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 four TSO segments */
54 int sysctl_tcp_limit_output_bytes __read_mostly
= 262144;
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 /* By default, RFC2861 behavior. */
63 int sysctl_tcp_slow_start_after_idle __read_mostly
= 1;
65 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
66 int push_one
, gfp_t gfp
);
68 /* Account for new data that has been sent to the network. */
69 static void tcp_event_new_data_sent(struct sock
*sk
, const struct sk_buff
*skb
)
71 struct inet_connection_sock
*icsk
= inet_csk(sk
);
72 struct tcp_sock
*tp
= tcp_sk(sk
);
73 unsigned int prior_packets
= tp
->packets_out
;
75 tcp_advance_send_head(sk
, skb
);
76 tp
->snd_nxt
= TCP_SKB_CB(skb
)->end_seq
;
78 tp
->packets_out
+= tcp_skb_pcount(skb
);
79 if (!prior_packets
|| icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
||
80 icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
) {
84 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
,
88 /* SND.NXT, if window was not shrunk.
89 * If window has been shrunk, what should we make? It is not clear at all.
90 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
91 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
92 * invalid. OK, let's make this for now:
94 static inline __u32
tcp_acceptable_seq(const struct sock
*sk
)
96 const struct tcp_sock
*tp
= tcp_sk(sk
);
98 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
))
101 return tcp_wnd_end(tp
);
104 /* Calculate mss to advertise in SYN segment.
105 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
107 * 1. It is independent of path mtu.
108 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
109 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
110 * attached devices, because some buggy hosts are confused by
112 * 4. We do not make 3, we advertise MSS, calculated from first
113 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
114 * This may be overridden via information stored in routing table.
115 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
116 * probably even Jumbo".
118 static __u16
tcp_advertise_mss(struct sock
*sk
)
120 struct tcp_sock
*tp
= tcp_sk(sk
);
121 const struct dst_entry
*dst
= __sk_dst_get(sk
);
122 int mss
= tp
->advmss
;
125 unsigned int metric
= dst_metric_advmss(dst
);
136 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
137 * This is the first part of cwnd validation mechanism.
139 void tcp_cwnd_restart(struct sock
*sk
, s32 delta
)
141 struct tcp_sock
*tp
= tcp_sk(sk
);
142 u32 restart_cwnd
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
143 u32 cwnd
= tp
->snd_cwnd
;
145 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
147 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
148 restart_cwnd
= min(restart_cwnd
, cwnd
);
150 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
152 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
153 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
154 tp
->snd_cwnd_used
= 0;
157 /* Congestion state accounting after a packet has been sent. */
158 static void tcp_event_data_sent(struct tcp_sock
*tp
,
161 struct inet_connection_sock
*icsk
= inet_csk(sk
);
162 const u32 now
= tcp_time_stamp
;
164 if (tcp_packets_in_flight(tp
) == 0)
165 tcp_ca_event(sk
, CA_EVENT_TX_START
);
169 /* If it is a reply for ato after last received
170 * packet, enter pingpong mode.
172 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
173 icsk
->icsk_ack
.pingpong
= 1;
176 /* Account for an ACK we sent. */
177 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
179 tcp_dec_quickack_mode(sk
, pkts
);
180 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
184 u32
tcp_default_init_rwnd(u32 mss
)
186 /* Initial receive window should be twice of TCP_INIT_CWND to
187 * enable proper sending of new unsent data during fast recovery
188 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
189 * limit when mss is larger than 1460.
191 u32 init_rwnd
= TCP_INIT_CWND
* 2;
194 init_rwnd
= max((1460 * init_rwnd
) / mss
, 2U);
198 /* Determine a window scaling and initial window to offer.
199 * Based on the assumption that the given amount of space
200 * will be offered. Store the results in the tp structure.
201 * NOTE: for smooth operation initial space offering should
202 * be a multiple of mss if possible. We assume here that mss >= 1.
203 * This MUST be enforced by all callers.
205 void tcp_select_initial_window(int __space
, __u32 mss
,
206 __u32
*rcv_wnd
, __u32
*window_clamp
,
207 int wscale_ok
, __u8
*rcv_wscale
,
210 unsigned int space
= (__space
< 0 ? 0 : __space
);
212 /* If no clamp set the clamp to the max possible scaled window */
213 if (*window_clamp
== 0)
214 (*window_clamp
) = (65535 << 14);
215 space
= min(*window_clamp
, space
);
217 /* Quantize space offering to a multiple of mss if possible. */
219 space
= (space
/ mss
) * mss
;
221 /* NOTE: offering an initial window larger than 32767
222 * will break some buggy TCP stacks. If the admin tells us
223 * it is likely we could be speaking with such a buggy stack
224 * we will truncate our initial window offering to 32K-1
225 * unless the remote has sent us a window scaling option,
226 * which we interpret as a sign the remote TCP is not
227 * misinterpreting the window field as a signed quantity.
229 if (sysctl_tcp_workaround_signed_windows
)
230 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
236 /* Set window scaling on max possible window
237 * See RFC1323 for an explanation of the limit to 14
239 space
= max_t(u32
, space
, sysctl_tcp_rmem
[2]);
240 space
= max_t(u32
, space
, sysctl_rmem_max
);
241 space
= min_t(u32
, space
, *window_clamp
);
242 while (space
> 65535 && (*rcv_wscale
) < 14) {
248 if (mss
> (1 << *rcv_wscale
)) {
249 if (!init_rcv_wnd
) /* Use default unless specified otherwise */
250 init_rcv_wnd
= tcp_default_init_rwnd(mss
);
251 *rcv_wnd
= min(*rcv_wnd
, init_rcv_wnd
* mss
);
254 /* Set the clamp no higher than max representable value */
255 (*window_clamp
) = min(65535U << (*rcv_wscale
), *window_clamp
);
257 EXPORT_SYMBOL(tcp_select_initial_window
);
259 /* Chose a new window to advertise, update state in tcp_sock for the
260 * socket, and return result with RFC1323 scaling applied. The return
261 * value can be stuffed directly into th->window for an outgoing
264 static u16
tcp_select_window(struct sock
*sk
)
266 struct tcp_sock
*tp
= tcp_sk(sk
);
267 u32 old_win
= tp
->rcv_wnd
;
268 u32 cur_win
= tcp_receive_window(tp
);
269 u32 new_win
= __tcp_select_window(sk
);
271 /* Never shrink the offered window */
272 if (new_win
< cur_win
) {
273 /* Danger Will Robinson!
274 * Don't update rcv_wup/rcv_wnd here or else
275 * we will not be able to advertise a zero
276 * window in time. --DaveM
278 * Relax Will Robinson.
281 NET_INC_STATS(sock_net(sk
),
282 LINUX_MIB_TCPWANTZEROWINDOWADV
);
283 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
285 tp
->rcv_wnd
= new_win
;
286 tp
->rcv_wup
= tp
->rcv_nxt
;
288 /* Make sure we do not exceed the maximum possible
291 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
292 new_win
= min(new_win
, MAX_TCP_WINDOW
);
294 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
296 /* RFC1323 scaling applied */
297 new_win
>>= tp
->rx_opt
.rcv_wscale
;
299 /* If we advertise zero window, disable fast path. */
303 NET_INC_STATS(sock_net(sk
),
304 LINUX_MIB_TCPTOZEROWINDOWADV
);
305 } else if (old_win
== 0) {
306 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPFROMZEROWINDOWADV
);
312 /* Packet ECN state for a SYN-ACK */
313 static void tcp_ecn_send_synack(struct sock
*sk
, struct sk_buff
*skb
)
315 const struct tcp_sock
*tp
= tcp_sk(sk
);
317 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_CWR
;
318 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
319 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_ECE
;
320 else if (tcp_ca_needs_ecn(sk
))
324 /* Packet ECN state for a SYN. */
325 static void tcp_ecn_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
327 struct tcp_sock
*tp
= tcp_sk(sk
);
328 bool use_ecn
= sock_net(sk
)->ipv4
.sysctl_tcp_ecn
== 1 ||
329 tcp_ca_needs_ecn(sk
);
332 const struct dst_entry
*dst
= __sk_dst_get(sk
);
334 if (dst
&& dst_feature(dst
, RTAX_FEATURE_ECN
))
341 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ECE
| TCPHDR_CWR
;
342 tp
->ecn_flags
= TCP_ECN_OK
;
343 if (tcp_ca_needs_ecn(sk
))
348 static void tcp_ecn_clear_syn(struct sock
*sk
, struct sk_buff
*skb
)
350 if (sock_net(sk
)->ipv4
.sysctl_tcp_ecn_fallback
)
351 /* tp->ecn_flags are cleared at a later point in time when
352 * SYN ACK is ultimatively being received.
354 TCP_SKB_CB(skb
)->tcp_flags
&= ~(TCPHDR_ECE
| TCPHDR_CWR
);
358 tcp_ecn_make_synack(const struct request_sock
*req
, struct tcphdr
*th
)
360 if (inet_rsk(req
)->ecn_ok
)
364 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
367 static void tcp_ecn_send(struct sock
*sk
, struct sk_buff
*skb
,
368 struct tcphdr
*th
, int tcp_header_len
)
370 struct tcp_sock
*tp
= tcp_sk(sk
);
372 if (tp
->ecn_flags
& TCP_ECN_OK
) {
373 /* Not-retransmitted data segment: set ECT and inject CWR. */
374 if (skb
->len
!= tcp_header_len
&&
375 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
377 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
378 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
380 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
382 } else if (!tcp_ca_needs_ecn(sk
)) {
383 /* ACK or retransmitted segment: clear ECT|CE */
384 INET_ECN_dontxmit(sk
);
386 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
391 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
392 * auto increment end seqno.
394 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
396 skb
->ip_summed
= CHECKSUM_PARTIAL
;
399 TCP_SKB_CB(skb
)->tcp_flags
= flags
;
400 TCP_SKB_CB(skb
)->sacked
= 0;
402 tcp_skb_pcount_set(skb
, 1);
404 TCP_SKB_CB(skb
)->seq
= seq
;
405 if (flags
& (TCPHDR_SYN
| TCPHDR_FIN
))
407 TCP_SKB_CB(skb
)->end_seq
= seq
;
410 static inline bool tcp_urg_mode(const struct tcp_sock
*tp
)
412 return tp
->snd_una
!= tp
->snd_up
;
415 #define OPTION_SACK_ADVERTISE (1 << 0)
416 #define OPTION_TS (1 << 1)
417 #define OPTION_MD5 (1 << 2)
418 #define OPTION_WSCALE (1 << 3)
419 #define OPTION_FAST_OPEN_COOKIE (1 << 8)
421 struct tcp_out_options
{
422 u16 options
; /* bit field of OPTION_* */
423 u16 mss
; /* 0 to disable */
424 u8 ws
; /* window scale, 0 to disable */
425 u8 num_sack_blocks
; /* number of SACK blocks to include */
426 u8 hash_size
; /* bytes in hash_location */
427 __u8
*hash_location
; /* temporary pointer, overloaded */
428 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
429 struct tcp_fastopen_cookie
*fastopen_cookie
; /* Fast open cookie */
432 /* Write previously computed TCP options to the packet.
434 * Beware: Something in the Internet is very sensitive to the ordering of
435 * TCP options, we learned this through the hard way, so be careful here.
436 * Luckily we can at least blame others for their non-compliance but from
437 * inter-operability perspective it seems that we're somewhat stuck with
438 * the ordering which we have been using if we want to keep working with
439 * those broken things (not that it currently hurts anybody as there isn't
440 * particular reason why the ordering would need to be changed).
442 * At least SACK_PERM as the first option is known to lead to a disaster
443 * (but it may well be that other scenarios fail similarly).
445 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
446 struct tcp_out_options
*opts
)
448 u16 options
= opts
->options
; /* mungable copy */
450 if (unlikely(OPTION_MD5
& options
)) {
451 *ptr
++ = htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
452 (TCPOPT_MD5SIG
<< 8) | TCPOLEN_MD5SIG
);
453 /* overload cookie hash location */
454 opts
->hash_location
= (__u8
*)ptr
;
458 if (unlikely(opts
->mss
)) {
459 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
460 (TCPOLEN_MSS
<< 16) |
464 if (likely(OPTION_TS
& options
)) {
465 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
466 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
467 (TCPOLEN_SACK_PERM
<< 16) |
468 (TCPOPT_TIMESTAMP
<< 8) |
470 options
&= ~OPTION_SACK_ADVERTISE
;
472 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
474 (TCPOPT_TIMESTAMP
<< 8) |
477 *ptr
++ = htonl(opts
->tsval
);
478 *ptr
++ = htonl(opts
->tsecr
);
481 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
482 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
484 (TCPOPT_SACK_PERM
<< 8) |
488 if (unlikely(OPTION_WSCALE
& options
)) {
489 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
490 (TCPOPT_WINDOW
<< 16) |
491 (TCPOLEN_WINDOW
<< 8) |
495 if (unlikely(opts
->num_sack_blocks
)) {
496 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
497 tp
->duplicate_sack
: tp
->selective_acks
;
500 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
503 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
504 TCPOLEN_SACK_PERBLOCK
)));
506 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
508 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
509 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
512 tp
->rx_opt
.dsack
= 0;
515 if (unlikely(OPTION_FAST_OPEN_COOKIE
& options
)) {
516 struct tcp_fastopen_cookie
*foc
= opts
->fastopen_cookie
;
518 u32 len
; /* Fast Open option length */
521 len
= TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
;
522 *ptr
= htonl((TCPOPT_EXP
<< 24) | (len
<< 16) |
523 TCPOPT_FASTOPEN_MAGIC
);
524 p
+= TCPOLEN_EXP_FASTOPEN_BASE
;
526 len
= TCPOLEN_FASTOPEN_BASE
+ foc
->len
;
527 *p
++ = TCPOPT_FASTOPEN
;
531 memcpy(p
, foc
->val
, foc
->len
);
532 if ((len
& 3) == 2) {
533 p
[foc
->len
] = TCPOPT_NOP
;
534 p
[foc
->len
+ 1] = TCPOPT_NOP
;
536 ptr
+= (len
+ 3) >> 2;
540 /* Compute TCP options for SYN packets. This is not the final
541 * network wire format yet.
543 static unsigned int tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
544 struct tcp_out_options
*opts
,
545 struct tcp_md5sig_key
**md5
)
547 struct tcp_sock
*tp
= tcp_sk(sk
);
548 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
549 struct tcp_fastopen_request
*fastopen
= tp
->fastopen_req
;
551 #ifdef CONFIG_TCP_MD5SIG
552 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
554 opts
->options
|= OPTION_MD5
;
555 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
561 /* We always get an MSS option. The option bytes which will be seen in
562 * normal data packets should timestamps be used, must be in the MSS
563 * advertised. But we subtract them from tp->mss_cache so that
564 * calculations in tcp_sendmsg are simpler etc. So account for this
565 * fact here if necessary. If we don't do this correctly, as a
566 * receiver we won't recognize data packets as being full sized when we
567 * should, and thus we won't abide by the delayed ACK rules correctly.
568 * SACKs don't matter, we never delay an ACK when we have any of those
570 opts
->mss
= tcp_advertise_mss(sk
);
571 remaining
-= TCPOLEN_MSS_ALIGNED
;
573 if (likely(sysctl_tcp_timestamps
&& !*md5
)) {
574 opts
->options
|= OPTION_TS
;
575 opts
->tsval
= tcp_skb_timestamp(skb
) + tp
->tsoffset
;
576 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
577 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
579 if (likely(sysctl_tcp_window_scaling
)) {
580 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
581 opts
->options
|= OPTION_WSCALE
;
582 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
584 if (likely(sysctl_tcp_sack
)) {
585 opts
->options
|= OPTION_SACK_ADVERTISE
;
586 if (unlikely(!(OPTION_TS
& opts
->options
)))
587 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
590 if (fastopen
&& fastopen
->cookie
.len
>= 0) {
591 u32 need
= fastopen
->cookie
.len
;
593 need
+= fastopen
->cookie
.exp
? TCPOLEN_EXP_FASTOPEN_BASE
:
594 TCPOLEN_FASTOPEN_BASE
;
595 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
596 if (remaining
>= need
) {
597 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
598 opts
->fastopen_cookie
= &fastopen
->cookie
;
600 tp
->syn_fastopen
= 1;
601 tp
->syn_fastopen_exp
= fastopen
->cookie
.exp
? 1 : 0;
605 return MAX_TCP_OPTION_SPACE
- remaining
;
608 /* Set up TCP options for SYN-ACKs. */
609 static unsigned int tcp_synack_options(struct request_sock
*req
,
610 unsigned int mss
, struct sk_buff
*skb
,
611 struct tcp_out_options
*opts
,
612 const struct tcp_md5sig_key
*md5
,
613 struct tcp_fastopen_cookie
*foc
)
615 struct inet_request_sock
*ireq
= inet_rsk(req
);
616 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
618 #ifdef CONFIG_TCP_MD5SIG
620 opts
->options
|= OPTION_MD5
;
621 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
623 /* We can't fit any SACK blocks in a packet with MD5 + TS
624 * options. There was discussion about disabling SACK
625 * rather than TS in order to fit in better with old,
626 * buggy kernels, but that was deemed to be unnecessary.
628 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
632 /* We always send an MSS option. */
634 remaining
-= TCPOLEN_MSS_ALIGNED
;
636 if (likely(ireq
->wscale_ok
)) {
637 opts
->ws
= ireq
->rcv_wscale
;
638 opts
->options
|= OPTION_WSCALE
;
639 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
641 if (likely(ireq
->tstamp_ok
)) {
642 opts
->options
|= OPTION_TS
;
643 opts
->tsval
= tcp_skb_timestamp(skb
) + tcp_rsk(req
)->ts_off
;
644 opts
->tsecr
= req
->ts_recent
;
645 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
647 if (likely(ireq
->sack_ok
)) {
648 opts
->options
|= OPTION_SACK_ADVERTISE
;
649 if (unlikely(!ireq
->tstamp_ok
))
650 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
652 if (foc
!= NULL
&& foc
->len
>= 0) {
655 need
+= foc
->exp
? TCPOLEN_EXP_FASTOPEN_BASE
:
656 TCPOLEN_FASTOPEN_BASE
;
657 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
658 if (remaining
>= need
) {
659 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
660 opts
->fastopen_cookie
= foc
;
665 return MAX_TCP_OPTION_SPACE
- remaining
;
668 /* Compute TCP options for ESTABLISHED sockets. This is not the
669 * final wire format yet.
671 static unsigned int tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
672 struct tcp_out_options
*opts
,
673 struct tcp_md5sig_key
**md5
)
675 struct tcp_sock
*tp
= tcp_sk(sk
);
676 unsigned int size
= 0;
677 unsigned int eff_sacks
;
681 #ifdef CONFIG_TCP_MD5SIG
682 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
683 if (unlikely(*md5
)) {
684 opts
->options
|= OPTION_MD5
;
685 size
+= TCPOLEN_MD5SIG_ALIGNED
;
691 if (likely(tp
->rx_opt
.tstamp_ok
)) {
692 opts
->options
|= OPTION_TS
;
693 opts
->tsval
= skb
? tcp_skb_timestamp(skb
) + tp
->tsoffset
: 0;
694 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
695 size
+= TCPOLEN_TSTAMP_ALIGNED
;
698 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
699 if (unlikely(eff_sacks
)) {
700 const unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
701 opts
->num_sack_blocks
=
702 min_t(unsigned int, eff_sacks
,
703 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
704 TCPOLEN_SACK_PERBLOCK
);
705 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
706 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
713 /* TCP SMALL QUEUES (TSQ)
715 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
716 * to reduce RTT and bufferbloat.
717 * We do this using a special skb destructor (tcp_wfree).
719 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
720 * needs to be reallocated in a driver.
721 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
723 * Since transmit from skb destructor is forbidden, we use a tasklet
724 * to process all sockets that eventually need to send more skbs.
725 * We use one tasklet per cpu, with its own queue of sockets.
728 struct tasklet_struct tasklet
;
729 struct list_head head
; /* queue of tcp sockets */
731 static DEFINE_PER_CPU(struct tsq_tasklet
, tsq_tasklet
);
733 static void tcp_tsq_handler(struct sock
*sk
)
735 if ((1 << sk
->sk_state
) &
736 (TCPF_ESTABLISHED
| TCPF_FIN_WAIT1
| TCPF_CLOSING
|
737 TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
)) {
738 struct tcp_sock
*tp
= tcp_sk(sk
);
740 if (tp
->lost_out
> tp
->retrans_out
&&
741 tp
->snd_cwnd
> tcp_packets_in_flight(tp
))
742 tcp_xmit_retransmit_queue(sk
);
744 tcp_write_xmit(sk
, tcp_current_mss(sk
), tp
->nonagle
,
749 * One tasklet per cpu tries to send more skbs.
750 * We run in tasklet context but need to disable irqs when
751 * transferring tsq->head because tcp_wfree() might
752 * interrupt us (non NAPI drivers)
754 static void tcp_tasklet_func(unsigned long data
)
756 struct tsq_tasklet
*tsq
= (struct tsq_tasklet
*)data
;
759 struct list_head
*q
, *n
;
763 local_irq_save(flags
);
764 list_splice_init(&tsq
->head
, &list
);
765 local_irq_restore(flags
);
767 list_for_each_safe(q
, n
, &list
) {
768 tp
= list_entry(q
, struct tcp_sock
, tsq_node
);
769 list_del(&tp
->tsq_node
);
771 sk
= (struct sock
*)tp
;
772 smp_mb__before_atomic();
773 clear_bit(TSQ_QUEUED
, &sk
->sk_tsq_flags
);
775 if (!sk
->sk_lock
.owned
&&
776 test_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
)) {
778 if (!sock_owned_by_user(sk
)) {
779 clear_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
);
789 #define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
790 TCPF_WRITE_TIMER_DEFERRED | \
791 TCPF_DELACK_TIMER_DEFERRED | \
792 TCPF_MTU_REDUCED_DEFERRED)
794 * tcp_release_cb - tcp release_sock() callback
797 * called from release_sock() to perform protocol dependent
798 * actions before socket release.
800 void tcp_release_cb(struct sock
*sk
)
802 unsigned long flags
, nflags
;
804 /* perform an atomic operation only if at least one flag is set */
806 flags
= sk
->sk_tsq_flags
;
807 if (!(flags
& TCP_DEFERRED_ALL
))
809 nflags
= flags
& ~TCP_DEFERRED_ALL
;
810 } while (cmpxchg(&sk
->sk_tsq_flags
, flags
, nflags
) != flags
);
812 if (flags
& TCPF_TSQ_DEFERRED
)
815 /* Here begins the tricky part :
816 * We are called from release_sock() with :
818 * 2) sk_lock.slock spinlock held
819 * 3) socket owned by us (sk->sk_lock.owned == 1)
821 * But following code is meant to be called from BH handlers,
822 * so we should keep BH disabled, but early release socket ownership
824 sock_release_ownership(sk
);
826 if (flags
& TCPF_WRITE_TIMER_DEFERRED
) {
827 tcp_write_timer_handler(sk
);
830 if (flags
& TCPF_DELACK_TIMER_DEFERRED
) {
831 tcp_delack_timer_handler(sk
);
834 if (flags
& TCPF_MTU_REDUCED_DEFERRED
) {
835 inet_csk(sk
)->icsk_af_ops
->mtu_reduced(sk
);
839 EXPORT_SYMBOL(tcp_release_cb
);
841 void __init
tcp_tasklet_init(void)
845 for_each_possible_cpu(i
) {
846 struct tsq_tasklet
*tsq
= &per_cpu(tsq_tasklet
, i
);
848 INIT_LIST_HEAD(&tsq
->head
);
849 tasklet_init(&tsq
->tasklet
,
856 * Write buffer destructor automatically called from kfree_skb.
857 * We can't xmit new skbs from this context, as we might already
860 void tcp_wfree(struct sk_buff
*skb
)
862 struct sock
*sk
= skb
->sk
;
863 struct tcp_sock
*tp
= tcp_sk(sk
);
864 unsigned long flags
, nval
, oval
;
867 /* Keep one reference on sk_wmem_alloc.
868 * Will be released by sk_free() from here or tcp_tasklet_func()
870 wmem
= atomic_sub_return(skb
->truesize
- 1, &sk
->sk_wmem_alloc
);
872 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
873 * Wait until our queues (qdisc + devices) are drained.
875 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
876 * - chance for incoming ACK (processed by another cpu maybe)
877 * to migrate this flow (skb->ooo_okay will be eventually set)
879 if (wmem
>= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current
)
882 for (oval
= READ_ONCE(sk
->sk_tsq_flags
);; oval
= nval
) {
883 struct tsq_tasklet
*tsq
;
886 if (!(oval
& TSQF_THROTTLED
) || (oval
& TSQF_QUEUED
))
889 nval
= (oval
& ~TSQF_THROTTLED
) | TSQF_QUEUED
| TCPF_TSQ_DEFERRED
;
890 nval
= cmpxchg(&sk
->sk_tsq_flags
, oval
, nval
);
894 /* queue this socket to tasklet queue */
895 local_irq_save(flags
);
896 tsq
= this_cpu_ptr(&tsq_tasklet
);
897 empty
= list_empty(&tsq
->head
);
898 list_add(&tp
->tsq_node
, &tsq
->head
);
900 tasklet_schedule(&tsq
->tasklet
);
901 local_irq_restore(flags
);
908 /* This routine actually transmits TCP packets queued in by
909 * tcp_do_sendmsg(). This is used by both the initial
910 * transmission and possible later retransmissions.
911 * All SKB's seen here are completely headerless. It is our
912 * job to build the TCP header, and pass the packet down to
913 * IP so it can do the same plus pass the packet off to the
916 * We are working here with either a clone of the original
917 * SKB, or a fresh unique copy made by the retransmit engine.
919 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
922 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
923 struct inet_sock
*inet
;
925 struct tcp_skb_cb
*tcb
;
926 struct tcp_out_options opts
;
927 unsigned int tcp_options_size
, tcp_header_size
;
928 struct tcp_md5sig_key
*md5
;
932 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
936 skb_mstamp_get(&skb
->skb_mstamp
);
937 TCP_SKB_CB(skb
)->tx
.in_flight
= TCP_SKB_CB(skb
)->end_seq
939 tcp_rate_skb_sent(sk
, skb
);
941 if (unlikely(skb_cloned(skb
)))
942 skb
= pskb_copy(skb
, gfp_mask
);
944 skb
= skb_clone(skb
, gfp_mask
);
950 tcb
= TCP_SKB_CB(skb
);
951 memset(&opts
, 0, sizeof(opts
));
953 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
))
954 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
956 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
958 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
960 /* if no packet is in qdisc/device queue, then allow XPS to select
961 * another queue. We can be called from tcp_tsq_handler()
962 * which holds one reference to sk_wmem_alloc.
964 * TODO: Ideally, in-flight pure ACK packets should not matter here.
965 * One way to get this would be to set skb->truesize = 2 on them.
967 skb
->ooo_okay
= sk_wmem_alloc_get(sk
) < SKB_TRUESIZE(1);
969 skb_push(skb
, tcp_header_size
);
970 skb_reset_transport_header(skb
);
974 skb
->destructor
= skb_is_tcp_pure_ack(skb
) ? __sock_wfree
: tcp_wfree
;
975 skb_set_hash_from_sk(skb
, sk
);
976 atomic_add(skb
->truesize
, &sk
->sk_wmem_alloc
);
978 skb_set_dst_pending_confirm(skb
, sk
->sk_dst_pending_confirm
);
980 /* Build TCP header and checksum it. */
981 th
= (struct tcphdr
*)skb
->data
;
982 th
->source
= inet
->inet_sport
;
983 th
->dest
= inet
->inet_dport
;
984 th
->seq
= htonl(tcb
->seq
);
985 th
->ack_seq
= htonl(tp
->rcv_nxt
);
986 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
992 /* The urg_mode check is necessary during a below snd_una win probe */
993 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
994 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
995 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
997 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
998 th
->urg_ptr
= htons(0xFFFF);
1003 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
1004 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
1005 if (likely(!(tcb
->tcp_flags
& TCPHDR_SYN
))) {
1006 th
->window
= htons(tcp_select_window(sk
));
1007 tcp_ecn_send(sk
, skb
, th
, tcp_header_size
);
1009 /* RFC1323: The window in SYN & SYN/ACK segments
1012 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
1014 #ifdef CONFIG_TCP_MD5SIG
1015 /* Calculate the MD5 hash, as we have all we need now */
1017 sk_nocaps_add(sk
, NETIF_F_GSO_MASK
);
1018 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
1023 icsk
->icsk_af_ops
->send_check(sk
, skb
);
1025 if (likely(tcb
->tcp_flags
& TCPHDR_ACK
))
1026 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
1028 if (skb
->len
!= tcp_header_size
) {
1029 tcp_event_data_sent(tp
, sk
);
1030 tp
->data_segs_out
+= tcp_skb_pcount(skb
);
1033 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
1034 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
,
1035 tcp_skb_pcount(skb
));
1037 tp
->segs_out
+= tcp_skb_pcount(skb
);
1038 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1039 skb_shinfo(skb
)->gso_segs
= tcp_skb_pcount(skb
);
1040 skb_shinfo(skb
)->gso_size
= tcp_skb_mss(skb
);
1042 /* Our usage of tstamp should remain private */
1045 /* Cleanup our debris for IP stacks */
1046 memset(skb
->cb
, 0, max(sizeof(struct inet_skb_parm
),
1047 sizeof(struct inet6_skb_parm
)));
1049 err
= icsk
->icsk_af_ops
->queue_xmit(sk
, skb
, &inet
->cork
.fl
);
1051 if (likely(err
<= 0))
1056 return net_xmit_eval(err
);
1059 /* This routine just queues the buffer for sending.
1061 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1062 * otherwise socket can stall.
1064 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
1066 struct tcp_sock
*tp
= tcp_sk(sk
);
1068 /* Advance write_seq and place onto the write_queue. */
1069 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
1070 __skb_header_release(skb
);
1071 tcp_add_write_queue_tail(sk
, skb
);
1072 sk
->sk_wmem_queued
+= skb
->truesize
;
1073 sk_mem_charge(sk
, skb
->truesize
);
1076 /* Initialize TSO segments for a packet. */
1077 static void tcp_set_skb_tso_segs(struct sk_buff
*skb
, unsigned int mss_now
)
1079 if (skb
->len
<= mss_now
|| skb
->ip_summed
== CHECKSUM_NONE
) {
1080 /* Avoid the costly divide in the normal
1083 tcp_skb_pcount_set(skb
, 1);
1084 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1086 tcp_skb_pcount_set(skb
, DIV_ROUND_UP(skb
->len
, mss_now
));
1087 TCP_SKB_CB(skb
)->tcp_gso_size
= mss_now
;
1091 /* When a modification to fackets out becomes necessary, we need to check
1092 * skb is counted to fackets_out or not.
1094 static void tcp_adjust_fackets_out(struct sock
*sk
, const struct sk_buff
*skb
,
1097 struct tcp_sock
*tp
= tcp_sk(sk
);
1099 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
1102 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
1103 tp
->fackets_out
-= decr
;
1106 /* Pcount in the middle of the write queue got changed, we need to do various
1107 * tweaks to fix counters
1109 static void tcp_adjust_pcount(struct sock
*sk
, const struct sk_buff
*skb
, int decr
)
1111 struct tcp_sock
*tp
= tcp_sk(sk
);
1113 tp
->packets_out
-= decr
;
1115 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1116 tp
->sacked_out
-= decr
;
1117 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1118 tp
->retrans_out
-= decr
;
1119 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
1120 tp
->lost_out
-= decr
;
1122 /* Reno case is special. Sigh... */
1123 if (tcp_is_reno(tp
) && decr
> 0)
1124 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
1126 tcp_adjust_fackets_out(sk
, skb
, decr
);
1128 if (tp
->lost_skb_hint
&&
1129 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
1130 (tcp_is_fack(tp
) || (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)))
1131 tp
->lost_cnt_hint
-= decr
;
1133 tcp_verify_left_out(tp
);
1136 static bool tcp_has_tx_tstamp(const struct sk_buff
*skb
)
1138 return TCP_SKB_CB(skb
)->txstamp_ack
||
1139 (skb_shinfo(skb
)->tx_flags
& SKBTX_ANY_TSTAMP
);
1142 static void tcp_fragment_tstamp(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1144 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
1146 if (unlikely(tcp_has_tx_tstamp(skb
)) &&
1147 !before(shinfo
->tskey
, TCP_SKB_CB(skb2
)->seq
)) {
1148 struct skb_shared_info
*shinfo2
= skb_shinfo(skb2
);
1149 u8 tsflags
= shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
1151 shinfo
->tx_flags
&= ~tsflags
;
1152 shinfo2
->tx_flags
|= tsflags
;
1153 swap(shinfo
->tskey
, shinfo2
->tskey
);
1154 TCP_SKB_CB(skb2
)->txstamp_ack
= TCP_SKB_CB(skb
)->txstamp_ack
;
1155 TCP_SKB_CB(skb
)->txstamp_ack
= 0;
1159 static void tcp_skb_fragment_eor(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1161 TCP_SKB_CB(skb2
)->eor
= TCP_SKB_CB(skb
)->eor
;
1162 TCP_SKB_CB(skb
)->eor
= 0;
1165 /* Function to create two new TCP segments. Shrinks the given segment
1166 * to the specified size and appends a new segment with the rest of the
1167 * packet to the list. This won't be called frequently, I hope.
1168 * Remember, these are still headerless SKBs at this point.
1170 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
1171 unsigned int mss_now
, gfp_t gfp
)
1173 struct tcp_sock
*tp
= tcp_sk(sk
);
1174 struct sk_buff
*buff
;
1175 int nsize
, old_factor
;
1179 if (WARN_ON(len
> skb
->len
))
1182 nsize
= skb_headlen(skb
) - len
;
1186 if (skb_unclone(skb
, gfp
))
1189 /* Get a new skb... force flag on. */
1190 buff
= sk_stream_alloc_skb(sk
, nsize
, gfp
, true);
1192 return -ENOMEM
; /* We'll just try again later. */
1194 sk
->sk_wmem_queued
+= buff
->truesize
;
1195 sk_mem_charge(sk
, buff
->truesize
);
1196 nlen
= skb
->len
- len
- nsize
;
1197 buff
->truesize
+= nlen
;
1198 skb
->truesize
-= nlen
;
1200 /* Correct the sequence numbers. */
1201 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1202 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1203 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1205 /* PSH and FIN should only be set in the second packet. */
1206 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1207 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1208 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1209 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1210 tcp_skb_fragment_eor(skb
, buff
);
1212 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
1213 /* Copy and checksum data tail into the new buffer. */
1214 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
1215 skb_put(buff
, nsize
),
1220 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
1222 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1223 skb_split(skb
, buff
, len
);
1226 buff
->ip_summed
= skb
->ip_summed
;
1228 buff
->tstamp
= skb
->tstamp
;
1229 tcp_fragment_tstamp(skb
, buff
);
1231 old_factor
= tcp_skb_pcount(skb
);
1233 /* Fix up tso_factor for both original and new SKB. */
1234 tcp_set_skb_tso_segs(skb
, mss_now
);
1235 tcp_set_skb_tso_segs(buff
, mss_now
);
1237 /* Update delivered info for the new segment */
1238 TCP_SKB_CB(buff
)->tx
= TCP_SKB_CB(skb
)->tx
;
1240 /* If this packet has been sent out already, we must
1241 * adjust the various packet counters.
1243 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1244 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1245 tcp_skb_pcount(buff
);
1248 tcp_adjust_pcount(sk
, skb
, diff
);
1251 /* Link BUFF into the send queue. */
1252 __skb_header_release(buff
);
1253 tcp_insert_write_queue_after(skb
, buff
, sk
);
1258 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1259 * eventually). The difference is that pulled data not copied, but
1260 * immediately discarded.
1262 static int __pskb_trim_head(struct sk_buff
*skb
, int len
)
1264 struct skb_shared_info
*shinfo
;
1267 eat
= min_t(int, len
, skb_headlen(skb
));
1269 __skb_pull(skb
, eat
);
1276 shinfo
= skb_shinfo(skb
);
1277 for (i
= 0; i
< shinfo
->nr_frags
; i
++) {
1278 int size
= skb_frag_size(&shinfo
->frags
[i
]);
1281 skb_frag_unref(skb
, i
);
1284 shinfo
->frags
[k
] = shinfo
->frags
[i
];
1286 shinfo
->frags
[k
].page_offset
+= eat
;
1287 skb_frag_size_sub(&shinfo
->frags
[k
], eat
);
1293 shinfo
->nr_frags
= k
;
1295 skb_reset_tail_pointer(skb
);
1296 skb
->data_len
-= len
;
1297 skb
->len
= skb
->data_len
;
1301 /* Remove acked data from a packet in the transmit queue. */
1302 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1306 if (skb_unclone(skb
, GFP_ATOMIC
))
1309 delta_truesize
= __pskb_trim_head(skb
, len
);
1311 TCP_SKB_CB(skb
)->seq
+= len
;
1312 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1314 if (delta_truesize
) {
1315 skb
->truesize
-= delta_truesize
;
1316 sk
->sk_wmem_queued
-= delta_truesize
;
1317 sk_mem_uncharge(sk
, delta_truesize
);
1318 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
1321 /* Any change of skb->len requires recalculation of tso factor. */
1322 if (tcp_skb_pcount(skb
) > 1)
1323 tcp_set_skb_tso_segs(skb
, tcp_skb_mss(skb
));
1328 /* Calculate MSS not accounting any TCP options. */
1329 static inline int __tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1331 const struct tcp_sock
*tp
= tcp_sk(sk
);
1332 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1335 /* Calculate base mss without TCP options:
1336 It is MMS_S - sizeof(tcphdr) of rfc1122
1338 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1340 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1341 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1342 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1344 if (dst
&& dst_allfrag(dst
))
1345 mss_now
-= icsk
->icsk_af_ops
->net_frag_header_len
;
1348 /* Clamp it (mss_clamp does not include tcp options) */
1349 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1350 mss_now
= tp
->rx_opt
.mss_clamp
;
1352 /* Now subtract optional transport overhead */
1353 mss_now
-= icsk
->icsk_ext_hdr_len
;
1355 /* Then reserve room for full set of TCP options and 8 bytes of data */
1361 /* Calculate MSS. Not accounting for SACKs here. */
1362 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1364 /* Subtract TCP options size, not including SACKs */
1365 return __tcp_mtu_to_mss(sk
, pmtu
) -
1366 (tcp_sk(sk
)->tcp_header_len
- sizeof(struct tcphdr
));
1369 /* Inverse of above */
1370 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1372 const struct tcp_sock
*tp
= tcp_sk(sk
);
1373 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1377 tp
->tcp_header_len
+
1378 icsk
->icsk_ext_hdr_len
+
1379 icsk
->icsk_af_ops
->net_header_len
;
1381 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1382 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1383 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1385 if (dst
&& dst_allfrag(dst
))
1386 mtu
+= icsk
->icsk_af_ops
->net_frag_header_len
;
1390 EXPORT_SYMBOL(tcp_mss_to_mtu
);
1392 /* MTU probing init per socket */
1393 void tcp_mtup_init(struct sock
*sk
)
1395 struct tcp_sock
*tp
= tcp_sk(sk
);
1396 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1397 struct net
*net
= sock_net(sk
);
1399 icsk
->icsk_mtup
.enabled
= net
->ipv4
.sysctl_tcp_mtu_probing
> 1;
1400 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1401 icsk
->icsk_af_ops
->net_header_len
;
1402 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, net
->ipv4
.sysctl_tcp_base_mss
);
1403 icsk
->icsk_mtup
.probe_size
= 0;
1404 if (icsk
->icsk_mtup
.enabled
)
1405 icsk
->icsk_mtup
.probe_timestamp
= tcp_time_stamp
;
1407 EXPORT_SYMBOL(tcp_mtup_init
);
1409 /* This function synchronize snd mss to current pmtu/exthdr set.
1411 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1412 for TCP options, but includes only bare TCP header.
1414 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1415 It is minimum of user_mss and mss received with SYN.
1416 It also does not include TCP options.
1418 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1420 tp->mss_cache is current effective sending mss, including
1421 all tcp options except for SACKs. It is evaluated,
1422 taking into account current pmtu, but never exceeds
1423 tp->rx_opt.mss_clamp.
1425 NOTE1. rfc1122 clearly states that advertised MSS
1426 DOES NOT include either tcp or ip options.
1428 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1429 are READ ONLY outside this function. --ANK (980731)
1431 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1433 struct tcp_sock
*tp
= tcp_sk(sk
);
1434 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1437 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1438 icsk
->icsk_mtup
.search_high
= pmtu
;
1440 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1441 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1443 /* And store cached results */
1444 icsk
->icsk_pmtu_cookie
= pmtu
;
1445 if (icsk
->icsk_mtup
.enabled
)
1446 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1447 tp
->mss_cache
= mss_now
;
1451 EXPORT_SYMBOL(tcp_sync_mss
);
1453 /* Compute the current effective MSS, taking SACKs and IP options,
1454 * and even PMTU discovery events into account.
1456 unsigned int tcp_current_mss(struct sock
*sk
)
1458 const struct tcp_sock
*tp
= tcp_sk(sk
);
1459 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1461 unsigned int header_len
;
1462 struct tcp_out_options opts
;
1463 struct tcp_md5sig_key
*md5
;
1465 mss_now
= tp
->mss_cache
;
1468 u32 mtu
= dst_mtu(dst
);
1469 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1470 mss_now
= tcp_sync_mss(sk
, mtu
);
1473 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1474 sizeof(struct tcphdr
);
1475 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1476 * some common options. If this is an odd packet (because we have SACK
1477 * blocks etc) then our calculated header_len will be different, and
1478 * we have to adjust mss_now correspondingly */
1479 if (header_len
!= tp
->tcp_header_len
) {
1480 int delta
= (int) header_len
- tp
->tcp_header_len
;
1487 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1488 * As additional protections, we do not touch cwnd in retransmission phases,
1489 * and if application hit its sndbuf limit recently.
1491 static void tcp_cwnd_application_limited(struct sock
*sk
)
1493 struct tcp_sock
*tp
= tcp_sk(sk
);
1495 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
1496 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
1497 /* Limited by application or receiver window. */
1498 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
1499 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
1500 if (win_used
< tp
->snd_cwnd
) {
1501 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1502 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
1504 tp
->snd_cwnd_used
= 0;
1506 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1509 static void tcp_cwnd_validate(struct sock
*sk
, bool is_cwnd_limited
)
1511 struct tcp_sock
*tp
= tcp_sk(sk
);
1513 /* Track the maximum number of outstanding packets in each
1514 * window, and remember whether we were cwnd-limited then.
1516 if (!before(tp
->snd_una
, tp
->max_packets_seq
) ||
1517 tp
->packets_out
> tp
->max_packets_out
) {
1518 tp
->max_packets_out
= tp
->packets_out
;
1519 tp
->max_packets_seq
= tp
->snd_nxt
;
1520 tp
->is_cwnd_limited
= is_cwnd_limited
;
1523 if (tcp_is_cwnd_limited(sk
)) {
1524 /* Network is feed fully. */
1525 tp
->snd_cwnd_used
= 0;
1526 tp
->snd_cwnd_stamp
= tcp_time_stamp
;
1528 /* Network starves. */
1529 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1530 tp
->snd_cwnd_used
= tp
->packets_out
;
1532 if (sysctl_tcp_slow_start_after_idle
&&
1533 (s32
)(tcp_time_stamp
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
)
1534 tcp_cwnd_application_limited(sk
);
1536 /* The following conditions together indicate the starvation
1537 * is caused by insufficient sender buffer:
1538 * 1) just sent some data (see tcp_write_xmit)
1539 * 2) not cwnd limited (this else condition)
1540 * 3) no more data to send (null tcp_send_head )
1541 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1543 if (!tcp_send_head(sk
) && sk
->sk_socket
&&
1544 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
) &&
1545 (1 << sk
->sk_state
) & (TCPF_ESTABLISHED
| TCPF_CLOSE_WAIT
))
1546 tcp_chrono_start(sk
, TCP_CHRONO_SNDBUF_LIMITED
);
1550 /* Minshall's variant of the Nagle send check. */
1551 static bool tcp_minshall_check(const struct tcp_sock
*tp
)
1553 return after(tp
->snd_sml
, tp
->snd_una
) &&
1554 !after(tp
->snd_sml
, tp
->snd_nxt
);
1557 /* Update snd_sml if this skb is under mss
1558 * Note that a TSO packet might end with a sub-mss segment
1559 * The test is really :
1560 * if ((skb->len % mss) != 0)
1561 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1562 * But we can avoid doing the divide again given we already have
1563 * skb_pcount = skb->len / mss_now
1565 static void tcp_minshall_update(struct tcp_sock
*tp
, unsigned int mss_now
,
1566 const struct sk_buff
*skb
)
1568 if (skb
->len
< tcp_skb_pcount(skb
) * mss_now
)
1569 tp
->snd_sml
= TCP_SKB_CB(skb
)->end_seq
;
1572 /* Return false, if packet can be sent now without violation Nagle's rules:
1573 * 1. It is full sized. (provided by caller in %partial bool)
1574 * 2. Or it contains FIN. (already checked by caller)
1575 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1576 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1577 * With Minshall's modification: all sent small packets are ACKed.
1579 static bool tcp_nagle_check(bool partial
, const struct tcp_sock
*tp
,
1583 ((nonagle
& TCP_NAGLE_CORK
) ||
1584 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
)));
1587 /* Return how many segs we'd like on a TSO packet,
1588 * to send one TSO packet per ms
1590 u32
tcp_tso_autosize(const struct sock
*sk
, unsigned int mss_now
,
1595 bytes
= min(sk
->sk_pacing_rate
>> 10,
1596 sk
->sk_gso_max_size
- 1 - MAX_TCP_HEADER
);
1598 /* Goal is to send at least one packet per ms,
1599 * not one big TSO packet every 100 ms.
1600 * This preserves ACK clocking and is consistent
1601 * with tcp_tso_should_defer() heuristic.
1603 segs
= max_t(u32
, bytes
/ mss_now
, min_tso_segs
);
1605 return min_t(u32
, segs
, sk
->sk_gso_max_segs
);
1607 EXPORT_SYMBOL(tcp_tso_autosize
);
1609 /* Return the number of segments we want in the skb we are transmitting.
1610 * See if congestion control module wants to decide; otherwise, autosize.
1612 static u32
tcp_tso_segs(struct sock
*sk
, unsigned int mss_now
)
1614 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1615 u32 tso_segs
= ca_ops
->tso_segs_goal
? ca_ops
->tso_segs_goal(sk
) : 0;
1618 tcp_tso_autosize(sk
, mss_now
, sysctl_tcp_min_tso_segs
);
1621 /* Returns the portion of skb which can be sent right away */
1622 static unsigned int tcp_mss_split_point(const struct sock
*sk
,
1623 const struct sk_buff
*skb
,
1624 unsigned int mss_now
,
1625 unsigned int max_segs
,
1628 const struct tcp_sock
*tp
= tcp_sk(sk
);
1629 u32 partial
, needed
, window
, max_len
;
1631 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1632 max_len
= mss_now
* max_segs
;
1634 if (likely(max_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1637 needed
= min(skb
->len
, window
);
1639 if (max_len
<= needed
)
1642 partial
= needed
% mss_now
;
1643 /* If last segment is not a full MSS, check if Nagle rules allow us
1644 * to include this last segment in this skb.
1645 * Otherwise, we'll split the skb at last MSS boundary
1647 if (tcp_nagle_check(partial
!= 0, tp
, nonagle
))
1648 return needed
- partial
;
1653 /* Can at least one segment of SKB be sent right now, according to the
1654 * congestion window rules? If so, return how many segments are allowed.
1656 static inline unsigned int tcp_cwnd_test(const struct tcp_sock
*tp
,
1657 const struct sk_buff
*skb
)
1659 u32 in_flight
, cwnd
, halfcwnd
;
1661 /* Don't be strict about the congestion window for the final FIN. */
1662 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
1663 tcp_skb_pcount(skb
) == 1)
1666 in_flight
= tcp_packets_in_flight(tp
);
1667 cwnd
= tp
->snd_cwnd
;
1668 if (in_flight
>= cwnd
)
1671 /* For better scheduling, ensure we have at least
1672 * 2 GSO packets in flight.
1674 halfcwnd
= max(cwnd
>> 1, 1U);
1675 return min(halfcwnd
, cwnd
- in_flight
);
1678 /* Initialize TSO state of a skb.
1679 * This must be invoked the first time we consider transmitting
1680 * SKB onto the wire.
1682 static int tcp_init_tso_segs(struct sk_buff
*skb
, unsigned int mss_now
)
1684 int tso_segs
= tcp_skb_pcount(skb
);
1686 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1687 tcp_set_skb_tso_segs(skb
, mss_now
);
1688 tso_segs
= tcp_skb_pcount(skb
);
1694 /* Return true if the Nagle test allows this packet to be
1697 static inline bool tcp_nagle_test(const struct tcp_sock
*tp
, const struct sk_buff
*skb
,
1698 unsigned int cur_mss
, int nonagle
)
1700 /* Nagle rule does not apply to frames, which sit in the middle of the
1701 * write_queue (they have no chances to get new data).
1703 * This is implemented in the callers, where they modify the 'nonagle'
1704 * argument based upon the location of SKB in the send queue.
1706 if (nonagle
& TCP_NAGLE_PUSH
)
1709 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1710 if (tcp_urg_mode(tp
) || (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
))
1713 if (!tcp_nagle_check(skb
->len
< cur_mss
, tp
, nonagle
))
1719 /* Does at least the first segment of SKB fit into the send window? */
1720 static bool tcp_snd_wnd_test(const struct tcp_sock
*tp
,
1721 const struct sk_buff
*skb
,
1722 unsigned int cur_mss
)
1724 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1726 if (skb
->len
> cur_mss
)
1727 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1729 return !after(end_seq
, tcp_wnd_end(tp
));
1732 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1733 * should be put on the wire right now. If so, it returns the number of
1734 * packets allowed by the congestion window.
1736 static unsigned int tcp_snd_test(const struct sock
*sk
, struct sk_buff
*skb
,
1737 unsigned int cur_mss
, int nonagle
)
1739 const struct tcp_sock
*tp
= tcp_sk(sk
);
1740 unsigned int cwnd_quota
;
1742 tcp_init_tso_segs(skb
, cur_mss
);
1744 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1747 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1748 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1754 /* Test if sending is allowed right now. */
1755 bool tcp_may_send_now(struct sock
*sk
)
1757 const struct tcp_sock
*tp
= tcp_sk(sk
);
1758 struct sk_buff
*skb
= tcp_send_head(sk
);
1761 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1762 (tcp_skb_is_last(sk
, skb
) ?
1763 tp
->nonagle
: TCP_NAGLE_PUSH
));
1766 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1767 * which is put after SKB on the list. It is very much like
1768 * tcp_fragment() except that it may make several kinds of assumptions
1769 * in order to speed up the splitting operation. In particular, we
1770 * know that all the data is in scatter-gather pages, and that the
1771 * packet has never been sent out before (and thus is not cloned).
1773 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1774 unsigned int mss_now
, gfp_t gfp
)
1776 struct sk_buff
*buff
;
1777 int nlen
= skb
->len
- len
;
1780 /* All of a TSO frame must be composed of paged data. */
1781 if (skb
->len
!= skb
->data_len
)
1782 return tcp_fragment(sk
, skb
, len
, mss_now
, gfp
);
1784 buff
= sk_stream_alloc_skb(sk
, 0, gfp
, true);
1785 if (unlikely(!buff
))
1788 sk
->sk_wmem_queued
+= buff
->truesize
;
1789 sk_mem_charge(sk
, buff
->truesize
);
1790 buff
->truesize
+= nlen
;
1791 skb
->truesize
-= nlen
;
1793 /* Correct the sequence numbers. */
1794 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1795 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1796 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1798 /* PSH and FIN should only be set in the second packet. */
1799 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1800 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1801 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1803 /* This packet was never sent out yet, so no SACK bits. */
1804 TCP_SKB_CB(buff
)->sacked
= 0;
1806 tcp_skb_fragment_eor(skb
, buff
);
1808 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1809 skb_split(skb
, buff
, len
);
1810 tcp_fragment_tstamp(skb
, buff
);
1812 /* Fix up tso_factor for both original and new SKB. */
1813 tcp_set_skb_tso_segs(skb
, mss_now
);
1814 tcp_set_skb_tso_segs(buff
, mss_now
);
1816 /* Link BUFF into the send queue. */
1817 __skb_header_release(buff
);
1818 tcp_insert_write_queue_after(skb
, buff
, sk
);
1823 /* Try to defer sending, if possible, in order to minimize the amount
1824 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1826 * This algorithm is from John Heffner.
1828 static bool tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
,
1829 bool *is_cwnd_limited
, u32 max_segs
)
1831 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1832 u32 age
, send_win
, cong_win
, limit
, in_flight
;
1833 struct tcp_sock
*tp
= tcp_sk(sk
);
1834 struct skb_mstamp now
;
1835 struct sk_buff
*head
;
1838 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1841 if (icsk
->icsk_ca_state
>= TCP_CA_Recovery
)
1844 /* Avoid bursty behavior by allowing defer
1845 * only if the last write was recent.
1847 if ((s32
)(tcp_time_stamp
- tp
->lsndtime
) > 0)
1850 in_flight
= tcp_packets_in_flight(tp
);
1852 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1854 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1856 /* From in_flight test above, we know that cwnd > in_flight. */
1857 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1859 limit
= min(send_win
, cong_win
);
1861 /* If a full-sized TSO skb can be sent, do it. */
1862 if (limit
>= max_segs
* tp
->mss_cache
)
1865 /* Middle in queue won't get any more data, full sendable already? */
1866 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1869 win_divisor
= ACCESS_ONCE(sysctl_tcp_tso_win_divisor
);
1871 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1873 /* If at least some fraction of a window is available,
1876 chunk
/= win_divisor
;
1880 /* Different approach, try not to defer past a single
1881 * ACK. Receiver should ACK every other full sized
1882 * frame, so if we have space for more than 3 frames
1885 if (limit
> tcp_max_tso_deferred_mss(tp
) * tp
->mss_cache
)
1889 head
= tcp_write_queue_head(sk
);
1890 skb_mstamp_get(&now
);
1891 age
= skb_mstamp_us_delta(&now
, &head
->skb_mstamp
);
1892 /* If next ACK is likely to come too late (half srtt), do not defer */
1893 if (age
< (tp
->srtt_us
>> 4))
1896 /* Ok, it looks like it is advisable to defer. */
1898 if (cong_win
< send_win
&& cong_win
<= skb
->len
)
1899 *is_cwnd_limited
= true;
1907 static inline void tcp_mtu_check_reprobe(struct sock
*sk
)
1909 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1910 struct tcp_sock
*tp
= tcp_sk(sk
);
1911 struct net
*net
= sock_net(sk
);
1915 interval
= net
->ipv4
.sysctl_tcp_probe_interval
;
1916 delta
= tcp_time_stamp
- icsk
->icsk_mtup
.probe_timestamp
;
1917 if (unlikely(delta
>= interval
* HZ
)) {
1918 int mss
= tcp_current_mss(sk
);
1920 /* Update current search range */
1921 icsk
->icsk_mtup
.probe_size
= 0;
1922 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+
1923 sizeof(struct tcphdr
) +
1924 icsk
->icsk_af_ops
->net_header_len
;
1925 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, mss
);
1927 /* Update probe time stamp */
1928 icsk
->icsk_mtup
.probe_timestamp
= tcp_time_stamp
;
1932 /* Create a new MTU probe if we are ready.
1933 * MTU probe is regularly attempting to increase the path MTU by
1934 * deliberately sending larger packets. This discovers routing
1935 * changes resulting in larger path MTUs.
1937 * Returns 0 if we should wait to probe (no cwnd available),
1938 * 1 if a probe was sent,
1941 static int tcp_mtu_probe(struct sock
*sk
)
1943 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1944 struct tcp_sock
*tp
= tcp_sk(sk
);
1945 struct sk_buff
*skb
, *nskb
, *next
;
1946 struct net
*net
= sock_net(sk
);
1953 /* Not currently probing/verifying,
1955 * have enough cwnd, and
1956 * not SACKing (the variable headers throw things off)
1958 if (likely(!icsk
->icsk_mtup
.enabled
||
1959 icsk
->icsk_mtup
.probe_size
||
1960 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
1961 tp
->snd_cwnd
< 11 ||
1962 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
))
1965 /* Use binary search for probe_size between tcp_mss_base,
1966 * and current mss_clamp. if (search_high - search_low)
1967 * smaller than a threshold, backoff from probing.
1969 mss_now
= tcp_current_mss(sk
);
1970 probe_size
= tcp_mtu_to_mss(sk
, (icsk
->icsk_mtup
.search_high
+
1971 icsk
->icsk_mtup
.search_low
) >> 1);
1972 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
1973 interval
= icsk
->icsk_mtup
.search_high
- icsk
->icsk_mtup
.search_low
;
1974 /* When misfortune happens, we are reprobing actively,
1975 * and then reprobe timer has expired. We stick with current
1976 * probing process by not resetting search range to its orignal.
1978 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
) ||
1979 interval
< net
->ipv4
.sysctl_tcp_probe_threshold
) {
1980 /* Check whether enough time has elaplased for
1981 * another round of probing.
1983 tcp_mtu_check_reprobe(sk
);
1987 /* Have enough data in the send queue to probe? */
1988 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
1991 if (tp
->snd_wnd
< size_needed
)
1993 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
1996 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1997 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
1998 if (!tcp_packets_in_flight(tp
))
2004 /* We're allowed to probe. Build it now. */
2005 nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
, false);
2008 sk
->sk_wmem_queued
+= nskb
->truesize
;
2009 sk_mem_charge(sk
, nskb
->truesize
);
2011 skb
= tcp_send_head(sk
);
2013 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
2014 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
2015 TCP_SKB_CB(nskb
)->tcp_flags
= TCPHDR_ACK
;
2016 TCP_SKB_CB(nskb
)->sacked
= 0;
2018 nskb
->ip_summed
= skb
->ip_summed
;
2020 tcp_insert_write_queue_before(nskb
, skb
, sk
);
2023 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
2024 copy
= min_t(int, skb
->len
, probe_size
- len
);
2025 if (nskb
->ip_summed
) {
2026 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
2028 __wsum csum
= skb_copy_and_csum_bits(skb
, 0,
2029 skb_put(nskb
, copy
),
2031 nskb
->csum
= csum_block_add(nskb
->csum
, csum
, len
);
2034 if (skb
->len
<= copy
) {
2035 /* We've eaten all the data from this skb.
2037 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
2038 tcp_unlink_write_queue(skb
, sk
);
2039 sk_wmem_free_skb(sk
, skb
);
2041 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
&
2042 ~(TCPHDR_FIN
|TCPHDR_PSH
);
2043 if (!skb_shinfo(skb
)->nr_frags
) {
2044 skb_pull(skb
, copy
);
2045 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2046 skb
->csum
= csum_partial(skb
->data
,
2049 __pskb_trim_head(skb
, copy
);
2050 tcp_set_skb_tso_segs(skb
, mss_now
);
2052 TCP_SKB_CB(skb
)->seq
+= copy
;
2057 if (len
>= probe_size
)
2060 tcp_init_tso_segs(nskb
, nskb
->len
);
2062 /* We're ready to send. If this fails, the probe will
2063 * be resegmented into mss-sized pieces by tcp_write_xmit().
2065 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
2066 /* Decrement cwnd here because we are sending
2067 * effectively two packets. */
2069 tcp_event_new_data_sent(sk
, nskb
);
2071 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
2072 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
2073 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
2081 /* TCP Small Queues :
2082 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2083 * (These limits are doubled for retransmits)
2085 * - better RTT estimation and ACK scheduling
2088 * Alas, some drivers / subsystems require a fair amount
2089 * of queued bytes to ensure line rate.
2090 * One example is wifi aggregation (802.11 AMPDU)
2092 static bool tcp_small_queue_check(struct sock
*sk
, const struct sk_buff
*skb
,
2093 unsigned int factor
)
2097 limit
= max(2 * skb
->truesize
, sk
->sk_pacing_rate
>> 10);
2098 limit
= min_t(u32
, limit
, sysctl_tcp_limit_output_bytes
);
2101 if (atomic_read(&sk
->sk_wmem_alloc
) > limit
) {
2102 /* Always send the 1st or 2nd skb in write queue.
2103 * No need to wait for TX completion to call us back,
2104 * after softirq/tasklet schedule.
2105 * This helps when TX completions are delayed too much.
2107 if (skb
== sk
->sk_write_queue
.next
||
2108 skb
->prev
== sk
->sk_write_queue
.next
)
2111 set_bit(TSQ_THROTTLED
, &sk
->sk_tsq_flags
);
2112 /* It is possible TX completion already happened
2113 * before we set TSQ_THROTTLED, so we must
2114 * test again the condition.
2116 smp_mb__after_atomic();
2117 if (atomic_read(&sk
->sk_wmem_alloc
) > limit
)
2123 static void tcp_chrono_set(struct tcp_sock
*tp
, const enum tcp_chrono
new)
2125 const u32 now
= tcp_time_stamp
;
2127 if (tp
->chrono_type
> TCP_CHRONO_UNSPEC
)
2128 tp
->chrono_stat
[tp
->chrono_type
- 1] += now
- tp
->chrono_start
;
2129 tp
->chrono_start
= now
;
2130 tp
->chrono_type
= new;
2133 void tcp_chrono_start(struct sock
*sk
, const enum tcp_chrono type
)
2135 struct tcp_sock
*tp
= tcp_sk(sk
);
2137 /* If there are multiple conditions worthy of tracking in a
2138 * chronograph then the highest priority enum takes precedence
2139 * over the other conditions. So that if something "more interesting"
2140 * starts happening, stop the previous chrono and start a new one.
2142 if (type
> tp
->chrono_type
)
2143 tcp_chrono_set(tp
, type
);
2146 void tcp_chrono_stop(struct sock
*sk
, const enum tcp_chrono type
)
2148 struct tcp_sock
*tp
= tcp_sk(sk
);
2151 /* There are multiple conditions worthy of tracking in a
2152 * chronograph, so that the highest priority enum takes
2153 * precedence over the other conditions (see tcp_chrono_start).
2154 * If a condition stops, we only stop chrono tracking if
2155 * it's the "most interesting" or current chrono we are
2156 * tracking and starts busy chrono if we have pending data.
2158 if (tcp_write_queue_empty(sk
))
2159 tcp_chrono_set(tp
, TCP_CHRONO_UNSPEC
);
2160 else if (type
== tp
->chrono_type
)
2161 tcp_chrono_set(tp
, TCP_CHRONO_BUSY
);
2164 /* This routine writes packets to the network. It advances the
2165 * send_head. This happens as incoming acks open up the remote
2168 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2169 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2170 * account rare use of URG, this is not a big flaw.
2172 * Send at most one packet when push_one > 0. Temporarily ignore
2173 * cwnd limit to force at most one packet out when push_one == 2.
2175 * Returns true, if no segments are in flight and we have queued segments,
2176 * but cannot send anything now because of SWS or another problem.
2178 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
2179 int push_one
, gfp_t gfp
)
2181 struct tcp_sock
*tp
= tcp_sk(sk
);
2182 struct sk_buff
*skb
;
2183 unsigned int tso_segs
, sent_pkts
;
2186 bool is_cwnd_limited
= false, is_rwnd_limited
= false;
2192 /* Do MTU probing. */
2193 result
= tcp_mtu_probe(sk
);
2196 } else if (result
> 0) {
2201 max_segs
= tcp_tso_segs(sk
, mss_now
);
2202 while ((skb
= tcp_send_head(sk
))) {
2205 tso_segs
= tcp_init_tso_segs(skb
, mss_now
);
2208 if (unlikely(tp
->repair
) && tp
->repair_queue
== TCP_SEND_QUEUE
) {
2209 /* "skb_mstamp" is used as a start point for the retransmit timer */
2210 skb_mstamp_get(&skb
->skb_mstamp
);
2211 goto repair
; /* Skip network transmission */
2214 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
2217 /* Force out a loss probe pkt. */
2223 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
))) {
2224 is_rwnd_limited
= true;
2228 if (tso_segs
== 1) {
2229 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
2230 (tcp_skb_is_last(sk
, skb
) ?
2231 nonagle
: TCP_NAGLE_PUSH
))))
2235 tcp_tso_should_defer(sk
, skb
, &is_cwnd_limited
,
2241 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
2242 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
2248 if (skb
->len
> limit
&&
2249 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
, gfp
)))
2252 if (test_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
))
2253 clear_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
);
2254 if (tcp_small_queue_check(sk
, skb
, 0))
2257 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
2261 /* Advance the send_head. This one is sent out.
2262 * This call will increment packets_out.
2264 tcp_event_new_data_sent(sk
, skb
);
2266 tcp_minshall_update(tp
, mss_now
, skb
);
2267 sent_pkts
+= tcp_skb_pcount(skb
);
2273 if (is_rwnd_limited
)
2274 tcp_chrono_start(sk
, TCP_CHRONO_RWND_LIMITED
);
2276 tcp_chrono_stop(sk
, TCP_CHRONO_RWND_LIMITED
);
2278 if (likely(sent_pkts
)) {
2279 if (tcp_in_cwnd_reduction(sk
))
2280 tp
->prr_out
+= sent_pkts
;
2282 /* Send one loss probe per tail loss episode. */
2284 tcp_schedule_loss_probe(sk
);
2285 is_cwnd_limited
|= (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
);
2286 tcp_cwnd_validate(sk
, is_cwnd_limited
);
2289 return !tp
->packets_out
&& tcp_send_head(sk
);
2292 bool tcp_schedule_loss_probe(struct sock
*sk
)
2294 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2295 struct tcp_sock
*tp
= tcp_sk(sk
);
2296 u32 timeout
, tlp_time_stamp
, rto_time_stamp
;
2297 u32 rtt
= usecs_to_jiffies(tp
->srtt_us
>> 3);
2299 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_EARLY_RETRANS
))
2301 /* No consecutive loss probes. */
2302 if (WARN_ON(icsk
->icsk_pending
== ICSK_TIME_LOSS_PROBE
)) {
2306 /* Don't do any loss probe on a Fast Open connection before 3WHS
2309 if (tp
->fastopen_rsk
)
2312 /* TLP is only scheduled when next timer event is RTO. */
2313 if (icsk
->icsk_pending
!= ICSK_TIME_RETRANS
)
2316 /* Schedule a loss probe in 2*RTT for SACK capable connections
2317 * in Open state, that are either limited by cwnd or application.
2319 if (sysctl_tcp_early_retrans
< 3 || !tp
->packets_out
||
2320 !tcp_is_sack(tp
) || inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
)
2323 if ((tp
->snd_cwnd
> tcp_packets_in_flight(tp
)) &&
2327 /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account
2328 * for delayed ack when there's one outstanding packet. If no RTT
2329 * sample is available then probe after TCP_TIMEOUT_INIT.
2331 timeout
= rtt
<< 1 ? : TCP_TIMEOUT_INIT
;
2332 if (tp
->packets_out
== 1)
2333 timeout
= max_t(u32
, timeout
,
2334 (rtt
+ (rtt
>> 1) + TCP_DELACK_MAX
));
2335 timeout
= max_t(u32
, timeout
, msecs_to_jiffies(10));
2337 /* If RTO is shorter, just schedule TLP in its place. */
2338 tlp_time_stamp
= tcp_time_stamp
+ timeout
;
2339 rto_time_stamp
= (u32
)inet_csk(sk
)->icsk_timeout
;
2340 if ((s32
)(tlp_time_stamp
- rto_time_stamp
) > 0) {
2341 s32 delta
= rto_time_stamp
- tcp_time_stamp
;
2346 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_LOSS_PROBE
, timeout
,
2351 /* Thanks to skb fast clones, we can detect if a prior transmit of
2352 * a packet is still in a qdisc or driver queue.
2353 * In this case, there is very little point doing a retransmit !
2355 static bool skb_still_in_host_queue(const struct sock
*sk
,
2356 const struct sk_buff
*skb
)
2358 if (unlikely(skb_fclone_busy(sk
, skb
))) {
2359 NET_INC_STATS(sock_net(sk
),
2360 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES
);
2366 /* When probe timeout (PTO) fires, try send a new segment if possible, else
2367 * retransmit the last segment.
2369 void tcp_send_loss_probe(struct sock
*sk
)
2371 struct tcp_sock
*tp
= tcp_sk(sk
);
2372 struct sk_buff
*skb
;
2374 int mss
= tcp_current_mss(sk
);
2376 skb
= tcp_send_head(sk
);
2378 if (tcp_snd_wnd_test(tp
, skb
, mss
)) {
2379 pcount
= tp
->packets_out
;
2380 tcp_write_xmit(sk
, mss
, TCP_NAGLE_OFF
, 2, GFP_ATOMIC
);
2381 if (tp
->packets_out
> pcount
)
2385 skb
= tcp_write_queue_prev(sk
, skb
);
2387 skb
= tcp_write_queue_tail(sk
);
2390 /* At most one outstanding TLP retransmission. */
2391 if (tp
->tlp_high_seq
)
2394 /* Retransmit last segment. */
2398 if (skb_still_in_host_queue(sk
, skb
))
2401 pcount
= tcp_skb_pcount(skb
);
2402 if (WARN_ON(!pcount
))
2405 if ((pcount
> 1) && (skb
->len
> (pcount
- 1) * mss
)) {
2406 if (unlikely(tcp_fragment(sk
, skb
, (pcount
- 1) * mss
, mss
,
2409 skb
= tcp_write_queue_next(sk
, skb
);
2412 if (WARN_ON(!skb
|| !tcp_skb_pcount(skb
)))
2415 if (__tcp_retransmit_skb(sk
, skb
, 1))
2418 /* Record snd_nxt for loss detection. */
2419 tp
->tlp_high_seq
= tp
->snd_nxt
;
2422 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPLOSSPROBES
);
2423 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2424 inet_csk(sk
)->icsk_pending
= 0;
2429 /* Push out any pending frames which were held back due to
2430 * TCP_CORK or attempt at coalescing tiny packets.
2431 * The socket must be locked by the caller.
2433 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
2436 /* If we are closed, the bytes will have to remain here.
2437 * In time closedown will finish, we empty the write queue and
2438 * all will be happy.
2440 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
2443 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0,
2444 sk_gfp_mask(sk
, GFP_ATOMIC
)))
2445 tcp_check_probe_timer(sk
);
2448 /* Send _single_ skb sitting at the send head. This function requires
2449 * true push pending frames to setup probe timer etc.
2451 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
2453 struct sk_buff
*skb
= tcp_send_head(sk
);
2455 BUG_ON(!skb
|| skb
->len
< mss_now
);
2457 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
2460 /* This function returns the amount that we can raise the
2461 * usable window based on the following constraints
2463 * 1. The window can never be shrunk once it is offered (RFC 793)
2464 * 2. We limit memory per socket
2467 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2468 * RECV.NEXT + RCV.WIN fixed until:
2469 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2471 * i.e. don't raise the right edge of the window until you can raise
2472 * it at least MSS bytes.
2474 * Unfortunately, the recommended algorithm breaks header prediction,
2475 * since header prediction assumes th->window stays fixed.
2477 * Strictly speaking, keeping th->window fixed violates the receiver
2478 * side SWS prevention criteria. The problem is that under this rule
2479 * a stream of single byte packets will cause the right side of the
2480 * window to always advance by a single byte.
2482 * Of course, if the sender implements sender side SWS prevention
2483 * then this will not be a problem.
2485 * BSD seems to make the following compromise:
2487 * If the free space is less than the 1/4 of the maximum
2488 * space available and the free space is less than 1/2 mss,
2489 * then set the window to 0.
2490 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2491 * Otherwise, just prevent the window from shrinking
2492 * and from being larger than the largest representable value.
2494 * This prevents incremental opening of the window in the regime
2495 * where TCP is limited by the speed of the reader side taking
2496 * data out of the TCP receive queue. It does nothing about
2497 * those cases where the window is constrained on the sender side
2498 * because the pipeline is full.
2500 * BSD also seems to "accidentally" limit itself to windows that are a
2501 * multiple of MSS, at least until the free space gets quite small.
2502 * This would appear to be a side effect of the mbuf implementation.
2503 * Combining these two algorithms results in the observed behavior
2504 * of having a fixed window size at almost all times.
2506 * Below we obtain similar behavior by forcing the offered window to
2507 * a multiple of the mss when it is feasible to do so.
2509 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2510 * Regular options like TIMESTAMP are taken into account.
2512 u32
__tcp_select_window(struct sock
*sk
)
2514 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2515 struct tcp_sock
*tp
= tcp_sk(sk
);
2516 /* MSS for the peer's data. Previous versions used mss_clamp
2517 * here. I don't know if the value based on our guesses
2518 * of peer's MSS is better for the performance. It's more correct
2519 * but may be worse for the performance because of rcv_mss
2520 * fluctuations. --SAW 1998/11/1
2522 int mss
= icsk
->icsk_ack
.rcv_mss
;
2523 int free_space
= tcp_space(sk
);
2524 int allowed_space
= tcp_full_space(sk
);
2525 int full_space
= min_t(int, tp
->window_clamp
, allowed_space
);
2528 if (unlikely(mss
> full_space
)) {
2533 if (free_space
< (full_space
>> 1)) {
2534 icsk
->icsk_ack
.quick
= 0;
2536 if (tcp_under_memory_pressure(sk
))
2537 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
2540 /* free_space might become our new window, make sure we don't
2541 * increase it due to wscale.
2543 free_space
= round_down(free_space
, 1 << tp
->rx_opt
.rcv_wscale
);
2545 /* if free space is less than mss estimate, or is below 1/16th
2546 * of the maximum allowed, try to move to zero-window, else
2547 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2548 * new incoming data is dropped due to memory limits.
2549 * With large window, mss test triggers way too late in order
2550 * to announce zero window in time before rmem limit kicks in.
2552 if (free_space
< (allowed_space
>> 4) || free_space
< mss
)
2556 if (free_space
> tp
->rcv_ssthresh
)
2557 free_space
= tp
->rcv_ssthresh
;
2559 /* Don't do rounding if we are using window scaling, since the
2560 * scaled window will not line up with the MSS boundary anyway.
2562 window
= tp
->rcv_wnd
;
2563 if (tp
->rx_opt
.rcv_wscale
) {
2564 window
= free_space
;
2566 /* Advertise enough space so that it won't get scaled away.
2567 * Import case: prevent zero window announcement if
2568 * 1<<rcv_wscale > mss.
2570 if (((window
>> tp
->rx_opt
.rcv_wscale
) << tp
->rx_opt
.rcv_wscale
) != window
)
2571 window
= (((window
>> tp
->rx_opt
.rcv_wscale
) + 1)
2572 << tp
->rx_opt
.rcv_wscale
);
2574 /* Get the largest window that is a nice multiple of mss.
2575 * Window clamp already applied above.
2576 * If our current window offering is within 1 mss of the
2577 * free space we just keep it. This prevents the divide
2578 * and multiply from happening most of the time.
2579 * We also don't do any window rounding when the free space
2582 if (window
<= free_space
- mss
|| window
> free_space
)
2583 window
= (free_space
/ mss
) * mss
;
2584 else if (mss
== full_space
&&
2585 free_space
> window
+ (full_space
>> 1))
2586 window
= free_space
;
2592 void tcp_skb_collapse_tstamp(struct sk_buff
*skb
,
2593 const struct sk_buff
*next_skb
)
2595 if (unlikely(tcp_has_tx_tstamp(next_skb
))) {
2596 const struct skb_shared_info
*next_shinfo
=
2597 skb_shinfo(next_skb
);
2598 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
2600 shinfo
->tx_flags
|= next_shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
2601 shinfo
->tskey
= next_shinfo
->tskey
;
2602 TCP_SKB_CB(skb
)->txstamp_ack
|=
2603 TCP_SKB_CB(next_skb
)->txstamp_ack
;
2607 /* Collapses two adjacent SKB's during retransmission. */
2608 static bool tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
2610 struct tcp_sock
*tp
= tcp_sk(sk
);
2611 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
2612 int skb_size
, next_skb_size
;
2614 skb_size
= skb
->len
;
2615 next_skb_size
= next_skb
->len
;
2617 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
2619 if (next_skb_size
) {
2620 if (next_skb_size
<= skb_availroom(skb
))
2621 skb_copy_bits(next_skb
, 0, skb_put(skb
, next_skb_size
),
2623 else if (!skb_shift(skb
, next_skb
, next_skb_size
))
2626 tcp_highest_sack_combine(sk
, next_skb
, skb
);
2628 tcp_unlink_write_queue(next_skb
, sk
);
2630 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
2631 skb
->ip_summed
= CHECKSUM_PARTIAL
;
2633 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2634 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
2636 /* Update sequence range on original skb. */
2637 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
2639 /* Merge over control information. This moves PSH/FIN etc. over */
2640 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(next_skb
)->tcp_flags
;
2642 /* All done, get rid of second SKB and account for it so
2643 * packet counting does not break.
2645 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
2646 TCP_SKB_CB(skb
)->eor
= TCP_SKB_CB(next_skb
)->eor
;
2648 /* changed transmit queue under us so clear hints */
2649 tcp_clear_retrans_hints_partial(tp
);
2650 if (next_skb
== tp
->retransmit_skb_hint
)
2651 tp
->retransmit_skb_hint
= skb
;
2653 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
2655 tcp_skb_collapse_tstamp(skb
, next_skb
);
2657 sk_wmem_free_skb(sk
, next_skb
);
2661 /* Check if coalescing SKBs is legal. */
2662 static bool tcp_can_collapse(const struct sock
*sk
, const struct sk_buff
*skb
)
2664 if (tcp_skb_pcount(skb
) > 1)
2666 if (skb_cloned(skb
))
2668 if (skb
== tcp_send_head(sk
))
2670 /* Some heuristics for collapsing over SACK'd could be invented */
2671 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2677 /* Collapse packets in the retransmit queue to make to create
2678 * less packets on the wire. This is only done on retransmission.
2680 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
2683 struct tcp_sock
*tp
= tcp_sk(sk
);
2684 struct sk_buff
*skb
= to
, *tmp
;
2687 if (!sysctl_tcp_retrans_collapse
)
2689 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2692 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
2693 if (!tcp_can_collapse(sk
, skb
))
2696 if (!tcp_skb_can_collapse_to(to
))
2709 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
2712 if (!tcp_collapse_retrans(sk
, to
))
2717 /* This retransmits one SKB. Policy decisions and retransmit queue
2718 * state updates are done by the caller. Returns non-zero if an
2719 * error occurred which prevented the send.
2721 int __tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int segs
)
2723 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2724 struct tcp_sock
*tp
= tcp_sk(sk
);
2725 unsigned int cur_mss
;
2729 /* Inconclusive MTU probe */
2730 if (icsk
->icsk_mtup
.probe_size
)
2731 icsk
->icsk_mtup
.probe_size
= 0;
2733 /* Do not sent more than we queued. 1/4 is reserved for possible
2734 * copying overhead: fragmentation, tunneling, mangling etc.
2736 if (atomic_read(&sk
->sk_wmem_alloc
) >
2737 min_t(u32
, sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2),
2741 if (skb_still_in_host_queue(sk
, skb
))
2744 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
2745 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
2747 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2751 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
2752 return -EHOSTUNREACH
; /* Routing failure or similar. */
2754 cur_mss
= tcp_current_mss(sk
);
2756 /* If receiver has shrunk his window, and skb is out of
2757 * new window, do not retransmit it. The exception is the
2758 * case, when window is shrunk to zero. In this case
2759 * our retransmit serves as a zero window probe.
2761 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
)) &&
2762 TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
2765 len
= cur_mss
* segs
;
2766 if (skb
->len
> len
) {
2767 if (tcp_fragment(sk
, skb
, len
, cur_mss
, GFP_ATOMIC
))
2768 return -ENOMEM
; /* We'll try again later. */
2770 if (skb_unclone(skb
, GFP_ATOMIC
))
2773 diff
= tcp_skb_pcount(skb
);
2774 tcp_set_skb_tso_segs(skb
, cur_mss
);
2775 diff
-= tcp_skb_pcount(skb
);
2777 tcp_adjust_pcount(sk
, skb
, diff
);
2778 if (skb
->len
< cur_mss
)
2779 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
2782 /* RFC3168, section 6.1.1.1. ECN fallback */
2783 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN_ECN
) == TCPHDR_SYN_ECN
)
2784 tcp_ecn_clear_syn(sk
, skb
);
2786 /* make sure skb->data is aligned on arches that require it
2787 * and check if ack-trimming & collapsing extended the headroom
2788 * beyond what csum_start can cover.
2790 if (unlikely((NET_IP_ALIGN
&& ((unsigned long)skb
->data
& 3)) ||
2791 skb_headroom(skb
) >= 0xFFFF)) {
2792 struct sk_buff
*nskb
;
2794 skb_mstamp_get(&skb
->skb_mstamp
);
2795 nskb
= __pskb_copy(skb
, MAX_TCP_HEADER
, GFP_ATOMIC
);
2796 err
= nskb
? tcp_transmit_skb(sk
, nskb
, 0, GFP_ATOMIC
) :
2799 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2803 segs
= tcp_skb_pcount(skb
);
2805 TCP_SKB_CB(skb
)->sacked
|= TCPCB_EVER_RETRANS
;
2806 /* Update global TCP statistics. */
2807 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
, segs
);
2808 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2809 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
2810 tp
->total_retrans
+= segs
;
2815 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int segs
)
2817 struct tcp_sock
*tp
= tcp_sk(sk
);
2818 int err
= __tcp_retransmit_skb(sk
, skb
, segs
);
2821 #if FASTRETRANS_DEBUG > 0
2822 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2823 net_dbg_ratelimited("retrans_out leaked\n");
2826 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
2827 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2829 /* Save stamp of the first retransmit. */
2830 if (!tp
->retrans_stamp
)
2831 tp
->retrans_stamp
= tcp_skb_timestamp(skb
);
2833 } else if (err
!= -EBUSY
) {
2834 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRETRANSFAIL
);
2837 if (tp
->undo_retrans
< 0)
2838 tp
->undo_retrans
= 0;
2839 tp
->undo_retrans
+= tcp_skb_pcount(skb
);
2843 /* Check if we forward retransmits are possible in the current
2844 * window/congestion state.
2846 static bool tcp_can_forward_retransmit(struct sock
*sk
)
2848 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2849 const struct tcp_sock
*tp
= tcp_sk(sk
);
2851 /* Forward retransmissions are possible only during Recovery. */
2852 if (icsk
->icsk_ca_state
!= TCP_CA_Recovery
)
2855 /* No forward retransmissions in Reno are possible. */
2856 if (tcp_is_reno(tp
))
2859 /* Yeah, we have to make difficult choice between forward transmission
2860 * and retransmission... Both ways have their merits...
2862 * For now we do not retransmit anything, while we have some new
2863 * segments to send. In the other cases, follow rule 3 for
2864 * NextSeg() specified in RFC3517.
2867 if (tcp_may_send_now(sk
))
2873 /* This gets called after a retransmit timeout, and the initially
2874 * retransmitted data is acknowledged. It tries to continue
2875 * resending the rest of the retransmit queue, until either
2876 * we've sent it all or the congestion window limit is reached.
2877 * If doing SACK, the first ACK which comes back for a timeout
2878 * based retransmit packet might feed us FACK information again.
2879 * If so, we use it to avoid unnecessarily retransmissions.
2881 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2883 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2884 struct tcp_sock
*tp
= tcp_sk(sk
);
2885 struct sk_buff
*skb
;
2886 struct sk_buff
*hole
= NULL
;
2887 u32 max_segs
, last_lost
;
2889 int fwd_rexmitting
= 0;
2891 if (!tp
->packets_out
)
2895 tp
->retransmit_high
= tp
->snd_una
;
2897 if (tp
->retransmit_skb_hint
) {
2898 skb
= tp
->retransmit_skb_hint
;
2899 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2900 if (after(last_lost
, tp
->retransmit_high
))
2901 last_lost
= tp
->retransmit_high
;
2903 skb
= tcp_write_queue_head(sk
);
2904 last_lost
= tp
->snd_una
;
2907 max_segs
= tcp_tso_segs(sk
, tcp_current_mss(sk
));
2908 tcp_for_write_queue_from(skb
, sk
) {
2912 if (skb
== tcp_send_head(sk
))
2914 /* we could do better than to assign each time */
2916 tp
->retransmit_skb_hint
= skb
;
2918 segs
= tp
->snd_cwnd
- tcp_packets_in_flight(tp
);
2921 sacked
= TCP_SKB_CB(skb
)->sacked
;
2922 /* In case tcp_shift_skb_data() have aggregated large skbs,
2923 * we need to make sure not sending too bigs TSO packets
2925 segs
= min_t(int, segs
, max_segs
);
2927 if (fwd_rexmitting
) {
2929 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_highest_sack_seq(tp
)))
2931 mib_idx
= LINUX_MIB_TCPFORWARDRETRANS
;
2933 } else if (!before(TCP_SKB_CB(skb
)->seq
, tp
->retransmit_high
)) {
2934 tp
->retransmit_high
= last_lost
;
2935 if (!tcp_can_forward_retransmit(sk
))
2937 /* Backtrack if necessary to non-L'ed skb */
2945 } else if (!(sacked
& TCPCB_LOST
)) {
2946 if (!hole
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2951 last_lost
= TCP_SKB_CB(skb
)->end_seq
;
2952 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2953 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2955 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2958 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2961 if (tcp_small_queue_check(sk
, skb
, 1))
2964 if (tcp_retransmit_skb(sk
, skb
, segs
))
2967 NET_ADD_STATS(sock_net(sk
), mib_idx
, tcp_skb_pcount(skb
));
2969 if (tcp_in_cwnd_reduction(sk
))
2970 tp
->prr_out
+= tcp_skb_pcount(skb
);
2972 if (skb
== tcp_write_queue_head(sk
))
2973 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2974 inet_csk(sk
)->icsk_rto
,
2979 /* We allow to exceed memory limits for FIN packets to expedite
2980 * connection tear down and (memory) recovery.
2981 * Otherwise tcp_send_fin() could be tempted to either delay FIN
2982 * or even be forced to close flow without any FIN.
2983 * In general, we want to allow one skb per socket to avoid hangs
2984 * with edge trigger epoll()
2986 void sk_forced_mem_schedule(struct sock
*sk
, int size
)
2990 if (size
<= sk
->sk_forward_alloc
)
2992 amt
= sk_mem_pages(size
);
2993 sk
->sk_forward_alloc
+= amt
* SK_MEM_QUANTUM
;
2994 sk_memory_allocated_add(sk
, amt
);
2996 if (mem_cgroup_sockets_enabled
&& sk
->sk_memcg
)
2997 mem_cgroup_charge_skmem(sk
->sk_memcg
, amt
);
3000 /* Send a FIN. The caller locks the socket for us.
3001 * We should try to send a FIN packet really hard, but eventually give up.
3003 void tcp_send_fin(struct sock
*sk
)
3005 struct sk_buff
*skb
, *tskb
= tcp_write_queue_tail(sk
);
3006 struct tcp_sock
*tp
= tcp_sk(sk
);
3008 /* Optimization, tack on the FIN if we have one skb in write queue and
3009 * this skb was not yet sent, or we are under memory pressure.
3010 * Note: in the latter case, FIN packet will be sent after a timeout,
3011 * as TCP stack thinks it has already been transmitted.
3013 if (tskb
&& (tcp_send_head(sk
) || tcp_under_memory_pressure(sk
))) {
3015 TCP_SKB_CB(tskb
)->tcp_flags
|= TCPHDR_FIN
;
3016 TCP_SKB_CB(tskb
)->end_seq
++;
3018 if (!tcp_send_head(sk
)) {
3019 /* This means tskb was already sent.
3020 * Pretend we included the FIN on previous transmit.
3021 * We need to set tp->snd_nxt to the value it would have
3022 * if FIN had been sent. This is because retransmit path
3023 * does not change tp->snd_nxt.
3029 skb
= alloc_skb_fclone(MAX_TCP_HEADER
, sk
->sk_allocation
);
3030 if (unlikely(!skb
)) {
3035 skb_reserve(skb
, MAX_TCP_HEADER
);
3036 sk_forced_mem_schedule(sk
, skb
->truesize
);
3037 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3038 tcp_init_nondata_skb(skb
, tp
->write_seq
,
3039 TCPHDR_ACK
| TCPHDR_FIN
);
3040 tcp_queue_skb(sk
, skb
);
3042 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
), TCP_NAGLE_OFF
);
3045 /* We get here when a process closes a file descriptor (either due to
3046 * an explicit close() or as a byproduct of exit()'ing) and there
3047 * was unread data in the receive queue. This behavior is recommended
3048 * by RFC 2525, section 2.17. -DaveM
3050 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
3052 struct sk_buff
*skb
;
3054 /* NOTE: No TCP options attached and we never retransmit this. */
3055 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
3057 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
3061 /* Reserve space for headers and prepare control bits. */
3062 skb_reserve(skb
, MAX_TCP_HEADER
);
3063 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
3064 TCPHDR_ACK
| TCPHDR_RST
);
3065 skb_mstamp_get(&skb
->skb_mstamp
);
3067 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
3068 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
3070 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
3073 /* Send a crossed SYN-ACK during socket establishment.
3074 * WARNING: This routine must only be called when we have already sent
3075 * a SYN packet that crossed the incoming SYN that caused this routine
3076 * to get called. If this assumption fails then the initial rcv_wnd
3077 * and rcv_wscale values will not be correct.
3079 int tcp_send_synack(struct sock
*sk
)
3081 struct sk_buff
*skb
;
3083 skb
= tcp_write_queue_head(sk
);
3084 if (!skb
|| !(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
3085 pr_debug("%s: wrong queue state\n", __func__
);
3088 if (!(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_ACK
)) {
3089 if (skb_cloned(skb
)) {
3090 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
3093 tcp_unlink_write_queue(skb
, sk
);
3094 __skb_header_release(nskb
);
3095 __tcp_add_write_queue_head(sk
, nskb
);
3096 sk_wmem_free_skb(sk
, skb
);
3097 sk
->sk_wmem_queued
+= nskb
->truesize
;
3098 sk_mem_charge(sk
, nskb
->truesize
);
3102 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ACK
;
3103 tcp_ecn_send_synack(sk
, skb
);
3105 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3109 * tcp_make_synack - Prepare a SYN-ACK.
3110 * sk: listener socket
3111 * dst: dst entry attached to the SYNACK
3112 * req: request_sock pointer
3114 * Allocate one skb and build a SYNACK packet.
3115 * @dst is consumed : Caller should not use it again.
3117 struct sk_buff
*tcp_make_synack(const struct sock
*sk
, struct dst_entry
*dst
,
3118 struct request_sock
*req
,
3119 struct tcp_fastopen_cookie
*foc
,
3120 enum tcp_synack_type synack_type
)
3122 struct inet_request_sock
*ireq
= inet_rsk(req
);
3123 const struct tcp_sock
*tp
= tcp_sk(sk
);
3124 struct tcp_md5sig_key
*md5
= NULL
;
3125 struct tcp_out_options opts
;
3126 struct sk_buff
*skb
;
3127 int tcp_header_size
;
3132 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
3133 if (unlikely(!skb
)) {
3137 /* Reserve space for headers. */
3138 skb_reserve(skb
, MAX_TCP_HEADER
);
3140 switch (synack_type
) {
3141 case TCP_SYNACK_NORMAL
:
3142 skb_set_owner_w(skb
, req_to_sk(req
));
3144 case TCP_SYNACK_COOKIE
:
3145 /* Under synflood, we do not attach skb to a socket,
3146 * to avoid false sharing.
3149 case TCP_SYNACK_FASTOPEN
:
3150 /* sk is a const pointer, because we want to express multiple
3151 * cpu might call us concurrently.
3152 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3154 skb_set_owner_w(skb
, (struct sock
*)sk
);
3157 skb_dst_set(skb
, dst
);
3159 mss
= dst_metric_advmss(dst
);
3160 user_mss
= READ_ONCE(tp
->rx_opt
.user_mss
);
3161 if (user_mss
&& user_mss
< mss
)
3164 memset(&opts
, 0, sizeof(opts
));
3165 #ifdef CONFIG_SYN_COOKIES
3166 if (unlikely(req
->cookie_ts
))
3167 skb
->skb_mstamp
.stamp_jiffies
= cookie_init_timestamp(req
);
3170 skb_mstamp_get(&skb
->skb_mstamp
);
3172 #ifdef CONFIG_TCP_MD5SIG
3174 md5
= tcp_rsk(req
)->af_specific
->req_md5_lookup(sk
, req_to_sk(req
));
3176 skb_set_hash(skb
, tcp_rsk(req
)->txhash
, PKT_HASH_TYPE_L4
);
3177 tcp_header_size
= tcp_synack_options(req
, mss
, skb
, &opts
, md5
, foc
) +
3180 skb_push(skb
, tcp_header_size
);
3181 skb_reset_transport_header(skb
);
3183 th
= (struct tcphdr
*)skb
->data
;
3184 memset(th
, 0, sizeof(struct tcphdr
));
3187 tcp_ecn_make_synack(req
, th
);
3188 th
->source
= htons(ireq
->ir_num
);
3189 th
->dest
= ireq
->ir_rmt_port
;
3190 /* Setting of flags are superfluous here for callers (and ECE is
3191 * not even correctly set)
3193 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
3194 TCPHDR_SYN
| TCPHDR_ACK
);
3196 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
3197 /* XXX data is queued and acked as is. No buffer/window check */
3198 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_nxt
);
3200 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3201 th
->window
= htons(min(req
->rsk_rcv_wnd
, 65535U));
3202 tcp_options_write((__be32
*)(th
+ 1), NULL
, &opts
);
3203 th
->doff
= (tcp_header_size
>> 2);
3204 __TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
3206 #ifdef CONFIG_TCP_MD5SIG
3207 /* Okay, we have all we need - do the md5 hash if needed */
3209 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
3210 md5
, req_to_sk(req
), skb
);
3214 /* Do not fool tcpdump (if any), clean our debris */
3218 EXPORT_SYMBOL(tcp_make_synack
);
3220 static void tcp_ca_dst_init(struct sock
*sk
, const struct dst_entry
*dst
)
3222 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3223 const struct tcp_congestion_ops
*ca
;
3224 u32 ca_key
= dst_metric(dst
, RTAX_CC_ALGO
);
3226 if (ca_key
== TCP_CA_UNSPEC
)
3230 ca
= tcp_ca_find_key(ca_key
);
3231 if (likely(ca
&& try_module_get(ca
->owner
))) {
3232 module_put(icsk
->icsk_ca_ops
->owner
);
3233 icsk
->icsk_ca_dst_locked
= tcp_ca_dst_locked(dst
);
3234 icsk
->icsk_ca_ops
= ca
;
3239 /* Do all connect socket setups that can be done AF independent. */
3240 static void tcp_connect_init(struct sock
*sk
)
3242 const struct dst_entry
*dst
= __sk_dst_get(sk
);
3243 struct tcp_sock
*tp
= tcp_sk(sk
);
3246 /* We'll fix this up when we get a response from the other end.
3247 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3249 tp
->tcp_header_len
= sizeof(struct tcphdr
) +
3250 (sysctl_tcp_timestamps
? TCPOLEN_TSTAMP_ALIGNED
: 0);
3252 #ifdef CONFIG_TCP_MD5SIG
3253 if (tp
->af_specific
->md5_lookup(sk
, sk
))
3254 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
3257 /* If user gave his TCP_MAXSEG, record it to clamp */
3258 if (tp
->rx_opt
.user_mss
)
3259 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
3262 tcp_sync_mss(sk
, dst_mtu(dst
));
3264 tcp_ca_dst_init(sk
, dst
);
3266 if (!tp
->window_clamp
)
3267 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
3268 tp
->advmss
= dst_metric_advmss(dst
);
3269 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->advmss
)
3270 tp
->advmss
= tp
->rx_opt
.user_mss
;
3272 tcp_initialize_rcv_mss(sk
);
3274 /* limit the window selection if the user enforce a smaller rx buffer */
3275 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
3276 (tp
->window_clamp
> tcp_full_space(sk
) || tp
->window_clamp
== 0))
3277 tp
->window_clamp
= tcp_full_space(sk
);
3279 tcp_select_initial_window(tcp_full_space(sk
),
3280 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
3283 sysctl_tcp_window_scaling
,
3285 dst_metric(dst
, RTAX_INITRWND
));
3287 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
3288 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
3291 sock_reset_flag(sk
, SOCK_DONE
);
3294 tp
->snd_una
= tp
->write_seq
;
3295 tp
->snd_sml
= tp
->write_seq
;
3296 tp
->snd_up
= tp
->write_seq
;
3297 tp
->snd_nxt
= tp
->write_seq
;
3299 if (likely(!tp
->repair
))
3302 tp
->rcv_tstamp
= tcp_time_stamp
;
3303 tp
->rcv_wup
= tp
->rcv_nxt
;
3304 tp
->copied_seq
= tp
->rcv_nxt
;
3306 inet_csk(sk
)->icsk_rto
= TCP_TIMEOUT_INIT
;
3307 inet_csk(sk
)->icsk_retransmits
= 0;
3308 tcp_clear_retrans(tp
);
3311 static void tcp_connect_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
3313 struct tcp_sock
*tp
= tcp_sk(sk
);
3314 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
3316 tcb
->end_seq
+= skb
->len
;
3317 __skb_header_release(skb
);
3318 __tcp_add_write_queue_tail(sk
, skb
);
3319 sk
->sk_wmem_queued
+= skb
->truesize
;
3320 sk_mem_charge(sk
, skb
->truesize
);
3321 tp
->write_seq
= tcb
->end_seq
;
3322 tp
->packets_out
+= tcp_skb_pcount(skb
);
3325 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
3326 * queue a data-only packet after the regular SYN, such that regular SYNs
3327 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3328 * only the SYN sequence, the data are retransmitted in the first ACK.
3329 * If cookie is not cached or other error occurs, falls back to send a
3330 * regular SYN with Fast Open cookie request option.
3332 static int tcp_send_syn_data(struct sock
*sk
, struct sk_buff
*syn
)
3334 struct tcp_sock
*tp
= tcp_sk(sk
);
3335 struct tcp_fastopen_request
*fo
= tp
->fastopen_req
;
3336 int syn_loss
= 0, space
, err
= 0;
3337 unsigned long last_syn_loss
= 0;
3338 struct sk_buff
*syn_data
;
3340 tp
->rx_opt
.mss_clamp
= tp
->advmss
; /* If MSS is not cached */
3341 tcp_fastopen_cache_get(sk
, &tp
->rx_opt
.mss_clamp
, &fo
->cookie
,
3342 &syn_loss
, &last_syn_loss
);
3343 /* Recurring FO SYN losses: revert to regular handshake temporarily */
3345 time_before(jiffies
, last_syn_loss
+ (60*HZ
<< syn_loss
))) {
3346 fo
->cookie
.len
= -1;
3350 if (sysctl_tcp_fastopen
& TFO_CLIENT_NO_COOKIE
)
3351 fo
->cookie
.len
= -1;
3352 else if (fo
->cookie
.len
<= 0)
3355 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3356 * user-MSS. Reserve maximum option space for middleboxes that add
3357 * private TCP options. The cost is reduced data space in SYN :(
3359 if (tp
->rx_opt
.user_mss
&& tp
->rx_opt
.user_mss
< tp
->rx_opt
.mss_clamp
)
3360 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
3361 space
= __tcp_mtu_to_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
) -
3362 MAX_TCP_OPTION_SPACE
;
3364 space
= min_t(size_t, space
, fo
->size
);
3366 /* limit to order-0 allocations */
3367 space
= min_t(size_t, space
, SKB_MAX_HEAD(MAX_TCP_HEADER
));
3369 syn_data
= sk_stream_alloc_skb(sk
, space
, sk
->sk_allocation
, false);
3372 syn_data
->ip_summed
= CHECKSUM_PARTIAL
;
3373 memcpy(syn_data
->cb
, syn
->cb
, sizeof(syn
->cb
));
3375 int copied
= copy_from_iter(skb_put(syn_data
, space
), space
,
3376 &fo
->data
->msg_iter
);
3377 if (unlikely(!copied
)) {
3378 kfree_skb(syn_data
);
3381 if (copied
!= space
) {
3382 skb_trim(syn_data
, copied
);
3386 /* No more data pending in inet_wait_for_connect() */
3387 if (space
== fo
->size
)
3391 tcp_connect_queue_skb(sk
, syn_data
);
3393 tcp_chrono_start(sk
, TCP_CHRONO_BUSY
);
3395 err
= tcp_transmit_skb(sk
, syn_data
, 1, sk
->sk_allocation
);
3397 syn
->skb_mstamp
= syn_data
->skb_mstamp
;
3399 /* Now full SYN+DATA was cloned and sent (or not),
3400 * remove the SYN from the original skb (syn_data)
3401 * we keep in write queue in case of a retransmit, as we
3402 * also have the SYN packet (with no data) in the same queue.
3404 TCP_SKB_CB(syn_data
)->seq
++;
3405 TCP_SKB_CB(syn_data
)->tcp_flags
= TCPHDR_ACK
| TCPHDR_PSH
;
3407 tp
->syn_data
= (fo
->copied
> 0);
3408 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
);
3413 /* Send a regular SYN with Fast Open cookie request option */
3414 if (fo
->cookie
.len
> 0)
3416 err
= tcp_transmit_skb(sk
, syn
, 1, sk
->sk_allocation
);
3418 tp
->syn_fastopen
= 0;
3420 fo
->cookie
.len
= -1; /* Exclude Fast Open option for SYN retries */
3424 /* Build a SYN and send it off. */
3425 int tcp_connect(struct sock
*sk
)
3427 struct tcp_sock
*tp
= tcp_sk(sk
);
3428 struct sk_buff
*buff
;
3431 tcp_connect_init(sk
);
3433 if (unlikely(tp
->repair
)) {
3434 tcp_finish_connect(sk
, NULL
);
3438 buff
= sk_stream_alloc_skb(sk
, 0, sk
->sk_allocation
, true);
3439 if (unlikely(!buff
))
3442 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPHDR_SYN
);
3443 tp
->retrans_stamp
= tcp_time_stamp
;
3444 tcp_connect_queue_skb(sk
, buff
);
3445 tcp_ecn_send_syn(sk
, buff
);
3447 /* Send off SYN; include data in Fast Open. */
3448 err
= tp
->fastopen_req
? tcp_send_syn_data(sk
, buff
) :
3449 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
3450 if (err
== -ECONNREFUSED
)
3453 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3454 * in order to make this packet get counted in tcpOutSegs.
3456 tp
->snd_nxt
= tp
->write_seq
;
3457 tp
->pushed_seq
= tp
->write_seq
;
3458 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
3460 /* Timer for repeating the SYN until an answer. */
3461 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3462 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3465 EXPORT_SYMBOL(tcp_connect
);
3467 /* Send out a delayed ack, the caller does the policy checking
3468 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3471 void tcp_send_delayed_ack(struct sock
*sk
)
3473 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3474 int ato
= icsk
->icsk_ack
.ato
;
3475 unsigned long timeout
;
3477 tcp_ca_event(sk
, CA_EVENT_DELAYED_ACK
);
3479 if (ato
> TCP_DELACK_MIN
) {
3480 const struct tcp_sock
*tp
= tcp_sk(sk
);
3481 int max_ato
= HZ
/ 2;
3483 if (icsk
->icsk_ack
.pingpong
||
3484 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
3485 max_ato
= TCP_DELACK_MAX
;
3487 /* Slow path, intersegment interval is "high". */
3489 /* If some rtt estimate is known, use it to bound delayed ack.
3490 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3494 int rtt
= max_t(int, usecs_to_jiffies(tp
->srtt_us
>> 3),
3501 ato
= min(ato
, max_ato
);
3504 /* Stay within the limit we were given */
3505 timeout
= jiffies
+ ato
;
3507 /* Use new timeout only if there wasn't a older one earlier. */
3508 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
3509 /* If delack timer was blocked or is about to expire,
3512 if (icsk
->icsk_ack
.blocked
||
3513 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
3518 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
3519 timeout
= icsk
->icsk_ack
.timeout
;
3521 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
3522 icsk
->icsk_ack
.timeout
= timeout
;
3523 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
3526 /* This routine sends an ack and also updates the window. */
3527 void tcp_send_ack(struct sock
*sk
)
3529 struct sk_buff
*buff
;
3531 /* If we have been reset, we may not send again. */
3532 if (sk
->sk_state
== TCP_CLOSE
)
3535 tcp_ca_event(sk
, CA_EVENT_NON_DELAYED_ACK
);
3537 /* We are not putting this on the write queue, so
3538 * tcp_transmit_skb() will set the ownership to this
3541 buff
= alloc_skb(MAX_TCP_HEADER
,
3542 sk_gfp_mask(sk
, GFP_ATOMIC
| __GFP_NOWARN
));
3543 if (unlikely(!buff
)) {
3544 inet_csk_schedule_ack(sk
);
3545 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
3546 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
3547 TCP_DELACK_MAX
, TCP_RTO_MAX
);
3551 /* Reserve space for headers and prepare control bits. */
3552 skb_reserve(buff
, MAX_TCP_HEADER
);
3553 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPHDR_ACK
);
3555 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3557 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3559 skb_set_tcp_pure_ack(buff
);
3561 /* Send it off, this clears delayed acks for us. */
3562 skb_mstamp_get(&buff
->skb_mstamp
);
3563 tcp_transmit_skb(sk
, buff
, 0, (__force gfp_t
)0);
3565 EXPORT_SYMBOL_GPL(tcp_send_ack
);
3567 /* This routine sends a packet with an out of date sequence
3568 * number. It assumes the other end will try to ack it.
3570 * Question: what should we make while urgent mode?
3571 * 4.4BSD forces sending single byte of data. We cannot send
3572 * out of window data, because we have SND.NXT==SND.MAX...
3574 * Current solution: to send TWO zero-length segments in urgent mode:
3575 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3576 * out-of-date with SND.UNA-1 to probe window.
3578 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
, int mib
)
3580 struct tcp_sock
*tp
= tcp_sk(sk
);
3581 struct sk_buff
*skb
;
3583 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3584 skb
= alloc_skb(MAX_TCP_HEADER
,
3585 sk_gfp_mask(sk
, GFP_ATOMIC
| __GFP_NOWARN
));
3589 /* Reserve space for headers and set control bits. */
3590 skb_reserve(skb
, MAX_TCP_HEADER
);
3591 /* Use a previous sequence. This should cause the other
3592 * end to send an ack. Don't queue or clone SKB, just
3595 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPHDR_ACK
);
3596 skb_mstamp_get(&skb
->skb_mstamp
);
3597 NET_INC_STATS(sock_net(sk
), mib
);
3598 return tcp_transmit_skb(sk
, skb
, 0, (__force gfp_t
)0);
3601 void tcp_send_window_probe(struct sock
*sk
)
3603 if (sk
->sk_state
== TCP_ESTABLISHED
) {
3604 tcp_sk(sk
)->snd_wl1
= tcp_sk(sk
)->rcv_nxt
- 1;
3605 tcp_xmit_probe_skb(sk
, 0, LINUX_MIB_TCPWINPROBE
);
3609 /* Initiate keepalive or window probe from timer. */
3610 int tcp_write_wakeup(struct sock
*sk
, int mib
)
3612 struct tcp_sock
*tp
= tcp_sk(sk
);
3613 struct sk_buff
*skb
;
3615 if (sk
->sk_state
== TCP_CLOSE
)
3618 skb
= tcp_send_head(sk
);
3619 if (skb
&& before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
3621 unsigned int mss
= tcp_current_mss(sk
);
3622 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
3624 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
3625 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
3627 /* We are probing the opening of a window
3628 * but the window size is != 0
3629 * must have been a result SWS avoidance ( sender )
3631 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
3633 seg_size
= min(seg_size
, mss
);
3634 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3635 if (tcp_fragment(sk
, skb
, seg_size
, mss
, GFP_ATOMIC
))
3637 } else if (!tcp_skb_pcount(skb
))
3638 tcp_set_skb_tso_segs(skb
, mss
);
3640 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3641 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3643 tcp_event_new_data_sent(sk
, skb
);
3646 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
3647 tcp_xmit_probe_skb(sk
, 1, mib
);
3648 return tcp_xmit_probe_skb(sk
, 0, mib
);
3652 /* A window probe timeout has occurred. If window is not closed send
3653 * a partial packet else a zero probe.
3655 void tcp_send_probe0(struct sock
*sk
)
3657 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3658 struct tcp_sock
*tp
= tcp_sk(sk
);
3659 struct net
*net
= sock_net(sk
);
3660 unsigned long probe_max
;
3663 err
= tcp_write_wakeup(sk
, LINUX_MIB_TCPWINPROBE
);
3665 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
3666 /* Cancel probe timer, if it is not required. */
3667 icsk
->icsk_probes_out
= 0;
3668 icsk
->icsk_backoff
= 0;
3673 if (icsk
->icsk_backoff
< net
->ipv4
.sysctl_tcp_retries2
)
3674 icsk
->icsk_backoff
++;
3675 icsk
->icsk_probes_out
++;
3676 probe_max
= TCP_RTO_MAX
;
3678 /* If packet was not sent due to local congestion,
3679 * do not backoff and do not remember icsk_probes_out.
3680 * Let local senders to fight for local resources.
3682 * Use accumulated backoff yet.
3684 if (!icsk
->icsk_probes_out
)
3685 icsk
->icsk_probes_out
= 1;
3686 probe_max
= TCP_RESOURCE_PROBE_INTERVAL
;
3688 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3689 tcp_probe0_when(sk
, probe_max
),
3693 int tcp_rtx_synack(const struct sock
*sk
, struct request_sock
*req
)
3695 const struct tcp_request_sock_ops
*af_ops
= tcp_rsk(req
)->af_specific
;
3699 tcp_rsk(req
)->txhash
= net_tx_rndhash();
3700 res
= af_ops
->send_synack(sk
, NULL
, &fl
, req
, NULL
, TCP_SYNACK_NORMAL
);
3702 __TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
3703 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
3704 if (unlikely(tcp_passive_fastopen(sk
)))
3705 tcp_sk(sk
)->total_retrans
++;
3709 EXPORT_SYMBOL(tcp_rtx_synack
);