1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_input.c 8.5 (Berkeley) 4/10/94 34 */ 35 36 #ifndef TUBA_INCLUDE 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/malloc.h> 40 #include <sys/mbuf.h> 41 #include <sys/protosw.h> 42 #include <sys/socket.h> 43 #include <sys/socketvar.h> 44 #include <sys/errno.h> 45 46 #include <net/if.h> 47 #include <net/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/in_systm.h> 51 #include <netinet/ip.h> 52 #include <netinet/in_pcb.h> 53 #include <netinet/ip_var.h> 54 #include <netinet/tcp.h> 55 #include <netinet/tcp_fsm.h> 56 #include <netinet/tcp_seq.h> 57 #include <netinet/tcp_timer.h> 58 #include <netinet/tcp_var.h> 59 #include <netinet/tcpip.h> 60 #include <netinet/tcp_debug.h> 61 62 int tcprexmtthresh = 3; 63 struct tcpiphdr tcp_saveti; 64 struct inpcb *tcp_last_inpcb = &tcb; 65 66 extern u_long sb_max; 67 68 #endif /* TUBA_INCLUDE */ 69 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) 70 71 /* for modulo comparisons of timestamps */ 72 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) 73 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) 74 75 76 /* 77 * Insert segment ti into reassembly queue of tcp with 78 * control block tp. Return TH_FIN if reassembly now includes 79 * a segment with FIN. The macro form does the common case inline 80 * (segment is the next to be received on an established connection, 81 * and the queue is empty), avoiding linkage into and removal 82 * from the queue and repetition of various conversions. 83 * Set DELACK for segments received in order, but ack immediately 84 * when segments are out of order (so fast retransmit can work). 85 */ 86 #define TCP_REASS(tp, ti, m, so, flags) { \ 87 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 88 (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 89 (tp)->t_state == TCPS_ESTABLISHED) { \ 90 tp->t_flags |= TF_DELACK; \ 91 (tp)->rcv_nxt += (ti)->ti_len; \ 92 flags = (ti)->ti_flags & TH_FIN; \ 93 tcpstat.tcps_rcvpack++;\ 94 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 95 sbappend(&(so)->so_rcv, (m)); \ 96 sorwakeup(so); \ 97 } else { \ 98 (flags) = tcp_reass((tp), (ti), (m)); \ 99 tp->t_flags |= TF_ACKNOW; \ 100 } \ 101 } 102 #ifndef TUBA_INCLUDE 103 104 int 105 tcp_reass(tp, ti, m) 106 register struct tcpcb *tp; 107 register struct tcpiphdr *ti; 108 struct mbuf *m; 109 { 110 register struct tcpiphdr *q; 111 struct socket *so = tp->t_inpcb->inp_socket; 112 int flags; 113 114 /* 115 * Call with ti==0 after become established to 116 * force pre-ESTABLISHED data up to user socket. 117 */ 118 if (ti == 0) 119 goto present; 120 121 /* 122 * Find a segment which begins after this one does. 123 */ 124 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 125 q = (struct tcpiphdr *)q->ti_next) 126 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 127 break; 128 129 /* 130 * If there is a preceding segment, it may provide some of 131 * our data already. If so, drop the data from the incoming 132 * segment. If it provides all of our data, drop us. 133 */ 134 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 135 register int i; 136 q = (struct tcpiphdr *)q->ti_prev; 137 /* conversion to int (in i) handles seq wraparound */ 138 i = q->ti_seq + q->ti_len - ti->ti_seq; 139 if (i > 0) { 140 if (i >= ti->ti_len) { 141 tcpstat.tcps_rcvduppack++; 142 tcpstat.tcps_rcvdupbyte += ti->ti_len; 143 m_freem(m); 144 return (0); 145 } 146 m_adj(m, i); 147 ti->ti_len -= i; 148 ti->ti_seq += i; 149 } 150 q = (struct tcpiphdr *)(q->ti_next); 151 } 152 tcpstat.tcps_rcvoopack++; 153 tcpstat.tcps_rcvoobyte += ti->ti_len; 154 REASS_MBUF(ti) = m; /* XXX */ 155 156 /* 157 * While we overlap succeeding segments trim them or, 158 * if they are completely covered, dequeue them. 159 */ 160 while (q != (struct tcpiphdr *)tp) { 161 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 162 if (i <= 0) 163 break; 164 if (i < q->ti_len) { 165 q->ti_seq += i; 166 q->ti_len -= i; 167 m_adj(REASS_MBUF(q), i); 168 break; 169 } 170 q = (struct tcpiphdr *)q->ti_next; 171 m = REASS_MBUF((struct tcpiphdr *)q->ti_prev); 172 remque(q->ti_prev); 173 m_freem(m); 174 } 175 176 /* 177 * Stick new segment in its place. 178 */ 179 insque(ti, q->ti_prev); 180 181 present: 182 /* 183 * Present data to user, advancing rcv_nxt through 184 * completed sequence space. 185 */ 186 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 187 return (0); 188 ti = tp->seg_next; 189 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 190 return (0); 191 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 192 return (0); 193 do { 194 tp->rcv_nxt += ti->ti_len; 195 flags = ti->ti_flags & TH_FIN; 196 remque(ti); 197 m = REASS_MBUF(ti); 198 ti = (struct tcpiphdr *)ti->ti_next; 199 if (so->so_state & SS_CANTRCVMORE) 200 m_freem(m); 201 else 202 sbappend(&so->so_rcv, m); 203 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 204 sorwakeup(so); 205 return (flags); 206 } 207 208 /* 209 * TCP input routine, follows pages 65-76 of the 210 * protocol specification dated September, 1981 very closely. 211 */ 212 void 213 tcp_input(m, iphlen) 214 register struct mbuf *m; 215 int iphlen; 216 { 217 register struct tcpiphdr *ti; 218 register struct inpcb *inp; 219 caddr_t optp = NULL; 220 int optlen = 0; 221 int len, tlen, off; 222 register struct tcpcb *tp = 0; 223 register int tiflags; 224 struct socket *so = 0; 225 int todrop, acked, ourfinisacked, needoutput = 0; 226 short ostate = 0; 227 struct in_addr laddr; 228 int dropsocket = 0; 229 int iss = 0; 230 u_long tiwin, ts_val, ts_ecr; 231 int ts_present = 0; 232 233 tcpstat.tcps_rcvtotal++; 234 /* 235 * Get IP and TCP header together in first mbuf. 236 * Note: IP leaves IP header in first mbuf. 237 */ 238 ti = mtod(m, struct tcpiphdr *); 239 if (iphlen > sizeof (struct ip)) 240 ip_stripoptions(m, (struct mbuf *)0); 241 if (m->m_len < sizeof (struct tcpiphdr)) { 242 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 243 tcpstat.tcps_rcvshort++; 244 return; 245 } 246 ti = mtod(m, struct tcpiphdr *); 247 } 248 249 /* 250 * Checksum extended TCP header and data. 251 */ 252 tlen = ((struct ip *)ti)->ip_len; 253 len = sizeof (struct ip) + tlen; 254 ti->ti_next = ti->ti_prev = 0; 255 ti->ti_x1 = 0; 256 ti->ti_len = (u_short)tlen; 257 HTONS(ti->ti_len); 258 if (ti->ti_sum = in_cksum(m, len)) { 259 tcpstat.tcps_rcvbadsum++; 260 goto drop; 261 } 262 #endif /* TUBA_INCLUDE */ 263 264 /* 265 * Check that TCP offset makes sense, 266 * pull out TCP options and adjust length. XXX 267 */ 268 off = ti->ti_off << 2; 269 if (off < sizeof (struct tcphdr) || off > tlen) { 270 tcpstat.tcps_rcvbadoff++; 271 goto drop; 272 } 273 tlen -= off; 274 ti->ti_len = tlen; 275 if (off > sizeof (struct tcphdr)) { 276 if (m->m_len < sizeof(struct ip) + off) { 277 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 278 tcpstat.tcps_rcvshort++; 279 return; 280 } 281 ti = mtod(m, struct tcpiphdr *); 282 } 283 optlen = off - sizeof (struct tcphdr); 284 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 285 /* 286 * Do quick retrieval of timestamp options ("options 287 * prediction?"). If timestamp is the only option and it's 288 * formatted as recommended in RFC 1323 appendix A, we 289 * quickly get the values now and not bother calling 290 * tcp_dooptions(), etc. 291 */ 292 if ((optlen == TCPOLEN_TSTAMP_APPA || 293 (optlen > TCPOLEN_TSTAMP_APPA && 294 optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && 295 *(u_long *)optp == htonl(TCPOPT_TSTAMP_HDR) && 296 (ti->ti_flags & TH_SYN) == 0) { 297 ts_present = 1; 298 ts_val = ntohl(*(u_long *)(optp + 4)); 299 ts_ecr = ntohl(*(u_long *)(optp + 8)); 300 optp = NULL; /* we've parsed the options */ 301 } 302 } 303 tiflags = ti->ti_flags; 304 305 /* 306 * Convert TCP protocol specific fields to host format. 307 */ 308 NTOHL(ti->ti_seq); 309 NTOHL(ti->ti_ack); 310 NTOHS(ti->ti_win); 311 NTOHS(ti->ti_urp); 312 313 /* 314 * Locate pcb for segment. 315 */ 316 findpcb: 317 inp = tcp_last_inpcb; 318 if (inp->inp_lport != ti->ti_dport || 319 inp->inp_fport != ti->ti_sport || 320 inp->inp_faddr.s_addr != ti->ti_src.s_addr || 321 inp->inp_laddr.s_addr != ti->ti_dst.s_addr) { 322 inp = in_pcblookup(&tcb, ti->ti_src, ti->ti_sport, 323 ti->ti_dst, ti->ti_dport, INPLOOKUP_WILDCARD); 324 if (inp) 325 tcp_last_inpcb = inp; 326 ++tcpstat.tcps_pcbcachemiss; 327 } 328 329 /* 330 * If the state is CLOSED (i.e., TCB does not exist) then 331 * all data in the incoming segment is discarded. 332 * If the TCB exists but is in CLOSED state, it is embryonic, 333 * but should either do a listen or a connect soon. 334 */ 335 if (inp == 0) 336 goto dropwithreset; 337 tp = intotcpcb(inp); 338 if (tp == 0) 339 goto dropwithreset; 340 if (tp->t_state == TCPS_CLOSED) 341 goto drop; 342 343 /* Unscale the window into a 32-bit value. */ 344 if ((tiflags & TH_SYN) == 0) 345 tiwin = ti->ti_win << tp->snd_scale; 346 else 347 tiwin = ti->ti_win; 348 349 so = inp->inp_socket; 350 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 351 if (so->so_options & SO_DEBUG) { 352 ostate = tp->t_state; 353 tcp_saveti = *ti; 354 } 355 if (so->so_options & SO_ACCEPTCONN) { 356 so = sonewconn(so, 0); 357 if (so == 0) 358 goto drop; 359 /* 360 * This is ugly, but .... 361 * 362 * Mark socket as temporary until we're 363 * committed to keeping it. The code at 364 * ``drop'' and ``dropwithreset'' check the 365 * flag dropsocket to see if the temporary 366 * socket created here should be discarded. 367 * We mark the socket as discardable until 368 * we're committed to it below in TCPS_LISTEN. 369 */ 370 dropsocket++; 371 inp = (struct inpcb *)so->so_pcb; 372 inp->inp_laddr = ti->ti_dst; 373 inp->inp_lport = ti->ti_dport; 374 #if BSD>=43 375 inp->inp_options = ip_srcroute(); 376 #endif 377 tp = intotcpcb(inp); 378 tp->t_state = TCPS_LISTEN; 379 380 /* Compute proper scaling value from buffer space 381 */ 382 while (tp->request_r_scale < TCP_MAX_WINSHIFT && 383 TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) 384 tp->request_r_scale++; 385 } 386 } 387 388 /* 389 * Segment received on connection. 390 * Reset idle time and keep-alive timer. 391 */ 392 tp->t_idle = 0; 393 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 394 395 /* 396 * Process options if not in LISTEN state, 397 * else do it below (after getting remote address). 398 */ 399 if (optp && tp->t_state != TCPS_LISTEN) 400 tcp_dooptions(tp, optp, optlen, ti, 401 &ts_present, &ts_val, &ts_ecr); 402 403 /* 404 * Header prediction: check for the two common cases 405 * of a uni-directional data xfer. If the packet has 406 * no control flags, is in-sequence, the window didn't 407 * change and we're not retransmitting, it's a 408 * candidate. If the length is zero and the ack moved 409 * forward, we're the sender side of the xfer. Just 410 * free the data acked & wake any higher level process 411 * that was blocked waiting for space. If the length 412 * is non-zero and the ack didn't move, we're the 413 * receiver side. If we're getting packets in-order 414 * (the reassembly queue is empty), add the data to 415 * the socket buffer and note that we need a delayed ack. 416 */ 417 if (tp->t_state == TCPS_ESTABLISHED && 418 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 419 (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && 420 ti->ti_seq == tp->rcv_nxt && 421 tiwin && tiwin == tp->snd_wnd && 422 tp->snd_nxt == tp->snd_max) { 423 424 /* 425 * If last ACK falls within this segment's sequence numbers, 426 * record the timestamp. 427 */ 428 if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 429 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) { 430 tp->ts_recent_age = tcp_now; 431 tp->ts_recent = ts_val; 432 } 433 434 if (ti->ti_len == 0) { 435 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 436 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 437 tp->snd_cwnd >= tp->snd_wnd) { 438 /* 439 * this is a pure ack for outstanding data. 440 */ 441 ++tcpstat.tcps_predack; 442 if (ts_present) 443 tcp_xmit_timer(tp, tcp_now-ts_ecr+1); 444 else if (tp->t_rtt && 445 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 446 tcp_xmit_timer(tp, tp->t_rtt); 447 acked = ti->ti_ack - tp->snd_una; 448 tcpstat.tcps_rcvackpack++; 449 tcpstat.tcps_rcvackbyte += acked; 450 sbdrop(&so->so_snd, acked); 451 tp->snd_una = ti->ti_ack; 452 m_freem(m); 453 454 /* 455 * If all outstanding data are acked, stop 456 * retransmit timer, otherwise restart timer 457 * using current (possibly backed-off) value. 458 * If process is waiting for space, 459 * wakeup/selwakeup/signal. If data 460 * are ready to send, let tcp_output 461 * decide between more output or persist. 462 */ 463 if (tp->snd_una == tp->snd_max) 464 tp->t_timer[TCPT_REXMT] = 0; 465 else if (tp->t_timer[TCPT_PERSIST] == 0) 466 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 467 468 if (so->so_snd.sb_flags & SB_NOTIFY) 469 sowwakeup(so); 470 if (so->so_snd.sb_cc) 471 (void) tcp_output(tp); 472 return; 473 } 474 } else if (ti->ti_ack == tp->snd_una && 475 tp->seg_next == (struct tcpiphdr *)tp && 476 ti->ti_len <= sbspace(&so->so_rcv)) { 477 /* 478 * this is a pure, in-sequence data packet 479 * with nothing on the reassembly queue and 480 * we have enough buffer space to take it. 481 */ 482 ++tcpstat.tcps_preddat; 483 tp->rcv_nxt += ti->ti_len; 484 tcpstat.tcps_rcvpack++; 485 tcpstat.tcps_rcvbyte += ti->ti_len; 486 /* 487 * Drop TCP, IP headers and TCP options then add data 488 * to socket buffer. 489 */ 490 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 491 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 492 sbappend(&so->so_rcv, m); 493 sorwakeup(so); 494 tp->t_flags |= TF_DELACK; 495 return; 496 } 497 } 498 499 /* 500 * Drop TCP, IP headers and TCP options. 501 */ 502 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 503 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 504 505 /* 506 * Calculate amount of space in receive window, 507 * and then do TCP input processing. 508 * Receive window is amount of space in rcv queue, 509 * but not less than advertised window. 510 */ 511 { int win; 512 513 win = sbspace(&so->so_rcv); 514 if (win < 0) 515 win = 0; 516 tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 517 } 518 519 switch (tp->t_state) { 520 521 /* 522 * If the state is LISTEN then ignore segment if it contains an RST. 523 * If the segment contains an ACK then it is bad and send a RST. 524 * If it does not contain a SYN then it is not interesting; drop it. 525 * Don't bother responding if the destination was a broadcast. 526 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 527 * tp->iss, and send a segment: 528 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 529 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 530 * Fill in remote peer address fields if not previously specified. 531 * Enter SYN_RECEIVED state, and process any other fields of this 532 * segment in this state. 533 */ 534 case TCPS_LISTEN: { 535 struct mbuf *am; 536 register struct sockaddr_in *sin; 537 538 if (tiflags & TH_RST) 539 goto drop; 540 if (tiflags & TH_ACK) 541 goto dropwithreset; 542 if ((tiflags & TH_SYN) == 0) 543 goto drop; 544 /* 545 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 546 * in_broadcast() should never return true on a received 547 * packet with M_BCAST not set. 548 */ 549 if (m->m_flags & (M_BCAST|M_MCAST) || 550 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 551 goto drop; 552 am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ 553 if (am == NULL) 554 goto drop; 555 am->m_len = sizeof (struct sockaddr_in); 556 sin = mtod(am, struct sockaddr_in *); 557 sin->sin_family = AF_INET; 558 sin->sin_len = sizeof(*sin); 559 sin->sin_addr = ti->ti_src; 560 sin->sin_port = ti->ti_sport; 561 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 562 laddr = inp->inp_laddr; 563 if (inp->inp_laddr.s_addr == INADDR_ANY) 564 inp->inp_laddr = ti->ti_dst; 565 if (in_pcbconnect(inp, am)) { 566 inp->inp_laddr = laddr; 567 (void) m_free(am); 568 goto drop; 569 } 570 (void) m_free(am); 571 tp->t_template = tcp_template(tp); 572 if (tp->t_template == 0) { 573 tp = tcp_drop(tp, ENOBUFS); 574 dropsocket = 0; /* socket is already gone */ 575 goto drop; 576 } 577 if (optp) 578 tcp_dooptions(tp, optp, optlen, ti, 579 &ts_present, &ts_val, &ts_ecr); 580 if (iss) 581 tp->iss = iss; 582 else 583 tp->iss = tcp_iss; 584 tcp_iss += TCP_ISSINCR/2; 585 tp->irs = ti->ti_seq; 586 tcp_sendseqinit(tp); 587 tcp_rcvseqinit(tp); 588 tp->t_flags |= TF_ACKNOW; 589 tp->t_state = TCPS_SYN_RECEIVED; 590 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 591 dropsocket = 0; /* committed to socket */ 592 tcpstat.tcps_accepts++; 593 goto trimthenstep6; 594 } 595 596 /* 597 * If the state is SYN_SENT: 598 * if seg contains an ACK, but not for our SYN, drop the input. 599 * if seg contains a RST, then drop the connection. 600 * if seg does not contain SYN, then drop it. 601 * Otherwise this is an acceptable SYN segment 602 * initialize tp->rcv_nxt and tp->irs 603 * if seg contains ack then advance tp->snd_una 604 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 605 * arrange for segment to be acked (eventually) 606 * continue processing rest of data/controls, beginning with URG 607 */ 608 case TCPS_SYN_SENT: 609 if ((tiflags & TH_ACK) && 610 (SEQ_LEQ(ti->ti_ack, tp->iss) || 611 SEQ_GT(ti->ti_ack, tp->snd_max))) 612 goto dropwithreset; 613 if (tiflags & TH_RST) { 614 if (tiflags & TH_ACK) 615 tp = tcp_drop(tp, ECONNREFUSED); 616 goto drop; 617 } 618 if ((tiflags & TH_SYN) == 0) 619 goto drop; 620 if (tiflags & TH_ACK) { 621 tp->snd_una = ti->ti_ack; 622 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 623 tp->snd_nxt = tp->snd_una; 624 } 625 tp->t_timer[TCPT_REXMT] = 0; 626 tp->irs = ti->ti_seq; 627 tcp_rcvseqinit(tp); 628 tp->t_flags |= TF_ACKNOW; 629 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 630 tcpstat.tcps_connects++; 631 soisconnected(so); 632 tp->t_state = TCPS_ESTABLISHED; 633 /* Do window scaling on this connection? */ 634 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 635 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 636 tp->snd_scale = tp->requested_s_scale; 637 tp->rcv_scale = tp->request_r_scale; 638 } 639 (void) tcp_reass(tp, (struct tcpiphdr *)0, 640 (struct mbuf *)0); 641 /* 642 * if we didn't have to retransmit the SYN, 643 * use its rtt as our initial srtt & rtt var. 644 */ 645 if (tp->t_rtt) 646 tcp_xmit_timer(tp, tp->t_rtt); 647 } else 648 tp->t_state = TCPS_SYN_RECEIVED; 649 650 trimthenstep6: 651 /* 652 * Advance ti->ti_seq to correspond to first data byte. 653 * If data, trim to stay within window, 654 * dropping FIN if necessary. 655 */ 656 ti->ti_seq++; 657 if (ti->ti_len > tp->rcv_wnd) { 658 todrop = ti->ti_len - tp->rcv_wnd; 659 m_adj(m, -todrop); 660 ti->ti_len = tp->rcv_wnd; 661 tiflags &= ~TH_FIN; 662 tcpstat.tcps_rcvpackafterwin++; 663 tcpstat.tcps_rcvbyteafterwin += todrop; 664 } 665 tp->snd_wl1 = ti->ti_seq - 1; 666 tp->rcv_up = ti->ti_seq; 667 goto step6; 668 } 669 670 /* 671 * States other than LISTEN or SYN_SENT. 672 * First check timestamp, if present. 673 * Then check that at least some bytes of segment are within 674 * receive window. If segment begins before rcv_nxt, 675 * drop leading data (and SYN); if nothing left, just ack. 676 * 677 * RFC 1323 PAWS: If we have a timestamp reply on this segment 678 * and it's less than ts_recent, drop it. 679 */ 680 if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && 681 TSTMP_LT(ts_val, tp->ts_recent)) { 682 683 /* Check to see if ts_recent is over 24 days old. */ 684 if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 685 /* 686 * Invalidate ts_recent. If this segment updates 687 * ts_recent, the age will be reset later and ts_recent 688 * will get a valid value. If it does not, setting 689 * ts_recent to zero will at least satisfy the 690 * requirement that zero be placed in the timestamp 691 * echo reply when ts_recent isn't valid. The 692 * age isn't reset until we get a valid ts_recent 693 * because we don't want out-of-order segments to be 694 * dropped when ts_recent is old. 695 */ 696 tp->ts_recent = 0; 697 } else { 698 tcpstat.tcps_rcvduppack++; 699 tcpstat.tcps_rcvdupbyte += ti->ti_len; 700 tcpstat.tcps_pawsdrop++; 701 goto dropafterack; 702 } 703 } 704 705 todrop = tp->rcv_nxt - ti->ti_seq; 706 if (todrop > 0) { 707 if (tiflags & TH_SYN) { 708 tiflags &= ~TH_SYN; 709 ti->ti_seq++; 710 if (ti->ti_urp > 1) 711 ti->ti_urp--; 712 else 713 tiflags &= ~TH_URG; 714 todrop--; 715 } 716 if (todrop >= ti->ti_len) { 717 tcpstat.tcps_rcvduppack++; 718 tcpstat.tcps_rcvdupbyte += ti->ti_len; 719 /* 720 * If segment is just one to the left of the window, 721 * check two special cases: 722 * 1. Don't toss RST in response to 4.2-style keepalive. 723 * 2. If the only thing to drop is a FIN, we can drop 724 * it, but check the ACK or we will get into FIN 725 * wars if our FINs crossed (both CLOSING). 726 * In either case, send ACK to resynchronize, 727 * but keep on processing for RST or ACK. 728 */ 729 if ((tiflags & TH_FIN && todrop == ti->ti_len + 1) 730 #ifdef TCP_COMPAT_42 731 || (tiflags & TH_RST && ti->ti_seq == tp->rcv_nxt - 1) 732 #endif 733 ) { 734 todrop = ti->ti_len; 735 tiflags &= ~TH_FIN; 736 tp->t_flags |= TF_ACKNOW; 737 } else { 738 /* 739 * Handle the case when a bound socket connects 740 * to itself. Allow packets with a SYN and 741 * an ACK to continue with the processing. 742 */ 743 if (todrop != 0 || (tiflags & TH_ACK) == 0) 744 goto dropafterack; 745 } 746 } else { 747 tcpstat.tcps_rcvpartduppack++; 748 tcpstat.tcps_rcvpartdupbyte += todrop; 749 } 750 m_adj(m, todrop); 751 ti->ti_seq += todrop; 752 ti->ti_len -= todrop; 753 if (ti->ti_urp > todrop) 754 ti->ti_urp -= todrop; 755 else { 756 tiflags &= ~TH_URG; 757 ti->ti_urp = 0; 758 } 759 } 760 761 /* 762 * If new data are received on a connection after the 763 * user processes are gone, then RST the other end. 764 */ 765 if ((so->so_state & SS_NOFDREF) && 766 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 767 tp = tcp_close(tp); 768 tcpstat.tcps_rcvafterclose++; 769 goto dropwithreset; 770 } 771 772 /* 773 * If segment ends after window, drop trailing data 774 * (and PUSH and FIN); if nothing left, just ACK. 775 */ 776 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 777 if (todrop > 0) { 778 tcpstat.tcps_rcvpackafterwin++; 779 if (todrop >= ti->ti_len) { 780 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 781 /* 782 * If a new connection request is received 783 * while in TIME_WAIT, drop the old connection 784 * and start over if the sequence numbers 785 * are above the previous ones. 786 */ 787 if (tiflags & TH_SYN && 788 tp->t_state == TCPS_TIME_WAIT && 789 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 790 iss = tp->rcv_nxt + TCP_ISSINCR; 791 tp = tcp_close(tp); 792 goto findpcb; 793 } 794 /* 795 * If window is closed can only take segments at 796 * window edge, and have to drop data and PUSH from 797 * incoming segments. Continue processing, but 798 * remember to ack. Otherwise, drop segment 799 * and ack. 800 */ 801 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 802 tp->t_flags |= TF_ACKNOW; 803 tcpstat.tcps_rcvwinprobe++; 804 } else 805 goto dropafterack; 806 } else 807 tcpstat.tcps_rcvbyteafterwin += todrop; 808 m_adj(m, -todrop); 809 ti->ti_len -= todrop; 810 tiflags &= ~(TH_PUSH|TH_FIN); 811 } 812 813 /* 814 * If last ACK falls within this segment's sequence numbers, 815 * record its timestamp. 816 */ 817 if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 818 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len + 819 ((tiflags & (TH_SYN|TH_FIN)) != 0))) { 820 tp->ts_recent_age = tcp_now; 821 tp->ts_recent = ts_val; 822 } 823 824 /* 825 * If the RST bit is set examine the state: 826 * SYN_RECEIVED STATE: 827 * If passive open, return to LISTEN state. 828 * If active open, inform user that connection was refused. 829 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 830 * Inform user that connection was reset, and close tcb. 831 * CLOSING, LAST_ACK, TIME_WAIT STATES 832 * Close the tcb. 833 */ 834 if (tiflags&TH_RST) switch (tp->t_state) { 835 836 case TCPS_SYN_RECEIVED: 837 so->so_error = ECONNREFUSED; 838 goto close; 839 840 case TCPS_ESTABLISHED: 841 case TCPS_FIN_WAIT_1: 842 case TCPS_FIN_WAIT_2: 843 case TCPS_CLOSE_WAIT: 844 so->so_error = ECONNRESET; 845 close: 846 tp->t_state = TCPS_CLOSED; 847 tcpstat.tcps_drops++; 848 tp = tcp_close(tp); 849 goto drop; 850 851 case TCPS_CLOSING: 852 case TCPS_LAST_ACK: 853 case TCPS_TIME_WAIT: 854 tp = tcp_close(tp); 855 goto drop; 856 } 857 858 /* 859 * If a SYN is in the window, then this is an 860 * error and we send an RST and drop the connection. 861 */ 862 if (tiflags & TH_SYN) { 863 tp = tcp_drop(tp, ECONNRESET); 864 goto dropwithreset; 865 } 866 867 /* 868 * If the ACK bit is off we drop the segment and return. 869 */ 870 if ((tiflags & TH_ACK) == 0) 871 goto drop; 872 873 /* 874 * Ack processing. 875 */ 876 switch (tp->t_state) { 877 878 /* 879 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 880 * ESTABLISHED state and continue processing, otherwise 881 * send an RST. 882 */ 883 case TCPS_SYN_RECEIVED: 884 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 885 SEQ_GT(ti->ti_ack, tp->snd_max)) 886 goto dropwithreset; 887 tcpstat.tcps_connects++; 888 soisconnected(so); 889 tp->t_state = TCPS_ESTABLISHED; 890 /* Do window scaling? */ 891 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 892 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 893 tp->snd_scale = tp->requested_s_scale; 894 tp->rcv_scale = tp->request_r_scale; 895 } 896 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); 897 tp->snd_wl1 = ti->ti_seq - 1; 898 /* fall into ... */ 899 900 /* 901 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 902 * ACKs. If the ack is in the range 903 * tp->snd_una < ti->ti_ack <= tp->snd_max 904 * then advance tp->snd_una to ti->ti_ack and drop 905 * data from the retransmission queue. If this ACK reflects 906 * more up to date window information we update our window information. 907 */ 908 case TCPS_ESTABLISHED: 909 case TCPS_FIN_WAIT_1: 910 case TCPS_FIN_WAIT_2: 911 case TCPS_CLOSE_WAIT: 912 case TCPS_CLOSING: 913 case TCPS_LAST_ACK: 914 case TCPS_TIME_WAIT: 915 916 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 917 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 918 tcpstat.tcps_rcvdupack++; 919 /* 920 * If we have outstanding data (other than 921 * a window probe), this is a completely 922 * duplicate ack (ie, window info didn't 923 * change), the ack is the biggest we've 924 * seen and we've seen exactly our rexmt 925 * threshhold of them, assume a packet 926 * has been dropped and retransmit it. 927 * Kludge snd_nxt & the congestion 928 * window so we send only this one 929 * packet. 930 * 931 * We know we're losing at the current 932 * window size so do congestion avoidance 933 * (set ssthresh to half the current window 934 * and pull our congestion window back to 935 * the new ssthresh). 936 * 937 * Dup acks mean that packets have left the 938 * network (they're now cached at the receiver) 939 * so bump cwnd by the amount in the receiver 940 * to keep a constant cwnd packets in the 941 * network. 942 */ 943 if (tp->t_timer[TCPT_REXMT] == 0 || 944 ti->ti_ack != tp->snd_una) 945 tp->t_dupacks = 0; 946 else if (++tp->t_dupacks == tcprexmtthresh) { 947 tcp_seq onxt = tp->snd_nxt; 948 u_int win = 949 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 950 tp->t_maxseg; 951 952 if (win < 2) 953 win = 2; 954 tp->snd_ssthresh = win * tp->t_maxseg; 955 tp->t_timer[TCPT_REXMT] = 0; 956 tp->t_rtt = 0; 957 tp->snd_nxt = ti->ti_ack; 958 tp->snd_cwnd = tp->t_maxseg; 959 (void) tcp_output(tp); 960 tp->snd_cwnd = tp->snd_ssthresh + 961 tp->t_maxseg * tp->t_dupacks; 962 if (SEQ_GT(onxt, tp->snd_nxt)) 963 tp->snd_nxt = onxt; 964 goto drop; 965 } else if (tp->t_dupacks > tcprexmtthresh) { 966 tp->snd_cwnd += tp->t_maxseg; 967 (void) tcp_output(tp); 968 goto drop; 969 } 970 } else 971 tp->t_dupacks = 0; 972 break; 973 } 974 /* 975 * If the congestion window was inflated to account 976 * for the other side's cached packets, retract it. 977 */ 978 if (tp->t_dupacks > tcprexmtthresh && 979 tp->snd_cwnd > tp->snd_ssthresh) 980 tp->snd_cwnd = tp->snd_ssthresh; 981 tp->t_dupacks = 0; 982 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 983 tcpstat.tcps_rcvacktoomuch++; 984 goto dropafterack; 985 } 986 acked = ti->ti_ack - tp->snd_una; 987 tcpstat.tcps_rcvackpack++; 988 tcpstat.tcps_rcvackbyte += acked; 989 990 /* 991 * If we have a timestamp reply, update smoothed 992 * round trip time. If no timestamp is present but 993 * transmit timer is running and timed sequence 994 * number was acked, update smoothed round trip time. 995 * Since we now have an rtt measurement, cancel the 996 * timer backoff (cf., Phil Karn's retransmit alg.). 997 * Recompute the initial retransmit timer. 998 */ 999 if (ts_present) 1000 tcp_xmit_timer(tp, tcp_now-ts_ecr+1); 1001 else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 1002 tcp_xmit_timer(tp,tp->t_rtt); 1003 1004 /* 1005 * If all outstanding data is acked, stop retransmit 1006 * timer and remember to restart (more output or persist). 1007 * If there is more data to be acked, restart retransmit 1008 * timer, using current (possibly backed-off) value. 1009 */ 1010 if (ti->ti_ack == tp->snd_max) { 1011 tp->t_timer[TCPT_REXMT] = 0; 1012 needoutput = 1; 1013 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1014 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1015 /* 1016 * When new data is acked, open the congestion window. 1017 * If the window gives us less than ssthresh packets 1018 * in flight, open exponentially (maxseg per packet). 1019 * Otherwise open linearly: maxseg per window 1020 * (maxseg^2 / cwnd per packet), plus a constant 1021 * fraction of a packet (maxseg/8) to help larger windows 1022 * open quickly enough. 1023 */ 1024 { 1025 register u_int cw = tp->snd_cwnd; 1026 register u_int incr = tp->t_maxseg; 1027 1028 if (cw > tp->snd_ssthresh) 1029 incr = incr * incr / cw + incr / 8; 1030 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1031 } 1032 if (acked > so->so_snd.sb_cc) { 1033 tp->snd_wnd -= so->so_snd.sb_cc; 1034 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1035 ourfinisacked = 1; 1036 } else { 1037 sbdrop(&so->so_snd, acked); 1038 tp->snd_wnd -= acked; 1039 ourfinisacked = 0; 1040 } 1041 if (so->so_snd.sb_flags & SB_NOTIFY) 1042 sowwakeup(so); 1043 tp->snd_una = ti->ti_ack; 1044 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1045 tp->snd_nxt = tp->snd_una; 1046 1047 switch (tp->t_state) { 1048 1049 /* 1050 * In FIN_WAIT_1 STATE in addition to the processing 1051 * for the ESTABLISHED state if our FIN is now acknowledged 1052 * then enter FIN_WAIT_2. 1053 */ 1054 case TCPS_FIN_WAIT_1: 1055 if (ourfinisacked) { 1056 /* 1057 * If we can't receive any more 1058 * data, then closing user can proceed. 1059 * Starting the timer is contrary to the 1060 * specification, but if we don't get a FIN 1061 * we'll hang forever. 1062 */ 1063 if (so->so_state & SS_CANTRCVMORE) { 1064 soisdisconnected(so); 1065 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 1066 } 1067 tp->t_state = TCPS_FIN_WAIT_2; 1068 } 1069 break; 1070 1071 /* 1072 * In CLOSING STATE in addition to the processing for 1073 * the ESTABLISHED state if the ACK acknowledges our FIN 1074 * then enter the TIME-WAIT state, otherwise ignore 1075 * the segment. 1076 */ 1077 case TCPS_CLOSING: 1078 if (ourfinisacked) { 1079 tp->t_state = TCPS_TIME_WAIT; 1080 tcp_canceltimers(tp); 1081 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1082 soisdisconnected(so); 1083 } 1084 break; 1085 1086 /* 1087 * In LAST_ACK, we may still be waiting for data to drain 1088 * and/or to be acked, as well as for the ack of our FIN. 1089 * If our FIN is now acknowledged, delete the TCB, 1090 * enter the closed state and return. 1091 */ 1092 case TCPS_LAST_ACK: 1093 if (ourfinisacked) { 1094 tp = tcp_close(tp); 1095 goto drop; 1096 } 1097 break; 1098 1099 /* 1100 * In TIME_WAIT state the only thing that should arrive 1101 * is a retransmission of the remote FIN. Acknowledge 1102 * it and restart the finack timer. 1103 */ 1104 case TCPS_TIME_WAIT: 1105 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1106 goto dropafterack; 1107 } 1108 } 1109 1110 step6: 1111 /* 1112 * Update window information. 1113 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1114 */ 1115 if ((tiflags & TH_ACK) && 1116 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 1117 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 1118 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))) { 1119 /* keep track of pure window updates */ 1120 if (ti->ti_len == 0 && 1121 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1122 tcpstat.tcps_rcvwinupd++; 1123 tp->snd_wnd = tiwin; 1124 tp->snd_wl1 = ti->ti_seq; 1125 tp->snd_wl2 = ti->ti_ack; 1126 if (tp->snd_wnd > tp->max_sndwnd) 1127 tp->max_sndwnd = tp->snd_wnd; 1128 needoutput = 1; 1129 } 1130 1131 /* 1132 * Process segments with URG. 1133 */ 1134 if ((tiflags & TH_URG) && ti->ti_urp && 1135 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1136 /* 1137 * This is a kludge, but if we receive and accept 1138 * random urgent pointers, we'll crash in 1139 * soreceive. It's hard to imagine someone 1140 * actually wanting to send this much urgent data. 1141 */ 1142 if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { 1143 ti->ti_urp = 0; /* XXX */ 1144 tiflags &= ~TH_URG; /* XXX */ 1145 goto dodata; /* XXX */ 1146 } 1147 /* 1148 * If this segment advances the known urgent pointer, 1149 * then mark the data stream. This should not happen 1150 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1151 * a FIN has been received from the remote side. 1152 * In these states we ignore the URG. 1153 * 1154 * According to RFC961 (Assigned Protocols), 1155 * the urgent pointer points to the last octet 1156 * of urgent data. We continue, however, 1157 * to consider it to indicate the first octet 1158 * of data past the urgent section as the original 1159 * spec states (in one of two places). 1160 */ 1161 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1162 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1163 so->so_oobmark = so->so_rcv.sb_cc + 1164 (tp->rcv_up - tp->rcv_nxt) - 1; 1165 if (so->so_oobmark == 0) 1166 so->so_state |= SS_RCVATMARK; 1167 sohasoutofband(so); 1168 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1169 } 1170 /* 1171 * Remove out of band data so doesn't get presented to user. 1172 * This can happen independent of advancing the URG pointer, 1173 * but if two URG's are pending at once, some out-of-band 1174 * data may creep in... ick. 1175 */ 1176 if (ti->ti_urp <= (u_long)ti->ti_len 1177 #ifdef SO_OOBINLINE 1178 && (so->so_options & SO_OOBINLINE) == 0 1179 #endif 1180 ) 1181 tcp_pulloutofband(so, ti, m); 1182 } else 1183 /* 1184 * If no out of band data is expected, 1185 * pull receive urgent pointer along 1186 * with the receive window. 1187 */ 1188 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1189 tp->rcv_up = tp->rcv_nxt; 1190 dodata: /* XXX */ 1191 1192 /* 1193 * Process the segment text, merging it into the TCP sequencing queue, 1194 * and arranging for acknowledgment of receipt if necessary. 1195 * This process logically involves adjusting tp->rcv_wnd as data 1196 * is presented to the user (this happens in tcp_usrreq.c, 1197 * case PRU_RCVD). If a FIN has already been received on this 1198 * connection then we just ignore the text. 1199 */ 1200 if ((ti->ti_len || (tiflags&TH_FIN)) && 1201 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1202 TCP_REASS(tp, ti, m, so, tiflags); 1203 /* 1204 * Note the amount of data that peer has sent into 1205 * our window, in order to estimate the sender's 1206 * buffer size. 1207 */ 1208 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1209 } else { 1210 m_freem(m); 1211 tiflags &= ~TH_FIN; 1212 } 1213 1214 /* 1215 * If FIN is received ACK the FIN and let the user know 1216 * that the connection is closing. 1217 */ 1218 if (tiflags & TH_FIN) { 1219 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1220 socantrcvmore(so); 1221 tp->t_flags |= TF_ACKNOW; 1222 tp->rcv_nxt++; 1223 } 1224 switch (tp->t_state) { 1225 1226 /* 1227 * In SYN_RECEIVED and ESTABLISHED STATES 1228 * enter the CLOSE_WAIT state. 1229 */ 1230 case TCPS_SYN_RECEIVED: 1231 case TCPS_ESTABLISHED: 1232 tp->t_state = TCPS_CLOSE_WAIT; 1233 break; 1234 1235 /* 1236 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1237 * enter the CLOSING state. 1238 */ 1239 case TCPS_FIN_WAIT_1: 1240 tp->t_state = TCPS_CLOSING; 1241 break; 1242 1243 /* 1244 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1245 * starting the time-wait timer, turning off the other 1246 * standard timers. 1247 */ 1248 case TCPS_FIN_WAIT_2: 1249 tp->t_state = TCPS_TIME_WAIT; 1250 tcp_canceltimers(tp); 1251 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1252 soisdisconnected(so); 1253 break; 1254 1255 /* 1256 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1257 */ 1258 case TCPS_TIME_WAIT: 1259 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1260 break; 1261 } 1262 } 1263 if (so->so_options & SO_DEBUG) 1264 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1265 1266 /* 1267 * Return any desired output. 1268 */ 1269 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1270 (void) tcp_output(tp); 1271 return; 1272 1273 dropafterack: 1274 /* 1275 * Generate an ACK dropping incoming segment if it occupies 1276 * sequence space, where the ACK reflects our state. 1277 */ 1278 if (tiflags & TH_RST) 1279 goto drop; 1280 m_freem(m); 1281 tp->t_flags |= TF_ACKNOW; 1282 (void) tcp_output(tp); 1283 return; 1284 1285 dropwithreset: 1286 /* 1287 * Generate a RST, dropping incoming segment. 1288 * Make ACK acceptable to originator of segment. 1289 * Don't bother to respond if destination was broadcast/multicast. 1290 */ 1291 if ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) || 1292 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 1293 goto drop; 1294 if (tiflags & TH_ACK) 1295 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1296 else { 1297 if (tiflags & TH_SYN) 1298 ti->ti_len++; 1299 tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1300 TH_RST|TH_ACK); 1301 } 1302 /* destroy temporarily created socket */ 1303 if (dropsocket) 1304 (void) soabort(so); 1305 return; 1306 1307 drop: 1308 /* 1309 * Drop space held by incoming segment and return. 1310 */ 1311 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1312 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1313 m_freem(m); 1314 /* destroy temporarily created socket */ 1315 if (dropsocket) 1316 (void) soabort(so); 1317 return; 1318 #ifndef TUBA_INCLUDE 1319 } 1320 1321 void 1322 tcp_dooptions(tp, cp, cnt, ti, ts_present, ts_val, ts_ecr) 1323 struct tcpcb *tp; 1324 u_char *cp; 1325 int cnt; 1326 struct tcpiphdr *ti; 1327 int *ts_present; 1328 u_long *ts_val, *ts_ecr; 1329 { 1330 u_short mss; 1331 int opt, optlen; 1332 1333 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1334 opt = cp[0]; 1335 if (opt == TCPOPT_EOL) 1336 break; 1337 if (opt == TCPOPT_NOP) 1338 optlen = 1; 1339 else { 1340 optlen = cp[1]; 1341 if (optlen <= 0) 1342 break; 1343 } 1344 switch (opt) { 1345 1346 default: 1347 continue; 1348 1349 case TCPOPT_MAXSEG: 1350 if (optlen != TCPOLEN_MAXSEG) 1351 continue; 1352 if (!(ti->ti_flags & TH_SYN)) 1353 continue; 1354 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); 1355 NTOHS(mss); 1356 (void) tcp_mss(tp, mss); /* sets t_maxseg */ 1357 break; 1358 1359 case TCPOPT_WINDOW: 1360 if (optlen != TCPOLEN_WINDOW) 1361 continue; 1362 if (!(ti->ti_flags & TH_SYN)) 1363 continue; 1364 tp->t_flags |= TF_RCVD_SCALE; 1365 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 1366 break; 1367 1368 case TCPOPT_TIMESTAMP: 1369 if (optlen != TCPOLEN_TIMESTAMP) 1370 continue; 1371 *ts_present = 1; 1372 bcopy((char *)cp + 2, (char *) ts_val, sizeof(*ts_val)); 1373 NTOHL(*ts_val); 1374 bcopy((char *)cp + 6, (char *) ts_ecr, sizeof(*ts_ecr)); 1375 NTOHL(*ts_ecr); 1376 1377 /* 1378 * A timestamp received in a SYN makes 1379 * it ok to send timestamp requests and replies. 1380 */ 1381 if (ti->ti_flags & TH_SYN) { 1382 tp->t_flags |= TF_RCVD_TSTMP; 1383 tp->ts_recent = *ts_val; 1384 tp->ts_recent_age = tcp_now; 1385 } 1386 break; 1387 } 1388 } 1389 } 1390 1391 /* 1392 * Pull out of band byte out of a segment so 1393 * it doesn't appear in the user's data queue. 1394 * It is still reflected in the segment length for 1395 * sequencing purposes. 1396 */ 1397 void 1398 tcp_pulloutofband(so, ti, m) 1399 struct socket *so; 1400 struct tcpiphdr *ti; 1401 register struct mbuf *m; 1402 { 1403 int cnt = ti->ti_urp - 1; 1404 1405 while (cnt >= 0) { 1406 if (m->m_len > cnt) { 1407 char *cp = mtod(m, caddr_t) + cnt; 1408 struct tcpcb *tp = sototcpcb(so); 1409 1410 tp->t_iobc = *cp; 1411 tp->t_oobflags |= TCPOOB_HAVEDATA; 1412 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1413 m->m_len--; 1414 return; 1415 } 1416 cnt -= m->m_len; 1417 m = m->m_next; 1418 if (m == 0) 1419 break; 1420 } 1421 panic("tcp_pulloutofband"); 1422 } 1423 1424 /* 1425 * Collect new round-trip time estimate 1426 * and update averages and current timeout. 1427 */ 1428 void 1429 tcp_xmit_timer(tp, rtt) 1430 register struct tcpcb *tp; 1431 short rtt; 1432 { 1433 register short delta; 1434 1435 tcpstat.tcps_rttupdated++; 1436 if (tp->t_srtt != 0) { 1437 /* 1438 * srtt is stored as fixed point with 3 bits after the 1439 * binary point (i.e., scaled by 8). The following magic 1440 * is equivalent to the smoothing algorithm in rfc793 with 1441 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 1442 * point). Adjust rtt to origin 0. 1443 */ 1444 delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT); 1445 if ((tp->t_srtt += delta) <= 0) 1446 tp->t_srtt = 1; 1447 /* 1448 * We accumulate a smoothed rtt variance (actually, a 1449 * smoothed mean difference), then set the retransmit 1450 * timer to smoothed rtt + 4 times the smoothed variance. 1451 * rttvar is stored as fixed point with 2 bits after the 1452 * binary point (scaled by 4). The following is 1453 * equivalent to rfc793 smoothing with an alpha of .75 1454 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 1455 * rfc793's wired-in beta. 1456 */ 1457 if (delta < 0) 1458 delta = -delta; 1459 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); 1460 if ((tp->t_rttvar += delta) <= 0) 1461 tp->t_rttvar = 1; 1462 } else { 1463 /* 1464 * No rtt measurement yet - use the unsmoothed rtt. 1465 * Set the variance to half the rtt (so our first 1466 * retransmit happens at 3*rtt). 1467 */ 1468 tp->t_srtt = rtt << TCP_RTT_SHIFT; 1469 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 1470 } 1471 tp->t_rtt = 0; 1472 tp->t_rxtshift = 0; 1473 1474 /* 1475 * the retransmit should happen at rtt + 4 * rttvar. 1476 * Because of the way we do the smoothing, srtt and rttvar 1477 * will each average +1/2 tick of bias. When we compute 1478 * the retransmit timer, we want 1/2 tick of rounding and 1479 * 1 extra tick because of +-1/2 tick uncertainty in the 1480 * firing of the timer. The bias will give us exactly the 1481 * 1.5 tick we need. But, because the bias is 1482 * statistical, we have to test that we don't drop below 1483 * the minimum feasible timer (which is 2 ticks). 1484 */ 1485 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 1486 tp->t_rttmin, TCPTV_REXMTMAX); 1487 1488 /* 1489 * We received an ack for a packet that wasn't retransmitted; 1490 * it is probably safe to discard any error indications we've 1491 * received recently. This isn't quite right, but close enough 1492 * for now (a route might have failed after we sent a segment, 1493 * and the return path might not be symmetrical). 1494 */ 1495 tp->t_softerror = 0; 1496 } 1497 1498 /* 1499 * Determine a reasonable value for maxseg size. 1500 * If the route is known, check route for mtu. 1501 * If none, use an mss that can be handled on the outgoing 1502 * interface without forcing IP to fragment; if bigger than 1503 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 1504 * to utilize large mbufs. If no route is found, route has no mtu, 1505 * or the destination isn't local, use a default, hopefully conservative 1506 * size (usually 512 or the default IP max size, but no more than the mtu 1507 * of the interface), as we can't discover anything about intervening 1508 * gateways or networks. We also initialize the congestion/slow start 1509 * window to be a single segment if the destination isn't local. 1510 * While looking at the routing entry, we also initialize other path-dependent 1511 * parameters from pre-set or cached values in the routing entry. 1512 */ 1513 int 1514 tcp_mss(tp, offer) 1515 register struct tcpcb *tp; 1516 u_int offer; 1517 { 1518 struct route *ro; 1519 register struct rtentry *rt; 1520 struct ifnet *ifp; 1521 register int rtt, mss; 1522 u_long bufsize; 1523 struct inpcb *inp; 1524 struct socket *so; 1525 extern int tcp_mssdflt; 1526 1527 inp = tp->t_inpcb; 1528 ro = &inp->inp_route; 1529 1530 if ((rt = ro->ro_rt) == (struct rtentry *)0) { 1531 /* No route yet, so try to acquire one */ 1532 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1533 ro->ro_dst.sa_family = AF_INET; 1534 ro->ro_dst.sa_len = sizeof(ro->ro_dst); 1535 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1536 inp->inp_faddr; 1537 rtalloc(ro); 1538 } 1539 if ((rt = ro->ro_rt) == (struct rtentry *)0) 1540 return (tcp_mssdflt); 1541 } 1542 ifp = rt->rt_ifp; 1543 so = inp->inp_socket; 1544 1545 #ifdef RTV_MTU /* if route characteristics exist ... */ 1546 /* 1547 * While we're here, check if there's an initial rtt 1548 * or rttvar. Convert from the route-table units 1549 * to scaled multiples of the slow timeout timer. 1550 */ 1551 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 1552 /* 1553 * XXX the lock bit for MTU indicates that the value 1554 * is also a minimum value; this is subject to time. 1555 */ 1556 if (rt->rt_rmx.rmx_locks & RTV_RTT) 1557 tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ); 1558 tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 1559 if (rt->rt_rmx.rmx_rttvar) 1560 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 1561 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 1562 else 1563 /* default variation is +- 1 rtt */ 1564 tp->t_rttvar = 1565 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 1566 TCPT_RANGESET(tp->t_rxtcur, 1567 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 1568 tp->t_rttmin, TCPTV_REXMTMAX); 1569 } 1570 /* 1571 * if there's an mtu associated with the route, use it 1572 */ 1573 if (rt->rt_rmx.rmx_mtu) 1574 mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 1575 else 1576 #endif /* RTV_MTU */ 1577 { 1578 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1579 #if (MCLBYTES & (MCLBYTES - 1)) == 0 1580 if (mss > MCLBYTES) 1581 mss &= ~(MCLBYTES-1); 1582 #else 1583 if (mss > MCLBYTES) 1584 mss = mss / MCLBYTES * MCLBYTES; 1585 #endif 1586 if (!in_localaddr(inp->inp_faddr)) 1587 mss = min(mss, tcp_mssdflt); 1588 } 1589 /* 1590 * The current mss, t_maxseg, is initialized to the default value. 1591 * If we compute a smaller value, reduce the current mss. 1592 * If we compute a larger value, return it for use in sending 1593 * a max seg size option, but don't store it for use 1594 * unless we received an offer at least that large from peer. 1595 * However, do not accept offers under 32 bytes. 1596 */ 1597 if (offer) 1598 mss = min(mss, offer); 1599 mss = max(mss, 32); /* sanity */ 1600 if (mss < tp->t_maxseg || offer != 0) { 1601 /* 1602 * If there's a pipesize, change the socket buffer 1603 * to that size. Make the socket buffers an integral 1604 * number of mss units; if the mss is larger than 1605 * the socket buffer, decrease the mss. 1606 */ 1607 #ifdef RTV_SPIPE 1608 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 1609 #endif 1610 bufsize = so->so_snd.sb_hiwat; 1611 if (bufsize < mss) 1612 mss = bufsize; 1613 else { 1614 bufsize = roundup(bufsize, mss); 1615 if (bufsize > sb_max) 1616 bufsize = sb_max; 1617 (void)sbreserve(&so->so_snd, bufsize); 1618 } 1619 tp->t_maxseg = mss; 1620 1621 #ifdef RTV_RPIPE 1622 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 1623 #endif 1624 bufsize = so->so_rcv.sb_hiwat; 1625 if (bufsize > mss) { 1626 bufsize = roundup(bufsize, mss); 1627 if (bufsize > sb_max) 1628 bufsize = sb_max; 1629 (void)sbreserve(&so->so_rcv, bufsize); 1630 } 1631 } 1632 tp->snd_cwnd = mss; 1633 1634 #ifdef RTV_SSTHRESH 1635 if (rt->rt_rmx.rmx_ssthresh) { 1636 /* 1637 * There's some sort of gateway or interface 1638 * buffer limit on the path. Use this to set 1639 * the slow start threshhold, but set the 1640 * threshold to no less than 2*mss. 1641 */ 1642 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 1643 } 1644 #endif /* RTV_MTU */ 1645 return (mss); 1646 } 1647 #endif /* TUBA_INCLUDE */ 1648