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 * From: @(#)tcp_input.c 8.5 (Berkeley) 4/10/94 34 * $Id: tcp_input.c,v 1.23 1995/05/09 12:32:06 olah Exp $ 35 */ 36 37 #ifndef TUBA_INCLUDE 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/malloc.h> 41 #include <sys/mbuf.h> 42 #include <sys/protosw.h> 43 #include <sys/socket.h> 44 #include <sys/socketvar.h> 45 #include <sys/errno.h> 46 #include <sys/queue.h> 47 48 #include <net/if.h> 49 #include <net/route.h> 50 51 #include <netinet/in.h> 52 #include <netinet/in_systm.h> 53 #include <netinet/ip.h> 54 #include <netinet/in_pcb.h> 55 #include <netinet/ip_var.h> 56 #include <netinet/tcp.h> 57 #include <netinet/tcp_fsm.h> 58 #include <netinet/tcp_seq.h> 59 #include <netinet/tcp_timer.h> 60 #include <netinet/tcp_var.h> 61 #include <netinet/tcpip.h> 62 #ifdef TCPDEBUG 63 #include <netinet/tcp_debug.h> 64 struct tcpiphdr tcp_saveti; 65 #endif 66 67 int tcprexmtthresh = 3; 68 tcp_seq tcp_iss; 69 tcp_cc tcp_ccgen; 70 struct tcpstat tcpstat; 71 u_long tcp_now; 72 struct inpcbhead tcb; 73 struct inpcbinfo tcbinfo; 74 75 #endif /* TUBA_INCLUDE */ 76 77 /* 78 * Insert segment ti into reassembly queue of tcp with 79 * control block tp. Return TH_FIN if reassembly now includes 80 * a segment with FIN. The macro form does the common case inline 81 * (segment is the next to be received on an established connection, 82 * and the queue is empty), avoiding linkage into and removal 83 * from the queue and repetition of various conversions. 84 * Set DELACK for segments received in order, but ack immediately 85 * when segments are out of order (so fast retransmit can work). 86 */ 87 #ifdef TCP_ACK_HACK 88 #define TCP_REASS(tp, ti, m, so, flags) { \ 89 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 90 (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 91 (tp)->t_state == TCPS_ESTABLISHED) { \ 92 if (ti->ti_flags & TH_PUSH) \ 93 tp->t_flags |= TF_ACKNOW; \ 94 else \ 95 tp->t_flags |= TF_DELACK; \ 96 (tp)->rcv_nxt += (ti)->ti_len; \ 97 flags = (ti)->ti_flags & TH_FIN; \ 98 tcpstat.tcps_rcvpack++;\ 99 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 100 sbappend(&(so)->so_rcv, (m)); \ 101 sorwakeup(so); \ 102 } else { \ 103 (flags) = tcp_reass((tp), (ti), (m)); \ 104 tp->t_flags |= TF_ACKNOW; \ 105 } \ 106 } 107 #else 108 #define TCP_REASS(tp, ti, m, so, flags) { \ 109 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 110 (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 111 (tp)->t_state == TCPS_ESTABLISHED) { \ 112 tp->t_flags |= TF_DELACK; \ 113 (tp)->rcv_nxt += (ti)->ti_len; \ 114 flags = (ti)->ti_flags & TH_FIN; \ 115 tcpstat.tcps_rcvpack++;\ 116 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 117 sbappend(&(so)->so_rcv, (m)); \ 118 sorwakeup(so); \ 119 } else { \ 120 (flags) = tcp_reass((tp), (ti), (m)); \ 121 tp->t_flags |= TF_ACKNOW; \ 122 } \ 123 } 124 #endif 125 #ifndef TUBA_INCLUDE 126 127 int 128 tcp_reass(tp, ti, m) 129 register struct tcpcb *tp; 130 register struct tcpiphdr *ti; 131 struct mbuf *m; 132 { 133 register struct tcpiphdr *q; 134 struct socket *so = tp->t_inpcb->inp_socket; 135 int flags; 136 137 /* 138 * Call with ti==0 after become established to 139 * force pre-ESTABLISHED data up to user socket. 140 */ 141 if (ti == 0) 142 goto present; 143 144 /* 145 * Find a segment which begins after this one does. 146 */ 147 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 148 q = (struct tcpiphdr *)q->ti_next) 149 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 150 break; 151 152 /* 153 * If there is a preceding segment, it may provide some of 154 * our data already. If so, drop the data from the incoming 155 * segment. If it provides all of our data, drop us. 156 */ 157 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 158 register int i; 159 q = (struct tcpiphdr *)q->ti_prev; 160 /* conversion to int (in i) handles seq wraparound */ 161 i = q->ti_seq + q->ti_len - ti->ti_seq; 162 if (i > 0) { 163 if (i >= ti->ti_len) { 164 tcpstat.tcps_rcvduppack++; 165 tcpstat.tcps_rcvdupbyte += ti->ti_len; 166 m_freem(m); 167 /* 168 * Try to present any queued data 169 * at the left window edge to the user. 170 * This is needed after the 3-WHS 171 * completes. 172 */ 173 goto present; /* ??? */ 174 } 175 m_adj(m, i); 176 ti->ti_len -= i; 177 ti->ti_seq += i; 178 } 179 q = (struct tcpiphdr *)(q->ti_next); 180 } 181 tcpstat.tcps_rcvoopack++; 182 tcpstat.tcps_rcvoobyte += ti->ti_len; 183 REASS_MBUF(ti) = m; /* XXX */ 184 185 /* 186 * While we overlap succeeding segments trim them or, 187 * if they are completely covered, dequeue them. 188 */ 189 while (q != (struct tcpiphdr *)tp) { 190 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 191 if (i <= 0) 192 break; 193 if (i < q->ti_len) { 194 q->ti_seq += i; 195 q->ti_len -= i; 196 m_adj(REASS_MBUF(q), i); 197 break; 198 } 199 q = (struct tcpiphdr *)q->ti_next; 200 m = REASS_MBUF((struct tcpiphdr *)q->ti_prev); 201 remque(q->ti_prev); 202 m_freem(m); 203 } 204 205 /* 206 * Stick new segment in its place. 207 */ 208 insque(ti, q->ti_prev); 209 210 present: 211 /* 212 * Present data to user, advancing rcv_nxt through 213 * completed sequence space. 214 */ 215 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 216 return (0); 217 ti = tp->seg_next; 218 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 219 return (0); 220 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 221 return (0); 222 do { 223 tp->rcv_nxt += ti->ti_len; 224 flags = ti->ti_flags & TH_FIN; 225 remque(ti); 226 m = REASS_MBUF(ti); 227 ti = (struct tcpiphdr *)ti->ti_next; 228 if (so->so_state & SS_CANTRCVMORE) 229 m_freem(m); 230 else 231 sbappend(&so->so_rcv, m); 232 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 233 sorwakeup(so); 234 return (flags); 235 } 236 237 /* 238 * TCP input routine, follows pages 65-76 of the 239 * protocol specification dated September, 1981 very closely. 240 */ 241 void 242 tcp_input(m, iphlen) 243 register struct mbuf *m; 244 int iphlen; 245 { 246 register struct tcpiphdr *ti; 247 register struct inpcb *inp; 248 caddr_t optp = NULL; 249 int optlen = 0; 250 int len, tlen, off; 251 register struct tcpcb *tp = 0; 252 register int tiflags; 253 struct socket *so = 0; 254 int todrop, acked, ourfinisacked, needoutput = 0; 255 struct in_addr laddr; 256 int dropsocket = 0; 257 int iss = 0; 258 u_long tiwin; 259 struct tcpopt to; /* options in this segment */ 260 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 261 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 262 #ifdef TCPDEBUG 263 short ostate = 0; 264 #endif 265 266 bzero((char *)&to, sizeof(to)); 267 268 tcpstat.tcps_rcvtotal++; 269 /* 270 * Get IP and TCP header together in first mbuf. 271 * Note: IP leaves IP header in first mbuf. 272 */ 273 ti = mtod(m, struct tcpiphdr *); 274 if (iphlen > sizeof (struct ip)) 275 ip_stripoptions(m, (struct mbuf *)0); 276 if (m->m_len < sizeof (struct tcpiphdr)) { 277 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 278 tcpstat.tcps_rcvshort++; 279 return; 280 } 281 ti = mtod(m, struct tcpiphdr *); 282 } 283 284 /* 285 * Checksum extended TCP header and data. 286 */ 287 tlen = ((struct ip *)ti)->ip_len; 288 len = sizeof (struct ip) + tlen; 289 ti->ti_next = ti->ti_prev = 0; 290 ti->ti_x1 = 0; 291 ti->ti_len = (u_short)tlen; 292 HTONS(ti->ti_len); 293 ti->ti_sum = in_cksum(m, len); 294 if (ti->ti_sum) { 295 tcpstat.tcps_rcvbadsum++; 296 goto drop; 297 } 298 #endif /* TUBA_INCLUDE */ 299 300 /* 301 * Check that TCP offset makes sense, 302 * pull out TCP options and adjust length. XXX 303 */ 304 off = ti->ti_off << 2; 305 if (off < sizeof (struct tcphdr) || off > tlen) { 306 tcpstat.tcps_rcvbadoff++; 307 goto drop; 308 } 309 tlen -= off; 310 ti->ti_len = tlen; 311 if (off > sizeof (struct tcphdr)) { 312 if (m->m_len < sizeof(struct ip) + off) { 313 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 314 tcpstat.tcps_rcvshort++; 315 return; 316 } 317 ti = mtod(m, struct tcpiphdr *); 318 } 319 optlen = off - sizeof (struct tcphdr); 320 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 321 /* 322 * Do quick retrieval of timestamp options ("options 323 * prediction?"). If timestamp is the only option and it's 324 * formatted as recommended in RFC 1323 appendix A, we 325 * quickly get the values now and not bother calling 326 * tcp_dooptions(), etc. 327 */ 328 if ((optlen == TCPOLEN_TSTAMP_APPA || 329 (optlen > TCPOLEN_TSTAMP_APPA && 330 optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && 331 *(u_long *)optp == htonl(TCPOPT_TSTAMP_HDR) && 332 (ti->ti_flags & TH_SYN) == 0) { 333 to.to_flag |= TOF_TS; 334 to.to_tsval = ntohl(*(u_long *)(optp + 4)); 335 to.to_tsecr = ntohl(*(u_long *)(optp + 8)); 336 optp = NULL; /* we've parsed the options */ 337 } 338 } 339 tiflags = ti->ti_flags; 340 341 /* 342 * Convert TCP protocol specific fields to host format. 343 */ 344 NTOHL(ti->ti_seq); 345 NTOHL(ti->ti_ack); 346 NTOHS(ti->ti_win); 347 NTOHS(ti->ti_urp); 348 349 /* 350 * Drop TCP, IP headers and TCP options. 351 */ 352 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 353 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 354 355 /* 356 * Locate pcb for segment. 357 */ 358 findpcb: 359 /* 360 * First look for an exact match. 361 */ 362 inp = in_pcblookuphash(&tcbinfo, ti->ti_src, ti->ti_sport, 363 ti->ti_dst, ti->ti_dport); 364 /* 365 * ...and if that fails, do a wildcard search. 366 */ 367 if (inp == NULL) { 368 inp = in_pcblookup(&tcb, ti->ti_src, ti->ti_sport, 369 ti->ti_dst, ti->ti_dport, INPLOOKUP_WILDCARD); 370 } 371 372 /* 373 * If the state is CLOSED (i.e., TCB does not exist) then 374 * all data in the incoming segment is discarded. 375 * If the TCB exists but is in CLOSED state, it is embryonic, 376 * but should either do a listen or a connect soon. 377 */ 378 if (inp == NULL) 379 goto dropwithreset; 380 tp = intotcpcb(inp); 381 if (tp == 0) 382 goto dropwithreset; 383 if (tp->t_state == TCPS_CLOSED) 384 goto drop; 385 386 /* Unscale the window into a 32-bit value. */ 387 if ((tiflags & TH_SYN) == 0) 388 tiwin = ti->ti_win << tp->snd_scale; 389 else 390 tiwin = ti->ti_win; 391 392 so = inp->inp_socket; 393 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 394 #ifdef TCPDEBUG 395 if (so->so_options & SO_DEBUG) { 396 ostate = tp->t_state; 397 tcp_saveti = *ti; 398 } 399 #endif 400 if (so->so_options & SO_ACCEPTCONN) { 401 register struct tcpcb *tp0 = tp; 402 so = sonewconn(so, 0); 403 if (so == 0) 404 goto drop; 405 /* 406 * This is ugly, but .... 407 * 408 * Mark socket as temporary until we're 409 * committed to keeping it. The code at 410 * ``drop'' and ``dropwithreset'' check the 411 * flag dropsocket to see if the temporary 412 * socket created here should be discarded. 413 * We mark the socket as discardable until 414 * we're committed to it below in TCPS_LISTEN. 415 */ 416 dropsocket++; 417 inp = (struct inpcb *)so->so_pcb; 418 inp->inp_laddr = ti->ti_dst; 419 inp->inp_lport = ti->ti_dport; 420 in_pcbrehash(inp); 421 #if BSD>=43 422 inp->inp_options = ip_srcroute(); 423 #endif 424 tp = intotcpcb(inp); 425 tp->t_state = TCPS_LISTEN; 426 tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT); 427 428 /* Compute proper scaling value from buffer space */ 429 while (tp->request_r_scale < TCP_MAX_WINSHIFT && 430 TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) 431 tp->request_r_scale++; 432 } 433 } 434 435 /* 436 * Segment received on connection. 437 * Reset idle time and keep-alive timer. 438 */ 439 tp->t_idle = 0; 440 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 441 442 /* 443 * Process options if not in LISTEN state, 444 * else do it below (after getting remote address). 445 */ 446 if (optp && tp->t_state != TCPS_LISTEN) 447 tcp_dooptions(tp, optp, optlen, ti, 448 &to); 449 450 /* 451 * Header prediction: check for the two common cases 452 * of a uni-directional data xfer. If the packet has 453 * no control flags, is in-sequence, the window didn't 454 * change and we're not retransmitting, it's a 455 * candidate. If the length is zero and the ack moved 456 * forward, we're the sender side of the xfer. Just 457 * free the data acked & wake any higher level process 458 * that was blocked waiting for space. If the length 459 * is non-zero and the ack didn't move, we're the 460 * receiver side. If we're getting packets in-order 461 * (the reassembly queue is empty), add the data to 462 * the socket buffer and note that we need a delayed ack. 463 * Make sure that the hidden state-flags are also off. 464 * Since we check for TCPS_ESTABLISHED above, it can only 465 * be TH_NEEDSYN. 466 */ 467 if (tp->t_state == TCPS_ESTABLISHED && 468 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 469 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 470 ((to.to_flag & TOF_TS) == 0 || 471 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 472 /* 473 * Using the CC option is compulsory if once started: 474 * the segment is OK if no T/TCP was negotiated or 475 * if the segment has a CC option equal to CCrecv 476 */ 477 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 478 (to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv) && 479 ti->ti_seq == tp->rcv_nxt && 480 tiwin && tiwin == tp->snd_wnd && 481 tp->snd_nxt == tp->snd_max) { 482 483 /* 484 * If last ACK falls within this segment's sequence numbers, 485 * record the timestamp. 486 * NOTE that the test is modified according to the latest 487 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 488 */ 489 if ((to.to_flag & TOF_TS) != 0 && 490 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { 491 tp->ts_recent_age = tcp_now; 492 tp->ts_recent = to.to_tsval; 493 } 494 495 if (ti->ti_len == 0) { 496 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 497 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 498 tp->snd_cwnd >= tp->snd_wnd) { 499 /* 500 * this is a pure ack for outstanding data. 501 */ 502 ++tcpstat.tcps_predack; 503 if ((to.to_flag & TOF_TS) != 0) 504 tcp_xmit_timer(tp, 505 tcp_now - to.to_tsecr + 1); 506 else if (tp->t_rtt && 507 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 508 tcp_xmit_timer(tp, tp->t_rtt); 509 acked = ti->ti_ack - tp->snd_una; 510 tcpstat.tcps_rcvackpack++; 511 tcpstat.tcps_rcvackbyte += acked; 512 sbdrop(&so->so_snd, acked); 513 tp->snd_una = ti->ti_ack; 514 m_freem(m); 515 516 /* 517 * If all outstanding data are acked, stop 518 * retransmit timer, otherwise restart timer 519 * using current (possibly backed-off) value. 520 * If process is waiting for space, 521 * wakeup/selwakeup/signal. If data 522 * are ready to send, let tcp_output 523 * decide between more output or persist. 524 */ 525 if (tp->snd_una == tp->snd_max) 526 tp->t_timer[TCPT_REXMT] = 0; 527 else if (tp->t_timer[TCPT_PERSIST] == 0) 528 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 529 530 if (so->so_snd.sb_flags & SB_NOTIFY) 531 sowwakeup(so); 532 if (so->so_snd.sb_cc) 533 (void) tcp_output(tp); 534 return; 535 } 536 } else if (ti->ti_ack == tp->snd_una && 537 tp->seg_next == (struct tcpiphdr *)tp && 538 ti->ti_len <= sbspace(&so->so_rcv)) { 539 /* 540 * this is a pure, in-sequence data packet 541 * with nothing on the reassembly queue and 542 * we have enough buffer space to take it. 543 */ 544 ++tcpstat.tcps_preddat; 545 tp->rcv_nxt += ti->ti_len; 546 tcpstat.tcps_rcvpack++; 547 tcpstat.tcps_rcvbyte += ti->ti_len; 548 /* 549 * Add data to socket buffer. 550 */ 551 sbappend(&so->so_rcv, m); 552 sorwakeup(so); 553 #ifdef TCP_ACK_HACK 554 /* 555 * If this is a short packet, then ACK now - with Nagel 556 * congestion avoidance sender won't send more until 557 * he gets an ACK. 558 */ 559 if (tiflags & TH_PUSH) { 560 tp->t_flags |= TF_ACKNOW; 561 tcp_output(tp); 562 } else { 563 tp->t_flags |= TF_DELACK; 564 } 565 #else 566 tp->t_flags |= TF_DELACK; 567 #endif 568 return; 569 } 570 } 571 572 /* 573 * Calculate amount of space in receive window, 574 * and then do TCP input processing. 575 * Receive window is amount of space in rcv queue, 576 * but not less than advertised window. 577 */ 578 { int win; 579 580 win = sbspace(&so->so_rcv); 581 if (win < 0) 582 win = 0; 583 tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 584 } 585 586 switch (tp->t_state) { 587 588 /* 589 * If the state is LISTEN then ignore segment if it contains an RST. 590 * If the segment contains an ACK then it is bad and send a RST. 591 * If it does not contain a SYN then it is not interesting; drop it. 592 * Don't bother responding if the destination was a broadcast. 593 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 594 * tp->iss, and send a segment: 595 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 596 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 597 * Fill in remote peer address fields if not previously specified. 598 * Enter SYN_RECEIVED state, and process any other fields of this 599 * segment in this state. 600 */ 601 case TCPS_LISTEN: { 602 struct mbuf *am; 603 register struct sockaddr_in *sin; 604 605 if (tiflags & TH_RST) 606 goto drop; 607 if (tiflags & TH_ACK) 608 goto dropwithreset; 609 if ((tiflags & TH_SYN) == 0) 610 goto drop; 611 /* 612 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 613 * in_broadcast() should never return true on a received 614 * packet with M_BCAST not set. 615 */ 616 if (m->m_flags & (M_BCAST|M_MCAST) || 617 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 618 goto drop; 619 am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ 620 if (am == NULL) 621 goto drop; 622 am->m_len = sizeof (struct sockaddr_in); 623 sin = mtod(am, struct sockaddr_in *); 624 sin->sin_family = AF_INET; 625 sin->sin_len = sizeof(*sin); 626 sin->sin_addr = ti->ti_src; 627 sin->sin_port = ti->ti_sport; 628 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 629 laddr = inp->inp_laddr; 630 if (inp->inp_laddr.s_addr == INADDR_ANY) 631 inp->inp_laddr = ti->ti_dst; 632 if (in_pcbconnect(inp, am)) { 633 inp->inp_laddr = laddr; 634 (void) m_free(am); 635 goto drop; 636 } 637 (void) m_free(am); 638 tp->t_template = tcp_template(tp); 639 if (tp->t_template == 0) { 640 tp = tcp_drop(tp, ENOBUFS); 641 dropsocket = 0; /* socket is already gone */ 642 goto drop; 643 } 644 if ((taop = tcp_gettaocache(inp)) == NULL) { 645 taop = &tao_noncached; 646 bzero(taop, sizeof(*taop)); 647 } 648 if (optp) 649 tcp_dooptions(tp, optp, optlen, ti, 650 &to); 651 if (iss) 652 tp->iss = iss; 653 else 654 tp->iss = tcp_iss; 655 tcp_iss += TCP_ISSINCR/2; 656 tp->irs = ti->ti_seq; 657 tcp_sendseqinit(tp); 658 tcp_rcvseqinit(tp); 659 /* 660 * Initialization of the tcpcb for transaction; 661 * set SND.WND = SEG.WND, 662 * initialize CCsend and CCrecv. 663 */ 664 tp->snd_wnd = tiwin; /* initial send-window */ 665 tp->cc_send = CC_INC(tcp_ccgen); 666 tp->cc_recv = to.to_cc; 667 /* 668 * Perform TAO test on incoming CC (SEG.CC) option, if any. 669 * - compare SEG.CC against cached CC from the same host, 670 * if any. 671 * - if SEG.CC > chached value, SYN must be new and is accepted 672 * immediately: save new CC in the cache, mark the socket 673 * connected, enter ESTABLISHED state, turn on flag to 674 * send a SYN in the next segment. 675 * A virtual advertised window is set in rcv_adv to 676 * initialize SWS prevention. Then enter normal segment 677 * processing: drop SYN, process data and FIN. 678 * - otherwise do a normal 3-way handshake. 679 */ 680 if ((to.to_flag & TOF_CC) != 0) { 681 if (taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { 682 taop->tao_cc = to.to_cc; 683 tp->t_state = TCPS_ESTABLISHED; 684 685 /* 686 * If there is a FIN, or if there is data and the 687 * connection is local, then delay SYN,ACK(SYN) in 688 * the hope of piggy-backing it on a response 689 * segment. Otherwise must send ACK now in case 690 * the other side is slow starting. 691 */ 692 if ((tiflags & TH_FIN) || (ti->ti_len != 0 && 693 in_localaddr(inp->inp_faddr))) 694 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 695 else 696 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 697 tp->rcv_adv += tp->rcv_wnd; 698 tcpstat.tcps_connects++; 699 soisconnected(so); 700 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 701 dropsocket = 0; /* committed to socket */ 702 tcpstat.tcps_accepts++; 703 goto trimthenstep6; 704 } 705 /* else do standard 3-way handshake */ 706 } else { 707 /* 708 * No CC option, but maybe CC.NEW: 709 * invalidate cached value. 710 */ 711 taop->tao_cc = 0; 712 } 713 /* 714 * TAO test failed or there was no CC option, 715 * do a standard 3-way handshake. 716 */ 717 tp->t_flags |= TF_ACKNOW; 718 tp->t_state = TCPS_SYN_RECEIVED; 719 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 720 dropsocket = 0; /* committed to socket */ 721 tcpstat.tcps_accepts++; 722 goto trimthenstep6; 723 } 724 725 /* 726 * If the state is SYN_SENT: 727 * if seg contains an ACK, but not for our SYN, drop the input. 728 * if seg contains a RST, then drop the connection. 729 * if seg does not contain SYN, then drop it. 730 * Otherwise this is an acceptable SYN segment 731 * initialize tp->rcv_nxt and tp->irs 732 * if seg contains ack then advance tp->snd_una 733 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 734 * arrange for segment to be acked (eventually) 735 * continue processing rest of data/controls, beginning with URG 736 */ 737 case TCPS_SYN_SENT: 738 if ((taop = tcp_gettaocache(inp)) == NULL) { 739 taop = &tao_noncached; 740 bzero(taop, sizeof(*taop)); 741 } 742 743 if ((tiflags & TH_ACK) && 744 (SEQ_LEQ(ti->ti_ack, tp->iss) || 745 SEQ_GT(ti->ti_ack, tp->snd_max))) { 746 /* 747 * If we have a cached CCsent for the remote host, 748 * hence we haven't just crashed and restarted, 749 * do not send a RST. This may be a retransmission 750 * from the other side after our earlier ACK was lost. 751 * Our new SYN, when it arrives, will serve as the 752 * needed ACK. 753 */ 754 if (taop->tao_ccsent != 0) 755 goto drop; 756 else 757 goto dropwithreset; 758 } 759 if (tiflags & TH_RST) { 760 if (tiflags & TH_ACK) 761 tp = tcp_drop(tp, ECONNREFUSED); 762 goto drop; 763 } 764 if ((tiflags & TH_SYN) == 0) 765 goto drop; 766 tp->snd_wnd = ti->ti_win; /* initial send window */ 767 tp->cc_recv = to.to_cc; /* foreign CC */ 768 769 tp->irs = ti->ti_seq; 770 tcp_rcvseqinit(tp); 771 if (tiflags & TH_ACK && SEQ_GT(ti->ti_ack, tp->iss)) { 772 tcpstat.tcps_connects++; 773 soisconnected(so); 774 /* Do window scaling on this connection? */ 775 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 776 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 777 tp->snd_scale = tp->requested_s_scale; 778 tp->rcv_scale = tp->request_r_scale; 779 } 780 /* 781 * Our SYN was acked. If segment contains CC.ECHO 782 * option, check it to make sure this segment really 783 * matches our SYN. If not, just drop it as old 784 * duplicate, but send an RST if we're still playing 785 * by the old rules. 786 */ 787 if ((to.to_flag & TOF_CCECHO) && 788 tp->cc_send != to.to_ccecho) { 789 if (taop->tao_ccsent != 0) 790 goto drop; 791 else 792 goto dropwithreset; 793 } 794 /* Segment is acceptable, update cache if undefined. */ 795 if (taop->tao_ccsent == 0) 796 taop->tao_ccsent = to.to_ccecho; 797 798 tp->rcv_adv += tp->rcv_wnd; 799 tp->snd_una++; /* SYN is acked */ 800 /* 801 * If there's data, delay ACK; if there's also a FIN 802 * ACKNOW will be turned on later. 803 */ 804 if (ti->ti_len != 0) 805 tp->t_flags |= TF_DELACK; 806 else 807 tp->t_flags |= TF_ACKNOW; 808 /* 809 * Received <SYN,ACK> in SYN_SENT[*] state. 810 * Transitions: 811 * SYN_SENT --> ESTABLISHED 812 * SYN_SENT* --> FIN_WAIT_1 813 */ 814 if (tp->t_flags & TF_NEEDFIN) { 815 tp->t_state = TCPS_FIN_WAIT_1; 816 tp->t_flags &= ~TF_NEEDFIN; 817 tiflags &= ~TH_SYN; 818 } else 819 tp->t_state = TCPS_ESTABLISHED; 820 821 } else { 822 /* 823 * Received initial SYN in SYN-SENT[*] state => simul- 824 * taneous open. If segment contains CC option and there is 825 * a cached CC, apply TAO test; if it succeeds, connection is 826 * half-synchronized. Otherwise, do 3-way handshake: 827 * SYN-SENT -> SYN-RECEIVED 828 * SYN-SENT* -> SYN-RECEIVED* 829 * If there was no CC option, clear cached CC value. 830 */ 831 tp->t_flags |= TF_ACKNOW; 832 tp->t_timer[TCPT_REXMT] = 0; 833 if (to.to_flag & TOF_CC) { 834 if (taop->tao_cc != 0 && 835 CC_GT(to.to_cc, taop->tao_cc)) { 836 /* 837 * update cache and make transition: 838 * SYN-SENT -> ESTABLISHED* 839 * SYN-SENT* -> FIN-WAIT-1* 840 */ 841 taop->tao_cc = to.to_cc; 842 if (tp->t_flags & TF_NEEDFIN) { 843 tp->t_state = TCPS_FIN_WAIT_1; 844 tp->t_flags &= ~TF_NEEDFIN; 845 } else 846 tp->t_state = TCPS_ESTABLISHED; 847 tp->t_flags |= TF_NEEDSYN; 848 } else 849 tp->t_state = TCPS_SYN_RECEIVED; 850 } else { 851 /* CC.NEW or no option => invalidate cache */ 852 taop->tao_cc = 0; 853 tp->t_state = TCPS_SYN_RECEIVED; 854 } 855 } 856 857 trimthenstep6: 858 /* 859 * Advance ti->ti_seq to correspond to first data byte. 860 * If data, trim to stay within window, 861 * dropping FIN if necessary. 862 */ 863 ti->ti_seq++; 864 if (ti->ti_len > tp->rcv_wnd) { 865 todrop = ti->ti_len - tp->rcv_wnd; 866 m_adj(m, -todrop); 867 ti->ti_len = tp->rcv_wnd; 868 tiflags &= ~TH_FIN; 869 tcpstat.tcps_rcvpackafterwin++; 870 tcpstat.tcps_rcvbyteafterwin += todrop; 871 } 872 tp->snd_wl1 = ti->ti_seq - 1; 873 tp->rcv_up = ti->ti_seq; 874 /* 875 * Client side of transaction: already sent SYN and data. 876 * If the remote host used T/TCP to validate the SYN, 877 * our data will be ACK'd; if so, enter normal data segment 878 * processing in the middle of step 5, ack processing. 879 * Otherwise, goto step 6. 880 */ 881 if (tiflags & TH_ACK) 882 goto process_ACK; 883 goto step6; 884 /* 885 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 886 * if segment contains a SYN and CC [not CC.NEW] option: 887 * if state == TIME_WAIT and connection duration > MSL, 888 * drop packet and send RST; 889 * 890 * if SEG.CC > CCrecv then is new SYN, and can implicitly 891 * ack the FIN (and data) in retransmission queue. 892 * Complete close and delete TCPCB. Then reprocess 893 * segment, hoping to find new TCPCB in LISTEN state; 894 * 895 * else must be old SYN; drop it. 896 * else do normal processing. 897 */ 898 case TCPS_LAST_ACK: 899 case TCPS_CLOSING: 900 case TCPS_TIME_WAIT: 901 if ((tiflags & TH_SYN) && 902 (to.to_flag & TOF_CC) && tp->cc_recv != 0) { 903 if (tp->t_state == TCPS_TIME_WAIT && 904 tp->t_duration > TCPTV_MSL) 905 goto dropwithreset; 906 if (CC_GT(to.to_cc, tp->cc_recv)) { 907 tp = tcp_close(tp); 908 goto findpcb; 909 } 910 else 911 goto drop; 912 } 913 break; /* continue normal processing */ 914 } 915 916 /* 917 * States other than LISTEN or SYN_SENT. 918 * First check timestamp, if present. 919 * Then check the connection count, if present. 920 * Then check that at least some bytes of segment are within 921 * receive window. If segment begins before rcv_nxt, 922 * drop leading data (and SYN); if nothing left, just ack. 923 * 924 * RFC 1323 PAWS: If we have a timestamp reply on this segment 925 * and it's less than ts_recent, drop it. 926 */ 927 if ((to.to_flag & TOF_TS) != 0 && (tiflags & TH_RST) == 0 && 928 tp->ts_recent && TSTMP_LT(to.to_tsval, tp->ts_recent)) { 929 930 /* Check to see if ts_recent is over 24 days old. */ 931 if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 932 /* 933 * Invalidate ts_recent. If this segment updates 934 * ts_recent, the age will be reset later and ts_recent 935 * will get a valid value. If it does not, setting 936 * ts_recent to zero will at least satisfy the 937 * requirement that zero be placed in the timestamp 938 * echo reply when ts_recent isn't valid. The 939 * age isn't reset until we get a valid ts_recent 940 * because we don't want out-of-order segments to be 941 * dropped when ts_recent is old. 942 */ 943 tp->ts_recent = 0; 944 } else { 945 tcpstat.tcps_rcvduppack++; 946 tcpstat.tcps_rcvdupbyte += ti->ti_len; 947 tcpstat.tcps_pawsdrop++; 948 goto dropafterack; 949 } 950 } 951 952 /* 953 * T/TCP mechanism 954 * If T/TCP was negotiated and the segment doesn't have CC, 955 * or if it's CC is wrong then drop the segment. 956 * RST segments do not have to comply with this. 957 */ 958 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 959 ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc) && 960 (tiflags & TH_RST) == 0) 961 goto dropafterack; 962 963 todrop = tp->rcv_nxt - ti->ti_seq; 964 if (todrop > 0) { 965 if (tiflags & TH_SYN) { 966 tiflags &= ~TH_SYN; 967 ti->ti_seq++; 968 if (ti->ti_urp > 1) 969 ti->ti_urp--; 970 else 971 tiflags &= ~TH_URG; 972 todrop--; 973 } 974 /* 975 * Following if statement from Stevens, vol. 2, p. 960. 976 */ 977 if (todrop > ti->ti_len 978 || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) { 979 /* 980 * Any valid FIN must be to the left of the window. 981 * At this point the FIN must be a duplicate or out 982 * of sequence; drop it. 983 */ 984 tiflags &= ~TH_FIN; 985 986 /* 987 * Send an ACK to resynchronize and drop any data. 988 * But keep on processing for RST or ACK. 989 */ 990 tp->t_flags |= TF_ACKNOW; 991 todrop = ti->ti_len; 992 tcpstat.tcps_rcvduppack++; 993 tcpstat.tcps_rcvdupbyte += todrop; 994 } else { 995 tcpstat.tcps_rcvpartduppack++; 996 tcpstat.tcps_rcvpartdupbyte += todrop; 997 } 998 m_adj(m, todrop); 999 ti->ti_seq += todrop; 1000 ti->ti_len -= todrop; 1001 if (ti->ti_urp > todrop) 1002 ti->ti_urp -= todrop; 1003 else { 1004 tiflags &= ~TH_URG; 1005 ti->ti_urp = 0; 1006 } 1007 } 1008 1009 /* 1010 * If new data are received on a connection after the 1011 * user processes are gone, then RST the other end. 1012 */ 1013 if ((so->so_state & SS_NOFDREF) && 1014 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 1015 tp = tcp_close(tp); 1016 tcpstat.tcps_rcvafterclose++; 1017 goto dropwithreset; 1018 } 1019 1020 /* 1021 * If segment ends after window, drop trailing data 1022 * (and PUSH and FIN); if nothing left, just ACK. 1023 */ 1024 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 1025 if (todrop > 0) { 1026 tcpstat.tcps_rcvpackafterwin++; 1027 if (todrop >= ti->ti_len) { 1028 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 1029 /* 1030 * If a new connection request is received 1031 * while in TIME_WAIT, drop the old connection 1032 * and start over if the sequence numbers 1033 * are above the previous ones. 1034 */ 1035 if (tiflags & TH_SYN && 1036 tp->t_state == TCPS_TIME_WAIT && 1037 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 1038 iss = tp->rcv_nxt + TCP_ISSINCR; 1039 tp = tcp_close(tp); 1040 goto findpcb; 1041 } 1042 /* 1043 * If window is closed can only take segments at 1044 * window edge, and have to drop data and PUSH from 1045 * incoming segments. Continue processing, but 1046 * remember to ack. Otherwise, drop segment 1047 * and ack. 1048 */ 1049 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 1050 tp->t_flags |= TF_ACKNOW; 1051 tcpstat.tcps_rcvwinprobe++; 1052 } else 1053 goto dropafterack; 1054 } else 1055 tcpstat.tcps_rcvbyteafterwin += todrop; 1056 m_adj(m, -todrop); 1057 ti->ti_len -= todrop; 1058 tiflags &= ~(TH_PUSH|TH_FIN); 1059 } 1060 1061 /* 1062 * If last ACK falls within this segment's sequence numbers, 1063 * record its timestamp. 1064 * NOTE that the test is modified according to the latest 1065 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1066 */ 1067 if ((to.to_flag & TOF_TS) != 0 && 1068 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { 1069 tp->ts_recent_age = tcp_now; 1070 tp->ts_recent = to.to_tsval; 1071 } 1072 1073 /* 1074 * If the RST bit is set examine the state: 1075 * SYN_RECEIVED STATE: 1076 * If passive open, return to LISTEN state. 1077 * If active open, inform user that connection was refused. 1078 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 1079 * Inform user that connection was reset, and close tcb. 1080 * CLOSING, LAST_ACK, TIME_WAIT STATES 1081 * Close the tcb. 1082 */ 1083 if (tiflags&TH_RST) switch (tp->t_state) { 1084 1085 case TCPS_SYN_RECEIVED: 1086 so->so_error = ECONNREFUSED; 1087 goto close; 1088 1089 case TCPS_ESTABLISHED: 1090 case TCPS_FIN_WAIT_1: 1091 case TCPS_FIN_WAIT_2: 1092 case TCPS_CLOSE_WAIT: 1093 so->so_error = ECONNRESET; 1094 close: 1095 tp->t_state = TCPS_CLOSED; 1096 tcpstat.tcps_drops++; 1097 tp = tcp_close(tp); 1098 goto drop; 1099 1100 case TCPS_CLOSING: 1101 case TCPS_LAST_ACK: 1102 case TCPS_TIME_WAIT: 1103 tp = tcp_close(tp); 1104 goto drop; 1105 } 1106 1107 /* 1108 * If a SYN is in the window, then this is an 1109 * error and we send an RST and drop the connection. 1110 */ 1111 if (tiflags & TH_SYN) { 1112 tp = tcp_drop(tp, ECONNRESET); 1113 goto dropwithreset; 1114 } 1115 1116 /* 1117 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1118 * flag is on (half-synchronized state), then queue data for 1119 * later processing; else drop segment and return. 1120 */ 1121 if ((tiflags & TH_ACK) == 0) { 1122 if (tp->t_state == TCPS_SYN_RECEIVED || 1123 (tp->t_flags & TF_NEEDSYN)) 1124 goto step6; 1125 else 1126 goto drop; 1127 } 1128 1129 /* 1130 * Ack processing. 1131 */ 1132 switch (tp->t_state) { 1133 1134 /* 1135 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 1136 * ESTABLISHED state and continue processing, otherwise 1137 * send an RST. 1138 */ 1139 case TCPS_SYN_RECEIVED: 1140 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 1141 SEQ_GT(ti->ti_ack, tp->snd_max)) 1142 goto dropwithreset; 1143 1144 tcpstat.tcps_connects++; 1145 soisconnected(so); 1146 /* Do window scaling? */ 1147 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1148 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1149 tp->snd_scale = tp->requested_s_scale; 1150 tp->rcv_scale = tp->request_r_scale; 1151 } 1152 /* 1153 * Upon successful completion of 3-way handshake, 1154 * update cache.CC if it was undefined, pass any queued 1155 * data to the user, and advance state appropriately. 1156 */ 1157 if ((taop = tcp_gettaocache(inp)) != NULL && 1158 taop->tao_cc == 0) 1159 taop->tao_cc = tp->cc_recv; 1160 1161 /* 1162 * Make transitions: 1163 * SYN-RECEIVED -> ESTABLISHED 1164 * SYN-RECEIVED* -> FIN-WAIT-1 1165 */ 1166 if (tp->t_flags & TF_NEEDFIN) { 1167 tp->t_state = TCPS_FIN_WAIT_1; 1168 tp->t_flags &= ~TF_NEEDFIN; 1169 } else 1170 tp->t_state = TCPS_ESTABLISHED; 1171 /* 1172 * If segment contains data or ACK, will call tcp_reass() 1173 * later; if not, do so now to pass queued data to user. 1174 */ 1175 if (ti->ti_len == 0 && (tiflags & TH_FIN) == 0) 1176 (void) tcp_reass(tp, (struct tcpiphdr *)0, 1177 (struct mbuf *)0); 1178 tp->snd_wl1 = ti->ti_seq - 1; 1179 /* fall into ... */ 1180 1181 /* 1182 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1183 * ACKs. If the ack is in the range 1184 * tp->snd_una < ti->ti_ack <= tp->snd_max 1185 * then advance tp->snd_una to ti->ti_ack and drop 1186 * data from the retransmission queue. If this ACK reflects 1187 * more up to date window information we update our window information. 1188 */ 1189 case TCPS_ESTABLISHED: 1190 case TCPS_FIN_WAIT_1: 1191 case TCPS_FIN_WAIT_2: 1192 case TCPS_CLOSE_WAIT: 1193 case TCPS_CLOSING: 1194 case TCPS_LAST_ACK: 1195 case TCPS_TIME_WAIT: 1196 1197 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 1198 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 1199 tcpstat.tcps_rcvdupack++; 1200 /* 1201 * If we have outstanding data (other than 1202 * a window probe), this is a completely 1203 * duplicate ack (ie, window info didn't 1204 * change), the ack is the biggest we've 1205 * seen and we've seen exactly our rexmt 1206 * threshhold of them, assume a packet 1207 * has been dropped and retransmit it. 1208 * Kludge snd_nxt & the congestion 1209 * window so we send only this one 1210 * packet. 1211 * 1212 * We know we're losing at the current 1213 * window size so do congestion avoidance 1214 * (set ssthresh to half the current window 1215 * and pull our congestion window back to 1216 * the new ssthresh). 1217 * 1218 * Dup acks mean that packets have left the 1219 * network (they're now cached at the receiver) 1220 * so bump cwnd by the amount in the receiver 1221 * to keep a constant cwnd packets in the 1222 * network. 1223 */ 1224 if (tp->t_timer[TCPT_REXMT] == 0 || 1225 ti->ti_ack != tp->snd_una) 1226 tp->t_dupacks = 0; 1227 else if (++tp->t_dupacks == tcprexmtthresh) { 1228 tcp_seq onxt = tp->snd_nxt; 1229 u_int win = 1230 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1231 tp->t_maxseg; 1232 1233 if (win < 2) 1234 win = 2; 1235 tp->snd_ssthresh = win * tp->t_maxseg; 1236 tp->t_timer[TCPT_REXMT] = 0; 1237 tp->t_rtt = 0; 1238 tp->snd_nxt = ti->ti_ack; 1239 tp->snd_cwnd = tp->t_maxseg; 1240 (void) tcp_output(tp); 1241 tp->snd_cwnd = tp->snd_ssthresh + 1242 tp->t_maxseg * tp->t_dupacks; 1243 if (SEQ_GT(onxt, tp->snd_nxt)) 1244 tp->snd_nxt = onxt; 1245 goto drop; 1246 } else if (tp->t_dupacks > tcprexmtthresh) { 1247 tp->snd_cwnd += tp->t_maxseg; 1248 (void) tcp_output(tp); 1249 goto drop; 1250 } 1251 } else 1252 tp->t_dupacks = 0; 1253 break; 1254 } 1255 /* 1256 * If the congestion window was inflated to account 1257 * for the other side's cached packets, retract it. 1258 */ 1259 if (tp->t_dupacks > tcprexmtthresh && 1260 tp->snd_cwnd > tp->snd_ssthresh) 1261 tp->snd_cwnd = tp->snd_ssthresh; 1262 tp->t_dupacks = 0; 1263 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 1264 tcpstat.tcps_rcvacktoomuch++; 1265 goto dropafterack; 1266 } 1267 /* 1268 * If we reach this point, ACK is not a duplicate, 1269 * i.e., it ACKs something we sent. 1270 */ 1271 if (tp->t_flags & TF_NEEDSYN) { 1272 /* 1273 * T/TCP: Connection was half-synchronized, and our 1274 * SYN has been ACK'd (so connection is now fully 1275 * synchronized). Go to non-starred state and 1276 * increment snd_una for ACK of SYN. 1277 */ 1278 tp->t_flags &= ~TF_NEEDSYN; 1279 tp->snd_una++; 1280 } 1281 1282 process_ACK: 1283 acked = ti->ti_ack - tp->snd_una; 1284 tcpstat.tcps_rcvackpack++; 1285 tcpstat.tcps_rcvackbyte += acked; 1286 1287 /* 1288 * If we have a timestamp reply, update smoothed 1289 * round trip time. If no timestamp is present but 1290 * transmit timer is running and timed sequence 1291 * number was acked, update smoothed round trip time. 1292 * Since we now have an rtt measurement, cancel the 1293 * timer backoff (cf., Phil Karn's retransmit alg.). 1294 * Recompute the initial retransmit timer. 1295 */ 1296 if (to.to_flag & TOF_TS) 1297 tcp_xmit_timer(tp, tcp_now - to.to_tsecr + 1); 1298 else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 1299 tcp_xmit_timer(tp,tp->t_rtt); 1300 1301 /* 1302 * If all outstanding data is acked, stop retransmit 1303 * timer and remember to restart (more output or persist). 1304 * If there is more data to be acked, restart retransmit 1305 * timer, using current (possibly backed-off) value. 1306 */ 1307 if (ti->ti_ack == tp->snd_max) { 1308 tp->t_timer[TCPT_REXMT] = 0; 1309 needoutput = 1; 1310 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1311 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1312 1313 /* 1314 * If no data (only SYN) was ACK'd, 1315 * skip rest of ACK processing. 1316 */ 1317 if (acked == 0) 1318 goto step6; 1319 1320 /* 1321 * When new data is acked, open the congestion window. 1322 * If the window gives us less than ssthresh packets 1323 * in flight, open exponentially (maxseg per packet). 1324 * Otherwise open linearly: maxseg per window 1325 * (maxseg^2 / cwnd per packet). 1326 */ 1327 { 1328 register u_int cw = tp->snd_cwnd; 1329 register u_int incr = tp->t_maxseg; 1330 1331 if (cw > tp->snd_ssthresh) 1332 incr = incr * incr / cw; 1333 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1334 } 1335 if (acked > so->so_snd.sb_cc) { 1336 tp->snd_wnd -= so->so_snd.sb_cc; 1337 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1338 ourfinisacked = 1; 1339 } else { 1340 sbdrop(&so->so_snd, acked); 1341 tp->snd_wnd -= acked; 1342 ourfinisacked = 0; 1343 } 1344 if (so->so_snd.sb_flags & SB_NOTIFY) 1345 sowwakeup(so); 1346 tp->snd_una = ti->ti_ack; 1347 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1348 tp->snd_nxt = tp->snd_una; 1349 1350 switch (tp->t_state) { 1351 1352 /* 1353 * In FIN_WAIT_1 STATE in addition to the processing 1354 * for the ESTABLISHED state if our FIN is now acknowledged 1355 * then enter FIN_WAIT_2. 1356 */ 1357 case TCPS_FIN_WAIT_1: 1358 if (ourfinisacked) { 1359 /* 1360 * If we can't receive any more 1361 * data, then closing user can proceed. 1362 * Starting the timer is contrary to the 1363 * specification, but if we don't get a FIN 1364 * we'll hang forever. 1365 */ 1366 if (so->so_state & SS_CANTRCVMORE) { 1367 soisdisconnected(so); 1368 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 1369 } 1370 tp->t_state = TCPS_FIN_WAIT_2; 1371 } 1372 break; 1373 1374 /* 1375 * In CLOSING STATE in addition to the processing for 1376 * the ESTABLISHED state if the ACK acknowledges our FIN 1377 * then enter the TIME-WAIT state, otherwise ignore 1378 * the segment. 1379 */ 1380 case TCPS_CLOSING: 1381 if (ourfinisacked) { 1382 tp->t_state = TCPS_TIME_WAIT; 1383 tcp_canceltimers(tp); 1384 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1385 if (tp->cc_recv != 0 && 1386 tp->t_duration < TCPTV_MSL) 1387 tp->t_timer[TCPT_2MSL] = 1388 tp->t_rxtcur * TCPTV_TWTRUNC; 1389 else 1390 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1391 soisdisconnected(so); 1392 } 1393 break; 1394 1395 /* 1396 * In LAST_ACK, we may still be waiting for data to drain 1397 * and/or to be acked, as well as for the ack of our FIN. 1398 * If our FIN is now acknowledged, delete the TCB, 1399 * enter the closed state and return. 1400 */ 1401 case TCPS_LAST_ACK: 1402 if (ourfinisacked) { 1403 tp = tcp_close(tp); 1404 goto drop; 1405 } 1406 break; 1407 1408 /* 1409 * In TIME_WAIT state the only thing that should arrive 1410 * is a retransmission of the remote FIN. Acknowledge 1411 * it and restart the finack timer. 1412 */ 1413 case TCPS_TIME_WAIT: 1414 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1415 goto dropafterack; 1416 } 1417 } 1418 1419 step6: 1420 /* 1421 * Update window information. 1422 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1423 */ 1424 if ((tiflags & TH_ACK) && 1425 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || 1426 (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 1427 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) { 1428 /* keep track of pure window updates */ 1429 if (ti->ti_len == 0 && 1430 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1431 tcpstat.tcps_rcvwinupd++; 1432 tp->snd_wnd = tiwin; 1433 tp->snd_wl1 = ti->ti_seq; 1434 tp->snd_wl2 = ti->ti_ack; 1435 if (tp->snd_wnd > tp->max_sndwnd) 1436 tp->max_sndwnd = tp->snd_wnd; 1437 needoutput = 1; 1438 } 1439 1440 /* 1441 * Process segments with URG. 1442 */ 1443 if ((tiflags & TH_URG) && ti->ti_urp && 1444 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1445 /* 1446 * This is a kludge, but if we receive and accept 1447 * random urgent pointers, we'll crash in 1448 * soreceive. It's hard to imagine someone 1449 * actually wanting to send this much urgent data. 1450 */ 1451 if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { 1452 ti->ti_urp = 0; /* XXX */ 1453 tiflags &= ~TH_URG; /* XXX */ 1454 goto dodata; /* XXX */ 1455 } 1456 /* 1457 * If this segment advances the known urgent pointer, 1458 * then mark the data stream. This should not happen 1459 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1460 * a FIN has been received from the remote side. 1461 * In these states we ignore the URG. 1462 * 1463 * According to RFC961 (Assigned Protocols), 1464 * the urgent pointer points to the last octet 1465 * of urgent data. We continue, however, 1466 * to consider it to indicate the first octet 1467 * of data past the urgent section as the original 1468 * spec states (in one of two places). 1469 */ 1470 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1471 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1472 so->so_oobmark = so->so_rcv.sb_cc + 1473 (tp->rcv_up - tp->rcv_nxt) - 1; 1474 if (so->so_oobmark == 0) 1475 so->so_state |= SS_RCVATMARK; 1476 sohasoutofband(so); 1477 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1478 } 1479 /* 1480 * Remove out of band data so doesn't get presented to user. 1481 * This can happen independent of advancing the URG pointer, 1482 * but if two URG's are pending at once, some out-of-band 1483 * data may creep in... ick. 1484 */ 1485 if (ti->ti_urp <= (u_long)ti->ti_len 1486 #ifdef SO_OOBINLINE 1487 && (so->so_options & SO_OOBINLINE) == 0 1488 #endif 1489 ) 1490 tcp_pulloutofband(so, ti, m); 1491 } else 1492 /* 1493 * If no out of band data is expected, 1494 * pull receive urgent pointer along 1495 * with the receive window. 1496 */ 1497 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1498 tp->rcv_up = tp->rcv_nxt; 1499 dodata: /* XXX */ 1500 1501 /* 1502 * Process the segment text, merging it into the TCP sequencing queue, 1503 * and arranging for acknowledgment of receipt if necessary. 1504 * This process logically involves adjusting tp->rcv_wnd as data 1505 * is presented to the user (this happens in tcp_usrreq.c, 1506 * case PRU_RCVD). If a FIN has already been received on this 1507 * connection then we just ignore the text. 1508 */ 1509 if ((ti->ti_len || (tiflags&TH_FIN)) && 1510 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1511 TCP_REASS(tp, ti, m, so, tiflags); 1512 /* 1513 * Note the amount of data that peer has sent into 1514 * our window, in order to estimate the sender's 1515 * buffer size. 1516 */ 1517 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1518 } else { 1519 m_freem(m); 1520 tiflags &= ~TH_FIN; 1521 } 1522 1523 /* 1524 * If FIN is received ACK the FIN and let the user know 1525 * that the connection is closing. 1526 */ 1527 if (tiflags & TH_FIN) { 1528 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1529 socantrcvmore(so); 1530 /* 1531 * If connection is half-synchronized 1532 * (ie SEND_SYN flag on) then delay ACK, 1533 * so it may be piggybacked when SYN is sent. 1534 * Otherwise, since we received a FIN then no 1535 * more input can be expected, send ACK now. 1536 */ 1537 if (tp->t_flags & TF_NEEDSYN) 1538 tp->t_flags |= TF_DELACK; 1539 else 1540 tp->t_flags |= TF_ACKNOW; 1541 tp->rcv_nxt++; 1542 } 1543 switch (tp->t_state) { 1544 1545 /* 1546 * In SYN_RECEIVED and ESTABLISHED STATES 1547 * enter the CLOSE_WAIT state. 1548 */ 1549 case TCPS_SYN_RECEIVED: 1550 case TCPS_ESTABLISHED: 1551 tp->t_state = TCPS_CLOSE_WAIT; 1552 break; 1553 1554 /* 1555 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1556 * enter the CLOSING state. 1557 */ 1558 case TCPS_FIN_WAIT_1: 1559 tp->t_state = TCPS_CLOSING; 1560 break; 1561 1562 /* 1563 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1564 * starting the time-wait timer, turning off the other 1565 * standard timers. 1566 */ 1567 case TCPS_FIN_WAIT_2: 1568 tp->t_state = TCPS_TIME_WAIT; 1569 tcp_canceltimers(tp); 1570 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1571 if (tp->cc_recv != 0 && 1572 tp->t_duration < TCPTV_MSL) { 1573 tp->t_timer[TCPT_2MSL] = 1574 tp->t_rxtcur * TCPTV_TWTRUNC; 1575 /* For transaction client, force ACK now. */ 1576 tp->t_flags |= TF_ACKNOW; 1577 } 1578 else 1579 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1580 soisdisconnected(so); 1581 break; 1582 1583 /* 1584 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1585 */ 1586 case TCPS_TIME_WAIT: 1587 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1588 break; 1589 } 1590 } 1591 #ifdef TCPDEBUG 1592 if (so->so_options & SO_DEBUG) 1593 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1594 #endif 1595 1596 /* 1597 * Return any desired output. 1598 */ 1599 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1600 (void) tcp_output(tp); 1601 return; 1602 1603 dropafterack: 1604 /* 1605 * Generate an ACK dropping incoming segment if it occupies 1606 * sequence space, where the ACK reflects our state. 1607 */ 1608 if (tiflags & TH_RST) 1609 goto drop; 1610 #ifdef TCPDEBUG 1611 if (so->so_options & SO_DEBUG) 1612 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1613 #endif 1614 m_freem(m); 1615 tp->t_flags |= TF_ACKNOW; 1616 (void) tcp_output(tp); 1617 return; 1618 1619 dropwithreset: 1620 /* 1621 * Generate a RST, dropping incoming segment. 1622 * Make ACK acceptable to originator of segment. 1623 * Don't bother to respond if destination was broadcast/multicast. 1624 */ 1625 if ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) || 1626 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 1627 goto drop; 1628 #ifdef TCPDEBUG 1629 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1630 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1631 #endif 1632 if (tiflags & TH_ACK) 1633 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1634 else { 1635 if (tiflags & TH_SYN) 1636 ti->ti_len++; 1637 tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1638 TH_RST|TH_ACK); 1639 } 1640 /* destroy temporarily created socket */ 1641 if (dropsocket) 1642 (void) soabort(so); 1643 return; 1644 1645 drop: 1646 /* 1647 * Drop space held by incoming segment and return. 1648 */ 1649 #ifdef TCPDEBUG 1650 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1651 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1652 #endif 1653 m_freem(m); 1654 /* destroy temporarily created socket */ 1655 if (dropsocket) 1656 (void) soabort(so); 1657 return; 1658 #ifndef TUBA_INCLUDE 1659 } 1660 1661 void 1662 tcp_dooptions(tp, cp, cnt, ti, to) 1663 struct tcpcb *tp; 1664 u_char *cp; 1665 int cnt; 1666 struct tcpiphdr *ti; 1667 struct tcpopt *to; 1668 { 1669 u_short mss = 0; 1670 int opt, optlen; 1671 1672 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1673 opt = cp[0]; 1674 if (opt == TCPOPT_EOL) 1675 break; 1676 if (opt == TCPOPT_NOP) 1677 optlen = 1; 1678 else { 1679 optlen = cp[1]; 1680 if (optlen <= 0) 1681 break; 1682 } 1683 switch (opt) { 1684 1685 default: 1686 continue; 1687 1688 case TCPOPT_MAXSEG: 1689 if (optlen != TCPOLEN_MAXSEG) 1690 continue; 1691 if (!(ti->ti_flags & TH_SYN)) 1692 continue; 1693 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); 1694 NTOHS(mss); 1695 break; 1696 1697 case TCPOPT_WINDOW: 1698 if (optlen != TCPOLEN_WINDOW) 1699 continue; 1700 if (!(ti->ti_flags & TH_SYN)) 1701 continue; 1702 tp->t_flags |= TF_RCVD_SCALE; 1703 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 1704 break; 1705 1706 case TCPOPT_TIMESTAMP: 1707 if (optlen != TCPOLEN_TIMESTAMP) 1708 continue; 1709 to->to_flag |= TOF_TS; 1710 bcopy((char *)cp + 2, 1711 (char *)&to->to_tsval, sizeof(to->to_tsval)); 1712 NTOHL(to->to_tsval); 1713 bcopy((char *)cp + 6, 1714 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 1715 NTOHL(to->to_tsecr); 1716 1717 /* 1718 * A timestamp received in a SYN makes 1719 * it ok to send timestamp requests and replies. 1720 */ 1721 if (ti->ti_flags & TH_SYN) { 1722 tp->t_flags |= TF_RCVD_TSTMP; 1723 tp->ts_recent = to->to_tsval; 1724 tp->ts_recent_age = tcp_now; 1725 } 1726 break; 1727 case TCPOPT_CC: 1728 if (optlen != TCPOLEN_CC) 1729 continue; 1730 to->to_flag |= TOF_CC; 1731 bcopy((char *)cp + 2, 1732 (char *)&to->to_cc, sizeof(to->to_cc)); 1733 NTOHL(to->to_cc); 1734 /* 1735 * A CC or CC.new option received in a SYN makes 1736 * it ok to send CC in subsequent segments. 1737 */ 1738 if (ti->ti_flags & TH_SYN) 1739 tp->t_flags |= TF_RCVD_CC; 1740 break; 1741 case TCPOPT_CCNEW: 1742 if (optlen != TCPOLEN_CC) 1743 continue; 1744 if (!(ti->ti_flags & TH_SYN)) 1745 continue; 1746 to->to_flag |= TOF_CCNEW; 1747 bcopy((char *)cp + 2, 1748 (char *)&to->to_cc, sizeof(to->to_cc)); 1749 NTOHL(to->to_cc); 1750 /* 1751 * A CC or CC.new option received in a SYN makes 1752 * it ok to send CC in subsequent segments. 1753 */ 1754 tp->t_flags |= TF_RCVD_CC; 1755 break; 1756 case TCPOPT_CCECHO: 1757 if (optlen != TCPOLEN_CC) 1758 continue; 1759 if (!(ti->ti_flags & TH_SYN)) 1760 continue; 1761 to->to_flag |= TOF_CCECHO; 1762 bcopy((char *)cp + 2, 1763 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 1764 NTOHL(to->to_ccecho); 1765 break; 1766 } 1767 } 1768 if (ti->ti_flags & TH_SYN) 1769 tcp_mss(tp, mss); /* sets t_maxseg */ 1770 } 1771 1772 /* 1773 * Pull out of band byte out of a segment so 1774 * it doesn't appear in the user's data queue. 1775 * It is still reflected in the segment length for 1776 * sequencing purposes. 1777 */ 1778 void 1779 tcp_pulloutofband(so, ti, m) 1780 struct socket *so; 1781 struct tcpiphdr *ti; 1782 register struct mbuf *m; 1783 { 1784 int cnt = ti->ti_urp - 1; 1785 1786 while (cnt >= 0) { 1787 if (m->m_len > cnt) { 1788 char *cp = mtod(m, caddr_t) + cnt; 1789 struct tcpcb *tp = sototcpcb(so); 1790 1791 tp->t_iobc = *cp; 1792 tp->t_oobflags |= TCPOOB_HAVEDATA; 1793 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1794 m->m_len--; 1795 return; 1796 } 1797 cnt -= m->m_len; 1798 m = m->m_next; 1799 if (m == 0) 1800 break; 1801 } 1802 panic("tcp_pulloutofband"); 1803 } 1804 1805 /* 1806 * Collect new round-trip time estimate 1807 * and update averages and current timeout. 1808 */ 1809 void 1810 tcp_xmit_timer(tp, rtt) 1811 register struct tcpcb *tp; 1812 short rtt; 1813 { 1814 register short delta; 1815 1816 tcpstat.tcps_rttupdated++; 1817 if (tp->t_srtt != 0) { 1818 /* 1819 * srtt is stored as fixed point with 3 bits after the 1820 * binary point (i.e., scaled by 8). The following magic 1821 * is equivalent to the smoothing algorithm in rfc793 with 1822 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 1823 * point). Adjust rtt to origin 0. 1824 */ 1825 delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT); 1826 if ((tp->t_srtt += delta) <= 0) 1827 tp->t_srtt = 1; 1828 /* 1829 * We accumulate a smoothed rtt variance (actually, a 1830 * smoothed mean difference), then set the retransmit 1831 * timer to smoothed rtt + 4 times the smoothed variance. 1832 * rttvar is stored as fixed point with 2 bits after the 1833 * binary point (scaled by 4). The following is 1834 * equivalent to rfc793 smoothing with an alpha of .75 1835 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 1836 * rfc793's wired-in beta. 1837 */ 1838 if (delta < 0) 1839 delta = -delta; 1840 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); 1841 if ((tp->t_rttvar += delta) <= 0) 1842 tp->t_rttvar = 1; 1843 } else { 1844 /* 1845 * No rtt measurement yet - use the unsmoothed rtt. 1846 * Set the variance to half the rtt (so our first 1847 * retransmit happens at 3*rtt). 1848 */ 1849 tp->t_srtt = rtt << TCP_RTT_SHIFT; 1850 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 1851 } 1852 tp->t_rtt = 0; 1853 tp->t_rxtshift = 0; 1854 1855 /* 1856 * the retransmit should happen at rtt + 4 * rttvar. 1857 * Because of the way we do the smoothing, srtt and rttvar 1858 * will each average +1/2 tick of bias. When we compute 1859 * the retransmit timer, we want 1/2 tick of rounding and 1860 * 1 extra tick because of +-1/2 tick uncertainty in the 1861 * firing of the timer. The bias will give us exactly the 1862 * 1.5 tick we need. But, because the bias is 1863 * statistical, we have to test that we don't drop below 1864 * the minimum feasible timer (which is 2 ticks). 1865 */ 1866 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 1867 tp->t_rttmin, TCPTV_REXMTMAX); 1868 1869 /* 1870 * We received an ack for a packet that wasn't retransmitted; 1871 * it is probably safe to discard any error indications we've 1872 * received recently. This isn't quite right, but close enough 1873 * for now (a route might have failed after we sent a segment, 1874 * and the return path might not be symmetrical). 1875 */ 1876 tp->t_softerror = 0; 1877 } 1878 1879 /* 1880 * Determine a reasonable value for maxseg size. 1881 * If the route is known, check route for mtu. 1882 * If none, use an mss that can be handled on the outgoing 1883 * interface without forcing IP to fragment; if bigger than 1884 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 1885 * to utilize large mbufs. If no route is found, route has no mtu, 1886 * or the destination isn't local, use a default, hopefully conservative 1887 * size (usually 512 or the default IP max size, but no more than the mtu 1888 * of the interface), as we can't discover anything about intervening 1889 * gateways or networks. We also initialize the congestion/slow start 1890 * window to be a single segment if the destination isn't local. 1891 * While looking at the routing entry, we also initialize other path-dependent 1892 * parameters from pre-set or cached values in the routing entry. 1893 * 1894 * Also take into account the space needed for options that we 1895 * send regularly. Make maxseg shorter by that amount to assure 1896 * that we can send maxseg amount of data even when the options 1897 * are present. Store the upper limit of the length of options plus 1898 * data in maxopd. 1899 * 1900 * NOTE that this routine is only called when we process an incoming 1901 * segment, for outgoing segments only tcp_mssopt is called. 1902 * 1903 * In case of T/TCP, we call this routine during implicit connection 1904 * setup as well (offer = -1), to initialize maxseg from the cached 1905 * MSS of our peer. 1906 */ 1907 void 1908 tcp_mss(tp, offer) 1909 struct tcpcb *tp; 1910 int offer; 1911 { 1912 register struct rtentry *rt; 1913 struct ifnet *ifp; 1914 register int rtt, mss; 1915 u_long bufsize; 1916 struct inpcb *inp; 1917 struct socket *so; 1918 struct rmxp_tao *taop; 1919 int origoffer = offer; 1920 1921 inp = tp->t_inpcb; 1922 if ((rt = tcp_rtlookup(inp)) == NULL) { 1923 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 1924 return; 1925 } 1926 ifp = rt->rt_ifp; 1927 so = inp->inp_socket; 1928 1929 taop = rmx_taop(rt->rt_rmx); 1930 /* 1931 * Offer == -1 means that we didn't receive SYN yet, 1932 * use cached value in that case; 1933 */ 1934 if (offer == -1) 1935 offer = taop->tao_mssopt; 1936 /* 1937 * Offer == 0 means that there was no MSS on the SYN segment, 1938 * in this case we use tcp_mssdflt. 1939 */ 1940 if (offer == 0) 1941 offer = tcp_mssdflt; 1942 else 1943 /* 1944 * Sanity check: make sure that maxopd will be large 1945 * enough to allow some data on segments even is the 1946 * all the option space is used (40bytes). Otherwise 1947 * funny things may happen in tcp_output. 1948 */ 1949 offer = max(offer, 64); 1950 taop->tao_mssopt = offer; 1951 1952 #ifdef RTV_MTU /* if route characteristics exist ... */ 1953 /* 1954 * While we're here, check if there's an initial rtt 1955 * or rttvar. Convert from the route-table units 1956 * to scaled multiples of the slow timeout timer. 1957 */ 1958 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 1959 /* 1960 * XXX the lock bit for RTT indicates that the value 1961 * is also a minimum value; this is subject to time. 1962 */ 1963 if (rt->rt_rmx.rmx_locks & RTV_RTT) 1964 tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ); 1965 tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 1966 if (rt->rt_rmx.rmx_rttvar) 1967 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 1968 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 1969 else 1970 /* default variation is +- 1 rtt */ 1971 tp->t_rttvar = 1972 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 1973 TCPT_RANGESET(tp->t_rxtcur, 1974 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 1975 tp->t_rttmin, TCPTV_REXMTMAX); 1976 } 1977 /* 1978 * if there's an mtu associated with the route, use it 1979 */ 1980 if (rt->rt_rmx.rmx_mtu) 1981 mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 1982 else 1983 #endif /* RTV_MTU */ 1984 { 1985 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1986 if (!in_localaddr(inp->inp_faddr)) 1987 mss = min(mss, tcp_mssdflt); 1988 } 1989 mss = min(mss, offer); 1990 /* 1991 * maxopd stores the maximum length of data AND options 1992 * in a segment; maxseg is the amount of data in a normal 1993 * segment. We need to store this value (maxopd) apart 1994 * from maxseg, because now every segment carries options 1995 * and thus we normally have somewhat less data in segments. 1996 */ 1997 tp->t_maxopd = mss; 1998 1999 /* 2000 * In case of T/TCP, origoffer==-1 indicates, that no segments 2001 * were received yet. In this case we just guess, otherwise 2002 * we do the same as before T/TCP. 2003 */ 2004 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2005 (origoffer == -1 || 2006 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2007 mss -= TCPOLEN_TSTAMP_APPA; 2008 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2009 (origoffer == -1 || 2010 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2011 mss -= TCPOLEN_CC_APPA; 2012 2013 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2014 if (mss > MCLBYTES) 2015 mss &= ~(MCLBYTES-1); 2016 #else 2017 if (mss > MCLBYTES) 2018 mss = mss / MCLBYTES * MCLBYTES; 2019 #endif 2020 /* 2021 * If there's a pipesize, change the socket buffer 2022 * to that size. Make the socket buffers an integral 2023 * number of mss units; if the mss is larger than 2024 * the socket buffer, decrease the mss. 2025 */ 2026 #ifdef RTV_SPIPE 2027 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2028 #endif 2029 bufsize = so->so_snd.sb_hiwat; 2030 if (bufsize < mss) 2031 mss = bufsize; 2032 else { 2033 bufsize = roundup(bufsize, mss); 2034 if (bufsize > sb_max) 2035 bufsize = sb_max; 2036 (void)sbreserve(&so->so_snd, bufsize); 2037 } 2038 tp->t_maxseg = mss; 2039 2040 #ifdef RTV_RPIPE 2041 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2042 #endif 2043 bufsize = so->so_rcv.sb_hiwat; 2044 if (bufsize > mss) { 2045 bufsize = roundup(bufsize, mss); 2046 if (bufsize > sb_max) 2047 bufsize = sb_max; 2048 (void)sbreserve(&so->so_rcv, bufsize); 2049 } 2050 /* 2051 * Don't force slow-start on local network. 2052 */ 2053 if (!in_localaddr(inp->inp_faddr)) 2054 tp->snd_cwnd = mss; 2055 2056 #ifdef RTV_SSTHRESH 2057 if (rt->rt_rmx.rmx_ssthresh) { 2058 /* 2059 * There's some sort of gateway or interface 2060 * buffer limit on the path. Use this to set 2061 * the slow start threshhold, but set the 2062 * threshold to no less than 2*mss. 2063 */ 2064 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2065 } 2066 #endif 2067 } 2068 2069 /* 2070 * Determine the MSS option to send on an outgoing SYN. 2071 */ 2072 int 2073 tcp_mssopt(tp) 2074 struct tcpcb *tp; 2075 { 2076 struct rtentry *rt; 2077 2078 rt = tcp_rtlookup(tp->t_inpcb); 2079 if (rt == NULL) 2080 return tcp_mssdflt; 2081 2082 /* 2083 * if there's an mtu associated with the route, use it 2084 */ 2085 if (rt->rt_rmx.rmx_mtu) 2086 return rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 2087 2088 return rt->rt_ifp->if_mtu - sizeof(struct tcpiphdr); 2089 } 2090 #endif /* TUBA_INCLUDE */ 2091