1 /* 2 * Copyright (c) 1982 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 6.21 (Berkeley) 02/23/86 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, newwin; 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 if (ti->ti_ack == tp->snd_max) 638 tp->t_timer[TCPT_REXMT] = 0; 639 else { 640 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 641 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 642 tp->t_rxtshift = 0; 643 } 644 /* 645 * When new data is acked, open the congestion window a bit. 646 */ 647 if (acked > 0) 648 tp->snd_cwnd = MIN(11 * tp->snd_cwnd / 10, 65535); 649 if (acked > so->so_snd.sb_cc) { 650 tp->snd_wnd -= so->so_snd.sb_cc; 651 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 652 } else { 653 sbdrop(&so->so_snd, acked); 654 tp->snd_wnd -= acked; 655 acked = 0; 656 } 657 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 658 sowwakeup(so); 659 tp->snd_una = ti->ti_ack; 660 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 661 tp->snd_nxt = tp->snd_una; 662 663 switch (tp->t_state) { 664 665 /* 666 * In FIN_WAIT_1 STATE in addition to the processing 667 * for the ESTABLISHED state if our FIN is now acknowledged 668 * then enter FIN_WAIT_2. 669 */ 670 case TCPS_FIN_WAIT_1: 671 if (ourfinisacked) { 672 /* 673 * If we can't receive any more 674 * data, then closing user can proceed. 675 * Starting the timer is contrary to the 676 * specification, but if we don't get a FIN 677 * we'll hang forever. 678 */ 679 if (so->so_state & SS_CANTRCVMORE) { 680 soisdisconnected(so); 681 tp->t_timer[TCPT_2MSL] = TCPTV_MAXIDLE; 682 } 683 tp->t_state = TCPS_FIN_WAIT_2; 684 } 685 break; 686 687 /* 688 * In CLOSING STATE in addition to the processing for 689 * the ESTABLISHED state if the ACK acknowledges our FIN 690 * then enter the TIME-WAIT state, otherwise ignore 691 * the segment. 692 */ 693 case TCPS_CLOSING: 694 if (ourfinisacked) { 695 tp->t_state = TCPS_TIME_WAIT; 696 tcp_canceltimers(tp); 697 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 698 soisdisconnected(so); 699 } 700 break; 701 702 /* 703 * The only thing that can arrive in LAST_ACK state 704 * is an acknowledgment of our FIN. If our FIN is now 705 * acknowledged, delete the TCB, enter the closed state 706 * and return. 707 */ 708 case TCPS_LAST_ACK: 709 if (ourfinisacked) 710 tp = tcp_close(tp); 711 goto drop; 712 713 /* 714 * In TIME_WAIT state the only thing that should arrive 715 * is a retransmission of the remote FIN. Acknowledge 716 * it and restart the finack timer. 717 */ 718 case TCPS_TIME_WAIT: 719 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 720 goto dropafterack; 721 } 722 #undef ourfinisacked 723 } 724 725 step6: 726 /* 727 * Update window information. 728 * Don't look at window if no ACK: TAC's send garbage on first SYN. 729 */ 730 if ((tiflags & TH_ACK) && 731 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 732 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 733 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) { 734 tp->snd_wnd = ti->ti_win; 735 tp->snd_wl1 = ti->ti_seq; 736 tp->snd_wl2 = ti->ti_ack; 737 if (tp->snd_wnd > tp->max_sndwnd) 738 tp->max_sndwnd = tp->snd_wnd; 739 newwin = 1; 740 } else 741 newwin = 0; 742 743 /* 744 * Process segments with URG. 745 */ 746 if ((tiflags & TH_URG) && ti->ti_urp && 747 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 748 /* 749 * This is a kludge, but if we receive and accept 750 * random urgent pointers, we'll crash in 751 * soreceive. It's hard to imagine someone 752 * actually wanting to send this much urgent data. 753 */ 754 if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) { 755 ti->ti_urp = 0; /* XXX */ 756 tiflags &= ~TH_URG; /* XXX */ 757 goto dodata; /* XXX */ 758 } 759 /* 760 * If this segment advances the known urgent pointer, 761 * then mark the data stream. This should not happen 762 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 763 * a FIN has been received from the remote side. 764 * In these states we ignore the URG. 765 */ 766 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 767 tp->rcv_up = ti->ti_seq + ti->ti_urp; 768 so->so_oobmark = so->so_rcv.sb_cc + 769 (tp->rcv_up - tp->rcv_nxt) - 1; 770 if (so->so_oobmark == 0) 771 so->so_state |= SS_RCVATMARK; 772 sohasoutofband(so); 773 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 774 } 775 /* 776 * Remove out of band data so doesn't get presented to user. 777 * This can happen independent of advancing the URG pointer, 778 * but if two URG's are pending at once, some out-of-band 779 * data may creep in... ick. 780 */ 781 if (ti->ti_urp <= ti->ti_len) 782 tcp_pulloutofband(so, ti); 783 } else 784 /* 785 * If no out of band data is expected, 786 * pull receive urgent pointer along 787 * with the receive window. 788 */ 789 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 790 tp->rcv_up = tp->rcv_nxt; 791 dodata: /* XXX */ 792 793 /* 794 * Process the segment text, merging it into the TCP sequencing queue, 795 * and arranging for acknowledgment of receipt if necessary. 796 * This process logically involves adjusting tp->rcv_wnd as data 797 * is presented to the user (this happens in tcp_usrreq.c, 798 * case PRU_RCVD). If a FIN has already been received on this 799 * connection then we just ignore the text. 800 */ 801 if ((ti->ti_len || (tiflags&TH_FIN)) && 802 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 803 TCP_REASS(tp, ti, m, so, tiflags); 804 if (tcpnodelack == 0) 805 tp->t_flags |= TF_DELACK; 806 else 807 tp->t_flags |= TF_ACKNOW; 808 /* 809 * Note the amount of data that peer has sent into 810 * our window, in order to estimate the sender's 811 * buffer size. 812 */ 813 len = so->so_rcv.sb_hiwat - (tp->rcv_nxt - tp->rcv_adv); 814 if (len > tp->max_rcvd) 815 tp->max_rcvd = len; 816 } else { 817 m_freem(m); 818 tiflags &= ~TH_FIN; 819 } 820 821 /* 822 * If FIN is received ACK the FIN and let the user know 823 * that the connection is closing. 824 */ 825 if (tiflags & TH_FIN) { 826 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 827 socantrcvmore(so); 828 tp->t_flags |= TF_ACKNOW; 829 tp->rcv_nxt++; 830 } 831 switch (tp->t_state) { 832 833 /* 834 * In SYN_RECEIVED and ESTABLISHED STATES 835 * enter the CLOSE_WAIT state. 836 */ 837 case TCPS_SYN_RECEIVED: 838 case TCPS_ESTABLISHED: 839 tp->t_state = TCPS_CLOSE_WAIT; 840 break; 841 842 /* 843 * If still in FIN_WAIT_1 STATE FIN has not been acked so 844 * enter the CLOSING state. 845 */ 846 case TCPS_FIN_WAIT_1: 847 tp->t_state = TCPS_CLOSING; 848 break; 849 850 /* 851 * In FIN_WAIT_2 state enter the TIME_WAIT state, 852 * starting the time-wait timer, turning off the other 853 * standard timers. 854 */ 855 case TCPS_FIN_WAIT_2: 856 tp->t_state = TCPS_TIME_WAIT; 857 tcp_canceltimers(tp); 858 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 859 soisdisconnected(so); 860 break; 861 862 /* 863 * In TIME_WAIT state restart the 2 MSL time_wait timer. 864 */ 865 case TCPS_TIME_WAIT: 866 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 867 break; 868 } 869 } 870 if (so->so_options & SO_DEBUG) 871 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 872 873 /* 874 * Return any desired output. 875 */ 876 if (newwin || (tp->t_flags & TF_ACKNOW)) 877 (void) tcp_output(tp); 878 return; 879 880 dropafterack: 881 /* 882 * Generate an ACK dropping incoming segment if it occupies 883 * sequence space, where the ACK reflects our state. 884 */ 885 if (tiflags & TH_RST) 886 goto drop; 887 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 888 tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 889 tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 890 return; 891 892 dropwithreset: 893 if (om) { 894 (void) m_free(om); 895 om = 0; 896 } 897 /* 898 * Generate a RST, dropping incoming segment. 899 * Make ACK acceptable to originator of segment. 900 * Don't bother to respond if destination was broadcast. 901 */ 902 if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst)) 903 goto drop; 904 if (tiflags & TH_ACK) 905 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 906 else { 907 if (tiflags & TH_SYN) 908 ti->ti_len++; 909 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 910 TH_RST|TH_ACK); 911 } 912 /* destroy temporarily created socket */ 913 if (dropsocket) 914 (void) soabort(so); 915 return; 916 917 drop: 918 if (om) 919 (void) m_free(om); 920 /* 921 * Drop space held by incoming segment and return. 922 */ 923 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 924 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 925 m_freem(m); 926 /* destroy temporarily created socket */ 927 if (dropsocket) 928 (void) soabort(so); 929 return; 930 } 931 932 tcp_dooptions(tp, om, ti) 933 struct tcpcb *tp; 934 struct mbuf *om; 935 struct tcpiphdr *ti; 936 { 937 register u_char *cp; 938 int opt, optlen, cnt; 939 940 cp = mtod(om, u_char *); 941 cnt = om->m_len; 942 for (; cnt > 0; cnt -= optlen, cp += optlen) { 943 opt = cp[0]; 944 if (opt == TCPOPT_EOL) 945 break; 946 if (opt == TCPOPT_NOP) 947 optlen = 1; 948 else { 949 optlen = cp[1]; 950 if (optlen <= 0) 951 break; 952 } 953 switch (opt) { 954 955 default: 956 break; 957 958 case TCPOPT_MAXSEG: 959 if (optlen != 4) 960 continue; 961 if (!(ti->ti_flags & TH_SYN)) 962 continue; 963 tp->t_maxseg = *(u_short *)(cp + 2); 964 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 965 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 966 break; 967 } 968 } 969 (void) m_free(om); 970 } 971 972 /* 973 * Pull out of band byte out of a segment so 974 * it doesn't appear in the user's data queue. 975 * It is still reflected in the segment length for 976 * sequencing purposes. 977 */ 978 tcp_pulloutofband(so, ti) 979 struct socket *so; 980 struct tcpiphdr *ti; 981 { 982 register struct mbuf *m; 983 int cnt = ti->ti_urp - 1; 984 985 m = dtom(ti); 986 while (cnt >= 0) { 987 if (m->m_len > cnt) { 988 char *cp = mtod(m, caddr_t) + cnt; 989 struct tcpcb *tp = sototcpcb(so); 990 991 tp->t_iobc = *cp; 992 tp->t_oobflags |= TCPOOB_HAVEDATA; 993 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 994 m->m_len--; 995 return; 996 } 997 cnt -= m->m_len; 998 m = m->m_next; 999 if (m == 0) 1000 break; 1001 } 1002 panic("tcp_pulloutofband"); 1003 } 1004 1005 /* 1006 * Determine a reasonable value for maxseg size. 1007 * If the route is known, use one that can be handled 1008 * on the given interface without forcing IP to fragment. 1009 * If bigger than a page (CLBYTES), round down to nearest pagesize 1010 * to utilize pagesize mbufs. 1011 * If interface pointer is unavailable, or the destination isn't local, 1012 * use a conservative size (512 or the default IP max size, but no more 1013 * than the mtu of the interface through which we route), 1014 * as we can't discover anything about intervening gateways or networks. 1015 * 1016 * This is ugly, and doesn't belong at this level, but has to happen somehow. 1017 */ 1018 tcp_mss(tp) 1019 register struct tcpcb *tp; 1020 { 1021 struct route *ro; 1022 struct ifnet *ifp; 1023 int mss; 1024 struct inpcb *inp; 1025 1026 inp = tp->t_inpcb; 1027 ro = &inp->inp_route; 1028 if ((ro->ro_rt == (struct rtentry *)0) || 1029 (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { 1030 /* No route yet, so try to acquire one */ 1031 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1032 ro->ro_dst.sa_family = AF_INET; 1033 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1034 inp->inp_faddr; 1035 rtalloc(ro); 1036 } 1037 if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) 1038 return (TCP_MSS); 1039 } 1040 1041 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1042 #if (CLBYTES & (CLBYTES - 1)) == 0 1043 if (mss > CLBYTES) 1044 mss &= ~(CLBYTES-1); 1045 #else 1046 if (mss > CLBYTES) 1047 mss = mss / CLBYTES * CLBYTES; 1048 #endif 1049 if (in_localaddr(inp->inp_faddr)) 1050 return (mss); 1051 return (MIN(mss, TCP_MSS)); 1052 } 1053