1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 2007-2008,2010 5 * Swinburne University of Technology, Melbourne, Australia. 6 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 7 * Copyright (c) 2010 The FreeBSD Foundation 8 * Copyright (c) 2010-2011 Juniper Networks, Inc. 9 * All rights reserved. 10 * 11 * Portions of this software were developed at the Centre for Advanced Internet 12 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 13 * James Healy and David Hayes, made possible in part by a grant from the Cisco 14 * University Research Program Fund at Community Foundation Silicon Valley. 15 * 16 * Portions of this software were developed at the Centre for Advanced 17 * Internet Architectures, Swinburne University of Technology, Melbourne, 18 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 19 * 20 * Portions of this software were developed by Robert N. M. Watson under 21 * contract to Juniper Networks, Inc. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the above copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 4. Neither the name of the University nor the names of its contributors 32 * may be used to endorse or promote products derived from this software 33 * without specific prior written permission. 34 * 35 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 36 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 38 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 39 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 40 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 41 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 42 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 43 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 44 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 45 * SUCH DAMAGE. 46 * 47 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 48 */ 49 50 #include <sys/cdefs.h> 51 __FBSDID("$FreeBSD$"); 52 53 #include "opt_ipfw.h" /* for ipfw_fwd */ 54 #include "opt_inet.h" 55 #include "opt_inet6.h" 56 #include "opt_ipsec.h" 57 #include "opt_tcpdebug.h" 58 59 #include <sys/param.h> 60 #include <sys/kernel.h> 61 #include <sys/hhook.h> 62 #include <sys/malloc.h> 63 #include <sys/mbuf.h> 64 #include <sys/proc.h> /* for proc0 declaration */ 65 #include <sys/protosw.h> 66 #include <sys/sdt.h> 67 #include <sys/signalvar.h> 68 #include <sys/socket.h> 69 #include <sys/socketvar.h> 70 #include <sys/sysctl.h> 71 #include <sys/syslog.h> 72 #include <sys/systm.h> 73 74 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 75 76 #include <vm/uma.h> 77 78 #include <net/if.h> 79 #include <net/if_var.h> 80 #include <net/route.h> 81 #include <net/vnet.h> 82 83 #define TCPSTATES /* for logging */ 84 85 #include <netinet/cc.h> 86 #include <netinet/in.h> 87 #include <netinet/in_kdtrace.h> 88 #include <netinet/in_pcb.h> 89 #include <netinet/in_systm.h> 90 #include <netinet/in_var.h> 91 #include <netinet/ip.h> 92 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 93 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 94 #include <netinet/ip_var.h> 95 #include <netinet/ip_options.h> 96 #include <netinet/ip6.h> 97 #include <netinet/icmp6.h> 98 #include <netinet6/in6_pcb.h> 99 #include <netinet6/ip6_var.h> 100 #include <netinet6/nd6.h> 101 #include <netinet/tcp_fsm.h> 102 #include <netinet/tcp_seq.h> 103 #include <netinet/tcp_timer.h> 104 #include <netinet/tcp_var.h> 105 #include <netinet6/tcp6_var.h> 106 #include <netinet/tcpip.h> 107 #include <netinet/tcp_syncache.h> 108 #ifdef TCPDEBUG 109 #include <netinet/tcp_debug.h> 110 #endif /* TCPDEBUG */ 111 #ifdef TCP_OFFLOAD 112 #include <netinet/tcp_offload.h> 113 #endif 114 115 #ifdef IPSEC 116 #include <netipsec/ipsec.h> 117 #include <netipsec/ipsec6.h> 118 #endif /*IPSEC*/ 119 120 #include <machine/in_cksum.h> 121 122 #include <security/mac/mac_framework.h> 123 124 const int tcprexmtthresh = 3; 125 126 int tcp_log_in_vain = 0; 127 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 128 &tcp_log_in_vain, 0, 129 "Log all incoming TCP segments to closed ports"); 130 131 VNET_DEFINE(int, blackhole) = 0; 132 #define V_blackhole VNET(blackhole) 133 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 134 &VNET_NAME(blackhole), 0, 135 "Do not send RST on segments to closed ports"); 136 137 VNET_DEFINE(int, tcp_delack_enabled) = 1; 138 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 139 &VNET_NAME(tcp_delack_enabled), 0, 140 "Delay ACK to try and piggyback it onto a data packet"); 141 142 VNET_DEFINE(int, drop_synfin) = 0; 143 #define V_drop_synfin VNET(drop_synfin) 144 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 145 &VNET_NAME(drop_synfin), 0, 146 "Drop TCP packets with SYN+FIN set"); 147 148 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 149 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 150 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 151 &VNET_NAME(tcp_do_rfc3042), 0, 152 "Enable RFC 3042 (Limited Transmit)"); 153 154 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 155 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 156 &VNET_NAME(tcp_do_rfc3390), 0, 157 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 158 159 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0, 160 "Experimental TCP extensions"); 161 162 VNET_DEFINE(int, tcp_do_initcwnd10) = 1; 163 SYSCTL_VNET_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_RW, 164 &VNET_NAME(tcp_do_initcwnd10), 0, 165 "Enable RFC 6928 (Increasing initial CWND to 10)"); 166 167 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 168 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW, 169 &VNET_NAME(tcp_do_rfc3465), 0, 170 "Enable RFC 3465 (Appropriate Byte Counting)"); 171 172 VNET_DEFINE(int, tcp_abc_l_var) = 2; 173 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW, 174 &VNET_NAME(tcp_abc_l_var), 2, 175 "Cap the max cwnd increment during slow-start to this number of segments"); 176 177 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 178 179 VNET_DEFINE(int, tcp_do_ecn) = 0; 180 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW, 181 &VNET_NAME(tcp_do_ecn), 0, 182 "TCP ECN support"); 183 184 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 185 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW, 186 &VNET_NAME(tcp_ecn_maxretries), 0, 187 "Max retries before giving up on ECN"); 188 189 VNET_DEFINE(int, tcp_insecure_rst) = 0; 190 #define V_tcp_insecure_rst VNET(tcp_insecure_rst) 191 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 192 &VNET_NAME(tcp_insecure_rst), 0, 193 "Follow the old (insecure) criteria for accepting RST packets"); 194 195 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 196 #define V_tcp_recvspace VNET(tcp_recvspace) 197 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW, 198 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 199 200 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 201 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 202 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 203 &VNET_NAME(tcp_do_autorcvbuf), 0, 204 "Enable automatic receive buffer sizing"); 205 206 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 207 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 208 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 209 &VNET_NAME(tcp_autorcvbuf_inc), 0, 210 "Incrementor step size of automatic receive buffer"); 211 212 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 213 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 214 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 215 &VNET_NAME(tcp_autorcvbuf_max), 0, 216 "Max size of automatic receive buffer"); 217 218 VNET_DEFINE(struct inpcbhead, tcb); 219 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 220 VNET_DEFINE(struct inpcbinfo, tcbinfo); 221 222 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 223 static void tcp_do_segment(struct mbuf *, struct tcphdr *, 224 struct socket *, struct tcpcb *, int, int, uint8_t, 225 int); 226 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 227 struct tcpcb *, int, int); 228 static void tcp_pulloutofband(struct socket *, 229 struct tcphdr *, struct mbuf *, int); 230 static void tcp_xmit_timer(struct tcpcb *, int); 231 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 232 static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th, 233 uint16_t type); 234 static void inline cc_conn_init(struct tcpcb *tp); 235 static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th); 236 static void inline hhook_run_tcp_est_in(struct tcpcb *tp, 237 struct tcphdr *th, struct tcpopt *to); 238 239 /* 240 * TCP statistics are stored in an "array" of counter(9)s. 241 */ 242 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 243 VNET_PCPUSTAT_SYSINIT(tcpstat); 244 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 245 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 246 247 #ifdef VIMAGE 248 VNET_PCPUSTAT_SYSUNINIT(tcpstat); 249 #endif /* VIMAGE */ 250 /* 251 * Kernel module interface for updating tcpstat. The argument is an index 252 * into tcpstat treated as an array. 253 */ 254 void 255 kmod_tcpstat_inc(int statnum) 256 { 257 258 counter_u64_add(VNET(tcpstat)[statnum], 1); 259 } 260 261 /* 262 * Wrapper for the TCP established input helper hook. 263 */ 264 static void inline 265 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 266 { 267 struct tcp_hhook_data hhook_data; 268 269 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 270 hhook_data.tp = tp; 271 hhook_data.th = th; 272 hhook_data.to = to; 273 274 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 275 tp->osd); 276 } 277 } 278 279 /* 280 * CC wrapper hook functions 281 */ 282 static void inline 283 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type) 284 { 285 INP_WLOCK_ASSERT(tp->t_inpcb); 286 287 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 288 if (tp->snd_cwnd <= tp->snd_wnd) 289 tp->ccv->flags |= CCF_CWND_LIMITED; 290 else 291 tp->ccv->flags &= ~CCF_CWND_LIMITED; 292 293 if (type == CC_ACK) { 294 if (tp->snd_cwnd > tp->snd_ssthresh) { 295 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 296 V_tcp_abc_l_var * tp->t_maxseg); 297 if (tp->t_bytes_acked >= tp->snd_cwnd) { 298 tp->t_bytes_acked -= tp->snd_cwnd; 299 tp->ccv->flags |= CCF_ABC_SENTAWND; 300 } 301 } else { 302 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 303 tp->t_bytes_acked = 0; 304 } 305 } 306 307 if (CC_ALGO(tp)->ack_received != NULL) { 308 /* XXXLAS: Find a way to live without this */ 309 tp->ccv->curack = th->th_ack; 310 CC_ALGO(tp)->ack_received(tp->ccv, type); 311 } 312 } 313 314 static void inline 315 cc_conn_init(struct tcpcb *tp) 316 { 317 struct hc_metrics_lite metrics; 318 struct inpcb *inp = tp->t_inpcb; 319 int rtt; 320 321 INP_WLOCK_ASSERT(tp->t_inpcb); 322 323 tcp_hc_get(&inp->inp_inc, &metrics); 324 325 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 326 tp->t_srtt = rtt; 327 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 328 TCPSTAT_INC(tcps_usedrtt); 329 if (metrics.rmx_rttvar) { 330 tp->t_rttvar = metrics.rmx_rttvar; 331 TCPSTAT_INC(tcps_usedrttvar); 332 } else { 333 /* default variation is +- 1 rtt */ 334 tp->t_rttvar = 335 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 336 } 337 TCPT_RANGESET(tp->t_rxtcur, 338 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 339 tp->t_rttmin, TCPTV_REXMTMAX); 340 } 341 if (metrics.rmx_ssthresh) { 342 /* 343 * There's some sort of gateway or interface 344 * buffer limit on the path. Use this to set 345 * the slow start threshhold, but set the 346 * threshold to no less than 2*mss. 347 */ 348 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh); 349 TCPSTAT_INC(tcps_usedssthresh); 350 } 351 352 /* 353 * Set the initial slow-start flight size. 354 * 355 * RFC5681 Section 3.1 specifies the default conservative values. 356 * RFC3390 specifies slightly more aggressive values. 357 * RFC6928 increases it to ten segments. 358 * 359 * If a SYN or SYN/ACK was lost and retransmitted, we have to 360 * reduce the initial CWND to one segment as congestion is likely 361 * requiring us to be cautious. 362 */ 363 if (tp->snd_cwnd == 1) 364 tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */ 365 else if (V_tcp_do_initcwnd10) 366 tp->snd_cwnd = min(10 * tp->t_maxseg, 367 max(2 * tp->t_maxseg, 14600)); 368 else if (V_tcp_do_rfc3390) 369 tp->snd_cwnd = min(4 * tp->t_maxseg, 370 max(2 * tp->t_maxseg, 4380)); 371 else { 372 /* Per RFC5681 Section 3.1 */ 373 if (tp->t_maxseg > 2190) 374 tp->snd_cwnd = 2 * tp->t_maxseg; 375 else if (tp->t_maxseg > 1095) 376 tp->snd_cwnd = 3 * tp->t_maxseg; 377 else 378 tp->snd_cwnd = 4 * tp->t_maxseg; 379 } 380 381 if (CC_ALGO(tp)->conn_init != NULL) 382 CC_ALGO(tp)->conn_init(tp->ccv); 383 } 384 385 void inline 386 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 387 { 388 INP_WLOCK_ASSERT(tp->t_inpcb); 389 390 switch(type) { 391 case CC_NDUPACK: 392 if (!IN_FASTRECOVERY(tp->t_flags)) { 393 tp->snd_recover = tp->snd_max; 394 if (tp->t_flags & TF_ECN_PERMIT) 395 tp->t_flags |= TF_ECN_SND_CWR; 396 } 397 break; 398 case CC_ECN: 399 if (!IN_CONGRECOVERY(tp->t_flags)) { 400 TCPSTAT_INC(tcps_ecn_rcwnd); 401 tp->snd_recover = tp->snd_max; 402 if (tp->t_flags & TF_ECN_PERMIT) 403 tp->t_flags |= TF_ECN_SND_CWR; 404 } 405 break; 406 case CC_RTO: 407 tp->t_dupacks = 0; 408 tp->t_bytes_acked = 0; 409 EXIT_RECOVERY(tp->t_flags); 410 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 411 tp->t_maxseg) * tp->t_maxseg; 412 tp->snd_cwnd = tp->t_maxseg; 413 break; 414 case CC_RTO_ERR: 415 TCPSTAT_INC(tcps_sndrexmitbad); 416 /* RTO was unnecessary, so reset everything. */ 417 tp->snd_cwnd = tp->snd_cwnd_prev; 418 tp->snd_ssthresh = tp->snd_ssthresh_prev; 419 tp->snd_recover = tp->snd_recover_prev; 420 if (tp->t_flags & TF_WASFRECOVERY) 421 ENTER_FASTRECOVERY(tp->t_flags); 422 if (tp->t_flags & TF_WASCRECOVERY) 423 ENTER_CONGRECOVERY(tp->t_flags); 424 tp->snd_nxt = tp->snd_max; 425 tp->t_flags &= ~TF_PREVVALID; 426 tp->t_badrxtwin = 0; 427 break; 428 } 429 430 if (CC_ALGO(tp)->cong_signal != NULL) { 431 if (th != NULL) 432 tp->ccv->curack = th->th_ack; 433 CC_ALGO(tp)->cong_signal(tp->ccv, type); 434 } 435 } 436 437 static void inline 438 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 439 { 440 INP_WLOCK_ASSERT(tp->t_inpcb); 441 442 /* XXXLAS: KASSERT that we're in recovery? */ 443 444 if (CC_ALGO(tp)->post_recovery != NULL) { 445 tp->ccv->curack = th->th_ack; 446 CC_ALGO(tp)->post_recovery(tp->ccv); 447 } 448 /* XXXLAS: EXIT_RECOVERY ? */ 449 tp->t_bytes_acked = 0; 450 } 451 452 #ifdef TCP_SIGNATURE 453 static inline int 454 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 455 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 456 { 457 int ret; 458 459 tcp_fields_to_net(th); 460 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 461 tcp_fields_to_host(th); 462 return (ret); 463 } 464 #endif 465 466 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 467 #ifdef INET6 468 #define ND6_HINT(tp) \ 469 do { \ 470 if ((tp) && (tp)->t_inpcb && \ 471 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 472 nd6_nud_hint(NULL, NULL, 0); \ 473 } while (0) 474 #else 475 #define ND6_HINT(tp) 476 #endif 477 478 /* 479 * Indicate whether this ack should be delayed. We can delay the ack if 480 * following conditions are met: 481 * - There is no delayed ack timer in progress. 482 * - Our last ack wasn't a 0-sized window. We never want to delay 483 * the ack that opens up a 0-sized window. 484 * - LRO wasn't used for this segment. We make sure by checking that the 485 * segment size is not larger than the MSS. 486 * - Delayed acks are enabled or this is a half-synchronized T/TCP 487 * connection. 488 */ 489 #define DELAY_ACK(tp, tlen) \ 490 ((!tcp_timer_active(tp, TT_DELACK) && \ 491 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 492 (tlen <= tp->t_maxopd) && \ 493 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 494 495 /* 496 * TCP input handling is split into multiple parts: 497 * tcp6_input is a thin wrapper around tcp_input for the extended 498 * ip6_protox[] call format in ip6_input 499 * tcp_input handles primary segment validation, inpcb lookup and 500 * SYN processing on listen sockets 501 * tcp_do_segment processes the ACK and text of the segment for 502 * establishing, established and closing connections 503 */ 504 #ifdef INET6 505 int 506 tcp6_input(struct mbuf **mp, int *offp, int proto) 507 { 508 struct mbuf *m = *mp; 509 struct in6_ifaddr *ia6; 510 511 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 512 513 /* 514 * draft-itojun-ipv6-tcp-to-anycast 515 * better place to put this in? 516 */ 517 ia6 = ip6_getdstifaddr(m); 518 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 519 struct ip6_hdr *ip6; 520 521 ifa_free(&ia6->ia_ifa); 522 ip6 = mtod(m, struct ip6_hdr *); 523 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 524 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 525 return (IPPROTO_DONE); 526 } 527 if (ia6) 528 ifa_free(&ia6->ia_ifa); 529 530 return (tcp_input(mp, offp, proto)); 531 } 532 #endif /* INET6 */ 533 534 int 535 tcp_input(struct mbuf **mp, int *offp, int proto) 536 { 537 struct mbuf *m = *mp; 538 struct tcphdr *th = NULL; 539 struct ip *ip = NULL; 540 struct inpcb *inp = NULL; 541 struct tcpcb *tp = NULL; 542 struct socket *so = NULL; 543 u_char *optp = NULL; 544 int off0; 545 int optlen = 0; 546 #ifdef INET 547 int len; 548 #endif 549 int tlen = 0, off; 550 int drop_hdrlen; 551 int thflags; 552 int rstreason = 0; /* For badport_bandlim accounting purposes */ 553 #ifdef TCP_SIGNATURE 554 uint8_t sig_checked = 0; 555 #endif 556 uint8_t iptos = 0; 557 struct m_tag *fwd_tag = NULL; 558 #ifdef INET6 559 struct ip6_hdr *ip6 = NULL; 560 int isipv6; 561 #else 562 const void *ip6 = NULL; 563 #endif /* INET6 */ 564 struct tcpopt to; /* options in this segment */ 565 char *s = NULL; /* address and port logging */ 566 int ti_locked; 567 #define TI_UNLOCKED 1 568 #define TI_WLOCKED 2 569 570 #ifdef TCPDEBUG 571 /* 572 * The size of tcp_saveipgen must be the size of the max ip header, 573 * now IPv6. 574 */ 575 u_char tcp_saveipgen[IP6_HDR_LEN]; 576 struct tcphdr tcp_savetcp; 577 short ostate = 0; 578 #endif 579 580 #ifdef INET6 581 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 582 #endif 583 584 off0 = *offp; 585 m = *mp; 586 *mp = NULL; 587 to.to_flags = 0; 588 TCPSTAT_INC(tcps_rcvtotal); 589 590 #ifdef INET6 591 if (isipv6) { 592 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 593 594 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 595 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 596 if (m == NULL) { 597 TCPSTAT_INC(tcps_rcvshort); 598 return (IPPROTO_DONE); 599 } 600 } 601 602 ip6 = mtod(m, struct ip6_hdr *); 603 th = (struct tcphdr *)((caddr_t)ip6 + off0); 604 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 605 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 606 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 607 th->th_sum = m->m_pkthdr.csum_data; 608 else 609 th->th_sum = in6_cksum_pseudo(ip6, tlen, 610 IPPROTO_TCP, m->m_pkthdr.csum_data); 611 th->th_sum ^= 0xffff; 612 } else 613 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 614 if (th->th_sum) { 615 TCPSTAT_INC(tcps_rcvbadsum); 616 goto drop; 617 } 618 619 /* 620 * Be proactive about unspecified IPv6 address in source. 621 * As we use all-zero to indicate unbounded/unconnected pcb, 622 * unspecified IPv6 address can be used to confuse us. 623 * 624 * Note that packets with unspecified IPv6 destination is 625 * already dropped in ip6_input. 626 */ 627 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 628 /* XXX stat */ 629 goto drop; 630 } 631 } 632 #endif 633 #if defined(INET) && defined(INET6) 634 else 635 #endif 636 #ifdef INET 637 { 638 /* 639 * Get IP and TCP header together in first mbuf. 640 * Note: IP leaves IP header in first mbuf. 641 */ 642 if (off0 > sizeof (struct ip)) { 643 ip_stripoptions(m); 644 off0 = sizeof(struct ip); 645 } 646 if (m->m_len < sizeof (struct tcpiphdr)) { 647 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 648 == NULL) { 649 TCPSTAT_INC(tcps_rcvshort); 650 return (IPPROTO_DONE); 651 } 652 } 653 ip = mtod(m, struct ip *); 654 th = (struct tcphdr *)((caddr_t)ip + off0); 655 tlen = ntohs(ip->ip_len) - off0; 656 657 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 658 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 659 th->th_sum = m->m_pkthdr.csum_data; 660 else 661 th->th_sum = in_pseudo(ip->ip_src.s_addr, 662 ip->ip_dst.s_addr, 663 htonl(m->m_pkthdr.csum_data + tlen + 664 IPPROTO_TCP)); 665 th->th_sum ^= 0xffff; 666 } else { 667 struct ipovly *ipov = (struct ipovly *)ip; 668 669 /* 670 * Checksum extended TCP header and data. 671 */ 672 len = off0 + tlen; 673 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 674 ipov->ih_len = htons(tlen); 675 th->th_sum = in_cksum(m, len); 676 /* Reset length for SDT probes. */ 677 ip->ip_len = htons(tlen + off0); 678 } 679 680 if (th->th_sum) { 681 TCPSTAT_INC(tcps_rcvbadsum); 682 goto drop; 683 } 684 /* Re-initialization for later version check */ 685 ip->ip_v = IPVERSION; 686 } 687 #endif /* INET */ 688 689 #ifdef INET6 690 if (isipv6) 691 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 692 #endif 693 #if defined(INET) && defined(INET6) 694 else 695 #endif 696 #ifdef INET 697 iptos = ip->ip_tos; 698 #endif 699 700 /* 701 * Check that TCP offset makes sense, 702 * pull out TCP options and adjust length. XXX 703 */ 704 off = th->th_off << 2; 705 if (off < sizeof (struct tcphdr) || off > tlen) { 706 TCPSTAT_INC(tcps_rcvbadoff); 707 goto drop; 708 } 709 tlen -= off; /* tlen is used instead of ti->ti_len */ 710 if (off > sizeof (struct tcphdr)) { 711 #ifdef INET6 712 if (isipv6) { 713 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 714 ip6 = mtod(m, struct ip6_hdr *); 715 th = (struct tcphdr *)((caddr_t)ip6 + off0); 716 } 717 #endif 718 #if defined(INET) && defined(INET6) 719 else 720 #endif 721 #ifdef INET 722 { 723 if (m->m_len < sizeof(struct ip) + off) { 724 if ((m = m_pullup(m, sizeof (struct ip) + off)) 725 == NULL) { 726 TCPSTAT_INC(tcps_rcvshort); 727 return (IPPROTO_DONE); 728 } 729 ip = mtod(m, struct ip *); 730 th = (struct tcphdr *)((caddr_t)ip + off0); 731 } 732 } 733 #endif 734 optlen = off - sizeof (struct tcphdr); 735 optp = (u_char *)(th + 1); 736 } 737 thflags = th->th_flags; 738 739 /* 740 * Convert TCP protocol specific fields to host format. 741 */ 742 tcp_fields_to_host(th); 743 744 /* 745 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 746 */ 747 drop_hdrlen = off0 + off; 748 749 /* 750 * Locate pcb for segment; if we're likely to add or remove a 751 * connection then first acquire pcbinfo lock. There are two cases 752 * where we might discover later we need a write lock despite the 753 * flags: ACKs moving a connection out of the syncache, and ACKs for 754 * a connection in TIMEWAIT. 755 */ 756 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) { 757 INP_INFO_WLOCK(&V_tcbinfo); 758 ti_locked = TI_WLOCKED; 759 } else 760 ti_locked = TI_UNLOCKED; 761 762 /* 763 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 764 */ 765 if ( 766 #ifdef INET6 767 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 768 #ifdef INET 769 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 770 #endif 771 #endif 772 #if defined(INET) && !defined(INET6) 773 (m->m_flags & M_IP_NEXTHOP) 774 #endif 775 ) 776 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 777 778 findpcb: 779 #ifdef INVARIANTS 780 if (ti_locked == TI_WLOCKED) { 781 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 782 } else { 783 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 784 } 785 #endif 786 #ifdef INET6 787 if (isipv6 && fwd_tag != NULL) { 788 struct sockaddr_in6 *next_hop6; 789 790 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 791 /* 792 * Transparently forwarded. Pretend to be the destination. 793 * Already got one like this? 794 */ 795 inp = in6_pcblookup_mbuf(&V_tcbinfo, 796 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 797 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 798 if (!inp) { 799 /* 800 * It's new. Try to find the ambushing socket. 801 * Because we've rewritten the destination address, 802 * any hardware-generated hash is ignored. 803 */ 804 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 805 th->th_sport, &next_hop6->sin6_addr, 806 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 807 th->th_dport, INPLOOKUP_WILDCARD | 808 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 809 } 810 } else if (isipv6) { 811 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 812 th->th_sport, &ip6->ip6_dst, th->th_dport, 813 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 814 m->m_pkthdr.rcvif, m); 815 } 816 #endif /* INET6 */ 817 #if defined(INET6) && defined(INET) 818 else 819 #endif 820 #ifdef INET 821 if (fwd_tag != NULL) { 822 struct sockaddr_in *next_hop; 823 824 next_hop = (struct sockaddr_in *)(fwd_tag+1); 825 /* 826 * Transparently forwarded. Pretend to be the destination. 827 * already got one like this? 828 */ 829 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 830 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 831 m->m_pkthdr.rcvif, m); 832 if (!inp) { 833 /* 834 * It's new. Try to find the ambushing socket. 835 * Because we've rewritten the destination address, 836 * any hardware-generated hash is ignored. 837 */ 838 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 839 th->th_sport, next_hop->sin_addr, 840 next_hop->sin_port ? ntohs(next_hop->sin_port) : 841 th->th_dport, INPLOOKUP_WILDCARD | 842 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 843 } 844 } else 845 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 846 th->th_sport, ip->ip_dst, th->th_dport, 847 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 848 m->m_pkthdr.rcvif, m); 849 #endif /* INET */ 850 851 /* 852 * If the INPCB does not exist then all data in the incoming 853 * segment is discarded and an appropriate RST is sent back. 854 * XXX MRT Send RST using which routing table? 855 */ 856 if (inp == NULL) { 857 /* 858 * Log communication attempts to ports that are not 859 * in use. 860 */ 861 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 862 tcp_log_in_vain == 2) { 863 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 864 log(LOG_INFO, "%s; %s: Connection attempt " 865 "to closed port\n", s, __func__); 866 } 867 /* 868 * When blackholing do not respond with a RST but 869 * completely ignore the segment and drop it. 870 */ 871 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 872 V_blackhole == 2) 873 goto dropunlock; 874 875 rstreason = BANDLIM_RST_CLOSEDPORT; 876 goto dropwithreset; 877 } 878 INP_WLOCK_ASSERT(inp); 879 if (!(inp->inp_flags & INP_HW_FLOWID) 880 && (m->m_flags & M_FLOWID) 881 && ((inp->inp_socket == NULL) 882 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) { 883 inp->inp_flags |= INP_HW_FLOWID; 884 inp->inp_flags &= ~INP_SW_FLOWID; 885 inp->inp_flowid = m->m_pkthdr.flowid; 886 inp->inp_flowtype = M_HASHTYPE_GET(m); 887 } 888 #ifdef IPSEC 889 #ifdef INET6 890 if (isipv6 && ipsec6_in_reject(m, inp)) { 891 IPSEC6STAT_INC(ips_in_polvio); 892 goto dropunlock; 893 } else 894 #endif /* INET6 */ 895 if (ipsec4_in_reject(m, inp) != 0) { 896 IPSECSTAT_INC(ips_in_polvio); 897 goto dropunlock; 898 } 899 #endif /* IPSEC */ 900 901 /* 902 * Check the minimum TTL for socket. 903 */ 904 if (inp->inp_ip_minttl != 0) { 905 #ifdef INET6 906 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 907 goto dropunlock; 908 else 909 #endif 910 if (inp->inp_ip_minttl > ip->ip_ttl) 911 goto dropunlock; 912 } 913 914 /* 915 * A previous connection in TIMEWAIT state is supposed to catch stray 916 * or duplicate segments arriving late. If this segment was a 917 * legitimate new connection attempt, the old INPCB gets removed and 918 * we can try again to find a listening socket. 919 * 920 * At this point, due to earlier optimism, we may hold only an inpcb 921 * lock, and not the inpcbinfo write lock. If so, we need to try to 922 * acquire it, or if that fails, acquire a reference on the inpcb, 923 * drop all locks, acquire a global write lock, and then re-acquire 924 * the inpcb lock. We may at that point discover that another thread 925 * has tried to free the inpcb, in which case we need to loop back 926 * and try to find a new inpcb to deliver to. 927 * 928 * XXXRW: It may be time to rethink timewait locking. 929 */ 930 relocked: 931 if (inp->inp_flags & INP_TIMEWAIT) { 932 if (ti_locked == TI_UNLOCKED) { 933 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { 934 in_pcbref(inp); 935 INP_WUNLOCK(inp); 936 INP_INFO_WLOCK(&V_tcbinfo); 937 ti_locked = TI_WLOCKED; 938 INP_WLOCK(inp); 939 if (in_pcbrele_wlocked(inp)) { 940 inp = NULL; 941 goto findpcb; 942 } 943 } else 944 ti_locked = TI_WLOCKED; 945 } 946 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 947 948 if (thflags & TH_SYN) 949 tcp_dooptions(&to, optp, optlen, TO_SYN); 950 /* 951 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 952 */ 953 if (tcp_twcheck(inp, &to, th, m, tlen)) 954 goto findpcb; 955 INP_INFO_WUNLOCK(&V_tcbinfo); 956 return (IPPROTO_DONE); 957 } 958 /* 959 * The TCPCB may no longer exist if the connection is winding 960 * down or it is in the CLOSED state. Either way we drop the 961 * segment and send an appropriate response. 962 */ 963 tp = intotcpcb(inp); 964 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 965 rstreason = BANDLIM_RST_CLOSEDPORT; 966 goto dropwithreset; 967 } 968 969 #ifdef TCP_OFFLOAD 970 if (tp->t_flags & TF_TOE) { 971 tcp_offload_input(tp, m); 972 m = NULL; /* consumed by the TOE driver */ 973 goto dropunlock; 974 } 975 #endif 976 977 /* 978 * We've identified a valid inpcb, but it could be that we need an 979 * inpcbinfo write lock but don't hold it. In this case, attempt to 980 * acquire using the same strategy as the TIMEWAIT case above. If we 981 * relock, we have to jump back to 'relocked' as the connection might 982 * now be in TIMEWAIT. 983 */ 984 #ifdef INVARIANTS 985 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) 986 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 987 #endif 988 if (tp->t_state != TCPS_ESTABLISHED) { 989 if (ti_locked == TI_UNLOCKED) { 990 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { 991 in_pcbref(inp); 992 INP_WUNLOCK(inp); 993 INP_INFO_WLOCK(&V_tcbinfo); 994 ti_locked = TI_WLOCKED; 995 INP_WLOCK(inp); 996 if (in_pcbrele_wlocked(inp)) { 997 inp = NULL; 998 goto findpcb; 999 } 1000 goto relocked; 1001 } else 1002 ti_locked = TI_WLOCKED; 1003 } 1004 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1005 } 1006 1007 #ifdef MAC 1008 INP_WLOCK_ASSERT(inp); 1009 if (mac_inpcb_check_deliver(inp, m)) 1010 goto dropunlock; 1011 #endif 1012 so = inp->inp_socket; 1013 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1014 #ifdef TCPDEBUG 1015 if (so->so_options & SO_DEBUG) { 1016 ostate = tp->t_state; 1017 #ifdef INET6 1018 if (isipv6) { 1019 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1020 } else 1021 #endif 1022 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1023 tcp_savetcp = *th; 1024 } 1025 #endif /* TCPDEBUG */ 1026 /* 1027 * When the socket is accepting connections (the INPCB is in LISTEN 1028 * state) we look into the SYN cache if this is a new connection 1029 * attempt or the completion of a previous one. Because listen 1030 * sockets are never in TCPS_ESTABLISHED, the V_tcbinfo lock will be 1031 * held in this case. 1032 */ 1033 if (so->so_options & SO_ACCEPTCONN) { 1034 struct in_conninfo inc; 1035 1036 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 1037 "tp not listening", __func__)); 1038 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1039 1040 bzero(&inc, sizeof(inc)); 1041 #ifdef INET6 1042 if (isipv6) { 1043 inc.inc_flags |= INC_ISIPV6; 1044 inc.inc6_faddr = ip6->ip6_src; 1045 inc.inc6_laddr = ip6->ip6_dst; 1046 } else 1047 #endif 1048 { 1049 inc.inc_faddr = ip->ip_src; 1050 inc.inc_laddr = ip->ip_dst; 1051 } 1052 inc.inc_fport = th->th_sport; 1053 inc.inc_lport = th->th_dport; 1054 inc.inc_fibnum = so->so_fibnum; 1055 1056 /* 1057 * Check for an existing connection attempt in syncache if 1058 * the flag is only ACK. A successful lookup creates a new 1059 * socket appended to the listen queue in SYN_RECEIVED state. 1060 */ 1061 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1062 /* 1063 * Parse the TCP options here because 1064 * syncookies need access to the reflected 1065 * timestamp. 1066 */ 1067 tcp_dooptions(&to, optp, optlen, 0); 1068 /* 1069 * NB: syncache_expand() doesn't unlock 1070 * inp and tcpinfo locks. 1071 */ 1072 if (!syncache_expand(&inc, &to, th, &so, m)) { 1073 /* 1074 * No syncache entry or ACK was not 1075 * for our SYN/ACK. Send a RST. 1076 * NB: syncache did its own logging 1077 * of the failure cause. 1078 */ 1079 rstreason = BANDLIM_RST_OPENPORT; 1080 goto dropwithreset; 1081 } 1082 if (so == NULL) { 1083 /* 1084 * We completed the 3-way handshake 1085 * but could not allocate a socket 1086 * either due to memory shortage, 1087 * listen queue length limits or 1088 * global socket limits. Send RST 1089 * or wait and have the remote end 1090 * retransmit the ACK for another 1091 * try. 1092 */ 1093 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1094 log(LOG_DEBUG, "%s; %s: Listen socket: " 1095 "Socket allocation failed due to " 1096 "limits or memory shortage, %s\n", 1097 s, __func__, 1098 V_tcp_sc_rst_sock_fail ? 1099 "sending RST" : "try again"); 1100 if (V_tcp_sc_rst_sock_fail) { 1101 rstreason = BANDLIM_UNLIMITED; 1102 goto dropwithreset; 1103 } else 1104 goto dropunlock; 1105 } 1106 /* 1107 * Socket is created in state SYN_RECEIVED. 1108 * Unlock the listen socket, lock the newly 1109 * created socket and update the tp variable. 1110 */ 1111 INP_WUNLOCK(inp); /* listen socket */ 1112 inp = sotoinpcb(so); 1113 INP_WLOCK(inp); /* new connection */ 1114 tp = intotcpcb(inp); 1115 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1116 ("%s: ", __func__)); 1117 #ifdef TCP_SIGNATURE 1118 if (sig_checked == 0) { 1119 tcp_dooptions(&to, optp, optlen, 1120 (thflags & TH_SYN) ? TO_SYN : 0); 1121 if (!tcp_signature_verify_input(m, off0, tlen, 1122 optlen, &to, th, tp->t_flags)) { 1123 1124 /* 1125 * In SYN_SENT state if it receives an 1126 * RST, it is allowed for further 1127 * processing. 1128 */ 1129 if ((thflags & TH_RST) == 0 || 1130 (tp->t_state == TCPS_SYN_SENT) == 0) 1131 goto dropunlock; 1132 } 1133 sig_checked = 1; 1134 } 1135 #endif 1136 1137 /* 1138 * Process the segment and the data it 1139 * contains. tcp_do_segment() consumes 1140 * the mbuf chain and unlocks the inpcb. 1141 */ 1142 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1143 iptos, ti_locked); 1144 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1145 return (IPPROTO_DONE); 1146 } 1147 /* 1148 * Segment flag validation for new connection attempts: 1149 * 1150 * Our (SYN|ACK) response was rejected. 1151 * Check with syncache and remove entry to prevent 1152 * retransmits. 1153 * 1154 * NB: syncache_chkrst does its own logging of failure 1155 * causes. 1156 */ 1157 if (thflags & TH_RST) { 1158 syncache_chkrst(&inc, th); 1159 goto dropunlock; 1160 } 1161 /* 1162 * We can't do anything without SYN. 1163 */ 1164 if ((thflags & TH_SYN) == 0) { 1165 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1166 log(LOG_DEBUG, "%s; %s: Listen socket: " 1167 "SYN is missing, segment ignored\n", 1168 s, __func__); 1169 TCPSTAT_INC(tcps_badsyn); 1170 goto dropunlock; 1171 } 1172 /* 1173 * (SYN|ACK) is bogus on a listen socket. 1174 */ 1175 if (thflags & TH_ACK) { 1176 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1177 log(LOG_DEBUG, "%s; %s: Listen socket: " 1178 "SYN|ACK invalid, segment rejected\n", 1179 s, __func__); 1180 syncache_badack(&inc); /* XXX: Not needed! */ 1181 TCPSTAT_INC(tcps_badsyn); 1182 rstreason = BANDLIM_RST_OPENPORT; 1183 goto dropwithreset; 1184 } 1185 /* 1186 * If the drop_synfin option is enabled, drop all 1187 * segments with both the SYN and FIN bits set. 1188 * This prevents e.g. nmap from identifying the 1189 * TCP/IP stack. 1190 * XXX: Poor reasoning. nmap has other methods 1191 * and is constantly refining its stack detection 1192 * strategies. 1193 * XXX: This is a violation of the TCP specification 1194 * and was used by RFC1644. 1195 */ 1196 if ((thflags & TH_FIN) && V_drop_synfin) { 1197 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1198 log(LOG_DEBUG, "%s; %s: Listen socket: " 1199 "SYN|FIN segment ignored (based on " 1200 "sysctl setting)\n", s, __func__); 1201 TCPSTAT_INC(tcps_badsyn); 1202 goto dropunlock; 1203 } 1204 /* 1205 * Segment's flags are (SYN) or (SYN|FIN). 1206 * 1207 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1208 * as they do not affect the state of the TCP FSM. 1209 * The data pointed to by TH_URG and th_urp is ignored. 1210 */ 1211 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1212 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1213 KASSERT(thflags & (TH_SYN), 1214 ("%s: Listen socket: TH_SYN not set", __func__)); 1215 #ifdef INET6 1216 /* 1217 * If deprecated address is forbidden, 1218 * we do not accept SYN to deprecated interface 1219 * address to prevent any new inbound connection from 1220 * getting established. 1221 * When we do not accept SYN, we send a TCP RST, 1222 * with deprecated source address (instead of dropping 1223 * it). We compromise it as it is much better for peer 1224 * to send a RST, and RST will be the final packet 1225 * for the exchange. 1226 * 1227 * If we do not forbid deprecated addresses, we accept 1228 * the SYN packet. RFC2462 does not suggest dropping 1229 * SYN in this case. 1230 * If we decipher RFC2462 5.5.4, it says like this: 1231 * 1. use of deprecated addr with existing 1232 * communication is okay - "SHOULD continue to be 1233 * used" 1234 * 2. use of it with new communication: 1235 * (2a) "SHOULD NOT be used if alternate address 1236 * with sufficient scope is available" 1237 * (2b) nothing mentioned otherwise. 1238 * Here we fall into (2b) case as we have no choice in 1239 * our source address selection - we must obey the peer. 1240 * 1241 * The wording in RFC2462 is confusing, and there are 1242 * multiple description text for deprecated address 1243 * handling - worse, they are not exactly the same. 1244 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1245 */ 1246 if (isipv6 && !V_ip6_use_deprecated) { 1247 struct in6_ifaddr *ia6; 1248 1249 ia6 = ip6_getdstifaddr(m); 1250 if (ia6 != NULL && 1251 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1252 ifa_free(&ia6->ia_ifa); 1253 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1254 log(LOG_DEBUG, "%s; %s: Listen socket: " 1255 "Connection attempt to deprecated " 1256 "IPv6 address rejected\n", 1257 s, __func__); 1258 rstreason = BANDLIM_RST_OPENPORT; 1259 goto dropwithreset; 1260 } 1261 if (ia6) 1262 ifa_free(&ia6->ia_ifa); 1263 } 1264 #endif /* INET6 */ 1265 /* 1266 * Basic sanity checks on incoming SYN requests: 1267 * Don't respond if the destination is a link layer 1268 * broadcast according to RFC1122 4.2.3.10, p. 104. 1269 * If it is from this socket it must be forged. 1270 * Don't respond if the source or destination is a 1271 * global or subnet broad- or multicast address. 1272 * Note that it is quite possible to receive unicast 1273 * link-layer packets with a broadcast IP address. Use 1274 * in_broadcast() to find them. 1275 */ 1276 if (m->m_flags & (M_BCAST|M_MCAST)) { 1277 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1278 log(LOG_DEBUG, "%s; %s: Listen socket: " 1279 "Connection attempt from broad- or multicast " 1280 "link layer address ignored\n", s, __func__); 1281 goto dropunlock; 1282 } 1283 #ifdef INET6 1284 if (isipv6) { 1285 if (th->th_dport == th->th_sport && 1286 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1287 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1288 log(LOG_DEBUG, "%s; %s: Listen socket: " 1289 "Connection attempt to/from self " 1290 "ignored\n", s, __func__); 1291 goto dropunlock; 1292 } 1293 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1294 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1295 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1296 log(LOG_DEBUG, "%s; %s: Listen socket: " 1297 "Connection attempt from/to multicast " 1298 "address ignored\n", s, __func__); 1299 goto dropunlock; 1300 } 1301 } 1302 #endif 1303 #if defined(INET) && defined(INET6) 1304 else 1305 #endif 1306 #ifdef INET 1307 { 1308 if (th->th_dport == th->th_sport && 1309 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1310 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1311 log(LOG_DEBUG, "%s; %s: Listen socket: " 1312 "Connection attempt from/to self " 1313 "ignored\n", s, __func__); 1314 goto dropunlock; 1315 } 1316 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1317 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1318 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1319 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1320 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1321 log(LOG_DEBUG, "%s; %s: Listen socket: " 1322 "Connection attempt from/to broad- " 1323 "or multicast address ignored\n", 1324 s, __func__); 1325 goto dropunlock; 1326 } 1327 } 1328 #endif 1329 /* 1330 * SYN appears to be valid. Create compressed TCP state 1331 * for syncache. 1332 */ 1333 #ifdef TCPDEBUG 1334 if (so->so_options & SO_DEBUG) 1335 tcp_trace(TA_INPUT, ostate, tp, 1336 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1337 #endif 1338 tcp_dooptions(&to, optp, optlen, TO_SYN); 1339 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1340 /* 1341 * Entry added to syncache and mbuf consumed. 1342 * Everything already unlocked by syncache_add(). 1343 */ 1344 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1345 return (IPPROTO_DONE); 1346 } else if (tp->t_state == TCPS_LISTEN) { 1347 /* 1348 * When a listen socket is torn down the SO_ACCEPTCONN 1349 * flag is removed first while connections are drained 1350 * from the accept queue in a unlock/lock cycle of the 1351 * ACCEPT_LOCK, opening a race condition allowing a SYN 1352 * attempt go through unhandled. 1353 */ 1354 goto dropunlock; 1355 } 1356 1357 #ifdef TCP_SIGNATURE 1358 if (sig_checked == 0) { 1359 tcp_dooptions(&to, optp, optlen, 1360 (thflags & TH_SYN) ? TO_SYN : 0); 1361 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1362 th, tp->t_flags)) { 1363 1364 /* 1365 * In SYN_SENT state if it receives an RST, it is 1366 * allowed for further processing. 1367 */ 1368 if ((thflags & TH_RST) == 0 || 1369 (tp->t_state == TCPS_SYN_SENT) == 0) 1370 goto dropunlock; 1371 } 1372 sig_checked = 1; 1373 } 1374 #endif 1375 1376 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1377 1378 /* 1379 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1380 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1381 * the inpcb, and unlocks pcbinfo. 1382 */ 1383 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1384 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1385 return (IPPROTO_DONE); 1386 1387 dropwithreset: 1388 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1389 1390 if (ti_locked == TI_WLOCKED) { 1391 INP_INFO_WUNLOCK(&V_tcbinfo); 1392 ti_locked = TI_UNLOCKED; 1393 } 1394 #ifdef INVARIANTS 1395 else { 1396 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1397 "ti_locked: %d", __func__, ti_locked)); 1398 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1399 } 1400 #endif 1401 1402 if (inp != NULL) { 1403 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1404 INP_WUNLOCK(inp); 1405 } else 1406 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1407 m = NULL; /* mbuf chain got consumed. */ 1408 goto drop; 1409 1410 dropunlock: 1411 if (m != NULL) 1412 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1413 1414 if (ti_locked == TI_WLOCKED) { 1415 INP_INFO_WUNLOCK(&V_tcbinfo); 1416 ti_locked = TI_UNLOCKED; 1417 } 1418 #ifdef INVARIANTS 1419 else { 1420 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1421 "ti_locked: %d", __func__, ti_locked)); 1422 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1423 } 1424 #endif 1425 1426 if (inp != NULL) 1427 INP_WUNLOCK(inp); 1428 1429 drop: 1430 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1431 if (s != NULL) 1432 free(s, M_TCPLOG); 1433 if (m != NULL) 1434 m_freem(m); 1435 return (IPPROTO_DONE); 1436 } 1437 1438 static void 1439 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1440 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1441 int ti_locked) 1442 { 1443 int thflags, acked, ourfinisacked, needoutput = 0; 1444 int rstreason, todrop, win; 1445 u_long tiwin; 1446 char *s; 1447 struct in_conninfo *inc; 1448 struct mbuf *mfree; 1449 struct tcpopt to; 1450 1451 #ifdef TCPDEBUG 1452 /* 1453 * The size of tcp_saveipgen must be the size of the max ip header, 1454 * now IPv6. 1455 */ 1456 u_char tcp_saveipgen[IP6_HDR_LEN]; 1457 struct tcphdr tcp_savetcp; 1458 short ostate = 0; 1459 #endif 1460 thflags = th->th_flags; 1461 inc = &tp->t_inpcb->inp_inc; 1462 tp->sackhint.last_sack_ack = 0; 1463 1464 /* 1465 * If this is either a state-changing packet or current state isn't 1466 * established, we require a write lock on tcbinfo. Otherwise, we 1467 * allow the tcbinfo to be in either alocked or unlocked, as the 1468 * caller may have unnecessarily acquired a write lock due to a race. 1469 */ 1470 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1471 tp->t_state != TCPS_ESTABLISHED) { 1472 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for " 1473 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1474 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1475 } else { 1476 #ifdef INVARIANTS 1477 if (ti_locked == TI_WLOCKED) 1478 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1479 else { 1480 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1481 "ti_locked: %d", __func__, ti_locked)); 1482 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1483 } 1484 #endif 1485 } 1486 INP_WLOCK_ASSERT(tp->t_inpcb); 1487 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1488 __func__)); 1489 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1490 __func__)); 1491 1492 /* 1493 * Segment received on connection. 1494 * Reset idle time and keep-alive timer. 1495 * XXX: This should be done after segment 1496 * validation to ignore broken/spoofed segs. 1497 */ 1498 tp->t_rcvtime = ticks; 1499 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1500 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 1501 1502 /* 1503 * Unscale the window into a 32-bit value. 1504 * For the SYN_SENT state the scale is zero. 1505 */ 1506 tiwin = th->th_win << tp->snd_scale; 1507 1508 /* 1509 * TCP ECN processing. 1510 */ 1511 if (tp->t_flags & TF_ECN_PERMIT) { 1512 if (thflags & TH_CWR) 1513 tp->t_flags &= ~TF_ECN_SND_ECE; 1514 switch (iptos & IPTOS_ECN_MASK) { 1515 case IPTOS_ECN_CE: 1516 tp->t_flags |= TF_ECN_SND_ECE; 1517 TCPSTAT_INC(tcps_ecn_ce); 1518 break; 1519 case IPTOS_ECN_ECT0: 1520 TCPSTAT_INC(tcps_ecn_ect0); 1521 break; 1522 case IPTOS_ECN_ECT1: 1523 TCPSTAT_INC(tcps_ecn_ect1); 1524 break; 1525 } 1526 /* Congestion experienced. */ 1527 if (thflags & TH_ECE) { 1528 cc_cong_signal(tp, th, CC_ECN); 1529 } 1530 } 1531 1532 /* 1533 * Parse options on any incoming segment. 1534 */ 1535 tcp_dooptions(&to, (u_char *)(th + 1), 1536 (th->th_off << 2) - sizeof(struct tcphdr), 1537 (thflags & TH_SYN) ? TO_SYN : 0); 1538 1539 /* 1540 * If echoed timestamp is later than the current time, 1541 * fall back to non RFC1323 RTT calculation. Normalize 1542 * timestamp if syncookies were used when this connection 1543 * was established. 1544 */ 1545 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1546 to.to_tsecr -= tp->ts_offset; 1547 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1548 to.to_tsecr = 0; 1549 } 1550 /* 1551 * If timestamps were negotiated during SYN/ACK they should 1552 * appear on every segment during this session and vice versa. 1553 */ 1554 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1555 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1556 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1557 "no action\n", s, __func__); 1558 free(s, M_TCPLOG); 1559 } 1560 } 1561 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1562 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1563 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1564 "no action\n", s, __func__); 1565 free(s, M_TCPLOG); 1566 } 1567 } 1568 1569 /* 1570 * Process options only when we get SYN/ACK back. The SYN case 1571 * for incoming connections is handled in tcp_syncache. 1572 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1573 * or <SYN,ACK>) segment itself is never scaled. 1574 * XXX this is traditional behavior, may need to be cleaned up. 1575 */ 1576 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1577 if ((to.to_flags & TOF_SCALE) && 1578 (tp->t_flags & TF_REQ_SCALE)) { 1579 tp->t_flags |= TF_RCVD_SCALE; 1580 tp->snd_scale = to.to_wscale; 1581 } 1582 /* 1583 * Initial send window. It will be updated with 1584 * the next incoming segment to the scaled value. 1585 */ 1586 tp->snd_wnd = th->th_win; 1587 if (to.to_flags & TOF_TS) { 1588 tp->t_flags |= TF_RCVD_TSTMP; 1589 tp->ts_recent = to.to_tsval; 1590 tp->ts_recent_age = tcp_ts_getticks(); 1591 } 1592 if (to.to_flags & TOF_MSS) 1593 tcp_mss(tp, to.to_mss); 1594 if ((tp->t_flags & TF_SACK_PERMIT) && 1595 (to.to_flags & TOF_SACKPERM) == 0) 1596 tp->t_flags &= ~TF_SACK_PERMIT; 1597 } 1598 1599 /* 1600 * Header prediction: check for the two common cases 1601 * of a uni-directional data xfer. If the packet has 1602 * no control flags, is in-sequence, the window didn't 1603 * change and we're not retransmitting, it's a 1604 * candidate. If the length is zero and the ack moved 1605 * forward, we're the sender side of the xfer. Just 1606 * free the data acked & wake any higher level process 1607 * that was blocked waiting for space. If the length 1608 * is non-zero and the ack didn't move, we're the 1609 * receiver side. If we're getting packets in-order 1610 * (the reassembly queue is empty), add the data to 1611 * the socket buffer and note that we need a delayed ack. 1612 * Make sure that the hidden state-flags are also off. 1613 * Since we check for TCPS_ESTABLISHED first, it can only 1614 * be TH_NEEDSYN. 1615 */ 1616 if (tp->t_state == TCPS_ESTABLISHED && 1617 th->th_seq == tp->rcv_nxt && 1618 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1619 tp->snd_nxt == tp->snd_max && 1620 tiwin && tiwin == tp->snd_wnd && 1621 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1622 tp->t_segq == NULL && ((to.to_flags & TOF_TS) == 0 || 1623 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1624 1625 /* 1626 * If last ACK falls within this segment's sequence numbers, 1627 * record the timestamp. 1628 * NOTE that the test is modified according to the latest 1629 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1630 */ 1631 if ((to.to_flags & TOF_TS) != 0 && 1632 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1633 tp->ts_recent_age = tcp_ts_getticks(); 1634 tp->ts_recent = to.to_tsval; 1635 } 1636 1637 if (tlen == 0) { 1638 if (SEQ_GT(th->th_ack, tp->snd_una) && 1639 SEQ_LEQ(th->th_ack, tp->snd_max) && 1640 !IN_RECOVERY(tp->t_flags) && 1641 (to.to_flags & TOF_SACK) == 0 && 1642 TAILQ_EMPTY(&tp->snd_holes)) { 1643 /* 1644 * This is a pure ack for outstanding data. 1645 */ 1646 if (ti_locked == TI_WLOCKED) 1647 INP_INFO_WUNLOCK(&V_tcbinfo); 1648 ti_locked = TI_UNLOCKED; 1649 1650 TCPSTAT_INC(tcps_predack); 1651 1652 /* 1653 * "bad retransmit" recovery. 1654 */ 1655 if (tp->t_rxtshift == 1 && 1656 tp->t_flags & TF_PREVVALID && 1657 (int)(ticks - tp->t_badrxtwin) < 0) { 1658 cc_cong_signal(tp, th, CC_RTO_ERR); 1659 } 1660 1661 /* 1662 * Recalculate the transmit timer / rtt. 1663 * 1664 * Some boxes send broken timestamp replies 1665 * during the SYN+ACK phase, ignore 1666 * timestamps of 0 or we could calculate a 1667 * huge RTT and blow up the retransmit timer. 1668 */ 1669 if ((to.to_flags & TOF_TS) != 0 && 1670 to.to_tsecr) { 1671 u_int t; 1672 1673 t = tcp_ts_getticks() - to.to_tsecr; 1674 if (!tp->t_rttlow || tp->t_rttlow > t) 1675 tp->t_rttlow = t; 1676 tcp_xmit_timer(tp, 1677 TCP_TS_TO_TICKS(t) + 1); 1678 } else if (tp->t_rtttime && 1679 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1680 if (!tp->t_rttlow || 1681 tp->t_rttlow > ticks - tp->t_rtttime) 1682 tp->t_rttlow = ticks - tp->t_rtttime; 1683 tcp_xmit_timer(tp, 1684 ticks - tp->t_rtttime); 1685 } 1686 acked = BYTES_THIS_ACK(tp, th); 1687 1688 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1689 hhook_run_tcp_est_in(tp, th, &to); 1690 1691 TCPSTAT_INC(tcps_rcvackpack); 1692 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1693 sbdrop(&so->so_snd, acked); 1694 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1695 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1696 tp->snd_recover = th->th_ack - 1; 1697 1698 /* 1699 * Let the congestion control algorithm update 1700 * congestion control related information. This 1701 * typically means increasing the congestion 1702 * window. 1703 */ 1704 cc_ack_received(tp, th, CC_ACK); 1705 1706 tp->snd_una = th->th_ack; 1707 /* 1708 * Pull snd_wl2 up to prevent seq wrap relative 1709 * to th_ack. 1710 */ 1711 tp->snd_wl2 = th->th_ack; 1712 tp->t_dupacks = 0; 1713 m_freem(m); 1714 ND6_HINT(tp); /* Some progress has been made. */ 1715 1716 /* 1717 * If all outstanding data are acked, stop 1718 * retransmit timer, otherwise restart timer 1719 * using current (possibly backed-off) value. 1720 * If process is waiting for space, 1721 * wakeup/selwakeup/signal. If data 1722 * are ready to send, let tcp_output 1723 * decide between more output or persist. 1724 */ 1725 #ifdef TCPDEBUG 1726 if (so->so_options & SO_DEBUG) 1727 tcp_trace(TA_INPUT, ostate, tp, 1728 (void *)tcp_saveipgen, 1729 &tcp_savetcp, 0); 1730 #endif 1731 if (tp->snd_una == tp->snd_max) 1732 tcp_timer_activate(tp, TT_REXMT, 0); 1733 else if (!tcp_timer_active(tp, TT_PERSIST)) 1734 tcp_timer_activate(tp, TT_REXMT, 1735 tp->t_rxtcur); 1736 sowwakeup(so); 1737 if (so->so_snd.sb_cc) 1738 (void) tcp_output(tp); 1739 goto check_delack; 1740 } 1741 } else if (th->th_ack == tp->snd_una && 1742 tlen <= sbspace(&so->so_rcv)) { 1743 int newsize = 0; /* automatic sockbuf scaling */ 1744 1745 /* 1746 * This is a pure, in-sequence data packet with 1747 * nothing on the reassembly queue and we have enough 1748 * buffer space to take it. 1749 */ 1750 if (ti_locked == TI_WLOCKED) 1751 INP_INFO_WUNLOCK(&V_tcbinfo); 1752 ti_locked = TI_UNLOCKED; 1753 1754 /* Clean receiver SACK report if present */ 1755 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1756 tcp_clean_sackreport(tp); 1757 TCPSTAT_INC(tcps_preddat); 1758 tp->rcv_nxt += tlen; 1759 /* 1760 * Pull snd_wl1 up to prevent seq wrap relative to 1761 * th_seq. 1762 */ 1763 tp->snd_wl1 = th->th_seq; 1764 /* 1765 * Pull rcv_up up to prevent seq wrap relative to 1766 * rcv_nxt. 1767 */ 1768 tp->rcv_up = tp->rcv_nxt; 1769 TCPSTAT_INC(tcps_rcvpack); 1770 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1771 ND6_HINT(tp); /* Some progress has been made */ 1772 #ifdef TCPDEBUG 1773 if (so->so_options & SO_DEBUG) 1774 tcp_trace(TA_INPUT, ostate, tp, 1775 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1776 #endif 1777 /* 1778 * Automatic sizing of receive socket buffer. Often the send 1779 * buffer size is not optimally adjusted to the actual network 1780 * conditions at hand (delay bandwidth product). Setting the 1781 * buffer size too small limits throughput on links with high 1782 * bandwidth and high delay (eg. trans-continental/oceanic links). 1783 * 1784 * On the receive side the socket buffer memory is only rarely 1785 * used to any significant extent. This allows us to be much 1786 * more aggressive in scaling the receive socket buffer. For 1787 * the case that the buffer space is actually used to a large 1788 * extent and we run out of kernel memory we can simply drop 1789 * the new segments; TCP on the sender will just retransmit it 1790 * later. Setting the buffer size too big may only consume too 1791 * much kernel memory if the application doesn't read() from 1792 * the socket or packet loss or reordering makes use of the 1793 * reassembly queue. 1794 * 1795 * The criteria to step up the receive buffer one notch are: 1796 * 1. Application has not set receive buffer size with 1797 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1798 * 2. the number of bytes received during the time it takes 1799 * one timestamp to be reflected back to us (the RTT); 1800 * 3. received bytes per RTT is within seven eighth of the 1801 * current socket buffer size; 1802 * 4. receive buffer size has not hit maximal automatic size; 1803 * 1804 * This algorithm does one step per RTT at most and only if 1805 * we receive a bulk stream w/o packet losses or reorderings. 1806 * Shrinking the buffer during idle times is not necessary as 1807 * it doesn't consume any memory when idle. 1808 * 1809 * TODO: Only step up if the application is actually serving 1810 * the buffer to better manage the socket buffer resources. 1811 */ 1812 if (V_tcp_do_autorcvbuf && 1813 to.to_tsecr && 1814 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1815 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1816 to.to_tsecr - tp->rfbuf_ts < hz) { 1817 if (tp->rfbuf_cnt > 1818 (so->so_rcv.sb_hiwat / 8 * 7) && 1819 so->so_rcv.sb_hiwat < 1820 V_tcp_autorcvbuf_max) { 1821 newsize = 1822 min(so->so_rcv.sb_hiwat + 1823 V_tcp_autorcvbuf_inc, 1824 V_tcp_autorcvbuf_max); 1825 } 1826 /* Start over with next RTT. */ 1827 tp->rfbuf_ts = 0; 1828 tp->rfbuf_cnt = 0; 1829 } else 1830 tp->rfbuf_cnt += tlen; /* add up */ 1831 } 1832 1833 /* Add data to socket buffer. */ 1834 SOCKBUF_LOCK(&so->so_rcv); 1835 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1836 m_freem(m); 1837 } else { 1838 /* 1839 * Set new socket buffer size. 1840 * Give up when limit is reached. 1841 */ 1842 if (newsize) 1843 if (!sbreserve_locked(&so->so_rcv, 1844 newsize, so, NULL)) 1845 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1846 m_adj(m, drop_hdrlen); /* delayed header drop */ 1847 sbappendstream_locked(&so->so_rcv, m); 1848 } 1849 /* NB: sorwakeup_locked() does an implicit unlock. */ 1850 sorwakeup_locked(so); 1851 if (DELAY_ACK(tp, tlen)) { 1852 tp->t_flags |= TF_DELACK; 1853 } else { 1854 tp->t_flags |= TF_ACKNOW; 1855 tcp_output(tp); 1856 } 1857 goto check_delack; 1858 } 1859 } 1860 1861 /* 1862 * Calculate amount of space in receive window, 1863 * and then do TCP input processing. 1864 * Receive window is amount of space in rcv queue, 1865 * but not less than advertised window. 1866 */ 1867 win = sbspace(&so->so_rcv); 1868 if (win < 0) 1869 win = 0; 1870 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1871 1872 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1873 tp->rfbuf_ts = 0; 1874 tp->rfbuf_cnt = 0; 1875 1876 switch (tp->t_state) { 1877 1878 /* 1879 * If the state is SYN_RECEIVED: 1880 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1881 */ 1882 case TCPS_SYN_RECEIVED: 1883 if ((thflags & TH_ACK) && 1884 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1885 SEQ_GT(th->th_ack, tp->snd_max))) { 1886 rstreason = BANDLIM_RST_OPENPORT; 1887 goto dropwithreset; 1888 } 1889 break; 1890 1891 /* 1892 * If the state is SYN_SENT: 1893 * if seg contains an ACK, but not for our SYN, drop the input. 1894 * if seg contains a RST, then drop the connection. 1895 * if seg does not contain SYN, then drop it. 1896 * Otherwise this is an acceptable SYN segment 1897 * initialize tp->rcv_nxt and tp->irs 1898 * if seg contains ack then advance tp->snd_una 1899 * if seg contains an ECE and ECN support is enabled, the stream 1900 * is ECN capable. 1901 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1902 * arrange for segment to be acked (eventually) 1903 * continue processing rest of data/controls, beginning with URG 1904 */ 1905 case TCPS_SYN_SENT: 1906 if ((thflags & TH_ACK) && 1907 (SEQ_LEQ(th->th_ack, tp->iss) || 1908 SEQ_GT(th->th_ack, tp->snd_max))) { 1909 rstreason = BANDLIM_UNLIMITED; 1910 goto dropwithreset; 1911 } 1912 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1913 TCP_PROBE5(connect__refused, NULL, tp, 1914 mtod(m, const char *), tp, th); 1915 tp = tcp_drop(tp, ECONNREFUSED); 1916 } 1917 if (thflags & TH_RST) 1918 goto drop; 1919 if (!(thflags & TH_SYN)) 1920 goto drop; 1921 1922 tp->irs = th->th_seq; 1923 tcp_rcvseqinit(tp); 1924 if (thflags & TH_ACK) { 1925 TCPSTAT_INC(tcps_connects); 1926 soisconnected(so); 1927 #ifdef MAC 1928 mac_socketpeer_set_from_mbuf(m, so); 1929 #endif 1930 /* Do window scaling on this connection? */ 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 } 1935 tp->rcv_adv += imin(tp->rcv_wnd, 1936 TCP_MAXWIN << tp->rcv_scale); 1937 tp->snd_una++; /* SYN is acked */ 1938 /* 1939 * If there's data, delay ACK; if there's also a FIN 1940 * ACKNOW will be turned on later. 1941 */ 1942 if (DELAY_ACK(tp, tlen) && tlen != 0) 1943 tcp_timer_activate(tp, TT_DELACK, 1944 tcp_delacktime); 1945 else 1946 tp->t_flags |= TF_ACKNOW; 1947 1948 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 1949 tp->t_flags |= TF_ECN_PERMIT; 1950 TCPSTAT_INC(tcps_ecn_shs); 1951 } 1952 1953 /* 1954 * Received <SYN,ACK> in SYN_SENT[*] state. 1955 * Transitions: 1956 * SYN_SENT --> ESTABLISHED 1957 * SYN_SENT* --> FIN_WAIT_1 1958 */ 1959 tp->t_starttime = ticks; 1960 if (tp->t_flags & TF_NEEDFIN) { 1961 tcp_state_change(tp, TCPS_FIN_WAIT_1); 1962 tp->t_flags &= ~TF_NEEDFIN; 1963 thflags &= ~TH_SYN; 1964 } else { 1965 tcp_state_change(tp, TCPS_ESTABLISHED); 1966 TCP_PROBE5(connect__established, NULL, tp, 1967 mtod(m, const char *), tp, th); 1968 cc_conn_init(tp); 1969 tcp_timer_activate(tp, TT_KEEP, 1970 TP_KEEPIDLE(tp)); 1971 } 1972 } else { 1973 /* 1974 * Received initial SYN in SYN-SENT[*] state => 1975 * simultaneous open. 1976 * If it succeeds, connection is * half-synchronized. 1977 * Otherwise, do 3-way handshake: 1978 * SYN-SENT -> SYN-RECEIVED 1979 * SYN-SENT* -> SYN-RECEIVED* 1980 */ 1981 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1982 tcp_timer_activate(tp, TT_REXMT, 0); 1983 tcp_state_change(tp, TCPS_SYN_RECEIVED); 1984 } 1985 1986 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: " 1987 "ti_locked %d", __func__, ti_locked)); 1988 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1989 INP_WLOCK_ASSERT(tp->t_inpcb); 1990 1991 /* 1992 * Advance th->th_seq to correspond to first data byte. 1993 * If data, trim to stay within window, 1994 * dropping FIN if necessary. 1995 */ 1996 th->th_seq++; 1997 if (tlen > tp->rcv_wnd) { 1998 todrop = tlen - tp->rcv_wnd; 1999 m_adj(m, -todrop); 2000 tlen = tp->rcv_wnd; 2001 thflags &= ~TH_FIN; 2002 TCPSTAT_INC(tcps_rcvpackafterwin); 2003 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2004 } 2005 tp->snd_wl1 = th->th_seq - 1; 2006 tp->rcv_up = th->th_seq; 2007 /* 2008 * Client side of transaction: already sent SYN and data. 2009 * If the remote host used T/TCP to validate the SYN, 2010 * our data will be ACK'd; if so, enter normal data segment 2011 * processing in the middle of step 5, ack processing. 2012 * Otherwise, goto step 6. 2013 */ 2014 if (thflags & TH_ACK) 2015 goto process_ACK; 2016 2017 goto step6; 2018 2019 /* 2020 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2021 * do normal processing. 2022 * 2023 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2024 */ 2025 case TCPS_LAST_ACK: 2026 case TCPS_CLOSING: 2027 break; /* continue normal processing */ 2028 } 2029 2030 /* 2031 * States other than LISTEN or SYN_SENT. 2032 * First check the RST flag and sequence number since reset segments 2033 * are exempt from the timestamp and connection count tests. This 2034 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2035 * below which allowed reset segments in half the sequence space 2036 * to fall though and be processed (which gives forged reset 2037 * segments with a random sequence number a 50 percent chance of 2038 * killing a connection). 2039 * Then check timestamp, if present. 2040 * Then check the connection count, if present. 2041 * Then check that at least some bytes of segment are within 2042 * receive window. If segment begins before rcv_nxt, 2043 * drop leading data (and SYN); if nothing left, just ack. 2044 * 2045 * 2046 * If the RST bit is set, check the sequence number to see 2047 * if this is a valid reset segment. 2048 * RFC 793 page 37: 2049 * In all states except SYN-SENT, all reset (RST) segments 2050 * are validated by checking their SEQ-fields. A reset is 2051 * valid if its sequence number is in the window. 2052 * Note: this does not take into account delayed ACKs, so 2053 * we should test against last_ack_sent instead of rcv_nxt. 2054 * The sequence number in the reset segment is normally an 2055 * echo of our outgoing acknowlegement numbers, but some hosts 2056 * send a reset with the sequence number at the rightmost edge 2057 * of our receive window, and we have to handle this case. 2058 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 2059 * that brute force RST attacks are possible. To combat this, 2060 * we use a much stricter check while in the ESTABLISHED state, 2061 * only accepting RSTs where the sequence number is equal to 2062 * last_ack_sent. In all other states (the states in which a 2063 * RST is more likely), the more permissive check is used. 2064 * If we have multiple segments in flight, the initial reset 2065 * segment sequence numbers will be to the left of last_ack_sent, 2066 * but they will eventually catch up. 2067 * In any case, it never made sense to trim reset segments to 2068 * fit the receive window since RFC 1122 says: 2069 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 2070 * 2071 * A TCP SHOULD allow a received RST segment to include data. 2072 * 2073 * DISCUSSION 2074 * It has been suggested that a RST segment could contain 2075 * ASCII text that encoded and explained the cause of the 2076 * RST. No standard has yet been established for such 2077 * data. 2078 * 2079 * If the reset segment passes the sequence number test examine 2080 * the state: 2081 * SYN_RECEIVED STATE: 2082 * If passive open, return to LISTEN state. 2083 * If active open, inform user that connection was refused. 2084 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 2085 * Inform user that connection was reset, and close tcb. 2086 * CLOSING, LAST_ACK STATES: 2087 * Close the tcb. 2088 * TIME_WAIT STATE: 2089 * Drop the segment - see Stevens, vol. 2, p. 964 and 2090 * RFC 1337. 2091 */ 2092 if (thflags & TH_RST) { 2093 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 2094 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2095 switch (tp->t_state) { 2096 2097 case TCPS_SYN_RECEIVED: 2098 so->so_error = ECONNREFUSED; 2099 goto close; 2100 2101 case TCPS_ESTABLISHED: 2102 if (V_tcp_insecure_rst == 0 && 2103 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 2104 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 2105 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 2106 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 2107 TCPSTAT_INC(tcps_badrst); 2108 goto drop; 2109 } 2110 /* FALLTHROUGH */ 2111 case TCPS_FIN_WAIT_1: 2112 case TCPS_FIN_WAIT_2: 2113 case TCPS_CLOSE_WAIT: 2114 so->so_error = ECONNRESET; 2115 close: 2116 KASSERT(ti_locked == TI_WLOCKED, 2117 ("tcp_do_segment: TH_RST 1 ti_locked %d", 2118 ti_locked)); 2119 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2120 2121 tcp_state_change(tp, TCPS_CLOSED); 2122 TCPSTAT_INC(tcps_drops); 2123 tp = tcp_close(tp); 2124 break; 2125 2126 case TCPS_CLOSING: 2127 case TCPS_LAST_ACK: 2128 KASSERT(ti_locked == TI_WLOCKED, 2129 ("tcp_do_segment: TH_RST 2 ti_locked %d", 2130 ti_locked)); 2131 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2132 2133 tp = tcp_close(tp); 2134 break; 2135 } 2136 } 2137 goto drop; 2138 } 2139 2140 /* 2141 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2142 * and it's less than ts_recent, drop it. 2143 */ 2144 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2145 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2146 2147 /* Check to see if ts_recent is over 24 days old. */ 2148 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2149 /* 2150 * Invalidate ts_recent. If this segment updates 2151 * ts_recent, the age will be reset later and ts_recent 2152 * will get a valid value. If it does not, setting 2153 * ts_recent to zero will at least satisfy the 2154 * requirement that zero be placed in the timestamp 2155 * echo reply when ts_recent isn't valid. The 2156 * age isn't reset until we get a valid ts_recent 2157 * because we don't want out-of-order segments to be 2158 * dropped when ts_recent is old. 2159 */ 2160 tp->ts_recent = 0; 2161 } else { 2162 TCPSTAT_INC(tcps_rcvduppack); 2163 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2164 TCPSTAT_INC(tcps_pawsdrop); 2165 if (tlen) 2166 goto dropafterack; 2167 goto drop; 2168 } 2169 } 2170 2171 /* 2172 * In the SYN-RECEIVED state, validate that the packet belongs to 2173 * this connection before trimming the data to fit the receive 2174 * window. Check the sequence number versus IRS since we know 2175 * the sequence numbers haven't wrapped. This is a partial fix 2176 * for the "LAND" DoS attack. 2177 */ 2178 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2179 rstreason = BANDLIM_RST_OPENPORT; 2180 goto dropwithreset; 2181 } 2182 2183 todrop = tp->rcv_nxt - th->th_seq; 2184 if (todrop > 0) { 2185 /* 2186 * If this is a duplicate SYN for our current connection, 2187 * advance over it and pretend and it's not a SYN. 2188 */ 2189 if (thflags & TH_SYN && th->th_seq == tp->irs) { 2190 thflags &= ~TH_SYN; 2191 th->th_seq++; 2192 if (th->th_urp > 1) 2193 th->th_urp--; 2194 else 2195 thflags &= ~TH_URG; 2196 todrop--; 2197 } 2198 /* 2199 * Following if statement from Stevens, vol. 2, p. 960. 2200 */ 2201 if (todrop > tlen 2202 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2203 /* 2204 * Any valid FIN must be to the left of the window. 2205 * At this point the FIN must be a duplicate or out 2206 * of sequence; drop it. 2207 */ 2208 thflags &= ~TH_FIN; 2209 2210 /* 2211 * Send an ACK to resynchronize and drop any data. 2212 * But keep on processing for RST or ACK. 2213 */ 2214 tp->t_flags |= TF_ACKNOW; 2215 todrop = tlen; 2216 TCPSTAT_INC(tcps_rcvduppack); 2217 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2218 } else { 2219 TCPSTAT_INC(tcps_rcvpartduppack); 2220 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2221 } 2222 drop_hdrlen += todrop; /* drop from the top afterwards */ 2223 th->th_seq += todrop; 2224 tlen -= todrop; 2225 if (th->th_urp > todrop) 2226 th->th_urp -= todrop; 2227 else { 2228 thflags &= ~TH_URG; 2229 th->th_urp = 0; 2230 } 2231 } 2232 2233 /* 2234 * If new data are received on a connection after the 2235 * user processes are gone, then RST the other end. 2236 */ 2237 if ((so->so_state & SS_NOFDREF) && 2238 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2239 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && " 2240 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2241 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2242 2243 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2244 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2245 "after socket was closed, " 2246 "sending RST and removing tcpcb\n", 2247 s, __func__, tcpstates[tp->t_state], tlen); 2248 free(s, M_TCPLOG); 2249 } 2250 tp = tcp_close(tp); 2251 TCPSTAT_INC(tcps_rcvafterclose); 2252 rstreason = BANDLIM_UNLIMITED; 2253 goto dropwithreset; 2254 } 2255 2256 /* 2257 * If segment ends after window, drop trailing data 2258 * (and PUSH and FIN); if nothing left, just ACK. 2259 */ 2260 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2261 if (todrop > 0) { 2262 TCPSTAT_INC(tcps_rcvpackafterwin); 2263 if (todrop >= tlen) { 2264 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2265 /* 2266 * If window is closed can only take segments at 2267 * window edge, and have to drop data and PUSH from 2268 * incoming segments. Continue processing, but 2269 * remember to ack. Otherwise, drop segment 2270 * and ack. 2271 */ 2272 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2273 tp->t_flags |= TF_ACKNOW; 2274 TCPSTAT_INC(tcps_rcvwinprobe); 2275 } else 2276 goto dropafterack; 2277 } else 2278 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2279 m_adj(m, -todrop); 2280 tlen -= todrop; 2281 thflags &= ~(TH_PUSH|TH_FIN); 2282 } 2283 2284 /* 2285 * If last ACK falls within this segment's sequence numbers, 2286 * record its timestamp. 2287 * NOTE: 2288 * 1) That the test incorporates suggestions from the latest 2289 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2290 * 2) That updating only on newer timestamps interferes with 2291 * our earlier PAWS tests, so this check should be solely 2292 * predicated on the sequence space of this segment. 2293 * 3) That we modify the segment boundary check to be 2294 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2295 * instead of RFC1323's 2296 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2297 * This modified check allows us to overcome RFC1323's 2298 * limitations as described in Stevens TCP/IP Illustrated 2299 * Vol. 2 p.869. In such cases, we can still calculate the 2300 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2301 */ 2302 if ((to.to_flags & TOF_TS) != 0 && 2303 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2304 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2305 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2306 tp->ts_recent_age = tcp_ts_getticks(); 2307 tp->ts_recent = to.to_tsval; 2308 } 2309 2310 /* 2311 * If a SYN is in the window, then this is an 2312 * error and we send an RST and drop the connection. 2313 */ 2314 if (thflags & TH_SYN) { 2315 KASSERT(ti_locked == TI_WLOCKED, 2316 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2317 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2318 2319 tp = tcp_drop(tp, ECONNRESET); 2320 rstreason = BANDLIM_UNLIMITED; 2321 goto drop; 2322 } 2323 2324 /* 2325 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2326 * flag is on (half-synchronized state), then queue data for 2327 * later processing; else drop segment and return. 2328 */ 2329 if ((thflags & TH_ACK) == 0) { 2330 if (tp->t_state == TCPS_SYN_RECEIVED || 2331 (tp->t_flags & TF_NEEDSYN)) 2332 goto step6; 2333 else if (tp->t_flags & TF_ACKNOW) 2334 goto dropafterack; 2335 else 2336 goto drop; 2337 } 2338 2339 /* 2340 * Ack processing. 2341 */ 2342 switch (tp->t_state) { 2343 2344 /* 2345 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2346 * ESTABLISHED state and continue processing. 2347 * The ACK was checked above. 2348 */ 2349 case TCPS_SYN_RECEIVED: 2350 2351 TCPSTAT_INC(tcps_connects); 2352 soisconnected(so); 2353 /* Do window scaling? */ 2354 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2355 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2356 tp->rcv_scale = tp->request_r_scale; 2357 tp->snd_wnd = tiwin; 2358 } 2359 /* 2360 * Make transitions: 2361 * SYN-RECEIVED -> ESTABLISHED 2362 * SYN-RECEIVED* -> FIN-WAIT-1 2363 */ 2364 tp->t_starttime = ticks; 2365 if (tp->t_flags & TF_NEEDFIN) { 2366 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2367 tp->t_flags &= ~TF_NEEDFIN; 2368 } else { 2369 tcp_state_change(tp, TCPS_ESTABLISHED); 2370 TCP_PROBE5(accept__established, NULL, tp, 2371 mtod(m, const char *), tp, th); 2372 cc_conn_init(tp); 2373 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2374 } 2375 /* 2376 * If segment contains data or ACK, will call tcp_reass() 2377 * later; if not, do so now to pass queued data to user. 2378 */ 2379 if (tlen == 0 && (thflags & TH_FIN) == 0) 2380 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2381 (struct mbuf *)0); 2382 tp->snd_wl1 = th->th_seq - 1; 2383 /* FALLTHROUGH */ 2384 2385 /* 2386 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2387 * ACKs. If the ack is in the range 2388 * tp->snd_una < th->th_ack <= tp->snd_max 2389 * then advance tp->snd_una to th->th_ack and drop 2390 * data from the retransmission queue. If this ACK reflects 2391 * more up to date window information we update our window information. 2392 */ 2393 case TCPS_ESTABLISHED: 2394 case TCPS_FIN_WAIT_1: 2395 case TCPS_FIN_WAIT_2: 2396 case TCPS_CLOSE_WAIT: 2397 case TCPS_CLOSING: 2398 case TCPS_LAST_ACK: 2399 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2400 TCPSTAT_INC(tcps_rcvacktoomuch); 2401 goto dropafterack; 2402 } 2403 if ((tp->t_flags & TF_SACK_PERMIT) && 2404 ((to.to_flags & TOF_SACK) || 2405 !TAILQ_EMPTY(&tp->snd_holes))) 2406 tcp_sack_doack(tp, &to, th->th_ack); 2407 2408 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2409 hhook_run_tcp_est_in(tp, th, &to); 2410 2411 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2412 if (tlen == 0 && tiwin == tp->snd_wnd) { 2413 /* 2414 * If this is the first time we've seen a 2415 * FIN from the remote, this is not a 2416 * duplicate and it needs to be processed 2417 * normally. This happens during a 2418 * simultaneous close. 2419 */ 2420 if ((thflags & TH_FIN) && 2421 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2422 tp->t_dupacks = 0; 2423 break; 2424 } 2425 TCPSTAT_INC(tcps_rcvdupack); 2426 /* 2427 * If we have outstanding data (other than 2428 * a window probe), this is a completely 2429 * duplicate ack (ie, window info didn't 2430 * change and FIN isn't set), 2431 * the ack is the biggest we've 2432 * seen and we've seen exactly our rexmt 2433 * threshhold of them, assume a packet 2434 * has been dropped and retransmit it. 2435 * Kludge snd_nxt & the congestion 2436 * window so we send only this one 2437 * packet. 2438 * 2439 * We know we're losing at the current 2440 * window size so do congestion avoidance 2441 * (set ssthresh to half the current window 2442 * and pull our congestion window back to 2443 * the new ssthresh). 2444 * 2445 * Dup acks mean that packets have left the 2446 * network (they're now cached at the receiver) 2447 * so bump cwnd by the amount in the receiver 2448 * to keep a constant cwnd packets in the 2449 * network. 2450 * 2451 * When using TCP ECN, notify the peer that 2452 * we reduced the cwnd. 2453 */ 2454 if (!tcp_timer_active(tp, TT_REXMT) || 2455 th->th_ack != tp->snd_una) 2456 tp->t_dupacks = 0; 2457 else if (++tp->t_dupacks > tcprexmtthresh || 2458 IN_FASTRECOVERY(tp->t_flags)) { 2459 cc_ack_received(tp, th, CC_DUPACK); 2460 if ((tp->t_flags & TF_SACK_PERMIT) && 2461 IN_FASTRECOVERY(tp->t_flags)) { 2462 int awnd; 2463 2464 /* 2465 * Compute the amount of data in flight first. 2466 * We can inject new data into the pipe iff 2467 * we have less than 1/2 the original window's 2468 * worth of data in flight. 2469 */ 2470 awnd = (tp->snd_nxt - tp->snd_fack) + 2471 tp->sackhint.sack_bytes_rexmit; 2472 if (awnd < tp->snd_ssthresh) { 2473 tp->snd_cwnd += tp->t_maxseg; 2474 if (tp->snd_cwnd > tp->snd_ssthresh) 2475 tp->snd_cwnd = tp->snd_ssthresh; 2476 } 2477 } else 2478 tp->snd_cwnd += tp->t_maxseg; 2479 (void) tcp_output(tp); 2480 goto drop; 2481 } else if (tp->t_dupacks == tcprexmtthresh) { 2482 tcp_seq onxt = tp->snd_nxt; 2483 2484 /* 2485 * If we're doing sack, check to 2486 * see if we're already in sack 2487 * recovery. If we're not doing sack, 2488 * check to see if we're in newreno 2489 * recovery. 2490 */ 2491 if (tp->t_flags & TF_SACK_PERMIT) { 2492 if (IN_FASTRECOVERY(tp->t_flags)) { 2493 tp->t_dupacks = 0; 2494 break; 2495 } 2496 } else { 2497 if (SEQ_LEQ(th->th_ack, 2498 tp->snd_recover)) { 2499 tp->t_dupacks = 0; 2500 break; 2501 } 2502 } 2503 /* Congestion signal before ack. */ 2504 cc_cong_signal(tp, th, CC_NDUPACK); 2505 cc_ack_received(tp, th, CC_DUPACK); 2506 tcp_timer_activate(tp, TT_REXMT, 0); 2507 tp->t_rtttime = 0; 2508 if (tp->t_flags & TF_SACK_PERMIT) { 2509 TCPSTAT_INC( 2510 tcps_sack_recovery_episode); 2511 tp->sack_newdata = tp->snd_nxt; 2512 tp->snd_cwnd = tp->t_maxseg; 2513 (void) tcp_output(tp); 2514 goto drop; 2515 } 2516 tp->snd_nxt = th->th_ack; 2517 tp->snd_cwnd = tp->t_maxseg; 2518 (void) tcp_output(tp); 2519 KASSERT(tp->snd_limited <= 2, 2520 ("%s: tp->snd_limited too big", 2521 __func__)); 2522 tp->snd_cwnd = tp->snd_ssthresh + 2523 tp->t_maxseg * 2524 (tp->t_dupacks - tp->snd_limited); 2525 if (SEQ_GT(onxt, tp->snd_nxt)) 2526 tp->snd_nxt = onxt; 2527 goto drop; 2528 } else if (V_tcp_do_rfc3042) { 2529 cc_ack_received(tp, th, CC_DUPACK); 2530 u_long oldcwnd = tp->snd_cwnd; 2531 tcp_seq oldsndmax = tp->snd_max; 2532 u_int sent; 2533 int avail; 2534 2535 KASSERT(tp->t_dupacks == 1 || 2536 tp->t_dupacks == 2, 2537 ("%s: dupacks not 1 or 2", 2538 __func__)); 2539 if (tp->t_dupacks == 1) 2540 tp->snd_limited = 0; 2541 tp->snd_cwnd = 2542 (tp->snd_nxt - tp->snd_una) + 2543 (tp->t_dupacks - tp->snd_limited) * 2544 tp->t_maxseg; 2545 /* 2546 * Only call tcp_output when there 2547 * is new data available to be sent. 2548 * Otherwise we would send pure ACKs. 2549 */ 2550 SOCKBUF_LOCK(&so->so_snd); 2551 avail = so->so_snd.sb_cc - 2552 (tp->snd_nxt - tp->snd_una); 2553 SOCKBUF_UNLOCK(&so->so_snd); 2554 if (avail > 0) 2555 (void) tcp_output(tp); 2556 sent = tp->snd_max - oldsndmax; 2557 if (sent > tp->t_maxseg) { 2558 KASSERT((tp->t_dupacks == 2 && 2559 tp->snd_limited == 0) || 2560 (sent == tp->t_maxseg + 1 && 2561 tp->t_flags & TF_SENTFIN), 2562 ("%s: sent too much", 2563 __func__)); 2564 tp->snd_limited = 2; 2565 } else if (sent > 0) 2566 ++tp->snd_limited; 2567 tp->snd_cwnd = oldcwnd; 2568 goto drop; 2569 } 2570 } else 2571 tp->t_dupacks = 0; 2572 break; 2573 } 2574 2575 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2576 ("%s: th_ack <= snd_una", __func__)); 2577 2578 /* 2579 * If the congestion window was inflated to account 2580 * for the other side's cached packets, retract it. 2581 */ 2582 if (IN_FASTRECOVERY(tp->t_flags)) { 2583 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2584 if (tp->t_flags & TF_SACK_PERMIT) 2585 tcp_sack_partialack(tp, th); 2586 else 2587 tcp_newreno_partial_ack(tp, th); 2588 } else 2589 cc_post_recovery(tp, th); 2590 } 2591 tp->t_dupacks = 0; 2592 /* 2593 * If we reach this point, ACK is not a duplicate, 2594 * i.e., it ACKs something we sent. 2595 */ 2596 if (tp->t_flags & TF_NEEDSYN) { 2597 /* 2598 * T/TCP: Connection was half-synchronized, and our 2599 * SYN has been ACK'd (so connection is now fully 2600 * synchronized). Go to non-starred state, 2601 * increment snd_una for ACK of SYN, and check if 2602 * we can do window scaling. 2603 */ 2604 tp->t_flags &= ~TF_NEEDSYN; 2605 tp->snd_una++; 2606 /* Do window scaling? */ 2607 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2608 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2609 tp->rcv_scale = tp->request_r_scale; 2610 /* Send window already scaled. */ 2611 } 2612 } 2613 2614 process_ACK: 2615 INP_WLOCK_ASSERT(tp->t_inpcb); 2616 2617 acked = BYTES_THIS_ACK(tp, th); 2618 TCPSTAT_INC(tcps_rcvackpack); 2619 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2620 2621 /* 2622 * If we just performed our first retransmit, and the ACK 2623 * arrives within our recovery window, then it was a mistake 2624 * to do the retransmit in the first place. Recover our 2625 * original cwnd and ssthresh, and proceed to transmit where 2626 * we left off. 2627 */ 2628 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2629 (int)(ticks - tp->t_badrxtwin) < 0) 2630 cc_cong_signal(tp, th, CC_RTO_ERR); 2631 2632 /* 2633 * If we have a timestamp reply, update smoothed 2634 * round trip time. If no timestamp is present but 2635 * transmit timer is running and timed sequence 2636 * number was acked, update smoothed round trip time. 2637 * Since we now have an rtt measurement, cancel the 2638 * timer backoff (cf., Phil Karn's retransmit alg.). 2639 * Recompute the initial retransmit timer. 2640 * 2641 * Some boxes send broken timestamp replies 2642 * during the SYN+ACK phase, ignore 2643 * timestamps of 0 or we could calculate a 2644 * huge RTT and blow up the retransmit timer. 2645 */ 2646 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2647 u_int t; 2648 2649 t = tcp_ts_getticks() - to.to_tsecr; 2650 if (!tp->t_rttlow || tp->t_rttlow > t) 2651 tp->t_rttlow = t; 2652 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2653 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2654 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2655 tp->t_rttlow = ticks - tp->t_rtttime; 2656 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2657 } 2658 2659 /* 2660 * If all outstanding data is acked, stop retransmit 2661 * timer and remember to restart (more output or persist). 2662 * If there is more data to be acked, restart retransmit 2663 * timer, using current (possibly backed-off) value. 2664 */ 2665 if (th->th_ack == tp->snd_max) { 2666 tcp_timer_activate(tp, TT_REXMT, 0); 2667 needoutput = 1; 2668 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2669 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2670 2671 /* 2672 * If no data (only SYN) was ACK'd, 2673 * skip rest of ACK processing. 2674 */ 2675 if (acked == 0) 2676 goto step6; 2677 2678 /* 2679 * Let the congestion control algorithm update congestion 2680 * control related information. This typically means increasing 2681 * the congestion window. 2682 */ 2683 cc_ack_received(tp, th, CC_ACK); 2684 2685 SOCKBUF_LOCK(&so->so_snd); 2686 if (acked > so->so_snd.sb_cc) { 2687 tp->snd_wnd -= so->so_snd.sb_cc; 2688 mfree = sbcut_locked(&so->so_snd, 2689 (int)so->so_snd.sb_cc); 2690 ourfinisacked = 1; 2691 } else { 2692 mfree = sbcut_locked(&so->so_snd, acked); 2693 tp->snd_wnd -= acked; 2694 ourfinisacked = 0; 2695 } 2696 /* NB: sowwakeup_locked() does an implicit unlock. */ 2697 sowwakeup_locked(so); 2698 m_freem(mfree); 2699 /* Detect una wraparound. */ 2700 if (!IN_RECOVERY(tp->t_flags) && 2701 SEQ_GT(tp->snd_una, tp->snd_recover) && 2702 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2703 tp->snd_recover = th->th_ack - 1; 2704 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2705 if (IN_RECOVERY(tp->t_flags) && 2706 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2707 EXIT_RECOVERY(tp->t_flags); 2708 } 2709 tp->snd_una = th->th_ack; 2710 if (tp->t_flags & TF_SACK_PERMIT) { 2711 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2712 tp->snd_recover = tp->snd_una; 2713 } 2714 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2715 tp->snd_nxt = tp->snd_una; 2716 2717 switch (tp->t_state) { 2718 2719 /* 2720 * In FIN_WAIT_1 STATE in addition to the processing 2721 * for the ESTABLISHED state if our FIN is now acknowledged 2722 * then enter FIN_WAIT_2. 2723 */ 2724 case TCPS_FIN_WAIT_1: 2725 if (ourfinisacked) { 2726 /* 2727 * If we can't receive any more 2728 * data, then closing user can proceed. 2729 * Starting the timer is contrary to the 2730 * specification, but if we don't get a FIN 2731 * we'll hang forever. 2732 * 2733 * XXXjl: 2734 * we should release the tp also, and use a 2735 * compressed state. 2736 */ 2737 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2738 soisdisconnected(so); 2739 tcp_timer_activate(tp, TT_2MSL, 2740 (tcp_fast_finwait2_recycle ? 2741 tcp_finwait2_timeout : 2742 TP_MAXIDLE(tp))); 2743 } 2744 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2745 } 2746 break; 2747 2748 /* 2749 * In CLOSING STATE in addition to the processing for 2750 * the ESTABLISHED state if the ACK acknowledges our FIN 2751 * then enter the TIME-WAIT state, otherwise ignore 2752 * the segment. 2753 */ 2754 case TCPS_CLOSING: 2755 if (ourfinisacked) { 2756 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2757 tcp_twstart(tp); 2758 INP_INFO_WUNLOCK(&V_tcbinfo); 2759 m_freem(m); 2760 return; 2761 } 2762 break; 2763 2764 /* 2765 * In LAST_ACK, we may still be waiting for data to drain 2766 * and/or to be acked, as well as for the ack of our FIN. 2767 * If our FIN is now acknowledged, delete the TCB, 2768 * enter the closed state and return. 2769 */ 2770 case TCPS_LAST_ACK: 2771 if (ourfinisacked) { 2772 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2773 tp = tcp_close(tp); 2774 goto drop; 2775 } 2776 break; 2777 } 2778 } 2779 2780 step6: 2781 INP_WLOCK_ASSERT(tp->t_inpcb); 2782 2783 /* 2784 * Update window information. 2785 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2786 */ 2787 if ((thflags & TH_ACK) && 2788 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2789 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2790 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2791 /* keep track of pure window updates */ 2792 if (tlen == 0 && 2793 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2794 TCPSTAT_INC(tcps_rcvwinupd); 2795 tp->snd_wnd = tiwin; 2796 tp->snd_wl1 = th->th_seq; 2797 tp->snd_wl2 = th->th_ack; 2798 if (tp->snd_wnd > tp->max_sndwnd) 2799 tp->max_sndwnd = tp->snd_wnd; 2800 needoutput = 1; 2801 } 2802 2803 /* 2804 * Process segments with URG. 2805 */ 2806 if ((thflags & TH_URG) && th->th_urp && 2807 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2808 /* 2809 * This is a kludge, but if we receive and accept 2810 * random urgent pointers, we'll crash in 2811 * soreceive. It's hard to imagine someone 2812 * actually wanting to send this much urgent data. 2813 */ 2814 SOCKBUF_LOCK(&so->so_rcv); 2815 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2816 th->th_urp = 0; /* XXX */ 2817 thflags &= ~TH_URG; /* XXX */ 2818 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2819 goto dodata; /* XXX */ 2820 } 2821 /* 2822 * If this segment advances the known urgent pointer, 2823 * then mark the data stream. This should not happen 2824 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2825 * a FIN has been received from the remote side. 2826 * In these states we ignore the URG. 2827 * 2828 * According to RFC961 (Assigned Protocols), 2829 * the urgent pointer points to the last octet 2830 * of urgent data. We continue, however, 2831 * to consider it to indicate the first octet 2832 * of data past the urgent section as the original 2833 * spec states (in one of two places). 2834 */ 2835 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2836 tp->rcv_up = th->th_seq + th->th_urp; 2837 so->so_oobmark = so->so_rcv.sb_cc + 2838 (tp->rcv_up - tp->rcv_nxt) - 1; 2839 if (so->so_oobmark == 0) 2840 so->so_rcv.sb_state |= SBS_RCVATMARK; 2841 sohasoutofband(so); 2842 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2843 } 2844 SOCKBUF_UNLOCK(&so->so_rcv); 2845 /* 2846 * Remove out of band data so doesn't get presented to user. 2847 * This can happen independent of advancing the URG pointer, 2848 * but if two URG's are pending at once, some out-of-band 2849 * data may creep in... ick. 2850 */ 2851 if (th->th_urp <= (u_long)tlen && 2852 !(so->so_options & SO_OOBINLINE)) { 2853 /* hdr drop is delayed */ 2854 tcp_pulloutofband(so, th, m, drop_hdrlen); 2855 } 2856 } else { 2857 /* 2858 * If no out of band data is expected, 2859 * pull receive urgent pointer along 2860 * with the receive window. 2861 */ 2862 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2863 tp->rcv_up = tp->rcv_nxt; 2864 } 2865 dodata: /* XXX */ 2866 INP_WLOCK_ASSERT(tp->t_inpcb); 2867 2868 /* 2869 * Process the segment text, merging it into the TCP sequencing queue, 2870 * and arranging for acknowledgment of receipt if necessary. 2871 * This process logically involves adjusting tp->rcv_wnd as data 2872 * is presented to the user (this happens in tcp_usrreq.c, 2873 * case PRU_RCVD). If a FIN has already been received on this 2874 * connection then we just ignore the text. 2875 */ 2876 if ((tlen || (thflags & TH_FIN)) && 2877 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2878 tcp_seq save_start = th->th_seq; 2879 m_adj(m, drop_hdrlen); /* delayed header drop */ 2880 /* 2881 * Insert segment which includes th into TCP reassembly queue 2882 * with control block tp. Set thflags to whether reassembly now 2883 * includes a segment with FIN. This handles the common case 2884 * inline (segment is the next to be received on an established 2885 * connection, and the queue is empty), avoiding linkage into 2886 * and removal from the queue and repetition of various 2887 * conversions. 2888 * Set DELACK for segments received in order, but ack 2889 * immediately when segments are out of order (so 2890 * fast retransmit can work). 2891 */ 2892 if (th->th_seq == tp->rcv_nxt && tp->t_segq == NULL && 2893 TCPS_HAVEESTABLISHED(tp->t_state)) { 2894 if (DELAY_ACK(tp, tlen)) 2895 tp->t_flags |= TF_DELACK; 2896 else 2897 tp->t_flags |= TF_ACKNOW; 2898 tp->rcv_nxt += tlen; 2899 thflags = th->th_flags & TH_FIN; 2900 TCPSTAT_INC(tcps_rcvpack); 2901 TCPSTAT_ADD(tcps_rcvbyte, tlen); 2902 ND6_HINT(tp); 2903 SOCKBUF_LOCK(&so->so_rcv); 2904 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2905 m_freem(m); 2906 else 2907 sbappendstream_locked(&so->so_rcv, m); 2908 /* NB: sorwakeup_locked() does an implicit unlock. */ 2909 sorwakeup_locked(so); 2910 } else { 2911 /* 2912 * XXX: Due to the header drop above "th" is 2913 * theoretically invalid by now. Fortunately 2914 * m_adj() doesn't actually frees any mbufs 2915 * when trimming from the head. 2916 */ 2917 thflags = tcp_reass(tp, th, &tlen, m); 2918 tp->t_flags |= TF_ACKNOW; 2919 } 2920 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 2921 tcp_update_sack_list(tp, save_start, save_start + tlen); 2922 #if 0 2923 /* 2924 * Note the amount of data that peer has sent into 2925 * our window, in order to estimate the sender's 2926 * buffer size. 2927 * XXX: Unused. 2928 */ 2929 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 2930 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2931 else 2932 len = so->so_rcv.sb_hiwat; 2933 #endif 2934 } else { 2935 m_freem(m); 2936 thflags &= ~TH_FIN; 2937 } 2938 2939 /* 2940 * If FIN is received ACK the FIN and let the user know 2941 * that the connection is closing. 2942 */ 2943 if (thflags & TH_FIN) { 2944 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2945 socantrcvmore(so); 2946 /* 2947 * If connection is half-synchronized 2948 * (ie NEEDSYN flag on) then delay ACK, 2949 * so it may be piggybacked when SYN is sent. 2950 * Otherwise, since we received a FIN then no 2951 * more input can be expected, send ACK now. 2952 */ 2953 if (tp->t_flags & TF_NEEDSYN) 2954 tp->t_flags |= TF_DELACK; 2955 else 2956 tp->t_flags |= TF_ACKNOW; 2957 tp->rcv_nxt++; 2958 } 2959 switch (tp->t_state) { 2960 2961 /* 2962 * In SYN_RECEIVED and ESTABLISHED STATES 2963 * enter the CLOSE_WAIT state. 2964 */ 2965 case TCPS_SYN_RECEIVED: 2966 tp->t_starttime = ticks; 2967 /* FALLTHROUGH */ 2968 case TCPS_ESTABLISHED: 2969 tcp_state_change(tp, TCPS_CLOSE_WAIT); 2970 break; 2971 2972 /* 2973 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2974 * enter the CLOSING state. 2975 */ 2976 case TCPS_FIN_WAIT_1: 2977 tcp_state_change(tp, TCPS_CLOSING); 2978 break; 2979 2980 /* 2981 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2982 * starting the time-wait timer, turning off the other 2983 * standard timers. 2984 */ 2985 case TCPS_FIN_WAIT_2: 2986 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2987 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata " 2988 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 2989 ti_locked)); 2990 2991 tcp_twstart(tp); 2992 INP_INFO_WUNLOCK(&V_tcbinfo); 2993 return; 2994 } 2995 } 2996 if (ti_locked == TI_WLOCKED) 2997 INP_INFO_WUNLOCK(&V_tcbinfo); 2998 ti_locked = TI_UNLOCKED; 2999 3000 #ifdef TCPDEBUG 3001 if (so->so_options & SO_DEBUG) 3002 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3003 &tcp_savetcp, 0); 3004 #endif 3005 3006 /* 3007 * Return any desired output. 3008 */ 3009 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3010 (void) tcp_output(tp); 3011 3012 check_delack: 3013 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 3014 __func__, ti_locked)); 3015 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3016 INP_WLOCK_ASSERT(tp->t_inpcb); 3017 3018 if (tp->t_flags & TF_DELACK) { 3019 tp->t_flags &= ~TF_DELACK; 3020 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3021 } 3022 INP_WUNLOCK(tp->t_inpcb); 3023 return; 3024 3025 dropafterack: 3026 /* 3027 * Generate an ACK dropping incoming segment if it occupies 3028 * sequence space, where the ACK reflects our state. 3029 * 3030 * We can now skip the test for the RST flag since all 3031 * paths to this code happen after packets containing 3032 * RST have been dropped. 3033 * 3034 * In the SYN-RECEIVED state, don't send an ACK unless the 3035 * segment we received passes the SYN-RECEIVED ACK test. 3036 * If it fails send a RST. This breaks the loop in the 3037 * "LAND" DoS attack, and also prevents an ACK storm 3038 * between two listening ports that have been sent forged 3039 * SYN segments, each with the source address of the other. 3040 */ 3041 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3042 (SEQ_GT(tp->snd_una, th->th_ack) || 3043 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3044 rstreason = BANDLIM_RST_OPENPORT; 3045 goto dropwithreset; 3046 } 3047 #ifdef TCPDEBUG 3048 if (so->so_options & SO_DEBUG) 3049 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3050 &tcp_savetcp, 0); 3051 #endif 3052 if (ti_locked == TI_WLOCKED) 3053 INP_INFO_WUNLOCK(&V_tcbinfo); 3054 ti_locked = TI_UNLOCKED; 3055 3056 tp->t_flags |= TF_ACKNOW; 3057 (void) tcp_output(tp); 3058 INP_WUNLOCK(tp->t_inpcb); 3059 m_freem(m); 3060 return; 3061 3062 dropwithreset: 3063 if (ti_locked == TI_WLOCKED) 3064 INP_INFO_WUNLOCK(&V_tcbinfo); 3065 ti_locked = TI_UNLOCKED; 3066 3067 if (tp != NULL) { 3068 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3069 INP_WUNLOCK(tp->t_inpcb); 3070 } else 3071 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3072 return; 3073 3074 drop: 3075 if (ti_locked == TI_WLOCKED) { 3076 INP_INFO_WUNLOCK(&V_tcbinfo); 3077 ti_locked = TI_UNLOCKED; 3078 } 3079 #ifdef INVARIANTS 3080 else 3081 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3082 #endif 3083 3084 /* 3085 * Drop space held by incoming segment and return. 3086 */ 3087 #ifdef TCPDEBUG 3088 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3089 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3090 &tcp_savetcp, 0); 3091 #endif 3092 if (tp != NULL) 3093 INP_WUNLOCK(tp->t_inpcb); 3094 m_freem(m); 3095 } 3096 3097 /* 3098 * Issue RST and make ACK acceptable to originator of segment. 3099 * The mbuf must still include the original packet header. 3100 * tp may be NULL. 3101 */ 3102 static void 3103 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3104 int tlen, int rstreason) 3105 { 3106 #ifdef INET 3107 struct ip *ip; 3108 #endif 3109 #ifdef INET6 3110 struct ip6_hdr *ip6; 3111 #endif 3112 3113 if (tp != NULL) { 3114 INP_WLOCK_ASSERT(tp->t_inpcb); 3115 } 3116 3117 /* Don't bother if destination was broadcast/multicast. */ 3118 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3119 goto drop; 3120 #ifdef INET6 3121 if (mtod(m, struct ip *)->ip_v == 6) { 3122 ip6 = mtod(m, struct ip6_hdr *); 3123 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3124 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3125 goto drop; 3126 /* IPv6 anycast check is done at tcp6_input() */ 3127 } 3128 #endif 3129 #if defined(INET) && defined(INET6) 3130 else 3131 #endif 3132 #ifdef INET 3133 { 3134 ip = mtod(m, struct ip *); 3135 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3136 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3137 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3138 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3139 goto drop; 3140 } 3141 #endif 3142 3143 /* Perform bandwidth limiting. */ 3144 if (badport_bandlim(rstreason) < 0) 3145 goto drop; 3146 3147 /* tcp_respond consumes the mbuf chain. */ 3148 if (th->th_flags & TH_ACK) { 3149 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3150 th->th_ack, TH_RST); 3151 } else { 3152 if (th->th_flags & TH_SYN) 3153 tlen++; 3154 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3155 (tcp_seq)0, TH_RST|TH_ACK); 3156 } 3157 return; 3158 drop: 3159 m_freem(m); 3160 } 3161 3162 /* 3163 * Parse TCP options and place in tcpopt. 3164 */ 3165 static void 3166 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3167 { 3168 int opt, optlen; 3169 3170 to->to_flags = 0; 3171 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3172 opt = cp[0]; 3173 if (opt == TCPOPT_EOL) 3174 break; 3175 if (opt == TCPOPT_NOP) 3176 optlen = 1; 3177 else { 3178 if (cnt < 2) 3179 break; 3180 optlen = cp[1]; 3181 if (optlen < 2 || optlen > cnt) 3182 break; 3183 } 3184 switch (opt) { 3185 case TCPOPT_MAXSEG: 3186 if (optlen != TCPOLEN_MAXSEG) 3187 continue; 3188 if (!(flags & TO_SYN)) 3189 continue; 3190 to->to_flags |= TOF_MSS; 3191 bcopy((char *)cp + 2, 3192 (char *)&to->to_mss, sizeof(to->to_mss)); 3193 to->to_mss = ntohs(to->to_mss); 3194 break; 3195 case TCPOPT_WINDOW: 3196 if (optlen != TCPOLEN_WINDOW) 3197 continue; 3198 if (!(flags & TO_SYN)) 3199 continue; 3200 to->to_flags |= TOF_SCALE; 3201 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3202 break; 3203 case TCPOPT_TIMESTAMP: 3204 if (optlen != TCPOLEN_TIMESTAMP) 3205 continue; 3206 to->to_flags |= TOF_TS; 3207 bcopy((char *)cp + 2, 3208 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3209 to->to_tsval = ntohl(to->to_tsval); 3210 bcopy((char *)cp + 6, 3211 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3212 to->to_tsecr = ntohl(to->to_tsecr); 3213 break; 3214 #ifdef TCP_SIGNATURE 3215 /* 3216 * XXX In order to reply to a host which has set the 3217 * TCP_SIGNATURE option in its initial SYN, we have to 3218 * record the fact that the option was observed here 3219 * for the syncache code to perform the correct response. 3220 */ 3221 case TCPOPT_SIGNATURE: 3222 if (optlen != TCPOLEN_SIGNATURE) 3223 continue; 3224 to->to_flags |= TOF_SIGNATURE; 3225 to->to_signature = cp + 2; 3226 break; 3227 #endif 3228 case TCPOPT_SACK_PERMITTED: 3229 if (optlen != TCPOLEN_SACK_PERMITTED) 3230 continue; 3231 if (!(flags & TO_SYN)) 3232 continue; 3233 if (!V_tcp_do_sack) 3234 continue; 3235 to->to_flags |= TOF_SACKPERM; 3236 break; 3237 case TCPOPT_SACK: 3238 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3239 continue; 3240 if (flags & TO_SYN) 3241 continue; 3242 to->to_flags |= TOF_SACK; 3243 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3244 to->to_sacks = cp + 2; 3245 TCPSTAT_INC(tcps_sack_rcv_blocks); 3246 break; 3247 default: 3248 continue; 3249 } 3250 } 3251 } 3252 3253 /* 3254 * Pull out of band byte out of a segment so 3255 * it doesn't appear in the user's data queue. 3256 * It is still reflected in the segment length for 3257 * sequencing purposes. 3258 */ 3259 static void 3260 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3261 int off) 3262 { 3263 int cnt = off + th->th_urp - 1; 3264 3265 while (cnt >= 0) { 3266 if (m->m_len > cnt) { 3267 char *cp = mtod(m, caddr_t) + cnt; 3268 struct tcpcb *tp = sototcpcb(so); 3269 3270 INP_WLOCK_ASSERT(tp->t_inpcb); 3271 3272 tp->t_iobc = *cp; 3273 tp->t_oobflags |= TCPOOB_HAVEDATA; 3274 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3275 m->m_len--; 3276 if (m->m_flags & M_PKTHDR) 3277 m->m_pkthdr.len--; 3278 return; 3279 } 3280 cnt -= m->m_len; 3281 m = m->m_next; 3282 if (m == NULL) 3283 break; 3284 } 3285 panic("tcp_pulloutofband"); 3286 } 3287 3288 /* 3289 * Collect new round-trip time estimate 3290 * and update averages and current timeout. 3291 */ 3292 static void 3293 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3294 { 3295 int delta; 3296 3297 INP_WLOCK_ASSERT(tp->t_inpcb); 3298 3299 TCPSTAT_INC(tcps_rttupdated); 3300 tp->t_rttupdated++; 3301 if (tp->t_srtt != 0) { 3302 /* 3303 * srtt is stored as fixed point with 5 bits after the 3304 * binary point (i.e., scaled by 8). The following magic 3305 * is equivalent to the smoothing algorithm in rfc793 with 3306 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3307 * point). Adjust rtt to origin 0. 3308 */ 3309 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3310 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3311 3312 if ((tp->t_srtt += delta) <= 0) 3313 tp->t_srtt = 1; 3314 3315 /* 3316 * We accumulate a smoothed rtt variance (actually, a 3317 * smoothed mean difference), then set the retransmit 3318 * timer to smoothed rtt + 4 times the smoothed variance. 3319 * rttvar is stored as fixed point with 4 bits after the 3320 * binary point (scaled by 16). The following is 3321 * equivalent to rfc793 smoothing with an alpha of .75 3322 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3323 * rfc793's wired-in beta. 3324 */ 3325 if (delta < 0) 3326 delta = -delta; 3327 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3328 if ((tp->t_rttvar += delta) <= 0) 3329 tp->t_rttvar = 1; 3330 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3331 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3332 } else { 3333 /* 3334 * No rtt measurement yet - use the unsmoothed rtt. 3335 * Set the variance to half the rtt (so our first 3336 * retransmit happens at 3*rtt). 3337 */ 3338 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3339 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3340 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3341 } 3342 tp->t_rtttime = 0; 3343 tp->t_rxtshift = 0; 3344 3345 /* 3346 * the retransmit should happen at rtt + 4 * rttvar. 3347 * Because of the way we do the smoothing, srtt and rttvar 3348 * will each average +1/2 tick of bias. When we compute 3349 * the retransmit timer, we want 1/2 tick of rounding and 3350 * 1 extra tick because of +-1/2 tick uncertainty in the 3351 * firing of the timer. The bias will give us exactly the 3352 * 1.5 tick we need. But, because the bias is 3353 * statistical, we have to test that we don't drop below 3354 * the minimum feasible timer (which is 2 ticks). 3355 */ 3356 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3357 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3358 3359 /* 3360 * We received an ack for a packet that wasn't retransmitted; 3361 * it is probably safe to discard any error indications we've 3362 * received recently. This isn't quite right, but close enough 3363 * for now (a route might have failed after we sent a segment, 3364 * and the return path might not be symmetrical). 3365 */ 3366 tp->t_softerror = 0; 3367 } 3368 3369 /* 3370 * Determine a reasonable value for maxseg size. 3371 * If the route is known, check route for mtu. 3372 * If none, use an mss that can be handled on the outgoing interface 3373 * without forcing IP to fragment. If no route is found, route has no mtu, 3374 * or the destination isn't local, use a default, hopefully conservative 3375 * size (usually 512 or the default IP max size, but no more than the mtu 3376 * of the interface), as we can't discover anything about intervening 3377 * gateways or networks. We also initialize the congestion/slow start 3378 * window to be a single segment if the destination isn't local. 3379 * While looking at the routing entry, we also initialize other path-dependent 3380 * parameters from pre-set or cached values in the routing entry. 3381 * 3382 * Also take into account the space needed for options that we 3383 * send regularly. Make maxseg shorter by that amount to assure 3384 * that we can send maxseg amount of data even when the options 3385 * are present. Store the upper limit of the length of options plus 3386 * data in maxopd. 3387 * 3388 * NOTE that this routine is only called when we process an incoming 3389 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3390 * settings are handled in tcp_mssopt(). 3391 */ 3392 void 3393 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3394 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3395 { 3396 int mss = 0; 3397 u_long maxmtu = 0; 3398 struct inpcb *inp = tp->t_inpcb; 3399 struct hc_metrics_lite metrics; 3400 int origoffer; 3401 #ifdef INET6 3402 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3403 size_t min_protoh = isipv6 ? 3404 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3405 sizeof (struct tcpiphdr); 3406 #else 3407 const size_t min_protoh = sizeof(struct tcpiphdr); 3408 #endif 3409 3410 INP_WLOCK_ASSERT(tp->t_inpcb); 3411 3412 if (mtuoffer != -1) { 3413 KASSERT(offer == -1, ("%s: conflict", __func__)); 3414 offer = mtuoffer - min_protoh; 3415 } 3416 origoffer = offer; 3417 3418 /* Initialize. */ 3419 #ifdef INET6 3420 if (isipv6) { 3421 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3422 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; 3423 } 3424 #endif 3425 #if defined(INET) && defined(INET6) 3426 else 3427 #endif 3428 #ifdef INET 3429 { 3430 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3431 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt; 3432 } 3433 #endif 3434 3435 /* 3436 * No route to sender, stay with default mss and return. 3437 */ 3438 if (maxmtu == 0) { 3439 /* 3440 * In case we return early we need to initialize metrics 3441 * to a defined state as tcp_hc_get() would do for us 3442 * if there was no cache hit. 3443 */ 3444 if (metricptr != NULL) 3445 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3446 return; 3447 } 3448 3449 /* What have we got? */ 3450 switch (offer) { 3451 case 0: 3452 /* 3453 * Offer == 0 means that there was no MSS on the SYN 3454 * segment, in this case we use tcp_mssdflt as 3455 * already assigned to t_maxopd above. 3456 */ 3457 offer = tp->t_maxopd; 3458 break; 3459 3460 case -1: 3461 /* 3462 * Offer == -1 means that we didn't receive SYN yet. 3463 */ 3464 /* FALLTHROUGH */ 3465 3466 default: 3467 /* 3468 * Prevent DoS attack with too small MSS. Round up 3469 * to at least minmss. 3470 */ 3471 offer = max(offer, V_tcp_minmss); 3472 } 3473 3474 /* 3475 * rmx information is now retrieved from tcp_hostcache. 3476 */ 3477 tcp_hc_get(&inp->inp_inc, &metrics); 3478 if (metricptr != NULL) 3479 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3480 3481 /* 3482 * If there's a discovered mtu in tcp hostcache, use it. 3483 * Else, use the link mtu. 3484 */ 3485 if (metrics.rmx_mtu) 3486 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3487 else { 3488 #ifdef INET6 3489 if (isipv6) { 3490 mss = maxmtu - min_protoh; 3491 if (!V_path_mtu_discovery && 3492 !in6_localaddr(&inp->in6p_faddr)) 3493 mss = min(mss, V_tcp_v6mssdflt); 3494 } 3495 #endif 3496 #if defined(INET) && defined(INET6) 3497 else 3498 #endif 3499 #ifdef INET 3500 { 3501 mss = maxmtu - min_protoh; 3502 if (!V_path_mtu_discovery && 3503 !in_localaddr(inp->inp_faddr)) 3504 mss = min(mss, V_tcp_mssdflt); 3505 } 3506 #endif 3507 /* 3508 * XXX - The above conditional (mss = maxmtu - min_protoh) 3509 * probably violates the TCP spec. 3510 * The problem is that, since we don't know the 3511 * other end's MSS, we are supposed to use a conservative 3512 * default. But, if we do that, then MTU discovery will 3513 * never actually take place, because the conservative 3514 * default is much less than the MTUs typically seen 3515 * on the Internet today. For the moment, we'll sweep 3516 * this under the carpet. 3517 * 3518 * The conservative default might not actually be a problem 3519 * if the only case this occurs is when sending an initial 3520 * SYN with options and data to a host we've never talked 3521 * to before. Then, they will reply with an MSS value which 3522 * will get recorded and the new parameters should get 3523 * recomputed. For Further Study. 3524 */ 3525 } 3526 mss = min(mss, offer); 3527 3528 /* 3529 * Sanity check: make sure that maxopd will be large 3530 * enough to allow some data on segments even if the 3531 * all the option space is used (40bytes). Otherwise 3532 * funny things may happen in tcp_output. 3533 */ 3534 mss = max(mss, 64); 3535 3536 /* 3537 * maxopd stores the maximum length of data AND options 3538 * in a segment; maxseg is the amount of data in a normal 3539 * segment. We need to store this value (maxopd) apart 3540 * from maxseg, because now every segment carries options 3541 * and thus we normally have somewhat less data in segments. 3542 */ 3543 tp->t_maxopd = mss; 3544 3545 /* 3546 * origoffer==-1 indicates that no segments were received yet. 3547 * In this case we just guess. 3548 */ 3549 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3550 (origoffer == -1 || 3551 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3552 mss -= TCPOLEN_TSTAMP_APPA; 3553 3554 tp->t_maxseg = mss; 3555 } 3556 3557 void 3558 tcp_mss(struct tcpcb *tp, int offer) 3559 { 3560 int mss; 3561 u_long bufsize; 3562 struct inpcb *inp; 3563 struct socket *so; 3564 struct hc_metrics_lite metrics; 3565 struct tcp_ifcap cap; 3566 3567 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3568 3569 bzero(&cap, sizeof(cap)); 3570 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3571 3572 mss = tp->t_maxseg; 3573 inp = tp->t_inpcb; 3574 3575 /* 3576 * If there's a pipesize, change the socket buffer to that size, 3577 * don't change if sb_hiwat is different than default (then it 3578 * has been changed on purpose with setsockopt). 3579 * Make the socket buffers an integral number of mss units; 3580 * if the mss is larger than the socket buffer, decrease the mss. 3581 */ 3582 so = inp->inp_socket; 3583 SOCKBUF_LOCK(&so->so_snd); 3584 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3585 bufsize = metrics.rmx_sendpipe; 3586 else 3587 bufsize = so->so_snd.sb_hiwat; 3588 if (bufsize < mss) 3589 mss = bufsize; 3590 else { 3591 bufsize = roundup(bufsize, mss); 3592 if (bufsize > sb_max) 3593 bufsize = sb_max; 3594 if (bufsize > so->so_snd.sb_hiwat) 3595 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3596 } 3597 SOCKBUF_UNLOCK(&so->so_snd); 3598 tp->t_maxseg = mss; 3599 3600 SOCKBUF_LOCK(&so->so_rcv); 3601 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3602 bufsize = metrics.rmx_recvpipe; 3603 else 3604 bufsize = so->so_rcv.sb_hiwat; 3605 if (bufsize > mss) { 3606 bufsize = roundup(bufsize, mss); 3607 if (bufsize > sb_max) 3608 bufsize = sb_max; 3609 if (bufsize > so->so_rcv.sb_hiwat) 3610 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3611 } 3612 SOCKBUF_UNLOCK(&so->so_rcv); 3613 3614 /* Check the interface for TSO capabilities. */ 3615 if (cap.ifcap & CSUM_TSO) { 3616 tp->t_flags |= TF_TSO; 3617 tp->t_tsomax = cap.tsomax; 3618 } 3619 } 3620 3621 /* 3622 * Determine the MSS option to send on an outgoing SYN. 3623 */ 3624 int 3625 tcp_mssopt(struct in_conninfo *inc) 3626 { 3627 int mss = 0; 3628 u_long maxmtu = 0; 3629 u_long thcmtu = 0; 3630 size_t min_protoh; 3631 3632 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3633 3634 #ifdef INET6 3635 if (inc->inc_flags & INC_ISIPV6) { 3636 mss = V_tcp_v6mssdflt; 3637 maxmtu = tcp_maxmtu6(inc, NULL); 3638 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3639 } 3640 #endif 3641 #if defined(INET) && defined(INET6) 3642 else 3643 #endif 3644 #ifdef INET 3645 { 3646 mss = V_tcp_mssdflt; 3647 maxmtu = tcp_maxmtu(inc, NULL); 3648 min_protoh = sizeof(struct tcpiphdr); 3649 } 3650 #endif 3651 #if defined(INET6) || defined(INET) 3652 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3653 #endif 3654 3655 if (maxmtu && thcmtu) 3656 mss = min(maxmtu, thcmtu) - min_protoh; 3657 else if (maxmtu || thcmtu) 3658 mss = max(maxmtu, thcmtu) - min_protoh; 3659 3660 return (mss); 3661 } 3662 3663 3664 /* 3665 * On a partial ack arrives, force the retransmission of the 3666 * next unacknowledged segment. Do not clear tp->t_dupacks. 3667 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3668 * be started again. 3669 */ 3670 static void 3671 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3672 { 3673 tcp_seq onxt = tp->snd_nxt; 3674 u_long ocwnd = tp->snd_cwnd; 3675 3676 INP_WLOCK_ASSERT(tp->t_inpcb); 3677 3678 tcp_timer_activate(tp, TT_REXMT, 0); 3679 tp->t_rtttime = 0; 3680 tp->snd_nxt = th->th_ack; 3681 /* 3682 * Set snd_cwnd to one segment beyond acknowledged offset. 3683 * (tp->snd_una has not yet been updated when this function is called.) 3684 */ 3685 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th); 3686 tp->t_flags |= TF_ACKNOW; 3687 (void) tcp_output(tp); 3688 tp->snd_cwnd = ocwnd; 3689 if (SEQ_GT(onxt, tp->snd_nxt)) 3690 tp->snd_nxt = onxt; 3691 /* 3692 * Partial window deflation. Relies on fact that tp->snd_una 3693 * not updated yet. 3694 */ 3695 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3696 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3697 else 3698 tp->snd_cwnd = 0; 3699 tp->snd_cwnd += tp->t_maxseg; 3700 } 3701