blob: 9f498a6c8895b63412c60e302fc9ea3245695d60 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Version: $Id: tcp_output.c,v 1.146 2002/02/01 22:01:04 davem Exp $
9 *
Jesper Juhl02c30a82005-05-05 16:16:16 -070010 * Authors: Ross Biro
Linus Torvalds1da177e2005-04-16 15:20:36 -070011 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
12 * Mark Evans, <evansmp@uhura.aston.ac.uk>
13 * Corey Minyard <wf-rch!minyard@relay.EU.net>
14 * Florian La Roche, <flla@stud.uni-sb.de>
15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
16 * Linus Torvalds, <torvalds@cs.helsinki.fi>
17 * Alan Cox, <gw4pts@gw4pts.ampr.org>
18 * Matthew Dillon, <dillon@apollo.west.oic.com>
19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no>
20 * Jorge Cwik, <jorge@laser.satlink.net>
21 */
22
23/*
24 * Changes: Pedro Roque : Retransmit queue handled by TCP.
25 * : Fragmentation on mtu decrease
26 * : Segment collapse on retransmit
27 * : AF independence
28 *
29 * Linus Torvalds : send_delayed_ack
30 * David S. Miller : Charge memory using the right skb
31 * during syn/ack processing.
32 * David S. Miller : Output engine completely rewritten.
33 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr.
34 * Cacophonix Gaul : draft-minshall-nagle-01
35 * J Hadi Salim : ECN support
36 *
37 */
38
39#include <net/tcp.h>
40
41#include <linux/compiler.h>
42#include <linux/module.h>
43#include <linux/smp_lock.h>
44
45/* People can turn this off for buggy TCP's found in printers etc. */
46int sysctl_tcp_retrans_collapse = 1;
47
48/* This limits the percentage of the congestion window which we
49 * will allow a single TSO frame to consume. Building TSO frames
50 * which are too large can cause TCP streams to be bursty.
51 */
David S. Millerc1b4a7e2005-07-05 15:24:38 -070052int sysctl_tcp_tso_win_divisor = 3;
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
Stephen Hemminger40efc6f2006-01-03 16:03:49 -080054static void update_send_head(struct sock *sk, struct tcp_sock *tp,
55 struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -070056{
57 sk->sk_send_head = skb->next;
58 if (sk->sk_send_head == (struct sk_buff *)&sk->sk_write_queue)
59 sk->sk_send_head = NULL;
60 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq;
61 tcp_packets_out_inc(sk, tp, skb);
62}
63
64/* SND.NXT, if window was not shrunk.
65 * If window has been shrunk, what should we make? It is not clear at all.
66 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-(
67 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already
68 * invalid. OK, let's make this for now:
69 */
70static inline __u32 tcp_acceptable_seq(struct sock *sk, struct tcp_sock *tp)
71{
72 if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt))
73 return tp->snd_nxt;
74 else
75 return tp->snd_una+tp->snd_wnd;
76}
77
78/* Calculate mss to advertise in SYN segment.
79 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that:
80 *
81 * 1. It is independent of path mtu.
82 * 2. Ideally, it is maximal possible segment size i.e. 65535-40.
83 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of
84 * attached devices, because some buggy hosts are confused by
85 * large MSS.
86 * 4. We do not make 3, we advertise MSS, calculated from first
87 * hop device mtu, but allow to raise it to ip_rt_min_advmss.
88 * This may be overridden via information stored in routing table.
89 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible,
90 * probably even Jumbo".
91 */
92static __u16 tcp_advertise_mss(struct sock *sk)
93{
94 struct tcp_sock *tp = tcp_sk(sk);
95 struct dst_entry *dst = __sk_dst_get(sk);
96 int mss = tp->advmss;
97
98 if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) {
99 mss = dst_metric(dst, RTAX_ADVMSS);
100 tp->advmss = mss;
101 }
102
103 return (__u16)mss;
104}
105
106/* RFC2861. Reset CWND after idle period longer RTO to "restart window".
107 * This is the first part of cwnd validation mechanism. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700108static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700110 struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700111 s32 delta = tcp_time_stamp - tp->lsndtime;
112 u32 restart_cwnd = tcp_init_cwnd(tp, dst);
113 u32 cwnd = tp->snd_cwnd;
114
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300115 tcp_ca_event(sk, CA_EVENT_CWND_RESTART);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -0300117 tp->snd_ssthresh = tcp_current_ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 restart_cwnd = min(restart_cwnd, cwnd);
119
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700120 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700121 cwnd >>= 1;
122 tp->snd_cwnd = max(cwnd, restart_cwnd);
123 tp->snd_cwnd_stamp = tcp_time_stamp;
124 tp->snd_cwnd_used = 0;
125}
126
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800127static void tcp_event_data_sent(struct tcp_sock *tp,
128 struct sk_buff *skb, struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700129{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700130 struct inet_connection_sock *icsk = inet_csk(sk);
131 const u32 now = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700132
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700133 if (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)
134 tcp_cwnd_restart(sk, __sk_dst_get(sk));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700135
136 tp->lsndtime = now;
137
138 /* If it is a reply for ato after last received
139 * packet, enter pingpong mode.
140 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700141 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato)
142 icsk->icsk_ack.pingpong = 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700143}
144
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800145static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700146{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700147 tcp_dec_quickack_mode(sk, pkts);
148 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700149}
150
151/* Determine a window scaling and initial window to offer.
152 * Based on the assumption that the given amount of space
153 * will be offered. Store the results in the tp structure.
154 * NOTE: for smooth operation initial space offering should
155 * be a multiple of mss if possible. We assume here that mss >= 1.
156 * This MUST be enforced by all callers.
157 */
158void tcp_select_initial_window(int __space, __u32 mss,
159 __u32 *rcv_wnd, __u32 *window_clamp,
160 int wscale_ok, __u8 *rcv_wscale)
161{
162 unsigned int space = (__space < 0 ? 0 : __space);
163
164 /* If no clamp set the clamp to the max possible scaled window */
165 if (*window_clamp == 0)
166 (*window_clamp) = (65535 << 14);
167 space = min(*window_clamp, space);
168
169 /* Quantize space offering to a multiple of mss if possible. */
170 if (space > mss)
171 space = (space / mss) * mss;
172
173 /* NOTE: offering an initial window larger than 32767
174 * will break some buggy TCP stacks. We try to be nice.
175 * If we are not window scaling, then this truncates
176 * our initial window offering to 32k. There should also
177 * be a sysctl option to stop being nice.
178 */
179 (*rcv_wnd) = min(space, MAX_TCP_WINDOW);
180 (*rcv_wscale) = 0;
181 if (wscale_ok) {
182 /* Set window scaling on max possible window
183 * See RFC1323 for an explanation of the limit to 14
184 */
185 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max);
186 while (space > 65535 && (*rcv_wscale) < 14) {
187 space >>= 1;
188 (*rcv_wscale)++;
189 }
190 }
191
192 /* Set initial window to value enough for senders,
David S. Miller6b251852005-09-28 16:31:48 -0700193 * following RFC2414. Senders, not following this RFC,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700194 * will be satisfied with 2.
195 */
196 if (mss > (1<<*rcv_wscale)) {
David S. Miller01ff3672005-09-29 17:07:20 -0700197 int init_cwnd = 4;
198 if (mss > 1460*3)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199 init_cwnd = 2;
David S. Miller01ff3672005-09-29 17:07:20 -0700200 else if (mss > 1460)
201 init_cwnd = 3;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700202 if (*rcv_wnd > init_cwnd*mss)
203 *rcv_wnd = init_cwnd*mss;
204 }
205
206 /* Set the clamp no higher than max representable value */
207 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp);
208}
209
210/* Chose a new window to advertise, update state in tcp_sock for the
211 * socket, and return result with RFC1323 scaling applied. The return
212 * value can be stuffed directly into th->window for an outgoing
213 * frame.
214 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800215static u16 tcp_select_window(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700216{
217 struct tcp_sock *tp = tcp_sk(sk);
218 u32 cur_win = tcp_receive_window(tp);
219 u32 new_win = __tcp_select_window(sk);
220
221 /* Never shrink the offered window */
222 if(new_win < cur_win) {
223 /* Danger Will Robinson!
224 * Don't update rcv_wup/rcv_wnd here or else
225 * we will not be able to advertise a zero
226 * window in time. --DaveM
227 *
228 * Relax Will Robinson.
229 */
230 new_win = cur_win;
231 }
232 tp->rcv_wnd = new_win;
233 tp->rcv_wup = tp->rcv_nxt;
234
235 /* Make sure we do not exceed the maximum possible
236 * scaled window.
237 */
238 if (!tp->rx_opt.rcv_wscale)
239 new_win = min(new_win, MAX_TCP_WINDOW);
240 else
241 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale));
242
243 /* RFC1323 scaling applied */
244 new_win >>= tp->rx_opt.rcv_wscale;
245
246 /* If we advertise zero window, disable fast path. */
247 if (new_win == 0)
248 tp->pred_flags = 0;
249
250 return new_win;
251}
252
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800253static void tcp_build_and_update_options(__u32 *ptr, struct tcp_sock *tp,
254 __u32 tstamp)
255{
256 if (tp->rx_opt.tstamp_ok) {
257 *ptr++ = __constant_htonl((TCPOPT_NOP << 24) |
258 (TCPOPT_NOP << 16) |
259 (TCPOPT_TIMESTAMP << 8) |
260 TCPOLEN_TIMESTAMP);
261 *ptr++ = htonl(tstamp);
262 *ptr++ = htonl(tp->rx_opt.ts_recent);
263 }
264 if (tp->rx_opt.eff_sacks) {
265 struct tcp_sack_block *sp = tp->rx_opt.dsack ? tp->duplicate_sack : tp->selective_acks;
266 int this_sack;
267
268 *ptr++ = htonl((TCPOPT_NOP << 24) |
269 (TCPOPT_NOP << 16) |
270 (TCPOPT_SACK << 8) |
271 (TCPOLEN_SACK_BASE + (tp->rx_opt.eff_sacks *
272 TCPOLEN_SACK_PERBLOCK)));
273 for(this_sack = 0; this_sack < tp->rx_opt.eff_sacks; this_sack++) {
274 *ptr++ = htonl(sp[this_sack].start_seq);
275 *ptr++ = htonl(sp[this_sack].end_seq);
276 }
277 if (tp->rx_opt.dsack) {
278 tp->rx_opt.dsack = 0;
279 tp->rx_opt.eff_sacks--;
280 }
281 }
282}
283
284/* Construct a tcp options header for a SYN or SYN_ACK packet.
285 * If this is every changed make sure to change the definition of
286 * MAX_SYN_SIZE to match the new maximum number of options that you
287 * can generate.
288 */
289static void tcp_syn_build_options(__u32 *ptr, int mss, int ts, int sack,
290 int offer_wscale, int wscale, __u32 tstamp,
291 __u32 ts_recent)
292{
293 /* We always get an MSS option.
294 * The option bytes which will be seen in normal data
295 * packets should timestamps be used, must be in the MSS
296 * advertised. But we subtract them from tp->mss_cache so
297 * that calculations in tcp_sendmsg are simpler etc.
298 * So account for this fact here if necessary. If we
299 * don't do this correctly, as a receiver we won't
300 * recognize data packets as being full sized when we
301 * should, and thus we won't abide by the delayed ACK
302 * rules correctly.
303 * SACKs don't matter, we never delay an ACK when we
304 * have any of those going out.
305 */
306 *ptr++ = htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | mss);
307 if (ts) {
308 if(sack)
309 *ptr++ = __constant_htonl((TCPOPT_SACK_PERM << 24) | (TCPOLEN_SACK_PERM << 16) |
310 (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP);
311 else
312 *ptr++ = __constant_htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
313 (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP);
314 *ptr++ = htonl(tstamp); /* TSVAL */
315 *ptr++ = htonl(ts_recent); /* TSECR */
316 } else if(sack)
317 *ptr++ = __constant_htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
318 (TCPOPT_SACK_PERM << 8) | TCPOLEN_SACK_PERM);
319 if (offer_wscale)
320 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_WINDOW << 16) | (TCPOLEN_WINDOW << 8) | (wscale));
321}
Linus Torvalds1da177e2005-04-16 15:20:36 -0700322
323/* This routine actually transmits TCP packets queued in by
324 * tcp_do_sendmsg(). This is used by both the initial
325 * transmission and possible later retransmissions.
326 * All SKB's seen here are completely headerless. It is our
327 * job to build the TCP header, and pass the packet down to
328 * IP so it can do the same plus pass the packet off to the
329 * device.
330 *
331 * We are working here with either a clone of the original
332 * SKB, or a fresh unique copy made by the retransmit engine.
333 */
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800334static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, gfp_t gfp_mask)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700335{
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800336 const struct inet_connection_sock *icsk = inet_csk(sk);
337 struct inet_sock *inet;
338 struct tcp_sock *tp;
339 struct tcp_skb_cb *tcb;
340 int tcp_header_size;
341 struct tcphdr *th;
342 int sysctl_flags;
343 int err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700344
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800345 BUG_ON(!skb || !tcp_skb_pcount(skb));
346
347 /* If congestion control is doing timestamping, we must
348 * take such a timestamp before we potentially clone/copy.
349 */
350 if (icsk->icsk_ca_ops->rtt_sample)
351 __net_timestamp(skb);
352
353 if (likely(clone_it)) {
354 if (unlikely(skb_cloned(skb)))
355 skb = pskb_copy(skb, gfp_mask);
356 else
357 skb = skb_clone(skb, gfp_mask);
358 if (unlikely(!skb))
359 return -ENOBUFS;
360 }
361
362 inet = inet_sk(sk);
363 tp = tcp_sk(sk);
364 tcb = TCP_SKB_CB(skb);
365 tcp_header_size = tp->tcp_header_len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700366
367#define SYSCTL_FLAG_TSTAMPS 0x1
368#define SYSCTL_FLAG_WSCALE 0x2
369#define SYSCTL_FLAG_SACK 0x4
370
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800371 sysctl_flags = 0;
372 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
373 tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS;
374 if(sysctl_tcp_timestamps) {
375 tcp_header_size += TCPOLEN_TSTAMP_ALIGNED;
376 sysctl_flags |= SYSCTL_FLAG_TSTAMPS;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700377 }
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800378 if (sysctl_tcp_window_scaling) {
379 tcp_header_size += TCPOLEN_WSCALE_ALIGNED;
380 sysctl_flags |= SYSCTL_FLAG_WSCALE;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700381 }
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800382 if (sysctl_tcp_sack) {
383 sysctl_flags |= SYSCTL_FLAG_SACK;
384 if (!(sysctl_flags & SYSCTL_FLAG_TSTAMPS))
385 tcp_header_size += TCPOLEN_SACKPERM_ALIGNED;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700386 }
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800387 } else if (unlikely(tp->rx_opt.eff_sacks)) {
388 /* A SACK is 2 pad bytes, a 2 byte header, plus
389 * 2 32-bit sequence numbers for each SACK block.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700390 */
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800391 tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED +
392 (tp->rx_opt.eff_sacks *
393 TCPOLEN_SACK_PERBLOCK));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700394 }
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800395
396 if (tcp_packets_in_flight(tp) == 0)
397 tcp_ca_event(sk, CA_EVENT_TX_START);
398
399 th = (struct tcphdr *) skb_push(skb, tcp_header_size);
400 skb->h.th = th;
401 skb_set_owner_w(skb, sk);
402
403 /* Build TCP header and checksum it. */
404 th->source = inet->sport;
405 th->dest = inet->dport;
406 th->seq = htonl(tcb->seq);
407 th->ack_seq = htonl(tp->rcv_nxt);
408 *(((__u16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) |
409 tcb->flags);
410
411 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
412 /* RFC1323: The window in SYN & SYN/ACK segments
413 * is never scaled.
414 */
415 th->window = htons(tp->rcv_wnd);
416 } else {
417 th->window = htons(tcp_select_window(sk));
418 }
419 th->check = 0;
420 th->urg_ptr = 0;
421
422 if (unlikely(tp->urg_mode &&
423 between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF))) {
424 th->urg_ptr = htons(tp->snd_up-tcb->seq);
425 th->urg = 1;
426 }
427
428 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) {
429 tcp_syn_build_options((__u32 *)(th + 1),
430 tcp_advertise_mss(sk),
431 (sysctl_flags & SYSCTL_FLAG_TSTAMPS),
432 (sysctl_flags & SYSCTL_FLAG_SACK),
433 (sysctl_flags & SYSCTL_FLAG_WSCALE),
434 tp->rx_opt.rcv_wscale,
435 tcb->when,
436 tp->rx_opt.ts_recent);
437 } else {
438 tcp_build_and_update_options((__u32 *)(th + 1),
439 tp, tcb->when);
440 TCP_ECN_send(sk, tp, skb, tcp_header_size);
441 }
442
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -0800443 icsk->icsk_af_ops->send_check(sk, skb->len, skb);
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800444
445 if (likely(tcb->flags & TCPCB_FLAG_ACK))
446 tcp_event_ack_sent(sk, tcp_skb_pcount(skb));
447
448 if (skb->len != tcp_header_size)
449 tcp_event_data_sent(tp, skb, sk);
450
451 TCP_INC_STATS(TCP_MIB_OUTSEGS);
452
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -0800453 err = icsk->icsk_af_ops->queue_xmit(skb, 0);
David S. Millerdfb4b9d2005-12-06 16:24:52 -0800454 if (unlikely(err <= 0))
455 return err;
456
457 tcp_enter_cwr(sk);
458
459 /* NET_XMIT_CN is special. It does not guarantee,
460 * that this packet is lost. It tells that device
461 * is about to start to drop packets or already
462 * drops some packets of the same priority and
463 * invokes us to send less aggressively.
464 */
465 return err == NET_XMIT_CN ? 0 : err;
466
Linus Torvalds1da177e2005-04-16 15:20:36 -0700467#undef SYSCTL_FLAG_TSTAMPS
468#undef SYSCTL_FLAG_WSCALE
469#undef SYSCTL_FLAG_SACK
470}
471
472
473/* This routine just queue's the buffer
474 *
475 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames,
476 * otherwise socket can stall.
477 */
478static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb)
479{
480 struct tcp_sock *tp = tcp_sk(sk);
481
482 /* Advance write_seq and place onto the write_queue. */
483 tp->write_seq = TCP_SKB_CB(skb)->end_seq;
484 skb_header_release(skb);
485 __skb_queue_tail(&sk->sk_write_queue, skb);
486 sk_charge_skb(sk, skb);
487
488 /* Queue it, remembering where we must start sending. */
489 if (sk->sk_send_head == NULL)
490 sk->sk_send_head = skb;
491}
492
David S. Miller846998a2005-08-04 19:52:01 -0700493static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
David S. Millerf6302d12005-07-05 15:18:03 -0700494{
David S. Miller846998a2005-08-04 19:52:01 -0700495 if (skb->len <= mss_now ||
David S. Millerf6302d12005-07-05 15:18:03 -0700496 !(sk->sk_route_caps & NETIF_F_TSO)) {
497 /* Avoid the costly divide in the normal
498 * non-TSO case.
499 */
500 skb_shinfo(skb)->tso_segs = 1;
501 skb_shinfo(skb)->tso_size = 0;
502 } else {
503 unsigned int factor;
504
David S. Miller846998a2005-08-04 19:52:01 -0700505 factor = skb->len + (mss_now - 1);
506 factor /= mss_now;
David S. Millerf6302d12005-07-05 15:18:03 -0700507 skb_shinfo(skb)->tso_segs = factor;
David S. Miller846998a2005-08-04 19:52:01 -0700508 skb_shinfo(skb)->tso_size = mss_now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700509 }
510}
511
Linus Torvalds1da177e2005-04-16 15:20:36 -0700512/* Function to create two new TCP segments. Shrinks the given segment
513 * to the specified size and appends a new segment with the rest of the
514 * packet to the list. This won't be called frequently, I hope.
515 * Remember, these are still headerless SKBs at this point.
516 */
David S. Miller6475be12005-09-01 22:47:01 -0700517int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700518{
519 struct tcp_sock *tp = tcp_sk(sk);
520 struct sk_buff *buff;
David S. Miller6475be12005-09-01 22:47:01 -0700521 int nsize, old_factor;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700522 u16 flags;
523
Herbert Xub2cc99f2005-10-20 17:13:13 -0200524 BUG_ON(len > skb->len);
Stephen Hemminger6a438bb2005-11-10 17:14:59 -0800525
526 clear_all_retrans_hints(tp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700527 nsize = skb_headlen(skb) - len;
528 if (nsize < 0)
529 nsize = 0;
530
531 if (skb_cloned(skb) &&
532 skb_is_nonlinear(skb) &&
533 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
534 return -ENOMEM;
535
536 /* Get a new skb... force flag on. */
537 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC);
538 if (buff == NULL)
539 return -ENOMEM; /* We'll just try again later. */
540 sk_charge_skb(sk, buff);
541
542 /* Correct the sequence numbers. */
543 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
544 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
545 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
546
547 /* PSH and FIN should only be set in the second packet. */
548 flags = TCP_SKB_CB(skb)->flags;
549 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
550 TCP_SKB_CB(buff)->flags = flags;
Herbert Xue14c3ca2005-09-19 18:18:38 -0700551 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700552 TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL;
553
554 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_HW) {
555 /* Copy and checksum data tail into the new buffer. */
556 buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize),
557 nsize, 0);
558
559 skb_trim(skb, len);
560
561 skb->csum = csum_block_sub(skb->csum, buff->csum, len);
562 } else {
563 skb->ip_summed = CHECKSUM_HW;
564 skb_split(skb, buff, len);
565 }
566
567 buff->ip_summed = skb->ip_summed;
568
569 /* Looks stupid, but our code really uses when of
570 * skbs, which it never sent before. --ANK
571 */
572 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when;
Patrick McHardya61bbcf2005-08-14 17:24:31 -0700573 buff->tstamp = skb->tstamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700574
David S. Miller6475be12005-09-01 22:47:01 -0700575 old_factor = tcp_skb_pcount(skb);
576
Linus Torvalds1da177e2005-04-16 15:20:36 -0700577 /* Fix up tso_factor for both original and new SKB. */
David S. Miller846998a2005-08-04 19:52:01 -0700578 tcp_set_skb_tso_segs(sk, skb, mss_now);
579 tcp_set_skb_tso_segs(sk, buff, mss_now);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700580
David S. Miller6475be12005-09-01 22:47:01 -0700581 /* If this packet has been sent out already, we must
582 * adjust the various packet counters.
583 */
Herbert Xucf0b4502005-09-08 15:10:52 -0700584 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) {
David S. Miller6475be12005-09-01 22:47:01 -0700585 int diff = old_factor - tcp_skb_pcount(skb) -
586 tcp_skb_pcount(buff);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700587
David S. Miller6475be12005-09-01 22:47:01 -0700588 tp->packets_out -= diff;
Herbert Xue14c3ca2005-09-19 18:18:38 -0700589
590 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)
591 tp->sacked_out -= diff;
592 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)
593 tp->retrans_out -= diff;
594
David S. Miller6475be12005-09-01 22:47:01 -0700595 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) {
596 tp->lost_out -= diff;
597 tp->left_out -= diff;
598 }
Herbert Xu83ca28b2005-09-22 23:32:56 -0700599
David S. Miller6475be12005-09-01 22:47:01 -0700600 if (diff > 0) {
Herbert Xu83ca28b2005-09-22 23:32:56 -0700601 /* Adjust Reno SACK estimate. */
602 if (!tp->rx_opt.sack_ok) {
603 tp->sacked_out -= diff;
604 if ((int)tp->sacked_out < 0)
605 tp->sacked_out = 0;
606 tcp_sync_left_out(tp);
607 }
608
David S. Miller6475be12005-09-01 22:47:01 -0700609 tp->fackets_out -= diff;
610 if ((int)tp->fackets_out < 0)
611 tp->fackets_out = 0;
612 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700613 }
614
615 /* Link BUFF into the send queue. */
David S. Millerf44b5272005-07-05 15:18:34 -0700616 skb_header_release(buff);
David S. Miller8728b832005-08-09 19:25:21 -0700617 __skb_append(skb, buff, &sk->sk_write_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700618
619 return 0;
620}
621
622/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c
623 * eventually). The difference is that pulled data not copied, but
624 * immediately discarded.
625 */
626static unsigned char *__pskb_trim_head(struct sk_buff *skb, int len)
627{
628 int i, k, eat;
629
630 eat = len;
631 k = 0;
632 for (i=0; i<skb_shinfo(skb)->nr_frags; i++) {
633 if (skb_shinfo(skb)->frags[i].size <= eat) {
634 put_page(skb_shinfo(skb)->frags[i].page);
635 eat -= skb_shinfo(skb)->frags[i].size;
636 } else {
637 skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i];
638 if (eat) {
639 skb_shinfo(skb)->frags[k].page_offset += eat;
640 skb_shinfo(skb)->frags[k].size -= eat;
641 eat = 0;
642 }
643 k++;
644 }
645 }
646 skb_shinfo(skb)->nr_frags = k;
647
648 skb->tail = skb->data;
649 skb->data_len -= len;
650 skb->len = skb->data_len;
651 return skb->tail;
652}
653
654int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len)
655{
656 if (skb_cloned(skb) &&
657 pskb_expand_head(skb, 0, 0, GFP_ATOMIC))
658 return -ENOMEM;
659
660 if (len <= skb_headlen(skb)) {
661 __skb_pull(skb, len);
662 } else {
663 if (__pskb_trim_head(skb, len-skb_headlen(skb)) == NULL)
664 return -ENOMEM;
665 }
666
667 TCP_SKB_CB(skb)->seq += len;
668 skb->ip_summed = CHECKSUM_HW;
669
670 skb->truesize -= len;
671 sk->sk_wmem_queued -= len;
672 sk->sk_forward_alloc += len;
673 sock_set_flag(sk, SOCK_QUEUE_SHRUNK);
674
675 /* Any change of skb->len requires recalculation of tso
676 * factor and mss.
677 */
678 if (tcp_skb_pcount(skb) > 1)
David S. Miller846998a2005-08-04 19:52:01 -0700679 tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700680
681 return 0;
682}
683
684/* This function synchronize snd mss to current pmtu/exthdr set.
685
686 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts
687 for TCP options, but includes only bare TCP header.
688
689 tp->rx_opt.mss_clamp is mss negotiated at connection setup.
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -0800690 It is minimum of user_mss and mss received with SYN.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700691 It also does not include TCP options.
692
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800693 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700694
695 tp->mss_cache is current effective sending mss, including
696 all tcp options except for SACKs. It is evaluated,
697 taking into account current pmtu, but never exceeds
698 tp->rx_opt.mss_clamp.
699
700 NOTE1. rfc1122 clearly states that advertised MSS
701 DOES NOT include either tcp or ip options.
702
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800703 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache
704 are READ ONLY outside this function. --ANK (980731)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700705 */
706
707unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu)
708{
709 struct tcp_sock *tp = tcp_sk(sk);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800710 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700711 /* Calculate base mss without TCP options:
712 It is MMS_S - sizeof(tcphdr) of rfc1122
713 */
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800714 int mss_now = (pmtu - icsk->icsk_af_ops->net_header_len -
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -0800715 sizeof(struct tcphdr));
Linus Torvalds1da177e2005-04-16 15:20:36 -0700716
717 /* Clamp it (mss_clamp does not include tcp options) */
718 if (mss_now > tp->rx_opt.mss_clamp)
719 mss_now = tp->rx_opt.mss_clamp;
720
721 /* Now subtract optional transport overhead */
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800722 mss_now -= icsk->icsk_ext_hdr_len;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700723
724 /* Then reserve room for full set of TCP options and 8 bytes of data */
725 if (mss_now < 48)
726 mss_now = 48;
727
728 /* Now subtract TCP options size, not including SACKs */
729 mss_now -= tp->tcp_header_len - sizeof(struct tcphdr);
730
731 /* Bound mss with half of window */
732 if (tp->max_window && mss_now > (tp->max_window>>1))
733 mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len);
734
735 /* And store cached results */
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800736 icsk->icsk_pmtu_cookie = pmtu;
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700737 tp->mss_cache = mss_now;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700738
739 return mss_now;
740}
741
742/* Compute the current effective MSS, taking SACKs and IP options,
743 * and even PMTU discovery events into account.
744 *
745 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up
746 * cannot be large. However, taking into account rare use of URG, this
747 * is not a big flaw.
748 */
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700749unsigned int tcp_current_mss(struct sock *sk, int large_allowed)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700750{
751 struct tcp_sock *tp = tcp_sk(sk);
752 struct dst_entry *dst = __sk_dst_get(sk);
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700753 u32 mss_now;
754 u16 xmit_size_goal;
755 int doing_tso = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700756
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700757 mss_now = tp->mss_cache;
758
759 if (large_allowed &&
760 (sk->sk_route_caps & NETIF_F_TSO) &&
761 !tp->urg_mode)
762 doing_tso = 1;
763
Linus Torvalds1da177e2005-04-16 15:20:36 -0700764 if (dst) {
765 u32 mtu = dst_mtu(dst);
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800766 if (mtu != inet_csk(sk)->icsk_pmtu_cookie)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700767 mss_now = tcp_sync_mss(sk, mtu);
768 }
769
Linus Torvalds1da177e2005-04-16 15:20:36 -0700770 if (tp->rx_opt.eff_sacks)
771 mss_now -= (TCPOLEN_SACK_BASE_ALIGNED +
772 (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK));
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700773
774 xmit_size_goal = mss_now;
775
776 if (doing_tso) {
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -0800777 xmit_size_goal = (65535 -
778 inet_csk(sk)->icsk_af_ops->net_header_len -
Arnaldo Carvalho de Melod83d8462005-12-13 23:26:10 -0800779 inet_csk(sk)->icsk_ext_hdr_len -
780 tp->tcp_header_len);
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700781
782 if (tp->max_window &&
783 (xmit_size_goal > (tp->max_window >> 1)))
784 xmit_size_goal = max((tp->max_window >> 1),
785 68U - tp->tcp_header_len);
786
787 xmit_size_goal -= (xmit_size_goal % mss_now);
788 }
789 tp->xmit_size_goal = xmit_size_goal;
790
Linus Torvalds1da177e2005-04-16 15:20:36 -0700791 return mss_now;
792}
793
David S. Millera762a982005-07-05 15:18:51 -0700794/* Congestion window validation. (RFC2861) */
795
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800796static void tcp_cwnd_validate(struct sock *sk, struct tcp_sock *tp)
David S. Millera762a982005-07-05 15:18:51 -0700797{
798 __u32 packets_out = tp->packets_out;
799
800 if (packets_out >= tp->snd_cwnd) {
801 /* Network is feed fully. */
802 tp->snd_cwnd_used = 0;
803 tp->snd_cwnd_stamp = tcp_time_stamp;
804 } else {
805 /* Network starves. */
806 if (tp->packets_out > tp->snd_cwnd_used)
807 tp->snd_cwnd_used = tp->packets_out;
808
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -0700809 if ((s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto)
David S. Millera762a982005-07-05 15:18:51 -0700810 tcp_cwnd_application_limited(sk);
811 }
812}
813
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700814static unsigned int tcp_window_allows(struct tcp_sock *tp, struct sk_buff *skb, unsigned int mss_now, unsigned int cwnd)
815{
816 u32 window, cwnd_len;
817
818 window = (tp->snd_una + tp->snd_wnd - TCP_SKB_CB(skb)->seq);
819 cwnd_len = mss_now * cwnd;
820 return min(window, cwnd_len);
821}
822
823/* Can at least one segment of SKB be sent right now, according to the
824 * congestion window rules? If so, return how many segments are allowed.
825 */
826static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *skb)
827{
828 u32 in_flight, cwnd;
829
830 /* Don't be strict about the congestion window for the final FIN. */
831 if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
832 return 1;
833
834 in_flight = tcp_packets_in_flight(tp);
835 cwnd = tp->snd_cwnd;
836 if (in_flight < cwnd)
837 return (cwnd - in_flight);
838
839 return 0;
840}
841
842/* This must be invoked the first time we consider transmitting
843 * SKB onto the wire.
844 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -0800845static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now)
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700846{
847 int tso_segs = tcp_skb_pcount(skb);
848
David S. Miller846998a2005-08-04 19:52:01 -0700849 if (!tso_segs ||
850 (tso_segs > 1 &&
851 skb_shinfo(skb)->tso_size != mss_now)) {
852 tcp_set_skb_tso_segs(sk, skb, mss_now);
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700853 tso_segs = tcp_skb_pcount(skb);
854 }
855 return tso_segs;
856}
857
858static inline int tcp_minshall_check(const struct tcp_sock *tp)
859{
860 return after(tp->snd_sml,tp->snd_una) &&
861 !after(tp->snd_sml, tp->snd_nxt);
862}
863
864/* Return 0, if packet can be sent now without violation Nagle's rules:
865 * 1. It is full sized.
866 * 2. Or it contains FIN. (already checked by caller)
867 * 3. Or TCP_NODELAY was set.
868 * 4. Or TCP_CORK is not set, and all sent packets are ACKed.
869 * With Minshall's modification: all sent small packets are ACKed.
870 */
871
872static inline int tcp_nagle_check(const struct tcp_sock *tp,
873 const struct sk_buff *skb,
874 unsigned mss_now, int nonagle)
875{
876 return (skb->len < mss_now &&
877 ((nonagle&TCP_NAGLE_CORK) ||
878 (!nonagle &&
879 tp->packets_out &&
880 tcp_minshall_check(tp))));
881}
882
883/* Return non-zero if the Nagle test allows this packet to be
884 * sent now.
885 */
886static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb,
887 unsigned int cur_mss, int nonagle)
888{
889 /* Nagle rule does not apply to frames, which sit in the middle of the
890 * write_queue (they have no chances to get new data).
891 *
892 * This is implemented in the callers, where they modify the 'nonagle'
893 * argument based upon the location of SKB in the send queue.
894 */
895 if (nonagle & TCP_NAGLE_PUSH)
896 return 1;
897
898 /* Don't use the nagle rule for urgent data (or for the final FIN). */
899 if (tp->urg_mode ||
900 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN))
901 return 1;
902
903 if (!tcp_nagle_check(tp, skb, cur_mss, nonagle))
904 return 1;
905
906 return 0;
907}
908
909/* Does at least the first segment of SKB fit into the send window? */
910static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, unsigned int cur_mss)
911{
912 u32 end_seq = TCP_SKB_CB(skb)->end_seq;
913
914 if (skb->len > cur_mss)
915 end_seq = TCP_SKB_CB(skb)->seq + cur_mss;
916
917 return !after(end_seq, tp->snd_una + tp->snd_wnd);
918}
919
920/* This checks if the data bearing packet SKB (usually sk->sk_send_head)
921 * should be put on the wire right now. If so, it returns the number of
922 * packets allowed by the congestion window.
923 */
924static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb,
925 unsigned int cur_mss, int nonagle)
926{
927 struct tcp_sock *tp = tcp_sk(sk);
928 unsigned int cwnd_quota;
929
David S. Miller846998a2005-08-04 19:52:01 -0700930 tcp_init_tso_segs(sk, skb, cur_mss);
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700931
932 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle))
933 return 0;
934
935 cwnd_quota = tcp_cwnd_test(tp, skb);
936 if (cwnd_quota &&
937 !tcp_snd_wnd_test(tp, skb, cur_mss))
938 cwnd_quota = 0;
939
940 return cwnd_quota;
941}
942
943static inline int tcp_skb_is_last(const struct sock *sk,
944 const struct sk_buff *skb)
945{
946 return skb->next == (struct sk_buff *)&sk->sk_write_queue;
947}
948
949int tcp_may_send_now(struct sock *sk, struct tcp_sock *tp)
950{
951 struct sk_buff *skb = sk->sk_send_head;
952
953 return (skb &&
954 tcp_snd_test(sk, skb, tcp_current_mss(sk, 1),
955 (tcp_skb_is_last(sk, skb) ?
956 TCP_NAGLE_PUSH :
957 tp->nonagle)));
958}
959
960/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet
961 * which is put after SKB on the list. It is very much like
962 * tcp_fragment() except that it may make several kinds of assumptions
963 * in order to speed up the splitting operation. In particular, we
964 * know that all the data is in scatter-gather pages, and that the
965 * packet has never been sent out before (and thus is not cloned).
966 */
David S. Miller846998a2005-08-04 19:52:01 -0700967static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now)
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700968{
969 struct sk_buff *buff;
970 int nlen = skb->len - len;
971 u16 flags;
972
973 /* All of a TSO frame must be composed of paged data. */
Herbert Xuc8ac3772005-08-16 20:43:40 -0700974 if (skb->len != skb->data_len)
975 return tcp_fragment(sk, skb, len, mss_now);
David S. Millerc1b4a7e2005-07-05 15:24:38 -0700976
977 buff = sk_stream_alloc_pskb(sk, 0, 0, GFP_ATOMIC);
978 if (unlikely(buff == NULL))
979 return -ENOMEM;
980
981 buff->truesize = nlen;
982 skb->truesize -= nlen;
983
984 /* Correct the sequence numbers. */
985 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len;
986 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq;
987 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq;
988
989 /* PSH and FIN should only be set in the second packet. */
990 flags = TCP_SKB_CB(skb)->flags;
991 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH);
992 TCP_SKB_CB(buff)->flags = flags;
993
994 /* This packet was never sent out yet, so no SACK bits. */
995 TCP_SKB_CB(buff)->sacked = 0;
996
997 buff->ip_summed = skb->ip_summed = CHECKSUM_HW;
998 skb_split(skb, buff, len);
999
1000 /* Fix up tso_factor for both original and new SKB. */
David S. Miller846998a2005-08-04 19:52:01 -07001001 tcp_set_skb_tso_segs(sk, skb, mss_now);
1002 tcp_set_skb_tso_segs(sk, buff, mss_now);
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001003
1004 /* Link BUFF into the send queue. */
1005 skb_header_release(buff);
David S. Miller8728b832005-08-09 19:25:21 -07001006 __skb_append(skb, buff, &sk->sk_write_queue);
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001007
1008 return 0;
1009}
1010
1011/* Try to defer sending, if possible, in order to minimize the amount
1012 * of TSO splitting we do. View it as a kind of TSO Nagle test.
1013 *
1014 * This algorithm is from John Heffner.
1015 */
1016static int tcp_tso_should_defer(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb)
1017{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001018 const struct inet_connection_sock *icsk = inet_csk(sk);
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001019 u32 send_win, cong_win, limit, in_flight;
1020
1021 if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)
1022 return 0;
1023
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001024 if (icsk->icsk_ca_state != TCP_CA_Open)
David S. Miller908a75c2005-07-05 15:43:58 -07001025 return 0;
1026
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001027 in_flight = tcp_packets_in_flight(tp);
1028
1029 BUG_ON(tcp_skb_pcount(skb) <= 1 ||
1030 (tp->snd_cwnd <= in_flight));
1031
1032 send_win = (tp->snd_una + tp->snd_wnd) - TCP_SKB_CB(skb)->seq;
1033
1034 /* From in_flight test above, we know that cwnd > in_flight. */
1035 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache;
1036
1037 limit = min(send_win, cong_win);
1038
David S. Millerba244fe2006-03-11 18:51:49 -08001039 /* If a full-sized TSO skb can be sent, do it. */
1040 if (limit >= 65536)
1041 return 0;
1042
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001043 if (sysctl_tcp_tso_win_divisor) {
1044 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache);
1045
1046 /* If at least some fraction of a window is available,
1047 * just use it.
1048 */
1049 chunk /= sysctl_tcp_tso_win_divisor;
1050 if (limit >= chunk)
1051 return 0;
1052 } else {
1053 /* Different approach, try not to defer past a single
1054 * ACK. Receiver should ACK every other full sized
1055 * frame, so if we have space for more than 3 frames
1056 * then send now.
1057 */
1058 if (limit > tcp_max_burst(tp) * tp->mss_cache)
1059 return 0;
1060 }
1061
1062 /* Ok, it looks like it is advisable to defer. */
1063 return 1;
1064}
1065
Linus Torvalds1da177e2005-04-16 15:20:36 -07001066/* This routine writes packets to the network. It advances the
1067 * send_head. This happens as incoming acks open up the remote
1068 * window for us.
1069 *
1070 * Returns 1, if no segments are in flight and we have queued segments, but
1071 * cannot send anything now because of SWS or another problem.
1072 */
David S. Millera2e2a592005-07-05 15:19:23 -07001073static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074{
1075 struct tcp_sock *tp = tcp_sk(sk);
David S. Miller92df7b52005-07-05 15:19:06 -07001076 struct sk_buff *skb;
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001077 unsigned int tso_segs, sent_pkts;
1078 int cwnd_quota;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001079
1080 /* If we are closed, the bytes will have to remain here.
1081 * In time closedown will finish, we empty the write queue and all
1082 * will be happy.
1083 */
David S. Miller92df7b52005-07-05 15:19:06 -07001084 if (unlikely(sk->sk_state == TCP_CLOSE))
1085 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001086
David S. Miller92df7b52005-07-05 15:19:06 -07001087 sent_pkts = 0;
Herbert Xub68e9f82005-08-04 19:52:02 -07001088 while ((skb = sk->sk_send_head)) {
Herbert Xuc8ac3772005-08-16 20:43:40 -07001089 unsigned int limit;
1090
Herbert Xub68e9f82005-08-04 19:52:02 -07001091 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001092 BUG_ON(!tso_segs);
David S. Milleraa934662005-07-05 15:20:09 -07001093
Herbert Xub68e9f82005-08-04 19:52:02 -07001094 cwnd_quota = tcp_cwnd_test(tp, skb);
1095 if (!cwnd_quota)
1096 break;
1097
1098 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now)))
1099 break;
1100
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001101 if (tso_segs == 1) {
1102 if (unlikely(!tcp_nagle_test(tp, skb, mss_now,
1103 (tcp_skb_is_last(sk, skb) ?
1104 nonagle : TCP_NAGLE_PUSH))))
1105 break;
1106 } else {
1107 if (tcp_tso_should_defer(sk, tp, skb))
1108 break;
1109 }
David S. Milleraa934662005-07-05 15:20:09 -07001110
Herbert Xuc8ac3772005-08-16 20:43:40 -07001111 limit = mss_now;
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001112 if (tso_segs > 1) {
Herbert Xuc8ac3772005-08-16 20:43:40 -07001113 limit = tcp_window_allows(tp, skb,
1114 mss_now, cwnd_quota);
David S. Milleraa934662005-07-05 15:20:09 -07001115
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001116 if (skb->len < limit) {
1117 unsigned int trim = skb->len % mss_now;
1118
1119 if (trim)
1120 limit = skb->len - trim;
1121 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001122 }
1123
Herbert Xuc8ac3772005-08-16 20:43:40 -07001124 if (skb->len > limit &&
1125 unlikely(tso_fragment(sk, skb, limit, mss_now)))
1126 break;
1127
David S. Miller92df7b52005-07-05 15:19:06 -07001128 TCP_SKB_CB(skb)->when = tcp_time_stamp;
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001129
David S. Millerdfb4b9d2005-12-06 16:24:52 -08001130 if (unlikely(tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC)))
David S. Miller92df7b52005-07-05 15:19:06 -07001131 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001132
David S. Miller92df7b52005-07-05 15:19:06 -07001133 /* Advance the send_head. This one is sent out.
1134 * This call will increment packets_out.
1135 */
1136 update_send_head(sk, tp, skb);
1137
1138 tcp_minshall_update(tp, mss_now, skb);
David S. Milleraa934662005-07-05 15:20:09 -07001139 sent_pkts++;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001140 }
David S. Miller92df7b52005-07-05 15:19:06 -07001141
David S. Milleraa934662005-07-05 15:20:09 -07001142 if (likely(sent_pkts)) {
David S. Miller92df7b52005-07-05 15:19:06 -07001143 tcp_cwnd_validate(sk, tp);
1144 return 0;
1145 }
David S. Miller92df7b52005-07-05 15:19:06 -07001146 return !tp->packets_out && sk->sk_send_head;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001147}
1148
David S. Millera762a982005-07-05 15:18:51 -07001149/* Push out any pending frames which were held back due to
1150 * TCP_CORK or attempt at coalescing tiny packets.
1151 * The socket must be locked by the caller.
1152 */
1153void __tcp_push_pending_frames(struct sock *sk, struct tcp_sock *tp,
David S. Millera2e2a592005-07-05 15:19:23 -07001154 unsigned int cur_mss, int nonagle)
David S. Millera762a982005-07-05 15:18:51 -07001155{
1156 struct sk_buff *skb = sk->sk_send_head;
1157
1158 if (skb) {
David S. Miller55c97f32005-07-05 15:19:38 -07001159 if (tcp_write_xmit(sk, cur_mss, nonagle))
David S. Millera762a982005-07-05 15:18:51 -07001160 tcp_check_probe_timer(sk, tp);
1161 }
1162}
1163
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001164/* Send _single_ skb sitting at the send head. This function requires
1165 * true push pending frames to setup probe timer etc.
1166 */
1167void tcp_push_one(struct sock *sk, unsigned int mss_now)
1168{
1169 struct tcp_sock *tp = tcp_sk(sk);
1170 struct sk_buff *skb = sk->sk_send_head;
1171 unsigned int tso_segs, cwnd_quota;
1172
1173 BUG_ON(!skb || skb->len < mss_now);
1174
David S. Miller846998a2005-08-04 19:52:01 -07001175 tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001176 cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH);
1177
1178 if (likely(cwnd_quota)) {
Herbert Xuc8ac3772005-08-16 20:43:40 -07001179 unsigned int limit;
1180
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001181 BUG_ON(!tso_segs);
1182
Herbert Xuc8ac3772005-08-16 20:43:40 -07001183 limit = mss_now;
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001184 if (tso_segs > 1) {
Herbert Xuc8ac3772005-08-16 20:43:40 -07001185 limit = tcp_window_allows(tp, skb,
1186 mss_now, cwnd_quota);
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001187
1188 if (skb->len < limit) {
1189 unsigned int trim = skb->len % mss_now;
1190
1191 if (trim)
1192 limit = skb->len - trim;
1193 }
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001194 }
1195
Herbert Xuc8ac3772005-08-16 20:43:40 -07001196 if (skb->len > limit &&
1197 unlikely(tso_fragment(sk, skb, limit, mss_now)))
1198 return;
1199
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001200 /* Send it out now. */
1201 TCP_SKB_CB(skb)->when = tcp_time_stamp;
1202
David S. Millerdfb4b9d2005-12-06 16:24:52 -08001203 if (likely(!tcp_transmit_skb(sk, skb, 1, sk->sk_allocation))) {
David S. Millerc1b4a7e2005-07-05 15:24:38 -07001204 update_send_head(sk, tp, skb);
1205 tcp_cwnd_validate(sk, tp);
1206 return;
1207 }
1208 }
1209}
1210
Linus Torvalds1da177e2005-04-16 15:20:36 -07001211/* This function returns the amount that we can raise the
1212 * usable window based on the following constraints
1213 *
1214 * 1. The window can never be shrunk once it is offered (RFC 793)
1215 * 2. We limit memory per socket
1216 *
1217 * RFC 1122:
1218 * "the suggested [SWS] avoidance algorithm for the receiver is to keep
1219 * RECV.NEXT + RCV.WIN fixed until:
1220 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)"
1221 *
1222 * i.e. don't raise the right edge of the window until you can raise
1223 * it at least MSS bytes.
1224 *
1225 * Unfortunately, the recommended algorithm breaks header prediction,
1226 * since header prediction assumes th->window stays fixed.
1227 *
1228 * Strictly speaking, keeping th->window fixed violates the receiver
1229 * side SWS prevention criteria. The problem is that under this rule
1230 * a stream of single byte packets will cause the right side of the
1231 * window to always advance by a single byte.
1232 *
1233 * Of course, if the sender implements sender side SWS prevention
1234 * then this will not be a problem.
1235 *
1236 * BSD seems to make the following compromise:
1237 *
1238 * If the free space is less than the 1/4 of the maximum
1239 * space available and the free space is less than 1/2 mss,
1240 * then set the window to 0.
1241 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ]
1242 * Otherwise, just prevent the window from shrinking
1243 * and from being larger than the largest representable value.
1244 *
1245 * This prevents incremental opening of the window in the regime
1246 * where TCP is limited by the speed of the reader side taking
1247 * data out of the TCP receive queue. It does nothing about
1248 * those cases where the window is constrained on the sender side
1249 * because the pipeline is full.
1250 *
1251 * BSD also seems to "accidentally" limit itself to windows that are a
1252 * multiple of MSS, at least until the free space gets quite small.
1253 * This would appear to be a side effect of the mbuf implementation.
1254 * Combining these two algorithms results in the observed behavior
1255 * of having a fixed window size at almost all times.
1256 *
1257 * Below we obtain similar behavior by forcing the offered window to
1258 * a multiple of the mss when it is feasible to do so.
1259 *
1260 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes.
1261 * Regular options like TIMESTAMP are taken into account.
1262 */
1263u32 __tcp_select_window(struct sock *sk)
1264{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001265 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001266 struct tcp_sock *tp = tcp_sk(sk);
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08001267 /* MSS for the peer's data. Previous versions used mss_clamp
Linus Torvalds1da177e2005-04-16 15:20:36 -07001268 * here. I don't know if the value based on our guesses
1269 * of peer's MSS is better for the performance. It's more correct
1270 * but may be worse for the performance because of rcv_mss
1271 * fluctuations. --SAW 1998/11/1
1272 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001273 int mss = icsk->icsk_ack.rcv_mss;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001274 int free_space = tcp_space(sk);
1275 int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk));
1276 int window;
1277
1278 if (mss > full_space)
1279 mss = full_space;
1280
1281 if (free_space < full_space/2) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001282 icsk->icsk_ack.quick = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001283
1284 if (tcp_memory_pressure)
1285 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss);
1286
1287 if (free_space < mss)
1288 return 0;
1289 }
1290
1291 if (free_space > tp->rcv_ssthresh)
1292 free_space = tp->rcv_ssthresh;
1293
1294 /* Don't do rounding if we are using window scaling, since the
1295 * scaled window will not line up with the MSS boundary anyway.
1296 */
1297 window = tp->rcv_wnd;
1298 if (tp->rx_opt.rcv_wscale) {
1299 window = free_space;
1300
1301 /* Advertise enough space so that it won't get scaled away.
1302 * Import case: prevent zero window announcement if
1303 * 1<<rcv_wscale > mss.
1304 */
1305 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window)
1306 window = (((window >> tp->rx_opt.rcv_wscale) + 1)
1307 << tp->rx_opt.rcv_wscale);
1308 } else {
1309 /* Get the largest window that is a nice multiple of mss.
1310 * Window clamp already applied above.
1311 * If our current window offering is within 1 mss of the
1312 * free space we just keep it. This prevents the divide
1313 * and multiply from happening most of the time.
1314 * We also don't do any window rounding when the free space
1315 * is too small.
1316 */
1317 if (window <= free_space - mss || window > free_space)
1318 window = (free_space/mss)*mss;
1319 }
1320
1321 return window;
1322}
1323
1324/* Attempt to collapse two adjacent SKB's during retransmission. */
1325static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now)
1326{
1327 struct tcp_sock *tp = tcp_sk(sk);
1328 struct sk_buff *next_skb = skb->next;
1329
1330 /* The first test we must make is that neither of these two
1331 * SKB's are still referenced by someone else.
1332 */
1333 if (!skb_cloned(skb) && !skb_cloned(next_skb)) {
1334 int skb_size = skb->len, next_skb_size = next_skb->len;
1335 u16 flags = TCP_SKB_CB(skb)->flags;
1336
1337 /* Also punt if next skb has been SACK'd. */
1338 if(TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED)
1339 return;
1340
1341 /* Next skb is out of window. */
1342 if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd))
1343 return;
1344
1345 /* Punt if not enough space exists in the first SKB for
1346 * the data in the second, or the total combined payload
1347 * would exceed the MSS.
1348 */
1349 if ((next_skb_size > skb_tailroom(skb)) ||
1350 ((skb_size + next_skb_size) > mss_now))
1351 return;
1352
1353 BUG_ON(tcp_skb_pcount(skb) != 1 ||
1354 tcp_skb_pcount(next_skb) != 1);
1355
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001356 /* changing transmit queue under us so clear hints */
1357 clear_all_retrans_hints(tp);
1358
1359 /* Ok. We will be able to collapse the packet. */
David S. Miller8728b832005-08-09 19:25:21 -07001360 __skb_unlink(next_skb, &sk->sk_write_queue);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001361
1362 memcpy(skb_put(skb, next_skb_size), next_skb->data, next_skb_size);
1363
1364 if (next_skb->ip_summed == CHECKSUM_HW)
1365 skb->ip_summed = CHECKSUM_HW;
1366
1367 if (skb->ip_summed != CHECKSUM_HW)
1368 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size);
1369
1370 /* Update sequence range on original skb. */
1371 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq;
1372
1373 /* Merge over control information. */
1374 flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */
1375 TCP_SKB_CB(skb)->flags = flags;
1376
1377 /* All done, get rid of second SKB and account for it so
1378 * packet counting does not break.
1379 */
1380 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL);
1381 if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS)
1382 tp->retrans_out -= tcp_skb_pcount(next_skb);
1383 if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) {
1384 tp->lost_out -= tcp_skb_pcount(next_skb);
1385 tp->left_out -= tcp_skb_pcount(next_skb);
1386 }
1387 /* Reno case is special. Sigh... */
1388 if (!tp->rx_opt.sack_ok && tp->sacked_out) {
1389 tcp_dec_pcount_approx(&tp->sacked_out, next_skb);
1390 tp->left_out -= tcp_skb_pcount(next_skb);
1391 }
1392
1393 /* Not quite right: it can be > snd.fack, but
1394 * it is better to underestimate fackets.
1395 */
1396 tcp_dec_pcount_approx(&tp->fackets_out, next_skb);
1397 tcp_packets_out_dec(tp, next_skb);
1398 sk_stream_free_skb(sk, next_skb);
1399 }
1400}
1401
1402/* Do a simple retransmit without using the backoff mechanisms in
1403 * tcp_timer. This is used for path mtu discovery.
1404 * The socket is already locked here.
1405 */
1406void tcp_simple_retransmit(struct sock *sk)
1407{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001408 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001409 struct tcp_sock *tp = tcp_sk(sk);
1410 struct sk_buff *skb;
1411 unsigned int mss = tcp_current_mss(sk, 0);
1412 int lost = 0;
1413
1414 sk_stream_for_retrans_queue(skb, sk) {
1415 if (skb->len > mss &&
1416 !(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) {
1417 if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
1418 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
1419 tp->retrans_out -= tcp_skb_pcount(skb);
1420 }
1421 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) {
1422 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;
1423 tp->lost_out += tcp_skb_pcount(skb);
1424 lost = 1;
1425 }
1426 }
1427 }
1428
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001429 clear_all_retrans_hints(tp);
1430
Linus Torvalds1da177e2005-04-16 15:20:36 -07001431 if (!lost)
1432 return;
1433
1434 tcp_sync_left_out(tp);
1435
1436 /* Don't muck with the congestion window here.
1437 * Reason is that we do not increase amount of _data_
1438 * in network, but units changed and effective
1439 * cwnd/ssthresh really reduced now.
1440 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001441 if (icsk->icsk_ca_state != TCP_CA_Loss) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001442 tp->high_seq = tp->snd_nxt;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001443 tp->snd_ssthresh = tcp_current_ssthresh(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001444 tp->prior_ssthresh = 0;
1445 tp->undo_marker = 0;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001446 tcp_set_ca_state(sk, TCP_CA_Loss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001447 }
1448 tcp_xmit_retransmit_queue(sk);
1449}
1450
1451/* This retransmits one SKB. Policy decisions and retransmit queue
1452 * state updates are done by the caller. Returns non-zero if an
1453 * error occurred which prevented the send.
1454 */
1455int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb)
1456{
1457 struct tcp_sock *tp = tcp_sk(sk);
1458 unsigned int cur_mss = tcp_current_mss(sk, 0);
1459 int err;
1460
1461 /* Do not sent more than we queued. 1/4 is reserved for possible
Stephen Hemmingercaa20d9a2005-11-10 17:13:47 -08001462 * copying overhead: fragmentation, tunneling, mangling etc.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001463 */
1464 if (atomic_read(&sk->sk_wmem_alloc) >
1465 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf))
1466 return -EAGAIN;
1467
1468 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) {
1469 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
1470 BUG();
Linus Torvalds1da177e2005-04-16 15:20:36 -07001471 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq))
1472 return -ENOMEM;
1473 }
1474
1475 /* If receiver has shrunk his window, and skb is out of
1476 * new window, do not retransmit it. The exception is the
1477 * case, when window is shrunk to zero. In this case
1478 * our retransmit serves as a zero window probe.
1479 */
1480 if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)
1481 && TCP_SKB_CB(skb)->seq != tp->snd_una)
1482 return -EAGAIN;
1483
1484 if (skb->len > cur_mss) {
David S. Miller846998a2005-08-04 19:52:01 -07001485 if (tcp_fragment(sk, skb, cur_mss, cur_mss))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001486 return -ENOMEM; /* We'll try again later. */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001487 }
1488
1489 /* Collapse two adjacent packets if worthwhile and we can. */
1490 if(!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) &&
1491 (skb->len < (cur_mss >> 1)) &&
1492 (skb->next != sk->sk_send_head) &&
1493 (skb->next != (struct sk_buff *)&sk->sk_write_queue) &&
1494 (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(skb->next)->nr_frags == 0) &&
1495 (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(skb->next) == 1) &&
1496 (sysctl_tcp_retrans_collapse != 0))
1497 tcp_retrans_try_collapse(sk, skb, cur_mss);
1498
Arnaldo Carvalho de Melo8292a172005-12-13 23:15:52 -08001499 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001500 return -EHOSTUNREACH; /* Routing failure or similar. */
1501
1502 /* Some Solaris stacks overoptimize and ignore the FIN on a
1503 * retransmit when old data is attached. So strip it off
1504 * since it is cheap to do so and saves bytes on the network.
1505 */
1506 if(skb->len > 0 &&
1507 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) &&
1508 tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) {
1509 if (!pskb_trim(skb, 0)) {
1510 TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1;
1511 skb_shinfo(skb)->tso_segs = 1;
1512 skb_shinfo(skb)->tso_size = 0;
1513 skb->ip_summed = CHECKSUM_NONE;
1514 skb->csum = 0;
1515 }
1516 }
1517
1518 /* Make a copy, if the first transmission SKB clone we made
1519 * is still in somebody's hands, else make a clone.
1520 */
1521 TCP_SKB_CB(skb)->when = tcp_time_stamp;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001522
David S. Millerdfb4b9d2005-12-06 16:24:52 -08001523 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001524
1525 if (err == 0) {
1526 /* Update global TCP statistics. */
1527 TCP_INC_STATS(TCP_MIB_RETRANSSEGS);
1528
1529 tp->total_retrans++;
1530
1531#if FASTRETRANS_DEBUG > 0
1532 if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) {
1533 if (net_ratelimit())
1534 printk(KERN_DEBUG "retrans_out leaked.\n");
1535 }
1536#endif
1537 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS;
1538 tp->retrans_out += tcp_skb_pcount(skb);
1539
1540 /* Save stamp of the first retransmit. */
1541 if (!tp->retrans_stamp)
1542 tp->retrans_stamp = TCP_SKB_CB(skb)->when;
1543
1544 tp->undo_retrans++;
1545
1546 /* snd_nxt is stored to detect loss of retransmitted segment,
1547 * see tcp_input.c tcp_sacktag_write_queue().
1548 */
1549 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt;
1550 }
1551 return err;
1552}
1553
1554/* This gets called after a retransmit timeout, and the initially
1555 * retransmitted data is acknowledged. It tries to continue
1556 * resending the rest of the retransmit queue, until either
1557 * we've sent it all or the congestion window limit is reached.
1558 * If doing SACK, the first ACK which comes back for a timeout
1559 * based retransmit packet might feed us FACK information again.
1560 * If so, we use it to avoid unnecessarily retransmissions.
1561 */
1562void tcp_xmit_retransmit_queue(struct sock *sk)
1563{
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001564 const struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001565 struct tcp_sock *tp = tcp_sk(sk);
1566 struct sk_buff *skb;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001567 int packet_cnt;
1568
1569 if (tp->retransmit_skb_hint) {
1570 skb = tp->retransmit_skb_hint;
1571 packet_cnt = tp->retransmit_cnt_hint;
1572 }else{
1573 skb = sk->sk_write_queue.next;
1574 packet_cnt = 0;
1575 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001576
1577 /* First pass: retransmit lost packets. */
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001578 if (tp->lost_out) {
1579 sk_stream_for_retrans_queue_from(skb, sk) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001580 __u8 sacked = TCP_SKB_CB(skb)->sacked;
1581
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001582 /* we could do better than to assign each time */
1583 tp->retransmit_skb_hint = skb;
1584 tp->retransmit_cnt_hint = packet_cnt;
1585
Linus Torvalds1da177e2005-04-16 15:20:36 -07001586 /* Assume this retransmit will generate
1587 * only one packet for congestion window
1588 * calculation purposes. This works because
1589 * tcp_retransmit_skb() will chop up the
1590 * packet to be MSS sized and all the
1591 * packet counting works out.
1592 */
1593 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
1594 return;
1595
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001596 if (sacked & TCPCB_LOST) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001597 if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001598 if (tcp_retransmit_skb(sk, skb)) {
1599 tp->retransmit_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001600 return;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001601 }
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001602 if (icsk->icsk_ca_state != TCP_CA_Loss)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001603 NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS);
1604 else
1605 NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS);
1606
1607 if (skb ==
1608 skb_peek(&sk->sk_write_queue))
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001609 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07001610 inet_csk(sk)->icsk_rto,
1611 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001612 }
1613
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001614 packet_cnt += tcp_skb_pcount(skb);
1615 if (packet_cnt >= tp->lost_out)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001616 break;
1617 }
1618 }
1619 }
1620
1621 /* OK, demanded retransmission is finished. */
1622
1623 /* Forward retransmissions are possible only during Recovery. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03001624 if (icsk->icsk_ca_state != TCP_CA_Recovery)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001625 return;
1626
1627 /* No forward retransmissions in Reno are possible. */
1628 if (!tp->rx_opt.sack_ok)
1629 return;
1630
1631 /* Yeah, we have to make difficult choice between forward transmission
1632 * and retransmission... Both ways have their merits...
1633 *
1634 * For now we do not retransmit anything, while we have some new
1635 * segments to send.
1636 */
1637
1638 if (tcp_may_send_now(sk, tp))
1639 return;
1640
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001641 if (tp->forward_skb_hint) {
1642 skb = tp->forward_skb_hint;
1643 packet_cnt = tp->forward_cnt_hint;
1644 } else{
1645 skb = sk->sk_write_queue.next;
1646 packet_cnt = 0;
1647 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001648
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001649 sk_stream_for_retrans_queue_from(skb, sk) {
1650 tp->forward_cnt_hint = packet_cnt;
1651 tp->forward_skb_hint = skb;
1652
Linus Torvalds1da177e2005-04-16 15:20:36 -07001653 /* Similar to the retransmit loop above we
1654 * can pretend that the retransmitted SKB
1655 * we send out here will be composed of one
1656 * real MSS sized packet because tcp_retransmit_skb()
1657 * will fragment it if necessary.
1658 */
1659 if (++packet_cnt > tp->fackets_out)
1660 break;
1661
1662 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)
1663 break;
1664
1665 if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS)
1666 continue;
1667
1668 /* Ok, retransmit it. */
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001669 if (tcp_retransmit_skb(sk, skb)) {
1670 tp->forward_skb_hint = NULL;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001671 break;
Stephen Hemminger6a438bb2005-11-10 17:14:59 -08001672 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001673
1674 if (skb == skb_peek(&sk->sk_write_queue))
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07001675 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1676 inet_csk(sk)->icsk_rto,
1677 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001678
1679 NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS);
1680 }
1681}
1682
1683
1684/* Send a fin. The caller locks the socket for us. This cannot be
1685 * allowed to fail queueing a FIN frame under any circumstances.
1686 */
1687void tcp_send_fin(struct sock *sk)
1688{
1689 struct tcp_sock *tp = tcp_sk(sk);
1690 struct sk_buff *skb = skb_peek_tail(&sk->sk_write_queue);
1691 int mss_now;
1692
1693 /* Optimization, tack on the FIN if we have a queue of
1694 * unsent frames. But be careful about outgoing SACKS
1695 * and IP options.
1696 */
1697 mss_now = tcp_current_mss(sk, 1);
1698
1699 if (sk->sk_send_head != NULL) {
1700 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN;
1701 TCP_SKB_CB(skb)->end_seq++;
1702 tp->write_seq++;
1703 } else {
1704 /* Socket is locked, keep trying until memory is available. */
1705 for (;;) {
David S. Millerd179cd12005-08-17 14:57:30 -07001706 skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001707 if (skb)
1708 break;
1709 yield();
1710 }
1711
1712 /* Reserve space for headers and prepare control bits. */
1713 skb_reserve(skb, MAX_TCP_HEADER);
1714 skb->csum = 0;
1715 TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN);
1716 TCP_SKB_CB(skb)->sacked = 0;
1717 skb_shinfo(skb)->tso_segs = 1;
1718 skb_shinfo(skb)->tso_size = 0;
1719
1720 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */
1721 TCP_SKB_CB(skb)->seq = tp->write_seq;
1722 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
1723 tcp_queue_skb(sk, skb);
1724 }
1725 __tcp_push_pending_frames(sk, tp, mss_now, TCP_NAGLE_OFF);
1726}
1727
1728/* We get here when a process closes a file descriptor (either due to
1729 * an explicit close() or as a byproduct of exit()'ing) and there
1730 * was unread data in the receive queue. This behavior is recommended
1731 * by draft-ietf-tcpimpl-prob-03.txt section 3.10. -DaveM
1732 */
Al Virodd0fc662005-10-07 07:46:04 +01001733void tcp_send_active_reset(struct sock *sk, gfp_t priority)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001734{
1735 struct tcp_sock *tp = tcp_sk(sk);
1736 struct sk_buff *skb;
1737
1738 /* NOTE: No TCP options attached and we never retransmit this. */
1739 skb = alloc_skb(MAX_TCP_HEADER, priority);
1740 if (!skb) {
1741 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
1742 return;
1743 }
1744
1745 /* Reserve space for headers and prepare control bits. */
1746 skb_reserve(skb, MAX_TCP_HEADER);
1747 skb->csum = 0;
1748 TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST);
1749 TCP_SKB_CB(skb)->sacked = 0;
1750 skb_shinfo(skb)->tso_segs = 1;
1751 skb_shinfo(skb)->tso_size = 0;
1752
1753 /* Send it off. */
1754 TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk, tp);
1755 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
1756 TCP_SKB_CB(skb)->when = tcp_time_stamp;
David S. Millerdfb4b9d2005-12-06 16:24:52 -08001757 if (tcp_transmit_skb(sk, skb, 0, priority))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001758 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED);
1759}
1760
1761/* WARNING: This routine must only be called when we have already sent
1762 * a SYN packet that crossed the incoming SYN that caused this routine
1763 * to get called. If this assumption fails then the initial rcv_wnd
1764 * and rcv_wscale values will not be correct.
1765 */
1766int tcp_send_synack(struct sock *sk)
1767{
1768 struct sk_buff* skb;
1769
1770 skb = skb_peek(&sk->sk_write_queue);
1771 if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) {
1772 printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n");
1773 return -EFAULT;
1774 }
1775 if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) {
1776 if (skb_cloned(skb)) {
1777 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC);
1778 if (nskb == NULL)
1779 return -ENOMEM;
1780 __skb_unlink(skb, &sk->sk_write_queue);
1781 skb_header_release(nskb);
1782 __skb_queue_head(&sk->sk_write_queue, nskb);
1783 sk_stream_free_skb(sk, skb);
1784 sk_charge_skb(sk, nskb);
1785 skb = nskb;
1786 }
1787
1788 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK;
1789 TCP_ECN_send_synack(tcp_sk(sk), skb);
1790 }
1791 TCP_SKB_CB(skb)->when = tcp_time_stamp;
David S. Millerdfb4b9d2005-12-06 16:24:52 -08001792 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001793}
1794
1795/*
1796 * Prepare a SYN-ACK.
1797 */
1798struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst,
Arnaldo Carvalho de Melo60236fd2005-06-18 22:47:21 -07001799 struct request_sock *req)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001800{
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001801 struct inet_request_sock *ireq = inet_rsk(req);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001802 struct tcp_sock *tp = tcp_sk(sk);
1803 struct tcphdr *th;
1804 int tcp_header_size;
1805 struct sk_buff *skb;
1806
1807 skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC);
1808 if (skb == NULL)
1809 return NULL;
1810
1811 /* Reserve space for headers. */
1812 skb_reserve(skb, MAX_TCP_HEADER);
1813
1814 skb->dst = dst_clone(dst);
1815
1816 tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS +
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001817 (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) +
1818 (ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) +
Linus Torvalds1da177e2005-04-16 15:20:36 -07001819 /* SACK_PERM is in the place of NOP NOP of TS */
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001820 ((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0));
Linus Torvalds1da177e2005-04-16 15:20:36 -07001821 skb->h.th = th = (struct tcphdr *) skb_push(skb, tcp_header_size);
1822
1823 memset(th, 0, sizeof(struct tcphdr));
1824 th->syn = 1;
1825 th->ack = 1;
1826 if (dst->dev->features&NETIF_F_TSO)
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001827 ireq->ecn_ok = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001828 TCP_ECN_make_synack(req, th);
1829 th->source = inet_sk(sk)->sport;
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001830 th->dest = ireq->rmt_port;
1831 TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001832 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1;
1833 TCP_SKB_CB(skb)->sacked = 0;
1834 skb_shinfo(skb)->tso_segs = 1;
1835 skb_shinfo(skb)->tso_size = 0;
1836 th->seq = htonl(TCP_SKB_CB(skb)->seq);
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001837 th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001838 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */
1839 __u8 rcv_wscale;
1840 /* Set this up on the first call only */
1841 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW);
1842 /* tcp_full_space because it is guaranteed to be the first packet */
1843 tcp_select_initial_window(tcp_full_space(sk),
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001844 dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0),
Linus Torvalds1da177e2005-04-16 15:20:36 -07001845 &req->rcv_wnd,
1846 &req->window_clamp,
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001847 ireq->wscale_ok,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001848 &rcv_wscale);
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001849 ireq->rcv_wscale = rcv_wscale;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001850 }
1851
1852 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */
1853 th->window = htons(req->rcv_wnd);
1854
1855 TCP_SKB_CB(skb)->when = tcp_time_stamp;
Arnaldo Carvalho de Melo2e6599c2005-06-18 22:46:52 -07001856 tcp_syn_build_options((__u32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok,
1857 ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale,
Linus Torvalds1da177e2005-04-16 15:20:36 -07001858 TCP_SKB_CB(skb)->when,
1859 req->ts_recent);
1860
1861 skb->csum = 0;
1862 th->doff = (tcp_header_size >> 2);
1863 TCP_INC_STATS(TCP_MIB_OUTSEGS);
1864 return skb;
1865}
1866
1867/*
1868 * Do all connect socket setups that can be done AF independent.
1869 */
Stephen Hemminger40efc6f2006-01-03 16:03:49 -08001870static void tcp_connect_init(struct sock *sk)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001871{
1872 struct dst_entry *dst = __sk_dst_get(sk);
1873 struct tcp_sock *tp = tcp_sk(sk);
1874 __u8 rcv_wscale;
1875
1876 /* We'll fix this up when we get a response from the other end.
1877 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT.
1878 */
1879 tp->tcp_header_len = sizeof(struct tcphdr) +
1880 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0);
1881
1882 /* If user gave his TCP_MAXSEG, record it to clamp */
1883 if (tp->rx_opt.user_mss)
1884 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss;
1885 tp->max_window = 0;
1886 tcp_sync_mss(sk, dst_mtu(dst));
1887
1888 if (!tp->window_clamp)
1889 tp->window_clamp = dst_metric(dst, RTAX_WINDOW);
1890 tp->advmss = dst_metric(dst, RTAX_ADVMSS);
1891 tcp_initialize_rcv_mss(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001892
1893 tcp_select_initial_window(tcp_full_space(sk),
1894 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0),
1895 &tp->rcv_wnd,
1896 &tp->window_clamp,
1897 sysctl_tcp_window_scaling,
1898 &rcv_wscale);
1899
1900 tp->rx_opt.rcv_wscale = rcv_wscale;
1901 tp->rcv_ssthresh = tp->rcv_wnd;
1902
1903 sk->sk_err = 0;
1904 sock_reset_flag(sk, SOCK_DONE);
1905 tp->snd_wnd = 0;
1906 tcp_init_wl(tp, tp->write_seq, 0);
1907 tp->snd_una = tp->write_seq;
1908 tp->snd_sml = tp->write_seq;
1909 tp->rcv_nxt = 0;
1910 tp->rcv_wup = 0;
1911 tp->copied_seq = 0;
1912
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001913 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT;
1914 inet_csk(sk)->icsk_retransmits = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001915 tcp_clear_retrans(tp);
1916}
1917
1918/*
1919 * Build a SYN and send it off.
1920 */
1921int tcp_connect(struct sock *sk)
1922{
1923 struct tcp_sock *tp = tcp_sk(sk);
1924 struct sk_buff *buff;
1925
1926 tcp_connect_init(sk);
1927
David S. Millerd179cd12005-08-17 14:57:30 -07001928 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001929 if (unlikely(buff == NULL))
1930 return -ENOBUFS;
1931
1932 /* Reserve space for headers. */
1933 skb_reserve(buff, MAX_TCP_HEADER);
1934
1935 TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN;
1936 TCP_ECN_send_syn(sk, tp, buff);
1937 TCP_SKB_CB(buff)->sacked = 0;
1938 skb_shinfo(buff)->tso_segs = 1;
1939 skb_shinfo(buff)->tso_size = 0;
1940 buff->csum = 0;
1941 TCP_SKB_CB(buff)->seq = tp->write_seq++;
1942 TCP_SKB_CB(buff)->end_seq = tp->write_seq;
1943 tp->snd_nxt = tp->write_seq;
1944 tp->pushed_seq = tp->write_seq;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001945
1946 /* Send it off. */
1947 TCP_SKB_CB(buff)->when = tcp_time_stamp;
1948 tp->retrans_stamp = TCP_SKB_CB(buff)->when;
1949 skb_header_release(buff);
1950 __skb_queue_tail(&sk->sk_write_queue, buff);
1951 sk_charge_skb(sk, buff);
1952 tp->packets_out += tcp_skb_pcount(buff);
David S. Millerdfb4b9d2005-12-06 16:24:52 -08001953 tcp_transmit_skb(sk, buff, 1, GFP_KERNEL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001954 TCP_INC_STATS(TCP_MIB_ACTIVEOPENS);
1955
1956 /* Timer for repeating the SYN until an answer. */
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07001957 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
1958 inet_csk(sk)->icsk_rto, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001959 return 0;
1960}
1961
1962/* Send out a delayed ack, the caller does the policy checking
1963 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check()
1964 * for details.
1965 */
1966void tcp_send_delayed_ack(struct sock *sk)
1967{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001968 struct inet_connection_sock *icsk = inet_csk(sk);
1969 int ato = icsk->icsk_ack.ato;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001970 unsigned long timeout;
1971
1972 if (ato > TCP_DELACK_MIN) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001973 const struct tcp_sock *tp = tcp_sk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001974 int max_ato = HZ/2;
1975
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001976 if (icsk->icsk_ack.pingpong || (icsk->icsk_ack.pending & ICSK_ACK_PUSHED))
Linus Torvalds1da177e2005-04-16 15:20:36 -07001977 max_ato = TCP_DELACK_MAX;
1978
1979 /* Slow path, intersegment interval is "high". */
1980
1981 /* If some rtt estimate is known, use it to bound delayed ack.
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001982 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements
Linus Torvalds1da177e2005-04-16 15:20:36 -07001983 * directly.
1984 */
1985 if (tp->srtt) {
1986 int rtt = max(tp->srtt>>3, TCP_DELACK_MIN);
1987
1988 if (rtt < max_ato)
1989 max_ato = rtt;
1990 }
1991
1992 ato = min(ato, max_ato);
1993 }
1994
1995 /* Stay within the limit we were given */
1996 timeout = jiffies + ato;
1997
1998 /* Use new timeout only if there wasn't a older one earlier. */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07001999 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002000 /* If delack timer was blocked or is about to expire,
2001 * send ACK now.
2002 */
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002003 if (icsk->icsk_ack.blocked ||
2004 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07002005 tcp_send_ack(sk);
2006 return;
2007 }
2008
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002009 if (!time_before(timeout, icsk->icsk_ack.timeout))
2010 timeout = icsk->icsk_ack.timeout;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002011 }
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002012 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER;
2013 icsk->icsk_ack.timeout = timeout;
2014 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002015}
2016
2017/* This routine sends an ack and also updates the window. */
2018void tcp_send_ack(struct sock *sk)
2019{
2020 /* If we have been reset, we may not send again. */
2021 if (sk->sk_state != TCP_CLOSE) {
2022 struct tcp_sock *tp = tcp_sk(sk);
2023 struct sk_buff *buff;
2024
2025 /* We are not putting this on the write queue, so
2026 * tcp_transmit_skb() will set the ownership to this
2027 * sock.
2028 */
2029 buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2030 if (buff == NULL) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002031 inet_csk_schedule_ack(sk);
2032 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN;
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002033 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
2034 TCP_DELACK_MAX, TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035 return;
2036 }
2037
2038 /* Reserve space for headers and prepare control bits. */
2039 skb_reserve(buff, MAX_TCP_HEADER);
2040 buff->csum = 0;
2041 TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK;
2042 TCP_SKB_CB(buff)->sacked = 0;
2043 skb_shinfo(buff)->tso_segs = 1;
2044 skb_shinfo(buff)->tso_size = 0;
2045
2046 /* Send it off, this clears delayed acks for us. */
2047 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk, tp);
2048 TCP_SKB_CB(buff)->when = tcp_time_stamp;
David S. Millerdfb4b9d2005-12-06 16:24:52 -08002049 tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002050 }
2051}
2052
2053/* This routine sends a packet with an out of date sequence
2054 * number. It assumes the other end will try to ack it.
2055 *
2056 * Question: what should we make while urgent mode?
2057 * 4.4BSD forces sending single byte of data. We cannot send
2058 * out of window data, because we have SND.NXT==SND.MAX...
2059 *
2060 * Current solution: to send TWO zero-length segments in urgent mode:
2061 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is
2062 * out-of-date with SND.UNA-1 to probe window.
2063 */
2064static int tcp_xmit_probe_skb(struct sock *sk, int urgent)
2065{
2066 struct tcp_sock *tp = tcp_sk(sk);
2067 struct sk_buff *skb;
2068
2069 /* We don't queue it, tcp_transmit_skb() sets ownership. */
2070 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC);
2071 if (skb == NULL)
2072 return -1;
2073
2074 /* Reserve space for headers and set control bits. */
2075 skb_reserve(skb, MAX_TCP_HEADER);
2076 skb->csum = 0;
2077 TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK;
2078 TCP_SKB_CB(skb)->sacked = urgent;
2079 skb_shinfo(skb)->tso_segs = 1;
2080 skb_shinfo(skb)->tso_size = 0;
2081
2082 /* Use a previous sequence. This should cause the other
2083 * end to send an ack. Don't queue or clone SKB, just
2084 * send it.
2085 */
2086 TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1;
2087 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq;
2088 TCP_SKB_CB(skb)->when = tcp_time_stamp;
David S. Millerdfb4b9d2005-12-06 16:24:52 -08002089 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002090}
2091
2092int tcp_write_wakeup(struct sock *sk)
2093{
2094 if (sk->sk_state != TCP_CLOSE) {
2095 struct tcp_sock *tp = tcp_sk(sk);
2096 struct sk_buff *skb;
2097
2098 if ((skb = sk->sk_send_head) != NULL &&
2099 before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) {
2100 int err;
2101 unsigned int mss = tcp_current_mss(sk, 0);
2102 unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq;
2103
2104 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq))
2105 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq;
2106
2107 /* We are probing the opening of a window
2108 * but the window size is != 0
2109 * must have been a result SWS avoidance ( sender )
2110 */
2111 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq ||
2112 skb->len > mss) {
2113 seg_size = min(seg_size, mss);
2114 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
David S. Miller846998a2005-08-04 19:52:01 -07002115 if (tcp_fragment(sk, skb, seg_size, mss))
Linus Torvalds1da177e2005-04-16 15:20:36 -07002116 return -1;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002117 } else if (!tcp_skb_pcount(skb))
David S. Miller846998a2005-08-04 19:52:01 -07002118 tcp_set_skb_tso_segs(sk, skb, mss);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002119
2120 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH;
2121 TCP_SKB_CB(skb)->when = tcp_time_stamp;
David S. Millerdfb4b9d2005-12-06 16:24:52 -08002122 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002123 if (!err) {
2124 update_send_head(sk, tp, skb);
2125 }
2126 return err;
2127 } else {
2128 if (tp->urg_mode &&
2129 between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF))
2130 tcp_xmit_probe_skb(sk, TCPCB_URG);
2131 return tcp_xmit_probe_skb(sk, 0);
2132 }
2133 }
2134 return -1;
2135}
2136
2137/* A window probe timeout has occurred. If window is not closed send
2138 * a partial packet else a zero probe.
2139 */
2140void tcp_send_probe0(struct sock *sk)
2141{
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002142 struct inet_connection_sock *icsk = inet_csk(sk);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002143 struct tcp_sock *tp = tcp_sk(sk);
2144 int err;
2145
2146 err = tcp_write_wakeup(sk);
2147
2148 if (tp->packets_out || !sk->sk_send_head) {
2149 /* Cancel probe timer, if it is not required. */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002150 icsk->icsk_probes_out = 0;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002151 icsk->icsk_backoff = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002152 return;
2153 }
2154
2155 if (err <= 0) {
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002156 if (icsk->icsk_backoff < sysctl_tcp_retries2)
2157 icsk->icsk_backoff++;
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002158 icsk->icsk_probes_out++;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002159 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002160 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX),
2161 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002162 } else {
2163 /* If packet was not sent due to local congestion,
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002164 * do not backoff and do not remember icsk_probes_out.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002165 * Let local senders to fight for local resources.
2166 *
2167 * Use accumulated backoff yet.
2168 */
Arnaldo Carvalho de Melo6687e982005-08-10 04:03:31 -03002169 if (!icsk->icsk_probes_out)
2170 icsk->icsk_probes_out = 1;
Arnaldo Carvalho de Melo463c84b2005-08-09 20:10:42 -07002171 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
2172 min(icsk->icsk_rto << icsk->icsk_backoff,
Arnaldo Carvalho de Melo3f421ba2005-08-09 20:11:08 -07002173 TCP_RESOURCE_PROBE_INTERVAL),
2174 TCP_RTO_MAX);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002175 }
2176}
2177
2178EXPORT_SYMBOL(tcp_connect);
2179EXPORT_SYMBOL(tcp_make_synack);
2180EXPORT_SYMBOL(tcp_simple_retransmit);
2181EXPORT_SYMBOL(tcp_sync_mss);
Stephen Hemmingerf4805ed2005-11-10 16:53:30 -08002182EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor);