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 void tcp_ecn_send_synack(struct sock
*sk
, struct sk_buff
*skb
)
323 const struct tcp_sock
*tp
= tcp_sk(sk
);
325 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_CWR
;
326 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
327 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_ECE
;
328 else if (tcp_ca_needs_ecn(sk
))
332 /* Packet ECN state for a SYN. */
333 static void tcp_ecn_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
335 struct tcp_sock
*tp
= tcp_sk(sk
);
338 if (sock_net(sk
)->ipv4
.sysctl_tcp_ecn
== 1 ||
339 tcp_ca_needs_ecn(sk
)) {
340 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ECE
| TCPHDR_CWR
;
341 tp
->ecn_flags
= TCP_ECN_OK
;
342 if (tcp_ca_needs_ecn(sk
))
348 tcp_ecn_make_synack(const struct request_sock
*req
, struct tcphdr
*th
,
351 if (inet_rsk(req
)->ecn_ok
) {
353 if (tcp_ca_needs_ecn(sk
))
358 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
361 static void tcp_ecn_send(struct sock
*sk
, struct sk_buff
*skb
,
364 struct tcp_sock
*tp
= tcp_sk(sk
);
366 if (tp
->ecn_flags
& TCP_ECN_OK
) {
367 /* Not-retransmitted data segment: set ECT and inject CWR. */
368 if (skb
->len
!= tcp_header_len
&&
369 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
371 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
372 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
373 tcp_hdr(skb
)->cwr
= 1;
374 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
376 } else if (!tcp_ca_needs_ecn(sk
)) {
377 /* ACK or retransmitted segment: clear ECT|CE */
378 INET_ECN_dontxmit(sk
);
380 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
381 tcp_hdr(skb
)->ece
= 1;
385 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
386 * auto increment end seqno.
388 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
390 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
392 skb
->ip_summed
= CHECKSUM_PARTIAL
;
395 TCP_SKB_CB(skb
)->tcp_flags
= flags
;
396 TCP_SKB_CB(skb
)->sacked
= 0;
398 tcp_skb_pcount_set(skb
, 1);
399 shinfo
->gso_size
= 0;
400 shinfo
->gso_type
= 0;
402 TCP_SKB_CB(skb
)->seq
= seq
;
403 if (flags
& (TCPHDR_SYN
| TCPHDR_FIN
))
405 TCP_SKB_CB(skb
)->end_seq
= seq
;
408 static inline bool tcp_urg_mode(const struct tcp_sock
*tp
)
410 return tp
->snd_una
!= tp
->snd_up
;
413 #define OPTION_SACK_ADVERTISE (1 << 0)
414 #define OPTION_TS (1 << 1)
415 #define OPTION_MD5 (1 << 2)
416 #define OPTION_WSCALE (1 << 3)
417 #define OPTION_FAST_OPEN_COOKIE (1 << 8)
419 struct tcp_out_options
{
420 u16 options
; /* bit field of OPTION_* */
421 u16 mss
; /* 0 to disable */
422 u8 ws
; /* window scale, 0 to disable */
423 u8 num_sack_blocks
; /* number of SACK blocks to include */
424 u8 hash_size
; /* bytes in hash_location */
425 __u8
*hash_location
; /* temporary pointer, overloaded */
426 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
427 struct tcp_fastopen_cookie
*fastopen_cookie
; /* Fast open cookie */
430 /* Write previously computed TCP options to the packet.
432 * Beware: Something in the Internet is very sensitive to the ordering of
433 * TCP options, we learned this through the hard way, so be careful here.
434 * Luckily we can at least blame others for their non-compliance but from
435 * inter-operability perspective it seems that we're somewhat stuck with
436 * the ordering which we have been using if we want to keep working with
437 * those broken things (not that it currently hurts anybody as there isn't
438 * particular reason why the ordering would need to be changed).
440 * At least SACK_PERM as the first option is known to lead to a disaster
441 * (but it may well be that other scenarios fail similarly).
443 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
444 struct tcp_out_options
*opts
)
446 u16 options
= opts
->options
; /* mungable copy */
448 if (unlikely(OPTION_MD5
& options
)) {
449 *ptr
++ = htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
450 (TCPOPT_MD5SIG
<< 8) | TCPOLEN_MD5SIG
);
451 /* overload cookie hash location */
452 opts
->hash_location
= (__u8
*)ptr
;
456 if (unlikely(opts
->mss
)) {
457 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
458 (TCPOLEN_MSS
<< 16) |
462 if (likely(OPTION_TS
& options
)) {
463 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
464 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
465 (TCPOLEN_SACK_PERM
<< 16) |
466 (TCPOPT_TIMESTAMP
<< 8) |
468 options
&= ~OPTION_SACK_ADVERTISE
;
470 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
472 (TCPOPT_TIMESTAMP
<< 8) |
475 *ptr
++ = htonl(opts
->tsval
);
476 *ptr
++ = htonl(opts
->tsecr
);
479 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
480 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
482 (TCPOPT_SACK_PERM
<< 8) |
486 if (unlikely(OPTION_WSCALE
& options
)) {
487 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
488 (TCPOPT_WINDOW
<< 16) |
489 (TCPOLEN_WINDOW
<< 8) |
493 if (unlikely(opts
->num_sack_blocks
)) {
494 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
495 tp
->duplicate_sack
: tp
->selective_acks
;
498 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
501 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
502 TCPOLEN_SACK_PERBLOCK
)));
504 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
506 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
507 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
510 tp
->rx_opt
.dsack
= 0;
513 if (unlikely(OPTION_FAST_OPEN_COOKIE
& options
)) {
514 struct tcp_fastopen_cookie
*foc
= opts
->fastopen_cookie
;
516 *ptr
++ = htonl((TCPOPT_EXP
<< 24) |
517 ((TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
) << 16) |
518 TCPOPT_FASTOPEN_MAGIC
);
520 memcpy(ptr
, foc
->val
, foc
->len
);
521 if ((foc
->len
& 3) == 2) {
522 u8
*align
= ((u8
*)ptr
) + foc
->len
;
523 align
[0] = align
[1] = TCPOPT_NOP
;
525 ptr
+= (foc
->len
+ 3) >> 2;
529 /* Compute TCP options for SYN packets. This is not the final
530 * network wire format yet.
532 static unsigned int tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
533 struct tcp_out_options
*opts
,
534 struct tcp_md5sig_key
**md5
)
536 struct tcp_sock
*tp
= tcp_sk(sk
);
537 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
538 struct tcp_fastopen_request
*fastopen
= tp
->fastopen_req
;
540 #ifdef CONFIG_TCP_MD5SIG
541 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
543 opts
->options
|= OPTION_MD5
;
544 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
550 /* We always get an MSS option. The option bytes which will be seen in
551 * normal data packets should timestamps be used, must be in the MSS
552 * advertised. But we subtract them from tp->mss_cache so that
553 * calculations in tcp_sendmsg are simpler etc. So account for this
554 * fact here if necessary. If we don't do this correctly, as a
555 * receiver we won't recognize data packets as being full sized when we
556 * should, and thus we won't abide by the delayed ACK rules correctly.
557 * SACKs don't matter, we never delay an ACK when we have any of those
559 opts
->mss
= tcp_advertise_mss(sk
);
560 remaining
-= TCPOLEN_MSS_ALIGNED
;
562 if (likely(sysctl_tcp_timestamps
&& *md5
== NULL
)) {
563 opts
->options
|= OPTION_TS
;
564 opts
->tsval
= tcp_skb_timestamp(skb
) + tp
->tsoffset
;
565 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
566 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
568 if (likely(sysctl_tcp_window_scaling
)) {
569 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
570 opts
->options
|= OPTION_WSCALE
;
571 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
573 if (likely(sysctl_tcp_sack
)) {
574 opts
->options
|= OPTION_SACK_ADVERTISE
;
575 if (unlikely(!(OPTION_TS
& opts
->options
)))
576 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
579 if (fastopen
&& fastopen
->cookie
.len
>= 0) {
580 u32 need
= TCPOLEN_EXP_FASTOPEN_BASE
+ fastopen
->cookie
.len
;
581 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
582 if (remaining
>= need
) {
583 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
584 opts
->fastopen_cookie
= &fastopen
->cookie
;
586 tp
->syn_fastopen
= 1;
590 return MAX_TCP_OPTION_SPACE
- remaining
;
593 /* Set up TCP options for SYN-ACKs. */
594 static unsigned int tcp_synack_options(struct sock
*sk
,
595 struct request_sock
*req
,
596 unsigned int mss
, struct sk_buff
*skb
,
597 struct tcp_out_options
*opts
,
598 struct tcp_md5sig_key
**md5
,
599 struct tcp_fastopen_cookie
*foc
)
601 struct inet_request_sock
*ireq
= inet_rsk(req
);
602 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
604 #ifdef CONFIG_TCP_MD5SIG
605 *md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
607 opts
->options
|= OPTION_MD5
;
608 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
610 /* We can't fit any SACK blocks in a packet with MD5 + TS
611 * options. There was discussion about disabling SACK
612 * rather than TS in order to fit in better with old,
613 * buggy kernels, but that was deemed to be unnecessary.
615 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
621 /* We always send an MSS option. */
623 remaining
-= TCPOLEN_MSS_ALIGNED
;
625 if (likely(ireq
->wscale_ok
)) {
626 opts
->ws
= ireq
->rcv_wscale
;
627 opts
->options
|= OPTION_WSCALE
;
628 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
630 if (likely(ireq
->tstamp_ok
)) {
631 opts
->options
|= OPTION_TS
;
632 opts
->tsval
= tcp_skb_timestamp(skb
);
633 opts
->tsecr
= req
->ts_recent
;
634 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
636 if (likely(ireq
->sack_ok
)) {
637 opts
->options
|= OPTION_SACK_ADVERTISE
;
638 if (unlikely(!ireq
->tstamp_ok
))
639 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
641 if (foc
!= NULL
&& foc
->len
>= 0) {
642 u32 need
= TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
;
643 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
644 if (remaining
>= need
) {
645 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
646 opts
->fastopen_cookie
= foc
;
651 return MAX_TCP_OPTION_SPACE
- remaining
;
654 /* Compute TCP options for ESTABLISHED sockets. This is not the
655 * final wire format yet.
657 static unsigned int tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
658 struct tcp_out_options
*opts
,
659 struct tcp_md5sig_key
**md5
)
661 struct tcp_sock
*tp
= tcp_sk(sk
);
662 unsigned int size
= 0;
663 unsigned int eff_sacks
;
667 #ifdef CONFIG_TCP_MD5SIG
668 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
669 if (unlikely(*md5
)) {
670 opts
->options
|= OPTION_MD5
;
671 size
+= TCPOLEN_MD5SIG_ALIGNED
;
677 if (likely(tp
->rx_opt
.tstamp_ok
)) {
678 opts
->options
|= OPTION_TS
;
679 opts
->tsval
= skb
? tcp_skb_timestamp(skb
) + tp
->tsoffset
: 0;
680 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
681 size
+= TCPOLEN_TSTAMP_ALIGNED
;
684 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
685 if (unlikely(eff_sacks
)) {
686 const unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
687 opts
->num_sack_blocks
=
688 min_t(unsigned int, eff_sacks
,
689 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
690 TCPOLEN_SACK_PERBLOCK
);
691 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
692 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
699 /* TCP SMALL QUEUES (TSQ)
701 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
702 * to reduce RTT and bufferbloat.
703 * We do this using a special skb destructor (tcp_wfree).
705 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
706 * needs to be reallocated in a driver.
707 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
709 * Since transmit from skb destructor is forbidden, we use a tasklet
710 * to process all sockets that eventually need to send more skbs.
711 * We use one tasklet per cpu, with its own queue of sockets.
714 struct tasklet_struct tasklet
;
715 struct list_head head
; /* queue of tcp sockets */
717 static DEFINE_PER_CPU(struct tsq_tasklet
, tsq_tasklet
);
719 static void tcp_tsq_handler(struct sock
*sk
)
721 if ((1 << sk
->sk_state
) &
722 (TCPF_ESTABLISHED
| TCPF_FIN_WAIT1
| TCPF_CLOSING
|
723 TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
))
724 tcp_write_xmit(sk
, tcp_current_mss(sk
), tcp_sk(sk
)->nonagle
,
728 * One tasklet per cpu tries to send more skbs.
729 * We run in tasklet context but need to disable irqs when
730 * transferring tsq->head because tcp_wfree() might
731 * interrupt us (non NAPI drivers)
733 static void tcp_tasklet_func(unsigned long data
)
735 struct tsq_tasklet
*tsq
= (struct tsq_tasklet
*)data
;
738 struct list_head
*q
, *n
;
742 local_irq_save(flags
);
743 list_splice_init(&tsq
->head
, &list
);
744 local_irq_restore(flags
);
746 list_for_each_safe(q
, n
, &list
) {
747 tp
= list_entry(q
, struct tcp_sock
, tsq_node
);
748 list_del(&tp
->tsq_node
);
750 sk
= (struct sock
*)tp
;
753 if (!sock_owned_by_user(sk
)) {
756 /* defer the work to tcp_release_cb() */
757 set_bit(TCP_TSQ_DEFERRED
, &tp
->tsq_flags
);
761 clear_bit(TSQ_QUEUED
, &tp
->tsq_flags
);
766 #define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
767 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
768 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
769 (1UL << TCP_MTU_REDUCED_DEFERRED))
771 * tcp_release_cb - tcp release_sock() callback
774 * called from release_sock() to perform protocol dependent
775 * actions before socket release.
777 void tcp_release_cb(struct sock
*sk
)
779 struct tcp_sock
*tp
= tcp_sk(sk
);
780 unsigned long flags
, nflags
;
782 /* perform an atomic operation only if at least one flag is set */
784 flags
= tp
->tsq_flags
;
785 if (!(flags
& TCP_DEFERRED_ALL
))
787 nflags
= flags
& ~TCP_DEFERRED_ALL
;
788 } while (cmpxchg(&tp
->tsq_flags
, flags
, nflags
) != flags
);
790 if (flags
& (1UL << TCP_TSQ_DEFERRED
))
793 /* Here begins the tricky part :
794 * We are called from release_sock() with :
796 * 2) sk_lock.slock spinlock held
797 * 3) socket owned by us (sk->sk_lock.owned == 1)
799 * But following code is meant to be called from BH handlers,
800 * so we should keep BH disabled, but early release socket ownership
802 sock_release_ownership(sk
);
804 if (flags
& (1UL << TCP_WRITE_TIMER_DEFERRED
)) {
805 tcp_write_timer_handler(sk
);
808 if (flags
& (1UL << TCP_DELACK_TIMER_DEFERRED
)) {
809 tcp_delack_timer_handler(sk
);
812 if (flags
& (1UL << TCP_MTU_REDUCED_DEFERRED
)) {
813 inet_csk(sk
)->icsk_af_ops
->mtu_reduced(sk
);
817 EXPORT_SYMBOL(tcp_release_cb
);
819 void __init
tcp_tasklet_init(void)
823 for_each_possible_cpu(i
) {
824 struct tsq_tasklet
*tsq
= &per_cpu(tsq_tasklet
, i
);
826 INIT_LIST_HEAD(&tsq
->head
);
827 tasklet_init(&tsq
->tasklet
,
834 * Write buffer destructor automatically called from kfree_skb.
835 * We can't xmit new skbs from this context, as we might already
838 void tcp_wfree(struct sk_buff
*skb
)
840 struct sock
*sk
= skb
->sk
;
841 struct tcp_sock
*tp
= tcp_sk(sk
);
843 if (test_and_clear_bit(TSQ_THROTTLED
, &tp
->tsq_flags
) &&
844 !test_and_set_bit(TSQ_QUEUED
, &tp
->tsq_flags
)) {
846 struct tsq_tasklet
*tsq
;
848 /* Keep a ref on socket.
849 * This last ref will be released in tcp_tasklet_func()
851 atomic_sub(skb
->truesize
- 1, &sk
->sk_wmem_alloc
);
853 /* queue this socket to tasklet queue */
854 local_irq_save(flags
);
855 tsq
= &__get_cpu_var(tsq_tasklet
);
856 list_add(&tp
->tsq_node
, &tsq
->head
);
857 tasklet_schedule(&tsq
->tasklet
);
858 local_irq_restore(flags
);
864 /* This routine actually transmits TCP packets queued in by
865 * tcp_do_sendmsg(). This is used by both the initial
866 * transmission and possible later retransmissions.
867 * All SKB's seen here are completely headerless. It is our
868 * job to build the TCP header, and pass the packet down to
869 * IP so it can do the same plus pass the packet off to the
872 * We are working here with either a clone of the original
873 * SKB, or a fresh unique copy made by the retransmit engine.
875 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
878 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
879 struct inet_sock
*inet
;
881 struct tcp_skb_cb
*tcb
;
882 struct tcp_out_options opts
;
883 unsigned int tcp_options_size
, tcp_header_size
;
884 struct tcp_md5sig_key
*md5
;
888 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
891 skb_mstamp_get(&skb
->skb_mstamp
);
893 if (unlikely(skb_cloned(skb
)))
894 skb
= pskb_copy(skb
, gfp_mask
);
896 skb
= skb_clone(skb
, gfp_mask
);
903 tcb
= TCP_SKB_CB(skb
);
904 memset(&opts
, 0, sizeof(opts
));
906 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
))
907 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
909 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
911 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
913 if (tcp_packets_in_flight(tp
) == 0)
914 tcp_ca_event(sk
, CA_EVENT_TX_START
);
916 /* if no packet is in qdisc/device queue, then allow XPS to select
919 skb
->ooo_okay
= sk_wmem_alloc_get(sk
) == 0;
921 skb_push(skb
, tcp_header_size
);
922 skb_reset_transport_header(skb
);
926 skb
->destructor
= tcp_wfree
;
927 skb_set_hash_from_sk(skb
, sk
);
928 atomic_add(skb
->truesize
, &sk
->sk_wmem_alloc
);
930 /* Build TCP header and checksum it. */
932 th
->source
= inet
->inet_sport
;
933 th
->dest
= inet
->inet_dport
;
934 th
->seq
= htonl(tcb
->seq
);
935 th
->ack_seq
= htonl(tp
->rcv_nxt
);
936 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
939 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
)) {
940 /* RFC1323: The window in SYN & SYN/ACK segments
943 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
945 th
->window
= htons(tcp_select_window(sk
));
950 /* The urg_mode check is necessary during a below snd_una win probe */
951 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
952 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
953 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
955 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
956 th
->urg_ptr
= htons(0xFFFF);
961 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
962 if (likely((tcb
->tcp_flags
& TCPHDR_SYN
) == 0))
963 tcp_ecn_send(sk
, skb
, tcp_header_size
);
965 #ifdef CONFIG_TCP_MD5SIG
966 /* Calculate the MD5 hash, as we have all we need now */
968 sk_nocaps_add(sk
, NETIF_F_GSO_MASK
);
969 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
974 icsk
->icsk_af_ops
->send_check(sk
, skb
);
976 if (likely(tcb
->tcp_flags
& TCPHDR_ACK
))
977 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
979 if (skb
->len
!= tcp_header_size
)
980 tcp_event_data_sent(tp
, sk
);
982 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
983 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
,
984 tcp_skb_pcount(skb
));
986 /* OK, its time to fill skb_shinfo(skb)->gso_segs */
987 skb_shinfo(skb
)->gso_segs
= tcp_skb_pcount(skb
);
989 /* Our usage of tstamp should remain private */
990 skb
->tstamp
.tv64
= 0;
992 /* Cleanup our debris for IP stacks */
993 memset(skb
->cb
, 0, max(sizeof(struct inet_skb_parm
),
994 sizeof(struct inet6_skb_parm
)));
996 err
= icsk
->icsk_af_ops
->queue_xmit(sk
, skb
, &inet
->cork
.fl
);
998 if (likely(err
<= 0))
1003 return net_xmit_eval(err
);
1006 /* This routine just queues the buffer for sending.
1008 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1009 * otherwise socket can stall.
1011 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
1013 struct tcp_sock
*tp
= tcp_sk(sk
);
1015 /* Advance write_seq and place onto the write_queue. */
1016 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
1017 __skb_header_release(skb
);
1018 tcp_add_write_queue_tail(sk
, skb
);
1019 sk
->sk_wmem_queued
+= skb
->truesize
;
1020 sk_mem_charge(sk
, skb
->truesize
);
1023 /* Initialize TSO segments for a packet. */
1024 static void tcp_set_skb_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
1025 unsigned int mss_now
)
1027 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
1029 /* Make sure we own this skb before messing gso_size/gso_segs */
1030 WARN_ON_ONCE(skb_cloned(skb
));
1032 if (skb
->len
<= mss_now
|| skb
->ip_summed
== CHECKSUM_NONE
) {
1033 /* Avoid the costly divide in the normal
1036 tcp_skb_pcount_set(skb
, 1);
1037 shinfo
->gso_size
= 0;
1038 shinfo
->gso_type
= 0;
1040 tcp_skb_pcount_set(skb
, DIV_ROUND_UP(skb
->len
, mss_now
));
1041 shinfo
->gso_size
= mss_now
;
1042 shinfo
->gso_type
= sk
->sk_gso_type
;
1046 /* When a modification to fackets out becomes necessary, we need to check
1047 * skb is counted to fackets_out or not.
1049 static void tcp_adjust_fackets_out(struct sock
*sk
, const struct sk_buff
*skb
,
1052 struct tcp_sock
*tp
= tcp_sk(sk
);
1054 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
1057 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
1058 tp
->fackets_out
-= decr
;
1061 /* Pcount in the middle of the write queue got changed, we need to do various
1062 * tweaks to fix counters
1064 static void tcp_adjust_pcount(struct sock
*sk
, const struct sk_buff
*skb
, int decr
)
1066 struct tcp_sock
*tp
= tcp_sk(sk
);
1068 tp
->packets_out
-= decr
;
1070 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1071 tp
->sacked_out
-= decr
;
1072 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1073 tp
->retrans_out
-= decr
;
1074 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
1075 tp
->lost_out
-= decr
;
1077 /* Reno case is special. Sigh... */
1078 if (tcp_is_reno(tp
) && decr
> 0)
1079 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
1081 tcp_adjust_fackets_out(sk
, skb
, decr
);
1083 if (tp
->lost_skb_hint
&&
1084 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
1085 (tcp_is_fack(tp
) || (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)))
1086 tp
->lost_cnt_hint
-= decr
;
1088 tcp_verify_left_out(tp
);
1091 static void tcp_fragment_tstamp(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1093 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
1095 if (unlikely(shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
) &&
1096 !before(shinfo
->tskey
, TCP_SKB_CB(skb2
)->seq
)) {
1097 struct skb_shared_info
*shinfo2
= skb_shinfo(skb2
);
1098 u8 tsflags
= shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
1100 shinfo
->tx_flags
&= ~tsflags
;
1101 shinfo2
->tx_flags
|= tsflags
;
1102 swap(shinfo
->tskey
, shinfo2
->tskey
);
1106 /* Function to create two new TCP segments. Shrinks the given segment
1107 * to the specified size and appends a new segment with the rest of the
1108 * packet to the list. This won't be called frequently, I hope.
1109 * Remember, these are still headerless SKBs at this point.
1111 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
1112 unsigned int mss_now
, gfp_t gfp
)
1114 struct tcp_sock
*tp
= tcp_sk(sk
);
1115 struct sk_buff
*buff
;
1116 int nsize
, old_factor
;
1120 if (WARN_ON(len
> skb
->len
))
1123 nsize
= skb_headlen(skb
) - len
;
1127 if (skb_unclone(skb
, gfp
))
1130 /* Get a new skb... force flag on. */
1131 buff
= sk_stream_alloc_skb(sk
, nsize
, gfp
);
1133 return -ENOMEM
; /* We'll just try again later. */
1135 sk
->sk_wmem_queued
+= buff
->truesize
;
1136 sk_mem_charge(sk
, buff
->truesize
);
1137 nlen
= skb
->len
- len
- nsize
;
1138 buff
->truesize
+= nlen
;
1139 skb
->truesize
-= nlen
;
1141 /* Correct the sequence numbers. */
1142 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1143 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1144 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1146 /* PSH and FIN should only be set in the second packet. */
1147 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1148 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1149 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1150 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1152 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
1153 /* Copy and checksum data tail into the new buffer. */
1154 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
1155 skb_put(buff
, nsize
),
1160 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
1162 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1163 skb_split(skb
, buff
, len
);
1166 buff
->ip_summed
= skb
->ip_summed
;
1168 buff
->tstamp
= skb
->tstamp
;
1169 tcp_fragment_tstamp(skb
, buff
);
1171 old_factor
= tcp_skb_pcount(skb
);
1173 /* Fix up tso_factor for both original and new SKB. */
1174 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1175 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1177 /* If this packet has been sent out already, we must
1178 * adjust the various packet counters.
1180 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1181 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1182 tcp_skb_pcount(buff
);
1185 tcp_adjust_pcount(sk
, skb
, diff
);
1188 /* Link BUFF into the send queue. */
1189 __skb_header_release(buff
);
1190 tcp_insert_write_queue_after(skb
, buff
, sk
);
1195 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1196 * eventually). The difference is that pulled data not copied, but
1197 * immediately discarded.
1199 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
1201 struct skb_shared_info
*shinfo
;
1204 eat
= min_t(int, len
, skb_headlen(skb
));
1206 __skb_pull(skb
, eat
);
1213 shinfo
= skb_shinfo(skb
);
1214 for (i
= 0; i
< shinfo
->nr_frags
; i
++) {
1215 int size
= skb_frag_size(&shinfo
->frags
[i
]);
1218 skb_frag_unref(skb
, i
);
1221 shinfo
->frags
[k
] = shinfo
->frags
[i
];
1223 shinfo
->frags
[k
].page_offset
+= eat
;
1224 skb_frag_size_sub(&shinfo
->frags
[k
], eat
);
1230 shinfo
->nr_frags
= k
;
1232 skb_reset_tail_pointer(skb
);
1233 skb
->data_len
-= len
;
1234 skb
->len
= skb
->data_len
;
1237 /* Remove acked data from a packet in the transmit queue. */
1238 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1240 if (skb_unclone(skb
, GFP_ATOMIC
))
1243 __pskb_trim_head(skb
, len
);
1245 TCP_SKB_CB(skb
)->seq
+= len
;
1246 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1248 skb
->truesize
-= len
;
1249 sk
->sk_wmem_queued
-= len
;
1250 sk_mem_uncharge(sk
, len
);
1251 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
1253 /* Any change of skb->len requires recalculation of tso factor. */
1254 if (tcp_skb_pcount(skb
) > 1)
1255 tcp_set_skb_tso_segs(sk
, skb
, tcp_skb_mss(skb
));
1260 /* Calculate MSS not accounting any TCP options. */
1261 static inline int __tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1263 const struct tcp_sock
*tp
= tcp_sk(sk
);
1264 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1267 /* Calculate base mss without TCP options:
1268 It is MMS_S - sizeof(tcphdr) of rfc1122
1270 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1272 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1273 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1274 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1276 if (dst
&& dst_allfrag(dst
))
1277 mss_now
-= icsk
->icsk_af_ops
->net_frag_header_len
;
1280 /* Clamp it (mss_clamp does not include tcp options) */
1281 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1282 mss_now
= tp
->rx_opt
.mss_clamp
;
1284 /* Now subtract optional transport overhead */
1285 mss_now
-= icsk
->icsk_ext_hdr_len
;
1287 /* Then reserve room for full set of TCP options and 8 bytes of data */
1293 /* Calculate MSS. Not accounting for SACKs here. */
1294 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1296 /* Subtract TCP options size, not including SACKs */
1297 return __tcp_mtu_to_mss(sk
, pmtu
) -
1298 (tcp_sk(sk
)->tcp_header_len
- sizeof(struct tcphdr
));
1301 /* Inverse of above */
1302 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1304 const struct tcp_sock
*tp
= tcp_sk(sk
);
1305 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1309 tp
->tcp_header_len
+
1310 icsk
->icsk_ext_hdr_len
+
1311 icsk
->icsk_af_ops
->net_header_len
;
1313 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1314 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1315 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1317 if (dst
&& dst_allfrag(dst
))
1318 mtu
+= icsk
->icsk_af_ops
->net_frag_header_len
;
1323 /* MTU probing init per socket */
1324 void tcp_mtup_init(struct sock
*sk
)
1326 struct tcp_sock
*tp
= tcp_sk(sk
);
1327 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1329 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
1330 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1331 icsk
->icsk_af_ops
->net_header_len
;
1332 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
1333 icsk
->icsk_mtup
.probe_size
= 0;
1335 EXPORT_SYMBOL(tcp_mtup_init
);
1337 /* This function synchronize snd mss to current pmtu/exthdr set.
1339 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1340 for TCP options, but includes only bare TCP header.
1342 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1343 It is minimum of user_mss and mss received with SYN.
1344 It also does not include TCP options.
1346 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1348 tp->mss_cache is current effective sending mss, including
1349 all tcp options except for SACKs. It is evaluated,
1350 taking into account current pmtu, but never exceeds
1351 tp->rx_opt.mss_clamp.
1353 NOTE1. rfc1122 clearly states that advertised MSS
1354 DOES NOT include either tcp or ip options.
1356 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1357 are READ ONLY outside this function. --ANK (980731)
1359 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1361 struct tcp_sock
*tp
= tcp_sk(sk
);
1362 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1365 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1366 icsk
->icsk_mtup
.search_high
= pmtu
;
1368 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1369 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1371 /* And store cached results */
1372 icsk
->icsk_pmtu_cookie
= pmtu
;
1373 if (icsk
->icsk_mtup
.enabled
)
1374 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1375 tp
->mss_cache
= mss_now
;
1379 EXPORT_SYMBOL(tcp_sync_mss
);
1381 /* Compute the current effective MSS, taking SACKs and IP options,
1382 * and even PMTU discovery events into account.
1384 unsigned int tcp_current_mss(struct sock
*sk
)
1386 const struct tcp_sock
*tp
= tcp_sk(sk
);
1387 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1389 unsigned int header_len
;
1390 struct tcp_out_options opts
;
1391 struct tcp_md5sig_key
*md5
;
1393 mss_now
= tp
->mss_cache
;
1396 u32 mtu
= dst_mtu(dst
);
1397 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1398 mss_now
= tcp_sync_mss(sk
, mtu
);
1401 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1402 sizeof(struct tcphdr
);
1403 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1404 * some common options. If this is an odd packet (because we have SACK
1405 * blocks etc) then our calculated header_len will be different, and
1406 * we have to adjust mss_now correspondingly */
1407 if (header_len
!= tp
->tcp_header_len
) {
1408 int delta
= (int) header_len
- tp
->tcp_header_len
;
1415 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1416 * As additional protections, we do not touch cwnd in retransmission phases,
1417 * and if application hit its sndbuf limit recently.
1419 static void tcp_cwnd_application_limited(struct sock
*sk
)
1421 struct tcp_sock
*tp
= tcp_sk(sk
);
1423 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
1424 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
1425 /* Limited by application or receiver window. */
1426 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
1427 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
1428 if (win_used
< tp
->snd_cwnd
) {
1429 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1430 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
1432 tp
->snd_cwnd_used
= 0;
1434 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1437 static void tcp_cwnd_validate(struct sock
*sk
, bool is_cwnd_limited
)
1439 struct tcp_sock
*tp
= tcp_sk(sk
);
1441 /* Track the maximum number of outstanding packets in each
1442 * window, and remember whether we were cwnd-limited then.
1444 if (!before(tp
->snd_una
, tp
->max_packets_seq
) ||
1445 tp
->packets_out
> tp
->max_packets_out
) {
1446 tp
->max_packets_out
= tp
->packets_out
;
1447 tp
->max_packets_seq
= tp
->snd_nxt
;
1448 tp
->is_cwnd_limited
= is_cwnd_limited
;
1451 if (tcp_is_cwnd_limited(sk
)) {
1452 /* Network is feed fully. */
1453 tp
->snd_cwnd_used
= 0;
1454 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1456 /* Network starves. */
1457 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1458 tp
->snd_cwnd_used
= tp
->packets_out
;
1460 if (sysctl_tcp_slow_start_after_idle
&&
1461 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1462 tcp_cwnd_application_limited(sk
);
1466 /* Minshall's variant of the Nagle send check. */
1467 static bool tcp_minshall_check(const struct tcp_sock
*tp
)
1469 return after(tp
->snd_sml
, tp
->snd_una
) &&
1470 !after(tp
->snd_sml
, tp
->snd_nxt
);
1473 /* Update snd_sml if this skb is under mss
1474 * Note that a TSO packet might end with a sub-mss segment
1475 * The test is really :
1476 * if ((skb->len % mss) != 0)
1477 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1478 * But we can avoid doing the divide again given we already have
1479 * skb_pcount = skb->len / mss_now
1481 static void tcp_minshall_update(struct tcp_sock
*tp
, unsigned int mss_now
,
1482 const struct sk_buff
*skb
)
1484 if (skb
->len
< tcp_skb_pcount(skb
) * mss_now
)
1485 tp
->snd_sml
= TCP_SKB_CB(skb
)->end_seq
;
1488 /* Return false, if packet can be sent now without violation Nagle's rules:
1489 * 1. It is full sized. (provided by caller in %partial bool)
1490 * 2. Or it contains FIN. (already checked by caller)
1491 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1492 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1493 * With Minshall's modification: all sent small packets are ACKed.
1495 static bool tcp_nagle_check(bool partial
, const struct tcp_sock
*tp
,
1499 ((nonagle
& TCP_NAGLE_CORK
) ||
1500 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
)));
1502 /* Returns the portion of skb which can be sent right away */
1503 static unsigned int tcp_mss_split_point(const struct sock
*sk
,
1504 const struct sk_buff
*skb
,
1505 unsigned int mss_now
,
1506 unsigned int max_segs
,
1509 const struct tcp_sock
*tp
= tcp_sk(sk
);
1510 u32 partial
, needed
, window
, max_len
;
1512 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1513 max_len
= mss_now
* max_segs
;
1515 if (likely(max_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1518 needed
= min(skb
->len
, window
);
1520 if (max_len
<= needed
)
1523 partial
= needed
% mss_now
;
1524 /* If last segment is not a full MSS, check if Nagle rules allow us
1525 * to include this last segment in this skb.
1526 * Otherwise, we'll split the skb at last MSS boundary
1528 if (tcp_nagle_check(partial
!= 0, tp
, nonagle
))
1529 return needed
- partial
;
1534 /* Can at least one segment of SKB be sent right now, according to the
1535 * congestion window rules? If so, return how many segments are allowed.
1537 static inline unsigned int tcp_cwnd_test(const struct tcp_sock
*tp
,
1538 const struct sk_buff
*skb
)
1540 u32 in_flight
, cwnd
;
1542 /* Don't be strict about the congestion window for the final FIN. */
1543 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
1544 tcp_skb_pcount(skb
) == 1)
1547 in_flight
= tcp_packets_in_flight(tp
);
1548 cwnd
= tp
->snd_cwnd
;
1549 if (in_flight
< cwnd
)
1550 return (cwnd
- in_flight
);
1555 /* Initialize TSO state of a skb.
1556 * This must be invoked the first time we consider transmitting
1557 * SKB onto the wire.
1559 static int tcp_init_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
1560 unsigned int mss_now
)
1562 int tso_segs
= tcp_skb_pcount(skb
);
1564 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1565 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1566 tso_segs
= tcp_skb_pcount(skb
);
1572 /* Return true if the Nagle test allows this packet to be
1575 static inline bool tcp_nagle_test(const struct tcp_sock
*tp
, const struct sk_buff
*skb
,
1576 unsigned int cur_mss
, int nonagle
)
1578 /* Nagle rule does not apply to frames, which sit in the middle of the
1579 * write_queue (they have no chances to get new data).
1581 * This is implemented in the callers, where they modify the 'nonagle'
1582 * argument based upon the location of SKB in the send queue.
1584 if (nonagle
& TCP_NAGLE_PUSH
)
1587 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1588 if (tcp_urg_mode(tp
) || (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
))
1591 if (!tcp_nagle_check(skb
->len
< cur_mss
, tp
, nonagle
))
1597 /* Does at least the first segment of SKB fit into the send window? */
1598 static bool tcp_snd_wnd_test(const struct tcp_sock
*tp
,
1599 const struct sk_buff
*skb
,
1600 unsigned int cur_mss
)
1602 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1604 if (skb
->len
> cur_mss
)
1605 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1607 return !after(end_seq
, tcp_wnd_end(tp
));
1610 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1611 * should be put on the wire right now. If so, it returns the number of
1612 * packets allowed by the congestion window.
1614 static unsigned int tcp_snd_test(const struct sock
*sk
, struct sk_buff
*skb
,
1615 unsigned int cur_mss
, int nonagle
)
1617 const struct tcp_sock
*tp
= tcp_sk(sk
);
1618 unsigned int cwnd_quota
;
1620 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1622 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1625 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1626 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1632 /* Test if sending is allowed right now. */
1633 bool tcp_may_send_now(struct sock
*sk
)
1635 const struct tcp_sock
*tp
= tcp_sk(sk
);
1636 struct sk_buff
*skb
= tcp_send_head(sk
);
1639 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1640 (tcp_skb_is_last(sk
, skb
) ?
1641 tp
->nonagle
: TCP_NAGLE_PUSH
));
1644 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1645 * which is put after SKB on the list. It is very much like
1646 * tcp_fragment() except that it may make several kinds of assumptions
1647 * in order to speed up the splitting operation. In particular, we
1648 * know that all the data is in scatter-gather pages, and that the
1649 * packet has never been sent out before (and thus is not cloned).
1651 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1652 unsigned int mss_now
, gfp_t gfp
)
1654 struct sk_buff
*buff
;
1655 int nlen
= skb
->len
- len
;
1658 /* All of a TSO frame must be composed of paged data. */
1659 if (skb
->len
!= skb
->data_len
)
1660 return tcp_fragment(sk
, skb
, len
, mss_now
, gfp
);
1662 buff
= sk_stream_alloc_skb(sk
, 0, gfp
);
1663 if (unlikely(buff
== NULL
))
1666 sk
->sk_wmem_queued
+= buff
->truesize
;
1667 sk_mem_charge(sk
, buff
->truesize
);
1668 buff
->truesize
+= nlen
;
1669 skb
->truesize
-= nlen
;
1671 /* Correct the sequence numbers. */
1672 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1673 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1674 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1676 /* PSH and FIN should only be set in the second packet. */
1677 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1678 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1679 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1681 /* This packet was never sent out yet, so no SACK bits. */
1682 TCP_SKB_CB(buff
)->sacked
= 0;
1684 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1685 skb_split(skb
, buff
, len
);
1686 tcp_fragment_tstamp(skb
, buff
);
1688 /* Fix up tso_factor for both original and new SKB. */
1689 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1690 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1692 /* Link BUFF into the send queue. */
1693 __skb_header_release(buff
);
1694 tcp_insert_write_queue_after(skb
, buff
, sk
);
1699 /* Try to defer sending, if possible, in order to minimize the amount
1700 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1702 * This algorithm is from John Heffner.
1704 static bool tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
,
1705 bool *is_cwnd_limited
)
1707 struct tcp_sock
*tp
= tcp_sk(sk
);
1708 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1709 u32 send_win
, cong_win
, limit
, in_flight
;
1712 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1715 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1718 /* Defer for less than two clock ticks. */
1719 if (tp
->tso_deferred
&&
1720 (((u32
)jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1723 in_flight
= tcp_packets_in_flight(tp
);
1725 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1727 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1729 /* From in_flight test above, we know that cwnd > in_flight. */
1730 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1732 limit
= min(send_win
, cong_win
);
1734 /* If a full-sized TSO skb can be sent, do it. */
1735 if (limit
>= min_t(unsigned int, sk
->sk_gso_max_size
,
1736 tp
->xmit_size_goal_segs
* tp
->mss_cache
))
1739 /* Middle in queue won't get any more data, full sendable already? */
1740 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1743 win_divisor
= ACCESS_ONCE(sysctl_tcp_tso_win_divisor
);
1745 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1747 /* If at least some fraction of a window is available,
1750 chunk
/= win_divisor
;
1754 /* Different approach, try not to defer past a single
1755 * ACK. Receiver should ACK every other full sized
1756 * frame, so if we have space for more than 3 frames
1759 if (limit
> tcp_max_tso_deferred_mss(tp
) * tp
->mss_cache
)
1763 /* Ok, it looks like it is advisable to defer.
1764 * Do not rearm the timer if already set to not break TCP ACK clocking.
1766 if (!tp
->tso_deferred
)
1767 tp
->tso_deferred
= 1 | (jiffies
<< 1);
1769 if (cong_win
< send_win
&& cong_win
< skb
->len
)
1770 *is_cwnd_limited
= true;
1775 tp
->tso_deferred
= 0;
1779 /* Create a new MTU probe if we are ready.
1780 * MTU probe is regularly attempting to increase the path MTU by
1781 * deliberately sending larger packets. This discovers routing
1782 * changes resulting in larger path MTUs.
1784 * Returns 0 if we should wait to probe (no cwnd available),
1785 * 1 if a probe was sent,
1788 static int tcp_mtu_probe(struct sock
*sk
)
1790 struct tcp_sock
*tp
= tcp_sk(sk
);
1791 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1792 struct sk_buff
*skb
, *nskb
, *next
;
1799 /* Not currently probing/verifying,
1801 * have enough cwnd, and
1802 * not SACKing (the variable headers throw things off) */
1803 if (!icsk
->icsk_mtup
.enabled
||
1804 icsk
->icsk_mtup
.probe_size
||
1805 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1806 tp
->snd_cwnd
< 11 ||
1807 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
)
1810 /* Very simple search strategy: just double the MSS. */
1811 mss_now
= tcp_current_mss(sk
);
1812 probe_size
= 2 * tp
->mss_cache
;
1813 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1814 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1815 /* TODO: set timer for probe_converge_event */
1819 /* Have enough data in the send queue to probe? */
1820 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1823 if (tp
->snd_wnd
< size_needed
)
1825 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1828 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1829 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1830 if (!tcp_packets_in_flight(tp
))
1836 /* We're allowed to probe. Build it now. */
1837 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1839 sk
->sk_wmem_queued
+= nskb
->truesize
;
1840 sk_mem_charge(sk
, nskb
->truesize
);
1842 skb
= tcp_send_head(sk
);
1844 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1845 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1846 TCP_SKB_CB(nskb
)->tcp_flags
= TCPHDR_ACK
;
1847 TCP_SKB_CB(nskb
)->sacked
= 0;
1849 nskb
->ip_summed
= skb
->ip_summed
;
1851 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1854 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1855 copy
= min_t(int, skb
->len
, probe_size
- len
);
1856 if (nskb
->ip_summed
)
1857 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1859 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1860 skb_put(nskb
, copy
),
1863 if (skb
->len
<= copy
) {
1864 /* We've eaten all the data from this skb.
1866 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1867 tcp_unlink_write_queue(skb
, sk
);
1868 sk_wmem_free_skb(sk
, skb
);
1870 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
&
1871 ~(TCPHDR_FIN
|TCPHDR_PSH
);
1872 if (!skb_shinfo(skb
)->nr_frags
) {
1873 skb_pull(skb
, copy
);
1874 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1875 skb
->csum
= csum_partial(skb
->data
,
1878 __pskb_trim_head(skb
, copy
);
1879 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1881 TCP_SKB_CB(skb
)->seq
+= copy
;
1886 if (len
>= probe_size
)
1889 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1891 /* We're ready to send. If this fails, the probe will
1892 * be resegmented into mss-sized pieces by tcp_write_xmit().
1894 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1895 /* Decrement cwnd here because we are sending
1896 * effectively two packets. */
1898 tcp_event_new_data_sent(sk
, nskb
);
1900 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1901 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1902 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1910 /* This routine writes packets to the network. It advances the
1911 * send_head. This happens as incoming acks open up the remote
1914 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1915 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1916 * account rare use of URG, this is not a big flaw.
1918 * Send at most one packet when push_one > 0. Temporarily ignore
1919 * cwnd limit to force at most one packet out when push_one == 2.
1921 * Returns true, if no segments are in flight and we have queued segments,
1922 * but cannot send anything now because of SWS or another problem.
1924 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
1925 int push_one
, gfp_t gfp
)
1927 struct tcp_sock
*tp
= tcp_sk(sk
);
1928 struct sk_buff
*skb
;
1929 unsigned int tso_segs
, sent_pkts
;
1932 bool is_cwnd_limited
= false;
1937 /* Do MTU probing. */
1938 result
= tcp_mtu_probe(sk
);
1941 } else if (result
> 0) {
1946 while ((skb
= tcp_send_head(sk
))) {
1949 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1952 if (unlikely(tp
->repair
) && tp
->repair_queue
== TCP_SEND_QUEUE
) {
1953 /* "skb_mstamp" is used as a start point for the retransmit timer */
1954 skb_mstamp_get(&skb
->skb_mstamp
);
1955 goto repair
; /* Skip network transmission */
1958 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1960 is_cwnd_limited
= true;
1962 /* Force out a loss probe pkt. */
1968 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1971 if (tso_segs
== 1) {
1972 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1973 (tcp_skb_is_last(sk
, skb
) ?
1974 nonagle
: TCP_NAGLE_PUSH
))))
1978 tcp_tso_should_defer(sk
, skb
, &is_cwnd_limited
))
1982 /* TCP Small Queues :
1983 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
1985 * - better RTT estimation and ACK scheduling
1988 * Alas, some drivers / subsystems require a fair amount
1989 * of queued bytes to ensure line rate.
1990 * One example is wifi aggregation (802.11 AMPDU)
1992 limit
= max_t(unsigned int, sysctl_tcp_limit_output_bytes
,
1993 sk
->sk_pacing_rate
>> 10);
1995 if (atomic_read(&sk
->sk_wmem_alloc
) > limit
) {
1996 set_bit(TSQ_THROTTLED
, &tp
->tsq_flags
);
1997 /* It is possible TX completion already happened
1998 * before we set TSQ_THROTTLED, so we must
1999 * test again the condition.
2001 smp_mb__after_atomic();
2002 if (atomic_read(&sk
->sk_wmem_alloc
) > limit
)
2007 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
2008 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
2011 sk
->sk_gso_max_segs
),
2014 if (skb
->len
> limit
&&
2015 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
, gfp
)))
2018 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
2022 /* Advance the send_head. This one is sent out.
2023 * This call will increment packets_out.
2025 tcp_event_new_data_sent(sk
, skb
);
2027 tcp_minshall_update(tp
, mss_now
, skb
);
2028 sent_pkts
+= tcp_skb_pcount(skb
);
2034 if (likely(sent_pkts
)) {
2035 if (tcp_in_cwnd_reduction(sk
))
2036 tp
->prr_out
+= sent_pkts
;
2038 /* Send one loss probe per tail loss episode. */
2040 tcp_schedule_loss_probe(sk
);
2041 tcp_cwnd_validate(sk
, is_cwnd_limited
);
2044 return (push_one
== 2) || (!tp
->packets_out
&& tcp_send_head(sk
));
2047 bool tcp_schedule_loss_probe(struct sock
*sk
)
2049 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2050 struct tcp_sock
*tp
= tcp_sk(sk
);
2051 u32 timeout
, tlp_time_stamp
, rto_time_stamp
;
2052 u32 rtt
= usecs_to_jiffies(tp
->srtt_us
>> 3);
2054 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
))
2056 /* No consecutive loss probes. */
2057 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)) {
2061 /* Don't do any loss probe on a Fast Open connection before 3WHS
2064 if (sk
->sk_state
== TCP_SYN_RECV
)
2067 /* TLP is only scheduled when next timer event is RTO. */
2068 if (icsk
->icsk_pending
!= ICSK_TIME_RETRANS
)
2071 /* Schedule a loss probe in 2*RTT for SACK capable connections
2072 * in Open state, that are either limited by cwnd or application.
2074 if (sysctl_tcp_early_retrans
< 3 || !tp
->srtt_us
|| !tp
->packets_out
||
2075 !tcp_is_sack(tp
) || inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
2078 if ((tp
->snd_cwnd
> tcp_packets_in_flight(tp
)) &&
2082 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2083 * for delayed ack when there's one outstanding packet.
2086 if (tp
->packets_out
== 1)
2087 timeout
= max_t(u32
, timeout
,
2088 (rtt
+ (rtt
>> 1) + TCP_DELACK_MAX
));
2089 timeout
= max_t(u32
, timeout
, msecs_to_jiffies(10));
2091 /* If RTO is shorter, just schedule TLP in its place. */
2092 tlp_time_stamp
= tcp_time_stamp
+ timeout
;
2093 rto_time_stamp
= (u32
)inet_csk(sk
)->icsk_timeout
;
2094 if ((s32
)(tlp_time_stamp
- rto_time_stamp
) > 0) {
2095 s32 delta
= rto_time_stamp
- tcp_time_stamp
;
2100 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_LOSS_PROBE
, timeout
,
2105 /* Thanks to skb fast clones, we can detect if a prior transmit of
2106 * a packet is still in a qdisc or driver queue.
2107 * In this case, there is very little point doing a retransmit !
2108 * Note: This is called from BH context only.
2110 static bool skb_still_in_host_queue(const struct sock
*sk
,
2111 const struct sk_buff
*skb
)
2113 const struct sk_buff
*fclone
= skb
+ 1;
2115 if (unlikely(skb
->fclone
== SKB_FCLONE_ORIG
&&
2116 fclone
->fclone
== SKB_FCLONE_CLONE
)) {
2117 NET_INC_STATS_BH(sock_net(sk
),
2118 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES
);
2124 /* When probe timeout (PTO) fires, send a new segment if one exists, else
2125 * retransmit the last segment.
2127 void tcp_send_loss_probe(struct sock
*sk
)
2129 struct tcp_sock
*tp
= tcp_sk(sk
);
2130 struct sk_buff
*skb
;
2132 int mss
= tcp_current_mss(sk
);
2135 if (tcp_send_head(sk
) != NULL
) {
2136 err
= tcp_write_xmit(sk
, mss
, TCP_NAGLE_OFF
, 2, GFP_ATOMIC
);
2140 /* At most one outstanding TLP retransmission. */
2141 if (tp
->tlp_high_seq
)
2144 /* Retransmit last segment. */
2145 skb
= tcp_write_queue_tail(sk
);
2149 if (skb_still_in_host_queue(sk
, skb
))
2152 pcount
= tcp_skb_pcount(skb
);
2153 if (WARN_ON(!pcount
))
2156 if ((pcount
> 1) && (skb
->len
> (pcount
- 1) * mss
)) {
2157 if (unlikely(tcp_fragment(sk
, skb
, (pcount
- 1) * mss
, mss
,
2160 skb
= tcp_write_queue_tail(sk
);
2163 if (WARN_ON(!skb
|| !tcp_skb_pcount(skb
)))
2166 err
= __tcp_retransmit_skb(sk
, skb
);
2168 /* Record snd_nxt for loss detection. */
2170 tp
->tlp_high_seq
= tp
->snd_nxt
;
2173 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2174 inet_csk(sk
)->icsk_rto
,
2178 NET_INC_STATS_BH(sock_net(sk
),
2179 LINUX_MIB_TCPLOSSPROBES
);
2182 /* Push out any pending frames which were held back due to
2183 * TCP_CORK or attempt at coalescing tiny packets.
2184 * The socket must be locked by the caller.
2186 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
2189 /* If we are closed, the bytes will have to remain here.
2190 * In time closedown will finish, we empty the write queue and
2191 * all will be happy.
2193 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
2196 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0,
2197 sk_gfp_atomic(sk
, GFP_ATOMIC
)))
2198 tcp_check_probe_timer(sk
);
2201 /* Send _single_ skb sitting at the send head. This function requires
2202 * true push pending frames to setup probe timer etc.
2204 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
2206 struct sk_buff
*skb
= tcp_send_head(sk
);
2208 BUG_ON(!skb
|| skb
->len
< mss_now
);
2210 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
2213 /* This function returns the amount that we can raise the
2214 * usable window based on the following constraints
2216 * 1. The window can never be shrunk once it is offered (RFC 793)
2217 * 2. We limit memory per socket
2220 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2221 * RECV.NEXT + RCV.WIN fixed until:
2222 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2224 * i.e. don't raise the right edge of the window until you can raise
2225 * it at least MSS bytes.
2227 * Unfortunately, the recommended algorithm breaks header prediction,
2228 * since header prediction assumes th->window stays fixed.
2230 * Strictly speaking, keeping th->window fixed violates the receiver
2231 * side SWS prevention criteria. The problem is that under this rule
2232 * a stream of single byte packets will cause the right side of the
2233 * window to always advance by a single byte.
2235 * Of course, if the sender implements sender side SWS prevention
2236 * then this will not be a problem.
2238 * BSD seems to make the following compromise:
2240 * If the free space is less than the 1/4 of the maximum
2241 * space available and the free space is less than 1/2 mss,
2242 * then set the window to 0.
2243 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2244 * Otherwise, just prevent the window from shrinking
2245 * and from being larger than the largest representable value.
2247 * This prevents incremental opening of the window in the regime
2248 * where TCP is limited by the speed of the reader side taking
2249 * data out of the TCP receive queue. It does nothing about
2250 * those cases where the window is constrained on the sender side
2251 * because the pipeline is full.
2253 * BSD also seems to "accidentally" limit itself to windows that are a
2254 * multiple of MSS, at least until the free space gets quite small.
2255 * This would appear to be a side effect of the mbuf implementation.
2256 * Combining these two algorithms results in the observed behavior
2257 * of having a fixed window size at almost all times.
2259 * Below we obtain similar behavior by forcing the offered window to
2260 * a multiple of the mss when it is feasible to do so.
2262 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2263 * Regular options like TIMESTAMP are taken into account.
2265 u32
__tcp_select_window(struct sock
*sk
)
2267 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2268 struct tcp_sock
*tp
= tcp_sk(sk
);
2269 /* MSS for the peer's data. Previous versions used mss_clamp
2270 * here. I don't know if the value based on our guesses
2271 * of peer's MSS is better for the performance. It's more correct
2272 * but may be worse for the performance because of rcv_mss
2273 * fluctuations. --SAW 1998/11/1
2275 int mss
= icsk
->icsk_ack
.rcv_mss
;
2276 int free_space
= tcp_space(sk
);
2277 int allowed_space
= tcp_full_space(sk
);
2278 int full_space
= min_t(int, tp
->window_clamp
, allowed_space
);
2281 if (mss
> full_space
)
2284 if (free_space
< (full_space
>> 1)) {
2285 icsk
->icsk_ack
.quick
= 0;
2287 if (sk_under_memory_pressure(sk
))
2288 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
2291 /* free_space might become our new window, make sure we don't
2292 * increase it due to wscale.
2294 free_space
= round_down(free_space
, 1 << tp
->rx_opt
.rcv_wscale
);
2296 /* if free space is less than mss estimate, or is below 1/16th
2297 * of the maximum allowed, try to move to zero-window, else
2298 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2299 * new incoming data is dropped due to memory limits.
2300 * With large window, mss test triggers way too late in order
2301 * to announce zero window in time before rmem limit kicks in.
2303 if (free_space
< (allowed_space
>> 4) || free_space
< mss
)
2307 if (free_space
> tp
->rcv_ssthresh
)
2308 free_space
= tp
->rcv_ssthresh
;
2310 /* Don't do rounding if we are using window scaling, since the
2311 * scaled window will not line up with the MSS boundary anyway.
2313 window
= tp
->rcv_wnd
;
2314 if (tp
->rx_opt
.rcv_wscale
) {
2315 window
= free_space
;
2317 /* Advertise enough space so that it won't get scaled away.
2318 * Import case: prevent zero window announcement if
2319 * 1<<rcv_wscale > mss.
2321 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
2322 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
2323 << tp
->rx_opt
.rcv_wscale
);
2325 /* Get the largest window that is a nice multiple of mss.
2326 * Window clamp already applied above.
2327 * If our current window offering is within 1 mss of the
2328 * free space we just keep it. This prevents the divide
2329 * and multiply from happening most of the time.
2330 * We also don't do any window rounding when the free space
2333 if (window
<= free_space
- mss
|| window
> free_space
)
2334 window
= (free_space
/ mss
) * mss
;
2335 else if (mss
== full_space
&&
2336 free_space
> window
+ (full_space
>> 1))
2337 window
= free_space
;
2343 /* Collapses two adjacent SKB's during retransmission. */
2344 static void tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
2346 struct tcp_sock
*tp
= tcp_sk(sk
);
2347 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
2348 int skb_size
, next_skb_size
;
2350 skb_size
= skb
->len
;
2351 next_skb_size
= next_skb
->len
;
2353 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
2355 tcp_highest_sack_combine(sk
, next_skb
, skb
);
2357 tcp_unlink_write_queue(next_skb
, sk
);
2359 skb_copy_from_linear_data(next_skb
, skb_put(skb
, next_skb_size
),
2362 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
2363 skb
->ip_summed
= CHECKSUM_PARTIAL
;
2365 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2366 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
2368 /* Update sequence range on original skb. */
2369 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
2371 /* Merge over control information. This moves PSH/FIN etc. over */
2372 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(next_skb
)->tcp_flags
;
2374 /* All done, get rid of second SKB and account for it so
2375 * packet counting does not break.
2377 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
2379 /* changed transmit queue under us so clear hints */
2380 tcp_clear_retrans_hints_partial(tp
);
2381 if (next_skb
== tp
->retransmit_skb_hint
)
2382 tp
->retransmit_skb_hint
= skb
;
2384 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
2386 sk_wmem_free_skb(sk
, next_skb
);
2389 /* Check if coalescing SKBs is legal. */
2390 static bool tcp_can_collapse(const struct sock
*sk
, const struct sk_buff
*skb
)
2392 if (tcp_skb_pcount(skb
) > 1)
2394 /* TODO: SACK collapsing could be used to remove this condition */
2395 if (skb_shinfo(skb
)->nr_frags
!= 0)
2397 if (skb_cloned(skb
))
2399 if (skb
== tcp_send_head(sk
))
2401 /* Some heurestics for collapsing over SACK'd could be invented */
2402 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2408 /* Collapse packets in the retransmit queue to make to create
2409 * less packets on the wire. This is only done on retransmission.
2411 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
2414 struct tcp_sock
*tp
= tcp_sk(sk
);
2415 struct sk_buff
*skb
= to
, *tmp
;
2418 if (!sysctl_tcp_retrans_collapse
)
2420 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2423 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
2424 if (!tcp_can_collapse(sk
, skb
))
2436 /* Punt if not enough space exists in the first SKB for
2437 * the data in the second
2439 if (skb
->len
> skb_availroom(to
))
2442 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
2445 tcp_collapse_retrans(sk
, to
);
2449 /* This retransmits one SKB. Policy decisions and retransmit queue
2450 * state updates are done by the caller. Returns non-zero if an
2451 * error occurred which prevented the send.
2453 int __tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2455 struct tcp_sock
*tp
= tcp_sk(sk
);
2456 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2457 unsigned int cur_mss
;
2460 /* Inconslusive MTU probe */
2461 if (icsk
->icsk_mtup
.probe_size
) {
2462 icsk
->icsk_mtup
.probe_size
= 0;
2465 /* Do not sent more than we queued. 1/4 is reserved for possible
2466 * copying overhead: fragmentation, tunneling, mangling etc.
2468 if (atomic_read(&sk
->sk_wmem_alloc
) >
2469 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
2472 if (skb_still_in_host_queue(sk
, skb
))
2475 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
2476 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
2478 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2482 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
2483 return -EHOSTUNREACH
; /* Routing failure or similar. */
2485 cur_mss
= tcp_current_mss(sk
);
2487 /* If receiver has shrunk his window, and skb is out of
2488 * new window, do not retransmit it. The exception is the
2489 * case, when window is shrunk to zero. In this case
2490 * our retransmit serves as a zero window probe.
2492 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
)) &&
2493 TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
2496 if (skb
->len
> cur_mss
) {
2497 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
, GFP_ATOMIC
))
2498 return -ENOMEM
; /* We'll try again later. */
2500 int oldpcount
= tcp_skb_pcount(skb
);
2502 if (unlikely(oldpcount
> 1)) {
2503 if (skb_unclone(skb
, GFP_ATOMIC
))
2505 tcp_init_tso_segs(sk
, skb
, cur_mss
);
2506 tcp_adjust_pcount(sk
, skb
, oldpcount
- tcp_skb_pcount(skb
));
2510 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
2512 /* Make a copy, if the first transmission SKB clone we made
2513 * is still in somebody's hands, else make a clone.
2516 /* make sure skb->data is aligned on arches that require it
2517 * and check if ack-trimming & collapsing extended the headroom
2518 * beyond what csum_start can cover.
2520 if (unlikely((NET_IP_ALIGN
&& ((unsigned long)skb
->data
& 3)) ||
2521 skb_headroom(skb
) >= 0xFFFF)) {
2522 struct sk_buff
*nskb
= __pskb_copy(skb
, MAX_TCP_HEADER
,
2524 err
= nskb
? tcp_transmit_skb(sk
, nskb
, 0, GFP_ATOMIC
) :
2527 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2531 TCP_SKB_CB(skb
)->sacked
|= TCPCB_EVER_RETRANS
;
2532 /* Update global TCP statistics. */
2533 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
2534 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2535 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
2536 tp
->total_retrans
++;
2541 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2543 struct tcp_sock
*tp
= tcp_sk(sk
);
2544 int err
= __tcp_retransmit_skb(sk
, skb
);
2547 #if FASTRETRANS_DEBUG > 0
2548 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2549 net_dbg_ratelimited("retrans_out leaked\n");
2552 if (!tp
->retrans_out
)
2553 tp
->lost_retrans_low
= tp
->snd_nxt
;
2554 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
2555 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2557 /* Save stamp of the first retransmit. */
2558 if (!tp
->retrans_stamp
)
2559 tp
->retrans_stamp
= tcp_skb_timestamp(skb
);
2561 /* snd_nxt is stored to detect loss of retransmitted segment,
2562 * see tcp_input.c tcp_sacktag_write_queue().
2564 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
2565 } else if (err
!= -EBUSY
) {
2566 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRETRANSFAIL
);
2569 if (tp
->undo_retrans
< 0)
2570 tp
->undo_retrans
= 0;
2571 tp
->undo_retrans
+= tcp_skb_pcount(skb
);
2575 /* Check if we forward retransmits are possible in the current
2576 * window/congestion state.
2578 static bool tcp_can_forward_retransmit(struct sock
*sk
)
2580 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2581 const struct tcp_sock
*tp
= tcp_sk(sk
);
2583 /* Forward retransmissions are possible only during Recovery. */
2584 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
2587 /* No forward retransmissions in Reno are possible. */
2588 if (tcp_is_reno(tp
))
2591 /* Yeah, we have to make difficult choice between forward transmission
2592 * and retransmission... Both ways have their merits...
2594 * For now we do not retransmit anything, while we have some new
2595 * segments to send. In the other cases, follow rule 3 for
2596 * NextSeg() specified in RFC3517.
2599 if (tcp_may_send_now(sk
))
2605 /* This gets called after a retransmit timeout, and the initially
2606 * retransmitted data is acknowledged. It tries to continue
2607 * resending the rest of the retransmit queue, until either
2608 * we've sent it all or the congestion window limit is reached.
2609 * If doing SACK, the first ACK which comes back for a timeout
2610 * based retransmit packet might feed us FACK information again.
2611 * If so, we use it to avoid unnecessarily retransmissions.
2613 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2615 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2616 struct tcp_sock
*tp
= tcp_sk(sk
);
2617 struct sk_buff
*skb
;
2618 struct sk_buff
*hole
= NULL
;
2621 int fwd_rexmitting
= 0;
2623 if (!tp
->packets_out
)
2627 tp
->retransmit_high
= tp
->snd_una
;
2629 if (tp
->retransmit_skb_hint
) {
2630 skb
= tp
->retransmit_skb_hint
;
2631 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2632 if (after(last_lost
, tp
->retransmit_high
))
2633 last_lost
= tp
->retransmit_high
;
2635 skb
= tcp_write_queue_head(sk
);
2636 last_lost
= tp
->snd_una
;
2639 tcp_for_write_queue_from(skb
, sk
) {
2640 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
2642 if (skb
== tcp_send_head(sk
))
2644 /* we could do better than to assign each time */
2646 tp
->retransmit_skb_hint
= skb
;
2648 /* Assume this retransmit will generate
2649 * only one packet for congestion window
2650 * calculation purposes. This works because
2651 * tcp_retransmit_skb() will chop up the
2652 * packet to be MSS sized and all the
2653 * packet counting works out.
2655 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2658 if (fwd_rexmitting
) {
2660 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2662 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2664 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2665 tp
->retransmit_high
= last_lost
;
2666 if (!tcp_can_forward_retransmit(sk
))
2668 /* Backtrack if necessary to non-L'ed skb */
2676 } else if (!(sacked
& TCPCB_LOST
)) {
2677 if (hole
== NULL
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2682 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2683 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2684 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2686 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2689 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2692 if (tcp_retransmit_skb(sk
, skb
))
2695 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2697 if (tcp_in_cwnd_reduction(sk
))
2698 tp
->prr_out
+= tcp_skb_pcount(skb
);
2700 if (skb
== tcp_write_queue_head(sk
))
2701 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2702 inet_csk(sk
)->icsk_rto
,
2707 /* Send a fin. The caller locks the socket for us. This cannot be
2708 * allowed to fail queueing a FIN frame under any circumstances.
2710 void tcp_send_fin(struct sock
*sk
)
2712 struct tcp_sock
*tp
= tcp_sk(sk
);
2713 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2716 /* Optimization, tack on the FIN if we have a queue of
2717 * unsent frames. But be careful about outgoing SACKS
2720 mss_now
= tcp_current_mss(sk
);
2722 if (tcp_send_head(sk
) != NULL
) {
2723 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_FIN
;
2724 TCP_SKB_CB(skb
)->end_seq
++;
2727 /* Socket is locked, keep trying until memory is available. */
2729 skb
= alloc_skb_fclone(MAX_TCP_HEADER
,
2736 /* Reserve space for headers and prepare control bits. */
2737 skb_reserve(skb
, MAX_TCP_HEADER
);
2738 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2739 tcp_init_nondata_skb(skb
, tp
->write_seq
,
2740 TCPHDR_ACK
| TCPHDR_FIN
);
2741 tcp_queue_skb(sk
, skb
);
2743 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2746 /* We get here when a process closes a file descriptor (either due to
2747 * an explicit close() or as a byproduct of exit()'ing) and there
2748 * was unread data in the receive queue. This behavior is recommended
2749 * by RFC 2525, section 2.17. -DaveM
2751 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2753 struct sk_buff
*skb
;
2755 /* NOTE: No TCP options attached and we never retransmit this. */
2756 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2758 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2762 /* Reserve space for headers and prepare control bits. */
2763 skb_reserve(skb
, MAX_TCP_HEADER
);
2764 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
2765 TCPHDR_ACK
| TCPHDR_RST
);
2767 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2768 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2770 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
2773 /* Send a crossed SYN-ACK during socket establishment.
2774 * WARNING: This routine must only be called when we have already sent
2775 * a SYN packet that crossed the incoming SYN that caused this routine
2776 * to get called. If this assumption fails then the initial rcv_wnd
2777 * and rcv_wscale values will not be correct.
2779 int tcp_send_synack(struct sock
*sk
)
2781 struct sk_buff
*skb
;
2783 skb
= tcp_write_queue_head(sk
);
2784 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
2785 pr_debug("%s: wrong queue state\n", __func__
);
2788 if (!(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_ACK
)) {
2789 if (skb_cloned(skb
)) {
2790 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2793 tcp_unlink_write_queue(skb
, sk
);
2794 __skb_header_release(nskb
);
2795 __tcp_add_write_queue_head(sk
, nskb
);
2796 sk_wmem_free_skb(sk
, skb
);
2797 sk
->sk_wmem_queued
+= nskb
->truesize
;
2798 sk_mem_charge(sk
, nskb
->truesize
);
2802 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ACK
;
2803 tcp_ecn_send_synack(sk
, skb
);
2805 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2809 * tcp_make_synack - Prepare a SYN-ACK.
2810 * sk: listener socket
2811 * dst: dst entry attached to the SYNACK
2812 * req: request_sock pointer
2814 * Allocate one skb and build a SYNACK packet.
2815 * @dst is consumed : Caller should not use it again.
2817 struct sk_buff
*tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2818 struct request_sock
*req
,
2819 struct tcp_fastopen_cookie
*foc
)
2821 struct tcp_out_options opts
;
2822 struct inet_request_sock
*ireq
= inet_rsk(req
);
2823 struct tcp_sock
*tp
= tcp_sk(sk
);
2825 struct sk_buff
*skb
;
2826 struct tcp_md5sig_key
*md5
;
2827 int tcp_header_size
;
2830 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
, 1, GFP_ATOMIC
);
2831 if (unlikely(!skb
)) {
2835 /* Reserve space for headers. */
2836 skb_reserve(skb
, MAX_TCP_HEADER
);
2838 skb_dst_set(skb
, dst
);
2839 security_skb_owned_by(skb
, sk
);
2841 mss
= dst_metric_advmss(dst
);
2842 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< mss
)
2843 mss
= tp
->rx_opt
.user_mss
;
2845 memset(&opts
, 0, sizeof(opts
));
2846 #ifdef CONFIG_SYN_COOKIES
2847 if (unlikely(req
->cookie_ts
))
2848 skb
->skb_mstamp
.stamp_jiffies
= cookie_init_timestamp(req
);
2851 skb_mstamp_get(&skb
->skb_mstamp
);
2852 tcp_header_size
= tcp_synack_options(sk
, req
, mss
, skb
, &opts
, &md5
,
2855 skb_push(skb
, tcp_header_size
);
2856 skb_reset_transport_header(skb
);
2859 memset(th
, 0, sizeof(struct tcphdr
));
2862 tcp_ecn_make_synack(req
, th
, sk
);
2863 th
->source
= htons(ireq
->ir_num
);
2864 th
->dest
= ireq
->ir_rmt_port
;
2865 /* Setting of flags are superfluous here for callers (and ECE is
2866 * not even correctly set)
2868 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
2869 TCPHDR_SYN
| TCPHDR_ACK
);
2871 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2872 /* XXX data is queued and acked as is. No buffer/window check */
2873 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_nxt
);
2875 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2876 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2877 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
2878 th
->doff
= (tcp_header_size
>> 2);
2879 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_OUTSEGS
);
2881 #ifdef CONFIG_TCP_MD5SIG
2882 /* Okay, we have all we need - do the md5 hash if needed */
2884 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
2885 md5
, NULL
, req
, skb
);
2891 EXPORT_SYMBOL(tcp_make_synack
);
2893 /* Do all connect socket setups that can be done AF independent. */
2894 static void tcp_connect_init(struct sock
*sk
)
2896 const struct dst_entry
*dst
= __sk_dst_get(sk
);
2897 struct tcp_sock
*tp
= tcp_sk(sk
);
2900 /* We'll fix this up when we get a response from the other end.
2901 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2903 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2904 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2906 #ifdef CONFIG_TCP_MD5SIG
2907 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2908 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2911 /* If user gave his TCP_MAXSEG, record it to clamp */
2912 if (tp
->rx_opt
.user_mss
)
2913 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2916 tcp_sync_mss(sk
, dst_mtu(dst
));
2918 if (!tp
->window_clamp
)
2919 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2920 tp
->advmss
= dst_metric_advmss(dst
);
2921 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
2922 tp
->advmss
= tp
->rx_opt
.user_mss
;
2924 tcp_initialize_rcv_mss(sk
);
2926 /* limit the window selection if the user enforce a smaller rx buffer */
2927 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
2928 (tp
->window_clamp
> tcp_full_space(sk
) || tp
->window_clamp
== 0))
2929 tp
->window_clamp
= tcp_full_space(sk
);
2931 tcp_select_initial_window(tcp_full_space(sk
),
2932 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2935 sysctl_tcp_window_scaling
,
2937 dst_metric(dst
, RTAX_INITRWND
));
2939 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2940 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2943 sock_reset_flag(sk
, SOCK_DONE
);
2946 tp
->snd_una
= tp
->write_seq
;
2947 tp
->snd_sml
= tp
->write_seq
;
2948 tp
->snd_up
= tp
->write_seq
;
2949 tp
->snd_nxt
= tp
->write_seq
;
2951 if (likely(!tp
->repair
))
2954 tp
->rcv_tstamp
= tcp_time_stamp
;
2955 tp
->rcv_wup
= tp
->rcv_nxt
;
2956 tp
->copied_seq
= tp
->rcv_nxt
;
2958 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2959 inet_csk(sk
)->icsk_retransmits
= 0;
2960 tcp_clear_retrans(tp
);
2963 static void tcp_connect_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
2965 struct tcp_sock
*tp
= tcp_sk(sk
);
2966 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
2968 tcb
->end_seq
+= skb
->len
;
2969 __skb_header_release(skb
);
2970 __tcp_add_write_queue_tail(sk
, skb
);
2971 sk
->sk_wmem_queued
+= skb
->truesize
;
2972 sk_mem_charge(sk
, skb
->truesize
);
2973 tp
->write_seq
= tcb
->end_seq
;
2974 tp
->packets_out
+= tcp_skb_pcount(skb
);
2977 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
2978 * queue a data-only packet after the regular SYN, such that regular SYNs
2979 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
2980 * only the SYN sequence, the data are retransmitted in the first ACK.
2981 * If cookie is not cached or other error occurs, falls back to send a
2982 * regular SYN with Fast Open cookie request option.
2984 static int tcp_send_syn_data(struct sock
*sk
, struct sk_buff
*syn
)
2986 struct tcp_sock
*tp
= tcp_sk(sk
);
2987 struct tcp_fastopen_request
*fo
= tp
->fastopen_req
;
2988 int syn_loss
= 0, space
, i
, err
= 0, iovlen
= fo
->data
->msg_iovlen
;
2989 struct sk_buff
*syn_data
= NULL
, *data
;
2990 unsigned long last_syn_loss
= 0;
2992 tp
->rx_opt
.mss_clamp
= tp
->advmss
; /* If MSS is not cached */
2993 tcp_fastopen_cache_get(sk
, &tp
->rx_opt
.mss_clamp
, &fo
->cookie
,
2994 &syn_loss
, &last_syn_loss
);
2995 /* Recurring FO SYN losses: revert to regular handshake temporarily */
2997 time_before(jiffies
, last_syn_loss
+ (60*HZ
<< syn_loss
))) {
2998 fo
->cookie
.len
= -1;
3002 if (sysctl_tcp_fastopen
& TFO_CLIENT_NO_COOKIE
)
3003 fo
->cookie
.len
= -1;
3004 else if (fo
->cookie
.len
<= 0)
3007 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3008 * user-MSS. Reserve maximum option space for middleboxes that add
3009 * private TCP options. The cost is reduced data space in SYN :(
3011 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->rx_opt
.mss_clamp
)
3012 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
3013 space
= __tcp_mtu_to_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
) -
3014 MAX_TCP_OPTION_SPACE
;
3016 space
= min_t(size_t, space
, fo
->size
);
3018 /* limit to order-0 allocations */
3019 space
= min_t(size_t, space
, SKB_MAX_HEAD(MAX_TCP_HEADER
));
3021 syn_data
= skb_copy_expand(syn
, MAX_TCP_HEADER
, space
,
3023 if (syn_data
== NULL
)
3026 for (i
= 0; i
< iovlen
&& syn_data
->len
< space
; ++i
) {
3027 struct iovec
*iov
= &fo
->data
->msg_iov
[i
];
3028 unsigned char __user
*from
= iov
->iov_base
;
3029 int len
= iov
->iov_len
;
3031 if (syn_data
->len
+ len
> space
)
3032 len
= space
- syn_data
->len
;
3033 else if (i
+ 1 == iovlen
)
3034 /* No more data pending in inet_wait_for_connect() */
3037 if (skb_add_data(syn_data
, from
, len
))
3041 /* Queue a data-only packet after the regular SYN for retransmission */
3042 data
= pskb_copy(syn_data
, sk
->sk_allocation
);
3045 TCP_SKB_CB(data
)->seq
++;
3046 TCP_SKB_CB(data
)->tcp_flags
&= ~TCPHDR_SYN
;
3047 TCP_SKB_CB(data
)->tcp_flags
= (TCPHDR_ACK
|TCPHDR_PSH
);
3048 tcp_connect_queue_skb(sk
, data
);
3049 fo
->copied
= data
->len
;
3051 /* syn_data is about to be sent, we need to take current time stamps
3052 * for the packets that are in write queue : SYN packet and DATA
3054 skb_mstamp_get(&syn
->skb_mstamp
);
3055 data
->skb_mstamp
= syn
->skb_mstamp
;
3057 if (tcp_transmit_skb(sk
, syn_data
, 0, sk
->sk_allocation
) == 0) {
3058 tp
->syn_data
= (fo
->copied
> 0);
3059 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
);
3065 /* Send a regular SYN with Fast Open cookie request option */
3066 if (fo
->cookie
.len
> 0)
3068 err
= tcp_transmit_skb(sk
, syn
, 1, sk
->sk_allocation
);
3070 tp
->syn_fastopen
= 0;
3071 kfree_skb(syn_data
);
3073 fo
->cookie
.len
= -1; /* Exclude Fast Open option for SYN retries */
3077 /* Build a SYN and send it off. */
3078 int tcp_connect(struct sock
*sk
)
3080 struct tcp_sock
*tp
= tcp_sk(sk
);
3081 struct sk_buff
*buff
;
3084 tcp_connect_init(sk
);
3086 if (unlikely(tp
->repair
)) {
3087 tcp_finish_connect(sk
, NULL
);
3091 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
3092 if (unlikely(buff
== NULL
))
3095 /* Reserve space for headers. */
3096 skb_reserve(buff
, MAX_TCP_HEADER
);
3098 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPHDR_SYN
);
3099 tp
->retrans_stamp
= tcp_time_stamp
;
3100 tcp_connect_queue_skb(sk
, buff
);
3101 tcp_ecn_send_syn(sk
, buff
);
3103 /* Send off SYN; include data in Fast Open. */
3104 err
= tp
->fastopen_req
? tcp_send_syn_data(sk
, buff
) :
3105 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
3106 if (err
== -ECONNREFUSED
)
3109 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3110 * in order to make this packet get counted in tcpOutSegs.
3112 tp
->snd_nxt
= tp
->write_seq
;
3113 tp
->pushed_seq
= tp
->write_seq
;
3114 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
3116 /* Timer for repeating the SYN until an answer. */
3117 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3118 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3121 EXPORT_SYMBOL(tcp_connect
);
3123 /* Send out a delayed ack, the caller does the policy checking
3124 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3127 void tcp_send_delayed_ack(struct sock
*sk
)
3129 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3130 int ato
= icsk
->icsk_ack
.ato
;
3131 unsigned long timeout
;
3133 tcp_ca_event(sk
, CA_EVENT_DELAYED_ACK
);
3135 if (ato
> TCP_DELACK_MIN
) {
3136 const struct tcp_sock
*tp
= tcp_sk(sk
);
3137 int max_ato
= HZ
/ 2;
3139 if (icsk
->icsk_ack
.pingpong
||
3140 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
3141 max_ato
= TCP_DELACK_MAX
;
3143 /* Slow path, intersegment interval is "high". */
3145 /* If some rtt estimate is known, use it to bound delayed ack.
3146 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3150 int rtt
= max_t(int, usecs_to_jiffies(tp
->srtt_us
>> 3),
3157 ato
= min(ato
, max_ato
);
3160 /* Stay within the limit we were given */
3161 timeout
= jiffies
+ ato
;
3163 /* Use new timeout only if there wasn't a older one earlier. */
3164 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
3165 /* If delack timer was blocked or is about to expire,
3168 if (icsk
->icsk_ack
.blocked
||
3169 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
3174 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
3175 timeout
= icsk
->icsk_ack
.timeout
;
3177 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
3178 icsk
->icsk_ack
.timeout
= timeout
;
3179 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
3182 /* This routine sends an ack and also updates the window. */
3183 void tcp_send_ack(struct sock
*sk
)
3185 struct sk_buff
*buff
;
3187 /* If we have been reset, we may not send again. */
3188 if (sk
->sk_state
== TCP_CLOSE
)
3191 tcp_ca_event(sk
, CA_EVENT_NON_DELAYED_ACK
);
3193 /* We are not putting this on the write queue, so
3194 * tcp_transmit_skb() will set the ownership to this
3197 buff
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3199 inet_csk_schedule_ack(sk
);
3200 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
3201 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
3202 TCP_DELACK_MAX
, TCP_RTO_MAX
);
3206 /* Reserve space for headers and prepare control bits. */
3207 skb_reserve(buff
, MAX_TCP_HEADER
);
3208 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPHDR_ACK
);
3210 /* Send it off, this clears delayed acks for us. */
3211 skb_mstamp_get(&buff
->skb_mstamp
);
3212 tcp_transmit_skb(sk
, buff
, 0, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3214 EXPORT_SYMBOL_GPL(tcp_send_ack
);
3216 /* This routine sends a packet with an out of date sequence
3217 * number. It assumes the other end will try to ack it.
3219 * Question: what should we make while urgent mode?
3220 * 4.4BSD forces sending single byte of data. We cannot send
3221 * out of window data, because we have SND.NXT==SND.MAX...
3223 * Current solution: to send TWO zero-length segments in urgent mode:
3224 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3225 * out-of-date with SND.UNA-1 to probe window.
3227 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
3229 struct tcp_sock
*tp
= tcp_sk(sk
);
3230 struct sk_buff
*skb
;
3232 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3233 skb
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3237 /* Reserve space for headers and set control bits. */
3238 skb_reserve(skb
, MAX_TCP_HEADER
);
3239 /* Use a previous sequence. This should cause the other
3240 * end to send an ack. Don't queue or clone SKB, just
3243 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPHDR_ACK
);
3244 skb_mstamp_get(&skb
->skb_mstamp
);
3245 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
3248 void tcp_send_window_probe(struct sock
*sk
)
3250 if (sk
->sk_state
== TCP_ESTABLISHED
) {
3251 tcp_sk(sk
)->snd_wl1
= tcp_sk(sk
)->rcv_nxt
- 1;
3252 tcp_xmit_probe_skb(sk
, 0);
3256 /* Initiate keepalive or window probe from timer. */
3257 int tcp_write_wakeup(struct sock
*sk
)
3259 struct tcp_sock
*tp
= tcp_sk(sk
);
3260 struct sk_buff
*skb
;
3262 if (sk
->sk_state
== TCP_CLOSE
)
3265 if ((skb
= tcp_send_head(sk
)) != NULL
&&
3266 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
3268 unsigned int mss
= tcp_current_mss(sk
);
3269 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
3271 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
3272 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
3274 /* We are probing the opening of a window
3275 * but the window size is != 0
3276 * must have been a result SWS avoidance ( sender )
3278 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
3280 seg_size
= min(seg_size
, mss
);
3281 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3282 if (tcp_fragment(sk
, skb
, seg_size
, mss
, GFP_ATOMIC
))
3284 } else if (!tcp_skb_pcount(skb
))
3285 tcp_set_skb_tso_segs(sk
, skb
, mss
);
3287 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3288 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3290 tcp_event_new_data_sent(sk
, skb
);
3293 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
3294 tcp_xmit_probe_skb(sk
, 1);
3295 return tcp_xmit_probe_skb(sk
, 0);
3299 /* A window probe timeout has occurred. If window is not closed send
3300 * a partial packet else a zero probe.
3302 void tcp_send_probe0(struct sock
*sk
)
3304 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3305 struct tcp_sock
*tp
= tcp_sk(sk
);
3306 unsigned long probe_max
;
3309 err
= tcp_write_wakeup(sk
);
3311 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
3312 /* Cancel probe timer, if it is not required. */
3313 icsk
->icsk_probes_out
= 0;
3314 icsk
->icsk_backoff
= 0;
3319 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
3320 icsk
->icsk_backoff
++;
3321 icsk
->icsk_probes_out
++;
3322 probe_max
= TCP_RTO_MAX
;
3324 /* If packet was not sent due to local congestion,
3325 * do not backoff and do not remember icsk_probes_out.
3326 * Let local senders to fight for local resources.
3328 * Use accumulated backoff yet.
3330 if (!icsk
->icsk_probes_out
)
3331 icsk
->icsk_probes_out
= 1;
3332 probe_max
= TCP_RESOURCE_PROBE_INTERVAL
;
3334 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3335 inet_csk_rto_backoff(icsk
, probe_max
),
3339 int tcp_rtx_synack(struct sock
*sk
, struct request_sock
*req
)
3341 const struct tcp_request_sock_ops
*af_ops
= tcp_rsk(req
)->af_specific
;
3345 res
= af_ops
->send_synack(sk
, NULL
, &fl
, req
, 0, NULL
);
3347 TCP_INC_STATS_BH(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
3348 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
3352 EXPORT_SYMBOL(tcp_rtx_synack
);