Input: xilinx_ps2 - use resource_size
[firewire-audio.git] / net / ipv4 / tcp_output.c
blob383ce237640fdb8b2d79d205fd8cb8a7f123ee7f
1 /*
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).
8 * Authors: Ross Biro
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
25 * : AF independence
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 #include <net/tcp.h>
39 #include <linux/compiler.h>
40 #include <linux/module.h>
42 /* People can turn this off for buggy TCP's found in printers etc. */
43 int sysctl_tcp_retrans_collapse __read_mostly = 1;
45 /* People can turn this on to work with those rare, broken TCPs that
46 * interpret the window field as a signed quantity.
48 int sysctl_tcp_workaround_signed_windows __read_mostly = 0;
50 /* This limits the percentage of the congestion window which we
51 * will allow a single TSO frame to consume. Building TSO frames
52 * which are too large can cause TCP streams to be bursty.
54 int sysctl_tcp_tso_win_divisor __read_mostly = 3;
56 int sysctl_tcp_mtu_probing __read_mostly = 0;
57 int sysctl_tcp_base_mss __read_mostly = 512;
59 /* By default, RFC2861 behavior. */
60 int sysctl_tcp_slow_start_after_idle __read_mostly = 1;
62 int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */
63 EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size);
66 /* Account for new data that has been sent to the network. */
67 static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb)
69 struct tcp_sock *tp = tcp_sk(sk);
70 unsigned int prior_packets = tp->packets_out;
72 tcp_advance_send_head(sk, skb);
73 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
75 /* Don't override Nagle indefinately with F-RTO */
76 if (tp->frto_counter == 2)
77 tp->frto_counter = 3;
79 tp->packets_out += tcp_skb_pcount(skb);
80 if (!prior_packets)
81 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
82 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
85 /* SND.NXT, if window was not shrunk.
86 * If window has been shrunk, what should we make? It is not clear at all.
87 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
88 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
89 * invalid. OK, let's make this for now:
91 static inline __u32 tcp_acceptable_seq(struct sock *sk)
93 struct tcp_sock *tp = tcp_sk(sk);
95 if (!before(tcp_wnd_end(tp), tp->snd_nxt))
96 return tp->snd_nxt;
97 else
98 return tcp_wnd_end(tp);
101 /* Calculate mss to advertise in SYN segment.
102 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
104 * 1. It is independent of path mtu.
105 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
106 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
107 * attached devices, because some buggy hosts are confused by
108 * large MSS.
109 * 4. We do not make 3, we advertise MSS, calculated from first
110 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
111 * This may be overridden via information stored in routing table.
112 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
113 * probably even Jumbo".
115 static __u16 tcp_advertise_mss(struct sock *sk)
117 struct tcp_sock *tp = tcp_sk(sk);
118 struct dst_entry *dst = __sk_dst_get(sk);
119 int mss = tp->advmss;
121 if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) {
122 mss = dst_metric(dst, RTAX_ADVMSS);
123 tp->advmss = mss;
126 return (__u16)mss;
129 /* RFC2861. Reset CWND after idle period longer RTO to "restart window".
130 * This is the first part of cwnd validation mechanism. */
131 static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst)
133 struct tcp_sock *tp = tcp_sk(sk);
134 s32 delta = tcp_time_stamp - tp->lsndtime;
135 u32 restart_cwnd = tcp_init_cwnd(tp, dst);
136 u32 cwnd = tp->snd_cwnd;
138 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
140 tp->snd_ssthresh = tcp_current_ssthresh(sk);
141 restart_cwnd = min(restart_cwnd, cwnd);
143 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
144 cwnd >>= 1;
145 tp->snd_cwnd = max(cwnd, restart_cwnd);
146 tp->snd_cwnd_stamp = tcp_time_stamp;
147 tp->snd_cwnd_used = 0;
150 /* Congestion state accounting after a packet has been sent. */
151 static void tcp_event_data_sent(struct tcp_sock *tp,
152 struct sk_buff *skb, struct sock *sk)
154 struct inet_connection_sock *icsk = inet_csk(sk);
155 const u32 now = tcp_time_stamp;
157 if (sysctl_tcp_slow_start_after_idle &&
158 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
159 tcp_cwnd_restart(sk, __sk_dst_get(sk));
161 tp->lsndtime = now;
163 /* If it is a reply for ato after last received
164 * packet, enter pingpong mode.
166 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
167 icsk->icsk_ack.pingpong = 1;
170 /* Account for an ACK we sent. */
171 static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
173 tcp_dec_quickack_mode(sk, pkts);
174 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
177 /* Determine a window scaling and initial window to offer.
178 * Based on the assumption that the given amount of space
179 * will be offered. Store the results in the tp structure.
180 * NOTE: for smooth operation initial space offering should
181 * be a multiple of mss if possible. We assume here that mss >= 1.
182 * This MUST be enforced by all callers.
184 void tcp_select_initial_window(int __space, __u32 mss,
185 __u32 *rcv_wnd, __u32 *window_clamp,
186 int wscale_ok, __u8 *rcv_wscale)
188 unsigned int space = (__space < 0 ? 0 : __space);
190 /* If no clamp set the clamp to the max possible scaled window */
191 if (*window_clamp == 0)
192 (*window_clamp) = (65535 << 14);
193 space = min(*window_clamp, space);
195 /* Quantize space offering to a multiple of mss if possible. */
196 if (space > mss)
197 space = (space / mss) * mss;
199 /* NOTE: offering an initial window larger than 32767
200 * will break some buggy TCP stacks. If the admin tells us
201 * it is likely we could be speaking with such a buggy stack
202 * we will truncate our initial window offering to 32K-1
203 * unless the remote has sent us a window scaling option,
204 * which we interpret as a sign the remote TCP is not
205 * misinterpreting the window field as a signed quantity.
207 if (sysctl_tcp_workaround_signed_windows)
208 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
209 else
210 (*rcv_wnd) = space;
212 (*rcv_wscale) = 0;
213 if (wscale_ok) {
214 /* Set window scaling on max possible window
215 * See RFC1323 for an explanation of the limit to 14
217 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
218 space = min_t(u32, space, *window_clamp);
219 while (space > 65535 && (*rcv_wscale) < 14) {
220 space >>= 1;
221 (*rcv_wscale)++;
225 /* Set initial window to value enough for senders,
226 * following RFC2414. Senders, not following this RFC,
227 * will be satisfied with 2.
229 if (mss > (1 << *rcv_wscale)) {
230 int init_cwnd = 4;
231 if (mss > 1460 * 3)
232 init_cwnd = 2;
233 else if (mss > 1460)
234 init_cwnd = 3;
235 if (*rcv_wnd > init_cwnd * mss)
236 *rcv_wnd = init_cwnd * mss;
239 /* Set the clamp no higher than max representable value */
240 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
243 /* Chose a new window to advertise, update state in tcp_sock for the
244 * socket, and return result with RFC1323 scaling applied. The return
245 * value can be stuffed directly into th->window for an outgoing
246 * frame.
248 static u16 tcp_select_window(struct sock *sk)
250 struct tcp_sock *tp = tcp_sk(sk);
251 u32 cur_win = tcp_receive_window(tp);
252 u32 new_win = __tcp_select_window(sk);
254 /* Never shrink the offered window */
255 if (new_win < cur_win) {
256 /* Danger Will Robinson!
257 * Don't update rcv_wup/rcv_wnd here or else
258 * we will not be able to advertise a zero
259 * window in time. --DaveM
261 * Relax Will Robinson.
263 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale);
265 tp->rcv_wnd = new_win;
266 tp->rcv_wup = tp->rcv_nxt;
268 /* Make sure we do not exceed the maximum possible
269 * scaled window.
271 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows)
272 new_win = min(new_win, MAX_TCP_WINDOW);
273 else
274 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
276 /* RFC1323 scaling applied */
277 new_win >>= tp->rx_opt.rcv_wscale;
279 /* If we advertise zero window, disable fast path. */
280 if (new_win == 0)
281 tp->pred_flags = 0;
283 return new_win;
286 /* Packet ECN state for a SYN-ACK */
287 static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb)
289 TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_CWR;
290 if (!(tp->ecn_flags & TCP_ECN_OK))
291 TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_ECE;
294 /* Packet ECN state for a SYN. */
295 static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb)
297 struct tcp_sock *tp = tcp_sk(sk);
299 tp->ecn_flags = 0;
300 if (sysctl_tcp_ecn == 1) {
301 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ECE | TCPCB_FLAG_CWR;
302 tp->ecn_flags = TCP_ECN_OK;
306 static __inline__ void
307 TCP_ECN_make_synack(struct request_sock *req, struct tcphdr *th)
309 if (inet_rsk(req)->ecn_ok)
310 th->ece = 1;
313 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to
314 * be sent.
316 static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb,
317 int tcp_header_len)
319 struct tcp_sock *tp = tcp_sk(sk);
321 if (tp->ecn_flags & TCP_ECN_OK) {
322 /* Not-retransmitted data segment: set ECT and inject CWR. */
323 if (skb->len != tcp_header_len &&
324 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) {
325 INET_ECN_xmit(sk);
326 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) {
327 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
328 tcp_hdr(skb)->cwr = 1;
329 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;
331 } else {
332 /* ACK or retransmitted segment: clear ECT|CE */
333 INET_ECN_dontxmit(sk);
335 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR)
336 tcp_hdr(skb)->ece = 1;
340 /* Constructs common control bits of non-data skb. If SYN/FIN is present,
341 * auto increment end seqno.
343 static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags)
345 skb->csum = 0;
347 TCP_SKB_CB(skb)->flags = flags;
348 TCP_SKB_CB(skb)->sacked = 0;
350 skb_shinfo(skb)->gso_segs = 1;
351 skb_shinfo(skb)->gso_size = 0;
352 skb_shinfo(skb)->gso_type = 0;
354 TCP_SKB_CB(skb)->seq = seq;
355 if (flags & (TCPCB_FLAG_SYN | TCPCB_FLAG_FIN))
356 seq++;
357 TCP_SKB_CB(skb)->end_seq = seq;
360 static inline int tcp_urg_mode(const struct tcp_sock *tp)
362 return tp->snd_una != tp->snd_up;
365 #define OPTION_SACK_ADVERTISE (1 << 0)
366 #define OPTION_TS (1 << 1)
367 #define OPTION_MD5 (1 << 2)
368 #define OPTION_WSCALE (1 << 3)
369 #define OPTION_COOKIE_EXTENSION (1 << 4)
371 struct tcp_out_options {
372 u8 options; /* bit field of OPTION_* */
373 u8 ws; /* window scale, 0 to disable */
374 u8 num_sack_blocks; /* number of SACK blocks to include */
375 u8 hash_size; /* bytes in hash_location */
376 u16 mss; /* 0 to disable */
377 __u32 tsval, tsecr; /* need to include OPTION_TS */
378 __u8 *hash_location; /* temporary pointer, overloaded */
381 /* The sysctl int routines are generic, so check consistency here.
383 static u8 tcp_cookie_size_check(u8 desired)
385 if (desired > 0) {
386 /* previously specified */
387 return desired;
389 if (sysctl_tcp_cookie_size <= 0) {
390 /* no default specified */
391 return 0;
393 if (sysctl_tcp_cookie_size <= TCP_COOKIE_MIN) {
394 /* value too small, specify minimum */
395 return TCP_COOKIE_MIN;
397 if (sysctl_tcp_cookie_size >= TCP_COOKIE_MAX) {
398 /* value too large, specify maximum */
399 return TCP_COOKIE_MAX;
401 if (0x1 & sysctl_tcp_cookie_size) {
402 /* 8-bit multiple, illegal, fix it */
403 return (u8)(sysctl_tcp_cookie_size + 0x1);
405 return (u8)sysctl_tcp_cookie_size;
408 /* Write previously computed TCP options to the packet.
410 * Beware: Something in the Internet is very sensitive to the ordering of
411 * TCP options, we learned this through the hard way, so be careful here.
412 * Luckily we can at least blame others for their non-compliance but from
413 * inter-operatibility perspective it seems that we're somewhat stuck with
414 * the ordering which we have been using if we want to keep working with
415 * those broken things (not that it currently hurts anybody as there isn't
416 * particular reason why the ordering would need to be changed).
418 * At least SACK_PERM as the first option is known to lead to a disaster
419 * (but it may well be that other scenarios fail similarly).
421 static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp,
422 struct tcp_out_options *opts)
424 u8 options = opts->options; /* mungable copy */
426 /* Having both authentication and cookies for security is redundant,
427 * and there's certainly not enough room. Instead, the cookie-less
428 * extension variant is proposed.
430 * Consider the pessimal case with authentication. The options
431 * could look like:
432 * COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40
434 if (unlikely(OPTION_MD5 & options)) {
435 if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
436 *ptr++ = htonl((TCPOPT_COOKIE << 24) |
437 (TCPOLEN_COOKIE_BASE << 16) |
438 (TCPOPT_MD5SIG << 8) |
439 TCPOLEN_MD5SIG);
440 } else {
441 *ptr++ = htonl((TCPOPT_NOP << 24) |
442 (TCPOPT_NOP << 16) |
443 (TCPOPT_MD5SIG << 8) |
444 TCPOLEN_MD5SIG);
446 options &= ~OPTION_COOKIE_EXTENSION;
447 /* overload cookie hash location */
448 opts->hash_location = (__u8 *)ptr;
449 ptr += 4;
452 if (unlikely(opts->mss)) {
453 *ptr++ = htonl((TCPOPT_MSS << 24) |
454 (TCPOLEN_MSS << 16) |
455 opts->mss);
458 if (likely(OPTION_TS & options)) {
459 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
460 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) |
461 (TCPOLEN_SACK_PERM << 16) |
462 (TCPOPT_TIMESTAMP << 8) |
463 TCPOLEN_TIMESTAMP);
464 options &= ~OPTION_SACK_ADVERTISE;
465 } else {
466 *ptr++ = htonl((TCPOPT_NOP << 24) |
467 (TCPOPT_NOP << 16) |
468 (TCPOPT_TIMESTAMP << 8) |
469 TCPOLEN_TIMESTAMP);
471 *ptr++ = htonl(opts->tsval);
472 *ptr++ = htonl(opts->tsecr);
475 /* Specification requires after timestamp, so do it now.
477 * Consider the pessimal case without authentication. The options
478 * could look like:
479 * MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40
481 if (unlikely(OPTION_COOKIE_EXTENSION & options)) {
482 __u8 *cookie_copy = opts->hash_location;
483 u8 cookie_size = opts->hash_size;
485 /* 8-bit multiple handled in tcp_cookie_size_check() above,
486 * and elsewhere.
488 if (0x2 & cookie_size) {
489 __u8 *p = (__u8 *)ptr;
491 /* 16-bit multiple */
492 *p++ = TCPOPT_COOKIE;
493 *p++ = TCPOLEN_COOKIE_BASE + cookie_size;
494 *p++ = *cookie_copy++;
495 *p++ = *cookie_copy++;
496 ptr++;
497 cookie_size -= 2;
498 } else {
499 /* 32-bit multiple */
500 *ptr++ = htonl(((TCPOPT_NOP << 24) |
501 (TCPOPT_NOP << 16) |
502 (TCPOPT_COOKIE << 8) |
503 TCPOLEN_COOKIE_BASE) +
504 cookie_size);
507 if (cookie_size > 0) {
508 memcpy(ptr, cookie_copy, cookie_size);
509 ptr += (cookie_size / 4);
513 if (unlikely(OPTION_SACK_ADVERTISE & options)) {
514 *ptr++ = htonl((TCPOPT_NOP << 24) |
515 (TCPOPT_NOP << 16) |
516 (TCPOPT_SACK_PERM << 8) |
517 TCPOLEN_SACK_PERM);
520 if (unlikely(OPTION_WSCALE & options)) {
521 *ptr++ = htonl((TCPOPT_NOP << 24) |
522 (TCPOPT_WINDOW << 16) |
523 (TCPOLEN_WINDOW << 8) |
524 opts->ws);
527 if (unlikely(opts->num_sack_blocks)) {
528 struct tcp_sack_block *sp = tp->rx_opt.dsack ?
529 tp->duplicate_sack : tp->selective_acks;
530 int this_sack;
532 *ptr++ = htonl((TCPOPT_NOP << 24) |
533 (TCPOPT_NOP << 16) |
534 (TCPOPT_SACK << 8) |
535 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks *
536 TCPOLEN_SACK_PERBLOCK)));
538 for (this_sack = 0; this_sack < opts->num_sack_blocks;
539 ++this_sack) {
540 *ptr++ = htonl(sp[this_sack].start_seq);
541 *ptr++ = htonl(sp[this_sack].end_seq);
544 tp->rx_opt.dsack = 0;
548 /* Compute TCP options for SYN packets. This is not the final
549 * network wire format yet.
551 static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb,
552 struct tcp_out_options *opts,
553 struct tcp_md5sig_key **md5) {
554 struct tcp_sock *tp = tcp_sk(sk);
555 struct tcp_cookie_values *cvp = tp->cookie_values;
556 unsigned remaining = MAX_TCP_OPTION_SPACE;
557 u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ?
558 tcp_cookie_size_check(cvp->cookie_desired) :
561 #ifdef CONFIG_TCP_MD5SIG
562 *md5 = tp->af_specific->md5_lookup(sk, sk);
563 if (*md5) {
564 opts->options |= OPTION_MD5;
565 remaining -= TCPOLEN_MD5SIG_ALIGNED;
567 #else
568 *md5 = NULL;
569 #endif
571 /* We always get an MSS option. The option bytes which will be seen in
572 * normal data packets should timestamps be used, must be in the MSS
573 * advertised. But we subtract them from tp->mss_cache so that
574 * calculations in tcp_sendmsg are simpler etc. So account for this
575 * fact here if necessary. If we don't do this correctly, as a
576 * receiver we won't recognize data packets as being full sized when we
577 * should, and thus we won't abide by the delayed ACK rules correctly.
578 * SACKs don't matter, we never delay an ACK when we have any of those
579 * going out. */
580 opts->mss = tcp_advertise_mss(sk);
581 remaining -= TCPOLEN_MSS_ALIGNED;
583 if (likely(sysctl_tcp_timestamps && *md5 == NULL)) {
584 opts->options |= OPTION_TS;
585 opts->tsval = TCP_SKB_CB(skb)->when;
586 opts->tsecr = tp->rx_opt.ts_recent;
587 remaining -= TCPOLEN_TSTAMP_ALIGNED;
589 if (likely(sysctl_tcp_window_scaling)) {
590 opts->ws = tp->rx_opt.rcv_wscale;
591 opts->options |= OPTION_WSCALE;
592 remaining -= TCPOLEN_WSCALE_ALIGNED;
594 if (likely(sysctl_tcp_sack)) {
595 opts->options |= OPTION_SACK_ADVERTISE;
596 if (unlikely(!(OPTION_TS & opts->options)))
597 remaining -= TCPOLEN_SACKPERM_ALIGNED;
600 /* Note that timestamps are required by the specification.
602 * Odd numbers of bytes are prohibited by the specification, ensuring
603 * that the cookie is 16-bit aligned, and the resulting cookie pair is
604 * 32-bit aligned.
606 if (*md5 == NULL &&
607 (OPTION_TS & opts->options) &&
608 cookie_size > 0) {
609 int need = TCPOLEN_COOKIE_BASE + cookie_size;
611 if (0x2 & need) {
612 /* 32-bit multiple */
613 need += 2; /* NOPs */
615 if (need > remaining) {
616 /* try shrinking cookie to fit */
617 cookie_size -= 2;
618 need -= 4;
621 while (need > remaining && TCP_COOKIE_MIN <= cookie_size) {
622 cookie_size -= 4;
623 need -= 4;
625 if (TCP_COOKIE_MIN <= cookie_size) {
626 opts->options |= OPTION_COOKIE_EXTENSION;
627 opts->hash_location = (__u8 *)&cvp->cookie_pair[0];
628 opts->hash_size = cookie_size;
630 /* Remember for future incarnations. */
631 cvp->cookie_desired = cookie_size;
633 if (cvp->cookie_desired != cvp->cookie_pair_size) {
634 /* Currently use random bytes as a nonce,
635 * assuming these are completely unpredictable
636 * by hostile users of the same system.
638 get_random_bytes(&cvp->cookie_pair[0],
639 cookie_size);
640 cvp->cookie_pair_size = cookie_size;
643 remaining -= need;
646 return MAX_TCP_OPTION_SPACE - remaining;
649 /* Set up TCP options for SYN-ACKs. */
650 static unsigned tcp_synack_options(struct sock *sk,
651 struct request_sock *req,
652 unsigned mss, struct sk_buff *skb,
653 struct tcp_out_options *opts,
654 struct tcp_md5sig_key **md5,
655 struct tcp_extend_values *xvp)
657 struct inet_request_sock *ireq = inet_rsk(req);
658 unsigned remaining = MAX_TCP_OPTION_SPACE;
659 u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ?
660 xvp->cookie_plus :
662 bool doing_ts = ireq->tstamp_ok;
664 #ifdef CONFIG_TCP_MD5SIG
665 *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req);
666 if (*md5) {
667 opts->options |= OPTION_MD5;
668 remaining -= TCPOLEN_MD5SIG_ALIGNED;
670 /* We can't fit any SACK blocks in a packet with MD5 + TS
671 * options. There was discussion about disabling SACK
672 * rather than TS in order to fit in better with old,
673 * buggy kernels, but that was deemed to be unnecessary.
675 doing_ts &= !ireq->sack_ok;
677 #else
678 *md5 = NULL;
679 #endif
681 /* We always send an MSS option. */
682 opts->mss = mss;
683 remaining -= TCPOLEN_MSS_ALIGNED;
685 if (likely(ireq->wscale_ok)) {
686 opts->ws = ireq->rcv_wscale;
687 opts->options |= OPTION_WSCALE;
688 remaining -= TCPOLEN_WSCALE_ALIGNED;
690 if (likely(doing_ts)) {
691 opts->options |= OPTION_TS;
692 opts->tsval = TCP_SKB_CB(skb)->when;
693 opts->tsecr = req->ts_recent;
694 remaining -= TCPOLEN_TSTAMP_ALIGNED;
696 if (likely(ireq->sack_ok)) {
697 opts->options |= OPTION_SACK_ADVERTISE;
698 if (unlikely(!doing_ts))
699 remaining -= TCPOLEN_SACKPERM_ALIGNED;
702 /* Similar rationale to tcp_syn_options() applies here, too.
703 * If the <SYN> options fit, the same options should fit now!
705 if (*md5 == NULL &&
706 doing_ts &&
707 cookie_plus > TCPOLEN_COOKIE_BASE) {
708 int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */
710 if (0x2 & need) {
711 /* 32-bit multiple */
712 need += 2; /* NOPs */
714 if (need <= remaining) {
715 opts->options |= OPTION_COOKIE_EXTENSION;
716 opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE;
717 remaining -= need;
718 } else {
719 /* There's no error return, so flag it. */
720 xvp->cookie_out_never = 1; /* true */
721 opts->hash_size = 0;
724 return MAX_TCP_OPTION_SPACE - remaining;
727 /* Compute TCP options for ESTABLISHED sockets. This is not the
728 * final wire format yet.
730 static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb,
731 struct tcp_out_options *opts,
732 struct tcp_md5sig_key **md5) {
733 struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL;
734 struct tcp_sock *tp = tcp_sk(sk);
735 unsigned size = 0;
736 unsigned int eff_sacks;
738 #ifdef CONFIG_TCP_MD5SIG
739 *md5 = tp->af_specific->md5_lookup(sk, sk);
740 if (unlikely(*md5)) {
741 opts->options |= OPTION_MD5;
742 size += TCPOLEN_MD5SIG_ALIGNED;
744 #else
745 *md5 = NULL;
746 #endif
748 if (likely(tp->rx_opt.tstamp_ok)) {
749 opts->options |= OPTION_TS;
750 opts->tsval = tcb ? tcb->when : 0;
751 opts->tsecr = tp->rx_opt.ts_recent;
752 size += TCPOLEN_TSTAMP_ALIGNED;
755 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;
756 if (unlikely(eff_sacks)) {
757 const unsigned remaining = MAX_TCP_OPTION_SPACE - size;
758 opts->num_sack_blocks =
759 min_t(unsigned, eff_sacks,
760 (remaining - TCPOLEN_SACK_BASE_ALIGNED) /
761 TCPOLEN_SACK_PERBLOCK);
762 size += TCPOLEN_SACK_BASE_ALIGNED +
763 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK;
766 return size;
769 /* This routine actually transmits TCP packets queued in by
770 * tcp_do_sendmsg(). This is used by both the initial
771 * transmission and possible later retransmissions.
772 * All SKB's seen here are completely headerless. It is our
773 * job to build the TCP header, and pass the packet down to
774 * IP so it can do the same plus pass the packet off to the
775 * device.
777 * We are working here with either a clone of the original
778 * SKB, or a fresh unique copy made by the retransmit engine.
780 static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
781 gfp_t gfp_mask)
783 const struct inet_connection_sock *icsk = inet_csk(sk);
784 struct inet_sock *inet;
785 struct tcp_sock *tp;
786 struct tcp_skb_cb *tcb;
787 struct tcp_out_options opts;
788 unsigned tcp_options_size, tcp_header_size;
789 struct tcp_md5sig_key *md5;
790 struct tcphdr *th;
791 int err;
793 BUG_ON(!skb || !tcp_skb_pcount(skb));
795 /* If congestion control is doing timestamping, we must
796 * take such a timestamp before we potentially clone/copy.
798 if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP)
799 __net_timestamp(skb);
801 if (likely(clone_it)) {
802 if (unlikely(skb_cloned(skb)))
803 skb = pskb_copy(skb, gfp_mask);
804 else
805 skb = skb_clone(skb, gfp_mask);
806 if (unlikely(!skb))
807 return -ENOBUFS;
810 inet = inet_sk(sk);
811 tp = tcp_sk(sk);
812 tcb = TCP_SKB_CB(skb);
813 memset(&opts, 0, sizeof(opts));
815 if (unlikely(tcb->flags & TCPCB_FLAG_SYN))
816 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5);
817 else
818 tcp_options_size = tcp_established_options(sk, skb, &opts,
819 &md5);
820 tcp_header_size = tcp_options_size + sizeof(struct tcphdr);
822 if (tcp_packets_in_flight(tp) == 0)
823 tcp_ca_event(sk, CA_EVENT_TX_START);
825 skb_push(skb, tcp_header_size);
826 skb_reset_transport_header(skb);
827 skb_set_owner_w(skb, sk);
829 /* Build TCP header and checksum it. */
830 th = tcp_hdr(skb);
831 th->source = inet->inet_sport;
832 th->dest = inet->inet_dport;
833 th->seq = htonl(tcb->seq);
834 th->ack_seq = htonl(tp->rcv_nxt);
835 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
836 tcb->flags);
838 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
839 /* RFC1323: The window in SYN & SYN/ACK segments
840 * is never scaled.
842 th->window = htons(min(tp->rcv_wnd, 65535U));
843 } else {
844 th->window = htons(tcp_select_window(sk));
846 th->check = 0;
847 th->urg_ptr = 0;
849 /* The urg_mode check is necessary during a below snd_una win probe */
850 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) {
851 if (before(tp->snd_up, tcb->seq + 0x10000)) {
852 th->urg_ptr = htons(tp->snd_up - tcb->seq);
853 th->urg = 1;
854 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) {
855 th->urg_ptr = 0xFFFF;
856 th->urg = 1;
860 tcp_options_write((__be32 *)(th + 1), tp, &opts);
861 if (likely((tcb->flags & TCPCB_FLAG_SYN) == 0))
862 TCP_ECN_send(sk, skb, tcp_header_size);
864 #ifdef CONFIG_TCP_MD5SIG
865 /* Calculate the MD5 hash, as we have all we need now */
866 if (md5) {
867 sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
868 tp->af_specific->calc_md5_hash(opts.hash_location,
869 md5, sk, NULL, skb);
871 #endif
873 icsk->icsk_af_ops->send_check(sk, skb->len, skb);
875 if (likely(tcb->flags & TCPCB_FLAG_ACK))
876 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
878 if (skb->len != tcp_header_size)
879 tcp_event_data_sent(tp, skb, sk);
881 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq)
882 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
884 err = icsk->icsk_af_ops->queue_xmit(skb, 0);
885 if (likely(err <= 0))
886 return err;
888 tcp_enter_cwr(sk, 1);
890 return net_xmit_eval(err);
893 /* This routine just queues the buffer for sending.
895 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
896 * otherwise socket can stall.
898 static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
900 struct tcp_sock *tp = tcp_sk(sk);
902 /* Advance write_seq and place onto the write_queue. */
903 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
904 skb_header_release(skb);
905 tcp_add_write_queue_tail(sk, skb);
906 sk->sk_wmem_queued += skb->truesize;
907 sk_mem_charge(sk, skb->truesize);
910 /* Initialize TSO segments for a packet. */
911 static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb,
912 unsigned int mss_now)
914 if (skb->len <= mss_now || !sk_can_gso(sk) ||
915 skb->ip_summed == CHECKSUM_NONE) {
916 /* Avoid the costly divide in the normal
917 * non-TSO case.
919 skb_shinfo(skb)->gso_segs = 1;
920 skb_shinfo(skb)->gso_size = 0;
921 skb_shinfo(skb)->gso_type = 0;
922 } else {
923 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now);
924 skb_shinfo(skb)->gso_size = mss_now;
925 skb_shinfo(skb)->gso_type = sk->sk_gso_type;
929 /* When a modification to fackets out becomes necessary, we need to check
930 * skb is counted to fackets_out or not.
932 static void tcp_adjust_fackets_out(struct sock *sk, struct sk_buff *skb,
933 int decr)
935 struct tcp_sock *tp = tcp_sk(sk);
937 if (!tp->sacked_out || tcp_is_reno(tp))
938 return;
940 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq))
941 tp->fackets_out -= decr;
944 /* Pcount in the middle of the write queue got changed, we need to do various
945 * tweaks to fix counters
947 static void tcp_adjust_pcount(struct sock *sk, struct sk_buff *skb, int decr)
949 struct tcp_sock *tp = tcp_sk(sk);
951 tp->packets_out -= decr;
953 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
954 tp->sacked_out -= decr;
955 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
956 tp->retrans_out -= decr;
957 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)
958 tp->lost_out -= decr;
960 /* Reno case is special. Sigh... */
961 if (tcp_is_reno(tp) && decr > 0)
962 tp->sacked_out -= min_t(u32, tp->sacked_out, decr);
964 tcp_adjust_fackets_out(sk, skb, decr);
966 if (tp->lost_skb_hint &&
967 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) &&
968 (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)))
969 tp->lost_cnt_hint -= decr;
971 tcp_verify_left_out(tp);
974 /* Function to create two new TCP segments. Shrinks the given segment
975 * to the specified size and appends a new segment with the rest of the
976 * packet to the list. This won't be called frequently, I hope.
977 * Remember, these are still headerless SKBs at this point.
979 int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len,
980 unsigned int mss_now)
982 struct tcp_sock *tp = tcp_sk(sk);
983 struct sk_buff *buff;
984 int nsize, old_factor;
985 int nlen;
986 u8 flags;
988 BUG_ON(len > skb->len);
990 nsize = skb_headlen(skb) - len;
991 if (nsize < 0)
992 nsize = 0;
994 if (skb_cloned(skb) &&
995 skb_is_nonlinear(skb) &&
996 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
997 return -ENOMEM;
999 /* Get a new skb... force flag on. */
1000 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
1001 if (buff == NULL)
1002 return -ENOMEM; /* We'll just try again later. */
1004 sk->sk_wmem_queued += buff->truesize;
1005 sk_mem_charge(sk, buff->truesize);
1006 nlen = skb->len - len - nsize;
1007 buff->truesize += nlen;
1008 skb->truesize -= nlen;
1010 /* Correct the sequence numbers. */
1011 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1012 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1013 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1015 /* PSH and FIN should only be set in the second packet. */
1016 flags = TCP_SKB_CB(skb)->flags;
1017 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH);
1018 TCP_SKB_CB(buff)->flags = flags;
1019 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
1021 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) {
1022 /* Copy and checksum data tail into the new buffer. */
1023 buff->csum = csum_partial_copy_nocheck(skb->data + len,
1024 skb_put(buff, nsize),
1025 nsize, 0);
1027 skb_trim(skb, len);
1029 skb->csum = csum_block_sub(skb->csum, buff->csum, len);
1030 } else {
1031 skb->ip_summed = CHECKSUM_PARTIAL;
1032 skb_split(skb, buff, len);
1035 buff->ip_summed = skb->ip_summed;
1037 /* Looks stupid, but our code really uses when of
1038 * skbs, which it never sent before. --ANK
1040 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
1041 buff->tstamp = skb->tstamp;
1043 old_factor = tcp_skb_pcount(skb);
1045 /* Fix up tso_factor for both original and new SKB. */
1046 tcp_set_skb_tso_segs(sk, skb, mss_now);
1047 tcp_set_skb_tso_segs(sk, buff, mss_now);
1049 /* If this packet has been sent out already, we must
1050 * adjust the various packet counters.
1052 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
1053 int diff = old_factor - tcp_skb_pcount(skb) -
1054 tcp_skb_pcount(buff);
1056 if (diff)
1057 tcp_adjust_pcount(sk, skb, diff);
1060 /* Link BUFF into the send queue. */
1061 skb_header_release(buff);
1062 tcp_insert_write_queue_after(skb, buff, sk);
1064 return 0;
1067 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
1068 * eventually). The difference is that pulled data not copied, but
1069 * immediately discarded.
1071 static void __pskb_trim_head(struct sk_buff *skb, int len)
1073 int i, k, eat;
1075 eat = len;
1076 k = 0;
1077 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
1078 if (skb_shinfo(skb)->frags[i].size <= eat) {
1079 put_page(skb_shinfo(skb)->frags[i].page);
1080 eat -= skb_shinfo(skb)->frags[i].size;
1081 } else {
1082 skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
1083 if (eat) {
1084 skb_shinfo(skb)->frags[k].page_offset += eat;
1085 skb_shinfo(skb)->frags[k].size -= eat;
1086 eat = 0;
1088 k++;
1091 skb_shinfo(skb)->nr_frags = k;
1093 skb_reset_tail_pointer(skb);
1094 skb->data_len -= len;
1095 skb->len = skb->data_len;
1098 /* Remove acked data from a packet in the transmit queue. */
1099 int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
1101 if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
1102 return -ENOMEM;
1104 /* If len == headlen, we avoid __skb_pull to preserve alignment. */
1105 if (unlikely(len < skb_headlen(skb)))
1106 __skb_pull(skb, len);
1107 else
1108 __pskb_trim_head(skb, len - skb_headlen(skb));
1110 TCP_SKB_CB(skb)->seq += len;
1111 skb->ip_summed = CHECKSUM_PARTIAL;
1113 skb->truesize -= len;
1114 sk->sk_wmem_queued -= len;
1115 sk_mem_uncharge(sk, len);
1116 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
1118 /* Any change of skb->len requires recalculation of tso
1119 * factor and mss.
1121 if (tcp_skb_pcount(skb) > 1)
1122 tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk));
1124 return 0;
1127 /* Calculate MSS. Not accounting for SACKs here. */
1128 int tcp_mtu_to_mss(struct sock *sk, int pmtu)
1130 struct tcp_sock *tp = tcp_sk(sk);
1131 struct inet_connection_sock *icsk = inet_csk(sk);
1132 int mss_now;
1134 /* Calculate base mss without TCP options:
1135 It is MMS_S - sizeof(tcphdr) of rfc1122
1137 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr);
1139 /* Clamp it (mss_clamp does not include tcp options) */
1140 if (mss_now > tp->rx_opt.mss_clamp)
1141 mss_now = tp->rx_opt.mss_clamp;
1143 /* Now subtract optional transport overhead */
1144 mss_now -= icsk->icsk_ext_hdr_len;
1146 /* Then reserve room for full set of TCP options and 8 bytes of data */
1147 if (mss_now < 48)
1148 mss_now = 48;
1150 /* Now subtract TCP options size, not including SACKs */
1151 mss_now -= tp->tcp_header_len - sizeof(struct tcphdr);
1153 return mss_now;
1156 /* Inverse of above */
1157 int tcp_mss_to_mtu(struct sock *sk, int mss)
1159 struct tcp_sock *tp = tcp_sk(sk);
1160 struct inet_connection_sock *icsk = inet_csk(sk);
1161 int mtu;
1163 mtu = mss +
1164 tp->tcp_header_len +
1165 icsk->icsk_ext_hdr_len +
1166 icsk->icsk_af_ops->net_header_len;
1168 return mtu;
1171 /* MTU probing init per socket */
1172 void tcp_mtup_init(struct sock *sk)
1174 struct tcp_sock *tp = tcp_sk(sk);
1175 struct inet_connection_sock *icsk = inet_csk(sk);
1177 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1;
1178 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
1179 icsk->icsk_af_ops->net_header_len;
1180 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss);
1181 icsk->icsk_mtup.probe_size = 0;
1184 /* This function synchronize snd mss to current pmtu/exthdr set.
1186 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
1187 for TCP options, but includes only bare TCP header.
1189 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
1190 It is minimum of user_mss and mss received with SYN.
1191 It also does not include TCP options.
1193 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
1195 tp->mss_cache is current effective sending mss, including
1196 all tcp options except for SACKs. It is evaluated,
1197 taking into account current pmtu, but never exceeds
1198 tp->rx_opt.mss_clamp.
1200 NOTE1. rfc1122 clearly states that advertised MSS
1201 DOES NOT include either tcp or ip options.
1203 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
1204 are READ ONLY outside this function. --ANK (980731)
1206 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
1208 struct tcp_sock *tp = tcp_sk(sk);
1209 struct inet_connection_sock *icsk = inet_csk(sk);
1210 int mss_now;
1212 if (icsk->icsk_mtup.search_high > pmtu)
1213 icsk->icsk_mtup.search_high = pmtu;
1215 mss_now = tcp_mtu_to_mss(sk, pmtu);
1216 mss_now = tcp_bound_to_half_wnd(tp, mss_now);
1218 /* And store cached results */
1219 icsk->icsk_pmtu_cookie = pmtu;
1220 if (icsk->icsk_mtup.enabled)
1221 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low));
1222 tp->mss_cache = mss_now;
1224 return mss_now;
1227 /* Compute the current effective MSS, taking SACKs and IP options,
1228 * and even PMTU discovery events into account.
1230 unsigned int tcp_current_mss(struct sock *sk)
1232 struct tcp_sock *tp = tcp_sk(sk);
1233 struct dst_entry *dst = __sk_dst_get(sk);
1234 u32 mss_now;
1235 unsigned header_len;
1236 struct tcp_out_options opts;
1237 struct tcp_md5sig_key *md5;
1239 mss_now = tp->mss_cache;
1241 if (dst) {
1242 u32 mtu = dst_mtu(dst);
1243 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
1244 mss_now = tcp_sync_mss(sk, mtu);
1247 header_len = tcp_established_options(sk, NULL, &opts, &md5) +
1248 sizeof(struct tcphdr);
1249 /* The mss_cache is sized based on tp->tcp_header_len, which assumes
1250 * some common options. If this is an odd packet (because we have SACK
1251 * blocks etc) then our calculated header_len will be different, and
1252 * we have to adjust mss_now correspondingly */
1253 if (header_len != tp->tcp_header_len) {
1254 int delta = (int) header_len - tp->tcp_header_len;
1255 mss_now -= delta;
1258 return mss_now;
1261 /* Congestion window validation. (RFC2861) */
1262 static void tcp_cwnd_validate(struct sock *sk)
1264 struct tcp_sock *tp = tcp_sk(sk);
1266 if (tp->packets_out >= tp->snd_cwnd) {
1267 /* Network is feed fully. */
1268 tp->snd_cwnd_used = 0;
1269 tp->snd_cwnd_stamp = tcp_time_stamp;
1270 } else {
1271 /* Network starves. */
1272 if (tp->packets_out > tp->snd_cwnd_used)
1273 tp->snd_cwnd_used = tp->packets_out;
1275 if (sysctl_tcp_slow_start_after_idle &&
1276 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
1277 tcp_cwnd_application_limited(sk);
1281 /* Returns the portion of skb which can be sent right away without
1282 * introducing MSS oddities to segment boundaries. In rare cases where
1283 * mss_now != mss_cache, we will request caller to create a small skb
1284 * per input skb which could be mostly avoided here (if desired).
1286 * We explicitly want to create a request for splitting write queue tail
1287 * to a small skb for Nagle purposes while avoiding unnecessary modulos,
1288 * thus all the complexity (cwnd_len is always MSS multiple which we
1289 * return whenever allowed by the other factors). Basically we need the
1290 * modulo only when the receiver window alone is the limiting factor or
1291 * when we would be allowed to send the split-due-to-Nagle skb fully.
1293 static unsigned int tcp_mss_split_point(struct sock *sk, struct sk_buff *skb,
1294 unsigned int mss_now, unsigned int cwnd)
1296 struct tcp_sock *tp = tcp_sk(sk);
1297 u32 needed, window, cwnd_len;
1299 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1300 cwnd_len = mss_now * cwnd;
1302 if (likely(cwnd_len <= window && skb != tcp_write_queue_tail(sk)))
1303 return cwnd_len;
1305 needed = min(skb->len, window);
1307 if (cwnd_len <= needed)
1308 return cwnd_len;
1310 return needed - needed % mss_now;
1313 /* Can at least one segment of SKB be sent right now, according to the
1314 * congestion window rules? If so, return how many segments are allowed.
1316 static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp,
1317 struct sk_buff *skb)
1319 u32 in_flight, cwnd;
1321 /* Don't be strict about the congestion window for the final FIN. */
1322 if ((TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
1323 tcp_skb_pcount(skb) == 1)
1324 return 1;
1326 in_flight = tcp_packets_in_flight(tp);
1327 cwnd = tp->snd_cwnd;
1328 if (in_flight < cwnd)
1329 return (cwnd - in_flight);
1331 return 0;
1334 /* Intialize TSO state of a skb.
1335 * This must be invoked the first time we consider transmitting
1336 * SKB onto the wire.
1338 static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb,
1339 unsigned int mss_now)
1341 int tso_segs = tcp_skb_pcount(skb);
1343 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) {
1344 tcp_set_skb_tso_segs(sk, skb, mss_now);
1345 tso_segs = tcp_skb_pcount(skb);
1347 return tso_segs;
1350 /* Minshall's variant of the Nagle send check. */
1351 static inline int tcp_minshall_check(const struct tcp_sock *tp)
1353 return after(tp->snd_sml, tp->snd_una) &&
1354 !after(tp->snd_sml, tp->snd_nxt);
1357 /* Return 0, if packet can be sent now without violation Nagle's rules:
1358 * 1. It is full sized.
1359 * 2. Or it contains FIN. (already checked by caller)
1360 * 3. Or TCP_NODELAY was set.
1361 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
1362 * With Minshall's modification: all sent small packets are ACKed.
1364 static inline int tcp_nagle_check(const struct tcp_sock *tp,
1365 const struct sk_buff *skb,
1366 unsigned mss_now, int nonagle)
1368 return (skb->len < mss_now &&
1369 ((nonagle & TCP_NAGLE_CORK) ||
1370 (!nonagle && tp->packets_out && tcp_minshall_check(tp))));
1373 /* Return non-zero if the Nagle test allows this packet to be
1374 * sent now.
1376 static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb,
1377 unsigned int cur_mss, int nonagle)
1379 /* Nagle rule does not apply to frames, which sit in the middle of the
1380 * write_queue (they have no chances to get new data).
1382 * This is implemented in the callers, where they modify the 'nonagle'
1383 * argument based upon the location of SKB in the send queue.
1385 if (nonagle & TCP_NAGLE_PUSH)
1386 return 1;
1388 /* Don't use the nagle rule for urgent data (or for the final FIN).
1389 * Nagle can be ignored during F-RTO too (see RFC4138).
1391 if (tcp_urg_mode(tp) || (tp->frto_counter == 2) ||
1392 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN))
1393 return 1;
1395 if (!tcp_nagle_check(tp, skb, cur_mss, nonagle))
1396 return 1;
1398 return 0;
1401 /* Does at least the first segment of SKB fit into the send window? */
1402 static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb,
1403 unsigned int cur_mss)
1405 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
1407 if (skb->len > cur_mss)
1408 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
1410 return !after(end_seq, tcp_wnd_end(tp));
1413 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk))
1414 * should be put on the wire right now. If so, it returns the number of
1415 * packets allowed by the congestion window.
1417 static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
1418 unsigned int cur_mss, int nonagle)
1420 struct tcp_sock *tp = tcp_sk(sk);
1421 unsigned int cwnd_quota;
1423 tcp_init_tso_segs(sk, skb, cur_mss);
1425 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
1426 return 0;
1428 cwnd_quota = tcp_cwnd_test(tp, skb);
1429 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss))
1430 cwnd_quota = 0;
1432 return cwnd_quota;
1435 /* Test if sending is allowed right now. */
1436 int tcp_may_send_now(struct sock *sk)
1438 struct tcp_sock *tp = tcp_sk(sk);
1439 struct sk_buff *skb = tcp_send_head(sk);
1441 return (skb &&
1442 tcp_snd_test(sk, skb, tcp_current_mss(sk),
1443 (tcp_skb_is_last(sk, skb) ?
1444 tp->nonagle : TCP_NAGLE_PUSH)));
1447 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
1448 * which is put after SKB on the list. It is very much like
1449 * tcp_fragment() except that it may make several kinds of assumptions
1450 * in order to speed up the splitting operation. In particular, we
1451 * know that all the data is in scatter-gather pages, and that the
1452 * packet has never been sent out before (and thus is not cloned).
1454 static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len,
1455 unsigned int mss_now)
1457 struct sk_buff *buff;
1458 int nlen = skb->len - len;
1459 u8 flags;
1461 /* All of a TSO frame must be composed of paged data. */
1462 if (skb->len != skb->data_len)
1463 return tcp_fragment(sk, skb, len, mss_now);
1465 buff = sk_stream_alloc_skb(sk, 0, GFP_ATOMIC);
1466 if (unlikely(buff == NULL))
1467 return -ENOMEM;
1469 sk->sk_wmem_queued += buff->truesize;
1470 sk_mem_charge(sk, buff->truesize);
1471 buff->truesize += nlen;
1472 skb->truesize -= nlen;
1474 /* Correct the sequence numbers. */
1475 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
1476 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
1477 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
1479 /* PSH and FIN should only be set in the second packet. */
1480 flags = TCP_SKB_CB(skb)->flags;
1481 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH);
1482 TCP_SKB_CB(buff)->flags = flags;
1484 /* This packet was never sent out yet, so no SACK bits. */
1485 TCP_SKB_CB(buff)->sacked = 0;
1487 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL;
1488 skb_split(skb, buff, len);
1490 /* Fix up tso_factor for both original and new SKB. */
1491 tcp_set_skb_tso_segs(sk, skb, mss_now);
1492 tcp_set_skb_tso_segs(sk, buff, mss_now);
1494 /* Link BUFF into the send queue. */
1495 skb_header_release(buff);
1496 tcp_insert_write_queue_after(skb, buff, sk);
1498 return 0;
1501 /* Try to defer sending, if possible, in order to minimize the amount
1502 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1504 * This algorithm is from John Heffner.
1506 static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb)
1508 struct tcp_sock *tp = tcp_sk(sk);
1509 const struct inet_connection_sock *icsk = inet_csk(sk);
1510 u32 send_win, cong_win, limit, in_flight;
1512 if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
1513 goto send_now;
1515 if (icsk->icsk_ca_state != TCP_CA_Open)
1516 goto send_now;
1518 /* Defer for less than two clock ticks. */
1519 if (tp->tso_deferred &&
1520 (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1)
1521 goto send_now;
1523 in_flight = tcp_packets_in_flight(tp);
1525 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight));
1527 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
1529 /* From in_flight test above, we know that cwnd > in_flight. */
1530 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1532 limit = min(send_win, cong_win);
1534 /* If a full-sized TSO skb can be sent, do it. */
1535 if (limit >= sk->sk_gso_max_size)
1536 goto send_now;
1538 /* Middle in queue won't get any more data, full sendable already? */
1539 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len))
1540 goto send_now;
1542 if (sysctl_tcp_tso_win_divisor) {
1543 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1545 /* If at least some fraction of a window is available,
1546 * just use it.
1548 chunk /= sysctl_tcp_tso_win_divisor;
1549 if (limit >= chunk)
1550 goto send_now;
1551 } else {
1552 /* Different approach, try not to defer past a single
1553 * ACK. Receiver should ACK every other full sized
1554 * frame, so if we have space for more than 3 frames
1555 * then send now.
1557 if (limit > tcp_max_burst(tp) * tp->mss_cache)
1558 goto send_now;
1561 /* Ok, it looks like it is advisable to defer. */
1562 tp->tso_deferred = 1 | (jiffies << 1);
1564 return 1;
1566 send_now:
1567 tp->tso_deferred = 0;
1568 return 0;
1571 /* Create a new MTU probe if we are ready.
1572 * MTU probe is regularly attempting to increase the path MTU by
1573 * deliberately sending larger packets. This discovers routing
1574 * changes resulting in larger path MTUs.
1576 * Returns 0 if we should wait to probe (no cwnd available),
1577 * 1 if a probe was sent,
1578 * -1 otherwise
1580 static int tcp_mtu_probe(struct sock *sk)
1582 struct tcp_sock *tp = tcp_sk(sk);
1583 struct inet_connection_sock *icsk = inet_csk(sk);
1584 struct sk_buff *skb, *nskb, *next;
1585 int len;
1586 int probe_size;
1587 int size_needed;
1588 int copy;
1589 int mss_now;
1591 /* Not currently probing/verifying,
1592 * not in recovery,
1593 * have enough cwnd, and
1594 * not SACKing (the variable headers throw things off) */
1595 if (!icsk->icsk_mtup.enabled ||
1596 icsk->icsk_mtup.probe_size ||
1597 inet_csk(sk)->icsk_ca_state != TCP_CA_Open ||
1598 tp->snd_cwnd < 11 ||
1599 tp->rx_opt.num_sacks || tp->rx_opt.dsack)
1600 return -1;
1602 /* Very simple search strategy: just double the MSS. */
1603 mss_now = tcp_current_mss(sk);
1604 probe_size = 2 * tp->mss_cache;
1605 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache;
1606 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) {
1607 /* TODO: set timer for probe_converge_event */
1608 return -1;
1611 /* Have enough data in the send queue to probe? */
1612 if (tp->write_seq - tp->snd_nxt < size_needed)
1613 return -1;
1615 if (tp->snd_wnd < size_needed)
1616 return -1;
1617 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp)))
1618 return 0;
1620 /* Do we need to wait to drain cwnd? With none in flight, don't stall */
1621 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) {
1622 if (!tcp_packets_in_flight(tp))
1623 return -1;
1624 else
1625 return 0;
1628 /* We're allowed to probe. Build it now. */
1629 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL)
1630 return -1;
1631 sk->sk_wmem_queued += nskb->truesize;
1632 sk_mem_charge(sk, nskb->truesize);
1634 skb = tcp_send_head(sk);
1636 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq;
1637 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size;
1638 TCP_SKB_CB(nskb)->flags = TCPCB_FLAG_ACK;
1639 TCP_SKB_CB(nskb)->sacked = 0;
1640 nskb->csum = 0;
1641 nskb->ip_summed = skb->ip_summed;
1643 tcp_insert_write_queue_before(nskb, skb, sk);
1645 len = 0;
1646 tcp_for_write_queue_from_safe(skb, next, sk) {
1647 copy = min_t(int, skb->len, probe_size - len);
1648 if (nskb->ip_summed)
1649 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy);
1650 else
1651 nskb->csum = skb_copy_and_csum_bits(skb, 0,
1652 skb_put(nskb, copy),
1653 copy, nskb->csum);
1655 if (skb->len <= copy) {
1656 /* We've eaten all the data from this skb.
1657 * Throw it away. */
1658 TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags;
1659 tcp_unlink_write_queue(skb, sk);
1660 sk_wmem_free_skb(sk, skb);
1661 } else {
1662 TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags &
1663 ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
1664 if (!skb_shinfo(skb)->nr_frags) {
1665 skb_pull(skb, copy);
1666 if (skb->ip_summed != CHECKSUM_PARTIAL)
1667 skb->csum = csum_partial(skb->data,
1668 skb->len, 0);
1669 } else {
1670 __pskb_trim_head(skb, copy);
1671 tcp_set_skb_tso_segs(sk, skb, mss_now);
1673 TCP_SKB_CB(skb)->seq += copy;
1676 len += copy;
1678 if (len >= probe_size)
1679 break;
1681 tcp_init_tso_segs(sk, nskb, nskb->len);
1683 /* We're ready to send. If this fails, the probe will
1684 * be resegmented into mss-sized pieces by tcp_write_xmit(). */
1685 TCP_SKB_CB(nskb)->when = tcp_time_stamp;
1686 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) {
1687 /* Decrement cwnd here because we are sending
1688 * effectively two packets. */
1689 tp->snd_cwnd--;
1690 tcp_event_new_data_sent(sk, nskb);
1692 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len);
1693 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq;
1694 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq;
1696 return 1;
1699 return -1;
1702 /* This routine writes packets to the network. It advances the
1703 * send_head. This happens as incoming acks open up the remote
1704 * window for us.
1706 * LARGESEND note: !tcp_urg_mode is overkill, only frames between
1707 * snd_up-64k-mss .. snd_up cannot be large. However, taking into
1708 * account rare use of URG, this is not a big flaw.
1710 * Returns 1, if no segments are in flight and we have queued segments, but
1711 * cannot send anything now because of SWS or another problem.
1713 static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
1714 int push_one, gfp_t gfp)
1716 struct tcp_sock *tp = tcp_sk(sk);
1717 struct sk_buff *skb;
1718 unsigned int tso_segs, sent_pkts;
1719 int cwnd_quota;
1720 int result;
1722 sent_pkts = 0;
1724 if (!push_one) {
1725 /* Do MTU probing. */
1726 result = tcp_mtu_probe(sk);
1727 if (!result) {
1728 return 0;
1729 } else if (result > 0) {
1730 sent_pkts = 1;
1734 while ((skb = tcp_send_head(sk))) {
1735 unsigned int limit;
1737 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
1738 BUG_ON(!tso_segs);
1740 cwnd_quota = tcp_cwnd_test(tp, skb);
1741 if (!cwnd_quota)
1742 break;
1744 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
1745 break;
1747 if (tso_segs == 1) {
1748 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
1749 (tcp_skb_is_last(sk, skb) ?
1750 nonagle : TCP_NAGLE_PUSH))))
1751 break;
1752 } else {
1753 if (!push_one && tcp_tso_should_defer(sk, skb))
1754 break;
1757 limit = mss_now;
1758 if (tso_segs > 1 && !tcp_urg_mode(tp))
1759 limit = tcp_mss_split_point(sk, skb, mss_now,
1760 cwnd_quota);
1762 if (skb->len > limit &&
1763 unlikely(tso_fragment(sk, skb, limit, mss_now)))
1764 break;
1766 TCP_SKB_CB(skb)->when = tcp_time_stamp;
1768 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
1769 break;
1771 /* Advance the send_head. This one is sent out.
1772 * This call will increment packets_out.
1774 tcp_event_new_data_sent(sk, skb);
1776 tcp_minshall_update(tp, mss_now, skb);
1777 sent_pkts++;
1779 if (push_one)
1780 break;
1783 if (likely(sent_pkts)) {
1784 tcp_cwnd_validate(sk);
1785 return 0;
1787 return !tp->packets_out && tcp_send_head(sk);
1790 /* Push out any pending frames which were held back due to
1791 * TCP_CORK or attempt at coalescing tiny packets.
1792 * The socket must be locked by the caller.
1794 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
1795 int nonagle)
1797 struct sk_buff *skb = tcp_send_head(sk);
1799 if (!skb)
1800 return;
1802 /* If we are closed, the bytes will have to remain here.
1803 * In time closedown will finish, we empty the write queue and
1804 * all will be happy.
1806 if (unlikely(sk->sk_state == TCP_CLOSE))
1807 return;
1809 if (tcp_write_xmit(sk, cur_mss, nonagle, 0, GFP_ATOMIC))
1810 tcp_check_probe_timer(sk);
1813 /* Send _single_ skb sitting at the send head. This function requires
1814 * true push pending frames to setup probe timer etc.
1816 void tcp_push_one(struct sock *sk, unsigned int mss_now)
1818 struct sk_buff *skb = tcp_send_head(sk);
1820 BUG_ON(!skb || skb->len < mss_now);
1822 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation);
1825 /* This function returns the amount that we can raise the
1826 * usable window based on the following constraints
1828 * 1. The window can never be shrunk once it is offered (RFC 793)
1829 * 2. We limit memory per socket
1831 * RFC 1122:
1832 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1833 * RECV.NEXT + RCV.WIN fixed until:
1834 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1836 * i.e. don't raise the right edge of the window until you can raise
1837 * it at least MSS bytes.
1839 * Unfortunately, the recommended algorithm breaks header prediction,
1840 * since header prediction assumes th->window stays fixed.
1842 * Strictly speaking, keeping th->window fixed violates the receiver
1843 * side SWS prevention criteria. The problem is that under this rule
1844 * a stream of single byte packets will cause the right side of the
1845 * window to always advance by a single byte.
1847 * Of course, if the sender implements sender side SWS prevention
1848 * then this will not be a problem.
1850 * BSD seems to make the following compromise:
1852 * If the free space is less than the 1/4 of the maximum
1853 * space available and the free space is less than 1/2 mss,
1854 * then set the window to 0.
1855 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1856 * Otherwise, just prevent the window from shrinking
1857 * and from being larger than the largest representable value.
1859 * This prevents incremental opening of the window in the regime
1860 * where TCP is limited by the speed of the reader side taking
1861 * data out of the TCP receive queue. It does nothing about
1862 * those cases where the window is constrained on the sender side
1863 * because the pipeline is full.
1865 * BSD also seems to "accidentally" limit itself to windows that are a
1866 * multiple of MSS, at least until the free space gets quite small.
1867 * This would appear to be a side effect of the mbuf implementation.
1868 * Combining these two algorithms results in the observed behavior
1869 * of having a fixed window size at almost all times.
1871 * Below we obtain similar behavior by forcing the offered window to
1872 * a multiple of the mss when it is feasible to do so.
1874 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1875 * Regular options like TIMESTAMP are taken into account.
1877 u32 __tcp_select_window(struct sock *sk)
1879 struct inet_connection_sock *icsk = inet_csk(sk);
1880 struct tcp_sock *tp = tcp_sk(sk);
1881 /* MSS for the peer's data. Previous versions used mss_clamp
1882 * here. I don't know if the value based on our guesses
1883 * of peer's MSS is better for the performance. It's more correct
1884 * but may be worse for the performance because of rcv_mss
1885 * fluctuations. --SAW 1998/11/1
1887 int mss = icsk->icsk_ack.rcv_mss;
1888 int free_space = tcp_space(sk);
1889 int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));
1890 int window;
1892 if (mss > full_space)
1893 mss = full_space;
1895 if (free_space < (full_space >> 1)) {
1896 icsk->icsk_ack.quick = 0;
1898 if (tcp_memory_pressure)
1899 tp->rcv_ssthresh = min(tp->rcv_ssthresh,
1900 4U * tp->advmss);
1902 if (free_space < mss)
1903 return 0;
1906 if (free_space > tp->rcv_ssthresh)
1907 free_space = tp->rcv_ssthresh;
1909 /* Don't do rounding if we are using window scaling, since the
1910 * scaled window will not line up with the MSS boundary anyway.
1912 window = tp->rcv_wnd;
1913 if (tp->rx_opt.rcv_wscale) {
1914 window = free_space;
1916 /* Advertise enough space so that it won't get scaled away.
1917 * Import case: prevent zero window announcement if
1918 * 1<<rcv_wscale > mss.
1920 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
1921 window = (((window >> tp->rx_opt.rcv_wscale) + 1)
1922 << tp->rx_opt.rcv_wscale);
1923 } else {
1924 /* Get the largest window that is a nice multiple of mss.
1925 * Window clamp already applied above.
1926 * If our current window offering is within 1 mss of the
1927 * free space we just keep it. This prevents the divide
1928 * and multiply from happening most of the time.
1929 * We also don't do any window rounding when the free space
1930 * is too small.
1932 if (window <= free_space - mss || window > free_space)
1933 window = (free_space / mss) * mss;
1934 else if (mss == full_space &&
1935 free_space > window + (full_space >> 1))
1936 window = free_space;
1939 return window;
1942 /* Collapses two adjacent SKB's during retransmission. */
1943 static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb)
1945 struct tcp_sock *tp = tcp_sk(sk);
1946 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb);
1947 int skb_size, next_skb_size;
1949 skb_size = skb->len;
1950 next_skb_size = next_skb->len;
1952 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1);
1954 tcp_highest_sack_combine(sk, next_skb, skb);
1956 tcp_unlink_write_queue(next_skb, sk);
1958 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size),
1959 next_skb_size);
1961 if (next_skb->ip_summed == CHECKSUM_PARTIAL)
1962 skb->ip_summed = CHECKSUM_PARTIAL;
1964 if (skb->ip_summed != CHECKSUM_PARTIAL)
1965 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
1967 /* Update sequence range on original skb. */
1968 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
1970 /* Merge over control information. This moves PSH/FIN etc. over */
1971 TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(next_skb)->flags;
1973 /* All done, get rid of second SKB and account for it so
1974 * packet counting does not break.
1976 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS;
1978 /* changed transmit queue under us so clear hints */
1979 tcp_clear_retrans_hints_partial(tp);
1980 if (next_skb == tp->retransmit_skb_hint)
1981 tp->retransmit_skb_hint = skb;
1983 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb));
1985 sk_wmem_free_skb(sk, next_skb);
1988 /* Check if coalescing SKBs is legal. */
1989 static int tcp_can_collapse(struct sock *sk, struct sk_buff *skb)
1991 if (tcp_skb_pcount(skb) > 1)
1992 return 0;
1993 /* TODO: SACK collapsing could be used to remove this condition */
1994 if (skb_shinfo(skb)->nr_frags != 0)
1995 return 0;
1996 if (skb_cloned(skb))
1997 return 0;
1998 if (skb == tcp_send_head(sk))
1999 return 0;
2000 /* Some heurestics for collapsing over SACK'd could be invented */
2001 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
2002 return 0;
2004 return 1;
2007 /* Collapse packets in the retransmit queue to make to create
2008 * less packets on the wire. This is only done on retransmission.
2010 static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to,
2011 int space)
2013 struct tcp_sock *tp = tcp_sk(sk);
2014 struct sk_buff *skb = to, *tmp;
2015 int first = 1;
2017 if (!sysctl_tcp_retrans_collapse)
2018 return;
2019 if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN)
2020 return;
2022 tcp_for_write_queue_from_safe(skb, tmp, sk) {
2023 if (!tcp_can_collapse(sk, skb))
2024 break;
2026 space -= skb->len;
2028 if (first) {
2029 first = 0;
2030 continue;
2033 if (space < 0)
2034 break;
2035 /* Punt if not enough space exists in the first SKB for
2036 * the data in the second
2038 if (skb->len > skb_tailroom(to))
2039 break;
2041 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp)))
2042 break;
2044 tcp_collapse_retrans(sk, to);
2048 /* This retransmits one SKB. Policy decisions and retransmit queue
2049 * state updates are done by the caller. Returns non-zero if an
2050 * error occurred which prevented the send.
2052 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
2054 struct tcp_sock *tp = tcp_sk(sk);
2055 struct inet_connection_sock *icsk = inet_csk(sk);
2056 unsigned int cur_mss;
2057 int err;
2059 /* Inconslusive MTU probe */
2060 if (icsk->icsk_mtup.probe_size) {
2061 icsk->icsk_mtup.probe_size = 0;
2064 /* Do not sent more than we queued. 1/4 is reserved for possible
2065 * copying overhead: fragmentation, tunneling, mangling etc.
2067 if (atomic_read(&sk->sk_wmem_alloc) >
2068 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
2069 return -EAGAIN;
2071 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
2072 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
2073 BUG();
2074 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
2075 return -ENOMEM;
2078 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
2079 return -EHOSTUNREACH; /* Routing failure or similar. */
2081 cur_mss = tcp_current_mss(sk);
2083 /* If receiver has shrunk his window, and skb is out of
2084 * new window, do not retransmit it. The exception is the
2085 * case, when window is shrunk to zero. In this case
2086 * our retransmit serves as a zero window probe.
2088 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) &&
2089 TCP_SKB_CB(skb)->seq != tp->snd_una)
2090 return -EAGAIN;
2092 if (skb->len > cur_mss) {
2093 if (tcp_fragment(sk, skb, cur_mss, cur_mss))
2094 return -ENOMEM; /* We'll try again later. */
2095 } else {
2096 int oldpcount = tcp_skb_pcount(skb);
2098 if (unlikely(oldpcount > 1)) {
2099 tcp_init_tso_segs(sk, skb, cur_mss);
2100 tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb));
2104 tcp_retrans_try_collapse(sk, skb, cur_mss);
2106 /* Some Solaris stacks overoptimize and ignore the FIN on a
2107 * retransmit when old data is attached. So strip it off
2108 * since it is cheap to do so and saves bytes on the network.
2110 if (skb->len > 0 &&
2111 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
2112 tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
2113 if (!pskb_trim(skb, 0)) {
2114 /* Reuse, even though it does some unnecessary work */
2115 tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1,
2116 TCP_SKB_CB(skb)->flags);
2117 skb->ip_summed = CHECKSUM_NONE;
2121 /* Make a copy, if the first transmission SKB clone we made
2122 * is still in somebody's hands, else make a clone.
2124 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2126 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2128 if (err == 0) {
2129 /* Update global TCP statistics. */
2130 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
2132 tp->total_retrans++;
2134 #if FASTRETRANS_DEBUG > 0
2135 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) {
2136 if (net_ratelimit())
2137 printk(KERN_DEBUG "retrans_out leaked.\n");
2139 #endif
2140 if (!tp->retrans_out)
2141 tp->lost_retrans_low = tp->snd_nxt;
2142 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
2143 tp->retrans_out += tcp_skb_pcount(skb);
2145 /* Save stamp of the first retransmit. */
2146 if (!tp->retrans_stamp)
2147 tp->retrans_stamp = TCP_SKB_CB(skb)->when;
2149 tp->undo_retrans++;
2151 /* snd_nxt is stored to detect loss of retransmitted segment,
2152 * see tcp_input.c tcp_sacktag_write_queue().
2154 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
2156 return err;
2159 /* Check if we forward retransmits are possible in the current
2160 * window/congestion state.
2162 static int tcp_can_forward_retransmit(struct sock *sk)
2164 const struct inet_connection_sock *icsk = inet_csk(sk);
2165 struct tcp_sock *tp = tcp_sk(sk);
2167 /* Forward retransmissions are possible only during Recovery. */
2168 if (icsk->icsk_ca_state != TCP_CA_Recovery)
2169 return 0;
2171 /* No forward retransmissions in Reno are possible. */
2172 if (tcp_is_reno(tp))
2173 return 0;
2175 /* Yeah, we have to make difficult choice between forward transmission
2176 * and retransmission... Both ways have their merits...
2178 * For now we do not retransmit anything, while we have some new
2179 * segments to send. In the other cases, follow rule 3 for
2180 * NextSeg() specified in RFC3517.
2183 if (tcp_may_send_now(sk))
2184 return 0;
2186 return 1;
2189 /* This gets called after a retransmit timeout, and the initially
2190 * retransmitted data is acknowledged. It tries to continue
2191 * resending the rest of the retransmit queue, until either
2192 * we've sent it all or the congestion window limit is reached.
2193 * If doing SACK, the first ACK which comes back for a timeout
2194 * based retransmit packet might feed us FACK information again.
2195 * If so, we use it to avoid unnecessarily retransmissions.
2197 void tcp_xmit_retransmit_queue(struct sock *sk)
2199 const struct inet_connection_sock *icsk = inet_csk(sk);
2200 struct tcp_sock *tp = tcp_sk(sk);
2201 struct sk_buff *skb;
2202 struct sk_buff *hole = NULL;
2203 u32 last_lost;
2204 int mib_idx;
2205 int fwd_rexmitting = 0;
2207 if (!tp->lost_out)
2208 tp->retransmit_high = tp->snd_una;
2210 if (tp->retransmit_skb_hint) {
2211 skb = tp->retransmit_skb_hint;
2212 last_lost = TCP_SKB_CB(skb)->end_seq;
2213 if (after(last_lost, tp->retransmit_high))
2214 last_lost = tp->retransmit_high;
2215 } else {
2216 skb = tcp_write_queue_head(sk);
2217 last_lost = tp->snd_una;
2220 tcp_for_write_queue_from(skb, sk) {
2221 __u8 sacked = TCP_SKB_CB(skb)->sacked;
2223 if (skb == tcp_send_head(sk))
2224 break;
2225 /* we could do better than to assign each time */
2226 if (hole == NULL)
2227 tp->retransmit_skb_hint = skb;
2229 /* Assume this retransmit will generate
2230 * only one packet for congestion window
2231 * calculation purposes. This works because
2232 * tcp_retransmit_skb() will chop up the
2233 * packet to be MSS sized and all the
2234 * packet counting works out.
2236 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
2237 return;
2239 if (fwd_rexmitting) {
2240 begin_fwd:
2241 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp)))
2242 break;
2243 mib_idx = LINUX_MIB_TCPFORWARDRETRANS;
2245 } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) {
2246 tp->retransmit_high = last_lost;
2247 if (!tcp_can_forward_retransmit(sk))
2248 break;
2249 /* Backtrack if necessary to non-L'ed skb */
2250 if (hole != NULL) {
2251 skb = hole;
2252 hole = NULL;
2254 fwd_rexmitting = 1;
2255 goto begin_fwd;
2257 } else if (!(sacked & TCPCB_LOST)) {
2258 if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED)))
2259 hole = skb;
2260 continue;
2262 } else {
2263 last_lost = TCP_SKB_CB(skb)->end_seq;
2264 if (icsk->icsk_ca_state != TCP_CA_Loss)
2265 mib_idx = LINUX_MIB_TCPFASTRETRANS;
2266 else
2267 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS;
2270 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))
2271 continue;
2273 if (tcp_retransmit_skb(sk, skb))
2274 return;
2275 NET_INC_STATS_BH(sock_net(sk), mib_idx);
2277 if (skb == tcp_write_queue_head(sk))
2278 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2279 inet_csk(sk)->icsk_rto,
2280 TCP_RTO_MAX);
2284 /* Send a fin. The caller locks the socket for us. This cannot be
2285 * allowed to fail queueing a FIN frame under any circumstances.
2287 void tcp_send_fin(struct sock *sk)
2289 struct tcp_sock *tp = tcp_sk(sk);
2290 struct sk_buff *skb = tcp_write_queue_tail(sk);
2291 int mss_now;
2293 /* Optimization, tack on the FIN if we have a queue of
2294 * unsent frames. But be careful about outgoing SACKS
2295 * and IP options.
2297 mss_now = tcp_current_mss(sk);
2299 if (tcp_send_head(sk) != NULL) {
2300 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
2301 TCP_SKB_CB(skb)->end_seq++;
2302 tp->write_seq++;
2303 } else {
2304 /* Socket is locked, keep trying until memory is available. */
2305 for (;;) {
2306 skb = alloc_skb_fclone(MAX_TCP_HEADER,
2307 sk->sk_allocation);
2308 if (skb)
2309 break;
2310 yield();
2313 /* Reserve space for headers and prepare control bits. */
2314 skb_reserve(skb, MAX_TCP_HEADER);
2315 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
2316 tcp_init_nondata_skb(skb, tp->write_seq,
2317 TCPCB_FLAG_ACK | TCPCB_FLAG_FIN);
2318 tcp_queue_skb(sk, skb);
2320 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF);
2323 /* We get here when a process closes a file descriptor (either due to
2324 * an explicit close() or as a byproduct of exit()'ing) and there
2325 * was unread data in the receive queue. This behavior is recommended
2326 * by RFC 2525, section 2.17. -DaveM
2328 void tcp_send_active_reset(struct sock *sk, gfp_t priority)
2330 struct sk_buff *skb;
2332 /* NOTE: No TCP options attached and we never retransmit this. */
2333 skb = alloc_skb(MAX_TCP_HEADER, priority);
2334 if (!skb) {
2335 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2336 return;
2339 /* Reserve space for headers and prepare control bits. */
2340 skb_reserve(skb, MAX_TCP_HEADER);
2341 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
2342 TCPCB_FLAG_ACK | TCPCB_FLAG_RST);
2343 /* Send it off. */
2344 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2345 if (tcp_transmit_skb(sk, skb, 0, priority))
2346 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
2348 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS);
2351 /* Send a crossed SYN-ACK during socket establishment.
2352 * WARNING: This routine must only be called when we have already sent
2353 * a SYN packet that crossed the incoming SYN that caused this routine
2354 * to get called. If this assumption fails then the initial rcv_wnd
2355 * and rcv_wscale values will not be correct.
2357 int tcp_send_synack(struct sock *sk)
2359 struct sk_buff *skb;
2361 skb = tcp_write_queue_head(sk);
2362 if (skb == NULL || !(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN)) {
2363 printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n");
2364 return -EFAULT;
2366 if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_ACK)) {
2367 if (skb_cloned(skb)) {
2368 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
2369 if (nskb == NULL)
2370 return -ENOMEM;
2371 tcp_unlink_write_queue(skb, sk);
2372 skb_header_release(nskb);
2373 __tcp_add_write_queue_head(sk, nskb);
2374 sk_wmem_free_skb(sk, skb);
2375 sk->sk_wmem_queued += nskb->truesize;
2376 sk_mem_charge(sk, nskb->truesize);
2377 skb = nskb;
2380 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK;
2381 TCP_ECN_send_synack(tcp_sk(sk), skb);
2383 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2384 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2387 /* Prepare a SYN-ACK. */
2388 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
2389 struct request_sock *req,
2390 struct request_values *rvp)
2392 struct tcp_out_options opts;
2393 struct tcp_extend_values *xvp = tcp_xv(rvp);
2394 struct inet_request_sock *ireq = inet_rsk(req);
2395 struct tcp_sock *tp = tcp_sk(sk);
2396 struct tcphdr *th;
2397 struct sk_buff *skb;
2398 struct tcp_md5sig_key *md5;
2399 int tcp_header_size;
2400 int mss;
2402 skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
2403 if (skb == NULL)
2404 return NULL;
2406 /* Reserve space for headers. */
2407 skb_reserve(skb, MAX_TCP_HEADER);
2409 skb_dst_set(skb, dst_clone(dst));
2411 mss = dst_metric(dst, RTAX_ADVMSS);
2412 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss)
2413 mss = tp->rx_opt.user_mss;
2415 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
2416 __u8 rcv_wscale;
2417 /* Set this up on the first call only */
2418 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
2419 /* tcp_full_space because it is guaranteed to be the first packet */
2420 tcp_select_initial_window(tcp_full_space(sk),
2421 mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
2422 &req->rcv_wnd,
2423 &req->window_clamp,
2424 ireq->wscale_ok,
2425 &rcv_wscale);
2426 ireq->rcv_wscale = rcv_wscale;
2429 memset(&opts, 0, sizeof(opts));
2430 #ifdef CONFIG_SYN_COOKIES
2431 if (unlikely(req->cookie_ts))
2432 TCP_SKB_CB(skb)->when = cookie_init_timestamp(req);
2433 else
2434 #endif
2435 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2436 tcp_header_size = tcp_synack_options(sk, req, mss,
2437 skb, &opts, &md5, xvp)
2438 + sizeof(*th);
2440 skb_push(skb, tcp_header_size);
2441 skb_reset_transport_header(skb);
2443 th = tcp_hdr(skb);
2444 memset(th, 0, sizeof(struct tcphdr));
2445 th->syn = 1;
2446 th->ack = 1;
2447 TCP_ECN_make_synack(req, th);
2448 th->source = ireq->loc_port;
2449 th->dest = ireq->rmt_port;
2450 /* Setting of flags are superfluous here for callers (and ECE is
2451 * not even correctly set)
2453 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn,
2454 TCPCB_FLAG_SYN | TCPCB_FLAG_ACK);
2456 if (OPTION_COOKIE_EXTENSION & opts.options) {
2457 const struct tcp_cookie_values *cvp = tp->cookie_values;
2459 if (cvp != NULL &&
2460 cvp->s_data_constant &&
2461 cvp->s_data_desired > 0) {
2462 u8 *buf = skb_put(skb, cvp->s_data_desired);
2464 /* copy data directly from the listening socket. */
2465 memcpy(buf, cvp->s_data_payload, cvp->s_data_desired);
2466 TCP_SKB_CB(skb)->end_seq += cvp->s_data_desired;
2469 if (opts.hash_size > 0) {
2470 __u32 workspace[SHA_WORKSPACE_WORDS];
2471 u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS];
2472 u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1];
2474 /* Secret recipe depends on the Timestamp, (future)
2475 * Sequence and Acknowledgment Numbers, Initiator
2476 * Cookie, and others handled by IP variant caller.
2478 *tail-- ^= opts.tsval;
2479 *tail-- ^= tcp_rsk(req)->rcv_isn + 1;
2480 *tail-- ^= TCP_SKB_CB(skb)->seq + 1;
2482 /* recommended */
2483 *tail-- ^= ((th->dest << 16) | th->source);
2484 *tail-- ^= (u32)(unsigned long)cvp; /* per sockopt */
2486 sha_transform((__u32 *)&xvp->cookie_bakery[0],
2487 (char *)mess,
2488 &workspace[0]);
2489 opts.hash_location =
2490 (__u8 *)&xvp->cookie_bakery[0];
2494 th->seq = htonl(TCP_SKB_CB(skb)->seq);
2495 th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
2497 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
2498 th->window = htons(min(req->rcv_wnd, 65535U));
2499 tcp_options_write((__be32 *)(th + 1), tp, &opts);
2500 th->doff = (tcp_header_size >> 2);
2501 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS);
2503 #ifdef CONFIG_TCP_MD5SIG
2504 /* Okay, we have all we need - do the md5 hash if needed */
2505 if (md5) {
2506 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location,
2507 md5, NULL, req, skb);
2509 #endif
2511 return skb;
2514 /* Do all connect socket setups that can be done AF independent. */
2515 static void tcp_connect_init(struct sock *sk)
2517 struct dst_entry *dst = __sk_dst_get(sk);
2518 struct tcp_sock *tp = tcp_sk(sk);
2519 __u8 rcv_wscale;
2521 /* We'll fix this up when we get a response from the other end.
2522 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
2524 tp->tcp_header_len = sizeof(struct tcphdr) +
2525 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
2527 #ifdef CONFIG_TCP_MD5SIG
2528 if (tp->af_specific->md5_lookup(sk, sk) != NULL)
2529 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED;
2530 #endif
2532 /* If user gave his TCP_MAXSEG, record it to clamp */
2533 if (tp->rx_opt.user_mss)
2534 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
2535 tp->max_window = 0;
2536 tcp_mtup_init(sk);
2537 tcp_sync_mss(sk, dst_mtu(dst));
2539 if (!tp->window_clamp)
2540 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
2541 tp->advmss = dst_metric(dst, RTAX_ADVMSS);
2542 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss)
2543 tp->advmss = tp->rx_opt.user_mss;
2545 tcp_initialize_rcv_mss(sk);
2547 tcp_select_initial_window(tcp_full_space(sk),
2548 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
2549 &tp->rcv_wnd,
2550 &tp->window_clamp,
2551 sysctl_tcp_window_scaling,
2552 &rcv_wscale);
2554 tp->rx_opt.rcv_wscale = rcv_wscale;
2555 tp->rcv_ssthresh = tp->rcv_wnd;
2557 sk->sk_err = 0;
2558 sock_reset_flag(sk, SOCK_DONE);
2559 tp->snd_wnd = 0;
2560 tcp_init_wl(tp, 0);
2561 tp->snd_una = tp->write_seq;
2562 tp->snd_sml = tp->write_seq;
2563 tp->snd_up = tp->write_seq;
2564 tp->rcv_nxt = 0;
2565 tp->rcv_wup = 0;
2566 tp->copied_seq = 0;
2568 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
2569 inet_csk(sk)->icsk_retransmits = 0;
2570 tcp_clear_retrans(tp);
2573 /* Build a SYN and send it off. */
2574 int tcp_connect(struct sock *sk)
2576 struct tcp_sock *tp = tcp_sk(sk);
2577 struct sk_buff *buff;
2579 tcp_connect_init(sk);
2581 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
2582 if (unlikely(buff == NULL))
2583 return -ENOBUFS;
2585 /* Reserve space for headers. */
2586 skb_reserve(buff, MAX_TCP_HEADER);
2588 tp->snd_nxt = tp->write_seq;
2589 tcp_init_nondata_skb(buff, tp->write_seq++, TCPCB_FLAG_SYN);
2590 TCP_ECN_send_syn(sk, buff);
2592 /* Send it off. */
2593 TCP_SKB_CB(buff)->when = tcp_time_stamp;
2594 tp->retrans_stamp = TCP_SKB_CB(buff)->when;
2595 skb_header_release(buff);
2596 __tcp_add_write_queue_tail(sk, buff);
2597 sk->sk_wmem_queued += buff->truesize;
2598 sk_mem_charge(sk, buff->truesize);
2599 tp->packets_out += tcp_skb_pcount(buff);
2600 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation);
2602 /* We change tp->snd_nxt after the tcp_transmit_skb() call
2603 * in order to make this packet get counted in tcpOutSegs.
2605 tp->snd_nxt = tp->write_seq;
2606 tp->pushed_seq = tp->write_seq;
2607 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS);
2609 /* Timer for repeating the SYN until an answer. */
2610 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
2611 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
2612 return 0;
2615 /* Send out a delayed ack, the caller does the policy checking
2616 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
2617 * for details.
2619 void tcp_send_delayed_ack(struct sock *sk)
2621 struct inet_connection_sock *icsk = inet_csk(sk);
2622 int ato = icsk->icsk_ack.ato;
2623 unsigned long timeout;
2625 if (ato > TCP_DELACK_MIN) {
2626 const struct tcp_sock *tp = tcp_sk(sk);
2627 int max_ato = HZ / 2;
2629 if (icsk->icsk_ack.pingpong ||
2630 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
2631 max_ato = TCP_DELACK_MAX;
2633 /* Slow path, intersegment interval is "high". */
2635 /* If some rtt estimate is known, use it to bound delayed ack.
2636 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
2637 * directly.
2639 if (tp->srtt) {
2640 int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN);
2642 if (rtt < max_ato)
2643 max_ato = rtt;
2646 ato = min(ato, max_ato);
2649 /* Stay within the limit we were given */
2650 timeout = jiffies + ato;
2652 /* Use new timeout only if there wasn't a older one earlier. */
2653 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
2654 /* If delack timer was blocked or is about to expire,
2655 * send ACK now.
2657 if (icsk->icsk_ack.blocked ||
2658 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
2659 tcp_send_ack(sk);
2660 return;
2663 if (!time_before(timeout, icsk->icsk_ack.timeout))
2664 timeout = icsk->icsk_ack.timeout;
2666 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
2667 icsk->icsk_ack.timeout = timeout;
2668 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
2671 /* This routine sends an ack and also updates the window. */
2672 void tcp_send_ack(struct sock *sk)
2674 struct sk_buff *buff;
2676 /* If we have been reset, we may not send again. */
2677 if (sk->sk_state == TCP_CLOSE)
2678 return;
2680 /* We are not putting this on the write queue, so
2681 * tcp_transmit_skb() will set the ownership to this
2682 * sock.
2684 buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2685 if (buff == NULL) {
2686 inet_csk_schedule_ack(sk);
2687 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
2688 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
2689 TCP_DELACK_MAX, TCP_RTO_MAX);
2690 return;
2693 /* Reserve space for headers and prepare control bits. */
2694 skb_reserve(buff, MAX_TCP_HEADER);
2695 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPCB_FLAG_ACK);
2697 /* Send it off, this clears delayed acks for us. */
2698 TCP_SKB_CB(buff)->when = tcp_time_stamp;
2699 tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC);
2702 /* This routine sends a packet with an out of date sequence
2703 * number. It assumes the other end will try to ack it.
2705 * Question: what should we make while urgent mode?
2706 * 4.4BSD forces sending single byte of data. We cannot send
2707 * out of window data, because we have SND.NXT==SND.MAX...
2709 * Current solution: to send TWO zero-length segments in urgent mode:
2710 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2711 * out-of-date with SND.UNA-1 to probe window.
2713 static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
2715 struct tcp_sock *tp = tcp_sk(sk);
2716 struct sk_buff *skb;
2718 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2719 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2720 if (skb == NULL)
2721 return -1;
2723 /* Reserve space for headers and set control bits. */
2724 skb_reserve(skb, MAX_TCP_HEADER);
2725 /* Use a previous sequence. This should cause the other
2726 * end to send an ack. Don't queue or clone SKB, just
2727 * send it.
2729 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPCB_FLAG_ACK);
2730 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2731 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
2734 /* Initiate keepalive or window probe from timer. */
2735 int tcp_write_wakeup(struct sock *sk)
2737 struct tcp_sock *tp = tcp_sk(sk);
2738 struct sk_buff *skb;
2740 if (sk->sk_state == TCP_CLOSE)
2741 return -1;
2743 if ((skb = tcp_send_head(sk)) != NULL &&
2744 before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) {
2745 int err;
2746 unsigned int mss = tcp_current_mss(sk);
2747 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq;
2749 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
2750 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
2752 /* We are probing the opening of a window
2753 * but the window size is != 0
2754 * must have been a result SWS avoidance ( sender )
2756 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
2757 skb->len > mss) {
2758 seg_size = min(seg_size, mss);
2759 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
2760 if (tcp_fragment(sk, skb, seg_size, mss))
2761 return -1;
2762 } else if (!tcp_skb_pcount(skb))
2763 tcp_set_skb_tso_segs(sk, skb, mss);
2765 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
2766 TCP_SKB_CB(skb)->when = tcp_time_stamp;
2767 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
2768 if (!err)
2769 tcp_event_new_data_sent(sk, skb);
2770 return err;
2771 } else {
2772 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF))
2773 tcp_xmit_probe_skb(sk, 1);
2774 return tcp_xmit_probe_skb(sk, 0);
2778 /* A window probe timeout has occurred. If window is not closed send
2779 * a partial packet else a zero probe.
2781 void tcp_send_probe0(struct sock *sk)
2783 struct inet_connection_sock *icsk = inet_csk(sk);
2784 struct tcp_sock *tp = tcp_sk(sk);
2785 int err;
2787 err = tcp_write_wakeup(sk);
2789 if (tp->packets_out || !tcp_send_head(sk)) {
2790 /* Cancel probe timer, if it is not required. */
2791 icsk->icsk_probes_out = 0;
2792 icsk->icsk_backoff = 0;
2793 return;
2796 if (err <= 0) {
2797 if (icsk->icsk_backoff < sysctl_tcp_retries2)
2798 icsk->icsk_backoff++;
2799 icsk->icsk_probes_out++;
2800 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2801 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2802 TCP_RTO_MAX);
2803 } else {
2804 /* If packet was not sent due to local congestion,
2805 * do not backoff and do not remember icsk_probes_out.
2806 * Let local senders to fight for local resources.
2808 * Use accumulated backoff yet.
2810 if (!icsk->icsk_probes_out)
2811 icsk->icsk_probes_out = 1;
2812 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2813 min(icsk->icsk_rto << icsk->icsk_backoff,
2814 TCP_RESOURCE_PROBE_INTERVAL),
2815 TCP_RTO_MAX);
2819 EXPORT_SYMBOL(tcp_select_initial_window);
2820 EXPORT_SYMBOL(tcp_connect);
2821 EXPORT_SYMBOL(tcp_make_synack);
2822 EXPORT_SYMBOL(tcp_simple_retransmit);
2823 EXPORT_SYMBOL(tcp_sync_mss);
2824 EXPORT_SYMBOL(tcp_mtup_init);