1 /* tcp_input.c 1.95 83/06/14 */ 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 "../h/errno.h" 10 11 #include "../net/if.h" 12 #include "../net/route.h" 13 14 #include "../netinet/in.h" 15 #include "../netinet/in_pcb.h" 16 #include "../netinet/in_systm.h" 17 #include "../netinet/ip.h" 18 #include "../netinet/ip_var.h" 19 #include "../netinet/tcp.h" 20 #include "../netinet/tcp_fsm.h" 21 #include "../netinet/tcp_seq.h" 22 #include "../netinet/tcp_timer.h" 23 #include "../netinet/tcp_var.h" 24 #include "../netinet/tcpip.h" 25 #include "../netinet/tcp_debug.h" 26 27 int tcpprintfs = 0; 28 int tcpcksum = 1; 29 struct tcpiphdr tcp_saveti; 30 extern tcpnodelack; 31 32 struct tcpcb *tcp_newtcpcb(); 33 /* 34 * TCP input routine, follows pages 65-76 of the 35 * protocol specification dated September, 1981 very closely. 36 */ 37 tcp_input(m0) 38 struct mbuf *m0; 39 { 40 register struct tcpiphdr *ti; 41 struct inpcb *inp; 42 register struct mbuf *m; 43 struct mbuf *om = 0; 44 int len, tlen, off; 45 register struct tcpcb *tp = 0; 46 register int tiflags; 47 struct socket *so; 48 int todrop, acked; 49 short ostate; 50 struct in_addr laddr; 51 int dropsocket = 0; 52 53 /* 54 * Get IP and TCP header together in first mbuf. 55 * Note: IP leaves IP header in first mbuf. 56 */ 57 m = m0; 58 ti = mtod(m, struct tcpiphdr *); 59 if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) 60 ip_stripoptions((struct ip *)ti, (struct mbuf *)0); 61 if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { 62 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 63 tcpstat.tcps_hdrops++; 64 return; 65 } 66 ti = mtod(m, struct tcpiphdr *); 67 } 68 69 /* 70 * Checksum extended TCP header and data. 71 */ 72 tlen = ((struct ip *)ti)->ip_len; 73 len = sizeof (struct ip) + tlen; 74 if (tcpcksum) { 75 ti->ti_next = ti->ti_prev = 0; 76 ti->ti_x1 = 0; 77 ti->ti_len = (u_short)tlen; 78 ti->ti_len = htons((u_short)ti->ti_len); 79 if (ti->ti_sum = in_cksum(m, len)) { 80 if (tcpprintfs) 81 printf("tcp sum: src %x\n", ti->ti_src); 82 tcpstat.tcps_badsum++; 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 if (tcpprintfs) 94 printf("tcp off: src %x off %d\n", ti->ti_src, off); 95 tcpstat.tcps_badoff++; 96 goto drop; 97 } 98 tlen -= off; 99 ti->ti_len = tlen; 100 if (off > sizeof (struct tcphdr)) { 101 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 102 tcpstat.tcps_hdrops++; 103 return; 104 } 105 ti = mtod(m, struct tcpiphdr *); 106 om = m_get(M_DONTWAIT, MT_DATA); 107 if (om == 0) 108 goto drop; 109 om->m_len = off - sizeof (struct tcphdr); 110 { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 111 bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len); 112 m->m_len -= om->m_len; 113 bcopy(op+om->m_len, op, 114 (unsigned)(m->m_len-sizeof (struct tcpiphdr))); 115 } 116 } 117 tiflags = ti->ti_flags; 118 119 /* 120 * Drop TCP and IP headers. 121 */ 122 off += sizeof (struct ip); 123 m->m_off += off; 124 m->m_len -= off; 125 126 /* 127 * Convert TCP protocol specific fields to host format. 128 */ 129 ti->ti_seq = ntohl(ti->ti_seq); 130 ti->ti_ack = ntohl(ti->ti_ack); 131 ti->ti_win = ntohs(ti->ti_win); 132 ti->ti_urp = ntohs(ti->ti_urp); 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 /* 160 * This is ugly, but .... 161 * 162 * Mark socket as temporary until we're 163 * committed to keeping it. The code at 164 * ``drop'' and ``dropwithreset'' check the 165 * flag dropsocket to see if the temporary 166 * socket created here should be discarded. 167 * We mark the socket as discardable until 168 * we're committed to it below in TCPS_LISTEN. 169 */ 170 dropsocket++; 171 inp = (struct inpcb *)so->so_pcb; 172 inp->inp_laddr = ti->ti_dst; 173 inp->inp_lport = ti->ti_dport; 174 tp = intotcpcb(inp); 175 tp->t_state = TCPS_LISTEN; 176 } 177 178 /* 179 * Segment received on connection. 180 * Reset idle time and keep-alive timer. 181 */ 182 tp->t_idle = 0; 183 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 184 185 /* 186 * Process options. 187 */ 188 if (om) { 189 tcp_dooptions(tp, om); 190 om = 0; 191 } 192 193 /* 194 * Calculate amount of space in receive window, 195 * and then do TCP input processing. 196 */ 197 tp->rcv_wnd = sbspace(&so->so_rcv); 198 if (tp->rcv_wnd < 0) 199 tp->rcv_wnd = 0; 200 201 switch (tp->t_state) { 202 203 /* 204 * If the state is LISTEN then ignore segment if it contains an RST. 205 * If the segment contains an ACK then it is bad and send a RST. 206 * If it does not contain a SYN then it is not interesting; drop it. 207 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 208 * tp->iss, and send a segment: 209 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 210 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 211 * Fill in remote peer address fields if not previously specified. 212 * Enter SYN_RECEIVED state, and process any other fields of this 213 * segment in this state. 214 */ 215 case TCPS_LISTEN: { 216 struct mbuf *am; 217 register struct sockaddr_in *sin; 218 219 if (tiflags & TH_RST) 220 goto drop; 221 if (tiflags & TH_ACK) 222 goto dropwithreset; 223 if ((tiflags & TH_SYN) == 0) 224 goto drop; 225 am = m_get(M_DONTWAIT, MT_SONAME); 226 if (am == NULL) 227 goto drop; 228 am->m_len = sizeof (struct sockaddr_in); 229 sin = mtod(am, struct sockaddr_in *); 230 sin->sin_family = AF_INET; 231 sin->sin_addr = ti->ti_src; 232 sin->sin_port = ti->ti_sport; 233 laddr = inp->inp_laddr; 234 if (inp->inp_laddr.s_addr == INADDR_ANY) 235 inp->inp_laddr = ti->ti_dst; 236 if (in_pcbconnect(inp, am)) { 237 inp->inp_laddr = laddr; 238 (void) m_free(am); 239 goto drop; 240 } 241 (void) m_free(am); 242 tp->t_template = tcp_template(tp); 243 if (tp->t_template == 0) { 244 in_pcbdisconnect(inp); 245 inp->inp_laddr = laddr; 246 tp = 0; 247 goto drop; 248 } 249 tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; 250 tp->irs = ti->ti_seq; 251 tcp_sendseqinit(tp); 252 tcp_rcvseqinit(tp); 253 tp->t_state = TCPS_SYN_RECEIVED; 254 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 255 dropsocket = 0; /* committed to socket */ 256 goto trimthenstep6; 257 } 258 259 /* 260 * If the state is SYN_SENT: 261 * if seg contains an ACK, but not for our SYN, drop the input. 262 * if seg contains a RST, then drop the connection. 263 * if seg does not contain SYN, then drop it. 264 * Otherwise this is an acceptable SYN segment 265 * initialize tp->rcv_nxt and tp->irs 266 * if seg contains ack then advance tp->snd_una 267 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 268 * arrange for segment to be acked (eventually) 269 * continue processing rest of data/controls, beginning with URG 270 */ 271 case TCPS_SYN_SENT: 272 if ((tiflags & TH_ACK) && 273 /* this should be SEQ_LT; is SEQ_LEQ for BBN vax TCP only */ 274 (SEQ_LT(ti->ti_ack, tp->iss) || 275 SEQ_GT(ti->ti_ack, tp->snd_max))) 276 goto dropwithreset; 277 if (tiflags & TH_RST) { 278 if (tiflags & TH_ACK) 279 tp = tcp_drop(tp, ECONNREFUSED); 280 goto drop; 281 } 282 if ((tiflags & TH_SYN) == 0) 283 goto drop; 284 tp->snd_una = ti->ti_ack; 285 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 286 tp->snd_nxt = tp->snd_una; 287 tp->t_timer[TCPT_REXMT] = 0; 288 tp->irs = ti->ti_seq; 289 tcp_rcvseqinit(tp); 290 tp->t_flags |= TF_ACKNOW; 291 if (SEQ_GT(tp->snd_una, tp->iss)) { 292 soisconnected(so); 293 tp->t_state = TCPS_ESTABLISHED; 294 (void) tcp_reass(tp, (struct tcpiphdr *)0); 295 } else 296 tp->t_state = TCPS_SYN_RECEIVED; 297 goto trimthenstep6; 298 299 trimthenstep6: 300 /* 301 * Advance ti->ti_seq to correspond to first data byte. 302 * If data, trim to stay within window, 303 * dropping FIN if necessary. 304 */ 305 ti->ti_seq++; 306 if (ti->ti_len > tp->rcv_wnd) { 307 todrop = ti->ti_len - tp->rcv_wnd; 308 m_adj(m, -todrop); 309 ti->ti_len = tp->rcv_wnd; 310 ti->ti_flags &= ~TH_FIN; 311 } 312 tp->snd_wl1 = ti->ti_seq - 1; 313 goto step6; 314 } 315 316 /* 317 * States other than LISTEN or SYN_SENT. 318 * First check that at least some bytes of segment are within 319 * receive window. 320 */ 321 if (tp->rcv_wnd == 0) { 322 /* 323 * If window is closed can only take segments at 324 * window edge, and have to drop data and PUSH from 325 * incoming segments. 326 */ 327 if (tp->rcv_nxt != ti->ti_seq) 328 goto dropafterack; 329 if (ti->ti_len > 0) { 330 m_adj(m, ti->ti_len); 331 ti->ti_len = 0; 332 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 333 } 334 } else { 335 /* 336 * If segment begins before rcv_nxt, drop leading 337 * data (and SYN); if nothing left, just ack. 338 */ 339 todrop = tp->rcv_nxt - ti->ti_seq; 340 if (todrop > 0) { 341 if (tiflags & TH_SYN) { 342 tiflags &= ~TH_SYN; 343 ti->ti_flags &= ~TH_SYN; 344 ti->ti_seq++; 345 if (ti->ti_urp > 1) 346 ti->ti_urp--; 347 else 348 tiflags &= ~TH_URG; 349 todrop--; 350 } 351 if (todrop > ti->ti_len || 352 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) 353 goto dropafterack; 354 m_adj(m, todrop); 355 ti->ti_seq += todrop; 356 ti->ti_len -= todrop; 357 if (ti->ti_urp > todrop) 358 ti->ti_urp -= todrop; 359 else { 360 tiflags &= ~TH_URG; 361 ti->ti_flags &= ~TH_URG; 362 ti->ti_urp = 0; 363 } 364 } 365 /* 366 * If segment ends after window, drop trailing data 367 * (and PUSH and FIN); if nothing left, just ACK. 368 */ 369 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 370 if (todrop > 0) { 371 if (todrop >= ti->ti_len) 372 goto dropafterack; 373 m_adj(m, -todrop); 374 ti->ti_len -= todrop; 375 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 376 } 377 } 378 379 /* 380 * If data is received on a connection after the 381 * user processes are gone, then RST the other end. 382 */ 383 if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && 384 ti->ti_len) { 385 tp = tcp_close(tp); 386 goto dropwithreset; 387 } 388 389 /* 390 * If the RST bit is set examine the state: 391 * SYN_RECEIVED STATE: 392 * If passive open, return to LISTEN state. 393 * If active open, inform user that connection was refused. 394 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 395 * Inform user that connection was reset, and close tcb. 396 * CLOSING, LAST_ACK, TIME_WAIT STATES 397 * Close the tcb. 398 */ 399 if (tiflags&TH_RST) switch (tp->t_state) { 400 401 case TCPS_SYN_RECEIVED: 402 tp = tcp_drop(tp, ECONNREFUSED); 403 goto drop; 404 405 case TCPS_ESTABLISHED: 406 case TCPS_FIN_WAIT_1: 407 case TCPS_FIN_WAIT_2: 408 case TCPS_CLOSE_WAIT: 409 tp = tcp_drop(tp, ECONNRESET); 410 goto drop; 411 412 case TCPS_CLOSING: 413 case TCPS_LAST_ACK: 414 case TCPS_TIME_WAIT: 415 tp = tcp_close(tp); 416 goto drop; 417 } 418 419 /* 420 * If a SYN is in the window, then this is an 421 * error and we send an RST and drop the connection. 422 */ 423 if (tiflags & TH_SYN) { 424 tp = tcp_drop(tp, ECONNRESET); 425 goto dropwithreset; 426 } 427 428 /* 429 * If the ACK bit is off we drop the segment and return. 430 */ 431 if ((tiflags & TH_ACK) == 0) 432 goto drop; 433 434 /* 435 * Ack processing. 436 */ 437 switch (tp->t_state) { 438 439 /* 440 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 441 * ESTABLISHED state and continue processing, othewise 442 * send an RST. 443 */ 444 case TCPS_SYN_RECEIVED: 445 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 446 SEQ_GT(ti->ti_ack, tp->snd_max)) 447 goto dropwithreset; 448 tp->snd_una++; /* SYN acked */ 449 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 450 tp->snd_nxt = tp->snd_una; 451 tp->t_timer[TCPT_REXMT] = 0; 452 soisconnected(so); 453 tp->t_state = TCPS_ESTABLISHED; 454 (void) tcp_reass(tp, (struct tcpiphdr *)0); 455 tp->snd_wl1 = ti->ti_seq - 1; 456 /* fall into ... */ 457 458 /* 459 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 460 * ACKs. If the ack is in the range 461 * tp->snd_una < ti->ti_ack <= tp->snd_max 462 * then advance tp->snd_una to ti->ti_ack and drop 463 * data from the retransmission queue. If this ACK reflects 464 * more up to date window information we update our window information. 465 */ 466 case TCPS_ESTABLISHED: 467 case TCPS_FIN_WAIT_1: 468 case TCPS_FIN_WAIT_2: 469 case TCPS_CLOSE_WAIT: 470 case TCPS_CLOSING: 471 case TCPS_LAST_ACK: 472 case TCPS_TIME_WAIT: 473 #define ourfinisacked (acked > 0) 474 475 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) 476 break; 477 if (SEQ_GT(ti->ti_ack, tp->snd_max)) 478 goto dropafterack; 479 acked = ti->ti_ack - tp->snd_una; 480 481 /* 482 * If transmit timer is running and timed sequence 483 * number was acked, update smoothed round trip time. 484 */ 485 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 486 if (tp->t_srtt == 0) 487 tp->t_srtt = tp->t_rtt; 488 else 489 tp->t_srtt = 490 tcp_alpha * tp->t_srtt + 491 (1 - tcp_alpha) * tp->t_rtt; 492 tp->t_rtt = 0; 493 } 494 495 if (ti->ti_ack == tp->snd_max) 496 tp->t_timer[TCPT_REXMT] = 0; 497 else { 498 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 499 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 500 tp->t_rtt = 1; 501 tp->t_rxtshift = 0; 502 } 503 if (acked > so->so_snd.sb_cc) { 504 sbdrop(&so->so_snd, so->so_snd.sb_cc); 505 tp->snd_wnd -= so->so_snd.sb_cc; 506 } else { 507 sbdrop(&so->so_snd, acked); 508 tp->snd_wnd -= acked; 509 acked = 0; 510 } 511 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 512 sowwakeup(so); 513 tp->snd_una = ti->ti_ack; 514 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 515 tp->snd_nxt = tp->snd_una; 516 517 switch (tp->t_state) { 518 519 /* 520 * In FIN_WAIT_1 STATE in addition to the processing 521 * for the ESTABLISHED state if our FIN is now acknowledged 522 * then enter FIN_WAIT_2. 523 */ 524 case TCPS_FIN_WAIT_1: 525 if (ourfinisacked) { 526 /* 527 * If we can't receive any more 528 * data, then closing user can proceed. 529 */ 530 if (so->so_state & SS_CANTRCVMORE) 531 soisdisconnected(so); 532 tp->t_state = TCPS_FIN_WAIT_2; 533 } 534 break; 535 536 /* 537 * In CLOSING STATE in addition to the processing for 538 * the ESTABLISHED state if the ACK acknowledges our FIN 539 * then enter the TIME-WAIT state, otherwise ignore 540 * the segment. 541 */ 542 case TCPS_CLOSING: 543 if (ourfinisacked) { 544 tp->t_state = TCPS_TIME_WAIT; 545 tcp_canceltimers(tp); 546 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 547 soisdisconnected(so); 548 } 549 break; 550 551 /* 552 * The only thing that can arrive in LAST_ACK state 553 * is an acknowledgment of our FIN. If our FIN is now 554 * acknowledged, delete the TCB, enter the closed state 555 * and return. 556 */ 557 case TCPS_LAST_ACK: 558 if (ourfinisacked) 559 tp = tcp_close(tp); 560 goto drop; 561 562 /* 563 * In TIME_WAIT state the only thing that should arrive 564 * is a retransmission of the remote FIN. Acknowledge 565 * it and restart the finack timer. 566 */ 567 case TCPS_TIME_WAIT: 568 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 569 goto dropafterack; 570 } 571 #undef ourfinisacked 572 } 573 574 step6: 575 /* 576 * Update window information. 577 */ 578 if (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 579 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 580 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)) { 581 tp->snd_wnd = ti->ti_win; 582 tp->snd_wl1 = ti->ti_seq; 583 tp->snd_wl2 = ti->ti_ack; 584 if (tp->snd_wnd != 0) 585 tp->t_timer[TCPT_PERSIST] = 0; 586 } 587 588 /* 589 * Process segments with URG. 590 */ 591 if ((tiflags & TH_URG) && ti->ti_urp && 592 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 593 /* 594 * This is a kludge, but if we receive accept 595 * random urgent pointers, we'll crash in 596 * soreceive. It's hard to imagine someone 597 * actually wanting to send this much urgent data. 598 */ 599 if (ti->ti_urp > tp->t_maxseg) { /* XXX */ 600 ti->ti_urp = 0; /* XXX */ 601 tiflags &= ~TH_URG; /* XXX */ 602 ti->ti_flags &= ~TH_URG; /* XXX */ 603 goto badurp; /* XXX */ 604 } 605 /* 606 * If this segment advances the known urgent pointer, 607 * then mark the data stream. This should not happen 608 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 609 * a FIN has been received from the remote side. 610 * In these states we ignore the URG. 611 */ 612 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 613 tp->rcv_up = ti->ti_seq + ti->ti_urp; 614 so->so_oobmark = so->so_rcv.sb_cc + 615 (tp->rcv_up - tp->rcv_nxt) - 1; 616 if (so->so_oobmark == 0) 617 so->so_state |= SS_RCVATMARK; 618 sohasoutofband(so); 619 tp->t_oobflags &= ~TCPOOB_HAVEDATA; 620 } 621 /* 622 * Remove out of band data so doesn't get presented to user. 623 * This can happen independent of advancing the URG pointer, 624 * but if two URG's are pending at once, some out-of-band 625 * data may creep in... ick. 626 */ 627 if (ti->ti_urp <= ti->ti_len) 628 tcp_pulloutofband(so, ti); 629 } 630 badurp: /* XXX */ 631 632 /* 633 * Process the segment text, merging it into the TCP sequencing queue, 634 * and arranging for acknowledgment of receipt if necessary. 635 * This process logically involves adjusting tp->rcv_wnd as data 636 * is presented to the user (this happens in tcp_usrreq.c, 637 * case PRU_RCVD). If a FIN has already been received on this 638 * connection then we just ignore the text. 639 */ 640 if ((ti->ti_len || (tiflags&TH_FIN)) && 641 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 642 tiflags = tcp_reass(tp, ti); 643 if (tcpnodelack == 0) 644 tp->t_flags |= TF_DELACK; 645 else 646 tp->t_flags |= TF_ACKNOW; 647 } else { 648 m_freem(m); 649 tiflags &= ~TH_FIN; 650 } 651 652 /* 653 * If FIN is received ACK the FIN and let the user know 654 * that the connection is closing. 655 */ 656 if (tiflags & TH_FIN) { 657 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 658 socantrcvmore(so); 659 tp->t_flags |= TF_ACKNOW; 660 tp->rcv_nxt++; 661 } 662 switch (tp->t_state) { 663 664 /* 665 * In SYN_RECEIVED and ESTABLISHED STATES 666 * enter the CLOSE_WAIT state. 667 */ 668 case TCPS_SYN_RECEIVED: 669 case TCPS_ESTABLISHED: 670 tp->t_state = TCPS_CLOSE_WAIT; 671 break; 672 673 /* 674 * If still in FIN_WAIT_1 STATE FIN has not been acked so 675 * enter the CLOSING state. 676 */ 677 case TCPS_FIN_WAIT_1: 678 tp->t_state = TCPS_CLOSING; 679 break; 680 681 /* 682 * In FIN_WAIT_2 state enter the TIME_WAIT state, 683 * starting the time-wait timer, turning off the other 684 * standard timers. 685 */ 686 case TCPS_FIN_WAIT_2: 687 tp->t_state = TCPS_TIME_WAIT; 688 tcp_canceltimers(tp); 689 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 690 soisdisconnected(so); 691 break; 692 693 /* 694 * In TIME_WAIT state restart the 2 MSL time_wait timer. 695 */ 696 case TCPS_TIME_WAIT: 697 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 698 break; 699 } 700 } 701 if (so->so_options & SO_DEBUG) 702 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 703 704 /* 705 * Return any desired output. 706 */ 707 (void) tcp_output(tp); 708 return; 709 710 dropafterack: 711 /* 712 * Generate an ACK dropping incoming segment if it occupies 713 * sequence space, where the ACK reflects our state. 714 */ 715 if ((tiflags&TH_RST) || 716 tlen == 0 && (tiflags&(TH_SYN|TH_FIN)) == 0) 717 goto drop; 718 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 719 tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 720 tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 721 return; 722 723 dropwithreset: 724 if (om) { 725 (void) m_free(om); 726 om = 0; 727 } 728 /* 729 * Generate a RST, dropping incoming segment. 730 * Make ACK acceptable to originator of segment. 731 */ 732 if (tiflags & TH_RST) 733 goto drop; 734 if (tiflags & TH_ACK) 735 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 736 else { 737 if (tiflags & TH_SYN) 738 ti->ti_len++; 739 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 740 TH_RST|TH_ACK); 741 } 742 /* destroy temporarily created socket */ 743 if (dropsocket) 744 (void) soabort(so); 745 return; 746 747 drop: 748 if (om) 749 (void) m_free(om); 750 /* 751 * Drop space held by incoming segment and return. 752 */ 753 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 754 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 755 m_freem(m); 756 /* destroy temporarily created socket */ 757 if (dropsocket) 758 (void) soabort(so); 759 return; 760 } 761 762 tcp_dooptions(tp, om) 763 struct tcpcb *tp; 764 struct mbuf *om; 765 { 766 register u_char *cp; 767 int opt, optlen, cnt; 768 769 cp = mtod(om, u_char *); 770 cnt = om->m_len; 771 for (; cnt > 0; cnt -= optlen, cp += optlen) { 772 opt = cp[0]; 773 if (opt == TCPOPT_EOL) 774 break; 775 if (opt == TCPOPT_NOP) 776 optlen = 1; 777 else { 778 optlen = cp[1]; 779 if (optlen <= 0) 780 break; 781 } 782 switch (opt) { 783 784 default: 785 break; 786 787 case TCPOPT_MAXSEG: 788 if (optlen != 4) 789 continue; 790 tp->t_maxseg = *(u_short *)(cp + 2); 791 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 792 break; 793 } 794 } 795 (void) m_free(om); 796 } 797 798 /* 799 * Pull out of band byte out of a segment so 800 * it doesn't appear in the user's data queue. 801 * It is still reflected in the segment length for 802 * sequencing purposes. 803 */ 804 tcp_pulloutofband(so, ti) 805 struct socket *so; 806 struct tcpiphdr *ti; 807 { 808 register struct mbuf *m; 809 int cnt = ti->ti_urp - 1; 810 811 m = dtom(ti); 812 while (cnt >= 0) { 813 if (m->m_len > cnt) { 814 char *cp = mtod(m, caddr_t) + cnt; 815 struct tcpcb *tp = sototcpcb(so); 816 817 tp->t_iobc = *cp; 818 tp->t_oobflags |= TCPOOB_HAVEDATA; 819 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 820 m->m_len--; 821 return; 822 } 823 cnt -= m->m_len; 824 m = m->m_next; 825 if (m == 0) 826 break; 827 } 828 panic("tcp_pulloutofband"); 829 } 830 831 /* 832 * Insert segment ti into reassembly queue of tcp with 833 * control block tp. Return TH_FIN if reassembly now includes 834 * a segment with FIN. 835 */ 836 tcp_reass(tp, ti) 837 register struct tcpcb *tp; 838 register struct tcpiphdr *ti; 839 { 840 register struct tcpiphdr *q; 841 struct socket *so = tp->t_inpcb->inp_socket; 842 struct mbuf *m; 843 int flags; 844 845 /* 846 * Call with ti==0 after become established to 847 * force pre-ESTABLISHED data up to user socket. 848 */ 849 if (ti == 0) 850 goto present; 851 852 /* 853 * Find a segment which begins after this one does. 854 */ 855 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 856 q = (struct tcpiphdr *)q->ti_next) 857 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 858 break; 859 860 /* 861 * If there is a preceding segment, it may provide some of 862 * our data already. If so, drop the data from the incoming 863 * segment. If it provides all of our data, drop us. 864 */ 865 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 866 register int i; 867 q = (struct tcpiphdr *)q->ti_prev; 868 /* conversion to int (in i) handles seq wraparound */ 869 i = q->ti_seq + q->ti_len - ti->ti_seq; 870 if (i > 0) { 871 if (i >= ti->ti_len) 872 goto drop; 873 m_adj(dtom(ti), i); 874 ti->ti_len -= i; 875 ti->ti_seq += i; 876 } 877 q = (struct tcpiphdr *)(q->ti_next); 878 } 879 880 /* 881 * While we overlap succeeding segments trim them or, 882 * if they are completely covered, dequeue them. 883 */ 884 while (q != (struct tcpiphdr *)tp) { 885 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 886 if (i <= 0) 887 break; 888 if (i < q->ti_len) { 889 q->ti_seq += i; 890 q->ti_len -= i; 891 m_adj(dtom(q), i); 892 break; 893 } 894 q = (struct tcpiphdr *)q->ti_next; 895 m = dtom(q->ti_prev); 896 remque(q->ti_prev); 897 m_freem(m); 898 } 899 900 /* 901 * Stick new segment in its place. 902 */ 903 insque(ti, q->ti_prev); 904 905 present: 906 /* 907 * Present data to user, advancing rcv_nxt through 908 * completed sequence space. 909 */ 910 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 911 return (0); 912 ti = tp->seg_next; 913 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 914 return (0); 915 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 916 return (0); 917 do { 918 tp->rcv_nxt += ti->ti_len; 919 flags = ti->ti_flags & TH_FIN; 920 remque(ti); 921 m = dtom(ti); 922 ti = (struct tcpiphdr *)ti->ti_next; 923 if (so->so_state & SS_CANTRCVMORE) 924 m_freem(m); 925 else 926 sbappend(&so->so_rcv, m); 927 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 928 sorwakeup(so); 929 return (flags); 930 drop: 931 m_freem(dtom(ti)); 932 return (0); 933 } 934