tcp_input.c revision 1.52
1 /* $NetBSD: tcp_input.c,v 1.52 1998/04/28 21:52:16 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation 9 * Facility, NASA Ames Research Center. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /* 41 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 42 * The Regents of the University of California. All rights reserved. 43 * 44 * Redistribution and use in source and binary forms, with or without 45 * modification, are permitted provided that the following conditions 46 * are met: 47 * 1. Redistributions of source code must retain the above copyright 48 * notice, this list of conditions and the following disclaimer. 49 * 2. Redistributions in binary form must reproduce the above copyright 50 * notice, this list of conditions and the following disclaimer in the 51 * documentation and/or other materials provided with the distribution. 52 * 3. All advertising materials mentioning features or use of this software 53 * must display the following acknowledgement: 54 * This product includes software developed by the University of 55 * California, Berkeley and its contributors. 56 * 4. Neither the name of the University nor the names of its contributors 57 * may be used to endorse or promote products derived from this software 58 * without specific prior written permission. 59 * 60 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 61 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 62 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 63 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 64 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 65 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 66 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 67 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 68 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 69 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 70 * SUCH DAMAGE. 71 * 72 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 73 */ 74 75 /* 76 * TODO list for SYN cache stuff: 77 * 78 * Find room for a "state" field, which is needed to keep a 79 * compressed state for TIME_WAIT TCBs. It's been noted already 80 * that this is fairly important for very high-volume web and 81 * mail servers, which use a large number of short-lived 82 * connections. 83 */ 84 85 #ifndef TUBA_INCLUDE 86 #include <sys/param.h> 87 #include <sys/systm.h> 88 #include <sys/malloc.h> 89 #include <sys/mbuf.h> 90 #include <sys/protosw.h> 91 #include <sys/socket.h> 92 #include <sys/socketvar.h> 93 #include <sys/errno.h> 94 #include <sys/syslog.h> 95 96 #include <net/if.h> 97 #include <net/route.h> 98 99 #include <netinet/in.h> 100 #include <netinet/in_systm.h> 101 #include <netinet/ip.h> 102 #include <netinet/in_pcb.h> 103 #include <netinet/ip_var.h> 104 #include <netinet/tcp.h> 105 #include <netinet/tcp_fsm.h> 106 #include <netinet/tcp_seq.h> 107 #include <netinet/tcp_timer.h> 108 #include <netinet/tcp_var.h> 109 #include <netinet/tcpip.h> 110 #include <netinet/tcp_debug.h> 111 112 #include <machine/stdarg.h> 113 114 int tcprexmtthresh = 3; 115 struct tcpiphdr tcp_saveti; 116 117 extern u_long sb_max; 118 119 #endif /* TUBA_INCLUDE */ 120 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) 121 122 /* for modulo comparisons of timestamps */ 123 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) 124 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) 125 126 /* 127 * Macro to compute ACK transmission behavior. Delay the ACK unless 128 * we have already delayed an ACK (must send an ACK every two segments). 129 */ 130 #define TCP_SETUP_ACK(tp, ti) \ 131 do { \ 132 if ((tp)->t_flags & TF_DELACK) \ 133 tp->t_flags |= TF_ACKNOW; \ 134 else \ 135 TCP_SET_DELACK(tp); \ 136 } while (0) 137 138 /* 139 * Insert segment ti into reassembly queue of tcp with 140 * control block tp. Return TH_FIN if reassembly now includes 141 * a segment with FIN. The macro form does the common case inline 142 * (segment is the next to be received on an established connection, 143 * and the queue is empty), avoiding linkage into and removal 144 * from the queue and repetition of various conversions. 145 * Set DELACK for segments received in order, but ack immediately 146 * when segments are out of order (so fast retransmit can work). 147 */ 148 #define TCP_REASS(tp, ti, m, so, flags) { \ 149 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 150 (tp)->segq.lh_first == NULL && \ 151 (tp)->t_state == TCPS_ESTABLISHED) { \ 152 TCP_SETUP_ACK(tp, ti); \ 153 (tp)->rcv_nxt += (ti)->ti_len; \ 154 flags = (ti)->ti_flags & TH_FIN; \ 155 tcpstat.tcps_rcvpack++;\ 156 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 157 sbappend(&(so)->so_rcv, (m)); \ 158 sorwakeup(so); \ 159 } else { \ 160 (flags) = tcp_reass((tp), (ti), (m)); \ 161 tp->t_flags |= TF_ACKNOW; \ 162 } \ 163 } 164 #ifndef TUBA_INCLUDE 165 166 int 167 tcp_reass(tp, ti, m) 168 register struct tcpcb *tp; 169 register struct tcpiphdr *ti; 170 struct mbuf *m; 171 { 172 register struct ipqent *p, *q, *nq, *tiqe; 173 struct socket *so = tp->t_inpcb->inp_socket; 174 int flags; 175 176 /* 177 * Call with ti==0 after become established to 178 * force pre-ESTABLISHED data up to user socket. 179 */ 180 if (ti == 0) 181 goto present; 182 183 /* 184 * Allocate a new queue entry, before we throw away any data. 185 * If we can't, just drop the packet. XXX 186 */ 187 MALLOC(tiqe, struct ipqent *, sizeof (struct ipqent), M_IPQ, M_NOWAIT); 188 if (tiqe == NULL) { 189 tcpstat.tcps_rcvmemdrop++; 190 m_freem(m); 191 return (0); 192 } 193 194 /* 195 * Find a segment which begins after this one does. 196 */ 197 for (p = NULL, q = tp->segq.lh_first; q != NULL; 198 p = q, q = q->ipqe_q.le_next) 199 if (SEQ_GT(q->ipqe_tcp->ti_seq, ti->ti_seq)) 200 break; 201 202 /* 203 * If there is a preceding segment, it may provide some of 204 * our data already. If so, drop the data from the incoming 205 * segment. If it provides all of our data, drop us. 206 */ 207 if (p != NULL) { 208 register struct tcpiphdr *phdr = p->ipqe_tcp; 209 register int i; 210 211 /* conversion to int (in i) handles seq wraparound */ 212 i = phdr->ti_seq + phdr->ti_len - ti->ti_seq; 213 if (i > 0) { 214 if (i >= ti->ti_len) { 215 tcpstat.tcps_rcvduppack++; 216 tcpstat.tcps_rcvdupbyte += ti->ti_len; 217 m_freem(m); 218 FREE(tiqe, M_IPQ); 219 return (0); 220 } 221 m_adj(m, i); 222 ti->ti_len -= i; 223 ti->ti_seq += i; 224 } 225 } 226 tcpstat.tcps_rcvoopack++; 227 tcpstat.tcps_rcvoobyte += ti->ti_len; 228 229 /* 230 * While we overlap succeeding segments trim them or, 231 * if they are completely covered, dequeue them. 232 */ 233 for (; q != NULL; q = nq) { 234 register struct tcpiphdr *qhdr = q->ipqe_tcp; 235 register int i = (ti->ti_seq + ti->ti_len) - qhdr->ti_seq; 236 237 if (i <= 0) 238 break; 239 if (i < qhdr->ti_len) { 240 qhdr->ti_seq += i; 241 qhdr->ti_len -= i; 242 m_adj(q->ipqe_m, i); 243 break; 244 } 245 nq = q->ipqe_q.le_next; 246 m_freem(q->ipqe_m); 247 LIST_REMOVE(q, ipqe_q); 248 FREE(q, M_IPQ); 249 } 250 251 /* Insert the new fragment queue entry into place. */ 252 tiqe->ipqe_m = m; 253 tiqe->ipqe_tcp = ti; 254 if (p == NULL) { 255 LIST_INSERT_HEAD(&tp->segq, tiqe, ipqe_q); 256 } else { 257 LIST_INSERT_AFTER(p, tiqe, ipqe_q); 258 } 259 260 present: 261 /* 262 * Present data to user, advancing rcv_nxt through 263 * completed sequence space. 264 */ 265 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 266 return (0); 267 q = tp->segq.lh_first; 268 if (q == NULL || q->ipqe_tcp->ti_seq != tp->rcv_nxt) 269 return (0); 270 if (tp->t_state == TCPS_SYN_RECEIVED && q->ipqe_tcp->ti_len) 271 return (0); 272 do { 273 tp->rcv_nxt += q->ipqe_tcp->ti_len; 274 flags = q->ipqe_tcp->ti_flags & TH_FIN; 275 276 nq = q->ipqe_q.le_next; 277 LIST_REMOVE(q, ipqe_q); 278 if (so->so_state & SS_CANTRCVMORE) 279 m_freem(q->ipqe_m); 280 else 281 sbappend(&so->so_rcv, q->ipqe_m); 282 FREE(q, M_IPQ); 283 q = nq; 284 } while (q != NULL && q->ipqe_tcp->ti_seq == tp->rcv_nxt); 285 sorwakeup(so); 286 return (flags); 287 } 288 289 /* 290 * TCP input routine, follows pages 65-76 of the 291 * protocol specification dated September, 1981 very closely. 292 */ 293 void 294 #if __STDC__ 295 tcp_input(struct mbuf *m, ...) 296 #else 297 tcp_input(m, va_alist) 298 register struct mbuf *m; 299 #endif 300 { 301 register struct tcpiphdr *ti; 302 register struct inpcb *inp; 303 caddr_t optp = NULL; 304 int optlen = 0; 305 int len, tlen, off, hdroptlen; 306 register struct tcpcb *tp = 0; 307 register int tiflags; 308 struct socket *so = NULL; 309 int todrop, acked, ourfinisacked, needoutput = 0; 310 short ostate = 0; 311 int iss = 0; 312 u_long tiwin; 313 struct tcp_opt_info opti; 314 int iphlen; 315 va_list ap; 316 317 va_start(ap, m); 318 iphlen = va_arg(ap, int); 319 va_end(ap); 320 321 tcpstat.tcps_rcvtotal++; 322 323 opti.ts_present = 0; 324 opti.maxseg = 0; 325 326 /* 327 * Get IP and TCP header together in first mbuf. 328 * Note: IP leaves IP header in first mbuf. 329 */ 330 ti = mtod(m, struct tcpiphdr *); 331 if (iphlen > sizeof (struct ip)) 332 ip_stripoptions(m, (struct mbuf *)0); 333 if (m->m_len < sizeof (struct tcpiphdr)) { 334 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 335 tcpstat.tcps_rcvshort++; 336 return; 337 } 338 ti = mtod(m, struct tcpiphdr *); 339 } 340 341 /* 342 * Checksum extended TCP header and data. 343 */ 344 tlen = ((struct ip *)ti)->ip_len; 345 len = sizeof (struct ip) + tlen; 346 bzero(ti->ti_x1, sizeof ti->ti_x1); 347 ti->ti_len = (u_int16_t)tlen; 348 HTONS(ti->ti_len); 349 if ((ti->ti_sum = in_cksum(m, len)) != 0) { 350 tcpstat.tcps_rcvbadsum++; 351 goto drop; 352 } 353 #endif /* TUBA_INCLUDE */ 354 355 /* 356 * Check that TCP offset makes sense, 357 * pull out TCP options and adjust length. XXX 358 */ 359 off = ti->ti_off << 2; 360 if (off < sizeof (struct tcphdr) || off > tlen) { 361 tcpstat.tcps_rcvbadoff++; 362 goto drop; 363 } 364 tlen -= off; 365 ti->ti_len = tlen; 366 if (off > sizeof (struct tcphdr)) { 367 if (m->m_len < sizeof(struct ip) + off) { 368 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 369 tcpstat.tcps_rcvshort++; 370 return; 371 } 372 ti = mtod(m, struct tcpiphdr *); 373 } 374 optlen = off - sizeof (struct tcphdr); 375 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 376 /* 377 * Do quick retrieval of timestamp options ("options 378 * prediction?"). If timestamp is the only option and it's 379 * formatted as recommended in RFC 1323 appendix A, we 380 * quickly get the values now and not bother calling 381 * tcp_dooptions(), etc. 382 */ 383 if ((optlen == TCPOLEN_TSTAMP_APPA || 384 (optlen > TCPOLEN_TSTAMP_APPA && 385 optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && 386 *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) && 387 (ti->ti_flags & TH_SYN) == 0) { 388 opti.ts_present = 1; 389 opti.ts_val = ntohl(*(u_int32_t *)(optp + 4)); 390 opti.ts_ecr = ntohl(*(u_int32_t *)(optp + 8)); 391 optp = NULL; /* we've parsed the options */ 392 } 393 } 394 tiflags = ti->ti_flags; 395 396 /* 397 * Convert TCP protocol specific fields to host format. 398 */ 399 NTOHL(ti->ti_seq); 400 NTOHL(ti->ti_ack); 401 NTOHS(ti->ti_win); 402 NTOHS(ti->ti_urp); 403 404 /* 405 * Locate pcb for segment. 406 */ 407 findpcb: 408 inp = in_pcblookup_connect(&tcbtable, ti->ti_src, ti->ti_sport, 409 ti->ti_dst, ti->ti_dport); 410 if (inp == 0) { 411 ++tcpstat.tcps_pcbhashmiss; 412 inp = in_pcblookup_bind(&tcbtable, ti->ti_dst, ti->ti_dport); 413 if (inp == 0) { 414 ++tcpstat.tcps_noport; 415 goto dropwithreset; 416 } 417 } 418 419 /* 420 * If the state is CLOSED (i.e., TCB does not exist) then 421 * all data in the incoming segment is discarded. 422 * If the TCB exists but is in CLOSED state, it is embryonic, 423 * but should either do a listen or a connect soon. 424 */ 425 tp = intotcpcb(inp); 426 if (tp == 0) 427 goto dropwithreset; 428 if (tp->t_state == TCPS_CLOSED) 429 goto drop; 430 431 /* Unscale the window into a 32-bit value. */ 432 if ((tiflags & TH_SYN) == 0) 433 tiwin = ti->ti_win << tp->snd_scale; 434 else 435 tiwin = ti->ti_win; 436 437 so = inp->inp_socket; 438 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 439 if (so->so_options & SO_DEBUG) { 440 ostate = tp->t_state; 441 tcp_saveti = *ti; 442 } 443 if (so->so_options & SO_ACCEPTCONN) { 444 if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 445 if (tiflags & TH_RST) { 446 syn_cache_reset(ti); 447 } else if ((tiflags & (TH_ACK|TH_SYN)) == 448 (TH_ACK|TH_SYN)) { 449 /* 450 * Received a SYN,ACK. This should 451 * never happen while we are in 452 * LISTEN. Send an RST. 453 */ 454 goto badsyn; 455 } else if (tiflags & TH_ACK) { 456 so = syn_cache_get(so, m); 457 if (so == NULL) { 458 /* 459 * We don't have a SYN for 460 * this ACK; send an RST. 461 */ 462 goto badsyn; 463 } else if (so == 464 (struct socket *)(-1)) { 465 /* 466 * We were unable to create 467 * the connection. If the 468 * 3-way handshake was 469 * completeed, and RST has 470 * been sent to the peer. 471 * Since the mbuf might be 472 * in use for the reply, 473 * do not free it. 474 */ 475 m = NULL; 476 } else { 477 /* 478 * We have created a 479 * full-blown connection. 480 */ 481 inp = sotoinpcb(so); 482 tp = intotcpcb(inp); 483 tiwin <<= tp->snd_scale; 484 goto after_listen; 485 } 486 } 487 } else { 488 /* 489 * Received a SYN. 490 */ 491 if (in_hosteq(ti->ti_src, ti->ti_dst) && 492 ti->ti_sport == ti->ti_dport) { 493 /* 494 * LISTEN socket received a SYN 495 * from itself? This can't possibly 496 * be valid; drop the packet. 497 */ 498 tcpstat.tcps_badsyn++; 499 goto drop; 500 } 501 /* 502 * SYN looks ok; create compressed TCP 503 * state for it. 504 */ 505 if (so->so_qlen <= so->so_qlimit && 506 syn_cache_add(so, m, optp, optlen, &opti)) 507 m = NULL; 508 } 509 goto drop; 510 } 511 } 512 513 after_listen: 514 #ifdef DIAGNOSTIC 515 /* 516 * Should not happen now that all embryonic connections 517 * are handled with compressed state. 518 */ 519 if (tp->t_state == TCPS_LISTEN) 520 panic("tcp_input: TCPS_LISTEN"); 521 #endif 522 523 /* 524 * Segment received on connection. 525 * Reset idle time and keep-alive timer. 526 */ 527 tp->t_idle = 0; 528 if (TCPS_HAVEESTABLISHED(tp->t_state)) 529 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 530 531 /* 532 * Process options. 533 */ 534 if (optp) 535 tcp_dooptions(tp, optp, optlen, ti, &opti); 536 537 /* 538 * Header prediction: check for the two common cases 539 * of a uni-directional data xfer. If the packet has 540 * no control flags, is in-sequence, the window didn't 541 * change and we're not retransmitting, it's a 542 * candidate. If the length is zero and the ack moved 543 * forward, we're the sender side of the xfer. Just 544 * free the data acked & wake any higher level process 545 * that was blocked waiting for space. If the length 546 * is non-zero and the ack didn't move, we're the 547 * receiver side. If we're getting packets in-order 548 * (the reassembly queue is empty), add the data to 549 * the socket buffer and note that we need a delayed ack. 550 */ 551 if (tp->t_state == TCPS_ESTABLISHED && 552 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 553 (!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) && 554 ti->ti_seq == tp->rcv_nxt && 555 tiwin && tiwin == tp->snd_wnd && 556 tp->snd_nxt == tp->snd_max) { 557 558 /* 559 * If last ACK falls within this segment's sequence numbers, 560 * record the timestamp. 561 */ 562 if (opti.ts_present && 563 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 564 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) { 565 tp->ts_recent_age = tcp_now; 566 tp->ts_recent = opti.ts_val; 567 } 568 569 if (ti->ti_len == 0) { 570 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 571 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 572 tp->snd_cwnd >= tp->snd_wnd && 573 tp->t_dupacks < tcprexmtthresh) { 574 /* 575 * this is a pure ack for outstanding data. 576 */ 577 ++tcpstat.tcps_predack; 578 if (opti.ts_present) 579 tcp_xmit_timer(tp, 580 tcp_now-opti.ts_ecr+1); 581 else if (tp->t_rtt && 582 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 583 tcp_xmit_timer(tp, tp->t_rtt); 584 acked = ti->ti_ack - tp->snd_una; 585 tcpstat.tcps_rcvackpack++; 586 tcpstat.tcps_rcvackbyte += acked; 587 sbdrop(&so->so_snd, acked); 588 tp->snd_una = ti->ti_ack; 589 m_freem(m); 590 591 /* 592 * If all outstanding data are acked, stop 593 * retransmit timer, otherwise restart timer 594 * using current (possibly backed-off) value. 595 * If process is waiting for space, 596 * wakeup/selwakeup/signal. If data 597 * are ready to send, let tcp_output 598 * decide between more output or persist. 599 */ 600 if (tp->snd_una == tp->snd_max) 601 tp->t_timer[TCPT_REXMT] = 0; 602 else if (tp->t_timer[TCPT_PERSIST] == 0) 603 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 604 605 if (sb_notify(&so->so_snd)) 606 sowwakeup(so); 607 if (so->so_snd.sb_cc) 608 (void) tcp_output(tp); 609 return; 610 } 611 } else if (ti->ti_ack == tp->snd_una && 612 tp->segq.lh_first == NULL && 613 ti->ti_len <= sbspace(&so->so_rcv)) { 614 /* 615 * this is a pure, in-sequence data packet 616 * with nothing on the reassembly queue and 617 * we have enough buffer space to take it. 618 */ 619 ++tcpstat.tcps_preddat; 620 tp->rcv_nxt += ti->ti_len; 621 tcpstat.tcps_rcvpack++; 622 tcpstat.tcps_rcvbyte += ti->ti_len; 623 /* 624 * Drop TCP, IP headers and TCP options then add data 625 * to socket buffer. 626 */ 627 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 628 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 629 sbappend(&so->so_rcv, m); 630 sorwakeup(so); 631 TCP_SETUP_ACK(tp, ti); 632 if (tp->t_flags & TF_ACKNOW) 633 (void) tcp_output(tp); 634 return; 635 } 636 } 637 638 /* 639 * Drop TCP, IP headers and TCP options. 640 */ 641 hdroptlen = sizeof(struct tcpiphdr) + off - sizeof(struct tcphdr); 642 m->m_data += hdroptlen; 643 m->m_len -= hdroptlen; 644 645 /* 646 * Calculate amount of space in receive window, 647 * and then do TCP input processing. 648 * Receive window is amount of space in rcv queue, 649 * but not less than advertised window. 650 */ 651 { int win; 652 653 win = sbspace(&so->so_rcv); 654 if (win < 0) 655 win = 0; 656 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 657 } 658 659 switch (tp->t_state) { 660 661 /* 662 * If the state is SYN_SENT: 663 * if seg contains an ACK, but not for our SYN, drop the input. 664 * if seg contains a RST, then drop the connection. 665 * if seg does not contain SYN, then drop it. 666 * Otherwise this is an acceptable SYN segment 667 * initialize tp->rcv_nxt and tp->irs 668 * if seg contains ack then advance tp->snd_una 669 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 670 * arrange for segment to be acked (eventually) 671 * continue processing rest of data/controls, beginning with URG 672 */ 673 case TCPS_SYN_SENT: 674 if ((tiflags & TH_ACK) && 675 (SEQ_LEQ(ti->ti_ack, tp->iss) || 676 SEQ_GT(ti->ti_ack, tp->snd_max))) 677 goto dropwithreset; 678 if (tiflags & TH_RST) { 679 if (tiflags & TH_ACK) 680 tp = tcp_drop(tp, ECONNREFUSED); 681 goto drop; 682 } 683 if ((tiflags & TH_SYN) == 0) 684 goto drop; 685 if (tiflags & TH_ACK) { 686 tp->snd_una = ti->ti_ack; 687 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 688 tp->snd_nxt = tp->snd_una; 689 } 690 tp->t_timer[TCPT_REXMT] = 0; 691 tp->irs = ti->ti_seq; 692 tcp_rcvseqinit(tp); 693 tp->t_flags |= TF_ACKNOW; 694 tcp_mss_from_peer(tp, opti.maxseg); 695 696 /* 697 * Initialize the initial congestion window. If we 698 * had to retransmit the SYN, we must initialize cwnd 699 * to 1 segment. 700 */ 701 tp->snd_cwnd = 702 TCP_INITIAL_WINDOW((tp->t_flags & TF_SYN_REXMT) ? 1 : 703 tcp_init_win, tp->t_peermss); 704 705 tcp_rmx_rtt(tp); 706 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 707 tcpstat.tcps_connects++; 708 soisconnected(so); 709 tcp_established(tp); 710 /* Do window scaling on this connection? */ 711 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 712 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 713 tp->snd_scale = tp->requested_s_scale; 714 tp->rcv_scale = tp->request_r_scale; 715 } 716 (void) tcp_reass(tp, (struct tcpiphdr *)0, 717 (struct mbuf *)0); 718 /* 719 * if we didn't have to retransmit the SYN, 720 * use its rtt as our initial srtt & rtt var. 721 */ 722 if (tp->t_rtt) 723 tcp_xmit_timer(tp, tp->t_rtt); 724 } else 725 tp->t_state = TCPS_SYN_RECEIVED; 726 727 /* 728 * Advance ti->ti_seq to correspond to first data byte. 729 * If data, trim to stay within window, 730 * dropping FIN if necessary. 731 */ 732 ti->ti_seq++; 733 if (ti->ti_len > tp->rcv_wnd) { 734 todrop = ti->ti_len - tp->rcv_wnd; 735 m_adj(m, -todrop); 736 ti->ti_len = tp->rcv_wnd; 737 tiflags &= ~TH_FIN; 738 tcpstat.tcps_rcvpackafterwin++; 739 tcpstat.tcps_rcvbyteafterwin += todrop; 740 } 741 tp->snd_wl1 = ti->ti_seq - 1; 742 tp->rcv_up = ti->ti_seq; 743 goto step6; 744 745 /* 746 * If the state is SYN_RECEIVED: 747 * If seg contains an ACK, but not for our SYN, drop the input 748 * and generate an RST. See page 36, rfc793 749 */ 750 case TCPS_SYN_RECEIVED: 751 if ((tiflags & TH_ACK) && 752 (SEQ_LEQ(ti->ti_ack, tp->iss) || 753 SEQ_GT(ti->ti_ack, tp->snd_max))) 754 goto dropwithreset; 755 break; 756 } 757 758 /* 759 * States other than LISTEN or SYN_SENT. 760 * First check timestamp, if present. 761 * Then check that at least some bytes of segment are within 762 * receive window. If segment begins before rcv_nxt, 763 * drop leading data (and SYN); if nothing left, just ack. 764 * 765 * RFC 1323 PAWS: If we have a timestamp reply on this segment 766 * and it's less than ts_recent, drop it. 767 */ 768 if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && 769 TSTMP_LT(opti.ts_val, tp->ts_recent)) { 770 771 /* Check to see if ts_recent is over 24 days old. */ 772 if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 773 /* 774 * Invalidate ts_recent. If this segment updates 775 * ts_recent, the age will be reset later and ts_recent 776 * will get a valid value. If it does not, setting 777 * ts_recent to zero will at least satisfy the 778 * requirement that zero be placed in the timestamp 779 * echo reply when ts_recent isn't valid. The 780 * age isn't reset until we get a valid ts_recent 781 * because we don't want out-of-order segments to be 782 * dropped when ts_recent is old. 783 */ 784 tp->ts_recent = 0; 785 } else { 786 tcpstat.tcps_rcvduppack++; 787 tcpstat.tcps_rcvdupbyte += ti->ti_len; 788 tcpstat.tcps_pawsdrop++; 789 goto dropafterack; 790 } 791 } 792 793 todrop = tp->rcv_nxt - ti->ti_seq; 794 if (todrop > 0) { 795 if (tiflags & TH_SYN) { 796 tiflags &= ~TH_SYN; 797 ti->ti_seq++; 798 if (ti->ti_urp > 1) 799 ti->ti_urp--; 800 else { 801 tiflags &= ~TH_URG; 802 ti->ti_urp = 0; 803 } 804 todrop--; 805 } 806 if (todrop > ti->ti_len || 807 (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) { 808 /* 809 * Any valid FIN must be to the left of the window. 810 * At this point the FIN must be a duplicate or 811 * out of sequence; drop it. 812 */ 813 tiflags &= ~TH_FIN; 814 /* 815 * Send an ACK to resynchronize and drop any data. 816 * But keep on processing for RST or ACK. 817 */ 818 tp->t_flags |= TF_ACKNOW; 819 todrop = ti->ti_len; 820 tcpstat.tcps_rcvdupbyte += todrop; 821 tcpstat.tcps_rcvduppack++; 822 } else { 823 tcpstat.tcps_rcvpartduppack++; 824 tcpstat.tcps_rcvpartdupbyte += todrop; 825 } 826 m_adj(m, todrop); 827 ti->ti_seq += todrop; 828 ti->ti_len -= todrop; 829 if (ti->ti_urp > todrop) 830 ti->ti_urp -= todrop; 831 else { 832 tiflags &= ~TH_URG; 833 ti->ti_urp = 0; 834 } 835 } 836 837 /* 838 * If new data are received on a connection after the 839 * user processes are gone, then RST the other end. 840 */ 841 if ((so->so_state & SS_NOFDREF) && 842 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 843 tp = tcp_close(tp); 844 tcpstat.tcps_rcvafterclose++; 845 goto dropwithreset; 846 } 847 848 /* 849 * If segment ends after window, drop trailing data 850 * (and PUSH and FIN); if nothing left, just ACK. 851 */ 852 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 853 if (todrop > 0) { 854 tcpstat.tcps_rcvpackafterwin++; 855 if (todrop >= ti->ti_len) { 856 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 857 /* 858 * If a new connection request is received 859 * while in TIME_WAIT, drop the old connection 860 * and start over if the sequence numbers 861 * are above the previous ones. 862 */ 863 if (tiflags & TH_SYN && 864 tp->t_state == TCPS_TIME_WAIT && 865 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 866 iss = tcp_new_iss(tp, sizeof(struct tcpcb), 867 tp->rcv_nxt); 868 tp = tcp_close(tp); 869 /* 870 * We have already advanced the mbuf 871 * pointers past the IP+TCP headers and 872 * options. Restore those pointers before 873 * attempting to use the TCP header again. 874 */ 875 m->m_data -= hdroptlen; 876 m->m_len += hdroptlen; 877 goto findpcb; 878 } 879 /* 880 * If window is closed can only take segments at 881 * window edge, and have to drop data and PUSH from 882 * incoming segments. Continue processing, but 883 * remember to ack. Otherwise, drop segment 884 * and ack. 885 */ 886 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 887 tp->t_flags |= TF_ACKNOW; 888 tcpstat.tcps_rcvwinprobe++; 889 } else 890 goto dropafterack; 891 } else 892 tcpstat.tcps_rcvbyteafterwin += todrop; 893 m_adj(m, -todrop); 894 ti->ti_len -= todrop; 895 tiflags &= ~(TH_PUSH|TH_FIN); 896 } 897 898 /* 899 * If last ACK falls within this segment's sequence numbers, 900 * record its timestamp. 901 */ 902 if (opti.ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 903 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len + 904 ((tiflags & (TH_SYN|TH_FIN)) != 0))) { 905 tp->ts_recent_age = tcp_now; 906 tp->ts_recent = opti.ts_val; 907 } 908 909 /* 910 * If the RST bit is set examine the state: 911 * SYN_RECEIVED STATE: 912 * If passive open, return to LISTEN state. 913 * If active open, inform user that connection was refused. 914 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 915 * Inform user that connection was reset, and close tcb. 916 * CLOSING, LAST_ACK, TIME_WAIT STATES 917 * Close the tcb. 918 */ 919 if (tiflags&TH_RST) switch (tp->t_state) { 920 921 case TCPS_SYN_RECEIVED: 922 so->so_error = ECONNREFUSED; 923 goto close; 924 925 case TCPS_ESTABLISHED: 926 case TCPS_FIN_WAIT_1: 927 case TCPS_FIN_WAIT_2: 928 case TCPS_CLOSE_WAIT: 929 so->so_error = ECONNRESET; 930 close: 931 tp->t_state = TCPS_CLOSED; 932 tcpstat.tcps_drops++; 933 tp = tcp_close(tp); 934 goto drop; 935 936 case TCPS_CLOSING: 937 case TCPS_LAST_ACK: 938 case TCPS_TIME_WAIT: 939 tp = tcp_close(tp); 940 goto drop; 941 } 942 943 /* 944 * If a SYN is in the window, then this is an 945 * error and we send an RST and drop the connection. 946 */ 947 if (tiflags & TH_SYN) { 948 tp = tcp_drop(tp, ECONNRESET); 949 goto dropwithreset; 950 } 951 952 /* 953 * If the ACK bit is off we drop the segment and return. 954 */ 955 if ((tiflags & TH_ACK) == 0) 956 goto drop; 957 958 /* 959 * Ack processing. 960 */ 961 switch (tp->t_state) { 962 963 /* 964 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 965 * ESTABLISHED state and continue processing, otherwise 966 * send an RST. 967 */ 968 case TCPS_SYN_RECEIVED: 969 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 970 SEQ_GT(ti->ti_ack, tp->snd_max)) 971 goto dropwithreset; 972 tcpstat.tcps_connects++; 973 soisconnected(so); 974 tcp_established(tp); 975 /* Do window scaling? */ 976 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 977 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 978 tp->snd_scale = tp->requested_s_scale; 979 tp->rcv_scale = tp->request_r_scale; 980 } 981 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); 982 tp->snd_wl1 = ti->ti_seq - 1; 983 /* fall into ... */ 984 985 /* 986 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 987 * ACKs. If the ack is in the range 988 * tp->snd_una < ti->ti_ack <= tp->snd_max 989 * then advance tp->snd_una to ti->ti_ack and drop 990 * data from the retransmission queue. If this ACK reflects 991 * more up to date window information we update our window information. 992 */ 993 case TCPS_ESTABLISHED: 994 case TCPS_FIN_WAIT_1: 995 case TCPS_FIN_WAIT_2: 996 case TCPS_CLOSE_WAIT: 997 case TCPS_CLOSING: 998 case TCPS_LAST_ACK: 999 case TCPS_TIME_WAIT: 1000 1001 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 1002 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 1003 tcpstat.tcps_rcvdupack++; 1004 /* 1005 * If we have outstanding data (other than 1006 * a window probe), this is a completely 1007 * duplicate ack (ie, window info didn't 1008 * change), the ack is the biggest we've 1009 * seen and we've seen exactly our rexmt 1010 * threshhold of them, assume a packet 1011 * has been dropped and retransmit it. 1012 * Kludge snd_nxt & the congestion 1013 * window so we send only this one 1014 * packet. 1015 * 1016 * We know we're losing at the current 1017 * window size so do congestion avoidance 1018 * (set ssthresh to half the current window 1019 * and pull our congestion window back to 1020 * the new ssthresh). 1021 * 1022 * Dup acks mean that packets have left the 1023 * network (they're now cached at the receiver) 1024 * so bump cwnd by the amount in the receiver 1025 * to keep a constant cwnd packets in the 1026 * network. 1027 */ 1028 if (tp->t_timer[TCPT_REXMT] == 0 || 1029 ti->ti_ack != tp->snd_una) 1030 tp->t_dupacks = 0; 1031 else if (++tp->t_dupacks == tcprexmtthresh) { 1032 tcp_seq onxt = tp->snd_nxt; 1033 u_int win = 1034 min(tp->snd_wnd, tp->snd_cwnd) / 1035 2 / tp->t_segsz; 1036 1037 if (win < 2) 1038 win = 2; 1039 tp->snd_ssthresh = win * tp->t_segsz; 1040 tp->t_timer[TCPT_REXMT] = 0; 1041 tp->t_rtt = 0; 1042 tp->snd_nxt = ti->ti_ack; 1043 tp->snd_cwnd = tp->t_segsz; 1044 (void) tcp_output(tp); 1045 tp->snd_cwnd = tp->snd_ssthresh + 1046 tp->t_segsz * tp->t_dupacks; 1047 if (SEQ_GT(onxt, tp->snd_nxt)) 1048 tp->snd_nxt = onxt; 1049 goto drop; 1050 } else if (tp->t_dupacks > tcprexmtthresh) { 1051 tp->snd_cwnd += tp->t_segsz; 1052 (void) tcp_output(tp); 1053 goto drop; 1054 } 1055 } else 1056 tp->t_dupacks = 0; 1057 break; 1058 } 1059 /* 1060 * If the congestion window was inflated to account 1061 * for the other side's cached packets, retract it. 1062 */ 1063 if (tp->t_dupacks >= tcprexmtthresh && 1064 tp->snd_cwnd > tp->snd_ssthresh) 1065 tp->snd_cwnd = tp->snd_ssthresh; 1066 tp->t_dupacks = 0; 1067 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 1068 tcpstat.tcps_rcvacktoomuch++; 1069 goto dropafterack; 1070 } 1071 acked = ti->ti_ack - tp->snd_una; 1072 tcpstat.tcps_rcvackpack++; 1073 tcpstat.tcps_rcvackbyte += acked; 1074 1075 /* 1076 * If we have a timestamp reply, update smoothed 1077 * round trip time. If no timestamp is present but 1078 * transmit timer is running and timed sequence 1079 * number was acked, update smoothed round trip time. 1080 * Since we now have an rtt measurement, cancel the 1081 * timer backoff (cf., Phil Karn's retransmit alg.). 1082 * Recompute the initial retransmit timer. 1083 */ 1084 if (opti.ts_present) 1085 tcp_xmit_timer(tp, tcp_now - opti.ts_ecr + 1); 1086 else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 1087 tcp_xmit_timer(tp,tp->t_rtt); 1088 1089 /* 1090 * If all outstanding data is acked, stop retransmit 1091 * timer and remember to restart (more output or persist). 1092 * If there is more data to be acked, restart retransmit 1093 * timer, using current (possibly backed-off) value. 1094 */ 1095 if (ti->ti_ack == tp->snd_max) { 1096 tp->t_timer[TCPT_REXMT] = 0; 1097 needoutput = 1; 1098 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1099 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1100 /* 1101 * When new data is acked, open the congestion window. 1102 * If the window gives us less than ssthresh packets 1103 * in flight, open exponentially (segsz per packet). 1104 * Otherwise open linearly: segsz per window 1105 * (segsz^2 / cwnd per packet), plus a constant 1106 * fraction of a packet (segsz/8) to help larger windows 1107 * open quickly enough. 1108 */ 1109 { 1110 register u_int cw = tp->snd_cwnd; 1111 register u_int incr = tp->t_segsz; 1112 1113 if (cw > tp->snd_ssthresh) 1114 incr = incr * incr / cw; 1115 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1116 } 1117 if (acked > so->so_snd.sb_cc) { 1118 tp->snd_wnd -= so->so_snd.sb_cc; 1119 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1120 ourfinisacked = 1; 1121 } else { 1122 sbdrop(&so->so_snd, acked); 1123 tp->snd_wnd -= acked; 1124 ourfinisacked = 0; 1125 } 1126 if (sb_notify(&so->so_snd)) 1127 sowwakeup(so); 1128 tp->snd_una = ti->ti_ack; 1129 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1130 tp->snd_nxt = tp->snd_una; 1131 1132 switch (tp->t_state) { 1133 1134 /* 1135 * In FIN_WAIT_1 STATE in addition to the processing 1136 * for the ESTABLISHED state if our FIN is now acknowledged 1137 * then enter FIN_WAIT_2. 1138 */ 1139 case TCPS_FIN_WAIT_1: 1140 if (ourfinisacked) { 1141 /* 1142 * If we can't receive any more 1143 * data, then closing user can proceed. 1144 * Starting the timer is contrary to the 1145 * specification, but if we don't get a FIN 1146 * we'll hang forever. 1147 */ 1148 if (so->so_state & SS_CANTRCVMORE) { 1149 soisdisconnected(so); 1150 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 1151 } 1152 tp->t_state = TCPS_FIN_WAIT_2; 1153 } 1154 break; 1155 1156 /* 1157 * In CLOSING STATE in addition to the processing for 1158 * the ESTABLISHED state if the ACK acknowledges our FIN 1159 * then enter the TIME-WAIT state, otherwise ignore 1160 * the segment. 1161 */ 1162 case TCPS_CLOSING: 1163 if (ourfinisacked) { 1164 tp->t_state = TCPS_TIME_WAIT; 1165 tcp_canceltimers(tp); 1166 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1167 soisdisconnected(so); 1168 } 1169 break; 1170 1171 /* 1172 * In LAST_ACK, we may still be waiting for data to drain 1173 * and/or to be acked, as well as for the ack of our FIN. 1174 * If our FIN is now acknowledged, delete the TCB, 1175 * enter the closed state and return. 1176 */ 1177 case TCPS_LAST_ACK: 1178 if (ourfinisacked) { 1179 tp = tcp_close(tp); 1180 goto drop; 1181 } 1182 break; 1183 1184 /* 1185 * In TIME_WAIT state the only thing that should arrive 1186 * is a retransmission of the remote FIN. Acknowledge 1187 * it and restart the finack timer. 1188 */ 1189 case TCPS_TIME_WAIT: 1190 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1191 goto dropafterack; 1192 } 1193 } 1194 1195 step6: 1196 /* 1197 * Update window information. 1198 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1199 */ 1200 if (((tiflags & TH_ACK) && SEQ_LT(tp->snd_wl1, ti->ti_seq)) || 1201 (tp->snd_wl1 == ti->ti_seq && SEQ_LT(tp->snd_wl2, ti->ti_ack)) || 1202 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd)) { 1203 /* keep track of pure window updates */ 1204 if (ti->ti_len == 0 && 1205 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1206 tcpstat.tcps_rcvwinupd++; 1207 tp->snd_wnd = tiwin; 1208 tp->snd_wl1 = ti->ti_seq; 1209 tp->snd_wl2 = ti->ti_ack; 1210 if (tp->snd_wnd > tp->max_sndwnd) 1211 tp->max_sndwnd = tp->snd_wnd; 1212 needoutput = 1; 1213 } 1214 1215 /* 1216 * Process segments with URG. 1217 */ 1218 if ((tiflags & TH_URG) && ti->ti_urp && 1219 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1220 /* 1221 * This is a kludge, but if we receive and accept 1222 * random urgent pointers, we'll crash in 1223 * soreceive. It's hard to imagine someone 1224 * actually wanting to send this much urgent data. 1225 */ 1226 if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { 1227 ti->ti_urp = 0; /* XXX */ 1228 tiflags &= ~TH_URG; /* XXX */ 1229 goto dodata; /* XXX */ 1230 } 1231 /* 1232 * If this segment advances the known urgent pointer, 1233 * then mark the data stream. This should not happen 1234 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1235 * a FIN has been received from the remote side. 1236 * In these states we ignore the URG. 1237 * 1238 * According to RFC961 (Assigned Protocols), 1239 * the urgent pointer points to the last octet 1240 * of urgent data. We continue, however, 1241 * to consider it to indicate the first octet 1242 * of data past the urgent section as the original 1243 * spec states (in one of two places). 1244 */ 1245 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1246 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1247 so->so_oobmark = so->so_rcv.sb_cc + 1248 (tp->rcv_up - tp->rcv_nxt) - 1; 1249 if (so->so_oobmark == 0) 1250 so->so_state |= SS_RCVATMARK; 1251 sohasoutofband(so); 1252 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1253 } 1254 /* 1255 * Remove out of band data so doesn't get presented to user. 1256 * This can happen independent of advancing the URG pointer, 1257 * but if two URG's are pending at once, some out-of-band 1258 * data may creep in... ick. 1259 */ 1260 if (ti->ti_urp <= (u_int16_t) ti->ti_len 1261 #ifdef SO_OOBINLINE 1262 && (so->so_options & SO_OOBINLINE) == 0 1263 #endif 1264 ) 1265 tcp_pulloutofband(so, ti, m); 1266 } else 1267 /* 1268 * If no out of band data is expected, 1269 * pull receive urgent pointer along 1270 * with the receive window. 1271 */ 1272 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1273 tp->rcv_up = tp->rcv_nxt; 1274 dodata: /* XXX */ 1275 1276 /* 1277 * Process the segment text, merging it into the TCP sequencing queue, 1278 * and arranging for acknowledgment of receipt if necessary. 1279 * This process logically involves adjusting tp->rcv_wnd as data 1280 * is presented to the user (this happens in tcp_usrreq.c, 1281 * case PRU_RCVD). If a FIN has already been received on this 1282 * connection then we just ignore the text. 1283 */ 1284 if ((ti->ti_len || (tiflags & TH_FIN)) && 1285 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1286 TCP_REASS(tp, ti, m, so, tiflags); 1287 /* 1288 * Note the amount of data that peer has sent into 1289 * our window, in order to estimate the sender's 1290 * buffer size. 1291 */ 1292 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1293 } else { 1294 m_freem(m); 1295 tiflags &= ~TH_FIN; 1296 } 1297 1298 /* 1299 * If FIN is received ACK the FIN and let the user know 1300 * that the connection is closing. Ignore a FIN received before 1301 * the connection is fully established. 1302 */ 1303 if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) { 1304 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1305 socantrcvmore(so); 1306 tp->t_flags |= TF_ACKNOW; 1307 tp->rcv_nxt++; 1308 } 1309 switch (tp->t_state) { 1310 1311 /* 1312 * In ESTABLISHED STATE enter the CLOSE_WAIT state. 1313 */ 1314 case TCPS_ESTABLISHED: 1315 tp->t_state = TCPS_CLOSE_WAIT; 1316 break; 1317 1318 /* 1319 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1320 * enter the CLOSING state. 1321 */ 1322 case TCPS_FIN_WAIT_1: 1323 tp->t_state = TCPS_CLOSING; 1324 break; 1325 1326 /* 1327 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1328 * starting the time-wait timer, turning off the other 1329 * standard timers. 1330 */ 1331 case TCPS_FIN_WAIT_2: 1332 tp->t_state = TCPS_TIME_WAIT; 1333 tcp_canceltimers(tp); 1334 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1335 soisdisconnected(so); 1336 break; 1337 1338 /* 1339 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1340 */ 1341 case TCPS_TIME_WAIT: 1342 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1343 break; 1344 } 1345 } 1346 if (so->so_options & SO_DEBUG) 1347 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1348 1349 /* 1350 * Return any desired output. 1351 */ 1352 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1353 (void) tcp_output(tp); 1354 return; 1355 1356 badsyn: 1357 /* 1358 * Received a bad SYN. Increment counters and dropwithreset. 1359 */ 1360 tcpstat.tcps_badsyn++; 1361 tp = NULL; 1362 goto dropwithreset; 1363 1364 dropafterack: 1365 /* 1366 * Generate an ACK dropping incoming segment if it occupies 1367 * sequence space, where the ACK reflects our state. 1368 */ 1369 if (tiflags & TH_RST) 1370 goto drop; 1371 m_freem(m); 1372 tp->t_flags |= TF_ACKNOW; 1373 (void) tcp_output(tp); 1374 return; 1375 1376 dropwithreset: 1377 /* 1378 * Generate a RST, dropping incoming segment. 1379 * Make ACK acceptable to originator of segment. 1380 * Don't bother to respond if destination was broadcast/multicast. 1381 */ 1382 if ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) || 1383 IN_MULTICAST(ti->ti_dst.s_addr)) 1384 goto drop; 1385 if (tiflags & TH_ACK) 1386 (void)tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1387 else { 1388 if (tiflags & TH_SYN) 1389 ti->ti_len++; 1390 (void)tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1391 TH_RST|TH_ACK); 1392 } 1393 return; 1394 1395 drop: 1396 /* 1397 * Drop space held by incoming segment and return. 1398 */ 1399 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1400 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1401 m_freem(m); 1402 return; 1403 #ifndef TUBA_INCLUDE 1404 } 1405 1406 void 1407 tcp_dooptions(tp, cp, cnt, ti, oi) 1408 struct tcpcb *tp; 1409 u_char *cp; 1410 int cnt; 1411 struct tcpiphdr *ti; 1412 struct tcp_opt_info *oi; 1413 { 1414 u_int16_t mss; 1415 int opt, optlen; 1416 1417 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1418 opt = cp[0]; 1419 if (opt == TCPOPT_EOL) 1420 break; 1421 if (opt == TCPOPT_NOP) 1422 optlen = 1; 1423 else { 1424 optlen = cp[1]; 1425 if (optlen <= 0) 1426 break; 1427 } 1428 switch (opt) { 1429 1430 default: 1431 continue; 1432 1433 case TCPOPT_MAXSEG: 1434 if (optlen != TCPOLEN_MAXSEG) 1435 continue; 1436 if (!(ti->ti_flags & TH_SYN)) 1437 continue; 1438 bcopy(cp + 2, &mss, sizeof(mss)); 1439 oi->maxseg = ntohs(mss); 1440 break; 1441 1442 case TCPOPT_WINDOW: 1443 if (optlen != TCPOLEN_WINDOW) 1444 continue; 1445 if (!(ti->ti_flags & TH_SYN)) 1446 continue; 1447 tp->t_flags |= TF_RCVD_SCALE; 1448 tp->requested_s_scale = cp[2]; 1449 if (tp->requested_s_scale > TCP_MAX_WINSHIFT) { 1450 log(LOG_ERR, "TCP: invalid wscale %d from " 1451 "0x%08x, assuming %d\n", 1452 tp->requested_s_scale, 1453 ntohl(ti->ti_src.s_addr), 1454 TCP_MAX_WINSHIFT); 1455 tp->requested_s_scale = TCP_MAX_WINSHIFT; 1456 } 1457 break; 1458 1459 case TCPOPT_TIMESTAMP: 1460 if (optlen != TCPOLEN_TIMESTAMP) 1461 continue; 1462 oi->ts_present = 1; 1463 bcopy(cp + 2, &oi->ts_val, sizeof(oi->ts_val)); 1464 NTOHL(oi->ts_val); 1465 bcopy(cp + 6, &oi->ts_ecr, sizeof(oi->ts_ecr)); 1466 NTOHL(oi->ts_ecr); 1467 1468 /* 1469 * A timestamp received in a SYN makes 1470 * it ok to send timestamp requests and replies. 1471 */ 1472 if (ti->ti_flags & TH_SYN) { 1473 tp->t_flags |= TF_RCVD_TSTMP; 1474 tp->ts_recent = oi->ts_val; 1475 tp->ts_recent_age = tcp_now; 1476 } 1477 break; 1478 } 1479 } 1480 } 1481 1482 /* 1483 * Pull out of band byte out of a segment so 1484 * it doesn't appear in the user's data queue. 1485 * It is still reflected in the segment length for 1486 * sequencing purposes. 1487 */ 1488 void 1489 tcp_pulloutofband(so, ti, m) 1490 struct socket *so; 1491 struct tcpiphdr *ti; 1492 register struct mbuf *m; 1493 { 1494 int cnt = ti->ti_urp - 1; 1495 1496 while (cnt >= 0) { 1497 if (m->m_len > cnt) { 1498 char *cp = mtod(m, caddr_t) + cnt; 1499 struct tcpcb *tp = sototcpcb(so); 1500 1501 tp->t_iobc = *cp; 1502 tp->t_oobflags |= TCPOOB_HAVEDATA; 1503 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1504 m->m_len--; 1505 return; 1506 } 1507 cnt -= m->m_len; 1508 m = m->m_next; 1509 if (m == 0) 1510 break; 1511 } 1512 panic("tcp_pulloutofband"); 1513 } 1514 1515 /* 1516 * Collect new round-trip time estimate 1517 * and update averages and current timeout. 1518 */ 1519 void 1520 tcp_xmit_timer(tp, rtt) 1521 register struct tcpcb *tp; 1522 short rtt; 1523 { 1524 register short delta; 1525 short rttmin; 1526 1527 tcpstat.tcps_rttupdated++; 1528 --rtt; 1529 if (tp->t_srtt != 0) { 1530 /* 1531 * srtt is stored as fixed point with 3 bits after the 1532 * binary point (i.e., scaled by 8). The following magic 1533 * is equivalent to the smoothing algorithm in rfc793 with 1534 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 1535 * point). Adjust rtt to origin 0. 1536 */ 1537 delta = (rtt << 2) - (tp->t_srtt >> TCP_RTT_SHIFT); 1538 if ((tp->t_srtt += delta) <= 0) 1539 tp->t_srtt = 1 << 2; 1540 /* 1541 * We accumulate a smoothed rtt variance (actually, a 1542 * smoothed mean difference), then set the retransmit 1543 * timer to smoothed rtt + 4 times the smoothed variance. 1544 * rttvar is stored as fixed point with 2 bits after the 1545 * binary point (scaled by 4). The following is 1546 * equivalent to rfc793 smoothing with an alpha of .75 1547 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 1548 * rfc793's wired-in beta. 1549 */ 1550 if (delta < 0) 1551 delta = -delta; 1552 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); 1553 if ((tp->t_rttvar += delta) <= 0) 1554 tp->t_rttvar = 1 << 2; 1555 } else { 1556 /* 1557 * No rtt measurement yet - use the unsmoothed rtt. 1558 * Set the variance to half the rtt (so our first 1559 * retransmit happens at 3*rtt). 1560 */ 1561 tp->t_srtt = rtt << (TCP_RTT_SHIFT + 2); 1562 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT + 2 - 1); 1563 } 1564 tp->t_rtt = 0; 1565 tp->t_rxtshift = 0; 1566 1567 /* 1568 * the retransmit should happen at rtt + 4 * rttvar. 1569 * Because of the way we do the smoothing, srtt and rttvar 1570 * will each average +1/2 tick of bias. When we compute 1571 * the retransmit timer, we want 1/2 tick of rounding and 1572 * 1 extra tick because of +-1/2 tick uncertainty in the 1573 * firing of the timer. The bias will give us exactly the 1574 * 1.5 tick we need. But, because the bias is 1575 * statistical, we have to test that we don't drop below 1576 * the minimum feasible timer (which is 2 ticks). 1577 */ 1578 if (tp->t_rttmin > rtt + 2) 1579 rttmin = tp->t_rttmin; 1580 else 1581 rttmin = rtt + 2; 1582 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rttmin, TCPTV_REXMTMAX); 1583 1584 /* 1585 * We received an ack for a packet that wasn't retransmitted; 1586 * it is probably safe to discard any error indications we've 1587 * received recently. This isn't quite right, but close enough 1588 * for now (a route might have failed after we sent a segment, 1589 * and the return path might not be symmetrical). 1590 */ 1591 tp->t_softerror = 0; 1592 } 1593 1594 /* 1595 * TCP compressed state engine. Currently used to hold compressed 1596 * state for SYN_RECEIVED. 1597 */ 1598 1599 u_long syn_cache_count; 1600 u_int32_t syn_hash1, syn_hash2; 1601 1602 #define SYN_HASH(sa, sp, dp) \ 1603 ((((sa)->s_addr^syn_hash1)*(((((u_int32_t)(dp))<<16) + \ 1604 ((u_int32_t)(sp)))^syn_hash2))) 1605 1606 #define eptosp(ep, e, s) ((struct s *)((char *)(ep) - \ 1607 ((char *)(&((struct s *)0)->e) - (char *)0))) 1608 1609 #define SYN_CACHE_RM(sc, p, scp) { \ 1610 *(p) = (sc)->sc_next; \ 1611 if ((sc)->sc_next) \ 1612 (sc)->sc_next->sc_timer += (sc)->sc_timer; \ 1613 else { \ 1614 (scp)->sch_timer_sum -= (sc)->sc_timer; \ 1615 if ((scp)->sch_timer_sum <= 0) \ 1616 (scp)->sch_timer_sum = -1; \ 1617 /* If need be, fix up the last pointer */ \ 1618 if ((scp)->sch_first) \ 1619 (scp)->sch_last = eptosp(p, sc_next, syn_cache); \ 1620 } \ 1621 (scp)->sch_length--; \ 1622 syn_cache_count--; \ 1623 } 1624 1625 void 1626 syn_cache_insert(sc, prevp, headp) 1627 struct syn_cache *sc; 1628 struct syn_cache ***prevp; 1629 struct syn_cache_head **headp; 1630 { 1631 struct syn_cache_head *scp, *scp2, *sce; 1632 struct syn_cache *sc2; 1633 static u_int timeo_val; 1634 int s; 1635 1636 /* Initialize the hash secrets when adding the first entry */ 1637 if (syn_cache_count == 0) { 1638 struct timeval tv; 1639 microtime(&tv); 1640 syn_hash1 = random() ^ (u_long)≻ 1641 syn_hash2 = random() ^ tv.tv_usec; 1642 } 1643 1644 sc->sc_hash = SYN_HASH(&sc->sc_src, sc->sc_sport, sc->sc_dport); 1645 sc->sc_next = NULL; 1646 scp = &tcp_syn_cache[sc->sc_hash % tcp_syn_cache_size]; 1647 *headp = scp; 1648 1649 /* 1650 * Make sure that we don't overflow the per-bucket 1651 * limit or the total cache size limit. 1652 */ 1653 s = splsoftnet(); 1654 if (scp->sch_length >= tcp_syn_bucket_limit) { 1655 tcpstat.tcps_sc_bucketoverflow++; 1656 sc2 = scp->sch_first; 1657 scp->sch_first = sc2->sc_next; 1658 if (sc2->sc_ipopts) 1659 (void) m_free(sc2->sc_ipopts); 1660 FREE(sc2, M_PCB); 1661 } else if (syn_cache_count >= tcp_syn_cache_limit) { 1662 tcpstat.tcps_sc_overflowed++; 1663 /* 1664 * The cache is full. Toss the first (i.e, oldest) 1665 * element in this bucket. 1666 */ 1667 scp2 = scp; 1668 if (scp2->sch_first == NULL) { 1669 sce = &tcp_syn_cache[tcp_syn_cache_size]; 1670 for (++scp2; scp2 != scp; scp2++) { 1671 if (scp2 >= sce) 1672 scp2 = &tcp_syn_cache[0]; 1673 if (scp2->sch_first) 1674 break; 1675 } 1676 } 1677 sc2 = scp2->sch_first; 1678 if (sc2 == NULL) { 1679 if (sc->sc_ipopts) 1680 (void) m_free(sc->sc_ipopts); 1681 FREE(sc, M_PCB); 1682 return; 1683 } 1684 if ((scp2->sch_first = sc2->sc_next) == NULL) 1685 scp2->sch_last = NULL; 1686 else 1687 sc2->sc_next->sc_timer += sc2->sc_timer; 1688 if (sc2->sc_ipopts) 1689 (void) m_free(sc2->sc_ipopts); 1690 FREE(sc2, M_PCB); 1691 } else { 1692 scp->sch_length++; 1693 syn_cache_count++; 1694 } 1695 tcpstat.tcps_sc_added++; 1696 1697 /* 1698 * Put it into the bucket. 1699 */ 1700 if (scp->sch_first == NULL) 1701 *prevp = &scp->sch_first; 1702 else { 1703 *prevp = &scp->sch_last->sc_next; 1704 tcpstat.tcps_sc_collisions++; 1705 } 1706 **prevp = sc; 1707 scp->sch_last = sc; 1708 1709 /* 1710 * If the timeout value has changed 1711 * 1) force it to fit in a u_char 1712 * 2) Run the timer routine to truncate all 1713 * existing entries to the new timeout value. 1714 */ 1715 if (timeo_val != tcp_syn_cache_timeo) { 1716 tcp_syn_cache_timeo = min(tcp_syn_cache_timeo, UCHAR_MAX); 1717 if (timeo_val > tcp_syn_cache_timeo) 1718 syn_cache_timer(timeo_val - tcp_syn_cache_timeo); 1719 timeo_val = tcp_syn_cache_timeo; 1720 } 1721 if (scp->sch_timer_sum > 0) 1722 sc->sc_timer = tcp_syn_cache_timeo - scp->sch_timer_sum; 1723 else { 1724 if (scp->sch_timer_sum == 0) { 1725 /* 1726 * When the bucket timer is 0, it is not in the 1727 * cache queue. 1728 */ 1729 scp->sch_headq = tcp_syn_cache_first; 1730 tcp_syn_cache_first = scp; 1731 } 1732 sc->sc_timer = tcp_syn_cache_timeo; 1733 } 1734 scp->sch_timer_sum = tcp_syn_cache_timeo; 1735 splx(s); 1736 } 1737 1738 /* 1739 * Walk down the cache list, decrementing the timer of 1740 * the first element on each entry. If the timer goes 1741 * to zero, remove it and all successive entries with 1742 * a zero timer. 1743 */ 1744 void 1745 syn_cache_timer(interval) 1746 int interval; 1747 { 1748 struct syn_cache_head *scp, **pscp; 1749 struct syn_cache *sc, *scn; 1750 int n, s; 1751 1752 pscp = &tcp_syn_cache_first; 1753 scp = tcp_syn_cache_first; 1754 s = splsoftnet(); 1755 while (scp) { 1756 /* 1757 * Remove any empty hash buckets 1758 * from the cache queue. 1759 */ 1760 if ((sc = scp->sch_first) == NULL) { 1761 *pscp = scp->sch_headq; 1762 scp->sch_headq = NULL; 1763 scp->sch_timer_sum = 0; 1764 scp->sch_first = scp->sch_last = NULL; 1765 scp->sch_length = 0; 1766 scp = *pscp; 1767 continue; 1768 } 1769 1770 scp->sch_timer_sum -= interval; 1771 if (scp->sch_timer_sum <= 0) 1772 scp->sch_timer_sum = -1; 1773 n = interval; 1774 while (sc->sc_timer <= n) { 1775 n -= sc->sc_timer; 1776 scn = sc->sc_next; 1777 tcpstat.tcps_sc_timed_out++; 1778 syn_cache_count--; 1779 if (sc->sc_ipopts) 1780 (void) m_free(sc->sc_ipopts); 1781 FREE(sc, M_PCB); 1782 scp->sch_length--; 1783 if ((sc = scn) == NULL) 1784 break; 1785 } 1786 if ((scp->sch_first = sc) != NULL) { 1787 sc->sc_timer -= n; 1788 pscp = &scp->sch_headq; 1789 scp = scp->sch_headq; 1790 } 1791 } 1792 splx(s); 1793 } 1794 1795 /* 1796 * Find an entry in the syn cache. 1797 */ 1798 struct syn_cache * 1799 syn_cache_lookup(ti, prevp, headp) 1800 struct tcpiphdr *ti; 1801 struct syn_cache ***prevp; 1802 struct syn_cache_head **headp; 1803 { 1804 struct syn_cache *sc, **prev; 1805 struct syn_cache_head *head; 1806 u_int32_t hash; 1807 int s; 1808 1809 hash = SYN_HASH(&ti->ti_src, ti->ti_sport, ti->ti_dport); 1810 1811 head = &tcp_syn_cache[hash % tcp_syn_cache_size]; 1812 *headp = head; 1813 prev = &head->sch_first; 1814 s = splsoftnet(); 1815 for (sc = head->sch_first; sc; prev = &sc->sc_next, sc = sc->sc_next) { 1816 if (sc->sc_hash != hash) 1817 continue; 1818 if (sc->sc_src.s_addr == ti->ti_src.s_addr && 1819 sc->sc_sport == ti->ti_sport && 1820 sc->sc_dport == ti->ti_dport && 1821 sc->sc_dst.s_addr == ti->ti_dst.s_addr) { 1822 *prevp = prev; 1823 splx(s); 1824 return (sc); 1825 } 1826 } 1827 splx(s); 1828 return (NULL); 1829 } 1830 1831 /* 1832 * This function gets called when we receive an ACK for a 1833 * socket in the LISTEN state. We look up the connection 1834 * in the syn cache, and if its there, we pull it out of 1835 * the cache and turn it into a full-blown connection in 1836 * the SYN-RECEIVED state. 1837 * 1838 * The return values may not be immediately obvious, and their effects 1839 * can be subtle, so here they are: 1840 * 1841 * NULL SYN was not found in cache; caller should drop the 1842 * packet and send an RST. 1843 * 1844 * -1 We were unable to create the new connection, and are 1845 * aborting it. An ACK,RST is being sent to the peer 1846 * (unless we got screwey sequence numbners; see below), 1847 * because the 3-way handshake has been completed. Caller 1848 * should not free the mbuf, since we may be using it. If 1849 * we are not, we will free it. 1850 * 1851 * Otherwise, the return value is a pointer to the new socket 1852 * associated with the connection. 1853 */ 1854 struct socket * 1855 syn_cache_get(so, m) 1856 struct socket *so; 1857 struct mbuf *m; 1858 { 1859 struct syn_cache *sc, **sc_prev; 1860 struct syn_cache_head *head; 1861 register struct inpcb *inp; 1862 register struct tcpcb *tp = 0; 1863 register struct tcpiphdr *ti; 1864 struct sockaddr_in *sin; 1865 struct mbuf *am; 1866 long win; 1867 int s; 1868 1869 ti = mtod(m, struct tcpiphdr *); 1870 s = splsoftnet(); 1871 if ((sc = syn_cache_lookup(ti, &sc_prev, &head)) == NULL) { 1872 splx(s); 1873 return (NULL); 1874 } 1875 1876 win = sbspace(&so->so_rcv); 1877 if (win > TCP_MAXWIN) 1878 win = TCP_MAXWIN; 1879 1880 /* 1881 * Verify the sequence and ack numbers. 1882 */ 1883 if ((ti->ti_ack != sc->sc_iss + 1) || 1884 SEQ_LEQ(ti->ti_seq, sc->sc_irs) || 1885 SEQ_GT(ti->ti_seq, sc->sc_irs + 1 + win)) { 1886 (void) syn_cache_respond(sc, m, ti, win, 0); 1887 splx(s); 1888 return ((struct socket *)(-1)); 1889 } 1890 1891 /* Remove this cache entry */ 1892 SYN_CACHE_RM(sc, sc_prev, head); 1893 splx(s); 1894 1895 /* 1896 * Ok, create the full blown connection, and set things up 1897 * as they would have been set up if we had created the 1898 * connection when the SYN arrived. If we can't create 1899 * the connection, abort it. 1900 */ 1901 so = sonewconn(so, SS_ISCONNECTED); 1902 if (so == NULL) 1903 goto resetandabort; 1904 1905 inp = sotoinpcb(so); 1906 inp->inp_laddr = sc->sc_dst; 1907 inp->inp_lport = sc->sc_dport; 1908 in_pcbstate(inp, INP_BOUND); 1909 inp->inp_options = ip_srcroute(); 1910 if (inp->inp_options == NULL) { 1911 inp->inp_options = sc->sc_ipopts; 1912 sc->sc_ipopts = NULL; 1913 } 1914 1915 am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ 1916 if (am == NULL) 1917 goto resetandabort; 1918 am->m_len = sizeof(struct sockaddr_in); 1919 sin = mtod(am, struct sockaddr_in *); 1920 sin->sin_family = AF_INET; 1921 sin->sin_len = sizeof(*sin); 1922 sin->sin_addr = sc->sc_src; 1923 sin->sin_port = sc->sc_sport; 1924 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 1925 if (in_pcbconnect(inp, am)) { 1926 (void) m_free(am); 1927 goto resetandabort; 1928 } 1929 (void) m_free(am); 1930 1931 tp = intotcpcb(inp); 1932 if (sc->sc_request_r_scale != 15) { 1933 tp->requested_s_scale = sc->sc_requested_s_scale; 1934 tp->request_r_scale = sc->sc_request_r_scale; 1935 tp->snd_scale = sc->sc_requested_s_scale; 1936 tp->rcv_scale = sc->sc_request_r_scale; 1937 tp->t_flags |= TF_RCVD_SCALE; 1938 } 1939 if (sc->sc_flags & SCF_TIMESTAMP) 1940 tp->t_flags |= TF_RCVD_TSTMP; 1941 1942 tp->t_template = tcp_template(tp); 1943 if (tp->t_template == 0) { 1944 tp = tcp_drop(tp, ENOBUFS); /* destroys socket */ 1945 so = NULL; 1946 m_freem(m); 1947 goto abort; 1948 } 1949 1950 tp->iss = sc->sc_iss; 1951 tp->irs = sc->sc_irs; 1952 tcp_sendseqinit(tp); 1953 tcp_rcvseqinit(tp); 1954 tp->t_state = TCPS_SYN_RECEIVED; 1955 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 1956 tcpstat.tcps_accepts++; 1957 1958 /* Initialize tp->t_ourmss before we deal with the peer's! */ 1959 tp->t_ourmss = sc->sc_ourmaxseg; 1960 tcp_mss_from_peer(tp, sc->sc_peermaxseg); 1961 1962 /* 1963 * Initialize the initial congestion window. If we 1964 * had to retransmit the SYN,ACK, we must initialize cwnd 1965 * to 1 segment. 1966 */ 1967 tp->snd_cwnd = 1968 TCP_INITIAL_WINDOW((sc->sc_flags & SCF_SYNACK_REXMT) ? 1 : 1969 tcp_init_win, tp->t_peermss); 1970 1971 tcp_rmx_rtt(tp); 1972 tp->snd_wl1 = sc->sc_irs; 1973 tp->rcv_up = sc->sc_irs + 1; 1974 1975 /* 1976 * This is what whould have happened in tcp_ouput() when 1977 * the SYN,ACK was sent. 1978 */ 1979 tp->snd_up = tp->snd_una; 1980 tp->snd_max = tp->snd_nxt = tp->iss+1; 1981 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1982 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 1983 tp->rcv_adv = tp->rcv_nxt + win; 1984 tp->last_ack_sent = tp->rcv_nxt; 1985 1986 tcpstat.tcps_sc_completed++; 1987 if (sc->sc_ipopts) 1988 (void) m_free(sc->sc_ipopts); 1989 FREE(sc, M_PCB); 1990 return (so); 1991 1992 resetandabort: 1993 (void) tcp_respond(NULL, ti, m, ti->ti_seq+ti->ti_len, 1994 (tcp_seq)0, TH_RST|TH_ACK); 1995 abort: 1996 if (so != NULL) 1997 (void) soabort(so); 1998 if (sc->sc_ipopts) 1999 (void) m_free(sc->sc_ipopts); 2000 FREE(sc, M_PCB); 2001 tcpstat.tcps_sc_aborted++; 2002 return ((struct socket *)(-1)); 2003 } 2004 2005 /* 2006 * This function is called when we get a RST for a 2007 * non-existant connection, so that we can see if the 2008 * connection is in the syn cache. If it is, zap it. 2009 */ 2010 2011 void 2012 syn_cache_reset(ti) 2013 register struct tcpiphdr *ti; 2014 { 2015 struct syn_cache *sc, **sc_prev; 2016 struct syn_cache_head *head; 2017 int s = splsoftnet(); 2018 2019 if ((sc = syn_cache_lookup(ti, &sc_prev, &head)) == NULL) { 2020 splx(s); 2021 return; 2022 } 2023 if (SEQ_LT(ti->ti_seq,sc->sc_irs) || 2024 SEQ_GT(ti->ti_seq, sc->sc_irs+1)) { 2025 splx(s); 2026 return; 2027 } 2028 SYN_CACHE_RM(sc, sc_prev, head); 2029 splx(s); 2030 tcpstat.tcps_sc_reset++; 2031 if (sc->sc_ipopts) 2032 (void) m_free(sc->sc_ipopts); 2033 FREE(sc, M_PCB); 2034 } 2035 2036 void 2037 syn_cache_unreach(ip, th) 2038 struct ip *ip; 2039 struct tcphdr *th; 2040 { 2041 struct syn_cache *sc, **sc_prev; 2042 struct syn_cache_head *head; 2043 struct tcpiphdr ti2; 2044 int s; 2045 2046 ti2.ti_src.s_addr = ip->ip_dst.s_addr; 2047 ti2.ti_dst.s_addr = ip->ip_src.s_addr; 2048 ti2.ti_sport = th->th_dport; 2049 ti2.ti_dport = th->th_sport; 2050 2051 s = splsoftnet(); 2052 if ((sc = syn_cache_lookup(&ti2, &sc_prev, &head)) == NULL) { 2053 splx(s); 2054 return; 2055 } 2056 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 2057 if (ntohl (th->th_seq) != sc->sc_iss) { 2058 splx(s); 2059 return; 2060 } 2061 SYN_CACHE_RM(sc, sc_prev, head); 2062 splx(s); 2063 tcpstat.tcps_sc_unreach++; 2064 if (sc->sc_ipopts) 2065 (void) m_free(sc->sc_ipopts); 2066 FREE(sc, M_PCB); 2067 } 2068 2069 /* 2070 * Given a LISTEN socket and an inbound SYN request, add 2071 * this to the syn cache, and send back a segment: 2072 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 2073 * to the source. 2074 * 2075 * XXX We don't properly handle SYN-with-data! 2076 */ 2077 2078 int 2079 syn_cache_add(so, m, optp, optlen, oi) 2080 struct socket *so; 2081 struct mbuf *m; 2082 u_char *optp; 2083 int optlen; 2084 struct tcp_opt_info *oi; 2085 { 2086 register struct tcpiphdr *ti; 2087 struct tcpcb tb, *tp; 2088 long win; 2089 struct syn_cache *sc, **sc_prev; 2090 struct syn_cache_head *scp; 2091 struct mbuf *ipopts; 2092 extern int tcp_do_rfc1323; 2093 2094 tp = sototcpcb(so); 2095 ti = mtod(m, struct tcpiphdr *); 2096 2097 /* 2098 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 2099 * in_broadcast() should never return true on a received 2100 * packet with M_BCAST not set. 2101 */ 2102 if (m->m_flags & (M_BCAST|M_MCAST) || 2103 IN_MULTICAST(ti->ti_src.s_addr) || 2104 IN_MULTICAST(ti->ti_dst.s_addr)) 2105 return (0); 2106 2107 /* 2108 * Initialize some local state. 2109 */ 2110 win = sbspace(&so->so_rcv); 2111 if (win > TCP_MAXWIN) 2112 win = TCP_MAXWIN; 2113 2114 /* 2115 * Remember the IP options, if any. 2116 */ 2117 ipopts = ip_srcroute(); 2118 2119 if (optp) { 2120 tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 2121 tcp_dooptions(&tb, optp, optlen, ti, oi); 2122 } else 2123 tb.t_flags = 0; 2124 2125 /* 2126 * See if we already have an entry for this connection. 2127 * If we do, resend the SYN,ACK, and remember since the 2128 * initial congestion window must be initialized to 1 2129 * segment when the connection completes. 2130 */ 2131 if ((sc = syn_cache_lookup(ti, &sc_prev, &scp)) != NULL) { 2132 tcpstat.tcps_sc_dupesyn++; 2133 sc->sc_flags |= SCF_SYNACK_REXMT; 2134 2135 if (ipopts) { 2136 /* 2137 * If we were remembering a previous source route, 2138 * forget it and use the new one we've been given. 2139 */ 2140 if (sc->sc_ipopts) 2141 (void) m_free(sc->sc_ipopts); 2142 sc->sc_ipopts = ipopts; 2143 } 2144 2145 if (syn_cache_respond(sc, m, ti, win, tb.ts_recent) == 0) { 2146 tcpstat.tcps_sndacks++; 2147 tcpstat.tcps_sndtotal++; 2148 } 2149 return (1); 2150 } 2151 2152 MALLOC(sc, struct syn_cache *, sizeof(*sc), M_PCB, M_NOWAIT); 2153 if (sc == NULL) { 2154 if (ipopts) 2155 (void) m_free(ipopts); 2156 return (0); 2157 } 2158 2159 /* 2160 * Fill in the cache, and put the necessary IP and TCP 2161 * options into the reply. 2162 */ 2163 sc->sc_src.s_addr = ti->ti_src.s_addr; 2164 sc->sc_dst.s_addr = ti->ti_dst.s_addr; 2165 sc->sc_sport = ti->ti_sport; 2166 sc->sc_dport = ti->ti_dport; 2167 sc->sc_flags = 0; 2168 sc->sc_ipopts = ipopts; 2169 sc->sc_irs = ti->ti_seq; 2170 sc->sc_iss = tcp_new_iss(sc, sizeof(struct syn_cache), 0); 2171 sc->sc_peermaxseg = oi->maxseg; 2172 sc->sc_ourmaxseg = tcp_mss_to_advertise(m->m_flags & M_PKTHDR ? 2173 m->m_pkthdr.rcvif : NULL); 2174 if (tcp_do_rfc1323 && (tb.t_flags & TF_RCVD_TSTMP)) 2175 sc->sc_flags |= SCF_TIMESTAMP; 2176 if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2177 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2178 sc->sc_requested_s_scale = tb.requested_s_scale; 2179 sc->sc_request_r_scale = 0; 2180 while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT && 2181 TCP_MAXWIN << sc->sc_request_r_scale < 2182 so->so_rcv.sb_hiwat) 2183 sc->sc_request_r_scale++; 2184 } else { 2185 sc->sc_requested_s_scale = 15; 2186 sc->sc_request_r_scale = 15; 2187 } 2188 if (syn_cache_respond(sc, m, ti, win, tb.ts_recent) == 0) { 2189 syn_cache_insert(sc, &sc_prev, &scp); 2190 tcpstat.tcps_sndacks++; 2191 tcpstat.tcps_sndtotal++; 2192 } else { 2193 if (sc->sc_ipopts) 2194 (void) m_free(sc->sc_ipopts); 2195 FREE(sc, M_PCB); 2196 tcpstat.tcps_sc_dropped++; 2197 } 2198 return (1); 2199 } 2200 2201 int 2202 syn_cache_respond(sc, m, ti, win, ts) 2203 struct syn_cache *sc; 2204 struct mbuf *m; 2205 register struct tcpiphdr *ti; 2206 long win; 2207 u_long ts; 2208 { 2209 u_int8_t *optp; 2210 int optlen; 2211 2212 /* 2213 * Tack on the TCP options. If there isn't enough trailing 2214 * space for them, move up the fixed header to make space. 2215 */ 2216 optlen = 4 + (sc->sc_request_r_scale != 15 ? 4 : 0) + 2217 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0); 2218 if (optlen > M_TRAILINGSPACE(m)) { 2219 if (M_LEADINGSPACE(m) >= optlen) { 2220 m->m_data -= optlen; 2221 m->m_len += optlen; 2222 } else { 2223 struct mbuf *m0 = m; 2224 if ((m = m_gethdr(M_DONTWAIT, MT_HEADER)) == NULL) { 2225 m_freem(m0); 2226 return (ENOBUFS); 2227 } 2228 MH_ALIGN(m, sizeof(*ti) + optlen); 2229 m->m_next = m0; /* this gets freed below */ 2230 } 2231 ovbcopy((caddr_t)ti, mtod(m, caddr_t), sizeof(*ti)); 2232 ti = mtod(m, struct tcpiphdr *); 2233 } 2234 2235 optp = (u_int8_t *)(ti + 1); 2236 optp[0] = TCPOPT_MAXSEG; 2237 optp[1] = 4; 2238 optp[2] = (sc->sc_ourmaxseg >> 8) & 0xff; 2239 optp[3] = sc->sc_ourmaxseg & 0xff; 2240 optlen = 4; 2241 2242 if (sc->sc_request_r_scale != 15) { 2243 *((u_int32_t *)(optp + optlen)) = htonl(TCPOPT_NOP << 24 | 2244 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 2245 sc->sc_request_r_scale); 2246 optlen += 4; 2247 } 2248 2249 if (sc->sc_flags & SCF_TIMESTAMP) { 2250 u_int32_t *lp = (u_int32_t *)(optp + optlen); 2251 /* Form timestamp option as shown in appendix A of RFC 1323. */ 2252 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 2253 *lp++ = htonl(tcp_now); 2254 *lp = htonl(ts); 2255 optlen += TCPOLEN_TSTAMP_APPA; 2256 } 2257 2258 /* 2259 * Toss any trailing mbufs. No need to worry about 2260 * m_len and m_pkthdr.len, since tcp_respond() will 2261 * unconditionally set them. 2262 */ 2263 if (m->m_next) { 2264 m_freem(m->m_next); 2265 m->m_next = NULL; 2266 } 2267 2268 /* 2269 * Fill in the fields that tcp_respond() will not touch, and 2270 * then send the response. 2271 */ 2272 ti->ti_off = (sizeof(struct tcphdr) + optlen) >> 2; 2273 ti->ti_win = htons(win); 2274 return (tcp_respond(NULL, ti, m, sc->sc_irs + 1, sc->sc_iss, 2275 TH_SYN|TH_ACK)); 2276 } 2277 #endif /* TUBA_INCLUDE */ 2278
Indexes created Tue Sep 23 13:09:54 GMT 2025