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sys/netinet/tcp_input.c
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1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 34 * $FreeBSD$ 35 */ 36 37 #include "opt_ipfw.h" /* for ipfw_fwd */ 38 #include "opt_tcpdebug.h" 39 #include "opt_tcp_input.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/kernel.h> 44 #include <sys/sysctl.h> 45 #include <sys/malloc.h> 46 #include <sys/mbuf.h> 47 #include <sys/proc.h> /* for proc0 declaration */ 48 #include <sys/protosw.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/syslog.h> 52 53 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 54 55 #include <net/if.h> 56 #include <net/route.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/ip.h> 61 #include <netinet/ip_icmp.h> /* for ICMP_BANDLIM */ 62 #include <netinet/in_pcb.h> 63 #include <netinet/ip_var.h> 64 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 65 #include <netinet/tcp.h> 66 #include <netinet/tcp_fsm.h> 67 #include <netinet/tcp_seq.h> 68 #include <netinet/tcp_timer.h> 69 #include <netinet/tcp_var.h> 70 #include <netinet/tcpip.h> 71 #ifdef TCPDEBUG 72 #include <netinet/tcp_debug.h> 73 static struct tcpiphdr tcp_saveti; 74 #endif 75 76 static int tcprexmtthresh = 3; 77 tcp_seq tcp_iss; 78 tcp_cc tcp_ccgen; 79 80 struct tcpstat tcpstat; 81 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, 82 CTLFLAG_RD, &tcpstat , tcpstat, ""); 83 84 static int log_in_vain = 0; 85 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 86 &log_in_vain, 0, ""); 87 88 int tcp_delack_enabled = 1; 89 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 90 &tcp_delack_enabled, 0, ""); 91 92 #ifdef TCP_DROP_SYNFIN 93 static int drop_synfin = 0; 94 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 95 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 96 #endif 97 98 #ifdef TCP_RESTRICT_RST 99 static int restrict_rst = 0; 100 SYSCTL_INT(_net_inet_tcp, OID_AUTO, restrict_rst, CTLFLAG_RW, 101 &restrict_rst, 0, "Restrict RST emission"); 102 #endif 103 104 u_long tcp_now; 105 struct inpcbhead tcb; 106 struct inpcbinfo tcbinfo; 107 108 static void tcp_dooptions __P((struct tcpcb *, 109 u_char *, int, struct tcpiphdr *, struct tcpopt *)); 110 static void tcp_pulloutofband __P((struct socket *, 111 struct tcpiphdr *, struct mbuf *)); 112 static int tcp_reass __P((struct tcpcb *, struct tcpiphdr *, struct mbuf *)); 113 static void tcp_xmit_timer __P((struct tcpcb *, int)); 114 115 116 /* 117 * Insert segment ti into reassembly queue of tcp with 118 * control block tp. Return TH_FIN if reassembly now includes 119 * a segment with FIN. The macro form does the common case inline 120 * (segment is the next to be received on an established connection, 121 * and the queue is empty), avoiding linkage into and removal 122 * from the queue and repetition of various conversions. 123 * Set DELACK for segments received in order, but ack immediately 124 * when segments are out of order (so fast retransmit can work). 125 */ 126 #define TCP_REASS(tp, ti, m, so, flags) { \ 127 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 128 (tp)->t_segq == NULL && \ 129 (tp)->t_state == TCPS_ESTABLISHED) { \ 130 if (tcp_delack_enabled) \ 131 tp->t_flags |= TF_DELACK; \ 132 else \ 133 tp->t_flags |= TF_ACKNOW; \ 134 (tp)->rcv_nxt += (ti)->ti_len; \ 135 flags = (ti)->ti_flags & TH_FIN; \ 136 tcpstat.tcps_rcvpack++;\ 137 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 138 sbappend(&(so)->so_rcv, (m)); \ 139 sorwakeup(so); \ 140 } else { \ 141 (flags) = tcp_reass((tp), (ti), (m)); \ 142 tp->t_flags |= TF_ACKNOW; \ 143 } \ 144 } 145 146 static int 147 tcp_reass(tp, ti, m) 148 register struct tcpcb *tp; 149 register struct tcpiphdr *ti; 150 struct mbuf *m; 151 { 152 struct mbuf *q; 153 struct mbuf *p; 154 struct mbuf *nq; 155 struct socket *so = tp->t_inpcb->inp_socket; 156 int flags; 157 158 #define GETTCP(m) ((struct tcpiphdr *)m->m_pkthdr.header) 159 160 /* 161 * Call with ti==0 after become established to 162 * force pre-ESTABLISHED data up to user socket. 163 */ 164 if (ti == 0) 165 goto present; 166 167 m->m_pkthdr.header = ti; 168 169 /* 170 * Find a segment which begins after this one does. 171 */ 172 for (q = tp->t_segq, p = NULL; q; p = q, q = q->m_nextpkt) 173 if (SEQ_GT(GETTCP(q)->ti_seq, ti->ti_seq)) 174 break; 175 176 /* 177 * If there is a preceding segment, it may provide some of 178 * our data already. If so, drop the data from the incoming 179 * segment. If it provides all of our data, drop us. 180 */ 181 if (p != NULL) { 182 register int i; 183 /* conversion to int (in i) handles seq wraparound */ 184 i = GETTCP(p)->ti_seq + GETTCP(p)->ti_len - ti->ti_seq; 185 if (i > 0) { 186 if (i >= ti->ti_len) { 187 tcpstat.tcps_rcvduppack++; 188 tcpstat.tcps_rcvdupbyte += ti->ti_len; 189 m_freem(m); 190 /* 191 * Try to present any queued data 192 * at the left window edge to the user. 193 * This is needed after the 3-WHS 194 * completes. 195 */ 196 goto present; /* ??? */ 197 } 198 m_adj(m, i); 199 ti->ti_len -= i; 200 ti->ti_seq += i; 201 } 202 } 203 tcpstat.tcps_rcvoopack++; 204 tcpstat.tcps_rcvoobyte += ti->ti_len; 205 206 /* 207 * While we overlap succeeding segments trim them or, 208 * if they are completely covered, dequeue them. 209 */ 210 while (q) { 211 register int i = (ti->ti_seq + ti->ti_len) - GETTCP(q)->ti_seq; 212 if (i <= 0) 213 break; 214 if (i < GETTCP(q)->ti_len) { 215 GETTCP(q)->ti_seq += i; 216 GETTCP(q)->ti_len -= i; 217 m_adj(q, i); 218 break; 219 } 220 221 nq = q->m_nextpkt; 222 if (p) 223 p->m_nextpkt = nq; 224 else 225 tp->t_segq = nq; 226 m_freem(q); 227 q = nq; 228 } 229 230 if (p == NULL) { 231 m->m_nextpkt = tp->t_segq; 232 tp->t_segq = m; 233 } else { 234 m->m_nextpkt = p->m_nextpkt; 235 p->m_nextpkt = m; 236 } 237 238 present: 239 /* 240 * Present data to user, advancing rcv_nxt through 241 * completed sequence space. 242 */ 243 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 244 return (0); 245 q = tp->t_segq; 246 if (!q || GETTCP(q)->ti_seq != tp->rcv_nxt) 247 return (0); 248 do { 249 tp->rcv_nxt += GETTCP(q)->ti_len; 250 flags = GETTCP(q)->ti_flags & TH_FIN; 251 nq = q->m_nextpkt; 252 tp->t_segq = nq; 253 q->m_nextpkt = NULL; 254 if (so->so_state & SS_CANTRCVMORE) 255 m_freem(q); 256 else 257 sbappend(&so->so_rcv, q); 258 q = nq; 259 } while (q && GETTCP(q)->ti_seq == tp->rcv_nxt); 260 sorwakeup(so); 261 return (flags); 262 263 #undef GETTCP 264 } 265 266 /* 267 * TCP input routine, follows pages 65-76 of the 268 * protocol specification dated September, 1981 very closely. 269 */ 270 void 271 tcp_input(m, iphlen) 272 register struct mbuf *m; 273 int iphlen; 274 { 275 register struct tcpiphdr *ti; 276 register struct inpcb *inp; 277 u_char *optp = NULL; 278 int optlen = 0; 279 int len, tlen, off; 280 register struct tcpcb *tp = 0; 281 register int tiflags; 282 struct socket *so = 0; 283 int todrop, acked, ourfinisacked, needoutput = 0; 284 struct in_addr laddr; 285 int dropsocket = 0; 286 int iss = 0; 287 u_long tiwin; 288 struct tcpopt to; /* options in this segment */ 289 struct rmxp_tao *taop; /* pointer to our TAO cache entry */ 290 struct rmxp_tao tao_noncached; /* in case there's no cached entry */ 291 #ifdef TCPDEBUG 292 short ostate = 0; 293 #endif 294 295 bzero((char *)&to, sizeof(to)); 296 297 tcpstat.tcps_rcvtotal++; 298 /* 299 * Get IP and TCP header together in first mbuf. 300 * Note: IP leaves IP header in first mbuf. 301 */ 302 ti = mtod(m, struct tcpiphdr *); 303 if (iphlen > sizeof (struct ip)) 304 ip_stripoptions(m, (struct mbuf *)0); 305 if (m->m_len < sizeof (struct tcpiphdr)) { 306 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 307 tcpstat.tcps_rcvshort++; 308 return; 309 } 310 ti = mtod(m, struct tcpiphdr *); 311 } 312 313 /* 314 * Checksum extended TCP header and data. 315 */ 316 tlen = ((struct ip *)ti)->ip_len; 317 len = sizeof (struct ip) + tlen; 318 bzero(ti->ti_x1, sizeof(ti->ti_x1)); 319 ti->ti_len = (u_short)tlen; 320 HTONS(ti->ti_len); 321 ti->ti_sum = in_cksum(m, len); 322 if (ti->ti_sum) { 323 tcpstat.tcps_rcvbadsum++; 324 goto drop; 325 } 326 327 /* 328 * Check that TCP offset makes sense, 329 * pull out TCP options and adjust length. XXX 330 */ 331 off = ti->ti_off << 2; 332 if (off < sizeof (struct tcphdr) || off > tlen) { 333 tcpstat.tcps_rcvbadoff++; 334 goto drop; 335 } 336 tlen -= off; 337 ti->ti_len = tlen; 338 if (off > sizeof (struct tcphdr)) { 339 if (m->m_len < sizeof(struct ip) + off) { 340 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 341 tcpstat.tcps_rcvshort++; 342 return; 343 } 344 ti = mtod(m, struct tcpiphdr *); 345 } 346 optlen = off - sizeof (struct tcphdr); 347 optp = mtod(m, u_char *) + sizeof (struct tcpiphdr); 348 } 349 tiflags = ti->ti_flags; 350 351 #ifdef TCP_DROP_SYNFIN 352 /* 353 * If the drop_synfin option is enabled, drop all packets with 354 * both the SYN and FIN bits set. This prevents e.g. nmap from 355 * identifying the TCP/IP stack. 356 * 357 * This is incompatible with RFC1644 extensions (T/TCP). 358 */ 359 if (drop_synfin && (tiflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) 360 goto drop; 361 #endif 362 363 /* 364 * Convert TCP protocol specific fields to host format. 365 */ 366 NTOHL(ti->ti_seq); 367 NTOHL(ti->ti_ack); 368 NTOHS(ti->ti_win); 369 NTOHS(ti->ti_urp); 370 371 /* 372 * Drop TCP, IP headers and TCP options. 373 */ 374 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 375 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 376 377 /* 378 * Locate pcb for segment. 379 */ 380 findpcb: 381 #ifdef IPFIREWALL_FORWARD 382 if (ip_fw_fwd_addr != NULL) { 383 /* 384 * Diverted. Pretend to be the destination. 385 * already got one like this? 386 */ 387 inp = in_pcblookup_hash(&tcbinfo, ti->ti_src, ti->ti_sport, 388 ti->ti_dst, ti->ti_dport, 0); 389 if (!inp) { 390 /* 391 * No, then it's new. Try find the ambushing socket 392 */ 393 if (!ip_fw_fwd_addr->sin_port) { 394 inp = in_pcblookup_hash(&tcbinfo, ti->ti_src, 395 ti->ti_sport, ip_fw_fwd_addr->sin_addr, 396 ti->ti_dport, 1); 397 } else { 398 inp = in_pcblookup_hash(&tcbinfo, 399 ti->ti_src, ti->ti_sport, 400 ip_fw_fwd_addr->sin_addr, 401 ntohs(ip_fw_fwd_addr->sin_port), 1); 402 } 403 } 404 ip_fw_fwd_addr = NULL; 405 } else 406 #endif /* IPFIREWALL_FORWARD */ 407 408 inp = in_pcblookup_hash(&tcbinfo, ti->ti_src, ti->ti_sport, 409 ti->ti_dst, ti->ti_dport, 1); 410 411 /* 412 * If the state is CLOSED (i.e., TCB does not exist) then 413 * all data in the incoming segment is discarded. 414 * If the TCB exists but is in CLOSED state, it is embryonic, 415 * but should either do a listen or a connect soon. 416 */ 417 if (inp == NULL) { 418 if (log_in_vain && tiflags & TH_SYN) { 419 char buf[4*sizeof "123"]; 420 421 strcpy(buf, inet_ntoa(ti->ti_dst)); 422 log(LOG_INFO, 423 "Connection attempt to TCP %s:%d from %s:%d\n", 424 buf, ntohs(ti->ti_dport), inet_ntoa(ti->ti_src), 425 ntohs(ti->ti_sport)); 426 } 427 #ifdef ICMP_BANDLIM 428 if (badport_bandlim(1) < 0) 429 goto drop; 430 #endif 431 goto dropwithreset; 432 } 433 tp = intotcpcb(inp); 434 if (tp == 0) 435 goto maybedropwithreset; 436 if (tp->t_state == TCPS_CLOSED) 437 goto drop; 438 439 /* Unscale the window into a 32-bit value. */ 440 if ((tiflags & TH_SYN) == 0) 441 tiwin = ti->ti_win << tp->snd_scale; 442 else 443 tiwin = ti->ti_win; 444 445 so = inp->inp_socket; 446 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 447 #ifdef TCPDEBUG 448 if (so->so_options & SO_DEBUG) { 449 ostate = tp->t_state; 450 tcp_saveti = *ti; 451 } 452 #endif 453 if (so->so_options & SO_ACCEPTCONN) { 454 register struct tcpcb *tp0 = tp; 455 struct socket *so2; 456 if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { 457 /* 458 * Note: dropwithreset makes sure we don't 459 * send a RST in response to a RST. 460 */ 461 if (tiflags & TH_ACK) { 462 tcpstat.tcps_badsyn++; 463 goto maybedropwithreset; 464 } 465 goto drop; 466 } 467 so2 = sonewconn(so, 0); 468 if (so2 == 0) { 469 tcpstat.tcps_listendrop++; 470 so2 = sodropablereq(so); 471 if (so2) { 472 tcp_drop(sototcpcb(so2), ETIMEDOUT); 473 so2 = sonewconn(so, 0); 474 } 475 if (!so2) 476 goto drop; 477 } 478 so = so2; 479 /* 480 * This is ugly, but .... 481 * 482 * Mark socket as temporary until we're 483 * committed to keeping it. The code at 484 * ``drop'' and ``dropwithreset'' check the 485 * flag dropsocket to see if the temporary 486 * socket created here should be discarded. 487 * We mark the socket as discardable until 488 * we're committed to it below in TCPS_LISTEN. 489 */ 490 dropsocket++; 491 inp = (struct inpcb *)so->so_pcb; 492 inp->inp_laddr = ti->ti_dst; 493 inp->inp_lport = ti->ti_dport; 494 if (in_pcbinshash(inp) != 0) { 495 /* 496 * Undo the assignments above if we failed to put 497 * the PCB on the hash lists. 498 */ 499 inp->inp_laddr.s_addr = INADDR_ANY; 500 inp->inp_lport = 0; 501 goto drop; 502 } 503 inp->inp_options = ip_srcroute(); 504 tp = intotcpcb(inp); 505 tp->t_state = TCPS_LISTEN; 506 tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT); 507 508 /* Compute proper scaling value from buffer space */ 509 while (tp->request_r_scale < TCP_MAX_WINSHIFT && 510 TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) 511 tp->request_r_scale++; 512 } 513 } 514 515 /* 516 * Segment received on connection. 517 * Reset idle time and keep-alive timer. 518 */ 519 tp->t_idle = 0; 520 if (TCPS_HAVEESTABLISHED(tp->t_state)) 521 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 522 523 /* 524 * Process options if not in LISTEN state, 525 * else do it below (after getting remote address). 526 */ 527 if (tp->t_state != TCPS_LISTEN) 528 tcp_dooptions(tp, optp, optlen, ti, &to); 529 530 /* 531 * Header prediction: check for the two common cases 532 * of a uni-directional data xfer. If the packet has 533 * no control flags, is in-sequence, the window didn't 534 * change and we're not retransmitting, it's a 535 * candidate. If the length is zero and the ack moved 536 * forward, we're the sender side of the xfer. Just 537 * free the data acked & wake any higher level process 538 * that was blocked waiting for space. If the length 539 * is non-zero and the ack didn't move, we're the 540 * receiver side. If we're getting packets in-order 541 * (the reassembly queue is empty), add the data to 542 * the socket buffer and note that we need a delayed ack. 543 * Make sure that the hidden state-flags are also off. 544 * Since we check for TCPS_ESTABLISHED above, it can only 545 * be TH_NEEDSYN. 546 */ 547 if (tp->t_state == TCPS_ESTABLISHED && 548 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 549 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 550 ((to.to_flag & TOF_TS) == 0 || 551 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && 552 /* 553 * Using the CC option is compulsory if once started: 554 * the segment is OK if no T/TCP was negotiated or 555 * if the segment has a CC option equal to CCrecv 556 */ 557 ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || 558 ((to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && 559 ti->ti_seq == tp->rcv_nxt && 560 tiwin && tiwin == tp->snd_wnd && 561 tp->snd_nxt == tp->snd_max) { 562 563 /* 564 * If last ACK falls within this segment's sequence numbers, 565 * record the timestamp. 566 * NOTE that the test is modified according to the latest 567 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 568 */ 569 if ((to.to_flag & TOF_TS) != 0 && 570 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { 571 tp->ts_recent_age = tcp_now; 572 tp->ts_recent = to.to_tsval; 573 } 574 575 if (ti->ti_len == 0) { 576 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 577 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 578 tp->snd_cwnd >= tp->snd_wnd && 579 tp->t_dupacks < tcprexmtthresh) { 580 /* 581 * this is a pure ack for outstanding data. 582 */ 583 ++tcpstat.tcps_predack; 584 if ((to.to_flag & TOF_TS) != 0) 585 tcp_xmit_timer(tp, 586 tcp_now - to.to_tsecr + 1); 587 else if (tp->t_rtt && 588 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 589 tcp_xmit_timer(tp, tp->t_rtt); 590 acked = ti->ti_ack - tp->snd_una; 591 tcpstat.tcps_rcvackpack++; 592 tcpstat.tcps_rcvackbyte += acked; 593 sbdrop(&so->so_snd, acked); 594 tp->snd_una = ti->ti_ack; 595 m_freem(m); 596 597 /* 598 * If all outstanding data are acked, stop 599 * retransmit timer, otherwise restart timer 600 * using current (possibly backed-off) value. 601 * If process is waiting for space, 602 * wakeup/selwakeup/signal. If data 603 * are ready to send, let tcp_output 604 * decide between more output or persist. 605 */ 606 if (tp->snd_una == tp->snd_max) 607 tp->t_timer[TCPT_REXMT] = 0; 608 else if (tp->t_timer[TCPT_PERSIST] == 0) 609 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 610 611 sowwakeup(so); 612 if (so->so_snd.sb_cc) 613 (void) tcp_output(tp); 614 return; 615 } 616 } else if (ti->ti_ack == tp->snd_una && 617 tp->t_segq == NULL && 618 ti->ti_len <= sbspace(&so->so_rcv)) { 619 /* 620 * this is a pure, in-sequence data packet 621 * with nothing on the reassembly queue and 622 * we have enough buffer space to take it. 623 */ 624 ++tcpstat.tcps_preddat; 625 tp->rcv_nxt += ti->ti_len; 626 tcpstat.tcps_rcvpack++; 627 tcpstat.tcps_rcvbyte += ti->ti_len; 628 /* 629 * Add data to socket buffer. 630 */ 631 sbappend(&so->so_rcv, m); 632 sorwakeup(so); 633 if (tcp_delack_enabled) { 634 tp->t_flags |= TF_DELACK; 635 } else { 636 tp->t_flags |= TF_ACKNOW; 637 tcp_output(tp); 638 } 639 return; 640 } 641 } 642 643 /* 644 * Calculate amount of space in receive window, 645 * and then do TCP input processing. 646 * Receive window is amount of space in rcv queue, 647 * but not less than advertised window. 648 */ 649 { int win; 650 651 win = sbspace(&so->so_rcv); 652 if (win < 0) 653 win = 0; 654 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 655 } 656 657 switch (tp->t_state) { 658 659 /* 660 * If the state is LISTEN then ignore segment if it contains an RST. 661 * If the segment contains an ACK then it is bad and send a RST. 662 * If it does not contain a SYN then it is not interesting; drop it. 663 * If it is from this socket, drop it, it must be forged. 664 * Don't bother responding if the destination was a broadcast. 665 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 666 * tp->iss, and send a segment: 667 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 668 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 669 * Fill in remote peer address fields if not previously specified. 670 * Enter SYN_RECEIVED state, and process any other fields of this 671 * segment in this state. 672 */ 673 case TCPS_LISTEN: { 674 register struct sockaddr_in *sin; 675 676 if (tiflags & TH_RST) 677 goto drop; 678 if (tiflags & TH_ACK) 679 goto maybedropwithreset; 680 if ((tiflags & TH_SYN) == 0) 681 goto drop; 682 if ((ti->ti_dport == ti->ti_sport) && 683 (ti->ti_dst.s_addr == ti->ti_src.s_addr)) 684 goto drop; 685 /* 686 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 687 * in_broadcast() should never return true on a received 688 * packet with M_BCAST not set. 689 */ 690 if (m->m_flags & (M_BCAST|M_MCAST) || 691 IN_MULTICAST(ntohl(ti->ti_src.s_addr)) || 692 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 693 goto drop; 694 MALLOC(sin, struct sockaddr_in *, sizeof *sin, M_SONAME, 695 M_NOWAIT); 696 if (sin == NULL) 697 goto drop; 698 sin->sin_family = AF_INET; 699 sin->sin_len = sizeof(*sin); 700 sin->sin_addr = ti->ti_src; 701 sin->sin_port = ti->ti_sport; 702 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 703 laddr = inp->inp_laddr; 704 if (inp->inp_laddr.s_addr == INADDR_ANY) 705 inp->inp_laddr = ti->ti_dst; 706 if (in_pcbconnect(inp, (struct sockaddr *)sin, &proc0)) { 707 inp->inp_laddr = laddr; 708 FREE(sin, M_SONAME); 709 goto drop; 710 } 711 FREE(sin, M_SONAME); 712 tp->t_template = tcp_template(tp); 713 if (tp->t_template == 0) { 714 tp = tcp_drop(tp, ENOBUFS); 715 dropsocket = 0; /* socket is already gone */ 716 goto drop; 717 } 718 if ((taop = tcp_gettaocache(inp)) == NULL) { 719 taop = &tao_noncached; 720 bzero(taop, sizeof(*taop)); 721 } 722 tcp_dooptions(tp, optp, optlen, ti, &to); 723 if (iss) 724 tp->iss = iss; 725 else { 726 #ifdef TCP_COMPAT_42 727 tcp_iss += TCP_ISSINCR/2; 728 tp->iss = tcp_iss; 729 #else 730 tp->iss = tcp_rndiss_next(); 731 #endif /* TCP_COMPAT_42 */ 732 } 733 tp->irs = ti->ti_seq; 734 tcp_sendseqinit(tp); 735 tcp_rcvseqinit(tp); 736 /* 737 * Initialization of the tcpcb for transaction; 738 * set SND.WND = SEG.WND, 739 * initialize CCsend and CCrecv. 740 */ 741 tp->snd_wnd = tiwin; /* initial send-window */ 742 tp->cc_send = CC_INC(tcp_ccgen); 743 tp->cc_recv = to.to_cc; 744 /* 745 * Perform TAO test on incoming CC (SEG.CC) option, if any. 746 * - compare SEG.CC against cached CC from the same host, 747 * if any. 748 * - if SEG.CC > chached value, SYN must be new and is accepted 749 * immediately: save new CC in the cache, mark the socket 750 * connected, enter ESTABLISHED state, turn on flag to 751 * send a SYN in the next segment. 752 * A virtual advertised window is set in rcv_adv to 753 * initialize SWS prevention. Then enter normal segment 754 * processing: drop SYN, process data and FIN. 755 * - otherwise do a normal 3-way handshake. 756 */ 757 if ((to.to_flag & TOF_CC) != 0) { 758 if (((tp->t_flags & TF_NOPUSH) != 0) && 759 taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { 760 761 taop->tao_cc = to.to_cc; 762 tp->t_state = TCPS_ESTABLISHED; 763 764 /* 765 * If there is a FIN, or if there is data and the 766 * connection is local, then delay SYN,ACK(SYN) in 767 * the hope of piggy-backing it on a response 768 * segment. Otherwise must send ACK now in case 769 * the other side is slow starting. 770 */ 771 if (tcp_delack_enabled && ((tiflags & TH_FIN) || (ti->ti_len != 0 && 772 in_localaddr(inp->inp_faddr)))) 773 tp->t_flags |= (TF_DELACK | TF_NEEDSYN); 774 else 775 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 776 777 /* 778 * Limit the `virtual advertised window' to TCP_MAXWIN 779 * here. Even if we requested window scaling, it will 780 * become effective only later when our SYN is acked. 781 */ 782 tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN); 783 tcpstat.tcps_connects++; 784 soisconnected(so); 785 tp->t_timer[TCPT_KEEP] = tcp_keepinit; 786 dropsocket = 0; /* committed to socket */ 787 tcpstat.tcps_accepts++; 788 goto trimthenstep6; 789 } 790 /* else do standard 3-way handshake */ 791 } else { 792 /* 793 * No CC option, but maybe CC.NEW: 794 * invalidate cached value. 795 */ 796 taop->tao_cc = 0; 797 } 798 /* 799 * TAO test failed or there was no CC option, 800 * do a standard 3-way handshake. 801 */ 802 tp->t_flags |= TF_ACKNOW; 803 tp->t_state = TCPS_SYN_RECEIVED; 804 tp->t_timer[TCPT_KEEP] = tcp_keepinit; 805 dropsocket = 0; /* committed to socket */ 806 tcpstat.tcps_accepts++; 807 goto trimthenstep6; 808 } 809 810 /* 811 * If the state is SYN_RECEIVED: 812 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 813 */ 814 case TCPS_SYN_RECEIVED: 815 if ((tiflags & TH_ACK) && 816 (SEQ_LEQ(ti->ti_ack, tp->snd_una) || 817 SEQ_GT(ti->ti_ack, tp->snd_max))) 818 goto maybedropwithreset; 819 break; 820 821 /* 822 * If the state is SYN_SENT: 823 * if seg contains an ACK, but not for our SYN, drop the input. 824 * if seg contains a RST, then drop the connection. 825 * if seg does not contain SYN, then drop it. 826 * Otherwise this is an acceptable SYN segment 827 * initialize tp->rcv_nxt and tp->irs 828 * if seg contains ack then advance tp->snd_una 829 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 830 * arrange for segment to be acked (eventually) 831 * continue processing rest of data/controls, beginning with URG 832 */ 833 case TCPS_SYN_SENT: 834 if ((taop = tcp_gettaocache(inp)) == NULL) { 835 taop = &tao_noncached; 836 bzero(taop, sizeof(*taop)); 837 } 838 839 if ((tiflags & TH_ACK) && 840 (SEQ_LEQ(ti->ti_ack, tp->iss) || 841 SEQ_GT(ti->ti_ack, tp->snd_max))) { 842 /* 843 * If we have a cached CCsent for the remote host, 844 * hence we haven't just crashed and restarted, 845 * do not send a RST. This may be a retransmission 846 * from the other side after our earlier ACK was lost. 847 * Our new SYN, when it arrives, will serve as the 848 * needed ACK. 849 */ 850 if (taop->tao_ccsent != 0) 851 goto drop; 852 else 853 goto dropwithreset; 854 } 855 if (tiflags & TH_RST) { 856 if (tiflags & TH_ACK) 857 tp = tcp_drop(tp, ECONNREFUSED); 858 goto drop; 859 } 860 if ((tiflags & TH_SYN) == 0) 861 goto drop; 862 tp->snd_wnd = ti->ti_win; /* initial send window */ 863 tp->cc_recv = to.to_cc; /* foreign CC */ 864 865 tp->irs = ti->ti_seq; 866 tcp_rcvseqinit(tp); 867 if (tiflags & TH_ACK) { 868 /* 869 * Our SYN was acked. If segment contains CC.ECHO 870 * option, check it to make sure this segment really 871 * matches our SYN. If not, just drop it as old 872 * duplicate, but send an RST if we're still playing 873 * by the old rules. If no CC.ECHO option, make sure 874 * we don't get fooled into using T/TCP. 875 */ 876 if (to.to_flag & TOF_CCECHO) { 877 if (tp->cc_send != to.to_ccecho) 878 if (taop->tao_ccsent != 0) 879 goto drop; 880 else 881 goto dropwithreset; 882 } else 883 tp->t_flags &= ~TF_RCVD_CC; 884 tcpstat.tcps_connects++; 885 soisconnected(so); 886 /* Do window scaling on this connection? */ 887 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 888 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 889 tp->snd_scale = tp->requested_s_scale; 890 tp->rcv_scale = tp->request_r_scale; 891 } 892 /* Segment is acceptable, update cache if undefined. */ 893 if (taop->tao_ccsent == 0) 894 taop->tao_ccsent = to.to_ccecho; 895 896 tp->rcv_adv += tp->rcv_wnd; 897 tp->snd_una++; /* SYN is acked */ 898 /* 899 * If there's data, delay ACK; if there's also a FIN 900 * ACKNOW will be turned on later. 901 */ 902 if (tcp_delack_enabled && ti->ti_len != 0) 903 tp->t_flags |= TF_DELACK; 904 else 905 tp->t_flags |= TF_ACKNOW; 906 /* 907 * Received <SYN,ACK> in SYN_SENT[*] state. 908 * Transitions: 909 * SYN_SENT --> ESTABLISHED 910 * SYN_SENT* --> FIN_WAIT_1 911 */ 912 if (tp->t_flags & TF_NEEDFIN) { 913 tp->t_state = TCPS_FIN_WAIT_1; 914 tp->t_flags &= ~TF_NEEDFIN; 915 tiflags &= ~TH_SYN; 916 } else { 917 tp->t_state = TCPS_ESTABLISHED; 918 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 919 } 920 } else { 921 /* 922 * Received initial SYN in SYN-SENT[*] state => simul- 923 * taneous open. If segment contains CC option and there is 924 * a cached CC, apply TAO test; if it succeeds, connection is 925 * half-synchronized. Otherwise, do 3-way handshake: 926 * SYN-SENT -> SYN-RECEIVED 927 * SYN-SENT* -> SYN-RECEIVED* 928 * If there was no CC option, clear cached CC value. 929 */ 930 tp->t_flags |= TF_ACKNOW; 931 tp->t_timer[TCPT_REXMT] = 0; 932 if (to.to_flag & TOF_CC) { 933 if (taop->tao_cc != 0 && 934 CC_GT(to.to_cc, taop->tao_cc)) { 935 /* 936 * update cache and make transition: 937 * SYN-SENT -> ESTABLISHED* 938 * SYN-SENT* -> FIN-WAIT-1* 939 */ 940 taop->tao_cc = to.to_cc; 941 if (tp->t_flags & TF_NEEDFIN) { 942 tp->t_state = TCPS_FIN_WAIT_1; 943 tp->t_flags &= ~TF_NEEDFIN; 944 } else { 945 tp->t_state = TCPS_ESTABLISHED; 946 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 947 } 948 tp->t_flags |= TF_NEEDSYN; 949 } else 950 tp->t_state = TCPS_SYN_RECEIVED; 951 } else { 952 /* CC.NEW or no option => invalidate cache */ 953 taop->tao_cc = 0; 954 tp->t_state = TCPS_SYN_RECEIVED; 955 } 956 } 957 958 trimthenstep6: 959 /* 960 * Advance ti->ti_seq to correspond to first data byte. 961 * If data, trim to stay within window, 962 * dropping FIN if necessary. 963 */ 964 ti->ti_seq++; 965 if (ti->ti_len > tp->rcv_wnd) { 966 todrop = ti->ti_len - tp->rcv_wnd; 967 m_adj(m, -todrop); 968 ti->ti_len = tp->rcv_wnd; 969 tiflags &= ~TH_FIN; 970 tcpstat.tcps_rcvpackafterwin++; 971 tcpstat.tcps_rcvbyteafterwin += todrop; 972 } 973 tp->snd_wl1 = ti->ti_seq - 1; 974 tp->rcv_up = ti->ti_seq; 975 /* 976 * Client side of transaction: already sent SYN and data. 977 * If the remote host used T/TCP to validate the SYN, 978 * our data will be ACK'd; if so, enter normal data segment 979 * processing in the middle of step 5, ack processing. 980 * Otherwise, goto step 6. 981 */ 982 if (tiflags & TH_ACK) 983 goto process_ACK; 984 goto step6; 985 /* 986 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 987 * if segment contains a SYN and CC [not CC.NEW] option: 988 * if state == TIME_WAIT and connection duration > MSL, 989 * drop packet and send RST; 990 * 991 * if SEG.CC > CCrecv then is new SYN, and can implicitly 992 * ack the FIN (and data) in retransmission queue. 993 * Complete close and delete TCPCB. Then reprocess 994 * segment, hoping to find new TCPCB in LISTEN state; 995 * 996 * else must be old SYN; drop it. 997 * else do normal processing. 998 */ 999 case TCPS_LAST_ACK: 1000 case TCPS_CLOSING: 1001 case TCPS_TIME_WAIT: 1002 if ((tiflags & TH_SYN) && 1003 (to.to_flag & TOF_CC) && tp->cc_recv != 0) { 1004 if (tp->t_state == TCPS_TIME_WAIT && 1005 tp->t_duration > TCPTV_MSL) 1006 goto dropwithreset; 1007 if (CC_GT(to.to_cc, tp->cc_recv)) { 1008 tp = tcp_close(tp); 1009 goto findpcb; 1010 } 1011 else 1012 goto drop; 1013 } 1014 break; /* continue normal processing */ 1015 } 1016 1017 /* 1018 * States other than LISTEN or SYN_SENT. 1019 * First check the RST flag and sequence number since reset segments 1020 * are exempt from the timestamp and connection count tests. This 1021 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1022 * below which allowed reset segments in half the sequence space 1023 * to fall though and be processed (which gives forged reset 1024 * segments with a random sequence number a 50 percent chance of 1025 * killing a connection). 1026 * Then check timestamp, if present. 1027 * Then check the connection count, if present. 1028 * Then check that at least some bytes of segment are within 1029 * receive window. If segment begins before rcv_nxt, 1030 * drop leading data (and SYN); if nothing left, just ack. 1031 * 1032 * 1033 * If the RST bit is set, check the sequence number to see 1034 * if this is a valid reset segment. 1035 * RFC 793 page 37: 1036 * In all states except SYN-SENT, all reset (RST) segments 1037 * are validated by checking their SEQ-fields. A reset is 1038 * valid if its sequence number is in the window. 1039 * Note: this does not take into account delayed ACKs, so 1040 * we should test against last_ack_sent instead of rcv_nxt. 1041 * Also, it does not make sense to allow reset segments with 1042 * sequence numbers greater than last_ack_sent to be processed 1043 * since these sequence numbers are just the acknowledgement 1044 * numbers in our outgoing packets being echoed back at us, 1045 * and these acknowledgement numbers are monotonically 1046 * increasing. 1047 * If we have multiple segments in flight, the intial reset 1048 * segment sequence numbers will be to the left of last_ack_sent, 1049 * but they will eventually catch up. 1050 * In any case, it never made sense to trim reset segments to 1051 * fit the receive window since RFC 1122 says: 1052 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1053 * 1054 * A TCP SHOULD allow a received RST segment to include data. 1055 * 1056 * DISCUSSION 1057 * It has been suggested that a RST segment could contain 1058 * ASCII text that encoded and explained the cause of the 1059 * RST. No standard has yet been established for such 1060 * data. 1061 * 1062 * If the reset segment passes the sequence number test examine 1063 * the state: 1064 * SYN_RECEIVED STATE: 1065 * If passive open, return to LISTEN state. 1066 * If active open, inform user that connection was refused. 1067 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 1068 * Inform user that connection was reset, and close tcb. 1069 * CLOSING, LAST_ACK, TIME_WAIT STATES 1070 * Close the tcb. 1071 * TIME_WAIT state: 1072 * Drop the segment - see Stevens, vol. 2, p. 964 and 1073 * RFC 1337. 1074 */ 1075 if (tiflags & TH_RST) { 1076 if (tp->last_ack_sent == ti->ti_seq) { 1077 switch (tp->t_state) { 1078 1079 case TCPS_SYN_RECEIVED: 1080 so->so_error = ECONNREFUSED; 1081 goto close; 1082 1083 case TCPS_ESTABLISHED: 1084 case TCPS_FIN_WAIT_1: 1085 case TCPS_FIN_WAIT_2: 1086 case TCPS_CLOSE_WAIT: 1087 so->so_error = ECONNRESET; 1088 close: 1089 tp->t_state = TCPS_CLOSED; 1090 tcpstat.tcps_drops++; 1091 tp = tcp_close(tp); 1092 break; 1093 1094 case TCPS_CLOSING: 1095 case TCPS_LAST_ACK: 1096 tp = tcp_close(tp); 1097 break; 1098 1099 case TCPS_TIME_WAIT: 1100 break; 1101 } 1102 } 1103 goto drop; 1104 } 1105 1106 /* 1107 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1108 * and it's less than ts_recent, drop it. 1109 */ 1110 if ((to.to_flag & TOF_TS) != 0 && tp->ts_recent && 1111 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1112 1113 /* Check to see if ts_recent is over 24 days old. */ 1114 if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1115 /* 1116 * Invalidate ts_recent. If this segment updates 1117 * ts_recent, the age will be reset later and ts_recent 1118 * will get a valid value. If it does not, setting 1119 * ts_recent to zero will at least satisfy the 1120 * requirement that zero be placed in the timestamp 1121 * echo reply when ts_recent isn't valid. The 1122 * age isn't reset until we get a valid ts_recent 1123 * because we don't want out-of-order segments to be 1124 * dropped when ts_recent is old. 1125 */ 1126 tp->ts_recent = 0; 1127 } else { 1128 tcpstat.tcps_rcvduppack++; 1129 tcpstat.tcps_rcvdupbyte += ti->ti_len; 1130 tcpstat.tcps_pawsdrop++; 1131 goto dropafterack; 1132 } 1133 } 1134 1135 /* 1136 * T/TCP mechanism 1137 * If T/TCP was negotiated and the segment doesn't have CC, 1138 * or if its CC is wrong then drop the segment. 1139 * RST segments do not have to comply with this. 1140 */ 1141 if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && 1142 ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) 1143 goto dropafterack; 1144 1145 /* 1146 * In the SYN-RECEIVED state, validate that the packet belongs to 1147 * this connection before trimming the data to fit the receive 1148 * window. Check the sequence number versus IRS since we know 1149 * the sequence numbers haven't wrapped. This is a partial fix 1150 * for the "LAND" DoS attack. 1151 */ 1152 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(ti->ti_seq, tp->irs)) 1153 goto dropwithreset; 1154 1155 todrop = tp->rcv_nxt - ti->ti_seq; 1156 if (todrop > 0) { 1157 if (tiflags & TH_SYN) { 1158 tiflags &= ~TH_SYN; 1159 ti->ti_seq++; 1160 if (ti->ti_urp > 1) 1161 ti->ti_urp--; 1162 else 1163 tiflags &= ~TH_URG; 1164 todrop--; 1165 } 1166 /* 1167 * Following if statement from Stevens, vol. 2, p. 960. 1168 */ 1169 if (todrop > ti->ti_len 1170 || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) { 1171 /* 1172 * Any valid FIN must be to the left of the window. 1173 * At this point the FIN must be a duplicate or out 1174 * of sequence; drop it. 1175 */ 1176 tiflags &= ~TH_FIN; 1177 1178 /* 1179 * Send an ACK to resynchronize and drop any data. 1180 * But keep on processing for RST or ACK. 1181 */ 1182 tp->t_flags |= TF_ACKNOW; 1183 todrop = ti->ti_len; 1184 tcpstat.tcps_rcvduppack++; 1185 tcpstat.tcps_rcvdupbyte += todrop; 1186 } else { 1187 tcpstat.tcps_rcvpartduppack++; 1188 tcpstat.tcps_rcvpartdupbyte += todrop; 1189 } 1190 m_adj(m, todrop); 1191 ti->ti_seq += todrop; 1192 ti->ti_len -= todrop; 1193 if (ti->ti_urp > todrop) 1194 ti->ti_urp -= todrop; 1195 else { 1196 tiflags &= ~TH_URG; 1197 ti->ti_urp = 0; 1198 } 1199 } 1200 1201 /* 1202 * If new data are received on a connection after the 1203 * user processes are gone, then RST the other end. 1204 */ 1205 if ((so->so_state & SS_NOFDREF) && 1206 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 1207 tp = tcp_close(tp); 1208 tcpstat.tcps_rcvafterclose++; 1209 goto dropwithreset; 1210 } 1211 1212 /* 1213 * If segment ends after window, drop trailing data 1214 * (and PUSH and FIN); if nothing left, just ACK. 1215 */ 1216 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 1217 if (todrop > 0) { 1218 tcpstat.tcps_rcvpackafterwin++; 1219 if (todrop >= ti->ti_len) { 1220 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 1221 /* 1222 * If a new connection request is received 1223 * while in TIME_WAIT, drop the old connection 1224 * and start over if the sequence numbers 1225 * are above the previous ones. 1226 */ 1227 if (tiflags & TH_SYN && 1228 tp->t_state == TCPS_TIME_WAIT && 1229 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 1230 #ifdef TCP_COMPAT_42 1231 iss = tp->snd_nxt + TCP_ISSINCR; 1232 #else 1233 iss = tcp_rndiss_next(); 1234 #endif /* TCP_COMPAT_42 */ 1235 tp = tcp_close(tp); 1236 goto findpcb; 1237 } 1238 /* 1239 * If window is closed can only take segments at 1240 * window edge, and have to drop data and PUSH from 1241 * incoming segments. Continue processing, but 1242 * remember to ack. Otherwise, drop segment 1243 * and ack. 1244 */ 1245 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 1246 tp->t_flags |= TF_ACKNOW; 1247 tcpstat.tcps_rcvwinprobe++; 1248 } else 1249 goto dropafterack; 1250 } else 1251 tcpstat.tcps_rcvbyteafterwin += todrop; 1252 m_adj(m, -todrop); 1253 ti->ti_len -= todrop; 1254 tiflags &= ~(TH_PUSH|TH_FIN); 1255 } 1256 1257 /* 1258 * If last ACK falls within this segment's sequence numbers, 1259 * record its timestamp. 1260 * NOTE that the test is modified according to the latest 1261 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1262 */ 1263 if ((to.to_flag & TOF_TS) != 0 && 1264 SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { 1265 tp->ts_recent_age = tcp_now; 1266 tp->ts_recent = to.to_tsval; 1267 } 1268 1269 /* 1270 * If a SYN is in the window, then this is an 1271 * error and we send an RST and drop the connection. 1272 */ 1273 if (tiflags & TH_SYN) { 1274 tp = tcp_drop(tp, ECONNRESET); 1275 goto dropwithreset; 1276 } 1277 1278 /* 1279 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1280 * flag is on (half-synchronized state), then queue data for 1281 * later processing; else drop segment and return. 1282 */ 1283 if ((tiflags & TH_ACK) == 0) { 1284 if (tp->t_state == TCPS_SYN_RECEIVED || 1285 (tp->t_flags & TF_NEEDSYN)) 1286 goto step6; 1287 else 1288 goto drop; 1289 } 1290 1291 /* 1292 * Ack processing. 1293 */ 1294 switch (tp->t_state) { 1295 1296 /* 1297 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1298 * ESTABLISHED state and continue processing. 1299 * The ACK was checked above. 1300 */ 1301 case TCPS_SYN_RECEIVED: 1302 1303 tcpstat.tcps_connects++; 1304 soisconnected(so); 1305 /* Do window scaling? */ 1306 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1307 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1308 tp->snd_scale = tp->requested_s_scale; 1309 tp->rcv_scale = tp->request_r_scale; 1310 } 1311 /* 1312 * Upon successful completion of 3-way handshake, 1313 * update cache.CC if it was undefined, pass any queued 1314 * data to the user, and advance state appropriately. 1315 */ 1316 if ((taop = tcp_gettaocache(inp)) != NULL && 1317 taop->tao_cc == 0) 1318 taop->tao_cc = tp->cc_recv; 1319 1320 /* 1321 * Make transitions: 1322 * SYN-RECEIVED -> ESTABLISHED 1323 * SYN-RECEIVED* -> FIN-WAIT-1 1324 */ 1325 if (tp->t_flags & TF_NEEDFIN) { 1326 tp->t_state = TCPS_FIN_WAIT_1; 1327 tp->t_flags &= ~TF_NEEDFIN; 1328 } else { 1329 tp->t_state = TCPS_ESTABLISHED; 1330 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 1331 } 1332 /* 1333 * If segment contains data or ACK, will call tcp_reass() 1334 * later; if not, do so now to pass queued data to user. 1335 */ 1336 if (ti->ti_len == 0 && (tiflags & TH_FIN) == 0) 1337 (void) tcp_reass(tp, (struct tcpiphdr *)0, 1338 (struct mbuf *)0); 1339 tp->snd_wl1 = ti->ti_seq - 1; 1340 /* fall into ... */ 1341 1342 /* 1343 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1344 * ACKs. If the ack is in the range 1345 * tp->snd_una < ti->ti_ack <= tp->snd_max 1346 * then advance tp->snd_una to ti->ti_ack and drop 1347 * data from the retransmission queue. If this ACK reflects 1348 * more up to date window information we update our window information. 1349 */ 1350 case TCPS_ESTABLISHED: 1351 case TCPS_FIN_WAIT_1: 1352 case TCPS_FIN_WAIT_2: 1353 case TCPS_CLOSE_WAIT: 1354 case TCPS_CLOSING: 1355 case TCPS_LAST_ACK: 1356 case TCPS_TIME_WAIT: 1357 1358 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 1359 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 1360 tcpstat.tcps_rcvdupack++; 1361 /* 1362 * If we have outstanding data (other than 1363 * a window probe), this is a completely 1364 * duplicate ack (ie, window info didn't 1365 * change), the ack is the biggest we've 1366 * seen and we've seen exactly our rexmt 1367 * threshhold of them, assume a packet 1368 * has been dropped and retransmit it. 1369 * Kludge snd_nxt & the congestion 1370 * window so we send only this one 1371 * packet. 1372 * 1373 * We know we're losing at the current 1374 * window size so do congestion avoidance 1375 * (set ssthresh to half the current window 1376 * and pull our congestion window back to 1377 * the new ssthresh). 1378 * 1379 * Dup acks mean that packets have left the 1380 * network (they're now cached at the receiver) 1381 * so bump cwnd by the amount in the receiver 1382 * to keep a constant cwnd packets in the 1383 * network. 1384 */ 1385 if (tp->t_timer[TCPT_REXMT] == 0 || 1386 ti->ti_ack != tp->snd_una) 1387 tp->t_dupacks = 0; 1388 else if (++tp->t_dupacks == tcprexmtthresh) { 1389 tcp_seq onxt = tp->snd_nxt; 1390 u_int win = 1391 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1392 tp->t_maxseg; 1393 1394 if (win < 2) 1395 win = 2; 1396 tp->snd_ssthresh = win * tp->t_maxseg; 1397 tp->t_timer[TCPT_REXMT] = 0; 1398 tp->t_rtt = 0; 1399 tp->snd_nxt = ti->ti_ack; 1400 tp->snd_cwnd = tp->t_maxseg; 1401 (void) tcp_output(tp); 1402 tp->snd_cwnd = tp->snd_ssthresh + 1403 tp->t_maxseg * tp->t_dupacks; 1404 if (SEQ_GT(onxt, tp->snd_nxt)) 1405 tp->snd_nxt = onxt; 1406 goto drop; 1407 } else if (tp->t_dupacks > tcprexmtthresh) { 1408 tp->snd_cwnd += tp->t_maxseg; 1409 (void) tcp_output(tp); 1410 goto drop; 1411 } 1412 } else 1413 tp->t_dupacks = 0; 1414 break; 1415 } 1416 /* 1417 * If the congestion window was inflated to account 1418 * for the other side's cached packets, retract it. 1419 */ 1420 if (tp->t_dupacks >= tcprexmtthresh && 1421 tp->snd_cwnd > tp->snd_ssthresh) 1422 tp->snd_cwnd = tp->snd_ssthresh; 1423 tp->t_dupacks = 0; 1424 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 1425 tcpstat.tcps_rcvacktoomuch++; 1426 goto dropafterack; 1427 } 1428 /* 1429 * If we reach this point, ACK is not a duplicate, 1430 * i.e., it ACKs something we sent. 1431 */ 1432 if (tp->t_flags & TF_NEEDSYN) { 1433 /* 1434 * T/TCP: Connection was half-synchronized, and our 1435 * SYN has been ACK'd (so connection is now fully 1436 * synchronized). Go to non-starred state, 1437 * increment snd_una for ACK of SYN, and check if 1438 * we can do window scaling. 1439 */ 1440 tp->t_flags &= ~TF_NEEDSYN; 1441 tp->snd_una++; 1442 /* Do window scaling? */ 1443 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1444 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1445 tp->snd_scale = tp->requested_s_scale; 1446 tp->rcv_scale = tp->request_r_scale; 1447 } 1448 } 1449 1450 process_ACK: 1451 acked = ti->ti_ack - tp->snd_una; 1452 tcpstat.tcps_rcvackpack++; 1453 tcpstat.tcps_rcvackbyte += acked; 1454 1455 /* 1456 * If we have a timestamp reply, update smoothed 1457 * round trip time. If no timestamp is present but 1458 * transmit timer is running and timed sequence 1459 * number was acked, update smoothed round trip time. 1460 * Since we now have an rtt measurement, cancel the 1461 * timer backoff (cf., Phil Karn's retransmit alg.). 1462 * Recompute the initial retransmit timer. 1463 */ 1464 if (to.to_flag & TOF_TS) 1465 tcp_xmit_timer(tp, tcp_now - to.to_tsecr + 1); 1466 else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 1467 tcp_xmit_timer(tp,tp->t_rtt); 1468 1469 /* 1470 * If all outstanding data is acked, stop retransmit 1471 * timer and remember to restart (more output or persist). 1472 * If there is more data to be acked, restart retransmit 1473 * timer, using current (possibly backed-off) value. 1474 */ 1475 if (ti->ti_ack == tp->snd_max) { 1476 tp->t_timer[TCPT_REXMT] = 0; 1477 needoutput = 1; 1478 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1479 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1480 1481 /* 1482 * If no data (only SYN) was ACK'd, 1483 * skip rest of ACK processing. 1484 */ 1485 if (acked == 0) 1486 goto step6; 1487 1488 /* 1489 * When new data is acked, open the congestion window. 1490 * If the window gives us less than ssthresh packets 1491 * in flight, open exponentially (maxseg per packet). 1492 * Otherwise open linearly: maxseg per window 1493 * (maxseg^2 / cwnd per packet). 1494 */ 1495 { 1496 register u_int cw = tp->snd_cwnd; 1497 register u_int incr = tp->t_maxseg; 1498 1499 if (cw > tp->snd_ssthresh) 1500 incr = incr * incr / cw; 1501 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1502 } 1503 if (acked > so->so_snd.sb_cc) { 1504 tp->snd_wnd -= so->so_snd.sb_cc; 1505 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1506 ourfinisacked = 1; 1507 } else { 1508 sbdrop(&so->so_snd, acked); 1509 tp->snd_wnd -= acked; 1510 ourfinisacked = 0; 1511 } 1512 sowwakeup(so); 1513 tp->snd_una = ti->ti_ack; 1514 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1515 tp->snd_nxt = tp->snd_una; 1516 1517 switch (tp->t_state) { 1518 1519 /* 1520 * In FIN_WAIT_1 STATE in addition to the processing 1521 * for the ESTABLISHED state if our FIN is now acknowledged 1522 * then enter FIN_WAIT_2. 1523 */ 1524 case TCPS_FIN_WAIT_1: 1525 if (ourfinisacked) { 1526 /* 1527 * If we can't receive any more 1528 * data, then closing user can proceed. 1529 * Starting the timer is contrary to the 1530 * specification, but if we don't get a FIN 1531 * we'll hang forever. 1532 */ 1533 if (so->so_state & SS_CANTRCVMORE) { 1534 soisdisconnected(so); 1535 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 1536 } 1537 tp->t_state = TCPS_FIN_WAIT_2; 1538 } 1539 break; 1540 1541 /* 1542 * In CLOSING STATE in addition to the processing for 1543 * the ESTABLISHED state if the ACK acknowledges our FIN 1544 * then enter the TIME-WAIT state, otherwise ignore 1545 * the segment. 1546 */ 1547 case TCPS_CLOSING: 1548 if (ourfinisacked) { 1549 tp->t_state = TCPS_TIME_WAIT; 1550 tcp_canceltimers(tp); 1551 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1552 if (tp->cc_recv != 0 && 1553 tp->t_duration < TCPTV_MSL) 1554 tp->t_timer[TCPT_2MSL] = 1555 tp->t_rxtcur * TCPTV_TWTRUNC; 1556 else 1557 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1558 soisdisconnected(so); 1559 } 1560 break; 1561 1562 /* 1563 * In LAST_ACK, we may still be waiting for data to drain 1564 * and/or to be acked, as well as for the ack of our FIN. 1565 * If our FIN is now acknowledged, delete the TCB, 1566 * enter the closed state and return. 1567 */ 1568 case TCPS_LAST_ACK: 1569 if (ourfinisacked) { 1570 tp = tcp_close(tp); 1571 goto drop; 1572 } 1573 break; 1574 1575 /* 1576 * In TIME_WAIT state the only thing that should arrive 1577 * is a retransmission of the remote FIN. Acknowledge 1578 * it and restart the finack timer. 1579 */ 1580 case TCPS_TIME_WAIT: 1581 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1582 goto dropafterack; 1583 } 1584 } 1585 1586 step6: 1587 /* 1588 * Update window information. 1589 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1590 */ 1591 if ((tiflags & TH_ACK) && 1592 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || 1593 (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 1594 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) { 1595 /* keep track of pure window updates */ 1596 if (ti->ti_len == 0 && 1597 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1598 tcpstat.tcps_rcvwinupd++; 1599 tp->snd_wnd = tiwin; 1600 tp->snd_wl1 = ti->ti_seq; 1601 tp->snd_wl2 = ti->ti_ack; 1602 if (tp->snd_wnd > tp->max_sndwnd) 1603 tp->max_sndwnd = tp->snd_wnd; 1604 needoutput = 1; 1605 } 1606 1607 /* 1608 * Process segments with URG. 1609 */ 1610 if ((tiflags & TH_URG) && ti->ti_urp && 1611 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1612 /* 1613 * This is a kludge, but if we receive and accept 1614 * random urgent pointers, we'll crash in 1615 * soreceive. It's hard to imagine someone 1616 * actually wanting to send this much urgent data. 1617 */ 1618 if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { 1619 ti->ti_urp = 0; /* XXX */ 1620 tiflags &= ~TH_URG; /* XXX */ 1621 goto dodata; /* XXX */ 1622 } 1623 /* 1624 * If this segment advances the known urgent pointer, 1625 * then mark the data stream. This should not happen 1626 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1627 * a FIN has been received from the remote side. 1628 * In these states we ignore the URG. 1629 * 1630 * According to RFC961 (Assigned Protocols), 1631 * the urgent pointer points to the last octet 1632 * of urgent data. We continue, however, 1633 * to consider it to indicate the first octet 1634 * of data past the urgent section as the original 1635 * spec states (in one of two places). 1636 */ 1637 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1638 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1639 so->so_oobmark = so->so_rcv.sb_cc + 1640 (tp->rcv_up - tp->rcv_nxt) - 1; 1641 if (so->so_oobmark == 0) 1642 so->so_state |= SS_RCVATMARK; 1643 sohasoutofband(so); 1644 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1645 } 1646 /* 1647 * Remove out of band data so doesn't get presented to user. 1648 * This can happen independent of advancing the URG pointer, 1649 * but if two URG's are pending at once, some out-of-band 1650 * data may creep in... ick. 1651 */ 1652 if (ti->ti_urp <= (u_long)ti->ti_len 1653 #ifdef SO_OOBINLINE 1654 && (so->so_options & SO_OOBINLINE) == 0 1655 #endif 1656 ) 1657 tcp_pulloutofband(so, ti, m); 1658 } else 1659 /* 1660 * If no out of band data is expected, 1661 * pull receive urgent pointer along 1662 * with the receive window. 1663 */ 1664 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1665 tp->rcv_up = tp->rcv_nxt; 1666 dodata: /* XXX */ 1667 1668 /* 1669 * Process the segment text, merging it into the TCP sequencing queue, 1670 * and arranging for acknowledgment of receipt if necessary. 1671 * This process logically involves adjusting tp->rcv_wnd as data 1672 * is presented to the user (this happens in tcp_usrreq.c, 1673 * case PRU_RCVD). If a FIN has already been received on this 1674 * connection then we just ignore the text. 1675 */ 1676 if ((ti->ti_len || (tiflags&TH_FIN)) && 1677 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1678 TCP_REASS(tp, ti, m, so, tiflags); 1679 /* 1680 * Note the amount of data that peer has sent into 1681 * our window, in order to estimate the sender's 1682 * buffer size. 1683 */ 1684 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1685 } else { 1686 m_freem(m); 1687 tiflags &= ~TH_FIN; 1688 } 1689 1690 /* 1691 * If FIN is received ACK the FIN and let the user know 1692 * that the connection is closing. 1693 */ 1694 if (tiflags & TH_FIN) { 1695 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1696 socantrcvmore(so); 1697 /* 1698 * If connection is half-synchronized 1699 * (ie NEEDSYN flag on) then delay ACK, 1700 * so it may be piggybacked when SYN is sent. 1701 * Otherwise, since we received a FIN then no 1702 * more input can be expected, send ACK now. 1703 */ 1704 if (tcp_delack_enabled && (tp->t_flags & TF_NEEDSYN)) 1705 tp->t_flags |= TF_DELACK; 1706 else 1707 tp->t_flags |= TF_ACKNOW; 1708 tp->rcv_nxt++; 1709 } 1710 switch (tp->t_state) { 1711 1712 /* 1713 * In SYN_RECEIVED and ESTABLISHED STATES 1714 * enter the CLOSE_WAIT state. 1715 */ 1716 case TCPS_SYN_RECEIVED: 1717 case TCPS_ESTABLISHED: 1718 tp->t_state = TCPS_CLOSE_WAIT; 1719 break; 1720 1721 /* 1722 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1723 * enter the CLOSING state. 1724 */ 1725 case TCPS_FIN_WAIT_1: 1726 tp->t_state = TCPS_CLOSING; 1727 break; 1728 1729 /* 1730 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1731 * starting the time-wait timer, turning off the other 1732 * standard timers. 1733 */ 1734 case TCPS_FIN_WAIT_2: 1735 tp->t_state = TCPS_TIME_WAIT; 1736 tcp_canceltimers(tp); 1737 /* Shorten TIME_WAIT [RFC-1644, p.28] */ 1738 if (tp->cc_recv != 0 && 1739 tp->t_duration < TCPTV_MSL) { 1740 tp->t_timer[TCPT_2MSL] = 1741 tp->t_rxtcur * TCPTV_TWTRUNC; 1742 /* For transaction client, force ACK now. */ 1743 tp->t_flags |= TF_ACKNOW; 1744 } 1745 else 1746 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1747 soisdisconnected(so); 1748 break; 1749 1750 /* 1751 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1752 */ 1753 case TCPS_TIME_WAIT: 1754 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1755 break; 1756 } 1757 } 1758 #ifdef TCPDEBUG 1759 if (so->so_options & SO_DEBUG) 1760 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1761 #endif 1762 1763 /* 1764 * Return any desired output. 1765 */ 1766 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1767 (void) tcp_output(tp); 1768 return; 1769 1770 dropafterack: 1771 /* 1772 * Generate an ACK dropping incoming segment if it occupies 1773 * sequence space, where the ACK reflects our state. 1774 * 1775 * We can now skip the test for the RST flag since all 1776 * paths to this code happen after packets containing 1777 * RST have been dropped. 1778 * 1779 * In the SYN-RECEIVED state, don't send an ACK unless the 1780 * segment we received passes the SYN-RECEIVED ACK test. 1781 * If it fails send a RST. This breaks the loop in the 1782 * "LAND" DoS attack, and also prevents an ACK storm 1783 * between two listening ports that have been sent forged 1784 * SYN segments, each with the source address of the other. 1785 */ 1786 if (tp->t_state == TCPS_SYN_RECEIVED && (tiflags & TH_ACK) && 1787 (SEQ_GT(tp->snd_una, ti->ti_ack) || 1788 SEQ_GT(ti->ti_ack, tp->snd_max)) ) 1789 goto maybedropwithreset; 1790 #ifdef TCPDEBUG 1791 if (so->so_options & SO_DEBUG) 1792 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1793 #endif 1794 m_freem(m); 1795 tp->t_flags |= TF_ACKNOW; 1796 (void) tcp_output(tp); 1797 return; 1798 1799 /* 1800 * Conditionally drop with reset or just drop depending on whether 1801 * we think we are under attack or not. 1802 */ 1803 maybedropwithreset: 1804 #ifdef ICMP_BANDLIM 1805 if (badport_bandlim(1) < 0) 1806 goto drop; 1807 #endif 1808 /* fall through */ 1809 dropwithreset: 1810 #ifdef TCP_RESTRICT_RST 1811 if (restrict_rst) 1812 goto drop; 1813 #endif 1814 /* 1815 * Generate a RST, dropping incoming segment. 1816 * Make ACK acceptable to originator of segment. 1817 * Don't bother to respond if destination was broadcast/multicast. 1818 */ 1819 if ((tiflags & TH_RST) || 1820 m->m_flags & (M_BCAST|M_MCAST) || 1821 IN_MULTICAST(ntohl(ti->ti_src.s_addr)) || 1822 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 1823 goto drop; 1824 #ifdef TCPDEBUG 1825 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1826 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1827 #endif 1828 if (tiflags & TH_ACK) 1829 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1830 else { 1831 if (tiflags & TH_SYN) 1832 ti->ti_len++; 1833 tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1834 TH_RST|TH_ACK); 1835 } 1836 /* destroy temporarily created socket */ 1837 if (dropsocket) 1838 (void) soabort(so); 1839 return; 1840 1841 drop: 1842 /* 1843 * Drop space held by incoming segment and return. 1844 */ 1845 #ifdef TCPDEBUG 1846 if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1847 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1848 #endif 1849 m_freem(m); 1850 /* destroy temporarily created socket */ 1851 if (dropsocket) 1852 (void) soabort(so); 1853 return; 1854 } 1855 1856 static void 1857 tcp_dooptions(tp, cp, cnt, ti, to) 1858 struct tcpcb *tp; 1859 u_char *cp; 1860 int cnt; 1861 struct tcpiphdr *ti; 1862 struct tcpopt *to; 1863 { 1864 u_short mss = 0; 1865 int opt, optlen; 1866 1867 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1868 opt = cp[0]; 1869 if (opt == TCPOPT_EOL) 1870 break; 1871 if (opt == TCPOPT_NOP) 1872 optlen = 1; 1873 else { 1874 optlen = cp[1]; 1875 if (optlen <= 0) 1876 break; 1877 } 1878 switch (opt) { 1879 1880 default: 1881 continue; 1882 1883 case TCPOPT_MAXSEG: 1884 if (optlen != TCPOLEN_MAXSEG) 1885 continue; 1886 if (!(ti->ti_flags & TH_SYN)) 1887 continue; 1888 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); 1889 NTOHS(mss); 1890 break; 1891 1892 case TCPOPT_WINDOW: 1893 if (optlen != TCPOLEN_WINDOW) 1894 continue; 1895 if (!(ti->ti_flags & TH_SYN)) 1896 continue; 1897 tp->t_flags |= TF_RCVD_SCALE; 1898 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 1899 break; 1900 1901 case TCPOPT_TIMESTAMP: 1902 if (optlen != TCPOLEN_TIMESTAMP) 1903 continue; 1904 to->to_flag |= TOF_TS; 1905 bcopy((char *)cp + 2, 1906 (char *)&to->to_tsval, sizeof(to->to_tsval)); 1907 NTOHL(to->to_tsval); 1908 bcopy((char *)cp + 6, 1909 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 1910 NTOHL(to->to_tsecr); 1911 1912 /* 1913 * A timestamp received in a SYN makes 1914 * it ok to send timestamp requests and replies. 1915 */ 1916 if (ti->ti_flags & TH_SYN) { 1917 tp->t_flags |= TF_RCVD_TSTMP; 1918 tp->ts_recent = to->to_tsval; 1919 tp->ts_recent_age = tcp_now; 1920 } 1921 break; 1922 case TCPOPT_CC: 1923 if (optlen != TCPOLEN_CC) 1924 continue; 1925 to->to_flag |= TOF_CC; 1926 bcopy((char *)cp + 2, 1927 (char *)&to->to_cc, sizeof(to->to_cc)); 1928 NTOHL(to->to_cc); 1929 /* 1930 * A CC or CC.new option received in a SYN makes 1931 * it ok to send CC in subsequent segments. 1932 */ 1933 if (ti->ti_flags & TH_SYN) 1934 tp->t_flags |= TF_RCVD_CC; 1935 break; 1936 case TCPOPT_CCNEW: 1937 if (optlen != TCPOLEN_CC) 1938 continue; 1939 if (!(ti->ti_flags & TH_SYN)) 1940 continue; 1941 to->to_flag |= TOF_CCNEW; 1942 bcopy((char *)cp + 2, 1943 (char *)&to->to_cc, sizeof(to->to_cc)); 1944 NTOHL(to->to_cc); 1945 /* 1946 * A CC or CC.new option received in a SYN makes 1947 * it ok to send CC in subsequent segments. 1948 */ 1949 tp->t_flags |= TF_RCVD_CC; 1950 break; 1951 case TCPOPT_CCECHO: 1952 if (optlen != TCPOLEN_CC) 1953 continue; 1954 if (!(ti->ti_flags & TH_SYN)) 1955 continue; 1956 to->to_flag |= TOF_CCECHO; 1957 bcopy((char *)cp + 2, 1958 (char *)&to->to_ccecho, sizeof(to->to_ccecho)); 1959 NTOHL(to->to_ccecho); 1960 break; 1961 } 1962 } 1963 if (ti->ti_flags & TH_SYN) 1964 tcp_mss(tp, mss); /* sets t_maxseg */ 1965 } 1966 1967 /* 1968 * Pull out of band byte out of a segment so 1969 * it doesn't appear in the user's data queue. 1970 * It is still reflected in the segment length for 1971 * sequencing purposes. 1972 */ 1973 static void 1974 tcp_pulloutofband(so, ti, m) 1975 struct socket *so; 1976 struct tcpiphdr *ti; 1977 register struct mbuf *m; 1978 { 1979 int cnt = ti->ti_urp - 1; 1980 1981 while (cnt >= 0) { 1982 if (m->m_len > cnt) { 1983 char *cp = mtod(m, caddr_t) + cnt; 1984 struct tcpcb *tp = sototcpcb(so); 1985 1986 tp->t_iobc = *cp; 1987 tp->t_oobflags |= TCPOOB_HAVEDATA; 1988 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1989 m->m_len--; 1990 return; 1991 } 1992 cnt -= m->m_len; 1993 m = m->m_next; 1994 if (m == 0) 1995 break; 1996 } 1997 panic("tcp_pulloutofband"); 1998 } 1999 2000 /* 2001 * Collect new round-trip time estimate 2002 * and update averages and current timeout. 2003 */ 2004 static void 2005 tcp_xmit_timer(tp, rtt) 2006 register struct tcpcb *tp; 2007 short rtt; 2008 { 2009 register int delta; 2010 2011 tcpstat.tcps_rttupdated++; 2012 tp->t_rttupdated++; 2013 if (tp->t_srtt != 0) { 2014 /* 2015 * srtt is stored as fixed point with 5 bits after the 2016 * binary point (i.e., scaled by 8). The following magic 2017 * is equivalent to the smoothing algorithm in rfc793 with 2018 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2019 * point). Adjust rtt to origin 0. 2020 */ 2021 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2022 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2023 2024 if ((tp->t_srtt += delta) <= 0) 2025 tp->t_srtt = 1; 2026 2027 /* 2028 * We accumulate a smoothed rtt variance (actually, a 2029 * smoothed mean difference), then set the retransmit 2030 * timer to smoothed rtt + 4 times the smoothed variance. 2031 * rttvar is stored as fixed point with 4 bits after the 2032 * binary point (scaled by 16). The following is 2033 * equivalent to rfc793 smoothing with an alpha of .75 2034 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2035 * rfc793's wired-in beta. 2036 */ 2037 if (delta < 0) 2038 delta = -delta; 2039 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2040 if ((tp->t_rttvar += delta) <= 0) 2041 tp->t_rttvar = 1; 2042 } else { 2043 /* 2044 * No rtt measurement yet - use the unsmoothed rtt. 2045 * Set the variance to half the rtt (so our first 2046 * retransmit happens at 3*rtt). 2047 */ 2048 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2049 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2050 } 2051 tp->t_rtt = 0; 2052 tp->t_rxtshift = 0; 2053 2054 /* 2055 * the retransmit should happen at rtt + 4 * rttvar. 2056 * Because of the way we do the smoothing, srtt and rttvar 2057 * will each average +1/2 tick of bias. When we compute 2058 * the retransmit timer, we want 1/2 tick of rounding and 2059 * 1 extra tick because of +-1/2 tick uncertainty in the 2060 * firing of the timer. The bias will give us exactly the 2061 * 1.5 tick we need. But, because the bias is 2062 * statistical, we have to test that we don't drop below 2063 * the minimum feasible timer (which is 2 ticks). 2064 */ 2065 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2066 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2067 2068 /* 2069 * We received an ack for a packet that wasn't retransmitted; 2070 * it is probably safe to discard any error indications we've 2071 * received recently. This isn't quite right, but close enough 2072 * for now (a route might have failed after we sent a segment, 2073 * and the return path might not be symmetrical). 2074 */ 2075 tp->t_softerror = 0; 2076 } 2077 2078 /* 2079 * Determine a reasonable value for maxseg size. 2080 * If the route is known, check route for mtu. 2081 * If none, use an mss that can be handled on the outgoing 2082 * interface without forcing IP to fragment; if bigger than 2083 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2084 * to utilize large mbufs. If no route is found, route has no mtu, 2085 * or the destination isn't local, use a default, hopefully conservative 2086 * size (usually 512 or the default IP max size, but no more than the mtu 2087 * of the interface), as we can't discover anything about intervening 2088 * gateways or networks. We also initialize the congestion/slow start 2089 * window to be a single segment if the destination isn't local. 2090 * While looking at the routing entry, we also initialize other path-dependent 2091 * parameters from pre-set or cached values in the routing entry. 2092 * 2093 * Also take into account the space needed for options that we 2094 * send regularly. Make maxseg shorter by that amount to assure 2095 * that we can send maxseg amount of data even when the options 2096 * are present. Store the upper limit of the length of options plus 2097 * data in maxopd. 2098 * 2099 * NOTE that this routine is only called when we process an incoming 2100 * segment, for outgoing segments only tcp_mssopt is called. 2101 * 2102 * In case of T/TCP, we call this routine during implicit connection 2103 * setup as well (offer = -1), to initialize maxseg from the cached 2104 * MSS of our peer. 2105 */ 2106 void 2107 tcp_mss(tp, offer) 2108 struct tcpcb *tp; 2109 int offer; 2110 { 2111 register struct rtentry *rt; 2112 struct ifnet *ifp; 2113 register int rtt, mss; 2114 u_long bufsize; 2115 struct inpcb *inp; 2116 struct socket *so; 2117 struct rmxp_tao *taop; 2118 int origoffer = offer; 2119 2120 inp = tp->t_inpcb; 2121 if ((rt = tcp_rtlookup(inp)) == NULL) { 2122 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2123 return; 2124 } 2125 ifp = rt->rt_ifp; 2126 so = inp->inp_socket; 2127 2128 taop = rmx_taop(rt->rt_rmx); 2129 /* 2130 * Offer == -1 means that we didn't receive SYN yet, 2131 * use cached value in that case; 2132 */ 2133 if (offer == -1) 2134 offer = taop->tao_mssopt; 2135 /* 2136 * Offer == 0 means that there was no MSS on the SYN segment, 2137 * in this case we use tcp_mssdflt. 2138 */ 2139 if (offer == 0) 2140 offer = tcp_mssdflt; 2141 else 2142 /* 2143 * Sanity check: make sure that maxopd will be large 2144 * enough to allow some data on segments even is the 2145 * all the option space is used (40bytes). Otherwise 2146 * funny things may happen in tcp_output. 2147 */ 2148 offer = max(offer, 64); 2149 taop->tao_mssopt = offer; 2150 2151 /* 2152 * While we're here, check if there's an initial rtt 2153 * or rttvar. Convert from the route-table units 2154 * to scaled multiples of the slow timeout timer. 2155 */ 2156 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 2157 /* 2158 * XXX the lock bit for RTT indicates that the value 2159 * is also a minimum value; this is subject to time. 2160 */ 2161 if (rt->rt_rmx.rmx_locks & RTV_RTT) 2162 tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ); 2163 tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 2164 tcpstat.tcps_usedrtt++; 2165 if (rt->rt_rmx.rmx_rttvar) { 2166 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 2167 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 2168 tcpstat.tcps_usedrttvar++; 2169 } else { 2170 /* default variation is +- 1 rtt */ 2171 tp->t_rttvar = 2172 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2173 } 2174 TCPT_RANGESET(tp->t_rxtcur, 2175 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2176 tp->t_rttmin, TCPTV_REXMTMAX); 2177 } 2178 /* 2179 * if there's an mtu associated with the route, use it 2180 */ 2181 if (rt->rt_rmx.rmx_mtu) 2182 mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 2183 else 2184 { 2185 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 2186 if (!in_localaddr(inp->inp_faddr)) 2187 mss = min(mss, tcp_mssdflt); 2188 } 2189 mss = min(mss, offer); 2190 /* 2191 * maxopd stores the maximum length of data AND options 2192 * in a segment; maxseg is the amount of data in a normal 2193 * segment. We need to store this value (maxopd) apart 2194 * from maxseg, because now every segment carries options 2195 * and thus we normally have somewhat less data in segments. 2196 */ 2197 tp->t_maxopd = mss; 2198 2199 /* 2200 * In case of T/TCP, origoffer==-1 indicates, that no segments 2201 * were received yet. In this case we just guess, otherwise 2202 * we do the same as before T/TCP. 2203 */ 2204 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2205 (origoffer == -1 || 2206 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2207 mss -= TCPOLEN_TSTAMP_APPA; 2208 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && 2209 (origoffer == -1 || 2210 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)) 2211 mss -= TCPOLEN_CC_APPA; 2212 2213 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2214 if (mss > MCLBYTES) 2215 mss &= ~(MCLBYTES-1); 2216 #else 2217 if (mss > MCLBYTES) 2218 mss = mss / MCLBYTES * MCLBYTES; 2219 #endif 2220 /* 2221 * If there's a pipesize, change the socket buffer 2222 * to that size. Make the socket buffers an integral 2223 * number of mss units; if the mss is larger than 2224 * the socket buffer, decrease the mss. 2225 */ 2226 #ifdef RTV_SPIPE 2227 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 2228 #endif 2229 bufsize = so->so_snd.sb_hiwat; 2230 if (bufsize < mss) 2231 mss = bufsize; 2232 else { 2233 bufsize = roundup(bufsize, mss); 2234 if (bufsize > sb_max) 2235 bufsize = sb_max; 2236 (void)sbreserve(&so->so_snd, bufsize); 2237 } 2238 tp->t_maxseg = mss; 2239 2240 #ifdef RTV_RPIPE 2241 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 2242 #endif 2243 bufsize = so->so_rcv.sb_hiwat; 2244 if (bufsize > mss) { 2245 bufsize = roundup(bufsize, mss); 2246 if (bufsize > sb_max) 2247 bufsize = sb_max; 2248 (void)sbreserve(&so->so_rcv, bufsize); 2249 } 2250 /* 2251 * Don't force slow-start on local network. 2252 */ 2253 if (!in_localaddr(inp->inp_faddr)) 2254 tp->snd_cwnd = mss; 2255 2256 if (rt->rt_rmx.rmx_ssthresh) { 2257 /* 2258 * There's some sort of gateway or interface 2259 * buffer limit on the path. Use this to set 2260 * the slow start threshhold, but set the 2261 * threshold to no less than 2*mss. 2262 */ 2263 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 2264 tcpstat.tcps_usedssthresh++; 2265 } 2266 } 2267 2268 /* 2269 * Determine the MSS option to send on an outgoing SYN. 2270 */ 2271 int 2272 tcp_mssopt(tp) 2273 struct tcpcb *tp; 2274 { 2275 struct rtentry *rt; 2276 2277 rt = tcp_rtlookup(tp->t_inpcb); 2278 if (rt == NULL) 2279 return tcp_mssdflt; 2280 2281 return rt->rt_ifp->if_mtu - sizeof(struct tcpiphdr); 2282 }
Cache object: 6bd523d143759947cefff63027f9777c
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