: to send TWO zero-length segments in urgent mode:
2718 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2719 * out-of-date with SND.UNA-1 to probe window.
2721 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
2723 struct tcp_sock
*tp
= tcp_sk(sk
);
2724 struct sk_buff
*skb
;
2726 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2727 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
2731 /* Reserve space for headers and set control bits. */
2732 skb_reserve(skb
, MAX_TCP_HEADER
);
2733 /* Use a previous sequence. This should cause the other
2734 * end to send an ack. Don't queue or clone SKB, just
2737 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPCB_FLAG_ACK
);
2738 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2739 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
2742 /* Initiate keepalive or window probe from timer. */
2743 int tcp_write_wakeup(struct sock
*sk
)
2745 struct tcp_sock
*tp
= tcp_sk(sk
);
2746 struct sk_buff
*skb
;
2748 if (sk
->sk_state
== TCP_CLOSE
)
2751 if ((skb
= tcp_send_head(sk
)) != NULL
&&
2752 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
2754 unsigned int mss
= tcp_current_mss(sk
);
2755 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
2757 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
2758 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
2760 /* We are probing the opening of a window
2761 * but the window size is != 0
2762 * must have been a result SWS avoidance ( sender )
2764 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
2766 seg_size
= min(seg_size
, mss
);
2767 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2768 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
2770 } else if (!tcp_skb_pcount(skb
))
2771 tcp_set_skb_tso_segs(sk
, skb
, mss
);
2773 TCP_SKB_CB(skb
)->flags
|= TCPCB_FLAG_PSH
;
2774 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2775 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2777 tcp_event_new_data_sent(sk
, skb
);
2780 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
2781 tcp_xmit_probe_skb(sk
, 1);
2782 return tcp_xmit_probe_skb(sk
, 0);
2786 /* A window probe timeout has occurred. If window is not closed send
2787 * a partial packet else a zero probe.
2789 void tcp_send_probe0(struct sock
*sk
)
2791 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2792 struct tcp_sock
*tp
= tcp_sk(sk
);
2795 err
= tcp_write_wakeup(sk
);
2797 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
2798 /* Cancel probe timer, if it is not required. */
2799 icsk
->icsk_probes_out
= 0;
2800 icsk
->icsk_backoff
= 0;
2805 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
2806 icsk
->icsk_backoff
++;
2807 icsk
->icsk_probes_out
++;
2808 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2809 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
2812 /* If packet was not sent due to local congestion,
2813 * do not backoff and do not remember icsk_probes_out.
2814 * Let local senders to fight for local resources.
2816 * Use accumulated backoff yet.
2818 if (!icsk
->icsk_probes_out
)
2819 icsk
->icsk_probes_out
= 1;
2820 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
2821 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
2822 TCP_RESOURCE_PROBE_INTERVAL
),
2827 EXPORT_SYMBOL(tcp_select_initial_window
);
2828 EXPORT_SYMBOL(tcp_connect
);
2829 EXPORT_SYMBOL(tcp_make_synack
);
2830 EXPORT_SYMBOL(tcp_simple_retransmit
);
2831 EXPORT_SYMBOL(tcp_sync_mss
);
2832 EXPORT_SYMBOL(tcp_mtup_init
);