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 6.18 (Berkeley) 01/07/86 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; 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 tp->rcv_wnd = sbspace(&so->so_rcv); 329 if (tp->rcv_wnd < 0) 330 tp->rcv_wnd = 0; 331 tp->rcv_wnd = MAX(tp->rcv_wnd, (short)(tp->rcv_adv - tp->rcv_nxt)); 332 333 switch (tp->t_state) { 334 335 /* 336 * If the state is LISTEN then ignore segment if it contains an RST. 337 * If the segment contains an ACK then it is bad and send a RST. 338 * If it does not contain a SYN then it is not interesting; drop it. 339 * Don't bother responding if the destination was a broadcast. 340 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 341 * tp->iss, and send a segment: 342 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 343 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 344 * Fill in remote peer address fields if not previously specified. 345 * Enter SYN_RECEIVED state, and process any other fields of this 346 * segment in this state. 347 */ 348 case TCPS_LISTEN: { 349 struct mbuf *am; 350 register struct sockaddr_in *sin; 351 352 if (tiflags & TH_RST) 353 goto drop; 354 if (tiflags & TH_ACK) 355 goto dropwithreset; 356 if ((tiflags & TH_SYN) == 0) 357 goto drop; 358 if (in_broadcast(ti->ti_dst)) 359 goto drop; 360 am = m_get(M_DONTWAIT, MT_SONAME); 361 if (am == NULL) 362 goto drop; 363 am->m_len = sizeof (struct sockaddr_in); 364 sin = mtod(am, struct sockaddr_in *); 365 sin->sin_family = AF_INET; 366 sin->sin_addr = ti->ti_src; 367 sin->sin_port = ti->ti_sport; 368 laddr = inp->inp_laddr; 369 if (inp->inp_laddr.s_addr == INADDR_ANY) 370 inp->inp_laddr = ti->ti_dst; 371 if (in_pcbconnect(inp, am)) { 372 inp->inp_laddr = laddr; 373 (void) m_free(am); 374 goto drop; 375 } 376 (void) m_free(am); 377 tp->t_template = tcp_template(tp); 378 if (tp->t_template == 0) { 379 in_pcbdisconnect(inp); 380 dropsocket = 0; /* socket is already gone */ 381 tp = 0; 382 goto drop; 383 } 384 if (om) { 385 tcp_dooptions(tp, om, ti); 386 om = 0; 387 } 388 tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; 389 tp->irs = ti->ti_seq; 390 tcp_sendseqinit(tp); 391 tcp_rcvseqinit(tp); 392 tp->t_state = TCPS_SYN_RECEIVED; 393 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 394 dropsocket = 0; /* committed to socket */ 395 goto trimthenstep6; 396 } 397 398 /* 399 * If the state is SYN_SENT: 400 * if seg contains an ACK, but not for our SYN, drop the input. 401 * if seg contains a RST, then drop the connection. 402 * if seg does not contain SYN, then drop it. 403 * Otherwise this is an acceptable SYN segment 404 * initialize tp->rcv_nxt and tp->irs 405 * if seg contains ack then advance tp->snd_una 406 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 407 * arrange for segment to be acked (eventually) 408 * continue processing rest of data/controls, beginning with URG 409 */ 410 case TCPS_SYN_SENT: 411 if ((tiflags & TH_ACK) && 412 (SEQ_LEQ(ti->ti_ack, tp->iss) || 413 SEQ_GT(ti->ti_ack, tp->snd_max))) 414 goto dropwithreset; 415 if (tiflags & TH_RST) { 416 if (tiflags & TH_ACK) 417 tp = tcp_drop(tp, ECONNREFUSED); 418 goto drop; 419 } 420 if ((tiflags & TH_SYN) == 0) 421 goto drop; 422 tp->snd_una = ti->ti_ack; 423 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 424 tp->snd_nxt = tp->snd_una; 425 tp->t_timer[TCPT_REXMT] = 0; 426 tp->irs = ti->ti_seq; 427 tcp_rcvseqinit(tp); 428 tp->t_flags |= TF_ACKNOW; 429 if (SEQ_GT(tp->snd_una, tp->iss)) { 430 soisconnected(so); 431 tp->t_state = TCPS_ESTABLISHED; 432 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 433 (void) tcp_reass(tp, (struct tcpiphdr *)0); 434 } else 435 tp->t_state = TCPS_SYN_RECEIVED; 436 goto trimthenstep6; 437 438 trimthenstep6: 439 /* 440 * Advance ti->ti_seq to correspond to first data byte. 441 * If data, trim to stay within window, 442 * dropping FIN if necessary. 443 */ 444 ti->ti_seq++; 445 if (ti->ti_len > tp->rcv_wnd) { 446 todrop = ti->ti_len - tp->rcv_wnd; 447 m_adj(m, -todrop); 448 ti->ti_len = tp->rcv_wnd; 449 ti->ti_flags &= ~TH_FIN; 450 } 451 tp->snd_wl1 = ti->ti_seq - 1; 452 goto step6; 453 } 454 455 /* 456 * If data is received on a connection after the 457 * user processes are gone, then RST the other end. 458 */ 459 if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && 460 ti->ti_len) { 461 tp = tcp_close(tp); 462 goto dropwithreset; 463 } 464 465 /* 466 * States other than LISTEN or SYN_SENT. 467 * First check that at least some bytes of segment are within 468 * receive window. 469 */ 470 if (tp->rcv_wnd == 0) { 471 /* 472 * If window is closed can only take segments at 473 * window edge, and have to drop data and PUSH from 474 * incoming segments. 475 */ 476 if (tp->rcv_nxt != ti->ti_seq) 477 goto dropafterack; 478 if (ti->ti_len > 0) { 479 m_adj(m, ti->ti_len); 480 ti->ti_len = 0; 481 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 482 } 483 } else { 484 /* 485 * If segment begins before rcv_nxt, drop leading 486 * data (and SYN); if nothing left, just ack. 487 */ 488 todrop = tp->rcv_nxt - ti->ti_seq; 489 if (todrop > 0) { 490 if (tiflags & TH_SYN) { 491 tiflags &= ~TH_SYN; 492 ti->ti_flags &= ~TH_SYN; 493 ti->ti_seq++; 494 if (ti->ti_urp > 1) 495 ti->ti_urp--; 496 else 497 tiflags &= ~TH_URG; 498 todrop--; 499 } 500 if (todrop > ti->ti_len || 501 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) 502 goto dropafterack; 503 m_adj(m, todrop); 504 ti->ti_seq += todrop; 505 ti->ti_len -= todrop; 506 if (ti->ti_urp > todrop) 507 ti->ti_urp -= todrop; 508 else { 509 tiflags &= ~TH_URG; 510 ti->ti_flags &= ~TH_URG; 511 ti->ti_urp = 0; 512 } 513 } 514 /* 515 * If segment ends after window, drop trailing data 516 * (and PUSH and FIN); if nothing left, just ACK. 517 */ 518 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 519 if (todrop > 0) { 520 if (todrop >= ti->ti_len) 521 goto dropafterack; 522 m_adj(m, -todrop); 523 ti->ti_len -= todrop; 524 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 525 } 526 } 527 528 /* 529 * If the RST bit is set examine the state: 530 * SYN_RECEIVED STATE: 531 * If passive open, return to LISTEN state. 532 * If active open, inform user that connection was refused. 533 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 534 * Inform user that connection was reset, and close tcb. 535 * CLOSING, LAST_ACK, TIME_WAIT STATES 536 * Close the tcb. 537 */ 538 if (tiflags&TH_RST) switch (tp->t_state) { 539 540 case TCPS_SYN_RECEIVED: 541 tp = tcp_drop(tp, ECONNREFUSED); 542 goto drop; 543 544 case TCPS_ESTABLISHED: 545 case TCPS_FIN_WAIT_1: 546 case TCPS_FIN_WAIT_2: 547 case TCPS_CLOSE_WAIT: 548 tp = tcp_drop(tp, ECONNRESET); 549 goto drop; 550 551 case TCPS_CLOSING: 552 case TCPS_LAST_ACK: 553 case TCPS_TIME_WAIT: 554 tp = tcp_close(tp); 555 goto drop; 556 } 557 558 /* 559 * If a SYN is in the window, then this is an 560 * error and we send an RST and drop the connection. 561 */ 562 if (tiflags & TH_SYN) { 563 tp = tcp_drop(tp, ECONNRESET); 564 goto dropwithreset; 565 } 566 567 /* 568 * If the ACK bit is off we drop the segment and return. 569 */ 570 if ((tiflags & TH_ACK) == 0) 571 goto drop; 572 573 /* 574 * Ack processing. 575 */ 576 switch (tp->t_state) { 577 578 /* 579 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 580 * ESTABLISHED state and continue processing, othewise 581 * send an RST. 582 */ 583 case TCPS_SYN_RECEIVED: 584 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 585 SEQ_GT(ti->ti_ack, tp->snd_max)) 586 goto dropwithreset; 587 tp->snd_una++; /* SYN acked */ 588 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 589 tp->snd_nxt = tp->snd_una; 590 tp->t_timer[TCPT_REXMT] = 0; 591 soisconnected(so); 592 tp->t_state = TCPS_ESTABLISHED; 593 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 594 (void) tcp_reass(tp, (struct tcpiphdr *)0); 595 tp->snd_wl1 = ti->ti_seq - 1; 596 /* fall into ... */ 597 598 /* 599 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 600 * ACKs. If the ack is in the range 601 * tp->snd_una < ti->ti_ack <= tp->snd_max 602 * then advance tp->snd_una to ti->ti_ack and drop 603 * data from the retransmission queue. If this ACK reflects 604 * more up to date window information we update our window information. 605 */ 606 case TCPS_ESTABLISHED: 607 case TCPS_FIN_WAIT_1: 608 case TCPS_FIN_WAIT_2: 609 case TCPS_CLOSE_WAIT: 610 case TCPS_CLOSING: 611 case TCPS_LAST_ACK: 612 case TCPS_TIME_WAIT: 613 #define ourfinisacked (acked > 0) 614 615 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) 616 break; 617 if (SEQ_GT(ti->ti_ack, tp->snd_max)) 618 goto dropafterack; 619 acked = ti->ti_ack - tp->snd_una; 620 621 /* 622 * If transmit timer is running and timed sequence 623 * number was acked, update smoothed round trip time. 624 */ 625 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 626 if (tp->t_srtt == 0) 627 tp->t_srtt = tp->t_rtt; 628 else 629 tp->t_srtt = 630 tcp_alpha * tp->t_srtt + 631 (1 - tcp_alpha) * tp->t_rtt; 632 tp->t_rtt = 0; 633 } 634 635 if (ti->ti_ack == tp->snd_max) 636 tp->t_timer[TCPT_REXMT] = 0; 637 else { 638 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 639 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 640 tp->t_rxtshift = 0; 641 } 642 /* 643 * When new data is acked, open the congestion window a bit. 644 */ 645 if (acked > 0) 646 tp->snd_cwnd = MIN(11 * tp->snd_cwnd / 10, 65535); 647 if (acked > so->so_snd.sb_cc) { 648 tp->snd_wnd -= so->so_snd.sb_cc; 649 sbdrop(&so->so_snd, so->so_snd.sb_cc); 650 } else { 651 sbdrop(&so->so_snd, acked); 652 tp->snd_wnd -= acked; 653 acked = 0; 654 } 655 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 656 sowwakeup(so); 657 tp->snd_una = ti->ti_ack; 658 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 659 tp->snd_nxt = tp->snd_una; 660 661 switch (tp->t_state) { 662 663 /* 664 * In FIN_WAIT_1 STATE in addition to the processing 665 * for the ESTABLISHED state if our FIN is now acknowledged 666 * then enter FIN_WAIT_2. 667 */ 668 case TCPS_FIN_WAIT_1: 669 if (ourfinisacked) { 670 /* 671 * If we can't receive any more 672 * data, then closing user can proceed. 673 * Starting the timer is contrary to the 674 * specification, but if we don't get a FIN 675 * we'll hang forever. 676 */ 677 if (so->so_state & SS_CANTRCVMORE) { 678 soisdisconnected(so); 679 tp->t_timer[TCPT_2MSL] = TCPTV_MAXIDLE; 680 } 681 tp->t_state = TCPS_FIN_WAIT_2; 682 } 683 break; 684 685 /* 686 * In CLOSING STATE in addition to the processing for 687 * the ESTABLISHED state if the ACK acknowledges our FIN 688 * then enter the TIME-WAIT state, otherwise ignore 689 * the segment. 690 */ 691 case TCPS_CLOSING: 692 if (ourfinisacked) { 693 tp->t_state = TCPS_TIME_WAIT; 694 tcp_canceltimers(tp); 695 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 696 soisdisconnected(so); 697 } 698 break; 699 700 /* 701 * The only thing that can arrive in LAST_ACK state 702 * is an acknowledgment of our FIN. If our FIN is now 703 * acknowledged, delete the TCB, enter the closed state 704 * and return. 705 */ 706 case TCPS_LAST_ACK: 707 if (ourfinisacked) 708 tp = tcp_close(tp); 709 goto drop; 710 711 /* 712 * In TIME_WAIT state the only thing that should arrive 713 * is a retransmission of the remote FIN. Acknowledge 714 * it and restart the finack timer. 715 */ 716 case TCPS_TIME_WAIT: 717 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 718 goto dropafterack; 719 } 720 #undef ourfinisacked 721 } 722 723 step6: 724 /* 725 * Update window information. 726 */ 727 if (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 728 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 729 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)) { 730 tp->snd_wnd = ti->ti_win; 731 tp->snd_wl1 = ti->ti_seq; 732 tp->snd_wl2 = ti->ti_ack; 733 if (tp->snd_wnd > tp->max_sndwnd) 734 tp->max_sndwnd = tp->snd_wnd; 735 } 736 737 /* 738 * Process segments with URG. 739 */ 740 if ((tiflags & TH_URG) && ti->ti_urp && 741 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 742 /* 743 * This is a kludge, but if we receive accept 744 * random urgent pointers, we'll crash in 745 * soreceive. It's hard to imagine someone 746 * actually wanting to send this much urgent data. 747 */ 748 if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) { 749 ti->ti_urp = 0; /* XXX */ 750 tiflags &= ~TH_URG; /* XXX */ 751 ti->ti_flags &= ~TH_URG; /* XXX */ 752 goto badurp; /* XXX */ 753 } 754 /* 755 * If this segment advances the known urgent pointer, 756 * then mark the data stream. This should not happen 757 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 758 * a FIN has been received from the remote side. 759 * In these states we ignore the URG. 760 */ 761 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 762 tp->rcv_up = ti->ti_seq + ti->ti_urp; 763 so->so_oobmark = so->so_rcv.sb_cc + 764 (tp->rcv_up - tp->rcv_nxt) - 1; 765 if (so->so_oobmark == 0) 766 so->so_state |= SS_RCVATMARK; 767 sohasoutofband(so); 768 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 769 } 770 /* 771 * Remove out of band data so doesn't get presented to user. 772 * This can happen independent of advancing the URG pointer, 773 * but if two URG's are pending at once, some out-of-band 774 * data may creep in... ick. 775 */ 776 if (ti->ti_urp <= ti->ti_len) 777 tcp_pulloutofband(so, ti); 778 } 779 badurp: /* XXX */ 780 781 /* 782 * Process the segment text, merging it into the TCP sequencing queue, 783 * and arranging for acknowledgment of receipt if necessary. 784 * This process logically involves adjusting tp->rcv_wnd as data 785 * is presented to the user (this happens in tcp_usrreq.c, 786 * case PRU_RCVD). If a FIN has already been received on this 787 * connection then we just ignore the text. 788 */ 789 if ((ti->ti_len || (tiflags&TH_FIN)) && 790 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 791 TCP_REASS(tp, ti, m, so, tiflags); 792 if (tcpnodelack == 0) 793 tp->t_flags |= TF_DELACK; 794 else 795 tp->t_flags |= TF_ACKNOW; 796 /* 797 * Note the amount of data that peer has sent into 798 * our window, in order to estimate the sender's 799 * buffer size. 800 */ 801 len = so->so_rcv.sb_hiwat - (tp->rcv_nxt - tp->rcv_adv); 802 if (len > tp->max_rcvd) 803 tp->max_rcvd = len; 804 } else { 805 m_freem(m); 806 tiflags &= ~TH_FIN; 807 } 808 809 /* 810 * If FIN is received ACK the FIN and let the user know 811 * that the connection is closing. 812 */ 813 if (tiflags & TH_FIN) { 814 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 815 socantrcvmore(so); 816 tp->t_flags |= TF_ACKNOW; 817 tp->rcv_nxt++; 818 } 819 switch (tp->t_state) { 820 821 /* 822 * In SYN_RECEIVED and ESTABLISHED STATES 823 * enter the CLOSE_WAIT state. 824 */ 825 case TCPS_SYN_RECEIVED: 826 case TCPS_ESTABLISHED: 827 tp->t_state = TCPS_CLOSE_WAIT; 828 break; 829 830 /* 831 * If still in FIN_WAIT_1 STATE FIN has not been acked so 832 * enter the CLOSING state. 833 */ 834 case TCPS_FIN_WAIT_1: 835 tp->t_state = TCPS_CLOSING; 836 break; 837 838 /* 839 * In FIN_WAIT_2 state enter the TIME_WAIT state, 840 * starting the time-wait timer, turning off the other 841 * standard timers. 842 */ 843 case TCPS_FIN_WAIT_2: 844 tp->t_state = TCPS_TIME_WAIT; 845 tcp_canceltimers(tp); 846 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 847 soisdisconnected(so); 848 break; 849 850 /* 851 * In TIME_WAIT state restart the 2 MSL time_wait timer. 852 */ 853 case TCPS_TIME_WAIT: 854 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 855 break; 856 } 857 } 858 if (so->so_options & SO_DEBUG) 859 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 860 861 /* 862 * Return any desired output. 863 */ 864 (void) tcp_output(tp); 865 return; 866 867 dropafterack: 868 /* 869 * Generate an ACK dropping incoming segment if it occupies 870 * sequence space, where the ACK reflects our state. 871 */ 872 if ((tiflags&TH_RST) || 873 tlen == 0 && (tiflags&(TH_SYN|TH_FIN)) == 0) 874 goto drop; 875 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 876 tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 877 tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 878 return; 879 880 dropwithreset: 881 if (om) { 882 (void) m_free(om); 883 om = 0; 884 } 885 /* 886 * Generate a RST, dropping incoming segment. 887 * Make ACK acceptable to originator of segment. 888 * Don't bother to respond if destination was broadcast. 889 */ 890 if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst)) 891 goto drop; 892 if (tiflags & TH_ACK) 893 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 894 else { 895 if (tiflags & TH_SYN) 896 ti->ti_len++; 897 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 898 TH_RST|TH_ACK); 899 } 900 /* destroy temporarily created socket */ 901 if (dropsocket) 902 (void) soabort(so); 903 return; 904 905 drop: 906 if (om) 907 (void) m_free(om); 908 /* 909 * Drop space held by incoming segment and return. 910 */ 911 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 912 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 913 m_freem(m); 914 /* destroy temporarily created socket */ 915 if (dropsocket) 916 (void) soabort(so); 917 return; 918 } 919 920 tcp_dooptions(tp, om, ti) 921 struct tcpcb *tp; 922 struct mbuf *om; 923 struct tcpiphdr *ti; 924 { 925 register u_char *cp; 926 int opt, optlen, cnt; 927 928 cp = mtod(om, u_char *); 929 cnt = om->m_len; 930 for (; cnt > 0; cnt -= optlen, cp += optlen) { 931 opt = cp[0]; 932 if (opt == TCPOPT_EOL) 933 break; 934 if (opt == TCPOPT_NOP) 935 optlen = 1; 936 else { 937 optlen = cp[1]; 938 if (optlen <= 0) 939 break; 940 } 941 switch (opt) { 942 943 default: 944 break; 945 946 case TCPOPT_MAXSEG: 947 if (optlen != 4) 948 continue; 949 if (!(ti->ti_flags & TH_SYN)) 950 continue; 951 tp->t_maxseg = *(u_short *)(cp + 2); 952 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 953 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 954 break; 955 } 956 } 957 (void) m_free(om); 958 } 959 960 /* 961 * Pull out of band byte out of a segment so 962 * it doesn't appear in the user's data queue. 963 * It is still reflected in the segment length for 964 * sequencing purposes. 965 */ 966 tcp_pulloutofband(so, ti) 967 struct socket *so; 968 struct tcpiphdr *ti; 969 { 970 register struct mbuf *m; 971 int cnt = ti->ti_urp - 1; 972 973 m = dtom(ti); 974 while (cnt >= 0) { 975 if (m->m_len > cnt) { 976 char *cp = mtod(m, caddr_t) + cnt; 977 struct tcpcb *tp = sototcpcb(so); 978 979 tp->t_iobc = *cp; 980 tp->t_oobflags |= TCPOOB_HAVEDATA; 981 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 982 m->m_len--; 983 return; 984 } 985 cnt -= m->m_len; 986 m = m->m_next; 987 if (m == 0) 988 break; 989 } 990 panic("tcp_pulloutofband"); 991 } 992 993 /* 994 * Determine a reasonable value for maxseg size. 995 * If the route is known, use one that can be handled 996 * on the given interface without forcing IP to fragment. 997 * If bigger than a page (CLBYTES), round down to nearest pagesize 998 * to utilize pagesize mbufs. 999 * If interface pointer is unavailable, or the destination isn't local, 1000 * use a conservative size (512 or the default IP max size, but no more 1001 * than the mtu of the interface through which we route), 1002 * as we can't discover anything about intervening gateways or networks. 1003 * 1004 * This is ugly, and doesn't belong at this level, but has to happen somehow. 1005 */ 1006 tcp_mss(tp) 1007 register struct tcpcb *tp; 1008 { 1009 struct route *ro; 1010 struct ifnet *ifp; 1011 int mss; 1012 struct inpcb *inp; 1013 1014 inp = tp->t_inpcb; 1015 ro = &inp->inp_route; 1016 if ((ro->ro_rt == (struct rtentry *)0) || 1017 (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { 1018 /* No route yet, so try to acquire one */ 1019 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1020 ro->ro_dst.sa_family = AF_INET; 1021 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1022 inp->inp_faddr; 1023 rtalloc(ro); 1024 } 1025 if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) 1026 return (TCP_MSS); 1027 } 1028 1029 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1030 #if (CLBYTES & (CLBYTES - 1)) == 0 1031 if (mss > CLBYTES) 1032 mss &= ~(CLBYTES-1); 1033 #else 1034 if (mss > CLBYTES) 1035 mss = mss / CLBYTES * CLBYTES; 1036 #endif 1037 if (in_localaddr(inp->inp_faddr)) 1038 return (mss); 1039 return (MIN(mss, TCP_MSS)); 1040 } 1041