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
37 #define pr_fmt(fmt) "TCP: " fmt
41 #include <linux/compiler.h>
42 #include <linux/gfp.h>
43 #include <linux/module.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 /* Default TSQ limit of two TSO segments */
54 int sysctl_tcp_limit_output_bytes __read_mostly
= 131072;
56 /* This limits the percentage of the congestion window which we
57 * will allow a single TSO frame to consume. Building TSO frames
58 * which are too large can cause TCP streams to be bursty.
60 int sysctl_tcp_tso_win_divisor __read_mostly
= 3;
62 int sysctl_tcp_mtu_probing __read_mostly
= 0;
63 int sysctl_tcp_base_mss __read_mostly
= TCP_BASE_MSS
;
65 /* By default, RFC2861 behavior. */
66 int sysctl_tcp_slow_start_after_idle __read_mostly
= 1;
68 int sysctl_tcp_cookie_size __read_mostly
= 0; /* TCP_COOKIE_MAX */
69 EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size
);
71 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
72 int push_one
, gfp_t gfp
);
74 /* Account for new data that has been sent to the network. */
75 static void tcp_event_new_data_sent(struct sock
*sk
, const struct sk_buff
*skb
)
77 struct tcp_sock
*tp
= tcp_sk(sk
);
78 unsigned int prior_packets
= tp
->packets_out
;
80 tcp_advance_send_head(sk
, skb
);
81 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
83 /* Don't override Nagle indefinitely with F-RTO */
84 if (tp
->frto_counter
== 2)
87 tp
->packets_out
+= tcp_skb_pcount(skb
);
88 if (!prior_packets
|| tp
->early_retrans_delayed
)
92 /* SND.NXT, if window was not shrunk.
93 * If window has been shrunk, what should we make? It is not clear at all.
94 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
95 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
96 * invalid. OK, let's make this for now:
98 static inline __u32
tcp_acceptable_seq(const struct sock
*sk
)
100 const struct tcp_sock
*tp
= tcp_sk(sk
);
102 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
))
105 return tcp_wnd_end(tp
);
108 /* Calculate mss to advertise in SYN segment.
109 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
111 * 1. It is independent of path mtu.
112 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
113 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
114 * attached devices, because some buggy hosts are confused by
116 * 4. We do not make 3, we advertise MSS, calculated from first
117 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
118 * This may be overridden via information stored in routing table.
119 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
120 * probably even Jumbo".
122 static __u16
tcp_advertise_mss(struct sock
*sk
)
124 struct tcp_sock
*tp
= tcp_sk(sk
);
125 const struct dst_entry
*dst
= __sk_dst_get(sk
);
126 int mss
= tp
->advmss
;
129 unsigned int metric
= dst_metric_advmss(dst
);
140 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
141 * This is the first part of cwnd validation mechanism. */
142 static void tcp_cwnd_restart(struct sock
*sk
, const struct dst_entry
*dst
)
144 struct tcp_sock
*tp
= tcp_sk(sk
);
145 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
146 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
147 u32 cwnd
= tp
->snd_cwnd
;
149 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
151 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
152 restart_cwnd
= min(restart_cwnd
, cwnd
);
154 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
156 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
157 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
158 tp
->snd_cwnd_used
= 0;
161 /* Congestion state accounting after a packet has been sent. */
162 static void tcp_event_data_sent(struct tcp_sock
*tp
,
165 struct inet_connection_sock
*icsk
= inet_csk(sk
);
166 const u32 now
= tcp_time_stamp
;
168 if (sysctl_tcp_slow_start_after_idle
&&
169 (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
))
170 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
174 /* If it is a reply for ato after last received
175 * packet, enter pingpong mode.
177 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
178 icsk
->icsk_ack
.pingpong
= 1;
181 /* Account for an ACK we sent. */
182 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
184 tcp_dec_quickack_mode(sk
, pkts
);
185 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
188 /* Determine a window scaling and initial window to offer.
189 * Based on the assumption that the given amount of space
190 * will be offered. Store the results in the tp structure.
191 * NOTE: for smooth operation initial space offering should
192 * be a multiple of mss if possible. We assume here that mss >= 1.
193 * This MUST be enforced by all callers.
195 void tcp_select_initial_window(int __space
, __u32 mss
,
196 __u32
*rcv_wnd
, __u32
*window_clamp
,
197 int wscale_ok
, __u8
*rcv_wscale
,
200 unsigned int space
= (__space
< 0 ? 0 : __space
);
202 /* If no clamp set the clamp to the max possible scaled window */
203 if (*window_clamp
== 0)
204 (*window_clamp
) = (65535 << 14);
205 space
= min(*window_clamp
, space
);
207 /* Quantize space offering to a multiple of mss if possible. */
209 space
= (space
/ mss
) * mss
;
211 /* NOTE: offering an initial window larger than 32767
212 * will break some buggy TCP stacks. If the admin tells us
213 * it is likely we could be speaking with such a buggy stack
214 * we will truncate our initial window offering to 32K-1
215 * unless the remote has sent us a window scaling option,
216 * which we interpret as a sign the remote TCP is not
217 * misinterpreting the window field as a signed quantity.
219 if (sysctl_tcp_workaround_signed_windows
)
220 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
226 /* Set window scaling on max possible window
227 * See RFC1323 for an explanation of the limit to 14
229 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
230 space
= min_t(u32
, space
, *window_clamp
);
231 while (space
> 65535 && (*rcv_wscale
) < 14) {
237 /* Set initial window to a value enough for senders starting with
238 * initial congestion window of TCP_DEFAULT_INIT_RCVWND. Place
239 * a limit on the initial window when mss is larger than 1460.
241 if (mss
> (1 << *rcv_wscale
)) {
242 int init_cwnd
= TCP_DEFAULT_INIT_RCVWND
;
245 max_t(u32
, (1460 * TCP_DEFAULT_INIT_RCVWND
) / mss
, 2);
246 /* when initializing use the value from init_rcv_wnd
247 * rather than the default from above
250 *rcv_wnd
= min(*rcv_wnd
, init_rcv_wnd
* mss
);
252 *rcv_wnd
= min(*rcv_wnd
, init_cwnd
* mss
);
255 /* Set the clamp no higher than max representable value */
256 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
258 EXPORT_SYMBOL(tcp_select_initial_window
);
260 /* Chose a new window to advertise, update state in tcp_sock for the
261 * socket, and return result with RFC1323 scaling applied. The return
262 * value can be stuffed directly into th->window for an outgoing
265 static u16
tcp_select_window(struct sock
*sk
)
267 struct tcp_sock
*tp
= tcp_sk(sk
);
268 u32 cur_win
= tcp_receive_window(tp
);
269 u32 new_win
= __tcp_select_window(sk
);
271 /* Never shrink the offered window */
272 if (new_win
< cur_win
) {
273 /* Danger Will Robinson!
274 * Don't update rcv_wup/rcv_wnd here or else
275 * we will not be able to advertise a zero
276 * window in time. --DaveM
278 * Relax Will Robinson.
280 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
282 tp
->rcv_wnd
= new_win
;
283 tp
->rcv_wup
= tp
->rcv_nxt
;
285 /* Make sure we do not exceed the maximum possible
288 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
289 new_win
= min(new_win
, MAX_TCP_WINDOW
);
291 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
293 /* RFC1323 scaling applied */
294 new_win
>>= tp
->rx_opt
.rcv_wscale
;
296 /* If we advertise zero window, disable fast path. */
303 /* Packet ECN state for a SYN-ACK */
304 static inline void TCP_ECN_send_synack(const struct tcp_sock
*tp
, struct sk_buff
*skb
)
306 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_CWR
;
307 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
308 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_ECE
;
311 /* Packet ECN state for a SYN. */
312 static inline void TCP_ECN_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
314 struct tcp_sock
*tp
= tcp_sk(sk
);
317 if (sysctl_tcp_ecn
== 1) {
318 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ECE
| TCPHDR_CWR
;
319 tp
->ecn_flags
= TCP_ECN_OK
;
323 static __inline__
void
324 TCP_ECN_make_synack(const struct request_sock
*req
, struct tcphdr
*th
)
326 if (inet_rsk(req
)->ecn_ok
)
330 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
333 static inline void TCP_ECN_send(struct sock
*sk
, struct sk_buff
*skb
,
336 struct tcp_sock
*tp
= tcp_sk(sk
);
338 if (tp
->ecn_flags
& TCP_ECN_OK
) {
339 /* Not-retransmitted data segment: set ECT and inject CWR. */
340 if (skb
->len
!= tcp_header_len
&&
341 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
343 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
344 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
345 tcp_hdr(skb
)->cwr
= 1;
346 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
349 /* ACK or retransmitted segment: clear ECT|CE */
350 INET_ECN_dontxmit(sk
);
352 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
353 tcp_hdr(skb
)->ece
= 1;
357 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
358 * auto increment end seqno.
360 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
362 skb
->ip_summed
= CHECKSUM_PARTIAL
;
365 TCP_SKB_CB(skb
)->tcp_flags
= flags
;
366 TCP_SKB_CB(skb
)->sacked
= 0;
368 skb_shinfo(skb
)->gso_segs
= 1;
369 skb_shinfo(skb
)->gso_size
= 0;
370 skb_shinfo(skb
)->gso_type
= 0;
372 TCP_SKB_CB(skb
)->seq
= seq
;
373 if (flags
& (TCPHDR_SYN
| TCPHDR_FIN
))
375 TCP_SKB_CB(skb
)->end_seq
= seq
;
378 static inline bool tcp_urg_mode(const struct tcp_sock
*tp
)
380 return tp
->snd_una
!= tp
->snd_up
;
383 #define OPTION_SACK_ADVERTISE (1 << 0)
384 #define OPTION_TS (1 << 1)
385 #define OPTION_MD5 (1 << 2)
386 #define OPTION_WSCALE (1 << 3)
387 #define OPTION_COOKIE_EXTENSION (1 << 4)
388 #define OPTION_FAST_OPEN_COOKIE (1 << 8)
390 struct tcp_out_options
{
391 u16 options
; /* bit field of OPTION_* */
392 u16 mss
; /* 0 to disable */
393 u8 ws
; /* window scale, 0 to disable */
394 u8 num_sack_blocks
; /* number of SACK blocks to include */
395 u8 hash_size
; /* bytes in hash_location */
396 __u8
*hash_location
; /* temporary pointer, overloaded */
397 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
398 struct tcp_fastopen_cookie
*fastopen_cookie
; /* Fast open cookie */
401 /* The sysctl int routines are generic, so check consistency here.
403 static u8
tcp_cookie_size_check(u8 desired
)
408 /* previously specified */
411 cookie_size
= ACCESS_ONCE(sysctl_tcp_cookie_size
);
412 if (cookie_size
<= 0)
413 /* no default specified */
416 if (cookie_size
<= TCP_COOKIE_MIN
)
417 /* value too small, specify minimum */
418 return TCP_COOKIE_MIN
;
420 if (cookie_size
>= TCP_COOKIE_MAX
)
421 /* value too large, specify maximum */
422 return TCP_COOKIE_MAX
;
425 /* 8-bit multiple, illegal, fix it */
428 return (u8
)cookie_size
;
431 /* Write previously computed TCP options to the packet.
433 * Beware: Something in the Internet is very sensitive to the ordering of
434 * TCP options, we learned this through the hard way, so be careful here.
435 * Luckily we can at least blame others for their non-compliance but from
436 * inter-operatibility perspective it seems that we're somewhat stuck with
437 * the ordering which we have been using if we want to keep working with
438 * those broken things (not that it currently hurts anybody as there isn't
439 * particular reason why the ordering would need to be changed).
441 * At least SACK_PERM as the first option is known to lead to a disaster
442 * (but it may well be that other scenarios fail similarly).
444 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
445 struct tcp_out_options
*opts
)
447 u16 options
= opts
->options
; /* mungable copy */
449 /* Having both authentication and cookies for security is redundant,
450 * and there's certainly not enough room. Instead, the cookie-less
451 * extension variant is proposed.
453 * Consider the pessimal case with authentication. The options
455 * COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40
457 if (unlikely(OPTION_MD5
& options
)) {
458 if (unlikely(OPTION_COOKIE_EXTENSION
& options
)) {
459 *ptr
++ = htonl((TCPOPT_COOKIE
<< 24) |
460 (TCPOLEN_COOKIE_BASE
<< 16) |
461 (TCPOPT_MD5SIG
<< 8) |
464 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
466 (TCPOPT_MD5SIG
<< 8) |
469 options
&= ~OPTION_COOKIE_EXTENSION
;
470 /* overload cookie hash location */
471 opts
->hash_location
= (__u8
*)ptr
;
475 if (unlikely(opts
->mss
)) {
476 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
477 (TCPOLEN_MSS
<< 16) |
481 if (likely(OPTION_TS
& options
)) {
482 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
483 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
484 (TCPOLEN_SACK_PERM
<< 16) |
485 (TCPOPT_TIMESTAMP
<< 8) |
487 options
&= ~OPTION_SACK_ADVERTISE
;
489 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
491 (TCPOPT_TIMESTAMP
<< 8) |
494 *ptr
++ = htonl(opts
->tsval
);
495 *ptr
++ = htonl(opts
->tsecr
);
498 /* Specification requires after timestamp, so do it now.
500 * Consider the pessimal case without authentication. The options
502 * MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40
504 if (unlikely(OPTION_COOKIE_EXTENSION
& options
)) {
505 __u8
*cookie_copy
= opts
->hash_location
;
506 u8 cookie_size
= opts
->hash_size
;
508 /* 8-bit multiple handled in tcp_cookie_size_check() above,
511 if (0x2 & cookie_size
) {
512 __u8
*p
= (__u8
*)ptr
;
514 /* 16-bit multiple */
515 *p
++ = TCPOPT_COOKIE
;
516 *p
++ = TCPOLEN_COOKIE_BASE
+ cookie_size
;
517 *p
++ = *cookie_copy
++;
518 *p
++ = *cookie_copy
++;
522 /* 32-bit multiple */
523 *ptr
++ = htonl(((TCPOPT_NOP
<< 24) |
525 (TCPOPT_COOKIE
<< 8) |
526 TCPOLEN_COOKIE_BASE
) +
530 if (cookie_size
> 0) {
531 memcpy(ptr
, cookie_copy
, cookie_size
);
532 ptr
+= (cookie_size
/ 4);
536 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
537 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
539 (TCPOPT_SACK_PERM
<< 8) |
543 if (unlikely(OPTION_WSCALE
& options
)) {
544 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
545 (TCPOPT_WINDOW
<< 16) |
546 (TCPOLEN_WINDOW
<< 8) |
550 if (unlikely(opts
->num_sack_blocks
)) {
551 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
552 tp
->duplicate_sack
: tp
->selective_acks
;
555 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
558 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
559 TCPOLEN_SACK_PERBLOCK
)));
561 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
563 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
564 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
567 tp
->rx_opt
.dsack
= 0;
570 if (unlikely(OPTION_FAST_OPEN_COOKIE
& options
)) {
571 struct tcp_fastopen_cookie
*foc
= opts
->fastopen_cookie
;
573 *ptr
++ = htonl((TCPOPT_EXP
<< 24) |
574 ((TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
) << 16) |
575 TCPOPT_FASTOPEN_MAGIC
);
577 memcpy(ptr
, foc
->val
, foc
->len
);
578 if ((foc
->len
& 3) == 2) {
579 u8
*align
= ((u8
*)ptr
) + foc
->len
;
580 align
[0] = align
[1] = TCPOPT_NOP
;
582 ptr
+= (foc
->len
+ 3) >> 2;
586 /* Compute TCP options for SYN packets. This is not the final
587 * network wire format yet.
589 static unsigned int tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
590 struct tcp_out_options
*opts
,
591 struct tcp_md5sig_key
**md5
)
593 struct tcp_sock
*tp
= tcp_sk(sk
);
594 struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
595 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
596 u8 cookie_size
= (!tp
->rx_opt
.cookie_out_never
&& cvp
!= NULL
) ?
597 tcp_cookie_size_check(cvp
->cookie_desired
) :
599 struct tcp_fastopen_request
*fastopen
= tp
->fastopen_req
;
601 #ifdef CONFIG_TCP_MD5SIG
602 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
604 opts
->options
|= OPTION_MD5
;
605 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
611 /* We always get an MSS option. The option bytes which will be seen in
612 * normal data packets should timestamps be used, must be in the MSS
613 * advertised. But we subtract them from tp->mss_cache so that
614 * calculations in tcp_sendmsg are simpler etc. So account for this
615 * fact here if necessary. If we don't do this correctly, as a
616 * receiver we won't recognize data packets as being full sized when we
617 * should, and thus we won't abide by the delayed ACK rules correctly.
618 * SACKs don't matter, we never delay an ACK when we have any of those
620 opts
->mss
= tcp_advertise_mss(sk
);
621 remaining
-= TCPOLEN_MSS_ALIGNED
;
623 if (likely(sysctl_tcp_timestamps
&& *md5
== NULL
)) {
624 opts
->options
|= OPTION_TS
;
625 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
626 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
627 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
629 if (likely(sysctl_tcp_window_scaling
)) {
630 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
631 opts
->options
|= OPTION_WSCALE
;
632 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
634 if (likely(sysctl_tcp_sack
)) {
635 opts
->options
|= OPTION_SACK_ADVERTISE
;
636 if (unlikely(!(OPTION_TS
& opts
->options
)))
637 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
640 if (fastopen
&& fastopen
->cookie
.len
>= 0) {
641 u32 need
= TCPOLEN_EXP_FASTOPEN_BASE
+ fastopen
->cookie
.len
;
642 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
643 if (remaining
>= need
) {
644 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
645 opts
->fastopen_cookie
= &fastopen
->cookie
;
647 tp
->syn_fastopen
= 1;
650 /* Note that timestamps are required by the specification.
652 * Odd numbers of bytes are prohibited by the specification, ensuring
653 * that the cookie is 16-bit aligned, and the resulting cookie pair is
657 (OPTION_TS
& opts
->options
) &&
659 int need
= TCPOLEN_COOKIE_BASE
+ cookie_size
;
662 /* 32-bit multiple */
663 need
+= 2; /* NOPs */
665 if (need
> remaining
) {
666 /* try shrinking cookie to fit */
671 while (need
> remaining
&& TCP_COOKIE_MIN
<= cookie_size
) {
675 if (TCP_COOKIE_MIN
<= cookie_size
) {
676 opts
->options
|= OPTION_COOKIE_EXTENSION
;
677 opts
->hash_location
= (__u8
*)&cvp
->cookie_pair
[0];
678 opts
->hash_size
= cookie_size
;
680 /* Remember for future incarnations. */
681 cvp
->cookie_desired
= cookie_size
;
683 if (cvp
->cookie_desired
!= cvp
->cookie_pair_size
) {
684 /* Currently use random bytes as a nonce,
685 * assuming these are completely unpredictable
686 * by hostile users of the same system.
688 get_random_bytes(&cvp
->cookie_pair
[0],
690 cvp
->cookie_pair_size
= cookie_size
;
696 return MAX_TCP_OPTION_SPACE
- remaining
;
699 /* Set up TCP options for SYN-ACKs. */
700 static unsigned int tcp_synack_options(struct sock
*sk
,
701 struct request_sock
*req
,
702 unsigned int mss
, struct sk_buff
*skb
,
703 struct tcp_out_options
*opts
,
704 struct tcp_md5sig_key
**md5
,
705 struct tcp_extend_values
*xvp
)
707 struct inet_request_sock
*ireq
= inet_rsk(req
);
708 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
709 u8 cookie_plus
= (xvp
!= NULL
&& !xvp
->cookie_out_never
) ?
713 #ifdef CONFIG_TCP_MD5SIG
714 *md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
716 opts
->options
|= OPTION_MD5
;
717 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
719 /* We can't fit any SACK blocks in a packet with MD5 + TS
720 * options. There was discussion about disabling SACK
721 * rather than TS in order to fit in better with old,
722 * buggy kernels, but that was deemed to be unnecessary.
724 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
730 /* We always send an MSS option. */
732 remaining
-= TCPOLEN_MSS_ALIGNED
;
734 if (likely(ireq
->wscale_ok
)) {
735 opts
->ws
= ireq
->rcv_wscale
;
736 opts
->options
|= OPTION_WSCALE
;
737 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
739 if (likely(ireq
->tstamp_ok
)) {
740 opts
->options
|= OPTION_TS
;
741 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
742 opts
->tsecr
= req
->ts_recent
;
743 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
745 if (likely(ireq
->sack_ok
)) {
746 opts
->options
|= OPTION_SACK_ADVERTISE
;
747 if (unlikely(!ireq
->tstamp_ok
))
748 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
751 /* Similar rationale to tcp_syn_options() applies here, too.
752 * If the <SYN> options fit, the same options should fit now!
756 cookie_plus
> TCPOLEN_COOKIE_BASE
) {
757 int need
= cookie_plus
; /* has TCPOLEN_COOKIE_BASE */
760 /* 32-bit multiple */
761 need
+= 2; /* NOPs */
763 if (need
<= remaining
) {
764 opts
->options
|= OPTION_COOKIE_EXTENSION
;
765 opts
->hash_size
= cookie_plus
- TCPOLEN_COOKIE_BASE
;
768 /* There's no error return, so flag it. */
769 xvp
->cookie_out_never
= 1; /* true */
773 return MAX_TCP_OPTION_SPACE
- remaining
;
776 /* Compute TCP options for ESTABLISHED sockets. This is not the
777 * final wire format yet.
779 static unsigned int tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
780 struct tcp_out_options
*opts
,
781 struct tcp_md5sig_key
**md5
)
783 struct tcp_skb_cb
*tcb
= skb
? TCP_SKB_CB(skb
) : NULL
;
784 struct tcp_sock
*tp
= tcp_sk(sk
);
785 unsigned int size
= 0;
786 unsigned int eff_sacks
;
788 #ifdef CONFIG_TCP_MD5SIG
789 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
790 if (unlikely(*md5
)) {
791 opts
->options
|= OPTION_MD5
;
792 size
+= TCPOLEN_MD5SIG_ALIGNED
;
798 if (likely(tp
->rx_opt
.tstamp_ok
)) {
799 opts
->options
|= OPTION_TS
;
800 opts
->tsval
= tcb
? tcb
->when
: 0;
801 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
802 size
+= TCPOLEN_TSTAMP_ALIGNED
;
805 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
806 if (unlikely(eff_sacks
)) {
807 const unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
808 opts
->num_sack_blocks
=
809 min_t(unsigned int, eff_sacks
,
810 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
811 TCPOLEN_SACK_PERBLOCK
);
812 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
813 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
820 /* TCP SMALL QUEUES (TSQ)
822 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
823 * to reduce RTT and bufferbloat.
824 * We do this using a special skb destructor (tcp_wfree).
826 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
827 * needs to be reallocated in a driver.
828 * The invariant being skb->truesize substracted from sk->sk_wmem_alloc
830 * Since transmit from skb destructor is forbidden, we use a tasklet
831 * to process all sockets that eventually need to send more skbs.
832 * We use one tasklet per cpu, with its own queue of sockets.
835 struct tasklet_struct tasklet
;
836 struct list_head head
; /* queue of tcp sockets */
838 static DEFINE_PER_CPU(struct tsq_tasklet
, tsq_tasklet
);
840 static void tcp_tsq_handler(struct sock
*sk
)
842 if ((1 << sk
->sk_state
) &
843 (TCPF_ESTABLISHED
| TCPF_FIN_WAIT1
| TCPF_CLOSING
|
844 TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
))
845 tcp_write_xmit(sk
, tcp_current_mss(sk
), 0, 0, GFP_ATOMIC
);
848 * One tasklest per cpu tries to send more skbs.
849 * We run in tasklet context but need to disable irqs when
850 * transfering tsq->head because tcp_wfree() might
851 * interrupt us (non NAPI drivers)
853 static void tcp_tasklet_func(unsigned long data
)
855 struct tsq_tasklet
*tsq
= (struct tsq_tasklet
*)data
;
858 struct list_head
*q
, *n
;
862 local_irq_save(flags
);
863 list_splice_init(&tsq
->head
, &list
);
864 local_irq_restore(flags
);
866 list_for_each_safe(q
, n
, &list
) {
867 tp
= list_entry(q
, struct tcp_sock
, tsq_node
);
868 list_del(&tp
->tsq_node
);
870 sk
= (struct sock
*)tp
;
873 if (!sock_owned_by_user(sk
)) {
876 /* defer the work to tcp_release_cb() */
877 set_bit(TCP_TSQ_DEFERRED
, &tp
->tsq_flags
);
881 clear_bit(TSQ_QUEUED
, &tp
->tsq_flags
);
886 #define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
887 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
888 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
889 (1UL << TCP_MTU_REDUCED_DEFERRED))
891 * tcp_release_cb - tcp release_sock() callback
894 * called from release_sock() to perform protocol dependent
895 * actions before socket release.
897 void tcp_release_cb(struct sock
*sk
)
899 struct tcp_sock
*tp
= tcp_sk(sk
);
900 unsigned long flags
, nflags
;
902 /* perform an atomic operation only if at least one flag is set */
904 flags
= tp
->tsq_flags
;
905 if (!(flags
& TCP_DEFERRED_ALL
))
907 nflags
= flags
& ~TCP_DEFERRED_ALL
;
908 } while (cmpxchg(&tp
->tsq_flags
, flags
, nflags
) != flags
);
910 if (flags
& (1UL << TCP_TSQ_DEFERRED
))
913 if (flags
& (1UL << TCP_WRITE_TIMER_DEFERRED
)) {
914 tcp_write_timer_handler(sk
);
917 if (flags
& (1UL << TCP_DELACK_TIMER_DEFERRED
)) {
918 tcp_delack_timer_handler(sk
);
921 if (flags
& (1UL << TCP_MTU_REDUCED_DEFERRED
)) {
922 sk
->sk_prot
->mtu_reduced(sk
);
926 EXPORT_SYMBOL(tcp_release_cb
);
928 void __init
tcp_tasklet_init(void)
932 for_each_possible_cpu(i
) {
933 struct tsq_tasklet
*tsq
= &per_cpu(tsq_tasklet
, i
);
935 INIT_LIST_HEAD(&tsq
->head
);
936 tasklet_init(&tsq
->tasklet
,
943 * Write buffer destructor automatically called from kfree_skb.
944 * We cant xmit new skbs from this context, as we might already
947 static void tcp_wfree(struct sk_buff
*skb
)
949 struct sock
*sk
= skb
->sk
;
950 struct tcp_sock
*tp
= tcp_sk(sk
);
952 if (test_and_clear_bit(TSQ_THROTTLED
, &tp
->tsq_flags
) &&
953 !test_and_set_bit(TSQ_QUEUED
, &tp
->tsq_flags
)) {
955 struct tsq_tasklet
*tsq
;
957 /* Keep a ref on socket.
958 * This last ref will be released in tcp_tasklet_func()
960 atomic_sub(skb
->truesize
- 1, &sk
->sk_wmem_alloc
);
962 /* queue this socket to tasklet queue */
963 local_irq_save(flags
);
964 tsq
= &__get_cpu_var(tsq_tasklet
);
965 list_add(&tp
->tsq_node
, &tsq
->head
);
966 tasklet_schedule(&tsq
->tasklet
);
967 local_irq_restore(flags
);
973 /* This routine actually transmits TCP packets queued in by
974 * tcp_do_sendmsg(). This is used by both the initial
975 * transmission and possible later retransmissions.
976 * All SKB's seen here are completely headerless. It is our
977 * job to build the TCP header, and pass the packet down to
978 * IP so it can do the same plus pass the packet off to the
981 * We are working here with either a clone of the original
982 * SKB, or a fresh unique copy made by the retransmit engine.
984 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
987 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
988 struct inet_sock
*inet
;
990 struct tcp_skb_cb
*tcb
;
991 struct tcp_out_options opts
;
992 unsigned int tcp_options_size
, tcp_header_size
;
993 struct tcp_md5sig_key
*md5
;
997 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
999 /* If congestion control is doing timestamping, we must
1000 * take such a timestamp before we potentially clone/copy.
1002 if (icsk
->icsk_ca_ops
->flags
& TCP_CONG_RTT_STAMP
)
1003 __net_timestamp(skb
);
1005 if (likely(clone_it
)) {
1006 if (unlikely(skb_cloned(skb
)))
1007 skb
= pskb_copy(skb
, gfp_mask
);
1009 skb
= skb_clone(skb
, gfp_mask
);
1016 tcb
= TCP_SKB_CB(skb
);
1017 memset(&opts
, 0, sizeof(opts
));
1019 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
))
1020 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
1022 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
1024 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
1026 if (tcp_packets_in_flight(tp
) == 0) {
1027 tcp_ca_event(sk
, CA_EVENT_TX_START
);
1032 skb_push(skb
, tcp_header_size
);
1033 skb_reset_transport_header(skb
);
1037 skb
->destructor
= (sysctl_tcp_limit_output_bytes
> 0) ?
1038 tcp_wfree
: sock_wfree
;
1039 atomic_add(skb
->truesize
, &sk
->sk_wmem_alloc
);
1041 /* Build TCP header and checksum it. */
1043 th
->source
= inet
->inet_sport
;
1044 th
->dest
= inet
->inet_dport
;
1045 th
->seq
= htonl(tcb
->seq
);
1046 th
->ack_seq
= htonl(tp
->rcv_nxt
);
1047 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
1050 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
)) {
1051 /* RFC1323: The window in SYN & SYN/ACK segments
1054 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
1056 th
->window
= htons(tcp_select_window(sk
));
1061 /* The urg_mode check is necessary during a below snd_una win probe */
1062 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
1063 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
1064 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
1066 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
1067 th
->urg_ptr
= htons(0xFFFF);
1072 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
1073 if (likely((tcb
->tcp_flags
& TCPHDR_SYN
) == 0))
1074 TCP_ECN_send(sk
, skb
, tcp_header_size
);
1076 #ifdef CONFIG_TCP_MD5SIG
1077 /* Calculate the MD5 hash, as we have all we need now */
1079 sk_nocaps_add(sk
, NETIF_F_GSO_MASK
);
1080 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
1081 md5
, sk
, NULL
, skb
);
1085 icsk
->icsk_af_ops
->send_check(sk
, skb
);
1087 if (likely(tcb
->tcp_flags
& TCPHDR_ACK
))
1088 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
1090 if (skb
->len
!= tcp_header_size
)
1091 tcp_event_data_sent(tp
, sk
);
1093 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
1094 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
,
1095 tcp_skb_pcount(skb
));
1097 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, &inet
->cork
.fl
);
1098 if (likely(err
<= 0))
1101 tcp_enter_cwr(sk
, 1);
1103 return net_xmit_eval(err
);
1106 /* This routine just queues the buffer for sending.
1108 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1109 * otherwise socket can stall.
1111 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
1113 struct tcp_sock
*tp
= tcp_sk(sk
);
1115 /* Advance write_seq and place onto the write_queue. */
1116 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
1117 skb_header_release(skb
);
1118 tcp_add_write_queue_tail(sk
, skb
);
1119 sk
->sk_wmem_queued
+= skb
->truesize
;
1120 sk_mem_charge(sk
, skb
->truesize
);
1123 /* Initialize TSO segments for a packet. */
1124 static void tcp_set_skb_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
1125 unsigned int mss_now
)
1127 if (skb
->len
<= mss_now
|| !sk_can_gso(sk
) ||
1128 skb
->ip_summed
== CHECKSUM_NONE
) {
1129 /* Avoid the costly divide in the normal
1132 skb_shinfo(skb
)->gso_segs
= 1;
1133 skb_shinfo(skb
)->gso_size
= 0;
1134 skb_shinfo(skb
)->gso_type
= 0;
1136 skb_shinfo(skb
)->gso_segs
= DIV_ROUND_UP(skb
->len
, mss_now
);
1137 skb_shinfo(skb
)->gso_size
= mss_now
;
1138 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
1142 /* When a modification to fackets out becomes necessary, we need to check
1143 * skb is counted to fackets_out or not.
1145 static void tcp_adjust_fackets_out(struct sock
*sk
, const struct sk_buff
*skb
,
1148 struct tcp_sock
*tp
= tcp_sk(sk
);
1150 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
1153 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
1154 tp
->fackets_out
-= decr
;
1157 /* Pcount in the middle of the write queue got changed, we need to do various
1158 * tweaks to fix counters
1160 static void tcp_adjust_pcount(struct sock
*sk
, const struct sk_buff
*skb
, int decr
)
1162 struct tcp_sock
*tp
= tcp_sk(sk
);
1164 tp
->packets_out
-= decr
;
1166 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1167 tp
->sacked_out
-= decr
;
1168 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1169 tp
->retrans_out
-= decr
;
1170 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
1171 tp
->lost_out
-= decr
;
1173 /* Reno case is special. Sigh... */
1174 if (tcp_is_reno(tp
) && decr
> 0)
1175 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
1177 tcp_adjust_fackets_out(sk
, skb
, decr
);
1179 if (tp
->lost_skb_hint
&&
1180 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
1181 (tcp_is_fack(tp
) || (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)))
1182 tp
->lost_cnt_hint
-= decr
;
1184 tcp_verify_left_out(tp
);
1187 /* Function to create two new TCP segments. Shrinks the given segment
1188 * to the specified size and appends a new segment with the rest of the
1189 * packet to the list. This won't be called frequently, I hope.
1190 * Remember, these are still headerless SKBs at this point.
1192 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
1193 unsigned int mss_now
)
1195 struct tcp_sock
*tp
= tcp_sk(sk
);
1196 struct sk_buff
*buff
;
1197 int nsize
, old_factor
;
1201 if (WARN_ON(len
> skb
->len
))
1204 nsize
= skb_headlen(skb
) - len
;
1208 if (skb_cloned(skb
) &&
1209 skb_is_nonlinear(skb
) &&
1210 pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
1213 /* Get a new skb... force flag on. */
1214 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
1216 return -ENOMEM
; /* We'll just try again later. */
1218 sk
->sk_wmem_queued
+= buff
->truesize
;
1219 sk_mem_charge(sk
, buff
->truesize
);
1220 nlen
= skb
->len
- len
- nsize
;
1221 buff
->truesize
+= nlen
;
1222 skb
->truesize
-= nlen
;
1224 /* Correct the sequence numbers. */
1225 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1226 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1227 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1229 /* PSH and FIN should only be set in the second packet. */
1230 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1231 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1232 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1233 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1235 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
1236 /* Copy and checksum data tail into the new buffer. */
1237 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
1238 skb_put(buff
, nsize
),
1243 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
1245 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1246 skb_split(skb
, buff
, len
);
1249 buff
->ip_summed
= skb
->ip_summed
;
1251 /* Looks stupid, but our code really uses when of
1252 * skbs, which it never sent before. --ANK
1254 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
1255 buff
->tstamp
= skb
->tstamp
;
1257 old_factor
= tcp_skb_pcount(skb
);
1259 /* Fix up tso_factor for both original and new SKB. */
1260 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1261 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1263 /* If this packet has been sent out already, we must
1264 * adjust the various packet counters.
1266 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1267 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1268 tcp_skb_pcount(buff
);
1271 tcp_adjust_pcount(sk
, skb
, diff
);
1274 /* Link BUFF into the send queue. */
1275 skb_header_release(buff
);
1276 tcp_insert_write_queue_after(skb
, buff
, sk
);
1281 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1282 * eventually). The difference is that pulled data not copied, but
1283 * immediately discarded.
1285 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
1289 eat
= min_t(int, len
, skb_headlen(skb
));
1291 __skb_pull(skb
, eat
);
1292 skb
->avail_size
-= eat
;
1299 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
1300 int size
= skb_frag_size(&skb_shinfo(skb
)->frags
[i
]);
1303 skb_frag_unref(skb
, i
);
1306 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
1308 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
1309 skb_frag_size_sub(&skb_shinfo(skb
)->frags
[k
], eat
);
1315 skb_shinfo(skb
)->nr_frags
= k
;
1317 skb_reset_tail_pointer(skb
);
1318 skb
->data_len
-= len
;
1319 skb
->len
= skb
->data_len
;
1322 /* Remove acked data from a packet in the transmit queue. */
1323 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1325 if (skb_cloned(skb
) && pskb_expand_head(skb
, 0, 0, GFP_ATOMIC
))
1328 __pskb_trim_head(skb
, len
);
1330 TCP_SKB_CB(skb
)->seq
+= len
;
1331 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1333 skb
->truesize
-= len
;
1334 sk
->sk_wmem_queued
-= len
;
1335 sk_mem_uncharge(sk
, len
);
1336 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
1338 /* Any change of skb->len requires recalculation of tso factor. */
1339 if (tcp_skb_pcount(skb
) > 1)
1340 tcp_set_skb_tso_segs(sk
, skb
, tcp_skb_mss(skb
));
1345 /* Calculate MSS. Not accounting for SACKs here. */
1346 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1348 const struct tcp_sock
*tp
= tcp_sk(sk
);
1349 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1352 /* Calculate base mss without TCP options:
1353 It is MMS_S - sizeof(tcphdr) of rfc1122
1355 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1357 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1358 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1359 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1361 if (dst
&& dst_allfrag(dst
))
1362 mss_now
-= icsk
->icsk_af_ops
->net_frag_header_len
;
1365 /* Clamp it (mss_clamp does not include tcp options) */
1366 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1367 mss_now
= tp
->rx_opt
.mss_clamp
;
1369 /* Now subtract optional transport overhead */
1370 mss_now
-= icsk
->icsk_ext_hdr_len
;
1372 /* Then reserve room for full set of TCP options and 8 bytes of data */
1376 /* Now subtract TCP options size, not including SACKs */
1377 mss_now
-= tp
->tcp_header_len
- sizeof(struct tcphdr
);
1382 /* Inverse of above */
1383 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1385 const struct tcp_sock
*tp
= tcp_sk(sk
);
1386 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1390 tp
->tcp_header_len
+
1391 icsk
->icsk_ext_hdr_len
+
1392 icsk
->icsk_af_ops
->net_header_len
;
1394 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1395 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1396 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1398 if (dst
&& dst_allfrag(dst
))
1399 mtu
+= icsk
->icsk_af_ops
->net_frag_header_len
;
1404 /* MTU probing init per socket */
1405 void tcp_mtup_init(struct sock
*sk
)
1407 struct tcp_sock
*tp
= tcp_sk(sk
);
1408 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1410 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
1411 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1412 icsk
->icsk_af_ops
->net_header_len
;
1413 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
1414 icsk
->icsk_mtup
.probe_size
= 0;
1416 EXPORT_SYMBOL(tcp_mtup_init
);
1418 /* This function synchronize snd mss to current pmtu/exthdr set.
1420 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1421 for TCP options, but includes only bare TCP header.
1423 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1424 It is minimum of user_mss and mss received with SYN.
1425 It also does not include TCP options.
1427 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1429 tp->mss_cache is current effective sending mss, including
1430 all tcp options except for SACKs. It is evaluated,
1431 taking into account current pmtu, but never exceeds
1432 tp->rx_opt.mss_clamp.
1434 NOTE1. rfc1122 clearly states that advertised MSS
1435 DOES NOT include either tcp or ip options.
1437 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1438 are READ ONLY outside this function. --ANK (980731)
1440 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1442 struct tcp_sock
*tp
= tcp_sk(sk
);
1443 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1446 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1447 icsk
->icsk_mtup
.search_high
= pmtu
;
1449 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1450 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1452 /* And store cached results */
1453 icsk
->icsk_pmtu_cookie
= pmtu
;
1454 if (icsk
->icsk_mtup
.enabled
)
1455 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1456 tp
->mss_cache
= mss_now
;
1460 EXPORT_SYMBOL(tcp_sync_mss
);
1462 /* Compute the current effective MSS, taking SACKs and IP options,
1463 * and even PMTU discovery events into account.
1465 unsigned int tcp_current_mss(struct sock
*sk
)
1467 const struct tcp_sock
*tp
= tcp_sk(sk
);
1468 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1470 unsigned int header_len
;
1471 struct tcp_out_options opts
;
1472 struct tcp_md5sig_key
*md5
;
1474 mss_now
= tp
->mss_cache
;
1477 u32 mtu
= dst_mtu(dst
);
1478 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1479 mss_now
= tcp_sync_mss(sk
, mtu
);
1482 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1483 sizeof(struct tcphdr
);
1484 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1485 * some common options. If this is an odd packet (because we have SACK
1486 * blocks etc) then our calculated header_len will be different, and
1487 * we have to adjust mss_now correspondingly */
1488 if (header_len
!= tp
->tcp_header_len
) {
1489 int delta
= (int) header_len
- tp
->tcp_header_len
;
1496 /* Congestion window validation. (RFC2861) */
1497 static void tcp_cwnd_validate(struct sock
*sk
)
1499 struct tcp_sock
*tp
= tcp_sk(sk
);
1501 if (tp
->packets_out
>= tp
->snd_cwnd
) {
1502 /* Network is feed fully. */
1503 tp
->snd_cwnd_used
= 0;
1504 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1506 /* Network starves. */
1507 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1508 tp
->snd_cwnd_used
= tp
->packets_out
;
1510 if (sysctl_tcp_slow_start_after_idle
&&
1511 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1512 tcp_cwnd_application_limited(sk
);
1516 /* Returns the portion of skb which can be sent right away without
1517 * introducing MSS oddities to segment boundaries. In rare cases where
1518 * mss_now != mss_cache, we will request caller to create a small skb
1519 * per input skb which could be mostly avoided here (if desired).
1521 * We explicitly want to create a request for splitting write queue tail
1522 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
1523 * thus all the complexity (cwnd_len is always MSS multiple which we
1524 * return whenever allowed by the other factors). Basically we need the
1525 * modulo only when the receiver window alone is the limiting factor or
1526 * when we would be allowed to send the split-due-to-Nagle skb fully.
1528 static unsigned int tcp_mss_split_point(const struct sock
*sk
, const struct sk_buff
*skb
,
1529 unsigned int mss_now
, unsigned int max_segs
)
1531 const struct tcp_sock
*tp
= tcp_sk(sk
);
1532 u32 needed
, window
, max_len
;
1534 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1535 max_len
= mss_now
* max_segs
;
1537 if (likely(max_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1540 needed
= min(skb
->len
, window
);
1542 if (max_len
<= needed
)
1545 return needed
- needed
% mss_now
;
1548 /* Can at least one segment of SKB be sent right now, according to the
1549 * congestion window rules? If so, return how many segments are allowed.
1551 static inline unsigned int tcp_cwnd_test(const struct tcp_sock
*tp
,
1552 const struct sk_buff
*skb
)
1554 u32 in_flight
, cwnd
;
1556 /* Don't be strict about the congestion window for the final FIN. */
1557 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
1558 tcp_skb_pcount(skb
) == 1)
1561 in_flight
= tcp_packets_in_flight(tp
);
1562 cwnd
= tp
->snd_cwnd
;
1563 if (in_flight
< cwnd
)
1564 return (cwnd
- in_flight
);
1569 /* Initialize TSO state of a skb.
1570 * This must be invoked the first time we consider transmitting
1571 * SKB onto the wire.
1573 static int tcp_init_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
1574 unsigned int mss_now
)
1576 int tso_segs
= tcp_skb_pcount(skb
);
1578 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1579 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1580 tso_segs
= tcp_skb_pcount(skb
);
1585 /* Minshall's variant of the Nagle send check. */
1586 static inline bool tcp_minshall_check(const struct tcp_sock
*tp
)
1588 return after(tp
->snd_sml
, tp
->snd_una
) &&
1589 !after(tp
->snd_sml
, tp
->snd_nxt
);
1592 /* Return false, if packet can be sent now without violation Nagle's rules:
1593 * 1. It is full sized.
1594 * 2. Or it contains FIN. (already checked by caller)
1595 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1596 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1597 * With Minshall's modification: all sent small packets are ACKed.
1599 static inline bool tcp_nagle_check(const struct tcp_sock
*tp
,
1600 const struct sk_buff
*skb
,
1601 unsigned int mss_now
, int nonagle
)
1603 return skb
->len
< mss_now
&&
1604 ((nonagle
& TCP_NAGLE_CORK
) ||
1605 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
)));
1608 /* Return true if the Nagle test allows this packet to be
1611 static inline bool tcp_nagle_test(const struct tcp_sock
*tp
, const struct sk_buff
*skb
,
1612 unsigned int cur_mss
, int nonagle
)
1614 /* Nagle rule does not apply to frames, which sit in the middle of the
1615 * write_queue (they have no chances to get new data).
1617 * This is implemented in the callers, where they modify the 'nonagle'
1618 * argument based upon the location of SKB in the send queue.
1620 if (nonagle
& TCP_NAGLE_PUSH
)
1623 /* Don't use the nagle rule for urgent data (or for the final FIN).
1624 * Nagle can be ignored during F-RTO too (see RFC4138).
1626 if (tcp_urg_mode(tp
) || (tp
->frto_counter
== 2) ||
1627 (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
))
1630 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
1636 /* Does at least the first segment of SKB fit into the send window? */
1637 static bool tcp_snd_wnd_test(const struct tcp_sock
*tp
,
1638 const struct sk_buff
*skb
,
1639 unsigned int cur_mss
)
1641 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1643 if (skb
->len
> cur_mss
)
1644 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1646 return !after(end_seq
, tcp_wnd_end(tp
));
1649 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1650 * should be put on the wire right now. If so, it returns the number of
1651 * packets allowed by the congestion window.
1653 static unsigned int tcp_snd_test(const struct sock
*sk
, struct sk_buff
*skb
,
1654 unsigned int cur_mss
, int nonagle
)
1656 const struct tcp_sock
*tp
= tcp_sk(sk
);
1657 unsigned int cwnd_quota
;
1659 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1661 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1664 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1665 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1671 /* Test if sending is allowed right now. */
1672 bool tcp_may_send_now(struct sock
*sk
)
1674 const struct tcp_sock
*tp
= tcp_sk(sk
);
1675 struct sk_buff
*skb
= tcp_send_head(sk
);
1678 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1679 (tcp_skb_is_last(sk
, skb
) ?
1680 tp
->nonagle
: TCP_NAGLE_PUSH
));
1683 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1684 * which is put after SKB on the list. It is very much like
1685 * tcp_fragment() except that it may make several kinds of assumptions
1686 * in order to speed up the splitting operation. In particular, we
1687 * know that all the data is in scatter-gather pages, and that the
1688 * packet has never been sent out before (and thus is not cloned).
1690 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1691 unsigned int mss_now
, gfp_t gfp
)
1693 struct sk_buff
*buff
;
1694 int nlen
= skb
->len
- len
;
1697 /* All of a TSO frame must be composed of paged data. */
1698 if (skb
->len
!= skb
->data_len
)
1699 return tcp_fragment(sk
, skb
, len
, mss_now
);
1701 buff
= sk_stream_alloc_skb(sk
, 0, gfp
);
1702 if (unlikely(buff
== NULL
))
1705 sk
->sk_wmem_queued
+= buff
->truesize
;
1706 sk_mem_charge(sk
, buff
->truesize
);
1707 buff
->truesize
+= nlen
;
1708 skb
->truesize
-= nlen
;
1710 /* Correct the sequence numbers. */
1711 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1712 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1713 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1715 /* PSH and FIN should only be set in the second packet. */
1716 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1717 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1718 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1720 /* This packet was never sent out yet, so no SACK bits. */
1721 TCP_SKB_CB(buff
)->sacked
= 0;
1723 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1724 skb_split(skb
, buff
, len
);
1726 /* Fix up tso_factor for both original and new SKB. */
1727 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1728 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1730 /* Link BUFF into the send queue. */
1731 skb_header_release(buff
);
1732 tcp_insert_write_queue_after(skb
, buff
, sk
);
1737 /* Try to defer sending, if possible, in order to minimize the amount
1738 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1740 * This algorithm is from John Heffner.
1742 static bool tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
)
1744 struct tcp_sock
*tp
= tcp_sk(sk
);
1745 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1746 u32 send_win
, cong_win
, limit
, in_flight
;
1749 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1752 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1755 /* Defer for less than two clock ticks. */
1756 if (tp
->tso_deferred
&&
1757 (((u32
)jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1760 in_flight
= tcp_packets_in_flight(tp
);
1762 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1764 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1766 /* From in_flight test above, we know that cwnd > in_flight. */
1767 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1769 limit
= min(send_win
, cong_win
);
1771 /* If a full-sized TSO skb can be sent, do it. */
1772 if (limit
>= min_t(unsigned int, sk
->sk_gso_max_size
,
1773 sk
->sk_gso_max_segs
* tp
->mss_cache
))
1776 /* Middle in queue won't get any more data, full sendable already? */
1777 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1780 win_divisor
= ACCESS_ONCE(sysctl_tcp_tso_win_divisor
);
1782 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1784 /* If at least some fraction of a window is available,
1787 chunk
/= win_divisor
;
1791 /* Different approach, try not to defer past a single
1792 * ACK. Receiver should ACK every other full sized
1793 * frame, so if we have space for more than 3 frames
1796 if (limit
> tcp_max_tso_deferred_mss(tp
) * tp
->mss_cache
)
1800 /* Ok, it looks like it is advisable to defer. */
1801 tp
->tso_deferred
= 1 | (jiffies
<< 1);
1806 tp
->tso_deferred
= 0;
1810 /* Create a new MTU probe if we are ready.
1811 * MTU probe is regularly attempting to increase the path MTU by
1812 * deliberately sending larger packets. This discovers routing
1813 * changes resulting in larger path MTUs.
1815 * Returns 0 if we should wait to probe (no cwnd available),
1816 * 1 if a probe was sent,
1819 static int tcp_mtu_probe(struct sock
*sk
)
1821 struct tcp_sock
*tp
= tcp_sk(sk
);
1822 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1823 struct sk_buff
*skb
, *nskb
, *next
;
1830 /* Not currently probing/verifying,
1832 * have enough cwnd, and
1833 * not SACKing (the variable headers throw things off) */
1834 if (!icsk
->icsk_mtup
.enabled
||
1835 icsk
->icsk_mtup
.probe_size
||
1836 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1837 tp
->snd_cwnd
< 11 ||
1838 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
)
1841 /* Very simple search strategy: just double the MSS. */
1842 mss_now
= tcp_current_mss(sk
);
1843 probe_size
= 2 * tp
->mss_cache
;
1844 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1845 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1846 /* TODO: set timer for probe_converge_event */
1850 /* Have enough data in the send queue to probe? */
1851 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1854 if (tp
->snd_wnd
< size_needed
)
1856 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1859 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1860 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1861 if (!tcp_packets_in_flight(tp
))
1867 /* We're allowed to probe. Build it now. */
1868 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1870 sk
->sk_wmem_queued
+= nskb
->truesize
;
1871 sk_mem_charge(sk
, nskb
->truesize
);
1873 skb
= tcp_send_head(sk
);
1875 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1876 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1877 TCP_SKB_CB(nskb
)->tcp_flags
= TCPHDR_ACK
;
1878 TCP_SKB_CB(nskb
)->sacked
= 0;
1880 nskb
->ip_summed
= skb
->ip_summed
;
1882 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1885 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1886 copy
= min_t(int, skb
->len
, probe_size
- len
);
1887 if (nskb
->ip_summed
)
1888 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1890 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1891 skb_put(nskb
, copy
),
1894 if (skb
->len
<= copy
) {
1895 /* We've eaten all the data from this skb.
1897 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1898 tcp_unlink_write_queue(skb
, sk
);
1899 sk_wmem_free_skb(sk
, skb
);
1901 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
&
1902 ~(TCPHDR_FIN
|TCPHDR_PSH
);
1903 if (!skb_shinfo(skb
)->nr_frags
) {
1904 skb_pull(skb
, copy
);
1905 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1906 skb
->csum
= csum_partial(skb
->data
,
1909 __pskb_trim_head(skb
, copy
);
1910 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1912 TCP_SKB_CB(skb
)->seq
+= copy
;
1917 if (len
>= probe_size
)
1920 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1922 /* We're ready to send. If this fails, the probe will
1923 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1924 TCP_SKB_CB(nskb
)->when
= tcp_time_stamp
;
1925 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1926 /* Decrement cwnd here because we are sending
1927 * effectively two packets. */
1929 tcp_event_new_data_sent(sk
, nskb
);
1931 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1932 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1933 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1941 /* This routine writes packets to the network. It advances the
1942 * send_head. This happens as incoming acks open up the remote
1945 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1946 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1947 * account rare use of URG, this is not a big flaw.
1949 * Returns true, if no segments are in flight and we have queued segments,
1950 * but cannot send anything now because of SWS or another problem.
1952 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
1953 int push_one
, gfp_t gfp
)
1955 struct tcp_sock
*tp
= tcp_sk(sk
);
1956 struct sk_buff
*skb
;
1957 unsigned int tso_segs
, sent_pkts
;
1964 /* Do MTU probing. */
1965 result
= tcp_mtu_probe(sk
);
1968 } else if (result
> 0) {
1973 while ((skb
= tcp_send_head(sk
))) {
1977 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1980 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1984 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1987 if (tso_segs
== 1) {
1988 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1989 (tcp_skb_is_last(sk
, skb
) ?
1990 nonagle
: TCP_NAGLE_PUSH
))))
1993 if (!push_one
&& tcp_tso_should_defer(sk
, skb
))
1997 /* TSQ : sk_wmem_alloc accounts skb truesize,
1998 * including skb overhead. But thats OK.
2000 if (atomic_read(&sk
->sk_wmem_alloc
) >= sysctl_tcp_limit_output_bytes
) {
2001 set_bit(TSQ_THROTTLED
, &tp
->tsq_flags
);
2005 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
2006 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
2009 sk
->sk_gso_max_segs
));
2011 if (skb
->len
> limit
&&
2012 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
, gfp
)))
2015 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2017 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
2020 /* Advance the send_head. This one is sent out.
2021 * This call will increment packets_out.
2023 tcp_event_new_data_sent(sk
, skb
);
2025 tcp_minshall_update(tp
, mss_now
, skb
);
2026 sent_pkts
+= tcp_skb_pcount(skb
);
2031 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Recovery
)
2032 tp
->prr_out
+= sent_pkts
;
2034 if (likely(sent_pkts
)) {
2035 tcp_cwnd_validate(sk
);
2038 return !tp
->packets_out
&& tcp_send_head(sk
);
2041 /* Push out any pending frames which were held back due to
2042 * TCP_CORK or attempt at coalescing tiny packets.
2043 * The socket must be locked by the caller.
2045 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
2048 /* If we are closed, the bytes will have to remain here.
2049 * In time closedown will finish, we empty the write queue and
2050 * all will be happy.
2052 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
2055 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0,
2056 sk_gfp_atomic(sk
, GFP_ATOMIC
)))
2057 tcp_check_probe_timer(sk
);
2060 /* Send _single_ skb sitting at the send head. This function requires
2061 * true push pending frames to setup probe timer etc.
2063 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
2065 struct sk_buff
*skb
= tcp_send_head(sk
);
2067 BUG_ON(!skb
|| skb
->len
< mss_now
);
2069 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
2072 /* This function returns the amount that we can raise the
2073 * usable window based on the following constraints
2075 * 1. The window can never be shrunk once it is offered (RFC 793)
2076 * 2. We limit memory per socket
2079 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2080 * RECV.NEXT + RCV.WIN fixed until:
2081 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2083 * i.e. don't raise the right edge of the window until you can raise
2084 * it at least MSS bytes.
2086 * Unfortunately, the recommended algorithm breaks header prediction,
2087 * since header prediction assumes th->window stays fixed.
2089 * Strictly speaking, keeping th->window fixed violates the receiver
2090 * side SWS prevention criteria. The problem is that under this rule
2091 * a stream of single byte packets will cause the right side of the
2092 * window to always advance by a single byte.
2094 * Of course, if the sender implements sender side SWS prevention
2095 * then this will not be a problem.
2097 * BSD seems to make the following compromise:
2099 * If the free space is less than the 1/4 of the maximum
2100 * space available and the free space is less than 1/2 mss,
2101 * then set the window to 0.
2102 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2103 * Otherwise, just prevent the window from shrinking
2104 * and from being larger than the largest representable value.
2106 * This prevents incremental opening of the window in the regime
2107 * where TCP is limited by the speed of the reader side taking
2108 * data out of the TCP receive queue. It does nothing about
2109 * those cases where the window is constrained on the sender side
2110 * because the pipeline is full.
2112 * BSD also seems to "accidentally" limit itself to windows that are a
2113 * multiple of MSS, at least until the free space gets quite small.
2114 * This would appear to be a side effect of the mbuf implementation.
2115 * Combining these two algorithms results in the observed behavior
2116 * of having a fixed window size at almost all times.
2118 * Below we obtain similar behavior by forcing the offered window to
2119 * a multiple of the mss when it is feasible to do so.
2121 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2122 * Regular options like TIMESTAMP are taken into account.
2124 u32
__tcp_select_window(struct sock
*sk
)
2126 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2127 struct tcp_sock
*tp
= tcp_sk(sk
);
2128 /* MSS for the peer's data. Previous versions used mss_clamp
2129 * here. I don't know if the value based on our guesses
2130 * of peer's MSS is better for the performance. It's more correct
2131 * but may be worse for the performance because of rcv_mss
2132 * fluctuations. --SAW 1998/11/1
2134 int mss
= icsk
->icsk_ack
.rcv_mss
;
2135 int free_space
= tcp_space(sk
);
2136 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
2139 if (mss
> full_space
)
2142 if (free_space
< (full_space
>> 1)) {
2143 icsk
->icsk_ack
.quick
= 0;
2145 if (sk_under_memory_pressure(sk
))
2146 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
2149 if (free_space
< mss
)
2153 if (free_space
> tp
->rcv_ssthresh
)
2154 free_space
= tp
->rcv_ssthresh
;
2156 /* Don't do rounding if we are using window scaling, since the
2157 * scaled window will not line up with the MSS boundary anyway.
2159 window
= tp
->rcv_wnd
;
2160 if (tp
->rx_opt
.rcv_wscale
) {
2161 window
= free_space
;
2163 /* Advertise enough space so that it won't get scaled away.
2164 * Import case: prevent zero window announcement if
2165 * 1<<rcv_wscale > mss.
2167 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
2168 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
2169 << tp
->rx_opt
.rcv_wscale
);
2171 /* Get the largest window that is a nice multiple of mss.
2172 * Window clamp already applied above.
2173 * If our current window offering is within 1 mss of the
2174 * free space we just keep it. This prevents the divide
2175 * and multiply from happening most of the time.
2176 * We also don't do any window rounding when the free space
2179 if (window
<= free_space
- mss
|| window
> free_space
)
2180 window
= (free_space
/ mss
) * mss
;
2181 else if (mss
== full_space
&&
2182 free_space
> window
+ (full_space
>> 1))
2183 window
= free_space
;
2189 /* Collapses two adjacent SKB's during retransmission. */
2190 static void tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
2192 struct tcp_sock
*tp
= tcp_sk(sk
);
2193 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
2194 int skb_size
, next_skb_size
;
2196 skb_size
= skb
->len
;
2197 next_skb_size
= next_skb
->len
;
2199 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
2201 tcp_highest_sack_combine(sk
, next_skb
, skb
);
2203 tcp_unlink_write_queue(next_skb
, sk
);
2205 skb_copy_from_linear_data(next_skb
, skb_put(skb
, next_skb_size
),
2208 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
2209 skb
->ip_summed
= CHECKSUM_PARTIAL
;
2211 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2212 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
2214 /* Update sequence range on original skb. */
2215 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
2217 /* Merge over control information. This moves PSH/FIN etc. over */
2218 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(next_skb
)->tcp_flags
;
2220 /* All done, get rid of second SKB and account for it so
2221 * packet counting does not break.
2223 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
2225 /* changed transmit queue under us so clear hints */
2226 tcp_clear_retrans_hints_partial(tp
);
2227 if (next_skb
== tp
->retransmit_skb_hint
)
2228 tp
->retransmit_skb_hint
= skb
;
2230 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
2232 sk_wmem_free_skb(sk
, next_skb
);
2235 /* Check if coalescing SKBs is legal. */
2236 static bool tcp_can_collapse(const struct sock
*sk
, const struct sk_buff
*skb
)
2238 if (tcp_skb_pcount(skb
) > 1)
2240 /* TODO: SACK collapsing could be used to remove this condition */
2241 if (skb_shinfo(skb
)->nr_frags
!= 0)
2243 if (skb_cloned(skb
))
2245 if (skb
== tcp_send_head(sk
))
2247 /* Some heurestics for collapsing over SACK'd could be invented */
2248 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2254 /* Collapse packets in the retransmit queue to make to create
2255 * less packets on the wire. This is only done on retransmission.
2257 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
2260 struct tcp_sock
*tp
= tcp_sk(sk
);
2261 struct sk_buff
*skb
= to
, *tmp
;
2264 if (!sysctl_tcp_retrans_collapse
)
2266 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2269 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
2270 if (!tcp_can_collapse(sk
, skb
))
2282 /* Punt if not enough space exists in the first SKB for
2283 * the data in the second
2285 if (skb
->len
> skb_availroom(to
))
2288 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
2291 tcp_collapse_retrans(sk
, to
);
2295 /* This retransmits one SKB. Policy decisions and retransmit queue
2296 * state updates are done by the caller. Returns non-zero if an
2297 * error occurred which prevented the send.
2299 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2301 struct tcp_sock
*tp
= tcp_sk(sk
);
2302 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2303 unsigned int cur_mss
;
2306 /* Inconslusive MTU probe */
2307 if (icsk
->icsk_mtup
.probe_size
) {
2308 icsk
->icsk_mtup
.probe_size
= 0;
2311 /* Do not sent more than we queued. 1/4 is reserved for possible
2312 * copying overhead: fragmentation, tunneling, mangling etc.
2314 if (atomic_read(&sk
->sk_wmem_alloc
) >
2315 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
2318 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
2319 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
2321 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2325 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
2326 return -EHOSTUNREACH
; /* Routing failure or similar. */
2328 cur_mss
= tcp_current_mss(sk
);
2330 /* If receiver has shrunk his window, and skb is out of
2331 * new window, do not retransmit it. The exception is the
2332 * case, when window is shrunk to zero. In this case
2333 * our retransmit serves as a zero window probe.
2335 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
)) &&
2336 TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
2339 if (skb
->len
> cur_mss
) {
2340 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
2341 return -ENOMEM
; /* We'll try again later. */
2343 int oldpcount
= tcp_skb_pcount(skb
);
2345 if (unlikely(oldpcount
> 1)) {
2346 tcp_init_tso_segs(sk
, skb
, cur_mss
);
2347 tcp_adjust_pcount(sk
, skb
, oldpcount
- tcp_skb_pcount(skb
));
2351 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
2353 /* Some Solaris stacks overoptimize and ignore the FIN on a
2354 * retransmit when old data is attached. So strip it off
2355 * since it is cheap to do so and saves bytes on the network.
2358 (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
2359 tp
->snd_una
== (TCP_SKB_CB(skb
)->end_seq
- 1)) {
2360 if (!pskb_trim(skb
, 0)) {
2361 /* Reuse, even though it does some unnecessary work */
2362 tcp_init_nondata_skb(skb
, TCP_SKB_CB(skb
)->end_seq
- 1,
2363 TCP_SKB_CB(skb
)->tcp_flags
);
2364 skb
->ip_summed
= CHECKSUM_NONE
;
2368 /* Make a copy, if the first transmission SKB clone we made
2369 * is still in somebody's hands, else make a clone.
2371 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2373 /* make sure skb->data is aligned on arches that require it */
2374 if (unlikely(NET_IP_ALIGN
&& ((unsigned long)skb
->data
& 3))) {
2375 struct sk_buff
*nskb
= __pskb_copy(skb
, MAX_TCP_HEADER
,
2377 err
= nskb
? tcp_transmit_skb(sk
, nskb
, 0, GFP_ATOMIC
) :
2380 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2384 /* Update global TCP statistics. */
2385 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
2387 tp
->total_retrans
++;
2389 #if FASTRETRANS_DEBUG > 0
2390 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2391 net_dbg_ratelimited("retrans_out leaked\n");
2394 if (!tp
->retrans_out
)
2395 tp
->lost_retrans_low
= tp
->snd_nxt
;
2396 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
2397 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2399 /* Save stamp of the first retransmit. */
2400 if (!tp
->retrans_stamp
)
2401 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
2403 tp
->undo_retrans
+= tcp_skb_pcount(skb
);
2405 /* snd_nxt is stored to detect loss of retransmitted segment,
2406 * see tcp_input.c tcp_sacktag_write_queue().
2408 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
2413 /* Check if we forward retransmits are possible in the current
2414 * window/congestion state.
2416 static bool tcp_can_forward_retransmit(struct sock
*sk
)
2418 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2419 const struct tcp_sock
*tp
= tcp_sk(sk
);
2421 /* Forward retransmissions are possible only during Recovery. */
2422 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
2425 /* No forward retransmissions in Reno are possible. */
2426 if (tcp_is_reno(tp
))
2429 /* Yeah, we have to make difficult choice between forward transmission
2430 * and retransmission... Both ways have their merits...
2432 * For now we do not retransmit anything, while we have some new
2433 * segments to send. In the other cases, follow rule 3 for
2434 * NextSeg() specified in RFC3517.
2437 if (tcp_may_send_now(sk
))
2443 /* This gets called after a retransmit timeout, and the initially
2444 * retransmitted data is acknowledged. It tries to continue
2445 * resending the rest of the retransmit queue, until either
2446 * we've sent it all or the congestion window limit is reached.
2447 * If doing SACK, the first ACK which comes back for a timeout
2448 * based retransmit packet might feed us FACK information again.
2449 * If so, we use it to avoid unnecessarily retransmissions.
2451 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2453 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2454 struct tcp_sock
*tp
= tcp_sk(sk
);
2455 struct sk_buff
*skb
;
2456 struct sk_buff
*hole
= NULL
;
2459 int fwd_rexmitting
= 0;
2461 if (!tp
->packets_out
)
2465 tp
->retransmit_high
= tp
->snd_una
;
2467 if (tp
->retransmit_skb_hint
) {
2468 skb
= tp
->retransmit_skb_hint
;
2469 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2470 if (after(last_lost
, tp
->retransmit_high
))
2471 last_lost
= tp
->retransmit_high
;
2473 skb
= tcp_write_queue_head(sk
);
2474 last_lost
= tp
->snd_una
;
2477 tcp_for_write_queue_from(skb
, sk
) {
2478 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
2480 if (skb
== tcp_send_head(sk
))
2482 /* we could do better than to assign each time */
2484 tp
->retransmit_skb_hint
= skb
;
2486 /* Assume this retransmit will generate
2487 * only one packet for congestion window
2488 * calculation purposes. This works because
2489 * tcp_retransmit_skb() will chop up the
2490 * packet to be MSS sized and all the
2491 * packet counting works out.
2493 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2496 if (fwd_rexmitting
) {
2498 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2500 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2502 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2503 tp
->retransmit_high
= last_lost
;
2504 if (!tcp_can_forward_retransmit(sk
))
2506 /* Backtrack if necessary to non-L'ed skb */
2514 } else if (!(sacked
& TCPCB_LOST
)) {
2515 if (hole
== NULL
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2520 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2521 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2522 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2524 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2527 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2530 if (tcp_retransmit_skb(sk
, skb
)) {
2531 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRETRANSFAIL
);
2534 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2536 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Recovery
)
2537 tp
->prr_out
+= tcp_skb_pcount(skb
);
2539 if (skb
== tcp_write_queue_head(sk
))
2540 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2541 inet_csk(sk
)->icsk_rto
,
2546 /* Send a fin. The caller locks the socket for us. This cannot be
2547 * allowed to fail queueing a FIN frame under any circumstances.
2549 void tcp_send_fin(struct sock
*sk
)
2551 struct tcp_sock
*tp
= tcp_sk(sk
);
2552 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2555 /* Optimization, tack on the FIN if we have a queue of
2556 * unsent frames. But be careful about outgoing SACKS
2559 mss_now
= tcp_current_mss(sk
);
2561 if (tcp_send_head(sk
) != NULL
) {
2562 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_FIN
;
2563 TCP_SKB_CB(skb
)->end_seq
++;
2566 /* Socket is locked, keep trying until memory is available. */
2568 skb
= alloc_skb_fclone(MAX_TCP_HEADER
,
2575 /* Reserve space for headers and prepare control bits. */
2576 skb_reserve(skb
, MAX_TCP_HEADER
);
2577 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2578 tcp_init_nondata_skb(skb
, tp
->write_seq
,
2579 TCPHDR_ACK
| TCPHDR_FIN
);
2580 tcp_queue_skb(sk
, skb
);
2582 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2585 /* We get here when a process closes a file descriptor (either due to
2586 * an explicit close() or as a byproduct of exit()'ing) and there
2587 * was unread data in the receive queue. This behavior is recommended
2588 * by RFC 2525, section 2.17. -DaveM
2590 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2592 struct sk_buff
*skb
;
2594 /* NOTE: No TCP options attached and we never retransmit this. */
2595 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2597 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2601 /* Reserve space for headers and prepare control bits. */
2602 skb_reserve(skb
, MAX_TCP_HEADER
);
2603 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
2604 TCPHDR_ACK
| TCPHDR_RST
);
2606 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2607 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2608 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2610 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
2613 /* Send a crossed SYN-ACK during socket establishment.
2614 * WARNING: This routine must only be called when we have already sent
2615 * a SYN packet that crossed the incoming SYN that caused this routine
2616 * to get called. If this assumption fails then the initial rcv_wnd
2617 * and rcv_wscale values will not be correct.
2619 int tcp_send_synack(struct sock
*sk
)
2621 struct sk_buff
*skb
;
2623 skb
= tcp_write_queue_head(sk
);
2624 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
2625 pr_debug("%s: wrong queue state\n", __func__
);
2628 if (!(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_ACK
)) {
2629 if (skb_cloned(skb
)) {
2630 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2633 tcp_unlink_write_queue(skb
, sk
);
2634 skb_header_release(nskb
);
2635 __tcp_add_write_queue_head(sk
, nskb
);
2636 sk_wmem_free_skb(sk
, skb
);
2637 sk
->sk_wmem_queued
+= nskb
->truesize
;
2638 sk_mem_charge(sk
, nskb
->truesize
);
2642 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ACK
;
2643 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2645 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2646 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2650 * tcp_make_synack - Prepare a SYN-ACK.
2651 * sk: listener socket
2652 * dst: dst entry attached to the SYNACK
2653 * req: request_sock pointer
2654 * rvp: request_values pointer
2656 * Allocate one skb and build a SYNACK packet.
2657 * @dst is consumed : Caller should not use it again.
2659 struct sk_buff
*tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2660 struct request_sock
*req
,
2661 struct request_values
*rvp
)
2663 struct tcp_out_options opts
;
2664 struct tcp_extend_values
*xvp
= tcp_xv(rvp
);
2665 struct inet_request_sock
*ireq
= inet_rsk(req
);
2666 struct tcp_sock
*tp
= tcp_sk(sk
);
2667 const struct tcp_cookie_values
*cvp
= tp
->cookie_values
;
2669 struct sk_buff
*skb
;
2670 struct tcp_md5sig_key
*md5
;
2671 int tcp_header_size
;
2673 int s_data_desired
= 0;
2675 if (cvp
!= NULL
&& cvp
->s_data_constant
&& cvp
->s_data_desired
)
2676 s_data_desired
= cvp
->s_data_desired
;
2677 skb
= alloc_skb(MAX_TCP_HEADER
+ 15 + s_data_desired
,
2678 sk_gfp_atomic(sk
, GFP_ATOMIC
));
2679 if (unlikely(!skb
)) {
2683 /* Reserve space for headers. */
2684 skb_reserve(skb
, MAX_TCP_HEADER
);
2686 skb_dst_set(skb
, dst
);
2688 mss
= dst_metric_advmss(dst
);
2689 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< mss
)
2690 mss
= tp
->rx_opt
.user_mss
;
2692 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
2694 /* Set this up on the first call only */
2695 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
2697 /* limit the window selection if the user enforce a smaller rx buffer */
2698 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
2699 (req
->window_clamp
> tcp_full_space(sk
) || req
->window_clamp
== 0))
2700 req
->window_clamp
= tcp_full_space(sk
);
2702 /* tcp_full_space because it is guaranteed to be the first packet */
2703 tcp_select_initial_window(tcp_full_space(sk
),
2704 mss
- (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
2709 dst_metric(dst
, RTAX_INITRWND
));
2710 ireq
->rcv_wscale
= rcv_wscale
;
2713 memset(&opts
, 0, sizeof(opts
));
2714 #ifdef CONFIG_SYN_COOKIES
2715 if (unlikely(req
->cookie_ts
))
2716 TCP_SKB_CB(skb
)->when
= cookie_init_timestamp(req
);
2719 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2720 tcp_header_size
= tcp_synack_options(sk
, req
, mss
,
2721 skb
, &opts
, &md5
, xvp
)
2724 skb_push(skb
, tcp_header_size
);
2725 skb_reset_transport_header(skb
);
2728 memset(th
, 0, sizeof(struct tcphdr
));
2731 TCP_ECN_make_synack(req
, th
);
2732 th
->source
= ireq
->loc_port
;
2733 th
->dest
= ireq
->rmt_port
;
2734 /* Setting of flags are superfluous here for callers (and ECE is
2735 * not even correctly set)
2737 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
2738 TCPHDR_SYN
| TCPHDR_ACK
);
2740 if (OPTION_COOKIE_EXTENSION
& opts
.options
) {
2741 if (s_data_desired
) {
2742 u8
*buf
= skb_put(skb
, s_data_desired
);
2744 /* copy data directly from the listening socket. */
2745 memcpy(buf
, cvp
->s_data_payload
, s_data_desired
);
2746 TCP_SKB_CB(skb
)->end_seq
+= s_data_desired
;
2749 if (opts
.hash_size
> 0) {
2750 __u32 workspace
[SHA_WORKSPACE_WORDS
];
2751 u32
*mess
= &xvp
->cookie_bakery
[COOKIE_DIGEST_WORDS
];
2752 u32
*tail
= &mess
[COOKIE_MESSAGE_WORDS
-1];
2754 /* Secret recipe depends on the Timestamp, (future)
2755 * Sequence and Acknowledgment Numbers, Initiator
2756 * Cookie, and others handled by IP variant caller.
2758 *tail
-- ^= opts
.tsval
;
2759 *tail
-- ^= tcp_rsk(req
)->rcv_isn
+ 1;
2760 *tail
-- ^= TCP_SKB_CB(skb
)->seq
+ 1;
2763 *tail
-- ^= (((__force u32
)th
->dest
<< 16) | (__force u32
)th
->source
);
2764 *tail
-- ^= (u32
)(unsigned long)cvp
; /* per sockopt */
2766 sha_transform((__u32
*)&xvp
->cookie_bakery
[0],
2769 opts
.hash_location
=
2770 (__u8
*)&xvp
->cookie_bakery
[0];
2774 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2775 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_isn
+ 1);
2777 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2778 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2779 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
2780 th
->doff
= (tcp_header_size
>> 2);
2781 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
, tcp_skb_pcount(skb
));
2783 #ifdef CONFIG_TCP_MD5SIG
2784 /* Okay, we have all we need - do the md5 hash if needed */
2786 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
2787 md5
, NULL
, req
, skb
);
2793 EXPORT_SYMBOL(tcp_make_synack
);
2795 /* Do all connect socket setups that can be done AF independent. */
2796 void tcp_connect_init(struct sock
*sk
)
2798 const struct dst_entry
*dst
= __sk_dst_get(sk
);
2799 struct tcp_sock
*tp
= tcp_sk(sk
);
2802 /* We'll fix this up when we get a response from the other end.
2803 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2805 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2806 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2808 #ifdef CONFIG_TCP_MD5SIG
2809 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2810 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2813 /* If user gave his TCP_MAXSEG, record it to clamp */
2814 if (tp
->rx_opt
.user_mss
)
2815 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2818 tcp_sync_mss(sk
, dst_mtu(dst
));
2820 if (!tp
->window_clamp
)
2821 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2822 tp
->advmss
= dst_metric_advmss(dst
);
2823 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
2824 tp
->advmss
= tp
->rx_opt
.user_mss
;
2826 tcp_initialize_rcv_mss(sk
);
2828 /* limit the window selection if the user enforce a smaller rx buffer */
2829 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
2830 (tp
->window_clamp
> tcp_full_space(sk
) || tp
->window_clamp
== 0))
2831 tp
->window_clamp
= tcp_full_space(sk
);
2833 tcp_select_initial_window(tcp_full_space(sk
),
2834 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2837 sysctl_tcp_window_scaling
,
2839 dst_metric(dst
, RTAX_INITRWND
));
2841 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2842 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2845 sock_reset_flag(sk
, SOCK_DONE
);
2848 tp
->snd_una
= tp
->write_seq
;
2849 tp
->snd_sml
= tp
->write_seq
;
2850 tp
->snd_up
= tp
->write_seq
;
2851 tp
->snd_nxt
= tp
->write_seq
;
2853 if (likely(!tp
->repair
))
2855 tp
->rcv_wup
= tp
->rcv_nxt
;
2856 tp
->copied_seq
= tp
->rcv_nxt
;
2858 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2859 inet_csk(sk
)->icsk_retransmits
= 0;
2860 tcp_clear_retrans(tp
);
2863 static void tcp_connect_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
2865 struct tcp_sock
*tp
= tcp_sk(sk
);
2866 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
2868 tcb
->end_seq
+= skb
->len
;
2869 skb_header_release(skb
);
2870 __tcp_add_write_queue_tail(sk
, skb
);
2871 sk
->sk_wmem_queued
+= skb
->truesize
;
2872 sk_mem_charge(sk
, skb
->truesize
);
2873 tp
->write_seq
= tcb
->end_seq
;
2874 tp
->packets_out
+= tcp_skb_pcount(skb
);
2877 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
2878 * queue a data-only packet after the regular SYN, such that regular SYNs
2879 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
2880 * only the SYN sequence, the data are retransmitted in the first ACK.
2881 * If cookie is not cached or other error occurs, falls back to send a
2882 * regular SYN with Fast Open cookie request option.
2884 static int tcp_send_syn_data(struct sock
*sk
, struct sk_buff
*syn
)
2886 struct tcp_sock
*tp
= tcp_sk(sk
);
2887 struct tcp_fastopen_request
*fo
= tp
->fastopen_req
;
2888 int syn_loss
= 0, space
, i
, err
= 0, iovlen
= fo
->data
->msg_iovlen
;
2889 struct sk_buff
*syn_data
= NULL
, *data
;
2890 unsigned long last_syn_loss
= 0;
2892 tp
->rx_opt
.mss_clamp
= tp
->advmss
; /* If MSS is not cached */
2893 tcp_fastopen_cache_get(sk
, &tp
->rx_opt
.mss_clamp
, &fo
->cookie
,
2894 &syn_loss
, &last_syn_loss
);
2895 /* Recurring FO SYN losses: revert to regular handshake temporarily */
2897 time_before(jiffies
, last_syn_loss
+ (60*HZ
<< syn_loss
))) {
2898 fo
->cookie
.len
= -1;
2902 if (sysctl_tcp_fastopen
& TFO_CLIENT_NO_COOKIE
)
2903 fo
->cookie
.len
= -1;
2904 else if (fo
->cookie
.len
<= 0)
2907 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
2908 * user-MSS. Reserve maximum option space for middleboxes that add
2909 * private TCP options. The cost is reduced data space in SYN :(
2911 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->rx_opt
.mss_clamp
)
2912 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2913 space
= tcp_mtu_to_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
) -
2914 MAX_TCP_OPTION_SPACE
;
2916 syn_data
= skb_copy_expand(syn
, skb_headroom(syn
), space
,
2918 if (syn_data
== NULL
)
2921 for (i
= 0; i
< iovlen
&& syn_data
->len
< space
; ++i
) {
2922 struct iovec
*iov
= &fo
->data
->msg_iov
[i
];
2923 unsigned char __user
*from
= iov
->iov_base
;
2924 int len
= iov
->iov_len
;
2926 if (syn_data
->len
+ len
> space
)
2927 len
= space
- syn_data
->len
;
2928 else if (i
+ 1 == iovlen
)
2929 /* No more data pending in inet_wait_for_connect() */
2932 if (skb_add_data(syn_data
, from
, len
))
2936 /* Queue a data-only packet after the regular SYN for retransmission */
2937 data
= pskb_copy(syn_data
, sk
->sk_allocation
);
2940 TCP_SKB_CB(data
)->seq
++;
2941 TCP_SKB_CB(data
)->tcp_flags
&= ~TCPHDR_SYN
;
2942 TCP_SKB_CB(data
)->tcp_flags
= (TCPHDR_ACK
|TCPHDR_PSH
);
2943 tcp_connect_queue_skb(sk
, data
);
2944 fo
->copied
= data
->len
;
2946 if (tcp_transmit_skb(sk
, syn_data
, 0, sk
->sk_allocation
) == 0) {
2947 tp
->syn_data
= (fo
->copied
> 0);
2948 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
2954 /* Send a regular SYN with Fast Open cookie request option */
2955 if (fo
->cookie
.len
> 0)
2957 err
= tcp_transmit_skb(sk
, syn
, 1, sk
->sk_allocation
);
2959 tp
->syn_fastopen
= 0;
2960 kfree_skb(syn_data
);
2962 fo
->cookie
.len
= -1; /* Exclude Fast Open option for SYN retries */
2966 /* Build a SYN and send it off. */
2967 int tcp_connect(struct sock
*sk
)
2969 struct tcp_sock
*tp
= tcp_sk(sk
);
2970 struct sk_buff
*buff
;
2973 tcp_connect_init(sk
);
2975 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
2976 if (unlikely(buff
== NULL
))
2979 /* Reserve space for headers. */
2980 skb_reserve(buff
, MAX_TCP_HEADER
);
2982 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPHDR_SYN
);
2983 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2984 tcp_connect_queue_skb(sk
, buff
);
2985 TCP_ECN_send_syn(sk
, buff
);
2987 /* Send off SYN; include data in Fast Open. */
2988 err
= tp
->fastopen_req
? tcp_send_syn_data(sk
, buff
) :
2989 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
2990 if (err
== -ECONNREFUSED
)
2993 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2994 * in order to make this packet get counted in tcpOutSegs.
2996 tp
->snd_nxt
= tp
->write_seq
;
2997 tp
->pushed_seq
= tp
->write_seq
;
2998 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
3000 /* Timer for repeating the SYN until an answer. */
3001 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3002 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3005 EXPORT_SYMBOL(tcp_connect
);
3007 /* Send out a delayed ack, the caller does the policy checking
3008 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3011 void tcp_send_delayed_ack(struct sock
*sk
)
3013 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3014 int ato
= icsk
->icsk_ack
.ato
;
3015 unsigned long timeout
;
3017 if (ato
> TCP_DELACK_MIN
) {
3018 const struct tcp_sock
*tp
= tcp_sk(sk
);
3019 int max_ato
= HZ
/ 2;
3021 if (icsk
->icsk_ack
.pingpong
||
3022 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
3023 max_ato
= TCP_DELACK_MAX
;
3025 /* Slow path, intersegment interval is "high". */
3027 /* If some rtt estimate is known, use it to bound delayed ack.
3028 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3032 int rtt
= max(tp
->srtt
>> 3, TCP_DELACK_MIN
);
3038 ato
= min(ato
, max_ato
);
3041 /* Stay within the limit we were given */
3042 timeout
= jiffies
+ ato
;
3044 /* Use new timeout only if there wasn't a older one earlier. */
3045 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
3046 /* If delack timer was blocked or is about to expire,
3049 if (icsk
->icsk_ack
.blocked
||
3050 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
3055 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
3056 timeout
= icsk
->icsk_ack
.timeout
;
3058 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
3059 icsk
->icsk_ack
.timeout
= timeout
;
3060 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
3063 /* This routine sends an ack and also updates the window. */
3064 void tcp_send_ack(struct sock
*sk
)
3066 struct sk_buff
*buff
;
3068 /* If we have been reset, we may not send again. */
3069 if (sk
->sk_state
== TCP_CLOSE
)
3072 /* We are not putting this on the write queue, so
3073 * tcp_transmit_skb() will set the ownership to this
3076 buff
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3078 inet_csk_schedule_ack(sk
);
3079 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
3080 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
3081 TCP_DELACK_MAX
, TCP_RTO_MAX
);
3085 /* Reserve space for headers and prepare control bits. */
3086 skb_reserve(buff
, MAX_TCP_HEADER
);
3087 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPHDR_ACK
);
3089 /* Send it off, this clears delayed acks for us. */
3090 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
3091 tcp_transmit_skb(sk
, buff
, 0, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3094 /* This routine sends a packet with an out of date sequence
3095 * number. It assumes the other end will try to ack it.
3097 * Question: what should we make while urgent mode?
3098 * 4.4BSD forces sending single byte of data. We cannot send
3099 * out of window data, because we have SND.NXT==SND.MAX...
3101 * Current solution: to send TWO zero-length segments in urgent mode:
3102 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3103 * out-of-date with SND.UNA-1 to probe window.
3105 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
3107 struct tcp_sock
*tp
= tcp_sk(sk
);
3108 struct sk_buff
*skb
;
3110 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3111 skb
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3115 /* Reserve space for headers and set control bits. */
3116 skb_reserve(skb
, MAX_TCP_HEADER
);
3117 /* Use a previous sequence. This should cause the other
3118 * end to send an ack. Don't queue or clone SKB, just
3121 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPHDR_ACK
);
3122 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
3123 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
3126 void tcp_send_window_probe(struct sock
*sk
)
3128 if (sk
->sk_state
== TCP_ESTABLISHED
) {
3129 tcp_sk(sk
)->snd_wl1
= tcp_sk(sk
)->rcv_nxt
- 1;
3130 tcp_sk(sk
)->snd_nxt
= tcp_sk(sk
)->write_seq
;
3131 tcp_xmit_probe_skb(sk
, 0);
3135 /* Initiate keepalive or window probe from timer. */
3136 int tcp_write_wakeup(struct sock
*sk
)
3138 struct tcp_sock
*tp
= tcp_sk(sk
);
3139 struct sk_buff
*skb
;
3141 if (sk
->sk_state
== TCP_CLOSE
)
3144 if ((skb
= tcp_send_head(sk
)) != NULL
&&
3145 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
3147 unsigned int mss
= tcp_current_mss(sk
);
3148 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
3150 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
3151 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
3153 /* We are probing the opening of a window
3154 * but the window size is != 0
3155 * must have been a result SWS avoidance ( sender )
3157 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
3159 seg_size
= min(seg_size
, mss
);
3160 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3161 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
3163 } else if (!tcp_skb_pcount(skb
))
3164 tcp_set_skb_tso_segs(sk
, skb
, mss
);
3166 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3167 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
3168 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3170 tcp_event_new_data_sent(sk
, skb
);
3173 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
3174 tcp_xmit_probe_skb(sk
, 1);
3175 return tcp_xmit_probe_skb(sk
, 0);
3179 /* A window probe timeout has occurred. If window is not closed send
3180 * a partial packet else a zero probe.
3182 void tcp_send_probe0(struct sock
*sk
)
3184 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3185 struct tcp_sock
*tp
= tcp_sk(sk
);
3188 err
= tcp_write_wakeup(sk
);
3190 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
3191 /* Cancel probe timer, if it is not required. */
3192 icsk
->icsk_probes_out
= 0;
3193 icsk
->icsk_backoff
= 0;
3198 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
3199 icsk
->icsk_backoff
++;
3200 icsk
->icsk_probes_out
++;
3201 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3202 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3205 /* If packet was not sent due to local congestion,
3206 * do not backoff and do not remember icsk_probes_out.
3207 * Let local senders to fight for local resources.
3209 * Use accumulated backoff yet.
3211 if (!icsk
->icsk_probes_out
)
3212 icsk
->icsk_probes_out
= 1;
3213 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3214 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
3215 TCP_RESOURCE_PROBE_INTERVAL
),