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 7.2 (Berkeley) 02/19/87 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 tcpstat.tcps_rcvpack++;\ 55 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 56 sbappend(&(so)->so_rcv, (m)); \ 57 sorwakeup(so); \ 58 } else \ 59 (flags) = tcp_reass((tp), (ti)); \ 60 } 61 62 tcp_reass(tp, ti) 63 register struct tcpcb *tp; 64 register struct tcpiphdr *ti; 65 { 66 register struct tcpiphdr *q; 67 struct socket *so = tp->t_inpcb->inp_socket; 68 struct mbuf *m; 69 int flags; 70 71 /* 72 * Call with ti==0 after become established to 73 * force pre-ESTABLISHED data up to user socket. 74 */ 75 if (ti == 0) 76 goto present; 77 78 /* 79 * Find a segment which begins after this one does. 80 */ 81 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 82 q = (struct tcpiphdr *)q->ti_next) 83 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 84 break; 85 86 /* 87 * If there is a preceding segment, it may provide some of 88 * our data already. If so, drop the data from the incoming 89 * segment. If it provides all of our data, drop us. 90 */ 91 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 92 register int i; 93 q = (struct tcpiphdr *)q->ti_prev; 94 /* conversion to int (in i) handles seq wraparound */ 95 i = q->ti_seq + q->ti_len - ti->ti_seq; 96 if (i > 0) { 97 if (i >= ti->ti_len) { 98 tcpstat.tcps_rcvduppack++; 99 tcpstat.tcps_rcvdupbyte += ti->ti_len; 100 goto drop; 101 } 102 m_adj(dtom(ti), i); 103 ti->ti_len -= i; 104 ti->ti_seq += i; 105 } 106 q = (struct tcpiphdr *)(q->ti_next); 107 } 108 tcpstat.tcps_rcvoopack++; 109 tcpstat.tcps_rcvoobyte += ti->ti_len; 110 111 /* 112 * While we overlap succeeding segments trim them or, 113 * if they are completely covered, dequeue them. 114 */ 115 while (q != (struct tcpiphdr *)tp) { 116 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 117 if (i <= 0) 118 break; 119 if (i < q->ti_len) { 120 q->ti_seq += i; 121 q->ti_len -= i; 122 m_adj(dtom(q), i); 123 break; 124 } 125 q = (struct tcpiphdr *)q->ti_next; 126 m = dtom(q->ti_prev); 127 remque(q->ti_prev); 128 m_freem(m); 129 } 130 131 /* 132 * Stick new segment in its place. 133 */ 134 insque(ti, q->ti_prev); 135 136 present: 137 /* 138 * Present data to user, advancing rcv_nxt through 139 * completed sequence space. 140 */ 141 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 142 return (0); 143 ti = tp->seg_next; 144 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 145 return (0); 146 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 147 return (0); 148 do { 149 tp->rcv_nxt += ti->ti_len; 150 flags = ti->ti_flags & TH_FIN; 151 remque(ti); 152 m = dtom(ti); 153 ti = (struct tcpiphdr *)ti->ti_next; 154 if (so->so_state & SS_CANTRCVMORE) 155 m_freem(m); 156 else 157 sbappend(&so->so_rcv, m); 158 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 159 sorwakeup(so); 160 return (flags); 161 drop: 162 m_freem(dtom(ti)); 163 return (0); 164 } 165 166 /* 167 * TCP input routine, follows pages 65-76 of the 168 * protocol specification dated September, 1981 very closely. 169 */ 170 tcp_input(m0) 171 struct mbuf *m0; 172 { 173 register struct tcpiphdr *ti; 174 struct inpcb *inp; 175 register struct mbuf *m; 176 struct mbuf *om = 0; 177 int len, tlen, off; 178 register struct tcpcb *tp = 0; 179 register int tiflags; 180 struct socket *so; 181 int todrop, acked, needoutput = 0; 182 short ostate; 183 struct in_addr laddr; 184 int dropsocket = 0; 185 int iss = 0; 186 187 tcpstat.tcps_rcvtotal++; 188 /* 189 * Get IP and TCP header together in first mbuf. 190 * Note: IP leaves IP header in first mbuf. 191 */ 192 m = m0; 193 ti = mtod(m, struct tcpiphdr *); 194 if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) 195 ip_stripoptions((struct ip *)ti, (struct mbuf *)0); 196 if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { 197 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 198 tcpstat.tcps_rcvshort++; 199 return; 200 } 201 ti = mtod(m, struct tcpiphdr *); 202 } 203 204 /* 205 * Checksum extended TCP header and data. 206 */ 207 tlen = ((struct ip *)ti)->ip_len; 208 len = sizeof (struct ip) + tlen; 209 if (tcpcksum) { 210 ti->ti_next = ti->ti_prev = 0; 211 ti->ti_x1 = 0; 212 ti->ti_len = (u_short)tlen; 213 ti->ti_len = htons((u_short)ti->ti_len); 214 if (ti->ti_sum = in_cksum(m, len)) { 215 if (tcpprintfs) 216 printf("tcp sum: src %x\n", ti->ti_src); 217 tcpstat.tcps_rcvbadsum++; 218 goto drop; 219 } 220 } 221 222 /* 223 * Check that TCP offset makes sense, 224 * pull out TCP options and adjust length. 225 */ 226 off = ti->ti_off << 2; 227 if (off < sizeof (struct tcphdr) || off > tlen) { 228 if (tcpprintfs) 229 printf("tcp off: src %x off %d\n", ti->ti_src, off); 230 tcpstat.tcps_rcvbadoff++; 231 goto drop; 232 } 233 tlen -= off; 234 ti->ti_len = tlen; 235 if (off > sizeof (struct tcphdr)) { 236 if (m->m_len < sizeof(struct ip) + off) { 237 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 238 tcpstat.tcps_rcvshort++; 239 return; 240 } 241 ti = mtod(m, struct tcpiphdr *); 242 } 243 om = m_get(M_DONTWAIT, MT_DATA); 244 if (om == 0) 245 goto drop; 246 om->m_len = off - sizeof (struct tcphdr); 247 { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 248 bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len); 249 m->m_len -= om->m_len; 250 bcopy(op+om->m_len, op, 251 (unsigned)(m->m_len-sizeof (struct tcpiphdr))); 252 } 253 } 254 tiflags = ti->ti_flags; 255 256 /* 257 * Drop TCP and IP headers; TCP options were dropped above. 258 */ 259 m->m_off += sizeof(struct tcpiphdr); 260 m->m_len -= sizeof(struct tcpiphdr); 261 262 /* 263 * Convert TCP protocol specific fields to host format. 264 */ 265 ti->ti_seq = ntohl(ti->ti_seq); 266 ti->ti_ack = ntohl(ti->ti_ack); 267 ti->ti_win = ntohs(ti->ti_win); 268 ti->ti_urp = ntohs(ti->ti_urp); 269 270 /* 271 * Locate pcb for segment. 272 */ 273 findpcb: 274 inp = in_pcblookup 275 (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, 276 INPLOOKUP_WILDCARD); 277 278 /* 279 * If the state is CLOSED (i.e., TCB does not exist) then 280 * all data in the incoming segment is discarded. 281 */ 282 if (inp == 0) 283 goto dropwithreset; 284 tp = intotcpcb(inp); 285 if (tp == 0) 286 goto dropwithreset; 287 so = inp->inp_socket; 288 if (so->so_options & SO_DEBUG) { 289 ostate = tp->t_state; 290 tcp_saveti = *ti; 291 } 292 if (so->so_options & SO_ACCEPTCONN) { 293 so = sonewconn(so); 294 if (so == 0) 295 goto drop; 296 /* 297 * This is ugly, but .... 298 * 299 * Mark socket as temporary until we're 300 * committed to keeping it. The code at 301 * ``drop'' and ``dropwithreset'' check the 302 * flag dropsocket to see if the temporary 303 * socket created here should be discarded. 304 * We mark the socket as discardable until 305 * we're committed to it below in TCPS_LISTEN. 306 */ 307 dropsocket++; 308 inp = (struct inpcb *)so->so_pcb; 309 inp->inp_laddr = ti->ti_dst; 310 inp->inp_lport = ti->ti_dport; 311 inp->inp_options = ip_srcroute(); 312 tp = intotcpcb(inp); 313 tp->t_state = TCPS_LISTEN; 314 } 315 316 /* 317 * Segment received on connection. 318 * Reset idle time and keep-alive timer. 319 */ 320 tp->t_idle = 0; 321 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 322 323 /* 324 * Process options if not in LISTEN state, 325 * else do it below (after getting remote address). 326 */ 327 if (om && tp->t_state != TCPS_LISTEN) { 328 tcp_dooptions(tp, om, ti); 329 om = 0; 330 } 331 332 /* 333 * Calculate amount of space in receive window, 334 * and then do TCP input processing. 335 * Receive window is amount of space in rcv queue, 336 * but not less than advertised window. 337 */ 338 { int win; 339 340 win = sbspace(&so->so_rcv); 341 if (win < 0) 342 win = 0; 343 tp->rcv_wnd = MAX(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 344 } 345 346 switch (tp->t_state) { 347 348 /* 349 * If the state is LISTEN then ignore segment if it contains an RST. 350 * If the segment contains an ACK then it is bad and send a RST. 351 * If it does not contain a SYN then it is not interesting; drop it. 352 * Don't bother responding if the destination was a broadcast. 353 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 354 * tp->iss, and send a segment: 355 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 356 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 357 * Fill in remote peer address fields if not previously specified. 358 * Enter SYN_RECEIVED state, and process any other fields of this 359 * segment in this state. 360 */ 361 case TCPS_LISTEN: { 362 struct mbuf *am; 363 register struct sockaddr_in *sin; 364 365 if (tiflags & TH_RST) 366 goto drop; 367 if (tiflags & TH_ACK) 368 goto dropwithreset; 369 if ((tiflags & TH_SYN) == 0) 370 goto drop; 371 if (in_broadcast(ti->ti_dst)) 372 goto drop; 373 am = m_get(M_DONTWAIT, MT_SONAME); 374 if (am == NULL) 375 goto drop; 376 am->m_len = sizeof (struct sockaddr_in); 377 sin = mtod(am, struct sockaddr_in *); 378 sin->sin_family = AF_INET; 379 sin->sin_addr = ti->ti_src; 380 sin->sin_port = ti->ti_sport; 381 laddr = inp->inp_laddr; 382 if (inp->inp_laddr.s_addr == INADDR_ANY) 383 inp->inp_laddr = ti->ti_dst; 384 if (in_pcbconnect(inp, am)) { 385 inp->inp_laddr = laddr; 386 (void) m_free(am); 387 goto drop; 388 } 389 (void) m_free(am); 390 tp->t_template = tcp_template(tp); 391 if (tp->t_template == 0) { 392 tp = tcp_drop(tp, ENOBUFS); 393 dropsocket = 0; /* socket is already gone */ 394 goto drop; 395 } 396 if (om) { 397 tcp_dooptions(tp, om, ti); 398 om = 0; 399 } 400 if (iss) 401 tp->iss = iss; 402 else 403 tp->iss = tcp_iss; 404 tcp_iss += TCP_ISSINCR/2; 405 tp->irs = ti->ti_seq; 406 tcp_sendseqinit(tp); 407 tcp_rcvseqinit(tp); 408 tp->t_flags |= TF_ACKNOW; 409 tp->t_state = TCPS_SYN_RECEIVED; 410 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 411 dropsocket = 0; /* committed to socket */ 412 tcpstat.tcps_accepts++; 413 goto trimthenstep6; 414 } 415 416 /* 417 * If the state is SYN_SENT: 418 * if seg contains an ACK, but not for our SYN, drop the input. 419 * if seg contains a RST, then drop the connection. 420 * if seg does not contain SYN, then drop it. 421 * Otherwise this is an acceptable SYN segment 422 * initialize tp->rcv_nxt and tp->irs 423 * if seg contains ack then advance tp->snd_una 424 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 425 * arrange for segment to be acked (eventually) 426 * continue processing rest of data/controls, beginning with URG 427 */ 428 case TCPS_SYN_SENT: 429 if ((tiflags & TH_ACK) && 430 (SEQ_LEQ(ti->ti_ack, tp->iss) || 431 SEQ_GT(ti->ti_ack, tp->snd_max))) 432 goto dropwithreset; 433 if (tiflags & TH_RST) { 434 if (tiflags & TH_ACK) 435 tp = tcp_drop(tp, ECONNREFUSED); 436 goto drop; 437 } 438 if ((tiflags & TH_SYN) == 0) 439 goto drop; 440 tp->snd_una = ti->ti_ack; 441 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 442 tp->snd_nxt = tp->snd_una; 443 tp->t_timer[TCPT_REXMT] = 0; 444 tp->irs = ti->ti_seq; 445 tcp_rcvseqinit(tp); 446 tp->t_flags |= TF_ACKNOW; 447 if (SEQ_GT(tp->snd_una, tp->iss)) { 448 tcpstat.tcps_connects++; 449 soisconnected(so); 450 tp->t_state = TCPS_ESTABLISHED; 451 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 452 (void) tcp_reass(tp, (struct tcpiphdr *)0); 453 } else 454 tp->t_state = TCPS_SYN_RECEIVED; 455 456 trimthenstep6: 457 /* 458 * Advance ti->ti_seq to correspond to first data byte. 459 * If data, trim to stay within window, 460 * dropping FIN if necessary. 461 */ 462 ti->ti_seq++; 463 if (ti->ti_len > tp->rcv_wnd) { 464 todrop = ti->ti_len - tp->rcv_wnd; 465 m_adj(m, -todrop); 466 ti->ti_len = tp->rcv_wnd; 467 tiflags &= ~TH_FIN; 468 tcpstat.tcps_rcvpackafterwin++; 469 tcpstat.tcps_rcvbyteafterwin += todrop; 470 } 471 tp->snd_wl1 = ti->ti_seq - 1; 472 tp->rcv_up = ti->ti_seq; 473 goto step6; 474 } 475 476 /* 477 * States other than LISTEN or SYN_SENT. 478 * First check that at least some bytes of segment are within 479 * receive window. If segment begins before rcv_nxt, 480 * drop leading data (and SYN); if nothing left, just ack. 481 */ 482 todrop = tp->rcv_nxt - ti->ti_seq; 483 if (todrop > 0) { 484 if (tiflags & TH_SYN) { 485 tiflags &= ~TH_SYN; 486 ti->ti_seq++; 487 if (ti->ti_urp > 1) 488 ti->ti_urp--; 489 else 490 tiflags &= ~TH_URG; 491 todrop--; 492 } 493 if (todrop > ti->ti_len || 494 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) { 495 tcpstat.tcps_rcvduppack++; 496 tcpstat.tcps_rcvdupbyte += ti->ti_len; 497 goto dropafterack; 498 } 499 tcpstat.tcps_rcvpartduppack++; 500 tcpstat.tcps_rcvpartdupbyte += todrop; 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_urp = 0; 509 } 510 } 511 512 if (tp->rcv_wnd == 0) { 513 /* 514 * If window is closed can only take segments at 515 * window edge, and have to drop data and PUSH from 516 * incoming segments. 517 * 518 * If new data is received on a connection after the 519 * user processes are gone, then RST the other end. 520 */ 521 if ((so->so_state & SS_NOFDREF) && 522 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 523 tp = tcp_close(tp); 524 tcpstat.tcps_rcvafterclose++; 525 goto dropwithreset; 526 } 527 if (tp->rcv_nxt != ti->ti_seq) { 528 tcpstat.tcps_rcvpackafterwin++; 529 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 530 goto dropafterack; 531 } 532 if (ti->ti_len > 0) { 533 if (ti->ti_len == 1) 534 tcpstat.tcps_rcvwinprobe++; 535 else { 536 tcpstat.tcps_rcvpackafterwin++; 537 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 538 } 539 m_adj(m, ti->ti_len); 540 ti->ti_len = 0; 541 tiflags &= ~(TH_PUSH|TH_FIN); 542 } 543 } else { 544 /* 545 * If segment ends after window, drop trailing data 546 * (and PUSH and FIN); if nothing left, just ACK. 547 */ 548 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 549 if (todrop > 0) { 550 if (todrop >= ti->ti_len) { 551 /* 552 * If a new connection request is received 553 * while in TIME_WAIT, drop the old connection 554 * and start over if the sequence numbers 555 * are above the previous ones. 556 */ 557 if (tiflags & TH_SYN && 558 tp->t_state == TCPS_TIME_WAIT && 559 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 560 iss = tp->rcv_nxt + TCP_ISSINCR; 561 (void) tcp_close(tp); 562 goto findpcb; 563 } 564 if (todrop == 1) 565 tcpstat.tcps_rcvwinprobe++; 566 else { 567 tcpstat.tcps_rcvpackafterwin++; 568 tcpstat.tcps_rcvbyteafterwin += todrop; 569 } 570 goto dropafterack; 571 } 572 tcpstat.tcps_rcvpackafterwin++; 573 tcpstat.tcps_rcvbyteafterwin += todrop; 574 m_adj(m, -todrop); 575 ti->ti_len -= todrop; 576 tiflags &= ~(TH_PUSH|TH_FIN); 577 } 578 } 579 580 /* 581 * If the RST bit is set examine the state: 582 * SYN_RECEIVED STATE: 583 * If passive open, return to LISTEN state. 584 * If active open, inform user that connection was refused. 585 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 586 * Inform user that connection was reset, and close tcb. 587 * CLOSING, LAST_ACK, TIME_WAIT STATES 588 * Close the tcb. 589 */ 590 if (tiflags&TH_RST) switch (tp->t_state) { 591 592 case TCPS_SYN_RECEIVED: 593 tp = tcp_drop(tp, ECONNREFUSED); 594 goto drop; 595 596 case TCPS_ESTABLISHED: 597 case TCPS_FIN_WAIT_1: 598 case TCPS_FIN_WAIT_2: 599 case TCPS_CLOSE_WAIT: 600 tp = tcp_drop(tp, ECONNRESET); 601 goto drop; 602 603 case TCPS_CLOSING: 604 case TCPS_LAST_ACK: 605 case TCPS_TIME_WAIT: 606 tp = tcp_close(tp); 607 goto drop; 608 } 609 610 /* 611 * If a SYN is in the window, then this is an 612 * error and we send an RST and drop the connection. 613 */ 614 if (tiflags & TH_SYN) { 615 tp = tcp_drop(tp, ECONNRESET); 616 goto dropwithreset; 617 } 618 619 /* 620 * If the ACK bit is off we drop the segment and return. 621 */ 622 if ((tiflags & TH_ACK) == 0) 623 goto drop; 624 625 /* 626 * Ack processing. 627 */ 628 switch (tp->t_state) { 629 630 /* 631 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 632 * ESTABLISHED state and continue processing, othewise 633 * send an RST. 634 */ 635 case TCPS_SYN_RECEIVED: 636 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 637 SEQ_GT(ti->ti_ack, tp->snd_max)) 638 goto dropwithreset; 639 tp->snd_una++; /* SYN acked */ 640 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 641 tp->snd_nxt = tp->snd_una; 642 tp->t_timer[TCPT_REXMT] = 0; 643 tcpstat.tcps_connects++; 644 soisconnected(so); 645 tp->t_state = TCPS_ESTABLISHED; 646 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 647 (void) tcp_reass(tp, (struct tcpiphdr *)0); 648 tp->snd_wl1 = ti->ti_seq - 1; 649 /* fall into ... */ 650 651 /* 652 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 653 * ACKs. If the ack is in the range 654 * tp->snd_una < ti->ti_ack <= tp->snd_max 655 * then advance tp->snd_una to ti->ti_ack and drop 656 * data from the retransmission queue. If this ACK reflects 657 * more up to date window information we update our window information. 658 */ 659 case TCPS_ESTABLISHED: 660 case TCPS_FIN_WAIT_1: 661 case TCPS_FIN_WAIT_2: 662 case TCPS_CLOSE_WAIT: 663 case TCPS_CLOSING: 664 case TCPS_LAST_ACK: 665 case TCPS_TIME_WAIT: 666 667 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 668 if (ti->ti_len == 0) 669 tcpstat.tcps_rcvdupack++; 670 break; 671 } 672 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 673 tcpstat.tcps_rcvacktoomuch++; 674 goto dropafterack; 675 } 676 acked = ti->ti_ack - tp->snd_una; 677 tcpstat.tcps_rcvackpack++; 678 tcpstat.tcps_rcvackbyte += acked; 679 680 /* 681 * If transmit timer is running and timed sequence 682 * number was acked, update smoothed round trip time. 683 */ 684 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 685 tcpstat.tcps_rttupdated++; 686 if (tp->t_srtt == 0) 687 tp->t_srtt = tp->t_rtt; 688 else 689 tp->t_srtt = 690 tcp_alpha * tp->t_srtt + 691 (1 - tcp_alpha) * tp->t_rtt; 692 tp->t_rtt = 0; 693 } 694 695 /* 696 * If all outstanding data is acked, stop retransmit 697 * timer and remember to restart (more output or persist). 698 * If there is more data to be acked, restart retransmit 699 * timer. 700 */ 701 if (ti->ti_ack == tp->snd_max) { 702 tp->t_timer[TCPT_REXMT] = 0; 703 needoutput = 1; 704 } else if (tp->t_timer[TCPT_PERSIST] == 0) { 705 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 706 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 707 tp->t_rxtshift = 0; 708 } 709 /* 710 * When new data is acked, open the congestion window a bit. 711 */ 712 tp->snd_cwnd = MIN(11 * tp->snd_cwnd / 10, 65535); 713 if (acked > so->so_snd.sb_cc) { 714 tp->snd_wnd -= so->so_snd.sb_cc; 715 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 716 #define ourfinisacked (acked > 0) 717 } else { 718 sbdrop(&so->so_snd, acked); 719 tp->snd_wnd -= acked; 720 acked = 0; 721 } 722 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 723 sowwakeup(so); 724 tp->snd_una = ti->ti_ack; 725 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 726 tp->snd_nxt = tp->snd_una; 727 728 switch (tp->t_state) { 729 730 /* 731 * In FIN_WAIT_1 STATE in addition to the processing 732 * for the ESTABLISHED state if our FIN is now acknowledged 733 * then enter FIN_WAIT_2. 734 */ 735 case TCPS_FIN_WAIT_1: 736 if (ourfinisacked) { 737 /* 738 * If we can't receive any more 739 * data, then closing user can proceed. 740 * Starting the timer is contrary to the 741 * specification, but if we don't get a FIN 742 * we'll hang forever. 743 */ 744 if (so->so_state & SS_CANTRCVMORE) { 745 soisdisconnected(so); 746 tp->t_timer[TCPT_2MSL] = TCPTV_MAXIDLE; 747 } 748 tp->t_state = TCPS_FIN_WAIT_2; 749 } 750 break; 751 752 /* 753 * In CLOSING STATE in addition to the processing for 754 * the ESTABLISHED state if the ACK acknowledges our FIN 755 * then enter the TIME-WAIT state, otherwise ignore 756 * the segment. 757 */ 758 case TCPS_CLOSING: 759 if (ourfinisacked) { 760 tp->t_state = TCPS_TIME_WAIT; 761 tcp_canceltimers(tp); 762 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 763 soisdisconnected(so); 764 } 765 break; 766 767 /* 768 * The only thing that can arrive in LAST_ACK state 769 * is an acknowledgment of our FIN. If our FIN is now 770 * acknowledged, delete the TCB, enter the closed state 771 * and return. 772 */ 773 case TCPS_LAST_ACK: 774 if (ourfinisacked) 775 tp = tcp_close(tp); 776 goto drop; 777 778 /* 779 * In TIME_WAIT state the only thing that should arrive 780 * is a retransmission of the remote FIN. Acknowledge 781 * it and restart the finack timer. 782 */ 783 case TCPS_TIME_WAIT: 784 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 785 goto dropafterack; 786 } 787 #undef ourfinisacked 788 } 789 790 step6: 791 /* 792 * Update window information. 793 * Don't look at window if no ACK: TAC's send garbage on first SYN. 794 */ 795 if ((tiflags & TH_ACK) && 796 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 797 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 798 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) { 799 /* keep track of pure window updates */ 800 if (ti->ti_len == 0 && 801 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd) { 802 tcpstat.tcps_rcvwinupd++; 803 tcpstat.tcps_rcvdupack--; 804 } 805 tp->snd_wnd = ti->ti_win; 806 tp->snd_wl1 = ti->ti_seq; 807 tp->snd_wl2 = ti->ti_ack; 808 if (tp->snd_wnd > tp->max_sndwnd) 809 tp->max_sndwnd = tp->snd_wnd; 810 needoutput = 1; 811 } 812 813 /* 814 * Process segments with URG. 815 */ 816 if ((tiflags & TH_URG) && ti->ti_urp && 817 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 818 /* 819 * This is a kludge, but if we receive and accept 820 * random urgent pointers, we'll crash in 821 * soreceive. It's hard to imagine someone 822 * actually wanting to send this much urgent data. 823 */ 824 if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) { 825 ti->ti_urp = 0; /* XXX */ 826 tiflags &= ~TH_URG; /* XXX */ 827 goto dodata; /* XXX */ 828 } 829 /* 830 * If this segment advances the known urgent pointer, 831 * then mark the data stream. This should not happen 832 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 833 * a FIN has been received from the remote side. 834 * In these states we ignore the URG. 835 * 836 * According to RFC961 (Assigned Protocols), 837 * the urgent pointer points to the last octet 838 * of urgent data. We continue, however, 839 * to consider it to indicate the first octet 840 * of data past the urgent section 841 * as the original spec states. 842 */ 843 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 844 tp->rcv_up = ti->ti_seq + ti->ti_urp; 845 so->so_oobmark = so->so_rcv.sb_cc + 846 (tp->rcv_up - tp->rcv_nxt) - 1; 847 if (so->so_oobmark == 0) 848 so->so_state |= SS_RCVATMARK; 849 sohasoutofband(so); 850 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 851 } 852 /* 853 * Remove out of band data so doesn't get presented to user. 854 * This can happen independent of advancing the URG pointer, 855 * but if two URG's are pending at once, some out-of-band 856 * data may creep in... ick. 857 */ 858 if (ti->ti_urp <= ti->ti_len && 859 (so->so_options & SO_OOBINLINE) == 0) 860 tcp_pulloutofband(so, ti); 861 } else 862 /* 863 * If no out of band data is expected, 864 * pull receive urgent pointer along 865 * with the receive window. 866 */ 867 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 868 tp->rcv_up = tp->rcv_nxt; 869 dodata: /* XXX */ 870 871 /* 872 * Process the segment text, merging it into the TCP sequencing queue, 873 * and arranging for acknowledgment of receipt if necessary. 874 * This process logically involves adjusting tp->rcv_wnd as data 875 * is presented to the user (this happens in tcp_usrreq.c, 876 * case PRU_RCVD). If a FIN has already been received on this 877 * connection then we just ignore the text. 878 */ 879 if ((ti->ti_len || (tiflags&TH_FIN)) && 880 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 881 TCP_REASS(tp, ti, m, so, tiflags); 882 if (tcpnodelack == 0) 883 tp->t_flags |= TF_DELACK; 884 else 885 tp->t_flags |= TF_ACKNOW; 886 /* 887 * Note the amount of data that peer has sent into 888 * our window, in order to estimate the sender's 889 * buffer size. 890 */ 891 len = so->so_rcv.sb_hiwat - (tp->rcv_nxt - tp->rcv_adv); 892 if (len > tp->max_rcvd) 893 tp->max_rcvd = len; 894 } else { 895 m_freem(m); 896 tiflags &= ~TH_FIN; 897 } 898 899 /* 900 * If FIN is received ACK the FIN and let the user know 901 * that the connection is closing. 902 */ 903 if (tiflags & TH_FIN) { 904 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 905 socantrcvmore(so); 906 tp->t_flags |= TF_ACKNOW; 907 tp->rcv_nxt++; 908 } 909 switch (tp->t_state) { 910 911 /* 912 * In SYN_RECEIVED and ESTABLISHED STATES 913 * enter the CLOSE_WAIT state. 914 */ 915 case TCPS_SYN_RECEIVED: 916 case TCPS_ESTABLISHED: 917 tp->t_state = TCPS_CLOSE_WAIT; 918 break; 919 920 /* 921 * If still in FIN_WAIT_1 STATE FIN has not been acked so 922 * enter the CLOSING state. 923 */ 924 case TCPS_FIN_WAIT_1: 925 tp->t_state = TCPS_CLOSING; 926 break; 927 928 /* 929 * In FIN_WAIT_2 state enter the TIME_WAIT state, 930 * starting the time-wait timer, turning off the other 931 * standard timers. 932 */ 933 case TCPS_FIN_WAIT_2: 934 tp->t_state = TCPS_TIME_WAIT; 935 tcp_canceltimers(tp); 936 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 937 soisdisconnected(so); 938 break; 939 940 /* 941 * In TIME_WAIT state restart the 2 MSL time_wait timer. 942 */ 943 case TCPS_TIME_WAIT: 944 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 945 break; 946 } 947 } 948 if (so->so_options & SO_DEBUG) 949 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 950 951 /* 952 * Return any desired output. 953 */ 954 if (needoutput || (tp->t_flags & TF_ACKNOW)) 955 (void) tcp_output(tp); 956 return; 957 958 dropafterack: 959 /* 960 * Generate an ACK dropping incoming segment if it occupies 961 * sequence space, where the ACK reflects our state. 962 */ 963 if (tiflags & TH_RST) 964 goto drop; 965 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 966 tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 967 tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 968 return; 969 970 dropwithreset: 971 if (om) { 972 (void) m_free(om); 973 om = 0; 974 } 975 /* 976 * Generate a RST, dropping incoming segment. 977 * Make ACK acceptable to originator of segment. 978 * Don't bother to respond if destination was broadcast. 979 */ 980 if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst)) 981 goto drop; 982 if (tiflags & TH_ACK) 983 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 984 else { 985 if (tiflags & TH_SYN) 986 ti->ti_len++; 987 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 988 TH_RST|TH_ACK); 989 } 990 /* destroy temporarily created socket */ 991 if (dropsocket) 992 (void) soabort(so); 993 return; 994 995 drop: 996 if (om) 997 (void) m_free(om); 998 /* 999 * Drop space held by incoming segment and return. 1000 */ 1001 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1002 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1003 m_freem(m); 1004 /* destroy temporarily created socket */ 1005 if (dropsocket) 1006 (void) soabort(so); 1007 return; 1008 } 1009 1010 tcp_dooptions(tp, om, ti) 1011 struct tcpcb *tp; 1012 struct mbuf *om; 1013 struct tcpiphdr *ti; 1014 { 1015 register u_char *cp; 1016 int opt, optlen, cnt; 1017 1018 cp = mtod(om, u_char *); 1019 cnt = om->m_len; 1020 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1021 opt = cp[0]; 1022 if (opt == TCPOPT_EOL) 1023 break; 1024 if (opt == TCPOPT_NOP) 1025 optlen = 1; 1026 else { 1027 optlen = cp[1]; 1028 if (optlen <= 0) 1029 break; 1030 } 1031 switch (opt) { 1032 1033 default: 1034 break; 1035 1036 case TCPOPT_MAXSEG: 1037 if (optlen != 4) 1038 continue; 1039 if (!(ti->ti_flags & TH_SYN)) 1040 continue; 1041 tp->t_maxseg = *(u_short *)(cp + 2); 1042 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 1043 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 1044 break; 1045 } 1046 } 1047 (void) m_free(om); 1048 } 1049 1050 /* 1051 * Pull out of band byte out of a segment so 1052 * it doesn't appear in the user's data queue. 1053 * It is still reflected in the segment length for 1054 * sequencing purposes. 1055 */ 1056 tcp_pulloutofband(so, ti) 1057 struct socket *so; 1058 struct tcpiphdr *ti; 1059 { 1060 register struct mbuf *m; 1061 int cnt = ti->ti_urp - 1; 1062 1063 m = dtom(ti); 1064 while (cnt >= 0) { 1065 if (m->m_len > cnt) { 1066 char *cp = mtod(m, caddr_t) + cnt; 1067 struct tcpcb *tp = sototcpcb(so); 1068 1069 tp->t_iobc = *cp; 1070 tp->t_oobflags |= TCPOOB_HAVEDATA; 1071 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1072 m->m_len--; 1073 return; 1074 } 1075 cnt -= m->m_len; 1076 m = m->m_next; 1077 if (m == 0) 1078 break; 1079 } 1080 panic("tcp_pulloutofband"); 1081 } 1082 1083 /* 1084 * Determine a reasonable value for maxseg size. 1085 * If the route is known, use one that can be handled 1086 * on the given interface without forcing IP to fragment. 1087 * If bigger than a page (CLBYTES), round down to nearest pagesize 1088 * to utilize pagesize mbufs. 1089 * If interface pointer is unavailable, or the destination isn't local, 1090 * use a conservative size (512 or the default IP max size, but no more 1091 * than the mtu of the interface through which we route), 1092 * as we can't discover anything about intervening gateways or networks. 1093 * 1094 * This is ugly, and doesn't belong at this level, but has to happen somehow. 1095 */ 1096 tcp_mss(tp) 1097 register struct tcpcb *tp; 1098 { 1099 struct route *ro; 1100 struct ifnet *ifp; 1101 int mss; 1102 struct inpcb *inp; 1103 1104 inp = tp->t_inpcb; 1105 ro = &inp->inp_route; 1106 if ((ro->ro_rt == (struct rtentry *)0) || 1107 (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { 1108 /* No route yet, so try to acquire one */ 1109 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1110 ro->ro_dst.sa_family = AF_INET; 1111 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1112 inp->inp_faddr; 1113 rtalloc(ro); 1114 } 1115 if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) 1116 return (TCP_MSS); 1117 } 1118 1119 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1120 #if (CLBYTES & (CLBYTES - 1)) == 0 1121 if (mss > CLBYTES) 1122 mss &= ~(CLBYTES-1); 1123 #else 1124 if (mss > CLBYTES) 1125 mss = mss / CLBYTES * CLBYTES; 1126 #endif 1127 if (in_localaddr(inp->inp_faddr)) 1128 return (mss); 1129 return (MIN(mss, TCP_MSS)); 1130 } 1131