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1.1 root 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. 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.
20: *
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.
32: *
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
35: */
36:
37: /*
38: * Changes and additions relating to SLiRP
39: * Copyright (c) 1995 Danny Gasparovski.
40: *
41: * Please read the file COPYRIGHT for the
42: * terms and conditions of the copyright.
43: */
44:
45: #include <slirp.h>
46: #include "ip_icmp.h"
47:
48: struct socket tcb;
49:
50: int tcprexmtthresh = 3;
51: struct socket *tcp_last_so = &tcb;
52:
53: tcp_seq tcp_iss; /* tcp initial send seq # */
54:
55: #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ)
56:
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)
60:
61: /*
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).
70: */
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: tcpstat.tcps_rcvpack++;\
83: 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: } \
93: }
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: tcpstat.tcps_rcvpack++;\
103: 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; \
112: } \
113: }
114: #endif
115:
116: int
117: tcp_reass(tp, ti, m)
118: register struct tcpcb *tp;
119: register struct tcpiphdr *ti;
120: struct mbuf *m;
121: {
122: register struct tcpiphdr *q;
123: struct socket *so = tp->t_socket;
124: int flags;
125:
126: /*
127: * Call with ti==0 after become established to
128: * force pre-ESTABLISHED data up to user socket.
129: */
130: if (ti == 0)
131: goto present;
132:
133: /*
134: * Find a segment which begins after this one does.
135: */
136: for (q = (struct tcpiphdr *)tp->seg_next; q != (struct tcpiphdr *)tp;
137: q = (struct tcpiphdr *)q->ti_next)
138: if (SEQ_GT(q->ti_seq, ti->ti_seq))
139: break;
140:
141: /*
142: * If there is a preceding segment, it may provide some of
143: * our data already. If so, drop the data from the incoming
144: * segment. If it provides all of our data, drop us.
145: */
146: if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) {
147: register int i;
148: q = (struct tcpiphdr *)q->ti_prev;
149: /* conversion to int (in i) handles seq wraparound */
150: i = q->ti_seq + q->ti_len - ti->ti_seq;
151: if (i > 0) {
152: if (i >= ti->ti_len) {
153: tcpstat.tcps_rcvduppack++;
154: tcpstat.tcps_rcvdupbyte += ti->ti_len;
155: m_freem(m);
156: /*
157: * Try to present any queued data
158: * at the left window edge to the user.
159: * This is needed after the 3-WHS
160: * completes.
161: */
162: goto present; /* ??? */
163: }
164: m_adj(m, i);
165: ti->ti_len -= i;
166: ti->ti_seq += i;
167: }
168: q = (struct tcpiphdr *)(q->ti_next);
169: }
170: tcpstat.tcps_rcvoopack++;
171: tcpstat.tcps_rcvoobyte += ti->ti_len;
172: REASS_MBUF(ti) = (mbufp_32) m; /* XXX */
173:
174: /*
175: * While we overlap succeeding segments trim them or,
176: * if they are completely covered, dequeue them.
177: */
178: while (q != (struct tcpiphdr *)tp) {
179: register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
180: if (i <= 0)
181: break;
182: if (i < q->ti_len) {
183: q->ti_seq += i;
184: q->ti_len -= i;
185: m_adj((struct mbuf *) REASS_MBUF(q), i);
186: break;
187: }
188: q = (struct tcpiphdr *)q->ti_next;
189: m = (struct mbuf *) REASS_MBUF((struct tcpiphdr *)q->ti_prev);
190: remque_32((void *)(q->ti_prev));
191: m_freem(m);
192: }
193:
194: /*
195: * Stick new segment in its place.
196: */
197: insque_32(ti, (void *)(q->ti_prev));
198:
199: present:
200: /*
201: * Present data to user, advancing rcv_nxt through
202: * completed sequence space.
203: */
204: if (!TCPS_HAVEESTABLISHED(tp->t_state))
205: return (0);
206: ti = (struct tcpiphdr *) tp->seg_next;
207: if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt)
208: return (0);
209: if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
210: return (0);
211: do {
212: tp->rcv_nxt += ti->ti_len;
213: flags = ti->ti_flags & TH_FIN;
214: remque_32(ti);
215: m = (struct mbuf *) REASS_MBUF(ti); /* XXX */
216: ti = (struct tcpiphdr *)ti->ti_next;
217: /* if (so->so_state & SS_FCANTRCVMORE) */
218: if (so->so_state & SS_FCANTSENDMORE)
219: m_freem(m);
220: else {
221: if (so->so_emu) {
222: if (tcp_emu(so,m)) sbappend(so, m);
223: } else
224: sbappend(so, m);
225: }
226: } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
227: /* sorwakeup(so); */
228: return (flags);
229: }
230:
231: /*
232: * TCP input routine, follows pages 65-76 of the
233: * protocol specification dated September, 1981 very closely.
234: */
235: void
236: tcp_input(m, iphlen, inso)
237: register struct mbuf *m;
238: int iphlen;
239: struct socket *inso;
240: {
241: struct ip save_ip, *ip;
242: register struct tcpiphdr *ti;
243: caddr_t optp = NULL;
244: int optlen = 0;
245: int len, tlen, off;
246: register struct tcpcb *tp = 0;
247: register int tiflags;
248: struct socket *so = 0;
249: int todrop, acked, ourfinisacked, needoutput = 0;
250: /* int dropsocket = 0; */
251: int iss = 0;
252: u_long tiwin;
253: int ret;
254: /* int ts_present = 0; */
255:
256: DEBUG_CALL("tcp_input");
257: DEBUG_ARGS((dfd," m = %8lx iphlen = %2d inso = %lx\n",
258: (long )m, iphlen, (long )inso ));
259:
260: /*
261: * If called with m == 0, then we're continuing the connect
262: */
263: if (m == NULL) {
264: so = inso;
265:
266: /* Re-set a few variables */
267: tp = sototcpcb(so);
268: m = so->so_m;
269: so->so_m = 0;
270: ti = so->so_ti;
271: tiwin = ti->ti_win;
272: tiflags = ti->ti_flags;
273:
274: goto cont_conn;
275: }
276:
277:
278: tcpstat.tcps_rcvtotal++;
279: /*
280: * Get IP and TCP header together in first mbuf.
281: * Note: IP leaves IP header in first mbuf.
282: */
283: ti = mtod(m, struct tcpiphdr *);
284: if (iphlen > sizeof(struct ip )) {
285: ip_stripoptions(m, (struct mbuf *)0);
286: iphlen=sizeof(struct ip );
287: }
288: /* XXX Check if too short */
289:
290:
291: /*
292: * Save a copy of the IP header in case we want restore it
293: * for sending an ICMP error message in response.
294: */
295: ip=mtod(m, struct ip *);
296: save_ip = *ip;
297: save_ip.ip_len+= iphlen;
298:
299: /*
300: * Checksum extended TCP header and data.
301: */
302: tlen = ((struct ip *)ti)->ip_len;
303: ti->ti_next = ti->ti_prev = 0;
304: ti->ti_x1 = 0;
305: ti->ti_len = htons((u_int16_t)tlen);
306: len = sizeof(struct ip ) + tlen;
307: /* keep checksum for ICMP reply
308: * ti->ti_sum = cksum(m, len);
309: * if (ti->ti_sum) { */
310: if(cksum(m, len)) {
311: tcpstat.tcps_rcvbadsum++;
312: goto drop;
313: }
314:
315: /*
316: * Check that TCP offset makes sense,
317: * pull out TCP options and adjust length. XXX
318: */
319: off = ti->ti_off << 2;
320: if (off < sizeof (struct tcphdr) || off > tlen) {
321: tcpstat.tcps_rcvbadoff++;
322: goto drop;
323: }
324: tlen -= off;
325: ti->ti_len = tlen;
326: if (off > sizeof (struct tcphdr)) {
327: optlen = off - sizeof (struct tcphdr);
328: optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
329:
330: /*
331: * Do quick retrieval of timestamp options ("options
332: * prediction?"). If timestamp is the only option and it's
333: * formatted as recommended in RFC 1323 appendix A, we
334: * quickly get the values now and not bother calling
335: * tcp_dooptions(), etc.
336: */
337: /* if ((optlen == TCPOLEN_TSTAMP_APPA ||
338: * (optlen > TCPOLEN_TSTAMP_APPA &&
339: * optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
340: * *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
341: * (ti->ti_flags & TH_SYN) == 0) {
342: * ts_present = 1;
343: * ts_val = ntohl(*(u_int32_t *)(optp + 4));
344: * ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
345: * optp = NULL; / * we've parsed the options * /
346: * }
347: */
348: }
349: tiflags = ti->ti_flags;
350:
351: /*
352: * Convert TCP protocol specific fields to host format.
353: */
354: NTOHL(ti->ti_seq);
355: NTOHL(ti->ti_ack);
356: NTOHS(ti->ti_win);
357: NTOHS(ti->ti_urp);
358:
359: /*
360: * Drop TCP, IP headers and TCP options.
361: */
362: m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
363: m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
364:
365: /*
366: * Locate pcb for segment.
367: */
368: findso:
369: so = tcp_last_so;
370: if (so->so_fport != ti->ti_dport ||
371: so->so_lport != ti->ti_sport ||
372: so->so_laddr.s_addr != ti->ti_src.s_addr ||
373: so->so_faddr.s_addr != ti->ti_dst.s_addr) {
374: so = solookup(&tcb, ti->ti_src, ti->ti_sport,
375: ti->ti_dst, ti->ti_dport);
376: if (so)
377: tcp_last_so = so;
378: ++tcpstat.tcps_socachemiss;
379: }
380:
381: /*
382: * If the state is CLOSED (i.e., TCB does not exist) then
383: * all data in the incoming segment is discarded.
384: * If the TCB exists but is in CLOSED state, it is embryonic,
385: * but should either do a listen or a connect soon.
386: *
387: * state == CLOSED means we've done socreate() but haven't
388: * attached it to a protocol yet...
389: *
390: * XXX If a TCB does not exist, and the TH_SYN flag is
391: * the only flag set, then create a session, mark it
392: * as if it was LISTENING, and continue...
393: */
394: if (so == 0) {
395: if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN)
396: goto dropwithreset;
397:
398: if ((so = socreate()) == NULL)
399: goto dropwithreset;
400: if (tcp_attach(so) < 0) {
401: free(so); /* Not sofree (if it failed, it's not insqued) */
402: goto dropwithreset;
403: }
404:
405: sbreserve(&so->so_snd, tcp_sndspace);
406: sbreserve(&so->so_rcv, tcp_rcvspace);
407:
408: /* tcp_last_so = so; */ /* XXX ? */
409: /* tp = sototcpcb(so); */
410:
411: so->so_laddr = ti->ti_src;
412: so->so_lport = ti->ti_sport;
413: so->so_faddr = ti->ti_dst;
414: so->so_fport = ti->ti_dport;
415:
416: if ((so->so_iptos = tcp_tos(so)) == 0)
417: so->so_iptos = ((struct ip *)ti)->ip_tos;
418:
419: tp = sototcpcb(so);
420: tp->t_state = TCPS_LISTEN;
421: }
422:
423: /*
424: * If this is a still-connecting socket, this probably
425: * a retransmit of the SYN. Whether it's a retransmit SYN
426: * or something else, we nuke it.
427: */
428: if (so->so_state & SS_ISFCONNECTING)
429: goto drop;
430:
431: tp = sototcpcb(so);
432:
433: /* XXX Should never fail */
434: if (tp == 0)
435: goto dropwithreset;
436: if (tp->t_state == TCPS_CLOSED)
437: goto drop;
438:
439: /* Unscale the window into a 32-bit value. */
440: /* if ((tiflags & TH_SYN) == 0)
441: * tiwin = ti->ti_win << tp->snd_scale;
442: * else
443: */
444: tiwin = ti->ti_win;
445:
446: /*
447: * Segment received on connection.
448: * Reset idle time and keep-alive timer.
449: */
450: tp->t_idle = 0;
451: if (so_options)
452: tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
453: else
454: tp->t_timer[TCPT_KEEP] = tcp_keepidle;
455:
456: /*
457: * Process options if not in LISTEN state,
458: * else do it below (after getting remote address).
459: */
460: if (optp && tp->t_state != TCPS_LISTEN)
461: tcp_dooptions(tp, (u_char *)optp, optlen, ti);
462: /* , */
463: /* &ts_present, &ts_val, &ts_ecr); */
464:
465: /*
466: * Header prediction: check for the two common cases
467: * of a uni-directional data xfer. If the packet has
468: * no control flags, is in-sequence, the window didn't
469: * change and we're not retransmitting, it's a
470: * candidate. If the length is zero and the ack moved
471: * forward, we're the sender side of the xfer. Just
472: * free the data acked & wake any higher level process
473: * that was blocked waiting for space. If the length
474: * is non-zero and the ack didn't move, we're the
475: * receiver side. If we're getting packets in-order
476: * (the reassembly queue is empty), add the data to
477: * the socket buffer and note that we need a delayed ack.
478: *
479: * XXX Some of these tests are not needed
480: * eg: the tiwin == tp->snd_wnd prevents many more
481: * predictions.. with no *real* advantage..
482: */
483: if (tp->t_state == TCPS_ESTABLISHED &&
484: (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
485: /* (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && */
486: ti->ti_seq == tp->rcv_nxt &&
487: tiwin && tiwin == tp->snd_wnd &&
488: tp->snd_nxt == tp->snd_max) {
489: /*
490: * If last ACK falls within this segment's sequence numbers,
491: * record the timestamp.
492: */
493: /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
494: * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) {
495: * tp->ts_recent_age = tcp_now;
496: * tp->ts_recent = ts_val;
497: * }
498: */
499: if (ti->ti_len == 0) {
500: if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
501: SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
502: tp->snd_cwnd >= tp->snd_wnd) {
503: /*
504: * this is a pure ack for outstanding data.
505: */
506: ++tcpstat.tcps_predack;
507: /* if (ts_present)
508: * tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
509: * else
510: */ if (tp->t_rtt &&
511: SEQ_GT(ti->ti_ack, tp->t_rtseq))
512: tcp_xmit_timer(tp, tp->t_rtt);
513: acked = ti->ti_ack - tp->snd_una;
514: tcpstat.tcps_rcvackpack++;
515: tcpstat.tcps_rcvackbyte += acked;
516: sbdrop(&so->so_snd, acked);
517: tp->snd_una = ti->ti_ack;
518: m_freem(m);
519:
520: /*
521: * If all outstanding data are acked, stop
522: * retransmit timer, otherwise restart timer
523: * using current (possibly backed-off) value.
524: * If process is waiting for space,
525: * wakeup/selwakeup/signal. If data
526: * are ready to send, let tcp_output
527: * decide between more output or persist.
528: */
529: if (tp->snd_una == tp->snd_max)
530: tp->t_timer[TCPT_REXMT] = 0;
531: else if (tp->t_timer[TCPT_PERSIST] == 0)
532: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
533:
534: /*
535: * There's room in so_snd, sowwakup will read()
536: * from the socket if we can
537: */
538: /* if (so->so_snd.sb_flags & SB_NOTIFY)
539: * sowwakeup(so);
540: */
541: /*
542: * This is called because sowwakeup might have
543: * put data into so_snd. Since we don't so sowwakeup,
544: * we don't need this.. XXX???
545: */
546: if (so->so_snd.sb_cc)
547: (void) tcp_output(tp);
548:
549: return;
550: }
551: } else if (ti->ti_ack == tp->snd_una &&
552: tp->seg_next == (tcpiphdrp_32)tp &&
553: ti->ti_len <= sbspace(&so->so_rcv)) {
554: /*
555: * this is a pure, in-sequence data packet
556: * with nothing on the reassembly queue and
557: * we have enough buffer space to take it.
558: */
559: ++tcpstat.tcps_preddat;
560: tp->rcv_nxt += ti->ti_len;
561: tcpstat.tcps_rcvpack++;
562: tcpstat.tcps_rcvbyte += ti->ti_len;
563: /*
564: * Add data to socket buffer.
565: */
566: if (so->so_emu) {
567: if (tcp_emu(so,m)) sbappend(so, m);
568: } else
569: sbappend(so, m);
570:
571: /*
572: * XXX This is called when data arrives. Later, check
573: * if we can actually write() to the socket
574: * XXX Need to check? It's be NON_BLOCKING
575: */
576: /* sorwakeup(so); */
577:
578: /*
579: * If this is a short packet, then ACK now - with Nagel
580: * congestion avoidance sender won't send more until
581: * he gets an ACK.
582: *
1.1.1.2 ! root 583: * It is better to not delay acks at all to maximize
! 584: * TCP throughput. See RFC 2581.
1.1 root 585: */
1.1.1.2 ! root 586: tp->t_flags |= TF_ACKNOW;
! 587: tcp_output(tp);
1.1 root 588: return;
589: }
590: } /* header prediction */
591: /*
592: * Calculate amount of space in receive window,
593: * and then do TCP input processing.
594: * Receive window is amount of space in rcv queue,
595: * but not less than advertised window.
596: */
597: { int win;
598: win = sbspace(&so->so_rcv);
599: if (win < 0)
600: win = 0;
601: tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt));
602: }
603:
604: switch (tp->t_state) {
605:
606: /*
607: * If the state is LISTEN then ignore segment if it contains an RST.
608: * If the segment contains an ACK then it is bad and send a RST.
609: * If it does not contain a SYN then it is not interesting; drop it.
610: * Don't bother responding if the destination was a broadcast.
611: * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
612: * tp->iss, and send a segment:
613: * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
614: * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
615: * Fill in remote peer address fields if not previously specified.
616: * Enter SYN_RECEIVED state, and process any other fields of this
617: * segment in this state.
618: */
619: case TCPS_LISTEN: {
620:
621: if (tiflags & TH_RST)
622: goto drop;
623: if (tiflags & TH_ACK)
624: goto dropwithreset;
625: if ((tiflags & TH_SYN) == 0)
626: goto drop;
627:
628: /*
629: * This has way too many gotos...
630: * But a bit of spaghetti code never hurt anybody :)
631: */
632:
633: /*
634: * If this is destined for the control address, then flag to
635: * tcp_ctl once connected, otherwise connect
636: */
637: if ((so->so_faddr.s_addr&htonl(0xffffff00)) == special_addr.s_addr) {
638: int lastbyte=ntohl(so->so_faddr.s_addr) & 0xff;
639: if (lastbyte!=CTL_ALIAS && lastbyte!=CTL_DNS) {
640: #if 0
641: if(lastbyte==CTL_CMD || lastbyte==CTL_EXEC) {
642: /* Command or exec adress */
643: so->so_state |= SS_CTL;
644: } else
645: #endif
646: {
647: /* May be an add exec */
648: struct ex_list *ex_ptr;
649: for(ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
650: if(ex_ptr->ex_fport == so->so_fport &&
651: lastbyte == ex_ptr->ex_addr) {
652: so->so_state |= SS_CTL;
653: break;
654: }
655: }
656: }
657: if(so->so_state & SS_CTL) goto cont_input;
658: }
659: /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
660: }
661:
662: if (so->so_emu & EMU_NOCONNECT) {
663: so->so_emu &= ~EMU_NOCONNECT;
664: goto cont_input;
665: }
666:
667: if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && (errno != EWOULDBLOCK)) {
668: u_char code=ICMP_UNREACH_NET;
669: DEBUG_MISC((dfd," tcp fconnect errno = %d-%s\n",
670: errno,strerror(errno)));
671: if(errno == ECONNREFUSED) {
672: /* ACK the SYN, send RST to refuse the connection */
673: tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0,
674: TH_RST|TH_ACK);
675: } else {
676: if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST;
677: HTONL(ti->ti_seq); /* restore tcp header */
678: HTONL(ti->ti_ack);
679: HTONS(ti->ti_win);
680: HTONS(ti->ti_urp);
681: m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
682: m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
683: *ip=save_ip;
684: icmp_error(m, ICMP_UNREACH,code, 0,strerror(errno));
685: }
686: tp = tcp_close(tp);
687: m_free(m);
688: } else {
689: /*
690: * Haven't connected yet, save the current mbuf
691: * and ti, and return
692: * XXX Some OS's don't tell us whether the connect()
693: * succeeded or not. So we must time it out.
694: */
695: so->so_m = m;
696: so->so_ti = ti;
697: tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
698: tp->t_state = TCPS_SYN_RECEIVED;
699: }
700: return;
701:
702: cont_conn:
703: /* m==NULL
704: * Check if the connect succeeded
705: */
706: if (so->so_state & SS_NOFDREF) {
707: tp = tcp_close(tp);
708: goto dropwithreset;
709: }
710: cont_input:
711: tcp_template(tp);
712:
713: if (optp)
714: tcp_dooptions(tp, (u_char *)optp, optlen, ti);
715: /* , */
716: /* &ts_present, &ts_val, &ts_ecr); */
717:
718: if (iss)
719: tp->iss = iss;
720: else
721: tp->iss = tcp_iss;
722: tcp_iss += TCP_ISSINCR/2;
723: tp->irs = ti->ti_seq;
724: tcp_sendseqinit(tp);
725: tcp_rcvseqinit(tp);
726: tp->t_flags |= TF_ACKNOW;
727: tp->t_state = TCPS_SYN_RECEIVED;
728: tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
729: tcpstat.tcps_accepts++;
730: goto trimthenstep6;
731: } /* case TCPS_LISTEN */
732:
733: /*
734: * If the state is SYN_SENT:
735: * if seg contains an ACK, but not for our SYN, drop the input.
736: * if seg contains a RST, then drop the connection.
737: * if seg does not contain SYN, then drop it.
738: * Otherwise this is an acceptable SYN segment
739: * initialize tp->rcv_nxt and tp->irs
740: * if seg contains ack then advance tp->snd_una
741: * if SYN has been acked change to ESTABLISHED else SYN_RCVD state
742: * arrange for segment to be acked (eventually)
743: * continue processing rest of data/controls, beginning with URG
744: */
745: case TCPS_SYN_SENT:
746: if ((tiflags & TH_ACK) &&
747: (SEQ_LEQ(ti->ti_ack, tp->iss) ||
748: SEQ_GT(ti->ti_ack, tp->snd_max)))
749: goto dropwithreset;
750:
751: if (tiflags & TH_RST) {
752: if (tiflags & TH_ACK)
753: tp = tcp_drop(tp,0); /* XXX Check t_softerror! */
754: goto drop;
755: }
756:
757: if ((tiflags & TH_SYN) == 0)
758: goto drop;
759: if (tiflags & TH_ACK) {
760: tp->snd_una = ti->ti_ack;
761: if (SEQ_LT(tp->snd_nxt, tp->snd_una))
762: tp->snd_nxt = tp->snd_una;
763: }
764:
765: tp->t_timer[TCPT_REXMT] = 0;
766: tp->irs = ti->ti_seq;
767: tcp_rcvseqinit(tp);
768: tp->t_flags |= TF_ACKNOW;
769: if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
770: tcpstat.tcps_connects++;
771: soisfconnected(so);
772: tp->t_state = TCPS_ESTABLISHED;
773:
774: /* Do window scaling on this connection? */
775: /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
776: * (TF_RCVD_SCALE|TF_REQ_SCALE)) {
777: * tp->snd_scale = tp->requested_s_scale;
778: * tp->rcv_scale = tp->request_r_scale;
779: * }
780: */
781: (void) tcp_reass(tp, (struct tcpiphdr *)0,
782: (struct mbuf *)0);
783: /*
784: * if we didn't have to retransmit the SYN,
785: * use its rtt as our initial srtt & rtt var.
786: */
787: if (tp->t_rtt)
788: tcp_xmit_timer(tp, tp->t_rtt);
789: } else
790: tp->t_state = TCPS_SYN_RECEIVED;
791:
792: trimthenstep6:
793: /*
794: * Advance ti->ti_seq to correspond to first data byte.
795: * If data, trim to stay within window,
796: * dropping FIN if necessary.
797: */
798: ti->ti_seq++;
799: if (ti->ti_len > tp->rcv_wnd) {
800: todrop = ti->ti_len - tp->rcv_wnd;
801: m_adj(m, -todrop);
802: ti->ti_len = tp->rcv_wnd;
803: tiflags &= ~TH_FIN;
804: tcpstat.tcps_rcvpackafterwin++;
805: tcpstat.tcps_rcvbyteafterwin += todrop;
806: }
807: tp->snd_wl1 = ti->ti_seq - 1;
808: tp->rcv_up = ti->ti_seq;
809: goto step6;
810: } /* switch tp->t_state */
811: /*
812: * States other than LISTEN or SYN_SENT.
813: * First check timestamp, if present.
814: * Then check that at least some bytes of segment are within
815: * receive window. If segment begins before rcv_nxt,
816: * drop leading data (and SYN); if nothing left, just ack.
817: *
818: * RFC 1323 PAWS: If we have a timestamp reply on this segment
819: * and it's less than ts_recent, drop it.
820: */
821: /* if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
822: * TSTMP_LT(ts_val, tp->ts_recent)) {
823: *
824: */ /* Check to see if ts_recent is over 24 days old. */
825: /* if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
826: */ /*
827: * * Invalidate ts_recent. If this segment updates
828: * * ts_recent, the age will be reset later and ts_recent
829: * * will get a valid value. If it does not, setting
830: * * ts_recent to zero will at least satisfy the
831: * * requirement that zero be placed in the timestamp
832: * * echo reply when ts_recent isn't valid. The
833: * * age isn't reset until we get a valid ts_recent
834: * * because we don't want out-of-order segments to be
835: * * dropped when ts_recent is old.
836: * */
837: /* tp->ts_recent = 0;
838: * } else {
839: * tcpstat.tcps_rcvduppack++;
840: * tcpstat.tcps_rcvdupbyte += ti->ti_len;
841: * tcpstat.tcps_pawsdrop++;
842: * goto dropafterack;
843: * }
844: * }
845: */
846:
847: todrop = tp->rcv_nxt - ti->ti_seq;
848: if (todrop > 0) {
849: if (tiflags & TH_SYN) {
850: tiflags &= ~TH_SYN;
851: ti->ti_seq++;
852: if (ti->ti_urp > 1)
853: ti->ti_urp--;
854: else
855: tiflags &= ~TH_URG;
856: todrop--;
857: }
858: /*
859: * Following if statement from Stevens, vol. 2, p. 960.
860: */
861: if (todrop > ti->ti_len
862: || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {
863: /*
864: * Any valid FIN must be to the left of the window.
865: * At this point the FIN must be a duplicate or out
866: * of sequence; drop it.
867: */
868: tiflags &= ~TH_FIN;
869:
870: /*
871: * Send an ACK to resynchronize and drop any data.
872: * But keep on processing for RST or ACK.
873: */
874: tp->t_flags |= TF_ACKNOW;
875: todrop = ti->ti_len;
876: tcpstat.tcps_rcvduppack++;
877: tcpstat.tcps_rcvdupbyte += todrop;
878: } else {
879: tcpstat.tcps_rcvpartduppack++;
880: tcpstat.tcps_rcvpartdupbyte += todrop;
881: }
882: m_adj(m, todrop);
883: ti->ti_seq += todrop;
884: ti->ti_len -= todrop;
885: if (ti->ti_urp > todrop)
886: ti->ti_urp -= todrop;
887: else {
888: tiflags &= ~TH_URG;
889: ti->ti_urp = 0;
890: }
891: }
892: /*
893: * If new data are received on a connection after the
894: * user processes are gone, then RST the other end.
895: */
896: if ((so->so_state & SS_NOFDREF) &&
897: tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
898: tp = tcp_close(tp);
899: tcpstat.tcps_rcvafterclose++;
900: goto dropwithreset;
901: }
902:
903: /*
904: * If segment ends after window, drop trailing data
905: * (and PUSH and FIN); if nothing left, just ACK.
906: */
907: todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
908: if (todrop > 0) {
909: tcpstat.tcps_rcvpackafterwin++;
910: if (todrop >= ti->ti_len) {
911: tcpstat.tcps_rcvbyteafterwin += ti->ti_len;
912: /*
913: * If a new connection request is received
914: * while in TIME_WAIT, drop the old connection
915: * and start over if the sequence numbers
916: * are above the previous ones.
917: */
918: if (tiflags & TH_SYN &&
919: tp->t_state == TCPS_TIME_WAIT &&
920: SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
921: iss = tp->rcv_nxt + TCP_ISSINCR;
922: tp = tcp_close(tp);
923: goto findso;
924: }
925: /*
926: * If window is closed can only take segments at
927: * window edge, and have to drop data and PUSH from
928: * incoming segments. Continue processing, but
929: * remember to ack. Otherwise, drop segment
930: * and ack.
931: */
932: if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) {
933: tp->t_flags |= TF_ACKNOW;
934: tcpstat.tcps_rcvwinprobe++;
935: } else
936: goto dropafterack;
937: } else
938: tcpstat.tcps_rcvbyteafterwin += todrop;
939: m_adj(m, -todrop);
940: ti->ti_len -= todrop;
941: tiflags &= ~(TH_PUSH|TH_FIN);
942: }
943:
944: /*
945: * If last ACK falls within this segment's sequence numbers,
946: * record its timestamp.
947: */
948: /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
949: * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len +
950: * ((tiflags & (TH_SYN|TH_FIN)) != 0))) {
951: * tp->ts_recent_age = tcp_now;
952: * tp->ts_recent = ts_val;
953: * }
954: */
955:
956: /*
957: * If the RST bit is set examine the state:
958: * SYN_RECEIVED STATE:
959: * If passive open, return to LISTEN state.
960: * If active open, inform user that connection was refused.
961: * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
962: * Inform user that connection was reset, and close tcb.
963: * CLOSING, LAST_ACK, TIME_WAIT STATES
964: * Close the tcb.
965: */
966: if (tiflags&TH_RST) switch (tp->t_state) {
967:
968: case TCPS_SYN_RECEIVED:
969: /* so->so_error = ECONNREFUSED; */
970: goto close;
971:
972: case TCPS_ESTABLISHED:
973: case TCPS_FIN_WAIT_1:
974: case TCPS_FIN_WAIT_2:
975: case TCPS_CLOSE_WAIT:
976: /* so->so_error = ECONNRESET; */
977: close:
978: tp->t_state = TCPS_CLOSED;
979: tcpstat.tcps_drops++;
980: tp = tcp_close(tp);
981: goto drop;
982:
983: case TCPS_CLOSING:
984: case TCPS_LAST_ACK:
985: case TCPS_TIME_WAIT:
986: tp = tcp_close(tp);
987: goto drop;
988: }
989:
990: /*
991: * If a SYN is in the window, then this is an
992: * error and we send an RST and drop the connection.
993: */
994: if (tiflags & TH_SYN) {
995: tp = tcp_drop(tp,0);
996: goto dropwithreset;
997: }
998:
999: /*
1000: * If the ACK bit is off we drop the segment and return.
1001: */
1002: if ((tiflags & TH_ACK) == 0) goto drop;
1003:
1004: /*
1005: * Ack processing.
1006: */
1007: switch (tp->t_state) {
1008: /*
1009: * In SYN_RECEIVED state if the ack ACKs our SYN then enter
1010: * ESTABLISHED state and continue processing, otherwise
1011: * send an RST. una<=ack<=max
1012: */
1013: case TCPS_SYN_RECEIVED:
1014:
1015: if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
1016: SEQ_GT(ti->ti_ack, tp->snd_max))
1017: goto dropwithreset;
1018: tcpstat.tcps_connects++;
1019: tp->t_state = TCPS_ESTABLISHED;
1020: /*
1021: * The sent SYN is ack'ed with our sequence number +1
1022: * The first data byte already in the buffer will get
1023: * lost if no correction is made. This is only needed for
1024: * SS_CTL since the buffer is empty otherwise.
1025: * tp->snd_una++; or:
1026: */
1027: tp->snd_una=ti->ti_ack;
1028: if (so->so_state & SS_CTL) {
1029: /* So tcp_ctl reports the right state */
1030: ret = tcp_ctl(so);
1031: if (ret == 1) {
1032: soisfconnected(so);
1033: so->so_state &= ~SS_CTL; /* success XXX */
1034: } else if (ret == 2) {
1035: so->so_state = SS_NOFDREF; /* CTL_CMD */
1036: } else {
1037: needoutput = 1;
1038: tp->t_state = TCPS_FIN_WAIT_1;
1039: }
1040: } else {
1041: soisfconnected(so);
1042: }
1043:
1044: /* Do window scaling? */
1045: /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1046: * (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1047: * tp->snd_scale = tp->requested_s_scale;
1048: * tp->rcv_scale = tp->request_r_scale;
1049: * }
1050: */
1051: (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
1052: tp->snd_wl1 = ti->ti_seq - 1;
1053: /* Avoid ack processing; snd_una==ti_ack => dup ack */
1054: goto synrx_to_est;
1055: /* fall into ... */
1056:
1057: /*
1058: * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
1059: * ACKs. If the ack is in the range
1060: * tp->snd_una < ti->ti_ack <= tp->snd_max
1061: * then advance tp->snd_una to ti->ti_ack and drop
1062: * data from the retransmission queue. If this ACK reflects
1063: * more up to date window information we update our window information.
1064: */
1065: case TCPS_ESTABLISHED:
1066: case TCPS_FIN_WAIT_1:
1067: case TCPS_FIN_WAIT_2:
1068: case TCPS_CLOSE_WAIT:
1069: case TCPS_CLOSING:
1070: case TCPS_LAST_ACK:
1071: case TCPS_TIME_WAIT:
1072:
1073: if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
1074: if (ti->ti_len == 0 && tiwin == tp->snd_wnd) {
1075: tcpstat.tcps_rcvdupack++;
1076: DEBUG_MISC((dfd," dup ack m = %lx so = %lx \n",
1077: (long )m, (long )so));
1078: /*
1079: * If we have outstanding data (other than
1080: * a window probe), this is a completely
1081: * duplicate ack (ie, window info didn't
1082: * change), the ack is the biggest we've
1083: * seen and we've seen exactly our rexmt
1084: * threshold of them, assume a packet
1085: * has been dropped and retransmit it.
1086: * Kludge snd_nxt & the congestion
1087: * window so we send only this one
1088: * packet.
1089: *
1090: * We know we're losing at the current
1091: * window size so do congestion avoidance
1092: * (set ssthresh to half the current window
1093: * and pull our congestion window back to
1094: * the new ssthresh).
1095: *
1096: * Dup acks mean that packets have left the
1097: * network (they're now cached at the receiver)
1098: * so bump cwnd by the amount in the receiver
1099: * to keep a constant cwnd packets in the
1100: * network.
1101: */
1102: if (tp->t_timer[TCPT_REXMT] == 0 ||
1103: ti->ti_ack != tp->snd_una)
1104: tp->t_dupacks = 0;
1105: else if (++tp->t_dupacks == tcprexmtthresh) {
1106: tcp_seq onxt = tp->snd_nxt;
1107: u_int win =
1108: min(tp->snd_wnd, tp->snd_cwnd) / 2 /
1109: tp->t_maxseg;
1110:
1111: if (win < 2)
1112: win = 2;
1113: tp->snd_ssthresh = win * tp->t_maxseg;
1114: tp->t_timer[TCPT_REXMT] = 0;
1115: tp->t_rtt = 0;
1116: tp->snd_nxt = ti->ti_ack;
1117: tp->snd_cwnd = tp->t_maxseg;
1118: (void) tcp_output(tp);
1119: tp->snd_cwnd = tp->snd_ssthresh +
1120: tp->t_maxseg * tp->t_dupacks;
1121: if (SEQ_GT(onxt, tp->snd_nxt))
1122: tp->snd_nxt = onxt;
1123: goto drop;
1124: } else if (tp->t_dupacks > tcprexmtthresh) {
1125: tp->snd_cwnd += tp->t_maxseg;
1126: (void) tcp_output(tp);
1127: goto drop;
1128: }
1129: } else
1130: tp->t_dupacks = 0;
1131: break;
1132: }
1133: synrx_to_est:
1134: /*
1135: * If the congestion window was inflated to account
1136: * for the other side's cached packets, retract it.
1137: */
1138: if (tp->t_dupacks > tcprexmtthresh &&
1139: tp->snd_cwnd > tp->snd_ssthresh)
1140: tp->snd_cwnd = tp->snd_ssthresh;
1141: tp->t_dupacks = 0;
1142: if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
1143: tcpstat.tcps_rcvacktoomuch++;
1144: goto dropafterack;
1145: }
1146: acked = ti->ti_ack - tp->snd_una;
1147: tcpstat.tcps_rcvackpack++;
1148: tcpstat.tcps_rcvackbyte += acked;
1149:
1150: /*
1151: * If we have a timestamp reply, update smoothed
1152: * round trip time. If no timestamp is present but
1153: * transmit timer is running and timed sequence
1154: * number was acked, update smoothed round trip time.
1155: * Since we now have an rtt measurement, cancel the
1156: * timer backoff (cf., Phil Karn's retransmit alg.).
1157: * Recompute the initial retransmit timer.
1158: */
1159: /* if (ts_present)
1160: * tcp_xmit_timer(tp, tcp_now-ts_ecr+1);
1161: * else
1162: */
1163: if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
1164: tcp_xmit_timer(tp,tp->t_rtt);
1165:
1166: /*
1167: * If all outstanding data is acked, stop retransmit
1168: * timer and remember to restart (more output or persist).
1169: * If there is more data to be acked, restart retransmit
1170: * timer, using current (possibly backed-off) value.
1171: */
1172: if (ti->ti_ack == tp->snd_max) {
1173: tp->t_timer[TCPT_REXMT] = 0;
1174: needoutput = 1;
1175: } else if (tp->t_timer[TCPT_PERSIST] == 0)
1176: tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
1177: /*
1178: * When new data is acked, open the congestion window.
1179: * If the window gives us less than ssthresh packets
1180: * in flight, open exponentially (maxseg per packet).
1181: * Otherwise open linearly: maxseg per window
1182: * (maxseg^2 / cwnd per packet).
1183: */
1184: {
1185: register u_int cw = tp->snd_cwnd;
1186: register u_int incr = tp->t_maxseg;
1187:
1188: if (cw > tp->snd_ssthresh)
1189: incr = incr * incr / cw;
1190: tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale);
1191: }
1192: if (acked > so->so_snd.sb_cc) {
1193: tp->snd_wnd -= so->so_snd.sb_cc;
1194: sbdrop(&so->so_snd, (int )so->so_snd.sb_cc);
1195: ourfinisacked = 1;
1196: } else {
1197: sbdrop(&so->so_snd, acked);
1198: tp->snd_wnd -= acked;
1199: ourfinisacked = 0;
1200: }
1201: /*
1202: * XXX sowwakup is called when data is acked and there's room for
1203: * for more data... it should read() the socket
1204: */
1205: /* if (so->so_snd.sb_flags & SB_NOTIFY)
1206: * sowwakeup(so);
1207: */
1208: tp->snd_una = ti->ti_ack;
1209: if (SEQ_LT(tp->snd_nxt, tp->snd_una))
1210: tp->snd_nxt = tp->snd_una;
1211:
1212: switch (tp->t_state) {
1213:
1214: /*
1215: * In FIN_WAIT_1 STATE in addition to the processing
1216: * for the ESTABLISHED state if our FIN is now acknowledged
1217: * then enter FIN_WAIT_2.
1218: */
1219: case TCPS_FIN_WAIT_1:
1220: if (ourfinisacked) {
1221: /*
1222: * If we can't receive any more
1223: * data, then closing user can proceed.
1224: * Starting the timer is contrary to the
1225: * specification, but if we don't get a FIN
1226: * we'll hang forever.
1227: */
1228: if (so->so_state & SS_FCANTRCVMORE) {
1229: soisfdisconnected(so);
1230: tp->t_timer[TCPT_2MSL] = tcp_maxidle;
1231: }
1232: tp->t_state = TCPS_FIN_WAIT_2;
1233: }
1234: break;
1235:
1236: /*
1237: * In CLOSING STATE in addition to the processing for
1238: * the ESTABLISHED state if the ACK acknowledges our FIN
1239: * then enter the TIME-WAIT state, otherwise ignore
1240: * the segment.
1241: */
1242: case TCPS_CLOSING:
1243: if (ourfinisacked) {
1244: tp->t_state = TCPS_TIME_WAIT;
1245: tcp_canceltimers(tp);
1246: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1247: soisfdisconnected(so);
1248: }
1249: break;
1250:
1251: /*
1252: * In LAST_ACK, we may still be waiting for data to drain
1253: * and/or to be acked, as well as for the ack of our FIN.
1254: * If our FIN is now acknowledged, delete the TCB,
1255: * enter the closed state and return.
1256: */
1257: case TCPS_LAST_ACK:
1258: if (ourfinisacked) {
1259: tp = tcp_close(tp);
1260: goto drop;
1261: }
1262: break;
1263:
1264: /*
1265: * In TIME_WAIT state the only thing that should arrive
1266: * is a retransmission of the remote FIN. Acknowledge
1267: * it and restart the finack timer.
1268: */
1269: case TCPS_TIME_WAIT:
1270: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1271: goto dropafterack;
1272: }
1273: } /* switch(tp->t_state) */
1274:
1275: step6:
1276: /*
1277: * Update window information.
1278: * Don't look at window if no ACK: TAC's send garbage on first SYN.
1279: */
1280: if ((tiflags & TH_ACK) &&
1281: (SEQ_LT(tp->snd_wl1, ti->ti_seq) ||
1282: (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
1283: (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) {
1284: /* keep track of pure window updates */
1285: if (ti->ti_len == 0 &&
1286: tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd)
1287: tcpstat.tcps_rcvwinupd++;
1288: tp->snd_wnd = tiwin;
1289: tp->snd_wl1 = ti->ti_seq;
1290: tp->snd_wl2 = ti->ti_ack;
1291: if (tp->snd_wnd > tp->max_sndwnd)
1292: tp->max_sndwnd = tp->snd_wnd;
1293: needoutput = 1;
1294: }
1295:
1296: /*
1297: * Process segments with URG.
1298: */
1299: if ((tiflags & TH_URG) && ti->ti_urp &&
1300: TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1301: /*
1302: * This is a kludge, but if we receive and accept
1303: * random urgent pointers, we'll crash in
1304: * soreceive. It's hard to imagine someone
1305: * actually wanting to send this much urgent data.
1306: */
1307: if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) {
1308: ti->ti_urp = 0;
1309: tiflags &= ~TH_URG;
1310: goto dodata;
1311: }
1312: /*
1313: * If this segment advances the known urgent pointer,
1314: * then mark the data stream. This should not happen
1315: * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
1316: * a FIN has been received from the remote side.
1317: * In these states we ignore the URG.
1318: *
1319: * According to RFC961 (Assigned Protocols),
1320: * the urgent pointer points to the last octet
1321: * of urgent data. We continue, however,
1322: * to consider it to indicate the first octet
1323: * of data past the urgent section as the original
1324: * spec states (in one of two places).
1325: */
1326: if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
1327: tp->rcv_up = ti->ti_seq + ti->ti_urp;
1328: so->so_urgc = so->so_rcv.sb_cc +
1329: (tp->rcv_up - tp->rcv_nxt); /* -1; */
1330: tp->rcv_up = ti->ti_seq + ti->ti_urp;
1331:
1332: }
1333: } else
1334: /*
1335: * If no out of band data is expected,
1336: * pull receive urgent pointer along
1337: * with the receive window.
1338: */
1339: if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
1340: tp->rcv_up = tp->rcv_nxt;
1341: dodata:
1342:
1343: /*
1344: * Process the segment text, merging it into the TCP sequencing queue,
1345: * and arranging for acknowledgment of receipt if necessary.
1346: * This process logically involves adjusting tp->rcv_wnd as data
1347: * is presented to the user (this happens in tcp_usrreq.c,
1348: * case PRU_RCVD). If a FIN has already been received on this
1349: * connection then we just ignore the text.
1350: */
1351: if ((ti->ti_len || (tiflags&TH_FIN)) &&
1352: TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1353: TCP_REASS(tp, ti, m, so, tiflags);
1354: /*
1355: * Note the amount of data that peer has sent into
1356: * our window, in order to estimate the sender's
1357: * buffer size.
1358: */
1359: len = so->so_rcv.sb_datalen - (tp->rcv_adv - tp->rcv_nxt);
1360: } else {
1361: m_free(m);
1362: tiflags &= ~TH_FIN;
1363: }
1364:
1365: /*
1366: * If FIN is received ACK the FIN and let the user know
1367: * that the connection is closing.
1368: */
1369: if (tiflags & TH_FIN) {
1370: if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
1371: /*
1372: * If we receive a FIN we can't send more data,
1373: * set it SS_FDRAIN
1374: * Shutdown the socket if there is no rx data in the
1375: * buffer.
1376: * soread() is called on completion of shutdown() and
1377: * will got to TCPS_LAST_ACK, and use tcp_output()
1378: * to send the FIN.
1379: */
1380: /* sofcantrcvmore(so); */
1381: sofwdrain(so);
1382:
1383: tp->t_flags |= TF_ACKNOW;
1384: tp->rcv_nxt++;
1385: }
1386: switch (tp->t_state) {
1387:
1388: /*
1389: * In SYN_RECEIVED and ESTABLISHED STATES
1390: * enter the CLOSE_WAIT state.
1391: */
1392: case TCPS_SYN_RECEIVED:
1393: case TCPS_ESTABLISHED:
1394: if(so->so_emu == EMU_CTL) /* no shutdown on socket */
1395: tp->t_state = TCPS_LAST_ACK;
1396: else
1397: tp->t_state = TCPS_CLOSE_WAIT;
1398: break;
1399:
1400: /*
1401: * If still in FIN_WAIT_1 STATE FIN has not been acked so
1402: * enter the CLOSING state.
1403: */
1404: case TCPS_FIN_WAIT_1:
1405: tp->t_state = TCPS_CLOSING;
1406: break;
1407:
1408: /*
1409: * In FIN_WAIT_2 state enter the TIME_WAIT state,
1410: * starting the time-wait timer, turning off the other
1411: * standard timers.
1412: */
1413: case TCPS_FIN_WAIT_2:
1414: tp->t_state = TCPS_TIME_WAIT;
1415: tcp_canceltimers(tp);
1416: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1417: soisfdisconnected(so);
1418: break;
1419:
1420: /*
1421: * In TIME_WAIT state restart the 2 MSL time_wait timer.
1422: */
1423: case TCPS_TIME_WAIT:
1424: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
1425: break;
1426: }
1427: }
1428:
1429: /*
1430: * If this is a small packet, then ACK now - with Nagel
1431: * congestion avoidance sender won't send more until
1432: * he gets an ACK.
1433: *
1434: * See above.
1435: */
1436: /* if (ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg) {
1437: */
1438: /* if ((ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg &&
1439: * (so->so_iptos & IPTOS_LOWDELAY) == 0) ||
1440: * ((so->so_iptos & IPTOS_LOWDELAY) &&
1441: * ((struct tcpiphdr_2 *)ti)->first_char == (char)27)) {
1442: */
1443: if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
1444: ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
1445: tp->t_flags |= TF_ACKNOW;
1446: }
1447:
1448: /*
1449: * Return any desired output.
1450: */
1451: if (needoutput || (tp->t_flags & TF_ACKNOW)) {
1452: (void) tcp_output(tp);
1453: }
1454: return;
1455:
1456: dropafterack:
1457: /*
1458: * Generate an ACK dropping incoming segment if it occupies
1459: * sequence space, where the ACK reflects our state.
1460: */
1461: if (tiflags & TH_RST)
1462: goto drop;
1463: m_freem(m);
1464: tp->t_flags |= TF_ACKNOW;
1465: (void) tcp_output(tp);
1466: return;
1467:
1468: dropwithreset:
1469: /* reuses m if m!=NULL, m_free() unnecessary */
1470: if (tiflags & TH_ACK)
1471: tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST);
1472: else {
1473: if (tiflags & TH_SYN) ti->ti_len++;
1474: tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0,
1475: TH_RST|TH_ACK);
1476: }
1477:
1478: return;
1479:
1480: drop:
1481: /*
1482: * Drop space held by incoming segment and return.
1483: */
1484: m_free(m);
1485:
1486: return;
1487: }
1488:
1489: /* , ts_present, ts_val, ts_ecr) */
1490: /* int *ts_present;
1491: * u_int32_t *ts_val, *ts_ecr;
1492: */
1493: void
1494: tcp_dooptions(tp, cp, cnt, ti)
1495: struct tcpcb *tp;
1496: u_char *cp;
1497: int cnt;
1498: struct tcpiphdr *ti;
1499: {
1500: u_int16_t mss;
1501: int opt, optlen;
1502:
1503: DEBUG_CALL("tcp_dooptions");
1504: DEBUG_ARGS((dfd," tp = %lx cnt=%i \n", (long )tp, cnt));
1505:
1506: for (; cnt > 0; cnt -= optlen, cp += optlen) {
1507: opt = cp[0];
1508: if (opt == TCPOPT_EOL)
1509: break;
1510: if (opt == TCPOPT_NOP)
1511: optlen = 1;
1512: else {
1513: optlen = cp[1];
1514: if (optlen <= 0)
1515: break;
1516: }
1517: switch (opt) {
1518:
1519: default:
1520: continue;
1521:
1522: case TCPOPT_MAXSEG:
1523: if (optlen != TCPOLEN_MAXSEG)
1524: continue;
1525: if (!(ti->ti_flags & TH_SYN))
1526: continue;
1527: memcpy((char *) &mss, (char *) cp + 2, sizeof(mss));
1528: NTOHS(mss);
1529: (void) tcp_mss(tp, mss); /* sets t_maxseg */
1530: break;
1531:
1532: /* case TCPOPT_WINDOW:
1533: * if (optlen != TCPOLEN_WINDOW)
1534: * continue;
1535: * if (!(ti->ti_flags & TH_SYN))
1536: * continue;
1537: * tp->t_flags |= TF_RCVD_SCALE;
1538: * tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
1539: * break;
1540: */
1541: /* case TCPOPT_TIMESTAMP:
1542: * if (optlen != TCPOLEN_TIMESTAMP)
1543: * continue;
1544: * *ts_present = 1;
1545: * memcpy((char *) ts_val, (char *)cp + 2, sizeof(*ts_val));
1546: * NTOHL(*ts_val);
1547: * memcpy((char *) ts_ecr, (char *)cp + 6, sizeof(*ts_ecr));
1548: * NTOHL(*ts_ecr);
1549: *
1550: */ /*
1551: * * A timestamp received in a SYN makes
1552: * * it ok to send timestamp requests and replies.
1553: * */
1554: /* if (ti->ti_flags & TH_SYN) {
1555: * tp->t_flags |= TF_RCVD_TSTMP;
1556: * tp->ts_recent = *ts_val;
1557: * tp->ts_recent_age = tcp_now;
1558: * }
1559: */ break;
1560: }
1561: }
1562: }
1563:
1564:
1565: /*
1566: * Pull out of band byte out of a segment so
1567: * it doesn't appear in the user's data queue.
1568: * It is still reflected in the segment length for
1569: * sequencing purposes.
1570: */
1571:
1572: #ifdef notdef
1573:
1574: void
1575: tcp_pulloutofband(so, ti, m)
1576: struct socket *so;
1577: struct tcpiphdr *ti;
1578: register struct mbuf *m;
1579: {
1580: int cnt = ti->ti_urp - 1;
1581:
1582: while (cnt >= 0) {
1583: if (m->m_len > cnt) {
1584: char *cp = mtod(m, caddr_t) + cnt;
1585: struct tcpcb *tp = sototcpcb(so);
1586:
1587: tp->t_iobc = *cp;
1588: tp->t_oobflags |= TCPOOB_HAVEDATA;
1589: memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1));
1590: m->m_len--;
1591: return;
1592: }
1593: cnt -= m->m_len;
1594: m = m->m_next; /* XXX WRONG! Fix it! */
1595: if (m == 0)
1596: break;
1597: }
1598: panic("tcp_pulloutofband");
1599: }
1600:
1601: #endif /* notdef */
1602:
1603: /*
1604: * Collect new round-trip time estimate
1605: * and update averages and current timeout.
1606: */
1607:
1608: void
1609: tcp_xmit_timer(tp, rtt)
1610: register struct tcpcb *tp;
1611: int rtt;
1612: {
1613: register short delta;
1614:
1615: DEBUG_CALL("tcp_xmit_timer");
1616: DEBUG_ARG("tp = %lx", (long)tp);
1617: DEBUG_ARG("rtt = %d", rtt);
1618:
1619: tcpstat.tcps_rttupdated++;
1620: if (tp->t_srtt != 0) {
1621: /*
1622: * srtt is stored as fixed point with 3 bits after the
1623: * binary point (i.e., scaled by 8). The following magic
1624: * is equivalent to the smoothing algorithm in rfc793 with
1625: * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
1626: * point). Adjust rtt to origin 0.
1627: */
1628: delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT);
1629: if ((tp->t_srtt += delta) <= 0)
1630: tp->t_srtt = 1;
1631: /*
1632: * We accumulate a smoothed rtt variance (actually, a
1633: * smoothed mean difference), then set the retransmit
1634: * timer to smoothed rtt + 4 times the smoothed variance.
1635: * rttvar is stored as fixed point with 2 bits after the
1636: * binary point (scaled by 4). The following is
1637: * equivalent to rfc793 smoothing with an alpha of .75
1638: * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
1639: * rfc793's wired-in beta.
1640: */
1641: if (delta < 0)
1642: delta = -delta;
1643: delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
1644: if ((tp->t_rttvar += delta) <= 0)
1645: tp->t_rttvar = 1;
1646: } else {
1647: /*
1648: * No rtt measurement yet - use the unsmoothed rtt.
1649: * Set the variance to half the rtt (so our first
1650: * retransmit happens at 3*rtt).
1651: */
1652: tp->t_srtt = rtt << TCP_RTT_SHIFT;
1653: tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
1654: }
1655: tp->t_rtt = 0;
1656: tp->t_rxtshift = 0;
1657:
1658: /*
1659: * the retransmit should happen at rtt + 4 * rttvar.
1660: * Because of the way we do the smoothing, srtt and rttvar
1661: * will each average +1/2 tick of bias. When we compute
1662: * the retransmit timer, we want 1/2 tick of rounding and
1663: * 1 extra tick because of +-1/2 tick uncertainty in the
1664: * firing of the timer. The bias will give us exactly the
1665: * 1.5 tick we need. But, because the bias is
1666: * statistical, we have to test that we don't drop below
1667: * the minimum feasible timer (which is 2 ticks).
1668: */
1669: TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
1670: (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */
1671:
1672: /*
1673: * We received an ack for a packet that wasn't retransmitted;
1674: * it is probably safe to discard any error indications we've
1675: * received recently. This isn't quite right, but close enough
1676: * for now (a route might have failed after we sent a segment,
1677: * and the return path might not be symmetrical).
1678: */
1679: tp->t_softerror = 0;
1680: }
1681:
1682: /*
1683: * Determine a reasonable value for maxseg size.
1684: * If the route is known, check route for mtu.
1685: * If none, use an mss that can be handled on the outgoing
1686: * interface without forcing IP to fragment; if bigger than
1687: * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
1688: * to utilize large mbufs. If no route is found, route has no mtu,
1689: * or the destination isn't local, use a default, hopefully conservative
1690: * size (usually 512 or the default IP max size, but no more than the mtu
1691: * of the interface), as we can't discover anything about intervening
1692: * gateways or networks. We also initialize the congestion/slow start
1693: * window to be a single segment if the destination isn't local.
1694: * While looking at the routing entry, we also initialize other path-dependent
1695: * parameters from pre-set or cached values in the routing entry.
1696: */
1697:
1698: int
1699: tcp_mss(tp, offer)
1700: register struct tcpcb *tp;
1701: u_int offer;
1702: {
1703: struct socket *so = tp->t_socket;
1704: int mss;
1705:
1706: DEBUG_CALL("tcp_mss");
1707: DEBUG_ARG("tp = %lx", (long)tp);
1708: DEBUG_ARG("offer = %d", offer);
1709:
1710: mss = min(if_mtu, if_mru) - sizeof(struct tcpiphdr);
1711: if (offer)
1712: mss = min(mss, offer);
1713: mss = max(mss, 32);
1714: if (mss < tp->t_maxseg || offer != 0)
1715: tp->t_maxseg = mss;
1716:
1717: tp->snd_cwnd = mss;
1718:
1719: sbreserve(&so->so_snd, tcp_sndspace+((tcp_sndspace%mss)?(mss-(tcp_sndspace%mss)):0));
1720: sbreserve(&so->so_rcv, tcp_rcvspace+((tcp_rcvspace%mss)?(mss-(tcp_rcvspace%mss)):0));
1721:
1722: DEBUG_MISC((dfd, " returning mss = %d\n", mss));
1723:
1724: return mss;
1725: }
This archive runs on limited infrastructure. Preserving old code on modern bandwidth. Automated agents are requested to crawl responsibly.