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 unsigned int sysctl_tcp_notsent_lowat __read_mostly
= UINT_MAX
;
69 EXPORT_SYMBOL(sysctl_tcp_notsent_lowat
);
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 inet_connection_sock
*icsk
= inet_csk(sk
);
78 struct tcp_sock
*tp
= tcp_sk(sk
);
79 unsigned int prior_packets
= tp
->packets_out
;
81 tcp_advance_send_head(sk
, skb
);
82 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
84 tp
->packets_out
+= tcp_skb_pcount(skb
);
85 if (!prior_packets
|| icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
86 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
90 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
,
94 /* SND.NXT, if window was not shrunk.
95 * If window has been shrunk, what should we make? It is not clear at all.
96 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
97 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
98 * invalid. OK, let's make this for now:
100 static inline __u32
tcp_acceptable_seq(const struct sock
*sk
)
102 const struct tcp_sock
*tp
= tcp_sk(sk
);
104 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
))
107 return tcp_wnd_end(tp
);
110 /* Calculate mss to advertise in SYN segment.
111 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
113 * 1. It is independent of path mtu.
114 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
115 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
116 * attached devices, because some buggy hosts are confused by
118 * 4. We do not make 3, we advertise MSS, calculated from first
119 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
120 * This may be overridden via information stored in routing table.
121 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
122 * probably even Jumbo".
124 static __u16
tcp_advertise_mss(struct sock
*sk
)
126 struct tcp_sock
*tp
= tcp_sk(sk
);
127 const struct dst_entry
*dst
= __sk_dst_get(sk
);
128 int mss
= tp
->advmss
;
131 unsigned int metric
= dst_metric_advmss(dst
);
142 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
143 * This is the first part of cwnd validation mechanism. */
144 static void tcp_cwnd_restart(struct sock
*sk
, const struct dst_entry
*dst
)
146 struct tcp_sock
*tp
= tcp_sk(sk
);
147 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
148 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
149 u32 cwnd
= tp
->snd_cwnd
;
151 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
153 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
154 restart_cwnd
= min(restart_cwnd
, cwnd
);
156 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
158 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
159 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
160 tp
->snd_cwnd_used
= 0;
163 /* Congestion state accounting after a packet has been sent. */
164 static void tcp_event_data_sent(struct tcp_sock
*tp
,
167 struct inet_connection_sock
*icsk
= inet_csk(sk
);
168 const u32 now
= tcp_time_stamp
;
169 const struct dst_entry
*dst
= __sk_dst_get(sk
);
171 if (sysctl_tcp_slow_start_after_idle
&&
172 (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
))
173 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
177 /* If it is a reply for ato after last received
178 * packet, enter pingpong mode.
180 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
&&
181 (!dst
|| !dst_metric(dst
, RTAX_QUICKACK
)))
182 icsk
->icsk_ack
.pingpong
= 1;
185 /* Account for an ACK we sent. */
186 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
188 tcp_dec_quickack_mode(sk
, pkts
);
189 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
193 u32
tcp_default_init_rwnd(u32 mss
)
195 /* Initial receive window should be twice of TCP_INIT_CWND to
196 * enable proper sending of new unsent data during fast recovery
197 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
198 * limit when mss is larger than 1460.
200 u32 init_rwnd
= TCP_INIT_CWND
* 2;
203 init_rwnd
= max((1460 * init_rwnd
) / mss
, 2U);
207 /* Determine a window scaling and initial window to offer.
208 * Based on the assumption that the given amount of space
209 * will be offered. Store the results in the tp structure.
210 * NOTE: for smooth operation initial space offering should
211 * be a multiple of mss if possible. We assume here that mss >= 1.
212 * This MUST be enforced by all callers.
214 void tcp_select_initial_window(int __space
, __u32 mss
,
215 __u32
*rcv_wnd
, __u32
*window_clamp
,
216 int wscale_ok
, __u8
*rcv_wscale
,
219 unsigned int space
= (__space
< 0 ? 0 : __space
);
221 /* If no clamp set the clamp to the max possible scaled window */
222 if (*window_clamp
== 0)
223 (*window_clamp
) = (65535 << 14);
224 space
= min(*window_clamp
, space
);
226 /* Quantize space offering to a multiple of mss if possible. */
228 space
= (space
/ mss
) * mss
;
230 /* NOTE: offering an initial window larger than 32767
231 * will break some buggy TCP stacks. If the admin tells us
232 * it is likely we could be speaking with such a buggy stack
233 * we will truncate our initial window offering to 32K-1
234 * unless the remote has sent us a window scaling option,
235 * which we interpret as a sign the remote TCP is not
236 * misinterpreting the window field as a signed quantity.
238 if (sysctl_tcp_workaround_signed_windows
)
239 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
245 /* Set window scaling on max possible window
246 * See RFC1323 for an explanation of the limit to 14
248 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
249 space
= min_t(u32
, space
, *window_clamp
);
250 while (space
> 65535 && (*rcv_wscale
) < 14) {
256 if (mss
> (1 << *rcv_wscale
)) {
257 if (!init_rcv_wnd
) /* Use default unless specified otherwise */
258 init_rcv_wnd
= tcp_default_init_rwnd(mss
);
259 *rcv_wnd
= min(*rcv_wnd
, init_rcv_wnd
* mss
);
262 /* Set the clamp no higher than max representable value */
263 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
265 EXPORT_SYMBOL(tcp_select_initial_window
);
267 /* Chose a new window to advertise, update state in tcp_sock for the
268 * socket, and return result with RFC1323 scaling applied. The return
269 * value can be stuffed directly into th->window for an outgoing
272 static u16
tcp_select_window(struct sock
*sk
)
274 struct tcp_sock
*tp
= tcp_sk(sk
);
275 u32 old_win
= tp
->rcv_wnd
;
276 u32 cur_win
= tcp_receive_window(tp
);
277 u32 new_win
= __tcp_select_window(sk
);
279 /* Never shrink the offered window */
280 if (new_win
< cur_win
) {
281 /* Danger Will Robinson!
282 * Don't update rcv_wup/rcv_wnd here or else
283 * we will not be able to advertise a zero
284 * window in time. --DaveM
286 * Relax Will Robinson.
289 NET_INC_STATS(sock_net(sk
),
290 LINUX_MIB_TCPWANTZEROWINDOWADV
);
291 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
293 tp
->rcv_wnd
= new_win
;
294 tp
->rcv_wup
= tp
->rcv_nxt
;
296 /* Make sure we do not exceed the maximum possible
299 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
300 new_win
= min(new_win
, MAX_TCP_WINDOW
);
302 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
304 /* RFC1323 scaling applied */
305 new_win
>>= tp
->rx_opt
.rcv_wscale
;
307 /* If we advertise zero window, disable fast path. */
311 NET_INC_STATS(sock_net(sk
),
312 LINUX_MIB_TCPTOZEROWINDOWADV
);
313 } else if (old_win
== 0) {
314 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPFROMZEROWINDOWADV
);
320 /* Packet ECN state for a SYN-ACK */
321 static inline void TCP_ECN_send_synack(const struct tcp_sock
*tp
, struct sk_buff
*skb
)
323 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_CWR
;
324 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
325 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_ECE
;
328 /* Packet ECN state for a SYN. */
329 static inline void TCP_ECN_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
331 struct tcp_sock
*tp
= tcp_sk(sk
);
334 if (sock_net(sk
)->ipv4
.sysctl_tcp_ecn
== 1) {
335 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ECE
| TCPHDR_CWR
;
336 tp
->ecn_flags
= TCP_ECN_OK
;
340 static __inline__
void
341 TCP_ECN_make_synack(const struct request_sock
*req
, struct tcphdr
*th
)
343 if (inet_rsk(req
)->ecn_ok
)
347 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
350 static inline void TCP_ECN_send(struct sock
*sk
, struct sk_buff
*skb
,
353 struct tcp_sock
*tp
= tcp_sk(sk
);
355 if (tp
->ecn_flags
& TCP_ECN_OK
) {
356 /* Not-retransmitted data segment: set ECT and inject CWR. */
357 if (skb
->len
!= tcp_header_len
&&
358 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
360 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
361 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
362 tcp_hdr(skb
)->cwr
= 1;
363 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
366 /* ACK or retransmitted segment: clear ECT|CE */
367 INET_ECN_dontxmit(sk
);
369 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
370 tcp_hdr(skb
)->ece
= 1;
374 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
375 * auto increment end seqno.
377 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
379 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
381 skb
->ip_summed
= CHECKSUM_PARTIAL
;
384 TCP_SKB_CB(skb
)->tcp_flags
= flags
;
385 TCP_SKB_CB(skb
)->sacked
= 0;
387 shinfo
->gso_segs
= 1;
388 shinfo
->gso_size
= 0;
389 shinfo
->gso_type
= 0;
391 TCP_SKB_CB(skb
)->seq
= seq
;
392 if (flags
& (TCPHDR_SYN
| TCPHDR_FIN
))
394 TCP_SKB_CB(skb
)->end_seq
= seq
;
397 static inline bool tcp_urg_mode(const struct tcp_sock
*tp
)
399 return tp
->snd_una
!= tp
->snd_up
;
402 #define OPTION_SACK_ADVERTISE (1 << 0)
403 #define OPTION_TS (1 << 1)
404 #define OPTION_MD5 (1 << 2)
405 #define OPTION_WSCALE (1 << 3)
406 #define OPTION_FAST_OPEN_COOKIE (1 << 8)
408 struct tcp_out_options
{
409 u16 options
; /* bit field of OPTION_* */
410 u16 mss
; /* 0 to disable */
411 u8 ws
; /* window scale, 0 to disable */
412 u8 num_sack_blocks
; /* number of SACK blocks to include */
413 u8 hash_size
; /* bytes in hash_location */
414 __u8
*hash_location
; /* temporary pointer, overloaded */
415 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
416 struct tcp_fastopen_cookie
*fastopen_cookie
; /* Fast open cookie */
419 /* Write previously computed TCP options to the packet.
421 * Beware: Something in the Internet is very sensitive to the ordering of
422 * TCP options, we learned this through the hard way, so be careful here.
423 * Luckily we can at least blame others for their non-compliance but from
424 * inter-operability perspective it seems that we're somewhat stuck with
425 * the ordering which we have been using if we want to keep working with
426 * those broken things (not that it currently hurts anybody as there isn't
427 * particular reason why the ordering would need to be changed).
429 * At least SACK_PERM as the first option is known to lead to a disaster
430 * (but it may well be that other scenarios fail similarly).
432 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
433 struct tcp_out_options
*opts
)
435 u16 options
= opts
->options
; /* mungable copy */
437 if (unlikely(OPTION_MD5
& options
)) {
438 *ptr
++ = htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
439 (TCPOPT_MD5SIG
<< 8) | TCPOLEN_MD5SIG
);
440 /* overload cookie hash location */
441 opts
->hash_location
= (__u8
*)ptr
;
445 if (unlikely(opts
->mss
)) {
446 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
447 (TCPOLEN_MSS
<< 16) |
451 if (likely(OPTION_TS
& options
)) {
452 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
453 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
454 (TCPOLEN_SACK_PERM
<< 16) |
455 (TCPOPT_TIMESTAMP
<< 8) |
457 options
&= ~OPTION_SACK_ADVERTISE
;
459 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
461 (TCPOPT_TIMESTAMP
<< 8) |
464 *ptr
++ = htonl(opts
->tsval
);
465 *ptr
++ = htonl(opts
->tsecr
);
468 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
469 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
471 (TCPOPT_SACK_PERM
<< 8) |
475 if (unlikely(OPTION_WSCALE
& options
)) {
476 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
477 (TCPOPT_WINDOW
<< 16) |
478 (TCPOLEN_WINDOW
<< 8) |
482 if (unlikely(opts
->num_sack_blocks
)) {
483 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
484 tp
->duplicate_sack
: tp
->selective_acks
;
487 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
490 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
491 TCPOLEN_SACK_PERBLOCK
)));
493 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
495 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
496 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
499 tp
->rx_opt
.dsack
= 0;
502 if (unlikely(OPTION_FAST_OPEN_COOKIE
& options
)) {
503 struct tcp_fastopen_cookie
*foc
= opts
->fastopen_cookie
;
505 *ptr
++ = htonl((TCPOPT_EXP
<< 24) |
506 ((TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
) << 16) |
507 TCPOPT_FASTOPEN_MAGIC
);
509 memcpy(ptr
, foc
->val
, foc
->len
);
510 if ((foc
->len
& 3) == 2) {
511 u8
*align
= ((u8
*)ptr
) + foc
->len
;
512 align
[0] = align
[1] = TCPOPT_NOP
;
514 ptr
+= (foc
->len
+ 3) >> 2;
518 /* Compute TCP options for SYN packets. This is not the final
519 * network wire format yet.
521 static unsigned int tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
522 struct tcp_out_options
*opts
,
523 struct tcp_md5sig_key
**md5
)
525 struct tcp_sock
*tp
= tcp_sk(sk
);
526 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
527 struct tcp_fastopen_request
*fastopen
= tp
->fastopen_req
;
529 #ifdef CONFIG_TCP_MD5SIG
530 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
532 opts
->options
|= OPTION_MD5
;
533 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
539 /* We always get an MSS option. The option bytes which will be seen in
540 * normal data packets should timestamps be used, must be in the MSS
541 * advertised. But we subtract them from tp->mss_cache so that
542 * calculations in tcp_sendmsg are simpler etc. So account for this
543 * fact here if necessary. If we don't do this correctly, as a
544 * receiver we won't recognize data packets as being full sized when we
545 * should, and thus we won't abide by the delayed ACK rules correctly.
546 * SACKs don't matter, we never delay an ACK when we have any of those
548 opts
->mss
= tcp_advertise_mss(sk
);
549 remaining
-= TCPOLEN_MSS_ALIGNED
;
551 if (likely(sysctl_tcp_timestamps
&& *md5
== NULL
)) {
552 opts
->options
|= OPTION_TS
;
553 opts
->tsval
= tcp_skb_timestamp(skb
) + tp
->tsoffset
;
554 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
555 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
557 if (likely(sysctl_tcp_window_scaling
)) {
558 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
559 opts
->options
|= OPTION_WSCALE
;
560 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
562 if (likely(sysctl_tcp_sack
)) {
563 opts
->options
|= OPTION_SACK_ADVERTISE
;
564 if (unlikely(!(OPTION_TS
& opts
->options
)))
565 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
568 if (fastopen
&& fastopen
->cookie
.len
>= 0) {
569 u32 need
= TCPOLEN_EXP_FASTOPEN_BASE
+ fastopen
->cookie
.len
;
570 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
571 if (remaining
>= need
) {
572 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
573 opts
->fastopen_cookie
= &fastopen
->cookie
;
575 tp
->syn_fastopen
= 1;
579 return MAX_TCP_OPTION_SPACE
- remaining
;
582 /* Set up TCP options for SYN-ACKs. */
583 static unsigned int tcp_synack_options(struct sock
*sk
,
584 struct request_sock
*req
,
585 unsigned int mss
, struct sk_buff
*skb
,
586 struct tcp_out_options
*opts
,
587 struct tcp_md5sig_key
**md5
,
588 struct tcp_fastopen_cookie
*foc
)
590 struct inet_request_sock
*ireq
= inet_rsk(req
);
591 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
593 #ifdef CONFIG_TCP_MD5SIG
594 *md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
596 opts
->options
|= OPTION_MD5
;
597 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
599 /* We can't fit any SACK blocks in a packet with MD5 + TS
600 * options. There was discussion about disabling SACK
601 * rather than TS in order to fit in better with old,
602 * buggy kernels, but that was deemed to be unnecessary.
604 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
610 /* We always send an MSS option. */
612 remaining
-= TCPOLEN_MSS_ALIGNED
;
614 if (likely(ireq
->wscale_ok
)) {
615 opts
->ws
= ireq
->rcv_wscale
;
616 opts
->options
|= OPTION_WSCALE
;
617 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
619 if (likely(ireq
->tstamp_ok
)) {
620 opts
->options
|= OPTION_TS
;
621 opts
->tsval
= tcp_skb_timestamp(skb
);
622 opts
->tsecr
= req
->ts_recent
;
623 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
625 if (likely(ireq
->sack_ok
)) {
626 opts
->options
|= OPTION_SACK_ADVERTISE
;
627 if (unlikely(!ireq
->tstamp_ok
))
628 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
630 if (foc
!= NULL
&& foc
->len
>= 0) {
631 u32 need
= TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
;
632 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
633 if (remaining
>= need
) {
634 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
635 opts
->fastopen_cookie
= foc
;
640 return MAX_TCP_OPTION_SPACE
- remaining
;
643 /* Compute TCP options for ESTABLISHED sockets. This is not the
644 * final wire format yet.
646 static unsigned int tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
647 struct tcp_out_options
*opts
,
648 struct tcp_md5sig_key
**md5
)
650 struct tcp_sock
*tp
= tcp_sk(sk
);
651 unsigned int size
= 0;
652 unsigned int eff_sacks
;
656 #ifdef CONFIG_TCP_MD5SIG
657 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
658 if (unlikely(*md5
)) {
659 opts
->options
|= OPTION_MD5
;
660 size
+= TCPOLEN_MD5SIG_ALIGNED
;
666 if (likely(tp
->rx_opt
.tstamp_ok
)) {
667 opts
->options
|= OPTION_TS
;
668 opts
->tsval
= skb
? tcp_skb_timestamp(skb
) + tp
->tsoffset
: 0;
669 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
670 size
+= TCPOLEN_TSTAMP_ALIGNED
;
673 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
674 if (unlikely(eff_sacks
)) {
675 const unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
676 opts
->num_sack_blocks
=
677 min_t(unsigned int, eff_sacks
,
678 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
679 TCPOLEN_SACK_PERBLOCK
);
680 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
681 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
688 /* TCP SMALL QUEUES (TSQ)
690 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
691 * to reduce RTT and bufferbloat.
692 * We do this using a special skb destructor (tcp_wfree).
694 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
695 * needs to be reallocated in a driver.
696 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
698 * Since transmit from skb destructor is forbidden, we use a tasklet
699 * to process all sockets that eventually need to send more skbs.
700 * We use one tasklet per cpu, with its own queue of sockets.
703 struct tasklet_struct tasklet
;
704 struct list_head head
; /* queue of tcp sockets */
706 static DEFINE_PER_CPU(struct tsq_tasklet
, tsq_tasklet
);
708 static void tcp_tsq_handler(struct sock
*sk
)
710 if ((1 << sk
->sk_state
) &
711 (TCPF_ESTABLISHED
| TCPF_FIN_WAIT1
| TCPF_CLOSING
|
712 TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
))
713 tcp_write_xmit(sk
, tcp_current_mss(sk
), tcp_sk(sk
)->nonagle
,
717 * One tasklet per cpu tries to send more skbs.
718 * We run in tasklet context but need to disable irqs when
719 * transferring tsq->head because tcp_wfree() might
720 * interrupt us (non NAPI drivers)
722 static void tcp_tasklet_func(unsigned long data
)
724 struct tsq_tasklet
*tsq
= (struct tsq_tasklet
*)data
;
727 struct list_head
*q
, *n
;
731 local_irq_save(flags
);
732 list_splice_init(&tsq
->head
, &list
);
733 local_irq_restore(flags
);
735 list_for_each_safe(q
, n
, &list
) {
736 tp
= list_entry(q
, struct tcp_sock
, tsq_node
);
737 list_del(&tp
->tsq_node
);
739 sk
= (struct sock
*)tp
;
742 if (!sock_owned_by_user(sk
)) {
745 /* defer the work to tcp_release_cb() */
746 set_bit(TCP_TSQ_DEFERRED
, &tp
->tsq_flags
);
750 clear_bit(TSQ_QUEUED
, &tp
->tsq_flags
);
755 #define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
756 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
757 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
758 (1UL << TCP_MTU_REDUCED_DEFERRED))
760 * tcp_release_cb - tcp release_sock() callback
763 * called from release_sock() to perform protocol dependent
764 * actions before socket release.
766 void tcp_release_cb(struct sock
*sk
)
768 struct tcp_sock
*tp
= tcp_sk(sk
);
769 unsigned long flags
, nflags
;
771 /* perform an atomic operation only if at least one flag is set */
773 flags
= tp
->tsq_flags
;
774 if (!(flags
& TCP_DEFERRED_ALL
))
776 nflags
= flags
& ~TCP_DEFERRED_ALL
;
777 } while (cmpxchg(&tp
->tsq_flags
, flags
, nflags
) != flags
);
779 if (flags
& (1UL << TCP_TSQ_DEFERRED
))
782 /* Here begins the tricky part :
783 * We are called from release_sock() with :
785 * 2) sk_lock.slock spinlock held
786 * 3) socket owned by us (sk->sk_lock.owned == 1)
788 * But following code is meant to be called from BH handlers,
789 * so we should keep BH disabled, but early release socket ownership
791 sock_release_ownership(sk
);
793 if (flags
& (1UL << TCP_WRITE_TIMER_DEFERRED
)) {
794 tcp_write_timer_handler(sk
);
797 if (flags
& (1UL << TCP_DELACK_TIMER_DEFERRED
)) {
798 tcp_delack_timer_handler(sk
);
801 if (flags
& (1UL << TCP_MTU_REDUCED_DEFERRED
)) {
802 inet_csk(sk
)->icsk_af_ops
->mtu_reduced(sk
);
806 EXPORT_SYMBOL(tcp_release_cb
);
808 void __init
tcp_tasklet_init(void)
812 for_each_possible_cpu(i
) {
813 struct tsq_tasklet
*tsq
= &per_cpu(tsq_tasklet
, i
);
815 INIT_LIST_HEAD(&tsq
->head
);
816 tasklet_init(&tsq
->tasklet
,
823 * Write buffer destructor automatically called from kfree_skb.
824 * We can't xmit new skbs from this context, as we might already
827 void tcp_wfree(struct sk_buff
*skb
)
829 struct sock
*sk
= skb
->sk
;
830 struct tcp_sock
*tp
= tcp_sk(sk
);
832 if (test_and_clear_bit(TSQ_THROTTLED
, &tp
->tsq_flags
) &&
833 !test_and_set_bit(TSQ_QUEUED
, &tp
->tsq_flags
)) {
835 struct tsq_tasklet
*tsq
;
837 /* Keep a ref on socket.
838 * This last ref will be released in tcp_tasklet_func()
840 atomic_sub(skb
->truesize
- 1, &sk
->sk_wmem_alloc
);
842 /* queue this socket to tasklet queue */
843 local_irq_save(flags
);
844 tsq
= &__get_cpu_var(tsq_tasklet
);
845 list_add(&tp
->tsq_node
, &tsq
->head
);
846 tasklet_schedule(&tsq
->tasklet
);
847 local_irq_restore(flags
);
853 /* This routine actually transmits TCP packets queued in by
854 * tcp_do_sendmsg(). This is used by both the initial
855 * transmission and possible later retransmissions.
856 * All SKB's seen here are completely headerless. It is our
857 * job to build the TCP header, and pass the packet down to
858 * IP so it can do the same plus pass the packet off to the
861 * We are working here with either a clone of the original
862 * SKB, or a fresh unique copy made by the retransmit engine.
864 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
867 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
868 struct inet_sock
*inet
;
870 struct tcp_skb_cb
*tcb
;
871 struct tcp_out_options opts
;
872 unsigned int tcp_options_size
, tcp_header_size
;
873 struct tcp_md5sig_key
*md5
;
877 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
880 skb_mstamp_get(&skb
->skb_mstamp
);
882 if (unlikely(skb_cloned(skb
)))
883 skb
= pskb_copy(skb
, gfp_mask
);
885 skb
= skb_clone(skb
, gfp_mask
);
892 tcb
= TCP_SKB_CB(skb
);
893 memset(&opts
, 0, sizeof(opts
));
895 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
))
896 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
898 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
900 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
902 if (tcp_packets_in_flight(tp
) == 0)
903 tcp_ca_event(sk
, CA_EVENT_TX_START
);
905 /* if no packet is in qdisc/device queue, then allow XPS to select
908 skb
->ooo_okay
= sk_wmem_alloc_get(sk
) == 0;
910 skb_push(skb
, tcp_header_size
);
911 skb_reset_transport_header(skb
);
915 skb
->destructor
= tcp_wfree
;
916 skb_set_hash_from_sk(skb
, sk
);
917 atomic_add(skb
->truesize
, &sk
->sk_wmem_alloc
);
919 /* Build TCP header and checksum it. */
921 th
->source
= inet
->inet_sport
;
922 th
->dest
= inet
->inet_dport
;
923 th
->seq
= htonl(tcb
->seq
);
924 th
->ack_seq
= htonl(tp
->rcv_nxt
);
925 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
928 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
)) {
929 /* RFC1323: The window in SYN & SYN/ACK segments
932 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
934 th
->window
= htons(tcp_select_window(sk
));
939 /* The urg_mode check is necessary during a below snd_una win probe */
940 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
941 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
942 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
944 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
945 th
->urg_ptr
= htons(0xFFFF);
950 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
951 if (likely((tcb
->tcp_flags
& TCPHDR_SYN
) == 0))
952 TCP_ECN_send(sk
, skb
, tcp_header_size
);
954 #ifdef CONFIG_TCP_MD5SIG
955 /* Calculate the MD5 hash, as we have all we need now */
957 sk_nocaps_add(sk
, NETIF_F_GSO_MASK
);
958 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
963 icsk
->icsk_af_ops
->send_check(sk
, skb
);
965 if (likely(tcb
->tcp_flags
& TCPHDR_ACK
))
966 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
968 if (skb
->len
!= tcp_header_size
)
969 tcp_event_data_sent(tp
, sk
);
971 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
972 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
,
973 tcp_skb_pcount(skb
));
975 /* Our usage of tstamp should remain private */
976 skb
->tstamp
.tv64
= 0;
978 /* Cleanup our debris for IP stacks */
979 memset(skb
->cb
, 0, max(sizeof(struct inet_skb_parm
),
980 sizeof(struct inet6_skb_parm
)));
982 err
= icsk
->icsk_af_ops
->queue_xmit(sk
, skb
, &inet
->cork
.fl
);
984 if (likely(err
<= 0))
989 return net_xmit_eval(err
);
992 /* This routine just queues the buffer for sending.
994 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
995 * otherwise socket can stall.
997 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
999 struct tcp_sock
*tp
= tcp_sk(sk
);
1001 /* Advance write_seq and place onto the write_queue. */
1002 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
1003 __skb_header_release(skb
);
1004 tcp_add_write_queue_tail(sk
, skb
);
1005 sk
->sk_wmem_queued
+= skb
->truesize
;
1006 sk_mem_charge(sk
, skb
->truesize
);
1009 /* Initialize TSO segments for a packet. */
1010 static void tcp_set_skb_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
1011 unsigned int mss_now
)
1013 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
1015 /* Make sure we own this skb before messing gso_size/gso_segs */
1016 WARN_ON_ONCE(skb_cloned(skb
));
1018 if (skb
->len
<= mss_now
|| skb
->ip_summed
== CHECKSUM_NONE
) {
1019 /* Avoid the costly divide in the normal
1022 shinfo
->gso_segs
= 1;
1023 shinfo
->gso_size
= 0;
1024 shinfo
->gso_type
= 0;
1026 shinfo
->gso_segs
= DIV_ROUND_UP(skb
->len
, mss_now
);
1027 shinfo
->gso_size
= mss_now
;
1028 shinfo
->gso_type
= sk
->sk_gso_type
;
1032 /* When a modification to fackets out becomes necessary, we need to check
1033 * skb is counted to fackets_out or not.
1035 static void tcp_adjust_fackets_out(struct sock
*sk
, const struct sk_buff
*skb
,
1038 struct tcp_sock
*tp
= tcp_sk(sk
);
1040 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
1043 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
1044 tp
->fackets_out
-= decr
;
1047 /* Pcount in the middle of the write queue got changed, we need to do various
1048 * tweaks to fix counters
1050 static void tcp_adjust_pcount(struct sock
*sk
, const struct sk_buff
*skb
, int decr
)
1052 struct tcp_sock
*tp
= tcp_sk(sk
);
1054 tp
->packets_out
-= decr
;
1056 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1057 tp
->sacked_out
-= decr
;
1058 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1059 tp
->retrans_out
-= decr
;
1060 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
1061 tp
->lost_out
-= decr
;
1063 /* Reno case is special. Sigh... */
1064 if (tcp_is_reno(tp
) && decr
> 0)
1065 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
1067 tcp_adjust_fackets_out(sk
, skb
, decr
);
1069 if (tp
->lost_skb_hint
&&
1070 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
1071 (tcp_is_fack(tp
) || (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)))
1072 tp
->lost_cnt_hint
-= decr
;
1074 tcp_verify_left_out(tp
);
1077 static void tcp_fragment_tstamp(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1079 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
1081 if (unlikely(shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
) &&
1082 !before(shinfo
->tskey
, TCP_SKB_CB(skb2
)->seq
)) {
1083 struct skb_shared_info
*shinfo2
= skb_shinfo(skb2
);
1084 u8 tsflags
= shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
1086 shinfo
->tx_flags
&= ~tsflags
;
1087 shinfo2
->tx_flags
|= tsflags
;
1088 swap(shinfo
->tskey
, shinfo2
->tskey
);
1092 /* Function to create two new TCP segments. Shrinks the given segment
1093 * to the specified size and appends a new segment with the rest of the
1094 * packet to the list. This won't be called frequently, I hope.
1095 * Remember, these are still headerless SKBs at this point.
1097 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
1098 unsigned int mss_now
, gfp_t gfp
)
1100 struct tcp_sock
*tp
= tcp_sk(sk
);
1101 struct sk_buff
*buff
;
1102 int nsize
, old_factor
;
1106 if (WARN_ON(len
> skb
->len
))
1109 nsize
= skb_headlen(skb
) - len
;
1113 if (skb_unclone(skb
, gfp
))
1116 /* Get a new skb... force flag on. */
1117 buff
= sk_stream_alloc_skb(sk
, nsize
, gfp
);
1119 return -ENOMEM
; /* We'll just try again later. */
1121 sk
->sk_wmem_queued
+= buff
->truesize
;
1122 sk_mem_charge(sk
, buff
->truesize
);
1123 nlen
= skb
->len
- len
- nsize
;
1124 buff
->truesize
+= nlen
;
1125 skb
->truesize
-= nlen
;
1127 /* Correct the sequence numbers. */
1128 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1129 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1130 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1132 /* PSH and FIN should only be set in the second packet. */
1133 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1134 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1135 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1136 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1138 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
1139 /* Copy and checksum data tail into the new buffer. */
1140 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
1141 skb_put(buff
, nsize
),
1146 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
1148 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1149 skb_split(skb
, buff
, len
);
1152 buff
->ip_summed
= skb
->ip_summed
;
1154 buff
->tstamp
= skb
->tstamp
;
1155 tcp_fragment_tstamp(skb
, buff
);
1157 old_factor
= tcp_skb_pcount(skb
);
1159 /* Fix up tso_factor for both original and new SKB. */
1160 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1161 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1163 /* If this packet has been sent out already, we must
1164 * adjust the various packet counters.
1166 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1167 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1168 tcp_skb_pcount(buff
);
1171 tcp_adjust_pcount(sk
, skb
, diff
);
1174 /* Link BUFF into the send queue. */
1175 __skb_header_release(buff
);
1176 tcp_insert_write_queue_after(skb
, buff
, sk
);
1181 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1182 * eventually). The difference is that pulled data not copied, but
1183 * immediately discarded.
1185 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
1187 struct skb_shared_info
*shinfo
;
1190 eat
= min_t(int, len
, skb_headlen(skb
));
1192 __skb_pull(skb
, eat
);
1199 shinfo
= skb_shinfo(skb
);
1200 for (i
= 0; i
< shinfo
->nr_frags
; i
++) {
1201 int size
= skb_frag_size(&shinfo
->frags
[i
]);
1204 skb_frag_unref(skb
, i
);
1207 shinfo
->frags
[k
] = shinfo
->frags
[i
];
1209 shinfo
->frags
[k
].page_offset
+= eat
;
1210 skb_frag_size_sub(&shinfo
->frags
[k
], eat
);
1216 shinfo
->nr_frags
= k
;
1218 skb_reset_tail_pointer(skb
);
1219 skb
->data_len
-= len
;
1220 skb
->len
= skb
->data_len
;
1223 /* Remove acked data from a packet in the transmit queue. */
1224 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1226 if (skb_unclone(skb
, GFP_ATOMIC
))
1229 __pskb_trim_head(skb
, len
);
1231 TCP_SKB_CB(skb
)->seq
+= len
;
1232 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1234 skb
->truesize
-= len
;
1235 sk
->sk_wmem_queued
-= len
;
1236 sk_mem_uncharge(sk
, len
);
1237 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
1239 /* Any change of skb->len requires recalculation of tso factor. */
1240 if (tcp_skb_pcount(skb
) > 1)
1241 tcp_set_skb_tso_segs(sk
, skb
, tcp_skb_mss(skb
));
1246 /* Calculate MSS not accounting any TCP options. */
1247 static inline int __tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1249 const struct tcp_sock
*tp
= tcp_sk(sk
);
1250 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1253 /* Calculate base mss without TCP options:
1254 It is MMS_S - sizeof(tcphdr) of rfc1122
1256 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1258 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1259 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1260 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1262 if (dst
&& dst_allfrag(dst
))
1263 mss_now
-= icsk
->icsk_af_ops
->net_frag_header_len
;
1266 /* Clamp it (mss_clamp does not include tcp options) */
1267 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1268 mss_now
= tp
->rx_opt
.mss_clamp
;
1270 /* Now subtract optional transport overhead */
1271 mss_now
-= icsk
->icsk_ext_hdr_len
;
1273 /* Then reserve room for full set of TCP options and 8 bytes of data */
1279 /* Calculate MSS. Not accounting for SACKs here. */
1280 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1282 /* Subtract TCP options size, not including SACKs */
1283 return __tcp_mtu_to_mss(sk
, pmtu
) -
1284 (tcp_sk(sk
)->tcp_header_len
- sizeof(struct tcphdr
));
1287 /* Inverse of above */
1288 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1290 const struct tcp_sock
*tp
= tcp_sk(sk
);
1291 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1295 tp
->tcp_header_len
+
1296 icsk
->icsk_ext_hdr_len
+
1297 icsk
->icsk_af_ops
->net_header_len
;
1299 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1300 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1301 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1303 if (dst
&& dst_allfrag(dst
))
1304 mtu
+= icsk
->icsk_af_ops
->net_frag_header_len
;
1309 /* MTU probing init per socket */
1310 void tcp_mtup_init(struct sock
*sk
)
1312 struct tcp_sock
*tp
= tcp_sk(sk
);
1313 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1315 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
1316 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1317 icsk
->icsk_af_ops
->net_header_len
;
1318 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
1319 icsk
->icsk_mtup
.probe_size
= 0;
1321 EXPORT_SYMBOL(tcp_mtup_init
);
1323 /* This function synchronize snd mss to current pmtu/exthdr set.
1325 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1326 for TCP options, but includes only bare TCP header.
1328 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1329 It is minimum of user_mss and mss received with SYN.
1330 It also does not include TCP options.
1332 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1334 tp->mss_cache is current effective sending mss, including
1335 all tcp options except for SACKs. It is evaluated,
1336 taking into account current pmtu, but never exceeds
1337 tp->rx_opt.mss_clamp.
1339 NOTE1. rfc1122 clearly states that advertised MSS
1340 DOES NOT include either tcp or ip options.
1342 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1343 are READ ONLY outside this function. --ANK (980731)
1345 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1347 struct tcp_sock
*tp
= tcp_sk(sk
);
1348 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1351 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1352 icsk
->icsk_mtup
.search_high
= pmtu
;
1354 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1355 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1357 /* And store cached results */
1358 icsk
->icsk_pmtu_cookie
= pmtu
;
1359 if (icsk
->icsk_mtup
.enabled
)
1360 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1361 tp
->mss_cache
= mss_now
;
1365 EXPORT_SYMBOL(tcp_sync_mss
);
1367 /* Compute the current effective MSS, taking SACKs and IP options,
1368 * and even PMTU discovery events into account.
1370 unsigned int tcp_current_mss(struct sock
*sk
)
1372 const struct tcp_sock
*tp
= tcp_sk(sk
);
1373 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1375 unsigned int header_len
;
1376 struct tcp_out_options opts
;
1377 struct tcp_md5sig_key
*md5
;
1379 mss_now
= tp
->mss_cache
;
1382 u32 mtu
= dst_mtu(dst
);
1383 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1384 mss_now
= tcp_sync_mss(sk
, mtu
);
1387 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1388 sizeof(struct tcphdr
);
1389 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1390 * some common options. If this is an odd packet (because we have SACK
1391 * blocks etc) then our calculated header_len will be different, and
1392 * we have to adjust mss_now correspondingly */
1393 if (header_len
!= tp
->tcp_header_len
) {
1394 int delta
= (int) header_len
- tp
->tcp_header_len
;
1401 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1402 * As additional protections, we do not touch cwnd in retransmission phases,
1403 * and if application hit its sndbuf limit recently.
1405 static void tcp_cwnd_application_limited(struct sock
*sk
)
1407 struct tcp_sock
*tp
= tcp_sk(sk
);
1409 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
1410 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
1411 /* Limited by application or receiver window. */
1412 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
1413 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
1414 if (win_used
< tp
->snd_cwnd
) {
1415 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1416 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
1418 tp
->snd_cwnd_used
= 0;
1420 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1423 static void tcp_cwnd_validate(struct sock
*sk
, bool is_cwnd_limited
)
1425 struct tcp_sock
*tp
= tcp_sk(sk
);
1427 /* Track the maximum number of outstanding packets in each
1428 * window, and remember whether we were cwnd-limited then.
1430 if (!before(tp
->snd_una
, tp
->max_packets_seq
) ||
1431 tp
->packets_out
> tp
->max_packets_out
) {
1432 tp
->max_packets_out
= tp
->packets_out
;
1433 tp
->max_packets_seq
= tp
->snd_nxt
;
1434 tp
->is_cwnd_limited
= is_cwnd_limited
;
1437 if (tcp_is_cwnd_limited(sk
)) {
1438 /* Network is feed fully. */
1439 tp
->snd_cwnd_used
= 0;
1440 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1442 /* Network starves. */
1443 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1444 tp
->snd_cwnd_used
= tp
->packets_out
;
1446 if (sysctl_tcp_slow_start_after_idle
&&
1447 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1448 tcp_cwnd_application_limited(sk
);
1452 /* Minshall's variant of the Nagle send check. */
1453 static bool tcp_minshall_check(const struct tcp_sock
*tp
)
1455 return after(tp
->snd_sml
, tp
->snd_una
) &&
1456 !after(tp
->snd_sml
, tp
->snd_nxt
);
1459 /* Update snd_sml if this skb is under mss
1460 * Note that a TSO packet might end with a sub-mss segment
1461 * The test is really :
1462 * if ((skb->len % mss) != 0)
1463 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1464 * But we can avoid doing the divide again given we already have
1465 * skb_pcount = skb->len / mss_now
1467 static void tcp_minshall_update(struct tcp_sock
*tp
, unsigned int mss_now
,
1468 const struct sk_buff
*skb
)
1470 if (skb
->len
< tcp_skb_pcount(skb
) * mss_now
)
1471 tp
->snd_sml
= TCP_SKB_CB(skb
)->end_seq
;
1474 /* Return false, if packet can be sent now without violation Nagle's rules:
1475 * 1. It is full sized. (provided by caller in %partial bool)
1476 * 2. Or it contains FIN. (already checked by caller)
1477 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1478 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1479 * With Minshall's modification: all sent small packets are ACKed.
1481 static bool tcp_nagle_check(bool partial
, const struct tcp_sock
*tp
,
1485 ((nonagle
& TCP_NAGLE_CORK
) ||
1486 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
)));
1488 /* Returns the portion of skb which can be sent right away */
1489 static unsigned int tcp_mss_split_point(const struct sock
*sk
,
1490 const struct sk_buff
*skb
,
1491 unsigned int mss_now
,
1492 unsigned int max_segs
,
1495 const struct tcp_sock
*tp
= tcp_sk(sk
);
1496 u32 partial
, needed
, window
, max_len
;
1498 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1499 max_len
= mss_now
* max_segs
;
1501 if (likely(max_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1504 needed
= min(skb
->len
, window
);
1506 if (max_len
<= needed
)
1509 partial
= needed
% mss_now
;
1510 /* If last segment is not a full MSS, check if Nagle rules allow us
1511 * to include this last segment in this skb.
1512 * Otherwise, we'll split the skb at last MSS boundary
1514 if (tcp_nagle_check(partial
!= 0, tp
, nonagle
))
1515 return needed
- partial
;
1520 /* Can at least one segment of SKB be sent right now, according to the
1521 * congestion window rules? If so, return how many segments are allowed.
1523 static inline unsigned int tcp_cwnd_test(const struct tcp_sock
*tp
,
1524 const struct sk_buff
*skb
)
1526 u32 in_flight
, cwnd
;
1528 /* Don't be strict about the congestion window for the final FIN. */
1529 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
1530 tcp_skb_pcount(skb
) == 1)
1533 in_flight
= tcp_packets_in_flight(tp
);
1534 cwnd
= tp
->snd_cwnd
;
1535 if (in_flight
< cwnd
)
1536 return (cwnd
- in_flight
);
1541 /* Initialize TSO state of a skb.
1542 * This must be invoked the first time we consider transmitting
1543 * SKB onto the wire.
1545 static int tcp_init_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
1546 unsigned int mss_now
)
1548 int tso_segs
= tcp_skb_pcount(skb
);
1550 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1551 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1552 tso_segs
= tcp_skb_pcount(skb
);
1558 /* Return true if the Nagle test allows this packet to be
1561 static inline bool tcp_nagle_test(const struct tcp_sock
*tp
, const struct sk_buff
*skb
,
1562 unsigned int cur_mss
, int nonagle
)
1564 /* Nagle rule does not apply to frames, which sit in the middle of the
1565 * write_queue (they have no chances to get new data).
1567 * This is implemented in the callers, where they modify the 'nonagle'
1568 * argument based upon the location of SKB in the send queue.
1570 if (nonagle
& TCP_NAGLE_PUSH
)
1573 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1574 if (tcp_urg_mode(tp
) || (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
))
1577 if (!tcp_nagle_check(skb
->len
< cur_mss
, tp
, nonagle
))
1583 /* Does at least the first segment of SKB fit into the send window? */
1584 static bool tcp_snd_wnd_test(const struct tcp_sock
*tp
,
1585 const struct sk_buff
*skb
,
1586 unsigned int cur_mss
)
1588 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1590 if (skb
->len
> cur_mss
)
1591 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1593 return !after(end_seq
, tcp_wnd_end(tp
));
1596 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1597 * should be put on the wire right now. If so, it returns the number of
1598 * packets allowed by the congestion window.
1600 static unsigned int tcp_snd_test(const struct sock
*sk
, struct sk_buff
*skb
,
1601 unsigned int cur_mss
, int nonagle
)
1603 const struct tcp_sock
*tp
= tcp_sk(sk
);
1604 unsigned int cwnd_quota
;
1606 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1608 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1611 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1612 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1618 /* Test if sending is allowed right now. */
1619 bool tcp_may_send_now(struct sock
*sk
)
1621 const struct tcp_sock
*tp
= tcp_sk(sk
);
1622 struct sk_buff
*skb
= tcp_send_head(sk
);
1625 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1626 (tcp_skb_is_last(sk
, skb
) ?
1627 tp
->nonagle
: TCP_NAGLE_PUSH
));
1630 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1631 * which is put after SKB on the list. It is very much like
1632 * tcp_fragment() except that it may make several kinds of assumptions
1633 * in order to speed up the splitting operation. In particular, we
1634 * know that all the data is in scatter-gather pages, and that the
1635 * packet has never been sent out before (and thus is not cloned).
1637 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1638 unsigned int mss_now
, gfp_t gfp
)
1640 struct sk_buff
*buff
;
1641 int nlen
= skb
->len
- len
;
1644 /* All of a TSO frame must be composed of paged data. */
1645 if (skb
->len
!= skb
->data_len
)
1646 return tcp_fragment(sk
, skb
, len
, mss_now
, gfp
);
1648 buff
= sk_stream_alloc_skb(sk
, 0, gfp
);
1649 if (unlikely(buff
== NULL
))
1652 sk
->sk_wmem_queued
+= buff
->truesize
;
1653 sk_mem_charge(sk
, buff
->truesize
);
1654 buff
->truesize
+= nlen
;
1655 skb
->truesize
-= nlen
;
1657 /* Correct the sequence numbers. */
1658 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1659 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1660 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1662 /* PSH and FIN should only be set in the second packet. */
1663 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1664 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1665 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1667 /* This packet was never sent out yet, so no SACK bits. */
1668 TCP_SKB_CB(buff
)->sacked
= 0;
1670 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1671 skb_split(skb
, buff
, len
);
1672 tcp_fragment_tstamp(skb
, buff
);
1674 /* Fix up tso_factor for both original and new SKB. */
1675 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1676 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1678 /* Link BUFF into the send queue. */
1679 __skb_header_release(buff
);
1680 tcp_insert_write_queue_after(skb
, buff
, sk
);
1685 /* Try to defer sending, if possible, in order to minimize the amount
1686 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1688 * This algorithm is from John Heffner.
1690 static bool tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
,
1691 bool *is_cwnd_limited
)
1693 struct tcp_sock
*tp
= tcp_sk(sk
);
1694 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1695 u32 send_win
, cong_win
, limit
, in_flight
;
1698 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1701 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1704 /* Defer for less than two clock ticks. */
1705 if (tp
->tso_deferred
&&
1706 (((u32
)jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1709 in_flight
= tcp_packets_in_flight(tp
);
1711 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1713 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1715 /* From in_flight test above, we know that cwnd > in_flight. */
1716 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1718 limit
= min(send_win
, cong_win
);
1720 /* If a full-sized TSO skb can be sent, do it. */
1721 if (limit
>= min_t(unsigned int, sk
->sk_gso_max_size
,
1722 tp
->xmit_size_goal_segs
* tp
->mss_cache
))
1725 /* Middle in queue won't get any more data, full sendable already? */
1726 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1729 win_divisor
= ACCESS_ONCE(sysctl_tcp_tso_win_divisor
);
1731 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1733 /* If at least some fraction of a window is available,
1736 chunk
/= win_divisor
;
1740 /* Different approach, try not to defer past a single
1741 * ACK. Receiver should ACK every other full sized
1742 * frame, so if we have space for more than 3 frames
1745 if (limit
> tcp_max_tso_deferred_mss(tp
) * tp
->mss_cache
)
1749 /* Ok, it looks like it is advisable to defer.
1750 * Do not rearm the timer if already set to not break TCP ACK clocking.
1752 if (!tp
->tso_deferred
)
1753 tp
->tso_deferred
= 1 | (jiffies
<< 1);
1755 if (cong_win
< send_win
&& cong_win
< skb
->len
)
1756 *is_cwnd_limited
= true;
1761 tp
->tso_deferred
= 0;
1765 /* Create a new MTU probe if we are ready.
1766 * MTU probe is regularly attempting to increase the path MTU by
1767 * deliberately sending larger packets. This discovers routing
1768 * changes resulting in larger path MTUs.
1770 * Returns 0 if we should wait to probe (no cwnd available),
1771 * 1 if a probe was sent,
1774 static int tcp_mtu_probe(struct sock
*sk
)
1776 struct tcp_sock
*tp
= tcp_sk(sk
);
1777 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1778 struct sk_buff
*skb
, *nskb
, *next
;
1785 /* Not currently probing/verifying,
1787 * have enough cwnd, and
1788 * not SACKing (the variable headers throw things off) */
1789 if (!icsk
->icsk_mtup
.enabled
||
1790 icsk
->icsk_mtup
.probe_size
||
1791 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1792 tp
->snd_cwnd
< 11 ||
1793 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
)
1796 /* Very simple search strategy: just double the MSS. */
1797 mss_now
= tcp_current_mss(sk
);
1798 probe_size
= 2 * tp
->mss_cache
;
1799 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1800 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1801 /* TODO: set timer for probe_converge_event */
1805 /* Have enough data in the send queue to probe? */
1806 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1809 if (tp
->snd_wnd
< size_needed
)
1811 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1814 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1815 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1816 if (!tcp_packets_in_flight(tp
))
1822 /* We're allowed to probe. Build it now. */
1823 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1825 sk
->sk_wmem_queued
+= nskb
->truesize
;
1826 sk_mem_charge(sk
, nskb
->truesize
);
1828 skb
= tcp_send_head(sk
);
1830 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1831 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1832 TCP_SKB_CB(nskb
)->tcp_flags
= TCPHDR_ACK
;
1833 TCP_SKB_CB(nskb
)->sacked
= 0;
1835 nskb
->ip_summed
= skb
->ip_summed
;
1837 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1840 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1841 copy
= min_t(int, skb
->len
, probe_size
- len
);
1842 if (nskb
->ip_summed
)
1843 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1845 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1846 skb_put(nskb
, copy
),
1849 if (skb
->len
<= copy
) {
1850 /* We've eaten all the data from this skb.
1852 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1853 tcp_unlink_write_queue(skb
, sk
);
1854 sk_wmem_free_skb(sk
, skb
);
1856 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
&
1857 ~(TCPHDR_FIN
|TCPHDR_PSH
);
1858 if (!skb_shinfo(skb
)->nr_frags
) {
1859 skb_pull(skb
, copy
);
1860 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1861 skb
->csum
= csum_partial(skb
->data
,
1864 __pskb_trim_head(skb
, copy
);
1865 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1867 TCP_SKB_CB(skb
)->seq
+= copy
;
1872 if (len
>= probe_size
)
1875 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1877 /* We're ready to send. If this fails, the probe will
1878 * be resegmented into mss-sized pieces by tcp_write_xmit().
1880 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1881 /* Decrement cwnd here because we are sending
1882 * effectively two packets. */
1884 tcp_event_new_data_sent(sk
, nskb
);
1886 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1887 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1888 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1896 /* This routine writes packets to the network. It advances the
1897 * send_head. This happens as incoming acks open up the remote
1900 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1901 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1902 * account rare use of URG, this is not a big flaw.
1904 * Send at most one packet when push_one > 0. Temporarily ignore
1905 * cwnd limit to force at most one packet out when push_one == 2.
1907 * Returns true, if no segments are in flight and we have queued segments,
1908 * but cannot send anything now because of SWS or another problem.
1910 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
1911 int push_one
, gfp_t gfp
)
1913 struct tcp_sock
*tp
= tcp_sk(sk
);
1914 struct sk_buff
*skb
;
1915 unsigned int tso_segs
, sent_pkts
;
1918 bool is_cwnd_limited
= false;
1923 /* Do MTU probing. */
1924 result
= tcp_mtu_probe(sk
);
1927 } else if (result
> 0) {
1932 while ((skb
= tcp_send_head(sk
))) {
1935 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1938 if (unlikely(tp
->repair
) && tp
->repair_queue
== TCP_SEND_QUEUE
) {
1939 /* "skb_mstamp" is used as a start point for the retransmit timer */
1940 skb_mstamp_get(&skb
->skb_mstamp
);
1941 goto repair
; /* Skip network transmission */
1944 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1946 is_cwnd_limited
= true;
1948 /* Force out a loss probe pkt. */
1954 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1957 if (tso_segs
== 1) {
1958 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1959 (tcp_skb_is_last(sk
, skb
) ?
1960 nonagle
: TCP_NAGLE_PUSH
))))
1964 tcp_tso_should_defer(sk
, skb
, &is_cwnd_limited
))
1968 /* TCP Small Queues :
1969 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
1971 * - better RTT estimation and ACK scheduling
1974 * Alas, some drivers / subsystems require a fair amount
1975 * of queued bytes to ensure line rate.
1976 * One example is wifi aggregation (802.11 AMPDU)
1978 limit
= max_t(unsigned int, sysctl_tcp_limit_output_bytes
,
1979 sk
->sk_pacing_rate
>> 10);
1981 if (atomic_read(&sk
->sk_wmem_alloc
) > limit
) {
1982 set_bit(TSQ_THROTTLED
, &tp
->tsq_flags
);
1983 /* It is possible TX completion already happened
1984 * before we set TSQ_THROTTLED, so we must
1985 * test again the condition.
1987 smp_mb__after_atomic();
1988 if (atomic_read(&sk
->sk_wmem_alloc
) > limit
)
1993 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
1994 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
1997 sk
->sk_gso_max_segs
),
2000 if (skb
->len
> limit
&&
2001 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
, gfp
)))
2004 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
2008 /* Advance the send_head. This one is sent out.
2009 * This call will increment packets_out.
2011 tcp_event_new_data_sent(sk
, skb
);
2013 tcp_minshall_update(tp
, mss_now
, skb
);
2014 sent_pkts
+= tcp_skb_pcount(skb
);
2020 if (likely(sent_pkts
)) {
2021 if (tcp_in_cwnd_reduction(sk
))
2022 tp
->prr_out
+= sent_pkts
;
2024 /* Send one loss probe per tail loss episode. */
2026 tcp_schedule_loss_probe(sk
);
2027 tcp_cwnd_validate(sk
, is_cwnd_limited
);
2030 return (push_one
== 2) || (!tp
->packets_out
&& tcp_send_head(sk
));
2033 bool tcp_schedule_loss_probe(struct sock
*sk
)
2035 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2036 struct tcp_sock
*tp
= tcp_sk(sk
);
2037 u32 timeout
, tlp_time_stamp
, rto_time_stamp
;
2038 u32 rtt
= usecs_to_jiffies(tp
->srtt_us
>> 3);
2040 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
))
2042 /* No consecutive loss probes. */
2043 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)) {
2047 /* Don't do any loss probe on a Fast Open connection before 3WHS
2050 if (sk
->sk_state
== TCP_SYN_RECV
)
2053 /* TLP is only scheduled when next timer event is RTO. */
2054 if (icsk
->icsk_pending
!= ICSK_TIME_RETRANS
)
2057 /* Schedule a loss probe in 2*RTT for SACK capable connections
2058 * in Open state, that are either limited by cwnd or application.
2060 if (sysctl_tcp_early_retrans
< 3 || !tp
->srtt_us
|| !tp
->packets_out
||
2061 !tcp_is_sack(tp
) || inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
2064 if ((tp
->snd_cwnd
> tcp_packets_in_flight(tp
)) &&
2068 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2069 * for delayed ack when there's one outstanding packet.
2072 if (tp
->packets_out
== 1)
2073 timeout
= max_t(u32
, timeout
,
2074 (rtt
+ (rtt
>> 1) + TCP_DELACK_MAX
));
2075 timeout
= max_t(u32
, timeout
, msecs_to_jiffies(10));
2077 /* If RTO is shorter, just schedule TLP in its place. */
2078 tlp_time_stamp
= tcp_time_stamp
+ timeout
;
2079 rto_time_stamp
= (u32
)inet_csk(sk
)->icsk_timeout
;
2080 if ((s32
)(tlp_time_stamp
- rto_time_stamp
) > 0) {
2081 s32 delta
= rto_time_stamp
- tcp_time_stamp
;
2086 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_LOSS_PROBE
, timeout
,
2091 /* Thanks to skb fast clones, we can detect if a prior transmit of
2092 * a packet is still in a qdisc or driver queue.
2093 * In this case, there is very little point doing a retransmit !
2094 * Note: This is called from BH context only.
2096 static bool skb_still_in_host_queue(const struct sock
*sk
,
2097 const struct sk_buff
*skb
)
2099 const struct sk_buff
*fclone
= skb
+ 1;
2101 if (unlikely(skb
->fclone
== SKB_FCLONE_ORIG
&&
2102 fclone
->fclone
== SKB_FCLONE_CLONE
)) {
2103 NET_INC_STATS_BH(sock_net(sk
),
2104 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES
);
2110 /* When probe timeout (PTO) fires, send a new segment if one exists, else
2111 * retransmit the last segment.
2113 void tcp_send_loss_probe(struct sock
*sk
)
2115 struct tcp_sock
*tp
= tcp_sk(sk
);
2116 struct sk_buff
*skb
;
2118 int mss
= tcp_current_mss(sk
);
2121 if (tcp_send_head(sk
) != NULL
) {
2122 err
= tcp_write_xmit(sk
, mss
, TCP_NAGLE_OFF
, 2, GFP_ATOMIC
);
2126 /* At most one outstanding TLP retransmission. */
2127 if (tp
->tlp_high_seq
)
2130 /* Retransmit last segment. */
2131 skb
= tcp_write_queue_tail(sk
);
2135 if (skb_still_in_host_queue(sk
, skb
))
2138 pcount
= tcp_skb_pcount(skb
);
2139 if (WARN_ON(!pcount
))
2142 if ((pcount
> 1) && (skb
->len
> (pcount
- 1) * mss
)) {
2143 if (unlikely(tcp_fragment(sk
, skb
, (pcount
- 1) * mss
, mss
,
2146 skb
= tcp_write_queue_tail(sk
);
2149 if (WARN_ON(!skb
|| !tcp_skb_pcount(skb
)))
2152 err
= __tcp_retransmit_skb(sk
, skb
);
2154 /* Record snd_nxt for loss detection. */
2156 tp
->tlp_high_seq
= tp
->snd_nxt
;
2159 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2160 inet_csk(sk
)->icsk_rto
,
2164 NET_INC_STATS_BH(sock_net(sk
),
2165 LINUX_MIB_TCPLOSSPROBES
);
2168 /* Push out any pending frames which were held back due to
2169 * TCP_CORK or attempt at coalescing tiny packets.
2170 * The socket must be locked by the caller.
2172 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
2175 /* If we are closed, the bytes will have to remain here.
2176 * In time closedown will finish, we empty the write queue and
2177 * all will be happy.
2179 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
2182 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0,
2183 sk_gfp_atomic(sk
, GFP_ATOMIC
)))
2184 tcp_check_probe_timer(sk
);
2187 /* Send _single_ skb sitting at the send head. This function requires
2188 * true push pending frames to setup probe timer etc.
2190 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
2192 struct sk_buff
*skb
= tcp_send_head(sk
);
2194 BUG_ON(!skb
|| skb
->len
< mss_now
);
2196 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
2199 /* This function returns the amount that we can raise the
2200 * usable window based on the following constraints
2202 * 1. The window can never be shrunk once it is offered (RFC 793)
2203 * 2. We limit memory per socket
2206 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2207 * RECV.NEXT + RCV.WIN fixed until:
2208 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2210 * i.e. don't raise the right edge of the window until you can raise
2211 * it at least MSS bytes.
2213 * Unfortunately, the recommended algorithm breaks header prediction,
2214 * since header prediction assumes th->window stays fixed.
2216 * Strictly speaking, keeping th->window fixed violates the receiver
2217 * side SWS prevention criteria. The problem is that under this rule
2218 * a stream of single byte packets will cause the right side of the
2219 * window to always advance by a single byte.
2221 * Of course, if the sender implements sender side SWS prevention
2222 * then this will not be a problem.
2224 * BSD seems to make the following compromise:
2226 * If the free space is less than the 1/4 of the maximum
2227 * space available and the free space is less than 1/2 mss,
2228 * then set the window to 0.
2229 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2230 * Otherwise, just prevent the window from shrinking
2231 * and from being larger than the largest representable value.
2233 * This prevents incremental opening of the window in the regime
2234 * where TCP is limited by the speed of the reader side taking
2235 * data out of the TCP receive queue. It does nothing about
2236 * those cases where the window is constrained on the sender side
2237 * because the pipeline is full.
2239 * BSD also seems to "accidentally" limit itself to windows that are a
2240 * multiple of MSS, at least until the free space gets quite small.
2241 * This would appear to be a side effect of the mbuf implementation.
2242 * Combining these two algorithms results in the observed behavior
2243 * of having a fixed window size at almost all times.
2245 * Below we obtain similar behavior by forcing the offered window to
2246 * a multiple of the mss when it is feasible to do so.
2248 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2249 * Regular options like TIMESTAMP are taken into account.
2251 u32
__tcp_select_window(struct sock
*sk
)
2253 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2254 struct tcp_sock
*tp
= tcp_sk(sk
);
2255 /* MSS for the peer's data. Previous versions used mss_clamp
2256 * here. I don't know if the value based on our guesses
2257 * of peer's MSS is better for the performance. It's more correct
2258 * but may be worse for the performance because of rcv_mss
2259 * fluctuations. --SAW 1998/11/1
2261 int mss
= icsk
->icsk_ack
.rcv_mss
;
2262 int free_space
= tcp_space(sk
);
2263 int allowed_space
= tcp_full_space(sk
);
2264 int full_space
= min_t(int, tp
->window_clamp
, allowed_space
);
2267 if (mss
> full_space
)
2270 if (free_space
< (full_space
>> 1)) {
2271 icsk
->icsk_ack
.quick
= 0;
2273 if (sk_under_memory_pressure(sk
))
2274 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
2277 /* free_space might become our new window, make sure we don't
2278 * increase it due to wscale.
2280 free_space
= round_down(free_space
, 1 << tp
->rx_opt
.rcv_wscale
);
2282 /* if free space is less than mss estimate, or is below 1/16th
2283 * of the maximum allowed, try to move to zero-window, else
2284 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2285 * new incoming data is dropped due to memory limits.
2286 * With large window, mss test triggers way too late in order
2287 * to announce zero window in time before rmem limit kicks in.
2289 if (free_space
< (allowed_space
>> 4) || free_space
< mss
)
2293 if (free_space
> tp
->rcv_ssthresh
)
2294 free_space
= tp
->rcv_ssthresh
;
2296 /* Don't do rounding if we are using window scaling, since the
2297 * scaled window will not line up with the MSS boundary anyway.
2299 window
= tp
->rcv_wnd
;
2300 if (tp
->rx_opt
.rcv_wscale
) {
2301 window
= free_space
;
2303 /* Advertise enough space so that it won't get scaled away.
2304 * Import case: prevent zero window announcement if
2305 * 1<<rcv_wscale > mss.
2307 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
2308 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
2309 << tp
->rx_opt
.rcv_wscale
);
2311 /* Get the largest window that is a nice multiple of mss.
2312 * Window clamp already applied above.
2313 * If our current window offering is within 1 mss of the
2314 * free space we just keep it. This prevents the divide
2315 * and multiply from happening most of the time.
2316 * We also don't do any window rounding when the free space
2319 if (window
<= free_space
- mss
|| window
> free_space
)
2320 window
= (free_space
/ mss
) * mss
;
2321 else if (mss
== full_space
&&
2322 free_space
> window
+ (full_space
>> 1))
2323 window
= free_space
;
2329 /* Collapses two adjacent SKB's during retransmission. */
2330 static void tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
2332 struct tcp_sock
*tp
= tcp_sk(sk
);
2333 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
2334 int skb_size
, next_skb_size
;
2336 skb_size
= skb
->len
;
2337 next_skb_size
= next_skb
->len
;
2339 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
2341 tcp_highest_sack_combine(sk
, next_skb
, skb
);
2343 tcp_unlink_write_queue(next_skb
, sk
);
2345 skb_copy_from_linear_data(next_skb
, skb_put(skb
, next_skb_size
),
2348 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
2349 skb
->ip_summed
= CHECKSUM_PARTIAL
;
2351 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2352 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
2354 /* Update sequence range on original skb. */
2355 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
2357 /* Merge over control information. This moves PSH/FIN etc. over */
2358 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(next_skb
)->tcp_flags
;
2360 /* All done, get rid of second SKB and account for it so
2361 * packet counting does not break.
2363 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
2365 /* changed transmit queue under us so clear hints */
2366 tcp_clear_retrans_hints_partial(tp
);
2367 if (next_skb
== tp
->retransmit_skb_hint
)
2368 tp
->retransmit_skb_hint
= skb
;
2370 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
2372 sk_wmem_free_skb(sk
, next_skb
);
2375 /* Check if coalescing SKBs is legal. */
2376 static bool tcp_can_collapse(const struct sock
*sk
, const struct sk_buff
*skb
)
2378 if (tcp_skb_pcount(skb
) > 1)
2380 /* TODO: SACK collapsing could be used to remove this condition */
2381 if (skb_shinfo(skb
)->nr_frags
!= 0)
2383 if (skb_cloned(skb
))
2385 if (skb
== tcp_send_head(sk
))
2387 /* Some heurestics for collapsing over SACK'd could be invented */
2388 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2394 /* Collapse packets in the retransmit queue to make to create
2395 * less packets on the wire. This is only done on retransmission.
2397 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
2400 struct tcp_sock
*tp
= tcp_sk(sk
);
2401 struct sk_buff
*skb
= to
, *tmp
;
2404 if (!sysctl_tcp_retrans_collapse
)
2406 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2409 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
2410 if (!tcp_can_collapse(sk
, skb
))
2422 /* Punt if not enough space exists in the first SKB for
2423 * the data in the second
2425 if (skb
->len
> skb_availroom(to
))
2428 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
2431 tcp_collapse_retrans(sk
, to
);
2435 /* This retransmits one SKB. Policy decisions and retransmit queue
2436 * state updates are done by the caller. Returns non-zero if an
2437 * error occurred which prevented the send.
2439 int __tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2441 struct tcp_sock
*tp
= tcp_sk(sk
);
2442 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2443 unsigned int cur_mss
;
2446 /* Inconslusive MTU probe */
2447 if (icsk
->icsk_mtup
.probe_size
) {
2448 icsk
->icsk_mtup
.probe_size
= 0;
2451 /* Do not sent more than we queued. 1/4 is reserved for possible
2452 * copying overhead: fragmentation, tunneling, mangling etc.
2454 if (atomic_read(&sk
->sk_wmem_alloc
) >
2455 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
2458 if (skb_still_in_host_queue(sk
, skb
))
2461 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
2462 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
2464 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2468 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
2469 return -EHOSTUNREACH
; /* Routing failure or similar. */
2471 cur_mss
= tcp_current_mss(sk
);
2473 /* If receiver has shrunk his window, and skb is out of
2474 * new window, do not retransmit it. The exception is the
2475 * case, when window is shrunk to zero. In this case
2476 * our retransmit serves as a zero window probe.
2478 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
)) &&
2479 TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
2482 if (skb
->len
> cur_mss
) {
2483 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
, GFP_ATOMIC
))
2484 return -ENOMEM
; /* We'll try again later. */
2486 int oldpcount
= tcp_skb_pcount(skb
);
2488 if (unlikely(oldpcount
> 1)) {
2489 if (skb_unclone(skb
, GFP_ATOMIC
))
2491 tcp_init_tso_segs(sk
, skb
, cur_mss
);
2492 tcp_adjust_pcount(sk
, skb
, oldpcount
- tcp_skb_pcount(skb
));
2496 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
2498 /* Make a copy, if the first transmission SKB clone we made
2499 * is still in somebody's hands, else make a clone.
2502 /* make sure skb->data is aligned on arches that require it
2503 * and check if ack-trimming & collapsing extended the headroom
2504 * beyond what csum_start can cover.
2506 if (unlikely((NET_IP_ALIGN
&& ((unsigned long)skb
->data
& 3)) ||
2507 skb_headroom(skb
) >= 0xFFFF)) {
2508 struct sk_buff
*nskb
= __pskb_copy(skb
, MAX_TCP_HEADER
,
2510 err
= nskb
? tcp_transmit_skb(sk
, nskb
, 0, GFP_ATOMIC
) :
2513 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2517 TCP_SKB_CB(skb
)->sacked
|= TCPCB_EVER_RETRANS
;
2518 /* Update global TCP statistics. */
2519 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
2520 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2521 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
2522 tp
->total_retrans
++;
2527 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2529 struct tcp_sock
*tp
= tcp_sk(sk
);
2530 int err
= __tcp_retransmit_skb(sk
, skb
);
2533 #if FASTRETRANS_DEBUG > 0
2534 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2535 net_dbg_ratelimited("retrans_out leaked\n");
2538 if (!tp
->retrans_out
)
2539 tp
->lost_retrans_low
= tp
->snd_nxt
;
2540 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
2541 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2543 /* Save stamp of the first retransmit. */
2544 if (!tp
->retrans_stamp
)
2545 tp
->retrans_stamp
= tcp_skb_timestamp(skb
);
2547 /* snd_nxt is stored to detect loss of retransmitted segment,
2548 * see tcp_input.c tcp_sacktag_write_queue().
2550 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
2551 } else if (err
!= -EBUSY
) {
2552 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRETRANSFAIL
);
2555 if (tp
->undo_retrans
< 0)
2556 tp
->undo_retrans
= 0;
2557 tp
->undo_retrans
+= tcp_skb_pcount(skb
);
2561 /* Check if we forward retransmits are possible in the current
2562 * window/congestion state.
2564 static bool tcp_can_forward_retransmit(struct sock
*sk
)
2566 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2567 const struct tcp_sock
*tp
= tcp_sk(sk
);
2569 /* Forward retransmissions are possible only during Recovery. */
2570 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
2573 /* No forward retransmissions in Reno are possible. */
2574 if (tcp_is_reno(tp
))
2577 /* Yeah, we have to make difficult choice between forward transmission
2578 * and retransmission... Both ways have their merits...
2580 * For now we do not retransmit anything, while we have some new
2581 * segments to send. In the other cases, follow rule 3 for
2582 * NextSeg() specified in RFC3517.
2585 if (tcp_may_send_now(sk
))
2591 /* This gets called after a retransmit timeout, and the initially
2592 * retransmitted data is acknowledged. It tries to continue
2593 * resending the rest of the retransmit queue, until either
2594 * we've sent it all or the congestion window limit is reached.
2595 * If doing SACK, the first ACK which comes back for a timeout
2596 * based retransmit packet might feed us FACK information again.
2597 * If so, we use it to avoid unnecessarily retransmissions.
2599 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2601 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2602 struct tcp_sock
*tp
= tcp_sk(sk
);
2603 struct sk_buff
*skb
;
2604 struct sk_buff
*hole
= NULL
;
2607 int fwd_rexmitting
= 0;
2609 if (!tp
->packets_out
)
2613 tp
->retransmit_high
= tp
->snd_una
;
2615 if (tp
->retransmit_skb_hint
) {
2616 skb
= tp
->retransmit_skb_hint
;
2617 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2618 if (after(last_lost
, tp
->retransmit_high
))
2619 last_lost
= tp
->retransmit_high
;
2621 skb
= tcp_write_queue_head(sk
);
2622 last_lost
= tp
->snd_una
;
2625 tcp_for_write_queue_from(skb
, sk
) {
2626 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
2628 if (skb
== tcp_send_head(sk
))
2630 /* we could do better than to assign each time */
2632 tp
->retransmit_skb_hint
= skb
;
2634 /* Assume this retransmit will generate
2635 * only one packet for congestion window
2636 * calculation purposes. This works because
2637 * tcp_retransmit_skb() will chop up the
2638 * packet to be MSS sized and all the
2639 * packet counting works out.
2641 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2644 if (fwd_rexmitting
) {
2646 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2648 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2650 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2651 tp
->retransmit_high
= last_lost
;
2652 if (!tcp_can_forward_retransmit(sk
))
2654 /* Backtrack if necessary to non-L'ed skb */
2662 } else if (!(sacked
& TCPCB_LOST
)) {
2663 if (hole
== NULL
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2668 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2669 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2670 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2672 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2675 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2678 if (tcp_retransmit_skb(sk
, skb
))
2681 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2683 if (tcp_in_cwnd_reduction(sk
))
2684 tp
->prr_out
+= tcp_skb_pcount(skb
);
2686 if (skb
== tcp_write_queue_head(sk
))
2687 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2688 inet_csk(sk
)->icsk_rto
,
2693 /* Send a fin. The caller locks the socket for us. This cannot be
2694 * allowed to fail queueing a FIN frame under any circumstances.
2696 void tcp_send_fin(struct sock
*sk
)
2698 struct tcp_sock
*tp
= tcp_sk(sk
);
2699 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2702 /* Optimization, tack on the FIN if we have a queue of
2703 * unsent frames. But be careful about outgoing SACKS
2706 mss_now
= tcp_current_mss(sk
);
2708 if (tcp_send_head(sk
) != NULL
) {
2709 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_FIN
;
2710 TCP_SKB_CB(skb
)->end_seq
++;
2713 /* Socket is locked, keep trying until memory is available. */
2715 skb
= alloc_skb_fclone(MAX_TCP_HEADER
,
2722 /* Reserve space for headers and prepare control bits. */
2723 skb_reserve(skb
, MAX_TCP_HEADER
);
2724 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2725 tcp_init_nondata_skb(skb
, tp
->write_seq
,
2726 TCPHDR_ACK
| TCPHDR_FIN
);
2727 tcp_queue_skb(sk
, skb
);
2729 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2732 /* We get here when a process closes a file descriptor (either due to
2733 * an explicit close() or as a byproduct of exit()'ing) and there
2734 * was unread data in the receive queue. This behavior is recommended
2735 * by RFC 2525, section 2.17. -DaveM
2737 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2739 struct sk_buff
*skb
;
2741 /* NOTE: No TCP options attached and we never retransmit this. */
2742 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2744 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2748 /* Reserve space for headers and prepare control bits. */
2749 skb_reserve(skb
, MAX_TCP_HEADER
);
2750 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
2751 TCPHDR_ACK
| TCPHDR_RST
);
2753 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2754 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2756 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
2759 /* Send a crossed SYN-ACK during socket establishment.
2760 * WARNING: This routine must only be called when we have already sent
2761 * a SYN packet that crossed the incoming SYN that caused this routine
2762 * to get called. If this assumption fails then the initial rcv_wnd
2763 * and rcv_wscale values will not be correct.
2765 int tcp_send_synack(struct sock
*sk
)
2767 struct sk_buff
*skb
;
2769 skb
= tcp_write_queue_head(sk
);
2770 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
2771 pr_debug("%s: wrong queue state\n", __func__
);
2774 if (!(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_ACK
)) {
2775 if (skb_cloned(skb
)) {
2776 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2779 tcp_unlink_write_queue(skb
, sk
);
2780 __skb_header_release(nskb
);
2781 __tcp_add_write_queue_head(sk
, nskb
);
2782 sk_wmem_free_skb(sk
, skb
);
2783 sk
->sk_wmem_queued
+= nskb
->truesize
;
2784 sk_mem_charge(sk
, nskb
->truesize
);
2788 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ACK
;
2789 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2791 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2795 * tcp_make_synack - Prepare a SYN-ACK.
2796 * sk: listener socket
2797 * dst: dst entry attached to the SYNACK
2798 * req: request_sock pointer
2800 * Allocate one skb and build a SYNACK packet.
2801 * @dst is consumed : Caller should not use it again.
2803 struct sk_buff
*tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2804 struct request_sock
*req
,
2805 struct tcp_fastopen_cookie
*foc
)
2807 struct tcp_out_options opts
;
2808 struct inet_request_sock
*ireq
= inet_rsk(req
);
2809 struct tcp_sock
*tp
= tcp_sk(sk
);
2811 struct sk_buff
*skb
;
2812 struct tcp_md5sig_key
*md5
;
2813 int tcp_header_size
;
2816 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
, 1, GFP_ATOMIC
);
2817 if (unlikely(!skb
)) {
2821 /* Reserve space for headers. */
2822 skb_reserve(skb
, MAX_TCP_HEADER
);
2824 skb_dst_set(skb
, dst
);
2825 security_skb_owned_by(skb
, sk
);
2827 mss
= dst_metric_advmss(dst
);
2828 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< mss
)
2829 mss
= tp
->rx_opt
.user_mss
;
2831 memset(&opts
, 0, sizeof(opts
));
2832 #ifdef CONFIG_SYN_COOKIES
2833 if (unlikely(req
->cookie_ts
))
2834 skb
->skb_mstamp
.stamp_jiffies
= cookie_init_timestamp(req
);
2837 skb_mstamp_get(&skb
->skb_mstamp
);
2838 tcp_header_size
= tcp_synack_options(sk
, req
, mss
, skb
, &opts
, &md5
,
2841 skb_push(skb
, tcp_header_size
);
2842 skb_reset_transport_header(skb
);
2845 memset(th
, 0, sizeof(struct tcphdr
));
2848 TCP_ECN_make_synack(req
, th
);
2849 th
->source
= htons(ireq
->ir_num
);
2850 th
->dest
= ireq
->ir_rmt_port
;
2851 /* Setting of flags are superfluous here for callers (and ECE is
2852 * not even correctly set)
2854 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
2855 TCPHDR_SYN
| TCPHDR_ACK
);
2857 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2858 /* XXX data is queued and acked as is. No buffer/window check */
2859 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_nxt
);
2861 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2862 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2863 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
2864 th
->doff
= (tcp_header_size
>> 2);
2865 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_OUTSEGS
);
2867 #ifdef CONFIG_TCP_MD5SIG
2868 /* Okay, we have all we need - do the md5 hash if needed */
2870 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
2871 md5
, NULL
, req
, skb
);
2877 EXPORT_SYMBOL(tcp_make_synack
);
2879 /* Do all connect socket setups that can be done AF independent. */
2880 static void tcp_connect_init(struct sock
*sk
)
2882 const struct dst_entry
*dst
= __sk_dst_get(sk
);
2883 struct tcp_sock
*tp
= tcp_sk(sk
);
2886 /* We'll fix this up when we get a response from the other end.
2887 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2889 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2890 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2892 #ifdef CONFIG_TCP_MD5SIG
2893 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2894 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2897 /* If user gave his TCP_MAXSEG, record it to clamp */
2898 if (tp
->rx_opt
.user_mss
)
2899 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2902 tcp_sync_mss(sk
, dst_mtu(dst
));
2904 if (!tp
->window_clamp
)
2905 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2906 tp
->advmss
= dst_metric_advmss(dst
);
2907 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
2908 tp
->advmss
= tp
->rx_opt
.user_mss
;
2910 tcp_initialize_rcv_mss(sk
);
2912 /* limit the window selection if the user enforce a smaller rx buffer */
2913 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
2914 (tp
->window_clamp
> tcp_full_space(sk
) || tp
->window_clamp
== 0))
2915 tp
->window_clamp
= tcp_full_space(sk
);
2917 tcp_select_initial_window(tcp_full_space(sk
),
2918 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2921 sysctl_tcp_window_scaling
,
2923 dst_metric(dst
, RTAX_INITRWND
));
2925 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2926 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2929 sock_reset_flag(sk
, SOCK_DONE
);
2932 tp
->snd_una
= tp
->write_seq
;
2933 tp
->snd_sml
= tp
->write_seq
;
2934 tp
->snd_up
= tp
->write_seq
;
2935 tp
->snd_nxt
= tp
->write_seq
;
2937 if (likely(!tp
->repair
))
2940 tp
->rcv_tstamp
= tcp_time_stamp
;
2941 tp
->rcv_wup
= tp
->rcv_nxt
;
2942 tp
->copied_seq
= tp
->rcv_nxt
;
2944 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2945 inet_csk(sk
)->icsk_retransmits
= 0;
2946 tcp_clear_retrans(tp
);
2949 static void tcp_connect_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
2951 struct tcp_sock
*tp
= tcp_sk(sk
);
2952 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
2954 tcb
->end_seq
+= skb
->len
;
2955 __skb_header_release(skb
);
2956 __tcp_add_write_queue_tail(sk
, skb
);
2957 sk
->sk_wmem_queued
+= skb
->truesize
;
2958 sk_mem_charge(sk
, skb
->truesize
);
2959 tp
->write_seq
= tcb
->end_seq
;
2960 tp
->packets_out
+= tcp_skb_pcount(skb
);
2963 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
2964 * queue a data-only packet after the regular SYN, such that regular SYNs
2965 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
2966 * only the SYN sequence, the data are retransmitted in the first ACK.
2967 * If cookie is not cached or other error occurs, falls back to send a
2968 * regular SYN with Fast Open cookie request option.
2970 static int tcp_send_syn_data(struct sock
*sk
, struct sk_buff
*syn
)
2972 struct tcp_sock
*tp
= tcp_sk(sk
);
2973 struct tcp_fastopen_request
*fo
= tp
->fastopen_req
;
2974 int syn_loss
= 0, space
, i
, err
= 0, iovlen
= fo
->data
->msg_iovlen
;
2975 struct sk_buff
*syn_data
= NULL
, *data
;
2976 unsigned long last_syn_loss
= 0;
2978 tp
->rx_opt
.mss_clamp
= tp
->advmss
; /* If MSS is not cached */
2979 tcp_fastopen_cache_get(sk
, &tp
->rx_opt
.mss_clamp
, &fo
->cookie
,
2980 &syn_loss
, &last_syn_loss
);
2981 /* Recurring FO SYN losses: revert to regular handshake temporarily */
2983 time_before(jiffies
, last_syn_loss
+ (60*HZ
<< syn_loss
))) {
2984 fo
->cookie
.len
= -1;
2988 if (sysctl_tcp_fastopen
& TFO_CLIENT_NO_COOKIE
)
2989 fo
->cookie
.len
= -1;
2990 else if (fo
->cookie
.len
<= 0)
2993 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
2994 * user-MSS. Reserve maximum option space for middleboxes that add
2995 * private TCP options. The cost is reduced data space in SYN :(
2997 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->rx_opt
.mss_clamp
)
2998 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2999 space
= __tcp_mtu_to_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
) -
3000 MAX_TCP_OPTION_SPACE
;
3002 space
= min_t(size_t, space
, fo
->size
);
3004 /* limit to order-0 allocations */
3005 space
= min_t(size_t, space
, SKB_MAX_HEAD(MAX_TCP_HEADER
));
3007 syn_data
= skb_copy_expand(syn
, MAX_TCP_HEADER
, space
,
3009 if (syn_data
== NULL
)
3012 for (i
= 0; i
< iovlen
&& syn_data
->len
< space
; ++i
) {
3013 struct iovec
*iov
= &fo
->data
->msg_iov
[i
];
3014 unsigned char __user
*from
= iov
->iov_base
;
3015 int len
= iov
->iov_len
;
3017 if (syn_data
->len
+ len
> space
)
3018 len
= space
- syn_data
->len
;
3019 else if (i
+ 1 == iovlen
)
3020 /* No more data pending in inet_wait_for_connect() */
3023 if (skb_add_data(syn_data
, from
, len
))
3027 /* Queue a data-only packet after the regular SYN for retransmission */
3028 data
= pskb_copy(syn_data
, sk
->sk_allocation
);
3031 TCP_SKB_CB(data
)->seq
++;
3032 TCP_SKB_CB(data
)->tcp_flags
&= ~TCPHDR_SYN
;
3033 TCP_SKB_CB(data
)->tcp_flags
= (TCPHDR_ACK
|TCPHDR_PSH
);
3034 tcp_connect_queue_skb(sk
, data
);
3035 fo
->copied
= data
->len
;
3037 /* syn_data is about to be sent, we need to take current time stamps
3038 * for the packets that are in write queue : SYN packet and DATA
3040 skb_mstamp_get(&syn
->skb_mstamp
);
3041 data
->skb_mstamp
= syn
->skb_mstamp
;
3043 if (tcp_transmit_skb(sk
, syn_data
, 0, sk
->sk_allocation
) == 0) {
3044 tp
->syn_data
= (fo
->copied
> 0);
3045 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
);
3051 /* Send a regular SYN with Fast Open cookie request option */
3052 if (fo
->cookie
.len
> 0)
3054 err
= tcp_transmit_skb(sk
, syn
, 1, sk
->sk_allocation
);
3056 tp
->syn_fastopen
= 0;
3057 kfree_skb(syn_data
);
3059 fo
->cookie
.len
= -1; /* Exclude Fast Open option for SYN retries */
3063 /* Build a SYN and send it off. */
3064 int tcp_connect(struct sock
*sk
)
3066 struct tcp_sock
*tp
= tcp_sk(sk
);
3067 struct sk_buff
*buff
;
3070 tcp_connect_init(sk
);
3072 if (unlikely(tp
->repair
)) {
3073 tcp_finish_connect(sk
, NULL
);
3077 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
3078 if (unlikely(buff
== NULL
))
3081 /* Reserve space for headers. */
3082 skb_reserve(buff
, MAX_TCP_HEADER
);
3084 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPHDR_SYN
);
3085 tp
->retrans_stamp
= tcp_time_stamp
;
3086 tcp_connect_queue_skb(sk
, buff
);
3087 TCP_ECN_send_syn(sk
, buff
);
3089 /* Send off SYN; include data in Fast Open. */
3090 err
= tp
->fastopen_req
? tcp_send_syn_data(sk
, buff
) :
3091 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
3092 if (err
== -ECONNREFUSED
)
3095 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3096 * in order to make this packet get counted in tcpOutSegs.
3098 tp
->snd_nxt
= tp
->write_seq
;
3099 tp
->pushed_seq
= tp
->write_seq
;
3100 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
3102 /* Timer for repeating the SYN until an answer. */
3103 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3104 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3107 EXPORT_SYMBOL(tcp_connect
);
3109 /* Send out a delayed ack, the caller does the policy checking
3110 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3113 void tcp_send_delayed_ack(struct sock
*sk
)
3115 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3116 int ato
= icsk
->icsk_ack
.ato
;
3117 unsigned long timeout
;
3119 if (ato
> TCP_DELACK_MIN
) {
3120 const struct tcp_sock
*tp
= tcp_sk(sk
);
3121 int max_ato
= HZ
/ 2;
3123 if (icsk
->icsk_ack
.pingpong
||
3124 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
3125 max_ato
= TCP_DELACK_MAX
;
3127 /* Slow path, intersegment interval is "high". */
3129 /* If some rtt estimate is known, use it to bound delayed ack.
3130 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3134 int rtt
= max_t(int, usecs_to_jiffies(tp
->srtt_us
>> 3),
3141 ato
= min(ato
, max_ato
);
3144 /* Stay within the limit we were given */
3145 timeout
= jiffies
+ ato
;
3147 /* Use new timeout only if there wasn't a older one earlier. */
3148 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
3149 /* If delack timer was blocked or is about to expire,
3152 if (icsk
->icsk_ack
.blocked
||
3153 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
3158 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
3159 timeout
= icsk
->icsk_ack
.timeout
;
3161 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
3162 icsk
->icsk_ack
.timeout
= timeout
;
3163 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
3166 /* This routine sends an ack and also updates the window. */
3167 void tcp_send_ack(struct sock
*sk
)
3169 struct sk_buff
*buff
;
3171 /* If we have been reset, we may not send again. */
3172 if (sk
->sk_state
== TCP_CLOSE
)
3175 /* We are not putting this on the write queue, so
3176 * tcp_transmit_skb() will set the ownership to this
3179 buff
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3181 inet_csk_schedule_ack(sk
);
3182 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
3183 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
3184 TCP_DELACK_MAX
, TCP_RTO_MAX
);
3188 /* Reserve space for headers and prepare control bits. */
3189 skb_reserve(buff
, MAX_TCP_HEADER
);
3190 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPHDR_ACK
);
3192 /* Send it off, this clears delayed acks for us. */
3193 skb_mstamp_get(&buff
->skb_mstamp
);
3194 tcp_transmit_skb(sk
, buff
, 0, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3197 /* This routine sends a packet with an out of date sequence
3198 * number. It assumes the other end will try to ack it.
3200 * Question: what should we make while urgent mode?
3201 * 4.4BSD forces sending single byte of data. We cannot send
3202 * out of window data, because we have SND.NXT==SND.MAX...
3204 * Current solution: to send TWO zero-length segments in urgent mode:
3205 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3206 * out-of-date with SND.UNA-1 to probe window.
3208 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
3210 struct tcp_sock
*tp
= tcp_sk(sk
);
3211 struct sk_buff
*skb
;
3213 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3214 skb
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3218 /* Reserve space for headers and set control bits. */
3219 skb_reserve(skb
, MAX_TCP_HEADER
);
3220 /* Use a previous sequence. This should cause the other
3221 * end to send an ack. Don't queue or clone SKB, just
3224 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPHDR_ACK
);
3225 skb_mstamp_get(&skb
->skb_mstamp
);
3226 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
3229 void tcp_send_window_probe(struct sock
*sk
)
3231 if (sk
->sk_state
== TCP_ESTABLISHED
) {
3232 tcp_sk(sk
)->snd_wl1
= tcp_sk(sk
)->rcv_nxt
- 1;
3233 tcp_xmit_probe_skb(sk
, 0);
3237 /* Initiate keepalive or window probe from timer. */
3238 int tcp_write_wakeup(struct sock
*sk
)
3240 struct tcp_sock
*tp
= tcp_sk(sk
);
3241 struct sk_buff
*skb
;
3243 if (sk
->sk_state
== TCP_CLOSE
)
3246 if ((skb
= tcp_send_head(sk
)) != NULL
&&
3247 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
3249 unsigned int mss
= tcp_current_mss(sk
);
3250 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
3252 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
3253 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
3255 /* We are probing the opening of a window
3256 * but the window size is != 0
3257 * must have been a result SWS avoidance ( sender )
3259 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
3261 seg_size
= min(seg_size
, mss
);
3262 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3263 if (tcp_fragment(sk
, skb
, seg_size
, mss
, GFP_ATOMIC
))
3265 } else if (!tcp_skb_pcount(skb
))
3266 tcp_set_skb_tso_segs(sk
, skb
, mss
);
3268 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3269 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3271 tcp_event_new_data_sent(sk
, skb
);
3274 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
3275 tcp_xmit_probe_skb(sk
, 1);
3276 return tcp_xmit_probe_skb(sk
, 0);
3280 /* A window probe timeout has occurred. If window is not closed send
3281 * a partial packet else a zero probe.
3283 void tcp_send_probe0(struct sock
*sk
)
3285 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3286 struct tcp_sock
*tp
= tcp_sk(sk
);
3287 unsigned long probe_max
;
3290 err
= tcp_write_wakeup(sk
);
3292 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
3293 /* Cancel probe timer, if it is not required. */
3294 icsk
->icsk_probes_out
= 0;
3295 icsk
->icsk_backoff
= 0;
3300 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
3301 icsk
->icsk_backoff
++;
3302 icsk
->icsk_probes_out
++;
3303 probe_max
= TCP_RTO_MAX
;
3305 /* If packet was not sent due to local congestion,
3306 * do not backoff and do not remember icsk_probes_out.
3307 * Let local senders to fight for local resources.
3309 * Use accumulated backoff yet.
3311 if (!icsk
->icsk_probes_out
)
3312 icsk
->icsk_probes_out
= 1;
3313 probe_max
= TCP_RESOURCE_PROBE_INTERVAL
;
3315 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3316 inet_csk_rto_backoff(icsk
, probe_max
),
3320 int tcp_rtx_synack(struct sock
*sk
, struct request_sock
*req
)
3322 const struct tcp_request_sock_ops
*af_ops
= tcp_rsk(req
)->af_specific
;
3326 res
= af_ops
->send_synack(sk
, NULL
, &fl
, req
, 0, NULL
);
3328 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
3329 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
3333 EXPORT_SYMBOL(tcp_rtx_synack
);