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sys/netinet/tcp_input.c
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1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 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 8.12 (Berkeley) 5/24/95 34 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.54.2.14 1999/09/05 08:18:40 peter Exp $ 35 */ 36 37 #include "opt_tcpdebug.h" 38 39 #ifndef TUBA_INCLUDE 40 #include <sys/param.h> 41 #include <sys/queue.h> 42 #include <sys/systm.h> 43 #include <sys/kernel.h> 44 #include <sys/sysctl.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/protosw.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/errno.h> 51 #include <sys/syslog.h> 52 53 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 54 55 #include <net/if.h> 56 #include <net/route.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/ip_var.h> 63 #include <netinet/tcp.h> 64 #include <netinet/tcp_fsm.h> 65 #include <netinet/tcp_seq.h> 66 #include <netinet/tcp_timer.h> 67 #include <netinet/tcp_var.h> 68 #include <netinet/tcpip.h> 69 #ifdef TCPDEBUG 70 #include <netinet/tcp_debug.h> 71 static struct tcpiphdr tcp_saveti; 72 #endif 73 74 static int tcprexmtthresh = 3; 75 tcp_seq tcp_iss; 76 tcp_cc tcp_ccgen; 77 78 struct tcpstat tcpstat; 79 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, 80 CTLFLAG_RD, &tcpstat , tcpstat, ""); 81 82 static int log_in_vain = 0; 83 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 84 &log_in_vain, 0, ""); 85 86 static int no_local_slowstart = 0; 87 SYSCTL_INT(_net_inet_tcp, OID_AUTO, no_local_slowstart, CTLFLAG_RW, 88 &no_local_slowstart, 0, ""); 89 90 u_long tcp_now; 91 struct inpcbhead tcb; 92 struct inpcbinfo tcbinfo; 93 94 static void tcp_dooptions __P((struct tcpcb *, 95 u_char *, int, struct tcpiphdr *, struct tcpopt *)); 96 static void tcp_pulloutofband __P((struct socket *, 97 struct tcpiphdr *, struct mbuf *)); 98 static int tcp_reass __P((struct tcpcb *, struct tcpiphdr *, struct mbuf *)); 99 static void tcp_xmit_timer __P((struct tcpcb *, int)); 100 101 #endif /* TUBA_INCLUDE */ 102 103 /* 104 * Insert segment ti into reassembly queue of tcp with 105 * control block tp. Return TH_FIN if reassembly now includes 106 * a segment with FIN. The macro form does the common case inline 107 * (segment is the next to be received on an established connection, 108 * and the queue is empty), avoiding linkage into and removal 109 * from the queue and repetition of various conversions. 110 * Set DELACK for segments received in order, but ack immediately 111 * when segments are out of order (so fast retransmit can work). 112 */ 113 #ifdef TCP_ACK_HACK 114 #define TCP_REASS(tp, ti, m, so, flags) { \ 115 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 116 (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 117 (tp)->t_state == TCPS_ESTABLISHED) { \ 118 if (ti->ti_flags & TH_PUSH) \ 119 tp->t_flags |= TF_ACKNOW; \ 120 else \ 121 tp->t_flags |= TF_DELACK; \ 122 (tp)->rcv_nxt += (ti)->ti_len; \ 123 flags = (ti)->ti_flags & TH_FIN; \ 124 tcpstat.tcps_rcvpack++;\ 125 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 126 sbappend(&(so)->so_rcv, (m)); \ 127 sorwakeup(so); \ 128 } else { \ 129 (flags) = tcp_reass((tp), (ti), (m)); \ 130 tp->t_flags |= TF_ACKNOW; \ 131 } \ 132 } 133 #else 134 #define TCP_REASS(tp, ti, m, so, flags) { \ 135 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 136 (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 137 (tp)->t_state == TCPS_ESTABLISHED) { \ 138 tp->t_flags |= TF_DELACK; \ 139 (tp)->rcv_nxt += (ti)->ti_len; \ 140 flags = (ti)->ti_flags & TH_FIN; \ 141 tcpstat.tcps_rcvpack++;\ 142 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 143 sbappend(&(so)->so_rcv, (m)); \ 144 sorwakeup(so); \ 145 } else { \ 146 (flags) = tcp_reass((tp), (ti), (m)); \ 147 tp->t_flags |= TF_ACKNOW; \ 148 } \ 149 } 150 #endif 151 #ifndef TUBA_INCLUDE 152 153 static int 154 tcp_reass(tp, ti, m) 155 register struct tcpcb *tp; 156 register struct tcpiphdr *ti; 157 struct mbuf *m; 158 { 159 register struct tcpiphdr *q; 160 struct socket *so = tp->t_inpcb->inp_socket; 161 int flags; 162 163 /* 164 * Call with ti==0 after become established to 165 * force pre-ESTABLISHED data up to user socket. 166 */ 167 if (ti == 0) 168 goto present; 169 170 /* 171 * Find a segment which begins after this one does. 172 */ 173 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 174 q = (struct tcpiphdr *)q->ti_next) 175 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 176 break; 177 178 /* 179 * If there is a preceding segment, it may provide some of 180 * our data already. If so, drop the data from the incoming 181 * segment. If it provides all of our data, drop us. 182 */ 183 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 184 register int i; 185 q = (struct tcpiphdr *)q->ti_prev; 186 /* conversion to int (in i) handles seq wraparound */ 187 i = q->ti_seq + q->ti_len - ti->ti_seq; 188 if (i > 0) { 189 if (i >= ti->ti_len) { 190 tcpstat.tcps_rcvduppack++; 191 tcpstat.tcps_rcvdupbyte += ti->ti_len; 192 m_freem(m); 193 /* 194 * Try to present any queued data 195 * at the left window edge to the user. 196 * This is needed after the 3-WHS 197 * completes. 198 */ 199 goto present; /* ??? */ 200 } 201 m_adj(m, i); 202 ti->ti_len -= i; 203 ti->ti_seq += i; 204 } 205 q = (struct tcpiphdr *)(q->ti_next); 206 } 207 tcpstat.tcps_rcvoopack++; 208 tcpstat.tcps_rcvoobyte += ti->ti_len; 209 REASS_MBUF(ti) = m; /* XXX */ 210 211 /* 212 * While we overlap succeeding segments trim them or, 213 * if they are completely covered, dequeue them. 214 */ 215 while (q != (struct tcpiphdr *)tp) { 216 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 217 if (i <= 0) 218 break; 219 if (i < q->ti_len) { 220 q->ti_seq += i; 221 q->ti_len -= i; 222 m_adj(REASS_MBUF(q), i); 223 break; 224 } 225 q = (struct tcpiphdr *)q->ti_next; 226 m = REASS_MBUF((struct tcpiphdr *)q->ti_prev); 227 remque(q->ti_prev); 228 m_freem(m); 229 } 230 231 /* 232 * Stick new segment in its place. 233 */ 234 insque(ti, q->ti_prev); 235 236 present: 237 /* 238 * Present data to user, advancing rcv_nxt through 239 * completed sequence space. 240 */ 241 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 242 return (0); 243 ti = tp->seg_next; 244 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 245 return (0); 246 do { 247 tp->rcv_nxt += ti->ti_len; 248 flags = ti->ti_flags & TH_FIN; 249 remque(ti); 250 m = REASS_MBUF(ti); 251 ti = (struct tcpiphdr *)ti->ti_next; 252 if (so->so_state & SS_CANTRCVMORE) 253 m_freem(m); 254 else 255 sbappend(&so->so_rcv, m); 256 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 257 sorwakeup(so); 258 return (flags); 259 } 260 261 /* 262 * TCP input routine, follows pages 65-76 of the 263 * protocol specification dated September, 1981 very closely. 264 */ 265 void 266 tcp_input(m, iphlen) 267 register struct mbuf *m; 268 int iphlen; 269 { 270 register struct tcpiphdr *ti; 271 register struct inpcb *inp; 272 u_char *optp = NULL; 273 int optlen = 0; 274 int len, tlen, off; 275 register struct tcpcb *tp = 0; 276 register int tiflags; 277 struct socket *so = 0; 278 int todrop, acked, ourfinisacked, needoutput = 0; 279 struct in_addr laddr; 280 int dropsocket = 0; 281 int iss = 0; 282 u_long tiwin; 283 struct tcpopt to; /* options in this segment */ 284 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 285 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 286 #ifdef TCPDEBUG 287 short ostate = 0; 288 #endif 289 290 bzero((char *)&to, sizeof(to)); 291 292 tcpstat.tcps_rcvtotal++; 293 /* 294 * Get IP and TCP header together in first mbuf. 295 * Note: IP leaves IP header in first mbuf. 296 */ 297 ti = mtod(m, struct tcpiphdr *); 298 if (iphlen > sizeof (struct ip)) 299 ip_stripoptions(m, (struct mbuf *)0); 300 if (m->m_len < sizeof (struct tcpiphdr)) { 301 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 302 tcpstat.tcps_rcvshort++; 303 return; 304 } 305 ti = mtod(m, struct tcpiphdr *); 306 } 307 308 /* 309 * Checksum extended TCP header and data. 310 */ 311 tlen = ((struct ip *)ti)->ip_len; 312 len = sizeof (struct ip) + tlen; 313 ti->ti_next = ti->ti_prev = 0; 314 ti->ti_x1 = 0; 315 ti->ti_len = (u_short)tlen; 316 HTONS(ti->ti_len); 317 ti->ti_sum = in_cksum(m, len); 318 if (ti->ti_sum) { 319 tcpstat.tcps_rcvbadsum++; 320 goto drop; 321 } 322 #endif /* TUBA_INCLUDE */ 323 324 /* 325 * Check that TCP offset makes sense, 326 * pull out TCP options and adjust length. XXX 327 */ 328 off = ti->ti_off << 2; 329 if (off < sizeof (struct tcphdr) || off > tlen) { 330 tcpstat.tcps_rcvbadoff++; 331 goto drop; 332 } 333 tlen -= off; 334 ti->ti_len = tlen; 335 if (off > sizeof (struct tcphdr)) { 336 if (m->m_len < sizeof(struct ip) + off) { 337 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 338 tcpstat.tcps_rcvshort++; 339 return; 340 } 341 ti = mtod(m, struct tcpiphdr *); 342 } 343 optlen = off - sizeof (struct tcphdr); 344 optp = mtod(m, u_char *) + sizeof (struct tcpiphdr); 345 } 346 tiflags = ti->ti_flags; 347 348 /* 349 * Convert TCP protocol specific fields to host format. 350 */ 351 NTOHL(ti->ti_seq); 352 NTOHL(ti->ti_ack); 353 NTOHS(ti->ti_win); 354 NTOHS(ti->ti_urp); 355 356 /* 357 * Drop TCP, IP headers and TCP options. 358 */ 359 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 360 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 361 362 /* 363 * Locate pcb for segment. 364 */ 365 findpcb: 366 inp = in_pcblookuphash(&tcbinfo, ti->ti_src, ti->ti_sport, 367 ti->ti_dst, ti->ti_dport, 1); 368 369 /* 370 * If the state is CLOSED (i.e., TCB does not exist) then 371 * all data in the incoming segment is discarded. 372 * If the TCB exists but is in CLOSED state, it is embryonic, 373 * but should either do a listen or a connect soon. 374 */ 375 if (inp == NULL) { 376 if (log_in_vain && tiflags & TH_SYN) { 377 char buf[4*sizeof "123"]; 378 379 strcpy(buf, inet_ntoa(ti->ti_dst)); 380 log(LOG_INFO, "Connection attempt to TCP %s:%d" 381 " from %s:%d\n", 382 buf, ntohs(ti->ti_dport), 383 inet_ntoa(ti->ti_src), ntohs(ti->ti_sport)); 384 } 385 goto dropwithreset; 386 } 387 tp = intotcpcb(inp); 388 if (tp == 0) 389 goto dropwithreset; 390 if (tp->t_state == TCPS_CLOSED) 391 goto drop; 392 393 /* Unscale the window into a 32-bit value. */ 394 if ((tiflags & TH_SYN) == 0) 395 tiwin = ti->ti_win << tp->snd_scale; 396 else 397 tiwin = ti->ti_win; 398 399 so = inp->inp_socket; 400 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 401 #ifdef TCPDEBUG 402 if (so->so_options & SO_DEBUG) { 403 ostate = tp->t_state; 404 tcp_saveti = *ti; 405 } 406 #endif 407 if (so->so_options & SO_ACCEPTCONN) { 408 register struct tcpcb *tp0 = tp; 409 struct socket *so2; 410 if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 411 /* 412 * Note: dropwithreset makes sure we don't 413 * send a RST in response to a RST. 414 */ 415 if (tiflags & TH_ACK) { 416 tcpstat.tcps_badsyn++; 417 goto dropwithreset; 418 } 419 goto drop; 420 } 421 so2 = sonewconn(so, 0); 422 if (so2 == 0) { 423 tcpstat.tcps_listendrop++; 424 so2 = sodropablereq(so); 425 if (so2) { 426 tcp_drop(sototcpcb(so2), ETIMEDOUT); 427 so2 = sonewconn(so, 0); 428 } 429 if (!so2) 430 goto drop; 431 } 432 so = so2; 433 /* 434 * This is ugly, but .... 435 * 436 * Mark socket as temporary until we're 437 * committed to keeping it. The code at 438 * ``drop'' and ``dropwithreset'' check the 439 * flag dropsocket to see if the temporary 440 * socket created here should be discarded. 441 * We mark the socket as discardable until 442 * we're committed to it below in TCPS_LISTEN. 443 */ 444 dropsocket++; 445 inp = (struct inpcb *)so->so_pcb; 446 inp->inp_laddr = ti->ti_dst; 447 inp->inp_lport = ti->ti_dport; 448 in_pcbrehash(inp); 449 #if BSD>=43 450 inp->inp_options = ip_srcroute(); 451 #endif 452 tp = intotcpcb(inp); 453 tp->t_state = TCPS_LISTEN; 454 tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT); 455 456 /* Compute proper scaling value from buffer space */ 457 while (tp->request_r_scale < TCP_MAX_WINSHIFT && 458 TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) 459 tp->request_r_scale++; 460 } 461 } 462 463 /* 464 * Segment received on connection. 465 * Reset idle time and keep-alive timer. 466 */ 467 tp->t_idle = 0; 468 if (TCPS_HAVEESTABLISHED(tp->t_state)) 469 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 470 471 /* 472 * Process options if not in LISTEN state, 473 * else do it below (after getting remote address). 474 */ 475 if (tp->t_state != TCPS_LISTEN) 476 tcp_dooptions(tp, optp, optlen, ti, &to); 477 478 /* 479 * Header prediction: check for the two common cases 480 * of a uni-directional data xfer. If the packet has 481 * no control flags, is in-sequence, the window didn't 482 * change and we're not retransmitting, it's a 483 * candidate. If the length is zero and the ack moved 484 * forward, we're the sender side of the xfer. Just 485 * free the data acked & wake any higher level process 486 * that was blocked waiting for space. If the length 487 * is non-zero and the ack didn't move, we're the 488 * receiver side. If we're getting packets in-order 489 * (the reassembly queue is empty), add the data to 490 * the socket buffer and note that we need a delayed ack. 491 * Make sure that the hidden state-flags are also off. 492 * Since we check for TCPS_ESTABLISHED above, it can only 493 * be TH_NEEDSYN. 494 */ 495 if (tp->t_state == TCPS_ESTABLISHED && 496 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 497 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 498 ((to.to_flag & TOF_TS) == 0 || 499 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 500 /* 501 * Using the CC option is compulsory if once started: 502 * the segment is OK if no T/TCP was negotiated or 503 * if the segment has a CC option equal to CCrecv 504 */ 505 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 506 (to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv) && 507 ti->ti_seq == tp->rcv_nxt && 508 tiwin && tiwin == tp->snd_wnd && 509 tp->snd_nxt == tp->snd_max) { 510 511 /* 512 * If last ACK falls within this segment's sequence numbers, 513 * record the timestamp. 514 * NOTE that the test is modified according to the latest 515 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 516 */ 517 if ((to.to_flag & TOF_TS) != 0 && 518 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { 519 tp->ts_recent_age = tcp_now; 520 tp->ts_recent = to.to_tsval; 521 } 522 523 if (ti->ti_len == 0) { 524 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 525 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 526 tp->snd_cwnd >= tp->snd_wnd && 527 tp->t_dupacks < tcprexmtthresh) { 528 /* 529 * this is a pure ack for outstanding data. 530 */ 531 ++tcpstat.tcps_predack; 532 if ((to.to_flag & TOF_TS) != 0) 533 tcp_xmit_timer(tp, 534 tcp_now - to.to_tsecr + 1); 535 else if (tp->t_rtt && 536 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 537 tcp_xmit_timer(tp, tp->t_rtt); 538 acked = ti->ti_ack - tp->snd_una; 539 tcpstat.tcps_rcvackpack++; 540 tcpstat.tcps_rcvackbyte += acked; 541 sbdrop(&so->so_snd, acked); 542 tp->snd_una = ti->ti_ack; 543 m_freem(m); 544 545 /* 546 * If all outstanding data are acked, stop 547 * retransmit timer, otherwise restart timer 548 * using current (possibly backed-off) value. 549 * If process is waiting for space, 550 * wakeup/selwakeup/signal. If data 551 * are ready to send, let tcp_output 552 * decide between more output or persist. 553 */ 554 if (tp->snd_una == tp->snd_max) 555 tp->t_timer[TCPT_REXMT] = 0; 556 else if (tp->t_timer[TCPT_PERSIST] == 0) 557 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 558 559 if (so->so_snd.sb_flags & SB_NOTIFY) 560 sowwakeup(so); 561 if (so->so_snd.sb_cc) 562 (void) tcp_output(tp); 563 return; 564 } 565 } else if (ti->ti_ack == tp->snd_una && 566 tp->seg_next == (struct tcpiphdr *)tp && 567 ti->ti_len <= sbspace(&so->so_rcv)) { 568 /* 569 * this is a pure, in-sequence data packet 570 * with nothing on the reassembly queue and 571 * we have enough buffer space to take it. 572 */ 573 ++tcpstat.tcps_preddat; 574 tp->rcv_nxt += ti->ti_len; 575 tcpstat.tcps_rcvpack++; 576 tcpstat.tcps_rcvbyte += ti->ti_len; 577 /* 578 * Add data to socket buffer. 579 */ 580 sbappend(&so->so_rcv, m); 581 sorwakeup(so); 582 #ifdef TCP_ACK_HACK 583 /* 584 * If this is a short packet, then ACK now - with Nagel 585 * congestion avoidance sender won't send more until 586 * he gets an ACK. 587 */ 588 if (tiflags & TH_PUSH) { 589 tp->t_flags |= TF_ACKNOW; 590 tcp_output(tp); 591 } else { 592 tp->t_flags |= TF_DELACK; 593 } 594 #else 595 tp->t_flags |= TF_DELACK; 596 #endif 597 return; 598 } 599 } 600 601 /* 602 * Calculate amount of space in receive window, 603 * and then do TCP input processing. 604 * Receive window is amount of space in rcv queue, 605 * but not less than advertised window. 606 */ 607 { int win; 608 609 win = sbspace(&so->so_rcv); 610 if (win < 0) 611 win = 0; 612 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 613 } 614 615 switch (tp->t_state) { 616 617 /* 618 * If the state is LISTEN then ignore segment if it contains an RST. 619 * If the segment contains an ACK then it is bad and send a RST. 620 * If it does not contain a SYN then it is not interesting; drop it. 621 * If it is from this socket, drop it, it must be forged. 622 * Don't bother responding if the destination was a broadcast. 623 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 624 * tp->iss, and send a segment: 625 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 626 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 627 * Fill in remote peer address fields if not previously specified. 628 * Enter SYN_RECEIVED state, and process any other fields of this 629 * segment in this state. 630 */ 631 case TCPS_LISTEN: { 632 struct mbuf *am; 633 register struct sockaddr_in *sin; 634 635 if (tiflags & TH_RST) 636 goto drop; 637 if (tiflags & TH_ACK) 638 goto dropwithreset; 639 if ((tiflags & TH_SYN) == 0) 640 goto drop; 641 if ((ti->ti_dport == ti->ti_sport) && 642 (ti->ti_dst.s_addr == ti->ti_src.s_addr)) 643 goto drop; 644 /* 645 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 646 * in_broadcast() should never return true on a received 647 * packet with M_BCAST not set. 648 */ 649 if (m->m_flags & (M_BCAST|M_MCAST) || 650 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 651 goto drop; 652 am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ 653 if (am == NULL) 654 goto drop; 655 am->m_len = sizeof (struct sockaddr_in); 656 sin = mtod(am, struct sockaddr_in *); 657 sin->sin_family = AF_INET; 658 sin->sin_len = sizeof(*sin); 659 sin->sin_addr = ti->ti_src; 660 sin->sin_port = ti->ti_sport; 661 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 662 laddr = inp->inp_laddr; 663 if (inp->inp_laddr.s_addr == INADDR_ANY) 664 inp->inp_laddr = ti->ti_dst; 665 if (in_pcbconnect(inp, am)) { 666 inp->inp_laddr = laddr; 667 (void) m_free(am); 668 goto drop; 669 } 670 (void) m_free(am); 671 tp->t_template = tcp_template(tp); 672 if (tp->t_template == 0) { 673 tp = tcp_drop(tp, ENOBUFS); 674 dropsocket = 0; /* socket is already gone */ 675 goto drop; 676 } 677 if ((taop = tcp_gettaocache(inp)) == NULL) { 678 taop = &tao_noncached; 679 bzero(taop, sizeof(*taop)); 680 } 681 tcp_dooptions(tp, optp, optlen, ti, &to); 682 if (iss) 683 tp->iss = iss; 684 else 685 tp->iss = tcp_iss; 686 tcp_iss += TCP_ISSINCR/4; 687 tp->irs = ti->ti_seq; 688 tcp_sendseqinit(tp); 689 tcp_rcvseqinit(tp); 690 /* 691 * Initialization of the tcpcb for transaction; 692 * set SND.WND = SEG.WND, 693 * initialize CCsend and CCrecv. 694 */ 695 tp->snd_wnd = tiwin; /* initial send-window */ 696 tp->cc_send = CC_INC(tcp_ccgen); 697 tp->cc_recv = to.to_cc; 698 /* 699 * Perform TAO test on incoming CC (SEG.CC) option, if any. 700 * - compare SEG.CC against cached CC from the same host, 701 * if any. 702 * - if SEG.CC > chached value, SYN must be new and is accepted 703 * immediately: save new CC in the cache, mark the socket 704 * connected, enter ESTABLISHED state, turn on flag to 705 * send a SYN in the next segment. 706 * A virtual advertised window is set in rcv_adv to 707 * initialize SWS prevention. Then enter normal segment 708 * processing: drop SYN, process data and FIN. 709 * - otherwise do a normal 3-way handshake. 710 */ 711 if ((to.to_flag & TOF_CC) != 0) { 712 if (((tp->t_flags & TF_NOPUSH) != 0) && 713 taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { 714 715 taop->tao_cc = to.to_cc; 716 tp->t_state = TCPS_ESTABLISHED; 717 718 /* 719 * If there is a FIN, or if there is data and the 720 * connection is local, then delay SYN,ACK(SYN) in 721 * the hope of piggy-backing it on a response 722 * segment. Otherwise must send ACK now in case 723 * the other side is slow starting. 724 */ 725 if ((tiflags & TH_FIN) || (ti->ti_len != 0 && 726 in_localaddr(inp->inp_faddr))) 727 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 728 else 729 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 730 731 /* 732 * Limit the `virtual advertised window' to TCP_MAXWIN 733 * here. Even if we requested window scaling, it will 734 * become effective only later when our SYN is acked. 735 */ 736 tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN); 737 tcpstat.tcps_connects++; 738 soisconnected(so); 739 tp->t_timer[TCPT_KEEP] = tcp_keepinit; 740 dropsocket = 0; /* committed to socket */ 741 tcpstat.tcps_accepts++; 742 goto trimthenstep6; 743 } 744 /* else do standard 3-way handshake */ 745 } else { 746 /* 747 * No CC option, but maybe CC.NEW: 748 * invalidate cached value. 749 */ 750 taop->tao_cc = 0; 751 } 752 /* 753 * TAO test failed or there was no CC option, 754 * do a standard 3-way handshake. 755 */ 756 tp->t_flags |= TF_ACKNOW; 757 tp->t_state = TCPS_SYN_RECEIVED; 758 tp->t_timer[TCPT_KEEP] = tcp_keepinit; 759 dropsocket = 0; /* committed to socket */ 760 tcpstat.tcps_accepts++; 761 goto trimthenstep6; 762 } 763 764 /* 765 * If the state is SYN_RECEIVED: 766 * if seg contains SYN/ACK, send a RST. 767 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 768 */ 769 case TCPS_SYN_RECEIVED: 770 if (tiflags & TH_ACK) { 771 if (tiflags & TH_SYN) { 772 tcpstat.tcps_badsyn++; 773 goto dropwithreset; 774 } 775 if (SEQ_LEQ(ti->ti_ack, tp->snd_una) || 776 SEQ_GT(ti->ti_ack, tp->snd_max)) 777 goto dropwithreset; 778 } 779 break; 780 781 /* 782 * If the state is SYN_SENT: 783 * if seg contains an ACK, but not for our SYN, drop the input. 784 * if seg contains a RST, then drop the connection. 785 * if seg does not contain SYN, then drop it. 786 * Otherwise this is an acceptable SYN segment 787 * initialize tp->rcv_nxt and tp->irs 788 * if seg contains ack then advance tp->snd_una 789 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 790 * arrange for segment to be acked (eventually) 791 * continue processing rest of data/controls, beginning with URG 792 */ 793 case TCPS_SYN_SENT: 794 if ((taop = tcp_gettaocache(inp)) == NULL) { 795 taop = &tao_noncached; 796 bzero(taop, sizeof(*taop)); 797 } 798 799 if ((tiflags & TH_ACK) && 800 (SEQ_LEQ(ti->ti_ack, tp->iss) || 801 SEQ_GT(ti->ti_ack, tp->snd_max))) { 802 /* 803 * If we have a cached CCsent for the remote host, 804 * hence we haven't just crashed and restarted, 805 * do not send a RST. This may be a retransmission 806 * from the other side after our earlier ACK was lost. 807 * Our new SYN, when it arrives, will serve as the 808 * needed ACK. 809 */ 810 if (taop->tao_ccsent != 0) 811 goto drop; 812 else 813 goto dropwithreset; 814 } 815 if (tiflags & TH_RST) { 816 if (tiflags & TH_ACK) 817 tp = tcp_drop(tp, ECONNREFUSED); 818 goto drop; 819 } 820 if ((tiflags & TH_SYN) == 0) 821 goto drop; 822 tp->snd_wnd = ti->ti_win; /* initial send window */ 823 tp->cc_recv = to.to_cc; /* foreign CC */ 824 825 tp->irs = ti->ti_seq; 826 tcp_rcvseqinit(tp); 827 if (tiflags & TH_ACK) { 828 /* 829 * Our SYN was acked. If segment contains CC.ECHO 830 * option, check it to make sure this segment really 831 * matches our SYN. If not, just drop it as old 832 * duplicate, but send an RST if we're still playing 833 * by the old rules. If no CC.ECHO option, make sure 834 * we don't get fooled into using T/TCP. 835 */ 836 if (to.to_flag & TOF_CCECHO) { 837 if (tp->cc_send != to.to_ccecho) 838 if (taop->tao_ccsent != 0) 839 goto drop; 840 else 841 goto dropwithreset; 842 } else 843 tp->t_flags &= ~TF_RCVD_CC; 844 tcpstat.tcps_connects++; 845 soisconnected(so); 846 /* Do window scaling on this connection? */ 847 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 848 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 849 tp->snd_scale = tp->requested_s_scale; 850 tp->rcv_scale = tp->request_r_scale; 851 } 852 /* Segment is acceptable, update cache if undefined. */ 853 if (taop->tao_ccsent == 0) 854 taop->tao_ccsent = to.to_ccecho; 855 856 tp->rcv_adv += tp->rcv_wnd; 857 tp->snd_una++; /* SYN is acked */ 858 /* 859 * If there's data, delay ACK; if there's also a FIN 860 * ACKNOW will be turned on later. 861 */ 862 if (ti->ti_len != 0) 863 tp->t_flags |= TF_DELACK; 864 else 865 tp->t_flags |= TF_ACKNOW; 866 /* 867 * Received <SYN,ACK> in SYN_SENT[*] state. 868 * Transitions: 869 * SYN_SENT --> ESTABLISHED 870 * SYN_SENT* --> FIN_WAIT_1 871 */ 872 if (tp->t_flags & TF_NEEDFIN) { 873 tp->t_state = TCPS_FIN_WAIT_1; 874 tp->t_flags &= ~TF_NEEDFIN; 875 tiflags &= ~TH_SYN; 876 } else { 877 tp->t_state = TCPS_ESTABLISHED; 878 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 879 } 880 } else { 881 /* 882 * Received initial SYN in SYN-SENT[*] state => simul- 883 * taneous open. If segment contains CC option and there is 884 * a cached CC, apply TAO test; if it succeeds, connection is 885 * half-synchronized. Otherwise, do 3-way handshake: 886 * SYN-SENT -> SYN-RECEIVED 887 * SYN-SENT* -> SYN-RECEIVED* 888 * If there was no CC option, clear cached CC value. 889 */ 890 tp->t_flags |= TF_ACKNOW; 891 tp->t_timer[TCPT_REXMT] = 0; 892 if (to.to_flag & TOF_CC) { 893 if (taop->tao_cc != 0 && 894 CC_GT(to.to_cc, taop->tao_cc)) { 895 /* 896 * update cache and make transition: 897 * SYN-SENT -> ESTABLISHED* 898 * SYN-SENT* -> FIN-WAIT-1* 899 */ 900 taop->tao_cc = to.to_cc; 901 if (tp->t_flags & TF_NEEDFIN) { 902 tp->t_state = TCPS_FIN_WAIT_1; 903 tp->t_flags &= ~TF_NEEDFIN; 904 } else { 905 tp->t_state = TCPS_ESTABLISHED; 906 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 907 } 908 tp->t_flags |= TF_NEEDSYN; 909 } else 910 tp->t_state = TCPS_SYN_RECEIVED; 911 } else { 912 /* CC.NEW or no option => invalidate cache */ 913 taop->tao_cc = 0; 914 tp->t_state = TCPS_SYN_RECEIVED; 915 } 916 } 917 918 trimthenstep6: 919 /* 920 * Advance ti->ti_seq to correspond to first data byte. 921 * If data, trim to stay within window, 922 * dropping FIN if necessary. 923 */ 924 ti->ti_seq++; 925 if (ti->ti_len > tp->rcv_wnd) { 926 todrop = ti->ti_len - tp->rcv_wnd; 927 m_adj(m, -todrop); 928 ti->ti_len = tp->rcv_wnd; 929 tiflags &= ~TH_FIN; 930 tcpstat.tcps_rcvpackafterwin++; 931 tcpstat.tcps_rcvbyteafterwin += todrop; 932 } 933 tp->snd_wl1 = ti->ti_seq - 1; 934 tp->rcv_up = ti->ti_seq; 935 /* 936 * Client side of transaction: already sent SYN and data. 937 * If the remote host used T/TCP to validate the SYN, 938 * our data will be ACK'd; if so, enter normal data segment 939 * processing in the middle of step 5, ack processing. 940 * Otherwise, goto step 6. 941 */ 942 if (tiflags & TH_ACK) 943 goto process_ACK; 944 goto step6; 945 /* 946 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 947 * if segment contains a SYN and CC [not CC.NEW] option: 948 * if state == TIME_WAIT and connection duration > MSL, 949 * drop packet and send RST; 950 * 951 * if SEG.CC > CCrecv then is new SYN, and can implicitly 952 * ack the FIN (and data) in retransmission queue. 953 * Complete close and delete TCPCB. Then reprocess 954 * segment, hoping to find new TCPCB in LISTEN state; 955 * 956 * else must be old SYN; drop it. 957 * else do normal processing. 958 */ 959 case TCPS_LAST_ACK: 960 case TCPS_CLOSING: 961 case TCPS_TIME_WAIT: 962 if ((tiflags & TH_SYN) && 963 (to.to_flag & TOF_CC) && tp->cc_recv != 0) { 964 if (tp->t_state == TCPS_TIME_WAIT && 965 tp->t_duration > TCPTV_MSL) 966 goto dropwithreset; 967 if (CC_GT(to.to_cc, tp->cc_recv)) { 968 tp = tcp_close(tp); 969 goto findpcb; 970 } 971 else 972 goto drop; 973 } 974 break; /* continue normal processing */ 975 } 976 977 /* 978 * States other than LISTEN or SYN_SENT. 979 * First check the RST flag and sequence number since reset segments 980 * are exempt from the timestamp and connection count tests. This 981 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 982 * below which allowed reset segments in half the sequence space 983 * to fall though and be processed (which gives forged reset 984 * segments with a random sequence number a 50 percent chance of 985 * killing a connection). 986 * Then check timestamp, if present. 987 * Then check the connection count, if present. 988 * Then check that at least some bytes of segment are within 989 * receive window. If segment begins before rcv_nxt, 990 * drop leading data (and SYN); if nothing left, just ack. 991 * 992 * 993 * If the RST bit is set, check the sequence number to see 994 * if this is a valid reset segment. 995 * RFC 793 page 37: 996 * In all states except SYN-SENT, all reset (RST) segments 997 * are validated by checking their SEQ-fields. A reset is 998 * valid if its sequence number is in the window. 999 * Note: this does not take into account delayed ACKs, so 1000 * we should test against last_ack_sent instead of rcv_nxt. 1001 * Also, it does not make sense to allow reset segments with 1002 * sequence numbers greater than last_ack_sent to be processed 1003 * since these sequence numbers are just the acknowledgement 1004 * numbers in our outgoing packets being echoed back at us, 1005 * and these acknowledgement numbers are monotonically 1006 * increasing. 1007 * If we have multiple segments in flight, the intial reset 1008 * segment sequence numbers will be to the left of last_ack_sent, 1009 * but they will eventually catch up. 1010 * In any case, it never made sense to trim reset segments to 1011 * fit the receive window since RFC 1122 says: 1012 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1013 * 1014 * A TCP SHOULD allow a received RST segment to include data. 1015 * 1016 * DISCUSSION 1017 * It has been suggested that a RST segment could contain 1018 * ASCII text that encoded and explained the cause of the 1019 * RST. No standard has yet been established for such 1020 * data. 1021 * 1022 * If the reset segment passes the sequence number test examine 1023 * the state: 1024 * SYN_RECEIVED STATE: 1025 * If passive open, return to LISTEN state. 1026 * If active open, inform user that connection was refused. 1027 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 1028 * Inform user that connection was reset, and close tcb. 1029 * CLOSING, LAST_ACK, TIME_WAIT STATES 1030 * Close the tcb. 1031 * TIME_WAIT state: 1032 * Drop the segment - see Stevens, vol. 2, p. 964 and 1033 * RFC 1337. 1034 */ 1035 if (tiflags & TH_RST) { 1036 if (tp->last_ack_sent == ti->ti_seq) { 1037 switch (tp->t_state) { 1038 1039 case TCPS_SYN_RECEIVED: 1040 so->so_error = ECONNREFUSED; 1041 goto close; 1042 1043 case TCPS_ESTABLISHED: 1044 case TCPS_FIN_WAIT_1: 1045 case TCPS_FIN_WAIT_2: 1046 case TCPS_CLOSE_WAIT: 1047 so->so_error = ECONNRESET; 1048 close: 1049 tp->t_state = TCPS_CLOSED; 1050 tcpstat.tcps_drops++; 1051 tp = tcp_close(tp); 1052 break; 1053 1054 case TCPS_CLOSING: 1055 case TCPS_LAST_ACK: 1056 tp = tcp_close(tp); 1057 break; 1058 1059 case TCPS_TIME_WAIT: 1060 break; 1061 } 1062 } 1063 goto drop; 1064 } 1065 1066 /* 1067 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1068 * and it's less than ts_recent, drop it. 1069 */ 1070 if ((to.to_flag & TOF_TS) != 0 && tp->ts_recent && 1071 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1072 1073 /* Check to see if ts_recent is over 24 days old. */ 1074 if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1075 /* 1076 * Invalidate ts_recent. If this segment updates 1077 * ts_recent, the age will be reset later and ts_recent 1078 * will get a valid value. If it does not, setting 1079 * ts_recent to zero will at least satisfy the 1080 * requirement that zero be placed in the timestamp 1081 * echo reply when ts_recent isn't valid. The 1082 * age isn't reset until we get a valid ts_recent 1083 * because we don't want out-of-order segments to be 1084 * dropped when ts_recent is old. 1085 */ 1086 tp->ts_recent = 0; 1087 } else { 1088 tcpstat.tcps_rcvduppack++; 1089 tcpstat.tcps_rcvdupbyte += ti->ti_len; 1090 tcpstat.tcps_pawsdrop++; 1091 goto dropafterack; 1092 } 1093 } 1094 1095 /* 1096 * T/TCP mechanism 1097 * If T/TCP was negotiated and the segment doesn't have CC, 1098 * or if it's CC is wrong then drop the segment. 1099 * RST segments do not have to comply with this. 1100 */ 1101 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1102 ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1103 goto dropafterack; 1104 1105 /* 1106 * In the SYN-RECEIVED state, validate that the packet belongs to 1107 * this connection before trimming the data to fit the receive 1108 * window. Check the sequence number versus IRS since we know 1109 * the sequence numbers haven't wrapped. This is a partial fix 1110 * for the "LAND" DoS attack. 1111 */ 1112 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(ti->ti_seq, tp->irs)) 1113 goto dropwithreset; 1114 1115 todrop = tp->rcv_nxt - ti->ti_seq; 1116 if (todrop > 0) { 1117 if (tiflags & TH_SYN) { 1118 tiflags &= ~TH_SYN; 1119 ti->ti_seq++; 1120 if (ti->ti_urp > 1) 1121 ti->ti_urp--; 1122 else 1123 tiflags &= ~TH_URG; 1124 todrop--; 1125 } 1126 /* 1127 * Following if statement from Stevens, vol. 2, p. 960. 1128 */ 1129 if (todrop > ti->ti_len 1130 || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) { 1131 /* 1132 * Any valid FIN must be to the left of the window. 1133 * At this point the FIN must be a duplicate or out 1134 * of sequence; drop it. 1135 */ 1136 tiflags &= ~TH_FIN; 1137 1138 /* 1139 * Send an ACK to resynchronize and drop any data. 1140 * But keep on processing for RST or ACK. 1141 */ 1142 tp->t_flags |= TF_ACKNOW; 1143 todrop = ti->ti_len; 1144 tcpstat.tcps_rcvduppack++; 1145 tcpstat.tcps_rcvdupbyte += todrop; 1146 } else { 1147 tcpstat.tcps_rcvpartduppack++; 1148 tcpstat.tcps_rcvpartdupbyte += todrop; 1149 } 1150 m_adj(m, todrop); 1151 ti->ti_seq += todrop; 1152 ti->ti_len -= todrop; 1153 if (ti->ti_urp > todrop) 1154 ti->ti_urp -= todrop; 1155 else { 1156 tiflags &= ~TH_URG; 1157 ti->ti_urp = 0; 1158 } 1159 } 1160 1161 /* 1162 * If new data are received on a connection after the 1163 * user processes are gone, then RST the other end. 1164 */ 1165 if ((so->so_state & SS_NOFDREF) && 1166 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 1167 tp = tcp_close(tp); 1168 tcpstat.tcps_rcvafterclose++; 1169 goto dropwithreset; 1170 } 1171 1172 /* 1173 * If segment ends after window, drop trailing data 1174 * (and PUSH and FIN); if nothing left, just ACK. 1175 */ 1176 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 1177 if (todrop > 0) { 1178 tcpstat.tcps_rcvpackafterwin++; 1179 if (todrop >= ti->ti_len) { 1180 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 1181 /* 1182 * If a new connection request is received 1183 * while in TIME_WAIT, drop the old connection 1184 * and start over if the sequence numbers 1185 * are above the previous ones. 1186 */ 1187 if (tiflags & TH_SYN && 1188 tp->t_state == TCPS_TIME_WAIT && 1189 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 1190 iss = tp->rcv_nxt + TCP_ISSINCR; 1191 tp = tcp_close(tp); 1192 goto findpcb; 1193 } 1194 /* 1195 * If window is closed can only take segments at 1196 * window edge, and have to drop data and PUSH from 1197 * incoming segments. Continue processing, but 1198 * remember to ack. Otherwise, drop segment 1199 * and ack. 1200 */ 1201 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 1202 tp->t_flags |= TF_ACKNOW; 1203 tcpstat.tcps_rcvwinprobe++; 1204 } else 1205 goto dropafterack; 1206 } else 1207 tcpstat.tcps_rcvbyteafterwin += todrop; 1208 m_adj(m, -todrop); 1209 ti->ti_len -= todrop; 1210 tiflags &= ~(TH_PUSH|TH_FIN); 1211 } 1212 1213 /* 1214 * If last ACK falls within this segment's sequence numbers, 1215 * record its timestamp. 1216 * NOTE that the test is modified according to the latest 1217 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1218 */ 1219 if ((to.to_flag & TOF_TS) != 0 && 1220 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { 1221 tp->ts_recent_age = tcp_now; 1222 tp->ts_recent = to.to_tsval; 1223 } 1224 1225 /* 1226 * If a SYN is in the window, then this is an 1227 * error and we send an RST and drop the connection. 1228 */ 1229 if (tiflags & TH_SYN) { 1230 tp = tcp_drop(tp, ECONNRESET); 1231 goto dropwithreset; 1232 } 1233 1234 /* 1235 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1236 * flag is on (half-synchronized state), then queue data for 1237 * later processing; else drop segment and return. 1238 */ 1239 if ((tiflags & TH_ACK) == 0) { 1240 if (tp->t_state == TCPS_SYN_RECEIVED || 1241 (tp->t_flags & TF_NEEDSYN)) 1242 goto step6; 1243 else 1244 goto drop; 1245 } 1246 1247 /* 1248 * Ack processing. 1249 */ 1250 switch (tp->t_state) { 1251 1252 /* 1253 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1254 * ESTABLISHED state and continue processing. 1255 * The ACK was checked above. 1256 */ 1257 case TCPS_SYN_RECEIVED: 1258 1259 tcpstat.tcps_connects++; 1260 soisconnected(so); 1261 /* Do window scaling? */ 1262 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1263 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1264 tp->snd_scale = tp->requested_s_scale; 1265 tp->rcv_scale = tp->request_r_scale; 1266 } 1267 /* 1268 * Upon successful completion of 3-way handshake, 1269 * update cache.CC if it was undefined, pass any queued 1270 * data to the user, and advance state appropriately. 1271 */ 1272 if ((taop = tcp_gettaocache(inp)) != NULL && 1273 taop->tao_cc == 0) 1274 taop->tao_cc = tp->cc_recv; 1275 1276 /* 1277 * Make transitions: 1278 * SYN-RECEIVED -> ESTABLISHED 1279 * SYN-RECEIVED* -> FIN-WAIT-1 1280 */ 1281 if (tp->t_flags & TF_NEEDFIN) { 1282 tp->t_state = TCPS_FIN_WAIT_1; 1283 tp->t_flags &= ~TF_NEEDFIN; 1284 } else { 1285 tp->t_state = TCPS_ESTABLISHED; 1286 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 1287 } 1288 /* 1289 * If segment contains data or ACK, will call tcp_reass() 1290 * later; if not, do so now to pass queued data to user. 1291 */ 1292 if (ti->ti_len == 0 && (tiflags & TH_FIN) == 0) 1293 (void) tcp_reass(tp, (struct tcpiphdr *)0, 1294 (struct mbuf *)0); 1295 tp->snd_wl1 = ti->ti_seq - 1; 1296 /* fall into ... */ 1297 1298 /* 1299 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1300 * ACKs. If the ack is in the range 1301 * tp->snd_una < ti->ti_ack <= tp->snd_max 1302 * then advance tp->snd_una to ti->ti_ack and drop 1303 * data from the retransmission queue. If this ACK reflects 1304 * more up to date window information we update our window information. 1305 */ 1306 case TCPS_ESTABLISHED: 1307 case TCPS_FIN_WAIT_1: 1308 case TCPS_FIN_WAIT_2: 1309 case TCPS_CLOSE_WAIT: 1310 case TCPS_CLOSING: 1311 case TCPS_LAST_ACK: 1312 case TCPS_TIME_WAIT: 1313 1314 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 1315 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 1316 tcpstat.tcps_rcvdupack++; 1317 /* 1318 * If we have outstanding data (other than 1319 * a window probe), this is a completely 1320 * duplicate ack (ie, window info didn't 1321 * change), the ack is the biggest we've 1322 * seen and we've seen exactly our rexmt 1323 * threshhold of them, assume a packet 1324 * has been dropped and retransmit it. 1325 * Kludge snd_nxt & the congestion 1326 * window so we send only this one 1327 * packet. 1328 * 1329 * We know we're losing at the current 1330 * window size so do congestion avoidance 1331 * (set ssthresh to half the current window 1332 * and pull our congestion window back to 1333 * the new ssthresh). 1334 * 1335 * Dup acks mean that packets have left the 1336 * network (they're now cached at the receiver) 1337 * so bump cwnd by the amount in the receiver 1338 * to keep a constant cwnd packets in the 1339 * network. 1340 */ 1341 if (tp->t_timer[TCPT_REXMT] == 0 || 1342 ti->ti_ack != tp->snd_una) 1343 tp->t_dupacks = 0; 1344 else if (++tp->t_dupacks == tcprexmtthresh) { 1345 tcp_seq onxt = tp->snd_nxt; 1346 u_int win = 1347 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1348 tp->t_maxseg; 1349 1350 if (win < 2) 1351 win = 2; 1352 tp->snd_ssthresh = win * tp->t_maxseg; 1353 tp->t_timer[TCPT_REXMT] = 0; 1354 tp->t_rtt = 0; 1355 tp->snd_nxt = ti->ti_ack; 1356 tp->snd_cwnd = tp->t_maxseg; 1357 (void) tcp_output(tp); 1358 tp->snd_cwnd = tp->snd_ssthresh + 1359 tp->t_maxseg * tp->t_dupacks; 1360 if (SEQ_GT(onxt, tp->snd_nxt)) 1361 tp->snd_nxt = onxt; 1362 goto drop; 1363 } else if (tp->t_dupacks > tcprexmtthresh) { 1364 tp->snd_cwnd += tp->t_maxseg; 1365 (void) tcp_output(tp); 1366 goto drop; 1367 } 1368 } else 1369 tp->t_dupacks = 0; 1370 break; 1371 } 1372 /* 1373 * If the congestion window was inflated to account 1374 * for the other side's cached packets, retract it. 1375 */ 1376 if (tp->t_dupacks >= tcprexmtthresh && 1377 tp->snd_cwnd > tp->snd_ssthresh) 1378 tp->snd_cwnd = tp->snd_ssthresh; 1379 tp->t_dupacks = 0; 1380 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 1381 tcpstat.tcps_rcvacktoomuch++; 1382 goto dropafterack; 1383 } 1384 /* 1385 * If we reach this point, ACK is not a duplicate, 1386 * i.e., it ACKs something we sent. 1387 */ 1388 if (tp->t_flags & TF_NEEDSYN) { 1389 /* 1390 * T/TCP: Connection was half-synchronized, and our 1391 * SYN has been ACK'd (so connection is now fully 1392 * synchronized). Go to non-starred state, 1393 * increment snd_una for ACK of SYN, and check if 1394 * we can do window scaling. 1395 */ 1396 tp->t_flags &= ~TF_NEEDSYN; 1397 tp->snd_una++; 1398 /* Do window scaling? */ 1399 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1400 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1401 tp->snd_scale = tp->requested_s_scale; 1402 tp->rcv_scale = tp->request_r_scale; 1403 } 1404 } 1405 1406 process_ACK: 1407 acked = ti->ti_ack - tp->snd_una; 1408 tcpstat.tcps_rcvackpack++; 1409 tcpstat.tcps_rcvackbyte += acked; 1410 1411 /* 1412 * If we have a timestamp reply, update smoothed 1413 * round trip time. If no timestamp is present but 1414 * transmit timer is running and timed sequence 1415 * number was acked, update smoothed round trip time. 1416 * Since we now have an rtt measurement, cancel the 1417 * timer backoff (cf., Phil Karn's retransmit alg.). 1418 * Recompute the initial retransmit timer. 1419 */ 1420 if (to.to_flag & TOF_TS) 1421 tcp_xmit_timer(tp, tcp_now - to.to_tsecr + 1); 1422 else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 1423 tcp_xmit_timer(tp,tp->t_rtt); 1424 1425 /* 1426 * If all outstanding data is acked, stop retransmit 1427 * timer and remember to restart (more output or persist). 1428 * If there is more data to be acked, restart retransmit 1429 * timer, using current (possibly backed-off) value. 1430 */ 1431 if (ti->ti_ack == tp->snd_max) { 1432 tp->t_timer[TCPT_REXMT] = 0; 1433 needoutput = 1; 1434 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1435 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1436 1437 /* 1438 * If no data (only SYN) was ACK'd, 1439 * skip rest of ACK processing. 1440 */ 1441 if (acked == 0) 1442 goto step6; 1443 1444 /* 1445 * When new data is acked, open the congestion window. 1446 * If the window gives us less than ssthresh packets 1447 * in flight, open exponentially (maxseg per packet). 1448 * Otherwise open linearly: maxseg per window 1449 * (maxseg^2 / cwnd per packet). 1450 */ 1451 { 1452 register u_int cw = tp->snd_cwnd; 1453 register u_int incr = tp->t_maxseg; 1454 1455 if (cw > tp->snd_ssthresh) 1456 incr = incr * incr / cw; 1457 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1458 } 1459 if (acked > so->so_snd.sb_cc) { 1460 tp->snd_wnd -= so->so_snd.sb_cc; 1461 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1462 ourfinisacked = 1; 1463 } else { 1464 sbdrop(&so->so_snd, acked); 1465 tp->snd_wnd -= acked; 1466 ourfinisacked = 0; 1467 } 1468 if (so->so_snd.sb_flags & SB_NOTIFY) 1469 sowwakeup(so); 1470 tp->snd_una = ti->ti_ack; 1471 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1472 tp->snd_nxt = tp->snd_una; 1473 1474 switch (tp->t_state) { 1475 1476 /* 1477 * In FIN_WAIT_1 STATE in addition to the processing 1478 * for the ESTABLISHED state if our FIN is now acknowledged 1479 * then enter FIN_WAIT_2. 1480 */ 1481 case TCPS_FIN_WAIT_1: 1482 if (ourfinisacked) { 1483 /* 1484 * If we can't receive any more 1485 * data, then closing user can proceed. 1486 * Starting the timer is contrary to the 1487 * specification, but if we don't get a FIN 1488 * we'll hang forever. 1489 */ 1490 if (so->so_state & SS_CANTRCVMORE) { 1491 soisdisconnected(so); 1492 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 1493 } 1494 tp->t_state = TCPS_FIN_WAIT_2; 1495 } 1496 break; 1497 1498 /* 1499 * In CLOSING STATE in addition to the processing for 1500 * the ESTABLISHED state if the ACK acknowledges our FIN 1501 * then enter the TIME-WAIT state, otherwise ignore 1502 * the segment. 1503 */ 1504 case TCPS_CLOSING: 1505 if (ourfinisacked) { 1506 tp->t_state = TCPS_TIME_WAIT; 1507 tcp_canceltimers(tp); 1508 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1509 if (tp->cc_recv != 0 && 1510 tp->t_duration < TCPTV_MSL) 1511 tp->t_timer[TCPT_2MSL] = 1512 tp->t_rxtcur * TCPTV_TWTRUNC; 1513 else 1514 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1515 soisdisconnected(so); 1516 } 1517 break; 1518 1519 /* 1520 * In LAST_ACK, we may still be waiting for data to drain 1521 * and/or to be acked, as well as for the ack of our FIN. 1522 * If our FIN is now acknowledged, delete the TCB, 1523 * enter the closed state and return. 1524 */ 1525 case TCPS_LAST_ACK: 1526 if (ourfinisacked) { 1527 tp = tcp_close(tp); 1528 goto drop; 1529 } 1530 break; 1531 1532 /* 1533 * In TIME_WAIT state the only thing that should arrive 1534 * is a retransmission of the remote FIN. Acknowledge 1535 * it and restart the finack timer. 1536 */ 1537 case TCPS_TIME_WAIT: 1538 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1539 goto dropafterack; 1540 } 1541 } 1542 1543 step6: 1544 /* 1545 * Update window information. 1546 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1547 */ 1548 if ((tiflags & TH_ACK) && 1549 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || 1550 (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 1551 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) { 1552 /* keep track of pure window updates */ 1553 if (ti->ti_len == 0 && 1554 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1555 tcpstat.tcps_rcvwinupd++; 1556 tp->snd_wnd = tiwin; 1557 tp->snd_wl1 = ti->ti_seq; 1558 tp->snd_wl2 = ti->ti_ack; 1559 if (tp->snd_wnd > tp->max_sndwnd) 1560 tp->max_sndwnd = tp->snd_wnd; 1561 needoutput = 1; 1562 } 1563 1564 /* 1565 * Process segments with URG. 1566 */ 1567 if ((tiflags & TH_URG) && ti->ti_urp && 1568 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1569 /* 1570 * This is a kludge, but if we receive and accept 1571 * random urgent pointers, we'll crash in 1572 * soreceive. It's hard to imagine someone 1573 * actually wanting to send this much urgent data. 1574 */ 1575 if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { 1576 ti->ti_urp = 0; /* XXX */ 1577 tiflags &= ~TH_URG; /* XXX */ 1578 goto dodata; /* XXX */ 1579 } 1580 /* 1581 * If this segment advances the known urgent pointer, 1582 * then mark the data stream. This should not happen 1583 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1584 * a FIN has been received from the remote side. 1585 * In these states we ignore the URG. 1586 * 1587 * According to RFC961 (Assigned Protocols), 1588 * the urgent pointer points to the last octet 1589 * of urgent data. We continue, however, 1590 * to consider it to indicate the first octet 1591 * of data past the urgent section as the original 1592 * spec states (in one of two places). 1593 */ 1594 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1595 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1596 so->so_oobmark = so->so_rcv.sb_cc + 1597 (tp->rcv_up - tp->rcv_nxt) - 1; 1598 if (so->so_oobmark == 0) 1599 so->so_state |= SS_RCVATMARK; 1600 sohasoutofband(so); 1601 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1602 } 1603 /* 1604 * Remove out of band data so doesn't get presented to user. 1605 * This can happen independent of advancing the URG pointer, 1606 * but if two URG's are pending at once, some out-of-band 1607 * data may creep in... ick. 1608 */ 1609 if (ti->ti_urp <= (u_long)ti->ti_len 1610 #ifdef SO_OOBINLINE 1611 && (so->so_options & SO_OOBINLINE) == 0 1612 #endif 1613 ) 1614 tcp_pulloutofband(so, ti, m); 1615 } else 1616 /* 1617 * If no out of band data is expected, 1618 * pull receive urgent pointer along 1619 * with the receive window. 1620 */ 1621 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1622 tp->rcv_up = tp->rcv_nxt; 1623 dodata: /* XXX */ 1624 1625 /* 1626 * Process the segment text, merging it into the TCP sequencing queue, 1627 * and arranging for acknowledgment of receipt if necessary. 1628 * This process logically involves adjusting tp->rcv_wnd as data 1629 * is presented to the user (this happens in tcp_usrreq.c, 1630 * case PRU_RCVD). If a FIN has already been received on this 1631 * connection then we just ignore the text. 1632 */ 1633 if ((ti->ti_len || (tiflags&TH_FIN)) && 1634 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1635 TCP_REASS(tp, ti, m, so, tiflags); 1636 /* 1637 * Note the amount of data that peer has sent into 1638 * our window, in order to estimate the sender's 1639 * buffer size. 1640 */ 1641 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1642 } else { 1643 m_freem(m); 1644 tiflags &= ~TH_FIN; 1645 } 1646 1647 /* 1648 * If FIN is received ACK the FIN and let the user know 1649 * that the connection is closing. 1650 */ 1651 if (tiflags & TH_FIN) { 1652 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1653 socantrcvmore(so); 1654 /* 1655 * If connection is half-synchronized 1656 * (ie NEEDSYN flag on) then delay ACK, 1657 * so it may be piggybacked when SYN is sent. 1658 * Otherwise, since we received a FIN then no 1659 * more input can be expected, send ACK now. 1660 */ 1661 if (tp->t_flags & TF_NEEDSYN) 1662 tp->t_flags |= TF_DELACK; 1663 else 1664 tp->t_flags |= TF_ACKNOW; 1665 tp->rcv_nxt++; 1666 } 1667 switch (tp->t_state) { 1668 1669 /* 1670 * In SYN_RECEIVED and ESTABLISHED STATES 1671 * enter the CLOSE_WAIT state. 1672 */ 1673 case TCPS_SYN_RECEIVED: 1674 case TCPS_ESTABLISHED: 1675 tp->t_state = TCPS_CLOSE_WAIT; 1676 break; 1677 1678 /* 1679 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1680 * enter the CLOSING state. 1681 */ 1682 case TCPS_FIN_WAIT_1: 1683 tp->t_state = TCPS_CLOSING; 1684 break; 1685 1686 /* 1687 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1688 * starting the time-wait timer, turning off the other 1689 * standard timers. 1690 */ 1691 case TCPS_FIN_WAIT_2: 1692 tp->t_state = TCPS_TIME_WAIT; 1693 tcp_canceltimers(tp); 1694 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1695 if (tp->cc_recv != 0 && 1696 tp->t_duration < TCPTV_MSL) { 1697 tp->t_timer[TCPT_2MSL] = 1698 tp->t_rxtcur * TCPTV_TWTRUNC; 1699 /* For transaction client, force ACK now. */ 1700 tp->t_flags |= TF_ACKNOW; 1701 } 1702 else 1703 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1704 soisdisconnected(so); 1705 break; 1706 1707 /* 1708 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1709 */ 1710 case TCPS_TIME_WAIT: 1711 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1712 break; 1713 } 1714 } 1715 #ifdef TCPDEBUG 1716 if (so->so_options & SO_DEBUG) 1717 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1718 #endif 1719 1720 /* 1721 * Return any desired output. 1722 */ 1723 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1724 (void) tcp_output(tp); 1725 return; 1726 1727 dropafterack: 1728 /* 1729 * Generate an ACK dropping incoming segment if it occupies 1730 * sequence space, where the ACK reflects our state. 1731 * 1732 * We can now skip the test for the RST flag since all 1733 * paths to this code happen after packets containing 1734 * RST have been dropped. 1735 * 1736 * In the SYN-RECEIVED state, don't send an ACK unless the 1737 * segment we received passes the SYN-RECEIVED ACK test. 1738 * If it fails send a RST. This breaks the loop in the 1739 * "LAND" DoS attack, and also prevents an ACK storm 1740 * between two listening ports that have been sent forged 1741 * SYN segments, each with the source address of the other. 1742 */ 1743 if (tp->t_state == TCPS_SYN_RECEIVED && (tiflags & TH_ACK) && 1744 (SEQ_GT(tp->snd_una, ti->ti_ack) || 1745 SEQ_GT(ti->ti_ack, tp->snd_max)) ) 1746 goto dropwithreset; 1747 #ifdef TCPDEBUG 1748 if (so->so_options & SO_DEBUG) 1749 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1750 #endif 1751 m_freem(m); 1752 tp->t_flags |= TF_ACKNOW; 1753 (void) tcp_output(tp); 1754 return; 1755 1756 dropwithreset: 1757 /* 1758 * Generate a RST, dropping incoming segment. 1759 * Make ACK acceptable to originator of segment. 1760 * Don't bother to respond if destination was broadcast/multicast. 1761 */ 1762 if ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) || 1763 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 1764 goto drop; 1765 #ifdef TCPDEBUG 1766 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1767 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1768 #endif 1769 if (tiflags & TH_ACK) 1770 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1771 else { 1772 if (tiflags & TH_SYN) 1773 ti->ti_len++; 1774 tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1775 TH_RST|TH_ACK); 1776 } 1777 /* destroy temporarily created socket */ 1778 if (dropsocket) 1779 (void) soabort(so); 1780 return; 1781 1782 drop: 1783 /* 1784 * Drop space held by incoming segment and return. 1785 */ 1786 #ifdef TCPDEBUG 1787 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1788 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1789 #endif 1790 m_freem(m); 1791 /* destroy temporarily created socket */ 1792 if (dropsocket) 1793 (void) soabort(so); 1794 return; 1795 #ifndef TUBA_INCLUDE 1796 } 1797 1798 static void 1799 tcp_dooptions(tp, cp, cnt, ti, to) 1800 struct tcpcb *tp; 1801 u_char *cp; 1802 int cnt; 1803 struct tcpiphdr *ti; 1804 struct tcpopt *to; 1805 { 1806 u_short mss = 0; 1807 int opt, optlen; 1808 1809 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1810 opt = cp[0]; 1811 if (opt == TCPOPT_EOL) 1812 break; 1813 if (opt == TCPOPT_NOP) 1814 optlen = 1; 1815 else { 1816 optlen = cp[1]; 1817 if (optlen <= 0) 1818 break; 1819 } 1820 switch (opt) { 1821 1822 default: 1823 continue; 1824 1825 case TCPOPT_MAXSEG: 1826 if (optlen != TCPOLEN_MAXSEG) 1827 continue; 1828 if (!(ti->ti_flags & TH_SYN)) 1829 continue; 1830 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); 1831 NTOHS(mss); 1832 break; 1833 1834 case TCPOPT_WINDOW: 1835 if (optlen != TCPOLEN_WINDOW) 1836 continue; 1837 if (!(ti->ti_flags & TH_SYN)) 1838 continue; 1839 tp->t_flags |= TF_RCVD_SCALE; 1840 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 1841 break; 1842 1843 case TCPOPT_TIMESTAMP: 1844 if (optlen != TCPOLEN_TIMESTAMP) 1845 continue; 1846 to->to_flag |= TOF_TS; 1847 bcopy((char *)cp + 2, 1848 (char *)&to->to_tsval, sizeof(to->to_tsval)); 1849 NTOHL(to->to_tsval); 1850 bcopy((char *)cp + 6, 1851 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 1852 NTOHL(to->to_tsecr); 1853 1854 /* 1855 * A timestamp received in a SYN makes 1856 * it ok to send timestamp requests and replies. 1857 */ 1858 if (ti->ti_flags & TH_SYN) { 1859 tp->t_flags |= TF_RCVD_TSTMP; 1860 tp->ts_recent = to->to_tsval; 1861 tp->ts_recent_age = tcp_now; 1862 } 1863 break; 1864 case TCPOPT_CC: 1865 if (optlen != TCPOLEN_CC) 1866 continue; 1867 to->to_flag |= TOF_CC; 1868 bcopy((char *)cp + 2, 1869 (char *)&to->to_cc, sizeof(to->to_cc)); 1870 NTOHL(to->to_cc); 1871 /* 1872 * A CC or CC.new option received in a SYN makes 1873 * it ok to send CC in subsequent segments. 1874 */ 1875 if (ti->ti_flags & TH_SYN) 1876 tp->t_flags |= TF_RCVD_CC; 1877 break; 1878 case TCPOPT_CCNEW: 1879 if (optlen != TCPOLEN_CC) 1880 continue; 1881 if (!(ti->ti_flags & TH_SYN)) 1882 continue; 1883 to->to_flag |= TOF_CCNEW; 1884 bcopy((char *)cp + 2, 1885 (char *)&to->to_cc, sizeof(to->to_cc)); 1886 NTOHL(to->to_cc); 1887 /* 1888 * A CC or CC.new option received in a SYN makes 1889 * it ok to send CC in subsequent segments. 1890 */ 1891 tp->t_flags |= TF_RCVD_CC; 1892 break; 1893 case TCPOPT_CCECHO: 1894 if (optlen != TCPOLEN_CC) 1895 continue; 1896 if (!(ti->ti_flags & TH_SYN)) 1897 continue; 1898 to->to_flag |= TOF_CCECHO; 1899 bcopy((char *)cp + 2, 1900 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 1901 NTOHL(to->to_ccecho); 1902 break; 1903 } 1904 } 1905 if (ti->ti_flags & TH_SYN) 1906 tcp_mss(tp, mss); /* sets t_maxseg */ 1907 } 1908 1909 /* 1910 * Pull out of band byte out of a segment so 1911 * it doesn't appear in the user's data queue. 1912 * It is still reflected in the segment length for 1913 * sequencing purposes. 1914 */ 1915 static void 1916 tcp_pulloutofband(so, ti, m) 1917 struct socket *so; 1918 struct tcpiphdr *ti; 1919 register struct mbuf *m; 1920 { 1921 int cnt = ti->ti_urp - 1; 1922 1923 while (cnt >= 0) { 1924 if (m->m_len > cnt) { 1925 char *cp = mtod(m, caddr_t) + cnt; 1926 struct tcpcb *tp = sototcpcb(so); 1927 1928 tp->t_iobc = *cp; 1929 tp->t_oobflags |= TCPOOB_HAVEDATA; 1930 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1931 m->m_len--; 1932 return; 1933 } 1934 cnt -= m->m_len; 1935 m = m->m_next; 1936 if (m == 0) 1937 break; 1938 } 1939 panic("tcp_pulloutofband"); 1940 } 1941 1942 /* 1943 * Collect new round-trip time estimate 1944 * and update averages and current timeout. 1945 */ 1946 static void 1947 tcp_xmit_timer(tp, rtt) 1948 register struct tcpcb *tp; 1949 short rtt; 1950 { 1951 register int delta; 1952 1953 tcpstat.tcps_rttupdated++; 1954 tp->t_rttupdated++; 1955 if (tp->t_srtt != 0) { 1956 /* 1957 * srtt is stored as fixed point with 5 bits after the 1958 * binary point (i.e., scaled by 8). The following magic 1959 * is equivalent to the smoothing algorithm in rfc793 with 1960 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 1961 * point). Adjust rtt to origin 0. 1962 */ 1963 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 1964 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 1965 1966 if ((tp->t_srtt += delta) <= 0) 1967 tp->t_srtt = 1; 1968 1969 /* 1970 * We accumulate a smoothed rtt variance (actually, a 1971 * smoothed mean difference), then set the retransmit 1972 * timer to smoothed rtt + 4 times the smoothed variance. 1973 * rttvar is stored as fixed point with 4 bits after the 1974 * binary point (scaled by 16). The following is 1975 * equivalent to rfc793 smoothing with an alpha of .75 1976 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 1977 * rfc793's wired-in beta. 1978 */ 1979 if (delta < 0) 1980 delta = -delta; 1981 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 1982 if ((tp->t_rttvar += delta) <= 0) 1983 tp->t_rttvar = 1; 1984 } else { 1985 /* 1986 * No rtt measurement yet - use the unsmoothed rtt. 1987 * Set the variance to half the rtt (so our first 1988 * retransmit happens at 3*rtt). 1989 */ 1990 tp->t_srtt = rtt << TCP_RTT_SHIFT; 1991 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 1992 } 1993 tp->t_rtt = 0; 1994 tp->t_rxtshift = 0; 1995 1996 /* 1997 * the retransmit should happen at rtt + 4 * rttvar. 1998 * Because of the way we do the smoothing, srtt and rttvar 1999 * will each average +1/2 tick of bias. When we compute 2000 * the retransmit timer, we want 1/2 tick of rounding and 2001 * 1 extra tick because of +-1/2 tick uncertainty in the 2002 * firing of the timer. The bias will give us exactly the 2003 * 1.5 tick we need. But, because the bias is 2004 * statistical, we have to test that we don't drop below 2005 * the minimum feasible timer (which is 2 ticks). 2006 */ 2007 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2008 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2009 2010 /* 2011 * We received an ack for a packet that wasn't retransmitted; 2012 * it is probably safe to discard any error indications we've 2013 * received recently. This isn't quite right, but close enough 2014 * for now (a route might have failed after we sent a segment, 2015 * and the return path might not be symmetrical). 2016 */ 2017 tp->t_softerror = 0; 2018 } 2019 2020 /* 2021 * Determine a reasonable value for maxseg size. 2022 * If the route is known, check route for mtu. 2023 * If none, use an mss that can be handled on the outgoing 2024 * interface without forcing IP to fragment; if bigger than 2025 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2026 * to utilize large mbufs. If no route is found, route has no mtu, 2027 * or the destination isn't local, use a default, hopefully conservative 2028 * size (usually 512 or the default IP max size, but no more than the mtu 2029 * of the interface), as we can't discover anything about intervening 2030 * gateways or networks. We also initialize the congestion/slow start 2031 * window to be a single segment if the destination isn't local. 2032 * While looking at the routing entry, we also initialize other path-dependent 2033 * parameters from pre-set or cached values in the routing entry. 2034 * 2035 * Also take into account the space needed for options that we 2036 * send regularly. Make maxseg shorter by that amount to assure 2037 * that we can send maxseg amount of data even when the options 2038 * are present. Store the upper limit of the length of options plus 2039 * data in maxopd. 2040 * 2041 * NOTE that this routine is only called when we process an incoming 2042 * segment, for outgoing segments only tcp_mssopt is called. 2043 * 2044 * In case of T/TCP, we call this routine during implicit connection 2045 * setup as well (offer = -1), to initialize maxseg from the cached 2046 * MSS of our peer. 2047 */ 2048 void 2049 tcp_mss(tp, offer) 2050 struct tcpcb *tp; 2051 int offer; 2052 { 2053 register struct rtentry *rt; 2054 struct ifnet *ifp; 2055 register int rtt, mss; 2056 u_long bufsize; 2057 struct inpcb *inp; 2058 struct socket *so; 2059 struct rmxp_tao *taop; 2060 int origoffer = offer; 2061 2062 inp = tp->t_inpcb; 2063 if ((rt = tcp_rtlookup(inp)) == NULL) { 2064 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2065 return; 2066 } 2067 ifp = rt->rt_ifp; 2068 so = inp->inp_socket; 2069 2070 taop = rmx_taop(rt->rt_rmx); 2071 /* 2072 * Offer == -1 means that we didn't receive SYN yet, 2073 * use cached value in that case; 2074 */ 2075 if (offer == -1) 2076 offer = taop->tao_mssopt; 2077 /* 2078 * Offer == 0 means that there was no MSS on the SYN segment, 2079 * in this case we use tcp_mssdflt. 2080 */ 2081 if (offer == 0) 2082 offer = tcp_mssdflt; 2083 else 2084 /* 2085 * Sanity check: make sure that maxopd will be large 2086 * enough to allow some data on segments even is the 2087 * all the option space is used (40bytes). Otherwise 2088 * funny things may happen in tcp_output. 2089 */ 2090 offer = max(offer, 64); 2091 taop->tao_mssopt = offer; 2092 2093 /* 2094 * While we're here, check if there's an initial rtt 2095 * or rttvar. Convert from the route-table units 2096 * to scaled multiples of the slow timeout timer. 2097 */ 2098 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2099 /* 2100 * XXX the lock bit for RTT indicates that the value 2101 * is also a minimum value; this is subject to time. 2102 */ 2103 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2104 tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ); 2105 tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 2106 tcpstat.tcps_usedrtt++; 2107 if (rt->rt_rmx.rmx_rttvar) { 2108 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2109 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 2110 tcpstat.tcps_usedrttvar++; 2111 } else { 2112 /* default variation is +- 1 rtt */ 2113 tp->t_rttvar = 2114 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2115 } 2116 TCPT_RANGESET(tp->t_rxtcur, 2117 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2118 tp->t_rttmin, TCPTV_REXMTMAX); 2119 } 2120 /* 2121 * if there's an mtu associated with the route, use it 2122 */ 2123 if (rt->rt_rmx.rmx_mtu) 2124 mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 2125 else 2126 { 2127 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 2128 if (!in_localaddr(inp->inp_faddr)) 2129 mss = min(mss, tcp_mssdflt); 2130 } 2131 mss = min(mss, offer); 2132 /* 2133 * maxopd stores the maximum length of data AND options 2134 * in a segment; maxseg is the amount of data in a normal 2135 * segment. We need to store this value (maxopd) apart 2136 * from maxseg, because now every segment carries options 2137 * and thus we normally have somewhat less data in segments. 2138 */ 2139 tp->t_maxopd = mss; 2140 2141 /* 2142 * In case of T/TCP, origoffer==-1 indicates, that no segments 2143 * were received yet. In this case we just guess, otherwise 2144 * we do the same as before T/TCP. 2145 */ 2146 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2147 (origoffer == -1 || 2148 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2149 mss -= TCPOLEN_TSTAMP_APPA; 2150 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2151 (origoffer == -1 || 2152 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2153 mss -= TCPOLEN_CC_APPA; 2154 2155 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2156 if (mss > MCLBYTES) 2157 mss &= ~(MCLBYTES-1); 2158 #else 2159 if (mss > MCLBYTES) 2160 mss = mss / MCLBYTES * MCLBYTES; 2161 #endif 2162 /* 2163 * If there's a pipesize, change the socket buffer 2164 * to that size. Make the socket buffers an integral 2165 * number of mss units; if the mss is larger than 2166 * the socket buffer, decrease the mss. 2167 */ 2168 #ifdef RTV_SPIPE 2169 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2170 #endif 2171 bufsize = so->so_snd.sb_hiwat; 2172 if (bufsize < mss) 2173 mss = bufsize; 2174 else { 2175 bufsize = roundup(bufsize, mss); 2176 if (bufsize > sb_max) 2177 bufsize = sb_max; 2178 (void)sbreserve(&so->so_snd, bufsize); 2179 } 2180 tp->t_maxseg = mss; 2181 2182 #ifdef RTV_RPIPE 2183 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2184 #endif 2185 bufsize = so->so_rcv.sb_hiwat; 2186 if (bufsize > mss) { 2187 bufsize = roundup(bufsize, mss); 2188 if (bufsize > sb_max) 2189 bufsize = sb_max; 2190 (void)sbreserve(&so->so_rcv, bufsize); 2191 } 2192 /* 2193 * Don't force slow-start on local network. 2194 * Make this depend on the sysctl variable below 2195 */ 2196 if (!no_local_slowstart || !in_localaddr(inp->inp_faddr)) 2197 tp->snd_cwnd = mss; 2198 2199 if (rt->rt_rmx.rmx_ssthresh) { 2200 /* 2201 * There's some sort of gateway or interface 2202 * buffer limit on the path. Use this to set 2203 * the slow start threshhold, but set the 2204 * threshold to no less than 2*mss. 2205 */ 2206 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2207 tcpstat.tcps_usedssthresh++; 2208 } 2209 } 2210 2211 /* 2212 * Determine the MSS option to send on an outgoing SYN. 2213 */ 2214 int 2215 tcp_mssopt(tp) 2216 struct tcpcb *tp; 2217 { 2218 struct rtentry *rt; 2219 2220 rt = tcp_rtlookup(tp->t_inpcb); 2221 if (rt == NULL) 2222 return tcp_mssdflt; 2223 2224 return rt->rt_ifp->if_mtu - sizeof(struct tcpiphdr); 2225 } 2226 #endif /* TUBA_INCLUDE */
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