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
) {
91 /* SND.NXT, if window was not shrunk.
92 * If window has been shrunk, what should we make? It is not clear at all.
93 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
94 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
95 * invalid. OK, let's make this for now:
97 static inline __u32
tcp_acceptable_seq(const struct sock
*sk
)
99 const struct tcp_sock
*tp
= tcp_sk(sk
);
101 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
))
104 return tcp_wnd_end(tp
);
107 /* Calculate mss to advertise in SYN segment.
108 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
110 * 1. It is independent of path mtu.
111 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
112 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
113 * attached devices, because some buggy hosts are confused by
115 * 4. We do not make 3, we advertise MSS, calculated from first
116 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
117 * This may be overridden via information stored in routing table.
118 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
119 * probably even Jumbo".
121 static __u16
tcp_advertise_mss(struct sock
*sk
)
123 struct tcp_sock
*tp
= tcp_sk(sk
);
124 const struct dst_entry
*dst
= __sk_dst_get(sk
);
125 int mss
= tp
->advmss
;
128 unsigned int metric
= dst_metric_advmss(dst
);
139 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
140 * This is the first part of cwnd validation mechanism. */
141 static void tcp_cwnd_restart(struct sock
*sk
, const struct dst_entry
*dst
)
143 struct tcp_sock
*tp
= tcp_sk(sk
);
144 s32 delta
= tcp_time_stamp
- tp
->lsndtime
;
145 u32 restart_cwnd
= tcp_init_cwnd(tp
, dst
);
146 u32 cwnd
= tp
->snd_cwnd
;
148 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
150 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
151 restart_cwnd
= min(restart_cwnd
, cwnd
);
153 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
155 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
156 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
157 tp
->snd_cwnd_used
= 0;
160 /* Congestion state accounting after a packet has been sent. */
161 static void tcp_event_data_sent(struct tcp_sock
*tp
,
164 struct inet_connection_sock
*icsk
= inet_csk(sk
);
165 const u32 now
= tcp_time_stamp
;
166 const struct dst_entry
*dst
= __sk_dst_get(sk
);
168 if (sysctl_tcp_slow_start_after_idle
&&
169 (!tp
->packets_out
&& (s32
)(now
- tp
->lsndtime
) > icsk
->icsk_rto
))
170 tcp_cwnd_restart(sk
, __sk_dst_get(sk
));
174 /* If it is a reply for ato after last received
175 * packet, enter pingpong mode.
177 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
&&
178 (!dst
|| !dst_metric(dst
, RTAX_QUICKACK
)))
179 icsk
->icsk_ack
.pingpong
= 1;
182 /* Account for an ACK we sent. */
183 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
185 tcp_dec_quickack_mode(sk
, pkts
);
186 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
190 u32
tcp_default_init_rwnd(u32 mss
)
192 /* Initial receive window should be twice of TCP_INIT_CWND to
193 * enable proper sending of new unsent data during fast recovery
194 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
195 * limit when mss is larger than 1460.
197 u32 init_rwnd
= TCP_INIT_CWND
* 2;
200 init_rwnd
= max((1460 * init_rwnd
) / mss
, 2U);
204 /* Determine a window scaling and initial window to offer.
205 * Based on the assumption that the given amount of space
206 * will be offered. Store the results in the tp structure.
207 * NOTE: for smooth operation initial space offering should
208 * be a multiple of mss if possible. We assume here that mss >= 1.
209 * This MUST be enforced by all callers.
211 void tcp_select_initial_window(int __space
, __u32 mss
,
212 __u32
*rcv_wnd
, __u32
*window_clamp
,
213 int wscale_ok
, __u8
*rcv_wscale
,
216 unsigned int space
= (__space
< 0 ? 0 : __space
);
218 /* If no clamp set the clamp to the max possible scaled window */
219 if (*window_clamp
== 0)
220 (*window_clamp
) = (65535 << 14);
221 space
= min(*window_clamp
, space
);
223 /* Quantize space offering to a multiple of mss if possible. */
225 space
= (space
/ mss
) * mss
;
227 /* NOTE: offering an initial window larger than 32767
228 * will break some buggy TCP stacks. If the admin tells us
229 * it is likely we could be speaking with such a buggy stack
230 * we will truncate our initial window offering to 32K-1
231 * unless the remote has sent us a window scaling option,
232 * which we interpret as a sign the remote TCP is not
233 * misinterpreting the window field as a signed quantity.
235 if (sysctl_tcp_workaround_signed_windows
)
236 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
242 /* Set window scaling on max possible window
243 * See RFC1323 for an explanation of the limit to 14
245 space
= max_t(u32
, sysctl_tcp_rmem
[2], sysctl_rmem_max
);
246 space
= min_t(u32
, space
, *window_clamp
);
247 while (space
> 65535 && (*rcv_wscale
) < 14) {
253 if (mss
> (1 << *rcv_wscale
)) {
254 if (!init_rcv_wnd
) /* Use default unless specified otherwise */
255 init_rcv_wnd
= tcp_default_init_rwnd(mss
);
256 *rcv_wnd
= min(*rcv_wnd
, init_rcv_wnd
* mss
);
259 /* Set the clamp no higher than max representable value */
260 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
262 EXPORT_SYMBOL(tcp_select_initial_window
);
264 /* Chose a new window to advertise, update state in tcp_sock for the
265 * socket, and return result with RFC1323 scaling applied. The return
266 * value can be stuffed directly into th->window for an outgoing
269 static u16
tcp_select_window(struct sock
*sk
)
271 struct tcp_sock
*tp
= tcp_sk(sk
);
272 u32 cur_win
= tcp_receive_window(tp
);
273 u32 new_win
= __tcp_select_window(sk
);
275 /* Never shrink the offered window */
276 if (new_win
< cur_win
) {
277 /* Danger Will Robinson!
278 * Don't update rcv_wup/rcv_wnd here or else
279 * we will not be able to advertise a zero
280 * window in time. --DaveM
282 * Relax Will Robinson.
284 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
286 tp
->rcv_wnd
= new_win
;
287 tp
->rcv_wup
= tp
->rcv_nxt
;
289 /* Make sure we do not exceed the maximum possible
292 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
293 new_win
= min(new_win
, MAX_TCP_WINDOW
);
295 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
297 /* RFC1323 scaling applied */
298 new_win
>>= tp
->rx_opt
.rcv_wscale
;
300 /* If we advertise zero window, disable fast path. */
307 /* Packet ECN state for a SYN-ACK */
308 static inline void TCP_ECN_send_synack(const struct tcp_sock
*tp
, struct sk_buff
*skb
)
310 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_CWR
;
311 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
312 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_ECE
;
315 /* Packet ECN state for a SYN. */
316 static inline void TCP_ECN_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
318 struct tcp_sock
*tp
= tcp_sk(sk
);
321 if (sock_net(sk
)->ipv4
.sysctl_tcp_ecn
== 1) {
322 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ECE
| TCPHDR_CWR
;
323 tp
->ecn_flags
= TCP_ECN_OK
;
327 static __inline__
void
328 TCP_ECN_make_synack(const struct request_sock
*req
, struct tcphdr
*th
)
330 if (inet_rsk(req
)->ecn_ok
)
334 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
337 static inline void TCP_ECN_send(struct sock
*sk
, struct sk_buff
*skb
,
340 struct tcp_sock
*tp
= tcp_sk(sk
);
342 if (tp
->ecn_flags
& TCP_ECN_OK
) {
343 /* Not-retransmitted data segment: set ECT and inject CWR. */
344 if (skb
->len
!= tcp_header_len
&&
345 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
347 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
348 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
349 tcp_hdr(skb
)->cwr
= 1;
350 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
353 /* ACK or retransmitted segment: clear ECT|CE */
354 INET_ECN_dontxmit(sk
);
356 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
357 tcp_hdr(skb
)->ece
= 1;
361 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
362 * auto increment end seqno.
364 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
366 skb
->ip_summed
= CHECKSUM_PARTIAL
;
369 TCP_SKB_CB(skb
)->tcp_flags
= flags
;
370 TCP_SKB_CB(skb
)->sacked
= 0;
372 skb_shinfo(skb
)->gso_segs
= 1;
373 skb_shinfo(skb
)->gso_size
= 0;
374 skb_shinfo(skb
)->gso_type
= 0;
376 TCP_SKB_CB(skb
)->seq
= seq
;
377 if (flags
& (TCPHDR_SYN
| TCPHDR_FIN
))
379 TCP_SKB_CB(skb
)->end_seq
= seq
;
382 static inline bool tcp_urg_mode(const struct tcp_sock
*tp
)
384 return tp
->snd_una
!= tp
->snd_up
;
387 #define OPTION_SACK_ADVERTISE (1 << 0)
388 #define OPTION_TS (1 << 1)
389 #define OPTION_MD5 (1 << 2)
390 #define OPTION_WSCALE (1 << 3)
391 #define OPTION_FAST_OPEN_COOKIE (1 << 8)
393 struct tcp_out_options
{
394 u16 options
; /* bit field of OPTION_* */
395 u16 mss
; /* 0 to disable */
396 u8 ws
; /* window scale, 0 to disable */
397 u8 num_sack_blocks
; /* number of SACK blocks to include */
398 u8 hash_size
; /* bytes in hash_location */
399 __u8
*hash_location
; /* temporary pointer, overloaded */
400 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
401 struct tcp_fastopen_cookie
*fastopen_cookie
; /* Fast open cookie */
404 /* Write previously computed TCP options to the packet.
406 * Beware: Something in the Internet is very sensitive to the ordering of
407 * TCP options, we learned this through the hard way, so be careful here.
408 * Luckily we can at least blame others for their non-compliance but from
409 * inter-operatibility perspective it seems that we're somewhat stuck with
410 * the ordering which we have been using if we want to keep working with
411 * those broken things (not that it currently hurts anybody as there isn't
412 * particular reason why the ordering would need to be changed).
414 * At least SACK_PERM as the first option is known to lead to a disaster
415 * (but it may well be that other scenarios fail similarly).
417 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
418 struct tcp_out_options
*opts
)
420 u16 options
= opts
->options
; /* mungable copy */
422 if (unlikely(OPTION_MD5
& options
)) {
423 *ptr
++ = htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
424 (TCPOPT_MD5SIG
<< 8) | TCPOLEN_MD5SIG
);
425 /* overload cookie hash location */
426 opts
->hash_location
= (__u8
*)ptr
;
430 if (unlikely(opts
->mss
)) {
431 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
432 (TCPOLEN_MSS
<< 16) |
436 if (likely(OPTION_TS
& options
)) {
437 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
438 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
439 (TCPOLEN_SACK_PERM
<< 16) |
440 (TCPOPT_TIMESTAMP
<< 8) |
442 options
&= ~OPTION_SACK_ADVERTISE
;
444 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
446 (TCPOPT_TIMESTAMP
<< 8) |
449 *ptr
++ = htonl(opts
->tsval
);
450 *ptr
++ = htonl(opts
->tsecr
);
453 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
454 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
456 (TCPOPT_SACK_PERM
<< 8) |
460 if (unlikely(OPTION_WSCALE
& options
)) {
461 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
462 (TCPOPT_WINDOW
<< 16) |
463 (TCPOLEN_WINDOW
<< 8) |
467 if (unlikely(opts
->num_sack_blocks
)) {
468 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
469 tp
->duplicate_sack
: tp
->selective_acks
;
472 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
475 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
476 TCPOLEN_SACK_PERBLOCK
)));
478 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
480 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
481 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
484 tp
->rx_opt
.dsack
= 0;
487 if (unlikely(OPTION_FAST_OPEN_COOKIE
& options
)) {
488 struct tcp_fastopen_cookie
*foc
= opts
->fastopen_cookie
;
490 *ptr
++ = htonl((TCPOPT_EXP
<< 24) |
491 ((TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
) << 16) |
492 TCPOPT_FASTOPEN_MAGIC
);
494 memcpy(ptr
, foc
->val
, foc
->len
);
495 if ((foc
->len
& 3) == 2) {
496 u8
*align
= ((u8
*)ptr
) + foc
->len
;
497 align
[0] = align
[1] = TCPOPT_NOP
;
499 ptr
+= (foc
->len
+ 3) >> 2;
503 /* Compute TCP options for SYN packets. This is not the final
504 * network wire format yet.
506 static unsigned int tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
507 struct tcp_out_options
*opts
,
508 struct tcp_md5sig_key
**md5
)
510 struct tcp_sock
*tp
= tcp_sk(sk
);
511 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
512 struct tcp_fastopen_request
*fastopen
= tp
->fastopen_req
;
514 #ifdef CONFIG_TCP_MD5SIG
515 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
517 opts
->options
|= OPTION_MD5
;
518 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
524 /* We always get an MSS option. The option bytes which will be seen in
525 * normal data packets should timestamps be used, must be in the MSS
526 * advertised. But we subtract them from tp->mss_cache so that
527 * calculations in tcp_sendmsg are simpler etc. So account for this
528 * fact here if necessary. If we don't do this correctly, as a
529 * receiver we won't recognize data packets as being full sized when we
530 * should, and thus we won't abide by the delayed ACK rules correctly.
531 * SACKs don't matter, we never delay an ACK when we have any of those
533 opts
->mss
= tcp_advertise_mss(sk
);
534 remaining
-= TCPOLEN_MSS_ALIGNED
;
536 if (likely(sysctl_tcp_timestamps
&& *md5
== NULL
)) {
537 opts
->options
|= OPTION_TS
;
538 opts
->tsval
= TCP_SKB_CB(skb
)->when
+ tp
->tsoffset
;
539 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
540 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
542 if (likely(sysctl_tcp_window_scaling
)) {
543 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
544 opts
->options
|= OPTION_WSCALE
;
545 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
547 if (likely(sysctl_tcp_sack
)) {
548 opts
->options
|= OPTION_SACK_ADVERTISE
;
549 if (unlikely(!(OPTION_TS
& opts
->options
)))
550 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
553 if (fastopen
&& fastopen
->cookie
.len
>= 0) {
554 u32 need
= TCPOLEN_EXP_FASTOPEN_BASE
+ fastopen
->cookie
.len
;
555 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
556 if (remaining
>= need
) {
557 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
558 opts
->fastopen_cookie
= &fastopen
->cookie
;
560 tp
->syn_fastopen
= 1;
564 return MAX_TCP_OPTION_SPACE
- remaining
;
567 /* Set up TCP options for SYN-ACKs. */
568 static unsigned int tcp_synack_options(struct sock
*sk
,
569 struct request_sock
*req
,
570 unsigned int mss
, struct sk_buff
*skb
,
571 struct tcp_out_options
*opts
,
572 struct tcp_md5sig_key
**md5
,
573 struct tcp_fastopen_cookie
*foc
)
575 struct inet_request_sock
*ireq
= inet_rsk(req
);
576 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
578 #ifdef CONFIG_TCP_MD5SIG
579 *md5
= tcp_rsk(req
)->af_specific
->md5_lookup(sk
, req
);
581 opts
->options
|= OPTION_MD5
;
582 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
584 /* We can't fit any SACK blocks in a packet with MD5 + TS
585 * options. There was discussion about disabling SACK
586 * rather than TS in order to fit in better with old,
587 * buggy kernels, but that was deemed to be unnecessary.
589 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
595 /* We always send an MSS option. */
597 remaining
-= TCPOLEN_MSS_ALIGNED
;
599 if (likely(ireq
->wscale_ok
)) {
600 opts
->ws
= ireq
->rcv_wscale
;
601 opts
->options
|= OPTION_WSCALE
;
602 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
604 if (likely(ireq
->tstamp_ok
)) {
605 opts
->options
|= OPTION_TS
;
606 opts
->tsval
= TCP_SKB_CB(skb
)->when
;
607 opts
->tsecr
= req
->ts_recent
;
608 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
610 if (likely(ireq
->sack_ok
)) {
611 opts
->options
|= OPTION_SACK_ADVERTISE
;
612 if (unlikely(!ireq
->tstamp_ok
))
613 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
616 u32 need
= TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
;
617 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
618 if (remaining
>= need
) {
619 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
620 opts
->fastopen_cookie
= foc
;
625 return MAX_TCP_OPTION_SPACE
- remaining
;
628 /* Compute TCP options for ESTABLISHED sockets. This is not the
629 * final wire format yet.
631 static unsigned int tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
632 struct tcp_out_options
*opts
,
633 struct tcp_md5sig_key
**md5
)
635 struct tcp_skb_cb
*tcb
= skb
? TCP_SKB_CB(skb
) : NULL
;
636 struct tcp_sock
*tp
= tcp_sk(sk
);
637 unsigned int size
= 0;
638 unsigned int eff_sacks
;
642 #ifdef CONFIG_TCP_MD5SIG
643 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
644 if (unlikely(*md5
)) {
645 opts
->options
|= OPTION_MD5
;
646 size
+= TCPOLEN_MD5SIG_ALIGNED
;
652 if (likely(tp
->rx_opt
.tstamp_ok
)) {
653 opts
->options
|= OPTION_TS
;
654 opts
->tsval
= tcb
? tcb
->when
+ tp
->tsoffset
: 0;
655 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
656 size
+= TCPOLEN_TSTAMP_ALIGNED
;
659 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
660 if (unlikely(eff_sacks
)) {
661 const unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
662 opts
->num_sack_blocks
=
663 min_t(unsigned int, eff_sacks
,
664 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
665 TCPOLEN_SACK_PERBLOCK
);
666 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
667 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
674 /* TCP SMALL QUEUES (TSQ)
676 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
677 * to reduce RTT and bufferbloat.
678 * We do this using a special skb destructor (tcp_wfree).
680 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
681 * needs to be reallocated in a driver.
682 * The invariant being skb->truesize substracted from sk->sk_wmem_alloc
684 * Since transmit from skb destructor is forbidden, we use a tasklet
685 * to process all sockets that eventually need to send more skbs.
686 * We use one tasklet per cpu, with its own queue of sockets.
689 struct tasklet_struct tasklet
;
690 struct list_head head
; /* queue of tcp sockets */
692 static DEFINE_PER_CPU(struct tsq_tasklet
, tsq_tasklet
);
694 static void tcp_tsq_handler(struct sock
*sk
)
696 if ((1 << sk
->sk_state
) &
697 (TCPF_ESTABLISHED
| TCPF_FIN_WAIT1
| TCPF_CLOSING
|
698 TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
))
699 tcp_write_xmit(sk
, tcp_current_mss(sk
), 0, 0, GFP_ATOMIC
);
702 * One tasklest per cpu tries to send more skbs.
703 * We run in tasklet context but need to disable irqs when
704 * transfering tsq->head because tcp_wfree() might
705 * interrupt us (non NAPI drivers)
707 static void tcp_tasklet_func(unsigned long data
)
709 struct tsq_tasklet
*tsq
= (struct tsq_tasklet
*)data
;
712 struct list_head
*q
, *n
;
716 local_irq_save(flags
);
717 list_splice_init(&tsq
->head
, &list
);
718 local_irq_restore(flags
);
720 list_for_each_safe(q
, n
, &list
) {
721 tp
= list_entry(q
, struct tcp_sock
, tsq_node
);
722 list_del(&tp
->tsq_node
);
724 sk
= (struct sock
*)tp
;
727 if (!sock_owned_by_user(sk
)) {
730 /* defer the work to tcp_release_cb() */
731 set_bit(TCP_TSQ_DEFERRED
, &tp
->tsq_flags
);
735 clear_bit(TSQ_QUEUED
, &tp
->tsq_flags
);
740 #define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \
741 (1UL << TCP_WRITE_TIMER_DEFERRED) | \
742 (1UL << TCP_DELACK_TIMER_DEFERRED) | \
743 (1UL << TCP_MTU_REDUCED_DEFERRED))
745 * tcp_release_cb - tcp release_sock() callback
748 * called from release_sock() to perform protocol dependent
749 * actions before socket release.
751 void tcp_release_cb(struct sock
*sk
)
753 struct tcp_sock
*tp
= tcp_sk(sk
);
754 unsigned long flags
, nflags
;
756 /* perform an atomic operation only if at least one flag is set */
758 flags
= tp
->tsq_flags
;
759 if (!(flags
& TCP_DEFERRED_ALL
))
761 nflags
= flags
& ~TCP_DEFERRED_ALL
;
762 } while (cmpxchg(&tp
->tsq_flags
, flags
, nflags
) != flags
);
764 if (flags
& (1UL << TCP_TSQ_DEFERRED
))
767 if (flags
& (1UL << TCP_WRITE_TIMER_DEFERRED
)) {
768 tcp_write_timer_handler(sk
);
771 if (flags
& (1UL << TCP_DELACK_TIMER_DEFERRED
)) {
772 tcp_delack_timer_handler(sk
);
775 if (flags
& (1UL << TCP_MTU_REDUCED_DEFERRED
)) {
776 sk
->sk_prot
->mtu_reduced(sk
);
780 EXPORT_SYMBOL(tcp_release_cb
);
782 void __init
tcp_tasklet_init(void)
786 for_each_possible_cpu(i
) {
787 struct tsq_tasklet
*tsq
= &per_cpu(tsq_tasklet
, i
);
789 INIT_LIST_HEAD(&tsq
->head
);
790 tasklet_init(&tsq
->tasklet
,
797 * Write buffer destructor automatically called from kfree_skb.
798 * We cant xmit new skbs from this context, as we might already
801 void tcp_wfree(struct sk_buff
*skb
)
803 struct sock
*sk
= skb
->sk
;
804 struct tcp_sock
*tp
= tcp_sk(sk
);
806 if (test_and_clear_bit(TSQ_THROTTLED
, &tp
->tsq_flags
) &&
807 !test_and_set_bit(TSQ_QUEUED
, &tp
->tsq_flags
)) {
809 struct tsq_tasklet
*tsq
;
811 /* Keep a ref on socket.
812 * This last ref will be released in tcp_tasklet_func()
814 atomic_sub(skb
->truesize
- 1, &sk
->sk_wmem_alloc
);
816 /* queue this socket to tasklet queue */
817 local_irq_save(flags
);
818 tsq
= &__get_cpu_var(tsq_tasklet
);
819 list_add(&tp
->tsq_node
, &tsq
->head
);
820 tasklet_schedule(&tsq
->tasklet
);
821 local_irq_restore(flags
);
827 /* This routine actually transmits TCP packets queued in by
828 * tcp_do_sendmsg(). This is used by both the initial
829 * transmission and possible later retransmissions.
830 * All SKB's seen here are completely headerless. It is our
831 * job to build the TCP header, and pass the packet down to
832 * IP so it can do the same plus pass the packet off to the
835 * We are working here with either a clone of the original
836 * SKB, or a fresh unique copy made by the retransmit engine.
838 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
841 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
842 struct inet_sock
*inet
;
844 struct tcp_skb_cb
*tcb
;
845 struct tcp_out_options opts
;
846 unsigned int tcp_options_size
, tcp_header_size
;
847 struct tcp_md5sig_key
*md5
;
851 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
854 const struct sk_buff
*fclone
= skb
+ 1;
856 /* If congestion control is doing timestamping, we must
857 * take such a timestamp before we potentially clone/copy.
859 if (icsk
->icsk_ca_ops
->flags
& TCP_CONG_RTT_STAMP
)
860 __net_timestamp(skb
);
862 if (unlikely(skb
->fclone
== SKB_FCLONE_ORIG
&&
863 fclone
->fclone
== SKB_FCLONE_CLONE
))
864 NET_INC_STATS_BH(sock_net(sk
),
865 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES
);
867 if (unlikely(skb_cloned(skb
)))
868 skb
= pskb_copy(skb
, gfp_mask
);
870 skb
= skb_clone(skb
, gfp_mask
);
877 tcb
= TCP_SKB_CB(skb
);
878 memset(&opts
, 0, sizeof(opts
));
880 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
))
881 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
883 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
885 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
887 if (tcp_packets_in_flight(tp
) == 0)
888 tcp_ca_event(sk
, CA_EVENT_TX_START
);
890 /* if no packet is in qdisc/device queue, then allow XPS to select
893 skb
->ooo_okay
= sk_wmem_alloc_get(sk
) == 0;
895 skb_push(skb
, tcp_header_size
);
896 skb_reset_transport_header(skb
);
900 skb
->destructor
= tcp_wfree
;
901 atomic_add(skb
->truesize
, &sk
->sk_wmem_alloc
);
903 /* Build TCP header and checksum it. */
905 th
->source
= inet
->inet_sport
;
906 th
->dest
= inet
->inet_dport
;
907 th
->seq
= htonl(tcb
->seq
);
908 th
->ack_seq
= htonl(tp
->rcv_nxt
);
909 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
912 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
)) {
913 /* RFC1323: The window in SYN & SYN/ACK segments
916 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
918 th
->window
= htons(tcp_select_window(sk
));
923 /* The urg_mode check is necessary during a below snd_una win probe */
924 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
925 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
926 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
928 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
929 th
->urg_ptr
= htons(0xFFFF);
934 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
935 if (likely((tcb
->tcp_flags
& TCPHDR_SYN
) == 0))
936 TCP_ECN_send(sk
, skb
, tcp_header_size
);
938 #ifdef CONFIG_TCP_MD5SIG
939 /* Calculate the MD5 hash, as we have all we need now */
941 sk_nocaps_add(sk
, NETIF_F_GSO_MASK
);
942 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
947 icsk
->icsk_af_ops
->send_check(sk
, skb
);
949 if (likely(tcb
->tcp_flags
& TCPHDR_ACK
))
950 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
952 if (skb
->len
!= tcp_header_size
)
953 tcp_event_data_sent(tp
, sk
);
955 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
956 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
,
957 tcp_skb_pcount(skb
));
959 err
= icsk
->icsk_af_ops
->queue_xmit(skb
, &inet
->cork
.fl
);
960 if (likely(err
<= 0))
963 tcp_enter_cwr(sk
, 1);
965 return net_xmit_eval(err
);
968 /* This routine just queues the buffer for sending.
970 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
971 * otherwise socket can stall.
973 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
975 struct tcp_sock
*tp
= tcp_sk(sk
);
977 /* Advance write_seq and place onto the write_queue. */
978 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
979 skb_header_release(skb
);
980 tcp_add_write_queue_tail(sk
, skb
);
981 sk
->sk_wmem_queued
+= skb
->truesize
;
982 sk_mem_charge(sk
, skb
->truesize
);
985 /* Initialize TSO segments for a packet. */
986 static void tcp_set_skb_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
987 unsigned int mss_now
)
989 /* Make sure we own this skb before messing gso_size/gso_segs */
990 WARN_ON_ONCE(skb_cloned(skb
));
992 if (skb
->len
<= mss_now
|| skb
->ip_summed
== CHECKSUM_NONE
) {
993 /* Avoid the costly divide in the normal
996 skb_shinfo(skb
)->gso_segs
= 1;
997 skb_shinfo(skb
)->gso_size
= 0;
998 skb_shinfo(skb
)->gso_type
= 0;
1000 skb_shinfo(skb
)->gso_segs
= DIV_ROUND_UP(skb
->len
, mss_now
);
1001 skb_shinfo(skb
)->gso_size
= mss_now
;
1002 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
1006 /* When a modification to fackets out becomes necessary, we need to check
1007 * skb is counted to fackets_out or not.
1009 static void tcp_adjust_fackets_out(struct sock
*sk
, const struct sk_buff
*skb
,
1012 struct tcp_sock
*tp
= tcp_sk(sk
);
1014 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
1017 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
1018 tp
->fackets_out
-= decr
;
1021 /* Pcount in the middle of the write queue got changed, we need to do various
1022 * tweaks to fix counters
1024 static void tcp_adjust_pcount(struct sock
*sk
, const struct sk_buff
*skb
, int decr
)
1026 struct tcp_sock
*tp
= tcp_sk(sk
);
1028 tp
->packets_out
-= decr
;
1030 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1031 tp
->sacked_out
-= decr
;
1032 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1033 tp
->retrans_out
-= decr
;
1034 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
1035 tp
->lost_out
-= decr
;
1037 /* Reno case is special. Sigh... */
1038 if (tcp_is_reno(tp
) && decr
> 0)
1039 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
1041 tcp_adjust_fackets_out(sk
, skb
, decr
);
1043 if (tp
->lost_skb_hint
&&
1044 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
1045 (tcp_is_fack(tp
) || (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)))
1046 tp
->lost_cnt_hint
-= decr
;
1048 tcp_verify_left_out(tp
);
1051 /* Function to create two new TCP segments. Shrinks the given segment
1052 * to the specified size and appends a new segment with the rest of the
1053 * packet to the list. This won't be called frequently, I hope.
1054 * Remember, these are still headerless SKBs at this point.
1056 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
1057 unsigned int mss_now
)
1059 struct tcp_sock
*tp
= tcp_sk(sk
);
1060 struct sk_buff
*buff
;
1061 int nsize
, old_factor
;
1065 if (WARN_ON(len
> skb
->len
))
1068 nsize
= skb_headlen(skb
) - len
;
1072 if (skb_unclone(skb
, GFP_ATOMIC
))
1075 /* Get a new skb... force flag on. */
1076 buff
= sk_stream_alloc_skb(sk
, nsize
, GFP_ATOMIC
);
1078 return -ENOMEM
; /* We'll just try again later. */
1080 sk
->sk_wmem_queued
+= buff
->truesize
;
1081 sk_mem_charge(sk
, buff
->truesize
);
1082 nlen
= skb
->len
- len
- nsize
;
1083 buff
->truesize
+= nlen
;
1084 skb
->truesize
-= nlen
;
1086 /* Correct the sequence numbers. */
1087 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1088 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1089 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1091 /* PSH and FIN should only be set in the second packet. */
1092 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1093 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1094 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1095 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1097 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
1098 /* Copy and checksum data tail into the new buffer. */
1099 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
1100 skb_put(buff
, nsize
),
1105 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
1107 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1108 skb_split(skb
, buff
, len
);
1111 buff
->ip_summed
= skb
->ip_summed
;
1113 /* Looks stupid, but our code really uses when of
1114 * skbs, which it never sent before. --ANK
1116 TCP_SKB_CB(buff
)->when
= TCP_SKB_CB(skb
)->when
;
1117 buff
->tstamp
= skb
->tstamp
;
1119 old_factor
= tcp_skb_pcount(skb
);
1121 /* Fix up tso_factor for both original and new SKB. */
1122 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1123 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1125 /* If this packet has been sent out already, we must
1126 * adjust the various packet counters.
1128 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1129 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1130 tcp_skb_pcount(buff
);
1133 tcp_adjust_pcount(sk
, skb
, diff
);
1136 /* Link BUFF into the send queue. */
1137 skb_header_release(buff
);
1138 tcp_insert_write_queue_after(skb
, buff
, sk
);
1143 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1144 * eventually). The difference is that pulled data not copied, but
1145 * immediately discarded.
1147 static void __pskb_trim_head(struct sk_buff
*skb
, int len
)
1151 eat
= min_t(int, len
, skb_headlen(skb
));
1153 __skb_pull(skb
, eat
);
1160 for (i
= 0; i
< skb_shinfo(skb
)->nr_frags
; i
++) {
1161 int size
= skb_frag_size(&skb_shinfo(skb
)->frags
[i
]);
1164 skb_frag_unref(skb
, i
);
1167 skb_shinfo(skb
)->frags
[k
] = skb_shinfo(skb
)->frags
[i
];
1169 skb_shinfo(skb
)->frags
[k
].page_offset
+= eat
;
1170 skb_frag_size_sub(&skb_shinfo(skb
)->frags
[k
], eat
);
1176 skb_shinfo(skb
)->nr_frags
= k
;
1178 skb_reset_tail_pointer(skb
);
1179 skb
->data_len
-= len
;
1180 skb
->len
= skb
->data_len
;
1183 /* Remove acked data from a packet in the transmit queue. */
1184 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1186 if (skb_unclone(skb
, GFP_ATOMIC
))
1189 __pskb_trim_head(skb
, len
);
1191 TCP_SKB_CB(skb
)->seq
+= len
;
1192 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1194 skb
->truesize
-= len
;
1195 sk
->sk_wmem_queued
-= len
;
1196 sk_mem_uncharge(sk
, len
);
1197 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
1199 /* Any change of skb->len requires recalculation of tso factor. */
1200 if (tcp_skb_pcount(skb
) > 1)
1201 tcp_set_skb_tso_segs(sk
, skb
, tcp_skb_mss(skb
));
1206 /* Calculate MSS not accounting any TCP options. */
1207 static inline int __tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1209 const struct tcp_sock
*tp
= tcp_sk(sk
);
1210 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1213 /* Calculate base mss without TCP options:
1214 It is MMS_S - sizeof(tcphdr) of rfc1122
1216 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1218 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1219 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1220 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1222 if (dst
&& dst_allfrag(dst
))
1223 mss_now
-= icsk
->icsk_af_ops
->net_frag_header_len
;
1226 /* Clamp it (mss_clamp does not include tcp options) */
1227 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1228 mss_now
= tp
->rx_opt
.mss_clamp
;
1230 /* Now subtract optional transport overhead */
1231 mss_now
-= icsk
->icsk_ext_hdr_len
;
1233 /* Then reserve room for full set of TCP options and 8 bytes of data */
1239 /* Calculate MSS. Not accounting for SACKs here. */
1240 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1242 /* Subtract TCP options size, not including SACKs */
1243 return __tcp_mtu_to_mss(sk
, pmtu
) -
1244 (tcp_sk(sk
)->tcp_header_len
- sizeof(struct tcphdr
));
1247 /* Inverse of above */
1248 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1250 const struct tcp_sock
*tp
= tcp_sk(sk
);
1251 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1255 tp
->tcp_header_len
+
1256 icsk
->icsk_ext_hdr_len
+
1257 icsk
->icsk_af_ops
->net_header_len
;
1259 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1260 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1261 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1263 if (dst
&& dst_allfrag(dst
))
1264 mtu
+= icsk
->icsk_af_ops
->net_frag_header_len
;
1269 /* MTU probing init per socket */
1270 void tcp_mtup_init(struct sock
*sk
)
1272 struct tcp_sock
*tp
= tcp_sk(sk
);
1273 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1275 icsk
->icsk_mtup
.enabled
= sysctl_tcp_mtu_probing
> 1;
1276 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1277 icsk
->icsk_af_ops
->net_header_len
;
1278 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, sysctl_tcp_base_mss
);
1279 icsk
->icsk_mtup
.probe_size
= 0;
1281 EXPORT_SYMBOL(tcp_mtup_init
);
1283 /* This function synchronize snd mss to current pmtu/exthdr set.
1285 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1286 for TCP options, but includes only bare TCP header.
1288 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1289 It is minimum of user_mss and mss received with SYN.
1290 It also does not include TCP options.
1292 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1294 tp->mss_cache is current effective sending mss, including
1295 all tcp options except for SACKs. It is evaluated,
1296 taking into account current pmtu, but never exceeds
1297 tp->rx_opt.mss_clamp.
1299 NOTE1. rfc1122 clearly states that advertised MSS
1300 DOES NOT include either tcp or ip options.
1302 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1303 are READ ONLY outside this function. --ANK (980731)
1305 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1307 struct tcp_sock
*tp
= tcp_sk(sk
);
1308 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1311 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1312 icsk
->icsk_mtup
.search_high
= pmtu
;
1314 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1315 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1317 /* And store cached results */
1318 icsk
->icsk_pmtu_cookie
= pmtu
;
1319 if (icsk
->icsk_mtup
.enabled
)
1320 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1321 tp
->mss_cache
= mss_now
;
1325 EXPORT_SYMBOL(tcp_sync_mss
);
1327 /* Compute the current effective MSS, taking SACKs and IP options,
1328 * and even PMTU discovery events into account.
1330 unsigned int tcp_current_mss(struct sock
*sk
)
1332 const struct tcp_sock
*tp
= tcp_sk(sk
);
1333 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1335 unsigned int header_len
;
1336 struct tcp_out_options opts
;
1337 struct tcp_md5sig_key
*md5
;
1339 mss_now
= tp
->mss_cache
;
1342 u32 mtu
= dst_mtu(dst
);
1343 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1344 mss_now
= tcp_sync_mss(sk
, mtu
);
1347 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1348 sizeof(struct tcphdr
);
1349 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1350 * some common options. If this is an odd packet (because we have SACK
1351 * blocks etc) then our calculated header_len will be different, and
1352 * we have to adjust mss_now correspondingly */
1353 if (header_len
!= tp
->tcp_header_len
) {
1354 int delta
= (int) header_len
- tp
->tcp_header_len
;
1361 /* Congestion window validation. (RFC2861) */
1362 static void tcp_cwnd_validate(struct sock
*sk
)
1364 struct tcp_sock
*tp
= tcp_sk(sk
);
1366 if (tp
->packets_out
>= tp
->snd_cwnd
) {
1367 /* Network is feed fully. */
1368 tp
->snd_cwnd_used
= 0;
1369 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1371 /* Network starves. */
1372 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1373 tp
->snd_cwnd_used
= tp
->packets_out
;
1375 if (sysctl_tcp_slow_start_after_idle
&&
1376 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1377 tcp_cwnd_application_limited(sk
);
1381 /* Returns the portion of skb which can be sent right away without
1382 * introducing MSS oddities to segment boundaries. In rare cases where
1383 * mss_now != mss_cache, we will request caller to create a small skb
1384 * per input skb which could be mostly avoided here (if desired).
1386 * We explicitly want to create a request for splitting write queue tail
1387 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
1388 * thus all the complexity (cwnd_len is always MSS multiple which we
1389 * return whenever allowed by the other factors). Basically we need the
1390 * modulo only when the receiver window alone is the limiting factor or
1391 * when we would be allowed to send the split-due-to-Nagle skb fully.
1393 static unsigned int tcp_mss_split_point(const struct sock
*sk
, const struct sk_buff
*skb
,
1394 unsigned int mss_now
, unsigned int max_segs
)
1396 const struct tcp_sock
*tp
= tcp_sk(sk
);
1397 u32 needed
, window
, max_len
;
1399 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1400 max_len
= mss_now
* max_segs
;
1402 if (likely(max_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1405 needed
= min(skb
->len
, window
);
1407 if (max_len
<= needed
)
1410 return needed
- needed
% mss_now
;
1413 /* Can at least one segment of SKB be sent right now, according to the
1414 * congestion window rules? If so, return how many segments are allowed.
1416 static inline unsigned int tcp_cwnd_test(const struct tcp_sock
*tp
,
1417 const struct sk_buff
*skb
)
1419 u32 in_flight
, cwnd
;
1421 /* Don't be strict about the congestion window for the final FIN. */
1422 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
1423 tcp_skb_pcount(skb
) == 1)
1426 in_flight
= tcp_packets_in_flight(tp
);
1427 cwnd
= tp
->snd_cwnd
;
1428 if (in_flight
< cwnd
)
1429 return (cwnd
- in_flight
);
1434 /* Initialize TSO state of a skb.
1435 * This must be invoked the first time we consider transmitting
1436 * SKB onto the wire.
1438 static int tcp_init_tso_segs(const struct sock
*sk
, struct sk_buff
*skb
,
1439 unsigned int mss_now
)
1441 int tso_segs
= tcp_skb_pcount(skb
);
1443 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1444 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1445 tso_segs
= tcp_skb_pcount(skb
);
1450 /* Minshall's variant of the Nagle send check. */
1451 static inline bool tcp_minshall_check(const struct tcp_sock
*tp
)
1453 return after(tp
->snd_sml
, tp
->snd_una
) &&
1454 !after(tp
->snd_sml
, tp
->snd_nxt
);
1457 /* Return false, if packet can be sent now without violation Nagle's rules:
1458 * 1. It is full sized.
1459 * 2. Or it contains FIN. (already checked by caller)
1460 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1461 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1462 * With Minshall's modification: all sent small packets are ACKed.
1464 static inline bool tcp_nagle_check(const struct tcp_sock
*tp
,
1465 const struct sk_buff
*skb
,
1466 unsigned int mss_now
, int nonagle
)
1468 return skb
->len
< mss_now
&&
1469 ((nonagle
& TCP_NAGLE_CORK
) ||
1470 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
)));
1473 /* Return true if the Nagle test allows this packet to be
1476 static inline bool tcp_nagle_test(const struct tcp_sock
*tp
, const struct sk_buff
*skb
,
1477 unsigned int cur_mss
, int nonagle
)
1479 /* Nagle rule does not apply to frames, which sit in the middle of the
1480 * write_queue (they have no chances to get new data).
1482 * This is implemented in the callers, where they modify the 'nonagle'
1483 * argument based upon the location of SKB in the send queue.
1485 if (nonagle
& TCP_NAGLE_PUSH
)
1488 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1489 if (tcp_urg_mode(tp
) || (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
))
1492 if (!tcp_nagle_check(tp
, skb
, cur_mss
, nonagle
))
1498 /* Does at least the first segment of SKB fit into the send window? */
1499 static bool tcp_snd_wnd_test(const struct tcp_sock
*tp
,
1500 const struct sk_buff
*skb
,
1501 unsigned int cur_mss
)
1503 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1505 if (skb
->len
> cur_mss
)
1506 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1508 return !after(end_seq
, tcp_wnd_end(tp
));
1511 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1512 * should be put on the wire right now. If so, it returns the number of
1513 * packets allowed by the congestion window.
1515 static unsigned int tcp_snd_test(const struct sock
*sk
, struct sk_buff
*skb
,
1516 unsigned int cur_mss
, int nonagle
)
1518 const struct tcp_sock
*tp
= tcp_sk(sk
);
1519 unsigned int cwnd_quota
;
1521 tcp_init_tso_segs(sk
, skb
, cur_mss
);
1523 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1526 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1527 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1533 /* Test if sending is allowed right now. */
1534 bool tcp_may_send_now(struct sock
*sk
)
1536 const struct tcp_sock
*tp
= tcp_sk(sk
);
1537 struct sk_buff
*skb
= tcp_send_head(sk
);
1540 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1541 (tcp_skb_is_last(sk
, skb
) ?
1542 tp
->nonagle
: TCP_NAGLE_PUSH
));
1545 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1546 * which is put after SKB on the list. It is very much like
1547 * tcp_fragment() except that it may make several kinds of assumptions
1548 * in order to speed up the splitting operation. In particular, we
1549 * know that all the data is in scatter-gather pages, and that the
1550 * packet has never been sent out before (and thus is not cloned).
1552 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1553 unsigned int mss_now
, gfp_t gfp
)
1555 struct sk_buff
*buff
;
1556 int nlen
= skb
->len
- len
;
1559 /* All of a TSO frame must be composed of paged data. */
1560 if (skb
->len
!= skb
->data_len
)
1561 return tcp_fragment(sk
, skb
, len
, mss_now
);
1563 buff
= sk_stream_alloc_skb(sk
, 0, gfp
);
1564 if (unlikely(buff
== NULL
))
1567 sk
->sk_wmem_queued
+= buff
->truesize
;
1568 sk_mem_charge(sk
, buff
->truesize
);
1569 buff
->truesize
+= nlen
;
1570 skb
->truesize
-= nlen
;
1572 /* Correct the sequence numbers. */
1573 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1574 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1575 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1577 /* PSH and FIN should only be set in the second packet. */
1578 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1579 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1580 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1582 /* This packet was never sent out yet, so no SACK bits. */
1583 TCP_SKB_CB(buff
)->sacked
= 0;
1585 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1586 skb_split(skb
, buff
, len
);
1588 /* Fix up tso_factor for both original and new SKB. */
1589 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1590 tcp_set_skb_tso_segs(sk
, buff
, mss_now
);
1592 /* Link BUFF into the send queue. */
1593 skb_header_release(buff
);
1594 tcp_insert_write_queue_after(skb
, buff
, sk
);
1599 /* Try to defer sending, if possible, in order to minimize the amount
1600 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1602 * This algorithm is from John Heffner.
1604 static bool tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
)
1606 struct tcp_sock
*tp
= tcp_sk(sk
);
1607 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1608 u32 send_win
, cong_win
, limit
, in_flight
;
1611 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1614 if (icsk
->icsk_ca_state
!= TCP_CA_Open
)
1617 /* Defer for less than two clock ticks. */
1618 if (tp
->tso_deferred
&&
1619 (((u32
)jiffies
<< 1) >> 1) - (tp
->tso_deferred
>> 1) > 1)
1622 in_flight
= tcp_packets_in_flight(tp
);
1624 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1626 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1628 /* From in_flight test above, we know that cwnd > in_flight. */
1629 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1631 limit
= min(send_win
, cong_win
);
1633 /* If a full-sized TSO skb can be sent, do it. */
1634 if (limit
>= min_t(unsigned int, sk
->sk_gso_max_size
,
1635 tp
->xmit_size_goal_segs
* tp
->mss_cache
))
1638 /* Middle in queue won't get any more data, full sendable already? */
1639 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1642 win_divisor
= ACCESS_ONCE(sysctl_tcp_tso_win_divisor
);
1644 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1646 /* If at least some fraction of a window is available,
1649 chunk
/= win_divisor
;
1653 /* Different approach, try not to defer past a single
1654 * ACK. Receiver should ACK every other full sized
1655 * frame, so if we have space for more than 3 frames
1658 if (limit
> tcp_max_tso_deferred_mss(tp
) * tp
->mss_cache
)
1662 /* Ok, it looks like it is advisable to defer.
1663 * Do not rearm the timer if already set to not break TCP ACK clocking.
1665 if (!tp
->tso_deferred
)
1666 tp
->tso_deferred
= 1 | (jiffies
<< 1);
1671 tp
->tso_deferred
= 0;
1675 /* Create a new MTU probe if we are ready.
1676 * MTU probe is regularly attempting to increase the path MTU by
1677 * deliberately sending larger packets. This discovers routing
1678 * changes resulting in larger path MTUs.
1680 * Returns 0 if we should wait to probe (no cwnd available),
1681 * 1 if a probe was sent,
1684 static int tcp_mtu_probe(struct sock
*sk
)
1686 struct tcp_sock
*tp
= tcp_sk(sk
);
1687 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1688 struct sk_buff
*skb
, *nskb
, *next
;
1695 /* Not currently probing/verifying,
1697 * have enough cwnd, and
1698 * not SACKing (the variable headers throw things off) */
1699 if (!icsk
->icsk_mtup
.enabled
||
1700 icsk
->icsk_mtup
.probe_size
||
1701 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1702 tp
->snd_cwnd
< 11 ||
1703 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
)
1706 /* Very simple search strategy: just double the MSS. */
1707 mss_now
= tcp_current_mss(sk
);
1708 probe_size
= 2 * tp
->mss_cache
;
1709 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1710 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
)) {
1711 /* TODO: set timer for probe_converge_event */
1715 /* Have enough data in the send queue to probe? */
1716 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1719 if (tp
->snd_wnd
< size_needed
)
1721 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1724 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1725 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1726 if (!tcp_packets_in_flight(tp
))
1732 /* We're allowed to probe. Build it now. */
1733 if ((nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
)) == NULL
)
1735 sk
->sk_wmem_queued
+= nskb
->truesize
;
1736 sk_mem_charge(sk
, nskb
->truesize
);
1738 skb
= tcp_send_head(sk
);
1740 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
1741 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
1742 TCP_SKB_CB(nskb
)->tcp_flags
= TCPHDR_ACK
;
1743 TCP_SKB_CB(nskb
)->sacked
= 0;
1745 nskb
->ip_summed
= skb
->ip_summed
;
1747 tcp_insert_write_queue_before(nskb
, skb
, sk
);
1750 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
1751 copy
= min_t(int, skb
->len
, probe_size
- len
);
1752 if (nskb
->ip_summed
)
1753 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
1755 nskb
->csum
= skb_copy_and_csum_bits(skb
, 0,
1756 skb_put(nskb
, copy
),
1759 if (skb
->len
<= copy
) {
1760 /* We've eaten all the data from this skb.
1762 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
1763 tcp_unlink_write_queue(skb
, sk
);
1764 sk_wmem_free_skb(sk
, skb
);
1766 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
&
1767 ~(TCPHDR_FIN
|TCPHDR_PSH
);
1768 if (!skb_shinfo(skb
)->nr_frags
) {
1769 skb_pull(skb
, copy
);
1770 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
1771 skb
->csum
= csum_partial(skb
->data
,
1774 __pskb_trim_head(skb
, copy
);
1775 tcp_set_skb_tso_segs(sk
, skb
, mss_now
);
1777 TCP_SKB_CB(skb
)->seq
+= copy
;
1782 if (len
>= probe_size
)
1785 tcp_init_tso_segs(sk
, nskb
, nskb
->len
);
1787 /* We're ready to send. If this fails, the probe will
1788 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1789 TCP_SKB_CB(nskb
)->when
= tcp_time_stamp
;
1790 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
1791 /* Decrement cwnd here because we are sending
1792 * effectively two packets. */
1794 tcp_event_new_data_sent(sk
, nskb
);
1796 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
1797 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
1798 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
1806 /* This routine writes packets to the network. It advances the
1807 * send_head. This happens as incoming acks open up the remote
1810 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1811 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1812 * account rare use of URG, this is not a big flaw.
1814 * Send at most one packet when push_one > 0. Temporarily ignore
1815 * cwnd limit to force at most one packet out when push_one == 2.
1817 * Returns true, if no segments are in flight and we have queued segments,
1818 * but cannot send anything now because of SWS or another problem.
1820 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
1821 int push_one
, gfp_t gfp
)
1823 struct tcp_sock
*tp
= tcp_sk(sk
);
1824 struct sk_buff
*skb
;
1825 unsigned int tso_segs
, sent_pkts
;
1832 /* Do MTU probing. */
1833 result
= tcp_mtu_probe(sk
);
1836 } else if (result
> 0) {
1841 while ((skb
= tcp_send_head(sk
))) {
1844 tso_segs
= tcp_init_tso_segs(sk
, skb
, mss_now
);
1847 if (unlikely(tp
->repair
) && tp
->repair_queue
== TCP_SEND_QUEUE
)
1848 goto repair
; /* Skip network transmission */
1850 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1853 /* Force out a loss probe pkt. */
1859 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
)))
1862 if (tso_segs
== 1) {
1863 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
1864 (tcp_skb_is_last(sk
, skb
) ?
1865 nonagle
: TCP_NAGLE_PUSH
))))
1868 if (!push_one
&& tcp_tso_should_defer(sk
, skb
))
1872 /* TCP Small Queues :
1873 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
1875 * - better RTT estimation and ACK scheduling
1879 limit
= max(skb
->truesize
, sk
->sk_pacing_rate
>> 10);
1881 if (atomic_read(&sk
->sk_wmem_alloc
) > limit
) {
1882 set_bit(TSQ_THROTTLED
, &tp
->tsq_flags
);
1887 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
1888 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
1891 sk
->sk_gso_max_segs
));
1893 if (skb
->len
> limit
&&
1894 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
, gfp
)))
1897 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
1899 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
1903 /* Advance the send_head. This one is sent out.
1904 * This call will increment packets_out.
1906 tcp_event_new_data_sent(sk
, skb
);
1908 tcp_minshall_update(tp
, mss_now
, skb
);
1909 sent_pkts
+= tcp_skb_pcount(skb
);
1915 if (likely(sent_pkts
)) {
1916 if (tcp_in_cwnd_reduction(sk
))
1917 tp
->prr_out
+= sent_pkts
;
1919 /* Send one loss probe per tail loss episode. */
1921 tcp_schedule_loss_probe(sk
);
1922 tcp_cwnd_validate(sk
);
1925 return (push_one
== 2) || (!tp
->packets_out
&& tcp_send_head(sk
));
1928 bool tcp_schedule_loss_probe(struct sock
*sk
)
1930 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1931 struct tcp_sock
*tp
= tcp_sk(sk
);
1932 u32 timeout
, tlp_time_stamp
, rto_time_stamp
;
1933 u32 rtt
= tp
->srtt
>> 3;
1935 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
))
1937 /* No consecutive loss probes. */
1938 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)) {
1942 /* Don't do any loss probe on a Fast Open connection before 3WHS
1945 if (sk
->sk_state
== TCP_SYN_RECV
)
1948 /* TLP is only scheduled when next timer event is RTO. */
1949 if (icsk
->icsk_pending
!= ICSK_TIME_RETRANS
)
1952 /* Schedule a loss probe in 2*RTT for SACK capable connections
1953 * in Open state, that are either limited by cwnd or application.
1955 if (sysctl_tcp_early_retrans
< 3 || !rtt
|| !tp
->packets_out
||
1956 !tcp_is_sack(tp
) || inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
1959 if ((tp
->snd_cwnd
> tcp_packets_in_flight(tp
)) &&
1963 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
1964 * for delayed ack when there's one outstanding packet.
1967 if (tp
->packets_out
== 1)
1968 timeout
= max_t(u32
, timeout
,
1969 (rtt
+ (rtt
>> 1) + TCP_DELACK_MAX
));
1970 timeout
= max_t(u32
, timeout
, msecs_to_jiffies(10));
1972 /* If RTO is shorter, just schedule TLP in its place. */
1973 tlp_time_stamp
= tcp_time_stamp
+ timeout
;
1974 rto_time_stamp
= (u32
)inet_csk(sk
)->icsk_timeout
;
1975 if ((s32
)(tlp_time_stamp
- rto_time_stamp
) > 0) {
1976 s32 delta
= rto_time_stamp
- tcp_time_stamp
;
1981 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_LOSS_PROBE
, timeout
,
1986 /* When probe timeout (PTO) fires, send a new segment if one exists, else
1987 * retransmit the last segment.
1989 void tcp_send_loss_probe(struct sock
*sk
)
1991 struct tcp_sock
*tp
= tcp_sk(sk
);
1992 struct sk_buff
*skb
;
1994 int mss
= tcp_current_mss(sk
);
1997 if (tcp_send_head(sk
) != NULL
) {
1998 err
= tcp_write_xmit(sk
, mss
, TCP_NAGLE_OFF
, 2, GFP_ATOMIC
);
2002 /* At most one outstanding TLP retransmission. */
2003 if (tp
->tlp_high_seq
)
2006 /* Retransmit last segment. */
2007 skb
= tcp_write_queue_tail(sk
);
2011 pcount
= tcp_skb_pcount(skb
);
2012 if (WARN_ON(!pcount
))
2015 if ((pcount
> 1) && (skb
->len
> (pcount
- 1) * mss
)) {
2016 if (unlikely(tcp_fragment(sk
, skb
, (pcount
- 1) * mss
, mss
)))
2018 skb
= tcp_write_queue_tail(sk
);
2021 if (WARN_ON(!skb
|| !tcp_skb_pcount(skb
)))
2024 /* Probe with zero data doesn't trigger fast recovery. */
2026 err
= __tcp_retransmit_skb(sk
, skb
);
2028 /* Record snd_nxt for loss detection. */
2030 tp
->tlp_high_seq
= tp
->snd_nxt
;
2033 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2034 inet_csk(sk
)->icsk_rto
,
2038 NET_INC_STATS_BH(sock_net(sk
),
2039 LINUX_MIB_TCPLOSSPROBES
);
2043 /* Push out any pending frames which were held back due to
2044 * TCP_CORK or attempt at coalescing tiny packets.
2045 * The socket must be locked by the caller.
2047 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
2050 /* If we are closed, the bytes will have to remain here.
2051 * In time closedown will finish, we empty the write queue and
2052 * all will be happy.
2054 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
2057 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0,
2058 sk_gfp_atomic(sk
, GFP_ATOMIC
)))
2059 tcp_check_probe_timer(sk
);
2062 /* Send _single_ skb sitting at the send head. This function requires
2063 * true push pending frames to setup probe timer etc.
2065 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
2067 struct sk_buff
*skb
= tcp_send_head(sk
);
2069 BUG_ON(!skb
|| skb
->len
< mss_now
);
2071 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
2074 /* This function returns the amount that we can raise the
2075 * usable window based on the following constraints
2077 * 1. The window can never be shrunk once it is offered (RFC 793)
2078 * 2. We limit memory per socket
2081 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2082 * RECV.NEXT + RCV.WIN fixed until:
2083 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2085 * i.e. don't raise the right edge of the window until you can raise
2086 * it at least MSS bytes.
2088 * Unfortunately, the recommended algorithm breaks header prediction,
2089 * since header prediction assumes th->window stays fixed.
2091 * Strictly speaking, keeping th->window fixed violates the receiver
2092 * side SWS prevention criteria. The problem is that under this rule
2093 * a stream of single byte packets will cause the right side of the
2094 * window to always advance by a single byte.
2096 * Of course, if the sender implements sender side SWS prevention
2097 * then this will not be a problem.
2099 * BSD seems to make the following compromise:
2101 * If the free space is less than the 1/4 of the maximum
2102 * space available and the free space is less than 1/2 mss,
2103 * then set the window to 0.
2104 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2105 * Otherwise, just prevent the window from shrinking
2106 * and from being larger than the largest representable value.
2108 * This prevents incremental opening of the window in the regime
2109 * where TCP is limited by the speed of the reader side taking
2110 * data out of the TCP receive queue. It does nothing about
2111 * those cases where the window is constrained on the sender side
2112 * because the pipeline is full.
2114 * BSD also seems to "accidentally" limit itself to windows that are a
2115 * multiple of MSS, at least until the free space gets quite small.
2116 * This would appear to be a side effect of the mbuf implementation.
2117 * Combining these two algorithms results in the observed behavior
2118 * of having a fixed window size at almost all times.
2120 * Below we obtain similar behavior by forcing the offered window to
2121 * a multiple of the mss when it is feasible to do so.
2123 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2124 * Regular options like TIMESTAMP are taken into account.
2126 u32
__tcp_select_window(struct sock
*sk
)
2128 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2129 struct tcp_sock
*tp
= tcp_sk(sk
);
2130 /* MSS for the peer's data. Previous versions used mss_clamp
2131 * here. I don't know if the value based on our guesses
2132 * of peer's MSS is better for the performance. It's more correct
2133 * but may be worse for the performance because of rcv_mss
2134 * fluctuations. --SAW 1998/11/1
2136 int mss
= icsk
->icsk_ack
.rcv_mss
;
2137 int free_space
= tcp_space(sk
);
2138 int full_space
= min_t(int, tp
->window_clamp
, tcp_full_space(sk
));
2141 if (mss
> full_space
)
2144 if (free_space
< (full_space
>> 1)) {
2145 icsk
->icsk_ack
.quick
= 0;
2147 if (sk_under_memory_pressure(sk
))
2148 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
2151 if (free_space
< mss
)
2155 if (free_space
> tp
->rcv_ssthresh
)
2156 free_space
= tp
->rcv_ssthresh
;
2158 /* Don't do rounding if we are using window scaling, since the
2159 * scaled window will not line up with the MSS boundary anyway.
2161 window
= tp
->rcv_wnd
;
2162 if (tp
->rx_opt
.rcv_wscale
) {
2163 window
= free_space
;
2165 /* Advertise enough space so that it won't get scaled away.
2166 * Import case: prevent zero window announcement if
2167 * 1<<rcv_wscale > mss.
2169 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
2170 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
2171 << tp
->rx_opt
.rcv_wscale
);
2173 /* Get the largest window that is a nice multiple of mss.
2174 * Window clamp already applied above.
2175 * If our current window offering is within 1 mss of the
2176 * free space we just keep it. This prevents the divide
2177 * and multiply from happening most of the time.
2178 * We also don't do any window rounding when the free space
2181 if (window
<= free_space
- mss
|| window
> free_space
)
2182 window
= (free_space
/ mss
) * mss
;
2183 else if (mss
== full_space
&&
2184 free_space
> window
+ (full_space
>> 1))
2185 window
= free_space
;
2191 /* Collapses two adjacent SKB's during retransmission. */
2192 static void tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
2194 struct tcp_sock
*tp
= tcp_sk(sk
);
2195 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
2196 int skb_size
, next_skb_size
;
2198 skb_size
= skb
->len
;
2199 next_skb_size
= next_skb
->len
;
2201 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
2203 tcp_highest_sack_combine(sk
, next_skb
, skb
);
2205 tcp_unlink_write_queue(next_skb
, sk
);
2207 skb_copy_from_linear_data(next_skb
, skb_put(skb
, next_skb_size
),
2210 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
2211 skb
->ip_summed
= CHECKSUM_PARTIAL
;
2213 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2214 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
2216 /* Update sequence range on original skb. */
2217 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
2219 /* Merge over control information. This moves PSH/FIN etc. over */
2220 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(next_skb
)->tcp_flags
;
2222 /* All done, get rid of second SKB and account for it so
2223 * packet counting does not break.
2225 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
2227 /* changed transmit queue under us so clear hints */
2228 tcp_clear_retrans_hints_partial(tp
);
2229 if (next_skb
== tp
->retransmit_skb_hint
)
2230 tp
->retransmit_skb_hint
= skb
;
2232 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
2234 sk_wmem_free_skb(sk
, next_skb
);
2237 /* Check if coalescing SKBs is legal. */
2238 static bool tcp_can_collapse(const struct sock
*sk
, const struct sk_buff
*skb
)
2240 if (tcp_skb_pcount(skb
) > 1)
2242 /* TODO: SACK collapsing could be used to remove this condition */
2243 if (skb_shinfo(skb
)->nr_frags
!= 0)
2245 if (skb_cloned(skb
))
2247 if (skb
== tcp_send_head(sk
))
2249 /* Some heurestics for collapsing over SACK'd could be invented */
2250 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2256 /* Collapse packets in the retransmit queue to make to create
2257 * less packets on the wire. This is only done on retransmission.
2259 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
2262 struct tcp_sock
*tp
= tcp_sk(sk
);
2263 struct sk_buff
*skb
= to
, *tmp
;
2266 if (!sysctl_tcp_retrans_collapse
)
2268 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2271 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
2272 if (!tcp_can_collapse(sk
, skb
))
2284 /* Punt if not enough space exists in the first SKB for
2285 * the data in the second
2287 if (skb
->len
> skb_availroom(to
))
2290 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
2293 tcp_collapse_retrans(sk
, to
);
2297 /* This retransmits one SKB. Policy decisions and retransmit queue
2298 * state updates are done by the caller. Returns non-zero if an
2299 * error occurred which prevented the send.
2301 int __tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2303 struct tcp_sock
*tp
= tcp_sk(sk
);
2304 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2305 unsigned int cur_mss
;
2307 /* Inconslusive MTU probe */
2308 if (icsk
->icsk_mtup
.probe_size
) {
2309 icsk
->icsk_mtup
.probe_size
= 0;
2312 /* Do not sent more than we queued. 1/4 is reserved for possible
2313 * copying overhead: fragmentation, tunneling, mangling etc.
2315 if (atomic_read(&sk
->sk_wmem_alloc
) >
2316 min(sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2), sk
->sk_sndbuf
))
2319 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
2320 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
2322 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2326 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
2327 return -EHOSTUNREACH
; /* Routing failure or similar. */
2329 cur_mss
= tcp_current_mss(sk
);
2331 /* If receiver has shrunk his window, and skb is out of
2332 * new window, do not retransmit it. The exception is the
2333 * case, when window is shrunk to zero. In this case
2334 * our retransmit serves as a zero window probe.
2336 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
)) &&
2337 TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
2340 if (skb
->len
> cur_mss
) {
2341 if (tcp_fragment(sk
, skb
, cur_mss
, cur_mss
))
2342 return -ENOMEM
; /* We'll try again later. */
2344 int oldpcount
= tcp_skb_pcount(skb
);
2346 if (unlikely(oldpcount
> 1)) {
2347 if (skb_unclone(skb
, GFP_ATOMIC
))
2349 tcp_init_tso_segs(sk
, skb
, cur_mss
);
2350 tcp_adjust_pcount(sk
, skb
, oldpcount
- tcp_skb_pcount(skb
));
2354 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
2356 /* Make a copy, if the first transmission SKB clone we made
2357 * is still in somebody's hands, else make a clone.
2359 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2361 /* make sure skb->data is aligned on arches that require it
2362 * and check if ack-trimming & collapsing extended the headroom
2363 * beyond what csum_start can cover.
2365 if (unlikely((NET_IP_ALIGN
&& ((unsigned long)skb
->data
& 3)) ||
2366 skb_headroom(skb
) >= 0xFFFF)) {
2367 struct sk_buff
*nskb
= __pskb_copy(skb
, MAX_TCP_HEADER
,
2369 return nskb
? tcp_transmit_skb(sk
, nskb
, 0, GFP_ATOMIC
) :
2372 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2376 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
)
2378 struct tcp_sock
*tp
= tcp_sk(sk
);
2379 int err
= __tcp_retransmit_skb(sk
, skb
);
2382 /* Update global TCP statistics. */
2383 TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
2385 tp
->total_retrans
++;
2387 #if FASTRETRANS_DEBUG > 0
2388 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2389 net_dbg_ratelimited("retrans_out leaked\n");
2392 if (!tp
->retrans_out
)
2393 tp
->lost_retrans_low
= tp
->snd_nxt
;
2394 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
2395 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2397 /* Save stamp of the first retransmit. */
2398 if (!tp
->retrans_stamp
)
2399 tp
->retrans_stamp
= TCP_SKB_CB(skb
)->when
;
2401 tp
->undo_retrans
+= tcp_skb_pcount(skb
);
2403 /* snd_nxt is stored to detect loss of retransmitted segment,
2404 * see tcp_input.c tcp_sacktag_write_queue().
2406 TCP_SKB_CB(skb
)->ack_seq
= tp
->snd_nxt
;
2408 NET_INC_STATS_BH(sock_net(sk
), LINUX_MIB_TCPRETRANSFAIL
);
2413 /* Check if we forward retransmits are possible in the current
2414 * window/congestion state.
2416 static bool tcp_can_forward_retransmit(struct sock
*sk
)
2418 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2419 const struct tcp_sock
*tp
= tcp_sk(sk
);
2421 /* Forward retransmissions are possible only during Recovery. */
2422 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
2425 /* No forward retransmissions in Reno are possible. */
2426 if (tcp_is_reno(tp
))
2429 /* Yeah, we have to make difficult choice between forward transmission
2430 * and retransmission... Both ways have their merits...
2432 * For now we do not retransmit anything, while we have some new
2433 * segments to send. In the other cases, follow rule 3 for
2434 * NextSeg() specified in RFC3517.
2437 if (tcp_may_send_now(sk
))
2443 /* This gets called after a retransmit timeout, and the initially
2444 * retransmitted data is acknowledged. It tries to continue
2445 * resending the rest of the retransmit queue, until either
2446 * we've sent it all or the congestion window limit is reached.
2447 * If doing SACK, the first ACK which comes back for a timeout
2448 * based retransmit packet might feed us FACK information again.
2449 * If so, we use it to avoid unnecessarily retransmissions.
2451 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2453 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2454 struct tcp_sock
*tp
= tcp_sk(sk
);
2455 struct sk_buff
*skb
;
2456 struct sk_buff
*hole
= NULL
;
2459 int fwd_rexmitting
= 0;
2461 if (!tp
->packets_out
)
2465 tp
->retransmit_high
= tp
->snd_una
;
2467 if (tp
->retransmit_skb_hint
) {
2468 skb
= tp
->retransmit_skb_hint
;
2469 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2470 if (after(last_lost
, tp
->retransmit_high
))
2471 last_lost
= tp
->retransmit_high
;
2473 skb
= tcp_write_queue_head(sk
);
2474 last_lost
= tp
->snd_una
;
2477 tcp_for_write_queue_from(skb
, sk
) {
2478 __u8 sacked
= TCP_SKB_CB(skb
)->sacked
;
2480 if (skb
== tcp_send_head(sk
))
2482 /* we could do better than to assign each time */
2484 tp
->retransmit_skb_hint
= skb
;
2486 /* Assume this retransmit will generate
2487 * only one packet for congestion window
2488 * calculation purposes. This works because
2489 * tcp_retransmit_skb() will chop up the
2490 * packet to be MSS sized and all the
2491 * packet counting works out.
2493 if (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
)
2496 if (fwd_rexmitting
) {
2498 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2500 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2502 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2503 tp
->retransmit_high
= last_lost
;
2504 if (!tcp_can_forward_retransmit(sk
))
2506 /* Backtrack if necessary to non-L'ed skb */
2514 } else if (!(sacked
& TCPCB_LOST
)) {
2515 if (hole
== NULL
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2520 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2521 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2522 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2524 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2527 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2530 if (tcp_retransmit_skb(sk
, skb
))
2533 NET_INC_STATS_BH(sock_net(sk
), mib_idx
);
2535 if (tcp_in_cwnd_reduction(sk
))
2536 tp
->prr_out
+= tcp_skb_pcount(skb
);
2538 if (skb
== tcp_write_queue_head(sk
))
2539 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2540 inet_csk(sk
)->icsk_rto
,
2545 /* Send a fin. The caller locks the socket for us. This cannot be
2546 * allowed to fail queueing a FIN frame under any circumstances.
2548 void tcp_send_fin(struct sock
*sk
)
2550 struct tcp_sock
*tp
= tcp_sk(sk
);
2551 struct sk_buff
*skb
= tcp_write_queue_tail(sk
);
2554 /* Optimization, tack on the FIN if we have a queue of
2555 * unsent frames. But be careful about outgoing SACKS
2558 mss_now
= tcp_current_mss(sk
);
2560 if (tcp_send_head(sk
) != NULL
) {
2561 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_FIN
;
2562 TCP_SKB_CB(skb
)->end_seq
++;
2565 /* Socket is locked, keep trying until memory is available. */
2567 skb
= alloc_skb_fclone(MAX_TCP_HEADER
,
2574 /* Reserve space for headers and prepare control bits. */
2575 skb_reserve(skb
, MAX_TCP_HEADER
);
2576 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2577 tcp_init_nondata_skb(skb
, tp
->write_seq
,
2578 TCPHDR_ACK
| TCPHDR_FIN
);
2579 tcp_queue_skb(sk
, skb
);
2581 __tcp_push_pending_frames(sk
, mss_now
, TCP_NAGLE_OFF
);
2584 /* We get here when a process closes a file descriptor (either due to
2585 * an explicit close() or as a byproduct of exit()'ing) and there
2586 * was unread data in the receive queue. This behavior is recommended
2587 * by RFC 2525, section 2.17. -DaveM
2589 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
2591 struct sk_buff
*skb
;
2593 /* NOTE: No TCP options attached and we never retransmit this. */
2594 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
2596 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2600 /* Reserve space for headers and prepare control bits. */
2601 skb_reserve(skb
, MAX_TCP_HEADER
);
2602 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
2603 TCPHDR_ACK
| TCPHDR_RST
);
2605 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2606 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
2607 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
2609 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
2612 /* Send a crossed SYN-ACK during socket establishment.
2613 * WARNING: This routine must only be called when we have already sent
2614 * a SYN packet that crossed the incoming SYN that caused this routine
2615 * to get called. If this assumption fails then the initial rcv_wnd
2616 * and rcv_wscale values will not be correct.
2618 int tcp_send_synack(struct sock
*sk
)
2620 struct sk_buff
*skb
;
2622 skb
= tcp_write_queue_head(sk
);
2623 if (skb
== NULL
|| !(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
2624 pr_debug("%s: wrong queue state\n", __func__
);
2627 if (!(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_ACK
)) {
2628 if (skb_cloned(skb
)) {
2629 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
2632 tcp_unlink_write_queue(skb
, sk
);
2633 skb_header_release(nskb
);
2634 __tcp_add_write_queue_head(sk
, nskb
);
2635 sk_wmem_free_skb(sk
, skb
);
2636 sk
->sk_wmem_queued
+= nskb
->truesize
;
2637 sk_mem_charge(sk
, nskb
->truesize
);
2641 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ACK
;
2642 TCP_ECN_send_synack(tcp_sk(sk
), skb
);
2644 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2645 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2649 * tcp_make_synack - Prepare a SYN-ACK.
2650 * sk: listener socket
2651 * dst: dst entry attached to the SYNACK
2652 * req: request_sock pointer
2654 * Allocate one skb and build a SYNACK packet.
2655 * @dst is consumed : Caller should not use it again.
2657 struct sk_buff
*tcp_make_synack(struct sock
*sk
, struct dst_entry
*dst
,
2658 struct request_sock
*req
,
2659 struct tcp_fastopen_cookie
*foc
)
2661 struct tcp_out_options opts
;
2662 struct inet_request_sock
*ireq
= inet_rsk(req
);
2663 struct tcp_sock
*tp
= tcp_sk(sk
);
2665 struct sk_buff
*skb
;
2666 struct tcp_md5sig_key
*md5
;
2667 int tcp_header_size
;
2670 skb
= sock_wmalloc(sk
, MAX_TCP_HEADER
+ 15, 1, GFP_ATOMIC
);
2671 if (unlikely(!skb
)) {
2675 /* Reserve space for headers. */
2676 skb_reserve(skb
, MAX_TCP_HEADER
);
2678 skb_dst_set(skb
, dst
);
2679 security_skb_owned_by(skb
, sk
);
2681 mss
= dst_metric_advmss(dst
);
2682 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< mss
)
2683 mss
= tp
->rx_opt
.user_mss
;
2685 if (req
->rcv_wnd
== 0) { /* ignored for retransmitted syns */
2687 /* Set this up on the first call only */
2688 req
->window_clamp
= tp
->window_clamp
? : dst_metric(dst
, RTAX_WINDOW
);
2690 /* limit the window selection if the user enforce a smaller rx buffer */
2691 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
2692 (req
->window_clamp
> tcp_full_space(sk
) || req
->window_clamp
== 0))
2693 req
->window_clamp
= tcp_full_space(sk
);
2695 /* tcp_full_space because it is guaranteed to be the first packet */
2696 tcp_select_initial_window(tcp_full_space(sk
),
2697 mss
- (ireq
->tstamp_ok
? TCPOLEN_TSTAMP_ALIGNED
: 0),
2702 dst_metric(dst
, RTAX_INITRWND
));
2703 ireq
->rcv_wscale
= rcv_wscale
;
2706 memset(&opts
, 0, sizeof(opts
));
2707 #ifdef CONFIG_SYN_COOKIES
2708 if (unlikely(req
->cookie_ts
))
2709 TCP_SKB_CB(skb
)->when
= cookie_init_timestamp(req
);
2712 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
2713 tcp_header_size
= tcp_synack_options(sk
, req
, mss
, skb
, &opts
, &md5
,
2716 skb_push(skb
, tcp_header_size
);
2717 skb_reset_transport_header(skb
);
2720 memset(th
, 0, sizeof(struct tcphdr
));
2723 TCP_ECN_make_synack(req
, th
);
2724 th
->source
= htons(ireq
->ir_num
);
2725 th
->dest
= ireq
->ir_rmt_port
;
2726 /* Setting of flags are superfluous here for callers (and ECE is
2727 * not even correctly set)
2729 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
2730 TCPHDR_SYN
| TCPHDR_ACK
);
2732 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
2733 /* XXX data is queued and acked as is. No buffer/window check */
2734 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_nxt
);
2736 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2737 th
->window
= htons(min(req
->rcv_wnd
, 65535U));
2738 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
2739 th
->doff
= (tcp_header_size
>> 2);
2740 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
, tcp_skb_pcount(skb
));
2742 #ifdef CONFIG_TCP_MD5SIG
2743 /* Okay, we have all we need - do the md5 hash if needed */
2745 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
2746 md5
, NULL
, req
, skb
);
2752 EXPORT_SYMBOL(tcp_make_synack
);
2754 /* Do all connect socket setups that can be done AF independent. */
2755 void tcp_connect_init(struct sock
*sk
)
2757 const struct dst_entry
*dst
= __sk_dst_get(sk
);
2758 struct tcp_sock
*tp
= tcp_sk(sk
);
2761 /* We'll fix this up when we get a response from the other end.
2762 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2764 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
2765 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
2767 #ifdef CONFIG_TCP_MD5SIG
2768 if (tp
->af_specific
->md5_lookup(sk
, sk
) != NULL
)
2769 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
2772 /* If user gave his TCP_MAXSEG, record it to clamp */
2773 if (tp
->rx_opt
.user_mss
)
2774 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2777 tcp_sync_mss(sk
, dst_mtu(dst
));
2779 if (!tp
->window_clamp
)
2780 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
2781 tp
->advmss
= dst_metric_advmss(dst
);
2782 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
2783 tp
->advmss
= tp
->rx_opt
.user_mss
;
2785 tcp_initialize_rcv_mss(sk
);
2787 /* limit the window selection if the user enforce a smaller rx buffer */
2788 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
2789 (tp
->window_clamp
> tcp_full_space(sk
) || tp
->window_clamp
== 0))
2790 tp
->window_clamp
= tcp_full_space(sk
);
2792 tcp_select_initial_window(tcp_full_space(sk
),
2793 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
2796 sysctl_tcp_window_scaling
,
2798 dst_metric(dst
, RTAX_INITRWND
));
2800 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
2801 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
2804 sock_reset_flag(sk
, SOCK_DONE
);
2807 tp
->snd_una
= tp
->write_seq
;
2808 tp
->snd_sml
= tp
->write_seq
;
2809 tp
->snd_up
= tp
->write_seq
;
2810 tp
->snd_nxt
= tp
->write_seq
;
2812 if (likely(!tp
->repair
))
2815 tp
->rcv_tstamp
= tcp_time_stamp
;
2816 tp
->rcv_wup
= tp
->rcv_nxt
;
2817 tp
->copied_seq
= tp
->rcv_nxt
;
2819 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
2820 inet_csk(sk
)->icsk_retransmits
= 0;
2821 tcp_clear_retrans(tp
);
2824 static void tcp_connect_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
2826 struct tcp_sock
*tp
= tcp_sk(sk
);
2827 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
2829 tcb
->end_seq
+= skb
->len
;
2830 skb_header_release(skb
);
2831 __tcp_add_write_queue_tail(sk
, skb
);
2832 sk
->sk_wmem_queued
+= skb
->truesize
;
2833 sk_mem_charge(sk
, skb
->truesize
);
2834 tp
->write_seq
= tcb
->end_seq
;
2835 tp
->packets_out
+= tcp_skb_pcount(skb
);
2838 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
2839 * queue a data-only packet after the regular SYN, such that regular SYNs
2840 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
2841 * only the SYN sequence, the data are retransmitted in the first ACK.
2842 * If cookie is not cached or other error occurs, falls back to send a
2843 * regular SYN with Fast Open cookie request option.
2845 static int tcp_send_syn_data(struct sock
*sk
, struct sk_buff
*syn
)
2847 struct tcp_sock
*tp
= tcp_sk(sk
);
2848 struct tcp_fastopen_request
*fo
= tp
->fastopen_req
;
2849 int syn_loss
= 0, space
, i
, err
= 0, iovlen
= fo
->data
->msg_iovlen
;
2850 struct sk_buff
*syn_data
= NULL
, *data
;
2851 unsigned long last_syn_loss
= 0;
2853 tp
->rx_opt
.mss_clamp
= tp
->advmss
; /* If MSS is not cached */
2854 tcp_fastopen_cache_get(sk
, &tp
->rx_opt
.mss_clamp
, &fo
->cookie
,
2855 &syn_loss
, &last_syn_loss
);
2856 /* Recurring FO SYN losses: revert to regular handshake temporarily */
2858 time_before(jiffies
, last_syn_loss
+ (60*HZ
<< syn_loss
))) {
2859 fo
->cookie
.len
= -1;
2863 if (sysctl_tcp_fastopen
& TFO_CLIENT_NO_COOKIE
)
2864 fo
->cookie
.len
= -1;
2865 else if (fo
->cookie
.len
<= 0)
2868 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
2869 * user-MSS. Reserve maximum option space for middleboxes that add
2870 * private TCP options. The cost is reduced data space in SYN :(
2872 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->rx_opt
.mss_clamp
)
2873 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
2874 space
= __tcp_mtu_to_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
) -
2875 MAX_TCP_OPTION_SPACE
;
2877 syn_data
= skb_copy_expand(syn
, skb_headroom(syn
), space
,
2879 if (syn_data
== NULL
)
2882 for (i
= 0; i
< iovlen
&& syn_data
->len
< space
; ++i
) {
2883 struct iovec
*iov
= &fo
->data
->msg_iov
[i
];
2884 unsigned char __user
*from
= iov
->iov_base
;
2885 int len
= iov
->iov_len
;
2887 if (syn_data
->len
+ len
> space
)
2888 len
= space
- syn_data
->len
;
2889 else if (i
+ 1 == iovlen
)
2890 /* No more data pending in inet_wait_for_connect() */
2893 if (skb_add_data(syn_data
, from
, len
))
2897 /* Queue a data-only packet after the regular SYN for retransmission */
2898 data
= pskb_copy(syn_data
, sk
->sk_allocation
);
2901 TCP_SKB_CB(data
)->seq
++;
2902 TCP_SKB_CB(data
)->tcp_flags
&= ~TCPHDR_SYN
;
2903 TCP_SKB_CB(data
)->tcp_flags
= (TCPHDR_ACK
|TCPHDR_PSH
);
2904 tcp_connect_queue_skb(sk
, data
);
2905 fo
->copied
= data
->len
;
2907 if (tcp_transmit_skb(sk
, syn_data
, 0, sk
->sk_allocation
) == 0) {
2908 tp
->syn_data
= (fo
->copied
> 0);
2909 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPFASTOPENACTIVE
);
2915 /* Send a regular SYN with Fast Open cookie request option */
2916 if (fo
->cookie
.len
> 0)
2918 err
= tcp_transmit_skb(sk
, syn
, 1, sk
->sk_allocation
);
2920 tp
->syn_fastopen
= 0;
2921 kfree_skb(syn_data
);
2923 fo
->cookie
.len
= -1; /* Exclude Fast Open option for SYN retries */
2927 /* Build a SYN and send it off. */
2928 int tcp_connect(struct sock
*sk
)
2930 struct tcp_sock
*tp
= tcp_sk(sk
);
2931 struct sk_buff
*buff
;
2934 tcp_connect_init(sk
);
2936 if (unlikely(tp
->repair
)) {
2937 tcp_finish_connect(sk
, NULL
);
2941 buff
= alloc_skb_fclone(MAX_TCP_HEADER
+ 15, sk
->sk_allocation
);
2942 if (unlikely(buff
== NULL
))
2945 /* Reserve space for headers. */
2946 skb_reserve(buff
, MAX_TCP_HEADER
);
2948 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPHDR_SYN
);
2949 tp
->retrans_stamp
= TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
2950 tcp_connect_queue_skb(sk
, buff
);
2951 TCP_ECN_send_syn(sk
, buff
);
2953 /* Send off SYN; include data in Fast Open. */
2954 err
= tp
->fastopen_req
? tcp_send_syn_data(sk
, buff
) :
2955 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
2956 if (err
== -ECONNREFUSED
)
2959 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2960 * in order to make this packet get counted in tcpOutSegs.
2962 tp
->snd_nxt
= tp
->write_seq
;
2963 tp
->pushed_seq
= tp
->write_seq
;
2964 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
2966 /* Timer for repeating the SYN until an answer. */
2967 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2968 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
2971 EXPORT_SYMBOL(tcp_connect
);
2973 /* Send out a delayed ack, the caller does the policy checking
2974 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2977 void tcp_send_delayed_ack(struct sock
*sk
)
2979 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2980 int ato
= icsk
->icsk_ack
.ato
;
2981 unsigned long timeout
;
2983 if (ato
> TCP_DELACK_MIN
) {
2984 const struct tcp_sock
*tp
= tcp_sk(sk
);
2985 int max_ato
= HZ
/ 2;
2987 if (icsk
->icsk_ack
.pingpong
||
2988 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
2989 max_ato
= TCP_DELACK_MAX
;
2991 /* Slow path, intersegment interval is "high". */
2993 /* If some rtt estimate is known, use it to bound delayed ack.
2994 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2998 int rtt
= max(tp
->srtt
>> 3, TCP_DELACK_MIN
);
3004 ato
= min(ato
, max_ato
);
3007 /* Stay within the limit we were given */
3008 timeout
= jiffies
+ ato
;
3010 /* Use new timeout only if there wasn't a older one earlier. */
3011 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
3012 /* If delack timer was blocked or is about to expire,
3015 if (icsk
->icsk_ack
.blocked
||
3016 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
3021 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
3022 timeout
= icsk
->icsk_ack
.timeout
;
3024 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
3025 icsk
->icsk_ack
.timeout
= timeout
;
3026 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
3029 /* This routine sends an ack and also updates the window. */
3030 void tcp_send_ack(struct sock
*sk
)
3032 struct sk_buff
*buff
;
3034 /* If we have been reset, we may not send again. */
3035 if (sk
->sk_state
== TCP_CLOSE
)
3038 /* We are not putting this on the write queue, so
3039 * tcp_transmit_skb() will set the ownership to this
3042 buff
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3044 inet_csk_schedule_ack(sk
);
3045 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
3046 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
3047 TCP_DELACK_MAX
, TCP_RTO_MAX
);
3051 /* Reserve space for headers and prepare control bits. */
3052 skb_reserve(buff
, MAX_TCP_HEADER
);
3053 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPHDR_ACK
);
3055 /* Send it off, this clears delayed acks for us. */
3056 TCP_SKB_CB(buff
)->when
= tcp_time_stamp
;
3057 tcp_transmit_skb(sk
, buff
, 0, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3060 /* This routine sends a packet with an out of date sequence
3061 * number. It assumes the other end will try to ack it.
3063 * Question: what should we make while urgent mode?
3064 * 4.4BSD forces sending single byte of data. We cannot send
3065 * out of window data, because we have SND.NXT==SND.MAX...
3067 * Current solution: to send TWO zero-length segments in urgent mode:
3068 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3069 * out-of-date with SND.UNA-1 to probe window.
3071 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
)
3073 struct tcp_sock
*tp
= tcp_sk(sk
);
3074 struct sk_buff
*skb
;
3076 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3077 skb
= alloc_skb(MAX_TCP_HEADER
, sk_gfp_atomic(sk
, GFP_ATOMIC
));
3081 /* Reserve space for headers and set control bits. */
3082 skb_reserve(skb
, MAX_TCP_HEADER
);
3083 /* Use a previous sequence. This should cause the other
3084 * end to send an ack. Don't queue or clone SKB, just
3087 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPHDR_ACK
);
3088 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
3089 return tcp_transmit_skb(sk
, skb
, 0, GFP_ATOMIC
);
3092 void tcp_send_window_probe(struct sock
*sk
)
3094 if (sk
->sk_state
== TCP_ESTABLISHED
) {
3095 tcp_sk(sk
)->snd_wl1
= tcp_sk(sk
)->rcv_nxt
- 1;
3096 tcp_sk(sk
)->snd_nxt
= tcp_sk(sk
)->write_seq
;
3097 tcp_xmit_probe_skb(sk
, 0);
3101 /* Initiate keepalive or window probe from timer. */
3102 int tcp_write_wakeup(struct sock
*sk
)
3104 struct tcp_sock
*tp
= tcp_sk(sk
);
3105 struct sk_buff
*skb
;
3107 if (sk
->sk_state
== TCP_CLOSE
)
3110 if ((skb
= tcp_send_head(sk
)) != NULL
&&
3111 before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
3113 unsigned int mss
= tcp_current_mss(sk
);
3114 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
3116 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
3117 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
3119 /* We are probing the opening of a window
3120 * but the window size is != 0
3121 * must have been a result SWS avoidance ( sender )
3123 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
3125 seg_size
= min(seg_size
, mss
);
3126 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3127 if (tcp_fragment(sk
, skb
, seg_size
, mss
))
3129 } else if (!tcp_skb_pcount(skb
))
3130 tcp_set_skb_tso_segs(sk
, skb
, mss
);
3132 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3133 TCP_SKB_CB(skb
)->when
= tcp_time_stamp
;
3134 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3136 tcp_event_new_data_sent(sk
, skb
);
3139 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
3140 tcp_xmit_probe_skb(sk
, 1);
3141 return tcp_xmit_probe_skb(sk
, 0);
3145 /* A window probe timeout has occurred. If window is not closed send
3146 * a partial packet else a zero probe.
3148 void tcp_send_probe0(struct sock
*sk
)
3150 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3151 struct tcp_sock
*tp
= tcp_sk(sk
);
3154 err
= tcp_write_wakeup(sk
);
3156 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
3157 /* Cancel probe timer, if it is not required. */
3158 icsk
->icsk_probes_out
= 0;
3159 icsk
->icsk_backoff
= 0;
3164 if (icsk
->icsk_backoff
< sysctl_tcp_retries2
)
3165 icsk
->icsk_backoff
++;
3166 icsk
->icsk_probes_out
++;
3167 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3168 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
, TCP_RTO_MAX
),
3171 /* If packet was not sent due to local congestion,
3172 * do not backoff and do not remember icsk_probes_out.
3173 * Let local senders to fight for local resources.
3175 * Use accumulated backoff yet.
3177 if (!icsk
->icsk_probes_out
)
3178 icsk
->icsk_probes_out
= 1;
3179 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3180 min(icsk
->icsk_rto
<< icsk
->icsk_backoff
,
3181 TCP_RESOURCE_PROBE_INTERVAL
),