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*/
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.
5 *
6 * Implementation of the Transmission Control Protocol(TCP).
7 *
8 * Version: @(#)tcp_input.c 1.0.16 05/25/93
9 *
10 * Authors: Ross Biro, <bir7@leland.Stanford.Edu>
11 * 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 #include <linux/config.h>
24 #include <net/tcp.h>
25
26 /*
27 * This is the main buffer sending routine. We queue the buffer
28 * having checked it is sane seeming.
29 */
30
31 void tcp_send_skb(struct sock *sk, struct sk_buff *skb)
/* ![[next]](../icons/right.png)
![[first]](../icons/n_first.png)
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*/
32 {
33 int size;
34 struct tcphdr * th = skb->h.th;
35
36 /*
37 * length of packet (not counting length of pre-tcp headers)
38 */
39
40 size = skb->len - ((unsigned char *) th - skb->data);
41
42 /*
43 * Sanity check it..
44 */
45
46 if (size < sizeof(struct tcphdr) || size > skb->len)
47 {
48 printk("tcp_send_skb: bad skb (skb = %p, data = %p, th = %p, len = %lu)\n",
49 skb, skb->data, th, skb->len);
50 kfree_skb(skb, FREE_WRITE);
51 return;
52 }
53
54 /*
55 * If we have queued a header size packet.. (these crash a few
56 * tcp stacks if ack is not set)
57 */
58
59 if (size == sizeof(struct tcphdr))
60 {
61 /* If it's got a syn or fin it's notionally included in the size..*/
62 if(!th->syn && !th->fin)
63 {
64 printk("tcp_send_skb: attempt to queue a bogon.\n");
65 kfree_skb(skb,FREE_WRITE);
66 return;
67 }
68 }
69
70 /*
71 * Actual processing.
72 */
73
74 tcp_statistics.TcpOutSegs++;
75 skb->seq = ntohl(th->seq);
76 skb->end_seq = skb->seq + size - 4*th->doff;
77
78 /*
79 * We must queue if
80 *
81 * a) The right edge of this frame exceeds the window
82 * b) We are retransmitting (Nagle's rule)
83 * c) We have too many packets 'in flight'
84 */
85
86 if (after(skb->end_seq, sk->window_seq) ||
87 (sk->retransmits && sk->ip_xmit_timeout == TIME_WRITE) ||
88 sk->packets_out >= sk->cong_window)
89 {
90 /* checksum will be supplied by tcp_write_xmit. So
91 * we shouldn't need to set it at all. I'm being paranoid */
92 th->check = 0;
93 if (skb->next != NULL)
94 {
95 printk("tcp_send_partial: next != NULL\n");
96 skb_unlink(skb);
97 }
98 skb_queue_tail(&sk->write_queue, skb);
99
100 if (before(sk->window_seq, sk->write_queue.next->end_seq) &&
101 sk->send_head == NULL && sk->ack_backlog == 0)
102 tcp_reset_xmit_timer(sk, TIME_PROBE0, sk->rto);
103 }
104 else
105 {
106 /*
107 * This is going straight out
108 */
109
110 th->ack_seq = htonl(sk->acked_seq);
111 th->window = htons(tcp_select_window(sk));
112
113 tcp_send_check(th, sk->saddr, sk->daddr, size, skb);
114
115 sk->sent_seq = sk->write_seq;
116
117 /*
118 * This is mad. The tcp retransmit queue is put together
119 * by the ip layer. This causes half the problems with
120 * unroutable FIN's and other things.
121 */
122
123 sk->prot->queue_xmit(sk, skb->dev, skb, 0);
124
125
126 sk->ack_backlog = 0;
127 sk->bytes_rcv = 0;
128
129 /*
130 * Set for next retransmit based on expected ACK time.
131 * FIXME: We set this every time which means our
132 * retransmits are really about a window behind.
133 */
134
135 tcp_reset_xmit_timer(sk, TIME_WRITE, sk->rto);
136 }
137 }
138
139 /*
140 * Locking problems lead us to a messy situation where we can have
141 * multiple partially complete buffers queued up. This is really bad
142 * as we don't want to be sending partial buffers. Fix this with
143 * a semaphore or similar to lock tcp_write per socket.
144 *
145 * These routines are pretty self descriptive.
146 */
147
148 struct sk_buff * tcp_dequeue_partial(struct sock * sk)
/* ![[previous]](../icons/left.png)
*/
149 {
150 struct sk_buff * skb;
151 unsigned long flags;
152
153 save_flags(flags);
154 cli();
155 skb = sk->partial;
156 if (skb) {
157 sk->partial = NULL;
158 del_timer(&sk->partial_timer);
159 }
160 restore_flags(flags);
161 return skb;
162 }
163
164 /*
165 * Empty the partial queue
166 */
167
168 void tcp_send_partial(struct sock *sk)
/* */
169 {
170 struct sk_buff *skb;
171
172 if (sk == NULL)
173 return;
174 while ((skb = tcp_dequeue_partial(sk)) != NULL)
175 tcp_send_skb(sk, skb);
176 }
177
178 /*
179 * Queue a partial frame
180 */
181
182 void tcp_enqueue_partial(struct sk_buff * skb, struct sock * sk)
/* */
183 {
184 struct sk_buff * tmp;
185 unsigned long flags;
186
187 save_flags(flags);
188 cli();
189 tmp = sk->partial;
190 if (tmp)
191 del_timer(&sk->partial_timer);
192 sk->partial = skb;
193 init_timer(&sk->partial_timer);
194 /*
195 * Wait up to 1 second for the buffer to fill.
196 */
197 sk->partial_timer.expires = jiffies+HZ;
198 sk->partial_timer.function = (void (*)(unsigned long)) tcp_send_partial;
199 sk->partial_timer.data = (unsigned long) sk;
200 add_timer(&sk->partial_timer);
201 restore_flags(flags);
202 if (tmp)
203 tcp_send_skb(sk, tmp);
204 }
205
206 /*
207 * This routine takes stuff off of the write queue,
208 * and puts it in the xmit queue. This happens as incoming acks
209 * open up the remote window for us.
210 */
211
212 void tcp_write_xmit(struct sock *sk)
/* */
213 {
214 struct sk_buff *skb;
215
216 /*
217 * The bytes will have to remain here. In time closedown will
218 * empty the write queue and all will be happy
219 */
220
221 if(sk->zapped)
222 return;
223
224 /*
225 * Anything on the transmit queue that fits the window can
226 * be added providing we are not
227 *
228 * a) retransmitting (Nagle's rule)
229 * b) exceeding our congestion window.
230 */
231
232 while((skb = skb_peek(&sk->write_queue)) != NULL &&
233 before(skb->end_seq, sk->window_seq + 1) &&
234 (sk->retransmits == 0 ||
235 sk->ip_xmit_timeout != TIME_WRITE ||
236 before(skb->end_seq, sk->rcv_ack_seq + 1))
237 && sk->packets_out < sk->cong_window)
238 {
239 IS_SKB(skb);
240 skb_unlink(skb);
241
242 /*
243 * See if we really need to send the packet.
244 */
245
246 if (before(skb->end_seq, sk->rcv_ack_seq +1))
247 {
248 /*
249 * This is acked data. We can discard it. This
250 * cannot currently occur.
251 */
252
253 sk->retransmits = 0;
254 kfree_skb(skb, FREE_WRITE);
255 if (!sk->dead)
256 sk->write_space(sk);
257 }
258 else
259 {
260 struct tcphdr *th;
261 struct iphdr *iph;
262 int size;
263 /*
264 * put in the ack seq and window at this point rather than earlier,
265 * in order to keep them monotonic. We really want to avoid taking
266 * back window allocations. That's legal, but RFC1122 says it's frowned on.
267 * Ack and window will in general have changed since this packet was put
268 * on the write queue.
269 */
270 iph = skb->ip_hdr;
271 th = (struct tcphdr *)(((char *)iph) +(iph->ihl << 2));
272 size = skb->len - (((unsigned char *) th) - skb->data);
273 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
274 if (size > sk->mtu - sizeof(struct iphdr))
275 {
276 iph->frag_off &= ~htons(IP_DF);
277 ip_send_check(iph);
278 }
279 #endif
280
281 th->ack_seq = htonl(sk->acked_seq);
282 th->window = htons(tcp_select_window(sk));
283
284 tcp_send_check(th, sk->saddr, sk->daddr, size, skb);
285
286 sk->sent_seq = skb->end_seq;
287
288 /*
289 * IP manages our queue for some crazy reason
290 */
291
292 sk->prot->queue_xmit(sk, skb->dev, skb, skb->free);
293
294
295 sk->ack_backlog = 0;
296 sk->bytes_rcv = 0;
297
298 /*
299 * Again we slide the timer wrongly
300 */
301
302 tcp_reset_xmit_timer(sk, TIME_WRITE, sk->rto);
303 }
304 }
305 }
306
307
308 /*
309 * A socket has timed out on its send queue and wants to do a
310 * little retransmitting. Currently this means TCP.
311 */
312
313 void tcp_do_retransmit(struct sock *sk, int all)
/* */
314 {
315 struct sk_buff * skb;
316 struct proto *prot;
317 struct device *dev;
318 int ct=0;
319 struct rtable *rt;
320
321 prot = sk->prot;
322 skb = sk->send_head;
323
324 while (skb != NULL)
325 {
326 struct tcphdr *th;
327 struct iphdr *iph;
328 int size;
329
330 dev = skb->dev;
331 IS_SKB(skb);
332 skb->when = jiffies;
333
334 /* dl1bke 960201 - @%$$! Hope this cures strange race conditions */
335 /* with AX.25 mode VC. (esp. DAMA) */
336 /* if the buffer is locked we should not retransmit */
337 /* anyway, so we don't need all the fuss to prepare */
338 /* the buffer in this case. */
339 /* (the skb_pull() changes skb->data while we may */
340 /* actually try to send the data. Ouch. A side */
341 /* effect is that we'll send some unnecessary data, */
342 /* but the alternative is disasterous... */
343
344 if (skb_device_locked(skb))
345 break;
346
347 /*
348 * Discard the surplus MAC header
349 */
350
351 skb_pull(skb,((unsigned char *)skb->ip_hdr)-skb->data);
352
353 /*
354 * In general it's OK just to use the old packet. However we
355 * need to use the current ack and window fields. Urg and
356 * urg_ptr could possibly stand to be updated as well, but we
357 * don't keep the necessary data. That shouldn't be a problem,
358 * if the other end is doing the right thing. Since we're
359 * changing the packet, we have to issue a new IP identifier.
360 */
361
362 iph = (struct iphdr *)skb->data;
363 th = (struct tcphdr *)(((char *)iph) + (iph->ihl << 2));
364 size = ntohs(iph->tot_len) - (iph->ihl<<2);
365
366 /*
367 * Note: We ought to check for window limits here but
368 * currently this is done (less efficiently) elsewhere.
369 */
370
371 /*
372 * Put a MAC header back on (may cause ARPing)
373 */
374
375 {
376 /* ANK: UGLY, but the bug, that was here, should be fixed.
377 */
378 struct options * opt = (struct options*)skb->proto_priv;
379 rt = ip_check_route(&sk->ip_route_cache, opt->srr?opt->faddr:iph->daddr, skb->localroute);
380 }
381
382 iph->id = htons(ip_id_count++);
383 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
384 if (rt && ntohs(iph->tot_len) > rt->rt_mtu)
385 iph->frag_off &= ~htons(IP_DF);
386 #endif
387 ip_send_check(iph);
388
389 if (rt==NULL) /* Deep poo */
390 {
391 if(skb->sk)
392 {
393 skb->sk->err_soft=ENETUNREACH;
394 skb->sk->error_report(skb->sk);
395 }
396 }
397 else
398 {
399 dev=rt->rt_dev;
400 skb->raddr=rt->rt_gateway;
401 skb->dev=dev;
402 skb->arp=1;
403 if (rt->rt_hh)
404 {
405 memcpy(skb_push(skb,dev->hard_header_len),rt->rt_hh->hh_data,dev->hard_header_len);
406 if (!rt->rt_hh->hh_uptodate)
407 {
408 skb->arp = 0;
409 #if RT_CACHE_DEBUG >= 2
410 printk("tcp_do_retransmit: hh miss %08x via %08x\n", iph->daddr, rt->rt_gateway);
411 #endif
412 }
413 }
414 else if (dev->hard_header)
415 {
416 if(dev->hard_header(skb, dev, ETH_P_IP, NULL, NULL, skb->len)<0)
417 skb->arp=0;
418 }
419
420 /*
421 * This is not the right way to handle this. We have to
422 * issue an up to date window and ack report with this
423 * retransmit to keep the odd buggy tcp that relies on
424 * the fact BSD does this happy.
425 * We don't however need to recalculate the entire
426 * checksum, so someone wanting a small problem to play
427 * with might like to implement RFC1141/RFC1624 and speed
428 * this up by avoiding a full checksum.
429 */
430
431 th->ack_seq = htonl(sk->acked_seq);
432 sk->ack_backlog = 0;
433 sk->bytes_rcv = 0;
434 th->window = ntohs(tcp_select_window(sk));
435 tcp_send_check(th, sk->saddr, sk->daddr, size, skb);
436
437 /*
438 * If the interface is (still) up and running, kick it.
439 */
440
441 if (dev->flags & IFF_UP)
442 {
443 /*
444 * If the packet is still being sent by the device/protocol
445 * below then don't retransmit. This is both needed, and good -
446 * especially with connected mode AX.25 where it stops resends
447 * occurring of an as yet unsent anyway frame!
448 * We still add up the counts as the round trip time wants
449 * adjusting.
450 */
451 if (sk && !skb_device_locked(skb))
452 {
453 /* Remove it from any existing driver queue first! */
454 skb_unlink(skb);
455 /* Now queue it */
456 ip_statistics.IpOutRequests++;
457 dev_queue_xmit(skb, dev, sk->priority);
458 }
459 }
460 }
461
462 /*
463 * Count retransmissions
464 */
465
466 ct++;
467 sk->retransmits++;
468 sk->prot->retransmits++;
469 tcp_statistics.TcpRetransSegs++;
470
471
472 /*
473 * Only one retransmit requested.
474 */
475
476 if (!all)
477 break;
478
479 /*
480 * This should cut it off before we send too many packets.
481 */
482
483 if (ct >= sk->cong_window)
484 break;
485 skb = skb->link3;
486 }
487 }
488
489 /*
490 * This routine will send an RST to the other tcp.
491 */
492
493 void tcp_send_reset(unsigned long saddr, unsigned long daddr, struct tcphdr *th,
/* */
494 struct proto *prot, struct options *opt, struct device *dev, int tos, int ttl)
495 {
496 struct sk_buff *buff;
497 struct tcphdr *t1;
498 int tmp;
499 struct device *ndev=NULL;
500
501 /*
502 * Cannot reset a reset (Think about it).
503 */
504
505 if(th->rst)
506 return;
507
508 /*
509 * We need to grab some memory, and put together an RST,
510 * and then put it into the queue to be sent.
511 */
512
513 buff = sock_wmalloc(NULL, MAX_RESET_SIZE, 1, GFP_ATOMIC);
514 if (buff == NULL)
515 return;
516
517 buff->sk = NULL;
518 buff->dev = dev;
519 buff->localroute = 0;
520 buff->csum = 0;
521
522 /*
523 * Put in the IP header and routing stuff.
524 */
525
526 tmp = prot->build_header(buff, saddr, daddr, &ndev, IPPROTO_TCP, opt,
527 sizeof(struct tcphdr),tos,ttl,NULL);
528 if (tmp < 0)
529 {
530 buff->free = 1;
531 sock_wfree(NULL, buff);
532 return;
533 }
534
535 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
536 memset(t1, 0, sizeof(*t1));
537
538 /*
539 * Swap the send and the receive.
540 */
541
542 t1->dest = th->source;
543 t1->source = th->dest;
544 t1->doff = sizeof(*t1)/4;
545 t1->rst = 1;
546
547 if(th->ack)
548 {
549 t1->seq = th->ack_seq;
550 }
551 else
552 {
553 t1->ack = 1;
554 if(!th->syn)
555 t1->ack_seq = th->seq;
556 else
557 t1->ack_seq = htonl(ntohl(th->seq)+1);
558 }
559
560 tcp_send_check(t1, saddr, daddr, sizeof(*t1), buff);
561 prot->queue_xmit(NULL, ndev, buff, 1);
562 tcp_statistics.TcpOutSegs++;
563 }
564
565 /*
566 * Send a fin.
567 */
568
569 void tcp_send_fin(struct sock *sk)
/* */
570 {
571 struct proto *prot =(struct proto *)sk->prot;
572 struct tcphdr *th =(struct tcphdr *)&sk->dummy_th;
573 struct tcphdr *t1;
574 struct sk_buff *buff;
575 struct device *dev=NULL;
576 int tmp;
577
578 buff = sock_wmalloc(sk, MAX_RESET_SIZE,1 , GFP_KERNEL);
579
580 if (buff == NULL)
581 {
582 /* This is a disaster if it occurs */
583 printk("tcp_send_fin: Impossible malloc failure");
584 return;
585 }
586
587 /*
588 * Administrivia
589 */
590
591 buff->sk = sk;
592 buff->localroute = sk->localroute;
593 buff->csum = 0;
594
595 /*
596 * Put in the IP header and routing stuff.
597 */
598
599 tmp = prot->build_header(buff,sk->saddr, sk->daddr, &dev,
600 IPPROTO_TCP, sk->opt,
601 sizeof(struct tcphdr),sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
602 if (tmp < 0)
603 {
604 int t;
605 /*
606 * Finish anyway, treat this as a send that got lost.
607 * (Not good).
608 */
609
610 buff->free = 1;
611 sock_wfree(sk,buff);
612 sk->write_seq++;
613 t=del_timer(&sk->timer);
614 if(t)
615 add_timer(&sk->timer);
616 else
617 tcp_reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
618 return;
619 }
620
621 /*
622 * We ought to check if the end of the queue is a buffer and
623 * if so simply add the fin to that buffer, not send it ahead.
624 */
625
626 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
627 buff->dev = dev;
628 memcpy(t1, th, sizeof(*t1));
629 buff->seq = sk->write_seq;
630 sk->write_seq++;
631 buff->end_seq = sk->write_seq;
632 t1->seq = htonl(buff->seq);
633 t1->ack_seq = htonl(sk->acked_seq);
634 t1->window = htons(sk->window=tcp_select_window(sk));
635 t1->fin = 1;
636 tcp_send_check(t1, sk->saddr, sk->daddr, sizeof(*t1), buff);
637
638 /*
639 * If there is data in the write queue, the fin must be appended to
640 * the write queue.
641 */
642
643 if (skb_peek(&sk->write_queue) != NULL)
644 {
645 buff->free = 0;
646 if (buff->next != NULL)
647 {
648 printk("tcp_send_fin: next != NULL\n");
649 skb_unlink(buff);
650 }
651 skb_queue_tail(&sk->write_queue, buff);
652 }
653 else
654 {
655 sk->sent_seq = sk->write_seq;
656 sk->prot->queue_xmit(sk, dev, buff, 0);
657 tcp_reset_xmit_timer(sk, TIME_WRITE, sk->rto);
658 }
659 }
660
661
662 void tcp_send_synack(struct sock * newsk, struct sock * sk, struct sk_buff * skb)
/* */
663 {
664 struct tcphdr *t1;
665 unsigned char *ptr;
666 struct sk_buff * buff;
667 struct device *ndev=NULL;
668 int tmp;
669
670 buff = sock_wmalloc(newsk, MAX_SYN_SIZE, 1, GFP_ATOMIC);
671 if (buff == NULL)
672 {
673 sk->err = ENOMEM;
674 destroy_sock(newsk);
675 kfree_skb(skb, FREE_READ);
676 tcp_statistics.TcpAttemptFails++;
677 return;
678 }
679
680 buff->sk = newsk;
681 buff->localroute = newsk->localroute;
682
683 /*
684 * Put in the IP header and routing stuff.
685 */
686
687 tmp = sk->prot->build_header(buff, newsk->saddr, newsk->daddr, &ndev,
688 IPPROTO_TCP, NULL, MAX_SYN_SIZE,sk->ip_tos,sk->ip_ttl,&newsk->ip_route_cache);
689
690 /*
691 * Something went wrong.
692 */
693
694 if (tmp < 0)
695 {
696 sk->err = tmp;
697 buff->free = 1;
698 kfree_skb(buff,FREE_WRITE);
699 destroy_sock(newsk);
700 skb->sk = sk;
701 kfree_skb(skb, FREE_READ);
702 tcp_statistics.TcpAttemptFails++;
703 return;
704 }
705
706 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
707
708 memcpy(t1, skb->h.th, sizeof(*t1));
709 buff->seq = newsk->write_seq++;
710 buff->end_seq = newsk->write_seq;
711 /*
712 * Swap the send and the receive.
713 */
714 t1->dest = skb->h.th->source;
715 t1->source = newsk->dummy_th.source;
716 t1->seq = ntohl(buff->seq);
717 newsk->sent_seq = newsk->write_seq;
718 t1->window = ntohs(tcp_select_window(newsk));
719 t1->syn = 1;
720 t1->ack = 1;
721 t1->urg = 0;
722 t1->rst = 0;
723 t1->psh = 0;
724 t1->ack_seq = htonl(newsk->acked_seq);
725 t1->doff = sizeof(*t1)/4+1;
726 ptr = skb_put(buff,4);
727 ptr[0] = 2;
728 ptr[1] = 4;
729 ptr[2] = ((newsk->mtu) >> 8) & 0xff;
730 ptr[3] =(newsk->mtu) & 0xff;
731 buff->csum = csum_partial(ptr, 4, 0);
732 tcp_send_check(t1, newsk->saddr, newsk->daddr, sizeof(*t1)+4, buff);
733 newsk->prot->queue_xmit(newsk, ndev, buff, 0);
734 tcp_reset_xmit_timer(newsk, TIME_WRITE , TCP_TIMEOUT_INIT);
735 skb->sk = newsk;
736
737 /*
738 * Charge the sock_buff to newsk.
739 */
740
741 sk->rmem_alloc -= skb->truesize;
742 newsk->rmem_alloc += skb->truesize;
743
744 skb_queue_tail(&sk->receive_queue,skb);
745 sk->ack_backlog++;
746 tcp_statistics.TcpOutSegs++;
747 }
748
749 /*
750 * This routine sends an ack and also updates the window.
751 */
752
753 void tcp_send_ack(u32 sequence, u32 ack,
/* */
754 struct sock *sk,
755 struct tcphdr *th, u32 daddr)
756 {
757 struct sk_buff *buff;
758 struct tcphdr *t1;
759 struct device *dev = NULL;
760 int tmp;
761
762 if(sk->zapped)
763 return; /* We have been reset, we may not send again */
764
765 /*
766 * We need to grab some memory, and put together an ack,
767 * and then put it into the queue to be sent.
768 */
769
770 buff = sock_wmalloc(sk, MAX_ACK_SIZE, 1, GFP_ATOMIC);
771 if (buff == NULL)
772 {
773 /*
774 * Force it to send an ack. We don't have to do this
775 * (ACK is unreliable) but it's much better use of
776 * bandwidth on slow links to send a spare ack than
777 * resend packets.
778 */
779
780 sk->ack_backlog++;
781 if (sk->ip_xmit_timeout != TIME_WRITE && tcp_connected(sk->state))
782 {
783 tcp_reset_xmit_timer(sk, TIME_WRITE, HZ);
784 }
785 return;
786 }
787
788 /*
789 * Assemble a suitable TCP frame
790 */
791
792 buff->sk = sk;
793 buff->localroute = sk->localroute;
794 buff->csum = 0;
795
796 /*
797 * Put in the IP header and routing stuff.
798 */
799
800 tmp = sk->prot->build_header(buff, sk->saddr, daddr, &dev,
801 IPPROTO_TCP, sk->opt, MAX_ACK_SIZE,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
802 if (tmp < 0)
803 {
804 buff->free = 1;
805 sock_wfree(sk, buff);
806 return;
807 }
808 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
809
810 memcpy(t1, &sk->dummy_th, sizeof(*t1));
811
812 /*
813 * Swap the send and the receive.
814 */
815
816 t1->dest = th->source;
817 t1->source = th->dest;
818 t1->seq = ntohl(sequence);
819 sk->window = tcp_select_window(sk);
820 t1->window = ntohs(sk->window);
821
822 /*
823 * If we have nothing queued for transmit and the transmit timer
824 * is on we are just doing an ACK timeout and need to switch
825 * to a keepalive.
826 */
827
828 if (ack == sk->acked_seq) {
829 sk->ack_backlog = 0;
830 sk->bytes_rcv = 0;
831 sk->ack_timed = 0;
832
833 if (sk->send_head == NULL && skb_peek(&sk->write_queue) == NULL
834 && sk->ip_xmit_timeout == TIME_WRITE)
835 if(sk->keepopen)
836 tcp_reset_xmit_timer(sk,TIME_KEEPOPEN,TCP_TIMEOUT_LEN);
837 else
838 delete_timer(sk);
839 }
840
841 /*
842 * Fill in the packet and send it
843 */
844
845 t1->ack_seq = htonl(ack);
846 tcp_send_check(t1, sk->saddr, daddr, sizeof(*t1), buff);
847 if (sk->debug)
848 printk("\rtcp_ack: seq %x ack %x\n", sequence, ack);
849 sk->prot->queue_xmit(sk, dev, buff, 1);
850 tcp_statistics.TcpOutSegs++;
851 }
852
853 /*
854 * This routine sends a packet with an out of date sequence
855 * number. It assumes the other end will try to ack it.
856 */
857
858 void tcp_write_wakeup(struct sock *sk)
/* */
859 {
860 struct sk_buff *buff,*skb;
861 struct tcphdr *t1;
862 struct device *dev=NULL;
863 int tmp;
864
865 if (sk->zapped)
866 return; /* After a valid reset we can send no more */
867
868 /*
869 * Write data can still be transmitted/retransmitted in the
870 * following states. If any other state is encountered, return.
871 * [listen/close will never occur here anyway]
872 */
873
874 if (sk->state != TCP_ESTABLISHED &&
875 sk->state != TCP_CLOSE_WAIT &&
876 sk->state != TCP_FIN_WAIT1 &&
877 sk->state != TCP_LAST_ACK &&
878 sk->state != TCP_CLOSING
879 )
880 {
881 return;
882 }
883 if ( before(sk->sent_seq, sk->window_seq) &&
884 (skb=skb_peek(&sk->write_queue)))
885 {
886 /*
887 * We are probing the opening of a window
888 * but the window size is != 0
889 * must have been a result SWS advoidance ( sender )
890 */
891
892 struct iphdr *iph;
893 struct tcphdr *th;
894 struct tcphdr *nth;
895 unsigned long win_size;
896 #if 0
897 unsigned long ow_size;
898 #endif
899
900 /*
901 * How many bytes can we send ?
902 */
903
904 win_size = sk->window_seq - sk->sent_seq;
905
906 /*
907 * Recover the buffer pointers
908 */
909
910 iph = (struct iphdr *)skb->ip_hdr;
911 th = (struct tcphdr *)(((char *)iph) +(iph->ihl << 2));
912
913 /*
914 * Grab the data for a temporary frame
915 */
916
917 buff = sock_wmalloc(sk, win_size + th->doff * 4 +
918 (iph->ihl << 2) +
919 sk->prot->max_header + 15,
920 1, GFP_ATOMIC);
921 if ( buff == NULL )
922 return;
923
924 /*
925 * If we strip the packet on the write queue we must
926 * be ready to retransmit this one
927 */
928
929 buff->free = /*0*/1;
930
931 buff->sk = sk;
932 buff->localroute = sk->localroute;
933
934 /*
935 * Put headers on the new packet
936 */
937
938 tmp = sk->prot->build_header(buff, sk->saddr, sk->daddr, &dev,
939 IPPROTO_TCP, sk->opt, buff->truesize,
940 sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
941 if (tmp < 0)
942 {
943 sock_wfree(sk, buff);
944 return;
945 }
946
947 /*
948 * Move the TCP header over
949 */
950
951 buff->dev = dev;
952
953 nth = (struct tcphdr *) skb_put(buff,sizeof(*th));
954
955 memcpy(nth, th, sizeof(*th));
956
957 /*
958 * Correct the new header
959 */
960
961 nth->ack = 1;
962 nth->ack_seq = htonl(sk->acked_seq);
963 nth->window = htons(tcp_select_window(sk));
964 nth->check = 0;
965
966 /*
967 * Copy TCP options and data start to our new buffer
968 */
969
970 buff->csum = csum_partial_copy((void *)(th + 1), skb_put(buff,win_size),
971 win_size + th->doff*4 - sizeof(*th), 0);
972
973 /*
974 * Remember our right edge sequence number.
975 */
976
977 buff->end_seq = sk->sent_seq + win_size;
978 sk->sent_seq = buff->end_seq; /* Hack */
979 if(th->urg && ntohs(th->urg_ptr) < win_size)
980 nth->urg = 0;
981
982 /*
983 * Checksum the split buffer
984 */
985
986 tcp_send_check(nth, sk->saddr, sk->daddr,
987 nth->doff * 4 + win_size , buff);
988 }
989 else
990 {
991 buff = sock_wmalloc(sk,MAX_ACK_SIZE,1, GFP_ATOMIC);
992 if (buff == NULL)
993 return;
994
995 buff->free = 1;
996 buff->sk = sk;
997 buff->localroute = sk->localroute;
998 buff->csum = 0;
999
1000 /*
1001 * Put in the IP header and routing stuff.
1002 */
1003
1004 tmp = sk->prot->build_header(buff, sk->saddr, sk->daddr, &dev,
1005 IPPROTO_TCP, sk->opt, MAX_ACK_SIZE,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
1006 if (tmp < 0)
1007 {
1008 sock_wfree(sk, buff);
1009 return;
1010 }
1011
1012 t1 = (struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
1013 memcpy(t1,(void *) &sk->dummy_th, sizeof(*t1));
1014
1015 /*
1016 * Use a previous sequence.
1017 * This should cause the other end to send an ack.
1018 */
1019
1020 t1->seq = htonl(sk->sent_seq-1);
1021 /* t1->fin = 0; -- We are sending a 'previous' sequence, and 0 bytes of data - thus no FIN bit */
1022 t1->ack_seq = htonl(sk->acked_seq);
1023 t1->window = htons(tcp_select_window(sk));
1024 tcp_send_check(t1, sk->saddr, sk->daddr, sizeof(*t1), buff);
1025
1026 }
1027
1028 /*
1029 * Send it.
1030 */
1031
1032 sk->prot->queue_xmit(sk, dev, buff, 1);
1033 tcp_statistics.TcpOutSegs++;
1034 }
1035
1036 /*
1037 * A window probe timeout has occurred.
1038 */
1039
1040 void tcp_send_probe0(struct sock *sk)
/* ![[last]](../icons/n_last.png)
*/
1041 {
1042 if (sk->zapped)
1043 return; /* After a valid reset we can send no more */
1044
1045 tcp_write_wakeup(sk);
1046
1047 sk->backoff++;
1048 sk->rto = min(sk->rto << 1, 120*HZ);
1049 sk->retransmits++;
1050 sk->prot->retransmits ++;
1051 tcp_reset_xmit_timer (sk, TIME_PROBE0, sk->rto);
1052 }
![[bottom]](../icons/n_bottom.png){kind=icon}
*/