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 7.10 (Berkeley) 08/10/87 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, ourfinisacked, 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 if (tiflags & TH_ACK) { 441 tp->snd_una = ti->ti_ack; 442 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 443 tp->snd_nxt = tp->snd_una; 444 } 445 tp->t_timer[TCPT_REXMT] = 0; 446 /* 447 * If we didn't have to retransmit, 448 * set the initial estimate of srtt. 449 * Set the variance to half the rtt 450 * (so our first retransmit happens at 2*rtt). 451 */ 452 if (tp->t_rtt) { 453 tp->t_srtt = tp->t_rtt << 3; 454 tp->t_rttvar = tp->t_rtt << 1; 455 tp->t_rtt = 0; 456 tp->t_rxtshift = 0; 457 TCPT_RANGESET(tp->t_rxtcur, 458 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 459 TCPTV_MIN, TCPTV_REXMTMAX); 460 } 461 tp->irs = ti->ti_seq; 462 tcp_rcvseqinit(tp); 463 tp->t_flags |= TF_ACKNOW; 464 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 465 tcpstat.tcps_connects++; 466 soisconnected(so); 467 tp->t_state = TCPS_ESTABLISHED; 468 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 469 (void) tcp_reass(tp, (struct tcpiphdr *)0); 470 } else 471 tp->t_state = TCPS_SYN_RECEIVED; 472 473 trimthenstep6: 474 /* 475 * Advance ti->ti_seq to correspond to first data byte. 476 * If data, trim to stay within window, 477 * dropping FIN if necessary. 478 */ 479 ti->ti_seq++; 480 if (ti->ti_len > tp->rcv_wnd) { 481 todrop = ti->ti_len - tp->rcv_wnd; 482 m_adj(m, -todrop); 483 ti->ti_len = tp->rcv_wnd; 484 tiflags &= ~TH_FIN; 485 tcpstat.tcps_rcvpackafterwin++; 486 tcpstat.tcps_rcvbyteafterwin += todrop; 487 } 488 tp->snd_wl1 = ti->ti_seq - 1; 489 tp->rcv_up = ti->ti_seq; 490 goto step6; 491 } 492 493 /* 494 * States other than LISTEN or SYN_SENT. 495 * First check that at least some bytes of segment are within 496 * receive window. If segment begins before rcv_nxt, 497 * drop leading data (and SYN); if nothing left, just ack. 498 */ 499 todrop = tp->rcv_nxt - ti->ti_seq; 500 if (todrop > 0) { 501 if (tiflags & TH_SYN) { 502 tiflags &= ~TH_SYN; 503 ti->ti_seq++; 504 if (ti->ti_urp > 1) 505 ti->ti_urp--; 506 else 507 tiflags &= ~TH_URG; 508 todrop--; 509 } 510 if (todrop > ti->ti_len || 511 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) { 512 #ifdef TCP_COMPAT_42 513 /* 514 * Don't toss RST in response to 4.2-style keepalive. 515 */ 516 if (ti->ti_seq == tp->rcv_nxt - 1 && tiflags & TH_RST) 517 goto do_rst; 518 #endif 519 tcpstat.tcps_rcvduppack++; 520 tcpstat.tcps_rcvdupbyte += ti->ti_len; 521 todrop = ti->ti_len; 522 tp->t_flags |= TF_ACKNOW; 523 } else { 524 tcpstat.tcps_rcvpartduppack++; 525 tcpstat.tcps_rcvpartdupbyte += todrop; 526 } 527 m_adj(m, todrop); 528 ti->ti_seq += todrop; 529 ti->ti_len -= todrop; 530 if (ti->ti_urp > todrop) 531 ti->ti_urp -= todrop; 532 else { 533 tiflags &= ~TH_URG; 534 ti->ti_urp = 0; 535 } 536 } 537 538 if (tp->rcv_wnd == 0) { 539 /* 540 * If window is closed can only take segments at 541 * window edge, and have to drop data and PUSH from 542 * incoming segments. 543 * 544 * If new data is received on a connection after the 545 * user processes are gone, then RST the other end. 546 */ 547 if ((so->so_state & SS_NOFDREF) && 548 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 549 tp = tcp_close(tp); 550 tcpstat.tcps_rcvafterclose++; 551 goto dropwithreset; 552 } 553 if (tp->rcv_nxt != ti->ti_seq) { 554 tcpstat.tcps_rcvpackafterwin++; 555 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 556 goto dropafterack; 557 } 558 if (ti->ti_len > 0) { 559 if (ti->ti_len == 1) 560 tcpstat.tcps_rcvwinprobe++; 561 else { 562 tcpstat.tcps_rcvpackafterwin++; 563 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 564 } 565 m_adj(m, ti->ti_len); 566 ti->ti_len = 0; 567 tiflags &= ~(TH_PUSH|TH_FIN); 568 } 569 } else { 570 /* 571 * If segment ends after window, drop trailing data 572 * (and PUSH and FIN); if nothing left, just ACK. 573 */ 574 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 575 if (todrop > 0) { 576 if (todrop >= ti->ti_len) { 577 /* 578 * If a new connection request is received 579 * while in TIME_WAIT, drop the old connection 580 * and start over if the sequence numbers 581 * are above the previous ones. 582 */ 583 if (tiflags & TH_SYN && 584 tp->t_state == TCPS_TIME_WAIT && 585 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 586 iss = tp->rcv_nxt + TCP_ISSINCR; 587 (void) tcp_close(tp); 588 goto findpcb; 589 } 590 if (todrop == 1) 591 tcpstat.tcps_rcvwinprobe++; 592 else { 593 tcpstat.tcps_rcvpackafterwin++; 594 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 595 } 596 goto dropafterack; 597 } 598 tcpstat.tcps_rcvpackafterwin++; 599 tcpstat.tcps_rcvbyteafterwin += todrop; 600 m_adj(m, -todrop); 601 ti->ti_len -= todrop; 602 tiflags &= ~(TH_PUSH|TH_FIN); 603 } 604 } 605 606 #ifdef TCP_COMPAT_42 607 do_rst: 608 #endif 609 /* 610 * If the RST bit is set examine the state: 611 * SYN_RECEIVED STATE: 612 * If passive open, return to LISTEN state. 613 * If active open, inform user that connection was refused. 614 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 615 * Inform user that connection was reset, and close tcb. 616 * CLOSING, LAST_ACK, TIME_WAIT STATES 617 * Close the tcb. 618 */ 619 if (tiflags&TH_RST) switch (tp->t_state) { 620 621 case TCPS_SYN_RECEIVED: 622 tp = tcp_drop(tp, ECONNREFUSED); 623 goto drop; 624 625 case TCPS_ESTABLISHED: 626 case TCPS_FIN_WAIT_1: 627 case TCPS_FIN_WAIT_2: 628 case TCPS_CLOSE_WAIT: 629 tp = tcp_drop(tp, ECONNRESET); 630 goto drop; 631 632 case TCPS_CLOSING: 633 case TCPS_LAST_ACK: 634 case TCPS_TIME_WAIT: 635 tp = tcp_close(tp); 636 goto drop; 637 } 638 639 /* 640 * If a SYN is in the window, then this is an 641 * error and we send an RST and drop the connection. 642 */ 643 if (tiflags & TH_SYN) { 644 tp = tcp_drop(tp, ECONNRESET); 645 goto dropwithreset; 646 } 647 648 /* 649 * If the ACK bit is off we drop the segment and return. 650 */ 651 if ((tiflags & TH_ACK) == 0) 652 goto drop; 653 654 /* 655 * Ack processing. 656 */ 657 switch (tp->t_state) { 658 659 /* 660 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 661 * ESTABLISHED state and continue processing, otherwise 662 * send an RST. 663 */ 664 case TCPS_SYN_RECEIVED: 665 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 666 SEQ_GT(ti->ti_ack, tp->snd_max)) 667 goto dropwithreset; 668 tcpstat.tcps_connects++; 669 soisconnected(so); 670 tp->t_state = TCPS_ESTABLISHED; 671 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 672 (void) tcp_reass(tp, (struct tcpiphdr *)0); 673 tp->snd_wl1 = ti->ti_seq - 1; 674 /* fall into ... */ 675 676 /* 677 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 678 * ACKs. If the ack is in the range 679 * tp->snd_una < ti->ti_ack <= tp->snd_max 680 * then advance tp->snd_una to ti->ti_ack and drop 681 * data from the retransmission queue. If this ACK reflects 682 * more up to date window information we update our window information. 683 */ 684 case TCPS_ESTABLISHED: 685 case TCPS_FIN_WAIT_1: 686 case TCPS_FIN_WAIT_2: 687 case TCPS_CLOSE_WAIT: 688 case TCPS_CLOSING: 689 case TCPS_LAST_ACK: 690 case TCPS_TIME_WAIT: 691 692 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 693 if (ti->ti_len == 0) 694 tcpstat.tcps_rcvdupack++; 695 break; 696 } 697 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 698 tcpstat.tcps_rcvacktoomuch++; 699 goto dropafterack; 700 } 701 acked = ti->ti_ack - tp->snd_una; 702 tcpstat.tcps_rcvackpack++; 703 tcpstat.tcps_rcvackbyte += acked; 704 705 /* 706 * If transmit timer is running and timed sequence 707 * number was acked, update smoothed round trip time. 708 * Since we now have an rtt measurement, cancel the 709 * timer backoff (cf., Phil Karn's retransmit alg.). 710 * Recompute the initial retransmit timer. 711 */ 712 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 713 tcpstat.tcps_rttupdated++; 714 if (tp->t_srtt != 0) { 715 register short delta; 716 717 /* 718 * srtt is stored as fixed point with 3 bits 719 * after the binary point (i.e., scaled by 8). 720 * The following magic is equivalent 721 * to the smoothing algorithm in rfc793 722 * with an alpha of .875 723 * (srtt = rtt/8 + srtt*7/8 in fixed point). 724 */ 725 delta = tp->t_rtt - (tp->t_srtt >> 3); 726 if ((tp->t_srtt += delta) <= 0) 727 tp->t_srtt = 1; 728 /* 729 * We accumulate a smoothed rtt variance 730 * (actually, a smoothed mean difference), 731 * then set the retransmit timer to smoothed 732 * rtt + 2 times the smoothed variance. 733 * rttvar is strored as fixed point 734 * with 2 bits after the binary point 735 * (scaled by 4). The following is equivalent 736 * to rfc793 smoothing with an alpha of .75 737 * (rttvar = rttvar*3/4 + |delta| / 4). 738 * This replaces rfc793's wired-in beta. 739 */ 740 if (delta < 0) 741 delta = -delta; 742 delta -= (tp->t_rttvar >> 2); 743 if ((tp->t_rttvar += delta) <= 0) 744 tp->t_rttvar = 1; 745 } else { 746 /* 747 * No rtt measurement yet - use the 748 * unsmoothed rtt. Set the variance 749 * to half the rtt (so our first 750 * retransmit happens at 2*rtt) 751 */ 752 tp->t_srtt = tp->t_rtt << 3; 753 tp->t_rttvar = tp->t_rtt << 1; 754 } 755 tp->t_rtt = 0; 756 tp->t_rxtshift = 0; 757 TCPT_RANGESET(tp->t_rxtcur, 758 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 759 TCPTV_MIN, TCPTV_REXMTMAX); 760 } 761 762 /* 763 * If all outstanding data is acked, stop retransmit 764 * timer and remember to restart (more output or persist). 765 * If there is more data to be acked, restart retransmit 766 * timer, using current (possibly backed-off) value. 767 */ 768 if (ti->ti_ack == tp->snd_max) { 769 tp->t_timer[TCPT_REXMT] = 0; 770 needoutput = 1; 771 } else if (tp->t_timer[TCPT_PERSIST] == 0) 772 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 773 /* 774 * When new data is acked, open the congestion window 775 * by one max-sized segment. 776 */ 777 tp->snd_cwnd = MIN(tp->snd_cwnd + tp->t_maxseg, 65535); 778 if (acked > so->so_snd.sb_cc) { 779 tp->snd_wnd -= so->so_snd.sb_cc; 780 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 781 ourfinisacked = 1; 782 } else { 783 sbdrop(&so->so_snd, acked); 784 tp->snd_wnd -= acked; 785 ourfinisacked = 0; 786 } 787 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 788 sowwakeup(so); 789 tp->snd_una = ti->ti_ack; 790 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 791 tp->snd_nxt = tp->snd_una; 792 793 switch (tp->t_state) { 794 795 /* 796 * In FIN_WAIT_1 STATE in addition to the processing 797 * for the ESTABLISHED state if our FIN is now acknowledged 798 * then enter FIN_WAIT_2. 799 */ 800 case TCPS_FIN_WAIT_1: 801 if (ourfinisacked) { 802 /* 803 * If we can't receive any more 804 * data, then closing user can proceed. 805 * Starting the timer is contrary to the 806 * specification, but if we don't get a FIN 807 * we'll hang forever. 808 */ 809 if (so->so_state & SS_CANTRCVMORE) { 810 soisdisconnected(so); 811 tp->t_timer[TCPT_2MSL] = TCPTV_MAXIDLE; 812 } 813 tp->t_state = TCPS_FIN_WAIT_2; 814 } 815 break; 816 817 /* 818 * In CLOSING STATE in addition to the processing for 819 * the ESTABLISHED state if the ACK acknowledges our FIN 820 * then enter the TIME-WAIT state, otherwise ignore 821 * the segment. 822 */ 823 case TCPS_CLOSING: 824 if (ourfinisacked) { 825 tp->t_state = TCPS_TIME_WAIT; 826 tcp_canceltimers(tp); 827 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 828 soisdisconnected(so); 829 } 830 break; 831 832 /* 833 * In LAST_ACK, we may still be waiting for data to drain 834 * and/or to be acked, as well as for the ack of our FIN. 835 * If our FIN is now acknowledged, delete the TCB, 836 * enter the closed state and return. 837 */ 838 case TCPS_LAST_ACK: 839 if (ourfinisacked) { 840 tp = tcp_close(tp); 841 goto drop; 842 } 843 break; 844 845 /* 846 * In TIME_WAIT state the only thing that should arrive 847 * is a retransmission of the remote FIN. Acknowledge 848 * it and restart the finack timer. 849 */ 850 case TCPS_TIME_WAIT: 851 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 852 goto dropafterack; 853 } 854 } 855 856 step6: 857 /* 858 * Update window information. 859 * Don't look at window if no ACK: TAC's send garbage on first SYN. 860 */ 861 if ((tiflags & TH_ACK) && 862 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 863 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 864 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) { 865 /* keep track of pure window updates */ 866 if (ti->ti_len == 0 && 867 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd) { 868 tcpstat.tcps_rcvwinupd++; 869 tcpstat.tcps_rcvdupack--; 870 } 871 tp->snd_wnd = ti->ti_win; 872 tp->snd_wl1 = ti->ti_seq; 873 tp->snd_wl2 = ti->ti_ack; 874 if (tp->snd_wnd > tp->max_sndwnd) 875 tp->max_sndwnd = tp->snd_wnd; 876 needoutput = 1; 877 } 878 879 /* 880 * Process segments with URG. 881 */ 882 if ((tiflags & TH_URG) && ti->ti_urp && 883 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 884 /* 885 * This is a kludge, but if we receive and accept 886 * random urgent pointers, we'll crash in 887 * soreceive. It's hard to imagine someone 888 * actually wanting to send this much urgent data. 889 */ 890 if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) { 891 ti->ti_urp = 0; /* XXX */ 892 tiflags &= ~TH_URG; /* XXX */ 893 goto dodata; /* XXX */ 894 } 895 /* 896 * If this segment advances the known urgent pointer, 897 * then mark the data stream. This should not happen 898 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 899 * a FIN has been received from the remote side. 900 * In these states we ignore the URG. 901 * 902 * According to RFC961 (Assigned Protocols), 903 * the urgent pointer points to the last octet 904 * of urgent data. We continue, however, 905 * to consider it to indicate the first octet 906 * of data past the urgent section 907 * as the original spec states. 908 */ 909 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 910 tp->rcv_up = ti->ti_seq + ti->ti_urp; 911 so->so_oobmark = so->so_rcv.sb_cc + 912 (tp->rcv_up - tp->rcv_nxt) - 1; 913 if (so->so_oobmark == 0) 914 so->so_state |= SS_RCVATMARK; 915 sohasoutofband(so); 916 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 917 } 918 /* 919 * Remove out of band data so doesn't get presented to user. 920 * This can happen independent of advancing the URG pointer, 921 * but if two URG's are pending at once, some out-of-band 922 * data may creep in... ick. 923 */ 924 if (ti->ti_urp <= ti->ti_len && 925 (so->so_options & SO_OOBINLINE) == 0) 926 tcp_pulloutofband(so, ti); 927 } else 928 /* 929 * If no out of band data is expected, 930 * pull receive urgent pointer along 931 * with the receive window. 932 */ 933 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 934 tp->rcv_up = tp->rcv_nxt; 935 dodata: /* XXX */ 936 937 /* 938 * Process the segment text, merging it into the TCP sequencing queue, 939 * and arranging for acknowledgment of receipt if necessary. 940 * This process logically involves adjusting tp->rcv_wnd as data 941 * is presented to the user (this happens in tcp_usrreq.c, 942 * case PRU_RCVD). If a FIN has already been received on this 943 * connection then we just ignore the text. 944 */ 945 if ((ti->ti_len || (tiflags&TH_FIN)) && 946 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 947 TCP_REASS(tp, ti, m, so, tiflags); 948 if (tcpnodelack == 0) 949 tp->t_flags |= TF_DELACK; 950 else 951 tp->t_flags |= TF_ACKNOW; 952 /* 953 * Note the amount of data that peer has sent into 954 * our window, in order to estimate the sender's 955 * buffer size. 956 */ 957 len = tp->rcv_nxt - tp->rcv_adv; 958 if (len > tp->max_rcvd) 959 tp->max_rcvd = len; 960 } else { 961 m_freem(m); 962 tiflags &= ~TH_FIN; 963 } 964 965 /* 966 * If FIN is received ACK the FIN and let the user know 967 * that the connection is closing. 968 */ 969 if (tiflags & TH_FIN) { 970 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 971 socantrcvmore(so); 972 tp->t_flags |= TF_ACKNOW; 973 tp->rcv_nxt++; 974 } 975 switch (tp->t_state) { 976 977 /* 978 * In SYN_RECEIVED and ESTABLISHED STATES 979 * enter the CLOSE_WAIT state. 980 */ 981 case TCPS_SYN_RECEIVED: 982 case TCPS_ESTABLISHED: 983 tp->t_state = TCPS_CLOSE_WAIT; 984 break; 985 986 /* 987 * If still in FIN_WAIT_1 STATE FIN has not been acked so 988 * enter the CLOSING state. 989 */ 990 case TCPS_FIN_WAIT_1: 991 tp->t_state = TCPS_CLOSING; 992 break; 993 994 /* 995 * In FIN_WAIT_2 state enter the TIME_WAIT state, 996 * starting the time-wait timer, turning off the other 997 * standard timers. 998 */ 999 case TCPS_FIN_WAIT_2: 1000 tp->t_state = TCPS_TIME_WAIT; 1001 tcp_canceltimers(tp); 1002 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1003 soisdisconnected(so); 1004 break; 1005 1006 /* 1007 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1008 */ 1009 case TCPS_TIME_WAIT: 1010 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1011 break; 1012 } 1013 } 1014 if (so->so_options & SO_DEBUG) 1015 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1016 1017 /* 1018 * Return any desired output. 1019 */ 1020 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1021 (void) tcp_output(tp); 1022 return; 1023 1024 dropafterack: 1025 /* 1026 * Generate an ACK dropping incoming segment if it occupies 1027 * sequence space, where the ACK reflects our state. 1028 */ 1029 if (tiflags & TH_RST) 1030 goto drop; 1031 m_freem(m); 1032 tp->t_flags |= TF_ACKNOW; 1033 (void) tcp_output(tp); 1034 return; 1035 1036 dropwithreset: 1037 if (om) { 1038 (void) m_free(om); 1039 om = 0; 1040 } 1041 /* 1042 * Generate a RST, dropping incoming segment. 1043 * Make ACK acceptable to originator of segment. 1044 * Don't bother to respond if destination was broadcast. 1045 */ 1046 if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst)) 1047 goto drop; 1048 if (tiflags & TH_ACK) 1049 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 1050 else { 1051 if (tiflags & TH_SYN) 1052 ti->ti_len++; 1053 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1054 TH_RST|TH_ACK); 1055 } 1056 /* destroy temporarily created socket */ 1057 if (dropsocket) 1058 (void) soabort(so); 1059 return; 1060 1061 drop: 1062 if (om) 1063 (void) m_free(om); 1064 /* 1065 * Drop space held by incoming segment and return. 1066 */ 1067 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1068 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1069 m_freem(m); 1070 /* destroy temporarily created socket */ 1071 if (dropsocket) 1072 (void) soabort(so); 1073 return; 1074 } 1075 1076 tcp_dooptions(tp, om, ti) 1077 struct tcpcb *tp; 1078 struct mbuf *om; 1079 struct tcpiphdr *ti; 1080 { 1081 register u_char *cp; 1082 int opt, optlen, cnt; 1083 1084 cp = mtod(om, u_char *); 1085 cnt = om->m_len; 1086 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1087 opt = cp[0]; 1088 if (opt == TCPOPT_EOL) 1089 break; 1090 if (opt == TCPOPT_NOP) 1091 optlen = 1; 1092 else { 1093 optlen = cp[1]; 1094 if (optlen <= 0) 1095 break; 1096 } 1097 switch (opt) { 1098 1099 default: 1100 break; 1101 1102 case TCPOPT_MAXSEG: 1103 if (optlen != 4) 1104 continue; 1105 if (!(ti->ti_flags & TH_SYN)) 1106 continue; 1107 tp->t_maxseg = *(u_short *)(cp + 2); 1108 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 1109 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 1110 break; 1111 } 1112 } 1113 (void) m_free(om); 1114 } 1115 1116 /* 1117 * Pull out of band byte out of a segment so 1118 * it doesn't appear in the user's data queue. 1119 * It is still reflected in the segment length for 1120 * sequencing purposes. 1121 */ 1122 tcp_pulloutofband(so, ti) 1123 struct socket *so; 1124 struct tcpiphdr *ti; 1125 { 1126 register struct mbuf *m; 1127 int cnt = ti->ti_urp - 1; 1128 1129 m = dtom(ti); 1130 while (cnt >= 0) { 1131 if (m->m_len > cnt) { 1132 char *cp = mtod(m, caddr_t) + cnt; 1133 struct tcpcb *tp = sototcpcb(so); 1134 1135 tp->t_iobc = *cp; 1136 tp->t_oobflags |= TCPOOB_HAVEDATA; 1137 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1138 m->m_len--; 1139 return; 1140 } 1141 cnt -= m->m_len; 1142 m = m->m_next; 1143 if (m == 0) 1144 break; 1145 } 1146 panic("tcp_pulloutofband"); 1147 } 1148 1149 /* 1150 * Determine a reasonable value for maxseg size. 1151 * If the route is known, use one that can be handled 1152 * on the given interface without forcing IP to fragment. 1153 * If bigger than an mbuf cluster (MCLBYTES), round down to nearest size 1154 * to utilize large mbufs. 1155 * If interface pointer is unavailable, or the destination isn't local, 1156 * use a conservative size (512 or the default IP max size, but no more 1157 * than the mtu of the interface through which we route), 1158 * as we can't discover anything about intervening gateways or networks. 1159 * We also initialize the congestion/slow start window to be a single 1160 * segment if the destination isn't local; this information should 1161 * probably all be saved with the routing entry at the transport level. 1162 * 1163 * This is ugly, and doesn't belong at this level, but has to happen somehow. 1164 */ 1165 tcp_mss(tp) 1166 register struct tcpcb *tp; 1167 { 1168 struct route *ro; 1169 struct ifnet *ifp; 1170 int mss; 1171 struct inpcb *inp; 1172 1173 inp = tp->t_inpcb; 1174 ro = &inp->inp_route; 1175 if ((ro->ro_rt == (struct rtentry *)0) || 1176 (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { 1177 /* No route yet, so try to acquire one */ 1178 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1179 ro->ro_dst.sa_family = AF_INET; 1180 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1181 inp->inp_faddr; 1182 rtalloc(ro); 1183 } 1184 if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) 1185 return (TCP_MSS); 1186 } 1187 1188 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1189 #if (MCLBYTES & (MCLBYTES - 1)) == 0 1190 if (mss > MCLBYTES) 1191 mss &= ~(MCLBYTES-1); 1192 #else 1193 if (mss > MCLBYTES) 1194 mss = mss / MCLBYTES * MCLBYTES; 1195 #endif 1196 if (in_localaddr(inp->inp_faddr)) 1197 return (mss); 1198 mss = MIN(mss, TCP_MSS); 1199 tp->snd_cwnd = mss; 1200 return (mss); 1201 } 1202