tcp_input.c revision 1.51
1 /* $NetBSD: tcp_input.c,v 1.51 1998/04/13 21:18:19 kml 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 95 #include <net/if.h> 96 #include <net/route.h> 97 98 #include <netinet/in.h> 99 #include <netinet/in_systm.h> 100 #include <netinet/ip.h> 101 #include <netinet/in_pcb.h> 102 #include <netinet/ip_var.h> 103 #include <netinet/tcp.h> 104 #include <netinet/tcp_fsm.h> 105 #include <netinet/tcp_seq.h> 106 #include <netinet/tcp_timer.h> 107 #include <netinet/tcp_var.h> 108 #include <netinet/tcpip.h> 109 #include <netinet/tcp_debug.h> 110 111 #include <machine/stdarg.h> 112 113 int tcprexmtthresh = 3; 114 struct tcpiphdr tcp_saveti; 115 116 extern u_long sb_max; 117 118 #endif /* TUBA_INCLUDE */ 119 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) 120 121 /* for modulo comparisons of timestamps */ 122 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) 123 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) 124 125 /* 126 * Macro to compute ACK transmission behavior. Delay the ACK unless 127 * we have already delayed an ACK (must send an ACK every two segments). 128 */ 129 #define TCP_SETUP_ACK(tp, ti) \ 130 do { \ 131 if ((tp)->t_flags & TF_DELACK) \ 132 tp->t_flags |= TF_ACKNOW; \ 133 else \ 134 TCP_SET_DELACK(tp); \ 135 } while (0) 136 137 /* 138 * Insert segment ti into reassembly queue of tcp with 139 * control block tp. Return TH_FIN if reassembly now includes 140 * a segment with FIN. The macro form does the common case inline 141 * (segment is the next to be received on an established connection, 142 * and the queue is empty), avoiding linkage into and removal 143 * from the queue and repetition of various conversions. 144 * Set DELACK for segments received in order, but ack immediately 145 * when segments are out of order (so fast retransmit can work). 146 */ 147 #define TCP_REASS(tp, ti, m, so, flags) { \ 148 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 149 (tp)->segq.lh_first == NULL && \ 150 (tp)->t_state == TCPS_ESTABLISHED) { \ 151 TCP_SETUP_ACK(tp, ti); \ 152 (tp)->rcv_nxt += (ti)->ti_len; \ 153 flags = (ti)->ti_flags & TH_FIN; \ 154 tcpstat.tcps_rcvpack++;\ 155 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 156 sbappend(&(so)->so_rcv, (m)); \ 157 sorwakeup(so); \ 158 } else { \ 159 (flags) = tcp_reass((tp), (ti), (m)); \ 160 tp->t_flags |= TF_ACKNOW; \ 161 } \ 162 } 163 #ifndef TUBA_INCLUDE 164 165 int 166 tcp_reass(tp, ti, m) 167 register struct tcpcb *tp; 168 register struct tcpiphdr *ti; 169 struct mbuf *m; 170 { 171 register struct ipqent *p, *q, *nq, *tiqe; 172 struct socket *so = tp->t_inpcb->inp_socket; 173 int flags; 174 175 /* 176 * Call with ti==0 after become established to 177 * force pre-ESTABLISHED data up to user socket. 178 */ 179 if (ti == 0) 180 goto present; 181 182 /* 183 * Allocate a new queue entry, before we throw away any data. 184 * If we can't, just drop the packet. XXX 185 */ 186 MALLOC(tiqe, struct ipqent *, sizeof (struct ipqent), M_IPQ, M_NOWAIT); 187 if (tiqe == NULL) { 188 tcpstat.tcps_rcvmemdrop++; 189 m_freem(m); 190 return (0); 191 } 192 193 /* 194 * Find a segment which begins after this one does. 195 */ 196 for (p = NULL, q = tp->segq.lh_first; q != NULL; 197 p = q, q = q->ipqe_q.le_next) 198 if (SEQ_GT(q->ipqe_tcp->ti_seq, ti->ti_seq)) 199 break; 200 201 /* 202 * If there is a preceding segment, it may provide some of 203 * our data already. If so, drop the data from the incoming 204 * segment. If it provides all of our data, drop us. 205 */ 206 if (p != NULL) { 207 register struct tcpiphdr *phdr = p->ipqe_tcp; 208 register int i; 209 210 /* conversion to int (in i) handles seq wraparound */ 211 i = phdr->ti_seq + phdr->ti_len - ti->ti_seq; 212 if (i > 0) { 213 if (i >= ti->ti_len) { 214 tcpstat.tcps_rcvduppack++; 215 tcpstat.tcps_rcvdupbyte += ti->ti_len; 216 m_freem(m); 217 FREE(tiqe, M_IPQ); 218 return (0); 219 } 220 m_adj(m, i); 221 ti->ti_len -= i; 222 ti->ti_seq += i; 223 } 224 } 225 tcpstat.tcps_rcvoopack++; 226 tcpstat.tcps_rcvoobyte += ti->ti_len; 227 228 /* 229 * While we overlap succeeding segments trim them or, 230 * if they are completely covered, dequeue them. 231 */ 232 for (; q != NULL; q = nq) { 233 register struct tcpiphdr *qhdr = q->ipqe_tcp; 234 register int i = (ti->ti_seq + ti->ti_len) - qhdr->ti_seq; 235 236 if (i <= 0) 237 break; 238 if (i < qhdr->ti_len) { 239 qhdr->ti_seq += i; 240 qhdr->ti_len -= i; 241 m_adj(q->ipqe_m, i); 242 break; 243 } 244 nq = q->ipqe_q.le_next; 245 m_freem(q->ipqe_m); 246 LIST_REMOVE(q, ipqe_q); 247 FREE(q, M_IPQ); 248 } 249 250 /* Insert the new fragment queue entry into place. */ 251 tiqe->ipqe_m = m; 252 tiqe->ipqe_tcp = ti; 253 if (p == NULL) { 254 LIST_INSERT_HEAD(&tp->segq, tiqe, ipqe_q); 255 } else { 256 LIST_INSERT_AFTER(p, tiqe, ipqe_q); 257 } 258 259 present: 260 /* 261 * Present data to user, advancing rcv_nxt through 262 * completed sequence space. 263 */ 264 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 265 return (0); 266 q = tp->segq.lh_first; 267 if (q == NULL || q->ipqe_tcp->ti_seq != tp->rcv_nxt) 268 return (0); 269 if (tp->t_state == TCPS_SYN_RECEIVED && q->ipqe_tcp->ti_len) 270 return (0); 271 do { 272 tp->rcv_nxt += q->ipqe_tcp->ti_len; 273 flags = q->ipqe_tcp->ti_flags & TH_FIN; 274 275 nq = q->ipqe_q.le_next; 276 LIST_REMOVE(q, ipqe_q); 277 if (so->so_state & SS_CANTRCVMORE) 278 m_freem(q->ipqe_m); 279 else 280 sbappend(&so->so_rcv, q->ipqe_m); 281 FREE(q, M_IPQ); 282 q = nq; 283 } while (q != NULL && q->ipqe_tcp->ti_seq == tp->rcv_nxt); 284 sorwakeup(so); 285 return (flags); 286 } 287 288 /* 289 * TCP input routine, follows pages 65-76 of the 290 * protocol specification dated September, 1981 very closely. 291 */ 292 void 293 #if __STDC__ 294 tcp_input(struct mbuf *m, ...) 295 #else 296 tcp_input(m, va_alist) 297 register struct mbuf *m; 298 #endif 299 { 300 register struct tcpiphdr *ti; 301 register struct inpcb *inp; 302 caddr_t optp = NULL; 303 int optlen = 0; 304 int len, tlen, off, hdroptlen; 305 register struct tcpcb *tp = 0; 306 register int tiflags; 307 struct socket *so = NULL; 308 int todrop, acked, ourfinisacked, needoutput = 0; 309 short ostate = 0; 310 int iss = 0; 311 u_long tiwin; 312 struct tcp_opt_info opti; 313 int iphlen; 314 va_list ap; 315 316 va_start(ap, m); 317 iphlen = va_arg(ap, int); 318 va_end(ap); 319 320 tcpstat.tcps_rcvtotal++; 321 322 opti.ts_present = 0; 323 opti.maxseg = 0; 324 325 /* 326 * Get IP and TCP header together in first mbuf. 327 * Note: IP leaves IP header in first mbuf. 328 */ 329 ti = mtod(m, struct tcpiphdr *); 330 if (iphlen > sizeof (struct ip)) 331 ip_stripoptions(m, (struct mbuf *)0); 332 if (m->m_len < sizeof (struct tcpiphdr)) { 333 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 334 tcpstat.tcps_rcvshort++; 335 return; 336 } 337 ti = mtod(m, struct tcpiphdr *); 338 } 339 340 /* 341 * Checksum extended TCP header and data. 342 */ 343 tlen = ((struct ip *)ti)->ip_len; 344 len = sizeof (struct ip) + tlen; 345 bzero(ti->ti_x1, sizeof ti->ti_x1); 346 ti->ti_len = (u_int16_t)tlen; 347 HTONS(ti->ti_len); 348 if ((ti->ti_sum = in_cksum(m, len)) != 0) { 349 tcpstat.tcps_rcvbadsum++; 350 goto drop; 351 } 352 #endif /* TUBA_INCLUDE */ 353 354 /* 355 * Check that TCP offset makes sense, 356 * pull out TCP options and adjust length. XXX 357 */ 358 off = ti->ti_off << 2; 359 if (off < sizeof (struct tcphdr) || off > tlen) { 360 tcpstat.tcps_rcvbadoff++; 361 goto drop; 362 } 363 tlen -= off; 364 ti->ti_len = tlen; 365 if (off > sizeof (struct tcphdr)) { 366 if (m->m_len < sizeof(struct ip) + off) { 367 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 368 tcpstat.tcps_rcvshort++; 369 return; 370 } 371 ti = mtod(m, struct tcpiphdr *); 372 } 373 optlen = off - sizeof (struct tcphdr); 374 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 375 /* 376 * Do quick retrieval of timestamp options ("options 377 * prediction?"). If timestamp is the only option and it's 378 * formatted as recommended in RFC 1323 appendix A, we 379 * quickly get the values now and not bother calling 380 * tcp_dooptions(), etc. 381 */ 382 if ((optlen == TCPOLEN_TSTAMP_APPA || 383 (optlen > TCPOLEN_TSTAMP_APPA && 384 optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && 385 *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) && 386 (ti->ti_flags & TH_SYN) == 0) { 387 opti.ts_present = 1; 388 opti.ts_val = ntohl(*(u_int32_t *)(optp + 4)); 389 opti.ts_ecr = ntohl(*(u_int32_t *)(optp + 8)); 390 optp = NULL; /* we've parsed the options */ 391 } 392 } 393 tiflags = ti->ti_flags; 394 395 /* 396 * Convert TCP protocol specific fields to host format. 397 */ 398 NTOHL(ti->ti_seq); 399 NTOHL(ti->ti_ack); 400 NTOHS(ti->ti_win); 401 NTOHS(ti->ti_urp); 402 403 /* 404 * Locate pcb for segment. 405 */ 406 findpcb: 407 inp = in_pcblookup_connect(&tcbtable, ti->ti_src, ti->ti_sport, 408 ti->ti_dst, ti->ti_dport); 409 if (inp == 0) { 410 ++tcpstat.tcps_pcbhashmiss; 411 inp = in_pcblookup_bind(&tcbtable, ti->ti_dst, ti->ti_dport); 412 if (inp == 0) { 413 ++tcpstat.tcps_noport; 414 goto dropwithreset; 415 } 416 } 417 418 /* 419 * If the state is CLOSED (i.e., TCB does not exist) then 420 * all data in the incoming segment is discarded. 421 * If the TCB exists but is in CLOSED state, it is embryonic, 422 * but should either do a listen or a connect soon. 423 */ 424 tp = intotcpcb(inp); 425 if (tp == 0) 426 goto dropwithreset; 427 if (tp->t_state == TCPS_CLOSED) 428 goto drop; 429 430 /* Unscale the window into a 32-bit value. */ 431 if ((tiflags & TH_SYN) == 0) 432 tiwin = ti->ti_win << tp->snd_scale; 433 else 434 tiwin = ti->ti_win; 435 436 so = inp->inp_socket; 437 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 438 if (so->so_options & SO_DEBUG) { 439 ostate = tp->t_state; 440 tcp_saveti = *ti; 441 } 442 if (so->so_options & SO_ACCEPTCONN) { 443 if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 444 if (tiflags & TH_RST) { 445 syn_cache_reset(ti); 446 } else if ((tiflags & (TH_ACK|TH_SYN)) == 447 (TH_ACK|TH_SYN)) { 448 /* 449 * Received a SYN,ACK. This should 450 * never happen while we are in 451 * LISTEN. Send an RST. 452 */ 453 goto badsyn; 454 } else if (tiflags & TH_ACK) { 455 so = syn_cache_get(so, m); 456 if (so == NULL) { 457 /* 458 * We don't have a SYN for 459 * this ACK; send an RST. 460 */ 461 goto badsyn; 462 } else if (so == 463 (struct socket *)(-1)) { 464 /* 465 * We were unable to create 466 * the connection. If the 467 * 3-way handshake was 468 * completeed, and RST has 469 * been sent to the peer. 470 * Since the mbuf might be 471 * in use for the reply, 472 * do not free it. 473 */ 474 m = NULL; 475 } else { 476 /* 477 * We have created a 478 * full-blown connection. 479 */ 480 inp = sotoinpcb(so); 481 tp = intotcpcb(inp); 482 tiwin <<= tp->snd_scale; 483 goto after_listen; 484 } 485 } 486 } else { 487 /* 488 * Received a SYN. 489 */ 490 if (in_hosteq(ti->ti_src, ti->ti_dst) && 491 ti->ti_sport == ti->ti_dport) { 492 /* 493 * LISTEN socket received a SYN 494 * from itself? This can't possibly 495 * be valid; drop the packet. 496 */ 497 tcpstat.tcps_badsyn++; 498 goto drop; 499 } 500 /* 501 * SYN looks ok; create compressed TCP 502 * state for it. 503 */ 504 if (so->so_qlen <= so->so_qlimit && 505 syn_cache_add(so, m, optp, optlen, &opti)) 506 m = NULL; 507 } 508 goto drop; 509 } 510 } 511 512 after_listen: 513 #ifdef DIAGNOSTIC 514 /* 515 * Should not happen now that all embryonic connections 516 * are handled with compressed state. 517 */ 518 if (tp->t_state == TCPS_LISTEN) 519 panic("tcp_input: TCPS_LISTEN"); 520 #endif 521 522 /* 523 * Segment received on connection. 524 * Reset idle time and keep-alive timer. 525 */ 526 tp->t_idle = 0; 527 if (TCPS_HAVEESTABLISHED(tp->t_state)) 528 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 529 530 /* 531 * Process options. 532 */ 533 if (optp) 534 tcp_dooptions(tp, optp, optlen, ti, &opti); 535 536 /* 537 * Header prediction: check for the two common cases 538 * of a uni-directional data xfer. If the packet has 539 * no control flags, is in-sequence, the window didn't 540 * change and we're not retransmitting, it's a 541 * candidate. If the length is zero and the ack moved 542 * forward, we're the sender side of the xfer. Just 543 * free the data acked & wake any higher level process 544 * that was blocked waiting for space. If the length 545 * is non-zero and the ack didn't move, we're the 546 * receiver side. If we're getting packets in-order 547 * (the reassembly queue is empty), add the data to 548 * the socket buffer and note that we need a delayed ack. 549 */ 550 if (tp->t_state == TCPS_ESTABLISHED && 551 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 552 (!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) && 553 ti->ti_seq == tp->rcv_nxt && 554 tiwin && tiwin == tp->snd_wnd && 555 tp->snd_nxt == tp->snd_max) { 556 557 /* 558 * If last ACK falls within this segment's sequence numbers, 559 * record the timestamp. 560 */ 561 if (opti.ts_present && 562 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 563 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) { 564 tp->ts_recent_age = tcp_now; 565 tp->ts_recent = opti.ts_val; 566 } 567 568 if (ti->ti_len == 0) { 569 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 570 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 571 tp->snd_cwnd >= tp->snd_wnd && 572 tp->t_dupacks < tcprexmtthresh) { 573 /* 574 * this is a pure ack for outstanding data. 575 */ 576 ++tcpstat.tcps_predack; 577 if (opti.ts_present) 578 tcp_xmit_timer(tp, 579 tcp_now-opti.ts_ecr+1); 580 else if (tp->t_rtt && 581 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 582 tcp_xmit_timer(tp, tp->t_rtt); 583 acked = ti->ti_ack - tp->snd_una; 584 tcpstat.tcps_rcvackpack++; 585 tcpstat.tcps_rcvackbyte += acked; 586 sbdrop(&so->so_snd, acked); 587 tp->snd_una = ti->ti_ack; 588 m_freem(m); 589 590 /* 591 * If all outstanding data are acked, stop 592 * retransmit timer, otherwise restart timer 593 * using current (possibly backed-off) value. 594 * If process is waiting for space, 595 * wakeup/selwakeup/signal. If data 596 * are ready to send, let tcp_output 597 * decide between more output or persist. 598 */ 599 if (tp->snd_una == tp->snd_max) 600 tp->t_timer[TCPT_REXMT] = 0; 601 else if (tp->t_timer[TCPT_PERSIST] == 0) 602 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 603 604 if (sb_notify(&so->so_snd)) 605 sowwakeup(so); 606 if (so->so_snd.sb_cc) 607 (void) tcp_output(tp); 608 return; 609 } 610 } else if (ti->ti_ack == tp->snd_una && 611 tp->segq.lh_first == NULL && 612 ti->ti_len <= sbspace(&so->so_rcv)) { 613 /* 614 * this is a pure, in-sequence data packet 615 * with nothing on the reassembly queue and 616 * we have enough buffer space to take it. 617 */ 618 ++tcpstat.tcps_preddat; 619 tp->rcv_nxt += ti->ti_len; 620 tcpstat.tcps_rcvpack++; 621 tcpstat.tcps_rcvbyte += ti->ti_len; 622 /* 623 * Drop TCP, IP headers and TCP options then add data 624 * to socket buffer. 625 */ 626 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 627 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 628 sbappend(&so->so_rcv, m); 629 sorwakeup(so); 630 TCP_SETUP_ACK(tp, ti); 631 if (tp->t_flags & TF_ACKNOW) 632 (void) tcp_output(tp); 633 return; 634 } 635 } 636 637 /* 638 * Drop TCP, IP headers and TCP options. 639 */ 640 hdroptlen = sizeof(struct tcpiphdr) + off - sizeof(struct tcphdr); 641 m->m_data += hdroptlen; 642 m->m_len -= hdroptlen; 643 644 /* 645 * Calculate amount of space in receive window, 646 * and then do TCP input processing. 647 * Receive window is amount of space in rcv queue, 648 * but not less than advertised window. 649 */ 650 { int win; 651 652 win = sbspace(&so->so_rcv); 653 if (win < 0) 654 win = 0; 655 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 656 } 657 658 switch (tp->t_state) { 659 660 /* 661 * If the state is SYN_SENT: 662 * if seg contains an ACK, but not for our SYN, drop the input. 663 * if seg contains a RST, then drop the connection. 664 * if seg does not contain SYN, then drop it. 665 * Otherwise this is an acceptable SYN segment 666 * initialize tp->rcv_nxt and tp->irs 667 * if seg contains ack then advance tp->snd_una 668 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 669 * arrange for segment to be acked (eventually) 670 * continue processing rest of data/controls, beginning with URG 671 */ 672 case TCPS_SYN_SENT: 673 if ((tiflags & TH_ACK) && 674 (SEQ_LEQ(ti->ti_ack, tp->iss) || 675 SEQ_GT(ti->ti_ack, tp->snd_max))) 676 goto dropwithreset; 677 if (tiflags & TH_RST) { 678 if (tiflags & TH_ACK) 679 tp = tcp_drop(tp, ECONNREFUSED); 680 goto drop; 681 } 682 if ((tiflags & TH_SYN) == 0) 683 goto drop; 684 if (tiflags & TH_ACK) { 685 tp->snd_una = ti->ti_ack; 686 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 687 tp->snd_nxt = tp->snd_una; 688 } 689 tp->t_timer[TCPT_REXMT] = 0; 690 tp->irs = ti->ti_seq; 691 tcp_rcvseqinit(tp); 692 tp->t_flags |= TF_ACKNOW; 693 tcp_mss_from_peer(tp, opti.maxseg); 694 695 /* 696 * Initialize the initial congestion window. If we 697 * had to retransmit the SYN, we must initialize cwnd 698 * to 1 segment. 699 */ 700 tp->snd_cwnd = 701 TCP_INITIAL_WINDOW((tp->t_flags & TF_SYN_REXMT) ? 1 : 702 tcp_init_win, tp->t_peermss); 703 704 tcp_rmx_rtt(tp); 705 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 706 tcpstat.tcps_connects++; 707 soisconnected(so); 708 tcp_established(tp); 709 /* Do window scaling on this connection? */ 710 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 711 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 712 tp->snd_scale = tp->requested_s_scale; 713 tp->rcv_scale = tp->request_r_scale; 714 } 715 (void) tcp_reass(tp, (struct tcpiphdr *)0, 716 (struct mbuf *)0); 717 /* 718 * if we didn't have to retransmit the SYN, 719 * use its rtt as our initial srtt & rtt var. 720 */ 721 if (tp->t_rtt) 722 tcp_xmit_timer(tp, tp->t_rtt); 723 } else 724 tp->t_state = TCPS_SYN_RECEIVED; 725 726 /* 727 * Advance ti->ti_seq to correspond to first data byte. 728 * If data, trim to stay within window, 729 * dropping FIN if necessary. 730 */ 731 ti->ti_seq++; 732 if (ti->ti_len > tp->rcv_wnd) { 733 todrop = ti->ti_len - tp->rcv_wnd; 734 m_adj(m, -todrop); 735 ti->ti_len = tp->rcv_wnd; 736 tiflags &= ~TH_FIN; 737 tcpstat.tcps_rcvpackafterwin++; 738 tcpstat.tcps_rcvbyteafterwin += todrop; 739 } 740 tp->snd_wl1 = ti->ti_seq - 1; 741 tp->rcv_up = ti->ti_seq; 742 goto step6; 743 744 /* 745 * If the state is SYN_RECEIVED: 746 * If seg contains an ACK, but not for our SYN, drop the input 747 * and generate an RST. See page 36, rfc793 748 */ 749 case TCPS_SYN_RECEIVED: 750 if ((tiflags & TH_ACK) && 751 (SEQ_LEQ(ti->ti_ack, tp->iss) || 752 SEQ_GT(ti->ti_ack, tp->snd_max))) 753 goto dropwithreset; 754 break; 755 } 756 757 /* 758 * States other than LISTEN or SYN_SENT. 759 * First check timestamp, if present. 760 * Then check that at least some bytes of segment are within 761 * receive window. If segment begins before rcv_nxt, 762 * drop leading data (and SYN); if nothing left, just ack. 763 * 764 * RFC 1323 PAWS: If we have a timestamp reply on this segment 765 * and it's less than ts_recent, drop it. 766 */ 767 if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && 768 TSTMP_LT(opti.ts_val, tp->ts_recent)) { 769 770 /* Check to see if ts_recent is over 24 days old. */ 771 if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 772 /* 773 * Invalidate ts_recent. If this segment updates 774 * ts_recent, the age will be reset later and ts_recent 775 * will get a valid value. If it does not, setting 776 * ts_recent to zero will at least satisfy the 777 * requirement that zero be placed in the timestamp 778 * echo reply when ts_recent isn't valid. The 779 * age isn't reset until we get a valid ts_recent 780 * because we don't want out-of-order segments to be 781 * dropped when ts_recent is old. 782 */ 783 tp->ts_recent = 0; 784 } else { 785 tcpstat.tcps_rcvduppack++; 786 tcpstat.tcps_rcvdupbyte += ti->ti_len; 787 tcpstat.tcps_pawsdrop++; 788 goto dropafterack; 789 } 790 } 791 792 todrop = tp->rcv_nxt - ti->ti_seq; 793 if (todrop > 0) { 794 if (tiflags & TH_SYN) { 795 tiflags &= ~TH_SYN; 796 ti->ti_seq++; 797 if (ti->ti_urp > 1) 798 ti->ti_urp--; 799 else { 800 tiflags &= ~TH_URG; 801 ti->ti_urp = 0; 802 } 803 todrop--; 804 } 805 if (todrop > ti->ti_len || 806 (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) { 807 /* 808 * Any valid FIN must be to the left of the window. 809 * At this point the FIN must be a duplicate or 810 * out of sequence; drop it. 811 */ 812 tiflags &= ~TH_FIN; 813 /* 814 * Send an ACK to resynchronize and drop any data. 815 * But keep on processing for RST or ACK. 816 */ 817 tp->t_flags |= TF_ACKNOW; 818 todrop = ti->ti_len; 819 tcpstat.tcps_rcvdupbyte += todrop; 820 tcpstat.tcps_rcvduppack++; 821 } else { 822 tcpstat.tcps_rcvpartduppack++; 823 tcpstat.tcps_rcvpartdupbyte += todrop; 824 } 825 m_adj(m, todrop); 826 ti->ti_seq += todrop; 827 ti->ti_len -= todrop; 828 if (ti->ti_urp > todrop) 829 ti->ti_urp -= todrop; 830 else { 831 tiflags &= ~TH_URG; 832 ti->ti_urp = 0; 833 } 834 } 835 836 /* 837 * If new data are received on a connection after the 838 * user processes are gone, then RST the other end. 839 */ 840 if ((so->so_state & SS_NOFDREF) && 841 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 842 tp = tcp_close(tp); 843 tcpstat.tcps_rcvafterclose++; 844 goto dropwithreset; 845 } 846 847 /* 848 * If segment ends after window, drop trailing data 849 * (and PUSH and FIN); if nothing left, just ACK. 850 */ 851 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 852 if (todrop > 0) { 853 tcpstat.tcps_rcvpackafterwin++; 854 if (todrop >= ti->ti_len) { 855 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 856 /* 857 * If a new connection request is received 858 * while in TIME_WAIT, drop the old connection 859 * and start over if the sequence numbers 860 * are above the previous ones. 861 */ 862 if (tiflags & TH_SYN && 863 tp->t_state == TCPS_TIME_WAIT && 864 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 865 iss = tcp_new_iss(tp, sizeof(struct tcpcb), 866 tp->rcv_nxt); 867 tp = tcp_close(tp); 868 /* 869 * We have already advanced the mbuf 870 * pointers past the IP+TCP headers and 871 * options. Restore those pointers before 872 * attempting to use the TCP header again. 873 */ 874 m->m_data -= hdroptlen; 875 m->m_len += hdroptlen; 876 goto findpcb; 877 } 878 /* 879 * If window is closed can only take segments at 880 * window edge, and have to drop data and PUSH from 881 * incoming segments. Continue processing, but 882 * remember to ack. Otherwise, drop segment 883 * and ack. 884 */ 885 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 886 tp->t_flags |= TF_ACKNOW; 887 tcpstat.tcps_rcvwinprobe++; 888 } else 889 goto dropafterack; 890 } else 891 tcpstat.tcps_rcvbyteafterwin += todrop; 892 m_adj(m, -todrop); 893 ti->ti_len -= todrop; 894 tiflags &= ~(TH_PUSH|TH_FIN); 895 } 896 897 /* 898 * If last ACK falls within this segment's sequence numbers, 899 * record its timestamp. 900 */ 901 if (opti.ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 902 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len + 903 ((tiflags & (TH_SYN|TH_FIN)) != 0))) { 904 tp->ts_recent_age = tcp_now; 905 tp->ts_recent = opti.ts_val; 906 } 907 908 /* 909 * If the RST bit is set examine the state: 910 * SYN_RECEIVED STATE: 911 * If passive open, return to LISTEN state. 912 * If active open, inform user that connection was refused. 913 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 914 * Inform user that connection was reset, and close tcb. 915 * CLOSING, LAST_ACK, TIME_WAIT STATES 916 * Close the tcb. 917 */ 918 if (tiflags&TH_RST) switch (tp->t_state) { 919 920 case TCPS_SYN_RECEIVED: 921 so->so_error = ECONNREFUSED; 922 goto close; 923 924 case TCPS_ESTABLISHED: 925 case TCPS_FIN_WAIT_1: 926 case TCPS_FIN_WAIT_2: 927 case TCPS_CLOSE_WAIT: 928 so->so_error = ECONNRESET; 929 close: 930 tp->t_state = TCPS_CLOSED; 931 tcpstat.tcps_drops++; 932 tp = tcp_close(tp); 933 goto drop; 934 935 case TCPS_CLOSING: 936 case TCPS_LAST_ACK: 937 case TCPS_TIME_WAIT: 938 tp = tcp_close(tp); 939 goto drop; 940 } 941 942 /* 943 * If a SYN is in the window, then this is an 944 * error and we send an RST and drop the connection. 945 */ 946 if (tiflags & TH_SYN) { 947 tp = tcp_drop(tp, ECONNRESET); 948 goto dropwithreset; 949 } 950 951 /* 952 * If the ACK bit is off we drop the segment and return. 953 */ 954 if ((tiflags & TH_ACK) == 0) 955 goto drop; 956 957 /* 958 * Ack processing. 959 */ 960 switch (tp->t_state) { 961 962 /* 963 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 964 * ESTABLISHED state and continue processing, otherwise 965 * send an RST. 966 */ 967 case TCPS_SYN_RECEIVED: 968 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 969 SEQ_GT(ti->ti_ack, tp->snd_max)) 970 goto dropwithreset; 971 tcpstat.tcps_connects++; 972 soisconnected(so); 973 tcp_established(tp); 974 /* Do window scaling? */ 975 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 976 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 977 tp->snd_scale = tp->requested_s_scale; 978 tp->rcv_scale = tp->request_r_scale; 979 } 980 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); 981 tp->snd_wl1 = ti->ti_seq - 1; 982 /* fall into ... */ 983 984 /* 985 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 986 * ACKs. If the ack is in the range 987 * tp->snd_una < ti->ti_ack <= tp->snd_max 988 * then advance tp->snd_una to ti->ti_ack and drop 989 * data from the retransmission queue. If this ACK reflects 990 * more up to date window information we update our window information. 991 */ 992 case TCPS_ESTABLISHED: 993 case TCPS_FIN_WAIT_1: 994 case TCPS_FIN_WAIT_2: 995 case TCPS_CLOSE_WAIT: 996 case TCPS_CLOSING: 997 case TCPS_LAST_ACK: 998 case TCPS_TIME_WAIT: 999 1000 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 1001 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 1002 tcpstat.tcps_rcvdupack++; 1003 /* 1004 * If we have outstanding data (other than 1005 * a window probe), this is a completely 1006 * duplicate ack (ie, window info didn't 1007 * change), the ack is the biggest we've 1008 * seen and we've seen exactly our rexmt 1009 * threshhold of them, assume a packet 1010 * has been dropped and retransmit it. 1011 * Kludge snd_nxt & the congestion 1012 * window so we send only this one 1013 * packet. 1014 * 1015 * We know we're losing at the current 1016 * window size so do congestion avoidance 1017 * (set ssthresh to half the current window 1018 * and pull our congestion window back to 1019 * the new ssthresh). 1020 * 1021 * Dup acks mean that packets have left the 1022 * network (they're now cached at the receiver) 1023 * so bump cwnd by the amount in the receiver 1024 * to keep a constant cwnd packets in the 1025 * network. 1026 */ 1027 if (tp->t_timer[TCPT_REXMT] == 0 || 1028 ti->ti_ack != tp->snd_una) 1029 tp->t_dupacks = 0; 1030 else if (++tp->t_dupacks == tcprexmtthresh) { 1031 tcp_seq onxt = tp->snd_nxt; 1032 u_int win = 1033 min(tp->snd_wnd, tp->snd_cwnd) / 1034 2 / tp->t_segsz; 1035 1036 if (win < 2) 1037 win = 2; 1038 tp->snd_ssthresh = win * tp->t_segsz; 1039 tp->t_timer[TCPT_REXMT] = 0; 1040 tp->t_rtt = 0; 1041 tp->snd_nxt = ti->ti_ack; 1042 tp->snd_cwnd = tp->t_segsz; 1043 (void) tcp_output(tp); 1044 tp->snd_cwnd = tp->snd_ssthresh + 1045 tp->t_segsz * tp->t_dupacks; 1046 if (SEQ_GT(onxt, tp->snd_nxt)) 1047 tp->snd_nxt = onxt; 1048 goto drop; 1049 } else if (tp->t_dupacks > tcprexmtthresh) { 1050 tp->snd_cwnd += tp->t_segsz; 1051 (void) tcp_output(tp); 1052 goto drop; 1053 } 1054 } else 1055 tp->t_dupacks = 0; 1056 break; 1057 } 1058 /* 1059 * If the congestion window was inflated to account 1060 * for the other side's cached packets, retract it. 1061 */ 1062 if (tp->t_dupacks >= tcprexmtthresh && 1063 tp->snd_cwnd > tp->snd_ssthresh) 1064 tp->snd_cwnd = tp->snd_ssthresh; 1065 tp->t_dupacks = 0; 1066 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 1067 tcpstat.tcps_rcvacktoomuch++; 1068 goto dropafterack; 1069 } 1070 acked = ti->ti_ack - tp->snd_una; 1071 tcpstat.tcps_rcvackpack++; 1072 tcpstat.tcps_rcvackbyte += acked; 1073 1074 /* 1075 * If we have a timestamp reply, update smoothed 1076 * round trip time. If no timestamp is present but 1077 * transmit timer is running and timed sequence 1078 * number was acked, update smoothed round trip time. 1079 * Since we now have an rtt measurement, cancel the 1080 * timer backoff (cf., Phil Karn's retransmit alg.). 1081 * Recompute the initial retransmit timer. 1082 */ 1083 if (opti.ts_present) 1084 tcp_xmit_timer(tp, tcp_now - opti.ts_ecr + 1); 1085 else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 1086 tcp_xmit_timer(tp,tp->t_rtt); 1087 1088 /* 1089 * If all outstanding data is acked, stop retransmit 1090 * timer and remember to restart (more output or persist). 1091 * If there is more data to be acked, restart retransmit 1092 * timer, using current (possibly backed-off) value. 1093 */ 1094 if (ti->ti_ack == tp->snd_max) { 1095 tp->t_timer[TCPT_REXMT] = 0; 1096 needoutput = 1; 1097 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1098 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1099 /* 1100 * When new data is acked, open the congestion window. 1101 * If the window gives us less than ssthresh packets 1102 * in flight, open exponentially (segsz per packet). 1103 * Otherwise open linearly: segsz per window 1104 * (segsz^2 / cwnd per packet), plus a constant 1105 * fraction of a packet (segsz/8) to help larger windows 1106 * open quickly enough. 1107 */ 1108 { 1109 register u_int cw = tp->snd_cwnd; 1110 register u_int incr = tp->t_segsz; 1111 1112 if (cw > tp->snd_ssthresh) 1113 incr = incr * incr / cw; 1114 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1115 } 1116 if (acked > so->so_snd.sb_cc) { 1117 tp->snd_wnd -= so->so_snd.sb_cc; 1118 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1119 ourfinisacked = 1; 1120 } else { 1121 sbdrop(&so->so_snd, acked); 1122 tp->snd_wnd -= acked; 1123 ourfinisacked = 0; 1124 } 1125 if (sb_notify(&so->so_snd)) 1126 sowwakeup(so); 1127 tp->snd_una = ti->ti_ack; 1128 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1129 tp->snd_nxt = tp->snd_una; 1130 1131 switch (tp->t_state) { 1132 1133 /* 1134 * In FIN_WAIT_1 STATE in addition to the processing 1135 * for the ESTABLISHED state if our FIN is now acknowledged 1136 * then enter FIN_WAIT_2. 1137 */ 1138 case TCPS_FIN_WAIT_1: 1139 if (ourfinisacked) { 1140 /* 1141 * If we can't receive any more 1142 * data, then closing user can proceed. 1143 * Starting the timer is contrary to the 1144 * specification, but if we don't get a FIN 1145 * we'll hang forever. 1146 */ 1147 if (so->so_state & SS_CANTRCVMORE) { 1148 soisdisconnected(so); 1149 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 1150 } 1151 tp->t_state = TCPS_FIN_WAIT_2; 1152 } 1153 break; 1154 1155 /* 1156 * In CLOSING STATE in addition to the processing for 1157 * the ESTABLISHED state if the ACK acknowledges our FIN 1158 * then enter the TIME-WAIT state, otherwise ignore 1159 * the segment. 1160 */ 1161 case TCPS_CLOSING: 1162 if (ourfinisacked) { 1163 tp->t_state = TCPS_TIME_WAIT; 1164 tcp_canceltimers(tp); 1165 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1166 soisdisconnected(so); 1167 } 1168 break; 1169 1170 /* 1171 * In LAST_ACK, we may still be waiting for data to drain 1172 * and/or to be acked, as well as for the ack of our FIN. 1173 * If our FIN is now acknowledged, delete the TCB, 1174 * enter the closed state and return. 1175 */ 1176 case TCPS_LAST_ACK: 1177 if (ourfinisacked) { 1178 tp = tcp_close(tp); 1179 goto drop; 1180 } 1181 break; 1182 1183 /* 1184 * In TIME_WAIT state the only thing that should arrive 1185 * is a retransmission of the remote FIN. Acknowledge 1186 * it and restart the finack timer. 1187 */ 1188 case TCPS_TIME_WAIT: 1189 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1190 goto dropafterack; 1191 } 1192 } 1193 1194 step6: 1195 /* 1196 * Update window information. 1197 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1198 */ 1199 if (((tiflags & TH_ACK) && SEQ_LT(tp->snd_wl1, ti->ti_seq)) || 1200 (tp->snd_wl1 == ti->ti_seq && SEQ_LT(tp->snd_wl2, ti->ti_ack)) || 1201 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd)) { 1202 /* keep track of pure window updates */ 1203 if (ti->ti_len == 0 && 1204 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1205 tcpstat.tcps_rcvwinupd++; 1206 tp->snd_wnd = tiwin; 1207 tp->snd_wl1 = ti->ti_seq; 1208 tp->snd_wl2 = ti->ti_ack; 1209 if (tp->snd_wnd > tp->max_sndwnd) 1210 tp->max_sndwnd = tp->snd_wnd; 1211 needoutput = 1; 1212 } 1213 1214 /* 1215 * Process segments with URG. 1216 */ 1217 if ((tiflags & TH_URG) && ti->ti_urp && 1218 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1219 /* 1220 * This is a kludge, but if we receive and accept 1221 * random urgent pointers, we'll crash in 1222 * soreceive. It's hard to imagine someone 1223 * actually wanting to send this much urgent data. 1224 */ 1225 if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { 1226 ti->ti_urp = 0; /* XXX */ 1227 tiflags &= ~TH_URG; /* XXX */ 1228 goto dodata; /* XXX */ 1229 } 1230 /* 1231 * If this segment advances the known urgent pointer, 1232 * then mark the data stream. This should not happen 1233 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1234 * a FIN has been received from the remote side. 1235 * In these states we ignore the URG. 1236 * 1237 * According to RFC961 (Assigned Protocols), 1238 * the urgent pointer points to the last octet 1239 * of urgent data. We continue, however, 1240 * to consider it to indicate the first octet 1241 * of data past the urgent section as the original 1242 * spec states (in one of two places). 1243 */ 1244 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1245 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1246 so->so_oobmark = so->so_rcv.sb_cc + 1247 (tp->rcv_up - tp->rcv_nxt) - 1; 1248 if (so->so_oobmark == 0) 1249 so->so_state |= SS_RCVATMARK; 1250 sohasoutofband(so); 1251 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1252 } 1253 /* 1254 * Remove out of band data so doesn't get presented to user. 1255 * This can happen independent of advancing the URG pointer, 1256 * but if two URG's are pending at once, some out-of-band 1257 * data may creep in... ick. 1258 */ 1259 if (ti->ti_urp <= (u_int16_t) ti->ti_len 1260 #ifdef SO_OOBINLINE 1261 && (so->so_options & SO_OOBINLINE) == 0 1262 #endif 1263 ) 1264 tcp_pulloutofband(so, ti, m); 1265 } else 1266 /* 1267 * If no out of band data is expected, 1268 * pull receive urgent pointer along 1269 * with the receive window. 1270 */ 1271 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1272 tp->rcv_up = tp->rcv_nxt; 1273 dodata: /* XXX */ 1274 1275 /* 1276 * Process the segment text, merging it into the TCP sequencing queue, 1277 * and arranging for acknowledgment of receipt if necessary. 1278 * This process logically involves adjusting tp->rcv_wnd as data 1279 * is presented to the user (this happens in tcp_usrreq.c, 1280 * case PRU_RCVD). If a FIN has already been received on this 1281 * connection then we just ignore the text. 1282 */ 1283 if ((ti->ti_len || (tiflags & TH_FIN)) && 1284 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1285 TCP_REASS(tp, ti, m, so, tiflags); 1286 /* 1287 * Note the amount of data that peer has sent into 1288 * our window, in order to estimate the sender's 1289 * buffer size. 1290 */ 1291 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1292 } else { 1293 m_freem(m); 1294 tiflags &= ~TH_FIN; 1295 } 1296 1297 /* 1298 * If FIN is received ACK the FIN and let the user know 1299 * that the connection is closing. Ignore a FIN received before 1300 * the connection is fully established. 1301 */ 1302 if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) { 1303 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1304 socantrcvmore(so); 1305 tp->t_flags |= TF_ACKNOW; 1306 tp->rcv_nxt++; 1307 } 1308 switch (tp->t_state) { 1309 1310 /* 1311 * In ESTABLISHED STATE enter the CLOSE_WAIT state. 1312 */ 1313 case TCPS_ESTABLISHED: 1314 tp->t_state = TCPS_CLOSE_WAIT; 1315 break; 1316 1317 /* 1318 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1319 * enter the CLOSING state. 1320 */ 1321 case TCPS_FIN_WAIT_1: 1322 tp->t_state = TCPS_CLOSING; 1323 break; 1324 1325 /* 1326 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1327 * starting the time-wait timer, turning off the other 1328 * standard timers. 1329 */ 1330 case TCPS_FIN_WAIT_2: 1331 tp->t_state = TCPS_TIME_WAIT; 1332 tcp_canceltimers(tp); 1333 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1334 soisdisconnected(so); 1335 break; 1336 1337 /* 1338 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1339 */ 1340 case TCPS_TIME_WAIT: 1341 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1342 break; 1343 } 1344 } 1345 if (so->so_options & SO_DEBUG) 1346 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1347 1348 /* 1349 * Return any desired output. 1350 */ 1351 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1352 (void) tcp_output(tp); 1353 return; 1354 1355 badsyn: 1356 /* 1357 * Received a bad SYN. Increment counters and dropwithreset. 1358 */ 1359 tcpstat.tcps_badsyn++; 1360 tp = NULL; 1361 goto dropwithreset; 1362 1363 dropafterack: 1364 /* 1365 * Generate an ACK dropping incoming segment if it occupies 1366 * sequence space, where the ACK reflects our state. 1367 */ 1368 if (tiflags & TH_RST) 1369 goto drop; 1370 m_freem(m); 1371 tp->t_flags |= TF_ACKNOW; 1372 (void) tcp_output(tp); 1373 return; 1374 1375 dropwithreset: 1376 /* 1377 * Generate a RST, dropping incoming segment. 1378 * Make ACK acceptable to originator of segment. 1379 * Don't bother to respond if destination was broadcast/multicast. 1380 */ 1381 if ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) || 1382 IN_MULTICAST(ti->ti_dst.s_addr)) 1383 goto drop; 1384 if (tiflags & TH_ACK) 1385 (void)tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1386 else { 1387 if (tiflags & TH_SYN) 1388 ti->ti_len++; 1389 (void)tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1390 TH_RST|TH_ACK); 1391 } 1392 return; 1393 1394 drop: 1395 /* 1396 * Drop space held by incoming segment and return. 1397 */ 1398 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1399 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1400 m_freem(m); 1401 return; 1402 #ifndef TUBA_INCLUDE 1403 } 1404 1405 void 1406 tcp_dooptions(tp, cp, cnt, ti, oi) 1407 struct tcpcb *tp; 1408 u_char *cp; 1409 int cnt; 1410 struct tcpiphdr *ti; 1411 struct tcp_opt_info *oi; 1412 { 1413 u_int16_t mss; 1414 int opt, optlen; 1415 1416 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1417 opt = cp[0]; 1418 if (opt == TCPOPT_EOL) 1419 break; 1420 if (opt == TCPOPT_NOP) 1421 optlen = 1; 1422 else { 1423 optlen = cp[1]; 1424 if (optlen <= 0) 1425 break; 1426 } 1427 switch (opt) { 1428 1429 default: 1430 continue; 1431 1432 case TCPOPT_MAXSEG: 1433 if (optlen != TCPOLEN_MAXSEG) 1434 continue; 1435 if (!(ti->ti_flags & TH_SYN)) 1436 continue; 1437 bcopy(cp + 2, &mss, sizeof(mss)); 1438 oi->maxseg = ntohs(mss); 1439 break; 1440 1441 case TCPOPT_WINDOW: 1442 if (optlen != TCPOLEN_WINDOW) 1443 continue; 1444 if (!(ti->ti_flags & TH_SYN)) 1445 continue; 1446 tp->t_flags |= TF_RCVD_SCALE; 1447 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 1448 break; 1449 1450 case TCPOPT_TIMESTAMP: 1451 if (optlen != TCPOLEN_TIMESTAMP) 1452 continue; 1453 oi->ts_present = 1; 1454 bcopy(cp + 2, &oi->ts_val, sizeof(oi->ts_val)); 1455 NTOHL(oi->ts_val); 1456 bcopy(cp + 6, &oi->ts_ecr, sizeof(oi->ts_ecr)); 1457 NTOHL(oi->ts_ecr); 1458 1459 /* 1460 * A timestamp received in a SYN makes 1461 * it ok to send timestamp requests and replies. 1462 */ 1463 if (ti->ti_flags & TH_SYN) { 1464 tp->t_flags |= TF_RCVD_TSTMP; 1465 tp->ts_recent = oi->ts_val; 1466 tp->ts_recent_age = tcp_now; 1467 } 1468 break; 1469 } 1470 } 1471 } 1472 1473 /* 1474 * Pull out of band byte out of a segment so 1475 * it doesn't appear in the user's data queue. 1476 * It is still reflected in the segment length for 1477 * sequencing purposes. 1478 */ 1479 void 1480 tcp_pulloutofband(so, ti, m) 1481 struct socket *so; 1482 struct tcpiphdr *ti; 1483 register struct mbuf *m; 1484 { 1485 int cnt = ti->ti_urp - 1; 1486 1487 while (cnt >= 0) { 1488 if (m->m_len > cnt) { 1489 char *cp = mtod(m, caddr_t) + cnt; 1490 struct tcpcb *tp = sototcpcb(so); 1491 1492 tp->t_iobc = *cp; 1493 tp->t_oobflags |= TCPOOB_HAVEDATA; 1494 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1495 m->m_len--; 1496 return; 1497 } 1498 cnt -= m->m_len; 1499 m = m->m_next; 1500 if (m == 0) 1501 break; 1502 } 1503 panic("tcp_pulloutofband"); 1504 } 1505 1506 /* 1507 * Collect new round-trip time estimate 1508 * and update averages and current timeout. 1509 */ 1510 void 1511 tcp_xmit_timer(tp, rtt) 1512 register struct tcpcb *tp; 1513 short rtt; 1514 { 1515 register short delta; 1516 short rttmin; 1517 1518 tcpstat.tcps_rttupdated++; 1519 --rtt; 1520 if (tp->t_srtt != 0) { 1521 /* 1522 * srtt is stored as fixed point with 3 bits after the 1523 * binary point (i.e., scaled by 8). The following magic 1524 * is equivalent to the smoothing algorithm in rfc793 with 1525 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 1526 * point). Adjust rtt to origin 0. 1527 */ 1528 delta = (rtt << 2) - (tp->t_srtt >> TCP_RTT_SHIFT); 1529 if ((tp->t_srtt += delta) <= 0) 1530 tp->t_srtt = 1 << 2; 1531 /* 1532 * We accumulate a smoothed rtt variance (actually, a 1533 * smoothed mean difference), then set the retransmit 1534 * timer to smoothed rtt + 4 times the smoothed variance. 1535 * rttvar is stored as fixed point with 2 bits after the 1536 * binary point (scaled by 4). The following is 1537 * equivalent to rfc793 smoothing with an alpha of .75 1538 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 1539 * rfc793's wired-in beta. 1540 */ 1541 if (delta < 0) 1542 delta = -delta; 1543 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); 1544 if ((tp->t_rttvar += delta) <= 0) 1545 tp->t_rttvar = 1 << 2; 1546 } else { 1547 /* 1548 * No rtt measurement yet - use the unsmoothed rtt. 1549 * Set the variance to half the rtt (so our first 1550 * retransmit happens at 3*rtt). 1551 */ 1552 tp->t_srtt = rtt << (TCP_RTT_SHIFT + 2); 1553 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT + 2 - 1); 1554 } 1555 tp->t_rtt = 0; 1556 tp->t_rxtshift = 0; 1557 1558 /* 1559 * the retransmit should happen at rtt + 4 * rttvar. 1560 * Because of the way we do the smoothing, srtt and rttvar 1561 * will each average +1/2 tick of bias. When we compute 1562 * the retransmit timer, we want 1/2 tick of rounding and 1563 * 1 extra tick because of +-1/2 tick uncertainty in the 1564 * firing of the timer. The bias will give us exactly the 1565 * 1.5 tick we need. But, because the bias is 1566 * statistical, we have to test that we don't drop below 1567 * the minimum feasible timer (which is 2 ticks). 1568 */ 1569 if (tp->t_rttmin > rtt + 2) 1570 rttmin = tp->t_rttmin; 1571 else 1572 rttmin = rtt + 2; 1573 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rttmin, TCPTV_REXMTMAX); 1574 1575 /* 1576 * We received an ack for a packet that wasn't retransmitted; 1577 * it is probably safe to discard any error indications we've 1578 * received recently. This isn't quite right, but close enough 1579 * for now (a route might have failed after we sent a segment, 1580 * and the return path might not be symmetrical). 1581 */ 1582 tp->t_softerror = 0; 1583 } 1584 1585 /* 1586 * TCP compressed state engine. Currently used to hold compressed 1587 * state for SYN_RECEIVED. 1588 */ 1589 1590 u_long syn_cache_count; 1591 u_int32_t syn_hash1, syn_hash2; 1592 1593 #define SYN_HASH(sa, sp, dp) \ 1594 ((((sa)->s_addr^syn_hash1)*(((((u_int32_t)(dp))<<16) + \ 1595 ((u_int32_t)(sp)))^syn_hash2))) 1596 1597 #define eptosp(ep, e, s) ((struct s *)((char *)(ep) - \ 1598 ((char *)(&((struct s *)0)->e) - (char *)0))) 1599 1600 #define SYN_CACHE_RM(sc, p, scp) { \ 1601 *(p) = (sc)->sc_next; \ 1602 if ((sc)->sc_next) \ 1603 (sc)->sc_next->sc_timer += (sc)->sc_timer; \ 1604 else { \ 1605 (scp)->sch_timer_sum -= (sc)->sc_timer; \ 1606 if ((scp)->sch_timer_sum <= 0) \ 1607 (scp)->sch_timer_sum = -1; \ 1608 /* If need be, fix up the last pointer */ \ 1609 if ((scp)->sch_first) \ 1610 (scp)->sch_last = eptosp(p, sc_next, syn_cache); \ 1611 } \ 1612 (scp)->sch_length--; \ 1613 syn_cache_count--; \ 1614 } 1615 1616 void 1617 syn_cache_insert(sc, prevp, headp) 1618 struct syn_cache *sc; 1619 struct syn_cache ***prevp; 1620 struct syn_cache_head **headp; 1621 { 1622 struct syn_cache_head *scp, *scp2, *sce; 1623 struct syn_cache *sc2; 1624 static u_int timeo_val; 1625 int s; 1626 1627 /* Initialize the hash secrets when adding the first entry */ 1628 if (syn_cache_count == 0) { 1629 struct timeval tv; 1630 microtime(&tv); 1631 syn_hash1 = random() ^ (u_long)≻ 1632 syn_hash2 = random() ^ tv.tv_usec; 1633 } 1634 1635 sc->sc_hash = SYN_HASH(&sc->sc_src, sc->sc_sport, sc->sc_dport); 1636 sc->sc_next = NULL; 1637 scp = &tcp_syn_cache[sc->sc_hash % tcp_syn_cache_size]; 1638 *headp = scp; 1639 1640 /* 1641 * Make sure that we don't overflow the per-bucket 1642 * limit or the total cache size limit. 1643 */ 1644 s = splsoftnet(); 1645 if (scp->sch_length >= tcp_syn_bucket_limit) { 1646 tcpstat.tcps_sc_bucketoverflow++; 1647 sc2 = scp->sch_first; 1648 scp->sch_first = sc2->sc_next; 1649 if (sc2->sc_ipopts) 1650 (void) m_free(sc2->sc_ipopts); 1651 FREE(sc2, M_PCB); 1652 } else if (syn_cache_count >= tcp_syn_cache_limit) { 1653 tcpstat.tcps_sc_overflowed++; 1654 /* 1655 * The cache is full. Toss the first (i.e, oldest) 1656 * element in this bucket. 1657 */ 1658 scp2 = scp; 1659 if (scp2->sch_first == NULL) { 1660 sce = &tcp_syn_cache[tcp_syn_cache_size]; 1661 for (++scp2; scp2 != scp; scp2++) { 1662 if (scp2 >= sce) 1663 scp2 = &tcp_syn_cache[0]; 1664 if (scp2->sch_first) 1665 break; 1666 } 1667 } 1668 sc2 = scp2->sch_first; 1669 if (sc2 == NULL) { 1670 if (sc->sc_ipopts) 1671 (void) m_free(sc->sc_ipopts); 1672 FREE(sc, M_PCB); 1673 return; 1674 } 1675 if ((scp2->sch_first = sc2->sc_next) == NULL) 1676 scp2->sch_last = NULL; 1677 else 1678 sc2->sc_next->sc_timer += sc2->sc_timer; 1679 if (sc2->sc_ipopts) 1680 (void) m_free(sc2->sc_ipopts); 1681 FREE(sc2, M_PCB); 1682 } else { 1683 scp->sch_length++; 1684 syn_cache_count++; 1685 } 1686 tcpstat.tcps_sc_added++; 1687 1688 /* 1689 * Put it into the bucket. 1690 */ 1691 if (scp->sch_first == NULL) 1692 *prevp = &scp->sch_first; 1693 else { 1694 *prevp = &scp->sch_last->sc_next; 1695 tcpstat.tcps_sc_collisions++; 1696 } 1697 **prevp = sc; 1698 scp->sch_last = sc; 1699 1700 /* 1701 * If the timeout value has changed 1702 * 1) force it to fit in a u_char 1703 * 2) Run the timer routine to truncate all 1704 * existing entries to the new timeout value. 1705 */ 1706 if (timeo_val != tcp_syn_cache_timeo) { 1707 tcp_syn_cache_timeo = min(tcp_syn_cache_timeo, UCHAR_MAX); 1708 if (timeo_val > tcp_syn_cache_timeo) 1709 syn_cache_timer(timeo_val - tcp_syn_cache_timeo); 1710 timeo_val = tcp_syn_cache_timeo; 1711 } 1712 if (scp->sch_timer_sum > 0) 1713 sc->sc_timer = tcp_syn_cache_timeo - scp->sch_timer_sum; 1714 else { 1715 if (scp->sch_timer_sum == 0) { 1716 /* 1717 * When the bucket timer is 0, it is not in the 1718 * cache queue. 1719 */ 1720 scp->sch_headq = tcp_syn_cache_first; 1721 tcp_syn_cache_first = scp; 1722 } 1723 sc->sc_timer = tcp_syn_cache_timeo; 1724 } 1725 scp->sch_timer_sum = tcp_syn_cache_timeo; 1726 splx(s); 1727 } 1728 1729 /* 1730 * Walk down the cache list, decrementing the timer of 1731 * the first element on each entry. If the timer goes 1732 * to zero, remove it and all successive entries with 1733 * a zero timer. 1734 */ 1735 void 1736 syn_cache_timer(interval) 1737 int interval; 1738 { 1739 struct syn_cache_head *scp, **pscp; 1740 struct syn_cache *sc, *scn; 1741 int n, s; 1742 1743 pscp = &tcp_syn_cache_first; 1744 scp = tcp_syn_cache_first; 1745 s = splsoftnet(); 1746 while (scp) { 1747 /* 1748 * Remove any empty hash buckets 1749 * from the cache queue. 1750 */ 1751 if ((sc = scp->sch_first) == NULL) { 1752 *pscp = scp->sch_headq; 1753 scp->sch_headq = NULL; 1754 scp->sch_timer_sum = 0; 1755 scp->sch_first = scp->sch_last = NULL; 1756 scp->sch_length = 0; 1757 scp = *pscp; 1758 continue; 1759 } 1760 1761 scp->sch_timer_sum -= interval; 1762 if (scp->sch_timer_sum <= 0) 1763 scp->sch_timer_sum = -1; 1764 n = interval; 1765 while (sc->sc_timer <= n) { 1766 n -= sc->sc_timer; 1767 scn = sc->sc_next; 1768 tcpstat.tcps_sc_timed_out++; 1769 syn_cache_count--; 1770 if (sc->sc_ipopts) 1771 (void) m_free(sc->sc_ipopts); 1772 FREE(sc, M_PCB); 1773 scp->sch_length--; 1774 if ((sc = scn) == NULL) 1775 break; 1776 } 1777 if ((scp->sch_first = sc) != NULL) { 1778 sc->sc_timer -= n; 1779 pscp = &scp->sch_headq; 1780 scp = scp->sch_headq; 1781 } 1782 } 1783 splx(s); 1784 } 1785 1786 /* 1787 * Find an entry in the syn cache. 1788 */ 1789 struct syn_cache * 1790 syn_cache_lookup(ti, prevp, headp) 1791 struct tcpiphdr *ti; 1792 struct syn_cache ***prevp; 1793 struct syn_cache_head **headp; 1794 { 1795 struct syn_cache *sc, **prev; 1796 struct syn_cache_head *head; 1797 u_int32_t hash; 1798 int s; 1799 1800 hash = SYN_HASH(&ti->ti_src, ti->ti_sport, ti->ti_dport); 1801 1802 head = &tcp_syn_cache[hash % tcp_syn_cache_size]; 1803 *headp = head; 1804 prev = &head->sch_first; 1805 s = splsoftnet(); 1806 for (sc = head->sch_first; sc; prev = &sc->sc_next, sc = sc->sc_next) { 1807 if (sc->sc_hash != hash) 1808 continue; 1809 if (sc->sc_src.s_addr == ti->ti_src.s_addr && 1810 sc->sc_sport == ti->ti_sport && 1811 sc->sc_dport == ti->ti_dport && 1812 sc->sc_dst.s_addr == ti->ti_dst.s_addr) { 1813 *prevp = prev; 1814 splx(s); 1815 return (sc); 1816 } 1817 } 1818 splx(s); 1819 return (NULL); 1820 } 1821 1822 /* 1823 * This function gets called when we receive an ACK for a 1824 * socket in the LISTEN state. We look up the connection 1825 * in the syn cache, and if its there, we pull it out of 1826 * the cache and turn it into a full-blown connection in 1827 * the SYN-RECEIVED state. 1828 * 1829 * The return values may not be immediately obvious, and their effects 1830 * can be subtle, so here they are: 1831 * 1832 * NULL SYN was not found in cache; caller should drop the 1833 * packet and send an RST. 1834 * 1835 * -1 We were unable to create the new connection, and are 1836 * aborting it. An ACK,RST is being sent to the peer 1837 * (unless we got screwey sequence numbners; see below), 1838 * because the 3-way handshake has been completed. Caller 1839 * should not free the mbuf, since we may be using it. If 1840 * we are not, we will free it. 1841 * 1842 * Otherwise, the return value is a pointer to the new socket 1843 * associated with the connection. 1844 */ 1845 struct socket * 1846 syn_cache_get(so, m) 1847 struct socket *so; 1848 struct mbuf *m; 1849 { 1850 struct syn_cache *sc, **sc_prev; 1851 struct syn_cache_head *head; 1852 register struct inpcb *inp; 1853 register struct tcpcb *tp = 0; 1854 register struct tcpiphdr *ti; 1855 struct sockaddr_in *sin; 1856 struct mbuf *am; 1857 long win; 1858 int s; 1859 1860 ti = mtod(m, struct tcpiphdr *); 1861 s = splsoftnet(); 1862 if ((sc = syn_cache_lookup(ti, &sc_prev, &head)) == NULL) { 1863 splx(s); 1864 return (NULL); 1865 } 1866 1867 win = sbspace(&so->so_rcv); 1868 if (win > TCP_MAXWIN) 1869 win = TCP_MAXWIN; 1870 1871 /* 1872 * Verify the sequence and ack numbers. 1873 */ 1874 if ((ti->ti_ack != sc->sc_iss + 1) || 1875 SEQ_LEQ(ti->ti_seq, sc->sc_irs) || 1876 SEQ_GT(ti->ti_seq, sc->sc_irs + 1 + win)) { 1877 (void) syn_cache_respond(sc, m, ti, win, 0); 1878 splx(s); 1879 return ((struct socket *)(-1)); 1880 } 1881 1882 /* Remove this cache entry */ 1883 SYN_CACHE_RM(sc, sc_prev, head); 1884 splx(s); 1885 1886 /* 1887 * Ok, create the full blown connection, and set things up 1888 * as they would have been set up if we had created the 1889 * connection when the SYN arrived. If we can't create 1890 * the connection, abort it. 1891 */ 1892 so = sonewconn(so, SS_ISCONNECTED); 1893 if (so == NULL) 1894 goto resetandabort; 1895 1896 inp = sotoinpcb(so); 1897 inp->inp_laddr = sc->sc_dst; 1898 inp->inp_lport = sc->sc_dport; 1899 in_pcbstate(inp, INP_BOUND); 1900 inp->inp_options = ip_srcroute(); 1901 if (inp->inp_options == NULL) { 1902 inp->inp_options = sc->sc_ipopts; 1903 sc->sc_ipopts = NULL; 1904 } 1905 1906 am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ 1907 if (am == NULL) 1908 goto resetandabort; 1909 am->m_len = sizeof(struct sockaddr_in); 1910 sin = mtod(am, struct sockaddr_in *); 1911 sin->sin_family = AF_INET; 1912 sin->sin_len = sizeof(*sin); 1913 sin->sin_addr = sc->sc_src; 1914 sin->sin_port = sc->sc_sport; 1915 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 1916 if (in_pcbconnect(inp, am)) { 1917 (void) m_free(am); 1918 goto resetandabort; 1919 } 1920 (void) m_free(am); 1921 1922 tp = intotcpcb(inp); 1923 if (sc->sc_request_r_scale != 15) { 1924 tp->requested_s_scale = sc->sc_requested_s_scale; 1925 tp->request_r_scale = sc->sc_request_r_scale; 1926 tp->snd_scale = sc->sc_requested_s_scale; 1927 tp->rcv_scale = sc->sc_request_r_scale; 1928 tp->t_flags |= TF_RCVD_SCALE; 1929 } 1930 if (sc->sc_flags & SCF_TIMESTAMP) 1931 tp->t_flags |= TF_RCVD_TSTMP; 1932 1933 tp->t_template = tcp_template(tp); 1934 if (tp->t_template == 0) { 1935 tp = tcp_drop(tp, ENOBUFS); /* destroys socket */ 1936 so = NULL; 1937 m_freem(m); 1938 goto abort; 1939 } 1940 1941 tp->iss = sc->sc_iss; 1942 tp->irs = sc->sc_irs; 1943 tcp_sendseqinit(tp); 1944 tcp_rcvseqinit(tp); 1945 tp->t_state = TCPS_SYN_RECEIVED; 1946 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 1947 tcpstat.tcps_accepts++; 1948 1949 /* Initialize tp->t_ourmss before we deal with the peer's! */ 1950 tp->t_ourmss = sc->sc_ourmaxseg; 1951 tcp_mss_from_peer(tp, sc->sc_peermaxseg); 1952 1953 /* 1954 * Initialize the initial congestion window. If we 1955 * had to retransmit the SYN,ACK, we must initialize cwnd 1956 * to 1 segment. 1957 */ 1958 tp->snd_cwnd = 1959 TCP_INITIAL_WINDOW((sc->sc_flags & SCF_SYNACK_REXMT) ? 1 : 1960 tcp_init_win, tp->t_peermss); 1961 1962 tcp_rmx_rtt(tp); 1963 tp->snd_wl1 = sc->sc_irs; 1964 tp->rcv_up = sc->sc_irs + 1; 1965 1966 /* 1967 * This is what whould have happened in tcp_ouput() when 1968 * the SYN,ACK was sent. 1969 */ 1970 tp->snd_up = tp->snd_una; 1971 tp->snd_max = tp->snd_nxt = tp->iss+1; 1972 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1973 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 1974 tp->rcv_adv = tp->rcv_nxt + win; 1975 tp->last_ack_sent = tp->rcv_nxt; 1976 1977 tcpstat.tcps_sc_completed++; 1978 if (sc->sc_ipopts) 1979 (void) m_free(sc->sc_ipopts); 1980 FREE(sc, M_PCB); 1981 return (so); 1982 1983 resetandabort: 1984 (void) tcp_respond(NULL, ti, m, ti->ti_seq+ti->ti_len, 1985 (tcp_seq)0, TH_RST|TH_ACK); 1986 abort: 1987 if (so != NULL) 1988 (void) soabort(so); 1989 if (sc->sc_ipopts) 1990 (void) m_free(sc->sc_ipopts); 1991 FREE(sc, M_PCB); 1992 tcpstat.tcps_sc_aborted++; 1993 return ((struct socket *)(-1)); 1994 } 1995 1996 /* 1997 * This function is called when we get a RST for a 1998 * non-existant connection, so that we can see if the 1999 * connection is in the syn cache. If it is, zap it. 2000 */ 2001 2002 void 2003 syn_cache_reset(ti) 2004 register struct tcpiphdr *ti; 2005 { 2006 struct syn_cache *sc, **sc_prev; 2007 struct syn_cache_head *head; 2008 int s = splsoftnet(); 2009 2010 if ((sc = syn_cache_lookup(ti, &sc_prev, &head)) == NULL) { 2011 splx(s); 2012 return; 2013 } 2014 if (SEQ_LT(ti->ti_seq,sc->sc_irs) || 2015 SEQ_GT(ti->ti_seq, sc->sc_irs+1)) { 2016 splx(s); 2017 return; 2018 } 2019 SYN_CACHE_RM(sc, sc_prev, head); 2020 splx(s); 2021 tcpstat.tcps_sc_reset++; 2022 if (sc->sc_ipopts) 2023 (void) m_free(sc->sc_ipopts); 2024 FREE(sc, M_PCB); 2025 } 2026 2027 void 2028 syn_cache_unreach(ip, th) 2029 struct ip *ip; 2030 struct tcphdr *th; 2031 { 2032 struct syn_cache *sc, **sc_prev; 2033 struct syn_cache_head *head; 2034 struct tcpiphdr ti2; 2035 int s; 2036 2037 ti2.ti_src.s_addr = ip->ip_dst.s_addr; 2038 ti2.ti_dst.s_addr = ip->ip_src.s_addr; 2039 ti2.ti_sport = th->th_dport; 2040 ti2.ti_dport = th->th_sport; 2041 2042 s = splsoftnet(); 2043 if ((sc = syn_cache_lookup(&ti2, &sc_prev, &head)) == NULL) { 2044 splx(s); 2045 return; 2046 } 2047 /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ 2048 if (ntohl (th->th_seq) != sc->sc_iss) { 2049 splx(s); 2050 return; 2051 } 2052 SYN_CACHE_RM(sc, sc_prev, head); 2053 splx(s); 2054 tcpstat.tcps_sc_unreach++; 2055 if (sc->sc_ipopts) 2056 (void) m_free(sc->sc_ipopts); 2057 FREE(sc, M_PCB); 2058 } 2059 2060 /* 2061 * Given a LISTEN socket and an inbound SYN request, add 2062 * this to the syn cache, and send back a segment: 2063 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 2064 * to the source. 2065 * 2066 * XXX We don't properly handle SYN-with-data! 2067 */ 2068 2069 int 2070 syn_cache_add(so, m, optp, optlen, oi) 2071 struct socket *so; 2072 struct mbuf *m; 2073 u_char *optp; 2074 int optlen; 2075 struct tcp_opt_info *oi; 2076 { 2077 register struct tcpiphdr *ti; 2078 struct tcpcb tb, *tp; 2079 long win; 2080 struct syn_cache *sc, **sc_prev; 2081 struct syn_cache_head *scp; 2082 struct mbuf *ipopts; 2083 extern int tcp_do_rfc1323; 2084 2085 tp = sototcpcb(so); 2086 ti = mtod(m, struct tcpiphdr *); 2087 2088 /* 2089 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 2090 * in_broadcast() should never return true on a received 2091 * packet with M_BCAST not set. 2092 */ 2093 if (m->m_flags & (M_BCAST|M_MCAST) || 2094 IN_MULTICAST(ti->ti_src.s_addr) || 2095 IN_MULTICAST(ti->ti_dst.s_addr)) 2096 return (0); 2097 2098 /* 2099 * Initialize some local state. 2100 */ 2101 win = sbspace(&so->so_rcv); 2102 if (win > TCP_MAXWIN) 2103 win = TCP_MAXWIN; 2104 2105 /* 2106 * Remember the IP options, if any. 2107 */ 2108 ipopts = ip_srcroute(); 2109 2110 if (optp) { 2111 tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 2112 tcp_dooptions(&tb, optp, optlen, ti, oi); 2113 } else 2114 tb.t_flags = 0; 2115 2116 /* 2117 * See if we already have an entry for this connection. 2118 * If we do, resend the SYN,ACK, and remember since the 2119 * initial congestion window must be initialized to 1 2120 * segment when the connection completes. 2121 */ 2122 if ((sc = syn_cache_lookup(ti, &sc_prev, &scp)) != NULL) { 2123 tcpstat.tcps_sc_dupesyn++; 2124 sc->sc_flags |= SCF_SYNACK_REXMT; 2125 2126 if (ipopts) { 2127 /* 2128 * If we were remembering a previous source route, 2129 * forget it and use the new one we've been given. 2130 */ 2131 if (sc->sc_ipopts) 2132 (void) m_free(sc->sc_ipopts); 2133 sc->sc_ipopts = ipopts; 2134 } 2135 2136 if (syn_cache_respond(sc, m, ti, win, tb.ts_recent) == 0) { 2137 tcpstat.tcps_sndacks++; 2138 tcpstat.tcps_sndtotal++; 2139 } 2140 return (1); 2141 } 2142 2143 MALLOC(sc, struct syn_cache *, sizeof(*sc), M_PCB, M_NOWAIT); 2144 if (sc == NULL) { 2145 if (ipopts) 2146 (void) m_free(ipopts); 2147 return (0); 2148 } 2149 2150 /* 2151 * Fill in the cache, and put the necessary IP and TCP 2152 * options into the reply. 2153 */ 2154 sc->sc_src.s_addr = ti->ti_src.s_addr; 2155 sc->sc_dst.s_addr = ti->ti_dst.s_addr; 2156 sc->sc_sport = ti->ti_sport; 2157 sc->sc_dport = ti->ti_dport; 2158 sc->sc_flags = 0; 2159 sc->sc_ipopts = ipopts; 2160 sc->sc_irs = ti->ti_seq; 2161 sc->sc_iss = tcp_new_iss(sc, sizeof(struct syn_cache), 0); 2162 sc->sc_peermaxseg = oi->maxseg; 2163 sc->sc_ourmaxseg = tcp_mss_to_advertise(m->m_flags & M_PKTHDR ? 2164 m->m_pkthdr.rcvif : NULL); 2165 if (tcp_do_rfc1323 && (tb.t_flags & TF_RCVD_TSTMP)) 2166 sc->sc_flags |= SCF_TIMESTAMP; 2167 if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2168 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2169 sc->sc_requested_s_scale = tb.requested_s_scale; 2170 sc->sc_request_r_scale = 0; 2171 while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT && 2172 TCP_MAXWIN << sc->sc_request_r_scale < 2173 so->so_rcv.sb_hiwat) 2174 sc->sc_request_r_scale++; 2175 } else { 2176 sc->sc_requested_s_scale = 15; 2177 sc->sc_request_r_scale = 15; 2178 } 2179 if (syn_cache_respond(sc, m, ti, win, tb.ts_recent) == 0) { 2180 syn_cache_insert(sc, &sc_prev, &scp); 2181 tcpstat.tcps_sndacks++; 2182 tcpstat.tcps_sndtotal++; 2183 } else { 2184 if (sc->sc_ipopts) 2185 (void) m_free(sc->sc_ipopts); 2186 FREE(sc, M_PCB); 2187 tcpstat.tcps_sc_dropped++; 2188 } 2189 return (1); 2190 } 2191 2192 int 2193 syn_cache_respond(sc, m, ti, win, ts) 2194 struct syn_cache *sc; 2195 struct mbuf *m; 2196 register struct tcpiphdr *ti; 2197 long win; 2198 u_long ts; 2199 { 2200 u_int8_t *optp; 2201 int optlen; 2202 2203 /* 2204 * Tack on the TCP options. If there isn't enough trailing 2205 * space for them, move up the fixed header to make space. 2206 */ 2207 optlen = 4 + (sc->sc_request_r_scale != 15 ? 4 : 0) + 2208 ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0); 2209 if (optlen > M_TRAILINGSPACE(m)) { 2210 if (M_LEADINGSPACE(m) >= optlen) { 2211 m->m_data -= optlen; 2212 m->m_len += optlen; 2213 } else { 2214 struct mbuf *m0 = m; 2215 if ((m = m_gethdr(M_DONTWAIT, MT_HEADER)) == NULL) { 2216 m_freem(m0); 2217 return (ENOBUFS); 2218 } 2219 MH_ALIGN(m, sizeof(*ti) + optlen); 2220 m->m_next = m0; /* this gets freed below */ 2221 } 2222 ovbcopy((caddr_t)ti, mtod(m, caddr_t), sizeof(*ti)); 2223 ti = mtod(m, struct tcpiphdr *); 2224 } 2225 2226 optp = (u_int8_t *)(ti + 1); 2227 optp[0] = TCPOPT_MAXSEG; 2228 optp[1] = 4; 2229 optp[2] = (sc->sc_ourmaxseg >> 8) & 0xff; 2230 optp[3] = sc->sc_ourmaxseg & 0xff; 2231 optlen = 4; 2232 2233 if (sc->sc_request_r_scale != 15) { 2234 *((u_int32_t *)(optp + optlen)) = htonl(TCPOPT_NOP << 24 | 2235 TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | 2236 sc->sc_request_r_scale); 2237 optlen += 4; 2238 } 2239 2240 if (sc->sc_flags & SCF_TIMESTAMP) { 2241 u_int32_t *lp = (u_int32_t *)(optp + optlen); 2242 /* Form timestamp option as shown in appendix A of RFC 1323. */ 2243 *lp++ = htonl(TCPOPT_TSTAMP_HDR); 2244 *lp++ = htonl(tcp_now); 2245 *lp = htonl(ts); 2246 optlen += TCPOLEN_TSTAMP_APPA; 2247 } 2248 2249 /* 2250 * Toss any trailing mbufs. No need to worry about 2251 * m_len and m_pkthdr.len, since tcp_respond() will 2252 * unconditionally set them. 2253 */ 2254 if (m->m_next) { 2255 m_freem(m->m_next); 2256 m->m_next = NULL; 2257 } 2258 2259 /* 2260 * Fill in the fields that tcp_respond() will not touch, and 2261 * then send the response. 2262 */ 2263 ti->ti_off = (sizeof(struct tcphdr) + optlen) >> 2; 2264 ti->ti_win = htons(win); 2265 return (tcp_respond(NULL, ti, m, sc->sc_irs + 1, sc->sc_iss, 2266 TH_SYN|TH_ACK)); 2267 } 2268 #endif /* TUBA_INCLUDE */ 2269
Indexes created Tue Sep 23 13:09:54 GMT 2025