1 /* tcp_input.c 1.80 82/10/20 */ 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 tcpiphdr tcp_saveti; 28 extern tcpnodelack; 29 30 struct tcpcb *tcp_newtcpcb(); 31 /* 32 * TCP input routine, follows pages 65-76 of the 33 * protocol specification dated September, 1981 very closely. 34 */ 35 tcp_input(m0) 36 struct mbuf *m0; 37 { 38 register struct tcpiphdr *ti; 39 struct inpcb *inp; 40 register struct mbuf *m; 41 struct mbuf *om = 0; 42 int len, tlen, off; 43 register struct tcpcb *tp = 0; 44 register int tiflags; 45 struct socket *so; 46 int todrop, acked; 47 short ostate; 48 struct in_addr laddr; 49 50 /* 51 * Get IP and TCP header together in first mbuf. 52 * Note: IP leaves IP header in first mbuf. 53 */ 54 m = m0; 55 ti = mtod(m, struct tcpiphdr *); 56 if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) 57 ip_stripoptions((struct ip *)ti, (struct mbuf *)0); 58 if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { 59 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 60 tcpstat.tcps_hdrops++; 61 return; 62 } 63 ti = mtod(m, struct tcpiphdr *); 64 } 65 66 /* 67 * Checksum extended TCP header and data. 68 */ 69 tlen = ((struct ip *)ti)->ip_len; 70 len = sizeof (struct ip) + tlen; 71 if (tcpcksum) { 72 ti->ti_next = ti->ti_prev = 0; 73 ti->ti_x1 = 0; 74 ti->ti_len = (u_short)tlen; 75 #if vax || pdp11 || ns16032 76 ti->ti_len = htons((u_short)ti->ti_len); 77 #endif 78 if (ti->ti_sum = in_cksum(m, len)) { 79 tcpstat.tcps_badsum++; 80 if (tcpprintfs) 81 printf("tcp cksum %x\n", ti->ti_sum); 82 goto drop; 83 } 84 } 85 86 /* 87 * Check that TCP offset makes sense, 88 * pull out TCP options and adjust length. 89 */ 90 off = ti->ti_off << 2; 91 if (off < sizeof (struct tcphdr) || off > tlen) { 92 tcpstat.tcps_badoff++; 93 goto drop; 94 } 95 tlen -= off; 96 ti->ti_len = tlen; 97 if (off > sizeof (struct tcphdr)) { 98 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 99 tcpstat.tcps_hdrops++; 100 goto drop; 101 } 102 ti = mtod(m, struct tcpiphdr *); 103 om = m_get(M_DONTWAIT); 104 if (om == 0) 105 goto drop; 106 om->m_len = off - sizeof (struct tcphdr); 107 { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 108 bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len); 109 m->m_len -= om->m_len; 110 bcopy(op+om->m_len, op, 111 (unsigned)(m->m_len-sizeof (struct tcpiphdr))); 112 } 113 } 114 tiflags = ti->ti_flags; 115 116 /* 117 * Drop TCP and IP headers. 118 */ 119 off += sizeof (struct ip); 120 m->m_off += off; 121 m->m_len -= off; 122 123 #if vax || pdp11 || ns16032 124 /* 125 * Convert TCP protocol specific fields to host format. 126 */ 127 ti->ti_seq = ntohl(ti->ti_seq); 128 ti->ti_ack = ntohl(ti->ti_ack); 129 ti->ti_win = ntohs(ti->ti_win); 130 ti->ti_urp = ntohs(ti->ti_urp); 131 #endif 132 133 /* 134 * Locate pcb for segment. 135 */ 136 inp = in_pcblookup 137 (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, 138 INPLOOKUP_WILDCARD); 139 140 /* 141 * If the state is CLOSED (i.e., TCB does not exist) then 142 * all data in the incoming segment is discarded. 143 */ 144 if (inp == 0) 145 goto dropwithreset; 146 tp = intotcpcb(inp); 147 if (tp == 0) 148 goto dropwithreset; 149 so = inp->inp_socket; 150 if (so->so_options & SO_DEBUG) { 151 ostate = tp->t_state; 152 tcp_saveti = *ti; 153 } 154 if (so->so_options & SO_ACCEPTCONN) { 155 so = sonewconn(so); 156 if (so == 0) 157 goto drop; 158 inp = (struct inpcb *)so->so_pcb; 159 inp->inp_laddr = ti->ti_dst; 160 inp->inp_lport = ti->ti_dport; 161 tp = intotcpcb(inp); 162 tp->t_state = TCPS_LISTEN; 163 } 164 165 /* 166 * Segment received on connection. 167 * Reset idle time and keep-alive timer. 168 */ 169 tp->t_idle = 0; 170 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 171 172 /* 173 * Process options. 174 */ 175 if (om) { 176 tcp_dooptions(tp, om); 177 om = 0; 178 } 179 180 /* 181 * Calculate amount of space in receive window, 182 * and then do TCP input processing. 183 */ 184 tp->rcv_wnd = sbspace(&so->so_rcv); 185 if (tp->rcv_wnd < 0) 186 tp->rcv_wnd = 0; 187 188 switch (tp->t_state) { 189 190 /* 191 * If the state is LISTEN then ignore segment if it contains an RST. 192 * If the segment contains an ACK then it is bad and send a RST. 193 * If it does not contain a SYN then it is not interesting; drop it. 194 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 195 * tp->iss, and send a segment: 196 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 197 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 198 * Fill in remote peer address fields if not previously specified. 199 * Enter SYN_RECEIVED state, and process any other fields of this 200 * segment in this state. 201 */ 202 case TCPS_LISTEN: { 203 struct mbuf *am = m_get(M_DONTWAIT); 204 register struct sockaddr_in *sin; 205 206 if (am == 0) 207 goto drop; 208 am->m_len = sizeof (struct sockaddr_in); 209 if (tiflags & TH_RST) 210 goto drop; 211 if (tiflags & TH_ACK) 212 goto dropwithreset; 213 if ((tiflags & TH_SYN) == 0) 214 goto drop; 215 sin = mtod(am, struct sockaddr_in *); 216 sin->sin_family = AF_INET; 217 sin->sin_addr = ti->ti_src; 218 sin->sin_port = ti->ti_sport; 219 laddr = inp->inp_laddr; 220 if (inp->inp_laddr.s_addr == 0) 221 inp->inp_laddr = ti->ti_dst; 222 if (in_pcbconnect(inp, am)) { 223 inp->inp_laddr = laddr; 224 m_free(am); 225 goto drop; 226 } 227 m_free(am); 228 tp->t_template = tcp_template(tp); 229 if (tp->t_template == 0) { 230 in_pcbdisconnect(inp); 231 inp->inp_laddr = laddr; 232 tp = 0; 233 goto drop; 234 } 235 tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; 236 tp->irs = ti->ti_seq; 237 tcp_sendseqinit(tp); 238 tcp_rcvseqinit(tp); 239 tp->t_state = TCPS_SYN_RECEIVED; 240 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 241 goto trimthenstep6; 242 } 243 244 /* 245 * If the state is SYN_SENT: 246 * if seg contains an ACK, but not for our SYN, drop the input. 247 * if seg contains a RST, then drop the connection. 248 * if seg does not contain SYN, then drop it. 249 * Otherwise this is an acceptable SYN segment 250 * initialize tp->rcv_nxt and tp->irs 251 * if seg contains ack then advance tp->snd_una 252 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 253 * arrange for segment to be acked (eventually) 254 * continue processing rest of data/controls, beginning with URG 255 */ 256 case TCPS_SYN_SENT: 257 if ((tiflags & TH_ACK) && 258 /* this should be SEQ_LT; is SEQ_LEQ for BBN vax TCP only */ 259 (SEQ_LT(ti->ti_ack, tp->iss) || 260 SEQ_GT(ti->ti_ack, tp->snd_max))) 261 goto dropwithreset; 262 if (tiflags & TH_RST) { 263 if (tiflags & TH_ACK) { 264 tcp_drop(tp, ECONNREFUSED); 265 tp = 0; 266 } 267 goto drop; 268 } 269 if ((tiflags & TH_SYN) == 0) 270 goto drop; 271 tp->snd_una = ti->ti_ack; 272 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 273 tp->snd_nxt = tp->snd_una; 274 tp->t_timer[TCPT_REXMT] = 0; 275 tp->irs = ti->ti_seq; 276 tcp_rcvseqinit(tp); 277 tp->t_flags |= TF_ACKNOW; 278 if (SEQ_GT(tp->snd_una, tp->iss)) { 279 soisconnected(so); 280 tp->t_state = TCPS_ESTABLISHED; 281 (void) tcp_reass(tp, (struct tcpiphdr *)0); 282 } else 283 tp->t_state = TCPS_SYN_RECEIVED; 284 goto trimthenstep6; 285 286 trimthenstep6: 287 /* 288 * Advance ti->ti_seq to correspond to first data byte. 289 * If data, trim to stay within window, 290 * dropping FIN if necessary. 291 */ 292 ti->ti_seq++; 293 if (ti->ti_len > tp->rcv_wnd) { 294 todrop = ti->ti_len - tp->rcv_wnd; 295 m_adj(m, -todrop); 296 ti->ti_len = tp->rcv_wnd; 297 ti->ti_flags &= ~TH_FIN; 298 } 299 tp->snd_wl1 = ti->ti_seq - 1; 300 goto step6; 301 } 302 303 /* 304 * States other than LISTEN or SYN_SENT. 305 * First check that at least some bytes of segment are within 306 * receive window. 307 */ 308 if (tp->rcv_wnd == 0) { 309 /* 310 * If window is closed can only take segments at 311 * window edge, and have to drop data and PUSH from 312 * incoming segments. 313 */ 314 if (tp->rcv_nxt != ti->ti_seq) 315 goto dropafterack; 316 if (ti->ti_len > 0) { 317 m_adj(m, ti->ti_len); 318 ti->ti_len = 0; 319 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 320 } 321 } else { 322 /* 323 * If segment begins before rcv_nxt, drop leading 324 * data (and SYN); if nothing left, just ack. 325 */ 326 todrop = tp->rcv_nxt - ti->ti_seq; 327 if (todrop > 0) { 328 if (tiflags & TH_SYN) { 329 tiflags &= ~TH_SYN; 330 ti->ti_flags &= ~TH_SYN; 331 ti->ti_seq++; 332 if (ti->ti_urp > 1) 333 ti->ti_urp--; 334 else 335 tiflags &= ~TH_URG; 336 todrop--; 337 } 338 if (todrop > ti->ti_len || 339 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) 340 goto dropafterack; 341 m_adj(m, todrop); 342 ti->ti_seq += todrop; 343 ti->ti_len -= todrop; 344 if (ti->ti_urp > todrop) 345 ti->ti_urp -= todrop; 346 else { 347 tiflags &= ~TH_URG; 348 ti->ti_flags &= ~TH_URG; 349 ti->ti_urp = 0; 350 } 351 } 352 /* 353 * If segment ends after window, drop trailing data 354 * (and PUSH and FIN); if nothing left, just ACK. 355 */ 356 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 357 if (todrop > 0) { 358 if (todrop >= ti->ti_len) 359 goto dropafterack; 360 m_adj(m, -todrop); 361 ti->ti_len -= todrop; 362 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 363 } 364 } 365 366 /* 367 * If a segment is received on a connection after the 368 * user processes are gone, then RST the other end. 369 */ 370 if (so->so_state & SS_NOFDREF) { 371 tcp_close(tp); 372 tp = 0; 373 goto dropwithreset; 374 } 375 376 /* 377 * If the RST bit is set examine the state: 378 * SYN_RECEIVED STATE: 379 * If passive open, return to LISTEN state. 380 * If active open, inform user that connection was refused. 381 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 382 * Inform user that connection was reset, and close tcb. 383 * CLOSING, LAST_ACK, TIME_WAIT STATES 384 * Close the tcb. 385 */ 386 if (tiflags&TH_RST) switch (tp->t_state) { 387 388 case TCPS_SYN_RECEIVED: 389 tcp_drop(tp, ECONNREFUSED); 390 tp = 0; 391 goto drop; 392 393 case TCPS_ESTABLISHED: 394 case TCPS_FIN_WAIT_1: 395 case TCPS_FIN_WAIT_2: 396 case TCPS_CLOSE_WAIT: 397 tcp_drop(tp, ECONNRESET); 398 tp = 0; 399 goto drop; 400 401 case TCPS_CLOSING: 402 case TCPS_LAST_ACK: 403 case TCPS_TIME_WAIT: 404 tcp_close(tp); 405 tp = 0; 406 goto drop; 407 } 408 409 /* 410 * If a SYN is in the window, then this is an 411 * error and we send an RST and drop the connection. 412 */ 413 if (tiflags & TH_SYN) { 414 tcp_drop(tp, ECONNRESET); 415 tp = 0; 416 goto dropwithreset; 417 } 418 419 /* 420 * If the ACK bit is off we drop the segment and return. 421 */ 422 if ((tiflags & TH_ACK) == 0) 423 goto drop; 424 425 /* 426 * Ack processing. 427 */ 428 switch (tp->t_state) { 429 430 /* 431 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 432 * ESTABLISHED state and continue processing, othewise 433 * send an RST. 434 */ 435 case TCPS_SYN_RECEIVED: 436 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 437 SEQ_GT(ti->ti_ack, tp->snd_max)) 438 goto dropwithreset; 439 tp->snd_una++; /* SYN acked */ 440 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 441 tp->snd_nxt = tp->snd_una; 442 tp->t_timer[TCPT_REXMT] = 0; 443 soisconnected(so); 444 tp->t_state = TCPS_ESTABLISHED; 445 (void) tcp_reass(tp, (struct tcpiphdr *)0); 446 tp->snd_wl1 = ti->ti_seq - 1; 447 /* fall into ... */ 448 449 /* 450 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 451 * ACKs. If the ack is in the range 452 * tp->snd_una < ti->ti_ack <= tp->snd_max 453 * then advance tp->snd_una to ti->ti_ack and drop 454 * data from the retransmission queue. If this ACK reflects 455 * more up to date window information we update our window information. 456 */ 457 case TCPS_ESTABLISHED: 458 case TCPS_FIN_WAIT_1: 459 case TCPS_FIN_WAIT_2: 460 case TCPS_CLOSE_WAIT: 461 case TCPS_CLOSING: 462 case TCPS_LAST_ACK: 463 case TCPS_TIME_WAIT: 464 #define ourfinisacked (acked > 0) 465 466 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) 467 break; 468 if (SEQ_GT(ti->ti_ack, tp->snd_max)) 469 goto dropafterack; 470 acked = ti->ti_ack - tp->snd_una; 471 472 /* 473 * If transmit timer is running and timed sequence 474 * number was acked, update smoothed round trip time. 475 */ 476 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 477 if (tp->t_srtt == 0) 478 tp->t_srtt = tp->t_rtt; 479 else 480 tp->t_srtt = 481 tcp_alpha * tp->t_srtt + 482 (1 - tcp_alpha) * tp->t_rtt; 483 /* printf("rtt %d srtt*100 now %d\n", tp->t_rtt, (int)(tp->t_srtt*100)); */ 484 tp->t_rtt = 0; 485 } 486 487 if (ti->ti_ack == tp->snd_max) 488 tp->t_timer[TCPT_REXMT] = 0; 489 else { 490 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 491 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 492 tp->t_rtt = 1; 493 tp->t_rxtshift = 0; 494 } 495 if (acked > so->so_snd.sb_cc) { 496 sbdrop(&so->so_snd, so->so_snd.sb_cc); 497 tp->snd_wnd -= so->so_snd.sb_cc; 498 } else { 499 sbdrop(&so->so_snd, acked); 500 tp->snd_wnd -= acked; 501 acked = 0; 502 } 503 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 504 sowwakeup(so); 505 tp->snd_una = ti->ti_ack; 506 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 507 tp->snd_nxt = tp->snd_una; 508 509 switch (tp->t_state) { 510 511 /* 512 * In FIN_WAIT_1 STATE in addition to the processing 513 * for the ESTABLISHED state if our FIN is now acknowledged 514 * then enter FIN_WAIT_2. 515 */ 516 case TCPS_FIN_WAIT_1: 517 if (ourfinisacked) { 518 /* 519 * If we can't receive any more 520 * data, then closing user can proceed. 521 */ 522 if (so->so_state & SS_CANTRCVMORE) 523 soisdisconnected(so); 524 tp->t_state = TCPS_FIN_WAIT_2; 525 } 526 break; 527 528 /* 529 * In CLOSING STATE in addition to the processing for 530 * the ESTABLISHED state if the ACK acknowledges our FIN 531 * then enter the TIME-WAIT state, otherwise ignore 532 * the segment. 533 */ 534 case TCPS_CLOSING: 535 if (ourfinisacked) { 536 tp->t_state = TCPS_TIME_WAIT; 537 tcp_canceltimers(tp); 538 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 539 soisdisconnected(so); 540 } 541 break; 542 543 /* 544 * The only thing that can arrive in LAST_ACK state 545 * is an acknowledgment of our FIN. If our FIN is now 546 * acknowledged, delete the TCB, enter the closed state 547 * and return. 548 */ 549 case TCPS_LAST_ACK: 550 if (ourfinisacked) { 551 tcp_close(tp); 552 tp = 0; 553 } 554 goto drop; 555 556 /* 557 * In TIME_WAIT state the only thing that should arrive 558 * is a retransmission of the remote FIN. Acknowledge 559 * it and restart the finack timer. 560 */ 561 case TCPS_TIME_WAIT: 562 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 563 goto dropafterack; 564 } 565 #undef ourfinisacked 566 } 567 568 step6: 569 /* 570 * Update window information. 571 */ 572 if (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 573 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 574 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)) { 575 tp->snd_wnd = ti->ti_win; 576 tp->snd_wl1 = ti->ti_seq; 577 tp->snd_wl2 = ti->ti_ack; 578 if (tp->snd_wnd != 0) 579 tp->t_timer[TCPT_PERSIST] = 0; 580 } 581 582 /* 583 * Process segments with URG. 584 */ 585 if ((tiflags & TH_URG) && ti->ti_urp && 586 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 587 /* 588 * If this segment advances the known urgent pointer, 589 * then mark the data stream. This should not happen 590 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 591 * a FIN has been received from the remote side. 592 * In these states we ignore the URG. 593 */ 594 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 595 tp->rcv_up = ti->ti_seq + ti->ti_urp; 596 so->so_oobmark = so->so_rcv.sb_cc + 597 (tp->rcv_up - tp->rcv_nxt) - 1; 598 if (so->so_oobmark == 0) 599 so->so_state |= SS_RCVATMARK; 600 sohasoutofband(so); 601 tp->t_oobflags &= ~TCPOOB_HAVEDATA; 602 } 603 /* 604 * Remove out of band data so doesn't get presented to user. 605 * This can happen independent of advancing the URG pointer, 606 * but if two URG's are pending at once, some out-of-band 607 * data may creep in... ick. 608 */ 609 if (ti->ti_urp <= ti->ti_len) 610 tcp_pulloutofband(so, ti); 611 } 612 613 /* 614 * Process the segment text, merging it into the TCP sequencing queue, 615 * and arranging for acknowledgment of receipt if necessary. 616 * This process logically involves adjusting tp->rcv_wnd as data 617 * is presented to the user (this happens in tcp_usrreq.c, 618 * case PRU_RCVD). If a FIN has already been received on this 619 * connection then we just ignore the text. 620 */ 621 if ((ti->ti_len || (tiflags&TH_FIN)) && 622 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 623 tiflags = tcp_reass(tp, ti); 624 if (tcpnodelack == 0) 625 tp->t_flags |= TF_DELACK; 626 else 627 tp->t_flags |= TF_ACKNOW; 628 } else { 629 m_freem(m); 630 tiflags &= ~TH_FIN; 631 } 632 633 /* 634 * If FIN is received ACK the FIN and let the user know 635 * that the connection is closing. 636 */ 637 if (tiflags & TH_FIN) { 638 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 639 socantrcvmore(so); 640 tp->t_flags |= TF_ACKNOW; 641 tp->rcv_nxt++; 642 } 643 switch (tp->t_state) { 644 645 /* 646 * In SYN_RECEIVED and ESTABLISHED STATES 647 * enter the CLOSE_WAIT state. 648 */ 649 case TCPS_SYN_RECEIVED: 650 case TCPS_ESTABLISHED: 651 tp->t_state = TCPS_CLOSE_WAIT; 652 break; 653 654 /* 655 * If still in FIN_WAIT_1 STATE FIN has not been acked so 656 * enter the CLOSING state. 657 */ 658 case TCPS_FIN_WAIT_1: 659 tp->t_state = TCPS_CLOSING; 660 break; 661 662 /* 663 * In FIN_WAIT_2 state enter the TIME_WAIT state, 664 * starting the time-wait timer, turning off the other 665 * standard timers. 666 */ 667 case TCPS_FIN_WAIT_2: 668 tp->t_state = TCPS_TIME_WAIT; 669 tcp_canceltimers(tp); 670 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 671 soisdisconnected(so); 672 break; 673 674 /* 675 * In TIME_WAIT state restart the 2 MSL time_wait timer. 676 */ 677 case TCPS_TIME_WAIT: 678 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 679 break; 680 } 681 } 682 if (so->so_options & SO_DEBUG) 683 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 684 685 /* 686 * Return any desired output. 687 */ 688 (void) tcp_output(tp); 689 return; 690 691 dropafterack: 692 /* 693 * Generate an ACK dropping incoming segment if it occupies 694 * sequence space, where the ACK reflects our state. 695 */ 696 if ((tiflags&TH_RST) || 697 tlen == 0 && (tiflags&(TH_SYN|TH_FIN)) == 0) 698 goto drop; 699 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 700 tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 701 tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 702 return; 703 704 dropwithreset: 705 if (om) 706 (void) m_free(om); 707 /* 708 * Generate a RST, dropping incoming segment. 709 * Make ACK acceptable to originator of segment. 710 */ 711 if (tiflags & TH_RST) 712 goto drop; 713 if (tiflags & TH_ACK) 714 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 715 else { 716 if (tiflags & TH_SYN) 717 ti->ti_len++; 718 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 719 TH_RST|TH_ACK); 720 } 721 return; 722 723 drop: 724 /* 725 * Drop space held by incoming segment and return. 726 */ 727 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 728 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 729 m_freem(m); 730 return; 731 } 732 733 tcp_dooptions(tp, om) 734 struct tcpcb *tp; 735 struct mbuf *om; 736 { 737 register u_char *cp; 738 int opt, optlen, cnt; 739 740 cp = mtod(om, u_char *); 741 cnt = om->m_len; 742 for (; cnt > 0; cnt -= optlen, cp += optlen) { 743 opt = cp[0]; 744 if (opt == TCPOPT_EOL) 745 break; 746 if (opt == TCPOPT_NOP) 747 optlen = 1; 748 else 749 optlen = cp[1]; 750 switch (opt) { 751 752 default: 753 break; 754 755 case TCPOPT_MAXSEG: 756 if (optlen != 4) 757 continue; 758 tp->t_maxseg = *(u_short *)(cp + 2); 759 #if vax || pdp11 || ns16032 760 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 761 #endif 762 break; 763 } 764 } 765 (void) m_free(om); 766 } 767 768 /* 769 * Pull out of band byte out of a segment so 770 * it doesn't appear in the user's data queue. 771 * It is still reflected in the segment length for 772 * sequencing purposes. 773 */ 774 tcp_pulloutofband(so, ti) 775 struct socket *so; 776 struct tcpiphdr *ti; 777 { 778 register struct mbuf *m; 779 int cnt = ti->ti_urp - 1; 780 781 m = dtom(ti); 782 while (cnt >= 0) { 783 if (m->m_len > cnt) { 784 char *cp = mtod(m, caddr_t) + cnt; 785 struct tcpcb *tp = sototcpcb(so); 786 787 tp->t_iobc = *cp; 788 tp->t_oobflags |= TCPOOB_HAVEDATA; 789 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 790 m->m_len--; 791 return; 792 } 793 cnt -= m->m_len; 794 m = m->m_next; 795 if (m == 0) 796 break; 797 } 798 panic("tcp_pulloutofband"); 799 } 800 801 /* 802 * Insert segment ti into reassembly queue of tcp with 803 * control block tp. Return TH_FIN if reassembly now includes 804 * a segment with FIN. 805 */ 806 tcp_reass(tp, ti) 807 register struct tcpcb *tp; 808 register struct tcpiphdr *ti; 809 { 810 register struct tcpiphdr *q; 811 struct socket *so = tp->t_inpcb->inp_socket; 812 struct mbuf *m; 813 int flags; 814 815 /* 816 * Call with ti==0 after become established to 817 * force pre-ESTABLISHED data up to user socket. 818 */ 819 if (ti == 0) 820 goto present; 821 822 /* 823 * Find a segment which begins after this one does. 824 */ 825 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 826 q = (struct tcpiphdr *)q->ti_next) 827 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 828 break; 829 830 /* 831 * If there is a preceding segment, it may provide some of 832 * our data already. If so, drop the data from the incoming 833 * segment. If it provides all of our data, drop us. 834 */ 835 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 836 register int i; 837 q = (struct tcpiphdr *)q->ti_prev; 838 /* conversion to int (in i) handles seq wraparound */ 839 i = q->ti_seq + q->ti_len - ti->ti_seq; 840 if (i > 0) { 841 if (i >= ti->ti_len) 842 goto drop; 843 m_adj(dtom(ti), i); 844 ti->ti_len -= i; 845 ti->ti_seq += i; 846 } 847 q = (struct tcpiphdr *)(q->ti_next); 848 } 849 850 /* 851 * While we overlap succeeding segments trim them or, 852 * if they are completely covered, dequeue them. 853 */ 854 while (q != (struct tcpiphdr *)tp) { 855 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 856 if (i <= 0) 857 break; 858 if (i < q->ti_len) { 859 q->ti_seq += i; 860 q->ti_len -= i; 861 m_adj(dtom(q), i); 862 break; 863 } 864 q = (struct tcpiphdr *)q->ti_next; 865 m = dtom(q->ti_prev); 866 remque(q->ti_prev); 867 m_freem(m); 868 } 869 870 /* 871 * Stick new segment in its place. 872 */ 873 insque(ti, q->ti_prev); 874 875 present: 876 /* 877 * Present data to user, advancing rcv_nxt through 878 * completed sequence space. 879 */ 880 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 881 return (0); 882 ti = tp->seg_next; 883 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 884 return (0); 885 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 886 return (0); 887 do { 888 tp->rcv_nxt += ti->ti_len; 889 flags = ti->ti_flags & TH_FIN; 890 remque(ti); 891 m = dtom(ti); 892 ti = (struct tcpiphdr *)ti->ti_next; 893 if (so->so_state & SS_CANTRCVMORE) 894 m_freem(m); 895 else { 896 SBCHECK(&so->so_rcv, "tcp_input before"); 897 sbappend(&so->so_rcv, m); 898 SBCHECK(&so->so_rcv, "tcp_input after"); 899 } 900 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 901 sorwakeup(so); 902 return (flags); 903 drop: 904 m_freem(dtom(ti)); 905 return (0); 906 } 907