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_LOSS_PROBE
)
82 NET_ADD_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
,
86 /* SND.NXT, if window was not shrunk or the amount of shrunk was less than one
87 * window scaling factor due to loss of precision.
88 * If window has been shrunk, what should we make? It is not clear at all.
89 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
90 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
91 * invalid. OK, let's make this for now:
93 static inline __u32
tcp_acceptable_seq(const struct sock
*sk
)
95 const struct tcp_sock
*tp
= tcp_sk(sk
);
97 if (!before(tcp_wnd_end(tp
), tp
->snd_nxt
) ||
98 (tp
->rx_opt
.wscale_ok
&&
99 ((tp
->snd_nxt
- tcp_wnd_end(tp
)) < (1 << tp
->rx_opt
.rcv_wscale
))))
102 return tcp_wnd_end(tp
);
105 /* Calculate mss to advertise in SYN segment.
106 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
108 * 1. It is independent of path mtu.
109 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
110 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
111 * attached devices, because some buggy hosts are confused by
113 * 4. We do not make 3, we advertise MSS, calculated from first
114 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
115 * This may be overridden via information stored in routing table.
116 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
117 * probably even Jumbo".
119 static __u16
tcp_advertise_mss(struct sock
*sk
)
121 struct tcp_sock
*tp
= tcp_sk(sk
);
122 const struct dst_entry
*dst
= __sk_dst_get(sk
);
123 int mss
= tp
->advmss
;
126 unsigned int metric
= dst_metric_advmss(dst
);
137 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
138 * This is the first part of cwnd validation mechanism.
140 void tcp_cwnd_restart(struct sock
*sk
, s32 delta
)
142 struct tcp_sock
*tp
= tcp_sk(sk
);
143 u32 restart_cwnd
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
144 u32 cwnd
= tp
->snd_cwnd
;
146 tcp_ca_event(sk
, CA_EVENT_CWND_RESTART
);
148 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
149 restart_cwnd
= min(restart_cwnd
, cwnd
);
151 while ((delta
-= inet_csk(sk
)->icsk_rto
) > 0 && cwnd
> restart_cwnd
)
153 tp
->snd_cwnd
= max(cwnd
, restart_cwnd
);
154 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
155 tp
->snd_cwnd_used
= 0;
158 /* Congestion state accounting after a packet has been sent. */
159 static void tcp_event_data_sent(struct tcp_sock
*tp
,
162 struct inet_connection_sock
*icsk
= inet_csk(sk
);
163 const u32 now
= tcp_jiffies32
;
165 if (tcp_packets_in_flight(tp
) == 0)
166 tcp_ca_event(sk
, CA_EVENT_TX_START
);
170 /* If it is a reply for ato after last received
171 * packet, enter pingpong mode.
173 if ((u32
)(now
- icsk
->icsk_ack
.lrcvtime
) < icsk
->icsk_ack
.ato
)
174 icsk
->icsk_ack
.pingpong
= 1;
177 /* Account for an ACK we sent. */
178 static inline void tcp_event_ack_sent(struct sock
*sk
, unsigned int pkts
)
180 tcp_dec_quickack_mode(sk
, pkts
);
181 inet_csk_clear_xmit_timer(sk
, ICSK_TIME_DACK
);
185 u32
tcp_default_init_rwnd(u32 mss
)
187 /* Initial receive window should be twice of TCP_INIT_CWND to
188 * enable proper sending of new unsent data during fast recovery
189 * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a
190 * limit when mss is larger than 1460.
192 u32 init_rwnd
= TCP_INIT_CWND
* 2;
195 init_rwnd
= max((1460 * init_rwnd
) / mss
, 2U);
199 /* Determine a window scaling and initial window to offer.
200 * Based on the assumption that the given amount of space
201 * will be offered. Store the results in the tp structure.
202 * NOTE: for smooth operation initial space offering should
203 * be a multiple of mss if possible. We assume here that mss >= 1.
204 * This MUST be enforced by all callers.
206 void tcp_select_initial_window(int __space
, __u32 mss
,
207 __u32
*rcv_wnd
, __u32
*window_clamp
,
208 int wscale_ok
, __u8
*rcv_wscale
,
211 unsigned int space
= (__space
< 0 ? 0 : __space
);
213 /* If no clamp set the clamp to the max possible scaled window */
214 if (*window_clamp
== 0)
215 (*window_clamp
) = (U16_MAX
<< TCP_MAX_WSCALE
);
216 space
= min(*window_clamp
, space
);
218 /* Quantize space offering to a multiple of mss if possible. */
220 space
= rounddown(space
, mss
);
222 /* NOTE: offering an initial window larger than 32767
223 * will break some buggy TCP stacks. If the admin tells us
224 * it is likely we could be speaking with such a buggy stack
225 * we will truncate our initial window offering to 32K-1
226 * unless the remote has sent us a window scaling option,
227 * which we interpret as a sign the remote TCP is not
228 * misinterpreting the window field as a signed quantity.
230 if (sysctl_tcp_workaround_signed_windows
)
231 (*rcv_wnd
) = min(space
, MAX_TCP_WINDOW
);
237 /* Set window scaling on max possible window */
238 space
= max_t(u32
, space
, sysctl_tcp_rmem
[2]);
239 space
= max_t(u32
, space
, sysctl_rmem_max
);
240 space
= min_t(u32
, space
, *window_clamp
);
241 while (space
> U16_MAX
&& (*rcv_wscale
) < TCP_MAX_WSCALE
) {
247 if (mss
> (1 << *rcv_wscale
)) {
248 if (!init_rcv_wnd
) /* Use default unless specified otherwise */
249 init_rcv_wnd
= tcp_default_init_rwnd(mss
);
250 *rcv_wnd
= min(*rcv_wnd
, init_rcv_wnd
* mss
);
253 /* Set the clamp no higher than max representable value */
254 (*window_clamp
) = min_t(__u32
, U16_MAX
<< (*rcv_wscale
), *window_clamp
);
256 EXPORT_SYMBOL(tcp_select_initial_window
);
258 /* Chose a new window to advertise, update state in tcp_sock for the
259 * socket, and return result with RFC1323 scaling applied. The return
260 * value can be stuffed directly into th->window for an outgoing
263 static u16
tcp_select_window(struct sock
*sk
)
265 struct tcp_sock
*tp
= tcp_sk(sk
);
266 u32 old_win
= tp
->rcv_wnd
;
267 u32 cur_win
= tcp_receive_window(tp
);
268 u32 new_win
= __tcp_select_window(sk
);
270 /* Never shrink the offered window */
271 if (new_win
< cur_win
) {
272 /* Danger Will Robinson!
273 * Don't update rcv_wup/rcv_wnd here or else
274 * we will not be able to advertise a zero
275 * window in time. --DaveM
277 * Relax Will Robinson.
280 NET_INC_STATS(sock_net(sk
),
281 LINUX_MIB_TCPWANTZEROWINDOWADV
);
282 new_win
= ALIGN(cur_win
, 1 << tp
->rx_opt
.rcv_wscale
);
284 tp
->rcv_wnd
= new_win
;
285 tp
->rcv_wup
= tp
->rcv_nxt
;
287 /* Make sure we do not exceed the maximum possible
290 if (!tp
->rx_opt
.rcv_wscale
&& sysctl_tcp_workaround_signed_windows
)
291 new_win
= min(new_win
, MAX_TCP_WINDOW
);
293 new_win
= min(new_win
, (65535U << tp
->rx_opt
.rcv_wscale
));
295 /* RFC1323 scaling applied */
296 new_win
>>= tp
->rx_opt
.rcv_wscale
;
300 NET_INC_STATS(sock_net(sk
),
301 LINUX_MIB_TCPTOZEROWINDOWADV
);
302 } else if (old_win
== 0) {
303 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPFROMZEROWINDOWADV
);
309 /* Packet ECN state for a SYN-ACK */
310 static void tcp_ecn_send_synack(struct sock
*sk
, struct sk_buff
*skb
)
312 const struct tcp_sock
*tp
= tcp_sk(sk
);
314 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_CWR
;
315 if (!(tp
->ecn_flags
& TCP_ECN_OK
))
316 TCP_SKB_CB(skb
)->tcp_flags
&= ~TCPHDR_ECE
;
317 else if (tcp_ca_needs_ecn(sk
) ||
318 tcp_bpf_ca_needs_ecn(sk
))
322 /* Packet ECN state for a SYN. */
323 static void tcp_ecn_send_syn(struct sock
*sk
, struct sk_buff
*skb
)
325 struct tcp_sock
*tp
= tcp_sk(sk
);
326 bool bpf_needs_ecn
= tcp_bpf_ca_needs_ecn(sk
);
327 bool use_ecn
= sock_net(sk
)->ipv4
.sysctl_tcp_ecn
== 1 ||
328 tcp_ca_needs_ecn(sk
) || bpf_needs_ecn
;
331 const struct dst_entry
*dst
= __sk_dst_get(sk
);
333 if (dst
&& dst_feature(dst
, RTAX_FEATURE_ECN
))
340 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ECE
| TCPHDR_CWR
;
341 tp
->ecn_flags
= TCP_ECN_OK
;
342 if (tcp_ca_needs_ecn(sk
) || bpf_needs_ecn
)
347 static void tcp_ecn_clear_syn(struct sock
*sk
, struct sk_buff
*skb
)
349 if (sock_net(sk
)->ipv4
.sysctl_tcp_ecn_fallback
)
350 /* tp->ecn_flags are cleared at a later point in time when
351 * SYN ACK is ultimatively being received.
353 TCP_SKB_CB(skb
)->tcp_flags
&= ~(TCPHDR_ECE
| TCPHDR_CWR
);
357 tcp_ecn_make_synack(const struct request_sock
*req
, struct tcphdr
*th
)
359 if (inet_rsk(req
)->ecn_ok
)
363 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
366 static void tcp_ecn_send(struct sock
*sk
, struct sk_buff
*skb
,
367 struct tcphdr
*th
, int tcp_header_len
)
369 struct tcp_sock
*tp
= tcp_sk(sk
);
371 if (tp
->ecn_flags
& TCP_ECN_OK
) {
372 /* Not-retransmitted data segment: set ECT and inject CWR. */
373 if (skb
->len
!= tcp_header_len
&&
374 !before(TCP_SKB_CB(skb
)->seq
, tp
->snd_nxt
)) {
376 if (tp
->ecn_flags
& TCP_ECN_QUEUE_CWR
) {
377 tp
->ecn_flags
&= ~TCP_ECN_QUEUE_CWR
;
379 skb_shinfo(skb
)->gso_type
|= SKB_GSO_TCP_ECN
;
381 } else if (!tcp_ca_needs_ecn(sk
)) {
382 /* ACK or retransmitted segment: clear ECT|CE */
383 INET_ECN_dontxmit(sk
);
385 if (tp
->ecn_flags
& TCP_ECN_DEMAND_CWR
)
390 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
391 * auto increment end seqno.
393 static void tcp_init_nondata_skb(struct sk_buff
*skb
, u32 seq
, u8 flags
)
395 skb
->ip_summed
= CHECKSUM_PARTIAL
;
398 TCP_SKB_CB(skb
)->tcp_flags
= flags
;
399 TCP_SKB_CB(skb
)->sacked
= 0;
401 tcp_skb_pcount_set(skb
, 1);
403 TCP_SKB_CB(skb
)->seq
= seq
;
404 if (flags
& (TCPHDR_SYN
| TCPHDR_FIN
))
406 TCP_SKB_CB(skb
)->end_seq
= seq
;
409 static inline bool tcp_urg_mode(const struct tcp_sock
*tp
)
411 return tp
->snd_una
!= tp
->snd_up
;
414 #define OPTION_SACK_ADVERTISE (1 << 0)
415 #define OPTION_TS (1 << 1)
416 #define OPTION_MD5 (1 << 2)
417 #define OPTION_WSCALE (1 << 3)
418 #define OPTION_FAST_OPEN_COOKIE (1 << 8)
420 struct tcp_out_options
{
421 u16 options
; /* bit field of OPTION_* */
422 u16 mss
; /* 0 to disable */
423 u8 ws
; /* window scale, 0 to disable */
424 u8 num_sack_blocks
; /* number of SACK blocks to include */
425 u8 hash_size
; /* bytes in hash_location */
426 __u8
*hash_location
; /* temporary pointer, overloaded */
427 __u32 tsval
, tsecr
; /* need to include OPTION_TS */
428 struct tcp_fastopen_cookie
*fastopen_cookie
; /* Fast open cookie */
431 /* Write previously computed TCP options to the packet.
433 * Beware: Something in the Internet is very sensitive to the ordering of
434 * TCP options, we learned this through the hard way, so be careful here.
435 * Luckily we can at least blame others for their non-compliance but from
436 * inter-operability perspective it seems that we're somewhat stuck with
437 * the ordering which we have been using if we want to keep working with
438 * those broken things (not that it currently hurts anybody as there isn't
439 * particular reason why the ordering would need to be changed).
441 * At least SACK_PERM as the first option is known to lead to a disaster
442 * (but it may well be that other scenarios fail similarly).
444 static void tcp_options_write(__be32
*ptr
, struct tcp_sock
*tp
,
445 struct tcp_out_options
*opts
)
447 u16 options
= opts
->options
; /* mungable copy */
449 if (unlikely(OPTION_MD5
& options
)) {
450 *ptr
++ = htonl((TCPOPT_NOP
<< 24) | (TCPOPT_NOP
<< 16) |
451 (TCPOPT_MD5SIG
<< 8) | TCPOLEN_MD5SIG
);
452 /* overload cookie hash location */
453 opts
->hash_location
= (__u8
*)ptr
;
457 if (unlikely(opts
->mss
)) {
458 *ptr
++ = htonl((TCPOPT_MSS
<< 24) |
459 (TCPOLEN_MSS
<< 16) |
463 if (likely(OPTION_TS
& options
)) {
464 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
465 *ptr
++ = htonl((TCPOPT_SACK_PERM
<< 24) |
466 (TCPOLEN_SACK_PERM
<< 16) |
467 (TCPOPT_TIMESTAMP
<< 8) |
469 options
&= ~OPTION_SACK_ADVERTISE
;
471 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
473 (TCPOPT_TIMESTAMP
<< 8) |
476 *ptr
++ = htonl(opts
->tsval
);
477 *ptr
++ = htonl(opts
->tsecr
);
480 if (unlikely(OPTION_SACK_ADVERTISE
& options
)) {
481 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
483 (TCPOPT_SACK_PERM
<< 8) |
487 if (unlikely(OPTION_WSCALE
& options
)) {
488 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
489 (TCPOPT_WINDOW
<< 16) |
490 (TCPOLEN_WINDOW
<< 8) |
494 if (unlikely(opts
->num_sack_blocks
)) {
495 struct tcp_sack_block
*sp
= tp
->rx_opt
.dsack
?
496 tp
->duplicate_sack
: tp
->selective_acks
;
499 *ptr
++ = htonl((TCPOPT_NOP
<< 24) |
502 (TCPOLEN_SACK_BASE
+ (opts
->num_sack_blocks
*
503 TCPOLEN_SACK_PERBLOCK
)));
505 for (this_sack
= 0; this_sack
< opts
->num_sack_blocks
;
507 *ptr
++ = htonl(sp
[this_sack
].start_seq
);
508 *ptr
++ = htonl(sp
[this_sack
].end_seq
);
511 tp
->rx_opt
.dsack
= 0;
514 if (unlikely(OPTION_FAST_OPEN_COOKIE
& options
)) {
515 struct tcp_fastopen_cookie
*foc
= opts
->fastopen_cookie
;
517 u32 len
; /* Fast Open option length */
520 len
= TCPOLEN_EXP_FASTOPEN_BASE
+ foc
->len
;
521 *ptr
= htonl((TCPOPT_EXP
<< 24) | (len
<< 16) |
522 TCPOPT_FASTOPEN_MAGIC
);
523 p
+= TCPOLEN_EXP_FASTOPEN_BASE
;
525 len
= TCPOLEN_FASTOPEN_BASE
+ foc
->len
;
526 *p
++ = TCPOPT_FASTOPEN
;
530 memcpy(p
, foc
->val
, foc
->len
);
531 if ((len
& 3) == 2) {
532 p
[foc
->len
] = TCPOPT_NOP
;
533 p
[foc
->len
+ 1] = TCPOPT_NOP
;
535 ptr
+= (len
+ 3) >> 2;
539 /* Compute TCP options for SYN packets. This is not the final
540 * network wire format yet.
542 static unsigned int tcp_syn_options(struct sock
*sk
, struct sk_buff
*skb
,
543 struct tcp_out_options
*opts
,
544 struct tcp_md5sig_key
**md5
)
546 struct tcp_sock
*tp
= tcp_sk(sk
);
547 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
548 struct tcp_fastopen_request
*fastopen
= tp
->fastopen_req
;
550 #ifdef CONFIG_TCP_MD5SIG
551 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
553 opts
->options
|= OPTION_MD5
;
554 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
560 /* We always get an MSS option. The option bytes which will be seen in
561 * normal data packets should timestamps be used, must be in the MSS
562 * advertised. But we subtract them from tp->mss_cache so that
563 * calculations in tcp_sendmsg are simpler etc. So account for this
564 * fact here if necessary. If we don't do this correctly, as a
565 * receiver we won't recognize data packets as being full sized when we
566 * should, and thus we won't abide by the delayed ACK rules correctly.
567 * SACKs don't matter, we never delay an ACK when we have any of those
569 opts
->mss
= tcp_advertise_mss(sk
);
570 remaining
-= TCPOLEN_MSS_ALIGNED
;
572 if (likely(sock_net(sk
)->ipv4
.sysctl_tcp_timestamps
&& !*md5
)) {
573 opts
->options
|= OPTION_TS
;
574 opts
->tsval
= tcp_skb_timestamp(skb
) + tp
->tsoffset
;
575 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
576 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
578 if (likely(sock_net(sk
)->ipv4
.sysctl_tcp_window_scaling
)) {
579 opts
->ws
= tp
->rx_opt
.rcv_wscale
;
580 opts
->options
|= OPTION_WSCALE
;
581 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
583 if (likely(sock_net(sk
)->ipv4
.sysctl_tcp_sack
)) {
584 opts
->options
|= OPTION_SACK_ADVERTISE
;
585 if (unlikely(!(OPTION_TS
& opts
->options
)))
586 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
589 if (fastopen
&& fastopen
->cookie
.len
>= 0) {
590 u32 need
= fastopen
->cookie
.len
;
592 need
+= fastopen
->cookie
.exp
? TCPOLEN_EXP_FASTOPEN_BASE
:
593 TCPOLEN_FASTOPEN_BASE
;
594 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
595 if (remaining
>= need
) {
596 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
597 opts
->fastopen_cookie
= &fastopen
->cookie
;
599 tp
->syn_fastopen
= 1;
600 tp
->syn_fastopen_exp
= fastopen
->cookie
.exp
? 1 : 0;
604 return MAX_TCP_OPTION_SPACE
- remaining
;
607 /* Set up TCP options for SYN-ACKs. */
608 static unsigned int tcp_synack_options(struct request_sock
*req
,
609 unsigned int mss
, struct sk_buff
*skb
,
610 struct tcp_out_options
*opts
,
611 const struct tcp_md5sig_key
*md5
,
612 struct tcp_fastopen_cookie
*foc
)
614 struct inet_request_sock
*ireq
= inet_rsk(req
);
615 unsigned int remaining
= MAX_TCP_OPTION_SPACE
;
617 #ifdef CONFIG_TCP_MD5SIG
619 opts
->options
|= OPTION_MD5
;
620 remaining
-= TCPOLEN_MD5SIG_ALIGNED
;
622 /* We can't fit any SACK blocks in a packet with MD5 + TS
623 * options. There was discussion about disabling SACK
624 * rather than TS in order to fit in better with old,
625 * buggy kernels, but that was deemed to be unnecessary.
627 ireq
->tstamp_ok
&= !ireq
->sack_ok
;
631 /* We always send an MSS option. */
633 remaining
-= TCPOLEN_MSS_ALIGNED
;
635 if (likely(ireq
->wscale_ok
)) {
636 opts
->ws
= ireq
->rcv_wscale
;
637 opts
->options
|= OPTION_WSCALE
;
638 remaining
-= TCPOLEN_WSCALE_ALIGNED
;
640 if (likely(ireq
->tstamp_ok
)) {
641 opts
->options
|= OPTION_TS
;
642 opts
->tsval
= tcp_skb_timestamp(skb
) + tcp_rsk(req
)->ts_off
;
643 opts
->tsecr
= req
->ts_recent
;
644 remaining
-= TCPOLEN_TSTAMP_ALIGNED
;
646 if (likely(ireq
->sack_ok
)) {
647 opts
->options
|= OPTION_SACK_ADVERTISE
;
648 if (unlikely(!ireq
->tstamp_ok
))
649 remaining
-= TCPOLEN_SACKPERM_ALIGNED
;
651 if (foc
!= NULL
&& foc
->len
>= 0) {
654 need
+= foc
->exp
? TCPOLEN_EXP_FASTOPEN_BASE
:
655 TCPOLEN_FASTOPEN_BASE
;
656 need
= (need
+ 3) & ~3U; /* Align to 32 bits */
657 if (remaining
>= need
) {
658 opts
->options
|= OPTION_FAST_OPEN_COOKIE
;
659 opts
->fastopen_cookie
= foc
;
664 return MAX_TCP_OPTION_SPACE
- remaining
;
667 /* Compute TCP options for ESTABLISHED sockets. This is not the
668 * final wire format yet.
670 static unsigned int tcp_established_options(struct sock
*sk
, struct sk_buff
*skb
,
671 struct tcp_out_options
*opts
,
672 struct tcp_md5sig_key
**md5
)
674 struct tcp_sock
*tp
= tcp_sk(sk
);
675 unsigned int size
= 0;
676 unsigned int eff_sacks
;
680 #ifdef CONFIG_TCP_MD5SIG
681 *md5
= tp
->af_specific
->md5_lookup(sk
, sk
);
682 if (unlikely(*md5
)) {
683 opts
->options
|= OPTION_MD5
;
684 size
+= TCPOLEN_MD5SIG_ALIGNED
;
690 if (likely(tp
->rx_opt
.tstamp_ok
)) {
691 opts
->options
|= OPTION_TS
;
692 opts
->tsval
= skb
? tcp_skb_timestamp(skb
) + tp
->tsoffset
: 0;
693 opts
->tsecr
= tp
->rx_opt
.ts_recent
;
694 size
+= TCPOLEN_TSTAMP_ALIGNED
;
697 eff_sacks
= tp
->rx_opt
.num_sacks
+ tp
->rx_opt
.dsack
;
698 if (unlikely(eff_sacks
)) {
699 const unsigned int remaining
= MAX_TCP_OPTION_SPACE
- size
;
700 opts
->num_sack_blocks
=
701 min_t(unsigned int, eff_sacks
,
702 (remaining
- TCPOLEN_SACK_BASE_ALIGNED
) /
703 TCPOLEN_SACK_PERBLOCK
);
704 size
+= TCPOLEN_SACK_BASE_ALIGNED
+
705 opts
->num_sack_blocks
* TCPOLEN_SACK_PERBLOCK
;
712 /* TCP SMALL QUEUES (TSQ)
714 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev)
715 * to reduce RTT and bufferbloat.
716 * We do this using a special skb destructor (tcp_wfree).
718 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb
719 * needs to be reallocated in a driver.
720 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc
722 * Since transmit from skb destructor is forbidden, we use a tasklet
723 * to process all sockets that eventually need to send more skbs.
724 * We use one tasklet per cpu, with its own queue of sockets.
727 struct tasklet_struct tasklet
;
728 struct list_head head
; /* queue of tcp sockets */
730 static DEFINE_PER_CPU(struct tsq_tasklet
, tsq_tasklet
);
732 static void tcp_tsq_handler(struct sock
*sk
)
734 if ((1 << sk
->sk_state
) &
735 (TCPF_ESTABLISHED
| TCPF_FIN_WAIT1
| TCPF_CLOSING
|
736 TCPF_CLOSE_WAIT
| TCPF_LAST_ACK
)) {
737 struct tcp_sock
*tp
= tcp_sk(sk
);
739 if (tp
->lost_out
> tp
->retrans_out
&&
740 tp
->snd_cwnd
> tcp_packets_in_flight(tp
))
741 tcp_xmit_retransmit_queue(sk
);
743 tcp_write_xmit(sk
, tcp_current_mss(sk
), tp
->nonagle
,
748 * One tasklet per cpu tries to send more skbs.
749 * We run in tasklet context but need to disable irqs when
750 * transferring tsq->head because tcp_wfree() might
751 * interrupt us (non NAPI drivers)
753 static void tcp_tasklet_func(unsigned long data
)
755 struct tsq_tasklet
*tsq
= (struct tsq_tasklet
*)data
;
758 struct list_head
*q
, *n
;
762 local_irq_save(flags
);
763 list_splice_init(&tsq
->head
, &list
);
764 local_irq_restore(flags
);
766 list_for_each_safe(q
, n
, &list
) {
767 tp
= list_entry(q
, struct tcp_sock
, tsq_node
);
768 list_del(&tp
->tsq_node
);
770 sk
= (struct sock
*)tp
;
771 smp_mb__before_atomic();
772 clear_bit(TSQ_QUEUED
, &sk
->sk_tsq_flags
);
774 if (!sk
->sk_lock
.owned
&&
775 test_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
)) {
777 if (!sock_owned_by_user(sk
)) {
778 clear_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
);
788 #define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \
789 TCPF_WRITE_TIMER_DEFERRED | \
790 TCPF_DELACK_TIMER_DEFERRED | \
791 TCPF_MTU_REDUCED_DEFERRED)
793 * tcp_release_cb - tcp release_sock() callback
796 * called from release_sock() to perform protocol dependent
797 * actions before socket release.
799 void tcp_release_cb(struct sock
*sk
)
801 unsigned long flags
, nflags
;
803 /* perform an atomic operation only if at least one flag is set */
805 flags
= sk
->sk_tsq_flags
;
806 if (!(flags
& TCP_DEFERRED_ALL
))
808 nflags
= flags
& ~TCP_DEFERRED_ALL
;
809 } while (cmpxchg(&sk
->sk_tsq_flags
, flags
, nflags
) != flags
);
811 if (flags
& TCPF_TSQ_DEFERRED
)
814 /* Here begins the tricky part :
815 * We are called from release_sock() with :
817 * 2) sk_lock.slock spinlock held
818 * 3) socket owned by us (sk->sk_lock.owned == 1)
820 * But following code is meant to be called from BH handlers,
821 * so we should keep BH disabled, but early release socket ownership
823 sock_release_ownership(sk
);
825 if (flags
& TCPF_WRITE_TIMER_DEFERRED
) {
826 tcp_write_timer_handler(sk
);
829 if (flags
& TCPF_DELACK_TIMER_DEFERRED
) {
830 tcp_delack_timer_handler(sk
);
833 if (flags
& TCPF_MTU_REDUCED_DEFERRED
) {
834 inet_csk(sk
)->icsk_af_ops
->mtu_reduced(sk
);
838 EXPORT_SYMBOL(tcp_release_cb
);
840 void __init
tcp_tasklet_init(void)
844 for_each_possible_cpu(i
) {
845 struct tsq_tasklet
*tsq
= &per_cpu(tsq_tasklet
, i
);
847 INIT_LIST_HEAD(&tsq
->head
);
848 tasklet_init(&tsq
->tasklet
,
855 * Write buffer destructor automatically called from kfree_skb.
856 * We can't xmit new skbs from this context, as we might already
859 void tcp_wfree(struct sk_buff
*skb
)
861 struct sock
*sk
= skb
->sk
;
862 struct tcp_sock
*tp
= tcp_sk(sk
);
863 unsigned long flags
, nval
, oval
;
865 /* Keep one reference on sk_wmem_alloc.
866 * Will be released by sk_free() from here or tcp_tasklet_func()
868 WARN_ON(refcount_sub_and_test(skb
->truesize
- 1, &sk
->sk_wmem_alloc
));
870 /* If this softirq is serviced by ksoftirqd, we are likely under stress.
871 * Wait until our queues (qdisc + devices) are drained.
873 * - less callbacks to tcp_write_xmit(), reducing stress (batches)
874 * - chance for incoming ACK (processed by another cpu maybe)
875 * to migrate this flow (skb->ooo_okay will be eventually set)
877 if (refcount_read(&sk
->sk_wmem_alloc
) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current
)
880 for (oval
= READ_ONCE(sk
->sk_tsq_flags
);; oval
= nval
) {
881 struct tsq_tasklet
*tsq
;
884 if (!(oval
& TSQF_THROTTLED
) || (oval
& TSQF_QUEUED
))
887 nval
= (oval
& ~TSQF_THROTTLED
) | TSQF_QUEUED
| TCPF_TSQ_DEFERRED
;
888 nval
= cmpxchg(&sk
->sk_tsq_flags
, oval
, nval
);
892 /* queue this socket to tasklet queue */
893 local_irq_save(flags
);
894 tsq
= this_cpu_ptr(&tsq_tasklet
);
895 empty
= list_empty(&tsq
->head
);
896 list_add(&tp
->tsq_node
, &tsq
->head
);
898 tasklet_schedule(&tsq
->tasklet
);
899 local_irq_restore(flags
);
906 /* Note: Called under hard irq.
907 * We can not call TCP stack right away.
909 enum hrtimer_restart
tcp_pace_kick(struct hrtimer
*timer
)
911 struct tcp_sock
*tp
= container_of(timer
, struct tcp_sock
, pacing_timer
);
912 struct sock
*sk
= (struct sock
*)tp
;
913 unsigned long nval
, oval
;
915 for (oval
= READ_ONCE(sk
->sk_tsq_flags
);; oval
= nval
) {
916 struct tsq_tasklet
*tsq
;
919 if (oval
& TSQF_QUEUED
)
922 nval
= (oval
& ~TSQF_THROTTLED
) | TSQF_QUEUED
| TCPF_TSQ_DEFERRED
;
923 nval
= cmpxchg(&sk
->sk_tsq_flags
, oval
, nval
);
927 if (!refcount_inc_not_zero(&sk
->sk_wmem_alloc
))
929 /* queue this socket to tasklet queue */
930 tsq
= this_cpu_ptr(&tsq_tasklet
);
931 empty
= list_empty(&tsq
->head
);
932 list_add(&tp
->tsq_node
, &tsq
->head
);
934 tasklet_schedule(&tsq
->tasklet
);
937 return HRTIMER_NORESTART
;
940 /* BBR congestion control needs pacing.
941 * Same remark for SO_MAX_PACING_RATE.
942 * sch_fq packet scheduler is efficiently handling pacing,
943 * but is not always installed/used.
944 * Return true if TCP stack should pace packets itself.
946 static bool tcp_needs_internal_pacing(const struct sock
*sk
)
948 return smp_load_acquire(&sk
->sk_pacing_status
) == SK_PACING_NEEDED
;
951 static void tcp_internal_pacing(struct sock
*sk
, const struct sk_buff
*skb
)
956 if (!tcp_needs_internal_pacing(sk
))
958 rate
= sk
->sk_pacing_rate
;
959 if (!rate
|| rate
== ~0U)
962 /* Should account for header sizes as sch_fq does,
963 * but lets make things simple.
965 len_ns
= (u64
)skb
->len
* NSEC_PER_SEC
;
966 do_div(len_ns
, rate
);
967 hrtimer_start(&tcp_sk(sk
)->pacing_timer
,
968 ktime_add_ns(ktime_get(), len_ns
),
969 HRTIMER_MODE_ABS_PINNED
);
972 /* This routine actually transmits TCP packets queued in by
973 * tcp_do_sendmsg(). This is used by both the initial
974 * transmission and possible later retransmissions.
975 * All SKB's seen here are completely headerless. It is our
976 * job to build the TCP header, and pass the packet down to
977 * IP so it can do the same plus pass the packet off to the
980 * We are working here with either a clone of the original
981 * SKB, or a fresh unique copy made by the retransmit engine.
983 static int tcp_transmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int clone_it
,
986 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
987 struct inet_sock
*inet
;
989 struct tcp_skb_cb
*tcb
;
990 struct tcp_out_options opts
;
991 unsigned int tcp_options_size
, tcp_header_size
;
992 struct tcp_md5sig_key
*md5
;
996 BUG_ON(!skb
|| !tcp_skb_pcount(skb
));
999 skb
->skb_mstamp
= tp
->tcp_mstamp
;
1001 TCP_SKB_CB(skb
)->tx
.in_flight
= TCP_SKB_CB(skb
)->end_seq
1003 tcp_rate_skb_sent(sk
, skb
);
1005 if (unlikely(skb_cloned(skb
)))
1006 skb
= pskb_copy(skb
, gfp_mask
);
1008 skb
= skb_clone(skb
, gfp_mask
);
1014 tcb
= TCP_SKB_CB(skb
);
1015 memset(&opts
, 0, sizeof(opts
));
1017 if (unlikely(tcb
->tcp_flags
& TCPHDR_SYN
))
1018 tcp_options_size
= tcp_syn_options(sk
, skb
, &opts
, &md5
);
1020 tcp_options_size
= tcp_established_options(sk
, skb
, &opts
,
1022 tcp_header_size
= tcp_options_size
+ sizeof(struct tcphdr
);
1024 /* if no packet is in qdisc/device queue, then allow XPS to select
1025 * another queue. We can be called from tcp_tsq_handler()
1026 * which holds one reference to sk_wmem_alloc.
1028 * TODO: Ideally, in-flight pure ACK packets should not matter here.
1029 * One way to get this would be to set skb->truesize = 2 on them.
1031 skb
->ooo_okay
= sk_wmem_alloc_get(sk
) < SKB_TRUESIZE(1);
1033 /* If we had to use memory reserve to allocate this skb,
1034 * this might cause drops if packet is looped back :
1035 * Other socket might not have SOCK_MEMALLOC.
1036 * Packets not looped back do not care about pfmemalloc.
1038 skb
->pfmemalloc
= 0;
1040 skb_push(skb
, tcp_header_size
);
1041 skb_reset_transport_header(skb
);
1045 skb
->destructor
= skb_is_tcp_pure_ack(skb
) ? __sock_wfree
: tcp_wfree
;
1046 skb_set_hash_from_sk(skb
, sk
);
1047 refcount_add(skb
->truesize
, &sk
->sk_wmem_alloc
);
1049 skb_set_dst_pending_confirm(skb
, sk
->sk_dst_pending_confirm
);
1051 /* Build TCP header and checksum it. */
1052 th
= (struct tcphdr
*)skb
->data
;
1053 th
->source
= inet
->inet_sport
;
1054 th
->dest
= inet
->inet_dport
;
1055 th
->seq
= htonl(tcb
->seq
);
1056 th
->ack_seq
= htonl(tp
->rcv_nxt
);
1057 *(((__be16
*)th
) + 6) = htons(((tcp_header_size
>> 2) << 12) |
1063 /* The urg_mode check is necessary during a below snd_una win probe */
1064 if (unlikely(tcp_urg_mode(tp
) && before(tcb
->seq
, tp
->snd_up
))) {
1065 if (before(tp
->snd_up
, tcb
->seq
+ 0x10000)) {
1066 th
->urg_ptr
= htons(tp
->snd_up
- tcb
->seq
);
1068 } else if (after(tcb
->seq
+ 0xFFFF, tp
->snd_nxt
)) {
1069 th
->urg_ptr
= htons(0xFFFF);
1074 tcp_options_write((__be32
*)(th
+ 1), tp
, &opts
);
1075 skb_shinfo(skb
)->gso_type
= sk
->sk_gso_type
;
1076 if (likely(!(tcb
->tcp_flags
& TCPHDR_SYN
))) {
1077 th
->window
= htons(tcp_select_window(sk
));
1078 tcp_ecn_send(sk
, skb
, th
, tcp_header_size
);
1080 /* RFC1323: The window in SYN & SYN/ACK segments
1083 th
->window
= htons(min(tp
->rcv_wnd
, 65535U));
1085 #ifdef CONFIG_TCP_MD5SIG
1086 /* Calculate the MD5 hash, as we have all we need now */
1088 sk_nocaps_add(sk
, NETIF_F_GSO_MASK
);
1089 tp
->af_specific
->calc_md5_hash(opts
.hash_location
,
1094 icsk
->icsk_af_ops
->send_check(sk
, skb
);
1096 if (likely(tcb
->tcp_flags
& TCPHDR_ACK
))
1097 tcp_event_ack_sent(sk
, tcp_skb_pcount(skb
));
1099 if (skb
->len
!= tcp_header_size
) {
1100 tcp_event_data_sent(tp
, sk
);
1101 tp
->data_segs_out
+= tcp_skb_pcount(skb
);
1102 tcp_internal_pacing(sk
, skb
);
1105 if (after(tcb
->end_seq
, tp
->snd_nxt
) || tcb
->seq
== tcb
->end_seq
)
1106 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
,
1107 tcp_skb_pcount(skb
));
1109 tp
->segs_out
+= tcp_skb_pcount(skb
);
1110 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */
1111 skb_shinfo(skb
)->gso_segs
= tcp_skb_pcount(skb
);
1112 skb_shinfo(skb
)->gso_size
= tcp_skb_mss(skb
);
1114 /* Our usage of tstamp should remain private */
1117 /* Cleanup our debris for IP stacks */
1118 memset(skb
->cb
, 0, max(sizeof(struct inet_skb_parm
),
1119 sizeof(struct inet6_skb_parm
)));
1121 err
= icsk
->icsk_af_ops
->queue_xmit(sk
, skb
, &inet
->cork
.fl
);
1123 if (likely(err
<= 0))
1128 return net_xmit_eval(err
);
1131 /* This routine just queues the buffer for sending.
1133 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
1134 * otherwise socket can stall.
1136 static void tcp_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
1138 struct tcp_sock
*tp
= tcp_sk(sk
);
1140 /* Advance write_seq and place onto the write_queue. */
1141 tp
->write_seq
= TCP_SKB_CB(skb
)->end_seq
;
1142 __skb_header_release(skb
);
1143 tcp_add_write_queue_tail(sk
, skb
);
1144 sk
->sk_wmem_queued
+= skb
->truesize
;
1145 sk_mem_charge(sk
, skb
->truesize
);
1148 /* Initialize TSO segments for a packet. */
1149 static void tcp_set_skb_tso_segs(struct sk_buff
*skb
, unsigned int mss_now
)
1151 if (skb
->len
<= mss_now
|| skb
->ip_summed
== CHECKSUM_NONE
) {
1152 /* Avoid the costly divide in the normal
1155 tcp_skb_pcount_set(skb
, 1);
1156 TCP_SKB_CB(skb
)->tcp_gso_size
= 0;
1158 tcp_skb_pcount_set(skb
, DIV_ROUND_UP(skb
->len
, mss_now
));
1159 TCP_SKB_CB(skb
)->tcp_gso_size
= mss_now
;
1163 /* When a modification to fackets out becomes necessary, we need to check
1164 * skb is counted to fackets_out or not.
1166 static void tcp_adjust_fackets_out(struct sock
*sk
, const struct sk_buff
*skb
,
1169 struct tcp_sock
*tp
= tcp_sk(sk
);
1171 if (!tp
->sacked_out
|| tcp_is_reno(tp
))
1174 if (after(tcp_highest_sack_seq(tp
), TCP_SKB_CB(skb
)->seq
))
1175 tp
->fackets_out
-= decr
;
1178 /* Pcount in the middle of the write queue got changed, we need to do various
1179 * tweaks to fix counters
1181 static void tcp_adjust_pcount(struct sock
*sk
, const struct sk_buff
*skb
, int decr
)
1183 struct tcp_sock
*tp
= tcp_sk(sk
);
1185 tp
->packets_out
-= decr
;
1187 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
1188 tp
->sacked_out
-= decr
;
1189 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
)
1190 tp
->retrans_out
-= decr
;
1191 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_LOST
)
1192 tp
->lost_out
-= decr
;
1194 /* Reno case is special. Sigh... */
1195 if (tcp_is_reno(tp
) && decr
> 0)
1196 tp
->sacked_out
-= min_t(u32
, tp
->sacked_out
, decr
);
1198 tcp_adjust_fackets_out(sk
, skb
, decr
);
1200 if (tp
->lost_skb_hint
&&
1201 before(TCP_SKB_CB(skb
)->seq
, TCP_SKB_CB(tp
->lost_skb_hint
)->seq
) &&
1202 (tcp_is_fack(tp
) || (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)))
1203 tp
->lost_cnt_hint
-= decr
;
1205 tcp_verify_left_out(tp
);
1208 static bool tcp_has_tx_tstamp(const struct sk_buff
*skb
)
1210 return TCP_SKB_CB(skb
)->txstamp_ack
||
1211 (skb_shinfo(skb
)->tx_flags
& SKBTX_ANY_TSTAMP
);
1214 static void tcp_fragment_tstamp(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1216 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
1218 if (unlikely(tcp_has_tx_tstamp(skb
)) &&
1219 !before(shinfo
->tskey
, TCP_SKB_CB(skb2
)->seq
)) {
1220 struct skb_shared_info
*shinfo2
= skb_shinfo(skb2
);
1221 u8 tsflags
= shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
1223 shinfo
->tx_flags
&= ~tsflags
;
1224 shinfo2
->tx_flags
|= tsflags
;
1225 swap(shinfo
->tskey
, shinfo2
->tskey
);
1226 TCP_SKB_CB(skb2
)->txstamp_ack
= TCP_SKB_CB(skb
)->txstamp_ack
;
1227 TCP_SKB_CB(skb
)->txstamp_ack
= 0;
1231 static void tcp_skb_fragment_eor(struct sk_buff
*skb
, struct sk_buff
*skb2
)
1233 TCP_SKB_CB(skb2
)->eor
= TCP_SKB_CB(skb
)->eor
;
1234 TCP_SKB_CB(skb
)->eor
= 0;
1237 /* Function to create two new TCP segments. Shrinks the given segment
1238 * to the specified size and appends a new segment with the rest of the
1239 * packet to the list. This won't be called frequently, I hope.
1240 * Remember, these are still headerless SKBs at this point.
1242 int tcp_fragment(struct sock
*sk
, struct sk_buff
*skb
, u32 len
,
1243 unsigned int mss_now
, gfp_t gfp
)
1245 struct tcp_sock
*tp
= tcp_sk(sk
);
1246 struct sk_buff
*buff
;
1247 int nsize
, old_factor
;
1251 if (WARN_ON(len
> skb
->len
))
1254 nsize
= skb_headlen(skb
) - len
;
1258 if (skb_unclone(skb
, gfp
))
1261 /* Get a new skb... force flag on. */
1262 buff
= sk_stream_alloc_skb(sk
, nsize
, gfp
, true);
1264 return -ENOMEM
; /* We'll just try again later. */
1266 sk
->sk_wmem_queued
+= buff
->truesize
;
1267 sk_mem_charge(sk
, buff
->truesize
);
1268 nlen
= skb
->len
- len
- nsize
;
1269 buff
->truesize
+= nlen
;
1270 skb
->truesize
-= nlen
;
1272 /* Correct the sequence numbers. */
1273 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1274 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1275 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1277 /* PSH and FIN should only be set in the second packet. */
1278 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1279 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1280 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1281 TCP_SKB_CB(buff
)->sacked
= TCP_SKB_CB(skb
)->sacked
;
1282 tcp_skb_fragment_eor(skb
, buff
);
1284 if (!skb_shinfo(skb
)->nr_frags
&& skb
->ip_summed
!= CHECKSUM_PARTIAL
) {
1285 /* Copy and checksum data tail into the new buffer. */
1286 buff
->csum
= csum_partial_copy_nocheck(skb
->data
+ len
,
1287 skb_put(buff
, nsize
),
1292 skb
->csum
= csum_block_sub(skb
->csum
, buff
->csum
, len
);
1294 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1295 skb_split(skb
, buff
, len
);
1298 buff
->ip_summed
= skb
->ip_summed
;
1300 buff
->tstamp
= skb
->tstamp
;
1301 tcp_fragment_tstamp(skb
, buff
);
1303 old_factor
= tcp_skb_pcount(skb
);
1305 /* Fix up tso_factor for both original and new SKB. */
1306 tcp_set_skb_tso_segs(skb
, mss_now
);
1307 tcp_set_skb_tso_segs(buff
, mss_now
);
1309 /* Update delivered info for the new segment */
1310 TCP_SKB_CB(buff
)->tx
= TCP_SKB_CB(skb
)->tx
;
1312 /* If this packet has been sent out already, we must
1313 * adjust the various packet counters.
1315 if (!before(tp
->snd_nxt
, TCP_SKB_CB(buff
)->end_seq
)) {
1316 int diff
= old_factor
- tcp_skb_pcount(skb
) -
1317 tcp_skb_pcount(buff
);
1320 tcp_adjust_pcount(sk
, skb
, diff
);
1323 /* Link BUFF into the send queue. */
1324 __skb_header_release(buff
);
1325 tcp_insert_write_queue_after(skb
, buff
, sk
);
1330 /* This is similar to __pskb_pull_tail(). The difference is that pulled
1331 * data is not copied, but immediately discarded.
1333 static int __pskb_trim_head(struct sk_buff
*skb
, int len
)
1335 struct skb_shared_info
*shinfo
;
1338 eat
= min_t(int, len
, skb_headlen(skb
));
1340 __skb_pull(skb
, eat
);
1347 shinfo
= skb_shinfo(skb
);
1348 for (i
= 0; i
< shinfo
->nr_frags
; i
++) {
1349 int size
= skb_frag_size(&shinfo
->frags
[i
]);
1352 skb_frag_unref(skb
, i
);
1355 shinfo
->frags
[k
] = shinfo
->frags
[i
];
1357 shinfo
->frags
[k
].page_offset
+= eat
;
1358 skb_frag_size_sub(&shinfo
->frags
[k
], eat
);
1364 shinfo
->nr_frags
= k
;
1366 skb
->data_len
-= len
;
1367 skb
->len
= skb
->data_len
;
1371 /* Remove acked data from a packet in the transmit queue. */
1372 int tcp_trim_head(struct sock
*sk
, struct sk_buff
*skb
, u32 len
)
1376 if (skb_unclone(skb
, GFP_ATOMIC
))
1379 delta_truesize
= __pskb_trim_head(skb
, len
);
1381 TCP_SKB_CB(skb
)->seq
+= len
;
1382 skb
->ip_summed
= CHECKSUM_PARTIAL
;
1384 if (delta_truesize
) {
1385 skb
->truesize
-= delta_truesize
;
1386 sk
->sk_wmem_queued
-= delta_truesize
;
1387 sk_mem_uncharge(sk
, delta_truesize
);
1388 sock_set_flag(sk
, SOCK_QUEUE_SHRUNK
);
1391 /* Any change of skb->len requires recalculation of tso factor. */
1392 if (tcp_skb_pcount(skb
) > 1)
1393 tcp_set_skb_tso_segs(skb
, tcp_skb_mss(skb
));
1398 /* Calculate MSS not accounting any TCP options. */
1399 static inline int __tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1401 const struct tcp_sock
*tp
= tcp_sk(sk
);
1402 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1405 /* Calculate base mss without TCP options:
1406 It is MMS_S - sizeof(tcphdr) of rfc1122
1408 mss_now
= pmtu
- icsk
->icsk_af_ops
->net_header_len
- sizeof(struct tcphdr
);
1410 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1411 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1412 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1414 if (dst
&& dst_allfrag(dst
))
1415 mss_now
-= icsk
->icsk_af_ops
->net_frag_header_len
;
1418 /* Clamp it (mss_clamp does not include tcp options) */
1419 if (mss_now
> tp
->rx_opt
.mss_clamp
)
1420 mss_now
= tp
->rx_opt
.mss_clamp
;
1422 /* Now subtract optional transport overhead */
1423 mss_now
-= icsk
->icsk_ext_hdr_len
;
1425 /* Then reserve room for full set of TCP options and 8 bytes of data */
1431 /* Calculate MSS. Not accounting for SACKs here. */
1432 int tcp_mtu_to_mss(struct sock
*sk
, int pmtu
)
1434 /* Subtract TCP options size, not including SACKs */
1435 return __tcp_mtu_to_mss(sk
, pmtu
) -
1436 (tcp_sk(sk
)->tcp_header_len
- sizeof(struct tcphdr
));
1439 /* Inverse of above */
1440 int tcp_mss_to_mtu(struct sock
*sk
, int mss
)
1442 const struct tcp_sock
*tp
= tcp_sk(sk
);
1443 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1447 tp
->tcp_header_len
+
1448 icsk
->icsk_ext_hdr_len
+
1449 icsk
->icsk_af_ops
->net_header_len
;
1451 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */
1452 if (icsk
->icsk_af_ops
->net_frag_header_len
) {
1453 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1455 if (dst
&& dst_allfrag(dst
))
1456 mtu
+= icsk
->icsk_af_ops
->net_frag_header_len
;
1460 EXPORT_SYMBOL(tcp_mss_to_mtu
);
1462 /* MTU probing init per socket */
1463 void tcp_mtup_init(struct sock
*sk
)
1465 struct tcp_sock
*tp
= tcp_sk(sk
);
1466 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1467 struct net
*net
= sock_net(sk
);
1469 icsk
->icsk_mtup
.enabled
= net
->ipv4
.sysctl_tcp_mtu_probing
> 1;
1470 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+ sizeof(struct tcphdr
) +
1471 icsk
->icsk_af_ops
->net_header_len
;
1472 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, net
->ipv4
.sysctl_tcp_base_mss
);
1473 icsk
->icsk_mtup
.probe_size
= 0;
1474 if (icsk
->icsk_mtup
.enabled
)
1475 icsk
->icsk_mtup
.probe_timestamp
= tcp_jiffies32
;
1477 EXPORT_SYMBOL(tcp_mtup_init
);
1479 /* This function synchronize snd mss to current pmtu/exthdr set.
1481 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1482 for TCP options, but includes only bare TCP header.
1484 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1485 It is minimum of user_mss and mss received with SYN.
1486 It also does not include TCP options.
1488 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1490 tp->mss_cache is current effective sending mss, including
1491 all tcp options except for SACKs. It is evaluated,
1492 taking into account current pmtu, but never exceeds
1493 tp->rx_opt.mss_clamp.
1495 NOTE1. rfc1122 clearly states that advertised MSS
1496 DOES NOT include either tcp or ip options.
1498 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1499 are READ ONLY outside this function. --ANK (980731)
1501 unsigned int tcp_sync_mss(struct sock
*sk
, u32 pmtu
)
1503 struct tcp_sock
*tp
= tcp_sk(sk
);
1504 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1507 if (icsk
->icsk_mtup
.search_high
> pmtu
)
1508 icsk
->icsk_mtup
.search_high
= pmtu
;
1510 mss_now
= tcp_mtu_to_mss(sk
, pmtu
);
1511 mss_now
= tcp_bound_to_half_wnd(tp
, mss_now
);
1513 /* And store cached results */
1514 icsk
->icsk_pmtu_cookie
= pmtu
;
1515 if (icsk
->icsk_mtup
.enabled
)
1516 mss_now
= min(mss_now
, tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_low
));
1517 tp
->mss_cache
= mss_now
;
1521 EXPORT_SYMBOL(tcp_sync_mss
);
1523 /* Compute the current effective MSS, taking SACKs and IP options,
1524 * and even PMTU discovery events into account.
1526 unsigned int tcp_current_mss(struct sock
*sk
)
1528 const struct tcp_sock
*tp
= tcp_sk(sk
);
1529 const struct dst_entry
*dst
= __sk_dst_get(sk
);
1531 unsigned int header_len
;
1532 struct tcp_out_options opts
;
1533 struct tcp_md5sig_key
*md5
;
1535 mss_now
= tp
->mss_cache
;
1538 u32 mtu
= dst_mtu(dst
);
1539 if (mtu
!= inet_csk(sk
)->icsk_pmtu_cookie
)
1540 mss_now
= tcp_sync_mss(sk
, mtu
);
1543 header_len
= tcp_established_options(sk
, NULL
, &opts
, &md5
) +
1544 sizeof(struct tcphdr
);
1545 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1546 * some common options. If this is an odd packet (because we have SACK
1547 * blocks etc) then our calculated header_len will be different, and
1548 * we have to adjust mss_now correspondingly */
1549 if (header_len
!= tp
->tcp_header_len
) {
1550 int delta
= (int) header_len
- tp
->tcp_header_len
;
1557 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto.
1558 * As additional protections, we do not touch cwnd in retransmission phases,
1559 * and if application hit its sndbuf limit recently.
1561 static void tcp_cwnd_application_limited(struct sock
*sk
)
1563 struct tcp_sock
*tp
= tcp_sk(sk
);
1565 if (inet_csk(sk
)->icsk_ca_state
== TCP_CA_Open
&&
1566 sk
->sk_socket
&& !test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
)) {
1567 /* Limited by application or receiver window. */
1568 u32 init_win
= tcp_init_cwnd(tp
, __sk_dst_get(sk
));
1569 u32 win_used
= max(tp
->snd_cwnd_used
, init_win
);
1570 if (win_used
< tp
->snd_cwnd
) {
1571 tp
->snd_ssthresh
= tcp_current_ssthresh(sk
);
1572 tp
->snd_cwnd
= (tp
->snd_cwnd
+ win_used
) >> 1;
1574 tp
->snd_cwnd_used
= 0;
1576 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
1579 static void tcp_cwnd_validate(struct sock
*sk
, bool is_cwnd_limited
)
1581 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1582 struct tcp_sock
*tp
= tcp_sk(sk
);
1584 /* Track the maximum number of outstanding packets in each
1585 * window, and remember whether we were cwnd-limited then.
1587 if (!before(tp
->snd_una
, tp
->max_packets_seq
) ||
1588 tp
->packets_out
> tp
->max_packets_out
) {
1589 tp
->max_packets_out
= tp
->packets_out
;
1590 tp
->max_packets_seq
= tp
->snd_nxt
;
1591 tp
->is_cwnd_limited
= is_cwnd_limited
;
1594 if (tcp_is_cwnd_limited(sk
)) {
1595 /* Network is feed fully. */
1596 tp
->snd_cwnd_used
= 0;
1597 tp
->snd_cwnd_stamp
= tcp_jiffies32
;
1599 /* Network starves. */
1600 if (tp
->packets_out
> tp
->snd_cwnd_used
)
1601 tp
->snd_cwnd_used
= tp
->packets_out
;
1603 if (sysctl_tcp_slow_start_after_idle
&&
1604 (s32
)(tcp_jiffies32
- tp
->snd_cwnd_stamp
) >= inet_csk(sk
)->icsk_rto
&&
1605 !ca_ops
->cong_control
)
1606 tcp_cwnd_application_limited(sk
);
1608 /* The following conditions together indicate the starvation
1609 * is caused by insufficient sender buffer:
1610 * 1) just sent some data (see tcp_write_xmit)
1611 * 2) not cwnd limited (this else condition)
1612 * 3) no more data to send (null tcp_send_head )
1613 * 4) application is hitting buffer limit (SOCK_NOSPACE)
1615 if (!tcp_send_head(sk
) && sk
->sk_socket
&&
1616 test_bit(SOCK_NOSPACE
, &sk
->sk_socket
->flags
) &&
1617 (1 << sk
->sk_state
) & (TCPF_ESTABLISHED
| TCPF_CLOSE_WAIT
))
1618 tcp_chrono_start(sk
, TCP_CHRONO_SNDBUF_LIMITED
);
1622 /* Minshall's variant of the Nagle send check. */
1623 static bool tcp_minshall_check(const struct tcp_sock
*tp
)
1625 return after(tp
->snd_sml
, tp
->snd_una
) &&
1626 !after(tp
->snd_sml
, tp
->snd_nxt
);
1629 /* Update snd_sml if this skb is under mss
1630 * Note that a TSO packet might end with a sub-mss segment
1631 * The test is really :
1632 * if ((skb->len % mss) != 0)
1633 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq;
1634 * But we can avoid doing the divide again given we already have
1635 * skb_pcount = skb->len / mss_now
1637 static void tcp_minshall_update(struct tcp_sock
*tp
, unsigned int mss_now
,
1638 const struct sk_buff
*skb
)
1640 if (skb
->len
< tcp_skb_pcount(skb
) * mss_now
)
1641 tp
->snd_sml
= TCP_SKB_CB(skb
)->end_seq
;
1644 /* Return false, if packet can be sent now without violation Nagle's rules:
1645 * 1. It is full sized. (provided by caller in %partial bool)
1646 * 2. Or it contains FIN. (already checked by caller)
1647 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set.
1648 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1649 * With Minshall's modification: all sent small packets are ACKed.
1651 static bool tcp_nagle_check(bool partial
, const struct tcp_sock
*tp
,
1655 ((nonagle
& TCP_NAGLE_CORK
) ||
1656 (!nonagle
&& tp
->packets_out
&& tcp_minshall_check(tp
)));
1659 /* Return how many segs we'd like on a TSO packet,
1660 * to send one TSO packet per ms
1662 u32
tcp_tso_autosize(const struct sock
*sk
, unsigned int mss_now
,
1667 bytes
= min(sk
->sk_pacing_rate
>> 10,
1668 sk
->sk_gso_max_size
- 1 - MAX_TCP_HEADER
);
1670 /* Goal is to send at least one packet per ms,
1671 * not one big TSO packet every 100 ms.
1672 * This preserves ACK clocking and is consistent
1673 * with tcp_tso_should_defer() heuristic.
1675 segs
= max_t(u32
, bytes
/ mss_now
, min_tso_segs
);
1677 return min_t(u32
, segs
, sk
->sk_gso_max_segs
);
1679 EXPORT_SYMBOL(tcp_tso_autosize
);
1681 /* Return the number of segments we want in the skb we are transmitting.
1682 * See if congestion control module wants to decide; otherwise, autosize.
1684 static u32
tcp_tso_segs(struct sock
*sk
, unsigned int mss_now
)
1686 const struct tcp_congestion_ops
*ca_ops
= inet_csk(sk
)->icsk_ca_ops
;
1687 u32 tso_segs
= ca_ops
->tso_segs_goal
? ca_ops
->tso_segs_goal(sk
) : 0;
1690 tcp_tso_autosize(sk
, mss_now
, sysctl_tcp_min_tso_segs
);
1693 /* Returns the portion of skb which can be sent right away */
1694 static unsigned int tcp_mss_split_point(const struct sock
*sk
,
1695 const struct sk_buff
*skb
,
1696 unsigned int mss_now
,
1697 unsigned int max_segs
,
1700 const struct tcp_sock
*tp
= tcp_sk(sk
);
1701 u32 partial
, needed
, window
, max_len
;
1703 window
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1704 max_len
= mss_now
* max_segs
;
1706 if (likely(max_len
<= window
&& skb
!= tcp_write_queue_tail(sk
)))
1709 needed
= min(skb
->len
, window
);
1711 if (max_len
<= needed
)
1714 partial
= needed
% mss_now
;
1715 /* If last segment is not a full MSS, check if Nagle rules allow us
1716 * to include this last segment in this skb.
1717 * Otherwise, we'll split the skb at last MSS boundary
1719 if (tcp_nagle_check(partial
!= 0, tp
, nonagle
))
1720 return needed
- partial
;
1725 /* Can at least one segment of SKB be sent right now, according to the
1726 * congestion window rules? If so, return how many segments are allowed.
1728 static inline unsigned int tcp_cwnd_test(const struct tcp_sock
*tp
,
1729 const struct sk_buff
*skb
)
1731 u32 in_flight
, cwnd
, halfcwnd
;
1733 /* Don't be strict about the congestion window for the final FIN. */
1734 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
) &&
1735 tcp_skb_pcount(skb
) == 1)
1738 in_flight
= tcp_packets_in_flight(tp
);
1739 cwnd
= tp
->snd_cwnd
;
1740 if (in_flight
>= cwnd
)
1743 /* For better scheduling, ensure we have at least
1744 * 2 GSO packets in flight.
1746 halfcwnd
= max(cwnd
>> 1, 1U);
1747 return min(halfcwnd
, cwnd
- in_flight
);
1750 /* Initialize TSO state of a skb.
1751 * This must be invoked the first time we consider transmitting
1752 * SKB onto the wire.
1754 static int tcp_init_tso_segs(struct sk_buff
*skb
, unsigned int mss_now
)
1756 int tso_segs
= tcp_skb_pcount(skb
);
1758 if (!tso_segs
|| (tso_segs
> 1 && tcp_skb_mss(skb
) != mss_now
)) {
1759 tcp_set_skb_tso_segs(skb
, mss_now
);
1760 tso_segs
= tcp_skb_pcount(skb
);
1766 /* Return true if the Nagle test allows this packet to be
1769 static inline bool tcp_nagle_test(const struct tcp_sock
*tp
, const struct sk_buff
*skb
,
1770 unsigned int cur_mss
, int nonagle
)
1772 /* Nagle rule does not apply to frames, which sit in the middle of the
1773 * write_queue (they have no chances to get new data).
1775 * This is implemented in the callers, where they modify the 'nonagle'
1776 * argument based upon the location of SKB in the send queue.
1778 if (nonagle
& TCP_NAGLE_PUSH
)
1781 /* Don't use the nagle rule for urgent data (or for the final FIN). */
1782 if (tcp_urg_mode(tp
) || (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
))
1785 if (!tcp_nagle_check(skb
->len
< cur_mss
, tp
, nonagle
))
1791 /* Does at least the first segment of SKB fit into the send window? */
1792 static bool tcp_snd_wnd_test(const struct tcp_sock
*tp
,
1793 const struct sk_buff
*skb
,
1794 unsigned int cur_mss
)
1796 u32 end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1798 if (skb
->len
> cur_mss
)
1799 end_seq
= TCP_SKB_CB(skb
)->seq
+ cur_mss
;
1801 return !after(end_seq
, tcp_wnd_end(tp
));
1804 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1805 * should be put on the wire right now. If so, it returns the number of
1806 * packets allowed by the congestion window.
1808 static unsigned int tcp_snd_test(const struct sock
*sk
, struct sk_buff
*skb
,
1809 unsigned int cur_mss
, int nonagle
)
1811 const struct tcp_sock
*tp
= tcp_sk(sk
);
1812 unsigned int cwnd_quota
;
1814 tcp_init_tso_segs(skb
, cur_mss
);
1816 if (!tcp_nagle_test(tp
, skb
, cur_mss
, nonagle
))
1819 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
1820 if (cwnd_quota
&& !tcp_snd_wnd_test(tp
, skb
, cur_mss
))
1826 /* Test if sending is allowed right now. */
1827 bool tcp_may_send_now(struct sock
*sk
)
1829 const struct tcp_sock
*tp
= tcp_sk(sk
);
1830 struct sk_buff
*skb
= tcp_send_head(sk
);
1833 tcp_snd_test(sk
, skb
, tcp_current_mss(sk
),
1834 (tcp_skb_is_last(sk
, skb
) ?
1835 tp
->nonagle
: TCP_NAGLE_PUSH
));
1838 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1839 * which is put after SKB on the list. It is very much like
1840 * tcp_fragment() except that it may make several kinds of assumptions
1841 * in order to speed up the splitting operation. In particular, we
1842 * know that all the data is in scatter-gather pages, and that the
1843 * packet has never been sent out before (and thus is not cloned).
1845 static int tso_fragment(struct sock
*sk
, struct sk_buff
*skb
, unsigned int len
,
1846 unsigned int mss_now
, gfp_t gfp
)
1848 struct sk_buff
*buff
;
1849 int nlen
= skb
->len
- len
;
1852 /* All of a TSO frame must be composed of paged data. */
1853 if (skb
->len
!= skb
->data_len
)
1854 return tcp_fragment(sk
, skb
, len
, mss_now
, gfp
);
1856 buff
= sk_stream_alloc_skb(sk
, 0, gfp
, true);
1857 if (unlikely(!buff
))
1860 sk
->sk_wmem_queued
+= buff
->truesize
;
1861 sk_mem_charge(sk
, buff
->truesize
);
1862 buff
->truesize
+= nlen
;
1863 skb
->truesize
-= nlen
;
1865 /* Correct the sequence numbers. */
1866 TCP_SKB_CB(buff
)->seq
= TCP_SKB_CB(skb
)->seq
+ len
;
1867 TCP_SKB_CB(buff
)->end_seq
= TCP_SKB_CB(skb
)->end_seq
;
1868 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(buff
)->seq
;
1870 /* PSH and FIN should only be set in the second packet. */
1871 flags
= TCP_SKB_CB(skb
)->tcp_flags
;
1872 TCP_SKB_CB(skb
)->tcp_flags
= flags
& ~(TCPHDR_FIN
| TCPHDR_PSH
);
1873 TCP_SKB_CB(buff
)->tcp_flags
= flags
;
1875 /* This packet was never sent out yet, so no SACK bits. */
1876 TCP_SKB_CB(buff
)->sacked
= 0;
1878 tcp_skb_fragment_eor(skb
, buff
);
1880 buff
->ip_summed
= skb
->ip_summed
= CHECKSUM_PARTIAL
;
1881 skb_split(skb
, buff
, len
);
1882 tcp_fragment_tstamp(skb
, buff
);
1884 /* Fix up tso_factor for both original and new SKB. */
1885 tcp_set_skb_tso_segs(skb
, mss_now
);
1886 tcp_set_skb_tso_segs(buff
, mss_now
);
1888 /* Link BUFF into the send queue. */
1889 __skb_header_release(buff
);
1890 tcp_insert_write_queue_after(skb
, buff
, sk
);
1895 /* Try to defer sending, if possible, in order to minimize the amount
1896 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1898 * This algorithm is from John Heffner.
1900 static bool tcp_tso_should_defer(struct sock
*sk
, struct sk_buff
*skb
,
1901 bool *is_cwnd_limited
, u32 max_segs
)
1903 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
1904 u32 age
, send_win
, cong_win
, limit
, in_flight
;
1905 struct tcp_sock
*tp
= tcp_sk(sk
);
1906 struct sk_buff
*head
;
1909 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_FIN
)
1912 if (icsk
->icsk_ca_state
>= TCP_CA_Recovery
)
1915 /* Avoid bursty behavior by allowing defer
1916 * only if the last write was recent.
1918 if ((s32
)(tcp_jiffies32
- tp
->lsndtime
) > 0)
1921 in_flight
= tcp_packets_in_flight(tp
);
1923 BUG_ON(tcp_skb_pcount(skb
) <= 1 || (tp
->snd_cwnd
<= in_flight
));
1925 send_win
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
1927 /* From in_flight test above, we know that cwnd > in_flight. */
1928 cong_win
= (tp
->snd_cwnd
- in_flight
) * tp
->mss_cache
;
1930 limit
= min(send_win
, cong_win
);
1932 /* If a full-sized TSO skb can be sent, do it. */
1933 if (limit
>= max_segs
* tp
->mss_cache
)
1936 /* Middle in queue won't get any more data, full sendable already? */
1937 if ((skb
!= tcp_write_queue_tail(sk
)) && (limit
>= skb
->len
))
1940 win_divisor
= ACCESS_ONCE(sysctl_tcp_tso_win_divisor
);
1942 u32 chunk
= min(tp
->snd_wnd
, tp
->snd_cwnd
* tp
->mss_cache
);
1944 /* If at least some fraction of a window is available,
1947 chunk
/= win_divisor
;
1951 /* Different approach, try not to defer past a single
1952 * ACK. Receiver should ACK every other full sized
1953 * frame, so if we have space for more than 3 frames
1956 if (limit
> tcp_max_tso_deferred_mss(tp
) * tp
->mss_cache
)
1960 head
= tcp_write_queue_head(sk
);
1962 age
= tcp_stamp_us_delta(tp
->tcp_mstamp
, head
->skb_mstamp
);
1963 /* If next ACK is likely to come too late (half srtt), do not defer */
1964 if (age
< (tp
->srtt_us
>> 4))
1967 /* Ok, it looks like it is advisable to defer. */
1969 if (cong_win
< send_win
&& cong_win
<= skb
->len
)
1970 *is_cwnd_limited
= true;
1978 static inline void tcp_mtu_check_reprobe(struct sock
*sk
)
1980 struct inet_connection_sock
*icsk
= inet_csk(sk
);
1981 struct tcp_sock
*tp
= tcp_sk(sk
);
1982 struct net
*net
= sock_net(sk
);
1986 interval
= net
->ipv4
.sysctl_tcp_probe_interval
;
1987 delta
= tcp_jiffies32
- icsk
->icsk_mtup
.probe_timestamp
;
1988 if (unlikely(delta
>= interval
* HZ
)) {
1989 int mss
= tcp_current_mss(sk
);
1991 /* Update current search range */
1992 icsk
->icsk_mtup
.probe_size
= 0;
1993 icsk
->icsk_mtup
.search_high
= tp
->rx_opt
.mss_clamp
+
1994 sizeof(struct tcphdr
) +
1995 icsk
->icsk_af_ops
->net_header_len
;
1996 icsk
->icsk_mtup
.search_low
= tcp_mss_to_mtu(sk
, mss
);
1998 /* Update probe time stamp */
1999 icsk
->icsk_mtup
.probe_timestamp
= tcp_jiffies32
;
2003 /* Create a new MTU probe if we are ready.
2004 * MTU probe is regularly attempting to increase the path MTU by
2005 * deliberately sending larger packets. This discovers routing
2006 * changes resulting in larger path MTUs.
2008 * Returns 0 if we should wait to probe (no cwnd available),
2009 * 1 if a probe was sent,
2012 static int tcp_mtu_probe(struct sock
*sk
)
2014 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2015 struct tcp_sock
*tp
= tcp_sk(sk
);
2016 struct sk_buff
*skb
, *nskb
, *next
;
2017 struct net
*net
= sock_net(sk
);
2024 /* Not currently probing/verifying,
2026 * have enough cwnd, and
2027 * not SACKing (the variable headers throw things off)
2029 if (likely(!icsk
->icsk_mtup
.enabled
||
2030 icsk
->icsk_mtup
.probe_size
||
2031 inet_csk(sk
)->icsk_ca_state
!= TCP_CA_Open
||
2032 tp
->snd_cwnd
< 11 ||
2033 tp
->rx_opt
.num_sacks
|| tp
->rx_opt
.dsack
))
2036 /* Use binary search for probe_size between tcp_mss_base,
2037 * and current mss_clamp. if (search_high - search_low)
2038 * smaller than a threshold, backoff from probing.
2040 mss_now
= tcp_current_mss(sk
);
2041 probe_size
= tcp_mtu_to_mss(sk
, (icsk
->icsk_mtup
.search_high
+
2042 icsk
->icsk_mtup
.search_low
) >> 1);
2043 size_needed
= probe_size
+ (tp
->reordering
+ 1) * tp
->mss_cache
;
2044 interval
= icsk
->icsk_mtup
.search_high
- icsk
->icsk_mtup
.search_low
;
2045 /* When misfortune happens, we are reprobing actively,
2046 * and then reprobe timer has expired. We stick with current
2047 * probing process by not resetting search range to its orignal.
2049 if (probe_size
> tcp_mtu_to_mss(sk
, icsk
->icsk_mtup
.search_high
) ||
2050 interval
< net
->ipv4
.sysctl_tcp_probe_threshold
) {
2051 /* Check whether enough time has elaplased for
2052 * another round of probing.
2054 tcp_mtu_check_reprobe(sk
);
2058 /* Have enough data in the send queue to probe? */
2059 if (tp
->write_seq
- tp
->snd_nxt
< size_needed
)
2062 if (tp
->snd_wnd
< size_needed
)
2064 if (after(tp
->snd_nxt
+ size_needed
, tcp_wnd_end(tp
)))
2067 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
2068 if (tcp_packets_in_flight(tp
) + 2 > tp
->snd_cwnd
) {
2069 if (!tcp_packets_in_flight(tp
))
2075 /* We're allowed to probe. Build it now. */
2076 nskb
= sk_stream_alloc_skb(sk
, probe_size
, GFP_ATOMIC
, false);
2079 sk
->sk_wmem_queued
+= nskb
->truesize
;
2080 sk_mem_charge(sk
, nskb
->truesize
);
2082 skb
= tcp_send_head(sk
);
2084 TCP_SKB_CB(nskb
)->seq
= TCP_SKB_CB(skb
)->seq
;
2085 TCP_SKB_CB(nskb
)->end_seq
= TCP_SKB_CB(skb
)->seq
+ probe_size
;
2086 TCP_SKB_CB(nskb
)->tcp_flags
= TCPHDR_ACK
;
2087 TCP_SKB_CB(nskb
)->sacked
= 0;
2089 nskb
->ip_summed
= skb
->ip_summed
;
2091 tcp_insert_write_queue_before(nskb
, skb
, sk
);
2094 tcp_for_write_queue_from_safe(skb
, next
, sk
) {
2095 copy
= min_t(int, skb
->len
, probe_size
- len
);
2096 if (nskb
->ip_summed
) {
2097 skb_copy_bits(skb
, 0, skb_put(nskb
, copy
), copy
);
2099 __wsum csum
= skb_copy_and_csum_bits(skb
, 0,
2100 skb_put(nskb
, copy
),
2102 nskb
->csum
= csum_block_add(nskb
->csum
, csum
, len
);
2105 if (skb
->len
<= copy
) {
2106 /* We've eaten all the data from this skb.
2108 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
;
2109 tcp_unlink_write_queue(skb
, sk
);
2110 sk_wmem_free_skb(sk
, skb
);
2112 TCP_SKB_CB(nskb
)->tcp_flags
|= TCP_SKB_CB(skb
)->tcp_flags
&
2113 ~(TCPHDR_FIN
|TCPHDR_PSH
);
2114 if (!skb_shinfo(skb
)->nr_frags
) {
2115 skb_pull(skb
, copy
);
2116 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2117 skb
->csum
= csum_partial(skb
->data
,
2120 __pskb_trim_head(skb
, copy
);
2121 tcp_set_skb_tso_segs(skb
, mss_now
);
2123 TCP_SKB_CB(skb
)->seq
+= copy
;
2128 if (len
>= probe_size
)
2131 tcp_init_tso_segs(nskb
, nskb
->len
);
2133 /* We're ready to send. If this fails, the probe will
2134 * be resegmented into mss-sized pieces by tcp_write_xmit().
2136 if (!tcp_transmit_skb(sk
, nskb
, 1, GFP_ATOMIC
)) {
2137 /* Decrement cwnd here because we are sending
2138 * effectively two packets. */
2140 tcp_event_new_data_sent(sk
, nskb
);
2142 icsk
->icsk_mtup
.probe_size
= tcp_mss_to_mtu(sk
, nskb
->len
);
2143 tp
->mtu_probe
.probe_seq_start
= TCP_SKB_CB(nskb
)->seq
;
2144 tp
->mtu_probe
.probe_seq_end
= TCP_SKB_CB(nskb
)->end_seq
;
2152 static bool tcp_pacing_check(const struct sock
*sk
)
2154 return tcp_needs_internal_pacing(sk
) &&
2155 hrtimer_active(&tcp_sk(sk
)->pacing_timer
);
2158 /* TCP Small Queues :
2159 * Control number of packets in qdisc/devices to two packets / or ~1 ms.
2160 * (These limits are doubled for retransmits)
2162 * - better RTT estimation and ACK scheduling
2165 * Alas, some drivers / subsystems require a fair amount
2166 * of queued bytes to ensure line rate.
2167 * One example is wifi aggregation (802.11 AMPDU)
2169 static bool tcp_small_queue_check(struct sock
*sk
, const struct sk_buff
*skb
,
2170 unsigned int factor
)
2174 limit
= max(2 * skb
->truesize
, sk
->sk_pacing_rate
>> 10);
2175 limit
= min_t(u32
, limit
, sysctl_tcp_limit_output_bytes
);
2178 if (refcount_read(&sk
->sk_wmem_alloc
) > limit
) {
2179 /* Always send the 1st or 2nd skb in write queue.
2180 * No need to wait for TX completion to call us back,
2181 * after softirq/tasklet schedule.
2182 * This helps when TX completions are delayed too much.
2184 if (skb
== sk
->sk_write_queue
.next
||
2185 skb
->prev
== sk
->sk_write_queue
.next
)
2188 set_bit(TSQ_THROTTLED
, &sk
->sk_tsq_flags
);
2189 /* It is possible TX completion already happened
2190 * before we set TSQ_THROTTLED, so we must
2191 * test again the condition.
2193 smp_mb__after_atomic();
2194 if (refcount_read(&sk
->sk_wmem_alloc
) > limit
)
2200 static void tcp_chrono_set(struct tcp_sock
*tp
, const enum tcp_chrono
new)
2202 const u32 now
= tcp_jiffies32
;
2203 enum tcp_chrono old
= tp
->chrono_type
;
2205 if (old
> TCP_CHRONO_UNSPEC
)
2206 tp
->chrono_stat
[old
- 1] += now
- tp
->chrono_start
;
2207 tp
->chrono_start
= now
;
2208 tp
->chrono_type
= new;
2211 void tcp_chrono_start(struct sock
*sk
, const enum tcp_chrono type
)
2213 struct tcp_sock
*tp
= tcp_sk(sk
);
2215 /* If there are multiple conditions worthy of tracking in a
2216 * chronograph then the highest priority enum takes precedence
2217 * over the other conditions. So that if something "more interesting"
2218 * starts happening, stop the previous chrono and start a new one.
2220 if (type
> tp
->chrono_type
)
2221 tcp_chrono_set(tp
, type
);
2224 void tcp_chrono_stop(struct sock
*sk
, const enum tcp_chrono type
)
2226 struct tcp_sock
*tp
= tcp_sk(sk
);
2229 /* There are multiple conditions worthy of tracking in a
2230 * chronograph, so that the highest priority enum takes
2231 * precedence over the other conditions (see tcp_chrono_start).
2232 * If a condition stops, we only stop chrono tracking if
2233 * it's the "most interesting" or current chrono we are
2234 * tracking and starts busy chrono if we have pending data.
2236 if (tcp_write_queue_empty(sk
))
2237 tcp_chrono_set(tp
, TCP_CHRONO_UNSPEC
);
2238 else if (type
== tp
->chrono_type
)
2239 tcp_chrono_set(tp
, TCP_CHRONO_BUSY
);
2242 /* This routine writes packets to the network. It advances the
2243 * send_head. This happens as incoming acks open up the remote
2246 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
2247 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
2248 * account rare use of URG, this is not a big flaw.
2250 * Send at most one packet when push_one > 0. Temporarily ignore
2251 * cwnd limit to force at most one packet out when push_one == 2.
2253 * Returns true, if no segments are in flight and we have queued segments,
2254 * but cannot send anything now because of SWS or another problem.
2256 static bool tcp_write_xmit(struct sock
*sk
, unsigned int mss_now
, int nonagle
,
2257 int push_one
, gfp_t gfp
)
2259 struct tcp_sock
*tp
= tcp_sk(sk
);
2260 struct sk_buff
*skb
;
2261 unsigned int tso_segs
, sent_pkts
;
2264 bool is_cwnd_limited
= false, is_rwnd_limited
= false;
2270 /* Do MTU probing. */
2271 result
= tcp_mtu_probe(sk
);
2274 } else if (result
> 0) {
2279 max_segs
= tcp_tso_segs(sk
, mss_now
);
2280 tcp_mstamp_refresh(tp
);
2281 while ((skb
= tcp_send_head(sk
))) {
2284 if (tcp_pacing_check(sk
))
2287 tso_segs
= tcp_init_tso_segs(skb
, mss_now
);
2290 if (unlikely(tp
->repair
) && tp
->repair_queue
== TCP_SEND_QUEUE
) {
2291 /* "skb_mstamp" is used as a start point for the retransmit timer */
2292 skb
->skb_mstamp
= tp
->tcp_mstamp
;
2293 goto repair
; /* Skip network transmission */
2296 cwnd_quota
= tcp_cwnd_test(tp
, skb
);
2299 /* Force out a loss probe pkt. */
2305 if (unlikely(!tcp_snd_wnd_test(tp
, skb
, mss_now
))) {
2306 is_rwnd_limited
= true;
2310 if (tso_segs
== 1) {
2311 if (unlikely(!tcp_nagle_test(tp
, skb
, mss_now
,
2312 (tcp_skb_is_last(sk
, skb
) ?
2313 nonagle
: TCP_NAGLE_PUSH
))))
2317 tcp_tso_should_defer(sk
, skb
, &is_cwnd_limited
,
2323 if (tso_segs
> 1 && !tcp_urg_mode(tp
))
2324 limit
= tcp_mss_split_point(sk
, skb
, mss_now
,
2330 if (skb
->len
> limit
&&
2331 unlikely(tso_fragment(sk
, skb
, limit
, mss_now
, gfp
)))
2334 if (test_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
))
2335 clear_bit(TCP_TSQ_DEFERRED
, &sk
->sk_tsq_flags
);
2336 if (tcp_small_queue_check(sk
, skb
, 0))
2339 if (unlikely(tcp_transmit_skb(sk
, skb
, 1, gfp
)))
2343 /* Advance the send_head. This one is sent out.
2344 * This call will increment packets_out.
2346 tcp_event_new_data_sent(sk
, skb
);
2348 tcp_minshall_update(tp
, mss_now
, skb
);
2349 sent_pkts
+= tcp_skb_pcount(skb
);
2355 if (is_rwnd_limited
)
2356 tcp_chrono_start(sk
, TCP_CHRONO_RWND_LIMITED
);
2358 tcp_chrono_stop(sk
, TCP_CHRONO_RWND_LIMITED
);
2360 if (likely(sent_pkts
)) {
2361 if (tcp_in_cwnd_reduction(sk
))
2362 tp
->prr_out
+= sent_pkts
;
2364 /* Send one loss probe per tail loss episode. */
2366 tcp_schedule_loss_probe(sk
);
2367 is_cwnd_limited
|= (tcp_packets_in_flight(tp
) >= tp
->snd_cwnd
);
2368 tcp_cwnd_validate(sk
, is_cwnd_limited
);
2371 return !tp
->packets_out
&& tcp_send_head(sk
);
2374 bool tcp_schedule_loss_probe(struct sock
*sk
)
2376 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2377 struct tcp_sock
*tp
= tcp_sk(sk
);
2378 u32 timeout
, rto_delta_us
;
2380 /* Don't do any loss probe on a Fast Open connection before 3WHS
2383 if (tp
->fastopen_rsk
)
2386 /* Schedule a loss probe in 2*RTT for SACK capable connections
2387 * in Open state, that are either limited by cwnd or application.
2389 if ((sysctl_tcp_early_retrans
!= 3 && sysctl_tcp_early_retrans
!= 4) ||
2390 !tp
->packets_out
|| !tcp_is_sack(tp
) ||
2391 icsk
->icsk_ca_state
!= TCP_CA_Open
)
2394 if ((tp
->snd_cwnd
> tcp_packets_in_flight(tp
)) &&
2398 /* Probe timeout is 2*rtt. Add minimum RTO to account
2399 * for delayed ack when there's one outstanding packet. If no RTT
2400 * sample is available then probe after TCP_TIMEOUT_INIT.
2403 timeout
= usecs_to_jiffies(tp
->srtt_us
>> 2);
2404 if (tp
->packets_out
== 1)
2405 timeout
+= TCP_RTO_MIN
;
2407 timeout
+= TCP_TIMEOUT_MIN
;
2409 timeout
= TCP_TIMEOUT_INIT
;
2412 /* If the RTO formula yields an earlier time, then use that time. */
2413 rto_delta_us
= tcp_rto_delta_us(sk
); /* How far in future is RTO? */
2414 if (rto_delta_us
> 0)
2415 timeout
= min_t(u32
, timeout
, usecs_to_jiffies(rto_delta_us
));
2417 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_LOSS_PROBE
, timeout
,
2422 /* Thanks to skb fast clones, we can detect if a prior transmit of
2423 * a packet is still in a qdisc or driver queue.
2424 * In this case, there is very little point doing a retransmit !
2426 static bool skb_still_in_host_queue(const struct sock
*sk
,
2427 const struct sk_buff
*skb
)
2429 if (unlikely(skb_fclone_busy(sk
, skb
))) {
2430 NET_INC_STATS(sock_net(sk
),
2431 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES
);
2437 /* When probe timeout (PTO) fires, try send a new segment if possible, else
2438 * retransmit the last segment.
2440 void tcp_send_loss_probe(struct sock
*sk
)
2442 struct tcp_sock
*tp
= tcp_sk(sk
);
2443 struct sk_buff
*skb
;
2445 int mss
= tcp_current_mss(sk
);
2447 skb
= tcp_send_head(sk
);
2449 if (tcp_snd_wnd_test(tp
, skb
, mss
)) {
2450 pcount
= tp
->packets_out
;
2451 tcp_write_xmit(sk
, mss
, TCP_NAGLE_OFF
, 2, GFP_ATOMIC
);
2452 if (tp
->packets_out
> pcount
)
2456 skb
= tcp_write_queue_prev(sk
, skb
);
2458 skb
= tcp_write_queue_tail(sk
);
2461 /* At most one outstanding TLP retransmission. */
2462 if (tp
->tlp_high_seq
)
2465 /* Retransmit last segment. */
2469 if (skb_still_in_host_queue(sk
, skb
))
2472 pcount
= tcp_skb_pcount(skb
);
2473 if (WARN_ON(!pcount
))
2476 if ((pcount
> 1) && (skb
->len
> (pcount
- 1) * mss
)) {
2477 if (unlikely(tcp_fragment(sk
, skb
, (pcount
- 1) * mss
, mss
,
2480 skb
= tcp_write_queue_next(sk
, skb
);
2483 if (WARN_ON(!skb
|| !tcp_skb_pcount(skb
)))
2486 if (__tcp_retransmit_skb(sk
, skb
, 1))
2489 /* Record snd_nxt for loss detection. */
2490 tp
->tlp_high_seq
= tp
->snd_nxt
;
2493 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPLOSSPROBES
);
2494 /* Reset s.t. tcp_rearm_rto will restart timer from now */
2495 inet_csk(sk
)->icsk_pending
= 0;
2500 /* Push out any pending frames which were held back due to
2501 * TCP_CORK or attempt at coalescing tiny packets.
2502 * The socket must be locked by the caller.
2504 void __tcp_push_pending_frames(struct sock
*sk
, unsigned int cur_mss
,
2507 /* If we are closed, the bytes will have to remain here.
2508 * In time closedown will finish, we empty the write queue and
2509 * all will be happy.
2511 if (unlikely(sk
->sk_state
== TCP_CLOSE
))
2514 if (tcp_write_xmit(sk
, cur_mss
, nonagle
, 0,
2515 sk_gfp_mask(sk
, GFP_ATOMIC
)))
2516 tcp_check_probe_timer(sk
);
2519 /* Send _single_ skb sitting at the send head. This function requires
2520 * true push pending frames to setup probe timer etc.
2522 void tcp_push_one(struct sock
*sk
, unsigned int mss_now
)
2524 struct sk_buff
*skb
= tcp_send_head(sk
);
2526 BUG_ON(!skb
|| skb
->len
< mss_now
);
2528 tcp_write_xmit(sk
, mss_now
, TCP_NAGLE_PUSH
, 1, sk
->sk_allocation
);
2531 /* This function returns the amount that we can raise the
2532 * usable window based on the following constraints
2534 * 1. The window can never be shrunk once it is offered (RFC 793)
2535 * 2. We limit memory per socket
2538 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
2539 * RECV.NEXT + RCV.WIN fixed until:
2540 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
2542 * i.e. don't raise the right edge of the window until you can raise
2543 * it at least MSS bytes.
2545 * Unfortunately, the recommended algorithm breaks header prediction,
2546 * since header prediction assumes th->window stays fixed.
2548 * Strictly speaking, keeping th->window fixed violates the receiver
2549 * side SWS prevention criteria. The problem is that under this rule
2550 * a stream of single byte packets will cause the right side of the
2551 * window to always advance by a single byte.
2553 * Of course, if the sender implements sender side SWS prevention
2554 * then this will not be a problem.
2556 * BSD seems to make the following compromise:
2558 * If the free space is less than the 1/4 of the maximum
2559 * space available and the free space is less than 1/2 mss,
2560 * then set the window to 0.
2561 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
2562 * Otherwise, just prevent the window from shrinking
2563 * and from being larger than the largest representable value.
2565 * This prevents incremental opening of the window in the regime
2566 * where TCP is limited by the speed of the reader side taking
2567 * data out of the TCP receive queue. It does nothing about
2568 * those cases where the window is constrained on the sender side
2569 * because the pipeline is full.
2571 * BSD also seems to "accidentally" limit itself to windows that are a
2572 * multiple of MSS, at least until the free space gets quite small.
2573 * This would appear to be a side effect of the mbuf implementation.
2574 * Combining these two algorithms results in the observed behavior
2575 * of having a fixed window size at almost all times.
2577 * Below we obtain similar behavior by forcing the offered window to
2578 * a multiple of the mss when it is feasible to do so.
2580 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
2581 * Regular options like TIMESTAMP are taken into account.
2583 u32
__tcp_select_window(struct sock
*sk
)
2585 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2586 struct tcp_sock
*tp
= tcp_sk(sk
);
2587 /* MSS for the peer's data. Previous versions used mss_clamp
2588 * here. I don't know if the value based on our guesses
2589 * of peer's MSS is better for the performance. It's more correct
2590 * but may be worse for the performance because of rcv_mss
2591 * fluctuations. --SAW 1998/11/1
2593 int mss
= icsk
->icsk_ack
.rcv_mss
;
2594 int free_space
= tcp_space(sk
);
2595 int allowed_space
= tcp_full_space(sk
);
2596 int full_space
= min_t(int, tp
->window_clamp
, allowed_space
);
2599 if (unlikely(mss
> full_space
)) {
2604 if (free_space
< (full_space
>> 1)) {
2605 icsk
->icsk_ack
.quick
= 0;
2607 if (tcp_under_memory_pressure(sk
))
2608 tp
->rcv_ssthresh
= min(tp
->rcv_ssthresh
,
2611 /* free_space might become our new window, make sure we don't
2612 * increase it due to wscale.
2614 free_space
= round_down(free_space
, 1 << tp
->rx_opt
.rcv_wscale
);
2616 /* if free space is less than mss estimate, or is below 1/16th
2617 * of the maximum allowed, try to move to zero-window, else
2618 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and
2619 * new incoming data is dropped due to memory limits.
2620 * With large window, mss test triggers way too late in order
2621 * to announce zero window in time before rmem limit kicks in.
2623 if (free_space
< (allowed_space
>> 4) || free_space
< mss
)
2627 if (free_space
> tp
->rcv_ssthresh
)
2628 free_space
= tp
->rcv_ssthresh
;
2630 /* Don't do rounding if we are using window scaling, since the
2631 * scaled window will not line up with the MSS boundary anyway.
2633 if (tp
->rx_opt
.rcv_wscale
) {
2634 window
= free_space
;
2636 /* Advertise enough space so that it won't get scaled away.
2637 * Import case: prevent zero window announcement if
2638 * 1<<rcv_wscale > mss.
2640 window
= ALIGN(window
, (1 << tp
->rx_opt
.rcv_wscale
));
2642 window
= tp
->rcv_wnd
;
2643 /* Get the largest window that is a nice multiple of mss.
2644 * Window clamp already applied above.
2645 * If our current window offering is within 1 mss of the
2646 * free space we just keep it. This prevents the divide
2647 * and multiply from happening most of the time.
2648 * We also don't do any window rounding when the free space
2651 if (window
<= free_space
- mss
|| window
> free_space
)
2652 window
= rounddown(free_space
, mss
);
2653 else if (mss
== full_space
&&
2654 free_space
> window
+ (full_space
>> 1))
2655 window
= free_space
;
2661 void tcp_skb_collapse_tstamp(struct sk_buff
*skb
,
2662 const struct sk_buff
*next_skb
)
2664 if (unlikely(tcp_has_tx_tstamp(next_skb
))) {
2665 const struct skb_shared_info
*next_shinfo
=
2666 skb_shinfo(next_skb
);
2667 struct skb_shared_info
*shinfo
= skb_shinfo(skb
);
2669 shinfo
->tx_flags
|= next_shinfo
->tx_flags
& SKBTX_ANY_TSTAMP
;
2670 shinfo
->tskey
= next_shinfo
->tskey
;
2671 TCP_SKB_CB(skb
)->txstamp_ack
|=
2672 TCP_SKB_CB(next_skb
)->txstamp_ack
;
2676 /* Collapses two adjacent SKB's during retransmission. */
2677 static bool tcp_collapse_retrans(struct sock
*sk
, struct sk_buff
*skb
)
2679 struct tcp_sock
*tp
= tcp_sk(sk
);
2680 struct sk_buff
*next_skb
= tcp_write_queue_next(sk
, skb
);
2681 int skb_size
, next_skb_size
;
2683 skb_size
= skb
->len
;
2684 next_skb_size
= next_skb
->len
;
2686 BUG_ON(tcp_skb_pcount(skb
) != 1 || tcp_skb_pcount(next_skb
) != 1);
2688 if (next_skb_size
) {
2689 if (next_skb_size
<= skb_availroom(skb
))
2690 skb_copy_bits(next_skb
, 0, skb_put(skb
, next_skb_size
),
2692 else if (!skb_shift(skb
, next_skb
, next_skb_size
))
2695 tcp_highest_sack_combine(sk
, next_skb
, skb
);
2697 tcp_unlink_write_queue(next_skb
, sk
);
2699 if (next_skb
->ip_summed
== CHECKSUM_PARTIAL
)
2700 skb
->ip_summed
= CHECKSUM_PARTIAL
;
2702 if (skb
->ip_summed
!= CHECKSUM_PARTIAL
)
2703 skb
->csum
= csum_block_add(skb
->csum
, next_skb
->csum
, skb_size
);
2705 /* Update sequence range on original skb. */
2706 TCP_SKB_CB(skb
)->end_seq
= TCP_SKB_CB(next_skb
)->end_seq
;
2708 /* Merge over control information. This moves PSH/FIN etc. over */
2709 TCP_SKB_CB(skb
)->tcp_flags
|= TCP_SKB_CB(next_skb
)->tcp_flags
;
2711 /* All done, get rid of second SKB and account for it so
2712 * packet counting does not break.
2714 TCP_SKB_CB(skb
)->sacked
|= TCP_SKB_CB(next_skb
)->sacked
& TCPCB_EVER_RETRANS
;
2715 TCP_SKB_CB(skb
)->eor
= TCP_SKB_CB(next_skb
)->eor
;
2717 /* changed transmit queue under us so clear hints */
2718 tcp_clear_retrans_hints_partial(tp
);
2719 if (next_skb
== tp
->retransmit_skb_hint
)
2720 tp
->retransmit_skb_hint
= skb
;
2722 tcp_adjust_pcount(sk
, next_skb
, tcp_skb_pcount(next_skb
));
2724 tcp_skb_collapse_tstamp(skb
, next_skb
);
2726 sk_wmem_free_skb(sk
, next_skb
);
2730 /* Check if coalescing SKBs is legal. */
2731 static bool tcp_can_collapse(const struct sock
*sk
, const struct sk_buff
*skb
)
2733 if (tcp_skb_pcount(skb
) > 1)
2735 if (skb_cloned(skb
))
2737 if (skb
== tcp_send_head(sk
))
2739 /* Some heuristics for collapsing over SACK'd could be invented */
2740 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_ACKED
)
2746 /* Collapse packets in the retransmit queue to make to create
2747 * less packets on the wire. This is only done on retransmission.
2749 static void tcp_retrans_try_collapse(struct sock
*sk
, struct sk_buff
*to
,
2752 struct tcp_sock
*tp
= tcp_sk(sk
);
2753 struct sk_buff
*skb
= to
, *tmp
;
2756 if (!sysctl_tcp_retrans_collapse
)
2758 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2761 tcp_for_write_queue_from_safe(skb
, tmp
, sk
) {
2762 if (!tcp_can_collapse(sk
, skb
))
2765 if (!tcp_skb_can_collapse_to(to
))
2778 if (after(TCP_SKB_CB(skb
)->end_seq
, tcp_wnd_end(tp
)))
2781 if (!tcp_collapse_retrans(sk
, to
))
2786 /* This retransmits one SKB. Policy decisions and retransmit queue
2787 * state updates are done by the caller. Returns non-zero if an
2788 * error occurred which prevented the send.
2790 int __tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int segs
)
2792 struct inet_connection_sock
*icsk
= inet_csk(sk
);
2793 struct tcp_sock
*tp
= tcp_sk(sk
);
2794 unsigned int cur_mss
;
2798 /* Inconclusive MTU probe */
2799 if (icsk
->icsk_mtup
.probe_size
)
2800 icsk
->icsk_mtup
.probe_size
= 0;
2802 /* Do not sent more than we queued. 1/4 is reserved for possible
2803 * copying overhead: fragmentation, tunneling, mangling etc.
2805 if (refcount_read(&sk
->sk_wmem_alloc
) >
2806 min_t(u32
, sk
->sk_wmem_queued
+ (sk
->sk_wmem_queued
>> 2),
2810 if (skb_still_in_host_queue(sk
, skb
))
2813 if (before(TCP_SKB_CB(skb
)->seq
, tp
->snd_una
)) {
2814 if (before(TCP_SKB_CB(skb
)->end_seq
, tp
->snd_una
))
2816 if (tcp_trim_head(sk
, skb
, tp
->snd_una
- TCP_SKB_CB(skb
)->seq
))
2820 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
2821 return -EHOSTUNREACH
; /* Routing failure or similar. */
2823 cur_mss
= tcp_current_mss(sk
);
2825 /* If receiver has shrunk his window, and skb is out of
2826 * new window, do not retransmit it. The exception is the
2827 * case, when window is shrunk to zero. In this case
2828 * our retransmit serves as a zero window probe.
2830 if (!before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
)) &&
2831 TCP_SKB_CB(skb
)->seq
!= tp
->snd_una
)
2834 len
= cur_mss
* segs
;
2835 if (skb
->len
> len
) {
2836 if (tcp_fragment(sk
, skb
, len
, cur_mss
, GFP_ATOMIC
))
2837 return -ENOMEM
; /* We'll try again later. */
2839 if (skb_unclone(skb
, GFP_ATOMIC
))
2842 diff
= tcp_skb_pcount(skb
);
2843 tcp_set_skb_tso_segs(skb
, cur_mss
);
2844 diff
-= tcp_skb_pcount(skb
);
2846 tcp_adjust_pcount(sk
, skb
, diff
);
2847 if (skb
->len
< cur_mss
)
2848 tcp_retrans_try_collapse(sk
, skb
, cur_mss
);
2851 /* RFC3168, section 6.1.1.1. ECN fallback */
2852 if ((TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN_ECN
) == TCPHDR_SYN_ECN
)
2853 tcp_ecn_clear_syn(sk
, skb
);
2855 /* Update global and local TCP statistics. */
2856 segs
= tcp_skb_pcount(skb
);
2857 TCP_ADD_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
, segs
);
2858 if (TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)
2859 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
2860 tp
->total_retrans
+= segs
;
2862 /* make sure skb->data is aligned on arches that require it
2863 * and check if ack-trimming & collapsing extended the headroom
2864 * beyond what csum_start can cover.
2866 if (unlikely((NET_IP_ALIGN
&& ((unsigned long)skb
->data
& 3)) ||
2867 skb_headroom(skb
) >= 0xFFFF)) {
2868 struct sk_buff
*nskb
;
2870 skb
->skb_mstamp
= tp
->tcp_mstamp
;
2871 nskb
= __pskb_copy(skb
, MAX_TCP_HEADER
, GFP_ATOMIC
);
2872 err
= nskb
? tcp_transmit_skb(sk
, nskb
, 0, GFP_ATOMIC
) :
2875 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
2879 TCP_SKB_CB(skb
)->sacked
|= TCPCB_EVER_RETRANS
;
2880 } else if (err
!= -EBUSY
) {
2881 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPRETRANSFAIL
);
2886 int tcp_retransmit_skb(struct sock
*sk
, struct sk_buff
*skb
, int segs
)
2888 struct tcp_sock
*tp
= tcp_sk(sk
);
2889 int err
= __tcp_retransmit_skb(sk
, skb
, segs
);
2892 #if FASTRETRANS_DEBUG > 0
2893 if (TCP_SKB_CB(skb
)->sacked
& TCPCB_SACKED_RETRANS
) {
2894 net_dbg_ratelimited("retrans_out leaked\n");
2897 TCP_SKB_CB(skb
)->sacked
|= TCPCB_RETRANS
;
2898 tp
->retrans_out
+= tcp_skb_pcount(skb
);
2900 /* Save stamp of the first retransmit. */
2901 if (!tp
->retrans_stamp
)
2902 tp
->retrans_stamp
= tcp_skb_timestamp(skb
);
2906 if (tp
->undo_retrans
< 0)
2907 tp
->undo_retrans
= 0;
2908 tp
->undo_retrans
+= tcp_skb_pcount(skb
);
2912 /* This gets called after a retransmit timeout, and the initially
2913 * retransmitted data is acknowledged. It tries to continue
2914 * resending the rest of the retransmit queue, until either
2915 * we've sent it all or the congestion window limit is reached.
2916 * If doing SACK, the first ACK which comes back for a timeout
2917 * based retransmit packet might feed us FACK information again.
2918 * If so, we use it to avoid unnecessarily retransmissions.
2920 void tcp_xmit_retransmit_queue(struct sock
*sk
)
2922 const struct inet_connection_sock
*icsk
= inet_csk(sk
);
2923 struct tcp_sock
*tp
= tcp_sk(sk
);
2924 struct sk_buff
*skb
;
2925 struct sk_buff
*hole
= NULL
;
2929 if (!tp
->packets_out
)
2932 if (tp
->retransmit_skb_hint
) {
2933 skb
= tp
->retransmit_skb_hint
;
2935 skb
= tcp_write_queue_head(sk
);
2938 max_segs
= tcp_tso_segs(sk
, tcp_current_mss(sk
));
2939 tcp_for_write_queue_from(skb
, sk
) {
2943 if (skb
== tcp_send_head(sk
))
2946 if (tcp_pacing_check(sk
))
2949 /* we could do better than to assign each time */
2951 tp
->retransmit_skb_hint
= skb
;
2953 segs
= tp
->snd_cwnd
- tcp_packets_in_flight(tp
);
2956 sacked
= TCP_SKB_CB(skb
)->sacked
;
2957 /* In case tcp_shift_skb_data() have aggregated large skbs,
2958 * we need to make sure not sending too bigs TSO packets
2960 segs
= min_t(int, segs
, max_segs
);
2962 if (tp
->retrans_out
>= tp
->lost_out
) {
2964 } else if (!(sacked
& TCPCB_LOST
)) {
2965 if (!hole
&& !(sacked
& (TCPCB_SACKED_RETRANS
|TCPCB_SACKED_ACKED
)))
2970 if (icsk
->icsk_ca_state
!= TCP_CA_Loss
)
2971 mib_idx
= LINUX_MIB_TCPFASTRETRANS
;
2973 mib_idx
= LINUX_MIB_TCPSLOWSTARTRETRANS
;
2976 if (sacked
& (TCPCB_SACKED_ACKED
|TCPCB_SACKED_RETRANS
))
2979 if (tcp_small_queue_check(sk
, skb
, 1))
2982 if (tcp_retransmit_skb(sk
, skb
, segs
))
2985 NET_ADD_STATS(sock_net(sk
), mib_idx
, tcp_skb_pcount(skb
));
2987 if (tcp_in_cwnd_reduction(sk
))
2988 tp
->prr_out
+= tcp_skb_pcount(skb
);
2990 if (skb
== tcp_write_queue_head(sk
) &&
2991 icsk
->icsk_pending
!= ICSK_TIME_REO_TIMEOUT
)
2992 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
2993 inet_csk(sk
)->icsk_rto
,
2998 /* We allow to exceed memory limits for FIN packets to expedite
2999 * connection tear down and (memory) recovery.
3000 * Otherwise tcp_send_fin() could be tempted to either delay FIN
3001 * or even be forced to close flow without any FIN.
3002 * In general, we want to allow one skb per socket to avoid hangs
3003 * with edge trigger epoll()
3005 void sk_forced_mem_schedule(struct sock
*sk
, int size
)
3009 if (size
<= sk
->sk_forward_alloc
)
3011 amt
= sk_mem_pages(size
);
3012 sk
->sk_forward_alloc
+= amt
* SK_MEM_QUANTUM
;
3013 sk_memory_allocated_add(sk
, amt
);
3015 if (mem_cgroup_sockets_enabled
&& sk
->sk_memcg
)
3016 mem_cgroup_charge_skmem(sk
->sk_memcg
, amt
);
3019 /* Send a FIN. The caller locks the socket for us.
3020 * We should try to send a FIN packet really hard, but eventually give up.
3022 void tcp_send_fin(struct sock
*sk
)
3024 struct sk_buff
*skb
, *tskb
= tcp_write_queue_tail(sk
);
3025 struct tcp_sock
*tp
= tcp_sk(sk
);
3027 /* Optimization, tack on the FIN if we have one skb in write queue and
3028 * this skb was not yet sent, or we are under memory pressure.
3029 * Note: in the latter case, FIN packet will be sent after a timeout,
3030 * as TCP stack thinks it has already been transmitted.
3032 if (tskb
&& (tcp_send_head(sk
) || tcp_under_memory_pressure(sk
))) {
3034 TCP_SKB_CB(tskb
)->tcp_flags
|= TCPHDR_FIN
;
3035 TCP_SKB_CB(tskb
)->end_seq
++;
3037 if (!tcp_send_head(sk
)) {
3038 /* This means tskb was already sent.
3039 * Pretend we included the FIN on previous transmit.
3040 * We need to set tp->snd_nxt to the value it would have
3041 * if FIN had been sent. This is because retransmit path
3042 * does not change tp->snd_nxt.
3048 skb
= alloc_skb_fclone(MAX_TCP_HEADER
, sk
->sk_allocation
);
3049 if (unlikely(!skb
)) {
3054 skb_reserve(skb
, MAX_TCP_HEADER
);
3055 sk_forced_mem_schedule(sk
, skb
->truesize
);
3056 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
3057 tcp_init_nondata_skb(skb
, tp
->write_seq
,
3058 TCPHDR_ACK
| TCPHDR_FIN
);
3059 tcp_queue_skb(sk
, skb
);
3061 __tcp_push_pending_frames(sk
, tcp_current_mss(sk
), TCP_NAGLE_OFF
);
3064 /* We get here when a process closes a file descriptor (either due to
3065 * an explicit close() or as a byproduct of exit()'ing) and there
3066 * was unread data in the receive queue. This behavior is recommended
3067 * by RFC 2525, section 2.17. -DaveM
3069 void tcp_send_active_reset(struct sock
*sk
, gfp_t priority
)
3071 struct sk_buff
*skb
;
3073 TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTRSTS
);
3075 /* NOTE: No TCP options attached and we never retransmit this. */
3076 skb
= alloc_skb(MAX_TCP_HEADER
, priority
);
3078 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
3082 /* Reserve space for headers and prepare control bits. */
3083 skb_reserve(skb
, MAX_TCP_HEADER
);
3084 tcp_init_nondata_skb(skb
, tcp_acceptable_seq(sk
),
3085 TCPHDR_ACK
| TCPHDR_RST
);
3086 tcp_mstamp_refresh(tcp_sk(sk
));
3088 if (tcp_transmit_skb(sk
, skb
, 0, priority
))
3089 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPABORTFAILED
);
3092 /* Send a crossed SYN-ACK during socket establishment.
3093 * WARNING: This routine must only be called when we have already sent
3094 * a SYN packet that crossed the incoming SYN that caused this routine
3095 * to get called. If this assumption fails then the initial rcv_wnd
3096 * and rcv_wscale values will not be correct.
3098 int tcp_send_synack(struct sock
*sk
)
3100 struct sk_buff
*skb
;
3102 skb
= tcp_write_queue_head(sk
);
3103 if (!skb
|| !(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_SYN
)) {
3104 pr_debug("%s: wrong queue state\n", __func__
);
3107 if (!(TCP_SKB_CB(skb
)->tcp_flags
& TCPHDR_ACK
)) {
3108 if (skb_cloned(skb
)) {
3109 struct sk_buff
*nskb
= skb_copy(skb
, GFP_ATOMIC
);
3112 tcp_unlink_write_queue(skb
, sk
);
3113 __skb_header_release(nskb
);
3114 __tcp_add_write_queue_head(sk
, nskb
);
3115 sk_wmem_free_skb(sk
, skb
);
3116 sk
->sk_wmem_queued
+= nskb
->truesize
;
3117 sk_mem_charge(sk
, nskb
->truesize
);
3121 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_ACK
;
3122 tcp_ecn_send_synack(sk
, skb
);
3124 return tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3128 * tcp_make_synack - Prepare a SYN-ACK.
3129 * sk: listener socket
3130 * dst: dst entry attached to the SYNACK
3131 * req: request_sock pointer
3133 * Allocate one skb and build a SYNACK packet.
3134 * @dst is consumed : Caller should not use it again.
3136 struct sk_buff
*tcp_make_synack(const struct sock
*sk
, struct dst_entry
*dst
,
3137 struct request_sock
*req
,
3138 struct tcp_fastopen_cookie
*foc
,
3139 enum tcp_synack_type synack_type
)
3141 struct inet_request_sock
*ireq
= inet_rsk(req
);
3142 const struct tcp_sock
*tp
= tcp_sk(sk
);
3143 struct tcp_md5sig_key
*md5
= NULL
;
3144 struct tcp_out_options opts
;
3145 struct sk_buff
*skb
;
3146 int tcp_header_size
;
3150 skb
= alloc_skb(MAX_TCP_HEADER
, GFP_ATOMIC
);
3151 if (unlikely(!skb
)) {
3155 /* Reserve space for headers. */
3156 skb_reserve(skb
, MAX_TCP_HEADER
);
3158 switch (synack_type
) {
3159 case TCP_SYNACK_NORMAL
:
3160 skb_set_owner_w(skb
, req_to_sk(req
));
3162 case TCP_SYNACK_COOKIE
:
3163 /* Under synflood, we do not attach skb to a socket,
3164 * to avoid false sharing.
3167 case TCP_SYNACK_FASTOPEN
:
3168 /* sk is a const pointer, because we want to express multiple
3169 * cpu might call us concurrently.
3170 * sk->sk_wmem_alloc in an atomic, we can promote to rw.
3172 skb_set_owner_w(skb
, (struct sock
*)sk
);
3175 skb_dst_set(skb
, dst
);
3177 mss
= tcp_mss_clamp(tp
, dst_metric_advmss(dst
));
3179 memset(&opts
, 0, sizeof(opts
));
3180 #ifdef CONFIG_SYN_COOKIES
3181 if (unlikely(req
->cookie_ts
))
3182 skb
->skb_mstamp
= cookie_init_timestamp(req
);
3185 skb
->skb_mstamp
= tcp_clock_us();
3187 #ifdef CONFIG_TCP_MD5SIG
3189 md5
= tcp_rsk(req
)->af_specific
->req_md5_lookup(sk
, req_to_sk(req
));
3191 skb_set_hash(skb
, tcp_rsk(req
)->txhash
, PKT_HASH_TYPE_L4
);
3192 tcp_header_size
= tcp_synack_options(req
, mss
, skb
, &opts
, md5
, foc
) +
3195 skb_push(skb
, tcp_header_size
);
3196 skb_reset_transport_header(skb
);
3198 th
= (struct tcphdr
*)skb
->data
;
3199 memset(th
, 0, sizeof(struct tcphdr
));
3202 tcp_ecn_make_synack(req
, th
);
3203 th
->source
= htons(ireq
->ir_num
);
3204 th
->dest
= ireq
->ir_rmt_port
;
3205 skb
->mark
= ireq
->ir_mark
;
3206 /* Setting of flags are superfluous here for callers (and ECE is
3207 * not even correctly set)
3209 tcp_init_nondata_skb(skb
, tcp_rsk(req
)->snt_isn
,
3210 TCPHDR_SYN
| TCPHDR_ACK
);
3212 th
->seq
= htonl(TCP_SKB_CB(skb
)->seq
);
3213 /* XXX data is queued and acked as is. No buffer/window check */
3214 th
->ack_seq
= htonl(tcp_rsk(req
)->rcv_nxt
);
3216 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
3217 th
->window
= htons(min(req
->rsk_rcv_wnd
, 65535U));
3218 tcp_options_write((__be32
*)(th
+ 1), NULL
, &opts
);
3219 th
->doff
= (tcp_header_size
>> 2);
3220 __TCP_INC_STATS(sock_net(sk
), TCP_MIB_OUTSEGS
);
3222 #ifdef CONFIG_TCP_MD5SIG
3223 /* Okay, we have all we need - do the md5 hash if needed */
3225 tcp_rsk(req
)->af_specific
->calc_md5_hash(opts
.hash_location
,
3226 md5
, req_to_sk(req
), skb
);
3230 /* Do not fool tcpdump (if any), clean our debris */
3234 EXPORT_SYMBOL(tcp_make_synack
);
3236 static void tcp_ca_dst_init(struct sock
*sk
, const struct dst_entry
*dst
)
3238 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3239 const struct tcp_congestion_ops
*ca
;
3240 u32 ca_key
= dst_metric(dst
, RTAX_CC_ALGO
);
3242 if (ca_key
== TCP_CA_UNSPEC
)
3246 ca
= tcp_ca_find_key(ca_key
);
3247 if (likely(ca
&& try_module_get(ca
->owner
))) {
3248 module_put(icsk
->icsk_ca_ops
->owner
);
3249 icsk
->icsk_ca_dst_locked
= tcp_ca_dst_locked(dst
);
3250 icsk
->icsk_ca_ops
= ca
;
3255 /* Do all connect socket setups that can be done AF independent. */
3256 static void tcp_connect_init(struct sock
*sk
)
3258 const struct dst_entry
*dst
= __sk_dst_get(sk
);
3259 struct tcp_sock
*tp
= tcp_sk(sk
);
3263 /* We'll fix this up when we get a response from the other end.
3264 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
3266 tp
->tcp_header_len
= sizeof(struct tcphdr
);
3267 if (sock_net(sk
)->ipv4
.sysctl_tcp_timestamps
)
3268 tp
->tcp_header_len
+= TCPOLEN_TSTAMP_ALIGNED
;
3270 #ifdef CONFIG_TCP_MD5SIG
3271 if (tp
->af_specific
->md5_lookup(sk
, sk
))
3272 tp
->tcp_header_len
+= TCPOLEN_MD5SIG_ALIGNED
;
3275 /* If user gave his TCP_MAXSEG, record it to clamp */
3276 if (tp
->rx_opt
.user_mss
)
3277 tp
->rx_opt
.mss_clamp
= tp
->rx_opt
.user_mss
;
3280 tcp_sync_mss(sk
, dst_mtu(dst
));
3282 tcp_ca_dst_init(sk
, dst
);
3284 if (!tp
->window_clamp
)
3285 tp
->window_clamp
= dst_metric(dst
, RTAX_WINDOW
);
3286 tp
->advmss
= tcp_mss_clamp(tp
, dst_metric_advmss(dst
));
3288 tcp_initialize_rcv_mss(sk
);
3290 /* limit the window selection if the user enforce a smaller rx buffer */
3291 if (sk
->sk_userlocks
& SOCK_RCVBUF_LOCK
&&
3292 (tp
->window_clamp
> tcp_full_space(sk
) || tp
->window_clamp
== 0))
3293 tp
->window_clamp
= tcp_full_space(sk
);
3295 rcv_wnd
= tcp_rwnd_init_bpf(sk
);
3297 rcv_wnd
= dst_metric(dst
, RTAX_INITRWND
);
3299 tcp_select_initial_window(tcp_full_space(sk
),
3300 tp
->advmss
- (tp
->rx_opt
.ts_recent_stamp
? tp
->tcp_header_len
- sizeof(struct tcphdr
) : 0),
3303 sock_net(sk
)->ipv4
.sysctl_tcp_window_scaling
,
3307 tp
->rx_opt
.rcv_wscale
= rcv_wscale
;
3308 tp
->rcv_ssthresh
= tp
->rcv_wnd
;
3311 sock_reset_flag(sk
, SOCK_DONE
);
3314 tp
->snd_una
= tp
->write_seq
;
3315 tp
->snd_sml
= tp
->write_seq
;
3316 tp
->snd_up
= tp
->write_seq
;
3317 tp
->snd_nxt
= tp
->write_seq
;
3319 if (likely(!tp
->repair
))
3322 tp
->rcv_tstamp
= tcp_jiffies32
;
3323 tp
->rcv_wup
= tp
->rcv_nxt
;
3324 tp
->copied_seq
= tp
->rcv_nxt
;
3326 inet_csk(sk
)->icsk_rto
= tcp_timeout_init(sk
);
3327 inet_csk(sk
)->icsk_retransmits
= 0;
3328 tcp_clear_retrans(tp
);
3331 static void tcp_connect_queue_skb(struct sock
*sk
, struct sk_buff
*skb
)
3333 struct tcp_sock
*tp
= tcp_sk(sk
);
3334 struct tcp_skb_cb
*tcb
= TCP_SKB_CB(skb
);
3336 tcb
->end_seq
+= skb
->len
;
3337 __skb_header_release(skb
);
3338 __tcp_add_write_queue_tail(sk
, skb
);
3339 sk
->sk_wmem_queued
+= skb
->truesize
;
3340 sk_mem_charge(sk
, skb
->truesize
);
3341 tp
->write_seq
= tcb
->end_seq
;
3342 tp
->packets_out
+= tcp_skb_pcount(skb
);
3345 /* Build and send a SYN with data and (cached) Fast Open cookie. However,
3346 * queue a data-only packet after the regular SYN, such that regular SYNs
3347 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges
3348 * only the SYN sequence, the data are retransmitted in the first ACK.
3349 * If cookie is not cached or other error occurs, falls back to send a
3350 * regular SYN with Fast Open cookie request option.
3352 static int tcp_send_syn_data(struct sock
*sk
, struct sk_buff
*syn
)
3354 struct tcp_sock
*tp
= tcp_sk(sk
);
3355 struct tcp_fastopen_request
*fo
= tp
->fastopen_req
;
3357 struct sk_buff
*syn_data
;
3359 tp
->rx_opt
.mss_clamp
= tp
->advmss
; /* If MSS is not cached */
3360 if (!tcp_fastopen_cookie_check(sk
, &tp
->rx_opt
.mss_clamp
, &fo
->cookie
))
3363 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and
3364 * user-MSS. Reserve maximum option space for middleboxes that add
3365 * private TCP options. The cost is reduced data space in SYN :(
3367 tp
->rx_opt
.mss_clamp
= tcp_mss_clamp(tp
, tp
->rx_opt
.mss_clamp
);
3369 space
= __tcp_mtu_to_mss(sk
, inet_csk(sk
)->icsk_pmtu_cookie
) -
3370 MAX_TCP_OPTION_SPACE
;
3372 space
= min_t(size_t, space
, fo
->size
);
3374 /* limit to order-0 allocations */
3375 space
= min_t(size_t, space
, SKB_MAX_HEAD(MAX_TCP_HEADER
));
3377 syn_data
= sk_stream_alloc_skb(sk
, space
, sk
->sk_allocation
, false);
3380 syn_data
->ip_summed
= CHECKSUM_PARTIAL
;
3381 memcpy(syn_data
->cb
, syn
->cb
, sizeof(syn
->cb
));
3383 int copied
= copy_from_iter(skb_put(syn_data
, space
), space
,
3384 &fo
->data
->msg_iter
);
3385 if (unlikely(!copied
)) {
3386 kfree_skb(syn_data
);
3389 if (copied
!= space
) {
3390 skb_trim(syn_data
, copied
);
3394 /* No more data pending in inet_wait_for_connect() */
3395 if (space
== fo
->size
)
3399 tcp_connect_queue_skb(sk
, syn_data
);
3401 tcp_chrono_start(sk
, TCP_CHRONO_BUSY
);
3403 err
= tcp_transmit_skb(sk
, syn_data
, 1, sk
->sk_allocation
);
3405 syn
->skb_mstamp
= syn_data
->skb_mstamp
;
3407 /* Now full SYN+DATA was cloned and sent (or not),
3408 * remove the SYN from the original skb (syn_data)
3409 * we keep in write queue in case of a retransmit, as we
3410 * also have the SYN packet (with no data) in the same queue.
3412 TCP_SKB_CB(syn_data
)->seq
++;
3413 TCP_SKB_CB(syn_data
)->tcp_flags
= TCPHDR_ACK
| TCPHDR_PSH
;
3415 tp
->syn_data
= (fo
->copied
> 0);
3416 NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPORIGDATASENT
);
3421 /* Send a regular SYN with Fast Open cookie request option */
3422 if (fo
->cookie
.len
> 0)
3424 err
= tcp_transmit_skb(sk
, syn
, 1, sk
->sk_allocation
);
3426 tp
->syn_fastopen
= 0;
3428 fo
->cookie
.len
= -1; /* Exclude Fast Open option for SYN retries */
3432 /* Build a SYN and send it off. */
3433 int tcp_connect(struct sock
*sk
)
3435 struct tcp_sock
*tp
= tcp_sk(sk
);
3436 struct sk_buff
*buff
;
3439 tcp_call_bpf(sk
, BPF_SOCK_OPS_TCP_CONNECT_CB
);
3441 if (inet_csk(sk
)->icsk_af_ops
->rebuild_header(sk
))
3442 return -EHOSTUNREACH
; /* Routing failure or similar. */
3444 tcp_connect_init(sk
);
3446 if (unlikely(tp
->repair
)) {
3447 tcp_finish_connect(sk
, NULL
);
3451 buff
= sk_stream_alloc_skb(sk
, 0, sk
->sk_allocation
, true);
3452 if (unlikely(!buff
))
3455 tcp_init_nondata_skb(buff
, tp
->write_seq
++, TCPHDR_SYN
);
3456 tcp_mstamp_refresh(tp
);
3457 tp
->retrans_stamp
= tcp_time_stamp(tp
);
3458 tcp_connect_queue_skb(sk
, buff
);
3459 tcp_ecn_send_syn(sk
, buff
);
3461 /* Send off SYN; include data in Fast Open. */
3462 err
= tp
->fastopen_req
? tcp_send_syn_data(sk
, buff
) :
3463 tcp_transmit_skb(sk
, buff
, 1, sk
->sk_allocation
);
3464 if (err
== -ECONNREFUSED
)
3467 /* We change tp->snd_nxt after the tcp_transmit_skb() call
3468 * in order to make this packet get counted in tcpOutSegs.
3470 tp
->snd_nxt
= tp
->write_seq
;
3471 tp
->pushed_seq
= tp
->write_seq
;
3472 TCP_INC_STATS(sock_net(sk
), TCP_MIB_ACTIVEOPENS
);
3474 /* Timer for repeating the SYN until an answer. */
3475 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_RETRANS
,
3476 inet_csk(sk
)->icsk_rto
, TCP_RTO_MAX
);
3479 EXPORT_SYMBOL(tcp_connect
);
3481 /* Send out a delayed ack, the caller does the policy checking
3482 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
3485 void tcp_send_delayed_ack(struct sock
*sk
)
3487 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3488 int ato
= icsk
->icsk_ack
.ato
;
3489 unsigned long timeout
;
3491 tcp_ca_event(sk
, CA_EVENT_DELAYED_ACK
);
3493 if (ato
> TCP_DELACK_MIN
) {
3494 const struct tcp_sock
*tp
= tcp_sk(sk
);
3495 int max_ato
= HZ
/ 2;
3497 if (icsk
->icsk_ack
.pingpong
||
3498 (icsk
->icsk_ack
.pending
& ICSK_ACK_PUSHED
))
3499 max_ato
= TCP_DELACK_MAX
;
3501 /* Slow path, intersegment interval is "high". */
3503 /* If some rtt estimate is known, use it to bound delayed ack.
3504 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
3508 int rtt
= max_t(int, usecs_to_jiffies(tp
->srtt_us
>> 3),
3515 ato
= min(ato
, max_ato
);
3518 /* Stay within the limit we were given */
3519 timeout
= jiffies
+ ato
;
3521 /* Use new timeout only if there wasn't a older one earlier. */
3522 if (icsk
->icsk_ack
.pending
& ICSK_ACK_TIMER
) {
3523 /* If delack timer was blocked or is about to expire,
3526 if (icsk
->icsk_ack
.blocked
||
3527 time_before_eq(icsk
->icsk_ack
.timeout
, jiffies
+ (ato
>> 2))) {
3532 if (!time_before(timeout
, icsk
->icsk_ack
.timeout
))
3533 timeout
= icsk
->icsk_ack
.timeout
;
3535 icsk
->icsk_ack
.pending
|= ICSK_ACK_SCHED
| ICSK_ACK_TIMER
;
3536 icsk
->icsk_ack
.timeout
= timeout
;
3537 sk_reset_timer(sk
, &icsk
->icsk_delack_timer
, timeout
);
3540 /* This routine sends an ack and also updates the window. */
3541 void tcp_send_ack(struct sock
*sk
)
3543 struct sk_buff
*buff
;
3545 /* If we have been reset, we may not send again. */
3546 if (sk
->sk_state
== TCP_CLOSE
)
3549 tcp_ca_event(sk
, CA_EVENT_NON_DELAYED_ACK
);
3551 /* We are not putting this on the write queue, so
3552 * tcp_transmit_skb() will set the ownership to this
3555 buff
= alloc_skb(MAX_TCP_HEADER
,
3556 sk_gfp_mask(sk
, GFP_ATOMIC
| __GFP_NOWARN
));
3557 if (unlikely(!buff
)) {
3558 inet_csk_schedule_ack(sk
);
3559 inet_csk(sk
)->icsk_ack
.ato
= TCP_ATO_MIN
;
3560 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_DACK
,
3561 TCP_DELACK_MAX
, TCP_RTO_MAX
);
3565 /* Reserve space for headers and prepare control bits. */
3566 skb_reserve(buff
, MAX_TCP_HEADER
);
3567 tcp_init_nondata_skb(buff
, tcp_acceptable_seq(sk
), TCPHDR_ACK
);
3569 /* We do not want pure acks influencing TCP Small Queues or fq/pacing
3571 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784
3573 skb_set_tcp_pure_ack(buff
);
3575 /* Send it off, this clears delayed acks for us. */
3576 tcp_transmit_skb(sk
, buff
, 0, (__force gfp_t
)0);
3578 EXPORT_SYMBOL_GPL(tcp_send_ack
);
3580 /* This routine sends a packet with an out of date sequence
3581 * number. It assumes the other end will try to ack it.
3583 * Question: what should we make while urgent mode?
3584 * 4.4BSD forces sending single byte of data. We cannot send
3585 * out of window data, because we have SND.NXT==SND.MAX...
3587 * Current solution: to send TWO zero-length segments in urgent mode:
3588 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
3589 * out-of-date with SND.UNA-1 to probe window.
3591 static int tcp_xmit_probe_skb(struct sock
*sk
, int urgent
, int mib
)
3593 struct tcp_sock
*tp
= tcp_sk(sk
);
3594 struct sk_buff
*skb
;
3596 /* We don't queue it, tcp_transmit_skb() sets ownership. */
3597 skb
= alloc_skb(MAX_TCP_HEADER
,
3598 sk_gfp_mask(sk
, GFP_ATOMIC
| __GFP_NOWARN
));
3602 /* Reserve space for headers and set control bits. */
3603 skb_reserve(skb
, MAX_TCP_HEADER
);
3604 /* Use a previous sequence. This should cause the other
3605 * end to send an ack. Don't queue or clone SKB, just
3608 tcp_init_nondata_skb(skb
, tp
->snd_una
- !urgent
, TCPHDR_ACK
);
3609 NET_INC_STATS(sock_net(sk
), mib
);
3610 return tcp_transmit_skb(sk
, skb
, 0, (__force gfp_t
)0);
3613 /* Called from setsockopt( ... TCP_REPAIR ) */
3614 void tcp_send_window_probe(struct sock
*sk
)
3616 if (sk
->sk_state
== TCP_ESTABLISHED
) {
3617 tcp_sk(sk
)->snd_wl1
= tcp_sk(sk
)->rcv_nxt
- 1;
3618 tcp_mstamp_refresh(tcp_sk(sk
));
3619 tcp_xmit_probe_skb(sk
, 0, LINUX_MIB_TCPWINPROBE
);
3623 /* Initiate keepalive or window probe from timer. */
3624 int tcp_write_wakeup(struct sock
*sk
, int mib
)
3626 struct tcp_sock
*tp
= tcp_sk(sk
);
3627 struct sk_buff
*skb
;
3629 if (sk
->sk_state
== TCP_CLOSE
)
3632 skb
= tcp_send_head(sk
);
3633 if (skb
&& before(TCP_SKB_CB(skb
)->seq
, tcp_wnd_end(tp
))) {
3635 unsigned int mss
= tcp_current_mss(sk
);
3636 unsigned int seg_size
= tcp_wnd_end(tp
) - TCP_SKB_CB(skb
)->seq
;
3638 if (before(tp
->pushed_seq
, TCP_SKB_CB(skb
)->end_seq
))
3639 tp
->pushed_seq
= TCP_SKB_CB(skb
)->end_seq
;
3641 /* We are probing the opening of a window
3642 * but the window size is != 0
3643 * must have been a result SWS avoidance ( sender )
3645 if (seg_size
< TCP_SKB_CB(skb
)->end_seq
- TCP_SKB_CB(skb
)->seq
||
3647 seg_size
= min(seg_size
, mss
);
3648 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3649 if (tcp_fragment(sk
, skb
, seg_size
, mss
, GFP_ATOMIC
))
3651 } else if (!tcp_skb_pcount(skb
))
3652 tcp_set_skb_tso_segs(skb
, mss
);
3654 TCP_SKB_CB(skb
)->tcp_flags
|= TCPHDR_PSH
;
3655 err
= tcp_transmit_skb(sk
, skb
, 1, GFP_ATOMIC
);
3657 tcp_event_new_data_sent(sk
, skb
);
3660 if (between(tp
->snd_up
, tp
->snd_una
+ 1, tp
->snd_una
+ 0xFFFF))
3661 tcp_xmit_probe_skb(sk
, 1, mib
);
3662 return tcp_xmit_probe_skb(sk
, 0, mib
);
3666 /* A window probe timeout has occurred. If window is not closed send
3667 * a partial packet else a zero probe.
3669 void tcp_send_probe0(struct sock
*sk
)
3671 struct inet_connection_sock
*icsk
= inet_csk(sk
);
3672 struct tcp_sock
*tp
= tcp_sk(sk
);
3673 struct net
*net
= sock_net(sk
);
3674 unsigned long probe_max
;
3677 err
= tcp_write_wakeup(sk
, LINUX_MIB_TCPWINPROBE
);
3679 if (tp
->packets_out
|| !tcp_send_head(sk
)) {
3680 /* Cancel probe timer, if it is not required. */
3681 icsk
->icsk_probes_out
= 0;
3682 icsk
->icsk_backoff
= 0;
3687 if (icsk
->icsk_backoff
< net
->ipv4
.sysctl_tcp_retries2
)
3688 icsk
->icsk_backoff
++;
3689 icsk
->icsk_probes_out
++;
3690 probe_max
= TCP_RTO_MAX
;
3692 /* If packet was not sent due to local congestion,
3693 * do not backoff and do not remember icsk_probes_out.
3694 * Let local senders to fight for local resources.
3696 * Use accumulated backoff yet.
3698 if (!icsk
->icsk_probes_out
)
3699 icsk
->icsk_probes_out
= 1;
3700 probe_max
= TCP_RESOURCE_PROBE_INTERVAL
;
3702 inet_csk_reset_xmit_timer(sk
, ICSK_TIME_PROBE0
,
3703 tcp_probe0_when(sk
, probe_max
),
3707 int tcp_rtx_synack(const struct sock
*sk
, struct request_sock
*req
)
3709 const struct tcp_request_sock_ops
*af_ops
= tcp_rsk(req
)->af_specific
;
3713 tcp_rsk(req
)->txhash
= net_tx_rndhash();
3714 res
= af_ops
->send_synack(sk
, NULL
, &fl
, req
, NULL
, TCP_SYNACK_NORMAL
);
3716 __TCP_INC_STATS(sock_net(sk
), TCP_MIB_RETRANSSEGS
);
3717 __NET_INC_STATS(sock_net(sk
), LINUX_MIB_TCPSYNRETRANS
);
3718 if (unlikely(tcp_passive_fastopen(sk
)))
3719 tcp_sk(sk
)->total_retrans
++;
3723 EXPORT_SYMBOL(tcp_rtx_synack
);