1 /* tcp_input.c 1.76 82/10/09 */ 2 3 #include "../h/param.h" 4 #include "../h/systm.h" 5 #include "../h/mbuf.h" 6 #include "../h/protosw.h" 7 #include "../h/socket.h" 8 #include "../h/socketvar.h" 9 #include "../netinet/in.h" 10 #include "../net/route.h" 11 #include "../netinet/in_pcb.h" 12 #include "../netinet/in_systm.h" 13 #include "../net/if.h" 14 #include "../netinet/ip.h" 15 #include "../netinet/ip_var.h" 16 #include "../netinet/tcp.h" 17 #include "../netinet/tcp_fsm.h" 18 #include "../netinet/tcp_seq.h" 19 #include "../netinet/tcp_timer.h" 20 #include "../netinet/tcp_var.h" 21 #include "../netinet/tcpip.h" 22 #include "../netinet/tcp_debug.h" 23 #include <errno.h> 24 25 int tcpprintfs = 0; 26 int tcpcksum = 1; 27 struct mbuf tcp_mb; 28 struct tcpiphdr tcp_saveti; 29 extern tcpnodelack; 30 31 struct tcpcb *tcp_newtcpcb(); 32 /* 33 * TCP input routine, follows pages 65-76 of the 34 * protocol specification dated September, 1981 very closely. 35 */ 36 tcp_input(m0) 37 struct mbuf *m0; 38 { 39 register struct tcpiphdr *ti; 40 struct inpcb *inp; 41 register struct mbuf *m; 42 struct mbuf *om = 0; 43 int len, tlen, off; 44 register struct tcpcb *tp = 0; 45 register int tiflags; 46 struct socket *so; 47 int todrop, acked; 48 short ostate; 49 struct in_addr laddr; 50 51 /* 52 * Get IP and TCP header together in first mbuf. 53 * Note: IP leaves IP header in first mbuf. 54 */ 55 m = m0; 56 ti = mtod(m, struct tcpiphdr *); 57 if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) 58 ip_stripoptions((struct ip *)ti, (struct mbuf *)0); 59 if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { 60 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 61 tcpstat.tcps_hdrops++; 62 return; 63 } 64 ti = mtod(m, struct tcpiphdr *); 65 } 66 67 /* 68 * Checksum extended TCP header and data. 69 */ 70 tlen = ((struct ip *)ti)->ip_len; 71 len = sizeof (struct ip) + tlen; 72 if (tcpcksum) { 73 ti->ti_next = ti->ti_prev = 0; 74 ti->ti_x1 = 0; 75 ti->ti_len = (u_short)tlen; 76 #if vax || pdp11 77 ti->ti_len = htons((u_short)ti->ti_len); 78 #endif 79 if (ti->ti_sum = in_cksum(m, len)) { 80 tcpstat.tcps_badsum++; 81 if (tcpprintfs) 82 printf("tcp cksum %x\n", ti->ti_sum); 83 goto drop; 84 } 85 } 86 87 /* 88 * Check that TCP offset makes sense, 89 * pull out TCP options and adjust length. 90 */ 91 off = ti->ti_off << 2; 92 if (off < sizeof (struct tcphdr) || off > tlen) { 93 tcpstat.tcps_badoff++; 94 goto drop; 95 } 96 tlen -= off; 97 ti->ti_len = tlen; 98 if (off > sizeof (struct tcphdr)) { 99 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 100 tcpstat.tcps_hdrops++; 101 goto drop; 102 } 103 ti = mtod(m, struct tcpiphdr *); 104 om = m_get(M_DONTWAIT); 105 if (om == 0) 106 goto drop; 107 om->m_len = off - sizeof (struct tcphdr); 108 { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 109 bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len); 110 m->m_len -= om->m_len; 111 bcopy(op+om->m_len, op, 112 (unsigned)(m->m_len-sizeof (struct tcpiphdr))); 113 } 114 } 115 tiflags = ti->ti_flags; 116 117 /* 118 * Drop TCP and IP headers. 119 */ 120 off += sizeof (struct ip); 121 m->m_off += off; 122 m->m_len -= off; 123 124 #if vax || pdp11 125 /* 126 * Convert TCP protocol specific fields to host format. 127 */ 128 ti->ti_seq = ntohl(ti->ti_seq); 129 ti->ti_ack = ntohl(ti->ti_ack); 130 ti->ti_win = ntohs(ti->ti_win); 131 ti->ti_urp = ntohs(ti->ti_urp); 132 #endif 133 134 /* 135 * Locate pcb for segment. 136 */ 137 inp = in_pcblookup 138 (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, 139 INPLOOKUP_WILDCARD); 140 141 /* 142 * If the state is CLOSED (i.e., TCB does not exist) then 143 * all data in the incoming segment is discarded. 144 */ 145 if (inp == 0) 146 goto dropwithreset; 147 tp = intotcpcb(inp); 148 if (tp == 0) 149 goto dropwithreset; 150 so = inp->inp_socket; 151 if (so->so_options & SO_DEBUG) { 152 ostate = tp->t_state; 153 tcp_saveti = *ti; 154 } 155 if (so->so_options & SO_ACCEPTCONN) { 156 so = sonewconn(so); 157 if (so == 0) 158 goto drop; 159 inp = (struct inpcb *)so->so_pcb; 160 inp->inp_laddr = ti->ti_dst; 161 inp->inp_lport = ti->ti_dport; 162 tp = intotcpcb(inp); 163 tp->t_state = TCPS_LISTEN; 164 } 165 166 /* 167 * Segment received on connection. 168 * Reset idle time and keep-alive timer. 169 */ 170 tp->t_idle = 0; 171 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 172 173 /* 174 * Process options. 175 */ 176 if (om) { 177 tcp_dooptions(tp, om); 178 om = 0; 179 } 180 181 /* 182 * Calculate amount of space in receive window, 183 * and then do TCP input processing. 184 */ 185 tp->rcv_wnd = sbspace(&so->so_rcv); 186 if (tp->rcv_wnd < 0) 187 tp->rcv_wnd = 0; 188 189 switch (tp->t_state) { 190 191 /* 192 * If the state is LISTEN then ignore segment if it contains an RST. 193 * If the segment contains an ACK then it is bad and send a RST. 194 * If it does not contain a SYN then it is not interesting; drop it. 195 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 196 * tp->iss, and send a segment: 197 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 198 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 199 * Fill in remote peer address fields if not previously specified. 200 * Enter SYN_RECEIVED state, and process any other fields of this 201 * segment in this state. 202 */ 203 case TCPS_LISTEN: { 204 struct mbuf *m = m_get(M_DONTWAIT); 205 register struct sockaddr_in *sin; 206 207 if (m == 0) 208 goto drop; 209 m->m_len = sizeof (struct sockaddr_in); 210 if (tiflags & TH_RST) 211 goto drop; 212 if (tiflags & TH_ACK) 213 goto dropwithreset; 214 if ((tiflags & TH_SYN) == 0) 215 goto drop; 216 sin = mtod(m, struct sockaddr_in *); 217 sin->sin_family = AF_INET; 218 sin->sin_addr = ti->ti_src; 219 sin->sin_port = ti->ti_sport; 220 laddr = inp->inp_laddr; 221 if (inp->inp_laddr.s_addr == 0) 222 inp->inp_laddr = ti->ti_dst; 223 if (in_pcbconnect(inp, m)) { 224 inp->inp_laddr = laddr; 225 m_free(m); 226 goto drop; 227 } 228 m_free(m); 229 tp->t_template = tcp_template(tp); 230 if (tp->t_template == 0) { 231 in_pcbdisconnect(inp); 232 inp->inp_laddr = laddr; 233 tp = 0; 234 goto drop; 235 } 236 tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; 237 tp->irs = ti->ti_seq; 238 tcp_sendseqinit(tp); 239 tcp_rcvseqinit(tp); 240 tp->t_state = TCPS_SYN_RECEIVED; 241 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 242 goto trimthenstep6; 243 } 244 245 /* 246 * If the state is SYN_SENT: 247 * if seg contains an ACK, but not for our SYN, drop the input. 248 * if seg contains a RST, then drop the connection. 249 * if seg does not contain SYN, then drop it. 250 * Otherwise this is an acceptable SYN segment 251 * initialize tp->rcv_nxt and tp->irs 252 * if seg contains ack then advance tp->snd_una 253 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 254 * arrange for segment to be acked (eventually) 255 * continue processing rest of data/controls, beginning with URG 256 */ 257 case TCPS_SYN_SENT: 258 if ((tiflags & TH_ACK) && 259 /* this should be SEQ_LT; is SEQ_LEQ for BBN vax TCP only */ 260 (SEQ_LT(ti->ti_ack, tp->iss) || 261 SEQ_GT(ti->ti_ack, tp->snd_max))) 262 goto dropwithreset; 263 if (tiflags & TH_RST) { 264 if (tiflags & TH_ACK) { 265 tcp_drop(tp, ECONNREFUSED); 266 tp = 0; 267 } 268 goto drop; 269 } 270 if ((tiflags & TH_SYN) == 0) 271 goto drop; 272 tp->snd_una = ti->ti_ack; 273 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 274 tp->snd_nxt = tp->snd_una; 275 tp->t_timer[TCPT_REXMT] = 0; 276 tp->irs = ti->ti_seq; 277 tcp_rcvseqinit(tp); 278 tp->t_flags |= TF_ACKNOW; 279 if (SEQ_GT(tp->snd_una, tp->iss)) { 280 soisconnected(so); 281 tp->t_state = TCPS_ESTABLISHED; 282 (void) tcp_reass(tp, (struct tcpiphdr *)0); 283 } else 284 tp->t_state = TCPS_SYN_RECEIVED; 285 goto trimthenstep6; 286 287 trimthenstep6: 288 /* 289 * Advance ti->ti_seq to correspond to first data byte. 290 * If data, trim to stay within window, 291 * dropping FIN if necessary. 292 */ 293 ti->ti_seq++; 294 if (ti->ti_len > tp->rcv_wnd) { 295 todrop = ti->ti_len - tp->rcv_wnd; 296 m_adj(m, -todrop); 297 ti->ti_len = tp->rcv_wnd; 298 ti->ti_flags &= ~TH_FIN; 299 } 300 tp->snd_wl1 = ti->ti_seq - 1; 301 goto step6; 302 } 303 304 /* 305 * States other than LISTEN or SYN_SENT. 306 * First check that at least some bytes of segment are within 307 * receive window. 308 */ 309 if (tp->rcv_wnd == 0) { 310 /* 311 * If window is closed can only take segments at 312 * window edge, and have to drop data and PUSH from 313 * incoming segments. 314 */ 315 if (tp->rcv_nxt != ti->ti_seq) 316 goto dropafterack; 317 if (ti->ti_len > 0) { 318 m_adj(m, ti->ti_len); 319 ti->ti_len = 0; 320 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 321 } 322 } else { 323 /* 324 * If segment begins before rcv_nxt, drop leading 325 * data (and SYN); if nothing left, just ack. 326 */ 327 todrop = tp->rcv_nxt - ti->ti_seq; 328 if (todrop > 0) { 329 if (tiflags & TH_SYN) { 330 tiflags &= ~TH_SYN; 331 ti->ti_flags &= ~TH_SYN; 332 ti->ti_seq++; 333 if (ti->ti_urp > 1) 334 ti->ti_urp--; 335 else 336 tiflags &= ~TH_URG; 337 todrop--; 338 } 339 if (todrop > ti->ti_len || 340 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) 341 goto dropafterack; 342 m_adj(m, todrop); 343 ti->ti_seq += todrop; 344 ti->ti_len -= todrop; 345 if (ti->ti_urp > todrop) 346 ti->ti_urp -= todrop; 347 else { 348 tiflags &= ~TH_URG; 349 ti->ti_flags &= ~TH_URG; 350 ti->ti_urp = 0; 351 } 352 } 353 /* 354 * If segment ends after window, drop trailing data 355 * (and PUSH and FIN); if nothing left, just ACK. 356 */ 357 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 358 if (todrop > 0) { 359 if (todrop >= ti->ti_len) 360 goto dropafterack; 361 m_adj(m, -todrop); 362 ti->ti_len -= todrop; 363 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 364 } 365 } 366 367 /* 368 * If a segment is received on a connection after the 369 * user processes are gone, then RST the other end. 370 */ 371 if (so->so_state & SS_NOFDREF) { 372 tcp_close(tp); 373 tp = 0; 374 goto dropwithreset; 375 } 376 377 /* 378 * If the RST bit is set examine the state: 379 * SYN_RECEIVED STATE: 380 * If passive open, return to LISTEN state. 381 * If active open, inform user that connection was refused. 382 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 383 * Inform user that connection was reset, and close tcb. 384 * CLOSING, LAST_ACK, TIME_WAIT STATES 385 * Close the tcb. 386 */ 387 if (tiflags&TH_RST) switch (tp->t_state) { 388 389 case TCPS_SYN_RECEIVED: 390 tcp_drop(tp, ECONNREFUSED); 391 tp = 0; 392 goto drop; 393 394 case TCPS_ESTABLISHED: 395 case TCPS_FIN_WAIT_1: 396 case TCPS_FIN_WAIT_2: 397 case TCPS_CLOSE_WAIT: 398 tcp_drop(tp, ECONNRESET); 399 tp = 0; 400 goto drop; 401 402 case TCPS_CLOSING: 403 case TCPS_LAST_ACK: 404 case TCPS_TIME_WAIT: 405 tcp_close(tp); 406 tp = 0; 407 goto drop; 408 } 409 410 /* 411 * If a SYN is in the window, then this is an 412 * error and we send an RST and drop the connection. 413 */ 414 if (tiflags & TH_SYN) { 415 tcp_drop(tp, ECONNRESET); 416 tp = 0; 417 goto dropwithreset; 418 } 419 420 /* 421 * If the ACK bit is off we drop the segment and return. 422 */ 423 if ((tiflags & TH_ACK) == 0) 424 goto drop; 425 426 /* 427 * Ack processing. 428 */ 429 switch (tp->t_state) { 430 431 /* 432 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 433 * ESTABLISHED state and continue processing, othewise 434 * send an RST. 435 */ 436 case TCPS_SYN_RECEIVED: 437 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 438 SEQ_GT(ti->ti_ack, tp->snd_max)) 439 goto dropwithreset; 440 tp->snd_una++; /* SYN acked */ 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 soisconnected(so); 445 tp->t_state = TCPS_ESTABLISHED; 446 (void) tcp_reass(tp, (struct tcpiphdr *)0); 447 tp->snd_wl1 = ti->ti_seq - 1; 448 /* fall into ... */ 449 450 /* 451 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 452 * ACKs. If the ack is in the range 453 * tp->snd_una < ti->ti_ack <= tp->snd_max 454 * then advance tp->snd_una to ti->ti_ack and drop 455 * data from the retransmission queue. If this ACK reflects 456 * more up to date window information we update our window information. 457 */ 458 case TCPS_ESTABLISHED: 459 case TCPS_FIN_WAIT_1: 460 case TCPS_FIN_WAIT_2: 461 case TCPS_CLOSE_WAIT: 462 case TCPS_CLOSING: 463 case TCPS_LAST_ACK: 464 case TCPS_TIME_WAIT: 465 #define ourfinisacked (acked > 0) 466 467 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) 468 break; 469 if (SEQ_GT(ti->ti_ack, tp->snd_max)) 470 goto dropafterack; 471 acked = ti->ti_ack - tp->snd_una; 472 473 /* 474 * If transmit timer is running and timed sequence 475 * number was acked, update smoothed round trip time. 476 */ 477 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 478 if (tp->t_srtt == 0) 479 tp->t_srtt = tp->t_rtt; 480 else 481 tp->t_srtt = 482 tcp_alpha * tp->t_srtt + 483 (1 - tcp_alpha) * tp->t_rtt; 484 /* printf("rtt %d srtt*100 now %d\n", tp->t_rtt, (int)(tp->t_srtt*100)); */ 485 tp->t_rtt = 0; 486 } 487 488 if (ti->ti_ack == tp->snd_max) 489 tp->t_timer[TCPT_REXMT] = 0; 490 else { 491 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 492 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 493 tp->t_rtt = 1; 494 tp->t_rxtshift = 0; 495 } 496 if (acked > so->so_snd.sb_cc) { 497 sbdrop(&so->so_snd, so->so_snd.sb_cc); 498 tp->snd_wnd -= so->so_snd.sb_cc; 499 } else { 500 sbdrop(&so->so_snd, acked); 501 tp->snd_wnd -= acked; 502 acked = 0; 503 } 504 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 505 sowwakeup(so); 506 tp->snd_una = ti->ti_ack; 507 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 508 tp->snd_nxt = tp->snd_una; 509 510 switch (tp->t_state) { 511 512 /* 513 * In FIN_WAIT_1 STATE in addition to the processing 514 * for the ESTABLISHED state if our FIN is now acknowledged 515 * then enter FIN_WAIT_2. 516 */ 517 case TCPS_FIN_WAIT_1: 518 if (ourfinisacked) { 519 /* 520 * If we can't receive any more 521 * data, then closing user can proceed. 522 */ 523 if (so->so_state & SS_CANTRCVMORE) 524 soisdisconnected(so); 525 tp->t_state = TCPS_FIN_WAIT_2; 526 } 527 break; 528 529 /* 530 * In CLOSING STATE in addition to the processing for 531 * the ESTABLISHED state if the ACK acknowledges our FIN 532 * then enter the TIME-WAIT state, otherwise ignore 533 * the segment. 534 */ 535 case TCPS_CLOSING: 536 if (ourfinisacked) { 537 tp->t_state = TCPS_TIME_WAIT; 538 tcp_canceltimers(tp); 539 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 540 soisdisconnected(so); 541 } 542 break; 543 544 /* 545 * The only thing that can arrive in LAST_ACK state 546 * is an acknowledgment of our FIN. If our FIN is now 547 * acknowledged, delete the TCB, enter the closed state 548 * and return. 549 */ 550 case TCPS_LAST_ACK: 551 if (ourfinisacked) { 552 tcp_close(tp); 553 tp = 0; 554 } 555 goto drop; 556 557 /* 558 * In TIME_WAIT state the only thing that should arrive 559 * is a retransmission of the remote FIN. Acknowledge 560 * it and restart the finack timer. 561 */ 562 case TCPS_TIME_WAIT: 563 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 564 goto dropafterack; 565 } 566 #undef ourfinisacked 567 } 568 569 step6: 570 /* 571 * Update window information. 572 */ 573 if (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 574 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 575 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)) { 576 tp->snd_wnd = ti->ti_win; 577 tp->snd_wl1 = ti->ti_seq; 578 tp->snd_wl2 = ti->ti_ack; 579 if (tp->snd_wnd > 0) 580 tp->t_timer[TCPT_PERSIST] = 0; 581 } 582 583 /* 584 * Process segments with URG. 585 */ 586 if ((tiflags & TH_URG) && ti->ti_urp && 587 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 588 /* 589 * If this segment advances the known urgent pointer, 590 * then mark the data stream. This should not happen 591 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 592 * a FIN has been received from the remote side. 593 * In these states we ignore the URG. 594 */ 595 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 596 tp->rcv_up = ti->ti_seq + ti->ti_urp; 597 so->so_oobmark = so->so_rcv.sb_cc + 598 (tp->rcv_up - tp->rcv_nxt) - 1; 599 if (so->so_oobmark == 0) 600 so->so_state |= SS_RCVATMARK; 601 sohasoutofband(so); 602 tp->t_oobflags &= ~TCPOOB_HAVEDATA; 603 } 604 /* 605 * Remove out of band data so doesn't get presented to user. 606 * This can happen independent of advancing the URG pointer, 607 * but if two URG's are pending at once, some out-of-band 608 * data may creep in... ick. 609 */ 610 if (ti->ti_urp <= ti->ti_len) 611 tcp_pulloutofband(so, ti); 612 } 613 614 /* 615 * Process the segment text, merging it into the TCP sequencing queue, 616 * and arranging for acknowledgment of receipt if necessary. 617 * This process logically involves adjusting tp->rcv_wnd as data 618 * is presented to the user (this happens in tcp_usrreq.c, 619 * case PRU_RCVD). If a FIN has already been received on this 620 * connection then we just ignore the text. 621 */ 622 if ((ti->ti_len || (tiflags&TH_FIN)) && 623 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 624 tiflags = tcp_reass(tp, ti); 625 if (tcpnodelack == 0) 626 tp->t_flags |= TF_DELACK; 627 else 628 tp->t_flags |= TF_ACKNOW; 629 } else { 630 m_freem(m); 631 tiflags &= ~TH_FIN; 632 } 633 634 /* 635 * If FIN is received ACK the FIN and let the user know 636 * that the connection is closing. 637 */ 638 if (tiflags & TH_FIN) { 639 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 640 socantrcvmore(so); 641 tp->t_flags |= TF_ACKNOW; 642 tp->rcv_nxt++; 643 } 644 switch (tp->t_state) { 645 646 /* 647 * In SYN_RECEIVED and ESTABLISHED STATES 648 * enter the CLOSE_WAIT state. 649 */ 650 case TCPS_SYN_RECEIVED: 651 case TCPS_ESTABLISHED: 652 tp->t_state = TCPS_CLOSE_WAIT; 653 break; 654 655 /* 656 * If still in FIN_WAIT_1 STATE FIN has not been acked so 657 * enter the CLOSING state. 658 */ 659 case TCPS_FIN_WAIT_1: 660 tp->t_state = TCPS_CLOSING; 661 break; 662 663 /* 664 * In FIN_WAIT_2 state enter the TIME_WAIT state, 665 * starting the time-wait timer, turning off the other 666 * standard timers. 667 */ 668 case TCPS_FIN_WAIT_2: 669 tp->t_state = TCPS_TIME_WAIT; 670 tcp_canceltimers(tp); 671 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 672 soisdisconnected(so); 673 break; 674 675 /* 676 * In TIME_WAIT state restart the 2 MSL time_wait timer. 677 */ 678 case TCPS_TIME_WAIT: 679 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 680 break; 681 } 682 } 683 if (so->so_options & SO_DEBUG) 684 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 685 686 /* 687 * Return any desired output. 688 */ 689 (void) tcp_output(tp); 690 return; 691 692 dropafterack: 693 /* 694 * Generate an ACK dropping incoming segment if it occupies 695 * sequence space, where the ACK reflects our state. 696 */ 697 if ((tiflags&TH_RST) || 698 tlen == 0 && (tiflags&(TH_SYN|TH_FIN)) == 0) 699 goto drop; 700 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 701 tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 702 tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 703 return; 704 705 dropwithreset: 706 if (om) 707 (void) m_free(om); 708 /* 709 * Generate a RST, dropping incoming segment. 710 * Make ACK acceptable to originator of segment. 711 */ 712 if (tiflags & TH_RST) 713 goto drop; 714 if (tiflags & TH_ACK) 715 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 716 else { 717 if (tiflags & TH_SYN) 718 ti->ti_len++; 719 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 720 TH_RST|TH_ACK); 721 } 722 return; 723 724 drop: 725 /* 726 * Drop space held by incoming segment and return. 727 */ 728 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 729 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 730 m_freem(m); 731 return; 732 } 733 734 tcp_dooptions(tp, om) 735 struct tcpcb *tp; 736 struct mbuf *om; 737 { 738 register u_char *cp; 739 int opt, optlen, cnt; 740 741 cp = mtod(om, u_char *); 742 cnt = om->m_len; 743 for (; cnt > 0; cnt -= optlen, cp += optlen) { 744 opt = cp[0]; 745 if (opt == TCPOPT_EOL) 746 break; 747 if (opt == TCPOPT_NOP) 748 optlen = 1; 749 else 750 optlen = cp[1]; 751 switch (opt) { 752 753 default: 754 break; 755 756 case TCPOPT_MAXSEG: 757 if (optlen != 4) 758 continue; 759 tp->t_maxseg = *(u_short *)(cp + 2); 760 #if vax || pdp11 761 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 762 #endif 763 break; 764 } 765 } 766 (void) m_free(om); 767 } 768 769 /* 770 * Pull out of band byte out of a segment so 771 * it doesn't appear in the user's data queue. 772 * It is still reflected in the segment length for 773 * sequencing purposes. 774 */ 775 tcp_pulloutofband(so, ti) 776 struct socket *so; 777 struct tcpiphdr *ti; 778 { 779 register struct mbuf *m; 780 int cnt = ti->ti_urp - 1; 781 782 m = dtom(ti); 783 while (cnt >= 0) { 784 if (m->m_len > cnt) { 785 char *cp = mtod(m, caddr_t) + cnt; 786 struct tcpcb *tp = sototcpcb(so); 787 788 tp->t_iobc = *cp; 789 tp->t_oobflags |= TCPOOB_HAVEDATA; 790 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 791 m->m_len--; 792 return; 793 } 794 cnt -= m->m_len; 795 m = m->m_next; 796 if (m == 0) 797 break; 798 } 799 panic("tcp_pulloutofband"); 800 } 801 802 /* 803 * Insert segment ti into reassembly queue of tcp with 804 * control block tp. Return TH_FIN if reassembly now includes 805 * a segment with FIN. 806 */ 807 tcp_reass(tp, ti) 808 register struct tcpcb *tp; 809 register struct tcpiphdr *ti; 810 { 811 register struct tcpiphdr *q; 812 struct socket *so = tp->t_inpcb->inp_socket; 813 struct mbuf *m; 814 int flags; 815 816 /* 817 * Call with ti==0 after become established to 818 * force pre-ESTABLISHED data up to user socket. 819 */ 820 if (ti == 0) 821 goto present; 822 823 /* 824 * Find a segment which begins after this one does. 825 */ 826 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 827 q = (struct tcpiphdr *)q->ti_next) 828 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 829 break; 830 831 /* 832 * If there is a preceding segment, it may provide some of 833 * our data already. If so, drop the data from the incoming 834 * segment. If it provides all of our data, drop us. 835 */ 836 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 837 register int i; 838 q = (struct tcpiphdr *)q->ti_prev; 839 /* conversion to int (in i) handles seq wraparound */ 840 i = q->ti_seq + q->ti_len - ti->ti_seq; 841 if (i > 0) { 842 if (i >= ti->ti_len) 843 goto drop; 844 m_adj(dtom(ti), i); 845 ti->ti_len -= i; 846 ti->ti_seq += i; 847 } 848 q = (struct tcpiphdr *)(q->ti_next); 849 } 850 851 /* 852 * While we overlap succeeding segments trim them or, 853 * if they are completely covered, dequeue them. 854 */ 855 while (q != (struct tcpiphdr *)tp) { 856 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 857 if (i <= 0) 858 break; 859 if (i < q->ti_len) { 860 q->ti_seq += i; 861 q->ti_len -= i; 862 m_adj(dtom(q), i); 863 break; 864 } 865 q = (struct tcpiphdr *)q->ti_next; 866 m = dtom(q->ti_prev); 867 remque(q->ti_prev); 868 m_freem(m); 869 } 870 871 /* 872 * Stick new segment in its place. 873 */ 874 insque(ti, q->ti_prev); 875 876 present: 877 /* 878 * Present data to user, advancing rcv_nxt through 879 * completed sequence space. 880 */ 881 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 882 return (0); 883 ti = tp->seg_next; 884 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 885 return (0); 886 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 887 return (0); 888 do { 889 tp->rcv_nxt += ti->ti_len; 890 flags = ti->ti_flags & TH_FIN; 891 remque(ti); 892 m = dtom(ti); 893 ti = (struct tcpiphdr *)ti->ti_next; 894 if (so->so_state & SS_CANTRCVMORE) 895 m_freem(m); 896 else 897 sbappend(&so->so_rcv, m); 898 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 899 sorwakeup(so); 900 return (flags); 901 drop: 902 m_freem(dtom(ti)); 903 return (0); 904 } 905