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 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD$"); 34 35 #include "opt_ipfw.h" /* for ipfw_fwd */ 36 #include "opt_inet.h" 37 #include "opt_inet6.h" 38 #include "opt_ipsec.h" 39 #include "opt_mac.h" 40 #include "opt_tcpdebug.h" 41 42 #include <sys/param.h> 43 #include <sys/kernel.h> 44 #include <sys/malloc.h> 45 #include <sys/mbuf.h> 46 #include <sys/proc.h> /* for proc0 declaration */ 47 #include <sys/protosw.h> 48 #include <sys/signalvar.h> 49 #include <sys/socket.h> 50 #include <sys/socketvar.h> 51 #include <sys/sysctl.h> 52 #include <sys/syslog.h> 53 #include <sys/systm.h> 54 55 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 56 57 #include <vm/uma.h> 58 59 #include <net/if.h> 60 #include <net/route.h> 61 62 #define TCPSTATES /* for logging */ 63 64 #include <netinet/in.h> 65 #include <netinet/in_pcb.h> 66 #include <netinet/in_systm.h> 67 #include <netinet/in_var.h> 68 #include <netinet/ip.h> 69 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 70 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 71 #include <netinet/ip_var.h> 72 #include <netinet/ip_options.h> 73 #include <netinet/ip6.h> 74 #include <netinet/icmp6.h> 75 #include <netinet6/in6_pcb.h> 76 #include <netinet6/ip6_var.h> 77 #include <netinet6/nd6.h> 78 #include <netinet/tcp.h> 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #include <netinet6/tcp6_var.h> 84 #include <netinet/tcpip.h> 85 #include <netinet/tcp_syncache.h> 86 #ifdef TCPDEBUG 87 #include <netinet/tcp_debug.h> 88 #endif /* TCPDEBUG */ 89 90 #ifdef IPSEC 91 #include <netipsec/ipsec.h> 92 #include <netipsec/ipsec6.h> 93 #endif /*IPSEC*/ 94 95 #include <machine/in_cksum.h> 96 97 #include <security/mac/mac_framework.h> 98 99 static const int tcprexmtthresh = 3; 100 101 struct tcpstat tcpstat; 102 SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 103 &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 104 105 int tcp_log_in_vain = 0; 106 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 107 &tcp_log_in_vain, 0, "Log all incoming TCP segments to closed ports"); 108 109 static int blackhole = 0; 110 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 111 &blackhole, 0, "Do not send RST on segments to closed ports"); 112 113 int tcp_delack_enabled = 1; 114 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 115 &tcp_delack_enabled, 0, 116 "Delay ACK to try and piggyback it onto a data packet"); 117 118 static int drop_synfin = 0; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 120 &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); 121 122 static int tcp_do_rfc3042 = 1; 123 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 124 &tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)"); 125 126 static int tcp_do_rfc3390 = 1; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 128 &tcp_do_rfc3390, 0, 129 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 130 131 static int tcp_insecure_rst = 0; 132 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 133 &tcp_insecure_rst, 0, 134 "Follow the old (insecure) criteria for accepting RST packets"); 135 136 int tcp_do_autorcvbuf = 1; 137 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 138 &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); 139 140 int tcp_autorcvbuf_inc = 16*1024; 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 142 &tcp_autorcvbuf_inc, 0, 143 "Incrementor step size of automatic receive buffer"); 144 145 int tcp_autorcvbuf_max = 256*1024; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 147 &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); 148 149 struct inpcbhead tcb; 150 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 151 struct inpcbinfo tcbinfo; 152 153 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 154 static void tcp_do_segment(struct mbuf *, struct tcphdr *, 155 struct socket *, struct tcpcb *, int, int); 156 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 157 struct tcpcb *, int, int); 158 static void tcp_pulloutofband(struct socket *, 159 struct tcphdr *, struct mbuf *, int); 160 static void tcp_xmit_timer(struct tcpcb *, int); 161 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 162 163 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 164 #ifdef INET6 165 #define ND6_HINT(tp) \ 166 do { \ 167 if ((tp) && (tp)->t_inpcb && \ 168 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 169 nd6_nud_hint(NULL, NULL, 0); \ 170 } while (0) 171 #else 172 #define ND6_HINT(tp) 173 #endif 174 175 /* 176 * Indicate whether this ack should be delayed. We can delay the ack if 177 * - there is no delayed ack timer in progress and 178 * - our last ack wasn't a 0-sized window. We never want to delay 179 * the ack that opens up a 0-sized window and 180 * - delayed acks are enabled or 181 * - this is a half-synchronized T/TCP connection. 182 */ 183 #define DELAY_ACK(tp) \ 184 ((!tcp_timer_active(tp, TT_DELACK) && \ 185 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 186 (tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 187 188 189 /* 190 * TCP input handling is split into multiple parts: 191 * tcp6_input is a thin wrapper around tcp_input for the extended 192 * ip6_protox[] call format in ip6_input 193 * tcp_input handles primary segment validation, inpcb lookup and 194 * SYN processing on listen sockets 195 * tcp_do_segment processes the ACK and text of the segment for 196 * establishing, established and closing connections 197 */ 198 #ifdef INET6 199 int 200 tcp6_input(struct mbuf **mp, int *offp, int proto) 201 { 202 struct mbuf *m = *mp; 203 struct in6_ifaddr *ia6; 204 205 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 206 207 /* 208 * draft-itojun-ipv6-tcp-to-anycast 209 * better place to put this in? 210 */ 211 ia6 = ip6_getdstifaddr(m); 212 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 213 struct ip6_hdr *ip6; 214 215 ip6 = mtod(m, struct ip6_hdr *); 216 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 217 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 218 return IPPROTO_DONE; 219 } 220 221 tcp_input(m, *offp); 222 return IPPROTO_DONE; 223 } 224 #endif 225 226 void 227 tcp_input(struct mbuf *m, int off0) 228 { 229 struct tcphdr *th; 230 struct ip *ip = NULL; 231 struct ipovly *ipov; 232 struct inpcb *inp = NULL; 233 struct tcpcb *tp = NULL; 234 struct socket *so = NULL; 235 u_char *optp = NULL; 236 int optlen = 0; 237 int len, tlen, off; 238 int drop_hdrlen; 239 int thflags; 240 int rstreason = 0; /* For badport_bandlim accounting purposes */ 241 #ifdef IPFIREWALL_FORWARD 242 struct m_tag *fwd_tag; 243 #endif 244 #ifdef INET6 245 struct ip6_hdr *ip6 = NULL; 246 int isipv6; 247 #else 248 const void *ip6 = NULL; 249 const int isipv6 = 0; 250 #endif 251 struct tcpopt to; /* options in this segment */ 252 char *s = NULL; /* address and port logging */ 253 254 #ifdef TCPDEBUG 255 /* 256 * The size of tcp_saveipgen must be the size of the max ip header, 257 * now IPv6. 258 */ 259 u_char tcp_saveipgen[IP6_HDR_LEN]; 260 struct tcphdr tcp_savetcp; 261 short ostate = 0; 262 #endif 263 264 #ifdef INET6 265 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 266 #endif 267 268 to.to_flags = 0; 269 tcpstat.tcps_rcvtotal++; 270 271 if (isipv6) { 272 #ifdef INET6 273 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 274 ip6 = mtod(m, struct ip6_hdr *); 275 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 276 if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { 277 tcpstat.tcps_rcvbadsum++; 278 goto drop; 279 } 280 th = (struct tcphdr *)((caddr_t)ip6 + off0); 281 282 /* 283 * Be proactive about unspecified IPv6 address in source. 284 * As we use all-zero to indicate unbounded/unconnected pcb, 285 * unspecified IPv6 address can be used to confuse us. 286 * 287 * Note that packets with unspecified IPv6 destination is 288 * already dropped in ip6_input. 289 */ 290 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 291 /* XXX stat */ 292 goto drop; 293 } 294 #else 295 th = NULL; /* XXX: Avoid compiler warning. */ 296 #endif 297 } else { 298 /* 299 * Get IP and TCP header together in first mbuf. 300 * Note: IP leaves IP header in first mbuf. 301 */ 302 if (off0 > sizeof (struct ip)) { 303 ip_stripoptions(m, (struct mbuf *)0); 304 off0 = sizeof(struct ip); 305 } 306 if (m->m_len < sizeof (struct tcpiphdr)) { 307 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 308 == NULL) { 309 tcpstat.tcps_rcvshort++; 310 return; 311 } 312 } 313 ip = mtod(m, struct ip *); 314 ipov = (struct ipovly *)ip; 315 th = (struct tcphdr *)((caddr_t)ip + off0); 316 tlen = ip->ip_len; 317 318 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 319 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 320 th->th_sum = m->m_pkthdr.csum_data; 321 else 322 th->th_sum = in_pseudo(ip->ip_src.s_addr, 323 ip->ip_dst.s_addr, 324 htonl(m->m_pkthdr.csum_data + 325 ip->ip_len + 326 IPPROTO_TCP)); 327 th->th_sum ^= 0xffff; 328 #ifdef TCPDEBUG 329 ipov->ih_len = (u_short)tlen; 330 ipov->ih_len = htons(ipov->ih_len); 331 #endif 332 } else { 333 /* 334 * Checksum extended TCP header and data. 335 */ 336 len = sizeof (struct ip) + tlen; 337 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 338 ipov->ih_len = (u_short)tlen; 339 ipov->ih_len = htons(ipov->ih_len); 340 th->th_sum = in_cksum(m, len); 341 } 342 if (th->th_sum) { 343 tcpstat.tcps_rcvbadsum++; 344 goto drop; 345 } 346 /* Re-initialization for later version check */ 347 ip->ip_v = IPVERSION; 348 } 349 350 /* 351 * Check that TCP offset makes sense, 352 * pull out TCP options and adjust length. XXX 353 */ 354 off = th->th_off << 2; 355 if (off < sizeof (struct tcphdr) || off > tlen) { 356 tcpstat.tcps_rcvbadoff++; 357 goto drop; 358 } 359 tlen -= off; /* tlen is used instead of ti->ti_len */ 360 if (off > sizeof (struct tcphdr)) { 361 if (isipv6) { 362 #ifdef INET6 363 IP6_EXTHDR_CHECK(m, off0, off, ); 364 ip6 = mtod(m, struct ip6_hdr *); 365 th = (struct tcphdr *)((caddr_t)ip6 + off0); 366 #endif 367 } else { 368 if (m->m_len < sizeof(struct ip) + off) { 369 if ((m = m_pullup(m, sizeof (struct ip) + off)) 370 == NULL) { 371 tcpstat.tcps_rcvshort++; 372 return; 373 } 374 ip = mtod(m, struct ip *); 375 ipov = (struct ipovly *)ip; 376 th = (struct tcphdr *)((caddr_t)ip + off0); 377 } 378 } 379 optlen = off - sizeof (struct tcphdr); 380 optp = (u_char *)(th + 1); 381 } 382 thflags = th->th_flags; 383 384 /* 385 * Convert TCP protocol specific fields to host format. 386 */ 387 th->th_seq = ntohl(th->th_seq); 388 th->th_ack = ntohl(th->th_ack); 389 th->th_win = ntohs(th->th_win); 390 th->th_urp = ntohs(th->th_urp); 391 392 /* 393 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 394 */ 395 drop_hdrlen = off0 + off; 396 397 /* 398 * Locate pcb for segment. 399 */ 400 INP_INFO_WLOCK(&tcbinfo); 401 findpcb: 402 INP_INFO_WLOCK_ASSERT(&tcbinfo); 403 #ifdef IPFIREWALL_FORWARD 404 /* 405 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 406 */ 407 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 408 409 if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */ 410 struct sockaddr_in *next_hop; 411 412 next_hop = (struct sockaddr_in *)(fwd_tag+1); 413 /* 414 * Transparently forwarded. Pretend to be the destination. 415 * already got one like this? 416 */ 417 inp = in_pcblookup_hash(&tcbinfo, 418 ip->ip_src, th->th_sport, 419 ip->ip_dst, th->th_dport, 420 0, m->m_pkthdr.rcvif); 421 if (!inp) { 422 /* It's new. Try to find the ambushing socket. */ 423 inp = in_pcblookup_hash(&tcbinfo, 424 ip->ip_src, th->th_sport, 425 next_hop->sin_addr, 426 next_hop->sin_port ? 427 ntohs(next_hop->sin_port) : 428 th->th_dport, 429 INPLOOKUP_WILDCARD, 430 m->m_pkthdr.rcvif); 431 } 432 /* Remove the tag from the packet. We don't need it anymore. */ 433 m_tag_delete(m, fwd_tag); 434 } else 435 #endif /* IPFIREWALL_FORWARD */ 436 { 437 if (isipv6) { 438 #ifdef INET6 439 inp = in6_pcblookup_hash(&tcbinfo, 440 &ip6->ip6_src, th->th_sport, 441 &ip6->ip6_dst, th->th_dport, 442 INPLOOKUP_WILDCARD, 443 m->m_pkthdr.rcvif); 444 #endif 445 } else 446 inp = in_pcblookup_hash(&tcbinfo, 447 ip->ip_src, th->th_sport, 448 ip->ip_dst, th->th_dport, 449 INPLOOKUP_WILDCARD, 450 m->m_pkthdr.rcvif); 451 } 452 453 /* 454 * If the INPCB does not exist then all data in the incoming 455 * segment is discarded and an appropriate RST is sent back. 456 */ 457 if (inp == NULL) { 458 /* 459 * Log communication attempts to ports that are not 460 * in use. 461 */ 462 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 463 tcp_log_in_vain == 2) { 464 if ((s = tcp_log_addrs(NULL, th, (void *)ip, ip6))) 465 log(LOG_INFO, "%s; %s: Connection attempt " 466 "to closed port\n", s, __func__); 467 } 468 /* 469 * When blackholing do not respond with a RST but 470 * completely ignore the segment and drop it. 471 */ 472 if ((blackhole == 1 && (thflags & TH_SYN)) || 473 blackhole == 2) 474 goto dropunlock; 475 476 rstreason = BANDLIM_RST_CLOSEDPORT; 477 goto dropwithreset; 478 } 479 INP_WLOCK(inp); 480 481 #ifdef IPSEC 482 #ifdef INET6 483 if (isipv6 && ipsec6_in_reject(m, inp)) { 484 ipsec6stat.in_polvio++; 485 goto dropunlock; 486 } else 487 #endif /* INET6 */ 488 if (ipsec4_in_reject(m, inp) != 0) { 489 ipsec4stat.in_polvio++; 490 goto dropunlock; 491 } 492 #endif /* IPSEC */ 493 494 /* 495 * Check the minimum TTL for socket. 496 */ 497 if (inp->inp_ip_minttl != 0) { 498 #ifdef INET6 499 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 500 goto dropunlock; 501 else 502 #endif 503 if (inp->inp_ip_minttl > ip->ip_ttl) 504 goto dropunlock; 505 } 506 507 /* 508 * A previous connection in TIMEWAIT state is supposed to catch 509 * stray or duplicate segments arriving late. If this segment 510 * was a legitimate new connection attempt the old INPCB gets 511 * removed and we can try again to find a listening socket. 512 */ 513 if (inp->inp_vflag & INP_TIMEWAIT) { 514 if (thflags & TH_SYN) 515 tcp_dooptions(&to, optp, optlen, TO_SYN); 516 /* 517 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 518 */ 519 if (tcp_twcheck(inp, &to, th, m, tlen)) 520 goto findpcb; 521 INP_INFO_WUNLOCK(&tcbinfo); 522 return; 523 } 524 /* 525 * The TCPCB may no longer exist if the connection is winding 526 * down or it is in the CLOSED state. Either way we drop the 527 * segment and send an appropriate response. 528 */ 529 tp = intotcpcb(inp); 530 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 531 rstreason = BANDLIM_RST_CLOSEDPORT; 532 goto dropwithreset; 533 } 534 535 #ifdef MAC 536 INP_WLOCK_ASSERT(inp); 537 if (mac_inpcb_check_deliver(inp, m)) 538 goto dropunlock; 539 #endif 540 so = inp->inp_socket; 541 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 542 #ifdef TCPDEBUG 543 if (so->so_options & SO_DEBUG) { 544 ostate = tp->t_state; 545 if (isipv6) { 546 #ifdef INET6 547 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 548 #endif 549 } else 550 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 551 tcp_savetcp = *th; 552 } 553 #endif 554 /* 555 * When the socket is accepting connections (the INPCB is in LISTEN 556 * state) we look into the SYN cache if this is a new connection 557 * attempt or the completion of a previous one. 558 */ 559 if (so->so_options & SO_ACCEPTCONN) { 560 struct in_conninfo inc; 561 562 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 563 "tp not listening", __func__)); 564 565 bzero(&inc, sizeof(inc)); 566 inc.inc_isipv6 = isipv6; 567 #ifdef INET6 568 if (isipv6) { 569 inc.inc6_faddr = ip6->ip6_src; 570 inc.inc6_laddr = ip6->ip6_dst; 571 } else 572 #endif 573 { 574 inc.inc_faddr = ip->ip_src; 575 inc.inc_laddr = ip->ip_dst; 576 } 577 inc.inc_fport = th->th_sport; 578 inc.inc_lport = th->th_dport; 579 580 /* 581 * Check for an existing connection attempt in syncache if 582 * the flag is only ACK. A successful lookup creates a new 583 * socket appended to the listen queue in SYN_RECEIVED state. 584 */ 585 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 586 /* 587 * Parse the TCP options here because 588 * syncookies need access to the reflected 589 * timestamp. 590 */ 591 tcp_dooptions(&to, optp, optlen, 0); 592 /* 593 * NB: syncache_expand() doesn't unlock 594 * inp and tcpinfo locks. 595 */ 596 if (!syncache_expand(&inc, &to, th, &so, m)) { 597 /* 598 * No syncache entry or ACK was not 599 * for our SYN/ACK. Send a RST. 600 * NB: syncache did its own logging 601 * of the failure cause. 602 */ 603 rstreason = BANDLIM_RST_OPENPORT; 604 goto dropwithreset; 605 } 606 if (so == NULL) { 607 /* 608 * We completed the 3-way handshake 609 * but could not allocate a socket 610 * either due to memory shortage, 611 * listen queue length limits or 612 * global socket limits. Send RST 613 * or wait and have the remote end 614 * retransmit the ACK for another 615 * try. 616 */ 617 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 618 log(LOG_DEBUG, "%s; %s: Listen socket: " 619 "Socket allocation failed due to " 620 "limits or memory shortage, %s\n", 621 s, __func__, (tcp_sc_rst_sock_fail ? 622 "sending RST" : "try again")); 623 if (tcp_sc_rst_sock_fail) { 624 rstreason = BANDLIM_UNLIMITED; 625 goto dropwithreset; 626 } else 627 goto dropunlock; 628 } 629 /* 630 * Socket is created in state SYN_RECEIVED. 631 * Unlock the listen socket, lock the newly 632 * created socket and update the tp variable. 633 */ 634 INP_WUNLOCK(inp); /* listen socket */ 635 inp = sotoinpcb(so); 636 INP_WLOCK(inp); /* new connection */ 637 tp = intotcpcb(inp); 638 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 639 ("%s: ", __func__)); 640 /* 641 * Process the segment and the data it 642 * contains. tcp_do_segment() consumes 643 * the mbuf chain and unlocks the inpcb. 644 */ 645 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen); 646 INP_INFO_UNLOCK_ASSERT(&tcbinfo); 647 return; 648 } 649 /* 650 * Segment flag validation for new connection attempts: 651 * 652 * Our (SYN|ACK) response was rejected. 653 * Check with syncache and remove entry to prevent 654 * retransmits. 655 * 656 * NB: syncache_chkrst does its own logging of failure 657 * causes. 658 */ 659 if (thflags & TH_RST) { 660 syncache_chkrst(&inc, th); 661 goto dropunlock; 662 } 663 /* 664 * We can't do anything without SYN. 665 */ 666 if ((thflags & TH_SYN) == 0) { 667 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 668 log(LOG_DEBUG, "%s; %s: Listen socket: " 669 "SYN is missing, segment ignored\n", 670 s, __func__); 671 tcpstat.tcps_badsyn++; 672 goto dropunlock; 673 } 674 /* 675 * (SYN|ACK) is bogus on a listen socket. 676 */ 677 if (thflags & TH_ACK) { 678 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 679 log(LOG_DEBUG, "%s; %s: Listen socket: " 680 "SYN|ACK invalid, segment rejected\n", 681 s, __func__); 682 syncache_badack(&inc); /* XXX: Not needed! */ 683 tcpstat.tcps_badsyn++; 684 rstreason = BANDLIM_RST_OPENPORT; 685 goto dropwithreset; 686 } 687 /* 688 * If the drop_synfin option is enabled, drop all 689 * segments with both the SYN and FIN bits set. 690 * This prevents e.g. nmap from identifying the 691 * TCP/IP stack. 692 * XXX: Poor reasoning. nmap has other methods 693 * and is constantly refining its stack detection 694 * strategies. 695 * XXX: This is a violation of the TCP specification 696 * and was used by RFC1644. 697 */ 698 if ((thflags & TH_FIN) && drop_synfin) { 699 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 700 log(LOG_DEBUG, "%s; %s: Listen socket: " 701 "SYN|FIN segment ignored (based on " 702 "sysctl setting)\n", s, __func__); 703 tcpstat.tcps_badsyn++; 704 goto dropunlock; 705 } 706 /* 707 * Segment's flags are (SYN) or (SYN|FIN). 708 * 709 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 710 * as they do not affect the state of the TCP FSM. 711 * The data pointed to by TH_URG and th_urp is ignored. 712 */ 713 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 714 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 715 KASSERT(thflags & (TH_SYN), 716 ("%s: Listen socket: TH_SYN not set", __func__)); 717 #ifdef INET6 718 /* 719 * If deprecated address is forbidden, 720 * we do not accept SYN to deprecated interface 721 * address to prevent any new inbound connection from 722 * getting established. 723 * When we do not accept SYN, we send a TCP RST, 724 * with deprecated source address (instead of dropping 725 * it). We compromise it as it is much better for peer 726 * to send a RST, and RST will be the final packet 727 * for the exchange. 728 * 729 * If we do not forbid deprecated addresses, we accept 730 * the SYN packet. RFC2462 does not suggest dropping 731 * SYN in this case. 732 * If we decipher RFC2462 5.5.4, it says like this: 733 * 1. use of deprecated addr with existing 734 * communication is okay - "SHOULD continue to be 735 * used" 736 * 2. use of it with new communication: 737 * (2a) "SHOULD NOT be used if alternate address 738 * with sufficient scope is available" 739 * (2b) nothing mentioned otherwise. 740 * Here we fall into (2b) case as we have no choice in 741 * our source address selection - we must obey the peer. 742 * 743 * The wording in RFC2462 is confusing, and there are 744 * multiple description text for deprecated address 745 * handling - worse, they are not exactly the same. 746 * I believe 5.5.4 is the best one, so we follow 5.5.4. 747 */ 748 if (isipv6 && !ip6_use_deprecated) { 749 struct in6_ifaddr *ia6; 750 751 if ((ia6 = ip6_getdstifaddr(m)) && 752 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 753 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 754 log(LOG_DEBUG, "%s; %s: Listen socket: " 755 "Connection attempt to deprecated " 756 "IPv6 address rejected\n", 757 s, __func__); 758 rstreason = BANDLIM_RST_OPENPORT; 759 goto dropwithreset; 760 } 761 } 762 #endif 763 /* 764 * Basic sanity checks on incoming SYN requests: 765 * Don't respond if the destination is a link layer 766 * broadcast according to RFC1122 4.2.3.10, p. 104. 767 * If it is from this socket it must be forged. 768 * Don't respond if the source or destination is a 769 * global or subnet broad- or multicast address. 770 * Note that it is quite possible to receive unicast 771 * link-layer packets with a broadcast IP address. Use 772 * in_broadcast() to find them. 773 */ 774 if (m->m_flags & (M_BCAST|M_MCAST)) { 775 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 776 log(LOG_DEBUG, "%s; %s: Listen socket: " 777 "Connection attempt from broad- or multicast " 778 "link layer address ignored\n", s, __func__); 779 goto dropunlock; 780 } 781 if (isipv6) { 782 #ifdef INET6 783 if (th->th_dport == th->th_sport && 784 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 785 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 786 log(LOG_DEBUG, "%s; %s: Listen socket: " 787 "Connection attempt to/from self " 788 "ignored\n", s, __func__); 789 goto dropunlock; 790 } 791 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 792 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 793 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 794 log(LOG_DEBUG, "%s; %s: Listen socket: " 795 "Connection attempt from/to multicast " 796 "address ignored\n", s, __func__); 797 goto dropunlock; 798 } 799 #endif 800 } else { 801 if (th->th_dport == th->th_sport && 802 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 803 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 804 log(LOG_DEBUG, "%s; %s: Listen socket: " 805 "Connection attempt from/to self " 806 "ignored\n", s, __func__); 807 goto dropunlock; 808 } 809 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 810 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 811 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 812 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 813 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 814 log(LOG_DEBUG, "%s; %s: Listen socket: " 815 "Connection attempt from/to broad- " 816 "or multicast address ignored\n", 817 s, __func__); 818 goto dropunlock; 819 } 820 } 821 /* 822 * SYN appears to be valid. Create compressed TCP state 823 * for syncache. 824 */ 825 #ifdef TCPDEBUG 826 if (so->so_options & SO_DEBUG) 827 tcp_trace(TA_INPUT, ostate, tp, 828 (void *)tcp_saveipgen, &tcp_savetcp, 0); 829 #endif 830 tcp_dooptions(&to, optp, optlen, TO_SYN); 831 syncache_add(&inc, &to, th, inp, &so, m); 832 /* 833 * Entry added to syncache and mbuf consumed. 834 * Everything already unlocked by syncache_add(). 835 */ 836 INP_INFO_UNLOCK_ASSERT(&tcbinfo); 837 return; 838 } 839 840 /* 841 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 842 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 843 * the inpcb, and unlocks pcbinfo. 844 */ 845 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen); 846 INP_INFO_UNLOCK_ASSERT(&tcbinfo); 847 return; 848 849 dropwithreset: 850 INP_INFO_WLOCK_ASSERT(&tcbinfo); 851 tcp_dropwithreset(m, th, tp, tlen, rstreason); 852 m = NULL; /* mbuf chain got consumed. */ 853 dropunlock: 854 INP_INFO_WLOCK_ASSERT(&tcbinfo); 855 if (inp != NULL) 856 INP_WUNLOCK(inp); 857 INP_INFO_WUNLOCK(&tcbinfo); 858 drop: 859 INP_INFO_UNLOCK_ASSERT(&tcbinfo); 860 if (s != NULL) 861 free(s, M_TCPLOG); 862 if (m != NULL) 863 m_freem(m); 864 return; 865 } 866 867 static void 868 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 869 struct tcpcb *tp, int drop_hdrlen, int tlen) 870 { 871 int thflags, acked, ourfinisacked, needoutput = 0; 872 int headlocked = 1; 873 int rstreason, todrop, win; 874 u_long tiwin; 875 struct tcpopt to; 876 877 #ifdef TCPDEBUG 878 /* 879 * The size of tcp_saveipgen must be the size of the max ip header, 880 * now IPv6. 881 */ 882 u_char tcp_saveipgen[IP6_HDR_LEN]; 883 struct tcphdr tcp_savetcp; 884 short ostate = 0; 885 #endif 886 thflags = th->th_flags; 887 888 INP_INFO_WLOCK_ASSERT(&tcbinfo); 889 INP_WLOCK_ASSERT(tp->t_inpcb); 890 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 891 __func__)); 892 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 893 __func__)); 894 895 /* 896 * Segment received on connection. 897 * Reset idle time and keep-alive timer. 898 * XXX: This should be done after segment 899 * validation to ignore broken/spoofed segs. 900 */ 901 tp->t_rcvtime = ticks; 902 if (TCPS_HAVEESTABLISHED(tp->t_state)) 903 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 904 905 /* 906 * Unscale the window into a 32-bit value. 907 * For the SYN_SENT state the scale is zero. 908 */ 909 tiwin = th->th_win << tp->snd_scale; 910 911 /* 912 * Parse options on any incoming segment. 913 */ 914 tcp_dooptions(&to, (u_char *)(th + 1), 915 (th->th_off << 2) - sizeof(struct tcphdr), 916 (thflags & TH_SYN) ? TO_SYN : 0); 917 918 /* 919 * If echoed timestamp is later than the current time, 920 * fall back to non RFC1323 RTT calculation. Normalize 921 * timestamp if syncookies were used when this connection 922 * was established. 923 */ 924 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 925 to.to_tsecr -= tp->ts_offset; 926 if (TSTMP_GT(to.to_tsecr, ticks)) 927 to.to_tsecr = 0; 928 } 929 930 /* 931 * Process options only when we get SYN/ACK back. The SYN case 932 * for incoming connections is handled in tcp_syncache. 933 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 934 * or <SYN,ACK>) segment itself is never scaled. 935 * XXX this is traditional behavior, may need to be cleaned up. 936 */ 937 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 938 if ((to.to_flags & TOF_SCALE) && 939 (tp->t_flags & TF_REQ_SCALE)) { 940 tp->t_flags |= TF_RCVD_SCALE; 941 tp->snd_scale = to.to_wscale; 942 } 943 /* 944 * Initial send window. It will be updated with 945 * the next incoming segment to the scaled value. 946 */ 947 tp->snd_wnd = th->th_win; 948 if (to.to_flags & TOF_TS) { 949 tp->t_flags |= TF_RCVD_TSTMP; 950 tp->ts_recent = to.to_tsval; 951 tp->ts_recent_age = ticks; 952 } 953 if (to.to_flags & TOF_MSS) 954 tcp_mss(tp, to.to_mss); 955 if ((tp->t_flags & TF_SACK_PERMIT) && 956 (to.to_flags & TOF_SACKPERM) == 0) 957 tp->t_flags &= ~TF_SACK_PERMIT; 958 } 959 960 /* 961 * Header prediction: check for the two common cases 962 * of a uni-directional data xfer. If the packet has 963 * no control flags, is in-sequence, the window didn't 964 * change and we're not retransmitting, it's a 965 * candidate. If the length is zero and the ack moved 966 * forward, we're the sender side of the xfer. Just 967 * free the data acked & wake any higher level process 968 * that was blocked waiting for space. If the length 969 * is non-zero and the ack didn't move, we're the 970 * receiver side. If we're getting packets in-order 971 * (the reassembly queue is empty), add the data to 972 * the socket buffer and note that we need a delayed ack. 973 * Make sure that the hidden state-flags are also off. 974 * Since we check for TCPS_ESTABLISHED first, it can only 975 * be TH_NEEDSYN. 976 */ 977 if (tp->t_state == TCPS_ESTABLISHED && 978 th->th_seq == tp->rcv_nxt && 979 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 980 tp->snd_nxt == tp->snd_max && 981 tiwin && tiwin == tp->snd_wnd && 982 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 983 LIST_EMPTY(&tp->t_segq) && 984 ((to.to_flags & TOF_TS) == 0 || 985 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 986 987 /* 988 * If last ACK falls within this segment's sequence numbers, 989 * record the timestamp. 990 * NOTE that the test is modified according to the latest 991 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 992 */ 993 if ((to.to_flags & TOF_TS) != 0 && 994 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 995 tp->ts_recent_age = ticks; 996 tp->ts_recent = to.to_tsval; 997 } 998 999 if (tlen == 0) { 1000 if (SEQ_GT(th->th_ack, tp->snd_una) && 1001 SEQ_LEQ(th->th_ack, tp->snd_max) && 1002 tp->snd_cwnd >= tp->snd_wnd && 1003 ((!tcp_do_newreno && 1004 !(tp->t_flags & TF_SACK_PERMIT) && 1005 tp->t_dupacks < tcprexmtthresh) || 1006 ((tcp_do_newreno || 1007 (tp->t_flags & TF_SACK_PERMIT)) && 1008 !IN_FASTRECOVERY(tp) && 1009 (to.to_flags & TOF_SACK) == 0 && 1010 TAILQ_EMPTY(&tp->snd_holes)))) { 1011 KASSERT(headlocked, 1012 ("%s: headlocked", __func__)); 1013 INP_INFO_WUNLOCK(&tcbinfo); 1014 headlocked = 0; 1015 /* 1016 * This is a pure ack for outstanding data. 1017 */ 1018 ++tcpstat.tcps_predack; 1019 /* 1020 * "bad retransmit" recovery. 1021 */ 1022 if (tp->t_rxtshift == 1 && 1023 ticks < tp->t_badrxtwin) { 1024 ++tcpstat.tcps_sndrexmitbad; 1025 tp->snd_cwnd = tp->snd_cwnd_prev; 1026 tp->snd_ssthresh = 1027 tp->snd_ssthresh_prev; 1028 tp->snd_recover = tp->snd_recover_prev; 1029 if (tp->t_flags & TF_WASFRECOVERY) 1030 ENTER_FASTRECOVERY(tp); 1031 tp->snd_nxt = tp->snd_max; 1032 tp->t_badrxtwin = 0; 1033 } 1034 1035 /* 1036 * Recalculate the transmit timer / rtt. 1037 * 1038 * Some boxes send broken timestamp replies 1039 * during the SYN+ACK phase, ignore 1040 * timestamps of 0 or we could calculate a 1041 * huge RTT and blow up the retransmit timer. 1042 */ 1043 if ((to.to_flags & TOF_TS) != 0 && 1044 to.to_tsecr) { 1045 if (!tp->t_rttlow || 1046 tp->t_rttlow > ticks - to.to_tsecr) 1047 tp->t_rttlow = ticks - to.to_tsecr; 1048 tcp_xmit_timer(tp, 1049 ticks - to.to_tsecr + 1); 1050 } else if (tp->t_rtttime && 1051 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1052 if (!tp->t_rttlow || 1053 tp->t_rttlow > ticks - tp->t_rtttime) 1054 tp->t_rttlow = ticks - tp->t_rtttime; 1055 tcp_xmit_timer(tp, 1056 ticks - tp->t_rtttime); 1057 } 1058 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1059 acked = th->th_ack - tp->snd_una; 1060 tcpstat.tcps_rcvackpack++; 1061 tcpstat.tcps_rcvackbyte += acked; 1062 sbdrop(&so->so_snd, acked); 1063 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1064 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1065 tp->snd_recover = th->th_ack - 1; 1066 tp->snd_una = th->th_ack; 1067 /* 1068 * Pull snd_wl2 up to prevent seq wrap relative 1069 * to th_ack. 1070 */ 1071 tp->snd_wl2 = th->th_ack; 1072 tp->t_dupacks = 0; 1073 m_freem(m); 1074 ND6_HINT(tp); /* Some progress has been made. */ 1075 1076 /* 1077 * If all outstanding data are acked, stop 1078 * retransmit timer, otherwise restart timer 1079 * using current (possibly backed-off) value. 1080 * If process is waiting for space, 1081 * wakeup/selwakeup/signal. If data 1082 * are ready to send, let tcp_output 1083 * decide between more output or persist. 1084 */ 1085 #ifdef TCPDEBUG 1086 if (so->so_options & SO_DEBUG) 1087 tcp_trace(TA_INPUT, ostate, tp, 1088 (void *)tcp_saveipgen, 1089 &tcp_savetcp, 0); 1090 #endif 1091 if (tp->snd_una == tp->snd_max) 1092 tcp_timer_activate(tp, TT_REXMT, 0); 1093 else if (!tcp_timer_active(tp, TT_PERSIST)) 1094 tcp_timer_activate(tp, TT_REXMT, 1095 tp->t_rxtcur); 1096 sowwakeup(so); 1097 if (so->so_snd.sb_cc) 1098 (void) tcp_output(tp); 1099 goto check_delack; 1100 } 1101 } else if (th->th_ack == tp->snd_una && 1102 tlen <= sbspace(&so->so_rcv)) { 1103 int newsize = 0; /* automatic sockbuf scaling */ 1104 1105 KASSERT(headlocked, ("%s: headlocked", __func__)); 1106 INP_INFO_WUNLOCK(&tcbinfo); 1107 headlocked = 0; 1108 /* 1109 * This is a pure, in-sequence data packet 1110 * with nothing on the reassembly queue and 1111 * we have enough buffer space to take it. 1112 */ 1113 /* Clean receiver SACK report if present */ 1114 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1115 tcp_clean_sackreport(tp); 1116 ++tcpstat.tcps_preddat; 1117 tp->rcv_nxt += tlen; 1118 /* 1119 * Pull snd_wl1 up to prevent seq wrap relative to 1120 * th_seq. 1121 */ 1122 tp->snd_wl1 = th->th_seq; 1123 /* 1124 * Pull rcv_up up to prevent seq wrap relative to 1125 * rcv_nxt. 1126 */ 1127 tp->rcv_up = tp->rcv_nxt; 1128 tcpstat.tcps_rcvpack++; 1129 tcpstat.tcps_rcvbyte += tlen; 1130 ND6_HINT(tp); /* Some progress has been made */ 1131 #ifdef TCPDEBUG 1132 if (so->so_options & SO_DEBUG) 1133 tcp_trace(TA_INPUT, ostate, tp, 1134 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1135 #endif 1136 /* 1137 * Automatic sizing of receive socket buffer. Often the send 1138 * buffer size is not optimally adjusted to the actual network 1139 * conditions at hand (delay bandwidth product). Setting the 1140 * buffer size too small limits throughput on links with high 1141 * bandwidth and high delay (eg. trans-continental/oceanic links). 1142 * 1143 * On the receive side the socket buffer memory is only rarely 1144 * used to any significant extent. This allows us to be much 1145 * more aggressive in scaling the receive socket buffer. For 1146 * the case that the buffer space is actually used to a large 1147 * extent and we run out of kernel memory we can simply drop 1148 * the new segments; TCP on the sender will just retransmit it 1149 * later. Setting the buffer size too big may only consume too 1150 * much kernel memory if the application doesn't read() from 1151 * the socket or packet loss or reordering makes use of the 1152 * reassembly queue. 1153 * 1154 * The criteria to step up the receive buffer one notch are: 1155 * 1. the number of bytes received during the time it takes 1156 * one timestamp to be reflected back to us (the RTT); 1157 * 2. received bytes per RTT is within seven eighth of the 1158 * current socket buffer size; 1159 * 3. receive buffer size has not hit maximal automatic size; 1160 * 1161 * This algorithm does one step per RTT at most and only if 1162 * we receive a bulk stream w/o packet losses or reorderings. 1163 * Shrinking the buffer during idle times is not necessary as 1164 * it doesn't consume any memory when idle. 1165 * 1166 * TODO: Only step up if the application is actually serving 1167 * the buffer to better manage the socket buffer resources. 1168 */ 1169 if (tcp_do_autorcvbuf && 1170 to.to_tsecr && 1171 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1172 if (to.to_tsecr > tp->rfbuf_ts && 1173 to.to_tsecr - tp->rfbuf_ts < hz) { 1174 if (tp->rfbuf_cnt > 1175 (so->so_rcv.sb_hiwat / 8 * 7) && 1176 so->so_rcv.sb_hiwat < 1177 tcp_autorcvbuf_max) { 1178 newsize = 1179 min(so->so_rcv.sb_hiwat + 1180 tcp_autorcvbuf_inc, 1181 tcp_autorcvbuf_max); 1182 } 1183 /* Start over with next RTT. */ 1184 tp->rfbuf_ts = 0; 1185 tp->rfbuf_cnt = 0; 1186 } else 1187 tp->rfbuf_cnt += tlen; /* add up */ 1188 } 1189 1190 /* Add data to socket buffer. */ 1191 SOCKBUF_LOCK(&so->so_rcv); 1192 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1193 m_freem(m); 1194 } else { 1195 /* 1196 * Set new socket buffer size. 1197 * Give up when limit is reached. 1198 */ 1199 if (newsize) 1200 if (!sbreserve_locked(&so->so_rcv, 1201 newsize, so, curthread)) 1202 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1203 m_adj(m, drop_hdrlen); /* delayed header drop */ 1204 sbappendstream_locked(&so->so_rcv, m); 1205 } 1206 /* NB: sorwakeup_locked() does an implicit unlock. */ 1207 sorwakeup_locked(so); 1208 if (DELAY_ACK(tp)) { 1209 tp->t_flags |= TF_DELACK; 1210 } else { 1211 tp->t_flags |= TF_ACKNOW; 1212 tcp_output(tp); 1213 } 1214 goto check_delack; 1215 } 1216 } 1217 1218 /* 1219 * Calculate amount of space in receive window, 1220 * and then do TCP input processing. 1221 * Receive window is amount of space in rcv queue, 1222 * but not less than advertised window. 1223 */ 1224 win = sbspace(&so->so_rcv); 1225 if (win < 0) 1226 win = 0; 1227 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1228 1229 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1230 tp->rfbuf_ts = 0; 1231 tp->rfbuf_cnt = 0; 1232 1233 switch (tp->t_state) { 1234 1235 /* 1236 * If the state is SYN_RECEIVED: 1237 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1238 */ 1239 case TCPS_SYN_RECEIVED: 1240 if ((thflags & TH_ACK) && 1241 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1242 SEQ_GT(th->th_ack, tp->snd_max))) { 1243 rstreason = BANDLIM_RST_OPENPORT; 1244 goto dropwithreset; 1245 } 1246 break; 1247 1248 /* 1249 * If the state is SYN_SENT: 1250 * if seg contains an ACK, but not for our SYN, drop the input. 1251 * if seg contains a RST, then drop the connection. 1252 * if seg does not contain SYN, then drop it. 1253 * Otherwise this is an acceptable SYN segment 1254 * initialize tp->rcv_nxt and tp->irs 1255 * if seg contains ack then advance tp->snd_una 1256 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1257 * arrange for segment to be acked (eventually) 1258 * continue processing rest of data/controls, beginning with URG 1259 */ 1260 case TCPS_SYN_SENT: 1261 if ((thflags & TH_ACK) && 1262 (SEQ_LEQ(th->th_ack, tp->iss) || 1263 SEQ_GT(th->th_ack, tp->snd_max))) { 1264 rstreason = BANDLIM_UNLIMITED; 1265 goto dropwithreset; 1266 } 1267 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) 1268 tp = tcp_drop(tp, ECONNREFUSED); 1269 if (thflags & TH_RST) 1270 goto drop; 1271 if (!(thflags & TH_SYN)) 1272 goto drop; 1273 1274 tp->irs = th->th_seq; 1275 tcp_rcvseqinit(tp); 1276 if (thflags & TH_ACK) { 1277 tcpstat.tcps_connects++; 1278 soisconnected(so); 1279 #ifdef MAC 1280 SOCK_LOCK(so); 1281 mac_socketpeer_set_from_mbuf(m, so); 1282 SOCK_UNLOCK(so); 1283 #endif 1284 /* Do window scaling on this connection? */ 1285 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1286 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1287 tp->rcv_scale = tp->request_r_scale; 1288 } 1289 tp->rcv_adv += tp->rcv_wnd; 1290 tp->snd_una++; /* SYN is acked */ 1291 /* 1292 * If there's data, delay ACK; if there's also a FIN 1293 * ACKNOW will be turned on later. 1294 */ 1295 if (DELAY_ACK(tp) && tlen != 0) 1296 tcp_timer_activate(tp, TT_DELACK, 1297 tcp_delacktime); 1298 else 1299 tp->t_flags |= TF_ACKNOW; 1300 /* 1301 * Received <SYN,ACK> in SYN_SENT[*] state. 1302 * Transitions: 1303 * SYN_SENT --> ESTABLISHED 1304 * SYN_SENT* --> FIN_WAIT_1 1305 */ 1306 tp->t_starttime = ticks; 1307 if (tp->t_flags & TF_NEEDFIN) { 1308 tp->t_state = TCPS_FIN_WAIT_1; 1309 tp->t_flags &= ~TF_NEEDFIN; 1310 thflags &= ~TH_SYN; 1311 } else { 1312 tp->t_state = TCPS_ESTABLISHED; 1313 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 1314 } 1315 } else { 1316 /* 1317 * Received initial SYN in SYN-SENT[*] state => 1318 * simultaneous open. If segment contains CC option 1319 * and there is a cached CC, apply TAO test. 1320 * If it succeeds, connection is * half-synchronized. 1321 * Otherwise, do 3-way handshake: 1322 * SYN-SENT -> SYN-RECEIVED 1323 * SYN-SENT* -> SYN-RECEIVED* 1324 * If there was no CC option, clear cached CC value. 1325 */ 1326 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1327 tcp_timer_activate(tp, TT_REXMT, 0); 1328 tp->t_state = TCPS_SYN_RECEIVED; 1329 } 1330 1331 KASSERT(headlocked, ("%s: trimthenstep6: head not locked", 1332 __func__)); 1333 INP_WLOCK_ASSERT(tp->t_inpcb); 1334 1335 /* 1336 * Advance th->th_seq to correspond to first data byte. 1337 * If data, trim to stay within window, 1338 * dropping FIN if necessary. 1339 */ 1340 th->th_seq++; 1341 if (tlen > tp->rcv_wnd) { 1342 todrop = tlen - tp->rcv_wnd; 1343 m_adj(m, -todrop); 1344 tlen = tp->rcv_wnd; 1345 thflags &= ~TH_FIN; 1346 tcpstat.tcps_rcvpackafterwin++; 1347 tcpstat.tcps_rcvbyteafterwin += todrop; 1348 } 1349 tp->snd_wl1 = th->th_seq - 1; 1350 tp->rcv_up = th->th_seq; 1351 /* 1352 * Client side of transaction: already sent SYN and data. 1353 * If the remote host used T/TCP to validate the SYN, 1354 * our data will be ACK'd; if so, enter normal data segment 1355 * processing in the middle of step 5, ack processing. 1356 * Otherwise, goto step 6. 1357 */ 1358 if (thflags & TH_ACK) 1359 goto process_ACK; 1360 1361 goto step6; 1362 1363 /* 1364 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1365 * do normal processing. 1366 * 1367 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1368 */ 1369 case TCPS_LAST_ACK: 1370 case TCPS_CLOSING: 1371 break; /* continue normal processing */ 1372 } 1373 1374 /* 1375 * States other than LISTEN or SYN_SENT. 1376 * First check the RST flag and sequence number since reset segments 1377 * are exempt from the timestamp and connection count tests. This 1378 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 1379 * below which allowed reset segments in half the sequence space 1380 * to fall though and be processed (which gives forged reset 1381 * segments with a random sequence number a 50 percent chance of 1382 * killing a connection). 1383 * Then check timestamp, if present. 1384 * Then check the connection count, if present. 1385 * Then check that at least some bytes of segment are within 1386 * receive window. If segment begins before rcv_nxt, 1387 * drop leading data (and SYN); if nothing left, just ack. 1388 * 1389 * 1390 * If the RST bit is set, check the sequence number to see 1391 * if this is a valid reset segment. 1392 * RFC 793 page 37: 1393 * In all states except SYN-SENT, all reset (RST) segments 1394 * are validated by checking their SEQ-fields. A reset is 1395 * valid if its sequence number is in the window. 1396 * Note: this does not take into account delayed ACKs, so 1397 * we should test against last_ack_sent instead of rcv_nxt. 1398 * The sequence number in the reset segment is normally an 1399 * echo of our outgoing acknowlegement numbers, but some hosts 1400 * send a reset with the sequence number at the rightmost edge 1401 * of our receive window, and we have to handle this case. 1402 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 1403 * that brute force RST attacks are possible. To combat this, 1404 * we use a much stricter check while in the ESTABLISHED state, 1405 * only accepting RSTs where the sequence number is equal to 1406 * last_ack_sent. In all other states (the states in which a 1407 * RST is more likely), the more permissive check is used. 1408 * If we have multiple segments in flight, the intial reset 1409 * segment sequence numbers will be to the left of last_ack_sent, 1410 * but they will eventually catch up. 1411 * In any case, it never made sense to trim reset segments to 1412 * fit the receive window since RFC 1122 says: 1413 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 1414 * 1415 * A TCP SHOULD allow a received RST segment to include data. 1416 * 1417 * DISCUSSION 1418 * It has been suggested that a RST segment could contain 1419 * ASCII text that encoded and explained the cause of the 1420 * RST. No standard has yet been established for such 1421 * data. 1422 * 1423 * If the reset segment passes the sequence number test examine 1424 * the state: 1425 * SYN_RECEIVED STATE: 1426 * If passive open, return to LISTEN state. 1427 * If active open, inform user that connection was refused. 1428 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 1429 * Inform user that connection was reset, and close tcb. 1430 * CLOSING, LAST_ACK STATES: 1431 * Close the tcb. 1432 * TIME_WAIT STATE: 1433 * Drop the segment - see Stevens, vol. 2, p. 964 and 1434 * RFC 1337. 1435 */ 1436 if (thflags & TH_RST) { 1437 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1438 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 1439 switch (tp->t_state) { 1440 1441 case TCPS_SYN_RECEIVED: 1442 so->so_error = ECONNREFUSED; 1443 goto close; 1444 1445 case TCPS_ESTABLISHED: 1446 if (tcp_insecure_rst == 0 && 1447 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 1448 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 1449 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 1450 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 1451 tcpstat.tcps_badrst++; 1452 goto drop; 1453 } 1454 /* FALLTHROUGH */ 1455 case TCPS_FIN_WAIT_1: 1456 case TCPS_FIN_WAIT_2: 1457 case TCPS_CLOSE_WAIT: 1458 so->so_error = ECONNRESET; 1459 close: 1460 tp->t_state = TCPS_CLOSED; 1461 tcpstat.tcps_drops++; 1462 KASSERT(headlocked, ("%s: trimthenstep6: " 1463 "tcp_close: head not locked", __func__)); 1464 tp = tcp_close(tp); 1465 break; 1466 1467 case TCPS_CLOSING: 1468 case TCPS_LAST_ACK: 1469 KASSERT(headlocked, ("%s: trimthenstep6: " 1470 "tcp_close.2: head not locked", __func__)); 1471 tp = tcp_close(tp); 1472 break; 1473 } 1474 } 1475 goto drop; 1476 } 1477 1478 /* 1479 * RFC 1323 PAWS: If we have a timestamp reply on this segment 1480 * and it's less than ts_recent, drop it. 1481 */ 1482 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 1483 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 1484 1485 /* Check to see if ts_recent is over 24 days old. */ 1486 if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { 1487 /* 1488 * Invalidate ts_recent. If this segment updates 1489 * ts_recent, the age will be reset later and ts_recent 1490 * will get a valid value. If it does not, setting 1491 * ts_recent to zero will at least satisfy the 1492 * requirement that zero be placed in the timestamp 1493 * echo reply when ts_recent isn't valid. The 1494 * age isn't reset until we get a valid ts_recent 1495 * because we don't want out-of-order segments to be 1496 * dropped when ts_recent is old. 1497 */ 1498 tp->ts_recent = 0; 1499 } else { 1500 tcpstat.tcps_rcvduppack++; 1501 tcpstat.tcps_rcvdupbyte += tlen; 1502 tcpstat.tcps_pawsdrop++; 1503 if (tlen) 1504 goto dropafterack; 1505 goto drop; 1506 } 1507 } 1508 1509 /* 1510 * In the SYN-RECEIVED state, validate that the packet belongs to 1511 * this connection before trimming the data to fit the receive 1512 * window. Check the sequence number versus IRS since we know 1513 * the sequence numbers haven't wrapped. This is a partial fix 1514 * for the "LAND" DoS attack. 1515 */ 1516 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 1517 rstreason = BANDLIM_RST_OPENPORT; 1518 goto dropwithreset; 1519 } 1520 1521 todrop = tp->rcv_nxt - th->th_seq; 1522 if (todrop > 0) { 1523 if (thflags & TH_SYN) { 1524 thflags &= ~TH_SYN; 1525 th->th_seq++; 1526 if (th->th_urp > 1) 1527 th->th_urp--; 1528 else 1529 thflags &= ~TH_URG; 1530 todrop--; 1531 } 1532 /* 1533 * Following if statement from Stevens, vol. 2, p. 960. 1534 */ 1535 if (todrop > tlen 1536 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 1537 /* 1538 * Any valid FIN must be to the left of the window. 1539 * At this point the FIN must be a duplicate or out 1540 * of sequence; drop it. 1541 */ 1542 thflags &= ~TH_FIN; 1543 1544 /* 1545 * Send an ACK to resynchronize and drop any data. 1546 * But keep on processing for RST or ACK. 1547 */ 1548 tp->t_flags |= TF_ACKNOW; 1549 todrop = tlen; 1550 tcpstat.tcps_rcvduppack++; 1551 tcpstat.tcps_rcvdupbyte += todrop; 1552 } else { 1553 tcpstat.tcps_rcvpartduppack++; 1554 tcpstat.tcps_rcvpartdupbyte += todrop; 1555 } 1556 drop_hdrlen += todrop; /* drop from the top afterwards */ 1557 th->th_seq += todrop; 1558 tlen -= todrop; 1559 if (th->th_urp > todrop) 1560 th->th_urp -= todrop; 1561 else { 1562 thflags &= ~TH_URG; 1563 th->th_urp = 0; 1564 } 1565 } 1566 1567 /* 1568 * If new data are received on a connection after the 1569 * user processes are gone, then RST the other end. 1570 */ 1571 if ((so->so_state & SS_NOFDREF) && 1572 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 1573 char *s; 1574 1575 KASSERT(headlocked, ("%s: trimthenstep6: tcp_close.3: head " 1576 "not locked", __func__)); 1577 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) { 1578 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data after socket " 1579 "was closed, sending RST and removing tcpcb\n", 1580 s, __func__, tcpstates[tp->t_state], tlen); 1581 free(s, M_TCPLOG); 1582 } 1583 tp = tcp_close(tp); 1584 tcpstat.tcps_rcvafterclose++; 1585 rstreason = BANDLIM_UNLIMITED; 1586 goto dropwithreset; 1587 } 1588 1589 /* 1590 * If segment ends after window, drop trailing data 1591 * (and PUSH and FIN); if nothing left, just ACK. 1592 */ 1593 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 1594 if (todrop > 0) { 1595 tcpstat.tcps_rcvpackafterwin++; 1596 if (todrop >= tlen) { 1597 tcpstat.tcps_rcvbyteafterwin += tlen; 1598 /* 1599 * If window is closed can only take segments at 1600 * window edge, and have to drop data and PUSH from 1601 * incoming segments. Continue processing, but 1602 * remember to ack. Otherwise, drop segment 1603 * and ack. 1604 */ 1605 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 1606 tp->t_flags |= TF_ACKNOW; 1607 tcpstat.tcps_rcvwinprobe++; 1608 } else 1609 goto dropafterack; 1610 } else 1611 tcpstat.tcps_rcvbyteafterwin += todrop; 1612 m_adj(m, -todrop); 1613 tlen -= todrop; 1614 thflags &= ~(TH_PUSH|TH_FIN); 1615 } 1616 1617 /* 1618 * If last ACK falls within this segment's sequence numbers, 1619 * record its timestamp. 1620 * NOTE: 1621 * 1) That the test incorporates suggestions from the latest 1622 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1623 * 2) That updating only on newer timestamps interferes with 1624 * our earlier PAWS tests, so this check should be solely 1625 * predicated on the sequence space of this segment. 1626 * 3) That we modify the segment boundary check to be 1627 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 1628 * instead of RFC1323's 1629 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 1630 * This modified check allows us to overcome RFC1323's 1631 * limitations as described in Stevens TCP/IP Illustrated 1632 * Vol. 2 p.869. In such cases, we can still calculate the 1633 * RTT correctly when RCV.NXT == Last.ACK.Sent. 1634 */ 1635 if ((to.to_flags & TOF_TS) != 0 && 1636 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 1637 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 1638 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 1639 tp->ts_recent_age = ticks; 1640 tp->ts_recent = to.to_tsval; 1641 } 1642 1643 /* 1644 * If a SYN is in the window, then this is an 1645 * error and we send an RST and drop the connection. 1646 */ 1647 if (thflags & TH_SYN) { 1648 KASSERT(headlocked, ("%s: tcp_drop: trimthenstep6: " 1649 "head not locked", __func__)); 1650 tp = tcp_drop(tp, ECONNRESET); 1651 rstreason = BANDLIM_UNLIMITED; 1652 goto drop; 1653 } 1654 1655 /* 1656 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 1657 * flag is on (half-synchronized state), then queue data for 1658 * later processing; else drop segment and return. 1659 */ 1660 if ((thflags & TH_ACK) == 0) { 1661 if (tp->t_state == TCPS_SYN_RECEIVED || 1662 (tp->t_flags & TF_NEEDSYN)) 1663 goto step6; 1664 else if (tp->t_flags & TF_ACKNOW) 1665 goto dropafterack; 1666 else 1667 goto drop; 1668 } 1669 1670 /* 1671 * Ack processing. 1672 */ 1673 switch (tp->t_state) { 1674 1675 /* 1676 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 1677 * ESTABLISHED state and continue processing. 1678 * The ACK was checked above. 1679 */ 1680 case TCPS_SYN_RECEIVED: 1681 1682 tcpstat.tcps_connects++; 1683 soisconnected(so); 1684 /* Do window scaling? */ 1685 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1686 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1687 tp->rcv_scale = tp->request_r_scale; 1688 tp->snd_wnd = tiwin; 1689 } 1690 /* 1691 * Make transitions: 1692 * SYN-RECEIVED -> ESTABLISHED 1693 * SYN-RECEIVED* -> FIN-WAIT-1 1694 */ 1695 tp->t_starttime = ticks; 1696 if (tp->t_flags & TF_NEEDFIN) { 1697 tp->t_state = TCPS_FIN_WAIT_1; 1698 tp->t_flags &= ~TF_NEEDFIN; 1699 } else { 1700 tp->t_state = TCPS_ESTABLISHED; 1701 tcp_timer_activate(tp, TT_KEEP, tcp_keepidle); 1702 } 1703 /* 1704 * If segment contains data or ACK, will call tcp_reass() 1705 * later; if not, do so now to pass queued data to user. 1706 */ 1707 if (tlen == 0 && (thflags & TH_FIN) == 0) 1708 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 1709 (struct mbuf *)0); 1710 tp->snd_wl1 = th->th_seq - 1; 1711 /* FALLTHROUGH */ 1712 1713 /* 1714 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1715 * ACKs. If the ack is in the range 1716 * tp->snd_una < th->th_ack <= tp->snd_max 1717 * then advance tp->snd_una to th->th_ack and drop 1718 * data from the retransmission queue. If this ACK reflects 1719 * more up to date window information we update our window information. 1720 */ 1721 case TCPS_ESTABLISHED: 1722 case TCPS_FIN_WAIT_1: 1723 case TCPS_FIN_WAIT_2: 1724 case TCPS_CLOSE_WAIT: 1725 case TCPS_CLOSING: 1726 case TCPS_LAST_ACK: 1727 if (SEQ_GT(th->th_ack, tp->snd_max)) { 1728 tcpstat.tcps_rcvacktoomuch++; 1729 goto dropafterack; 1730 } 1731 if ((tp->t_flags & TF_SACK_PERMIT) && 1732 ((to.to_flags & TOF_SACK) || 1733 !TAILQ_EMPTY(&tp->snd_holes))) 1734 tcp_sack_doack(tp, &to, th->th_ack); 1735 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 1736 if (tlen == 0 && tiwin == tp->snd_wnd) { 1737 tcpstat.tcps_rcvdupack++; 1738 /* 1739 * If we have outstanding data (other than 1740 * a window probe), this is a completely 1741 * duplicate ack (ie, window info didn't 1742 * change), the ack is the biggest we've 1743 * seen and we've seen exactly our rexmt 1744 * threshhold of them, assume a packet 1745 * has been dropped and retransmit it. 1746 * Kludge snd_nxt & the congestion 1747 * window so we send only this one 1748 * packet. 1749 * 1750 * We know we're losing at the current 1751 * window size so do congestion avoidance 1752 * (set ssthresh to half the current window 1753 * and pull our congestion window back to 1754 * the new ssthresh). 1755 * 1756 * Dup acks mean that packets have left the 1757 * network (they're now cached at the receiver) 1758 * so bump cwnd by the amount in the receiver 1759 * to keep a constant cwnd packets in the 1760 * network. 1761 */ 1762 if (!tcp_timer_active(tp, TT_REXMT) || 1763 th->th_ack != tp->snd_una) 1764 tp->t_dupacks = 0; 1765 else if (++tp->t_dupacks > tcprexmtthresh || 1766 ((tcp_do_newreno || 1767 (tp->t_flags & TF_SACK_PERMIT)) && 1768 IN_FASTRECOVERY(tp))) { 1769 if ((tp->t_flags & TF_SACK_PERMIT) && 1770 IN_FASTRECOVERY(tp)) { 1771 int awnd; 1772 1773 /* 1774 * Compute the amount of data in flight first. 1775 * We can inject new data into the pipe iff 1776 * we have less than 1/2 the original window's 1777 * worth of data in flight. 1778 */ 1779 awnd = (tp->snd_nxt - tp->snd_fack) + 1780 tp->sackhint.sack_bytes_rexmit; 1781 if (awnd < tp->snd_ssthresh) { 1782 tp->snd_cwnd += tp->t_maxseg; 1783 if (tp->snd_cwnd > tp->snd_ssthresh) 1784 tp->snd_cwnd = tp->snd_ssthresh; 1785 } 1786 } else 1787 tp->snd_cwnd += tp->t_maxseg; 1788 (void) tcp_output(tp); 1789 goto drop; 1790 } else if (tp->t_dupacks == tcprexmtthresh) { 1791 tcp_seq onxt = tp->snd_nxt; 1792 u_int win; 1793 1794 /* 1795 * If we're doing sack, check to 1796 * see if we're already in sack 1797 * recovery. If we're not doing sack, 1798 * check to see if we're in newreno 1799 * recovery. 1800 */ 1801 if (tp->t_flags & TF_SACK_PERMIT) { 1802 if (IN_FASTRECOVERY(tp)) { 1803 tp->t_dupacks = 0; 1804 break; 1805 } 1806 } else if (tcp_do_newreno) { 1807 if (SEQ_LEQ(th->th_ack, 1808 tp->snd_recover)) { 1809 tp->t_dupacks = 0; 1810 break; 1811 } 1812 } 1813 win = min(tp->snd_wnd, tp->snd_cwnd) / 1814 2 / tp->t_maxseg; 1815 if (win < 2) 1816 win = 2; 1817 tp->snd_ssthresh = win * tp->t_maxseg; 1818 ENTER_FASTRECOVERY(tp); 1819 tp->snd_recover = tp->snd_max; 1820 tcp_timer_activate(tp, TT_REXMT, 0); 1821 tp->t_rtttime = 0; 1822 if (tp->t_flags & TF_SACK_PERMIT) { 1823 tcpstat.tcps_sack_recovery_episode++; 1824 tp->sack_newdata = tp->snd_nxt; 1825 tp->snd_cwnd = tp->t_maxseg; 1826 (void) tcp_output(tp); 1827 goto drop; 1828 } 1829 tp->snd_nxt = th->th_ack; 1830 tp->snd_cwnd = tp->t_maxseg; 1831 (void) tcp_output(tp); 1832 KASSERT(tp->snd_limited <= 2, 1833 ("%s: tp->snd_limited too big", 1834 __func__)); 1835 tp->snd_cwnd = tp->snd_ssthresh + 1836 tp->t_maxseg * 1837 (tp->t_dupacks - tp->snd_limited); 1838 if (SEQ_GT(onxt, tp->snd_nxt)) 1839 tp->snd_nxt = onxt; 1840 goto drop; 1841 } else if (tcp_do_rfc3042) { 1842 u_long oldcwnd = tp->snd_cwnd; 1843 tcp_seq oldsndmax = tp->snd_max; 1844 u_int sent; 1845 1846 KASSERT(tp->t_dupacks == 1 || 1847 tp->t_dupacks == 2, 1848 ("%s: dupacks not 1 or 2", 1849 __func__)); 1850 if (tp->t_dupacks == 1) 1851 tp->snd_limited = 0; 1852 tp->snd_cwnd = 1853 (tp->snd_nxt - tp->snd_una) + 1854 (tp->t_dupacks - tp->snd_limited) * 1855 tp->t_maxseg; 1856 (void) tcp_output(tp); 1857 sent = tp->snd_max - oldsndmax; 1858 if (sent > tp->t_maxseg) { 1859 KASSERT((tp->t_dupacks == 2 && 1860 tp->snd_limited == 0) || 1861 (sent == tp->t_maxseg + 1 && 1862 tp->t_flags & TF_SENTFIN), 1863 ("%s: sent too much", 1864 __func__)); 1865 tp->snd_limited = 2; 1866 } else if (sent > 0) 1867 ++tp->snd_limited; 1868 tp->snd_cwnd = oldcwnd; 1869 goto drop; 1870 } 1871 } else 1872 tp->t_dupacks = 0; 1873 break; 1874 } 1875 1876 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 1877 ("%s: th_ack <= snd_una", __func__)); 1878 1879 /* 1880 * If the congestion window was inflated to account 1881 * for the other side's cached packets, retract it. 1882 */ 1883 if (tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) { 1884 if (IN_FASTRECOVERY(tp)) { 1885 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 1886 if (tp->t_flags & TF_SACK_PERMIT) 1887 tcp_sack_partialack(tp, th); 1888 else 1889 tcp_newreno_partial_ack(tp, th); 1890 } else { 1891 /* 1892 * Out of fast recovery. 1893 * Window inflation should have left us 1894 * with approximately snd_ssthresh 1895 * outstanding data. 1896 * But in case we would be inclined to 1897 * send a burst, better to do it via 1898 * the slow start mechanism. 1899 */ 1900 if (SEQ_GT(th->th_ack + 1901 tp->snd_ssthresh, 1902 tp->snd_max)) 1903 tp->snd_cwnd = tp->snd_max - 1904 th->th_ack + 1905 tp->t_maxseg; 1906 else 1907 tp->snd_cwnd = tp->snd_ssthresh; 1908 } 1909 } 1910 } else { 1911 if (tp->t_dupacks >= tcprexmtthresh && 1912 tp->snd_cwnd > tp->snd_ssthresh) 1913 tp->snd_cwnd = tp->snd_ssthresh; 1914 } 1915 tp->t_dupacks = 0; 1916 /* 1917 * If we reach this point, ACK is not a duplicate, 1918 * i.e., it ACKs something we sent. 1919 */ 1920 if (tp->t_flags & TF_NEEDSYN) { 1921 /* 1922 * T/TCP: Connection was half-synchronized, and our 1923 * SYN has been ACK'd (so connection is now fully 1924 * synchronized). Go to non-starred state, 1925 * increment snd_una for ACK of SYN, and check if 1926 * we can do window scaling. 1927 */ 1928 tp->t_flags &= ~TF_NEEDSYN; 1929 tp->snd_una++; 1930 /* Do window scaling? */ 1931 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1932 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1933 tp->rcv_scale = tp->request_r_scale; 1934 /* Send window already scaled. */ 1935 } 1936 } 1937 1938 process_ACK: 1939 KASSERT(headlocked, ("%s: process_ACK: head not locked", 1940 __func__)); 1941 INP_WLOCK_ASSERT(tp->t_inpcb); 1942 1943 acked = th->th_ack - tp->snd_una; 1944 tcpstat.tcps_rcvackpack++; 1945 tcpstat.tcps_rcvackbyte += acked; 1946 1947 /* 1948 * If we just performed our first retransmit, and the ACK 1949 * arrives within our recovery window, then it was a mistake 1950 * to do the retransmit in the first place. Recover our 1951 * original cwnd and ssthresh, and proceed to transmit where 1952 * we left off. 1953 */ 1954 if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { 1955 ++tcpstat.tcps_sndrexmitbad; 1956 tp->snd_cwnd = tp->snd_cwnd_prev; 1957 tp->snd_ssthresh = tp->snd_ssthresh_prev; 1958 tp->snd_recover = tp->snd_recover_prev; 1959 if (tp->t_flags & TF_WASFRECOVERY) 1960 ENTER_FASTRECOVERY(tp); 1961 tp->snd_nxt = tp->snd_max; 1962 tp->t_badrxtwin = 0; /* XXX probably not required */ 1963 } 1964 1965 /* 1966 * If we have a timestamp reply, update smoothed 1967 * round trip time. If no timestamp is present but 1968 * transmit timer is running and timed sequence 1969 * number was acked, update smoothed round trip time. 1970 * Since we now have an rtt measurement, cancel the 1971 * timer backoff (cf., Phil Karn's retransmit alg.). 1972 * Recompute the initial retransmit timer. 1973 * 1974 * Some boxes send broken timestamp replies 1975 * during the SYN+ACK phase, ignore 1976 * timestamps of 0 or we could calculate a 1977 * huge RTT and blow up the retransmit timer. 1978 */ 1979 if ((to.to_flags & TOF_TS) != 0 && 1980 to.to_tsecr) { 1981 if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr) 1982 tp->t_rttlow = ticks - to.to_tsecr; 1983 tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); 1984 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 1985 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 1986 tp->t_rttlow = ticks - tp->t_rtttime; 1987 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 1988 } 1989 tcp_xmit_bandwidth_limit(tp, th->th_ack); 1990 1991 /* 1992 * If all outstanding data is acked, stop retransmit 1993 * timer and remember to restart (more output or persist). 1994 * If there is more data to be acked, restart retransmit 1995 * timer, using current (possibly backed-off) value. 1996 */ 1997 if (th->th_ack == tp->snd_max) { 1998 tcp_timer_activate(tp, TT_REXMT, 0); 1999 needoutput = 1; 2000 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2001 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2002 2003 /* 2004 * If no data (only SYN) was ACK'd, 2005 * skip rest of ACK processing. 2006 */ 2007 if (acked == 0) 2008 goto step6; 2009 2010 /* 2011 * When new data is acked, open the congestion window. 2012 * If the window gives us less than ssthresh packets 2013 * in flight, open exponentially (maxseg per packet). 2014 * Otherwise open linearly: maxseg per window 2015 * (maxseg^2 / cwnd per packet). 2016 */ 2017 if ((!tcp_do_newreno && !(tp->t_flags & TF_SACK_PERMIT)) || 2018 !IN_FASTRECOVERY(tp)) { 2019 u_int cw = tp->snd_cwnd; 2020 u_int incr = tp->t_maxseg; 2021 if (cw > tp->snd_ssthresh) 2022 incr = incr * incr / cw; 2023 tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale); 2024 } 2025 SOCKBUF_LOCK(&so->so_snd); 2026 if (acked > so->so_snd.sb_cc) { 2027 tp->snd_wnd -= so->so_snd.sb_cc; 2028 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2029 ourfinisacked = 1; 2030 } else { 2031 sbdrop_locked(&so->so_snd, acked); 2032 tp->snd_wnd -= acked; 2033 ourfinisacked = 0; 2034 } 2035 /* NB: sowwakeup_locked() does an implicit unlock. */ 2036 sowwakeup_locked(so); 2037 /* Detect una wraparound. */ 2038 if ((tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) && 2039 !IN_FASTRECOVERY(tp) && 2040 SEQ_GT(tp->snd_una, tp->snd_recover) && 2041 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2042 tp->snd_recover = th->th_ack - 1; 2043 if ((tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) && 2044 IN_FASTRECOVERY(tp) && 2045 SEQ_GEQ(th->th_ack, tp->snd_recover)) 2046 EXIT_FASTRECOVERY(tp); 2047 tp->snd_una = th->th_ack; 2048 if (tp->t_flags & TF_SACK_PERMIT) { 2049 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2050 tp->snd_recover = tp->snd_una; 2051 } 2052 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2053 tp->snd_nxt = tp->snd_una; 2054 2055 switch (tp->t_state) { 2056 2057 /* 2058 * In FIN_WAIT_1 STATE in addition to the processing 2059 * for the ESTABLISHED state if our FIN is now acknowledged 2060 * then enter FIN_WAIT_2. 2061 */ 2062 case TCPS_FIN_WAIT_1: 2063 if (ourfinisacked) { 2064 /* 2065 * If we can't receive any more 2066 * data, then closing user can proceed. 2067 * Starting the timer is contrary to the 2068 * specification, but if we don't get a FIN 2069 * we'll hang forever. 2070 * 2071 * XXXjl: 2072 * we should release the tp also, and use a 2073 * compressed state. 2074 */ 2075 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2076 int timeout; 2077 2078 soisdisconnected(so); 2079 timeout = (tcp_fast_finwait2_recycle) ? 2080 tcp_finwait2_timeout : tcp_maxidle; 2081 tcp_timer_activate(tp, TT_2MSL, timeout); 2082 } 2083 tp->t_state = TCPS_FIN_WAIT_2; 2084 } 2085 break; 2086 2087 /* 2088 * In CLOSING STATE in addition to the processing for 2089 * the ESTABLISHED state if the ACK acknowledges our FIN 2090 * then enter the TIME-WAIT state, otherwise ignore 2091 * the segment. 2092 */ 2093 case TCPS_CLOSING: 2094 if (ourfinisacked) { 2095 KASSERT(headlocked, ("%s: process_ACK: " 2096 "head not locked", __func__)); 2097 tcp_twstart(tp); 2098 INP_INFO_WUNLOCK(&tcbinfo); 2099 headlocked = 0; 2100 m_freem(m); 2101 return; 2102 } 2103 break; 2104 2105 /* 2106 * In LAST_ACK, we may still be waiting for data to drain 2107 * and/or to be acked, as well as for the ack of our FIN. 2108 * If our FIN is now acknowledged, delete the TCB, 2109 * enter the closed state and return. 2110 */ 2111 case TCPS_LAST_ACK: 2112 if (ourfinisacked) { 2113 KASSERT(headlocked, ("%s: process_ACK: " 2114 "tcp_close: head not locked", __func__)); 2115 tp = tcp_close(tp); 2116 goto drop; 2117 } 2118 break; 2119 } 2120 } 2121 2122 step6: 2123 KASSERT(headlocked, ("%s: step6: head not locked", __func__)); 2124 INP_WLOCK_ASSERT(tp->t_inpcb); 2125 2126 /* 2127 * Update window information. 2128 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2129 */ 2130 if ((thflags & TH_ACK) && 2131 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2132 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2133 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2134 /* keep track of pure window updates */ 2135 if (tlen == 0 && 2136 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2137 tcpstat.tcps_rcvwinupd++; 2138 tp->snd_wnd = tiwin; 2139 tp->snd_wl1 = th->th_seq; 2140 tp->snd_wl2 = th->th_ack; 2141 if (tp->snd_wnd > tp->max_sndwnd) 2142 tp->max_sndwnd = tp->snd_wnd; 2143 needoutput = 1; 2144 } 2145 2146 /* 2147 * Process segments with URG. 2148 */ 2149 if ((thflags & TH_URG) && th->th_urp && 2150 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2151 /* 2152 * This is a kludge, but if we receive and accept 2153 * random urgent pointers, we'll crash in 2154 * soreceive. It's hard to imagine someone 2155 * actually wanting to send this much urgent data. 2156 */ 2157 SOCKBUF_LOCK(&so->so_rcv); 2158 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2159 th->th_urp = 0; /* XXX */ 2160 thflags &= ~TH_URG; /* XXX */ 2161 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2162 goto dodata; /* XXX */ 2163 } 2164 /* 2165 * If this segment advances the known urgent pointer, 2166 * then mark the data stream. This should not happen 2167 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2168 * a FIN has been received from the remote side. 2169 * In these states we ignore the URG. 2170 * 2171 * According to RFC961 (Assigned Protocols), 2172 * the urgent pointer points to the last octet 2173 * of urgent data. We continue, however, 2174 * to consider it to indicate the first octet 2175 * of data past the urgent section as the original 2176 * spec states (in one of two places). 2177 */ 2178 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2179 tp->rcv_up = th->th_seq + th->th_urp; 2180 so->so_oobmark = so->so_rcv.sb_cc + 2181 (tp->rcv_up - tp->rcv_nxt) - 1; 2182 if (so->so_oobmark == 0) 2183 so->so_rcv.sb_state |= SBS_RCVATMARK; 2184 sohasoutofband(so); 2185 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2186 } 2187 SOCKBUF_UNLOCK(&so->so_rcv); 2188 /* 2189 * Remove out of band data so doesn't get presented to user. 2190 * This can happen independent of advancing the URG pointer, 2191 * but if two URG's are pending at once, some out-of-band 2192 * data may creep in... ick. 2193 */ 2194 if (th->th_urp <= (u_long)tlen && 2195 !(so->so_options & SO_OOBINLINE)) { 2196 /* hdr drop is delayed */ 2197 tcp_pulloutofband(so, th, m, drop_hdrlen); 2198 } 2199 } else { 2200 /* 2201 * If no out of band data is expected, 2202 * pull receive urgent pointer along 2203 * with the receive window. 2204 */ 2205 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2206 tp->rcv_up = tp->rcv_nxt; 2207 } 2208 dodata: /* XXX */ 2209 KASSERT(headlocked, ("%s: dodata: head not locked", __func__)); 2210 INP_WLOCK_ASSERT(tp->t_inpcb); 2211 2212 /* 2213 * Process the segment text, merging it into the TCP sequencing queue, 2214 * and arranging for acknowledgment of receipt if necessary. 2215 * This process logically involves adjusting tp->rcv_wnd as data 2216 * is presented to the user (this happens in tcp_usrreq.c, 2217 * case PRU_RCVD). If a FIN has already been received on this 2218 * connection then we just ignore the text. 2219 */ 2220 if ((tlen || (thflags & TH_FIN)) && 2221 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2222 tcp_seq save_start = th->th_seq; 2223 m_adj(m, drop_hdrlen); /* delayed header drop */ 2224 /* 2225 * Insert segment which includes th into TCP reassembly queue 2226 * with control block tp. Set thflags to whether reassembly now 2227 * includes a segment with FIN. This handles the common case 2228 * inline (segment is the next to be received on an established 2229 * connection, and the queue is empty), avoiding linkage into 2230 * and removal from the queue and repetition of various 2231 * conversions. 2232 * Set DELACK for segments received in order, but ack 2233 * immediately when segments are out of order (so 2234 * fast retransmit can work). 2235 */ 2236 if (th->th_seq == tp->rcv_nxt && 2237 LIST_EMPTY(&tp->t_segq) && 2238 TCPS_HAVEESTABLISHED(tp->t_state)) { 2239 if (DELAY_ACK(tp)) 2240 tp->t_flags |= TF_DELACK; 2241 else 2242 tp->t_flags |= TF_ACKNOW; 2243 tp->rcv_nxt += tlen; 2244 thflags = th->th_flags & TH_FIN; 2245 tcpstat.tcps_rcvpack++; 2246 tcpstat.tcps_rcvbyte += tlen; 2247 ND6_HINT(tp); 2248 SOCKBUF_LOCK(&so->so_rcv); 2249 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2250 m_freem(m); 2251 else 2252 sbappendstream_locked(&so->so_rcv, m); 2253 /* NB: sorwakeup_locked() does an implicit unlock. */ 2254 sorwakeup_locked(so); 2255 } else { 2256 /* 2257 * XXX: Due to the header drop above "th" is 2258 * theoretically invalid by now. Fortunately 2259 * m_adj() doesn't actually frees any mbufs 2260 * when trimming from the head. 2261 */ 2262 thflags = tcp_reass(tp, th, &tlen, m); 2263 tp->t_flags |= TF_ACKNOW; 2264 } 2265 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 2266 tcp_update_sack_list(tp, save_start, save_start + tlen); 2267 #if 0 2268 /* 2269 * Note the amount of data that peer has sent into 2270 * our window, in order to estimate the sender's 2271 * buffer size. 2272 * XXX: Unused. 2273 */ 2274 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2275 #endif 2276 } else { 2277 m_freem(m); 2278 thflags &= ~TH_FIN; 2279 } 2280 2281 /* 2282 * If FIN is received ACK the FIN and let the user know 2283 * that the connection is closing. 2284 */ 2285 if (thflags & TH_FIN) { 2286 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2287 socantrcvmore(so); 2288 /* 2289 * If connection is half-synchronized 2290 * (ie NEEDSYN flag on) then delay ACK, 2291 * so it may be piggybacked when SYN is sent. 2292 * Otherwise, since we received a FIN then no 2293 * more input can be expected, send ACK now. 2294 */ 2295 if (tp->t_flags & TF_NEEDSYN) 2296 tp->t_flags |= TF_DELACK; 2297 else 2298 tp->t_flags |= TF_ACKNOW; 2299 tp->rcv_nxt++; 2300 } 2301 switch (tp->t_state) { 2302 2303 /* 2304 * In SYN_RECEIVED and ESTABLISHED STATES 2305 * enter the CLOSE_WAIT state. 2306 */ 2307 case TCPS_SYN_RECEIVED: 2308 tp->t_starttime = ticks; 2309 /* FALLTHROUGH */ 2310 case TCPS_ESTABLISHED: 2311 tp->t_state = TCPS_CLOSE_WAIT; 2312 break; 2313 2314 /* 2315 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2316 * enter the CLOSING state. 2317 */ 2318 case TCPS_FIN_WAIT_1: 2319 tp->t_state = TCPS_CLOSING; 2320 break; 2321 2322 /* 2323 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2324 * starting the time-wait timer, turning off the other 2325 * standard timers. 2326 */ 2327 case TCPS_FIN_WAIT_2: 2328 KASSERT(headlocked == 1, ("%s: dodata: " 2329 "TCP_FIN_WAIT_2: head not locked", __func__)); 2330 tcp_twstart(tp); 2331 INP_INFO_WUNLOCK(&tcbinfo); 2332 return; 2333 } 2334 } 2335 INP_INFO_WUNLOCK(&tcbinfo); 2336 headlocked = 0; 2337 #ifdef TCPDEBUG 2338 if (so->so_options & SO_DEBUG) 2339 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2340 &tcp_savetcp, 0); 2341 #endif 2342 2343 /* 2344 * Return any desired output. 2345 */ 2346 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2347 (void) tcp_output(tp); 2348 2349 check_delack: 2350 KASSERT(headlocked == 0, ("%s: check_delack: head locked", 2351 __func__)); 2352 INP_INFO_UNLOCK_ASSERT(&tcbinfo); 2353 INP_WLOCK_ASSERT(tp->t_inpcb); 2354 if (tp->t_flags & TF_DELACK) { 2355 tp->t_flags &= ~TF_DELACK; 2356 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 2357 } 2358 INP_WUNLOCK(tp->t_inpcb); 2359 return; 2360 2361 dropafterack: 2362 KASSERT(headlocked, ("%s: dropafterack: head not locked", __func__)); 2363 /* 2364 * Generate an ACK dropping incoming segment if it occupies 2365 * sequence space, where the ACK reflects our state. 2366 * 2367 * We can now skip the test for the RST flag since all 2368 * paths to this code happen after packets containing 2369 * RST have been dropped. 2370 * 2371 * In the SYN-RECEIVED state, don't send an ACK unless the 2372 * segment we received passes the SYN-RECEIVED ACK test. 2373 * If it fails send a RST. This breaks the loop in the 2374 * "LAND" DoS attack, and also prevents an ACK storm 2375 * between two listening ports that have been sent forged 2376 * SYN segments, each with the source address of the other. 2377 */ 2378 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 2379 (SEQ_GT(tp->snd_una, th->th_ack) || 2380 SEQ_GT(th->th_ack, tp->snd_max)) ) { 2381 rstreason = BANDLIM_RST_OPENPORT; 2382 goto dropwithreset; 2383 } 2384 #ifdef TCPDEBUG 2385 if (so->so_options & SO_DEBUG) 2386 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2387 &tcp_savetcp, 0); 2388 #endif 2389 KASSERT(headlocked, ("%s: headlocked should be 1", __func__)); 2390 INP_INFO_WUNLOCK(&tcbinfo); 2391 tp->t_flags |= TF_ACKNOW; 2392 (void) tcp_output(tp); 2393 INP_WUNLOCK(tp->t_inpcb); 2394 m_freem(m); 2395 return; 2396 2397 dropwithreset: 2398 KASSERT(headlocked, ("%s: dropwithreset: head not locked", __func__)); 2399 2400 tcp_dropwithreset(m, th, tp, tlen, rstreason); 2401 2402 if (tp != NULL) 2403 INP_WUNLOCK(tp->t_inpcb); 2404 if (headlocked) 2405 INP_INFO_WUNLOCK(&tcbinfo); 2406 return; 2407 2408 drop: 2409 /* 2410 * Drop space held by incoming segment and return. 2411 */ 2412 #ifdef TCPDEBUG 2413 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 2414 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 2415 &tcp_savetcp, 0); 2416 #endif 2417 if (tp != NULL) 2418 INP_WUNLOCK(tp->t_inpcb); 2419 if (headlocked) 2420 INP_INFO_WUNLOCK(&tcbinfo); 2421 m_freem(m); 2422 return; 2423 } 2424 2425 /* 2426 * Issue RST and make ACK acceptable to originator of segment. 2427 * The mbuf must still include the original packet header. 2428 * tp may be NULL. 2429 */ 2430 static void 2431 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 2432 int tlen, int rstreason) 2433 { 2434 struct ip *ip; 2435 #ifdef INET6 2436 struct ip6_hdr *ip6; 2437 #endif 2438 2439 if (tp != NULL) { 2440 INP_WLOCK_ASSERT(tp->t_inpcb); 2441 } 2442 2443 /* Don't bother if destination was broadcast/multicast. */ 2444 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 2445 goto drop; 2446 #ifdef INET6 2447 if (mtod(m, struct ip *)->ip_v == 6) { 2448 ip6 = mtod(m, struct ip6_hdr *); 2449 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 2450 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 2451 goto drop; 2452 /* IPv6 anycast check is done at tcp6_input() */ 2453 } else 2454 #endif 2455 { 2456 ip = mtod(m, struct ip *); 2457 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 2458 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 2459 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 2460 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 2461 goto drop; 2462 } 2463 2464 /* Perform bandwidth limiting. */ 2465 if (badport_bandlim(rstreason) < 0) 2466 goto drop; 2467 2468 /* tcp_respond consumes the mbuf chain. */ 2469 if (th->th_flags & TH_ACK) { 2470 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 2471 th->th_ack, TH_RST); 2472 } else { 2473 if (th->th_flags & TH_SYN) 2474 tlen++; 2475 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 2476 (tcp_seq)0, TH_RST|TH_ACK); 2477 } 2478 return; 2479 drop: 2480 m_freem(m); 2481 return; 2482 } 2483 2484 /* 2485 * Parse TCP options and place in tcpopt. 2486 */ 2487 static void 2488 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 2489 { 2490 int opt, optlen; 2491 2492 to->to_flags = 0; 2493 for (; cnt > 0; cnt -= optlen, cp += optlen) { 2494 opt = cp[0]; 2495 if (opt == TCPOPT_EOL) 2496 break; 2497 if (opt == TCPOPT_NOP) 2498 optlen = 1; 2499 else { 2500 if (cnt < 2) 2501 break; 2502 optlen = cp[1]; 2503 if (optlen < 2 || optlen > cnt) 2504 break; 2505 } 2506 switch (opt) { 2507 case TCPOPT_MAXSEG: 2508 if (optlen != TCPOLEN_MAXSEG) 2509 continue; 2510 if (!(flags & TO_SYN)) 2511 continue; 2512 to->to_flags |= TOF_MSS; 2513 bcopy((char *)cp + 2, 2514 (char *)&to->to_mss, sizeof(to->to_mss)); 2515 to->to_mss = ntohs(to->to_mss); 2516 break; 2517 case TCPOPT_WINDOW: 2518 if (optlen != TCPOLEN_WINDOW) 2519 continue; 2520 if (!(flags & TO_SYN)) 2521 continue; 2522 to->to_flags |= TOF_SCALE; 2523 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 2524 break; 2525 case TCPOPT_TIMESTAMP: 2526 if (optlen != TCPOLEN_TIMESTAMP) 2527 continue; 2528 to->to_flags |= TOF_TS; 2529 bcopy((char *)cp + 2, 2530 (char *)&to->to_tsval, sizeof(to->to_tsval)); 2531 to->to_tsval = ntohl(to->to_tsval); 2532 bcopy((char *)cp + 6, 2533 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 2534 to->to_tsecr = ntohl(to->to_tsecr); 2535 break; 2536 #ifdef TCP_SIGNATURE 2537 /* 2538 * XXX In order to reply to a host which has set the 2539 * TCP_SIGNATURE option in its initial SYN, we have to 2540 * record the fact that the option was observed here 2541 * for the syncache code to perform the correct response. 2542 */ 2543 case TCPOPT_SIGNATURE: 2544 if (optlen != TCPOLEN_SIGNATURE) 2545 continue; 2546 to->to_flags |= TOF_SIGNATURE; 2547 to->to_signature = cp + 2; 2548 break; 2549 #endif 2550 case TCPOPT_SACK_PERMITTED: 2551 if (optlen != TCPOLEN_SACK_PERMITTED) 2552 continue; 2553 if (!(flags & TO_SYN)) 2554 continue; 2555 if (!tcp_do_sack) 2556 continue; 2557 to->to_flags |= TOF_SACKPERM; 2558 break; 2559 case TCPOPT_SACK: 2560 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 2561 continue; 2562 if (flags & TO_SYN) 2563 continue; 2564 to->to_flags |= TOF_SACK; 2565 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 2566 to->to_sacks = cp + 2; 2567 tcpstat.tcps_sack_rcv_blocks++; 2568 break; 2569 default: 2570 continue; 2571 } 2572 } 2573 } 2574 2575 /* 2576 * Pull out of band byte out of a segment so 2577 * it doesn't appear in the user's data queue. 2578 * It is still reflected in the segment length for 2579 * sequencing purposes. 2580 */ 2581 static void 2582 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 2583 int off) 2584 { 2585 int cnt = off + th->th_urp - 1; 2586 2587 while (cnt >= 0) { 2588 if (m->m_len > cnt) { 2589 char *cp = mtod(m, caddr_t) + cnt; 2590 struct tcpcb *tp = sototcpcb(so); 2591 2592 INP_WLOCK_ASSERT(tp->t_inpcb); 2593 2594 tp->t_iobc = *cp; 2595 tp->t_oobflags |= TCPOOB_HAVEDATA; 2596 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 2597 m->m_len--; 2598 if (m->m_flags & M_PKTHDR) 2599 m->m_pkthdr.len--; 2600 return; 2601 } 2602 cnt -= m->m_len; 2603 m = m->m_next; 2604 if (m == NULL) 2605 break; 2606 } 2607 panic("tcp_pulloutofband"); 2608 } 2609 2610 /* 2611 * Collect new round-trip time estimate 2612 * and update averages and current timeout. 2613 */ 2614 static void 2615 tcp_xmit_timer(struct tcpcb *tp, int rtt) 2616 { 2617 int delta; 2618 2619 INP_WLOCK_ASSERT(tp->t_inpcb); 2620 2621 tcpstat.tcps_rttupdated++; 2622 tp->t_rttupdated++; 2623 if (tp->t_srtt != 0) { 2624 /* 2625 * srtt is stored as fixed point with 5 bits after the 2626 * binary point (i.e., scaled by 8). The following magic 2627 * is equivalent to the smoothing algorithm in rfc793 with 2628 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 2629 * point). Adjust rtt to origin 0. 2630 */ 2631 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 2632 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 2633 2634 if ((tp->t_srtt += delta) <= 0) 2635 tp->t_srtt = 1; 2636 2637 /* 2638 * We accumulate a smoothed rtt variance (actually, a 2639 * smoothed mean difference), then set the retransmit 2640 * timer to smoothed rtt + 4 times the smoothed variance. 2641 * rttvar is stored as fixed point with 4 bits after the 2642 * binary point (scaled by 16). The following is 2643 * equivalent to rfc793 smoothing with an alpha of .75 2644 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 2645 * rfc793's wired-in beta. 2646 */ 2647 if (delta < 0) 2648 delta = -delta; 2649 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 2650 if ((tp->t_rttvar += delta) <= 0) 2651 tp->t_rttvar = 1; 2652 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 2653 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2654 } else { 2655 /* 2656 * No rtt measurement yet - use the unsmoothed rtt. 2657 * Set the variance to half the rtt (so our first 2658 * retransmit happens at 3*rtt). 2659 */ 2660 tp->t_srtt = rtt << TCP_RTT_SHIFT; 2661 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 2662 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 2663 } 2664 tp->t_rtttime = 0; 2665 tp->t_rxtshift = 0; 2666 2667 /* 2668 * the retransmit should happen at rtt + 4 * rttvar. 2669 * Because of the way we do the smoothing, srtt and rttvar 2670 * will each average +1/2 tick of bias. When we compute 2671 * the retransmit timer, we want 1/2 tick of rounding and 2672 * 1 extra tick because of +-1/2 tick uncertainty in the 2673 * firing of the timer. The bias will give us exactly the 2674 * 1.5 tick we need. But, because the bias is 2675 * statistical, we have to test that we don't drop below 2676 * the minimum feasible timer (which is 2 ticks). 2677 */ 2678 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 2679 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 2680 2681 /* 2682 * We received an ack for a packet that wasn't retransmitted; 2683 * it is probably safe to discard any error indications we've 2684 * received recently. This isn't quite right, but close enough 2685 * for now (a route might have failed after we sent a segment, 2686 * and the return path might not be symmetrical). 2687 */ 2688 tp->t_softerror = 0; 2689 } 2690 2691 /* 2692 * Determine a reasonable value for maxseg size. 2693 * If the route is known, check route for mtu. 2694 * If none, use an mss that can be handled on the outgoing 2695 * interface without forcing IP to fragment; if bigger than 2696 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 2697 * to utilize large mbufs. If no route is found, route has no mtu, 2698 * or the destination isn't local, use a default, hopefully conservative 2699 * size (usually 512 or the default IP max size, but no more than the mtu 2700 * of the interface), as we can't discover anything about intervening 2701 * gateways or networks. We also initialize the congestion/slow start 2702 * window to be a single segment if the destination isn't local. 2703 * While looking at the routing entry, we also initialize other path-dependent 2704 * parameters from pre-set or cached values in the routing entry. 2705 * 2706 * Also take into account the space needed for options that we 2707 * send regularly. Make maxseg shorter by that amount to assure 2708 * that we can send maxseg amount of data even when the options 2709 * are present. Store the upper limit of the length of options plus 2710 * data in maxopd. 2711 * 2712 * In case of T/TCP, we call this routine during implicit connection 2713 * setup as well (offer = -1), to initialize maxseg from the cached 2714 * MSS of our peer. 2715 * 2716 * NOTE that this routine is only called when we process an incoming 2717 * segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt(). 2718 */ 2719 void 2720 tcp_mss(struct tcpcb *tp, int offer) 2721 { 2722 int rtt, mss; 2723 u_long bufsize; 2724 u_long maxmtu; 2725 struct inpcb *inp = tp->t_inpcb; 2726 struct socket *so; 2727 struct hc_metrics_lite metrics; 2728 int origoffer = offer; 2729 int mtuflags = 0; 2730 #ifdef INET6 2731 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 2732 size_t min_protoh = isipv6 ? 2733 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 2734 sizeof (struct tcpiphdr); 2735 #else 2736 const size_t min_protoh = sizeof(struct tcpiphdr); 2737 #endif 2738 2739 INP_WLOCK_ASSERT(tp->t_inpcb); 2740 2741 /* Initialize. */ 2742 #ifdef INET6 2743 if (isipv6) { 2744 maxmtu = tcp_maxmtu6(&inp->inp_inc, &mtuflags); 2745 tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt; 2746 } else 2747 #endif 2748 { 2749 maxmtu = tcp_maxmtu(&inp->inp_inc, &mtuflags); 2750 tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; 2751 } 2752 2753 /* 2754 * No route to sender, stay with default mss and return. 2755 */ 2756 if (maxmtu == 0) 2757 return; 2758 2759 /* What have we got? */ 2760 switch (offer) { 2761 case 0: 2762 /* 2763 * Offer == 0 means that there was no MSS on the SYN 2764 * segment, in this case we use tcp_mssdflt as 2765 * already assigned to t_maxopd above. 2766 */ 2767 offer = tp->t_maxopd; 2768 break; 2769 2770 case -1: 2771 /* 2772 * Offer == -1 means that we didn't receive SYN yet. 2773 */ 2774 /* FALLTHROUGH */ 2775 2776 default: 2777 /* 2778 * Prevent DoS attack with too small MSS. Round up 2779 * to at least minmss. 2780 */ 2781 offer = max(offer, tcp_minmss); 2782 /* 2783 * Sanity check: make sure that maxopd will be large 2784 * enough to allow some data on segments even if the 2785 * all the option space is used (40bytes). Otherwise 2786 * funny things may happen in tcp_output. 2787 */ 2788 offer = max(offer, 64); 2789 } 2790 2791 /* 2792 * rmx information is now retrieved from tcp_hostcache. 2793 */ 2794 tcp_hc_get(&inp->inp_inc, &metrics); 2795 2796 /* 2797 * If there's a discovered mtu int tcp hostcache, use it 2798 * else, use the link mtu. 2799 */ 2800 if (metrics.rmx_mtu) 2801 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 2802 else { 2803 #ifdef INET6 2804 if (isipv6) { 2805 mss = maxmtu - min_protoh; 2806 if (!path_mtu_discovery && 2807 !in6_localaddr(&inp->in6p_faddr)) 2808 mss = min(mss, tcp_v6mssdflt); 2809 } else 2810 #endif 2811 { 2812 mss = maxmtu - min_protoh; 2813 if (!path_mtu_discovery && 2814 !in_localaddr(inp->inp_faddr)) 2815 mss = min(mss, tcp_mssdflt); 2816 } 2817 } 2818 mss = min(mss, offer); 2819 2820 /* 2821 * maxopd stores the maximum length of data AND options 2822 * in a segment; maxseg is the amount of data in a normal 2823 * segment. We need to store this value (maxopd) apart 2824 * from maxseg, because now every segment carries options 2825 * and thus we normally have somewhat less data in segments. 2826 */ 2827 tp->t_maxopd = mss; 2828 2829 /* 2830 * origoffer==-1 indicates that no segments were received yet. 2831 * In this case we just guess. 2832 */ 2833 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 2834 (origoffer == -1 || 2835 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 2836 mss -= TCPOLEN_TSTAMP_APPA; 2837 2838 #if (MCLBYTES & (MCLBYTES - 1)) == 0 2839 if (mss > MCLBYTES) 2840 mss &= ~(MCLBYTES-1); 2841 #else 2842 if (mss > MCLBYTES) 2843 mss = mss / MCLBYTES * MCLBYTES; 2844 #endif 2845 tp->t_maxseg = mss; 2846 2847 /* 2848 * If there's a pipesize, change the socket buffer to that size, 2849 * don't change if sb_hiwat is different than default (then it 2850 * has been changed on purpose with setsockopt). 2851 * Make the socket buffers an integral number of mss units; 2852 * if the mss is larger than the socket buffer, decrease the mss. 2853 */ 2854 so = inp->inp_socket; 2855 SOCKBUF_LOCK(&so->so_snd); 2856 if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe) 2857 bufsize = metrics.rmx_sendpipe; 2858 else 2859 bufsize = so->so_snd.sb_hiwat; 2860 if (bufsize < mss) 2861 mss = bufsize; 2862 else { 2863 bufsize = roundup(bufsize, mss); 2864 if (bufsize > sb_max) 2865 bufsize = sb_max; 2866 if (bufsize > so->so_snd.sb_hiwat) 2867 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 2868 } 2869 SOCKBUF_UNLOCK(&so->so_snd); 2870 tp->t_maxseg = mss; 2871 2872 SOCKBUF_LOCK(&so->so_rcv); 2873 if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe) 2874 bufsize = metrics.rmx_recvpipe; 2875 else 2876 bufsize = so->so_rcv.sb_hiwat; 2877 if (bufsize > mss) { 2878 bufsize = roundup(bufsize, mss); 2879 if (bufsize > sb_max) 2880 bufsize = sb_max; 2881 if (bufsize > so->so_rcv.sb_hiwat) 2882 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 2883 } 2884 SOCKBUF_UNLOCK(&so->so_rcv); 2885 /* 2886 * While we're here, check the others too. 2887 */ 2888 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 2889 tp->t_srtt = rtt; 2890 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 2891 tcpstat.tcps_usedrtt++; 2892 if (metrics.rmx_rttvar) { 2893 tp->t_rttvar = metrics.rmx_rttvar; 2894 tcpstat.tcps_usedrttvar++; 2895 } else { 2896 /* default variation is +- 1 rtt */ 2897 tp->t_rttvar = 2898 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 2899 } 2900 TCPT_RANGESET(tp->t_rxtcur, 2901 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 2902 tp->t_rttmin, TCPTV_REXMTMAX); 2903 } 2904 if (metrics.rmx_ssthresh) { 2905 /* 2906 * There's some sort of gateway or interface 2907 * buffer limit on the path. Use this to set 2908 * the slow start threshhold, but set the 2909 * threshold to no less than 2*mss. 2910 */ 2911 tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh); 2912 tcpstat.tcps_usedssthresh++; 2913 } 2914 if (metrics.rmx_bandwidth) 2915 tp->snd_bandwidth = metrics.rmx_bandwidth; 2916 2917 /* 2918 * Set the slow-start flight size depending on whether this 2919 * is a local network or not. 2920 * 2921 * Extend this so we cache the cwnd too and retrieve it here. 2922 * Make cwnd even bigger than RFC3390 suggests but only if we 2923 * have previous experience with the remote host. Be careful 2924 * not make cwnd bigger than remote receive window or our own 2925 * send socket buffer. Maybe put some additional upper bound 2926 * on the retrieved cwnd. Should do incremental updates to 2927 * hostcache when cwnd collapses so next connection doesn't 2928 * overloads the path again. 2929 * 2930 * RFC3390 says only do this if SYN or SYN/ACK didn't got lost. 2931 * We currently check only in syncache_socket for that. 2932 */ 2933 #define TCP_METRICS_CWND 2934 #ifdef TCP_METRICS_CWND 2935 if (metrics.rmx_cwnd) 2936 tp->snd_cwnd = max(mss, 2937 min(metrics.rmx_cwnd / 2, 2938 min(tp->snd_wnd, so->so_snd.sb_hiwat))); 2939 else 2940 #endif 2941 if (tcp_do_rfc3390) 2942 tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380)); 2943 #ifdef INET6 2944 else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || 2945 (!isipv6 && in_localaddr(inp->inp_faddr))) 2946 #else 2947 else if (in_localaddr(inp->inp_faddr)) 2948 #endif 2949 tp->snd_cwnd = mss * ss_fltsz_local; 2950 else 2951 tp->snd_cwnd = mss * ss_fltsz; 2952 2953 /* Check the interface for TSO capabilities. */ 2954 if (mtuflags & CSUM_TSO) 2955 tp->t_flags |= TF_TSO; 2956 } 2957 2958 /* 2959 * Determine the MSS option to send on an outgoing SYN. 2960 */ 2961 int 2962 tcp_mssopt(struct in_conninfo *inc) 2963 { 2964 int mss = 0; 2965 u_long maxmtu = 0; 2966 u_long thcmtu = 0; 2967 size_t min_protoh; 2968 #ifdef INET6 2969 int isipv6 = inc->inc_isipv6 ? 1 : 0; 2970 #endif 2971 2972 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 2973 2974 #ifdef INET6 2975 if (isipv6) { 2976 mss = tcp_v6mssdflt; 2977 maxmtu = tcp_maxmtu6(inc, NULL); 2978 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 2979 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 2980 } else 2981 #endif 2982 { 2983 mss = tcp_mssdflt; 2984 maxmtu = tcp_maxmtu(inc, NULL); 2985 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 2986 min_protoh = sizeof(struct tcpiphdr); 2987 } 2988 if (maxmtu && thcmtu) 2989 mss = min(maxmtu, thcmtu) - min_protoh; 2990 else if (maxmtu || thcmtu) 2991 mss = max(maxmtu, thcmtu) - min_protoh; 2992 2993 return (mss); 2994 } 2995 2996 2997 /* 2998 * On a partial ack arrives, force the retransmission of the 2999 * next unacknowledged segment. Do not clear tp->t_dupacks. 3000 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3001 * be started again. 3002 */ 3003 static void 3004 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3005 { 3006 tcp_seq onxt = tp->snd_nxt; 3007 u_long ocwnd = tp->snd_cwnd; 3008 3009 INP_WLOCK_ASSERT(tp->t_inpcb); 3010 3011 tcp_timer_activate(tp, TT_REXMT, 0); 3012 tp->t_rtttime = 0; 3013 tp->snd_nxt = th->th_ack; 3014 /* 3015 * Set snd_cwnd to one segment beyond acknowledged offset. 3016 * (tp->snd_una has not yet been updated when this function is called.) 3017 */ 3018 tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); 3019 tp->t_flags |= TF_ACKNOW; 3020 (void) tcp_output(tp); 3021 tp->snd_cwnd = ocwnd; 3022 if (SEQ_GT(onxt, tp->snd_nxt)) 3023 tp->snd_nxt = onxt; 3024 /* 3025 * Partial window deflation. Relies on fact that tp->snd_una 3026 * not updated yet. 3027 */ 3028 if (tp->snd_cwnd > th->th_ack - tp->snd_una) 3029 tp->snd_cwnd -= th->th_ack - tp->snd_una; 3030 else 3031 tp->snd_cwnd = 0; 3032 tp->snd_cwnd += tp->t_maxseg; 3033 } 3034