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 6.14 (Berkeley) 10/14/85 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. 249 */ 250 off += sizeof (struct ip); 251 m->m_off += off; 252 m->m_len -= off; 253 254 /* 255 * Convert TCP protocol specific fields to host format. 256 */ 257 ti->ti_seq = ntohl(ti->ti_seq); 258 ti->ti_ack = ntohl(ti->ti_ack); 259 ti->ti_win = ntohs(ti->ti_win); 260 ti->ti_urp = ntohs(ti->ti_urp); 261 262 /* 263 * Locate pcb for segment. 264 */ 265 inp = in_pcblookup 266 (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, 267 INPLOOKUP_WILDCARD); 268 269 /* 270 * If the state is CLOSED (i.e., TCB does not exist) then 271 * all data in the incoming segment is discarded. 272 */ 273 if (inp == 0) 274 goto dropwithreset; 275 tp = intotcpcb(inp); 276 if (tp == 0) 277 goto dropwithreset; 278 so = inp->inp_socket; 279 if (so->so_options & SO_DEBUG) { 280 ostate = tp->t_state; 281 tcp_saveti = *ti; 282 } 283 if (so->so_options & SO_ACCEPTCONN) { 284 so = sonewconn(so); 285 if (so == 0) 286 goto drop; 287 /* 288 * This is ugly, but .... 289 * 290 * Mark socket as temporary until we're 291 * committed to keeping it. The code at 292 * ``drop'' and ``dropwithreset'' check the 293 * flag dropsocket to see if the temporary 294 * socket created here should be discarded. 295 * We mark the socket as discardable until 296 * we're committed to it below in TCPS_LISTEN. 297 */ 298 dropsocket++; 299 inp = (struct inpcb *)so->so_pcb; 300 inp->inp_laddr = ti->ti_dst; 301 inp->inp_lport = ti->ti_dport; 302 inp->inp_options = ip_srcroute(); 303 tp = intotcpcb(inp); 304 tp->t_state = TCPS_LISTEN; 305 } 306 307 /* 308 * Segment received on connection. 309 * Reset idle time and keep-alive timer. 310 */ 311 tp->t_idle = 0; 312 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 313 314 /* 315 * Process options if not in LISTEN state, 316 * else do it below (after getting remote address). 317 */ 318 if (om && tp->t_state != TCPS_LISTEN) { 319 tcp_dooptions(tp, om, ti); 320 om = 0; 321 } 322 323 /* 324 * Calculate amount of space in receive window, 325 * and then do TCP input processing. 326 * Receive window is amount of space in rcv queue, 327 * but not less than advertised window. 328 */ 329 tp->rcv_wnd = sbspace(&so->so_rcv); 330 if (tp->rcv_wnd < 0) 331 tp->rcv_wnd = 0; 332 tp->rcv_wnd = MAX(tp->rcv_wnd, (short)(tp->rcv_adv - tp->rcv_nxt)); 333 334 switch (tp->t_state) { 335 336 /* 337 * If the state is LISTEN then ignore segment if it contains an RST. 338 * If the segment contains an ACK then it is bad and send a RST. 339 * If it does not contain a SYN then it is not interesting; drop it. 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 am = m_get(M_DONTWAIT, MT_SONAME); 359 if (am == NULL) 360 goto drop; 361 am->m_len = sizeof (struct sockaddr_in); 362 sin = mtod(am, struct sockaddr_in *); 363 sin->sin_family = AF_INET; 364 sin->sin_addr = ti->ti_src; 365 sin->sin_port = ti->ti_sport; 366 laddr = inp->inp_laddr; 367 if (inp->inp_laddr.s_addr == INADDR_ANY) 368 inp->inp_laddr = ti->ti_dst; 369 if (in_pcbconnect(inp, am)) { 370 inp->inp_laddr = laddr; 371 (void) m_free(am); 372 goto drop; 373 } 374 (void) m_free(am); 375 tp->t_template = tcp_template(tp); 376 if (tp->t_template == 0) { 377 in_pcbdisconnect(inp); 378 dropsocket = 0; /* socket is already gone */ 379 tp = 0; 380 goto drop; 381 } 382 if (om) { 383 tcp_dooptions(tp, om, ti); 384 om = 0; 385 } 386 tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; 387 tp->irs = ti->ti_seq; 388 tcp_sendseqinit(tp); 389 tcp_rcvseqinit(tp); 390 tp->t_state = TCPS_SYN_RECEIVED; 391 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 392 dropsocket = 0; /* committed to socket */ 393 goto trimthenstep6; 394 } 395 396 /* 397 * If the state is SYN_SENT: 398 * if seg contains an ACK, but not for our SYN, drop the input. 399 * if seg contains a RST, then drop the connection. 400 * if seg does not contain SYN, then drop it. 401 * Otherwise this is an acceptable SYN segment 402 * initialize tp->rcv_nxt and tp->irs 403 * if seg contains ack then advance tp->snd_una 404 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 405 * arrange for segment to be acked (eventually) 406 * continue processing rest of data/controls, beginning with URG 407 */ 408 case TCPS_SYN_SENT: 409 if ((tiflags & TH_ACK) && 410 (SEQ_LEQ(ti->ti_ack, tp->iss) || 411 SEQ_GT(ti->ti_ack, tp->snd_max))) 412 goto dropwithreset; 413 if (tiflags & TH_RST) { 414 if (tiflags & TH_ACK) 415 tp = tcp_drop(tp, ECONNREFUSED); 416 goto drop; 417 } 418 if ((tiflags & TH_SYN) == 0) 419 goto drop; 420 tp->snd_una = ti->ti_ack; 421 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 422 tp->snd_nxt = tp->snd_una; 423 tp->t_timer[TCPT_REXMT] = 0; 424 tp->irs = ti->ti_seq; 425 tcp_rcvseqinit(tp); 426 tp->t_flags |= TF_ACKNOW; 427 if (SEQ_GT(tp->snd_una, tp->iss)) { 428 soisconnected(so); 429 tp->t_state = TCPS_ESTABLISHED; 430 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 431 (void) tcp_reass(tp, (struct tcpiphdr *)0); 432 } else 433 tp->t_state = TCPS_SYN_RECEIVED; 434 goto trimthenstep6; 435 436 trimthenstep6: 437 /* 438 * Advance ti->ti_seq to correspond to first data byte. 439 * If data, trim to stay within window, 440 * dropping FIN if necessary. 441 */ 442 ti->ti_seq++; 443 if (ti->ti_len > tp->rcv_wnd) { 444 todrop = ti->ti_len - tp->rcv_wnd; 445 m_adj(m, -todrop); 446 ti->ti_len = tp->rcv_wnd; 447 ti->ti_flags &= ~TH_FIN; 448 } 449 tp->snd_wl1 = ti->ti_seq - 1; 450 goto step6; 451 } 452 453 /* 454 * If data is received on a connection after the 455 * user processes are gone, then RST the other end. 456 */ 457 if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && 458 ti->ti_len) { 459 tp = tcp_close(tp); 460 goto dropwithreset; 461 } 462 463 /* 464 * States other than LISTEN or SYN_SENT. 465 * First check that at least some bytes of segment are within 466 * receive window. 467 */ 468 if (tp->rcv_wnd == 0) { 469 /* 470 * If window is closed can only take segments at 471 * window edge, and have to drop data and PUSH from 472 * incoming segments. 473 */ 474 if (tp->rcv_nxt != ti->ti_seq) 475 goto dropafterack; 476 if (ti->ti_len > 0) { 477 m_adj(m, ti->ti_len); 478 ti->ti_len = 0; 479 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 480 } 481 } else { 482 /* 483 * If segment begins before rcv_nxt, drop leading 484 * data (and SYN); if nothing left, just ack. 485 */ 486 todrop = tp->rcv_nxt - ti->ti_seq; 487 if (todrop > 0) { 488 if (tiflags & TH_SYN) { 489 tiflags &= ~TH_SYN; 490 ti->ti_flags &= ~TH_SYN; 491 ti->ti_seq++; 492 if (ti->ti_urp > 1) 493 ti->ti_urp--; 494 else 495 tiflags &= ~TH_URG; 496 todrop--; 497 } 498 if (todrop > ti->ti_len || 499 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) 500 goto dropafterack; 501 m_adj(m, todrop); 502 ti->ti_seq += todrop; 503 ti->ti_len -= todrop; 504 if (ti->ti_urp > todrop) 505 ti->ti_urp -= todrop; 506 else { 507 tiflags &= ~TH_URG; 508 ti->ti_flags &= ~TH_URG; 509 ti->ti_urp = 0; 510 } 511 } 512 /* 513 * If segment ends after window, drop trailing data 514 * (and PUSH and FIN); if nothing left, just ACK. 515 */ 516 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 517 if (todrop > 0) { 518 if (todrop >= ti->ti_len) 519 goto dropafterack; 520 m_adj(m, -todrop); 521 ti->ti_len -= todrop; 522 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 523 } 524 } 525 526 /* 527 * If the RST bit is set examine the state: 528 * SYN_RECEIVED STATE: 529 * If passive open, return to LISTEN state. 530 * If active open, inform user that connection was refused. 531 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 532 * Inform user that connection was reset, and close tcb. 533 * CLOSING, LAST_ACK, TIME_WAIT STATES 534 * Close the tcb. 535 */ 536 if (tiflags&TH_RST) switch (tp->t_state) { 537 538 case TCPS_SYN_RECEIVED: 539 tp = tcp_drop(tp, ECONNREFUSED); 540 goto drop; 541 542 case TCPS_ESTABLISHED: 543 case TCPS_FIN_WAIT_1: 544 case TCPS_FIN_WAIT_2: 545 case TCPS_CLOSE_WAIT: 546 tp = tcp_drop(tp, ECONNRESET); 547 goto drop; 548 549 case TCPS_CLOSING: 550 case TCPS_LAST_ACK: 551 case TCPS_TIME_WAIT: 552 tp = tcp_close(tp); 553 goto drop; 554 } 555 556 /* 557 * If a SYN is in the window, then this is an 558 * error and we send an RST and drop the connection. 559 */ 560 if (tiflags & TH_SYN) { 561 tp = tcp_drop(tp, ECONNRESET); 562 goto dropwithreset; 563 } 564 565 /* 566 * If the ACK bit is off we drop the segment and return. 567 */ 568 if ((tiflags & TH_ACK) == 0) 569 goto drop; 570 571 /* 572 * Ack processing. 573 */ 574 switch (tp->t_state) { 575 576 /* 577 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 578 * ESTABLISHED state and continue processing, othewise 579 * send an RST. 580 */ 581 case TCPS_SYN_RECEIVED: 582 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 583 SEQ_GT(ti->ti_ack, tp->snd_max)) 584 goto dropwithreset; 585 tp->snd_una++; /* SYN acked */ 586 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 587 tp->snd_nxt = tp->snd_una; 588 tp->t_timer[TCPT_REXMT] = 0; 589 soisconnected(so); 590 tp->t_state = TCPS_ESTABLISHED; 591 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 592 (void) tcp_reass(tp, (struct tcpiphdr *)0); 593 tp->snd_wl1 = ti->ti_seq - 1; 594 /* fall into ... */ 595 596 /* 597 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 598 * ACKs. If the ack is in the range 599 * tp->snd_una < ti->ti_ack <= tp->snd_max 600 * then advance tp->snd_una to ti->ti_ack and drop 601 * data from the retransmission queue. If this ACK reflects 602 * more up to date window information we update our window information. 603 */ 604 case TCPS_ESTABLISHED: 605 case TCPS_FIN_WAIT_1: 606 case TCPS_FIN_WAIT_2: 607 case TCPS_CLOSE_WAIT: 608 case TCPS_CLOSING: 609 case TCPS_LAST_ACK: 610 case TCPS_TIME_WAIT: 611 #define ourfinisacked (acked > 0) 612 613 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) 614 break; 615 if (SEQ_GT(ti->ti_ack, tp->snd_max)) 616 goto dropafterack; 617 acked = ti->ti_ack - tp->snd_una; 618 619 /* 620 * If transmit timer is running and timed sequence 621 * number was acked, update smoothed round trip time. 622 */ 623 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 624 if (tp->t_srtt == 0) 625 tp->t_srtt = tp->t_rtt; 626 else 627 tp->t_srtt = 628 tcp_alpha * tp->t_srtt + 629 (1 - tcp_alpha) * tp->t_rtt; 630 tp->t_rtt = 0; 631 } 632 633 if (ti->ti_ack == tp->snd_max) 634 tp->t_timer[TCPT_REXMT] = 0; 635 else { 636 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 637 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 638 tp->t_rxtshift = 0; 639 } 640 /* 641 * When new data is acked, open the congestion window a bit. 642 */ 643 if (acked > 0) 644 tp->snd_cwnd = MIN(11 * tp->snd_cwnd / 10, 65535); 645 if (acked > so->so_snd.sb_cc) { 646 tp->snd_wnd -= so->so_snd.sb_cc; 647 sbdrop(&so->so_snd, so->so_snd.sb_cc); 648 } else { 649 sbdrop(&so->so_snd, acked); 650 tp->snd_wnd -= acked; 651 acked = 0; 652 } 653 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 654 sowwakeup(so); 655 tp->snd_una = ti->ti_ack; 656 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 657 tp->snd_nxt = tp->snd_una; 658 659 switch (tp->t_state) { 660 661 /* 662 * In FIN_WAIT_1 STATE in addition to the processing 663 * for the ESTABLISHED state if our FIN is now acknowledged 664 * then enter FIN_WAIT_2. 665 */ 666 case TCPS_FIN_WAIT_1: 667 if (ourfinisacked) { 668 /* 669 * If we can't receive any more 670 * data, then closing user can proceed. 671 * Starting the timer is contrary to the 672 * specification, but if we don't get a FIN 673 * we'll hang forever. 674 */ 675 if (so->so_state & SS_CANTRCVMORE) { 676 soisdisconnected(so); 677 tp->t_timer[TCPT_2MSL] = TCPTV_MAXIDLE; 678 } 679 tp->t_state = TCPS_FIN_WAIT_2; 680 } 681 break; 682 683 /* 684 * In CLOSING STATE in addition to the processing for 685 * the ESTABLISHED state if the ACK acknowledges our FIN 686 * then enter the TIME-WAIT state, otherwise ignore 687 * the segment. 688 */ 689 case TCPS_CLOSING: 690 if (ourfinisacked) { 691 tp->t_state = TCPS_TIME_WAIT; 692 tcp_canceltimers(tp); 693 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 694 soisdisconnected(so); 695 } 696 break; 697 698 /* 699 * The only thing that can arrive in LAST_ACK state 700 * is an acknowledgment of our FIN. If our FIN is now 701 * acknowledged, delete the TCB, enter the closed state 702 * and return. 703 */ 704 case TCPS_LAST_ACK: 705 if (ourfinisacked) 706 tp = tcp_close(tp); 707 goto drop; 708 709 /* 710 * In TIME_WAIT state the only thing that should arrive 711 * is a retransmission of the remote FIN. Acknowledge 712 * it and restart the finack timer. 713 */ 714 case TCPS_TIME_WAIT: 715 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 716 goto dropafterack; 717 } 718 #undef ourfinisacked 719 } 720 721 step6: 722 /* 723 * Update window information. 724 */ 725 if (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 726 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 727 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)) { 728 tp->snd_wnd = ti->ti_win; 729 tp->snd_wl1 = ti->ti_seq; 730 tp->snd_wl2 = ti->ti_ack; 731 } 732 733 /* 734 * Process segments with URG. 735 */ 736 if ((tiflags & TH_URG) && ti->ti_urp && 737 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 738 /* 739 * This is a kludge, but if we receive accept 740 * random urgent pointers, we'll crash in 741 * soreceive. It's hard to imagine someone 742 * actually wanting to send this much urgent data. 743 */ 744 if (ti->ti_urp + (unsigned) so->so_rcv.sb_cc > 32767) { 745 ti->ti_urp = 0; /* XXX */ 746 tiflags &= ~TH_URG; /* XXX */ 747 ti->ti_flags &= ~TH_URG; /* XXX */ 748 goto badurp; /* XXX */ 749 } 750 /* 751 * If this segment advances the known urgent pointer, 752 * then mark the data stream. This should not happen 753 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 754 * a FIN has been received from the remote side. 755 * In these states we ignore the URG. 756 */ 757 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 758 tp->rcv_up = ti->ti_seq + ti->ti_urp; 759 so->so_oobmark = so->so_rcv.sb_cc + 760 (tp->rcv_up - tp->rcv_nxt) - 1; 761 if (so->so_oobmark == 0) 762 so->so_state |= SS_RCVATMARK; 763 sohasoutofband(so); 764 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 765 } 766 /* 767 * Remove out of band data so doesn't get presented to user. 768 * This can happen independent of advancing the URG pointer, 769 * but if two URG's are pending at once, some out-of-band 770 * data may creep in... ick. 771 */ 772 if (ti->ti_urp <= ti->ti_len) 773 tcp_pulloutofband(so, ti); 774 } 775 badurp: /* XXX */ 776 777 /* 778 * Process the segment text, merging it into the TCP sequencing queue, 779 * and arranging for acknowledgment of receipt if necessary. 780 * This process logically involves adjusting tp->rcv_wnd as data 781 * is presented to the user (this happens in tcp_usrreq.c, 782 * case PRU_RCVD). If a FIN has already been received on this 783 * connection then we just ignore the text. 784 */ 785 if ((ti->ti_len || (tiflags&TH_FIN)) && 786 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 787 TCP_REASS(tp, ti, m, so, tiflags); 788 if (tcpnodelack == 0) 789 tp->t_flags |= TF_DELACK; 790 else 791 tp->t_flags |= TF_ACKNOW; 792 } else { 793 m_freem(m); 794 tiflags &= ~TH_FIN; 795 } 796 797 /* 798 * If FIN is received ACK the FIN and let the user know 799 * that the connection is closing. 800 */ 801 if (tiflags & TH_FIN) { 802 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 803 socantrcvmore(so); 804 tp->t_flags |= TF_ACKNOW; 805 tp->rcv_nxt++; 806 } 807 switch (tp->t_state) { 808 809 /* 810 * In SYN_RECEIVED and ESTABLISHED STATES 811 * enter the CLOSE_WAIT state. 812 */ 813 case TCPS_SYN_RECEIVED: 814 case TCPS_ESTABLISHED: 815 tp->t_state = TCPS_CLOSE_WAIT; 816 break; 817 818 /* 819 * If still in FIN_WAIT_1 STATE FIN has not been acked so 820 * enter the CLOSING state. 821 */ 822 case TCPS_FIN_WAIT_1: 823 tp->t_state = TCPS_CLOSING; 824 break; 825 826 /* 827 * In FIN_WAIT_2 state enter the TIME_WAIT state, 828 * starting the time-wait timer, turning off the other 829 * standard timers. 830 */ 831 case TCPS_FIN_WAIT_2: 832 tp->t_state = TCPS_TIME_WAIT; 833 tcp_canceltimers(tp); 834 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 835 soisdisconnected(so); 836 break; 837 838 /* 839 * In TIME_WAIT state restart the 2 MSL time_wait timer. 840 */ 841 case TCPS_TIME_WAIT: 842 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 843 break; 844 } 845 } 846 if (so->so_options & SO_DEBUG) 847 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 848 849 /* 850 * Return any desired output. 851 */ 852 (void) tcp_output(tp); 853 return; 854 855 dropafterack: 856 /* 857 * Generate an ACK dropping incoming segment if it occupies 858 * sequence space, where the ACK reflects our state. 859 */ 860 if ((tiflags&TH_RST) || 861 tlen == 0 && (tiflags&(TH_SYN|TH_FIN)) == 0) 862 goto drop; 863 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 864 tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 865 tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 866 return; 867 868 dropwithreset: 869 if (om) { 870 (void) m_free(om); 871 om = 0; 872 } 873 /* 874 * Generate a RST, dropping incoming segment. 875 * Make ACK acceptable to originator of segment. 876 */ 877 if (tiflags & TH_RST) 878 goto drop; 879 if (tiflags & TH_ACK) 880 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 881 else { 882 if (tiflags & TH_SYN) 883 ti->ti_len++; 884 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 885 TH_RST|TH_ACK); 886 } 887 /* destroy temporarily created socket */ 888 if (dropsocket) 889 (void) soabort(so); 890 return; 891 892 drop: 893 if (om) 894 (void) m_free(om); 895 /* 896 * Drop space held by incoming segment and return. 897 */ 898 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 899 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 900 m_freem(m); 901 /* destroy temporarily created socket */ 902 if (dropsocket) 903 (void) soabort(so); 904 return; 905 } 906 907 tcp_dooptions(tp, om, ti) 908 struct tcpcb *tp; 909 struct mbuf *om; 910 struct tcpiphdr *ti; 911 { 912 register u_char *cp; 913 int opt, optlen, cnt; 914 915 cp = mtod(om, u_char *); 916 cnt = om->m_len; 917 for (; cnt > 0; cnt -= optlen, cp += optlen) { 918 opt = cp[0]; 919 if (opt == TCPOPT_EOL) 920 break; 921 if (opt == TCPOPT_NOP) 922 optlen = 1; 923 else { 924 optlen = cp[1]; 925 if (optlen <= 0) 926 break; 927 } 928 switch (opt) { 929 930 default: 931 break; 932 933 case TCPOPT_MAXSEG: 934 if (optlen != 4) 935 continue; 936 if (!(ti->ti_flags & TH_SYN)) 937 continue; 938 tp->t_maxseg = *(u_short *)(cp + 2); 939 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 940 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 941 break; 942 } 943 } 944 (void) m_free(om); 945 } 946 947 /* 948 * Pull out of band byte out of a segment so 949 * it doesn't appear in the user's data queue. 950 * It is still reflected in the segment length for 951 * sequencing purposes. 952 */ 953 tcp_pulloutofband(so, ti) 954 struct socket *so; 955 struct tcpiphdr *ti; 956 { 957 register struct mbuf *m; 958 int cnt = ti->ti_urp - 1; 959 960 m = dtom(ti); 961 while (cnt >= 0) { 962 if (m->m_len > cnt) { 963 char *cp = mtod(m, caddr_t) + cnt; 964 struct tcpcb *tp = sototcpcb(so); 965 966 tp->t_iobc = *cp; 967 tp->t_oobflags |= TCPOOB_HAVEDATA; 968 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 969 m->m_len--; 970 return; 971 } 972 cnt -= m->m_len; 973 m = m->m_next; 974 if (m == 0) 975 break; 976 } 977 panic("tcp_pulloutofband"); 978 } 979 980 /* 981 * Determine a reasonable value for maxseg size. 982 * If the route is known, use one that can be handled 983 * on the given interface without forcing IP to fragment. 984 * If bigger than a page (CLBYTES), round down to nearest pagesize 985 * to utilize pagesize mbufs. 986 * If interface pointer is unavailable, or the destination isn't local, 987 * use a conservative size (512 or the default IP max size, but no more 988 * than the mtu of the interface through which we route), 989 * as we can't discover anything about intervening gateways or networks. 990 * 991 * This is ugly, and doesn't belong at this level, but has to happen somehow. 992 */ 993 tcp_mss(tp) 994 register struct tcpcb *tp; 995 { 996 struct route *ro; 997 struct ifnet *ifp; 998 int mss; 999 struct inpcb *inp; 1000 1001 inp = tp->t_inpcb; 1002 ro = &inp->inp_route; 1003 if ((ro->ro_rt == (struct rtentry *)0) || 1004 (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { 1005 /* No route yet, so try to acquire one */ 1006 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1007 ro->ro_dst.sa_family = AF_INET; 1008 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1009 inp->inp_faddr; 1010 rtalloc(ro); 1011 } 1012 if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) 1013 return (TCP_MSS); 1014 } 1015 1016 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1017 #if (CLBYTES & (CLBYTES - 1)) == 0 1018 if (mss > CLBYTES) 1019 mss &= ~(CLBYTES-1); 1020 #else 1021 if (mss > CLBYTES) 1022 mss = mss / CLBYTES * CLBYTES; 1023 #endif 1024 if (in_localaddr(inp->inp_faddr)) 1025 return (mss); 1026 return (MIN(mss, TCP_MSS)); 1027 } 1028