1 /*
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * @(#)tcp_input.c 8.5 (Berkeley) 4/10/94
30 * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp
31 */
32
33 /*
34 * Changes and additions relating to SLiRP
35 * Copyright (c) 1995 Danny Gasparovski.
36 *
37 * Please read the file COPYRIGHT for the
38 * terms and conditions of the copyright.
39 */
40
41 #include "qemu/osdep.h"
42 #include "slirp.h"
43 #include "ip_icmp.h"
44
45 #define TCPREXMTTHRESH 3
46
47 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ)
48
49 /* for modulo comparisons of timestamps */
50 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
51 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)
52
53 /*
54 * Insert segment ti into reassembly queue of tcp with
55 * control block tp. Return TH_FIN if reassembly now includes
56 * a segment with FIN. The macro form does the common case inline
57 * (segment is the next to be received on an established connection,
58 * and the queue is empty), avoiding linkage into and removal
59 * from the queue and repetition of various conversions.
60 * Set DELACK for segments received in order, but ack immediately
61 * when segments are out of order (so fast retransmit can work).
62 */
63 #ifdef TCP_ACK_HACK
64 #define TCP_REASS(tp, ti, m, so, flags) {\
65 if ((ti)->ti_seq == (tp)->rcv_nxt && \
66 tcpfrag_list_empty(tp) && \
67 (tp)->t_state == TCPS_ESTABLISHED) {\
68 if (ti->ti_flags & TH_PUSH) \
69 tp->t_flags |= TF_ACKNOW; \
70 else \
71 tp->t_flags |= TF_DELACK; \
72 (tp)->rcv_nxt += (ti)->ti_len; \
73 flags = (ti)->ti_flags & TH_FIN; \
74 if (so->so_emu) { \
75 if (tcp_emu((so),(m))) sbappend((so), (m)); \
76 } else \
77 sbappend((so), (m)); \
78 } else {\
79 (flags) = tcp_reass((tp), (ti), (m)); \
80 tp->t_flags |= TF_ACKNOW; \
81 } \
82 }
83 #else
84 #define TCP_REASS(tp, ti, m, so, flags) { \
85 if ((ti)->ti_seq == (tp)->rcv_nxt && \
86 tcpfrag_list_empty(tp) && \
87 (tp)->t_state == TCPS_ESTABLISHED) { \
88 tp->t_flags |= TF_DELACK; \
89 (tp)->rcv_nxt += (ti)->ti_len; \
90 flags = (ti)->ti_flags & TH_FIN; \
91 if (so->so_emu) { \
92 if (tcp_emu((so),(m))) sbappend(so, (m)); \
93 } else \
94 sbappend((so), (m)); \
95 } else { \
96 (flags) = tcp_reass((tp), (ti), (m)); \
97 tp->t_flags |= TF_ACKNOW; \
98 } \
99 }
100 #endif
101 static void tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt,
102 struct tcpiphdr *ti);
103 static void tcp_xmit_timer(register struct tcpcb *tp, int rtt);
104
105 static int
tcp_reass(register struct tcpcb * tp,register struct tcpiphdr * ti,struct mbuf * m)106 tcp_reass(register struct tcpcb *tp, register struct tcpiphdr *ti,
107 struct mbuf *m)
108 {
109 register struct tcpiphdr *q;
110 struct socket *so = tp->t_socket;
111 int flags;
112
113 /*
114 * Call with ti==NULL after become established to
115 * force pre-ESTABLISHED data up to user socket.
116 */
117 if (ti == NULL)
118 goto present;
119
120 /*
121 * Find a segment which begins after this one does.
122 */
123 for (q = tcpfrag_list_first(tp); !tcpfrag_list_end(q, tp);
124 q = tcpiphdr_next(q))
125 if (SEQ_GT(q->ti_seq, ti->ti_seq))
126 break;
127
128 /*
129 * If there is a preceding segment, it may provide some of
130 * our data already. If so, drop the data from the incoming
131 * segment. If it provides all of our data, drop us.
132 */
133 if (!tcpfrag_list_end(tcpiphdr_prev(q), tp)) {
134 register int i;
135 q = tcpiphdr_prev(q);
136 /* conversion to int (in i) handles seq wraparound */
137 i = q->ti_seq + q->ti_len - ti->ti_seq;
138 if (i > 0) {
139 if (i >= ti->ti_len) {
140 m_free(m);
141 /*
142 * Try to present any queued data
143 * at the left window edge to the user.
144 * This is needed after the 3-WHS
145 * completes.
146 */
147 goto present; /* ??? */
148 }
149 m_adj(m, i);
150 ti->ti_len -= i;
151 ti->ti_seq += i;
152 }
153 q = tcpiphdr_next(q);
154 }
155 ti->ti_mbuf = m;
156
157 /*
158 * While we overlap succeeding segments trim them or,
159 * if they are completely covered, dequeue them.
160 */
161 while (!tcpfrag_list_end(q, tp)) {
162 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
163 if (i <= 0)
164 break;
165 if (i < q->ti_len) {
166 q->ti_seq += i;
167 q->ti_len -= i;
168 m_adj(q->ti_mbuf, i);
169 break;
170 }
171 q = tcpiphdr_next(q);
172 m = tcpiphdr_prev(q)->ti_mbuf;
173 remque(tcpiphdr2qlink(tcpiphdr_prev(q)));
174 m_free(m);
175 }
176
177 /*
178 * Stick new segment in its place.
179 */
180 insque(tcpiphdr2qlink(ti), tcpiphdr2qlink(tcpiphdr_prev(q)));
181
182 present:
183 /*
184 * Present data to user, advancing rcv_nxt through
185 * completed sequence space.
186 */
187 if (!TCPS_HAVEESTABLISHED(tp->t_state))
188 return (0);
189 ti = tcpfrag_list_first(tp);
190 if (tcpfrag_list_end(ti, tp) || ti->ti_seq != tp->rcv_nxt)
191 return (0);
192 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
193 return (0);
194 do {
195 tp->rcv_nxt += ti->ti_len;
196 flags = ti->ti_flags & TH_FIN;
197 remque(tcpiphdr2qlink(ti));
198 m = ti->ti_mbuf;
199 ti = tcpiphdr_next(ti);
200 if (so->so_state & SS_FCANTSENDMORE)
201 m_free(m);
202 else {
203 if (so->so_emu) {
204 if (tcp_emu(so,m)) sbappend(so, m);
205 } else
206 sbappend(so, m);
207 }
208 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
209 return (flags);
210 }
211
212 /*
213 * TCP input routine, follows pages 65-76 of the
214 * protocol specification dated September, 1981 very closely.
215 */
216 void
tcp_input(struct mbuf * m,int iphlen,struct socket * inso,unsigned short af)217 tcp_input(struct mbuf *m, int iphlen, struct socket *inso, unsigned short af)
218 {
219 struct ip save_ip, *ip;
220 struct ip6 save_ip6, *ip6;
221 register struct tcpiphdr *ti;
222 caddr_t optp = NULL;
223 int optlen = 0;
224 int len, tlen, off;
225 register struct tcpcb *tp = NULL;
226 register int tiflags;
227 struct socket *so = NULL;
228 int todrop, acked, ourfinisacked, needoutput = 0;
229 int iss = 0;
230 u_long tiwin;
231 int ret;
232 struct sockaddr_storage lhost, fhost;
233 struct sockaddr_in *lhost4, *fhost4;
234 struct sockaddr_in6 *lhost6, *fhost6;
235 struct ex_list *ex_ptr;
236 Slirp *slirp;
237
238 DEBUG_CALL("tcp_input");
239 DEBUG_ARGS((dfd, " m = %p iphlen = %2d inso = %p\n",
240 m, iphlen, inso));
241
242 /*
243 * If called with m == 0, then we're continuing the connect
244 */
245 if (m == NULL) {
246 so = inso;
247 slirp = so->slirp;
248
249 /* Re-set a few variables */
250 tp = sototcpcb(so);
251 m = so->so_m;
252 so->so_m = NULL;
253 ti = so->so_ti;
254 tiwin = ti->ti_win;
255 tiflags = ti->ti_flags;
256
257 goto cont_conn;
258 }
259 slirp = m->slirp;
260
261 ip = mtod(m, struct ip *);
262 ip6 = mtod(m, struct ip6 *);
263
264 switch (af) {
265 case AF_INET:
266 if (iphlen > sizeof(struct ip)) {
267 ip_stripoptions(m, (struct mbuf *)0);
268 iphlen = sizeof(struct ip);
269 }
270 /* XXX Check if too short */
271
272
273 /*
274 * Save a copy of the IP header in case we want restore it
275 * for sending an ICMP error message in response.
276 */
277 save_ip = *ip;
278 save_ip.ip_len += iphlen;
279
280 /*
281 * Get IP and TCP header together in first mbuf.
282 * Note: IP leaves IP header in first mbuf.
283 */
284 m->m_data -= sizeof(struct tcpiphdr) - sizeof(struct ip)
285 - sizeof(struct tcphdr);
286 m->m_len += sizeof(struct tcpiphdr) - sizeof(struct ip)
287 - sizeof(struct tcphdr);
288 ti = mtod(m, struct tcpiphdr *);
289
290 /*
291 * Checksum extended TCP header and data.
292 */
293 tlen = ip->ip_len;
294 tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
295 memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
296 memset(&ti->ti, 0, sizeof(ti->ti));
297 ti->ti_x0 = 0;
298 ti->ti_src = save_ip.ip_src;
299 ti->ti_dst = save_ip.ip_dst;
300 ti->ti_pr = save_ip.ip_p;
301 ti->ti_len = htons((uint16_t)tlen);
302 break;
303
304 case AF_INET6:
305 /*
306 * Save a copy of the IP header in case we want restore it
307 * for sending an ICMP error message in response.
308 */
309 save_ip6 = *ip6;
310 /*
311 * Get IP and TCP header together in first mbuf.
312 * Note: IP leaves IP header in first mbuf.
313 */
314 m->m_data -= sizeof(struct tcpiphdr) - (sizeof(struct ip6)
315 + sizeof(struct tcphdr));
316 m->m_len += sizeof(struct tcpiphdr) - (sizeof(struct ip6)
317 + sizeof(struct tcphdr));
318 ti = mtod(m, struct tcpiphdr *);
319
320 tlen = ip6->ip_pl;
321 tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL;
322 memset(&ti->ih_mbuf, 0 , sizeof(struct mbuf_ptr));
323 memset(&ti->ti, 0, sizeof(ti->ti));
324 ti->ti_x0 = 0;
325 ti->ti_src6 = save_ip6.ip_src;
326 ti->ti_dst6 = save_ip6.ip_dst;
327 ti->ti_nh6 = save_ip6.ip_nh;
328 ti->ti_len = htons((uint16_t)tlen);
329 break;
330
331 default:
332 g_assert_not_reached();
333 }
334
335 len = ((sizeof(struct tcpiphdr) - sizeof(struct tcphdr)) + tlen);
336 if (cksum(m, len)) {
337 goto drop;
338 }
339
340 /*
341 * Check that TCP offset makes sense,
342 * pull out TCP options and adjust length. XXX
343 */
344 off = ti->ti_off << 2;
345 if (off < sizeof (struct tcphdr) || off > tlen) {
346 goto drop;
347 }
348 tlen -= off;
349 ti->ti_len = tlen;
350 if (off > sizeof (struct tcphdr)) {
351 optlen = off - sizeof (struct tcphdr);
352 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
353 }
354 tiflags = ti->ti_flags;
355
356 /*
357 * Convert TCP protocol specific fields to host format.
358 */
359 NTOHL(ti->ti_seq);
360 NTOHL(ti->ti_ack);
361 NTOHS(ti->ti_win);
362 NTOHS(ti->ti_urp);
363
364 /*
365 * Drop TCP, IP headers and TCP options.
366 */
367 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
368 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
369
370 /*
371 * Locate pcb for segment.
372 */
373 findso:
374 lhost.ss_family = af;
375 fhost.ss_family = af;
376 switch (af) {
377 case AF_INET:
378 lhost4 = (struct sockaddr_in *) &lhost;
379 lhost4->sin_addr = ti->ti_src;
380 lhost4->sin_port = ti->ti_sport;
381 fhost4 = (struct sockaddr_in *) &fhost;
382 fhost4->sin_addr = ti->ti_dst;
383 fhost4->sin_port = ti->ti_dport;
384 break;
385 case AF_INET6:
386 lhost6 = (struct sockaddr_in6 *) &lhost;
387 lhost6->sin6_addr = ti->ti_src6;
388 lhost6->sin6_port = ti->ti_sport;
389 fhost6 = (struct sockaddr_in6 *) &fhost;
390 fhost6->sin6_addr = ti->ti_dst6;
391 fhost6->sin6_port = ti->ti_dport;
392 break;
393 default:
394 g_assert_not_reached();
395 }
396
397 so = solookup(&slirp->tcp_last_so, &slirp->tcb, &lhost, &fhost);
398
399 /*
400 * If the state is CLOSED (i.e., TCB does not exist) then
401 * all data in the incoming segment is discarded.
402 * If the TCB exists but is in CLOSED state, it is embryonic,
403 * but should either do a listen or a connect soon.
404 *
405 * state == CLOSED means we've done socreate() but haven't
406 * attached it to a protocol yet...
407 *
408 * XXX If a TCB does not exist, and the TH_SYN flag is
409 * the only flag set, then create a session, mark it
410 * as if it was LISTENING, and continue...
411 */
412 if (so == NULL) {
413 if (slirp->restricted) {
414 /* Any hostfwds will have an existing socket, so we only get here
415 * for non-hostfwd connections. These should be dropped, unless it
416 * happens to be a guestfwd.
417 */
418 for (ex_ptr = slirp->exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
419 if (ex_ptr->ex_fport == ti->ti_dport &&
420 ti->ti_dst.s_addr == ex_ptr->ex_addr.s_addr) {
421 break;
422 }
423 }
424 if (!ex_ptr) {
425 goto dropwithreset;
426 }
427 }
428
429 if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
430 goto dropwithreset;
431
432 if ((so = socreate(slirp)) == NULL)
433 goto dropwithreset;
434 if (tcp_attach(so) < 0) {
435 free(so); /* Not sofree (if it failed, it's not insqued) */
436 goto dropwithreset;
437 }
438
439 sbreserve(&so->so_snd, TCP_SNDSPACE);
440 sbreserve(&so->so_rcv, TCP_RCVSPACE);
441
442 so->lhost.ss = lhost;
443 so->fhost.ss = fhost;
444
445 so->so_iptos = tcp_tos(so);
446 if (so->so_iptos == 0) {
447 switch (af) {
448 case AF_INET:
449 so->so_iptos = ((struct ip *)ti)->ip_tos;
450 break;
451 case AF_INET6:
452 break;
453 default:
454 g_assert_not_reached();
455 }
456 }
457
458 tp = sototcpcb(so);
459 tp->t_state = TCPS_LISTEN;
460 }
461
462 /*
463 * If this is a still-connecting socket, this probably
464 * a retransmit of the SYN. Whether it's a retransmit SYN
465 * or something else, we nuke it.
466 */
467 if (so->so_state & SS_ISFCONNECTING)
468 goto drop;
469
470 tp = sototcpcb(so);
471
472 /* XXX Should never fail */
473 if (tp == NULL)
474 goto dropwithreset;
475 if (tp->t_state == TCPS_CLOSED)
476 goto drop;
477
478 tiwin = ti->ti_win;
479
480 /*
481 * Segment received on connection.
482 * Reset idle time and keep-alive timer.
483 */
484 tp->t_idle = 0;
485 if (SO_OPTIONS)
486 tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
487 else
488 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
489
490 /*
491 * Process options if not in LISTEN state,
492 * else do it below (after getting remote address).
493 */
494 if (optp && tp->t_state != TCPS_LISTEN)
495 tcp_dooptions(tp, (u_char *)optp, optlen, ti);
496
497 /*
498 * Header prediction: check for the two common cases
499 * of a uni-directional data xfer. If the packet has
500 * no control flags, is in-sequence, the window didn't
501 * change and we're not retransmitting, it's a
502 * candidate. If the length is zero and the ack moved
503 * forward, we're the sender side of the xfer. Just
504 * free the data acked & wake any higher level process
505 * that was blocked waiting for space. If the length
506 * is non-zero and the ack didn't move, we're the
507 * receiver side. If we're getting packets in-order
508 * (the reassembly queue is empty), add the data to
509 * the socket buffer and note that we need a delayed ack.
510 *
511 * XXX Some of these tests are not needed
512 * eg: the tiwin == tp->snd_wnd prevents many more
513 * predictions.. with no *real* advantage..
514 */
515 if (tp->t_state == TCPS_ESTABLISHED &&
516 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
517 ti->ti_seq == tp->rcv_nxt &&
518 tiwin && tiwin == tp->snd_wnd &&
519 tp->snd_nxt == tp->snd_max) {
520 if (ti->ti_len == 0) {
521 if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
522 SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
523 tp->snd_cwnd >= tp->snd_wnd) {
524 /*
525 * this is a pure ack for outstanding data.
526 */
527 if (tp->t_rtt &&
528 SEQ_GT(ti->ti_ack, tp->t_rtseq))
529 tcp_xmit_timer(tp, tp->t_rtt);
530 acked = ti->ti_ack - tp->snd_una;
531 sbdrop(&so->so_snd, acked);
532 tp->snd_una = ti->ti_ack;
533 m_free(m);
534
535 /*
536 * If all outstanding data are acked, stop
537 * retransmit timer, otherwise restart timer
538 * using current (possibly backed-off) value.
539 * If process is waiting for space,
540 * wakeup/selwakeup/signal. If data
541 * are ready to send, let tcp_output
542 * decide between more output or persist.
543 */
544 if (tp->snd_una == tp->snd_max)
545 tp->t_timer[TCPT_REXMT] = 0;
546 else if (tp->t_timer[TCPT_PERSIST] == 0)
547 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
548
549 /*
550 * This is called because sowwakeup might have
551 * put data into so_snd. Since we don't so sowwakeup,
552 * we don't need this.. XXX???
553 */
554 if (so->so_snd.sb_cc)
555 (void) tcp_output(tp);
556
557 return;
558 }
559 } else if (ti->ti_ack == tp->snd_una &&
560 tcpfrag_list_empty(tp) &&
561 ti->ti_len <= sbspace(&so->so_rcv)) {
562 /*
563 * this is a pure, in-sequence data packet
564 * with nothing on the reassembly queue and
565 * we have enough buffer space to take it.
566 */
567 tp->rcv_nxt += ti->ti_len;
568 /*
569 * Add data to socket buffer.
570 */
571 if (so->so_emu) {
572 if (tcp_emu(so,m)) sbappend(so, m);
573 } else
574 sbappend(so, m);
575
576 /*
577 * If this is a short packet, then ACK now - with Nagel
578 * congestion avoidance sender won't send more until
579 * he gets an ACK.
580 *
581 * It is better to not delay acks at all to maximize
582 * TCP throughput. See RFC 2581.
583 */
584 tp->t_flags |= TF_ACKNOW;
585 tcp_output(tp);
586 return;
587 }
588 } /* header prediction */
589 /*
590 * Calculate amount of space in receive window,
591 * and then do TCP input processing.
592 * Receive window is amount of space in rcv queue,
593 * but not less than advertised window.
594 */
595 { int win;
596 win = sbspace(&so->so_rcv);
597 if (win < 0)
598 win = 0;
599 tp->rcv_wnd = MAX(win, (int)(tp->rcv_adv - tp->rcv_nxt));
600 }
601
602 switch (tp->t_state) {
603
604 /*
605 * If the state is LISTEN then ignore segment if it contains an RST.
606 * If the segment contains an ACK then it is bad and send a RST.
607 * If it does not contain a SYN then it is not interesting; drop it.
608 * Don't bother responding if the destination was a broadcast.
609 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
610 * tp->iss, and send a segment:
611 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
612 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
613 * Fill in remote peer address fields if not previously specified.
614 * Enter SYN_RECEIVED state, and process any other fields of this
615 * segment in this state.
616 */
617 case TCPS_LISTEN: {
618
619 if (tiflags & TH_RST)
620 goto drop;
621 if (tiflags & TH_ACK)
622 goto dropwithreset;
623 if ((tiflags & TH_SYN) == 0)
624 goto drop;
625
626 /*
627 * This has way too many gotos...
628 * But a bit of spaghetti code never hurt anybody :)
629 */
630
631 /*
632 * If this is destined for the control address, then flag to
633 * tcp_ctl once connected, otherwise connect
634 */
635 if (af == AF_INET &&
636 (so->so_faddr.s_addr & slirp->vnetwork_mask.s_addr) ==
637 slirp->vnetwork_addr.s_addr) {
638 if (so->so_faddr.s_addr != slirp->vhost_addr.s_addr &&
639 so->so_faddr.s_addr != slirp->vnameserver_addr.s_addr) {
640 /* May be an add exec */
641 for (ex_ptr = slirp->exec_list; ex_ptr;
642 ex_ptr = ex_ptr->ex_next) {
643 if(ex_ptr->ex_fport == so->so_fport &&
644 so->so_faddr.s_addr == ex_ptr->ex_addr.s_addr) {
645 so->so_state |= SS_CTL;
646 break;
647 }
648 }
649 if (so->so_state & SS_CTL) {
650 goto cont_input;
651 }
652 }
653 /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
654 }
655
656 if (so->so_emu & EMU_NOCONNECT) {
657 so->so_emu &= ~EMU_NOCONNECT;
658 goto cont_input;
659 }
660
661 if ((tcp_fconnect(so, so->so_ffamily) == -1) &&
662 (errno != EAGAIN) &&
663 (errno != EINPROGRESS) && (errno != EWOULDBLOCK)
664 ) {
665 uint8_t code;
666 DEBUG_MISC((dfd, " tcp fconnect errno = %d-%s\n",
667 errno,strerror(errno)));
668 if(errno == ECONNREFUSED) {
669 /* ACK the SYN, send RST to refuse the connection */
670 tcp_respond(tp, ti, m, ti->ti_seq + 1, (tcp_seq) 0,
671 TH_RST | TH_ACK, af);
672 } else {
673 switch (af) {
674 case AF_INET:
675 code = ICMP_UNREACH_NET;
676 if (errno == EHOSTUNREACH) {
677 code = ICMP_UNREACH_HOST;
678 }
679 break;
680 case AF_INET6:
681 code = ICMP6_UNREACH_NO_ROUTE;
682 if (errno == EHOSTUNREACH) {
683 code = ICMP6_UNREACH_ADDRESS;
684 }
685 break;
686 default:
687 g_assert_not_reached();
688 }
689 HTONL(ti->ti_seq); /* restore tcp header */
690 HTONL(ti->ti_ack);
691 HTONS(ti->ti_win);
692 HTONS(ti->ti_urp);
693 m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
694 m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
695 switch (af) {
696 case AF_INET:
697 m->m_data += sizeof(struct tcpiphdr) - sizeof(struct ip)
698 - sizeof(struct tcphdr);
699 m->m_len -= sizeof(struct tcpiphdr) - sizeof(struct ip)
700 - sizeof(struct tcphdr);
701 *ip = save_ip;
702 icmp_send_error(m, ICMP_UNREACH, code, 0, strerror(errno));
703 break;
704 case AF_INET6:
705 m->m_data += sizeof(struct tcpiphdr) - (sizeof(struct ip6)
706 + sizeof(struct tcphdr));
707 m->m_len -= sizeof(struct tcpiphdr) - (sizeof(struct ip6)
708 + sizeof(struct tcphdr));
709 *ip6 = save_ip6;
710 icmp6_send_error(m, ICMP6_UNREACH, code);
711 break;
712 default:
713 g_assert_not_reached();
714 }
715 }
716 tcp_close(tp);
717 m_free(m);
718 } else {
719 /*
720 * Haven't connected yet, save the current mbuf
721 * and ti, and return
722 * XXX Some OS's don't tell us whether the connect()
723 * succeeded or not. So we must time it out.
724 */
725 so->so_m = m;
726 so->so_ti = ti;
727 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
728 tp->t_state = TCPS_SYN_RECEIVED;
729 /*
730 * Initialize receive sequence numbers now so that we can send a
731 * valid RST if the remote end rejects our connection.
732 */
733 tp->irs = ti->ti_seq;
734 tcp_rcvseqinit(tp);
735 tcp_template(tp);
736 }
737 return;
738
739 cont_conn:
740 /* m==NULL
741 * Check if the connect succeeded
742 */
743 if (so->so_state & SS_NOFDREF) {
744 tp = tcp_close(tp);
745 goto dropwithreset;
746 }
747 cont_input:
748 tcp_template(tp);
749
750 if (optp)
751 tcp_dooptions(tp, (u_char *)optp, optlen, ti);
752
753 if (iss)
754 tp->iss = iss;
755 else
756 tp->iss = slirp->tcp_iss;
757 slirp->tcp_iss += TCP_ISSINCR/2;
758 tp->irs = ti->ti_seq;
759 tcp_sendseqinit(tp);
760 tcp_rcvseqinit(tp);
761 tp->t_flags |= TF_ACKNOW;
762 tp->t_state = TCPS_SYN_RECEIVED;
763 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
764 goto trimthenstep6;
765 } /* case TCPS_LISTEN */
766
767 /*
768 * If the state is SYN_SENT:
769 * if seg contains an ACK, but not for our SYN, drop the input.
770 * if seg contains a RST, then drop the connection.
771 * if seg does not contain SYN, then drop it.
772 * Otherwise this is an acceptable SYN segment
773 * initialize tp->rcv_nxt and tp->irs
774 * if seg contains ack then advance tp->snd_una
775 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
776 * arrange for segment to be acked (eventually)
777 * continue processing rest of data/controls, beginning with URG
778 */
779 case TCPS_SYN_SENT:
780 if ((tiflags & TH_ACK) &&
781 (SEQ_LEQ(ti->ti_ack, tp->iss) ||
782 SEQ_GT(ti->ti_ack, tp->snd_max)))
783 goto dropwithreset;
784
785 if (tiflags & TH_RST) {
786 if (tiflags & TH_ACK) {
787 tcp_drop(tp, 0); /* XXX Check t_softerror! */
788 }
789 goto drop;
790 }
791
792 if ((tiflags & TH_SYN) == 0)
793 goto drop;
794 if (tiflags & TH_ACK) {
795 tp->snd_una = ti->ti_ack;
796 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
797 tp->snd_nxt = tp->snd_una;
798 }
799
800 tp->t_timer[TCPT_REXMT] = 0;
801 tp->irs = ti->ti_seq;
802 tcp_rcvseqinit(tp);
803 tp->t_flags |= TF_ACKNOW;
804 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
805 soisfconnected(so);
806 tp->t_state = TCPS_ESTABLISHED;
807
808 (void) tcp_reass(tp, (struct tcpiphdr *)0,
809 (struct mbuf *)0);
810 /*
811 * if we didn't have to retransmit the SYN,
812 * use its rtt as our initial srtt & rtt var.
813 */
814 if (tp->t_rtt)
815 tcp_xmit_timer(tp, tp->t_rtt);
816 } else
817 tp->t_state = TCPS_SYN_RECEIVED;
818
819 trimthenstep6:
820 /*
821 * Advance ti->ti_seq to correspond to first data byte.
822 * If data, trim to stay within window,
823 * dropping FIN if necessary.
824 */
825 ti->ti_seq++;
826 if (ti->ti_len > tp->rcv_wnd) {
827 todrop = ti->ti_len - tp->rcv_wnd;
828 m_adj(m, -todrop);
829 ti->ti_len = tp->rcv_wnd;
830 tiflags &= ~TH_FIN;
831 }
832 tp->snd_wl1 = ti->ti_seq - 1;
833 tp->rcv_up = ti->ti_seq;
834 goto step6;
835 } /* switch tp->t_state */
836 /*
837 * States other than LISTEN or SYN_SENT.
838 * Check that at least some bytes of segment are within
839 * receive window. If segment begins before rcv_nxt,
840 * drop leading data (and SYN); if nothing left, just ack.
841 */
842 todrop = tp->rcv_nxt - ti->ti_seq;
843 if (todrop > 0) {
844 if (tiflags & TH_SYN) {
845 tiflags &= ~TH_SYN;
846 ti->ti_seq++;
847 if (ti->ti_urp > 1)
848 ti->ti_urp--;
849 else
850 tiflags &= ~TH_URG;
851 todrop--;
852 }
853 /*
854 * Following if statement from Stevens, vol. 2, p. 960.
855 */
856 if (todrop > ti->ti_len
857 || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
858 /*
859 * Any valid FIN must be to the left of the window.
860 * At this point the FIN must be a duplicate or out
861 * of sequence; drop it.
862 */
863 tiflags &= ~TH_FIN;
864
865 /*
866 * Send an ACK to resynchronize and drop any data.
867 * But keep on processing for RST or ACK.
868 */
869 tp->t_flags |= TF_ACKNOW;
870 todrop = ti->ti_len;
871 }
872 m_adj(m, todrop);
873 ti->ti_seq += todrop;
874 ti->ti_len -= todrop;
875 if (ti->ti_urp > todrop)
876 ti->ti_urp -= todrop;
877 else {
878 tiflags &= ~TH_URG;
879 ti->ti_urp = 0;
880 }
881 }
882 /*
883 * If new data are received on a connection after the
884 * user processes are gone, then RST the other end.
885 */
886 if ((so->so_state & SS_NOFDREF) &&
887 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
888 tp = tcp_close(tp);
889 goto dropwithreset;
890 }
891
892 /*
893 * If segment ends after window, drop trailing data
894 * (and PUSH and FIN); if nothing left, just ACK.
895 */
896 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
897 if (todrop > 0) {
898 if (todrop >= ti->ti_len) {
899 /*
900 * If a new connection request is received
901 * while in TIME_WAIT, drop the old connection
902 * and start over if the sequence numbers
903 * are above the previous ones.
904 */
905 if (tiflags & TH_SYN &&
906 tp->t_state == TCPS_TIME_WAIT &&
907 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
908 iss = tp->rcv_nxt + TCP_ISSINCR;
909 tp = tcp_close(tp);
910 goto findso;
911 }
912 /*
913 * If window is closed can only take segments at
914 * window edge, and have to drop data and PUSH from
915 * incoming segments. Continue processing, but
916 * remember to ack. Otherwise, drop segment
917 * and ack.
918 */
919 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) {
920 tp->t_flags |= TF_ACKNOW;
921 } else {
922 goto dropafterack;
923 }
924 }
925 m_adj(m, -todrop);
926 ti->ti_len -= todrop;
927 tiflags &= ~(TH_PUSH|TH_FIN);
928 }
929
930 /*
931 * If the RST bit is set examine the state:
932 * SYN_RECEIVED STATE:
933 * If passive open, return to LISTEN state.
934 * If active open, inform user that connection was refused.
935 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
936 * Inform user that connection was reset, and close tcb.
937 * CLOSING, LAST_ACK, TIME_WAIT STATES
938 * Close the tcb.
939 */
940 if (tiflags&TH_RST) switch (tp->t_state) {
941
942 case TCPS_SYN_RECEIVED:
943 case TCPS_ESTABLISHED:
944 case TCPS_FIN_WAIT_1:
945 case TCPS_FIN_WAIT_2:
946 case TCPS_CLOSE_WAIT:
947 tp->t_state = TCPS_CLOSED;
948 tcp_close(tp);
949 goto drop;
950
951 case TCPS_CLOSING:
952 case TCPS_LAST_ACK:
953 case TCPS_TIME_WAIT:
954 tcp_close(tp);
955 goto drop;
956 }
957
958 /*
959 * If a SYN is in the window, then this is an
960 * error and we send an RST and drop the connection.
961 */
962 if (tiflags & TH_SYN) {
963 tp = tcp_drop(tp,0);
964 goto dropwithreset;
965 }
966
967 /*
968 * If the ACK bit is off we drop the segment and return.
969 */
970 if ((tiflags & TH_ACK) == 0) goto drop;
971
972 /*
973 * Ack processing.
974 */
975 switch (tp->t_state) {
976 /*
977 * In SYN_RECEIVED state if the ack ACKs our SYN then enter
978 * ESTABLISHED state and continue processing, otherwise
979 * send an RST. una<=ack<=max
980 */
981 case TCPS_SYN_RECEIVED:
982
983 if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
984 SEQ_GT(ti->ti_ack, tp->snd_max))
985 goto dropwithreset;
986 tp->t_state = TCPS_ESTABLISHED;
987 /*
988 * The sent SYN is ack'ed with our sequence number +1
989 * The first data byte already in the buffer will get
990 * lost if no correction is made. This is only needed for
991 * SS_CTL since the buffer is empty otherwise.
992 * tp->snd_una++; or:
993 */
994 tp->snd_una=ti->ti_ack;
995 if (so->so_state & SS_CTL) {
996 /* So tcp_ctl reports the right state */
997 ret = tcp_ctl(so);
998 if (ret == 1) {
999 soisfconnected(so);
1000 so->so_state &= ~SS_CTL; /* success XXX */
1001 } else if (ret == 2) {
1002 so->so_state &= SS_PERSISTENT_MASK;
1003 so->so_state |= SS_NOFDREF; /* CTL_CMD */
1004 } else {
1005 needoutput = 1;
1006 tp->t_state = TCPS_FIN_WAIT_1;
1007 }
1008 } else {
1009 soisfconnected(so);
1010 }
1011
1012 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
1013 tp->snd_wl1 = ti->ti_seq - 1;
1014 /* Avoid ack processing; snd_una==ti_ack => dup ack */
1015 goto synrx_to_est;
1016 /* fall into ... */
1017
1018 /*
1019 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1020 * ACKs. If the ack is in the range
1021 * tp->snd_una < ti->ti_ack <= tp->snd_max
1022 * then advance tp->snd_una to ti->ti_ack and drop
1023 * data from the retransmission queue. If this ACK reflects
1024 * more up to date window information we update our window information.
1025 */
1026 case TCPS_ESTABLISHED:
1027 case TCPS_FIN_WAIT_1:
1028 case TCPS_FIN_WAIT_2:
1029 case TCPS_CLOSE_WAIT:
1030 case TCPS_CLOSING:
1031 case TCPS_LAST_ACK:
1032 case TCPS_TIME_WAIT:
1033
1034 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
1035 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) {
1036 DEBUG_MISC((dfd, " dup ack m = %p so = %p\n",
1037 m, so));
1038 /*
1039 * If we have outstanding data (other than
1040 * a window probe), this is a completely
1041 * duplicate ack (ie, window info didn't
1042 * change), the ack is the biggest we've
1043 * seen and we've seen exactly our rexmt
1044 * threshold of them, assume a packet
1045 * has been dropped and retransmit it.
1046 * Kludge snd_nxt & the congestion
1047 * window so we send only this one
1048 * packet.
1049 *
1050 * We know we're losing at the current
1051 * window size so do congestion avoidance
1052 * (set ssthresh to half the current window
1053 * and pull our congestion window back to
1054 * the new ssthresh).
1055 *
1056 * Dup acks mean that packets have left the
1057 * network (they're now cached at the receiver)
1058 * so bump cwnd by the amount in the receiver
1059 * to keep a constant cwnd packets in the
1060 * network.
1061 */
1062 if (tp->t_timer[TCPT_REXMT] == 0 ||
1063 ti->ti_ack != tp->snd_una)
1064 tp->t_dupacks = 0;
1065 else if (++tp->t_dupacks == TCPREXMTTHRESH) {
1066 tcp_seq onxt = tp->snd_nxt;
1067 u_int win =
1068 MIN(tp->snd_wnd, tp->snd_cwnd) /
1069 2 / tp->t_maxseg;
1070
1071 if (win < 2)
1072 win = 2;
1073 tp->snd_ssthresh = win * tp->t_maxseg;
1074 tp->t_timer[TCPT_REXMT] = 0;
1075 tp->t_rtt = 0;
1076 tp->snd_nxt = ti->ti_ack;
1077 tp->snd_cwnd = tp->t_maxseg;
1078 (void) tcp_output(tp);
1079 tp->snd_cwnd = tp->snd_ssthresh +
1080 tp->t_maxseg * tp->t_dupacks;
1081 if (SEQ_GT(onxt, tp->snd_nxt))
1082 tp->snd_nxt = onxt;
1083 goto drop;
1084 } else if (tp->t_dupacks > TCPREXMTTHRESH) {
1085 tp->snd_cwnd += tp->t_maxseg;
1086 (void) tcp_output(tp);
1087 goto drop;
1088 }
1089 } else
1090 tp->t_dupacks = 0;
1091 break;
1092 }
1093 synrx_to_est:
1094 /*
1095 * If the congestion window was inflated to account
1096 * for the other side's cached packets, retract it.
1097 */
1098 if (tp->t_dupacks > TCPREXMTTHRESH &&
1099 tp->snd_cwnd > tp->snd_ssthresh)
1100 tp->snd_cwnd = tp->snd_ssthresh;
1101 tp->t_dupacks = 0;
1102 if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
1103 goto dropafterack;
1104 }
1105 acked = ti->ti_ack - tp->snd_una;
1106
1107 /*
1108 * If transmit timer is running and timed sequence
1109 * number was acked, update smoothed round trip time.
1110 * Since we now have an rtt measurement, cancel the
1111 * timer backoff (cf., Phil Karn's retransmit alg.).
1112 * Recompute the initial retransmit timer.
1113 */
1114 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
1115 tcp_xmit_timer(tp,tp->t_rtt);
1116
1117 /*
1118 * If all outstanding data is acked, stop retransmit
1119 * timer and remember to restart (more output or persist).
1120 * If there is more data to be acked, restart retransmit
1121 * timer, using current (possibly backed-off) value.
1122 */
1123 if (ti->ti_ack == tp->snd_max) {
1124 tp->t_timer[TCPT_REXMT] = 0;
1125 needoutput = 1;
1126 } else if (tp->t_timer[TCPT_PERSIST] == 0)
1127 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
1128 /*
1129 * When new data is acked, open the congestion window.
1130 * If the window gives us less than ssthresh packets
1131 * in flight, open exponentially (maxseg per packet).
1132 * Otherwise open linearly: maxseg per window
1133 * (maxseg^2 / cwnd per packet).
1134 */
1135 {
1136 register u_int cw = tp->snd_cwnd;
1137 register u_int incr = tp->t_maxseg;
1138
1139 if (cw > tp->snd_ssthresh)
1140 incr = incr * incr / cw;
1141 tp->snd_cwnd = MIN(cw + incr, TCP_MAXWIN << tp->snd_scale);
1142 }
1143 if (acked > so->so_snd.sb_cc) {
1144 tp->snd_wnd -= so->so_snd.sb_cc;
1145 sbdrop(&so->so_snd, (int )so->so_snd.sb_cc);
1146 ourfinisacked = 1;
1147 } else {
1148 sbdrop(&so->so_snd, acked);
1149 tp->snd_wnd -= acked;
1150 ourfinisacked = 0;
1151 }
1152 tp->snd_una = ti->ti_ack;
1153 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1154 tp->snd_nxt = tp->snd_una;
1155
1156 switch (tp->t_state) {
1157
1158 /*
1159 * In FIN_WAIT_1 STATE in addition to the processing
1160 * for the ESTABLISHED state if our FIN is now acknowledged
1161 * then enter FIN_WAIT_2.
1162 */
1163 case TCPS_FIN_WAIT_1:
1164 if (ourfinisacked) {
1165 /*
1166 * If we can't receive any more
1167 * data, then closing user can proceed.
1168 * Starting the timer is contrary to the
1169 * specification, but if we don't get a FIN
1170 * we'll hang forever.
1171 */
1172 if (so->so_state & SS_FCANTRCVMORE) {
1173 tp->t_timer[TCPT_2MSL] = TCP_MAXIDLE;
1174 }
1175 tp->t_state = TCPS_FIN_WAIT_2;
1176 }
1177 break;
1178
1179 /*
1180 * In CLOSING STATE in addition to the processing for
1181 * the ESTABLISHED state if the ACK acknowledges our FIN
1182 * then enter the TIME-WAIT state, otherwise ignore
1183 * the segment.
1184 */
1185 case TCPS_CLOSING:
1186 if (ourfinisacked) {
1187 tp->t_state = TCPS_TIME_WAIT;
1188 tcp_canceltimers(tp);
1189 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1190 }
1191 break;
1192
1193 /*
1194 * In LAST_ACK, we may still be waiting for data to drain
1195 * and/or to be acked, as well as for the ack of our FIN.
1196 * If our FIN is now acknowledged, delete the TCB,
1197 * enter the closed state and return.
1198 */
1199 case TCPS_LAST_ACK:
1200 if (ourfinisacked) {
1201 tcp_close(tp);
1202 goto drop;
1203 }
1204 break;
1205
1206 /*
1207 * In TIME_WAIT state the only thing that should arrive
1208 * is a retransmission of the remote FIN. Acknowledge
1209 * it and restart the finack timer.
1210 */
1211 case TCPS_TIME_WAIT:
1212 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1213 goto dropafterack;
1214 }
1215 } /* switch(tp->t_state) */
1216
1217 step6:
1218 /*
1219 * Update window information.
1220 * Don't look at window if no ACK: TAC's send garbage on first SYN.
1221 */
1222 if ((tiflags & TH_ACK) &&
1223 (SEQ_LT(tp->snd_wl1, ti->ti_seq) ||
1224 (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
1225 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) {
1226 tp->snd_wnd = tiwin;
1227 tp->snd_wl1 = ti->ti_seq;
1228 tp->snd_wl2 = ti->ti_ack;
1229 if (tp->snd_wnd > tp->max_sndwnd)
1230 tp->max_sndwnd = tp->snd_wnd;
1231 needoutput = 1;
1232 }
1233
1234 /*
1235 * Process segments with URG.
1236 */
1237 if ((tiflags & TH_URG) && ti->ti_urp &&
1238 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1239 /*
1240 * This is a kludge, but if we receive and accept
1241 * random urgent pointers, we'll crash in
1242 * soreceive. It's hard to imagine someone
1243 * actually wanting to send this much urgent data.
1244 */
1245 if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) {
1246 ti->ti_urp = 0;
1247 tiflags &= ~TH_URG;
1248 goto dodata;
1249 }
1250 /*
1251 * If this segment advances the known urgent pointer,
1252 * then mark the data stream. This should not happen
1253 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
1254 * a FIN has been received from the remote side.
1255 * In these states we ignore the URG.
1256 *
1257 * According to RFC961 (Assigned Protocols),
1258 * the urgent pointer points to the last octet
1259 * of urgent data. We continue, however,
1260 * to consider it to indicate the first octet
1261 * of data past the urgent section as the original
1262 * spec states (in one of two places).
1263 */
1264 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
1265 tp->rcv_up = ti->ti_seq + ti->ti_urp;
1266 so->so_urgc = so->so_rcv.sb_cc +
1267 (tp->rcv_up - tp->rcv_nxt); /* -1; */
1268 tp->rcv_up = ti->ti_seq + ti->ti_urp;
1269
1270 }
1271 } else
1272 /*
1273 * If no out of band data is expected,
1274 * pull receive urgent pointer along
1275 * with the receive window.
1276 */
1277 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
1278 tp->rcv_up = tp->rcv_nxt;
1279 dodata:
1280
1281 /*
1282 * If this is a small packet, then ACK now - with Nagel
1283 * congestion avoidance sender won't send more until
1284 * he gets an ACK.
1285 */
1286 if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
1287 ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
1288 tp->t_flags |= TF_ACKNOW;
1289 }
1290
1291 /*
1292 * Process the segment text, merging it into the TCP sequencing queue,
1293 * and arranging for acknowledgment of receipt if necessary.
1294 * This process logically involves adjusting tp->rcv_wnd as data
1295 * is presented to the user (this happens in tcp_usrreq.c,
1296 * case PRU_RCVD). If a FIN has already been received on this
1297 * connection then we just ignore the text.
1298 */
1299 if ((ti->ti_len || (tiflags&TH_FIN)) &&
1300 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1301 TCP_REASS(tp, ti, m, so, tiflags);
1302 } else {
1303 m_free(m);
1304 tiflags &= ~TH_FIN;
1305 }
1306
1307 /*
1308 * If FIN is received ACK the FIN and let the user know
1309 * that the connection is closing.
1310 */
1311 if (tiflags & TH_FIN) {
1312 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1313 /*
1314 * If we receive a FIN we can't send more data,
1315 * set it SS_FDRAIN
1316 * Shutdown the socket if there is no rx data in the
1317 * buffer.
1318 * soread() is called on completion of shutdown() and
1319 * will got to TCPS_LAST_ACK, and use tcp_output()
1320 * to send the FIN.
1321 */
1322 sofwdrain(so);
1323
1324 tp->t_flags |= TF_ACKNOW;
1325 tp->rcv_nxt++;
1326 }
1327 switch (tp->t_state) {
1328
1329 /*
1330 * In SYN_RECEIVED and ESTABLISHED STATES
1331 * enter the CLOSE_WAIT state.
1332 */
1333 case TCPS_SYN_RECEIVED:
1334 case TCPS_ESTABLISHED:
1335 if(so->so_emu == EMU_CTL) /* no shutdown on socket */
1336 tp->t_state = TCPS_LAST_ACK;
1337 else
1338 tp->t_state = TCPS_CLOSE_WAIT;
1339 break;
1340
1341 /*
1342 * If still in FIN_WAIT_1 STATE FIN has not been acked so
1343 * enter the CLOSING state.
1344 */
1345 case TCPS_FIN_WAIT_1:
1346 tp->t_state = TCPS_CLOSING;
1347 break;
1348
1349 /*
1350 * In FIN_WAIT_2 state enter the TIME_WAIT state,
1351 * starting the time-wait timer, turning off the other
1352 * standard timers.
1353 */
1354 case TCPS_FIN_WAIT_2:
1355 tp->t_state = TCPS_TIME_WAIT;
1356 tcp_canceltimers(tp);
1357 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1358 break;
1359
1360 /*
1361 * In TIME_WAIT state restart the 2 MSL time_wait timer.
1362 */
1363 case TCPS_TIME_WAIT:
1364 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1365 break;
1366 }
1367 }
1368
1369 /*
1370 * Return any desired output.
1371 */
1372 if (needoutput || (tp->t_flags & TF_ACKNOW)) {
1373 (void) tcp_output(tp);
1374 }
1375 return;
1376
1377 dropafterack:
1378 /*
1379 * Generate an ACK dropping incoming segment if it occupies
1380 * sequence space, where the ACK reflects our state.
1381 */
1382 if (tiflags & TH_RST)
1383 goto drop;
1384 m_free(m);
1385 tp->t_flags |= TF_ACKNOW;
1386 (void) tcp_output(tp);
1387 return;
1388
1389 dropwithreset:
1390 /* reuses m if m!=NULL, m_free() unnecessary */
1391 if (tiflags & TH_ACK)
1392 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST, af);
1393 else {
1394 if (tiflags & TH_SYN) ti->ti_len++;
1395 tcp_respond(tp, ti, m, ti->ti_seq + ti->ti_len, (tcp_seq) 0,
1396 TH_RST | TH_ACK, af);
1397 }
1398
1399 return;
1400
1401 drop:
1402 /*
1403 * Drop space held by incoming segment and return.
1404 */
1405 m_free(m);
1406 }
1407
1408 static void
tcp_dooptions(struct tcpcb * tp,u_char * cp,int cnt,struct tcpiphdr * ti)1409 tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti)
1410 {
1411 uint16_t mss;
1412 int opt, optlen;
1413
1414 DEBUG_CALL("tcp_dooptions");
1415 DEBUG_ARGS((dfd, " tp = %p cnt=%i\n", tp, cnt));
1416
1417 for (; cnt > 0; cnt -= optlen, cp += optlen) {
1418 opt = cp[0];
1419 if (opt == TCPOPT_EOL)
1420 break;
1421 if (opt == TCPOPT_NOP)
1422 optlen = 1;
1423 else {
1424 optlen = cp[1];
1425 if (optlen <= 0)
1426 break;
1427 }
1428 switch (opt) {
1429
1430 default:
1431 continue;
1432
1433 case TCPOPT_MAXSEG:
1434 if (optlen != TCPOLEN_MAXSEG)
1435 continue;
1436 if (!(ti->ti_flags & TH_SYN))
1437 continue;
1438 memcpy((char *) &mss, (char *) cp + 2, sizeof(mss));
1439 NTOHS(mss);
1440 (void) tcp_mss(tp, mss); /* sets t_maxseg */
1441 break;
1442 }
1443 }
1444 }
1445
1446
1447 /*
1448 * Pull out of band byte out of a segment so
1449 * it doesn't appear in the user's data queue.
1450 * It is still reflected in the segment length for
1451 * sequencing purposes.
1452 */
1453
1454 #ifdef notdef
1455
1456 void
tcp_pulloutofband(so,ti,m)1457 tcp_pulloutofband(so, ti, m)
1458 struct socket *so;
1459 struct tcpiphdr *ti;
1460 register struct mbuf *m;
1461 {
1462 int cnt = ti->ti_urp - 1;
1463
1464 while (cnt >= 0) {
1465 if (m->m_len > cnt) {
1466 char *cp = mtod(m, caddr_t) + cnt;
1467 struct tcpcb *tp = sototcpcb(so);
1468
1469 tp->t_iobc = *cp;
1470 tp->t_oobflags |= TCPOOB_HAVEDATA;
1471 memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1));
1472 m->m_len--;
1473 return;
1474 }
1475 cnt -= m->m_len;
1476 m = m->m_next; /* XXX WRONG! Fix it! */
1477 if (m == 0)
1478 break;
1479 }
1480 panic("tcp_pulloutofband");
1481 }
1482
1483 #endif /* notdef */
1484
1485 /*
1486 * Collect new round-trip time estimate
1487 * and update averages and current timeout.
1488 */
1489
1490 static void
tcp_xmit_timer(register struct tcpcb * tp,int rtt)1491 tcp_xmit_timer(register struct tcpcb *tp, int rtt)
1492 {
1493 register short delta;
1494
1495 DEBUG_CALL("tcp_xmit_timer");
1496 DEBUG_ARG("tp = %p", tp);
1497 DEBUG_ARG("rtt = %d", rtt);
1498
1499 if (tp->t_srtt != 0) {
1500 /*
1501 * srtt is stored as fixed point with 3 bits after the
1502 * binary point (i.e., scaled by 8). The following magic
1503 * is equivalent to the smoothing algorithm in rfc793 with
1504 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
1505 * point). Adjust rtt to origin 0.
1506 */
1507 delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
1508 if ((tp->t_srtt += delta) <= 0)
1509 tp->t_srtt = 1;
1510 /*
1511 * We accumulate a smoothed rtt variance (actually, a
1512 * smoothed mean difference), then set the retransmit
1513 * timer to smoothed rtt + 4 times the smoothed variance.
1514 * rttvar is stored as fixed point with 2 bits after the
1515 * binary point (scaled by 4). The following is
1516 * equivalent to rfc793 smoothing with an alpha of .75
1517 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
1518 * rfc793's wired-in beta.
1519 */
1520 if (delta < 0)
1521 delta = -delta;
1522 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
1523 if ((tp->t_rttvar += delta) <= 0)
1524 tp->t_rttvar = 1;
1525 } else {
1526 /*
1527 * No rtt measurement yet - use the unsmoothed rtt.
1528 * Set the variance to half the rtt (so our first
1529 * retransmit happens at 3*rtt).
1530 */
1531 tp->t_srtt = rtt << TCP_RTT_SHIFT;
1532 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
1533 }
1534 tp->t_rtt = 0;
1535 tp->t_rxtshift = 0;
1536
1537 /*
1538 * the retransmit should happen at rtt + 4 * rttvar.
1539 * Because of the way we do the smoothing, srtt and rttvar
1540 * will each average +1/2 tick of bias. When we compute
1541 * the retransmit timer, we want 1/2 tick of rounding and
1542 * 1 extra tick because of +-1/2 tick uncertainty in the
1543 * firing of the timer. The bias will give us exactly the
1544 * 1.5 tick we need. But, because the bias is
1545 * statistical, we have to test that we don't drop below
1546 * the minimum feasible timer (which is 2 ticks).
1547 */
1548 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
1549 (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
1550
1551 /*
1552 * We received an ack for a packet that wasn't retransmitted;
1553 * it is probably safe to discard any error indications we've
1554 * received recently. This isn't quite right, but close enough
1555 * for now (a route might have failed after we sent a segment,
1556 * and the return path might not be symmetrical).
1557 */
1558 tp->t_softerror = 0;
1559 }
1560
1561 /*
1562 * Determine a reasonable value for maxseg size.
1563 * If the route is known, check route for mtu.
1564 * If none, use an mss that can be handled on the outgoing
1565 * interface without forcing IP to fragment; if bigger than
1566 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
1567 * to utilize large mbufs. If no route is found, route has no mtu,
1568 * or the destination isn't local, use a default, hopefully conservative
1569 * size (usually 512 or the default IP max size, but no more than the mtu
1570 * of the interface), as we can't discover anything about intervening
1571 * gateways or networks. We also initialize the congestion/slow start
1572 * window to be a single segment if the destination isn't local.
1573 * While looking at the routing entry, we also initialize other path-dependent
1574 * parameters from pre-set or cached values in the routing entry.
1575 */
1576
1577 int
tcp_mss(struct tcpcb * tp,u_int offer)1578 tcp_mss(struct tcpcb *tp, u_int offer)
1579 {
1580 struct socket *so = tp->t_socket;
1581 int mss;
1582
1583 DEBUG_CALL("tcp_mss");
1584 DEBUG_ARG("tp = %p", tp);
1585 DEBUG_ARG("offer = %d", offer);
1586
1587 switch (so->so_ffamily) {
1588 case AF_INET:
1589 mss = MIN(IF_MTU, IF_MRU) - sizeof(struct tcphdr)
1590 - sizeof(struct ip);
1591 break;
1592 case AF_INET6:
1593 mss = MIN(IF_MTU, IF_MRU) - sizeof(struct tcphdr)
1594 - sizeof(struct ip6);
1595 break;
1596 default:
1597 g_assert_not_reached();
1598 }
1599
1600 if (offer)
1601 mss = MIN(mss, offer);
1602 mss = MAX(mss, 32);
1603 if (mss < tp->t_maxseg || offer != 0)
1604 tp->t_maxseg = mss;
1605
1606 tp->snd_cwnd = mss;
1607
1608 sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ?
1609 (mss - (TCP_SNDSPACE % mss)) :
1610 0));
1611 sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ?
1612 (mss - (TCP_RCVSPACE % mss)) :
1613 0));
1614
1615 DEBUG_MISC((dfd, " returning mss = %d\n", mss));
1616
1617 return mss;
1618 }
1619