Build fix for !CONFIG_GDBSTUB case
[qemu-kvm/fedora.git] / slirp / tcp_input.c
blob17a9387f041633ab51ba72859080ea2acbb28885
1 /*
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
3 * The Regents of the University of California. All rights reserved.
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. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
33 * @(#)tcp_input.c 8.5 (Berkeley) 4/10/94
34 * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp
38 * Changes and additions relating to SLiRP
39 * Copyright (c) 1995 Danny Gasparovski.
41 * Please read the file COPYRIGHT for the
42 * terms and conditions of the copyright.
45 #include <slirp.h>
46 #include "ip_icmp.h"
48 struct socket tcb;
50 #define TCPREXMTTHRESH 3
51 struct socket *tcp_last_so = &tcb;
53 tcp_seq tcp_iss; /* tcp initial send seq # */
55 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ)
57 /* for modulo comparisons of timestamps */
58 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
59 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)
62 * Insert segment ti into reassembly queue of tcp with
63 * control block tp. Return TH_FIN if reassembly now includes
64 * a segment with FIN. The macro form does the common case inline
65 * (segment is the next to be received on an established connection,
66 * and the queue is empty), avoiding linkage into and removal
67 * from the queue and repetition of various conversions.
68 * Set DELACK for segments received in order, but ack immediately
69 * when segments are out of order (so fast retransmit can work).
71 #ifdef TCP_ACK_HACK
72 #define TCP_REASS(tp, ti, m, so, flags) {\
73 if ((ti)->ti_seq == (tp)->rcv_nxt && \
74 (tp)->seg_next == (tcpiphdrp_32)(tp) && \
75 (tp)->t_state == TCPS_ESTABLISHED) {\
76 if (ti->ti_flags & TH_PUSH) \
77 tp->t_flags |= TF_ACKNOW; \
78 else \
79 tp->t_flags |= TF_DELACK; \
80 (tp)->rcv_nxt += (ti)->ti_len; \
81 flags = (ti)->ti_flags & TH_FIN; \
82 STAT(tcpstat.tcps_rcvpack++); \
83 STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \
84 if (so->so_emu) { \
85 if (tcp_emu((so),(m))) sbappend((so), (m)); \
86 } else \
87 sbappend((so), (m)); \
88 /* sorwakeup(so); */ \
89 } else {\
90 (flags) = tcp_reass((tp), (ti), (m)); \
91 tp->t_flags |= TF_ACKNOW; \
92 } \
94 #else
95 #define TCP_REASS(tp, ti, m, so, flags) { \
96 if ((ti)->ti_seq == (tp)->rcv_nxt && \
97 (tp)->seg_next == (tcpiphdrp_32)(tp) && \
98 (tp)->t_state == TCPS_ESTABLISHED) { \
99 tp->t_flags |= TF_DELACK; \
100 (tp)->rcv_nxt += (ti)->ti_len; \
101 flags = (ti)->ti_flags & TH_FIN; \
102 STAT(tcpstat.tcps_rcvpack++); \
103 STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \
104 if (so->so_emu) { \
105 if (tcp_emu((so),(m))) sbappend(so, (m)); \
106 } else \
107 sbappend((so), (m)); \
108 /* sorwakeup(so); */ \
109 } else { \
110 (flags) = tcp_reass((tp), (ti), (m)); \
111 tp->t_flags |= TF_ACKNOW; \
114 #endif
115 static void tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt,
116 struct tcpiphdr *ti);
117 static void tcp_xmit_timer(register struct tcpcb *tp, int rtt);
119 static int
120 tcp_reass(register struct tcpcb *tp, register struct tcpiphdr *ti,
121 struct mbuf *m)
123 register struct tcpiphdr *q;
124 struct socket *so = tp->t_socket;
125 int flags;
128 * Call with ti==0 after become established to
129 * force pre-ESTABLISHED data up to user socket.
131 if (ti == 0)
132 goto present;
135 * Find a segment which begins after this one does.
137 for (q = (struct tcpiphdr *)tp->seg_next; q != (struct tcpiphdr *)tp;
138 q = (struct tcpiphdr *)q->ti_next)
139 if (SEQ_GT(q->ti_seq, ti->ti_seq))
140 break;
143 * If there is a preceding segment, it may provide some of
144 * our data already. If so, drop the data from the incoming
145 * segment. If it provides all of our data, drop us.
147 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) {
148 register int i;
149 q = (struct tcpiphdr *)q->ti_prev;
150 /* conversion to int (in i) handles seq wraparound */
151 i = q->ti_seq + q->ti_len - ti->ti_seq;
152 if (i > 0) {
153 if (i >= ti->ti_len) {
154 STAT(tcpstat.tcps_rcvduppack++);
155 STAT(tcpstat.tcps_rcvdupbyte += ti->ti_len);
156 m_freem(m);
158 * Try to present any queued data
159 * at the left window edge to the user.
160 * This is needed after the 3-WHS
161 * completes.
163 goto present; /* ??? */
165 m_adj(m, i);
166 ti->ti_len -= i;
167 ti->ti_seq += i;
169 q = (struct tcpiphdr *)(q->ti_next);
171 STAT(tcpstat.tcps_rcvoopack++);
172 STAT(tcpstat.tcps_rcvoobyte += ti->ti_len);
173 REASS_MBUF(ti) = (mbufp_32) m; /* XXX */
176 * While we overlap succeeding segments trim them or,
177 * if they are completely covered, dequeue them.
179 while (q != (struct tcpiphdr *)tp) {
180 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
181 if (i <= 0)
182 break;
183 if (i < q->ti_len) {
184 q->ti_seq += i;
185 q->ti_len -= i;
186 m_adj((struct mbuf *) REASS_MBUF(q), i);
187 break;
189 q = (struct tcpiphdr *)q->ti_next;
190 m = (struct mbuf *) REASS_MBUF((struct tcpiphdr *)q->ti_prev);
191 remque_32((void *)(q->ti_prev));
192 m_freem(m);
196 * Stick new segment in its place.
198 insque_32(ti, (void *)(q->ti_prev));
200 present:
202 * Present data to user, advancing rcv_nxt through
203 * completed sequence space.
205 if (!TCPS_HAVEESTABLISHED(tp->t_state))
206 return (0);
207 ti = (struct tcpiphdr *) tp->seg_next;
208 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt)
209 return (0);
210 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
211 return (0);
212 do {
213 tp->rcv_nxt += ti->ti_len;
214 flags = ti->ti_flags & TH_FIN;
215 remque_32(ti);
216 m = (struct mbuf *) REASS_MBUF(ti); /* XXX */
217 ti = (struct tcpiphdr *)ti->ti_next;
218 /* if (so->so_state & SS_FCANTRCVMORE) */
219 if (so->so_state & SS_FCANTSENDMORE)
220 m_freem(m);
221 else {
222 if (so->so_emu) {
223 if (tcp_emu(so,m)) sbappend(so, m);
224 } else
225 sbappend(so, m);
227 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
228 /* sorwakeup(so); */
229 return (flags);
233 * TCP input routine, follows pages 65-76 of the
234 * protocol specification dated September, 1981 very closely.
236 void
237 tcp_input(m, iphlen, inso)
238 register struct mbuf *m;
239 int iphlen;
240 struct socket *inso;
242 struct ip save_ip, *ip;
243 register struct tcpiphdr *ti;
244 caddr_t optp = NULL;
245 int optlen = 0;
246 int len, tlen, off;
247 register struct tcpcb *tp = 0;
248 register int tiflags;
249 struct socket *so = 0;
250 int todrop, acked, ourfinisacked, needoutput = 0;
251 /* int dropsocket = 0; */
252 int iss = 0;
253 u_long tiwin;
254 int ret;
255 /* int ts_present = 0; */
257 DEBUG_CALL("tcp_input");
258 DEBUG_ARGS((dfd," m = %8lx iphlen = %2d inso = %lx\n",
259 (long )m, iphlen, (long )inso ));
262 * If called with m == 0, then we're continuing the connect
264 if (m == NULL) {
265 so = inso;
267 /* Re-set a few variables */
268 tp = sototcpcb(so);
269 m = so->so_m;
270 so->so_m = 0;
271 ti = so->so_ti;
272 tiwin = ti->ti_win;
273 tiflags = ti->ti_flags;
275 goto cont_conn;
279 STAT(tcpstat.tcps_rcvtotal++);
281 * Get IP and TCP header together in first mbuf.
282 * Note: IP leaves IP header in first mbuf.
284 ti = mtod(m, struct tcpiphdr *);
285 if (iphlen > sizeof(struct ip )) {
286 ip_stripoptions(m, (struct mbuf *)0);
287 iphlen=sizeof(struct ip );
289 /* XXX Check if too short */
293 * Save a copy of the IP header in case we want restore it
294 * for sending an ICMP error message in response.
296 ip=mtod(m, struct ip *);
297 save_ip = *ip;
298 save_ip.ip_len+= iphlen;
301 * Checksum extended TCP header and data.
303 tlen = ((struct ip *)ti)->ip_len;
304 ti->ti_next = ti->ti_prev = 0;
305 ti->ti_x1 = 0;
306 ti->ti_len = htons((u_int16_t)tlen);
307 len = sizeof(struct ip ) + tlen;
308 /* keep checksum for ICMP reply
309 * ti->ti_sum = cksum(m, len);
310 * if (ti->ti_sum) { */
311 if(cksum(m, len)) {
312 STAT(tcpstat.tcps_rcvbadsum++);
313 goto drop;
317 * Check that TCP offset makes sense,
318 * pull out TCP options and adjust length. XXX
320 off = ti->ti_off << 2;
321 if (off < sizeof (struct tcphdr) || off > tlen) {
322 STAT(tcpstat.tcps_rcvbadoff++);
323 goto drop;
325 tlen -= off;
326 ti->ti_len = tlen;
327 if (off > sizeof (struct tcphdr)) {
328 optlen = off - sizeof (struct tcphdr);
329 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
332 * Do quick retrieval of timestamp options ("options
333 * prediction?"). If timestamp is the only option and it's
334 * formatted as recommended in RFC 1323 appendix A, we
335 * quickly get the values now and not bother calling
336 * tcp_dooptions(), etc.
338 /* if ((optlen == TCPOLEN_TSTAMP_APPA ||
339 * (optlen > TCPOLEN_TSTAMP_APPA &&
340 * optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
341 * *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
342 * (ti->ti_flags & TH_SYN) == 0) {
343 * ts_present = 1;
344 * ts_val = ntohl(*(u_int32_t *)(optp + 4));
345 * ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
346 * optp = NULL; / * we've parsed the options * /
350 tiflags = ti->ti_flags;
353 * Convert TCP protocol specific fields to host format.
355 NTOHL(ti->ti_seq);
356 NTOHL(ti->ti_ack);
357 NTOHS(ti->ti_win);
358 NTOHS(ti->ti_urp);
361 * Drop TCP, IP headers and TCP options.
363 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
364 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
367 * Locate pcb for segment.
369 findso:
370 so = tcp_last_so;
371 if (so->so_fport != ti->ti_dport ||
372 so->so_lport != ti->ti_sport ||
373 so->so_laddr.s_addr != ti->ti_src.s_addr ||
374 so->so_faddr.s_addr != ti->ti_dst.s_addr) {
375 so = solookup(&tcb, ti->ti_src, ti->ti_sport,
376 ti->ti_dst, ti->ti_dport);
377 if (so)
378 tcp_last_so = so;
379 STAT(tcpstat.tcps_socachemiss++);
383 * If the state is CLOSED (i.e., TCB does not exist) then
384 * all data in the incoming segment is discarded.
385 * If the TCB exists but is in CLOSED state, it is embryonic,
386 * but should either do a listen or a connect soon.
388 * state == CLOSED means we've done socreate() but haven't
389 * attached it to a protocol yet...
391 * XXX If a TCB does not exist, and the TH_SYN flag is
392 * the only flag set, then create a session, mark it
393 * as if it was LISTENING, and continue...
395 if (so == 0) {
396 if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
397 goto dropwithreset;
399 if ((so = socreate()) == NULL)
400 goto dropwithreset;
401 if (tcp_attach(so) < 0) {
402 free(so); /* Not sofree (if it failed, it's not insqued) */
403 goto dropwithreset;
406 sbreserve(&so->so_snd, TCP_SNDSPACE);
407 sbreserve(&so->so_rcv, TCP_RCVSPACE);
409 /* tcp_last_so = so; */ /* XXX ? */
410 /* tp = sototcpcb(so); */
412 so->so_laddr = ti->ti_src;
413 so->so_lport = ti->ti_sport;
414 so->so_faddr = ti->ti_dst;
415 so->so_fport = ti->ti_dport;
417 if ((so->so_iptos = tcp_tos(so)) == 0)
418 so->so_iptos = ((struct ip *)ti)->ip_tos;
420 tp = sototcpcb(so);
421 tp->t_state = TCPS_LISTEN;
425 * If this is a still-connecting socket, this probably
426 * a retransmit of the SYN. Whether it's a retransmit SYN
427 * or something else, we nuke it.
429 if (so->so_state & SS_ISFCONNECTING)
430 goto drop;
432 tp = sototcpcb(so);
434 /* XXX Should never fail */
435 if (tp == 0)
436 goto dropwithreset;
437 if (tp->t_state == TCPS_CLOSED)
438 goto drop;
440 /* Unscale the window into a 32-bit value. */
441 /* if ((tiflags & TH_SYN) == 0)
442 * tiwin = ti->ti_win << tp->snd_scale;
443 * else
445 tiwin = ti->ti_win;
448 * Segment received on connection.
449 * Reset idle time and keep-alive timer.
451 tp->t_idle = 0;
452 if (SO_OPTIONS)
453 tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL;
454 else
455 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE;
458 * Process options if not in LISTEN state,
459 * else do it below (after getting remote address).
461 if (optp && tp->t_state != TCPS_LISTEN)
462 tcp_dooptions(tp, (u_char *)optp, optlen, ti);
463 /* , */
464 /* &ts_present, &ts_val, &ts_ecr); */
467 * Header prediction: check for the two common cases
468 * of a uni-directional data xfer. If the packet has
469 * no control flags, is in-sequence, the window didn't
470 * change and we're not retransmitting, it's a
471 * candidate. If the length is zero and the ack moved
472 * forward, we're the sender side of the xfer. Just
473 * free the data acked & wake any higher level process
474 * that was blocked waiting for space. If the length
475 * is non-zero and the ack didn't move, we're the
476 * receiver side. If we're getting packets in-order
477 * (the reassembly queue is empty), add the data to
478 * the socket buffer and note that we need a delayed ack.
480 * XXX Some of these tests are not needed
481 * eg: the tiwin == tp->snd_wnd prevents many more
482 * predictions.. with no *real* advantage..
484 if (tp->t_state == TCPS_ESTABLISHED &&
485 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
486 /* (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && */
487 ti->ti_seq == tp->rcv_nxt &&
488 tiwin && tiwin == tp->snd_wnd &&
489 tp->snd_nxt == tp->snd_max) {
491 * If last ACK falls within this segment's sequence numbers,
492 * record the timestamp.
494 /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
495 * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) {
496 * tp->ts_recent_age = tcp_now;
497 * tp->ts_recent = ts_val;
500 if (ti->ti_len == 0) {
501 if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
502 SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
503 tp->snd_cwnd >= tp->snd_wnd) {
505 * this is a pure ack for outstanding data.
507 STAT(tcpstat.tcps_predack++);
508 /* if (ts_present)
509 * tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
510 * else
511 */ if (tp->t_rtt &&
512 SEQ_GT(ti->ti_ack, tp->t_rtseq))
513 tcp_xmit_timer(tp, tp->t_rtt);
514 acked = ti->ti_ack - tp->snd_una;
515 STAT(tcpstat.tcps_rcvackpack++);
516 STAT(tcpstat.tcps_rcvackbyte += acked);
517 sbdrop(&so->so_snd, acked);
518 tp->snd_una = ti->ti_ack;
519 m_freem(m);
522 * If all outstanding data are acked, stop
523 * retransmit timer, otherwise restart timer
524 * using current (possibly backed-off) value.
525 * If process is waiting for space,
526 * wakeup/selwakeup/signal. If data
527 * are ready to send, let tcp_output
528 * decide between more output or persist.
530 if (tp->snd_una == tp->snd_max)
531 tp->t_timer[TCPT_REXMT] = 0;
532 else if (tp->t_timer[TCPT_PERSIST] == 0)
533 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
536 * There's room in so_snd, sowwakup will read()
537 * from the socket if we can
539 /* if (so->so_snd.sb_flags & SB_NOTIFY)
540 * sowwakeup(so);
543 * This is called because sowwakeup might have
544 * put data into so_snd. Since we don't so sowwakeup,
545 * we don't need this.. XXX???
547 if (so->so_snd.sb_cc)
548 (void) tcp_output(tp);
550 return;
552 } else if (ti->ti_ack == tp->snd_una &&
553 tp->seg_next == (tcpiphdrp_32)tp &&
554 ti->ti_len <= sbspace(&so->so_rcv)) {
556 * this is a pure, in-sequence data packet
557 * with nothing on the reassembly queue and
558 * we have enough buffer space to take it.
560 STAT(tcpstat.tcps_preddat++);
561 tp->rcv_nxt += ti->ti_len;
562 STAT(tcpstat.tcps_rcvpack++);
563 STAT(tcpstat.tcps_rcvbyte += ti->ti_len);
565 * Add data to socket buffer.
567 if (so->so_emu) {
568 if (tcp_emu(so,m)) sbappend(so, m);
569 } else
570 sbappend(so, m);
573 * XXX This is called when data arrives. Later, check
574 * if we can actually write() to the socket
575 * XXX Need to check? It's be NON_BLOCKING
577 /* sorwakeup(so); */
580 * If this is a short packet, then ACK now - with Nagel
581 * congestion avoidance sender won't send more until
582 * he gets an ACK.
584 * It is better to not delay acks at all to maximize
585 * TCP throughput. See RFC 2581.
587 tp->t_flags |= TF_ACKNOW;
588 tcp_output(tp);
589 return;
591 } /* header prediction */
593 * Calculate amount of space in receive window,
594 * and then do TCP input processing.
595 * Receive window is amount of space in rcv queue,
596 * but not less than advertised window.
598 { int win;
599 win = sbspace(&so->so_rcv);
600 if (win < 0)
601 win = 0;
602 tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt));
605 switch (tp->t_state) {
608 * If the state is LISTEN then ignore segment if it contains an RST.
609 * If the segment contains an ACK then it is bad and send a RST.
610 * If it does not contain a SYN then it is not interesting; drop it.
611 * Don't bother responding if the destination was a broadcast.
612 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
613 * tp->iss, and send a segment:
614 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
615 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
616 * Fill in remote peer address fields if not previously specified.
617 * Enter SYN_RECEIVED state, and process any other fields of this
618 * segment in this state.
620 case TCPS_LISTEN: {
622 if (tiflags & TH_RST)
623 goto drop;
624 if (tiflags & TH_ACK)
625 goto dropwithreset;
626 if ((tiflags & TH_SYN) == 0)
627 goto drop;
630 * This has way too many gotos...
631 * But a bit of spaghetti code never hurt anybody :)
635 * If this is destined for the control address, then flag to
636 * tcp_ctl once connected, otherwise connect
638 if ((so->so_faddr.s_addr&htonl(0xffffff00)) == special_addr.s_addr) {
639 int lastbyte=ntohl(so->so_faddr.s_addr) & 0xff;
640 if (lastbyte!=CTL_ALIAS && lastbyte!=CTL_DNS) {
641 #if 0
642 if(lastbyte==CTL_CMD || lastbyte==CTL_EXEC) {
643 /* Command or exec adress */
644 so->so_state |= SS_CTL;
645 } else
646 #endif
648 /* May be an add exec */
649 struct ex_list *ex_ptr;
650 for(ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
651 if(ex_ptr->ex_fport == so->so_fport &&
652 lastbyte == ex_ptr->ex_addr) {
653 so->so_state |= SS_CTL;
654 break;
658 if(so->so_state & SS_CTL) goto cont_input;
660 /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
663 if (so->so_emu & EMU_NOCONNECT) {
664 so->so_emu &= ~EMU_NOCONNECT;
665 goto cont_input;
668 if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && (errno != EWOULDBLOCK)) {
669 u_char code=ICMP_UNREACH_NET;
670 DEBUG_MISC((dfd," tcp fconnect errno = %d-%s\n",
671 errno,strerror(errno)));
672 if(errno == ECONNREFUSED) {
673 /* ACK the SYN, send RST to refuse the connection */
674 tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0,
675 TH_RST|TH_ACK);
676 } else {
677 if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST;
678 HTONL(ti->ti_seq); /* restore tcp header */
679 HTONL(ti->ti_ack);
680 HTONS(ti->ti_win);
681 HTONS(ti->ti_urp);
682 m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
683 m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
684 *ip=save_ip;
685 icmp_error(m, ICMP_UNREACH,code, 0,strerror(errno));
687 tp = tcp_close(tp);
688 m_free(m);
689 } else {
691 * Haven't connected yet, save the current mbuf
692 * and ti, and return
693 * XXX Some OS's don't tell us whether the connect()
694 * succeeded or not. So we must time it out.
696 so->so_m = m;
697 so->so_ti = ti;
698 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
699 tp->t_state = TCPS_SYN_RECEIVED;
701 return;
703 cont_conn:
704 /* m==NULL
705 * Check if the connect succeeded
707 if (so->so_state & SS_NOFDREF) {
708 tp = tcp_close(tp);
709 goto dropwithreset;
711 cont_input:
712 tcp_template(tp);
714 if (optp)
715 tcp_dooptions(tp, (u_char *)optp, optlen, ti);
716 /* , */
717 /* &ts_present, &ts_val, &ts_ecr); */
719 if (iss)
720 tp->iss = iss;
721 else
722 tp->iss = tcp_iss;
723 tcp_iss += TCP_ISSINCR/2;
724 tp->irs = ti->ti_seq;
725 tcp_sendseqinit(tp);
726 tcp_rcvseqinit(tp);
727 tp->t_flags |= TF_ACKNOW;
728 tp->t_state = TCPS_SYN_RECEIVED;
729 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
730 STAT(tcpstat.tcps_accepts++);
731 goto trimthenstep6;
732 } /* case TCPS_LISTEN */
735 * If the state is SYN_SENT:
736 * if seg contains an ACK, but not for our SYN, drop the input.
737 * if seg contains a RST, then drop the connection.
738 * if seg does not contain SYN, then drop it.
739 * Otherwise this is an acceptable SYN segment
740 * initialize tp->rcv_nxt and tp->irs
741 * if seg contains ack then advance tp->snd_una
742 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
743 * arrange for segment to be acked (eventually)
744 * continue processing rest of data/controls, beginning with URG
746 case TCPS_SYN_SENT:
747 if ((tiflags & TH_ACK) &&
748 (SEQ_LEQ(ti->ti_ack, tp->iss) ||
749 SEQ_GT(ti->ti_ack, tp->snd_max)))
750 goto dropwithreset;
752 if (tiflags & TH_RST) {
753 if (tiflags & TH_ACK)
754 tp = tcp_drop(tp,0); /* XXX Check t_softerror! */
755 goto drop;
758 if ((tiflags & TH_SYN) == 0)
759 goto drop;
760 if (tiflags & TH_ACK) {
761 tp->snd_una = ti->ti_ack;
762 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
763 tp->snd_nxt = tp->snd_una;
766 tp->t_timer[TCPT_REXMT] = 0;
767 tp->irs = ti->ti_seq;
768 tcp_rcvseqinit(tp);
769 tp->t_flags |= TF_ACKNOW;
770 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
771 STAT(tcpstat.tcps_connects++);
772 soisfconnected(so);
773 tp->t_state = TCPS_ESTABLISHED;
775 /* Do window scaling on this connection? */
776 /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
777 * (TF_RCVD_SCALE|TF_REQ_SCALE)) {
778 * tp->snd_scale = tp->requested_s_scale;
779 * tp->rcv_scale = tp->request_r_scale;
782 (void) tcp_reass(tp, (struct tcpiphdr *)0,
783 (struct mbuf *)0);
785 * if we didn't have to retransmit the SYN,
786 * use its rtt as our initial srtt & rtt var.
788 if (tp->t_rtt)
789 tcp_xmit_timer(tp, tp->t_rtt);
790 } else
791 tp->t_state = TCPS_SYN_RECEIVED;
793 trimthenstep6:
795 * Advance ti->ti_seq to correspond to first data byte.
796 * If data, trim to stay within window,
797 * dropping FIN if necessary.
799 ti->ti_seq++;
800 if (ti->ti_len > tp->rcv_wnd) {
801 todrop = ti->ti_len - tp->rcv_wnd;
802 m_adj(m, -todrop);
803 ti->ti_len = tp->rcv_wnd;
804 tiflags &= ~TH_FIN;
805 STAT(tcpstat.tcps_rcvpackafterwin++);
806 STAT(tcpstat.tcps_rcvbyteafterwin += todrop);
808 tp->snd_wl1 = ti->ti_seq - 1;
809 tp->rcv_up = ti->ti_seq;
810 goto step6;
811 } /* switch tp->t_state */
813 * States other than LISTEN or SYN_SENT.
814 * First check timestamp, if present.
815 * Then check that at least some bytes of segment are within
816 * receive window. If segment begins before rcv_nxt,
817 * drop leading data (and SYN); if nothing left, just ack.
819 * RFC 1323 PAWS: If we have a timestamp reply on this segment
820 * and it's less than ts_recent, drop it.
822 /* if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
823 * TSTMP_LT(ts_val, tp->ts_recent)) {
825 */ /* Check to see if ts_recent is over 24 days old. */
826 /* if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
827 */ /*
828 * * Invalidate ts_recent. If this segment updates
829 * * ts_recent, the age will be reset later and ts_recent
830 * * will get a valid value. If it does not, setting
831 * * ts_recent to zero will at least satisfy the
832 * * requirement that zero be placed in the timestamp
833 * * echo reply when ts_recent isn't valid. The
834 * * age isn't reset until we get a valid ts_recent
835 * * because we don't want out-of-order segments to be
836 * * dropped when ts_recent is old.
837 * */
838 /* tp->ts_recent = 0;
839 * } else {
840 * tcpstat.tcps_rcvduppack++;
841 * tcpstat.tcps_rcvdupbyte += ti->ti_len;
842 * tcpstat.tcps_pawsdrop++;
843 * goto dropafterack;
848 todrop = tp->rcv_nxt - ti->ti_seq;
849 if (todrop > 0) {
850 if (tiflags & TH_SYN) {
851 tiflags &= ~TH_SYN;
852 ti->ti_seq++;
853 if (ti->ti_urp > 1)
854 ti->ti_urp--;
855 else
856 tiflags &= ~TH_URG;
857 todrop--;
860 * Following if statement from Stevens, vol. 2, p. 960.
862 if (todrop > ti->ti_len
863 || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
865 * Any valid FIN must be to the left of the window.
866 * At this point the FIN must be a duplicate or out
867 * of sequence; drop it.
869 tiflags &= ~TH_FIN;
872 * Send an ACK to resynchronize and drop any data.
873 * But keep on processing for RST or ACK.
875 tp->t_flags |= TF_ACKNOW;
876 todrop = ti->ti_len;
877 STAT(tcpstat.tcps_rcvduppack++);
878 STAT(tcpstat.tcps_rcvdupbyte += todrop);
879 } else {
880 STAT(tcpstat.tcps_rcvpartduppack++);
881 STAT(tcpstat.tcps_rcvpartdupbyte += todrop);
883 m_adj(m, todrop);
884 ti->ti_seq += todrop;
885 ti->ti_len -= todrop;
886 if (ti->ti_urp > todrop)
887 ti->ti_urp -= todrop;
888 else {
889 tiflags &= ~TH_URG;
890 ti->ti_urp = 0;
894 * If new data are received on a connection after the
895 * user processes are gone, then RST the other end.
897 if ((so->so_state & SS_NOFDREF) &&
898 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
899 tp = tcp_close(tp);
900 STAT(tcpstat.tcps_rcvafterclose++);
901 goto dropwithreset;
905 * If segment ends after window, drop trailing data
906 * (and PUSH and FIN); if nothing left, just ACK.
908 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
909 if (todrop > 0) {
910 STAT(tcpstat.tcps_rcvpackafterwin++);
911 if (todrop >= ti->ti_len) {
912 STAT(tcpstat.tcps_rcvbyteafterwin += ti->ti_len);
914 * If a new connection request is received
915 * while in TIME_WAIT, drop the old connection
916 * and start over if the sequence numbers
917 * are above the previous ones.
919 if (tiflags & TH_SYN &&
920 tp->t_state == TCPS_TIME_WAIT &&
921 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
922 iss = tp->rcv_nxt + TCP_ISSINCR;
923 tp = tcp_close(tp);
924 goto findso;
927 * If window is closed can only take segments at
928 * window edge, and have to drop data and PUSH from
929 * incoming segments. Continue processing, but
930 * remember to ack. Otherwise, drop segment
931 * and ack.
933 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) {
934 tp->t_flags |= TF_ACKNOW;
935 STAT(tcpstat.tcps_rcvwinprobe++);
936 } else
937 goto dropafterack;
938 } else
939 STAT(tcpstat.tcps_rcvbyteafterwin += todrop);
940 m_adj(m, -todrop);
941 ti->ti_len -= todrop;
942 tiflags &= ~(TH_PUSH|TH_FIN);
946 * If last ACK falls within this segment's sequence numbers,
947 * record its timestamp.
949 /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
950 * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len +
951 * ((tiflags & (TH_SYN|TH_FIN)) != 0))) {
952 * tp->ts_recent_age = tcp_now;
953 * tp->ts_recent = ts_val;
958 * If the RST bit is set examine the state:
959 * SYN_RECEIVED STATE:
960 * If passive open, return to LISTEN state.
961 * If active open, inform user that connection was refused.
962 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
963 * Inform user that connection was reset, and close tcb.
964 * CLOSING, LAST_ACK, TIME_WAIT STATES
965 * Close the tcb.
967 if (tiflags&TH_RST) switch (tp->t_state) {
969 case TCPS_SYN_RECEIVED:
970 /* so->so_error = ECONNREFUSED; */
971 goto close;
973 case TCPS_ESTABLISHED:
974 case TCPS_FIN_WAIT_1:
975 case TCPS_FIN_WAIT_2:
976 case TCPS_CLOSE_WAIT:
977 /* so->so_error = ECONNRESET; */
978 close:
979 tp->t_state = TCPS_CLOSED;
980 STAT(tcpstat.tcps_drops++);
981 tp = tcp_close(tp);
982 goto drop;
984 case TCPS_CLOSING:
985 case TCPS_LAST_ACK:
986 case TCPS_TIME_WAIT:
987 tp = tcp_close(tp);
988 goto drop;
992 * If a SYN is in the window, then this is an
993 * error and we send an RST and drop the connection.
995 if (tiflags & TH_SYN) {
996 tp = tcp_drop(tp,0);
997 goto dropwithreset;
1001 * If the ACK bit is off we drop the segment and return.
1003 if ((tiflags & TH_ACK) == 0) goto drop;
1006 * Ack processing.
1008 switch (tp->t_state) {
1010 * In SYN_RECEIVED state if the ack ACKs our SYN then enter
1011 * ESTABLISHED state and continue processing, otherwise
1012 * send an RST. una<=ack<=max
1014 case TCPS_SYN_RECEIVED:
1016 if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
1017 SEQ_GT(ti->ti_ack, tp->snd_max))
1018 goto dropwithreset;
1019 STAT(tcpstat.tcps_connects++);
1020 tp->t_state = TCPS_ESTABLISHED;
1022 * The sent SYN is ack'ed with our sequence number +1
1023 * The first data byte already in the buffer will get
1024 * lost if no correction is made. This is only needed for
1025 * SS_CTL since the buffer is empty otherwise.
1026 * tp->snd_una++; or:
1028 tp->snd_una=ti->ti_ack;
1029 if (so->so_state & SS_CTL) {
1030 /* So tcp_ctl reports the right state */
1031 ret = tcp_ctl(so);
1032 if (ret == 1) {
1033 soisfconnected(so);
1034 so->so_state &= ~SS_CTL; /* success XXX */
1035 } else if (ret == 2) {
1036 so->so_state = SS_NOFDREF; /* CTL_CMD */
1037 } else {
1038 needoutput = 1;
1039 tp->t_state = TCPS_FIN_WAIT_1;
1041 } else {
1042 soisfconnected(so);
1045 /* Do window scaling? */
1046 /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1047 * (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1048 * tp->snd_scale = tp->requested_s_scale;
1049 * tp->rcv_scale = tp->request_r_scale;
1052 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
1053 tp->snd_wl1 = ti->ti_seq - 1;
1054 /* Avoid ack processing; snd_una==ti_ack => dup ack */
1055 goto synrx_to_est;
1056 /* fall into ... */
1059 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1060 * ACKs. If the ack is in the range
1061 * tp->snd_una < ti->ti_ack <= tp->snd_max
1062 * then advance tp->snd_una to ti->ti_ack and drop
1063 * data from the retransmission queue. If this ACK reflects
1064 * more up to date window information we update our window information.
1066 case TCPS_ESTABLISHED:
1067 case TCPS_FIN_WAIT_1:
1068 case TCPS_FIN_WAIT_2:
1069 case TCPS_CLOSE_WAIT:
1070 case TCPS_CLOSING:
1071 case TCPS_LAST_ACK:
1072 case TCPS_TIME_WAIT:
1074 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
1075 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) {
1076 STAT(tcpstat.tcps_rcvdupack++);
1077 DEBUG_MISC((dfd," dup ack m = %lx so = %lx \n",
1078 (long )m, (long )so));
1080 * If we have outstanding data (other than
1081 * a window probe), this is a completely
1082 * duplicate ack (ie, window info didn't
1083 * change), the ack is the biggest we've
1084 * seen and we've seen exactly our rexmt
1085 * threshold of them, assume a packet
1086 * has been dropped and retransmit it.
1087 * Kludge snd_nxt & the congestion
1088 * window so we send only this one
1089 * packet.
1091 * We know we're losing at the current
1092 * window size so do congestion avoidance
1093 * (set ssthresh to half the current window
1094 * and pull our congestion window back to
1095 * the new ssthresh).
1097 * Dup acks mean that packets have left the
1098 * network (they're now cached at the receiver)
1099 * so bump cwnd by the amount in the receiver
1100 * to keep a constant cwnd packets in the
1101 * network.
1103 if (tp->t_timer[TCPT_REXMT] == 0 ||
1104 ti->ti_ack != tp->snd_una)
1105 tp->t_dupacks = 0;
1106 else if (++tp->t_dupacks == TCPREXMTTHRESH) {
1107 tcp_seq onxt = tp->snd_nxt;
1108 u_int win =
1109 min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1110 tp->t_maxseg;
1112 if (win < 2)
1113 win = 2;
1114 tp->snd_ssthresh = win * tp->t_maxseg;
1115 tp->t_timer[TCPT_REXMT] = 0;
1116 tp->t_rtt = 0;
1117 tp->snd_nxt = ti->ti_ack;
1118 tp->snd_cwnd = tp->t_maxseg;
1119 (void) tcp_output(tp);
1120 tp->snd_cwnd = tp->snd_ssthresh +
1121 tp->t_maxseg * tp->t_dupacks;
1122 if (SEQ_GT(onxt, tp->snd_nxt))
1123 tp->snd_nxt = onxt;
1124 goto drop;
1125 } else if (tp->t_dupacks > TCPREXMTTHRESH) {
1126 tp->snd_cwnd += tp->t_maxseg;
1127 (void) tcp_output(tp);
1128 goto drop;
1130 } else
1131 tp->t_dupacks = 0;
1132 break;
1134 synrx_to_est:
1136 * If the congestion window was inflated to account
1137 * for the other side's cached packets, retract it.
1139 if (tp->t_dupacks > TCPREXMTTHRESH &&
1140 tp->snd_cwnd > tp->snd_ssthresh)
1141 tp->snd_cwnd = tp->snd_ssthresh;
1142 tp->t_dupacks = 0;
1143 if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
1144 STAT(tcpstat.tcps_rcvacktoomuch++);
1145 goto dropafterack;
1147 acked = ti->ti_ack - tp->snd_una;
1148 STAT(tcpstat.tcps_rcvackpack++);
1149 STAT(tcpstat.tcps_rcvackbyte += acked);
1152 * If we have a timestamp reply, update smoothed
1153 * round trip time. If no timestamp is present but
1154 * transmit timer is running and timed sequence
1155 * number was acked, update smoothed round trip time.
1156 * Since we now have an rtt measurement, cancel the
1157 * timer backoff (cf., Phil Karn's retransmit alg.).
1158 * Recompute the initial retransmit timer.
1160 /* if (ts_present)
1161 * tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
1162 * else
1164 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
1165 tcp_xmit_timer(tp,tp->t_rtt);
1168 * If all outstanding data is acked, stop retransmit
1169 * timer and remember to restart (more output or persist).
1170 * If there is more data to be acked, restart retransmit
1171 * timer, using current (possibly backed-off) value.
1173 if (ti->ti_ack == tp->snd_max) {
1174 tp->t_timer[TCPT_REXMT] = 0;
1175 needoutput = 1;
1176 } else if (tp->t_timer[TCPT_PERSIST] == 0)
1177 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
1179 * When new data is acked, open the congestion window.
1180 * If the window gives us less than ssthresh packets
1181 * in flight, open exponentially (maxseg per packet).
1182 * Otherwise open linearly: maxseg per window
1183 * (maxseg^2 / cwnd per packet).
1186 register u_int cw = tp->snd_cwnd;
1187 register u_int incr = tp->t_maxseg;
1189 if (cw > tp->snd_ssthresh)
1190 incr = incr * incr / cw;
1191 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale);
1193 if (acked > so->so_snd.sb_cc) {
1194 tp->snd_wnd -= so->so_snd.sb_cc;
1195 sbdrop(&so->so_snd, (int )so->so_snd.sb_cc);
1196 ourfinisacked = 1;
1197 } else {
1198 sbdrop(&so->so_snd, acked);
1199 tp->snd_wnd -= acked;
1200 ourfinisacked = 0;
1203 * XXX sowwakup is called when data is acked and there's room for
1204 * for more data... it should read() the socket
1206 /* if (so->so_snd.sb_flags & SB_NOTIFY)
1207 * sowwakeup(so);
1209 tp->snd_una = ti->ti_ack;
1210 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1211 tp->snd_nxt = tp->snd_una;
1213 switch (tp->t_state) {
1216 * In FIN_WAIT_1 STATE in addition to the processing
1217 * for the ESTABLISHED state if our FIN is now acknowledged
1218 * then enter FIN_WAIT_2.
1220 case TCPS_FIN_WAIT_1:
1221 if (ourfinisacked) {
1223 * If we can't receive any more
1224 * data, then closing user can proceed.
1225 * Starting the timer is contrary to the
1226 * specification, but if we don't get a FIN
1227 * we'll hang forever.
1229 if (so->so_state & SS_FCANTRCVMORE) {
1230 soisfdisconnected(so);
1231 tp->t_timer[TCPT_2MSL] = TCP_MAXIDLE;
1233 tp->t_state = TCPS_FIN_WAIT_2;
1235 break;
1238 * In CLOSING STATE in addition to the processing for
1239 * the ESTABLISHED state if the ACK acknowledges our FIN
1240 * then enter the TIME-WAIT state, otherwise ignore
1241 * the segment.
1243 case TCPS_CLOSING:
1244 if (ourfinisacked) {
1245 tp->t_state = TCPS_TIME_WAIT;
1246 tcp_canceltimers(tp);
1247 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1248 soisfdisconnected(so);
1250 break;
1253 * In LAST_ACK, we may still be waiting for data to drain
1254 * and/or to be acked, as well as for the ack of our FIN.
1255 * If our FIN is now acknowledged, delete the TCB,
1256 * enter the closed state and return.
1258 case TCPS_LAST_ACK:
1259 if (ourfinisacked) {
1260 tp = tcp_close(tp);
1261 goto drop;
1263 break;
1266 * In TIME_WAIT state the only thing that should arrive
1267 * is a retransmission of the remote FIN. Acknowledge
1268 * it and restart the finack timer.
1270 case TCPS_TIME_WAIT:
1271 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1272 goto dropafterack;
1274 } /* switch(tp->t_state) */
1276 step6:
1278 * Update window information.
1279 * Don't look at window if no ACK: TAC's send garbage on first SYN.
1281 if ((tiflags & TH_ACK) &&
1282 (SEQ_LT(tp->snd_wl1, ti->ti_seq) ||
1283 (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
1284 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) {
1285 /* keep track of pure window updates */
1286 if (ti->ti_len == 0 &&
1287 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd)
1288 STAT(tcpstat.tcps_rcvwinupd++);
1289 tp->snd_wnd = tiwin;
1290 tp->snd_wl1 = ti->ti_seq;
1291 tp->snd_wl2 = ti->ti_ack;
1292 if (tp->snd_wnd > tp->max_sndwnd)
1293 tp->max_sndwnd = tp->snd_wnd;
1294 needoutput = 1;
1298 * Process segments with URG.
1300 if ((tiflags & TH_URG) && ti->ti_urp &&
1301 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1303 * This is a kludge, but if we receive and accept
1304 * random urgent pointers, we'll crash in
1305 * soreceive. It's hard to imagine someone
1306 * actually wanting to send this much urgent data.
1308 if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) {
1309 ti->ti_urp = 0;
1310 tiflags &= ~TH_URG;
1311 goto dodata;
1314 * If this segment advances the known urgent pointer,
1315 * then mark the data stream. This should not happen
1316 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
1317 * a FIN has been received from the remote side.
1318 * In these states we ignore the URG.
1320 * According to RFC961 (Assigned Protocols),
1321 * the urgent pointer points to the last octet
1322 * of urgent data. We continue, however,
1323 * to consider it to indicate the first octet
1324 * of data past the urgent section as the original
1325 * spec states (in one of two places).
1327 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
1328 tp->rcv_up = ti->ti_seq + ti->ti_urp;
1329 so->so_urgc = so->so_rcv.sb_cc +
1330 (tp->rcv_up - tp->rcv_nxt); /* -1; */
1331 tp->rcv_up = ti->ti_seq + ti->ti_urp;
1334 } else
1336 * If no out of band data is expected,
1337 * pull receive urgent pointer along
1338 * with the receive window.
1340 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
1341 tp->rcv_up = tp->rcv_nxt;
1342 dodata:
1345 * Process the segment text, merging it into the TCP sequencing queue,
1346 * and arranging for acknowledgment of receipt if necessary.
1347 * This process logically involves adjusting tp->rcv_wnd as data
1348 * is presented to the user (this happens in tcp_usrreq.c,
1349 * case PRU_RCVD). If a FIN has already been received on this
1350 * connection then we just ignore the text.
1352 if ((ti->ti_len || (tiflags&TH_FIN)) &&
1353 TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1354 TCP_REASS(tp, ti, m, so, tiflags);
1356 * Note the amount of data that peer has sent into
1357 * our window, in order to estimate the sender's
1358 * buffer size.
1360 len = so->so_rcv.sb_datalen - (tp->rcv_adv - tp->rcv_nxt);
1361 } else {
1362 m_free(m);
1363 tiflags &= ~TH_FIN;
1367 * If FIN is received ACK the FIN and let the user know
1368 * that the connection is closing.
1370 if (tiflags & TH_FIN) {
1371 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1373 * If we receive a FIN we can't send more data,
1374 * set it SS_FDRAIN
1375 * Shutdown the socket if there is no rx data in the
1376 * buffer.
1377 * soread() is called on completion of shutdown() and
1378 * will got to TCPS_LAST_ACK, and use tcp_output()
1379 * to send the FIN.
1381 /* sofcantrcvmore(so); */
1382 sofwdrain(so);
1384 tp->t_flags |= TF_ACKNOW;
1385 tp->rcv_nxt++;
1387 switch (tp->t_state) {
1390 * In SYN_RECEIVED and ESTABLISHED STATES
1391 * enter the CLOSE_WAIT state.
1393 case TCPS_SYN_RECEIVED:
1394 case TCPS_ESTABLISHED:
1395 if(so->so_emu == EMU_CTL) /* no shutdown on socket */
1396 tp->t_state = TCPS_LAST_ACK;
1397 else
1398 tp->t_state = TCPS_CLOSE_WAIT;
1399 break;
1402 * If still in FIN_WAIT_1 STATE FIN has not been acked so
1403 * enter the CLOSING state.
1405 case TCPS_FIN_WAIT_1:
1406 tp->t_state = TCPS_CLOSING;
1407 break;
1410 * In FIN_WAIT_2 state enter the TIME_WAIT state,
1411 * starting the time-wait timer, turning off the other
1412 * standard timers.
1414 case TCPS_FIN_WAIT_2:
1415 tp->t_state = TCPS_TIME_WAIT;
1416 tcp_canceltimers(tp);
1417 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1418 soisfdisconnected(so);
1419 break;
1422 * In TIME_WAIT state restart the 2 MSL time_wait timer.
1424 case TCPS_TIME_WAIT:
1425 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1426 break;
1431 * If this is a small packet, then ACK now - with Nagel
1432 * congestion avoidance sender won't send more until
1433 * he gets an ACK.
1435 * See above.
1437 /* if (ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg) {
1439 /* if ((ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg &&
1440 * (so->so_iptos & IPTOS_LOWDELAY) == 0) ||
1441 * ((so->so_iptos & IPTOS_LOWDELAY) &&
1442 * ((struct tcpiphdr_2 *)ti)->first_char == (char)27)) {
1444 if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
1445 ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
1446 tp->t_flags |= TF_ACKNOW;
1450 * Return any desired output.
1452 if (needoutput || (tp->t_flags & TF_ACKNOW)) {
1453 (void) tcp_output(tp);
1455 return;
1457 dropafterack:
1459 * Generate an ACK dropping incoming segment if it occupies
1460 * sequence space, where the ACK reflects our state.
1462 if (tiflags & TH_RST)
1463 goto drop;
1464 m_freem(m);
1465 tp->t_flags |= TF_ACKNOW;
1466 (void) tcp_output(tp);
1467 return;
1469 dropwithreset:
1470 /* reuses m if m!=NULL, m_free() unnecessary */
1471 if (tiflags & TH_ACK)
1472 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST);
1473 else {
1474 if (tiflags & TH_SYN) ti->ti_len++;
1475 tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0,
1476 TH_RST|TH_ACK);
1479 return;
1481 drop:
1483 * Drop space held by incoming segment and return.
1485 m_free(m);
1487 return;
1490 /* , ts_present, ts_val, ts_ecr) */
1491 /* int *ts_present;
1492 * u_int32_t *ts_val, *ts_ecr;
1494 static void
1495 tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti)
1497 u_int16_t mss;
1498 int opt, optlen;
1500 DEBUG_CALL("tcp_dooptions");
1501 DEBUG_ARGS((dfd," tp = %lx cnt=%i \n", (long )tp, cnt));
1503 for (; cnt > 0; cnt -= optlen, cp += optlen) {
1504 opt = cp[0];
1505 if (opt == TCPOPT_EOL)
1506 break;
1507 if (opt == TCPOPT_NOP)
1508 optlen = 1;
1509 else {
1510 optlen = cp[1];
1511 if (optlen <= 0)
1512 break;
1514 switch (opt) {
1516 default:
1517 continue;
1519 case TCPOPT_MAXSEG:
1520 if (optlen != TCPOLEN_MAXSEG)
1521 continue;
1522 if (!(ti->ti_flags & TH_SYN))
1523 continue;
1524 memcpy((char *) &mss, (char *) cp + 2, sizeof(mss));
1525 NTOHS(mss);
1526 (void) tcp_mss(tp, mss); /* sets t_maxseg */
1527 break;
1529 /* case TCPOPT_WINDOW:
1530 * if (optlen != TCPOLEN_WINDOW)
1531 * continue;
1532 * if (!(ti->ti_flags & TH_SYN))
1533 * continue;
1534 * tp->t_flags |= TF_RCVD_SCALE;
1535 * tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
1536 * break;
1538 /* case TCPOPT_TIMESTAMP:
1539 * if (optlen != TCPOLEN_TIMESTAMP)
1540 * continue;
1541 * *ts_present = 1;
1542 * memcpy((char *) ts_val, (char *)cp + 2, sizeof(*ts_val));
1543 * NTOHL(*ts_val);
1544 * memcpy((char *) ts_ecr, (char *)cp + 6, sizeof(*ts_ecr));
1545 * NTOHL(*ts_ecr);
1547 */ /*
1548 * * A timestamp received in a SYN makes
1549 * * it ok to send timestamp requests and replies.
1550 * */
1551 /* if (ti->ti_flags & TH_SYN) {
1552 * tp->t_flags |= TF_RCVD_TSTMP;
1553 * tp->ts_recent = *ts_val;
1554 * tp->ts_recent_age = tcp_now;
1556 */ break;
1563 * Pull out of band byte out of a segment so
1564 * it doesn't appear in the user's data queue.
1565 * It is still reflected in the segment length for
1566 * sequencing purposes.
1569 #ifdef notdef
1571 void
1572 tcp_pulloutofband(so, ti, m)
1573 struct socket *so;
1574 struct tcpiphdr *ti;
1575 register struct mbuf *m;
1577 int cnt = ti->ti_urp - 1;
1579 while (cnt >= 0) {
1580 if (m->m_len > cnt) {
1581 char *cp = mtod(m, caddr_t) + cnt;
1582 struct tcpcb *tp = sototcpcb(so);
1584 tp->t_iobc = *cp;
1585 tp->t_oobflags |= TCPOOB_HAVEDATA;
1586 memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1));
1587 m->m_len--;
1588 return;
1590 cnt -= m->m_len;
1591 m = m->m_next; /* XXX WRONG! Fix it! */
1592 if (m == 0)
1593 break;
1595 panic("tcp_pulloutofband");
1598 #endif /* notdef */
1601 * Collect new round-trip time estimate
1602 * and update averages and current timeout.
1605 static void
1606 tcp_xmit_timer(register struct tcpcb *tp, int rtt)
1608 register short delta;
1610 DEBUG_CALL("tcp_xmit_timer");
1611 DEBUG_ARG("tp = %lx", (long)tp);
1612 DEBUG_ARG("rtt = %d", rtt);
1614 STAT(tcpstat.tcps_rttupdated++);
1615 if (tp->t_srtt != 0) {
1617 * srtt is stored as fixed point with 3 bits after the
1618 * binary point (i.e., scaled by 8). The following magic
1619 * is equivalent to the smoothing algorithm in rfc793 with
1620 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
1621 * point). Adjust rtt to origin 0.
1623 delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
1624 if ((tp->t_srtt += delta) <= 0)
1625 tp->t_srtt = 1;
1627 * We accumulate a smoothed rtt variance (actually, a
1628 * smoothed mean difference), then set the retransmit
1629 * timer to smoothed rtt + 4 times the smoothed variance.
1630 * rttvar is stored as fixed point with 2 bits after the
1631 * binary point (scaled by 4). The following is
1632 * equivalent to rfc793 smoothing with an alpha of .75
1633 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
1634 * rfc793's wired-in beta.
1636 if (delta < 0)
1637 delta = -delta;
1638 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
1639 if ((tp->t_rttvar += delta) <= 0)
1640 tp->t_rttvar = 1;
1641 } else {
1643 * No rtt measurement yet - use the unsmoothed rtt.
1644 * Set the variance to half the rtt (so our first
1645 * retransmit happens at 3*rtt).
1647 tp->t_srtt = rtt << TCP_RTT_SHIFT;
1648 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
1650 tp->t_rtt = 0;
1651 tp->t_rxtshift = 0;
1654 * the retransmit should happen at rtt + 4 * rttvar.
1655 * Because of the way we do the smoothing, srtt and rttvar
1656 * will each average +1/2 tick of bias. When we compute
1657 * the retransmit timer, we want 1/2 tick of rounding and
1658 * 1 extra tick because of +-1/2 tick uncertainty in the
1659 * firing of the timer. The bias will give us exactly the
1660 * 1.5 tick we need. But, because the bias is
1661 * statistical, we have to test that we don't drop below
1662 * the minimum feasible timer (which is 2 ticks).
1664 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
1665 (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
1668 * We received an ack for a packet that wasn't retransmitted;
1669 * it is probably safe to discard any error indications we've
1670 * received recently. This isn't quite right, but close enough
1671 * for now (a route might have failed after we sent a segment,
1672 * and the return path might not be symmetrical).
1674 tp->t_softerror = 0;
1678 * Determine a reasonable value for maxseg size.
1679 * If the route is known, check route for mtu.
1680 * If none, use an mss that can be handled on the outgoing
1681 * interface without forcing IP to fragment; if bigger than
1682 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
1683 * to utilize large mbufs. If no route is found, route has no mtu,
1684 * or the destination isn't local, use a default, hopefully conservative
1685 * size (usually 512 or the default IP max size, but no more than the mtu
1686 * of the interface), as we can't discover anything about intervening
1687 * gateways or networks. We also initialize the congestion/slow start
1688 * window to be a single segment if the destination isn't local.
1689 * While looking at the routing entry, we also initialize other path-dependent
1690 * parameters from pre-set or cached values in the routing entry.
1694 tcp_mss(tp, offer)
1695 register struct tcpcb *tp;
1696 u_int offer;
1698 struct socket *so = tp->t_socket;
1699 int mss;
1701 DEBUG_CALL("tcp_mss");
1702 DEBUG_ARG("tp = %lx", (long)tp);
1703 DEBUG_ARG("offer = %d", offer);
1705 mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr);
1706 if (offer)
1707 mss = min(mss, offer);
1708 mss = max(mss, 32);
1709 if (mss < tp->t_maxseg || offer != 0)
1710 tp->t_maxseg = mss;
1712 tp->snd_cwnd = mss;
1714 sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ?
1715 (mss - (TCP_SNDSPACE % mss)) :
1716 0));
1717 sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ?
1718 (mss - (TCP_RCVSPACE % mss)) :
1719 0));
1721 DEBUG_MISC((dfd, " returning mss = %d\n", mss));
1723 return mss;