1: /*
   2:  * Copyright (c) 1982, 1986 Regents of the University of California.
   3:  * All rights reserved.  The Berkeley software License Agreement
   4:  * specifies the terms and conditions for redistribution.
   5:  *
   6:  *	@(#)tcp_input.c	7.1 (Berkeley) 6/5/86
   7:  */
   8: 
   9: #include "param.h"
  10: #include "systm.h"
  11: #include "mbuf.h"
  12: #include "protosw.h"
  13: #include "socket.h"
  14: #include "socketvar.h"
  15: #include "errno.h"
  16: 
  17: #include "../net/if.h"
  18: #include "../net/route.h"
  19: 
  20: #include "in.h"
  21: #include "in_pcb.h"
  22: #include "in_systm.h"
  23: #include "ip.h"
  24: #include "ip_var.h"
  25: #include "tcp.h"
  26: #include "tcp_fsm.h"
  27: #include "tcp_seq.h"
  28: #include "tcp_timer.h"
  29: #include "tcp_var.h"
  30: #include "tcpip.h"
  31: #include "tcp_debug.h"
  32: 
  33: int tcpprintfs = 0;
  34: int tcpcksum = 1;
  35: struct  tcpiphdr tcp_saveti;
  36: extern  tcpnodelack;
  37: 
  38: struct  tcpcb *tcp_newtcpcb();
  39: 
  40: /*
  41:  * Insert segment ti into reassembly queue of tcp with
  42:  * control block tp.  Return TH_FIN if reassembly now includes
  43:  * a segment with FIN.  The macro form does the common case inline
  44:  * (segment is the next to be received on an established connection,
  45:  * and the queue is empty), avoiding linkage into and removal
  46:  * from the queue and repetition of various conversions.
  47:  */
  48: #define TCP_REASS(tp, ti, m, so, flags) { \
  49:     if ((ti)->ti_seq == (tp)->rcv_nxt && \
  50:         (tp)->seg_next == (struct tcpiphdr *)(tp) && \
  51:         (tp)->t_state == TCPS_ESTABLISHED) { \
  52:         (tp)->rcv_nxt += (ti)->ti_len; \
  53:         flags = (ti)->ti_flags & TH_FIN; \
  54:         sbappend(&(so)->so_rcv, (m)); \
  55:         sorwakeup(so); \
  56:     } else \
  57:         (flags) = tcp_reass((tp), (ti)); \
  58: }
  59: 
  60: tcp_reass(tp, ti)
  61:     register struct tcpcb *tp;
  62:     register struct tcpiphdr *ti;
  63: {
  64:     register struct tcpiphdr *q;
  65:     struct socket *so = tp->t_inpcb->inp_socket;
  66:     struct mbuf *m;
  67:     int flags;
  68: 
  69:     /*
  70: 	 * Call with ti==0 after become established to
  71: 	 * force pre-ESTABLISHED data up to user socket.
  72: 	 */
  73:     if (ti == 0)
  74:         goto present;
  75: 
  76:     /*
  77: 	 * Find a segment which begins after this one does.
  78: 	 */
  79:     for (q = tp->seg_next; q != (struct tcpiphdr *)tp;
  80:         q = (struct tcpiphdr *)q->ti_next)
  81:         if (SEQ_GT(q->ti_seq, ti->ti_seq))
  82:             break;
  83: 
  84:     /*
  85: 	 * If there is a preceding segment, it may provide some of
  86: 	 * our data already.  If so, drop the data from the incoming
  87: 	 * segment.  If it provides all of our data, drop us.
  88: 	 */
  89:     if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) {
  90:         register int i;
  91:         q = (struct tcpiphdr *)q->ti_prev;
  92:         /* conversion to int (in i) handles seq wraparound */
  93:         i = q->ti_seq + q->ti_len - ti->ti_seq;
  94:         if (i > 0) {
  95:             if (i >= ti->ti_len)
  96:                 goto drop;
  97:             m_adj(dtom(ti), i);
  98:             ti->ti_len -= i;
  99:             ti->ti_seq += i;
 100:         }
 101:         q = (struct tcpiphdr *)(q->ti_next);
 102:     }
 103: 
 104:     /*
 105: 	 * While we overlap succeeding segments trim them or,
 106: 	 * if they are completely covered, dequeue them.
 107: 	 */
 108:     while (q != (struct tcpiphdr *)tp) {
 109:         register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
 110:         if (i <= 0)
 111:             break;
 112:         if (i < q->ti_len) {
 113:             q->ti_seq += i;
 114:             q->ti_len -= i;
 115:             m_adj(dtom(q), i);
 116:             break;
 117:         }
 118:         q = (struct tcpiphdr *)q->ti_next;
 119:         m = dtom(q->ti_prev);
 120:         remque(q->ti_prev);
 121:         m_freem(m);
 122:     }
 123: 
 124:     /*
 125: 	 * Stick new segment in its place.
 126: 	 */
 127:     insque(ti, q->ti_prev);
 128: 
 129: present:
 130:     /*
 131: 	 * Present data to user, advancing rcv_nxt through
 132: 	 * completed sequence space.
 133: 	 */
 134:     if (TCPS_HAVERCVDSYN(tp->t_state) == 0)
 135:         return (0);
 136:     ti = tp->seg_next;
 137:     if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt)
 138:         return (0);
 139:     if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
 140:         return (0);
 141:     do {
 142:         tp->rcv_nxt += ti->ti_len;
 143:         flags = ti->ti_flags & TH_FIN;
 144:         remque(ti);
 145:         m = dtom(ti);
 146:         ti = (struct tcpiphdr *)ti->ti_next;
 147:         if (so->so_state & SS_CANTRCVMORE)
 148:             m_freem(m);
 149:         else
 150:             sbappend(&so->so_rcv, m);
 151:     } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
 152:     sorwakeup(so);
 153:     return (flags);
 154: drop:
 155:     m_freem(dtom(ti));
 156:     return (0);
 157: }
 158: 
 159: /*
 160:  * TCP input routine, follows pages 65-76 of the
 161:  * protocol specification dated September, 1981 very closely.
 162:  */
 163: tcp_input(m0)
 164:     struct mbuf *m0;
 165: {
 166:     register struct tcpiphdr *ti;
 167:     struct inpcb *inp;
 168:     register struct mbuf *m;
 169:     struct mbuf *om = 0;
 170:     int len, tlen, off;
 171:     register struct tcpcb *tp = 0;
 172:     register int tiflags;
 173:     struct socket *so;
 174:     int todrop, acked, needoutput = 0;
 175:     short ostate;
 176:     struct in_addr laddr;
 177:     int dropsocket = 0;
 178: 
 179:     /*
 180: 	 * Get IP and TCP header together in first mbuf.
 181: 	 * Note: IP leaves IP header in first mbuf.
 182: 	 */
 183:     m = m0;
 184:     ti = mtod(m, struct tcpiphdr *);
 185:     if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2))
 186:         ip_stripoptions((struct ip *)ti, (struct mbuf *)0);
 187:     if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) {
 188:         if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
 189:             tcpstat.tcps_hdrops++;
 190:             return;
 191:         }
 192:         ti = mtod(m, struct tcpiphdr *);
 193:     }
 194: 
 195:     /*
 196: 	 * Checksum extended TCP header and data.
 197: 	 */
 198:     tlen = ((struct ip *)ti)->ip_len;
 199:     len = sizeof (struct ip) + tlen;
 200:     if (tcpcksum) {
 201:         ti->ti_next = ti->ti_prev = 0;
 202:         ti->ti_x1 = 0;
 203:         ti->ti_len = (u_short)tlen;
 204:         ti->ti_len = htons((u_short)ti->ti_len);
 205:         if (ti->ti_sum = in_cksum(m, len)) {
 206:             if (tcpprintfs)
 207:                 printf("tcp sum: src %x\n", ti->ti_src);
 208:             tcpstat.tcps_badsum++;
 209:             goto drop;
 210:         }
 211:     }
 212: 
 213:     /*
 214: 	 * Check that TCP offset makes sense,
 215: 	 * pull out TCP options and adjust length.
 216: 	 */
 217:     off = ti->ti_off << 2;
 218:     if (off < sizeof (struct tcphdr) || off > tlen) {
 219:         if (tcpprintfs)
 220:             printf("tcp off: src %x off %d\n", ti->ti_src, off);
 221:         tcpstat.tcps_badoff++;
 222:         goto drop;
 223:     }
 224:     tlen -= off;
 225:     ti->ti_len = tlen;
 226:     if (off > sizeof (struct tcphdr)) {
 227:         if (m->m_len < sizeof(struct ip) + off) {
 228:             if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) {
 229:                 tcpstat.tcps_hdrops++;
 230:                 return;
 231:             }
 232:             ti = mtod(m, struct tcpiphdr *);
 233:         }
 234:         om = m_get(M_DONTWAIT, MT_DATA);
 235:         if (om == 0)
 236:             goto drop;
 237:         om->m_len = off - sizeof (struct tcphdr);
 238:         { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
 239:           bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len);
 240:           m->m_len -= om->m_len;
 241:           bcopy(op+om->m_len, op,
 242:            (unsigned)(m->m_len-sizeof (struct tcpiphdr)));
 243:         }
 244:     }
 245:     tiflags = ti->ti_flags;
 246: 
 247:     /*
 248: 	 * Drop TCP and IP headers; TCP options were dropped above.
 249: 	 */
 250:     m->m_off += sizeof(struct tcpiphdr);
 251:     m->m_len -= sizeof(struct tcpiphdr);
 252: 
 253:     /*
 254: 	 * Convert TCP protocol specific fields to host format.
 255: 	 */
 256:     ti->ti_seq = ntohl(ti->ti_seq);
 257:     ti->ti_ack = ntohl(ti->ti_ack);
 258:     ti->ti_win = ntohs(ti->ti_win);
 259:     ti->ti_urp = ntohs(ti->ti_urp);
 260: 
 261:     /*
 262: 	 * Locate pcb for segment.
 263: 	 */
 264:     inp = in_pcblookup
 265:         (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport,
 266:         INPLOOKUP_WILDCARD);
 267: 
 268:     /*
 269: 	 * If the state is CLOSED (i.e., TCB does not exist) then
 270: 	 * all data in the incoming segment is discarded.
 271: 	 */
 272:     if (inp == 0)
 273:         goto dropwithreset;
 274:     tp = intotcpcb(inp);
 275:     if (tp == 0)
 276:         goto dropwithreset;
 277:     so = inp->inp_socket;
 278:     if (so->so_options & SO_DEBUG) {
 279:         ostate = tp->t_state;
 280:         tcp_saveti = *ti;
 281:     }
 282:     if (so->so_options & SO_ACCEPTCONN) {
 283:         so = sonewconn(so);
 284:         if (so == 0)
 285:             goto drop;
 286:         /*
 287: 		 * This is ugly, but ....
 288: 		 *
 289: 		 * Mark socket as temporary until we're
 290: 		 * committed to keeping it.  The code at
 291: 		 * ``drop'' and ``dropwithreset'' check the
 292: 		 * flag dropsocket to see if the temporary
 293: 		 * socket created here should be discarded.
 294: 		 * We mark the socket as discardable until
 295: 		 * we're committed to it below in TCPS_LISTEN.
 296: 		 */
 297:         dropsocket++;
 298:         inp = (struct inpcb *)so->so_pcb;
 299:         inp->inp_laddr = ti->ti_dst;
 300:         inp->inp_lport = ti->ti_dport;
 301:         inp->inp_options = ip_srcroute();
 302:         tp = intotcpcb(inp);
 303:         tp->t_state = TCPS_LISTEN;
 304:     }
 305: 
 306:     /*
 307: 	 * Segment received on connection.
 308: 	 * Reset idle time and keep-alive timer.
 309: 	 */
 310:     tp->t_idle = 0;
 311:     tp->t_timer[TCPT_KEEP] = TCPTV_KEEP;
 312: 
 313:     /*
 314: 	 * Process options if not in LISTEN state,
 315: 	 * else do it below (after getting remote address).
 316: 	 */
 317:     if (om && tp->t_state != TCPS_LISTEN) {
 318:         tcp_dooptions(tp, om, ti);
 319:         om = 0;
 320:     }
 321: 
 322:     /*
 323: 	 * Calculate amount of space in receive window,
 324: 	 * and then do TCP input processing.
 325: 	 * Receive window is amount of space in rcv queue,
 326: 	 * but not less than advertised window.
 327: 	 */
 328:     { int win;
 329: 
 330:     win = sbspace(&so->so_rcv);
 331:     if (win < 0)
 332:         win = 0;
 333:     tp->rcv_wnd = MAX(win, (int)(tp->rcv_adv - tp->rcv_nxt));
 334:     }
 335: 
 336:     switch (tp->t_state) {
 337: 
 338:     /*
 339: 	 * If the state is LISTEN then ignore segment if it contains an RST.
 340: 	 * If the segment contains an ACK then it is bad and send a RST.
 341: 	 * If it does not contain a SYN then it is not interesting; drop it.
 342: 	 * Don't bother responding if the destination was a broadcast.
 343: 	 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial
 344: 	 * tp->iss, and send a segment:
 345: 	 *     <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
 346: 	 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss.
 347: 	 * Fill in remote peer address fields if not previously specified.
 348: 	 * Enter SYN_RECEIVED state, and process any other fields of this
 349: 	 * segment in this state.
 350: 	 */
 351:     case TCPS_LISTEN: {
 352:         struct mbuf *am;
 353:         register struct sockaddr_in *sin;
 354: 
 355:         if (tiflags & TH_RST)
 356:             goto drop;
 357:         if (tiflags & TH_ACK)
 358:             goto dropwithreset;
 359:         if ((tiflags & TH_SYN) == 0)
 360:             goto drop;
 361:         if (in_broadcast(ti->ti_dst))
 362:             goto drop;
 363:         am = m_get(M_DONTWAIT, MT_SONAME);
 364:         if (am == NULL)
 365:             goto drop;
 366:         am->m_len = sizeof (struct sockaddr_in);
 367:         sin = mtod(am, struct sockaddr_in *);
 368:         sin->sin_family = AF_INET;
 369:         sin->sin_addr = ti->ti_src;
 370:         sin->sin_port = ti->ti_sport;
 371:         laddr = inp->inp_laddr;
 372:         if (inp->inp_laddr.s_addr == INADDR_ANY)
 373:             inp->inp_laddr = ti->ti_dst;
 374:         if (in_pcbconnect(inp, am)) {
 375:             inp->inp_laddr = laddr;
 376:             (void) m_free(am);
 377:             goto drop;
 378:         }
 379:         (void) m_free(am);
 380:         tp->t_template = tcp_template(tp);
 381:         if (tp->t_template == 0) {
 382:             tp = tcp_drop(tp, ENOBUFS);
 383:             dropsocket = 0;     /* socket is already gone */
 384:             goto drop;
 385:         }
 386:         if (om) {
 387:             tcp_dooptions(tp, om, ti);
 388:             om = 0;
 389:         }
 390:         tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2;
 391:         tp->irs = ti->ti_seq;
 392:         tcp_sendseqinit(tp);
 393:         tcp_rcvseqinit(tp);
 394:         tp->t_flags |= TF_ACKNOW;
 395:         tp->t_state = TCPS_SYN_RECEIVED;
 396:         tp->t_timer[TCPT_KEEP] = TCPTV_KEEP;
 397:         dropsocket = 0;     /* committed to socket */
 398:         goto trimthenstep6;
 399:         }
 400: 
 401:     /*
 402: 	 * If the state is SYN_SENT:
 403: 	 *	if seg contains an ACK, but not for our SYN, drop the input.
 404: 	 *	if seg contains a RST, then drop the connection.
 405: 	 *	if seg does not contain SYN, then drop it.
 406: 	 * Otherwise this is an acceptable SYN segment
 407: 	 *	initialize tp->rcv_nxt and tp->irs
 408: 	 *	if seg contains ack then advance tp->snd_una
 409: 	 *	if SYN has been acked change to ESTABLISHED else SYN_RCVD state
 410: 	 *	arrange for segment to be acked (eventually)
 411: 	 *	continue processing rest of data/controls, beginning with URG
 412: 	 */
 413:     case TCPS_SYN_SENT:
 414:         if ((tiflags & TH_ACK) &&
 415:             (SEQ_LEQ(ti->ti_ack, tp->iss) ||
 416:              SEQ_GT(ti->ti_ack, tp->snd_max)))
 417:             goto dropwithreset;
 418:         if (tiflags & TH_RST) {
 419:             if (tiflags & TH_ACK)
 420:                 tp = tcp_drop(tp, ECONNREFUSED);
 421:             goto drop;
 422:         }
 423:         if ((tiflags & TH_SYN) == 0)
 424:             goto drop;
 425:         tp->snd_una = ti->ti_ack;
 426:         if (SEQ_LT(tp->snd_nxt, tp->snd_una))
 427:             tp->snd_nxt = tp->snd_una;
 428:         tp->t_timer[TCPT_REXMT] = 0;
 429:         tp->irs = ti->ti_seq;
 430:         tcp_rcvseqinit(tp);
 431:         tp->t_flags |= TF_ACKNOW;
 432:         if (SEQ_GT(tp->snd_una, tp->iss)) {
 433:             soisconnected(so);
 434:             tp->t_state = TCPS_ESTABLISHED;
 435:             tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp));
 436:             (void) tcp_reass(tp, (struct tcpiphdr *)0);
 437:         } else
 438:             tp->t_state = TCPS_SYN_RECEIVED;
 439:         goto trimthenstep6;
 440: 
 441: trimthenstep6:
 442:         /*
 443: 		 * Advance ti->ti_seq to correspond to first data byte.
 444: 		 * If data, trim to stay within window,
 445: 		 * dropping FIN if necessary.
 446: 		 */
 447:         ti->ti_seq++;
 448:         if (ti->ti_len > tp->rcv_wnd) {
 449:             todrop = ti->ti_len - tp->rcv_wnd;
 450:             m_adj(m, -todrop);
 451:             ti->ti_len = tp->rcv_wnd;
 452:             tiflags &= ~TH_FIN;
 453:         }
 454:         tp->snd_wl1 = ti->ti_seq - 1;
 455:         tp->rcv_up = ti->ti_seq;
 456:         goto step6;
 457:     }
 458: 
 459:     /*
 460: 	 * If data is received on a connection after the
 461: 	 * user processes are gone, then RST the other end.
 462: 	 */
 463:     if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT &&
 464:         ti->ti_len) {
 465:         tp = tcp_close(tp);
 466:         goto dropwithreset;
 467:     }
 468: 
 469:     /*
 470: 	 * States other than LISTEN or SYN_SENT.
 471: 	 * First check that at least some bytes of segment are within
 472: 	 * receive window.
 473: 	 */
 474:     if (tp->rcv_wnd == 0) {
 475:         /*
 476: 		 * If window is closed can only take segments at
 477: 		 * window edge, and have to drop data and PUSH from
 478: 		 * incoming segments.
 479: 		 */
 480:         if (tp->rcv_nxt != ti->ti_seq)
 481:             goto dropafterack;
 482:         if (ti->ti_len > 0) {
 483:             m_adj(m, ti->ti_len);
 484:             ti->ti_len = 0;
 485:             tiflags &= ~(TH_PUSH|TH_FIN);
 486:         }
 487:     } else {
 488:         /*
 489: 		 * If segment begins before rcv_nxt, drop leading
 490: 		 * data (and SYN); if nothing left, just ack.
 491: 		 */
 492:         todrop = tp->rcv_nxt - ti->ti_seq;
 493:         if (todrop > 0) {
 494:             if (tiflags & TH_SYN) {
 495:                 tiflags &= ~TH_SYN;
 496:                 ti->ti_seq++;
 497:                 if (ti->ti_urp > 1)
 498:                     ti->ti_urp--;
 499:                 else
 500:                     tiflags &= ~TH_URG;
 501:                 todrop--;
 502:             }
 503:             if (todrop > ti->ti_len ||
 504:                 todrop == ti->ti_len && (tiflags&TH_FIN) == 0)
 505:                 goto dropafterack;
 506:             m_adj(m, todrop);
 507:             ti->ti_seq += todrop;
 508:             ti->ti_len -= todrop;
 509:             if (ti->ti_urp > todrop)
 510:                 ti->ti_urp -= todrop;
 511:             else {
 512:                 tiflags &= ~TH_URG;
 513:                 ti->ti_urp = 0;
 514:             }
 515:         }
 516:         /*
 517: 		 * If segment ends after window, drop trailing data
 518: 		 * (and PUSH and FIN); if nothing left, just ACK.
 519: 		 */
 520:         todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
 521:         if (todrop > 0) {
 522:             if (todrop >= ti->ti_len)
 523:                 goto dropafterack;
 524:             m_adj(m, -todrop);
 525:             ti->ti_len -= todrop;
 526:             tiflags &= ~(TH_PUSH|TH_FIN);
 527:         }
 528:     }
 529: 
 530:     /*
 531: 	 * If the RST bit is set examine the state:
 532: 	 *    SYN_RECEIVED STATE:
 533: 	 *	If passive open, return to LISTEN state.
 534: 	 *	If active open, inform user that connection was refused.
 535: 	 *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
 536: 	 *	Inform user that connection was reset, and close tcb.
 537: 	 *    CLOSING, LAST_ACK, TIME_WAIT STATES
 538: 	 *	Close the tcb.
 539: 	 */
 540:     if (tiflags&TH_RST) switch (tp->t_state) {
 541: 
 542:     case TCPS_SYN_RECEIVED:
 543:         tp = tcp_drop(tp, ECONNREFUSED);
 544:         goto drop;
 545: 
 546:     case TCPS_ESTABLISHED:
 547:     case TCPS_FIN_WAIT_1:
 548:     case TCPS_FIN_WAIT_2:
 549:     case TCPS_CLOSE_WAIT:
 550:         tp = tcp_drop(tp, ECONNRESET);
 551:         goto drop;
 552: 
 553:     case TCPS_CLOSING:
 554:     case TCPS_LAST_ACK:
 555:     case TCPS_TIME_WAIT:
 556:         tp = tcp_close(tp);
 557:         goto drop;
 558:     }
 559: 
 560:     /*
 561: 	 * If a SYN is in the window, then this is an
 562: 	 * error and we send an RST and drop the connection.
 563: 	 */
 564:     if (tiflags & TH_SYN) {
 565:         tp = tcp_drop(tp, ECONNRESET);
 566:         goto dropwithreset;
 567:     }
 568: 
 569:     /*
 570: 	 * If the ACK bit is off we drop the segment and return.
 571: 	 */
 572:     if ((tiflags & TH_ACK) == 0)
 573:         goto drop;
 574: 
 575:     /*
 576: 	 * Ack processing.
 577: 	 */
 578:     switch (tp->t_state) {
 579: 
 580:     /*
 581: 	 * In SYN_RECEIVED state if the ack ACKs our SYN then enter
 582: 	 * ESTABLISHED state and continue processing, othewise
 583: 	 * send an RST.
 584: 	 */
 585:     case TCPS_SYN_RECEIVED:
 586:         if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
 587:             SEQ_GT(ti->ti_ack, tp->snd_max))
 588:             goto dropwithreset;
 589:         tp->snd_una++;          /* SYN acked */
 590:         if (SEQ_LT(tp->snd_nxt, tp->snd_una))
 591:             tp->snd_nxt = tp->snd_una;
 592:         tp->t_timer[TCPT_REXMT] = 0;
 593:         soisconnected(so);
 594:         tp->t_state = TCPS_ESTABLISHED;
 595:         tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp));
 596:         (void) tcp_reass(tp, (struct tcpiphdr *)0);
 597:         tp->snd_wl1 = ti->ti_seq - 1;
 598:         /* fall into ... */
 599: 
 600:     /*
 601: 	 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
 602: 	 * ACKs.  If the ack is in the range
 603: 	 *	tp->snd_una < ti->ti_ack <= tp->snd_max
 604: 	 * then advance tp->snd_una to ti->ti_ack and drop
 605: 	 * data from the retransmission queue.  If this ACK reflects
 606: 	 * more up to date window information we update our window information.
 607: 	 */
 608:     case TCPS_ESTABLISHED:
 609:     case TCPS_FIN_WAIT_1:
 610:     case TCPS_FIN_WAIT_2:
 611:     case TCPS_CLOSE_WAIT:
 612:     case TCPS_CLOSING:
 613:     case TCPS_LAST_ACK:
 614:     case TCPS_TIME_WAIT:
 615: #define ourfinisacked   (acked > 0)
 616: 
 617:         if (SEQ_LEQ(ti->ti_ack, tp->snd_una))
 618:             break;
 619:         if (SEQ_GT(ti->ti_ack, tp->snd_max))
 620:             goto dropafterack;
 621:         acked = ti->ti_ack - tp->snd_una;
 622: 
 623:         /*
 624: 		 * If transmit timer is running and timed sequence
 625: 		 * number was acked, update smoothed round trip time.
 626: 		 */
 627:         if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) {
 628:             if (tp->t_srtt == 0)
 629:                 tp->t_srtt = tp->t_rtt;
 630:             else
 631:                 tp->t_srtt =
 632:                     tcp_alpha * tp->t_srtt +
 633:                     (1 - tcp_alpha) * tp->t_rtt;
 634:             tp->t_rtt = 0;
 635:         }
 636: 
 637:         /*
 638: 		 * If all outstanding data is acked, stop retransmit
 639: 		 * timer and remember to restart (more output or persist).
 640: 		 * If there is more data to be acked, restart retransmit
 641: 		 * timer.
 642: 		 */
 643:         if (ti->ti_ack == tp->snd_max) {
 644:             tp->t_timer[TCPT_REXMT] = 0;
 645:             needoutput = 1;
 646:         } else if (tp->t_timer[TCPT_PERSIST] == 0) {
 647:             TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
 648:                 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX);
 649:             tp->t_rxtshift = 0;
 650:         }
 651:         /*
 652: 		 * When new data is acked, open the congestion window a bit.
 653: 		 */
 654:         if (acked > 0)
 655:             tp->snd_cwnd = MIN(11 * tp->snd_cwnd / 10, 65535);
 656:         if (acked > so->so_snd.sb_cc) {
 657:             tp->snd_wnd -= so->so_snd.sb_cc;
 658:             sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
 659:         } else {
 660:             sbdrop(&so->so_snd, acked);
 661:             tp->snd_wnd -= acked;
 662:             acked = 0;
 663:         }
 664:         if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel)
 665:             sowwakeup(so);
 666:         tp->snd_una = ti->ti_ack;
 667:         if (SEQ_LT(tp->snd_nxt, tp->snd_una))
 668:             tp->snd_nxt = tp->snd_una;
 669: 
 670:         switch (tp->t_state) {
 671: 
 672:         /*
 673: 		 * In FIN_WAIT_1 STATE in addition to the processing
 674: 		 * for the ESTABLISHED state if our FIN is now acknowledged
 675: 		 * then enter FIN_WAIT_2.
 676: 		 */
 677:         case TCPS_FIN_WAIT_1:
 678:             if (ourfinisacked) {
 679:                 /*
 680: 				 * If we can't receive any more
 681: 				 * data, then closing user can proceed.
 682: 				 * Starting the timer is contrary to the
 683: 				 * specification, but if we don't get a FIN
 684: 				 * we'll hang forever.
 685: 				 */
 686:                 if (so->so_state & SS_CANTRCVMORE) {
 687:                     soisdisconnected(so);
 688:                     tp->t_timer[TCPT_2MSL] = TCPTV_MAXIDLE;
 689:                 }
 690:                 tp->t_state = TCPS_FIN_WAIT_2;
 691:             }
 692:             break;
 693: 
 694:         /*
 695: 		 * In CLOSING STATE in addition to the processing for
 696: 		 * the ESTABLISHED state if the ACK acknowledges our FIN
 697: 		 * then enter the TIME-WAIT state, otherwise ignore
 698: 		 * the segment.
 699: 		 */
 700:         case TCPS_CLOSING:
 701:             if (ourfinisacked) {
 702:                 tp->t_state = TCPS_TIME_WAIT;
 703:                 tcp_canceltimers(tp);
 704:                 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 705:                 soisdisconnected(so);
 706:             }
 707:             break;
 708: 
 709:         /*
 710: 		 * The only thing that can arrive in  LAST_ACK state
 711: 		 * is an acknowledgment of our FIN.  If our FIN is now
 712: 		 * acknowledged, delete the TCB, enter the closed state
 713: 		 * and return.
 714: 		 */
 715:         case TCPS_LAST_ACK:
 716:             if (ourfinisacked)
 717:                 tp = tcp_close(tp);
 718:             goto drop;
 719: 
 720:         /*
 721: 		 * In TIME_WAIT state the only thing that should arrive
 722: 		 * is a retransmission of the remote FIN.  Acknowledge
 723: 		 * it and restart the finack timer.
 724: 		 */
 725:         case TCPS_TIME_WAIT:
 726:             tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 727:             goto dropafterack;
 728:         }
 729: #undef ourfinisacked
 730:     }
 731: 
 732: step6:
 733:     /*
 734: 	 * Update window information.
 735: 	 * Don't look at window if no ACK: TAC's send garbage on first SYN.
 736: 	 */
 737:     if ((tiflags & TH_ACK) &&
 738:         (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq &&
 739:         (SEQ_LT(tp->snd_wl2, ti->ti_ack) ||
 740:          tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) {
 741:         tp->snd_wnd = ti->ti_win;
 742:         tp->snd_wl1 = ti->ti_seq;
 743:         tp->snd_wl2 = ti->ti_ack;
 744:         if (tp->snd_wnd > tp->max_sndwnd)
 745:             tp->max_sndwnd = tp->snd_wnd;
 746:         needoutput = 1;
 747:     }
 748: 
 749:     /*
 750: 	 * Process segments with URG.
 751: 	 */
 752:     if ((tiflags & TH_URG) && ti->ti_urp &&
 753:         TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 754:         /*
 755: 		 * This is a kludge, but if we receive and accept
 756: 		 * random urgent pointers, we'll crash in
 757: 		 * soreceive.  It's hard to imagine someone
 758: 		 * actually wanting to send this much urgent data.
 759: 		 */
 760:         if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) {
 761:             ti->ti_urp = 0;         /* XXX */
 762:             tiflags &= ~TH_URG;     /* XXX */
 763:             goto dodata;            /* XXX */
 764:         }
 765:         /*
 766: 		 * If this segment advances the known urgent pointer,
 767: 		 * then mark the data stream.  This should not happen
 768: 		 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
 769: 		 * a FIN has been received from the remote side.
 770: 		 * In these states we ignore the URG.
 771: 		 *
 772: 		 * According to RFC961 (Assigned Protocols),
 773: 		 * the urgent pointer points to the last octet
 774: 		 * of urgent data.  We continue, however,
 775: 		 * to consider it to indicate the first octet
 776: 		 * of data past the urgent section
 777: 		 * as the original spec states.
 778: 		 */
 779:         if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
 780:             tp->rcv_up = ti->ti_seq + ti->ti_urp;
 781:             so->so_oobmark = so->so_rcv.sb_cc +
 782:                 (tp->rcv_up - tp->rcv_nxt) - 1;
 783:             if (so->so_oobmark == 0)
 784:                 so->so_state |= SS_RCVATMARK;
 785:             sohasoutofband(so);
 786:             tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
 787:         }
 788:         /*
 789: 		 * Remove out of band data so doesn't get presented to user.
 790: 		 * This can happen independent of advancing the URG pointer,
 791: 		 * but if two URG's are pending at once, some out-of-band
 792: 		 * data may creep in... ick.
 793: 		 */
 794:         if (ti->ti_urp <= ti->ti_len &&
 795:             (so->so_options & SO_OOBINLINE) == 0)
 796:             tcp_pulloutofband(so, ti);
 797:     } else
 798:         /*
 799: 		 * If no out of band data is expected,
 800: 		 * pull receive urgent pointer along
 801: 		 * with the receive window.
 802: 		 */
 803:         if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
 804:             tp->rcv_up = tp->rcv_nxt;
 805: dodata:                         /* XXX */
 806: 
 807:     /*
 808: 	 * Process the segment text, merging it into the TCP sequencing queue,
 809: 	 * and arranging for acknowledgment of receipt if necessary.
 810: 	 * This process logically involves adjusting tp->rcv_wnd as data
 811: 	 * is presented to the user (this happens in tcp_usrreq.c,
 812: 	 * case PRU_RCVD).  If a FIN has already been received on this
 813: 	 * connection then we just ignore the text.
 814: 	 */
 815:     if ((ti->ti_len || (tiflags&TH_FIN)) &&
 816:         TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 817:         TCP_REASS(tp, ti, m, so, tiflags);
 818:         if (tcpnodelack == 0)
 819:             tp->t_flags |= TF_DELACK;
 820:         else
 821:             tp->t_flags |= TF_ACKNOW;
 822:         /*
 823: 		 * Note the amount of data that peer has sent into
 824: 		 * our window, in order to estimate the sender's
 825: 		 * buffer size.
 826: 		 */
 827:         len = so->so_rcv.sb_hiwat - (tp->rcv_nxt - tp->rcv_adv);
 828:         if (len > tp->max_rcvd)
 829:             tp->max_rcvd = len;
 830:     } else {
 831:         m_freem(m);
 832:         tiflags &= ~TH_FIN;
 833:     }
 834: 
 835:     /*
 836: 	 * If FIN is received ACK the FIN and let the user know
 837: 	 * that the connection is closing.
 838: 	 */
 839:     if (tiflags & TH_FIN) {
 840:         if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
 841:             socantrcvmore(so);
 842:             tp->t_flags |= TF_ACKNOW;
 843:             tp->rcv_nxt++;
 844:         }
 845:         switch (tp->t_state) {
 846: 
 847:         /*
 848: 		 * In SYN_RECEIVED and ESTABLISHED STATES
 849: 		 * enter the CLOSE_WAIT state.
 850: 		 */
 851:         case TCPS_SYN_RECEIVED:
 852:         case TCPS_ESTABLISHED:
 853:             tp->t_state = TCPS_CLOSE_WAIT;
 854:             break;
 855: 
 856:         /*
 857: 		 * If still in FIN_WAIT_1 STATE FIN has not been acked so
 858: 		 * enter the CLOSING state.
 859: 		 */
 860:         case TCPS_FIN_WAIT_1:
 861:             tp->t_state = TCPS_CLOSING;
 862:             break;
 863: 
 864:         /*
 865: 		 * In FIN_WAIT_2 state enter the TIME_WAIT state,
 866: 		 * starting the time-wait timer, turning off the other
 867: 		 * standard timers.
 868: 		 */
 869:         case TCPS_FIN_WAIT_2:
 870:             tp->t_state = TCPS_TIME_WAIT;
 871:             tcp_canceltimers(tp);
 872:             tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 873:             soisdisconnected(so);
 874:             break;
 875: 
 876:         /*
 877: 		 * In TIME_WAIT state restart the 2 MSL time_wait timer.
 878: 		 */
 879:         case TCPS_TIME_WAIT:
 880:             tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
 881:             break;
 882:         }
 883:     }
 884:     if (so->so_options & SO_DEBUG)
 885:         tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0);
 886: 
 887:     /*
 888: 	 * Return any desired output.
 889: 	 */
 890:     if (needoutput || (tp->t_flags & TF_ACKNOW))
 891:         (void) tcp_output(tp);
 892:     return;
 893: 
 894: dropafterack:
 895:     /*
 896: 	 * Generate an ACK dropping incoming segment if it occupies
 897: 	 * sequence space, where the ACK reflects our state.
 898: 	 */
 899:     if (tiflags & TH_RST)
 900:         goto drop;
 901:     if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
 902:         tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0);
 903:     tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK);
 904:     return;
 905: 
 906: dropwithreset:
 907:     if (om) {
 908:         (void) m_free(om);
 909:         om = 0;
 910:     }
 911:     /*
 912: 	 * Generate a RST, dropping incoming segment.
 913: 	 * Make ACK acceptable to originator of segment.
 914: 	 * Don't bother to respond if destination was broadcast.
 915: 	 */
 916:     if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst))
 917:         goto drop;
 918:     if (tiflags & TH_ACK)
 919:         tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST);
 920:     else {
 921:         if (tiflags & TH_SYN)
 922:             ti->ti_len++;
 923:         tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0,
 924:             TH_RST|TH_ACK);
 925:     }
 926:     /* destroy temporarily created socket */
 927:     if (dropsocket)
 928:         (void) soabort(so);
 929:     return;
 930: 
 931: drop:
 932:     if (om)
 933:         (void) m_free(om);
 934:     /*
 935: 	 * Drop space held by incoming segment and return.
 936: 	 */
 937:     if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
 938:         tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0);
 939:     m_freem(m);
 940:     /* destroy temporarily created socket */
 941:     if (dropsocket)
 942:         (void) soabort(so);
 943:     return;
 944: }
 945: 
 946: tcp_dooptions(tp, om, ti)
 947:     struct tcpcb *tp;
 948:     struct mbuf *om;
 949:     struct tcpiphdr *ti;
 950: {
 951:     register u_char *cp;
 952:     int opt, optlen, cnt;
 953: 
 954:     cp = mtod(om, u_char *);
 955:     cnt = om->m_len;
 956:     for (; cnt > 0; cnt -= optlen, cp += optlen) {
 957:         opt = cp[0];
 958:         if (opt == TCPOPT_EOL)
 959:             break;
 960:         if (opt == TCPOPT_NOP)
 961:             optlen = 1;
 962:         else {
 963:             optlen = cp[1];
 964:             if (optlen <= 0)
 965:                 break;
 966:         }
 967:         switch (opt) {
 968: 
 969:         default:
 970:             break;
 971: 
 972:         case TCPOPT_MAXSEG:
 973:             if (optlen != 4)
 974:                 continue;
 975:             if (!(ti->ti_flags & TH_SYN))
 976:                 continue;
 977:             tp->t_maxseg = *(u_short *)(cp + 2);
 978:             tp->t_maxseg = ntohs((u_short)tp->t_maxseg);
 979:             tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp));
 980:             break;
 981:         }
 982:     }
 983:     (void) m_free(om);
 984: }
 985: 
 986: /*
 987:  * Pull out of band byte out of a segment so
 988:  * it doesn't appear in the user's data queue.
 989:  * It is still reflected in the segment length for
 990:  * sequencing purposes.
 991:  */
 992: tcp_pulloutofband(so, ti)
 993:     struct socket *so;
 994:     struct tcpiphdr *ti;
 995: {
 996:     register struct mbuf *m;
 997:     int cnt = ti->ti_urp - 1;
 998: 
 999:     m = dtom(ti);
1000:     while (cnt >= 0) {
1001:         if (m->m_len > cnt) {
1002:             char *cp = mtod(m, caddr_t) + cnt;
1003:             struct tcpcb *tp = sototcpcb(so);
1004: 
1005:             tp->t_iobc = *cp;
1006:             tp->t_oobflags |= TCPOOB_HAVEDATA;
1007:             bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
1008:             m->m_len--;
1009:             return;
1010:         }
1011:         cnt -= m->m_len;
1012:         m = m->m_next;
1013:         if (m == 0)
1014:             break;
1015:     }
1016:     panic("tcp_pulloutofband");
1017: }
1018: 
1019: /*
1020:  *  Determine a reasonable value for maxseg size.
1021:  *  If the route is known, use one that can be handled
1022:  *  on the given interface without forcing IP to fragment.
1023:  *  If bigger than a page (CLBYTES), round down to nearest pagesize
1024:  *  to utilize pagesize mbufs.
1025:  *  If interface pointer is unavailable, or the destination isn't local,
1026:  *  use a conservative size (512 or the default IP max size, but no more
1027:  *  than the mtu of the interface through which we route),
1028:  *  as we can't discover anything about intervening gateways or networks.
1029:  *
1030:  *  This is ugly, and doesn't belong at this level, but has to happen somehow.
1031:  */
1032: tcp_mss(tp)
1033:     register struct tcpcb *tp;
1034: {
1035:     struct route *ro;
1036:     struct ifnet *ifp;
1037:     int mss;
1038:     struct inpcb *inp;
1039: 
1040:     inp = tp->t_inpcb;
1041:     ro = &inp->inp_route;
1042:     if ((ro->ro_rt == (struct rtentry *)0) ||
1043:         (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) {
1044:         /* No route yet, so try to acquire one */
1045:         if (inp->inp_faddr.s_addr != INADDR_ANY) {
1046:             ro->ro_dst.sa_family = AF_INET;
1047:             ((struct sockaddr_in *) &ro->ro_dst)->sin_addr =
1048:                 inp->inp_faddr;
1049:             rtalloc(ro);
1050:         }
1051:         if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0)
1052:             return (TCP_MSS);
1053:     }
1054: 
1055:     mss = ifp->if_mtu - sizeof(struct tcpiphdr);
1056: #if (CLBYTES & (CLBYTES - 1)) == 0
1057:     if (mss > CLBYTES)
1058:         mss &= ~(CLBYTES-1);
1059: #else
1060:     if (mss > CLBYTES)
1061:         mss = mss / CLBYTES * CLBYTES;
1062: #endif
1063:     if (in_localaddr(inp->inp_faddr))
1064:         return (mss);
1065:     return (MIN(mss, TCP_MSS));
1066: }

Defined functions

tcp_dooptions defined in line 946; used 2 times
tcp_input defined in line 163; used 2 times
tcp_mss defined in line 1032; used 4 times
tcp_pulloutofband defined in line 992; used 1 times
tcp_reass defined in line 60; used 3 times

Defined variables

tcp_saveti defined in line 35; used 4 times
tcpcksum defined in line 34; used 1 times
tcpprintfs defined in line 33; used 2 times

Defined macros

TCP_REASS defined in line 48; used 1 times
ourfinisacked defined in line 615; used 4 times
Last modified: 1986-06-05
Generated: 2016-12-26
Generated by src2html V0.67
page hit count: 3055
Valid CSS Valid XHTML 1.0 Strict