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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.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 * Fixes:
23 * Alan Cox : Numerous verify_area() calls
24 * Alan Cox : Set the ACK bit on a reset
25 * Alan Cox : Stopped it crashing if it closed while
26 * sk->inuse=1 and was trying to connect
27 * (tcp_err()).
28 * Alan Cox : All icmp error handling was broken
29 * pointers passed where wrong and the
30 * socket was looked up backwards. Nobody
31 * tested any icmp error code obviously.
32 * Alan Cox : tcp_err() now handled properly. It
33 * wakes people on errors. select
34 * behaves and the icmp error race
35 * has gone by moving it into sock.c
36 * Alan Cox : tcp_reset() fixed to work for
37 * everything not just packets for
38 * unknown sockets.
39 * Alan Cox : tcp option processing.
40 * Alan Cox : Reset tweaked (still not 100%) [Had
41 * syn rule wrong]
42 * Herp Rosmanith : More reset fixes
43 * Alan Cox : No longer acks invalid rst frames.
44 * Acking any kind of RST is right out.
45 * Alan Cox : Sets an ignore me flag on an rst
46 * receive otherwise odd bits of prattle
47 * escape still
48 * Alan Cox : Fixed another acking RST frame bug.
49 * Should stop LAN workplace lockups.
50 * Alan Cox : Some tidyups using the new skb list
51 * facilities
52 * Alan Cox : sk->keepopen now seems to work
53 * Alan Cox : Pulls options out correctly on accepts
54 * Alan Cox : Fixed assorted sk->rqueue->next errors
55 * Alan Cox : PSH doesn't end a TCP read. Switched a
56 * bit to skb ops.
57 * Alan Cox : Tidied tcp_data to avoid a potential
58 * nasty.
59 * Alan Cox : Added some better commenting, as the
60 * tcp is hard to follow
61 * Alan Cox : Removed incorrect check for 20 * psh
62 * Michael O'Reilly : ack < copied bug fix.
63 * Johannes Stille : Misc tcp fixes (not all in yet).
64 * Alan Cox : FIN with no memory -> CRASH
65 * Alan Cox : Added socket option proto entries.
66 * Also added awareness of them to accept.
67 * Alan Cox : Added TCP options (SOL_TCP)
68 * Alan Cox : Switched wakeup calls to callbacks,
69 * so the kernel can layer network
70 * sockets.
71 * Alan Cox : Use ip_tos/ip_ttl settings.
72 * Alan Cox : Handle FIN (more) properly (we hope).
73 * Alan Cox : RST frames sent on unsynchronised
74 * state ack error.
75 * Alan Cox : Put in missing check for SYN bit.
76 * Alan Cox : Added tcp_select_window() aka NET2E
77 * window non shrink trick.
78 * Alan Cox : Added a couple of small NET2E timer
79 * fixes
80 * Charles Hedrick : TCP fixes
81 * Toomas Tamm : TCP window fixes
82 * Alan Cox : Small URG fix to rlogin ^C ack fight
83 * Charles Hedrick : Rewrote most of it to actually work
84 * Linus : Rewrote tcp_read() and URG handling
85 * completely
86 * Gerhard Koerting: Fixed some missing timer handling
87 * Matthew Dillon : Reworked TCP machine states as per RFC
88 * Gerhard Koerting: PC/TCP workarounds
89 * Adam Caldwell : Assorted timer/timing errors
90 * Matthew Dillon : Fixed another RST bug
91 * Alan Cox : Move to kernel side addressing changes.
92 * Alan Cox : Beginning work on TCP fastpathing
93 * (not yet usable)
94 * Arnt Gulbrandsen: Turbocharged tcp_check() routine.
95 * Alan Cox : TCP fast path debugging
96 * Alan Cox : Window clamping
97 * Michael Riepe : Bug in tcp_check()
98 * Matt Dillon : More TCP improvements and RST bug fixes
99 * Matt Dillon : Yet more small nasties remove from the
100 * TCP code (Be very nice to this man if
101 * tcp finally works 100%) 8)
102 * Alan Cox : BSD accept semantics.
103 * Alan Cox : Reset on closedown bug.
104 * Peter De Schrijver : ENOTCONN check missing in tcp_sendto().
105 * Michael Pall : Handle select() after URG properly in
106 * all cases.
107 * Michael Pall : Undo the last fix in tcp_read_urg()
108 * (multi URG PUSH broke rlogin).
109 * Michael Pall : Fix the multi URG PUSH problem in
110 * tcp_readable(), select() after URG
111 * works now.
112 * Michael Pall : recv(...,MSG_OOB) never blocks in the
113 * BSD api.
114 * Alan Cox : Changed the semantics of sk->socket to
115 * fix a race and a signal problem with
116 * accept() and async I/O.
117 * Alan Cox : Relaxed the rules on tcp_sendto().
118 * Yury Shevchuk : Really fixed accept() blocking problem.
119 * Craig I. Hagan : Allow for BSD compatible TIME_WAIT for
120 * clients/servers which listen in on
121 * fixed ports.
122 * Alan Cox : Cleaned the above up and shrank it to
123 * a sensible code size.
124 * Alan Cox : Self connect lockup fix.
125 * Alan Cox : No connect to multicast.
126 * Ross Biro : Close unaccepted children on master
127 * socket close.
128 * Alan Cox : Reset tracing code.
129 * Alan Cox : Spurious resets on shutdown.
130 * Alan Cox : Giant 15 minute/60 second timer error
131 * Alan Cox : Small whoops in selecting before an
132 * accept.
133 * Alan Cox : Kept the state trace facility since
134 * it's handy for debugging.
135 * Alan Cox : More reset handler fixes.
136 * Alan Cox : Started rewriting the code based on
137 * the RFC's for other useful protocol
138 * references see: Comer, KA9Q NOS, and
139 * for a reference on the difference
140 * between specifications and how BSD
141 * works see the 4.4lite source.
142 * A.N.Kuznetsov : Don't time wait on completion of tidy
143 * close.
144 * Linus Torvalds : Fin/Shutdown & copied_seq changes.
145 * Linus Torvalds : Fixed BSD port reuse to work first syn
146 * Alan Cox : Reimplemented timers as per the RFC
147 * and using multiple timers for sanity.
148 * Alan Cox : Small bug fixes, and a lot of new
149 * comments.
150 * Alan Cox : Fixed dual reader crash by locking
151 * the buffers (much like datagram.c)
152 * Alan Cox : Fixed stuck sockets in probe. A probe
153 * now gets fed up of retrying without
154 * (even a no space) answer.
155 * Alan Cox : Extracted closing code better
156 * Alan Cox : Fixed the closing state machine to
157 * resemble the RFC.
158 * Alan Cox : More 'per spec' fixes.
159 * Jorge Cwik : Even faster checksumming.
160 * Alan Cox : tcp_data() doesn't ack illegal PSH
161 * only frames. At least one pc tcp stack
162 * generates them.
163 * Alan Cox : Cache last socket.
164 * Alan Cox : Per route irtt.
165 * Matt Day : Select() match BSD precisely on error
166 * Alan Cox : New buffers
167 * Marc Tamsky : Various sk->prot->retransmits and
168 * sk->retransmits misupdating fixed.
169 * Fixed tcp_write_timeout: stuck close,
170 * and TCP syn retries gets used now.
171 * Mark Yarvis : In tcp_read_wakeup(), don't send an
172 * ack if stat is TCP_CLOSED.
173 * Alan Cox : Look up device on a retransmit - routes may
174 * change. Doesn't yet cope with MSS shrink right
175 * but its a start!
176 * Marc Tamsky : Closing in closing fixes.
177 * Mike Shaver : RFC1122 verifications.
178 * Alan Cox : rcv_saddr errors.
179 * Alan Cox : Block double connect().
180 * Alan Cox : Small hooks for enSKIP.
181 * Alexey Kuznetsov: Path MTU discovery.
182 * Alan Cox : Support soft errors.
183 * Alan Cox : Fix MTU discovery pathalogical case
184 * when the remote claims no mtu!
185 * Marc Tamsky : TCP_CLOSE fix.
186 *
187 * To Fix:
188 * Fast path the code. Two things here - fix the window calculation
189 * so it doesn't iterate over the queue, also spot packets with no funny
190 * options arriving in order and process directly.
191 *
192 * Rewrite output state machine to use a single queue and do low window
193 * situations as per the spec (RFC 1122)
194 * Speed up input assembly algorithm.
195 * RFC1323 - PAWS and window scaling. PAWS is required for IPv6 so we
196 * could do with it working on IPv4
197 * User settable/learned rtt/max window/mtu
198 * Fix the window handling to use PR's new code.
199 *
200 * Change the fundamental structure to a single send queue maintained
201 * by TCP (removing the bogus ip stuff [thus fixing mtu drops on
202 * active routes too]). Cut the queue off in tcp_retransmit/
203 * tcp_transmit.
204 * Change the receive queue to assemble as it goes. This lets us
205 * dispose of most of tcp_sequence, half of tcp_ack and chunks of
206 * tcp_data/tcp_read as well as the window shrink crud.
207 * Separate out duplicated code - tcp_alloc_skb, tcp_build_ack
208 * tcp_queue_skb seem obvious routines to extract.
209 *
210 * This program is free software; you can redistribute it and/or
211 * modify it under the terms of the GNU General Public License
212 * as published by the Free Software Foundation; either version
213 * 2 of the License, or(at your option) any later version.
214 *
215 * Description of States:
216 *
217 * TCP_SYN_SENT sent a connection request, waiting for ack
218 *
219 * TCP_SYN_RECV received a connection request, sent ack,
220 * waiting for final ack in three-way handshake.
221 *
222 * TCP_ESTABLISHED connection established
223 *
224 * TCP_FIN_WAIT1 our side has shutdown, waiting to complete
225 * transmission of remaining buffered data
226 *
227 * TCP_FIN_WAIT2 all buffered data sent, waiting for remote
228 * to shutdown
229 *
230 * TCP_CLOSING both sides have shutdown but we still have
231 * data we have to finish sending
232 *
233 * TCP_TIME_WAIT timeout to catch resent junk before entering
234 * closed, can only be entered from FIN_WAIT2
235 * or CLOSING. Required because the other end
236 * may not have gotten our last ACK causing it
237 * to retransmit the data packet (which we ignore)
238 *
239 * TCP_CLOSE_WAIT remote side has shutdown and is waiting for
240 * us to finish writing our data and to shutdown
241 * (we have to close() to move on to LAST_ACK)
242 *
243 * TCP_LAST_ACK out side has shutdown after remote has
244 * shutdown. There may still be data in our
245 * buffer that we have to finish sending
246 *
247 * TCP_CLOSE socket is finished
248 */
249
250 /*
251 * RFC1122 status:
252 * NOTE: I'm not going to be doing comments in the code for this one except
253 * for violations and the like. tcp.c is just too big... If I say something
254 * "does?" or "doesn't?", it means I'm not sure, and will have to hash it out
255 * with Alan. -- MS 950903
256 *
257 * Use of PSH (4.2.2.2)
258 * MAY aggregate data sent without the PSH flag. (does)
259 * MAY queue data recieved without the PSH flag. (does)
260 * SHOULD collapse successive PSH flags when it packetizes data. (doesn't)
261 * MAY implement PSH on send calls. (doesn't, thus:)
262 * MUST NOT buffer data indefinitely (doesn't [1 second])
263 * MUST set PSH on last segment (does)
264 * MAY pass received PSH to application layer (doesn't)
265 * SHOULD send maximum-sized segment whenever possible. (almost always does)
266 *
267 * Window Size (4.2.2.3, 4.2.2.16)
268 * MUST treat window size as an unsigned number (does)
269 * SHOULD treat window size as a 32-bit number (does not)
270 * MUST NOT shrink window once it is offered (does not normally)
271 *
272 * Urgent Pointer (4.2.2.4)
273 * **MUST point urgent pointer to last byte of urgent data (not right
274 * after). (doesn't, to be like BSD)
275 * MUST inform application layer asynchronously of incoming urgent
276 * data. (does)
277 * MUST provide application with means of determining the amount of
278 * urgent data pending. (does)
279 * **MUST support urgent data sequence of arbitrary length. (doesn't, but
280 * it's sort of tricky to fix, as urg_ptr is a 16-bit quantity)
281 * [Follows BSD 1 byte of urgent data]
282 *
283 * TCP Options (4.2.2.5)
284 * MUST be able to recieve TCP options in any segment. (does)
285 * MUST ignore unsupported options (does)
286 *
287 * Maximum Segment Size Option (4.2.2.6)
288 * MUST implement both sending and receiving MSS. (does)
289 * SHOULD send an MSS with every SYN where recieve MSS != 536 (MAY send
290 * it always). (does, even when MSS == 536, which is legal)
291 * MUST assume MSS == 536 if no MSS received at connection setup (does)
292 * MUST calculate "effective send MSS" correctly:
293 * min(physical_MTU, remote_MSS+20) - sizeof(tcphdr) - sizeof(ipopts)
294 * (does - but allows operator override)
295 *
296 * TCP Checksum (4.2.2.7)
297 * MUST generate and check TCP checksum. (does)
298 *
299 * Initial Sequence Number Selection (4.2.2.8)
300 * MUST use the RFC 793 clock selection mechanism. (doesn't, but it's
301 * OK: RFC 793 specifies a 250KHz clock, while we use 1MHz, which is
302 * necessary for 10Mbps networks - and harder than BSD to spoof!)
303 *
304 * Simultaneous Open Attempts (4.2.2.10)
305 * MUST support simultaneous open attempts (does)
306 *
307 * Recovery from Old Duplicate SYN (4.2.2.11)
308 * MUST keep track of active vs. passive open (does)
309 *
310 * RST segment (4.2.2.12)
311 * SHOULD allow an RST segment to contain data (does, but doesn't do
312 * anything with it, which is standard)
313 *
314 * Closing a Connection (4.2.2.13)
315 * MUST inform application of whether connectin was closed by RST or
316 * normal close. (does)
317 * MAY allow "half-duplex" close (treat connection as closed for the
318 * local app, even before handshake is done). (does)
319 * MUST linger in TIME_WAIT for 2 * MSL (does)
320 *
321 * Retransmission Timeout (4.2.2.15)
322 * MUST implement Jacobson's slow start and congestion avoidance
323 * stuff. (does)
324 *
325 * Probing Zero Windows (4.2.2.17)
326 * MUST support probing of zero windows. (does)
327 * MAY keep offered window closed indefinitely. (does)
328 * MUST allow remote window to stay closed indefinitely. (does)
329 *
330 * Passive Open Calls (4.2.2.18)
331 * MUST NOT let new passive open affect other connections. (doesn't)
332 * MUST support passive opens (LISTENs) concurrently. (does)
333 *
334 * Time to Live (4.2.2.19)
335 * MUST make TCP TTL configurable. (does - IP_TTL option)
336 *
337 * Event Processing (4.2.2.20)
338 * SHOULD queue out-of-order segments. (does)
339 * MUST aggregate ACK segments whenever possible. (does but badly)
340 *
341 * Retransmission Timeout Calculation (4.2.3.1)
342 * MUST implement Karn's algorithm and Jacobson's algorithm for RTO
343 * calculation. (does, or at least explains them in the comments 8*b)
344 * SHOULD initialize RTO to 0 and RTT to 3. (does)
345 *
346 * When to Send an ACK Segment (4.2.3.2)
347 * SHOULD implement delayed ACK. (does not)
348 * MUST keep ACK delay < 0.5 sec. (N/A)
349 *
350 * When to Send a Window Update (4.2.3.3)
351 * MUST implement receiver-side SWS. (does)
352 *
353 * When to Send Data (4.2.3.4)
354 * MUST implement sender-side SWS. (does)
355 * SHOULD implement Nagle algorithm. (does)
356 *
357 * TCP Connection Failures (4.2.3.5)
358 * MUST handle excessive retransmissions "properly" (see the RFC). (does)
359 * SHOULD inform application layer of soft errors. (does)
360 *
361 * TCP Keep-Alives (4.2.3.6)
362 * MAY provide keep-alives. (does)
363 * MUST make keep-alives configurable on a per-connection basis. (does)
364 * MUST default to no keep-alives. (does)
365 * **MUST make keep-alive interval configurable. (doesn't)
366 * **MUST make default keep-alive interval > 2 hours. (doesn't)
367 * MUST NOT interpret failure to ACK keep-alive packet as dead
368 * connection. (doesn't)
369 * SHOULD send keep-alive with no data. (does)
370 *
371 * TCP Multihoming (4.2.3.7)
372 * MUST get source address from IP layer before sending first
373 * SYN. (does)
374 * MUST use same local address for all segments of a connection. (does)
375 *
376 * IP Options (4.2.3.8)
377 * MUST ignore unsupported IP options. (does)
378 * MAY support Time Stamp and Record Route. (does)
379 * MUST allow application to specify a source route. (does)
380 * MUST allow receieved Source Route option to set route for all future
381 * segments on this connection. (does not (security issues))
382 *
383 * ICMP messages (4.2.3.9)
384 * MUST act on ICMP errors. (does)
385 * MUST slow transmission upon receipt of a Source Quench. (does)
386 * MUST NOT abort connection upon receipt of soft Destination
387 * Unreachables (0, 1, 5), Time Exceededs and Parameter
388 * Problems. (doesn't)
389 * SHOULD report soft Destination Unreachables etc. to the
390 * application. (does)
391 * SHOULD abort connection upon receipt of hard Destination Unreachable
392 * messages (2, 3, 4). (does)
393 *
394 * Remote Address Validation (4.2.3.10)
395 * MUST reject as an error OPEN for invalid remote IP address. (does)
396 * MUST ignore SYN with invalid source address. (does)
397 * MUST silently discard incoming SYN for broadcast/multicast
398 * address. (does)
399 *
400 * Asynchronous Reports (4.2.4.1)
401 * **MUST provide mechanism for reporting soft errors to application
402 * layer. (doesn't)
403 *
404 * Type of Service (4.2.4.2)
405 * MUST allow application layer to set Type of Service. (does IP_TOS)
406 *
407 * (Whew. -- MS 950903)
408 **/
409
410 #include <linux/types.h>
411 #include <linux/sched.h>
412 #include <linux/mm.h>
413 #include <linux/time.h>
414 #include <linux/string.h>
415 #include <linux/config.h>
416 #include <linux/socket.h>
417 #include <linux/sockios.h>
418 #include <linux/termios.h>
419 #include <linux/in.h>
420 #include <linux/fcntl.h>
421 #include <linux/inet.h>
422 #include <linux/netdevice.h>
423 #include <net/snmp.h>
424 #include <net/ip.h>
425 #include <net/protocol.h>
426 #include <net/icmp.h>
427 #include <net/tcp.h>
428 #include <net/arp.h>
429 #include <linux/skbuff.h>
430 #include <net/sock.h>
431 #include <net/route.h>
432 #include <linux/errno.h>
433 #include <linux/timer.h>
434 #include <asm/system.h>
435 #include <asm/segment.h>
436 #include <linux/mm.h>
437 #include <net/checksum.h>
438
439 /*
440 * The MSL timer is the 'normal' timer.
441 */
442
443 #define reset_msl_timer(x,y,z) reset_timer(x,y,z)
444
445 #define SEQ_TICK 3
446 unsigned long seq_offset;
447 struct tcp_mib tcp_statistics;
448
449 /*
450 * Cached last hit socket
451 */
452
453 volatile unsigned long th_cache_saddr,th_cache_daddr;
454 volatile unsigned short th_cache_dport, th_cache_sport;
455 volatile struct sock *th_cache_sk;
456
457 void tcp_cache_zap(void)
/* ![[next]](../icons/right.png)
![[first]](../icons/n_first.png)
![[top]](../icons/top.png)
*/
458 {
459 unsigned long flags;
460 save_flags(flags);
461 cli();
462 th_cache_saddr=0;
463 th_cache_daddr=0;
464 th_cache_dport=0;
465 th_cache_sport=0;
466 th_cache_sk=NULL;
467 restore_flags(flags);
468 }
469
470 static void tcp_close(struct sock *sk, int timeout);
471
472
473 /*
474 * The less said about this the better, but it works and will do for 1.2
475 */
476
477 static struct wait_queue *master_select_wakeup;
478
479 static __inline__ int min(unsigned int a, unsigned int b)
/* ![[previous]](../icons/left.png)
*/
480 {
481 if (a < b)
482 return(a);
483 return(b);
484 }
485
486 #undef STATE_TRACE
487
488 #ifdef STATE_TRACE
489 static char *statename[]={
490 "Unused","Established","Syn Sent","Syn Recv",
491 "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
492 "Close Wait","Last ACK","Listen","Closing"
493 };
494 #endif
495
496 static __inline__ void tcp_set_state(struct sock *sk, int state)
/* */
497 {
498 if(sk->state==TCP_ESTABLISHED)
499 tcp_statistics.TcpCurrEstab--;
500 #ifdef STATE_TRACE
501 if(sk->debug)
502 printk("TCP sk=%p, State %s -> %s\n",sk, statename[sk->state],statename[state]);
503 #endif
504 /* This is a hack but it doesn't occur often and it's going to
505 be a real to fix nicely */
506
507 if(state==TCP_ESTABLISHED && sk->state==TCP_SYN_RECV)
508 {
509 wake_up_interruptible(&master_select_wakeup);
510 }
511 sk->state=state;
512 if(state==TCP_ESTABLISHED)
513 tcp_statistics.TcpCurrEstab++;
514 if(sk->state==TCP_CLOSE)
515 tcp_cache_zap();
516 }
517
518 /*
519 * This routine picks a TCP windows for a socket based on
520 * the following constraints
521 *
522 * 1. The window can never be shrunk once it is offered (RFC 793)
523 * 2. We limit memory per socket
524 *
525 * For now we use NET2E3's heuristic of offering half the memory
526 * we have handy. All is not as bad as this seems however because
527 * of two things. Firstly we will bin packets even within the window
528 * in order to get the data we are waiting for into the memory limit.
529 * Secondly we bin common duplicate forms at receive time
530 * Better heuristics welcome
531 */
532
533 int tcp_select_window(struct sock *sk)
/* */
534 {
535 int new_window = sock_rspace(sk);
536
537 if(sk->window_clamp)
538 new_window=min(sk->window_clamp,new_window);
539 /*
540 * Two things are going on here. First, we don't ever offer a
541 * window less than min(sk->mss, MAX_WINDOW/2). This is the
542 * receiver side of SWS as specified in RFC1122.
543 * Second, we always give them at least the window they
544 * had before, in order to avoid retracting window. This
545 * is technically allowed, but RFC1122 advises against it and
546 * in practice it causes trouble.
547 *
548 * Fixme: This doesn't correctly handle the case where
549 * new_window > sk->window but not by enough to allow for the
550 * shift in sequence space.
551 */
552 if (new_window < min(sk->mss, MAX_WINDOW/2) || new_window < sk->window)
553 return(sk->window);
554 return(new_window);
555 }
556
557 /*
558 * Find someone to 'accept'. Must be called with
559 * sk->inuse=1 or cli()
560 */
561
562 static struct sk_buff *tcp_find_established(struct sock *s)
/* */
563 {
564 struct sk_buff *p=skb_peek(&s->receive_queue);
565 if(p==NULL)
566 return NULL;
567 do
568 {
569 if(p->sk->state == TCP_ESTABLISHED || p->sk->state >= TCP_FIN_WAIT1)
570 return p;
571 p=p->next;
572 }
573 while(p!=(struct sk_buff *)&s->receive_queue);
574 return NULL;
575 }
576
577 /*
578 * Remove a completed connection and return it. This is used by
579 * tcp_accept() to get connections from the queue.
580 */
581
582 static struct sk_buff *tcp_dequeue_established(struct sock *s)
/* */
583 {
584 struct sk_buff *skb;
585 unsigned long flags;
586 save_flags(flags);
587 cli();
588 skb=tcp_find_established(s);
589 if(skb!=NULL)
590 skb_unlink(skb); /* Take it off the queue */
591 restore_flags(flags);
592 return skb;
593 }
594
595 /*
596 * This routine closes sockets which have been at least partially
597 * opened, but not yet accepted. Currently it is only called by
598 * tcp_close, and timeout mirrors the value there.
599 */
600
601 static void tcp_close_pending (struct sock *sk)
/* */
602 {
603 struct sk_buff *skb;
604
605 while ((skb = skb_dequeue(&sk->receive_queue)) != NULL)
606 {
607 skb->sk->dead=1;
608 tcp_close(skb->sk, 0);
609 kfree_skb(skb, FREE_READ);
610 }
611 return;
612 }
613
614 /*
615 * Enter the time wait state.
616 */
617
618 static void tcp_time_wait(struct sock *sk)
/* */
619 {
620 tcp_set_state(sk,TCP_TIME_WAIT);
621 sk->shutdown = SHUTDOWN_MASK;
622 if (!sk->dead)
623 sk->state_change(sk);
624 reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
625 }
626
627 /*
628 * A socket has timed out on its send queue and wants to do a
629 * little retransmitting. Currently this means TCP.
630 */
631
632 void tcp_do_retransmit(struct sock *sk, int all)
/* */
633 {
634 struct sk_buff * skb;
635 struct proto *prot;
636 struct device *dev;
637 int ct=0;
638 struct rtable *rt;
639
640 prot = sk->prot;
641 skb = sk->send_head;
642
643 while (skb != NULL)
644 {
645 struct tcphdr *th;
646 struct iphdr *iph;
647 int size;
648
649 dev = skb->dev;
650 IS_SKB(skb);
651 skb->when = jiffies;
652
653 /*
654 * Discard the surplus MAC header
655 */
656
657 skb_pull(skb,((unsigned char *)skb->ip_hdr)-skb->data);
658
659 /*
660 * In general it's OK just to use the old packet. However we
661 * need to use the current ack and window fields. Urg and
662 * urg_ptr could possibly stand to be updated as well, but we
663 * don't keep the necessary data. That shouldn't be a problem,
664 * if the other end is doing the right thing. Since we're
665 * changing the packet, we have to issue a new IP identifier.
666 */
667
668 iph = (struct iphdr *)skb->data;
669 th = (struct tcphdr *)(((char *)iph) + (iph->ihl << 2));
670 size = ntohs(iph->tot_len) - (iph->ihl<<2);
671
672 /*
673 * Note: We ought to check for window limits here but
674 * currently this is done (less efficiently) elsewhere.
675 */
676
677 /*
678 * Put a MAC header back on (may cause ARPing)
679 */
680
681 {
682 /* ANK: UGLY, but the bug, that was here, should be fixed.
683 */
684 struct options * opt = (struct options*)skb->proto_priv;
685 rt = ip_check_route(&sk->ip_route_cache, opt->srr?opt->faddr:iph->daddr, skb->localroute);
686 }
687
688 iph->id = htons(ip_id_count++);
689 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
690 if (rt && ntohs(iph->tot_len) > rt->rt_mtu)
691 iph->frag_off &= ~htons(IP_DF);
692 #endif
693 ip_send_check(iph);
694
695 if (rt==NULL) /* Deep poo */
696 {
697 if(skb->sk)
698 {
699 skb->sk->err_soft=ENETUNREACH;
700 skb->sk->error_report(skb->sk);
701 }
702 }
703 else
704 {
705 dev=rt->rt_dev;
706 skb->raddr=rt->rt_gateway;
707 skb->dev=dev;
708 skb->arp=1;
709 if (rt->rt_hh)
710 {
711 memcpy(skb_push(skb,dev->hard_header_len),rt->rt_hh->hh_data,dev->hard_header_len);
712 if (!rt->rt_hh->hh_uptodate)
713 {
714 skb->arp = 0;
715 #if RT_CACHE_DEBUG >= 2
716 printk("tcp_do_retransmit: hh miss %08x via %08x\n", iph->daddr, rt->rt_gateway);
717 #endif
718 }
719 }
720 else if (dev->hard_header)
721 {
722 if(dev->hard_header(skb, dev, ETH_P_IP, NULL, NULL, skb->len)<0)
723 skb->arp=0;
724 }
725
726 /*
727 * This is not the right way to handle this. We have to
728 * issue an up to date window and ack report with this
729 * retransmit to keep the odd buggy tcp that relies on
730 * the fact BSD does this happy.
731 * We don't however need to recalculate the entire
732 * checksum, so someone wanting a small problem to play
733 * with might like to implement RFC1141/RFC1624 and speed
734 * this up by avoiding a full checksum.
735 */
736
737 th->ack_seq = htonl(sk->acked_seq);
738 th->window = ntohs(tcp_select_window(sk));
739 tcp_send_check(th, sk->saddr, sk->daddr, size, sk);
740
741 /*
742 * If the interface is (still) up and running, kick it.
743 */
744
745 if (dev->flags & IFF_UP)
746 {
747 /*
748 * If the packet is still being sent by the device/protocol
749 * below then don't retransmit. This is both needed, and good -
750 * especially with connected mode AX.25 where it stops resends
751 * occurring of an as yet unsent anyway frame!
752 * We still add up the counts as the round trip time wants
753 * adjusting.
754 */
755 if (sk && !skb_device_locked(skb))
756 {
757 /* Remove it from any existing driver queue first! */
758 skb_unlink(skb);
759 /* Now queue it */
760 ip_statistics.IpOutRequests++;
761 dev_queue_xmit(skb, dev, sk->priority);
762 }
763 }
764 }
765
766 /*
767 * Count retransmissions
768 */
769
770 ct++;
771 sk->retransmits++;
772 sk->prot->retransmits ++;
773 tcp_statistics.TcpRetransSegs++;
774
775
776 /*
777 * Only one retransmit requested.
778 */
779
780 if (!all)
781 break;
782
783 /*
784 * This should cut it off before we send too many packets.
785 */
786
787 if (ct >= sk->cong_window)
788 break;
789 skb = skb->link3;
790 }
791 }
792
793 /*
794 * Reset the retransmission timer
795 */
796
797 static void reset_xmit_timer(struct sock *sk, int why, unsigned long when)
/* */
798 {
799 del_timer(&sk->retransmit_timer);
800 sk->ip_xmit_timeout = why;
801 if((int)when < 0)
802 {
803 when=3;
804 printk("Error: Negative timer in xmit_timer\n");
805 }
806 sk->retransmit_timer.expires=jiffies+when;
807 add_timer(&sk->retransmit_timer);
808 }
809
810 /*
811 * This is the normal code called for timeouts. It does the retransmission
812 * and then does backoff. tcp_do_retransmit is separated out because
813 * tcp_ack needs to send stuff from the retransmit queue without
814 * initiating a backoff.
815 */
816
817
818 void tcp_retransmit_time(struct sock *sk, int all)
/* */
819 {
820 tcp_do_retransmit(sk, all);
821
822 /*
823 * Increase the timeout each time we retransmit. Note that
824 * we do not increase the rtt estimate. rto is initialized
825 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
826 * that doubling rto each time is the least we can get away with.
827 * In KA9Q, Karn uses this for the first few times, and then
828 * goes to quadratic. netBSD doubles, but only goes up to *64,
829 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is
830 * defined in the protocol as the maximum possible RTT. I guess
831 * we'll have to use something other than TCP to talk to the
832 * University of Mars.
833 *
834 * PAWS allows us longer timeouts and large windows, so once
835 * implemented ftp to mars will work nicely. We will have to fix
836 * the 120 second clamps though!
837 */
838
839 sk->retransmits++;
840 sk->prot->retransmits++;
841 sk->backoff++;
842 sk->rto = min(sk->rto << 1, 120*HZ);
843 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
844 }
845
846
847 /*
848 * A timer event has trigger a tcp retransmit timeout. The
849 * socket xmit queue is ready and set up to send. Because
850 * the ack receive code keeps the queue straight we do
851 * nothing clever here.
852 */
853
854 static void tcp_retransmit(struct sock *sk, int all)
/* */
855 {
856 if (all)
857 {
858 tcp_retransmit_time(sk, all);
859 return;
860 }
861
862 sk->ssthresh = sk->cong_window >> 1; /* remember window where we lost */
863 /* sk->ssthresh in theory can be zero. I guess that's OK */
864 sk->cong_count = 0;
865
866 sk->cong_window = 1;
867
868 /* Do the actual retransmit. */
869 tcp_retransmit_time(sk, all);
870 }
871
872 /*
873 * A write timeout has occurred. Process the after effects.
874 */
875
876 static int tcp_write_timeout(struct sock *sk)
/* */
877 {
878 /*
879 * Look for a 'soft' timeout.
880 */
881 if ((sk->state == TCP_ESTABLISHED && sk->retransmits && !(sk->retransmits & 7))
882 || (sk->state != TCP_ESTABLISHED && sk->retransmits > TCP_RETR1))
883 {
884 /*
885 * Attempt to recover if arp has changed (unlikely!) or
886 * a route has shifted (not supported prior to 1.3).
887 */
888 ip_rt_advice(&sk->ip_route_cache, 0);
889 }
890
891 /*
892 * Have we tried to SYN too many times (repent repent 8))
893 */
894
895 if(sk->retransmits > TCP_SYN_RETRIES && sk->state==TCP_SYN_SENT)
896 {
897 if(sk->err_soft)
898 sk->err=sk->err_soft;
899 else
900 sk->err=ETIMEDOUT;
901 sk->error_report(sk);
902 del_timer(&sk->retransmit_timer);
903 tcp_statistics.TcpAttemptFails++; /* Is this right ??? - FIXME - */
904 tcp_set_state(sk,TCP_CLOSE);
905 /* Don't FIN, we got nothing back */
906 release_sock(sk);
907 return 0;
908 }
909 /*
910 * Has it gone just too far ?
911 */
912 if (sk->retransmits > TCP_RETR2)
913 {
914 if(sk->err_soft)
915 sk->err = sk->err_soft;
916 else
917 sk->err = ETIMEDOUT;
918 sk->error_report(sk);
919 del_timer(&sk->retransmit_timer);
920 /*
921 * Time wait the socket
922 */
923 if (sk->state == TCP_FIN_WAIT1 || sk->state == TCP_FIN_WAIT2 || sk->state == TCP_CLOSING )
924 {
925 tcp_set_state(sk,TCP_TIME_WAIT);
926 reset_msl_timer (sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
927 }
928 else
929 {
930 /*
931 * Clean up time.
932 */
933 tcp_set_state(sk, TCP_CLOSE);
934 release_sock(sk);
935 return 0;
936 }
937 }
938 return 1;
939 }
940
941 /*
942 * The TCP retransmit timer. This lacks a few small details.
943 *
944 * 1. An initial rtt timeout on the probe0 should cause what we can
945 * of the first write queue buffer to be split and sent.
946 * 2. On a 'major timeout' as defined by RFC1122 we shouldn't report
947 * ETIMEDOUT if we know an additional 'soft' error caused this.
948 * tcp_err should save a 'soft error' for us.
949 */
950
951 static void retransmit_timer(unsigned long data)
/* */
952 {
953 struct sock *sk = (struct sock*)data;
954 int why = sk->ip_xmit_timeout;
955
956 /*
957 * We are reset. We will send no more retransmits.
958 */
959
960 if(sk->zapped)
961 return;
962
963 /*
964 * Only process if socket is not in use
965 */
966
967 cli();
968 if (sk->inuse || in_bh)
969 {
970 /* Try again in 1 second */
971 sk->retransmit_timer.expires = jiffies+HZ;
972 add_timer(&sk->retransmit_timer);
973 sti();
974 return;
975 }
976
977 sk->inuse = 1;
978 sti();
979
980 /* Always see if we need to send an ack. */
981
982 if (sk->ack_backlog)
983 {
984 sk->prot->read_wakeup (sk);
985 if (! sk->dead)
986 sk->data_ready(sk,0);
987 }
988
989 /* Now we need to figure out why the socket was on the timer. */
990
991 switch (why)
992 {
993 /* Window probing */
994 case TIME_PROBE0:
995 tcp_send_probe0(sk);
996 tcp_write_timeout(sk);
997 break;
998 /* Retransmitting */
999 case TIME_WRITE:
1000 /* It could be we got here because we needed to send an ack.
1001 * So we need to check for that.
1002 */
1003 {
1004 struct sk_buff *skb;
1005 unsigned long flags;
1006
1007 save_flags(flags);
1008 cli();
1009 skb = sk->send_head;
1010 if (!skb)
1011 {
1012 restore_flags(flags);
1013 }
1014 else
1015 {
1016 /*
1017 * Kicked by a delayed ack. Reset timer
1018 * correctly now
1019 */
1020 if (jiffies < skb->when + sk->rto)
1021 {
1022 reset_xmit_timer (sk, TIME_WRITE, skb->when + sk->rto - jiffies);
1023 restore_flags(flags);
1024 break;
1025 }
1026 restore_flags(flags);
1027 /*
1028 * Retransmission
1029 */
1030 sk->retransmits++;
1031 sk->prot->retransmits++;
1032 sk->prot->retransmit (sk, 0);
1033 tcp_write_timeout(sk);
1034 }
1035 break;
1036 }
1037 /* Sending Keepalives */
1038 case TIME_KEEPOPEN:
1039 /*
1040 * this reset_timer() call is a hack, this is not
1041 * how KEEPOPEN is supposed to work.
1042 */
1043 reset_xmit_timer (sk, TIME_KEEPOPEN, TCP_TIMEOUT_LEN);
1044
1045 /* Send something to keep the connection open. */
1046 if (sk->prot->write_wakeup)
1047 sk->prot->write_wakeup (sk);
1048 sk->retransmits++;
1049 sk->prot->retransmits++;
1050 tcp_write_timeout(sk);
1051 break;
1052 default:
1053 printk ("rexmit_timer: timer expired - reason unknown\n");
1054 break;
1055 }
1056 release_sock(sk);
1057 }
1058
1059 /*
1060 * This routine is called by the ICMP module when it gets some
1061 * sort of error condition. If err < 0 then the socket should
1062 * be closed and the error returned to the user. If err > 0
1063 * it's just the icmp type << 8 | icmp code. After adjustment
1064 * header points to the first 8 bytes of the tcp header. We need
1065 * to find the appropriate port.
1066 */
1067
1068 void tcp_err(int type, int code, unsigned char *header, __u32 daddr,
/* */
1069 __u32 saddr, struct inet_protocol *protocol)
1070 {
1071 struct tcphdr *th = (struct tcphdr *)header;
1072 struct sock *sk;
1073
1074 /*
1075 * This one is _WRONG_. FIXME urgently.
1076 */
1077 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
1078 struct iphdr *iph=(struct iphdr *)(header-sizeof(struct iphdr));
1079 #endif
1080 th =(struct tcphdr *)header;
1081 sk = get_sock(&tcp_prot, th->source, daddr, th->dest, saddr);
1082
1083 if (sk == NULL)
1084 return;
1085
1086 if (type == ICMP_SOURCE_QUENCH)
1087 {
1088 /*
1089 * FIXME:
1090 * For now we will just trigger a linear backoff.
1091 * The slow start code should cause a real backoff here.
1092 */
1093 if (sk->cong_window > 4)
1094 sk->cong_window--;
1095 return;
1096 }
1097
1098 if (type == ICMP_PARAMETERPROB)
1099 {
1100 sk->err=EPROTO;
1101 sk->error_report(sk);
1102 }
1103
1104 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
1105 if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED)
1106 {
1107 struct rtable * rt;
1108 /*
1109 * Ugly trick to pass MTU to protocol layer.
1110 * Really we should add argument "info" to error handler.
1111 */
1112 unsigned short new_mtu = ntohs(iph->id);
1113
1114 if ((rt = sk->ip_route_cache) != NULL)
1115 if (rt->rt_mtu > new_mtu)
1116 rt->rt_mtu = new_mtu;
1117
1118 if (sk->mtu > new_mtu - sizeof(struct iphdr) - sizeof(struct tcphdr)
1119 && new_mtu > sizeof(struct iphdr)+sizeof(struct tcphdr))
1120 sk->mtu = new_mtu - sizeof(struct iphdr) - sizeof(struct tcphdr);
1121
1122 return;
1123 }
1124 #endif
1125
1126 /*
1127 * If we've already connected we will keep trying
1128 * until we time out, or the user gives up.
1129 */
1130
1131 if (code < 13)
1132 {
1133 if(icmp_err_convert[code].fatal || sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
1134 {
1135 sk->err = icmp_err_convert[code].errno;
1136 if (sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
1137 {
1138 tcp_statistics.TcpAttemptFails++;
1139 tcp_set_state(sk,TCP_CLOSE);
1140 sk->error_report(sk); /* Wake people up to see the error (see connect in sock.c) */
1141 }
1142 }
1143 else /* Only an error on timeout */
1144 sk->err_soft = icmp_err_convert[code].errno;
1145 }
1146 }
1147
1148
1149 /*
1150 * Walk down the receive queue counting readable data until we hit the end or we find a gap
1151 * in the received data queue (ie a frame missing that needs sending to us). Not
1152 * sorting using two queues as data arrives makes life so much harder.
1153 */
1154
1155 static int tcp_readable(struct sock *sk)
/* */
1156 {
1157 unsigned long counted;
1158 unsigned long amount;
1159 struct sk_buff *skb;
1160 int sum;
1161 unsigned long flags;
1162
1163 if(sk && sk->debug)
1164 printk("tcp_readable: %p - ",sk);
1165
1166 save_flags(flags);
1167 cli();
1168 if (sk == NULL || (skb = skb_peek(&sk->receive_queue)) == NULL)
1169 {
1170 restore_flags(flags);
1171 if(sk && sk->debug)
1172 printk("empty\n");
1173 return(0);
1174 }
1175
1176 counted = sk->copied_seq; /* Where we are at the moment */
1177 amount = 0;
1178
1179 /*
1180 * Do until a push or until we are out of data.
1181 */
1182
1183 do
1184 {
1185 if (before(counted, skb->seq)) /* Found a hole so stops here */
1186 break;
1187 sum = skb->len - (counted - skb->seq); /* Length - header but start from where we are up to (avoid overlaps) */
1188 if (skb->h.th->syn)
1189 sum++;
1190 if (sum > 0)
1191 { /* Add it up, move on */
1192 amount += sum;
1193 if (skb->h.th->syn)
1194 amount--;
1195 counted += sum;
1196 }
1197 /*
1198 * Don't count urg data ... but do it in the right place!
1199 * Consider: "old_data (ptr is here) URG PUSH data"
1200 * The old code would stop at the first push because
1201 * it counted the urg (amount==1) and then does amount--
1202 * *after* the loop. This means tcp_readable() always
1203 * returned zero if any URG PUSH was in the queue, even
1204 * though there was normal data available. If we subtract
1205 * the urg data right here, we even get it to work for more
1206 * than one URG PUSH skb without normal data.
1207 * This means that select() finally works now with urg data
1208 * in the queue. Note that rlogin was never affected
1209 * because it doesn't use select(); it uses two processes
1210 * and a blocking read(). And the queue scan in tcp_read()
1211 * was correct. Mike <pall@rz.uni-karlsruhe.de>
1212 */
1213 if (skb->h.th->urg)
1214 amount--; /* don't count urg data */
1215 if (amount && skb->h.th->psh) break;
1216 skb = skb->next;
1217 }
1218 while(skb != (struct sk_buff *)&sk->receive_queue);
1219
1220 restore_flags(flags);
1221 if(sk->debug)
1222 printk("got %lu bytes.\n",amount);
1223 return(amount);
1224 }
1225
1226 /*
1227 * LISTEN is a special case for select..
1228 */
1229 static int tcp_listen_select(struct sock *sk, int sel_type, select_table *wait)
/* */
1230 {
1231 if (sel_type == SEL_IN) {
1232 int retval;
1233
1234 sk->inuse = 1;
1235 retval = (tcp_find_established(sk) != NULL);
1236 release_sock(sk);
1237 if (!retval)
1238 select_wait(&master_select_wakeup,wait);
1239 return retval;
1240 }
1241 return 0;
1242 }
1243
1244
1245 /*
1246 * Wait for a TCP event.
1247 *
1248 * Note that we don't need to set "sk->inuse", as the upper select layers
1249 * take care of normal races (between the test and the event) and we don't
1250 * go look at any of the socket buffers directly.
1251 */
1252 static int tcp_select(struct sock *sk, int sel_type, select_table *wait)
/* */
1253 {
1254 if (sk->state == TCP_LISTEN)
1255 return tcp_listen_select(sk, sel_type, wait);
1256
1257 switch(sel_type) {
1258 case SEL_IN:
1259 if (sk->err)
1260 return 1;
1261 if (sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
1262 break;
1263
1264 if (sk->shutdown & RCV_SHUTDOWN)
1265 return 1;
1266
1267 if (sk->acked_seq == sk->copied_seq)
1268 break;
1269
1270 if (sk->urg_seq != sk->copied_seq ||
1271 sk->acked_seq != sk->copied_seq+1 ||
1272 sk->urginline || !sk->urg_data)
1273 return 1;
1274 break;
1275
1276 case SEL_OUT:
1277 if (sk->err)
1278 return 1;
1279 if (sk->shutdown & SEND_SHUTDOWN)
1280 return 0;
1281 if (sk->state == TCP_SYN_SENT || sk->state == TCP_SYN_RECV)
1282 break;
1283 /*
1284 * This is now right thanks to a small fix
1285 * by Matt Dillon.
1286 */
1287
1288 if (sock_wspace(sk) < sk->mtu+128+sk->prot->max_header)
1289 break;
1290 return 1;
1291
1292 case SEL_EX:
1293 if (sk->urg_data)
1294 return 1;
1295 break;
1296 }
1297 select_wait(sk->sleep, wait);
1298 return 0;
1299 }
1300
1301 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg)
/* */
1302 {
1303 int err;
1304 switch(cmd)
1305 {
1306
1307 case TIOCINQ:
1308 #ifdef FIXME /* FIXME: */
1309 case FIONREAD:
1310 #endif
1311 {
1312 unsigned long amount;
1313
1314 if (sk->state == TCP_LISTEN)
1315 return(-EINVAL);
1316
1317 sk->inuse = 1;
1318 amount = tcp_readable(sk);
1319 release_sock(sk);
1320 err=verify_area(VERIFY_WRITE,(void *)arg, sizeof(int));
1321 if(err)
1322 return err;
1323 put_user(amount, (int *)arg);
1324 return(0);
1325 }
1326 case SIOCATMARK:
1327 {
1328 int answ = sk->urg_data && sk->urg_seq == sk->copied_seq;
1329
1330 err = verify_area(VERIFY_WRITE,(void *) arg, sizeof(int));
1331 if (err)
1332 return err;
1333 put_user(answ,(int *) arg);
1334 return(0);
1335 }
1336 case TIOCOUTQ:
1337 {
1338 unsigned long amount;
1339
1340 if (sk->state == TCP_LISTEN) return(-EINVAL);
1341 amount = sock_wspace(sk);
1342 err=verify_area(VERIFY_WRITE,(void *)arg, sizeof(int));
1343 if(err)
1344 return err;
1345 put_user(amount, (int *)arg);
1346 return(0);
1347 }
1348 default:
1349 return(-EINVAL);
1350 }
1351 }
1352
1353
1354 /*
1355 * This routine computes a TCP checksum.
1356 *
1357 * Modified January 1995 from a go-faster DOS routine by
1358 * Jorge Cwik <jorge@laser.satlink.net>
1359 */
1360
1361 unsigned short tcp_check(struct tcphdr *th, int len,
/* */
1362 unsigned long saddr, unsigned long daddr, unsigned long base)
1363 {
1364 return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1365 }
1366
1367
1368
1369 void tcp_send_check(struct tcphdr *th, unsigned long saddr,
/* */
1370 unsigned long daddr, int len, struct sock *sk)
1371 {
1372 th->check = 0;
1373 th->check = tcp_check(th, len, saddr, daddr,
1374 csum_partial((char *)th,len,0));
1375 return;
1376 }
1377
1378 /*
1379 * This is the main buffer sending routine. We queue the buffer
1380 * having checked it is sane seeming.
1381 */
1382
1383 static void tcp_send_skb(struct sock *sk, struct sk_buff *skb)
/* */
1384 {
1385 int size;
1386 struct tcphdr * th = skb->h.th;
1387
1388 /*
1389 * length of packet (not counting length of pre-tcp headers)
1390 */
1391
1392 size = skb->len - ((unsigned char *) th - skb->data);
1393
1394 /*
1395 * Sanity check it..
1396 */
1397
1398 if (size < sizeof(struct tcphdr) || size > skb->len)
1399 {
1400 printk("tcp_send_skb: bad skb (skb = %p, data = %p, th = %p, len = %lu)\n",
1401 skb, skb->data, th, skb->len);
1402 kfree_skb(skb, FREE_WRITE);
1403 return;
1404 }
1405
1406 /*
1407 * If we have queued a header size packet.. (these crash a few
1408 * tcp stacks if ack is not set)
1409 */
1410
1411 if (size == sizeof(struct tcphdr))
1412 {
1413 /* If it's got a syn or fin it's notionally included in the size..*/
1414 if(!th->syn && !th->fin)
1415 {
1416 printk("tcp_send_skb: attempt to queue a bogon.\n");
1417 kfree_skb(skb,FREE_WRITE);
1418 return;
1419 }
1420 }
1421
1422 /*
1423 * Actual processing.
1424 */
1425
1426 tcp_statistics.TcpOutSegs++;
1427 skb->seq = ntohl(th->seq);
1428 skb->end_seq = skb->seq + size - 4*th->doff;
1429
1430 /*
1431 * We must queue if
1432 *
1433 * a) The right edge of this frame exceeds the window
1434 * b) We are retransmitting (Nagle's rule)
1435 * c) We have too many packets 'in flight'
1436 */
1437
1438 if (after(skb->end_seq, sk->window_seq) ||
1439 (sk->retransmits && sk->ip_xmit_timeout == TIME_WRITE) ||
1440 sk->packets_out >= sk->cong_window)
1441 {
1442 /* checksum will be supplied by tcp_write_xmit. So
1443 * we shouldn't need to set it at all. I'm being paranoid */
1444 th->check = 0;
1445 if (skb->next != NULL)
1446 {
1447 printk("tcp_send_partial: next != NULL\n");
1448 skb_unlink(skb);
1449 }
1450 skb_queue_tail(&sk->write_queue, skb);
1451
1452 /*
1453 * If we don't fit we have to start the zero window
1454 * probes. This is broken - we really need to do a partial
1455 * send _first_ (This is what causes the Cisco and PC/TCP
1456 * grief).
1457 */
1458
1459 if (before(sk->window_seq, sk->write_queue.next->end_seq) &&
1460 sk->send_head == NULL && sk->ack_backlog == 0)
1461 reset_xmit_timer(sk, TIME_PROBE0, sk->rto);
1462 }
1463 else
1464 {
1465 /*
1466 * This is going straight out
1467 */
1468
1469 th->ack_seq = htonl(sk->acked_seq);
1470 th->window = htons(tcp_select_window(sk));
1471
1472 tcp_send_check(th, sk->saddr, sk->daddr, size, sk);
1473
1474 sk->sent_seq = sk->write_seq;
1475
1476 /*
1477 * This is mad. The tcp retransmit queue is put together
1478 * by the ip layer. This causes half the problems with
1479 * unroutable FIN's and other things.
1480 */
1481
1482 sk->prot->queue_xmit(sk, skb->dev, skb, 0);
1483
1484 /*
1485 * Set for next retransmit based on expected ACK time.
1486 * FIXME: We set this every time which means our
1487 * retransmits are really about a window behind.
1488 */
1489
1490 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
1491 }
1492 }
1493
1494 /*
1495 * Locking problems lead us to a messy situation where we can have
1496 * multiple partially complete buffers queued up. This is really bad
1497 * as we don't want to be sending partial buffers. Fix this with
1498 * a semaphore or similar to lock tcp_write per socket.
1499 *
1500 * These routines are pretty self descriptive.
1501 */
1502
1503 struct sk_buff * tcp_dequeue_partial(struct sock * sk)
/* */
1504 {
1505 struct sk_buff * skb;
1506 unsigned long flags;
1507
1508 save_flags(flags);
1509 cli();
1510 skb = sk->partial;
1511 if (skb) {
1512 sk->partial = NULL;
1513 del_timer(&sk->partial_timer);
1514 }
1515 restore_flags(flags);
1516 return skb;
1517 }
1518
1519 /*
1520 * Empty the partial queue
1521 */
1522
1523 static void tcp_send_partial(struct sock *sk)
/* */
1524 {
1525 struct sk_buff *skb;
1526
1527 if (sk == NULL)
1528 return;
1529 while ((skb = tcp_dequeue_partial(sk)) != NULL)
1530 tcp_send_skb(sk, skb);
1531 }
1532
1533 /*
1534 * Queue a partial frame
1535 */
1536
1537 void tcp_enqueue_partial(struct sk_buff * skb, struct sock * sk)
/* */
1538 {
1539 struct sk_buff * tmp;
1540 unsigned long flags;
1541
1542 save_flags(flags);
1543 cli();
1544 tmp = sk->partial;
1545 if (tmp)
1546 del_timer(&sk->partial_timer);
1547 sk->partial = skb;
1548 init_timer(&sk->partial_timer);
1549 /*
1550 * Wait up to 1 second for the buffer to fill.
1551 */
1552 sk->partial_timer.expires = jiffies+HZ;
1553 sk->partial_timer.function = (void (*)(unsigned long)) tcp_send_partial;
1554 sk->partial_timer.data = (unsigned long) sk;
1555 add_timer(&sk->partial_timer);
1556 restore_flags(flags);
1557 if (tmp)
1558 tcp_send_skb(sk, tmp);
1559 }
1560
1561
1562 /*
1563 * This routine sends an ack and also updates the window.
1564 */
1565
1566 static void tcp_send_ack(u32 sequence, u32 ack,
/* */
1567 struct sock *sk,
1568 struct tcphdr *th, unsigned long daddr)
1569 {
1570 struct sk_buff *buff;
1571 struct tcphdr *t1;
1572 struct device *dev = NULL;
1573 int tmp;
1574
1575 if(sk->zapped)
1576 return; /* We have been reset, we may not send again */
1577
1578 /*
1579 * We need to grab some memory, and put together an ack,
1580 * and then put it into the queue to be sent.
1581 */
1582
1583 buff = sock_wmalloc(sk, MAX_ACK_SIZE, 1, GFP_ATOMIC);
1584 if (buff == NULL)
1585 {
1586 /*
1587 * Force it to send an ack. We don't have to do this
1588 * (ACK is unreliable) but it's much better use of
1589 * bandwidth on slow links to send a spare ack than
1590 * resend packets.
1591 */
1592
1593 sk->ack_backlog++;
1594 if (sk->ip_xmit_timeout != TIME_WRITE && tcp_connected(sk->state))
1595 {
1596 reset_xmit_timer(sk, TIME_WRITE, HZ);
1597 }
1598 return;
1599 }
1600
1601 /*
1602 * Assemble a suitable TCP frame
1603 */
1604
1605 buff->sk = sk;
1606 buff->localroute = sk->localroute;
1607
1608 /*
1609 * Put in the IP header and routing stuff.
1610 */
1611
1612 tmp = sk->prot->build_header(buff, sk->saddr, daddr, &dev,
1613 IPPROTO_TCP, sk->opt, MAX_ACK_SIZE,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
1614 if (tmp < 0)
1615 {
1616 buff->free = 1;
1617 sock_wfree(sk, buff);
1618 return;
1619 }
1620 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
1621
1622 memcpy(t1, th, sizeof(*t1));
1623
1624 /*
1625 * Swap the send and the receive.
1626 */
1627
1628 t1->dest = th->source;
1629 t1->source = th->dest;
1630 t1->seq = ntohl(sequence);
1631 t1->ack = 1;
1632 sk->window = tcp_select_window(sk);
1633 t1->window = ntohs(sk->window);
1634 t1->res1 = 0;
1635 t1->res2 = 0;
1636 t1->rst = 0;
1637 t1->urg = 0;
1638 t1->syn = 0;
1639 t1->psh = 0;
1640 t1->fin = 0;
1641
1642 /*
1643 * If we have nothing queued for transmit and the transmit timer
1644 * is on we are just doing an ACK timeout and need to switch
1645 * to a keepalive.
1646 */
1647
1648 if (ack == sk->acked_seq)
1649 {
1650 sk->ack_backlog = 0;
1651 sk->bytes_rcv = 0;
1652 sk->ack_timed = 0;
1653 if (sk->send_head == NULL && skb_peek(&sk->write_queue) == NULL
1654 && sk->ip_xmit_timeout == TIME_WRITE)
1655 {
1656 if(sk->keepopen) {
1657 reset_xmit_timer(sk,TIME_KEEPOPEN,TCP_TIMEOUT_LEN);
1658 } else {
1659 delete_timer(sk);
1660 }
1661 }
1662 }
1663
1664 /*
1665 * Fill in the packet and send it
1666 */
1667
1668 t1->ack_seq = htonl(ack);
1669 t1->doff = sizeof(*t1)/4;
1670 tcp_send_check(t1, sk->saddr, daddr, sizeof(*t1), sk);
1671 if (sk->debug)
1672 printk("\rtcp_ack: seq %x ack %x\n", sequence, ack);
1673 tcp_statistics.TcpOutSegs++;
1674 sk->prot->queue_xmit(sk, dev, buff, 1);
1675 }
1676
1677
1678 /*
1679 * This routine builds a generic TCP header.
1680 */
1681
1682 extern __inline int tcp_build_header(struct tcphdr *th, struct sock *sk, int push)
/* */
1683 {
1684
1685 memcpy(th,(void *) &(sk->dummy_th), sizeof(*th));
1686 th->seq = htonl(sk->write_seq);
1687 th->psh =(push == 0) ? 1 : 0;
1688 th->doff = sizeof(*th)/4;
1689 th->ack = 1;
1690 th->fin = 0;
1691 sk->ack_backlog = 0;
1692 sk->bytes_rcv = 0;
1693 sk->ack_timed = 0;
1694 th->ack_seq = htonl(sk->acked_seq);
1695 sk->window = tcp_select_window(sk);
1696 th->window = htons(sk->window);
1697
1698 return(sizeof(*th));
1699 }
1700
1701 /*
1702 * This routine copies from a user buffer into a socket,
1703 * and starts the transmit system.
1704 */
1705
1706 static int tcp_sendmsg(struct sock *sk, struct msghdr *msg,
/* */
1707 int len, int nonblock, int flags)
1708 {
1709 int copied = 0;
1710 int copy;
1711 int tmp;
1712 int seglen;
1713 int iovct=0;
1714 struct sk_buff *skb;
1715 struct sk_buff *send_tmp;
1716 struct proto *prot;
1717 struct device *dev = NULL;
1718 unsigned char *from;
1719
1720 /*
1721 * Do sanity checking for sendmsg/sendto/send
1722 */
1723
1724 if (flags & ~(MSG_OOB|MSG_DONTROUTE))
1725 return -EINVAL;
1726 if (msg->msg_name)
1727 {
1728 struct sockaddr_in *addr=(struct sockaddr_in *)msg->msg_name;
1729 if(sk->state == TCP_CLOSE)
1730 return -ENOTCONN;
1731 if (msg->msg_namelen < sizeof(*addr))
1732 return -EINVAL;
1733 if (addr->sin_family && addr->sin_family != AF_INET)
1734 return -EINVAL;
1735 if (addr->sin_port != sk->dummy_th.dest)
1736 return -EISCONN;
1737 if (addr->sin_addr.s_addr != sk->daddr)
1738 return -EISCONN;
1739 }
1740
1741 /*
1742 * Ok commence sending
1743 */
1744
1745 while(iovct<msg->msg_iovlen)
1746 {
1747 seglen=msg->msg_iov[iovct].iov_len;
1748 from=msg->msg_iov[iovct++].iov_base;
1749 sk->inuse=1;
1750 prot = sk->prot;
1751 while(seglen > 0)
1752 {
1753 if (sk->err)
1754 { /* Stop on an error */
1755 release_sock(sk);
1756 if (copied)
1757 return(copied);
1758 return sock_error(sk);
1759 }
1760
1761 /*
1762 * First thing we do is make sure that we are established.
1763 */
1764
1765 if (sk->shutdown & SEND_SHUTDOWN)
1766 {
1767 release_sock(sk);
1768 sk->err = EPIPE;
1769 if (copied)
1770 return(copied);
1771 sk->err = 0;
1772 return(-EPIPE);
1773 }
1774
1775 /*
1776 * Wait for a connection to finish.
1777 */
1778
1779 while(sk->state != TCP_ESTABLISHED && sk->state != TCP_CLOSE_WAIT)
1780 {
1781 if (sk->err)
1782 {
1783 release_sock(sk);
1784 if (copied)
1785 return(copied);
1786 return sock_error(sk);
1787 }
1788
1789 if (sk->state != TCP_SYN_SENT && sk->state != TCP_SYN_RECV)
1790 {
1791 release_sock(sk);
1792 if (copied)
1793 return(copied);
1794
1795 if (sk->err)
1796 return sock_error(sk);
1797
1798 if (sk->keepopen)
1799 {
1800 send_sig(SIGPIPE, current, 0);
1801 }
1802 return(-EPIPE);
1803 }
1804
1805 if (nonblock || copied)
1806 {
1807 release_sock(sk);
1808 if (copied)
1809 return(copied);
1810 return(-EAGAIN);
1811 }
1812
1813 release_sock(sk);
1814 cli();
1815
1816 if (sk->state != TCP_ESTABLISHED &&
1817 sk->state != TCP_CLOSE_WAIT && sk->err == 0)
1818 {
1819 interruptible_sleep_on(sk->sleep);
1820 if (current->signal & ~current->blocked)
1821 {
1822 sti();
1823 if (copied)
1824 return(copied);
1825 return(-ERESTARTSYS);
1826 }
1827 }
1828 sk->inuse = 1;
1829 sti();
1830 }
1831
1832 /*
1833 * The following code can result in copy <= if sk->mss is ever
1834 * decreased. It shouldn't be. sk->mss is min(sk->mtu, sk->max_window).
1835 * sk->mtu is constant once SYN processing is finished. I.e. we
1836 * had better not get here until we've seen his SYN and at least one
1837 * valid ack. (The SYN sets sk->mtu and the ack sets sk->max_window.)
1838 * But ESTABLISHED should guarantee that. sk->max_window is by definition
1839 * non-decreasing. Note that any ioctl to set user_mss must be done
1840 * before the exchange of SYN's. If the initial ack from the other
1841 * end has a window of 0, max_window and thus mss will both be 0.
1842 */
1843
1844 /*
1845 * Now we need to check if we have a half built packet.
1846 */
1847 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
1848 /*
1849 * FIXME: I'm almost sure that this fragment is BUG,
1850 * but it works... I do not know why 8) --ANK
1851 *
1852 * Really, we should rebuild all the queues...
1853 * It's difficult. Temprorary hack is to send all
1854 * queued segments with allowed fragmentation.
1855 */
1856 {
1857 int new_mss = min(sk->mtu, sk->max_window);
1858 if (new_mss < sk->mss)
1859 {
1860 tcp_send_partial(sk);
1861 sk->mss = new_mss;
1862 }
1863 }
1864 #endif
1865
1866 if ((skb = tcp_dequeue_partial(sk)) != NULL)
1867 {
1868 int hdrlen;
1869
1870 /* IP header + TCP header */
1871 hdrlen = ((unsigned long)skb->h.th - (unsigned long)skb->data)
1872 + sizeof(struct tcphdr);
1873
1874 /* Add more stuff to the end of skb->len */
1875 if (!(flags & MSG_OOB))
1876 {
1877 copy = min(sk->mss - (skb->len - hdrlen), seglen);
1878 if (copy <= 0)
1879 {
1880 printk("TCP: **bug**: \"copy\" <= 0\n");
1881 return -EFAULT;
1882 }
1883 memcpy_fromfs(skb_put(skb,copy), from, copy);
1884 from += copy;
1885 copied += copy;
1886 len -= copy;
1887 sk->write_seq += copy;
1888 seglen -= copy;
1889 }
1890 if ((skb->len - hdrlen) >= sk->mss ||
1891 (flags & MSG_OOB) || !sk->packets_out)
1892 tcp_send_skb(sk, skb);
1893 else
1894 tcp_enqueue_partial(skb, sk);
1895 continue;
1896 }
1897
1898 /*
1899 * We also need to worry about the window.
1900 * If window < 1/2 the maximum window we've seen from this
1901 * host, don't use it. This is sender side
1902 * silly window prevention, as specified in RFC1122.
1903 * (Note that this is different than earlier versions of
1904 * SWS prevention, e.g. RFC813.). What we actually do is
1905 * use the whole MSS. Since the results in the right
1906 * edge of the packet being outside the window, it will
1907 * be queued for later rather than sent.
1908 */
1909
1910 copy = sk->window_seq - sk->write_seq;
1911 if (copy <= 0 || copy < (sk->max_window >> 1) || copy > sk->mss)
1912 copy = sk->mss;
1913 if (copy > seglen)
1914 copy = seglen;
1915
1916 /*
1917 * We should really check the window here also.
1918 */
1919
1920 send_tmp = NULL;
1921 if (copy < sk->mss && !(flags & MSG_OOB))
1922 {
1923 /*
1924 * We will release the socket in case we sleep here.
1925 */
1926 release_sock(sk);
1927 /*
1928 * NB: following must be mtu, because mss can be increased.
1929 * mss is always <= mtu
1930 */
1931 skb = sock_wmalloc(sk, sk->mtu + 128 + prot->max_header + 15, 0, GFP_KERNEL);
1932 sk->inuse = 1;
1933 send_tmp = skb;
1934 }
1935 else
1936 {
1937 /*
1938 * We will release the socket in case we sleep here.
1939 */
1940 release_sock(sk);
1941 skb = sock_wmalloc(sk, copy + prot->max_header + 15 , 0, GFP_KERNEL);
1942 sk->inuse = 1;
1943 }
1944
1945 /*
1946 * If we didn't get any memory, we need to sleep.
1947 */
1948
1949 if (skb == NULL)
1950 {
1951 sk->socket->flags |= SO_NOSPACE;
1952 if (nonblock)
1953 {
1954 release_sock(sk);
1955 if (copied)
1956 return(copied);
1957 return(-EAGAIN);
1958 }
1959
1960 /*
1961 * FIXME: here is another race condition.
1962 */
1963
1964 tmp = sk->wmem_alloc;
1965 release_sock(sk);
1966 cli();
1967 /*
1968 * Again we will try to avoid it.
1969 */
1970 if (tmp <= sk->wmem_alloc &&
1971 (sk->state == TCP_ESTABLISHED||sk->state == TCP_CLOSE_WAIT)
1972 && sk->err == 0)
1973 {
1974 sk->socket->flags &= ~SO_NOSPACE;
1975 interruptible_sleep_on(sk->sleep);
1976 if (current->signal & ~current->blocked)
1977 {
1978 sti();
1979 if (copied)
1980 return(copied);
1981 return(-ERESTARTSYS);
1982 }
1983 }
1984 sk->inuse = 1;
1985 sti();
1986 continue;
1987 }
1988
1989 skb->sk = sk;
1990 skb->free = 0;
1991 skb->localroute = sk->localroute|(flags&MSG_DONTROUTE);
1992
1993 /*
1994 * FIXME: we need to optimize this.
1995 * Perhaps some hints here would be good.
1996 */
1997
1998 tmp = prot->build_header(skb, sk->saddr, sk->daddr, &dev,
1999 IPPROTO_TCP, sk->opt, skb->truesize,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
2000 if (tmp < 0 )
2001 {
2002 sock_wfree(sk, skb);
2003 release_sock(sk);
2004 if (copied)
2005 return(copied);
2006 return(tmp);
2007 }
2008 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
2009 skb->ip_hdr->frag_off |= htons(IP_DF);
2010 #endif
2011 skb->dev = dev;
2012 skb->h.th =(struct tcphdr *)skb_put(skb,sizeof(struct tcphdr));
2013 tmp = tcp_build_header(skb->h.th, sk, seglen-copy);
2014 if (tmp < 0)
2015 {
2016 sock_wfree(sk, skb);
2017 release_sock(sk);
2018 if (copied)
2019 return(copied);
2020 return(tmp);
2021 }
2022
2023 if (flags & MSG_OOB)
2024 {
2025 skb->h.th->urg = 1;
2026 skb->h.th->urg_ptr = ntohs(copy);
2027 }
2028
2029 memcpy_fromfs(skb_put(skb,copy), from, copy);
2030
2031 from += copy;
2032 copied += copy;
2033 len -= copy;
2034 seglen -= copy;
2035 skb->free = 0;
2036 sk->write_seq += copy;
2037
2038 if (send_tmp != NULL && sk->packets_out)
2039 {
2040 tcp_enqueue_partial(send_tmp, sk);
2041 continue;
2042 }
2043 tcp_send_skb(sk, skb);
2044 }
2045 }
2046 sk->err = 0;
2047
2048 /*
2049 * Nagle's rule. Turn Nagle off with TCP_NODELAY for highly
2050 * interactive fast network servers. It's meant to be on and
2051 * it really improves the throughput though not the echo time
2052 * on my slow slip link - Alan
2053 */
2054
2055 /*
2056 * Avoid possible race on send_tmp - c/o Johannes Stille
2057 */
2058
2059 if(sk->partial && ((!sk->packets_out)
2060 /* If not nagling we can send on the before case too.. */
2061 || (sk->nonagle && before(sk->write_seq , sk->window_seq))
2062 ))
2063 tcp_send_partial(sk);
2064
2065 release_sock(sk);
2066 return(copied);
2067 }
2068
2069 /*
2070 * Send an ack if one is backlogged at this point. Ought to merge
2071 * this with tcp_send_ack().
2072 */
2073
2074 static void tcp_read_wakeup(struct sock *sk)
/* */
2075 {
2076 int tmp;
2077 struct device *dev = NULL;
2078 struct tcphdr *t1;
2079 struct sk_buff *buff;
2080
2081 if (!sk->ack_backlog)
2082 return;
2083
2084 /*
2085 * If we're closed, don't send an ack, or we'll get a RST
2086 * from the closed destination.
2087 */
2088 if ((sk->state == TCP_CLOSE) || (sk->state == TCP_TIME_WAIT))
2089 return;
2090
2091 /*
2092 * FIXME: we need to put code here to prevent this routine from
2093 * being called. Being called once in a while is ok, so only check
2094 * if this is the second time in a row.
2095 */
2096
2097 /*
2098 * We need to grab some memory, and put together an ack,
2099 * and then put it into the queue to be sent.
2100 */
2101
2102 buff = sock_wmalloc(sk,MAX_ACK_SIZE,1, GFP_ATOMIC);
2103 if (buff == NULL)
2104 {
2105 /* Try again real soon. */
2106 reset_xmit_timer(sk, TIME_WRITE, HZ);
2107 return;
2108 }
2109
2110 buff->sk = sk;
2111 buff->localroute = sk->localroute;
2112
2113 /*
2114 * Put in the IP header and routing stuff.
2115 */
2116
2117 tmp = sk->prot->build_header(buff, sk->saddr, sk->daddr, &dev,
2118 IPPROTO_TCP, sk->opt, MAX_ACK_SIZE,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
2119 if (tmp < 0)
2120 {
2121 buff->free = 1;
2122 sock_wfree(sk, buff);
2123 return;
2124 }
2125
2126 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
2127
2128 memcpy(t1,(void *) &sk->dummy_th, sizeof(*t1));
2129 t1->seq = htonl(sk->sent_seq);
2130 t1->ack = 1;
2131 t1->res1 = 0;
2132 t1->res2 = 0;
2133 t1->rst = 0;
2134 t1->urg = 0;
2135 t1->syn = 0;
2136 t1->psh = 0;
2137 sk->ack_backlog = 0;
2138 sk->bytes_rcv = 0;
2139 sk->window = tcp_select_window(sk);
2140 t1->window = htons(sk->window);
2141 t1->ack_seq = htonl(sk->acked_seq);
2142 t1->doff = sizeof(*t1)/4;
2143 tcp_send_check(t1, sk->saddr, sk->daddr, sizeof(*t1), sk);
2144 sk->prot->queue_xmit(sk, dev, buff, 1);
2145 tcp_statistics.TcpOutSegs++;
2146 }
2147
2148
2149 /*
2150 * FIXME:
2151 * This routine frees used buffers.
2152 * It should consider sending an ACK to let the
2153 * other end know we now have a bigger window.
2154 */
2155
2156 static void cleanup_rbuf(struct sock *sk)
/* */
2157 {
2158 unsigned long flags;
2159 unsigned long left;
2160 struct sk_buff *skb;
2161 unsigned long rspace;
2162
2163 if(sk->debug)
2164 printk("cleaning rbuf for sk=%p\n", sk);
2165
2166 save_flags(flags);
2167 cli();
2168
2169 left = sock_rspace(sk);
2170
2171 /*
2172 * We have to loop through all the buffer headers,
2173 * and try to free up all the space we can.
2174 */
2175
2176 while((skb=skb_peek(&sk->receive_queue)) != NULL)
2177 {
2178 if (!skb->used || skb->users)
2179 break;
2180 skb_unlink(skb);
2181 skb->sk = sk;
2182 kfree_skb(skb, FREE_READ);
2183 }
2184
2185 restore_flags(flags);
2186
2187 /*
2188 * FIXME:
2189 * At this point we should send an ack if the difference
2190 * in the window, and the amount of space is bigger than
2191 * TCP_WINDOW_DIFF.
2192 */
2193
2194 if(sk->debug)
2195 printk("sk->rspace = %lu, was %lu\n", sock_rspace(sk),
2196 left);
2197 if ((rspace=sock_rspace(sk)) != left)
2198 {
2199 /*
2200 * This area has caused the most trouble. The current strategy
2201 * is to simply do nothing if the other end has room to send at
2202 * least 3 full packets, because the ack from those will auto-
2203 * matically update the window. If the other end doesn't think
2204 * we have much space left, but we have room for at least 1 more
2205 * complete packet than it thinks we do, we will send an ack
2206 * immediately. Otherwise we will wait up to .5 seconds in case
2207 * the user reads some more.
2208 */
2209 sk->ack_backlog++;
2210 /*
2211 * It's unclear whether to use sk->mtu or sk->mss here. They differ only
2212 * if the other end is offering a window smaller than the agreed on MSS
2213 * (called sk->mtu here). In theory there's no connection between send
2214 * and receive, and so no reason to think that they're going to send
2215 * small packets. For the moment I'm using the hack of reducing the mss
2216 * only on the send side, so I'm putting mtu here.
2217 */
2218
2219 if (rspace > (sk->window - sk->bytes_rcv + sk->mtu))
2220 {
2221 /* Send an ack right now. */
2222 tcp_read_wakeup(sk);
2223 }
2224 else
2225 {
2226 /* Force it to send an ack soon. */
2227 int was_active = del_timer(&sk->retransmit_timer);
2228 if (!was_active || jiffies+TCP_ACK_TIME < sk->timer.expires)
2229 {
2230 reset_xmit_timer(sk, TIME_WRITE, TCP_ACK_TIME);
2231 }
2232 else
2233 add_timer(&sk->retransmit_timer);
2234 }
2235 }
2236 }
2237
2238
2239 /*
2240 * Handle reading urgent data. BSD has very simple semantics for
2241 * this, no blocking and very strange errors 8)
2242 */
2243
2244 static int tcp_recv_urg(struct sock * sk, int nonblock,
/* */
2245 struct msghdr *msg, int len, int flags, int *addr_len)
2246 {
2247 /*
2248 * No URG data to read
2249 */
2250 if (sk->urginline || !sk->urg_data || sk->urg_data == URG_READ)
2251 return -EINVAL; /* Yes this is right ! */
2252
2253 if (sk->err)
2254 return sock_error(sk);
2255
2256 if (sk->state == TCP_CLOSE || sk->done)
2257 {
2258 if (!sk->done)
2259 {
2260 sk->done = 1;
2261 return 0;
2262 }
2263 return -ENOTCONN;
2264 }
2265
2266 if (sk->shutdown & RCV_SHUTDOWN)
2267 {
2268 sk->done = 1;
2269 return 0;
2270 }
2271 sk->inuse = 1;
2272 if (sk->urg_data & URG_VALID)
2273 {
2274 char c = sk->urg_data;
2275 if (!(flags & MSG_PEEK))
2276 sk->urg_data = URG_READ;
2277 memcpy_toiovec(msg->msg_iov, &c, 1);
2278 if(msg->msg_name)
2279 {
2280 struct sockaddr_in *sin=(struct sockaddr_in *)msg->msg_name;
2281 sin->sin_family=AF_INET;
2282 sin->sin_addr.s_addr=sk->daddr;
2283 sin->sin_port=sk->dummy_th.dest;
2284 }
2285 if(addr_len)
2286 *addr_len=sizeof(struct sockaddr_in);
2287 release_sock(sk);
2288 return 1;
2289 }
2290 release_sock(sk);
2291
2292 /*
2293 * Fixed the recv(..., MSG_OOB) behaviour. BSD docs and
2294 * the available implementations agree in this case:
2295 * this call should never block, independent of the
2296 * blocking state of the socket.
2297 * Mike <pall@rz.uni-karlsruhe.de>
2298 */
2299 return -EAGAIN;
2300 }
2301
2302
2303 /*
2304 * This routine copies from a sock struct into the user buffer.
2305 */
2306
2307 static int tcp_recvmsg(struct sock *sk, struct msghdr *msg,
/* */
2308 int len, int nonblock, int flags, int *addr_len)
2309 {
2310 struct wait_queue wait = { current, NULL };
2311 int copied = 0;
2312 u32 peek_seq;
2313 volatile u32 *seq; /* So gcc doesn't overoptimise */
2314 unsigned long used;
2315
2316 /*
2317 * This error should be checked.
2318 */
2319
2320 if (sk->state == TCP_LISTEN)
2321 return -ENOTCONN;
2322
2323 /*
2324 * Urgent data needs to be handled specially.
2325 */
2326
2327 if (flags & MSG_OOB)
2328 return tcp_recv_urg(sk, nonblock, msg, len, flags, addr_len);
2329
2330 /*
2331 * Copying sequence to update. This is volatile to handle
2332 * the multi-reader case neatly (memcpy_to/fromfs might be
2333 * inline and thus not flush cached variables otherwise).
2334 */
2335
2336 peek_seq = sk->copied_seq;
2337 seq = &sk->copied_seq;
2338 if (flags & MSG_PEEK)
2339 seq = &peek_seq;
2340
2341 add_wait_queue(sk->sleep, &wait);
2342 sk->inuse = 1;
2343 while (len > 0)
2344 {
2345 struct sk_buff * skb;
2346 u32 offset;
2347
2348 /*
2349 * Are we at urgent data? Stop if we have read anything.
2350 */
2351
2352 if (copied && sk->urg_data && sk->urg_seq == *seq)
2353 break;
2354
2355 /*
2356 * Next get a buffer.
2357 */
2358
2359 current->state = TASK_INTERRUPTIBLE;
2360
2361 skb = skb_peek(&sk->receive_queue);
2362 do
2363 {
2364 if (!skb)
2365 break;
2366 if (before(*seq, skb->seq))
2367 break;
2368 offset = *seq - skb->seq;
2369 if (skb->h.th->syn)
2370 offset--;
2371 if (offset < skb->len)
2372 goto found_ok_skb;
2373 if (skb->h.th->fin)
2374 goto found_fin_ok;
2375 if (!(flags & MSG_PEEK))
2376 skb->used = 1;
2377 skb = skb->next;
2378 }
2379 while (skb != (struct sk_buff *)&sk->receive_queue);
2380
2381 if (copied)
2382 break;
2383
2384 if (sk->err)
2385 {
2386 copied = sock_error(sk);
2387 break;
2388 }
2389
2390 if (sk->state == TCP_CLOSE)
2391 {
2392 if (!sk->done)
2393 {
2394 sk->done = 1;
2395 break;
2396 }
2397 copied = -ENOTCONN;
2398 break;
2399 }
2400
2401 if (sk->shutdown & RCV_SHUTDOWN)
2402 {
2403 sk->done = 1;
2404 break;
2405 }
2406
2407 if (nonblock)
2408 {
2409 copied = -EAGAIN;
2410 break;
2411 }
2412
2413 cleanup_rbuf(sk);
2414 release_sock(sk);
2415 sk->socket->flags |= SO_WAITDATA;
2416 schedule();
2417 sk->socket->flags &= ~SO_WAITDATA;
2418 sk->inuse = 1;
2419
2420 if (current->signal & ~current->blocked)
2421 {
2422 copied = -ERESTARTSYS;
2423 break;
2424 }
2425 continue;
2426
2427 found_ok_skb:
2428 /*
2429 * Lock the buffer. We can be fairly relaxed as
2430 * an interrupt will never steal a buffer we are
2431 * using unless I've missed something serious in
2432 * tcp_data.
2433 */
2434
2435 skb->users++;
2436
2437 /*
2438 * Ok so how much can we use ?
2439 */
2440
2441 used = skb->len - offset;
2442 if (len < used)
2443 used = len;
2444 /*
2445 * Do we have urgent data here?
2446 */
2447
2448 if (sk->urg_data)
2449 {
2450 u32 urg_offset = sk->urg_seq - *seq;
2451 if (urg_offset < used)
2452 {
2453 if (!urg_offset)
2454 {
2455 if (!sk->urginline)
2456 {
2457 ++*seq;
2458 offset++;
2459 used--;
2460 }
2461 }
2462 else
2463 used = urg_offset;
2464 }
2465 }
2466
2467 /*
2468 * Copy it - We _MUST_ update *seq first so that we
2469 * don't ever double read when we have dual readers
2470 */
2471
2472 *seq += used;
2473
2474 /*
2475 * This memcpy_tofs can sleep. If it sleeps and we
2476 * do a second read it relies on the skb->users to avoid
2477 * a crash when cleanup_rbuf() gets called.
2478 */
2479
2480 memcpy_toiovec(msg->msg_iov,((unsigned char *)skb->h.th) +
2481 skb->h.th->doff*4 + offset, used);
2482 copied += used;
2483 len -= used;
2484
2485 /*
2486 * We now will not sleep again until we are finished
2487 * with skb. Sorry if you are doing the SMP port
2488 * but you'll just have to fix it neatly ;)
2489 */
2490
2491 skb->users --;
2492
2493 if (after(sk->copied_seq,sk->urg_seq))
2494 sk->urg_data = 0;
2495 if (used + offset < skb->len)
2496 continue;
2497
2498 /*
2499 * Process the FIN.
2500 */
2501
2502 if (skb->h.th->fin)
2503 goto found_fin_ok;
2504 if (flags & MSG_PEEK)
2505 continue;
2506 skb->used = 1;
2507 continue;
2508
2509 found_fin_ok:
2510 ++*seq;
2511 if (flags & MSG_PEEK)
2512 break;
2513
2514 /*
2515 * All is done
2516 */
2517
2518 skb->used = 1;
2519 sk->shutdown |= RCV_SHUTDOWN;
2520 break;
2521
2522 }
2523
2524 if(copied>0 && msg->msg_name)
2525 {
2526 struct sockaddr_in *sin=(struct sockaddr_in *)msg->msg_name;
2527 sin->sin_family=AF_INET;
2528 sin->sin_addr.s_addr=sk->daddr;
2529 sin->sin_port=sk->dummy_th.dest;
2530 }
2531 if(addr_len)
2532 *addr_len=sizeof(struct sockaddr_in);
2533
2534 remove_wait_queue(sk->sleep, &wait);
2535 current->state = TASK_RUNNING;
2536
2537 /* Clean up data we have read: This will do ACK frames */
2538 cleanup_rbuf(sk);
2539 release_sock(sk);
2540 return copied;
2541 }
2542
2543
2544
2545 /*
2546 * State processing on a close. This implements the state shift for
2547 * sending our FIN frame. Note that we only send a FIN for some
2548 * states. A shutdown() may have already sent the FIN, or we may be
2549 * closed.
2550 */
2551
2552 static int tcp_close_state(struct sock *sk, int dead)
/* */
2553 {
2554 int ns=TCP_CLOSE;
2555 int send_fin=0;
2556 switch(sk->state)
2557 {
2558 case TCP_SYN_SENT: /* No SYN back, no FIN needed */
2559 break;
2560 case TCP_SYN_RECV:
2561 case TCP_ESTABLISHED: /* Closedown begin */
2562 ns=TCP_FIN_WAIT1;
2563 send_fin=1;
2564 break;
2565 case TCP_FIN_WAIT1: /* Already closing, or FIN sent: no change */
2566 case TCP_FIN_WAIT2:
2567 case TCP_CLOSING:
2568 ns=sk->state;
2569 break;
2570 case TCP_CLOSE:
2571 case TCP_LISTEN:
2572 break;
2573 case TCP_CLOSE_WAIT: /* They have FIN'd us. We send our FIN and
2574 wait only for the ACK */
2575 ns=TCP_LAST_ACK;
2576 send_fin=1;
2577 }
2578
2579 tcp_set_state(sk,ns);
2580
2581 /*
2582 * This is a (useful) BSD violating of the RFC. There is a
2583 * problem with TCP as specified in that the other end could
2584 * keep a socket open forever with no application left this end.
2585 * We use a 3 minute timeout (about the same as BSD) then kill
2586 * our end. If they send after that then tough - BUT: long enough
2587 * that we won't make the old 4*rto = almost no time - whoops
2588 * reset mistake.
2589 */
2590 if(dead && ns==TCP_FIN_WAIT2)
2591 {
2592 int timer_active=del_timer(&sk->timer);
2593 if(timer_active)
2594 add_timer(&sk->timer);
2595 else
2596 reset_msl_timer(sk, TIME_CLOSE, TCP_FIN_TIMEOUT);
2597 }
2598
2599 return send_fin;
2600 }
2601
2602 /*
2603 * Send a fin.
2604 */
2605
2606 static void tcp_send_fin(struct sock *sk)
/* */
2607 {
2608 struct proto *prot =(struct proto *)sk->prot;
2609 struct tcphdr *th =(struct tcphdr *)&sk->dummy_th;
2610 struct tcphdr *t1;
2611 struct sk_buff *buff;
2612 struct device *dev=NULL;
2613 int tmp;
2614
2615 release_sock(sk); /* in case the malloc sleeps. */
2616
2617 buff = sock_wmalloc(sk, MAX_RESET_SIZE,1 , GFP_KERNEL);
2618 sk->inuse = 1;
2619
2620 if (buff == NULL)
2621 {
2622 /* This is a disaster if it occurs */
2623 printk("tcp_send_fin: Impossible malloc failure");
2624 return;
2625 }
2626
2627 /*
2628 * Administrivia
2629 */
2630
2631 buff->sk = sk;
2632 buff->localroute = sk->localroute;
2633
2634 /*
2635 * Put in the IP header and routing stuff.
2636 */
2637
2638 tmp = prot->build_header(buff,sk->saddr, sk->daddr, &dev,
2639 IPPROTO_TCP, sk->opt,
2640 sizeof(struct tcphdr),sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
2641 if (tmp < 0)
2642 {
2643 int t;
2644 /*
2645 * Finish anyway, treat this as a send that got lost.
2646 * (Not good).
2647 */
2648
2649 buff->free = 1;
2650 sock_wfree(sk,buff);
2651 sk->write_seq++;
2652 t=del_timer(&sk->timer);
2653 if(t)
2654 add_timer(&sk->timer);
2655 else
2656 reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
2657 return;
2658 }
2659
2660 /*
2661 * We ought to check if the end of the queue is a buffer and
2662 * if so simply add the fin to that buffer, not send it ahead.
2663 */
2664
2665 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
2666 buff->dev = dev;
2667 memcpy(t1, th, sizeof(*t1));
2668 buff->seq = sk->write_seq;
2669 sk->write_seq++;
2670 buff->end_seq = sk->write_seq;
2671 t1->seq = htonl(buff->seq);
2672 t1->ack = 1;
2673 t1->ack_seq = htonl(sk->acked_seq);
2674 t1->window = htons(sk->window=tcp_select_window(sk));
2675 t1->fin = 1;
2676 t1->rst = 0;
2677 t1->doff = sizeof(*t1)/4;
2678 tcp_send_check(t1, sk->saddr, sk->daddr, sizeof(*t1), sk);
2679
2680 /*
2681 * If there is data in the write queue, the fin must be appended to
2682 * the write queue.
2683 */
2684
2685 if (skb_peek(&sk->write_queue) != NULL)
2686 {
2687 buff->free = 0;
2688 if (buff->next != NULL)
2689 {
2690 printk("tcp_send_fin: next != NULL\n");
2691 skb_unlink(buff);
2692 }
2693 skb_queue_tail(&sk->write_queue, buff);
2694 }
2695 else
2696 {
2697 sk->sent_seq = sk->write_seq;
2698 sk->prot->queue_xmit(sk, dev, buff, 0);
2699 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
2700 }
2701 }
2702
2703 /*
2704 * Shutdown the sending side of a connection. Much like close except
2705 * that we don't receive shut down or set sk->dead=1.
2706 */
2707
2708 void tcp_shutdown(struct sock *sk, int how)
/* */
2709 {
2710 /*
2711 * We need to grab some memory, and put together a FIN,
2712 * and then put it into the queue to be sent.
2713 * Tim MacKenzie(tym@dibbler.cs.monash.edu.au) 4 Dec '92.
2714 */
2715
2716 if (!(how & SEND_SHUTDOWN))
2717 return;
2718
2719 /*
2720 * If we've already sent a FIN, or it's a closed state
2721 */
2722
2723 if (sk->state == TCP_FIN_WAIT1 ||
2724 sk->state == TCP_FIN_WAIT2 ||
2725 sk->state == TCP_CLOSING ||
2726 sk->state == TCP_LAST_ACK ||
2727 sk->state == TCP_TIME_WAIT ||
2728 sk->state == TCP_CLOSE ||
2729 sk->state == TCP_LISTEN
2730 )
2731 {
2732 return;
2733 }
2734 sk->inuse = 1;
2735
2736 /*
2737 * flag that the sender has shutdown
2738 */
2739
2740 sk->shutdown |= SEND_SHUTDOWN;
2741
2742 /*
2743 * Clear out any half completed packets.
2744 */
2745
2746 if (sk->partial)
2747 tcp_send_partial(sk);
2748
2749 /*
2750 * FIN if needed
2751 */
2752
2753 if(tcp_close_state(sk,0))
2754 tcp_send_fin(sk);
2755
2756 release_sock(sk);
2757 }
2758
2759 /*
2760 * This routine will send an RST to the other tcp.
2761 */
2762
2763 static void tcp_reset(unsigned long saddr, unsigned long daddr, struct tcphdr *th,
/* */
2764 struct proto *prot, struct options *opt, struct device *dev, int tos, int ttl)
2765 {
2766 struct sk_buff *buff;
2767 struct tcphdr *t1;
2768 int tmp;
2769 struct device *ndev=NULL;
2770
2771 /*
2772 * Cannot reset a reset (Think about it).
2773 */
2774
2775 if(th->rst)
2776 return;
2777
2778 /*
2779 * We need to grab some memory, and put together an RST,
2780 * and then put it into the queue to be sent.
2781 */
2782
2783 buff = sock_wmalloc(NULL, MAX_RESET_SIZE, 1, GFP_ATOMIC);
2784 if (buff == NULL)
2785 return;
2786
2787 buff->sk = NULL;
2788 buff->dev = dev;
2789 buff->localroute = 0;
2790
2791 /*
2792 * Put in the IP header and routing stuff.
2793 */
2794
2795 tmp = prot->build_header(buff, saddr, daddr, &ndev, IPPROTO_TCP, opt,
2796 sizeof(struct tcphdr),tos,ttl,NULL);
2797 if (tmp < 0)
2798 {
2799 buff->free = 1;
2800 sock_wfree(NULL, buff);
2801 return;
2802 }
2803
2804 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
2805 memcpy(t1, th, sizeof(*t1));
2806
2807 /*
2808 * Swap the send and the receive.
2809 */
2810
2811 t1->dest = th->source;
2812 t1->source = th->dest;
2813 t1->rst = 1;
2814 t1->window = 0;
2815
2816 if(th->ack)
2817 {
2818 t1->ack = 0;
2819 t1->seq = th->ack_seq;
2820 t1->ack_seq = 0;
2821 }
2822 else
2823 {
2824 t1->ack = 1;
2825 if(!th->syn)
2826 t1->ack_seq = th->seq;
2827 else
2828 t1->ack_seq = htonl(ntohl(th->seq)+1);
2829 t1->seq = 0;
2830 }
2831
2832 t1->syn = 0;
2833 t1->urg = 0;
2834 t1->fin = 0;
2835 t1->psh = 0;
2836 t1->doff = sizeof(*t1)/4;
2837 tcp_send_check(t1, saddr, daddr, sizeof(*t1), NULL);
2838 prot->queue_xmit(NULL, ndev, buff, 1);
2839 tcp_statistics.TcpOutSegs++;
2840 }
2841
2842
2843 /*
2844 * Look for tcp options. Parses everything but only knows about MSS.
2845 * This routine is always called with the packet containing the SYN.
2846 * However it may also be called with the ack to the SYN. So you
2847 * can't assume this is always the SYN. It's always called after
2848 * we have set up sk->mtu to our own MTU.
2849 *
2850 * We need at minimum to add PAWS support here. Possibly large windows
2851 * as Linux gets deployed on 100Mb/sec networks.
2852 */
2853
2854 static void tcp_options(struct sock *sk, struct tcphdr *th)
/* */
2855 {
2856 unsigned char *ptr;
2857 int length=(th->doff*4)-sizeof(struct tcphdr);
2858 int mss_seen = 0;
2859
2860 ptr = (unsigned char *)(th + 1);
2861
2862 while(length>0)
2863 {
2864 int opcode=*ptr++;
2865 int opsize=*ptr++;
2866 switch(opcode)
2867 {
2868 case TCPOPT_EOL:
2869 return;
2870 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */
2871 length--;
2872 ptr--; /* the opsize=*ptr++ above was a mistake */
2873 continue;
2874
2875 default:
2876 if(opsize<=2) /* Avoid silly options looping forever */
2877 return;
2878 switch(opcode)
2879 {
2880 case TCPOPT_MSS:
2881 if(opsize==4 && th->syn)
2882 {
2883 sk->mtu=min(sk->mtu,ntohs(*(unsigned short *)ptr));
2884 mss_seen = 1;
2885 }
2886 break;
2887 /* Add other options here as people feel the urge to implement stuff like large windows */
2888 }
2889 ptr+=opsize-2;
2890 length-=opsize;
2891 }
2892 }
2893 if (th->syn)
2894 {
2895 if (! mss_seen)
2896 sk->mtu=min(sk->mtu, 536); /* default MSS if none sent */
2897 }
2898 #ifdef CONFIG_INET_PCTCP
2899 sk->mss = min(sk->max_window >> 1, sk->mtu);
2900 #else
2901 sk->mss = min(sk->max_window, sk->mtu);
2902 #endif
2903 }
2904
2905 static inline unsigned long default_mask(unsigned long dst)
/* */
2906 {
2907 dst = ntohl(dst);
2908 if (IN_CLASSA(dst))
2909 return htonl(IN_CLASSA_NET);
2910 if (IN_CLASSB(dst))
2911 return htonl(IN_CLASSB_NET);
2912 return htonl(IN_CLASSC_NET);
2913 }
2914
2915 /*
2916 * Default sequence number picking algorithm.
2917 * As close as possible to RFC 793, which
2918 * suggests using a 250kHz clock.
2919 * Further reading shows this assumes 2MB/s networks.
2920 * For 10MB/s ethernet, a 1MHz clock is appropriate.
2921 * That's funny, Linux has one built in! Use it!
2922 */
2923
2924 extern inline u32 tcp_init_seq(void)
/* */
2925 {
2926 struct timeval tv;
2927 do_gettimeofday(&tv);
2928 return tv.tv_usec+tv.tv_sec*1000000;
2929 }
2930
2931 /*
2932 * This routine handles a connection request.
2933 * It should make sure we haven't already responded.
2934 * Because of the way BSD works, we have to send a syn/ack now.
2935 * This also means it will be harder to close a socket which is
2936 * listening.
2937 */
2938
2939 static void tcp_conn_request(struct sock *sk, struct sk_buff *skb,
/* */
2940 unsigned long daddr, unsigned long saddr,
2941 struct options *opt, struct device *dev, u32 seq)
2942 {
2943 struct sk_buff *buff;
2944 struct tcphdr *t1;
2945 unsigned char *ptr;
2946 struct sock *newsk;
2947 struct tcphdr *th;
2948 struct device *ndev=NULL;
2949 int tmp;
2950 struct rtable *rt;
2951
2952 th = skb->h.th;
2953
2954 /* If the socket is dead, don't accept the connection. */
2955 if (!sk->dead)
2956 {
2957 sk->data_ready(sk,0);
2958 }
2959 else
2960 {
2961 if(sk->debug)
2962 printk("Reset on %p: Connect on dead socket.\n",sk);
2963 tcp_reset(daddr, saddr, th, sk->prot, opt, dev, sk->ip_tos,sk->ip_ttl);
2964 tcp_statistics.TcpAttemptFails++;
2965 kfree_skb(skb, FREE_READ);
2966 return;
2967 }
2968
2969 /*
2970 * Make sure we can accept more. This will prevent a
2971 * flurry of syns from eating up all our memory.
2972 */
2973
2974 if (sk->ack_backlog >= sk->max_ack_backlog)
2975 {
2976 tcp_statistics.TcpAttemptFails++;
2977 kfree_skb(skb, FREE_READ);
2978 return;
2979 }
2980
2981 /*
2982 * We need to build a new sock struct.
2983 * It is sort of bad to have a socket without an inode attached
2984 * to it, but the wake_up's will just wake up the listening socket,
2985 * and if the listening socket is destroyed before this is taken
2986 * off of the queue, this will take care of it.
2987 */
2988
2989 newsk = (struct sock *) kmalloc(sizeof(struct sock), GFP_ATOMIC);
2990 if (newsk == NULL)
2991 {
2992 /* just ignore the syn. It will get retransmitted. */
2993 tcp_statistics.TcpAttemptFails++;
2994 kfree_skb(skb, FREE_READ);
2995 return;
2996 }
2997
2998 memcpy(newsk, sk, sizeof(*newsk));
2999 newsk->opt = NULL;
3000 newsk->ip_route_cache = NULL;
3001 if (opt && opt->optlen) {
3002 sk->opt = (struct options*)kmalloc(sizeof(struct options)+opt->optlen, GFP_ATOMIC);
3003 if (!sk->opt) {
3004 kfree_s(newsk, sizeof(struct sock));
3005 tcp_statistics.TcpAttemptFails++;
3006 kfree_skb(skb, FREE_READ);
3007 return;
3008 }
3009 if (ip_options_echo(sk->opt, opt, daddr, saddr, skb)) {
3010 kfree_s(sk->opt, sizeof(struct options)+opt->optlen);
3011 kfree_s(newsk, sizeof(struct sock));
3012 tcp_statistics.TcpAttemptFails++;
3013 kfree_skb(skb, FREE_READ);
3014 return;
3015 }
3016 }
3017 skb_queue_head_init(&newsk->write_queue);
3018 skb_queue_head_init(&newsk->receive_queue);
3019 newsk->send_head = NULL;
3020 newsk->send_tail = NULL;
3021 skb_queue_head_init(&newsk->back_log);
3022 newsk->rtt = 0; /*TCP_CONNECT_TIME<<3*/
3023 newsk->rto = TCP_TIMEOUT_INIT;
3024 newsk->mdev = 0;
3025 newsk->max_window = 0;
3026 newsk->cong_window = 1;
3027 newsk->cong_count = 0;
3028 newsk->ssthresh = 0;
3029 newsk->backoff = 0;
3030 newsk->blog = 0;
3031 newsk->intr = 0;
3032 newsk->proc = 0;
3033 newsk->done = 0;
3034 newsk->partial = NULL;
3035 newsk->pair = NULL;
3036 newsk->wmem_alloc = 0;
3037 newsk->rmem_alloc = 0;
3038 newsk->localroute = sk->localroute;
3039
3040 newsk->max_unacked = MAX_WINDOW - TCP_WINDOW_DIFF;
3041
3042 newsk->err = 0;
3043 newsk->shutdown = 0;
3044 newsk->ack_backlog = 0;
3045 newsk->acked_seq = skb->seq+1;
3046 newsk->copied_seq = skb->seq+1;
3047 newsk->fin_seq = skb->seq;
3048 newsk->state = TCP_SYN_RECV;
3049 newsk->timeout = 0;
3050 newsk->ip_xmit_timeout = 0;
3051 newsk->write_seq = seq;
3052 newsk->window_seq = newsk->write_seq;
3053 newsk->rcv_ack_seq = newsk->write_seq;
3054 newsk->urg_data = 0;
3055 newsk->retransmits = 0;
3056 newsk->linger=0;
3057 newsk->destroy = 0;
3058 init_timer(&newsk->timer);
3059 newsk->timer.data = (unsigned long)newsk;
3060 newsk->timer.function = &net_timer;
3061 init_timer(&newsk->retransmit_timer);
3062 newsk->retransmit_timer.data = (unsigned long)newsk;
3063 newsk->retransmit_timer.function=&retransmit_timer;
3064 newsk->dummy_th.source = skb->h.th->dest;
3065 newsk->dummy_th.dest = skb->h.th->source;
3066
3067 /*
3068 * Swap these two, they are from our point of view.
3069 */
3070
3071 newsk->daddr = saddr;
3072 newsk->saddr = daddr;
3073 newsk->rcv_saddr = daddr;
3074
3075 put_sock(newsk->num,newsk);
3076 newsk->dummy_th.res1 = 0;
3077 newsk->dummy_th.doff = 6;
3078 newsk->dummy_th.fin = 0;
3079 newsk->dummy_th.syn = 0;
3080 newsk->dummy_th.rst = 0;
3081 newsk->dummy_th.psh = 0;
3082 newsk->dummy_th.ack = 0;
3083 newsk->dummy_th.urg = 0;
3084 newsk->dummy_th.res2 = 0;
3085 newsk->acked_seq = skb->seq + 1;
3086 newsk->copied_seq = skb->seq + 1;
3087 newsk->socket = NULL;
3088
3089 /*
3090 * Grab the ttl and tos values and use them
3091 */
3092
3093 newsk->ip_ttl=sk->ip_ttl;
3094 newsk->ip_tos=skb->ip_hdr->tos;
3095
3096 /*
3097 * Use 512 or whatever user asked for
3098 */
3099
3100 /*
3101 * Note use of sk->user_mss, since user has no direct access to newsk
3102 */
3103
3104 rt = ip_rt_route(newsk->opt && newsk->opt->srr ? newsk->opt->faddr : saddr, 0);
3105 newsk->ip_route_cache = rt;
3106
3107 if(rt!=NULL && (rt->rt_flags&RTF_WINDOW))
3108 newsk->window_clamp = rt->rt_window;
3109 else
3110 newsk->window_clamp = 0;
3111
3112 if (sk->user_mss)
3113 newsk->mtu = sk->user_mss;
3114 else if (rt)
3115 newsk->mtu = rt->rt_mtu - sizeof(struct iphdr) - sizeof(struct tcphdr);
3116 else
3117 newsk->mtu = 576 - sizeof(struct iphdr) - sizeof(struct tcphdr);
3118
3119 /*
3120 * But not bigger than device MTU
3121 */
3122
3123 newsk->mtu = min(newsk->mtu, dev->mtu - sizeof(struct iphdr) - sizeof(struct tcphdr));
3124
3125 #ifdef CONFIG_SKIP
3126
3127 /*
3128 * SKIP devices set their MTU to 65535. This is so they can take packets
3129 * unfragmented to security process then fragment. They could lie to the
3130 * TCP layer about a suitable MTU, but its easier to let skip sort it out
3131 * simply because the final package we want unfragmented is going to be
3132 *
3133 * [IPHDR][IPSP][Security data][Modified TCP data][Security data]
3134 */
3135
3136 if(skip_pick_mtu!=NULL) /* If SKIP is loaded.. */
3137 sk->mtu=skip_pick_mtu(sk->mtu,dev);
3138 #endif
3139 /*
3140 * This will min with what arrived in the packet
3141 */
3142
3143 tcp_options(newsk,skb->h.th);
3144
3145 tcp_cache_zap();
3146
3147 buff = sock_wmalloc(newsk, MAX_SYN_SIZE, 1, GFP_ATOMIC);
3148 if (buff == NULL)
3149 {
3150 sk->err = ENOMEM;
3151 newsk->dead = 1;
3152 newsk->state = TCP_CLOSE;
3153 /* And this will destroy it */
3154 release_sock(newsk);
3155 kfree_skb(skb, FREE_READ);
3156 tcp_statistics.TcpAttemptFails++;
3157 return;
3158 }
3159
3160 buff->sk = newsk;
3161 buff->localroute = newsk->localroute;
3162
3163 /*
3164 * Put in the IP header and routing stuff.
3165 */
3166
3167 tmp = sk->prot->build_header(buff, newsk->saddr, newsk->daddr, &ndev,
3168 IPPROTO_TCP, NULL, MAX_SYN_SIZE,sk->ip_tos,sk->ip_ttl,&newsk->ip_route_cache);
3169
3170 /*
3171 * Something went wrong.
3172 */
3173
3174 if (tmp < 0)
3175 {
3176 sk->err = tmp;
3177 buff->free = 1;
3178 kfree_skb(buff,FREE_WRITE);
3179 newsk->dead = 1;
3180 newsk->state = TCP_CLOSE;
3181 release_sock(newsk);
3182 skb->sk = sk;
3183 kfree_skb(skb, FREE_READ);
3184 tcp_statistics.TcpAttemptFails++;
3185 return;
3186 }
3187
3188 t1 =(struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
3189
3190 memcpy(t1, skb->h.th, sizeof(*t1));
3191 buff->seq = newsk->write_seq++;
3192 buff->end_seq = newsk->write_seq;
3193 /*
3194 * Swap the send and the receive.
3195 */
3196 t1->dest = skb->h.th->source;
3197 t1->source = newsk->dummy_th.source;
3198 t1->seq = ntohl(buff->seq);
3199 t1->ack = 1;
3200 newsk->window = tcp_select_window(newsk);
3201 newsk->sent_seq = newsk->write_seq;
3202 t1->window = ntohs(newsk->window);
3203 t1->res1 = 0;
3204 t1->res2 = 0;
3205 t1->rst = 0;
3206 t1->urg = 0;
3207 t1->psh = 0;
3208 t1->syn = 1;
3209 t1->ack_seq = htonl(newsk->acked_seq);
3210 t1->doff = sizeof(*t1)/4+1;
3211 ptr = skb_put(buff,4);
3212 ptr[0] = 2;
3213 ptr[1] = 4;
3214 ptr[2] = ((newsk->mtu) >> 8) & 0xff;
3215 ptr[3] =(newsk->mtu) & 0xff;
3216
3217 tcp_send_check(t1, daddr, saddr, sizeof(*t1)+4, newsk);
3218 newsk->prot->queue_xmit(newsk, ndev, buff, 0);
3219 reset_xmit_timer(newsk, TIME_WRITE , TCP_TIMEOUT_INIT);
3220 skb->sk = newsk;
3221
3222 /*
3223 * Charge the sock_buff to newsk.
3224 */
3225
3226 sk->rmem_alloc -= skb->truesize;
3227 newsk->rmem_alloc += skb->truesize;
3228
3229 skb_queue_tail(&sk->receive_queue,skb);
3230 sk->ack_backlog++;
3231 release_sock(newsk);
3232 tcp_statistics.TcpOutSegs++;
3233 }
3234
3235
3236 static void tcp_close(struct sock *sk, int timeout)
/* */
3237 {
3238 /*
3239 * We need to grab some memory, and put together a FIN,
3240 * and then put it into the queue to be sent.
3241 */
3242
3243 sk->inuse = 1;
3244
3245 if(th_cache_sk==sk)
3246 tcp_cache_zap();
3247 if(sk->state == TCP_LISTEN)
3248 {
3249 /* Special case */
3250 tcp_set_state(sk, TCP_CLOSE);
3251 tcp_close_pending(sk);
3252 release_sock(sk);
3253 return;
3254 }
3255
3256 sk->keepopen = 1;
3257 sk->shutdown = SHUTDOWN_MASK;
3258
3259 if (!sk->dead)
3260 sk->state_change(sk);
3261
3262 if (timeout == 0)
3263 {
3264 struct sk_buff *skb;
3265
3266 /*
3267 * We need to flush the recv. buffs. We do this only on the
3268 * descriptor close, not protocol-sourced closes, because the
3269 * reader process may not have drained the data yet!
3270 */
3271
3272 while((skb=skb_dequeue(&sk->receive_queue))!=NULL)
3273 kfree_skb(skb, FREE_READ);
3274 /*
3275 * Get rid off any half-completed packets.
3276 */
3277
3278 if (sk->partial)
3279 tcp_send_partial(sk);
3280 }
3281
3282
3283 /*
3284 * Timeout is not the same thing - however the code likes
3285 * to send both the same way (sigh).
3286 */
3287
3288 if(timeout)
3289 {
3290 tcp_set_state(sk, TCP_CLOSE); /* Dead */
3291 }
3292 else
3293 {
3294 if(tcp_close_state(sk,1)==1)
3295 {
3296 tcp_send_fin(sk);
3297 }
3298 }
3299 release_sock(sk);
3300 }
3301
3302
3303 /*
3304 * This routine takes stuff off of the write queue,
3305 * and puts it in the xmit queue. This happens as incoming acks
3306 * open up the remote window for us.
3307 */
3308
3309 static void tcp_write_xmit(struct sock *sk)
/* */
3310 {
3311 struct sk_buff *skb;
3312
3313 /*
3314 * The bytes will have to remain here. In time closedown will
3315 * empty the write queue and all will be happy
3316 */
3317
3318 if(sk->zapped)
3319 return;
3320
3321 /*
3322 * Anything on the transmit queue that fits the window can
3323 * be added providing we are not
3324 *
3325 * a) retransmitting (Nagle's rule)
3326 * b) exceeding our congestion window.
3327 */
3328
3329 while((skb = skb_peek(&sk->write_queue)) != NULL &&
3330 before(skb->end_seq, sk->window_seq + 1) &&
3331 (sk->retransmits == 0 ||
3332 sk->ip_xmit_timeout != TIME_WRITE ||
3333 before(skb->end_seq, sk->rcv_ack_seq + 1))
3334 && sk->packets_out < sk->cong_window)
3335 {
3336 IS_SKB(skb);
3337 skb_unlink(skb);
3338
3339 /*
3340 * See if we really need to send the packet.
3341 */
3342
3343 if (before(skb->end_seq, sk->rcv_ack_seq +1))
3344 {
3345 /*
3346 * This is acked data. We can discard it. This
3347 * cannot currently occur.
3348 */
3349
3350 sk->retransmits = 0;
3351 kfree_skb(skb, FREE_WRITE);
3352 if (!sk->dead)
3353 sk->write_space(sk);
3354 }
3355 else
3356 {
3357 struct tcphdr *th;
3358 struct iphdr *iph;
3359 int size;
3360 /*
3361 * put in the ack seq and window at this point rather than earlier,
3362 * in order to keep them monotonic. We really want to avoid taking
3363 * back window allocations. That's legal, but RFC1122 says it's frowned on.
3364 * Ack and window will in general have changed since this packet was put
3365 * on the write queue.
3366 */
3367 iph = skb->ip_hdr;
3368 th = (struct tcphdr *)(((char *)iph) +(iph->ihl << 2));
3369 size = skb->len - (((unsigned char *) th) - skb->data);
3370 #ifndef CONFIG_NO_PATH_MTU_DISCOVERY
3371 if (size > sk->mtu - sizeof(struct iphdr))
3372 {
3373 iph->frag_off &= ~htons(IP_DF);
3374 ip_send_check(iph);
3375 }
3376 #endif
3377
3378 th->ack_seq = htonl(sk->acked_seq);
3379 th->window = htons(tcp_select_window(sk));
3380
3381 tcp_send_check(th, sk->saddr, sk->daddr, size, sk);
3382
3383 sk->sent_seq = skb->end_seq;
3384
3385 /*
3386 * IP manages our queue for some crazy reason
3387 */
3388
3389 sk->prot->queue_xmit(sk, skb->dev, skb, skb->free);
3390
3391 /*
3392 * Again we slide the timer wrongly
3393 */
3394
3395 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
3396 }
3397 }
3398 }
3399
3400
3401 /*
3402 * This routine deals with incoming acks, but not outgoing ones.
3403 */
3404
3405 extern __inline__ int tcp_ack(struct sock *sk, struct tcphdr *th, unsigned long saddr, int len)
/* */
3406 {
3407 u32 ack;
3408 int flag = 0;
3409
3410 /*
3411 * 1 - there was data in packet as well as ack or new data is sent or
3412 * in shutdown state
3413 * 2 - data from retransmit queue was acked and removed
3414 * 4 - window shrunk or data from retransmit queue was acked and removed
3415 */
3416
3417 if(sk->zapped)
3418 return(1); /* Dead, cant ack any more so why bother */
3419
3420 /*
3421 * Have we discovered a larger window
3422 */
3423
3424 ack = ntohl(th->ack_seq);
3425
3426 if (ntohs(th->window) > sk->max_window)
3427 {
3428 sk->max_window = ntohs(th->window);
3429 #ifdef CONFIG_INET_PCTCP
3430 /* Hack because we don't send partial packets to non SWS
3431 handling hosts */
3432 sk->mss = min(sk->max_window>>1, sk->mtu);
3433 #else
3434 sk->mss = min(sk->max_window, sk->mtu);
3435 #endif
3436 }
3437
3438 /*
3439 * We have dropped back to keepalive timeouts. Thus we have
3440 * no retransmits pending.
3441 */
3442
3443 if (sk->retransmits && sk->ip_xmit_timeout == TIME_KEEPOPEN)
3444 sk->retransmits = 0;
3445
3446 /*
3447 * If the ack is newer than sent or older than previous acks
3448 * then we can probably ignore it.
3449 */
3450
3451 if (after(ack, sk->sent_seq) || before(ack, sk->rcv_ack_seq))
3452 {
3453 if(sk->debug)
3454 printk("Ack ignored %u %u\n",ack,sk->sent_seq);
3455
3456 /*
3457 * Keepalive processing.
3458 */
3459
3460 if (after(ack, sk->sent_seq))
3461 {
3462 return(0);
3463 }
3464
3465 /*
3466 * Restart the keepalive timer.
3467 */
3468
3469 if (sk->keepopen)
3470 {
3471 if(sk->ip_xmit_timeout==TIME_KEEPOPEN)
3472 reset_xmit_timer(sk, TIME_KEEPOPEN, TCP_TIMEOUT_LEN);
3473 }
3474 return(1);
3475 }
3476
3477 /*
3478 * If there is data set flag 1
3479 */
3480
3481 if (len != th->doff*4)
3482 flag |= 1;
3483
3484 /*
3485 * See if our window has been shrunk.
3486 */
3487
3488 if (after(sk->window_seq, ack+ntohs(th->window)))
3489 {
3490 /*
3491 * We may need to move packets from the send queue
3492 * to the write queue, if the window has been shrunk on us.
3493 * The RFC says you are not allowed to shrink your window
3494 * like this, but if the other end does, you must be able
3495 * to deal with it.
3496 */
3497 struct sk_buff *skb;
3498 struct sk_buff *skb2;
3499 struct sk_buff *wskb = NULL;
3500
3501 skb2 = sk->send_head;
3502 sk->send_head = NULL;
3503 sk->send_tail = NULL;
3504
3505 /*
3506 * This is an artifact of a flawed concept. We want one
3507 * queue and a smarter send routine when we send all.
3508 */
3509
3510 flag |= 4; /* Window changed */
3511
3512 sk->window_seq = ack + ntohs(th->window);
3513 cli();
3514 while (skb2 != NULL)
3515 {
3516 skb = skb2;
3517 skb2 = skb->link3;
3518 skb->link3 = NULL;
3519 if (after(skb->end_seq, sk->window_seq))
3520 {
3521 if (sk->packets_out > 0)
3522 sk->packets_out--;
3523 /* We may need to remove this from the dev send list. */
3524 if (skb->next != NULL)
3525 {
3526 skb_unlink(skb);
3527 }
3528 /* Now add it to the write_queue. */
3529 if (wskb == NULL)
3530 skb_queue_head(&sk->write_queue,skb);
3531 else
3532 skb_append(wskb,skb);
3533 wskb = skb;
3534 }
3535 else
3536 {
3537 if (sk->send_head == NULL)
3538 {
3539 sk->send_head = skb;
3540 sk->send_tail = skb;
3541 }
3542 else
3543 {
3544 sk->send_tail->link3 = skb;
3545 sk->send_tail = skb;
3546 }
3547 skb->link3 = NULL;
3548 }
3549 }
3550 sti();
3551 }
3552
3553 /*
3554 * Pipe has emptied
3555 */
3556
3557 if (sk->send_tail == NULL || sk->send_head == NULL)
3558 {
3559 sk->send_head = NULL;
3560 sk->send_tail = NULL;
3561 sk->packets_out= 0;
3562 }
3563
3564 /*
3565 * Update the right hand window edge of the host
3566 */
3567
3568 sk->window_seq = ack + ntohs(th->window);
3569
3570 /*
3571 * We don't want too many packets out there.
3572 */
3573
3574 if (sk->ip_xmit_timeout == TIME_WRITE &&
3575 sk->cong_window < 2048 && after(ack, sk->rcv_ack_seq))
3576 {
3577 /*
3578 * This is Jacobson's slow start and congestion avoidance.
3579 * SIGCOMM '88, p. 328. Because we keep cong_window in integral
3580 * mss's, we can't do cwnd += 1 / cwnd. Instead, maintain a
3581 * counter and increment it once every cwnd times. It's possible
3582 * that this should be done only if sk->retransmits == 0. I'm
3583 * interpreting "new data is acked" as including data that has
3584 * been retransmitted but is just now being acked.
3585 */
3586 if (sk->cong_window < sk->ssthresh)
3587 /*
3588 * In "safe" area, increase
3589 */
3590 sk->cong_window++;
3591 else
3592 {
3593 /*
3594 * In dangerous area, increase slowly. In theory this is
3595 * sk->cong_window += 1 / sk->cong_window
3596 */
3597 if (sk->cong_count >= sk->cong_window)
3598 {
3599 sk->cong_window++;
3600 sk->cong_count = 0;
3601 }
3602 else
3603 sk->cong_count++;
3604 }
3605 }
3606
3607 /*
3608 * Remember the highest ack received.
3609 */
3610
3611 sk->rcv_ack_seq = ack;
3612
3613 /*
3614 * We passed data and got it acked, remove any soft error
3615 * log. Something worked...
3616 */
3617
3618 sk->err_soft = 0;
3619
3620 /*
3621 * If this ack opens up a zero window, clear backoff. It was
3622 * being used to time the probes, and is probably far higher than
3623 * it needs to be for normal retransmission.
3624 */
3625
3626 if (sk->ip_xmit_timeout == TIME_PROBE0)
3627 {
3628 sk->retransmits = 0; /* Our probe was answered */
3629
3630 /*
3631 * Was it a usable window open ?
3632 */
3633
3634 if (skb_peek(&sk->write_queue) != NULL && /* should always be non-null */
3635 ! before (sk->window_seq, sk->write_queue.next->end_seq))
3636 {
3637 sk->backoff = 0;
3638
3639 /*
3640 * Recompute rto from rtt. this eliminates any backoff.
3641 */
3642
3643 sk->rto = ((sk->rtt >> 2) + sk->mdev) >> 1;
3644 if (sk->rto > 120*HZ)
3645 sk->rto = 120*HZ;
3646 if (sk->rto < 20) /* Was 1*HZ, then 1 - turns out we must allow about
3647 .2 of a second because of BSD delayed acks - on a 100Mb/sec link
3648 .2 of a second is going to need huge windows (SIGH) */
3649 sk->rto = 20;
3650 }
3651 }
3652
3653 /*
3654 * See if we can take anything off of the retransmit queue.
3655 */
3656
3657 while(sk->send_head != NULL)
3658 {
3659 /* Check for a bug. */
3660 if (sk->send_head->link3 &&
3661 after(sk->send_head->end_seq, sk->send_head->link3->end_seq))
3662 printk("INET: tcp.c: *** bug send_list out of order.\n");
3663
3664 /*
3665 * If our packet is before the ack sequence we can
3666 * discard it as it's confirmed to have arrived the other end.
3667 */
3668
3669 if (before(sk->send_head->end_seq, ack+1))
3670 {
3671 struct sk_buff *oskb;
3672 if (sk->retransmits)
3673 {
3674 /*
3675 * We were retransmitting. don't count this in RTT est
3676 */
3677 flag |= 2;
3678
3679 /*
3680 * even though we've gotten an ack, we're still
3681 * retransmitting as long as we're sending from
3682 * the retransmit queue. Keeping retransmits non-zero
3683 * prevents us from getting new data interspersed with
3684 * retransmissions.
3685 */
3686
3687 if (sk->send_head->link3) /* Any more queued retransmits? */
3688 sk->retransmits = 1;
3689 else
3690 sk->retransmits = 0;
3691 }
3692 /*
3693 * Note that we only reset backoff and rto in the
3694 * rtt recomputation code. And that doesn't happen
3695 * if there were retransmissions in effect. So the
3696 * first new packet after the retransmissions is
3697 * sent with the backoff still in effect. Not until
3698 * we get an ack from a non-retransmitted packet do
3699 * we reset the backoff and rto. This allows us to deal
3700 * with a situation where the network delay has increased
3701 * suddenly. I.e. Karn's algorithm. (SIGCOMM '87, p5.)
3702 */
3703
3704 /*
3705 * We have one less packet out there.
3706 */
3707
3708 if (sk->packets_out > 0)
3709 sk->packets_out --;
3710 /*
3711 * Wake up the process, it can probably write more.
3712 */
3713 if (!sk->dead)
3714 sk->write_space(sk);
3715 oskb = sk->send_head;
3716
3717 if (!(flag&2)) /* Not retransmitting */
3718 {
3719 long m;
3720
3721 /*
3722 * The following amusing code comes from Jacobson's
3723 * article in SIGCOMM '88. Note that rtt and mdev
3724 * are scaled versions of rtt and mean deviation.
3725 * This is designed to be as fast as possible
3726 * m stands for "measurement".
3727 */
3728
3729 m = jiffies - oskb->when; /* RTT */
3730 if(m<=0)
3731 m=1; /* IS THIS RIGHT FOR <0 ??? */
3732 m -= (sk->rtt >> 3); /* m is now error in rtt est */
3733 sk->rtt += m; /* rtt = 7/8 rtt + 1/8 new */
3734 if (m < 0)
3735 m = -m; /* m is now abs(error) */
3736 m -= (sk->mdev >> 2); /* similar update on mdev */
3737 sk->mdev += m; /* mdev = 3/4 mdev + 1/4 new */
3738
3739 /*
3740 * Now update timeout. Note that this removes any backoff.
3741 */
3742
3743 sk->rto = ((sk->rtt >> 2) + sk->mdev) >> 1;
3744 if (sk->rto > 120*HZ)
3745 sk->rto = 120*HZ;
3746 if (sk->rto < 20) /* Was 1*HZ - keep .2 as minimum cos of the BSD delayed acks */
3747 sk->rto = 20;
3748 sk->backoff = 0;
3749 }
3750 flag |= (2|4); /* 2 is really more like 'don't adjust the rtt
3751 In this case as we just set it up */
3752 cli();
3753 oskb = sk->send_head;
3754 IS_SKB(oskb);
3755 sk->send_head = oskb->link3;
3756 if (sk->send_head == NULL)
3757 {
3758 sk->send_tail = NULL;
3759 }
3760
3761 /*
3762 * We may need to remove this from the dev send list.
3763 */
3764
3765 if (oskb->next)
3766 skb_unlink(oskb);
3767 sti();
3768 kfree_skb(oskb, FREE_WRITE); /* write. */
3769 if (!sk->dead)
3770 sk->write_space(sk);
3771 }
3772 else
3773 {
3774 break;
3775 }
3776 }
3777
3778 /*
3779 * XXX someone ought to look at this too.. at the moment, if skb_peek()
3780 * returns non-NULL, we complete ignore the timer stuff in the else
3781 * clause. We ought to organize the code so that else clause can
3782 * (should) be executed regardless, possibly moving the PROBE timer
3783 * reset over. The skb_peek() thing should only move stuff to the
3784 * write queue, NOT also manage the timer functions.
3785 */
3786
3787 /*
3788 * Maybe we can take some stuff off of the write queue,
3789 * and put it onto the xmit queue.
3790 */
3791 if (skb_peek(&sk->write_queue) != NULL)
3792 {
3793 if (after (sk->window_seq+1, sk->write_queue.next->end_seq) &&
3794 (sk->retransmits == 0 ||
3795 sk->ip_xmit_timeout != TIME_WRITE ||
3796 before(sk->write_queue.next->end_seq, sk->rcv_ack_seq + 1))
3797 && sk->packets_out < sk->cong_window)
3798 {
3799 /*
3800 * Add more data to the send queue.
3801 */
3802 flag |= 1;
3803 tcp_write_xmit(sk);
3804 }
3805 else if (before(sk->window_seq, sk->write_queue.next->end_seq) &&
3806 sk->send_head == NULL &&
3807 sk->ack_backlog == 0 &&
3808 sk->state != TCP_TIME_WAIT)
3809 {
3810 /*
3811 * Data to queue but no room.
3812 */
3813 reset_xmit_timer(sk, TIME_PROBE0, sk->rto);
3814 }
3815 }
3816 else
3817 {
3818 /*
3819 * from TIME_WAIT we stay in TIME_WAIT as long as we rx packets
3820 * from TCP_CLOSE we don't do anything
3821 *
3822 * from anything else, if there is write data (or fin) pending,
3823 * we use a TIME_WRITE timeout, else if keepalive we reset to
3824 * a KEEPALIVE timeout, else we delete the timer.
3825 *
3826 * We do not set flag for nominal write data, otherwise we may
3827 * force a state where we start to write itsy bitsy tidbits
3828 * of data.
3829 */
3830
3831 switch(sk->state) {
3832 case TCP_TIME_WAIT:
3833 /*
3834 * keep us in TIME_WAIT until we stop getting packets,
3835 * reset the timeout.
3836 */
3837 reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
3838 break;
3839 case TCP_CLOSE:
3840 /*
3841 * don't touch the timer.
3842 */
3843 break;
3844 default:
3845 /*
3846 * Must check send_head, write_queue, and ack_backlog
3847 * to determine which timeout to use.
3848 */
3849 if (sk->send_head || skb_peek(&sk->write_queue) != NULL || sk->ack_backlog) {
3850 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
3851 } else if (sk->keepopen) {
3852 reset_xmit_timer(sk, TIME_KEEPOPEN, TCP_TIMEOUT_LEN);
3853 } else {
3854 del_timer(&sk->retransmit_timer);
3855 sk->ip_xmit_timeout = 0;
3856 }
3857 break;
3858 }
3859 }
3860
3861 /*
3862 * We have nothing queued but space to send. Send any partial
3863 * packets immediately (end of Nagle rule application).
3864 */
3865
3866 if (sk->packets_out == 0 && sk->partial != NULL &&
3867 skb_peek(&sk->write_queue) == NULL && sk->send_head == NULL)
3868 {
3869 flag |= 1;
3870 tcp_send_partial(sk);
3871 }
3872
3873 /*
3874 * In the LAST_ACK case, the other end FIN'd us. We then FIN'd them, and
3875 * we are now waiting for an acknowledge to our FIN. The other end is
3876 * already in TIME_WAIT.
3877 *
3878 * Move to TCP_CLOSE on success.
3879 */
3880
3881 if (sk->state == TCP_LAST_ACK)
3882 {
3883 if (!sk->dead)
3884 sk->state_change(sk);
3885 if(sk->debug)
3886 printk("rcv_ack_seq: %X==%X, acked_seq: %X==%X\n",
3887 sk->rcv_ack_seq,sk->write_seq,sk->acked_seq,sk->fin_seq);
3888 if (sk->rcv_ack_seq == sk->write_seq /*&& sk->acked_seq == sk->fin_seq*/)
3889 {
3890 flag |= 1;
3891 sk->shutdown = SHUTDOWN_MASK;
3892 tcp_set_state(sk,TCP_CLOSE);
3893 return 1;
3894 }
3895 }
3896
3897 /*
3898 * Incoming ACK to a FIN we sent in the case of our initiating the close.
3899 *
3900 * Move to FIN_WAIT2 to await a FIN from the other end. Set
3901 * SEND_SHUTDOWN but not RCV_SHUTDOWN as data can still be coming in.
3902 */
3903
3904 if (sk->state == TCP_FIN_WAIT1)
3905 {
3906
3907 if (!sk->dead)
3908 sk->state_change(sk);
3909 if (sk->rcv_ack_seq == sk->write_seq)
3910 {
3911 flag |= 1;
3912 sk->shutdown |= SEND_SHUTDOWN;
3913 tcp_set_state(sk, TCP_FIN_WAIT2);
3914 }
3915 }
3916
3917 /*
3918 * Incoming ACK to a FIN we sent in the case of a simultaneous close.
3919 *
3920 * Move to TIME_WAIT
3921 */
3922
3923 if (sk->state == TCP_CLOSING)
3924 {
3925
3926 if (!sk->dead)
3927 sk->state_change(sk);
3928 if (sk->rcv_ack_seq == sk->write_seq)
3929 {
3930 flag |= 1;
3931 tcp_time_wait(sk);
3932 }
3933 }
3934
3935 /*
3936 * Final ack of a three way shake
3937 */
3938
3939 if(sk->state==TCP_SYN_RECV)
3940 {
3941 tcp_set_state(sk, TCP_ESTABLISHED);
3942 tcp_options(sk,th);
3943 sk->dummy_th.dest=th->source;
3944 sk->copied_seq = sk->acked_seq;
3945 if(!sk->dead)
3946 sk->state_change(sk);
3947 if(sk->max_window==0)
3948 {
3949 sk->max_window=32; /* Sanity check */
3950 sk->mss=min(sk->max_window,sk->mtu);
3951 }
3952 }
3953
3954 /*
3955 * I make no guarantees about the first clause in the following
3956 * test, i.e. "(!flag) || (flag&4)". I'm not entirely sure under
3957 * what conditions "!flag" would be true. However I think the rest
3958 * of the conditions would prevent that from causing any
3959 * unnecessary retransmission.
3960 * Clearly if the first packet has expired it should be
3961 * retransmitted. The other alternative, "flag&2 && retransmits", is
3962 * harder to explain: You have to look carefully at how and when the
3963 * timer is set and with what timeout. The most recent transmission always
3964 * sets the timer. So in general if the most recent thing has timed
3965 * out, everything before it has as well. So we want to go ahead and
3966 * retransmit some more. If we didn't explicitly test for this
3967 * condition with "flag&2 && retransmits", chances are "when + rto < jiffies"
3968 * would not be true. If you look at the pattern of timing, you can
3969 * show that rto is increased fast enough that the next packet would
3970 * almost never be retransmitted immediately. Then you'd end up
3971 * waiting for a timeout to send each packet on the retransmission
3972 * queue. With my implementation of the Karn sampling algorithm,
3973 * the timeout would double each time. The net result is that it would
3974 * take a hideous amount of time to recover from a single dropped packet.
3975 * It's possible that there should also be a test for TIME_WRITE, but
3976 * I think as long as "send_head != NULL" and "retransmit" is on, we've
3977 * got to be in real retransmission mode.
3978 * Note that tcp_do_retransmit is called with all==1. Setting cong_window
3979 * back to 1 at the timeout will cause us to send 1, then 2, etc. packets.
3980 * As long as no further losses occur, this seems reasonable.
3981 */
3982
3983 if (((!flag) || (flag&4)) && sk->send_head != NULL &&
3984 (((flag&2) && sk->retransmits) ||
3985 (sk->send_head->when + sk->rto < jiffies)))
3986 {
3987 if(sk->send_head->when + sk->rto < jiffies)
3988 tcp_retransmit(sk,0);
3989 else
3990 {
3991 tcp_do_retransmit(sk, 1);
3992 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
3993 }
3994 }
3995
3996 return(1);
3997 }
3998
3999
4000 /*
4001 * Process the FIN bit. This now behaves as it is supposed to work
4002 * and the FIN takes effect when it is validly part of sequence
4003 * space. Not before when we get holes.
4004 *
4005 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT
4006 * (and thence onto LAST-ACK and finally, CLOSE, we never enter
4007 * TIME-WAIT)
4008 *
4009 * If we are in FINWAIT-1, a received FIN indicates simultaneous
4010 * close and we go into CLOSING (and later onto TIME-WAIT)
4011 *
4012 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT.
4013 *
4014 */
4015
4016 static int tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th)
/* */
4017 {
4018 sk->fin_seq = skb->end_seq;
4019
4020 if (!sk->dead)
4021 {
4022 sk->state_change(sk);
4023 sock_wake_async(sk->socket, 1);
4024 }
4025
4026 switch(sk->state)
4027 {
4028 case TCP_SYN_RECV:
4029 case TCP_SYN_SENT:
4030 case TCP_ESTABLISHED:
4031 /*
4032 * move to CLOSE_WAIT, tcp_data() already handled
4033 * sending the ack.
4034 */
4035 tcp_set_state(sk,TCP_CLOSE_WAIT);
4036 if (th->rst)
4037 sk->shutdown = SHUTDOWN_MASK;
4038 break;
4039
4040 case TCP_CLOSE_WAIT:
4041 case TCP_CLOSING:
4042 /*
4043 * received a retransmission of the FIN, do
4044 * nothing.
4045 */
4046 break;
4047 case TCP_TIME_WAIT:
4048 /*
4049 * received a retransmission of the FIN,
4050 * restart the TIME_WAIT timer.
4051 */
4052 reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
4053 return(0);
4054 case TCP_FIN_WAIT1:
4055 /*
4056 * This case occurs when a simultaneous close
4057 * happens, we must ack the received FIN and
4058 * enter the CLOSING state.
4059 *
4060 * This causes a WRITE timeout, which will either
4061 * move on to TIME_WAIT when we timeout, or resend
4062 * the FIN properly (maybe we get rid of that annoying
4063 * FIN lost hang). The TIME_WRITE code is already correct
4064 * for handling this timeout.
4065 */
4066
4067 if(sk->ip_xmit_timeout != TIME_WRITE)
4068 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
4069 tcp_set_state(sk,TCP_CLOSING);
4070 break;
4071 case TCP_FIN_WAIT2:
4072 /*
4073 * received a FIN -- send ACK and enter TIME_WAIT
4074 */
4075 reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
4076 sk->shutdown|=SHUTDOWN_MASK;
4077 tcp_set_state(sk,TCP_TIME_WAIT);
4078 break;
4079 case TCP_CLOSE:
4080 /*
4081 * already in CLOSE
4082 */
4083 break;
4084 default:
4085 tcp_set_state(sk,TCP_LAST_ACK);
4086
4087 /* Start the timers. */
4088 reset_msl_timer(sk, TIME_CLOSE, TCP_TIMEWAIT_LEN);
4089 return(0);
4090 }
4091
4092 return(0);
4093 }
4094
4095
4096
4097 /*
4098 * This routine handles the data. If there is room in the buffer,
4099 * it will be have already been moved into it. If there is no
4100 * room, then we will just have to discard the packet.
4101 */
4102
4103 extern __inline__ int tcp_data(struct sk_buff *skb, struct sock *sk,
/* */
4104 unsigned long saddr, unsigned short len)
4105 {
4106 struct sk_buff *skb1, *skb2;
4107 struct tcphdr *th;
4108 int dup_dumped=0;
4109 u32 new_seq, shut_seq;
4110
4111 th = skb->h.th;
4112 skb_pull(skb,th->doff*4);
4113 skb_trim(skb,len-(th->doff*4));
4114
4115 /*
4116 * The bytes in the receive read/assembly queue has increased. Needed for the
4117 * low memory discard algorithm
4118 */
4119
4120 sk->bytes_rcv += skb->len;
4121
4122 if (skb->len == 0 && !th->fin)
4123 {
4124 /*
4125 * Don't want to keep passing ack's back and forth.
4126 * (someone sent us dataless, boring frame)
4127 */
4128 if (!th->ack)
4129 tcp_send_ack(sk->sent_seq, sk->acked_seq,sk, th, saddr);
4130 kfree_skb(skb, FREE_READ);
4131 return(0);
4132 }
4133
4134 /*
4135 * We no longer have anyone receiving data on this connection.
4136 */
4137
4138 #ifndef TCP_DONT_RST_SHUTDOWN
4139
4140 if(sk->shutdown & RCV_SHUTDOWN)
4141 {
4142 /*
4143 * FIXME: BSD has some magic to avoid sending resets to
4144 * broken 4.2 BSD keepalives. Much to my surprise a few non
4145 * BSD stacks still have broken keepalives so we want to
4146 * cope with it.
4147 */
4148
4149 if(skb->len) /* We don't care if it's just an ack or
4150 a keepalive/window probe */
4151 {
4152 new_seq = skb->seq + skb->len + th->syn; /* Right edge of _data_ part of frame */
4153
4154 /* Do this the way 4.4BSD treats it. Not what I'd
4155 regard as the meaning of the spec but it's what BSD
4156 does and clearly they know everything 8) */
4157
4158 /*
4159 * This is valid because of two things
4160 *
4161 * a) The way tcp_data behaves at the bottom.
4162 * b) A fin takes effect when read not when received.
4163 */
4164
4165 shut_seq = sk->acked_seq+1; /* Last byte */
4166
4167 if(after(new_seq,shut_seq))
4168 {
4169 if(sk->debug)
4170 printk("Data arrived on %p after close [Data right edge %X, Socket shut on %X] %d\n",
4171 sk, new_seq, shut_seq, sk->blog);
4172 if(sk->dead)
4173 {
4174 sk->acked_seq = new_seq + th->fin;
4175 tcp_reset(sk->saddr, sk->daddr, skb->h.th,
4176 sk->prot, NULL, skb->dev, sk->ip_tos, sk->ip_ttl);
4177 tcp_statistics.TcpEstabResets++;
4178 sk->err = EPIPE;
4179 sk->error_report(sk);
4180 sk->shutdown = SHUTDOWN_MASK;
4181 tcp_set_state(sk,TCP_CLOSE);
4182 kfree_skb(skb, FREE_READ);
4183 return 0;
4184 }
4185 }
4186 }
4187 }
4188
4189 #endif
4190
4191 /*
4192 * Now we have to walk the chain, and figure out where this one
4193 * goes into it. This is set up so that the last packet we received
4194 * will be the first one we look at, that way if everything comes
4195 * in order, there will be no performance loss, and if they come
4196 * out of order we will be able to fit things in nicely.
4197 *
4198 * [AC: This is wrong. We should assume in order first and then walk
4199 * forwards from the first hole based upon real traffic patterns.]
4200 *
4201 */
4202
4203 if (skb_peek(&sk->receive_queue) == NULL) /* Empty queue is easy case */
4204 {
4205 skb_queue_head(&sk->receive_queue,skb);
4206 skb1= NULL;
4207 }
4208 else
4209 {
4210 for(skb1=sk->receive_queue.prev; ; skb1 = skb1->prev)
4211 {
4212 if(sk->debug)
4213 {
4214 printk("skb1=%p :", skb1);
4215 printk("skb1->seq = %d: ", skb1->seq);
4216 printk("skb->seq = %d\n",skb->seq);
4217 printk("copied_seq = %d acked_seq = %d\n", sk->copied_seq,
4218 sk->acked_seq);
4219 }
4220
4221 /*
4222 * Optimisation: Duplicate frame or extension of previous frame from
4223 * same sequence point (lost ack case).
4224 * The frame contains duplicate data or replaces a previous frame
4225 * discard the previous frame (safe as sk->inuse is set) and put
4226 * the new one in its place.
4227 */
4228
4229 if (skb->seq==skb1->seq && skb->len>=skb1->len)
4230 {
4231 skb_append(skb1,skb);
4232 skb_unlink(skb1);
4233 kfree_skb(skb1,FREE_READ);
4234 dup_dumped=1;
4235 skb1=NULL;
4236 break;
4237 }
4238
4239 /*
4240 * Found where it fits
4241 */
4242
4243 if (after(skb->seq+1, skb1->seq))
4244 {
4245 skb_append(skb1,skb);
4246 break;
4247 }
4248
4249 /*
4250 * See if we've hit the start. If so insert.
4251 */
4252 if (skb1 == skb_peek(&sk->receive_queue))
4253 {
4254 skb_queue_head(&sk->receive_queue, skb);
4255 break;
4256 }
4257 }
4258 }
4259
4260 /*
4261 * Figure out what the ack value for this frame is
4262 */
4263
4264 if (before(sk->acked_seq, sk->copied_seq))
4265 {
4266 printk("*** tcp.c:tcp_data bug acked < copied\n");
4267 sk->acked_seq = sk->copied_seq;
4268 }
4269
4270 /*
4271 * Now figure out if we can ack anything. This is very messy because we really want two
4272 * receive queues, a completed and an assembly queue. We also want only one transmit
4273 * queue.
4274 */
4275
4276 if ((!dup_dumped && (skb1 == NULL || skb1->acked)) || before(skb->seq, sk->acked_seq+1))
4277 {
4278 if (before(skb->seq, sk->acked_seq+1))
4279 {
4280 int newwindow;
4281
4282 if (after(skb->end_seq, sk->acked_seq))
4283 {
4284 newwindow = sk->window - (skb->end_seq - sk->acked_seq);
4285 if (newwindow < 0)
4286 newwindow = 0;
4287 sk->window = newwindow;
4288 sk->acked_seq = skb->end_seq;
4289 }
4290 skb->acked = 1;
4291
4292 /*
4293 * When we ack the fin, we do the FIN
4294 * processing.
4295 */
4296
4297 if (skb->h.th->fin)
4298 {
4299 tcp_fin(skb,sk,skb->h.th);
4300 }
4301
4302 for(skb2 = skb->next;
4303 skb2 != (struct sk_buff *)&sk->receive_queue;
4304 skb2 = skb2->next)
4305 {
4306 if (before(skb2->seq, sk->acked_seq+1))
4307 {
4308 if (after(skb2->end_seq, sk->acked_seq))
4309 {
4310 newwindow = sk->window -
4311 (skb2->end_seq - sk->acked_seq);
4312 if (newwindow < 0)
4313 newwindow = 0;
4314 sk->window = newwindow;
4315 sk->acked_seq = skb2->end_seq;
4316 }
4317 skb2->acked = 1;
4318 /*
4319 * When we ack the fin, we do
4320 * the fin handling.
4321 */
4322 if (skb2->h.th->fin)
4323 {
4324 tcp_fin(skb,sk,skb->h.th);
4325 }
4326
4327 /*
4328 * Force an immediate ack.
4329 */
4330
4331 sk->ack_backlog = sk->max_ack_backlog;
4332 }
4333 else
4334 {
4335 break;
4336 }
4337 }
4338
4339 /*
4340 * This also takes care of updating the window.
4341 * This if statement needs to be simplified.
4342 */
4343 if (!sk->delay_acks ||
4344 sk->ack_backlog >= sk->max_ack_backlog ||
4345 sk->bytes_rcv > sk->max_unacked || th->fin) {
4346 /* tcp_send_ack(sk->sent_seq, sk->acked_seq,sk,th, saddr); */
4347 }
4348 else
4349 {
4350 sk->ack_backlog++;
4351 if(sk->debug)
4352 printk("Ack queued.\n");
4353 reset_xmit_timer(sk, TIME_WRITE, TCP_ACK_TIME);
4354 }
4355 }
4356 }
4357
4358 /*
4359 * If we've missed a packet, send an ack.
4360 * Also start a timer to send another.
4361 */
4362
4363 if (!skb->acked)
4364 {
4365
4366 /*
4367 * This is important. If we don't have much room left,
4368 * we need to throw out a few packets so we have a good
4369 * window. Note that mtu is used, not mss, because mss is really
4370 * for the send side. He could be sending us stuff as large as mtu.
4371 */
4372
4373 while (sock_rspace(sk) < sk->mtu)
4374 {
4375 skb1 = skb_peek(&sk->receive_queue);
4376 if (skb1 == NULL)
4377 {
4378 printk("INET: tcp.c:tcp_data memory leak detected.\n");
4379 break;
4380 }
4381
4382 /*
4383 * Don't throw out something that has been acked.
4384 */
4385
4386 if (skb1->acked)
4387 {
4388 break;
4389 }
4390
4391 skb_unlink(skb1);
4392 kfree_skb(skb1, FREE_READ);
4393 }
4394 tcp_send_ack(sk->sent_seq, sk->acked_seq, sk, th, saddr);
4395 sk->ack_backlog++;
4396 reset_xmit_timer(sk, TIME_WRITE, TCP_ACK_TIME);
4397 }
4398 else
4399 {
4400 tcp_send_ack(sk->sent_seq, sk->acked_seq, sk, th, saddr);
4401 }
4402
4403 /*
4404 * Now tell the user we may have some data.
4405 */
4406
4407 if (!sk->dead)
4408 {
4409 if(sk->debug)
4410 printk("Data wakeup.\n");
4411 sk->data_ready(sk,0);
4412 }
4413 return(0);
4414 }
4415
4416
4417 /*
4418 * This routine is only called when we have urgent data
4419 * signalled. Its the 'slow' part of tcp_urg. It could be
4420 * moved inline now as tcp_urg is only called from one
4421 * place. We handle URGent data wrong. We have to - as
4422 * BSD still doesn't use the correction from RFC961.
4423 */
4424
4425 static void tcp_check_urg(struct sock * sk, struct tcphdr * th)
/* */
4426 {
4427 u32 ptr = ntohs(th->urg_ptr);
4428
4429 if (ptr)
4430 ptr--;
4431 ptr += ntohl(th->seq);
4432
4433 /* ignore urgent data that we've already seen and read */
4434 if (after(sk->copied_seq, ptr))
4435 return;
4436
4437 /* do we already have a newer (or duplicate) urgent pointer? */
4438 if (sk->urg_data && !after(ptr, sk->urg_seq))
4439 return;
4440
4441 /* tell the world about our new urgent pointer */
4442 if (sk->proc != 0) {
4443 if (sk->proc > 0) {
4444 kill_proc(sk->proc, SIGURG, 1);
4445 } else {
4446 kill_pg(-sk->proc, SIGURG, 1);
4447 }
4448 }
4449 sk->urg_data = URG_NOTYET;
4450 sk->urg_seq = ptr;
4451 }
4452
4453 /*
4454 * This is the 'fast' part of urgent handling.
4455 */
4456
4457 extern __inline__ int tcp_urg(struct sock *sk, struct tcphdr *th,
/* */
4458 unsigned long saddr, unsigned long len)
4459 {
4460 u32 ptr;
4461
4462 /*
4463 * Check if we get a new urgent pointer - normally not
4464 */
4465
4466 if (th->urg)
4467 tcp_check_urg(sk,th);
4468
4469 /*
4470 * Do we wait for any urgent data? - normally not
4471 */
4472
4473 if (sk->urg_data != URG_NOTYET)
4474 return 0;
4475
4476 /*
4477 * Is the urgent pointer pointing into this packet?
4478 */
4479
4480 ptr = sk->urg_seq - ntohl(th->seq) + th->doff*4;
4481 if (ptr >= len)
4482 return 0;
4483
4484 /*
4485 * Ok, got the correct packet, update info
4486 */
4487
4488 sk->urg_data = URG_VALID | *(ptr + (unsigned char *) th);
4489 if (!sk->dead)
4490 sk->data_ready(sk,0);
4491 return 0;
4492 }
4493
4494 /*
4495 * This will accept the next outstanding connection.
4496 */
4497
4498 static struct sock *tcp_accept(struct sock *sk, int flags)
/* */
4499 {
4500 struct sock *newsk;
4501 struct sk_buff *skb;
4502
4503 /*
4504 * We need to make sure that this socket is listening,
4505 * and that it has something pending.
4506 */
4507
4508 if (sk->state != TCP_LISTEN)
4509 {
4510 sk->err = EINVAL;
4511 return(NULL);
4512 }
4513
4514 /* Avoid the race. */
4515 cli();
4516 sk->inuse = 1;
4517
4518 while((skb = tcp_dequeue_established(sk)) == NULL)
4519 {
4520 if (flags & O_NONBLOCK)
4521 {
4522 sti();
4523 release_sock(sk);
4524 sk->err = EAGAIN;
4525 return(NULL);
4526 }
4527
4528 release_sock(sk);
4529 interruptible_sleep_on(sk->sleep);
4530 if (current->signal & ~current->blocked)
4531 {
4532 sti();
4533 sk->err = ERESTARTSYS;
4534 return(NULL);
4535 }
4536 sk->inuse = 1;
4537 }
4538 sti();
4539
4540 /*
4541 * Now all we need to do is return skb->sk.
4542 */
4543
4544 newsk = skb->sk;
4545
4546 kfree_skb(skb, FREE_READ);
4547 sk->ack_backlog--;
4548 release_sock(sk);
4549 return(newsk);
4550 }
4551
4552
4553 /*
4554 * This will initiate an outgoing connection.
4555 */
4556
4557 static int tcp_connect(struct sock *sk, struct sockaddr_in *usin, int addr_len)
/* */
4558 {
4559 struct sk_buff *buff;
4560 struct device *dev=NULL;
4561 unsigned char *ptr;
4562 int tmp;
4563 int atype;
4564 struct tcphdr *t1;
4565 struct rtable *rt;
4566
4567 if (sk->state != TCP_CLOSE)
4568 return(-EISCONN);
4569
4570 /*
4571 * Don't allow a double connect.
4572 */
4573
4574 if(sk->daddr)
4575 return -EINVAL;
4576
4577 if (addr_len < 8)
4578 return(-EINVAL);
4579
4580 if (usin->sin_family && usin->sin_family != AF_INET)
4581 return(-EAFNOSUPPORT);
4582
4583 /*
4584 * connect() to INADDR_ANY means loopback (BSD'ism).
4585 */
4586
4587 if(usin->sin_addr.s_addr==INADDR_ANY)
4588 usin->sin_addr.s_addr=ip_my_addr();
4589
4590 /*
4591 * Don't want a TCP connection going to a broadcast address
4592 */
4593
4594 if ((atype=ip_chk_addr(usin->sin_addr.s_addr)) == IS_BROADCAST || atype==IS_MULTICAST)
4595 return -ENETUNREACH;
4596
4597 sk->inuse = 1;
4598 sk->daddr = usin->sin_addr.s_addr;
4599 sk->write_seq = tcp_init_seq();
4600 sk->window_seq = sk->write_seq;
4601 sk->rcv_ack_seq = sk->write_seq -1;
4602 sk->err = 0;
4603 sk->dummy_th.dest = usin->sin_port;
4604 release_sock(sk);
4605
4606 buff = sock_wmalloc(sk,MAX_SYN_SIZE,0, GFP_KERNEL);
4607 if (buff == NULL)
4608 {
4609 return(-ENOMEM);
4610 }
4611 sk->inuse = 1;
4612 buff->sk = sk;
4613 buff->free = 0;
4614 buff->localroute = sk->localroute;
4615
4616
4617 /*
4618 * Put in the IP header and routing stuff.
4619 */
4620
4621 tmp = sk->prot->build_header(buff, sk->saddr, sk->daddr, &dev,
4622 IPPROTO_TCP, NULL, MAX_SYN_SIZE,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
4623 if (tmp < 0)
4624 {
4625 sock_wfree(sk, buff);
4626 release_sock(sk);
4627 return(-ENETUNREACH);
4628 }
4629 if ((rt = sk->ip_route_cache) != NULL && !sk->saddr)
4630 sk->saddr = rt->rt_src;
4631 sk->rcv_saddr = sk->saddr;
4632
4633 t1 = (struct tcphdr *) skb_put(buff,sizeof(struct tcphdr));
4634
4635 memcpy(t1,(void *)&(sk->dummy_th), sizeof(*t1));
4636 buff->seq = sk->write_seq++;
4637 t1->seq = htonl(buff->seq);
4638 sk->sent_seq = sk->write_seq;
4639 buff->end_seq = sk->write_seq;
4640 t1->ack = 0;
4641 t1->window = 2;
4642 t1->res1=0;
4643 t1->res2=0;
4644 t1->rst = 0;
4645 t1->urg = 0;
4646 t1->psh = 0;
4647 t1->syn = 1;
4648 t1->urg_ptr = 0;
4649 t1->doff = 6;
4650 /* use 512 or whatever user asked for */
4651
4652 if(rt!=NULL && (rt->rt_flags&RTF_WINDOW))
4653 sk->window_clamp=rt->rt_window;
4654 else
4655 sk->window_clamp=0;
4656
4657 if (sk->user_mss)
4658 sk->mtu = sk->user_mss;
4659 else if (rt)
4660 sk->mtu = rt->rt_mtu - sizeof(struct iphdr) - sizeof(struct tcphdr);
4661 else
4662 sk->mtu = 576 - sizeof(struct iphdr) - sizeof(struct tcphdr);
4663
4664 /*
4665 * but not bigger than device MTU
4666 */
4667
4668 if(sk->mtu <32)
4669 sk->mtu = 32; /* Sanity limit */
4670
4671 sk->mtu = min(sk->mtu, dev->mtu - sizeof(struct iphdr) - sizeof(struct tcphdr));
4672
4673 #ifdef CONFIG_SKIP
4674
4675 /*
4676 * SKIP devices set their MTU to 65535. This is so they can take packets
4677 * unfragmented to security process then fragment. They could lie to the
4678 * TCP layer about a suitable MTU, but its easier to let skip sort it out
4679 * simply because the final package we want unfragmented is going to be
4680 *
4681 * [IPHDR][IPSP][Security data][Modified TCP data][Security data]
4682 */
4683
4684 if(skip_pick_mtu!=NULL) /* If SKIP is loaded.. */
4685 sk->mtu=skip_pick_mtu(sk->mtu,dev);
4686 #endif
4687
4688 /*
4689 * Put in the TCP options to say MTU.
4690 */
4691
4692 ptr = skb_put(buff,4);
4693 ptr[0] = 2;
4694 ptr[1] = 4;
4695 ptr[2] = (sk->mtu) >> 8;
4696 ptr[3] = (sk->mtu) & 0xff;
4697 tcp_send_check(t1, sk->saddr, sk->daddr,
4698 sizeof(struct tcphdr) + 4, sk);
4699
4700 /*
4701 * This must go first otherwise a really quick response will get reset.
4702 */
4703
4704 tcp_cache_zap();
4705 tcp_set_state(sk,TCP_SYN_SENT);
4706 if(rt&&rt->rt_flags&RTF_IRTT)
4707 sk->rto = rt->rt_irtt;
4708 else
4709 sk->rto = TCP_TIMEOUT_INIT;
4710 sk->retransmit_timer.function=&retransmit_timer;
4711 sk->retransmit_timer.data = (unsigned long)sk;
4712 reset_xmit_timer(sk, TIME_WRITE, sk->rto); /* Timer for repeating the SYN until an answer */
4713 sk->retransmits = 0; /* Now works the right way instead of a hacked
4714 initial setting */
4715
4716 sk->prot->queue_xmit(sk, dev, buff, 0);
4717 reset_xmit_timer(sk, TIME_WRITE, sk->rto);
4718 tcp_statistics.TcpActiveOpens++;
4719 tcp_statistics.TcpOutSegs++;
4720
4721 release_sock(sk);
4722 return(0);
4723 }
4724
4725
4726 /*
4727 * This functions checks to see if the tcp header is actually acceptable.
4728 */
4729
4730 extern __inline__ int tcp_sequence(struct sock *sk, struct tcphdr *th, short len,
/* */
4731 struct options *opt, unsigned long saddr, struct device *dev)
4732 {
4733 u32 next_seq;
4734
4735 next_seq = len - 4*th->doff;
4736 if (th->fin)
4737 next_seq++;
4738 /* if we have a zero window, we can't have any data in the packet.. */
4739 if (next_seq && !sk->window)
4740 goto ignore_it;
4741 next_seq += ntohl(th->seq);
4742
4743 /*
4744 * This isn't quite right. sk->acked_seq could be more recent
4745 * than sk->window. This is however close enough. We will accept
4746 * slightly more packets than we should, but it should not cause
4747 * problems unless someone is trying to forge packets.
4748 */
4749
4750 /* have we already seen all of this packet? */
4751 if (!after(next_seq+1, sk->acked_seq))
4752 goto ignore_it;
4753 /* or does it start beyond the window? */
4754 if (!before(ntohl(th->seq), sk->acked_seq + sk->window + 1))
4755 goto ignore_it;
4756
4757 /* ok, at least part of this packet would seem interesting.. */
4758 return 1;
4759
4760 ignore_it:
4761 if (th->rst)
4762 return 0;
4763
4764 /*
4765 * Send a reset if we get something not ours and we are
4766 * unsynchronized. Note: We don't do anything to our end. We
4767 * are just killing the bogus remote connection then we will
4768 * connect again and it will work (with luck).
4769 */
4770
4771 if (sk->state==TCP_SYN_SENT || sk->state==TCP_SYN_RECV)
4772 {
4773 tcp_reset(sk->saddr,sk->daddr,th,sk->prot,NULL,dev, sk->ip_tos,sk->ip_ttl);
4774 return 1;
4775 }
4776
4777 /* Try to resync things. */
4778 tcp_send_ack(sk->sent_seq, sk->acked_seq, sk, th, saddr);
4779 return 0;
4780 }
4781
4782 /*
4783 * When we get a reset we do this.
4784 */
4785
4786 static int tcp_std_reset(struct sock *sk, struct sk_buff *skb)
/* */
4787 {
4788 sk->zapped = 1;
4789 sk->err = ECONNRESET;
4790 if (sk->state == TCP_SYN_SENT)
4791 sk->err = ECONNREFUSED;
4792 if (sk->state == TCP_CLOSE_WAIT)
4793 sk->err = EPIPE;
4794 #ifdef TCP_DO_RFC1337
4795 /*
4796 * Time wait assassination protection [RFC1337]
4797 */
4798 if(sk->state!=TCP_TIME_WAIT)
4799 {
4800 tcp_set_state(sk,TCP_CLOSE);
4801 sk->shutdown = SHUTDOWN_MASK;
4802 }
4803 #else
4804 tcp_set_state(sk,TCP_CLOSE);
4805 sk->shutdown = SHUTDOWN_MASK;
4806 #endif
4807 if (!sk->dead)
4808 sk->state_change(sk);
4809 kfree_skb(skb, FREE_READ);
4810 release_sock(sk);
4811 return(0);
4812 }
4813
4814 /*
4815 * A TCP packet has arrived.
4816 * skb->h.raw is the TCP header.
4817 */
4818
4819 int tcp_rcv(struct sk_buff *skb, struct device *dev, struct options *opt,
/* */
4820 __u32 daddr, unsigned short len,
4821 __u32 saddr, int redo, struct inet_protocol * protocol)
4822 {
4823 struct tcphdr *th;
4824 struct sock *sk;
4825 int syn_ok=0;
4826
4827 tcp_statistics.TcpInSegs++;
4828 if(skb->pkt_type!=PACKET_HOST)
4829 {
4830 kfree_skb(skb,FREE_READ);
4831 return(0);
4832 }
4833
4834 th = skb->h.th;
4835
4836 /*
4837 * Find the socket, using the last hit cache if applicable.
4838 */
4839
4840 if(!redo && saddr==th_cache_saddr && daddr==th_cache_daddr && th->dest==th_cache_dport && th->source==th_cache_sport)
4841 {
4842 sk=(struct sock *)th_cache_sk;
4843 /*
4844 * We think this is causing the bug so
4845 */
4846 if(sk!=get_sock(&tcp_prot,th->dest, saddr, th->source, daddr))
4847 printk("Cache mismatch on TCP.\n");
4848 }
4849 else
4850 {
4851 sk = get_sock(&tcp_prot, th->dest, saddr, th->source, daddr);
4852 th_cache_saddr=saddr;
4853 th_cache_daddr=daddr;
4854 th_cache_dport=th->dest;
4855 th_cache_sport=th->source;
4856 th_cache_sk=sk;
4857 }
4858
4859 /*
4860 * If this socket has got a reset it's to all intents and purposes
4861 * really dead. Count closed sockets as dead.
4862 *
4863 * Note: BSD appears to have a bug here. A 'closed' TCP in BSD
4864 * simply drops data. This seems incorrect as a 'closed' TCP doesn't
4865 * exist so should cause resets as if the port was unreachable.
4866 */
4867
4868 if (sk!=NULL && (sk->zapped || sk->state==TCP_CLOSE))
4869 sk=NULL;
4870
4871 if (!redo)
4872 {
4873 /*
4874 * Pull up the IP header.
4875 */
4876 skb_pull(skb, skb->h.raw-skb->data);
4877 /*
4878 * Try to use the device checksum if provided.
4879 */
4880 if (
4881 (skb->ip_summed && tcp_check(th, len, saddr, daddr, skb->csum ))||
4882 (!skb->ip_summed && tcp_check(th, len, saddr, daddr, csum_partial((char *)th, len, 0)))
4883 )
4884 {
4885 skb->sk = NULL;
4886 kfree_skb(skb,FREE_READ);
4887 /*
4888 * We don't release the socket because it was
4889 * never marked in use.
4890 */
4891 return(0);
4892 }
4893
4894 skb->seq = ntohl(th->seq);
4895 skb->end_seq = skb->seq + th->syn + th->fin + len - th->doff*4;
4896 skb->ack_seq = ntohl(th->ack_seq);
4897
4898 /* See if we know about the socket. */
4899 if (sk == NULL)
4900 {
4901 /*
4902 * No such TCB. If th->rst is 0 send a reset (checked in tcp_reset)
4903 */
4904 tcp_reset(daddr, saddr, th, &tcp_prot, opt,dev,skb->ip_hdr->tos,255);
4905 skb->sk = NULL;
4906 /*
4907 * Discard frame
4908 */
4909 kfree_skb(skb, FREE_READ);
4910 return(0);
4911 }
4912
4913 skb->acked = 0;
4914 skb->used = 0;
4915 skb->free = 0;
4916 skb->saddr = daddr;
4917 skb->daddr = saddr;
4918
4919 /* We may need to add it to the backlog here. */
4920 cli();
4921 if (sk->inuse)
4922 {
4923 skb_queue_tail(&sk->back_log, skb);
4924 sti();
4925 return(0);
4926 }
4927 sk->inuse = 1;
4928 sti();
4929 }
4930 else
4931 {
4932 if (sk==NULL)
4933 {
4934 tcp_reset(daddr, saddr, th, &tcp_prot, opt,dev,skb->ip_hdr->tos,255);
4935 skb->sk = NULL;
4936 kfree_skb(skb, FREE_READ);
4937 return(0);
4938 }
4939 }
4940
4941
4942 if (!sk->prot)
4943 {
4944 printk("IMPOSSIBLE 3\n");
4945 return(0);
4946 }
4947
4948
4949 /*
4950 * Charge the memory to the socket.
4951 */
4952
4953 skb->sk=sk;
4954 sk->rmem_alloc += skb->truesize;
4955
4956 /*
4957 * This basically follows the flow suggested by RFC793, with the corrections in RFC1122. We
4958 * don't implement precedence and we process URG incorrectly (deliberately so) for BSD bug
4959 * compatibility. We also set up variables more thoroughly [Karn notes in the
4960 * KA9Q code the RFC793 incoming segment rules don't initialise the variables for all paths].
4961 */
4962
4963 if(sk->state!=TCP_ESTABLISHED) /* Skip this lot for normal flow */
4964 {
4965
4966 /*
4967 * Now deal with unusual cases.
4968 */
4969
4970 if(sk->state==TCP_LISTEN)
4971 {
4972 if(th->ack) /* These use the socket TOS.. might want to be the received TOS */
4973 tcp_reset(daddr,saddr,th,sk->prot,opt,dev,sk->ip_tos, sk->ip_ttl);
4974
4975 /*
4976 * We don't care for RST, and non SYN are absorbed (old segments)
4977 * Broadcast/multicast SYN isn't allowed. Note - bug if you change the
4978 * netmask on a running connection it can go broadcast. Even Sun's have
4979 * this problem so I'm ignoring it
4980 */
4981
4982 if(th->rst || !th->syn || th->ack || ip_chk_addr(daddr)!=IS_MYADDR)
4983 {
4984 kfree_skb(skb, FREE_READ);
4985 release_sock(sk);
4986 return 0;
4987 }
4988
4989 /*
4990 * Guess we need to make a new socket up
4991 */
4992
4993 tcp_conn_request(sk, skb, daddr, saddr, opt, dev, tcp_init_seq());
4994
4995 /*
4996 * Now we have several options: In theory there is nothing else
4997 * in the frame. KA9Q has an option to send data with the syn,
4998 * BSD accepts data with the syn up to the [to be] advertised window
4999 * and Solaris 2.1 gives you a protocol error. For now we just ignore
5000 * it, that fits the spec precisely and avoids incompatibilities. It
5001 * would be nice in future to drop through and process the data.
5002 */
5003
5004 release_sock(sk);
5005 return 0;
5006 }
5007
5008 /* retransmitted SYN? */
5009 if (sk->state == TCP_SYN_RECV && th->syn && skb->seq+1 == sk->acked_seq)
5010 {
5011 kfree_skb(skb, FREE_READ);
5012 release_sock(sk);
5013 return 0;
5014 }
5015
5016 /*
5017 * SYN sent means we have to look for a suitable ack and either reset
5018 * for bad matches or go to connected
5019 */
5020
5021 if(sk->state==TCP_SYN_SENT)
5022 {
5023 /* Crossed SYN or previous junk segment */
5024 if(th->ack)
5025 {
5026 /* We got an ack, but it's not a good ack */
5027 if(!tcp_ack(sk,th,saddr,len))
5028 {
5029 /* Reset the ack - its an ack from a
5030 different connection [ th->rst is checked in tcp_reset()] */
5031 tcp_statistics.TcpAttemptFails++;
5032 tcp_reset(daddr, saddr, th,
5033 sk->prot, opt,dev,sk->ip_tos,sk->ip_ttl);
5034 kfree_skb(skb, FREE_READ);
5035 release_sock(sk);
5036 return(0);
5037 }
5038 if(th->rst)
5039 return tcp_std_reset(sk,skb);
5040 if(!th->syn)
5041 {
5042 /* A valid ack from a different connection
5043 start. Shouldn't happen but cover it */
5044 kfree_skb(skb, FREE_READ);
5045 release_sock(sk);
5046 return 0;
5047 }
5048 /*
5049 * Ok.. it's good. Set up sequence numbers and
5050 * move to established.
5051 */
5052 syn_ok=1; /* Don't reset this connection for the syn */
5053 sk->acked_seq = skb->seq+1;
5054 sk->fin_seq = skb->seq;
5055 tcp_send_ack(sk->sent_seq,sk->acked_seq,sk,th,sk->daddr);
5056 tcp_set_state(sk, TCP_ESTABLISHED);
5057 tcp_options(sk,th);
5058 sk->dummy_th.dest=th->source;
5059 sk->copied_seq = sk->acked_seq;
5060 if(!sk->dead)
5061 {
5062 sk->state_change(sk);
5063 sock_wake_async(sk->socket, 0);
5064 }
5065 if(sk->max_window==0)
5066 {
5067 sk->max_window = 32;
5068 sk->mss = min(sk->max_window, sk->mtu);
5069 }
5070 }
5071 else
5072 {
5073 /* See if SYN's cross. Drop if boring */
5074 if(th->syn && !th->rst)
5075 {
5076 /* Crossed SYN's are fine - but talking to
5077 yourself is right out... */
5078 if(sk->saddr==saddr && sk->daddr==daddr &&
5079 sk->dummy_th.source==th->source &&
5080 sk->dummy_th.dest==th->dest)
5081 {
5082 tcp_statistics.TcpAttemptFails++;
5083 return tcp_std_reset(sk,skb);
5084 }
5085 tcp_set_state(sk,TCP_SYN_RECV);
5086
5087 /*
5088 * FIXME:
5089 * Must send SYN|ACK here
5090 */
5091 }
5092 /* Discard junk segment */
5093 kfree_skb(skb, FREE_READ);
5094 release_sock(sk);
5095 return 0;
5096 }
5097 /*
5098 * SYN_RECV with data maybe.. drop through
5099 */
5100 goto rfc_step6;
5101 }
5102
5103 /*
5104 * BSD has a funny hack with TIME_WAIT and fast reuse of a port. There is
5105 * a more complex suggestion for fixing these reuse issues in RFC1644
5106 * but not yet ready for general use. Also see RFC1379.
5107 */
5108
5109 #define BSD_TIME_WAIT
5110 #ifdef BSD_TIME_WAIT
5111 if (sk->state == TCP_TIME_WAIT && th->syn && sk->dead &&
5112 after(skb->seq, sk->acked_seq) && !th->rst)
5113 {
5114 u32 seq = sk->write_seq;
5115 if(sk->debug)
5116 printk("Doing a BSD time wait\n");
5117 tcp_statistics.TcpEstabResets++;
5118 sk->rmem_alloc -= skb->truesize;
5119 skb->sk = NULL;
5120 sk->err=ECONNRESET;
5121 tcp_set_state(sk, TCP_CLOSE);
5122 sk->shutdown = SHUTDOWN_MASK;
5123 release_sock(sk);
5124 sk=get_sock(&tcp_prot, th->dest, saddr, th->source, daddr);
5125 if (sk && sk->state==TCP_LISTEN)
5126 {
5127 sk->inuse=1;
5128 skb->sk = sk;
5129 sk->rmem_alloc += skb->truesize;
5130 tcp_conn_request(sk, skb, daddr, saddr,opt, dev,seq+128000);
5131 release_sock(sk);
5132 return 0;
5133 }
5134 kfree_skb(skb, FREE_READ);
5135 return 0;
5136 }
5137 #endif
5138 }
5139
5140 /*
5141 * We are now in normal data flow (see the step list in the RFC)
5142 * Note most of these are inline now. I'll inline the lot when
5143 * I have time to test it hard and look at what gcc outputs
5144 */
5145
5146 if(!tcp_sequence(sk,th,len,opt,saddr,dev))
5147 {
5148 kfree_skb(skb, FREE_READ);
5149 release_sock(sk);
5150 return 0;
5151 }
5152
5153 if(th->rst)
5154 return tcp_std_reset(sk,skb);
5155
5156 /*
5157 * !syn_ok is effectively the state test in RFC793.
5158 */
5159
5160 if(th->syn && !syn_ok)
5161 {
5162 tcp_reset(daddr,saddr,th, &tcp_prot, opt, dev, skb->ip_hdr->tos, 255);
5163 return tcp_std_reset(sk,skb);
5164 }
5165
5166 /*
5167 * Process the ACK
5168 */
5169
5170
5171 if(th->ack && !tcp_ack(sk,th,saddr,len))
5172 {
5173 /*
5174 * Our three way handshake failed.
5175 */
5176
5177 if(sk->state==TCP_SYN_RECV)
5178 {
5179 tcp_reset(daddr, saddr, th,sk->prot, opt, dev,sk->ip_tos,sk->ip_ttl);
5180 }
5181 kfree_skb(skb, FREE_READ);
5182 release_sock(sk);
5183 return 0;
5184 }
5185
5186 rfc_step6: /* I'll clean this up later */
5187
5188 /*
5189 * If the accepted buffer put us over our queue size we
5190 * now drop it (we must process the ack first to avoid
5191 * deadlock cases).
5192 */
5193
5194 if (sk->rmem_alloc >= sk->rcvbuf)
5195 {
5196 kfree_skb(skb, FREE_READ);
5197 release_sock(sk);
5198 return(0);
5199 }
5200
5201
5202 /*
5203 * Process urgent data
5204 */
5205
5206 if(tcp_urg(sk, th, saddr, len))
5207 {
5208 kfree_skb(skb, FREE_READ);
5209 release_sock(sk);
5210 return 0;
5211 }
5212
5213 /*
5214 * Process the encapsulated data
5215 */
5216
5217 if(tcp_data(skb,sk, saddr, len))
5218 {
5219 kfree_skb(skb, FREE_READ);
5220 release_sock(sk);
5221 return 0;
5222 }
5223
5224 /*
5225 * And done
5226 */
5227
5228 release_sock(sk);
5229 return 0;
5230 }
5231
5232 /*
5233 * This routine sends a packet with an out of date sequence
5234 * number. It assumes the other end will try to ack it.
5235 */
5236
5237 static void tcp_write_wakeup(struct sock *sk)
/* */
5238 {
5239 struct sk_buff *buff,*skb;
5240 struct tcphdr *t1;
5241 struct device *dev=NULL;
5242 int tmp;
5243
5244 if (sk->zapped)
5245 return; /* After a valid reset we can send no more */
5246
5247 /*
5248 * Write data can still be transmitted/retransmitted in the
5249 * following states. If any other state is encountered, return.
5250 * [listen/close will never occur here anyway]
5251 */
5252
5253 if (sk->state != TCP_ESTABLISHED &&
5254 sk->state != TCP_CLOSE_WAIT &&
5255 sk->state != TCP_FIN_WAIT1 &&
5256 sk->state != TCP_LAST_ACK &&
5257 sk->state != TCP_CLOSING
5258 )
5259 {
5260 return;
5261 }
5262 if ( before(sk->sent_seq, sk->window_seq) &&
5263 (skb=skb_peek(&sk->write_queue)))
5264 {
5265 /*
5266 * We are probing the opening of a window
5267 * but the window size is != 0
5268 * must have been a result SWS advoidance ( sender )
5269 */
5270
5271 struct iphdr *iph;
5272 struct tcphdr *th;
5273 struct tcphdr *nth;
5274 unsigned long win_size;
5275 #if 0
5276 unsigned long ow_size;
5277 #endif
5278 void * tcp_data_start;
5279
5280 /*
5281 * How many bytes can we send ?
5282 */
5283
5284 win_size = sk->window_seq - sk->sent_seq;
5285
5286 /*
5287 * Recover the buffer pointers
5288 */
5289
5290 iph = (struct iphdr *)skb->ip_hdr;
5291 th = (struct tcphdr *)(((char *)iph) +(iph->ihl << 2));
5292
5293 /*
5294 * Grab the data for a temporary frame
5295 */
5296
5297 buff = sock_wmalloc(sk, win_size + th->doff * 4 +
5298 (iph->ihl << 2) +
5299 sk->prot->max_header + 15,
5300 1, GFP_ATOMIC);
5301 if ( buff == NULL )
5302 return;
5303
5304 /*
5305 * If we strip the packet on the write queue we must
5306 * be ready to retransmit this one
5307 */
5308
5309 buff->free = /*0*/1;
5310
5311 buff->sk = sk;
5312 buff->localroute = sk->localroute;
5313
5314 /*
5315 * Put headers on the new packet
5316 */
5317
5318 tmp = sk->prot->build_header(buff, sk->saddr, sk->daddr, &dev,
5319 IPPROTO_TCP, sk->opt, buff->truesize,
5320 sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
5321 if (tmp < 0)
5322 {
5323 sock_wfree(sk, buff);
5324 return;
5325 }
5326
5327 /*
5328 * Move the TCP header over
5329 */
5330
5331 buff->dev = dev;
5332
5333 nth = (struct tcphdr *) skb_put(buff,th->doff*4);
5334
5335 memcpy(nth, th, th->doff * 4);
5336
5337 /*
5338 * Correct the new header
5339 */
5340
5341 nth->ack = 1;
5342 nth->ack_seq = htonl(sk->acked_seq);
5343 nth->window = htons(tcp_select_window(sk));
5344 nth->check = 0;
5345
5346 /*
5347 * Find the first data byte.
5348 */
5349
5350 tcp_data_start = (char *) th + (th->doff << 2);
5351
5352 /*
5353 * Add it to our new buffer
5354 */
5355
5356 memcpy(skb_put(buff,win_size), tcp_data_start, win_size);
5357
5358 /*
5359 * Remember our right edge sequence number.
5360 */
5361
5362 buff->end_seq = sk->sent_seq + win_size;
5363 sk->sent_seq = buff->end_seq; /* Hack */
5364 if(th->urg && ntohs(th->urg_ptr) < win_size)
5365 nth->urg = 0;
5366
5367 /*
5368 * Checksum the split buffer
5369 */
5370
5371 tcp_send_check(nth, sk->saddr, sk->daddr,
5372 nth->doff * 4 + win_size , sk);
5373 }
5374 else
5375 {
5376 buff = sock_wmalloc(sk,MAX_ACK_SIZE,1, GFP_ATOMIC);
5377 if (buff == NULL)
5378 return;
5379
5380 buff->free = 1;
5381 buff->sk = sk;
5382 buff->localroute = sk->localroute;
5383
5384 /*
5385 * Put in the IP header and routing stuff.
5386 */
5387
5388 tmp = sk->prot->build_header(buff, sk->saddr, sk->daddr, &dev,
5389 IPPROTO_TCP, sk->opt, MAX_ACK_SIZE,sk->ip_tos,sk->ip_ttl,&sk->ip_route_cache);
5390 if (tmp < 0)
5391 {
5392 sock_wfree(sk, buff);
5393 return;
5394 }
5395
5396 t1 = (struct tcphdr *)skb_put(buff,sizeof(struct tcphdr));
5397 memcpy(t1,(void *) &sk->dummy_th, sizeof(*t1));
5398
5399 /*
5400 * Use a previous sequence.
5401 * This should cause the other end to send an ack.
5402 */
5403
5404 t1->seq = htonl(sk->sent_seq-1);
5405 t1->ack = 1;
5406 t1->res1= 0;
5407 t1->res2= 0;
5408 t1->rst = 0;
5409 t1->urg = 0;
5410 t1->psh = 0;
5411 t1->fin = 0; /* We are sending a 'previous' sequence, and 0 bytes of data - thus no FIN bit */
5412 t1->syn = 0;
5413 t1->ack_seq = htonl(sk->acked_seq);
5414 t1->window = htons(tcp_select_window(sk));
5415 t1->doff = sizeof(*t1)/4;
5416 tcp_send_check(t1, sk->saddr, sk->daddr, sizeof(*t1), sk);
5417
5418 }
5419
5420 /*
5421 * Send it.
5422 */
5423
5424 sk->prot->queue_xmit(sk, dev, buff, 1);
5425 tcp_statistics.TcpOutSegs++;
5426 }
5427
5428 /*
5429 * A window probe timeout has occurred.
5430 */
5431
5432 void tcp_send_probe0(struct sock *sk)
/* */
5433 {
5434 if (sk->zapped)
5435 return; /* After a valid reset we can send no more */
5436
5437 tcp_write_wakeup(sk);
5438
5439 sk->backoff++;
5440 sk->rto = min(sk->rto << 1, 120*HZ);
5441 sk->retransmits++;
5442 sk->prot->retransmits ++;
5443 reset_xmit_timer (sk, TIME_PROBE0, sk->rto);
5444 }
5445
5446 /*
5447 * Socket option code for TCP.
5448 */
5449
5450 int tcp_setsockopt(struct sock *sk, int level, int optname, char *optval, int optlen)
/* */
5451 {
5452 int val,err;
5453
5454 if(level!=SOL_TCP)
5455 return ip_setsockopt(sk,level,optname,optval,optlen);
5456
5457 if (optval == NULL)
5458 return(-EINVAL);
5459
5460 err=verify_area(VERIFY_READ, optval, sizeof(int));
5461 if(err)
5462 return err;
5463
5464 val = get_user((int *)optval);
5465
5466 switch(optname)
5467 {
5468 case TCP_MAXSEG:
5469 /*
5470 * values greater than interface MTU won't take effect. however at
5471 * the point when this call is done we typically don't yet know
5472 * which interface is going to be used
5473 */
5474 if(val<1||val>MAX_WINDOW)
5475 return -EINVAL;
5476 sk->user_mss=val;
5477 return 0;
5478 case TCP_NODELAY:
5479 sk->nonagle=(val==0)?0:1;
5480 return 0;
5481 default:
5482 return(-ENOPROTOOPT);
5483 }
5484 }
5485
5486 int tcp_getsockopt(struct sock *sk, int level, int optname, char *optval, int *optlen)
/* ![[last]](../icons/n_last.png)
*/
5487 {
5488 int val,err;
5489
5490 if(level!=SOL_TCP)
5491 return ip_getsockopt(sk,level,optname,optval,optlen);
5492
5493 switch(optname)
5494 {
5495 case TCP_MAXSEG:
5496 val=sk->user_mss;
5497 break;
5498 case TCP_NODELAY:
5499 val=sk->nonagle;
5500 break;
5501 default:
5502 return(-ENOPROTOOPT);
5503 }
5504 err=verify_area(VERIFY_WRITE, optlen, sizeof(int));
5505 if(err)
5506 return err;
5507 put_user(sizeof(int),(int *) optlen);
5508
5509 err=verify_area(VERIFY_WRITE, optval, sizeof(int));
5510 if(err)
5511 return err;
5512 put_user(val,(int *)optval);
5513
5514 return(0);
5515 }
5516
5517
5518 struct proto tcp_prot = {
5519 tcp_close,
5520 ip_build_header,
5521 tcp_connect,
5522 tcp_accept,
5523 ip_queue_xmit,
5524 tcp_retransmit,
5525 tcp_write_wakeup,
5526 tcp_read_wakeup,
5527 tcp_rcv,
5528 tcp_select,
5529 tcp_ioctl,
5530 NULL,
5531 tcp_shutdown,
5532 tcp_setsockopt,
5533 tcp_getsockopt,
5534 tcp_sendmsg,
5535 tcp_recvmsg,
5536 NULL, /* No special bind() */
5537 128,
5538 0,
5539 "TCP",
5540 0, 0,
5541 {NULL,}
5542 };
![[bottom]](../icons/n_bottom.png){kind=icon}
*/